Oxophilic Sn to Promote Glucose Oxidation to Formic Acid in Ni Nanoparticles.

The electrochemical glucose oxidation reaction (GOR) presents an opportunity to produce hydrogen and high-value chemical products. Herein, we investigate the effect of Sn in Ni nanoparticles for the GOR to formic acid (FA). Electrochemical results show that the maximum activity is related to the amount of Ni, as Ni sites are responsible for catalyzing the GOR via the NiOOH/Ni(OH) pair.

Probing spin waves in CoO nanoparticles for magnonics applications.

The magnetic properties of spinel nanoparticles can be controlled by synthesizing particles of a specific shape and size. The synthesized nanorods, nanodots and cubic nanoparticles have different crystal planes selectively exposed on the surface. The surface effects on the static magnetic properties are well documented, while their influence on spin waves dispersion is still being debated.

A hexagon based Mn(II) rod metal-organic framework - structure, SF gas sorption, magnetism and electrochemistry.

A manganese(II) metal-organic framework based on the hexatopic hexakis(4-carboxyphenyl)benzene, cpb: [Mn(cpb)(dmf)], was solvothermally prepared showing a Langmuir area of 438 m g, rapid uptake OF sulfur hexafluoride (SF) as well as electrochemical and magnetic properties, while single crystal diffraction reveals an unusual rod-MOF topology.

Shape-induced superstructure formation in concentrated ferrofluids under applied magnetic fields.

The field-induced ordering of concentrated ferrofluids based on spherical and cuboidal maghemite nanoparticles is studied using small-angle neutron scattering, revealing a qualitative effect of the faceted shape on the interparticle interactions as shown in the structure factor and correlation lengths. Whereas a spatially disordered hard-sphere interaction potential with a short correlation length is found for ∼9 nm spherical nanoparticles, nanocubes of a comparable particle size exhibit a more pronounced interparticle interaction and the formation of linear arrangements. Analysis of the anisotropic two-dimensional pair distance correlation function gives insight into the real-space arrangement of the nanoparticles.

The Impact of Surface Charges of Carboxylated Cellulose Nanofibrils on the Water Motions in Hydrated Films.

Cellulose nanofibrils (CNFs) with carboxylated surface ligands are a class of materials with tunable surface functionality, good mechanical properties, and bio-/environmental friendliness. They have been used in many applications as scaffold, reinforcing, or functional materials, where the interaction between adsorbed moisture and the CNF could lead to different properties and structures and become critical to the performance of the materials. In this work, we exploited multiple experimental methods to study the water movement in hydrated films made of carboxylated CNFs prepared by TEMPO oxidation with two different surface charges of 600 and 1550 μmol·g.

Electrocatalytic Glycerol Oxidation with Concurrent Hydrogen Evolution Utilizing an Efficient MoO /Pt Catalyst.

Glycerol electrolysis affords a green and energetically favorable route for the production of value-added chemicals at the anode and H production in parallel at the cathode. Here, a facile method for trapping Pt nanoparticles at oxygen vacancies of molybdenum oxide (MoO ) nanosheets, yielding a high-performance MoO /Pt composite electrocatalyst for both the glycerol oxidation reaction (GOR) and the hydrogen evolution reaction (HER) in alkaline electrolytes, is reported. Combined electrochemical experiments and theoretical calculations reveal the important role of MoO nanosheets for the adsorption of glycerol molecules in GOR and the dissociation of water molecules in HER, as well as the strong electronic interaction with Pt.

SANS study of mixed cholesteric cellulose nanocrystal - gold nanorod suspensions.

Self-assembly of cellulose nanocrystals (CNCs) doped with anisotropic gold nanorods (AuNRs) was studied by small-angle neutron scattering. Correlation distances and structured domains were analysed to determine the influence of CNC and AuNR concentration on structuring. The transfer of the nematic structure of CNCs to AuNRs is explained in terms of an entropy-driven evolution from an isotropic to a cholesteric phase, with small nematic domains already present in the "isotropic" phase in equilibrium with the chiral nematic phase.

Feasibility of Chemically Modified Cellulose Nanofiber Membranes as Lithium-Ion Battery Separators.

Chemical modification of cellulose is beneficial to produce highly porous lithium-ion battery (LIB) separators, but introduction of high charge density adversely affects its electrochemical stability in a LiNiMnCoO (NMC)/graphite full cell. In this study, the influence of carboxylate functional groups in 2,2,6,6-tetramethylpiperidine-1-oxyl-mediated oxidized cellulose nanofibers (TOCNs) on the electrochemical performances of the LIB separator was investigated. X-ray photoelectron spectroscopy and in operando mass spectrometry measurements were used to elucidate the cause of failure of the batteries containing TOCN separators in the presence and absence of sodium counterions in the carboxylate groups and additives.

