Low cost tips for tip-enhanced Raman spectroscopy fabricated by two-step electrochemical etching of 125 mu m diameter gold wires

Tip-enhanced Raman spectroscopy (TERS) has become a well-applied technique for nanospectroscopy, allowing for single molecule sensitivity with sub-nanometer spatial resolution. The demand for efficient, reproducible and cost-effective probes for TERS is increasing. Here we report on a new electrochemical etching protocol to fabricate TERS tips starting from 125 mu m diameter gold wires in a reproducible way. The process is reliable (50% of the tips have radius of curvature <35 nm, 66% <80 nm), fast (less than 2 min) and 2.5 times cheaper than the etching of standard 250 mu m diameter wires. The TERS performance of the tips is tested on dyes, pigments and biomolecules and enhancement factors higher than 10(5) are observed. TERS mapping with a spatial resolution of 5 nm is demonstrated.