Growth of Au-Pd2Sn nanorods via galvanic replacement and their catalytic performance on hydrogenation and sonogashira coupling reactions

Colloidal Pd2Sn and Au–Pd2Sn nanorods (NRs) with tuned size were produced by the reduction of Pd and Sn salts in the presence of size- and shape-controlling agents and the posterior growth of Au tips through a galvanic replacement reaction. Pd2Sn and Au–Pd2Sn NRs exhibited high catalytic activity toward quasi-homogeneous hydrogenation of alkenes (styrene and 1-octene) and alkynes (phenylacetylene and 1-octyne) in dichloromethane. Au–Pd2Sn NRs showed higher activity than Pd2Sn for 1-octene, 1-octyne, and phenylacetylene. In Au–Pd2Sn heterostructures, X-ray photoelectron spectroscopy evidenced an electron donation from the Pd2Sn NR to the Au tips. Such heterostructures showed distinct catalytic behavior in the hydrogenation of compounds containing a triple bond such as tolan. This can be explained by the aurophilicity of triple bonds. To further study this effect, Pd2Sn and Au–Pd2Sn NRs were also tested in the Sonogashira coupling reaction between iodobenzene and phenylacetylene in N,N-dimethylformamide. At low concentration, this reaction provided the expected product, tolan. However, at high concentration, more reduced products such as stilbene and 1,2-diphenylethane were also obtained, even without the addition of H2. A mechanism for this unexpected reduction is proposed.Peer ReviewedPostprint (author's final draft

Scalable heating-up synthesis of monodisperse Cu2ZnSnS4 nanocrystals

Monodisperse Cu2ZnSnS4 (CZTS) nanocrystals (NCs), with quasi spherical shape, were prepared by a facile, high-yield, scalable, and high-concentration heat-up procedure. The key parameters to minimize the NC size distribution were efficient mixing and heat transfer in the reaction mixture through intensive argon bubbling and improved control of the heating ramp stability. Optimized synthetic conditions allowed the production of several grams of highly monodisperse CZTS NCs per batch, with up to 5 wt % concentration in a crude solution and a yield above 90%

Tuning branching in ceria nanocrystals

Branched nanocrystals (NCs) enable high atomic surface exposure within a crystalline network that provides avenues for charge transport. This combination of properties makes branched NCs particularly suitable for a range of applications where both interaction with the media and charge transport are involved. Herein we report on the colloidal synthesis of branched ceria NCs by means of a ligand-mediated overgrowth mechanism. In particular, the differential coverage of oleic acid as an X-type ligand at ceria facets with different atomic density, atomic coordination deficiency, and oxygen vacancy density resulted in a preferential growth in the [111] direction and thus in the formation of ceria octapods. Alcohols, through an esterification alcoholysis reaction, promoted faster growth rates that translated into nanostructures with higher geometrical complexity, increasing the branch aspect ratio and triggering the formation of side branches. On the other hand, the presence of water resulted in a significant reduction of the growth rate, decreasing the reaction yield and eliminating side branching, which we associate to a blocking of the surface reaction sites or a displacement of the alcoholysis reaction. Overall, adjusting the amounts of each chemical, well-defined branched ceria NCs with tuned number, thickness, and length of branches and with overall size ranging from 5 to 45 nm could be produced. We further demonstrate that such branched ceria NCs are able to provide higher surface areas and related oxygen storage capacities (OSC) than quasi-spherical NCs

Scalable heating-up synthesis of monodisperse Cu2ZnSnS4 nanocrystals

Monodisperse Cu2ZnSnS4 (CZTS) nanocrystals (NCs), with quasi-spherical shape, were prepared by a facile, high-yield, scalable, and high-concentration heat-up procedure. The key parameters to minimize the NC size distribution were efficient mixing and heat transfer in the reaction mixture through intensive argon bubbling and improved control of the heating ramp stability. Optimized synthetic conditions allowed the production of several grams of highly monodisperse CZTS NCs per batch, with up to 5 wt % concentration in a crude solution and a yield above 90%

