Ruthenium Nanoparticles Intercalated in Hectorite: A Reusable Hydrogenation Catalyst for Benzene and Toluene

The cationic organometallic aqua complexes formed by hydrolysis of [(C₆H₆)RuCl₂]₂ in water, mainly [(C₆H₆)Ru(H₂O)₃]²⁺, intercalate into sodium hectorite by ion exchange, replacing the sodium cations between the anionic silicate layers. The yellow hectorite thus obtained reacts in ethanol with molecular hydrogen (50 bar, 100°C) with decomposition of the organometallic aqua complexes to give a black material, in which ruthenium(0) nanoparticles (9–18 nm) are intercalated between the anionic silicate layers, the charges of which being balanced by hydronium cations. The black ruthenium-modified hectorite efficiently catalyses the hydrogenation of benzene and toluene in ethanol (50 bar H₂, 50°C), the turnover frequencies attaining 7000 catalytic cycles per hour. Dedicated to Professor Günter Schmid, pioneer of nanocluster chemistry, on the occasion of his 70th birthday     

Formation and characterization of phosphate-modified silicate materials derived from sol–gel process

Phosphate-containing silicate materials prepared using sol–gel method from Si(OC₂H₅) were investigated at the variation of the amount of phosphate modifier from 5 to 50 wt% in term of P₂O₅. Chemical composition, textural and structural properties of these materials were characterized by FTIR-spectroscopy, TEM, X-ray diffraction and nitrogen adsorption. It was shown that the materials posse monomodal pore size distribution of 5–20 nm for the samples dried at 100 °C and 40–60 nm for the specimens calcined at 600 °C. The mean pore size and surface area depended on the amount of phosphoric acid. Before the stage of high temperature treatment phosphoric acid, introduced into the structure of the materials as a modifying agent, was uniformly distributed inside a porous space of the material and was not chemically bonded with silicate. After high temperature treatment both chemical interaction of silicate with phosphate, providing the formation of silicate-phosphate structures, as well as redistribution of free modifier from the bulk of granules to their surface took place. The polyphosphate layer is formed on the material surface closing the internal porous space. However, in this case a part of the phosphate modifier remains chemically unbound to SiO₂ structure.     

Intercalation of water and guest molecules within Ca<Superscript>2+</Superscript>–Montmorillonite

The high potential for intercalations by water and various guest molecules is induced by the exchangeable cation inside Ca²⁺–Montmorillonite gallery. XRD peak for Mon at 2θ = 6.04° (d ₀₀₁ = 1.462 nm) shows the structural effect on the clay gallery influenced by the intercalated water layers. Further increases in the gallery height are observed with the intercalation of octadecyl ammonium cations in OMON (d ₀₀₁ = 1.840 nm) and ENR-50 matrix chains in CENR-50 (d ₀₀₁ = 1.954 nm). DSC studies on the other hand reveal the thermal behaviors of intercalated molecules that are linked to the exchangeable cations. The endothermic of Ca²⁺–Montmorillonite (H _Mon = 356.3 J/g) in low temperature range (30–100 °C) indicates the removal of free water and hydrogen bonded water molecules, while the endothermic around 150 °C is related to the induced skeletal layer of water within Ca²⁺–Montmorillonite. The OMON endothermic (H _OMON = 47.0 J/g, T _m = 36.94 °C) tells that cation exchange had modified the water structures and content inside the renewed clay. The intercalation of ENR-50 chains into OMON gallery reveals two endothermic with the T _m1 and T _m2 are at 86.24 and 113.80 °C, respectively. These T _ms confirm that the alkyl chain segment on octadecyl ammonium cation occupy the OMON interlayer space.     

