Characterization of gold-thiol-8-hydroxyquinoline self-assembled monolayers for selective recognition of aluminum ion using voltammetry and electrochemical impedance spectroscopy

Gold electrode surface is modified via covalent attachment of a synthesized thiol functionalized with 8-hydroxyquinoline, p-((8-hydroxyquinoline)azo) benzenethiol (SHQ), for the first time. The behavior of the nanostructured electrode surface (Au–SHQ) is characterized by electrochemical techniques including cyclic and differential pulse voltammetry (CV and DPV), and electrochemical impedance spectroscopy (EIS). The modified surface is stable in a wide range of potentials and pHs. A surface pK_a of 6.0 ± 0.1 is obtained for Au–SHQ electrode using surface acid/base titration curves constructed by CV and EIS measurements as a function of pH. These results helped to determine the charge state of the surface as a function of pH. The gold modified electrode surface showed good affinity for sensing the Al(III) ion at pH 5.5. The sensing process is based on (i) accumulation and complex formation between Al(III) from the solution phase and 8HQ function on the Au electrode surface (recognition step) and (ii) monitoring the impedance of the Au–SHQ–Al(III) complex against redox reaction rate of parabenzoquinone (PBQ) (signal transduction step). The PBQ is found to be a more suitable probe for this purpose, after testing several others. Thus, the sensor was tested for quantitative determination of Al(III) from the solution phase. At the optimized conditions, a linear response, from 1.0 × 10⁻¹¹ to 1.2 × 10⁻⁵ M Al(III) in semi-logarithmic scale, with a detection limit of 8.32 × 10⁻¹² M and mean relative standard deviation of 3.2% for n = 3 at 1.0 × 10⁻⁷ M Al(III) is obtained. Possible interferences from coexisting cations and anions are also studied. The results show that many ions do not interfere significantly with the sensor response for Al(III). Validity of the method and applicability of the sensor are successfully tested by determination of Al(III) in human blood serum samples.     

Zirconium Phosphate Nanoparticles for Solvent Free Acetylation of Phenols and Salicylic Acid: An Efficient and Eco‐friendly Solid Acid Catalyst for Synthesis of Acetyl Salicylic Acid (Aspirin)

A facile synthesis of zirconium phosphate (ZP) nanoparticles as an effective, eco‐friendly and recyclable solid acid catalyst were studied. PVA was used as the organic matrix which is the dispersing agent and acted as a template for the nanoparticle. It seems H‐bonds between ZP and PVA along polymer chains play an important role in the better dispersion of in situ formed ZP. The catalyst was characterized by several instrumental techniques such as BET, ICP‐OES, XRD, FT‐IR, SEM and TEM. The TPD‐NH₃ analysis suggests the presence of reasonable amount of Brönsted acid sites. The acidic properties of catalyst were studied in acetylation of phenols by acetic anhydride (AA), specifically synthesis of acetylsalicylic acid (ASA), commonly known as Aspirin, from salicylic acid (SA). The effects of reaction time, reaction temperature, mole ratio of reactants, as well as amount of catalysts on the synthesis of ASA were investigated, and the reaction conditions were therefore optimized. The excellent yield (96%) of the ASA was obtained under optimized reaction conditions. The catalyst was recovered from reaction media and reused for 4 times after that with a consistent high yield.     

Presentation of a new index for estimation of aromaticity in halo‐ and cyanobenzenes: The role of potential energy in aromaticity

A linear correlation has been obtained between average values of Hamiltonian kinetic energy ( ) and potential energy ( ) calculated at the bond critical points using atoms in molecules method. This relation was used to introduce a new index ( ) for estimation of aromaticity in halo‐ and cyanobenzenes. Potential energy has different terms such as attraction between nuclei and electrons, also repulsion of electrons which affect the inertia and mobility of electrons, respectively. Therefore, contribution of potential energy in this relation must be controlled. Contribution of potential energy in aromaticity has been managed using a fitting parameter. This parameter was obtained by fitting the aromaticity stabilization energy data with values of aromaticity calculated by index for halo‐ and cyanobenzenes. The contribution of potential energy in index is complete when molecule is nonaromatic and is negligible when molecule is antiaromatic. Indeed, molecule is aromatic when contribution of potential energy in index lies between above limits. © 2013 Wiley Periodicals, Inc.     

