最新刊期
卷 69 ， 期 3 ， 2023
- 摘要：Monoclinic α-Ag3VO4 photocatalyst was fabricated by a hydrothermal method with the assistance of cetyltrimethylammonium bromide (CTAB), and its morphology and structure were characterized. The photocatalytic activity for degradation of rhodamine B (RhB)and colorless molecule glyphosate (PMG) was tested. And then, the formation mechanism of morphological evolution was proposed. The results show that the prepared Ag3VO4 photocatalysts are monoclinic α-Ag3VO4; SVO-1.0 (CTAB 1.0%) is demonstrated to have the superior photocatalytic activity, and its first-order kinetic constants k for degradation of RhB and PMG are 1.8- and 4.7-fold those of SVO-0. Meanwhile, SVO-1.0 exhibited high stability and anti-photocorrosion. Singlet oxygen and hole are the main active species in the photocatalytic reaction of Ag3VO4 catalyst.关键词：semiconductor;silver-based catalyst;photocatalysis;template method;formation mechanism;stability
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发布时间：2023-07-11 - 摘要：The sunlight-driven photocatalytic hydrogen production is an important way to solve energy shortage and environmental pollution. In this work, natural red clay (R-Clay), a widely available and cheap mineral, was selected as a precursor and applied in photocatalytic hydrogen production under visible light (λ≥420 nm) after thermal modification at 400 oC under N2 atmosphere (labelled as R-Clay400). The results showed that after thermal treatment, the structure and morphology of R-Clay were modified with an increase in specific surface area, a significant decrease in surface hydroxyl groups (—OH) accompanied by an increase in oxygen vacancies and a decrease in bandgap energy, while its hydrogen production activity was significantly increased. The hydrogen production efficiency of R-Clay400 (28.634 μmol·g-1·h-1) was 2.27 times that of R-Clay (12.620 μmol·g-1·h-1). The X-ray photoelectron spectroscopy confirmed that the relative content of oxygen vacancies in R-Clay increased by 13.2% after thermal modification. The results of fluorescence spectroscopy and electrochemical impedance spectroscopy showed that the electron-hole recombination rate and interface charge resistance of R-Clay400 were lower than those of R-Clay, resulting in a higher photocatalytic activity towards hydrogen production under visible light irradiation.关键词：red clay;thermal modification;photocatalysis;hydrogen production
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发布时间：2023-07-11 - 摘要：Zr-based metal-organic framework UiO-66-NH2 was prepared by solvent-thermal method, and a composite metal-organic framework material UiO-66-NH2 (Ce) was prepared by UiO-66-NH2 doped with rare earth metal element Cerium (Ce), the two materials were characterized, and the adsorption performance of UiO-66-NH2 (Ce) on the anion dye acid orange 7 (AO7) was studied. The results show that the morphology and functional groups of the two materials are almost identical, but the specific surface area (618.50 m2/g) and pore volume (0.303 3 cm3/g) of UiO-66-NH2(Ce) are significantly larger than those of UiO-66-NH2. The adsorption capacity of UiO-66-NH2(Ce) for AO7 is 303.0 mg/g and the adsorption rate is 85.8% at pH 5.0, reaction temperature 25 ℃, initial mass concentration of AO7 50 mg/L and reaction time 60 min. The adsorption kinetics of UiO-66-NH2(Ce) to AO7 conforms to the quasi-secondary kinetic model, and the adsorption process conforms to the Langmuir monolayer chemisorption model, and the adsorption process is spontaneous and endothermic. After regeneration by analysis, the adsorption performance of UiO-66-NH2(Ce) decreased, and the regeneration rate was low because the material is powder crystal.关键词：metal-organic frameworks (MOFs);amino;doping;acid orange 7 (AO7);adsorption
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发布时间：2023-07-11 - 摘要：Climate change and human activities may cause change points in hydrological processes, which has serious impacts on the stability of watershed hydrological ecosystems. Based on daily streamflow data during 1961—2020 at 64 hydrological stations across the Yangtze River Basin, the Pettitt test method was used to identify change point in streamflow time series, and the generalized extreme value distribution was used to estimate the ecological water demand. The results show that: 1) due to the regulation of reservoirs and dams, ecological surplus (ecological deficit) tends to increase (decrease) in the dry season of the Yangtze River Basin, while these trends in ecological surplus/deficit are opposite in the wet season; 2) the degree of hydrological alterations in the trunk stream of the Yangtze River Basin is the highest (D0 reaches 50% or more), the river hydrological ecosystem is under high risk (the total DHRAM （Dundee hydrological regime alteration method） score is more than 10 points), and the biodiversity shows a significant downward trend; 3) climate change and human activities have opposite impacts on ecological instream flow of the Yangtze River Basin, that is, climate change/human activities increases/decrease ecological surplus. Overall, climate change is the leading factor affecting ecological surplus (the relative contribution is more than 50%).关键词：hydrological variation;ecological instream flow;ecological water demand;degree of hydrological alteration;Yangtze River Basin
