Cuili Xiang

Impedance based detection of pathogenic E. coli O157:H7 using a ferrocene-antimicrobial peptide modified biosensor.

Escherichia coli O157:H7 can cause life-threatening gastrointestinal diseases and has been a severe public health problem worldwide in recent years. A novel biosensor for the detection of E. coli O157:H7 is described here using a film composed of ferrocene-peptide conjugates, in which the antimicrobial peptide magainin I has been incorporated as the biorecognition element. Electrochemical impedance spectroscopy was employed to investigate the surface characteristics of the newly developed biosensor and to monitor the interactions between the peptide film and the pathogenic bacteria. X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry (ToF-SIMS) were employed to confirm the immobilization of ferrocene-conjugate onto the gold surface. Non-pathogenic E. coli K12, Staphylococcus epidermidis and Bacillus subtilis were used in this study to evaluate the selectivity of the proposed biosensor. The results have shown the order of the preferential selectivity of the method is E. coli O157:H7>non-pathogenic E. coli>gram positive species. The detection of E. coli O157:H7 with a sensitivity of 10(3)cfu/mL is enabled by the biosensor. The experimental conditions have been optimized and the plot of changes of charge transfer resistance (ΔRCT) and the logarithm of the cell concentration of E. coli O157:H7 shows a linear correlation in the range of 10(3)-10(7)cfu/mL with a correlation coefficient of 0.983.

Sensitive electrochemical detection of Salmonella with chitosan–gold nanoparticles composite film

An ultrasensitive electrochemical immunosensor for detection of Salmonella has been developed based on using high density gold nanoparticles (GNPs) well dispersed in chitosan hydrogel and modified glassy carbon electrode. The composite film has been oxidized in NaCl solution and used as a platform for the immobilization of capture antibody (Ab1) for biorecognition. After incubation in Salmonella suspension and horseradish peroxidase (HRP) conjugated secondary antibody (Ab2) solution, a sandwich electrochemical immunosensor has been constructed. The electrochemical signal was obtained and improved by comparing the composite film with chitosan film. The result has shown that the constructed sensor provides a wide linear range from 10 to 10(5) CFU/mL with a low detection limit of 5 CFU/mL (at the ratio of signal to noise, S/N=3:1). Furthermore, the proposed immunosensor has demonstrated good selectivity and reproducibility, which indicates its potential in the clinical diagnosis of Salmonella contaminations.

Amperometric glucose biosensor based on ultrafine platinum nanoparticles

Abstract In the present paper the ultrafine and highly dispersed platinum nanoparticles (average size 3 nm) were used for the construction of a glucose biosensor in a simple method. An excellent response to glucose has been obtained with a high sensitivity (137.7 µA mM−1 cm−2) and fast response time (5 s). The biosensor showed a detection limit of 5 µM (at the ratio of signal to noise, S/N=3) and a linear range form 0.2 to 3.2 mM with a correlation coefficient r=0.999. The apparent Michaelis–Menten constant (k m) and the maximum current were estimated to be 9.36 and 1.507 mA mM−1 cm−2, respectively. In addition, effects of pH value, applied potential and the interferents on the amperometric response of the sensor were investigated and discussed.

Fabrication and characterization of a novel nanoporous Co–Ni–W–B catalyst for rapid hydrogen generation

A highly active nanoporous Co–Ni–W–B alloy has been prepared using chemical reduction in an ethanol solution and tested as a novel catalyst for hydrolysis of ammonia borane. Compared with the alloy prepared in an aqueous solution, the as-prepared alloy shows a much higher surface area and hydrogen generation rate.

Simple synthesis of graphene-doped flower-like cobalt–nickel–tungsten–boron oxides with self-oxidation for high-performance supercapacitors

In this study, we devised an easy and simple approach to synthesize a composite of flower-like cobalt–nickel–tungsten–boron oxides (Co–Ni–W–B–O) that were doped with reduced graphene oxide (rGO); the composite was designed for supercapacitor applications. A Co–Ni–W–B alloy was first deposited on rGO through one-pot chemical reduction in an ethanol solution at room temperature. The resulting Co–Ni–W–B alloy self-oxidized in air on the rGO surface. The Co–Ni–W–B–O/rGO composites resembled three-dimensional flowers with a high surface area; they also exhibited superior electrochemical performance when compared to most previously reported electrodes based on nickel–cobalt oxides. Furthermore, the Co–Ni–W–B–O/rGO composite prepared in an ethanol solution showed much higher electrochemical performance than the composite prepared in water. The Co–Ni–W–B–O/rGO electrode showed an ultrahigh specific capacitance of 1189.1 F g−1 at 1 A g−1 and exhibited a high energy density of 49.9 W h kg−1 along with remarkable cycle stability (10 000 cycles with 80.7% capacitance retention at 15 A g−1), which is promising for its application in energy storage devices.

