Molecular optical switches: synthesis, structure, and photoluminescence of spirosila compounds

Starting from a silicon dichloro substituted silole and a silacyclobutene, a series of new organosilicon-based spiro compounds was synthesized by using standard organometallic reaction procedures. The spiro compounds that combine two organic photoactive subunits at one silicon center were fully characterized by the usual analytical and spectroscopic methods, which include molecular structure determination by single-crystal X-ray analysis. Photoluminescence spectra of the compounds were recorded in the solid state and also as dilute solutions in THF. Interpretation of the spectra revealed that photoluminescence in this series of compounds originated from the stilbene or its vinylogue subunits. Different linkages of these groups to the silicon atoms (cyclic or open structures, four- or five-membered cycles) strongly affected both the excitation and the emission spectra, which show different emission maxima depending on the state of the sample (solid state or in solution) and the wavelength of light used for excitation. Thus, owing to their optoelectronic properties these compounds might be useful tools for the design of sensitive sensor materials and of optical switches.     

Preparation and characterization of Fe3O4@SiO2/APTPOSS core–shell composite nanomagnetics as a novel family of reusable catalysts and their application in the one‐pot synthesis of 1,3‐thiazolidin‐4‐one derivatives

Octakis[3‐(3‐aminopropyltriethoxysilane)propyl]octasilsesquioxane (APTPOSS) as a polyhedral oligomeric silsesquioxane derivative was prepared and used as a pioneer reagent to obtain a novel core–shell composite using magnetic iron oxide nanoparticles as the core and the inorganic–organic hybrid polyhedral oligomeric silsesquioxane as the shell. Fe₃O₄@SiO₂/APTPOSS were confirmed using Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive spectroscopy, dynamic light scattering, thermogravimetric analysis, X‐ray diffraction and vibrating sample magnetometry. The inorganic–organic hybrid polyhedral oligomeric silsesquioxane magnetic nanoparticles were used as an efficient new heterogeneous catalyst for the one‐pot three‐component synthesis of 1,3‐thiazolidin‐4‐ones under solvent‐free conditions. Moreover, these nanoparticles could be easily separated using an external magnet and then reused several times without significant loss of catalytic activity. Copyright © 2016 John Wiley & Sons, Ltd.     

Molecular Imaging of Biological Samples on Nanophotonic Laser Desorption Ionization Platforms

Mass spectrometry imaging (MSI) is a comprehensive tool for the analysis of a wide range of biomolecules. The mainstream method for molecular MSI is matrix‐assisted laser desorption ionization, however, the presence of a matrix results in spectral interferences and the suppression of some analyte ions. Herein we demonstrate a new matrix‐free MSI technique using nanophotonic ionization based on laser desorption ionization (LDI) from a highly uniform silicon nanopost array (NAPA). In mouse brain and kidney tissue sections, the distributions of over 80 putatively annotated molecular species are determined with 40 μm spatial resolution. Furthermore, NAPA‐LDI‐MS is used to selectively analyze metabolites and lipids from sparsely distributed algal cells and the lamellipodia of human hepatocytes. Our results open the door for matrix‐free MSI of tissue sections and small cell populations by nanophotonic ionization.     

Decoration of electrospun polyacrylonitrile nanofibers with ZnO nanoparticles and their application for removal of Pb ions from waste water

The adsorption behavior of lead (II) from aqueous solutions utilizing ZnO/polyacrylonitrile (PAN) nanofibers was studied. ZnO/PAN nanofibers were prepared by electrospinning method. The changes of the parameters of adsorbent amount, pH, contact time, and temperature were tested in the adsorption experiments. The adsorption was well described by the Langmuir adsorption isotherm model. The thermodynamic parameters indicate that the adsorption process is exothermic. The dynamic behavior of the lead (II) ions adsorption by PAN/ZnO nanofibers was well described by the pseudo-second-order kinetic model. The adsorbent can be regenerated by suitable desorption processes for multiple uses without significant loss of its adsorption capacity.     

