One-step synthesis of Pt-decorated graphene–carbon nanotubes for the electrochemical sensing of dopamine, uric acid and ascorbic acid

Abstract

Platinum nanoparticle-decorated graphene and carbon nanotube (Pt–Gr–CNT) nanocomposites were synthesized by radio frequency chemical vapor deposition (RF-CVD) from ethanol, using a Pt/MgO catalyst. Morphological analysis showed Pt nanoparticles decorating graphene sheets and double-walled and multiwalled carbon nanotubes. It was observed that, upon encountering Pt nanoparticles, carbon nanotubes unravelled into graphene sheets. This may be due to graphitic carbon atoms from growing CNTs forming bonds with carbon atoms from other CNTs, particularly at the site of another Pt NP. The Pt–Gr–CNT-modified GCE showed high electrocatalytic activity towards the oxidation of ascorbic acid (AA), dopamine (DA) and uric acid (UA) in 0.1 M phosphate buffer solution (pH 7.0) in cyclic voltammetry (CV) and differential pulse voltammetry (DPV) studies. CV showed well-separated oxidation peaks of AA (−99 mV), DA (121 mV) and UA (261 mV). In DPV studies, the peak separation between AA–DA, DA–UA and AA–UA was 210 mV, 140 mV and 360 mV respectively. The simultaneous detection of AA, DA and UA using DPV, in respective concentration ranges of 200–900 μM, 0.2–30 μM, 0.1–50 μM, showed good linearity and sensitivities of 0.186 μA μM⁻¹ cm⁻² (AA), 9.199 μA μM⁻¹ cm⁻² (DA) and 9.386 μA μM⁻¹ cm⁻² (UA) respectively. The Pt–Gr–CNT/GCE was evaluated for the simultaneous detection of the three biomolecules in real sample solutions of a vitamin C tablet, human serum and urine. It showed recoveries in the range of 93–101%, indicating that it is a promising platform for further biosensor development.