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Xuping Sun

Publications and source records attributed to Xuping Sun.

13 recordsLinked to original sources
PubMed2006

Pt nanoparticles: Heat treatment-based preparation and Ru(bpy)(3)2+-mediated formation of aggregates that can form stable films on bare solid electrode surfaces for solid-state electrochemiluminescence detection.

A simple thermal process for the preparation of small Pt nanoparticles is presented, carried out by heating a H2PtCl6/3-thiophenemalonic acid aqueous solution. The following treatment of such colloidal Pt solution with Ru(bpy)(3)2+ causes the assembly of Pt nanoparticles into aggregates. Most importantly, directly placing such aggregates on bare solid electrode surfaces can produce very stable films exhibiting excellent electrochemiluminescence behaviors.

Journal Article↗
PubMed2006

A novel alcohol dehydrogenase biosensor based on solid-state electrogenerated chemiluminescence by assembling dehydrogenase to Ru(bpy)(3)2+-Au nanoparticles aggregates.

Based on electrogenerated chemiluminescence (ECL), a novel method for fabrication of alcohol dehydrogenase (ADH) biosensor by self-assembling ADH to Ru(bpy)(3)(2+)-AuNPs aggregates (Ru-AuNPs) on indium tin oxide (ITO) electrode surface has been developed. Positively charged Ru(bpy)(3)(2+) could be immobilized stably on the electrode surface with negatively charged AuNPs in the form of aggregate via electrostatic interaction. On the other hand, AuNPs are favourable candidates for the immobilization of enzymes because amine groups and cysteine residues in the enzymes are known to bind strongly with AuNPs. Moreover, AuNPs can act as tiny conduction centers to facilitate the transfer of electrons. Such biosensor combined enzymatic selectivity with the sensitivity of ECL detection for quantification of enzyme substrate, and it displayed wide linear range, high sensitivity and good stability.

Alcohol Dehydrogenase↗
PubMed2006

Rapid self-assembly of oligo(o-phenylenediamine) into one-dimensional structures through a facile reprecipitation route.

The self-assembly of oligo(o-phenylenediamine) (OPD) into 1-D nanostructures on a macroscopic length scale was found when they were transferred from N-methyl pyrrolidone to deionized water. Field emission scanning electron microscopy and confocal fluorescence microscopy were used to investigate the morphology of the precipitates. Results showed that large amounts of OPD 1-D supertructures could be obtained through the simple reprecipitation route, and the length of the fibers could be tuned from microscale to macroscale by adjusting the ratio of two solvents. X-ray diffraction patterns and UV-vis spectra revealed that pi-pi interactions between OPD molecules that facilitated the formation of 1-D structures became predominant when they were transferred from a good solvent to a bad one. Accordingly, a possible formation mechanism was proposed.

Journal Article↗
PubMed2006

Didodecyldimethylammonium bromide lipid bilayer-protected gold nanoparticles: synthesis, characterization, and self-assembly.

Didodecyldimethylammonium bromide (DDAB) lipid bilayer-protected gold nanoparticles (AuNPs), which were stable and hydrophilic, were synthesized by in situ reduction of HAuCl(4) with NaBH(4) in an aqueous medium in the presence of DDAB. As-prepared nanoparticles were characterized by UV-vis spectra, transmission electron microscopy, dynamic light scattering analysis, and X-ray photoelectron spectroscopy. All these data supported the formation of AuNPs. Fourier transform infrared spectroscopy (FTIR) and differential thermal analysis/thermogravimetric analysis data revealed that DDAB existed in a bilayer structure formed on the particle surface, resulting in a positively charged particle surface. The FTIR spectra also indicated that the DDAB bilayer coated on the surface of AuNPs was probably in the ordered gel phase with some end-gauche defects. On the basis of electrostatic interactions between such AuNPs and anionic polyelectrolyte poly(sodium 4-styrenesulfonate) (PSS), we successfully fabricated (PSS/AuNP)(n)() multilayers on a cationic polyelectrolyte poly(ethylenimine) coated indium tin oxide substrate via the layer-by-layer self-assembly technique and characterized as-formed multilayers with UV-vis spectra and atomic force microscopy.

