Elimination of oxidation and decomposition by SnCl₂ in the SERS study of pyridoxine on a roughened Au electrode

Abstract

Severe interference from the oxidation and laser carbonization was encountered in the measurements of surface-enhanced Raman scattering (SERS) spectra of pyridoxine (PN) on the roughened gold electrode. However, we found that high-quality SERS spectra of PN could be obtained by the introduction of SnCl 2 , which only has few Raman peaks at low wavenumbers. SnCl 2 , as a good reductive, is capable of removing the oxidative species on the gold substrate and the dissolved oxygen in solution, and as a result lowering the open circuit potential (OCP). Sn(II) can also strongly chemically adsorb on the gold surface and interact with PN through coordination/chelation, such that not only to prevent PN from damage by the giant electromagnetic field for the 'first-layer' effect, but also to give rise to very strong Raman scattering signals of PN where chemical enhancement plays an important role. Those are the main reasons for the elimination of the oxidation and decomposition of PN and for the high-quality SERS spectra of PN. The way the SnCl 2 confines PN within the enhanced electromagnetic field by its ability of adsorption and coordination/chelation can be utilized to improve the routine SERS analysis of analogous type of reactive organic/biomolecules. In addition, this method has been successfully extended to the SERS measurements of PN on the substrates of roughened silver and copper.

Surface-enhanced vibrational spectroscopy of B vitamins: what is the effect of SERS-active metals used?

“…It was concluded that molecules of pyridoxine are not "standing up" and that the parallel or tilted orientation is more probable. Chu et al [29] measured SERS spectra on gold, silver and copper electrodes at various potentials. To prevent oxidation and decomposition of pyridoxine, SnCl 2 was added before SERS measurement.…”

“…Several studies aimed at investigating the adsorption mechanism of nicotinic acid on several surfaces of various silver substrates were published during the last two decades [20][21][22][23][24][25]. Less attention has been paid to riboflavin [26,27], pyridoxine [28,29] and folic acid [30,31], probably because of the complexity of their spectra.…”

Fabrication of nano-network gold films via anodization of gold electrode and their application in SERS

“…We are pleased by the comparison results of SERS intensity on the nano-networks here and on the best substrates we could prepare by other electrochemical methods such as newly developed potential step [8][9][10] and the classical ORC [7]. It has been demonstrated that the enhancement factor on the substrate prepared by the potential step for 50 s in 2 M HCl was 23.3 times as high as that on a commercially available single-use SERS substrate Klarite™ [10].…”

“…Up to present, a number of electrochemical strategies have been developed for fabricating nanostructured gold electrodes for SERS substrates, including roughening gold electrodes with triangular-wave electrochemical oxidation reduction cycles (ORC) [6,7], anodic potential step [8][9][10] and square-wave potential-pulses [11], and templated electrodeposition [12]. Recently, a nanoporous gold film with thickness of approximately 1 μm was made by anodization of gold electrode in an aqueous solution of carboxylic acid or carboxylate [13,14].…”

Optimization of extinction efficiency of gold‐coated polystyrene bead substrates improves surface‐enhanced Raman scattering effects by post‐growth microwave heating treatment

“…[1] Recent work on other types of substrates suggests that the SERS performance of these orderly arranged substrates could be optimized by modifying the sizes of trenches and voids and surface roughness in the metal films. [5,6,15] These modifications may be realized by using conventional heating methods (e.g. annealing samples in a heating oven), [16] but the metal and PS films are both heated to high temperatures, resulting in the disfiguration and haphazard arrangement of the PS beads [17] prior to the effective surface modification of metal films.…”