Photoinduced Conversion of Silver Nanospheres to Nanoprisms

Abstract

A photoinduced method for converting large quantities of silver nanospheres into triangular nanoprisms is reported. The photo-process has been characterized by time-dependent ultraviolet-visible spectroscopy and transmission electron microscopy, allowing for the observation of several key intermediates in and characteristics of the conversion process. This light-driven process results in a colloid with distinctive optical properties that directly relate to the nanoprism shape of the particles. Theoretical calculations coupled with experimental observations allow for the assignment of the nanoprism plasmon bands and for the first identification of two distinct quadrupole plasmon resonances for a nanoparticle. Unlike the spherical particles they are derived from that Rayleigh light-scatter in the blue, these nanoprisms exhibit scattering in the red, which could be useful in developing multicolor diagnostic labels on the basis not only of nanoparticle composition and size but also of shape.

Selective synthesis of hexagonal Ag nanoplates in a solution-phase chemical reduction process

“…The in-plane dipole plasmon resonance peaks show a marked red-shift from 565 nm to 813 nm with increasing edge length. The slight red-shifts of the out-plane quadrupole and dipole plasmon resonance modes [15], from 341 nm to 344 nm and 373 nm to 389 nm respectively, could be indicative of a slight increase in the thickness of the nanoplates [3].…”

“…Nanosphere lithography (NSL) [13,14], a physical technique, gives good control over shape, size and interparticle spacing but requires sophisticated instruments and is not amenable to scale up. Photoinduced growth [15][16][17], first reported by Jin et al [15], has proved successful in the synthesis of triangular Ag nanoplates (TNPs) and has been extended to the preparation of hexagonal Ag nanoplates (HNPs) [18] or round Ag nanoplates [19] by transformation of Ag TNPs. To surmount the low yields and slow reaction rates of the photoinduced process, chemical solution reduction methods have been developed.…”

Surface-Enhanced Raman Spectroscopy

“…In this body of work, field enhancement has been studied as a function of nanoparticle aspect ratio and shape (20,21), extremely large SERS enhancement has been predicted in small nanoparticle assemblies (22,23), and interesting optical phenomena that occur in extended arrays of nanoparticles have been uncovered (24,25).…”

Capillary‐Force‐Assisted Optical Tuning of Coupled Plasmons

“…Although irradiation has been used to restructure the shape of Ag nanoparticles (NP) into nanoprisms, such bi‐state switching is irreversible, restricted to jump tuning, and has only a small tuning range 14, 15. When plasmonic elements are spaced within a few nm, the extreme optical confinement brings great sensitivity to the gap contents, which can be harnessed for tuning 16.…”