Under microwave irradiation, we systematically studied the formation of transition metal ions (TM), Ag+,
Mn2+, Cu2+, Fe2+, Co2+ and Ni2+, doped CdS semiconductor nanocrystals in a pure water solution. The center-doping strategy
is essential for achieving efficient internal-doping to improve the optical properties and stability of doped nanocrystals.
The resulting TM doped nanocrystals have a high photoluminescence quantum yield (~ 60%) and an amazingly large
range of the visible spectrum (480 ~ 650 nm). For Mn2+ doped CdS nanocrystals, significant high photoluminescence
quantum yield, between 20% and 50% even at more than 600 nm, was achieved and there is potential for them to be directly
used as a consummate toner for multicolor sensing and encoding without ligand exchange. Highly emissive-doped
nanocrystals synthesized under designed conditions have been found to have excellent stability; samples could be stored
for months without precipitation. In practice, this approach has great potential to promote the metal doping of various
semiconductor nanocrystals to realize the specific advantages of doped nanocrystals in water solution.