Introduction Of Oxygen-containing Functional Groups Research Articles

Photochemical modification of DLC films with oxygen functionalities and their chemical structure control

The photoreaction of diamond-like carbon (DLC) films in the presence of hydrogen peroxide leads to the covalent modification of their surface through the introduction of oxygen-containing functional groups, as confirmed by X-ray photoelectron, infrared and Raman spectroscopies. The DLC films modified with oxygen moieties showed high hydrophilicity, evaluated by their contact angle with water, compared with a pristine DLC film, and good tribological properties from the initial stage in water. The chemical structure of oxygen-terminated DLC films was also controlled by reduction of the oxygen moieties using hydride agents.

Carbon nanofiber supports for the preparation of Pt-based metal nanoparticles with high tolerance to sintering

Fishbone-typed carbon nanofibers (CNFs) that were formed by methane decomposition over silica-supported Ni catalysts were used as catalytic supports for Pt or Pt–Co alloy nanoparticles. The treatment of CNFs with concentrated HNO3 led to the formation of porous structures as well as to the introduction of oxygen-containing functional groups. Pt metal particles of a few nanometers in diameter could be stabilized on the CNFs treated with HNO3 and showed a high tolerance to sintering at high temperatures, whereas Pt metal particles supported on the CNFs without any treatment were seriously aggregated at high temperatures. The porous structures and functional groups in the CNFs worked as anchoring sites for Pt metal nanoparticles. Thus, Pt–Co alloy particles of a few nanometers in diameter could be prepared by using the CNF support since the CNFs inhibited the sintering of the alloy particles during the treatment at high temperatures to allow for alloy formation.

Multiwalled carbon nanotubes as adsorbents for removal of herbicide diuron from aqueous solution

The adsorption of diuron onto as-prepared and oxidized multiwalled carbon nanotubes (MWCNTs) from aqueous solution has been studied through batch experiments, in which the effect of contact time, temperature, pH and coexisting Cu2+ were investigated. The adsorption performance of diuron onto MWCNTs fitted the pseudo-second-order model and apparent equilibrium was reached within 1h. The experimental data showed good correlation with Freundlich, Langmuir and Polanyi–Manes models in the range of experimental concentrations, but followed Polanyi–Manes model most appropriate. The calculated thermodynamic parameters showed adsorption of diuron onto MWCNTs was exothermic and spontaneous. Except for the introduction of oxygen-containing functional groups onto the surfaces of MWCNTs, the oxidized treatment of as-prepared MWCNTs can also increase the surface area and the pore volume, which resulted in the increase adsorption of diuron in this study. The adsorption of diuron was found to be pH dependent, and more adsorption was observed under neutral and basic conditions. The presence of Cu2+ has no significant effect on the adsorption of diuron onto as-prepared MWCNTs, on the contrary, the presence of Cu2+ can greatly decrease the adsorption of diuron onto oxidized MWCNTs. In addition, competitive adsorption was greater at higher than at lower diuron concentrations.

The potential of electron beam radiation for simultaneous surface modification and bioresorption control of PLLA

Bioresorbable polymers have been widely investigated as materials exhibiting significant potential for successful application in the fields of tissue engineering and drug delivery. Further to the ability to control degradation, surface engineering of polymers has been highlighted as a key method central to their development. Previous work has demonstrated the ability of electron beam (e-beam) technology to control the degradation profiles and bioresorption of a number of commercially relevant bioresorbable polymers (poly-l-lactic acid (PLLA), L-lactide/DL-lactide co-polymer (PLDL) and poly(lactic-co-glycolic acid (PLGA)). This work investigates the further potential of e-beam technology to impart added biofunctionality through the manipulation of polymer (PLLA) surface properties. PLLA samples were subjected to e-beam treatments in air, with varying beam energies and doses. Surface characterization was then performed using contact angle analysis, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and atomic force microscopy. Results demonstrated a significant increase in surface wettability post e-beam treatment. In correlation with this, XPS data showed the introduction of oxygen-containing functional groups to the surface of PLLA. Raman spectroscopy indicated chain scission in the near surface region of PLLA (as predicted). However, e-beam effects on surface properties were not shown to be dependent on beam energy or dose. E-beam irradiation did not seem to affect the surface roughness of PLLA as a direct consequence of the treatment.

