Water-Accelerated Selective Synthesis of 1,2-Disubstituted Benzimidazoles at Room Temperature Catalyzed by Br⊘nsted Acidic Ionic Liquid

An environmentally benign method for the rapid and selective synthesis of 2-aryl-1-arylmethyl-1H-1,3-benzimidazoles by the reaction of o-phenylenediamines and aromatic aldehydes in the presence of 1-methylimidazolium triflouroacetate ([Hmim]TFA) at room temperature under aqueous conditions is described. The ionic liquid is reusable and could be recycled for several runs without any decrease in its efficiency.     

Studying the buckling and vibration characteristics of single-walled zinc oxide nanotubes using a nanoscale finite element model

The free vibration and axial buckling of achiral zinc oxide nanotubes (ZnONTs) are studied in this paper based on a three-dimensional finite-element model in which bonds are modeled using beam elements and mass elements are placed at the joints of beams instead of atoms. To determine the mechanical properties of the nanotubes, a linkage is established between molecular mechanics and density functional theory. The fundamental frequency and critical buckling load of ZnONTs with different geometries, chiralities and boundary conditions are calculated. It is shown that zigzag nanotubes are more stable than armchair ones. Investigating the effect of aspect ratio on the critical force shows that longer nanotubes are less stable. Also, it is indicated that increasing the length of the nanotubes will result in decreasing the frequency. Moreover, as the aspect ratio increases, the effect of end conditions diminishes.     

An efficient method for catalytic enantioselective addition of diethylzinc to aryl aldehydes by a C2-symmetric chiral imino alcohol

The enantioselective alkylation of aryl aldehydes with diethylzinc in the presence of a C₂-symmetric chiral ligand derived from 2-hydroxy-3-pinanone was achieved at room temperature with high enantiomeric excesses.     

immobilized cobalt chloride within nanoreactors of ?Si-MCM-48 as selective catalyst for epoxidation of alkenes

Summary It was found that immobilized CoCl₂ within nanoreactors of Si-MCM-48 catalyzes the oxidation of 1-octene, styrene, cyclohexene, norbornene, trans-stilbene and trans-2-hexene-1-ol with 35 to 95% conversion and 75 to 100% selectivity to the corresponding epoxides.     

Morphological changes towards enhancing piezoelectric properties of PVDF electrical generators using cellulose nanocrystals

For the first time, a nanocomposite of poly(vinylidene fluoride)/cellulose nanocrystal (PVDF/CNC) is developed as a piezoelectric energy harvester. This is implemented through electrospinning of PVDF solutions containing different levels of CNC loading, i.e., 0, 1, 3 and 5 % with respect to PVDF weight. Analytical techniques including DSC, FTIR and WAXD are conducted to monitor the polymorphism evolution within electrospun nanocomposites as the CNC content is varied. The results imply that CNCs at the optimum concentration (3 and 5 %) can effectively nucleate β crystalline phases. The nucleation of α crystalline phases is also prevented when CNCs are present within the structure of PVDF electrospun fibers. These changes in polymorphism give PVDF/CNC nanocomposites enhanced piezoelectric characteristics compared to pure PVDF nanofibers. We have demonstrated that the developed nanocomposites can charge a 33-μF capacitor over 6 V and light up a commercial LED for more than 30 s. It is envisaged that the PVDF/CNC nanocomposites provide the opportunity for the development of efficient electrical generators as self-powering devices to charge portable electronics.     

Ultrafast electrokinetics

The influence of a high electric field applied on both fluid flow and particle velocities is quantified at large Peclet numbers. The experiments involved simultaneous particle image velocimetry and flow rate measurements. These are conducted in polydimethylsiloxane channels with spherical nonconducting polystyrene particles and DI water as the background flow. The high electric field tests produced up to three orders of magnitude higher electrokinetic velocities than any previous reports. The maximum electroosmotic velocity and electrophoretic velocity measured were 3.55 and 2.3 m/s. Electrophoretic velocities are measured over the range of 100 V/cm < E < 250 000 V/cm. The results are separated according to the different nonlinear theoretical models, including low and high Peclet numbers, and weak and strong concentration polarization. They show good agreement with the models. Such fast velocities could be used for flow separation, mixing, transport, control, and manipulation of suspended particles as well as microthrust generation among other applications.     

[Hmim]TFA catalyzed multicomponent reaction: direct,mild, and efficient procedure for the synthesis of 1,2-dihydroquinazoline derivatives

4-Substituted-spiro-1,2-dihydroquinazolines and related compounds were synthesized by direct reaction of 2-aminobenzophenones, isatin, or 1,2-diketone derivatives and ammonium acetate in the presence of dual role catalyst-solvent ionic liquid, [Hmim]TFA. Excellent conversion of starting materials was achieved to the desired 1,2-dihydroquinazoline products.