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  • 1.
    Alecrim, Viviane
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Andres, Britta
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Zhang, Renyun
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Hummelgård, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Blomquist, Nicklas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Forsberg, Sven
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Engström, Ann-Christine
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Shimizu, Kenichi
    Umeå University.
    Andersson, Mattias
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Exfoliation of MoS2 for paper based applications2014Conference paper (Other academic)
  • 2.
    Alecrim, Viviane
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Andres, Britta
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Zhang, Renyun
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Hummelgård, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Shimizu, Kenichi
    Umeå University.
    Forsberg, Sven
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Andersson, Mattias
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Exfoliated MoS2 for paper based supercapacitors and photodetectors2014In: Collection of Extent Abstracts, 2014, p. 437-438Conference paper (Other academic)
  • 3.
    Alecrim, Viviane
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Zhang, Renyun
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Hummelgård, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Andersson, Henrik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Andersson, Mattias
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Olin, Hakan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Photoconductivity of bulk and liquid processed MoS22014Conference paper (Other academic)
  • 4.
    Alecrim, Viviane
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Zhang, Renyun
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Hummelgård, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Andres, Britta
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Dahlström, Christina
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Norgren, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Andersson, Mattias
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Exfoliated Layered Materials for Digital Fabrication2015In: NIP & Digital Fabrication Conference, 2015, Vol. 1, p. 192-194Conference paper (Refereed)
    Abstract [en]

    We introduced an exfoliation method of MoS2 in a 3% solution of sodium dodecyl surfactant at high concentration (i.e. 2 g/L). The bulk MoS2 was thinned by mechanical exfoliation between sand papers and the resulting powder was used to prepare dispersions by liquid exfoliation through probe sonication. The resulting dispersion consisted of very thin MoS2 nanosheets in surfactant solution with average lateral size around 126 nm. This may be interesting for applications in inkjet printed electronics.

  • 5.
    Andersson, Henrik
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Andres, Britta
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Manuilskiy, Anatoliy
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Forsberg, Sven
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Hummelgård, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Bäckström, Joakim
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Zhang, Renyun
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Contacting paper-based supercapacitors to printed electronics on paper substrates2012In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 27, no 2, p. 476-480Article in journal (Refereed)
    Abstract [en]

    Hybrid printed electronics, in which printed structures and silicon-based components co-exist will likely be among the first commercial solutions. In this case the paper substrate acts much in the same way as circuit boards, containing conductive tracks and acting as a carrier for the electrical components. It is important to consider the contacting of the components to be able to produce low resistance electrical contacts to the conductive tracks. Supercapacitors are able to deliver a large amount of current in a short time and are a good option for short term energy storage and if the printed product is to be used only one, or a few times, it can be the only power source needed. When manufacturing printed electronics, the overall resistance of the printed tracks as well as the contact resistance of the mounted components will add up to the total resistance of the system. A high resistance will cause a voltage drop from the power source to the component. This will waste power that goes to Joule heating and also the voltage and current available to components may be too low to drive them. If the intention is to use a power supply such as batteries or solar cells this becomes a limitation. In this article have been tested several conductive adhesives used to contact paper based supercapacitors to ink jet printed silver tracks on paper. The best adhesive gives about 0.3 Ω per contact, a factor 17 better compared to the worst which gave 5 Ω. The peak power that is possible to take out from a printed system with a flexible battery and super capacitors is about 10 times higher than compared with the same system with only the battery.

  • 6.
    Andres, Britta
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Forsberg, Sven
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Vilches, Ana Paola
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Zhang, Renyun
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Andersson, Henrik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Hummelgård, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Bäckström, Joakim
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Supercapacitors with graphene coated paper electrodes2012In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 27, no 2, p. 481-485Article in journal (Refereed)
    Abstract [en]

    Paper based supercapacitors are prepared by stacking a paper between two graphene electrodes and soaking these in an aqueous electrolyte. We demonstrate that supercapacitors can easily be manufactured by using proven paper technologies. Several different electrode materials were compared and two types of contacting material, silver and graphite foil were tested. The influence of the paper used as separator was also investigated. The supercapacitors with a graphene-gold nanoparticle composite as electrodes showed a specific capacitance of up to 100 F/g and an energy density of 1.27 Wh/kg. The energy density can further be increased by using other electrolytes. The silver contacts showed a pseudo capacitance, which the graphite contacts did not. The papers tested had a minor effect on the capacitance, but they have an influence on the weight and the volume of the supercapacitor.

  • 7.
    Deiana, L.
    et al.
    Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, 106 91 Stockholm, Sweden .
    Ghisu, L.
    Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, 106 91 Stockholm, Sweden .
    Córdova, O.
    Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, 106 91 Stockholm, Sweden .
    Afewerki, Samson
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Zhang, Renyun
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Córdova, Armando
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences. Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, 106 91 Stockholm, Sweden .
    Efficient and highly enantioselective aerobic oxidation-michael- carbocyclization cascade transformations by integrated Pd(0)-CPG nanoparticle/chiral amine relay catalysis2014In: Synthesis (Stuttgart), ISSN 0039-7881, E-ISSN 1437-210X, Vol. 46, no 10, p. 1303-1310Article in journal (Refereed)
    Abstract [en]

    A series of highly diastereo- and enantioselective aerobic oxidation-Michael-carbocyclization cascade transformations by integrated heterogeneous Pd(0)-CPG nanoparticle/chiral amine relay catalysis are disclosed. The heterogeneous Pd(0)-CPG nanoparticle catalysts were efficient for both the sequential aerobic oxidation and dynamic kinetic asymmetric Michael- carbocyclization transformations, resulting in 1) oxidation of a variety of allylic alcohols to enals and 2) formation of cyclopentenes containing an all-carbon quaternary stereocenter in good to high yields with up to 20:1 dr and 99.5:0.5 er. © Georg Thieme Verlag Stuttgart.New York.

  • 8.
    Forsberg, Viviane
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Andersson, Henrik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Engholm, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Thungström, Göran
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Zhang, Renyun
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Hummelgård, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Norgren, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Photodetector of multilayer exfoliated MoS2 deposited on polyimide films2018Conference paper (Other academic)
    Abstract [en]

    We fabricated a photodetector based on multilayer molybdenum disulfide (MoS2) by micromechanical cleavage of a molybdenite crystal using a polyimide film. We deposited 40 nm of gold by vacuum sputtering and copper tape was used for the contacts.  Without any surface treatment, we achieved high responsivity at different incident optical power. The calculated responsivity was 23 mA/W of incident optical power in the range between 400 and 800 nm. For the responsivity measurement it was estimated that MoS2 have a bandgap of 1.6 eV, which lies between monolayer and multilayer films. The thickness of the MoS2 thin film was determined by Raman spectroscopy evaluating the difference between the in plane  and out of plane  Raman modes. The measurement of IV curves indicated Ohmic contacts in respect to the Au regardless of the incident optical power. Our device fabrication was much simpler than previous reported devices and can be used to test the light absorption and luminescence capabilities of exfoliated MoS2.

