Surfactant-assisted spray pyrolyzed SnO₂ nanostructures for NO₂ gas-sensing application

Well-defined morphologies of tin oxide (SnO₂) nanostructures assisted by cationic surfactant such as cetyl trimethyl ammonium bromide (CTAB) have been obtained by simple and cost-effective spray pyrolysis technique (SPT) for NO₂ gas detection. The effect of concentrations of CTAB on the structural, morphological, electrical, optical, and gas-sensing properties of SnO₂ nanostructures was investigated using X-ray diffraction, field-emission scanning electroscope microscopy, two probe resistivity, and photoluminescence techniques. The XRD results revealed that high concentration of CTAB in the precursor solution leads to decrease in crystallite size with significant changes in the morphology of SnO₂ nanostructures. Photoluminescence studies of the SnO₂ nanostructures showed the emissions in visible region, which exhibit marked changes in the intensities upon variation of surfactants in the precursor solutions. The calculated crystallite size was found to be 10.78–24.57 nm. The optical band-gap energy was found to be in the range of 3.95–2.78 eV. Using indigenously built gas-sensing unit, the gas-sensing properties of synthesized thin film were studied. For NO₂ gas at 150 °C as an operating temperature and for 20 ppm concentration of the gas, the gas response for CTAB4 thin film is found to be 19.43.