A single Au nanoparticle (NP) with a diameter of 5 nm was transferred to the end of a Si-tip through a picking process, and an Ag shell with a controlled thickness was formed on the Au core. By carrying out tip-enhanced Raman scattering (TERS) measurements on biphenyl-4-thiol (BPT) with the Au@Ag NP-tip (overall diameter of 22-60 nm), we confirm that such tips show a plasmonic local-field enhancement which is sufficient for tip-enhanced spectro-microscopy.

We carried out the tip-enhanced Raman scattering (TERS) with a tip that is functionalized with a Aunanoparticle (AuNP, with a diameter of 250 nm). The AuNP tip is fabricated by a direct mechanical pickup of a AuNP from a flat substrate, and the TERS signal from the AuNP tip -organic monolayer -Au thin film (thickness of 10 nm) is recorded. We find that such a AuNP-tip interacting with a thin film routinely yields signal enhancement larger than ~10 4 , which is sufficient not only for local (with detection area of ~200 nm 2 ) Raman spectroscopy, but also the nanometric imaging of organic monolayers within a reasonable acquisition time (~20 minutes/image).