Ecotoxicological Effects of Titanium Aluminum Carbide Composites on Biochemical and Metabolic Parameters of Galleria mellonella.

Metal composites have been extensively used in various fields such as automotive industry, medicine and pharmacy. However, the high exposure of these chemicals may have an adverse effect on the living organisms. In this study, the effect of titanium aluminum carbide (Ti3AlC2) on the model organism Galleria mellonella was investigated. The change in the metabolic enzymes such as alanine transferase, aspartate transferase, gamma-glutamyl transferase, lactate dehydrogenase, amylase, creatine kinase, alkaline phosphatase in the hemolymph of G. mellonella which was exposed to Ti3AlC2 was determined. The contents of the bilirubin, albumin, uric acid and the total protein were also measured after the Ti3AlC2 exposure on the model organism. The results of our study clearly indicate that Ti3AlC2 has adverse effects on the model organism G. mellonella.

Reducible tungsten(VI) oxide-supported ruthenium(0) nanoparticles: highly active catalyst for hydrolytic dehydrogenation of ammonia borane.

Reducible WO3 powder with a mean diameter of 100 nm is used as support to stabilize ruthenium(0) nanoparticles. Ruthenium(0) nanoparticles are obtained by NaBH4 reduction of ruthenium(III) precursor on the surface of WO3 support at room temperature. Ruthenium(0) nanoparticles are uniformly dispersed on the surface of tungsten(VI) oxide. The obtained Ru0/WO3 nanoparticles are found to be active catalysts in hydrolytic dehydrogenation of ammonia borane. The turnover frequency (TOF) values of the Ru0/WO3 nanocatalysts with the metal loading of 1.0%, 2.0%, and 3.0% wt. Ru are 122, 106, and 83 min-1, respectively, in releasing hydrogen gas from the hydrolysis of ammonia borane at 25.0 °C. As the Ru0/WO3 (1.0% wt. Ru) nanocatalyst with an average particle size of 2.6 nm provides the highest activity among them, it is extensively investigated. Although the Ru0/WO3 (1.0% wt. Ru) nanocatalyst is not magnetically separable, it has extremely high reusability in the hydrolysis reaction as it preserves 100% of initial catalytic activity even after the 5th run of hydrolysis. The high activity and reusability of Ru0/WO3 (1.0% wt. Ru) nanocatalyst are attributed to the favorable metal-support interaction between the ruthenium(0) nanoparticles and the reducible tungsten(VI) oxide. The high catalytic activity and high stability of Ru0/WO3 nanoparticles increase the catalytic efficiency of precious ruthenium in hydrolytic dehydrogenation of ammonia borane.

Palladium nanoparticles supported on cobalt(II,III) oxide nanocatalyst: High reusability and outstanding catalytic activity in hydrolytic dehydrogenation of ammonia borane.

A new palladium(0) nanocatalyst is developed to enhance the catalytic efficiency of precious metal catalysts in hydrogen generation from the hydrolytic dehydrogenation of ammonia borane. Magnetically separable Pd0/Co3O4 nanocatalyst can readily be obtained by the reduction of palladium(II) cations impregnated on cobalt(II, III) oxide at room temperature. The obtained Pd0/Co3O4 nanocatalyst with 0.25% wt. palladium loading has outstanding catalytic activity with a record turnover frequency of 3048 min-1 in the releasing H2 from the hydrolysis of ammonia borane at 25.0 °C. They also provide outstanding reusability even after the tenth run of the hydrolysis of ammonia borane at 25.0 °C. The high activity and superb stability of magnetically isolable Pd0/Co3O4 nanoparticles are attributed to the favorable interaction of palladium with the surface of reducible cobalt oxide.

Magnetically separable nickel ferrite supported palladium nanoparticles: Highly reusable catalyst in Sonogashira cross-coupling reaction.

