Investigation of Tip-Enhanced Raman Spectroscopy on a Silver Nanohole Array Substrate

Tip-enhanced Raman spectroscopy (TERS) has received much attention due to excellent spatial resolution and high detection sensitivity. However, its performance depends crucially on the tip size and shape, and the tip-substrate distance. Substrates coated with roughened silver or gold films, or nanoparticles further limit its stability and reproducibility. Here, substrates with well-ordered silver nanohole arrays, were prepared for TERS by depositing silver on an anodic aluminum oxide (AAO) template. The TERS performance was investigated by varying the tip-substrate distance, position of the tip over different domains of the silver nanohole array, and changing the illumination polarization. We show that: (1) the proposed system is more efficient at controlling the distribution of Raman enhanced “hot spots”, and demonstrates a detection limit for a low concentration of 10⁻⁹ mol L⁻¹ for Rh6G and (2) the proposed approach has a high fidelity factor as the system is highly reproducible, making it suitable for probing over an area. Our experimental and theoretical results demonstrate that substrates with silver nanohole arrays are extremely promising for further application of TERS in surface plasmon resonance biosensing.