Tailored Synthesis and Multi-Domain Applications of PbS/CdS Quantum Dots

PbS/CdS quantum dots consist of a lead sulfide (PbS) core encapsulated within a cadmium sulfide (CdS) shell, providing improved stability and enhanced optical properties compared to their individual counterparts. These core/shell quantum dots, are semiconductor nanocrystals with unique optical and electronic properties that make them highly desirable for various applications in the field of nanotechnology.

PbS/CdS QDs from colloidal ALD. [1]

Characteristics of PbS/CdS Quantum Dots

• Optical Properties: PbS/CdS QDs exhibit tunable optical properties, including size-dependent absorption and emission spectra. It has been shown that PbS/CdS QDs display unusual non-monotonic energy gap temperature coefficient (dE/dT) changes with PbS size.

Size dependence of optical properties of PbS/CdS QDs. [2]

• Electronic Structure: The electronic structure of PbS/CdS QDs allows for efficient charge transport. The type-II heterojunction formed by PbS and CdS enhances the separation of photogenerated charge carriers, contributing to their exceptional electronic performance.
• Stability and Quantum Yield: PbS/CdS QDs offer high photoluminescence quantum yields, coupled with robust stability against photo-induced degradation.

PbS/CdS Quantum Dots from Alfa Chemistry

Catalog	Product Name
ACMA00022628	PbS/CdS Quantum Dots, Longer near-infrared region, Organic solvent, 1000nm
ACMA00022629	PbS/CdS Quantum Dots, Longer near-infrared region, Organic solvent, 900nm
ACMA00022630	PbS/CdS Quantum Dots, Longer near-infrared region, Organic solvent, 920nm
ACMA00022631	PbS/CdS Quantum Dots, Longer near-infrared region, Organic solvent, 940nm
ACMA00022632	PbS/CdS Quantum Dots, Longer near-infrared region, Organic solvent, 960nm
ACMA00022633	PbS/CdS Quantum Dots, Longer near-infrared region, Organic solvent, 980nm
ACMA00022634	PbS/CdS Quantum Dots, Longer near-infrared region, Water solvent, 1000nm
ACMA00022635	PbS/CdS Quantum Dots, Longer near-infrared region, Water solvent, 900nm
ACMA00022636	PbS/CdS Quantum Dots, Longer near-infrared region, Water solvent, 920nm
ACMA00022637	PbS/CdS Quantum Dots, Longer near-infrared region, Water solvent, 940nm
ACMA00022638	PbS/CdS Quantum Dots, Longer near-infrared region, Water solvent, 960nm
ACMA00022639	PbS/CdS Quantum Dots, Longer near-infrared region, Water solvent, 980nm

Synthesis Methods of PbS/CdS Quantum Dots

• Hot Injection Method

One of the widely employed techniques for synthesizing PbS/CdS QDs involves the hot injection method. In this approach, a mixture of precursors is rapidly injected into a heated solvent to trigger controlled nucleation and growth of the QDs. This method allows precise control over the QD size and composition.

• Cation Exchange Reaction

Another popular method for synthesizing PbS/CdS QDs is the cation exchange reaction. This involves the transformation of pre-synthesized PbS QDs into PbS/CdS core-shell structures by exposing them to a cadmium precursor. The process results in a uniform CdS shell deposition onto the PbS core, leading to enhanced quantum confinement effects and improved stability.

Core/shell structures at different stages of cation exchange reaction. [3]

• Colloidal Synthesis

Colloidal synthesis routes, such as the use of ligands and surfactants, enable the control of PbS/CdS QD morphology and surface chemistry. Laxmi Kishore Sagar et al. used colloidal atomic layer deposition approach to prepare PbS/CdS core/shell quantum dots at room temperature.

Applications of PbS/CdS Quantum Dots

• Photovoltaics

The tunable bandgap and high absorption coefficients of PbS/CdS QDs make them well-suited for utilization in next-generation solar cells. Lai-Hung Lai et al. fabricated PbS-CdS (core-shell) quantum dot (QD) sensitized solar cells by directly adsorbing core-shell quantum dots on mesoporous TiO₂ and then performing 3-mercaptopropionic acid ligand exchange.

PbS/CdS QDs for solar cell. [4]

• Photodetectors

PbS/CdS QDs have found applications in high-performance infrared photodetectors due to their sensitivity in the near-infrared spectral region.

• Light-Emitting Devices

The exceptional photoluminescence characteristics of PbS/CdS QDs enable their use in light-emitting diodes (LEDs) and display technologies.

• Biomedical Imaging

The biocompatibility and optical properties of PbS/CdS QDs make them suitable for bioimaging applications. Mingxi Zhang et al. developed a bright fluorescent probe based on PbS-CdS QDs that emits ~1,600 nm in the NIR-IIb window. The probe enables high-speed, non-invasive, millimeter-level depth fluorescence imaging as an in vivo research tool in preclinical animal models.

NIR-IIb-emitting PbS-CdS QDs. [5]

References

1. Sagar L K, et al. Chemistry of Materials, 2016, 28(19), 6953-6959.
2. Zhao H, et al. The Journal of Physical Chemistry C, 2014, 118(35), 20585-20593.
3. Cheng L, et al. Materials Research Bulletin, 2021, 140, 111298.
4. Lai L H, et al. Physical Chemistry Chemical Physics, 2014, 16(2), 736-742.
5. Zhang M, et al. Proceedings of the National Academy of Sciences, 2018, 115(26), 6590-6595.

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