Thin Oxide Shell Research Articles

Liquid Metal Alloys Enable Efficient Formate Electrosynthesis

AbstractLiquid metals are an interesting class of materials with the unique combination of metallic nature and liquid fluidity, and have recently been explored in many emerging fields. Their potential applications in catalysis, unfortunately, remain largely untapped. Herein, Ga‐mediated liquid metal alloying as an effective strategy is demonstrated to prepare functional alloys for catalysis. The alloying is carried out by dissolving indium or tin pellets in liquid gallium at room temperature or assisted by gentle heating, giving rise to binary Ga1−xInx and Ga1−xSnx liquid metal alloys with tunable chemical compositions. When further subjected to ultrasonication in water, they are ruptured into nanosized particles with liquid metal cores and thin surface oxide shells. Electrochemical measurements reveal that the liquid metal alloying significantly promotes electrocatalytic CO2 reduction to formate. Taking Ga0.75In0.25 as an example, its formate Faradaic efficiency is enhanced by 10%–20% compared to those of Ga and In, and its formate partial current density is 4–6 times larger than those of Ga and In. This enhancement is rationalized via computational simulations showing that the surrounding of In active sites with Ga atoms deactivates the undesirable reaction pathways to CO or H2, and facilitates selective formate electrosynthesis.

Photodeposition-Based Synthesis of TiO2@IrOx Core-Shell Catalyst for Proton Exchange Membrane Water Electrolysis with Low Iridium Loading.

The widespread application of green hydrogen production technologies requires cost reduction of crucial elements. To achieve this, a viable pathway to reduce the iridium loading in proton exchange membrane water electrolysis (PEMWE) is explored. Herein, a scalable synthesis method based on a photodeposition process for a TiO2@IrOx core-shell catalyst with a reduced iridium content as low as 40wt.% is presented. Using this synthesis method, titania support particles homogeneously coated with a thin iridium oxide shell of only 2.1±0.4nm are obtained. The catalyst exhibits not only high ex situ activity, but also decent stability compared to commercially available catalysts. Furthermore, the unique core-shell structure provides a threefold increased electrical powder conductivity compared to structures without the shell. In addition, the low iridium content facilitates the fabrication of sufficiently thick catalyst layers at decreased iridium loadings mitigating the impact of crack formation in the catalyst layer during PEMWE operation. It is demonstrated that the novel TiO2@IrOx core-shell catalyst clearly outperforms the commercial reference in single-cell tests with an iridium loading below 0.3mgIrcm-2 exhibiting a superior iridium-specific power density of 17.9kW gIr -1 compared to 10.4kW gIr -1 for the commercial reference.

Investigation of iron oxide shell and iron core in magnetically-assisted synthetized wire-like nanochains

The zerovalent iron (Fe0) nanomaterials tend to be spontaneously oxidized in the presence of oxygen. This leads to the formation of interface composed of iron core and thin iron oxide shell. These structures are frequently observed with transmission electron microscope but, at the same time, it is hard to determine the precise structural and chemical composition of oxide shell. This feature is very important for possible applications of Fe0 nanostructures. Hence, the present work aims to deliver more detailed insights in this topic. The investigations are performed for the iron nanochains prepared in the magnetic-field-induce reduction of FeCl3 by NaBH4. The high-resolution transmission electron microscopy, electron energy loss spectroscopy, and x-ray photoemission spectroscopy confirm that the iron nanochains are covered by very thin oxide layer not exceeding over 3 nm. Moreover, the detailed XPS analyses of O 1s and Fe 2p lines indicate that the iron oxide shell reveals Fe3O4 nature. Moreover, this work demonstrated that some by-products of the reaction containing boron are presented in the sample even after a removal of the thin iron oxide shell by Ar+ treatment.

