Fluorescent Organic Nanoparticles Constructed by a Facile "Self-Isolation Enhanced Emission" Strategy for Cell Imaging

To achieve the highly emissive features and overcome the troublesome photobleaching for fluorescent organic molecules, a facile and versatile strategy named "self-isolation enhanced emission (SIEE)" was developed to prevent the pi-pi stacking of organic fluorophores by linking alkyl chains on their conjugated backbones. As a proof-of-concept, one or two octyl groups were grafted onto the backbone of 4,7-di(thiophen-2-yl)benzo[c][1,2,5]thiadiazole (termed as DTBT-0), resulting in two different molecules, termed as DTBT-1 and DTBT-2, respectively. Compared with DTBT-0, DTBT-1 and DTBT-2 exhibited remarkably enhanced fluorescent properties in both aggregated thin films and nanoparticles, demonstrating that the SIEE method could isolate the fluorophores effectively and then prevent their pi-pi stacking to achieve the impressive fluorescent properties. After proper surface modification, excellent water dispersibility, biocompatibility, and improved resistance to photobleaching were also achieved for highly emissive DTBT-2-based nanoparticles, which were then successfully applied for cellular imaging.