Simultaneous and accurate analysis of multiple heavy metals (HMs) in environment by electrochemical method still faces huge challenges, such as complex experimental process, low detection efficiency and the interference arising from electrochemical interactions between different HMs. To address these issues, we propose a sensing platform combining S-TiO 2 @Ti 3 C 2 MXene with machine learning strategies for simultaneous electrochemical detection of Cu 2+ and Hg 2+ in water samples. Specifically, surface morphology and crystal structure of S-TiO 2 @Ti 3 C 2 were characterized via SEM, XRD, and XPS. Electrochemical behaviors were systematically investigated using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Orthogonal test-based multi-objective optimization method integrated with comprehensive balance approach were employed to determine the optimal sensing parameters, which were identified pH of 4.5, deposition time of 210 s, and deposition potential of −1.5 V. The fabricated sensor exhibited high sensitivities of 44.122 and 143.795 μA·L·mg −1 , low limits of detection of 0.392 and 0.093 μg·L −1 , and broad linear ranges of 0.001–1000 μg·L −1 for Cu 2+ and Hg 2+ , respectively. Furthermore, machine learning strategy was introduced to resolve the poor accuracy issue associated with traditional calibration curve analysis for the simultaneous detection of Cu 2+ and Hg 2+ across the entire linear range. The results indicated that minimum Redundancy Maximum Relevance (mRMR) algorithm effectively extracted valuable and critical information of Cu 2+ and Hg 2+ from the full voltammetric curves, and the constructed support vector machine (SVM) model remarkably improved detection accuracy. The reliability of the proposed SVM model was validated through simultaneous detection of HMs in actual environmental water samples, yielding favorable recovery rates.
Xiang Qin,Tiantian Yi,Rong Cao,Junchen Luo,Hui Luo,Lijun Ji
The development of efficient S-scheme heterojunctions was crucial for addressing the limitations of insufficient light absorption and rapid charge recombination in photocatalysis. In this study, a dual-synergistic 0D/2D/0D (001)TiO 2 /Ti 3 C 2 /ZnTCPP S-scheme heterojunction was rationally designed. The matched energy levels between (001)TiO 2 and ZnTCPP metalloporphyrin drove the formation of a robust built-in electric field, serving as the endogenous S-scheme charge separation core that preserved strong redox capacity. Meanwhile, the metallic Ti 3 C 2 MXene acted as an exogenous high-conductivity transport bridge, accelerating directional carrier migration to surface active sites. The composite was successfully fabricated via a hydrothermal method combined with electrostatic self-assembly. Comprehensive characterization by XRD, TEM, and XPS confirmed that (001)TiO 2 nanoparticles and amorphous ZnTCPP were uniformly anchored onto Ti 3 C 2 nanosheets, forming intimate 0D/2D/0D interfacial contacts with strong electronic interactions. The incorporation of ZnTCPP significantly extended the optical absorption into the visible region, while Ti 3 C 2 functioned as an efficient electron mediator and photothermal agent, further boosting reaction kinetics. Under visible-light irradiation, the optimized TTZ-2 composite exhibited exceptional dual-functional performance: a tetracycline degradation rate of 93.4% and a hydrogen evolution rate of 590.2 μmol·g −1 ·h −1 . Mechanistic investigations, supported by Kelvin probe force microscopy (KPFM) and density functional theory (DFT) calculations, revealed that the dual synergy between the endogenous built-in electric field and the exogenous Ti 3 C 2 channel synergistically facilitated the directional migration of photogenerated carriers along the S-scheme pathway, effectively suppressing recombination while preserving strong redox capabilities. This work demonstrated a viable strategy for designing multifunctional MXene-based photocatalysts for environmental remediation and solar energy conversion.
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