Utility of extrinsic [60] fullerenes as work function type sensors for amphetamine drug detection: DFT studies

Detection of illicit drugs is of increasing interest for police and drug communities because of their abuse. Using density functional calculations, we investigated the interaction of amphetamine (AA) drug with the pristine, B, Al, Ga (group IIIA), Si, and Ge (IIV group) doped C-60 fullerenes. The AA cycloaddition from its phenyl ring to the [6-6] bonds of C-60 is more favorable than that to the [5-6] bonds, in good agreement with experiment. When an AA molecule is adsorbed from its NH2 group on the C-60 fullerene, its work function is significantly decreased, showing a good sensitivity but the adsorption energy (-0.4 kcal/mol) is very small. Replacing a carbon atom of C-60 by the impurity atoms, the interaction between the AA and the C-60 is largely improved (adsorption energy similar to -38.6 to -65.6 kcal/mol). Upon the adsorption of AA on the doped fullerenes, the Fermi level is largely shifted to higher energy, especially in the case of Si and Ge-doped fullerenes, and thus, the work function decreases by about 22.7 and 24.9%, respectively. The electron emission largely increases which can be converted to an electronic noise. However, the Si and Ge-C-60 fullerenes are work function-type sensors for AA drug. (C) 2016 Elsevier Ltd. All rights reserved.