title: Precise subnanometer plasmonic junctions for SERS within gold nanoparticle assemblies using cucurbit[n]uril "glue".
abstract: Cucurbit[n]urils (CB[n]) are macrocyclic host molecules with subnanometer dimensions capable of binding to gold surfaces. Aggregation of gold nanoparticles with CB[n] produces a repeatable, fixed, and rigid interparticle separation of 0.9 nm, and thus such assemblies possess distinct and exquisitely sensitive plasmonics. Understanding the plasmonic evolution is key to their use as powerful SERS substrates. Furthermore, this unique spatial control permits fast nanoscale probing of the plasmonics of the aggregates "glued" together by CBs within different kinetic regimes using simultaneous extinction and SERS measurements. The kinetic rates determine the topology of the aggregates including the constituent structural motifs and allow the identification of discrete plasmon modes which are attributed to disordered chains of increasing lengths by theoretical simulations. The CBs directly report the near-field strength of the nanojunctions they create via their own SERS, allowing calibration of the enhancement. Owing to the unique barrel-shaped geometry of CB[n] and their ability to bind "guest" molecules, the aggregates afford a new type of in situ self-calibrated and reliable SERS substrate where molecules can be selectively trapped by the CB[n] and exposed to the nanojunction plasmonic field. Using this concept, a powerful molecular-recognition-based SERS assay is demonstrated by selective cucurbit[n]uril host-guest complexation.
authors.affiliation: NanoPhotonics Centre, Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, U.K.
authors.forename: Richard W
authors.initials: RW
authors.lastname: Taylor
authors.forename: Tung-Chun
authors.initials: TC
authors.lastname: Lee
authors.forename: Oren A
authors.initials: OA
authors.lastname: Scherman
authors.forename: Ruben
authors.initials: R
authors.lastname: Esteban
authors.forename: Javier
authors.initials: J
authors.lastname: Aizpurua
authors.forename: Fu Min
authors.initials: FM
authors.lastname: Huang
authors.forename: Jeremy J
authors.initials: JJ
authors.lastname: Baumberg
authors.forename: Sumeet
authors.initials: S
authors.lastname: Mahajan
mesh_terms: D000268:Adhesiveness; D001952:Bridged-Ring Compounds / Q000737:chemistry*; D006046:Gold / Q000737:chemistry*; D007093:Imidazoles / Q000737:chemistry*; D046911:Macromolecular Substances / Q000737:chemistry; D008422:Materials Testing; D008968:Molecular Conformation; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D010316:Particle Size; D020349:Surface Plasmon Resonance / Q000379:methods*; D013499:Surface Properties; D047028:Macrocyclic Compounds; D000099246:Cucurbit(n)urils
chemical_list: D001952:Bridged-Ring Compounds; D006046:Gold; D007093:Imidazoles; D046911:Macromolecular Substances; C523802:cucurbit(5)uril; D047028:Macrocyclic Compounds; D000099246:Cucurbit(n)urils