In Situ Small-Angle X-ray Scattering from Pd Nanoparticles Formed by Thermal Decomposition of Organo-Pd Catalyst Precursors Dissolved in Hydrocarbons

Abstract

The generation and growth of nanoparticles by thermal decomposition of organo-Pd precursors in toluene solution has been studied using in situ small-angle X-ray scattering. The results show that detectable concentrations of particles begin to form at solution temperatures above 130 °C, and both the size and volume of the particles increase with heating temperature and time. The radius of the particles detected ranges from 0.5 ± 0.1 nm to a few nanometers, depending on the temperature and heating time. The structure of the particles was probed by measurement of pair distribution functions, which demonstrated that the particles have structure identical to bulk metallic Pd. The identification of the particles as metallic Pd was confirmed by X-ray absorption near-edge structure spectroscopy, and transmission electron microscopy.

Operando Grazing Incidence Small-Angle X-ray Scattering/X-ray Diffraction of Model Ordered Mesoporous Lithium-Ion Battery Anodes

“…The scattered intensity at high q should arise from the NiCo 2 O 4 nanoparticles that comprise the mesoporous framework in these thin films. The scattering intensity, I ( q ), was expressed using standard decoupling approximation for analysis of nanoparticles as I ( q ) = N (Δρ) 2 F ( q ) S ( q ), − where q is the momentum transfer vector defined as q = (4π/λ) sin θ, N is the particle number density, Δρ is the electronic density contrast, λ is the X-ray wavelength, θ is one-half of the scattering angle, F ( q ) is the form factor, and S ( q ) is the structure factor. The shape, size, and polydispersity of NiCo 2 O 4 nanoparticles are described by F ( q ), and S ( q ) describes the positional correlation between particles.…”

Particle formation mechanisms supported by in situ synchrotron XAFS and SAXS studies: a review of metal, metal-oxide, semiconductor and selected other nanoparticle formation reactions

“…Too often presently mechanisms are claimed based on qualitative data or 'snapshots' and sometimes cartoons of what size particles are present at what times. These qualitative schematic models or just word-based pictorial models [189][190][191][192][193][194][195][196][197] are of some use, but are not, and should not be confused with, disproof-based, minimum mechanisms expressed in balanced reactions as detailed in Tables 1 and 2.…”

Palladium Acetate Trimer: Understanding Its Ligand-Induced Dissociation Thermochemistry Using Isothermal Titration Calorimetry, X-ray Absorption Fine Structure, and 31P Nuclear Magnetic Resonance

“…The stability and configuration of the metal complex and the ligand complex − interactions in specific solvent environments have significant effects on the Pd nanoparticle synthesis kinetics and catalytic properties. ,− However, little is known about the Pd 3 (OAc) 6 trimer’s dissociation into monomers in a nucleophilic environment and the binding of such monomers with donor ligands (e.g., phosphines). Challenges of such dissociation studies are as follows: (1) the comparatively high thermodynamic stability of Pd 3 (OAc) 6 trimer in a noncoordinating solvent and (2) even mild heating to facilitate the dissociation can lead to simultaneous reduction of Pd­(II) into Pd(0) . In contrast, coordinating solvents (e.g., pyridine) can break the trimers and form Pd­(OAc) 2 (solv) 2 monomers, which makes the phosphine ligand binding to Pd a ligand substitution instead of the ideal Pd­(OAc) 2 –phosphine binding. , The substitution may also modify the electronic properties of the Pd center and trigger other undesired reactions. ,− Therefore, a direct method for measurements of Pd 3 (OAc) 6 dissociation and consecutive binding of Pd­(OAc) 2 with ligands is required.…”

“…Challenges of such dissociation studies are as follows: (1) the comparatively high thermodynamic stability of Pd 3 (OAc) 6 trimer in a noncoordinating solvent and (2) even mild heating to facilitate the dissociation can lead to simultaneous reduction of Pd(II) into Pd(0). 21 In contrast, coordinating solvents (e.g., pyridine) can break the trimers and form Pd(OAc) 2 (solv) 2 monomers, which makes the phosphine ligand binding to Pd a ligand substitution instead of the ideal Pd(OAc) 2 −phosphine binding. 7,22 The substitution may also modify the electronic properties of the Pd center and trigger other undesired reactions.…”