The Periodate‐Based Double Perovskites M2NaIO6 (M = Ca,Sr, and Ba)

The crystal structures of the M₂NaIO₆ series (M = Ca, Sr, Ba), prepared at 650 °C by ceramic methods, were determined from conventional laboratory X‐ray powder diffraction data. Synthesis and crystal growth were made by oxidizing I^– with O₂^(air) to I⁷⁺ followed by crystal growth in the presence of NaF as mineralizator, or by the reaction of the alkali‐metal periodate with the alkaline‐earth metal hydroxide. All three compounds are insoluble and stable in water. The barium compound crystallizes in the cubic space group Fm3m (no. 225) with lattice parameters of a = 8.3384(1) Å, whereas the strontium and calcium compounds crystallize in the monoclinic space group P2₁/c (no. 14) with a = 5.7600(1) Å, b = 5.7759(1) Å, c = 9.9742(1) Å, β = 125.362(1)° and a = 5.5376(1) Å, b = 5.7911(1) Å, c = 9.6055(1) Å, β = 124.300(1)°, respectively. The crystal structure consists of either symmetric (for Ba) or distorted (for Sr and Ca) perovskite superstructures. Ba₂NaIO₆ contains the first perfectly octahedral [IO₆]^5– unit reported. The compounds of the ortho‐periodates are stable up to 800 °C. Spectroscopic measurements as well as DFT calculations show a reasonable agreement between calculated and observed IR‐ and Raman‐active vibrations.     

Controlled Click‐Assembly of Well‐Defined Hetero‐Bifunctional Cubic Silsesquioxanes and Their Application in Targeted Bioimaging

A general procedure for the assembly of hetero‐bifunctional cubic silsesquioxanes with diverse functionality and a perfectly controlled distribution of functional groups on the inorganic framework has been developed. The method is based on a two‐step sequence of mono‐ and hepta‐functionalization through the ligand‐accelerated copper(I)‐catalyzed azide–alkyne cycloaddition of a readily available octaazido cubic silsesquioxane. The stoichiometry of the reactants and the law of binomial distribution essentially determine the selectivity of the key monofunctionalization reaction when a copper catalyst with strong donor ligands is used. The methodology has been applied to the preparation of a set of bifunctional nano‐building‐blocks with orthogonal reactivity for the controlled assembly of precisely defined hybrid nanomaterials and a fluorescent multivalent probe for application in targeted cell‐imaging. The inorganic cage provides an improved photostability to the covalently attached dye as well as a convenient framework for the 3D multivalent display of the pendant epitopes. Thus, fluorescent bioprobes based on well‐defined cubic silsesquioxanes offer interesting advantages over more conventional fully organic analogues and ill‐defined hybrid nanoparticles and promise to become powerful tools for the study of cell biology and for biomedical applications.     

Highly sensitive ion preconcentration method based on flow sorbent extraction using multiwall carbon nanotubes

In this work a solid phase on-line uranium ion preconcentration system coupled with spectrophotometry has been developed. The method is based on uranyl ion preconcentration at pH 3.75 onto multiwall carbon nanotubes treated with HNO₃. After preconcentration, the uranyl ions are eluted with 0.32?mol?L^?1HCl followed by reaction with 3,6-bis[(2-arsonophenyl)-azo]-4,5-dihydroxy-2,7-naphthalendisulfonic acid 0.08%[w/v] (Arsenazo III), which had maximum monitored absorbance of 650?nm. Effects of the pertinent experimental parameters on the system were investigated by means of 2^6?2 fractional factorial design, while optimization was carried out using the Doehlert matrix. Under optimized conditions, detection and quantification limits were found to be 0.21 and 0.7?µg?L^?1, respectively. The analytical curve ranged from 5 to 150?µg?L^?1 (r?=?0.998), while the relative standard deviations (RSD) were 3.27 and 2.56% for the respective uranium concentrations of 10 and 100?µg?L^?1 (n?=?10). The features obtained for the on-line preconcentration system were: preconcentration factor of 228, concentration efficiency of 57?min^?1, consumption index of 0.13?mL and sample throughput of 15?h^?1. In order to assess the accuracy of the proposed method, addition and recovery studies were carried out on spring water samples from different sources and synthetic seawater with satisfactory results ranging from 94.85 up to 103.65%.     

