Synthesis of Gold Nanoparticles over CoAl Mixed Oxide for Ethanol Oxidation Reaction.

Catalytic total oxidation is an effective technique for the treatment of industrial VOCs principally resulting from industrial processes using solvents and usually containing mono-aromatics (BTEX) and oxygenated compounds (acetone, ethanol, butanone). The aim of this work is to deposit gold nanoparticles on CoAl mixed oxide issued from layered double hydroxide (LDH) precursor by using the deposition precipitation (DP) method, which is applied with two modifications, labeled method (A) and method (B), in order to enhance the interaction of the HAuCl4 precursor with the support. Method (A) involves the hydrolysis of the HAuCl4 precursor after addition of the support, while in method (B), the gold precursor is hydrolyzed before adding the support. The two methods were applied using as support the CoAl mixed oxide and the LDH precursor. Samples were characterized by several physical chemical techniques and evaluated for ethanol total oxidation. Method (B) allowed the ethanol oxidation activity to be enhanced for the resulting Au/CoAlOx catalysts thanks to the high surface concentration of Co2+ and improved reducibility at low temperature. The presence of gold permits to minimize the formation of by-products, notably, methanol, allowed for a total oxidation of ethanol at lower temperature than the corresponding support.

Highly Functionalized SWCNTs with a Dopamine Derivative as a Support for Pd Nanoparticles: A Recyclable Catalyst for the Reduction of Nitro Compounds and the Heck Reaction.

Single-walled carbon nanotubes (SWCNTs) were functionalized with a dopamine derivative in which the amine group was converted to azide (dopamine azide). The direct reaction of SWCNTs and dopamine azide in o-dichlorobenzene at high temperature (160 °C) led to very highly functionalized CNTs (≈60 wt.%). Surprisingly, despite this high degree of functionalization, Raman spectroscopy detected a low disruption of the π-network of the carbonaceous support. This finding was justified by the rehybridization from sp3 to sp2 of the sidewall carbon atoms of CNTs involved in the functionalization process. Further characterization by means of different techniques such as X-ray photoelectron spectroscopy (XPS) analysis and transmission electron microscopy (TEM) allowed to shed some light on the chemical composition and morphology of the obtained material. Moreover, the estimation of the total content of phenolic units and their reducing potential after CNTs functionalization was also assessed using Folin and Ciocalteu and 2,2-diphenyl-1-picryl hydrazide (DPPH) assays. The functionalization of CNTs was exploited to immobilize palladium(II) species that were subsequently reduced with NaBH4 leading to the formation of Pd nanoparticles (NPs). The so obtained hybrid material was used as a recyclable heterogeneous catalyst for the reduction of nitro compounds and the Heck reaction.

A Prato Tour on Carbon Nanotubes: Raman Insights.

The functionalisation of carbon nanotubes has been instrumental in broadening its application field, allowing especially its use in biological studies. Although numerous covalent and non-covalent functionalisation methods have been described, the characterisation of the final materials has always been an added challenge. Among the various techniques available, Raman spectroscopy is one of the most widely used to determine the covalent functionalisation of these species. However, Raman spectroscopy is not a quantitative technique, and no studies are reported comparing its performance when the same number of functional groups are added but using completely different reactions. In this work, we have experimentally and theoretically studied the functionalisation of carbon nanotubes using two of the most commonly used reactions: 1,3-dipolar cycloaddition of azomethylene ylides and diazonium-based radical addition. The number of groups introduced onto the tubes by these reactions has been determined by different characterisation techniques. The results of this study support the idea that data obtained by Raman spectra are only helpful for comparing functionalisations produced using the same type of reaction. However, they should be carefully analysed when comparing functionalisations produced using different reaction types.

Peculiar Properties of the La0.25Ba0.25Sr0.5Co0.8Fe0.2O3-δ Perovskite as Oxygen Reduction Electrocatalyst.

The electrochemical reduction of molecular oxygen is a fundamental process in Solid Oxide Fuel Cells and requires high efficiency cathode materials. Two La0.25Ba0.25Sr0.5Co0.8Fe0.2O3-δ-based perovskite compounds were prepared by solution combustion synthesis, and characterized for their structural, microstructural, surface, redox and electrochemical properties as potential cathodes in comparison with Ba0.5Sr0.5Co0.8Fe0.2O3-δ and La0.5Sr0.5Co0.8Fe0.2O3-δ perovskites. Results highlighted that calcination at 900 °C led to a "bi-perovskite heterostructure", where two different perovskite structures coexist, whereas at higher calcination temperatures a single-phase perovskite was formed. The results showed the effectiveness of the preparation procedures in co-doping the A-site of perovskites with barium and lanthanum as a strategy to optimize the cathode's properties. The formation of nanometric heterostructure co-doped in the A-site evidenced an improvement in oxygen vacancies' availability and in the redox properties, which promoted both processes: oxygen adsorption and oxygen ions drift, through the cathode material, to the electrolyte. A reduction in the total resistance was observed in the case of heterostructured material.

