Band 231, Heft 11-12

In this work, an amino-functionalized graphene oxide (AFGO) was synthesized by graphene oxide (GO) and ethylene diamine. A novel amino-functionalized graphene oxide/azobenzene polyimide (AFGO/ACPI) was synthesized with AFGO, azobenzene chromophore and pyromellitic dianhydride (PMDA). The structure, mechanical and thermal property of AFGO/ACPI were characterized and measured by fourier transform infrared, UV-visible spectroscopy, near-infrared spectrum, thermogravimetric analysis and differential scanning calorimetry. To obtain the refractive index of AFGO/ACPI at different temperature and wavelength (532 nm, 650 nm and 850 nm), the attenuated total reflection (ATR) method was used to measure, and thermo optic coefficients (dn/dT) were −7.22×10 −4 (532 nm), −6.20×10 −4 (650 nm) and −5.84×10 −4 (850 nm) °C −1 , respectively. The transmission loss of AFGO/ACPI thin film was surveyed using the CCD digital imaging devices and the value was 0.167 dB/cm. According to the thermo-optic effect of AFGO/ACPI film, the 1×2 Y-branch and 2×2 Mach-Zehnder optical switches were simulated. The results showed that the power consumptions of the 1×2 Y-branch and 2×2 Mach-Zehnder optical switches were only 0.63 mW and 1.45 mW. The response time was about 0.5 ms, and compared to the normal polymeric thermo-optic switch, it can improve the response time and contribute to researches of optical switches.

The objective of this work is to develop a low-cost, alternative UV-visible Spectrophotometer method using ninhydrin to the current chromatography techniques (GC and HPLC), which is usually use for the quantitation of glyphosate. The physico-chemical characterization, such as adsorption capacities, effect of time and temperature has been studied. The reaction between the ninhydrin and compounds that present NH 2 group, which leading to the formation of a solution of blue coloration, has been analyzed by spectrophotometrically at 570 nm. The experimental data demonstrate equilibrium statistics, were well fitted to Langmuir isotherm. Adsorption kinetics of glyphosate on the adsorbent has been also analyzed by pseudo-first-order and pseudo-second-order models. The adsorption process is favored by acidic pH and followed the second-order kinetics. It was found that adsorption as a function of temperature, increase the temperature, decreases the adsorption. The isotherms shows the adsorption tendency like Arg-Na<Arg-Ca<Arg-Zn<Arg-Al, Arg-Cu with the variation of pH, it was found that at pH 6.5 has greater adsorption than pH 3.0. The important information which has been obtained from this work is to perform adsorption isotherms of glyphosate in clay soils with different metals such as Sodium, Calcium, Zinc, Copper (II) and Aluminum (Na + , Ca 2+ , Zn 2+ ,Cu 2+ and Al 3+ ) in terms of models under different conditions of pH and temperature. It is noted that the rates of adsorption initially are fast and reached to maximum capacity up to 24 h in clay soil with sodium.

The densities, ρ and viscosities, η have been measured for DL- glycine (Gly) and glycylglycine (Gly-Gly) in aqueous β cyclodextrin, (β-CD) at temperature 298.15, 303.15, 308.15, 313.15 and 318.15 K. Interaction between macrocyclic β-CD and amino acids was studied by two independent technique: density and viscosity. The two different intensive properties are used to obtain various thermodynamic characteristics of the material behavior. Using the measured density data the apparent molar volumes, V ϕ , partial molar volume at infinite dilution, Vϕο,$V_\phi ^o,$ experimental slope, S V , isobaric expansibility, ϕE0,$\phi _E^0,$ and the partial molar volume of transfer at infinite dilution, ΔVϕ(tr)ο$\Delta V_{\phi (tr)}^o$ have been obtained. Moreover, the Falkenhagen’s theoretical coefficient, A, Jones-Dole coefficient, B, free energies of activation of viscous flow per mole of solvent, Δμ1ο#$\Delta \mu _1^{o\# }$ and per mole of solute, Δμ2ο#,$\Delta \mu _2^{o\# },$ enthalpy, Δ H o # and entropy, Δ S o # of activation of viscous flow have been evaluated by using viscosity data. The negative value of transfer volume for Gly and Gly-Gly in aqueous β-CD suggests that the hydrophobic-hydrophilic and hydrophobic-hydrophobic interactions are predominating over ionic-hydrophilic and hydrophilic-hydrophilic interactions. The results indicate the formation of a stable complexation between the β-CD cavity and structural hydration effect of amino acids on the thermodynamic of their interactions in solutions.