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发布时间：2023-07-11 - 摘要：Isocyanate and polyether polyol were the main raw materials of the reaction, water, methylene chloride, triethylene diamine, stannous caprylate and silicone oil were used as additives, and amino acid solution was used as antibacterial agent. Polyurethane foam modified by amino acid was prepared by one-step foaming method, and coated with polydopamine/carbon nanotubes. A new antibacterial oil-absorbing polyurethane foam was obtained. The structure and morphology of the modified foam were characterized, and the properties of the modified foam were studied. The results showed that the foam has a three-dimensional network structure. Compared with the foam before modification, the fracture strength was increased to about 1.9 times, the water contact angle was increased from 3.28° to 153.25°, and the oil could be adsorbed 23.46 times of its own mass. After 10 cycles, the oil absorption rate remained 96.3% of the initial oil absorption, and the inhibition rate of E. coli and S. aureus was 87.9% and 74.6% respectively.关键词：polyurethane;polydopamine;multi-walled carbon nanotubes;antibacterial property;hydrophobic and oil absorbing materials
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发布时间：2023-07-11 - 摘要：Sodium carboxymethyl cellulose (CMC-Na) with different viscosity-average molecular weight and degree of substitution were synthesized by twice alkalization and etherification process. The rheological properties of CMC-Na in different proportions of glycerol/water mixtures were studied, and the effects of the molecular weight, degree of substitution and concentration of CMC-Na on the rheological properties of mixed system during the preparation of tobacco sheets were studied. The results show that the mixed system is a non-Newtonian fluid with pseudoplasticity, and the rheological properties conform to the Ostwald-de Waele model. Glycerol has a great influence on the rheological properties of the mixed system, and the non-Newtonian properties of mixed system are the strongest when the mass fraction of glycerin is 0.8. The non-Newtonian properties of the hybrid system increases with the increase of the molecular weight, concentration and substitution degree of CMC-Na.关键词：sodium carboxymethyl cellulose (CMC-Na);mixed system;rheological properties;tobacco sheet
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发布时间：2023-07-11 - 摘要：A three-color fluorescent probe that can specifically recognize mercury ion (Hg2+) was constructed using graphene oxide (GO), two fluorescent dyes labeled single-stranded DNA and nucleic acid dye SYBR Green Ⅰ(SG-Ⅰ). A rapid, efficient and highly sensitive method for the quantitative detection of Hg2+ in water was developed through the probe. In this probe, the dyes tetramethyl-6-carboxyrhodamine （TAMRA） and cyanine-5 (Cy-5) are labeled at the 5' end of two single-stranded DNA strands. Some of the bases in the two single-stranded DNA are complementary, and the uncomplementary bases are thymine. In the absence of Hg2+, dye-labeled single-stranded DNA was adsorbed on the surface of GO, and TAMRA and Cy-5 were close to GO. Their fluorescence was quenched by GO, and their fluorescence signals were weak. At this time, SG-Ⅰ was adsorbed on the surface of GO or dissociated in solution, and its fluorescence signal was weak. In the presence of Hg2+, different fluorescent dyes-labeled single-stranded DNA was specifically bound to form double-stranded DNA through the structure of T-Hg2+-T, which separated from the surface of GO, TAMRA and Cy-5 were far away from GO, and their fluorescence signals recovered. At the same time, the fluorescence intensity of SG-Ⅰ was significantly enhanced by binding with double-stranded DNA. Hg2+ could be quantitatively analyzed according to the increase degree of fluorescence intensity of TAMRA, Cy-5 and SG-Ⅰ. Under the optimized conditions, there was a good linear relationship between the sum of fluorescence intensity of TAMRA, Cy-5 and SG-Ⅰ and the concentration of Hg2+ in the range of 1.0×10-9-5.0×10-8 mol/L, and the detection limit (LOD) of the method was 1.1×10-10 mol/L. The recoveries of water samples are 96.00%-105.00%. The method was applied to the detection of Hg2+ in actual water samples, and the satisfactory results were obtained.关键词：mercury ion;dye-labeled nucleic acids;three-color fluorescent probe;synchronous fluorescence analysis
