title: Toehold-mediated internal control to probe the near-field interaction between the metallic nanoparticle and the fluorophore.
abstract: Metallic nanoparticles (MNPs) are known to alter the emission of vicinal fluorophores through the near-field interaction, leading to either fluorescence quenching or enhancement. Much ambiguity remains in the experimental outcome of such a near-field interaction, particularly for bulk colloidal solution. It is hypothesized that the strong far-field interference from the inner filter effect of the MNPs could mask the true near-field MNP-fluorophore interaction significantly. Thus, in this work, a reliable internal control capable of decoupling the near-field interaction from far-field interference is established by the use of the DNA toehold concept to mediate the in situ assembly and disassembly of the MNP-fluorophore conjugate. A model gold nanoparticle (AuNP)-Cy3 system is used to investigate our proposed toehold-mediated internal control system. The maximum fluorescence enhancement is obtained for large-sized AuNP (58 nm) separated from Cy3 at an intermediate distance of 6.8 nm, while fluorescence quenching is observed for smaller-sized AuNP (11 nm and 23 nm), which is in agreement with the theoretical values reported in the literature. This work shows that the toehold-mediated internal control design can serve as a central system for evaluating the near-field interaction of other MNP-fluorophore combinations and facilitate the rational design of specific MNP-fluorophore systems for various applications.
authors.affiliation: Department of Chemical and Biomolecular Engineering, National University of Singapore, 10 Kent Ridge Crescent, Singapore 11920, Singapore. cheyly@nus.edu.sg.
authors.forename: Y S
authors.initials: YS
authors.lastname: Ang
authors.forename: L Y L
authors.initials: LY
authors.lastname: Yung
mesh_terms: D002232:Carbocyanines / Q000737:chemistry; D003102:Colloids / Q000737:chemistry; D004247:DNA / Q000737:chemistry; D005456:Fluorescent Dyes / Q000737:chemistry; D006046:Gold / Q000737:chemistry; D007700:Kinetics; D053768:Metal Nanoparticles / Q000737:chemistry*; D036103:Nanotechnology / Q000379:methods*; D009841:Oligonucleotides / Q000737:chemistry; D010316:Particle Size; D013050:Spectrometry, Fluorescence; D013438:Sulfhydryl Compounds
chemical_list: D002232:Carbocyanines; D003102:Colloids; D005456:Fluorescent Dyes; D009841:Oligonucleotides; D013438:Sulfhydryl Compounds; C089187:cyanine dye 3; D006046:Gold; D004247:DNA