Dual-target electrochemical aptasensor based on Mil101(Fe)-CQD-TiO₂ ternary composite for Cryptosporidium and cadmium...

A Mil101 (Fe)-carbon quantum dot-titanium dioxide (Mil101(Fe)-CQD-TiO₂) ternary composite was prepared using the hydrothermal method. The composite was thoroughly characterized using various physicochemical techniques to investigate the crystallinity of the materials, the functional groups present, chemical vibrations, elemental composition, and morphology, confirming the formation of the ternary composite. The electrochemical properties of the ternary composite were then evaluated through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). This ternary composite served as an electrode modifier for aptasensor fabrication. The aptasensor exhibited an electroactive surface area of 3.22 cm², indicating a higher number of active sites for analyte interaction. The aptasensing platform was optimized and evaluated in phosphate buffer solution and real water samples using square wave voltammetry (SWV). Additionally, the sensor demonstrated a limit of detection (LOD) of 0.001 µM for Cryptosporidium and 0.073 µM for cadmium ions with high sensitivities of 9 × 10^-4 mA/µM and 0.127 mA/µM in buffer solutions. The aptasensor demonstrated excellent selectivity, with recoveries ranging from 67 to 98.1% for Cryptosporidium and 72 to 89% for Cd²⁺.