QMG is a group of water soluble CdSSe/ZnS or CdSe/ZnS quantum dots with amphiphilic polymer and PEG coating. There is not any surface functional group on the surface of the nanocrystals. The zeta potential of QMG is from -10mV to 0. The thickness of the total organic layers is about 6 nm. The hydrodynamic size of the nanocrystals is about 12-14 nm larger than their inorganic core size measured by TEM. The colloidal stability of QMG is exceptionally high. It is stable in most buffer solutions in the pH range of 3-14.