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      Volume 40, Issue 6

      October 2017,   pages  1049-1289

    • Synthesis and characterization of Znq2 and Znq2:CTAB particles for optical applications

      V BHARATHI DEVI P ARULMOZHICHELVAN P MURUGAKOOTHAN

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      High luminescent zinc (ii)-bis (8-hydroxyquinoline) Znq2 nanoparticles were synthesized by the simpleprecipitation method in pure form and with cetyltrimethyl ammonium bromide (CTAB) as cationic surfactant. The crystallinenature of title samples was confirmed by powder X-ray diffraction. Thermo gravimetric analysis and differential thermal analysis were carried out to find the thermal stability of the synthesized samples. The morphology and elemental analyses of the samples were studied by scanning electron microscope and energy dispersive X-ray analyser, respectively. The functional groups of these nanoparticles were analysed and assigned using the Fourier transform infrared spectroscopy spectral study. The optical property of Znq2 and Znq2:CTAB was confirmed by UV–vis–NIR spectral study. The band gap of Znq2 was calculated. The synthesized Znq2 and Znq2:CTAB nanoparticles were confirmed by photoluminescence studies for organic-light-emitting diode applications as emission and electron transport layers.

    • Synthesis, characterization and electrochemical performance of Li$_2$Ni$_x$Fe$_{1−x}$SiO$_4$ cathode materials for lithium ion batteries

      A Y SHENOUDA M M S SANAD

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      Li$_2$Ni$_x$Fe$_{1−x}$SiO$_4$ ($x = 0$, 0.2, 0.4, 0.6, 0.8 and 1) samples were prepared by a sol–gel process. The crystalstructure of prepared samples of Li$_2$Ni$_x$Fe$_{1−x}$SiO$_4$ was characterized using an X-ray diffractometer. Different crystallographicparameters such as crystallite size and lattice cell parameters have been calculated. Scanning electron microscopy andFourier transform infrared spectroscopy investigations were carried out, which reveal the morphology and function groupsof the synthesized samples. Furthermore, electrochemical impedance spectra measurements are performed. The obtainedresults indicated that the highest conductivity is achieved for the Li$_2$Ni$_{0.4}$Fe$_{0.6}$SiO$_4$ electrode compound. It was observed that Li–Li$_2$Ni$_{0.4}$Fe$_{0.6}$SiO$_{4}$ battery has initial discharge capacity of 164 mAh g$^{−1}$ at 0.1~$C$ rate. The cycle life performance of all Li$_2$Ni$_x$Fe$_{1−x}$SiO$_4$ batteries ranged between 100 and 156 mAh g$^{−1}$ with coulombic efficiency range between 70.9 and 93.9%.

    • Synthesis of ZnO comb-like nanostructures for high sensitivity H$_2$S gas sensor fabrication at room temperature

      ABDULQADER DAWOOD FAISAL

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      Zinc oxide (ZnO) comb-like nanostructures were successfully synthesized on the silicon substrate without a catalyst via chemical vapour deposition. The morphology and crystal structure of the product were characterized by scanning electron microscope and X-ray diffractometer. In this research, a simple gas sensor was fabricated based on the principle of change in resistivity due to oxygen vacancies, which makes its surface chemically and electrically active. The fabricated ZnO nanostructures proved to be quite sensitive to low concentration of H$_2$S gas at room temperature. The sensitivity and response time were measured as a function of gas concentrations. Small response time (48–22 s) and long recovery time (540 s) were found at H$_2$S gas concentrations of 0.1–4 ppm, respectively. ZnO comb-like structures are considered as the most suitable materials for gas sensor fabrication due to their high sensing properties. These nanostructures growth and H$_2$S gas sensing mechanism were also discussed.

    • Hydrothermal growth of wheatear-shaped ZnO microstructures and their photocatalytic activity

      PING LI BIN LU ZHANZHOU LUO

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      A facile hydrothermal process was developed to synthesize novel wheatear-shaped ZnO microstructures at alow temperature (85$^{\circ}$C) without the assistance of any template agent. X-ray diffraction and field emission scanning electron microscopy were used to characterize the structure and morphology of the samples. Results showed that the length of the ‘wheatear’ was about 5.8 $\mu$m and the section width was 1.2 $\mu$m. The particles consisted of closely packed nanorods withaverage diameter of 100 nm. The growth of wheatear-shaped ZnO is very rapid and can be achieved in only 5 min. OH$^−$-driven oriented aggregation and multistep nucleation resulted in the formation of wheatear-shaped ZnO microstructures.The product had assembled open structures and it exhibited excellent photocatalytic activity in the degradation of methylorange under UV-light irradiation.

