Attachment of Hybrid SiO2 Coated CdTe Quantum Dots to Graphene for Ion Sensors

Hybrid SiO2 coated CdTe quantum dots (QDs) consisted of a CdTe core and a hybrid shell with CdS-like clusters inside were created via a two-step synthesis including a sol-gel route and a reflux process. Being coated with the hybrid SiO2 shell, the photoluminescence (PL) color of the QDs was red-shifted to yellow from green and their PL efficiency increased remarkably. Graphene oxide (GO) nanosheets are obtained through modified hummers' method. The attachment of the QDs was carried out through the covalent bond between the hybrid SiO2 shell and the oxygen-containing groups on the surface of GO. The GO was reduced into graphene in the reflux. The hybrid SiO2 coated CdTe QDs were quenched after grafted on the graphene. The photoelectrochemical performance of graphene-QD composites modified electrode has noteworthy change after it is immersed in Cu2+ ion solution, because the sedimentation equilibrium constant of CuS is much lower than that of CdS. Graphene-hybrid SiO2 coated CdTe QDs composites is less toxic, it opens up an application possibility for ion detection.