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Forsberg, Viviane
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Publications (10 of 23) Show all publications
Niskanen, I., Forsberg, V., Zakrisson, D., Reza, S., Hummelgård, M., Andres, B., . . . Thungström, G. (2019). Determination of nanoparticle size using Rayleigh approximation and Mie theory. Chemical Engineering Science, 201(29), 222-229
Open this publication in new window or tab >>Determination of nanoparticle size using Rayleigh approximation and Mie theory
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2019 (English)In: Chemical Engineering Science, ISSN 0009-2509, E-ISSN 1873-4405, Vol. 201, no 29, p. 222-229Article in journal (Refereed) Published
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.

Keywords
Nanoparticles, size, Rayleigh approximation, Mie theory, spectrophotometer, nanocellulose
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-35764 (URN)10.1016/j.ces.2019.02.020 (DOI)000462034900020 ()2-s2.0-85062846560 (Scopus ID)
Available from: 2019-03-08 Created: 2019-03-08 Last updated: 2019-05-20Bibliographically approved
Forsberg, V. & Norgren, M. (2018). Green materials for inkjet printing of 2D materials and transparent electronics. In: : . Paper presented at 10th Anniversary Symposium on Liquid Phase Exfoliation, Irland, August 2, 2018.
Open this publication in new window or tab >>Green materials for inkjet printing of 2D materials and transparent electronics
2018 (English)Conference paper, Poster (with or without abstract) (Other (popular science, discussion, etc.))
National Category
Materials Chemistry Paper, Pulp and Fiber Technology Polymer Technologies
Identifiers
urn:nbn:se:miun:diva-34234 (URN)
Conference
10th Anniversary Symposium on Liquid Phase Exfoliation, Irland, August 2, 2018
Projects
KM2 Sol
Funder
Knowledge Foundation
Available from: 2018-08-13 Created: 2018-08-13 Last updated: 2018-08-16Bibliographically approved
Maslik, J., Andersson, H., Forsberg, V., Engholm, M., Zhang, R. & Olin, H. (2018). PEDOT:PSS temperature sensor ink-jet printed on paper substrate. Journal of Instrumentation, 13, Article ID C12010.
Open this publication in new window or tab >>PEDOT:PSS temperature sensor ink-jet printed on paper substrate
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2018 (English)In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 13, article id C12010Article, review/survey (Refereed) Published
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.

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2018
Keywords
Detector design and construction technologies and materials; Manufacturing
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-35891 (URN)10.1088/1748-0221/13/12/C12010 (DOI)000452801600005 ()
Projects
LEAP
Available from: 2019-03-28 Created: 2019-03-28 Last updated: 2019-04-05Bibliographically approved
Zhang, R., Hummelgård, M., Forsberg, V., Andersson, H., Engholm, M., Öhlund, T., . . . Olin, H. (2018). Photoconductivity of acid exfoliated and flash-light-processed MoS2 films. Scientific Reports, 8, Article ID 3296.
Open this publication in new window or tab >>Photoconductivity of acid exfoliated and flash-light-processed MoS2 films
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2018 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, article id 3296Article in journal (Refereed) Published
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.

National Category
Physical Sciences
Identifiers
urn:nbn:se:miun:diva-33302 (URN)10.1038/s41598-018-21688-0 (DOI)000425380900079 ()29459668 (PubMedID)2-s2.0-85061713034 (Scopus ID)
Available from: 2018-03-19 Created: 2018-03-19 Last updated: 2019-03-20Bibliographically approved
Forsberg, V., Andersson, H., Engholm, M., Thungström, G., Zhang, R., Hummelgård, M., . . . Norgren, M. (2018). Photodetector of multilayer exfoliated MoS2 deposited on polyimide films. In: : . Paper presented at 20th International Workshop on Radiation Imaging Detectors, Sundsvall, 24-28 June, 2018.
Open this publication in new window or tab >>Photodetector of multilayer exfoliated MoS2 deposited on polyimide films
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2018 (English)Conference paper, Poster (with or without abstract) (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.

Keywords
Photodetector, MoS2
National Category
Chemical Engineering Materials Engineering Physical Sciences
Identifiers
urn:nbn:se:miun:diva-34035 (URN)
Conference
20th International Workshop on Radiation Imaging Detectors, Sundsvall, 24-28 June, 2018
Funder
Knowledge Foundation, 2600364
Available from: 2018-06-29 Created: 2018-06-29 Last updated: 2018-08-16Bibliographically approved
Forsberg, V., Maslik, J., Andersson, H., Hummelgård, M., Dahlström, C., Toivakka, M., . . . Norgren, M. (2018). Printability of functional inkjet inks onto commercial inkjet substrates and a taylor made pigmented coated paper. In: : . Paper presented at E-MRS, European Materials Research Society Spring Meeting 2018, Strasbourg, France, June 18-22, 2018. Strasbourg
Open this publication in new window or tab >>Printability of functional inkjet inks onto commercial inkjet substrates and a taylor made pigmented coated paper
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2018 (English)Conference paper, Poster (with or without abstract) (Other academic)
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.