    • Synthesis and up-conversion emissions of Yb$^{3+}$/Er$^{3+}, Yb$^{3+}$/Tm$^{3+}$ and Yb$^{3+}$/Tm$^{3+}$/Gd$^{3+}$ co-doped KLu$_2$F$_7$

      CHUNYAN CAO AN XIE HYEON MI NOH JUNG HYUN JEONG

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      Yb$^{3+}$/Er$^{3+}$, Yb$^{3+}$/Tm$^{3+}$, or Yb$^{3+}$/Tm$^{3+}$/Gd$^{3+}$ co-doped KLu$_2$F$_7$ up-conversion (UC) materials were synthesizedthrough a hydrothermal method or an additive-assisted hydrothermal method. The X-ray diffraction (XRD) resultssuggested that the materials crystallized in orthorhombic phase, yet, the potassium citrate (CitK) introduction affectedimmensely the crystalline purity of final material. The field emission scanning electron microscopy (FE-SEM) results suggestedthat the additive adding had effects on size and morphology of the material, which affected the UC emissions further. Green/red UC emissions of Er$^{3+}$, UV/blue/IR UC emissions of Tm$^{3+}$, and UV UC emissions of Gd$^{3+}$ were observed in the orthorhombic phase of KLu$_2$F$_7$ materials. The excitation power-dependent UC emissions illustrated that the UC emissionintensity initially increased, then decreased with the increase in excitation power. At the same time, the variation ratesof different transitions in Er$^{3+}$ or Tm$^{3+}$ are also different. In addition, the Er$*{3+} or Tm$^{3+}$ concentration-dependent UC emission results suggested that the optimal doping concentration of Er$^{3+}$ is 2 mol% and Tm$^{3+}$ is 0.5 mol% with the Yb$^{3+}$ concentration fixed as 20 mol%. The experimental results suggest that the orthorhombic phase of KLu$_2$F$_7$ should be a good host lattice for UC emitters.

    • Stability, magnetic and electronic properties of SiC sheet doped with B, N, Al and P

      L B DRISSI F EL YAHYAOUI

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      Using DFT-based calculations, we study chemical doping of silicene–graphene hybrid with (B, N, Al and P).Planar structure of SiC sheet remains unaffected on doping and all the systems are stable. P andNdopants are strongly bondedto the hybrid compared with Al and N. Charge transfer calculations show that (B,N)/(Al,P) behave like acceptors/donors,respectively. All configurations retain the semi-conductor character of pure SiC and show magnetic order. Curie temperatureis determined for the ferromagnetic structures. These results provide the possibility of tuning the gap and inducing magnetismin SiC as required for future applications.

    • Structural stability and magnetic properties of Cu$_m$Co$_n$NO ($m + n = 2–7$) clusters

      PEI-YING HUO XIU-RONG ZHANG JUN ZHU ZHI-CHENG YU

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      A theoretical study of NO adsorption on Cu$_m$Co$_n$ ($2 \leq m + n \leq 7$) clusters was carried out using a densityfunctional method. Generally, NO is absorbed at the top site via the N atom, except in Cu$_3$NO and Cu$_5$NO clusters,where NO is located at the bridge site. Co$_2$NO, Co$_3$NO, Cu$_2$Co$_2$NO, Co$_5$NO, Cu$_2$Co$_4$NO and Cu$_6$CoNO clusters have larger adsorption energies, indicating that NO of these clusters are more easily adsorbed. After adsorption, N–O bond is weakened and the activity is enhanced as a result of vibration frequency of N–O bond getting lower than that of a single NO molecule. Cu$_2$CoNO, Cu$_3$CoNO, Cu$_2$Co$_2$NO, Cu$_3$Co$_3$NO and CuCo$_5$NO clusters are more stable than their neighbours, while CuCoNO, Co$_3$NO, Cu$_3$CoNO, Cu$_2$Co$_3$NO, Cu$_3$Co$_3$NO and Cu$_6$CoNO clusters display stronger chemical stability. Magnetic and electronic properties are also discussed. The magnetic moment is affected by charge transfer and the spd hybridization.

    • Structural and physical properties of Sm$^{3+}$ doped magnesium zinc sulfophosphate glass

      F AHMADI R HUSSIN S K GHOSHAL

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      Samarium (Sm$^{3+}$) doped magnesium zinc sulfophosphate glass system of composition ($60–x$)P$_2$O$_5$–20MgO–20ZnSO$_4$–$x$Sm$_2$O$_3$ ($x = 0.0$, 0.5, 1.0, 1.5 and 2.0 mol%) were synthesized using melt-quenching technique. The structure and physical properties of prepared glass samples were characterized. The X-ray diffraction pattern verified their amorphous nature. The physical properties such as density, refractive index, molar volume, rare earth ion concentration, etc. were calculated. The decrease in the optical bandgap energy with increasing Sm$_2$O$_3$ contents was attributed to the alteration in the glass network structures. Fourier transformed infrared spectra and Raman analyses manifested the depolymerization ofZnSO$_4$ in the phosphate host matrix. The present findings may be beneficial for the advancement of functional glasses.

