The authors thank the financial support provided by the National Science Foundation under CHE (award #1710160) and the USDA National Institute of Food and Agriculture (award #2015-38422-24059). The Department of Chemistry at the University of Texas Rio Grande Valley is grateful for the generous support provided by a Departmental Grant from the Robert A. Welch Foundation (Grant No. BX-0048). S.K.G. would like to thank the United States-India Education Foundation (USIEF) and the Institute of International Education (IIE) for his Fulbright Nehru Postdoctoral Fellowship (award #2268/FNPDR/2017).

1. Preparation of&#160;Single-Source Complex Precursor via a Coprecipitation Route
<ol>
	<li>Preparation of lanthanum and hafnium precursor solution
	<ol>
		<li>Measure 200 mL of distilled water in a 500 mL beaker and start stirring at 300 rpm.</li>
		<li>Dissolve lanthanum and hafnium precursors in the stirring water [i.e., 2.165 g of lanthanum nitrate hexahydrate (La(NO3)3&#8226;6H2O) and 2.0476 g of hafnium dichloride oxide octahydrate (HfOCl2&#8226;8H2O)].</li>
		<li>Let the solution stir for 30 min before starting the titration.</li>
	</ol>
	</li>
	<li>Preparation of diluted ammonia solution
	<ol>
		<li>Prepare 200 mL of diluted ammonia solution with different concentrations, including 0.75%, 1.5%, 3.0%, 6.0%, and 7.5%. For example, add 20 mL of concentrated ammonia solution (NH4OH (aq), 28-30%) to 180 mL of distilled water in a separate beaker to make 3.0% diluted ammonia solution.</li>
	</ol>
	</li>
	<li>Titration and washing the single source complex precursor
	<ol>
		<li>Add the diluted ammonia solution prepared in the previous step into a burette and ensure that the burette is covered at all times, since ammonia solution tends to evaporate which decreases its concentration.</li>
		<li>Add the diluted ammonia solution in the burette into the stirring solution of lanthanum nitrate and hafnium dichloride oxide dropwise.</li>
		<li>Adjust the dropping speed of the ammonia solution accordingly so that it will be added over a period of 2 h.</li>
		<li>After several mL of ammonia solution have been delivered, ensure that the solution becomes cloudy. This is a simple sign that the precipitate of the single-source complex precursor of La(OH)3&#183;HfO(OH)2&#183;nH2O is forming.</li>
		<li>After 2 h, remove the stirring bar and allow the precipitate to age overnight.</li>
		<li>Check the pH of the coprecipitated solution before washing. Wash the precipitate with distilled water until the supernatant reaches a neutral pH, which normally takes 5-8 washes.</li>
	</ol>
	</li>
	<li>Vacuum filtration and drying of precursor
	<ol>
		<li>Vacuum filter the coprecipitated solution using a filter paper with a coarse porosity (40-60 &#181;m; see Table of Materials) to separate the solid precipitate from the supernatant.</li>
		<li>Ensure that all complex precursor remnants are washed from the walls of the beaker.</li>
		<li>Air dry the resulting single-source complex precursor La(OH)3&#183;HfO(OH)2&#183;nH2O at room temperature overnight.</li>
	</ol>
	</li>
</ol>
2. Molten-Salt Synthesis of Lanthanum Hafnate NPs
<ol>
	<li>Preparation of salt and precursor mixture
	<ol>
		<li>Measure 30 mmol (3.033 g) of potassium nitrate (KNO3) and 30 mmol (2.549 g) of sodium nitrate (NaNO3).</li>
		<li>Combine the measured salts with 0.35 g of the as-prepared single-source complex precursor La(OH)3&#183;HfO(OH)2&#183;nH2O.</li>
		<li>If necessary, add 1-5 mL of acetone or ethanol to the mixture to facilitate the grinding. Ensure that all the solvent is evaporated before placing the mixture into a crucible.</li>
		<li>Grind the mixed salts and precursor as fine as possible for about 30 min using a mortar and pestle.</li>
	</ol>
	</li>
	<li>Molten-salt processing
	<ol>
		<li>Place the resulting mixture in a corundum crucible, then place it in a muffle furnace.</li>
		<li>Set the furnace at 650 &#176;C for 6 h with a ramp rate of 10 &#176;C/min.</li>
		<li>After the sample and furnace have cooled to room temperature, take out the crucible and soak the sample in a beaker filled with distilled water overnight.</li>
	</ol>
	</li>
	<li>Washing and drying the La2Hf2O7&#160;NPs
	<ol>
		<li>Empty the sample from the crucible into a 1 L beaker.</li>
		<li>Wash the sample with distilled water 5-8 times until the supernatant is clear of salts and not cloudy anymore.</li>
		<li>Purify the product by centrifugation or vacuum filtration to remove any residual impurity.</li>
		<li>Dry the product in the oven at 90 &#176;C overnight.</li>
	</ol>
	</li>
</ol>

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There are no conflicts to declare.

