Home About us Contact
|
Home About us Contact | ||
|
|
||
Gold Substrate (gold + substrate)
Selected AbstractsFast Simultaneous Adsorptive Stripping Voltammetric Determination of Ni(II) and Co(II) at Lead Film Electrode Plated on Gold SubstrateELECTROANALYSIS, Issue 14 2007Katarzyna Tyszczuk Abstract A fast adsorptive stripping voltammetric procedure for simultaneous determination of Ni(II) and Co(II) in the presence of nioxime as a complexing agent at an in situ plated lead film electrode was described. The time of determination of these ions was shortened due to the application of gold as a substrate for lead film. At gold substrate lead film formation and accumulation of Ni(II) and Co(II) complexes with nioxime proceeds simultaneously. To obtain a stable signals for both ions a simple procedure of activation of the electrode was proposed. Calibration graphs for an accumulation time of 20,s were linear from 5×10,9 to 1×10,7 mol L,1 and from 5×10,10 to 1×10,8 mol L,1 for Ni(II) and Co(II), respectively. The procedure with the application of a lead film electrode on a gold substrate was validated in the course of Ni(II) and Co(II) determination in certified reference materials. [source] Nanopatterning by an Integrated Process Combining Capillary Force Lithography and Microcontact PrintingADVANCED FUNCTIONAL MATERIALS, Issue 4 2010Xuexin Duan Abstract A novel nanopatterning process was developed by combining capillary force lithography (CFL) and microcontact printing (µCP). Flat polydimethylsiloxane (PDMS) was used as the substrate in CFL, and after chemical functionalization, as the stamp in µCP, which increased the resolution of both methods. The polymer patterns, produced by CFL on a thin polymer film on the flat PDMS substrate, acted as a mask to oxidize the uncovered regions of the PDMS. The chemical patterns were subsequently formed by gas phase evaporation of a fluorinated silane. After removal of the polymer, these stamps were used to transfer thiol inks to a gold substrate by µCP. Gold patterns at a scale of less than 100,nm were successfully replicated by these chemically patterned flat PDMS stamps. [source] Electroactive Films of Multicomponent Building Blocks,ADVANCED FUNCTIONAL MATERIALS, Issue 5 2007I. Yildiz Abstract A ligand consisting of a 2,2,-bipyridine core and two 4,4,-bipyridinium arms terminated by a thiol group is prepared following a multistep synthetic procedure. Two of these ligands assemble around a single CuI center as a result of the tetrahedral coordination of their 2,2,-bipyridine cores by the metal. Both the ligand and the complex adsorb spontaneously on the surface of polycrystalline-gold electrodes. The surface coverage of the films prepared by immersing a gold substrate into a solution of the ligand increases from monolayer to multilayer values with immersion time. Instead, the complex can only form monolayers. The cyclic voltammograms of the resulting films show the characteristic response for the reversible reduction of the 4,4,-bipyridinium dications to their radical cations. In the case of the complex, a wave for the monoelectronic oxidation of the metal center can also be observed. The back reduction wave, however, is markedly broader and appears at significantly lower potentials. Model studies in solution indicate that this response is a result of the presence of free thiol groups and is consistent with a change in the coordination geometry of the metal. Specifically, the oxidation of the CuI center to a CuII ion is, presumably, accompanied by the folding of one of the thiol groups back to interact with the metal. Thus, oxidation/reduction cycles of the metal center can, in principle, be exploited to control reversibly large amplitude molecular motions at the electrode/solution interface in the shape of the folding/unfolding of oligomethylene chains. [source] Synthesis and Characterization of Iron Oxide Derivatized Mutant Cowpea Mosaic Virus Hybrid Nanoparticles,ADVANCED MATERIALS, Issue 24 2008Alfredo A. Martinez-Morales A novel nanoparticle hybrid is attained by the covalent attachment of iron oxide (, -Fe2O3) nanoclusters onto the surface of a mutagenized cow pea mosaic virus (CPMV-T184C). Using a stepwise substrate-based integration, monodisperse CPMV-IO hybrids are anchored on a gold substrate. The physical and magnetic properties of individual CPMV-IO hybrids are qualitatively investigated by atomic/magnetic force microscopy (AFM/ MFM). During MFM characterization a ,boundary-effect' is observed at the CPMV/IO interface. [source] Improved surface-enhanced Raman scattering of polypyrrole electrodeposited on roughened substrates composed of Au,Ag bimetallic nanoparticlesJOURNAL OF RAMAN SPECTROSCOPY, Issue 6-7 2005Thomas C. Chuang Abstract We report here the first electrochemical method to prepare a roughened gold substrate with bimetallic silver and gold nanoparticles. First, a silver substrate was roughened by a triangular-wave oxidation,reduction cycle in 0.1 N HCl aqueous solutions. Silver-containing complexes were found in the solution after the ORC