    • Structural, elastic, optoelectronic and magnetic properties of CdHo$_2$S$_4$ spinel: a first-principle study

      I HATRAF O MERABIHA T SEDDIK H BALTACHE R KHENATA R AHMED SALEEM A KHAN A BOUHEMADOU SIKANDER AZAM S BIN OMRAN

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      We report the results of the full-potential linearized augmented plane wave (FP-LAPW) calculations on the structural, elastic, optoelectronic and magnetic properties of CdHo$_2$S$_4$ spinel. Both the generalized gradient approximation (GGA) and Trans-Blaha modified Becke-Johnson potential (TB-mBJ) are used to model the exchange-correlation effects. The computed lattice parameter, internal coordinate and bulk modulus are in good agreement with the existing experimentaldata. According to the calculated elastic moduli, CdHo$_2$S$_4$ is mechanically stable with a ductile nature and a noticeableelastic anisotropy. The ferromagnetic phase of CdHo2S4 is energetically favourable compared to non-magnetic one, with ahigh magnetic moment of about 8.15 $\mu$B. The calculated band structure demonstrates that the title compound is a direct bandgap semiconductor. The TB-mBJ yields a band gap of $\sim$1.86 and $\sim$2.17 eV for the minority and majority spins, respectively.The calculated optical spectra reveal a strong response in the energy range between the visible light and the extreme UVregions.

    • Two-dimensional cadmium selenide electronic and optical properties: first principles studies

      J M GALICIA-HERNÁNDEZ A SÁNCHEZ-CASTILLO L MORALES DE LA GARZA GREGORIO H COCOLETZI

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      Structural, electronic and optical properties of two-dimensional (2D) cadmium selenide (CdSe) structures with$2\times 2$ periodicities are investigated. First principles total energy calculations are performed within the periodic densityfunctional theory. Initially, the structural properties are determined using the local density approximation as implementedin the PWscf code of quantum ESPRESSO package. To investigate the electronic properties, the GW method is applied todetermine the energy gap within the plasmon pole and the random phase approximations. Optical properties are investigatedto determine the dielectric constant and the Bethe–Salpeter theory is used to calculate the exciton binding energies. Zincblende and wurtzite phases are considered to calculate the bulk energy gaps, which are compared to the experimental values,finding good agreement. The 2D structure exhibits an energy gap larger than that of the bulk, indicating the effects ofreduction in dimensionality; these changes can be attributed to the dangling bonds that are present in the 2D layer.

    • High-pressure studies of superconductivity in BiO$_{0.75}$F$_{0.25}$BiS$_2$

      ZEBA HAQUE GOHIL S THAKUR GANESAN KALAI SELVAN SONACHALAM ARUMUGAM L C GUPTA A K GANGULI

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      BiO$_{0.75}$F$_{0.25}$BiS$_2$ crystallizes in tetragonal CeOBiS$_2$ structure (S. G. P4/nmm). We have investigated the effect of pressure on magnetization measurements. Our studies suggest improved superconducting properties in polycrystalline samples of BiO$_{0.75}$F$_{0.25}$BiS$_2$. The Tc in our sample is 5.3 K, at ambient pressure, which is marginal but definite enhancementover $T_c$ reported earlier ($=$5.1 K). The upper critical field Hc2(0) is greater than 3 T, which is higher than earlier report onthis material. As determined from the M–H curve, both H$_{c2}$ and H$_{c1}$ decrease under external pressure $P$ ($0 \leq P \leq 1$ GPa). We observe a decrease in critical current density and transition temperature on applying pressure in BiO$_{0.75}$F$_{0.25}$BiS$_2$.

    • Facile method to align crystalline needles composed of organic semiconducting materials using a balance between centrifugal and capillary forces

      MASASHI WATANABE KOUHEI TANAKA

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      Methods to align one-dimensional microstructures composed of organic materials have attracted much attentionbecause of their potential applications to devices such as field-effect transistors. Although dip coating is one of the methods(using self-assembly) used for the purpose, its disadvantage is that a larger amount of the material dissolves in the solutionthan what actually gets deposited on substrate. In this study, we developed a novel method that requires a small amountof precursor solution. By placing a polydimethylsiloxane block on a glass substrate and rotating the substrate using a spincoater, a small amount of the precursor solution was confined in a narrow region along the foot of the block.When we usedan organic semiconducting material, 9,10-dibromoanthracene, as a solute, aligned and roughly oriented crystalline needleswere precipitated. The thicknesses and lengths of the crystalline needles were controlled by the composition of the solventand the rotation speed.

