Nanoparticles encapsulation

Prior to inclusion of PVP-protected Pt nanoparticles the SBA-15 silica is calcined at 823K for 12h to remove residual templating polymer. Removal of PVP is required for catalyst activation. Due to the decomposition profile of PVP (Figure 6), temperatures > 623 K were chosen for ex situ calcination of Pt/SBA-15 catalysts. Ex-situ refers to calcination of 300-500 mg of catalyst in a tube furnace in pure oxygen for 12-24 h at temperatures ranging from 623 to 723 K (particle size dependent) [13]. Catalysts were activated in He for 1 h and reduced at 673 K in H2 for 1 h. After removal, the particle size was determined by chemisorption. Table 2 is a summary of chemisorption data for Cl catalysts as well as nanoparticle encapsulation (NE) catalysts (see description of these samples in proceeding section). 

Three-Dimensional Deposition of Pt Nanoparticles by Nanoparticle Encapsulation... 

The mechanical incorporation of active nanoparticles into the silica pore structure is very promising for the general synthesis of supported catalysts, although particles larger than the support s pore diameter cannot be incorporated into the mesopore structure. To overcome this limitation, pre-defined Pt particles were mixed with silica precursors, and the mesoporous silica structures were grown by a hydrothermal method. This process is referred to as nanoparticle encapsulation (NE) (Scheme 2) [16] because the resulting silica encapsulates metal nanoparticles inside the pore structure. 

For reaction conditions for capillary inclusion series, see Ref. [13]. For reaction conditions for nanoparticle encapsulation series, see Ref [16]. 

Table 4. Ag/Pt molar ratio and its influence on ethylene hydrogenation rates and apparent activation energy for nanoparticle encapsulated shape-controlled Pt nanoparticles [17].

Table 6. Cyclohexene hydrogenation-dehydrogenation rates on Pt/SBA-15 nanoparticle encapsulation catalyst series [18].

Cu-CuO% nanoparticles (with a content of about 10 wt.%) on titania are effective for the production of hydrogen under sacrificial conditions [176-178], A fairly low concentration of Cu (2.5 wt.%) was sufficient to allow promising H2 production from ethanol-water and glycerol-water mixtures in the case of CuO% nanoparticles encapsulated into porous titania [179]. A key limitation of this system is photocorrosion under oxidizing conditions (oxygen and carboxylic adds as by-products of partial oxidation of the sacrificial agent). However, in the presence of UV irradiation, Cu photodeposition can occur, preventing loss of Cu [179]. 

Modena, T., Conti, B. and Pavanetto, F. (2002) Effect of nanoparticle encapsulation on the photostability of the sunscreen agent,2-ethylhexyl-p-... 

TEM images of carbon filaments produced by decomposition of NG over Fe(10 wt%)/Al203 catalyst at 850°C. (a) Carbon filaments with embedded iron nanoparticles, (inset b) high-resolution TEM image of the wall of a carbon filament, and (c) = an iron nanoparticle encapsulated in carbon layers at the tip of a carbon filament. 

As an example of the latter technique, Volkman et al. demonstrated the feasibility of using spin-cast zinc oxide nanoparticles encapsulated in 1-dodecanethiol to fabricate a functional transistor.44 The zinc oxide was deposited on a thermally grown silicon dioxide layer on a conventional silicon wafer, with thermally evaporated gold source and drain electrodes. As reported, the process requires very small particles (3nm or less) and a 400 °C forming gas anneal. A similar approach was also reported by Petrat, demonstrating n-channel thin-film transistor operation using a nanoparticle solution of zinc oxide dispersed onto a thermally grown silicon dioxide layer on a conventional... 

Nanoparticles encapsulating 5-flurouracil were prepared by coacervation using cellulose derivatives [121]. An ethano-lic solution of ethyl cellulose was desolvated by stirring in distilled water producing particles with an average diameter of 472 nm, as determined using scanning electron... 

Bringley JF, Penner TL, Wang R, Harder JF, Harrison WJ, Buonemani L (2008) Silica nanoparticles encapsulating near-infrared emissive cyanine dyes. J Colloid Interface Sci 320 132-139... 

Fig. 5.18 Schematic and TEM image of reaction scheme to prepare metal nanoparticles encapsulated within metal oxide coating on oxidized MWCNTs. Metal NPs are added to developing metal alkoxide sol followed by addition of oxidized MWCNTs and water for hydrolysis. Adapted with permission from [228], (2012) American Chemical Society.

Zhou, X.S., et al., Self-assembled nanocomposite of silicon nanoparticles encapsulated in graphene through electrostatic attraction for lithium-ion batteries. Advanced Energy Materials, 2012. 2(9) p. 1086-1090. 

M.D. Chavanpatil, Y. Patil, and J. Panyam. Susceptibility of nanoparticle-encapsulated paclitaxel to P-glycoprotein-mediated drug efflux. Int J Pharm. 320 150-156 (2006). 

Toluene solutions of Pd encapsulated within dendrimer-templated inverted micelles have been tested for catalytic activity by examining their effectiveness towards hydrogenation of allyl alcohol in organic solvents [19]. The reaction product was confirmed to be n-propanol by H NMR spectroscopy, and the turnover frequency, calculated from the rate of hydrogen uptake, was 760 mol H2 (mol Pd) h at 20 °C. This value compares favorably with the value of 218 mol H2 (mol Pd) h obtained for the same reaction carried out in water using Pd nanoparticles encapsulated in hydroxy-terminated dendrimers. 

Hirano,T Oku,T. Suganuma, K. (1999) Formation of gold and iron oxide nanoparticles encapsulated in boron nitride sheets. J. Mat. 

Kumar R, Maitra AN, Patanjali PK, Sharma P (2005) Hollow gold nanoparticles encapsulating horseradish peroxidase. Biomaterials 26 6743-6753... 

Gupta M, Gupta AK (2004) Hydrogel pullulan nanoparticles encapsulating pBUDLacZ plasmid as an efficient gene delivery carrier. J Control Release 99(1) 157-166... 

Yu Y, Gu L, Zhu C, Van Aken PA, Maier J. Tin nanoparticles encapsulated in porous multichannel carbon microtubes preparation by single-nozzle electrospinning and application as anode material for high-performance Li-based batteries. J Am Chem Soc. 2009 131 15984-5. 

Mei Y, Lu Y, Polzer F, Ballauff M, Drechsler M (2007) Catalytic activity of palladium nanoparticles encapsulated in spherical polyelectrolyte brushes and core-shell microgels. Chem Mater 19 1062-1069... 

The magnetic nanoparticle encapsulation efficiency in the magnetic liposomes is calculated using the following formula (MAPmagnetic nanoparticles). 

Y.B. (2008) Direct electrochemistry of laccase immobilized on au nanoparticles encapsulated-dendrimer bonded conducting polymer application for a catechin sensor. Analytical Chemistry, 80 (21), 8020-8027. 

PLOA/HAp composite fiber with DNA-loaded Chitosan nanoparticles encapsulated inside... 

Fig. 10.12 PKH26-positive cells determined by flow cytometry of centrifuged PKH26 and nanoparticles encapsulating PKH26 at pH 7.4 and 6.0...

Fig. 10.20 Cytotoxicity of free and nanoparticle-encapsulated cisplatin to SKOV-3 adenocarcinoma cancer cells (2-h treatment) estimated with MTT Cell Proliferation Assay. Cisplatin dose, 0.25 ag/ml. Data represent mean SE (n = 3, P < 0.05) [97]...

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