Controlling Allotropism in Ruthenium Nanoparticles: A Pulsed-Flow Supercritical Synthesis and in Situ Synchrotron X-ray Diffraction Study

Abstract

Ruthenium nanoparticles have been synthesized by a novel pulsed-flow supercritical method using ethanol both as solvent and reducing agent. To improve the understanding of the formation and growth of Ru nanoparticles, the synthesis processes were also studied by in situ synchrotron radiation powder X-ray diffraction (SR-PXRD). Both the face-centered cubic (fcc) structure and the hexagonal close packed (hcp) structure of Ru can be synthesized in phase pure form by controlling the reaction conditions. When Ru(acac)3 is used as the precursor, fcc Ru is formed at a reaction temperature of 200 °C, while the hcp structure appears at higher temperatures. For syntheses with RuCl3 as the precursor, pure hcp Ru forms at all temperatures investigated, but an intermediate, yet unidentified, compound is detected in the reaction process at 200 °C. Both the pulsed-flow experiments and the in situ SR-PXRD experiments show that the reduction of the RuCl3 precursor proceeds faster than the reduction of the Ru(acac)3 precursor. Overall, the pulsed-flow supercritical approach provides a facile, green, and rapid synthesis of Ru nanoparticles with complete control of the allotropy.

In situ total X-ray scattering study of the formation mechanism and structural defects in anatase TiO2 nanoparticles under hydrothermal conditions

“…When different precursors are used for hydrothermal synthesis, it is often observed that the product has specific characteristics, e.g. [9][10][11][12][13] In particular, a few studies have been devoted to the study of TiO 2 crystallization and growth by in situ synchrotron PXRD under solvothermal, hydrothermal or sol-gel conditions. However, the processes occurring during the formation of nanoparticles are not well understood, and this, to a large extent, prevents rational synthesis of new materials.…”

Supercritical Flow Synthesis of Pt1–xRuxNanoparticles: Comparative Phase Diagram Study of Nanostructure versus Bulk

“…For Ru nanoparticles (x = 1) the unit cell parameters for the hcp phase are reported to slightly exceed the present data. In the studies by Mi et al, 10,11,37 the precursor Ru(acac)3 resulted in a mixture of fcc and hcp Ru at all temperatures (200-400°C) whereas for the RuCl3, pure hcp phase was consistently observed. This suggests that the formation of hcp Ru nanoparticles presumably progresses through a reactions path mediated by anions.…”

“…ethanol plus triethylene glycol resulted in pure fcc Ru. 37,39 Using ethanol with butanediol produced mixtures of the two crystal phases. 37,58 This likely hinges on the reported temperature-controlled reaction behavior of organic solvents at solvothermal condition.…”

“…37,39 Using ethanol with butanediol produced mixtures of the two crystal phases. 37,58 This likely hinges on the reported temperature-controlled reaction behavior of organic solvents at solvothermal condition. 35 Elemental The morphology of the particles has been studied by TEM in all samples.…”

In Situ Synchrotron X‐ray Characterization Shining Light on the Nucleation and Growth Kinetics of Colloidal Nanoparticles

“…This represents a typical example highlighting the importance of kinetic control on determining the shape of NPs. Similar in situ WAXS studies were also applied to the synthesis of NPs of varying materials including Ag, Ru, carbon‐supported Pt, silver halides, Cu 2− x S, CoSb 2 O 4 , yttrium/ytterbium aluminium garnet(Y 3− x Yb x Al 5 O 12 ), Fe 3 N/Fe 3 C, and TiO 2 …”