Changming Cheng

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.

Anodic Electrogenerated Chemiluminescence Behavior of Graphite-Like Carbon Nitride and Its Sensing for Rutin

In this paper, the anodic electrogenerated chemiluminescence (ECL) behavior of graphite-like carbon nitride (g-C3N4) is studied using cyclic voltammetry with triethanolamine (TEA) as a coreactant. The possible anodic ECL response mechanism of the g-C3N4/TEA system is proposed. Furthermore, it is observed that the anodic ECL signal can be quenched efficiently in the presence of rutin, on the basis of which a facile anodic ECL senor for the determination of rutin is developed. This ECL sensor is found to have a linear response in the range of 0.20-45.0 μM and a low detection limit of 0.14 μM (at signal-to-noise of 3). These results suggest that semiconductor g-C3N4 has great potential in extending the application in the ECL field as an efficient luminophore.

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.

Facile Fabrication of Mn2O3 Nanoparticle-Assembled Hierarchical Hollow Spheres and Their Sensing for Hydrogen Peroxide

In the present work, we described the facile hydrothermal fabrication of Mn2O3 nanoparticle-assembled hierarchical hollow spheres and their application for the electrochemical determination of hydrogen peroxide (H2O2). The composition and morphology of the as-prepared samples were well characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Because of the electrochemical responses toward H2O2, a novel nonenzymatic electrochemical sensor for the H2O2 determination based on Mn2O3 hollow spheres modified glassy carbon electrode was proposed. The electrochemical properties of the modified electrode were investigated by cyclic voltammetry, electrochemical impedance spectroscopy and chronoamperometry. The modified electrode displayed distinct amperometric response to H2O2 in a wide concentration range 0.10-1276.5 μM, with a linear range of 0.10-126.5 μM and a detection limit of 0.07 μM (S/N = 3). It exhibited excellent analytical performance in terms of long-time stability, good reproducibility and acceptable anti-interference ability. In addition, it was applied for the H2O2 determination in real samples directly with acceptable accuracy and recovery, demonstrating its potential application in routine H2O2 analysis.

A facile large-scale microwave synthesis of highly fluorescent carbon dots from benzenediol isomers

A fast large-scale synthesis of fluorescent carbon dots (CDs) has been developed in this work without high temperature or high pressure. Using benzenediols (catechol, resorcinol and hydroquinone) as the carbon precursor and sulfuric acid as the catalyst, three distinct CDs with strong and stable luminescence were prepared via a microwave-assisted method within 2 min. Characterizations through high-resolution transmission electron microscopy, X-ray diffraction, elemental analysis and infrared spectroscopy indicated the as-prepared CDs are dispersed spherical oxygenous carbon nanoparticles with 0.5–6 nm sizes. The structure differences caused by the isomer precursors were reflected in the chemical and fluorescent properties of CDs. The quantum yields of the three kinds of CDs derived from catechol, resorcinol and hydroquinone are 9.2%, 42.8% and 26.5%, respectively, and the fluorescence lifetimes of these CDs are on the nanosecond scale. The CDs derived from hydroquinone could easily penetrate into cells in a short time (30 min) and possess low cytotoxicity and good biocompatibility which may have great potential for bioimaging applications.

Facile synthesis of functionalizated carbon nanospheres for determination of Cu2

In this research, quantities of carbon nanospheres (CNSs) were prepared with a convenient and low cost method at atmospheric pressure and functionalized with the xanthate group in a simple way. The materials were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared spectra (FT-IR), and X-ray photoelectron spectroscopy (XPS). In addition, the carbon nanospheres (CNSs) xanthate was applied to fabricate a modified carbon paste electrode (CPE) for the selective and sensitive determination of Cu(2+). Also, the xanthate with a -CS2 group was applied as a chelating agent to enrich Cu(2+) in the determination of Cu(2+) ions. In square wave stripping voltammetry (SWSV), the carbon nanospheres xanthate-modified CPE displayed linear response to Cu(2+) in the concentration range of 8.0 × 10(-8) M to 2.2 × 10(-6) M with a detection limit (S/N = 3) of 3.55 × 10(-8) M. The modified electrode exhibited excellent analytical performance in terms of high repeatability. Finally, it was applied to detect Cu(2+) in the wastewater samples with high accuracy and good recovery, indicating its promising application in the routine analysis of metal ions.

In situ coordination of pyridine, quinoline, and quinoxaline with copper(I) iodide at the solid–liquid interface: Formation, characterization, and function of the microcrystal films

An in situ surface-reaction approach has been developed for the synthesis of microcrystals Cu 4 I 4 (C 6 H 5 N) 4 , Cu 4 I 4 (C 9 H 7 N) 4 , and Cu 2 I 2 (C 8 H 6 N 2 ) in solid films. Microcrystals of Cu 4 I 4 (C 6 H 5 N) 4 , Cu 4 I 4 (C 9 H 7 N) 4 , and Cu 2 I 2 (C 8 H 6 N 2 ) were easily formed on a copper substrate at the solid Cu–liquid pyridine (C 6 H 5 N),–quinoline (C 9 H 7 N), and–quinoxaline (C 8 H 6 N 2 ) interfaces. The resulting microcrystal films were characterized by photoluminescence spectroscopy, scanning electron microscopy, transmission electron microscopy, energy dispersive x-ray spectroscopy, x-ray diffraction, and electrochemical impedance spectroscopy. The effect of ligands on the morphology of the film materials and their chemical properties were also discussed. These microcrystal films possessing reversible photocurrent and photovoltage properties were studied in detail. The photoactive and mechanically stable complex films described here may provide new strategies for fabricating photoluminescence solid films, photomodulation potential, and current films. The potential applications of the microcrystal films are for small light-induced electronic junction and photoluminescence sensors.

A facile photochemical route for the synthesis of gold nanoparticles

Synthesis of high-quality, water-dispersed gold nanoparticles (AuNPs), has been prepared employing luminol as a special reductant, via direct irradiation of the molecular precursors rather than traditional heat of the solvent. The final quality of the photochemically generated nanomaterial was characterized by transmission electron microscopy, resonance light scattering spectra, and cyclic voltammetry. AuNPs could enhance the chemiluminescence intensity of the luminol-H2O2 system, attributing to their catalysis. On the basis, we developed a nanoparticle-based chemiluminescence method for the determination of H2O2. The results demonstrated that it was possible to detect hydrogen peroxide in the range of 10−8–10−3 M.