Shunping Xie

Electrogenerated Chemiluminescence Behavior of Graphite-like Carbon Nitride and Its Application in Selective Sensing Cu2+

This paper reports for the first time the electrogenerated chemiluminescence (ECL) behavior of graphite-like carbon nitride (g-C(3)N(4)) with K(2)S(2)O(8) as the coreactant. The possible ECL reaction mechanisms are proposed. The spectral features of the ECL emission and photoluminescence (PL) of g-C(3)N(4) are compared, and their resemblance demonstrates that the excited states of g-C(3)N(4) from both ECL and photoexcitation are the same. The effects of K(2)S(2)O(8) concentration, pH, g-C(3)N(4)/carbon powder ratio, and scan rate on the ECL intensity have been studied in detail. Furthermore, it is observed that the ECL intensity is efficiently quenched by trace amounts of Cu(2+). g-C(3)N(4) is thus employed to fabricate an ECL sensor which shows high selectivity to Cu(2+) determination. The limit of detection is determined as 0.9 nM. It is anticipated that g-C(3)N(4) could be a new class of promising material for fabricating ECL sensors.

Simultaneous determination of L-ascorbic acid, dopamine and uric acid with gold nanoparticles-β-cyclodextrin-graphene-modified electrode by square wave voltammetry.

Graphene decorated with gold nanoparticles (AuNPs-β-CD-Gra) has been synthesized by in situ thermal reduction of graphene oxide and HAuCl(4) with β-cyclodextrin (β-CD) under alkaline condition. The AuNPs-β-CD-Gra product was well characterized by infrared spectroscopy, X-ray powder diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, and selected area electron diffraction. This material was used to fabricate an AuNPs-β-CD-Gra-modified glassy carbon electrode (GCE) which showed excellent electro-oxidation of l-ascorbic acid (AA), dopamine (DA) and uric acid (UA) in 0.10 M NaH(2)PO(4)-HCl buffer solution (pH 2.0) by square wave voltammetry (SWV). Three well-resolved oxidation peaks of AA and DA and UA were obtained. The AuNPs-β-CD-Gra/GCE exhibits linear responses to AA, DA and UA in the ranges 30-2000, 0.5-150 and 0.5-60 μM, respectively. The detection limits (based on S/N=3 and preconcentration time=3.0 min) for AA, DA and UA are 10, 0.15 and 0.21 μM, respectively. The AuNPs-β-CD-Gra/GCE has been successfully applied to determine UA in human urine with satisfactory results. Our work provides a simple, convenient and green route to synthesize AuNPs on Gra which is potentially useful in electroanalysis.

Microwave-assisted non-aqueous homogenous precipitation of nanoball-like mesoporous α-Ni(OH)2 as a precursor for NiOx and its application as a pseudocapacitor

A novel facile and template-free method to prepare a nanoball-like NiOx material has been developed. The preparation involves the synthesis of an α-Ni(OH)2 precursor by microwave heating and calcination of the precursor. The NiOx material possesses a nanoball-like structure with a large surface area. The pseudo-capacitive properties of the NiOx material were evaluated by cyclic voltammetry and electro-chemical impedance spectroscopy in 6 M KOH solution. The specific capacitances were 951, 796, 713 and 650 F g−1, corresponding to the scan rates of 2.0, 5.0, 10 and 20 mV s−1, respectively. The NiOx material also showed excellent cycling stability and maintained 92% of its maximum specific capacitance after 1000 cycles. The hybrid supercapacitor based on this NiOx material exhibited moderate energy density and power density.

Separation and preconcentration of persistent organic pollutants by cloud point extraction.

