Fluorescence quenching and photobleaching in Au/Rh6G nanoassemblies: impact of competition between radiative and non-radiative decay

Abstract

We report the study of fluorescence quenching from nanoassemblies formed by Rhodamine 6G and gold nanoparticles (Au NPs) of 2.6 nm radius. The presence of Au NPs induces long-term degradation of the photostability (photobleaching) of Rhodamine 6G used as a gain medium in a Fabry-Perot laser cavity. We found that the degradation gets profound when the Au NPs concentration is significantly increased. Calculation of the radiative rate and direct time-resolved measurement of the fluorescence decay indicates that both the decrease of radiative decay rate and increase of non-radiative decay rate are responsible for the fluorescence quenching and photostability degradation. An energy transfer from the dye molecules to gold nanoparticles is dominating within small distance between them and suppresses the quantum efficiency of Rhodamine 6G drastically. In a long time scale, the photobleaching rate was slowing down, and the laser output intensity reached a stabilized level which depends on the gold nanoparticles concentration.

Bare laser‐synthesized Au‐based nanoparticles as nondisturbing surface‐enhanced Raman scattering probes for bacteria identification

“…First, these NPs are exempt of ligands or contaminants, which enables one to avoid undesirable Raman signals presenting background noise. Second, phenomena related to quenching of autofluorescence in a studied system due to the direct contact of target biomolecules with metal can profit from a high purity of bare laser‐synthesized nanomaterials. The advantages of bare nanomaterials were clearly visible during our recent comparative tests involving laser‐synthesized NPs and different chemical counterparts, including citrate‐coated NPs and gold nanostars, as SERS probes for the identification of beverage spoilage yeasts .…”

Photostability of gold nanoparticles with different shapes: the role of Ag clusters

“…Large developments of shape control enable nowadays to synthesize nanoparticles of non-spherical shapes, such as rods, prisms, cubes, cuboctahedrons, octahedrons, decahedrons, icosahedrons, truncated octahedrons, etc. Several studies about the stability under photoirradiation of gold nanoparticles have also been reported [37][38][39][40][41][42][43][44] . Synthesis of anisotropic structures such as gold nanorods and nanowires were widely studied since Murphy's 20 and El-Sayed's 21-23 pioneering works, and has attracted much attention due to the fine-tuning of light absorption from visible to near infrared just by changing the aspect ratios (length/diameter).…”

Photostability of lasing process from water solution of Rhodamine 6G with gold nanoparticles

“…2(b)], during the second stage. It resembles the intensity evolution presented in the previous study where small (2.6 nm) Au NPs were used, and it represents a signature of energy transfer between the dye molecules and the Au NPs [14]. Overall, with five samples containing Au NPs of different concentrations, we demonstrate a straightforward relation between the concentration ratio of Au NPs/Rh6G solution and the photostability of such gain medium-the higher is the ratio, the worse is the photostability.…”

“…The photodegradation becomes faster with an increasing concentration of Au NPs, which is similar to dye solutions containing small NPs [14]. All three samples with Au NPs (N1-N3) show a rapid intensity build-up stage at the very beginning, a slowly increasing build-up stage at the middle, and a quickly dropping build-up stage at the end.…”

“…However, compared to other inorganic NPs, the impact of noble metal NPs on the photostability of the gain medium in lasers is studied much less. In a previous study, an acceleration of photobleaching of Rhodamine 6G (Rh6G) in a typical (FabryPerot) laser cavity was observed with the presence of Au NPs of 2.6 nm radius [14]. The degradation was found to be related to the energy transfer from excited dye molecules to small size Au NPs.…”