Facile functionalization by π-stacking of macroscopic substrates made of vertically aligned carbon nanotubes: Tracing reactive groups by electrochemiluminescence

We report a simple, fast and reliable non-covalent route of functionalization of macroscopic carbon nanotubes (CNTs) surfaces based on the π-stacking of CNTs sidewall with fluorescein derivatives (i.e., amino- and isothiocyanate-). The electrochemiluminescent emission of Ru(bpy)₃²⁺ labels bearing –COOH and –NH₂ side groups coupled with colorimetric and XPS measurements allowed to estimate the quantity of –NH₂ and –NCS functions obtained. The evaluation of reactivity suggests that functionalized CNTs substrates, in particular those carrying –NCS groups, are suitable to covalently bind probe molecules such as proteins and oligonucleotides, thus opening up the possibility of future application in genomics and proteomics fields.     

Mn(II), Co(II) and Ni(II) complexes of 4-(2-thiazolylazo)resorcinol: Syntheses, characterization, catalase-like activity, thermal and electrochemical behaviour

Manganese(II), cobalt(II) and nickel(II) acetates react with the ligand, 4-(2-thiazolylazo)resorcinol, to form complexes of general formula [ML₂] for MCo(II), Ni(II) and [ML₂]·2H₂O for MMn(II). Each of the azo complexes was characterized using elemental analysis, electrolytic conductance, UV–visible spectroscopy and magnetic susceptibility. An octahedral structure is proposed for all complexes prepared, which molar conductance data revealed to be non-electrolytes. IR spectra reveal that the ligand is coordinated to the metal ions in a tridentate manner via the resorcinol OH, azo N and thiazole N groups as donor sites. The electrochemical behaviour of the ligand and its complexes were obtained by cyclic voltammetry. Thermal decomposition studies were undertaken to secure additional information on the structure of the investigated compounds. The manganese(II) complex catalysed the disproportionation of hydrogen peroxide in the presence of imidazole.     

Adsorption mechanism and property of novel composite material PMAA/SiO2 towards phenol

In this paper, functional macromolecule poly(methacrylic acid) (PMAA) was grafted on the surface of silica gel particles using 3-methacryloxypropyl trimethoxysilane (MPS) as intermedia, and the grafted particle PMAA/SiO₂ with strong adsorption ability for phenol was prepared. The adsorption mechanism and properties of PMAA/SiO₂ for phenol were researched by static and dynamic methods. The experimental results showed that PMAA/SiO₂ possesses strong adsorption ability for phenol with interaction of three kinds of hydrogen bonds including peculiar O–Hπ hydrogen bond (aromatic hydrogen bond) and O–HOC π hydrogen bond. The saturated adsorption amount could reach up to 162.88 mg g⁻¹. The empirical Freundlich isotherm was found to describe well the equilibrium adsorption data. pH and temperature were found to have great influence on the adsorption amount. Finally, PMAA/SiO₂ was observed to possess excellent reusability properties as well.     

Structure and performance of a novel TiO2-phosphonate composite photocatalyst

An innovative SiO₂-PO₄³⁻-TiO₂ photocatalyst is presented which is able to bond TiO₂ to Raschig rings (RR). Evidence for the formation on the catalyst surface of PO stretching bands near 1200–1250 cm⁻¹ is presented by FTIR spectroscopy. The TiO₂ Degussa P25 on the catalyst surface (RR) was further characterized by high-resolution transmission electron microscopy (HRTEM), and X-ray diffraction showing that the composite catalyst prepared at 500 °C does not alter the particle size or crystallographic composition of the TiO₂ Degussa P25 particles. The Ti- and P-distribution of the catalyst surface overlayers was obtained by Ar-sputtering eroding up to 100 topmost catalyst layers. By atomic force microscopy (AFM) the root mean square roughness (Rq) or rugosity of 771 nm and an average height of the catalyst layer of 1.52 μm were found on the glass surface. The root mean square roughness Rq varies very little in value before and after the photocatalysis indicating that the sample porosity is conserved during 4-CP photodegradation. The disappearance kinetics of 4-chlorophenol (4-CP) on the SiO₂-PO₄³⁻-TiO₂ composite occurred within 15 min and was faster than the 45 min needed with suspensions of TiO₂ Degussa P25 (1 g L⁻¹). The SiO₂-PO₄³⁻-TiO₂ photocatalyst was able to degrade repetitively 4-CP solutions without loss of activity. The effect of the light intensity, oxidant concentration and 4-CP concentration on the photodegradation kinetics was investigated and is reported in this study.     

