Graphene oxide (GO) films have a great potential for aerospace, electronics, and renewable energy applications due to their low cost and unique properties. For structural applications, they can achieve an exceptional combination of damping and stiffness. This study investigates the effect of packing density, reduction, and water removal on stiffness and damping of graphene oxide films. GO sheets dispersed in water are passed through a filter and deposited on a removable substrate. Through variations of the film fabrication process, films of both GO and reduced GO (rGO) are produced with varying levels of packing. Heat treatment is also used to remove the water in half of the films. The degree of packing is assessed through film density calculations. Microscopy as well as Raman and X-ray spectroscopy are used to measure the degree of packing while Dynamic Mechanical Analysis (DMA) is used to quantity mechanical damping and storage modulus of specimens in tension. Correlating mechanical properties to structure of films revealed new understanding of damping and stress transfer mechanisms in these materials. Optimal structures resulted in superior combinations of stiffness (18 GPa) and damping (0.14), potentially paving the way for using GO based films in advanced structural applications.
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Electrically Conductive, Reduced Graphene Oxide Structures Fabricated by Inkjet Printing and Low Temperature Plasma Reduction
Here, an environmentally‐friendly and scalable process is reported to synthesize reduced graphene oxide (RGO) thin films for printed electronics applications. The films are produced by inkjet printing GO flakes dispersed binder‐free in aqueous solutions followed by treatment with a nonthermal, radio‐frequency (RF) plasma containing only argon (Ar) gas. The plasma process is found to heat the substrate to temperatures no greater than 138 °C, enabling RGO to be printed directly on a wide range of temperature‐sensitive substrate materials including photo paper. Unlike other low‐temperature methods such as electrochemical reduction, plasma reduction is friendly to moisture absorbent materials. Moreover, the plasma treatment can be performed on nonconducting substrates, eliminating the need for film transfer. From an applications perspective, the printed, plasma‐reduced RGO exhibits excellent electrical, mechanical, and electrochemical properties. As a technology demonstrator, the working electrodes of hydrogen peroxide (H2O2) sensors fabricated from plasma‐reduced GO show a sensitivity of 277 ± 80 µA m
- NSF-PAR ID:
- 10459705
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Materials Technologies
- Volume:
- 4
- Issue:
- 12
- ISSN:
- 2365-709X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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The effect of functionalization of laser induced graphene (LIG) by electrodeposition and solution-based deposition of TMDs (molybdenum disulfide2and tungsten disulfide) and metal nanoparticles is studied. For different processing methods, electrochemical characteristics (such as electrochemically active surface area: ECSA and heterogenous electron transfer rate: k0) are extracted and correlated to surface chemistry and defect density obtained respectively using X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. These functionalization methods are observed to directly impact the sensitivity and limit of detection (LOD) of the graphene sensors for the studied neurotransmitters. For example, as compared to bare LIG, it is observed that electrodeposition of MoS2on LIG improves ECSA by 3 times and k0by 1.5 times.3Electrodeposition of MoS2also significantly reduces LOD of serotonin and dopamine in saliva, enabling detection of their physiologically relevant concentrations (in pM-nM range). In addition, chemical treatment of LIG sensors is carried out in the form of acetic acid treatment. Acetic acid treatment has been shown previously to improve C-C bonds improving the conductivity of LIG sensors.4In our work, in particular, acetic acid treatment leads to larger improvement of LOD of norepinephrine compared to MoS2electrodeposition.
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Future work includes expanding the plasma chemistry and conditions, studying the effect of precursor mixture in laser-induced solution-based functionalization, and understanding the interplay between molecule-material system. Work is also underway to improve the machine learning model by using nonlinear learning models such as neural networks to improve the sensor sensitivity, selectivity, and robustness.
References A. J. Steckl, P. Ray, (2018), doi:10.1021/acssensors.8b00726.
Y. Lei, D. Butler, M. C. Lucking, F. Zhang, T. Xia, K. Fujisawa, T. Granzier-Nakajima, R. Cruz-Silva, M. Endo, H. Terrones, M. Terrones, A. Ebrahimi,
Sci. Adv. 6 , 4250–4257 (2020).V. Kammarchedu, D. Butler, A. Ebrahimi,
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Adv. Mater. 31 , 1–12 (2019). -
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Abstract Thermoelectric generators are an environmentally friendly and reliable solid‐state energy conversion technology. Flexible and low‐cost thermoelectric generators are especially suited to power flexible electronics and sensors using body heat or other ambient heat sources. Bismuth telluride (Bi2Te3) based thermoelectric materials exhibit their best performance near room temperature making them an ideal candidate to power wearable electronics and sensors using body heat. In this report, Bi2Te3thin films are deposited on a flexible polyimide substrate using low‐cost and scalable manufacturing methods. The synthesized Bi2Te3nanocrystals have a thickness of 35 ± 15 nm and a lateral dimension of 692 ± 186 nm. Thin films fabricated from these nanocrystals exhibit a peak power factor of 0.35 mW m−1·K−2at 433 K, which is among the highest reported values for flexible thermoelectric films. In order to evaluate the flexibility of the thin films, static and dynamic bending tests are performed while monitoring the change in electrical resistivity. After 1000 bending cycles over a 50 mm radius of curvature, the change in electrical resistance of the film is 23%. Using Bi2Te3solutions, the ability to print thermoelectric thin films with an aerosol jet printer is demonstrated, highlighting the potential of additive manufacturing techniques for fabricating flexible thermoelectric generators.
