ABSTRACT

We illustrate some of the links between nanoparticle dimensions and luminescence. Properties, application, and techniques for studying luminescence in two distinct types of nanoparticles are described. Those in silica colloids require extrinsic labeling, while gold nanoparticles possess intrinsic luminescence. Firstly, extrinsically doped luminescence is typified in terms of its use to determine nanoparticle size by means of the rotational correlation time, which describes the fluorescence anisotropy decay due to Brownian rotation of a fluorescent dye attached to amorphous silica nanoparticles. Measurement optimization is described with respect to both dye and particle and robustly illustrated using LUDOX* colloids despite the complex fluorescence anisotropy decay observed. Good agreement of 4.0 ± 0.4 nm, 6.4 ± 0.5 nm, and 11.0 * LUDOX is a registered trade mark of DuPont Corporation.