Palladium(0) Nanoparticle Formation, Stabilization, and Mechanistic Studies: Pd(acac)(2) as a Preferred Precursor, [Bu4N](2)HPO4 Stabilizer, plus the Stoichiometry, Kinetics, and Minimal, Four-Step Mechanism of the Palladium Nanoparticle Formation and Subsequent Agglomeration Reactions

Date

2016-04-19

Author

Özkar, Saim

Metadata

Show full item record

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Item Usage Stats

131
views

0
downloads

Palladium(0) nanoparticles continue to be important in the field of catalysis. However, and despite the many prior reports of Pd(0)(n) nanoparticles,, missing is a study that reports the kinetically controlled formation of Pd(0)(n) nanoparticles with the simple stabilizer [Bu4N](2)HPO4 in an established, balanced formation reaction where the kinetics and mechanism of the nanoparticle-formation reaction are also provided. It is just such studies that are the focus of the present work. Specifically, the present studies reveal that Pd(acac)(2), in the presence of 1 equiv of [Bu4N](2)HPO4 as stabilizer in propylene carbonate, serves as a preferred precatalyst for the kinetically controlled nucleation following reduction under 40 +/- 1 psig initial H-2 pressure at 22.0 +/- 0.1 degrees C to yield 7 +/- 2 nm palladium(0) nanoparticles. Studies of the balanced stoichiometry of the Pd(0)(n) nanoparticle-formation reaction shows that 1.0 Pd(acac)(2) consumes 1.0 equiv of H-2 and produces 1.0 equiv of Pd(0)(n) while also releasing 2.0 +/- 0.2 equiv of acetylacetone. The inexpensive, readily available HPO42- also proved, to be as effective a Pd(0)(n) nanoparticle stabilizer as the more anionic, sterically larger, "Gold Standard" stabilizer P2W15Nb3O629-. The kinetics and associated minimal mechanism of formation of the [Bu4N](2)HPO4-stabilized Pd(0)(n) nanoparticles are also provided, arguably the most novel part of the present studies, specifically the four-step mechanism of nucleation (A -> B, rate constant k(1)), autocatalytic surface growth (A + B -> 2B, rate constant k(2)), bimolecular agglomeration (B + B -> C, rate constant k(3)), and secondary autocatalytic surface growth (A + C -> 1.5C, rate constant k(4)), where A is Pd(acac)(2), B represents the growing, smaller Pd(0)(n) nanopartieles, and C represents the larger, most catalytically active Pd(0)(n) nanoparticles. Additional details on the mechanism and catalytic properties of the resultant Pd(0)(n)center dot HPO42- nanoparticles are provided in this work.

Subject Keywords

Spectroscopy, Electrochemistry, General Materials Science, Surfaces and Interfaces, Condensed Matter Physics

