Effect of Adenine on the Photoluminescence Properties and Stability of Water-Soluble CdTe Quantum Dots

In this paper, it has been found that a small biomolecule adenine can greatly affect the photoluminescence properties and stability of water-soluble CdTe quantum dots. The interaction between CdTe QDs and adenine is characterized by TEM, fluorescence microscope, and photoluminescence (PL), IR, and UV-vis spectra. The influences of reflux time, pH value, ionic strength, storage time, the ratio of CdTe QDs to adenine on the PL intensity, and the stability of CdTe-adenine conjugates are investigated in detail. The PL intensity and stability of CdTe-adenine conjugate are largely enhanced compared to that of pure CdTe QDs. At the same time the fluorescence quantum yield of the CdTe-adenine conjugate reaches 23.04% in comparison with 20.27% of the parent CdTe QDs. The existence of coordinated bond and hydrogen bond between CdTe QDs and adenine is illuminated by IR analysis. These bonds together with the passivation of adenine on the surface of CdTe are possibly the main reasons for the stability of the conjugate. As a new stabilization agent, adenine has no effects on the properties of the biological system but can increase the stability and PL intensity of CdTe QDs, which will enlarge the application of QDs in biomedicine and other fields.