TiO2/Ag2O immobilized on cellulose paper: A new floating system for enhanced photocatalytic and antibacterial activities.

Paper-TiO2-Ag2O floating photocatalysts were produced under mild condition and their photocatalytic activity for the degradation of aromatic amine under sunlight stimulant was investigated. Characterizations by Raman, XRD, XPS, DRS and PL confirmed the presence of TiO2 and Ag2O, and the morphology of the appended TiO2/Ag2O layer was probed by FE-SEM. The photocatalytic activity of the prepared samples was investigated by the degradation of aniline (AN) in water under simulated sun-light illumination and constrained conditions, i.e. non-stirring and non-oxygenation. The presence of Ag2O combined with TiO2 was shown to improve the resistance of paper to bacteria attack, thus increasing the durability of the photocatalyst. Thanks to its hydrophobic character, the paper-TiO2-Ag2O NPs can be employed as useful floating photocatalyst and can be reused in continuous cycles.

Fullerene-ionic-liquid conjugates: a new class of hybrid materials with unprecedented properties.

A modular approach has been followed for the synthesis of a series of fullerene-ionic-liquid (IL) hybrids in which the number of IL moieties (two or twelve), anion, and cation have been varied. The combination of C60 and IL give rise to new unique properties in the conjugates such as solubility in water, which was higher than 800 mg mL(-1) in several cases. In addition, one of the C60 -IL hybrids has been employed for the immobilization of palladium nanoparticles through ion exchange followed by reduction with sodium borohydride. Surprisingly, during the reduction several carbon nanostructures were formed that comprised nano-onions and nanocages with few-layer graphene sidewalls, which have been characterized by means of thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy/energy-dispersive X-ray analysis (SEM-EDAX), and high-resolution transmission electron microscopy (HRTEM). Finally, the material thus obtained was successfully applied as catalyst in Suzuki and Mizoroki-Heck reactions in a concentration of just 0.2 mol %. In the former process it was recyclable for five runs with no loss in activity.

Palladium local structure of La(1-x)Sr(x)Co(1-y)Fe(y-0.03)Pd(0.03)O(3-δ) perovskites synthesized using a one pot citrate method.

Nanostructured La1-xSrxCo1-yFey-0.03Pd0.03O3-δ (LSCF-Pd) perovskites with fixed La-Sr composition (x = 0.4) and two different Fe contents (y = 0.2 and 0.8) were successfully synthesized using a one pot citrate method starting from nitrates of the metal cations. Pd-free La1-xSrxCo1-yFeyO3-δ (LSCF) systems were prepared for comparison. LSCF powders were calcined at 1300 °C and characterized by XRD and Rietveld refinement, EXAFS, XPS, TPR analyses. Promotion of La0.6Sr0.4Co0.8Fe0.2O3-δ and of La0.6Sr0.4Co0.2Fe0.8O3-δ by incorporation of palladium was evidenced by solving the local environment of Pd using EXAFS spectroscopy. XPS analyses, in agreement with TPR measurements, demonstrated an increase of superficial oxygen vacancies, the variation being much more pronounced in the La0.6Sr0.4Co0.8Fe0.17Pd0.03O3-δ sample. It is argued that this increase is associated with the introduction of Pd in the B site of LSCF. Moreover, ionic Pd(4+) was detected as the only palladium species on the perovskite surface, whereas Pd metal clusters of about 2 nm, not detectable in the surface, are embedded in the matrix and strongly interact with the bulk. This result has strong consequences in the synthesis and in the design of new perovskite materials that can be used as cathodes in fuel cell application at intermediate operating temperatures.

Beneficial effect of cerium excess on in situ grown Sr0.86Ce0.14FeO3-CeO2 thermocatalysts for the degradation of bisphenol A.