Self-assembly synthesis of nitrogen-doped mesoporous carbons used as high-performance electrode materials in lithium-ion batteries and supercapacitors

Nitrogen-doped mesoporous carbons (NMCs) have been employed as electrode materials for energy storage devices such as lithium-ion batteries (LIBs) and supercapacitors due to their high accessible porosity and nitrogen content. However, how to maintain the structural stability of NMCs with abundant nitrogen atoms in their 2D honeycomb lattice is still a significant challenge. Herein, NMCs with a high nitrogen content of 18.86 wt% have been successfully synthesized via a self-assembly route in the presence of guanine as a nitrogen source. Furthermore, the nitrogen content and porosity of NMCs can be tuned by controlling the experimental conditions. Benefiting from the high N content, appropriate specific surface area (455 m2 g−1), and high accessible porosity, NMC exhibits superior electrochemical performance. This NMC anode for LIBs can retain a discharge capacity as high as 610 mA h g−1 with a coulombic efficiency of 98.5% after 50 cycles. In addition, it also displays good potential towards supercapacitor application with a specific capacitance of 227 F g−1 (in 6 M KOH) at a current density of 0.5 A g−1. The enhanced electrochemical performance could be attributed to both the low charge transfer resistance and the incremental electrochemical activity resulting from the existence of optimized nitrogen atoms.

Direct Electron Transfer of Horseradish Peroxidase and Its Biosensor Based on Gold Nanoparticles/Chitosan/ITO Modified Electrode

Abstract Gold nanoparticles/chitosan modified indium tin oxide (ITO) coated glass electrode was prepared by a simple layer-by-layer self-assembly technique. Horseradish peroxidase (HRP) was successfully immobilized on the modified electrode by electrostatic adsorption. Direct electrochemistry and electrocatalysis of HRP were investigated. The composite film showed an obvious promotion for the direct electron transfer between HRP and the underlying electrode. The immobilized HRP exhibited an excellent electrocatalytic activity toward the reduction of H2O2. The catalysis currents increased linearly to the H2O2 concentration in a wide range of 2.0 × 10−5 to 6.5 × 10−3 M with a low detection limit of 3.5 × 10−6 M. The calculated apparent Michaelis-Menten constant (K ) was 4.43 mM.

Organic carbon gel assisted-synthesis of Li1.2Mn0.6Ni0.2O2 for a high-performance cathode material for Li-ion batteries

Lithium-rich layered oxide Li1.2Ni0.2Mn0.6O2 with a stable network flake structure has been synthesized through a facile resorcinol–formaldehyde (RF) organic carbon gel-assisted method. The as-prepared sample used as a cathode material in lithium ion batteries (LIBs) was characterized by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and electrochemical measurements. The stable network flake structure is assembled through a dense stack of nanoparticles with an average size of 50–200 nm. As an active material for LIB cathodes, the Li1.2Ni0.2Mn0.6O2 sample shows excellent rate capacities and cycling stability, and delivers a high initial discharge capacity of 273.3 mA h g−1 at 0.1C (1C = 200 mA g−1) between 2.0 V and 4.8 V. When the discharge rate is increased to 2C, an initial capacity of 196.7 mA h g−1 is obtained. After 150 cycles, a discharge capacity of 183.7 mA h g−1 and a high capacity retention of 93.4% are yielded at a rate of 2C.

Light metal borohydrides/amides combined hydrogen storage systems: composition, structure and properties

The implementation of a future economy based on hydrogen-related energy needs an urgent development of efficient, safe, and economic solid-state hydrogen-storage materials. During the search process for novel materials for storing hydrogen, research interests in the past few decades have been intensively focused on light metal borohydrides and amides as two representative chemical complex hydrides with high hydrogen capacities. Recently, a large number of studies have reported new borohydride/amide combined systems that expand the scope of hydrogen-storage materials. Here, we review the interaction between light metal borohydrides and amides for storing hydrogen, with a special emphasis on the synthetic strategies and structural, physical, and chemical properties, which reveal a correlation between the composition, structure, and dehydrogenation properties and also provide general principles to the design of new combined systems with tailored functionality. This review also demonstrates the current progress on the dehydrogenation kinetic improvement of borohydride/amide combined systems.

Nitrogen-rich sandwich-like carbon nanosheets as anodes with superior lithium storage properties

Carbon materials such as graphite have been used as anode material for Li-ion batteries (LIBs). However, the energy stored in carbon materials is greatly dependent on their structural characteristics. Herein, nitrogen-rich sandwich-like carbon nanosheets (NSCN) have been prepared through a facile hydrothermal carbonization (HTC) method followed by pyrolysis. The nitrogen-rich sandwich-like carbon nanosheets synthesized at 600 °C (NSCN-600) have a higher specific surface area of 1112 m2 g−1 and a total nitrogen content of 11.4 wt% (therein 9.30 wt% for both pyridinic-N and pyrrolic-N), giving rise to high discharge capacity (910 mA h g−1 at 100 mA g−1 after 50 cycles) and remarkable rate capability (719 mA h g−1 at 500 mA g−1 after 200 cycles and 390 mA h g−1 at 2000 mA g−1). Such desirable electrochemical properties could be attributed to the unique sandwich-like nanostructures consisting of a number of amorphous carbon nanoparticles closely covered with carbon sheet layers. Such a simple preparation method could provide a strategy for rational engineering of nanostructured nitrogen-rich carbonaceous materials for high-performance LIBs.