  • 9.
    Forsberg, Viviane
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Hummelgård, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Zhang, Renyun
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Cellulose stabilizers for 2D materials inkjet inks2017Conference paper (Refereed)
    Abstract [en]

    To date, the most promising scalable method for achieving 2D materials dispersions is through liquidbasedexfoliation of nanosheets in solvents. We study the use of high throughput shear exfoliation insteadof sonication to exfoliate water dispersions of MoS2 using environmental friendly stabilizers based oncellulose. The resulted dispersion was then concentrated and inkjet printed on a flexible substrate. We usedethyl cellulose, cellulose nanofibers (CNF) and ultra-fine cellulose nanofibers (UF-CNF). The stability wasevaluated by measuring the differences in concentration over time. The particle size distribution (PSD) ofthe dispersed particles was evaluated using statistical methods applied to SEM images of the dispersions(See Fig 1 and 2). The zeta potential and the mechanisms of stabilization involved was evaluated (See Fig4). All three stabilizers appear to work very well for MoS2 nanosheets even though the mechanisms ofstabilization were different i.e. steric stabilization for MoS2-EC and electrostatic stabilization for MoS2-CNF and MoS2-UF-CNF dispersions. For the MoS2-EC dispersions we achieved a broader PSD (Fig. 1)and higher stability. Thin nanosheets was observed from the SEM image of MoS2-EC dispersions depositedonto cellulose filters by vacuum filtration (Fig. 5) which demonstrated that the exfoliation technique usedwas successful. The estimated concentration of the MoS2-EC dispersion after 8 days of sample preparationwas 0.24 mg/mL, 77% of the initial concentration (see Fig. 6) and it was relatively steady after 40 days ofsample preparation (0.22 mg/mL). To adjust the concentration and the viscosity of the MoS2-EC dispersion,we concentrated it using a rotary evaporator solvent exchange technique. For this we used terpineol andadjusted the viscosity using ethanol. This paper presents the results of an inkjet 2D material ink usingenvironmental friendly components different than previous 2D materials inks that used organic solvents orwater based dispersions containing surfactants.

  • 10.
    Forsberg, Viviane
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Zhang, Renyun
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Andersson, Henrik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Bäckström, Joakim
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Dahlström, Christina
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Norgren, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Andres, Britta
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Liquid Exfoliation of Layered Materials in Water for Inkjet Printing2016In: Printing for Fabrication 2016: Materials, Applications, and Processes, USA: Curran Associates, Inc., 2016Conference paper (Refereed)
    Abstract [en]

    MoS2 is a layered material which is abundant and non-toxic and has been increasingly studied during the last few years as a semiconducting alternative to graphene. While most studies have been performed on single MoS2 nanosheets, for example to demonstrate high-performance electronic transistors, more work is needed to explore the use of MoS2 in printed electronics. The importance of using MoS2 as a printed electronic material could be understood by considering the several orders higher electron mobility in MoS2, even in several nanometer thick layers, compared to the organic and other materials used today. In the few studies performed so far on printing MoS2, the developed dispersions used mainly organic solvents that might be detrimental for the environment. Here, we show an environmentally friendly liquid-based exfoliation method in water where the solution was stabilized by sodium dodecyl sulfate (SDS) surfactant. The dispersions consisted of very thin MoS2 nanosheets with average lateral size of about 150 nm, surface tension of 28 mN m-1 and a shelf life of a year. Although both the concentration and viscosity was less than optimal, we were able to inkjet print the MoS2 solution on paper and on PET films, using multiple printing passes. By tuning the concentration/viscosity, this approach might lead to an environmentally friendly MoS2 ink suitable for printed electronics.

  • 11.
    Forsberg, Viviane
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Zhang, Renyun
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Andersson, Henrik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Bäckström, Joakim
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Dahlström, Christina
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Norgren, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Andres, Britta
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Liquid Exfoliation of Layered Materials in Water for Inkjet Printing2016In: Journal of Imaging Science and Technology, ISSN 1062-3701, E-ISSN 1943-3522, Vol. 60, no 4, p. 1-7, article id 040405Article in journal (Refereed)
    Abstract [en]

    MoS2 is a layered material which is abundant and non-toxic and has been increasingly studied during the last few years as a semiconducting alternative to graphene. While most studies have been performed on single MoS2 nanosheets, for example to demonstrate high-performance electronic transistors, more work is needed to explore the use of MoS2 in printed electronics. The importance of using MoS2 as a printed electronic material could be understood by considering the several orders higher electron mobility in MoS2, even in several nanometer thick layers, compared to the organic and other materials used today. In the few studies performed so far on printing MoS2, the developed dispersions used mainly organic solvents that might be detrimental for the environment. Here, we show an environmentally friendly liquid-based exfoliation method in water where the solution was stabilized by sodium dodecyl sulfate (SDS) surfactant. The dispersions consisted of very thin MoS2 nanosheets with average lateral size of about 150 nm, surface tension of 28 mN m(-1), and a shelf life of a year. Although both the concentration and viscosity was less than optimal, we were able to inkjet print the MoS2 solution on paper and on PET films, using multiple printing passes. By tuning the concentration/viscosity, this approach might lead to an environmentally friendly MoS2 ink suitable for printed electronics.

  • 12.
    Forsberg, Viviane
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Zhang, Renyun
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Hummelgård, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    The Influence of pH on the Stability of Inks of Two-Dimensional Materials for Digital Fabrication2017Conference paper (Refereed)
    Abstract [en]

    We aim to achieve stable printable 2D inks with environmental friendly solvents using a surfactant as a stabilizer. This study focuses on the influence of the pH on the stability of the MoS2 dispersionsin acetic acid at concentrations ranging from pH 1 to 5.The effectiveness of liquid-based exfoliation using shear exfoliation was also evaluated though SEM images and resulted in very thin nanosheets. We observed that at pH concentrations higher than 2, the dispersions were more stable.

  • 13.
    Forsberg, Viviane
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Zhang, Renyun
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Hummelgård, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Towards flexible and cheap printed electronics using inks of exfoliated 2D materials stabilized by cellulose2017Conference paper (Other academic)
    Abstract [en]

    Flexible and cheap electronics are needed for simple applications such as sensors and solar cells. To achieve this, thin functional materials should be deposited efficiently to flexible substrates such as paper. A promising method for the deposition of such materials is through inkjet printing that said a stable and printable dispersion is necessary. We achieved this through liquid-based exfoliation of 2D materials in water using shear exfoliation and cellulose stabilizers. The resulted dispersion was then concentrated and inkjet printed on a flexible substrate. We used ethyl cellulose, cellulose nanofibers (CNF) and ultra-fine cellulose nanofibers (UF-CNF). All three stabilizers appear to work very well for MoS2 nanosheets even though the mechanisms of stabilization were different among them. For the MoS2-EC dispersions we achieved a broader PSD and higher dispersion stability. Thin nanosheets were observed from the SEM image of MoS2-EC dispersions deposited onto cellulose filters. The estimated concentration of the MoS2-EC dispersion after 20 days of sample preparation was 0.20 mg/mL. This dispersion was further processed to adjust the concentration and viscosity.  Good coverage of the substrate was achieved after 50 printing passes. If the same technique is applied to other 2D materials such as graphene (conductor) and boro nitride (insulator), a transistor can be fabricated.

  • 14.
    Forsberg, Viviane
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Zhang, Renyun
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Hummelgård, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Towards stable 2D materials inkjet inks: a study of stabilizers and MoS2 grades2017Conference paper (Refereed)
  • 15.
    Forsberg, Viviane
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Zhang, Renyun
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Joakim, Bäckström
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Dahlström, Christina
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Andres, Britta
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Norgren, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Andersson, Mattias
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Hummelgård, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Exfoliated MoS2 in Water without Additives2016In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 11, no 4, article id 0154522Article in journal (Refereed)
    Abstract [en]

    Many solution processing methods of exfoliation of layered materials have been studied during the last few years; most of them are based on organic solvents or rely on surfactants andother funtionalization agents. Pure water should be an ideal solvent, however, it is generallybelieved, based on solubility theories that stable dispersions of water could not be achievedand systematic studies are lacking. Here we describe the use of water as a solvent and thestabilization process involved therein. We introduce an exfoliation method of molybdenumdisulfide (MoS2) in pure water at high concentration (i.e., 0.14±0.01 g L−1). This was achieved by thinning the bulk MoS2by mechanical exfoliation between sand papers and dis-persing it by liquid exfoliation through probe sonication in water. We observed thin MoS2nanosheets in water characterized by TEM, AFM and SEM images. The dimensions of thenanosheets were around 200 nm, the same range obtained in organic solvents. Electropho-retic mobility measurements indicated that electrical charges may be responsible for the sta-bilization of the dispersions. A probability decay equation was proposed to compare thestability of these dispersions with the ones reported in the literature. Water can be used as asolvent to disperse nanosheets and although the stability of the dispersions may not be ashigh as in organic solvents, the present method could be employed for a number of applications where the dispersions can be produced on site and organic solvents are not desirable.

