Preparation of MIP grafts for quercetin by tandem aryl diazonium surface chemistry and photopolymerization

The food antioxidant quercetin was used as a template in an ultrathin molecularly imprinted polymer (MIP) film prepared by photopolymerization. Indium tin oxide (ITO) plates were electrografted with aryl layers via a diazonium salt precursor bearing two terminal hydroxyethyl groups. The latter act as hydrogen donors for the photosensitizer isopropylthioxanthone and enabled the preparation of MIP grafts through radical photopolymerization of methacrylic acid (the functional monomer) and ethylene glycol dimethacrylate (the crosslinker) in the presence of quercetin (the template) on the ITO. The template was extracted, and the remaining ITO electrode used for the amperometric determination of quercetin at a working potential of 0.26 V (vs. SCE). The analytical range is from 5.10⁻⁸ to 10⁻⁴ mol L⁻¹, and the detection limit is 5.10⁻⁸ mol L⁻¹.

This work describes the grafting of a molecularly imprinted polymer (MIP) film by combining diazonium surface chemistry and surface-initiated photopolymerization. The MIP grafts specifically and selectively recognize quercetin in pure solution in THF and in real green tea infusion.

     

Preparation of water-soluble magnetic nanocrystals using aryl diazonium salt chemistry

A novel and facile methodology for the in situ surface functionalization of Fe(3)O(4) nanoparticles is proposed, based on the use of aryl diazonium salts chemistry. The grafting reaction involves the formation of diazoates in a basic medium. These species are unstable and dediazonize along a homolytic pathway to give aryl radicals which further react with the Fe(3)O(4) NPs during their formation and stop their growth. Advantages of the present approach rely not only on the simplicity, rapidity, and efficiency of the procedure but also on the formation of strong Fe(3)O(4)-aryl surface bonds, highly suitable for further applications.     

On the interfacial chemistry of aryl diazonium compounds in polymer science

This review emphasises the role of aryl diazonium compounds as a new class of coupling agents for grafting polymer thin layers onto carbon, diamond, metals, metal oxides, alloys, semi-conductors, ceramics, and polymers. Physical and chemical methods are first reported for anchoring aryl layers to the surfaces, then the review concentrates on the modification of the above substrates by thin polymer films via a range of the “grafting from” and “grafting onto” strategies. Some applications are described which highlight the important role that diazonium salts will continue to play in the near future in the polymer and surface sciences.     

Maleimide-activated aryl diazonium salts for electrode surface functionalization with biological and redox-active molecules

A versatile and simple method is introduced for formation of maleimide-functionalized surfaces using maleimide-activated aryl diazonium salts. We show for the first time electrodeposition of N-(4-diazophenyl)maleimide tetrafluoroborate on gold and carbon electrodes which was characterized via voltammetry, grazing angle FTIR, and ellipsometry. Electrodeposition conditions were used to control film thickness and yielded submonolayer-to-multilayer grafting. The resulting phenylmaleimide surfaces served as effective coupling agents for electrode functionalization with ferrocene and the redox-active protein cytochrome c. The utility of phenylmaleimide diazonium toward formation of a diazonium-activated conjugate, followed by direct electrodeposition of the diazonium-modified DNA onto the electrode surface, was also demonstrated. Effective electron transfer was obtained between immobilized molecules and the electrodes. This novel application of N-phenylmaleimide diazonium may facilitate the development of bioelectronic devices including biofuel cells, biosensors, and DNA and protein microarrays.     

Reaction of 3-oxodihydrothionaphthenes with aryl diazonium chlorides and aryl isothiocyanates

The reaction of 3-oxodihydrothionaphthenes with aryl diazonium chlorides gives 2-arylhydrazono-3-oxodihydrothionaphthenes. By oxidation of the latter with hydrogen peroxide in glacial acetic add, new 2-arylhydrazonodihydrothionaphthene-(3)-one-1, 1-dioxides are synthesized. Condensation of aryl isothiocyanates with 3-oxodihydrothionaphthenes in tetrahydrofuran gives 2-(arylthiocarbamyl)-3-oxodihydrothionaphthenes; cyclization of the latter with -bromoacetophene leads to the synthesis of 4-phenyl-3-aryl-2-(3 -oxodihydrothionaphthylidene-2)-⁴-thiazolines.     

