Giant Light-Harvesting in Dye-Loaded Nanoparticles Enhanced by Blank Hydrophobic Salts

Light-harvesting is a fundamental process in nature, which inspires researchers to develop artificial systems for photocatalysis, photovoltaics, and biosensing. A previously introduced light-harvesting nanoantenna, based on polymeric nanoparticles (NPs) loaded with rhodamine dyes and bulky hydrophobic counterions, provides a record-breaking antenna effect approximate to 1000. However, the high dye cooperativity of its thousands of encapsulated dyes causes energy losses by traces of self-quenched dye aggregates. Here, it is found that these imperfections can be suppressed by blank hydrophobic salts (BHS) formed by the same bulky counterion (fluorinated tetraphenylborate) with an optically inactive cation, analogs of ionic liquids. The presence of BHS increases twofold the fluorescence quantum yields and fluorescence lifetimes of NPs and suppresses their fluorescence blinking. This study assumes that BHS provides an excess of bulky counterions that excludes traces of dye aggregates. As a result, an efficient Forster resonance energy transfer (FRET) is achieved from 40 000 dye donors to a single acceptor within a 70 nm particle, leading to the antenna effect of 4800, which is by far the highest value reported to date. Using this nanoantenna, a single-molecule detection of the FRET acceptor is realized at low excitation power using an RGB camera of a smartphone. A previously introduced light-harvesting nanoantenna, based on polymeric nanoparticles loaded with rhodamine dyes and bulky hydrophobic counterions, provides an antenna effect of approximate to 1000. Here, blank hydrophobic salts (BHS) formed by the same bulky counterion with an optically inactive cation are found to suppress aggregation-cased quenching (ACQ) and fluorescence blinking within nanoparticles, leading to the record-breaking antenna effect of 4800. image