Xianlan Chen

Au/ZnO hybrid nanocatalysts impregnated in N-doped graphene for simultaneous determination of ascorbic acid, acetaminophen and dopamine.

The formation of nitrogen-doped (N-doped) graphene uses hydrothermal method with urea as reducing agent and nitrogen source. The surface elemental composition of the catalyst was analyzed through XPS, which showed a high content of a total N species (7.12at.%), indicative of the effective N-doping, present in the form of pyridinic N, pyrrolic N and graphitic N groups. Moreover, Au nanoparticles deposited on ZnO nanocrystals surface, forming Au/ZnO hybrid nanocatalysts, undergo a super-hydrophobic to super-hydrophilic conversion. Herein, we present Au/ZnO hybrid nanocatalysts impregnated in N-doped graphene sheets through sonication technique of the Au/ZnO/N-doped graphene hybrid nanostructures. The as-prepared Au/ZnO/N-doped graphene hybrid nanostructure modified glassy carbon electrode (Au/ZnO/N-doped graphene/GCE) was first employed for the simultaneous determination of ascorbic acid (AA), dopamine (DA) and acetaminophen (AC). The oxidation over-potentials of AA, DA and AC decreased dramatically, and their oxidation peak currents increased significantly at Au/ZnO/N-doped graphene/GCE compared to those obtained at the N-doped graphene/GCE and bare CCE. The peak separations between AA and DA, DA and AC, and AC and AA are large up to 195, 198 and 393mV, respectively. The calibration curves for AA, DA and AC were obtained in the range of 30.00-13.00×10(3), 2.00-0.18×10(3) and 5.00-3.10×10(3)μM, respectively. The detection limits (S/N=3) were 5.00, 0.40 and 0.80μM for AA, DA and AC, respectively.

Self-assembly of palladium nanoparticles on functional TiO2 nanotubes for a nonenzymatic glucose sensor.

Polydiallyldimethylammonium chloride, PDDA, was used as a stabilizer and linker for functionalized TiO2 nanotubes (TiO2 NTs). Self-assembled process with palladium nanoparticles (NPs) was successfully synthesized and used for the oxidation of glucose on glassy carbon electrodes. Based on the voltammetric and amperometric results, Pd NPs efficiently catalyzed the oxidation of glucose at -0.05 V in the presence of 0.1 M NaCl and showed excellent resistance toward interference poisoning from such interfering species as ascorbic acid, uric acid and urea. To further increase sensitivity, the Pd NPs-PDDA-TiO2 NTs/GCE was electrochemically treated with H2SO4 and NaOH, the glucose oxidation current was magnified 2.5 times than that before pretreatments due to greatly enhancing the electron transport property of the sensor based on the increased defect sites and surface oxide species. In view of the physiological level of glucose, the wide linear concentration range of glucose (4×10(-7)-8×10(-4)M) with a detection limit of 8×10(-8)M (S/N=3) was obviously good enough for clinical application.

Efficient Photoluminescence of Mn2+-Doped ZnS Quantum Dots Sensitized by Hypocrellin A

Mn2+-doped ZnS semiconductor quantum dots reveal remarkably intense photoluminescence with the 4T1(4G) f6A1(6S) transition. In this study, following growth doping technique, Mn2+-doped ZnS quantum dots (ZnS:Mn2+ QDs) with high-quality optical properties and narrow size distribution were synthesized successfully. The dopant emission has been optimized with various reaction parameters, and it has been found that the percentage of introduced dopant, reaction temperature, and time as well as the pH of a reaction mixture are key factors for controlling the intensity. Photoluminescence emission (PL) measurements of ZnS:Mn2+ QDs show Mn2+ d-d orange luminescence along with band-edge blue luminescence. Moreover, the electron transfer from singlet states of hypocrellin A (HA) to colloidal ZnS:Mn2+ QDs has been examined by absorption spectra and fluorescence quenching. The absorption spectrum gave an evidence of the increases in the extinction coefficient and the red-shift of the absorption maxima in the absorption spectra of HA in the presence of ZnS:Mn2+ QDs, demonstrating the occurrence of surface interactions between the sensitizer and the particle surface. Fluorescence quenching by ZnS:Mn2+ QDs also suggested that there were a complex association between HA and ZnS:Mn2+ QDs, which was necessary for observing the heterogeneous electron-transfer process at the interface of sensitizer-semiconductor.

Amperometric determination of dopamine Ndoped graphene/Au@Pt core-shell nanoparticles modified glassy carbon electrode

materials, Dopamine Abstract. The formation of N-doped graphene (NG) use hydrothermal method with urea as reducing agent and nitrogen source. The surface elemental composition of the catalyst was analyzed through XPS, which showed the atomic ratio of N/C is 5.0%, indicative of the effective N-doping. The Au@Pt core-shell nanoparticles were prepared by seed-mediated growth method, where tens of small Pt nanoparticles aggregated on gold seeds. Finally, the Au@ Pt core-shell nanoparticles was introduced into the interlayers of NG nanosheets to form Au@Pt/NG hybrid materials by sonication technique. The as-prepared Au@Pt/NG hybrid materials modified glassy carbon electrode (Au@Pt/NG/GCE) was first employed for the determination of DA. The DA oxidation current is linear to its concentration in the range of 6.0×10 -8 ~1.3×10 -6 M, and the detection limit was found to be 1.0×10 -8 (S/N=3).