In situ photopolymerization of biomaterials by thiol-yne click chemistry

The thiol-yne click chemistry reaction has been used for the in situ photocrosslinking of an aliphatic hyperbranched polyester. The biocompatibility of the resulting networks has been studied and marked cytotoxicity was not found for HeLa (human cervical carcinoma) tumoral cells and COS7 fibroblasts. The photoinduced thiol-yne process allows the generation of patterned structures with different geometries in films by DLW and these materials can be used as substrates for cell adhesion. The influence of the substrate geometry on cell adhesion has been studied by culturing cells onto these substrates and a preference for the photopatterned polymeric material can be seen in some of the structures by contrast phase microscopy. Actin and vinculin fluorescent staining revealed different adhesion behavior for HeLa cells and COS7 fibroblasts and this could be assigned to the different motility of cells. The thiol-yne photoreaction has proven to be an attractive approach for the preparation of micropatterned biomaterials.     

Preparation of antifog and antibacterial coatings by photopolymerization

This paper contains a kind of ultraviolet‐cured antifogging and antibacterial coating. A quaternary ammonium salt (14QAS), which was synthesized in this paper, has been implemented as a monomer. The chemical structure of 14QAS has been confirmed by Fourier transform infrared spectroscopy and nuclear magnetic resonance. The nitrogen atom on the surface of the coatings with 14QAS was observed by X‐ray photoelectron spectroscopy. The Surface wettability of the polymer film was studied by contact angle analysis, which confirmed the hydrophilicity of the coatings with low water contact angle (~25°). The antifog properties were evaluated under different conditions. The antibacterial activity of coatings with 14QAS reached 99.9% against S. aureus and E. coli. Copyright © 2014 John Wiley & Sons, Ltd.     

The copper-catalyzed cross-coupling reactions of aryl diazonium salts and isocyanides

The copper-catalyzed cross-coupling reaction of aryl diazonium salts and isocyanides has been performed. This is a successful example of preparation of arylcarboxyamides with moderate to good yield under mild conditions.     

Integrated surface modification of fully polymeric microfluidic devices using living radical photopolymerization chemistry

Surface modification using living radical polymerization (LRP) chemistry is a powerful technique for surface modification of polymeric substrates. This research demonstrates the ability to use LRP as a polymer substrate surface‐modification platform for covalently grafting polymer chains in a spatially and temporally controlled fashion. Specifically, dithiocarbamate functionalities are introduced onto polymer surfaces using tetraethylthiuram disulfide. This technique enables integration of LRP‐based grafting for the development of an integrated, covalent surface‐modification method for microfluidic device construction. The unique photolithographic method enables construction of devices that are not substrate‐limited. To demonstrate the utility of this approach, both controlled fluid flow and cell patterning applications were demonstrated upon modification with various chemical functionalities. Specifically, poly(ethylene glycol) (375) monoacrylate and trifluoroethyl acrylate were grafted to control fluidic flow on a microfluidic device. Before patterning, surface‐functionalized samples were characterized with both goniometric and infrared spectroscopy to ensure that photografting was occurring through pendant dithiocarbamate functionalities. Near‐infrared results demonstrated conversion of grafted monomers when dithiocarbamate‐functionalized surfaces were used, as compared to dormant control surfaces. Furthermore, attenuated total reflectance/infrared spectroscopy results verified the presence of dithiocarbamate functionalities on the substrate surfaces, which were useful in grafting chains of various functionalities whose contact angles ranged from 7 to 86°. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1404–1413, 2006     

Allylation and vinylation of aryl radicals generated from diazonium salts

Allylation and vinylation of aryl radicals generated from aryl diazonium salts provides rapid and efficient access to chlorinated and brominated derivatives of styrene and allylbenzene. Allyl chlorides were found to be better substrates than bromides due to decreased halogen transfer. Donor- and acceptor-substituted diazonium salts are well tolerated. The products represent important precursors for numerous further transformations.     

