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A novel NiMoO4@NiMoS4/NF nanocomposite is facilely grown on nickel foam (NF) via hydrothermal reaction and high-temperature calcination methods. The NiMoO4@NiMoS4/NF possesses a specific nanorods@nanosheets core–shell structure, greatly facilitating the transfer of electrons and ions. So, the NiMoO4@NiMoS4/NF shows excellent electrochemical performance. When a current density is 1 A g−1, the specific capacity (Cp) of NiMoO4@NiMoS4/NF reaches 1996 C g−1, which is 7 times that of single NiMoO4/NF, and its Cp is higher than the Cp of other Ni-Mo-based electrode materials reported in the literatures. Moreover, the NiMoO4@NiMoS4/NF has a long cycling life, and its capacity retention rate reaches 83.1% after 5000 cycles at 20 A g−1. The hybrid supercapacitor—NiMoO4@NiMoS4/NF-2//AC with NiMoO4@NiMoS4/NF as the positive electrode and AC as the negative electrode has an energy density of 32.75 Wh kg−1 and a power density of 725.09 W kg−1. So the NiMoO4@NiMoS4/NF is a promising high-performance electrode material for battery-type hybrid supercapacitors. [ABSTRACT FROM AUTHOR]

In this work, the binary nanocomposite of crosslinked polyaniline nanorods (CPANINRs) and molybdenum disulfide (MoS2) is first synthesized by in situ polymerization, and CPANINRs/MoS2 on functionalized carbon cloth (CPANINRs/MoS2/FCC) is facilely constructed by a drop-casting method. The composition, morphology, and structure of the CPANINRs, MoS2, and CPANINRs/MoS2 binary nanocomposite are characterized by transmission electron microscope (TEM), scanning electron microscope (SEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The electrochemical properties of the MoS2/FCC, CPANINRs/FCC, and CPANINRs/MoS2/FCC are tested by cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD). The experiment results show that the CPANINRs/MoS2/FCC exhibits excellent stability and high specific capacitance, and its specific capacitance reaches 618.75 F g−1 at a current density of 0.5 A g−1. The CPANINRs/MoS2/FCC has a long cycling life and the capacity retention of 91.46% is obtained after 2000 cycles at a large current density of 10 A g−1. Moreover, the CPANINRs/MoS2/FCC-based symmetric supercapacitor also exhibits excellent rate performance and good cycling stability. The specific capacitance based on the total mass of the two electrodes is 106.4 F g−1 at a current density of 0.5 A g−1 and the capacitance retention of 93.6% is obtained after 2000 cycles. [ABSTRACT FROM AUTHOR]

Bulk graphitic carbon nitride (g-CN) was obtained by pyrolysis of urea at 600 °C. The material was then subjected to protonation and exfoliation to obtain strongly fluorescent g-CN nanosheets. These nanosheets are representing a two-dimensional layered material that emits strong blue fluorescence peaking at 434 nm, and their quantum yield of up to 10.3 % is much higher than that of bulk g-CN (6.0 %). It was found that Cu(II) ions quench the fluorescence of the nanosheets due to photo-induced electron transfer (PET), probably the result of the stronger binding affinity between Cu(II) and the nitrogen and oxygen functional groups of the nanosheets. The probe responds to Cu(II) in the 0.01 to 0.4 nM concentration range, with a 8 pM detection limit. The method was applied to the determination of Cu(II) in spiked water samples. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

A new electrochemical sensor for HO was constructed by depositing copper doped CuO nanosheets on a glassy carbon electrode (GCE). The morphology and composition of the modified electrode were characterized via scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction. The electrochemical properties of the electrode were studied using cyclic voltammetry and electrochemical impedance spectroscopy. The catalytic performance of the sensor was studied in 100 mM NaOH solution via differential pulse voltammetry and revealed the sensor to display significantly improved electrocatalytic activity with respect to the analysis of the HO in comparison to a plain GCE or a GCE modified with copper only. The response to HO at a working voltage of −0.46 V (vs. Ag/AgCl) is linear in the 0.003 - 8 mM concentration range, and the detection limit is 0.21 mM (at an S/N ratio of 3). Satisfactory results were obtained in the analysis of tap, rain and river waters spiked with HO. The analytical performance of this electrode compares favorably to the results obtained with other commonly used techniques for analysis of HO. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

We report on a modified glassy carbon electrode (GCE) for sensing hydrogen peroxide (HO). It was constructed by consecutive electrochemical deposition of poly(anthranilic acid) and poly(diphenylamine sulfonate) on the GCE, followed by the deposition of copper oxide (CuO). The morphology and electrochemistry of the modified electrode was characterized by atomic force microscopy, X-ray diffraction, cyclic voltammetry, and electrochemical impedance spectroscopy. The catalytic performance of the sensor was studied with the use of differential pulse voltammetry under optimized conditions. This sensor displayed significantly better electrocatalytic activity for the reduction of HO in comparison to a GCE without or with modification with CuO or polymer films alone. The response to HO is linear in the range between 0.005 to ~11 mM, and the detection limit is 0.18 μM (at an S/N of 3). [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

A rapid kinetic method for the simultaneous determination of levodopa, dopamine, and dobutamine was examined and developed. It was based on a consecutive reaction of a reduction of Cu(II) to Cu(I) by catecholamines, followed by the complexation of Cu(I) with neocuproine to form a yellow product in an acetic acid-acetate buffer. Spectrophotometric data were recorded at 453 nm (wavelength at the yellow complex absorption maximum) for 300 s. Linear calibrations were obtained in the concentration ranges of (0.08-1.44) × 10 mol L, (0.08-1.44) × 10 mol L, and (0.16-1.44) × 10 mol L for levodopa, dopamine, and dobutamine, respectively. A variety of multivariate calibration models was developed for simultaneous analysis of the three analytes; while most models produced satisfactory prediction results for synthetic samples, the hybrid linear analysis method was arguably the best-performing (relative prediction error, RPET = 6.6 %). The proposed method was applied to an analysis of spiked rabbit serum samples and the results showed good agreement with the high performance liquid chromatography measurements. [ABSTRACT FROM AUTHOR]

