Mechanism of 3,3′-Disulfopropyl-5,5′-Dichlorothiacyanine Anion Interaction With Citrate-Capped Silver Nanoparticles: Adsorption and J-Aggregation

The paper presents the results of the experimental and theoretical study of 3,3′-disulfopropyl-5,5′-dichlorothiacyanine sodium salt (TC) adsorption and J-aggregation on the surface of citrate-capped silver nanoparticles (AgNPs) with an average particle size 10 nm. Various nanospectroscopy techniques such as UV–vis, TEM, AFM, DLS, ζ potential, and fluorescence measurements were carried out in order to characterize the hybrid system. Besides this, a set of simple density functional theory calculations (DFT) was performed and this suggested that TC dye, from the thermodynamical point of view, most likely interacted with AgNPs via oxygen atom from SO3– groups. The methods, which considered AgNPs as the macromolecule with several binding sites and TC dye as the ligand, were applied for the analysis of saturation curves constructed from the fluorescence data to obtain the binding constant (Ka = 1.5 × 106 M–1) and the average number of TC dye molecules bonded per AgNP (∼330). Moreover, TC fluorescence was quench...