Collective modes in some Fokker-Planck Coulomb systems: One-dimensional case

The collective modes in two Fokker-Planck Coulomb systems are studied in one dimension and in the long wavelength limit. The Fokker-Planck “friction coefficient”, which can be related to the viscosity of the medium through the Stokes' law, is treated as a parameter. In a single component system it is shown under what circumstances the propagative plasma mode can become a diffusive mode. Depending on an inequality involving the friction coefficient and the plasmon frequency, the collective mode can illustrate certain properties of the so-called central peak. A two-component Vlasov-Fokker-Planck system exhibits three modes analogous to the Rayleigh scattering in a viscous fluid.     

A simple field test for the detection of mercury in polluted water, air and soil samples

Summary A simple field test for the detection of mercury is described. The test is based on the ligand exchange reaction where hexacyanoferrate(III) exchanges its cyanide ions with chromogenic organic ligand succinyl dihydroxamic acid (SDHA). In the reaction the colourless SDHA reacts with yellow K₃Fe(CN)₆ to give a greenish blue coloured complex in a slightly acidic solution containing mercury. The reaction has been successfully applied for the detection of mercury in polluted water, air and soil samples. In air, at a velocity of 0.21/min of the impinging air and a reaction temperature of 70°C, mercury(II) as low as 0.01 g could be easily detected after 3 min exposure. In water the limit of identification and limit of dilution were found to be 0.2 g Hg(II) and 1:200000, respectively.     

Liquid crystalline polymers XV. Synthesis,properties and cytotoxicity of photoresponsive thermotropic liquid crystalline copoly(arylidene-ether)s based on 4-tert-butylcyclohexanone and cyclohexanone moieties in the main chain

A new series of photoresponsive thermotropic liquid crystalline copoly(arylidene-ether)s based on both 4-tert-butylcyclohexanone and cyclohexanone moieties in the main chain were synthesised using solution polycondensation technique of both with different 4,4?-diformyl-α,ω-diphenoxyalkane derivatives. Two model compounds were synthesised from the reaction of each cycloalkanone monomer with benzaldehyde, and their structures were determined using single crystal X-ray diffraction. The structure of the monomers and copolymers was confirmed by elemental and spectral analyses. In addition, the thermal stabilities of these copolymers were evaluated by thermogravimetric analysis. We performed both differential scanning calorimertric and polarised optical microscopic measurements to investigate the thermotropic liquid crystalline properties of synthesised copolymers. The UV?Vis absorption spectroscopy of the liquid crystalline copoly(arylidene-ether) 6f revealed that the system undergoes Entgegen/Zusammen (E/Z) photoisomerisation using UV lamp (450 nm). Moreover, the various characteristics of the prepared copolymers including: solubility, X-ray diffraction analysis, gel permeation chromatography (GPC) and scanning electron microscopy were determined and discussed. The cytotoxicity of the model compounds and selected examples of these copolymers was tested against MCF-7 breast cancer cells. All tested samples showed considerable results, where 6c copolymer gave the best result; it showed cytotoxicity against MCF-7 cell line with IC₅₀ of 0.26 µM.     

Biopolymer-layered polysilicate micro/nanocomposite based on chitosan intercalated in magadiite

On the basis of their high adsorption and cation exchange capacity, swelling potential and low toxicity, layered sodium silicate magadiite (Na–magadiite) is an attractive solid for intercalation of polymers. This study envisages the intercalation of cationic biopolymer chitosan (Chit) in Na–magadiite to prepare a Chit/magadiite micro/nanocomposite. Characterisation of starting-magadiite, pure chitosan and Chit/magadiite were investigated using powder X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy and thermal analysis. XRD confirmed that the chitosan had been intercalated into the interlayer space of magadiite by increasing the basal spacing, d₀₀₁ from 15.6 Å to 21.45 Å. The presence of characteristic bands of biopolymer and layered silicate in Chit/magadiite were confirmed by FTIR analysis. The thermal stability of micro/nanocomposite was evaluated by thermogravimetry analysis. The results suggested the formation of electrostatic interactions by protonated amine groups with the negatively charged magadiite surface as well as intercalation in the form of a predominant monolayer arrangement of chitosan chains in layered silicate magadiite.     