Defect-mediated energy transfer in ZnO thin films doped with rare-earth ions

The rare-earth (RE) (Eu, Er, Nd) doped ZnO thin films were fabricated by a cost-effective chemical solution deposition method. The emission properties of ZnO:RE films were investigated under different excitation conditions, where the RE ions were excited either through direct pumping into the 4f energy levels of RE ions or through indirect excitation by energy transfer from the host material. It is demonstrated that under both excitation methods, the films showed strong emission from the RE ions at room temperature, which confirms the hypothesis that the RE ions can be effectively excited by the host material. Moreover, the influence of RE doping on the development of the crystalline structure of the ZnO thin film was studied. Only a small amount of REs was incorporated into the ZnO grains; most of the REs remained segregated at the grain boundaries, forming a thin oxide shell that strongly suppresses the sintering of the grains and reduces their size.

Formation of Sn/Zn alloy or core-shell nanoparticles via pulsed nanosecond discharges in liquid toluene

In the exploration of new techniques for the synthesis of metallic nanoparticles, the possibility to exploit electrical discharges in liquid has arisen as an easy, high throughput and low-cost method. This technique of synthesis offers an extensive playground to produce a wide range of nanostructures with composition highly dependent on that of the electrode and of the liquid medium. Here, we demonstrate the formation of a Sn–Zn nanoalloy (particle diameter <10 nm) using electrical discharge between a Sn anode and a Zn cathode immersed in liquid toluene. Core/shell nanoparticles, with diameter between 12 and 20 nm, are also produced. These particles are composed of a Sn crystalline core and a shell made of Zn, Sn and O. A third class of particles was also found, although being rarer, constituted of large (hundreds of nm) Sn particles, with a thin Sn oxide shell. Detailed structural and chemical characterizations were accomplished via TEM and STEM imaging, as well as STEM-EDX analyses on the single nanoparticles and, considering the complex variety of phenomena taking place in in-liquid plasma, a plausible mechanism of synthesis is proposed.

Electrodeposition of Gallium and Indium from Non-aqueous Electrolytes

In this work, we studied the electrodeposition of gallium and indium from 1,2-dimethoxyethane (DME)-based and dimethyl sulfoxide (DMSO)-based electrolytes, respectively.1,2 Cyclic voltammetry in combination with rotating (ring) disk electrode and electrochemical quartz-crystal microbalance were used to identify the redox chemistry and electrodeposition behavior of both metals. Scanning electron microscopy (SEM) was used to investigate the structural morphology of the deposited materials.Gallium electrodeposition was studied from a bath composed of gallium(III) chloride, an inert background salt and DME. The electroreduction process occurred in two steps: (1) from gallium(III) to gallium(I), and (2) from gallium(I) to gallium(0). Metallic gallium was deposited as spheres with diameters of several hundreds of nanometers that were stacked on top of each other. X-ray photoelectron spectroscopy revealed that each gallium sphere was covered by a thin gallium oxide shell. These shells prevent individual gallium spheres from agglomerating to larger entities. Electrochemical experiments indicated that these oxide layers were electrically conductive. It was demonstrated that electrodeposition proceeded via a droplet-on-droplet electrodeposition mechanism. A growth mechanism for an individual growing gallium sphere was also postulated.Indium electrodeposition was studied from a bath composed of indium(III) methanesulfonate, a background salt and DMSO. indium(III) methanesulfonate was synthesized from methanesulfonic acid and indium(III) oxide. The latter is an intermediate formed during the purification of indium from primary and secondary resources. Conversion of indium(III) oxide into metallic indium could therefore lower the energetic cost of its production. Analogously to gallium, Indium(III) is reduced to indium(I), and then to indium(0). It was demonstrated that indium(I) disproportionates to indium(III) and indium(0), leading to the formation of micron-sized metallic indium particles in the electrolyte. At 26 °C, indium deposited as smooth, flat films whereas at 160 °C, it deposited as liquid indium droplets. Electrodeposition of indium above its melting point enables the process to be performed in a continuous manner; indium droplets accumulate and grow, and will ultimately glide off the electrode, and drop to the bottom of the cell, forming a liquid pool from which the metal can be tapped off.In the attached figure, SEM images of (1) gallium deposited at 26 °C and (2) indium, deposited at 26 °C and 160 °C are shown. Figure 1

