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Wu S.,Hefei University of Technology | Wu S.,Anhui Institute for Food and Drug Control | Shi T.,Hefei University of Technology | Zhang L.,Bengbu College
Fullerenes Nanotubes and Carbon Nanostructures

In this study, the new amphiphilic copolymer of sodium-4-styrenesulfonate (SS) and 2-acrylamido-2-methyl propane sulfonic acid (AMPS) [poly(SS-co-AMPS)] was prepared and first used as an effective stabilizer to prepare a high concentration and stable aqueous dispersion of graphene. It was found that the high concentration of the stable graphene dispersion can reach up to 12.0 mg/mL using the copolymer as a stabilizer. FT-IR and UV-Vis study show that owing to the coexistence of π-π interaction, hydrophobic attraction, and hydrogen bonding, the poly(SS-co-AMPS) exhibits a high adsorptivity for graphene sheets. In addition, the electrostatic repulsions and stereo-hindrance effect supplied by the sulfonic groups (-SO3 -) and the side chain can prevent the π-π stacking of graphene sheets effectively. The morphology of the exfoliated graphene sheets was investigated by atomic force microscopy and transmission electron microscopy with a 3.9-nm average thickness. Furthermore, this polymer-functionalized graphene can also be dispersed very well in polar organic solvents, such as N,N-dimethylmethanamide, acetone, and ethanol, to form stable homogeneous suspensions. © 2015 Taylor & Francis Group, LLC. Source

Wu S.,Hefei University of Technology | Wu S.,Anhui Institute for Food and Drug Control | Shi T.,Hefei University of Technology | Zhang L.,Bengbu College
High Performance Polymers

Amine-functionalized reduced graphene oxide (NH2-RGO), with primary amine (- NH2) groups linked onto surfaces by toluene-2,4-diisocynate), was successfully synthesized. Subsequently, the as-prepared NH2-RGO nanoplatelets were covalently incorporated into a waterborne polyurethane (WPU) matrix to fabricate NH2-RGO/WPU nanocomposites by the reaction of - NH2 groups with the isocyanate-terminated polyurethane prepolymer. Electron microscopic observations confirmed that the NH2-RGO nanoplatelets were homogenously dispersed in the WPU matrix. The NH2-RGO/WPU nanocomposites exhibited a significant improvement in their mechanical and thermal properties. The tensile strength and storage modulus of the nanocomposites increased by 73% and 973%, respectively, with the addition of 1.0 wt% NH2-RGO. The thermal degradation temperature was enhanced by about 40°C compared with the neat WPU. Meanwhile, the thermal conductivity increased by about 258%. © 2015 The Author(s). Source

Objective: To set up an HPLC method for the determination of hydrochlorothiazide, prazosin hydrochloride, romethazine hydrochloride, reserpine, and nifedipine illegally added into Qingnao Jiangya Tablets (QJT). Methods: HPLC method was used. Octadecyl silane bonded silica as a filler (APOLLO C18 column, 250 mm × 4.6 mm) was used with the mobile phase consisting of water containing 0.02% phosphoric acid and acetonitrile in gradient mode. The flow rate was 1.0 mL/min, column temperature was 25℃, and detection wavelength was set at UV 251 nm. Results: The calibration curve showed the good linearity for hydrochlorothiazide, prazosin hydrochloride, romethazine hydrochloride, reserpine, and nifedipine in the ranges of 21.24-2 124.0 ng (r = 1.000 0), 16.184-1 618.4 ng (r = 1.000 0), 19.72-1 972.0 ng (r = 1.000 0). 18.976-1 897.6 ng (r = 1.000 0), and 22.504-2 250.4 ng (r = 1.000 0), respectively; The average recovery rates (n = 6) were 100.93%, 101.61%, 103.07%, 97.58%, and 96.36%, respectively; RSD values were 1.52%, 1.21%, 1.08%, 0.73%, and 0.48%, respectively. Conclusion: The accurate and reproducible method can be used for the determination of hydrochlorothiazide, prazosin hydrochloride, romethazine hydrochloride, reserpine, and nifedipine illegally added into QJT. ©, 2014, Editorial Office of Chinese Traditional and Herbal Drugs. All right reserved. Source

Wu S.L.,Hefei University of Technology | Wu S.L.,Anhui Institute for Food and Drug Control | Shi T.J.,Hefei University of Technology | Zhang L.Y.,Bengbu College
Journal of Applied Polymer Science

This study describes a simple and effective method of synthesis of a polyurethane/graphene nanocomposite. Cationic waterborne polyurethane (CWPU) was used as the polymer matrix, and graphene oxide (GO) as a starting nanofiller. The CWPU/GO nanocomposite was prepared by first mixing a CWPU emulsion with a GO colloidal dispersion. The positively charged CWPU latex particles were assembled on the surfaces of the negatively charged GO nanoplatelets through electrostatic interactions. Then, the CWPU/chemically reduced GO (RGO) was obtained by treating the CWPU/GO with hydrazine hydrate in DMF. The results of X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and Raman analysis showed that the RGO nanoplatelets were well dispersed and exfoliated in the CWPU matrix. The electrical conductivity of the CWPU/RGO nanocomposite could reach 0.28 S m-1, and the thermal conductivity was as high as 1.71 W m-1 K-1. The oxygen transmission rate (OTR) of the CWPU/RGO-coated PET film was significantly decreased to 0.6 cm3m-2 day-1, indicating a high oxygen barrier property. This remarkable improvement in the electrical and thermal conductivity and barrier property of the CWPU/RGO nanocomposite is attributed to the electrostatic interactions and the molecular-level dispersion of RGO nanoplatelets in the CWPU matrix. © 2015 Wiley Periodicals, Inc. Source

With HPLC using a diode array detector (DAD), a method of substitution for reference substances in impurity profiling control was developed that combined peak tracking by the correlation of spectra with application of correction factors for determination of each impurity. For qualitative analysis, two-dimensional (2D) standard spectrochromatographic data produced by HPLC-DAD were compared with sample data to develop 2D chromatographic spectral correlative maps so that the three target impurities were recognized without preparation and injection of reference solutions. For quantitative analysis, correction factors among cefonicid and the three impurities were established. The correction factors were 1.06 for 5-mercapto-1,2,3,4-tetrazole 1-methyl sulfonic acid detected at 255 nm, 0.77 for 7-aminocephalosporanic acid detected at 265 nm, and 0.97 for methoxycefonicid detected at 268 nm. The method could be used in analysis of related substances in cefonicid for injection without recourse to chemical reference standards of the three impurities. Source

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