Expanding the Mechanochemical Toolbox: Combining X-Ray Absorption Spectroscopy and Scattering for in Situ Time-Resolved Monitoring of Gold Nanoparticle Mechanosynthesis

Abstract

<div>The development of time-resolved in situ approaches for monitoring mechanochemical</div><div>transformations has revolutionized the field of mechanochemistry. Currently, the established in</div><div>situ approaches greatly limit the scope of investigations that are possible. Here we develop a new</div><div>approach to simultaneously follow the evolution of bulk atomic and electronic structure during a</div><div>mechanochemical synthesis. This is achieved by coupling two complementary synchrotron-based</div><div>X-ray methods: X-ray absorption spectroscopy and X-ray diffraction. We apply this method to</div><div>investigate the bottom-up mechanosynthesis of technologically important Au nanoparticles in the</div><div>presence of three different reducing agents. Moreover, we demonstrate how X-ray absorption</div><div>spectroscopy offers unprecedented insight into the early stage generation of growth species (e.g.</div><div>monomers and clusters), which lead to the subsequent formation of nanoparticles. These</div><div>processes are beyond the detection capabilities of diffraction methods. The approach is general,</div><div>and not limited to monitoring NP mechanosynthesis. This combined X-ray approach paves the</div><div>way to new directions in mechanochemical research of advanced electronic materials.</div>

Role of Mixing and Milling in Mechanochemical Synthesis (Review)

“…Interest in the study of mechanochemical reactions directly in apparatuses in the in-situ/operando mode has splashed in recent years. There is a very wide range of instrumental methods that allow one to monitor the composition and structure of the reaction mixture at all transformation stages, detect intermediate products, and control the temperature; it includes, in particular, diffraction [96, 170-174, 192, 193, 197-212], Raman spectroscopy [154,[213][214][215], X-ray spectroscopy [216,217], and solid-state NMR [218]. Special designs of apparatuses for mechanical exposure have been proposed to be both combined with laboratory instruments and installed at workstations in synchrotron research centers [218][219][220][221].…”

In situ Study of Au Nanoparticle Growth in a Mechanochemical-Aging-Based Synthesis

“…[26,27] Conversely, in the solid state, there is a good understanding of the kinetics of mechanochemical gold reduction, from in depth in situ studied by powder X-ray diffraction (PXRD) [28] and X-ray absorption spectroscopy (XAS). [29] Our group has also presented the first theoretical model for AuNP nucleation under mechanochemical conditions, which introduced a ballistic term as a way to parametrize the role of mechanical energy in the formation of amine-stabilized AuNPs. [30] Yet data on NP formation and transformation is still lacking.…”

The mechanochemical excitation of crystalline LiN3

“…3 TRIS X-ray powder diffraction has been widely used to follow the formation and consumption of crystalline phases as a function of milling time, [4][5][6][7] and it has recently provided insights into the role of structural defects in activating mechanochemical transformations. 8,9 By using TRIS X-ray absorption spectroscopy 10 and optical fluorescence spectroscopy 11 changes in the electronic structure of matter can be followed during mechanochemical transformations. Additionally, vibrational [12][13][14][15][16] and NMR spectroscopies 17 provide insight into the evolution of molecular structure during milling.…”