High Temperature Stable Maghemite Nanoparticles Sandwiched between Hectorite Nanosheets

Maghemite (γ-Fe₂O₃) is a metastable iron oxide phase and usually undergoes fast phase transition to hematite at elevated temperatures (>350 °C). Maghemite nanoparticles were synthesized by the polyol method and then intercalated into a highly swollen (>100 nm separation) nematic phase of hectorite. A composite of maghemite nanoparticles sandwiched between nanosheets of synthetic hectorite was obtained. The confinement of the nanoparticles hampered Ostwald ripening up to 700 °C and consequently the phase transition to hematite is suppressed. Only above 700 °C γ-Fe₂O₃ nanoparticles started to grow and undergo phase transition to α-F₂O₃. The structure and the phase transition of the composite was evaluated using X-ray diffraction, TEM, SEM, physisorption, TGA/DSC, and Mößbauer spectroscopy.     

Facile synthesis of superparamagnetic manganese ferrite nanoparticles as a novel T2 MRI contrast agent

With co-precipitation method we successfully synthesized an aqueous dispersible, superparamagnetic manganese ferrite nanoparticles at relatively low temperature (190 ​°C). This material shows potential application as T₂ MRI contrast agent. Cost-effective and less toxic manganese (II) chloride (MnCl₂·4H₂O) and iron (III) chloride hexahydrate (FeCl₃·6H₂O) were used as precursors and 2-[2-(2-Hydroxyethoxy)ethoxy] ethanol (TEG) were utilized as solvent which served as stabilizer and provided a reduction system. The mean diameter of these nanoparticles is about 7 ​nm. Its saturation magnetization (Ms) and relaxivity value (r₂) are as high as 46 emu/g and 593.9 ​mM⁻¹s⁻¹ respectively. In vitro cell study demonstrated pancreatic cancer cells could keep viable when the manganese ferrite nanoparticles concentration reached up to 50 ​μg/mL.     

Synthesis and Characterization of Hyperbranched RuO2 Nanostructures

RuO₂ nanostructures were synthesized by heating Ru nanoparticles in air at 280°C using Cu as catalyst. The Ru nanoparticles were prepared by the pyrolysis of ruthenium precursors in a vacuum using multi-walled carbon nanotubes as templates. The RuO₂ nanostructures grew radically with diameters of 50–150 nm, and lengths of 0.5–2.0 μm. The growth of nanostructure mainly depends on the dispersivity of Ru nanoparticles on MWNTs. The electrochemical property of these nanostructures was studied by cyclic voltammetry. Electronic Supplementary Material Supplementary material for this article is available at and is accessible for authorized users.     

New photochromic xerogels composites based on nitrosyl complexes

New photoswitchable hybrid materials based on mononitrosyl complexes with excellent optical properties have been obtained by sol–gel process. Inclusion in silica matrix prepared from tetramethoxysilane precursor leads to new materials in which the ruthenium complex [RuCl(NO)py₄](PF₆)₂·1/2H₂O (py = pyridine) is stabilized as crystalline nanoparticles with diameters between 2 and 15 nm. Photochromic properties are maintained and have been evidenced by infrared spectroscopy under irradiation (λ = 473 nm) at low temperature (T = 100 K). The reversible transfer from the ground state (GS) to the metastable state (MS1) is about 40% in the composite, which is close to the value observed on the most studied sodium nitroprusside (50% on pure material).     

Cu-particle-dispersed (K<Subscript>0.5</Subscript>Na<Subscript>0.5</Subscript>)NbO<Subscript>3</Subscript> composite thin films derived from sol–gel processing

Sol–gel processing of Cu-particle-dispersed (K_0.5Na_0.5)NbO₃ (Cu/KNN) thin films was studied in an attempt to develop a method producing piezoelectric composite films with good mechanical performance. The Cu/KNN films were prepared via crystallization annealing at 650–750 °C for 1 min in air, followed by reduction annealing at 400–500 °C for 1–2 h in a 5% H₂ and 95% Ar gas mixture. The resultant composite films consisted of perovskite KNN, metallic Cu, and Cu₄O₃. This suggests that the decomposition of Cu sources takes two different ways in this study. The Cu/KNN composite films containing Cu₄O₃ phases were produced by the crystallization annealing at 700 °C for 1 min followed by the reduction annealing at 500 °C for 1 h. Surface morphology observations reveal that these films have dense KNN matrix with a grain size of ~200 nm and uniformly dispersed Cu or Cu₄O₃ particles with a size of <500 nm.     

