Large-area fibrous network of polyaniline formed on the surface of diatomite

Large-area fibrous network of polyaniline is obtained on the surface of diatomite by in situ polymerization of aniline without stirring. And it is characterized via Fourier-transform infrared spectroscopy, Raman spectroscopy, thermal analysis technology, four-probe technique and cyclic voltammetry, as well as specific surface, total pore volume, average pore size and pore size distribution. This composite contains 85% polyaniline, which conductivity is 5.08 S cm⁻¹ at 25 °C. It is more significant that its film electrode not only possesses good redox reversibility in the aqueous media ranging from pH 1.0 to 7.0, but also shows good electrochemical cycling stability in the aqueous media of pH 4.0. It will be a promising material for several applications due to increasing the operating pH window in the aqueous media and good conductivity.     

Wettability modification of pitch-based spherical activated carbon by air oxidation and its effects on phenol adsorption

The surface chemistry of pitch-based spherical activated carbon (PSAC) was modified by air oxidation to enhance its wettability as well as adsorption properties. Changes of PSAC after modification in texture, surface chemistry and wettability were studied by different techniques including N₂ adsorption, X-ray photoelectron spectroscopy (XPS) and dynamic contact angle analyzer (DCA). Phenol adsorption characteristics in different solvents on PSAC were also investigated. When PSAC was modified under an atmosphere with 20 vol.% oxygen at 400 and 450 °C for 5 h, surface acidic groups increased from 0.11 to 1.22 and 1.60 meq/g, while basic groups decreased from 0.52 to 0.03 and 0.02 meq/g, respectively. After PSAC was modified, the increase of the oxygen-containing groups, especially carboxylic and phenolic ones, is responsible for the increasing of the surface acidity and the significant improvement of the wettability of PSAC. PSAC with a relatively high oxygen content provided a low adsorption capacity to phenol in aqueous solution, and the adsorption isotherms change from Langmuir class (L) to the S-shaped curve; while the solvent is changed into cyclohexane, all adsorption isotherms are type L, and the adsorption capacity to phenol increases with increasing oxygen-containing groups. Possible reasons, including the solvent effect, π-π dispersion and donor-acceptor interactions are discussed.     

Surface modification and characterization of Jordanian kaolinite: Application for lead removal from aqueous solutions

Kaolinite clay was tested for removal of lead ions from aqueous solution. This clay was washed with sulfuric acid solution followed by chemical surface modification using 3-chloropropyltriethoxysilane and sodium hydroxide. XRF results showed that silica to alumina ratio was 2.8:1 for the treated sample compared to 1.6:1 for the raw one.XRD analysis displayed different distinct kaolinite and quartz peaks before treatment while kaolinite peaks were diminished after the treatment. SEM morphology indicated that the raw kaolinite appears as plate structure with no local pores on the plates. However, after treatment the surface was found to have micropores.Different adsorption isotherm models were applied to the experimental data and found that Shawabkeh-Tutunji equation best fit these data adequately. It was also found that chemisorption took place at the surface of the modified kaolinite with maximum adsorption capacity of 54.35 mg/g.     

The impact of carbon surface chemical composition on the adsorption of phenol determined at the real oxic and anoxic conditions

The results of phenol adsorption-desorption isotherms (at 310 K) measured on the series of activated carbons (D43/1, NORIT RO 0.8, D55/2) are presented. The effect of carbon surface chemical composition on phenol adsorption determined at real oxic and anoxic conditions is discussed. To obtain the real anoxic conditions the two station controlled atmosphere chamber with two catalyst heater units (Plas Labs, Lansing, MI, USA) was applied. It is shown that the adsorption under oxic conditions is always larger than that determined for anoxic ones for all studied carbons. The analysis of those differences shows that in the range of micropore filling they decrease with the equilibrium phenol mole fraction in solution. Contrary they increase after micropores being filled. The average differences between the adsorption properties are the linear function of the concentration of surface acidic groups (assigned from the Boehm's method as “carboxylic”) calculated per the apparent BET surface area of studied carbons.     

