Graphene nanosheets functionalized with Nile blue as a stable support for the oxidation of glucose and reduction of oxygen based on redox replacement of Pd-nanoparticles via nickel oxide

A novel, cheap and simple enzymeless glucose sensor is introduced based on Pd/NiO nanoparticles decorated on Nile blue functionalized reduced graphene oxide (rGO). First, NiO was decorated on rGO and/or Nile blue functionalized rGO. Then, they were converted to bimetallic system by replacement of NiO with Pd nanoparticles, (Pd/NiO@rGO and Pd/NiO@Nile-rGO) to prepare the modified carbon paste electrodes (CPE). Pd/NiO@Nile-rGO was prepared using functionalized graphene oxide with Nile blue through diazonium reaction and deposition of Pd-NiO nanoparticles with chemical reaction. The nanocomposites structure were characterized by spectroscopic and electrochemical methods. Electrochemical studies showed that Pd/NiO@Nile-rGO has higher electrocatalytic activities toward glucose oxidation compare to Pd/NiO@rGO nanoparticles. Potential cycling test was employed to confirm the high sensitivity and stability of Pd/NiO@Nile-rGO compare to Pd/NiO@rGO. Then, a sensitive amperometric detection of glucose is achieved at -0.040 V (vs. Ag/AgCl) with a low detection limit of 2.2 mmol L-1 and with a wide linear range of 0.020-20.0 mmol L-1 glucose using Pd/NiO@Nile-rGO/GCE. Five different Pd/NiO@Nile-rGO/CPEs were tested separately for the amperometric response of glucose, providing a relative standard deviation of 4.8%. The selectivity of the modified electrode was studied too. The applicability of Pd/NiO@Nile-rGO/CPE was investigated by determining glucose in blood serum samples with satisfactory results. In the second part of this work the electrocatalytic activity of the modified electrodes for the electro-reduction of oxygen have been studied too. The results of our studied confirmed that Pd/NiO@Nile-rGO nanocomposites act as an electrocatalyst for the oxidation of glucose and reduction of oxygen, beside them. Thus, the nanocomposite is a good candidate for glucose fuel cell. (C) 2015 Elsevier Ltd. All rights reserved.