Browsing by Subject "PEDOT:PSS"
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Item 3D-Inkjet Printing of Flexible and Stretchable Electronics(University of Texas at Austin, 2015) Vaithilingam, J.; Saleh, E.; Tuck, C.; Wildman, R.; Ashcroft, I.; Hague, R.; Dickens, P.Inkjet printing of conductive tracks on flexible and stretchable materials have gained considerable interest in recent years. Conductive inks including inks with silver nanoparticles, carbon based inks, inks containing poly (3,4-ethylenedioxythiophene) (PEDOT) doped with polystyrene sulfonic acid (PSS) are being researched widely to obtain a printed electronic patterns. In this study, we present drop-on-demand inkjet printing of conductive silver and PEDOT:PSS on a flexible and stretchable substrate. Process conditions for the inkjet printing of silver nano-particles and PEDOT:PSS were optimised and simple geometrical patterns (straight line and sinewave tracks) were printed. Surface profile, surface morphology and electrical resistance of the printed patterns were examined. The printed silver patterns were observed to be highly conductive; however when stretched, the patterns did not conduct due to the origination of cracks. The measured conductivity for the PEDOT:PSS patterns was significantly lower than the silver patterns; however, they remained conductive when stretched for up to 3 mm. When flexed, PEDOT:PSS remained conductive for a lower radius of curvature (10 mm) than the silver. Among the printed patterns, the sinewave pattern was observed to be superior for flexible electronics application.Item Conductive nickel nanostrand-reinforced polymer nanocomposites(2013-05) Lu, Chunhong; Krifa, MouradConductive and flexible nanocomposites can have wide applications in textiles, including wearable sensors, antenna, electrodes, etc. The objective of this research is to develop electrically conductive fibers and films that are flexible and deformable for use in textile structures able to accommodate the drape and movement of the human body. To achieve this objective, we evaluate the electrical properties of PEDOT:PSS/nickel nanostrand as well as nylon 6/nickel nanostrand nanocomposites. Nickel nanostrands (NiNS) were first used to reinforce an intrinsically conductive polymer, Poly(3,4-ethylenedioxythiophene) (PEDOT:PSS), in order to fabricate nanocomposite films with high electrical conductivity. The electrical properties of the films were evaluated by the Van der Pauw method. The addition of 10 wt% nanostrands in PDOT:PSS provided a two order of magnitude improvement in electrical conductivity. In addition to PDOT:PSS, nylon 6/NiNS nanocomposite fibers were produced using electrospinning and exhibited diameters in the sub-micron range. The NiNS-reinforced fibers had electrical conductivity that exceeded the ESD range, which offers the potential for use in protective textile applications.Item Structural and chemical characterization of responsive nanocrystalline materials(2021-01-21) Reimnitz, Lauren Christine; Milliron, Delia, (Delia Jane); Goodenough, John B.; Henkelman, Graeme A.; Hwang, Gyeong S.; Korgel, Brian A.Nanocrystalline materials have interesting applications in many technological arenas, including catalysis, smart windows, and sensing. These crystals, with characteristic dimensions on the order of hundreds of nanometers or less, offer some key advantages over other materials for approaching these technologies. For heterogeneous catalysis, this small characteristic dimension translates to a very high surface-area-to-volume ratio. This extremely high specific surface area offers more chemically active sites than the same mass of material in a bulk form. Nanocrystals (NCs) can also exhibit unique chemical and physical properties in their very small form. For example, NCs of metallic materials can exhibit localized surface plasmon resonance (LSPR), a physical phenomenon not seen for bulk metals, that can make the material more useful for chemical sensing and electronic applications. Because they can be synthesized and processed using colloidal methods, NCs have also been investigated and employed as smart window materials, where solution-based processing keeps the cost of manufacturing window coatings much less expensive than the alternative low-pressure, high-temperature methods. During my PhD, I have had the privilege of working on many classes of nanocrystalline materials, with a broad variety of potential applications. In chapter 1 of this dissertation I describe my work synthesizing vanadium sesquioxide (V2O3) NCs doped with transition metal ions. These NCs reversibly absorb oxygen, with a remarkably low oxygen uptake onset temperature, which we propose for use in solving the cold start problem in automotive catalysis. Dopants added to the NC increase the initial oxygen storage capacity of the material, and have a substantial effect on the degradation of the material over ten oxidation and reduction cycles. In chapter 2, I discuss my collaboration with researchers from Brian Korgel's group. In one such collaboration, the reversible thermochromic phase transition of nickel iodide specific to thin films is explored. This thermochromism is found to be deliquescent, meaning it depends on the availability of humid air. These two properties give the material potential applications in both smart windows, where the phase transition causes a controllable color change on a window surface, and in humidity sensing, where the color change would indicate the presence of air with a relative humidity surpassing the critical point of the material. Using the same in situ heating techniques, the irreversible phase transition of perovskite cesium lead iodide (CsPbI3) NCs from the metastable black CsPbI3 phase to the yellow delta-orthorhombic phase is found to occur upon heating the NC films. This transition is destructive to the material, since the metastable gamma-phase has excellent electronic structure for photovoltaic applications, while the thermodynamic delta-orthorhomic phase is inactive. We found that this irreversible transition depended weakly on the humidity, but also proceeded when heated in dry nitrogen environments. In chapter 3, the design of a transparent conductive composite material is described. The goal material will be designed and engineered to be applied to the outside surface of aircraft windshields, where the conductive overlayer can shuttle charge built up by friction with ice and dust within the atmosphere to the aircraft body. This will prevent the build up of static charge on the windshield, which can interfere with electronics onboard the aircraft and even cause dielectric fracture of the windshield in severe cases. By incorporating cerium-doped indium oxide NCs and the conducting polymer PEDOT:PSS into an insulating, mechanically robust polymer matrix, we intend to create a thick material with high enough conductivity to be suitable for this anti-static application. By incorporating cerium-doped indium oxide NCs, the visible transparency of the resulting coating can be kept high despite the presence of visibly dark PEDOT:PSS. Lastly, in chapter 4, I describe my supporting contributions to work in my research group involving indium oxide and tin-doped indium oxide NCs. Chapter 4 is broken into three parts. First, the independent synthetic control of size and shape of indium oxide NCs was achieved through the addition of spectating alkali ions Na+ and K+. Since size and shape are critical parameters for controlling the sensing, catalytic, and assembly properties of the resulting NCs, this is an enabling discovery for many studies in the future. Next, I describe my contributions to the demonstration of depletion effects in degenerately doped tin-doped indium oxide (Sn:In2O3) NCs. A well-known effect in other semiconducting materials, depletion causes noticeable changes in the LSPR that can be controlled using electrochemical charging, and depends strongly on the NCs size and dopant concentration. In the last part of chapter 4, I discuss my work using X-ray photoemission spectroscopy (XPS) to evaluate Sn:In2O3 NCs before and after use in electrochemical CO2 reduction. This reaction has received interest for its ability to convert the greenhouse gas CO2 into more industrially relevant chemicals. Sn:In2O3 NCs show high selectivity for formate and CO, and our analysis show the NCs are stable during the electrochemical reaction, with no change in particle size or dopant concentration. This dissertation describes work on a broad range of nanocrystalline materials, including metal oxides, inorganic perovskites, and nickel iodide thin films. In evaluating their characteristics for their varied applications, I gained experience with a broad range of analytical tools, including electron microscopy, optical microscopy, UV-visible spectroscopy, and X-ray diffraction, among others. With an eye toward technological applications, fundamental studies help de fine the properties and limitations of the materials at our disposal for solving a wide range of problems.