Modification of the Mechanical Properties of Core‐Shell Liquid Gallium Nanoparticles by Thermal Oxidation at Low Temperature

AbstractGallium nanoparticles (Ga NPs) are attracting increasing attention because of their appealing physical‐chemical properties. In particular, their mechanical properties play a key role in the implementation of these core‐shell structures on certain applications, such as soft and stretchable electronics. Thus, efforts are being addressed to modulate them mainly by chemical means. In contrast, this study investigates how the mechanical properties of the outer gallium thin oxide shell change when its thickness is increased through a thermal oxidation strategy. Specifically, as‐deposited Ga NPs, as well as those subjected to thermal oxidation at 300 °C for three different times, are studied by performing single‐particle indentations by atomic force microscopy over a wide range of NP radius. This analysis helps to confirm that the Reissner's thin‐shell model for small deformations within the elastic regime is obeyed. From these data, the dependence of the shell stiffness and the Young's modulus of the gallium oxide on the thermal treatment is obtained. It is found that the shell stiffness increases with the annealing time, even by a factor of 50 under prolonged thermal oxidation, while the gallium oxide Young's modulus, close to 30 GPa, does not change significantly.

Stabilization of Undercooled Metals via Passivating Oxide Layers

AbstractUndercooling metals relies on frustration of liquid–solid transition mainly by an increase in activation energy. Passivating oxide layers are a way to isolate the core from heterogenous nucleants (physical barrier) while also raising the activation energy (thermodynamic/kinetic barrier) needed for solidification. The latter is due to composition gradients (speciation) that establishes a sharp chemical potential gradient across the thin (0.7–5 nm) oxide shell, slowing homogeneous nucleation. When this speciation is properly tuned, the oxide layer presents a previously unaccounted for interfacial tension in the overall energy landscape of the relaxing material. We demonstrate that 1) the integrity of the passivation oxide is critical in stabilizing undercooled particle, a key tenet in developing heat‐free solders, 2) inductive effects play a critical role in undercooling, and 3) the magnitude of the influence of the passivating oxide can be larger than size effects in undercooling.

Stabilization of Undercooled Metals via Passivating Oxide Layers.

Undercooling metals relies on frustration of liquid-solid transition mainly by an increase in activation energy. Passivating oxide layers are a way to isolate the core from heterogenous nucleants (physical barrier) while also raising the activation energy (thermodynamic/kinetic barrier) needed for solidification. The latter is due to composition gradients (speciation) that establishes a sharp chemical potential gradient across the thin (0.7-5 nm) oxide shell, slowing homogeneous nucleation. When this speciation is properly tuned, the oxide layer presents a previously unaccounted for interfacial tension in the overall energy landscape of the relaxing material. We demonstrate that 1) the integrity of the passivation oxide is critical in stabilizing undercooled particle, a key tenet in developing heat-free solders, 2) inductive effects play a critical role in undercooling, and 3) the magnitude of the influence of the passivating oxide can be larger than size effects in undercooling.

Electrochemical behavior and electrodeposition of gallium in 1,2-dimethoxyethane-based electrolytes.

