Structure-optical property correlation in CdTe/CdS core-shell quantum dots and their effects on Cu2+ sensing mechanisms

Design an efficient photoelectrochemical aptasensor for PCB72 based on CdTe@CdS core@shell quantum dots-decorated TiO2 nanotubes

In this work, an efficient and novel photoelectrochemical (PEC) aptasensor for 2,3',5,5'-tetrachlorobiphenyl (PCB72) was constructed based on CdTe@CdS core@shell quantum dots (CdTe@CdS QDs)-decorated TiO₂ nanotubes (TiO₂ NTs). CdTe@CdS QDs were prepared by the combination of CdTe and CdS with a proper lattice mismatch. Due to their large band offsets, core@shell QDs can reduce undesirable carrier recombination, significantly improving their charge separation efficiency. Then the synthesized CdTe@CdS QDs were modified on TiO₂ NTs (CdTe@CdS QDs/TiO₂ NTs) through electrostatic adsorption method. The as-prepared composites exhibit a wide visible light absorption range, good PEC activity and high photoelectric conversion efficiency. Also, the PEC aptasensor prepared via the immobilization of anti-PCB72 aptamer on the composites exhibits outstanding analytical performance with high sensitivity and specificity for PCB72 under visible-light irradiation, achieving a detection limit as low as 0.03 ng/L. It was also applied to detect PCB72 in four different real environmental samples with satisfactory results.

Assaying of Cu2+ with near-infrared l-cysteine-capped CdSeTe/CdS quantum dots and its effect on cell imaging

Near-infrared (NIR) core-shell CdSeTe/CdS quantum dots (QDs) modified with l-cysteine were synthesized in aqueous solution. The QDs had a special NIR-emitting spectrum, high fluorescence stability and low cytotoxicity. In addition, they exhibited an obvious fluorescence quenching when Cu²⁺ was present. An NIR nanosensor was prepared for rapidly, sensitively, and selectively determining Cu²⁺ in solution quantitatively and monitoring the changes in Cu²⁺ in cells with fluorescence imaging in a semiquantitative way. The linear relationship between the relative fluorescence intensity (F₀ /F) and the concentration of Cu²⁺ from 5.12 × 10^-8  M to 2.56 × 10^-5  M in solution was observed using an NIR fluorescence spectrophotometer with R² equal to 0.9958. Moreover, in the experiment with the fluorescence microscope, F₀ /F versus the concentration of Cu²⁺ from 5.00 × 10^-8  M to 7.68 × 10^-6  M also showed a good linear relationship with R² equal to 0.9817. Practical water sample ion detecting experiments had good accuracy and recovery rates. Cell experiments showed that the NIR imaging intensity of cells was inversely proportional to the concentration of copper ions, therefore NIR QDs have great potential for detection of metal ions in solution and in cells.