Heterometallic 3d–4f coordination polymers: Synthesis,characterization and magnetic properties of 1D zigzag chains containing samarium and terbium

Reaction of the copper precursor [Cu(MeOsaltn)(H₂O)] (H₂MeOsaltn = N,N′-bis(3-methoxysalicylidene)-1,3-diaminopropane) with Ln(NO₃)₃·6H₂O (Ln = Sm and Tb) and pyrazine-2,3-dicarboxylic acid (H₂pyrdic) results in the formation of 1D zigzag chains with the general formula of [Cu(MeOsaltn)Ln(NO₃)(pyrdic)]_n·nDMF. X-ray crystal structures reveal that the samarium and terbium compounds are isostructural and crystalize in the orthorhombic space group Pbcn. The chains are composed of heterodinuclear copper–lanthanide building blocks which are linked by the pyrazine-2,3-dicarboxylate bridging units. Temperature-dependent susceptibility measurements indicate antiferromagnetic exchange interactions for the samarium–copper chain whereas for the terbium–copper compound ferromagnetic interactions are observed.     

The synthesis of free-standing films of polymer/nanocarbon composites using the carbon nanopowder's buoyancy

In this work we report the synthesis of free-standing films of polymer/nanocarbon composites. The method consists in forming a thin film of carbon nanoparticles onto the water's surface. Through the free infiltration of the polymer between the nanoparticles which form the film, after the polymer is cured, we obtain free-standing films of polymer/nanocarbon composites. The composite films are homogeneous; they have 5 wt.% carbon nanoparticles within the polymer matrix and are a few micrometers in thickness.     

Capillary waveguide fluoroimmunosensor with improved repeatability and detection sensitivity

An optical capillary waveguide fluoroimmunosensor based on glass capillaries internally coated with an ultrathin poly(dimethylsiloxane) (PDMS) film is presented. The evaluation of the capillaries developed was done in comparison with aminosilanized [3-(aminopropyl)triethoxysilane, APTES] glass and poly(methylpentene) (PMP) capillaries by immobilizing rabbit γ-globulins on the internal capillary wall. Following reaction with (R)-phycoerythrin-labelled antibody, the capillary was scanned with a laser beam and the fluorescence waveguided through the capillary wall was detected by a photomultiplier placed at one of its ends. The capillaries developed provided considerably improved protein coating homogeneity (intracapillary coefficients of variation 2.9–6.6%) and repeatability (intercapillary coefficients of variation 2.1–5.0%) compared with APTES-treated ones (7.9–13.4 and 8.5–15.2%, respectively). With use of these capillaries in a sandwich-type immunosensor for the determination of rabbit γ-globulins, the assay detection limit was improved eightfold (4.4 ng/mL) compared with that obtained using PMP capillaries (35.3 ng/mL), whereas the assay repeatability was improved threefold (intra-assay coefficients of variation 5.9–13.1%) compared with APTES-treated capillaries (15.6–36%). Optoelectronic set-up used to scan the capillaries (left) and representative fluorescence scannings of dual-band poly(methylpentene) (PMP), PDMS-modified glass and APTES treated glass capillaries     

A summability factor theorem for absolute summability involving quasi-monotone sequences

In this paper we prove a theorem on _|A|k,k≥1${\left|A\right|}_k,k\ge 1$, summability factors for an infinite series by replacing a weighted mean matrix with a triangular matrix.     

Solvent effects on the three-photon absorption cross-section of a highly conjugated fluorene derivative

Herein, we report the study of the three-photon absorption cross-section dependence on solvents parameters for a highly conjugated organic dye, 2,2'-(4,4'-(1E,1'E)-2,2'-(9,9-didecyl-9H-fluorene-2,7-diyl) bis(ethene-2,1-diyl)bis(4,1-phenylene))dibenzo[d]thiazole (A-pi-pi-pi-A). The three-photon absorption cross-section was measured for this organic dye in solution in four different solvents with polarity function, Deltaf between 0.162 and 0.247. The experiments show how the solvent's reorientation of the electrons and polarity contribute to the 3PA cross-section. Multiphoton-absorption experiments of A-pi-pi-pi-A in all four different solvents were performed with a tunable OPG pumped by a 25 picosecond Nd-YAG laser.     

The impact of the pi-electron conjugation length on the three-photon absorption cross section of fluorene derivatives

The three-photon absorption cross sections of three different fluorene derivatives, with extended pi-electron conjugation lengths was experimentally measured and compared with shorter pi-electron conjugation length analogs. The effect of the conjugation length on the three-photon absorption cross section sigma(3) (') of this family of molecules has been elucidated. It is demonstrated that sigma(3) (') of the asymmetric compound D-pi-pi-pi-A is 6.6 times larger than its shorter configuration D-pi-A, while for the symmetric compounds D-pi-pi-pi-D and A-pi-pi-pi-A a two-fold enhancement was found relative to their shorter conjugation length analogs. Measurements of the three-photon excitation of these compounds in THF solution (10(-3)M) were accomplished with a tunable optical pulse generation pumped by a 25 ps Nd-YAG laser.     

