Gold clusters on thiol-functionalized FE3O4@SIO2 nanoparticles: a novel bioreduced catalyst for oxidation of benzyl alcohol

Bioinspired synthesis of a magnetically recoverable gold nanoparticles (AuNPs) catalysts on Fe3O4@SiO2 support is reported. Firstly, AuNPs was prepared by using the aqueous leaf extract of Polygonum minus (kesum) as a reducing and stabilizing agent. The reduction of Au3+ ions to elemental Au was rapidly occurred and completed within 20 minutes at room temperature. The bioreduction process was monitored by UV-vis spectroscopy and the AuNPs were characterized by FTIR, XRD, TEM, and CV analyses. Then, same bioreduction process was employed in the preparation of Au catalysts supported on thiol-functionalized silica-coated magnetite nanoparticles. The supported Au catalysts were characterized by FTIR, XRD, TEM, XPS and AAS analyses. The performance of bioreduced supported Au catalysts was evaluated in the liquid phase oxidation of benzyl alcohol to benzaldehyde in water at 80o C using H2O2 as oxidant, reaction time of 6 h and 8 mg (4 µmol Au) of catalyst. Under these conditions, benzyl alcohol conversion of 58% and benzaldehyde selectivity of 100% with TON of 4,205 were achieved. The supported Au catalyst is stable and can be recovered and reused for three times without a significant loss in its activity and selectivity

Theoretical study of structural effects on reactivity and stability of isomeric pyrano-, thiopyrano- and selenopyranopyrroles

1311-1318In this study we have calculated global and local DFT reactivity descriptors for isomeric pyrano-, thiopyrano- and selenopyranopyrroles. The geometric optimization of the obtained structures have been realized with the density functional theory (DFT, B3LYP) at the level of 6-311G(d,p) and show these isomers have planar configurations. The structural properties such as dipole moments, bond lengths and bond angles of these isomers have been calculated. The heats of formation have also been calculated based on the optimized geometry. The energies of HOMO and LUMO molecular orbitals have been used to determine several global descriptors as a measure of their electronic properties, relative stabilities and chemical reactivities. These include total energy (E), ionization potential (I), electron affinity (A), chemical hardness (η), chemical softness (S), electronic chemical potentials (μ) and electrophilicity (ω). Selenopyrano[2,3-c]pyrrole possesses the highest electrophilicity and minimum chemical hardness among the calculated isomeric structures. The largest calculated dipole moment belongs to pyrano[2,3-c]pyrrole, while thiopyrano[3,4-b]pyrrole has the lowest

Single-step in situ seed-mediated biogenic synthesis of Au, Pd and Au-Pd nanoparicles by etlingera elatior leaf extract

The rapid formation of stable Au-Pd bimetallic nanospheres are based on a single-step, seed-mediated, growth method using Etlingera elatior leaf extract as a reducing, stabilizing and capping agent. The success of this synthesis is attributed to reduction potential difference of Au and Pd, where Pd initially form seeds in the reaction mixture, followed by growth of Au around the Pd seeds forming Au-Pd bimetallic nanoparticles. Consequently, monometallic Au nanoparticles with mixtures of shapes can be well controlled. The used of Etlingera elatior as a reducing agent is a simple one-pot environmentally friendly reaction, non-toxic and safe method without the need of additional surfactant, capping or stabilizing agent. The synthesized Au-Pd, Au and Pd nanoparticles were characterized via UV-vis, FTIR, XRD, CV, TEM and EDX analysis. TEM analysis revealed that Au-Pd nanoparticles consisted of only nanospheres with mean size of 17.8 ± 9.9 nm, as opposed to the Au nanoparticles that have mixtures of anisotropic nanoshapes with mean size of 15.8 ± 6 nm. FTIR spectroscopic analysis of the biosynthesized Au, Pd and Au-Pd nanoparticles confirmed the surface adsorption of the bioactive components in the leaf extract that acted as the reducing agent and stabilizer for the metal nanoparticles

Efficient conjugation of anti-HBsAg antibody to modified core-shell magnetic nanoparticles (Fe3O4@SiO2/NH2)