Hydroperoxides and aryl diazonium salts as reagents for the functionalization of non-activated olefins

Hydroperoxides, olefins, and arenediazonium salts selectively combine to give azo compounds via an iron(II)-mediated three-component reaction. Starting with a fragmentation liberating acetic acid, the hydroperoxides act as radical source and the diazonium ions as nitrogen-centered radical scavengers.     

Electrografting of aryl diazonium on thin layer platinum microbands: Towards customized surface functionalization within microsystems

The formation of organic thin layers on platinum microbands prepared by photolithography and sputtering techniques following the electrografting of a 4-azidobenzene diazonium salt was evaluated. The electrografting process was characterized by cyclic voltammetry in the presence of reversible redox probes. Further modification of the azide-modified platinum surfaces was achieved by the covalent attachment of ethynylferrocene via the copper(I)-catalyzed azide-alkyne cycloaddition-“click” reaction (CuAAC). Optimization of the electrografting method was performed based on the active ferrocene surface coverage reaching a maximum of 2.5 × 10^− 10 mol cm^− 2 after ten voltammetric scans. In addition, the modified microbands exhibited a high stability with a recovery of over 75% of the initial ferrocene response after 3 weeks of bench storage. This data supports the possibility of rapid and straightforward functionalization of platinum microbands for a range of analytical applications prior to their integration into microdevices.     

Intermolecular radical carboaminohydroxylation of olefins with aryl diazonium salts and TEMPO

Highly reactive aryl radicals can selectively be reacted with a broad variety of activated and nonactivated olefinic substrates in the presence of nitroxyl radicals. Direct recombination of the aryl radical and the nitroxide as well as telomerization of the olefin is successfully suppressed by the reaction conditions.     

A fast and efficient method for the preparation of aryl azides using stable aryl diazonium silica sulfates under mild conditions

An efficient, fast, and straightforward procedure for the synthesis of aromatic azides using aryl diazonium silica sulfates and sodium azide at room temperature under mild conditions is described. The use of inexpensive materials, simple and clean work-up, short reaction times and good yields are advantages of this method.     

Controlled swapping of nanocomposite surface wettability by multilayer photopolymerization

Single-layered photopolymerized nanocomposite films of polystyrene and TiO(2) nanorods change their wetting characteristics from hydrophobic to hydrophilic when deposited on substrates with decreasing hydrophilicity. Interestingly, the addition of a second photopolymerized layer causes a swapping in the wettability, so that the final samples result converted from hydrophobic to hydrophilic or vice versa. The wettability characteristics continue to be swapped as the number of photopolymerized layers increases. In fact, odd-layered samples show the same wetting behavior as single-layered ones, while even-layered samples have the same surface characteristics as double-layered ones. Analytical surface studies demonstrate that all samples, independently of the number of layers, have similar low roughness, and that the wettability swap is due to the different concentration of the nanocomposites constituents on the samples surface. Particularly, the different interactions between the hydrophilic TiO(2) nanorods and the underlying layer lead to different amounts of nanorods exposed on the nanocomposites surface. Moreover, due to the unique property of TiO(2) to reversibly increase its wettability upon UV irradiation and subsequent storage, the wetting characteristics of the multilayered nanocomposites can be tuned in a reversible manner. In this way, a combination of substrate, number of photopolymerized layers, and external UV light stimulus can be used in order to precisely control the surface wettability properties of nanocomposite films, opening the way to a vast number of potential applications in microfluidics, protein assays, and cell growth.     