treatment. Then a gold substrate was subsequently roughened by a similar oxidation,reduction treatment in this solution. Scanning electron microscopy and atomic force microscopy reveal that the surface of the roughened gold was intrinsically modified with silver nanoparticles, which demonstrates two different kinds of deposition domains. Encouragingly, surface-enhanced Raman scattering of polypyrrole electrodeposited on the roughened gold substrate, modified with finer silver nanoparticles, exhibits an eightfold higher intensity. Copyright © 2005 John Wiley & Sons, Ltd. [source] Directed self-immobilization of alkaline phosphatase on micro-patterned substrates via genetically fused metal-binding peptideBIOTECHNOLOGY & BIOENGINEERING, Issue 4 2009Turgay Kacar Abstract Current biotechnological applications such as biosensors, protein arrays, and microchips require oriented immobilization of enzymes. The characteristics of recognition, self-assembly and ease of genetic manipulation make inorganic binding peptides an ideal molecular tool for site-specific enzyme immobilization. Herein, we demonstrate the utilization of gold binding peptide (GBP1) as a molecular linker genetically fused to alkaline phosphatase (AP) and immobilized on gold substrate. Multiple tandem repeats (n,=,5, 6, 7, 9) of gold binding peptide were fused to N-terminus of AP (nGBP1-AP) and the enzymes were expressed in E. coli cells. The binding and enzymatic activities of the bi-functional fusion constructs were analyzed using quartz crystal microbalance spectroscopy and biochemical assays. Among the multiple-repeat constructs, 5GBP1-AP displayed the best bi-functional activity and, therefore, was chosen for self-immobilization studies. Adsorption and assembly properties of the fusion enzyme, 5GBP1-AP, were studied via surface plasmon resonance spectroscopy and atomic force microscopy. We demonstrated self-immobilization of the bi-functional enzyme on micro-patterned substrates where genetically linked 5GBP1-AP displayed higher enzymatic activity per area compared to that of AP. Our results demonstrate the promising use of inorganic binding peptides as site-specific molecular linkers for oriented enzyme immobilization with retained activity. Directed assembly of proteins on solids using genetically fused specific inorganic-binding peptides has a potential utility in a wide range of biosensing and bioconversion processes. Biotechnol. Bioeng. 2009;103: 696,705. © 2009 Wiley Periodicals, Inc. [source] Robust Self-Assembled Monolayers of RuII and OsII Polypyridines on Gold Surfaces: Exploring New PotentialsCHEMISTRY - A EUROPEAN JOURNAL, Issue 23 2009Frances Abstract Functional monolayers: RuII and OsII bis-terpyridine complexes have been attached through a piperazine-supported dithiocarbamate to a gold substrate (see picture). The robust tether, and the favourable reduction in oxidation potential induced by the electron-rich piperazine result in self-assembled monolayers with excellent reversible redox behaviour and exceptional stability. Metal complexes [M(phtpy)(pztpy)](PF6)2 (phtpy=4,-phenyl-2,2,:6,,2,,-terpyridine, pztpy=4,-(N -piperazinyl)-2,2,:6,,2,,-terpyridine, M=Ru, Os) were prepared and examined spectroscopically and electrochemically. The piperazine attachment was found to significantly modify the photophysical and electrochemical properties compared to the parent bis-terpyridine complexes, causing a red-shift of the 1MLCT (23,nm, 53.9,eV) and a substantial cathodic shift of the redox potential (0.3,V for Ru, 0.23,V for Os). Self-assembled monolayers (SAMs) of the complexes on polished gold electrodes were generated simply by the in situ formation of a dithiocarbamate (DTC) anchoring group at the terminal piperazinyl nitrogen on the pztpy ligand. Cyclic voltammetry revealed that the monolayers show excellent reversible behaviour and exceptional stability. The high stability of the SAMs is attributed to the strong bidentate attachment to the gold surface of the DTC tether and the favourable low oxidation potentials of the complexes which result from the electron-rich piperazine nitrogen on the pztpy ligand. Such DTC-based SAMs demonstrate a substantial improvement over commonly-employed thiol-based systems, and offer new scope for future development. [source] Surface-Grafted Multiporphyrin Arrays as Light-Harvesting Antennae to Amplify Photocurrent GenerationCHEMISTRY - A EUROPEAN JOURNAL, Issue 19 2005Mitsuhiko Morisue Dr. Abstract Organized multiporphyrin arrays were developed on the conductive surface by a novel coordination-directed molecular architecture aiming at efficient photoelectric conversion. The basic strategy employs the mutual coordination of two imidazolylporphyrinatozinc(II) units to form a cofacial dimer. Thus, meso,meso -linked bis(imidazolylporphyrinatozinc) (Zn2(ImP)2) was organized onto imidazolylporphyrinatozinc on the gold substrate as a self-assembled monolayer. The organized Zn2(ImP)2 bearing allyl side chains was covalently linked by ring-closing olefin metathesis catalyzed with Grubbs catalyst. Alternating