Fluorescence Quenching of 5,5′-Disulfopropyl-3,3′-dichlorothiacyanine Dye Adsorbed on Gold Nanoparticles

• Published in: Journal of physical chemistry. C Vol. 117; no. 13; pp. 6567 - 6577
• Main Authors: Vujačić, Ana, Vasić, Vesna, Dramićanin, Miroslav, Sovilj, Sofija P., Bibić, Nataša, Milonjić, Slobodan, Vodnik, Vesna
• Format: Journal Article
• Language: English
• Published: Columbus, OH American Chemical Society 04.04.2013
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Exact sciences and technology; Nanocrystals and nanoparticles; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures; Physics; Cyanine dyes; Ultrathin films; Gold; Organic dye; Fluorescence; Electron transfer; Coverage rate; Nanoparticles; Line intensity; Quantity ratio; Adsorption; Transition elements; Luminescence quenching
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/jp311015w

Nanoparticles (NPs) modified with fluorescent cyanine dyes can exhibit fluorescent quenching properties due to energy and/or electron transfer, and these systems have many applications in catalysis, drug delivery, nanoelectronics, medical diagnostics, and chemical sensing. The aim of this work was to investigate the adsorption of cyanine dye 5,5′-disulfopropyl-3,3′-dichlorothiacyanine (TC) on the surface of citrate capped gold nanoparticles (AuNPs) with the average core sizes of 9, 17, and 30 nm using various experimental techniques. The measurements of fluorescence corrected for inner filter effects (IFE) of the particle–dye assembly clearly indicated that the fluorescence of TC was quenched by AuNPs on the concentration dependent manner, and the equilibrium constants for the sorption of TC on the NP surface were calculated. Significant increase of fluorescence quenching was noticed when NP size increased, keeping the concentration of NPs of different size constant. By comparing experimental and calculated results for quenching of TC dye fluorescence, we assumed that the maximum quenching was restricted to full monolayer coverage of TC on the NP surface. The conclusion was drawn that the most probable orientation of TC dye molecules on the NP surface was slanted and that the dye approached NP surface with its positively charged thiazole ring.