Optimizing the monomer structure of polyhedral oligomeric silsesquioxane for ion transport in hybrid organic–inorganic block copolymers

Poly(ethylene oxide)-b-polyhedral oligomeric silsesquioxane (PEO–POSS) mixed with lithium bis(trifluoromethanesulfonyl)imide salt is a nanostructured hybrid organic–inorganic block copolymer electrolyte that may enable lithium metal batteries. The synthesis and characteristics of three PEO–POSS block copolymer electrolytes which only differ by their POSS silica cage substituents (ethyl, isobutyl, and isooctyl) is reported. Changing the POSS monomer structure results in differences in both thermodynamics and ion transport. All three neat polymers exhibit lamellar morphologies. Adding salt results in the formation of a disordered window which closes and gives way to lamellae at higher salt concentrations. The width of disordered window decreases with increasing length of the POSS alkyl chain substituent from ethyl to isobutyl and is absent in the isooctyl sample. Rheological measurements demonstrate good mechanical rigidity when compared with similar all-organic block copolymers. While salt diffusion coefficient and current ratio are unaffected by substituent length, ionic conductivity increases as the length of the alkyl chain substituent decreases: the ethyl substituent is optimal for ion transport. This is surprising because conventional wisdom suggests that ion transport occurs primarily in the PEO-rich domains, that is, ion transport should be unaffected by substituent length after accounting for the minor change in conducting phase volume fraction. © 2020 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2020 © 2020 Wiley Periodicals, Inc. J. Polym. Sci. 2020 , 58, 363–371     

Evaluation of novel ZnO–Ag cathode for CO2 electroreduction in solid oxide electrolyser

CO₂ and steam/CO₂ electroreduction to CO and methane in solid oxide electrolytic cells (SOEC) has gained major attention in the past few years. This work evaluates, for the very first time, the performance of two different ZnO–Ag cathodes: one where ZnO nanopowder was mixed with Ag powder for preparing the cathode ink (ZnO_mix–Ag cathode) and the other one where Ag cathode was infiltrated with a zinc nitrate solution (ZnO_inf –Ag cathode). ZnO_mix–Ag cathode had a better distribution of ZnO particles throughout the cathode, resulting in almost double CO generation while electrolysing both dry CO₂ and H₂/CO₂ (4:1 v/v). A maximum overall CO₂ conversion of 48% (in H₂/CO₂) at 1.7 V and 700 °C clearly indicated that as low as 5 wt% zinc loading is capable of CO₂ electroreduction. It was further revealed that for ZnO_inf –Ag cathode, most of CO generation took place through RWGS reaction, but for ZnO_mix–Ag cathode, it was the synergistic effect of both RWGS reaction and CO₂ electrolysis. Although ZnO_inf –Ag cathode produced trace amount of methane at higher voltages, with ZnO_mix–Ag cathode, there was absolutely no methane. This seems to be due to strong electronic interaction between Zn and Ag that might have suppressed the catalytic activity of the cathode towards methanation.

     

Synthesis,crystal structure and magnetic properties of a new tri‐nuclear iron (II,III) complex,a precursor for the preparation of superparamagnetic Fe3O4 nanoparticles applicable in the removal of Cd2+

This study reports the structural and spectroscopic characterization of a novel metal organic compound formulated as [Fe (bpy)₃] [Fe (dipic)₂]₂.7H₂O ( 1 ) (dipic = pyridine‐2,6‐dicarboxylate and bpy = 2,2^′‐bipyridine). 1 was investigated by elemental analysis, FT‐IR spectroscopy, powder X‐ray diffraction and single crystal X‐ray diffraction (SC‐XRD), which revealed a triclinic structure of expected composition. Thermal degradation of 1 was also investigated. Complex 1 was used as a precursor to prepare superparamagnetic nanoparticles of Fe₃O₄ by thermal analysis. The obtained Fe₃O₄ was characterized by Fourier transformed infrared spectroscopy (FT‐IR), powder X‐ray diffraction (XRD) and scanning electron microscopy (SEM). Fe₃O₄ nanoparticles were used as a nano‐adsorbent to remove Cd²⁺ from water at room temperature. The results showed that this nano‐adsorbent is effective in removing Cd²⁺ from contaminated water sources, and that the maximal effectivity of adsorption occurs at pH = 6. Magnetic measurements of complex 1 and Fe₃O₄ nanoparticles at room temperature revealed paramagnetic and superparamagnetic behavior, respectively.     

