Shape effects in plasmon resonance of individual colloidal silver nanoparticles

TLDR

Improved colloidal preparation could yield homogeneous populations of identical particle shapes and colors. The study systematically investigates how size and shape affect the spectral response of individual silver nanoparticles. The authors developed an optical far‑field detection method and correlated individual nanoparticle plasmon spectra to size and shape using high‑resolution TEM. Distinct geometries produce unique spectral responses, and mild heating can tune these spectra, enabling multicolor colloids for labeling, SERS, and near‑field microscopy across the visible spectrum.

Abstract

We present a systematic study of the effect of size and shape on the spectral response of individual silver nanoparticles. An experimental method has been developed that begins with the detection and characterization of isolated nanoparticles in the optical far field. The plasmon resonance optical spectrum of many individual nanoparticles are then correlated to their size and shape using high-resolution transmission electron microscopy. We find that specific geometrical shapes give distinct spectral responses. In addition, inducing subtle changes in the particles’ morphology by heating causes a shift in the individual particle spectrum and provides a simple means of tuning the spectral response to a desired optical wavelength. Improved colloidal preparation methods could potentially lead to homogeneous populations of identical particle shapes and colors. These multicolor colloids could be used as biological labels, surface enhanced Raman scattering substrates, or near field optical microscopy sources covering the full range of wavelengths in the visible spectrum.