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This article reviews the progress made in the past 5 years in the field of direct and non-enzymatic electrochemical sensing of glucose. Following a brief discussion of the merits and limitations of enzymatic glucose sensors, we discuss the history of unraveling the mechanism of direct oxidation of glucose and theories of non-enzymatic electrocatalysis. We then review non-enzymatic glucose electrodes based on the use of the metals platinum, gold, nickel, copper, of alloys and bimetals, of carbon materials (including graphene and graphene-based composites), and of metal-metal oxides and layered double hydroxides. This review contains more than 200 refs. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Abstract: The electrocatalytic performance of nanoengineered PtNiFe catalysts in proton exchange membrane fuel cells (PEMFC) is described in this report. The membrane electrode assembly was prepared using carbon-supported PtNiFe nanoparticles treated at two different temperatures as the cathode electrocatalysts in PEMFC. The PtNiFe/C catalysts were found to exhibit excellent fuel cell performance, much better than that of commercial Pt/C catalyst. In addition to assessing the mass activities in the kinetic current region, the fuel cell performance was also determined in the ohmic and mass transport regions. The electrocatalytic and fuel cell performance are shown to depend on the thermal treatment temperature of the trimetallic catalysts. The higher-temperature treated catalysts showed a higher power density than the lower-temperature treated catalysts. The results are also discussed in terms of the effect of lattice shrinking in the trimetallic alloy nanoparticles on the electrocatalytic activity. [Copyright &y& Elsevier]

Abstract: The report describes the findings of an investigation of nanoengineered gold–platinum (AuPt) catalysts in proton exchange membrane fuel cells. The membrane electrode assembly was prepared using carbon-supported Au n Pt100−n nanoparticles with controlled sizes and bimetallic compositions that were thermally treated under controlled temperature, atmosphere, and time. Examples shown in this report included Au22Pt78/C and Au49Pt51/C catalysts treated at 400–500°C. The electrocatalytic performances of these catalysts in the fuel cells was found to be dependent on the bimetallic composition and the nanoscale phase properties which are controlled by the thermal treatment parameters (temperature and time). Excellent fuel cell performance was observed for the catalysts which are characteristic of an alloyed AuPt phase with a lattice parameter approaching that for an Pt-rich alloy phase. The results have also demonstrated excellent stability of the nanoengineered AuPt catalysts in fuel cells. The observed combination of high activity and high durability of the selected AuPt catalysts indicated that this nanoengineered bimetallic catalyst system, upon further refinement and optimization of the nanoscale phase properties and durability serve as a promising candidate of electrocatalysts for the practical application in Proton Exchange Membrane fuel cells. [Copyright &y& Elsevier]

Abstract: Proton exchange membrane fuel cells (PEMFCs) are attractive because of their high conversion efficiency, low pollution, lightweight, and high power density. A major area of challenges is the design and engineering of active, robust, and low-cost electrocatalysts. This report discusses recent findings of our investigations of the design and nano-engineering of platinum–vanadium–iron catalysts for use in PEMFC. The membrane electrode assembly was prepared using nano-engineered PtVFe nanoparticles with controlled composition and size supported on carbon as cathode electrocatalysts. The electrocatalytic activity and stability of the catalysts have been characterized by both rotating disk electrode and membrane electrode assembly measurements. The trimetallic catalysts have been shown to exhibit excellent electrocatalytic performance in PEMFC in comparison with commercial platinum catalysts. The results exhibited a good agreement between obtained these two types of measurements in terms of the dependence on particle size, composition, and thermal treatment condition. The catalysts also showed good stability, which are potentially useful for practical application in PEMFCs. [ABSTRACT FROM AUTHOR]

Abstract: ZnO nanoflowers were synthesized by a simple process (ammonia-evaporation-induced synthetic method) and were applied to the hydrazine electrochemical sensor. The prepared material was characterized by means of scanning electron microscopy (SEM) and X-ray powder diffraction (XRD) and was then immobilized onto the surface of a glassy carbon electrode (GCE) via multi-walled carbon nanotubes (MWCNTs) to obtain ZnO/MWCNTs/GCE. The potential utility of the constructed electrodes was demonstrated by applying them to the analytical determination of hydrazine concentration. An optimized limit of detection of 0.18μM was obtained at a signal-to-noise ratio of 3 and with a fast response time (within 3s). Additionally, the ZnO/MWCNTs/GCE exhibited a wide linear range from 0.6 to 250μM and higher sensitivity for hydrazine than did the ZnO modified electrode without immobilization of MWCNTs. [Copyright &y& Elsevier]

