Jian-Jun Shi

Sonoelectrochemical fabrication of PDDA-RGO-PdPt nanocomposites as electrocatalyst for DAFCs

Sonoelectrochemical technique was successfully used to fabricate alloy–graphene nanocomposites. It not only provides a simple way to synthesize alloy nanoparticles, but also shows a general strategy for fabricating graphene-based nanostructures with anticipated properties. Pd was co-electrodeposited with Pt at different atomic ratios, and then was anchored with reduced graphene oxide (RGO) simultaneously in the presence of PDDA. The morphologies and structures of the as-prepared PDDA-RGO-PdPt nanocomposites were extensively investigated by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The composition was evaluated by energy dispersive X-ray spectrometry (EDS) and inductively coupled plasma–atomic emission spectroscopy (ICP-AES). Raman spectra revealed the surface properties of graphene and its interaction with metallic nanoparticles. Cyclic voltammetric (CV) and chronoamperometric experiments further exhibited their catalytic activity and stability for the electro-oxidation of ethanol in alkaline media, which could be applied as promising electrocatalysts for direct alcohol fuel cells (DAFCs).

Fabrication of a boron nitride–gold nanocluster composite and its versatile application for immunoassays

A multifunctional boron nitride-gold nanocluster composite was fabricated using poly-diallyldimethylammonium chloride as a stabilizer and a linker. The as-fabricated composite could be used as a fluorescent or an electrochemical label for immunosensing in the sensitive detection of interleukin-6.

Highly Sensitive and Selective Photoelectrochemical Biosensor for Hg2+ Detection Based on Dual Signal Amplification by Exciton Energy Transfer Coupled with Sensitization Effect

A highly sensitive and selective photoelectrochemical (PEC) biosensor for Hg(2+) detection was developed on the basis of the synergistic effect of exciton energy transfer (EET) between CdS quantum dots (QDs) and Au nanoparticles (NPs) coupled with sensitization of rhodamine 123 (Rh123) for signal amplification. First, the TiO2/CdS hybrid structure obtained by depositing CdS QDs on TiO2 film was employed as a matrix for immobilizing probe DNA (pDNA). Next, Rh123 was introduced into the pDNA terminal, and then Au NP labeled target DNA (Au-tDNA) was hybridized with pDNA to form a rod-like double helix structure. The detection of Hg(2+) was based on a conformational change of the pDNA after incubating with Hg(2+). In the absence of Hg(2+), Rh123 was located away from the electrode surface due to the DNA hybridization, leading to inhibition of the sensitization effect, and meanwhile, the occurrence of EET between CdS QDs and Au NPs resulted in a photocurrent decrease. However, after incubating with Hg(2+), the rod-like double helix was disrupted, and the energy transfer was broken. In this case, the photocurrent recovered, and meanwhile, the folded pDNA made the labeled Rh123 move closer to the electrode surface, leading to the formation of the sensitization structure, which evidently increased the photocurrent intensity. The sensitivity of the biosensor for Hg(2+) detection was greatly enhanced for the dual signal amplification strategy. The linear range was 10 fM to 200 nM, with a detection limit of 3.3 fM. This biosensor provides a promising new platform for detecting various heavy metal ions at ultralow levels.

Electron Transfer Mediated Electrochemical Biosensor for MicroRNAs Detection Based on Metal Ion Functionalized Titanium Phosphate Nanospheres at Attomole Level

MicroRNAs (miRNAs) have emerged as new candidates as diagnostic and prognostic biomarkers for the detection of a wide variety of cancers; thus, sensitive and selective detection of microRNAs is significant for early-phase cancer diagnosis and disease prevention. A novel and simple electrochemical miRNA biosensor was developed using Cd(2+)-modified titanium phosphate nanoparticles as signal unit, two DNA as capture probes, and Ru(NH3)6(3+) as electron transfer mediator. Large quantities of cadmium ions were mounted in titanium phosphate spheres to output the electrochemical signal. Because of the presence of Ru(NH3)6(3+) molecules that interacted with DNA base-pairs as electron wire, the electrochemical signal significantly increased more than 5 times. This approach achieved a wide dynamic linear range from 1.0 aM to 10.0 pM with an ultralow limit detection of 0.76 aM, exerting a substantial enhancement in sensitivity. Moreover, the proposed biosensor was sufficiently selective to discriminate the target miRNAs from homologous miRNAs and could be used for rapid and direct analysis of miRNAs in human serum. Therefore, this strategy provides a new and ultrasensitive platform for miRNA expression profiling in biomedical research and clinical diagnosis.

