Achieving Solidification and Redispersion of Semiconducting Polymer Dots by Layered Double Hydroxide Incorporation

Solidification and aqueous redispersion of fluorophores are characteristically challenging because of aggregation quenching and random shifts of emission. Carbon-based polymer dots (PDs) have recently shown photoluminescent (PL) performances superior to those of conventional dyes and inorganic quantum dots (QDs) but suffer from significant fluorescence (FL) quenching and irreversible aqueous dispersion after solidification, which limits their applications in practical biomedicine and optical devices. In this work, we have compared three strategies by utilizing layered double hydroxides (LDHs) to effectively solidify PDs as robust and redispersible composites with well-preserved high brightness against wide pH (pH = 4-12) and strong ionic strength conditions, more stable than the pristine PDs. The resulting PD-LDH nanocomposites also show in vitro/in vivo bioimaging ability with low cytotoxicity and improved photostability. In addition, these composites exhibit high thermal stability at 150 °C for at least 96 h. The composites produced by a one-step physical mixing approach (10 min) of LDHs and PDs (p-PLDH) exhibited PL performances comparable to those of the conventional multistep composites (m-PLDH), which require tremendous effort (at least 7 days) to prepare. Structural studies further revealed that the deshaping behavior of PDs and the interflake sandwich assembly of LDHs contributed to the robust FL properties. Because of the simple synthesis, durable photostability, high aqueous redispersion, and multicolor emissions (ranging from blue to near-IR) of these PD-LDH nanocomposites, we believe that they are promising candidates for advanced biorelated technologies and optoelectronics.