PVA modified ZnO nanowire based microsensors platform for relative humidity and soil moisture measurement

the present work, we have investigated Polyvinyl Alcohol (PVA) modified Zinc Oxide nanowires (ZnONW) heterostructure based microsensors platform to measure the relative humidity and gravimetricsoil moisture contents for agriculture applications. For this the hydrothermal growth of ZnO NW is carried out on Inter Digitated Electrodes (IDEs) patterned on Si/SiO2 substrates. Further, ZnO NW surfaceis functionalized by drop casting PVA solution. The surface characterization of the PVA coated ZnO NWs-film is carried out by X-Ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), ScanningElectron Microscopy (SEM) and Current-Voltage (IV) measurements. These measurements revealed the successful formation of PVA-ZnO NW heterostructure. The microsensors are exposed to different levels of relative humidity (% RH) ranging from 40 to 90% and various moisture contents of bentonite and redsoils. It is observed that the microsensors resistance decreases with increase in humidity (% RH) and gravimetric soil moisture contents (red and bentonite), respectively. The sensor exhibited a sensitivityof 4.6 K Omega / 0.1% change in RH. Further, sensitivities of 7.5 and 12.2 Omega/ 0.1% change in gravimetric water content when exposed to bentonite and red soil samples respectively were achieved. The low cost, goodre producibility, repeatability and good stability with time indicated that PVA modified ZnO NW hetero structure microsensors platform is potentially useful for measurement of humidity and soil moisture contents in agriculture applications. (C) 2017 Elsevier B.V. All rights reserved.