Baozhan Zheng

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.

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.

Influence of pH on the fluorescence properties of graphene quantum dots using ozonation pre-oxide hydrothermal synthesis

Recent research into graphene-based materials is largely focused on graphene quantum dots (GQDs) and their optical properties. A facile method has been developed to extract GQDs from reduced graphene oxide (RGO) by the ozonation pre-oxide method. The as-prepared GQDs, which were 2–5 nm in diameter, exhibited strong fluorescence activity ranging from ∼355 nm to ∼440 nm. The prepared GQDs possessed strong fluorescence with quantum yields from 3.18% to 9.48%. Whats more, the fluorescence properties of the GQDs could be determined by tuning the pH of the ozonation system. We speculated the mechanisms of ozonation, thermal and hydrothermal treatment. We found that pyrocatechol could lead to fluorescence quenching of the GQDs, which might produce novel potential for the detection of targets.

Microwave-assisted synthesis of BSA-stabilized and HSA-protected gold nanoclusters with red emission

A microwave (MW)-assisted synthesis method for preparation of fluorescent BSA-stabilized and HSA-protected gold nanoclusters (BSA–AuNCs and HSA–AuNCs) has been developed. The reaction time can be shortened from tens of hours to several minutes, thanks to the superheating and non-thermal effects of the MW energy. The optimal experimental conditions including concentrations of BSA, HAuCl4 and NaOH and the MW programme are investigated in detail. The as-synthesised BSA–AuNC product is well characterized by UV-vis spectroscopy, fluorescence spectroscopy, HRTEM, XPS, and IR spectroscopy. The HSA–AuNCs display strong red emission which is efficiently quenched by nitrogen oxides (NOx), demonstrating its great potential in determining the intracellular concentration of NOx. The proposed MW-assisted synthesis method is simple, fast and should be applicable to prepare various protein- or enzyme-protected metal nanoclusters.

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.

A fluorescent “turn-on” probe for the dual-channel detection of Hg(II) and Mg(II) and its application of imaging in living cells

A novel rhodamine-based fluorescent chemosensor (RND) was synthesized that contains two independent fluorophores and acts as a very sensitive, selective and reversible off-on probe for Hg(II). Importantly, this newly developed sensing system exhibited different fluorescent responses toward Hg(II) and Mg(II) at 589 nm and 523 nm, respectively. RND also displayed detectable color change upon treatment with Hg(II). Results from confocal laser scanning microscopy experiments demonstrated that this chemosensor is cell permeable and can be used as a fluorescent probe for monitoring Hg(II) or Mg(II) in living cells. This probe can also indirectly detect glutathione (GSH) and cysteine (Cys) with good linear relationships.

Rapid microwave-assisted fabrication of 3D cauliflower-like NiCo2S4 architectures for asymmetric supercapacitors

In this study, 3D cauliflower-like NiCo2S4 architectures have been synthesized through a facile, one-step and template-free microwave method. The cauliflower-like NiCo2S4 materials are made up of 3D microstructures with an average diameter of around 600 nm and each nanostructure is found to be constructed of many intertwined nanoparticles. The NiCo2S4-modified electrode was successfully applied to a pseudocapacitor. The electrochemical performance of the NiCo2S4 material was studied by cyclic voltammetry, galvanostatic charge–discharge and electrical impedance spectroscopy. The 3D cauliflower-like NiCo2S4 materials exhibit a maximum capacitance of 1471 F g−1 at 1 A g−1 and also show remarkable rate capability and prominent cycling stability. To improve the energy density of the supercapacitor, a NiCo2S4-modified electrode and activated carbon-modified electrode were used to assemble an asymmetric capacitor. The asymmetric capacitor demonstrates remarkable properties with a maximum energy density of 44.8 W h kg−1 and a maximum power density of 16.0 kW kg−1. Furthermore, two capacitors assembled together can successfully light up a red light-emitting diode (LED) and last for more than 10 min. The excellent capacitance performance demonstrates that the cauliflower-like NiCo2S4 has potential applications in supercapacitors.

