Diazonium salts for surface‐confined visible light radical photopolymerization

The surface chemistry of aryl diazonium salts has progressed at a remarkable pace in the last two decades, and opened many avenues in materials science. These compounds are excellent coupling agents for polymers to surfaces via several surface‐confined polymerization methods. For the first time, we demonstrate that diazonium salts are efficient for surface initiating radical photopolymerization in the visible light of methyl methacrylate (MMA) and 2‐hydroxyethyl methacrylate (HEMA) taken as model monomers. To do so, 4‐(dimethylamino)benzenediazonium salt was electroreduced on gold plates or flexible ITO sheets to provide 4‐(dimethylamino)phenyl (DMA) hydrogen donor layers; while excited state camphorquinone acted as the free hydrogen abstractor. In the same way, we co‐polymerized HEMA and MMA with ethylene glycol dimethacrylate in order to obtain crosslinked polymer grafts. We demonstrate by XPS that gold was efficiently screened by the polymer layers and that the wettability of the surfaces accounts for the hydrophilic or hydrophobic characters of the tethered polymers. Homo‐ and crosslinked PMMA grafts were found to resist removal by the paint stripper methyl ethyl ketone. The grafted DMA/camphorquinone system operating in the visible light holds great promises in terms of adhesion of in situ designed continuous or patterned polymer coatings on various substrates. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3506–3515     

Monolithic metal–organic framework MIL‐53(Al)‐polymethacrylate composite column for the reversed‐phase capillary liquid chromatography separation of small aromatics

A monolithic capillary column containing a composite of metal–organic framework MIL‐53(Al) incorporated into hexyl methacrylate‐co‐ethylene dimethacrylate was prepared to enhance the separation of mixtures of small aromatic compounds by using capillary liquid chromatography. The addition of 10 mg/mL MIL‐53(Al) microparticles increased the micropore content in the monolithic matrix and increased the Brunauer–Emmett–Teller surface area from 26.92 to 85.12 m²/g. The presence of 1,4‐benzenedicarboxylate moieties within the structure of MIL‐53(Al) as an organic linker greatly influenced the separation of aromatic mixtures through π–π interactions. High‐resolution separation was obtained for a series of alkylbenzenes (with resolution factors in the range 0.96–1.75) in less than 8 min, with 14 710 plates/m efficiency for propylbenzene, using a binary polar mobile phase of water/acetonitrile in isocratic mode. A reversed‐phase separation mechanism was indicated by the increased retention factor and resolution as the water percentage in the mobile phase increased. A stability study on the composite column showed excellent mechanical stability under various conditions. The higher resolution and faster separation observed at increased temperature indicated an exothermic separation, whereas the negative values for the free energy change of transfer indicated a spontaneous process.     

Phenacyl onium salt photoinitiators: synthesis, photolysis, and applications

Onium salts, namely sulfonium, phosphonium, ammonium, and pyridinium salts containing phenacyl group are photoinitiators appropriate for the polymerization of monomers such as oxiranes and vinyl ethers, which are not polymerizable by a free-radical mechanism. The initiation is accomplished by direct or indirect (sensitized) photolysis of the salts. Depending on the type of the salt, the direct photoinitiation of cationic polymerization involves reversible or irreversible processes. The photolysis of phenacylsulfonium compounds proceeds by a reversible process, while the other types undergo irreversible photolysis leading to complete fragmentation of the photoinitiator. An additionally useful tool, namely photosensitized generation of initiating species enlarges the versatility of these salts as photoinitiators. Photoinitiated free-radical and zwitterionic polymerizations by using phenacyl-type salts are also addressed. Keto-enol tautomerization of phenacyl pyridinium salts is discussed. Moreover, an interesting application concerning in situ synthesis of clay-poly(methyl methacrylate) nanocomposites with the aid of the phenacyl anilinium salt-based photopolymerization technique is noted.     

Gold nanoparticle included graphene oxide modified electrode: Picomole detection of metal ions in seawater by stripping voltammetry

We obtained a gold nanomaterial/graphene oxide-modified glassy carbon electrode and characterized it using transmission electron microscope, scanning electron microscope, cyclic voltammetry (CV), and X-ray photoelectron spectroscopy techniques. A response of the electrode using square wave anodic stripping voltammetry for Pb²⁺, Cu²⁺, and Hg²⁺ was found linear in the range from 1 × 10^–7 to 1 × 10^–11 M. The detection limits of Pb²⁺, Cu²⁺ and Hg²⁺ were 0.14, 0.5 and 1.2 pM, respectively. The method was applied to the simultaneous determination of Pb²⁺, Cu²⁺ and Hg²⁺ in seawater samples from a coastal region of Anatolia, and the results corresponded well with the values obtained by inductively coupled plasma-optical emission spectroscopy.     