Synthesis and Anticancer Activity of Long-Chain Isonicotinic Ester Ligand-Containing Arene Ruthenium Complexes and Nanoparticles

Arene ruthenium complexes containing long-chain N-ligands L¹ = NC₅H₄–4-COO–C₆H₄–4-O–(CH₂)₉–CH₃ or L² = NC₅H₄–4-COO–(CH₂)₁₀–O–C₆H₄–4-COO–C₆H₄–4-C₆H₄–4-CN derived from isonicotinic acid, of the type [(arene)Ru(L)Cl₂] (arene = C₆H₆, L = L¹: 1; arene = p-MeC₆H₄Pr ⁱ , L = L¹: 2; arene = C₆Me₆, L = L¹: 3; arene = C₆H₆, L = L²: 4; arene = p-MeC₆H₄Pr ⁱ , L = L²: 5; arene = C₆Me₆, L = L²: 6) have been synthesized from the corresponding [(arene)RuCl₂]₂ precursor with the long-chain N-ligand L in dichloromethane. Ruthenium nanoparticles stabilized by L¹ have been prepared by the solvent-free reduction of 1 with hydrogen or by reducing [(arene)Ru(H₂O)₃]SO₄ in ethanol in the presence of L¹ with hydrogen. These complexes and nanoparticles show a high anticancer activity towards human ovarian cell lines, the highest cytotoxicity being obtained for complex 2 (IC₅₀ = 2 μM for A2780 and 7 μM for A2780cisR).     

Synthesis of ZrB2 nanoparticles by sol-gel method

Zirconium diboride (ZrB₂) nanoparticles were synthesized by sol-gel method using zirconium n-propoxide (Zr(OPr)₄), boric acid (H₃BO₃), and sucrose (C₁₂H₂₂O₁₁). Additionally, acetylacetone (acac) was used as chemical modifier in a neutral condition to stabilize Zr(OPr)₄ which hydrolyzes easily. Here, C₁₂H₂₂O₁₁ was used since it can be completely decomposed to carbon. Thus, carbon might be accounted precisely for the carbothermal reduction reaction. A single phase ZrB₂ without residual ZrO₂ was obtained with a molar ratio of B/Zr = 2.3 for the starting materials at 1,550 °C and the average grain size of ZrB₂ nanoparticles was ca. 50 nm. The photomicrograph revealed a spherical round shape morphology of the ZrB₂ nanoparticles with an uniform size distribution. On the other hand, in the case of either B/Zr (mol.) = 2.0 or pyrolyzing temperature below 1,550 °C for B/Zr (mol.) = 2.3, there existed both m-ZrO₂ and t-ZrO₂ phases besides ZrB₂.     

Effects of strontium silicate on structure and magnetic properties of electrospun strontium ferrite nanofibers

