Search

In this contribution, all-inorganic lead-free halide perovskites Cs 2 SnX 6 (X = Cl, Br, I) were synthesized by simple room-temperature precipitation. Material characterization demonstrated their feature in rich defects of halogen vacancies. As room-temperature formaldehyde (HCHO) sensing materials, Cs 2 SnX 6 exhibited reliable sensitivity order of Cs 2 SnCl 6 < Cs 2 SnBr 6 < Cs 2 SnI 6. Notably, the Cs 2 SnI 6 sensor showed excellent selectivity for HCHO at room temperature with high response (S r = 78, 100 ppm), short response/recovery time (3.6 s/7.2 s), good repeatability and long-term stability. Finally, the HCHO sensing mechanism was investigated via in-situ infrared analysis, conforming abundant intermediates of dioxymethylene, formate, and carbonate. The excellent sensing performance is attributed to rich iodine vacancies (V I) as active sites induced boosted stepwise oxidation of HCHO molecules on Cs 2 SnI 6 surface. This work provides a fine candidate for practical HCHO detection at room temperature, and furthermore, gives new insights in designing halide perovskites for next-generation sensory devices. An all-inorganic lead-free halide perovskite Cs 2 SnI 6 with rich iodine vacancies (V I) was applied to room-temperature formaldehyde detection for the first time with boosted performance, especially high sensitivity and rapid response-recovery. [Display omitted] [ABSTRACT FROM AUTHOR]

Pure ZnO and carbon-doped ZnO hollow spheres were successfully synthesized by a hydrothermal-calcination process. The doping content of carbon in ZnO was controlled by different calcination temperatures at 500 ℃ and 600 ℃ (named as ZnO-500 and ZnO-600). Systematic material characterization indicates that mesoporous ZnO hollow spheres are featured in abundant defects induced by in-situ carbon doping. Used as gas sensing materials, the response of ZnO-600 towards 200 ppm dimethylamine (83.6) is 28.6 times and 2.5 times higher than that of Pure ZnO (2.9) and ZnO-500 (32.8) at the optimum operating temperature of 240 ℃. Remarkably, the response of ZnO-600 toward 1 ppm dimethylamine is as high as 7.2, and simultaneously the limit of detection is as low as 108 ppb. In addition, ZnO-600 hollow spheres hold excellent gas-sensing performance in response-recovery speed, selectivity, repeatability, long-term stability, and water resistance towards dimethylamine. The boosted dimethylamine sensing performance of ZnO-600 is mainly attributed to synergistic effects of the unique mesoporous microstructure and rich defects induced by in-situ carbon doping. This work provides a promising material for dimethylamine detection, the properties of which can be improved for practical applications in the future. Furthermore, this contribution gives new insights into nonmetal-doped metal oxide nanostructures for high-performance gas sensors via surface defect control. [Display omitted] • In-situ carbon-doped ZnO hollow spheres were successfully synthesized by a hydrothermal-calcination process. • ZnO hollow spheres doped with different carbon amounts were obtained by controlling the calcination temperature. • Carbon-doped ZnO hollow spheres exhibited excellent gas sensing properties to dimethylamine. • The enhanced response is attributed to the unique microstructure and abundant defects induced by in-situ carbon doping. [ABSTRACT FROM AUTHOR]

Defect-rich ultrathin heterovalent tin oxide (Sn 2 O 3) nanosheets with dominant polar (100) facets were synthesized via a facile hydrothermal method for the first time. The structure, morphology, chemical state, bandgap, defects, and specific surface area of these Sn 2 O 3 nanosheets were characterized by XRD, FE-SEM, TEM, XPS, UV–Vis, PL, N 2 -adsorption, respectively. Taking inspiration from the morphology, defects, and exposed facets that facilitate adsorption-interaction of molecules on the surface, gas and humidity sensors were fabricated based on Sn 2 O 3 nanosheets. The gas sensor response to 200 ppm ethanol at 200 °C is as high as 70.1, and response and recovery times are only 6 s and 3 s, respectively. At room temperature, the humidity sensor exhibits a response up to 2.76 × 103 with a small humidity hysteresis of 1.95%, and the response and recovery times are divided into 27 s and 124 s, respectively. Additionally, both gas and humidity sensors demonstrate excellent repeatability and stability. Finally, gas and humidity sensing mechanisms of the Sn 2 O 3 sensor have been discussed. This work provides a practical candidate for gas and humidity sensors and further develops a new promising application for heterovalent metal oxides in electrical sensory devices. In this contribution, defect-rich ultrathin Sn 2 O 3 nanosheets with dominant polar (100) facets are synthesized via a hydrothermal method for the first time that can be used as an attractive bifunctional sensing material. The enhanced gas and humidity response are mainly attributed to the ultrathin nanosheet morphology, large specific surface area, abundant intrinsic surface defects, and dominant polar (100) facets. [Display omitted] • Defect-rich ultrathin Sn 2 O 3 nanosheets with dominant polar (100) facets are synthesized for the first time. • Sn 2 O 3 nanosheets exhibit excellent gas sensing properties to 5-800 ppm ethanol at 200 °C. • Sn 2 O 3 nanosheets also show wonderful humidity sensing performance under different relative humidity at room temperature. • Enhanced gas/humidity response is attributed to the unique morphology, abundant defects, and dominant (100) facets. [ABSTRACT FROM AUTHOR]

