Structural, optical, and electrochemical performance of a novel lead-free Pd(II) perovskite for Zn2+ detection

Abstract

A novel two-dimensional lead-free Pd (II)-based perovskite, (C₄H₁₆N₃)[PdCl₄]Cl (abbreviated DET[PdCl₄]Cl), was successfully synthesized via slow evaporation at room temperature. Single-crystal X-ray diffraction analysis indicates that it crystallizes in the orthorhombic Pnma space group, forming a 2D layered structure comprising corner-sharing [PdCl₆] octahedra interconnected through organic diethylenetriammonium cations. The structure is stabilized through numerous N–H⋯Cl hydrogen bonds, which lead to a robust three-dimensional network. Infrared spectroscopy reveals the presence of functional groups as well as hydrogen bonding associations. At the same time, UV–Vis diffuse reflectance spectroscopy reveals three absorption bands and a direct optical bandgap of 2.7 eV, confirming the material's semiconductor nature. Photoluminescence studies show a strong emission peak at 530 nm, with CIE chromaticity coordinates (0.3648, 0.5026), indicating potential for optoelectronic and light-emitting applications. Thermal analysis (TGA-DTA) demonstrates high thermal stability up to 280 °C with three distinct decomposition stages and endothermic peaks associated with structural transitions. Electrochemical tests show that DET [PdCl₄]Cl-modified glassy carbon electrodes (GCEs) improve electron transfer and electrochemical performance. The sensor displays high sensitivity and selectivity for Zn²⁺ detection, with a low detection limit of 2 × 10⁻⁸ M and a linear range up to 1 × 10⁻⁵ M. It offers good stability and reproducibility, with a relative standard deviation of 1.51 %. Tests on real water samples show recovery rates between 97 % and 102 %, confirming the sensor's accuracy for environmental monitoring. Overall, DET [PdCl₄]Cl shows great potential for use in optoelectronic devices and heavy metal detection due to its thermal stability, semiconductor properties, and strong electrochemical performance.