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Degradation of melamine in aqueous systems by vacuum UV-(VUV-) photolysis. An alternative to photocatalysis
摘要： VUV-irradiation experiments with aqueous solutions of melamine and related triazine derivatives were carried out in the presence or absence of molecular oxygen. Substrate degradation, total organic carbon and evolution profiles of intermediates were monitored. Relevant mineralization of the substrates was observed, in particular for melamine, its extent depending on the concentration of dissolved O2 and on the number of amino substituents at the s-triazine moiety of the substrate. In all experiments, cyanuric acid was found to be the only persistent final product. Experimental results indicate that the route of reactions leading to mineralization is independent of that leading to amino group substitution. Mechanistic hypotheses are proposed and compared with findings coming from TiO2-based photocatalysis.
关键词： Photocatalysis,Melamine degradation,Cyanuric acid,VUV,Mineralization
更新于2025-09-04 15:30:14
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Selective recognition of salicylic acid employing new fluorescent imprinted membrane functionalized with poly(amidoamine) (PAMAM)-encapsulated Eu(TTA)3phen
摘要： Selective fluorescent molecularly imprinted membrane (FMIM) for salicylic acid (SA) was successfully prepared by phase inversion technique with SA as template molecule, chitosan (CHI) as functional polymer, and Eu(TTA)3phen/PAMAM composed of Eu(TTA)3phen and the dendrimer (PAMAM) as the fluorophore, which was characterized by SEM, AFM, and XPS techniques. The introduction of the hydrophilic Eu(TTA)3phen/PAMAM into FMIM was able to improve the flux and the adsorption capacity of SA with good fluorescent stability. Among the FMIM, the FMIM2 prepared with 2.0% Eu(TTA)3phen/PAMAM in the cast membrane fluid was the optimal fluorescent imprinted membrane for selective detection of SA, which displayed a relatively wider linear range and lower limit of detection (LOD) (24 mg L-1). The imprinted FMIM2 could selectively detect the SA from complicated samples without obvious interference from analogues compared to the non-imprinted FNIM2. Moreover, the FMIM had promising recycling performance. It can be potentially used as an alternative imprinted membrane for selective detection and separation of trace SA in water.
关键词： Salicylic acid,Selective detection and separation,Europium,Dendrimer,Fluorescent molecularly imprinted membrane
更新于2025-09-04 15:30:14
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Gas Adsorption and Fluorescent Sensing Properties of Two Porous Lanthanide Metal-Organic Frameworks Based on 3,5-Bis(2-carboxy-phenoxy)-Benzoic Acid
摘要： Two porous isomorphic 3D Eu(Ⅲ)/Nd(Ⅲ) lanthanide metal?organic frameworks (Ln-MOFs), formulated as {[Eu(BCPB)(H2O)(DMF)]·H2O·1.5CH3OH}n (1) and {[Nd(BCPB)(H2O)(DMF)]·2H2O}n (2), have been designed and synthesized by using the tripodal ligand of 3,5-bis(2-carboxy-phenoxy)-benzoic acid (H3BCPB) under solvothermal condition. Complexes 1 and 2 display 3D (3,6)-c net with the point symbol of {4.62}2{42.610.83}. Furthermore, fluorescent measurements showed 1 has highly selective detection for Fe3+ and CrO4 2- ions in aqueous solution, which shows that it acts as a chemical sensor for detecting Fe3+/CrO4 2- in aqueous solution. Meanwhile, gas adsorption properties of 1 and 2 have also been studied at different temperatures for N2, CH4 and CO2.
