Solvent-free modification of chitosan with sorbic acid for tunable stabilization of ZnS quantum dots

Hydrophobic chitosan derivatives were synthesized by solvent free reactive extrusion with sorbic acid and employed as stabilizing agents for ZnS quantum dots in aqueous media. Dynamic light scattering and transmission electron microscopy revealed that hydrophobic modification leads to the formation of more uniform polymer associates and suppresses nanoparticle aggregation, resulting in stable dispersions with hydrodynamic diameters increasing from 32 nm for unmodified chitosan to 43 and 87 nm for modified derivatives with the degree of substitution of 0.08 and 0.14, respectively, while the core size remains constant (2.3--2.5 nm). The proposed green approach provides a simple route to polymer stabilized nanohybrids with tunable properties.