Thiols are widely used in the preparation of self-assembled monolayers (SAMs) on metallic surfaces such as Ag, Cu and Au because of their strong affinity for such surfaces. These SAMs have various applications in nanotechnology and supramolecular chemistry. However, the chemistry of the metal surface and the thiol end is still vaguely understood, yet it fundamentally governs the properties of the SAMs. This paper reports density functional theory (DFT) and experimental findings focusing on vibrational Raman spectroscopy. 4-Mecaptobenzoic acid (4-MBA), a simple aromatic thiol was self-assembled onto Ag (111) and (100) fcc surfaces via the COO-/S- ends. The Ag(100)MBA self-assembled via the COO- end had the highest enthalpy of adsorption of -310.34 kJ/mol and it was the most stable plane contradicting the sulphur end consensus on previous papers. The experimental AgMBA vibrational frequencies showed the interaction of the 4-MBA with the Ag surface from both the S- and COO- atoms and the observation was supported by DFT predicted SERS and thermodynamic calculations. The adsorption of the 4-MBA moiety on the Ag surface was interplayed by the corrugation potential of the exposed surface and the thiol’s aromatic nature which resulted in the adsorption of 4-MBA predominately via the carbonyl end at slightly acidic pH conditions and a deprotonated thiol end.

硫醇因其对此类表面的强亲和力而广泛用于在金属表面（如Ag，Cu和Au）上制备自组装单层（SAM）。这些SAM在纳米技术和超分子化学中具有各种应用。但是，金属表面和硫醇末端的化学性质仍不清楚，但从根本上控制着SAM的性能。本文报道了密度泛函理论（DFT）和实验结果，重点是振动拉曼光谱。4-巯基苯甲酸（4-MBA）是一种简单的芳族硫醇，通过COO- / S-端自组装在Ag（111）和（100）fcc表面上。通过COO-末端自组装的Ag（100）MBA具有-310.34 kJ / mol的最高吸附焓，并且它是最稳定的平面，与先前论文的硫末端共识相矛盾。实验中的AgMBA振动频率显示了4-MBA与S和COO原子在Ag表面的相互作用，并且该观察得到了DFT预测的SERS和热力学计算的支持。暴露的表面的波纹电势和硫醇的芳香性共同作用于Ag表面上4-MBA的吸附，这导致4-MBA主要通过在弱酸性pH条件下的羰基端和去质子化的巯基进行吸附结束。