Carbon Quantum Dots As Antibacterial Photosensitizers and Their Polymer Nanocomposite Applications

Carbon quantum dots and their incorporation in various polymer matrices are reviewed. In general, the importance of such polymer nanocomposites in biomedical applications is highlighted. In particular, the physical and antimicrobial properties of carbon quantum dots and their ability to produce reactive oxygen species under certain conditions using the principle of photodynamic therapy are explored. The characterization, preparation, mechanism of action, and use of carbon quantum dots are discussed. The known combinations of polymers and carbon quantum dots and their use in various industries are also described.     

One catalyst for both enantiomers: uncovering the inversion of enantioselectivity in cinchona-mediated desymmetrization of glutaric meso-anhydrides

A puzzling inversion of enantioselectivity dependent on catalyst loading was observed during the quinine-mediated desymmetrization of glutaric meso-anhydrides. This study presents the improvement of the catalytic path by the inclusion of carboxylic acid additives up to synthetically useful levels. The novel protocol utilizing 0.1 equiv of alkaloid and xanthene-9-carboxylic acid at room temperature (rt) was found comparable to the protocol requiring 1.1 equiv of alkaloid at ?30 °C. Thus, by altering the protocol the same catalyst produces the opposite enantiomer.This occurrence was rationalized by an extensive computational study of the interactions governing the molecular complexes formed by quinine, methanol, 3-methylglutaric anhydride, and the acetic acid. It was found that in a quinine catalyzed reaction the alcohol and the anhydride were directly hydrogen bonded to the catalyst. On the other hand, in the reaction with additive the acid intercalates between the alcohol and quinine. Due to this insertion the alcohol approaches the anhydride from the opposite face, in agreement with the observed inversion of enantioselectivity     

Concise and highly efficient approach to three key pyrimidine precursors for rosuvastatin synthesis

We report the synthesis of 5-formyl-, 5-(hydroxymethyl)-, and 5-(bromomethyl) substituted N-[4-(4-fluorophenyl)-6-isopropylpyrimidin-2-yl]-N-methylmethanesulfonamide. The presented synthetic approach is based on highly efficient three step preparation of functionalized 5-methylpyrimidine. The methyl group is selectively brominated by NBS with irradiation into the bromomethyl derivative, which is then transformed into the hydroxymethyl or formyl groups in nearly quantitative yields. This approach is superior to the existing methodologies for the preparation of the key pyrimidine precursors used in the synthesis of rosuvastatin since no metal catalysis and no cryogenic reaction conditions are involved.     

Numerical modeling of atomistic-to-continuum coupling based on bridging domain method

Nano-submodeling is an approach that enables insertion of nano-refined submodel (atomistic) in the global model (continuum). In this work analysis of the spurious effects that may arise in the concurrent atomistic-to-continuum coupling is performed. The coupling is based on the overlapping domain decomposition (ODD) method called bridging domain [1, 2] (similar is Arlequin [3] method) where different models are overlapped and the displacements compatibility is enforced via Lagrange multipliers (LM). Some coupling options such as energy weighting, coupling zone geometry and LM field interpolation are tested. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Dynamic Mechanical and Dielectric Properties of Ethylene Vinyl Acetate/Carbon Nanotube Composites

A comparative study of the dielectric and mechanical properties of ethylene vinyl acetate copolymer (EVA) filled with various concentrations of pristine and modified carbon nanotubes is reported. The surface of the carbon nanotubes was modified with 4-(2-(cholesteryloxycarboxy)ethyl) phenyl to improve the interaction of the filler with the block copolymer matrix. The improved interaction and the better dispersion of the modified carbon nanotubes (mMWCNTs) were demonstrated by a detailed study of the EVA molecular mobility through dynamic mechanical analysis and broadband dielectric relaxation spectroscopy. The storage modulus of the nanocomposite with 6 wt.% of mMWCNTs at ?50°C was enhanced by 103%, whereas for the nanocomposite with the same amount of unmodified filler, the storage modulus was only enhanced by 76% compared to the pure elastomeric matrix. This difference is more pronounced in the rubbery region in which the storage moduli were increased by 117% and 48% for the composite with the modified and unmodified fillers, respectively. The morphologies of the nanocomposites were studied with scanning and transmission electron microscopies to demonstrate the dispersion of the mMWCNTs within the EVA matrix.     

Analysis of nucleosides and monophosphate nucleotides from mushrooms with reversed‐phase HPLC

The retention characteristics of five stationary phases were tested by using a selection of 5′‐mononucleotides and nucleosides with the aim to develop a simple, rapid and sensitive reversed‐phase liquid chromatography method without ion‐pair reagent usage. The method was optimized by changes in temperature, pH and ionic strength on a column showing a superior performance. The mobile phase consisted of a mixture of 0.05 M phosphate buffer and methanol, delivered at a flow rate of 0.4 mL/min and based on a gradient program. UV detection was used at a 254 nm wavelength. The method was validated for a quantitative analysis of 5′‐mononucleotides and nucleosides in wild edible mushrooms. For all nucleosides and nucleotides, the LOD and LOQ were less than 0.02 and 0.07 μg/mL, respectively. Validation parameters yielded recovery rates between 68.6 and 98.2%, with a precision expressed as a relative standard deviation of 7.6–15.3%. The content of 5′‐mononucleotides and nucleosides was determined for 10 samples of wild edible mushrooms found in Croatia and, accordingly, the equivalent umami concentrations were calculated.     

Evaluation of Oxidative Species in Gaseous and Liquid Phase Generated by Mini-Gliding Arc Discharge

Plasma Chemistry and Plasma Processing - The gliding arc discharge plasma reactors are known as a source of non-equilibrium plasma at atmospheric pressure. In the present study, generation of...     

Synthesis of 9-substituted homoadamantanes

9-Homoadamantanone was prepared conveniently from 1-homoadamantanol via $\text{10-homop}$rotoadamantan-4-one in 58% overall yield.