  • 16.
    Hammarling, Krister
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Zhang, Renyun
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Manuilskiy, Anatoliy
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Nilsson, Hans-Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    FBG based upon evaporated Silica nano particles2011In: 1st EOS Topical Meetingon On Micro- and Nano-Optoelectronic Systems, Bremen, December 7-9, 2011, 2011Conference paper (Refereed)
    Abstract [en]

    A fiber bragg grating was made by evaporating silica nano particles on the outside of a multimode silica fiber core using EISA method. We demonstrate that a cost effective bragg filter may be built by evaporating nano particles directly on a fiber core, which is tunable with the particle size.

  • 17.
    Hammarling, Krister
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Zhang, Renyun
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Manuilskiy, Anatoliy
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Nilsson, Hans-Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Fiber Bragg Grating filter using Evaporated Induced Self Assembly of silica nano particles2014In: Proceedings of SPIE - The International Society for Optical Engineering: Optical Components and Materials XI, 8982 / [ed] Michel J. F. Digonnet; Shibin Jiang, 2014, p. Art. no. 898225-Conference paper (Refereed)
    Abstract [en]

    In the present work we conduct a study of ber lters produced by evaporation of silica particles upon aMM-ber core. A band lter was designed and theoretically veried using a 2D Comsol simulation model ofa 3D problem, and calculated in the frequency domain in respect to refractive index. The ber lters werefabricated by stripping and chemically etching the middle part of an MM-ber until the core was exposed. Amono layer of silica nano particles were evaporated on the core using an Evaporation Induced Self-Assembly(EISA) method. The experimental results indicated a broader bandwidth than indicated by the simulationswhich can be explained by the mismatch in the particle size distributions, uneven particle packing and nallyby eects from multiple mode angles. Thus, there are several closely connected Bragg wavelengths that buildup the broader bandwidth. The experimental part shows that it is possible by narrowing the particle sizedistributing and better control of the particle packing, the lter eectiveness can be greatly improved.

  • 18.
    Hummelgård, Magnus
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Zhang, Renyun
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Carlberg, Torbjörn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Vengust, D
    Dvorsek, D
    Mihailovic, D
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Nanowire Transformation and Annealing by Joule Heating2010In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 21, no 16, p. 165704-165704Article in journal (Refereed)
    Abstract [en]

    Joule heating of bundles of Mo6S3I6 nanowires, in real time, was studied using in situ TEM probing. TEM imaging, electron diffraction, and conductivity measurements showed a complete transformation of Mo6S3I6 into Mo via thermal decomposition. The resulting Mo nanowires had a conductivity that was 2-3 orders higher than the starting material. The conductivity increased even further, up to 1.8 x 10(6) S m(-1), when the Mo nanowires went through annealing phases. These results suggest that Joule heating might be a general way to transform or anneal nanowires, pointing to applications such as metal nanowire fabrication, novel memory elements based on material transformation, or in situ improvement of field emitters.

  • 19.
    Hummelgård, Magnus
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Zhang, Renyun
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Nilsson, Hans-Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Electrical Sintering of Silver Nanoparticle Ink Studied by In-Situ TEM Probing2011In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 6, no 2, p. Art. no. e17209-Article in journal (Refereed)
    Abstract [en]

    Metallic nanoparticle inks are used for printed electronics, but to reach acceptable conductivity the structures need to be sintered, usually using a furnace. Recently, sintering by direct resistive heating has been demonstrated. For a microscopic understanding of this Joule heating sintering method, we studied the entire process in real time inside a transmission electron microscope equipped with a movable electrical probe. We found an onset of Joule heating induced sintering and coalescence of nanoparticles at power levels of 0.1-10 mW/mu m(3). In addition, a carbonization of the organic shells that stabilize the nanoparticles were found, with a conductivity of 4 10(5) Sm-1

  • 20.
    Maslik, Jan
    et al.
    Centre of Polymer Systems, University Institute, Tomas Bata University in Zlin, Zlin, Czech Republic.
    Andersson, Henrik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Forsberg, Viviane
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Engholm, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Zhang, Renyun
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    PEDOT:PSS temperature sensor ink-jet printed on paper substrate2018In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 13, article id C12010Article in journal (Refereed)
    Abstract [en]

    In this work we present an ink-jet printed temperature sensor consisting of PEDOT:PSSprinted on paper suitable for packaging, flexible electronics and other printed applications. Thesubstrate showed to have a large influence on both the resistance aswell as the temperature sensitivityof the PEDOT:PSS ink. This effect is most likely due to NaCl content in the photo paper coating,which reacts with the PEDOT:PSS. The temperature coefficient of a prepared device of α = -0.030relative to room temperature (22°C) was measured, which is higher than compared to for exampleSilicon α = -0.075.

  • 21.
    Mazlik, Jan
    et al.
    Tomas Bata University.
    Andersson, Henrik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Forsberg, Viviane
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Engholm, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Zhang, Renyun
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Temperature sensor based on PEDOT: PSS ink-jet printed on paper substrate2018Conference paper (Refereed)
    Abstract [en]

    Printed electronics is rapidly developing, where more and more components are printable. High speed roll-to-roll processesare preferred for low cost production of flexible electronics. Often, the substrates used for printed electronics are some typeof plastic such as PET or Kapton. An alternative to plastic is to use paper substrate that has the benefits of beingenvironmentally friendly, recyclable and renewable. Paper is also the material of choice for packages of various goods.In this work we have developed an ink-jet printable temperature sensor, a thermistor, consisting ofpoly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)( PEDOT:PSS) on paper substrate. The starting material is acommercial PEDOT:PSS ink-jet ink (Orgacon IJ-1005, Agfa). This ink was then modified to increase the thermal sensitivityby addition of the co-solvents Dimethyl sulfoxide (DMSO) and Polyethylene glycol (PEG) in different quantities. DMSO hasbeen shown to increase the conductance by arranging the PEDOT into more conductive pathways and by removing PSS[1] and PEG to increase the carrier density and mobility [2].The sensors consisted of modified PEDOT:PSS lines printed on photo-paper substrate between contacts printed usingsilver nano-particle ink. The line widths were varied from one pixel, corresponding to one pass of one nozzle up-to 20pixels. The linewidths were then measured to be from 45 μm up-to 450 μm. The thickness of the sensor was also varied asone, two or three printed layers. The characterization as a temperature sensor was performed by using a setup consistingof a Peltier cooler and a heating element to step the temperature. As a reference a PT-100 element fixed to the surface ofthe cooler/heater was used.An increase in resistance from 30.5 MΩ to 85 MΩ, corresponding to a change of 2.8 times, were measured when thetemperature were changed from 22 °C to -12 °C as can be seen in the figure. This gives a ΔR/ΔT of 0.093.Such a printed sensor can be used for applications where a low cost, printable solution is needed, such as printed directlyon packages, for environmental monitoring and similar.[1] C.S. Pathak, J.P. Singh, R. Singh, Effect of dimethyl sulfoxide on the electrical properties of PEDOT:PSS/ n-Siheterojunction diodes, Current Applied Physics, 15, (2015), 528-534[2] Yow-Jon Lin, Wei-Shih Ni and Jhe-You Lee, Effect of incorporation of ethylene glycol into PEDOT:PSS on electronphonon coupling and conductivity, Journal of Applied Physics 117, (2015), 215501

