Water Dispersible CdTe/CdSe/ZnS Quantum Dots
Alfa Chemistry provides water dispersible CdTe/CdSe/ZnS quantum dot products are CdTe as the core, CdSe and ZnS as the shell layer, the surface is wrapped by hydrophilic ligands core/shell/shell type fluorescent nanomaterials, the average quantum yield≧ 40%. Storage should avoid direct sunlight, 4 degrees sealed dark storage, can be customized for customers to produce 620-820 nm any wavelength of different grams of products. The product has the characteristics of uniform particle size, broad absorption spectrum, symmetric emission spectrum, high and stable fluorescence intensity.
Samanta et al. demonstrated the aqueous synthesis of colloidal nanocrystalline heterostructures consisting of a CdTe core wrapped by a CdS/ZnS or CdSe/ZnS shell. Near-infrared emission at peak wavelengths up to 730 nm was obtained by tuning the core size and shell thickness of CdTe/CdSe/ZnS nanocrystals. These methods can provide a simple, ultra-fast and continuous approach to prepare core/shell/shell quantum dots with enhanced oxidation resistance and stability. The internal CdTe/CdS and CdTe/CdSe heterostructures have type I, quasi-type II, or type II band shifts, depending on the size of the core and the thickness of the shell, and the external CdS/ZnS and CdSe/ZnS structures have type I band shifts. It was found that the emission maxima of the assembled heterostructures depend on the size of the CdTe core, with a wider range of spectral tunability observed for smaller cores. Due to the encapsulation effect, the formation of a continuous shell leads to a significant increase in photoluminescence quantum yield; however, to achieve the maximum quantum yield, the optimal shell thickness needs to be determined. Photoluminescence lifetime measurements show that the decrease in quantum yield of thick-shelled nanocrystals is caused by a large decrease in the radiation rate constant. By adjusting the diameter of the core and the thickness of each shell, a wide range of nanocrystal heterostructures with high quantum yields (up to 45%) were obtained with emission ranging from visible to near-infrared wavelengths (500-730 nm). This versatile way to design the optical properties of nanocrystal heterostructures will provide new opportunities for bioimaging and biomarker applications.
Fig.1 Schematic diagram of CdTe/CdSe/ZnS synthesis. (Samanta et al., 2012)
Biological Light Harvesting Complex Service
The light-harvesting complex (LHCII) of the plant photosynthesis apparatus is attached to type II core-shell CdTe/CdSe/ZnS nanocrystals (quantum dots, QD) that have an absorption band at 710 nm with a dihydrolipoic acid coating to facilitate water solubility.LHCII retains its function upon binding to the QD surface and greatly enhances the light utilization of the QD, similar to its role in light-harvesting function in photosynthesis. The fluorescence quenching of the donor (LHCII) and the sensitized emission of the acceptor (QD) showed an electron excitation energy transfer efficiency of about 50%, which was confirmed by time-resolved fluorescence measurements. The energy transfer efficiency is commensurate with the expected efficiency calculated on the basis of the estimated donor-acceptor separation according to Foster's theory. Light collection is particularly efficient in the red spectral domain where QD absorption is relatively low. Excitation of the entire visible spectrum was further improved by attaching a dye to the biopigments in LHCII; the dye was selected to absorb in the "green gap" of the LHCII absorption spectrum and to transfer its excitation energy eventually to the QD.
Fig.2 Schematic diagram of the bio-photocapture complex as an energy donor for semiconductor quantum dots. (Werwie et al., 2012)
Alfa Chemistry can provide a variety of complex and customized fluorescent quantum dot products. Our products involve a variety of fluorescent quantum dot products. Alfa Chemistry provides products with high fluorescence quantum yield, stable quality and relatively low price. Our products are constantly updated. If the product you need is not in our catalog, please feel free to contact us, we provide relevant custom services.
- Samanta, A. , Z. Deng , and A. Y. Liu . Aqueous synthesis of glutathione-capped CdTe/CdS/ZnS and CdTe/CdSe/ZnS core/shell/shell nanocrystal heterostructures.[J]. Langmuir the Acs Journal of Surfaces & Colloids, 2012, 28(21):8205.
- Werwie, M. , et al. Bio Serves Nano: Biological Light-Harvesting Complex as Energy Donor for Semiconductor Quantum Dots[J]. Langmuir, 2012, 28(13):5810-5818.
* It should be noted that our service is only used for research, not for clinical use.