Hollow gold nanoshells as unique near infrared optical materials for surface enhanced Raman scattering

Student thesis: Doctoral Thesis

Abstract

Hollow gold nanoshells (HGNs) demonstrate a tunable localised surface plasmon resonance (LSPR) from the visible to the near infrared (NIR). The NIR region of the electromagnetic spectrum is of particular interest as it provides an uncongested spectral window for optical analysis due to many molecules having reduced absorption and scattering backgrounds. In addition, the superior depth of light penetration and reduced interference which is observed in this region when compared to the visible region means that there is a great need to design SERS nanotags which can provide a unique vibrational fingerprint in this uncongested optical region. The research described herein demonstrates three ways in which red-shifted nanotags can be engineered to provide effective SERS signals in the NIR region. Firstly, NIR active HGNs were synthesised and encapsulated with seven non-resonant commercial Raman reporters and shown to provide effective SERS when excited with a 1064 nm laser. The nanotags were then tested using a 1280 nm laser excitation however; they were unsuccessful at providing a SERS spectrum. Through a successful collaboration with Professor Michael Detty's group (University at Buffalo) newly synthesised Raman reporters where obtained. The chalcogenopyrylium dyes were resonant from 650 to 1000 nm and when combined with HGNs, demonstrated an unprecedented performance. Through the design of these nanotags, extreme red-shifted SERS was achieved with laser excitations from 1064 nm up to 1550 nm and detection limits in the picomolar to femtomolar range where obtained. Finally, this research demonstrates that when hollow gold nanotags are functionalised with a thermopolymer such as poly(N-isopropylacrylamide), the LSPR can be shifted into the NIR region and laser induced plasmonic heating of the nanoshells can be used to turn on and off the SERS enhancement.Overall, the development of NIR active nanotags could provide the basis for future advancements in bio-chemical, medical and optical applications.
Date of Award1 Apr 2015
LanguageEnglish
Awarding Institution
  • University Of Strathclyde
SponsorsUniversity of Strathclyde & EPSRC (Engineering and Physical Sciences Research Council)
SupervisorDuncan Graham (Supervisor) & Karen Faulds (Supervisor)

Cite this