Xuping Sun

NiSe Nanowire Film Supported on Nickel Foam: An Efficient and Stable 3D Bifunctional Electrode for Full Water Splitting.

Active and stable electrocatalysts made from earth-abundant elements are key to water splitting for hydrogen production through electrolysis. The growth of NiSe nanowire film on nickel foam (NiSe/NF) in situ by hydrothermal treatment of NF using NaHSe as Se source is presented. When used as a 3D oxygen evolution electrode, the NiSe/NF exhibits high activity with an overpotential of 270 mV required to achieve 20 mA cm(-2) and strong durability in 1.0 M KOH, and the NiOOH species formed at the NiSe surface serves as the actual catalytic site. The system is also highly efficient for catalyzing the hydrogen evolution reaction in basic media. This bifunctional electrode enables a high-performance alkaline water electrolyzer with 10 mA cm(-2) at a cell voltage of 1.63 V.

One-pot green synthesis of Ag nanoparticles-graphene nanocomposites and their applications in SERS, H2O2, and glucose sensing

In this contribution, we demonstrate a green, cost-effective, one-pot preparative route toward Ag nanoparticles-graphene (AgNPs–G) nanocomposites in aqueous solution with the use of tannic acid (TA), an environmentally friendly and water-soluble polyphenol, as a reducing agent. Such AgNPs–G nanocomposites were synthesized through one-pot reduction of AgNO3 and GO by TA. We investigated surface enhanced Raman scattering (SERS) and electrochemical properties of the resultant AgNPs–G nanocomposites. It is found that such AgNPs–G nanocomposites show excellent SERS activity as SERS substrates and exhibit notable catalytic performance toward the reduction of H2O2. This enzymeless H2O2 sensor has a fast amperometric response time of less than 2 s. The linear range is estimated to be from 1 × 10−4 M to 0.01 M (r = 0.999) and the detection limit is estimated to be 7 × 10−6 M at a signal-to-noise ratio of 3. A glucose biosensor was further fabricated by immobilizing glucose oxidase (GOD) into chitosan–AgNPs–G nanocomposite film on the surface of a glassy carbon electrode (GCE). This sensor exhibits good response to glucose, and the linear response range is estimated to be from 2 to 10 mM (R = 0.996) at −0.5 V. The detection limit of 100 μM was achieved at a signal-to-noise ratio of 3. More importantly, we demonstrate successfully its application for glucose detection in human blood serum.

Synthesis of functional SiO2-coated graphene oxide nanosheets decorated with Ag nanoparticles for H2O2 and glucose detection

In this paper, we report on the first preparation of well-defined SiO(2)-coated graphene oxide (GO) nanosheets (SiO(2)/GO) without prior GO functionalization by combining sonication with sol-gel technique. The functional SiO(2)/GO nanocomposites (F-SiO(2)/GO) obtained by surface functionalization with NH(2) group were subsequently employed as a support for loading Ag nanoparticles (AgNPs) to synthesize AgNP-decorated F-SiO(2)/GO nanosheets (AgNP/F-SiO(2)/GO) by two different routes: (1) direct adsorption of preformed, negatively charged AgNPs; (2) in situ chemical reduction of silver salts. The morphologies of these nanocomposites were characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). It is found that the resultant AgNP/F-SiO(2)/GO exhibits remarkable catalytic performance for H(2)O(2) reduction. This H(2)O(2) sensor has a fast amperometric response time of less than 2s. The linear range is estimated to be from 1×10(-4) M to 0.26 M (r=0.998) and the detection limit is estimated to be 4 × 10(-6) M at a signal-to-noise ratio of 3, respectively. We also fabricated a glucose biosensor by immobilizing glucose oxidase (GOD) into AgNP/F-SiO(2)/GO nanocomposite-modified glassy carbon electrode (GCE) for glucose detection. Our study demonstrates that the resultant glucose biosensor can be used for the glucose detection in human blood serum.

In situ green synthesis of Au nanostructures on graphene oxide and their application for catalytic reduction of 4-nitrophenol

In this communication, we develop a relatively green, and environment friendly route for the synthesis of Au nanostructures on tannic acid (TA)-functionalized graphene oxide (GO) using TA as a reducing and immobilizing agent. The morphologies of Au nanostructures can be controlled by the amount of HAuCl4 used. The resultant Au nanostructures/GO nanocomposites exhibit good catalytic activity toward 4-nitrophenol (4-NP) reduction and the GO supports also enhance the catalytic activityvia a synergistic effect.

