The right nose for the job

Nature is the stage on which every natural scientist performs, and a first publication in Nature is also the first crowning achievement in every natural scientist’s career. As is usually the case, the names of several authors are listed for the article “A sensitivity-enhanced field-effect chiral sensor” in the May 2008 issue of nature materials. The group of ten scientists, who in the article describe their latest research into a special and highly-sensitive field-effect sensor, is headed by Prof. Luisa Torsi of the University of Bari in southern Italy.

The daughter of a chemist, she had her first encounters with natural phenomenon at an early age, although “my interest in research was piqued while obtaining my master’s degree in physics,” explains Torsi. The development of the first electrically conductive plastics around 1989 sparked her fascination in this completely new field at the boundary between physics and chemistry. “A group of outstanding chemists at my university was working on using this new technology for biosensors. I found this so exciting that I made it the topic of my dissertation in chemistry.”

Looking back, Prof. Torsi says that this path to an interdisciplinary career was really just a minor shift in her area of interest, but one that nevertheless did not come easily. “However, it did pave the way to my post-doc under Professor Ananth Dodabalapur at Bell Laboratories in New Jersey, USA, where I worked on organic thin-film transistors and experienced the most gratifying phase of my research career, from scientific and personal perspectives.”

Back in Bari, she used this technology to develop synthetic “noses,” which theoretically can even be produced by printing. Her research first culminated in the aforementioned publication in the May 2008 issue of Nature, in which she and her team presented a new class of what are known as chiral sensors. “The conventional organic thin-film sensors at that time,” she explains, “still reacted with little specificity to substances, and relatively high concentrations on the scale of one part per thousand of this substance were required for detection.”

Torsi, however, developed a highly sensitive gas sensor with two chiral layers. The outer layer has special “enantioselective” properties. “This combination enabled us to enhance the sensitivity for detection of optical isomers to concentrations in the range of one part per ten million of the substance.” In addition, this high sensitivity was achieved by means of the quasi-amplifying properties of additional layers that act like a field-effect transistor.

“Chirality itself is already quite a challenge,” explains the scientist. “Chirality” is used in reference to molecules that behave like mirror-images of each other. According to Torsi, this property harbors a bounty of as yet undiscovered possibilities for chemical analysis. “The two molecular structures undergo different changes in their chemical and physical properties when in contact with other substances, primarily upon contact with molecules which are likewise mirror-images of each other.”