Amount Of OH Groups Research Articles

Spectroscopic Study of Eu3+ Doped LaF3 Nanoparticles Prepared with Different PH Values

Europium doped lanthanide fluoride (LaF3) nanoparticles were prepared through a hydrothermal method with different PH values of precursor complex solution. The influence of PH value on the luminescence properties is investigated. It was found that the local symmetry of doped ions reduced with the increase of PH value, leading to the increase of the inversion symmetry ratio. The fluorescence quenching was observed for small nanoparticles, which was attributed to the large amount of OH groups absorbed to the surface of the nanoparticles.

Infrared Spectroscopy of Titania Sol-Gel Coatings on 316L Stainless Steel

Sol-gel titania films were deposited on 316L stainless steel using titanium isopropoxide as a chemical precursor. Dip-coating was performed at withdrawal speeds of 6 mm/min, 30 mm/min, and 60 mm/min. Deposited gel films were heat treated in air at 80℃, 100℃, 300℃, and 400℃. The structural evolution of the coatings was evaluated by infrared reflection-absorption spectroscopy. The influence of the withdrawal speed and the heat treatment temperature on the structure of the films was studied by varying the reflectance incidence angle during the infrared experiments and by Glow Discharge Spectrometry. Free functional groups were detected. The results indicate the formation of bidendate bridging coordination of carboxylic acid to titanium. Titanium atoms can also be pentacoordinated according to the processing conditions of the films. We observed a tendency of increasing amounts of OH groups with decreasing reflectance incidence angle. The film hardness was measured via Knoop microindenation hardness test.

The interaction of H2O with Fe‐doped SrTiO3(100) surfaces

AbstractThe interaction of H2O with 0.013 at.% Fe‐doped SrTiO3(100) was investigated in situ with Metastable Induced Electron Spectroscopy (MIES), Ultraviolet Photoelectron Spectroscopy (UPS) and XPS at room temperature. Low Energy Electron Diffraction (LEED) was applied to gather information about the surface termination. To clear up the influence of surface defects, untreated and weakly sputtered SrTiO3 surfaces were investigated. The sputtering results in the formation of oxygen‐related defects in the top surface layer.The interaction of untreated SrTiO3 surfaces with H2O is only weak. Small amounts of OH groups can be identified only with MIES due to its extreme surface sensitivity. Sputtered surfaces show a larger OH formation. Nondissociative H2O adsorption is not observed. We therefore conclude that the exposure of H2O to SrTiO3(100) results in the dissociation near surface defects only, resulting in the formation of surface hydroxyl groups. Copyright © 2010 John Wiley & Sons, Ltd.

Low temperature silicon dioxide by thermal atomic layer deposition: Investigation of material properties

SiO 2 is the most widely used dielectric material but its growth or deposition involves high thermal budgets or suffers from shadowing effects. The low-temperature method presented here (150 °C) for the preparation of SiO2 by thermal atomic layer deposition (ALD) provides perfect uniformity and surface coverage even into nanoscale pores, which may well suit recent demands in nanoelectronics and nanotechnology. The ALD reaction based on 3-aminopropyltriethoxysilane, water, and ozone provides outstanding SiO2 quality and is free of catalysts or corrosive by-products. A variety of optical, structural, and electrical properties are investigated by means of infrared spectroscopy, UV-Vis spectroscopy, secondary ion mass spectrometry, capacitance-voltage and current-voltage measurements, electron spin resonance, Rutherford backscattering, elastic recoil detection analysis, atomic force microscopy, and variable angle spectroscopic ellipsometry. Many features, such as the optical constants (n, k) and optical transmission and surface roughness (1.5 Å), are found to be similar to thermal oxide quality. Rapid thermal annealing (RTA) at 1000 °C is demonstrated to significantly improve certain properties, in particular by reducing the etch rate in hydrofluoric acid, oxide charges, and interface defects. Besides a small amount of OH groups and a few atomic per mille of nitrogen in the oxide remaining from the growth and curable by RTA no impurities could be traced. Altogether, the data point to a first reliable low temperature ALD-growth process for silicon dioxide.

