Synthesis of “Solid Solution” and “Core-Shell” Type Cobalt−Platinum Magnetic Nanoparticles via Transmetalation Reactions

In this article, we report the synthesis of “solid solution” and “core-shell” types of well-defined Co−Pt nanoalloys smaller than 10 nm. The formation of these alloys is driven by redox transmetalation reactions between the reagents without the need for any additional reductants. Also the reaction proceeds selectively as long as the redox potential between the two metals is favorable. The reaction between Co2(CO)8 and Pt(hfac)2 (hfac = hexafluoroacetylacetonate) results in the formation of “solid solution” type alloys such as CoPt3 nanoparticles. On the other hand, the reaction of Co nanoparticles with Pt(hfac)2 in solution results in “CocorePtshell” type nanoalloys. Nanoparticles synthesized by both reactions are moderately monodispersed (σ < 10%) without any further size selection processes. The composition of the alloys can also be tuned by adjusting the ratio of reactants. The magnetic and structural properties of the obtained nanoparticles and reaction byproducts are characterized by TEM, SQUID, UV/vis, IR, EDAX, and XRD

Unsymmetrical and Symmetrical Dipalladium Complexes with Bridging Diphenylsilyl Ligands. Structures of (Me₃P)Pd(μ-SiHPh₂)₂Pd(PMe₃)₂ and [(Me₃P)Pd(μ-SiHPh₂)]₂ in the Solid State and in Solution

Dinuclear palladium complexes with two bridging diphenylsilyl ligands, [(Me3P)Pd(μ-SiHPh2)]2 (1) and (Me3P)Pd(μ-SiHPh2)2Pd(PMe3)2 (2), were prepared and characterized by X-ray crystallography and NMR spectroscopy. The molecular structure of these complexes suggests an agostic interaction between H of μ-SiHPh2 and Pd. The symmetrical structure of 1 in solution is similar to that found in the crystals and is maintained in the temperature range +25 to −90 °C. The temperature-dependent 1H and 31P{1H} NMR spectra of 2 show dynamic behavior of the molecule caused by exchange of the phosphine ligands. The structure observed at −90 °C in the solution is similar to the crystallographic structure

Characterization of Superparamagnetic “Core−Shell” Nanoparticles and Monitoring Their Anisotropic Phase Transition to Ferromagnetic “Solid Solution” Nanoalloys

The structure, magnetism, and phase transition of core−shell type CoPt nanoparticles en route to solid solution alloy nanostructures are systematically investigated. The characterization of CocorePtshell nanoparticles obtained by a “redox transmetalation” process by transmission electron microscopy (TEM) and, in particular, X-ray absorption spectroscopy (XAS) provides clear evidence for the existence of a core−shell type bimetallic interfacial structure. Nanoscale phase transitions of the CocorePtshell structures toward c-axis compressed face-centered tetragonal (fct) solid solution alloy CoPt nanoparticles are monitored at various stages of a thermally induced annealing process and the obtained fct nanoalloys show a large enhancement of their magnetic properties with ferromagnetism. The relationship between the nanostructures and their magnetic properties is in part elucidated through the use of XAS as a critical analytical tool

Langmuir Monolayers of Co Nanoparticles and Their Patterning by Microcontact Printing

In this paper, we describe an easy and reliable method for the production of patterned monolayers of Co nanoparticles. A two-dimensional monolayer of Co nanoparticles is fabricated by spreading a nanoparticle solution over an air−water interface and then transferring it to a hydrophobic substrate by using the Langmuir−Blodgett (LB) method. Transmission electron microscopy (TEM) was used to show that, with increasing surface pressure, the Co nanoparticles become well-organized into a Langmuir monolayer with a hexagonal close-packed structure. By controlling the pH of the subphase, it was found that a monolayer of Co nanoparticles with long-range order could be obtained. Further, by transferring the Langmuir monolayer onto a poly(dimethoxysilane) (PDMS) mold, the selective micropatterning of the Co nanoparticles could be achieved on a patterned electronic circuit. The electronic transport properties of the Co nanoparticles showed the ohmic I−V curve

Redox−Transmetalation Process as a Generalized Synthetic Strategy for Core−Shell Magnetic Nanoparticles

Although multicomponent core−shell type nanomaterials are one of the highly desired structural motifs due to their simultaneous multifunctionalities, the fabrication strategy for such nanostructures is still in a primitive stage. Here, we present a redox−transmetalation process that is effective as a general protocol for the fabrication of high quality and well-defined core−shell type bimetallic nanoparticles on the sub-10 nm scale. Various core−shell type nanomaterials including Co@Au, Co@Pd, Co@Pt, and Co@Cu nanoparticles are fabricated via transmetalation reactions. Compared to conventional sequential reduction strategies, this transmetalation process has several advantages for the fabrication of core−shell type nanoparticles:  (i) no additional reducing agent is needed and (ii) spontaneous shell layer deposition occurs on top of the core nanoparticle surface and thus prevents self-nucleation of secondarily added metals. We also demonstrate the versatility of these core−shell structures by transferring Co@Au nanoparticles from an organic phase to an aqueous phase via a surface modification process. The nanostructures, magnetic properties, and reaction byproducts of these core−shell nanoparticles are spectroscopically characterized and identified, in part, to confirm the chemical process that promotes the core−shell structure formation

Cis and Trans Isomers of Pt(SiHAr₂)₂(PR₃)₂ (R = Me, Et) in the Solid State and in Solutions

trans-Pt(SiHPh2)2(PMe3)2 (1) is prepared from the reaction of H2SiPh2 with cis-PtEt2(PMe3)2 and is characterized by X-ray crystallography. Dissolution of 1 in THF-d8 or CD2Cl2 causes its isomerization into cis-Pt(SiHPh2)2(PMe3)2, which is equilibrated to 1 in the solutions. Temperature-dependent 1H NMR spectra of a mixture of the isomers provided thermodynamic parameters for the trans to cis isomerization, ΔH° = 5.7(3) kJ mol-1 and ΔS° = 6.7(7) J mol-1K-1 in CD2Cl2 and ΔH° = 3.8(2) kJ mol-1 and ΔS° = 3.5(6) J mol-1K-1 at 298 K in THF-d8, respectively. The reactions of H2SiAr2 with Pt(PEt3)4 give cis-Pt(SiHAr2)2(PEt3)2 (2, Ar = C6H5; 3, Ar = C6H4F-p), which are considerably more stable than the trans isomers in CD2Cl2 (ca. 96:4 in an equilibrated CD2Cl2 solution of Pt(SiHPh2)2(PEt3)2 at room temperature)

Supplementary Figures S1-S3. from Apicularen A Induces Cell Death through Fas Ligand Up-Regulation and Microtubule Disruption by Tubulin Down-Regulation in HM7 Human Colon Cancer Cells

Supplementary Figures S1-S3. from Apicularen A Induces Cell Death through Fas Ligand Up-Regulation and Microtubule Disruption by Tubulin Down-Regulation in HM7 Human Colon Cancer Cell