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

Abstract

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 π–π 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 π–π 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.

A Facilely Synthesized Dual‐State Emission Platform for Picric Acid Detection and Latent Fingerprint Visualization

“…[27][28][29][30][31] By using these highly emissive AIEgens, dual-state emission can be easily achieved and they have potential real-world applications, [32][33][34] such as in PA detection and LFP visualization. Recently,f lexible alkyl chains were introduced into conventionalf luorescent molecules to prevent close packing of their core structures as well as strong p-p intermolecular stacking interactions, [35][36][37] thereby openingr adiative channels to afford highlye missive features in aggregates.T herefore, based on these considera-tions, to achieve ah ighly efficient dual-state emission platform for PA detection and LFP visualization,i nt his work, flexible alkyl chains were facilelya ttached to the commercial organic dye 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA)t o afford the tetraalkyl 3,4,9,10-perylenetetracarboxylate target compounds PTCA-C4, PTCA-C6, and PTCA-C12 (fort he structures, see Figure 1). As we anticipated, impressive fluorescence characteristics with photoluminescence quantum yields (PLQYs) of up to 95.0, 96.9, and 93.2 %w ereo btained for PTCA-C4, PTCA-C6, and PTCA-C12 in THF solution, respectively.…”

A Strategy of “Self‐Isolated Enhanced Emission” to Achieve Highly Emissive Dual‐State Emission for Organic Luminescent Materials

“…To overcome the notoriousA CQ effect in OLMs, Tang et al proposedt he concept of "aggregation-induced emission'' (AIE) in 2001 and then developed tremendous AIE luminogens (AIEgens), which are usually non-or weakly emissive in dilute solution, buta re intensely emissive in the aggregated states ( Figure 1). [23] This developed SIEE method through alkyl chains could also provide the possibility to successfully obtain dual-state emission for OLMs ( Figure 1). Schematic diagrams of chemical structuresf or typical OLMs (ACQ, AIE, and SIEE) and their corresponding emission photographs in THF solution or aggregated states (with aw ater fraction of 0, 50, and 99 %, respectively) and in solid state.…”

“…nescent performance in aggregated states. [23] This developed SIEE method through alkyl chains could also provide the possibility to successfully obtain dual-state emission for OLMs ( Figure 1). Furthermore, it is interesting to note that, if the alkyl chains in conjugated molecules are proper constructed to preventt he strong p-p stacking in aggregateds tates, [24] a smart change from ACQ molecules to AIE molecules through the SIEE strategy coulda lso occur,w hich indicates the great role of the SIEE methodn ot only in fundamental understanding, but also in practical application.…”

“…According to the AIE nature in aggregated states, AIEgens with intramolecular charge‐transfer (ICT) features could also be emissive in the solution state and are thought to achieve the dual‐state emission and thus open a new chapter in the exploration of OLMs in future applications. Recently, our group also demonstrated that employing flexible alkyl chains in the conjugated molecules, such as ACQ fluorophores, can effectively isolate their closely packed molecular backbones and thereby suppress the π–π stacking, finally leading to highly emissive luminescent performance in aggregated states . This developed SIEE method through alkyl chains could also provide the possibility to successfully obtain dual‐state emission for OLMs (Figure ).…”

Fine Tuning of the HOMO–LUMO Gap of 6‐(Thiophen‐2‐yl) indolizino[3,2‐c]quinolines and their Self‐Assembly to Form Fluorescent Organic Nanoparticles: Rational Design and Theoretical Calculations

“…In contrast to the large number of studies reported for nanomaterials based on metals, polymers, quantum dots, and carbon dots, [16,18–22] nanoparticles (NPs) based on organic fluorophores have been rarely reported due to aggregation‐caused quenching (ACQ) in the condensed phase, which has been observed for most conventional fluorophores possessing an aromatic system with high planarity [23–24] . For biomedical imaging, the development of FONs with high brightness in water is critical [25–28] . Up to now, FONs with a controlled morphology and tunable emission have been rarely developed [29–31] …”