The Effects of Annealing Ambient on the Characteristics of La2O3 Films Deposited by RPALD

We investigated the effects of different annealing ambients on the physical and electrical properties of lanthanum oxide films grown by remote plasma atomic layer deposition (RPALD). Rapid thermal annealing was carried out at for 1 min in , , and vacuum ambients. The chemical bonding states at the interface between the Si substrate and the films were analyzed using X-ray photoemission spectroscopy. The amount of OH groups that were absorbed from air in the films decreased after annealing at . and its interfacial layer were affected by the different annealing ambients. The electrical properties of the films were studied using capacitance–voltage and current–voltage plots. Without annealing treatment, the flatband voltage for the film was measured to be −0.31 eV. When was annealed at in and ambients, positive shifts of 0.16 and 0.64 eV, respectively, were observed.

Preparation and characterization of novel highly omniphobic cellulose fibers organic–inorganic hybrid materials

This paper reports the preparation of class-II organic–inorganic hybrid materials by the heterogeneous chemical modification of cellulose fibers with (3-isocyanatopropyl)triethoxysilane, followed by the acid hydrolysis (and condensation) of the appended siloxane moieties as such, and in the presence of either tetraethoxysilane or 1 H,1 H,2 H,2 H-perfluorodecyltriethoxysilane. These modifications produced an inorganic “coating” around the fibers, while preserving their ultrastructure, as confirmed by XRD and SEM. The detailed characterization of these new hybrid materials by FTIR and 29Si NMR showed that, upon hydrolysis of the ethoxy groups, condensation reactions took place leading mainly to Si–O–Si linear sequences, followed by a smaller contribution of more branched moieties, and that a significant amount of OH groups were also formed, which gave rise to hydrophilic surfaces. The hybrids obtained by hydrolysis in the presence of 1 H,1 H,2 H,2 H-perfluorodecyltriethoxysilane displayed a very pronounced hydrophobic and lipophobic character (reaching contact angles with water and diiodomethane as high as 140° and 134°, respectively), due to the presence of the perfluorinated moieties.

Influence of the OH groups on the photocatalytic activity and photoinduced hydrophilicity of microwave assisted sol–gel TiO 2 film

In the present work the influence of the OH groups on the photocatalytic activity and the photoinduced hydrophilicity of microwave assisted sol–gel TiO 2 films was investigated. The prepared TiO 2 films were characterized using XRD and AFM. Furthermore, the surface of the TiO 2 films was examined by help of XPS in order to determine the amount of OH groups before and after UV irradiation at different humidities. The activity of the TiO 2 films was determined using stearic acid as a model compound and the photoinduced superhydrophilicity was investigated through contact angle measurements. The results of this investigation showed that the microwave assisted sol–gel technique produces highly homogeneous and efficient TiO 2 films without the need for heat treatment for crystallization. Based on the conducted experiments it is suggested that the amount of OH groups on the TiO 2 surface highly influence the photocatalytic activity and the photoinduced superhydrophilicity and that the two mechanisms may be closely related. It is suggested that the superhydrophilicity is obtained through a combination of photocatalytic degradation of organic contaminants and surface structural changes in form of an increased amount of OH-groups.

