Band 236, Heft 11-12

Steel is involved extensively in engineering vast constructing units in many industries and can undergo to corrosion by some chemical and/or electrochemical reactions with the environment. Therefore, designating an organic inhibitor with a specific chemical structure will participate in steel protection via enhancing their adsorption on the steel surface. Three gemini cationic surfactants based on azomethine with different hydrophobic tails labeled GSBI8, GSBI12, and GSBI16 have been designated and evaluated as corrosion inhibitors utilizing electrochemical impedance spectroscopy (EIS), gravimetrical and potentiodynamic polarization techniques. Importantly, the surfactant tail regulated the corrosion inhibition performance; with increasing the surfactant tail length, their inhibition efficiency enhanced because of their higher adsorption affinity. The inhibition efficiency of GSBI8, GSBI12, and GSBI16 reached 95.52, 96.72, and 97.1% respectively (EIS measurements). The Tafel examination clarified that GSBI8, GSBI12, and GSBI16 inhibitors behave as mixed type inhibitors following the modified Langmuir isotherm. The inhibitors adsorption on C-steel was confirmed by SEM surface examination. Finally, the DFT and MCs point of views investigation supported the experimental performance of the tested GSBI8, GSBI12, and GSBI16 inhibitors and specially their dependence on surfactant tail length.

Poly(N-isopropyl acrylamide-co-2-acrylamido methyl propane sulfonic acid) hydrogel was prepared and used as matrix for the fabrication of nickel and copper nanoparticles. Nickel and copper nanoparticles were fabricated via in situ reduction of Ni (II) and Cu (II) ions within the hydrogel matrix. The manufactured hydrogel and its corresponding composites with Ni and Cu nanoparticles were characterized by FTIR, XRD, EDX, TEM, and TGA. Thermal stability of hydrogel was found to be increased upon fabricating with metal nanoparticles. The hydrogel showed ability to absorb water 63 times of its weight in dried form. The Ni and Cu nanoparticles were observed to be well dispersed, spherical in shape and most of them were having diameters in the range of 12.5 to 38.8 nm and 58 to 102 nm, respectively. The as-prepared hydrogel-nickel and hydrogel-Cu nanocomposite were used as catalysts for the reduction of a toxic pollutant 4-nitrophenol. At 25 °C, the reduction of 4-NP was found to proceed with apparent rate constant ( k app ) of 0.107 and 0.122 min −1 in the presence of composite containing Ni and Cu nanoparticles, respectively. However, k app was increased with corresponding increase in temperature and its maximum value was found to be 0.815 min −1  at 88 °C with catalyst containing Ni nanoparticles. The formation of well dispersed Ni and Cu nanoparticles in the prepared hydrogel reflected that this hydrogel system can act as efficient stabilizing agent along with acting as a reactor medium. Recycling potential of catalysts was studied for five successive cycles.

Environmental pollution is the major issue of 21 st century. The toxic industrial effluents are crucially damaging aquatic environment, in the form of heavy metals, dyes and acids. The heavy metals are toxic, carcinogenic, non-degradable and therefore must be removed to save natural environment and human health. Batch sorption efficiency of Momordica Charantia L. stem and root (MCS and MCR) was studied for Cr(VI) metal ions removal under controlled adsorption parameters. The adsorbed and residual concentration of Cr(VI) was determined by atomic absorption spectrophotometer (AAS). The adsorbent surface morphology was determined by FTIR, BET, SEM and elemental analysis by EDX. The Freundlich and Langmuir equilibrium isotherm and pseudo 1st and 2nd order kinetic models were studied to understand bio-sorption mechanism. The Freundlich isotherm and pseudo 2nd order kinetic was best fitted model for MCS and MCR bio-sorption process. The maximum Langmuir adsorption capacity ( q max ) was 312.50 and 400 (mg/g) for MCS and MCR respectively. The trend of removal efficiency (%) and metal uptake ( q e ) was in order as MCS > MCR. All data was statistically analyzed using mean values ± standard deviation (SD). In conclusion, MCS and MCR are suggested as excellent sorbents for the elimination of numerous contaminants from the wastewater.

