Selectivity of an Ag/BTO-Based Nanocomposite as a Gas Sensor Between NO2 and SO2 Gases.

The novel Ag/BTO/TiO2 nanocomposite was assessed for its gas-sensing capabilities toward hazardous gases NO2 and SO2. It exhibited p-type behavior with increasing resistance for SO2 with a response and recovery time of ∼5 and ∼2 s, respectively, switching to n-type behavior when exposed to NO2 with a response and recovery time of ∼20 and ∼250 s, respectively. Analyte gas concentrations from 0 to 220 ppm were taken for analysis. Selectivity analysis at room temperature revealed NO2's superior response of ∼20% above 180 ppm, compared to SO2's < 3% response at 180 ppm. NO2(VC) achieved its highest response (∼45%) at 30 ppm and remained constant above 80 ppm, while SO2(VC) peaked at ∼30% at 60 ppm but declined with increasing flow rates. Further, the increasing temperature led to an amplified response for NO2, whereas SO2 showed an increase in response after 180 °C. SO2(VC) exhibited a significant response of ∼70% from 140 °C onward. Additionally, NO2(VC) showed distinct peaks at 160, 250, and 290 °C with responses of 50, 65, and 80%, respectively. The calculated limit of detection values were 236 ppm for NO2, 644.07 ppm for SO2, 401.32 ppm for NO2(VC), and 496.86 ppm for SO2(VC).

p-/n-Type Switching in the Ag/BTO/TiO2 Nanocomposite as a Gas Sensor toward Ethanol, Liquefied Petroleum Gas, and Ammonia.

A novel Ag/BTO/TiO2 nanocomposite was prepared using chemical reduction and sol-gel techniques followed by sintering at ∼950 °C to grow rutile TiO2 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/TiO2 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/TiO2 nanocomposite.

Low cost, p-ZnO/n-Si, rectifying, nano heterojunction diode: Fabrication and electrical characterization.

A low cost, highly rectifying, nano heterojunction (p-ZnO/n-Si) diode was fabricated using solution-processed, p-type, ZnO nanoparticles and an n-type Si substrate. p-type ZnO nanoparticles were synthesized using a chemical synthesis route and characterized by XRD and a Hall effect measurement system. The device was fabricated by forming thin film of synthesized p-ZnO nanoparticles on an n-Si substrate using a dip coating technique. The device was then characterized by current-voltage (I-V) and capacitance-voltage (C-V) measurements. The effect of UV illumination on the I-V characteristics was also explored and indicated the formation of a highly rectifying, nano heterojunction with a rectification ratio of 101 at 3 V, which increased nearly 2.5 times (232 at 3 V) under UV illumination. However, the cut-in voltage decreases from 1.5 V to 0.9 V under UV illumination. The fabricated device could be used in switches, rectifiers, clipper and clamper circuits, BJTs, MOSFETs and other electronic circuitry.