Dan Wen

Platinum nanoparticle ensemble-on-graphene hybrid nanosheet: one-pot, rapid synthesis, and used as new electrode material for electrochemical sensing.

The development of nanoscience and nanotechnology has inspired scientists to continuously explore new electrode materials for constructing an enhanced electrochemical platform for sensing. In this article, we proposed a new Pt nanoparticle (NP) ensemble-on-graphene hybrid nanosheet (PNEGHNs), a new electrode material, which was rapidly prepared through a one-step microwave-assisted heating procedure. The advantages of PNEGHNs modified glassy carbon electrode (GCE) (PNEGHNs/GCE) are illustrated from comparison with the graphenes (GNs) modified GCE for electrocatalytic and sensing applications. The electrocatalytic activities toward several organic and inorganic electroactive compounds at the PNEGHNs/GCE were investigated, all of which show a remarkable increase in electrochemical performance relative to GNs/GCE. Hydrogen peroxide (H2O2) and trinitrotoluene (TNT) were used as two representative analytes to demonstrate the sensing performance of PNEGHNs. It is found that PNEGHNs modified GCE shows a wide linear range and low detection limit for H2O2 and TNT detection. Therefore, PNEGHNs may be an attractive robust and advanced hybrid electrode material with great promise for electrochemical sensors and biosensors design.

Graphene oxide/polypyrrole nanocomposites: one-step electrochemical doping, coating and synergistic effect for energy storage

We introduce a facile method for the construction of graphene oxide/polypyrrole (GO/PPy) nanocomposites via one–step coelectrodeposition. In this process, the relatively large anionic GO serves as a weak electrolyte and is entrapped in the PPy nanocomposites during the electropolymerization of pyrrole, and also acts as an effective charge-balancing dopant within the PPy film. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) results demonstrate that the GO/PPy nanocomposites are successfully synthesized. The obtained GO/PPy nanocomposites exhibit good electrochemical properties and cycling performance, indicating a synergistic effect of PPy and GO. Taking its higher capacitance, lower cost and shorter processing time into consideration, GO may be a good choice for the fabrication of electrochemical supercapacitors based on conducting polymer nanocomposites. It should be noted that this coelectrodeposition is also applicable for the graphene oxide/poly[3,4-ethylenedioxythiophene] (GO/PEDOT) nanocomposites. Moreover, this facile and effective approach for the synthesis of GO/conducting polymer nanocomposites further extends the application of GO and should be very promising for the fabrication of inexpensive, high-performance electrochemical supercapacitors.

Biomolecule-stabilized Au nanoclusters as a fluorescence probe for sensitive detection of glucose

In this work, biomolecule-stabilized Au nanoclusters were demonstrated as a novel fluorescence probe for sensitive and selective detection of glucose. The fluorescence of Au nanoclusters was found to be quenched effectively by the enzymatically generated hydrogen peroxide (H(2)O(2)). By virtue of the specific response, the present assay allowed for the selective determination of glucose in the range of 1.0×10(-5) M to 0.5×10(-3) M with a detection limit of 5.0×10(-6) M. The absorption spectroscopy, X-ray photoelectron spectroscopy (XPS) and fluorescence decay studies were then performed to discuss the quenching mechanism. In addition, we demonstrated the application of the present approach in real serum samples, which suggested its great potential for diagnostic purposes.

Ionic liquid-graphene hybrid nanosheets as an enhanced material for electrochemical determination of trinitrotoluene

Trinitrotoluene, usually known as TNT, is a kind of chemical explosive with hazardous and toxic effects on the environment and human health. Ever-increasing needs for a secure society and green environment essentially require the detection of TNT with rapidity, high sensitivity and low cost. In this article, ionic liquid-graphene hybrid nanosheets (IL-GNs) have been used as an enhanced material for rapidly electrochemical detection of trinitrotoluene (TNT). IL-GNs were characterized by atomic force microscopy (AFM), transmission electron microscopy (TEM), X-ray photo-electron spectroscopy, electrochemical impedance spectroscopy, Fourier transform infrared (FT-IR) spectroscopy and Raman spectroscopy, which confirmed that IL has been effectively functionalized on the surface of GNs. Significantly, IL-GNs modified glassy carbon electrode (GCE) showed 6.2 and 51.4-folds higher current signals for TNT reduction than IL-CNTs/GCE and bare GCE, respectively. Adsorptive stripping voltammetry (ASV) for the detection of TNT on IL-GNs exhibited a good linear range from 0.03 to 1.5 ppm with a detection limit of 4 ppb on the basis of the signal-to-noise characteristics (S/N=3). Moreover, IL-GNs/GCE exhibited good stability and reproducibility for the detection of TNT. And, IL-GNs based electrochemical detection platform was also successfully demonstrated for the detection of TNT in ground water, tap water, and lake water with satisfactory results.