There is an increasing attention in developing highly efficient and reusable palladium-based catalysts used for the coupling reactions due to the high cost of palladium metal salts. Magnetically separable palladium nanoparticles have a high potential to be used as catalysts in numerous organic reactions due to their facile separation from the reaction medium by an external magnet. Herein, NiFe2O4 supported palladium nanoparticles (Pd/NiFe2O4) were successfully prepared by impregnation and reduction method in water and used as catalysts for Sonogashira cross-coupling reactions. Magnetically separable Pd/NiFe2O4 catalysts were found to be highly active and reusable in this reaction. Pd/NiFe2O4 provided an outstanding turnover frequency value (106.4 h-1) in the reaction between phenylacetylene and iodobenzene in ethanol at 70 °C and it was also found to be highly active in the water. Magnetically separable Pd/NiFe2O4 exhibited high catalytic performance even after the tenth use in this reaction.

Magnetically Isolable Pt0/Co3O4 Nanocatalysts: Outstanding Catalytic Activity and High Reusability in Hydrolytic Dehydrogenation of Ammonia Borane.

The development of a new platinum nanocatalyst to maximize the catalytic efficiency of the precious noble metal catalyst in releasing hydrogen from ammonia borane (AB) is reported. Platinum(0) nanoparticles are impregnated on a reducible cobalt(II,III) oxide surface, forming magnetically isolable Pt0/Co3O4 nanocatalysts, which have (i) superb catalytic activity providing a record turnover frequency (TOF) of 4366 min-1 for hydrogen evolution from the hydrolysis of AB at room temperature and (ii) excellent reusability, retaining the complete catalytic activity even after the 10th run of hydrolysis reaction. The outstanding activity and stability of the catalyst can be ascribed to the strong interaction between the platinum(0) nanoparticles and reducible cobalt oxide, which is supported by the results of XPS analysis. Pt0/Co3O4 exhibits the highest TOF among the reported platinum-nanocatalysts developed for hydrogen generation from the hydrolysis of AB.

Cobalt ferrite supported platinum nanoparticles: Superb catalytic activity and outstanding reusability in hydrogen generation from the hydrolysis of ammonia borane.

In this work, platinum(0) nanoparticles are deposited on the surface of magnetic cobalt ferrite forming magnetically separable Pt0/CoFe2O4 nanoparticles, which are efficient catalysts in H2 generation from the hydrolysis of ammonia borane. Catalytic activity of Pt0/CoFe2O4 nanoparticles decreases with the increasing platinum loading, parallel to the average particle size. Pt0/CoFe2O4 (0.23% wt. Pt) nanoparticles have an average diameter of 2.30 ± 0.47 nm and show an extraordinary turnover frequency of 3628 min-1 in releasing 3.0 equivalent H2 per mole of ammonia borane from the hydrolysis at 25.0 °C. Moreover, the magnetically separable Pt0/CoFe2O4 nanoparticles possess high reusability retaining 100% of their initial catalytic activity even after ten runs of hydrolysis. The superb catalytic activity and outstanding reusability make the Pt0/CoFe2O4 nanoparticles very attractive catalysts for the hydrogen generation systems in portable and stationary fuel cell applications.

Magnetically separable rhodium nanoparticles as catalysts for releasing hydrogen from the hydrolysis of ammonia borane.

Magnetically separable catalysts attract considerable attention in catalysis due to their facile separation from the reaction medium. This propensity is crucial for efficient multiple use of precious noble metal nanoparticles in catalysis. In fact, the isolation of catalysts from the reaction medium by filtration and washing results usually in the loss of huge amount of activity in the subsequent run of catalysis. Although many transition metal nanoparticle catalysts have been reported for the H2 generation from the hydrolysis of ammonia borane, there is no study reporting the magnetically separable rhodium based catalysts for the hydrolytic dehydrogenation of ammonia borane. Here, we report the preparation of rhodium(0) nanoparticles supported on the surface of Fe3O4 and CoFe2O4 magnetic nanopowders as the first example of magnetically separable rhodium nanocatalysts. The resulting magnetically separable Rh0/Fe3O4 and Rh0/CoFe2O4 nanoparticles are highly active, long-lived and reusable catalysts in H2 generation from the hydrolysis of ammonia borane providing a turnover frequency value of 273 and 720  min-1, respectively, at 25.0 ±â€¯0.1 °C. These magnetically separable catalysts show high reusability and long-term stability in the hydrolysis reaction. They retain their complete initial activity even after the 5th use releasing exactly 3.0 equivalent H2 gas per mole of ammonia borane. The long-term stability tests show that Rh0/Fe3O4 and Rh0/CoFe2O4 nanoparticles provide a total turnover number of 125,000 and 245,000, respectively, in releasing H2 from the hydrolysis of ammonia borane at room temperature. The long term stability and reusability of magnetically separable Rh0/Fe3O4 and Rh0/CoFe2O4 nanoparticles make them attractive catalysts for hydrogen generation in fuel cell applications.

