Photo-, thermally, and pH-responsive microgels

Microgels with photo-, thermally, and pH-responsive properties in aqueous suspension have been synthesized and characterized using dynamic light scattering and UV-visible spectroscopy. The new route involved first preparing poly(N-isopropylacrylamide) (PNIPAM)-allylamine copolymer microgels and a spiropyran photochrome (SP) bearing a carboxylic acid group. Then the functionalized spiropyran was coupled to the microgel via an amide bond. The dark-equilibrated gel particles feature spiropyran molecules in the polar, merocyanine form. After irradiation of visible light, the particle size becomes smaller because spiropyran changes to the relatively nonpolar, closed spiro form. The PNIPAM-SP microgels undergo a volume phase transition in water from a swollen state to a collapsed state with increasing temperature under all light conditions. However, the transition temperature range of the PNIPAM-SP is much broader than that for the PNIPAM without SP. The PNIPAM-SP microgels are monodisperse and self-assemble into a crystalline lattice while in suspension. The UV-visible spectra of an aqueous suspension of PNIPAM-SP microgel in the dark-adapted, merocyanine form showed both an absorption peak around 512 nm due to the merocyanine (giving a reddish color to the suspension) and two sharp peaks from Bragg diffraction of colloidal crystallites. Upon visible irradiation, the 512-nm band bleached significantly due to spiropyran photoisomerization. The spiropyran photoisomerization and accompanying color changes of the suspension were reversible upon alternating dark, UV, and visible light irradiation. Due to the residues of amine groups, the swelling capability of PNIPAM-SP microgels reduces as the pH value is changed from 7 to 10.     

Controlled coupling of spin-resolved quantum Hall edge states

We introduce and experimentally demonstrate a new method that allows us to controllably couple copropagating spin-resolved edge states of a two-dimensional electron gas (2DEG) in the integer quantum Hall regime. The scheme exploits a spatially periodic in-plane magnetic field that is created by an array of Cobalt nanomagnets placed at the boundary of the 2DEG. A maximum charge or spin transfer of 28±1% is achieved at 250 mK.     

Antimicrobial activity and cytotoxic effects of Magnolia dealbata and its active compounds

Multi-drug resistance is of great concern for public health worldwide and necessitates the search for new antimicrobials from sources such as plants. Several Magnolia (Magnoliaceae) species have been reported to exert antimicrobial effects on sensitive and multidrug-resistant microorganisms. However, the antimicrobial properties of Magnolia dealbata have not been experimentally evaluated. The antimicrobial effects of an ethanol extract of Magnolia dealbata seeds (MDE) and its active compounds honokiol (HK) and magnolol (MG) were tested against the phytopathogen Clavibacter michiganensis subsp. michiganensis and several human multi-drug resistant pathogens using the disk-diffusion assay. The effects of MDE and its active compounds on the viability of human peripheral blood mononuclear cells (PBMC) were evaluated using MTT assay. MDE and its active compounds had antimicrobial activity (inhibition zone > 10 mm) against C. michiganensis, Pseudomonas aeruginosa, Acinetobacter baumannii, Acinetobacter lwoffii, Candida albicans, Candida tropicalis and Trichosporon belgeii. The results suggest that M. dealbata and its active compounds have selective antimicrobial effects against drug-resistant fungal and Gram (-) bacteria and exert minimal toxic effects on human PMBC.     

A molecular probe for the optical detection of biogenic amines

A coumarin derivative was employed for the detection of biogenic amines in buffered aqueous solution by UV-Vis or fluorescence spectroscopy. Incorporated in a polymeric matrix, the dye can also be used for the optical detection of gaseous amines.     

A bright tetranuclear iridium(III) complex

A cyclic tetranuclear cyclometallated iridium(III) complex using cyanide anions as bridging ligands and displaying a tetrahedrally distorted square geometry has been obtained with high yield; photo- and electrochemical characterizations show that most interesting properties of mononuclear cyclometallated iridium complexes are retained in the tetranuclear assembly.     

Stability of Parathion-Methyl,Methiocarb, DDT and 2,4-D in Solid-Phase Extraction Precolumns Packed with a Polymeric Reversed Phase

Abstract

The stability of parathion-methyl, methiocarb, DDT and 2,4-D, adsorbed on the polymeric PLRP-S phase packed in small stainless steel precolumns was examined, with a view to propose the use of these precolumns as alternative means for the transport of water samples. First, water samples spiked with the studied pesticide at low μg/l concentration levels were extracted and preconcentrated in the precolumns, using appropriate conditions for a total recovery. Then, the precolumns were stored at room temperature (15—20°C) or at 35°C for different time periods. At the end of the respective period each precolumn was coupled to an HPLC column via a switching valve and was on-line analyzed by reversed phase chromatography with UV detection. The four pesticide recoveries after one week in the precolumn at room temperature were higher than 90%. The same was true at 35°C except for DDT, which suffered a 30% degradation in one week. Further studies showed that DDT and parathion-methyl were stable at least for five weeks in precolumns stored at room temperature. Methiocarb also was stable for this period but storing the precolumns at 4°C.     

The structure of azines derived from C‐formyl‐1H‐imidazoles in solution and in the solid state: tautomerism,configurational and conformational studies

The structures of three azines derived from 2‐formylimidazole, 4(5)‐formylimidazole, and 4(5)‐formyl‐5(4)‐methylimidazole have been determined in solution and in the solid state. Density Functional Theory (DFT) Polarizable Continuum Model (PCM) calculations (geometries, energies, and chemical shifts), NMR [solution and cross polarization magic‐angle spinning (CPMAS)], and X‐ray crystallography [azine of 4(5)‐formylimidazole] have been used. The configuration around the central C = N bonds has been determined and some insights about prototropic tautomerism and conformation have been gained. Copyright © 2013 John Wiley & Sons, Ltd.     

On the use of V-mask techniques to estimate variations in Cusum control charts by using a commercial spreadsheet

The laboratories verify data from control samples through the application of typical control charts by using commercial spreadsheets. The criteria to decide whether a measurement procedure is in statistical control involves the interpretation of the control chart after each analytical run although the decision is not always practical. So, to detect long term trends in the process, a Cusum chart graphic representation can be implemented. The use of a V-mask verification tool will show the point from which the deviations are significant. Since the construction of a V-mask is complicated in practice, in this article is proposed the definition of a visual representation and also how to construct a tabular procedure with a commercial spreadsheet form in which the V-mask serves as control limits for the Cusum chart.