Alternative Method For Synthesis Research Articles

Oxygen Reduction on Graphene-Based Materials of Different Origin

Graphene, the two-dimensional carbon nanomaterial with interesting properties, is still under an intense focus of research. The traditional method to obtain a high-quality graphene is by mechanical exfoliation. However, it has several drawbacks. For example, it is very time consuming method in addition to the low productivity. To overcome those problems, various alternative methods for graphene synthesis have been developed. Currently, one of the most extensively used method to produce graphene is to first, exfoliate graphene oxide (GO) from graphite oxide by solution-based processes followed by reduction of GO by chemical, thermal or UV-assisted approaches in order to obtain a reduced GO (rGO), which should have similar properties to pristine graphene. Also, an electrochemical exfoliation of graphite for the production of graphene has attracted considerable interest due to its high productivity as well as simplicity.1 The use of graphene-based nanomaterials as electrocatalysts for oxygen reduction reaction (ORR) occurring at the cathode of fuel cells and metal-air batteries, has received a great attention.2 Numerous studies have been carried out to prepare graphene-based materials doped with heteroatoms or non-precious metals with improved electrocatalytic activity toward the ORR. However, comparative studies on the ORR on pristine graphene of different origin are still insufficient. Based on the literature, the electrochemical behavior of various graphene-based materials (e.g. CVD-grown graphene, rGO, etc.) toward the ORR depends on the origin of the graphene.3,4 The main purpose of this work is to study the effect of graphene-based materials of different origin on the ORR activity in alkaline medium. Herein, two commercially available graphene samples and pre-synthesized rGO were selected. rGO samples were prepared from GO which in turn was synthesized using two different approaches: modified Hummer´s method and electrochemical exfoliation. Since GO is the starting material of rGO, glassy carbon (GC) electrodes were coated with GO under exactly the same conditions as were prepared with commercially available graphene samples and rGO for comparison purpose. The materials were studied through various characterization techniques such as transmission electron microscopy, scanning electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. In the literature, there are only a few reports in which OH‒ ionomer has been used instead of Nafion ionomer as a binder during the catalyst ink preparation. Therefore, it was of special interest to study the effect of OH‒ ionomer on the ORR process as well. For comparison purposes, the catalyst ink made from N,N-dimethylformamide (DMF) was also used. To evaluate the catalytic activity of these graphene-based materials for ORR in O2-saturated 0.1 M KOH solution, several techniques including linear sweep voltammetry and the rotating disk electrode method were applied. Since the rotating ring-disk electrode (RRDE) method gives additional information about intermediate peroxide species (OOH– in the alkaline solution) formed during the ORR process, hence, in some experiments, RRDE method was employed as well. Firstly, the results revealed that the ORR activity depended on the origin of the catalyst material. In more specific, the electrocatalytic behavior of commercially available graphene-based electrodes toward the ORR was higher than that of the rGO-modified GC electrode. In addition, the graphene-based electrodes prepared from the suspension in DMF showed better ORR activity than those made using the suspensions in 2-propanol containing OH‒ ionomer, referring to the inhibiting effect of the ionomer. However, the results also showed that the amount of OH‒ionomer in the catalyst layer should be optimized. Otherwise, the electrocatalytic activity of the catalyst material toward the ORR was significantly reduced. It was also clear that the electrochemical reduction of oxygen on all the studied materials followed a two-step ORR process with the formation of peroxide as an intermediate.

ChemInform Abstract: Three‐Component Domino Cyclization of Novel Carbazole and Indole Fused Pyrano[2,3‐c]pyridine Derivatives.

AbstractA facile and reliable three‐component intramolecular six‐membered heterocyclization as an alternative method for the efficient synthesis of fused carbazole and indole pyrano[2,3‐c]‐pyridine derivatives is reported, starting from commercially available hydroxycarbazole or hydroxyindole with diverse aromatic aldehydes and aminopropenetricarbonitrile.

Antibacterial Activity of Polyaniline Coated Silver Nanoparticles Synthesized from Piper Betle Leaves Extract.