    • Facile synthesis and characterization of rough surface V$_2$O$_5$ nanomaterials for pseudo-supercapacitor electrode material with high capacitance

      YIFU ZHANG YUTING HUANG

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      V$_2$O$_5$ nanomaterials with rough surface were synthesized using commercial V$_2$O$_5$, ethanol (EtOH) and H$_2$O as the starting materials by a simple hydrothermal route and combination of calcination. The electrochemical properties ofV$_2$O$_5$ nanomaterials as electrodes in a supercapacitor device were measured using cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) method. V$_2$O$_5$ nanomaterials exhibit the specific capacitance of 423 F g$^{−1}$ at the current density of 0.5 A g$^{−1}$ and retain 327 F g$^{−1}$ even at the high current density of 10 A g$^{−1}$. The influence of the ratio of EtOH/H$_2$O, the calcined time and temperature on the morphology, purity and electrochemical property of the products is discussed in detail. The results revealed that the ratio of EtOH/H$_2$O $=$ 10/25 and calcination at 400$^{\circ}$C for 2–4 h are favourable for preparing V$_2$O$_5$ nanomaterials and they exhibited the best electrochemical property. The novel morphology and high specific surface area are the main factors that contribute to high electrochemical performance of V$_2$O$_5$ nanomaterials during the charge–discharge processes. It turns out that V$_2$O$_5$ nanomaterials with rough surface is an ideal material for supercapacitor electrode in the present work.

    • Spectroscopic, morphological, thermal and dielectrical analysis of composite of polythiophene with photoactive transition metal complex of W(IV)

      SYED KAZIM MOOSVI KOWSAR MAJID

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      The present work involves the synthesis of polythiophene–potassium octacyanotungstate(IV) dihydrate compositevia in-situ oxidative chemical polymerization method using FeCl$_3$ as an oxidant. The resulting composite hasbeen subjected to Fourier transform infrared, X-ray diffraction (XRD) and scanning electron microscopy characterizationtechniques, which confirm the successful synthesis of the composite. XRD shows that the crystalline structure ofK$_4$[W(CN)$_8$] · 2H$_2$O has been retained in the composite. Thermogravimetric analysis data confirm the higher thermal stability of the composite in comparison with pure polythiophene, thus allowing it to be used as a promising material for high-temperature application purposes. Dielectric studies reveal that the dielectric constant and ac-conductivity of the compositeincreased by several orders of magnitude as compared with pure polythiophene at all frequencies, thus showing that thematerial can be used for various applications in the fields of charge storage devices and high-frequency device applications,and can also serve as a potential candidate for solar cell applications.

    • Effect of domains configuration on crystal structure in ferroelectric ceramics as revealed by XRD and dielectric spectrum

      JIWEN XU WEIDONG ZENG QINGNING LI LING YANG CHANGRONG ZHOU

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      It is well known that domains and crystal structure control the physical properties of ferroelectrics. The ex-situelectric field-dependent structural study, carried out in unpoled/poled crushed powder and bulk samples for (Li$_{0.5}$Nd$_{0.5}$)$^{2+}$ modified 0.95Bi$_{0.5}$Na$_{0.5}$TiO$_3$−0.05BaTiO$_3$ solid solution, established a correlation between domain configuration andcrystal structure variation. Under applying electric field, the smeared ferroelectric phase structure due to coherence diffractioneffect of nanodomains reappeared due to obsolescent coherence effect associated with the field-induced ordered nanodomains.The macroscopic characterizing techniques of domain configuration such as dielectric constant spectroscopy and X-raydiffraction measurement can provide a basis for understanding the correlation between domains configuration and crystalstructure in ferroelectric ceramics.

    • Microwave dielectrics: solid solution, ordering and microwave dielectric properties of $(1−x)$Ba(Mg$_{1/3}$Nb$_{2/3}$)O$_3$−$x$Ba(Mg$_{1/8}$Nb$_{3/4}$)O3 ceramics

      YOGITA BISHT RICHA TOMAR PULLANCHIYODAN ABHILASH DEEPA RAJENDRAN LEKSHMI M THIRUMAL

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      The effect of Ba(Mg$_{1/8}$Nb$_{3/4}$)O$_3$ phase on structure and dielectric properties of Ba(Mg$_{1/3}$Nb$_{2/3})O$_3$ was studied by synthesizing $(1−x)$Ba(Mg$_{1/3}$Nb$_{2/3}$)O$_{3}$−$x$Ba(Mg$_{1/8}$Nb$_{3/4}$)O$_3$ ($x = 0,$ 0.005, 0.01 and 0.02) ceramics. Superlattice reflections due to 1:2 ordering appear as low as 1000$^{\circ}$C. Ba(Mg$_{1/3}$Nb$_2/3}$)O$_3$ forms solid solution with Ba(Mg$_{1/8}$Nb$_{3/4}$)O$_3$for all ‘$$x’ values studied until 1350$^{\circ}$C. Ordering as confirmed by powder X-ray diffraction pattern, Raman study andHRTEM. Ceramic pucks can be sintered to density $>$92% of theoretical density. Temperature and frequency-stable dielectricconstant and nearly zero dielectric loss ($\tan \delta$) were observed at low frequencies (20 MHz). The sintered samples exhibit dielectric constant ($\epsilon_\tau$) between 30 and 32, high quality factor between 37000 and 74000 GHz and temperature coefficient of resonant frequency ($\tau_f$ ) between 21 and 24 ppm$^{\circ}$C$^{−1}$.

