(117f) Measuring the Accessible Surface Area within the Nanoparticle Corona Using Molecular Probe Adsorption

The corona phase, the adsorbed layer of polymer, surfactant or stabilizer molecules around a nanoparticle, is typically utilized to disperse nanoparticles into a solution or solid phase. Unfortunately, few methods can directly probe the structure of this corona phase due to issues with dilution, molecular mobility, and total radiation cross section. In this work, we introduce a Molecular Probe Adsorption (MPA) method for measuring the accessible nanoparticle surface area using a titration of a quenchable fluorescent molecule. As an example, riboflavin is utilized to measure the surface area of Au nanoparticle standards, as well as corona phases on single walled carbon nanotubes and on graphenes. A material balance on the titration yields the surface coverage parameters, including the ratio of the surface area to dissociation constant of the fluorophore, q/K_D as well as K_D alone. Total 14 different nanoparticle corona phases, on AuNP, SWNT and graphene are chosen and studied with the new method. Uncertainty and precision are discussed, as well as the correlation of these parameters across different experiments. This rapid, quantitative technique should prove useful to elucidating the structure-property relationships of the nanoparticle corona.