Wenbo Song

Three-dimensional network films of electrospun copper oxide nanofibers for glucose determination

Copper oxide nanofibers (CuO-NFs) prepared by electrospinning and subsequent thermal treatment processes were demonstrated for the first time for glucose non-enzymatic determination. The structures and morphologies of CuO-NFs were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and X-ray diffraction spectrum (XRD). Different dispersants were utilized for the suspension preparation and effects of ultrasonic time on the films electrode fabrication were investigated in detail. The assay performances to glucose were evaluated by cyclic voltammetry (CV) and chronoamperometry (I-t). Results revealed a high sensitivity (431.3 microAmM(-1)cm(-2)), fast response (about 1s), long-term stability and excellent resistance towards electrode fouling in the glucose determination at +0.40V. The improved performances of CuO-NFs films electrode for electro-oxidation glucose were ascribed to the high surface-to-volume ratio, complex pore structure, extremely long length of the as-prepared CuO-NFs, and the excellent three-dimensional network structure after immobilization. Results in this study suggest that electrospun CuO-NFs is a promising 1-D nanomaterial for further design and microfabrication of bioelectrochemical nanodevices for glucose determination.

Discrimination and simultaneous determination of hydroquinone and catechol by tunable polymerization of imidazolium-based ionic liquid on multi-walled carbon nanotube surfaces

Tunable polymerization of ionic liquid on the surfaces of multi-walled carbon nanotubes (MWCNTs) was achieved by a mild thermal-initiation-free radical reaction of 3-ethy-1-vinylimidazolium tetrafluoroborate in the presence of MWCNTs. Successful modification of polymeric ionic liquid (PIL) on MWCNTs surfaces (PIL-MWCNTs) was demonstrated by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis and X-ray photoelectron spectroscopy. The resulting PIL-MWCNTs possessed unique features of high dispersity in aqueous solution and tunable thickness of PIL layer, due to positive imidazole groups along PIL chains and controllable ionic liquid polymerization by tuning the ratio of precursor. Based on cation-π interaction between the positive imidazole groups on PIL-MWCNTs surface and hydroquinone (HQ) or catechol (CC), excellent discrimination ability toward HQ and CC and improved simultaneous detection performance were achieved. The linear range for HQ and CC were 1.0×10(-6) to 5.0×10(-4) M and 1.0×10(-6) to 4.0×10(-4) M, respectively. The detection limit for HQ was 4.0×10(-7) M and for CC 1.7×10(-7) M (S/N=3), correspondingly.

Application of the sol-gel technique to polyoxometalates: towards a new chemically modified electrode

Abstract A novel chemically-modified electrode containing 12-molybdophosphoric acid was achieved on the surface of platinum electrode by sol-gel technique. The electrochemical behavior of the modified electrode was characterized by cyclic voltammetry in detail. The film electrode obtained was very stable and exhibited electrocatalytic response for reduction of bromate, chlorate and hydrogen peroxide. Hydrogen peroxide was determined amperometrically at the modified electrode in the concentration range of 3×10 −2 to 2×10 −5 M and a detection limit of 7×10 −6 M (signal-to-noise ratio 3).

Electron and ion transfer through multilayers of gold nanoclusters covered by self-assembled monolayers of alkylthiols with various functional groups

The electrochemical characteristics of various kinds of multilayers of gold nanoclusters (GNCs) were investigated. Two types of gold nanoclusters, one covered by self-assembled monolayers (SAMs) of mercaptoundecanoic acid (MUA), hexanethiol (C6SH), and ferrocenylhexanethiol (FcC6SH), MHF-GNC, and the other with MUA and C6SH, MH-GNC, were used. The multilayers were constructed on a Au(111) surface based on a carboxylate/metal cation (Cu++)/carboxylate or carboxylate/cationic polymer (poly(allylamine hydrochloride):PAH)/carboxylate electrostatic interaction. While the multilayers constructed by the former method were stable only in nonaqueous solutions, those constructed by the latter method were stable even in aqueous solutions. Electrochemical measurements of the multilayers of MHF-GNCs showed a pair of waves corresponding to the redox of the ferrocene group around 350-480 mV and the charge of these peaks, i.e., the amount of adsorbed GNC, increased linearly with the construction cycle up to 6 cycles in the former and to 18 cycles in the latter. A rather reversible redox response of the ferrocene moiety was observed even at the gold electrodes with five GNC layers of two different sequences in which MHF-GNC exists as the layer closest to the gold electrode, ie., the first layer, or as the outermost layer with MH-GNC in the other layers. These results show the facile transfer of electrons and ions through the multilayers of the SAM-covered GNCs and electron transfer between the ferrocene moiety and the Au(111) electrode takes place through the GNC cores by hopping.

High visible light sensitive MoS2 ultrathin nanosheets for photoelectrochemical biosensing.

For the purpose of effectively utilizing the visible light, photoelectrochemical (PEC) detection represents a unique detection signal and different energy form of the excitation source. In this work, ultrathin MoS2 nanosheets with narrow band gap were successfully fabricated by a facile C3N4 sacrificial template assisted thermolytical approach. Upon immobilizing glucose oxidase, excellent photocatalytic activity towards glucose is achieved in neutral buffer solution. As a novel visible light sensitive photocatalytic material, ultrathin MoS2 nanosheets present a detection limit of ~0.61nM, which is much lower than those with the similar configurations reported previously. Based on the excellent anti-interference property, the feasibility of applying the proposed sensor to determine glucose in human serum is further demonstrated. This work provides new insight into the fabrication of promising visible light sensitive two-dimensional layered transition-metal chalcogenides nanostructures for construction of photoelectrochemical biosensors.

