Influence of different precursors and Mn doping concentrations on the structural,optical properties and photocatalytic activity of single-crystal manganese-doped ZnO

Mn-doped ZnO single-crystal micronuts were synthesized via hydrothermal method in an hexamethylenetetramine aqueous solution. These micronuts are of wurtzite crystal structure. The effects of Mn doping amount and precursor concentration on the structural, optical properties and photocatalytic activity have been investigated. The synthesized Mn-doped ZnO was characterized by X-ray powder diffraction, field emission scanning electron microscopy (FESEM), UV–Vis absorption and photoluminescence spectroscopy. The structural analyses based on X-ray diffraction revealed the absence of Mn-related secondary phases. According to FESEM results, the length of ZnO micronuts was in the range of 5–8 μm. The band gap energy increased on increasing Mn doping concentration. The photocatalytic activity was studied by degradation of methyl orange aqueous solution, which showed that the Mn-doped ZnO micronuts prepared in precursor concentration of 0.1 M and 4% Mn doping had the highest photocatalytic activity. The effects of crystal defect and band gap energy on photocatalytic activity of Mn-doped ZnO samples were studied in different precursors and Mn doping amounts.     

A parametric study of cohesive particle agglomeration in a shear flow—numerical simulations by the discrete element method

In this study, we investigate numerically the shear-induced agglomeration of cohesive inertial particles in a simple shear flow. We conduct a series of numerical simulations by implementing a soft-sphere collision model. Post-processing tools are developed in-house to analyze the results of the simulations in terms of transient and terminal numbers of primary particles and agglomerates, magnitudes and distributions of agglomerate size, and fractal dimension as functions of the salient physical parameters. The obtained numerical results compared with existing transient models suggest that, as the system transitions from formation of duplets to larger agglomerates, in most cases the number of agglomerates in the system reveals clear maxima. The results also show evidence of agglomerate densification, as weaker agglomerates with lower fractal dimensions are broken up and stronger ones with higher fractal dimensions are formed. Furthermore, we found that a simple theoretical model proposed by, among others, Chimmili et al. is able to predict the temporal development of the agglomerate size properly.     

Enhanced reactivity in a heterogeneous oxido-peroxido molybdenum(VI) complex of salicylidene 2-picoloyl hydrazone in catalytic epoxidation of olefins

A molybdenum(VI) oxido-diperoxido complex of salicylidene 2-picoloyl hydrazine (sal-phz) was synthesized and successfully grafted onto chloro-functionalised Fe₃O₄ nanoparticles. The resulting heterogeneous and magnetically recoverable nanoscale catalyst MoO₃(sal-phz)/Fe₃O₄ was characterized by physicochemical and spectroscopic techniques. The activity of this heterogeneous catalyst for the oxidation of olefins to corresponding epoxides was efficiently increased by increasing the reaction temperature up to 95 °C. The nanocatalyst proved to be efficient for the selective epoxidation of a variety of alkenes using t-BuOOH with high conversion and selectivity. Leaching and recycling tests showed that the nanocatalyst can be reused at least six times without significant decrease in efficiency.     

