Direct Aqueous Synthesis of Cysteamine-Stabilized CdTe Quantum Dots and Its Deoxyribonucleic Acid Bioconjugates

Cysteamine-stabilized CdTe nanocrystals were prepared by direct aqueous synthesis method. Absorption and fluorescence spectra showed that the as-prepared CdTe quantum dots had good optical properties. The structure and diameter were characterized by transmission electron microscopy (TEM). Cysteamine-capped CdTe nanocrystals showed some particular advantages: excited cysteamine-capped CdTe precursor emits luminescence without heating and emits strong luminescence after heating for 20 min at 100°C. However, other thiol-stabilized CdTe precursors do not emit luminescence without heating. The free amino functional group of the cysteamine-stabilized CdTe nanocrystals directly conjugates with DNA. The conjugates showed a redshift of 19 nm for the maximum emission position and an enhancement of fluorescence intensity of CdTe nanocrystals.