    • Enhanced infrared transmission characteristics of microwave-sintered Y$_2$O$_3$–MgO nanocomposite

      C T MATHEW SAM SOLOMON JACOB KOSHY JIJIMON K THOMAS

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      Infrared (IR) transparent ceramics are found to have applications in demanding defence and space missions. Inthis work, Y$_2$O$_3$–MgO nanocomposites were synthesised by a modified single-step combustion technique. The characterisation of the as-prepared powder by X-ray diffraction and transmission electron microscopy revealed the presence of cubicphases of ultra-fine nanostructured Y$_2$O$_3$ and MgO, with an average crystallite size of $\sim$19 nm. For the first time the resistive and microwave heatings were effectively coupled for sintering the sample, and it was found that the sintering temperature and soaking time were reduced considerably. The pellets were sintered to 99.2% of the theoretical density at 1430$^{\circ}$C for a soaking duration of 20 min. The well-sintered pellets with an average grain size of $\sim$200 nm showed better transmittance properties relative to pure yttria. The promising percentage transmission of 80% in the UV–visible region and 82% in the mid-IR region shown by Y$_2$O$_3$–MgO nanocomposites can be tailored and made cost-effective to fabricate high-quality IR windows for strategic defence and space missions.

    • Preparation, characterization of chitosan/bamboo charcoal/poly(methacrylate) composite beads

      DOROTHY CAMINOS-PERUELO WEI-CHIEH WANG TSUNG-SHUNE CHIN REGINA C SO RONALDO M FABICON MING-FA HSIEH

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      Preparation and characterization of a low-cost, novel steam-activated bamboo charcoal (BC) and poly(methacrylate) (PMAA) bound with chitosan (CTS) to form chitosan/bamboo charcoal/poly(methacrylate) (CTS/BC/PMAA) composite beads is reported for the first time in this paper. The characteristics are revealed by techniques such as X-ray photoelectron spectroscopy (XPS), thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC), scanning electron microscopy (SEM), Brunauer Emmett Teller (BET), solution pH and pH at pointof zero charge (pH$_{\rm pzc}$). The composite beads possessed a dominant acidic surface group of 0.663 mmol g$^{−1}$, as revealed by Boehm titration method. This acidity was confirmed by its solution pH of 6.46; pH$_{\rm pzc}$ of 6.70 and increase in oxygen surface via XPS analysis. N2 adsorption–desorption isotherms at 77 K of the beads revealed high BET surface area (SA) of 681.15 m$^2$ g$^{−1}$. Langmuir model affords a SA of 773.34 m$^{2}$ g$^{−1}$. SEM showed the microporous nature of the composite beads. The properties of CTS/BC/PMAA composite beads were compared to CTS/BC and neat BC. Thermal stability and successful coating of 5.1 wt% of PMAA and 6.8 wt% of CTS to CTS/BC/PMAA beads were shown by DSC and TGAanalyses. The composite beads showed low carbon particle released at pH 7.4 and 6.8. Furthermore, dynamic adsorptionrevealed that CTS/BC/PMAA composite beads can be used to capture a polar substance, such as creatinine.

    • Facile fabrication of organobentonite–carboxymethyl chitosan hybrid film that absorbs organophosphate insecticides

      DAU HUNG ANH KANCHANA DUMRI

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      Organophosphate (OP)-insecticide-absorbing hybrid film containing 10% (w/w) organobentonite and carboxymethylchitosan (CMCh) was fabricated and tested. Bentonite clay was modified to organobentonite by two stepsmodification with (1) NaCl and (2) plant alkaloid monovalent cation berberine. CMCh was synthesized from commercialshrimp chitosan. Afterwards, organobentonite was immobilized into CMCh matrix via in situ polymerization of CMCh tocast a hybrid film with 0.5 mm thickness. Scanning electron microscopy images of organobentonite powder and the filmrevealed the porous material and layer-upon-layer structure, respectively, which is supposed to enhance the water permeabilityof the film. Fourier transform infrared spectrometry analysis revealed similarly chemical characteristics of the CMChcomponent in the film and synthesized CMChpolymer powder. The film was then investigated to remove four OP insecticidesincluding profenofos, chlorpyrifos, methyl parathion and dimethoate of 5 ppm concentration in spiked water samples viabatch filtration. High-pressure liquid chromatography analysis showed that the removal rates for profenofos, chlorpyrifos,methyl parathion and dimethoate after seven batches were 42, 39, 24 and 20%, respectively. Hence, absorptivity of thisfilm for tested OP insecticides was demonstrated. Furthermore, the combination of organobentonite and natural chitosan ispromising for novel absorptive film material generation with regard to environmental clean-up study.