Flavonoid dihydromyricetin-mediated silver nanoparticles as potential nanomedicine for biomedical treatment of infections caused by opportunistic fungal pathogens

Dihydromyricetin-mediated silver nanoparticles (DMY-AgNPs) were synthesized and their efficacy against fungal pathogens tested in vitro. The shape of DMY-AgNPs appeared to be spherical with size of ~34 nm. Fourier-transform infrared (FT-IR) analysis indicated that –OH and C=O groups were involved in nanoparticle formation. The XRD pattern of DMY-AgNPs showed strong peaks at 38°, 44°, and 64°, corresponding to reflection from (111), (200), and (220) planes. Five opportunistic fungal pathogens, namely Aspergillus fumigatus, Aspergillus niger, Paecilomyces formosus, Candida albicans, and Candida parapsilosis, were isolated from patients suffering from respiratory tract infections. Growth of each fungal strain was inhibited by DMY-AgNPs. The zone of inhibition of DMY-AgNPs against A. fumigatus, A. niger, P. formosus, C. albicans, and C. parapsilosis was 17.6, 19.2, 22.2, 15.8, and 18.5 mm. The minimal inhibitory concentration was found to be 0.83, 0.73, 0.67, 0.95, and 0.89 µg mL^?1, respectively. This is the first report on DMY-AgNPs as an effective antifungal agent. DMY-AgNPs are a potential alternative to commercially available antifungal fungicidals.     

Synthesis,characterization, density functional theory,thermal, antimicrobial efficacy,and DNA binding/cleavage studies of Cu(II), Cr(III), Fe(III), Ni(II), Co(II), Zn(II), and Pt(IV) complexes with a derivative of 2-hydroxyphenoxymethylfuran-5-carbaldehyde

In this study, Seven new complexes incorporating (E)-2-(((5-([2-hydroxyphenoxy]methyl)furan-2-yl)methylene)amino)phenol derived from 2-hydroxyphenoxymethylfuran-5-carbaldehyde and 2-aminophenol have been synthesized using Cu(II), Cr(III), Fe(III), Ni(II), Co(II), Zn(II), and Pt(IV) metal salts. Thermal measurements, molar conductance, magnetic moment, elemental analyses, spectral (IR, UV–Vis, ¹H nuclear magnetic resonance (NMR), ESR, Mass), were used to characterize insulated solid complexes. The thermogravimetry (TG) and differential thermoanalysis (DTA) of the complexes were carried out in the range of 30–900°C. Magnetic susceptibility and electronic spectral data, as well as quantum chemical calculations, reveal the square planar geometry for Ni (II) complex, square planar/octahedral geometry for Cu (II) complex, while Co(II), Zn(II), Cr(III), Fe(III), and Pt (IV) complexes are octahedral geometry. Density functional theory (DFT) studies revealed that geometries of metal complexes and Schiff base were entirely optimized in relation to use energy by 6–31 + g (d,p) basis set. The complexes show a well-defined crystal system indicated by a powder-X-ray diffraction pattern. The scanning electron microscope showed complexes were nanocrystalline in nature, in addition to the interaction of the complexes with calf thymus CT-DNA, which was investigated via the UV–visible absorption method. Therefore, the DNA cleavage activity by the H₂L ligand and its metal complexes was performed. Finally, the synthesized complexes were tested for their in-vitro antimicrobial efficacy.     

