Electrostatically Driven Förster Resonance Energy Transfer between a Fluorescent Metal Nanoparticle and J-Aggregate in an Inorganic–Organic Nanohybrid Material

With an objective to understand the interaction between the inorganic and organic components of inorganic–organic hybrid nanomaterials, we have fabricated and studied the photonic properties of a nanocomposite system consisting of a silver-capped gold nanoparticle as the inorganic component and the J-aggregate of cyanine-based dye (S2165) as the organic component. The present hybrid construct has been fabricated by adopting electrostatically driven self-assembly of organic cyanine dye and inorganic silver-capped gold (AgCAu) nanoparticle. In contrast to the previously developed hybrid systems where fluorescent inorganic semiconductor quantum dots are integrated with J-aggregates, the formation of the hybrid system in the present work is carried out by exploiting the fluorescent AgCAu nanoparticle and the J-aggregate of the cyanine dye. The hybrid system has been characterized by spectroscopic and microscopic techniques. Steady-state and time-resolved fluorescence measurements have been performed on this hybrid system to understand the interaction of metal nanoparticles with the J-aggregate. Additionally, fluorescence lifetime imaging microscopy studies have also been done on the hybrid system to examine the heterogeneity in the fluorescence lifetime of the system. The composite system displays broad absorption in the ultraviolet part of the spectrum, typically associated with inorganic nanoparticles, and shows a peak in the visible region corresponding to the J-aggregate. The quenching of the fluorescence of AgCAu and the increase in the intensity of the J-aggregate on excitation of AgCAu reveal the process of energy-transfer process from AgCAu to J-aggregate. Analysis of the data in light of Forster theory reveals that inorganic AgCAu and organic J-aggregate in the hybrid system are electronically coupled. The zeta potential measurements on AgCAu and the hybrid system reveal that the interaction between AgCAu (donor) and J-aggregate (acceptor) and, consequently, the energy-transfer process between them is electrostatically driven. The observation of highly efficient energy transfer between the inorganic and organic units of the hybrid material indicates that the present hybrid material can be quite useful in various optoelectronic applications.