Chunhui Xiao

Direct electrochemistry of glucose oxidase and biosensing for glucose based on boron-doped carbon nanotubes modified electrode

Due to their unique physicochemical properties, doped carbon nanotubes are now extremely attractive and important nanomaterials in bioanalytical applications. In this work, selecting glucose oxidase (GOD) as a model enzyme, we investigated the direct electrochemistry of GOD based on the B-doped carbon nanotubes/glassy carbon (BCNTs/GC) electrode with cyclic voltammetry. A pair of well-defined, quasi-reversible redox peaks of the immobilized GOD was observed at the BCNTs based enzyme electrode in 0.1M phosphate buffer solution (pH 6.98) by direct electron transfer between the protein and the electrode. As a new platform in glucose analysis, the new glucose biosensor based on the BCNTs/GC electrode has a sensitivity of 111.57 microA mM(-1)cm(-2), a linear range from 0.05 to 0.3mM and a detection limit of 0.01mM (S/N=3). Furthermore, the BCNTs modified electrode exhibits good stability and excellent anti-interferent ability to the commonly co-existed uric acid and ascorbic acid. These indicate that boron-doped carbon nanotubes are the good candidate material for the direct electrochemistry of the redox-active enzyme and the construction of the related enzyme biosensors.

Construction of hybrid bowl-like structures by anchoring NiO nanosheets on flat carbon hollow particles with enhanced lithium storage properties

Bowl-like hybrid structures have been designed and fabricated by anchoring NiO nanosheets on flat carbon hollow particles. When evaluated as an anode material for lithium-ion batteries, these unique NiO/carbon hybrid particles exhibit superior lithium storage properties in terms of high capacity, long term cycling stability and excellent rate capability.

Hollow nitrogen-doped carbon microspheres pyrolyzed from self-polymerized dopamine and its application in simultaneous electrochemical determination of uric acid, ascorbic acid and dopamine.

Hollow nitrogen-doped carbon microspheres (HNCMS) as a novel carbon material have been prepared and the catalytic activities of HNCMS-modified glassy carbon (GC) electrode towards the electro-oxidation of uric acid (UA), ascorbic acid (AA) and dopamine (DA) have also been investigated. Comparing with the bare GC and carbon nanotubes (CNTs) modified GC (CNTs/GC) electrodes, the HNCMS modified GC (HNCMS/GC) electrode has higher catalytic activities towards the oxidation of UA, AA and DA. Moreover, the peak separations between AA and DA, and DA and UA at the HNCMS/GC electrode are up to 212 and 136 mV, respectively, which are superior to those at the CNTs/GC electrode (168 and 114 mV). Thus the simultaneous determination of UA, AA and DA was carried out successfully. In the co-existence system of UA, AA and DA, the linear response range for UA, AA and DA are 5-30 μM, 100-1000 μM and 3-75 μM, respectively and the detection limits (S/N = 3) are 0.04 μM, 0.91 μM and 0.02 μM, respectively. Meanwhile, the HNCMS/GC electrode can be applied to measure uric acid in human urine, and may be useful for measuring abnormally high concentration of AA or DA. The attractive features of HNCMS provide potential applications in the simultaneous determination of UA, AA and DA.

Hierarchical NiCoO2 nanosheets supported on amorphous carbon nanotubes for high-capacity lithium-ion batteries with a long cycle life

In this paper, we report a facile approach to the synthesis of one-dimension (1D) hierarchical NiCoO2 nanosheets (NSs)@amorphous CNT composites based on the templates and carbon source of polymeric nanotubes (PNTs). Importantly, these sulfonated PNTs can also be used to prepare many other functional 1D metal oxides@amorphous CNT nanostructures, such as TiO2, SnO2, CoO and NiO, etc. Due to the outstanding nanostructures and the synergistic effects of the NiCoO2 NSs and amorphous CNTs, an ultrahigh discharge capacity of 1309 mA h g−1 is delivered by the NiCoO2@CNT composites, even after 300 cycles at a current density of 400 mA g−1. The favorable improvements of the NiCoO2 based lithium-ion batteries (LIBs) reported in this work illustrate that the 1D amorphous carbon matrix offers significant benefits for high-capacity metal oxide anode nanomaterials.

A novel and simple strategy for selective and sensitive determination of dopamine based on the boron-doped carbon nanotubes modified electrode

The Boron-doped carbon nanotubes (BCNTs) modified glassy carbon (GC) electrode was obtained simply and used for highly selective and sensitive determination of dopamine (DA). Comparing with the bare GC and CNTs/GC electrodes, the BCNTs have higher catalytic activity toward the oxidation of DA and ascorbic acid (AA). Moreover, the voltammetric peaks of AA and DA were separated enough (ca. 238 mV) at the BCNTs/GC electrode, which is superior to that at the CNTs/GC electrode (ca. 122 mV). Thus, the selective determination of DA was carried out successfully in the presence of AA. A wide concentration range (2.0 x 10(-8)-7.5 x 10(-5)M) and low detection limit (1.4 nM, S/N=3) for the DA detection were obtained. The possibility of the BCNTs/GC electrode for the determination of DA in human blood serum has also been evaluated. The advantageous properties of this electrode for the DA determination lie in its excellent catalytic activity, selectivity and simplicity. The more edge plane sites presented on the BCNTs surface were partially responsible for its good analytical behavior.

Amperometric glucose biosensor based on boron-doped carbon nanotubes modified electrode.

