Zhi-min Cai

Nonenzymatic amperometric sensing of glucose by using palladium nanoparticles supported on functional carbon nanotubes

A nonenzymatic electrochemical method was developed for glucose detection using an electrode modified with palladium nanoparticles (PdNPs)-functional carbon nanotubes (FCNTs). PdNPs were homogeneously modified on FCNTs through a facile spontaneous redox reaction and characterized by transmission electron microscopy. Based on the voltammetric and amperometric results, PdNPs efficiently catalyzed the oxidation of glucose at 0.40 V in the presence of 0.2M NaCl and showed excellent resistance towards poisoning from such interfering species as ascorbic acid, uric acid, and p-acetamidophenol. This anti-poisoning ability was investigated using analysis of the electrocatalytic products by in situ subtractively normalized interfacial Fourier transform infrared reflection spectroscopy, and the results indicated that no strongly adsorbed CO(ad) species could be found in the oxidation products, which was obviously different from the results obtained using Pt-based electrodes. In order to verify the sensor reliability, it was applied to the determination of glucose in urine samples. The results indicated that the proposed approach provided a highly sensitive, wide linear range, more facile method with good reproducibility for glucose determination, promising the development of Pd-based material in nonenzymatic glucose sensing.

A novel non-enzymatic ECL sensor for glucose using palladium nanoparticles supported on functional carbon nanotubes

A novel non-enzymatic electrochemiluminescence (ECL) sensor based on palladium nanoparticles (PdNPs)-functional carbon nanotubes (FCNTs) was discovered for glucose detection. PdNPs were homogeneously modified on FCNTs using a facile spontaneous redox reaction method. Their morphologies were characterized by transmission electron microscopy (TEM). Based on ECL experimental results, the PdNPs-FCNTs-Nafion film modified electrode displayed high electrocatalytic activity towards the oxidation of glucose. The free radicals generated by the glucose oxidation reacted with the luminol anion (LH(-)), and enhanced the ECL signal. Under the optimized conditions, the linear response of ECL intensity to glucose concentration was valid in the range from 0.5 to 40 micromol L(-1) (r(2)=0.9974) with a detection limit (S/N=3) of 0.09 micromol L(-1). In addition, the modified electrode presented high resistance towards the poisoning of chloride ion, high selectivity and long-term stability. In order to verify the sensor reliability, it was applied to the determination of glucose in glucose injection samples. The results indicated that the proposed approach provided a highly sensitive, more facile method with good reproducibility for glucose determination, promising the development of a non-enzymatic ECL glucose sensor.

A facile synthesis of palladium nanoparticles supported on functional carbon nanotubes and its novel catalysis for ethanol electrooxidation

In this study, a novel material, palladium nanoparticles-carboxylic functional carbon nanotubes (PdNPs-CFCNTs), based on PdNPs supported on CFCNTs was synthesized by a facile spontaneous redox method. The material reveals high electrochemical activity and excellent catalytic characteristic for alcohol electrooxidation on a glassy carbon electrode (GCE) in an alkaline medium. The preparation mechanism was studied by the galvanic cell effect between PdCl(4)(2-) and functional defect sites on CFCNTs. Results from UV-visible absorption spectroscopy and electrochemical impedance spectroscopy revealed that the reduction of PdCl(4)(2-) to metallic Pd was successfully achieved. Morphologies of PdNPs supporting on CFCNTs (PdNPs-CFCNTs) were also characterized by transmission electron micrograph. PdNPs-CFCNTs with the best electrocatalytic characteristics were obtained under the condition as: the weight ratio of Pd to CFCNTs was kept at 2:1, the temperature was kept at 70 degrees C in the synthesis, and the scan rate of the applied potential was selected at 60 mV s(-1). The results indicate that PdNPs-CFCNTs could be a great potential material in direct ethanol fuel cells and ethanol sensors.

