▎ 摘　　要

In sensor research community, the advances in materials are main strategy for driving developments in the field, with an ultimate objective to enhance three interrelated analytical parameters that are sensor sensitivity, selectivity and response time. Herein, we demonstrate the design and fabrication of highly sensitive and selective amperometric sensor to detect ascorbic acid (AA) with rapid and reproducible response behavior. The sensor based on glassy carbon electrode (GCE) that initially modified with novel TiO2/reduced graphene oxide (rGO) nanocomposites synthesized by simple chemical and calcination processes. The as-synthesized nanocomposite was fully characterized by XRD, FITR-Raman, SEM-EDS and TEM, which revealed wrinkled wave like 2-D graphene nano-sheets with crystalline anatase phase of TiO2 nanoparticles anchored on the surface. Cyclic voltammetry and electrochemical impedance spectroscopy showed enhanced electrochemical activity of TiO2/rGO nanocomposite modified GCE compared to either bare GCE or TiO2 modified electrode. Sensor analytical parameters derived from amperometric measurements indicated outstanding sensing performance, giving a superior sensitivity 1.061 pA NM-1 cm-2, low limit of detection (LOD) 1.19 pM at (S/N = 3) within a linear range of AA concentration (25 to 725 pM) with a correlation coefficient R-2 = 0.9888 and a rapid response time < 5 s. The newly proposed sensor electrode exhibits unique electrochemical stability, repeatability and high selectivity in the presence of common interfering species of glucose, dopamine, citric acid or uric acid. The kinetic study indicated the electrode reaction proceeds via a diffusion-controlled process. The current TiO2/rGO nanocomposite modified GCE gives acceptable detection result towards a commercially available vitamin C supplement.