[en] Z-scheme g-C₃N₄/Au/BiVO₄ photocatalyst has been prepared successfully by assembling gold nanoparticles on the interface of super-thin porous g-C₃N₄ and BiVO₄, which exhibits outstanding photocatalytic performance toward hydrogen evolution and durable stability in the absence of cocatalyst. The highest photocatalytic hydrogen production rate of g-C₃N₄/Au/BiVO₄ was about 410.0 μmol g⁻¹ h⁻¹, which largely beyond that obtained of g-C₃N₄/BiVO₄ (23.3 μmol g⁻¹ h⁻¹), Au/g-C₃N₄ (244.6 μmol g⁻¹ h⁻¹) and pristine g-C₃N₄ (2.2 μmol g⁻¹ h⁻¹). The optimal apparent quantum efficiency was counted to be 6.8% at λ = 420 nm and 1.1% at λ = 600 nm. Moreover, the photocatalytic property of g-C₃N₄/Au/BiVO₄ could remain unchanged almost with 50 h in 5 cycles. The improvement of photocatalytic H₂ yield is attributed to the result of rapid separation of photogenic carriers in space and surface plasmon resonance effect of Au nanoparticles. In combination of photoelectrochemical measurement, active species capture experiment and electron paramagnetic resonance spectra, the underlying mechanism was illuminated. The pathway of charge carrier migration between semiconductor photocatalysts could be changed to Z-system through Au as an electron intermediate, which could not only benefit to maintain outstanding redox capability but also help to accelerate photo-generated carrier separation, and thus improve the photocatalytic activity.

[en] Highlights: • Ag/Bi°-BiVO₄ catalysts with multi-active sites were fabricated toward high-efficient reduction of aromatic nitrobenzene. • The catalysts presented excellent catalytic activity and good stability to 4-NP reduction. • The BiVO₄, Bi° and Ag offered multi-active sites to synergistically act on the reduction of nitrophenol. -- Abstract: In this work, we report on the preparation of silver nanoparticles modified bismuth/bismuth vanadate (Bi°-BiVO₄) catalyst with multi-active sites toward efficient reduction of aromatic nitrobenzene, aiming to tailor the synergistic effects of multi-active sites and specify the underlying catalytic mechanism. The as-prepared catalysts were characterized by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray and X-ray photoelectron spectroscopy. It is observed that Ag nanoparticles with diameter of 30 nm were anchored evenly on the surface of rod-shaped BiVO₄, which offered multi-active sites to contact with the reactants effectively and transfer interfacial electron to 4-nitrophenol (4-NP) rapidly. The activity factor k of Ag/Bi°-BiVO₄ for 4-NP reduction is estimated to 3933.4 min⁻¹ g⁻¹, which is much higher than that obtained from pristine BiVO₄ catalyst, Bi° and noble metal Ag nanoparticles. According to the experimental results, the reaction mechanism and reaction path of 4-NP reduction for BiVO₄, Bi and Ag were studied through the density functional theory (DFT) theoretical calculation, which suggested that they exhibit synergistic catalytic effect in the reaction process. This work may provide a feasible foundation for the mechanism research of semiconductor reduction to 4-nitrophenol.

[en] Highlights: • 2.0Bi₂O₃-Bi₃TaO₇ shows the highest photodegradation efficiency for TC (90.06%). • The formation of heterojunctions can effectively separate photogenerated carriers. • Holes (h⁺) and hydroxyl radial (.• OH) are the main active species. • Hydrothermal and calcination are mild and low-cost preparation method. -- Abstract: We have prepared a superfine powder Bi₃TaO₇ which was attached in worm-like Bi₂O₃ to form a Bi₂O₃-Bi₃TaO₇ composite by a simple facile calcination method. The as-obtained samples were measured by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray spectrum (EDX), Fourier transform infrared spectroscopy (FT-IR), UV–visible diffused reflectance spectrum (DRS) and X-ray photoelectron spectra (XPS). The optimal Bi₂O₃-Bi₃TaO₇ (2.0Bi₂O₃:1.0Bi₃TaO₇) sample show the highest photocatalytic eciency for tetracycline (TC) degradation (90.06%) irradiated with visible light, compared with that of a bare Bi₃TaO₇ catalyst. Meanwhile, radical capturing experiments indicate that the photo-induced holes (h⁺) and hydroxyl radial (• OH) are the main active species. Through the measurement of photocurrent density and electrochemical impedance spectrum, it indicates that the photogenerated carriers are significantly separated due to the formation of heterojunctions. Consequently, the Bi₂O₃-Bi₃TaO₇ photocatalyst may have potential applications in environmental purification.