Noble metal nanoparticles supported on activated carbon: Highly recyclable catalysts in hydrogen generation from the hydrolysis of ammonia borane.

Noble metal nanoparticles including rhodium, ruthenium and palladium have been extensively used in catalysis field. Since their limited abundance and high cost, many methods have been developed to obtain highly active and recyclable catalysts. In this work, Rh3+, Ru3+, Pd2+ ions were impregnated on activated carbon derived from pumpkin stalk in distilled water and then reduced with sodium borohydride to form Rh0, Ru0, Pd0 nanoparticles on the surface of carbon. The analyses show that these nanoparticles were successfully dispersed on the activated carbon. Rh0, Ru0 and Pd0 nanoparticles on activated carbon provide a turnover frequency value of 188 min-1, 235 min-1 and 40 min-1, respectively, at 25.0 ±â€¯0.1 °C. They preserve their activity even after multiple use in H2 generation from the hydrolysis of ammonia borane.

Ceria supported ruthenium(0) nanoparticles: Highly efficient catalysts in oxygen evolution reaction.

Ruthenium(0) nanoparticles were successfully prepared on the surface of ceria (Ru0/CeO2) and used as catalysts on glassy carbon electrode (GCE) in oxygen evolution reaction (OER) from water electrolysis at room temperature. Ru0/CeO2 on GCE exhibits high catalytic activity for OER in alkaline solution. It provides a low onset potential of 1.57 V vs. RHE and low overpotential of 420 mV vs. RHE to reach a current density of 10 mA cm-2. Ru0/CeO2 on GCE shows no change in the onset potential value even after 6.1 h electrochemical measurement in OER.

Decomposition of formic acid using tungsten(VI) oxide supported AgPd nanoparticles.

Formic acid (FA) is a crucial liquid H2 storage material due to its high gravimetric energy density. Therefore, dehydrogenation of FA using catalysts has attracted considerable attention. However, it is still a challenge to find a selective and active catalyst for this reaction. Bimetallic AgPd nanoparticles are well known combination to obtain efficient catalysts for the dehydrogenation of FA. Therefore, many efforts have been devoted on finding suitable supporting materials to increase the efficiency of AgPd NPs in dehydrogenation of FA. In this study, tungsten(VI) oxide, WO3 was used as a supporting material due to its multiple oxidation states which play an important role for obtaining highly efficient catalyst. Herein, bimetallic AgPd nanoparticles supported on WO3 were successfully prepared. The activity of AgPd/WO3 catalysts with different Ag loading was tested in dehydrogenation of FA in presence of sodium formate at 50.0 ±â€¯0.1 °C. Ag0.25Pd/WO3 catalyst with a TOF value of 683 h-1 exhibited high activity in this reaction. In addition, the effect of sodium formate on the decomposition of formic acid was investigated in detail.

Rhodium(0) nanoparticles supported on ceria as catalysts in hydrogenation of neat benzene at room temperature.

Rhodium(0) nanoparticles supported on ceria (Rh NPs/CeO2) were prepared from the reduction of Rh3+ ions on the surface of ceria in aqueous medium. Rh NPs/CeO2 catalyst was found to be highly active in hydrogenation of benzene under mild conditions. It provided a TOF value of 495 h-1 in hydrogenation of solventless benzene under ∼3 bar pressure of H2 gas at 25.0 ±â€¯0.1 °C. Rh NPs/CeO2 shows superior catalytic activity over titania, zirconia and hafnia supported Rh NPs in this reaction.