Hybrids based on borate-functionalized cellulose nanofibers and noble-metal nanoparticles as sustainable catalysts for environmental applications.

Polymeric supports from renewable resources such as cellulose nanomaterials are having a direct impact on the development of heterogenous sustainable catalysts. Recently, to increase the potentiality of these materials, research has been oriented towards novel functionalization possibilities. In this study, to increase the stability of cellulose nanofiber films as catalytic supports, by limiting the solubility in water, we report the synthesis of new hybrid catalysts (HC) based on silver, gold, and platinum nanoparticles, and the corresponding bimetallic nanoparticles, supported on cellulose nanofibers (CNFs) cross-linked with borate ions.

Fabrication of Maghemite Nanoparticles with High Surface Area.

Maghemite nanoparticles with high surface area were obtained from the dehydroxylation of lepidocrocite prismatic nanoparticles. The synthesis pathway from the precursor to the porous maghemite nanoparticles is inexpensive, simple and gives high surface area values for both lepidocrocite and maghemite. The obtained maghemite nanoparticles contained intraparticle and interparticle pores with a surface area ca.

Functionalization and patterning of nanocellulose films by surface-bound nanoparticles of hydrolyzable tannins and multivalent metal ions.

Inspired by the Bogolanfini dyeing technique, we report how flexible nanofibrillated cellulose (CNF) films can be functionalized and patterned by surface-bound nanoparticles of hydrolyzable tannins and multivalent metal ions with tunable colors. Molecular dynamics simulations show that gallic acid (GA) and ellagic acid (EA) rapidly adsorb and assemble on the CNF surface, and atomic force microscopy confirms that nanosized GA assemblies cover the surface of the CNF. CNF films were patterned with tannin-metal ion nanoparticles by an in-fibre reaction between the pre-impregnated tannin and the metal ions in the printing ink.

Assembly, Gelation, and Helicoidal Consolidation of Nanocellulose Dispersions.

The ability to probe the assembly, gelation, and helicoidal consolidation of cellulose nanocrystal (CNC) dispersions at high concentrations can provide unique insight into the assembly and can assist optimized manufacturing of CNC-based photonic and structural materials. In this Feature Article, we review and discuss the concentration dependence of the structural features, characterized by the particle separation distance and the helical pitch, at CNC concentrations ( c) that range from the isotropic state, over the biphasic range, to the fully liquid crystalline state. The structure evolution of CNC dispersions probed by time-resolved small-angle X-ray scattering during evaporation-induced assembly highlighted the importance of gelation and consolidation at high concentrations.

Anisotropic Diffusion and Phase Behavior of Cellulose Nanocrystal Suspensions.

In this paper, we use dynamic light scattering in polarized and depolarized modes to determine the translational and rotational diffusion coefficients of concentrated rodlike cellulose nanocrystals in aqueous suspension. Within the range of studied concentrations (1-5 wt %), the suspension starts a phase transition from an isotropic to an anisotropic state as shown by polarized light microscopy and viscosity measurements. Small-angle neutron scattering measurements also confirmed the start of cellulose nanocrystal alignment and a decreasing distance between the cellulose nanocrystals with increasing concentration.

Inducing nematic ordering of cellulose nanofibers using osmotic dehydration.

The formation of nematically-ordered cellulose nanofiber (CNF) suspensions with an order parameter f≈ 0.8 is studied by polarized optical microscopy, small-angle X-ray scattering (SAXS), and rheological measurements as a function of CNF concentration. The wide range of CNF concentrations, from 0.

Assembly of cellulose nanocrystals in a levitating drop probed by time-resolved small angle X-ray scattering.

Assembly of bio-based nano-sized particles into complex architectures and morphologies is an area of fundamental interest and technical importance. We have investigated the assembly of sulfonated cellulose nanocrystals (CNC) dispersed in a shrinking levitating aqueous drop using time-resolved small angle X-ray scattering (SAXS). Analysis of the scaling of the particle separation distance (d) with particle concentration (c) was used to follow the transition of CNC dispersions from an isotropic state at 1-2 vol% to a compressed nematic state at particle concentrations above 30 vol%.

Effects of Different Manufacturing Processes on TEMPO-Oxidized Carboxylated Cellulose Nanofiber Performance as Binder for Flexible Lithium-Ion Batteries.

Carboxylated cellulose nanofibers (CNF) prepared using the TEMPO-route are good binders of electrode components in flexible lithium-ion batteries (LIB). However, the different parameters employed for the defibrillation of CNF such as charge density and degree of homogenization affect its properties when used as binder. This work presents a systematic study of CNF prepared with different surface charge densities and varying degrees of homogenization and their performance as binder for flexible LiFePO electrodes.

