Blue TiO2 nanotube arrays as semimetallic materials with enhanced photoelectrochemical activity towards water splitting

In the past years there has been a great interest in self-doped TiO₂ nanotubes (blue TiO₂ nanotubes) compared to undoped ones owing to their high carrier density and conductivity. In this study, blue TiO₂ nanotubes are investigated as photoanode materials for photoelectrochemical water splitting. Blue TiO₂ nanotubes were fabricated with enhanced photoresponse behavior through electrochemical cathodic polarization on undoped and annealed TiO₂ nanotubes. The annealing temperature of undoped TiO₂ nanotubes was tuned before cathodic polarization, revealing that annealing at 500 °C improved the photoresponse of the nanotubes significantly. Further optimization of the blue TiO₂ nanotubes was achieved by adjusting the cathodic polarization parameters. Blue TiO₂ nanotubes obtained at the potential of –1.4 V (vs. SCE) with a duration of 10 min exhibited twice more photocurrent response (0.39 mA cm^-2) compared to the undoped TiO₂ nanotube arrays (0.19 mA cm^-2). Oxygen vacancies formed through the cathodic polarization decreased charge recombination and enhanced charge transfer rate; therefore, a high photoelectrochemical activity under visible light irradiation could be achieved.     

Preparation,characterization, DFT calculations and ethylene oligomerization studies of iron(II) complexes bearing 2-(1H-benzimidazol-2-yl)-phenol derivatives

Five 2-(1H-benzimidazol-2-yl)-phenol derivatives including 1H (HL₁), 5-chloro-(HL₂), 5-methyl-(HL₃), 5,6-dichloro-(HL₄), and 5,6-dimethyl-(HL₅) were synthesized by the reaction of their corresponding benzene-1,2-diamine precursors and 2-hydroxybenzaldehyde which subsequently was employed in complexation with Fe(II) to prepare complexes C1–C5, respectively. Indeed, in all complexes, the ligands were coordinated as bidentate, via the C=N nitrogen and hydroxy oxygen atom of benzimidazole moiety and phenol ring, respectively. The compounds were characterized by FTIR, UV–vis, ¹H- and ¹³C-NMR spectropscopy, ICP, and elemental analysis (C, H, and N). The purity of these compounds was determined by melting point (m.p )and TLC. The synthesized ligands and complexes were geometrically optimized by Gaussian09 software at B3LYP/TZVP level of theory and satisfactory theoretical–experimental agreement was achieved for analysis of IR data of the compounds. Catalytic behavior of the iron(II) complexes was investigated for ethylene reactivity. On activation with diethylaluminum chloride (Et₂AlCl), iron(II) complex (C4) showed the highest activity (1686 kg oligomers.mol^?1(Fe).h^?1) for ethylene oligomerization when it contains chlorine substituents and exhibits good selectivity for linear 1-butene. The steric and electronic effects of ligands were investigated in detail on the influence of their catalytic activities.     

CuI‐functionalized halloysite nanoclay as an efficient heterogeneous catalyst for promoting click reactions: Combination of experimental and computational chemistry

Amine‐functionalized halloysite nanotubes (HNTs‐2 N) were prepared and further modified by introduction of salicylaldehyde and formation of imine functionality (HNTs‐2 N‐Sal). The latter was subsequently used for immobilization of CuI and formation of CuI@HNTs‐2 N‐Sal, which could effectively promote click reactions of terminal alkynes, sodium azide and α‐haloketones or alkyl halides in aqueous media and under mild reaction conditions to afford 1,2,3‐triazoles in relatively short reaction times. Notably, the catalyst could be recycled in up to six reaction runs with negligible loss of catalytic activity and CuI leaching. Also, the geometry of CuI adsorption on the modified HNTs surface was explored by molecular simulation with density functional theory. Furthermore, topographic steric maps of possible coordination modes were obtained using the recently released SambVca2 web application tool. Based on obtained results, a catalytic site with superior performance was suggested.     

Study of the effect of the ligand structure on the catalytic activity of Pd@ ligand decorated halloysite: Combination of experimental and computational studies

Taking advantage of computational chemistry, the best diamine for the synthesis of a multi‐dentate ligand from the reaction with 3‐(trimethoxysilyl) propylisocyanate (TEPI) was selected. Actually, predictive Density Functional Theory (DFT) calculations provided the right diamino chain, i.e. ethylenediamine, capable to sequester a palladium atom, together with the relatively polar solvent toluene, and then undergo the experiments as a selective catalytic agent. The ligand was then prepared and applied for the decoration of the halloysite (Hal) outer surface to furnish an efficient support for the immobilization of Pd nanoparticles. The resulting catalyst exhibited high catalytic activity for hydrogenation of nitroarenes. Moreover, it showed high selectivity towards nitro functional group. The study of the catalyst recyclability confirmed that the catalyst could be recycled for several reaction runs with only slight loss of the catalytic activity and Pd leaching. Hot filtration test also proved the heterogeneous nature of the catalysis.     