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发布时间：2023-07-11 - 摘要：Using 2B pencil lead as raw material, fluorescent carbon dots (CDs) was prepared in aqueous phase by electric oxidation method, and then CDs@H2O2 was obtained by H2O2 oxidation. CDs and CDs@H2O2 were characterized by electron transmission electron microscopy (TEM), fluorescence spectroscopy, Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The results show that the surface of CDs@H2O2 has more hydroxyl functional groups than CDs. CDs and CDs@H2O2 were respectively used as co-reactant of Ru(bpy)32+ anode electrochemiluminescence (ECL). The ECL signal of Ru(bpy)32+/CDs@H2O2 system was 8.2 times that of Ru(bpy)32+/CDs system. It was confirmed that hydroxyl group was the active functional group of CDs as Ru(bpy)32+ coreactive agent. Based on the quenching effect of dopamine (DA) on ECL signal in Ru(bpy)32+/CDs@H2O2 system, the ECL quenching sensor for DA was constructed. The linear range of detection was 1.6-56.0 μmol/L, and the detection limit was 0.23 μmol/L (S/N=3). The detection of DA concentration in human serum was realized.关键词：carbon dot;dopamine;electrochemiluminescence;coreactant;Ru(bpy)32+;serum
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发布时间：2023-07-11 - 摘要：A core-shell molecularly imprinted polymer (MIP) possessing specific recognition for shikimic acid was prepared through the sol-gel method with metal organic framework MIL-101 as a substrate and shikimic acid as the template molecule. The MIP was characterized by a series of methods, including X-ray diffraction analysis (XRD), Fourier infrared spectroscopy (FT-IR), and transmission electron microscopy analysis (TEM). The results showed that the prepared MIL-101 had octahedral structure and molecularly imprinted polymer shell was uniformly coated on it. The adsorption performance of MIP was evaluated through the adsorption experiment, and the MIP reached adsorption equilibrium within 30 min with a saturated adsorption capacity of 93.16 mg/g. The prepared polymer was used as a solid-phase extraction adsorbent, showing good selective enrichment ability, and could selectively isolate and purify the shikimic acid in the star anise.关键词：shikimic acid;metal organic frameworks;MIL-101;sol-gel method;molecularly imprinted polymer (MIP)
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发布时间：2023-07-11 - 摘要：The chiral reversal mechanism of α-alanine (α-Ala) and trivalent chromium(Cr3+) complexes is investigated at the M06/6-311++G(d,p) and MN15/6-311++G(2df,pd) double level. The effect of aqueous solvent is investigated by using the SMD model method of polarized continuum. The chiral reverse of S-α-Ala·Cr3+ has 3 channels, and the amino group N atom acts as the medium for proton transfer in channel a; the combination of carbonyl group O atom and amino group N atom acts as the medium for proton transfer in channel b; the carbonyl group O atom acts as a medium for proton transfer in channel c. The research on potential energy surface shows: under the gas phase, the chiral reverse activation energies of S-α-Ala·Cr3+ in channel a, b and c are 295.6, 305.5 and 123.6 kJ/mol, respectively; Under the aqueous liquid phase the activation energy of S-α-Ala·Cr3+ decreases to 95.8 kJ/mol in channel a and it decreases to 108.0 kJ/mol in channel b and c. The results show that α-Ala·Cr3+ can be racemized slowly in the gas phase, and the optically pure α-Ala·Cr3+ cannot be preserved for a long time in the gas-solid phase; The racemization rate of α-Ala·Cr3+ is not very slow in aqueous liquid phase, and α-Ala·Cr3+ can be racemated slowly and minimally for supplementing α-Ala and Cr3+ to living organisms.关键词：α-alanine;trivalent chromium;density functional theory;chiral reverse;water solvent effect;energy barrier
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发布时间：2023-07-11 -
Mechanism of Cysteine Molecular Damage Induced by Hydroxyl Radical in Water-Liquid Phase Environment