Estimation of underground water radon danger in Bakreswar and Tantloi Geothermal Region,India

The main aim of the study is to present an evaluation of radon concentration in underground water of Bakreswar and Tantloi geothermal region which is mainly used for drinking purposes of the local people. Water samples were collected from tube-wells at 173 different locations. The radon (²²²Rn) concentration level was observed to fluctuate widely between 3.3 and 803.8 Bq/l with an average of 106.8 Bq/l. Nearly 42% of the samples had radon concentration above the safe limit of 100 Bq/l recommended by World Health Organisation (WHO) and European Union Commission (EU). Considering the WHO and International Commission on Radiological Protection recommended water consumption rate for adults (730 l/year) the corresponding total annual effective dose of the samples were estimated to assess the probable health risk. Total annual effective dose of the samples were varied between 16.72 and 4079.47 µSv/year with an average value of 541.92 µSv/year. About 95% samples exceed the WHO and EU Commission proposed safe limit of 100 µSv/year.     

Biocompatible Carbon Dot Decorated α-FeOOH Nanohybrid for an Effective Fluorometric Sensing of Cr (VI) in Wastewater and Living Cells

Journal of Fluorescence - This article reports the fluorometric detection of toxic hexavalent chromium Cr (VI)) in wastewater and Cr (VI) contaminated living cells using in-situ grown carbon...     

Microsphere based continuous-flow immunoassay in a microfluidic device for determination of clinically relevant insulin levels

This paper describes a miniaturized microsphere-based immunoassay integrated into a microfluidic device for rapid quantitation of insulin. Analysis of bionic pancreas studies have revealed that the rates of absorption of insulin analogs vary from patient to patient, and even within patients on different occasions. Thus development of an approach to monitor insulin continuously allows the pharmacokinetic characteristics of insulin analogs to be determined in real-time. The authors have developed a microsphere-based continuous flow assay in a microfluidic chip that allows for the detection of insulin within seconds with high sensitivity and specificity. The method was applied to near real-time monitoring of clinical samples. Calibration plot were established for different insulin analogs such as insulin aspart (Novolog), insulin lispro (Humalog), and regular human insulin (RHI) and the insulin detection limit was 0.26 ng.mL^?1 (44 pM). This sensitivity allows to detect the fasting insulin levels of T1D patients, which are reported in the range of 50–180 pM (0.3–1 ng.mL^?1), after treatment with subcutaneous insulin administration. This fast approach was also applied to sera collected in intervals from T1D patients after a bolus of insulin aspart delivery. The insulin profile obtained by this method is similar to the basal and peak insulin levels as determined using the standard non-continuous ELISA reference method. In our perception, this assay will improve healthcare by personalizing diagnostics for better clinical outcome and provide real-time feedback on sensing and actuation.

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Graphical abstract Schematic illustration of the microfluidic microsphere based Microfluidic Lab-On-Chip device for near real-time insulin monitoring.

     

Thermal degradation of alkyl triphenyl phosphonium intercalated montmorillonites

The decomposition mechanism of intercalated montmorillonites at a particular temperature region and the activation energy involved in it are the two important aspects which determines the thermal stability of intercalated montmorillonites. In this study, montmorillonite was intercalated with alkyl (methyl, ethyl, propyl, and dodecyl) triphenyl phosphonium intercalates. Differential thermogravimetric analysis of each intercalated montmorillonites showed different peaks with associated organic loss at different temperature zone. Intercalated montmorillonites were subjected to isothermal kinetic analysis corresponding to selected temperature zone obtained from DTG peaks. Activation energies of organic decomposition process at selected temperature zones were determined. Mass spectral analysis and FTIR were done to understand the decomposition mechanisms and to relate them with the estimated activation energies.     

Study of variation of soil radon exhalation rate with meteorological parameters in Bakreswar–Tantloi geothermal region of West Bengal and Jharkhand,India

Radon gas is the predominant ionizing radiation on earth. Its occurrence is controlled by the presence of uranium in all types of rocks in the earthcrust, apart from local geological features and atmospheric factors which influence its release into the atmosphere. The present work deals with 24 h observation of the dependence of radon exhalation rate from soil on local meteorological parameters at four locations in Bakreswar–Tantloi geothermal region, located in the highly faulted Chhotanagpur Plateau of eastern India. This study is the primary step towards the determination of soil radon exhalation dynamics in this geothermal area.

     

Spectral and electrochemical behavior of manganese dioxide nanodispersions prepared in reverse micelle

Nanodispersed aggregates of MnO₂ were prepared in the aqueous core of the H₂O/Aerosol OT (AOT)/heptane reverse micelle using the comproportionation reaction between and Mn²⁺ ions. The formed nanoparticles were characterized by transmission electron microscopy (TEM), UV–visible spectroscopy and cyclic voltammetry. The electro-oxidation of dextrose and fructose on platinum modified by reverse micellar MnO₂ deposits was studied. The oxidation of fructose was found to be much more facile than dextrose oxidation. There was a linear correlation between the steady state oxidation currents and the carbohydrate concentrations, which was shown to be useful for analytical application. The sensitivity for fructose detection was found to be about seven times higher than that of dextrose. The scope of developing an electroanalytical method for estimation of dextrose and fructose individually in their mixture was explored.