Electronic structure of Lewis acid sites on high surface area aluminium fluorides: a combined XPS and ab initio investigation

High surface area (HS) A1F3 samples have been examined by X-ray photoelectron spectroscopy (XPS). The experimentally observed binding energy (BE) shifts were analysed by reference to core level BEs obtained from ab initio total energy calculations on a range of different, clean and hydroxylated alpha- and beta-A1F3 surfaces. Examination of the two components visible in the A1 2p emission indicates that surface A13+ sites can, depending on the local geometric structure, contribute to both a high BE peak at 77.0 eV and a low BE peak at 76.1 eV. Consequently, the areas under the peaks do not quantitatively correlate with surface area or Lewis acidity. However, a significant correlation between the number of surface A1 centres with dangling F or OH groups and the appearance of an A1 2p emission component at a BE lower than in the alpha-A1F3 bulk is predicted. The experimental F 1s emission data indicate that dangling F species are essentially absent. Examination of the O 1s emission suggests that HS A1F3 handled at room temperature under any practical laboratory conditions, including glovebox environments, probably contains intrinsically a significant amount of OH groups and adsorbed water, which results in the covering of A1F3 surfaces by dangling or bridging OH groups. These Bronsted acid species must be removed by treatment at higher temperature before HS A1F3 reagents can fully develop their Lewis acidity.

Preparation of highly effective ferric hydroxide supported noble metal catalysts for CO oxidations: From gold to palladium

Ferric hydroxide supported Pd catalyst prepared by a simple co-precipitation method without calcinations at elevated temperatures and only reduced at 50 °C possessed unexpectedly higher activity for CO oxidations even compared with that of supported Au catalysts. XRD and TEM results showed that the support was mixture of Fe(OH) x and Fe 3O 4 and Pd was highly dispersed on it. XPS results showed that Pd existed as mixture of oxidation and metal state. The large amount of OH group on the supports may play an important role in O adsorption and activation.

Surface properties and photocatalytic activity of nanocrystalline titania films

In this work the efficiency and physicochemical details of a thin film produced by help of a microwave assisted sol gel technique is compared to different commercial powders (Degussa P25 and Hombikat UV100) deposited on glass substrates. Furthermore, a supercritical produced TiO 2 powder (SC 134) was included in the comparison. The prepared TiO 2 films were characterized using XRD, XPS, AFM, DSC and DLS. The photocatalytic activity was determined using stearic acid as a model compound. Investigation of the prepared films showed that the Degussa P25 film and the sol–gel film were the most photocatalytic active films. The activity of the films was found to be related to the crystallinity of the TiO 2 film and the amount of surface area and surface hydroxyl groups. Based on the XPS investigation of the films before and after UV irradiation it was suggested that the photocatalytic destruction of organic matter on TiO 2 films proceeds partly through formation of hydroxyl radicals which are formed from surface hydroxyl groups created by interactions between adsorbed water and vacancies on the TiO 2 surface. Furthermore a correlation between the amount of OH groups on the surface of the different TiO 2 films and the photocatalytic activity was found.

Microstructure and chemical degradation of adobe and clay bricks

The environmental degradation of adobe and fired clay brick was studied. Leaching media based on Na 2S 2O 5 solution and deionized water were used. The microstructure of the samples was evaluated by X-ray powder diffraction, nitrogen adsorption–desorption (BET method), Fourier transform infrared spectroscopy and scanning electron microscopy. The predominant phases detected were kaolinite and quartz for both the adobe and fired brick samples. The high surface reactivity, associated with a large amount of OH groups, contributes to the significant degradation of adobe. The fired clay brick showed a significant decrease in the average pore diameter after the first day of the leaching process; its specific surface area exhibited a reduction of about three orders of magnitude. The results of the present investigation contribute to a better understanding of the correlation between structure and leaching behaviour in adobe and clay brick, attending the renewed interest in these materials as environmentally attractive building blocks.

