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-from and grafting-to) and the oxidation level of CQD affect the functionalization. We found a series of significant differences in the structure of the CQD-PAMAM nanohybrid depending on the grafting approach and oxidation level of CQD. The "grafting-to" approach reveals a uniform extent of surface coverage by dendrimers, regardless of the oxidation level of CQD. Meanwhile, in the "grafting-from" case, the percentage of surface coverage by dendrimers was strongly determined by the topology of CQD. We also observed that, for a given grafting approach, the increase in the oxidation level of CQD leads to a more compact structure of grafted dendrimers and provides stronger interfacial energy between the two main components of the nanocomposites. Among the interfacial interactions, it was found that the electrostatic force and hydrogen bonding between the charged groups of dendrimers and CQD play a crucial role in controlling the architecture and stability of the formed structures.