Joseph Dentzer

Surface groups on nitric acid oxidized carbon black samples determined by chemical and thermodesorption analyses

Abstract Spheron 6 was oxidized with 1 1 nitric acid and the treated samples were submitted to elemental analysis and oxygenated surface group determination. The active surface area (ASA) of the samples was measured. Analysis was made of the gases (CO, CO2) evolved when the oxidized samples were heat treated up to 950°C. It is shown that the amount of oxygen which chemisorbs at 100°C on the preheated (800°C) carbon blacks corresponds to the amount of base-like groups (pyrone) which are formed after re-exposure to air.

Characterization of Carbon Surface Chemistry by Combined Temperature Programmed Desorption with in Situ X-ray Photoelectron Spectrometry and Temperature Programmed Desorption with Mass Spectrometry Analysis

The analysis of the surface chemistry of carbon materials is of prime importance in numerous applications, but it is still a challenge to identify and quantify the surface functional groups which are present on a given carbon. Temperature programmed desorption with mass spectrometry analysis (TPD-MS) and X-ray photoelectron spectroscopy with an in situ heating device (TPD-XPS) were combined in order to improve the characterization of carbon surface chemistry. TPD-MS analysis allowed the quantitative analysis of the released gases as a function of temperature, while the use of a TPD device inside the XPS setup enabled the determination of the functional groups that remain on the surface at the same temperatures. TPD-MS results were then used to add constraints on the deconvolution of the O1s envelope of the XPS spectra. Furthermore, a better knowledge of the evolution of oxygen functional groups with temperature during a thermal treatment could be obtained. Hence, we show here that the combination of these two methods allows to increase the reliability of the analysis of the surface chemistry of carbon materials.

A new Al,Mg-organoclay

A new inorganic–organic solid, with a 2∶1 phyllosilicate layer structure and octyl chains directly bound to the inorganic sheets via Si–C covalent bonds, was prepared at room temperature from an ethanolic gel with the molar composition RSiO3/2 ∶ 0.255 Al2O3 ∶ 0.5 MgO ∶ 130 CH3CH2OH ∶ 0.62 Na2O. Octyltriethoxysilane was used as the silica source. The introduction of octyl chains in the interlayer space was confirmed by the high d001 spacing values (2.5 nm). Thermogravimetric analyses show a major weight loss between 230 °C and 500 °C corresponding to the release of organic matter. The mass spectrometry analyses of the evolved gas are in agreement with the presence of octyl chains. Infrared and 13C MAS NMR spectra indicate that the Si–C bonds are intact and that the siloxane functions are fully hydrolyzed giving Si–O–Al and Si–O–Mg bonds in the inorganic layers. The substitution of Si and Mg by Al was confirmed by 29Si and 27Al MAS NMR.

Influence of Surface Chemistry on the Adsorption of Oxygenated Hydrocarbons on Activated Carbons

The objective of this work was to study the adsorption of different oxygenated hydrocarbons (methanol, ethanol, 1 and 2-butanol, methyl acetate) on activated carbons from organic mixtures with cyclohexane. Three activated carbons prepared by thermal and chemical treatments of a commercial carbon were employed for this purpose. Their textural properties were found to be similar, whereas their surface chemistries were modified, as shown by temperature-programmed desorption coupled to mass spectrometry (TPD-MS) and X-ray photoelectron spectroscopy (XPS). The adsorption isotherms were obtained by depletion method, and the analysis of adsorbed species was evaluated by TPD-MS to obtain new insight into the interactions between the different hydrocarbons and the carbon surface. Ethanol leads to a high-energy interaction between its hydroxyl function and the oxygenated surface groups and also to a lower energy interaction between the aliphatic part of the molecule and the carbon material. The desorption activation energy for this hydrophilic interaction is high (50 to 105 kJ/mol), and it is related to the nature of the carbon surface groups. The relative importance of these two interactions depend on the size of the alcohol/methanol is similar to ethanol, whereas butanols lead to more dispersive interactions. Methyl-acetate cannot undergo this kind of strong interaction and behaves like cyclohexane, having desorption activation energies ranging between 25 and 45 kJ/mol no matter the molecule and the carbon surface chemistry.

Synthesis of magnesium- and manganese-doped hydroxyapatite structures assisted by the simultaneous incorporation of strontium

Samples of crystalline hydroxyapatite (HA) with and without the addition of individual Mg(2+), Mn(2+) and Sr(2+) ions and samples with the addition of all three ions simultaneously were prepared using the precipitation method in an aqueous medium. Chemical, structural, spectroscopic and thermophysical analyses of the synthesized samples were conducted. The obtained results indicate that Sr(2+) ions were easily incorporated into the HA crystal structure, whereas it was difficult to incorporate Mg(2+) and Mn(2+) ions into the HA lattice when these ions were individually introduced into the samples. The synthesis of HA with Mg(2+) or Mn(2+) ions is characterized by the formation of HA with a low concentration of doping elements that is outweighed by the amount of these atoms present in less biocompatible phases that formed simultaneously. However, the incorporation of Sr(2+) along with Mg(2+) and Mn(2+) ions into the samples allowed for the synthesis of HA with considerably higher concentrations of Mg(2+) and Mn(2+) in the crystal lattice.

Temperature-programmed desorption as a tool for quantification of protein adsorption capacity in micro- and nanoporous materials.

