Cadmium Free Quantum Dots

Cadmium Free Quantum Dots List

Quantum dots are semiconductor nanocrystals with nanoscale particle size. They have many advantages, such as wide excitation spectrum, narrow emission spectrum, adjustable emission wavelength, anti-fluorescence bleaching, good stability, easy surface modification and functionalization. As a new type of green nanomaterial, cadmium free quantum dots have become the hotspot of researches in recent years.

Applications:

Because cadmium free quantum dots do not contain cadmium element, they have low biotoxicity and good biocompatibility, which is suitable for biologic applications. In addition, due to the excellent optical performances, cadmium free quantum dots are also widely used in the field of optoelectronics.

• Biologic field: Due to the low toxicity and good biocompatibility, cadmium free quantum dots will not affect cell growth and lead to cell death. In addition, cadmium free quantum dots have excellent fluorescence performance, such as strong fluorescence intensity, high fluorescence quantum yield. Therefore, cadmium free quantum dots can be widely applied in the field of biology, mainly including bioimaging, biosensor, fluorescent tracer, cancer treatment and the others.

Figure 1. An example of CuInS₂ quantum dots used in bioimaging.

• Display field: Cadmium free quantum dots also play an important role in display field. The OLED based on cadmium free quantum dots can meet the latest industry standards in color performance and energy saving efficiency requirements. Furthermore, the color performance is also improved, and the visual experience become more three-dimensional.
• The others: Cadmium free quantum dots can also be used in many other fields including lighting, solar cells, analysis field and the others.

Figure 2. An example of cadmium free quantum dots used in solar cells.

Classification:

There are various types of cadmium free quantum dots. Depending on their composition, they can be divided into the following categories.

• Graphene quantum dots: Graphene quantum dots are semiconductor crystals with particle sizes between 1 and 10 nm. Because of the low biotoxicity and easy surface modification, graphene quantum dots have been mostly used in the field of bioanalysis.
• CuInS₂ quantum dots: CuInS₂ quantum dot is a typical cadmium free quantum dot. The emission wavelength range of CuInS₂ quantum dot can be adjusted according to the composition ratio and reaction time of each component. Therefore, CuInS₂ quantum dots can be used to obtain various colors of quantum dots from visible light region to near infrared light region.
• Silicon quantum dots: Silicon quantum dots are semiconductor nanocrystals with indirect luminescence mechanism. Silicon quantum dots have very low toxicity and play an important role in the early diagnosis and treatment of diseases.
• The others: In addition to the mentioned categories, cadmium free quantum dots also include Ag₂Se quantum dots, ZnSe/ZnS quantum dots, PbSe/PbS quantum dots, InP/ZnS quantum dots and the others.

References

1. Lin Z, Fei X, Ma Q, et al. CuInS₂ quantum dots@silica near-infrared fluorescent nanoprobe for cell imaging[J]. New Journal of Chemistry, 2013, 38(1):90-96.
2. Sofia Paulo, Emilio Palomares, Eugenia Martinez-Ferrer. Graphene and Carbon Quantum Dot-Based Materials in Photovoltaic Devices: From Synthesis to Applications[J]. Nanomaterials, 2016.