Gly‐Gly‐His Immobilized On Monolayer Modified Back‐Side Contact Miniaturized Sensors for Complexation of Copper Ions

Miniaturized planar back‐side contact transducers (BSC) with chemically modified gold surface have been utilized as electrochemical sensors. The electrodes have been functionalized by sequential immobilization of aryl diazonium salts or alkanethiols and short peptide Gly‐Gly‐His. The applicability of gold substrates modified with aryl diazonium salts in voltammetric detection of copper(II) ions in aqueous solutions has been studied. The combination of two fundamental elements of the solid‐state electrode, i.e. back‐side contact (BSC) gold sensor and self‐assembled monolayers, allowed one to obtain reliable miniaturized copper(II) ion sensors. It can have important future applications in environmental sensing or in implantable biodevices.     

Nano-titanium oxide doped with gold,silver, and palladium — synthesis and structural characterization

Nano-titania doped with noble metals (Au/TiO₂, Ag/TiO₂, Pd/TiO₂) has been synthesized by mild hydrolysis of the mixture of metal salts or complexes and titanium isopropoxide ((iPr-O)₄Ti). After thermal decomposition of the obtained precursors, nanomaterials were formed. Morphological characterization of the nanomaterials was provided by scanning electron microscopy (SEM) and stereological analysis, determining the BET specific surface area, and BJH nanoporosity (pore volume, pore size). It has been found that the structure of nanomaterials (size of nanoparticles and agglomerates) depended strongly on the method of the (iPr-O)₄Ti hydrolysis. A minor dependence on the kind of solvents and precursors of noble metals was observed. The presence of doping metal nanoparticles was confirmed by transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX). Nanomaterial phases were identified by X-ray diffraction (XRD). According to the XRD patterns, Ag/TiO₂ and Pd/TiO₂ products with doping metals in their oxidized form contain Ag-Ti and Pd-Ti phases. Peaks of the metal oxides Ag₂O and PdO are absent in the XRD patterns. The average size of TiO₂ nanoparticles is situated in the region of 20–60 nm, whereas metals are present as about 10–15 nm sized particles and fine nanoparticles.     

Influence of the Regression Technique on the Extrapolated Retention Values of Single-Point Adsorption Compounds on Silica Gel

JPC – Journal of Planar Chromatography – Modern TLC - The retention (RM) values of nine one-point adsorption model compounds: diphenylamine, indol, 2-naphtol, 1-naphtol, 1-naphtylamine,...     

Voltammetric Analysis of Cadmium and Lead (Undesirable Elements) in Brine,Supported by Solid Phase Extraction – the Right Solution of the Analytical Challenge

The stripping voltammetry at HMDE is proposed for Cd and Pb (undesirable ingredients) determination in the natural brine (C_Cl >43 g L⁻¹). Samples with so high salinity have to be significantly diluted. For ICP MS, a 10^5–6 times dilution is required, which disqualifies this method. The proposed procedure allows to determine Cd (0.001 μg L⁻¹) and Pb (0.005 μg L⁻¹) after only 100 times dilution. The thermal chloride stripping or isolation by Chelex 100 increase the quality of obtained data. The recovery study was performed. The LOQs are below recommendations related to the use of brines in balneology.     

Modified 6‐Aza Uridines: Highly Emissive pH‐Sensitive Fluorescent Nucleosides

Optimized facile syntheses and highly desirable spectroscopic properties of two isomorphic fluorescent pyrimidines, comprising a 1,2,4‐triazine motif conjugated to a thiophene ( 1 a ) or a furan ( 1 b ), are described. Although structurally related to their 5‐modified uridine counterparts, these modified 6‐aza‐uridines reveal dramatically improved fluorescence properties and a remarkable sensitivity to polarity and pH changes. The thiophene derivative 1 a has an absorption maximum around 335 nm, which upon excitation yields visible emission with a polarity‐sensitive maximum and fluorescence quantum yield ranging from 415 nm (Φ=0.8) to 455 nm (Φ=0.2) in dioxane and water, respectively. Nucleoside 1 a also displays susceptibility to acidity. Correlating emission intensity and solution pH yields a pK_a value of 6.7–6.9, reasonably close to physiological pH values. The results illustrate that highly sought‐after fluorescence features (brightness and responsiveness) are not necessarily the trait of large fluorophores alone, but can be observed with probes that meet stringent isomorphic design criteria.     

The recognition of beer with flow-through sensor array based on miniaturized solid-state electrodes

Flow-through electronic tongue based on miniaturized solid-state potentiometric sensors has been developed. A simple technique, i.e. membrane solution casting on the surface of the planar Au transducers was applied for the preparation of classical ion-selective and partially selective microelectrodes, introduced in the flow-through sensor array. The performance of the designed electronic tongue was tested in the qualitative analysis of various brands of beer. Samples of the same brand of beer but with different manufacture dates, originating from different manufacture lots, have been applied in the studies. The combination of PLS and ANN techniques allowed the discrimination between different brands of beer with 83% of correct classifications.     

Nystatin in Langmuir monolayers at the air/water interface

The paper presents a thorough characteristics of Langmuir monolayers formed at the air/water interface by a polyene macrolide antibiotic-nystatin. The investigations are based on the analysis of pi/A isotherms recorded for monolayers formed by this antibiotic at different experimental conditions. A significant part of this work is devoted to the stability and relaxation phenomena. It has been found that nystatin forms at the air/water interface monolayers of the LE state. A plateau region, observed during the course of the isotherm compression, is suggested to be due to the orientational change of nystatin molecules from horizontal to vertical position. Quantitative analysis of the desorption of the monolayer material into bulk water indicates that the solubility of nystatin monolayers increases with surface pressure. At low surface pressures, the desorption of nystatin from a monolayer is controlled both by dissolution and by diffusion. However, at the plateau and in the post-plateau region, the desorption does not achieve a steady state and the monolayer is less stable than in the pre-plateau region. However, the presence of membrane lipids, even at a low mole fraction, considerably increases the stability of nystatin monolayers. This enables the application of the Langmuir monolayer technique to study nystatin in mixture with cellular membrane components, aiming at verifying its mode of action and the mechanism of toxicity.     

Microelectrode array fabricated in low temperature cofired ceramic (LTCC) technology

This work presents the development of a novel construction of an integrated microelectrode array. The device was fabricated on a ceramic support, with the use of low temperature cofired ceramics technology. Model potassium-selective membranes were applied on the surface of PdAg/AgCl electrodes formed on the ceramic substrate. The obtained microsensors exhibited very good repeatability, reproducibility, and sensitivity. The array of microelectrodes covered with polymeric layers of various selectivities was applied as an electronic tongue to differentiate between various diet supplements.     

Influence of Bis-NHC Ligand on Platinum-Catalyzed Hydrosilylation of Internal Alkynes

Synthesis and characterization of a new bifunctional N-heterocyclic carbene precursor with sterically expanded substituents is described. The obtained NHC is employed in the catalytic system for hydrosilylation of internal alkynes providing a fully selective and effective process in mild conditions under air. Comparison of the performance of the newly developed catalytic system with its analogs based on monofunctional NHC ligands proves that the presence of two metal atoms and the proper design of the steric environment around the metal center ensure a definitely greater activity in the hydrosilylation process.