Sustainable Nanotechnology: The Shift Towards Cadmium-Free Quantum Dots

The necessity to develop cadmium-free quantum dots stems from the environmental and health hazards associated with cadmium-based quantum dots. Cadmium is a toxic heavy metal with detrimental effects on ecosystems and human health. Its presence in quantum dots raises concerns about toxicity, disposal, and regulatory restrictions. Hence, the shift towards cadmium-free quantum dots is crucial to ensure sustainable nanotechnology applications without compromising safety or environmental well-being.

Cadmium Quantum Dots vs. Cadmium-Free Quantum Dots

Cadmium quantum dots have superior optical properties, offering high quantum yields and precise emission spectra. However, their toxicity poses significant challenges, limiting their widespread use. On the other hand, cadmium-free quantum dots, such as indium phosphide (InP), copper indium sulfide (CIS), and zinc sulfide (ZnS) quantum dots, provide a non-toxic alternative with comparable optical performance. This shift towards cadmium-free variants addresses concerns related to toxicity, allowing for safer and more sustainable applications.

Common Cadmium-Free Quantum Dots

• Indium Phosphide (InP) Quantum Dots

InP quantum dots are non-toxic alternatives with excellent fluorescent properties, making them suitable for bioimaging and optoelectronic applications.

• Copper Indium Sulfide (CIS) Quantum Dots

CIS quantum dots exhibit tunable bandgaps and low toxicity levels, enabling applications in solar cells, LEDs, and biological sensing.

• Zinc Sulfide (ZnS) Quantum Dots

ZnS quantum dots are widely used in biological imaging and display technologies due to their biocompatibility and optical properties.

Cadmium-Free Quantum Dots from Alfa Chemistry

Catalog	Product Name
ACMA00003158	Cadmium Free Quantum Dots, Organic Soluble, 540nm
ACMA00003159	Cadmium Free Quantum Dots, Organic Soluble, 560nm
ACMA00003160	Cadmium Free Quantum Dots, Organic Soluble, 580nm
ACMA00005762	Cadmium Free Quantum Dots, Organic Soluble, 600nm
ACMA00006071	Cadmium Free Quantum Dots, Organic Soluble, 620nm
ACMA00013409	Cadmium Free Quantum Dots, Organic Soluble, 640nm
ACMA00013437	Cadmium Free Quantum Dots, Organic Soluble, 660nm

Synthesis Methods of Cadmium-Free Quantum Dots

• Hot-Injection Method

In the hot-injection method, precursors of non-cadmium elements are injected into a hot solution to promote the nucleation and growth of cadmium-free quantum dots.

• Hydrothermal Synthesis

Hydrothermal synthesis utilizes high-temperature and high-pressure conditions to produce cadmium-free quantum dots with enhanced crystallinity and uniformity. Bing Deng et al. used a low-temperature (130°C) hot injection method combined with a multi-layer ZnS coating strategy to successfully prepare efficient green light-emitting CuInS2/ZnS core/shell quantum dots.

The low-temperature hot injection method. [1]

• Sol-Gel Technique

The sol-gel technique involves the hydrolysis and condensation of precursors to form a colloidal solution of cadmium-free quantum dots, offering control over size and properties.

• Microwave-Assisted Method

Microwave-assisted synthesis provides excellent process control for the synthesis of cadmium-free quantum dots and the ability to rapidly reach higher temperatures. Yang Liu et al. prepared CuInZnS/ZnS quantum dots with high quantum yield and good chemical stability through microwave-assisted hydrothermal synthesis. In addition, controlling the emission wavelength through microwave-assisted hydrothermal synthesis can also be used to synthesize multicolor quantum dots.

The microwave-assisted hydrothermal synthesis for CuInZnS/ZnS core/shell QDs. [2]

Applications of Cadmium-Free Quantum Dots

• Biological Imaging

Cadmium-free quantum dots are used as fluorescent probes for cellular imaging, providing high resolution and brightness without toxic effects.

• Optoelectronic Devices

InP, CIS, and ZnS quantum dots find applications in LEDs, solar cells, and displays, offering efficient light emission and absorption properties.

• Sensing

Cadmium-free quantum dots are employed in sensing applications for detecting pollutants, heavy metals, and biological markers and more due to their high sensitivity and selectivity. The CuInZnS/ZnS quantum dot microbeads prepared by Qiaoli Jin et al. have been verified to be used for quantitative detection of heart-type fatty acid binding protein (H-FABP), with a detection limit of 0.48 ng mL^-1.

CuInZnS/ZnS quantum dot for H-FABP detection.[3]

References

1. Bing Deng, et al. Journal of Alloys and Compounds, 2021, 851, 155439.
2. Yang Liu, et al. New Journal of Chemistry, 2018, 42(6), 4102-4108.
3. Qiaoli Jin, et al. Inorganic Chemistry, 2023, 62(8), 3474-3484.

Click here to get in touch with us

If you are interested in our Sustainable Nanotechnology: The Shift Towards Cadmium-Free Quantum Dots, please don't hesitate to place an order now!