Preparation of novel,liquid, solvent‐free,polyolefin‐based adhesives

An innovative procedure for functionalization of polyolefins was developed. It was found that synthesized polyolefins end‐capped with trimethoxysilane (silylated polyolefins) are new polyolefin‐based adhesives. To prepare the mentioned materials,1‐octene as a higher α‐olefin was cooligomerized with two linear, nonconjugated dienes (ie, 1,5‐hexadiene and 1,7‐octadiene) by using metallocene catalyst system, Cp₂HfCl₂/MAO, at room temperature. Then, amine‐terminated trimethoxysilane (3‐aminopropyltrimethoxysilane) was reacted with unsaturated bonds of synthesized cooligomers in the presence of palladium(II) acetate. Embedding of the dienes on 1‐octene oligomeric chains was explored by Fourier transform infrared (FTIR), ¹H, and ¹³C‐NMR spectroscopy. On the basis of the results, 1,5‐hexadiene showed both 1‐butene branch and five‐member ring. On the other hand, 1,7‐octadiene was incorporated by 1,2‐addition, forming both 1‐hexene branch and seven‐member ring in the cooligomer backbone. Mole percentage of C?C and cyclic moieties reached to a value of 28.54, 18.59% mol in 1‐octene/1,5‐hexadiene, and 38.04, 6.71% mol in 1‐octene/1,7‐octadiene cooligomers, respectively. Reaction of synthesized cooligomers with 3‐aminopropyltrimethoxysilane was confirmed by FTIR spectroscopy, which yielded targeted adhesives. To study the adhesion properties, resulting adhesives were applied to different substrates. Obtained results demonstrated that tensile shear strength of synthesized adhesives to polar substrates was 2.21% to 2.84% more than nonpolar substrates. Among studied systems, the best performance was achieved by1‐octene/1,7‐octadiene–based adhesive and Al substrate with tensile shear strength of 1.45 N/mm².     

Electrophoretic deposition and characterization of self-doped SrTiO3 thin films

Herein, titanium (Ti³⁺) self-doped strontium titanate (SrTiO₃), so-called blue SrTiO₃, with a bandgap of 2.6 eV and favorable photocatalytic characteristics was fabricated through a facile and effective method. For electrochemical investigations, the electrophoretic deposition was applied to produce SrTiO₃ thin films on (fluorine-doped tin oxide) FTO conductive substrates. The electrophoretic voltage of 20 V and a process duration of 10 min were optimized to reach transparent and uniform coatings on FTO. The blue SrTiO₃ reveals lower resistance (charge transfer resistance of 6.38 Ω cm^-2) and higher electron mobility (current density value of 0.25 mA cm^-2) compared to a pure SrTiO₃ electrode. These findings may provide new insights for developing high-performance visible light photocatalysts.     

Nano-ovalbumin: a green biocatalyst for biomimetic synthesis of tetrahydrodipyrazolo pyridines in water

Research on Chemical Intermediates - In this investigation, a simple and new protocol was used to prepare large quantities of purified nano-ovalbumin from egg white. Nano-ovalbumin, as a...     

Novel Fe2O3@CeO2 Coreshell‐based Electrochemical Nanosensor for the Voltammetric Determination of Norepinephrine

A new selective carbon paste electrode (CPE), was applied as an electrochemical sensor for the detection of norepinephrine (NOE). The sensor was modified with 6‐amino‐4‐(3,4‐dihydroxyphenyl)‐3‐methyl‐1,4‐dihydropyrano[2,3‐c],pyrazole‐5‐carbonitrile (ADPC) assisted Fe₂O₃@CeO₂ coreshell nanoparticles (CNs) synthesized by simple method. To identify the redox properties of the modified electrode, and to examine its electrochemical properties, cyclic voltammetry (CV), chronoamperometry and differential pulse voltammetry (DPV) were conducted. Through electrochemical investigations, the coefficient of electron transfer between ADPC and the CNs/CPE (i. e. carbon paste electrode which was modified with CNs), the apparent charge transfer rate constant (k_s), and the diffusion coefficient (D) were calculated. The NOE oxidation occurred at the optimum pH of 7.0 and a potential that was about 235 mV less positive than that of the unmodified carbon paste electrode. The interaction between the two metals in the Fe₂O₃@CeO₂ coreshell led to an increase in the surface area and, consequently a sharp increase in the current. The differential pulse voltammogram of NOE showed two linear dynamic ranges an excellent detection limit (3σ) of 40 nM. In addition, NOE, AC and Trp were simultaneously determined at the modified electrode. Finally, NOE was quantitated in a number of real samples.     

Preparation and properties of enhanced nanocomposites based on PLA/PC blends reinforced with silica nanoparticles

In order to lower brittleness of biobased polylactic acid (PLA), its blending with polycarbonate and nanosilica is aimed. In this line, to increase compatibility of the ingredients, dicumyl peroxide (DCP) and Cobalt (II) acetylacetonate (Co) were used as grafting and transesterification catalysts, respectively. The X‐ray diffraction (XRD) spectra demonstrated high compatibility of the ingredients by broadening of the PLA characteristic peaks and, also, good dispersion of nanosilica particles, especially in PLA/PC/Silica/Co sample. The EDX maps confirmed good nanosilica dispersion, too. The silica nanoparticle size was ranged from 20 to 100 nm in transmission electron microscopy (TEM) pictures. All nanocomposites showed improved thermal stability in thermogravimetric analysis (TGA). Differential scanning calorimetry (DSC) results demonstrated lower T_g, T_m, and crystallinity values for the fabricated nanocomposites. Notably, the dynamic mechanical thermal analysis (DMTA) curves confirmed the T_g, T_m, and T_cc trend obtained in DSC; moreover, much higher surface under tan δ peak for PLA/PC/Silica/Co sample was obtained, which implies its higher toughness. The precise tensile study of the samples confirmed significantly higher elongation at break of the nanocomposites, more considerably in PLA/PC/Silica/Co sample, with nearly negligible defect on tensile strength and modulus. In a concise, the obtained results confirmed the higher efficiency of Co catalyst, which leads to the sample with improved characteristics compared with DCP.