Plants or natural resources have been found to be a good alternative method for nanoparticles synthesis. In this study, polyaniline coated silver nanoparticles (AgNPs) synthesized from Piper betle leaves extract were investigated for their antibacterial activity. Silver nanoparticles were prepared from the reduction of silver nitrate and NaBH4 was used as reducing agent. Silver nanoparticles and extracts were mixed thoroughly and then coated by polyaniline. Prepared nanoparticles were characterized by Visual inspection, Ultraviolet-visible spectroscopy (UV), Fourier transform infrared Spectroscopy (FT-IR), Transmission Electron Microscopy (TEM) techniques. Antibacterial activities of the synthesized silver nanoparticles were tested against Staphylococcus aureus ATCC 25923, Salmonella typhi ATCC 14028, Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853. UV-Vis spectrum of reaction mixture showed strong absorption peak with centering at 400 nm. The FT-IR results imply that Ag-NPs were successfully synthesized and capped with bio-compounds present in P. betle. TEM image showed that Ag-NPs formed were well dispersed with a spherical structures and particle size ranging from 10 to 30 nm. The result revealed that Ag-Extract NPs showed 32.78±0.64 mm zone of inhibition against S. aureus, whereas norfloxacin (positive control) showed maximum 32.15±0.40 mm zone of inhibition for S. aureus. Again, maximum zone of inhibition 29.55±0.45 mm was found for S. typhi, 27.12±0.38 mm for E. coli and 21.95±0.45 mm for P. aeruginosa. The results obtained by this study can't be directly extrapolated to human; so further studies should be undertaken to established the strong antimicrobial activity of Ag-Extract NPs for drug development program.

Intriguing luminescence properties of (Ba, Sr)3Si6O9N4: Eu2+ phosphors via modifying synthesis method and cation substitution

Synthesizing pure phase Ba3Si6O9N4 by the conventional solid-state reaction method is challenging because of easily formed secondary phase Ba3Si6O12N2 showing similar crystal structure. In this work, an alternative low temperature synthesis method is presented, and a series of green to blue emitting (Ba, Sr)3Si6O9N4: Eu2+ phosphors were prepared by a mechanochemical activation route. Variations in photoluminescence properties and crystal structure, as induced by the change in phosphor composition, were investigated. Under ultraviolet-light excitation, Ba3Si6O9N4: Eu2+ phosphor exhibited a strong narrow green emission at 518 nm and simultaneously a weak emission at 405 nm, which are ascribed to different Eu/Ba sites in Ba3Si6O9N4 lattice proved by Density Functional Theory (DFT) calculations. A continuous green to blue emission in (Ba, Sr)3Si6O9N4: Eu2+ phosphors could be achieved by tuning the crystal structure and local coordination environment acting on Eu2+ with Sr/Ba substitution. More Sr/Ba substitution improved thermal quenching and resulted in a different characteristic of emission peak shift upon increasing the temperature.

ChemInform Abstract: Stereoselective Synthesis of Trisubstituted Alkenes Through Sequential Iron‐Catalyzed Reductive anti‐Carbozincation of Terminal Alkynes and Base‐Metal‐Catalyzed Negishi Cross‐Coupling.

AbstractAn alternative and general method for the stereoselective synthesis of trisubstituted alkenes is developed.

ChemInform Abstract: Mo‐V‐Phosphoric Heteropoly Acids and Their Salts: Aqueous Solution Preparation — Challenges and Perspectives

AbstractReview: [156 refs.

Direct Electrochemical Conversion of Nitrogen to Ammonia from Air and Water on Nitride Electro-Catalysts at Ambient Conditions