Comparison of the chemical composition of boron-doped diamond surfaces upon different oxidation processes

In spite of the high stability of polycrystalline diamond, oxidation of the hydrogenated surface is relatively easy to perform. This results in the introduction of ether (C–O–C), carbonyl (CO) and hydroxyl (C–OH) groups on the surface. For further surface functionalization, it is important to quantify the presence of each group on the diamond surface when different oxidation processes are used. In this paper, we investigate the composition of oxidized boron-doped diamond surfaces using X-ray photoelectron spectroscopy (XPS) when electrochemical, photochemical or oxygen plasma methods were employed to introduce oxygen functionalities on as-deposited diamond interfaces. Cyclic voltammetry and C–V measurements were additionally performed to identify more clearly the formation of C–OH, C–O–C and/or CO functions.     

Modification of electrodes with nanostructured functionalized thiadiazole polymer film and its application to the determination of ascorbic acid

We report the electropolymerization of 2-amino-1,3,4-thiadiazole (ATD) on glassy carbon (GC) and indium tin oxide (ITO) electrodes in 0.10 M H₂SO₄. The electropolymerized ATD (p-ATD) film was characterized by cyclic voltammetry, attenuated total reflectance (ATR)-FT-IR spectroscopy, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The AFM image showed that the p-ATD formed a spherical-like structure with a thickness of 25 nm. XPS of the p-ATD film showed binding energies at 398.7, 400.3 and 401.3 eV in the N 1s region corresponding to –N, –NH– and –N⁺H–, respectively, and at 285.5 and 287.0 eV in the C 1s region corresponding to C–N and CN, respectively. The appearance of binding energies at 285.5 and 287.0 eV confirmed that the p-ATD film proceeded via C–N and CN linkages and not via C–C or CC linkages. The p-ATD film deposited on the GC electrode was successfully used for the determination of ascorbic acid (AA) at physiological pH. The amperometric current was increased linearly from 7.5 × 10⁻⁸ to 2.0 × 10⁻⁵, and the detection limit was found to be 0.28 nM (S/N = 3).     

Effect of hydrophilic group on thin film formation using redox-active surfactants with an azobenzene group

Thin films of organic pigments were prepared at higher than pH 1 by the contact plating method using an anionic surfactant (AZNa, first figure of this article (part c) (n = 4)) containing an azobenzene moiety. The effects of hydrophilic group of the surfactants on the rate of following reaction of the reduction product were studied by cyclic voltammetry. The positive shift of the reduction peak potential of AZNa compared to those of cationic and non-ionic surfactants was ascribed to higher rate of following reaction of reduction product due to the presence of the anionic hydrophilic group of the surfactant. The present investigation revealed that the anionic hydrophilic group accelerates the cleavage of the NN bond of the azobenzene group. This phenomenon enabled us to prepare the organic thin film at higher pH condition.     

Optimisation of SFE method on-line coupled to FT-IR spectroscopy for the real-time monitoring of the extraction of tagitinin C in T. diversifolia

The monitoring in real time of dynamic extractions of tagitinin C from Tithonia diversifolia leaves was carried out with a home made high-pressure fiber optic cell which coupled a supercritical fluid extractor with carbon dioxide as the extraction medium and a FT-IR spectrometer equipped with a mercury cadmium telluride detector (MCT). The shape of extraction curves obtained during the monitoring was used to decide when to stop the supercritical fluid extraction (SFE).No significant density dependence of the molar absorption coefficient or wavenumber of the CO stretching vibration (ν_CO) of tagitinin C at 1668 cm⁻¹ was noticed.The physical characteristics of SCCO₂ governing the extraction yield of the active component from leaves were optimized by means of a central composite design (CCD). The studied variables were temperature (40, 60 and 80 °C) and pressure (8.0, 14.0 and 20.0 MPa) of the supercritical fluid.The composition profile of T. diversifolia extracts obtained by SFE was investigated in the range from 3400 to 2600 cm⁻¹ according to the pressure and temperature conditions of SCCO₂. The qualitative approach of the extracts composition was accomplished through the CH stretching vibrations (ν_CH) of components.     

