Stable and robust discriminative sensing of illicit drug molecules utilizing a specific geometry of nanotubes

The possibility of detecting and discriminating drug molecules is of utmost importance for several areas, including such important fields as security, public health and industry. The adequate detection of this type of substances then affects key sectors of society and is the subject of several studies and works that attempt to improve such detection and discrimination. Among the new devices used to detect drug molecules, the development, both experimental and theoretical, of nanosensors plays an increasingly important role and is expected to significantly increase the pace of progress in this field. In this work we have calculated the electronic and transport properties of a series of nanoscale devices based on carbon nanotubes and metallic heteronanotubes with hBN strips. These devices are specifically designed to sense drug molecules of a certain size and discriminate between three of them, namely cocaine, heroin, and morphine. We have found that the devices can effectively feel the presence of the drug molecules and distinguish between them through changes in the transmission, the conductance and the current. We have also found that such quantities depend on the angle of orientation, which shows that these systems have also the potential to determine the angle at which the molecule passes through it, i.e. to angularly discriminate between them. Furthermore, we have computed the Seebeck coefficient and found that such quantity can also be utilized to distinguish between the compounds. We have in addition found that the compounds behave as acceptors (they acquire charge) when the walls of the device are nanotubes and as donors (they lose charge) when the nanotube walls are heteronanotubes. Finally, we calculated the binding energies and found that the systems are exothermic. Such energies are not, however, big enough to promote the stick of the molecules to the walls of the devices, which shows the suitability of them for sensing the compounds.