Probing the structure-property interplay of plasmonic nanoparticle transducers using femtosecond laser spectroscopy

The characteristic feature of noble metal nanoparticles is the localized surface plasmon resonance (LSPR). Plasmon-supporting nanoparticles can function as transducers because of the LSPR's ability to amplify electromagnetic fields and its sensitivity to changes in the surrounding dielectric. The performance of these materials in transducer applications is inherently related to nanoparticle structure. This Perspective describes the use of femtosecond laser-based spectroscopies to elucidate the nanoscale structure-property interplay. First, femtosecond time-resolved transient extinction measurements that probe the LSPR following nanoparticle photoexcitation are described. These measurements illustrate how nanostructure dimensions influence sensitivity to changes in the interfacial dielectric. The combination of single-particle nonlinear optical (NLO) measurements and electron microscopy is also used to describe the symmetry of plasmon surface fields in nanoparticle assemblies. In particular, the use of continuous polarization variation-detected second-harmonic generation to describe electric and magnetic dipolar contributions to NLO properties is discussed.