Search

Hybrid fluorescent nanoparticles (NPs) were developed on the basis of a series of chemically close polyfluorene-based conjugated polymers and an amphiphilic polymer. NPs constructed from polyfluorene with 2,1,3-benzothiadiazole units incorporated in the backbone of polymer chains displayed Ag+-sensitive fluorescence emission features with high selectivity, which was demonstrated to be attributable to Ag+-induced aggregation and fluorescence quenching. The negatively charged sulfonic acid groups of amphiphilic polymer components located on the surfaces of the hybrid NPs and therefore provided binding sites for metal ions, which was found indispensable for the observed silver ion sensing features of the as-prepared hybrid NPs. Additionally, it was demonstrated that the benzothiadiazole-containing conjugated polymer components not only acted as the fluorescence signaling source but also participated in the metal binding/recognition processes. Thus, a mechanism of cooperative recognition-based aggregation-induced fluorescence static quenching and Ag+-triggered fluorescence dynamic quenching responsible for the observed Ag+ sensing results was confirmed.

Core-shell polymeric nanoparticles (NPs) containing photoswitchable spiropyrans (SP) and spirooxazines (SO) within the cores were fabricated. Fluorescence photoswitching studies revealed that the substituent groups on the photochromic SP/SO structures exerted significant influence on the fluorescence photoswitching behaviors of the as-prepared polymeric NPs, such as the reversibly interchangeable fluorescence color and the photoswitching kinetics. The electron-releasing and electron-withdrawing abilities of the substituent groups are believed to play important roles in controlling the electron configuration of the photochromic component and therefore be responsible for the tunable dual-color photoswitching performance.

This minireview highlights recent advances of research dedicated to photoswitchable fluorescent nanoparticles and their applications. Recently, several strategies have been developed to synthesize nanoparticles with optically switchable emission properties: either fluorescence on/off or dual-alternating-color fluorescence photoswitching. The underlying mechanisms of fluorescence photoswitching enable many different types of photoswitchable fluorescent nanoparticles to change fluorescence colors, thus validating the basis of the initial photoswitching design. Among all possible applications, the usage of photoswitchable fluorescent nanoparticles to empower super-resolution fluorescence imaging and to label biological targets was subsequently reviewed. Finally, we summarize the important areas regarding future research and development on photoswitchable fluorescent nanoparticles.