Saier Wang

This study examines the fluorescence characteristics of dissolved organic matter (DOM) in soils from different periods of rice–crayfish integrated systems (RCISs) in China. Utilizing three-dimensional excitation–emission matrix (3D-EEM) fluorescence spectroscopy, the study investigated the hydrophobicity, molecular weight distributions, and fluorescence properties of DOM in 2-, 5-, and 7-year RCIS operations, with rice monoculture (RM) serving as a control. The findings indicate that in the initial 2 years of an RCIS, factors such as rice straw deposition, root exudates, and crayfish excretions increase dissolved organic carbon (DOC) release and alter DOM composition, increasing the humic acid content in the soil. As the system matures at 5 years, improvements in soil structure and microbial activity lead to the breakdown of high-molecular-weight humic substances and a rise in small-molecular-weight amino acids. By the 7-year mark, as the aquatic ecosystem stabilizes, there is an increase in humic substances and the humification index in the soil DOM. These variations in DOM properties are essential for understanding the effects of integrated farming systems on soil quality and sustainability.

As a potential adsorbent material, loose, porous livestock manure biochar provides a new approach to livestock manure resource utilization. In this study, coconut husks (CH) and livestock manure, i.e., cow dung (CD), pig manure (PM), and chicken manure (CM) were used as biomass precursors for preparation of biochar via high-temperature pyrolysis and CO₂ activation. Characterization technologies, such as scanning electron microscopy, Fourier transform infrared spectroscopy, adsorption–desorption isotherms, and pore size distributions, were used to study the microscopic morphologies and physicochemical properties of unactivated and activated biochar materials. The results showed that CD biochar provides better adsorption performance (up to 29.81 mg H₂S/g) than CM or PM biochar. After activation at 650° for 1 h, the best adsorption performance was 38.23 mg H₂S/g. For comparison, the CH biochar removal performance was 30.44 mg H₂S/g. Its best performance was 38.73 mg H₂S/g after 1 h of activation at 750 °C. Its best removal performance is equivalent to that of CH biochar activated at a temperature that is 100 °C higher. Further material characterization indicates that the H₂S removal performance of livestock-manure–derived biochar is not entirely dependent on the specific surface area, but is closely related to the pore size distribution.

Fluorescence excitation–emission matrix (EEM) spectroscopy is a powerful tool for characterizing dissolved organic matter (DOM), a key component of anaerobic digestion. In this study, the fluorescence characteristics of DOM during 55 days of anaerobic digestion of oil crop straw inoculated with rumen liquid were investigated. EEM spectroscopy coupled with parallel factor analysis (PARAFAC) showed that three major fluorescence components, tyrosine- (C₁), humic- (C₂) and tryptophan-like substances (C₃), were identified in all DOM samples. The F_max values of C₁ and C₃ increased rapidly during the first 5 d, decreased dramatically from day 5 to day 35, and then remained stable, while C₂ was not biodegraded. The changes in the F_max values of the fluorescence components reflected the biodegradation of lignin and/or embedded cellulose by rumen microorganisms. The changes in the Stokes shift of the fluorescence peak were readily explained by the variation in the hydrophobic/hydrophilic fraction distribution. The humidification index (HIX) and A : T ratio of the DOM decreased after 5 d and then increased gradually. Compared with the McKnight fluorescence index (MFI), the Y fluorescence index (YFI) was better able to track the evolution of the DOM. Correlation analysis of the different fluorescence indices (intensities) and absorbance indices was also carried out. The EEM-PARAFAC individual components, HIX and A : T ratio were conveniently used to characterize the degree of anaerobic conversion of the organic matter, and the peak at the Stokes shift of ∼1.0 μm⁻¹ was used as one of the indicators showing the stabilization of anaerobic digestion. These findings may assist in developing fluorescence technology for monitoring the anaerobic digestion of crop straw.

