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The current study describes cucurbit[6]uril and 4-tert-butylcalix[6]arene as high-performance multifunctional additives for polyol lubricant base oils. Cucurbit[6]uril is a macrocyclic compound with an aliphatic core, while 4-tert-butylcalix[6]arene has an aromatic core. The tribological properties of cucurbit[6]uril and 4-tert-butylcalix[6]arene in terms of the friction coefficient and average wear scar diameter were evaluated by the four-ball test (ASTM D4172). The antioxidant properties of these additives were assessed via a universal oxidation test (IP-306) and anticorrosion study by standard ASTM D664. Of the two additives, cucurbit[6]uril shows great promise for applications in industrial areas, maintains excellent tribological ability and exhibits a better load-bearing tribofilm as per morphologies observed by scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy.

This study comprises the design and development of calix[4] arene-amido-based ionophores by varying structural stringency and steric hindrance at the lower rim to probe the anion sensing properties. The ionophores are prepared, purified, and characterized using various analytical techniques. The molecular structure of the most active ionophore I is established by single-crystal X-ray characterisation. Out of various anions investigated, iodide and cyanide show the highest sensitivity towards the ionophores investigated. Both anions are sensitive enough to give a visibly distinct color change. The binding properties of the ionophores are established with 1H & 127I NMR, fluorescence, and UV-vis spectroscopy, revealing that three ionophores strongly interact with CN− and I−. The binding constants are calculated via Benesi–Hildebrand plots using absorption data. The time-dependent 1H NMR revealed strong hydrogen bonding between the OH and NH groups of the ionophore and cyanide anion. The 127I NMR shows the highest 27.6 ppm shift after 6 h for ionophore I. The crystal structure revealed hydrogen bonding of N–H protons of the amide pendulum and phenolic oxygen of the calix rim. The Job's plot depicted the possibility of a 1 : 1 complex of ionophores with both anions.

Different aluminum and calcium based particles, montmorillonite (MMT), zeolites (NaY), bayerite (BAY) and hydroxyapatite (CaHAp), were compared and evaluated for water defluorination. The effect of parameters such as temperature of the medium, concentration (mass of adsorbent), reaction time and pH on the defluorination capacity were studied for the particles with best performance. MMT and CaHAp adsorbents showed increased fluoride rejections in batch experiments (approximate to 45 and 100%). The defluorination capacity of MMT is influenced by the concentration and pH, while for CaHAp is independent of the evaluated parameters within the measured range. Further, polymer composite membranes based on poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) and the adsorbents with higher defluorination capacity were prepared by thermally induced phase separation in order to produce active filters for fluoride removal from water. The composite membranes presented a homogeneous porous structure with degrees of porosity ranging between approximate to 20 and 76% and average pore size in the micron range. The permeability of the composite membranes ranged between 12,500 and 10,000 L/h.m(2).bar. A maximum fluoride rejection of 68% was obtained after 6 filtrations for the CaHAp/P(VDF-HFP) composite membranes. Thus, the composite membranes of P(VDF-HFP) with MMT and CaHAp show suitable performance for defluorination in water purification systems., This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2013. The funds provided by FCT through the Chemistry Research Centre of the University of Minho (UID/QUI/00686/2013 and UID/QUI/0686/2016) are also gratefully acknowledged. JNP wish to thank the financial support of the project Centro-01-0145-FEDER-000017 - EMaDeS - Energy, Materials and Sustainable Development, co-financed by the Portugal 2020 Program (PT 2020), within the Regional Operational Program of the Center (CENTRO 2020) and the European Union through the European Regional Development Fund (ERDF). The authors acknowledge funding by the Spanish Ministry of Economy and Competitiveness (MINECO) through the project MAT2016-76039-C4-3-R (AEI/FEDER, UE) (including the FEDER financial support), and financial support from the Basque Government Industry Department under the ELKARTEK and HAZITEK program. PRS gratefully acknowledge DST Women Scientists Scheme-A (WOS-A) for the research grant SR/WOS-A/CS-91/2013., info:eu-repo/semantics/publishedVersion

In this study, a series of mineral and organic acids are introduced to natural clay modification. Several analytical techniques are employed to identify the physical and chemical changes in clay. The effect of surfactants on these properties is also investigated. The samples are prepared using simple acid treatment without filtration. The alteration in surface morphology is proportional to the acid strength as evident from SEM and XRD analyses. Therefore, the treatment with mineral acid and organic acid/HNO3 results in the formation of new layers by surface modification as depicted in SEM images, and a higher degree of suppression in characteristic XRD reflections of clay is noticed. However, the treatment with organic acids modifies the existing interlayer spacing of clay, and therefore, the XRD characteristic reflections of clay are less affected. These observations are also supported by FT-IR analysis. The surface area of modified clay is dependent on the acid strength, composition and size of counter-anion of acid. An increase in surface area and porosity is noticed after surfactant modification of HNO3-treated clay, where the change is more prominent at the concentration higher than their respective critical micelle concentration. Thermal stability is dependent on the chemical composition and surface area of clay materials. A relatively higher absorbance is observed for modified clay materials compared with untreated clay during DRS analysis. The catalytic efficiency of modified clay materials in Eriochrome Black T degradation has been demonstrated.

