Department of Chemical and Biomolecular Engineering, 3 Engineering Drive 3, National University of Singapore, Singapore, 117582, Singapore.
Department of Chemistry, 3 Science Drive 3, National University of Singapore, Singapore, 117543, Singapore.
Sci Rep. 2018 Sep 20;8(1):14088. doi: 10.1038/s41598-018-32596-8.
In this paper, we demonstrate FRET-based multicolor lasing within chemically open droplet cavities that allow online modulation of the gain medium composition. To do this, we generated monodisperse microfluidic droplets loaded with coumarin 102 (donor), where the spherical droplets acted as whispering gallery mode (WGM) optical cavities in which coumarin 102 lasing (~ 470 nm) was observed. The lasing color was switched from blue to orange by the introduction of a second dye (acceptor, rhodamine 6 G) into the flowing droplet cavities; subsequent lasing from rhodamine 6 G (~ 590 nm) was observed together with the complete absence of coumarin 102 emission. The ability to control color switching online within the same droplet cavity enables sequential detection of multiple target molecules within or around the cavity. As a demonstration of this concept, we show how the presence of FITC-Dextran and methylene blue (MB) in the medium surrounding the lasing droplets can be sequentially detected by the blue and orange laser respectively. The method is simple and can be extended to a range of water-soluble dyes, thus enabling a wide spectral range for the lasing with the use of a single pump laser source.
在本文中，我们展示了基于 FRET 的多色激光在化学开放式液滴腔体内的应用，该腔体允许对增益介质组成进行在线调制。为此，我们生成了负载香豆素 102（供体）的单分散微流控液滴，其中球形液滴充当 whispering gallery mode（WGM）光学腔，在其中观察到香豆素 102 激光（470nm）。通过将第二种染料（受体，若丹明 6G）引入流动的液滴腔中，将激光颜色从蓝色切换到橙色；随后观察到若丹明 6G 的激光（590nm）发射，同时完全没有香豆素 102 的发射。在同一液滴腔体内在线控制颜色切换的能力使我们能够在腔体内或周围对多个目标分子进行顺序检测。作为该概念的演示，我们展示了如何通过蓝色和橙色激光分别检测到腔内激光液滴周围的 FITC-Dextran 和亚甲蓝（MB）的存在。该方法简单，可扩展到一系列水溶性染料，从而在使用单个泵浦激光源的情况下实现广泛的激光光谱范围。
