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

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.