title: Determination of colloidal gold nanoparticle surface areas, concentrations, and sizes through quantitative ligand adsorption.
abstract: Determination of the true surface areas, concentrations, and particle sizes of gold nanoparticles (AuNPs) is a challenging issue due to the nanoparticle morphological irregularity, surface roughness, and size distributions. A ligand adsorption-based technique for determining AuNP surface areas in solution is reported. Using a water-soluble, stable, and highly UV-vis active organothiol, 2-mercaptobenzimidazole (MBI), as the probe ligand, we demonstrated that the amount of ligand adsorbed is proportional to the AuNP surface area. The equivalent spherical AuNP sizes and concentrations were determined by combining the MBI adsorption measurement with Au(3+) quantification of aqua regia-digested AuNPs. The experimental results from the MBI adsorption method for a series of commercial colloidal AuNPs with nominal diameters of 10, 30, 50, and 90 nm were compared with those determined using dynamic light scattering, transmission electron microscopy, and localized surface plasmonic resonance methods. The ligand adsorption-based technique is highly reproducible and simple to implement. It only requires a UV-vis spectrophotometer for characterization of in-house-prepared AuNPs.
authors.affiliation: Department of Chemistry, Mississippi State University, Mississippi State, Starkville, MS 39762, USA.
authors.forename: Manuel
authors.initials: M
authors.lastname: Gadogbe
authors.forename: Siyam M
authors.initials: SM
authors.lastname: Ansar
authors.forename: Guoliang
authors.initials: G
authors.lastname: He
authors.forename: Willard E
authors.initials: WE
authors.lastname: Collier
authors.forename: Jose
authors.initials: J
authors.lastname: Rodriguez
authors.forename: Dong
authors.initials: D
authors.lastname: Liu
authors.forename: I-Wei
authors.initials: IW
authors.lastname: Chu
authors.forename: Dongmao
authors.initials: D
authors.lastname: Zhang
mesh_terms: D000327:Adsorption; D001562:Benzimidazoles / Q000737:chemistry; D006046:Gold / Q000737:chemistry; D017979:Gold Colloid / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008024:Ligands; D053768:Metal Nanoparticles / Q000737:chemistry*; D046529:Microscopy, Electron, Transmission / Q000379:methods; D015233:Models, Statistical; D053758:Nanoparticles / Q000737:chemistry; D010316:Particle Size; D015203:Reproducibility of Results; D013056:Spectrophotometry, Ultraviolet / Q000379:methods; D013438:Sulfhydryl Compounds / Q000737:chemistry; D020349:Surface Plasmon Resonance; D013499:Surface Properties
chemical_list: D001562:Benzimidazoles; D017979:Gold Colloid; D008024:Ligands; D013438:Sulfhydryl Compounds; C030698:2-mercaptobenzimidazole; D006046:Gold