Tuning CdTe quantum dots reactivity for multipoint detection of mercury(II), silver(I) and copper(II)

Highlights: • Tuning of QDs surface with distinct ligands and functional groups to adjust reactivity. • Combination of multiple QDs provided multipoint detection improving selectivity. • Chemometrics facilitated data analysis and processing and enhanced accuracy and reproducibility. -- Abstract: In this work we tuned the surface chemistry of distinctly-sized CdTe quantum dots (QDs), by using a variety of capping ligands with distinctive functional moieties, and combined them in multi-QDs probing solutions for Hg²⁺, Cu²⁺ and Ag⁺. Upon the individual interaction of the distinctly-capped QDs with each of the abovementioned metal ions, several parameters such as Stern-Volmer constants, equilibrium binding constants, the red-shift magnitude and photoluminescence (PL) lifetime values were thoroughly evaluated. Due to their great reactivity, selectivity could become a major issue in the application of semiconductor quantum dots in chemical analysis. Therefore, the combination in the same analysis of multiple QDs, capped with distinct ligands and emitting at different wavelengths, was exploited to guarantee a specific analyte-response profile. When coupled with chemometrics, for data analysis and processing, the developed approach provided enhanced selectivity and accuracy. In fact, the obtained results of all the partial least squares (PLS) models coefficient of determination of cross-validation (R²_CV) close to 1, root mean square error of calibration (RMSEC) and root mean square error of cross-validation (RMSECV) values ranging 0.0094–0.15 and 0.013–0.19 mg L⁻¹, respectively. demonstrated the possibility to perform accurate predictions of Hg²⁺ and Cu²⁺. Additionally, the sensitivity of the developed models was also calculated and allowed us to conclude which combination of distinctly-capped QDs assured a more sensitive quantification of Cu²⁺ (sensitivity = 653 L⁻¹ mg for 3-mercaptopropionic acid (MPA)/MPA conjugated probe) and Hg²⁺ (sensitivity = 14,017 L⁻¹ mg for reduced glutathione (GSH)/MPA-conjugated probe).