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We demonstrate in the present work through the utilization of classical Mie scattering theory in conjunction with a radiation damping and dynamic depolarization-corrected electrostatic approximation the significant effect that mechanical strain has on the optical properties of spherical silver nanoparticles. Through appropriate modifications of the bulk dielectric functions, we find that the application of tensile strain generates significant enhancements in the local electric field for the silver nanoparticles, leading to large SERS enhancements of more than 300% compared to bulk, unstrained nanoparticles when a 5% tensile strain is applied. While the strain-induced SERS enhancements are found to be strongest for nanoparticle diameters where radiation damping effects are minimized, we find that the surface plasmon resonance wavelengths are relatively unchanged by mechanical strain, and that the various measures of the far field optical efficiencies (absorption, scattering, extinction) can be enhanced by up to 150% through the application of tensile strain. The present findings indicate the opportunity to actively engineer and enhance the optical properties of silver nanoparticles through the application of mechanical deformation.

We utilize numerical simulations based on the discrete dipole approximation to study the effects of surface-stress-driven lattice contraction on the extinction spectra of silver nanowires with a square cross section of length 2 nm. The novel finding of the present work is the determination that the blue shift that is induced in the silver nanowires due to surface-stress-driven lattice contraction increases with an increase in the nanowire aspect ratio; the blue shift in the longitudinal plasmon resonance wavelength reaches 20 nm in air and 30 nm in water when the nanowire aspect ratio increases to six. Furthermore, we have delineated the lattice contraction effects on the relative contributions of the free (conduction) electrons and the ionic core (bound) electrons to the observed blue shift; specifically, due to the increasingly free electron optical response of the nanowires with increasing aspect ratio, the blue shift due to the contraction-driven increase in the free electron density is found to dominate the red shift due to the increase in the core electron density for larger nanowire aspect ratios. The results collectively indicate that surface-stress-driven lattice contraction plays an important role in blue shifting the longitudinal plasmon resonance wavelength for ultrasmall silver nanowires.