The present study details the green synthesis of silver nanoparticles using clove oil as a reducing and stabilizing agent. Cationic, anionic, nonionic and zwitterionic surfactants were introduced to study the change in size, shape, and morphology of nanoparticles. The nanoparticles were characterized using different techniques. The nanoparticles had shown specific surface Plasmon resonance band with absorbance between 380 and 385 nm. The X-ray diffraction study revealed that the nanoparticles are composed of spherical cubic crystals with average size between 136 and 180 nm while Dynamic Laser scattering (DLS) studies revealed an effective diameter of 82 nm and polydispersity index of 0.005. Thermogravimetric analysis suggested that the particles are stable even at 600 °C. All the samples presented good antibacterial and antifungal efficacies against Staphylococcus aureus , Klebsiella pneumonia and Candida albicans and good catalytic activities for the degradation of fast green and Allura red dyes. Further, thin edible films of the nanoparticles were prepared using sodium alginate for food preservation. The films were coated on fruits and vegetables for extending their shelf life to cope with demand and supply gap.

This theoretical study was conducted to evaluate the efficiency of fullerene C 60 and its metal functionalized nano clusters (C 59 Au, C 59 Hf, C 59 Ag and C 59 Ir) as a sensor for hydroxyurea (HXU). The various conclusions concerning the adsorption and sensing properties of the studied nano surfaces were achieved using density functional theory (DFT) at the M062X-D3/gen/LanL2DZ/def2svp level of theory. Among the nano clusters studied for this interaction, analysis of the HOMO–LUMO energy differences ( E g ) showed that HXU@C 59 Hg ( H2 ) reflects the least energy gap of 3.042 eV, indicating its greater reactivity, sensitivity and conductivity. Also, the adsorption phenomenon in this current study is best described as chemisorptions owing to the negative adsorption enthalpies observed. Thus, the adsorption energy ( E Ad ) follows an increasing pattern of: HXU@C 60 ( C1 ) (−0.218 eV) < HXU@C 59 Ir ( I1) (−1.361 eV) < HXU@C 59 Au ( A1) (−1.986 eV) < HXU@C 59 Hf ( H1) (−2.640 eV) < HXU@C 59 Hg ( H2) (−3.347 eV). Least E g , highest E Ad and non-covalent nature of interaction attributed to C 59 Hg surface are sufficient to show that, among all studied surfaces, C 59 Hg surface emerged as the most suitable adsorbent for the adsorption of HXU. Hence, it can be used in modeling future adsorbent material for hydroxyurea.

In present work, facile synthesis of a biocompatible hybrid biosorbent based on diethylenetriaminepentaacetic acid (DTPA) modified chitosan immobilized in organo-functionalized sodium alginate matrix (DTPA-MCSA) was carried out. DTPA-MCSA was casted in microspherical hydrogel beads. Three dimensional microporous geometry of the biosorbent remained well preserved as observed in SEM analysis which revealed the improved mechanical strength of the alginate matrix. Surface functionalization of base biopolymers was confirmed by FTIR and SEM analysis. Equilibrium sorption studies using DTPA-MCSA for Cu(II) from aqueous medium were carried out in batch mode and found considerably dependent on pH, contact sorption time, temperature and initial copper concentration. Isothermal sorption data showed close correlation with Langmuir model as evident from nonlinear fitting of data ( R 2  ˜ 0.99) at different temperatures. The experimental sorption capacity ( q e ) was found nearly 67 mg/g using 100 mg/L initial concentration of copper ions. Kinetic studies were conducted using different initial concentrations for better elucidation of results and it showed better correlation with pseudo second order rate equation which unveiled that strong ion pair coordination and complexation exist between Cu(II) and newly grafted chelating sites of DTPA-MCSA. Thermodynamic parameters suggested that the adsorption process is spontaneous and endothermic. The results concluded that DTPA-MCSA could be a better candidate for adsorptive remediation of copper ions from liquid waste.