Persistent organic pollutants (POPs) are recognized as a class of poisonous compounds which pose risks of causing adverse effects to human health and the environment. Thus, it is very important to detect POPs in environmental and biological samples. The identification and determination of very low levels of POPs in complex matrices is extremely difficult. Recently a promising environmentally benign extraction and preconcentration methodology based on cloud point extraction (CPE) has emerged as an efficient sample pretreatment technique for the determination of trace/ultra-trace POPs in complex matrices. The purpose of this paper is to review the past and latest use of CPE for preconcentrating POPs and its coupling to different contemporary instrumental methods of analysis. First, the comparison of various extraction techniques for POPs is described. Next, the general concept, influence factors and other methods associated with CPE technique are outlined and described. Last, the hyphenations of CPE to various instrumental methods for their determination are summarized and discussed.

Ultrahigh performance liquid chromatographic analysis and magnetic preconcentration of polycyclic aromatic hydrocarbons by Fe3O4-doped polymeric nanoparticles

This paper reports the synthesis of hydrophilic-hydrophobic magnetic Fe₃O₄-doped polymeric nanoparticles (MPNP) and its application for preconcentration of polycyclic aromatic hydrocarbons (PAHs) in environmental water samples for ultrahigh performance liquid chromatographic (UHPLC) analysis. The MPNP were prepared from highly charged poly(styrene-divinylbenzene-co-4-vinylbenzenesulfonic acid sodium salt) nanoparticles impregnated with Fe²⁺ via the electrostatic attraction and by microwave heating. The MPNP are relatively uniform in size with an average diameter of 50 nm and have a magnetic saturation value of 24.5 emu/g. The hydrophilic-hydrophobic MPNP could easily disperse in water. The phenyl moieties of MPNP assist the adsorption of PAHs via both hydrophobic and π-π interactions. The separation of the PAHs-adsorbed MPNP from water could be easily achieved by a permanent magnet and the adsorbed PAHs were back extracted into acetonitrile for UHPLC analysis. The UHPLC separation of PAHs is very quick and could be achieved within 1.6 min. Factors affecting the extraction and desorption were investigated in detail. Under the optimum experimental conditions, the recoveries of various PAHs including acenaphthylene, anthracene, fluoranthene, fluorene, phenanthrene, and pyrene in water samples at three different concentrations are 75.7-102.9, 77.8-101.2, 86.3-100.7, 88.5-99.7, 92.0-106.4, and 81.6-98.5%, respectively. The recovery SDs are 0.30-8.20% and the instrumental limits of detection are 10.83-18.53 nM. The proposed technique combining hydrophobic extraction and magnetic separation coupled with UHPLC could provide a fast, convenient and sensitive method for the determination of PAHs in water samples.

Electrogenerated chemiluminescence of anatase TiO2 nanotubes film

Highly ordered titanium dioxide (TiO(2)) nanotubes film was successfully synthesized via anodic oxidation of a Ti foil in an ammonium fluoride-based ethylene glycol solution. The electrogenerated chemiluminescence (ECL) behavior of the resulting TiO(2) nanotubes film was subsequently studied. Strong ECL emission was observed at -1.40V (vs. Ag/AgCl) and the ECL spectrum displayed three emission peaks which were bathochromatically shifted by ca. 140nm as compared to its corresponding photoluminescence (PL) emission peaks, indicating that the surface state plays an important role in the emission process. The ECL emission can also occur in a deareated solution attributing to the surface adsorbed O(2) molecules. The ECL emission intensity was quenched by dopamine and greatly enhanced in the presence of dissolved O(2) and H(2)O(2), making it possible to detect these analytes. The TiO(2) nanotubes film has been successfully applied to determine the dissolved O(2) content in river and pond water samples, the H(2)O(2) concentration in commercial disinfectant samples and the dopamine concentration in commercial dopamine injections with satisfactory results. The plausible ECL mechanisms of TiO(2) nanotubes film in aqueous solution are discussed.

Liesegang rings of dendritic silver crystals emerging from galvanic displacement reaction in a liquid-phase solution

Liesegang rings (LR) of various types of Ag dendrite crystals are observed from an aqueous solution based on a simple galvanic displacement reaction between a Zn plate and Ag2SO4. The growth process and formation mechanism of LR of Ag dendrites are investigated in detail. The synthesised LR of Ag dendrites have been successfully employed as a Raman probe for SERS analysis of melamine.