Preparation of In(OH)3 and In2O3 Nanorods through a Novel Hydrothermal Method and the Effect of Sn Dopant on Crystal Structures

Edge-oriented growth of cadmium sulfide nanoparticles on nickel metal-organic framework nanosheets for photocatalytic hydrogen evolution

In this study, a directional loading of cadmium sulfide (CdS) nanoparticles (NPs) was achieved on the opposite edges of nickel metal-organic framework (Ni-MOF) nanosheets (NSs) by adjusting the weight ratio of CdS NPs in the reaction process to produce effective visible light photocatalysts. The close contact between the zero-dimensional (0D) and two-dimensional (2D) regions and the matching positions of the bands promoted charge separation and heterojunction formation. The optimal CdS NPs loading of composite material was 40 wt%. At this ratio, CdS NPs grew primarily at the opposite edges of the Ni-MOF NSs rather than on their surfaces. When lactic acid was used as the sacrificial agent, the hydrogen production rate of the 40 %-CdS/Ni-MOF heterojunction under visible light irradiation was 19.6 mmol h-1 g-1, making a 20-fold enhancement compared to the original CdS NPs sample (1.0 mmol h-1 g-1). The charge carriers generated in CdS NPs were transferred to Ni-MOF NSs through heterojunctions, where Ni-MOF NSs also served as cocatalysts to improve hydrogen production. The combination of the two materials improved the light absorption ability. In particular, the 40 %-CdS/Ni-MOF heterojunction exhibited good photostability, effectively preventing the photocorrosion of CdS NPs. This study introduces an approach for constructing efficient and stable photocatalysts for visible light-driven photocatalytic hydrogen production.

Facile Synthesis of Heterogeneous Indium Nanoparticles for Formate Production via CO2 Electroreduction

In this study, a simple and scalable method to obtain heterogeneous indium nanoparticles and carbon-supported indium nanoparticles under mild conditions is described. Physicochemical characterization by X-ray diffraction (XRD), X-ray photoelectron microscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed heterogeneous morphologies for the In nanoparticles in all cases. Apart from In0, XPS revealed the presence of oxidized In species on the carbon-supported samples, whereas these species were not observed for the unsupported samples. The best-in-class catalyst (In50/C50) exhibited a high formate Faradaic efficiency (FE) near the unit (above 97%) at -1.6 V vs. Ag/AgCl, achieving a stable current density around -10 mA·cmgeo-2, in a common H-cell. While In0 sites are the main active sites for the reaction, the presence of oxidized In species could play a role in the improved performance of the supported samples.

Polyoxometalate-Complexed Indium Hydroxide: Atomically Homogeneous Impregnation via Countercation Exchange

Metal hydroxides catalyze organic transformations and photochemical processes and serve as precursors for the oxide layers of functional multicomponent devices. However, no general methods are available for the preparation of stable water-soluble complexes of metal hydroxide nanocrystals (NCs) that might be more effective in catalysis and serve as versatile precursors for the reproducible fabrication of multicomponent devices. We now report that In^III-substituted monodefect Wells-Dawson (WD) polyoxometalate (POM) cluster anions, [α₂-P₂W₁₇O₆₁In^IIIOH)]^8-, serve as ligands for stable, water-soluble complexes, 1, of platelike, predominantly cubic-phase (dzhalindite) In(OH)₃ NCs that after optimization contain ca. 10% InOOH. Images from cryogenic tranmsission electron microscopy reveal numerous WD ligands at the surfaces of platelike NCs, with average dimensions of 17 × 28 × 2 nm, each complexed by an average of ca. 450 In^III-substituted WD cluster anions and charge-balanced by 3600 Na⁺ countercations. Facilitated by the water solubility of 1, countercation exchange is used to stoichiometrically disperse ca. 1800 Cu²⁺ ions in an atomically homogeneous fashion around the surfaces of each NC core. The utility of this impregnation method is illustrated by using the ion-exchanged material as an electrocatalyst that reduces CO₂ to CO 15 times faster per milligram of Cu than does K₆Cu[P₂Cu^II(H₂O)W₁₇O₆₁] (control) alone. More generally, the findings point to POM complexation as a promising method for stabilizing and solubilizing reactive d-, p-, and f-block metal hydroxide NCs and for enabling their utilization as versatile components in the fabrication of functional multicomponent materials.

In2O3/CdIn2S4 heterojunction-based photoelectrochemical immunoassay of carcinoembryonic antigen with enzymatic biocatalytic precipitation for signal amplification

This work reported a split-type photoelectrochemical (PEC) immunoassay for the detection of carcinoembryonic antigen (CEA) based on target-induced biocatalytic precipitation (BCP) by using In₂O₃/CdIn₂S₄ heterojunctions as the photosensitizers. The synthesized In₂O₃/CdIn₂S₄ heterojunctions improved the efficiency of charge separation and shortened the electron convey path to enhance the photocurrent, thus exhibiting high conductivity and low complexation rates of photogenerated electrons and holes. In the presence of CEA, horseradish peroxidase (HRP) catalyzed 4-chloro-1-naphthol (4-CN) to produce benzo-4-chloro-hexadienone (4-CD) through H₂O₂. Then, 4-CD was deposited onto the surface of In₂O₃/CdIn₂S₄ to reduce the photocurrent and realized the signal amplification. The PEC immunoassay revealed an excellent photocurrent toward target CEA within a wide range of 0.01-50 ng mL^-1 at a low limit of detection of 2.8 pg mL^-1 under the optimum conditions. Multiple switching light excitation tests demonstrated the good reliability and stability of the fabricated PEC biosensor. The accuracy was acceptable in comparison with human CEA enzyme-linked immunosorbent assay (ELISA) kit.

