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  • 1.
    Alecrim, Viviane
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Andres, Britta
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Zhang, Renyun
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Hummelgård, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Blomquist, Nicklas
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Forsberg, Sven
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Engström, Ann-Christine
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Shimizu, Kenichi
    Umeå University.
    Andersson, Mattias
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Olin, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Exfoliation of MoS2 for paper based applications2014Konferensbidrag (Övrigt vetenskapligt)
  • 2.
    Alecrim, Viviane
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Andres, Britta
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Zhang, Renyun
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Hummelgård, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Shimizu, Kenichi
    Umeå University.
    Forsberg, Sven
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Andersson, Mattias
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Olin, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Exfoliated MoS2 for paper based supercapacitors and photodetectors2014Ingår i: Collection of Extent Abstracts, 2014, s. 437-438Konferensbidrag (Övrigt vetenskapligt)
  • 3.
    Alecrim, Viviane
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Mattias, Andersson
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Flexographic ink film’s resistance to inkjet ink’s solvent flow in Hybrid Printing2011Ingår i: International Conference on Digital Printing Technologies: Technical Programs and Proceedings / [ed] IS&T, The Society for Imaging Science and Technology, 2011, s. 79-85Konferensbidrag (Refereegranskat)
    Abstract [en]

    Through Darcy’s permeability coefficient, K, one can evaluate the resistance of a flexographic ink film to the solvent penetration of an inkjet ink through a paper substrate. This resistance plays an important role for the print quality in hybrid printing applications where flexography and inkjet printing are combined. If this resistance is too high, K→0, the inkjet ink’s solvent would not penetrate into the substrate and ink smearing would occur resulting in poor printability.

    Paper substrates were printed in a flexographic laboratory printing press. The flexographic printing dot area was varied to evaluate the influence of the full tone and halftone areas on K. These print outs were employed as filters for pigmented inkjet water based inks in a filtration setup. The inks had different pigment’s mean particle size which allowed us to address the influence of this parameter on the filter cake build up and consequently, its impact on K. The dot area had indeed an impact in the ink’s solvent penetration as we observed that the higher the dot area, the lower the K value, meaning that the resistance for ink´s solvent flow was higher. The pigment’s mean particle size also showed influence on K, as we observed that the bigger the pigment particles, the higher the K.

     The substrates were selected after a screening based on inkjet ink absorption speed evaluated through a print rub off test and line width measurements of printed lines.

    We also printed the pre-printed flexography images using a KM 512 piezoelectric printing head and one of the inks used during filtration to evaluate the inkjet printing quality for this hybrid printing approach. We observed wider, less blurry and ragged lines with increased dot area. No ink smearing was observed for the print outs.

  • 4.
    Alecrim, Viviane
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Zhang, Renyun
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Hummelgård, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Andersson, Henrik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Andersson, Mattias
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Olin, Hakan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Photoconductivity of bulk and liquid processed MoS22014Konferensbidrag (Övrigt vetenskapligt)
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  • 5.
    Alecrim, Viviane
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Zhang, Renyun
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Hummelgård, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Andres, Britta
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Dahlström, Christina
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Norgren, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Andersson, Mattias
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Olin, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Exfoliated Layered Materials for Digital Fabrication2015Ingår i: NIP & Digital Fabrication Conference, 2015, Vol. 1, s. 192-194Konferensbidrag (Refereegranskat)
    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.

  • 6.
    Ashraf, Shakeel
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Forsberg, Viviane
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap. KTH, Wallenberg Wood Science Center, Stockholm.
    Mattsson, Claes G.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Thungström, Göran
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Thermoelectric properties of n-type molybdenum disulfide (MoS2) thin film by using a simple measurement method2019Ingår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, nr 21, artikel-id 3521Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, a micrometre thin film of molybdenum disulfide (MoS2) is characterized for thermoelectric properties. The sample was prepared through mechanical exfoliation of a molybdenite crystal. The Seebeck coefficient measurement was performed by generating a temperature gradient across the sample and recording the induced electrical voltage, and for this purpose a simple measurement setup was developed. In the measurement, platinum was utilized as reference material in the electrodes. The Seebeck value of MoS2 was estimated to be approximately -600 μV/K at a temperature difference of 40 °C. The negative sign indicates that the polarity of the material is n-type. For measurement of the thermal conductivity, the sample was sandwiched between the heat source and the heat sink, and a steady-state power of 1.42Wwas provided while monitoring the temperature difference across the sample. Based on Fourier's law of conduction, the thermal conductivity of the sample was estimated to be approximately 0.26 Wm-1 K-. The electrical resistivity was estimated to be 29 W cm. The figure of merit of MoS2 was estimated to be 1.99 × 10-4. 

