Chaocan Zhang

The Cu-MOF-199/single-walled carbon nanotubes modified electrode for simultaneous determination of hydroquinone and catechol with extended linear ranges and lower detection limits.

A novel electrochemical sensor based on Cu-MOF-199 [Cu-MOF-199 = Cu3(BTC)2 (BTC = 1,3,5-benzenetricarboxylicacid)] and SWCNTs (single-walled carbon nanotubes) was fabricated for the simultaneous determination of hydroquinone (HQ) and catechol (CT). The modification procedure was carried out through casting SWCNTs on the bare glassy carbon electrode (GCE) and followed by the electrodeposition of Cu-MOF-199 on the SWCNTs modified electrode. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) were performed to characterize the electrochemical performance and surface characteristics of the as-prepared sensor. The composite electrode exhibited an excellent electrocatalytic activity with increased electrochemical signals towards the oxidation of HQ and CT, owing to the synergistic effect of SWCNTs and Cu-MOF-199. Under the optimized condition, the linear response range were from 0.1 to 1453 μmol L(-1) (RHQ = 0.9999) for HQ and 0.1-1150 μmol L(-1) (RCT = 0.9990) for CT. The detection limits for HQ and CT were as low as 0.08 and 0.1 μmol L(-1), respectively. Moreover, the modified electrode presented the good reproducibility and the excellent anti-interference performance. The analytical performance of the developed sensor for the simultaneous detection of HQ and CT had been evaluated in practical samples with satisfying results.

Synthesis and self-assembly of amphiphilic gradient copolymer via RAFT emulsifier-free emulsion polymerization.

The amphiphilic gradient copolymers of 2,2,2-trifluoroethyl methacrylate (TFEMA) and acrylic acid (AA) have been synthesized by using amphiphilic RAFT agent via emulsifier-free emulsion polymerization with a starved feed method of adding TFEMA. Different cosolvents are added into polymerization system to inhibit AAs homopolymerization of in aqueous phase. RAFT polymerization kinetics under different reaction conditions are discussed in detail. (1)H NMR results indicate that the obtained copolymer has a chain structure with AA segments gradually changing to TFEMA segments. The copolymer latexes exhibit good pH stability (pH value from 5 to 14) and Ca(2+) stability. The self-assembly behavior of gradient copolymers in selective solvents are observed and studied by transmission electron microscopy. All the copolymers can form spherical micelles, but the homogeneity and size of micelles are different.

Toxicity evaluation of CdTe quantum dots with different size on Escherichia coli.

Quantum dots (QDs) have a great potential for applications in nanomedicine. However, a few studies showed that they also exhibited toxicity. We used Escherichia coli (E. coli) as the model to study the effect of CdTe QDs on the cell growth by microcalorimetric technique, optical density (OD(600)) and attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectra. Three size aqueous-compatible CdTe QDs with maximum emission of 543 nm (green-emitting QDs, GQDs), 579 nm (yellow-emitting QDs, YQDs) and 647 nm (red-emitting QDs, RQDs) were tested. The growth rate constants (k) and half-inhibiting concentration (IC(50)) were calculated from the microcalorimetric data. The results indicated that CdTe QDs exhibited a dose-dependent inhibitory effect on cell growth. The order of toxicity is GQDs>YQDs>RQDs. The smaller the particle size of QDs is, the more toxicity it is. ATR-FTIR spectra indicated that the outer membrane of the cell was changed or damaged by the QDs, which may induce QDs and harmful by-products to enter into the cells. These could be one of the reasons that CdTe QDs have cytotoxic effects on E. coli.

Studies on Antibacterial Mechanisms of Copper Complexes with 1,10-phenanthroline and Amino Acid on Escherichia coli

The antibacterial mechanisms of Cu(phen)2Cl2·6H2O, [Cu(phen)(Gly)(H2O)]Cl·3H2O, [Cu(phen)(l-Ser)(H2O)Cl] (1,10-phenanthroline (phen)) on Escherichia coli were investigated. In the inductively coupled plasma atomic emission spectroscopy experiments, it showed that lipophilic phen ligand can cause elevation of intracellular copper, but intracellular copper is not the decisive factor. The UV–vis and gel electrophoresis experiments reveal that the DNA binding and cleavage activity are decisive factors for the antibacterial action of these compounds. It is revealed by the cyclic voltammetry experiments that the redox potential was bound to the cleave activity.

Hydrophilic modification of PVDF porous membrane via a simple dip-coating method in plant tannin solution

To improve the hydrophilicity of polyvinylidene fluoride (PVDF) porous membranes, herein, we report for the first time a low-cost and environmental plant tannin coating, which is strongly constructed on the surface of the PVDF membrane via a simple dip-coating method. An oxidation induced aggregation mechanism was detected in the tannin solution through the use of ultraviolet spectrophotometry (UV-Vis). The morphology and chemical composition of the tannin coated PVDF membrane were characterized via field-emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). After coating with the tannin coating, hydrophilicity and filtration performance are both greatly enhanced, and the modified membranes also have a good emulsion separation performance and excellent antifouling property (after emulsion separation, the flux recovery ratio even reaches 100%). Moreover, these membranes possess outstanding durability that is disclosed by a long-term rinsing experiment. These results indicate that the plant tannin coating has great potential application for the hydrophilic modification of hydrophobic membranes.

CdS QDs-chitosan microcapsules with stimuli-responsive property generated by gas-liquid microfluidic technique.

