In situultra-small-angle X-ray scattering study of the solution-mediated formation and growth of nanocrystalline ceria

Abstract

Results are presented for an in situ synchrotron-based ultra-small-angle X-ray scattering (USAXS) study of the solution-mediated formation and growth of nanocrystalline ceria (n-CeO 2 ) using a new remote-controlled, isothermal, circulating fluid flow cell. The fluid flow mitigates or reduces X-ray beaminduced damage, air bubbles or particulate flocculation within the bulk solution, but prevents any coarse particulates that do form from settling out from suspension. Combined with the large-scale range accessible in USAXS studies, the flow cell has enabled measurement, in situ and in real time, of structural characteristics from 10 Å to a few micrometres in size as a function of the changing physical and chemical conditions. By applying a multi-component model, the nanoparticle formation and growth component has been identified. Control and online monitoring of flow rate, temperature and pH suspension conditions have permitted real-time studies of the formation and growth of the individual n-CeO 2 particles from homogeneous dilute solution over several hours. Aspects of the nanoparticle nucleation and growth are revealed that have not been observed directly in measurements on this system. research papers J. Appl. Cryst. (2008). 41, 918-929 Andrew J. Allen et al. USAXS study of nanocrystalline ceria 919 research papers J. Appl. Cryst. (2008). 41, 918-929 Andrew J. Allen et al. USAXS study of nanocrystalline ceria 921 research papers J. Appl. Cryst. (2008). 41, 918-929 Andrew J. Allen et al. USAXS study of nanocrystalline ceria 925 Figure 6Volume-weighted mean, median and mode diameters, and numberweighted mean diameter for the principal particle population versus reaction time at (a) 308 K, (b) 298 K and (c) 293 K. Capped vertical bars are the estimated standard deviation uncertainties. The lines are logarithmic fits to the data, plotted from the time that a discernible principal particle volume fraction can be detected.

Size dependent compressibility of nano-ceria: Minimum near 33 nm

“…'s former students Sungjoo Kim, Joan Raitano, and Feng Zhang for their initial investigations. We thank Alastair MacDowell, Jinyuan Yan, and Andrew Doran for their help and guidance at LBL-ALS 12 …”

“…It is thought that the cage-like structure of HMT may play a role in directing the formation of particularly small and uniform nanoparticles. 12 Some of the resulting nanoceria was annealed in air (typically for two hours at temperatures ranging from 500 to 700 C with fast heating and cooling times) to coarsen the particles, and in this way moderately uniform nanocrystallite sizes from 15-100 nm were realized. X-ray diffraction (XRD) scans were performed on an Inel XRG 3000 diffractometer with a curved detector using Cu-K a1 radiation.…”

“…Details of homogeneous nucleation and subsequent uniform growth of nanoceria has been previously captured by synchrotron in-situ small angle x-ray scattering with flow cell and temperature control. 12 Initial nanoparticle sizes are typically in the range of 6-12 nm, depending on aqueous mixing time. It is thought that the cage-like structure of HMT may play a role in directing the formation of particularly small and uniform nanoparticles.…”

Challenges for physical characterization of silver nanoparticles under pristine and environmentally relevant conditions

“…[29][30][31] Experiments were performed at ambient temperature (approximately 25 C). The instrument is described in detail elsewhere.…”

In Situ Synchrotron X‐Ray Techniques for Real‐Time Probing of Colloidal Nanoparticle Synthesis

“…Both examples clearly show that the existence of templates significantly changes the nucleation and growth of nanoparticles. In addition to the metal nanoparticles, formation of colloidal nanoparticles made of oxides including SiO 2 , ZnO, CeO 2 , etc. has also been studied with in situ SAXS characterization.…”