The use of ammonia as an energy carrier, chemical feedstock and specially fertilizer has triggered increased interest in developing alternative methods for ammonia synthesis in pursuit of decentralized and environmentally friendly approach. Although Ru and Fe within the Haber-Bosch process show good activity for catalysing nitrogen conversion to ammonia, its expense, scarcity, harsh experimental conditions (extremely high temperature and pressure) and sophisticated industrial setup are prohibitive to its decentralization complicating ammonia production in regions with relatively undeveloped infrastructure such as developing countries. Besides, the reliance of this process on natural gases for supplying its necessary hydrogen feedstock not only promotes severe CO2 emission to the environment but it also makes the production of ammonia and accordingly food and biofuels vulnerable to natural gas price fluctuations and political conflict in the oil-rich regions. Nature, on the other hand, reduces atmospheric nitrogen to ammonia by solvated protons and electrons at very moderate conditions, but engineering man-made ammonia to duplicate this in a small-scale approach still remains one of the challenges in modern chemistry. Nonetheless, electro-catalytic ammonia synthesis is a particularly feasible method due to the potential of utilizing renewable energy sources and mild operating conditions. Solid-state electrolytes and polymeric membrane assemblies are the most promising electrochemical approaches developed thus far and have exhibited great success with respect to increased yield of ammonia at ambient conditions. Nevertheless, the yield still remains rather low and the complexity of systems of this sort necessitates a simpler approach for realistic commercialization. In our previous work (Abghoui et al., Physical Chemistry Chemical Physics, 17 (2015) 4909), first-principles (DFT) calculations are used to identify transition metal nitride catalysts that show evidence of being able to produce ammonia electrochemically under small over-potential at ambient conditions. Among a wide range of transition metal nitrides, the (100) facets of rocksalt structure of VN and ZrN were explored as nitride (electro-) catalysts, which are able to suppress the hydrogen evolution reaction and most likely to increase the yield of ammonia production. In the current work and with similar approach, the catalytic activity of the (111) facets of mono-nitrides is investigated through Mars-van Krevelen (MVK) mechanism. This introduces new (electro-) catalysts for direct conversion of nitrogen to ammonia electrochemically at applied potentials of -0.60 V to -1.0 V vs. SHE. Possibility of ammonia formation is also explored via associative, dissociative and mixed associative-dissociative mechanisms on the clean surface of all these nitrides. Besides, stability of these catalysts against poisoning and decomposition is investigated. Upon exposure of the catalyst to atmosphere or electrochemical media, there is a possibility of oxide formation on the surface. The potential required to reduce this oxide layer to water is estimated as well. Results presented here show that both associative and dissociative pathways for ammonia formation is deactivated at the surface of these nitrides due to extremely weak adsorption of N2 on the surface and very high activation barriers of above 2.0 eV for nitrogen splitting, respectively. Therefore, the MVK mechanism is the dominant pathway for effective reduction of nitrogen to ammonia at ambient conditions on these nitride (electro-) catalysts. Hence, with the high abundance of atmospheric nitrogen and by using water as a proton source these promising catalysts could facilitate low-cost, high-yield ammonia production at ambient conditions, with significant benefits to the environment and economy.

Mo‐V‐Phosphoric Heteropoly Acids and Their Salts: Aqueous Solution Preparation – Challenges and Perspectives

AbstractVanadium‐containing heteropoly acids (HPAs) are effective acidic and oxidizing catalysts in various reactions. The existing wide application of such catalysts requires their safe, waste‐free, and easy preparation on a large scale. Unfortunately, the so‐calledether method, first suggested more than 100 years ago, is still mainly used for the purpose, producing a lot of harmful waste material. Nowadays environmental safety requirements necessitate revision of such preparation processes and searching for alternative methods of synthesis. At present, there exist a range of new methods for preparing HPAs, with a so‐calledperoxide methodseeming to be the most generally applicable one. For this reason, the aim of this review is to discuss some recent progress in obtaining aqueous solutions of Keggin and Wells–Dawson Mo‐V‐P HPAs and their salts. These solutions can be used as individual homogeneous oxidation catalysts, bifunctional catalysts for one‐pot acidic and oxidizing transformations, or precursors for preparing their heterogeneous analogues.

Electrochemical properties of LiNi0.6Co0.2Mn0.2O2 as cathode material for Li-ion batteries prepared by ultrasonic spray pyrolysis

A robust synthesis method based on spray pyrolysis and solid state reaction is proposed to prepare LiNi0.6Co0.2Mn0.2O2 as cathode material for Li-ion batteries. Spherical Ni–Co–Mn–O precursor powder is synthesized by spray pyrolysis from chlorides solution. Scanning electron microscopy (SEM) images show that the spherical Ni–Co–Mn–O precursor powder turned to submicron-sized LiNi0.6Co0.2Mn0.2O2 powder after solid-state reaction with LiOH at 850°C. The as-prepared cathode material delivers an initial discharge capacity of 160.8mAhg−1 and capacity retention of 90.8% after 100 cycles at 1C (1C=170mAg−1) between 2.8 and 4.3V. Besides, the powder also exhibits excellent rate capability. These excellent performances demonstrate that the introduced strategy is a promising alternative synthesis method for the production of layered cathode materials.

