Search

Residual antibiotic tetracycline (TC) that is hard to degrade and active has adversely affected public health and ecosystems. Therefore, developing straightforward, rapid, and sensitive probes for TC detection is highly desirable. Herein, we present a facile yet versatile strategy to design and fabricate luminescence turn-on TC sensors by applying the concept of indicator displacement to metal–organic frameworks (MOFs). It is illustrated by an elaborated dual-emitting nanoporous europium–MOF (Eu–MOF) constructed by Eu3+ cations and 2-aminoterephthalic acid (BDC-NH2), in which the former serves as receptors and the latter acts as luminescent indicators. The indicator displacement is based on the competitive interactions within Eu–MOF, which is confirmed by high-resolution mass spectrometry, photoluminescence, and UV–vis spectroscopy. Once Eu–MOF contacts TC, the competitive coordination effect induces the release of BDC-NH2 molecules and the accompanying turn-on blue emission, whereas the red emission of Eu3+ barely changes, thereby resulting in a remarkable ratiometric luminescence response and luminescence color switching from red to blue that is readily observed by the naked eye. The sensitive and quantitative determination of TC is accomplished through multiple readouts involving ratiometric emission intensity and emission color, exhibiting detection limits of 0.08 and 0.95 μM, respectively. Notably, the visual detection of TC is achieved using a smartphone color-scanning app. Considering the excellent tunability in the composition and structure of MOFs and their compatibility with various host–guest interactions applicable to indicator displacement assays, this study helps to create a universal avenue for leveraging MOFs in constructing luminescence turn-on sensors. [ABSTRACT FROM AUTHOR]

A heterojunction interface with a rational design can overcome the limitation of a single photocatalyst structure and enable the separation and transport of photogenerated carriers. p‐n Heterojunctions of BiOI/ZnO nano‐flake were achieved by a simple one–step hydrothermal process for metronidazole (MNZ) degradation under visible light. The measurements show that the BiOI/ZnO could completely remove MNZ within 180 min, which is 2.6 times and 4.8 times higher than that of pristine ZnO and BiOI, respectively. Under visible light irradiation, the electrostatic field formed within the p‐n heterojunction drives the flow of photogenerated electrons from the conduction band of BiOI to the conduction band of ZnO, while the holes are retained, promoting photogenerated carrier separation and enhancing photocatalytic efficiency. The fact that BiOI/ZnO good stability and reusability demonstrates the importance of heterostructure construction of two different semiconductors in overcoming the defects of traditional semiconductor materials. [ABSTRACT FROM AUTHOR]

Volatile organic compounds (VOCs) are hazardous to human health and have a negative impact on productivity. Photocatalytic oxidation process is one of the most promising techniques for removing indoor VOCs. Here, S-doped g-C3N4 was synthesized using a high-pressure microwave-assisted sol–gel method. Toluene removal by S-doped g-C3N4 with a S/g-C3N4 mass ratio of 1 : 1 was nearly 100% after 180 min of UV irradiation or 360 min of visible light irradiation. S-doping reduces layer spacing and causes the formation of g-C3N4 lattice defects, allowing the photo-generated electron–hole pairs to be separated more effectively. The S-doping ratio is optimized to strike a favorable compromise between improving the photo-generated electron–hole separation efficiency and lowering the surface electron conductivity. DFT calculations was performed to analyze the energy band structure and electronic properties of S-doped g-C3N4 to explain the mechanism of S-doping to enhance the photocatalytic activity of g-C3N4. S-doped g-C3N4 has efficient catalytic activity and excellent photo-corrosion resistance, suggesting a potential practical application for VOC removal. [ABSTRACT FROM AUTHOR]