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1.
Galvanic displacement (GD), a type of electroless deposition, has been used to obtain ultrasmooth gold thin films on silicon <111>. The novel aspect of the method presented herein is the absence of fluoride ions in the liquid phase, and its principal advantage when compared to previous efforts is that the process is inherently self-limiting. The self-limiting factor is due to the fact that in the absence of fluorinated species, no silicon oxide is removed during the process. Thus, the maximum gold film thickness is achieved when elemental silicon is no longer available once the surface is oxidized completely during the galvanic displacement process. X-ray photoelectron spectroscopy has been used as a tool for thickness measurement, using the gold to silicon ratio as an analytical signal. Three gold plating solutions with different concentrations of KAuCl? (2, 0.2, and 0.02 mM) have been used to obtain information about the formation rate of the gold film. This XPS analysis demonstrates the formation of gold films to a maximum thickness of ~3.5 ?. Atomic force microscopy is used to confirm surface smoothness, suggesting that the monolayer growth does not follow the Volmer-Weber growth mode, in contrast to the GD process from aqueous conditions with fluorinated species. 相似文献
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This work focuses on the synthesis and characterization of gold films grown via galvanic displacement on Ge(111) substrates. The synthetic approach uses galvanic displacement, a type of electroless deposition that takes place in an efficient manner under aqueous, room temperature conditions. Investigations involving X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques were performed to study the crystallinity and orientation of the resulting gold-on-germanium films. A profound effect of HF(aq) concentration was noted, and although the SEM images did not show significant differences in the resulting gold films, a host of X-ray diffraction studies demonstrated that higher concentrations of HF(aq) led to epitaxial gold-on-germanium, whereas in the absence of HF(aq), lower degrees of order (fiber texture) resulted. Cross-sectional nanobeam diffraction analyses of the Au-Ge interface confirmed the epitaxial nature of the gold-on-germanium film. This epitaxial behavior can be attributed to the simultaneous etching of the germanium oxides, formed during the galvanic displacement process, in the presence of HF. High-resolution TEM analyses showed the coincident site lattice (CSL) interface of gold-on-germanium, which results in a small 3.8% lattice mismatch due to the coincidence of four gold lattices with three of germanium. 相似文献
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Lim H Noh JH Choi DG Kim WD Maboudian R 《Journal of nanoscience and nanotechnology》2010,10(8):5020-5026
Nanoscale patterning of gold layers on GaAs substrate is demonstrated using a combination of soft lithographic molding and galvanic displacement deposition. First, an electroless deposition method has been developed to plate gold on GaAs with ease and cost-effectiveness. The electroless metallization process is performed by dipping the GaAs substrates into a gold salt solution without any reducing agents or additives. The deposition proceeds via galvanic displacement in which gold ions in the aqueous solution are reduced by electrons arising from the GaAs substrate itself. The deposition rate, surface morphology and adhesion property can be modulated by the plating parameters such as the choice of acids and the immersion time. Second, soft lithographic patterning of nanodots, nanorings, and nanolines are demonstrated on GaAs substrates with hard-polydimethylsiloxane (h-PDMS) mold and plasma etching. This method can be easily applied to the metallization and nanopatterning of gold on GaAs surfaces. 相似文献
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H. G. Krüger A. Knote U. Schindler H. Kern A. R. Boccaccini 《Journal of Materials Science》2004,39(3):839-844
A method based on the combination of electrophoretic and galvanic deposition techniques has been developed to fabricate metal-ceramic composite coatings on metallic substrates. A ZrO2-Ni composite coating with interpenetrating microstructure was produced on stainless steel plates. For electrophoretic deposition of the ceramic component, a non-aqueous suspension consisting of zirconia nanoparticles, ethanol and addition of 4-hydroxybenzoic acid was optimised by electrokinetic sonic amplitude (ESA) measurements. The zirconia deposits were partially sintered to create an open porous structure (porosity = 40–50%), which was subsequently filled with Ni by galvanic deposition. The bonding strength between the composite coating and the stainless steel substrate was improved by a final heat-treatement at 950°C for 3 h which promoted the diffusion of Ni into the steel substrate and the formation of a diffusion interlayer. The high adhesion strength of the composite coating to the stainless steel substrate after the diffusion bonding heat-treatment was confirmed by 3-point flexural strength tests. The coating exhibited a homogeneous interpenetrating microstructure with hardness values >6 GPa. 相似文献
6.