A glassy carbon electrode (GCE) modified with ferrocenecarboxamide, gold nanoparticles and multiwall carbon nanotubes was constructed and characterized by field emission scanning electron microscopy and cyclic voltammetry. The electrochemical behavior of bilirubin (BR) on the modified electrode was investigated and it was found that the modified electrode had an obvious electrocatalytic effect on bilirubin. Compared with a bare GCE, the modified electrode exhibited a marked enhancement in the current response for bilirubin. Amperometry was employed to investigate the electrocatalytical oxidation of bilirubin on the modified electrode. As a result, it exhibits an excellent electrocatalytic response to bilirubin with a response time of less than 5 s, a broad linear range of 1 to 100 μmol L−1, as well as good long-term stability and reproducibility. [ABSTRACT FROM AUTHOR]

The article discusses a study which determined the characteristics of a modified glassy carbon (GC) electrode in response to uracil interaction. It describes the role of uracil in biochemical processes related to diseases and metabolic disorders, and explains the preparation of the polythionine/multiwall carbon nanotube/glassy carbon (PTH/MWNTs/GC) electrode. The study confirmed the efficacy of the modified GC electrode as a biosensing agent for determination of uracil concentrations.

The preparation of a gold electrode modified by aminylferrocene (FcAI) covalently bound to L-cysteine self-assembled monolayer (L-Cys/Au SAM) was described, and characterized by cyclic voltammogram (CV) and electrochemical impedance spectroscopy (EIS). In pH 7.4 buffers, FcAI incorporated in L-Cys/Au SAM gave a pair of well-defined and quasi-reversible cyclic voltammetric peaks at 0.109 vs. saturated calomel eletrode (SCE), characteristic of Fe(II)/Fe(III) redox couples of the Fc. The apparent surface electron transfer rate constant is 6.86 s -1 at the modified electrode. The immobilized Fc gave an excellent electrocatalytic activity for the oxidation of epinephrine (EP). The catalytic current of EP vs. its concentration has a good linear relation in the range of 1.7×10 -7 –1.0×10 -4 mol/L, with the correlation coefficient of 0.9975 and detection limit of 1.8×10 -8 mol/L. The modified electrode can be used for the determination of EP in practical injection. The method is simple, quick, sensitive, and accurate. [ABSTRACT FROM AUTHOR]

Hemoglobin(Hb) was successfully immobilized on gold nanoparticles(GNP) associated with a 1,4-benzenedimethanethiol(BDT) monolayer on a gold electrode surface and was characterized by cyclic voltammetry(CV) and electrochemical impedance spectroscopy(EIS). Direct electron transfer(DET) between Hb and the modified electrode was achieved without the aid of any electron mediator. GNP can greatly promote the redox of Hb, on which a pair of obvious CV peaks for Hb Fe(III)/Fe(II) redox couple were obtained in pH 6.2 phosphate buffer solution(PBS). In pH 6.2 PBS, the formal potential(E°') of Hb was−0.180 V(versus SCE), and the electron transfer rate constant was 5.2 s−1. The formal potential of Hb on gold colloidal modified electrode shifts linearly with pH with a slope of−55.5 mV/pH at 20°C, showing that the electron transfer is accompanied by single proton transportation. The high efficiency of the Hb/GNP/BDT modified gold electrode toward the catalytic electroreduction of hydrogen peroxide has been observed. The immobilized Hb gave an excellent electrocatalytic response to H2O2. Potential application of Hb/GNP/BDT modified gold electrode as biosensors to monitor H2O2 is proposed. [ABSTRACT FROM AUTHOR]

This report demonstrates a novel strategy of chromium-assisted synthesis of platinum nanocubes as electrocatalysts for oxygen reduction reaction with enhanced specific activity. [ABSTRACT FROM AUTHOR]

Abstract: This paper reports new findings of an investigation of the electrocatalytic performance of nanostructured PtVFe catalysts in proton exchange membrane fuel cells (PEMFC). The membrane electrode assembly was prepared using nano-engineered PtVFe nanoparticles with controlled composition and size supported on carbon as the cathode electrocatalysts. The results reveal that the PtVFe/C catalysts exhibited excellent fuel cell performance, better than that using the commercial Pt/C catalyst. This finding provides the first example demonstrating the viability of the PEMFC application of the nanostructured trimetallic catalysts. [Copyright &y& Elsevier]