This paper describes a kinetic spectrophotometric method for simultaneous determination of three cephalosporin antibiotics, cephradine, cefaclor and cefixime, with the aid of chemometrics. The method relies on their oxidation with KMnO to produce green manganate with different kinetic rates in alkaline medium. The proposed method was successfully applied to a pharmacokinetic study of three cephalosporin antibiotics in rabbit plasma via intravenous injections. The results indicated that the amount of cephradine, cefaclor and cefixime were reduced rapidly in rabbit blood, showing clear dose-dependency and the half-life of cefixime (160 min) was longer than those of cephradine (60 min) and cefaclor (60 min). [ABSTRACT FROM AUTHOR]

This work aimed to classify the categories (produced by different processes) and brands (obtained from different geographical origins) of Chinese soy sauces. Nine variables of physico-chemical properties (density, pH, dry matter, ashes, electric conductivity, amino nitrogen, salt, viscosity and total acidity) of 53 soy sauce samples were measured. The measured data was submitted to such pattern recognition as cluster analysis (CA), principal component analysis (PCA), discrimination partial least squares (DPLS), linear discrimination analysis (LDA) and K-nearest neighbor (KNN) to evaluate the data patterns and the possibility of differentiating Chinese soy sauces between different categories and brands. Two clusters corresponding to the two categories were obtained, and each cluster was divided into three subsets corresponding to three brands by the CA method. The variables for LDA and KNN were selected by the Fisher F-ratio approach. The prediction ability of all classifiers was evaluated by cross-validation. For the three supervised discrimination analyses, LDA and KNN gave 100% predications according to the sample category and brand. [ABSTRACT FROM AUTHOR]

A kinetic spectrophotometric method with aid of chemometrics is proposed for the simultaneous determination of norfloxacin and rifampicin in mixtures. The proposed method was applied for the simultaneous determination of these two compounds in pharmaceutical formulation and human urine samples, and the results obtained are similar to those obtained by high performance liquid chromatography. [ABSTRACT FROM AUTHOR]

Chromatographic fingerprints of 46 Eucommia Bark samples were obtained by liquid chromatography-diode array detector (LC-DAD). These samples were collected from eight provinces in China, with different geographical locations, and climates. Seven common LC peaks that could be used for fingerprinting this common popular traditional Chinese medicine were found, and six were identified as substituted resinols (4 compounds), geniposidic acid and chlorogenic acid by LC-MS. Principal components analysis (PCA) indicated that samples from the Sichuan, Hubei, Shanxi and Anhui—the SHSA provinces, clustered together. The other objects from the four provinces, Guizhou, Jiangxi, Gansu and Henan, were discriminated and widely scattered on the biplot in four province clusters. The SHSA provinces are geographically close together while the others are spread out. Thus, such results suggested that the composition of the Eucommia Bark samples was dependent on their geographic location and environment. In general, the basis for discrimination on the PCA biplot from the original 46 objects× 7 variables data matrix was the same as that for the SHSA subset (36 × 7 matrix). The seven marker compound loading vectors grouped into three sets: (1) three closely correlating substituted resinol compounds and chlorogenic acid; (2) the fourth resinol compound identified by the OCH3 substituent in the R4 position, and an unknown compound; and (3) the geniposidic acid, which was independent of the set 1 variables, and which negatively correlated with the set 2 ones above. These observations from the PCA biplot were supported by hierarchical cluster analysis, and indicated that Eucommia Bark preparations may be successfully compared with the use of the HPLC responses from the seven marker compounds and chemometric methods such as PCA and the complementary hierarchical cluster analysis (HCA). [ABSTRACT FROM AUTHOR]

A metal organic framework (MOF) of the type copper(II)-1,3,5-benzenetricarboxylic acid (Cu-BTC) was electrodeposited on electroreduced graphene oxide (ERGO) placed on a glassy carbon electrode (GCE). The modified GCE was used for highly sensitive electrochemical determination of 2,4,6-trinitrophenol (TNP). The fabrication process of the modified electrode was characterized by scanning electron microscopy and electrochemical impedance spectroscopy. Differential pulse voltammetry (DPV) demonstrates that the Cu-BTC/ERGO/GCE gives stronger signals for TNP reduction than Cu-BTC/GCE or ERGO/GCE alone. DPV also shows TNP to exhibit three reduction peaks, the first at a potential of −0.42 V (vs. SCE). This potential was selected because the other three similarly-structured compounds (2-nitrophenol, 4-nitrophenol, 2,4-dinitrophenol) do not give a signal at this potential. Response is linear in the 0.2 to 10 μM TNP concentration range, with a 0.1 μM detection limit (at S/N = 3) and a 15.98 μA∙μM−1∙cm−2 sensitivity under optimal conditions. The applicability of the sensor was evaluated by detecting TNP in spiked tap water and lake water samples. Recoveries ranged between 95 and 101%.Schematic presentation of an electrochemical sensor that was fabricated by electrodeposition of the metal-organic framework (MOF) of copper(II)-1,3,5-benzenetricarboxylic acid (Cu-BTC) onto the surface of electroreduced graphene oxide (ERGO) modified glassy carbon electrode (GCE). It was applied to sensitive and selective detection of 2,4,6-trinitrophenol (TNP). [ABSTRACT FROM AUTHOR]