Two phase photochemical synthesis of silver nanoparticles and their impact on the chlorophylls

Abstract

We have designed an experimental study dedicated to silver nanotoxicity using a suspension of citrate-silver nanoparticles, obtained by photochemical reduction. Fine granularity of generally symmetrical shape nanoparticles were evidenced by tansmission electron microscopy. The localized surface plasmon resonance spectral band revealed the intensification of silver nanoparticle formation under UV exposure. The nanotoxicity of silver nanoparticles was tested on cereal sprouts by measuring the concentrations of chlorophylls and carotenes in the green tissue. The differences between control samples, supplied with distilled water and test samples, loaded with different volumes of silver nanoparticles suspension were analyzed statistically, and compared with literature reports.     

Intrinsic broad-band white-light emission by a tuned, corrugated metal-organic framework

Herein we report on the broad-band direct white-light originating from a single component emitter, namely a novel three-periodic metal-organic framework (MOF). This material features an unprecedented topology with (3,4)-connected nodes. The structure-function relationship in this system is driven by two complementary unique structural features: corrugation and interpenetration. Good correlation between simulated and experimental emission spectra has been attained, resulting in optimized color properties that approach requirements for solid-state lighting (SSL). Guided by the optimized calculated spectra, the tunability of the assembly was proven by the successful in-framework co-doping of Eu(3+). This resulted in significantly improved color properties, opening new paths for the rational design of alternative materials for SSL applications.     

On the univalence of an integral operator defined by Hadamard product

In this paper, we introduce a new general integral operator defined by the Hadamard product. Furthermore, we obtained new sufficient conditions for this operator to be univalent in the open unit disk.     

Molecular modelling and spectral investigation of some triphenyltetrazolium chloride derivatives

The molecular parameters of 2,3,5-triphenyl-2H-tetrazolium chloride (TTC) and some compounds based on triphenylformazans (TPFs) — resulting from the enzymatic transformation of TTC, were subjected to comparative investigation on the basis of semi-empirical quantum-chemical simulations, revealing some changes in dipole moment and polarisability in the TPFs in comparison with TTC. Chemical shift due to substituents was discussed using electronic absorption bands in the UV-VIS range recorded for diluted solutions in various solvents as well as the absorption spectra recorded in the infrared range for KBr dispersions. The correlation of the spectral shift of the electronic absorption bands with a specific function on the solvent refractive index, as recommended by theoretical studies focused on solute-solvent interactions, revealed the major role played by dispersive and induction forces. For several solvents, a different behaviour could be assigned to specific interactions overlapping with universal solute-solvent interactions.     

Thermal behaviour and characterisation of new biologically active Cu(II) complexes with benzimidazole as main ligand

Four coordination compounds of copper(II) were synthesised and characterised in solid state by elemental analysis, infrared, electronic and EPR spectroscopy, as well as by thermal analysis (TG/DTA). The complexes were formulated on the basis of experimental data as: [Cu(BzIm)₂(H₂O)]·H₂O (1), [Cu₂(Acr)₄(HBzIm)₂] (2), [Cu(Acr)₂(HBzIm)₂] (3) and [Cu(Acr)₂(HBzIm)₂(H₂O)]·H₂O (4). IR data are in accordance with the unidentate nature of benzimidazole, in complexes (2), (3) and (4), and bridge bidentate nature of benzimidazole, in complex (1), while acrylato acts as uni- or bridge/chelate ligand. The electronic spectra display the characteristic pattern of square planar, square pyramidal, or octahedral stereochemistry, also confirmed by EPR spectra. Thermal decomposition evidenced several well-defined steps as dehydration of complexes (1) and (4), benzimidazole molecule releases for all complexes and acrylate decomposition in carbonate for complexes (3) and (4). In all four cases, the final residue after thermal treatment in air flow is copper(II) oxide, formed during the decomposition steps for complexes (3) and (4), and, respectively, after the oxidation of the metallic copper for complexes (1) and (2). Antimicrobial activities of the complexes have been determined by in vitro assays, against various Gram-negative and Gram-positive bacterial and fungal strains. Copper(II) complexes were also evaluated for their cytotoxicity on eukaryotic cells.     