The chart in Figure 4&#160;provides several reliable controlling factors of the MSS method and accounts for alternative pathways to fine-tune the features of synthesized nanomaterials. In addition, it helps identify critical steps in the MSS process.
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/58482/58482fig4.jpg" /> 
Figure 4: Flowchart of the critical steps of MSS indi...

Molten-salt synthesis (MSS) involves the use of a molten salt as the reaction medium for preparing nanomaterials from their constituent precursors. The molten salt acts as the solvent and facilitates the enhanced reaction rate by increasing the contact area between reactants and their mobility. The choice of molten salts is of paramount importance for the success of the MSS method. The salt must meet some important quality requirements such as low melting point, compatibility with reacting species, and optimum aqueous solubility. Molten salt has been used previously to enhance the rate of solid-state reactions; however, in a flux system, only a small amount of molten salt is used (unlike in MSS, in which a large quantity is added to form a soluble medium for the reaction and control the properties of the synthesized nanomaterials, such as particle size, shape, and crystallinity, etc.). In this sense, MSS is a modification of the powder metallurgical method and different from the flux method1,2,3. The employment of molten salt can (1) increase reaction kinetic rate4&#160;while decreasing synthesis temperature5, (2) increase the degree of reactant homogeneity6, (3) control crystalline size and morphology7, and (4) reduce the level of agglomeration.
Nanomaterials have been in high demand in scientific research and novel industrial applications because of their superior electrical, chemical, magnetic, optical, electronic, and thermal properties. Their properties are highly dependent on the particle size, shape, and crystallinity. Compared with other synthesis methods for nanomaterials, MSS has several obvious advantages; although, it is not yet as well-known as other synthesis methods in the nanoscience and nanotechnology community. As described below, these advantages include its simplicity, reliability, scalability, generalizability, environmental friendliness, cost effectiveness, relative low synthesis temperature, and free agglomeration of NPs with clean surface8.
Simplicity: The MSS process can be easily carried out in a simple laboratory with basic facilities. No sophisticated instrumentation is needed. Precursors and molten salts are air stable with no need for glove box handling.
Reliability: Once all initial synthesis parameters such as concentration, pH, processing time, and annealing temperature are optimized, high-quality and pure products are assured when using the MSS method. If all synthesis steps are carried out properly, the final products may attain all basic criteria needed for good-quality NPs. A novice to the MSS method will not change the synthesis outcome, as long as all synthesis parameters are properly and carefully followed.
Scalability: The MSS method&#39;s ability to produce large quantities of size- and shape-controlled particles is crucial. This critical factor is important because it allows for the determination of industrial usefulness and efficiency. Compared to other synthesis techniques, MSS can easily generate a sufficient amount of products by adjusting stoichiometric amounts during the process. This is an important feature of the method because it allows for convenience at the industrial level, making it a more desired approach due to this scalability9,10.
Generalizability: The MSS method is also a generalizable technique to produce nanoparticles with various compositions. Other than simple metal oxides and some fluorides, nanomaterials of complex metal oxides that have been successfully synthesized by the MSS method include perovskites (ABO3)10,11,12,13,14, spinel (AB2O4)15,16, pyrochlore (A2B2O7)4,17,18,19, and orthorhombic structures (A2B4O9)2,3,20. More specifically, these nanomaterials include ferrites, titanates, niobates, mullite, aluminium borate, wollastonite, and carbonated apatite7,9,21. The MSS method has also been used to produce nanomaterials of various morphologies such as&#160;nanospheres4, ceramics powder bodies22, nanoflakes23, nanoplates7, nanorods24, and core-shell nanoparticles (NPs)25, depending on synthesis conditions and crystal structure of the products.
