On the nature of SERS from plasmonic nanostructures

The nature of surface-enhanced Raman scattering (SERS) on nanostructured surfaces is explored using both inorganic and organic-based systems and a variety of environmental perturbation mechanisms. Experimental optical characterisation systems are developed and existing systems extended to facilitate this exploration. SERS of inorganic semiconducting quantum dots (QDs) is observed for the first time, paving the way for their use as spatially well-defined SERS markers. Tuning of the Raman excitation wavelength allows comparison between resonance and nonresonance QD SERS and identifies enhancement due to the plasmonic nanostructure. A gentle mechano-chemical process (carbon dioxide snow jet) is used to rearrange adsorbed organic thiol monolayers on a gold plasmonic nanostructure. The necessity of nanoscale roughness to the large SERS enhancement on pit-like plasmonic nanostructures is shown and demonstrates a new method to boost SERS signals (> 500 %) on plasmonic nanostructures. A multiplexed time-varied exposure technique is developed to track this molecular movement over time and highlights the different origins of the SERS peak and its accompanying background continuum. Using low-temperature cryogenics (down to 10 K) the SERS peak and background continuum intensity are shown to increase as the plasmonic metal damping reduces with temperature. Temperature dependent measurements of QD (resonance) SERS are shown to have strong wavelength dependence due to the excitonic transitions in QDs. Changes to the QD fluorescence at low temperature allows striking comparison between the Raman and fluorescence processes. The role of charge transfer and electromagnetic enhancement in the SERS intensity of p-aminothiophenol (pATP) is investigated on nanostructured plasmonic surfaces coupled to metallic nanoparticles. The results support the importance of charge transfer effects to the SERS of pATP, and highlight the difference between those of electromagnetic origin. Addition of nanoparticles to the nanostructured surface was seen to enhance SERS signals by up to 100×.

Name dc:type.qualificationname

Doctor of Philosophy (PhD)

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

University of Cambridge

Year dc:date.issued

2013

Author dc:creator

• Hugall, James T.

Advisor dc:contributor.advisor

• Baumberg, Jeremy J.

• Plasmonics
• SERS
• Raman spectroscopy
• Sensing
• Diagnostics
• Quantum Dots
• Fluorescence
• Raman
• Localized plasmons
• Surface plasmons
• SPPs
• Semiconductor Raman
• Nanoparticles
• Low temperature
• Nanophotonics
• Scattering
• Gold

Statement dc:rights

• Figure 4.2 contains a montage of third-party copyrighted images. Permission was obtained from respective publishers prior to publishing thesis, and appropriate citations for each image are made in the caption with a overall copyright notice.

Licence

• https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/0a764fe9-36a0-4f2d-9b62-8fda7471f10b/download
• https://www.rioxx.net/licenses/all-rights-reserved/

Language dc:language

en

Author Identifier

0000-0002-2711-6463
0000-0002-9606-9488

OAI identifier oai:identifier

oai:www.repository.cam.ac.uk:1810/267496