    • Fabrication of low specific resistance ceramic carbon composites by colloidal processing using glucose as soluble carbon source

      RAHUL KUMAR PARAG BHARGAVA

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      Ceramic carbon composites were fabricated by colloidal processing using glucose as soluble carbon source.Glucose is converted into conducting carbon at high temperature treatment. Ceramic carbon composites were sintered inflowing argon at 1400◦C showing resistor behaviour even at low carbon content (1 wt%). In this work, ceramic carboncomposites were fabricated using alumina–clay slurries with addition of glucose as a soluble carbon source. Morphology ofthe sintered samples was characterized by field emission gun (FEG) electron microscopy. Phase analysis was done by X-raydiffraction (XRD). Electrical properties of ceramic carbon composites were measured by broad band dielectric spectrometer.Carbon produced from glucose at high temperature was characterized independently by BET surface area, dynamic lightscattering, field emission gun scanning electron microscopy, field emission gun transmission electron microscopy, XRD andRaman spectroscopy.

    • One-pot synthesis of CaAl-layered double hydroxide–methotrexate nanohybrid for anticancer application

      MANJUSHA CHAKRABORTY MANOJ K MITRA JUI CHAKRABORTY

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      One-pot (co-precipitation) synthesis route was employed for the first time to synthesize pristine CaAl-layereddouble hydroxide (LDH) and in-situ intercalation of the anticancer drug methotrexate (MTX) to prepare CaAl-LDH–MTXnanohybrid. An increase in the interplanar spacing of the (003) plane from 8.6 $\AA$ in pristine CaAl-LDH bilayered structureto 18.26 $\AA$ in CaAl-LDH–MTX nanohybrid indicated successful intercalation of anionic MTX into the interlayer space ofCaAl-LDH. This was supported by the transmission electron micrographs, which showed an increase in average interlayerspacing from 8.7 $\AA$ in pristine LDH to 18.31 $\AA$ in LDH–MTX nanohybrid. Particle size and morphology analysis of pristineCaAl-LDH and LDH–MTX nanohybrid using both dynamic light scattering (DLS) technique and transmission electronmicroscopy (TEM) indicated a decrease in average particle size in LDH–MTX nanohybrid as compared with that of pristineLDH. Thermogravimetric analyses (TGA) revealed an enhancement in decomposition temperature of MTX bound to CaAl-LDH nanohybrid to 380$^{\circ}$C as compared with 290$^{\circ}$C in pure MTX molecule, indicating enhanced thermal stability, which supports stable electrostatic interaction of MTX within the interlayer position of LDH. CHN (carbon hydrogen nitrogen) analysis revealed nearly 49 wt% of MTX loading into CaAl-LDH, which closely matched with the result obtained from TGA of the nanohybrid. Cumulative release of MTX from CaAl-LDH–MTX in phosphate buffer solution showed a non-lineardependence with incubation time. Release mechanism of MTX from LDH–MTX nanohybrid was governed by diffusionmechanism at physiological pH of 7.4. The in vitro cytotoxicity study of LDH–MTX nanohybrid using MG-63 humanosteosarcoma cell line indicated enhanced inhibition of the cancer cell proliferation compared with the MTX drug alone.

    • Impact of nano-ZnO/grafted textile on the outer membrane permeability of some pathogenic bacteria

      M B EL-ARNAOUTY M EID S Y EL TABLAWY

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      Cotton textile grafted by chitosan hydroxyethyl methacrylate has been prepared by gamma radiation as a polymeric stabilizer for ZnO nanoparticles (NPs). The grafting percent and swelling property of the prepared grafted polymer in bi-distilled water were studied and the results showed that the swelling percent of the plain textile is higher than that of all different compositions. The morphology and structure of plain textile, grafted textile and nano-ZnO/grafted textile were examined by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). The presence of ZnO in the prepared samples was examined by energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). The particle size of the formed ZnO NPs has been estimated by transmission electron microscopy (TEM). The results indicate the nanoscale of the ZnO particles. Nano-ZnO/grafted textile was tested against some pathogenic strains, and the results show that the nano-ZnO/grafted textile was able to attenuate bacterial growth of MRSA and Klebsiella pneumoniae after 24 h of direct contact. Also, release of potassium ions, loss of absorbing materials and decrease of membrane surface potentialwere noticed, indicating alteration of cell membrane permeability. Furthermore, SEM observation showed bacterial cell deformation for growth on the nano-ZnO/grafted textile. These results have been promising in the antibacterial field.

