1 research outputs found
One-Pot Noninjection Route to CdS Quantum Dots via Hydrothermal Synthesis
Water-dispersible CdS quantum dots (QDs) emitting from
510 to 650
nm were synthesized in a simple one-pot noninjection hydrothermal
route using cadmium chloride, thiourea, and 3-mercaptopropionic acid
(MPA) as starting materials. All these chemicals were loaded at room
temperature in a Teflon sealed tube and the reaction mixture heated
at 100 °C. The effects of CdCl<sub>2</sub>/thiourea/MPA feed
molar ratios, pH, and concentrations of precursors affecting the growth
of the CdS QDs, was monitored via the temporal evolution of the optical
properties of the CdS nanocrystals. High concentration of precursors
and high MPA/Cd feed molar ratios were found to lead to an increase
in the diameter of the resulting CdS nanocrystals and of the trap
state emission of the dots. The combination of moderate pH value,
low concentration of precursors and slow growth rate plays the crucial
role in the good optical properties of the obtained CdS nanocrystals.
The highest photoluminescence achieved for CdS@MPA QDs of average
size 3.5 nm was 20%. As prepared colloids show rather narrow particle
size distribution, although all reactants were mixed at room temperature.
CdS@MPA QDs were characterized by UV–vis and photoluminescence
spectroscopy, powder X-ray diffraction, transmission electron microscopy,
energy-dispersive X-ray spectrometry and MALDI TOF mass spectrometry.
This noninjection one-pot approach features easy handling and large-scale
production with excellent synthetic reproducibility. Surface passivation
of CdS@MPA cores by a wider bandgap material, ZnS, led to enhanced
luminescence intensity. CdS@MPA and CdS/ZnS@MPA QDs exhibit high photochemical
stability and hold a good potential to be applied in optoelectronic
devices and biological applications