Brønsted acidic ionic liquid as an efficient and reusable catalyst for one-pot synthesis of 1-amidoalkyl 2-naphthols under solvent-free conditions

A mild and efficient method has been developed for the preparation of amidoalkyl naphthols from condensation of aldehydes with amides or urea and 2-naphthol in the presence of a catalytic amount of Brønsted acidic ionic liquid ([TEBSA][HSO₄]) under thermal solvent-free conditions. High yields, short reaction time, easy work-up and reusability of the catalyst are advantages of this procedure.     

Zr(HSO4)4 catalyzed one-pot strecker synthesis of α-amino nitriles from aldehydes and ketones under solvent-free conditions

A mild and efficient method has been developed for the preparation of α-amino nitriles from the condensation of aldehydes and ketones with aniline and TMSCN in the presence of a catalytic amount of Zr(HSO₄)₄ under solvent-free conditions at room temperature.     

Thermodynamic stability and retinol binding property of β-lactoglobulin in the presence of cationic surfactants

In this work the stability parameters of bovine β-lactoglobulin, variant A (BLG-A), with regard to their transition curves induced by dodecyltrimethylammonium bromide (C₁₂TAB), tetradecyltrimethylammonium bromide (C₁₄TAB) and hexadecyltrimethylammonium bromide (C₁₆TAB) as cationic surfactants, were determined at 298 K. For each transition curve, the conventional method of analysis which assumes a linear concentration dependence of the pre- and post-transition base lines, gave the most realistic values for ΔG_D(H₂O). The results represent the increase in the denaturating power of surfactants with an increase in hydrocarbon chain length. The value of about 22.27 kJ · mol^?1 was obtained for ΔG_D(H₂O) from transition curves. Subsequently, the retinol binding property of BLG as its functional indicator was investigated in the presence of these surfactants using the spectrofluorimeter titration method. The results represent the substantial enhancement of retinol binding affinity of BLG in the presence of these surfactants.     

Extended light absorption and enhanced photoelectrochemical activity of palladium‐decorated hematite nanotubes prepared by photodeposition method

Palladium particles were deposited on hematite nanotube surfaces via a facile photodeposition method. Anodization method was then used for direct vertical growth of hematite nanotube arrays (HNTs) on a pretreated iron substrate. Field emission scanning electron microscopy, X‐ray diffraction, diffraction reflection spectroscopy and X‐ray photoelectron spectroscopy analyses were then used to carry out morphological and structural investigations. Compared with the bare HNTs, Pd‐decorated hematite films (Pd/HNTs) exhibit intense visible light absorption and show a red shift of the band edge. Pd/HNTs are more photoelectrochemically active than the non‐decorated films, according to chronoamperometry measurements. Thus, a promising methodology has been developed for the design of a simple and effective photoelectrode for application in photoelectrochemical water splitting systems.     

Thermodynamic denaturation of β-lactoglobulin in the presence of cetylpyridinium chloride

In this work, we determined the stability parameters of bovine β-lactoglobulin, variant A, (BLG-A), in relation to their transition curves induced by cetylpyridinium chloride (CPC) as a cationic surfactant. The experiments took place over the temperature range of 298 K to 358 K. For each transition curve at any specific temperature, the conventional method of analysis, which assumes a linear concentration dependence of the pre- and post-transition base lines, gave the most realistic values for ΔG_D(H₂O). Results show that the minimum value of ΔG_D(H₂O) occurs at T = 328 K. Using the Gibbs–Helmholtz equation, the values of enthalpy, ΔH_D, and entropy, ΔS_D, of denaturation have been calculated considering temperature dependence of ΔG_D at any specified concentration of CPC. The values of 12.05 kJ · mol⁻¹, 18.54 kJ · mol⁻¹, and 18.32 J · mol⁻¹ · K⁻¹, were obtained for ΔG_D(H₂O), ΔH_D(H₂O), and ΔS_D(H₂O), respectively. The results show that the enthalpy term dominates the entropy term.     

Binding of biguanides to β-lactoglobulin: molecular-docking and molecular dynamics simulation studies

Biguanides are a class of drugs derived from biguanide and they are the most widely used drugs for diabetes mellitus or pre-diabetes treatment. An investigation of their interaction and a transport protein such as β-lactoglobulin (BLG) at atomic level could be a valuable factor in controlling their transport to biological sites. Molecular-docking and molecular dynamics simulation methods were used to study the interaction of metformin, phenformin and buformin as biguanides and BLG as transport protein. The molecular-docking results revealed that these biguanides bind to BLG and that the BLG affinity for binding the biguanides decreases in the following order: phenformin — buformin — metformin. The docking results also show the hydrophobic interactions to have a significant role in the BLG-biguanides complex stability. Analysis of molecular dynamic simulation trajectories shows that the root mean square deviation of various systems attained equilibrium and fluctuated around the mean value at various times. The time evolution of the radius of gyration and the total solvent-accessible surface of the protein showed that BLG and BLG-biguanide complexes became stable at approximately 2500 ps and that there was not any conformational change in the BLG-biguanide complexes. In addition, the profiles of atomic fluctuations show the rigidity of the ligand-binding site during the simulation.     

Photoinduced deposition of gold nanoparticles on TiO<Subscript>2</Subscript>–WO<Subscript>3</Subscript> nanotube films as efficient photoanodes for solar water splitting

Gold-modified TiO₂–WO₃ nanotubes with different amounts of gold were obtained by two methods; photoassisted deposition and one-step electrochemical anodizing method. The morphology, crystallinity and elemental composition were studied by FE-SEM, XRD and EDX. The photoelectrochemical performance was examined under Xe light illumination in 1 M NaOH electrolyte. Characterization of the as-prepared TiO₂–WO₃ samples indicated that sodium tungstate concentration in anodizing solution significantly influenced the morphology and photoelectrochemical activity of fabricated films. Also, photoelectrochemical characterizations show that the photocatalytic activity of Au/TiO₂–WO₃ nanotubes was improved as compared with that of bare TiO₂–WO₃ nanotubes. The experimental results showed that the photocatalytic activities of Au/TiO₂–WO₃ were significantly affected by the amount of Au nanoparticles. The amount of gold nanoparticles was effectively controlled by time of photoreduction of the chloroauric acid solution. These new photoanodes showed enhanced high photocurrent density with good stability and are a highly promising photoanodes for photocatalytic hydrogen production.     

Study of various aliphatic alcohols as sacrificial agents on photoelectrochemical behavior of nickel-platinum-modified Cr-TiO<Subscript>2</Subscript> nanotubes

Cr-TiO₂ nanotubes (Cr-TNTs) have been synthesized via facile one step anodization, followed by co-deposition by nickel-platinum via electroless deposition method. Field-emission scanning electron microscopy (FE-SEM), x-ray diffraction (XRD), and Raman spectroscopy have then been used to characterize the surface morphology and structure of the synthetic samples. The optical properties of the compounds have been investigated by ultraviolet-visible (UV-Vis) diffuse reflectance spectroscopy. Linear sweep voltammetry (LSV) and chronoamperometry were used to study the photoelectrochemical behavior of the obtained samples. The best electrochemical performer sample (t₂₀) was recognized and evaluated in the presence of various aliphatic alcohols, as sacrificial agents, in photoelectrochemical cells (PEC) water splitting. In terms of sacrificial agent used, photocurrent density production was as follows: methanol > ethanol > glycerol > n-propanol > isopropanol > ethylene glycol. Also methanol concentration was optimized. Thus, both co-deposition of Cr-TNTs and addition of scavengers are promising methods to enhance the performance of catalysts for PEC.