Atomically Dispersed Au on In2O3 Nanosheets for Highly Sensitive and Selective Detection of Formaldehyde

As an important industrial chemical, formaldehyde is used in various fields but is harmful to health. Developing a convenient detection device for formaldehyde is significant. Based on atomically dispersed Au on In₂O₃ nanosheets, a formaldehyde sensor was fabricated in this work. The highly dispersed Au obtained by the ultraviolet (UV) light-assisted reduction method helps improve the sensing performance. A meager loading amount (0.01 wt %) of Au on In₂O₃ nanosheets exhibits high sensitivity toward ppb-level formaldehyde. Au acts as an electron sink and promotes the oxidation of formaldehyde. Atomically dispersed Au on In₂O₃ nanosheets decreases the activation energy and increases the number of active sites, which result in a highly efficient conversion of formaldehyde and a marked resistance change of the fabricated sensors. The selective adsorption and oxidation of formaldehyde on single atom Au's uniform sites establish excellent selectivity. Besides, the sensor exhibits short response/recovery time and excellent stability, with promising applications in formaldehyde detection.

Ultra-sensitive ethanol gas sensors based on nanosheet-assembled hierarchical ZnO-In2O3 heterostructures

Developing efficient sensing materials with super sensitivity and selectivity is imperative to fabricate high-performance gas sensors for satisfying future needs. Herein, we report the preparation of ultrathin nanosheet-assembled 3D hierarchical ZnO/In₂O₃ heterostructures for the sensitive and selective detection of ethanol by sintering the 3D hierarchical Zn/In glycerolate precursors consisting of ultrathin nanosheets synthesized through a facile solvothermal method. The obtained ZnO/In₂O₃ heterostructures were carefully characterized by XRD, SEM, HRTEM, BET and XPS. The results showed that the 20%ZnO/In₂O₃ heterostructure is built up by many ultrathin nanosheets composed of intimately connected ZnO and In₂O₃ nanoparticles and have a specific surface area as high as 137.1 m² g^-1. Because of the unique hierarchical structure, abundant mesoporous and formation of ZnO-In₂O₃ n-n heterojunctions, the 20%ZnO/In₂O₃ heterostructure based sensor was ultra-sensitive to ethanol gas at 240 °C and exhibited a response as high as 170 toward 50 ppm of ethanol, which is about 3.3 times higher than that of pure In₂O₃ based sensor. Moreover, the sensor based on 20%ZnO/In₂O₃ heterostructure has virtues of excellent selectivity, good long-term stability and moderate response and recovery speed (35/46 s) toward ethanol. Therefore, the ultrathin nanosheet-assembled 3D hierarchical heterostructures are promising materials for fabricating high-performance gas sensors.

Urchin-like hierarchical H-Nb2O5 microspheres: synthesis, formation mechanism and their applications in lithium ion batteries

Urchin-like hierarchical Nb₂O₅ microspheres are successfully synthesized through a facile solvothermal method in glycerol-isopropanol mixed media followed by thermal treatment. The sample is characterized by XRD, FESEM, TEM, HRTEM, BET, and XPS, and the results reveal that the as-formed Nb₂O₅ microspheres have a pseudohexagonal structure and are composed of nanorods with an average diameter of ca. 20 nm. It is found that glycerol not only serves as a solvent but also acts as a reactant; furthermore, isopropanol plays an important part in the morphologies of the products. When used as anodic materials for lithium ion batteries, the Nb₂O₅ microspheres deliver initial discharge capacities of 201.7, 159.7, 148.5, 123.7, and 98.5 mA h g^-1 at the current densities of 0.5, 1, 2, 5, and 10C, respectively. Additionally, the discharge capacity of Nb₂O₅ remains at 105.5 mA h g^-1 even after 500 cycles at a high rate of 5C. The good electrochemical properties of the products may be ascribed to their large surface areas and hierarchical structures.

Green emission of indium oxide via hydrogen treatment

In this work, we prepared hydrogen treated indium oxide (H2-In2O3) and investigated the effect of hydrogen treatment on the optical and photoluminescence properties of In2O3. Hydrogen treatment has no influence on the crystal structure, but alters the intrinsic electronic structure and optical properties via introducing hydrogen induced defects such as shallow donor states (near the conduction band) and singly ionized oxygen vacancies in H2-In2O3. Both air-In2O3 (air calcinated) and H2-In2O3 show intense blue emission under UV excitation (280 nm). However, hydrogen treated In2O3 exhibited an additional green emission, which is absent in air-In2O3. This green emission arises from the passivation of singly ionized oxygen vacancies by hydrogen treatment. Hydrogen treatment could be a promising strategy to tune the electronic and optical properties of In2O3.

One-Step Synthesis of Co-Doped In2O3 Nanorods for High Response of Formaldehyde Sensor at Low Temperature

Uniform and monodisperse Co-doped In₂O₃ nanorods were fabricated by a facile and environmentally friendly hydrothermal strategy that combined the subsequent annealing process, and their morphology, structure, and formaldehyde (HCHO) gas sensing performance were investigated systematically. Both pure and Co-doped In₂O₃ nanorods had a high specific surface area, which could offer abundant reaction sites to gas molecular diffusion and improve the response of the gas sensor. Results revealed that the In₂O₃/1%Co nanorods exhibited a higher response of 23.2 for 10 ppm of HCHO than that of the pure In₂O₃ nanorods by 4.5 times at 130 °C. More importantly, the In₂O₃/1%Co nanorods also presented outstanding selectivity and long-term stability. The superior gas sensing properties were mainly attributed to the incorporation of Co, which suggested the important role of the amount of oxygen vacancies and adsorbed oxygen in enhancing HCHO sensing performance of In₂O₃ sensors.

Realizing Synergy between In2O3 Nanocubes and Nitrogen-Doped Reduced Graphene Oxide: An Excellent Nanocomposite for the Selective and Sensitive Detection of CO at Ambient Temperatures

Hierarchical mesoporous In₂O₃ nanocubes and nitrogen-doped reduced graphene oxide-indium oxide nanocube (In_NrGO) composites were prepared for carbon monoxide (CO) sensing. The as-synthesized materials were systematically investigated by different characterization techniques such as field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, thermogravimetic analysis, X-ray photoelectron spectroscopy, micro-Raman, Fourier transform infrared spectroscopy, and photoluminesce analysis. The obtained results are consistent with each other. The CO-sensing characteristics of the In₂O₃ nanocubes and In_NrGO composites were examined at different operating temperatures (35 °C < T_s < 300 °C) and CO concentrations (1-1000 ppm). Owing to their large surface-to-volume ratio and porosity, the In₂O₃ nanocubes exhibited a superior sensitivity with a detection limit of 1 ppm at 250 °C. Furthermore, to enhance the sensing characteristics and reduce the operating temperature, a composite of NrGO and In₂O₃ nanocubes was fabricated. The incorporation of NrGO drastically improved the sensing performance of the In₂O₃ nanocubes, showing an excellent sensitivity (S_R ∼ 3.6-5 ppm of CO at ∼35 °C) with appreciably fast response (Γ_RES ∼ 22 s) and recovery (Γ_REC ∼ 32 s) times. The sensing studies supported by the structural and morphological material characteristics lead to the plausible sensing mechanism proposed.

Synthesis of hierarchical nanosheet-assembled V2O5 microflowers with high sensing properties towards amines

Hierarchical three-dimensional nanosheet-assembled vanadium pentoxide (V₂O₅) microflowers are successfully synthesized by a hydrothermal method, followed by a high-temperature sintering treatment.