Laccase bound to cryogel functionalized with phenylalanine for the decolorization of textile dyes

In this study, amino acid functionalized poly(2-hydroxyethyl methacrylate-N-methacrylolyl-l-phenylalanine) [PHEMAPA] cryogel discs were prepared. In this respect, phenylalanine containing N-methacryloyl-(L)-phenylalanine methyl ester (MAPA) was polymerized with 2-hydroxyethyl methacrylate (HEMA) without requirement of any activation step. Laccase bound poly(2-hydroxyethyl methacrylate-N-methacryloyl-l-phenylalanine) [Lac-PHEMAPA] cryogel discs were applied for decolorization of Reactive Blue-247 (RB-247). The ability of Lac-PHEMAPA cryogel discs on dye decolorization was found to be as 90% in 2 h and even more within 4h. The decolorization activities of 86% and 73% were observed at relatively low (4°C) and high (60°C) temperatures, respectively. The effect of dye concentration on dye decolorization and 100% decolorization activity was achieved in dye concentration between 50–300 ppm. Lac-PHEMAPA cryogel discs maintained 80% of its decolorization activity after six cycles. Consequently, the PHEMAPA cryogel discs are promising materials for immobilizing laccase. The Lac-PHEMAPA has a rapid dye decolorization in a broad range of temperature. The preparation is furthermore very stable and activity is preserved during storage.     

Initiation of cationic polymerization by photoinduced electron transfer

The objective of this paper is to discuss: (i) the general approaches to the initiation of cationic polymerization by photinduced electron transfer reactions (ii) the use of photoinduced electron transfer reactions for block copolymer synthesis. For the first, it is concluded that three general methods are currently available which involve reduction of onium salts by (a) photogenerated radicals, (b) photoexcited sensitizers or (c) electron donor compounds in charge transfer complexes. According to this view, a variety of initiating systems are discussed. For the second, recent developments on the application of photoinduced electron transfer reactions to the synthesis of block copolymer of monomers polymerizable with different mechanisms are presented.     

Two interface effects: Exchange bias and magnetic proximity

Exchange bias and magnetic proximity effects are two novel phenomena that are in the limelight because of their fundamental and technological importance. Since both phenomena are interfacial in origin, we review these together. In the first part of this review, we have discussed the basics of these two phenomena. Subsequently, we have described numerous experimental examples involving a variety of composite magnetic materials and heterostructures. The recent theoretical models of these two interface phenomena have also been described. Finally, we have shed light on an obvious question: can one expect both these phenomena to occur together in any magnetically coupled system? We conclude that one can enhance the operating temperature of an exchange biased device by exploiting the magnetic proximity effect.     

Dynamics of optical solitons and nonautonomous complex wave solutions to the nonlinear Schrodinger equation with variable coefficients

Variable coefficients nonlinear evolution equations offer us with more real aspects in the inhomogeneities of media and nonuniformities of boundaries than their counter constant coefficients in some real-world problems. Under consideration is a nonlinear variable coefficients Schrödinger’s equation with spatio-temporal dispersion in the Kerr law media. We are aimed at constructing novel solutions to the equation under consideration. Bright and combined dark–bright optical solitons are successfully revealed with aid of the complex amplitude ansatz scheme. Using two test functions, two nonautonomous complex wave solutions in dark and bright optical solitons forms are successfully revealed. The effect of the variable coefficients on the reported results can be clearly seen on the 3-dimensional and contour graphs.

     

Determination of the chemical composition and Raman characterization of barite samples from Denizli and Akdamadeni,Turkey, using Energy Dispersive X-ray fluorescence and Raman microscopy

Accurate analysis of samples is very important for scientists working in many fields. XRF device is used very frequently especially in mine analysis. However, researchers are trying to reach accurate results with many different analysis methods. In addition to the known analysis methods, alternative research methods also guide the studies. In this study, two barite ore samples, collected from two regions of different nature (Denizli and Akda?madeni) by following specified sampling methods, were analyzed using Confocal Raman Spectroscopy (CRS) and Polarized Energy Dispersive X-Ray Fluorescence (PEDXRF) spectrometer. The first sample was from a metamorphic basement, and the second was from an alkali syenite rock unit. The main objective of this paper is to compare the optical characteristics of these two different barite samples collected from different regions under a polarized microscope, using CRS and PEDXRF. The results of polarized microscopy analysis showed that the barite taken from Denizli is associated with calcite. On the other hand, the barite taken from Akda?madeni is associated with galena, celestite, and quartz. Two different colors were observed in the barite samples. CRS and PEDXRF results showed that the barites collected from two regions differed in mineral association, chemical composition, and physical properties. The accuracy of the chemical analysis technique was ensured by following USGS standards, GBW 7109, and GBW-7309 Sediment. Barite ores were analyzed using HR-800 (HORIBA-Jobin Yvon) CRS and a polarized microscope (Leica DMLP). Thanks to this study, it has been shown that mineral analyzes can be performed with an accuracy close to XRF with Confocal Raman spectroscopy. Confocal Raman spectroscopy will also guide researchers for mineral analysis.