Place, publisher, year, edition, pages
Strasbourg: , 2018
Keywords
Z-depth Raman penetration, substrates printed electronics, 2D materials, transparent electronics
National Category
Physical Sciences Chemical Sciences Materials Engineering Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-34034 (URN)
Conference
E-MRS, European Materials Research Society Spring Meeting 2018, Strasbourg, France, June 18-22, 2018
Funder
Knowledge Foundation, 2600364
Note

Proceedings will be published on the Elsevier Journal Thin Solid Films. 

Available from: 2018-06-29 Created: 2018-06-29 Last updated: 2019-01-16Bibliographically approved
Mazlik, J., Andersson, H., Forsberg, V., Engholm, M., Zhang, R. & Olin, H. (2018). Temperature sensor based on PEDOT: PSS ink-jet printed on paper substrate. In: : . Paper presented at 20th International Workshop on Radiation Imaging Detectors, Sundsvall, 24-28 June, 2018.
Open this publication in new window or tab >>Temperature sensor based on PEDOT: PSS ink-jet printed on paper substrate
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2018 (English)Conference paper, Poster (with or without abstract) (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

Keywords
Temperature sensor; PEDOT:PSS
National Category
Materials Engineering Physical Sciences
Identifiers
urn:nbn:se:miun:diva-34037 (URN)
Conference
20th International Workshop on Radiation Imaging Detectors, Sundsvall, 24-28 June, 2018
Available from: 2018-06-29 Created: 2018-06-29 Last updated: 2018-08-17Bibliographically approved
Forsberg, V., Hummelgård, M., Zhang, R. & Olin, H. (2017). Cellulose stabilizers for 2D materials inkjet inks. In: : . Paper presented at 5th Nano today Conference, December 6-10, 2017, Waikoloa Beach Marriott, Hawaii, USA. Elsevier
Open this publication in new window or tab >>Cellulose stabilizers for 2D materials inkjet inks
2017 (English)Conference paper, Poster (with or without abstract) (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.

Place, publisher, year, edition, pages
Elsevier, 2017
Keywords
Cellulose stabilizers, Layered Materials Inks, 2D materials inks, MoS2, thin films
National Category
Materials Chemistry Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:miun:diva-31649 (URN)
Conference
5th Nano today Conference, December 6-10, 2017, Waikoloa Beach Marriott, Hawaii, USA
Projects
KM2
Funder
Knowledge Foundation
Available from: 2017-09-21 Created: 2017-09-21 Last updated: 2017-09-21Bibliographically approved
Forsberg, V., Zhang, R., Hummelgård, M. & Olin, H. (2017). The Influence of pH on the Stability of Inks of Two-Dimensional Materials for Digital Fabrication. In: : . Paper presented at Printing for Fabrication 2017. Materials, Applications, and Processes. The 33rd International Conference on Digital Printing Technologies (NIP), November 5-9, 2017, Denver, USA (pp. 29-31). USA: The Society for Imaging Science and Technology
Open this publication in new window or tab >>The Influence of pH on the Stability of Inks of Two-Dimensional Materials for Digital Fabrication
2017 (English)Conference paper, Published 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.

Place, publisher, year, edition, pages
USA: The Society for Imaging Science and Technology, 2017
Keywords
Acid Exfoliation, Acetic Acid, MoS2, 2D Ink, Flexible Electronics, Shear Exfoliation, pH
National Category
Materials Chemistry
Identifiers
urn:nbn:se:miun:diva-31650 (URN)2-s2.0-85042372014 (Scopus ID)
Conference
Printing for Fabrication 2017. Materials, Applications, and Processes. The 33rd International Conference on Digital Printing Technologies (NIP), November 5-9, 2017, Denver, USA
Projects
KM2
Funder
Knowledge Foundation
Available from: 2017-09-21 Created: 2017-09-21 Last updated: 2018-03-14Bibliographically approved
Forsberg, V., Zhang, R., Hummelgård, M. & Olin, H. (2017). Towards flexible and cheap printed electronics using inks of exfoliated 2D materials stabilized by cellulose. In: : . Paper presented at MWP Symposium “Treenomics – From Genomic Information to Business Opportunities”. Stockholm
Open this publication in new window or tab >>Towards flexible and cheap printed electronics using inks of exfoliated 2D materials stabilized by cellulose
2017 (English)Conference paper, Poster (with or without abstract) (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.

Place, publisher, year, edition, pages
Stockholm: , 2017
Keywords
Cellulose stabilizers, 2D ink, 2D materials, Flexible electronics, Cheap transistors
National Category
Materials Chemistry Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:miun:diva-31647 (URN)
Conference
MWP Symposium “Treenomics – From Genomic Information to Business Opportunities”
Projects
KM2
Funder
Knowledge Foundation
Available from: 2017-09-21 Created: 2017-09-21 Last updated: 2017-09-21Bibliographically approved
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