DNA as a Target for Anticancer Phen-Imidazole Pd(II) Complexes

Imidazole ring is a known structure in many natural or synthetic drug molecules and its metal complexes can interact with DNA and do the cleavage. Hence, to study the influence of the structure and size of the ligand on biological behavior of metal complexes, two water-soluble Pd(II) complexes of phen and FIP ligands (where phen is 1,10-phenanthroline and FIP is 2-(Furan-2-yl)-1H–Imidazo[4,5-f][1, 10]phenanthroline) with the formula of [Pd(phen)(FIP)](NO₃)₂ and [Pd(FIP)₂]Cl₂, that were activated against chronic myelogenous leukemia cell line, K562, were selected. Also, the interaction of these anticancer Pd(II) complexes with highly polymerized calf thymus DNA was extensively studied by means of electronic absorption, fluorescence, and circular dichroism in Tris-buffer. The results showed that the binding was positive cooperation and [Pd(phen)(FIP)](NO₃)₂ (K _f = 127 M^-1 G = 1.2) exhibited higher binding constant and number of binding sites than [Pd(FIP)₂]Cl₂ (K _f = 13 M^-1 G = 1.03) upon binding to DNA. The fluorescence data indicates that quenching effect for [Pd(phen)(FIP)](NO₃)₂ (K _SV = 58 mM^?1) was higher than [Pd(FIP)₂]Cl₂ (K _SV = 12 mM^?1). Also, [Pd(FIP)₂]Cl₂ interacts with ethidium bromide-DNA, as non-competitive inhibition, and can bind to DNA via groove binding and [Pd(phen)(FIP)](NO₃)₂ can intercalate in DNA. These results were confirmed by circular dichroism spectra. Docking data revealed that longer complexes have higher interaction energy and bind to DNA via groove binding.

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Graphical Abstract Two anticancer Pd(II) complexes of imidazole derivative have been synthesized and interacted with calf thymus DNA. Modes of binding have been studied by electronic absorption, fluorescence, and CD measurements. [Pd(FIP)₂]Cl₂ can bind to DNA via groove binding while intercalation mode of binding is observed for [Pd(phen)(FIP)](NO₃)₂.

     

Remarkable regioselectivities in the course of the synthesis of two new Luotonin A derivatives

Ethyl 4-oxo-3,4-dihydroquinazoline-2-carboxylate reacts selectively with trimethylaluminium-activated 2-amino- or 4-aminobenzoic acid ethyl esters to give the corresponding anilides without self-condensation of the aminobenzoate building blocks. After propargylation, the quinazolinones were treated with Hendrickson's reagent, but only the para-substituted ester was found to undergo the expected [4 + 2] cycloaddition reaction, affording a new Luotonin A derivative. A different regioselectivity was observed with the ortho-substituted ester which affords a benzoxazinone under identical conditions. When the ester group in the ortho-substituted intermediate is replaced with a nitrile function, the outcome of the reaction with Hendrickson's reagent depends on the absence or presence of a base (DBU), yielding either a triphenylphosphonium-substituted iminobenzoxazine or a 4-cyano-substituted Luotonin A derivative.     

Determination of hydroxylamine using a carbon paste electrode modified with graphene oxide nano sheets

A carbon paste electrode that was chemically modified with 3-(4'-amino-3'-hydroxy-biphenyl-4-yl)-acrylic acid (3,4-AA) was used as a selective electrochemical sensor for the detection of hydroxylamine. Cyclic voltammetry (CV), choronoamperometry (CHA) and square wave voltammetry (SWV) were used to investigate oxidation of hydroxylamine in aqueous solution. Under optimized concentration the electrocatalytic oxidation current peak for hydroxylamine increased linearly with concentration in the range of 0.025–10.0 μM. The detection limits for hydroxylamine was 0.012 μM. Finally, the modified electrode was applied to detection hydroxylamine in water samples.     

Copolymerization of ethylene α-olefin using MgCl2-ethanol adduct catalysts

The effects of the type and concentration of comonomers 1-hexene and 1-octene in the copolymerization of ethylene were investigated using pre polymerized Ziegler-Natta (catalyst a) and without pre polymerized (catalyst b) catalysts in the presence of hydrogen as a chain transfer agent. The properties of produced polymers were characterized by a set of techniques: (SEM), (EDX), (DSC), (GPC). TIBA and DEAC were used as co catalysts. The results of microscopic and SEM images showed the morphology and structure of catalysts (a) and (b) and the obtained spherical polymers. In the presence of 1-hexene, activity of catalyst (a) was at its maximum. The comonomer 1-octene at 32 mmol presented its activity (1.7 × 10³ g polymer/(g cat.h)) and after that, the activities decreased. Copolymerization of ethylene and 1-hexene by catalyst (b) showed higher activity (1.6 × 10³ g polymer/ polymer/(g cat.h)) at 40 mmol concentration of 1-hexene in comparison to catalyst (a).