Insights on Luminescent Micro- and Nanospheres of Infinite Coordination Polymers

Coordination polymers have been extensively studied in recent years. Some of these materials can exhibit several properties such as permanent porosity, high surface area, thermostability and light emission, as well as open sites for chemical functionalization. Concerning the fact that this kind of compounds are usually solids, the size and morphology of the particles are important parameters when an application is desired. Inside this context, there is a subclass of coordination polymers, named infinite coordination polymers (ICPs), which auto-organize as micro- or nanoparticles with low crystallinity. Specifically, the particles exhibiting spherical shapes and reduced sizes can be better dispersed, enter cells much easier than bulk crystals and be converted to inorganic materials by topotactic transformation. Luminescent ICPs, in particular, can find applications in several areas, such as sensing probes, light-emitting devices and bioimaging. In this review, we present the state-of-the-art of ICP-based spherical particles, including the growth mechanisms, some applications for luminescent ICPs and the challenges to overcome in future commercial usage of these materials.     

Reference measurement procedures for the quantification of platinum-group elements (PGEs) from automotive exhaust emissions

The major source of the anthropogenic platinum group element (PGE) emission is attributed to the use of catalytic converters in automobiles. This paper describes the work performed by three National Metrology Institutes (Laboratoire national de métrologie et d’essais, by the Physikalisch-technische bundesanstalt, Bundesanatalt für materialforschung und prûfung), in the framework of the Joint Research Project ‘PartEmission’ under the European Metrology Research Program. An analytical procedure based on a cationic exchange protocol and the isotope dilution or standard addition using an Inductived Coupled Plasma Mass Spectrometer, ICP-MS, for the quantification of the elements Pt, Pd and Rh from automotive exhaust emissions is described. Results obtained on a road dust certified reference (BCR 723) material showed a good agreement with the certified values, at ng/g levels, and relative expanded uncertainties within the range of 7–10%. Analysis of filters impacted with automotive exhaust particle emissions (from a diesel engine) showed the amount of collected PGE at levels of 10–1000 pg/filter. Their quantifications followed the developed analytical protocol that had been carried out with relative expanded uncertainties in the range of a few per cent up to 20% per filter. Nevertheless, a lack of homogeneity between the filters was observed, making the comparison between the project partners difficult in the sake of the validation of their analytical procedures on real samples.     

Iron Porphyrin Allows Fast and Selective Electrocatalytic Conversion of CO2 to CO in a Flow Cell

Molecular catalysts have been shown to have high selectivity for CO₂ electrochemical reduction to CO, but with current densities significantly below those obtained with solid-state materials. By depositing a simple Fe porphyrin mixed with carbon black onto a carbon paper support, it was possible to obtain a catalytic material that could be used in a flow cell for fast and selective conversion of CO₂ to CO. At neutral pH (7.3) a current density as high as 83.7 mA cm⁻² was obtained with a CO selectivity close to 98 %. In basic solution (pH 14), a current density of 27 mA cm⁻² was maintained for 24 h with 99.7 % selectivity for CO at only 50 mV overpotential, leading to a record energy efficiency of 71 %. In addition, a current density for CO production as high as 152 mA cm⁻² (>98 % selectivity) was obtained at a low overpotential of 470 mV, outperforming state-of-the-art noble metal based catalysts.     

Comparison of systematically functionalized heterogeneous and homogenous glycopolymers as toxin inhibitors

Multivalent glycosylated polymers and particles display enhanced binding affinity toward lectins compared to individual glycans. The design of glycopolymers with selectivity toward pathogen‐associated lectins (toxins) for sensing or in antiadhesion therapy is complicated due to lectins having promiscuous binding profiles and can be considered to be pattern recognition “readers,” with the capability to bind to several different glycans. Here, heterogeneous glycopolymers bearing variable densities of two different monosaccharides are synthesized by a three‐step postpolymerization modification approach, enabling systematic control over composition. It is found that heterogeneous polymers displayed increased inhibitory activity, compared to homogeneous polymers, against a RCA₁₂₀ and the cholera toxin. This demonstrates that embracing heterogeneity in glycomaterials could result in improved performance or emergent properties. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 40–47     

Dienamine‐Induced Divinylcyclopropane–Cycloheptadiene Rearrangements

Sigmatropic rearrangements constitute an important group of pericyclic reactions. In contrast to cycloaddition reactions, examples of catalytic variants of electrocyclic reactions and sigmatropic rearrangements are still scarce in the chemical literature. Herein, we report the first organocatalytic Cope rearrangement of in situ‐generated divinylcyclopropanes. The reactive motif was generated by condensation of 4‐(2‐vinylcyclopropyl)but‐2‐enal derivatives with a secondary amine catalyst to form a transient dienamine. The cycloheptadiene products could be obtained in high yield and excellent diastereoselectivity. Importantly, the reaction was demonstrated to be stereospecific, proceeding under mild conditions, while exhibiting broad functional group tolerance.     

Simultaneous quantification of lipopeptide isoforms by UPLC-MS in the fermentation broth from Bacillus subtilis CNPMS22

Analytical and Bioanalytical Chemistry - The rapid and accurate quantification of lipopeptide families in biological samples are challenging. We present the development and validation of a method...     

Development,Validation, and Performance of Chitosan‐Based Coatings Using Catechol Coupling

The use of long‐lasting polymer coatings on biodevice surfaces has been investigated to improve material–tissue interaction, minimize adverse effects, and enhance their functionality. Natural polymers, especially chitosan, are of particular interest due to their excellent biological properties, such as biocompatibility, non‐toxicity, and antimicrobial properties. One way to produce chitosan coating is by covalent grafting with catechol molecules such as dopamine, caffeic acid, and tannic acid, resulting in an attachment ten times stronger than that of simple physisorption. Caffeic acid presents an advantage over dopamine because it allows direct chitosan grafting, due to its terminal carboxylic acid group, without the need of a linking arm, as employed in the dopamine approach. In this study, the grafting of chitosan using caffeic acid, over surfaces or in solution, is compared with dopamine grafting using poly(ethylene glycol) as a linking arm. The following coating properties are observed; covering and homogeneity are assessed by X‐ray photoelectron spectroscopy and atomic force microscopy analyses, hydrophilicity with contact angle measurements, stability with aging tests, anticorrosion behavior, and coating non‐toxicity. Results show that grafting using caffeic acid/chitosan in solution over a metallic surface may be advantageous, compared to traditional dopamine coating.     

Thermal,spectroscopic and antimicrobial activity characterization of some norfloxacin complexes

Journal of Thermal Analysis and Calorimetry - Coordination compounds of transition metals with norfloxacin (Nor) have potential to improve its effectiveness, as already discussed for some compounds...     

Synthesis and characterization of a biopolymer of glycerol and macadamia oil

Journal of Thermal Analysis and Calorimetry - The present study investigates the conjugate heat transfer in a square cavity heated by a triangular solid and saturated with $$\text{Al}_2\text{O}_3$$...