Studies on surface modification of poly(tetrafluoroethylene) film by remote and direct Ar plasma

Poly(tetrafluoroethylene) (PTFE) surfaces are modified with remote and direct Ar plasma, and the effects of the modification on the hydrophilicity of PTFE are investigated. The surface microstructures and compositions of the PTFE film were characterized with the goniometer, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Results show that the remote and direct plasma treatments modify the PTFE surface in morphology and composition, and both modifications cause surface oxidation of PTFE films, in the forming of some polar functional groups enhancing polymer wettability. When the remote and direct Ar plasma treats PTFE film, the contact angles decrease from the untreated 108-58° and 65.2°, respectively. The effect of the remote Ar plasma is more noticeable. The role of all kinds of active species, e.g. electrons, ions and free radicals involved in plasma surface modification is further evaluated. This shows that remote Ar plasma can restrain the ion and electron etching reaction and enhance radical reaction.     

Titania surface modification and photovoltaic characteristics with tungsten oxide

WO₃-coated TiO₂ film was prepared by depositing TiO₂ suspension containing small amounts of ammonium tungstate solution. The morphology and structure of the samples were characterized with high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and photoluminescence (PL) emission spectrum. The results showed that WO₃ formed a coating layer on surface of TiO₂ and significantly reduced the surface traps of TiO₂ nanoparticles. Transient photovoltage and electrochemical impedance measurements (EIS) were employed to study the charge separation/recombination process. The results revealed that the charge recombination was greatly retarded and the electron lifetime was increased due to the coating layer of WO₃. These observations showed good correlation with current-voltage analyses of dye-sensitized solar cell fabricated from these films, with WO₃ overlayer resulting in an increase in open-circuit voltage of up to 37 mV and 11% improvement in overall device efficiency.     

Studies on chelating adsorption properties of novel composite material polyethyleneimine/silica gel for heavy-metal ions

Firstly, the coordination processes of line-type polyethyleneimine with Cu²⁺, Cd²⁺ and Zn²⁺ were studied by using visible light absorption spectroscopy and chelation conductivity titration method, and the structures of the chelates were determined. Afterwards, polyethyleneimine (PEI) was grafted onto the surface of silica gel particles via the coupling effect of γ-chloropropyl trimethoxysilane (CP), and the novel composite adsorption material PEI/SiO₂ with strong adsorption ability towards heavy-metal ions was prepared. The chelating adsorption properties of PEI/SiO₂ for Cu²⁺, Cd²⁺ and Zn²⁺ were researched by both static (batch) and dynamic (flow) methods. The experiment results show that water-soluble polyamine PEI with line-type structure reacts with Cu²⁺, Cd²⁺ and Zn²⁺ easily and quantitatively, and water-soluble chelates with four ligands are formed. The composite material PEI/SiO₂ possesses very strong chelating adsorption ability for heavy-metal ions, and the saturated adsorption amount can reach 25.94 mg g⁻¹ and 50.01 mg g⁻¹ for Cu²⁺ under static and dynamic conditions, respectively. The isothermal adsorption data fit to Langmuir equation, and the adsorption is typical chemical adsorption with monomolecular layer. The adsorbing ability of PEI/SiO₂ towards the three kinds of the ions follows the order of Cu²⁺ > Cd²⁺ > Zn²⁺. The pH value has great influence on the sorption, and at pH 6-7, the adsorption capacity is the greatest. The fact that adsorption capacity increases with temperature rising indicates the adsorbing process of PEI/SiO₂ for metal ions is endothermic. As diluted hydrochloric acid is used as eluent, the adsorbed heavy-metal ions are eluted easily from PEI/SiO₂, and the regeneration and reuse without decreasing sorption for PEI/SiO₂ are demonstrated.     

Hydrogen peroxide treatment on Ti-6Al-4V alloy: A promising surface modification technique for orthopaedic application

Ti-6Al-4V alloy was treated with various concentrations (5 wt.%, 15 wt.% and 25 wt.%) of hydrogen peroxide (H₂O₂) and then heat treated to produce an anatase titania layer. The surface modified substrates were immersed in simulated body fluid (SBF) solution for the growth of an apatite layer on the surface and the formed apatite layer was characterized using various surface characterization techniques. The results revealed that titania layer with anatase nature was observed for all H₂O₂ treated Ti-6Al-4V alloy, irrespective of the H₂O₂ concentrations. Ti-6Al-4V alloy treated with 15 wt.% and 25 wt.% of H₂O₂ induced apatite formation, however 5 wt.% of H₂O₂ treated Ti-6Al-4V failed to form apatite layer on the surface. The electrochemical behaviour of H₂O₂ treated specimens in SBF solution was studied using potentiodynamic polarization and electrochemical impedance spectroscopy. Ti-6Al-4V alloy treated with 25 wt.% of H₂O₂ solution exhibited low current density and high charge transfer resistance values compared to specimens treated with other concentrations of H₂O₂ and untreated Ti-6Al-4V alloy.     

