Millstone

Colloidal Nanoparticle Alloys

Jill Millstone, Assistant Professor, Department of Chemistry, University of Pittsburgh

From bronze to steel, alloyed materials have defined the technological capabilities of their times, and like their monometallic counterparts, can experience dramatic changes in their physical properties at the nanoscale. Indeed, multimetallic nanoparticles promise to provide improved catalysts for efficient use of fossil fuel resources as well as multifunctional tools in biomedical applications. However, current methods to prepare these particles afford limited tunability of particle composition, especially with respect to particle surface structure. Under ambient conditions, we use nanoparticle surface chemistry to modulate surface energy and control metal segregation within alloyed nanostructures. The resulting particles have facilitated some of the first observations of NIR luminescence from alloyed nanoparticles. The stoichiometry and atom distribution of metal throughout the particle is shown to systematically impact the both their emission wavelength and quantum yield. Particles exhibit emissions spanning 800-1200 nm and Stokes shifts up to 700 nm. The impact of this new class of NIR emitters is discussed in terms of NIR imaging and reaction-tracking applications.