  • 22.
    Olin, Håkan
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Zhang, Renyun
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Soap film coating2014Patent (Other (popular science, discussion, etc.))
  • 23.
    Olsen, Martin
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Örtegren, Jonas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Zhang, Renyun
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Reza, Salim
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Andersson, Henrik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Schottky model for triboelectric temperature dependence2018In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, no 1, article id 5293Article in journal (Refereed)
    Abstract [en]

    The triboelectric effect, charging by contact, is the working principle in a device called a triboelectric nanogenerator. They are used as efficient energy transducers in energy harvesting. In such generators the charging of surfaces at contact is followed by a separation of the surfaces increasing the electrical energy which can subsequently be used. Different materials have different triboelectric potentials leading to charging at contact. The temperature dependence of the charging has just recently been studied: the triboelectric effect is decreasing with temperature for a generator of Al-PTFE-Cu. Here, we suggest a mechanism to explain this effect assuming ion transfer using a two-level Schottky model where the two levels corresponds to the two surfaces. The difference in binding energy for ions on the two surfaces then enters the formula for charging. We fit the triboelectric power density as a function of temperature obtained from a two-level Schottky model to measured data for nanogenerators made of Al-PTFE-Cu found in three references. We obtain an average separation energy corresponding to a temperature of 365 K which is of the right magnitude for physically adsorbed atoms. We anticipate that this model could be used for many types of triboelectric nanogenerators.

  • 24.
    Zhang, Renyun
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Alecrim, Viviane
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Hummelgård, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Andres, Britta
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Forsberg, Sven
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Andersson, Mattias
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Thermally reduced kaolin-graphene oxide nanocomposites for gas sensing2015In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 5, p. Art. no. 7676-Article in journal (Refereed)
    Abstract [en]

    Highly sensitive graphene-based gas sensors can be made using large-area single layer graphene, but the cost of large-area pure graphene is high, making the simpler reduced graphene oxide (rGO) an attractive alternative. To use rGO for gas sensing, however, require a high active surface area and slightly different approach is needed. Here, we report on a simple method to produce kaolin-graphene oxide (GO) nanocomposites and an application of this nanocomposite as a gas sensor. The nanocomposite was made by binding the GO flakes to kaolin with the help of 3-Aminopropyltriethoxysilane (APTES). The GO flakes in the nanocomposite were contacting neighboring GO flakes as observed by electron microscopy. After thermal annealing, the nanocomposite become conductive as showed by sheet resistance measurements. Based on the conductance changes of the nanocomposite films, electrical gas sensing devices were made for detecting NH3 and HNO3. These devices had a higher sensitivity than thermally annealed multilayer GO films. This kaolin-GO nanocomposite might be useful in applications that require a low-cost material with large conductive surface area including the demonstrated gas sensors.

  • 25.
    Zhang, Renyun
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Andersson, Henrik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Andersson, Mattias
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Andres, Britta
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Edlund, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Edström, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Edvardsson, Sverker
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Forsberg, Sven
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Hummelgård, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Johansson, Niklas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Karlsson, Kristoffer
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Nilsson, Hans-Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Norgren, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Olsen, Martin
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Uesaka, Tetsu
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Öhlund, Thomas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Soap-film coating: High-speed deposition of multilayer nanofilms2013In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 3, p. Art. no. 1477-Article in journal (Refereed)
    Abstract [en]

    The coating of thin films is applied in numerous fields and many methods are employed for the deposition of these films. Some coating techniques may deposit films at high speed; for example, ordinary printing paper is coated with micrometre-thick layers of clay at a speed of tens of meters per second. However, to coat nanometre thin films at high speed, vacuum techniques are typically required, which increases the complexity of the process. Here, we report a simple wet chemical method for the high-speed coating of films with thicknesses at the nanometre level. This soap-film coating technique is based on forcing a substrate through a soap film that contains nanomaterials. Molecules and nanomaterials can be deposited at a thickness ranging from less than a monolayer to several layers at speeds up to meters per second. We believe that the soap-film coating method is potentially important for industrial-scale nanotechnology.

  • 26.
    Zhang, Renyun
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Andersson, Henrik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Andersson, Mattias
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Andres, Britta
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Edström, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Edvardsson, Sverker
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Forsberg, Sven
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Hummelgård, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Johansson, Niklas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Kalsson, Kristoffer
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Nilsson, Hans-Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Olsen, Martin
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Öhlund, Thomas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    High-speed deposition of multilayer nanofilms using soap-film coating2013Conference paper (Refereed)
    Abstract [en]

    High-speed deposition of multilayer nanofilms using soap-film coating

    Renyun Zhang, Henrik A. Andersson, Mattias Andersson, Britta Andres, Per Edström, Sverker Edvardsson, Sven Forsberg, Magnus Hummelgård, Niklas Johansson, Kristoffer Karlsson, Hans-Erik Nilsson, Martin Olsen, Tetsu Uesaka, Thomas Öhlund & Håkan Olin

    Department of Applied Science and Design, Mid Sweden University, SE-85170 Sundsvall, Sweden

    Email: renyun.zhang@miun.se or hakan.olin@miun.se

    Coating1 of thin films is of importance for making functionalized surfaces with applications in many fields from electronics to consumer packaging. To decrease the cost, large scale roll-to-roll2 coating techniques are usually done at high speed, for example, ordinary printing paper is coated at a speed of tens of meters per second by depositing micrometer thick layers of clay. However, nanometer thin films are harder to coat at high speed by wet-chemical methods, requiring special roll-to-roll vacuum techniques3 with the cost of higher complexity.

    Here, we report a simple wet chemical method for high-speed coating of films down to molecular thicknesses, called soap-film coating (SFC)4. The technique is based on forcing a substrate through a soap film that contains nanomaterials. In the simplest laboratory version, the films can be deposited by a hand-coating procedure set up in a couple of minutes. The method is quite general molecules or nanomaterials or sub-micrometer materials (Figure 1) with thicknesses ranging from less than a monolayer to several layers at speeds up to meters per second. The applications of soap-film coating is quite wide an we will show solar cells, electrochromic devices, optical nanoparticle crystals, and nano-film devices. We believe that the soap-film coating method is potentially important for industrial-scale nanotechnology.

    Fig. 1. Soap film coating of nanoparticles, layered materials, nanowires, and molecules. a sub-monolayer 240 nm silica nanoparticle (scale bar 2 µm) b monolayer c double layer. d monolayer gold nanoparticles. e single layer TiO2 nanoparticles. f sub-monolayer polystyrene (scale 2 µm), g monolayer of polystyrene. h triple-layer of polystyrene. i monolayer of Ferritin.  j AFM image of <1.5 layer GO film (3 µm x 2 µm). k clay on glass (scale 2 µm). l SFC coated nanocellulose. m Absorbance spectra Rhodamine B on a glass slide. AFM of SDS layers n (2 µm x 1.5 µm) and o (20 µm x 15 µm).