Ultrasensitive multi-analyte electrochemical immunoassay based on GNR-modified heated screen-printed carbon electrodes and PS@PDA-metal labels for rapid detection of MMP-9 and IL-6

An ultrasensitive electrochemical immunoassay was developed for rapid detection of interleukin-6 (IL-6) and matrix metallopeptidase-9 (MMP-9); the method utilized PS@PDA-metal nanocomposites based on graphene nanoribbon (GNR)-modified heated screen-printed carbon electrode (HSPCE). Because of the good hydrophilicity and low toxicity, GNRs were used to immobilize antibodies (Ab) and amplify the electrochemical signal. PS@PDA-metal was used to label antibodies and generate a strong electrochemical signal in acetic buffer. A sandwich strategy was adopted to achieve simultaneous detection of MMP-9 and IL-6 based on HSPCE without cross-talk between adjacent electrodes in the range of 10(-5) to 10(3) ng mL(-1) with detection limits of 5 fg mL(-1) and 0.1 pg mL(-1) (S/N=3), respectively. The proposed method showed wide detection range, low detection limit, acceptable stability and good reproducibility. Satisfactory results were also obtained in the practical samples, thus showing this is a promising technique for simultaneous clinical detection of biocomponent proteins.

A competitive electrochemical immunosensor for the detection of human interleukin-6 based on the electrically heated carbon electrode and silver nanoparticles functionalized labels

A facile one-step electrochemical reduction method was developed to prepare electrochemically reduced graphene oxide (ERGO) and gold-palladium bimetallic nanoparticles (AuPdNPs) as the platform of immunosensor. A novel competitive electrochemical immunosensor was then proposed by combining the ERGO-AuPdNPs platform with silver nanoparticles (AgNPs) functionalized polystyrene bionanolabel for the sensitive detection of human interleukin-6 (IL-6). An electrically heated carbon electrode (HCPE) was introduced in the detection procedure of the immunosensor, and further improved the sensitivity. The immunosensor exhibited a wide linear response to IL-6 ranging from 0.1 to 100000 pg mL(-1) with a detection limit of 0.059 pg mL(-1). The proposed method showed good precision, broad linear range, acceptable stability and high reproducibility, and could be used for the detection of IL-6 in real samples, which possessed promising application in clinical research.

Synthesis of stabilizer-free gold nanoparticles by pulse sonoelectrochemical method.

In this paper, stabilizer-free gold nanoparticles (Au NPs) were synthesized by a facile pulse sonoelectrochemical method in the absence of stabilizer. The size and shape of the Au NPs can be controlled by adjusting current density, reaction time and the pH value of the precursor solution. The morphology and structure of the Au NPs were characterized by transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), UV-visible spectra (UV-vis), energy-dispersive X-ray (EDX) and X-ray diffraction (XRD). The pH value has a great effect on the size and dispersion of the obtained Au NPs. The Au NPs could further used as substrate for fabrication of HRP biosensor which exhibited excellent biocatalytical activity with high sensitivity and rapid response. This method provides a facile route for the synthesis of stabilizer-free Au NPs. Since the preparation process do not need the addition of any surfactants/capping agent, the resulting Au NPs are suitable for the applications in fields of biology and catalysis.

Sonoelectrochemical synthesis of water-soluble CdTe quantum dots

A facile and fast one-pot method has been developed for the synthesis of CdTe quantum dots (QDs) in aqueous phase by a sonoelectrochemical route without the protection of N2. The morphology, structure and composition of the as-prepared products were investigated by high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and energy dispersive X-ray spectrometer (EDS). The influences of current intensity, current pulse width, and reaction temperature on the photoluminescence (PL) and quantum yield (QY) of the products were studied. The experimental results showed that the water-soluble CdTe QDs with high PL qualities can be conveniently synthesized without precursor preparation and N2 protection, and the PL emission wavelength and QY can be effectively controlled by adjusting some parameters. This method can be expected to prepare other QDs as promising building blocks in solar cell, photocatalysis and sensors.

Sonoelectrochemical synthesis and assembly of bismuth–antimony alloy: From nanocrystals to nanoflakes

Bismuth-based nanostructures have attracted growing interest because of their promising thermoelectric properties and applications in optics and electronics. Pulsed sonoelectrochemical technique was selected to fabricate bismuth-antimony (BiSb) flake-like alloy in ethylene glycol aqueous solution. The formation mechanism for the BiSb alloy was discussed. Ultrasonic played an important role in regenerating electrode and promoting the formation of BiSb nanoflakes. Citrate and polyvinylpyrrolidone (PVP) were introduced as mixed controlling agents during the nucleation and growth process.

DETERMINATION OF TRACE LEAD AND CADMIUM USING STRIPPING VOLTAMMETRY IN FLUIDIC MICROCHIP INTEGRATED WITH SCREEN-PRINTED CARBON ELECTRODES

A homemade fluidic microchip integrated with screen-printed carbon electrodes (SPCE) for direct detection of trace Pb(II) and Cd(II) has been designed. Analytes are accumulated and determined in a flow system with stripping voltammetry, and the methods of standardization are applied for self-calibration. The portable device produces a well-defined and reproducible electrochemical signal for monitoring Cd(II) and Pb(II), and limits of detection are low to 2.0 ppb and 3.0 ppb, respectively. Meanwhile, Pb(II) and Cd(II) in aqueous solutions are also qualitative measured with calibration both by internal standard and standard addition method. The proposed methodology possesses the advantages of simple, fast, high sensitivity, and stability. It has potential applications in the fields of environmental monitoring and biomedical science for real-time and online measurements.