Titania, zirconia and hafnia supported ruthenium(0) nanoparticles: Highly active hydrogen evolution catalysts.

Designing a cost-effective catalyst with high activity and stability for hydrogen evolution reaction (2H+ + 2e- → H2) is a big challenge due to increasing demand for energy. Herein, we report the electrocatalytic activity of glassy carbon electrodes with group 4 metal oxides (TiO2, ZrO2, HfO2) supported ruthenium(0) nanoparticles in hydrogen evolution reaction. Electrochemical activity of modified electrodes is investigated by recording linear sweep voltammograms in 0.5 M H2SO4 solution. The results of electrochemical measurements reveal that among the three electrodes the glassy carbon electrode with Ru0/TiO2 (1.20% wt. Ru) exhibits the highest activity with a relatively small Tafel slope of 52 mV dec-1, the highest exchange current density of 0.728 mA cm-2, and the smallest overpotential of 41 mV at j = 10 mA cm-2. Furthermore, it demonstrates superior stability in acidic solution with an unaltered onset potential for long term electrochemical measurement.

Nanoceria-Supported Ruthenium(0) Nanoparticles: Highly Active and Stable Catalysts for Hydrogen Evolution from Water.

Ruthenium(0) nanoparticles supported on nanoceria (Ru0/CeO2) were prepared by reduction of Ru3+ ions on the surface of ceria using aqueous solution of NaBH4. The Ru0/CeO2 samples were characterized by advanced analytical tools and employed as electrocatalysts on the glassy carbon electrode (GCE) in hydrogen evolution from water. The GCE, modified by Ru0/CeO2 (1.86 wt % Ru), provides an incredible electrocatalytic activity with a high exchange current density of 0.67 mA·cm-2, low overpotential of 47 mV at j = 10 mA·cm-2, and small Tafel slope of 41 mV·dec-1. Moreover, this modified GCE provides an unprecedented long-term stability without changing the onset potential (33 mV) even after 10 000 scans in acidic water splitting at room temperature. The hydrogen gas, evolved during the water splitting using the Ru0/CeO2 (1.86 wt % Ru) electrocatalyst, was also collected. The amount of the evolved H2 gas matches well with the calculated value, which indicates the achievement of nearly 100% Faradaic efficiency.

Nanozirconia supported ruthenium(0) nanoparticles: Highly active and reusable catalyst in hydrolytic dehydrogenation of ammonia borane.

Nanozirconia supported ruthenium(0) nanoparticles (Ru0/ZrO2) were prepared by impregnation of ruthenium(III) cations on the surface of zirconia followed by their reduction with sodium borohydride at room temperature. Ru0/ZrO2 was isolated from the reaction solution by centrifugation and characterized by ICP-OES, XRD, TEM, SEM-EDS and XPS techniques. All the results reveal that ruthenium(0) nanoparticles were successfully supported on zirconia and the resulting Ru0/ZrO2 is a highly active and reusable catalyst for hydrogen generation from the hydrolysis of ammonia borane with a turnover frequency value of 173 min-1 at 25 °C. The reusability and catalytic lifetime tests reveal that Ru0/ZrO2 is still active in the subsequent runs of hydrolysis of ammonia borane preserving 67% of the initial catalytic activity even after the fifth run and Ru0/ZrO2 provides 72,500 turnovers (mol H2/mol Ru) before deactivation at 25 °C. Our report also includes the results of kinetic studies depending on the catalyst concentration and temperature to determine the activation energy (Ea = 58 ±â€¯2 kJ/mol) for hydrolytic dehydrogenation of AB.

Nickel(0) nanoparticles supported on bare or coated cobalt ferrite as highly active, magnetically isolable and reusable catalyst for hydrolytic dehydrogenation of ammonia borane.

