Manipulating hot spots to increase biosensor sensitivity

(a) A 2μm2 AFM image of gold nanoparticles on a flat substrate. (b) SEM micrograph showing measurements of nanoparticles under a polymer film.


October 2011

Surface Plasmon Resonance (SPR) can be described as the resonant, collective movement of electrons activated by incident light that travels in a direction parallel to a surface. When two nanoparticles are placed in close proximity, the electric field is greatly enhanced creating a ‘hot spot.’ These hot spots are of particular interest to researcher Soon Ng, of Monash University. Working collaboratively with MCN’s Varsha Lal and Matteo Altissimo, Soon is manipulating these electric field hot spots to increase the sensitivity of his biosensors.

The JPK Nanowizard II AFM at the MCN was used to accurately measure the height of the particles as well as the overall topography. One of the key features of this instrument is that it allows imaging in both air and liquid.

Additionally, the FEG-SEM was used to measure the size of particles and to aid in the calculation of surface coverage. Future work on this project will utilise electron beam lithography to create templates for nanoparticle absorption in order to study the spatial configurations related to the hot spots. As well as having applications in biosensing, chemical detection and solar cell technologies, the properties of surface plasmon resonance may be used during characterisation and imaging processes.

This is an example of a project where multiple capabilities available at MCN were used in sequence and assembly and characterisation.