Amphetamine and methamphetamine adsorption on graphene surface; Insights toward detection applications; A comparative dispersion-corrected DFT study

Given the deep effects of amphetamine and methamphetamine on the brain and body, along with their high potential for addiction and the extensive social and familial consequences, investigating the various molecular aspects of these compounds is of great importance. In this study, alongside identifying the most stable structures of amphetamine and methamphetamine, and examining their adsorption and recognition by graphene, a methodological investigation on various DFT computational approaches including London dispersion interactions, such as B97D, ωB97XD, M062X-D3, B3LYP-D3, and B3LYP-D3(BJ) (as the reference bench, RB, method) has also been conducted. The adsorption energy (E ads ) of the amphetamine and methamphetamine on the graphene surface falls approximately within the range of 15-20 kcal/mol, which is an optimal value for adsorption applications. With deviations of about 8-11% from the RB method, ωB97XD method tends to overestimate, while B3LYP-D3 underestimates E ads . Inclusion of Becke-Johnson damping terms expressively corrects the latter’s underestimation. However, B97D method is strongly recommended as the most cost-effective approach. Among the combined approach examined, the M062X-D3//B97D yields the most accurate results with a maximum deviation of about 3.3% compared to the RB method. Reduced density gradient analysis on non-covalent interactions reveals that attractive van der Waals of staggered π-π stacking and NH-π/CH-π hydrogen bond type interactions govern the adsorption of amphetamine and methamphetamine onto the graphene sheet. E ads obtained in this study have been compared with those reported in previous researches on the similar adsorbate and adsorbent materials, revealing helpful outcomes. Charge transfer, frontier orbital energy, and density of states analyses raise doubts about the effectiveness of pristine graphene as a practical sensor for detecting amphetamine and methamphetamine.