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  • 7.
    Forsberg, Viviane
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Liquid Exfoliation of Molybdenum Disulfide for Inkjet Printing2016Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Sedan upptäckten av grafen har mycket arbete lagts på framställning och produktion av 2D-material. En viktig uppgift har varit att ta fram skalbara metoder för produktion av högkvalitativa  nanosheets via exfoliering. Den mest lovande skalbarametoden hittills har varit vätskebaserad exfoliering av nanosheets i lösningsmedel. Tunna filmer av nanosheets i dispersion kan anpassas med hjälp av tillsatser och användas för tillverkning av halvledare strukturer med inkjet-skrivare, vilket är den mest lovande metoden för på en industriell produktions nivå beläggaden typen av material på substrat. Även om det finns välutvecklade metalliska och organiskabläck för tryckt elektronik, så finns det fortfarande ett behov av att förbättra eller utveckla nya bläck baserade på halvledarmaterial som t.ex. TMD, som är stabila, har goda bestryknings  egenskaper och ger bra tryckkvalitet. Den inerta naturen tillsammans med de mekaniska egenskaperna som finns hosskiktade material, som t.ex. molybdendisulfid (MoS2), gör demlämpliga för flexibel elektronik och bearbetning i lösning. Dessutom gör den höga elektronmobiliteten i dessa 2D-halvledaredem till en stark kandidat som halvledarmaterial inom trycktelektronik. Det betyder att MoS2 är ett enkelt och robust material med goda halvledaregenskaper som är lämpligt för bestrykning från lösning och tryck, och är miljömässigt säker.Den metod som beskrivs här kan med fördel användas föratt exfoliera alla typer av 2D-material i lösning. Exfolieringensker i två steg; först mekanisk exfoliering av torr bulk med sandpapper, därefter används ultraljudsbehandling i lösning för att exfoliera nanosheets. De dispersioner som framställts i lösning med surfaktanter dekanterades och det övre skiktetanvändes i trycktester med en Dimatix inkjet-skrivare.Tryckprovet visar att det är möjligt att använda MoS2 -dispersion som ett inkjet-bläck och att optimering för särskildaskrivar- och substratkombinationer borde göras, såsom förbättringav bläcksammansättningen med avseende på droppbildning och break-off vid skrivarmunstycket, vilket i sin tur skulleförbättra tryckkvaliteten.

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  • 8.
    Forsberg, Viviane
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Liquid-Phase Exfoliation of Two-Dimensional Materials: Applications, deposition methods and printed electronics on paper2019Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    After the unprecedented success of graphene research, other materials that can also be exfoliated into thin layers, like Transition metal dichalcogenides (TMDs) such as molybdenum disulfide (MoS2), have also become the subjects of extensive studies. As one of the most promising methods for large scale production of such materials, liquid-phase exfoliation (LPE) has also been the subject of extensive research and is maturing as a field to the point that devices using additive manufacturing and printed nanosheets are often reported. The stability of the nanosheets in environmentally friendly solvents, particularly in water, with or without stabilizers, is still a focus of great interest for sustainable and commercial production. In this thesis, different methods of LPE in water with and without stabilizers are investigated and discussed. Stabilizers such as surfactant sodium dodecyl sulfate (SDS) and modified cellulose2-hydroxyethyl cellulose (HEC), were employed. Because waterdoes not have surface energy parameters that match those of2D materials, the dispersions in water do not usually have a high yield. Therefore, to circumvent the use of organic solvents that are known to be able to successfully exfoliate and stabilize nanosheets of two-dimensional materials, this thesis focuses on water as the solution-process medium for exfoliation and the assisting stabilizers used to keep the exfoliated nanomaterials in dispersion with a long half-time. Surfactant-assisted dispersions are discussed together with test-printing resultsusing inkjet to deposit the material. Process parameters for the LPE method using HEC as a stabilizer are presented together with thin nanosheets characterized by Raman spectroscopy. Dispersions using HEC presented the longest half-time among the studied methods, higher than previously reported values for methods using mixed low-boiling-point solvents. Devices using exfoliated nanosheets have been fabricated and presented in the present study. The photoconductivity of MoS2 using a device fabricated with LPE MoS2 nanosheets and the cathodoluminescence of LPE MoS2 are discussed. Although fabricated with mechanically exfoliated nanosheets and not LPE ones, another photodetector fabricated with one of the MoS2 grades used in this thesis is presented to highlight the excellent photoresponse of this material. A method of producing thin nanosheets with-out stabilizers by pre-processing the MoS2 grades withs and papers is introduced. With this method, nanosheets with a lateral size of around 200nm and a concentration around 0.14 g L−1 - that is half the concentration at the same processing conditions in solvent n-methyl pyrrolidone (NMP) - are discussed. Inkjet printing as a deposition method is discussed together with the requirements for the 2D inks. Printed organic electronics using the conductive polymer PEDOT:PSS are compared to those using commercially-available graphene ink, with a focus on printing on paper substrates. In order to bring the thesis into perspective from materials to device fabrication, I study the suitability of inkjet paper substrates for printed electronics, by extensively characterizing the chemical and physical properties of their ink-receiving layers (IRLs) and their impact on the electronic properties of the conductive printed lines.

