Facile covalent immobilization of cadmium sulfide quantum dots on graphene oxidenanosheets: preparation, characterization, and optical properties

Abstract

A facile approach for the preparation of a novel hybrid material containing graphene andan inorganic semiconducting material, cadmium sulfide quantum dots (CdS QDs), isdemonstrated for the first time. First, amino-functionalized CdS QDs were prepared bymodifications of the kinetic trapping method. Then, pristine graphite was oxidized andexfoliated to obtain graphene oxide nanosheets (GONS), which were then acylated withthionyl chloride to introduce acyl chloride groups on their surface. Subsequently,immobilization of the CdS QDs on the GONS surface was achieved through an amidationreaction between the amino groups located on the CdS QDs surface and the acyl chloridegroups bound to the GONS surface. Fourier transform infrared spectroscopy (FT-IR), 1H nuclear magneticresonance (1H-NMR), x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and energydispersive x-ray (EDX) spectroscopy were employed to investigate the changes in thesurface functionalities, while high resolution transmission electron microscopy (HR-TEM)and field emission scanning electronic microscopy (FE-SEM) were used to study themorphologies and distribution of the CdS QDs on the GONS surface. Thermogravimetricanalysis (TGA) was employed to characterize the weight loss of the samples onheating. Photoluminescence (PL) measurements were used to study the opticalproperties of the prepared CdS QDs and the CdS–graphene hybrid material.