Generally, CdSe cores in water solution have low fluorescence quantum yields (QY) due to surface-related trap states. However, this problem can be solved by growing wide band gap semiconducting shells around the core, such as zinc sulphide (best shell material for CdSe cores).
A complete line of Core(CdSe or CdSSe)/Shell(ZnS) QD in solid form are available from Strem. These products are sold as mixtures in organic solvents and water, despite the hydrophobic organic ligand coatings. A suitable surface coating provides stability in aqueous solutions and functionalizes the QDs for further surface modification. The emission wavelengths of QDs range from 450 nm (blue) to 665 nm (red), resulting in high quantum yield (>50%) and have narrow full-width half-maximum (FWHM).
https://www.strem.com/uploads/technical_notes/48-1610tech.pdf
Contact the team on 01223 873028 or enquiries@strem.co.uk for further information