One-Pot Noninjection Route to CdS Quantum Dots via Hydrothermal Synthesis

Abstract

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(2)/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.

Retracted Article: A facile cation exchange-based aqueous synthesis of highly stable and biocompatible Ag2S quantum dots emitting in the second near-infrared biological window

“…When compared with Ag 2 S, CdS (with a higher solubility product constant) can more easily dissociate out Cd 2+ ions, which have potential toxicity to cells. 34,49,50 Thus, this may be responsible for the marked cytotoxicity of the L929 cells after incubation with CdS QDs. These results indicate that Ag 2 S QDs are safe for applications in cells, and could be swallowed for cell imaging of tumor cells.…”

High selectivity in water soluble MoS2 quantum dots for sensing nitro explosives

“…22 Synthesis 1,4-Diaminobutane capped MoS 2 quantum dots (QDs) are synthesized using the following bottom-up approach.…”

Intense, stable and excitation wavelength-independent photoluminescence emission in the blue-violet region from phosphorene quantum dots

“…However, few studies on the PL emission of PQDs have been reported so far. On the other hand, because of the activity of black phosphorus in ambient conditions, the conventional methods to fabricate graphene, molybdenum disulphide and other two-dimensional Van der Waals crystal quantum dots, such as the hydrothermal route141516 acidic exfoliation17 and electrochemical strategies18 are not applicable methods for PQD materials1920. It was reported that black phosphorus quantum dots could be prepared in N-methylpyrrolidinone (NMP) solvent by an ultrasonic exfoliation route19.…”