Superparamagnetic γ-Fe2O3@SiO2 nanoparticles: a novel support for the immobilization of [VO(acac)2]

Abstract

This work reports a detailed investigation about the physicochemical properties of superparamagnetic gamma-Fe(2)O(3) nanomaterial synthesized by the co-precipitation method and coated with two silica shells, and its application as support for the immobilization of oxovanadium(IV) acetylacetonate ([VO(acac)(2)]). The influence of the silica coatings on the surface composition and physicochemical interactions of the core-shell nanocomposites is discussed based on the combination of several techniques: electron microscopy techniques (SEM and TEM with EDS), DLS, powder XRD, XPS, FTIR and magnetic characterization. The identity of the iron oxide, gamma-Fe(2)O(3), was confirmed by XPS, FTIR and by the Rietveld refinement of the PXRD pattern. The results obtained by electron microscopy techniques, XRD and magnetization indicated that the gamma-Fe(2)O(3) nanoparticles are superparamagnetic and present an average size of approximately 6.5 nm. The first silica coating leads to a core-shell nanomaterial with an average particle size of 21 nm and upon the second coating, the average size increases to 240 nm. Magnetic measurements revealed that the silica-coated nanomaterials maintain the superparamagnetic state at room temperature, although with an expected reduction of the magnetization saturation due to the increase of the silica shell thickness. Furthermore, a numerical fit of the temperature dependence of magnetization was performed to determine the core size distribution and the effect of the silica coatings on the dipolar magnetic interactions. [VO(acac)(2)] was covalently immobilized on the surface of the silica-coated magnetic nanoparticles functionalized with amine groups, as confirmed by chemical analysis and XPS. In a proof-of-principle experiment, we demonstrated the catalytic performance of the novel magnetic hybrid nanomaterial in the epoxidation of geraniol, which presented high selectivity towards the 2,3-epoxygeraniol product and easy recovery by magnetic separation.

Hydrogen production by the water-gas shift reaction using CuNi/Fe2O3 catalyst

“…Based on electroneutrality concepts, the negative shift in BE of the Cu 2p peak in the case of CuNi/Fe 2 O 3 catalyst relative to Cu/Fe 2 O 3 is expected to be accompanied by the shifting of the Ni 2p signal in an opposite direction which was actually observed as discussed above (Fig. The Cu/Fe 2 O 3 catalyst shows two peaks at 529.2 and 529.9 eV, which were attributed to the lattice oxygen of Fe 2 O 3 and CuO, respectively, 24,25 while that at 531.2 eV was attributed to the different oxygen defects. These observations clearly confirmed the formation of CuNi alloy.…”

Synthesis and Characterization of AICAR and DOX Conjugated Multifunctional Nanoparticles as a Platform for Synergistic Inhibition of Cancer Cell Growth

“…After 24 h, FITC-APTES ethanolic solution and 0.3 mL TEOS were added to the first microemulsion under stirring in dark for 24 h. Finally, ethanol was added to destabilize the microemulsion system. The FITC-incorporated silica-coated core− shell [ 22 First, folic acid was conjugated with APTES by an esterification reaction of the carboxyl group with the amine group. In brief, an APTES ester of FA (FA-APTES) was prepared by mixing folate (4.0 mg) with APTES (2.0 μL) in 40 mL dry dimethyl sulfoxide (DMSO) in the presence of NHS (1.1 mg) and DCC (4.7 mg) as the catalyst at room temperature for 2 h. After this, a mixture of Fe 3 O 4 @SiO 2 (FITC) nanoparticles (100 mg), FA-APTES conjugate, and free APTES (17 μL) in toluene (160 mL) was stirred at room temperature for 24 h to introduce FA-APTES conjugate and free APTES (to provide a linker for the subsequent conjugation of both AICAR and DOX) on the surface of silica-coated nanoparticles by hydrolysis and condensation of APTES through silanization.…”

Surfactant-encapsulated polyoxometalate building blocks: controlled assembly and their catalytic properties

“…7,107,108 With the increased control on the size and shape of NCs, the combinatorial properties of the hybrid material strongly depends on size, shape and inherent properties of the supporting material. [109][110][111] A precisely designed nanoscale support can form a perfect synergistic combination between host and guest materials. 112 For example, a carefully engineered support for NCs can result in charge transfer which may be exploited to design functional materials and devices.…”