Graphene thin film electrodes synthesized by thermally treating co-sputtered nickel–carbon mixed layers for detection of trace lead, cadmium and copper ions in acetate buffer solutions

• Synthesis of graphene films by thermally treating co-sputtered Ni–C mixed layers
• Modification of graphene electrodes by adding Bi ions in acetate buffer solutions
• Simultaneous detection of trace Pb2 +, Cd2 + and Cu2 + ions in acetate buffer solutions
• Enhanced repeatability of Bi modified graphene electrodes
• Effects of Si substrate surface condition and C content in Ni–C mixed layers

Graphene thin films were synthesized using a solid-state carbon diffusion method by thermally treating (heating at 1000 °C for 3 min and then cooling) nickel–carbon (Ni–C) mixed layers co-sputtered on silicon (Si) substrates with or without a silicon dioxide layer. Field-emission scanning electron microscopy, high resolution transmission electron microscopy and Raman spectroscopy were used to characterize the structure and composition of both the as-deposited and thermally treated Ni–C coated samples with respect to the C concentration of the Ni–C thin films. The graphene thin films were used as working electrodes in the simultaneous detection of trace heavy metal ions (Pb2 +, Cd2 + and Cu2 +) in acetate buffer solutions modified with bismuth ions (Bi3 +). The enhancing effect of Bi3 + on the electroanalytical performance of the graphene electrodes was studied.