Adsorption of thiourea (TU) and ethylthiourea(ETU) on roughened silver electrode was investigated using in- situ surface enhanced Raman spectroscopy(SERS).Using quantum chemistry and HSAB theories, the influences of electrode potential and the different substituent groups on SERS were discussed. TU is chemisorbed perpendicularly by Ag-S bond on silver at E=-0.3 V and adsorption of TU turns into a parallel orientation at E=-0.9 V. ETU is always chemisorbed at an angle from Ag. The adsorption of ETU is through C=C andC=O groups at E=-0.3 V, and mainly through C=C at E=-0.9V.
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