coordination/metathesis reactions allow the stepwise accumulation of multiporphyrin arrays on the gold electrode. A successive increase in absorption over a wide wavelength range occurred after each accumulation step of Zn2(ImP)2 on the gold electrode, and cathodic photocurrent generation was enhanced in the aqueous electrolyte system, containing viologen as an electron carrier. The significant increase of the photocurrent indicates that the multiporphyrin array works as a "light-harvesting antenna" on the gold electrode. [source] Topological and Electron-Transfer Properties of Yeast Cytochrome c Adsorbed on Bare Gold ElectrodesCHEMPHYSCHEM, Issue 11 2003Beatrice Bonanni Dr. Abstract The redox metalloprotein yeast cytochrome c was directly self-chemisorbed on "bare" gold electrodes through the free sulfur-containing group Cys102. Topological, spectroscopic, and electron transfer properties of the immobilised molecules were investigated by in situ scanning probe microscopy and cyclic voltammetry. Atomic force and scanning tunnelling microscopy revealed individual protein molecules adsorbed on the gold substrate, with no evidence of aggregates. The adsorbed proteins appear to be firmly bound to gold and display dimensions in good agreement with crystallographic data. Cyclic voltammetric analysis showed that up to 84,% of the electrode surface is functionalised with electroactive proteins whose measured redox midpoint potential is in good agreement with the formal potential. Our results clearly indicate that this variant of cytochrome c is adsorbed on bare gold electrodes with preservation of morphological properties and redox functionality. [source] Electrically Conductive Thin Films Prepared from Layer-by-Layer Assembly of Graphite PlateletsADVANCED FUNCTIONAL MATERIALS, Issue 7 2009Mubarak Alazemi Abstract Layer-by-layer (LBL) assembly of carbon nanoparticles for low electrical contact resistance thin film applications is demonstrated. The nanoparticles consist of irregularly shaped graphite platelets, with acrylamide/,, -methacryl-oxyethyl-trimethyl-ammonium copolymer as the cationic binder. Nanoparticle zeta (,,) potential and thereby electrostatic interactions are varied by altering the pH of graphite suspension as well as that of the binder suspension. Film thickness as a function of zeta potential, immersion time, and the number of layers deposited is obtained using Monte Carlo simulation of the energy dispersive spectroscopy measurements. Multilayer film surface morphology is visualized via field-emission scanning electron microscopy and atomic-force microscopy. Thin film electrical properties are characterized using electrical contact resistance measurements. Graphite nanoparticles are found to self-assemble onto gold substrates through two distinct yet overlapping mechanisms. The first mechanism is characterized by logarithmic carbon uptake with respect to the number of deposition cycles and slow clustering of nanoparticles on the gold surface. The second mechanism results from more rapid LBL nanoparticle assembly and is characterized by linear weight uptake with respect to the number of deposition cycles and a constant bilayer thickness of 15 to 21,nm. Thin-film electrical contact resistance is found to be proportional to the thickness after equilibration of the bilayer structure. Measured values range from 1.6,m,,cm,2 at 173,nm to 3.5,m,,cm,2 at 276,nm. Coating volume resistivity is reduced when electrostatic interactions are enhanced during LBL assembly. [source] A rapid synthesis of new benzene-centered porphyrin trimersJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 5 2007Cyril A. Papamicaël In connection with our study of the capability of forming ordered self-assembled monolayers on gold substrates, we described the full details concerning the rapid synthesis of two rigid, star-shaped D3 -symmetric arrays with a benzene core attached to three identical metalloporphyrins containing either ethyldisulfide functions or thienyl groups. [source] Electrodeposition study of ODN:SWCNT hybrids on gold substratesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 6 2008Roya R. Lahiji Abstract Sonication of short single-stranded DNA (oligodeoxyribonucleotide; ODN) with Single-Walled Carbon Nanotubes (SWCNTs) greatly facilitates the dispersion of SWCNTs from entangled ropes in an aqueous solution, creating ODN:SWCNT hybrids. Electrodeposition has been investigated to determine if well-dispersed ODN:SWCNT hybrids on a metal substrate can be created. Preliminary studies indicate that electrodeposition using an Au substrate held at +0.5 V produces ODN:SWCNT hybrids that are uniformly deposited across the Au substrate. This result can be compared to samples produced by drop casting and evaporation techniques which yield a thick tangled mat of ODN:SWCNT hybrids across the substrate. The resulting electrodeposited samples were characterized using Scanning Probe Microscope (SPM) and X-ray Photoemission Spectroscopy (XPS) techniques. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||