Superlattice growth and rearrangement during evaporation-induced nanoparticle self-assembly.

Understanding the assembly of nanoparticles into superlattices with well-defined morphology and structure is technologically important but challenging as it requires novel combinations of in-situ methods with suitable spatial and temporal resolution. In this study, we have followed evaporation-induced assembly during drop casting of superparamagnetic, oleate-capped γ-FeO nanospheres dispersed in toluene in real time with Grazing Incidence Small Angle X-ray Scattering (GISAXS) in combination with droplet height measurements and direct observation of the dispersion. The scattering data was evaluated with a novel method that yielded time-dependent information of the relative ratio of ordered (coherent) and disordered particles (incoherent scattering intensities), superlattice tilt angles, lattice constants, and lattice constant distributions.

Following in Real Time the Two-Step Assembly of Nanoparticles into Mesocrystals in Levitating Drops.

Mesocrystals composed of crystallographically aligned nanocrystals are present in biominerals and assembled materials which show strongly directional properties of importance for mechanical protection and functional devices. Mesocrystals are commonly formed by complex biomineralization processes and can also be generated by assembly of anisotropic nanocrystals. Here, we follow the evaporation-induced assembly of maghemite nanocubes into mesocrystals in real time in levitating drops.

Tunable High-Field Magnetization in Strongly Exchange-Coupled Freestanding Co/CoO Core/Shell Coaxial Nanowires.

The exchange bias properties of Co/CoO coaxial core/shell nanowires were investigated with cooling and applied fields perpendicular to the wire axis. This configuration leads to unexpected exchange-bias effects. First, the magnetization value at high fields is found to depend on the field-cooling conditions.

Tuning the structure and habit of iron oxide mesocrystals.

A precise control over the meso- and microstructure of ordered and aligned nanoparticle assemblies, i.e., mesocrystals, is essential in the quest for exploiting the collective material properties for potential applications.

3D Visualization of the Iron Oxidation State in FeO/Fe3O4 Core-Shell Nanocubes from Electron Energy Loss Tomography.

The physicochemical properties used in numerous advanced nanostructured devices are directly controlled by the oxidation states of their constituents. In this work we combine electron energy-loss spectroscopy, blind source separation, and computed tomography to reconstruct in three dimensions the distribution of Fe(2+) and Fe(3+) ions in a FeO/Fe3O4 core/shell cube-shaped nanoparticle with nanometric resolution. The results highlight the sharpness of the interface between both oxides and provide an average shell thickness, core volume, and average cube edge length measurements in agreement with the magnetic characterization of the sample.

Thin Water Films at Multifaceted Hematite Particle Surfaces.

Mineral surfaces exposed to moist air stabilize nanometer- to micrometer-thick water films. This study resolves the nature of thin water film formation at multifaceted hematite (α-Fe2O3) nanoparticle surfaces with crystallographic faces resolved by selected area electron diffraction. Dynamic vapor adsorption (DVA) in the 0-19 Torr range at 298 K showed that these particles stabilize water films consisting of up to 4-5 monolayers.

Fabrication of nanocellulose-hydroxyapatite composites and their application as water-resistant transparent coatings.

Nanosized composite rods ∼300 nm in length and ∼20 nm in width were produced by deposition of 22-77 wt% of a c-axis-oriented hydroxyapatite (HA) on cellulose nanocrystals (CNCs). The CNCs functionalized with sulphonic groups were covered with the HA nanocrystals through controlled nucleation and growth under a moderately supersaturated condition in a solution system based on a simulated body fluid. Water-resistant transparent coatings 2-4 μm thick were obtained via evaporation-induced assembly of CNC-HA nanocomposites by casting their suspension on a glass substrate and the subsequent growth of HA nanocrystals by vapour hydrothermal treatment.

Rod Packing in Chiral Nematic Cellulose Nanocrystal Dispersions Studied by Small-Angle X-ray Scattering and Laser Diffraction.

The packing of cellulose nanocrystals (CNC) in the anisotropic chiral nematic phase has been investigated over a wide concentration range by small-angle X-ray scattering (SAXS) and laser diffraction. The average separation distance between the CNCs and the average pitch of the chiral nematic phase have been determined over the entire isotropic-anisotropic biphasic region. The average separation distances range from 51 nm, at the onset of the anisotropic phase formation, to 25 nm above 6 vol % (fully liquid crystalline phase) whereas the average pitch varies from ≈15 μm down to ≈2 μm as ϕ increases from 2.