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    VivianeForsberg_doctoralthesis305
  • 9.
    Forsberg, Viviane
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Process parameters of liquid-phase exfoliation of MoS2 in waterstabilized with 2-hydroxyethyl celluloseManuskript (preprint) (Övrigt vetenskapligt)
  • 10.
    Forsberg, Viviane
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Andersson, Henrik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för elektronikkonstruktion.
    Engholm, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för elektronikkonstruktion.
    Thungström, Göran
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för elektronikkonstruktion.
    Zhang, Renyun
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Hummelgård, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Olin, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Norgren, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Photodetector of multilayer exfoliated MoS2 deposited on polyimide films2018Konferensbidrag (Övrigt vetenskapligt)
    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.

  • 11.
    Forsberg, Viviane
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Hummelgård, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Zhang, Renyun
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Olin, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Cellulose stabilizers for 2D materials inkjet inks2017Konferensbidrag (Refereegranskat)
    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.

  • 12.
    Forsberg, Viviane
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Maslik, Jan
    Tomas Bata University.
    Andersson, Henrik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för elektronikkonstruktion.
    Hummelgård, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Dahlström, Christina
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Toivakka, Martti
    Åbo Akademi University.
    Koppolu, Rajesh
    Åbo Akademi University.
    Olin, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Norgren, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Printability of functional inkjet inks onto commercial inkjet substrates and a taylor made pigmented coated paper2018Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Printed electronics are of increasing interest. The substrates used have primarily been plastics although the interest for cellulose-based substrates is increasing due to the environmental aspect as well as cost. The requirements of substrates for electronically active inks differs from graphical inks and therefore we have investigated a custom-made pigment based coated paper and compared it to commercial photo-papers and a coated PE film.

    Our goal with the study of different substrates was to select the most suitable substrate to print water based 2D materials inkjet inks for flexible electronics.

    The discovery of graphene, a layered material achieved from the exfoliation of graphite, has resulted in the study of other materials with similar properties to cover areas where graphene could not be used due to the absence of a bandgap in the material. For example in thin film transistors (TFT) a semiconductor layer is essential to enable turn on and off the device. This semiconductor layer can be achieved using various materials but particular interest have been dedicated to abundant and cheap 2D materials such as the transition metal dichalcogenide (TMD) molybdenum disulfide (MoS2). To date, most of the dispersions based on TMDs use organic solvents or water solutions of surfactants. Previously we focus on the study of environmental friendly inks produced by liquid phase exfoliation (LPE) of MoS2 in water using cellulose stabilizers such as ethyl cellulose (EC), cellulose nanofibrils (CNF) and nanofibrilcellulose (NFC). We have study various aspects of the ink fabrication includi  ng pH range, the source of MoS2, nanosheets thickness, particle size distribution,  ink stabilizers, ink concentration, viscosity and surface tension. These inks have very low concentration requiring a number of printing passes to cover the substrate. Therefore the substrate selection is crucial as a large amount of solvent is to be absorb by the substrate. Our goal was to use such an ink to print electrodes of MoS2 into a paper substrate after substrate selection.

