Preparation and Application of Stable Highly Luminescent CdTe Core/Shell Quantum Dots

Abstract

Bright photoluminescence (PL) emission and high stability are the prerequisites of Quantum dots (QDs) . In this paper, a newly stable highly luminescent CdTe/PVPy core/shell semiconductor quantum dots was synthesized by a stepwise layer-by-layer loading method while Mercaptopropionic acid (MPA) and poly (acrylic acid) (PAA) playing an important role in this procession. And its application in DNA fluorescence probe was also investigated. The MPA-stabilized CdTe QDs were gained in aqueous phase with N2 protection, and then refluxed for 1h, 2h, 3h and 4h respectively. The fluorescence emission spectrum (FL) suggested that when the refluxing time was 3 h, CdTe QDs have a obvious red shift and higher fluorescence intensity, and transmission electron microscope (TEM) showed that the average particle size of CdTe QDs were (4±1)nm in diameters. PAA acted as an effective host for the loading of CdTe QDs due to its rich of carboxyl groups, 4-vinylpyridine (VPy) acted as the outer quantum-dot shell because of its amino group in pyridine ring. It was found that the as prepared nanoparticle didn't precipitate during 2 months and the fluorescence intensity of CdTe/PVPy was higher than that of CdTe nanoparticles at the same pH value, which indicated that PAA improved the stability of CdTe nanoparticles at pH 7.5, and enhanced the fluorescence intensity of CdTe nanoparticles. The TEM indicated that the as-prepared CdTe/PVPy QDs were uniform-sized and 13.3 nm in diameters with perfect fluorescence emission property. Due to the pyridine ring on the surface, the as prepared QDs were linked to NH2-DNA and DNA strand respectively. As shown in FL, the CdTe/PVPy QDs can link to DNA directly which was not decorated by amidogen, and the FL intensity increased distinctly. That will reduce the cost in the preparation of DNA fluorescence probe obviously, and enlarge the application of DNA probe in various fields.