Syntheses of Indium Phosphide Magic Sized Clusters and Branched Nanostructures

Abstract

Indium phosphide (InP) quantum dots (QDs) are commercially used for a display material, and rational design of high-quality InP nanostructures (NSs) attracts great interest. Magic sized clusters (MSCs) can be isolated as intermediates in QD synthesis, and they provide pivotal clues in understanding QD growth mechanisms. Here, two kinds of chlorine (Cl)-incorporated InP MSCs (F360-InP:Cl MSCs; F399-InP:Cl MSCs) were synthesized. All the MSCs could be directly synthesized from conventional molecular precursors. Alternatively, each series of MSCs could be prepared by sequential conversions. 386-InP MSCs could be converted to F360-InP:Cl MSCs, then to F399-InP:Cl MSCs. As the conversion proceeded, the MSCs bore more QD-like characters. Photo-excited carrier dynamics revealed that 386-InP MSCs and F360-InP:Cl MSCs behave like small molecules whereas F399-InP:Cl MSCs have QD-like characters. To investigate the role of MSCs in the nucleation and growth to InP nanoparticles (NPs) and to find new ways to control the InP NP growth pathways, a kind of InP MSCs (386-InP MSCs) was used as a precursor to InP NPs. A series of heat-up syntheses using 386-InP MSCs were performed as varying the reaction conditions and extra additives. Upon heating, 386-InP MSCs underwent fragmentations before further evolutions. The fragmentations were significantly impeded by extra indium myristate complex and accelerated by extra fatty acids such as myristic acid. Co-use of the both resulted in InP branched nanostructures (BNSs) which include nanorods, pods, hyperbranched NSs and dendrimer-like NSs. Highly anisotropic InP structures such as various BNSs were obtained without using any structure-directing agent. This demonstrates that sophisticated controls over the growth pathways using MSCs offer novel NSs that cannot be attained by conventional synthetic protocols.