    References

    1. Tracton, A. A. Coating Technology Handbook (CRC Press, Boca Raton, 2006).

    2. Ohring, M. Materials science of thin films. (Academic press., 2001).

    3. Charles, B. Vacuum deposition onto webs, films and foils. (William Andrew, 2011).

    Zhang, R. Y., Andersson, H. A., Andersson, M., Andres, B., Edström, P., Edvardsson, S., Forsberg, S., Hummelgård, M., Johansson, N., Karlsson, K., Nilsson, H.-E., Olsen, M., Uesaka, T., Öhlund, T., Olin H. Soap film coating: High-speed deposition of multilayer nanofilms. Submitted.

  • 27.
    Zhang, Renyun
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Andersson, Henrik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Olsen, Martin
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Hummelgård, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Edvardsson, Sverker
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Nilsson, Hans-Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Piezoelectric gated ZnO nanowire diode studied by in situ TEM probing2014In: Nano Energy, ISSN 2211-2855, Vol. 3, p. 10-15Article in journal (Refereed)
    Abstract [en]

    The piezoelectricity of ZnO nanowires has shown rising interests during the last few years and fields such as piezotronics and piezophotonics are emerging with a number of applications and devices. One such device is the piezoelectric gated ZnO nanowire diode, where the p–n junction is replaced by a dynamically created potential barrier created simply by bending the otherwise homogeneously doped nanowire. To further study this type of diode we used in situ transmission electron microscope (TEM) probing, where one electrode was fixed at the end of a ZnO nanowire and another moveable electrode was used both for bending and contacting the wire. Thereby we were able to further characterise this diode and found that the diode characteristics depended on whether the contact was made to the stretched (p-type) surface or to the compressed (n-type) surface of the wire. When the neutral line of the wire contacted, between the stretched and the compressed side, the I–V characteristics were independent on the current direction. The performance of the diodes upon different bending intensity showed a rectifying ratio up to the high value of 60:1. The diode ideality factor was found to be about 5. Moreover, the reverse breakdown voltages of the diode were measured and a local but permanent damage to the diode action was found when the voltage went over the reverse breakdown voltage. 

  • 28.
    Zhang, Renyun
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Carlsson, Fredrik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Edman, Mattias
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Hummelgård, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Jonsson, Bengt-Gunnar
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Bylund, Dan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Escherichia coli Bacteria Develop Adaptive Resistance to Antibacterial ZnO Nanoparticles2018In: Advanced Biosystem, ISSN 2366-7478, Vol. 2, no 5, article id 1800019Article in journal (Refereed)
    Abstract [en]

    Antibacterial agents based on nanoparticles (NPs) have many important applications, e.g., for the textile industry, surface disinfection, wound dressing, water treatment, and food preservation. Because of their prevalent use it is important to understand whether bacteria could develop resistance to such antibacterial NPs similarly to the resistance that bacteria are known to develop to antibiotics. Here, it is reported that Escherichia coli(E. coli) develops adaptive resistance to antibacterial ZnO NPs after several days' exposure to the NPs. But, in contrast to antibiotics‐resistance, the observed resistance to ZnO NPs is not stable—after several days without exposure to the NPs, the bacteria regain their sensitivity to the NPs' antibacterial properties. Based on the analyses it is suggested that the observed resistance is caused by changes in the shape of the bacteria and the expressions of membrane proteins. The findings provide insights into the response of bacteria to antibacterial NPs, which is important to elucidate for designing and evaluating the risk of applications based on antibacterial NPs.

  • 29.
    Zhang, Renyun
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Engholm, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Recent Progress on the Fabrication and Properties of Silver Nanowire-Based Transparent Electrodes2018In: Nanomaterials, ISSN 2079-4991, Vol. 8, no 8, article id 628Article in journal (Refereed)
    Abstract [en]

    Transparent electrodes (TEs) made of metallic nanowires, such as Ag, Au, Cu, and Ni, are attracting increasing attention for several reasons: (1) they can act as a substitute for tin oxide-based TEs such as indium-tin oxide (ITO) and fluorine-doped tin oxide (FTO); (2) various methods exist for fabricating such TEs such as filtration, spraying, and Meyer bar coating; (3) greater compatibility with different substrates can be achieved due to the variety of fabrication methods; and (4) extra functions in addition to serving as electrodes, such as catalytic abilities, can be obtained due to the metals of which the TEs are composed. There are a large number of applications for TEs, ranging from electronics and sensors to biomedical devices. This short review is a summary of recent progress, mainly over the past five years, on silver nanowire-based TEs. The focus of the review is on theory development, mechanical, chemical, and thermal stability as well as optical properties. The many applications of TEs are outside the scope of this review.

  • 30.
    Zhang, Renyun
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Engholm, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Hummelgård, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Andersson, Henrik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Örtegren, Jonas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    High-performance transparent and flexible electrodes made by flash-light sintering of gold nanoparticles2018In: ACS Applied Energy Materials, E-ISSN 2574-0962, Vol. 1, no 12, p. 7191-7198Article in journal (Refereed)
    Abstract [en]

    Metallic nanowire-based transparent electrodes (TEs) are potential alternatives to indium tin oxide (ITO). To achieve a high performance [sheet resistance (Rs) < 100 Ω/sq, transmittance (T%) > 90%], the nanowires must have a high length-to-diameter (L/D) ratio to minimize the number of wire-to-wire junctions. Attempts to produce TEs with gold nanowires have been made, and the results reveal difficulties in achieving the requirements. A successful strategy involves creating templated gold nanonetworks through multiple procedures. Here, we present a simple and efficient method that uses flash-light sintering of a gold nanonetwork film into gold TEs (Rs: 82.9 Ω/sq, T %: 91.79%) on a thin polycarbonate film (25 μm). The produced gold TEs have excellent mechanical, electrical, optical, and chemical stabilities. Mechanisms of the formation of gold nanonetworks and the effect of flash-light have been analyzed. Our findings provide a scalable process for producing transparent and flexible gold electrodes with a total processing time of less than 8 min without the use of heating, vacuum processing, and organic chemicals and without any material loss. This is possible because all the gold nanoparticles have been aggregated and filtrated on the filter membranes. The area density of gold is 0.094 g/m2 leading low material costs, which is very competitive with the price of commercial TEs.

  • 31.
    Zhang, Renyun
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Hummelgård, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Dvorsek, D
    Jozef Stefan Institute, Slovenia and Mo6, Ljubljana, Slovenia.
    Mihailovic, D
    Jozef Stefan Institute, Slovenia and Mo6, Ljubljana, Slovenia.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Mo6S3I6-Au composites: Synthesis, Conductance, and Applications2010In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 348, no 2, p. 299-302Article in journal (Refereed)
    Abstract [en]

    A single-step, premixing method was used to directly deposit gold nanoparticles on Mo6S3I6 (MSI) molecular wire bundles. Gold nanoparticles with different sizes and densities were coated on the MSI by changing the concentration of the gold containing salt, HAuCl4. TEM, SEM, and EDX characterization showed deposition of gold nanoparticles on the MSI nanowire surface. The electrical resistance of these MSI-Au composites was more than 100 times lower than that for pure MSI, and was mainly dependent on the density of the deposited gold nanoparticles. Furthermore, we immobilized thiol group-labeled oligonucleotide on the composites and then hybridized with a fully matched sequence. The resistance of the MSI-Au composites increased during the thiol step, while it decreased by hybridizing, due to the conductance difference between single- and double-stranded DNA chains. These results indicate that this new kind of MSI-Au composite could be used as a platform for different applications, including biosensors.

