In Situ Generation of Strong Bases from Alkaline and Alkaline–Earth Carbonates

Strong bases from alkaline and alkaline-earth metal carbonates were generated in situ by adding a small amount of acetic acid at reflux in toluene under water-free conditions. Their basic strength reached superbasicity thus changing the color of 4-chloroaniline (H₋=26.5). The high conversion of ethyl acetate in its self-condensation over decomposed carbonates, which require strong basicity to abstract protons from ethyl acetate (pK_a=25), also confirmed the formation of strong bases. Adding acetic acid during the reaction indicated that metal oxides—decomposed materials from carbonates—were responsible for their high catalytic activity. The lack of sufficient coordination of in situ generated metal oxides was considered to be a plausible cause for their strong basicity.     

Fabrication of Pd–Au Clusters by In Situ Spontaneous Reduction of Reductive Layered Double Hydroxides

Catalysis Letters - In this work, layered double hydroxides (LDHs) including the variable valence Co2+ ions (CoAl-LDHs) is discovered to be capable of serving as the support and the reducing agent...     

CO Oxidation of Au–Pt Nanostructures: Enhancement of Catalytic Activity of Pt Nanoparticles by Au

The CO oxidation activity of Pt deposited on Ta₂O₅/Ta was studied with various amounts of Au post-deposited on Pt/Ta₂O₅/Ta. For Pt nanoparticles with a mean size of 2–4 nm, an enhancement in the CO oxidation activity with increasing amount of post-deposited Au was found. The mixed Au–Pt nanoparticles with sizes in the range of 2–4 nm exhibited higher stability than the bare Au nanoparticles with a similar size range. In contrast to the results obtained with the Pt nanoparticles, the catalytic activity of a thicker Pt film gradually decreased with increasing amount of Au deposited. Based on the CO desorption experiments, it is suggested that the surface of the catalytically active Au–Pt bimetallic structures consists of both Au and Pt sites.     

Preparation of Ultrafine Fe–Pt Alloy and Au Nanoparticle Colloids by KrF Excimer Laser Solution Photolysis

We prepared ultrafine Fe–Pt alloy nanoparticle colloids by UV laser solution photolysis (KrF excimer laser of 248 nm wavelength) using precursors of methanol solutions into which iron and platinum complexes were dissolved together with PVP dispersant to prevent aggregations. From TEM observations, the Fe–Pt nanoparticles were found to be composed of disordered FCC A1 phase with average diameters of 0.5–3 nm regardless of the preparation conditions. Higher iron compositions of nanoparticles require irradiations of higher laser pulse energies typically more than 350 mJ, which is considered to be due to the difficulty in dissociation of Fe(III) acetylacetonate compared with Pt(II) acetylacetonate. Au colloid preparation by the same method was also attempted, resulting in Au nanoparticle colloids with over 10 times larger diameters than the Fe–Pt nanoparticles and UV–visible absorption peaks around 530 nm that originate from the surface plasmon resonance. Differences between the Fe–Pt and Au nanoparticles prepared by the KrF excimer laser solution photolysis are also discussed.     

Fabrication and Optical Behaviors of Core–Shell ZnS Nanostructures

Novel core–shell nanostructures comprised of cubic sphalerite and hexagonal wurtzite ZnS have been synthesized at 150°C by a simple hydrothermal method. The results of HR-TEM and SAED investigation reveal that the cores of hexagonal wurtzite ZnS (ca. 200 nm in average diameter) are encapsulated by a shell of cubic sphalerite ZnS. The FE-SEM image of the nanomaterials shows a surface tightly packed with nanoparticles (<10 nm in size). The optical properties of the fabricated material have been studied in terms of ultraviolet–visible absorption and photoluminescence. Furthermore, a possible mechanism for the fabrication of the core–shell nanostructures has been presented.     