One two-dimensional Fe-based metal–organic framework (FeSC1) and one one-dimensional coordination polymer (FeSC2) have been solvothermally prepared through the reaction among FeSO₄·7H₂O, the tripodal ligand 4,4′,4″-s-triazine-2,4,6-triyl-tribenzoate (H₃TATB), and flexible secondary building blocks p/m-bis((1H-imidazole-1-yl)methyl)benzene (bib). Given that their abundant interlayer spaces and different coordination modes, two compounds have been employed as battery-type electrodes to understand how void space and different coordination modes affect their performances in three-electrode electrochemical systems. Both materials exhibit outstanding but different electrochemical performances (including distinct capacities and charge-transfer abilities) under three-electrode configurations, where the charge storage for each electrode material is mainly dominated by the diffusion-controlled section (i ∝ v^0.5) through power-law equations. Additionally, the partial phase transformations to more stable FeOOH are also detected in the long-term cycling loops. After coupling with the capacitive carbon-based electrode to assemble into the semi-solid-state battery–supercapacitor-hybrid (sss-BSH) devices, the sss-FeSC1//AC BSH device delivers excellent capacitance, superior energy and power density, and longstanding endurance as well as the potential practical property.

With the rapid development of metal–organic frameworks (MOFs), a variety of MOFs and their derivatives have been synthesized and reported in recent years. Commonly, multifunctional aromatic polycarboxylic acids and nitrogen-containing ligands are employed to construct MOFs with fascinating structures. 4,4′,4′′-(1,3,5-Triazine-2,4,6-triyl)tribenzoic acid (H₃TATB) and the bidentate nitrogen-containing ligand 1,3-bis[(imidazol-1-yl)methyl]benzene (bib) were selected to prepare a novel Zn^II-MOF under solvothermal conditions, namely poly[[tris{μ-1,3-bis[(imidazol-1-yl)methyl]benzene}bis[μ₃-4,4′,4′′-(1,3,5-triazine-2,4,6-triyl)tribenzoato]trizinc(II)] dimethylformamide disolvate trihydrate], {[Zn₃(C₂₄H₁₂N₃O₆)₂(C₁₄H₁₄N₄)₃]·2C₃H₇NO·3H₂O} _n (1). The structure of 1 was characterized by single-crystal X-ray diffraction, IR spectroscopy and powder X-ray diffraction. The properties of 1 were investigated by thermogravimetric and fluorescence analysis. Single-crystal X-ray diffraction shows that 1 belongs to the monoclinic space group Pc. The asymmetric unit contains three crystallographically independent Zn^II centres, two 4,4′,4′′-(1,3,5-triazine-2,4,6-triyl)tribenzoate (TATB³⁻) anions, three complete bib ligands, one and a half free dimethylformamide molecules and three guest water molecules. Each Zn^II centre is four-coordinated and displays a distorted tetrahedral coordination geometry. The Zn^II centres are connected by TATB³⁻ anions to form an angled ladder chain with large windows. Simultaneously, the bib ligands link Zn^II centres to give a helical Zn–bib–Zn chain. Furthermore, adjacent ladders are bridged by Zn–bib–Zn chains to form a fascinating three-dimensional self-penetrated framework with the short Schläfli symbol 6⁵·7·8¹³·9·10. In addition, the luminescence properties of 1 in the solid state and the fluorescence sensing of metal ions in suspension were studied. Significantly, compound 1 shows potential application as a fluorescent sensor with sensing properties for Zr⁴⁺ and Cu²⁺ ions.

Synthesizing kinetically stable coordination polymers (CPs) through ligand functionalization can effectively improve their supercapacitive performances. Herein, we have successfully synthesized three novel and topological Co-CPs by variation of flexible N-donor ligand and inorganic anions, namely interpenetrated [Co(HTATB)(o-bib)]•H2O, extended 2D layered Co(HTATB)(m-bib)•2H2O and 3D Co(HTATB)(m-bib), where bib is the flexibly N-donor bis((1H-imidazol-1-yl)methyl)benzene linker (o- and m- means ortha- and metra- separately) and HTATB is the deprotonation mode from 4,4',4''-s-triazine-2,4,6-triyl-tribenzoicacid (H3TATB). The various Co-CPs have been directly applied in the field of supercapacitors. All these framework materials exhibit high capacitance, excellent energy delivery efficiency and good cycling performance. For instance, the maximum specific capacitance for penetrated 3D networks is 2572 F g-1 at 2.0 A g-1, and the mean energy delivery efficiency is up to 92.7% based on the tested current densities. Comparing 2D layered and extended 3D networks, the 3D interpenetrated and polythreaded architectures, which could provide more active sites and thus promote fast charging and discharging process. Furthermore, the Li+ uptake-release abilities for the Co-based CPs are also investigated and the initial discharge capacity value for the 3D interpenetrated structures can reach up to 1792 mAh g-1 at a current density of 50 mA g-1.