The composite nanofibers of xSrSiO₃/(100 − x)SrFe₁₂O₁₉ (x = 0–13 wt%) with diameters around 110 nm have been prepared by calcination of the electrospun SrSiO₃/SrFe₁₂O₁₉/poly (vinyl pyrrolidone) (PVP) composite fibers at 800–900 °C. The composite nanofibers were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy and vibrating sample magnetometer. After calcined at 800° the M-type strontium ferrite is formed and the strontium silicate exists as an amorphous state when the calcination temperature below about 950 °C. The addition of SrSiO₃ has an obvious suppression effect on the strontium ferrite grain growth and the ferrite grain size decreases from 66.9 to 33.5 nm corresponding SrSiO₃ content from 0 to 9 wt% in the composite. The specific saturation magnetization (Ms) of the xSrSiO₃/(100 − x)SrFe₁₂O₁₉ composite nanofibers exhibits a continuous reduction from 58.0 to 45.6 A m² kg⁻¹ with the increase of SrSiO₃ content from 0 to 13 wt%. With addition of SrSiO₃ from 0 to 13 wt%, the coercivity of the composite nanofibers obtained at 900 °C initially increases, reaching a maximum value 501.1 kA m⁻¹ at the silicate content 7 wt%, and then shows a reduction tendency with the strontium silicate content increase further up to 13 wt%. This influence on the coercivity by strontium silicate can be attributed mainly to the ferrite grain growth suppression and the non-magnetic phase barrier for the domains misalignment.     

Catalytic soot combustion of α-Fe/Ce–K–O nanocomposites via citrate-gel route

The binary phase, porous, nanocomposite xα-Fe/(1 − x)Ce_0.9–K_0.1–O (x = 0.05–0.2) catalysts and the catalyst-coated honeycomb ceramic device have been prepared by the citrate-gel thermal decomposition-reduction process and the sol–gel assisted dip-coating method, respectively. The nanocomposite of fluorite-type structure CeO₂ nanoparticles about 18–51 nm and α-Fe nanoparticles about 32 nm is obtained at 600 °C for 2 h in a deoxidization atmosphere and the α-Fe in nanocomposite has the suppression effect on grain growth of CeO₂. With Fe content increasing from 0.05 to 0.1, the specific surface area for the nanocomposites increases dramatically from about 4.4 to 43.0 m²/g, reaching a maximum value 57.7 m²/g at x = 0.15, and the pores vary from macropores to micro- or mesopores. Due to the presence of nano α-Fe, all the catalysts exhibit a very high soot catalytic activity, with the lowest T₂₀ (255 °C) and T₅₀ (291 °C) for the nanocomposite with x = 0.15, and it is confirmed by the bench test under practical diesel exhaust gases.     

Crystallization process of lanthanum-substituted bismuth titanate synthesized by a facile sol–gel method

We present a facile sol–gel route to synthesize lanthanum-substituted bismuth titanate (BLT). The chemical reactions and crystallization process of this method using the initial materials of bismuth subnitrate [4BiNO₃(OH)₂·BiO(OH)], lanthanum nitrate [La(NO₃)₃·6H₂O] and tetrabutyl titanate [Ti(C₄H₉O)₄] were investigated by thermogravimetric and differential thermal analysis, IR spectroscopy, gas chromatography/mass spectrometry, Raman spectroscopy and XRD. The evaporation of the dissolved CO₂ in the amorphous BLT matrix is associated with the crystallization of BLT. The BLT gel is pure BLT perovskite when calcination temperature is higher than 500 °C. The grain size of the obtained nanoparticles ranges from 15 to 82 nm. The Arrhenius curve is obtained from the representation of the reduced sizes with respect to the calcination temperature. The activation energy of grain growth in BLT nanoparticles is 0.36 eV, which shows a rapidly growth process in the temperature range of 500–850 °C.     

Size effect of silica nanoparticles on thermal decomposition of PMMA

The size effect of silica nanoparticles (SiO₂) on thermal decomposition of poly(methylmethacrylate) (PMMA) was investigated by the controlled rate thermogravimetry. Thermal degradation temperature of PMMA–SiO₂ composites depended on both fraction and size of SiO₂, the thermal degradation temperature of 23 nm (diameter) SiO₂–PMMA (6.1 wt%) was 13.5 °C higher than that of PMMA. The thermal stabilities of 17 nm SiO₂–PMMA (3.2 wt%) and 13 nm SiO₂–PMMA (4.8 wt%) were 21 and 23 °C, respectively, higher than that of PMMA without SiO₂. The degree of degradation improvement was increased linearly with the surface area of SiO₂. The number of surface hydroxyl group in unit volume of SiO₂ particle increased with increasing the specific surface area of SiO₂, and the interaction between hydroxide group of SiO₂ and carbonyl group of PMMA had an important role to improve the thermal stability of PMMA.     

