The characterization of activated carbons with oxygen and nitrogen surface groups

Polymer/layered silicate (clay) nanocomposites: An overview of flame retardancy

This is the first time we report that simply air plasma treatment can also enhances the optical absorbance and absorption region of titanium oxide (TiO2) films, while keeping them transparent. TiO2 thin films having moderate doping of Fe and Co exhibit significant enhancement in the aforementioned optical properties upon air plasma treatment. The moderate doping could facilitate the formation of charge trap centers or avoid the formation of charge recombination centers. Variation in surface species viz. Ti3+, Ti4+, O2−, oxygen vacancies, OH group and optical properties was studied using X-ray photon spectroscopy (XPS) and UV-Vis spectroscopy. The air plasma treatment caused enhanced optical absorbance and optical absorption region as revealed by the formation of Ti3+ and oxygen vacancies in the band gap of TiO2 films. The samples were treated in plasma with varying treatment time from 0 to 60 seconds. With the increasing treatment time, Ti3+ and oxygen vacancies increased in the Fe and Co doped TiO2 films leading to increased absorbance; however, the increase in optical absorption region/red shift (from 3.22 to 3.00 eV) was observed in Fe doped TiO2 films, on the contrary Co doped TiO2 films exhibited blue shift (from 3.36 to 3.62 eV) due to Burstein Moss shift.

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Formation of oxygen vacancies and Ti 3+ state in TiO 2 thin film and enhanced optical properties by air plasma treatment

A biologically active, high-strength tissue adhesive is needed for numerous medical applications in tissue engineering and regenerative medicine. Integration of biomaterials or implants with surrounding native tissue is crucial for both immediate functionality and long-term performance of the tissue. Here, we use the biopolymer chondroitin sulphate (CS), one of the major components of cartilage extracellular matrix, to develop a novel bioadhesive that is readily applied and acts quickly. CS was chemically functionalized with methacrylate and aldehyde groups on the polysaccharide backbone to chemically bridge biomaterials and tissue proteins via a twofold covalent link. Three-dimensional hydrogels (with and without cells) bonded to articular cartilage defects. In in vitro and in vivo functional studies this approach led to mechanical stability of the hydrogel and tissue repair in cartilage defects.

Multifunctional chondroitin sulphate for cartilage tissue-biomaterial integration.

Graphitic carbon nitride has been predicted to be structurally analogous to carbon-only graphite, yet with an inherent bandgap. We have grown, for the first time, macroscopically large crystalline thin films of triazine-based, graphitic carbon nitride (TGCN) using an ionothermal, interfacial reaction starting with the abundant monomer dicyandiamide. The films consist of stacked, two-dimensional (2D) crystals between a few and several hundreds of atomic layers in thickness. Scanning force and transmission electron microscopy show long-range, in-plane order, while optical spectroscopy, X-ray photoelectron spectroscopy, and density functional theory calculations corroborate a direct bandgap between 1.6 and 2.0 eV. Thus TGCN is of interest for electronic devices, such as field-effect transistors and light-emitting diodes.

http://apinano.org.br/documentos/triazine-based-graphitic-carbon-nitride-a-two-dimensional-semiconductor.pdf

Triazine‐Based Graphitic Carbon Nitride: a Two‐Dimensional Semiconductor

Surface characterisation of plasma-nitrided titanium: an XPS study

A program for quantitative evaluation of x-ray photoelectron spectra has been developed to serve as a practical tool for surface chemists. The program uses the ‘classic’ approach of quantification and requires as input the integrated intensities of the measured XPS lines. The usual correction methods and factors can be applied and controlled independently. All necessary basic data for calculations are integrated into the main library of the program. Besides the usual ‘infinitely thick homogeneous sample’ geometry model, the program is able to calculate models for layered structures, both on flat and curved surfaces. Calculation for several samples or experimental data sets can be done together. Results can be presented in several forms, such as atomic %, atomic ratio, oxide molar ratio, etc., and can be stored, printed and charted. Data can be labelled and annotated. XPS MultiQuant is equipped with a user-friendly interface, full text help system and a ‘wizard’ for easy set-up of calculations. Copyright © 2004 John Wiley & Sons, Ltd.