Electro-oxidation of methanol catalysed by porous nanostructured Fe/Pd-Fe electrode in alkaline medium

Nanostructured Fe/Pd-Fe catalysts are prepared first by the deposition of Fe-Zn onto the Fe electrode surface, followed by replacement of the Zn by Pd at open circuit potential in a Pd-containing alkaline solution. The surface morphology and composition of coatings are determined by scanning electron microscopy and energy dispersive X-ray techniques. The results show that the Fe/Pd-Fe coatings are porous structure and the average particle size of Pd-Fe is low, in the range of 30–80 nm. The electrocatalytic activity and stability of Fe/Pd-Fe electrodes for oxidation of methanol are examined by cyclic voltammetry and chronoamperometry techniques. The new Fe/Pd-Fe catalyst has higher electrocatalytic activity and better stability for the electro-oxidation of methanol in an alkaline media than flat Pd and smooth Fe catalysts. The onset potential and peak potential on Fe/Pd-Fe catalysts are more negative than that on flat Pd and smooth Fe electrodes for methanol electro-oxidation. All results show that the nanostructured Fe/Pd-Fe electrode is a promising catalyst towards methanol oxidation in alkaline media for fuel cell applications.     

Investigation on surface properties of superhydrophobic nanocomposites based on polyvinyl chloride and correlation with cell adhesion behavior

The main aim was to study the roles of structural homogeneity and superhydrophobicity on the adhesion of SW colon cancer cells on the surface of polyvinyl chloride (PVC) nanocomposites. Concurrent use of a proper nonsolvent (ethanol) and silica nanoparticles resulted in superhydrophobic behavior and also different surface structures. The effect of added‐ethanol content on the surface properties of PVC nanocomposites was also studied. The synergetic combination of silica and ethanol has led to the formation of a porous surface layer resulting in a considerable boost in the hydrophobic behavior. The scanning electron microscopy, roughness, and X‐ray photoelectron spectroscopy (XPS) analysis results were all in total agreement indicating the substantial change in surface morphology, topography, and composition once the ethanol content was increased to 50 vol.%. The surface structure was notably changed by the addition of polyhedral oligomeric silsesquioxanes (POSS) nanoparticles. It was found that the induced inhomogeneity as a result of POSS addition had an adverse effect on the surface properties. In conclusion, superhydrophobicity could be regarded as a prerequisite for achieving cell‐repellent behavior, but it cannot guarantee a cell repellent surface especially if the surface layer possesses structural inhomogeneity.     

Nano‐TiO2 as an Efficient Catalyst for Tandem Knoevenagel–Michael‐Cyclocondensation Reaction of Dimedone with Aromatic Aldehydes and Ammonium Acetate or Aromatic Amines under Solvent‐free Conditions

TiO₂ nanoparticles in anatase and rutile forms was characterized and studied by several techniques including X‐ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM) and successfully applied as an efficient and heterogeneous catalyst in the synthesis of 1,8‐dioxo‐decahydroacridines via the one‐pot multi‐component condensation reaction of dimedone with aromatic aldehydes and ammonium acetate or aromatic amines under mild and solvent‐free conditions.     

The Specific Heat Capacity,Effective Thermal Conductivity,Density, and Viscosity of Coolants Containing Carboxylic Acid Functionalized Multi-Walled Carbon Nanotubes

Obviously, the behavior of thermophysical properties of covalently functionalized CNT-based water and -based ethylene glycol (EG) nanofluids cannot be predicted from the predicted models. We present a study of the specific heat capacity, effective thermal conductivity, density, and viscosity of coolants containing functionalized multi-walled carbon nanotubes (CNT-COOH) with carboxylic acid groups at different temperatures. After synthesizing of CNT-COOH-based water and CNT-COOH-based EG nanofluids, measurements on the prepared coolant were made at various concentrations by different experimental methods. While the thermal conductivity of both nanofluids illustrated a significant increase, the specific heat capacity of both samples showed a downward behavior with increasing temperature. Although the thermal conductivity of CNT-COOH-based water nanofluids is bigger than CNT-COOH-based EG nanofluids, CNT-COOH-based water has weaker temperature dependence than that of the CNT-COOH-based EG nanofluids. The viscosity was investigated in different shear rates and temperatures. It is noteworthy that CNT-COOH-based EG nanofluids show relatively a non-Newtonian behavior. Interestingly, specific heat capacities of both prepared nanofluids were decreased with increasing concentration. Also, the density of the CNT-COOH-based water and -based EG nanofluids increased and decreased smoothly with increasing CNT-COOH concentration and temperature, respectively.