Preparation of Polycarbonate-ZnO Nanocomposite Films: Surface Investigation after UV Irradiation

Polycarbonate (PC)-ZnO films with different percentages of ZnO were prepared by a solution stirring technique and subjected to ultraviolet (UV; λ = 254 nm) irradiation. Structural parameters of the samples and the effects of UV irradiation on the surface properties of the PC and PC-ZnO nanocomposites were evaluated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), water contact angle (WCA) measurements, and a Vickers microhardness (H_V) tester. The XRD patterns of the nanocomposite films were found to show an increase in crystallinity with the increasing ZnO nanoparticles percentage. The WCA was found to be reduced from 90° to 17° after 15 h of UV irradiation, which could be ascribed to the oxidation of the surface of the samples during the irradiation and exposure of the ZnO nanoparticles, a result that is also supported by the obtained XPS data. The microhardness value of the PC-ZnO films including 30 wt.% ZnO enhanced considerably after UV radiation, which can also be attributed to the exposition of the ZnO nanoparticles after photodegradation of the PC superficial layer of the nanocomposite films.     

Synthesis and spatial structure of new chiral dopants from allobetuline series for cholesteric liquid-crystal compositions

Structural Chemistry - New series of chiral dopants for cholesteric liquid-crystal compositions were synthesized on the base of 2-substituted allobetuline derivatives, and their steric structure...     

A note on infinite aS-groups

Let G be a group. If every nontrivial subgroup of G has a proper supplement, then G is called an aS-group. We study some properties of aS-groups. For instance, it is shown that a nilpotent group G is an aS-group if and only if G is a subdirect product of cyclic groups of prime orders. We prove that if G is an aS-group which satisfies the descending chain condition on subgroups, then G is finite. Among other results, we characterize all abelian groups for which every nontrivial quotient group is an aS-group. Finally, it is shown that if G is an aS-group and |G| ≠ pq, p, where p and q are primes, then G has a triple factorization.     

A minimalist NMR approach for the structural revision of mucoxin

In an attempt to revise the structural assignment of mucoxin, and faced with 64 diastereomeric possibilities, we resorted to the synthesis of truncated structures that contained the core stereochemical sites. Twelve stereochemical analogues were synthesized, their (1)H and (13)C NMR spectra were analyzed and four recurring stereochemical trends were distilled from the data. Applying the observed trends to the diastereomeric population pared the possible choices for the correct structure of mucoxin from 64 to 4. Synthesis of these analogues led to the identification of the correct structure of mucoxin.     

Selective oxidation of sulfides to sulfoxides using 30% hydrogen peroxide catalyzed with a recoverable silica-based tungstate interphase catalyst

Various types of aromatic and aliphatic sulfides are selectively oxidized to sulfoxides and sulfones in good to excellent yields using 30% H2O2 in the presence of catalytic amounts of a novel recoverable silica-based tungstate interphase catalyst at room temperature. The catalyst can be recovered and reused for at least eight reaction cycles under the described reaction conditions without considerable loss of reactivity. [reaction: see text]     

Aqueous solutions of ionic liquids: study of the solution/vapor interface using molecular dynamics simulations

We performed a detailed molecular dynamics study of the interfacial structure of aqueous solutions of 1-butyl-3-methylimidazolium tetrafluoroborate in order to explain the anomalous dependence of the surface tension on concentration. At low concentrations the surface tension decreases with concentration. At higher concentrations the surface becomes saturated; a plateau is observed in simulations with a non-polarizable force field while a possible increase is detected in simulations with a polarizable force field. The structure is characterized by a surplus of cations at the surface (with hydrophobic butyl chains pointing toward vacuum) which at low concentrations is only partly compensated by the anions because of asymmetric solvation. A more hydrophobic 1-butyl-3-methylimidazolium hexafluorophosphate is also simulated for comparison.     

A Proline-Based Aminophosphinic Acid Ligand and It’s Vanadyl Complex: Synthesis,Characterization and In Vitro Inhibitory Effects on α-Amylase And α-Glucosidase

Abstract

A proline-based aminophosphinic acid ligand and it's vanadium complex have been synthesized and characterized by spectroscopic techniques. The inhibitory activity on pancreatic α-amylase and Baker's yeast α-glucosidase has been examined in vitro. The novel complex showed more inhibitory potency against pancreatic α-amylase and Baker's yeast α-glucosidase compared to acarbose as an antidiabetic drug.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.     

Defect capture under rapid solidification of the melt induced by the action of femtosecond laser pulses and formation of periodic surface structures on a semiconductor surface

A theory of defect-strain instability with formation of periodic surface relief in semiconductors irradiated by ultra-short (τ_p=10^-13 s) powerful laser pulses is developed. The period and time of formation of surface relief are calculated. Regimes of multi-pulse laser ablation leading to formation of either a smooth surface or arrays of surface-relief spikes are pointed out and corresponding experimental results are interpreted from the viewpoint of the developed theory. Received: 4 December 2000 / Accepted: 23 July 2001 / Published online: 11 February 2002     

2, 4, 6-Trichloro-1, 3, 5-triazine/dimethylformamide as an efficient reagent for one-pot conversion of alcohols into N-alkylphthalimides

<正>An efficient and mild method for the direct conversion of alcohols into N-alkylphthalimides using 2,4,6-trichloro-1,3,5-triazine and dimethylformamide was described.The reaction was preceded via(alcoxymethylene) dimethylammonium chloride intermediate and produced corresponding N-alkylphthalimides in good-to-excellent yields.     

A novel and simple method for the preparation of (R)- and (S)-pyrrolidine-2-phosphonic acids: phosphonic acid analogues of proline

A simple and convenient method has been developed for the preparation of (R)- and (S)-pyrrolidine-2-phosphonic acids. The thermal reaction of proline with diethyl phosphite in the presence of benzaldehyde gave an N-benzyl derivative of diethyl pyrrolidine-2-phosphonate, which was transformed into two diastereomeric amides by sequential debenzylation and acylation with (+)-dibenzoyl-l-tartaric anhydride. The two diastereomeric amides were separated by column chromatography and the structure of one of them was determined by X-ray crystallographic analysis. Hydrolysis of the amides in the usual manner afforded (R)- and (S)-pyrrolidine-2-phosphonic acids. The advantages of the present method are that it is easy, rapid, and prepares both enantiomers of pyrrolidine-2-phosphonic acids.