Noble Metal Aerogels—Synthesis, Characterization, and Application as Electrocatalysts

Conspectus Metallic and catalytically active materials with high surface area and large porosity are a long-desired goal in both industry and academia. In this Account, we summarize the strategies for making a variety of self-supported noble metal aerogels consisting of extended metal backbone nanonetworks. We discuss their outstanding physical and chemical properties, including their three-dimensional network structure, the simple control over their composition, their large specific surface area, and their hierarchical porosity. Additionally, we show some initial results on their excellent performance as electrocatalysts combining both high catalytic activity and high durability for fuel cell reactions such as ethanol oxidation and the oxygen reduction reaction (ORR). Finally, we give some hints on the future challenges in the research area of metal aerogels. We believe that metal aerogels are a new, promising class of electrocatalysts for polymer electrolyte fuel cells (PEFCs) and will also open great opportunities for other electrochemical energy systems, catalysis, and sensors. The commercialization of PEFCs encounters three critical obstacles, viz., high cost, insufficient activity, and inadequate long-term durability. Besides others, the sluggish kinetics of the ORR and alcohol oxidation and insufficient catalyst stability are important reasons for these obstacles. Various approaches have been taken to overcome these obstacles, e.g., by controlling the catalyst particle size in an optimized range, forming multimetallic catalysts, controlling the surface compositions, shaping the catalysts into nanocrystals, and designing supportless catalysts with extended surfaces such as nanostructured thin films, nanotubes, and porous nanostructures. These efforts have produced plenty of excellent electrocatalysts, but the development of multisynergetic functional catalysts exhibiting low cost, high activity, and high durability still faces great challenges. In this Account, we demonstrate that the sol–gel process represents a powerful “bottom-up” strategy for creating nanostructured materials that tackles the problems mentioned above. Aerogels are unique solid materials with ultralow densities, large open pores, and ultimately high inner surface areas. They magnify the specific properties of nanomaterials to the macroscale via self-assembly, which endow them with superior properties. Despite numerous investigations of metal oxide aerogels, the investigation of metal aerogels is in the early stage. Recently, aerogels including Fe, Co, Ni, Sn, and Cu have been obtained by nanosmelting of hybrid polymer–metal oxide aerogels. We report here exclusively on mono-, bi- and multimetallic noble metal aerogels consisting of Ag, Au, Pt, and Pd and their application as electrocatalysts.

Gold nanowire assembling architecture for H2O2 electrochemical sensor

Morphological control of nanomaterials is of great interest due to their size and shape-dependent chemical and physical properties and very important applications in many fields such as biomedicine, sensors, electronics and others. In this paper, we reported a simple strategy for synthesizing gold nanowire assembling architecture at room temperature. It is found that two important factors, the proper volume ratio of ethanol to water and poly(vinyl pyrrolidone) (PVP), will play important roles in synthesizing flower-like short gold nanowire assembling spheres. Furthermore, the obtained flower-like gold assembling spheres with high surface-to-volume ratio have been employed as enhancing materials for electrochemical sensing H(2)O(2). The present electrochemical sensing platform exhibited good electrocatalytic activity towards the reduction of H(2)O(2). The detection limit for H(2)O(2) was found to be 1.2 microM, which was lower than certain enzyme-based biosensors.

Ultrathin Pd nanowire as a highly active electrode material for sensitive and selective detection of ascorbic acid.

