Introduction to Quantum Dots
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- Time of issue:2016-08-25
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(Summary description)In recent years, with the rapid development of nanotechnology, "nano" has gradually become a familiar term in life, and is no longer limited to the field of scientific research. This can more or less explain people's interest in nanotechnology and also explain nanotechnology. Unconsciously, it is gradually affecting the lives of human beings. As the basis of nanotechnology, nanomaterials have some special effects (quantum size effect, surface effect, macroscopic quantum tunneling effect, etc.), which gives it many new characteristics that macroscopic bulk materials do not have, and makes people have a better understanding of materials science. A new understanding.
Introduction to Quantum Dots
(Summary description)In recent years, with the rapid development of nanotechnology, "nano" has gradually become a familiar term in life, and is no longer limited to the field of scientific research. This can more or less explain people's interest in nanotechnology and also explain nanotechnology. Unconsciously, it is gradually affecting the lives of human beings. As the basis of nanotechnology, nanomaterials have some special effects (quantum size effect, surface effect, macroscopic quantum tunneling effect, etc.), which gives it many new characteristics that macroscopic bulk materials do not have, and makes people have a better understanding of materials science. A new understanding.
- Categories:Company News
- Author:
- Origin:
- Time of issue:2016-08-25
- Views:0
In recent years, with the rapid development of nanotechnology, "nano" has gradually become a familiar term in life, and is no longer limited to the field of scientific research. This can more or less explain people's interest in nanotechnology and also explain nanotechnology. Unconsciously, it is gradually affecting the lives of human beings. As the basis of nanotechnology, nanomaterials have some special effects (quantum size effect, surface effect, macroscopic quantum tunneling effect, etc.), which gives it many new characteristics that macroscopic bulk materials do not have, and makes people have a better understanding of materials science. A new understanding. There are many types of nanomaterials, and the most researchers are concerned about colloidal nanocrystals (colloidal nanocrystals). Colloidal nanocrystals (hereinafter referred to as "nanocrystals") refer to nano-sized crystals synthesized in a solution and dispersed in the solution. By adjusting the chemical composition, size and morphology of nanocrystals, its various properties can be adjusted. This makes nanocrystals the basis for the construction of new functional materials, such as fluorescent probes based on semiconductor nanocrystals (quantum dots), and Magnetic nanocrystals and quantum dot-based multifunctional probes that integrate magnetic separation and fluorescent labeling are also important reasons for people's interest in them.
Before the 1990s, people had been able to prepare some nanocrystals, of which Au nanocrystals were more classic. However, at this time, people did not have a deep understanding of the formation process of nanocrystals, and lack of relevant theories to guide the synthesis of various high-quality monodisperse nanocrystals. Until the early 1990s, the Brus research group and the Bawendi research group reported a new method for preparing CdSe nanocrystals from organometallic compounds in high-temperature organic phases, and obtained monodisperse CdSe nanocrystals with adjustable size, providing a new type of nanocrystals. Crystal synthesis route. On this basis, the Alivisatos research group proposed the "focusing of size distribution" theory in the synthesis of nanocrystals, and studied how to prepare high-quality monodisperse nanocrystals. And guidance on the synthesis of nanocrystals. Since then, nanocrystals have entered a new stage of high-speed development. Today, the synthesis technology of nanocrystals has been relatively mature, and high-quality nanocrystals with adjustable sizes and morphologies have been successfully synthesized, such as magnetic nanocrystals, fluorescent nanocrystals, Metal nanocrystals, etc. These nanocrystals will have huge application prospects in the fields of biomedicine, optoelectronic devices and catalysis.
Quantum dots usually refer to semiconductor nanocrystals with a radius smaller than or close to the Bohr radius of the exciton. The smaller the particle size of the quantum dot, the greater the quantum confinement effect of the excitons, the greater the corresponding fluorescence energy, and the shorter the emission wavelength1 (Figure 1). Since the bulk band gap widths of semiconductor crystals of different materials are different, by changing the composition and size of the quantum dots, quantum dots with different emission wavelengths from the visible light region to the near-infrared light region can be obtained (Figure 1).
图1. (A) Size- and material-dependent emission spectra of several surfactant-coated semiconductor nanocrystals in a variety of sizes. The blue series represents different sizes of CdSe nanocrystals with diameters of 2.1, 2.4, 3.1, 3.6, and 4.6 nm (from right to left). The green series is of InP nanocrystals with diameters of 3.0, 3.5, and 4.6 nm. The red series is of InAs nanocrystals with diameters of 2.8, 3.6, 4.6, and 6.0 nm. (B) A true-color image of a series of silica-coated core (CdSe)-shell (ZnS or CdS) nanocrystal probes in aqueous buffer, all illuminated simultaneously with a handheld ultraviolet lamp1.
在应用于生物成像时，量子点具有一些优异的特性2-6：荧光发射波长具有尺寸依赖性，可通过调控量子点的粒径以得到不同发射波长;激发光谱较宽(图2，虚线)，可用一种激发波长激发多种不同发射波长的量子点;荧光半峰宽比较窄(图2，实线)，应用于多色成像时，可以减少不同荧光发射光谱之间的重叠，降低它们之间的干扰;荧光稳定性好(图3)，可用于长时间成像。
图2. Excitation (dashed) and fluorescence (solid) spectra of a typical water-soluble nanocrystal (NC) sample in PBS. The NC was excited at 355 nm. Excitation spectra were collected with detection 533 nm (NC). The nanocrystals have a narrow emission, no red tail, and a broad, continuous excitation spectrum2.
Photostability comparison between QDs and Alexa 488. Quantitative analysis of changes in intensities of QD 608–streptavidin (stained microtubules) and Alexa 488–streptavidin (stained nuclear antigens) using specimens mounted with glycerol or antifade mounting medium Vectashield. Mean fluorescence intensity was automatically measured every 10 s for 3 min6.
尽管目前为止，有各种各样的量子点出现，但基于CdSe的量子点依旧是目前研究最广泛和最成熟的，已被广泛应用于生物医学成像、光电显示、LED以及太阳能电池等领域。
参考文献
1. Fu AH, Gu WW, Larabell C, Alivisatos AP. Semiconductor nanocrystals for biological imaging. Curr Opin Neurobiol. 2005;15:568-75.
2. Bruchez M, Moronne M, Gin P, Weiss S, Alivisatos AP. Semiconductor nanocrystals as fluorescent biological labels. Science. 1998;281:2013-6.
3.Alivisatos AP. Semiconductor clusters, nanocrystals, and quantum dots. Science. 1996;271:933-7.
4. Michalet X, Pinaud FF, Bentolila LA, Tsay JM, Doose S, Li JJ, et al. Quantum dots for live cells, in vivo imaging, and diagnostics. Science. 2005;307:538-44.
5. Wu X, Liu H, Liu J, Haley KN, Treadway JA, Larson JP, et al. Immunofluorescent labeling of cancer marker Her2 and other cellular targets with semiconductor quantum dots. Nat Biotech. 2003;21:41-6.
6. Medintz IL, Uyeda HT, Goldman ER, Mattoussi H. Quantum dot bioconjugates for imaging, labelling and sensing. Nat Mater. 2005;4:435-46.
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