    Commercial photo papers, a commercial coated PE film and a tailor made multilayer pigment coated paper substrate were used for the substrate selection analysis.  We print the substrates using a DIMATIX inkjet printer with a 10 pL printing head using the distillated water waveform supplied by the printer manufacturer. The voltage used was 23V and 4 nozzles were used for the print outs. The inkjet ink used was the organic PEDOT:PSS. We printed lines ranging from 1 pixel to 20 pixels with 1, 2 and 3 printing passes. The printing quality was evaluated through measurements of the waviness of the printed lines measured after imaging the printed samples with a SEM microscope. The line width measurement was done using the software from the SEM.

    We also evaluated the structure of the coatings using SEM and topography measurements. The ink penetration through the substrates was evaluated using Raman Spectroscopy. For the pigmented coated sample we measured 4% of ink penetration through the substrate for the 1pxl printed line printed once onto the paper.  Cross-section SEM images of the printed lines were made to visualize the ink penetration into the substrate.

    Regarding the electrical conductivity of the printed samples, the differences in resistivity varying the width of the printed lines and the number of printed passes were evaluated. The resistivity of the printed electrodes was evaluated using the 2-points probe method. Before the resistivity measurements, the printed substrates were heated at 50°C and 100°C for 30 minutes in an oven.

    We choose the PEDOT:PSS ink because it is a low price ink compared to metal nanoparticles inks for printed electronics. The print outs had low resistivity at a few printing passes with no need for sintering at high temperatures. The MoS2 ink has a very high resistance at a few printing passes due to lower coverage of the substrate therefore for this ink these measurements were not possible to be made. The main pigment composition of the paper coatings of the substrates was evaluated using FT-IR and EDX, these data plus the coating structure evaluated by SEM was related to the print quality.

    The best in test papers were used to print MoS2 electrodes. After the printing tests, another step for the optimization of the MoS2 ink properties shall be carried out in future studies for better print quality. We also evaluated the surface energy of the substrates through contact angle measurements to match the surface tension of the PEDOT:PSS ink and later the MoS2 ink. Although the pigmented coated printing substrate did not show better results than the commercial photo papers and PE foil in terms of line quality, it shows the lowest resistivity and sufficient results for low cost recyclable electronics, which do not require high conductivity. Nevertheless, the substrate was very thin and it could even be used in magazines as traditional lightweight coated papers (LWC) are used but with the additional of a printed electronic feature.

  • 13.
    Forsberg, Viviane
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap. KTH, Stockholm; Wallenberg Wood Science Centre, Stockholm.
    Mašlík, Jan
    Tomas Bata University in Zlín, Zlín, Czech Republic.
    Norgren, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för kemiteknik.
    Electronic performance of printed PEDOT:PSS lines correlated to the physical and chemical properties of coated inkjet papers2019Ingår i: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 9, nr 41, s. 23925-23938Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    PEDOT:PSS organic printed electronics chemical interactions with the ink-receiving layer (IRL) of monopolar inkjet paper substrates and coating color composition were evaluated through Raman spectroscopy mapping in Z (depth) and (XY) direction, Fourier transform infrared spectroscopy (FTIR) and energy dispersive X-ray spectroscopy (EDS). Other evaluated properties of the IRLs were pore size distribution (PSD), surface roughness, ink de-wetting, surface energy and the impact of such characteristics on the electronics performance of the printed layers. Resin-coated inkjet papers were compared to a multilayer coated paper substrate that also contained an IRL but did not contain the plastic polyethylene (PE) resin layer. This substrate showed better electronic performance (i.e., lower sheet resistance), which we attributed to the inert coating composition, higher surface roughness and higher polarity of the surface which influenced the de-wetting of the ink. The novelty is that this substrate was rougher and with somewhat lower printing quality but with better electronic performance and the advantage of not having PE in their composite structure, which favors recycling. © 2019 The Royal Society of Chemistry.

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  • 14.
    Forsberg, Viviane
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Norgren, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Green materials for inkjet printing of 2D materials and transparent electronics2018Konferensbidrag (Övrig (populärvetenskap, debatt, mm))
  • 15.
    Forsberg, Viviane
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Zhang, Renyun
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Andersson, Henrik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för elektronikkonstruktion.
    Bäckström, Joakim
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Dahlström, Christina
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Norgren, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Andres, Britta
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Olin, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Liquid Exfoliation of Layered Materials in Water for Inkjet Printing2016Ingår i: Printing for Fabrication 2016: Materials, Applications, and Processes, USA: Curran Associates, Inc., 2016Konferensbidrag (Refereegranskat)
    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.