Syntheses, characterization and biological activity of diorganotin(IV) derivatives of 2-amino-6-hydroxypurine (guanine)

Novel organotin(IV) derivatives of guanine of the general formula, R₂Sn(HGu)₂ (where, R = Me (1), n-Bu (2) and Ph (3)) have been synthesized by the reaction of R₂SnCl₂ with sodium salt of guanine (H₂Gu or 2-amino-6-hydroxypurine). The IR spectral studies suggest that guanine acts as a monobasic ligand coordinating through N(9) after its deprotonation. The weak bonding through C(6)O may also be evidenced, whereas ¹¹⁹Sn Mössbauer data suggest that the coordination number of tin is superior than four. The polyhedron around tin in R₂Sn(HGu)₂ is distorted trigonal–bipyramidal or pseudo-tetrahedral involving very weak interaction from CO group of neighboring molecule leading to polymerized structure. All the compounds exhibited potent anti-inflammatory activity with no appreciable side effects on blood pressure as evidenced by their very mild cardiovascular activity.     

The effect of crystallographic orientation and solution aging on the electrical properties of sol–gel derived Pb(Zr0.45Ti0.55)O3 thin films

Lead zirconate titanate—Pb(Zr_0.45Ti_0.55)O₃ thin films are grown on Pt_1 1 1/Ti/SiO₂/Si_1 0 0 substrates by a sol–gel method with 1 0 0/0 0 1 and 1 1 1 preferred orientations. Film orientation was controlled mainly by the annealing process and temperature. Films with 1 0 0/0 0 1 orientation consist of a uniform microstructure with micron size grains, whereas films with 1 1 1 orientation contain sub-micron grains. The electrical properties were influenced markedly by the microstructure and orientation of the films. The 1 1 1 oriented films exhibit a square-like hysteresis loop with remnant polarization (P_r) reaching 46 μC/cm² under 550 kV/cm, whereas 1 0 0/0 0 1 oriented films have a P_r of 20 μC/cm² with more slim hysteresis curves. Aging of the precursor solutions resulted in films growing with 1 0 0/0 0 1 texture and displaying inferior electrical properties.     

Ionic liquid effects on the reaction of β-enaminones and tert-butylhydrazine and applications for the synthesis of pyrazoles

In order to evaluate the effect of a series of 10 different ionic liquids ([BMIM][BF₄], [BMIM][Br], [OMIM][BF₄], [BMIM][PF₆], [DBMIM][Br], [DBMIM][BF₄], [BMIM][OH], [BMIM][SCN], [HMIM][HSO₄] and [HMIM][CF₃CO₂]) the cyclocondensation reaction between 4-dimethylamino-1-phenyl-3-alken-2-ones (RC(O)CHCHNMe₂, where R = Ph, 4-Me-Ph, 4-F-Ph, 4-Cl-Ph, 4-Br-Ph, 4-NO₂-Ph, thien-2-yl, fur-2-yl, pyrrol-2-yl, pyrid-2-yl, hexyl, dimethoxymethyl) and tert-butylhydrazine was performed. The effects of each ionic liquid are discussed and the best yields for the cyclocondensation reaction studied were obtained using [BMIM][BF₄].     

Cyclometalated platinum(II) complex with C^N^N tridentate ligand as sensitizer for lanthanide luminescence

The preparation, characterization and photophysical properties of heterobinuclear complexes {Pt(C^N^N)(CCbpy)}Ln(hfac)₃ (C^N^N = 2-(6-(naphthalen-3-yl)-4-phenylpyridin-2-yl)pyridine; HCCbpy = 5-ethynyl-2,2′-bipyridine; Ln = Nd, Eu, Yb; hfac = hexafluoroacetylacetonate) are described. With excitation at 390  λ_ex  500 nm which is the MLCT/LLCT absorption region of the Pt(C^N^N)(CCbpy) chromophore, lanthanide luminescence is successfully attained by Pt → Ln energy transfer from the platinum(II) antenna chromophore to the lanthanide center across the bridging CCbpy ligand.     