A series of dysprosium (Dy) doped LiMn2O4 based spinel cathode materials, LiMn2 − xDyxO4 (x = 0, 0.01, 0.02, 0.03, 0.04, 0.05) for Li ion rechargeable battery application were synthesized by sol-gel process. The physical properties were explored through X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray diffraction (EDX), field emission scanning electron microscopy (FE-SEM), and micro-Raman spectroscopy. Swagelok cell configurations were used for electrochemical characterizations e.g. cyclic voltammetry, rate performance, cycleability and AC impedance. The doping amount of dysprosium has improved the surface morphology (particle size

Download : Download high-res image (81KB) Download : Download full-size image The current study involves a simple hydrazine based colorimetric chemo-sensor for selective determination of various anions. The anion-binding ability of the ligand with various anions via polar-non polar interactions and hydrogen bonding has been examined. The sensor displayed significant UV–vis enhancement response to anions such as fluoride, acetate, hydroxide, cyanide and hydrogen sulphate, with respect to concentration and time. The rate constants (K) and binding constants, Ka, for these anions have been measured by using Benesi-Hildebrand equation. A time dependent NMR study revealed stronger interaction for cyanide and fluoride ions among competing anions.

The Ni/Co-natural clay catalysts have been prepared for the conversion of algae oil into diesel-grade hydrocarbons. Methyl oleate was used as a model compound for the present study. Ni/clay catalyst promotes decarboxylation/decarbonylation, whereas remarkable selectivity in hydrodeoxygenation (HDO) is achieved with Co/clay catalysts. Powder XRD and DRS studies of substrate mixed catalysts reveal a more prominent adsorption of substrate molecules over the Ni surface, which results in low HDO selectivity of nickel catalysts by surpassing the essential contribution of acidic sites. The HDO process provides higher carbon atom economy and energy value over decarboxylation/decarbonylation, while further reducing the formation of greenhouse gases such as CO2 and CH4. Total yield of saturated hydrocarbons from algae oil was 84–86 wt % with similar selectivity. The HDO rates of different fatty acids present in algae oil were independent of the fatty acid chain length. The catalysts are cost-effective and recyclabl...

The current study reveals the synthesis of polymer appended Calix[4]amidocrown-5 with specific binding affinity for iodide at ppm-level. The low detection limits are observed via UV-vis and fluorescence spectroscopy. The time-dependent solution and solid-state 127I NMR studies with 18.8 and 19 ppm shifts, indicate a strong sensing nature of resin towards iodide ion. A significant reduction in surface area and pore volume with higher thermostability of resin after iodide uptake indicated iodide inclusion in the amidocrown cavity. The mechanism of iodide sensing may be governed by noncovalent interactions of NH and OH protons present in amidocrown and phenyl ring as observed in terms of emission enhancement in fluorescence spectroscopy. The binding affinity and stoichiometric determinations are determined by Benesi-Hildebrand and Jobs plots, respectively.

The catalytic deoxygenation of biomass to produce renewable carbon energy addresses major concerns of limited energy sources. In particular, the second-generation biodiesel by selective deoxygenation possesses a higher cetane number, lower cloud point, and higher oxidation stability compared to the fatty acid ester-based biodiesel, and therefore, can be fed directly to the current diesel engines. In present work, we address the significant concerns of cost-effectiveness, high hydrodeoxygenation (HDO) selectivity, modest hydrogen environments, and solvent-free condition using high surface area silica-alumina-supported cobalt oxide nanoparticles as a catalyst to produce fuel-grade hydrocarbons from fatty acid-based feeds that are palm oil and jatropha oil. The catalytic performance is tested for methyl stearate to achieve the best conversion efficiency with remarkable deoxygenation selectivity. The HDO selectivity was as high as 87% at 250 °C and 30 bar H2 pressure, whereas moderate HDO selectivity with relatively higher cracking was observed at 300 °C and 2 bar H2 pressure. Remarkably, the HDO selectivity was comparable in the absence of solvent. The catalyst is recyclable with low metal leaching during the deoxygenation. The use of non-noble metal catalysts under solvent-free conditions offers facile production of fuel-grade hydrocarbons.

LiMn1.5Ni0.5O4 with spinel type of structure was synthesized by sol-gel method and doped by different rare-earth elements (Nd, Gd and Dy). It was found that the inclusion of rare-earth element preserves the cubic spinel structure, leads to smaller particle size and improves the cyclic performance of the produced batteries. The best battery performance was obtained after doping the spinel structure by Gd. Among the used rare-earth elements Gd is the only one with stable oxidation state of 3 + which leads to stabilization of the Mn dissolution.Thus, the improvements observed in battery performance (rate performance and cycle life) are due to the superior structural stability of the doped active materials. It is concluded that the LiMn1.48Ni0.5Gd0.02O4 sample is the one with the best overall performance to act as active material for cathodes in rechargeable lithium-ion batteries., This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2013. The authors thank FEDER funds through the COMPETE 2020 Programme and National Funds through FCT under the projects PTDC/CTM-ENE/5387/2014 and UID/CTM/50025/2013 and grants SFRH/BD/90313/2012 (A.G.), SFRH/BD/88397/2012 (R.G.) and SFRH/BPD/112547/2015 (C.M.C.). The authors are thankful for funding from the FCT under the Indo-Portuguese program of cooperation in science and technology (INT/Portugal/P-02/2013) 2014-2016. The fellowship from MHRD, Govt. of India was acknowledged for Pura Ram. Financial support from the Basque Government Industry Department under the ELKARTEK Program is also acknowledged. The authors acknowledge the MRC, MNIT, Jaipur, Rajasthan, India for TEM, RAMAN characterization facilities for material characterization., info:eu-repo/semantics/publishedVersion