Mn3O4@CoMn2O4-CoxOy nanoparticles : partial cation exchange synthesis and electrocatalytic properties toward the oxygen reduction and evolution reactions

Mn3O4@CoMn2O4 nanoparticles (NPs) were produced at low temperature and ambient atmosphere using a one -pot two-step synthesis protocol involving the cation exchange of Mn by Co in preformed Mn3O4 NPs. Selecting the proper cobalt precursor, the nucleation of CoxOy crystallites at the Mn3O4@a CoMn2O4 surface could be simultaneously promoted to form Mn3O4@CoMn2O4-CoxOy NPs. Such heterostructured NPs were investigated for oxygen reduction and evolution reactions (ORR, OER) in alkaline solution. Mn3O4@ CoMn2O4-Cox0y NPs with [Co]/[Mn] = 1 showed low overpotentials of 0.31 Vat(-3) mA.cm(-2) and a small Tafel slope of 52 mV.dec(-1) for ORR, and overpotentials of 0.31 V at 10 mAPeer ReviewedPostprint (author's final draft

NiSn bimetallic nanoparticles as stable electrocatalysts for methanol oxidation reaction

Nickel is an excellent alternative catalyst to high cost Pt and Pt-group metals as anode material in direct methanol fuel cells. However, nickel presents a relatively low stability under operation conditions, even in alkaline media. In this work, a synthetic route to produce bimetallic NiSn nanoparticles (NPs) with tuned composition is presented. Through co-reduction of the two metals in the presence of appropriate surfactants, 3–5¿nm NiSn NPs with tuned Ni/Sn ratios were produced. Such NPs were subsequently supported on carbon black and tested for methanol electro-oxidation in alkaline media. Among the different stoichiometries tested, the most Ni-rich alloy exhibited the highest electrocatalytic activity, with mass current density of 820¿mA¿mg-1 at 0.70¿V (vs. Hg/HgO). While this activity was comparable to that of pure nickel NPs, NiSn alloys showed highly improved stabilities over periods of 10,000¿s at 0.70¿V. We hypothesize this experimental fact to be associated to the collaborative oxidation of the byproducts of methanol which poison the Ni surface or to the prevention of the tight adsorption of these species on the Ni surface by modifying its surface chemistry or electronic density of states.Peer ReviewedPostprint (author's final draft

Tuning branching in ceria nanocrystals

Branched nanocrystals (NCs) enable high atomic surface exposure within a crystalline network that provides avenues for charge transport. This combination of properties makes branched NCs particularly suitable for a range of applications where both interaction with the media and charge transport are involved. Herein we report on the colloidal synthesis of branched ceria NCs by means of a ligand-mediated overgrowth mechanism. In particular, the differential coverage of oleic acid as an X-type ligand at ceria facets with different atomic density, atomic coordination deficiency, and oxygen vacancy density resulted in a preferential growth in the [111] direction and thus in the formation of ceria octapods. Alcohols, through an esterification alcoholysis reaction, promoted faster growth rates that translated into nanostructures with higher geometrical complexity, increasing the branch aspect ratio and triggering the formation of side branches. On the other hand, the presence of water resulted in a significant reduction of the growth rate, decreasing the reaction yield and eliminating side branching, which we associate to a blocking of the surface reaction sites or a displacement of the alcoholysis reaction. Overall, adjusting the amounts of each chemical, well-defined branched ceria NCs with tuned number, thickness, and length of branches and with overall size ranging from 5 to 45 nm could be produced. We further demonstrate that such branched ceria NCs are able to provide higher surface areas and related oxygen storage capacities (OSC) than quasi-spherical NCs

Compositionally tuned NixSn alloys as anode materials for lithium-ion and sodium-ion batteries with a high pseudocapacitive contribution