The protein adsorption capacity of porous sorbents is generally obtained by measuring the concentration of proteins desorbed from the materials after treatment by a detergent, or by measuring the decrease of protein concentration in the solution. These methods have some drawbacks and often lead to a low precision in the determination of the adsorption capacities. We describe in this paper a new method that allows to directly quantify the amount of proteins adsorbed on porous materials. This method is based on the quantitative analysis by mass spectrometry of some low mass gaseous species which evolve from the biomolecules during the heat treatment of a temperature-programmed desorption analysis (TPD-MS). The method has been applied to bovine serum albumin and cytochrome C adsorbed on an activated carbon. The adsorption uptake of the proteins on the carbon material could be measured by this direct analysis. A comparison with the depletion method was done, it shows that the two methods are complementary. The depletion method allows a determination of the total adsorption capacity, while the TPD-MS method focus on irreversible capacity.

Inorganic–Organic Thin Implant Coatings Deposited by Lasers

The lifetime of bone implants inside the human body is directly related to their osseointegration. Ideally, future materials should be inspired by human tissues and provide the material structure-function relationship from which synthetic advanced biomimetic materials capable of replacing, repairing, or regenerating human tissues can be produced. This work describes the development of biomimetic thin coatings on titanium implants to improve implant osseointegration. The assembly of an inorganic-organic biomimetic structure by UV laser pulses is reported. The structure consists of a hydroxyapatite (HA) film grown onto a titanium substrate by pulsed-laser deposition (PLD) and activated by a top fibronectin (FN) coating deposited by matrix-assisted pulsed laser evaporation (MAPLE). A pulsed KrF* laser source (λ = 248 nm, τ = 25 ns) was employed at fluences of 7 and 0.7J/cm(2) for HA and FN transfer, respectively. Films approximately 1500 and 450 nm thick were obtained for HA and FN, respectively. A new cryogenic temperature-programmed desorption mass spectrometry analysis method was employed to accurately measure the quantity of immobilized protein. We determined that less than 7 μg FN per cm(2) HA surface is adequate to improve adhesion, spreading, and differentiation of osteoprogenitor cells. We believe that the proposed fabrication method opens the door to combining and immobilizing two or more inorganic and organic materials on a solid substrate in a well-defined manner. The flexibility of this method enables the synthesis of new hybrid materials by simply tailoring the irradiation conditions according to the thermo-physical properties of the starting materials.

Variation of the surface properties of nickel oxide upon heat treatment evidenced by temperature programmed desorption and inverse gas chromatography studies

The surface properties (dispersive component γSdof surface energy and surface nanomorphology) of nickel oxide samplessubmitted to heat treatments up to 550°C were examined bytemperature programmed desorption (TPD) and inverse gaschromatography (IGC) methods. It is shown that the variation ofγSd is complex, first increasing as thetemperature reaches about 300°C, then decreasing and goingagain through a maximum, of lower amplitude, for a treatmenttemperature of about 600°C. These variations follow closelythe TPD curves that related the rate of H2O and, in a much lesserextend of CO2 releases as the heat treatment temperature augments.The surface nanomorphology changes also during this treatment. TheNiO surface becomes very interactive when treated around 250°C. The determination of the adsorption energy distributioncurves (energetic heterogeneity) clearly demonstrates the change insurface properties and development of the population of highadsorption energy sites. Rehydration of the sample treated at 300°C was not possible under our experimental conditions.

Facile and sustainable synthesis of nitrogen-doped polymer and carbon porous spheres

The development of green, sustainable and simple synthesis pathways for the design of polymer and carbonaceous materials with well controlled features is of great importance for many fields of applications. Herein, we report a green synthesis method for polymer and carbon particles with well-defined shape and size. This approach involves the use of green precursors, water as solvent, no templates 10 under ambient temperature and pressure conditions, simultaneously. Green polymer resins (phloroglucinol-glyoxylic acid) and a catalyst/nitrogen source (triethylenediamine) are dissolved in water at room temperature resulting in polymer particles which by subsequent thermal treatment transforms in carbon particles. Mainly spherical carbon particles with controlled size from 500 nm to 10 µm were obtained by simply adjusting the experimental conditions, i.e., the synthesis time and the molar ratio between the precursors or solvent. In some conditions, flower-like morphology was obtained as well. The synthesis mechanism from polymer resin spheres 15 formation to their conversion into carbon sphere was determined by several techniques, i.e., 13 C NMR spectroscopy, SEM, XPS and TPD-MS (temperature programmed desorption coupled by mass spectrometer). 20

Direct Laser Writing of Crystallized TiO2 and TiO2/Carbon Microstructures with Tunable Conductive Properties

Metal oxides are an important class of materials for optoelectronic applications. In this context, developing simple and versatile processes for integrating these materials at the microscale and nanoscale has become increasingly important. One of the major remaining challenges is to control the microstructuration and electro-optical properties in a single step. It is shown here that near-infrared femtosecond laser irradiation can be successfully used to prepare amorphous or crystallized TiO2 microstructures in a single step using a direct laser writing (DLW) approach from a TiO2 precursor thin film doped with a suitable dye. When laser writing is conducted under a nitrogen atmosphere, simultaneous to the crosslinking of the Ti-oxide precursor, the graphitization of the organic species embedded in the initial film is observed. In this case, a carbon network is generated within the TiO2 matrix, which significantly increases the conductivity. Moreover, the TiO2 /C nanocomposite exhibits piezoresistive behavior that is used in a pressure sensor device. Using this route, it is possible to use DLW to fabricate microsized pressure sensors.