Electrochemical Deposition of Silver in Room-Temperature Ionic Liquids and Its Surface-Enhanced Raman Scattering Effect

Abstract

The use of room-temperature ionic liquids (RTILs) as media for electrochemical application is very attractive. In this work, the electrochemical deposition of silver was investigated at a glassy carbon electrode in hydrophobic 1-n-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6) and hydrophilic 1-n-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4) RTILs and in KNO3 aqueous solution by cyclic voltammetric and potentiostatic transient techniques. The voltammograms showed the presence of reduction and oxidation peaks associated with the deposition and dissolution of silver from AgBF4 in both BMIMPF6 and BMIMBF(4), resembling the redox behavior of AgNO3 in KNO3 aqueous solution. A crossover loop was observed in all the cyclic voltammograms of these electrochemical systems, indicating a nucleation process. From the analysis of the experimental current transients, it was shown that the electrochemical deposition process of silver in these media was characteristic of 3D nucleation with diffusion-controlled hemispherical growth, and the silver nucleation closely followed the response predicted for progressive nucleation in BMIMPF6 and instantaneous nucleation in KNO3 aqueous solution, respectively. Compared with these two cases, the electrochemical deposition of silver in BMIMBF4 deviated from both the instantaneous and progressive nucleation models, which could be controlled by mixed kinetics and diffusion. On the basis of the experimental results, it was shown that parameters such as viscosity and water miscibility of RTILs would affect the electrodeposition behavior of silver. Atom force microscopy was employed to probe the surface morphology of the silver deposit, and it showed that the shining electrodeposit of silver was fairly dense and separate nanoclusters of <100 nm were in evidence, corresponding to an island growth model. The strongly enhanced Raman scattering from the monolayer film of 4-mercaptobenzoic acid demonstrated that as-prepared silver nanoparticular film was surface-enhanced Raman scattering (SERS) active. The enhancement factor was calculated to be up to 9.0 x 10(5) and 1.0 x 10(6) for the silver film obtained in BMIMPF6 and BMIMBF4 RTILs, respectively.

Raman Spectroscopy and Ab-Initio Model Calculations on Ionic Liquids

“…Each adsorbed [C 2 mim] þ ion was oriented with the imidazolium ring molecular plane nearly parallel to the electrode surface at certain potentials [80]. Similar type of results have been obtained by surface enhanced Raman scattering (SERS) for 1-butyl-3-methylimidazolium hexafluorophosphate [C 4 mim][PF 6 ] adsorbed on silver [78,81]. When the silver electrode was negatively charged some imidazolium ring vibrational modes and some N-CH 3 vibrations were enhanced, suggesting that the imidazolium rings were parallel to the surface [81].…”

“…The RTILs interact with surfaces and electrodes [19,78,79], and many more studies have been done that what we have room to cite. As one example, in situ Fourier-transform infrared reflection absorption spectroscopy (FT-IRAS) has been utilized to study the molecular structure of the electrified interphase between the 1-ethyl-3-methylimidazolium tetrafluoroborate [C 2 mim][BF 4 ] liquid and gold substrates [80].…”

Surface enhanced Raman scattering of p-aminothiophenol self-assembled monolayers in sandwich structure fabricated on glass

“…33,37,[53][54][55][56] The EF was defined as EF = I SERS /N ads I bulk /N bulk , where I SERS stands for the intensity of a vibrational mode in the SERS spectrum of p-ATP and I bulk for the intensity of the same vibrational mode in the Raman spectrum from the solution phase or solid sample. Both of these intensities can be directly obtained from the experiment.…”

Electrochemical Determination of Celecoxib on a Graphene Based Carbon Ionic Liquid Electrode Modified with Gold Nanoparticles and Its Application to Pharmaceutical Analysis

“…In recent years the carbon ionic liquid electrode (CILE) has aroused great interest due to its advantages, such as easy preparation, good reversibility, high sensitivity and ability to lower the over potential of electroactive compounds. 13 Graphene, is a flat monolayer of carbon atoms tightly packed into a two-dimensional (2D) honeycomb lattice, and can be considered as a basic building block for other kinds of graphitic materials, such as 0D fullerenes, 1D nanotubes or 3D graphite. 14 Because of their novel and fascinating properties, such as exceptional thermal and mechanical properties, as well as high electrical conductivity, graphene, as a ''rising star'' material 15 has been extensively studied for synthesizing nanocomposites 16 and fabricating various microelectrical devices, such as batterys, 17 field-effect transistors, 18 ultrasensitive sensors, 19 and electromechanical resonators.…”