Ce-doped SrFeO3 perovskite-type compounds are known as good thermocatalysts for the abatement of wastewater contaminants of emerging concern. In this work, Sr0.86Ce0.14FeO3-CeO2 perovskite-oxide systems with increasing amounts of cerium excess (0, 5, 10 and 15 mol% Ce), with respect to its maximum solubility in the perovskite, were prepared in one-pot by solution combustion synthesis and the effects of cerium excess on the chemical physical properties and thermocatalytic activity in the bisphenol A degradation were evaluated. The powders were characterized by powder X-ray diffraction combined with Rietveld refinement, X-ray photoelectron spectroscopy, thermal gravimetry, temperature programmed reduction, nitrogen adsorption, scanning electron microscopy and energy dispersive X-ray spectroscopy techniques. Results highlight that the perovskite structural, redox, surface, and morphological properties are affected by the in situ co-growth of the main perovskite phase and ceria and that a larger cerium excess has a beneficial effect on the thermocatalytic performance of the perovskite oxide-ceria biphasic system, although ceria is not active as a thermocatalyst itself. Perovskite properties and performance are enhanced by the tetragonal distortion induced by the introduction of cerium excess in the synthesis. It is supposed that a larger oxygen mobility and an easier reducibility are among the most relevant features that contribute to superior thermocatalytic properties of these perovskite oxide-based systems. These results also suggest new perspectives in the nanocomposite preparation and their catalytic applications.

Batch and Flow Green Microwave-Assisted Catalytic Conversion Of Levulinic Acid to Pyrrolidones.

This paper reports a new sustainable protocol for the microwave-assisted catalytic conversion of levulinic acid into N-substituted pyrrolidones over tailor-made mono (Pd, Au) or bimetallic (PdAu) catalysts supported on either highly mesoporous silica (HMS) or titania-doped HMS, exploiting the advantages of dielectric heating. MW-assisted reductive aminations of levulinic acid with several amines were first optimized in batch mode under hydrogen pressure (5 bar) in solvent-free conditions. Good-to-excellent yields were recorded at 150 °C in 90 min over the PdTiHMS and PdAuTiHMS, that proved recyclable and almost completely stable after six reaction cycles. Aiming to scale-up this protocol, a MW-assisted flow reactor was used in combination with different green solvents. Cyclopentyl methyl ether (CPME) provided a 99 % yield of N-(4-methoxyphenyl) pyrrolidin-2-one at 150 °C over PdTiHMS. The described MW-assisted flow synthesis proves to be a safe procedure suitable for further industrial applications, while averting the use of toxic organic solvents.

Ni-Based SBA-15 Catalysts Modified with CeMnOx for CO2 Valorization via Dry Reforming of Methane: Effect of Composition on Modulating Activity and H2/CO Ratio.

Dry reforming of methane with ratio CH4/CO2 = 1 is studied using supported Ni catalysts on SBA-15 modified by CeMnOx mixed oxides with different Ce/Mn ratios (0.25, 1 and 9). The obtained samples are characterized by wide-angle XRD, SAXS, N2 sorption, TPR-H2, TEM, UV-vis and Raman spectroscopies. The SBA-15 modification with CeMnOx decreases the sizes of NiO nanoparticles and enhances the NiO-support interaction. When Ce/Mn = 9, the NiO forms small particles on the surface of large CeO2 particles and/or interacts with CeO2, forming mixed phases. The best catalytic performance (at 650 °C, CH4 and CO2 conversions are 51 and 69%, respectively) is achieved over the Ni/CeMnOx/SBA-15 (9:1) catalyst. The peculiar CeMnOx composition (Ce/Mn = 9) also improves the catalyst stability: In a 24 h stability test, the CH4 conversion decreases by 18 rel.% as compared to a 30 rel.% decrease for unmodified catalyst. The enhanced catalytic stability of Ni/CeMnOx/SBA-15 (9:1) is attributed to the high concentration of reactive peroxo (O-) and superoxo (O2-) species that significantly lower the amount of coke in comparison with Ni-SBA-15 unmodified catalyst (weight loss of 2.7% vs. 42.2%). Ni-SBA-15 modified with equimolar Ce/Mn ratio or Mn excess is less performing. Ni/CeMnOx/SBA-15 (1:4) with the highest content of manganese shows the minimum conversions of reagents in the entire temperature range (X(CO2) = 4-36%, X(CH4) = 8-58%). This finding is possibly attributed to the presence of manganese oxide, which decorates the Ni particles due to its redistribution at the preparation stage.

Multiwalled carbon nanotubes drive the activity of metal@oxide core-shell catalysts in modular nanocomposites.

