Towards nanotube-based sensors for discrimination of drug molecules.

The proper detection of drug molecules is key for applications that have an impact in several fields, ranging from medical treatments to industrial applications. In case of illegal drugs, their correct and fast detection has important implications that affect different parts of society such as security or public health. Here we present a method based on nanoscale sensors made of carbon nanotubes modified with dopants that can detect three types of drug molecules: mephedrone, methamphetamine and heroin. We show that each molecule produces a distinctive feature in the density of states that can be used to detect it and distinguish it from other types of molecules. In particular, we show that for semiconducting nanotubes the inclusion of molecules reduces the gap around the Fermi energy and produces peaks in the density of states below the Fermi energy at positions that are different for each molecule. These results prove that it is possible to design nanoscale sensors based on carbon nanotubes tailored with dopants, in such a way that they might be able to discriminate between different types of compounds and, especially, drug molecules whose proper recognition has important consequences in different fields.