摘要：The reaction mechanism of cysteine molecular damage induced by hydroxyl radical in water-liquid phase environment was studied by means of M06-2X and MN15 methods based on density functional theory and SMD（solvation model based） model method of self consistent reaction field theory. The study shows that the damage of Cys can be achieved by three ways: OH• extracting its H atom, OH• adding to carboxyl C and single electron transferring to OH• from Cys molecule, all of which could induce Cys damage. Investigation on the potential energy surface shows that the reaction of OH• adding to carboxyl C has the most advantage, and the process is barrier-free; the lowest barriers for OH• radicals extracting α-H and protonating amino group H, mercapto group H and methylene H are 12.5, 4.6, 7.3 and 8.9 kJ/mol, respectively. The reaction of electron transferring to OH• from Cys molecule is a disadvantage channel with the barrier as 93.5 kJ/mol. The results show that OH• can cause Cys molecular damage easily in water-liquid phase environment.关键词：cysteine;hydroxyl radical;density functional theory;transient state;electron transfer;energy barrier;damage- 75
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发布时间：2023-07-11 - 摘要：The optical isomerism reaction mechanism of cysteine (Cys) molecule catalyzed by hydroxyl anion(OH-) in water-liquid phase environment was studied by means of M06-2X and MN15 methods based on density functional theory and SMD model method of self consistent reaction field theory. The study shows that the racemization reaction of amphoteric Cys molecule can be achieved through the process of OH- directly extracting α-H proton and Cys carbanion extracting the proton from water molecule(H2O), it can also be achieved through the process of OH- extracting α-H proton from amphoteric Cys and Cys carbanion extracting the proton from water molecule(H2O) after amphoteric Cys isomerizes to neutral. Investigation on the potential energy surface shows that the activation energy barrier of Cys racemization reaction in the first case is 45.8 kJ/mol, the activation energy barrier of Cys racemization reaction in the second case is 51.6 kJ/mol, both of barriers are much lower than the 104.0 kJ/mol activation barrier of Cys racemization reaction in water-liquid phase environment. The results show that OH- has a good catalytic effect on the reaction of Cys optical isomerism in water-liquid phase environment.关键词：cysteine;hydroxyl anion;density functional theory;transient state;self consistent response field theory;activation energy
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发布时间：2023-07-11 - 摘要：The current detectors are not robust enough to adversarial attacks. In this paper, we introduce a robust and universal adversarial attack scheme based on portrait relighting, by estimating and separating the original light distribution, and re-rendering the image with an elaborately-designed one, which can evade spatial-based, frequency-based and biological signal-based DeepFake detectors. We conduct our experiments to evaluate the efficiency, universality and robustness, and the results show that the attack success rate reaches 99.6% in the case of white box, and the optimal attack rate is 69.8% in the case of black box. Besides, the adversarial examples can resist against common image transformations, which shows great robustness and can be deployed in real-world environment.关键词：DeepFake;adversarial attack;portrait relight
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发布时间：2023-07-11 - 摘要：The fine-grained information in the text cannot be fully used by the existing fine-grained emotion analysis methods, leading to the weak relevance of the contextual semantic representation of the target. Moreover, the target is generally composed of multiple words, and average pooling will lose the content and relationship information inside, resulting in inaccurate classification. This paper proposes a novel classification method based on an interactive attention mechanism with fine-grained information（FGIA）. Our FGIA method can ensure that the interaction between target and context can be effectively completed, and simultaneously calculate the attention vectors of context and target. Finally, emotion classification can be obtained with its guidance. Extensive experimental results on the Chinese Dataset of COVID-19 Online Public Opinion demonstrate that our FGIA can effectively complete emotion classification. Compared with several state-of-the-art methods, our FGIA can yield superior performance according to the evaluation metrics.关键词：emotion classification;fine-grained information;interactive attention
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发布时间：2023-07-11 - 摘要：Hua domain is a generalization of Cartan-Egg domain. Its matrix form is much more complex. We mainly consider the Hua domain , in which
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发布时间：2023-07-11
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