Two-Step Nucleation of CdS Magic-Size Nanocluster MSC–311

Abstract

Nucleation has been generally acknowledged as a rapid but uncontrollable process that is difficult to decouple from the subsequent growth phase. Here, we report our finding that nucleation of semiconductor magic-size clusters (MSCs) can be well-regulated, without a subsequent evolution in size. Colloidal semiconductor CdS MSCs were synthesized by a two-step approach intentionally designed, without the simultaneous formation of nanocrystals of other sizes. The nuclei MSCs exhibit a sharp optical absorption peaking at 311 nm and are thus denoted by MSC−311. We prepared the immediate precursor for MSC−311 denoted by IP311 which is liquid-like, through a reaction which was normally performed to grow CdS conventional quantum dots (QDs), but at a different temperature (180°C) prior to the nucleation and growth of CdS QDs. We demonstrate that the nucleation of MSC−311 from IP311 followed first order kinetics remarkably well, and the presence of a small amount of methanol accelerated this process effectively. Moreover, the liquid-like prenucleation cluster IP311 and the nuclei MSC−311 have similar masses. Accordingly, we propose that the intramolecular reorganization of IP311 results in the nuclei MSC−311, the formation of which features a two-step nucleation pathway. The present study introduces methodology via absorption spectroscopy to monitor the nucleation kinetics of semiconductor MSCs from their immediate precursors. The repeatable, predictable, and controllable nucleation process investigated here brings a deeper insight into nucleation of other semiconductor nanocrystals and contributes to the foundation for the future development of advanced theoretical models for crystal nucleation.

Templated Growth of InP Nanocrystals with a Polytwistane Structure

“…Developing a rational understanding of the growth mechanisms of NCs is necessary to control morphology at the atomistic level. Growing evidence suggests that classical mechanisms are in many cases insufficient to explain the formation of semiconductor NCs . The existence of non‐classical cluster intermediates during crystal growth has been shown to have profound implications on the growth kinetics of NCs .…”

Templated Growth of InP Nanocrystals with a Polytwistane Structure

“…Thea bility to define structure at the nascent stage of nanocrystal (NC) nucleation has enabled the synthesis of awide variety of non-thermodynamic structures,including Al, Ge,and Au clusters, [1][2][3][4][5] metal chalcogenide superlattices, [6][7][8][9] allotropic phases such as e-Co, [10] and molecule-like crystals of InP and CdSe, [11][12][13][14] many of which exhibit unique surface chemistry and optical properties,a nd all of which redefine the classical ideas of material phase and crystal synthesis.Controlling the synthesis of these non-thermodynamic materials using soft-chemical methods presents ap articular challenge.E fforts in the field of semiconductor NC synthesis have revealed colloidal routes to,for example,new allotropes of Si [15] as well as metastable phases of CuInSe 2 [16] and SnS. Thea bility to define structure at the nascent stage of nanocrystal (NC) nucleation has enabled the synthesis of awide variety of non-thermodynamic structures,including Al, Ge,and Au clusters, [1][2][3][4][5] metal chalcogenide superlattices, [6][7][8][9] allotropic phases such as e-Co, [10] and molecule-like crystals of InP and CdSe, [11][12][13][14] many of which exhibit unique surface chemistry and optical properties,a nd all of which redefine the classical ideas of material phase and crystal synthesis.Controlling the synthesis of these non-thermodynamic materials using soft-chemical methods presents ap articular challenge.E fforts in the field of semiconductor NC synthesis have revealed colloidal routes to,for example,new allotropes of Si [15] as well as metastable phases of CuInSe 2 [16] and SnS.…”

“…Thea bility to define structure at the nascent stage of nanocrystal (NC) nucleation has enabled the synthesis of awide variety of non-thermodynamic structures,including Al, Ge,and Au clusters, [1][2][3][4][5] metal chalcogenide superlattices, [6][7][8][9] allotropic phases such as e-Co, [10] and molecule-like crystals of InP and CdSe, [11][12][13][14] many of which exhibit unique surface chemistry and optical properties,a nd all of which redefine the classical ideas of material phase and crystal synthesis.Controlling the synthesis of these non-thermodynamic materials using soft-chemical methods presents ap articular challenge.E fforts in the field of semiconductor NC synthesis have revealed colloidal routes to,for example,new allotropes of Si [15] as well as metastable phases of CuInSe 2 [16] and SnS. [12,[18][19][20] Theexistence of nonclassical cluster intermediates during crystal growth has been shown to have profound implications on the growth kinetics of NCs. Growing evidence suggests that classical mechanisms are in many cases insufficient to explain the formation of semiconductor NCs.…”

“…Growing evidence suggests that classical mechanisms are in many cases insufficient to explain the formation of semiconductor NCs. [12,[18][19][20] Theexistence of nonclassical cluster intermediates during crystal growth has been shown to have profound implications on the growth kinetics of NCs. [18,21,22] These locally stable intermediates,s oc alled magic-sized clusters,are characterized by their molecule-like monodispersity,u nusual stability,a nd in many cases their ability to seed the growth of kinetically accessible nanomaterial morphologies such as nanobelts,p latelets,a nd pyramids.…”

Synthesis of In₃₇P₂₀(O₂CR)₅₁ Clusters and Their Conversion to InP Quantum Dots

“…This is primarily because the nucleation and growth profile of InP nanoparticles follows a non-classical, two-step mechanism 13 . This mechanism is invoked due to the intermediacy of locally stable, atomically precise intermediates known as "magic-sized" clusters 14,15,16 . In particular, In 37 P 20 (O 2 CR) 51 has been identified as one key, isolable intermediate in the synthesis of InP from P(SiMe 3 ) 3 , indium carboxylate, and carboxylic acid 17 .…”