Quantum dot is a kind of nano material that is soluble in water and the size of the nanometer grain is between 1 nm to 100 nm. Quantum dot has a neat arrangement of atoms which is similar to that of bulk phase crystals. Quantum dots have many characteristics. First, quantum dots have a wide excitation wavelength range and a narrow emission wavelength range. Second, the emission peak of quantum dots is narrow and symmetric. Third, the emission wavelength of quantum dots can be tuned by controlling the size and composition. Fourth, quantum dots have high fluorescence intensity and the stability is high. Fifth, after chemical modification, the biocompatibility of quantum dots is excellent, which can be applied in biological fields. The chemical, optical and catalytic properties of quantum dots can be improved obviously by modifying the surface appropriately. Based on quantum size effect, quantum dots show many physical and chemical properties that different from those of macroscopic bulk materials.
Based on the excellent optical properties and special photoelectric properties, quantum dots are widely used in the field of life science and semiconductor devices.
- Fluorescent labeling field: Fluorescent dye molecules have been widely used in cell biology to label cells and quantum dot is an important dye in this field. With extremely excellent fluorescent stability, quantum dots can be applied for real-time monitoring and intracellular processes tracking. In addition, multiple target molecules can be observed by quantum dots with different colors, which can be used to study how their biological functions are realized inside the cell and how they are related to each other.
Figure 1. An example of quantum dot applied in fluorescent labeling field.
- Biological analysis field: Based on the mechanism of electrochemiluminescence (ECL), quantum dots can be applied in the field of biological analysis for immune analysis and nucleic acid analysis. In the field of biological analysis, quantum dots are usually used as ECL luminescence agents to achieve multi-component biological analysis. However, it also faces some practical problems such as biotoxicity, low sensitivity, non-specific binding and high working potential. These problems can be effectively solved by wrapping quantum dots with biocompatible molecules with low toxicity or by synthesizing quantum dots with low toxicity.
Figure 2. An example of quantum dot applied in biological analysis field.
- Drug delivery carrier system field: Due to the large specific surface and easy modification by multiple ligands, water-soluble quantum dots can be conjugated with drug molecules in the way of electrostatic binding or covalent binding to form a nano-drug carrier system. Furthermore, the fluorescence tracer study of drug molecules in cells or animals can be realized.
- Semiconductor device field: Quantum dots are also widely used in semiconductor devices, such as quantum dot lasers, quantum dot sensitized solar cells, quantum dot infrared detectors and the others.
There are many ways to classify quantum dots. According to the geometric shapes, quantum dots can be divided into box quantum dots, spherical quantum dots, tetrahedral quantum dots, cylindrical quantum dots, cubic quantum dots, disk-shaped quantum dots and external field induced quantum dots.
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- Gae Baik Kim and Young-Pil Kim. Analysis of Protease Activity Using Quantum Dots and Resonance Energy Transfer[J]. Theranostics, 2012.
- Cristian, T, Matea, et al. Quantum dots in imaging, drug delivery and sensor applications.[J].International journal of nanomedicine, 2017.