Localisation and Coupling of Plasmon Modes in Size-Selected Cluster Films Probed by EELS
Lead Research Organisation:
University of Birmingham
Department Name: School of Physics and Astronomy
Abstract
A lens in an optical microscope is made of glass - it has to be transparent. You make a mirror from a piece of glass by coating it with metal - which reflects light. But if you drill a series of tiny holes, much smaller than the wavelength of light, in a metal film, then, magically, the light goes through the metal. This remarkable behaviour is driven by plasmons - the oscillations of the electron gas in a metal. Plasmons can be created by the absorption of light and can decay by the emission of light: in other words, they provide a new way to transmit optical information. There is more than one kind of plasmon - small particles (clusters) have local plasmon modes but on an extended metal surface you get propagating modes, which show dispersion. This means that the frequency of the surface plasmon depends on the wavelength. We can imagine that if we place a metal cluster on top of a metal surface, the two different kinds of plasmon mode will couple together, and that at a special wavelength this coupling could be very strong. Effects like this could be exploited in novel optical devices, photonic circuits or biosensors. The aim of this project is to use a technique called electron energy loss spectroscopy to measure the plasmon dispersion on surfaces decorated with atomic clusters of selected size and shape, and to explore the phenomena of localisation and coupling of the plasmons in these systems. We need to design systems in which the frequency of the cluster mode is not far away from that of the surface mode. Silver clusters on a gold surface make a good choice, especially if the silver cluster is distorted in shape from spherical to ellipsoidal, which lowers its plasmon frequency. Then we may see a resonant coupling of the two modes at a specific wavelength. We can also envisage coupling other kinds of local excitation mode to the surface plasmons, such as so-called electron-hole pair excitations in semiconductor clusters or molecules. The experiment works the same way. But there is also a completely different type of measurement we want to attempt, where we measure the field of the plasmon in real space, on the nanometre scale, around and between the individual clusters. This is complementary way to explore the effects of the couping between the plasmons of the cluster and the surface, and exploits a new technique we have invented, called Scanning Probe Energy Loss Spectroscopy (SPELS). Like the plasmons, it's magic!
Organisations
People |
ORCID iD |
Richard Palmer (Principal Investigator) |
Publications
Alshammari K
(2020)
Optimization of sol-immobilized bimetallic Au-Pd/TiO2 catalysts: reduction of 4-nitrophenol to 4-aminophenol for wastewater remediation.
in Philosophical transactions. Series A, Mathematical, physical, and engineering sciences
Ayodele O
(2019)
Synergistic Computational-Experimental Discovery of Highly Selective PtCu Nanocluster Catalysts for Acetylene Semihydrogenation
in ACS Catalysis
Bauer K
(2017)
A proximal retarding field analyzer for scanning probe energy loss spectroscopy.
in Nanotechnology
Cai R
(2020)
Gas-Phase Deposition of Gold Nanoclusters to Produce Heterogeneous Glycerol Oxidation Catalysts
in ACS Applied Nano Materials
Cai R
(2018)
Performance of Preformed Au/Cu Nanoclusters Deposited on MgO Powders in the Catalytic Reduction of 4-Nitrophenol in Solution.
in Small (Weinheim an der Bergstrasse, Germany)
Cai R
(2017)
A new method to prepare colloids of size-controlled clusters from a matrix assembly cluster source
in APL Materials
Cai R
(2020)
Scale-Up of Cluster Beam Deposition to the Gram Scale with the Matrix Assembly Cluster Source for Heterogeneous Catalysis (Catalytic Ozonation of Nitrophenol in Aqueous Solution)
in ACS Applied Materials & Interfaces
Chen Y
(2020)
Insight into the intrinsic mechanism of improving electrochemical performance via constructing the preferred crystal orientation in lithium cobalt dioxide
in Chemical Engineering Journal
Description | Advancements in (1) the preparation and characterisation of size-selected cluster films, and (2) the measurement of plasmons on surfaces using electron energy loss spectroscopy (EELS) were achieved. Our findings provided the first report of a new surface plasmon mode, the so-called acoustic plasmon, arising from a 2D electron gas on a gold surface. We also achieved the first demonstration of modulating the plasmon energy dispersion through the attachment of a self-assembled monolayer. Additionally, we demonstrated coupling between plasmons from size-selected clusters and the supporting substrate or film or other nanostructures. |
Exploitation Route | Plasmon resonance effects in metal nanoparticles, such as size-selected clusters, are now being extensively investigated for light absorption (over a range of frequencies) and trapping in photovoltaic solar cells, in order to enhance the conversion efficiency of light into generated photocurrent (electricity). In particular, our findings on continuous, nanoscale gold films (and clusters) demonstrate that the acoustic plasmons cover the infra-red to visible range, indicating that the effect may be harnessed to achieve high efficiency conversion of infra-red radiation into electricity in solar cells. This would mean, for instance, solar cells that work even in cloudy weather! |
Sectors | Energy,Environment,Manufacturing, including Industrial Biotechology |
Description | The technology to produce size-selected clusters has been utilised by the spin-out company, Inanovate, which focuses on biochips for screening and analysing proteins. Additionally, the cluster source technology itself has been commercialised by selling entire systems (or parts of the apparatus) to research groups, e.g. in Denmark and China. |
First Year Of Impact | 2009 |
Sector | Manufacturing, including Industrial Biotechology,Pharmaceuticals and Medical Biotechnology |
Impact Types | Economic |