In this work, combined experimental and computational investigations of a promising organic nonlinear optical (NLO) material, bis(creatininium) succinate (BCS), are reported. The optical quality single crystals of BCS were grown with the dimensions of 12×2×2 mm 3 . Single crystal X-ray diffraction analysis reveals that BCS crystallized in the orthorhombic system with non-centrosymmetric (NCS) space group F2dd. Vibrational modes of various BCS functional groups were confirmed by using FTIR and FT-Raman spectrum. UV-Vis-NIR spectrum shows that BCS crystal has low near-UV cut-off wavelength at 261 nm and optical transparency window in the visible and near-IR (261–1100 nm) region. Photoconductivity study has been carried out magnificently for grown crystals. The nonlinear optical property such as nonlinear refractive index (n 2 ) and nonlinear absorption coefficient (β) have been investigated by z-scan technique. Density functional theory (DFT) studies were carried out to probe Mulliken charge analysis, frontier molecular orbitals (FMOs), molecular electrostatic potential (MEP) mapping and first order hyperpolarizability (β) for the optimized molecular structure. Experimental and computed vibrations were correlated well. All these characterization results endorse BCS as a suitable NLO candidate and are discussed in this work.

Hydrogen bonded liquid crystal (HBLC) binary mixture has been synthesized from mesogenic 4-methoxycinnamic acid (4MCA) and mesogenic 4-hexyloxybenzoic acid (6OBA) with different mole ratio. The mesomorphic phase behavior and corresponding phase transition temperatures along with the enthalpy values were investigated by differential scanning calorimetry (DSC). The characteristic textures of 4MCA+6OBA binary mixture were observed by using polarizing optical microscope (POM). Fourier transform infrared spectroscopic (FT-IR) studies confirm the formation of hydrogen bond in the present binary mixture. A note worthy observation in this complex is that pure mesogens have no smectic phase where as 4MCA+6OBA binary mixture exhibits a nematic phase along with higher order smectic C (Sm C) phase. Variation of mole ratio influences thermal properties such as phase peak, enthalpy values and thermal span width of the present HBLC binary mixture complex. The optical tilt angle of 4MCA+6OBA for smectic C phase and thermal stability factors have been investigated. Optical tilt angle for smectic C phase is determined and same is fitted to a power law.

A computationally simple thermodynamic framework has been presented to correlate the vapour-liquid equilibria of carbon dioxide absorption in five representative types of alkanolamine mixtures. The proposed model is an extension of modified Kent Eisenberg model for the carbon dioxide loaded aqueous alkanolamine mixtures. The model parameters are regressed on a large experimental data pool of carbon dioxide solubility in aqueous alkanolamine mixtures. The model is applicable to a wide range of temperature (298–393 K), pressure (0.1–6000 kPa) and alkanolamine concentration (0.3–5 M). The correlated results are compared to the experimental values and found to be in good agreement with the average deviations ranging between 6% and 20%. The model results are comparable to other thermodynamic models.

The influence of acetate on Mn 2+ oxidation by a platinum electrode has been investigated in aqueous solution with cyclic voltammetry. It is found that acetate at concentrations below 0.5 M gives rise to autocatalytic oxidation of Mn 2+ with MnO 2 serving as the catalyst, while in 0.5–1 M acetate (as well as in the absence of acetate) Mn 2+ is oxidized non-catalytically. The autocatalytic oxidation is revealed by a separate voltammetric wave which has a much sharper rise and a lower potential compared to non-catalytic waves, by a sigmoid kinetics during chronoamperometry and by an enhanced Mn 2+ uptake with electrodeposited MnO 2 . The increase in temperature and Mn 2+ concentration promotes autocatalysis while acidification and the increase in sweep rate inhibits it that is thought to be due to the acceleration or delay of MnO 2 formation from Mn 3+ . It is suggested that acetate acts in two ways: (1) thermodynamically stabilizes Mn 3+ by complexation to enable the autocatalytic reaction Mn 2+ +MnO 2 +OAc − +H + ↔Mn 3+ −OAc+ Mn III OOH and (2) delays the formation of MnO 2 (presumably on the stage of Mn(III) crystallization) which leads to the inhibition of autocatalysis at high acetate concentrations.