硫脲在HNO3介质中共吸附行为的喇曼光谱研究

用常规Ｒａｍａｎ谱，电化学现场表面增强喇曼散射光谱和时间分辨ＳＥＲＳ光谱研究了硫脲在ＨＮＯ３介质与ＮＯ＾－３的共吸附行为。实验结果表明，ＮＯ＾－３离子能被ＴＵ诱导共吸附在其质子化氨基上；ＴＵ以Ｓ端按σ配位键方式化学吸附在银电极表面。

Raman Spectroscopic Studies on Coadsorption of Thiourea in the Nitric Acid Medium

The coadsorption of thiourea(TU) with NO - 3 in aqueous HNO 3 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 NO - 3 can be induced by TU and coadsorbed on the electrode through the protonated amino of TU in the solution containing HNO 3. 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 HNO 3 and HClO 4 respectively was carried out. It indicates that TU is more stable in aqueous HNO 3 than in aqueous HClO 4 at the relatively negative potentials(<-0.8 V), consequentially, the SERS signal of TU can still be detected in aqueous HNO 3 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.