Functional graphene-gold nano-composite fabricated electrochemical biosensor for direct and rapid detection of bisphenol A

In this research, the graphene with excellent dispersity is prepared successfully by introducing gold nanoparticle to separate the individual sheets. Various techniques are adopted to characterize the prepared graphene and graphene-gold nanoparticle composite materials. This fabricated new composite material is used as the support material to construct a novel tyrosinase based biosensor for detection of bisphenol A (BPA). The electrochemical performances of the proposed new enzyme biosensor were investigated by differential pulse voltammetry (DPV) method. The proposed biosensor exhibited excellent performance for BPA determination with a wide linear range (2.5 × 10⁻³–3.0 μM), a highly reproducible response (RSD of 2.7%), low interferences and long-term stability. And more importantly, the calculated detection limit of the proposed biosensor was as low as 1 nM. Compared with other detection methods, this graphene-gold nanoparticle composite based tyrosinase biosensor is proved to be a promising and reliable tool for rapid detection of BPA for on-site analysis of emergency BPA related pollution affairs.     

苯基改性的中孔分子筛SBA-15的合成及其磺化

 在酸性条件下用正硅酸乙酯(TEOS)和苯基三乙氧基硅(PTES)直接缩合制备了苯基改性的中孔分子筛Ph-SBA-15,并用紫外光谱、红外光谱、X射线衍射、透射电镜和核磁共振等对改性后的样品进行了表征. 结果表明,在300 ℃下焙烧后,模板剂被脱除,而苯基可完整保留,苯基改性的SBA-15分子筛具有有序结构. 进一步用氯磺酸磺化改性后,可得到苯磺酸化的分子筛,其酸度可达4.19 mmol/g.     

A spectroscopic study on the reaction-controlled phase transfer catalyst in the epoxidation of cyclohexene

The epoxidation of cyclohexene with hydrogen peroxide in a biphase medium (H₂O/CHCl₃) was carried out with the reaction-controlled phase transfer catalyst composed of quaternary ammonium heteropolyoxotungstates [π-C₅H₅N(CH₂)₁₅CH₃]₃[PW₄O₁₆]. A conversion of about 90% and a selectivity of over 90% were obtained for epoxidation of cyclohexene on the catalyst. The fresh catalyst, the catalyst under reaction conditions and the used catalysts were characterized by FT-IR, Raman and ³¹P NMR spectroscopy. It appears that the insoluble catalyst could degrade into smaller species, [(PO₄){WO(O₂)₂}₄]³⁻, [(PO₄){WO(O₂)₂}₂{WO(O₂)₂(H₂O)}]³⁻, and [(PO₃(OH)){WO(O₂)₂}₂]²⁻ after the reaction with hydrogen peroxide and becomes soluble in the CHCl₃ solvent. The active oxygen in the [W₂O₂(O₂)₄] structure unit of these soluble species reacts with olefins to form the epoxides and consequently the corresponding W---Ob---W (corner-sharing) and W---Oc---W (edge-sharing) bonds are formed. The peroxo group [W₂O₂(O₂)₄] can be regenerated when the W---Ob---W and W---Oc---W bonds react with hydrogen peroxide again. These soluble species lose active oxygen and then polymerize into larger compounds with the W---Ob---W and W---Oc---W bonds and then precipitate from the reaction solution after the hydrogen peroxide is consumed up. Part of the used catalyst seems to form more stable compounds with Keggin structure under the reaction conditions.     

Alkanes-assisted low temperature formation of highly ordered SBA-15 with large cylindrical mesopores

Highly ordered SBA-15 silicas with large cylindrical mesopores (approximately 15 nm) are successfully obtained with the help of NH4F by controlling the initial reaction temperatures in the presence of excess amounts of alkanes.     

Determination of total phthalates in edible oils by high‐performance liquid chromatography coupled with photodiode array detection

The previously reported procedure for the determination of the total phthalate in fatty food involved the extraction of phthalates using chloroform/methanol followed by the removal of the solvents before alkaline hydrolysis requiring 20 h and derivatization of phthalic acid. In this study, a phase‐transfer catalyst (tetrabutylammonium chloride) was used in the liquid–liquid heterogeneous hydrolysis of phthalates in oil matrix shortening the reaction time to within 25 min. The resulting phthalic acid in the hydrolysate was extracted by a novel molecular complex based dispersive liquid–liquid microextraction method coupled with back‐extraction before high‐performance liquid chromatography coupled with photodiode array detection. Under the optimal experimental conditions, the linearity of the method was in the range of 0.5–12 nmol/g with the correlation coefficients (r) >0.997. The detection limit (S/N = 3) was 0.11 nmol/g. Intraday and interday repeatability values expressed as relative standard deviation were 3.9 and 7.1%, respectively. The recovery rates ranged from 82.4 to 99.0%. The developed method was successfully applied for the analysis of total phthalate in seven edible oils.     

