title: Detection of adsorption of Ru(II) and Os(II) polypyridyl complexes on gold and silver nanoparticles by single-photon counting emission measurements.
abstract: The present study describes a new application of ruthenium(II) tris(bipyridine) (Ru(bpy)3(2+)) and osmium(II) tris(bipyridine) (Os(bpy)3(2+)) as phosphorescent labels for the quantification of surface binding of molecules to gold and silver nanoparticles. The fraction of Ru(bpy)3(2+) and Os(bpy)3(2+) that is in solution can be distinguished from the surface-bound fraction by the relative lifetimes and integrated emission yields as determined by time-correlated single-photon counting (TCSPC) spectroscopy. Complementary steady-state measurements were carried out to confirm surface attachment of the phosphorescent label molecules. Although the emission of solutions of Ru(bpy)3(2+) and Os(bpy)3(2+) is quenched proportional to the concentration of 10 nm Au or 20 nm Ag nanoparticles, the quenching is static and not diffusional quenching observed in Stern-Volmer plots. The results demonstrate that time-resolved spectroscopy provides a rapid method for the measurement of surface binding of labeled molecules on metallic nanoparticles. While steady-state measurements require the preparation of a series of samples with varying quencher concentrations and a reference, the method described herein requires a single sample plus reference. The mechanism for phosphorescence quenching on Au and Ag nanoparticles is discussed in terms of energy and electron transfer theories.
authors.affiliation: Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, USA.
authors.forename: Wilhelm R
authors.initials: WR
authors.lastname: Glomm
authors.forename: Selina J
authors.initials: SJ
authors.lastname: Moses
authors.forename: Matthew K
authors.initials: MK
authors.lastname: Brennaman
authors.forename: John M
authors.initials: JM
authors.lastname: Papanikolas
authors.forename: Stefan
authors.initials: S
authors.lastname: Franzen
mesh_terms: D000327:Adsorption; D006046:Gold / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry*; D009942:Organometallic Compounds / Q000737:chemistry*; D009992:Osmium / Q000737:chemistry; D011725:Pyridines / Q000737:chemistry; D012428:Ruthenium / Q000737:chemistry; D012680:Sensitivity and Specificity; D012834:Silver / Q000737:chemistry*; D013499:Surface Properties; D013997:Time Factors; D014055:Tomography, Emission-Computed / Q000379:methods*
chemical_list: D009942:Organometallic Compounds; D011725:Pyridines; D009992:Osmium; D012834:Silver; D006046:Gold; D012428:Ruthenium