The electrochemical behavior and electrodeposition of gallium was studied in a non-aqueous electrolyte comprising of gallium(iii) chloride and 1,2-dimethoxyethane (DME). Electrochemical quartz crystal microbalance (EQCM) and rotating ring disk electrode (RRDE) measurements indicate that reduction of gallium(iii) is a two-step process: first from gallium(iii) to gallium(i), and then from gallium(i) to gallium(0). The morphology and elemental composition of the electrodeposited layer were examined using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). Metallic gallium was deposited as spheres with diameters of several hundred nanometers that were stacked on top of each other. X-ray photoelectron spectroscopy (XPS) revealed that each gallium sphere was covered by a thin gallium oxide shell. Electrochemical experiments indicated that these oxide layers are electrically conductive, as gallium can be electrodeposited and partially stripped on or from the layer of spheres below. This was further evidenced by simultaneous electrodeposition of gallium and indium, using indium as a tracer. Electrodeposition of gallium from an O2-containing electrolyte resulted in spheres with smaller diameters. This was due to the formation thicker oxide shells, through which diffusion of gallium atoms that were electrodeposited on the surface, was slower. The concentration of gallium adatoms on top of the gallium spheres to form a new sphere therefore reaches the critical concentration for nucleating a new gallium sphere sooner, leading to smaller spheres.

Sintering Mechanism of a Supersaturated Ag-Cu Nanoalloy Film for Power Electronic Packaging.

Ag-Cu bimetallic nanoparticles, combining the advantages of both Ag and Cu, are a promising material for power electronic packaging. In this work, a supersaturated Ag-7.3 wt % Cu alloy nanoparticle film was developed by using pulsed laser deposition. Unlike Cu nanoparticles, the supersaturated Ag-Cu alloy nanoparticles can conduct bonding in air without the assistance of a reduction agent. The shear strength was >20 MPa when the bonding temperature reached 300 °C, which was above the die shear standard (MIL-STD-883 K, 7.8 MPa) and compatible with the typical die attach process. The Cu separating behavior was accompanied by the bonding process at 250-400 °C, which was discussed systematically. Neck formation was delayed to about 250 °C because of the hindering effect of the thin oxide shell of the Ag-Cu alloy. The necking networks provide volume diffusion paths despite the growth of surface oxide, resulting in compact densification. The bondline under the SiC die consisted of a porous Ag-Cu alloy matrix with a dispersed secondary phase of Cu2O/CuO, which is supposed to have improved electrochemical migration resistance.

Magnetic-field-induced synthesis of amorphous iron-nickel wire-like nanostructures

Manufacturing process of wire-like binary or ternary metal nanoalloys applying the magnetic-field-induced (MFI) synthesis is still a challenging task. Hence, this work demonstrates for the first time how to produce the iron-nickel wire-like nanostructures with Fe0·75Ni0.25, Fe0·5Ni0.5 and Fe0·25Ni0.75 compositions. In a contrary to the previously reported synthesis of the Fe–Ni wire-like nanomaterials, this process has been carried out at room temperature without employment of templates, surfactants, organic solvents, and other chemical additives. The as-prepared samples exhibit specific structures with the amorphous bimetallic alloy cores covered by thin amorphous oxide shells. Moreover, they are composed of nanoparticles which are aligned in nearly linear chains. The Fe–Ni samples are ferromagnetic materials. Their coercivity values and saturation magnetizations depend on chemical compositions and dimensions of the investigated chains. The highest saturation magnetization and the lowest coercivity is found for the material with the lowest content of nickel and vice versa.

Cobalt-Based Nitride-Core Oxide-Shell Oxygen Reduction Electrocatalysts.

Developing high-performance, low-cost, and conductive nonprecious electrocatalysts for the oxygen reduction reaction (ORR) has been a key challenge for advancing fuel cell technologies. Here, we report on a novel family of cobalt nitrides (CoxN/C, x = 2, 3, 4) as ORR electrocatalysts in alkaline fuel cells. Co4N/C exhibited the highest ORR activity among the three types of cobalt nitrides studied, with a half-wave potential (E1/2) of 0.875 V vs RHE in 1 M KOH, rivaling that of commercial Pt/C (0.89 V). Moreover, Co4N/C showed an 8-fold improvement in mass activity at 0.85 V, when compared to cobalt oxide, Co3O4/C, and a negligible degradation (ΔE1/2 = 14 mV) after 10 000 potential cycles. The superior performance was ascribed to the formation of a conductive nitride core surrounded by a naturally formed thin oxide shell (about 2 nm). The conductive nitride core effectively mitigated the low conductivity of the metal oxide, and the thin oxide shell on the surface provided the active sites for the ORR. Strategies developed herein represent a promising approach for the design of other novel metal nitrides as electrocatalysts for fuel cells.

