Synthesis of size-controlled colloidal InAs quantum dots using triphenylarsine as a stable arsenic source

Colloidal indium arsenide (InAs) quantum dots (QDs) were synthesized by heating an organometallic solution containing the easy-to-handle arsenic source triphenylarsine and indium tribromide in a mixture of oleylamine, tri-n-octylphosphine and octadecene. The one-pot reaction was heated at 320 °C to give spherical, monodisperse QDs in less than 15 min; the size of the QDs was controlled in the range from 3 to 6 nm by changing the reaction time. Tetrahedral QDs composed of four enclosed {111} faces of zincblende InAs were obtained after reaction for 30 min. The dependence of the shape of the QDs on reaction time was rationalized in terms of the adsorption strength of the capping ligand. The obtained QDs exhibited size-dependent optical gaps and PL emission, indicating narrow size distribution and good crystal quality. Because the PL emission exhibited a large Stokes shift of 100-200 meV, the electronic transition responsible for the PL emission was related to defects inside the QDs, and must involve the relaxation of excited electrons at the quantized electron state 1S_e because of the large size-dependent energy variation.