The Future is Bright: The Emergence of Glassy Organic Dots for Biological Applications.

Glassy organic dots (g-Odots) are an emerging class of luminescent nanoparticles that offer enhanced photostability, superior brightness, and modular tunability compared to other commonly employed nanoparticles. In the last several years, they have been used as bioimaging probes for single- and multi-photon cellular imaging, exhibiting low cytotoxicity even after several days. While they are emerging as promising materials for use in biological applications, g-Odots face several key challenges before their use can become widespread.

Organelle-Targeting Polymer Dots Exhibiting Thermally Activated Delayed Fluorescence for Subcellular Imaging.

Selective imaging of specific subcellular structures provides valuable information about the cellular microenvironment. Materials exhibiting thermally activated delayed fluorescence (TADF) are rapidly emerging as metal-free probes with long-lived emission for intracellular time-gated imaging applications. Polymers incorporating TADF emitters can self-assemble into luminescent nanoparticles, termed polymer dots (Pdots), and this strategy enables them to circumvent the limitations of commercial organelle trackers and small molecule TADF emitters.

Polymer Dots with Delayed Fluorescence and Tunable Cellular Uptake for Photodynamic Therapy and Time-Gated Imaging.

By combining bioimaging and photodynamic therapy (PDT), it is possible to treat cancer through a theranostic approach with targeted action for minimum invasiveness and side effects. Thermally activated delayed fluorescence (TADF) probes have gained recent interest in theranostics due to their ability to generate singlet oxygen (O) while providing delayed emission that can be used in time-gated imaging. However, it is still challenging to design systems that simultaneously show (1) high contrast for imaging, (2) low dark toxicity but high phototoxicity and (3) tunable biological uptake.

Dibenzodipyridophenazines with Dendritic Electron Donors Exhibiting Deep-Red Emission and Thermally Activated Delayed Fluorescence.

The development of deep-red thermally activated delayed fluorescence (TADF) emitters is important for applications such as organic light-emitting diodes (OLEDs) and biological imaging. Design strategies for red-shifting emission include synthesizing rigid acceptor cores to limit nonradiative decay and employing strong electron-donating groups. In this work, three novel luminescent donor-acceptor compounds based on the dibenzo[,]dipyrido[3,2-h:20-30-]-phenazine-12-yl () acceptor were prepared using dendritic carbazole-based donors 3,3″,6,6″-tetramethoxy-9'-9,3':6',9″-tercarbazole (), ,,,-tetra--tolyl-9-carbazole-3,6-diamine (), and ,,,-tetrakis(4-methoxyphenyl)-9-carbazole-3,6-diamine ().

Polymer dots and glassy organic dots using dibenzodipyridophenazine dyes as water-dispersible TADF probes for cellular imaging.

Fluorescence imaging of living cells is key to better understanding cellular morphology and biological processes. Water-dispersible nanoparticles exhibiting thermally activated delayed fluorescence (TADF) have recently emerged as useful probes for time-resolved fluorescence imaging (TRFI), circumventing interference from biological autofluorescence. Many existing approaches, however, require TADF dyes with specific structural features, precluding many high-performance TADF materials from being used in this application.