Direct electron transfer between hemoglobin and a glassy carbon electrode facilitated by lipid-protected gold nanoparticles

We synthesized a kind of gold nanoparticle protected by a synthetic lipid (didodecyidimethylammonium bromide, DDAB). With the help of these gold nanoparticles, hemoglobin can exhibit a direct electron transfer (DET) reaction. The formal potential locates at -169 mV vs. Ag/AgCl. Spectral data indicated the hemoglobin on the electrode was not denatured. The lipid-protected gold nanoparticles were very stable (for at least 8 months). Their average diameter is 6.42 nm. It is the first time to use monolayer-protected nanoparticles to realize the direct electrochemistry of protein.

DNA-templated assembly and electropolymerization of aniline on gold surface

Biomolecule template gives new opportunities for the fabrication of novel materials with special features. Here we report a route to the formation of DNA-polyaniline (PAn) complex, using immobilized DNA as a template. A gold electrode was first modified with monolayer of 2-aminoethanethiol by self-assembly. Thereafter, by simply immersing the gold electrode into DNA solution, DNA molecules can be attached onto the gold surface, followed by the DNA-templated assembly and electropolymerization of protonated aniline. The electrostatic interactions between DNA and aniline can keep the aniline monomers aligning along the DNA strands. Investigations by surface plasmon resonance (SPR), electrochemistry and reflection absorption UV/Vis-Near IR spectroscopy substantially convince that PAn can be electrochemically grown around DNA template on gold surface. This work may be provides fundamental aspects for building PAn nanowires with DNA as template on solid surface if DNA molecules can be individually separated and stretched.

Investigation of electrochemical charging behaviors of "naked" gold nanoparticles ensembles in aqueous media

Gold nanopartides were Immobilized onto the electrode surface by simple self-assembly technique. Interestingly, the ensembles of these nanopartides exhibit quantized charging behaviors in aqueous solution. Possible mechanism for such behaviors was proposed.

Cationic cyclization of neoprene with a diethylaluminum chloride and organic chloride catalyst system

The cyclization of neoprene was achieved with the aid of a cationic catalyst system based on diethylaluminum chloride (Et2AlCl) and an organic chloride, allyl chloride (CH2=CHCH2Cl) or benzyl chloride (C6H5CH2Cl). The main parameters of the cyclization process were investigated. Elastomers with low intrinsic viscosity, ready solubility and some gelling were obtained. Xylene was a good solvent for the cyclization process, which took place in a very short time (less than or equal to5 min). The products were characterized with IR, H-1-NMR, differential scanning calorimetry, and gel permeation chromatography. The polycyclic structure was determined. The degree of cyctization and the incorporated solvent content were estimated with a H-1-NMR method.

Incorporation of surface-derivatized gold nanoparticles into electrochemically generated polymer films

Stable colloidal solutions of gold nanoparticles surface-derivatized with a thiol monolayer have been prepared using two-phase (water-nitrobenzene) reduction of AuCl4- by sodium borohydride in the presence of 2-mercapto-3-n-octylthiophene (MOT). This kind of surface-functionalized gold nanoparticles can be easily incorporated into the poly(3-octylthiophene) (POT) films on electrode in the process of electrochemical polymerization leading to POT-gold nanoparticle (POT-Au) composite films. Scanning probe microscopy (SPM) and X-ray photoelectric spectroscopy (XPS) have been employed to characterize the surface-derivatized particles and the resulting films. The method of incorporation of nanoparticles into polymer by surface-derivatization and in situ polymerization can also be employed to prepare many other polymer-nanoparticle compostie materials.

Formation of a supported hybrid bilayer membrane on gold: A sterically enhanced hydrophobic effect

Adsorption of a monolayer of didecanoyl-L-alpha-phosphatidylcholine (DDPC) from dispersions of small unilamellar vesicles onto hydrophobic surfaces was investigated by mean of cyclic voltammetry and impedance spectroscopy. The hydrophobic surfaces were self-assembled monolayers of 2-mereapto-3-n-octylthiophene (MOT) on gold. One characteristic of the MOT monolayer is its permeability to organic molecules in aqueous solution, thus providing a more energetically favorable hydrophobic surface for the addition of phospholipid vesicles. The kinetics of the lipid monolayer formation were followed by measuring the time-dependent interfacial capacitance. Unusual values of thickness and capacitance of the MOT/ DDPC bilayers were observed. An interdigitating conformation of the bilayer structure was proposed to interpret the experimental results, The horseradish peroxidase reconstituted into the bilayer demonstrated the expected protein activity, showing practical use in research and in biosensor application.

Preparation of Pt/C catalyst with solid phase reaction method

The PVC catalyst was prepared with solid phase reaction method (Pt/C(S)) for the first time. Its performances were compared with that prepared by the traditional liquid phase reaction method. The results demonstrate that the electrocatalytic activity of PVC catalyst with solid phase reaction method for methanol oxidation is higher than that with liquid phase reaction method. XRD and TEM measurements indicate that the Pt/C(S) possesses low crystalline extent and small particle size.