Surface modification of polyacrylonitrile-based carbon fiber and its interaction with imide

In this work, sized polyacrylonitrile (PAN)-based carbon fibers were chemically modified with nitric acid and maleic anhydride (MA) in order to improve the interaction between carbon fiber surface and polyimide matrix. Bismaleimide (BMI) was selected as a model compound of polyimide to react with modified carbon fiber. The surface characteristic changing after modification and surface reaction was investigated by element analysis (EA), scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and surface enhanced Raman scattering (SERS). The results indicated that the modification of carbon fiber surface with MA might follow the Diels Alder reaction mechanism. In the surface reaction between modified fibers and BMI, among the various surface functional groups, the hydroxyl group provided from phenolic hydroxyl group and bridged structure on carbon fiber may be the most effective group reacted with imide structure. The results may shed some light on the design of the appropriate surface structure, which could react with polyimide, and the manufacture of the carbon fiber-reinforced polyimide matrix composites.     

Corona-induced graft polymerization for surface modification of porous polyethersulfone membranes

Graft polymerization of acrylic acid (AA) onto porous polyethersulfone (PES) membrane surfaces was developed using corona discharge in atmospheric ambience as an activation process followed by polymerization of AA in aqueous solution. The effects of the corona parameters and graft polymerization conditions on grafting yield (GY) of AA were investigated. The grafting of AA on the PES membranes was confirmed by ATR-FTIR and X-ray photoelectron spectroscopy (XPS) analysis. Porosimetry measurements indicate the average pore diameters and porosities of the modified membranes decrease with the increase of the GY. The hydrophilicity and surface wetting properties of the original and modified membranes were evaluated by observing the dynamic changes of water contact angles. It is found that the grafting of AA occurs not only on the membrane surfaces, but also on the pore walls of the cells inside the membrane. The permeability experiments of protein solution reveal that the grafting of PAA endows the modified membranes with enhanced fluxes and anti-fouling properties. The optimized GY of AA is in the range of 150-200 μg/cm². In addition, the tensile experiments show the corona discharge treatment with the power lower than 150 W yields little damage to the mechanical strength of the membranes.     

The effects of hydrogen peroxide on the sonochemical degradation of phenol and bisphenol A

This report describes the effects of H₂O₂ concentration (0.01, 0.1, 1, and 10 mM) on the sonochemical degradation of phenol and bisphenol A (BPA) using an ultrasonic source of 35 kHz and 0.08 W/mL. The concentration of the target pollutants (phenol or BPA), total organic carbon (TOC), and H₂O₂ were monitored for each input concentration of H₂O₂. The effects of H₂O₂ on the sonochemical degradation of phenol was more significant than that of BPA because phenol has a high solubility and low octanol–water partition coefficient (K_ow) value and is subsequently very likely to remain in the aqueous phase, giving it a greater probability of reacting with H₂O₂. The removal of TOC was also enhanced by the addition of H₂O₂. Some intermediates of BPA have a high K_ow value and subsequently have a greater probability of pyrolyzing by the high temperatures and pressures inside of cavitation bubbles. Thus the removal efficiency of TOC in BPA was higher than that of phenol. The removal efficiencies of TOC were lower than the degradation efficiencies of phenol and BPA. This result is due to the fact that some intermediates cannot readily degrade during the sonochemical reaction. The H₂O₂ concentration decreased but was not completely consumed during the sonochemical degradation of pollutants. The initial H₂O₂ concentration and the physical/chemical characteristics of pollutants were considered to be important factors in determining the formation rate of the H₂O₂. When high concentration of H₂O₂ was added to the solution, the formation rates were relatively low compared to when low concentrations of H₂O₂ were used.     

