Synthesis of Monodisperse InP Quantum Dots: Use of an Acid-Free Indium Carboxylate Precursor.

The role of indium carboxylate precursors in the synthesis of monodisperse InP quantum dots was investigated. The reaction between acid-free indium palmitate and tris(trimethylsilyl)phosphine (P(TMS)3) was monitored by using high-temperature 31P NMR, indicating the presence of a single molecular phosphorus species throughout the duration of the reaction. The addition of varying amounts of carboxylic acid and its effects on both the reaction kinetics and the optical properties of InP QDs were studied. In the presence of acid, rapid protonation of P(TMS)3 led to the formation of a mixture of four HxP(TMS)3-x species, resulting in the poorer controlled formation of InP nanocrystals. Upon deposition of a gradated ZnSeS shell on the synthesized InP core, luminescent quantum dots were obtained (QY 67%; PL: FWHM 40 nm).