Gold↗
PubMed2005

Method for effective immobilization of Ru(bpy)(3)2+ on an electrode surface for solid-state electrochemiluminescene detection.

A novel method for effective immobilization of Ru(bpy)3(2+) on an electrode surface is developed. The whole process involves two steps: the electrostatic interactions between citrate-capped gold nanoparticles (AuNPs) and Ru(bpy)3Cl2 in aqueous medium were used to fabricate Ru(bpy)(3)2+-AuNP aggregates (Ru-AuNPs) first, and then the Au-S interactions between as-formed Ru-AuNPs and sulfhydryl groups were used to effectively immobilize the Ru-AuNPs on a sulfhydryl-derivated indium tin oxide (ITO) electrode surface. As-prepared ITO electrode shows excellent stability, and the ECL active species Ru(bpy)3(2+) contained therein exhibit excellent ECL behaviors.

Journal Article↗
PubMed2005

Rapid preparation and characterization of uniform, large, spherical Ag particles through a simple wet-chemical route.

In this article we report the rapid preparation of uniform, large, spherical Ag particles through a simple wet-chemical route. The formation of Ag particles with about 750 nm in diameter occurs in a single process, carried out by direct mix of AgNO3 aqueous solution and ortho-phenylenediamine N-methyl-2-pyrrolidone solution at room temperature, producing a relatively low-polydispersity product. It is also found that raising the temperature results in larger particles. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectra have been used to characterize the resulting product.

Particle Size↗
PubMed2005

Coordination-induced formation of submicrometer-scale, monodisperse, spherical colloids of organic-inorganic hybrid materials at room temperature.

In this communication, we demonstrate a novel coordination-based strategy to the fabrication of submicrometer-scale, monodisperse, spherical colloids of organic-inorganic hybrid materials, carried out by mixing H2PtCl6 and p-phenylenediamine (PPD) aqueous solutions at room temperature. The particle size and polydispersity can be controlled by the molar ratio and concentration of reactants, and the optimum experimental parameters for the production of monodisperse colloids are also given.

Colloids↗
PubMed2005

Designed nanostructured pt film for electrocatalytic activities by underpotential deposition combined chemical replacement techniques.

Multiple-deposited Pt overlayer modified Pt nanoparticle (MD-Pt overlayer/PtNPs) films were deliberately constructed on glassy carbon electrodes through alternately multiple underpotential deposition (UPD) of Ag followed redox replacement reaction by Pt (II) cations. The linear and regular growth of the films characterized by cyclic voltammetry was observed. Atomic force spectroscopy (AFM) provides the surface morphology of the nanostructured Pt films. Rotating disk electrode (RDE) voltammetry and rotating ring-disk electrode (RRDE) voltammetry demonstrate that the MD-Pt overlayer/PtNPs films can catalyze an almost four-electron reduction of O(2) to H(2)O in air-saturated 0.1 M H(2)SO(4). Thus-prepared Pt films behave as novel nanostructured electrocatalysts for dioxygen reduction and hydrogen evolution reaction (HER) with enhanced electrocatalytic activities, in terms of both reduction peak potential and peak current, when compared to that of the bulk polycrystalline Pt electrode. Additionally, it is noted that after multiple replacement cycles, the electrocatalytic activities improved remarkably, although the increased amount of Pt is very low in comparison to that of pre-modified PtNPs due to the intrinsic feature of the UPD-redox replacement technique. In other words, the electrocatalytic activities could be improved markedly without using very much Pt by the technique of tailoring the catalytic surface. These features may provide an interesting way to produce Pt catalysts with a reliable catalytic performance as well as a reduction in cost.

Journal Article↗
PubMed2005

One-step preparation of highly concentrated well-stable gold colloids by direct mix of polyelectrolyte and HAuCl4 aqueous solutions at room temperature.

