Precursor and Surface Reactivities Influence the Early Growth of Indium Oxide Nanocrystals in a Reagent-Driven, Continuous Addition Synthesis

Abstract

The structural attributes and structure-dependent properties of metal oxide nanocrystals are often defined during the earliest stages of nanocrystal growth. The species formed early in the growth process are notoriously difficult to study due to their small size and rapidly changing structures. Thus, despite many studies on the formation and initial growth of nanocrystals, little is known about how to control these steps during synthesis. Here, we investigate how the choice of reagentoleyl alcohol or oleylamineinfluences the earliest stages of indium oxide nanocrystal growth in a reagent-driven, continuous addition synthesis. The metal oxide precursor is activated through reaction with the reagent (through amidation or esterification) as opposed to thermal decomposition. Amidation proceeds faster than esterification, and this difference has a significant influence on the early steps of nanocrystal formation and growth. Fewer, larger nanocrystals are formed in the presence of oleylamine whereas more, but smaller, nanocrystals are formed in oleyl alcohol. Our studies suggest that differences in surface reactivity in the presence of the two reagents influence the transition from nanocrystal formation to growth. In the case of oleylamine, the reagent activates the surface of the nanocrystal through amidation reactions that expose more reactive metal hydroxyl species. Due to the higher concentration of these species, the rate of attachment of activated precursor to existing nanocrystals outpaces the rate of condensation of precursors to form new nanocrystals. As a result, the formation of new particles ends earlier in oleylamine than it does in oleyl alcohol, resulting in fewer particles being formed in the presence of amine. When mixtures of the amine and alcohol are used, the reactions also proceed through reagent-driven, rather than thermally driven, growth, and the ratio of reagents can be used to control the number of nanocrystals formed.

Nanoporous oxide electrodes for energy conversion and storage devices

“…Secondly, nanoporous oxides also include structures with pores formed within the volume space of matrices due to nanostructured architectures, which encompass a wider range. 13 These nanostructured oxides can exhibit various morphologies, such as nanoparticles, 14 nanowires, 15 nanotubes, 16 or nanosheets. 17 Furthermore, they can be diversified into distinct nanostructures that are advantageous in increasing the surface-to-volume ratio and accelerating the transport routes of mediators such as charge and light.…”

Unraveling the molecular and growth mechanism of colloidal black In2O3−x

“…The addition of OLAM producing pristine particles and no indium metal (although its role as reducing agent is well docu-mented), suggests it follows a much faster amidation analogue of path 2. 45,48,54 Hutchison and co-workers assessed the use of primary amine vs. primary alcohol in the preparation of In 2 O 3 and found that primary amines reacted much faster than the alcohol. 54 To validate this report, we performed the same 2 mL volume test by using OLAM instead of OLOH; analyzing aliquots at the same interval with NMR as the OLOH trials seen in Fig.…”

“…45,48,54 Hutchison and co-workers assessed the use of primary amine vs. primary alcohol in the preparation of In 2 O 3 and found that primary amines reacted much faster than the alcohol. 54 To validate this report, we performed the same 2 mL volume test by using OLAM instead of OLOH; analyzing aliquots at the same interval with NMR as the OLOH trials seen in Fig. S18.…”

Colloidal Synthesis of Monodisperse High-Entropy Spinel Oxide Nanocrystals

“…To test this hypothesis we modified literature procedures where metal carboxylates are reacted with alcohols to produce metal hydroxides (metal oxide monomers) via an esterification pathway (Table S1). − Assuming the Lewis acid character of the metal centers is the major factor determining esterification and thus precursor decomposition rate, we hypothesized that achieving HEO nanocrystals should be possible by choosing metals with similar electronegativities.…”