Visualizing plasmonic optical trapping by ToF-SIMS

Study level

Master of Philosophy
Vacation research experience scheme


Nanoparticles of plasmonic metals can intensely absorb visible light due to the localized surface plasmon resonance (LSPR) effect, the conduction electrons gain the energy of the incident light through LSPR effect. Furthermore, the oscillating electric dipole generates intense electromagnetic field in close proximity to the NP. The application of photo-excited energetic electrons in direct photocatalysis of metal NPs is well established by our previous studies. However, the plasmonic field enhancement property has not yet been widely used in important chemical synthesis due to the challenge of designing a feasible catalyst-reaction system directly applying the field enhancement.
On the plasmonic metal nanoparticle surface, light irradiation can change the molecule adsorption on the surface. This adsorption selectivity change is due to the enhanced electromagnetic field of the plasmonic metal. Different wavelengths contribute to tune this selectivity more accurately in a molecular level. We were only able to observe this phenomenon from the concentration change of bulk solution in our previous study, but not able to see directly from the surface. Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) is a surface-sensitive analytical method that uses a pulsed ion beam to identify molecules from the very outermost surface of the sample, which will be a helpful characterisation tool to visualizing the adsorption process.

Research Activities

In this project, we plan to investigate the wavelength dependent adsorption of molecules on metal nanoparticle surface by visualizing the process based on ToF-SIMS technique. Amine and nitroxide compounds are applied as target molecules to show selective adsorption on plasmonic metal surface when irradiated with different wavelengths.


Develop a ToF-SIMS based characterization of molecule adsorption on catalyst surface.

Skills and experience

Upon successful completion of this project, students will:
• Have the basic skills necessary to acquire, process, report and interpret research experimental data from a number of techniques, including sample preparation and analysis by ToF-SIMS, SEM-EDS, XRF, FTIR and organic compound analysis.
• Have an overview of practical approaches to the study of materials in relation to wider research questions.
• Be able to debate the role of science-based studies in physical and organic chemistry, including the potential advantages and constraints inherent within different approaches.
• Have the ability to critically assess reports and publications deriving from research project, as well as to propose analytical projects with physical chemistry relevance.