Microwave-Assisted Hydrothermal Synthesis of {100} and {111} Faceted LiFeO2 Truncated Octahedra: Investigations on Volatile Organic Compound Sensing Performance.

Growth of exposed crystal facets has received considerable attention because of their coordinatively unsaturated surface atoms and defect-related surface reactivities. Herein, LiFeO2 truncated octahedra exposed with 6 {100} facets and 8 {111} facets were prepared through a simple microwave-assisted hydrothermal method without using any additives, surfactants, and calcination processes. The detailed growth process revealed that the formation of LiFeO2 truncated octahedra occurred only at the optimized reaction temperature (180 °C), time (30 min), and reactant concentrations. The prepared LiFeO2 truncated octahedra showed excellent sensing responses toward aliphatic organic compounds compared to that against aromatic organic compounds and poor response to inorganic compounds. The response percentages of 150 ppm concentrations of acetone, ethanol, formaldehyde, and isopropyl alcohol are 81.84, 62.91, 62.68, and 69.41%, respectively, at a low operating temperature (100 °C). The presence of exposed facets with their coordinatively unsaturated Li/Fe surface atoms such as 5-fold {100}, 3-fold {111}, 3-fold {100}-{111}, 2-fold {111}-{111}, and 2-fold coordination with the O atom in the vertices facilitated more oxygen vacancies and led to improved surface reactivities as well as sensitivity.

Hierarchical Carbon Composites for High-Energy/Power-Density and High-Reliability Supercapacitors with Low Aging Rate.

A facile method for preparing hierarchical carbon composites that contain activated carbon (AC), carbon nanospheres (CNSs), and carbon nanotubes (CNTs) for use as the electrode material in supercapacitors (SCs) was developed. The CNS/CNT network enabled the formation of three-dimensional conducting pathways within the highly porous AC matrix, effectively reducing the internal resistance of an SC electrode. The specific capacitance, cyclability, voltage window, temperature profile during charging/discharging, leakage current, gas evolution, and self-discharge of the fabricated SCs were systematically investigated and the optimal CNS/CNT ratio was determined. A 2.5 V floating aging test at 70 °C was performed on SCs made with various hierarchical carbon electrodes. Electrochemical impedance spectroscopy, postmortem electron microscopy, Raman spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy analyses were conducted to examine the electrode aging behavior. A hierarchical carbon architecture with an appropriate AC/CNS/CNT constituent ratio could significantly improve charge-discharge performance, increase cell reliability, and decrease the aging-related degradation rate.

Surface grafting of Corchorus olitorius fibre: a green approach for the development of activated bioadsorbent.

The present work is an endeavor to prepare lignocellulosic biomass based adsorbent, suitable for removal of organic and inorganic pollutants from industrial effluents. Lignocellulosic Corchorus olitorius fibre (jute fibre) surface was grafted with naturally available polyphenol, tannin, preceded by the epoxy-activation of fibre surface with epichlorohydrin under mild condition in an aqueous suspension. The reaction parameters for the modification, viz., concentration of epichlorohydrin and tannin, time, and temperature were optimized. The successful occurrence of surface modification of jute fibre (JF) was characterized and estimated from weight gain percent, elemental analysis, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction, scanning electron and atomic force microscopy, and thermogravimetric analysis. An extensive analysis of deconvoluted FTIR spectra using the Voigt model was utilized to ensure the surface grafting. The microbiological susceptibility study revealed high persistency of JF towards biodegradation after efficient grafting with tannin.

Improvement in mechanical properties of jute fibres through mild alkali treatment as demonstrated by utilisation of the Weibull distribution model.

Chemically modified jute fibres are potentially useful as natural reinforcement in composite materials. Jute fibres were treated with 0.25%-1.0% sodium hydroxide (NaOH) solution for 0.5-48 h. The hydrophilicity, surface morphology, crystallinity index, thermal and mechanical characteristics of untreated and alkali treated fibres were studied.The two-parameter Weibull distribution model was applied to deal with the variation in mechanical properties of the natural fibres. Alkali treatment enhanced the tensile strength and elongation at break by 82% and 45%, respectively but decreased the hydrophilicity by 50.5% and the diameter of the fibres by 37%.