Synthesis and catalytic evaluation of Fe3O4/MWCNTs nanozyme as recyclable peroxidase mimetics: Biochemical and physicochemical characterization

In this research, the nanocomposite of multiwalled carbon nanotubes and magnetic metal oxide nanoparticles (Fe₃O₄/MWCNTs), as enzyme mimetic, was synthesized using an in situ chemical reduction method. The structure, composition and morphology of the prepared Fe₃O₄/MWCNT nanocomposite materials were characterized using X‐ray diffraction, FT‐IR and scanning electron microscopy with energy dispersive X‐ray spectroscopy, respectively. The magnetic properties of the nanocomposite were investigated by the vibrating sample magnetometer. A colorimetric system involving nanozyme, phenol/4‐aminoantipyrine and H₂O₂ was utilized for the determination of peroxidase mimetic catalytic assay. The obtained results confirmed that the synthesis of Fe₃O₄/MWCNTs nanostructures was successful. It was found that Fe₃O₄/MWCNTs nanohybrid exhibited peroxidase‐like activity without any pH limitation. Colorimetric data demonstrated that the prepared nanocatalyst had higher catalytic activity toward H₂O₂ than MWCNTs. The kinetic parameters of the nanozyme, K_m and V_max, were estimated to be 8.3 mm and 1.4 mm min^?1, respectively. The Fe₃O₄/MWCNTs nanostructures were also successfully applied for glucose detection. In addition, peroxidase‐like activity of the nanozyme increased in the presence of butyl‐imidazolium bromide ionic liquid. These biomimetic catalysts have some advantages, such as simplicity, stability, reusability and cost effectiveness, which makes them great candidates to be used in various fields of biotechnology applications.     

Electrochemical impedance spectroscopy analysis of porous silicon prepared by photo-electrochemical etching: current density effect

Electrical impedance characteristics of porous silicon nanostructures (PSiNs) in frequency function were studied. PSiNs were prepared through photo-electrochemical etching method at various current densities (15–40 mA/cm²) and constant etching time. The atomic force microscope images of PSiNs show that pore diameter and roughness increase when current density increases to 35 mA/cm². The surface roughness subsequently decreases because of continuous etching of pillars, and a second etching process occurs. Photoluminescence spectra show blue and red shift with increasing applied current density that is attributed to PSiNs size. Variations of electrical resistance and capacitance values of PSiNs were measured using electrochemical impedance spectroscopy analysis. These results indicate that PSiNs prepared at 20 mA/cm² current density have uniform porous structures with a large number of pillars. Furthermore, this PSiNs structure influences large values of charge transfer resistance and double layer capacitance, indicating potential application in sensors.     

One‐Pot,Three‐Component Synthesis of 2,3‐Dihydro‐4(1H)‐quinazolinones by Montmorillonite K‐10 as an Efficient and Reusable Catalyst

A wide range of mono‐ and disubstituted dihydroquinazolinones were synthesised via condensation of isatoic anhydride, primary amines, or ammonium salts with aromatic aldehydes in the presence of montmorillonite K‐10. The catalyst is reusable and could be recycled for several runs without any decrease in its efficiency.     

The effect of emitter geometry on lateral field emission diodes fabricated by AFM-based electrochemical nanolithography

Lateral field emission diodes were successfully fabricated using atomic force microscopy (AFM)-based electrochemical nanolithography and tetramethyl ammonium hydroxide (TMAH) wet etching method. Field emission (FE) current of the silicon emitter cathode was measured as a function of the applied anode voltage under vacuum environment. For narrowed nanogaps from 55 to 35 nm, the turn-on voltage was decreased from 21 to 16 V. The turn-on voltage of the 35 nm gap was reduced from 16 to 8 V by changing the curvature radius of the cathode tip. The sharper emitter had the lowest turn-on voltage, largest field-enhancement factor, and good stability, which were attributed to the small emitter radius at the cathode tip and very slight changes in the local field factor. These results indicate that the diodes fabricated using this technique had the lowest value of turn-on voltage ever reported for lateral silicon FE devices.     

Diammonium Hydrogen Phosphate as an Efficient and Inexpensive Catalyst for the Synthesis of Bis(indolyl)methanes under Solvent-Free Conditions

Summary. Bis(indolyl)methanes were synthesized by the reaction of indole derivatives and aromatic and aliphatic aldehydes in the presence of diammonium hydrogen phosphate as a solid catalyst under solvent-free conditions. This methodology offers significant improvements for the synthesis of bis(indolyl)methanes with regard to the yield of products, simplicity in operation, and green aspects by avoiding toxic catalysts and solvents.     

Silica‐supported terpyridine palladium(II) complex as an efficient and reusable catalyst for Heck and Suzuki cross‐coupling reactions

Silica‐supported terpyridine palladium(II) was prepared and used as an effective and recyclable catalyst in Mizoroki–Heck and Suzuki–Miyaura coupling reactions. The catalyst was very effective for the Mizoroki–Heck reaction of aryl halides with olefins and conversion was in most cases excellent. The catalyst showed good thermal stability (up to 230 °C) and could be recovered and reused for four reaction cycles. The Suzuki coupling of aryl iodides with aryl boronic acids in the presence of the catalyst was also investigated and the reaction proceeded with a short reaction time and excellent conversion. Copyright © 2013 John Wiley & Sons, Ltd.     

Combining a Click–Multicomponent Reaction: One-Pot Synthesis of 1,2,3-Triazol-4-ylmethyl 3-Amino-5,10-dihydro-5,10-dioxo-1H-pyrazolo[1,2-b]phthalazine-2-carboxylate Derivatives

(1,2,3-Triazol-4-yl)methyl-3-amino-5,10-dihydro-5,10-dioxo-1H-pyrazolo[1,2-b]phthalazine-2-carboxylate derivatives were synthesized by a four-component, one-pot condensation reaction of benzaldehyde derivatives, an active methylene compound (prop-2-ynyl-2-cyanoacetate), azides, and phthalhydrazide in the presence of Cu(OAc)₂/sodium ascorbate as catalysts and 1-methyl-1H-imidazolium trifluoroacetate ([Hmim]TFA) as an ionic liquid medium in good to excellent yields.     

SILICA SULFURIC ACID; AN EFFICIENT AND REUSABLE CATALYST FOR REGIOSELECTIVE RING OPENING OF EPOXIDES BY ALCOHOLS AND WATER

The nucleophilic ring opening reactions of epoxides by aliphatic alcohols and water are achieved efficiently in the presence of catalytic amounts of silica sulfuric acid with high degree of regioselectivity. The catalyst is reusable and can be applied several times without any decrease in the yield of reactions.     

Electroactive nanostructured scaffold produced by controlled deposition of PPy on electrospun PCL fibres

Research on Chemical Intermediates - The electrical conductivity of biodegradable polymeric scaffolds has shown promising results in tissue engineering, particularly for electrically excitable...