Papers by Keyword: Gas Sensor

Abstract: To meet future social and environmental objectives for diagnosis of human diseases has offered to develop the proficient gas sensors devices with higher selectivity and sensitivity. For the production of ZnO doped reduced graphene oxide (ZnO doped rGO) nanocomposite, a one-pot hydrothermal approach. The morphological, structural and composition of nanocomposite were investigated to confirm ZnO nanoparticle effectively doped on rGO nanosheets. The nanocomposite has exhibited a superior acetone sensing characteristics. Furthermore, the nanocomposite has a high selectivity for acetone vapour. These findings emphasise advantageous synergistic effects among ZnO and excellent rGO sheet substrate properties.

Abstract: The sensing characteristics of pristine, Ni-doped, and C-vacancy graphene towards CO and NO₂ gas molecules were studied using density functional theory (DFT). The adsorption energies, electronic properties, charge transfer, and stable geometries were calculated to evaluate the gas-surface interaction mechanisms. Both pristine and vacancy graphene have smaller CO and NO₂ adsorption energies and charge transfer than the Ni-doped graphene, whereas the adsorption energy on Ni-doped vacancy graphene is higher than that of Ni-doped graphene. The results indicate that both CO and NO₂ gas molecules only attach to pristine graphene through weak physical adsorption. Stronger chemisorption occurs when the gas molecules adsorb on the surface of vacancy, Ni-doped, and Ni-doped vacancy graphene. Additionally, the results demonstrated that Ni-doped vacancy graphene has higher sensitivity and selectivity towards the NO₂.

Abstract: Titanium dioxide and gold nanoparticles were synthesized using an environmentally friendly method to deposit undoped and Au-doped TiO₂ thin films on silicon and glass substrates via the spray pyrolysis technique. The effect of the Au nanoparticles concentrations on structural, morphological, and hydrogen sulfide (H₂S) gas sensing characteristics of TiO₂ thin films were investigated. An X-ray diffraction pattern confirmed the polycrystalline structure of the films deposited on glass and Si substrates with a dominant rutile phase and the formation of additional mixed-phases of Ti-Au bonding. According to a Field Emission-Scanning Electron Microscopy investigation, the cluster size ranged from 20 to 180 nm depending on the concentration of AuNPs. The sensing response of the prepared films was tested against H₂S at different operating temperatures. The effect of growing a mixture of titanium-gold phases as a suitable catalyst for hydrogen sulfide sensitivity is also discussed.

Abstract: The detection of volatile organic compounds (VOCs) including hydrochloric acid (HCl), acetic acid (CH₃COOH), and ammonia (NH₃) in indoor air is crucial due to human health safety. In this study, halochromic poly lactic acid (PLA) film sensor were prepared. PLA film were fabricated by addition of polyethylene glycol (PEG) and bromocresol purple (BCP) into PLA using solution casting method. Visual observation and mechanical properties of the film were determined as well as its spectral properties to assess the potential of halochromic film as gas sensor. The response of the PLA film to acidic and alkaline gas and its reversibility were tested. It was found that PEG increased the free volume of PLA and made it possible for the PEG and the dye to diffuse and entrap between PLA chains. However, increasing BCP did not have significant impact on the PLA film flexibility or reduced its halochromic sensitivity. The results revealed that the film showed significant effect on NH₃ which the film change from yellow to purple within a second and could also change its color back to yellow in the absence of the VOC. This properties enables wide potential in various applications that requires high sensitivity, rapid response and continuous monitoring.