Introduction: Further development of magnetic-based detection techniques could be of significant use in increasing the sensitivity of detection and quantification of hepatitis B virus (HBV) infection. The present work addresses the fabrication and characterization of a new bio-nano composite based on the immobilization of goat anti-HBsAg antibody on modified core-shell magnetic nanoparticles (NPs) by (3-aminopropyl) triethoxysilane (APTES), named Fe3O4@SiO2/NH2, and magnetic NPs modified by chitosan (Fe3O4@CS). Methods: At the first step, Fe3O4 was modified with the silica and APTES (Fe3O4@SiO2/NH2) and chitosan (Fe3O4@CS) separately. The goat anti-HBsAg antibody was activated by two different protocols: Sodium periodate and EDC-NHS. Then the resulted composites were conjugated with activated goat anti-HBsAg IgG. An external magnet collected Bio-super magnetic NPs (BSMNPs) and the remained solution was analyzed by the Bradford method to check the amount of attached antibody to the surface of BSMNPs. Results: The findings indicated that activation of antibodies by sodium periodate method 15-17 µg antibody immobilized on 1 mg of super magnetic nanoparticles (SMNPs). However, in the EDC-NHS method, 8-10 µg of antibody was conjugated with 1 mg of SMNPs. The resulting bio-magnetic NPs were applied for interaction with the HBsAg target using enzyme-linked immunosorbent assay (ELISA). About 1 µg antigen attached to 1 mg SMNPs, which demonstrated that the fabricated materials are applicable in the detection scope of HBsAg. Conclusion: In the present study, we developed new antibody-conjugated magnetic NPs for the detection of HBsAg using an efficient conjugation strategy. The results demonstrated that the binding capacity of Fe3O4@SiO2/NH2 was comparable with commercially available products. Our designed method for conjugating anti-HBsAg antibody to a magnetic nanoparticle opens the way to produce a high capacity of magnetic NPs

New sol-gel silica nanoparticles coated cyanopropyltriethoxysilane as alternative solid phase extraction sorbent for organophosphorus pesticides

Sorbents based on silica are widely used in solid phase extraction (SPE). The most common SPE material is C18.Recently nanoparticleshave gained interest as sorbent materials for analytical purpose. In this study silica-based nanoparticles with polar and non-polar groups were synthesized using cyanopropyltriethoxysilane (CNPrTEOS) and tetraethoxysilane (TEOS) as precursor in the presence of ammonia solution as catalyst and ethanol as solvent via sol-gel technology. The sol-gel SiO2-NPs-CNPrTEOS was used for the simultaneous extraction of three organophosphorus pesticides (OPPs) of different polarity namely dicrotophos, diazinon and chlorpyrifos prior to LC-UV detection at 270 nm. The sorbent produced was characterized using FTIR, FESEM, nitrogen gas adsorption and TGA. The surface area and average pore diameter of the sorbent are 570 m2 g-1 and 31Å (mesoporous), respectively. The average particle size of SiO2-NPs-CNPrTEOS is 54 nm. The mesoporous SiO2-NPs-CNPrTEOS showed superior extraction capability for the polar dicrotophos and also for the non-polar diazinon and chlorpyrifos compared to commercial cyano SPE. The new SiO2-NPs-CNPrTEOS exhibits high potential as a bipolar sorbent for the simultaneous extraction of polar and non-polar OPPs. Keywords Sol-gel, Solid phase extraction, Nanoparticles sorbent, Cyanopropyltriethoxysilane, Tetraethoxysilane, Organophosphorus pesticides, Liquid chromatography-UV detection

Direct carboxylation of aromatic compounds using the sodium hydrogen carbonate/triphenylphosphine ditriflate system

A new procedure was developed for the highly regioselective synthesis of aromatic carboxylic acids using the sodium hydrogen carbonate/triphenylphosphine ditriflate system in ethanol at room temperature. This metal-free system was used for the carboxylation of thiophenol with unexpected products in terms of selectivity. The simplicity of the procedure, readily available aromatic compounds, short reaction times, and mild reaction conditions are other advantages of this protocol.We have developed a novel approach for direct carboxylation of a wide range of aromatic compounds in moderate to good yields with high regioselectivity using NaHCO3/TPPD system in EtOH. This metal-free protocol does not need to use carbon monoxide or carbon dioxide gases

The Effects of DEM Resolution in Extraction of Physiographic and Hydrological Characteristics of Karde-Dam Watershed

This works evaluate the effect of DEM resolution on watershed delineation and particularization in Kardeh-Dam Watershed, Iran. A series of DEM at resolutions of 10, 20, 30, 40, 50 and 60 m resolution are investigated and compared with the reference DEN derived from the topographic map at scale of 1:25000.The HEC-GeoHMS is used as GIS tools for watershed delineation and particularization

Preparation of Arylthiocyanates Using N,N′-Dibromo-N,N′bis(2,5-dimethylbenzenesulphonyl) ethylenediamine and N,N- Dibromo-2,5-dimethylbenzenesulphonamide in the Presence of KSCN as a Novel Thiocyanating Reagent

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