Universal Oxide Shell Growth Enables in Situ Structural Studies of Perovskite Nanocrystals during the Anion Exchange Reaction.

The ability to tune thin oxide coatings by wet-chemistry is desirable for many applications, yet it remains a key synthetic challenge. In this work, we introduce a general colloidal atomic layer deposition (c-ALD) synthesis to grow an alumina shell with tunable thickness around nanocrystalline cores of various compositions spanning from ionic semiconductors (i.e., CsPbX3, with X = Br, I, Cl) to metal oxides and metals (i.e., CeO2 and Ag). The distinctive characteristics of each core (i.e., emission, facile surface functionalization, stability) allowed us to optimize and to elucidate the chemistry of the c-ALD process. Compared to gas-phase ALD, this newly developed synthesis has the advantage of preserving the colloidal stability of the nanocrystalline core while controlling the shell thickness from 1 to 6 nm. As one example of the opportunities offered by the growth of a thin oxide shell, we study the anion exchange reaction in the CsPbX3 perovskites nanocrystals by in situ X-ray diffraction, which had been impeded so far by the instability of this class of materials and by the fast exchange kinetics.

High-Performance Quantum Dots with Synergistic Doping and Oxide Shell Protection Synthesized by Cation Exchange Conversion of Ternary-Composition Nanoparticles.

The insertion of cation impurities into quantum dots (QDs) as a dopant has been proved to be an efficient way to tailor their optical, electronic, and magnetic properties; however, the low quantum yield (QY) and poor photostability strongly limit their further applications. We report a strategy to coat a thin oxide shell around the heterovalent doped QDs to enhance their QYs and photostabilities simultaneously. In the case of Ag+-doped CdS QDs, the controlled cation exchange reaction between Cd2+ and ternary Ag3SbS3 nanoparticles not only realizes the Ag+ doping in CdS QDs but also generates a thin Sb2O3 shell around the surface of the QDs. Enabled by such, as-prepared CdS:Ag@Sb2O3 QDs exhibited enhanced photostability and high QY of 66.5%. We envision that the findings presented here will inspire more novel protocols for advancing the practical applications of doped QDs.

Si/SiO2 Core/Shell Luminescent Silicon Nanocrystals and Porous Silicon Powders With High Quantum Yield, Long Lifetime, and Good Stability

Most of the highly efficient luminescent silicon nanocrystals (SiNCs) reported to date consists of organically capped silicon cores. Here, we report a method of obtaining Si/SiO2 core/shell nanoparticles emitting at a peak energy of 1.5 eV with very high quantum yields (53-61%). The same method led to quantum yields of ~ 30% for porous silicon powder emitting at 1.9 eV. The SiNCs were very stable under continuous excitation for several hours. The lifetime at 1.5 eV was over 232 μs, the longest ever reported for SiNCs, consistent with the very high luminescence efficiency. The SiNCs were first fabricated by non-thermal plasma synthesis or anodization in the case of porous silicon. Then, a thin oxide shell (~ 1 nm) was grown using high-pressure water vapor annealing. This oxidation process allows for the growth of very good quality oxide with low defect concentration and low stress, resulting in very good surface passivation, which explains the very high quantum yields obtained.