Abstract: The ability to engineer the composition and structure of nanoalloy catalysts is important for developing active, robust and low-cost catalysts for fuel cell applications. The recognition of the importance of structural and chemical alloying effects of nanoalloy particles on the electrocatalytic properties has been an important driving force for the exploration of various binary and ternary platinum-based alloy catalysts. In comparison with the extensive studies of binary alloy catalysts for oxygen reduction reaction, the exploration of ternary nanoalloy catalysts in the past few years has led to many intriguing discoveries in terms of enhanced catalytic activities. In this article, we highlight recent progress of our work in the synthesis, processing and electrochemical characterization of molecularly-capped ternary nanoalloy catalysts, focusing on the enhanced electrocatalytic activity of Pt-based ternary nanoalloy catalysts for oxygen reduction reaction in fuel cells. Selected examples of ternary nanoparticle catalysts for electrocatalytic oxygen reduction reaction will be discussed. While important insights have been gained from studies of detailed structural aspects based a variety of techniques, this report summarizes some of the major findings in the studies of the electrochemical and electrocatalytic properties of the ternary nanoalloys to highlight the importance of ternary composition for the design and preparation of electrocatalysts. [Copyright &y& Elsevier]

Abstract: Sub-10nm CeO2 nanoparticles decorated multi-walled carbon nanotubes has been constructed for electrochemial determination of guanine and adenine. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) were used to characterize the nanoparticles CeO2/MWCNTs. Electrochemical impedance spectroscopy (EIS) was used to characterize the electrode modifying process. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used to study the electrocatalytic activity toward the electrochemical oxidation of guanine and adenine. The detection limit (S/N=3) for adenine and guanine was found to be 20 and 10nM, respectively. The obtained sensitivity toward guanine and adenine was 1.26 and 1.13μA/μM in the linear concentration range 5–50μM and 5–35μM, respectively. These results demonstrate that the carbon nanotubes could provide huge locations and facilitate the adsorptive accumulation of the guanine and adenine, and the CeO2 nanoparticles are promising substrates for the development of high-performance electrocatalysts for biosensing. [Copyright &y& Elsevier]

Abstract: In this work, Ni(OH)2 nanoplates grown on the Cu substrate were synthesized and characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Then a novel Cu–Ni(OH)2 modified glass carbon electrode (Cu–Ni(OH)2/GCE) was fabricated and evaluated by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and typical amperometric response (i–t) method. Exhilaratingly, the Cu–Ni(OH)2/GCE shows significant electrocatalytic activity toward the reduction of H2O2. At an applied potential of −0.1V, the sensor produces an ultrahigh sensitivity of 408.1μAmM−1 with a low detection limit of 1.5μM (S/N=3). The response time of the proposed electrode was less than 5s. What''s more, the proposed sensor displays excellent selectivity, good stability, and satisfying repeatability. [Copyright &y& Elsevier]

Abstract: A novel route (electrodeposition) for the fabrication of porous ZnO nanofilms attached multi-walled carbon nanotubes (MWCNTs) modified glassy carbon electrodes (GCEs) was proposed. The morphological characterization of ZnO/MWCNT films was examined by scanning electron microscopy (SEM) and X-ray powder diffraction (XRD). The performances of the ZnO/MWCNTs/GCE were characterized with cyclic voltammetry (CV), Nyquist plot (EIS) and typical amperometric response (i–t). The potential utility of electrodes constructed was demonstrated by applying them to the analytical determination of hydroxylamine concentration. An optimized limit of detection of 0.12μM was obtained at a signal-to-noise ratio of 3 and with a fast response time (within 3s). Additionally, the ZnO/MWCNTs/GCE exhibited a wide linear range from 0.4 to 1.9×104 μM and higher sensitivity. The ease of fabrication, high stability, and low cost of the modified electrode are the promising features of the proposed sensor. [Copyright &y& Elsevier]

Abstract: Cu2O/MWCNT (multi-walled carbon nanotubes) nanocomposites were successfully prepared in large quantities with a new fixure-reduction method under low temperature. The morphology and shape of the Cu2O/MWCNTs nanocomposites were characterized by field emission scanning electron microscopes (FESEMs), energy dispersive X-ray (EDX), X-ray photoelectron spectroscopy (XPS) and X-ray powder diffraction (XRD), respectively. Cyclic voltammetry (CV) was used to evaluate the electrochemical performance of the Cu2O/MWCNTs nanocomposites modified electrode towards glucose. Compared to the bare GCE, the Cu2O nanoparticles and the MWCNTs modified electrode, the Cu2O/MWCNTs modified electrode displays high electrocatalytic activity towards the oxidation of glucose. With a potential of −0.20V, the Cu2O/MWCNTs modified electrode was used to determine glucose by amperometric, showing significantly lower overvoltage and a linear dependence (R =0.9958) in the concentration up to 10μM with a sensitivity of 6.53μAμmolL−1 and a detection limit of 0.05μmolL−1 (signal-to-noise ratio of 3). In summary, the preparation process of the nanocomposites is very simple and the nanocomposites could be used for the development of enzyme-free glucose sensor. [Copyright &y& Elsevier]