Nanomaterial modified electrode is useful for catalytic, analytical and biotechnological applications. Herein, a simple and sensitive method for the electrocatalytic detection of ascorbic acid (AA) using ultrathin Pd nanowire (NW) modified glassy carbon electrode is presented. Electrochemical data reveal that Pd NWs can effectively enhance the electron transfer between AA and electrode, and thus reduce the overpotential of AA oxidation. Particularly, the current-time curve shows that the catalytic oxidation current is linearly dependent on AA concentration in the range of 25 μM-0.9 mM with a correlation coefficient 0.9998, and a detection limit of 0.2 μM (S/N=3) is obtained with an excellent reproducibility. What is more, the present Pd NWs-based electrochemical sensing platform can successfully be used as enhanced element for the detection of AA in the practical samples such as human serum and vitamin C beverage with satisfactory results.

Self-Powered Sensor for Trace Hg2+ Detection

A self-powered electrochemical sensor has been facilely designed for sensitive detection of Hg(2+) based on the inhibition of biocatalysis process of enzymatic biofuel cell (BFC) for the first time. The as-prepared one-compartment BFC, which was consisted of alcohol dehydrogenase supported on single-walled carbon nanohorns-based mediator system as the anode and bilirubin oxidase as the cathodic biocatalyst, generated an open circuit potential (V(oc)) of 636 mV and a maximum power density of 137 μW cm(-2). It was interestingly found that the presence of Hg(2+) would affect the performance of the constructed BFC (e.g., V(oc)). Taking advantage of the inhibitive effect of Hg(2+), a novel self-powered Hg(2+) sensor has been developed, which showed a linear range of 1-500 nM (R(2) = 0.999) with a detection limit of 1 nM at room temperature. In addition, this BFC-type sensor exhibited good selectivity for Hg(2+) against other common environmental metal ions, and the feasibility of the method for Hg(2+) detection in actual water samples (i.e., tap, ground, and lake water) was demonstrated with satisfactory results.

A sensitive NADH and glucose biosensor tuned by visible light based on thionine bridged carbon nanotubes and gold nanoparticles multilayer

A NADH and glucose biosensor based on thionine cross-linked multiwalled carbon nanotubes (MWNTs) and Au nanoparticles (Au NPs) multilayer functionalized indium-doped tin oxide (ITO) electrode were presented in this paper. The effect of light irradiation on the enhancement of bioelectrocatalytic processes of the biocatalytic systems by the photovoltaic effect was investigated. This bioelectrode exhibited excellent catalytic activity of the oxidation towards dihydronicotinamide adenine dinucleotide (NADH). Most interesting, the performance of this NADH sensor could be tuned by the visible light. When the biosensor was performed in the dark, the anodic current increased linearly with NADH concentration over the range from 0.5 to 237 microM with detection limit 0.1 microM and sensitivity 17 nA microM(-1). The sensitivity became 115 nA microM(-1) with detection limit 0.05 microM with the light irradiation. Compared with the reaction in dark, the sensitivity increased around 7 folds while the detection limit decreased 2 folds. The glucose biosensor also exhibited the same behavior. The linear range was from 10 microM to 2.56 mM with the sensitivity of 7.8 microAmM(-1) and detection limit 5.0 microM in the dark. After the light irradiation, the linear range was from 1 microM to 3.25 mM with the sensitivity of 18.5 microA mM(-1) and detection limit 0.7 microM. It indicated a potential to provide an operational access to develop new kinds of photocontrolled dehydrogenase enzyme-based bioelectronics.

Highly ordered mesoporous carbons-based glucose/O2 biofuel cell

This study demonstrates a novel compartment-less glucose/O(2) biofuel cell (BFC) based on highly ordered mesoporous carbons (OMCs) with three-dimensionally (3D) interconnected and ordered pore structures. OMCs are used as supports for both stably confining the electrocatalyst (i.e., meldolas blue, MDB) for NADH oxidation and the anodic biocatalyst (i.e., NAD(+)-dependent glucose dehydrogenase, GDH) for glucose oxidation, and for facilitating direct electrochemistry of the cathodic biocatalyst (i.e., laccase, LAC) for O(2) electroreduction. In 0.10 M pH 6.0 PBS containing 20 mM NAD(+) and 60 mM glucose under the air-saturated atmosphere, the open circuit voltage (0.82 V) and the maximum power output (38.7 microW cm(-2) (at 0.54 V)) of the assembled compartment-less OMCs-based BFC are both higher than those of carbon nanotubes (CNTs)-based BFC (0.75 V and 2.1 microW cm(-2) (at 0.46 V)). These may make OMCs to be another kind of robust and advanced carbon electrode material besides CNTs for BFCs applications.