(Invited) Electrochemical Control of Epitaxial Growth and Magnetic Properties of Fe Nanostructures

The control of interfacial properties offers genuine routes to tailor magnetism at the nanoscale. Epitaxial growth on suitable substrates is one approach to define the shape and orientation of nanobjects. We investigated the electrodeposition of iron nanoparticles on GaAs(001) to achieve epitaxial growth. The use of an electrolyte with low iron ion concentration (0.01 mol/l FeSO4) and a short deposition time (10 s) resulted in the formation and growth of individual Fe nuclei. The interplay between metal nuclei growth and hydrogen evolution is found to be decisive for the epitaxial interface formation. For electrochemical conditions with dominating hydrogen evolution, the deposited nanoparticles exhibit a faceted shape, crystallographic alignment and notable magnetic in-plane anisotropy. The beneficial role of the hydrogen evolution on the epitaxy is found to be related to the effect of hydrogen adsorption during the Fe/GaAs interface formation [1]. In consequence, we applied a compliance voltage during immersion of the substrate to boost the hydrogen evolution at the very start of the deposition. This lead to the formation of epitaxial nanocuboids that are aligned throughout the substrate [2]. Surface {100} facets predominate with a thin crystalline oxide shell that protects the nanoparticles during prolonged storage in air. The single crystallinity of the iron in combination with structural alignment leads to an in-plane magnetic anisotropy. These immobilized, oriented, and stable nanoparticles are promising for applications in nanoelectronic, sensor, and data storage technologies, as well as for the detailed analysis of the effect of shape and size on magnetism at the nanoscale. While in the case of nanoelectrodeposition, electrochemistry at the interface is exploited to irreversibly define the shape, structure and magnetism of the iron nanoparticles, reversible manipulation of magnetism solid/liquid electrolyte interfaces can be achieved by magneto-ionic reactions. The magneto-ionic effect relies on voltage-triggered charge transfer reactions in solid or liquid electrolyte-gated architectures [3,4]. For instance, a repeatable electrochemical transformation between metal and oxide can be exploited to manipulate magnetic metals at room temperature and via the application of only a few volts. This makes the magneto-ionic approach very competitive to many other magnetoelectric mechanisms such as multiferroics and magnetic semiconductors. We showed that polarized Fe-O/Fe heterostructures in a liquid electrolyte, readily undergo repeatable oxidation and reduction reactions that give rise to enormous magnetic property changes [5,6]. Voltage-induced changes of the saturation magnetization and magnetic anisotropy were achieved with FeOx/Fe and FeOx/Fe/FePt thin film heterostructures prepared by vacuum methods [5]. Enhanced effects are expected when the interfacial area-to-volume ratio of the magnetic nanostructures is increased by, e.g., using nanogranular structures instead of continuous films. We show that ultrathin iron nanoislands suitable for magneto-ionic effects can be efficiently prepared by electrodeposition in ambient conditions. The 3D growth mode leads to a nanogranular morphology when the deposition is stopped prior to coalescence. Upon removal from the electrodeposition setup natural oxidation sets in and iron/iron oxide nanoislands are present as starting material. To achieve voltage-control of magnetism in these electrodeposited nanoislands, an aqueous electrolyte containing 1 mol/l KOH was chosen that was already proven to be suitable for magneto-ionic effects in sputter-deposited continuous FeOx/Fe films [5]. The magneto-ionic reactions are directly linked to the electrochemical processes at the solid/liquid interface [6]. The nanostructures were then repeatedly polarized in the electrolyte at suitable reduction and oxidation potentials, E red and E ox, respectively. The magneto-ionic changes were probed by in situ anomalous Hall Effect (AHE) measurements. The switching between E red and E ox leads to a repeatable reduction to the ferromagnetic metal iron and oxidation to a non-ferromagnetic oxide phase with significantly lower magnetization. Almost complete ON/OFF switching is achieved (see Figure 1). The effect is larger than in continuous sputtered films of similar nominal thickness [5], which can be seen as a direct result of the higher interface/volume ratio of the nanoisland structures. Thus, for the first time, the crucial impact of the morphology on the magneto-ionic effects is elucidated. The electrochemical synthesis of magneto-ionic starting material is especially favorable because tunable magnetic material can also be deposited in channel walls and recesses. [1] K. Leistner et al., J. Electrochem. Soc. 165 (2018) H3076. [2] K. Leistner et al., Nanoscale 9 (2017) 5315. [3] K. Leistner et al., Phys. Rev. B 87 (2013) 224411. [4] U. Bauer et al., Nat. Mater. 14 (2015) 174. [5] K. Duschek et al., APL Mater. 4 (2016) 032301. [6] K. Duschek et al., Electrochem. Comm. 72 (2016) 153. Figure 1