Superparamagnetic Iron Oxide Decorated Indium Hydroxide Nanocomposite: Synthesis, Characterization and Its Photocatalytic Activity

A simple and scalable liquid-based method was developed to produce a nanocomposite photocatalyst which was comprised of Fe3O4 nanoparticles (4-5 nm) decorated indium hydroxide nanorods (mean width 33 nm and average aspect ratio 2-3). The nanocomposite was produced at 25 ℃ in water via a hydroxide-induced co-precipitation ensued by a cathodic reduction during which the non-magnetic Fe(OH)3 intermediate was reduced to magnetic Fe3O4 at 20 V within 1 h. The incorporation of Fe3O4 nanoparticles served to bestow magnetic recoverability to the photocatalyst and helped enhance visible light absorption simultaneously. Interestingly, the addition of Fe3+ led to the formation of In(OH)3 nanorods rather than the commonly observed nanocubes. In comparison to the In(OH)3 system having a band gap of 4.60 eV), the band gap of the Fe3O4/In(OH)3 nanocomposite produced was determined to be 2.85 eV using the Tauc’s plot method. The effective reduction in band gap is expected to allow better absorption of visible light which in turns should help boost its photocatalytic performance. The Fe3O4/In(OH)3 nanocomposite was structurally characterized using a combination of PXRD, FESEM, EDS, and TEM and its paramagnetic property was proven with a positive mass susceptibility measured to be 1.30´10−5 cm3.g−1. Under visible light, a photocatalytic degradation efficiency of 83% was recorded within 1 hr for the nanocomposite using methylene blue as a dye. The photocatalytically-active Fe3O4/In(OH)3 should have good potential in visible-light driven waste water degradation once further optimized. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0). 

In situtailoring the morphology of In(OH)3nanostructures via surfactants during anodization and their transformation into In2O3nanoparticles

The present work reports the effect of various surfactants on the morphology of In(OH)₃nanostructures prepared via anodization. In-sheets were anodized in an environmentally benign electrolyte containing a small quantity of CTAB, CTAC, and PDDA surfactants at room temperature. The produced nanostructures were characterized using XRD, HRTEM, SAED, and EDAX. The morphology of indium hydroxide (In(OH)₃) nanostructures was successfully tailoredin situwith the help of surfactants in 1 M KCl aqueous electrolyte. XRD results confirmed the formation of In(OH)₃and indium oxyhydroxide (InOOH) nanostructures in the pristine form which were transformed into single-phase cubic In₂O₃nanoparticles (NPs) after calcination. HRTEM analyses showed that the morphology and size of the In(OH)₃nanostructures can be tuned to form nanorods, nanosheets and nanostrips using different surfactants. The results revealed that CTAC and PDDA surfactants have a profound effect on the morphology of In(OH)₃nanostructure compared to CTAB due to the higher concentration of Cl^-ion. The possible mechanism of surfactants effect on the morphology is proposed. Furthermore, annealing converted the In(OH)₃nanostructures into spherical In₂O₃NPs with uniform and homogeneous size. We anticipate that the morphology of other metal-oxides nanostructure can be tuned using this simple, facile and rapid technique. In₂O₃NPs prepared without and with CTAB surfactant were further explored for the non-enzymatic detection of hydrogen peroxide (H₂O₂). Electrochemical measurements showed enhanced electrocatalytic performance with fast electron transfer (∼2s) between the redox centers of H₂O₂and electrode surface. The In₂O₃NPs prepared using CTAB/Au electrode exhibited about 4-fold increase in sensitivity compared to the bare Au electrode. The biosensor also demonstrated good reproducibility, higher selectivity, and increased shelf life.

Simple synthesis of hierarchically porous Sn/TiO2/graphitic carbon microspheres for CO2 reduction with H2O under simulated solar irradiation

A simple colloidal crystal template method was used to prepare Sn/TiO₂/graphite carbon microsphere composites (xSn/TiO₂/GCM, x = 2.0, 1.0, 0.2, 0.5) with porous layers. Then, the composites were represented using X-ray diffraction, energy dispersive spectrometry, scanning electron microscopy, transmission electron microscopy, and nitrogen physical adsorption/desorption. Meanwhile, the photocatalytic activities in CO₂ reduction were studied under simulation of visible light exposure. It was confirmed that the Sn/TiO₂/GCM composites had layered porosity, graphitized carbon matrix, and high metal compound content, and their morphology was greatly affected by the acetone amount. The outputs of CO and CH₄ coming into the photocatalytic CO₂ reduction reaction of Sn/TiO₂/GCM were 619.46 and 14.46 μmol g^-1, respectively. Among the two products, the highest production rate observed in 0.5Sn/TiO₂/GCM. Because of these factors, the layered porous Sn/TiO₂/GCM composites have good photocatalytic performance under simulated visible light irradiation and have unique composition and structure characteristics, which give broad application prospects in electrode materials, catalysts, and adsorbents. Graphical abstract.

Designed synthesis of Co-doped sponge-like In2O3 for highly sensitive detection of acetone gas

Materials based on Co-doped sponge-like In₂O₃ with high sensing properties were fabricated for easier detection of acetone gas.