Detection of low-concentration heavy metal exploiting Tamm resonance in a porous TiO2 photonic crystal

Abstract

The detection of heavy metal ions, particularly Hg²⁺, has gained significant attention due to their severe adverse effects on human health and ecosystems. Conventional methods for monitoring these metals in freshwater often suffer from limitations in sensitivity, accuracy, and cost-effectiveness. This work introduces a novel heavy metal sensor based on Tamm resonance within a one-dimensional (1D) porous TiO₂ photonic crystal structure. The sensor design includes a prism, a silver (Ag) layer, a cavity, and a ternary multilayer porous TiO₂ layer. Reflectance spectra are analyzed using the transfer matrix method. A key aspect of this study is the optimization of sensor performance, which involves adjusting the thicknesses of all layers and the porosity of the multilayer porous TiO₂. This optimization strategy is critical for achieving high sensitivity. The results demonstrate that the optimized sensor exhibits a high sensitivity of 0.045 nm ppm⁻¹ for Hg²⁺ solutions. This sensitivity arises from the effective integration of Tamm resonance with the properties of the porous TiO₂ photonic crystal. The proposed structure shows great potential for applications in heavy metal sensing, especially for detecting Hg²⁺ ion contamination in drinking water with high sensitivity and accuracy. In addition to its high performance, the photonic crystal sensor offers extended lifetime, rapid measurement capabilities, cost-effectiveness, and potential for integration into compact devices, making it a promising solution for environmental monitoring and water quality assessment.