  • 32.
    Zhang, Renyun
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Hummelgård, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Forsberg, Viviane
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Andersson, Henrik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Engholm, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Öhlund, Thomas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Olsen, Martin
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Örtegren, Jonas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Photoconductivity of acid exfoliated and flash-light-processed MoS2 films2018In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, article id 3296Article in journal (Refereed)
    Abstract [en]

    MoS2 has been studied intensively during recent years as a semiconducting material in several fields, including optoelectronics, for applications such as solar cells and phototransistors. The photoresponse mechanisms of MoS2 have been discussed but are not fully understood, especially the phenomenon in which the photocurrent slowly increases. Here, we report on a study of the photoresponse flash-light-processed MoS2 films of different thicknesses and areas. The photoresponse of such films under different light intensities and bias voltages was measured, showing significant current changes with a quick response followed by a slow one upon exposure to pulsed light. Our in-depth study suggested that the slow response was due to the photothermal effect that heats the MoS2; this hypothesis was supported by the resistivity change at different temperatures. The results obtained from MoS2 films with various thicknesses indicated that the minority-carrier diffusion length was 1.36 mu m. This study explained the mechanism of the slow response of the MoS2 film and determined the effective thickness of MoS2 for a photoresponse to occur. The method used here for fabricating MoS2 films could be used for fabricating optoelectronic devices due to its simplicity.

  • 33.
    Zhang, Renyun
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Hummelgård, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Lv, Gang
    N China Elect Power Univ, Dept Math & Phys, Baoding 071003, Peoples R China.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Real time monitoring of the drug release of rhodamine B on graphene oxide2011In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 49, no 4, p. 1126-1132Article in journal (Refereed)
    Abstract [en]

    A real time method for monitoring the drug load and release on graphene oxide (GO) in a cuvette is reported using rhodamine B (RB) as a model for a drug. The mechanisms of the release of RB at different pH were investigated, by monitoring the time dependency of the accumulative drug release. In vitro real time experimental results indicated that RB could be loaded on GO with a capacity of 0.5 mg/mg. The drug release of RB was pH sensitive as observed at pH 7.4 and pH 4.5 PBS solutions. The higher pH values lead to weaker hydrophobic force and hydrogen bonds, and thus higher release rate. The ionic strength also influenced the release of RB, as shown from the different release rates between PBS solutions and double distilled water. These results indicated a case II transport process at pH 7.4 and an anomalous diffusion process at pH 4.5 and in water. The method described here allows real time detection of the drug release rate, in contrast to common dialysis analysis. This method also points to other real time detections in biomedical investigations.

  • 34.
    Zhang, Renyun
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Hummelgård, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    A facile one-step method for synthesising a parallelogram-shaped single-crystalline ZnO nanosheet2014In: Materials Science and Engineering: B, ISSN 0921-5107, Vol. 184, p. 1-6Article in journal (Refereed)
    Abstract [en]

    ZnO nanosheets are found to be useful in many fields such as sensors and electronics. Non-uniform- shaped ZnO nanosheets are synthesised using several methods; moreover, uniformly shaped ones are less studied. Here, we report on a simple one-step method to synthesise parallelogram-shaped single- crystalline ZnO nanosheets. By controlling the reaction of Zn(NO3 )2 and hexamethylenetetramine (HMT) in ethanol, average 30 nm-thick nanosheets with a high aspect ratio of 1:100 were obtained. The par- allelogram angles were between 97◦ and 99◦. Transmission electron microscopy (TEM) diffraction and X-ray diffraction (XRD) showed that the nanosheets were wurtzite-structured single-crystalline ZnO. Moreover, a growth mechanism of these parallelogram nanosheets is suggested based on the experi- mental results. These results suggest a new simple solution process to synthesise uniformly shaped ZnO nanosheets allowing large-scale production to be employed. 

  • 35.
    Zhang, Renyun
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Hummelgård, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Carbon nanocages grown by gold templating2010In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 48, no 2, p. 424-430Article in journal (Refereed)
    Abstract [en]

    A method for growing carbon cages using gold nanoparticles as templates is reported. Gold nanoparticles were deposited on carbon nanotubes (CNTs). The nanocages were grown on the gold particles by electrical Joule heating of the CNT. The gold was subsequently evaporated, leaving the cages intact. A special in-situ TEM-holder equipped with a small scanning tunneling microscope was used as an electrical probe to drive current through the CNT, while the TEM was used for imaging of the entire growth process. The method might provide a general way for making carbon structures limited only by the shapes allowed by the fabrication methods of the gold nanostructures.

  • 36.
    Zhang, Renyun
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Hummelgård, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Carbon nanocages templated by gold nanostructures2010In: Vacuum Electron Sources Conference and Nanocarbon (IVESC), 2010 8th International, IEEE conference proceedings, 2010, p. 469-469Conference paper (Refereed)
    Abstract [en]

    Summary form only given. Hollow nanocages are useful in many applications including catalyst support, batteries and drug delivery. Several systems have been pursued to produce nanocages, but for carbon, studied cages are mainly smaller ones, like fullerenes. Attempts to make larger carbon nanocages are more limited, resulting in foam-like structures with relatively thick walls or by methods that do not easily get controllable sizes. For applications of nanocages there are needs for methods that allow carbon cages to be fabricated with determined size and shape. Here, we report on a new method to grow large carbon cages, using gold nanoparticles on carbon nanotubes as templates (Figure 1). The experiments were done inside a TEM using a special in-situ holder, called TEMSTM, with movable electrical probes, allowing a detailed observation and control of the entire process. The cages were grown on the nanoparticles under electrical Joule heating and the gold were subsequently evaporated, leaving the cages intact. The templating gold nanoparticles could be made in different sizes allowing size adjustments of the resulting carbon nanocages. The obtained cages may have wide applications including drug delivery and hydrogen storage.

  • 37.
    Zhang, Renyun
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Hummelgård, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Graphite-carbon nanotube flexible electrodes for dye-sensitized solar cells2014Conference paper (Refereed)
    Abstract [en]

    Dye-sensitized solar cell (DSSC) is a low cost and efficient way to transform solar radiation to electricity. Indium tin oxide (ITO) and fluorine doped tin oxide (FTO) coated glass are two kinds of transparent electrodes that are mostly used to fabricate DSSCs. However, these two kinds electrodes lack flexibility, limiting their development. [1] Flexible electrodes are desired in DSSC because of they are lightweight, low cost and ro田l-to-roll compatible. There are attempts to replace both [1] or one [2] of the two electrodes in DSSC. However, the efficiencies are relatively low. Here we reported a simple method to fabricate graphite-carbon nanotube (G-CNT) composited flexible electrode for using as counter electrode in DSSC. The electrodes are simple fabricated by reverse filtration and flash sintering, leading to highly flexible (360 °C) and conductive (sheet resistance, 100 Ohm/sq) electrodes that can be used as both catalyzer and current collector. The energy conversion efficiency of such electrode based DSSC can reach 2.02% with fill factor of 0.56 (Figure 1).

     

    Figure 1. Photograph of the G-CNT composited flexible electrode, and the J-V characterization of the fabricated DSSC.

     

     

    References:

     

    [1]    W. Wang, Q. Zhang, H. Li, G. W. Wu, D. C. Zou, D. P. Yu, Adv. Funct. Mater. 2012, 22, 2775-2782.

    [2]    B. Wang, L. L. Kerr, Sol. Energy Mater. Sol. Cells. 2011, 95, 2531-2535.