Experimental and Modelling Study of Gravity Drainage in a Three-Block System

Transport in Porous Media - Gravity drainage is known as the controlling mechanism of oil recovery in naturally fractured reservoirs. The efficiency of this mechanism is controlled by...     

Local anisotropy in globally isotropic granular packings

We report on two-dimensional computer simulations of frictionless granular packings at various area fractions φ above the jamming point φ(c). We measure the anisotropy in coarse-grained stress ε(s) and shear modulus ε(m) as functions of coarse-graining scale, R. ε(s) can be collapsed onto a master curve after rescaling R by a characteristic length scale ξ and ε(s) by an anisotropy magnitude A. Both A and ξ accelerate as φ→φ(c) from above, consistent with a divergence at φ(c). ε(m) shows no characteristic length scale and has a nontrivial power-law form, ε(m)~R(-0.62), over almost the entire range of R at all φ. These results suggest that the force chains present in the spatial structure of the quenched stress may be governed by different physics than the anomalous elastic response near jamming.     

Numerical simulation of hydrothermal features of Cu–H2O nanofluid natural convection within a porous annulus considering diverse configurations of heater

Journal of Thermal Analysis and Calorimetry - The purpose of the current study is to numerically investigate the effects of shape factors of nanoparticles on natural convection in a fluid-saturated...     

Using graphene/TiO2 nanocomposite as a new route for preparation of electroconductive,self-cleaning,antibacterial and antifungal cotton fabric without toxicity

A novel and efficient process is reported for fabrication of electroconductive, self-cleaning, antibacterial and antifungal cellulose textiles using a graphene/titanium dioxide nanocomposite. Cotton fabric was loaded with graphene oxide using a simple dipping coating method. The graphene oxide-coated cotton fabrics were then immersed in TiCl₃ aqueous solution as both a reducing agent and a precursor to yield a fabric coated with graphene/titanium dioxide nanocomposite. The crystal phase, morphology, microstructure and other physicochemical properties of the as-prepared samples were characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy and UV-Vis reflectance spectroscopy. Electrical resistance, self-cleaning performance, antimicrobial activity and cytotoxicity of treated fabrics were also assessed. The electrical conductivity of the graphene/titanium dioxide nanocomposite-coated fabrics was improved significantly by the presence of graphene on the surface of cotton fabrics. The self-cleaning efficiency of the treated fabrics was tested by degradation of methylene blue in aqueous solution under UV and sunlight irradiations. The results indicated that the decomposition rates of methylene blue were improved by the addition of graphene to the TiO₂ treatment on fabrics. Moreover, the graphene/titanium dioxide nanocomposite-coated cotton samples had negligible toxicity and possessed excellent antimicrobial activity.     

High-performance supercapacitors based on an ionic liquid-derived nanofibrillated mesoporous carbon

This article reports the superior specific capacitance, energy, and power density of a nanofibrillated mesoporous carbon derived from an ionic liquid source (IFMC). It was concluded that high specific capacitance and good electrical conductivity were originated from contribution of nitrogen content of IFMC, also the interesting nanofibrillated structure. A specific capacitance of 235 F g^?1 at a high discharge current of 5 A g^?1 was estimated for IFMC-based electrode which is higher than the most reported capacitance for carbon materials. An excellent performance of the nanofibrillated mesoporous carbon along with proper concentration of nitrogen constituent in the carbonaceous framework is indicative for important effects of tuning the carbon nanostructure for energy storage applications.     

Isocyanide‐Based Multicomponent Synthesis of Functionalized 2,6‐Dioxohexahydropyrimidines in 1 M Aqueous Glucose

An effective route to novel 2,6‐dioxohexahydropyrimidines is described. This involves reaction of alkyl isocyanides and dialkyl acetylenedicarboxylates in the presence of N,N′‐dimethylurea in 1M aq. glucose.