Artificial light-harvesting nanoparticles based on a tripodal fluorescence sensor mediated by multiple luminescence mechanisms

Abstract

It is highly desirable to precisely control the luminescence properties of organic molecules through the combination of multiple fluorescence mechanisms. In this work, we designed and synthesized a tripodal sensor molecule G, which contains three tetraphenylethylene (TPE) groups and three Schiff base groups. The G molecules can form nanoparticles in H₂O/THF mixed solvent (f_w = 90%) through the reprecipitation method. Moreover, by co-precipitation with an energy acceptor dye NDI, efficient artificial light harvesting nanoparticles (G–NDI NPs) could be obtained. As a result, a combination of three fluorescence mechanisms was introduced into this binary system: excited-state intramolecular proton-transfer (ESIPT) based on Schiff base groups, aggregation-induced emission (AIE) based on TPE groups, and Förster resonance energy transfer (FRET) between the donor and acceptor. At a relatively high donor/acceptor ratio (200/1), the antenna effect can reach 11.4 and the energy transfer efficiency can reach 22.0%. Furthermore, these assembled NPs were successfully used in the detection of Fe³⁺ and Cu²⁺ ions and showed good probing abilities with large Stokes shifts and red fluorescence quenching phenomena. This study will further inspire the development of multi-color luminescent materials by controlling multiple mechanisms and show great potentials in chemical sensing, bioimaging, and photoluminescent devices.