Abstract: Heterostructure thin films of indium and zinc oxides (IZO) were prepared by spray pyrolysis from an aqueous solution of the precursors at different substrate temperatures (T_S). The polycrystalline structure of bixbyite appeared at a low temperature. The crystallinity was enhanced with the emergence of the zinc oxide phase. By increasing the T_S to 623 K, the crystallite size was increased. SEM images reveal that the deposited sample at 523 K is composed of irregularly shaped nanoparticles with a lack of links. Increasing the T_S to 573 K increases the average particle diameters, and the particles appeared as polyhedrons well connected with cavities between them, which candidates for gas sensing applications. Increasing T_S to 623 K resulted in the particles merging. NO₂ gas sensor results confirmed the enhancement of IZO sensitivity performance at 573 K. Keywords: Gas sensor, thin film metal oxide, spray pyrolysis, In₂O₃– ZnO

Abstract: This work presents the development of n-type (TiO₂) and p-type (ZnO) gas-sensitive materials from ZnO doped TiO₂ thin films prepared by pulsed laser deposition technique (PLD) on a glass substrate as a gas sensor of CO₂ gas. TiO₂ gas-sensing layers have been deposited over a range of ZnO content (0, 20, and 40) wt %. The obtained thin films analysis by atomic force microscopy (AFM), and X-ray diffraction (XRD). Electrical characterization shows that TiO₂:ZnO thin films were p-type conductivity and ZnO added was unable to change the composition to the n-type conductivity. There are notable gas-sensing response differences between n-type and p-type ZnO doped TiO₂ thin film. The responses toward all tested oxidizing gases tend to increase with operating temperature for the n-type TiO₂ films. Besides, the p-type ZnO doping results in a significant response improvement toward tested oxidizing gases such as CO₂ gas at the low operating temperature of 60 °C.

Abstract: Hydroxyapatite (HA) is a phosphate mineral with the chemical formula of Ca₁₀(PO₄)₆(OH)₂. The presence of pores in HA allows easy interaction with other compounds, so it can be used to detect the CO gas. Other than that, the hydroxyl group in hydroxyapatite allows the ion exchange process, a significant reaction in a gas sensor. The interaction of hydroxyapatite with CO gas has been studied using density functional theory. The HA adsorption potential energy surface was investigated using slab model with (001) expansion and 10 Å vacuum. CO gas kept fixed 1.0 Å above the HA surface and traced along the surface with grid 10×10. The result shows that the surface is divided into two main potentials that more likely and unlikely for CO to stay. The CO gas is most likely to stay between two oxygen from (PO₃) tetrahedral that pointing down.

Abstract: Metal oxide semiconductor has been widely used for breath analyzer applications. In this work, Acetone gas is the target gas as it an important breath marker for diabetes disease. Among the different p-type metal oxide nanostructures, Nickel oxide nanospheres are used as the sensing material as it is a promising candidate for Acetone sensing. The variation of resistance of the sensing material with the concentration of the target gas was analyzed. As Acetone is a reducing gas, the resistance of the sensing layer was found to increase when the sensing layer was exposed to the target gas. The simulation was done using COMSOL Multiphysics.

Abstract: A resistive ethanol gas sensor with a high sensitivity has been proposed. The fabricated gas sensor has a very promising response and recovery at room temperature. The proposed sensor has been fabricated by depositing sensitive nanostructured material on printed circuit board interdigitated electrodes. As the sensitive material, ZnO nanorods of high uniformity have been synthesized by hydrothermal method and then decorated by PbS nanoparticles. The synthesized decorated nanorods were characterized by X-ray diffraction and scanning electron microscope which confirmed the formation of the desired nanostructures. The ethanol gas sensing properties of the ZnO nanorods decorated with PdS nanoparticles was measured in a test chamber. The minimum ethanol concentration detected by the sensor has been 10 ppm. The results showed the higher sensitivity of the proposed sensor to the ethanol at room temperature compared to similar works.

Abstract: In an article, studies of tin dioxide films for challenging sensitive elements of gas sensors for monitoring gaseous impurities in air have been described. The technological influence issues parameters of the process producing of tin dioxide films by magnetron sputtering at a fixed magnetron power on their crystal structure and phase composition were considered. The substrate temperature, layer thickness, and oxygen concentration in the atomized gas were considered as parameters. The foundation for improving the constructive and technological solutions of film gas sensors based on the research results was laid.