Nickel tin alloy nanoparticles (NPs) with tuned composition NixSn (0.6 ≤ x ≤ 1.9) were synthesized by a solution-based procedure and used as anode materials for Li-ion batteries (LIBs) and Na-ion batteries (SIBs). Among the compositions tested, Ni₀₉Sn-based electrodes exhibited the best performance in both LIBs and SIBs. As LIB anodes, Ni₀₉Sn-based electrodes delivered charge-discharge capacities of 980 mAh g⁻¹ after 340 cycles at 0.2 A g⁻¹ rate, which surpassed their maximum theoretical capacity considering that only Sn is lithiated. A kinetic characterization of the charge-discharge process demonstrated the electrode performance to be aided by a significant pseudocapacitive contribution that compensated for the loss of energy storage capacity associated to the solid-electrolyte interphase formation. This significant pseudocapacitive contribution, which not only translated into higher capacities but also longer durability, was associated to the small size of the crystal domains and the proper electrode composition. The performance of NixSn-based electrodes toward Na-ion storage was also characterized, reaching significant capacities above 200 mAh g⁻¹ at 0.1 A g⁻¹ but with a relatively fast fade over 120 continuous cycles. A relatively larger pseudocapacitive contribution was obtained in Ni Sn-based electrodes for SIBs when compared with LIBs, consistently with the lower contribution of the Na ion diffusion associated to its larger size

Co–Sn nanocrystalline solid solutions as anode materials in lithium-ion batteries with high pseudocapacitive contribution

Co–Sn solid-solution nanoparticles with Sn crystal structure and tuned metal ratios were synthesized by a facile one pot solution-based procedure involving the initial reduction of a Sn precursor followed by incorporation of Co within the Sn lattice. These nanoparticles were used as anode materials for Li-ion batteries. Among the different compositions tested, Co0.7Sn and Co0.9Sn electrodes provided the highest capacities with values above 1500 mAh¿g-1 at a current density of 0.2 A¿g-1 after 220 cycles, and up to 800 mAh¿g-1 at 1.0 A¿g-1 after 400 cycles. Up to 81¿% pseudocapacitance contribution was measured for these electrodes at a sweep rate of 1.0 mV¿s-1, thereby indicating fast kinetics and long durability. The excellent performance of Co–Sn nanoparticle alloy-based electrodes was attributed to both the small size of the crystal domains and their suitable composition, which buffered volume changes of Sn and contributed to a suitable electrode restructuration.Postprint (author's final draft

Identification of Water-Soluble Compounds from Cinnamomum kanehirae Hay Promoting the Asexual Sporulation of Antrodia cinnamomea and Optimization of Their Addition Levels in the Culture Medium

In order to determine compounds present in the aqueous extract of Cinnamomum kanehirae Hay (CWE) that promote the asexual sporulation of Antrodia cinnamomea in submerged fermentation. First, CWE was isolated by alcohol precipitation and fractional extraction with different organic solvents. The influence of the obtained fractions on the asexual sporulation of A. cinnamomea was investigated. It was showed that the chloroform (at 30 μg/mL) and ethyl acetate (at 50 μg/mL) extracts of the supernatant after ethanol precipitation of CWE presented remarkable promoting effects on the sporulation of A. cinnamomea, and the effect of LFE was significantly more pronounced than that of YZE, indicating that both LFE and YZE contained compounds that promote the sporulation of A. cinnamomea. Subsequently, liquid chromatography-mass spectrometry (LC-MS) was used to analyze the chemical components of the fractions obtained from CWE, and erythritol was considered as the major component that promotes the sporulation of A. cinnamomea. Finally, the effect of erythritol with a purity of 98% on the fermentation performance of A. cinnamomead was investigated. The result showed that erythritol did significantly promote the sporulation of A. cinnamomea and increased the spore production by 55.17% compared with the control group at the optimal concentration of 1.0 μg/mL. Meanwhile, 1.0 μg/mL erythritol significantly promoted the mycelial growth and synthesis of intracellular polysaccharides (IPS) of A. cinnamomea in submerged fermentation and increased the biomass and the yield of IPS by 18.65% and 260.13%, respectively. However, erythritol had no significant effect on the synthesis of triterpenes in A. cinnamomea