Synthesis and Characterization of CdTe/PAA/P-4-VP Quantum Dots

Abstract

In this article, a novel kind of nanomaterials called CdTe/PAA/P-4-VP quantum dots (QDs) was studied. CdTe quantum dots were synthesized by mixing CdCl2 solution containing Mercaptopropionic Acid (MPA) stabilizer at pH 9.1 with NaHTe aqueous solution and refluxing 1 h at 96 °C. Then, CdTe solution obtained was adjusted to pH 7.5 by poly(acrylic acid) (PAA) which could provide many carboxyl groups to CdTe QDs. PAA-modified CdTe (CdTe/PAA)solution was transparent during 2 months and the fluorescence of CdTe/PAA was higher than that of CdTe at the same pH, which indicated that PAA increased the stability and fluorescence intension of CdTe QDs. Then poly(4-vinylpyridine)-coated CdTe/PAA QDs (CdTe/PAA/P-4-VP QDs) were prepared after 4-VP was polymerized on the surface of CdTe/PAA nanoparticles by using N, N'-Methylenebisacrylamide as crosslinker and potassium persulfate as initiator. The parallel experiment in which PAA was replaced by HCl was also arranged and CdTe/P-4-VP QDs was gained. Fluorescence emission spectrum (FE), transmission electron microscope (TEM), and infrared spectrum (IR) were used to characterize CdTe/PAA/P-4-VP and CdTe/P-4-VP QDs. The FE spectrum of CdTe/PAA/P-4-VP QDs had an obviously red shift compared with that of CdTe QDs while the red shift in FE spectrum of CdTe/P-4-VP QDs was not obvious, which indicated that PAA played an important role in the synthesis of P-4-VP-coated CdTe QDs. The fluorescence of CdTe/PAA/P-4-VP QDs was one times higher than that of CdTe QDs, which suggested the advantage of CdTe/PAA/P-4-VP QDs in fluorescence application. TEM photos showed that the average size of CdTe/PAA/P-4-VP QDs was 13.3nm. The IR spectrum of CdTe/PAA/P-4-VP QDs showed that characteristic absorption peak of carboxyl groups from PAA or/and MPA was wide and other absorption peaks of CdTe/PAA/P-4-VP QDs were the same with that of 4-VP which confirmed that P-4-VP coated CdTe QDs.