Development of nanoparticles sizing method based on fluorescence polarization

We suggest a novel nanoparticle sizing method based on fluorescence polarization analysis. Particle size evaluation can be achieved by measuring the rotational diffusion coefficient, which is sensitive to the particle size. We develop a rotational diffusion coefficient measurement system and a fluorescent probe, which is labelled to particle. In order to verify the feasibility of the proposed method, fundamental experiments are performed. We measure the rotational diffusion coefficients of gold nanoparticles, whose diameters are 5 nm, 10 nm and 15 nm, using the developed system. The measured rotational diffusion coefficients decrease with increasing the particle size. It indicates that nanoparticle size, which is below 15 nm, can be measured with at least 5 nm resolution.