An alternative approach on the calculation of cohesive energy density and isothermal compressibility of alkali metal halides

In the present paper, new and useful theoretical methods for the estimation of cohesive energy density (Ced) and isothermal compressibility (k_T) of alkali metal halides are described. The mentioned theoretical methods include the use of Kaya molecular hardness equation published by us in recent years. Cohesive energy density and isothermal compressibility of alkali metal halides were calculated in the framework of mentioned theoretical methods and the results obtained were compared with both experimental data and the results of previous theoretical methods proposed to calculate the aforementioned quantities, namely cohesive energy density and isothermal compressibility. It is important to note that the results obtained in the study are in good agreement with the available experimental data and with the results of previous theoretical methods. Additionally, we also investigated the correlation with lattice energy of cohesive energy density and isothermal compressibility for alkali halides.     

Fluorescence of copper, manganese and antimony ions in phosphate glass host

The paper presents a study based on luminescence characteristics of phosphate glasses containing Cu²⁺, Mn⁴⁺ and Sb³⁺. The glass samples obtained by a wet chemical route belong to Li₂O–BaO–Al₂O₃–La₂O₃–P₂O₅ oxide system. The oxide composition of the glass samples is calculated to obtain a vitreous network composed of metaphosphate chains bonded by modifier ions (Li⁺, Ba²⁺ and La³⁺) and fluorescent ions. The absorption spectra of the samples were acquired in the UV domain in order to establish the excitation wavelength for each fluorescent ion. The absorption peaks of Sb³⁺ ion are ranged at 285 nm and 250 nm, Mn²⁺ ion at 280 nm and 365 nm, Cu²⁺ ion at 295 nm and 313 nm. The luminescence peaks of Cu²⁺, Mn⁴⁺ and Sb³⁺ ions are found in the visible domain at different wavelengths, depending on the oxidation state and coordination symmetry of each fluorescent ion. The fluorescence of Sb³⁺ ion has a strong signal at 450 nm and a weak one at 465 nm, Mn²⁺ ion shows a fluorescence peak at 600 nm and the pair Cu²⁺/Cu⁺ ions reveals a fluorescence emission at 460 nm.     

Silver–titanium dioxide nanocomposites as effective antimicrobial and antibiofilm agents

Recent studies have revealed the existence of liver cancer stem cells (CSCs). Therefore, there is an urgent need for new and effective treatment strategies specific to liver CSCs. In this work, the poly(d,l-lactide-coglycolide) nanoparticles containing paclitaxel were prepared by emulsification-solvent evaporation method. The nanoparticles decorated with anti-CD133 antibody, termed targeted nanoparticles, were prepared by carbodiimide chemistry for liver CSCs. The physicochemical characteristics of the nanoparticles (i.e., encapsulation efficiency, particle size distribution, morphology, and in vitro release) were investigated. Cellular uptake and accumulation in tumor tissue of nanoparticles were observed. To assess anti-tumor activity of nanoparticles in vitro and in vivo, cell survival assay and tumor regression study were carried out using liver cancer cell lines (Huh7 and HepG2) and their xenografts. Particle size of targeted nanoparticles was 429.26 ± 41.53 nm with zeta potential of ?11.2 mV. Targeted nanoparticles possessed spherical morphology and high encapsulation efficiency (87.53 ± 5.9 %). The accumulation of targeted nanoparticles depends on dual effects of passive and active targeting. Drug-loaded nanoparticles showed cytotoxicity on the tumor cells in vitro and in vivo. Targeted nanoparticles resulted in significant improvement in therapeutic response through selectively eliminating CD133 positive subpopulation. These results suggested that the novel nanoparticles could be a promising candidate with excellent therapeutic efficacy for targeting liver CSCs.     

A new ONO3- trianionic pincer-type ligand for generating highly nucleophilic metal-carbon multiple bonds

Appending an amine to a C═C double bond drastically increases the nucleophilicity of the β-carbon atom of the alkene to form an enamine. In this report, we present the synthesis and characterization of a novel CF(3)-ONO(3-) trianionic pincer-type ligand, rationally designed to mimic enamines within a metal coordination sphere. Presented is a synthetic strategy to create enhanced nucleophilic tungsten-alkylidene and -alkylidyne complexes. Specifically, we present the synthesis and characterization of the new CF(3)-ONO(3-) trianionic pincer tungsten-alkylidene [CF(3)-ONO]W═CH(Et)(O(t)Bu) (2) and -alkylidyne {MePPh(3)}{[CF(3)-ONO]W≡C(Et)(O(t)Bu)} (3) complexes. Characterization involves a combination of multinuclear NMR spectroscopy, combustion analysis, DFT computations, and single crystal X-ray analysis for complexes 2 and 3. Exhibiting unique nucleophilic reactivity, 3 reacts with MeOTf to yield [CF(3)-ONO]W═C(Me)(Et)(O(t)Bu) (4), but the bulkier Me(3)SiOTf silylates the tert-butoxide, which subsequently undergoes isobutylene expulsion to form [CF(3)-ONO]W═CH(Et)(OSiMe(3)) (5). A DFT calculation performed on a model complex of 3, namely, [CF(3)-ONO]W≡C(Et)(O(t)Bu) (3'), reveals the amide participates in an enamine-type bonding combination. For complex 2, the Lewis acids MeOTf, Me(3)SiOTf, and B(C(6)F(5))(3) catalyze isobutylene expulsion to yield the tungsten-oxo complex [CF(3)-ONO]W(O)((n)Pr) (6).