An electrochemical sensor based on label-free functional allosteric molecular beacons for detection target DNA/miRNA

We report two novel electrochemical sensors (E-sensors) for the detection of target DNA and miRNA. The E-sensors were fabricated using label-free functional allosteric molecular beacons (aMBs), which can form streptavidin aptamers to bind to streptavidin peroxidase polymer and so generate catalytic currents in the presence of the targets. These E-sensors eliminate the antigen antibody interactions which require sophisticated DNA modification. During the experiment, we found a pair of CV peaks located at around 0.17 V. These peaks contributed to the redox reaction between TMB and TMB(+), and the adsorption-desorption process of TMB(+) to the negative aMB backbone. When the E-sensor was hybridized with the complement of the aMB sequence, a pair of CV peaks were found at around 0.47 V which were related to the redox reaction between TMB(+) and TMB(2+), and the process of intercalation of the planar structure of TMB(2+) to dsDNA. The RSV-aMB E-sensor could detect 44 amol RSV DNA in the 4 μL sample and performed well in complicated biological environments. The let-7a-aMB E-sensor reached a detection limit of 13.6 amol let-7a miRNA in the 4 μL sample and showed good selectivity for one base mismatched miRNA.

Electrogenerated chemiluminescence ethanol biosensor based on alcohol dehydrogenase functionalized Ru(bpy)32+ doped silica nanoparticles

An ethanol biosensor, based on the electrogenerated chemiluminescence of Ru(bpy)(3)(2+)-doped silica nanoparticles (RuSiNPs), was investigated in this study. The biosensor was a modified glassy carbon electrode, where alcohol dehydrogenase was crosslinked to RuSiNPs, and then immobilized on the electrode surface using chitosan. The results indicated that the biosensor exhibited excellent performance during ethanol determination with a wide linear range (10(-7) to 10(-2) M), low detection limit (5.0x10(-8) M) and good stability.

Electrochemiluminescence detection of methamphetamine based on a Ru(bpy)32+‐doped silica nanoparticles/Nafion composite film modified electrode

An electrochemiluminescence (ECL) approach for methamphetamine determination was developed based on a glassy carbon electrode modified with a Ru(bpy)₃ (2+)-doped silica nanoparticles/Nafion composite film. The monodispersed nanoparticles, which were about 50 nm in size, were synthesized using the water-in-oil microemulsion method. The ECL results revealed that Ru(bpy)₃ (2+) doped in silica nanoparticles retained its original photo- and electrochemical properties. The ECL intensity was found to be proportional to methamphetamine concentration over the range from 1.0 × 10(-7) to 1.0 × 10(-5) mol L(-1), and the detection limit was found to be 2.6 × 10(-8) mol L(-1). The proposed ECL approach was used to analyze the methamphetamine content in drugs.

Electrochemiluminescence detection of dichlorvos pesticide in luminol-CTAB medium

A simple, novel electrochemiluminescence (ECL) method for the detection of dichlorvos pesticide (DDVP) with high sensitivity was discovered. Detection was carried out in a static ECL system, in which a glassy carbon electrode was selected as the working electrode. ECL parameters, including the concentrations of cetyrltrimethylammonium bromide and luminol, the solution pH, and the scan rate of the applied potential, were optimized. Under these optimal conditions, the linear response of ECL-emission versus DDVP concentration was valid in the range 5-8000 ng/L (r(2)=0.9982) with a relative standard deviation of 4.3% at 2000 ng/L (n=10), yielding a detection limit (S/N=3) of 0.42 ng/L. The ECL emission was caused by a radical reaction process, in which the dissolved oxygen in the luminol solution reacted with the DDVP and generated free radicals. The free radicals reacted with the luminol anion and yielded the luminol radical. The approach presented was successfully applied to the determination of DDVP residues in vegetable samples.

Encoding electrochemiluminescence using Ru(bpy)(3)(2+) and fluorescein isothiocyanate co-doped silica nanoparticles

In this paper, an electrochemiluminescence (ECL) encoding method was developed for the first time, based on a dual-dye system including Ru(bpy)(3)(2+) as an ECL emitter and fluorescein isothiocyanate (FITC) as a coding dye.