  • 38.
    Zhang, Renyun
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Hummelgård, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Large area porous gold films deposited by evaporation-induced colloidal crystal growth2009In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 340, no 1, p. 58-61Article in journal (Refereed)
    Abstract [en]

    Films that are nanostructured in two- or three-dimensions, such as porous ones, are made by several methods including templated growth and self-assembly. Here, we report on a new method that is based on evaporation-induced growth of nanoparticle gold films on a water surface. The film growth was done in a similar way to the well-known evaporation-induced colloidal crystal growth method, but in contrast, we did not directly deposit the film on a solid substrate. The films were instead created on top of a water surface. After the growth process, the films were deposited directly on substrates by a simple pick-up procedure. The deposited porous gold films were uniform with a thickness of 100 nm and had a sheet resistance of 100 Ω/sq. There are several advantages with our method, including simplicity of the protocol, large film area, flexibility in the choice of substrate to be coated, and the ability for multilayer coatings. The latter points to opportunities for fabrication of multilayer 3D porous structure, which may have wide applications in sensors and electrochemical determinations.

  • 39.
    Zhang, Renyun
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Hummelgård, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Simple and efficient gold nanoparticles deposition on carbon nanotubes with controllable particle sizes2009In: Materials Science & Engineering: B. Solid-state Materials for Advanced Technology, ISSN 0921-5107, E-ISSN 1873-4944, Vol. 158, no 1-3, p. 48-52Article in journal (Refereed)
    Abstract [en]

    There are important applications of multiwalled carbon nanotubes (MWCNT) with deposited nanoparticles and several methods exist for synthesizing these nanocomposites. However, a simpler and more efficient method is desired in many cases. Here, we introduce a method where MWCNT were pre-mixed with sodium citrate, and using ultrasonication, shells of sodium citrate were formed on the nanotubes. These functionalized MWCNTs served as substrates for gold nanoparticle growth. When HAuCl4 was added to the reaction system, Au3+ was directly reduced at the surface of the MWCNT and gold nanoparticles were assembled along the MWCNT. Transmission electron microscopy (TEM) demonstrated that the density of the gold nanoparticle coating process depended on the amount of the carbon nanotubes when the sodium citrate concentration was keep unchanged. In addition, by controlling the concentration of sodium citrate and HAuCl4, the size of gold nanoparticles could be controlled. Scanning electron microscope (SEM), energy dispersive X-ray (EDX), and UV–vis were also used to characterize the MWCNT–Au nanocomposites. Compared with other methods, the procedure described here required only water solutions and there are no needs for high temperature steps, surfactants or organic solvents, resulting in a simple and fast method for efficient gold nanoparticle decoration of carbon nanotubes.

  • 40.
    Zhang, Renyun
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Hummelgård, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Simple Fabrication of Gold Nanobelts and Patterns2012In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 7, no 1, p. Art. no. e30469-Article in journal (Refereed)
    Abstract [en]

    Gold nanobelts are of interest in several areas; however, there are only few methods available to produce these belts. We report here on a simple evaporation induced self-assembly (EISA) method to produce porous gold nanobelts with dimensions that scale across nanometer (thickness ~80 nm) and micrometer (width ~20 μm), to decimeter (length ~0.15 m). The gold nanobelts are well packed on the beaker wall and can be easily made to float on the surface of the solution for depositing onto other substrates. Microscopy showed that gold nanobelts had a different structure on the two sides of the belt; the density of gold nanowires on one side was greater than on the other side. Electrical measurements showed that these nanobelts were sensitive to compressive or tensile forces, indicating a potential use as a strain sensor. The patterned nanobelts were further used as a template to grow ZnO nanowires for potential use in applications such as piezo-electronics. © 2012 Zhang et al.

  • 41.
    Zhang, Renyun
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Hummelgård, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Simple Synthesis of Clay-Gold Nanocomposites with Tunable Color2010In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 26, no 8, p. 5823-5828Article in journal (Refereed)
    Abstract [en]

    Clay-based nanocomposites have been studied for several decades, mainly focusing on clay-polymer nanocomposites. Here, we report on a simple wet chemical method to synthesize clay-APTES-Au (CAAu) nanocomposites, where 3-aminopropyltriethoxysilane (APTES) acts as the linkage. The silane terminal of APTES formed bonds with the clay surface, while the other -NH(2) terminal bonds to gold nanoparticles. The color of clay changed when these CAAu nanocomposites were formed. By changing the size of the gold nanoparticles, the color of CAAu could be adjusted, simply by changing process parameters. TEM characterization of the synthesized nanocomposites showed an even distribution of gold nanoparticles on the clay surfaces. The nanocomposites were stable in strong acid and high concentration of salt conditions, while strong basic solution like NaOH could slightly influence the status of the gold nanoparticles due to the rupture of the Si-O-Si bonds between APTES and clay. To demonstrate the potential for label free sensing application of CAAu nanocomposites, we made hybrids of clay-APTES-Au-HD-Au (CAAuHAu), where hexamethylene diamine (HD) served as links between CAAu nanocomposites and the gold nanoparticles. The color of the composites changed from red to blue, when the hybrids were formed. Moreover, hemoglobin was loaded on the CAAu nanocomposites, which can potentially be used as a biosensor. These synthesized nanocomposites may combine the catalytic properties of clay and the well-known excellent properties of gold nanoparticles, such as the ability to anchor biological and chemical molecules. Furthermore, the color change of CAAu, when the CAAuHAu hybrids were observed, suggests the applications of these nanocomposites in biochemical and chemical sensing.

  • 42.
    Zhang, Renyun
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Hummelgård, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Single layer porous gold films grown at different temperatures2010In: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 405, no 21, p. 4517-4522Article in journal (Refereed)
    Abstract [en]

    Large area porous gold films can be used in several areas including electrochemical electrodes, as an essential component in sensors, or as a conducting material in electronics. Here, we report on evaporation induced crystal growth of large area porous gold films at 20, 40 and 60 °C. The gold films were grown on liquid surface at 20 °C, while the films were grown on the wall of beakers when temperature increased to 40 and 60 °C. The porous gold films consisted of a dense network of gold nanowires as characterized by TEM and SEM. TEM diffraction results indicated that higher temperature formed larger crystallites of gold wires. An in situ TEM imaging of the coalescence of gold nanoparticles mimicked the process of the growth of these porous films, and a plotting of the coalescence time and the neck radius showed a diffusion process. The densities of these gold films were also characterized by transmittance, and the results showed film grown at 20 °C had the highest density, while the film grown at 60 °C had the lowest consistent with SEM and TEM characterization. Electrical measurements of these gold films showed that the most conductive films were the ones grown at 40 °C. The conductivities of the gold films were related to the amount of contamination, density and the diameter of the gold nanowires in the films. In addition, a gold film/gold nanoparticle hybrid was made, which showed a 10% decrease in transmittance during hybridization, pointing to applications as chemical and biological sensors. © 2010 Elsevier B.V. All rights reserved.

  • 43.
    Zhang, Renyun
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Hummelgård, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Size and concentration controlled growth of porous gold nanofilm2012In: Physica status solidi. A, Applied research, ISSN 0031-8965, E-ISSN 1521-396X, Vol. 209, no 3, p. 519-523Article in journal (Refereed)
    Abstract [en]

    At an air/water interface, diffusion-limited aggregation (DLA) of gold nanoparticles can form porous gold thin films. This porous film roughly consists of a network of irregular nanowires. For this air–water system, external parameters like temperature are well studied, while the influence of internal parameters, e.g., the size and concentration of the nanoparticles, have not been studied in detail. Here, we report on the growth of porous gold nanofilms for different nanoparticle sizes and concentrations to get a relationship between the morphology of the films and the internal parameters. The gold nanoparticles were synthesized by reducing HAuCl4 using sodium citrate. Transmission electron microscopy (TEM) characterization

    showed a linear relation between the formed gold nanowires and the concentration of HAuCl4 if the concentration of sodium citrate is unchanged. A linear dependency was also found between the wire diameter and the gold nanoparticle concen- tration, and between the wire diameter and volume fraction of the nanoparticles. The electrical resistance of the films was measured, showing a linear relation between resistance and the inverse of the cross-sectional area of the nanowires. This study shows the relation between the morphology and resistance of the grown porous films and the controllable internal parameters that will be useful in further exploration of this thin-film growth method.