Rational nanostructure manipulation has been used to prepare nanocomposites in which multiwalled carbon nanotubes (MWCNTs) were embedded inside mesoporous layers of oxides (TiO(2), ZrO(2), or CeO(2)), which in turn contained dispersed metal nanoparticles (Pd or Pt). We show that the MWCNTs induce the crystallization of the oxide layer at room temperature and that the mesoporous oxide shell allows the particles to be accessible for catalytic reactions. In contrast to samples prepared in the absence of MWCNTs, both the activity and the stability of core-shell catalysts is largely enhanced, resulting in nanocomposites with remarkable performance for the water-gas-shift reaction, photocatalytic reforming of methanol, and Suzuki coupling. The modular approach shown here demonstrates that high-performance catalytic materials can be obtained through the precise organization of nanoscale building blocks.

Dehydration of Fructose to 5-HMF over Acidic TiO2 Catalysts.

Different solid sulfonic titania-based catalysts were investigated for the hydrothermal dehydration of fructose to 5-hydroxymethylfurfural (5-HMF). The catalytic behavior of the materials was evaluated in terms of fructose conversion and selectivity to 5-HMF. The surface and structural properties of the catalysts were investigated by means of X-ray diffraction (XRD), N2 adsorption isotherms, thermo-gravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and acid capacity measurements. Special attention was focused on the reaction conditions, both in terms of 5-HMF selectivity and the sustainability of the process, choosing water as the solvent. Among the various process condition studied, TiO2-SO3H catalyzed a complete conversion (99%) of 1.1M fructose and 5-HMF selectivity (50%) and yield (50%) at 165 °C. An important improvement of the HMF selectivity (71%) was achieved when the reaction was carried out by using a lower fructose concentration (0.1M) and lower temperature (140 °C). The catalytic activities of the materials were related to their acid capacities as much as their textural properties. In particular, a counterbalance between the acidity and the structure of the pores in which the catalytic sites are located, results in the key issue for switch the selectivity towards the achievement of 5-HMF.

Microwave-Assisted Glycerol Etherification Over Sulfonic Acid Catalysts.

Glycerol is the main by-product of biodiesel production. For this reason, its valorization into value-added products, by using green procedures, represents an important goal. Different sulfonic acid silica- or titania-based catalysts were prepared, characterized and tested in the glycerol etherification process, assisted by microwaves, in order to obtain biodiesel additives. The surface and structural properties of the catalysts were investigated by means of N2 adsorption isotherms, thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and acid capacity measurements by X-Ray Fluorescence Spectroscopy (XRF). The best performance in terms of activity was achieved in the presence of the sulfonic function directly linked to the amorphous silica. By the correlation of the structure properties of the materials and their activity, the performance of the catalysts was shown to be influenced mainly by the surface area, pore volume and acidity. Recycling experiments performed over the most active systems showed that the sulfonic silica-based materials maintained their performance during several cycles.

Sustainable Recycling of Insoluble Rust Waste for the Synthesis of Iron-Containing Perovskite-Type Catalysts.

Insoluble rust waste from the scraping of rusted iron-containing materials represents a cheap, eco-friendly, and available source of iron. LaFeO3 perovskite-type powders were successfully prepared by solution combustion synthesis using rust waste from an electricity transmission tower manufacturer. Solution combustion synthesis enabled introduction of this insoluble iron precursor directly into the final product, bypassing complex extraction procedures. Catalytic activity in the propylene oxidation of the waste-derived LaFeO3 with stoichiometric Fe/La ratio was almost identical to the commercial iron nitrate-derived LaFeO3, thus demonstrating the viability of this recycling solution. The amount of waste iron precursor was varied and its effect on the powder properties was investigated. A lesser stoichiometric amount of precursor produced a LaFeO3-La2O3 binary system, whereas a higher stoichiometric amount led to a LaFeO3-Fe2O3 binary system. Catalytic activity of iron-rich compositions in the propylene oxidation was only slightly lower than the stoichiometric one, whereas iron-poor compositions were much less active. This eco-friendly methodology can be easily extended to other iron perovskites with different chemical compositions and to other iron-containing compounds.

Salmeterol Xinafoate (SX) loaded into mucoadhesive solid lipid microparticles for COPD treatment.

