Fabrication of AFM tips for tip-enhanced Raman spectroscopy using Au nanoparticle monolayer films and electrodeposition

Abstract

Tip-enhanced Raman spectroscopy integrates the high spatial resolution of scanning probe microscopy (SPM) with ultrahigh sensitivity for chemical information recognition of surface-enhanced Raman spectroscopy (SERS). It enables the simultaneous morphological and chemical imaging of samples. It is well known that the quality of the tips is a crucial factor for TERS technology. Therefore, the development of a cost-effective and feasible method for fabricating AFM-TERS tips with stable TERS imaging capabilities is highly desired. Herein, a facile approach combining the assembly of nanoparticles with electrodeposition was developed to fabricate AFM-TERS tips. Different fabrication methods were carefully compared to identify the appropriate approach. Utilizing p-nitrobenzenethiol (pNTP) as the probe molecule, the results revealed that annealing treatment assisted with electrochemical deposition of additional gold outer layers significantly improved the stability and cleanness of the tips. Annealing at 105 °C followed by the electrodeposition process of a 10 nm gold outer layer resulted in a controllable morphology, featuring a radius of curvature (ROC) of approximately 35 nm and an enhancement factor of roughly 3.2 × 10⁴. The results suggest that the approach is a promising tool and could be served as a general routine for the cost-effective fabrication of AFM-TERS tips for extending the practical application of TERS technology.