QSQ is a group of water soluble alloy CdSSe/ZnS or CdSe/ZnS core/shell quantum dots with amphiphilic polymer and polydiallydimethylammounium chloride (PDDA) coating. There is no linkable reactive group on the surface of QSQ. The zeta potential of QSQ is more than +50 mV. Their organic layers consist of a monolayer of oleic acid/octadecylamine, a monolayer of amphiphilic polymer and a monolayer of PDDA. The thickness of the total organic layers is about 8 nm. The hydrodynamic size of the QDs is about 14-16 nm larger than their inorganic core size measured by TEM.
QSQ is very stable in most buffer solutions in the pH range of 5-10.