A method to construct a third-generation horseradish peroxidase biosensor: Self-assembling gold nanoparticles to three-dimensional sol-gel network

A novel method for fabrication of horseradish peroxidase biosensor has been developed by self-assembling gold nanoparticles to a thiol-containing sol-gel network. A cleaned gold electrode was first immersed in a hydrolyzed (3-mercaptopropyl)-trimethoxysilane (MPS) sol-gel solution to assemble three-dimensional silica gel, and then gold nanoparticles were chemisorbed onto the thiol groups of the sol-gel network. Finally, horseradish peroxidase (HRP) was adsorbed onto the surface of the gold nanoparticles. The distribution of gold nanoparticles and HRP was examined by atomic force microscopy (AFM). The immobilized horseradish peroxidase exhibited direct electrochemical behavior toward the reduction of hydrogen peroxide. The performance and factors influencing the performance of the resulting biosensor were studied in detail. The resulting biosensor exhibited fast amperometric response (2.5 s) to H2O2. The detection limit of the biosensor was 2.0 mumol L-1, and the linear range was from 5.0 mumol L-1 to 10.0 mmol L-1. Moreover, the studied biosensor exhibited high sensitivity, good reproducibility, and long-term stability.

Silane bridged polymerized metallocene catalyst for ethylene polymerization

The polymerized metallocene catalyst 4 was prepared by the co-polymerization of ansa-zirconocene complex [CH3Si(2)]ZrCl2 (3) containing vinyl substituted silane bridge with styrene in the presence of radical initiator. Catalyst 4 was found to display high ethylene polymerization activity of 2.28 x 10(6) g PE/(mol . h) with a viscosity average molecular weight (M-eta) value of 61.6 x 10(3) using methylalumoxane (MAO) as a co-catalyst. The ethylene polymerization has been investigated under different conditions.

Influence of capping ligands on the self-organizations of gold nanoparticles into superlattice from CTAB reverse micelles

Gold nanoparticles with size 3-10 nm (diameter) were prepared by the reduction of HAuCl4 in a CTAB/octane + 1-butanol/H2O reverse micelle system using NaBH4 as the reducing agent. The as-formed gold nanoparticle colloid was characterized by UV/vis absorption spectrum and transmission electron microscopy(TEM). Various capping ligands, such as alkylthiols with different chain length and shape, trioctylphosphine (TOP), and pyridine are used to passivate the gold nanoparticles for the purpose of self-organization into superstructures. It is shown that the ligands have a great influence on the self-organization of gold nanoparticles into superlattices, and dodecanethiol C12H25SH is confirmed to be the best ligand for the self-organization. Self-organization of C12H25SH-capped gold nanoparticles into 1D, 2D and 3D superlattices has been observed on the carbon-coated copper grid by TEM without using any selective precipitation process.

Seed-mediated growth of large, monodisperse core-shell gold-silver nanoparticles with Ag-like optical properties

Large, monodisperse core-shell Au-Ag nanoparticles with Ag-like optical properties have been prepared by the seeding growth method in micellar media.

Polymerized unsymmetrical iron post-metallocene catalyst for ethylene polymerization

The unsymmetrical allyl containing post-metallocene complex [ArN = C( Me)] [(ArN)-N-' = C(Me)]C5H3NFeCl2 [Ar = 2,6(i- Pr)(2)C6H3, Ar' = 4-allyl-2,6-(i-Pr)(2)C6H3] (3) has been prepared and characterized. Complex (3) can be co-polymerized with styrene in the presence of radical initiator to produce polymerized post-metallocene catalyst which exhibits high activity for ethylene polymerization (2.5 x 10(6) g PE/mol Fe.h).

C-13 NMR study of ethylene/propylene/octene-1 terpolymers synthesized with TiCl4/MgCl2/i-Bu3Al as the catalyst

The theory of chemical shift effect of substituent was applied to the assignment of the C-13 NMR spectra of the ethylene/propylene and ethylene/octene-1 copolymers. Using the parameters derived above and the DEFT technique, we then entirely assigned the C-13 NMR spectra of the ethylene/propylene/octene(-1) terpolymers synthesized in the presence of the same heterogeneous supported Ziegler-Natta catalyst, TiCl4/MgCl2/i-Bu3Al. The present paper also covers the terpolymer composition and the monomer sequence distributions of a series of ethylene/propylene/octene-1 terpolymers.

Fabrication and electrochemical behaviors of multilayers composed of heteropholyanions and poly(diallyldimethylammonium chloride) on 4-aminothiophenol modified gold electrodes

Multilayer films composed of heteropolyanions (HPAS, SiMo11 VO405-) and cationic polymer poly(diallyldimethylammonium chloride) on 4-aminothiophenol self-assembled-monolayer were fabricated by electrochemical growth. Growth processes of the composite films were characterized by cyclic voltammetry. The results prove the third redox peak of Mo increases more rapidly, otherwise the other Mo redox peaks increase very slowly when the number of layers of heteropolyanions is greater. The peak potentials of composite films shift linearly to negative position with higher pH, which implies that protons are involved in the redox processes of HPA. The investigation of electrocatalytic behaviors of composite films shows a good catalytic activity for the reductions of HNO2 and BrO3-. Catalytic currents increase with increasing number of layers of heteropolyanions, moreover, the catalytic currents have a good linear relationship with the concentrations of BrO3-.