Pulsed field gradient nuclear magnetic resonance (PFG-NMR) spectroscopy has been developed as a method for quantitative measurements of self-diffusion coefficients of nanomaterials. It is possible to distinguish the individual diffusion components by monitoring NMR signals at different chemical shifts simultaneously.

Accurate diffusion coefficients were obtained using special NMR cells and the precise size determination of nanomaterials was accomplished by extrapolation methods varying both the concentrations of the nanomaterials and the surfactants in aqueous solution. In addition, the slow diffusions of solvent and surfactant molecules in colloidal nanoparticle aqueous dispersion were directly observed. The slow diffusions of molecules were attributed to the strongly adsorbed molecules on the nanomaterials and the amount of bound molecules was estimated ^(Figure). Our improved PFG-NMR method has promising potentials in the field of the characterization of functional nanomaterials and their nano-toxicity assessments.