Copper nanoparticles (Cu NPs) were made by electroless deposition on Ge disks as substrates for surface-enhanced infrared absorption (SEIRA). Previous X-ray photoelectron spectra had shown that elemental copper is deposited on the Ge substrate and that the nanoparticulate film remains resistant to oxidation even after several days of air exposure at room temperature. SEIRA spectra of p-nitrothiophenol (p-NTP) adsorbed on the copper nanoparticles were measured. Freshly made substrates made by electroless deposition gave higher enhancements than both the 12-day-old oxidized substrates and substrates made by physical vapor deposition. The intensity of the antisymmetric NO(2) stretching band of p-NTP relative to that of the symmetric stretch was significantly higher for p-NTP adsorbed on copper than on silver nanofilms, indicating that the C(2) axis of the aromatic ring is tilted with respect to the copper surface. 相似文献
7.
Domínguez-Vera JM Welte L Gálvez N Fernández B Gómez-Herrero J Zamora F 《Nanotechnology》2008,19(2):025302
Ferritin nanoparticles have been deposited immobilized onto a properly modified gold surface by specific covalent bonding through lysine rests at the ferritin external surface. Atomic force microscopy (AFM) images confirmed the existence of a single ferritin monolayer. This is an easy and flexible route to form stable ferritin networks, which are covalently fixed to a gold substrate. 相似文献
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Four different gold nanostructures: octahedra, rhombic dodecahedra, truncated ditetragonal prisms, and concave cubes, have been synthesized using a seed-mediated growth method by strategically varying the Ag(+) concentration in the reaction solution. Using X-ray photoelectron spectroscopy and inductively coupled plasma atomic emission spectroscopy, we provide quantitative evidence that Ag underpotential deposition is responsible for stabilizing the various surface facets that enclose the above nanoparticles. Increasing concentrations of Ag(+) in the growth solution stabilize more open surface facets, and experimental values for Ag coverage on the surface of the particles fit well with a calculated monolayer coverage of Ag, as expected via underpotential deposition. 相似文献
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In this work, we report a new and clean electrochemical pathway to prepare enriched gold nanoparticles in aqueous solutions via the aid of chitosan without addition of any other stabilizer and reductant. First, an Au substrate was cycled in a deoxygenated aqueous solution containing 0.1 N NaCl and 1 g/L chitosan from − 0.28 to + 1.22 V vs Ag/AgCl at 500 mV/s with 500 scans. Then the Au working electrode was immediately replaced by a Pt electrode, and a cathodic overpotential of 0.6 V from the open circuit potential (OCP) of ca. 0.84 V vs Ag/AgCl was applied under sonification to synthesize Au nanoparticles. Experimental results indicate the concentration and the particle sizes of prepared Au nanoparticles are ca. 50 ppm and 10 nm in diameter, respectively. No aggregation of Au nanoparticles is observed in an ambient atmosphere for at least 3 months. 相似文献
11.
V. S. Gorelik L. I. Zlobina V. A. Karavanskii O. A. Troitskii R. I. Chanieva 《Inorganic Materials》2010,46(8):862-865
A technique has been developed for infiltrating gold nanoparticles into the pores of synthetic opal using laser ablation and
high-temperature annealing, and the reflection spectra of gold-infiltrated opal photonic crystals have been measured. When
a halogen lamp was used as a broadband light source, the peak-reflection wavelength of the gold-infiltrated opal was longer
than that of the uninfiltrated opal. We calculated the dispersion laws for the two lower photon bands of the synthesized photonic
crystals and obtained the corresponding frequency dependences of the refractive index. 相似文献
12.