Core–Shell Nanoparticles Containing Peptide Dendrimers

Dealloying of bimetallic gold core–silver shell nanoparticles (NPs) is achieved using peptide dendrimers from generation 1 to generation 3. The resulting NPs exhibit optical properties characteristic of Au/Ag core–shell NPs with weak surface plasmon resonance interactions between the core and shell. Transmission electron microscopy and x-ray photoelectron spectroscopy of the core–shell NPs exhibit a size and composition dependence on the dendrimer generation number. Rutherford backscattering spectrometric analyses of core–shell NPs containing dendrimer innerlayer indicates that the NPs are consisting of discrete domains of Ag–shell and Au–core.     

Baeyer–Villiger Oxidation of Cyclohexanone in Aqueous Medium with In Situ Generation of Peracid Catalyzed by Perhydrolase CLEA

A perhydrolase, immobilized as a cross linked enzyme aggregate (CLEA), was employed to catalyze the in situ formation of peracetic acid (PAA) from ethylene glycol diacetate (EGDA) and hydrogen peroxide. The produced PAA was used for the Baeyer–Villiger oxidation of cyclohexanone, which afforded caprolactone in 63 % yield. The effect of type and amount of acyl donor, solvent, pH, temperature and ratio of cyclohexanone to hydrogen peroxide on the production of caprolactone was studied. The highest caprolactone yield was obtained with 100 mM EGDA as the acyl donor at pH 6 and room temperature using a ratio of cyclohexanone to hydrogen peroxide ratio of 1:4. Interestingly, the perhydrolase CLEA exhibited the highest activity in aqueous medium in contrast to the well studied lipase B from Candida antarctica. The perhydrolase CLEA proved to be a very efficient catalyst; the K _m and V_max values were 118 mM and 56.3 μmol min^?1, respectively.     

Synthesis and Characterization of FePt/NiO Core–Shell Nanoparticles

Monodisperse FePt nanoparticles were successfully synthesized using the chemical polyol process. Annealing at the high temperatures is required to achieve the hard ferromagnetic behavior with L1₀ phase. Annealing causes the surfactant surrounding particles to be decomposed. Under such circumstances, FePt particles are agglomerated, and their size increases. In this research, NiO oxide particle with a high melting point was used for the first time as the shell around FePt core particles to prevent agglomeration. As a result, coercivity, H_c, of FePt and FePt/NiO nanoparticles after annealing at 750?°C are equal to 10 and 7?kOe, respectively.     

Core–Shell and Nanoporous Particle Architectures and Their Effect on the Activity and Stability of Pt ORR Electrocatalysts

We review our recent progress in the development of Pt–Ni bimetallic electrocatalysts with both high sustained activity and sustained stability for oxygen reduction reaction (ORR). This was achieved by an atomic understanding and rational control of the core–shell compositional patterns and size-related nanoporosity within the bimetallic nanoparticles formed during chemical and electrochemical pretreatment and electrocatalysis. In particular, we reveal how the size of the nanoparticle directly influences the nanoporosity formation and thereby the near surface composition, catalytic activity and stability. Our atomic insights provide a clearer picture on how bimetallic nanoparticles should be tailored for optimal ORR performance.     

Research Regarding a Correlation Core–Shell Morphology–Thermal Stability of Silica–Silver Nanoparticles

Silica nanoparticles repeatedly inhaled lead to acute and chronic lung inflammation and finally to pulmonary fibrosis and lung cancer, people with chronic respiratory diseases like asthma or allergic rhinitis being even more susceptible to their toxic effects. In order to reduce these above-mentioned toxic effects, the aim of this study was to engineer the environmental silica nanoparticles with silver and subsequent thermal treatment. Nanometer-sized and spherical silica particles were synthesized in a homogeneous state, using a simple one-pot chemical method. An applicable approach resulted in silver particles forming over the surface of the silica. The outcome was materialized in extremely small silver particles attached to silica core particles. Playing their well-known decisive role, precursors and catalysts effectively controlled the size of silver and silica particles. The synchronized structure of the synthesized particles was revealed by the electrostatic repulsion among the silica spheres and the electrostatic attraction between silica spheres and silver particles. The morphological images are revealed by means of a scanning electron microscope. The formation of silver–silica composite particles was confirmed by using infrared spectroscopy and X-ray photoelectron spectroscopy analysis. Following thermal analysis, the results concerning the thermal stability of the prepared particles provided higher temperature applications.     

