In this paper, a series of indium oxides were prepared by calcining the In(OH) 3 precursors, which were synthesized by hydrothermal method using the mixed solution of ethylenediamine (En) and water as a solvent. The morphologies, particle sizes, pore structure, crystallinity and surface defect concentration of these photocatalysts were adjusted by varying the ratio of En to water during the preparation of In(OH) 3 precursors. The results revealed that In 2 O 3 photocatalysts obtained from the precursor prepared in En containing solvent exhibited much higher photocatalytic activities for CO 2 reduction with H 2 O when compared to that derived from the precursor prepared in pure water. This result can be ascribed to several reasons as following. Firstly, the En addition with a suitable amount can improve the crystallinity of In 2 O 3 and decrease the surface defect concentration, which obviously depressed the recombination of photogenerated electrons and holes. Also, the addition of En during the preparation of precursor can decrease the particle size, increase specific surface area and pore structure, resulting into the increase of active sites. Finally, the band gap of In 2 O 3 can be slightly narrowed after the addition of En, resulting in enhanced light absorption in the visible region. When the ratio of ethylenediamine to water is 1:1, the as-prepared In 2 O 3 possessing the largest specific surface area and pore volume, enhanced light absorption ability and higher hole–electron separation efficiency, exhibited the highest photocatalytic activity. Under visible light irradiation, the H 2 , CO and CH 4 production rates of 5.3, 8.3 and 27.2 µmol/g cat /h can be achieved, respectively.
The performance of chemiresistive gas sensors greatly depends on the sensing materials. Till now, it is still a hot topic to develop high-performance sensing materials. In this study, hollow Fe 2 O 3 octahedrons incorporated into porous In 2 O 3 nanofibers (Fe 2 O 3 @In 2 O 3 ) have been prepared using the electrospinning method , followed by thermal oxidation . Through the electrospinning technique , MIL-101(Fe) octahedrons are incorporated as sacrificial templates into the precursor nanofibers containing In 3+ . The precursor nanofibers are transformed into porous In 2 O 3 nanofibers by calcination in air, and MIL-101(Fe) are simultaneously changed into hollow Fe 2 O 3 octahedrons, forming Fe 2 O 3 @In 2 O 3 nanofibers. Considering their unique morphology, the gas sensing properties of the prepared nanofibers are investigated. The results demonstrate that they exhibit high response and selectivity toward triethylamine (TEA) with a good stability. Furthermore, their dynamic sensing behaviors are investigated under the modulation of working temperature by triangular wave heating voltage. According to their characteristic response curves, TEA can be effectively discriminated among all the detected gases in combination with a simple principal component analysis (PCA)-based recognition algorithm. Additionally, TEA can be quantitatively analyzed through the relationship between its concentration and the response at the characteristic point of the response curves.
NO 2 is one of the most important atmosphere pollutants, causing great harm to the human body at very low concentrations (ppb levels). Herein, a novel fabrication idea for gas sensing materials was reported to detect ppb-level NO 2 via MOF-derived porous In 2 O 3 nanospheres (NSs) sensitized by CdS quantum dots (QDs). The good distribution of CdS QDs (2.5–4.0 nm) on porous In 2 O 3 NSs was verified by the transmission electron microscopy and element mapping analyses. In comparison to In 2 O 3 NSs, the CdS@In 2 O 3 composite nanospheres (CNSs) exhibited exceptional responses to ppb-level concentrations of NO 2 ( S =425.1@100 ppb) at room temperature (RT, 25 °C), while also demonstrating good selectivity and response reproducibility. These improvements in sensing performance were attributed to the synergies of the electronic effects of CdS QDs, MOF-derived porous nanostructures , and enhanced adsorption of NO 2 and active O 2 – by well-dispersed CdS QDs. This work emphasizes that the MOF-derived In 2 O 3 porous NSs sensitized by CdS QDs can accurately detect ppb-level concentrations of the NO 2 at RT.
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