Dr Conor Hogan

Nanotechnology is not all about tiny optical devices travelling through the human body sending back creepy images of our internal cavities to men in white coats.

To chemists, the idea of a miniature world of activity is not at all foreign. In fact, chemists deal with molecules on a daily basis. They are the bread and butter of their research.

What does excite chemists like La Trobe's Dr Conor Hogan is the new way of looking at this research, from the bottom up from the point of view of the molecule rather than from the top down.

In terms of size, the diameter of an average molecule is less than one nanometre and chemists are finding innovative ways of coaxing them to do what they want, often one at a time.

It's the realisation of the potential power of this approach, says Dr Hogan that has inspired research into new ways of testing for chemicals and bacteria in the environment and medicine.

Dr Hogan is involved in two new applications of nanotechnology with La Trobe physicist Dr Paul Pigram and microbiologist Professor Robert Seviour from the Bendigo campus. Both of these applications hinge on a monolayer of molecules acting as an interface.

In the first project, the nanostructure is laid onto the surface of a micro-sensor in the form of a layer of luminescent material made by Dr Hogan's team based on an iridium complex.

'Most analytical chemistry is done with instruments that sit on the benchtop,' says the chemist. 'We want to make instruments that you can put in your pocket.

'If you are an environmental scientist out in a boat, or a forensic scientist at a crime scene for example, and want to take a sample you can do it there and then, instead of sending it to a laboratory. If a doctor wants to test for toxins in the blood he sends it to the lab and gets the results three hours later. What if the patient dies in the meantime?'

Dr Hogan has built a prototype of his pocket instrument which he has tested on a variety of substances of pharmaceutical and environmental importance such as codeine, psueudoephedrine and -lactam antibiotics, which concentrate in milk. It works on a sample by measuring the light that comes off the surface of the sensor. A luminescent molecule is electrically stimulated into releasing photons in the presence of the analyte. The amount of light that is given off is related to its concentration.

'This is different to the tradition of luminescence spectroscopy,' Dr Hogan says. 'Instead of using light to excite luminescent molecules we use an electrical pulse. This has an advantage because light is scattered and detectors pick it up as interference. With our method, it is possible to detect lower levels of concentration of these substances.'

The application – in environmental and medical testing – has grown out of the cross-correlation of ideas that comes out of the creative environment in universities. Dr Hogan got the idea from literature related to light-emitting devices from a different field to analytical chemistry. Some of them are used in plasma TVs.

'I looked at the types of molecules used in these devices that might be useful in the sensor concept,' he said.

Future work will be done in collaboration with a local nanotechnology company Minifab with the aim of coming up with a commercially viable device. Related concepts are being developed with the CSIRO.

The second project employs a similar concept to detect strands of bacterial DNA found in waste water sludge using electrochemical luminescence. The scientists are coaxing single strands of DNA onto a sensor which is then exposed to a sample. DNA strands in the sludge bind to their complementary strands at which time a luminescent molecule inserts itself within the DNA. Voltage is applied and light is emitted, the amount of which correlates with the concentration of bacteria in the solution.

'What drives us is not just getting intellectual property but finding out how molecules behave,' Dr Hogan says. 'Chemistry has been trying to understand the way molecules work for centuries.'