Three-layered nanoplates and amorphous/crystalline interface synergism boost CO2 photoreduction on bismuth oxychloride nanospheres.

Structural features like 3D nano-size, ultrathin thickness and amorphous/crystalline interfaces play crucial roles in regulating charge separation and active sites of photocatalysts. However, their co-occurrence in a single catalyst and exploitation in photocatalytic CO2 reduction (PCR) remains challenging. Herein, nano-sized bismuth oxychloride spheres (BiOCl-NS) confining three-layered nanoplates (∼2.2 nm ultrathin) and an amorphous/crystalline interface are exclusively developed via intrinsic engineering for an enhanced sacrificial-reagent-free PCR system. The results uncover a unique synergism wherein the three-layered nanoplates accelerate electron-hole separation, and the amorphous/crystalline interface exposes electron-localized active sites (Bi-Ovac-Bi). Consequently, BiOCl-NS exhibit efficient CO2 adsorption and activation with the lowering of rate-determining-step energy barriers, leading to remarkable CO production (102.72 µmol g-1 h-1) with high selectivity (>99%), stability (>30 h), and apparent quantum efficiency (0.51%), outperforming conventional counterparts. Our work provides a facile structural engineering approach for boosting PCR and offers distinct synergism for advancing diverse materials.

An organic hole-transporting material spiro-OMeTAD doped with a Mn complex for efficient perovskite solar cells with high conversion efficiency.

2,{2}',7,{7}'-Tetrakis(N,N-di-p-methoxyphenylamine)-9,{9}'-spiro-bi-fluorene(spiro-OMeTAD) has often been used as a hole-transporting material (HTM) in mesoscopic perovskite solar cells (PSCs). However, its potential applications are limited due to its poor conductivity of approximately 10-6 to 10-5 cm2 V s-1 in pristine form, and this influences the stability and intrinsic hole conductivity of the device. In this work, a Mn complex [(Mn(Me-tpen)(ClO4)2 -)]2+ is introduced as a p-dopant to improve the properties of spiro-OMeTAD-based PSCs, including the optical, electrical, conductivity, and stability properties. Interestingly, the use of spiro-OMeTAD with an optimum concentration (1.0% w/w) of Mn complex in mesoscopic PSCs achieves a remarkable power conversion efficiency of 17.62% with a high conductivity of 99.05%. Spiro-OMeTAD with Mn complex as a p-dopant under UV-vis spectroscopy shows a different peak at 520 nm, confirming that oxidation occurs upon the addition of the Mn complex. The enhanced efficiency of the PSCs may be attributed to an increase in the optical and electrical properties of the HTM in the spiro-OMeTAD doped Mn complex.

Sr2NiWO6 Double Perovskite Oxide as a Novel Visible-Light-Responsive Water Oxidation Photocatalyst.

Screening of stable visible-light-responsive water oxidation semiconductor photocatalysts is highly desired for the development of photocatalytic water splitting systems. Herein, a visible-light-absorbing Sr2NiWO6 double perovskite oxide photocatalyst was successfully prepared via a conventional solid-state reaction method. The intrinsic Sr2NiWO6 shows photocatalytic oxygen evaluation reaction (OER) activity of 60 µmol h-1 g-1, even without loading any cocatalysts. The DFT calculation indicates that the Ni species on the surface is the active site for the OER. The photocatalytic OER activity was further improved by loading Pt and RuO2 dual redox cocatalysts on the surface of Sr2NiWO6 to achieve a photocatalytic OER activity of 420 µmol h-1 g-1, which corresponds to a remarkable apparent quantum efficiency (AQE) of 8.6% (λ ≈ 420 nm). The result indicates that Sr2NiWO6 is one of the best double perovskite oxide-based photocatalysts for the photocatalytic OER, and the activity is even comparable to the benchmark BiVO4-based photocatalyst. The improvement of the photocatalytic OER activity is due to the provision of more active redox sites as well as the synergetic effect of the dual redox cocatalysts in facilitating charge separation and transfer. This work demonstrates that double perovskite oxides may serve as a novel class of efficient and stable oxide-based semiconductor photocatalysts for water splitting.

Sensitive and selective colorimetric nitrite ion assay using silver nanoparticles easily synthesized and stabilized by AHNDMS and functionalized with PABA.

Nitrite ions (NO2 -), as one of the important inorganic anions, exhibit considerable effects towards the environment and human health. Moreover, over intake of this anion may cause dangerous diseases. Herein, we successfully fabricated silver nanoparticles (AgNPs) using 4-amino-5-hydroxynaphthalene-2, 7-disulphonic acid monosodium salt (AHNDMS) and functionalized them with p-aminobenzoic acid (PABA), and used the functionalised AgNPs as a sensitive and selective colorimetric sensor for nitrite ions. The structure of the as-prepared pure AgNPs was experimentally characterized by different characterizations methods, namely, UV-vis, FT-IR, CV, DPVs, SEM, TEM, and XRD. Additionally, the nitrite ion sensitively and selectively changes the brownish yellow color of the dispersed AgNPs to pinkish red, indicating aggregation of AgNPs, with a detection limit of 0.016 ppm (0.348 µM) and 0.0069 ppm (0.149 µM) by the naked-eye and by UV-vis spectroscopy, respectively. The color change suggested that the aggregation of AgNPs was induced by nitrite-selective diazo-coupling. UV-vis spectra show the disappearance of the absorbance at 474 nm and appearance of a new peak at 532 nm, presumably due to the conversion of AgNPs to silver ions. Moreover, the studies of interference in the proposed sensor confirm its selectivity in the presence of anions as well as cations. Furthermore, linearity was observed between the absorption and the concentration of nitrite ions. More importantly, the proposed sensor was practicably applied for the determination of nitrite in different water samples, such as distilled water, river water, and tap water.