Influence of silver nanoparticles on absorption and fluorescence properties of laser dyes

The interaction of silver nanoparticles with four laser dyes, namely, LD-425, LD-489, LD-473, and LD-423, dispersed in methanol has been studied at room temperature by absorption and fluorescence spectroscopy. The silver nanoparticles were synthesized by chemical reduction and estimated size is 11 nm according to Mie theory. The changes in absorption spectrum of these dyes with the addition of silver nanoparticles suggest possible interaction with the silver nanoparticles. The magnitudes of the association constants are estimated using the Benesi-Hildebrand model. Fluorescence quenching has been observed for all the dyes with the addition of silver nanoparticles of different concentrations. The Stern-Volmer plots of fluorescence quenching in the case of LD-425 and LD-489 are found to be linear, suggesting the fluorescence quenching is because of the dynamic quenching process. But in the case of LD-473 and LD-423, the Stern-Volmer plots are nonlinear showing positive deviation and the fluorescence quenching in these dyes is because of static quenching processes. Also, it is found that the fluorescence quenching is not solely due to diffusion. PACS Nos.: 33.20.-t, 33.50.Dq, 36.40.Mr, 78.67.Bf, 82.80.Dx. Utilisant la spectroscopie par absorption et fluorescence a la temperature de la piece, nous etudions l'interaction de nanoparticules d'argent avec quatre colorants, nommement le LD-425, le LD-489, le LD-473 et le LD-423 dans du methanol. Les nanoparticules sont synthetisees par reduction chimique et leur grosseur estimee est de 11 nm selon la theorie de Mie. Les changements dans le spectre d'absorption de ces colorants, suivant l'ajout de nanoparticules, suggere une interaction possible avec les nanoparticules d'argent. Nous estimons la valeur des constantes d'interaction a l'aide de la methode de Benesi-Hildebrand. Nous observons une extinction de la fluorescence pour tous les colorants suite a l'ajout de nanoparticules d'argent a differentes concentrations. Les graphiques de Sturm-Volmer de l'extinction de fluorescence sont lineaires dans les cas de LD-425 et LD-489, ce qui suggere un mecanisme d'extinction dynamique. Ils sont non lineaires avec deviation positive dans les cas de LD-473 et LD-423, ce qui suggere un mecanisme statique d'extinction. Nous trouvons egalement que l'extinction de fluorescence n'est pas due exclusivement a la diffusion. [Traduit par la Redaction]
Introduction Metal nanoparticles have been a subject of great interest because of their potential applications in electronics, nonlinear optics, chemical and biochemical sensors, and in catalysis [1]. Because of surface [...]