A complexant-assisted hydrothermal procedure for growing well-dispersed InP nanocrystals

Well-dispersed InP nanocrystals have been synthesized via a hydrothermal reaction of In–ethylenediamine tetraacetic acid (EDTA) complex with red phosphorus and KBH₄ in aqueous solution at 160–200 °C for 26 h. The InP nanocrystals were characterized by powder X-ray diffraction (XRD), Raman spectroscopy and transmission electron microscopy (TEM). The XRD patterns showed (1 1 1), (2 0 0), (2 2 0), (3 1 1), (2 2 2), (4 0 0) and (3 3 1) diffraction lines of the cubic InP nanocrystals. The TEM study revealed that the morphology of InP nanocrystals are of well-dispersed spherical shape. The size of InP nanocrystals can be controlled by changing the reaction temperature. The average InP nanocrystallites diameter is increased from 8.7 to 15.8 nm as the temperature increases from 160 to 200 °C. The Raman spectrum showed the transverse-optic (TO) and longitudinal-optic (LO) mode from InP nanocrystallites, and the LO and TO modes shift to lower frequencies with a decrease in the size of InP nanocrystals. The EDTA plays a key role in the nucleation and growth of InP nanocrystals, and the reaction mechanism is discussed.