Mechanistic Study of the Role of Primary Amines in Precursor Conversions to Semiconductor Nanocrystals at Low Temperature

Abstract

Primary alkyl amines (RNH2) have been empirically used to engineer various colloidal semiconductor nanocrystals (NCs). Here, we present a general mechanism in which the amine acts as a hydrogen/proton donor in the precursor conversion to nanocrystals at low temperature, which was assisted by the presence of a secondary phosphine. Our findings introduce the strategy of using a secondary phosphine together with a primary amine as new routes to prepare high-quality NCs at low reaction temperatures but with high particle yields and reproducibility and thus, potentially, low production costs.

Precursor Self‐Assembly Identified as a General Pathway for Colloidal Semiconductor Magic‐Size Clusters

“…This equilibrium is heavily weighted toward the left, but high M‐to‐SeTOP feed molar ratios facilitate its shift to the right due to the coordination between M and TOP . SePPh 2 H is much more reactive than SeTOP .…”

“…Colloidal semiconductor magic‐size clusters (MSCs) are essential to our understanding of the evolution of fundamental properties from molecules to quantum dots (QDs). Semiconductor QDs have emerged as a special class of functional nanomaterials and have attracted a great deal of attention for more than two decades . Interestingly, the current effort on semiconductor nanocrystals (NCs) has marched heavily into application‐oriented research, with limited attention paid to the synthesis of MSCs in a single‐ensemble form without the coexistence of other‐size NCs .…”

“…The presence of MSCs has been associated with the occurrence of sharp peaks at persistent positions in optical absorption . The reactions involved in the formation of M 2 E n RQDs and MSCs and monomers (where M represents monovalent to trivalent cations and E stands for chalcogenides) have been established to be the same, based on the same phosphorus‐containing products monitored by 31 P NMR . However, little has been known about the formation pathway of MSCs.…”

Alloyed CuInS2–ZnS nanorods: synthesis, structure and optical properties

“…We attribute this secondary growth to the changes in the stabilization of the particles, caused by the reaction between oleylamine and oleic acid, which takes place at elevated temperatures in the presence of metal cations. 54,55 In the absence of Zn, it leads to the formation of networks of nanorods. 27 Such strong aggregation is not observed here, indicating a more efficient stabilization of ZCIS, compared to pure CIS nanorods.…”

The synthesis of hollow CuInS2 microspheres with hierarchical structures

“…Many belts appeared on the surface of wurtzite CuInS 2 microspheres prepared at 200 C, while zincblende CuInS 2 microspheres prepared at 220e260 C had only sheets and bulges on their surface. Originated from the thermal decomposition of indium diethyl dithiocarbamates [40,41], the indium intermediates at the elevated temperature are under unstable state. It may possess prior opportunity to transform into zincblende CuInS 2 microspheres directly by the reaction with Cu 2 S, rather than been introduced into Cu 2 S, diffused and extracted from the Cu 2 S nanoparticles to form wurtzite CuInS 2 nanobelts.…”