A New Approach of Controlled Single Step In Situ Fabrication of Graphene Composite Sensor for Simultaneous Sensing of Small Biomolecules in Human Urine

A new approach is introduced to develop a nanostructured pseudo-cup-shaped 3D graphene composite (s3D-GR) on the graphite pencil electrode (GPE) surface for simultaneous sensitive sensing of small biomolecules. A pseudo-cup-shaped 3D architecture of graphene was achieved by instant composition controlled interaction of the methylene blue (MTLB) with graphene oxide. The 3D graphene architecture appeared with inner, outer, upper walls and the pseudo-cup-shaped bottom. The SEM images revealed the formation of 3D graphene network on graphite pencil electrode. 3D pseudo-cup-shaped wrinkled graphene displayed a huge electroactive surface area (2.353 cm²) compared to 2D graphene (0.141 cm²). The 3D graphene composite contained more electroactive sites and improved surface kinetics. The fabricated electrode surface was comprehensively evaluated by field emission scanning electron microscopy (FE-SEM), Raman spectroscopy, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). The s3D-MTLB-GR/GPE was exceptionally sensitive for dopamine (DA), uric acid (UA), l-tyrosine (Tyr) and displayed low limit of detection (LOD) 15, 27, 247 nM, respectively. The peak separation between DA-UA, UA-Tyr, and DA-Tyr were observed 140 mV, 319 mV, and 459 mV, respectively. Sensor behaved well in the presence of potential interferences and real urine sample. The pseudo-cup-shaped 3D graphene sensor can be proved a valuable tool for the simultaneous sensing of small biomolecules.