Chronic obstructive pulmonary disease (COPD) is one of the main health problems worldwide. It is characterised by chronic inflammation in the lungs that leads to progressive, chronic, largely irreversible airflow obstruction. The use of long-acting ß agonists remain today the frontline treatment for COPD with the aim of minimizing side effects and enhancing therapeutic usefulness. To this purpose, in this paper, mucoadhesive solid lipid microparticles (SLMs) containing a long-acting ß-2 agonist, Salmeterol Xinafoate (SX) were prepared, characterised (size, z-potential, aerodynamic diameter, turbidimetric evaluations, drug loading and entrapping efficiency) and tested in a model of bronchial epithelial cells. It was demonstrated that the incorporation of SX into SLMs led to the production of particles suitable for inhalation and more efficient than the free molecule at increasing the cAMP expression in bronchial epithelial cells. In conclusion, the prepared systems, due to their aerodynamic behaviour and mucoadhesive properties, could improve the retention time of SX in the lung epithelium and its therapeutic effect, thus representing a good strategy for the treatment of COPD patients.

Amorphous boron-doped sodium titanates hydrates: Efficient and reusable adsorbents for the removal of Pb2+ from water.

Amorphous titanium hydroxide and boron-doped (B-doped) sodium titanates hydrates were synthetized and used as adsorbents for the removal of Pb2+ from water. The use of sodium borohydride (NaBH4) and titanium(IV) isopropoxide (TTIP) as precursors permits a very easy synthesis of B-doped adsorbents at 298K. The new adsorbent materials were first chemically characterized (XRD, XPS, SEM, DRIFT and elemental analysis) and then tested in Pb2+ adsorption batch experiments, in order to define kinetics and equilibrium studies. The nature of interaction between such sorbent materials and Pb2+ was also well defined: besides a pure adsorption due to hydroxyl interaction functionalities, there is also an ionic exchange between Pb2+ and sodium ions even working at pH 4.4. Langmuir model presented the best fitting with a maximum adsorption capacity up to 385mg/g. The effect of solution pH and common ions (i.e. Na+, Ca2+ and Mg2+) onto Pb2+ sorption were also investigated. Finally, recovery was positively conducted using EDTA. Very efficient adsorption (>99.9%) was verified even using tap water spiked with traces of Pb2+ (50ppb).

Single-Walled Carbon Nanotube-Polyamidoamine Dendrimer Hybrids for Heterogeneous Catalysis.

We report the synthesis and catalytic properties of single-walled carbon nanotube-polyamidoamine dendrimers hybrids (SWCNT-PAMAM), prepared via a convergent strategy. The direct reaction of cystamine-based PAMAM dendrimers (generations 2.5 and 3.0) with pristine SWCNTs in refluxing toluene, followed by immobilization and reduction of [PdCl4](2-), led to the formation of highly dispersed small palladium nanoparticles homogeneously confined throughout the nanotube length. One of these functional materials proved to be an efficient catalyst in Suzuki and Heck reactions, able to promote the above processes down to 0.002 mol % showing a turnover number (TON) of 48 000 and a turnover frequency (TOF) of 566 000 h(-1). In addition, the hybrid material could be recovered and recycled for up to 6 times. No leaching of the metal has been detected during the Suzuki coupling. Additional experiments carried out on the spent catalyst permitted to suggest that a "release and catch" mechanism is operative in both reactions, although during Heck reaction small catalytically active soluble Pd species are also present.

Highly Loaded Multi-Walled Carbon Nanotubes Non-Covalently Modified with a Bis-Imidazolium Salt and their Use as Catalyst Supports.

The surfaces of multi-walled carbon nanotubes (MWCNTs) were non-covalently modified using two bis-imidazolium dibromide derivatives having phenyl or pyrene groups. Due to the presence of the two pyrene groups the bis(pyren-1-ylmethylimidazolium) dibromide derivative was immobilised at a loading of about 15-16 wt %, whereas only <3 wt % of the phenyl derivative was immobilised. The presence of the two imidazolium cations helped the immobilisation of tetrachloropalladate ions after exchange with bromide ions. Tetrachloropalladate was used as pre-catalyst in several Suzuki-Miyaura carbon-carbon cross-coupling reactions in water or water/ethanol at 50 °C in only 0.1 mol % and compared with the non-supported pre-catalyst. The MWCNT-supported material was used in five consecutive cycles of the Suzuki-Miyaura reaction. Recycling using phenylboronic acid and 4-bromobenzaldehyde in water/ethanol was achieved with only a minor loss in activity. HRTEM images clearly showed the presence of the bis(pyren-1-ylmethylimidazolium) derivative on the sidewalls of MWCNTs.

A nanocellulose-dye conjugate for multi-format optical pH-sensing.

A pH-sensitive azo-dye covalently grafted onto cellulose nanocrystals yields nanostructured optodes in the form of membranes, sticks, and water-based inks for optical pH detection.