Pre-Adsorbed Methylene Blue at Carbon-Modified TiO2 Electrode: Application for Lead Sensing in Water

Carbon modified titanium dioxide nanostructured (CMTN) was successfully fabricated by ethanol carbonization method and applied to modify the surface of glassy carbon electrode. This modified electrode was employed in the extraction and the electrochemical determination of methylene blue. The considerable increment in the voltammetric signal for pre-adsorbed methylene blue compared with those for solution, demonstrated a strong tendency of methylene blue to CMTN which was rooted in porous structure of CMTN and the electrostatic interaction between cationic methylene blue with negative surface of the CMTN. By applying differential pulse voltammetry, a calibration curve is obtained for methylene blue in the range of $1.0 \times 10^{-8}$ to $1.0 \times 10^{-5}$ M and the limit of detection was evaluated to be $3.0\times 10^{-9}$ M. In addition, the pre-adsorbed methylene blue on the surface of the modified electrode performed well in the determination of the trace amounts of lead in the real samples such as lake and tap water. Dynamic linear range for lead was investigated in the range of $1.0 \times 10^{-7}$ to $5.0 \times 10^{-4}$ M and the limit of detection was calculated to be $3.0\times 10^{-8}$ M.

I. Introduction

The demand for environmental monitoring has encouraged researchers to investigate efficient methods to detect trace and ultra-trace amounts of organic and inorganic pollutants in water samples such as waste water, ground water and surface waters [1]. Among water pollutants, dyes and heavy metal ions have been concerned extensively due to their neglecting will cause severe damage on nature as well as human health and hygiene [2].