Nanoparticle sizing method based on fluorescence anisotropy analysis

• Novel nanoparticle sizing method for nanoparticle is presented.
• Rotational diffusion coefficient for nanoparticles from 6 nm to 20 nm in diameter is presented.
• Relation between rotation of nanoparticle and that of fluorescent probe connected to nanoparticle is investigated.

Demand for applications of nanoparticles in electric architecture has been increasing. Nanoparticles provide new opportunities for improving circuit response. We discuss a novel method for evaluating nanoparticle sizes based on fluorescence anisotropy analysis. Particle size evaluation is possible through measurements of the rotational diffusion coefficient, which is sensitive to particle size. We develop a system for measuring rotational diffusion coefficients by using a fluorescent probe to label a particle. We report fundamental experiments that verify the feasibility of the proposed method. The rotational diffusion coefficients of gold nanoparticles with diameters ranging 6–20 nm were measured using the proposed method. The measured rotational diffusion coefficients decrease with increasing particle size. This finding indicates that nanoparticles smaller than 15 nm can be measured with fine resolution.