Sonication-assisted preparation of a nanocomposite consisting of reduced graphene oxide and CdSe quantum dots, and its application to simultaneous voltammetric determination of ascorbic acid, dopamine and uric acid

Cadmium selenide quantum dots were capped with reduced graphene oxide that was modified with thioglycolic acid. The nanocomposite was prepared by 5-min sonication of a solution of graphene oxide, thioglycolic acid, and cadmium(II) nitrate and selenium powder in the presence of NaBH4. X-ray diffraction and transmission electron microscopy were used to characterize the nanocomposite. A glassy carbon electrode (GCE) was modified with this nanocomposite and used for simultaneous determination of dopamine (DA), ascorbic acid (A) and uric acid (UA). The modified GCE was characterized by using cyclic voltammetry and differential pulse voltammetry. Simultaneous determination of AA, DA and UA was accomplished at working voltages of -50, +148 and+280mV (all vs. Ag/AgCl), respectively. The voltammetric response to DA is linear in the 4.9 to 74.0M concentration range, and the detection limit (defined as 3 sigma of the blank) is 0.11M. The respective data are 0.39-1.0mM and 66M for AA, and 9.0 to 120.0M and 0.12M for UA. The electrode was successfully applied to the determination of the 3 species in spiked urine samples.