Dual-functional porphyrinic zirconium-based metal-organic framework for the fluorescent sensing of histidine enantiomers and Hg2.

A novel fluorescence sensor based on a porphyrinic zirconium-based metal-organic framework, L-cysteine-modified PCN-222 (L-Cys/PCN-222), was developed to selectively recognize histidine enantiomers and sensitively detect Hg2+. The dual-functional sensor was successfully prepared via the solvent-assisted ligand incorporation method and characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), 1H nuclear magnetic resonance (1H NMR) spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, circular dichroism (CD), X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption-desorption analyses. L-Cys/PCN-222 not only showed a higher quenching response for L-histidine than that for D-histidine with a fast fluorescent response rate of <40 s but also exhibited low detection limits for L- and D-histidine (2.48 µmol L-1 and 3.85 µmol L-1, respectively). Moreover, L-Cys/PCN-222 was employed as a fluorescent and visual sensor for the highly sensitive detection of Hg2+ in the linear range of 10-500 µmol L-1, and the detection limit was calculated to be 2.79 µmol L-1 in surface water. The specific and selective recognition of chiral compounds and metal ions by our probe make it suitable for real field applications.

Enantioseparation by zeolitic imidazolate framework-8-silica hybrid monolithic column with sulfobutylether-ß-cyclodextrin as a chiral additive in capillary electrochromatography.

A zeolitic imidazolate framework (ZIF)-8-silica hybrid monolithic column was prepared by one-step sol-gel method. The stationary phase in the monolithic column was characterized by Fourier-transform infrared spectra, X-ray diffraction, thermogravimetric analysis, nitrogen adsorption/desorption, and zeta potential. The results showed that ZIF-8-silica hybrid monolithic materials had abundant functional groups, good crystallinity, large specific surface area, and good thermal stability. A capillary electrochromatography (CEC) chiral separation system was for the first time constructed with ZIF-8-silica hybrid monolithic column and sulfobutylether-ß-cyclodextrin (SBE-ß-CD) as a chiral additive and was applied to separate the selected single and mixed chiral compounds (13 natural amino acids and 5 chiral pesticides). Under the optimized CEC conditions, all the single analytes achieved baseline separation with resolution of 2.14-5.94 and selectivity factor of 1.06-1.49 in less than 6 min, and the mixed amino acids with similar properties were also simultaneously enantioseparated (Rs ≥ 1.82). Relative standard deviations (RSDs) of migration time and column efficiency were lower than 4.26% and did not change significantly after 200 runs, evidencing excellent reproducibility and stability. These results demonstrate that the application of SBE-ß-CD as a chiral additive for ZIF-8-silica hybrid monolithic columns is a promising method for the separation of chiral compounds.

ZnS:Eu @ZIF-8: Selective formation of ZnS:Eu QDs within a zinc methylimidazole framework for chemical sensing applications.

Light harvesting based on a microporous zeolite imidazole backbone (MOF) has attracted considerable interest as a fluorescent sensor for the detection of analytes. In this work, we have prepared a novel complex containing quantum dots of doped rare earth elements by a one-pot method. to be applied to the fluorescence detection of pollution hazards. Because of the solid framework, the prepared ZnS:Eu@ZIF-8 composite shows desirable fluorescence properties. The selectivity and sensitivity of ZnS:Eu@ZIF -8 to TNP, which has a detection limit of 0.19 µmol/L, is further investigated and its sensing mechanism is discussed by means of fluorescence lifetime measurements in combination with emission and UV spectra. It should also be noted that this is the first doped quantum dot to be encapsulated in a MOF to be used for the potential detection of phenolic compounds in the aqueous environment, while the framework remains in place and no structural changes have occurred.

Chiral covalent organic framework-based open tubular capillary electrochromatography column for enantioseparation of selected amino acids and pesticides.