Gum Tragacanth-Mediated Synthesis of Nanocrystalline ZnO Powder for Use in Varistors

Zinc oxide nanopowders were synthesized by a sol–gel method with gum tragacanth and zinc nitrate as raw materials. Gum tragacanth was used as stabilizer to control the mobility of zinc cations and the growth of the nanopowders. Thermo-gravimetric analysis, x-ray diffraction, Fourier-transform infrared spectroscopy, transmission electron microscopy, energy dispersive x-ray spectroscopy, and scanning electron microscopy were used to characterize the as-prepared samples. Zinc oxide (ZnO) nanoparticles calcined at different temperatures had a hexagonal wurtzite structure with average particle size ranging from 32.29 nm to 42.83 nm. The crystallinity of ZnO nanoparticles was improved by increasing the calcination temperature. The density of ZnO varistor ceramics sintered at 1150°C for 2 h in air was 5.46 g/cm3, which was 97.5% of the theoretical density, their breakdown voltage was 4572 V/cm, and their nonlinear coefficient was ~16.8. This method can be used as an excellent alternative method for synthesis of ZnO nanoparticles with a plant extract as a raw material. Our experimental results show our method had the advantage of improving the electrical performance of ZnO varistors.

Non‐isocyanate polyurethanes: synthesis, properties, and applications

Conventional polyurethanes are typically obtained from polyisocyanates, polyols, and chain extenders. The main starting materials—isocyanates used in this process—raise severe health hazard concerns. Therefore, there is a growing demand for environment‐friendly processes and products. This review article summarizes progress that has been made in recent years in the development of alternative methods of polyurethane synthesis. In most of them, carbon dioxide is applied as a sustainable feedstock for polyurethane production directly or indirectly. The resulting non‐isocyanate polyurethanes are characterized by a solvent‐free synthesis, resistance to chemical degradation, 20% more wear resistance than conventional polyurethane, and can be applied on wet substrates and cured under cold conditions. Three general polymer synthetic methods, step‐growth polyaddition, polycondensation, and ring‐opening polymerization, are presented in the review. Much attention is given to the most popular and having potential industrial importance method of obtaining non‐isocyanate polyurethanes, poly(hydroxy‐urethane)s, based upon multicyclic carbonates and aliphatic amines. It is evident from the present review that considerable effort has been made during the last years to develop environmentally friendly methods of obtaining polyurethanes, especially those with the use of carbon dioxide or simple esters of carbonic acid. Copyright © 2015 John Wiley & Sons, Ltd.

Novel process for synthesis of nanocrystalline WC from wolframite ore

This paper describes the synthesis of nanocrystalline WC directly from the wolframite ore containing nearly 50% impurities in as received form. The mixture of wolframite ore, activated charcoal and magnesium is found to produce nanocrystalline WC by heating at 800°C in an autoclave. After the synthesis impurities were leached out using dilute HCl (1:1) and concentrated HF, unlike the conventional methods where prior removal of impurities is done. The reduction and carburization processes were studied by plotting Ellingham diagrams. The powders were characterized by X-ray diffraction and transmission electron microscopy (TEM). The lattice parameters were calculated from Rietveld analysis using Fullprof program. This is a simple and economical alternate method for synthesis of nanocrystalline WC.

Effects of Selenization Conditions on the Properties of Cu-In-Ga-Se Thin Films Prepared by Pulsed Laser Deposition

In this paper, Pulsed laser deposition (PLD) is attempted to be an alternative synthesis method for Cu-Ga-In (CIGS) thin films. Cu-In-Ga prefabricated metal films were grown on the quartz substrates by PLD method. Then the CIGS films with different Se content were synthesized by the post-selenization(Se)-annealing processes. The structure, element component proportion and optical properties of the CIGS films were investigated. The experimental results indicate that the CIGS films can be well obtained by the PLD method with Se-annealing. The performances of the CIGS films are much affect by the Se-annealing processes, including Se-annealing temperature, annealing time, and the way of Se-annealing. The CIGS films prepared by PLD method with Se-annealing present fine visible light absorption properties.

