Microspectroscopy of Single Nanoparticles

Abstract

Traditional approaches for studying the optical and electronic properties of nanoparticle are to measure their electronic absorption and emission spectra, and the samples are prepared to have a well-defined chemical structure and the distributions of their size and shape are adjusted to be narrow. Even when much effort has been paid for sample preparation, a bulk sample is of course a composition of nanoparticles with different sizes and shapes. Thus, some ambiguity of conventional spectroscopic results arises from the fact that the optical response from the system under investigation is an averaged result for an ensemble of many particles. Scatter of their size, shape and chemical structure lead to inhomogeneous broadening in the frequency domain and non-exponential decay in the time domain. Measuring and characterizing single nanoparticles provide direct information on their chemical and physical properties that would be hidden in the ensemble average of bulk measurements. It is important to attempt single nanoparticle spectroscopy both with a wide spectral range and with a high temporal resolution in order to give a precise description of the optical response relating to the photophysical and photochemical properties of nanoparticles.