As a thermoelectric (TE) material suited to applications for recycling waste-heat into electricity through the Seebeck effect, poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonic acid) (PEDOT:PSS) is of great interest.

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The demand for supercapacitors (SCs) with high capacitance, high charge–discharge rate, and long lifespan has been increasing because of the rapid development of wearable devices. In particular, flexible and durable SCs are essential for applications in wearable devices. A reasonable strategy to achieve such SCs involves the design and fabrication of SCs with flexible materials. In this study, we present a flexible SC with highly oriented carbon nanotube (CNT) sheets, which exhibit all the component functions of SCs: activated materials, conductive materials, and current collectors. Repeated bending tests validated the robustness of the flexible SCs. The SCs demonstrated extremely high durability with >99.9% capacitance retention after 50 000 bending cycles. Furthermore, we observed that the orientation angle of the CNT sheets with respect to the current flow direction (θ) was crucial for determining the performance of SCs. The SCs with CNT sheets oriented in the current flow direction (θ = 0°) showed a higher scan rate and robustness than those with other CNT sheet orientations (θ = 45 or 90°), because of the ease of access of charge carriers to the electrodes of the entire CNT sheet. Well-designed flexible and durable CNT-SCs can drastically improve the performance of future flexible devices.

Carbon nanohorns (CNHs) are mixed with cellulose to make freestanding thin-film conductive sheets. CNHs, at different ratios (5, 10, 25, 50 wt%), form composites with cellulose (hydroxyethylcellulose). Freestanding cellulose-carbon nanohorn (CCN) sheets were fabricated using a 100 μm-thick metal bar coater. Surfactants or any other chemical treatments to tailor the surface properties of CNHs were avoided to obtain composite sheets from pristine CNHs and cellulose. Utilizing the hygroscopic property of hydroxyethylcellulose and the electrical conductivity of CNHs paved a path to perform this experiment. The synthesis technique is simple, and the fabrication and drying of the sheets were effortless. As the loading concentration of CNH increased, the resistance, flexibility, and strength of the CCN composite sheets decreased. The maximum loading concentration possible to obtain a freestanding CCN sheet is 50 wt%. The resistance of the maximum loading concentration of CNH was 53 kΩ. The response of the CCN sheets to water vapor was 4 s and recover time was 13 s, and it is feasible to obtain a response for different concentrations of water vapor. High-resolution transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, resistance measurement, tensile strength measurement, and thermogravimetric analysis were used to investigate the mechanical, morphological, electrical, and chemical properties of the CCN sheets.

A simple method to synthesize metal nanoparticles (Nps) has been proposed using high vacuum thermal deposition (HVTD) by reverse engineering of thin films to Nps. Metal Nps synthesized by this technique corresponds to the top-down approach of nanomaterial synthesis from bulk metals of silver and copper wires to metal Nps. A high-vacuum thermal deposition is a commonly used technique for thin-film deposition in many applications. Synthesis of metal Nps by HVTD is simple, efficient, and can provide particle of about few tens of nanometers is effortless. A precoated thin layer of polyethylene glycol (PEG) on a glass substrate (Petri dish), is allowed deposit with a metallic thin film by thermionically evaporating bulk metal wires in high vacuum. The deposited metal thin film is removed along with the PEG coating into a liquid medium and subjected to sonication, stirring, and deoxidation. Obtaining the particle size in tens of nanometer range in one step is one projecting factor by HVTD technique. Also, providing the feasibility of reusing large particles as precursors after synthesis is a unique vantage point. The Nps were analyzed by various characterizations tools to evaluate the underlying properties.