Photoresponsive surfaces with two independent wavelength-selective functional levels

Two photoremovable protecting groups, namely, nitroveratryloxycarbonyl (NVo) and diethylamino-coumarin-4-yl (DEACM), have been tested for wavelength-selective, independent removal. The chromophores were attached to the amine group of aminopropyltriethoxysilane and used for the modification of silica surfaces. A photolytic experiment on the photosensitive layers allowed us to identify the irradiation conditions for the selective cleavage of the chromophores. UV measurements revealed that the photolabile DEACM group can be cleaved off with UV light at 412 nm without damaging the NVo group. The NVo group could then be removed at 365 nm. Masked irradiation of substrates modified with a 1:1 molar mixture of both silanes allowed the generation of bifunctional patterns after the selective cleavage of DEACM and NVo in a sequential irradiation process. The deprotection reaction was confirmed by coupling two different fluorescent dyes to the liberated amine groups. The expected two-color pattern could be observed by fluorescence microscopy.     

Specific features of the solubilization of multinuclear aromatic hydrocarbons in triton X-100 micelles

Via the spectral shift method, it is shown that the molecules of phenanthrene, fluorene, and naphthalene solubilized by Triton X-100 micelles are localized at the boundary between hydrophobic and hydrophilic regions of a micelle. Changes in the volumes of the cavities in the micelles containing the aforementioned aromatic hydrocarbons are estimated in comparison with the volumes of corresponding cavities in benzene and n-paraffins.     

Photopatterned surfaces for site-specific and functional immobilization of proteins

Photosensitive silanes containing nitroveratryl (Nvoc)-caged amine groups and protein repellent tetraethylene glycol units were synthesized and used for modification of silica surfaces. Functional surface layers containing different densities of caged amine groups were prepared and activated by UV-irradiation of the surface. The performance of these layers for functional and site-selective immobilization of proteins was tested. For this purpose, biotin and tris-nitrilotriacetic acid (tris-NTA) were fist coupled to the activated surface, and the interaction of streptavidin and His-tagged proteins with the functionalized surfaces was monitored by real-time label-free detection. After optimizing the coupling protocols, highly selective functionalization of the deprotected amine groups was possible. Furthermore, the degree of functionalization (and therefore the amount of immobilized protein) was controlled by diluting the surface concentration of the amine-functionalized silane with a nonreactive (OMe-terminated) tetraethylene glycol silane. Immobilized proteins were highly functional on these surfaces, as demonstrated by protein-protein interaction assays with the type I interferon receptor. Protein micropatterns were successfully generated after masked irradiation and functionalization of the caged surface following the optimized coupling protocols.     

Intercalation of Cyclic Amines into α-Titanium Phosphate

The intercalation of some amines (aniline, benzylamine, cyclohexylamine,piperidine, pyridine, pyrazine and piperazine) into -titaniumphosphate, Ti(HPO₄)_2×H₂O,has been investigated by the batch method and/or by exposing the host to thevapour of the amines. The changes in the interlayer distance of the solidduring the intercalation process was followed by X-ray powder diffraction.The new intercalates were characterised by chemical and thermal analysis.Materials with a monolaminar and/or bilaminar arrangement of amine moleculesin the phosphate interlayer region are obtained depending on the nature ofthe amine. Due to steric hindrance, saturated phases are not obtained forall amines studied. The thermal decomposition of the intercalates (nitrogenatmosphere), takes place in three stages: dehydration, removal of amines andcondensation of the hydrogenphosphate to pyrophosphate groups.     

Nafion/tetraruthenated porphyrin glassy carbon-modified electrode: characterization and voltammetric studies of sulfite oxidation in water–ethanol solutions

In this work, the modification of a glassy carbon electrode with tetraruthenated porphyrins electrostatically assembled onto a Nafion film, previously adsorbed on the electrode surface, is reported. This modified electrode was characterized by scanning electron microscopy–energy-dispersive X-ray, Raman spectroscopy, UV-Vis spectroelectrochemistry, and cyclic voltammetry. The Nafion film onto the glassy carbon electrode shows a smooth disposition; when the tetraruthenated porphyrin is incorporated on the Nafion film, the complex is adsorbed in a homogeneous way. The modified electrode catalyzes HSO₃⁻ oxidation in water–ethanol solutions and shows an enhanced stability compared with the electrode modified with the dip coating method. Rotating disk electrode experiments showed a kinetic limitation to the electron transfer controlled by charge propagation in the film. I/E curves show a Tafel slope of 120 mV/decade corresponding to a first electron-transfer reaction, depending on the potential, as the determining step. Spectroelectrochemical experiments demonstrated that Ru(II) is the active site for the electrocatalysis.     

