Colloidal TiO2 modified CVD graphene based Hybrid for Electroanalytical Sensing

An UV photoactive hybrid material, based on graphene film grown by chemical vapor deposition (CVD) and decorated with a closely packed multilayer nanostructured layer of 1-pyrene butyric acid (PBA) coated TiO2 nanocrystals (NCs), has been fabricated by a facile solution-based procedure, for the electrochemical detection of analytes of medical and pharmaceutical interest. A comprehensive investigation of the structural, morphological, spectroscopic, electrical and (photo)electrochemical properties of the hybrid material, as well as of the sensitivity of the composite to selected model analytes upon integration in an electrochemical sensor, are reported. Motivation and results Graphene (G) is an extraordinary structural material for sensors, due its excellent electrical conductivity, high surface area and mechanical strength. [1] Its potential application in sensors can be further extended by a further functionalization with organic and inorganic materials. Indeed, the reactivity of graphene, as a two-dimensional platform, opens the venue to a large variety of strategies of hybridization, including molecular decoration approaches with other nanostructured compounds, finally resulting in novel functional composites, that improve the pristine properties and exhibit specific molecular recognition capabilities. Colloidal nanocrystals (NCs), prepared by using solutionbased colloidal chemistry routes, are particularly suited for the chemical decoration of graphene and hence for achieving an effective combination of the original size- and shape-dependent properties of the nano-objects with the unique functionalities of graphene. [2] Here, a solution-based procedure [3] has been implemented, for manufacturing a UV photoactive hybrid material, based on CVD graphene films decorated with UV-light absorbing 1-pyrene butyric acid (PBA) surface coated TiO2 NCs. The hybrid was prepared by exposing the CVD graphene film to a solution of PBA-capped TiO2 NCs, obtained by a ligand exchange procedure, onto pre-synthesized organic-capped NCs (Figure 1 A). The pyrene molecules can anchor the NCs to graphene by \u3c0-\u3c0 stacking interactions, still preserving their aromatic character, while concomitantly interligand \u3c0-\u3c0 forces allow the NC assembling in a highly interconnected nanostructured multilayer coating (Figure 1 B), with retention of the NC geometry and composition. The functional properties of the obtained hybrid have been demonstrated by electrical and (photo)electrochemical investigation and by testing its detection capability towards analytes of medical and pharmaceutical interest in an electrochemical sensor. The results show that the hybrid exhibits higher electrical conductivity, electroactivity (Figure 1 C) and a photoelectric response than bare graphene, preserving concomitantly its high charge mobility and structural properties, and results sensitive to the investigated analytes. Word count: 392 words References [1] K. S. Novoselov et al. (2012): A roadmap for graphene. Nature 490, 192-200 [2] M. L. Curri et al. (2010) Emerging methods for fabricating functional structures by patterning and assembling engineered nanocrystals. Phys. Chem. Chem. Phys. 12, 11197-11207 [3] C. Ingrosso et al. (2015) Photoactive hybrid material based on pyrene functionalized PbS nanocrystals decorating CVD monolayer graphene. ACS Appl. Mater. & Interfaces 7, 4151-4159 Corresponding author: Chiara Ingrosso, CNR-IPCF, Sez. Bari, c/o Dip. di Chimica, Universit\ue0 di Bari, Bari, Italy. Tel:(+39)0805442027, fax: (+39)0805442128, c.ingrosso@ba.ipcf.cnr.i