In-situ liquid phase TEM observations of nucleation and growth processes

Abstract

Nucleation and growth of crystals is a pervasive phenomenon in the synthesis of man-made materials, as well as mineral formation within geochemical and biological environments. Over the past two decades, numerous ex situ studies of crystallization have concluded that nucleation and growth pathways are more complex than envisioned within classical models. The recent development of in situ liquid phase TEM (LP-TEM) has led to new insights into such pathways by enabling direct, real-time observations of nucleation and growth events. Here we report results from LP-TEM studies of Au nanoparticle, CaCO3 and iron oxide formation. We show how these in situ data can be used to obtain direct evidence for the mechanisms underlying crystallization, as well as dynamic information that provides constraints on important kinetic and thermodynamic parameters not available through ex situ methods.

Electrophoretic and potentiometric signatures of multistage CaCO3 nucleation

“…We observed signatures of multistage nucleation dynamics in the time-evolution of the aqueous composition and z-potential consistent with the initial precipitation of metastable vaterite that subsequently transforms into calcite via dissolution of the former and recrystallization of the latter, consistently with the previously reported sequence [29]. [2,[11][12][13][14][15][16][17], (ii) dehydration and local ordering [21][22][23][24][25][26] (iii) precipitation-dissolution transformation or spherulitic growth [28][29][30][31][32][33], and finally (iv) formation of the most stable CaCO3 mineral. In Panel (b) we show a schematic diagram of the electrical double layer formed at the carbonate/NaClelectrolyte interface.…”

Further insights into the Fe(ii) reduction of 2-line ferrihydrite: a semi in situ and in situ TEM study

“…20,21,23,[29][30][31] Development of LC TEM and the environmental TEM, as well as their use over the last couple of decades, has revolutionized the way we have understood nucleation pathways of nanoparticles; their coalescence; nano-crystal growth and dissolution; shape and crystal face evolution; nano-particle solution dynamics; electrochemical reactions and some biological processes. [32][33][34][35][36][37][38][39] However, to the best of the author's knowledge, the biotic or abiotic reduction of FH (or other iron(III) oxyhydroxides) with Fe(II) (aq) via the use of LC TEM has not yet been investigated. Some hydrogen gas reduction of FH to MG via in situ TEM has been reported by Hummingbird Scientic 40 but to date, no literature exists for such reactions in liquids via semi in situ or in situ in LC TEM.…”

In Situ Techniques for Probing Kinetics and Mechanism of Hollowing Nanostructures through Direct Chemical Transformations

“…It becomes extremely challenging to in situ probe the hollowing process of colloidal nanoparticles in volatile liquids, which easily vaporize under the low pressure of EM operation to damage the microscopes. Benefiting from the significant advance in microfabrication and materials engineering, miniaturized cells have been successfully fabricated to place liquid dispersions of colloidal nanoparticles in TEM chambers for in situ study . A typical in situ TEM liquid cell is constructed with two electron‐transparent Si 3 N 4 films of < 100 nm in thickness, which are separated to provide a thin space (usually < 200 nm) to host the desired colloidal nanoparticle dispersions.…”

“…Benefiting from the significant advance in microfabrication and materials engineering, miniaturized cells have been successfully fabricated to place liquid dispersions of colloidal nanoparticles in TEM chambers for in situ study. [53,[108][109][110][111][112] A typical in situ TEM liquid cell is constructed with two electrontransparent Si 3 N 4 films of < 100 nm in thickness, which are separated to provide a thin space (usually < 200 nm) to host the desired colloidal nanoparticle dispersions. The exceptional mechanical strength of the thin Si 3 N 4 films enables them to well seal the dispersion liquids in the high-vacuum TEM chambers.…”