Development of a novel flow injection liquid-liquid microextraction method for the on-line separation and preconcentration for determination of zinc(II) using 5-(8-hydroxy-2-quinolinylmethyl)-2,8-dithia-5-aza-2,6-pyridinophane as a sensitive and selective fluorescent chemosensor

A novel flow injection analysis (FIA) system based on liquid-liquid microextraction and fluorimetric determination was developed for the determination of traces of the Zn²⁺ ion using 5-(8-hydroxy-2-quinolinylmethyl)-2,8-dithia-5-aza-2,6-pyridinophane (L) as a sensitive and selective fluorimetric sensor, with λ_ex = 373 nm and λ_em = 530 nm, and hexanol as the extracting organic solvent. In the designed FIA system, the phase separation takes place via gravitation forces in the absence of any segmenter. The influence of pH and ionic strength of the solution, amount of ligand, nature of counter ion, volume of organic solvent, extraction time and coil length was investigated. Under optimized experimental conditions, the calibration curve found to be liner over a concentration range of 0.025-4.53 μg mL⁻¹ (R² = 0.9951) with a limit of detection of 2.3 ng mL⁻¹. The enrichment factor was 45 and relative standard deviation for 7 replicate determinations was 2.43%. The method is very fast and uses low levels of organic solvents. The proposed method was applied successfully to the determination of zinc(II) in human hair, human serum and two inorganic sludge samples.     

A one-pot pseudo nine-component isocyanide-based reaction: synthesis of a new class of zinc 1,5-disubstituted 1H-tetrazol-5-yl coordination complexes

A novel one-pot pseudo nine-component synthesis of zinc 1,5-disubstituted 1H-tetrazol-5-yl coordination complexes in good yields starting from simple and readily available substrates, including a 1,3-dicarbonyl compound, an isocyanide, N,N-dimethylformamide dimethyl acetal, sodium azide, and zinc chloride in methanol at ambient temperature, is described.     

The influence of surface effects on Frederiks transition in nematic liquid crystal doped with ferroelectric nanoparticles

Motivated by our recent work,in this work,we present the numerical study of the anchoring effect on the Frederiks threshold field in a nematic liquid crystal doped with ferroelectric colloidal nanoparticles.Assuming weak anchoring conditions,we employ the relaxation method and Maxwell construction to numerically solve the Euler–Lagrangian differential equation for the total free energy together the Rapini–Papoular surface energy to take into account anchoring of nematic liquid crystal molecules at the substrates.In this study,we focus our attention on obtaining the phase diagrams of Frederiks transition for different values of anchoring strength which have been not computed in our previous work.In this way,the effect of nanoparticle radius,nanoparticle volume fraction,nanoparticle polarization,and cell thickness on the Frederiks transition for different values of anchoring conditions are summarized in the phase diagrams.The numerical results show that by increasing the nanoparticles size and nanoparticle volume fraction in the ferronematic system,the Frederiks threshold field is strongly reduced.     

Biodegradable Cell-Seeded Collagen Based Polymer Scaffolds for Wound Healing and Skin Reconstruction

In the present study a collagen-glycosaminoglycans scaffold, following chemical modifications, was prepared as an analog of the extracellular matrix (ECM) by a freeze drying method. Appropriate tests related to its use for wound healing (evaluation of the structure by scanning electron microscopy, swelling properties, biodegradability properties, Fourier transform infrared spectroscopy and cell culture) were done on the scaffolds. Amniotic fluid-derived stem (AFS) cell seeded scaffolds were shown to be potentially useful for wound healing.     

8-Hydroxyquinoline Functionalized Graphene Oxide: an Efficient Fluorescent Nanosensor for Zn<Superscript>2+</Superscript> in Aqueous Media

A nanosensor, based on 8-hydroxyquinoline functionalized graphene oxide, was developed for the fluorescence detection of Zn²⁺. It showed high selectivity and sensitivity for Zn²⁺ion in aqueous solution over other metal ions such as Li⁺, Na⁺, Ca²⁺, Mg²⁺, Al³⁺, Cd²⁺, Co²⁺, Cu²⁺, Hg²⁺, Ni²⁺, Pb²⁺, Fe²⁺, Fe³⁺and Cr³⁺. Due to the linearity of the emission intensity toward Zn²⁺ concentration, fluorescent technique could be used for the detection of Zn²⁺ ion even at very low concentrations.