Nickel(0) nanoparticles supported on cobalt ferrite (Ni0/CoFe2O4), polydopamine coated cobalt ferrite (Ni0/PDA-CoFe2O4) or silica coated cobalt ferrite (Ni0/SiO2-CoFe2O4) are prepared and used as catalysts in hydrogen generation from the hydrolysis of ammonia borane at room temperature. Ni0/CoFe2O4 (4.0% wt. Ni) shows the highest catalytic activity with a TOF value of 38.3min-1 in hydrogen generation from the hydrolysis of ammonia borane at 25.0±0.1°C. However, the initial catalytic activity of Ni0/CoFe2O4 catalyst is not preserved in subsequent runs of hydrolysis. Coating the surface of cobalt ferrite support with polydopamine or silica leads to a significant improvement in the stability of catalysts. The TOF values of Ni0/PDA-CoFe2O4 and Ni0/SiO2-CoFe2O4 are found to be 7.6 and 5.3min-1, respectively, at 25.0±0.1°C. Ni0/PDA-CoFe2O4 catalyst shows high reusability as compared to the Ni0/CoFe2O4 and Ni0/SiO2-CoFe2O4 catalysts in hydrolytic dehydrogenation of ammonia borane at room temperature. All the catalysts are characterized by using a combination of various advanced analytical techniques. The results reveal that nickel nanoparticles with an average size of 12.3±0.7nm are well dispersed on the surface of PDA-CoFe2O4. .

Facile Synthesis of Three-Dimensional Pt-TiO2 Nano-networks: A Highly Active Catalyst for the Hydrolytic Dehydrogenation of Ammonia-Borane.

Three-dimensional (3D) porous metal and metal oxide nanostructures have received considerable interest because organization of inorganic materials into 3D nanomaterials holds extraordinary properties such as low density, high porosity, and high surface area. Supramolecular self-assembled peptide nanostructures were exploited as an organic template for catalytic 3D Pt-TiO2 nano-network fabrication. A 3D peptide nanofiber aerogel was conformally coated with TiO2 by atomic layer deposition (ALD) with angstrom-level thickness precision. The 3D peptide-TiO2 nano-network was further decorated with highly monodisperse Pt nanoparticles by using ozone-assisted ALD. The 3D TiO2 nano-network decorated with Pt nanoparticles shows superior catalytic activity in hydrolysis of ammonia-borane, generating three equivalents of H2 .

Ceria-supported ruthenium nanoparticles as highly active and long-lived catalysts in hydrogen generation from the hydrolysis of ammonia borane.

Ruthenium(0) nanoparticles supported on ceria (Ru(0)/CeO2) were in situ generated from the reduction of ruthenium(iii) ions impregnated on ceria during the hydrolysis of ammonia borane. Ru(0)/CeO2 was isolated from the reaction solution by centrifugation and characterized by ICP-OES, BET, XRD, TEM, SEM-EDS and XPS techniques. All the results reveal that ruthenium(0) nanoparticles were successfully supported on ceria and the resulting Ru(0)/CeO2 is a highly active, reusable and long-lived catalyst for hydrogen generation from the hydrolysis of ammonia borane with a turnover frequency value of 361 min(-1). The reusability tests reveal that Ru(0)/CeO2 is still active in the subsequent runs of hydrolysis of ammonia borane preserving 60% of the initial catalytic activity even after the fifth run. Ru(0)/CeO2 provides a superior catalytic lifetime (TTO = 135 100) in hydrogen generation from the hydrolysis of ammonia borane at 25.0 ± 0.1 °C before deactivation. The work reported here includes the formation kinetics of ruthenium(0) nanoparticles. The rate constants for the slow nucleation and autocatalytic surface growth of ruthenium(0) nanoparticles were obtained using hydrogen evolution as a reporter reaction. An evaluation of rate constants at various temperatures enabled the estimation of activation energies for both the reactions, Ea = 60 ± 7 kJ mol(-1) for the nucleation and Ea = 47 ± 2 kJ mol(-1) for the autocatalytic surface growth of ruthenium(0) nanoparticles, as well as the activation energy of Ea = 51 ± 2 kJ mol(-1) for the catalytic hydrolysis of ammonia borane.

Ruthenium(0) nanoparticles supported on xonotlite nanowire: a long-lived catalyst for hydrolytic dehydrogenation of ammonia-borane.

