Harnessing the Potential of CdS/ZnS & CdSSe/ZnS Quantum Dots

Understanding CdS/ZnS Quantum Dots

CdS/ZnS quantum dots are semiconductor nanoparticles composed of a cadmium sulfide (CdS) core and a zinc sulfide (ZnS) shell. These quantum dots possess unique optical and electronic properties due to quantum confinement effects and have gained significant attention in various scientific and industrial applications. The design of CdS/ZnS quantum dots involves incorporating a ZnS shell to enhance the stability and luminescence efficiency of the CdS core.

CdS/ZnS quantum dots exhibit a tunable bandgap, high photoluminescence quantum yield, and excellent photostability. The core-shell structure provides improved resistance to oxidation and enhances the quantum yield, making CdS/ZnS quantum dots valuable in biological imaging, light-emitting diodes, and photovoltaic devices.

Understanding CdSSe/ZnS Quantum Dots

CdSSe/ZnS quantum dots share similarities with CdS/ZnS quantum dots, with the main distinction being the incorporation of selenium (Se) alongside sulfur (S). These quantum dots possess a ternary alloy core, combining the semiconductor properties of cadmium sulfide and cadmium selenide. The ZnS shell is added to the CdSSe core to further enhance its optical properties and stability.

The introduction of selenium in the core structure expands the range of emission wavelengths achievable by CdSSe/ZnS quantum dots, making them particularly useful in multicolor imaging and display technologies. For example, Meenakshi Rana developed glutathione-terminated core/shell CdSeS/ZnS quantum dots (L-GSH-CdSeS/ZnS QDs) as a medical imaging tool for cancer cells.

L-GSH-CdSeS/ZnS QDs for imaging of live cancer cells.[1]

CdS/ZnS & CdSSe/ZnS Quantum Dots from Alfa Chemistry

Catalog	Product Name
ACMA00014351	CdS/ZnS & CdSSe/ZnS Quantum Dots, Blue/Green, Organic soluble, 420nm
ACMA00014356	CdS/ZnS & CdSSe/ZnS Quantum Dots, Blue/Green, Organic soluble, 440nm
ACMA00014358	CdS/ZnS & CdSSe/ZnS Quantum Dots, Blue/Green, Organic soluble, 460nm
ACMA00014373	CdS/ZnS & CdSSe/ZnS Quantum Dots, Blue/Green, Organic soluble, 480nm
ACMA00014385	CdS/ZnS & CdSSe/ZnS Quantum Dots, Blue/Green, Organic soluble, 500nm
ACMA00014419	CdS/ZnS & CdSSe/ZnS Quantum Dots, Blue/Green, Organic soluble, 520nm
ACMA00016088	CdS/ZnS & CdSSe/ZnS Quantum Dots, Blue/Green, Water soluble, 420nm
ACMA00016103	CdS/ZnS & CdSSe/ZnS Quantum Dots, Blue/Green, Water soluble, 440nm
ACMA00016748	CdS/ZnS & CdSSe/ZnS Quantum Dots, Blue/Green, Water soluble, 460nm
ACMA00016749	CdS/ZnS & CdSSe/ZnS Quantum Dots, Blue/Green, Water soluble, 480nm
ACMA00016755	CdS/ZnS & CdSSe/ZnS Quantum Dots, Blue/Green, Water soluble, 500nm
ACMA00016761	CdS/ZnS & CdSSe/ZnS Quantum Dots, Blue/Green, Water soluble, 520nm

Synthesis of CdS/ZnS & CdSSe/ZnS Quantum Dots

The synthesis of CdS/ZnS and CdSSe/ZnS quantum dots typically involves a two-step process:

• The formation of core nanoparticles

The core nanoparticles are first prepared using methods such as colloidal synthesis, hydrothermal synthesis, or hot injection techniques. The size and composition of the core can be precisely controlled to achieve desired electronic and optical properties.

• The growth of shell

After the core formation, the ZnS or ZnS-based shell is grown around the core nanoparticles to enhance their stability and optical characteristics. This can be accomplished through methods such as successive ionic layer adsorption and reaction (SILAR), molecular layer deposition (MLD), or seed-mediated growth. The shell growth process allows fine-tuning of the quantum dot properties, such as emission wavelength, quantum yield, and stability.

Applications of CdS/ZnS & CdSSe/ZnS Quantum Dots

• Biological Imaging

CdS/ZnS and CdSSe/ZnS quantum dots are widely used as fluorescent probes, and they can be conjugated with biomolecules to label cellular structures and track biological processes with high specificity and resolution. Yi Zhang et al. prepared PEI-CdS/ZnS QD fluorescent probes by self-assembly of folic acid (FA) onto polyethylenimine (PEI)-coated CdS/ZnS quantum dots, which can be used to target FR overexpressing cancer cells for fluorescence imaging.

PEI-CdS/ZnS QDs for targeted imaging of FR overexpressed cancer cells. [2]

• Light-Emitting Diodes (LEDs)

The exceptional optical properties of CdS/ZnS and CdSSe/ZnS quantum dots make them promising materials for use in next-generation light-emitting diodes. Their efficient and tunable emission, along with their compatibility with solution processing, enables the development of highly efficient and flexible LED devices for display and lighting applications.

• Photovoltaic Devices

The tunable bandgap of CdS/ZnS and CdSSe/ZnS quantum dots makes them suitable for utilization in photovoltaic devices. These quantum dots can be incorporated into solar cells to enhance light absorption and improve the efficiency of energy conversion. Their solution-processability allows for the fabrication of cost-effective and lightweight photovoltaic devices.

• Sensing and Detection

The sensitive response of CdS/ZnS and CdSSe/ZnS quantum dots to environmental changes and their ability to emit light of different colors enable their use in fluorescence-based sensors for detecting various analytes, including ions, biomolecules, and contaminants. Parveen Kumar et al. conjugated amine-functionalized CdSSe/ZnS core/shell quantum dots with anti-ERα antibodies through bioconjugation to achieve molecular sensing of breast cancer antigens.

CdSSe/ZnS QDs for molecular sensing of a breast cancer antigen. [3]

References

1. Rana M, et al. Inorganic Chemistry Communications, 2020, 112, 107723.
2. Zhang Y, et al. Analytical chemistry, 2013, 85(1), 228-234.
3. Kumar P, et al. Sensors and Actuators B: Chemical, 2014, 202, 404-409.

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