Ultrathin film sensory system based on resonance energy transfer between the monolayers consisting of non-covalently linked fluorophores

1. Download high-res image (145KB)
2. Download full-size image

     

Influence of hybrid system of nanofillers on the functional properties of postconsumer PET‐G–based nanocomposites

In this article, postconsumer poly (ethylene glycol‐co‐1,4‐cyclohexanedimethanol terephthalate) (PET‐G) foils have been modified with three types of carbon nanofillers that differ in size and shape, ie, multiwalled carbon nanotubes (MWCNTs), graphene nanoplatelets (GNP), and nanosized carbon black (nCB), thus enabling the reusage of recyclate in receiving new functional materials. The series of polymer hybrid nanocomposites have been prepared via a two‐stage polycondensation process, be means of glycolysis of postconsumer PET‐G foil, followed by polycondensation in the presence of carbon nanofillers. The scanning electron microscopy revealed that nanoadditives were uniformly dispersed into the whole volume of polymer matrix. The results present the synergistic effect of hybrid system of nanofillers in improving tensile properties of PET‐G. It has been found that the incorporation of three types of carbon nanofillers has not affected the glass transition temperature of the polymer matrix. Moreover, the incorporation of carbon nanofillers, and the mixture of two, or even three of those, caused an improvement in thermal conductivity and thermal stability.     

A thermogravimetric study of the alunites of sodium, potassium and ammonium

Thermogravimetry in tandem with mass spectrometry has been used to characterise the thermal decomposition of synthetic alunites of potassium, sodium and ammonium. Three mechanisms of decomposition are observed (a) dehydration, (b) dehydroxylation and (c) desulphation. The thermal decomposition of the three alunites is different. For NH₄-alunite, an additional process of de-ammoniation is observed which occurs simultaneously with dehydration. Dehydroxylation takes place in a series of four steps. De-sulphation occurs for K-alunite at 680 °C in a single step in comparison with Na and NH₄ alunites where de-sulphation is observed in a series of four steps. The temperature of desulphation is cation dependent. The thermal decomposition is not completed until around 800 °C.     

Transalkylation of alkyl aryl sulfides with alkylating agents

The reaction of methyl iodide with tert-butylphenylsulfide in DMF leads to a transalkylation that produces methylphenylsulfide. This transalkylation reaction was further studied by ¹H NMR spectroscopy. The polarity of the solvent, the electron density on the sulfur atom, and the strength of the alkylating agent (MeI, EtI, BuI, dimethyl sulfate, or dimethyl carbonate) played important roles in the reaction. The suggested mechanism of the reaction involves the formation of a dialkyl aryl sulfonium salt that subsequently eliminates the radical. This mechanism was supported by the observation of higher conversion rates for compounds with more branched alkyl groups on the sulfur atom, which may lead to the formation of more stable radicals.     

Phosphorylated flavonoids as selective carboxylesterase inhibitors

1. Download high-res image (133KB)
2. Download full-size image

     

Spin fluctuations in hydrogen-stabilized Laves phase UTi2H5

Uranium Laves phase UTi₂ does not exist in a pure form, but can be stabilised by the presence of hydrogen, which can be absorbed in concentration exceeding 5?H atoms/f.u. Low temperature specific heat, magnetic susceptibility, and resistivity indicate that UTi₂H₅ is a spin fluctuator close to the verge of magnetic ordering. Its susceptibility follows at high temperatures the Curie–Weiss law with U effective moment µ_eff[ ?= 3.1?µ_B/U and paramagnetic Curie temperature Θ_p = ?200 K. The temperature dependence of specific heat exhibits a pronounced and weakly field dependent upturn in C_p/T versus T below 10 K reflecting the effect of spin fluctuations. It can be described by an additional T^½ term. The Sommerfeld coefficient γ = 256?mJ/mol K² classifies the compound as a mid-weight heavy fermion. Spin fluctuations are affecting also electrical and thermal transport and thermoelectric power, which all resemble UAl₂. A lattice anomaly at ≈ 240?K, attributed to the melting of hydrogen sublattice, reflects in most of bulk properties.