The structure and thermooxidative transformations of polymethylsilsesquioxanes

The structure and thermooxidative stability of highly crosslinked polymethylsilsesquioxanes in the temperature range 400–700°C were compared. Using nonlinear multifactor regression analysis, the statistically effective equations were obtained allowing the comparative estimation of the structure of basic fragments of polymethylsilsesquioxanes, the determination of the composition of solid products of thermooxidation of these polymers, and prediction of their thermooxidative stability. It was found that stability characteristics, such as the degree of degradation by carbon, mass loss, and the amount of OH groups in the products of thermooxidation of polymethylsilsesquioxanes, are determined by the interchain distances and the entropy of the polymer network structure. It was shown that the oxidation stability of methyl substituents and the degree of conversion of OH groups upon thermooxidative transformations of polymethylsilsesquioxanes correlate with the position and intensity of the bands of bending vibrations of CH3 groups and asymmetric stretching vibrations of the siloxane bond.

Controlled hydroxylation of diamond for covalent attachment of fullerene molecules

Diamond can adopt a p-type sheet conductivity by surface transfer doping. Fullerene and fluorinated fullerene derivatives have been shown in the past to take the role as efficient surface acceptors. In order to improve the thermal stability of the sheet conductivity so obtained, we have studied the covalent attachment of C 60F 48 to a hydrogen terminated and partially hydroxylated diamond (100) surface by photoelectron spectroscopy and in situ conductivity measurements. A careful control of the hydroxylation process turned out to be crucial in order to obtain a sufficient amount of OH groups on the surface and keep the concentration of ketone, ether, and carboxyl small.

Rheological properties of solutions and gels of combined systems hydrophobically modified polyacrylamides-new viscoelastic cationic surfactants

The rheological properties (viscosity and dynamic elasticity modulus) of solutions and gels of combined systems composed of hydrophobically modified polymers containing main-chain charged groups or lacking these groups and of newly synthesized viscoelastic cationic surfactants with different amounts of OH groups and long nonpolar saturated and trans monounsaturated radicals have been studied. It has been shown that the maximum viscosity of solutions of polymer-surfactant complexes corresponds to the very low concentration of the surfactant. Regions where homogeneous and heterogeneous combined solutions and gels exist are considered. An increase in the viscosity of the combined solutions with temperature is discovered and discussed. The synergistic effect of polymers and surfactants is demonstrated, and a more efficient role of surfactants in the case of uncharged polymers is revealed. The roles of the number of OH groups and the length of the nonpolar radical in a surfactant molecule and a difference in the properties of systems containing surfactants with saturated and unsaturated radicals are considered.

Contribution to the study of hydroxymethylation reaction of alkali lignin

The hydroxymethylation of alkali lignin with formaldehyde in alkaline solution was studied. The influence of reaction conditions of the hydroxymethylation of alkali lignin was followed by modifying the temperature, time, and the ratios of NaOH to lignin and CH2O to lignin. Three different types of alkali lignin were utilized. The reaction was followed by total consumption of formaldehyde, and the resulting products were characterized through FTIR-spectra, thermogravimetry analysis, ash and moisture contents, as well as by the amounts of OH groups.

Photoluminescence Characteristics of Sol?Gel Materials Prepared from Bimetallic Erbium Alkoxides Coordinated by Al or Ti

Er3+-doped Al2O3–SiO2 and TiO2–SiO2 powders were prepared by the sol–gel process using bimetallic erbium isopropoxides coordinated with Al or Ti. The local environment surrounding Er3+ ions was controlled orderly at the precursor stage. The phase development of two different systems as a function of temperature was characterized by XRD, and the amount of OH groups remaining within the samples was investigated by a Fourier-transformed infrared spectrometer with increasing annealing temperatures. The photoluminescence spectra and lifetimes of two systems annealed at different temperatures were measured and discussed. The strong emission and long lifetime were observed in Er3+-doped Al2O3–SiO2 system, ascribed to the homogeneous distribution of Er3+ ion.

Gate Dielectric Dependent on Pentacene Growth and Electrical Stability in OTFTs

ABSTRACTWe report on the effects of modifying the gate dielectrics by spin coating of HMDS, PVP and PVA which cause different surface energy and surface roughness owing to the different functional groups. In changing the surface state with applying various surface treatments, I-V and C-V measurements of the OTFTs were performed. The PVP-coated OTFTs, which has smoother and lesser amount of OH-groups on the gate dielectric surface, showed enhanced pentacene growth and nearly free hysteresis behavior than that of the HMDS and PVA-coated OTFTs.