Using hydro-alcoholic extract of Willow leaf, zinc oxide nanoparticles (ZnO NPs) were synthesized via four accelerated different heating methods namely, Bain-Marie heating (40 °C for 2 h), Conventional heating with stirrer (80 °C for 2 h), hydrothermal autoclave (1.5 atm and 121 °C for 15 min) and microwave irradiation (800 W and 160 °C for 3 min). Calcination process was finally completed on the obtained colloidal solutions in a furnace (350 °C for 2 h). The characteristics of the resulted ZnO NPs including particle size, grain size, crystallinity, specific surface area, morphology, photocatalytic, antioxidant bactericidal activities were estimated using X-ray diffractometry, scanning electron microscopy and Ultraviolet-visible spectroscopy techniques. Attained results indicated that among four different utilized synthetic methods, the fabricated ZnO NPs via Bain-Marie heating, had desired physico-chemical characteristics and bactericidal effect including small particle size (70 nm), high specific area (284 m 2 /gr), antioxidant activity (28.5%), photocatalytic activity (degradation of 50% of Methylene Blue), and bactericidal effects against Escherichia coli (clear zone diameter of 1.4 ± 0.1 cm) and Staphylococcus aureus (1.3 ± 0.1 cm).

Two series, A and B, of PVC based nanocomposite polymer membranes (nCPMs) were prepared using PbO only and PbO/graphite mixture as a filler by solution casting method. Seven samples with varying compositions (5–35%) of filler particles were prepared for each series and were compared by thickness measurements, porosity, water uptake, swelling degree, ionic conductivity, ion exchange capacity (IEC), membrane potential and transport number. The maximum values for these characteristics were observed as 0.402 mm, 0.77, 141.3%, 0.11, 0.0033 Scm −1 , 8.6 milli-eq.g −1 , 0.19 V and 0.01391 for series-A composites whereas that of 0.367 mm, 0.83, 63.4%, 0.019, 0.00981 Scm −1 , 5.21 milli-eq.g −1 , 0.13 V and 0.0108 for series-B nCPMs respectively. The SEM images of membranes showed greater voids produced in the series-B compared to series-A composites. The maximum Ionic conductivity, IEC, membrane potential and transport number were observed for membrane with 25% PbO/graphite, 20% PbO and 35% PbO particles respectively.

The optimization of the fluorescence enhancement factor of the IgG-FITC conjugate as an immunofluorescent marker, depending on the optical and topographic parameters of the colloidal silver film on the surface of a polystyrene plate for immunoassay, was carried out for the first time, and the factors effecting the enhancement were identified. By means of time-resolved spectroscopy as well as by detection the relative concentrations of IgG-FITC adsorbed on the solid phase with enzyme-linked immunoassay, it was shown that fluorescence enhancement in the presence of silver nanoparticles is a resonance process associated with plasmon effects. The most important parameters correlating with the fluorescence enhancement factor are the optical density value at the wavelength of excitation and emission of the fluorophore. The maximum enhancement factor of 10.2 times was obtained for Ag films with the highest optical density.

In the present work, how the position of the second nitrogen in the conjugate acids of the three pyridazines viz., 1,2-pyridazine, 1,3-pyridazine (the pyrimidine) and 1,4-pyridazine (the pyrazine) and three naphthyridines viz., cinnoline, quinazoline and quinoxaline changes the p K aH systematically is taken up. They decrease nearly by a factor of half each time in the class of their own. In contrast there is an increase in the p K aH when we move from pyrazole to imidazole. The p K aH of pyrazole is less than imidazole by −4.45 units. Suitable explanations are given.

Tautomers of sildenafil (5-{2-Ethoxy-5-[(4-methylpiperazin-1-yl)sulfonyl]phenyl}-1-methyl-3-propyl-1,6-dihydro-7H-pyrazolo[4,3-d]pyrimidin-7-one), a drug commonly used for treating the erectile dysfunction and pulmonary arterial hypertension were studied computationally at the DFT (B3LYP/6-311++G**) level. Four possible structures of sildenafil tautomers structures were considered. The geometries and chemical shifts of carbon and nitrogen nuclei were calculated and compared with available experimental data. The theoretical calculations proved to be consistent with experimental data and indicate the same lowest energy sildenafil structure. The energies of the all considered sildenafil tautomers were determined and ranked according to their energy values. This article presents calculations of several properties (aromaticity, atomic charges, atomic energies, intramolecular hydrogen bonding) and discusses their influence on the relative energies of sildenafil tautomers.