Environmental friendliness: Several traditional methods for making nanomaterials involve the use of large amounts of organic solvents and toxic agents that generate environmental issues. The partial or total elimination of the use of them and the generation of waste by sustainable processes is in demand of green chemistry nowadays8. The MSS method is an environmentally friendly approach to synthesize nanomaterials by employing nontoxic chemical and renewable materials and minimizing waste, byproducts, and energy.
Relative low synthesis temperature: The processing temperature of the MSS method is relatively low compared to that required in a conventional solid-state reaction26&#160;or a sol-gel combustion reaction27. This lower temperature saves energy while producing high-quality NPs.
Cost effectiveness: The MSS method does not require any harsh or costly reactants or solvents nor any specialized instrumentation. Water is the main solvent used for washing away the used molten salts, which are also cheap. Moreover, experimental setup needed includes only simple glassware and a furnace without specialized instrumentation, while nanomaterials with complex composition and refractory nature can be produced.
Agglomeration free with clean surface: During the MSS process, the formed nanoparticles are well-dispersed in the molten salt medium due to its large quantity, used along with its high ionic strength and viscosity1,6,8. Unlike colloidal synthesis and most hydrothermal/solvothermal processes, no protective surface layer is necessary to prevent the continuous growth and agglomeration of the formed NPs.
Exemplary synthesis of complex metal oxide NPs by the MSS method: The MSS method as a universal and cost-effective approach to rationally and large-scale synthesize nanomaterials for a sufficiently wide spectrum of material may be highly welcomed by scientists working in nanoscience and nanotechnology. Here, lanthanum hafnate (La2Hf2O7) was selected because of its multifunctional applications in the areas of X-ray imaging, high k-dielectric, luminescence, thermographic phosphor, thermal barrier coating, and nuclear waste host. La2Hf2O7&#160;is also a good host for doped scintillators due to its high density, large effective atomic number, and the possibility of its crystal structure to be engineered along with an order-disorder phase transition. It belongs to the A2B2O7&#160;family of compounds, in which &#34;A&#34; is a rare-earth element with a +3 oxidation state, and &#34;B&#34; represents a transition metallic element with a +4 oxidation state. However, due to the refractory nature and complex chemical composition, there has been a lack of proper low-temperature and large-scale synthesis methods for La2Hf2O7&#160;NPs.
For fundamental scientific investigation and advanced technological applications, it is a prerequisite to make monodisperse, high-quality, and uniform A2B2O7&#160;NPs. Here we use the synthesis of highly crystalline La2Hf2O7&#160;NPs as an example to demonstrate the advantages of the MSS method. As schematically shown in Figure 1, La2Hf2O7&#160;NPs were prepared by the MSS method with a two-step process following our previous reports. First, a single-source complex precursor of La(OH)3&#183;HfO(OH)2&#183;nH2O was prepared via a coprecipitation route. In the second step, size-controllable La2Hf2O7&#160;NPs were synthesized through the facile MSS process using the single-source complex precursor and nitrate mixture (NaNO3:KNO3&#160;=&#160;1:1, molar ratio) at 650 &#176;C for 6 h.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/58482/58482fig1.jpg" /> 
Figure 1: Schematic of the synthesis steps for La2Hf2O7&#160;NPs via the MSS method. <a href="https://www.jove.com/files/ftp_upload/58482/58482fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

