Chemical Considerations for Colloidal Nanocrystal Synthesis

Abstract

We take here the perspective of a nanochemist on the field of colloidal nanocrystals, focusing specifically on nanocrystal synthesis. Considering the three components of a colloidal synthesis, we discuss the chemistry that occurs with precursors, ligands, and solvents. Insight into the coordination chemistry and the organic chemistry of nanocrystal syntheses brings us one step closer to a retro-synthetic analysis of a nanocrystal reaction. We also reflect on different crystallization mechanisms (either under thermodynamic or kinetic control). We consider the possibility that the different models are simply describing different experimental conditions and are not fundamentally at odds with one another. However, we do critically evaluate the use of the terms monomer and burst nucleation. Finally, we discuss good chemical practices for a nanochemist, and we try to define nanocrystal purity. This perspective will hopefully inspire researchers in colloidal nanoscience to think more about chemical equations, consider reaction by-products, and come together as a field to agree on standard reporting practices for colloidal nanocrystals.

Large-Scale Colloidal Synthesis of Chalcogenides for Thermoelectric Applications

“…In the classic hot-injection colloidal synthesis, one can obtain colloidal chalcogenide nanoparticles with narrow size and shape distributions, albeit usually in low quantities on a milligram scale. 20,21 On the other hand, our versatile heatingup colloidal synthesis allows to obtain multigram quantities of highly crystalline and defect-free chalcogenide particles with interesting morphologies just in one run, highlighting the applicability of the synthesis for upscaled production of chalcogenide-based TE materials. Interestingly, the chalcogenide particles synthesized in the current study by heating-up colloidal synthesis demonstrate peculiar morphological appearances, namely, cubic-, tetrapod-, and rod-like shapes for PbTe, PbSe, and SnSe, respectively.…”

“…16 In addition, doping can afford interesting solution-processed TE materials, with maximum ZT ≈ 1.75 at 873 K reached for 3 mol % Ge doping, 17 ZT ≈ 1.7 at 823 K for 2.3 atom % Cd doping, 18 and ZT ≈ 1.05 at 805 K for 2 atom % Te doping. 19 Our laboratory has been exploring colloidal syntheses 20,21 of the chalcogenides in the context of TE applications, wherein the as-synthesized low-dimension particles serve as building blocks for the preparation of either TE thin films with reduced thermal conductivity 22−24 or bulk chalcogenides samples with enhanced ZT. Originally, we developed gram-scale colloidal synthesis of CuInSe 2 particles 25 and then extended the scope of the developed synthesis protocol to the preparation of hexagonal-shaped plate-like Bi 2 Te 2.7 Se 0.3 nanoparticles.…”

Colloidal Approaches to Zinc Oxide Nanocrystals

“…In the context of the established theoretical knowledge, here we provide a brief note on the types of colloidal reactions conducted experimentally. More detailed expositions on this topic may be found in other dedicated reviews. ,− The classical idea of colloid formation involves a short nucleation event to generate the initial nuclei followed by the (slow) growth of these nuclei to their final size. This idea was captured by La Mer and termed “burst nucleation”, which describes a system wherein a very high supersaturation is generated in a short period of time followed by slower continual growth .…”

Solution-Processed Inorganic Thermoelectric Materials: Opportunities and Challenges

“…Colloidal syntheses use surfactants to dissolve the precursors, direct the synthesis, and provide colloidal stability, , enabling the production of particles with an ever-increasing number of elements, the creation of nanoheterostructures with high sophistication levels, , and extraordinary control over size, monodispersity, shape, crystal phase, and even surface termination (Figure ). − …”