ZnSe/ZnS Quantum Dots

ZnSe/ZnS Quantum Dots List

Traditional quantum dots usually contain Cd elements, such as CdSe and CdTe quantum dots. These quantum dots show high luminous efficiency, but their application is limited due to their biological toxicity. In order to reduce the toxicity, many Cd-free quantum dots have been developed, among which ZnSe/ZnS quantum dots are an important type. ZnSe/ZnS quantum dots are core-shell type fluorescent quantum dots. In the structure of ZnSe/ZnS quantum dots, ZnSe is the core material and ZnS is the shell material. ZnS shell structure has lattice constant that can match with ZnSe core material, but the band gap is wider. As the shell, ZnS can effectively eliminate a large number of defects on the surface of ZnSe, and improve the luminescence performances. Due to the non-toxic and harmless properties of Zn element, ZnSe/ZnS quantum dots are a kind of green and environment-friendly quantum dots, and have attracted more and more attention in recent years.

Applications:

• Solar cell field: Solar cells can convert light energy into electricity, which is an important direction of new energy development, and silicon-based solar cells are a kind of important solar cells. In short wave spectral region, silicon-based solar cells have low responsibility and the band reflectance is relatively high. Therefore, silicon-based solar cells have low quantum efficiency in shortwave region. In order to solve this problem, luminescent down-shifting layers can be used to transform the short-wave regional spectrum into the band that solar cells have strong spectral response. ZnSe/ZnS quantum dots can be used as the luminescent material of the down-shifting layers to improve the quantum efficiency of solar cells.

Figure 1. Scheme of down shifting mechanism of ZnSe/ZnS QDs and proof-of-concept solar cell.

• Biomarker fields: ZnSe/ZnS quantum dots is a new kind of inorganic fluorescent biomarkers with high luminous efficiency. Compared with organic fluorescent dyes, ZnSe/ZnS quantum dots have many obvious advantages. On the one hand, ZnSe/ZnS quantum dots have a narrow emission spectrum, which can be adjusted in the ultraviolet, visible and infrared regions, according to requirements. Moreover, ZnSe/ZnS quantum dots have wide excitation bands, so different wavelengths can be obtained by using a single excitation wavelength. On the other hand, ZnSe/ZnS quantum dots show good photostability, anti-photobleaching, and excellent sensitivity.
• The others: ZnSe/ZnS quantum dots can also be used in LED field, tumor therapy field, analysis and testing field and the others. As a new kind of luminescent material, ZnSe/ZnS quantum dots have been used as a luminescent layer in the manufacture of light-emitting diodes (LEDs). Due to the special size effect, the LEDs based on ZnSe/ZnS quantum dots have advantages such as high luminous efficiency, high color rendering index, long service life, low cost and simple processing technology, which has a very broad development prospect.

Figure 2. An example of ZnSe/ZnS quantum dots used in analysis and testing field.

Classification:

According to the solubility, ZnSe/ZnS quantum dots can be divided into water-soluble ZnSe/ZnS quantum dots and non-water-soluble ZnSe/ZnS quantum dots.

• Water-soluble ZnSe/ZnS quantum dots: Water-soluble ZnSe/ZnS quantum dots can be well dispersed in aqueous phase solution and are suitable for the applications in aqueous phase environment, especially in the biological field.
• Non-water-soluble ZnSe/ZnS quantum dots: After modified by hydrophobic ligands, non-water-soluble ZnSe/ZnS quantum dots can be obtained, and the fluorescence emission wavelength can be customized according to requirements.

References

1. Liu, Ni, Xue, et al. ZnSe/ZnS core-shell quantum dots incorporated with Ag nanoparticles as luminescent down-shifting layers to enhance the efficiency of Si solar cells[J]. Journal of Alloys & Compounds An Interdisciplinary Journal of Materials Science & Solid State Chemistry & Physics, 2018. 696-702
2. Mir I A, Rawat K, Solanki P R, et al. ZnSe Core and ZnSe@ZnS Core-Shell Quantum Dots as Platform for Folic Acid Sensing[J]. Journal of Nanoparticle Research, 2017, 19(7):260.