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A series of sensing hybrid-materials of Au nanoparticle loaded ZnO nanowires (ZnO NWs) was successfully synthesized by electrostatic spinning and solution processing. Firstly, ZnO NWs were prepared by electrostatic spinning with polyvinylpyrrolidone (PVP) as a solvent. Afterwards, the prepared ZnO NWs were added to HAuCl4 aqueous solution with adjusted pH to load the Au nanoparticles onto them. Finally, the ZnO NWs were obtained with different sizes of Au nanoparticle loaded via annealing at different annealing temperatures. The X-ray diffraction (XRD) characterization indicates the good crystallinity and purity of the material, while transmission electron microscopy (TEM) images show the different sizes of Au nanoparticles on the ZnO NWs. The gas sensitivity test results show that all the Au-loaded ZnO NW samples show excellent gas sensitivity performance at a low operating temperature, and the loaded Au particles have an obvious influence on the sensing performance. A sensor loaded with large Au particles has a maximum response of 151.86 to 50 ppm ethanol at 200 °C, while a sensor loaded with small Au particles can respond to 50 ppm ethanol at 125 °C up to 108.22. Most importantly, the sensor shows high selectivity and long-term stability against a low concentration of ethanol. To interpret the gas-sensitivity mechanism of different responses under loadings of different Au particle sizes, the spillover effect of noble metal loads and the increase in the Schottky barrier due to the interaction of the noble metal with metal oxide semiconductor electrons are considered to explain the different sensor responses. [ABSTRACT FROM AUTHOR]

Band alignment and dipole formation at the hetero-interface still remain fascinating and, hence, are being intensively investigated. In this study, we experimentally investigate the dipole formation by employing a dielectric/dielectric (Al2O3/GeO2) interface. We investigate the dipole dependence on various post-deposition annealing (PDA) ambiences from the viewpoints of electrical extraction and the X-ray photoelectron spectroscopy measurement. The core level shift at the Al2O3/GeO2 interface is consistent with the dipole changes in various PDA ambiences. We discover that the dipole formation can be well explained by the interface gap state and charge neutrality level theory. These results further confirm the feasibility of gap state theory in explaining the band alignment at hetero-junctions. This study can be a booster to enhance the comprehension of dipole origin at hetero-junction interfaces. [ABSTRACT FROM AUTHOR]

[Display omitted] • SnO 2 nanocrystals are capable of detecting low concentrations of NO 2 at 80 °C. • The SnO2 sensor has excellent sensing characteristics. • Introduction of F-factor to predict the response trend of the sensor. • Experimental and calculations to verify the important role of surface oxygen vacancies. • Superoxide anion formed by surface oxygen vacancies increases the sensing characteristics. N-type metal oxide semiconductors are widely used in the field of gas sensors, but achieving high sensor response at low temperatures with low concentrations is challenging. In this paper, we report a high-performance gas sensor for NO 2. SnO 2 grains with different sizes and oxygen vacancies were prepared by a simple hydrothermal method followed by high-temperature calcination, and the electronic and chemical properties of the SnO 2 grains were significantly changed. The results demonstrate that the sensor prepared from SnO 2 grains hydrothermally grown at 180 °C has the optimal gas sensing performance with a response up to 4358.8 for 1 ppm NO 2 at a low temperature of 80 °C, a rapid response recovery (7 s), and a detection limit down to 9 ppb. Together with some series characterization, an empirical factor F between the sensor response and the influencing factors is proposed. In addition, through experimental and density generalization studies, the oxygen vacancies are distinguished into surface oxygen vacancies and subsurface oxygen vacancies. The dominance of the surface oxygen vacancies in dictating the gas response is demonstrated. The excellent sensor characteristics demonstrated and the elucidation of the gas-sensitive mechanism provide a clear framework for the preparation of high-performance gas sensors. [ABSTRACT FROM AUTHOR]

