Molecular Dynamics Simulations of Carbon Quantum Dots/Polyamidoamine Dendrimer Nanocomposites

The covalent modification of carbon quantum dot (CQD)with polyamidoamine(PAMAM) dendrimers was studied using molecular dynamics simulations.Our main objective was to determine how the grafting technique (grafting-fromand grafting-to) and the oxidation level of CQD affect the functionalization.We found a series of significant differences in the structure of theCQD-PAMAM nanohybrid depending on the grafting approach and oxidationlevel of CQD. The "grafting-to" approach reveals a uniformextent of surface coverage by dendrimers, regardless of the oxidationlevel of CQD. Meanwhile, in the "grafting-from" case,the percentage of surface coverage by dendrimers was strongly determinedby the topology of CQD. We also observed that, for a given graftingapproach, the increase in the oxidation level of CQD leads to a morecompact structure of grafted dendrimers and provides stronger interfacialenergy between the two main components of the nanocomposites. Amongthe interfacial interactions, it was found that the electrostaticforce and hydrogen bonding between the charged groups of dendrimersand CQD play a crucial role in controlling the architecture and stabilityof the formed structures.