A novel chiral covalent organic framework (CCOF) was synthesized with an imine covalent organic framework TpBD (synthesized via Schiff-base reaction between phloroglucinol (Tp) and benzidine (BD)) modified using (1S)-(+)-10-camphorsulfonyl chloride as chiral ligand by chemical bonding method for the first time, and was characterized by X-ray diffraction, Fourier-transform infrared spectra, X-ray photoelectron spectroscopy, nitrogen adsorption/desorption, thermogravimetry analysis, and zeta-potential. The results revealed that the CCOF had good crystallinity, high specific surface area and good thermal stability. Then, the CCOF was employed as stationary phase in open-tubular capillary electrochromatography (OT-CEC) column (the CCOF-bonded OT-CEC column) for enantioseparation of 21 single chiral compounds (12 natural amino acids including acidic, neutral and basic, 9 pesticides including herbicides, insecticides and fungicides) and simultaneous enantioseparation of mixture amino acids and pesticides with similar structures or properties. Under the optimized CEC conditions, all the analytes reached the baseline separation with high resolutions of 1.67-25.93 and selectivity factors of 1.06-3.49 in 8 min. Finally, the reproducibility and stability of the CCOF-bonded OT-CEC column were measured. Relative standard deviations (RSDs) of retention time and separation efficiency were 0.58-4.57% and 1.85-4.98%, and not obviously changed after 150 runs. These results demonstrate that COFs-modified OT-CEC explore a promising method to separate chiral compounds.

A chiral fluorescent COF prepared by post-synthesis modification for optosensing of imazamox enantiomers.

We report a post-synthesis modification for the preparation of a novel chiral fluorescent covalent organic framework (COF) for selective recognization of imazamox enantiomers. In this study, chiral COF was firstly synthesized via a Schiff-base reaction between 2,5-dihydroxyterephthalaldehyde (Dha) and 1,3,5-tris(4-aminophenyl)benzene (Tab) followed by a nucleophilic substitution using (1S)-(+)-10-camphorsulfonyl chloride as chiral modifier. The resulting regular spherical chiral COF Dha Tab not only presented the high optical efficiency, strong covalent bond structure, good crystallinity, large specific surface area but also showed the specific enantioselectivity and quick identification for imazamox enantiomers among five pesticide enantiomers (S/R-imazamox, acephate, acetochlor, propisochlor and metalaxyl). The detection limits for S- and R-imazamox were 4.20 µmol/L and 3.03 µmol/L, respectively. Meanwhile, the enantiomeric excess value (5.30 %) manifested that the chiral COF Dha Tab had the strong adsorption ability to imazamox enantiomers and more higher affinity for R-imazamox. This chiral fluorescent COF opened up a new way for the recognition of enantiomers.

Preparation of a zeolite imidazole skeleton-silica hybrid monolithic column for amino acid analysis via capillary electrochromatography.

We developed a novel, convenient and low-cost one-pot strategy for preparing a zeolitic imidazolate framework-8 (ZIF-8)-silica hybrid monolithic column by adding ZIF-8 directly to a polymer solution of the silica matrix. The simulated stationary phase and monolithic column prepared under optimal conditions were characterized using X-ray diffraction, scanning electron microscopy, Fourier-transform infrared spectroscopy, thermogravimetric analysis nitrogen physisorption and zeta potential. The results obtained confirmed the successful introduction of ZIF-8 into the silica monolithic column, and the prepared monolithic column exhibited good permeability and physicochemical stability. A capillary electrochromatography method was developed based on a ZIF-8-silica hybrid monolithic column through which 15 mixed amino acids, 4 neutral compounds, 4 nipagin esters and 2 chlorinated fungicides were separated in 14, 5, 7 and 6 min, respectively, under optimal conditions. The relative standard deviations retention times and column efficiencies in run-to-run, day-to-day and column-to-column varied in the ranges of 1.90%-2.21%, 2.13%-2.51% and 3.08%-6.65%, respectively, which demonstrated that ZIF-8-silica hybrid monolithic column exhibited satisfactory reproducibility and stability. The incorporation of ZIF-8 into a silica monolithic column is a promising method for preparing novel monolithic columns composed of a metal-organic framework.

One-pot synthesis of a novel chiral Zr-based metal-organic framework for capillary electrochromatographic enantioseparation.

A novel chiral stationary phase (CSP) of Zr-based metal-organic framework, l-Cys-PCN-224, was prepared by one-pot method and applied for the enantioseparation by capillary electrochromatography. The CSP was characterized by X-ray diffraction, thermogravimetric analysis, X-ray photoelectron spectroscopy, Fourier-transform infrared spectra, nitrogen adsorption/desorption, circular dichroism spectrum, zeta-potential, and so on. The results revealed that the CSP had good crystallinity, high specific surface area (2580 m2 /g), and good thermal stability. Meanwhile, the cross-section of l-Cys-PCN-224-bonded open-tubular (OT) column was observed by a scanning electron microscope, which proved the successful bonding of l-Cys-PCN-224 particles to the inner wall. Relative standard deviations of the column efficiencies were 3.87%-9.14%, and not obviously changed after 200 runs, which indicated that l-Cys-PCN-224-bonded OT column had the better stability and reproducibility. Excellent chiral separation performance was verified with nine kinds of natural amino acids including acidic, neutral, and basic as the analytes. All amino acids studied achieved good separation with the resolution of 1.38-13.9 and selector factor of 1.11-3.71. These results demonstrated that the CSP had an excellent potential in the chiral separation field.