Low-temperature NO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> Selective Reduction by Hydrocarbons on H-Mordenite Catalysts in Dielectric Barrier Discharge Plasma

Toward achieving selective catalytic reduction of NO _x by hydrocarbons at low temperatures (especially lower than 200 °C), C₂H₂ selective reduction of NO _x was explored on H-mordenite (H-MOR) catalysts in dielectric barrier discharge (DBD) plasma. This work reported significant synergistic effects of DBD plasmas and H-MOR catalysts for C₂H₂ selective reduction of NO _x at low temperatures (100–200 °C ) and across a wide range of O₂ content (0–15%). At 100 °C, NO _x conversions were 3.3, 11.6 and 66.7% for the plasma alone, catalyst alone and in-plasma catalysis (IPC) cases (with a reactant gas mixture of 500 ppm NO, 500 ppm C₂H₂, 10% O₂ in N₂, GHSV = 12,000 h⁻¹ and input energy density of 125 J L ⁻¹), respectively. At 200 °C, NO _x conversions were 3.8, 54.0 and 91.4% for the above three cases, respectively. Also, strong signals of hydrogen cyanide (HCN) byproduct were observed in the catalyst alone system by an on-line mass spectrometer. By contrast, almost no HCN was detected in the IPC system.     

Ruthenium catalysts supported on TiO<Subscript>2</Subscript> prepared by sol–gel way for <Emphasis Type="Italic">p</Emphasis>-hydroxybenzoic acid wet air oxidation

The wet air oxidation of p-hydroxybenzoic acid, chosen as a model compound of olive mills wastewaters was carried out at 140 °C and 50 bar air over Ru catalysts supported on TiO₂ prepared by sol–gel method. These catalysts were characterized by means of N₂ adsorption–desorption, XRD and TEM. Optimization of the catalytic performances was obtained by studying some parameters such as the catalyst preparation method, the solvent evacuation way, the nature of the hydrolysis agent, the influence of the ruthenium salt used as the metal precursor (Ru(NO)(NO₃)₃ or Ru(acac)₃) and the catalyst pretreatment. The pre-calcination of the catalyst precursor at 300 °C under oxygen, before the reduction step under hydrogen, was detrimental to the activity. The results showed that the use of nitric acid as hydrolysis agent, drying under supercritical conditions and the use of Ru(NO)(NO₃)₃ leads to the more efficient catalyst with high TOC abatement.     

Sol–gel derived 12BaO·7Al<Subscript>2</Subscript>O<Subscript>3</Subscript> thin films using metal alkoxides

The 12BaO·7Al₂O₃ (B12A7) thin films have been prepared via sol–gel process. Optical and electrical properties of B12A7 films have been investigated. The films were coated on soda lime float glass by the dip coating process, and annealed in air and hydrogen (H₂) at 450 °C for 2 h. The UV absorption edge was red shifted for films annealed in H₂ atmosphere. The B12A7 films had high transparency about 90% in wide visible range with maximum of 95% at 575 nm wavelength. The sheet resistance of the 300 nm films corresponding to 90.57 and 0.974 kΩ per square has been observed for air and H₂ annealed, respectively.     