Ruthenium(0) nanoparticles supported on xonotlite nanowire (Ru(0)@X-NW) were prepared by the ion exchange of Ru(3+) ions with Ca(2+) ions in the lattice of xonotlite nanowire followed by their reduction with sodium borohydride in aqueous solution at room temperature. Ru(0)@X-NW were characterized by a combination of advanced analytical techniques. The results show that (i) highly dispersed ruthenium(0) nanoparticles of 4.4 ± 0.4 nm size were formed on the surface of xonotlite nanowire, (ii) Ru(0)@X-NW show high catalytic activity in hydrogen generation from the hydrolytic dehydrogenation of ammonia borane with a turnover frequency value up to 135 min(-1) at 25.0 ± 0.1 °C. (iii) They provide unprecedented catalytic life time (TTO = 134,100) for hydrogen generation from the hydrolysis of ammonia borane at 25.0 ± 0.1 °C. (iv) The results of a kinetic study on the hydrogen generation from the hydrolysis of ammonia borane were also reported including the activation energy of 77 ± 2 kJ mol(-1) for this reaction.

Ruthenium(0) nanoparticles supported on multiwalled carbon nanotube as highly active catalyst for hydrogen generation from ammonia-borane.

Ruthenium(0) nanoparticles supported on multiwalled carbon nanotubes (Ru(0)@MWCNT) were in situ formed during the hydrolysis of ammonia-borane (AB) and could be isolated from the reaction solution by filtration and characterized by ICP-OES, XRD, TEM, SEM, EDX, and XPS techniques. The results reveal that ruthenium(0) nanoparticles of size in the range 1.4-3.0 nm are well-dispersed on multiwalled carbon nanotubes. They were found to be highly active catalyst in hydrogen generation from the hydrolysis of AB with a turnover frequency value of 329 min⁻¹. The reusability experiments show that Ru(0)@MWCNTs are isolable and redispersible in aqueous solution; when redispersed they are still active catalyst in the hydrolysis of AB exhibiting a release of 3.0 equivalents of H2 per mole of NH3BH3 and preserving 41% of the initial catalytic activity even after the fourth run of hydrolysis. The lifetime of Ru(0)@MWCNTs was measured as 26400 turnovers over 29 h in the hydrolysis of AB at 25.0 ± 0.1 °C before deactivation. The work reported here also includes the kinetic studies depending on the temperature to determine the activation energy of the reaction (E(a) = 33 ± 2 kJ/mol) and the effect of catalyst concentration on the rate of the catalytic hydrolysis of AB, respectively.

Osmium(0) nanoclusters stabilized by zeolite framework; highly active catalyst in the aerobic oxidation of alcohols under mild conditions.

Osmium(0) nanoclusters stabilized by zeolite-Y framework were reproducibly prepared by a simple two step procedure involving the incorporation of osmium(III) cations into the zeolite matrix by ion-exchange, followed by their reduction within the cavities of zeolite with sodium borohydride in aqueous solution all at room temperature. The composition and morphology of osmium(0) nanoclusters stabilized by zeolite framework, as well as the integrity and crystallinity of the host material were investigated by using ICP-OES, XRD, XPS, SEM, TEM, HRTEM, TEM/EDX, mid-IR, far-IR spectroscopies, and N(2)-adsorption/desorption technique. The results of the multiprong analysis reveal the formation of osmium(0) nanoclusters within the cavities of zeolite-Y without causing alteration in the framework lattice, formation of mesopores, or loss in the crystallinity of the host material. More importantly, far-IR studies showed that after the reduction of Os(3+) cations by sodium borohydride the Na(+) cations reoccupy their authentic cation sites restoring the integrity of zeolite-Y. The catalytic activity of osmium(0) nanoclusters stabilized by zeolite framework was tested in the aerobic oxidation of activated, unactivated and heteroatom containing alcohols to carbonyl compounds and was found to provide high activity and selectivity even under mild conditions (80 degrees C and 1 atm O(2) or air). Moreover, they were found to be stable enough to be isolated and bottled as solid material, which can be reused as active catalyst under the identical conditions of the first run.