Atom-Economical Synthesis of the Versatile Ruthenium Precursor [TpRuCl(COD)] (Tp = Hydrotris(pyrazol-1-yl)borate) Discloses a Diamine Ligand Dealkylation Process

An atom-economical, more environmentally friendly alternative method of synthesis of the versatile complex [TpRuCl(COD)] (1) (Tp = hydrotris(pyrazol-1-yl)borate; COD = 1,5-cyclooctadiene) has been developed. Instead of starting from [RuHCl(COD)(NH2NMe2)3]+, 1 can be conveniently prepared by reaction of the derivative trans-[RuCl2(COD)(Me2NCH2CH2NHMe)] (2) with KTp in acetone at 55 °C. Compound 2, which has been structurally characterized by X-ray crystallography, results from an unexpected diamine dealkylation process which takes place in the course of the reaction of [{RuCl2(COD)}n] with tmeda (tmeda = Me2NCH2CH2NMe2) in toluene at 80 °C. This process had been overlooked in the literature, as compound 2 had been misidentified as cis-[RuCl2(COD)(tmeda)], and suggests that amine dealkylation might occur more commonly than previously anticipated.

Study on nanocomposite construction based on the multi-functional biotemplate self-assembled by the recombinant TMGMV coat protein for potential biomedical applications.

Nowadays there is a growing interest in bio-scaffolded nanoarchitectures. Rapid progress in nanobiotechnology and molecular biology has allowed the engineering of inorganic-binding peptides termed as genetically engineered polypeptides for inorganics (GEPIs) into self-assembling biological structures to facilitate the design of novel biomedical or bioimaging devices. Here we introduce a novel nanocomposite comprising a self-assembled protein scaffold based on a recombinant tobacco mild green mosaic tobamovirus (TMGMV) coat protein (CP) and the photocatalytic TiO2 nanoparticles attached to it, which may provide a generic method for materials engineering. A template containing a modified TMGMV CP (mCP) gene, with the first six C-terminal amino acid residues deleted to accommodate more foreign peptides and expressing a site-directed mutation of A123C for bioconjugation utility, and two genetically engineered mutants, Escherichia coli-based P-mCP-Ti7 containing a C-terminal TiO2 GEPI sequence of seven peptides (Ti7) and Hi5 insect cells-derived E-CP-Ti7-His6 C-terminally fused with Ti7+His6 tag were created. Expression vectors and protocols for enriching of the two CP variants were established and the resultant proteins were identified by western blot analysis. Their RNA-free self-assembling structures were analyzed by transmission electron microscopy (TEM) and immuno-gold labeling TEM analysis. Adherence of nanoparticles to the P-mCP-Ti7 induced protein scaffold was visualized by TEM analysis. Also discussed is the Cysteine thiol reactivity in bioconjugation reactions with the maleimide-functionalized porphyrin photosensitizers which can function as clinical photodynamic therapy agents. This study introduced a novel approach to producing an assembly-competent recombinant TMGMV CP, examined its ability to serve as a novel platform for the multivalent display of surface ligands and demonstrated an alternative method for nanodevice synthesis for nanobiotechnological applications by combining GEPIs-mediated immobilization with the controllability of self-assembling recombinant TMGMV CP.

Synthesis of Hydraulically Active Calcium Silicates Produced by Combustion Methods

ABSTRACTPortland cement is synthesized from a mixture of limestone and clay at high temperature (1450 °C) via a conventional process (solid-phase synthesis), in which partial fusion of raw materials and the formation of clinker nodules are produced. The clinker is mixed with a small percentage of gypsum and ground together to make the cement. This synthesis process holds the cement industry accountable for 5–8% of global anthropogenic CO2 emissions. The production of a ton of cement emits between 0.62 and 0.97 tons of CO2 into the atmosphere, depending on the processing plant. Furthermore, the use of fossil fuels in cement production is another important factor in the environmental impact of this industry. The production of 1 ton of clinker consumes approximately 5.86 GJ per tons of clinker produced in wet processes and 3.35 GJ per tons of clinker produced by dry process. Some researches have reported the possibility to obtain silicate and aluminate cements by alternative synthesis methods, which optimize both time and temperature, such as Pechini method, sol-gel method and microwave assisted method. The combustion methods, another alternative, are chemical redox processes in which the use of chemical precursors and organic fuels at high temperature generate a self-sustaining fastwave. The said wave is characterized by the fact that once the initial exothermic reaction starts, it generates a reaction wave (0.1–10 cm/s) at high temperature (1000–3000 °C) that propagates, in a self-sustaining way, through the heterogeneous mixture which leads to the formation of the solid material. For this reason, and the irreplaceable role of cement in the construction industry, this paper shows the advances in the production of silicates, similar to those found in the Portland cement, by combustion synthesis method.This paper shows the production of calcium silicates similar to the silicates of Portland cement, by combustion synthesis. Thermal analysis and XRD techniques were used to compare the syhthetized silicates with alite and belite of Portland cement.