[en] A novel fluorescent sensor (L) based on 1,8-naphthalic anhydride has been developed which can selectively detect Cu²⁺ in CH₃CN medium over other metal ions at 408 nm in the fluorescence spectra. When Cu²⁺ was added into L, L showed fluorescent turn-off by coordinating with Cu²⁺. A fresh absorption band was found at the position of 290 nm as was a red-shifted absorption band from 356 nm to 376 nm in UV-vis spectra which might be attributed to the intramolecular charge transfer (ICT). Meanwhile, L-Cu²⁺ showed fluorescence quenching via photoinduced electron transfer (PET). The complexation ratio was proposed to be 1:1 which was determined by Job’s plot, fluorescence titration and ¹H NMR titration. The detection limit was 9.1 × 10⁻⁸ mol·L⁻¹, a satisfying level to detect Cu²⁺ in the micromolar scale. Corresponding molecular geometries, orbital energies and electron contributions of sensor L were calculated by the DMol3 program package using the density functional theory.

[en] A series of Ag₃PO₄/Bi₂MoO₆ p–n heterojunctions were assembled via the thin Bi₂MoO₆ nanosheets attached to the surface of rhombic dodecahedral Ag₃PO₄. The self-optimized Ag⁺/Ag⁰ pairs existed in the as-prepared heterojunction which are regarded as charge transmission bridge to accelerate the reaction. The samples presented much higher photocatalytic activity for the degradation of the target pollutions (completely degradation under solar light illuminating of 70 min for rhodamine B, 80 min for aureomycin and 70 min for tetracycline). It was found during the recycle test, photocatalytic performance of Ag₃PO₄/Bi₂MoO₆ underwent a successive increase since the second cycle in which the completely degradation of RhB was achieved after only 60 min visible light irradiation, confirming the composite is reusable with well stability. The oxidative mechanism was carefully investigation based on the scavengers trapping test, ESR spectra, XPS spectrum, photocurrent responses, and electrochemical impedance spectroscopy analysis. It proved Ag⁰ gradually generated from the as-prepared composite under solar light illuminating is fixed at an optimized content. The charge transfer was consequentially enhanced during the suitable level turning of Ag⁺/Ag⁰ pairs. Mediated by Ag⁰ sandwiched in p–n junction, the active species of the present photooxidative reaction experienced various period from ^·OH and h⁺ in the initial reaction to the additional ^·O₂⁻ in the successive recycle experiment owing to generation of the rectifying contact and Schottky junction. This study provides a new cognition for the improved reusability of the photocorrosion materials via the mutual transformation of metal monomers and ions.

[en] Highlights: • ZIF-67@Yeast was synthesized by using a hydrothermally carbonized yeast as a substrate material. • The adsorption capacity of Pb²⁺ by ZIF-67@Yeast is larger than that of Pb²⁺ by individual yeast and ZIF-67. • Many MOFs could also be compounded with yeast as a base material. -- Abstract: ZIF-67@Yeast was synthesized with in-situ growth procedure by using hydrothermally carbonized yeast as the substrate material. The prepared ZIF-67@Yeast was characterized in detail by SEM, BET, XRD and TG analysis. In addition, the adsorption properties of Pb²⁺ by ZIF-67@Yeast were also investigated. The results show that the adsorption capacity of Pb²⁺ by ZIF-67@Yeast is larger than the sum of the adsorption capacity of Pb²⁺ by individual yeast and ZIF-67. Yeast could maintain a stable morphology after hydrothermal carbonization at 180 °C. Therefore, many MOFs synthesized by hydrothermal or microwave methods at 180 °C could also be compounded with Yeast as a base material. This provides more possibilities that heavy metal ions are adsorbed by the synthesis of more diverse MOFs composites.

[en] Iron is one of the most important elements in the biochemical processes in all living system, both deficiency or excess of iron will lead to metabolism disorder diseases. However, Fe³⁺ is one of the most efficient fluorescence quenchers among the transition-metal ions because of its paramagnetic nature. The realization of Fe³⁺ ratiometric and self-calibrated fluorescent sensor is highly-challenging. We synthesized a novel luminescent -OH functionalized EuOHBDC (Eu₂(OH-BDC)₃, OH-BDC=2-hydroxyterephthalic acid) by hydrothermal reaction and in situ ligand synthesis, and used it as a rare ratiomatric luminescent sensor for Fe³⁺ ions. The -OH functional group facilitates both electron transfer and binding interaction between EuOHBDC and Fe³⁺, which lead to luminescent quenching of ligand-based emission while enhancement of a new peak emission, and thus enables ratiometric detection of Fe³⁺. The relative fluorescent intensity ratio (I₃₇₅/I₄₂₇) increased linearly with increasing Fe³⁺ concentration in the 10–50 μM range with 1.17 μM (65 ppb) detection limit. The EuOHBDC also shows excellent selectivity towards different metal ions, particularly can discriminate Fe³⁺ and Fe²⁺ through different luminescent responses. This result clearly demonstrates the superiority of -OH functionalized MOF for Fe³⁺ detection, which can contribute to develop high performance luminescent probe for detection of metal ions in environmental and biomedical applications.