[Display omitted] • The response of the 7P4R WO 3 sensor with a 742-fold enhancement up to 1010 towards 1 ppm H 2 at 70 °C. • The sensor can identify ultralow concentration of H 2 with a theoretical detection limit of 0.252 ppb. • The sensor has good repeatability, selectivity, and high response (6 5 0) even at 65 % humidity to 1 ppm H 2. • Ex-situ Raman and HER results explained the mechanism of the response' enhancement. Hydrogen is the cleanest fuel, but the safe storage and transportation of hydrogen is a relatively troublesome task, thus, developing high-performance hydrogen sensors has certain challenges. In this paper, high-performance hydrogen sensing material at near-ambient temperatures was prepared by using platinum and ruthenium co-modified the surface of WO 3 nanowires obtained via electrospinning. When the atomic percentages of platinum (Pt) & ruthenium (Ru) to tungsten (W) is 7:4, the response value of sensors to 1 ppm hydrogen at near room temperature (70 °C) is 1010, making it suitable for practical application. Particularly, the sensor has a low detection limit of 252 ppt, good repeatability, selectivity and long-term stability. In addition, the electrocatalytic dehydrogenation (HER) performance of the samples was investigated and combined with the Raman study to explore the hydrogen sensing mechanism in this work. This work demonstrated that the modification of double noble metals could significantly improve the hydrogen sensing performance of WO 3 nanowires, and it is expected to be extended to the practical application of metal oxide semiconductors based chemiresistive hydrogen sensors, which is of great significance for the large-scale safe use of hydrogen energy in the future. [ABSTRACT FROM AUTHOR]

• A series of rare earth (Ce, Tm, Eu, Er, and Tb) doped In 2 O 3 nanotubes (RE-In 2 O 3 NTs) were synthesized by a facile electrospinning technique. • Gas sensing results revealed that all RE-In 2 O 3 NTs showed increase in the response to ethanol vapor compared to the pristine In 2 O 3 NTs, particularly the Tb doped In 2 O 3 NTs. • Different rare earth doping can adjust the content distribution of three kinds of oxygen species on the surface of In 2 O 3 -based sensor material. • Tb doping can not only increase the oxygen ions adsorbed on the surface, but also inhibit the adsorption of harmful molecules such as water molecules on the gas sensitive response process, which has great potential in the application of gas sensors. Herein, pristine indium oxide (In 2 O 3) and rare earth (Ce, Tm, Eu, Er, and Tb)-doped In 2 O 3 nanotubes were synthesized by a facile one-step electrospinning method. Rare-earth (RE) doping increases the number of active sites on the surface, which enhances the electrical response and gas-sensing performance of In 2 O 3 , with different RE elements causing different enhancement effects. Transmission electron microscopy elemental mapping shows a homogeneous distribution of RE elements on the whole nanotube. Analysis of the gas-sensing mechanism shows that RE doping modifies the oxygen species adsorbed on the sensor surface. Our findings promote the development of new dopant-based metal oxide semiconductors for high-performance gas sensing. [ABSTRACT FROM AUTHOR]

• A series of bimetallic Ni/Au-decorated In 2 O 3 nanotubes with different Au contents by a facile electrospinning technique. • INO-Au NTs not only greatly enhances the gas sensing response to ethanol, but also reduces the operating temperature. • Mechanism was explained by chemical sensitization of Ni and Au, and the electronic sensitization by formation of Schottky barrier. • This work suggests that bimetallic modified 1D metal oxide semiconductor has great potential applications in gas sensors. In this work, we report on a high-performance ethanol sensor using Au decorated Ni-doped In 2 O 3 nanotubes (NIO-Au NTs). The morphology, microstructure and surface chemistry of pristine In 2 O 3 , NIO and NIO-Au NTs have been discussed by the analysis of SEM, TEM, XRD and XPS spectra. Gas sensing test results reveal that NIO-Au NTs with optimal Au decorated concentration of 2 mol% (NIO-2 mol% Au) exhibits the highest response of 167 towards 50 ppm ethanol at lower working temperature (180 °C), which is about 18 times and 13 times higher than pristine In 2 O 3 NTs and Ni-doped In 2 O 3 NTs, respectively. Moreover, some other important gas sensing properties of NIO-2 mol% Au NTs, such as selectivity and stability, have been proved to be greatly improved. The approach and results proposed in this study are attributed to the catalysis of Ni, the spillover effect of Au and formation of Schottky barrier. The proposed functional hybrid nanomaterial-based sensing strategy offers an effective design for highly sensitive and efficient VOC detection devices, which can operate well at low temperatures also. [ABSTRACT FROM AUTHOR]