A covalent organic framework for chiral capillary electrochromatography using a cyclodextrin mobile phase additive.

Covalent organic frameworks (COFs) have been recognized as promising solid phases in capillary electrochromatography (CEC). Imine-based COF-coated open-tubular CEC column (COF TpBD-coated OT column) was prepared and characterized by X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectra, thermogravimetric analysis (TGA), nitrogen adsorption/desorption (Brunauer-Emmett-Teller [BET]), and scanning electron microscopy (SEM). The results showed that the column efficiency was up to 26,776 plate/m, and the thickness of stationary phase was about 6.00 µm for the column prepared under the optimal conditions. Enantioseparation of 15 kinds of the single chiral compounds (histidine, arginine, lysine, leucine, threonine, methionine, valine, aspartic acid and glutamic acid, fipronil, diclofop, imazamox, quizalofop-p, imazethapyr, and acephate) and 3 kinds of mixed amino acids racemaces (valine, methionine, and glutamic acid) were performed with three methods: capillary electrochromatography with COF TpBD-coated OT column (Method 1), CEC with COF TpBD-coated OT column as the separation channels, and capillary electrophoresis (CE) with HP-ß-CD as the chiral mobile phase additive (Method 2) and CE with HP-ß-CD as the chiral mobile phase additive (Method 3). Separation efficiency and chiral selectivity of Method 2 was best among the three methods. Under the optimal separation conditions of Method 2, all the enantiomers reached the baseline separation regardless of the single chiral compounds or the mixed amino acids. Relative standard deviation (RSDs) of the mean column efficiency for reproducibility and stability was in the range of 0.46-1.49%. This combination of CEC and CE has great potential for use in chiral separation.

Dual-emission ratiometric fluorescence probe based on copper nanoclusters for the detection of rutin and picric acid.

In this paper, polyvinylpyrrolidone-templated copper nanoclusters (PVP-CuNCs) were synthesised using a hydrothermal method. Through the electrostatic interaction between PVP-CuNCs and rhodamine 6G, a dual-emission ratiometric fluorescent probe was constructed, and two well-separated emission peaks appeared at 420 nm and 570 nm. The selective detection of rutin and picric acid was achieved by fitting the relationship between the ratiometric fluorescence intensity (F420/F570) and the concentration of the target detection substance. The limits of detection of rutin and picric acid were 0.84 µM and 0.27 µM, respectively. The synthesised material has high stability and successfully allows the determination of rutin content in drugs and picric acid content in water samples with satisfactory recoveries.

ß-Cyclodextrin-modified covalent organic framework as chiral stationary phase for the separation of amino acids and ß-blockers by capillary electrochromatography.

Covalent organic frameworks (COFs) as a novel stationary phase have attracted much attention in the field of chromatography owing to their permanent nanoscale porosity, higher surface area, and exceptional stabilities. Here, a novel isocyanate-ß-cyclodextrin-modified COF (MDI-ß-CD-modified COF) was synthesized using isocyanate-ß-cyclodextrin as the chiral selector and imine-based TpPa-1 COF as the matrix by a bottom-up strategy. The reaction condition and the structure of MDI-ß-CD-modified COF were optimized and characterized by X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectra, nitrogen adsorption/desorption (Brunauer-Emmett-Teller [BET]), and thermogravimetric analysis (TGA). And then the coated open-tubular column (OT column) was prepared using MDI-ß-CD-modified COF as chiral stationary phase (CSP) by in situ growth approach, which exhibited excellent stability and repeatability. For seven consecutive runs, the intraday and interday relative standard deviations (RSDs) were in range from 0.35% to 2.21% for the migration time of histidine. The column-to-column reproducibility ranged from 2.39% to 3.08%. Meanwhile, the separation of eight compounds including four amino acids and four ß-blockers by capillary electrochromatography sufficiently verified the favorable chiral resolution properties of the MDI-ß-CD-modified COF-coated OT column. This strategy of fabricating MDI-ß-CD-modified COF-coated OT column expanded the application of imine-based COFs in chromatographic analytical fields.

Hyphenation of field-amplified sample injection and transient isotachophoresis in CE for the determination of sotalol and metoprolol in human urine samples.

