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 C60 fullerenes. The AA cycloaddition from its phenyl ring to the [6–6] bonds of C60 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 C60 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 C60 by the impurity atoms, the interaction between the AA and the C60 is largely improved (adsorption energy ∼ −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-C60 fullerenes are work function-type sensors for AA drug.