Physico-chemical properties of ambiently dried sodium silicate based aerogels catalyzed with various acids

Experimental results on the physico-chemical properties of ambiently dried sodium silicate based aerogels catalyzed with various acids are reported. The aerogels were prepared by hydrolysis and polycondensation of sodium silicate followed by subsequent washings, surface chemical modification and ambient pressure drying using 10 various acid catalysts consisting of strong and weak acids. The strength and concentration of acids have the major effect on the gelation of sol and hence the physico-chemical properties of the silica aerogels. Strong acids such as HCl, HNO₃ and H₂SO₄ resulted in shrunk (70–95%) aerogels whereas weak acids such as citric and tartaric acids resulted in less shrunk (34–50%) aerogels. The physical properties of silica aerogels were studied by measuring bulk density, volume shrinkage (%), porosity (%), pore volume, thermal conductivity, contact angle with water, Transmission Electron Microscopy (TEM), Atomic Absorption Spectroscopy (AAS), Fourier Transform Infrared Spectroscopy (FTIR), Thermo Gravimetric-Differential Thermal (TG-DT) analyses and N₂ adsorption–desorption BET surface analyzer. The best quality silica aerogels in terms of low density (0.086 g/cm³), low volume shrinkage (34%), high porosity (95%), low thermal conductivity (0.09 W/m K) and hydrophobic (148°) were obtained for molar ratio of Na₂SiO₃:H₂O:citric acid:TMCS at 1:146.67:0.72:9.46 with 20 min gelation time. The resulting aerogels exhibited the thermal stability up to around 420 °C.     

Preparation and photocatalytic activity of TiO<Subscript>2</Subscript> films with Ni nanoparticles

Titania thin films were synthesized by sol–gel dip-coating method with metallic Ni nanoparticles synthesized separately from an organometallic precursor Ni(COD)₂ (COD = cycloocta-1,5-diene) in presence of 1,3-diaminopropane as a stabilizer. Titania was obtained from a titanium isopropoxide precursor solution in presence of acetic acid. A Ni/TiO₂ sol system was used to coat glass substrate spheres (6, 4 and 3 mm diameter sizes), and further heat treatment at 400 °C was carried out to promote the crystallization of titania. XRD analysis of the TiO₂ films revealed the crystallization of the anatase phase. Transmission Electron Microscopy (TEM) and High Resolution TEM studies of Ni nanoparticles before mixing with the TiO₂ solution revealed the formation of Ni nanostructures with an average size of 5–10 nm. High-angle annular dark-field images of the Ni/TiO₂ system revealed well-dispersed Ni nanoparticles supported on TiO₂ and confirmed by AFM analysis. The photocatalytic activity of the Ni/TiO₂ films was evaluated in hydrogen evolution from the decomposition of ethanol using a mercury lamp for UV light irradiation. Titania films in presence of Ni nanoparticles show higher efficiency in their photocatalytic properties in comparison with TiO₂.     

Synthesis and properties of Co–Pt alloy silica core-shell particles

This paper describes a method for fabrication of silica-coated Co–Pt alloy nanoparticles in a liquid phase process. The Co–Pt nanoparticles were prepared from CoCl₂ (4.2 × 10⁻⁵ M), H₂PtCl₆ (1.8 × 10⁻⁵ M), citric acid (4 × 10⁻⁴ M) and NaBH₄ (1.2 × 10⁻² M) with a Co:Pt mole ratio of 7:3. The silica coating was performed in water/ethanol solution with a silane coupling agent, 3-aminopropyltrimethoxysilane (8 × 10⁻⁵ M), and a silica source, tetraethoxyorthosilicate (7.2 × 10⁻⁴ M) in the presence of the Co–Pt nanoparticles. Observations with a transmittance electron microscope and a scanning transmission electron microscope revealed that the Co-rich and Pt-rich nanoparticles were coated with silica. According to X-ray diffraction measurements, core particles were crystallized to metallic Co crystallites and fcc Co–Pt alloy crystallites with annealing in air at 300–500 °C. Magnetic properties of the silica-coated particles were strongly dependent on annealing temperature. Maximum values of 11.4 emu/g-sample for saturation magnetization and 365 Oe for coercive field were obtained for the particles annealed at 300 and 500 °C, respectively. Annealing at a temperature as high as 700 °C destroyed the coating structures because of crystallization of silica shell, resulting in reduction in saturation magnetization and coercive field.