CVD graphene decorated with colloidal titanium oxide nanocrystals: (photo)electrochemical characterization and electroanalytical applications

Electroanalytical sensors based on the use of graphene (G) can benefit from its important characteristics: excellent electrical conductivity, high surface area and mechanical strength [1]. The peculiar properties of graphene can be extended by further functionalization with organic and inorganic materials. In this work, we present a solution-based procedure [2] for manufacturing UV-light absorbing and photoactive hybrid materials, based on CVD graphene layers decorated with colloidal titanium oxide nanocrystals (NCs), surface functionalized with 1-pyrene butyric acid. The physical-chemical properties of the manufactured hybrid materials have been investigated by (photo)electrochemical characterizations. In particular, Cyclic Voltammetry and Electrochemical Impedance Spectroscopy measurements recorded in the presence of an outer- or an inner-sphere probe ([Ru(NH3)6]Cl3 and K4[Fe(CN)6], respectively allowed to study the electron transfer and the electrochemical properties of the electrodes modified with the prepared hybrid materials. The immobilization of the pyrene-coated TiO2 NCs on the graphene platform increases its electroactivity, its capacitive behaviour and the photo-electrochemical response, preserving concomitantly its high charge mobility. The results show an enhancement of the photocurrent of 50% with respect to that of bare graphene based electrodes and a long transient decay time (τ = 185 ± 2 s), studied by the transient photocurrent decay that occurs immediately after UV-light illumination. The manufactured composite is an interesting optically transparent photoactive material for manufacturing photoanodes to integrate in solar cells or photodetectors and for fabricating components to apply in FETs or (photo)electrochemical sensors. For example, the electroanalytical performances of the devices, tested for the detection of some analytes of medical and pharmaceutical interest (e.g. dopamine, norepinephrine), show promising results. References [1] K.S. Noselov et al., Nature, 490, (2012), 192-200. [2] C. Ingrosso et al., ACS Appl. Mater. & Interfaces, 7, (2015), 4151-4159. Acknowledgements The authors acknowledge the MIUR National Project PRIN 2012 (prot. 20128ZZS2H).