An interfacial C-S bond bridged S-scheme ZnS/C3N5 for photocatalytic H2 evolution: Opposite internal-electric-field of ZnS/C3N4, increased field strength, and accelerated surface reaction.

An interfacial C-S bond bridged ZnS/C3N5 heterojunction was constructed for photocatalytic H2 evolution. Different from traditional type-II ZnS/C3N4 heterojunction, the electron transfer followed S-scheme pathway, due to opposite internal-electric-field (IEF) directions in these two heterojunctions. The C-S bond formation was carefully investigated, and they were susceptive to the preparation temperatures. In photocatalytic reaction, C-S bond was functioned as the "high-speed channel" for electron separation and transfer, and the IEF strength in ZnS/C3N5 was 1.86 × 108 V/m, 2.6 times higher than that in ZnS/C3N4. Moreover, the C-S bond also altered the surface molecular structure of ZnS/C3N5, and hence the surface reaction was accelerated via improving H2O adsorption and activation behaviors. Benefiting from the S-scheme pathway, enhanced IEF strength, and accelerated surface reaction, the photocatalytic H2 production over ZnS/C3N5 reached up to 20.18 mmol/g/h, 3.2 and 2.5 times higher than those of ZnS/C3N4 and ZnS/C3N5-300 without C-S bond.

Preparation of double-yolk egg-like nanoreactor: Enhanced catalytic activity in Fenton-like reaction and insight on confinement effect.

Peroxymonosulfate (PMS)-based Fenton-like reaction is an effective technique for the pollutant degradation, and the Co-based metal organic frameworks displayed the excellent activity for the PMS activation. Nevertheless, how to further improve the catalytic activity, suppress the leaching of toxic cobalt ions, and realize the rapid separation were still challenges for practical application. In this work, a novel solution was proposed: encapsulating Fe3O4 and Prussian blue analogue (PBA) into the polypyrrole (PPy) shell and constructing a "double-yolk egg-like" Fe3O4/PBA@PPy as a nanoreactor. In Fe3O4/PBA@PPy-10, the catalytic performance was remarkably enhanced with the help of confinement effect, and the degradation rate (0.38 L·min·mol-1) was 5.1 times than that of reference Fe3O4/PBA-10 (0.074 L·min·mol-1). In addition, the concentration of leached cobalt ions was reduced to only 0.174 mg/L by the protective function from the PPy shell. Moreover, the nanoreactor could be magnetically separated from the reaction solution due to the encapsulation of Fe3O4 nanospheres, and 84.5% of activity still preserved after the 4th cycle. The main active species involved in Fe3O4/PBA@PPy-10 system was 1O2, while that in reference Fe3O4/PBA-10 system was OH. Electron spin resonance analysis and radical trapping experiment revealed that the different catalytic mechanisms were attributed to the confinement effect inside the hollow cavity. This work not only presents a feasible way to prepare rarely-reported double-yolk egg-like nanoreactor, but also provides a new insight to solve the bottlenecks in Fenton-like reaction.

Integrating ecosystem services and landscape connectivity into the optimization of ecological security pattern: a case study of the Pearl River Delta, China.

The ecological security pattern (ESP) focuses on key ecological elements in ecosystems by identifying, combining, and evaluating these elements. This study attempts to identify the ESP of the Pearl River Delta (PRD) and provide suggestions for optimization. Ecosystem services were calculated and applied to construct the ecological resistance surface; morphological spatial pattern analysis (MSPA) and landscape connectivity analysis were used to identify ecological sources; and minimum cumulative resistance (MCR) model was applied to extract ecological corridors and ecological nodes. The results show that during 1995 to 2015, the main landscape transformation occurred between forest, cropland, and urban land, and the location of the transformation was mainly in the central part of the study area. Regarding the ESP, the average resistance value increased from 0.30 to 0.33; the area of ecological sources decreased by 5.12%; the ratio of total cumulative resistance to the length of the corridors increased by 14.82%; and the number of ecological nodes increased from 71 to 99. For the ESP optimization, based on the correction of the resistance surface, 1348 km blue corridors and 61 blue nodes were extracted. Based on hot spot analysis, nine stepping stones were identified. This optimization compensates for the lack of ecological elements in the center of the study area, enhances weaker corridors, and improves the connectivity of the ESP, thus making the ESP more stable and complete. The ESP constructed and optimized in this paper holds great significance and serves as a valuable reference for ecological protection and environmental management.

