Enhanced LPG sensing property of sol–gel synthesized ZnO nanoparticles-based gas sensors

In this paper, we have studied the effective use of HCl acid in sol–gel method to demonstrate a ZnO nanoparticles (NPs)-based liquid petroleum gas (LPG) sensor with enhanced sensitivity. ZnO NPs were prepared by adopting standard sol–gel method with modification. The size of the NPs varies from 12 to 40 nm. The growth parameters were tuned to allow the formation of more oxygen vacancies in the as-grown sample, which was confirmed from the absorption study and EDX data. Then, the gas sensors were fabricated using as-prepared ZnO NPs and it was tested for LPG. Interestingly, it was found that the solvent used in the sol–gel method is playing a crucial role in the sensing of LPG. An enhanced sensitivity (~60%) with 1000 ppm of LPG at a lower operating temperature and good performance stability were achieved when aqueous HCl acid was used as a solvent. Commonly used solvent in the sol–gel method is DI water which results in almost similar morphology of the NPs and a sensitivity of 50% only with 1000 ppm of LPG. Response time of 67 s and reset time of 40 s were observed at an operating temperature of 250°C. Use of HCl acid over the commonly used DI depicts better sensing performance of LPG. The effect of operating temperature and concentration of the LPG were investigated in detail to understand the effectiveness of the modified sol–gel-synthesized ZnO NPs sensor for LPG gas and found to be very efficient.