Rapid green synthesis of gold nanoparticles using Rosa hybrida petal extract at room temperature

This study reports a green method for the synthesis of gold nanoparticles using the aqueous extract of rose petals. The effects of gold salt concentration, extract concentration and extract quantity were investigated on nanoparticles synthesis. Gold nanoparticles were characterized with different techniques such as UV-vis spectroscopy, FT-IR spectroscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, dynamic light scattering and transmission electron microscopy. Transmission electron microscopy experiments showed that these nanoparticles are formed with various shapes. FT-IR spectroscopy revealed that gold nanoparticles were functionalized with biomolecules that have primary amine group (-NH2), carbonyl group, -OH groups and other stabilizing functional groups. X-ray diffraction pattern showed high purity and face centered cubic structure of gold nanoparticles. Dynamic light scattering technique was used for particle size measurement, and it was found to be about 10nm. The rate of the reaction was high and it was completed within 5 min.     

Nanocomposite membranes for organic solvent nanofiltration

Organic solvent nanofiltration (OSN) is a molecular separation method which offers a sustainable and reliable solution compared to the conventional energy-intensive separation processes. OSN can be successfully applied to several applications, such as food, pharmaceutical, petrochemical and fine-chemical industries. Current research on OSN membranes mainly focuses on polymeric materials due to the ease of processing, controlled formation of pores, lower fabrication costs and higher flexibility as compared with inorganic materials. However, there are some limitations for the polymeric membranes which can be partially surmounted by adding nanoscale fillers into the polymeric matrix to make nanocomposite membranes. This review aims to comprehensively evaluate and report the advances in nanocomposite membranes prepared by using either different nanoscale fillers or various fabrication methods for OSN applications. Nanoparticles that will be discussed include metal-organic framework, graphene oxide, carbon nanotubes, silica, titanium, gold, zeolite and other fillers. The incorporation of these nanoscale fillers into the polymeric membranes can positively influence the mechanical strength, chemical and thermal stability, hydrophilicity, solute selectivity and solvent permeance. This study may provide helpful insights to develop next-generation of OSN membranes for years to come.     

Complete basis set,hybrid-DFT study,and NBO interpretations of the conformational behavior of 1,2-dihaloethanes

The conformational behavior of 1,2-difluoroethane (1), 1,2-dichloroethane (2), 1,2-dibromoethane (3), and 1,2-diiodoethane (4) have been analyzed by means of complete basis set CBS-QB3, hybrid-density functional theory (B3LYP/Def2-TZVPP) based methods and natural bond orbital (NBO) interpretation. Both methods showed the expected greater stability of the gauche conformation of compound 1 compared to its anti conformation. Contrary to compound 1, the anti conformations of compounds 2–4 are more stable than their gauche conformation. The stability of the anti conformation compared to the gauche conformation increases from compound 1 to compound 4. The NBO analysis of donor–acceptor (σ → σ*) interactions showed that the generalized anomeric effect (GAE) is in favor of the gauche conformation of compound 1. Contrary to compound 1, GAE is in favor of the anti conformations of compounds 2–4. The GAE values calculated (i.e., GAE_anti − GAE_gauche) increase from compound 1 to compound 4. On the other hand, the calculated dipole moment values for the gauche conformations decrease from compound 1 to compound 4. In the conflict between the GAE and dipole moments, the former succeeded in accounting for the increase of the anti conformation stability from compound 1 to compound 4. There is a direct correlation between the calculated GAE, ∆[r _c–c(G) − r _c–c(A)] and ∆[r _c–x(A) − r _c–x(G)] parameters. The correlations between the GAE, bond orders, total steric exchange energies (TSEEs), ΔG _{Anti–Gauche}, ΔG ^‡(Gauche → Gauche′, C _2v), ΔG ^‡(Anti → Gauche, C ₂), dipole–dipole interactions, structural parameters, and conformational behaviors of compounds 1–4 have been investigated.     

Positive Cooperativity Induced by Interstrand Interactions in Silver(I) Complexes with α,α′-Diimine Ligands

The allosteric positive cooperativity accompanying the formation of compact [Cu^I(α,α′-diimine)₂]⁺ building blocks contributed to the historically efficient synthesis of metal-containing catenates and knotted assemblies. However, its limited magnitude can easily be overcome by the negative chelate cooperativity that controls the overall formation of related polymetallic multistranded helicates and grids. Despite the more abundant use of analogous dioxygen-resistant [Ag^I(α,α′-diimine)₂]⁺ units in modern entangled metallo-supramolecular assemblies, a related thermodynamic justification was absent. Solid-state structural characterizations show the successive formation of [Ag^I(α,α′-diimine)(CH₃CN)][X] and [Ag^I(α,α′-diimine)₂][X] upon the stepwise reactions of α,α′-diimine=2,2′-bipyridine (bpy) or 1,10-phenanthroline (phen) derivatives with AgX (X=BF₄⁻, ClO₄⁻, PF₆⁻). In room-temperature, 5–10 mM acetonitrile solutions, these cationic complexes exist as mixtures in fast exchange on the NMR timescale. Spectrophotometric titrations using the unsubstituted bpy and phen ligands point to the statistical (=non-cooperative) binding of two successive bidentate ligands around Ag^I, a mechanism probably driven by the formation of hydrophobic belts, that overcomes the unfavorable decrease in the positive charge borne by the metallic cation. Surprisingly, the addition of methyl groups adjacent to the nitrogen donors (6,6′ positions in dmbpy; 2,9 positions in dmphen) induces positive cooperativity for the formation of [Ag(dmbpy)₂]⁺ and [Ag(dmphen)₂]⁺, a trend assigned to additional stabilizing interligand interactions. Adding rigid and polarizable phenyl side arms in [Ag(Brdmbpy)₂]⁺ further reinforces the positively cooperative process, while limiting the overall decrease in metal–ligand affinity.     

Regioselective bromination and iodination of aromatic substrates promoted by trans-3,5-dihydroperoxy-3,5-dimethyl-1,2-dioxolane

Selective and efficient bromination and iodination of aromatic compounds by ammonium bromide and ammonium iodide, respectively, under promotion of trans-3,5-dihydroperoxy-3,5-dimethyl-1,2-dioxolane have been explored. Mild reaction conditions, high selectivity and yield, and high reaction rate are some of the major advantages of this synthetic method.     

THE USE OF NAFION-H® AS AN EFFICIENT CATALYST FOR THE DEPROTECTION OF TRIMETHYLSILYL ETHERS TO THEIR CORRESPONDING ALCOHOLS UNDER MILD AND HETEROGENEOUS CONDITIONS

Trimethylsilyl ethers were converted to their corresponding alcohols in the presence Nafion-H® and wet SiO ₂ with good-to-excellent yields under mild and heterogeneous conditions.