Super-resolution surface-enhanced Raman scattering (SERS) imaging is used to map out SERS hot spots in aggregated silver nanoparticles labeled with the electrochemically-active probe molecule Nile Blue. In super-resolution SERS, the diffraction-limited emission from a SERS-active nanoparticle aggregate is fit to a 2-dimensional Gaussian in order to localize the site of emission, or emission centroid, with 5-10 nm precision. This strategy typically involves working at or near the single molecule concentration level, in order to avoid the super-position of signals from multiple emitters, which leads to an ensemble-averaged centroid position and no spatial information about the location of individual emitters. We have proposed working above the single molecule concentration by using electrochemical control to transition the Nile Blue between its emissive (oxidized) and non-emissive (reduced) form, in order to spatially isolate individual Nile Blue molecules on the surface of aggregated silver nanoparticles. Using this electrochemical modulation strategy, SERS-active regions on nanoparticle aggregates can be mapped out by fitting the centroid location of the emitters as a function of applied potential. Interestingly, while the modulation of Nile Blue SERS intensity does not follow the expected on/off trend with applied potential, we find that we are still able to map out SERS hot spots even while working above the single molecule level.

Date Published: 22 May 2015
PDF: 10 pages
Proc. SPIE 9467, Micro- and Nanotechnology Sensors, Systems, and Applications VII, 946710 (22 May 2015); doi: 10.1117/12.2178074

Published in SPIE Proceedings Vol. 9467:
Micro- and Nanotechnology Sensors, Systems, and Applications VII
Thomas George; Achyut K. Dutta; M. Saif Islam, Editor(s)