Abstract:
Cobalt oxide (Co3O4) and zinc oxide (ZnO) nanoparticles were synthesized by a direct
precipitation method whereas the binary ZnO/Co3O4 nanocomposite and ternary
ZnO/Co3O4/rGO nanocomposite were synthesized by simple hydrothermal method using
hexahydrate cobalt nitrate and zinc nitrate salts. The as-synthesized nano-ZnO, Co3O4,
ZnO/Co3O4 and ZnO/Co3O4/rGO nanocomposite were characterized by FTIR, XRD and UvVis
spectroscopic techniques. The Uv-visible spectroscopy studies showed that the absorption
peak for ZnO/Co3O4/rGO nanocomposite has a red shift toward visible wavelengths compared
with the ZnO and Co3O4 nanoparticles. The XRD diffraction patterns depicted the face centred
cubic crystalline structure of Co3O4 nanoparticles(NPs) and hexagonal crystalline planes of
ZnO NPs. The ternary ZnO/Co3O4/rGO nanocomposite shows highest surface area as a result
of the decreased particle size due to the synergistic effects between the components of ZnO,
Co3O4 and rGO in the composite system. Furthermore, the electrochemical properties of the
as synthesized nanomaterials were characterized by CV, EIS and single potential time base
(TB) ameperimmetry in 0.1M NaOH aqueous solution. The ternary ZnO/Co3O4/rGO
nanocomposite exhibited excellent electrochemical performance with higher catalytic activity,
lower working potential (0.55V) and low charge transfer resistance for electrochemical
oxidation of glucose, which can be attributed to the presence of high conductive reduced
graphene oxide sheet on the surface of the electrode. Under optimal conditions (E=0.55V,
electrolyte Concentration=0.1M), the ZnO/Co3O4/rGO glassy carbon electrode (GCE)
modified electrochemical glucose sensor demonstrated wide linear range (0.015 mM-10 mM),
high sensitivity (1551.38 μAmM-1
cm
-2
), low detection limit (0.043 μM), fast response time( 3
s) and low cost to glucose determination. In addition, the ZnO/Co3O4/rGO/GCE sensor was
able to detect the glucose even in the presence of biologically interfering molecules and
chloride ions. The sensor achieved appreciable repeatability, reproducibility and long term
stability. Moreover, the practical application of ZnO/Co3O4/rGO/GCE electrochemical sensor
is very appropriate for the detection of glucose in real sample analysis in medical diagnostic
and food industries and the results were positively agreed with the spectrophotometric method
in hospital and the glucose label value of food industries