• Mesoporous ZnO nanosheet-assembled spheres with abundant defects are synthesized via a hydrothermal method. • ZnO spheres are further decorated with Zn 3 (VO 4) 2 nanoparticles by an impregnation–calcination process. • Zn 3 (VO 4) 2 decorated ZnO exhibits excellent gas sensing properties to 0.1–1000 ppm acetone at 350 °C. • The enhanced acetone response of Zn 3 (VO 4) 2- ZnO is mainly attributed to combined actions of heterojunction and defects. Integration of two oxides to form heterojunction nanostructures reveals drastic effects on chemiresistive gas sensing performance, however transition metal vanadates (TMVs) decoration onto metal oxide backbone material (e.g. ZnO) has not been reported yet. In this contribution, ZnO nanosheets assembled spheres were synthesized by a hydrothermal method and then decorated with different amount of Zn 3 (VO 4) 2 via a facile impregnation–calcination process. Material characterization indicates that mesoporous ZnO nanosheets assembled spheres with abundant defects are successfully decorated by different content of Zn 3 (VO 4) 2 nanoparticles. Taking acetone (C 3 H 6 O) as a probe molecule, gas sensing properties of both pristine ZnO (P-ZnO) and Zn 3 (VO 4) 2 decorated ZnO (V 2 -ZnO) were systematically investigated. Compared with P-ZnO, V 2 -ZnO exhibits improved acetone response at the optimum operation temperature of 350 °C with an optimal Zn 3 (VO 4) 2 capacity of 1.0 % in molar ratio (named as 1.0 %V 2 -ZnO). The sensor response of 1.0 %V 2 -ZnO spheres is as high as 303.6 towards 200 ppm acetone that is nearly 10 times higher than that of P-ZnO. Simultaneously, 1.0 %V 2 -ZnO spheres show much shorter response/recovery time than that of P-ZnO. The excellent acetone sensing performance of V 2 -ZnO spheres is mainly attributed to synergistic effects of heterojunction interface, abundant defects, small thickness, and mesoporous construction induced electronic and chemical sensitization. [ABSTRACT FROM AUTHOR]

In this work, polycrystalline Co 3 O 4 nanoparticles rich in doubly ionized oxygen vacancies (V O ¨) exhibit superior NH 3 sensing performance at room temperature. Adjusting charge states of oxygen vacancy has been extended to p-type metal oxide (Co 3 O 4) for the first time. [Display omitted] • Polycrystalline Co 3 O 4 nanoparticles are synthesized by hydrothermal-calcination. • Co 3 O 4 is rich in oxygen vacancy mainly with doubly positive charges (V O ¨). • Co 3 O 4 exhibits excellent performance for NH 3 sensing at room temperature. • Adjusting charge states of V O has been extended to p-type metal oxide (Co 3 O 4) for the first time. • Enhanced sensitivity is attributed to high content of Co3+ and V O ¨. Polycrystalline Co 3 O 4 nanoparticles were synthesized using a hydrothermal method with calcination. The microstructure and surface defects of these materials were investigated systematically. Room temperature gas sensing properties of Co 3 O 4 nanoparticles were tested towards ammonia (NH 3). The response value of Co 3 O 4 -2 h gas sensor to 200 ppm NH 3 is 102.8 with response and recovery time of 65 s and 208 s, respectively. The Co 3 O 4 -2 h sensor also exhibited high selectivity, good repeatability and long-term stability. After excluding the impact of specific surface area and grain-size effect on sensitivity, the boosted sensing performance of Co 3 O 4 -2 h nanoparticles is mainly attributed to the high Co3+ concentration and the abundant doubly ionized oxygen vacancies (V O ¨). This work provides a promising strategy to enhance gas sensing properties of p-type oxides by adjusting charge states of oxygen vacancy. [ABSTRACT FROM AUTHOR]