UV- and thermal-curing behaviors of dual-curable adhesives based on epoxy acrylate oligomers

Dual-curable adhesives were prepared using various epoxy acrylate oligomers, a reactive diluent, photoinitiators, a thermal-curing agent and a filler. The UV- and thermal-curing behaviors of the dual-curable adhesives were investigated using photo-differential scanning calorimetry (photo-DSC), Fourier transform infrared-attenuated total reflection (FTIR-ATR) spectroscopy, and the determination of the gel fraction, pendulum hardness and adhesion strength.The reaction rate and extent of UV curing were found to be strongly dependent on the concentration of CC bonds in the epoxy acrylate oligomers. The FTIR-ATR absorption peak areas representing the relative concentration of CC bonds in the epoxy acrylate oligomers and trifunctional monomer decreased with increase in UV dose because of photopolymerization. When the dual-curable adhesives were irradiated with UV light, the gel fraction increased with increase in CC bond contents in the epoxy acrylate oligomers. Also, after thermal curing, the gel fraction was highly enhanced due to the cross-linking reaction of the unreacted glycidyl groups in epoxy acrylate oligomers induced by the thermal-curing agent. This cross-linked structure of the dual-curable adhesives affects the pendulum hardness and adhesion strength.     

Effects of sodium promoter on the mechanism of biphenol hydrogenation over Pd/C catalyst

The effect of sodium promoter on the catalytic hydrogenation of biphenol (BP) was investigated. Several reaction products were identified and the change in their distribution with time was analyzed to find the reaction mechanism. Different amount of sodium salt was impregnated on Pd/C to observe its effect on the composing reactions of BP hydrogenation. The existence of sodium metal decreased the CC bond hydrogenation, but accelerated the CO bond hydrogenation resulting in the increase of the yield to bicyclohexyl-4,4′-diol (BHD). The promotional effect of Na on the supported palladium on carbon catalysts were explained by electronic and geometric factors.     

Zeolite-encapsulated Ru(III) tetrahydro-Schiff base complex: An efficient heterogeneous catalyst for the hydrogenation of benzene under mild conditions

A series of Ru(III) tetrahydro-Schiff base complexes (denoted as Ru[H₄]-Schiff base with Schiff base = salen, salpn and salcn, see Scheme 1) were encapsulated in the supercages of zeolite Y by flexible ligand method. The prepared catalysts were characterized by X-ray diffraction, diffuse reflectance UV–Vis spectroscopy, Infrared spectroscopy, elemental analysis, as well as N₂ adsorption techniques. It was shown that upon encapsulation in zeolite Y, Ru(III) tetrahydro-Schiff base complexes exhibited higher activity for the hydrogenation of benzene than the corresponding Ru(III)-Schiff base complexes. This indicates that hydrogenation of the CN bond of the Schiff base ligands led to a modification of the coordination environment of the central Ru(III) cations. The stability of the prepared catalysts has also been confirmed against leaching of the complex molecule from the zeolite cavities, as revealed by the result that no loss of catalytic activity was observed within three successive runs with regeneration.     

Adsorption and oxidation of NH3 over V2O5/AC surface

V₂O₅/AC has been reported to be active for selective catalytic reduction (SCR) of NO with NH₃ at around 200 °C and resistant to SO₂ deactivation. To elucidate its SCR mechanism, adsorption and oxidation of NH₃ over V₂O₅/AC are studied in this paper using TG, MS and DRIFTS techniques. It is found that the adsorption and oxidation of NH₃ take place mainly at VO bond of V₂O₅. A higher V₂O₅ loading results in more NH₃ adsorption on the catalyst. V₂O₅ contains both Brnsted and Lewis acid sites; NH₄⁺ on Brnsted acid sites is less stable and easier to be oxidized than NH₃ on Lewis acid sites. Gaseous O₂ promotes interaction of NH₃ with AC and oxidation of NH₃ over V₂O₅/AC. NH₃ is oxidized into NH₂ and acylamide structures and then to isocyanate species, which is an intermediate for N₂ formation.     

