Hydrothermally Synthesized Functional Nanomaterials for Dielectric, Triboelectric and Photocatalytic Applications

Abstract

Hydrothermally synthesized functional nanomaterials are utilized for various applications. The functional nanomaterials, like TiO2, La2O3, ZnO, GO and rGO/ZnO were synthesized and used for various applications, like parallel plate capacitor, triboelectric nanogenerators and photocatalytic applications. This method not only yielded nanomaterials with uniform dimensions, but also permitted to tailor the dimensions and morphologies. The materials were characterized to examine the structure, morphology and nature. The primary objective was to explore the potential of hydrothermally synthesized TiO2 in parallel plate capacitor applications. The flexibility of the TiO2 was achieved by incorporating TiO2 nanoparticles in Nylon-6 polymer. These materials were characterized to find the dielectric permittivity (ε) using impedance spectroscopy. The results showed that the ε value is 124 at 1 kHz for Nylon-6/TiO2 polymer nanocomposites and 4472 at 1 kHz for hydrothermally grown unique microstructural films exhibiting colossal dielectric permittivity. The La2O3-based and ZnO-based triboelectric nanogenerator (TENG) devices were fabricated by screen-printing the hydrothermally synthesized La2O3 and ZnO nanomaterials on copper foil (conductive substrate), respectively, with Teflon film (back coated on copper foil) as counter material. The TENG was subjected to mechanical motion by means of a in-house built motorized fixture. The maximum power density generated by La2O3-based TENG device was 7.125 W/m2 at an external load resistance of 30 MΩ and ZnO-based TENG was 0.58 W/m2 at 3 MΩ. The operation life-cycle of the TENG device was analyzed by decay in the voltage after prolonged cycle of operations. The decay in the voltage generated by the TENG devices was negligible after 105 cycles of tapping operations. The TENG device generated enough power and was capable to carry out the smooth functioning of the self-powered devices. The hydrothermally synthesized graphene oxide (GO) was used in the preparation of rGO/ZnO nanocomposites for the methyl orange dye degradation. The advantages of the hydrothermal synthesis of GO over Modified Hummers’ method is the use of less harmful chemicals, less instrumentation and eco-friendly nature. The nanocomposite was capable of degrading the methyl orange with almost equal kinetic rate constant (0.0523 min-1) compared to the rGO/ZnO nanocomposite, where GO prepared following the Modified Hummers’ method. Low-constant, low-temperature, eco-friendly and industrial scalability are the main advantages of the hydrothermally synthesized functional nanomaterials, which can be further used in various applications.