  • 16.
    Forsberg, Viviane
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Zhang, Renyun
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Andersson, Henrik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för elektronikkonstruktion.
    Bäckström, Joakim
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Dahlström, Christina
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Norgren, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Andres, Britta
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Olin, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Liquid Exfoliation of Layered Materials in Water for Inkjet Printing2016Ingår i: Journal of Imaging Science and Technology, ISSN 1062-3701, E-ISSN 1943-3522, Vol. 60, nr 4, s. 1-7, artikel-id 040405Artikel i tidskrift (Refereegranskat)
    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.

  • 17.
    Forsberg, Viviane
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Zhang, Renyun
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Hummelgård, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Olin, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    The Influence of pH on the Stability of Inks of Two-Dimensional Materials for Digital Fabrication2017Konferensbidrag (Refereegranskat)
    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.

  • 18.
    Forsberg, Viviane
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Zhang, Renyun
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Hummelgård, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Olin, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Towards flexible and cheap printed electronics using inks of exfoliated 2D materials stabilized by cellulose2017Konferensbidrag (Övrigt vetenskapligt)
    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.

  • 19.
    Forsberg, Viviane
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Zhang, Renyun
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Hummelgård, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Olin, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Towards stable 2D materials inkjet inks: a study of stabilizers and MoS2 grades2017Konferensbidrag (Refereegranskat)
  • 20.
    Forsberg, Viviane
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Zhang, Renyun
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Joakim, Bäckström
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Dahlström, Christina
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Andres, Britta
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Norgren, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Andersson, Mattias
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Hummelgård, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Olin, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Exfoliated MoS2 in Water without Additives2016Ingår i: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 11, nr 4, artikel-id 0154522Artikel i tidskrift (Refereegranskat)
    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.

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  • 21. Marianne, Klaman
    et al.
    Erik, Blohm
    Per-Åke, Johansson
    Jon, Lofthus
    Viviane, Alecrim
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Jonas, Örtegren
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Hybrid printing - print quality mechanisms when offset and inkjet are combined2011Ingår i: Advances in Printing and Media Technology, Vol. XXXVIII / [ed] IARIGAI, International Association of Research Organizations for the Information, Media and Graphic Arts Industrie (IARIGAI), 2011Konferensbidrag (Refereegranskat)
  • 22.
    Maslik, Jan
    et al.
    Tomas Bata University in Zlin, Czech Republic.
    Andersson, Henrik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för elektronikkonstruktion.
    Forsberg, Viviane
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Engholm, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för elektronikkonstruktion.
    Zhang, Renyun
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Olin, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    PEDOT:PSS temperature sensor ink-jet printed on paper substrate2018Ingår i: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 13, artikel-id C12010Artikel, forskningsöversikt (Refereegranskat)
    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= -0.030 relative to room temperature (22°C) was measured, which is higher than compared to for exampleSilicon α = -0.075.

  • 23.
    Mazlik, Jan
    et al.
    Tomas Bata University.
    Andersson, Henrik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för elektronikkonstruktion.
    Forsberg, Viviane
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Engholm, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för elektronikkonstruktion.
    Zhang, Renyun
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Olin, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Temperature sensor based on PEDOT: PSS ink-jet printed on paper substrate2018Konferensbidrag (Refereegranskat)
    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

  • 24.
    Niga, Petru
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    Örtegren, Jonas
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    Alecrim, Viviane
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    Klaman, Marianne
    Innventia AB, Stockholm, Sweden.
    Blohm, Erik
    Innventia AB, Stockholm, Sweden.
    Lofthus, Jon
    Innventia AB, Stockholm, Sweden.
    Hybrid printing: paper media for combined flexographic and inkjet printing2012Ingår i: Conference proceedings International Paper Physics Conference, Stockholm: Innventia , 2012, s. 79-81Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Hybrid printing combining inkjet technology with flexography can be used to add customer specific information into the production of packaging and print. However, in order to improve print quality, a comprehensive understanding of the mechanisms governing print quality is required. In this work, inkjet printing using three aqueous inkjet inks was performed on top of flexographic printouts on four paper substrates. For comparative reasons, inkjet printouts were made on the four papers as well. The flexographic film contained tone values ranging from 0 to 100% ink coverage. Line width and print density of the inkjet printouts were evaluated. It was found that paper characteristics such as surface energy, porosity, absorption coefficient and surface roughness play an important role in defining the final print quality. These findings are further supported by micrograph images.

