Raman spectroscopic studies on coadsorption of thiourea in the nitric acid medium
- 化学化工－已发表论文 
The coadsorption of thiourea (TU) with NO3- in aqueous HNO3 was studied by using normal Raman spectroscopy (NRS), surface enhanced Raman scattering spectroscopy (SERS) and time-resolved SERS (TRSERS). It was found that TU is chemically adsorbed on the surface of silver electrode via S, and NO3- can be induced by TU and coadsorbed on the electrode through the protonated amino of TU in the solution containing HNO3. The experimental results show that, at the potentials more positive than -0.6 V, TU is vertically adsorbed on the surface, while when the electrode potential goes negatively it gradually tends to tilt, even flat. A comparative study on the stability of TU adsorbed on the silver surface in the medium of HNO3 and HClO4 respectively was carried out. It indicates that TU is more stable in aqueous HNO3 than in aqueous HClO4 at the relatively negative potentials (< -0.8 V), consequentially, the SERS signal of TU can still be detected in aqueous HNO3 at the potential of -2.0 V while it is out of detection even at -1.4 V in the latter medium. The origin has been discussed in detail in this paper.