Titanium dioxide-graphene composite electrochemical sensor for detection of hexavalent chromium

Hexavalent chromium (Cr(VI)) compound is useful to various industries but is toxic and carcinogenic. In this research work, we fabricate an amperometric sensor for the determination of Cr(VI), using a titanium dioxide (TiO₂)-reduced graphene oxide (rGO) composite as the sensing element. The composite was synthesized following sol−gel chemistry, yielding TiO₂ nanoparticles of ~50 nm in size, immobilized on chemically exfoliated rGO sheets. The composite was employed in a 3-electrode electrochemical cell and operated in an amperometric mode, exhibiting good responses to the 50 to 500 ppb Cr(VI). Our best result from pH 3 Mcilvane’s buffer medium reveals the sensitivity of 9.12 × 10⁻⁴ ppb⁻¹ and a detection limit of 6 ppb with no signal interference from 200 ppm Ca(II), 150 ppm Mg(II), and 50 ppb Pb(II). The excellent results of the TiO₂-rGO sensor can be attributed to synergic effects between TiO₂ and rGO, resulting from the presence of n-p heterojunctions and the formation of the TiO₂ nanoparticles on rGO.