  • 44.
    Zhang, Renyun
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Hummelgård, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Olsen, Martin
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Örtegren, Jonas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Nanogenerator made of ZnO nanosheet networks2017In: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 32, no 5, article id 054002Article in journal (Refereed)
    Abstract [en]

    The piezoelectricity of nanomaterials attracts a great deal of attention due to its broad application, including the harvesting of ambient mechanical energy to power small electronics devices. We report here a simple method to fabricate piezoelectric nanogenerators consisting of networks of ZnO nanosheets grown on aluminum (Al) foils, where the Al acts as both a substrate for growth and as an electrode contacting the ZnO network. A second, top electrode was tapped, rolled, or rubbed against the ZnO to generate piezoelectricity. This second electrode was either a copper foil or fluorine doped tin oxide (FTO) glass. A piezo voltage of up to 0.924 V was detected during rolling and 6 μA was the highest current observed when rubbing the ZnO film with a FTO glass. Due to its simplicity, this nanogenerator fabrication method has the potential to be scaled up for the industrial production of piezoelectric energy harvesting devices.

  • 45.
    Zhang, Renyun
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Hummelgård, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Örtegren, Jonas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Olsen, Martin
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Andersson, Henrik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Interaction of the human body with triboelectric nanogenerators2019In: Nano Energy, ISSN 2211-2855, E-ISSN 2211-3282, Vol. 57, p. 279-292Article in journal (Refereed)
    Abstract [en]

    The use of triboelectric nanogenerators (TENGs) is a new technique for energy harvesting at both small and large scales. Almost all types of mechanical energy can be harvested with TENGs by using four modes of operation that cover almost all mechanical motions. The interactions of the human body with TENGs range from energy harvesting, motion sensing, and biomedical applications to human-computer communications. Different types of TENGs have been developed to directly or indirectly involve the human body. This review will summarize the recent advances in the interaction of the human body with TENGs.

  • 46.
    Zhang, Renyun
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Hummelgård, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Örtegren, Jonas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Olsen, Martin
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Andersson, Henrik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Yang, Ya
    CAS Center for Excellence in Nanoscience, Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences, Beijing 100083, P. R. China.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Human body constituted triboelectric nanogenerators as energy harvesters, code transmitters and motion sensors2018In: ACS Applied Energy Materials, ISSN 2574-0962, Vol. 1, no 6, p. 2955-2960Article in journal (Refereed)
    Abstract [en]

    Human skin is a dielectric material that can be used as a triboelectric material for harvesting energy from body motions. The output power of such a human skin-based triboelectric nanogenerator (TENG) is relatively low. Here, we assembled high-output human body constituted TENGs (H-TENGs) by taking advantage of the unique electrical properties of the human body, such as high skin impedance, low tissue resistance, body capacitance, and conductivity. The output of a H-TENG can reach 30 W/m2, which is enough to drive small electronic devices, such as a timer or a calculator. The unique feature of the H-TENG is that it can perform the four fundamental modes of TENGs, which has not been reported elsewhere. Such a feature allows the H-TENG to act as a code transmitter to send light and electrical signals, such as Morse code. H-TENGs also benefit the development of high-performance, self-powered body motion sensors. Our findings suggest new strategies for harvesting energy from human body motions, as well as new types of motion sensors and signal senders.

  • 47.
    Zhang, Renyun
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Carbon nanomaterials as drug carriers: Real time drug release investigation2012In: Materials science & engineering. C, biomimetic materials, sensors and systems, ISSN 0928-4931, E-ISSN 1873-0191, Vol. 32, no 5, p. 1247-1252Article in journal (Refereed)
    Abstract [en]

    The use of carbon nanomaterials in biomedical applications and the cytotoxicity of these materials have been areas of great interest during the last decade. In vitro drug load and release, as well as in vivo animal tests, have been carried out using carbon nanomaterials. However, no comparison studies on the drug load and the release of different carbon nanomaterials have been reported. Here, we report on a real time investigation of the drug release of carbon black (CB) nanoparticles, carbon nanotubes (CNTs) and graphene oxide (GO), using rhodamine B (RB) as a model of drug. The binding of RB to the nanomaterials were characterized by FTIR and UV-vis. The mass loading capacities of these nanomaterials were also studied, showing that GO had the highest capacity. The real time drug release experiment indicated different accumulative release modes of these nanomaterials at different pH values, due to their different binding modes with RB, which is also discussed as being the reason for the mechanism differences. Moreover, the comparison of the drug release capacity of CNT-RB and f-CNT-RB (functionalized-CNT-RB) indicated an influence of hydrogen bonds in both drug loading and release, as the hydrogen bonds increased the loading capacity of the carbon nanotube after acid treatment and changed the drug release mechanism at pH 7.4. Thus, here we identified the drug release modes of the different carbon nanomaterials. The results of the influence of functional groups and hydrogen bonds point also out a potential way of controlling the drug release behavior of carbon nanomaterials by surface modification. © 2012 Elsevier B.V. All rights reserved.

  • 48.
    Zhang, RenYun
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Gold-carbon nanotube nanocomposites - synthesis and applications2011In: International Journal of Biomedical Nanoscience and Nanotechnology, ISSN 1756-0799, Vol. 2, no 2, p. 112-135Article, review/survey (Refereed)
    Abstract [en]

    Nanocomposites are combinations of nanomaterials with other molecules or nanoscaled materials, such as nanoparticles or nanotubes. In general, these novel nanocomposites have different physical and chemical properties from the constituent particles or wires, and will thus allow new kinds of applications. Among these nanocomposites, gold-carbon nanotube (Au-CNT) composites are of particular interests, due to their easy fabrication protocols and broad potential applications. Au-CNT nanocomposites commonly refer to gold nanoparticles deposited on carbon nanotubes. To obtain Au-CNT nanocomposites, different methods have been developed, including direct and linked deposition of gold nanoparticles on CNT. Au-CNT nanocomposites combine the excellent physical and chemical properties of both gold nanoparticles and carbon nanotubes. The easy modification surface of gold nanoparticle and the excellent conductivity of carbon nanotube as well the high surface area, point towards a broad range of applications, such as biosensing, gas sensing, and electrochemistry. This paper reviews the recent progress of different kinds of Au-CNT nanocomposites and their synthesis and applications.

  • 49.
    Zhang, Renyun
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Magnetic Nanoparticles in Biomedical Applications2011In: OMICS: Biomedical Perspectives and Applications / [ed] Debmalya Barh, Kenneth Blum, Margaret A. Madigan, CRC Press, 2011, 1Chapter in book (Refereed)
  • 50.
    Zhang, Renyun
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Porous Gold Films: A Short Review on Recent Progress2014In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 7, p. 3834-3854Article, review/survey (Refereed)
    Abstract [en]

    Porous gold films have attracted increasing interest over the last ten years due to the unique properties of high specific surface area and electrical conductivity combined with chemical stability and ability to alter the surface chemistry. Several methods have been developed to synthesize porous gold films such as de-alloying, templating, electrochemical, and self-assembling. These porous gold films are used in diverse fields, for example, as electrochemical and Raman sensors or for chemical catalysis. Here, we provide a short review on the progress of porous gold films over the past ten years, including the synthesis and applications of such films.

12 1 - 50 of 52
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