Synthesis and Characterization of Inorganic – Polyaniline Hybrid Nanostructures for Sensing Applications

Abstract

Abstract In this study, PAni NFs and metal oxides nanostructures [tin oxide (SnO2) and copper oxide (CuO)] have successfully synthesized by using hydrothermal method and depositing PAni NFs, SnO2 and CuO and their composites on silicon and glass substrates by spin coating technique at room temperature with thickness of about 325 nm. The structural, surface morphological, optical, electrical, photoconductivity and gas sensing properties have been investigated for Inorganic – Polyaniline films. The XRD results showed that PAni films have crystalline nature, SnO2 and PAni/SnO2 nanostructure composite are polycrystalline in nature with tetragonal structure , CuO and PAni/CuO nanostructure composite are polycrystalline in nature with Monoclinic structure, The crystallite size is estimated by Scherrer formula and W-H analyses and it is found that it increases as the concentration ratio of SnO2 and CuO increasing. The FESEM images of Polyaniline clearly indicate that the polymer possesses nanofiber like structure, where's the SnO2 and CuO films have cauliflower like and regular shapes respectively. The surface morphology of composites are nanofiber caped with inorganic material which are SnO2 and CuO as core-shell structure. The optical properties show that the energy gap follows allowed direct electronic transition calculated using Tauc’s equation and it is noticed that the band gap value decreases as the SnO2, CuO ratios increases. PL showed that peaks intensity increases as the concentration of SnO2 and CuO increases. The electrical properties include Resistance–Temperature Characteristic, D.C. electric conductivity and Hall effect measurements. The resistance of the films decreases as the temperature increased which shows a semiconductor behavior and activation energies and electrical conductivity (σRT ) are decreases with increasing of addition of inorganic semiconductors into PAni NFs. The results of Hall coefficient showed p-type semiconductor behavior for all films except that for pure SnO2 films which is n-type. The built-in potential (Vbi) increases with increasing by addition of inorganic composites into polymer matrix. The photoconductivity properties, in current-voltage (I-V) characteristics, the value of ideality factor and tunneling factor increase with increasing by adding of inorganic semiconductors into polymer matrix, the responsivity, G%, D and D* increase with increases of SnO2 and CuO nanostructures ratio except NEP is decreases, and the current -time (I-t) characteristics investigate that the response had square pulse for UV-Vis light region that means fast response for all films. The sensitivity to H2S gas increased with increases of operating temperatures and SnO2 and CuO concentration. The maximum sensitivity to H2S gas was observed to nanocomposites PAni/CuO films at high amount of CuO and found to be 260 % at ( To= 200 oC ). The response and recovery time increased with increase in operating temperature and SnO2 and CuO concentration and the nanocomposites PAni/CuO films at concentration 3mL from CuO exhibits a fast response speed (0.753s) with recovery time (0.787s) at (30oC), while the slow response speed was observed for 7mL CuO (0.921s) with recovery time of (0.857s).