p-/n-Type Switching in the Ag/BTO/TiO Nanocomposite as a Gas Sensor toward Ethanol, Liquefied Petroleum Gas, and Ammonia.

A novel Ag/BTO/TiO nanocomposite was prepared using chemical reduction and sol-gel techniques followed by sintering at ∼950 °C to grow rutile TiO and remove organic materials and hydroxyl groups. The structural, optical, morphological, dielectric, and gas-sensing properties were investigated using X-ray diffraction, Fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, and inductance, capacitance, and resistance meter, respectively. The surface plasmon resonance peak of Ag was observed at 428 nm, and the absorption edge of the Ag/BTO/TiO nanocomposite was observed at 235 nm, with an energy bandgap of 5.42 eV. The dielectric constant is lower at 25 °C and becomes highest at 350 °C and low frequency. The percentage response is better toward ammonia than ethanol and liquefied petroleum gas (LPG) at 25 °C, while it is greater, ∼87%, for LPG at a higher temperature. The p-/n-type switching and vice versa were recorded in the whole gas-sensing measurement. During response-recovery time, the device performed as n type for ethanol and ammonia and p type for LPG, with a very fast response time of ∼4 s for all gases. The recovery time for ethanol was achieved at 20-25 s, while for LPG and ammonia, it was ∼60 s. Moreover, the negative and positive activation energies also confirm the switching behavior in the novel Ag/BTO/TiO nanocomposite.