LiMn2-xGdxO4 (x=0.00, 0.01 and x=0.04) spinel active material were prepared by sol-gel method. The morphology, crystal structure, thermal stability and electrochemical properties of the synthesized samples were evaluated. Gd-doping maintains the cubic spinel structure of LiMn2O4, leads to a decrease of the average particle size, and has a strong influence on the electrochemical properties of the cathodes. LiMn2-xGdxO4 cathode materials show two pairs of separated redox peaks, independently of the Gd-doping. After 40 charge-discharge cycles at C2, the discharge capacity was 55.9 mAh.g-1 and 33 mAh.g-1 for x=0.04 and x=0, respectively, corresponding to a capacity retention of 80% and 70%, respectively. The Gd-doped with x=0.04 showed improved cycling performance with respect to pristine LiMn2O4 due the smaller particle size and superior structural stability, showing its suitability for lithium-ion battery applications., The authors thank FEDER funds through the COMPETE 2020 Programme and National Funds through FCT - Portuguese Foundation for Science and Technology under Strategic Funding UID/FIS/04650/2013. A. G., C.M.C. and S. F. thank the FCT for grants SFRH/BD/90313/2012, SFRH/BPD/112547/2015 and IF/01516/2013, respectively. The authors thank funding from the FCT under the Indo-Portuguese program of cooperation in science and technology grant INT/Portugal/P-02/2013, 2014-2016. The authors are thankful for HRTEM and Raman characterization support from MRC, MNIT, Jairpur, INDIA. The fellowship from MHRD, Govt. of India was acknowledged for Pura Ram. SLM thanks financial support from the Basque Government Industry Department under the ELKARTEK Program.

The article elaborates the development of gravity-based water filtration systems capable of removing fluoride using natural organic material. In this study, the precipitation and dissolution reaction occurring in suspension of hydroxyapatite (HAP) as addition of fluoride were investigated under well-defined condition. This process is set to occur in a quasi-static gravity-based water filter system. This system is a (pond sand, organic material (gaur seed powder, neem, sesame sawdust, and Ayurvedic waste), water, and HAP mixture) composite ceramic. This article illustrates these ceramic material systems manufactured using distinct permutations of pond sand and organic materials. HAP is introduced into the composite mix of pond sand and organic materials to manufacture some of the sintered ceramic filtration material systems tested here. The fluoride removal efficiency of these variant systems is discussed. The energy dispersive X-ray spectroscopy studies of the ceramics provided the mineral content...

The current work presents the effect of stirring hours and drying temperature on the quality of slurry, its surface morphology, and electrochemical performances of electrodes. Physical characterization studies, such as XRD, SEM, and SEM of slurry, and electrochemical characterization studies, namely, the investigation of charge-discharge capacities, rate performances, cyclability, and AC-impedance, were carried out. The cathode slurry was prepared at four different stirring intervals of 3 h, 4 h, 5 h, and 6 h and six different drying temperatures of 80, 90, 100, 110, 120, and 130 °C. The results showed that slurry obtained at a stirring time of 5 h and at a drying temperature of 120 °C exhibited best physical and electrochemical performances. SEM images showed that slurry obtained at a stirring time of 5 h has better surface uniformity and homogeneity compared to others. The electrodes prepared from this slurry also showed improved charge-discharge capacity and rate performance and low impedance. The initial discharge capacities of the electrodes, made from slurry with stirring times of 4 h, 5 h, and 6 h, were 54, 73, and 58 mA hg−1, respectively at a current rate of C/10. The current study also provides clear-cut outline steps to prepare good quality cathode slurry. This study may provide guidelines for new researchers in the field of Li-ion battery technology to overcome these issues and get first hand good quality slurry for better results.

The present study describes non-covalent interaction and complexation behaviour of sodium ascorbate (SA) with cucurbit[6]uril (CB[6]) at neutral pH in aqueous Na2SO4 solution. The interaction behaviour is investigated using various analytical techniques like NMR, UV–Vis, fluorescence, TGA and DRS. The substantial increase in the intensity of emission and absorption spectra of sodium ascorbate is observed. The Benesi–Hildebrand evaluation method is used to determine the stoichiometry and equilibrium constant of the cucurbit[6]uril–sodium ascorbate complex, which suggested the 1:1 complex. Time-dependent 1H NMR, 13C CP MAS and CD studies also echoed non-covalent interaction between SA with CB[6].