URI

https://hdl.handle.net/11511/36165

Journal

LANGMUIR

DOI

https://doi.org/10.1021/acs.langmuir.6b00013

Collections

Department of Chemistry, Article

Suggestions

OpenMETU
Core

Encapsulated Hydrogels by E-beam Lithography and Their Use in Enzyme Cascade Reactions Mancini, Rock J.; Paluck, Samantha J.; Bat, Erhan; Maynard, Heather D. (American Chemical Society (ACS), 2016-04-26) Electron beam (e-beam) lithography was employed to prepare one protein immobilized hydrogel encapsulated inside another by first fabricating protein-reactive hydrogels of orthogonal reactivity and subsequently conjugating the biomolecules. Exposure of thin films of eight arm star poly(ethylene glycol) (PEG) functionalized with biotin (Biotin PEG), alkyne (Alkyne-PEG) or aminooxy (AO-PEG) end groups to e-beam radiation resulted in cross-linked hydrogels with the respective functionality. It was determined vi...
In Situ Formed "Weakly Ligated/Labile Ligand" Iridium(0) Nanoparticles and Aggregates as Catalysts for the Complete Hydrogenation of Neat Benzene at Room Temperature and Mild Pressures Bayram, Ercan; Zahmakiran, Mehmet; Özkar, Saim; Finke, Richard G. (American Chemical Society (ACS), 2010-07-20) "Weakly ligated/labile ligand" nanoparticles, that is nanoparticles where only weakly coordinated ligands plus the desired catalytic reactants are present, are of fundamental interest. Described herein is a catalyst system for benzene hydrogenation to cyclohexane consisting of "weakly ligated/labile ligand" Ir(0) nanoparticles and aggregates plus dry-HCl formed formed in situ from commercially available [(1,5-COD)IrCl](2) plus 40 +/- 1 psig (similar to 2.7 atm) H(2) at 22 +/- 0.1 degrees C. Multiple control...
Liposomal Nanoreactors for the Synthesis of Monodisperse Palladium Nanoparticles Using Glycerol Clergeaud, Gael; Genc, Rukan; Ortiz, Mayreli; O'Sullivan, Ciara K. (American Chemical Society (ACS), 2013-12-10) The synthesis of highly stable ultrasmall monodisperse populations of palladium nanoparticles in the range of 1-3 nm in size was achieved via polyol reduction within 1,2-dioleoyl-sn-glycero-3-phosphor-rac(1-glycerol) liposomal nanoreactors exploiting glycerol as both reducing and stabilizing agent. The liposome-based green method was compared with synthesis in solution, and the reducing agent concentration and the lipidic composition of the liposomal nanoreactors were demonstrated to have a strong effect on...
Industrial Ziegler-Type Hydrogenation Catalysts Made from Co(neodecanoate)(2) or Ni(2-ethylhexanoate)(2) and AlEt3: Evidence for Nanoclusters and Sub-Nanocluster or Larger Ziegler-Nanocluster Based Catalysis Alley, William M.; Hamdemir, Isil K.; Wang, Qi; Frenkel, Anatoly I.; Li, Long; Yang, Judith C.; Menard, Laurent D.; Nuzzo, Ralph G.; Özkar, Saim; Yih, Kuang-Hway; Johnson, Kimberly A.; Finke, Richard G. (American Chemical Society (ACS), 2011-05-17) Ziegler-type hydrogenation catalysts are important for industrial processes, namely, the large-scale selective hydrogenation of styrenic block copolymers. Ziegler-type hydrogenation catalysts are composed of a group 8-10 transition metal precatalyst plus an alkylaluminum cocatalyst (and they are not the same as Ziegler-Natta polymerization catalysts). However, for similar to 50 years two unsettled issues central to Ziegler-type hydrogenation catalysis are the nature of the metal species present after cataly...
Active Janus Particles at Interfaces of Liquid Crystals Mangal, Rahul; Nayani, Karthik; Kim, Young-Ki; Büküşoğlu, Emre; Cordova-Figueroa, Ubaldo M.; Abbott, Nicholas. L. (American Chemical Society (ACS), 2017-10-17) We report an investigation of the active motion of silica palladium Janus particles (JPs) adsorbed at interfaces formed between nematic liquid crystals (LCs) and aqueous phases containing hydrogen peroxide (H2O2). In comparison to isotropic oil aqueous interfaces, we observe the elasticity and anisotropic viscosity of the nematic phase to change qualitatively the active motion of the JPs at the LC interfaces. Although contact line pinning on the surface of the JPs is observed. to restrict out-of-plane rotat...

Citation Formats

S. Özkar, “Palladium(0) Nanoparticle Formation, Stabilization, and Mechanistic Studies: Pd(acac)(2) as a Preferred Precursor, [Bu4N](2)HPO4 Stabilizer, plus the Stoichiometry, Kinetics, and Minimal, Four-Step Mechanism of the Palladium Nanoparticle Formation and Subsequent Agglomeration Reactions,” LANGMUIR, pp. 3699–3716, 2016, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/36165.