Functionalized graphene pieces to trap the insecticide imidacloprid: a theoretical analysis

Eleven adducts for the interaction between imidacloprid (IMI) and some activated carbon (AC) pieces are proposed in this work. Activated carbon pieces were obtained by using a finite zig-zag graphene structure saturated with hydrogen atoms on the edges giving a pristine model with 70 carbon atoms and 22 hydrogen atoms. The zig-zag graphene structure was oxidized with -O, -COOH, -OH, and -O- groups. In this process, two identical groups were inserted over selected sites of the pristine model. All of these structures yielded ten IMI-AC adducts by using the PBE0-D3/6-31G* method, which predicts stable adducts at 0 K, and six of our models give negative free energies changes at room temperature. Thus, we expect that our IMI-AC models can be present when IMI interacts with an AC model. For one of the IMI-AC adducts, we applied solid-state techniques to avoid border effects, and we found that the imidacloprid is deprotonated giving reactive species, suggesting a new path to degrade this insecticide. Additionally, from this analysis, we proposed an additional IMI-AC adduct, which involves high free energy at room temperature. With this study, we show that our AC models can trap imidacloprid, which is quite convenient to remove this insecticide from our environment. Although it is well recognized that functionalized graphene structures are designed to trap some chemical compounds, to the best of our knowledge, this is the first time where IMI-graphene pieces interactions are studied in detail, and hydrogen bonds are analyzed through some scalar fields defined in quantum chemistry like the electron density and the non-covalent interactions index.