Confined Pt and CoFe₂O₄Nanoparticles in a Mesoporous Core/Shell Silica Microsphere and Their Catalytic Activity

Abstract

Confined Pt and CoFe 2 O 4 nanoparticles (NPs) in a mesoporous core/shell silica microsphere, Pt-CoFe 2 O 4 @meso-SiO 2 , were prepared using a bi-functional linker molecule. A large number of Pt NPs in Pt-CoFe 2 O 4 @meso-SiO 2 , ranging from 5 to 8 nm, are embedded into the shell and some of them are in close contact with CoFe 2 O 4 NPs. The hydrogenation of cyclohexene over the Pt-CoFe 2 O 4 @meso-SiO 2 microsphere at 25 o C and 1 atm of H 2 yields cyclohexane as a major product. In addition, it gives oxygenated products. Control experiments with 18O-labelled water and acetone suggest that surface-bound oxygen atoms in CoFe 2 O 4 are associated with the formation of the oxygenated products. This oxidation reaction is operative only if CoFe 2 O 4 and Pt NPs are in close contact. The Pt-CoFe 2 O 4 @meso-SiO 2 catalyst is separated simply by a magnet, which can be re-used without affecting the catalytic efficiency.

A Highly Stable and Magnetically Recyclable Nanocatalyst System: Mesoporous Silica Spheres Embedded with FeCo/Graphitic Shell Magnetic Nanoparticles and Pt Nanocatalysts

“…The resulting Pt-immobilized FeCo/GC@MSS( Pt-FeCo/GC@MSS) is annealed at 300 8Ct oi mprove the crystallinity of Pt nanoparticles and ensure the stronga dhesion of the nanoparticles on the silica surface. [21] Figure 2a shows the transmission electron microscopy( TEM) images of the uniform Pt-FeCo/GC@MSS.T he small dots that originated from % 5.6 nm FeCo/GC nanocrystals and % 3. Figure 2c clearly shows the lattice fringeso ft he bcc-FeCo (d spacing = 2.02 for a( 110) reflection) and the fcc-Pt (d spacing = 2.26 f or a( 111)r eflection), while as ingle-layer graphitic carbon shell on the FeCo core is not observed duet ot he presence of silica.…”

“…It has been known that Pt and CoFe 2 O 4 nanoparticles, when they are in close contact with each other within mesopores,c an oxidize cyclohexene in the absence of oxidant. [21] The presence of oxideso nt he surface of FeCo was not detected from the Ramans pectrum of Pt-FeCo@MSS due to the small amount and low crystallinity of the oxides (see Figure S1 in the SupportingI nformation). [39] However, it has been proven that FeCo is easily oxidized from the surfacew hen it is exposed to the air.…”

“…[20] They can also provide an oxygen source in catalytic reactions, eventually giving unexpected mixturep roducts. [21] It has been reported that uncoated magnetite nanoparticles are not inert in some catalytic processes when they are functionalized with organo-catalysts through direct bindingt ot he surface. The background catalysis by the magnetic nanoparticles led to am arked drop in the activity and selectivity of the organocatalyst.…”

Cerium oxide-deposited mesoporous silica nanoparticles for the determination of carcinoembryonic antigen in serum using inductively coupled plasma-mass spectrometry

“…The analytical technique developed in this work offers the advantage of long linear dynamic range by ICP-MS and high sensitivity by magnetic concentration. In addition, it has a potential for multiplex detection because the deposited CeO 2 can be substituted by other metals or metal oxides, such as CoFe 2 O 4 or Pt [19]. Since the method used the immunoreaction through antigen-antibody reaction, the cross-reactivity was tested against ceruloplasmin with similar functionality.…”

Au nanoparticle@hollow mesoporous carbon with FeCo/graphitic shell nanoparticls as a magnetically recyclable yolk–shell nanocatalyst for catalytic reduction of nitroaromatics

“…Among various magnetic materials, iron oxides have been most widely used as supports in catalysis because of their low cost and easy preparation 11 . However, iron oxides are not desirable for certain applications because they are inherently unstable in acidic media 12 , 13 , not inert in some catalytic processes 14 – 16 , not very strong in magnetic properties ( M s of bulk magnetite ≤92 emu g −1 ) 17 , and can provide an oxygen source in catalytic reactions, eventually giving unexpected product mixtures 18 . To circumvent such problems, graphitic carbon-coated metal NPs with very strong magnetic properties have been used as magnetic materials for magnetically recoverable catalysis.…”