    • Thickness and photocatalytic activity relation in TiO$_2$:N films grown by atomic layer deposition with methylene-blue and E. coli bacteria

      M M M CONTRERAS TURRUBIARTES E LÓPEZ LUNA J L ENRIQUEZ-CARREJO A PEDROZA RODRIGUEZ J C SALCEDO REYES M A VIDAL BORBOLLA P G MANI-GONZALEZ

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      This study presents an analysis of the photocatalytic efficiency in TiO$_2$:N thin films grown by atomic layer deposition related to the film thickness. The nitriding process was carried out with nitrogen plasma by molecular nitrogen decomposition after TiO$_2$ deposition. The study was performed using the time-dependent degradation of colour units for methylene-blue solutions and inactivation percentages for Escherichia coli bacteria, for potential applications in sewage purification. To determine the optoelectronic properties of the films, the optical, structural, surface and thickness characterizations were carried out by photoluminescence, Raman spectroscopy, atomic force microscopy and scanning electron microscopy, respectively.

    • Phosphate-dependent modulation of antibacterial strategy: a redox state-controlled toxicity of cerium oxide nanoparticles

      BHAKTI SARGIA JUHI SHAH RAGINI SINGH HOMICA ARYA MAITRI SHAH AJAY S KARAKOTI SANJAY SINGH

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      Specific reactivity of cerium oxide nanoparticles with phosphate ions was used to design a novel antibacterialsystem. The redox sensitivity of cerium oxide nanoparticles (CeNPs) was used to irreversibly scavenge phosphate ions fromthe microbial growth media resulting in nutrient starvation in microbes. Cerium oxide nanoparticles surface was engineeredwith different ratios of (Ce ($+$3)/Ce ($+$4)) cerium oxidation states and the effect of surface oxidation states was evaluatedon the antibacterial activity. The nutrient depletion-based antibacterial activity is demonstrated selectively by CeNPs withhigher Ce ($+$3)/Ce ($+$4) ratio on the surface. The surface chemistry of Ce ($+$3) is altered in the presence of phosphate,resulting in the irreversible formation of surface cerium phosphates leading to the loss of its intrinsic superoxide dismutase(SOD) activity. It is hypothesized that nutrient starvation by Ce ($+$3) leads to oxidative stress in microbes which is notneutralized by the altered surface chemistry of CeNPs with high (Ce ($+$3)/Ce ($+$4)) ratio. On the contrary, CeNPs withhigher (Ce ($+$4)/Ce ($+$3)) ratio did not show any reactivity towards phosphate, thus depicted no antibacterial activity,confirming the hypothesis that surface chemistry, rather than size or morphology-dependent toxicity is the main reason forthe observed antibacterial activity of CeNPs.

    • Melt-assisted synthesis to lanthanum hexaboride nanoparticles and cubes

      CHUN-LIANG HANG LI-XIA YANG FENG WANG YAN-BIN XU CHEN-YU YI

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      Lanthanum hexaboride (LaB$_6$) nanocrystals and cubes were successfully synthesized at 700$^{\circ}$C for 2 h underargon atmosphere by a melt-assisted method using LaCl$_3$ and NaBH$_4$ as reactants, NaCl–KCl or zinc or NaCl–KCl–zincas reaction melt. The obtained products were characterized by X-ray diffraction (XRD), scanning electron microscopy(SEM), transmission electron microscopy (TEM) and Raman spectroscopy. XRD patterns and Raman spectra confirmedthe formation of LaB6 with high purity. TEM and SEM results showed LaB6 powders prepared in mixed molten salts ofNaCl–KCl were mainly composed of nanoparticles with sizes of ca. 8 nm. The morphology of LaB$_6$ presented as regularcubes (100–300 nm) when metal zinc was used as reaction melt. Photothermal conversion test indicated that nanoparticleshad a better photothermal conversion performance than cubes.

    • Effects of multi-wall carbon nanotubes on structural and mechanical properties of poly(3-hydroxybutyrate)/chitosan electrospun scaffolds for cartilage tissue engineering

      SAEED KARBASI ZAHRA MOHAMMAD ALIZADEH

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      Poly(3-hydroxybutyrate) (PHB)/chitosan electrospun scaffold was recently prepared for cartilage tissue engineering purpose. The drawback of this scaffold was its low mechanical properties. This study was carried out to see if addition of multi-wall carbon nanotubes (MWNTs) to PHB/chitosan polymeric blend can show better mechanical and structural properties. To do this, three different amounts of MWNTs (0.5, 0.75 and 1wt%) were added to PHB/chitosan solution. Then, the prepared solution was electrospun. The fibre’s diameter and uniformity were assessed by SEM. The solution components entity authenticity was approved by FTIR. The porosity assessment was illustrated by a porous structure with 81–83% porosity.Water contact angle (WCA) test showed the decrease in contact angle with the increase in MWNTs. Mechanical property results showed the strength of about 4–10 MPa for composites with different percentages of MWNTs,while PHB/chitosan showed the strength of 3 MPa. Actually, the mechanical properties of composite showed higher valueswhen compared to polymeric blend scaffold. All the results reveal that the addition of 1 wt% of MWNTs to the polymericsolution is the most optimal percentage whose values are close to cartilage properties.

