Michael Berger from Nanowerk has an interesting post about the efforts of scientists in the Kavli Institute of NanoScience at Delft University of Technology in The Netherlands to use individual carbon nanotubes (CNTs) as nanoscale biosensors, with a potential to detect the presence of just a single molecule. What Iddo Heller, a PhD student, and colleagues discovered was a hitherto unrecognized sensing mechanism.
Since the discovery that individual carbon nanotubes (CNTs) can be used as nanoscale transistors, researchers have recognized their outstanding potential for electronic detection of biomolecules in solution, possibly down to single-molecule sensitivity. To detect biologically derived electronic signals, CNTs are often – but not always – functionalized with (conductive) linkers such as proteins and peptides to interface with soluble biologically relevant targets (linkers need not be conductive as long as they are capable of localizing the target molecule in close vicinity of the tube). Although CNT transistors have been used as biosensors for some years now, the ultimate single-molecule sensitivity, which is theoretically possible, has not been reached yet. One of the reasons that hampers the full exploitation of these promising nanosensors is that the sensing mechanism is still not well understood. Although a variety of different sensing mechanisms has been suggested previously, various studies contradict one another, and the sensing mechanism remained under debate. Researchers in The Netherlands – through modeling and specific control experiments – now have succeeded in identifying the sensing mechanism. They found that the majority of their experiments can be explained by a combination of electrostatic gating and Schottky barrier effects. Because these two mechanisms have different gate-potential dependence, the choice of gate potential can strongly affect the outcome of real-time biosensing experiments.
Intrigued? Find out more: Biosensing mechanism with carbon nanotubes explained …