A sensitive approach of capillary electrophoresis coupled with field-amplified sample injection and transient isotachophoresis was developed for the simultaneous determination of two ß-blockers: sotalol and metoprolol. In this dual focusing technique, the samples were prepared via only dissolution in ultrapure water and then injected electrokinetically. Phosphate acted as both the background electrolyte and the leading electrolyte. Its optimized concentration was 80 mM. A total of 25 mM of glycine was used as the terminating electrolyte. Under optimum conditions, good separation of sotalol and metoprolol was achieved within 10 min. In comparison with the conventional method, the sensitivity enhancement factors were up to 1031 and 919 for sotalol and metoprolol, respectively. The proposed method was employed in the determination of sotalol and metoprolol in spiked human urine samples. The limits of detection and limits of quantitation obtained via ultraviolet detection were 5 and 12 ng/mL, respectively, for sotalol, and 10 and 25 ng/mL, respectively, for metoprolol. The intraday repeatability values were lower than 2.7 and 1.7% for peak area and migration time, respectively. The assay is a simple and efficient strategy with potential for application in clinical and biochemical laboratories for monitoring sotalol and metoprolol.

Determination of sulfamerazine in aquatic products by molecularly imprinted capillary electrochromatography.

A molecularly imprinted monolith was prepared and evaluated for the special selective separation of sulfamerazine (SMR) by capillary electrochromatography (CEC). The single-step in situ polymerization method was applied through thermally immobilized vinyl groups of itaconic acid and a derivatization capillary column using SMR as the template. The monolith with optimal selectivity and permeability was performed at 45°C for 7 h according to the molar ratios of 1 : 4 : 10 (template/functional monomer/cross-linker). Under the optimized separation conditions of 75% acetonitrile in 20 mM phosphate buffer with pH 5.0, 15 kV applied voltage and 20°C column temperature, the imprinted monolith showed strong recognition ability for SMR and high column performance. Finally, the molecularly imprinted monolith coupled with the CEC method was successfully developed for the quantification of SMR in aquatic products, which was properly validated by a good linear relationship, recoveries and limit of detection. The coupling technique of the molecularly imprinted technology and CEC achieved pre-treatment enrichment and separation analysis in only one miniaturized chromatographic column.

Preparation and characterization of a new open-tubular capillary column for enantioseparation by capillary electrochromatography.

In order to use the enantioseparation capability of cationic cyclodextrin and to combine the advantages of capillary electrochromatography (CEC) with open-tubular (OT) column, in this study, a new OT-CEC, coated with cationic cyclodextrin (1-allylimidazolium-ß-cyclodextrin [AI-ß-CD]) as chiral stationary phase (CSP), was prepared and applied for enantioseparation. Synthesized AI-ß-CD was characterized by infrared (IR) spectrometry and mass spectrometry (MS). The preparation conditions for the AI-ß-CD-coated column were optimized with the orthogonal experiment design L9 (34 ). The column prepared was characterized by scanning electron microscopy (SEM) and elemental analysis (EA). The results showed that the thickness of stationary phase in the inner surface of the AI-ß-CD-coated columns was about 0.2 to 0.5 µm. The AI-ß-CD content in stationary phase based on the EA was approximately 2.77 mmol·m-2 . The AI-ß-CD-coated columns could separate all 14 chiral compounds (histidine, lysine, arginine, glutamate, aspartic acid, cysteine, serine, valine, isoleucine, phenylalanine, salbutamol, atenolol, ibuprofen, and napropamide) successfully in the study and exhibit excellent reproducibility and stability. We propose that the column, coated with AI-ß-CD, has a great potential for enantioseparation in OT-CEC.

Facile Synthesis and High Activity of Novel Composite C/Fe-BiVO4 Photocatalyst for Degradation of Cipfloxacin.

A novel C/Fe-BiVO4 nanosheet composite photocatalyst combining the properties of both semiconductor and Fenton like catalyst was prepared via a two-step method involving Resin carbonization and hydrothermal process. The samples were characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM) and energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), UV-vis diffuse reflectance spectra (DRS), X-ray photoelectron spectroscopy (XPS), Fourier transformed infrared spectroscopy (FT-IR) and nitrogen adsorption-desorption measurements and fluorescence spectrum technique. Structure analyses indicated that C/Fe-BiVO4 presented a nanosheet and macro-meso dual porosity structure. Photocatalytic degradation of cipfloxacin (CIP) (10 mg/L) was studied using C/Fe-BiVO4 under simulated solar light (SSL) irradiation in a cylindrical reactor. Three experimental parameters were chosen as independent variables: pH, C/Fe-BiVO4 concentration, and H2O2 concentration. The catalyst shows high catalytic activity in cipfloxacin photodegradation reaction with the cipfloxacin conversion efficiency higher than 95.61% at experimental conditions (catalyst dose, 0.75 g · L-1; H2O2 dose, 200 mg · L-1; solution pH, 5.0). The process obeyed the pseudo first-order kinetics by assuming a constant concentration of OH•. The as-prepared composite exhibited high efficiency in the photocatalytic decomposition of Cipfloxacin (CIP) by the assistance of H2O2. This method is promising due to its inexpensive starting materials and good photocatalyst for degradation of emerging micropollutants.