    • Molecular dynamics study on the relaxation properties of bilayered graphene with defects

      WEI ZHANG JIU-REN YIN PING ZHANG YAN-HUAI DING YONG J IANG

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      The influence of defects on the relaxation properties of bilayered graphene (BLG) has been studied by moleculardynamics simulation in nanometre sizes. Type and position of defects were taken into account in the calculated model. Theresults show that great changes begin to occur in the morphology after introducing defects into BLG sheets. Compared withpoint defects, line defects have a significant effect on the relaxation properties of BLG.

    • Adsorption of small gas molecules on pure and Al-doped graphene sheet: a quantum mechanical study

      DHARMVEER SINGH ASHEESH KUMAR DEVESH KUMAR

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      The interaction of small gas molecules (CCl$_4$, CH$_4$, NH$_3$, CO$_2$, N$_2$, CO, NO$_2$ CCl$_2$F$_2$, SO$_2$, CF$_4$, H$_2$) on pure and aluminium-doped graphene were investigated by using the density functional theory to explore their potential applications as sensors. It has been found that all gas molecules show much stronger adsorption on the Al-doped graphene than that of pure graphene (PG). The Al-doped graphene shows the highest adsorption energy with NO$_2$, NH$_3$ and CO$_2$ molecules, whereas the PG binds strongly with NO$_2$. Therefore, the strong interactions between the adsorbed gas molecules and the Al-doped graphene induce dramatic changes to graphene’s electronic properties. These results reveal that the sensitivity of graphene-based gas sensor could be drastically improved by introducing the appropriate dopant or defect. It also carried out the highest occupied molecular orbital–lowest unoccupied molecular orbital energy gap of the complex molecular structure that has been explored by M06/6-31++G$^{**}$ method. These results indicate that the energy gap fine tuning of the pure and Al-doped graphene can be affected through the binding of small gas molecules.

    • Influence of electrodeposition parameters on the characteristics of Mn–Co coatings on Crofer 22 APU ferritic stainless steel

      HADI EBRAHIMIFAR MORTEZA ZANDRAHIMI

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      Manganese–cobalt coatings are promising candidates for solid oxide fuel cell (SOFC) interconnection applications because of their high conductivity and good oxidation resistance. In the present study, manganese and cobalt are electrodeposited onCrofer 22APU ferritic stainless steel. The effects of current density, pH, sodium gluconate (NaC$_6$H$_{11}$O$_7$)concentration, cobalt sulphate concentration (CoSO$_4$·7H$_2$O) and deposition duration on the microstructure and cathodic efficiency are characterized by means of scanning electron microscopy, weight gain measurements and energy-dispersive X-ray spectrometry, respectively. Results show that increases in current density and deposition duration lead to decrease in current efficiency and deposition rate. Increasing the pH to 2.5 causes an initial rise of current efficiency and depositionrate, followed by subsequent decline. In addition, the increases in sodium gluconate and cobalt sulphate concentrations inthe electrolyte solution result in an increase in current efficiency and deposition rate. Moreover, the results demonstratethat the variations in the current density, pH, sodium gluconate (NaC$_6$H$_{11}$O$_7$) concentration, cobalt sulphate concentration (CoSO$_4$·7H$_2$O) and duration have a significant effect on grain size, uniformity and the adherence of the coating.

    • Bipolar resistive switching behaviour in Mn$_{0.03}$Zn$_{0.97}$O/amorphous La$_{0.7}$Zn$_{0.3}$MnO$_3$ heterostructure films

      HUA WANG QISONG CHEN JIWEN XU XIAOWEN ZHANG SHUAISHUAI YAN

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      Mn$_{0.03}$Zn$_{0.97}$O (MZO)/amorphous La$_{0.7}Zn$_{0.3}$MnO$_3$ (LZMO) heterostructures were deposited on p$^+$-Si substratesthrough sol–gel spin coating. Ag/MZO/LZMO/p$^+$-Si and Ag/LZMO/MZO/p$^+$-Si devices exhibit a bipolar, reversibleand remarkable resistive switching behaviour at room temperature. The ratio of the resistance at high-resistance state (HRS)to that at low-resistance state (LRS) ($R_{\rm HRS}/R_{\rm LRS}$) in the Ag/LZMO/MZO/p$^+$-Si device is approximately five orders of magnitude, and is maintained after over 10$^3$ successive switching cycles or over a period of $2\times 10^6$ s, indicating good endurance property and retention characteristics. Conversely, the ratio in the Ag/MZO/LZMO/p$^+$-Si device began to decrease after 100 successive switching cycles. The LZMO/MZO interface could play an important role in the resistive switching behaviour of the devices. The dominant conduction mechanism of the two devices is charge-trap emission.

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