Two non-linear azide containing heteronuclear complexes: crystal structure and thermal decomposition

Bis-N,N′(salicylidene)-2,2′-dimethyl-1,3-propanediamine (LDMH₂) has a high tendency to form polynuclear complexes. Two trinuclear complexes were obtained using this ligand and azide ions; (CuLDM)₂ · Mn(N₃)₂ · (DMF)₂, [(C₁₉H₂₀N₂O₂Cu)₂ · Mn(N₃)₂ · (C₃H₇NO)₂] and (CuLDM)₂ · Cd(N₃)₂ · (DMF)₂, [(C₁₉H₂₀N₂O₂Cu)₂ · Cd(N₃)₂ · (C₃H₇NO)₂]. The structures were identified with X-ray methods. TG and DSC methods were also employed to these complexes. Studies showed the (CuLDM)₂ · Mn(N₃)₂ · (DMF)₂ and (CuLDM)₂ · Cd(N₃)₂ · (DMF)₂ to be non-linear. Also μ-bridges were not encountered for the azide ions but were seen to form between the Cu and other metal via phenolic oxygens. Thermal analysis showed exothermic degradation of the azide ions destroying the trinuclear structure. Although azide containing structures show explosive characteristics, this was not observed for the present compounds.     

Polymesomorphism and orientation in liquid crystalline poly(triethylene glycol p,p′-bibenzoate)

The phase transitions and the orientational behavior of liquid crystalline poly(triethylene glycol p,p′-bibenzoate) have been studied. The real-time synchrotron diffraction results indicate that, on cooling from the isotropic melt, an orthogonal SmA mesophase is formed first, and later it is transformed into a tilted SmC mesophase. However, the SmA mesophase is stable in a rather wide temperature interval, and the transformation into the SmC phase occurs at temperatures close to the glass transition, so that not very high tilting angles are attained. The uniaxial deformation of the SmC mesophase indicates that usual parallel orientation of the molecular axes in relation to the stretching direction is obtained at high strain rates, while anomalous perpendicular orientation occurs at low deformation rates, with the smectic layers aligned with the stretching direction and the molecular axes almost perpendicular. A mixture of the two types of orientation is observed at intermediate rates, with rather interesting features.     

Electrocatalytic Properties of a Novel Poly‐1‐Naphthylamine‐Modified Electrode Using Ascorbic Acid as Molecule Probe

A glassy carbon electrode was modified with an electropolymerized film of 1‐naphthylamine in aqueous solution. The electrocatalytic properties of this modified electrode (ME) were investigated using ascorbic acid (AA) as probe molecule. The electrochemical behavior of AA in buffer solution was examined by voltammetry and amperometry. The results showed that the ME exhibited good electrocatalytic activity towards the oxidation of AA, as a consequence, it can be used as amperometric sensor of this analyte in a flow injection system with good sensitivity. Calibration curves were linear over the concentration range 0.05–1.50 mM with a phosphate buffer solution pH 3 as the carrier, the detection limit was 1 ppm (S/N=3). The methods were applied to the determination of AA in beverages and pharmaceutical products. A good correlation with a reference method was attained.     

Response surface methodology for the microwave-assisted extraction of insecticides from soil samples

The extraction of two pyrethroid insecticides (deltamethrin and α-cypermethrin) together with three organophosphorus insecticides (dimethoate, diazinon and malathion) from soil samples was carried out with microwave-assisted technology. Experimental designs showed that extraction temperature, addition of water to the extractant and solvent/soil ratio were the variables that affected the recoveries of the pesticide the most. Response surface methodology was applied to find the optimum values of the variables involved in the extractions of the analytes. In addition, in order to achieve near-optimal extraction conditions, a desirability function was used to optimize the five pesticides simultaneously. The optimized conditions were applied to different types of soils.     

Low-resolution 1H spin-spin relaxation of n-decane/water emulsions stabilized by beta-casein

A low-resolution ¹H NMR relaxometry study on the dynamics of an n-decane/water emulsion stabilized by β-casein is presented. Spin–spin (transverse) relaxation time constants (T₂) were used to assess relative mobilities of emulsion components, by a selective deuteration procedure. Data analysis allowed the emulsion investigated to be described by a heterogeneous collection of dynamically distinct populations. A major population of n-decane molecules presented an average mobility that very nearly approached that of pure solvent, which is compatible with its occurrence in the emulsion continuous microphase. β-Casein molecules displayed a prevalent population with significantly decreased mobility as compared to the free protein in solution, which is in accordance with the protein location at the oil/water interface. Also, a major H₂O population with significantly lower average T₂ as compared to the pure liquid was detected and has been assigned to interfacial water.