Construction of Z-scheme heterojunction by coupling Bi2Sn2O7 and BiOBr with abundant oxygen vacancies: Enhanced photodegradation performance and mechanism insight.

Promoting charge migration and enhancing redox ability of photogenerated carriers are important for the development of highly efficient semiconductor-based photocatalyst. Here, BiOBr/Bi2Sn2O7 heterojunction with oxygen vacancies (OVs) was constructed by homogeneously depositing Bi2Sn2O7 nanoparticles on the Vo-BiOBr surface. The experimental results manifested that Vo-BiOBr/Bi2Sn2O7 displayed better performance for rhodamine B, ciprofloxacin, and tetracycline degradation than counterparts without OVs. The characterization results proved OVs played the essential role for enhanced performance via improving the separation efficiency of charge carriers, increasing the visible light harvest, and lowering conduction band position. Moreover, mechanism study revealed that an inner electric field was built at the interface, leading to a Z-scheme path of photogenerated electron. This study provided an efficient strategy for designing highly efficient photocatalyst for solving environmental pollution.

A stable lanthanum-based metal-organic framework as fluorescent sensor for detecting TNP and Fe3+ with hyper-sensitivity and ultra-selectivity.

A new Lanthanum-based luminescent metal-organic framework, {[La(H2O)4(HL)]·H2O} (1), has been successfully synthesized by employing 3,3',5,5'-azodioxybenzenetetracarboxylic acid (H4L) as a rigid organic linker through the solvothermal reactions. 1 exhibits a two-dimensional (2D) layered structure and a three-dimensional (3D) supramolecular structure is formed by hydrogen bonds between the layers. Stability studies indicate that 1 has good chemical stability and thermostability. Meanwhile, the Ksv values for TNP is 4.61 × 104 M-1 with the LOD of 4.13 × 10-6 M and the Ksv value for Fe3+ is 1.22 × 104 M-1 with the LOD of 1.72 × 10-5 M, respectively, which demonstrated that 1 exhibits high sensitivity and excellent selectivity for the detection of TNP and Fe3+via fluorescence quenching. Significantly, 1 shows high regenerability after five recycling progress for sensing Fe3+. The possible mechanisms associated with the luminescent quenching are discussed in detail through some relevant experiments and tests, as well as the DFT calculations. Based on the above excellent properties of 1, it will have extremely potential to be used as a dual functional sensor for both detecting TNP and Fe3+ in aqueous solution, simultaneously.

A luminescent Cd(II)-metal organic frameworks combined of TPT and H3BTC detecting 2,4,6-trinitrophenol and chromate anions in aqueous.

A new luminescence Cd(II)-MOF (1) ([Cd3(BTC)2(TPT)(H2O)2]·4H2O, TPT = tris(4-pyridyl)triazine, H3BTC = 1,3,5-benzenetricarboxylic acid) was successfully synthesized under solvothermal conditions. 1 contains 3D framework which consist of Cd atoms and btc3- anions with the large channels along c axis. Then, tpt ligands locate in the channels by utilizing three N atoms to bridge two Cd1 atoms and one Cd2 atom. 1 not only possesses remarkable thermal stability, but also can steadily exist in different organic solvents and various acid/base solutions (pH = 3-12). Moreover, 1 can detect 2,4,6-trinitrophenol (TNP) and chromate (CrO42-/Cr2O72-) anions with high selectivity and sensitivity in water via the luminescent quenching. The detection limits of 1 for TNP and CrO42-/Cr2O72- are 6.23 µM and 2.13 µM/2.87 µM. The mechanism of TNP luminescence quenching may be attributed to photoinduced electron transfer and resonance energy transfer, and CrO42-/Cr2O72- quenching involves resonance energy transfer and competitive absorption of light. Additionally, 1 has the great anti-interference ability and repeatability for detecting TNP and CrO42-/Cr2O72-, which can display the feasibility of this material as a stable luminescent probe in aqueous system.