Photochemical Growth of Silver Nanotriangles Immobilized on a Substrate: Tunable Platform for Plasmonic Application

The photochemical growth of silver nanotriangles immobilized on a solid substrate, under the photoirradiation at a suitable wavelength by a depolarized light source, has been reported in this work using both glass and indium-titanium oxide-coated glass substrates. A 2D growth of the surface-immobilized silver nanotriangles is observed, which leads mostly to the formation of larger nanotriangles along with a small population of other plate-like nanostructures. This observation is rationalized by invoking the role of surface plasmon resonances at optical frequencies, especially the in-plane dipolar and higher order plasmon modes that are rather efficiently excited due to fixed orientation of surface-bound nanotriangles. By this technique, a large-scale 2D array of nanoplates with a tunable surface coverage, suitable for development of modulable templates for surface-active applications, is created. A tunable surface enhanced Raman scattering (SERS) response, as a prototype for plasmonic application, has also been demonstrated in the present study, obtaining a high SERS enhancement factor of ≈10⁵ with the signal intensity correlated with the number-density of the surface-grown nanoparticles. Apart from tunable SERS sensitivity, the current protocol of surface-immobilized nanotriangle synthesis will also be useful for creating plasmonic nanoarchitecture for optical applications and portable sensor for biomolecules.