This article describes a straightforward gas-liquid microfluidic approach to generate uniform-sized chitosan microcapsules containing CdS quantum dots (QDs). CdS QDs are encapsulated into the liquid-core of the microcapsules. The sizes of the microcapsules can be conveniently controlled by gas flow rate. QDs-chitosan microcapsules show good fluorescent stability in water, and exhibit fluorescent responses to chemical environmental stimuli. α-Cyclodextrin (α-CD) causes the microcapsules to deform and even collapse. More interestingly, α-CD induces obvious changes on the fluorescent color of the microcapsules. However, β-cyclodextrin (β-CD) has little influence on the shape and fluorescent color of the microcapsules. Based on the results of scanning electron microscopy, the possible mechanism about the effects of α-CD on the chitosan microcapsules is analyzed. These stimuli-responsive microcapsules are low-cost and easy to be prepared by gas-liquid microfluidic technique, and can be applied as a potential micro-detector to chemicals, such as CDs.

Self-storage: a novel family of stimuli-responsive polymer materials for optical and electrochemical switching.

For most stimuli-responsive polymer materials (SRPMs), such as polymer gels, micelles, and brushes, the responsive mechanism is based on the solubility or compatibility with liquid media. That basis always results in distorting or collapsing the materials appearance and relies on external liquids. Here, a novel kind of SRPMs is proposed. Unlike most SRPMs, liquid is stored within special domains rather than expelled, so it is deforming-free and relying on no external liquid, which is referred to as self-storage SRPMs (SS-SRPMs). The facile and universal route to fabricate SS-SRPMs allows for another novel family of SRPMs. Furthermore, it is validated that SS-SRPMs can drastically respond to outside temperature like switchers, especially for optical and electrochemical responses. Those features hold prospects for applications in functional devices, such as smart optical lenses or anti-self-discharge electrolytes for energy devices.

Joint toxicity of heavy metals and chlorobenzenes to pyriformis Tetrahymena.

Chlorobenzens and heavy metals are frequently detected in the environment, but few studies have assessed the joint toxicity of organic and inorganic contaminants. The joint toxicity of heavy metals and chlorobenzenes was evaluated in the present study. Growth metabolism of the joint toxicity was studied by microcalorimetry at 28°C, the growth constant (k) and inhibitory ratio (I) were calculated. Toxic unit (TU) and additional index (AI) were introduced to determine the outcome in combined tests, and the coexistence of Cu, Cd, Cr(III) and p-chlorobenzene was antagonism, and the effect of Cu, Cd, Cr(III) and o-chlorobenzene, Cu and 1,2,4-trichlorobenzene were synergism. In addition, micro-situation of the cell membrane surface of pyriformis Tetrahymena was observed by SEM. The cells suffered serious damage after sufficient acting time. ATR-FTIR spectra revealed that amide groups and PO2(-) of the phospholipid phospho-diester, both in the hydrophobic end exposed to the outer layer, were the easiest to be damaged.

A simple modified electrode based on MIL-53(Fe) for the highly sensitive detection of hydrogen peroxide and nitrite

A modified matrix of an iron terephthalate metal–organic framework (MIL-53(Fe)), as a simple and efficient electroactive material for use as an electrochemical biosensor, was investigated. The morphology and structure of MIL-53(Fe) were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and X-ray powder diffraction (XRD). The electrochemical properties of the MIL-53(Fe) modified electrode were observed through cyclic voltammetry (CV) and chronoamperometry analysis. The modified electrode (MIL-53(Fe)/GCE) exhibited excellent electrocatalytic activity for the electrochemical reaction of hydrogen peroxide (H2O2) and nitrite (NO2−). Under the optimized experimental conditions, wide linear ranges of 0.1–2000 μM for H2O2 and 0.4–7000 μM for NO2− were obtained, with corresponding detection limits of 0.075 μM and 0.36 μM (S/N = 3), respectively. In addition, the as-prepared electrode also showed excellent reproducibility and long-time stability. Finally, the electrochemical sensor was successfully applied in the analysis of disinfection water and tap water to detect H2O2 and NO2−, respectively.

The action of norfloxacin complexes on Tetrahymena investigated by microcalorimetry

Cu(nor)2·H2O (1), Zn(nor)2·4H2O (2), Ni(nor)2·2H2O (3), [Cu(nor)(phen)]NO3·4H2O (4), [Zn(nor)(phen)]NO3·2H2O (5), and [Ni(nor)(phen)]NO3·3H2O (6) were synthesized and their action on Tetrahymena growth was studied by microcalorimetry. The growth constant (k), inhibitory ratio (I), and half-inhibiting concentration (IC50) were calculated, which showed that the complexes had a strong inhibitory effect on Tetrahymena. All these complexes can inhibit the growth of Tetrahymena more strongly than norfloxacin. The norfloxacin–metal complexes exhibited better inhibitory activity than nor–phen–metal complexes. The power–time curves of Tetrahymena growth in the presence of norfloxacin were also measured. It was found that all complexes showed higher inhibitory activity than norfloxacin. And the inhibitory mechanism was discussed preliminarily. The diverse inhibition may be due to the ability of the complexes to penetrate into cells and the effect of these complexes on the nucleic acid. Microcalorimetry has been used extensively in many biological and chemical investigations as a universal, non-destructive, continuously running, and highly sensitive tool.