Adsorption of Lead(II) on O2-Plasma-Oxidized Multiwalled Carbon Nanotubes: Thermodynamics, Kinetics, and Desorption

O(2)-plasma-oxidized multiwalled carbon nanotubes (po-MWCNTs) have been used as an adsorbent for adsorption of lead(II) in water. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and Raman spectroscopy measurements show that the bulk properties of MWCNTs were not changed after O(2)-plasma oxidation. The adsorption capacity of MWCNTs for lead(II) was greatly enhanced after plasma oxidation mainly because of the introduction of oxygen-containing functional groups onto the surface of MWCNTs. The removal of lead(II) by po-MWCNTs occurs rather quickly, and the adsorption kinetics can be well described by the pseudo-second-order model. The adsorption isotherm of lead(II) onto MWCNTs fits the Langmuir isotherm model. The adsorption of lead(II) onto MWCNTs is strongly dependent upon the pH values. X-ray photoelectron spectroscopy analysis shows that the adsorption mechanism is mainly due to the chemical interaction between lead(II) and the surface functional groups of po-MWCNTs. The thermodynamic parameters (ΔH°, ΔS°, and ΔG°) calculated from the adsorption isotherms suggest that the adsorption of lead(II) onto MWCNTs is endothermic and spontaneous. The regeneration performance shows that lead(II) can be easily regenerated from po-MWCNTs by altering the pH values of the solution.

Effects of corona discharge on the surface structure, morphology and properties of multi-walled carbon nanotubes

Multi-walled carbon nanotubes (MWCNTs) were modified by corona discharge and then heat treated in the air. The influences of corona discharge parameters such as treatment time and processing power were investigated. The results of energy dispersive X-ray analysis (EDX) and thermogravimetric analysis (TGA) indicated the introduction of oxygen-containing functional groups onto the surface of the MWCNTs after heat treatment. The water contact angle tests showed that the hydrophobicity of the MWCNTs was decreased to some extent. The static water contact angle was reduced from 146° to 122° when the time of the corona discharge treatment reached 3 min at the processing power of 200 W. The enhanced thermomechanical and mechanical properties of epoxy nanocomposites filled with the corona discharge treated MWCNTs were observed. The modified MWCNTs conferred better properties on the composites than the pristine MWCNTs because of the improved dispersion of MWCNTs in matrix and the enhanced interfacial interaction between the treated MWCNTs and epoxy.

Study of Cherry Stones as a Precursor in the Preparation of Low Cost Carbonaceous Adsorbent

A cherry stone-based activated carbon was electrochemically and chemically oxidized to enhance its adsorbent property for comparison with as-produced. The samples obtained were characterized by Boehm's titration, pH titration, zeta potential measurement, FT-IR, Brunauer–Emmet–Teller surface area, and pore size distribution. A significant increase in the concentration of surface functional groups was obtained from the oxidation of the samples due to the introduction of oxygen-containing functional groups, as confirmed by Boehm's titration, FT-IR, PZC, and IEP analyses. Activation methods significantly improved the amount of oxygen-containing surface functional groups that make the carbonaceous adsorbents more hydrophilic and acidic, decreasing the pH of their point of zero charge, and increasing their surface charge density. The activated carbon samples obtained were predominantly microporous, and their pore volumes decreased as a function of activation period and temperature. The surface chemistry development of carbons was correlated to increasing removal ability of heavy metals.

Polypropylene surface modification model in atmospheric pressure dielectric barrier discharge

To optimize the effects of some discharge parameters on the surface wettability of polypropylene (PP) in atmospheric pressure dielectric barrier discharge, a surface modification model is created based on statistical theory and orthogonal experimental design method. Contact angle measurements, atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) are used to study the changes in the surface wettability, surface topology and chemical compositions of the samples. The results show that surface wettability has been improved due to roughness increasing and the introduction of oxygen-containing functional groups. High-resolution XPS of C1s peak deconvolution indicates that the types and contents of oxidized functional groups are different in different discharge conditions or plasma energy. Moreover, the model analysis reveals that it has better predictive ability, and different discharge parameters has selective influence on water contact angle and surface O atom percentage.

