Evaluation of interparticle interaction between colloidal Ag nanoparticles coated with trisodium citrate and safranine by using FRET: Spectroscopic and mechanistic approach

► This study is useful in spectroscopic ruler. ► The present work explores the effect of the energy transfer efficiency between AgNPs and dye. ► Study will helps to understand large scale conformational dynamics of complex biomolecules. ► AgNPs can be used as donors in biophysical experiments. Current study employs fluorescence spectroscopy, UV–Vis absorbance spectroscopy, dynamic light scattering (DLS) and cyclic voltammetry (CV) to investigate the interaction of safranine dye with spherical shaped silver nanoparticles (AgNPs) coated with trisodium citrate. In fluorescence spectroscopic study we used the AgNPs and safranine dye as component molecules for the construction of FRET, whereas AgNPs serve as donor fluorophore and safranine as acceptor. The fluorescence quenching of AgNPs followed by sensitization of safranine occurs almost simultaneously by addition of safranine dye with different concentrations, indicating fluorescence energy transfer observed between them. Interaction between safranine and AgNPs is also confirmed by using UV–Vis absorption spectroscopy. Addition of safranine results in the significant decrease in the absorbance of AgNPs at 423nm and simultaneous increase in the absorbance of safranine at 518, 276 and 248nm which is indication of rapid binding of safranine molecules with AgNPs. However CV measurements reveals that the safranine molecule does not alter the redox properties of the AgNPs but the safranine molecule lose their redox properties upon getting bonded with AgNPs. This clearly confirms that the safranine molecules get attached on the surface of AgNPs which was also supported by the DLS as well as zeta potential measurement.