New catalytic functions of Pd–Zn, Pd–Ga, Pd–In, Pt–Zn, Pt–Ga and Pt–In alloys in the conversions of methanol

Pd and Pt supported on ZnO, Ga₂O₃ and In₂O₃ exhibit high catalytic performance for the steam reforming of methanol, CH₃OH+H₂OCO₂+3HH₂, and the dehydrogenation of methanol to HCOOCH₃, 2CH₃OHHCOOCH₃+2HH₂. Combined results with temperature-programmed reduction (TPR) and XRD method revealed that Pd–Zn, Pd–Ga, Pd–In, Pt–Zn, Pt–Ga and Pt–In alloys were produced upon reduction. Over the catalysts having the alloy phase, the reactions proceeded selectively, whereas the catalysts having metallic phase exhibited poor selectivities.     

Corrosion of Au–Pd–In alloy in simulated physiological solutions

The corrosion of Au–Pd–In alloy, which is of great importance in dentistry, has been studied using an electrochemical quartz crystal microbalance (EQCM) in simulated physiological solutions. The alloy was deposited on quartz substrates by means of magnetron sputtering (MS). Analysis performed using X-ray photoelectron spectroscopy showed that the chemical composition of the sputtered deposit was similar to that of the MS target made of conventional casting alloy. Investigations by X-ray diffraction indicated a crystalline structure of the MS alloy. The electrochemical and corrosion behaviour of the Au–Pd–In alloy was studied in three simulated physiological solutions: 0.9 M NaCl, 0.1 M NaCl + 0.1 M lactic acid and artificial saliva. Determination of break down potential was complicated by the anodic gold dissolution due to formation of a chloride complex. The onset of anodic currents, therefore, indicated not the potential at which the passive layer starts to be destroyed, but the exceeding of the Au/AuCl₄ ^– equilibrium potential, which does not directly reflect corrosion resistance. The EQCM measurements under open circuit conditions indicated corrosion as an increase in mass, caused by the accumulation of corrosion products on the alloy surface. The increase in mass in acidic solution (pH 2.2) was similar to that in neutral solution (pH 6.5), which implies dissolution of corrosion products to be insignificant.     

Synthesis and Characterization of Hybrid Core–Shell Systems Based on Molecular Silicasols

New hybrid “rigid inorganic core–soft organic shell” systems based on molecular silicasols were synthesized by applying different synthetic schemes. Inorganic core was composed of molecular silicasols, which were synthesized from hyperbranched polyethoxysiloxane and tetraethoxysilane by polymer chemistry methods. Different organic modifiers were used to form soft shell of the hybrid particles. Obtained compounds were characterized by elemental analysis, GPC, IR and NMR spectroscopy. These systems will be designated for use as model objects for investigation of nanoparticles–polymer matrix interactions in polymer nanocomposites.     

Synthesis of Polystyrene Microsphere-Supported Ag–Ni-Alloyed Catalysts with Core–Shell Structures for Electrocatalytic Performance

Rationally designed synthesis strategy for well-defined morphology which can endow the catalysts with unexpectedly enhanced catalytic properties remains a significant challenge in heterogeneous catalytic reactions. Hence, here we report a facile and controllable synthesis of polystyrene microsphere-supported Ag–Ni-alloyed catalysts (PS@Ag–Ni) with uniform core–shell structures through sulfonated treatment coupled with the subsequent liquid-phase reduction strategy. In this typical synthesis, sulfuric acid acts as the bifunctional roles in directing the core–shell morphology and the linker between the polystyrene microspheres and Ag–Ni alloy. The as-obtained PS@Ag–Ni optimized by tuning in a mass ratio of 1:1 shows superior oxygen reduction reaction activity and electrocatalytic performance toward the degradation of p-nitrophenol in comparison with other range of polystyrene microspheres and Ag–Ni alloy feeding ratios. The superior electrocatalytic and oxygen reduction reaction activity are attributed to its highly uniform core–shell morphology and exposure of much more active sites. Moreover, our as-prepared core–shell electrocatalysts will enable further investigation in other catalytic reactions.