XPS MultiQuant: multimodel XPS quantification software

Surface modification of graphene and graphite by nitrogen plasma: Determination of chemical state alterations and assignments by quantitative X-ray photoelectron spectroscopy

Acid catalysts based on ordered mesoporous silica materials (MCM-41, HMS, and SBS-15) with covalently anchored propanesulfonic or benzenesulfonic acid groups were synthesized. Six samples were prepared by co-condensation of tetraethylorthosilicate with 3-mercaptopropyltrimethoxysilane or phenyltriethoxysilane in the presence of appropriate templating agents. Six other samples were made by post-synthesis modification of the parent silica materials. Syntheses were followed by oxidation or sulfonation to form surface sulfonic acid groups. Sample characterization was performed by physical (low-angle X-ray powder diffraction, nitrogen adsorption and desorption, diffuse reflectance IR, Raman, NMR, and X-ray photoelectron spectroscopies) and chemical (acid–base titration) methods. Spectroscopic techniques proved successful incorporation of the functional groups. Functionalization of the parent silicas, however, results in changes in structural characteristics (decreasing BET surface areas, changes in pore size distribution, decreasing long range orders). The samples exhibit high activities in various catalytic transformations. Catalysts with anchored benzenesulfonic acid groups of high acid strength and high acid site densities allow the selective synthesis of the cyclic dimer indan product in the dimerization of 2-phenylpropene. 2,3,5-Trimethylhydroquinone diacetate can also be produced in similar high yields in the rearrangement–aromatization of ketoisophorone. Characteristic differences in selectivities are interpreted by taking into account of differences in acid site densities, active site distribution, and the polarity of reactants and catalyst surface. The low activity and selectivity of samples made by grafting in the transformation of ketoisophorone are attributed to the non-random distribution of the acidic functions.

A comparative study of solid sulfonic acid catalysts based on various ordered mesoporous silica materials

The influence of calcium and zinc ions on the corrosion inhibition effect of 1‐hydroxyethane‐1,1‐diphosphonic acid (HEDP) on carbon steel has been investigated by electrochemical techniques, X‐ray photoelectron spectroscopy, and atomic force microscopy. Addition of calcium or zinc ions greatly increased the inhibition efficiency of HEDP in a synergistic manner. The highest inhibition effect was obtained for molar ratios of Ca/HEDP = 0.5 and Zn/HEDP = 3 for . The corrosion inhibition mechanism in the presence of these additives proved to be different from that with HEDP alone and was related to the formation of different complex species between HEDP and cation additives. The frequency response of the studied system was described by a transfer function containing two relaxation time constants corresponding to the charge‐transfer process and the porous oxide layer. Higher zinc and phosphorous content in the inhibitor layer and a continuous change in the O‒Fe and HO‒Fe ratio were achieved by increasing zinc concentration in the solution (in the range Zn/HEDP = 0.5–3) as supported by XPS measurements. Changes in the chemical structure were established in the oxide‐hydroxide layer developed spontaneously on the steel surface. The synergistic effect of inhibitor compounds appeared also in surface morphology, leading to the development of smooth, i.e., dense, protective layers as revealed by atomic force microscopy. © 1999 The Electrochemical Society. All rights reserved.

Miklós Mohai

Papers

Surface characterisation of plasma-nitrided titanium: an XPS study

XPS MultiQuant: multimodel XPS quantification software

Surface modification of graphene and graphite by nitrogen plasma: Determination of chemical state alterations and assignments by quantitative X-ray photoelectron spectroscopy

A comparative study of solid sulfonic acid catalysts based on various ordered mesoporous silica materials

Effects of Bivalent Cations on Corrosion Inhibition of Steel by 1‐Hydroxyethane‐1,1‐diphosphonic Acid