Deposition of Nanostructured Ag Films on Silicon Wafers by Electrochemical/Electrophoretic Deposition for Electrochemical and SERS Sensing

Abstract

Electrolysis of ultrapure water in a two-electrode cell with silver anode and conductive substrate (Si wafer) as a cathode leads to the formation of nanostructured silver layers deposited on cathode. In the process, the silver anode is electrochemically dissolved to silver cations, which react with water (or OH • radicals derived from water electrolysis) forming silver oxide nanoparticles, which fill the interelectrode space by electrophoretic movement, diffusion and convection induced by temperature effects of electrolysis. During the process the silver oxide nanoparticles are partially transformed into silver nanoparticles. On the cathode, silver cations and silver / silver oxide nanoparticles undergo reduction to form nanostructured silver film. The results of the present study open a new, extremely simple and ultra-low cost way to prepare nanostructured silver films on conducting and semiconducting substrates. The prepared nanosilver coated silicon substrates exhibit high performances as amperometric sensors for hydrogen peroxide and also as SERS substrates.The marked progress in the development of efficient and reproducible synthetic routes of well separated and stable nanoparticles via size and shape engineering during the past decade 1,2 has been currently succeeded by intensive research efforts focused on the deposition of organized nanoparticles' assemblies on the surface of solid substrates, suitable for specific applications. 3,4 Deposition of nanostructured metallic layers (including noble metals) on conductive and/or semiconducting substrates is a specific issue of this research direction, 5 targeted into the development of novel, highly sensitive electrochemical and surface enhanced Raman scattering (SERS) sensors.Silver, especially in the form of nanoparticles, is a highly effective electrocatalyst for cathodic hydrogen peroxide sensing. Amperometric hydrogen peroxide sensors find their use in the design of biosensors based on oxidase enzymes, which yield hydrogen peroxide as a result of the oxidase catalyzed substrate oxidation by oxygen. For this purpose, sensors working in the cathodic region of potentials have an inherent advantage due to their insensitivity to easily oxidisable compounds (e.g. ascorbic acid, uric acid, polyphenols etc.), often present in high quantities in biological matrices. Monitoring hydrogen peroxide in industrial processes may require sensing high concentrations of hydrogen peroxide over extended periods of time. In our earlier work, 6 we demonstrated that porous silver layer coated electrodes are sufficiently stable (hours) to sense high concentrations of hydrogen peroxide (up to 0.1 M) with sufficient linearity. Such an extended linear region of amperometric sensing is typical for nanoparticle coated surfaces, the linearity limit of bulk silver metal electrodes is ca. 20x lower.Nanostuctured metal films, of which silver films are of primary interest, also find an ideal application as substrates for surface-enhanced Raman spectroscopy, a highly sensitive and specific in...

Comparative Study of Antimicrobial Activity of AgBr and Ag Nanoparticles (NPs)

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Facile preparation of nanostructured copper-coated carbon microelectrodes for amperometric sensing of carbohydrates

“…The procedure for CFME modication by copper is based on a methodology 15 previously described by ourselves for the preparation of nanostructured silver layers, i.e. electrodeposition of the material formed by the dissolution of the anode.…”

“…[8][9][10][11][12] In our previous works, we have reported that carbon ber microelectrodes (CFMEs) can be utilized as highly sensitive electrochemical detectors, especially in HPLC. [13][14][15][16] Thereby, we developed a facile technique enabling CFMEs to be modied with nanostructured copper layers. The dimensions of a carbon ber (3-4 mm in length, 7 mm in diameter) enable the direct insertion of the active electrode tip into a narrow-bore capillary even aer the modication with copper.…”

Improved Surface-Enhanced-Raman Scattering Sensitivity Using Si Nanowires/Silver Nanostructures by a Single Step Metal-Assisted Chemical Etching

“…The sensitivity of conventional Raman scattering is inherently low due to the fact that only a small fraction of photons is used for detection (inelastically scattered photons) leading to very small cross sections of the order of 10–30 cm 2 /sr [ 8 ]. This intrinsic limitation can be overcome by the use of rough and/or nanostructured substrates covered by coinage metals, mainly silver and/or gold nanoparticles, or copper, which provide significant enhancement factors of the order of 10 4 –10 7 as a result of the excitation of localized surface plasmons [ 9 , 10 , 11 ]. SERS can take place near a metallic nanoparticle, which is irradiated at the resonance frequency or near resonance of its localized surface plasmons resulting in a large enhancement of both the local and radiation fields in the vicinity of the metallic nanoparticles and thus in a marked amplification of the Raman signal from adsorbed molecules [ 12 ].…”