<table><tbody><tr><td>Acetone, ACS, 99.5+%</td><td>Alfa Aesar</td><td>67-64-1</td><td>Dried over 4A sieves</td></tr><tr><td>Hafnium dichloride oxide octahydrate, 98+% (metals basis excluding Zr), Zr &amp;lt;1.5%</td><td>Alfa Aesar</td><td>14456-34-9</td><td>Hygroscopic</td></tr><tr><td>Lanthanum(III) nitrate hexahydrate</td><td>Aldrich</td><td>10277-43-7</td><td>Hygroscopic</td></tr><tr><td>Potassium nitrate, ReagentPlus R, &amp;ge;99.0%</td><td>Sigma-Aldrich</td><td>7757-79-1</td><td>Hygroscopic</td></tr><tr><td>Sodium nitrate, ReagentPlus R, &amp;ge;99.0%</td><td>Sigma-Aldrich</td><td>7631-99-4</td><td></td></tr><tr><td>Ammonium hydroxide, 28% NH3, NH4OH</td><td>Alfa Aesar</td><td>1336-21-6</td><td></td></tr><tr><td>Filter paper, P8 grade</td><td>Fisherbrand</td><td></td><td></td></tr></tbody></table>

molten-salt synthesis of complex metal oxide nanoparticles

The development of feasible synthesis methods is critical for the successful exploration of novel properties and potential applications of nanomaterials. Here, we introduce the molten-salt synthesis (MSS) method for making metal oxide nanomaterials. Advantages over other methods include its simplicity, greenness, reliability, scalability, and generalizability. Using pyrochlore lanthanum hafnium oxide (La2Hf2O7) as a representative, we describe the MSS protocol for the successful synthesis of complex metal oxide nanoparticles (NPs). Furthermore, this method has the unique ability to produce NPs with different material features by changing various synthesis parameters such as pH, temperature, duration, and post-annealing. By fine-tuning these parameters, we are able to synthesize highly uniform, non-agglomerated, and highly crystalline NPs. As a specific example, we vary the particle size of the La2Hf2O7&#160;NPs by changing the concentration of the ammonium hydroxide solution used in the MSS process, which allows us to further explore the effect of particle size on various properties. It is expected that the MSS method will become a more popular synthesis method for nanomaterials and more widely employed in the nanoscience and nanotechnology community in the upcoming years.

The as-synthesized La2Hf2O7&#160;NPs may exist in the ordered pyrochlore phase. However, chemical doping, pressure, and temperature could modify the phase to defect fluorite. It is possible for our material to have multiple phases; however, here we focus only on the pyrochlore phase for simplicity. X-ray diffraction (XRD) and Raman spectroscopy have been used to systematically characterize their phase purity, structure, and phase. The crystalline size can ...

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Molten-Salt Synthesis of Complex Metal Oxide Nanoparticles

Here, we demonstrate a unique, relatively low-temperature, molten-salt synthesis method for preparing uniform complex metal oxide lanthanum hafnate nanoparticles.

The development of feasible synthesis methods is critical for the successful exploration of novel properties and potential applications of nanomaterials. ...

molten-salt-synthesis-of-complex-metal-oxide-nanoparticles

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17.8K Views.  University of Texas Rio Grande Valley. Here, we demonstrate a unique, relatively low-temperature, molten-salt synthesis method for preparing uniform complex metal oxide lanthanum hafnate nanoparticles.

Video: Molten-Salt Synthesis of Complex Metal Oxide Nanoparticles

Fabrication of Spatially Confined Complex Oxides

Complex materials such as high Tc superconductors, multiferroics, and colossal magnetoresistors have electronic and magnetic properties that arise from the inherent strong electron correlations that reside within them. These materials can also possess electronic phase separation in which regions of vastly different resistive and magnetic behavior can coexist within a single crystal alloy material. By reducing the scale of these materials to length scales at and below the inherent size of the electronic domains, novel behaviors can be exposed. Because of this and the fact that spin-charge-lattice-orbital order parameters each involve correlation lengths, spatially reducing these materials for transport measurements is a critical step in understanding the fundamental physics that drives complex behaviors. These materials also offer great potential to become the next generation of electronic devices 1-3. Thus, the fabrication of low dimensional nano- or micro-structures is extremely important to achieve new functionality. This involves multiple controllable processes from high quality thin film growth to accurate electronic property characterization. Here, we present fabrication protocols of high quality microstructures for complex oxide manganite devices. Detailed descriptions and required equipment of thin film growth, photo-lithography, and wire-bonding are presented.

We describe the use of pulsed laser deposition (PLD), photolithography and wire-bonding techniques to create micrometer scale complex oxides devices. The PLD is utilized to grow epitaxial thin films. Photolithography and wire-bonding techniques are introduced to create practical devices for measurement purposes.

Complex materials such as high Tc superconductors, multiferroics, and colossal magnetoresistors have electronic and magnetic properties that arise from ...

Engineering

Reverse Microemulsion-mediated Synthesis of Monometallic and Bimetallic Early Transition Metal Carbide and Nitride Nanoparticles