关键词： Fluorescent Properties,Adsorption Properties,Lanthanide Metal?Organic Frameworks,3,5-Bis(2-Carboxy-Phenoxy)-Benzoic Acid
更新于2025-09-04 15:30:14
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Kinetic spectrophotometric method for real-time monitoring of ultraviolet photoreactions: A mini-photoreactor
摘要： Photoreactors in research laboratories generally consist of UV-C or UV-A mercury lamps and vessels of volume ranging up to about 1.0 L of solutions (suspensions, solvents, reactants and catalysts). This photoreactor’s design implies in large amounts of chemicals - cost problems, considerable amount of co-generated waste - environmental issues, safety problems and the need of large laboratory space. Currently, there is an effort by the scientific community to apply the principles of “green chemistry”, tending to miniaturize reactors and formats [1-8] and use modern sources of radiation such as light-emitting diodes (UV-LEDs), which are much more environmentally friendly than mercury lamps [9-13]. Another disadvantage of classical photochemical reactors is the withdrawal of aliquots at several times intervals. This procedure modifies the total volume of solutions and, consequently, the total number of absorbed photons per chromophore. Besides that, this methodology is time and labor consuming, and sometimes it is unsafe. In this way, a low amount of experimental points can limit the full kinetic description and lead to misinterpretations in kinetic parameters such as reaction order and rate constants. Accurate determinations are also limited by temperature control, which is not commonly effective in classical photoreactors. Here in it is proposed an interesting mini-photoreactor constituted by one UV-LED and a traditional quartz cuvette of 1.00 cm optical length that allows the reaction execution and, simultaneously, continuous monitoring via UV-Vis spectrophotometry (real-time kinetic analysis). In order to validate the use of this new mini-photoreactor we employed the photodegradation of methylene blue (MB) and salicylic acid (SA) in homogeneous and heterogeneous systems. For the proposition, it is necessary a specific spectrophotometer apparatus with a detection system that is not influenced by external light [14] and a Peltier system for controlling temperature with a mini-bar magnetic agitation. Continuous kinetic monitoring was performed in a spectrophotometer with a xenon flash lamp and silicon diode detectors, which emit flashes only during data collection, which prevents extra photodegradation for very photosensitive samples. Another spectrophotometer’s type that can be employed is that one based on diode-array system, whose external light also does not affect the spectrophotometric measurement.
关键词： methylene blue,mini-photoreactor,UV-LED,real-time monitoring,salicylic acid,ZnO,photodegradation
更新于2025-09-04 15:30:14
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Synthesis and Characterization of Glucuronic Acid Capped CdO and CdS Nanoparticles
摘要： Cadmium oxide and cadmium sulphide nanoparticles have been prepared with variety of stabilizers for different purposes and glucuronic acid is used for capping CdS and CdS nanoparticles. These nanoparticles were prepared by using cadmium acetate with thioacetamide for CdS and cadmium chloride and the strong base for CdO nanoparticles. The as obtained CdO and CdS nanoparticles were characterized by a combination of microscopy and spectroscopic techniques for their morphology, size and crystallinity. The glucuronic acid-capped CdS and CdO nanoparticles showed blue shifts in their absorption band edges and with emission maxima red shifted from the band edge. The particles were obtained with good crystallinity and spherical in shape with relatively narrow size distribution.
关键词： Cadmium sulphide,Cadmium oxide,Nanoparticles,Thioacetamide,Glucuronic acid
更新于2025-09-04 15:30:14
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Optimization of photocatalytic degradation of dye?wastewater?by CuFe<sub>2</sub>O<sub>4</sub>/AgBr composite using response surface methodology
摘要： In this paper, a simple response surface methodology (RSM) based on central composite design (CCD) was applied to determine the optimum processing parameters of photocatalytic degradation of acid red 88 (AR88) by CuFe2O4/AgBr composites. The effect of CuFe2O4 loading, initial concentration of pollutant, and photocatalyst concentration on the yield of AR88 degradation rate was investigated. Based on the statistical experimental design, the maximum degradation rate of 94.7% was achieved under optimal conditions: the 34.69% of CuFe2O4 loading, 16.34mg/L of intial concentration of AR88, 1.51g/L of photocatalyst concentration. The kinetics exploration indicated that the degradation process fitted pseudo-first order kinetic model. What’t more, the trapping experiment of active species demonstrated that ·O2- and ·OH were the dominant species.
关键词： CuFe2O4/AgBr composites,response surface methodology,central composite design,acid red 88,photocatalysis
更新于2025-09-04 15:30:14
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A DNA-based fluorescent reporter maps HOCl production in the maturing phagosome
摘要： Phagocytes destroy pathogens by trapping them in a transient organelle called the phagosome, where they are bombarded with reactive oxygen species (ROS) and reactive nitrogen species (RNS). Imaging reactive species within the phagosome would directly reveal the chemical dynamics underlying pathogen destruction. Here we introduce a fluorescent, DNA-based combination reporter, cHOClate, which simultaneously images hypochlorous acid (HOCl) and pH quantitatively. Using cHOClate targeted to phagosomes in live cells, we successfully map phagosomal production of a specific ROS, HOCl, as a function of phagosome maturation. We found that phagosomal acidification was gradual in macrophages and upon completion, HOCl was released in a burst. This revealed that phagosome–lysosome fusion was essential not only for phagosome acidification, but also for providing the chloride necessary for myeloperoxidase activity. This method can be expanded to image several kinds of ROS and RNS and be readily applied to identify how resistant pathogens evade phagosomal killing.