Synthesis of O-[4,6-Di-O-Acetyl-4-O-(2,3,4,6-Tetra-O-Acetyl-β-D-Galactopyranosyl)-2-Deoxy-2-Hydroxyimino-D-Arabino-Hexopyranosyl]-N-Benzyloxycarbonyl-L-Serine Methyl Esters And Their Transformations

ABSTRACT

3,6-Di-O-acetyl-4-O-(2,3,4,6-tetra-O-acetyl-β-D-galactopyranosyl)-2-deoxy-2-hydroxyimino-α- and -β-D-arabino-hexopyranosides of N-benzyloxycarbonyl-L-serine methyl ester as well as of ethanol have been synthesised from D-lactal hexaacetate via nitrosyl chloride, followed by condensation with L-serine derivatives and ethanol, respectively. The compounds of L-serine thus obtained were modified at C-2 and C-3 to afford L-serine derivatives attached to disaccharides containing terminal α-D-gluco-, 2-acetamido-α-D-gluco-, β-D-manno, 2-acetamido-β-D-manno-pyranosyl, 3-azido-2-hydroxyimino-α-D-arabino-, and α-D-ribo-hexopyranosyl residues.     

Mass spectrometry of substituted 1,3-dihydro-2H-imidazole-2-thiones

The electron impact mass spectra of the 4-formyl-1, 3-dihydro-2H-imidazole-2-thione, its six 1-methyl(n-propyl, n-hexyl)-3-methyl(phenyl)-disubstptuted derivatives, and the 1,3-dihydro-1-phenyl-2H-imidazole-2-thiome are discussed. The fragmentation pattern is strongly influenced by the alkyl or phenyl N-substituents, as well as by the length of the alkyl chain. The odd-electron ions containing an N-phenyl substituent, but not a propyl or hexyl group, eject a hydrogen atom from the phenyl ring, while the presence of a long alkyl chain greatly enhances the loss of the sulphyhydryl radical and facilitates the expulsion of several alkenes, and alkyl and alkenyl radicals.     

Electrochemical Sensor for Selective Detection of Meldonium in Urine by Voltammetry

A highly sensitive electrochemical sensor based on arenediazonium tosylates was designed to detect meldonium in urine. The effect of the concentration of ArN2⁺OTs⁻ arenediazonium tosylate modifier and various substituents was studied. Basic operating parameters for voltammetric meldonium detection were established and the procedure for urine sample preparation was developed. The following values were obtained: limit of detection (LOD) 0.005 mg ⋅ L⁻¹ (P=0.95) and limit of quantification (LOQ) 0.01 mg ⋅ L⁻¹. The relationship between the analytical signal and meldonium concentration in the solution ranging from 0.01 to 400 mg ⋅ L⁻¹ was described by a linear function. The meldonium concentration error did not exceed 18 %. The analysis time for a single urine sample was reduced to 15 minutes.     

Measuring local pH in electrochemistry

Localized pH measurements are important in various areas of electrochemistry, from corrosion to bio-electrochemistry and electrocatalysis. Different techniques are available to perform these measurements and offer numerous possibilities in terms of spatial and temporal resolution, sensitivity, and precision. In this brief review we present the recent progress made and summarize the main techniques available for localized pH measurements in electrochemistry such as scanning probe techniques (SECM, SICM, SIET), laser (confocal) fluorescence microscopy, rotating ring-disc electrode (RRDE) voltammetry, and infra-red spectroscopy, among others.     

How to handle nanomaterials? The re-entry of individuals into the philosophy of chemistry

In this paper we will argue that the categories of physical individuals and chemical stuff are not sufficient to face the chemical ontology if nanomaterials are taken into account. From a perspective that considers ontological questions and wonders which the items involved in science are, we will argue that the domain of nanoscience must be considered as populated by entities that are neither individuals, as those of physics, nor stuff, as those items of macro-chemistry. This discussion, in virtue of the analysis of the nature of nanomaterials, leads to propose a proper ontological category for nanoparticles: nanoindividuals. Nanomaterials are sorts of individuals, but they are different from physical individuals and from chemical stuff. We will also claim to contribute to the growing field of the philosophy of chemistry, especially regarding discussions that manifest not only epistemological but also ontological issues. In this scenario, the field on nanoscience is particularly challenging.