Preparation of gold nanoparticles on eggshell membrane and their biosensing application.

A facile green biosynthesis method has been successfully developed to prepare gold nanoparticles (AuNPs) of various core sizes (25+/-7 nm) using a natural biomaterial, eggshell membrane (ESM) at ambient conditions. In situ synthesis of AuNPs-immobilized ESM is conducted in a simple manner by immersing ESM in a pH 6.0 aqueous solution of HAuCl(4) without adding any reductant. The formation of AuNPs on ESM protein fibers is attributed to the reduction of Au(III) ions to Au(0) by the aldehyde moieties of the natural ESM fibers. Energy dispersive X-ray spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, and X-ray powder diffraction unambiguously identify the presence of AuNPs on ESM. The effect of pH on the in situ synthesis of AuNPs on ESM has been investigated in detail. The pH of the gold precursor (HAuCl(4)) solution can influence the formation rate, dispersion and size of AuNPs on ESM. At pH < or =3.0 and > or =7.0, no AuNPs are observed on ESM while small AuNPs are homogeneously dispersed on ESM at pH 4.0-6.0. The optimal pH for AuNPs formation on ESM is 6.0. AuNPs/ESMs are used to immobilize glucose oxidase (GO(x)) for glucose biosensing. AuNPs on ESM can increase the enzyme activity of GO(x). The linear response range of the glucose biosensor is 20 microM to 0.80 mM glucose with a detection limit of 17 microM (S/N=3). The biosensor has been successfully applied to determine the glucose content in commercial glucose injections. Our work provides a very simple, non-toxic, convenient, and green route to synthesize AuNPs on ESM which is potentially useful in the biosensing field.

Improvement of sensitive CuO NFs–ITO nonenzymatic glucose sensor based on in situ electrospun fiber

CuO nanofibers (NFs), prepared by electrospinning and calcination technologies, have been applied for the fabrication of glucose sensors with high sensitivity and selectivity. Cu(NO(3))(2) and polyvinylpyrrolidone (PVP) composite nanofibers were initially electrospun on the surface of indium tin oxide (ITO) glass, and then the CuO NFs-ITO electrode was formed simply by removing PVP through heat treatment. The structures and morphologies of CuO nanofibers were characterized by X-ray diffraction, scanning electron microscopy and thermogravimetric analysis. The direct electrocatalytic oxidation of glucose in alkaline medium at CuO NFs-ITO electrode has also been investigated in detail with cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. The effects of NaOH concentration, electrospinning time, Cu(NO(3))(2):PVP mass ratios and calcination temperature on the response to glucose were investigated. Under optimized experimental conditions, the CuO NFs-ITO electrode produced high and reproducible sensitivity to glucose of 873 μA mM(-1)cm(-2). Linear responses were obtained over a concentration range from 0.20 μM to 1.3mM with a detection limit of 40 nM (S/N=3). The CuO NFs-ITO electrode also has good selectivity, stability and fast amperometic sensing of glucose, thus it can be used for the future development of non-enzymatic glucose sensors.

Three-dimensional amorphous tungsten-doped nickel phosphide microsphere as an efficient electrocatalyst for hydrogen evolution

Amorphous tungsten-doped nickel phosphide (a-WNP) microspheres with three-dimensional (3D) ravine-like nanostructures on the surface were successfully fabricated via a fast and facile grain-mediated electroless method. The resulting W-doped NixP exhibits an outstanding electrocatalytic activity for hydrogen evolution reaction with a low onset potential of −50 mV, overpotential of 110 mV at 20 mA cm−2, and small Tafel slope of 39 mV dec−1. The amorphous architecture and the doping of W are considered to be major contributions for the improvement of catalytic performance. The results in this paper might promote a new route to gain both amorphous and doped materials with special electrochemical properties for advanced catalysts and other devices.