Quantum Dots

What about this?

Quantum dots are crystalline clumps of a few hundred atoms, coated with an insulating outer shell of a different material [1]. When a photon of visible light hits such a minute particle, a quantum-physics reflect confines all the photon’s energy to the crystal core before being emitted as an extraordinary bright fluorescence. The QDs absorb light at a wide range of wavelengths, but emit almost monochromatic light of a wavelength that depends on the size of the crystals [2]. The visualization properties of quantum dots (fluorescence wavelength) are strongly size dependent. The optical properties of quantum dots depend upon their structure as they are composed of an outer shell and a metallic core. Quantum dot core is usually made up of cadmium selenide, cadmium sulfide, or cadmium telluride. The outer shell is fabricated on the core with high band gap energy in order to provide electrical insulation with preservation of fluorescence properties of quantum dots. The fine-tuned core and shells with different sizes and compositions with visualization properties of specific wavelength provide a large number of biomarkers [3]. Quantum dots are conjugated with different ligands in order to obtain specific binding to biological receptors. Quantum dots offer significant advantages over the conventional dyes such as narrow bandwidth emission, higher photostability, and extended absorption spectrum for the single excitation source. Moreover, the challenge of hydrophobicity in quantum dots has been overcome by making them water soluble. An example of the aqueous quantum dots with long retention time in biological fluids is the development of highly fluorescent metal sulfide (MS) quantum dots fabricated with thiol-containing charged groups [4].


If we illuminate a quantum dot with UV light, an electron in the QD can be excited and it will change to a state of higher energy! The excited electron can drop into the valence band relasing its energy by the emission of light. The color of that light depends on the energy difference between the conductance band and the valence band.

How to synthesize a QDs?

Here we explain the method to synthesize the QD.

Figure 1. Diagram of Schlenk sintesis for QDs core CdSe [6].

Figure 2. Diagram of SILAR technique for QDs shell Zn [7].

Figure 3. Diagram of conjugation of spike protein antibodies to QDs via oxidized Fc-carbohydrate groups [8].

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Nanotechnology can be exploited to improve the utility of fluorescent markers used for diagnostic purposes. They can be filled with a large number of imaging particles such as optically active compounds and radionuclides for the detection with imaging equipment. Although fluorescent markers are routinely used in basic research and clinical diagnostic applications, there are several inherent disadvantages with current techniques, including the requirement of color-matched lasers, the fluorescence bleaching, and the lack of discriminatory capacity of multiple dyes. Fluorescent nanocrystals potentially overcome these issues [2].

. • QDs are used in LEDs and solid state lightning, displays and photovoltaics owing to their bright colors and their ability to emit rainbow of colors coupled with their high efficiencies, longer lifetimes and high extinction coefficient.
• Another application for QDs is owing to being zero dimensional and having a sharper density of states than higher dimensional structures and it is including transistors, solar cells, ultrafast all-optical switches and logic gates, among others.
• The particular size of QDs allow them to go anywhere in the body what makes them suitable for different biomedical applications like imaging and biosensors.


1) Sanjeeb, K. and Vinod, L. (2003) Nanotech approaches to drug delivery and imaging. Elsevier Science. 24, 1116-1117
2) Chan, W.C. et al. (2002) Luminescent quantum dots for multiplexed biological detection and imaging. Curr. Opin. Biotechnol. 13, 40–46
3) Mitchell, P. (2001) Turning the spotlight on cellular imaging. Nat. Biotechnol. 19, 1013–1017
4) Mohs, A. and Provenzale, J. (2010) Applications of nanotechnology to imaging and therapy of brain tumors. Neuroimaging Clin N Am 20(3), 283–292
5) Shih, W., Shih, W., Li, H., Schillo, M. (2009) Water soluble quantum dots. Google Patents.
6) Luengo, J. et. al. (2017) Estudio de mojabilidad y caracterización del sistema pdms - vidrio en dispositivos microfluídicos. AFA 28, 10-14.
7)Asim N., et.al. (2014) Research and development aspects on chemical preparation techniques of photoanodes for dye sensitized solar cells. International Journal of Photoenergy.
8)Feng, W., et. al. (2016) Ultra Sensitive Detection of Influenza A Virus Based on Cdse/Zns Quantum Dots Immunoassay. SOJ Biochemistry.