Oxide reduced silicon nanowires

Core crystalline silicon nanowires with a heavily reduced amorphous shell have been successfully synthesised using palladium as a metal catalyst. We present two approaches to reduce the oxidation of the nanowires during the thermal annealing growth. The ratios of the amorphous shell to crystalline core of the nanowires produced, from the two methods, are compared and show a remarkable drop (hence thinner oxide) compared to wires fabricated using currently available techniques. In addition, a focused ion beam was utilised to contact the oxide-reduced nanowires for transport measurements, without first removing the thin oxide shell. The oxygen-reduced core-shell silicon nanowires showed a very low electrical resistivity (4 × 10−1 Ω cm). Our novel approach presents a new alternative to the production of low cost, high yield, highly conducting silicon nanowires offering a wide range of opportunities for semiconductor based technology.

Characterization and Manipulation of Interfacial Activity for Aqueous Galinstan Dispersions

AbstractRoom temperature liquid eutectic metals have the potential to maintain electrical and thermal conductivity during deformation, a combination of properties difficult to obtain. Two such metals, eutectic gallium–indium (EGaIn) and galinstan (eutectic gallium–indium–tin), exhibit similar flow behavior attributed to a thin oxide shell. Understanding the oxide shell is critical for understanding the interactions that influence mixing and stability of the liquid metals in other media. In this paper, the effect of aqueous HCl on the interfacial tension (IFT), interfacial rheology, and dispersibility of galinstan are systematically evaluated. It is determined that the IFT of galinstan/water and galinstan/1 m HCl are similar (≈530 mN m−1), but at 0.001 to 0.5 m HCl IFT decreases to 160 mN m−1. Similar discontinuous behavior is observed in the interfacial rheology. The low IFT coupled with a mechanically strong interface at intermediate acid concentrations suggests a change in interface composition. This is supported by SnO2 particles, present during the dispersion process, producing more stable galinstan dispersions than Ga2O3 or In2O3. Interestingly, SnO2 also improves the dispersion of EGaIn despite its lack of tin. This new interfacial manipulation method enables galinstan dispersions in a range of aqueous and nonaqueous phases to enhance the electrical and thermal properties.

Synthesis, Characterization and Reactivity of Nanostructured Zero-Valent Iron Particles for Degradation of Azo Dyes

Nanostructured zero-valent iron (NSZVI) particles were synthesized by the method of ferric ion reduction with sodium borohydride with subsequent drying and passivation at room temperature in technical grade nitrogen. The obtained sample was characterized by means of X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy and dynamic light scattering studies. The prepared NSZVI particles represent 100–200[Formula: see text]nm aggregates, which consist of 20–30[Formula: see text]nm iron nanoparticles in zero-valent oxidation state covered by thin oxide shell. The reactivity of the NSZVI sample, as the removal efficiency of refractory azo dyes, was investigated in this study. Two azo dye compounds, namely, orange G and methyl orange, are commonly detected in waste water of textile production. Experimental variables such as NSZVI dosage, initial dye concentration and solution pH were investigated. The kinetic rates of degradation of both dyes by NSZVI increased with the decrease of solution pH from 10 to 3 and with the increase of NSZVI dosage, but decreased with the increase of initial dye concentration. The removal efficiencies achieved for both orange G and methyl orange were higher than 90% after 80[Formula: see text]min of treatment.