Silica-encapsulated CdTe/MPA quantum dots: microstructural,thermal, and chemical stability characterization

In this paper, we describe the synthesis of silica-encapsulated CdTe/MPA quantum dot (QD) nanocomposites (CdTe/MPA@SiO₂) at room temperature starting from water-soluble CdTe QDs capped with 3-mercaptopropionic acid (MPA) as surface ligand (CdTe/MPA), followed by their encapsulation with a thin layer of silica using the sol–gel process. The objective of this work was to evaluate the microstructural, thermal, and chemical properties of the encapsulated material as a way to evaluate these characteristics for possible applications in different technological areas. Transmission electron microscopy results proved that CdTe QDs (2.5 nm in size) were inside the SiO₂ nanoparticles, and the spherical CdTe/MPA@SiO₂ nanocomposite with a 69-nm thick shell. The photoluminescence intensity was evaluated as a function of pH in the range of 2–12. The CdTe/MPA@SiO₂ nanocomposite showed better chemical stability and greater intensity of photoluminescence in the pH 2–12 range than CdTe/MPA. In addition, the CdTe/MPA@SiO₂ nanocomposites showed good heat stability up to 125 °C. The changes in their optical properties were also evaluated by means of photoluminescence spectroscopy. The materials were also characterized by diffuse reflectance spectroscopy, X-ray diffraction, infrared spectroscopy, and thermogravimetric analysis.

Open image in new window

Graphical abstract ?