Photoluminescence study of the surface modified and MEH-PPV coated cotton fibers

In this paper, we report a study on the photoluminescence properties of pure cotton fibers from chemically surface and morphology modified and coated with MEH-PPV polymer samples by dip-coating method. The treated and coated fibers surfaces were characterized using scanning electron microscopy (SEM), luminescence and FT-IR spectroscopy. The SEM photos showed that cotton fiber surface was covered by a layer of MEH-PPV with the thickness around 1 μm. The effects on the crystalline structure and photoluminescence (PL) were studied as a function of the alkali modification conditions. It was found that the blue light intensity of the mercerized and bleached specimen is approximately two orders higher than the scoured one. The performance of fibers with MEH-PPV polymer as a coating component was investigated and an excellent white-light emission which consists of blue-, green-, and red-light-emitting bands was demonstrated.     

Surface modification of the polyethyleneimine layer on silicone oxide film via UV radiation

We herein report a novel method of employing 254 nm of UV radiation (UV) for the modification of a polyethyleneimine (PEI) layer on silicone oxide film. In this study, a PEI layer composed of a 50 mM sodium carbonate solution (pH 8.2) was formed on the surface of a silicone oxide film with spontaneous adsorption. Then, thin film of PEI was patterned by UV radiation. To determine the effect of the UV radiation, fluorescence microscopy, X-ray electron spectroscopy (XPS), and Fourier Transform Infrared spectroscopy (FT-IR) analyses were performed. These results indicated that UV radiation could cause changes in the surface characteristics of the PEI layer. Subsequently, FT-IR analysis showed changes in the chemical composition of the PEI exposed to UV radiation, such as the disappearance of the amine. Based on these results, we can conclude that UV radiation could be used to eliminate the amine group selectively and that this technique could be applied to create a pattern on the surface of a PEI layer.     

Vacuum ultraviolet-induced surface modification of cyclo-olefin polymer substrates for photochemical activation bonding

The surface of cyclo-olefin polymer (COP) was treated with vacuum ultraviolet (VUV) light at 172 nm wavelength to improve the wettability and adhesion properties. Through VUV treatment in air, the terminal groups of the COP surface were oxidized into oxygen functional groups, containing CO, CO, and COO components, making the COP surface hydrophilic. The extent of oxygenation was evaluated by XPS and FTIR-ATR spectra, and it was shown that the surface properties, hydrophilicity, and functionalization were dependent on both VUV irradiation distance and irradiation time, which have an effect on the concentration of oxygen functional groups. VUV-light treatment with a short irradiation distance was more effective in introducing oxygen functional groups.     

Polymer surface modification and characterization of particulate calcium carbonate fillers

The efficacy of the surface treatment of particulate fillers depends on the chemical character of the components, on the method and conditions of the treatment, and on the amount of the treating agent. Here, the ultra-fine calcium carbonate is surface treated with 1, 2, 3 and 4 wt.% polyacrylic acid (PAA) synthesized by ourselves, which has strong ionic interaction and is an efficient surface modifier. The PAA coated filler is submitted to the measurement of the surface bonded amount, bonding efficacy, X-ray photoelectron spectroscopy (XPS) and inverse gas chromatography. Maximum efficacy is expected at the monolayer coverage of the surface, which is about 0.6 wt.% according to the calculation based on the way they are aligned and is basically in agreement with the “substrate overlayer” model based on the mole ratio of C²⁸⁶ and C²⁹⁰ taking no account of the possible underestimation because of the inaccuracy or because of the CH_x contamination present originally on the CaCO₃. The initial decrease of the mole ratio of C²⁹⁰/O and C²⁹⁰/Ca with the surface bonded PAA may indicate that the bonding interaction between the polymer and the filler surface is the leaving of one molecular carbon dioxide. The IGC measurement shows that there is a considerable surface tension falling in the case of the PAA modified filler compared with the reference. An abnormal high surface energy in the case of filler treated with 4% PAA is observed.     

