Electrostatic association complex of a polymer capped CdTe(S) quantum dot and a small molecule dye as a robust ratiometric fluorescence probe of copper ions

A ratiometric fluorescence probe for robust and rapid Cu2+ detection was established based on an electrostatic association complex of polyallylamine capped CdTe(S) quantum dots (CdTe(S)@PAI QDs) and a small molecule dye 5-oxo-3,5-dihydro-2H-thiazolo[3,2-a]pyridine-7-carboxylic acid (TPCA). Both of the components are easy to make. Strongly fluorescent CdTe(S)@PAI QDs could be simply prepared through a one-step UV irradiation while TPCA could be obtained directly through the hydrothermal method. The ratiometric probe was built through mixing of both components, neither organic solvent nor other harsh conditions is involved. The as-prepared probe shows dual-emission at 525 nm and 420 nm under excitation wavelength of 350 nm. The fluorescence ratio (I525nm/I420nm) remains constant with concentration changes of the complex up to ± 20% and a temperature variation from 20 to 50 °C, but shows significant change in the presence of Cu2+. The proposed probe exhibits excellent selectivity and sensitivity for Cu2+. The fluorescence ratio (I525nm/I420nm) show good linear relationship with the Cu2+ concentration range from 0.05 to 1.6 μM and the limit of detection (S/N = 3) can reach 24 nM . Its applicability was demonstrated by detecting Cu2+ ions in certified reference materials and real samples with recoveries in a range of 91.0-107.3%.