Arylations using diazonium tetrafluoroborate and pyridine A convenient source of aryl radicals

Benzenediazonium tetrafluoroborate together with one equivalent of pyridine provides a convenient source of phenyl radicals via the homolysis of N-phenylazopyridinium tetrafluoroborate. Partial rate factors and total rate ratios have been determined for attack of a number of aromatic substrates by phenyl radicals produced in this way and are found to be similar to the values obtained using benzoyl peroxide as the source of phenyl radicals. The ratios of isomers formed in the decompositions in moderate and in large excesses of pyridine differ from one another. The results are discussed.     

Ion chromatography on carbon clad zirconia modified by diazonium chemistry and functionalized latex particles

This work explores the potential of 3 μm carbon coated zirconia particles as a stationary phase for ion chromatography for the separation of organic acids and inorganic ions. A 4-phenylsulfonic acid functionality is introduced onto the carbon surface by reducing 4-phenylsulfonic acid diazonium chloride with borohydride in the presence of carbon clad zirconia particles. The elemental sulfur analysis gave 132 μeq-SO(3)H/g carbon clad zirconia and 2% S atomic concentration by XPS analysis. The -SO(3)(-) groups serve as electrostatic anchors for latex nanoparticles bearing quaternary triethylamine functional groups. The agglomeration step in 5 × 0.4 cm i.d. columns converts the packed particles into an anion exchanger. The breakthrough curves with nitrate indicate a capacity of 3 μeq/column. Separation of common organic acids and inorganic ions using carbonate eluent and suppressed conductivity detection yield plate heights (H) of 0.023-0.05 mm.     

Preparation of quercetin imprinted core-shell organosilicate microspheres using surface imprinting technique

In this work,the quercetin imprinted core-shell microspheres were prepared using silica surface imprinting technique.A simple sol-gel procedure was used for the synthesis of the imprinted materials with 3-aminopropyltriethoxysilane as functional monomer and tetraethyl orthosilicate as crosslinker.The SEM images indicated that the MIPs shell was successfully grafted onto the silica surface.The characteristics of the molecularly imprinted polymers such as capacity,selectivity and absorption dynamic were investigated by rebinding experiments.The results showed that the prepared MIPs had good imprinting effect and adsorption amount of quercetin.     

Construction of a biointerface for glucose oxidase through diazonium chemistry and electrostatic self-assembly technique

In this study, a new procedure for the fabrication of biosensors was developed. The method is based on the covalent attachment of nitrophenyl groups to the electrode surface via diazonium salt reaction followed by their conversion to amine moieties through electrochemical reduction and electrostatic layer-by-layer (LbL) assembly technique. In this procedure, highly stable iron oxide (Fe₃O₄) nanoparticles (IONPs), chitosan (CHIt), GOx, and Nile blue (NB) were assembled on the surface of aminophenyl modified glassy carbon electrode (AP/GCE) by LbL assembly technique. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to characterize the interfaces. The surface coverage of the active GOx and Michaelis–Menten constant (K _M) of the immobilized GOx were Γ?=?3.38?×?10^?11 mol cm^?2 and 2.54 mM, respectively. The developed biosensor displayed a well-defined amperometric response for glucose determination with high sensitivity (8.07 μA mM^?1) and low limit of detection (LOD) of 19.0 μM. The proposed approach allows simple biointerface regeneration by increasing pH which causes disruption of the ionic interactions and release of the electrostatic attached layers. The biosensor can then be reconstructed again using fresh enzyme. Simple preparation, good chemical and mechanical stabilities, and easy surface renewal are remarkable advantages of the proposed biosensor fabrication procedure.     

On-chip generation and reaction of unstable intermediates-monolithic nanoreactors for diazonium chemistry: azo dyes

Monolithic nanoreactors for the safe and expedient continuous synthesis of products requiring unstable intermediates were fabricated and tested by the synthesis of azo dyes under hydrodynamic pumping regimes.