The crack tip opening displacement (CTOD) initiation toughness has been obtained by different methods in Cr and Cr-Mo steels at 30, 200 and 400 C. The crack tip stretching and grain deformation has been investigated by scanning electron microscope and optical microscopic studies and by microhardness measurements. The resistance curve approach is used employing the average and the maximum crack growth and the initiation toughness determined are with respect to 0.2 mm crack growth (
0.2), the stretched zone width (SZW) and also using a blunting line approach. In addition, an initiation toughness using stretched zone depth (SZD) measurement is also obtained. The various initiation toughness values have been compared and an attempt has been made to identify the realistic plane strain CTOD toughness amongst the different values. The-CTOD relationship has also been investigated. 相似文献
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A.M. Mancini A. Quirini L. Vasanelli E. Perillo E. Rosato G. Spadaccini 《Thin solid films》1982,89(4):407-412
Rutherford backscattering measurements were performed on CdTe samples covered with gold films obtained by precipitation from gold chloride solutions. A considerable removal of cadmium from the interface region was observed. Moreover, the behaviour of the cadmium and tellurium depth profiles in the interface region is correlated with the gold film thickness. These features of the electroless gold contact on CdTe can account for its electrical properties. 相似文献
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High density gold nanoparticles (GNPs) on indium tin oxide (ITO) film coated glass have been prepared by one-step electrochemical deposition from KAu(CN)2 in phosphate buffer (pH 8.0) solution. The resulting electrode surface was characterized by scanning electron microscopy (SEM), UV-vis spectroscopy, X-ray diffraction (XRD) and electrochemical method. Experimental results revealed that the number density of the nanoparticles was increased by the negative shift of the applied potential, while the coverage of the deposited GNPs on ITO substrate surface was also increased by means of the increasing deposition cycles. The presence of GNPs with high coverage improved the electrochemical response of Fe(CN)6 (3-/4-). This high coverage GNP/ITO substrate was applied to immobilization superoxide dismutase (SOD) for fabrication of electrochemical biosensors. The direct electron transfer between enzyme and electrode was realized, and the electrochemical performance of the SOD electrode was improved with the high coverage of GNPs. The biosensor exhibited a rapid and high response to superoxide anion. 相似文献
16.
Using pulsed laser irradiation (532 nm), dodecanethiol-capped gold nanoparticles (DT-Au) were deposited on the laser-irradiated region of a hydrophobic glass substrate modified with dimethyloctadecylchlorosilane (DMOS). After removal of deposited DT-Au, the laser-deposited region on the substrate was hydrophilic, as verified by static water contact angles. X-ray photoelectron spectroscopy suggested that the naked glass surface was not exposed at the hydrophilic region. Immersion of the substrate into gold nanorod (NR) solution selectively immobilized NRs on the hydrophilic surface via electrostatic interactions, indicating that the hydrophilic region was an anionic surface. From these results, it is expected that some immobilized DMOS groups on the laser-irradiated region of the substrate were oxidized during DT-Au deposition and fragmentation of the deposited DT-Au. 相似文献
17.
Pol VG Wildermuth G Felsche J Gedanken A Calderon-Moreno J 《Journal of nanoscience and nanotechnology》2005,5(6):975-979
In this article, sub-micron size particles of titania were coated by a nanosized gold particles with the aid of power ultrasound. We could achieve a uniform coating of gold nanoparticles on a titania surface with a maximum gold loading of 10 wt%. In addition, we report on the experimental evidence for a significant decrease in the melting point of gold nanoparticles (<2 nm) by approximately 850 degrees C from that of the bulk material. 相似文献
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Juliet Q. Dalagan Erwin P. Enriquez Lain-Jong Li Cheng-Te Lin 《Materials Science-Poland》2013,31(2):226-231
In this study, the growth of copper on porous diatom silica by electroless deposition method has been demonstrated for the first time. Raman peaks of copper (145, 213, and 640 cm?1) appeared in the copper-coated, Amphora sp. and Skeletonema sp. diatom samples, confirming the successful deposition of copper. Scanning electron microscopy (SEM) indicated the presence of copper on the diatom silica surface. The 3D intricate structure of diatom was still evident by optical and scanning electron microscopy analyses when the diatom samples were immersed in the copper bath for only 5 hours. Incubating the diatom samples in the copper bath for 24 h produced a dense coating on the diatom surface and covered the intricate 3D structure of the diatom silica. These results present possibilities of the fabrication of hierarchically organized copper with 3D diatom replica structures. 相似文献
20.
Foultier B Moreno-Hagelsieb L Flandre D Remacle J 《IEE proceedings. Nanobiotechnology》2005,152(1):3-12
DNA microarrays are an emerging technology for the parallel detection of DNA molecules. Fluorescent molecules are the current standard for a DNA array's optical readout but they possess some drawbacks including the stability of the dyes and the cost of the scanners. Therefore alternative labelling strategies are of considerable interests. One such strategy is the use of nanoparticles which offers several advantages in terms of stability and versatility of the detection mode. The authors present a review on the different ways DNA can be detected, mainly onto a solid support, using nanoparticle labels. 相似文献