Electroless Gold as a Substrate for Self-Assembled Monolayers

Abstract

We demonstrate that close-packed self-assembled monolayers (SAMs) can be formed from long chain alkanethiols on the surface of electroless gold. Gold films were deposited on glass microscope slides, high-index glass, and polycarbonate “track-etch” (PCTE) membranes using an electroless plating technique. The roughness of the surface of electroless gold was large but could be reduced to levels comparable to those for evaporated films by thermal annealing of samples supported on glass substrates. Although the largest peaks in X-ray diffraction patterns corresponded to Au(111), electroless gold has significant (200), (220), and (311) reflections and is, therefore, different from Au(111) textured gold films prepared by evaporation. Self-assembled monolayers formed from alkanethiols on electroless gold were characterized by contact angles of hexadecane, cyclic voltammetry, and grazing-angle FTIR spectroscopy. To form close-packed SAMs, it was necessary to apply postplating treatments to the electroless gold such as immersion in 25% HNO3 for membrane-supported gold and thermal annealing in combination with electrochemical cleaning for glass-supported gold. The coverage of SAMs on electroless gold, as estimated from cyclic voltammograms, was greater than 99.8%. Peak positions of C−H stretching modes in IR spectra were consistent with past measurements obtained using SAMs supported on evaporated films of gold. The IR spectra suggested, however, a smaller tilt angle (from the surface normal) of the alkyl chains on electroless gold than on evaporated gold, a conclusion that is consistent with the presence of Au(200) on the surface of electroless gold.

Surface-Confined Nanoparticles as Substrates for Photopolymerizable Self-Assembled Monolayers

“…[21] Other methods for electroless deposition of gold layers as substrates for SAMs have been recently reported. [22] In this communication, a solution-based fabrication method is demonstrated for the self-assembly and photopolymerization of diacetylene-containing disulfides. Using this approach, highly conjugated monolayer structures with controllable molecular architecture can be fabricated in a broad range of substrate environments.…”

“…Optimization of the plating process, in terms of surface roughness, is expected to be possible by systematic variation of the fabrication protocol or a post-plating treatment. [22] Formation of self-assembled monolayer structures is accomplished by equilibrating colloidal gold monolayers and plated gold layers with solutions of octadecanethiol (C18) or di(nonacosa-10,12-diyn) disulfide (15,9DA) in chloroform. After formation, the peak position of the nanoparticle surface plasmon band is shifted only very slightly, indicating negligible particle aggregation during SAM formation, which is facilitated by the strong binding of the nanoparticles to the surface.…”

Conductive Gold Films Assembled on Electrospun Poly(methyl methacrylate) Fibrous Mats

“…After the mat is plated with 400 mL plating solution, the XRD pattern shows clearly the diffraction peak of Au(111) at 38.15°, Au(200) at 44.51°, Au(220) at 64.68°, and Au(311) at 77.66°. In contrast to the result of electroless gold plating on high-index glass, [18] the peaks of Au(220) and Au(311) do not have very small intensities compared to the Au(111) peak, indicating that gold particles on the surface of ultrafine fibers are less oriented than on the surface of glass.…”

Template-based syntheses for shape controlled nanostructures

“…Electrochemistry can be used in combination with electroless deposition, where slow electroless plating (no mass transfer limitations) allows for a uniform metallic film. The metal deposition occurs uniformly at the pore walls creating hollow metallic nanotubes inside the pores [103][104][105][106][107][108]. For multiscale nanostructures such as nanotubes, nanofibers, and nanocables, it is important to know which characteristic length scale, nm or μm, governs the deposition process [109].…”