title: Shedding light on the extinction-enhancement duality in gold nanostar-enhanced Raman spectroscopy.
abstract: Surface-enhanced Raman spectroscopy (SERS) has evolved from an esoteric physical phenomenon to a robust and effective analytical method recently. The need of addressing both the field enhancement and the extinction of nanoparticle suspensions, however, has been underappreciated despite its substantive impact on the sensing performance. A systematic experimental investigation of SERS enhancement and attenuation is performed in suspensions of gold nanostars, which exhibit a markedly different behavior in relation to conventional nanoparticles. The relationship is elucidated between the SERS enhancement and the localized surface plasmon resonance band, and the effect of the concentration of the gold nanostars on the signal propagation is investigated. It is shown that an optimal concentration of gold nanostars exists to maximize the enhancement factor (EF), and the maximum EF occurs when the LSPR band is blue-shifted from the excitation wavelength rather than at the on-resonance position.
authors.affiliation: Laser Biomedical Research Center, George R. Harrison Spectroscopy Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139 (USA); Departments of Mechanical and Biomedical Engineering, Johns Hopkins University, Baltimore, MD 21218 (USA).
authors.forename: Ming
authors.initials: M
authors.lastname: Li
authors.forename: Jeon Woong
authors.initials: JW
authors.lastname: Kang
authors.forename: Ramachandra Rao
authors.initials: RR
authors.lastname: Dasari
authors.forename: Ishan
authors.initials: I
authors.lastname: Barman
mesh_terms: D006046:Gold / Q000737:chemistry*; D008027:Light; D053768:Metal Nanoparticles / Q000737:chemistry*; D010316:Particle Size; D013059:Spectrum Analysis, Raman; D013499:Surface Properties
chemical_list: D006046:Gold
keywords: nanoparticles; optical extinction; plasmonics; surface-enhanced Raman spectroscopy; suspension