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  • 25.
    Niskanen, Ilpo
    et al.
    University of Oulu, Oulu, Finland.
    Forsberg, Viviane
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap. KTH, Stockholm.
    Zakrisson, Daniel
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Engberg, Birgitta A.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för kemiteknik.
    Heikkilä, Rauno
    University of Oulu, Oulu, Finland.
    Thungström, Göran
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Determination of relative solids concentration in homogeneous dual component pulp-filler suspension by multi-spectrophotometer2020Ingår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 35, nr 1, s. 71-77Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The concentration of fibers and fillers in the pulp suspension is an important parameter in the monitoring process. This paper proposes a versatile optical measurement system to estimate the concentration of a solids mixture in water. The geometry used in a multi-spectrophotometer (MSM) enables the controlled observation of transmission, and forward scattering light from the suspension in the UV-visible spectral range. We have developed the new fibers mixing system which gives a homogenous distribution of the fines and fillers making it possible to increase the reproducibility and accuracy of the measurement. The data analysis is based on the Beer-Lambert law and CIELAB color space equations. The results show that the proposed method is accurate for measuring the fines and filler concentrations in multicomponent suspensions. 

  • 26.
    Niskanen, Ilpo
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion. University of Oulu, Oulu, Finland.
    Forsberg, Viviane
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap. KTH.
    Zakrisson, Daniel
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Reza, Salim
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Hummelgård, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Andres, Britta
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Fedorov, Igor
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Suopajärvi, Terhi
    University of Oulu, Oulu, Finland.
    Liimatainen, Henrikki
    University of Oulu, Oulu, Finland.
    Thungström, Göran
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Determination of nanoparticle size using Rayleigh approximation and Mie theory2019Ingår i: Chemical Engineering Science, ISSN 0009-2509, E-ISSN 1873-4405, Vol. 201, nr 29, s. 222-229Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Accurate determination of the size of nanoparticles has an important role in many different scientific and industrial purposes, such as in material, medical and environment sciences, colloidal chemistry and astrophysics. We describe an effective optical method to determine the size of nanoparticles by analysis of transmission and scattering of visible spectral range data from a designed UV-Vis multi-spectrophotometer. The size of the nanoparticles was calculated from the extinction cross section of the particles using Rayleigh approximation and Mie theory. We validated the method using polystyrene nanospheres, cellulose nanofibrils, and cellulose nanocrystals. A good agreement was achieved through graphical analysis between measured extinction cross section values and theoretical Rayleigh approximation and Mie theory predictions for the sizes of polystyrene nanospheres at wavelength range 450 - 750 nm. Provided that Rayleigh approximation's forward scattering (FS)/back scattering (BS) ratio was smaller than 1.3 and Mie theory's FS/BS ratio was smaller than 1.8. A good fit for the hydrodynamic diameter of nanocellulose was achieved using the Mie theory and Rayleigh approximation. However, due to the high aspect ratio of nanocellulose, the obtained results do not directly reflect the actual cross-sectional diameters of the nanocellulose. Overall, the method is a fast, relatively easy, and simple technique to determine the size of a particle by a spectrophotometer. Consequently, the method can be utilized for example in production and quality control purposes as well as for research and development applications.

  • 27.
    Zhang, Renyun
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Alecrim, Viviane
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Hummelgård, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Andres, Britta
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Forsberg, Sven
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Andersson, Mattias
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Olin, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Thermally reduced kaolin-graphene oxide nanocomposites for gas sensing2015Ingår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 5, s. Art. no. 7676-Artikel i tidskrift (Refereegranskat)
    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.

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  • 28.
    Zhang, Renyun
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Hummelgård, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Forsberg, Viviane
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Andersson, Henrik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för elektronikkonstruktion.
    Engholm, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för elektronikkonstruktion.
    Öhlund, Thomas
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Olsen, Martin
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Örtegren, Jonas
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Olin, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Photoconductivity of acid exfoliated and flash-light-processed MoS2 films2018Ingår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, artikel-id 3296Artikel i tidskrift (Refereegranskat)
    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.

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