TiO2-coated 2D photonic crystals for reflectometric determination of malachite green.

Abstract

A "detect and destroy" strategy is reported for the spectroscopic determination and photocatalytic degradation of Malachite Green (MG) in aqueous solutions. The intensity of the reflection peak maxima from the TiO2-coated 2D-photonic crystal (PhC) at 633nm wavelength undergoes a gradual decrease with increasing concentrations of MG. The determination of MG was readily achieved in thenanomolar range due to the quenching of the reflection intensity of the peak, measured using a fiber optic probe. The assay works in the 1.0 nM to 10μM MG concentration range with a detection limit of 1.3 nM. The same TiO2-coated 2D-PhC surface can photocatalytically degrade MG in aqueous solutions under UV irradiation. The photocatalytic degradation in the presence of TiO2-coated 2D-PhC becomes evident as the blue color of MG changes to colorless with increasing irradiation time. The decrease in absorption is detected at 617nm. It was found that the photocatalytic efficiency of TiO2 was synergistically enhanced in the presence of 2D-PhCs. It is concluded that each component of theTiO2-coated 2D-PhCsystem plays a key role in the detection and degradation of MG. Graphical abstractSchematic representation for reflectometric detection and photocatalytic degradation of hazardous Malachite Green dye using TiO2-coated two-dimensional photonic crystals.