Size-controllable preparation of palladium nanoparticles assembled on TiO2/graphene nanosheets and their electrocatalytic activity for glucose biosensing

Abstract

In this work, for the first time, size-controllable preparation of Pd nanoparticles assembled on graphene was realized through UV reduction by TiO₂. Firstly, a hybrid nanocomposite of graphene/TiO₂ (GT) was synthesized via a reported one-pot water-phase approach. It was interesting to find that when altering the additive volume of TiCl₃ (reductant) in the reaction system (e.g., 0.6, 1.2, 1.8, 2.4 and 3.0 mL), the morphology of TiO₂ on graphene sheets also changed, from particle to irregular rod-like. Then, these GT_x nanocomposites were further employed as supporting materials for the reduction and dispersion of Pd nanoparticles (NPs). The photogenerated electrons from UV-irradiated TiO₂ are transported across the GT_x composites to stepwise reduce Pd²⁺ to Pd NPs. Our results demonstrated that the diameters of these as-prepared Pd NPs showed a similar GT_x-dependent behavior, ranging from 4.5 ± 0.8 to 5.8 ± 0.9 nm. Finally, using H₂O₂ as the electrochemical probe, the five resultant GT_x–Pd hybrid nanocomposites displayed distinct electrocatalytic activity to H₂O₂ as a function of the feeding volume of TiCl₃. The above hybrid nanocomposites were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), Raman spectroscopy, etc. More importantly, a novel glucose biosensor with high sensitivity and selectivity was accordingly fabricated by a layer-by-layer method, which facilitates the fast electron transfer of glucose oxidase at graphene-based films because of the excellent electroactivity of GT_1.2–Pd hybrids.