Research CdTe Quantum Dots Fluorescence Quenching Of Gold Nanoparticles

Compared with organic fluorescent dyes, quantum dots (QDs) present many considerable fluorescent properties such as broade excitation spectrum, tunable and narrow emission spectrum, high quantum yield and good stability, which make them been extensively used as fluorescence probes. Gold nanoparticles (AuNPs) have aroused much attention as fluorescence quencher because of many advantages, such as easy preparation, large absorption coefficient and broad spectrum in visible region. In this thesis, CdTe QDs and AuNPs were synthesized in aqueous solution. Factors affecting the quenching activity of AuNPs on the fluorescence of CdTe QDs were investigated in detail.1. Effect of electrostatic interaction on AuNPs quenching fluorescence of CdTe QDsThe surface charge of CdTe QDs and AuNPs directly affects the electrostatic interaction that exists between them. Different electrostatic interactions will lead to different quenching activity of AuNPs on the fluorescence of CdTe QDs. The positively-charged and negatively-charged CdTe QDs with the same size were synthesized in aqueous solution. The quenching activity of negatively-charged AuNPs on the fluorescence of CdTe QDs was investigated. The results indicate that the negatively-charged AuNPs have stronger quenching capacity on the fluorescence of the positively-charged CdTe QDs. Further experiments showed that the positively-charged AuNPs have stronger quenching capacity on the fluorescence of the negatively-charged CdTe QDs. So, the electrostatic attraction between AuNPs and CdTe QDs can enhance the quenching activity of AuNPs.2. Effect of ionic strength on AuNPs quenching fluorescence of CdTe QDsThe water-soluble CdTe QDs with different surface charge, ligands and sizes were synthesized. The effect of ionic strength on quenching activity of AuNPs on the fluorescence of CdTe QDs was investigated. The results indicate that ionic strength has significant impact on quenching activity of AuNPs on the fluorescence of CdTe QDs. Then, mechanism of the effect of ion strength on fluorescence quenching was discussed. Ionic strength not only affects dispersity of AuNPs and spectral overlap between AuNPs and CdTe QDs, but also affects the electrostatic effect and relative distance between them. The results indicate that effect of ionic strength is closely related to steric hindrance of stabilizer and independent of size and surface charge of CdTe QDs. Ionic strength mainly affects the electrostatic effect and relative distance between them for CdTe QDs with small steric hindrance of the stabilizer, while affects the dispersity of AuNPs and the spectral overlap between them for CdTe QDs with big steric hindrance of the stabilizer.