SYNTHESIS OF SnO2 NANOFIBERS BY ELECTROSPINNING METHOD AND STUDY OF ITS ETHANOL AND ACETONE SENSING PROPERTIES

Abstract

Gas sensors are crucial in multiple aspects of daily life, such as environmental and food quality monitoring, human and industrial safety, and illness detection. Among semiconducting metal oxides, SnO2 has been extensively investigated for gas-sensing applications owing to its wide bandgap, non-stoichiometric nature, excellent electronic mobility, and stability. To tailor its gas sensing functionalities, numerous approaches regarding its synthesis into useful nanostructured morphologies have been explored. For this purpose, electrospinning proved to be one of the most simple, versatile and low-cost method for producing nanofibers with high surface area-to-volume ratio and interconnectivity of nanoparticles. For the preparation of the electrospinning solution, a dimethylformamide DMF/ethanol (weight % = 40:60) solvent system was used. Separately, tin(II) chloride dihydrate (SnCl2·2H2O) and polyvinylpyrrolidone (PVP) were dissolved in this solvent system. Finally, both solutions were mixed and stirred further to obtain a clear and transparent solution for electrospinning. Optimal conditions for electrospinning were: applied voltage of 20 kV, a needle-to-collector distance of 18 cm, a flow rate of 0.7 mL/h, and a collector rotation speed of 1000 rpm, using aluminum foil as the substrate. Nanofibers were collected over multiple electrospinning cycles, and after each cycle, the fiber-coated foils were dried to remove residual solvent. The dried nanofibers were calcined at 550 °C for 1 h to induce complete crystallization. TGA of nanofibers indicates complete decomposition of the organics at 550 °C and their XRD analysis confirms the formation of pure tin oxide. The specific surface area of the as spun nanofibers was 75 m²/g with pore radius of 4.5 nm. FESEM study shows cylindrical fibers with diameter in the range of 20–50 nm with aspect ratio >1000. The sensing films were prepared by screen-printing a paste composed of calcined nanofibers dispersed in terpineol onto Al2O3 substrates pre-patterned with interdigitated electrodes and integrated microheaters. The printed films were subsequently heated at 160 °C for 1 h to remove the organic binder and improve adhesion between the sensing layer and the substrate. The gas sensors were tested using a dynamic gas sensing measurement system. Ethanol and acetone sensing of the nanofibers showed a good and desirable sensing behavior such as high sensitivity, fast response and recovery times