关键词： hypochlorous acid,phagosome,reactive oxygen species,DNA-based reporter,myeloperoxidase
更新于2025-09-04 15:30:14
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Continuous multi-channel sensing of volatile acid and organic amine gases using a fluorescent self-assembly system
摘要： A new gelator (1) was designed and synthesized through a Knoevenagel condensation reaction between 4-dimethylaminocinnamaldehyde and a gallic acid derivative containing a carbanion. This gelator could form stable organogels in hexane, petroleum ether, DMSO and acetonitrile. The self-assembly processes of 1 in four solvents were carefully investigated via UV-vis absorption, fluorescence, FTIR, XRD, water-contact angles and field emission scanning electron microscopy (FESEM). Nanofibre and microsphere structures were observed in their self-assembly systems. The xerogel 1 film surfaces exhibited different hydrophobicities with water contact angles of 113.5–1551. The J-type aggregation mode was employed in the self-assembly process, and hydrogen bonding and p–p stacking were the main driving forces for organogel formation. Fluorescence emission of organogel 1 from acetonitrile was shifted from 558 nm of its corresponding diluted acetonitrile solution to 601 nm with a red-shift of 43 nm. Interestingly, compound 1 could sensitively respond to volatile acid, and further to organic amine gases along with obvious color changes. The detection limit for trifluoroacetic acid (TFA) by solution 1 in acetonitrile was 1.03 × 10?8 M with a corresponding association constant (K) of 6.85 × 104 M?1. The detection limit for triethylamine (TEA) by solution 1 in acetonitrile with 1.8 eq. of TFA was 1.27 × 10?8 M with a corresponding association constant (K) of 4.027 × 104 M?1. The yellow color of solution 1 could be reversibly changed to colorless in the titration process. At the same time, xerogel 1 exhibited sensitive response abilities for volatile acids and organic amines. The fluorescence of xerogel 1 could be quenched when in contact with a volatile acid within 7 s and recovered under further contact with a volatile amine within 15 s. The detection limit of xerogel film 1 towards trifluoroacetic acid (TFA) gases was 3.2 ppb. Organogel 1 exhibited sensitive response abilities towards TFA and TEA, and then rapidly expressed fluorescence, a gel state and a color change. This research would provide a new window into fast and sensitive detection of volatile acids and organic amines.
关键词： organic amine gases,sensing,volatile acid,fluorescent self-assembly system,gelator
更新于2025-09-04 15:30:14
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Crystal Structure and Luminescent Property of a One-Dimensional Chain Based on 1-(4-Nitrophenyl)-1,2,4-Triazole
摘要： A neutral one-dimensional CdII coordination polymer [Cd(NO2–BDC)(NPT)(H2O)2]n (1) (NO2–H2BDC=5-nitro-1,3-benzenedicarboxylic acid, NPT=1-(4-nitrophenyl)-1,2,4-triazole) is prepared and characterized through IR, elemental and thermal analyses, and single crystal X-ray diffraction. The single crystal X-ray diffraction analysis reveals that complex 1 is comprised of neutral 1D zigzag chains. The luminescence and thermal stability of complex 1 are investigated.
关键词： 1-(4-nitrophenyl)-1,2,4-triazole,one-dimensional chain,luminescence,coordination polymer,synthesis,5-nitro-1,3-benzenedicarboxylic acid
更新于2025-09-04 15:30:14
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Large-Volume Injection Gas Chromatography -Vacuum Ultraviolet Spectroscopy for the Qualitative and Quantitative Analysis of Fatty Acids in Blood Plasma
摘要： Qualitative and quantitative determination of fatty acids in plasma is of extreme importance as these are indicators of metabolic diseases. In this work, a sensitive and rugged method for detecting and quantifying fatty acids (as fatty acid methyl ester derivatives, FAMEs) in blood plasma was developed. The use of large-volume injection (LVI) gas chromatography-vacuum ultraviolet spectroscopy (GC-VUV) for analysis of fatty acids in blood plasma allowed the injection of higher sample volumes to accommodate sufficient analyte on-column for necessary detection ranges with a run time of 45 min. Calibration curves exhibited consistent linearity and reproducibility and were used along with internal standards for the quantification of 11 saturated and 21 unsaturated fatty acids. Intra-day and inter-day (n=6) CVs had an average of 5 and 6%, respectively, and recoveries an average of 105%. The concentrations of EPA, DHA, and AA, as well as the omega-3 index and omega-6/omega-3 ratio, were calculated and compared with clinically actionable measurement ranges. Due to the use of LVI, the more volatile analyte (C8:0) was lost and therefore impossible to quantify. The volatility cutoff was determined to be the C10:0 analyte of a molecular weight of 186.295 g/mol.
关键词： deconvolution,GC-VUV,clinical reference intervals,fatty acid methyl esters,Large volume injection
更新于2025-09-04 15:30:14