Enhanced Reactivity of Magic-Sized Inorganic Clusters by Engineering the Surface Ligand Networks

Abstract

The carboxylate-ligated In37P20 is an intriguing magic-sized cluster (MSC) whose high stability (i.e., magic size) stems from a delicate balance between the energy cost and gain associated with its partially disordered, In-rich core and its passivation by the bidentate ligands. In order to use such MSCs as intermediates for non-classical nucleation and growth of quantum dots, it is essential to control the reactivity (or stability) of MSCs by disrupting the energetic balance. Here, using ab initio molecular dynamics simulations, we reveal the destabilization process of the InP MSC induced by a modification of the surface ligand network beyond a critical limit. When three In(O2CR)3 subunits are released from the cluster at high temperatures, the remaining In34P20 core suddenly loses its stability and undergoes a structural transformation through In–P bond breaking and rearrangement. The net effect of the isomerization is an In–P bond exchange between a pair of In atoms, thereby leading to a rupture on the cluster surface. We elucidate the mechanism for the MSC instability by studying the intricate interactions between the surface ligand network and the inorganic core. Finally, we discuss the similarity and fundamental differences in the cluster isomerization of group III–V InP and group II–VI CdS MSCs.

Ligand Steric Profile Tunes the Reactivity of Indium Phosphide Clusters

“…Claims of structural homologies have been made by Robinson and co-workers regarding an α-CdS cluster and the In 37 P 20 cluster . This spurred two computational studies by Kang and co-workers investigating the possibility of analogous structures in the two materials systems and why InP does not show the bond exchange isomerization under the same conditions that are observed for CdS. , Despite these computational efforts, there has yet to be a definitive experimental validation of this structural relationship between III–V and II–VI clusters.…”

“…Beyond the study of surface attack-driven conversion, ab initio molecular dynamics calculations have been performed to better understand the initial mechanistic steps in the thermally-induced conversion of clusters. 15 Kang and co-workers identified three indium carboxylate units on the cluster surface, the release of which is what initiates cluster dissolution. Once again, the carboxylate network on the cluster surface is cited as the culprit for directing the structural rearrangement.…”

Mapping the Identity of Transition Metal Doping and Surface Passivation in Indium Phosphide with Theoretical Calculation

“…In 2022, calculations performed by Prins et al proved that the structural relaxation of Cu is most likely ultrafast with a low reorganization energy . In 2023, Shim et al claimed that the instability of the InP MSCs originated from the intricate interactions between the surface ligand network and the inorganic core . Herein, MSCs are useful to indicate the growth trends of how dopants influence doping favorability and manipulate the electronic properties of InP QDs.…”

“…In terms of the requirement for atomically precise control over surface structure and stoichiometry, the magic size clusters (MSCs) composed of a certain number of atoms have been reported as a bridge between early-stage clusters and mature QDs. 9 Recently, density functional theory (DFT) calculations are capable of providing feasibility to investigate the electronic structure of MSCs, which have been structurally studied as intermediates for InP QDs. 10 In 2018, Hassan et al reported that the cluster seed protocol was feasible to obtain Cu 4 :InP on the basis of large-scale DFT calculations.…”

“…12 In 2023, Shim et al claimed that the instability of the InP MSCs originated from the intricate interactions between the surface ligand network and the inorganic core. 9 Herein, MSCs are useful to indicate the growth trends of how dopants influence doping favorability and manipulate the electronic properties of InP QDs. However, most studies have concentrated on the influence of pure InP-or Cu-doped InP MSCs and are lacked of a series of experimental support about different centers like Ag + and Mn 2+ .…”