Self-assembled graphene platelet–glucose oxidase nanostructures for glucose biosensing

Graphene platelet-glucose oxidase (GP-GOD) nanostructures have been prepared through self-assembly of GOD and chitosan (CS) functionalized GPs by electrostatic attraction in aqueous solution. The stable aqueous dispersion of GPs was prepared by chemical reduction of graphene oxide with the use of CS as a reducing and stabilizing agent. UV-vis spectroscopy, X-ray diffraction, transmission electron microscopy, scanning electron microscopy and X-ray photoelectron spectroscopy were used to characterize the resulting GPs and GP-GOD nanostructures. Furthermore, a glucose biosensor was constructed by deposition of the resultant GP-GOD on the surface of glassy carbon electrode. It was found that the resulting biosensor exhibits good response to glucose. The linear detection range is estimated to be from 2 to 22 mM (r=0.9987), and the detection limit is estimated to be 20 μM at a signal-to-noise ratio of 3.

A general strategy for the production of photoluminescent carbon nitride dots from organic amines and their application as novel peroxidase-like catalysts for colorimetric detection of H2O2 and glucose

The present communication reports on a general strategy for the production of photoluminescent carbon nitride dots (CNDs) by microwave heating of organic amines in the presence of acid. The resultant CNDs possess intrinsic peroxidase-like activity and have been successfully used as peroxidase mimetics for the colorimetric detection of H2O2 and glucose for the first time.

Carbon nanoparticle for highly sensitive and selective fluorescent detection of mercury(II) ion in aqueous solution.

In this article, carbon nanoparticles (CNPs) were used as a novel fluorescent sensing platform for highly sensitive and selective Hg(2+) detection. To the best of our knowledge, this is the first example of CNPs obtained from candle soot used in this type of sensor. The general concept used in this approach is based on that adsorption of the fluorescently labeled single-stranded DNA (ssDNA) probe by CNP via π-π stacking interactions between DNA bases and CNP leads to substantial dye fluorescence quenching; however, in the presence of Hg(2+), T-Hg(2+)-T induced hairpin structure does not adsorb on CNP and thus retains the dye fluorescence. A detection limit as low as 10nM was achieved. The present CNP-based biosensor for Hg(2+) detection exhibits remarkable specificity against other possible metal ions. Furthermore, superior selectivity performance was observed when Hg(2+) detection was carried out in the presence of a large amount of other interference ions. Finally, in order to evaluate its potential practical application, Hg(2+) detection was conducted with the use of lake water other than pure buffer and it is believed that it holds great promise for real sample analysis upon further development.

Synthesis of Au nanoparticles decorated graphene oxide nanosheets: Noncovalent functionalization by TWEEN 20 in situ reduction of aqueous chloroaurate ions for hydrazine detection and catalytic reduction of 4-nitrophenol

In this paper, we develop a cost-effective and simple route for the synthesis of Au nanoparticles (AuNPs) decorated graphene oxide (GO) nanosheets using polyoxyethylene sorbitol anhydride monolaurate (TWEEN 20) as a stabilizing agent for GO as well as a reducing and immobilizing agent for AuNPs. The AuNPs assemble on the surface of TWEEN-functionalized GO by the in situ reduction of HAuCl(4) aqueous solution. The morphologies of these composites were characterized by atomic force microscopy (AFM) and transmission electron microscopy (TEM). It is found that the resultant AuNPs decorated GO nanosheets (AuNPs/TWEEN/GO) exhibit remarkable catalytic performance for hydrazine oxidation. This hydrazine sensor has a fast amperometric response time of less than 3s. The linear range is estimated to be from 5 μM to 3 mM (r=0.999), and the detection limit is estimated to be 78 nM at a signal-to-noise ratio of 3. The AuNPs/TWEEN/GO composites also exhibit good catalytic activity toward 4-nitrophenol (4-NP) reduction and the GO supports also enhance the catalytic activity via a synergistic effect.

Cobalt Phosphide Nanowires: Efficient Nanostructures for Fluorescence Sensing of Biomolecules and Photocatalytic Evolution of Dihydrogen from Water under Visible Light

The detection of specific DNA sequences plays an important role in the identification of disease-causing pathogens and genetic diseases, and photochemical water splitting offers a promising avenue to sustainable, environmentally friendly hydrogen production. Cobalt-phosphorus nanowires (CoP NWs) show a high fluorescence quenching ability and different affinity toward single- versus double-stranded DNA. Based on this result, the utilization of CoP NWs as fluorescent DNA nanosensors with a detection limit of 100 pM and a selectivity down to single-base mismatch was demonstrated. The use of a thrombin-specific DNA aptamer also enabled the selective detection of thrombin. The photoinduced electron transfer from the excited dye that labels the oligonucleotide probe to the CoP semiconductor led to efficient fluorescence quenching, and largely enhanced the photocatalytic evolution of hydrogen from water under visible light.

Preparation of photoluminescent carbon nitride dots from CCl4 and 1,2-ethylenediamine: a heat-treatment-based strategy

In this communication, we report on our recent finding that photoluminescent carbon nitride dots (CNDs) can be prepared by a simple heat-treatment-based strategy for the first time. It suggests the CNDs thus obtained exhibit strong fluorescence. The formation of such CNDs can be attributed to the polymerization of CCl4 and 1,2-ethylenediamine under reflux, microwave, or solvothermal heating.