Ultrabright Fluorescent and Lasing Microspheres from a Conjugated Polymer

Abstract

Fluorescent microspheres are used for biomarkers, assay substrates, chemical diagnostics, flow cytometry, and biological imaging. These applications demand the highest fluorescence intensity achievable; however, concentration quenching limits the amount of dye that can be practically incorporated in conventional fluorescent microspheres. Conjugated polymers (CPs) can be less susceptible to concentration quenching, suggesting that they can be excellent candidates for a new class of light‐emitting microspheres. Due to their long‐chain‐conjugated backbone, however, CPs can be resistant to forming smoothly curved or spherical structures. Here, strongly fluorescent CP microspheres as large as 100 µm in diameter are synthesized. Whispering gallery modes (WGMs) appear in the fluorescence spectra, and the microspheres show clear evidence of lasing above a threshold pump intensity. These conjugated polymer beads are up to 50 times larger than CP microspheres obtained by other methods, and they exceed the emission intensity of conventional fluorescent microspheres by more than an order of magnitude.

Review of biosensing with whispering-gallery mode lasers

“…Most organic fluorescent dyes suffer from photobleaching, which restricts repetitive measurements and the use of high pump powers to enhance the signal unless the fluorescent material is regenerated 83 . One of the possible ways to address this problem is the replacement of dyes with polymers 84 . For example, an optofluidic microlaser with an ultralow threshold down to 7.8 µJ cm −2 in an ultrahigh‐Q WGM microcavity filled with a biocompatible conjugated polymer has been demonstrated 85 .…”

Multi-wavelength colloidal quantum dot lasers in distributed feedback cavities

“…Recently, different kinds of lightemitting materials are used to advance the laser technology, including polymers and dyes [1][2][3][4][5]. Among them, colloidal quantum dots (CQDs) are the most promising candidate to achieve cheap and versatile optical sources because of its low-cost effective chemical manufacturing process and high photoluminescence quantum yield [6,7].…”

Facile microfluidic fabrication of monodispersed self‐coupling microcavity with fine tunability

“…Rao's work showed how to build a high-throughput platform with high sensitivity [37]. There are some investigation of microcavity fabrication from conjugate polymers [33,38] and Yamamoto even combine WGM with Förster resonance energy transfer (FRET), which has explored the possibility of time resolution spectrum [39]. Yu has showed the photopatterning can be obtained via WGM selective reflection [40].…”