Observation of stimulated emission from Rhodamine 6G-polymer aggregate adsorbed at foam interfaces

Ketan Pancholi,Neil S Beattie,Dehong Huo,Peter K J Robertson,Paul Okpozo

doi:10.1088/2515-7655/aaec3d

Abstract

This paper reports for the first time the observation of stimulated emissions from the gas–liquid interface between two adjacent bubbles in highly ordered foams containing Rhodamine 6 G and surfactant. Stimulated emissions centred at 595 nm were observed when a monolayer of foam (∼liquid fraction 0.11), placed on a highly reflective surface, was pumped with a 532 nm continuous wave laser directed along ∼45° from the direction perpendicular to the substrate. Additionally, using confocal microscopy and micro-photoluminescence, it was found that the liquid fraction of the foam, the gap between two adjacent bubbles and the incidence angle of the laser are important parameters in guiding the light and promoting stimulated emissions at the interface. The adsorption of the polymer and dye increased the local concentration at the narrowest gaps between pairs of bubbles, which led to the formation of hemispherical micelles-dye agglomerates. The presence of the micelles aggregation caused random scattering induced stimulated emission. These results could have a significant impact on a number of applications, such as photocatalytic conversion at bubble interfaces, where TiO2 can scatter light and hence reaction rates may be increased.

Highlights

Aggregation of the dye and nanoparticle materials are of great interest as a structure with potential applications in drug delivery measurement [1, 2], solar cells [3], sensors [4] and catalysis [5]
A similar observation was made in the two-dimensional confocal images, where the interfaces between adjacent bubbles appeared brighter than rest of the foam, as shown in figure 2(c)
Since the cross section of the interface was similar to a concave lens (figure 2(b)), the interface would be widest at the top surface; the gap between two adjacent bubbles decreases on moving through the thickness of the foam

Summary

Introduction

Aggregation of the dye and nanoparticle materials are of great interest as a structure with potential applications in drug delivery measurement [1, 2], solar cells [3], sensors [4] and catalysis [5]. The multiple charges do not remain stored on the catalyst surface for long enough time for reaction to proceed. The charges are, stored in the confined spaced between TiO2 nanoparticles in agglomerates and may become available for reactions to proceed [8]. The aggregates of Rhodamine 6 G dye adsorbed on amyloid protein fibres are found to produce the laser-like emissions through a random lasing process [10]. Such molecular complexes of dyes form the basis of biophotonics materials that is useful in improving diagnostic capabilities and other microlaser sensing applications [10]

Methods

Results

Conclusion