Investigations on the electronic properties and effect of chitosan capping on the structural and optical properties of zinc aluminate quantum dots

Quantum confined uncapped and chitosan capped nanoparticles of ZnAl2O4 synthesized by microwave-assisted sol-gel method were investigated by structural analysis and optical techniques. X-ray diffraction studies confirmed the formation of cubic spinels with crystallite size 4.5 nm and 3.4 nm, respectively for uncapped and chitosan capped ZnAl2O4 nanoparticles. Chitosan capping produced a blue shift in bandgap energy (3.84 to 3.94 eV) agreeing with size effects according to the Brus equation. A blue shift in emission peak and enhancement in photoluminescence intensity was also observed upon chitosan capping. The electronic band structure and the density of states of the bulk spinel were also calculated using density functional theory. The effective masses of electrons and holes estimated based on the band structure were used to extract the excitonic Bohr radius.

Automated summary

The structural and optical properties of uncapped and chitosan capped ZnAl2O4 nanoparticles synthesized by microwave-assisted sol-gel method were investigated. Chitosan capping led to a blue shift in bandgap energy and enhanced photoluminescence intensity. The bulk spinel electronic band structure and density of states were also calculated using density functional theory.