Giant light-harvesting nanoantenna for single-molecule detection in ambient light

Abstract

Here, we explore the enhancement of single molecule emission by polymeric nano-antenna that can harvest energy from thousands of donor dyes to a single acceptor. In this nano-antenna, the cationic dyes are brought together in very close proximity using bulky counterions, thus enabling ultrafast diffusion of excitation energy (≤30 fs) with minimal losses. Our 60-nm nanoparticles containing >10,000 rhodamine-based donor dyes can efficiently transfer energy to 1-2 acceptors resulting in an antenna effect of ~1,000. Therefore, single Cy5-based acceptors become 25-fold brighter than quantum dots QD655. This unprecedented amplification of the acceptor dye emission enables observation of single molecules at illumination powers (1-10 mW cm-2) that are >10,000-fold lower than typically required in single-molecule measurements. Finally, using a basic setup, which includes a 20X air objective and a sCMOS camera, we could detect single Cy5 molecules by simply shining divergent light on the sample at powers equivalent to sunlight.

Fighting Aggregation‐Caused Quenching and Leakage of Dyes in Fluorescent Polymer Nanoparticles: Universal Role of Counterion

“…This result underlines that the counterion can strongly alter organization of dyes inside the polymer matrix. Thus, in line with our original works on F5‐TPB, the bulky hydrophobic (TPB) counterions tend to organize the dyes in form of clusters where the dyes undergo very fast EET . Our recent work suggested that with F5‐TPB, EET within R18 dyes can reach unprecedented time scales of ≤30 fs .…”

“…On one hand, NPs with clustered dyes, produced by bulky hydrophobic counterions, will be of high interest for superresolution imaging, light harvesting and FRET‐based sensing. Indeed, we showed recently that R18 dye salt with bulky hydrophobic counterion F5‐TPB loaded at high concentration in polymer NPs enables ultrafast EET at the fs time scale, producing highly efficient light‐harvesting process, with antenna effect >1000 . This high dye cooperativity, favored by F5‐TPB, has already enabled preparation of ultra‐bright FRET platforms (100‐fold brighter than corresponding quantum dots) for amplified detection of nucleic acids .…”

“…The latter was previously reported for NPs loaded with R18/F5‐TPB, and was assigned to unprecedented communication of R18 dyes, assembled inside the polymer matrix by the F5‐TPB counterion. The counterion plays the role of both spacer, which prevents dyes from ACQ, and “glue” that brings the dyes together and ensures fast EET . In these conditions, any transient dark species inside a particle can quench the entire particle.…”

“…Moreover, F5‐TPB counterion can be replaced with another fluorinated tetraphenylborate and a fluorinated aliphatic aluminate . Finally, the counterion‐based approach was recently applied to create an unprecedented giant light‐harvesting nanoantenna that allowed detection of single molecules in ambient light conditions, and amplified detection of nucleic acids …”

“…[18] Moreover,F 5-TPB counterion can be replaced with another fluorinated tetraphenylborate [18] and af luorinated aliphatic aluminate. [19] Finally,t he counterion-based approach was recently applied to create an unprecedented giant lightharvesting nanoantenna that allowed detection of single molecules in ambientl ight conditions, [20] and amplifiedd etection of nucleic acids. [21] These bulky hydrophobic counterions belong to the class of weakly coordinating anions, characterizedb yh igh charge delocalization,l arge size, absence of basic sites, presenting mainly fluorine or hydrogen at their anions urface.…”