The functionalized ionic liquid-stabilized palladium nanoparticles catalyzed selective hydrogenation in ionic liquid

The functionalized ionic liquid (2,3-dimethyl-1-[3-N,N-bis(2-pyridyl)-propylamido] imidazolium hexafluorophosphate, [BMMDPA][PF₆]) stabilized and modified palladium nanoparticles were obtained by reducing palladium(II) complex with molecular hydrogen. The as-synthesized palladium nanoparticles have been characterized by different methods. It was demonstrated that the Pd nanoparticles were very efficient catalysts for the selective hydrogenation of the CC bonds of various functionalized alkenes under mild conditions in neat ionic liquid (1-n-butyl-2,3-dimethylimidazolium hexafluorophosphate, [BMMIM][PF₆]). An efficient separation of the products from reaction mixture (ionic liquid phase) was realized and the catalyst’s nano-dispersion and high performance could be preserved.     

Analysis of the formation of Ta2O5 passive films in acid media through mechanistic modeling

Electrochemical impedance spectroscopy (EIS) analyses are carried out to evaluate the passive features of tantalum oxide films (Ta₂O₅) formed at different potentiostatic conditions (0.5, 1.0, 1.5 and 2.0 V vs SSE). A supporting electrolyte of 0.1 M H₂SO₄ (pH 1) has been used to emulate acidic corrosive conditions for the growth of films with an n-type electronic character. A modification of the point defect model (PDM) accounting for the formation of molecular hydrogen (blistering damage) is used to fit the experimental EIS diagrams, and obtain the kinetic parameters that best describe the semiconductive behavior of the passive films. After this analysis, diffusivities in the order of 5.37 ± 1.6 × 10⁻¹⁷ and 1.98 ± 1.4 × 10⁻²⁰ cm² s⁻¹ were obtained for the oxygen (DVO) and hydroxyl vacancies (DVOH), respectively. These findings show the capabilities of the EIS and the physicochemical modeling to account for the formation of valve-metal oxide films on a different range of conditions.     

Photocatalytic reduction of graphene oxides hybridized by ZnO nanoparticles in ethanol

Graphene oxide platelets synthesized by using a chemical exfoliation method were dispersed in a suspension of ZnO nanoparticles to fabricate ZnO/graphene oxide composite. Formation of graphene oxide platelets (with average thickness of ∼0.8 nm) hybridized by ZnO nanoparticles (with average diameter of ∼20 nm) was investigated. The 2D band in Raman spectrum confirmed formation of single-layer graphene oxides. The gradual photocatalytic reduction of the graphene oxide sheets in the ZnO/graphene oxide suspension of ethanol was studied by using X-ray photoelectron spectroscopy for different ultra violet (UV)–visible irradiation times. After 2 h irradiation, the relative concentration of the C–OH, CO and OC–OH bonds showed nearly 80% reduction relative to the corresponding concentrations before irradiation. The chemical reduction was accompanied by variations in the optical absorption of the ZnO/graphene (oxide) suspension, as its color changed from light brown to black. The current–voltage measurement showed that electrical sheets resistance of the ZnO/graphene oxide sheets decreased by increasing the irradiation time. Therefore, the ZnO nanoparticles in the ZnO/graphene oxide composite could be applied in gradual chemical reduction and consequently tuning the electrical conductivity of the graphene oxide platelets by variation of UV irradiation time in a photocatalytic process.     

Mechanism of heterogeneous catalytic ozonation of nitrobenzene in aqueous solution with modified ceramic honeycomb

The degradation efficiencies of nitrobenzene in aqueous solution were investigated by semi-continuous experiments in the processes of ozone alone, ozone/ceramic honeycomb (CH) and ozone/modified ceramic honeycomb (MCH). MCH with 1.0% Mn and 0.5% Cu had more pronounced catalytic ability than CH to accelerate the degradation of nitrobenzene, to increase the utilization efficiency of ozone, to improve the concentrations of hydrogen peroxide (H₂O₂) formation and hydroxyl radical (OH) initiation, and to enhance the removal efficiency of TOC. The modification process of CH with the metals enhanced the density of surface hydroxyl groups, which determines the initiation of OH from ozone decomposition and the generation of intermediate species on heterogeneous catalytic surface, yielding the acceleration of the degradation of nitrobenzene in aqueous solution. Possible reaction mechanism of ozone with heterogeneous catalytic surface in aqueous solution was proposed, and the formation mechanism of H₂O₂ and OH was also discussed according to the combined reactions in heterogeneous and homogeneous catalytic systems.