Structural screening by multiple reaction monitoring as a new approach for tandem mass spectrometry: presented for the determination of pyrrolizidine alkaloids in plants

In tandem mass spectrometry the multiple reaction monitoring (MRM) mode is normally used for targeted analysis but this mode also has the potential to screen for structural similarities of analytes. On the basis of the fact that in general similar molecular structures result in similar fragments or losses of neutrals, this approach was used for pyrrolizidine alkaloid (PA) screening but could also be easily adapted to screen for other compound classes. PA are plant toxins of which several hundred individual compounds have been identified. Our MRM screening approach uses the structural relation and similar core structure of all PA which results in a common and thus predictable mass spectrometric fragmentation behaviour. On this basis a method was developed which screens for PA structures by MRM transitions and allows the detection of each individual PA down to a low microgram per kilogram concentration range. The approach was applied to investigate plants from the families of Asteraceae (several species of Senecio and Eupatorium), Boraginaceae (Echium, Cynoglossum, Borago and Anchusa officinalis as well as Heliotropium europaeum) and Fabaceae (Crotalaria incana) for a complete qualitative and quantitative PA characterisation. All analytes that were detected as possible PA by MRM screening were further investigated by recording product ion spectra. Analytes which exhibited a typical PA fragmentation pattern were either confirmed as PA or otherwise deleted as false positive signals (false positive rate was below 10 %). Sum formulas of confirmed PA were determined by additional measurements applying high resolution mass spectrometry. In that way 121 unknown PA were identified and for the first time complete PA profiles of different PA plants were delivered.     

Analytic Functions Related with the Hyperbola

The author considers a new class SHm λμ(α) of normalized analytic functions defined by a diferential operator. Several basic properties and characteristics of the functions belonging to the class SHm λμ(α) are investigated. These include integral representations, coefcient bounds, the Fekete-Szego¨ problem, class-preserving operators and T δ-neighborhoods.     

Evaluating the biological potential of some new cobalt (II) complexes with acrylate and benzimidazole derivatives

This paper presents the synthesis, physico‐chemical and biological properties of four new coordination compounds with mixed ligands: acrylate ion (acr) and benzimidazole/benzimidazole derivatives with the general formula [Co(L) ₂ (acr) ₂ ]·nH ₂ O [ (1) L: benzimidazole (HBzIm), n: 0.5; (2) L: 2‐methylbenzimidazole (2‐MeBzIm), n: 0.5; (3) L: 5‐methylbenzimidazole (5‐MeBzIm), n: 0; (4) L: 5,6‐dimethylbenzimidazole (5,6‐Me₂BzIm), n: 0]. Their chemical formulae were achieved correlating the chemical analysis with mass spectrometry data, the ligands coordination modes were assigned by Fourier transform‐infrared measurements, and the trigonal bipyramidal geometry of cobalt ion in complexes was assigned by data correlation of UV–Vis‐NIR spectra and magnetic moments measurements. Single‐crystal X‐ray diffraction reveals a mononuclear structure with a pentacoordinated cobalt (II) ion, connected to two acrylato coordinated in different modes and two unidentate 5,6‐dimethylbenzimidazole ligands for compound (4) . The biological tests were performed against several microbial strains, the cytotoxicity was evaluated on HCT8 cellular lines and the cell cycle analysis was performed on HT29 cellular lines. Microbiological assays indicated that Co (II) complexes present a very good to good activity against Candida albicans 1760, Enterococcus faecium E5, Bacillus subtilis ATCC 6683 and Escherichia coli ATCC 25922. Predictive pharmacokinetic (ADME), toxicity and drug‐likeness profiles were evaluated for Co (II) complexes. Our results highlight that Co (II) complexes depicted in the present study are suitable to be used as efficient pharmacological agents.     

A multivariate time series approach to projected life tables

The method of mortality forecasting proposed by Lee and Carter describes a time series of age‐specific log‐death rates as a sum of an independent of time age‐specific component and a bilinear term in which one of the component is a time‐varying factor reflecting general change in mortality and the second one is an age‐specific parameter. Such a rigid model structure implies that on average the mortality improvements for different age groups should be proportional, regardless of the calendar period: a single time factor drives the future death rates. This paper investigates the use of multivariate time series techniques for forecasting age‐specific death rates. This approach allows for relative speed of decline in the log death rates specific to the different ages. The dynamic factor analysis and the Johansen cointegration methodology are successfully applied to project mortality. The inclusion of several time factors allows the model to capture the imperfect correlations in death rates from 1 year to the next. The benchmark Lee–Carter model appears as a special case of these approaches. An empirical study is conducted with the help of the Johansen cointegration methodology. A vector‐error correction model is fitted to Belgian general population death rates. A comparison is performed with the forecast of life expectancies obtained from the classical Lee–Carter model. Copyright © 2009 John Wiley & Sons, Ltd.     

Higher degree layer potentials for non-smooth domains with arbitrary topology

We consider layer potentials associated with the Hodge-Laplacian acting on differential forms of arbitrary degree defined on Lipschitz subdomains of a Riemannian manifold. The main emphasis is on the interplay between the mapping properties of such layer potentials and the topology of the underlying domain.Partially supported by a UMC Research Board GrantPartially supported by NSF grant DMS-9870018