Highly concentrated, well-stable gold colloids can be prepared directly from an amine-bearing polyelectrolyte-HAuCl4 aqueous solution at room temperature. It is found that increasing molar ratio of polyelectrolyte to gold leads to increasing particle size. UV-vis spectra, transmission electron microscopy (TEM), and X-ray photoelectron spectra (XPS) were used to characterize the products thus formed.

Journal Article↗
PubMed2005

4-(Dimethylamino)butyric acid labeling for electrochemiluminescence detection of biological substances by increasing sensitivity with gold nanoparticle amplification.

4-(Dimethylamino)butyric acid (DMBA) labeling combined with gold nanoparticle amplification for electrochemiluminescence (ECL) determination of a biological substance (bovine serum albumin (BSA) and immunoglobulin G (IgG) as models) was presented. After DMBA, an analogue of tripropylamine, was tagged on the (anti)analytes, an ECL signal related to the content of the analytes was generated when the analyte tagged with DMBA was in contact with tris(2,2'-bipyridine)ruthenium (Ru(bpy)(3)2+) solution and a potential was applied. To improve the adsorption capacity, a gold nanoparticle layer was first combined into the surface of the 2-mm-diameter gold electrode. For the determination of BSA, avidin was covalently conjugated to a self-assembled monolayer of 3-mercaptopropanoic acid on the gold nanoparticle layer. Biotinylated BSA-DMBA was then immobilized on the gold nanoparticle layer of the gold electrode via the avidin-biotin reaction. IgG was tested via a typical sandwich-type immobilization method. ECL signals were generated from the electrodes immobilized with BSA or IgG by immersing them in a 1 mmol L-1 Ru(bpy)(3)2+ solution and scanning from 0.5 to 1.3 V versus Ag/AgCl. With gold nanoparticle amplification, the ECL peak intensity was proportional to the concentration over the range 1-80 and 5-100 microg/mL for BSA and IgG consuming 50 microL of sample, respectively. A 10- and 6-fold sensitivity enhancement was obtained for BSA and IgG over their direct immobilization on an electrode using DMBA labeling. The relative standard deviations of five replicate determinations of 10 microg/mL BSA and 20 microg/mL IgG were 8.4 and 10.2%, respectively. High biocompatibility and low cost were the main advantages of the present DMBA labeling technique over the traditional Ru(bpy)(3)2+ labeling.

2,2'-Dipyridyl↗
PubMed2005

Alternate assemblies of platinum nanoparticles and metalloporphyrins as tunable electrocatalysts for dioxygen reduction.

Through electrostatic layer-by-layer (LBL) assembly, negatively charged citrate-stabilized platinum nanoparticles (PtNPs) and positively charged [tetrakis(N-methylpyridyl)porphyrinato] cobalt were alternately deposited on a 4-aminobenzoic acid-modified glassy carbon electrode and also on indium tin oxide substrates, directly forming the three-dimensional nanostructured materials. Thus-prepared multilayer films were characterized by UV--visible spectroscopy, surface plasmon resonance (SPR) spectroscopy, atomic force microscopy (AFM), and cyclic voltammetry. Regular growth of the multilayer films is monitored by UV--visible spectroscopy and SPR spectroscopy. AFM provides the morphology of the multilayer films. The PtNPs containing multilayer films exhibit high electrocatalytic activity for the reduction of dioxygen with high stability. Rotating disk electrode voltammetry and rotating ring-disk electrode voltammetry demonstrate that the PtNP-containing multilayer films can catalyze an almost four-electron reduction of O(2) to H(2)O in an air-saturated 0.5 M H(2)SO(4) solution. Furthermore, the electrocatalytic activity of the films could be further tailored by simply choosing different cycles in the LBL process or more specifically the amount of the assembly components in the films. The high electrocatalytic activity and good stability for dioxygen reduction make the PtNP-containing multilayer films potential candidates for the efficient cathode material in fuel cells.

Metalloporphyrins↗