In our previous work on this topic, the Lennard-Jones potential was used to derive a semi-empirical formula relating the enthalpy of vaporization of a liquid to the density of the liquid and vapour at equilibrium with it, and a very good agreement between the formula and experimental data was demonstrated. In the present work, this approach has been further developed. The purpose of this work was to apply the Lennard-Jones potential to derive a semi-empirical formula describing the dependence of the surface tension of a liquid on temperature, as well as the dependence of the formation enthalpy of a binary solution on its composition. Solution formation was considered as consisting of two stages: 1) removal of x moles of the first component and 1– x moles of the second component from pure liquids into vacuum; in this case, the expended energy is equal to the energy of interaction of these molecules with all molecules in the volume of these liquids in accordance with the Lennard-Jones potential; 2) their movement from vacuum to an infinitely large volume of a solution of composition x ; in this case, the released energy is equal to the energy of interaction of these molecules with all the molecules of the solution. The enthalpy of solution formation is equal to the algebraic sum of the mentioned interaction energies. Since surface tension is due to the action of the same forces of intermolecular interaction, a similar formula can be used to describe the dependence of surface tension on temperature. A comparison of the derived equations with the experiment shows that the resulting equations are in exceptionally good agreement with the experimental data.

Sumac Leaves ( Rhus Coriaria L ), were used as a possible adsorbent of Basic Blue 3 (BB3) removal. The main affecting parameters on adsorption such as concentration, pH and temperature were investigated. Adsorption equilibrium was reached in 30 min. The ultrasonic effect was also enhanced the dyestuff removal. Adsorption capacity was rised from 0.566 to 1.826 mg/g, as rising the concentration from 4 μg/mL to 10 μg/mL. Several isotherm models including Langmuir, Freundlich and Temkin were applied for explaining the adsorption mechanism. Temkin and Langmuir isotherm models describe the system well. Pseudo first order, pseudo second order and intra particle kinetics were evaluated. Pseudo second order diffusion model supports the adsoprption and also intra particle diffusion plays an important role for BB3 removal. Thermodynamics of the adsorption were commented. −2219.5 J/mol of Gibbs energy showed us a spontaneous and physical adsorption.

The current study focuses on graphene oxide (GO) and its composite with zinc oxide and titanium dioxide nanoparticles to develop a simple nano chemistry-based clean and efficient process for the effective degradation of methylene blue (MB) dye. Graphene oxide composite with zinc oxide and titanium dioxide nanoparticles were fabricated via a thermal coupling process that demonstrates exclusive physiochemical properties. A detailed comparison of the structure, morphology, and surface analysis of synthesized GO and nanocomposites, as well as their electrochemical properties, has been accomplished. By using the degradation of methylene blue (MB) dye the photocatalytic function of nanocomposites was studied. Results reveal that the rate constants of GO, GO-TiO 2 , and GO-ZnO photocatalysts are 1.06 × 10 −3 min −1 , 2.56 × 10 −3 min −1 , and 1.63 × 10 −3 min −1 respectively which discloses GO-TiO 2 nanocomposite shows maximum degradation of MB dye among both catalysts. The reuse of photocatalyst even after five cycles retained the degradation efficiency of 80, 77, and 49% respectively for GO-TiO 2 , GO-ZnO, and GO when tested against MB. Hence, as a result, it was determined that these photocatalysts are ideal for the remediation of dye-contaminated wastewater.

This review is focusing on photocatalytic hydrogen (H 2 ) production as a viable fuel. The limitations of different production methods for H 2 generation and the importance of photocatalytic process are discussed, which renders this process as highly promising to meet the future energy crises. TiO 2 is one of most effective material to generate the H 2 via photocatalytic processes. Therefore, advantages of the catalyst over other semiconductors have been thoroughly analyzed. Starting from synthesis of TiO 2 and factors affecting the whole process of photocatalytic H 2 production have been discussed. Modifications for improvement in TiO 2 and the photocatalytic reaction are critically reviewed as well as the mechanism of TiO 2 modification has been described. Metal doping, non-metal doping, impurity addition and defect introduction processes have been analyzed and the comparison of experimental results is developed based on H 2 production efficiency. A critical review of the literature from 2004 to 2021 concludes that H 2 production as fuel using TiO 2 photocatalytic method is efficient and environment friendly, which have potential for practical applications for H 2 generation.