Nanoparticle Synthesis and Shape Control

Above: False-color transmission electron microscopy (TEM) image of gold nanoprisms with an edge length of roughly 230 nm.

The Mirkin group developed the first photochemical methods for synthesizing anisotropic structures (i.e., silver triangular nanoprisms) with control over particle dimensions in 2001. In 2005, they introduced the first high-yielding route to gold triangular prisms, allowing a theoretically predicted quadrupole plasmon mode to be observed. In addition to these key examples, the Mirkin group has devised a number of other novel routes to complex, highly faceted, anisotropic materials and introduced the concept of the plasmonic seed, a particle that could be excited to control nanocluster growth and at the same time be used as an electron microscopy label to understand shape evolution. Nanoparticles, pioneered by the Mirkin group, have been utilized as biological labels, spectroscopic enhancers (e.g., Raman), and building blocks for all sorts of interesting colloidal superlattice materials.

Left: Gold nanoparticles of different shapes synthesized by tailoring the reaction conditions of the same high-quality spherical seeds. Clockwise from the top left: cubes, concave rhombic dodecahedra, octahedra, tetrahexahedra, truncated ditetragonal prisms, cuboctahedra, concave cubes, and rhombic dodecahedra. Each panel is arranged as left: TEM image (scale bars are 100 nm) with an inset showing a 3D graphic rendering of the shape and right: scanning electron microscopy (SEM) image of crystallized nanoparticles (scale bars are 500 nm) with a fast Fourier transform (FFT) pattern inset.  Taken from J. Am. Chem. Soc. 2014, 136, 7603.