title: Tailoring surface plasmons of high-density gold nanostar assemblies on metal films for surface-enhanced Raman spectroscopy.
abstract: Plasmonic systems based on metal nanoparticles on a metal film have generated great interest for surface-enhanced Raman spectroscopy (SERS) chemical sensors. In this study, we describe the fabrication of ultrasensitive SERS substrates based on high-density gold nanostar assemblies on silver films with tailored surface plasmons, where multiple field enhancements from particle-film and interparticle plasmon couplings and lightening rod effects of sharp tips of nanostars contribute to the enormous Raman enhancements. We show that the interplay between interparticle and particle-film plasmon couplings of high-density gold nanostars (GNSs) on metal and dielectric films as a function of interparticle separation can be tailored to provide maximum SERS effects. We observe that the SERS enhancement factor (EF) of GNSs on a metal film as a function of interparticle separation follows a broken power law function, where the EF increases with the interparticle separation for the strong interparticle coupling range below an interparticle separation of ~0.8 times the GNS size, but decreases for the weak interparticle coupling range (for an interparticle separation of >0.8 times the GNS size). Finally, we demonstrate the use of tailored plasmonic substrates as ultrasensitive SERS chemical sensors with an attomole level of detection capability of 2,4-dinitrotoluene, a model compound of nitroaromatic explosives.
authors.affiliation: School of Energy and Chemical Engineering, Ulsan National Institute Science and Technology (UNIST), Ulsan, Republic of Korea. hyunhko@unist.ac.kr.
authors.forename: Jiwon
authors.initials: J
authors.lastname: Lee
authors.forename: Bo
authors.initials: B
authors.lastname: Hua
authors.forename: Seungyoung
authors.initials: S
authors.lastname: Park
authors.forename: Minjeong
authors.initials: M
authors.lastname: Ha
authors.forename: Youngsu
authors.initials: Y
authors.lastname: Lee
authors.forename: Zhiyong
authors.initials: Z
authors.lastname: Fan
authors.forename: Hyunhyub
authors.initials: H
authors.lastname: Ko