Tip-enhanced Raman spectroscopy for investigating adsorbed nonresonant molecules on single-crystal surfaces: tip regeneration, probe molecule, and enhancement effect

• Published in: Journal of Raman spectroscopy Vol. 40; no. 10; pp. 1400 - 1406
• Main Authors: Liu, Zheng, Wang, Xiang, Dai, Ke, Jin, Shan, Zeng, Zhi-Cong, Zhuang, Mu-De, Yang, Zhi-Lin, Wu, De-Yin, Ren, Bin, Tian, Zhong-Qun
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01.10.2009
• Subjects: benzenedithiol; Finite difference method; gold tip; Lasers; Mathematical analysis; oligo(phenylene ethynylene); Quantum chemistry; Raman spectroscopy; Reproducibility; Simulation; Single crystals; surface-enhanced Raman spectroscopy; tip-enhanced Raman spectroscopy
• ISSN: 0377-0486; 1097-4555
• DOI: 10.1002/jrs.2431

Tip, substrate, molecular species, and laser are the four main factors determining the detection sensitivity and spatial resolution of tip‐enhanced Raman spectroscopy (TERS). In this paper, we deal with the tip and molecular species. We will first introduce a simple method to regenerate Au tips fabricated by electrochemical etching for TERS to ensure good experimental reproducibility. Some criteria are proposed to choose molecular species as the probe molecules for reliable TERS investigation of the surface processes and TERS mechanism after a comparison of the TERS and SERS signal of benzenedithiol and 4,4′‐bipyridine. Then, high‐quality TERS signals of a series of molecules of oligo(phenylene ethynylene)s (OPEs) of different lengths adsorbed on a Au(111) single crystal surface are demonstrated. The possible explanation assisted by finite‐difference time‐domain (FDTD) simulation and quantum chemical calculation is used to understand the molecular length‐dependent change of the TERS signal. The potential application of TERS for studying systems related to molecular electronics is proposed. Finally, a method is proposed to calculate the tip enhancement for the nonresonant surface species in TERS. Copyright © 2009 John Wiley & Sons, Ltd. A simple method was introduced for regenerating Au tip‐enhanced Raman spectroscopy (TERS) tips to ensure a good reproducibility in TERS measurements. A series of molecules adsorbed on Au(111) single crystal surface has been studied in order to choose good probe molecules for TERS. 4,4′‐Bipyridine and oligo(phenylene ethynylene)s (OPE) with different molecular lengths adsorbed on were studied by TERS, and the result indicates that the OPE molecules are good TERS probes with the very stable and strong TERS signal.