Template synthesis of the Cu2O nanoparticle-doped hollow carbon nanofibres and their application as non-enzymatic glucose biosensors.

The cuprous oxide nanoparticle (Cu2O NP)-doped hollow carbon nanofibres (Cu2O/HCFs) were directly synthesized by the anodic aluminium oxide (AAO) template. The doped Cu2O NPs were formed by in situ deposition by direct reduction reaction of precursor carbonization in thermal decomposition and could act as functionalized nanoparticles. The synthesized Cu2O/HCFs were characterized in detail by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and inductively coupled plasma mass spectrometry (ICP-MS). The results reveal that Cu2O/HCFs have a tubular structure with an average diameter of approximately 60 nm. The shape of the Cu2O/HCFs is straight and Cu2O NPs are uniformly distributed and highly dispersed in HCFs. Cu2O/HCFs have good dispersibility. The electrochemical activity of Cu2O/HCFs was investigated by cyclic voltammetry (CV), the glucose sensors display high electrochemical activity towards the oxidation of glucose. Cu2O/HCFs can effectively accelerate the transmission of electrons on the electrode surface. Cu2O/HCFs are applied in the detection of glucose with a detection limit of 0.48 µM, a linear detection range from 7.99 to 33.33 µM and with a high sensitivity of 1218.3 µA cm-2 mM-1. Moreover, the experimental results demonstrate that Cu2O/HCFs have good stability, reproducibility and selectivity. Our results suggest that Cu2O/HCFs could be a promising candidate for the construction of non-enzymatic sensor.

Activity, toxicity, molecular docking, and environmental effects of three imidazolinone herbicides enantiomers.

All imidazolinone (IMI) herbicides are chiral consisting of two enantiomers; however, studies on the enantioselectivities of their interactions are limited. This study is a systematic assessment of the enantiomers and racemates of IMI herbicides, including semi-preparation and determination of absolute configurations, stereoselective bioactivity toward target organisms (Echinochloa crus-galli and Microcystis aeruginosa), and toxicity toward Michigan Cancer Foundation-7 (MCF-7) cells. R-imidazolinones were found to be more active than S-IMIs in the inhibition of target organisms, and neither enantiomer had estrogenic activity. Moreover, the relationship between the molecular structures and the efficiency of target growth inhibition by the IMI herbicides was investigated. Molecular modeling provided the rational structural basis for the enantioselectivity of the acetohydroxyacid synthase (AHAS) activity of the IMIs. These findings encourage the application of enantiopure R-IMI herbicides to capitalize on their advantages over the racemates.

Behavior and distribution of heavy metals including rare Earth elements, thorium, and uranium in sludge from industry water treatment plant and recovery method of metals by biosurfactants application.

In order to investigate the behavior, distribution, and characteristics of heavy metals including rare earth elements (REEs), thorium (Th), and uranium (U) in sludge, the total and fractional concentrations of these elements in sludge collected from an industry water treatment plant were determined and compared with those in natural soil. In addition, the removal/recovery process of heavy metals (Pb, Cr, and Ni) from the polluted sludge was studied with biosurfactant (saponin and sophorolipid) elution by batch and column experiments to evaluate the efficiency of biosurfactant for the removal of heavy metals. Consequently, the following matters have been largely clarified. (1) Heavy metallic elements in sludge have generally larger concentrations and exist as more unstable fraction than those in natural soil. (2) Nonionic saponin including carboxyl group is more efficient than sophorolipid for the removal of heavy metals in polluted sludge. Saponin has selectivity for the mobilization of heavy metals and mainly reacts with heavy metals in F3 (the fraction bound to carbonates) and F5 (the fraction bound to Fe-Mn oxides). (3) The recovery efficiency of heavy metals (Pb, Ni, and Cr) reached about 90-100% using a precipitation method with alkaline solution.