Nanocrystals and Nanosensors
Once a semiconducting crystal is less than about 100Å in diameter, its optical, electronic and fluorescent properties begin to change. In this size regime, the properties lie between those of a molecule and those of the bulk crystal. In this size regime, we can build designer crystals with tunable colours and brilliant variable luminescence from UV to NIR. The changes occur because the energy levels are those of a particle in a box, i.e., the electronic energy levels are quantised in three dimensions – hence the name quantum dots or QDs. QDs are the building blocks for future developments in nanostructured materials. Potential applications include electroluminescence, LEDs, waveguides and tunable lasers, biochemical markers, photonic crystals and nanomechanics.
In addition to our work on nanocrystals, we are also developing microcantilever based sensors in collaboration with Dr John Sader in Applied Maths. This work forms the basis for determining the spring constants and material properties of cantilevers in atomic force microscopes, and is used by AFM manufacturers worldwide.
The dream in nanoscience is to work with single nanocrystals and nanocantilevers and begin examining how to manipulate and exploit nanoscale objects, as well as to understand fundamental quantum size effects.
We are currently pursuing these goals through collaborations with National Laboratories in Germany, universities in Spain, Japan and US, with the Department of Electronic Materials Engineering at ANU and with Quantum Dot Corporation, a biotech company in Silicon Valley.
Within the Chemistry School, the photophysics of these materials are being investigated with Dr. Trevor Smith and Dr. Evan Bieske.
The picture below (ref. 4) shows the luminescence from CdSe nanocrystals doped into a sol-gel matrix for optical applications. The green emitting particles are about 2nm in diameter while the red luminescence is from 8nm CdSe nanocrystals.
Improving the monodispersity and quantum efficiency is a major synthetic goal. Instrumentation for single nanocrystal experiments is being developed.
For more information, visit our nanoparticle website
Selected Publications:
- Bullen, C.R.; Mulvaney, P.; Nanoletters 2004, 4, 2303-7.
- Hu, M.; Hillyard, P.; Hartland, G.V.; Perez-Juste, J.; Mulvaney, P. Nanoletters, 2004, 4, 2493-7.
- Gómez, D.; Pastoriza-Santos, I.; Mulvaney, P.; Small, 2005, 1, 238-241.
- Pacifico, J.; Gomez, D.; Mulvaney, P., Adv. Mater. 2005, 14, 415-418.
- Perez-Juste, J.; Liz-Marzan, L.M.; Carnie, S.; Chan, D.Y.C.; Mulvaney, P., Adv. Funct. Mater. 2004, 14, 571-579.
- Hu, M. ; Wang, X.; Hartland, G. V.; Mulvaney, P.; Perez-Juste, J.; Sader, J. E.; J. Am. Chem. Soc. 2003, 125, 14925-14933.
- Hamanaka, Y.; Fukuta, K.; Nakamura, A.; Liz-Marzán, L. M.; Mulvaney P., Appl. Phys. Lett. 2004, 84, 4938-4940.
- Green, C.P.; Lioe, H.; Cleveland, J.P.; Proksch, R.; Mulvaney, P.; Sader, J.E., Rev. Sci. Instr., 2004, 75, 1988-1996.
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