Spectroscopic Study of H2 and CO Adsorption on Platinum-Promoted Sulfated Zirconia Catalysts

H2 adsorption over two Pt/SO42-−ZrO2 (Pt/SZ) samples pretreated under different conditions (one is catalytically active and the other is inactive in n-butane isomerization) was investigated by in-situ Fourier transform infrared (FTIR) spectroscopy and temperature-programmed desorption (TPD). It was found that the formation of H2O was the crucial difference between the active and inactive Pt/SZ samples upon H2 adsorption at 523 K, with isolated zirconium OH groups forming on both samples. Under the same conditions, neither H2O nor zirconium OH groups formed on SO42-−ZrO2 (SZ), and only a small amount of OH groups formed on Pt/ZrO2. CO adsorption results reveal the presence of both Brφnsted and Lewis acid sites on the surface of Pt/SZ, as well as the transformation of Lewis acid sites to Brφnsted acid sites upon H2 adsorption at 523 K. These results present direct evidence of H2 spillover from Pt to the sulfated zirconia surface. The formation mechanism of H2O and OH groups is discussed, and it is suggested that the active oxygen species, which should be associated with the intermediate sulfate species on the active Pt/SZ surface, plays an essential role as active sites on Pt/SZ in n-butane isomerization.

Synthesis of Glycidyl Methacrylate-Divinylbenzene Microsheres with Aminoalcohol Groups and Their Adsorption Properties for Boron

New adsorbents (AP, AMP, AHMP and MG) were prepared by introducing the aminoalcohol groups such as 3-amino-1, 2-propanediol, 2-amino-2-methyl-1, 3-propanediol, 2-amino-2-hydroxymethyl-1, 3-propandiol and N-methyl-D (-) -glucamine, respectively, to glycidyl methacrylate-divinylbenzene microspheres (GD) in order to investigate the adsorption properties of boron. All experiments were carried out using a batch method. The amount of OH group introduced to microspheres is the following order: MG>AMP>AHMP>AP. The adsorption of boron showed maximums at pH 6-8 for all adsorbents. The adsorption capacity and the adsorption equilibrium constant were determined using the Langmuir equation. Their adsorption capacities for boron are the following order: AHMP>MG>AP>AMP. Although the amount of OH group introduced to AP is less than AMP, the adsorption capacity of AP is higher than AMP. This result suggests that boron prefers the five-membered chelating ring to the six-membered chelating ring. Boron adsorbed on AMP was easily desorbed using 1 mol·dm-3 hydrochloric acid.

Influence of water on the tracer diffusion of sodium in glasses

Experimental results for the diffusion of the radioactive tracer Na-22 in Corning Code 1737 glass (an alkaline-earth aluminoborosilicate glass), in type I silica glass (Infrasil 302) and in model glasses of the type (CaO·Al2O3)x(2SiO2)1−x are reviewed. In addition, data for the incorporation of water into these glasses and for the influence of this water on the diffusion of sodium are considered. It was observed by FTIR spectroscopy that the overall concentration of water incorporated into glass in the form of OH groups as a function of the water uptake time follows a parabolic rate law. The water uptake leads to a very significant decrease in the sodium diffusivity in the near-surface region of the glass. The width of the near-surface region with a reduced sodium mobility as a function of the water uptake time follows a parabolic rate law. The decrease in the sodium tracer diffusion coefficient in the near-surface region is on the order of 100 to 1000, depending on the glass considered, the temperature, and, possibly to a small extent, the amount of OH groups generated. The observed decrease in the sodium diffusivity in the near-surface region is attributed to a structural relaxation that is enabled by the OH groups generated upon the uptake of water.