Year-end Sale % OFF 
Abstract
Enhancement of sub-wavelength optical fields using sub-micron plasmonic probes has found many applications in chemical, material, biological and medical sciences. The enhancement is via localised surface-plasmon resonance (LSPR) which enables the highly sensitive vibrational-spectroscopy technique of surface-enhanced Raman scattering (SERS). Combining SERS with optical fibres can allow the monitoring of biochemical reactions in situ with high resolution. Here, we study the electromagnetic-field enhancement of a tapered optical fibre-tip coated with gold nanoparticles (AuNPs) using finite-element simulations. We investigate the electric-field enhancement associated with metallic NPs and study the effect of parameters such as tip-aperture radius, cone angle, nanoparticle size and gaps between them. Our study provides an understanding of the design and application of metal-nanoparticle-coated optical-fibre-tip probes for SERS. The approach of using fibre-coupled delivery adds flexibility and simplifies the system requirements in SERS, making it suitable for cellular imaging and mapping bio-interfaces.
Highlights
It is often desirable to measure physiological and biological parameters with a high spatial resolution at a preferred location
Decreasing the tip diameter will lead to losing light gradually due to concomitant loss of the propagating modes, whereas a probe that has a more abrupt reduction in the diameter will lose most of the light at a single point which acts as a cut-off for many modes
In order to observe the sensitivity of Surface-enhanced Raman scattering (SERS) signals on tip morphology, we compared a simple flat cleaved fibre end with a tapered fibre tip, both coated with 60 nm gold nanoparticles and functionalised by 4-mercaptobenzoic acid (MBA), a Raman-active molecule. 60 nm gold nanoparticles were selected as they give high SERS-enhancement factors under 633 nm excitation conditions [39] and are optimally suited for coating on the fibre tips from their colloidal suspension
Summary
It is often desirable to measure physiological and biological parameters with a high spatial resolution at a preferred location. Surface-enhanced Raman scattering (SERS) is a powerful vibrational spectroscopy technique capable of single-molecule detection [5,6,7] It is increasingly being used for probing and imaging live cells, to provide molecular structural information on their cellular environment [8]. An important aspect is to improve the light coupling between the metallic NPs on the fibre-tip surface to obtain the highest enhancements The design of such probes has to take into account a consideration of the excitation and plasmon coupling in the metal nanoparticles and enhancement factors, which should be optimised for the Ramanexcitation wavelength used
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