CdSe Nanoparticles with Clean Surfaces: Gas Phase Synthesis and Optical Properties

CdSe nanoparticles (NPs) were generated in gas phase with a magnetron plasma gas aggregation cluster beam source. Coagulation-free CdSe nanocrystals with very clean particle surface and interface, as well as a fairly uniform spatial distribution were obtained. The deposited NPs have a good dispersity with a mean diameter of about 4.8nm. A strong photoluminescence band corresponding to the near- band-edge transition of the CdSe NPs was observed. The CdSe NP films show a significant photoconductance induced by laser irradiation. With an applied bias voltage of 10V, the photo- induced current can be as high as 0.4mA under 0.01mW/mm 2 405nm laser illumination. Our approach offers an alternative method for CdSe NP synthesis, which has the advantages such as high purity, good process and product control, as well as mass production, as compared to the existing methods.

Large-scale and patternable graphene: direct transformation of amorphous carbon film into graphene/graphite on insulators via Cu mediation engineering and its application to all-carbon based devices.

Chemical vapour deposition of graphene was the preferred way to synthesize graphene for multiple applications. However, several problems related to transfer processes, such as wrinkles, cleanness and scratches, have limited its application at the industrial scale. Intense research was triggered into developing alternative synthesis methods to directly deposit graphene on insulators at low cost with high uniformity and large area. In this work, we demonstrate a new concept to directly achieve growth of graphene on non-metal substrates. By exposing an amorphous carbon (a-C) film in Cu gaseous molecules after annealing at 850 °C, the carbon (a-C) film surprisingly undergoes a noticeable transformation to crystalline graphene. Furthermore, the thickness of graphene could be controlled, depending on the thickness of the pre-deposited a-C film. The transformation mechanism was investigated and explained in detail. This approach enables development of a one-step process to fabricate electrical devices made of all carbon material, highlighting the uniqueness of the novel approach for developing graphene electronic devices. Interestingly, the carbon electrodes made directly on the graphene layer by our approach offer a good ohmic contact compared with the Schottky barriers usually observed on graphene devices using metals as electrodes.

KOH self-templating synthesis of three-dimensional hierarchical porous carbon materials for high performance supercapacitors

We report a KOH self-templating synthesis of three-dimensional hierarchical porous carbon using resol as the precursor and KOH as both the template and activating agent. The resulting resol-derived porous carbon (RPC) exhibits a high surface area (up to 2700 m2 g−1) and well-interconnected macropores with micropores and mesopores decorated on the carbon walls. Consequently, the RPC shows low internal resistance, high specific capacitance, good rate capability and excellent cycling stability in 6 M KOH as a supercapacitor electrode. Because of its easy fabrication and low cost, it offers a good alternative method for synthesis of carbon electrodes for energy-storage devices such as Li-ion batteries, fuel cells and supercapacitors.

Analysis of the carbonatation process of nanosized Ca(OH)2particles synthesized by exchange ion process

Calcium hydroxide nanoparticles in hydro-alcoholic dispersion are introduced as an effective conservation material for carbonatic substrates, thanks to their promising carbonation efficacy in ambient air. However, the current methods to synthesize such dispersions are characterized by some drawbacks that strongly limit applications. The aim of this work is to investigate structure, morphology and carbonatation efficacy of calcium hydroxide nanoparticles in aqueous suspension, produced by our alternative and original method of synthesis, based on the use of an ion exchange resin. Actually, the method allows to produce pure, nanosized and reactive Ca(OH)2particles, operating at room temperature, without intermediate steps to eliminate undesired compounds, drastically reducing the time, and with a potential ability to be easily scaled up to provide larger amounts of nanoparticles. By X-ray diffraction techniques, we have investigated reactivity of the synthesized nanoparticles, in relation to the carbonatation process in air, by varying the suspension concentration. Preliminary results on the kinetics of the carbonatation process are presented too. Morphological analysis, performed by transmission electron microscopy, shows both hexagonal particles, often quarries, of side dimensions less than 100 nm, and spherical particles (<50 nm).