Irmak Karaduman

CO2 gas detection properties of a TIO2/Al2O3 heterostructure under UV light irradiation

Al/TiO2/p-Si and Al/TIO2/Al2O3/p-Si samples were prepared using the atomic layer deposition method (ALD) and their gas sensing properties were investigated. The electrical properties of the samples were studied using a two probe method in the temperature range 25–230 °C and at room temperature UV conditions. The TiO2/Al2O3 heterojunction sample exhibited an excellent gas sensing response to CO2 gas at room temperature and improved the effect of UV light irradiation. The results showed that heterostructures helped to improve the gas sensor properties, affected the sensing at room temperature and thus guided the design of photocatalysts. The TiO2/ Al2O3 heterojunction prepared using this method can be used as a material for semiconductor gas sensors detecting poisonous gases like CO2 at room temperature with high sensitivity and selectivity.

The effect of ultraviolet irradiation on the ultra-thin HfO2 based CO gas sensor

In this work, an effort has been made to fabricate ultrathin HfO2/Al2O3 sample by atomic layer deposition method for the fast detection of CO gas at room temperature. The effect of the operating temperature and the UV light on the gas sensing characteristics has been studied. We investigated the optimum operating temperature for the sample by sensing 25 ppm CO and CO2 gases from room temperature to 150 °C for 10 °C steps. The maximum response was obtained at 150 °C for both gases in the measurement temperature range. Also, the photoresponse measurements clearly show the effect of UV light on the sample. At room temperature, sensor showed superior response (14%) for 5 ppm CO gas. The response time of sensor is 6 s to 5 ppm CO gas concentration. The ultrathin HfO2 based sample shows acceptable gas sensitivity for 5 ppm CO gas at room temperature under UV light irradiation.

Effect of Doping Materials on the Low-Level NO Gas Sensing Properties of ZnO Thin Films

In this study, undoped, Cu-doped, and Ni-doped ZnO thin films have been successfully prepared by successive ionic layer adsorption and reaction method. The structural, compositional, and morphological properties of the thin films are characterized by x-ray diffractometer, energy dispersive x-ray analysis (EDX), and scanning electron microscopy, respectively. Doping effects on the NO gas sensing properties of these thin films were investigated depending on gas concentration and operating temperature. Cu-doped ZnO thin film exhibited a higher gas response than undoped and Ni-doped ZnO thin film at the operating temperature range. The sensor with Cu-doped ZnO thin film gave faster responses and recovery speeds than other sensors, so that is significant for the convenient application of gas sensor. The response and recovery speeds could be associated with the effective electron transfer between the Cu-doped ZnO and the NO molecules.

Influence of Different Aluminum Sources on the NH 3 Gas-Sensing Properties of ZnO Thin Films

Herein we report Al-doped ZnO films (AZO) deposited on the ZnO seed layer by chemical bath deposition method. Al powder, Al oxide and Al chloride were used as sources for the deposition process and investigated for their different effects on the NH3 gas-sensing performance. The morphological and microstructural properties were investigated by employing x-ray powder diffraction, scanning electron microscopy analysis and energy-dispersive x-ray spectroscopy. The characterization studies showed that the AZO thin films are crystalline and exhibit a hexagonal wurtzite structure. Ammonia (NH3) gas-sensing measurements of AZO films were performed at different concentration levels and different operation temperatures from 50°C to 210°C. The sample based on powder-Al source showed a higher response, selectivity and short response/recovery time than the remaining samples. The powder Al sample exhibited 33% response to 10-ppm ammonia gas at 190°C, confirming a strong dependence on the dopant source type.

Green synthesis of γ-Fe 2 O 3 nanoparticles for methane gas sensing

Green synthesis is becoming increasingly important as an eco-friendly alternative to the traditional production process because of its growing industrial applications. In this study, peroxidase enzymes of the leaf extracts of the plants Ficus carica (Fig) and Euphorbia amygdaloides (Euphorbia) were used for the synthesis of γ-Fe2O3 nanoparticles (NPs). The structural, morphological and methane gas sensing properties of γ-Fe2O3 NPs were investigated. γ-Fe2O3 NPs obtained from the Fig plant peroxidase enzyme showed a higher response, selectivity and short response/recovery time than γ-Fe2O3 NPs obtained from the Euphorbia plant peroxidase enzyme, which exhibited 15% response to 1-ppm methane gas at 150 °C. Impedance spectroscopy analysis showed that the resistance due to the grain boundaries significantly contributed to the characteristics of gas sensing. It can be seen from results that γ-Fe2O3 NPs produced from peroxidase enzymes that purified from Fig plant have great potential for industrial applications.