Phthalate sum determination in farmland soils using high‐performance liquid chromatography with tandem mass spectrometry

A selective and low organic‐solvent‐consuming method of sample preparation combined with high‐performance liquid chromatography and tandem mass spectrometry is introduced for phthalate sum analysis in farmland soil. Sample treatment involves a one‐step hydrolysis of phthalates using methanol and alkaline and tetrabutylammonium bromide for 20 min at 80℃. Then, the resulting phthalic acid in the acidified hydrolysate is extracted using an octanol‐based supramolecular solvent without purification. Under optimized conditions, the correlation coefficients were 0.992–0.999 and standard errors (S_y/x) were 0.018–0.138 for calibration curves within the range of 50–2000 ng/mL. No obvious matrix effect occurred between the pure supramolecular solvent and soil extract. The recovery rates ranged from 91 to 107% with the relative standard deviation ranging from 0.5–7.3%. Intra‐ and interday repeatability, expressed as relative standard deviation, was less than 8.0 and 11.0%, respectively. The detected limit was 2.49 nmol/g, and the quantification limit was 3.64 nmol/g. Fifteen soil samples were analysed, and the background corrected phthalate sum ranged from 1.44 to 120 nmol/g.     

W-SBA-15介孔分子筛的直接合成及其对环己烯环氧化反应的催化性能

 分别以Na2WO4和H2WO4为钨源,以正硅酸四乙酯为硅源直接合成了W-SBA-15介孔分子筛样品,并用小角XRD,N2吸附,FT-IR,UV-Vis,SEM和XRF等手段对合成的分子筛进行了表征. 结果表明,只用P123(EO20PO70EO20)为模板剂时,分子筛中钨的含量只是投料量的一半; 而以P123和十六烷基三甲基溴化铵为混合模板剂时,钨能有效地掺杂到SBA-15分子筛中. 当原料中的Si/W摩尔比为40时,W-SBA-15分子筛中的钨物种以高度分散状态存在,且以H2WO4为钨源比以Na2WO4为钨源更易将钨掺杂到SBA-15介孔分子筛中. W-SBA-15分子筛催化剂对环己烯环氧化反应具有较高的催化活性.     

An aptamer-based colorimetric assay for chloramphenicol using a polymeric HRP-antibody conjugate for signal amplification

We describe an aptamer-based colorimetric assay for chloramphenicol (CAP) based on the ability of anti-single-stranded DNA antibody (anti-ssDNA Ab) to recognize ssDNA, and the catalytic ability of PowerVision (PV), which is a polymeric conjugate of horseradish peroxidase and antibody with a high enzyme-to-antibody ratio. The complementary DNA of the aptamer (cDNA) was immobilized on magnetic gold nanoparticles (Fe₃O₄@Au) and used as a capture probe (AuMNPs-cDNA). The ssDNA Ab and PV were conjugated to AuNPs to form signal tags that recognize ssDNA with anti-ssDNA Ab to form beads containing the amplified probe (AuMNPs-cDNA@anti-ssDNA Ab/PV-AuNPs). The PV on their surface catalyzes the oxidation of the substrate 3,3’,5,5’-tetramethylbenzidine to produce a color change which is quantified by absorptiometry at 652 nm. The assay has a linear calibration plot for CAP in the 0.01 to 100 ng mL⁻¹ range, with a detection limit as low as 3 pg mL⁻¹. The method was successfully employed to detect CAP in real samples. Results were consistent with data obtained using a conventional enzyme-linked immunosorbent assay.

PowerVision- labeled gold nanoparticles acting as signal tag catalyze the H₂O₂-mediated oxidation of TMB for color development, which can be observed by bare eyes and quantified by ultraviolet-visible spectroscopy.

     

Ag/SiO2: a novel catalyst with high activity and selectivity for hydrogenation of chloronitrobenzenes

Ag/SiO2 prepared by an in situ reduction method are found, for the first time, to be highly effective and recyclable catalysts for the selective hydrogenation of a range of chloronitrobenzes to their corresponding chloroanilines, which are of great potential as industrially viable and cheap novel catalysts for the production of chloroanilines.