Solvatochromism and fluoride sensing of thienyl-containing benzodiazaboroles

Static and time-resolved fluorescence studies were carried out to investigate the photophysical properties and fluoride sensing abilities of highly fluorescent thienyl-containing 1,3-diethyl-1,3,2-benzodiazaboroles. Absorption and fluorescence spectra were measured in various solvents, showing the fluorophores to emit in the visible wavelength region with colors varying from blue to orange and quantum yields ranging between 0.21 and 1. Measured Stokes shifts of 2898 cm(-1) to 9308 cm(-1) were used to calculate the difference between excited- and ground-state dipole moments of the fluorophores. Values up to 18.8 D are of the same magnitude as for designed polarity probes such as PRODAN, supporting the idea of internal charge transfer transitions. Quenching studies with pyridine observing static and time-resolved fluorescence revealed a purely dynamic quenching mechanism and low Lewis acidity of the boron within the benzodiazaborolyl moiety compared to other triarylboranes. In contrast to this, quenching with fluoride was shown to stem from adduct formation. Reversible complexation of fluoride follows a simple mechanism for multi-functionalized benzodiazaboroles 2b and 2c, while those containing only one benzodiazaborole moiety (1 and 2a) show a more complicated behaviour, which might be explained by aggregation. Combining a benzodiazaborole group and a dimesitylborane function results in spectrally switchable fluoride sensors 3a and 3b, since the two boron sides can be deactivated for fluorescence in a stepwise manner.     

Liquid crystalline polymers XVI*. Thermotropic liquid crystalline copoly(arylidene-ether)/TiO2 Nanocomposites: synthesis,characterisation and applications

ABSTRACT

Polymer nanocomposites are already a part of many important worldwide businesses. Among many nanocomposite precursors, titanium dioxide (TiO₂) nanopowder is increasingly being investigated due to its special properties. In this work, the feasibility of synthesising a new series of materials, copoly(arylidene-ether)/titanium dioxide nanocomposites, using in-situ copolymerisation technique has been investigated. This can be performed by the interaction of both cyclohexanone and 4-tert-butylcyclohexanone monomers with 4,4′-diformyl-2,2′-dimethoxy-α,ω-diphenoxyalkanes Ia–e, respectively, using different additions of titanium dioxide-P25. The structure of the prepared nanocomposites IIa–e/TiO₂ (0.2–3.0%) was confirmed by elemental analysis (energy dispersive X-ray spectroscopy) and spectral data (Fourier transform-infrared [FT-IR]). FT-IR verified the dispersion of nanofillers in the copolymer. Then, the characterisation and applications of these nanocomposites are extensively discussed depending on the investigation of how the addition of titanium dioxide nanoparticles affected on their properties using various techniques, such as X-ray diffraction, SEM, transmission electron microscopy, Water Contact Angle (WCA), thermogravimetric analysis, differential thermogravimetric, differential thermal analysis (DTA), polarising optical microscope and UV–vis absorption spectroscopy. The nanoparticles affected on the copolymer thermal behaviour in different ways (discrepancy results) depending on how these nanoparticles are dispersed in the copolymer matrix. UV–vis absorption spectra displayed a decrease in the optical band gap of some nanocomposites, which resulted from the addition of titanium dioxide to these copolymers, and this can improve the efficiency of them as organic emitting materials.     

A wet chemical preparation of transparent conducting thin films of Ga-doped ZnO nanoparticles

Crystalline gallium doped zinc oxide (GZO) nanopowders were synthesized using hydrothermal treatment processing. The doping concentration affected the phase structure as well as the shape of the nanopowder from nano rod-like structure to nanoparticulate one. The specific BET surface area increases with increasing the gallium doping concentration. Transparent conducting films were deposited on borosilicate glass substrate by spin coating using sols containing GZO nanoparticles dispersed in 1-propanol. The films are crystalline with a hexagonal structure. The effect of Ga doping concentration, sintering temperature and thickness of the layers has been investigated. The lowest resistivity achieved was 6.4 × 10^?2 Ω cm for a thickness of 150 nm. The films present a transmittance in the visible range as high as 90 %.     

Tunable Spin‐Crossover Behavior of the Hofmann‐like Network {Fe(bpac)[Pt(CN)4]} through Host–Guest Chemistry

A study of the spin‐crossover (SCO) behavior of the tridimensional porous coordination polymer {Fe(bpac)[Pt(CN)₄]} (bpac=bis(4‐pyridyl)acetylene) on adsorption of different mono‐ and polyhalobenzene guest molecules is presented. The resolution of the crystal structure of {Fe(bpac)[Pt(CN)₄]} ? G (G=1,2,4‐trichlorobenzene) shows preferential guest sites establishing π???π stacking interactions with the host framework. These host–guest interactions may explain the relationship between the modification of the SCO behavior and both the chemical nature of the guest molecule (electronic factors) and the number of adsorbed molecules (steric factors).