Doped carbon nanotubes are now extremely attractive and important nanomaterials in bioanalytical applications due to their unique physicochemical properties. In this paper, the boron-doped carbon nanotubes (BCNTs) were used in amperometric biosensors. It has been found that the electrocatalytic activity of the BCNTs modified glassy carbon (GC) electrode toward the oxidation of hydrogen peroxide is much higher than that of the un-doped CNTs modified electrode due to the large amount of edge sites and oxygen-rich groups located at the defective sites induced by boron doping. Glucose oxidase (GOD) was selected as the model enzyme and immobilized on the BCNTs modified glassy carbon electrode by entrapping GOD into poly(o-aminophenol) film. The performance of the sensor was investigated by electrochemical methods. At an optimum potential of +0.60 V and pH 7.0, the biosensor exhibits good characteristics, such as high sensitivity (171.2 nA mM(-1)), low detection limit (3.6 microM), short response time (within 6s), satisfactory anti-interference ability and good stability. The apparent Michaelis-Menten constant (K(m)(app)) is 15.19 mM. The applicability to the whole blood analysis of the enzyme electrode was also evaluated.

Polymerized ionic liquid-wrapped carbon nanotubes: The promising composites for direct electrochemistry and biosensing of redox protein

Polymerized ionic liquid-wrapped carbon nanotubes (PIL-CNTs) were firstly designed for direct electrochemistry and biosensing of redox proteins. The CNTs were coated successfully with polymerized ionic liquid (PIL) layer, as verified by transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and Fourier transform infrared (FT-IR) spectroscopy. The PIL-CNTs were dispersed better in water and showed superior electrocatalysis toward O(2) and H(2)O(2) comparing to pristine CNTs and the mixture of IL monomer and CNTs. With glucose oxidase (GOD) as a protein model, the direct electrochemistry of the redox protein was investigated on the PIL-CNTs modified glassy carbon (GC) electrode and excellent direct electrochemical performance of GOD molecules was observed. The proposed biosensor (GOD/PIL-CNTs/GC electrode) displayed good analytical performance for glucose with linear response up to 6mM, response sensitivity of 0.853 microA mM(-1), good stability and selectivity.

MoS2 nanosheets grown on amorphous carbon nanotubes for enhanced sodium storage

In this work, we demonstrate a step-wise route to build a novel one-dimensional (1D) architecture formed by MoS2 nanosheets and amorphous carbon nanotubes (ACNTs). Being evaluated as an anode material for NIBs, the as-prepared MoS2@ACNT electrode is capable of exhibiting a remarkable reversible capacity of 461 mA h g−1 at a current density of 500 mA g−1 over 150 cycles. Moreover, the coulombic efficiency is almost up to 100% except for the initial few cycles during the whole cycling test. The smart electrode architecture and appropriate synergistic effect between MoS2 and ACNTs are probably responsible for the enhanced electrochemical performance.

Electrochemical oxidation of purine and pyrimidine bases based on the boron-doped nanotubes modified electrode.

Based on the excellent physicochemical properties of boron-doped carbon nanotubes (BCNTs), the electrochemical analysis of four free DNA bases at the BCNTs modified glassy carbon (GC) electrode was investigated. Herein, the BCNTs/GC electrode exhibited remarkable electrocatalytic activity towards the oxidation of purine bases (guanine (G), adenine (A)). More significantly, the direct oxidation of pyrimidine bases (thymine (T), cytosine (C)) was realized. It may be due to that BCNTs have the advantages of high electron transfer kinetics, large surface area, prominent antifouling ability and electrode activity. On basis of this, a novel and simple strategy for the determination of G, A, T and C was proposed. The BCNTs/GC electrode showed high sensitivity, wide linear range and capability of detection for the electrochemical determination of G, A, T, and C. On the other hand, the electrochemical oxidation of quaternary mixture of G, A, T, and C at the BCNTs/GC electrode was investigated. It was obtained that the peak separation between G and A, A and T, T and C were large enough for their potential recognition in mixture without any separation or pretreatment. The BCNTs/GC electrode also displayed good stability, reproducibility and excellent anti-interferent ability. Therefore, it can be believed that the BCNTs/GC electrode would provide a potential application for the electrochemical detection of DNA in the field of genetic-disease diagnosis.

Dynamics of redox processes in ionic liquids and their interplay for discriminative electrochemical sensing.

Motivated by the use of ionic liquids (ILs) as green replacers of traditional electrolytes, a mechanistic study has been systematically conducted to comprehend various design principles responsible for electrochemical profiling of redox-active species in ILs. The full spectrum of properties associated with ILs is exploited to assess the viability of this platform, thus revealing the correlation between the redox properties and the physiochemical parameters of the species involved. This includes the evaluation of (1) the variation of redox responses toward analytes with similar molecular structures or functionalities of ILs, (2) the influence in terms of physical criteria of the system such as viscosity and conductivity as well as chemical structure of ILs, and (3) the sustainability in harsh conditions (high temperature or humidity) and interferences. The principle is exemplified via trinitrotoluene (TNT) and dinitrotoluene (DNT) with inherent redox activity as analytes and IL membranes as solvents and electrolytes using glassy carbon (GC) electrodes. A discrete response pattern is generated that is analyzed through linear discriminant analysis (LDA) leading to 100% classification accuracy even for the mixture of analytes. Quantitative analysis through square wave voltammetry (SWV) gave rise to the detection limits in liquid phase of 190 and 230 nM for TNT and DNT, respectively, with a linear range up to 100 μM. Gas-phase analysis shows strong redox signals for the estimated concentrations of 0.27 and 2.05 ppm in the gas phase for TNT and DNT, respectively, highlighting that ILs adopt a role as a preconcentrator to add on sensitivity with enhanced selectivity coming from their physiochemical diversity, thus addressing the major concerns usually referred to most sensor systems.