Effects of Support Surface Chemistry in Hydrodeoxygenation Reactions over CoMo/Activated Carbon Sulfided Catalysts

The influence of the nature of the surface of activated carbon supports on the activity of CoMo/activated carbon sulfided catalysts for hydrodeoxygenation of model compounds representative of the composition of pyrolysis oils has been studied. For this purpose, an activated carbon support was subjected to oxidative treatments with HNO3 at various temperatures to modify its surface chemistry. Supported sulfided CoMo catalysts on the resulting activated carbons were prepared. These catalysts were tested for hydrodeoxygenation of model compounds, 4-methylacetophenone (4MA), ethyl decanoate (ED), and 2-methoxyphenol (GUA), representative of the oxygenated functions that should be eliminated for improving oil stability. The activities of the various CoMo catalysts for the hydrogenation of the carbonyl group of 4MA were very similar, and the conversion reached 100% in less than 120 min at 280 °C and 7 MPa. Introduction of oxygen-containing functional groups to the carbon supports led to higher decarboxylation in the conversion of the carboxyl group of ED and higher phenol/catechol selectivity from 2-methoxyphenol. The surface chemistry of the support determined the precursor/support interaction and, hence, the nature of the sulfided phases present in the catalyst after activation. The different natures of the metal sulfides formed from the oxide precursors that were bound or not to the oxygen groups on the carbon supports could be responsible for the differences in selectivity displayed by these catalysts. Almost no coking reactions were observed. The results suggest that catalytic conversion of oils obtained from biomass pyrolysis can be controlled and modified by appropriate modifications of the surface chemistry of the activated carbon supports.

Introduction of Oxygen-Containing Functional Groups onto Diamond Electrode Surfaces by Oxygen Plasma and Anodic Polarization

Introduction of Oxygen-Containing Functional Groups onto Diamond Electrode Surfaces by Oxygen Plasma and Anodic Polarization

Effect of Surface Oxidation of the Support on the Thiophene Hydrodesulfurization Activity of Mo, Ni, and NiMo Catalysts Supported on Activated Carbon

The present investigation attempts to provide a better understanding of the influence of the nature of the carbon support on the HDS activity of Mo, Ni, and NiMo catalysts. For this purpose a high purity activated carbon was subjected to oxidative treatments with HNO3to modify its surface properties. NiMo catalysts supported on the resulting activated carbons were prepared and characterized by TPR, XRD, and SEM–EDX, and their activity for HDS of thiophene at 30 bars and 375°C was evaluated. The results obtained showed that oxidation of the carbon surface does not affect the HDS activity and other characteristics of the supported Mo phase. In contrast, the HDS activity of the Ni catalysts is enhanced by acid treatments of the carbon support. In this case, introduction of oxygen-containing functional groups (O(s)) leads to a strong interaction of O(s)–Ni during impregnation, which becomes essential to achieving and preserving high nickel dispersion. This effect on Ni dispersion is also reflected on the HDS activity of the bimetallic NiMo/C catalysts. The synergistic effect of the bimetallic catalysts is observed only when oxygen functional groups are present on the carbon surface, which are necessary for a good HDS activity, mainly because they enhance Ni–Mo interactions that produce the highly active Ni–Mo–S phase. A NiMoO4-like phase formed during impregnation seems to be the precursor for the active sulfide phase over the present NiMo/C catalysts.

Surface Modification of Carbon Fiber by Photosensitized Oxygenation

A new surface modification method using a photosensitizer of carbon fiber (CF) has been investigated. This method consists of treating carbon fiber merely by photosensitizer dipping, rinsing and drying. An easier handling and a better energy-saving as compared with conventional surface modifying methods are the features of the new method. The modifying effect was examined for wettability and dispersibility, through microscopic observation and surface analysis.The results are as follows: 1) Wettability of CF for water is improved by a mere photosensitizer painting. This effect is not degraded by washing/rinsing.2) Increase of O/C ratio and introduction of oxygen-containing functional groups on CF surface by the treatment are confirmed.3) Dispersion of modified CF into resin is improved remarkably.4) Mechanism of surface modification of CF by photosensitizer is considered attributable to reaction of photosensitized oxygenation.