Electroless deposition of silver on synthesized calcite via surface modification

Metallic silver was deposited on the surface of synthesized calcite via a simple electroless deposition method. Calcite with cubic morphology was prepared first by homogeneous precipitation and it was subsequently surface modified using ammonium oxalate. The electroless deposition was carried out using formaldehyde as the reducing agent and silver nitrate as the silver source. Both calcite and the silver deposited calcite were characterized by different techniques. Surface modification of calcite with ammonium oxalate is necessary for the deposition of silver and the size of the deposited silver particles could be controlled by changing the deposition parameters such as concentration of the reagents and the deposition time. Lower concentration of silver ions (e.g. 0.01 M AgNO₃) and shorter deposition times (e.g. 30 min) lead to the formation of silver nanoparticles on calcite.     

Micro double tapered optical fiber sensors based on the evanescent field-effect and surface modification

A double tapered optical fiber sensor based on evanescent field-effect and surface modification technology was introduced in this work. Whether the liquid and gas molecules had polarities or not, they all could be detected by the sensors modified in different silane coupling agents. At the same time, the sensing characters of the single mode optical fiber with three different tapering lengths were researched, and it came to a conclusion that the optical fiber sensor had stronger evanescent field effect and higher sensitivity when length of tapered fiber was 30 mm. The functionalized tapered fibers modified by 3-aminopropyltrimethoxy silane (APTES) or 3-methylpropenylacyloxy propyltrimethoxy silane (MPAPTES), were employed to detect the polar or nonpolar molecules which had corresponding features. Further, the results of quantitative tests showed that the fiber optic sensor was sensitive to the change of the ethanol concentration and the characteristic peaks of the absorption power spectra could reach to 3–5 dB.     

Ultrasonically assisted surface modified CeO2 nanospindle catalysts for conversion of CO2 and methanol to DMC

This study developed a facile and effective approach to engineer the surface properties of cerium oxide (CeO₂) nanospindle catalysts for the direct synthesis of dimethyl carbonate (DMC) from CO₂ and methanol. CeO₂ nanospindles were first prepared by a simple precipitation method followed by wet chemical redox etching with sodium borohydride (NaBH₄) under high intensity ultrasonication (ultrasonic horn, 20 kHz, 150 W/cm²). The ultrasonically assisted surface modification of the CeO₂ nanospindles in NaBH₄ led to particle collisions and surface reduction that resulted in an increase in the number of surface-active sites of exposed Ce³⁺ and oxygen vacancies. The surface modified CeO₂ nanospindles showed an improvement of catalytic activity for DMC formation, yielding 17.90 mmol·g_cat⁻¹ with 100 % DMC selectivity. This study offers a simple and effective method to modify a CeO₂ surface, and it can further be applied for other chemical activities.     

Fabrication of hydrophobic alumina aerogel monoliths by surface modification and ambient pressure drying

Hydrophobic crack-free alumina aerogel monoliths were fabricated by -Si(CH₃)₃ (trimethylsilyl substituent) modification of alcogels followed by an ambient pressure drying procedure. One-step solvent exchange and surface modification were simultaneously progressed by immersing alumina alcogels in trimethylmethoxysilane (TMMOS)/hexane solution. It is found that the hydrophobic property of alumina aerogels is affected by the contents of TMMOS from the measurements of contact angle and Fourier transform infrared spectrometry. Thermogravimetry/differential scanning calorimetry analyses reveal that the modified aerogels maintain their hydrophobic behavior up to a temperature of 260 °C. The structure and morphology of the obtained hydrophobic alumina aerogels were characterized by the measurements of N₂ physical adsorption and scanning electron microscopy, which showed that they were highly porous materials with narrow slit-like pore geometry and a high degree of pore size uniformity.     

Introduction of amino groups on the surface of thin photo definable epoxy resin layers via chemical modification

The introduction of amine groups on the surface of dielectric resins improves the adhesion with electrochemically deposited metals. In this work, etched epoxy resin surfaces are modified with aliphatic amines via a two step wet chemical reaction approach. First, cyanuric chloride is introduced on the surface. Next, the remaining reactive sites of cyanuric chloride are used to couple an aliphatic polyamine. Both reaction steps are optimized by variation of reaction parameters such as concentration, chemicals, temperature and time. A detailed surface characterization after each reaction step is provided using following techniques: ATR-IR, SEM-EDS, XPS and AFM.