Confining MoS2 nanodots in 3D porous nitrogen-doped graphene with amendable ORR performance

MoS2 nanodots (NDs) were successfully embedded in the three-dimensional (3D) porous frameworks of N-doped graphene (NGr) via in situ pyrolysis of glucose, a layered C3N4 sacrificial template and monolayered MoS2 NDs. The monolayered MoS2 NDs were hydrothermally pre-synthesized and acted as size-controlled precursors. By varying the content of the MoS2 NDs, a series of MoS2 NDs/NGr was obtained, which displayed amendable activity towards oxygen reduction reaction (ORR) in basic solution, due to the balance between the exposed edge sites of the MoS2 NDs and the internal conductive channels of the 3D porous NGr. The optimal composition generated an efficient Pt-free ORR catalyst with good four-electron selectivity, and was shown to have a more positive shift in both the onset and peak potentials than its counterparts. The novel catalyst also demonstrated superior tolerance against methanol and better durability than commercial Pt/C.

Incorporated oxygen in MoS2 ultrathin nanosheets for efficient ORR catalysis

Controllable engineering of high-electronegativity oxygen (O)-heteroatoms into MoS2 ultrathin nanosheets is realized via a facile post-modification process. The incorporated oxygen atoms impart a dramatically enhanced ORR activity to the pristine nanosheets, with a 7.8-fold current increase as well as 180 mV and 160 mV positive shifts in both onset and half-wave potentials that are almost comparable with the commercial Pt/C catalyst. Furthermore, oxygen incorporation also triggers a transformation of the process from two-electron to a four-electron process. The improved topical conductivity, as well as the preferential adsorption of oxygen molecules originating from the heteroatoms engineering is supposed to be responsible for the efficient ORR. The prospect of controllably engineering heteroatoms into MoS2 ultrathin nanosheets with versatile applications is also highlighted in this work.

One-Step Pyrolytic Synthesis of Nitrogen and Sulfur Dual-Doped Porous Carbon with High Catalytic Activity and Good Accessibility to Small Biomolecules

As one of promising catalysts that contain high density of active sites, N doped carbons have been extensively researched, while the reports for N, S dual-doped carbon materials are far less exhaustive. Herein, devoid of activation process and template, N, S dual-doped porous carbon (N-S-PC) was prepared for the first time via one-step pyrolysis of sodium citrate and cysteine. Possessing unique porous structure and large pore volume as well as good accessibility, N-S-PC demonstrates significantly improved electrocatalytic activity toward oxidation of ascorbic acid (AA), dopamine (DA), and uric acid (UA). In the coexisting system, the peak potential separation between AA and DA is up to 251 mV, which is much larger than for most of the other carbons. On the basis of large potential separation and high current response, selective and sensitive simultaneous determination of AA, DA, and UA was successfully accomplished by differential pulse voltammetry, displaying a linear response from 50 to 2000 μM, from 0.1 to 50 μM, and from 0.1 to 50 μM with a detection limit (S/N = 3) of 0.78, 0.02, and 0.06 μM. This work highlights the importance of N, S dual doping and hierarchical porous carbons for efficient catalysis.

Sodium dodecyl benzene sulfonate functionalized graphene for confined electrochemical growth of metal/oxide nanocomposites for sensing application

The electrochemical fructose sensor attracts considerable attention in the food industry and for clinical applications. Here, a novel fructose biosensor was developed based on immobilization of highly dispersed CuO-Cu nanocomposites on Graphene that was non-covalently functionalized by sodium dodecyl benzene sulfonate (SDBS) (denoted briefly as SDBS/GR/CuO-Cu). The structure and morphology of SDBS/GR/CuO-Cu were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemistry and electrocatalysis were evaluated by cyclic voltammetry (CV). The fructose sensing performances were evaluated by chronoamperometry (i-t). Those properties were also compared with that of CuO-Cu. Results revealed the distinctly enhanced sensing properties of SDBS/GR/CuOCu towards fructose, showing significantly lowered overpotential of +0.40V, ultrafast (<1s) and ultra-sensitive current response (932 μAm M(-1)cm(-2)) in a wide linear range of 3-1000 μM, with satisfactory reproducibility and stability. Those could be ascribed to the good electrical conductivity, large specific surface area, high dispersing ability and chemical stability of GR upon being functionalized non-covalently by SDBS, as well as the outstanding cation anchoring ability of SDBS on GR to resist aggregation among Cu-based nanoparticles during electro-reduction. More importantly, an improved selectivity in fructose detection was achieved. SDBS/GR/CuO-Cu is one of the promising electrode materials for electrochemical detection of fructose.

One-step pyrolytic synthesis of small iron carbide nanoparticles/3D porous nitrogen-rich graphene for efficient electrocatalysis

Uniform iron carbide nanoparticles (Fe3C, ∼10 nm), size evolved from nano-scaled Fe-MIL-88b, were one-pot pyrolytically embedded in 3D porous N-rich graphene. Extra ORR catalytic activity with four-electron selectivity was achieved in an alkaline electrolyte. The onset and peak potential were 10 mV and 40 mV more positive, respectively, than commercial Pt/C.