Quantum Dots

What is Quantum Dots?

Quantum dots are zero-dimensional nano-semiconductor materials, and their particle size is generally less than 10 nm. Common quantum dots include nanocrystals, atomic clusters and some nanosemiconductor devices, which are generally composed of II-VI or III-V elements. Due to the small particle size (1-10 nm) of quantum dots, quantum dots have many properties that macroscopic materials do not possess, such as small size effect, surface effect, quantum size effect, etc. The effects of these nanomaterials enable quantum dots to have good optical properties, which are mainly reflected in narrow emission peaks, wide absorption peaks, high luminous efficiency, stable luminescence properties, and repeatable excitation. Moreover, due to the quantum confinement effect, quantum dots have a wide range of excitation wavelengths, so they can be excited by light waves with wavelengths shorter than the emission wavelength. The position of the emission wavelength can also be adjusted by changing the size of the quantum dots, so that the emission wavelength covers the entire visible light region. Quantum dots have novel electronic and optical properties and can be used in many important fields, such as optoelectronics, catalysis, and biology.

Figure 1. Fluorescence emission of quantum dots CdSe

What are the Application of Quantum Dots?

• Quantum Dots for Biological Field: In the field of live cell imaging, quantum dot-labeled immunoglobulin can specifically identify membrane proteins on the cell surface, microtubules in the cytoplasm and antigenic substances in the nucleus. In this regard, quantum dots have stable fluorescence properties, which provide convenience for tumor detection and diagnosis. In the field of molecular probes, quantum dots can also detect heavy metal ions.
• Quantum Dots for Optoelectronics Field: After compounding quantum dots with excellent fluorescence properties and organic/polymer luminescent materials, high-performance electroluminescent devices with high color purity, narrow band and tunable in the visible light range can be obtained. Quantum dot fluorescent devices have the advantages of good luminescence performance and long service life. The application of quantum dot materials in solar cells can effectively modify and replace both the electron transport layer and the hole transport layer, which greatly improves the conversion efficiency and other related properties of solar cells.
• Quantum Dots for Catalysis Field: Noble metal nanoparticles are widely used due to their excellent catalytic performance, but the main synthesis method of noble metal nanoparticles is chemical reduction method, which is usually cumbersome and time-consuming, and the reagents have certain pollution. When the new carbon quantum dots are applied to the synthesis process of noble metal nanoparticles, the carbon quantum dots not only act as reducing agents, but also act as stabilizers in the solvent, making the whole reaction process simple, fast and environmentally friendly.
• Quantum Dots for Security Field: Nano-sized quantum dots have the advantages of sensitive optical properties, wide and flexible surface modification space and uniform dispersion. The introduction of quantum dots in fingerprint display can optically mark fingerprint residues and improve the sensitivity of the display method.

Reference:

1. Chang-Yeol Han, Hyun-Sik Kim, Heesun Yang. Quantum Dots and Applications [J]. Materials, 2020, 13(4), 897.