Water Dispersible CdSeTe/ZnS Quantum Dots
Product Description
Alfa Chemistry offers CdSeTe/ZnS quantum dot products, which are core/shell fluorescent nanomaterials with CdSeTe as the core, ZnS as the shell layer, and hydrophilic ligands wrapped on the surface, with an average quantum yield of 40%. We can provide our customers with different grams of products at any wavelength from 640 nm to 820 nm.
Features
The product has the characteristics of uniform particle size, broad absorption spectrum, symmetric emission spectrum, high and stable fluorescence intensity.
There are three main types of functionalized modifications of quantum dots as follows:
1. Surface ligand exchange, using water-soluble groups of ligands to replace the ligands on the surface of hydrophobic quantum dots.
2. Polymer wrapping, the hydrophobic part of the polymer molecules and the quantum dot surface of the long-chain alkanes through the van der Waals interaction between the formation of micelles and wrapped quantum dots.
3. Silica layer wrapping, which generally replaces the hydrophobic ligands on the surface of quantum dots with silanes containing sulfhydryl groups.
Types of Water-soluble CdSeTe/ZnS Quantum Dots
(1) Carboxyl group with negative charge on the surface, 3-mercaptopropionic acid as a capping agent.
(2) Carboxyl groups with negatively charged surfaces and amphiphilic polymers as capping agents.
(3) Carboxyl groups with negatively charged surfaces, containing PEG chains with excellent biocompatibility for attachment of antibody proteins with amino groups.
(4) Amino groups with positive charge on the surface, containing PEG chains, excellent biocompatibility, and can be attached to antibody proteins with carboxyl groups.
Applications
Biosensors
Near-infrared (NIR) quantum dot (QD) films for cholesterol detection were investigated by Stewart et al. Water-soluble 2-(dimethylamino)ethylene glycol (DAET)-protected 800 nm CdSeTe/ZnS core-shell QDs were prepared and incorporated into chitosan films. NIR electrochemiluminescence (ECL) of QD/chitosan films upon reaction with H2O2 (produced as a byproduct of cholesterol oxidase catalyzed oxidation of cholesterol) at -1.35 V. Ag/AgCl contrast produced a strong ECL signal. The sensor shows a linear response in the clinically relevant range (0.25 ≤ [cholesterol] ≤ 5 mM), allowing rapid detection of cholesterol.
Fig.1 Schematic diagram of CdSeTe/ZnS quantum dot biosensor. (Stewart et al., 2015)
Detection of Cu2+
To reduce toxicity and maintain high PL intensity, Shen et al. prepared CdSeTe@ZnS-SiO2 Qdots (HQdots) by a microwave-assisted method to fill ZnS-like clusters into SiO2 shells. The ZnS doped into the SiO2 shell can greatly improve the PL properties of the Qdots and passivate their surfaces. Meanwhile, SiO2 and ZnS facilitate the reduction of cytotoxicity. Microwave irradiation is environmentally friendly and energy efficient, and it can provide uniform nucleation and growth conditions. It can greatly reduce the reaction time and improve the PL intensity in preparation. As a result, the nucleoshell HQdots have an intense and tunable luminescence with low toxicity. In addition, the HQdots have been applied to the detection of Cu2+.
Fig.2 Synthetic pathway for the preparation of CdSeTe@ZnS–SiO2 Qdots. (Shen et al., 2012)
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References
- Stewart, A. J. , et al. A Cholesterol Biosensor Based on the NIR Electrogenerated-Chemiluminescence (ECL) of Water-Soluble CdSeTe/ZnS Quantum Dots[J]. Electrochimica Acta, 2015, 157(23).
- Shen, Y. , et al. Microwave-assisted synthesis of highly luminescent CdSeTe@ZnS-SiO2 quantum dots and their application in the detection of Cu(II)[J]. Chemical Communications, 2012, 48(16):2222-2224.
* It should be noted that our service is only used for research, not for clinical use.
