Photoelectrochemical Sensing of Sulfide Using CdSe Quantum Dots-Sensitized TiO₂ Electrodes

This article describes the development and analytical performance of a photoelectrode for the photoelectrochemical (PEC) detection of hydrogen sulfide (HS-) in aqueous solutions. The photoelectrode consists of a TiO2 nanotube film that has been sensitized with CdSe quantum dots. In order to assemble the PEC sensor, TiO2 nanotubes were first obtained by an electro-anodization of a Ti surface, later modified by adsorption of previously synthesized CdSe quantum dots with 5.1 nm in diameter (CdSe-QDs). Analytical performance toward detection of aqueous HS- was evaluated by considering the dependence of photocurrent with the concentration of the analyte under different conditions, including light intensity and solution pH. Also, the influence of storing and aging on the stability of the photoelectrodes was evaluated. A linear detection range of approximately 1 to 10 mM was established, contingent upon the light intensity, with limits of detection (LOD) and quantification (LOQ) recorded at 197 and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$944~\mu $ </tex-math></inline-formula>mol<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\cdot $ </tex-math></inline-formula>L-1, respectively.