Colloidal InP nanocrystals as efficient emitters covering blue to near-infrared

High quality InP nanocrystals in the size range from 1 to 8 nm were synthesize at relatively low temperature (< 190 degrees C). The low temperature was enabled by the activation of In carboxylate precursors with fatty amines. The reduced temperature enabled the elimination of the thorough degassing step usually needed in the existing schemes. By simply varying the concentration and chain length of the ligand and activation reagents, the absorption peak position was tuned continuously from 390 to 720 nm without prolonged heating. This new synthetic scheme further enabled the direct synthesis of InP/ZnS core/shell nanocrystals in a one-pot fashion. The resulting InP/ZnS core/shell nanocrystals can emit from about 450 to 750 nm, with a quantum yield as high as over 40%. The bright core/shell nanocrystals were stable in air and could be dispersed in water with hydrophilic thiols ligands. The thiol ligand replacement did not quench the emission, and the resulting water-soluble nanocrystals were stable under ambient conditions for at least 3 months.