Shedding Light on the Extinction-Enhancement Duality in Gold Nanostar-Enhanced Raman Spectroscopy

• Published in: Angewandte Chemie (International ed.) Vol. 53; no. 51; pp. 14115 - 14119
• Main Authors: Li, Ming, Kang, Jeon Woong, Dasari, Ramachandra Rao, Barman, Ishan
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 15.12.2014; WILEY‐VCH Verlag; Wiley Subscription Services, Inc
• Edition: International ed. in English
• Subjects: Attenuation; Excitation; Extinction; Gold; Gold - chemistry; Light; Metal Nanoparticles - chemistry; Nanoparticles; Nanostructure; optical extinction; Particle Size; plasmonics; Plasmons; Raman spectroscopy; Spectrum analysis; Spectrum Analysis, Raman; Surface chemistry; Surface Properties; surface-enhanced Raman spectroscopy; suspension; Wavelengths; nanoparticles; plasmonics; suspension; optical extinction; surface-enhanced Raman spectroscopy
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201409314

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. Gold nanostars: The relationship between the enhancement by surface‐enhanced Raman spectroscopy (SERS) and the localized surface plasmon resonance (LSPR) band is investigated (see picture). The competition between the field enhancement and the optical extinction causes the maximum enhancement factor occurring at a blue‐shifted LSPR band from the excitation wavelength rather than at the on‐resonance position.