A reverse microemulsion is used to encapsulate monometallic or bimetallic early transition metal oxide nanoparticles in microporous silica shells. The silica-encapsulated metal oxide nanoparticles are then carburized in a methane/hydrogen atmosphere at temperatures over 800 &#176;C to form silica-encapsulated early transition metal carbide nanoparticles. During the carburization process, the silica shells prevent the sintering of adjacent carbide nanoparticles while also preventing the deposition of excess surface carbon. Alternatively, the silica-encapsulated metal oxide nanoparticles can be nitridized in an ammonia atmosphere at temperatures over 800 &#176;C to form silica-encapsulated early transition metal nitride nanoparticles. By adjusting the reverse microemulsion parameters, the thickness of the silica shells, and the carburization/nitridation conditions, the transition metal carbide or nitride nanoparticles can be tuned to various sizes, compositions, and crystal phases. After carburization or nitridation, the silica shells are then removed using either a room-temperature aqueous ammonium bifluoride solution or a 0.1 to 0.5 M NaOH solution at 40-60 &#176;C. While the silica shells are dissolving, a high surface area support, such as carbon black, can be added to these solutions to obtain supported early transition metal carbide or nitride nanoparticles. If no high surface area support is added, then the nanoparticles can be stored as a nanodispersion or centrifuged to obtain a nanopowder.

A &#8220;removable ceramic coating method&#8221; is presented in visual format for the synthesis of non-sintered and metal-terminated monometallic and bimetallic early transition metal carbide and nitride nanoparticles with tunable sizes and crystal structures.

A reverse microemulsion is used to encapsulate monometallic or bimetallic early transition metal oxide nanoparticles in microporous silica shells. The ...

Synthesis and Reaction Chemistry of Nanosize Monosodium Titanate

This paper describes the synthesis and peroxide-modification of nanosize monosodium titanate (nMST), along with an ion-exchange reaction to load the material with Au(III) ions. The synthesis method was derived from a sol-gel process used to produce micron-sized monosodium titanate (MST), with several key modifications, including altering reagent concentrations, omitting a particle seed step, and introducing a non-ionic surfactant to facilitate control of particle formation and growth. The resultant nMST material exhibits spherical-shaped particle morphology with a monodisperse distribution of particle diameters in the range from 100 to 150&#160;nm. The nMST material was found to have a Brunauer-Emmett-Teller (BET) surface area of 285 m2g-1, which is more than an order of magnitude higher than the micron-sized MST. The isoelectric point of the nMST measured 3.34 pH units, which is a pH unit lower than that measured for the micron-size MST. The nMST material was found to serve as an effective ion exchanger under weakly acidic conditions for the preparation of an Au(III)-exchange nanotitanate. In addition, the formation of the corresponding peroxotitanate was demonstrated by reaction of the nMST with hydrogen peroxide.

The surfactant mediated sol-gel synthesis of nanosized monosodium titanate is described, along with preparation of the corresponding peroxide modified material. An ion-exchange reaction with Au(III) is also presented.

This paper describes the synthesis and peroxide-modification of nanosize monosodium titanate (nMST), along with an ion-exchange reaction to load the ...

Generation of Zerovalent Metal Core Nanoparticles Using n-(2-aminoethyl)-3-aminosilanetriol

In this work, a facile one-pot reaction for the formation of metal nanoparticles in a water solution through the use of n-(2-aminoethyl)-3-aminosilanetriol is presented. This compound can be used to effectively reduce and complex metal salts into metal core nanoparticles coated with the compound. By controlling the concentrations of salt and silane one is able to control reaction rates, particle size, and nanoparticle coating. The effects of these changes were characterized through transmission electron microscopy (TEM), UV-Vis spectrometry (UV-Vis), Nuclear Magnetic Resonance spectroscopy (NMR) and Fourier Transform Infrared spectroscopy (FTIR). A unique aspect to this reaction is that usually silanes hydrolyze and cross-link in water; however, in this system the silane is water-soluble and stable. It is known that silicon and amino moieties can form complexes with metal salts. The silicon is known to extend its coordination sphere to form penta- or hexa-coordinated species. Furthermore, the silanol group can undergo hydrolysis to form a Si-O-Si silica network, thereby transforming the metal nanoparticles into a functionalized nanocomposites.

Generation of Zerovalent Metal Core Nanoparticles Using n-2-aminoethyl-3-aminosilanetriol

A novel method for metal core nanoparticle synthesis using a water stable silanol is described.

In this work, a facile one-pot reaction for the formation of metal nanoparticles in a water solution through the use of ...

Synthesis of a Water-soluble Metal&#8211;Organic Complex Array

We demonstrate a method for the synthesis of a water-soluble multimetallic peptidic array containing a predetermined sequence of metal centers such as Ru(II), Pt(II), and Rh(III). The compound, named as a water-soluble metal-organic complex array (WSMOCA), is obtained through 1) the conventional solution-chemistry-based preparation of the corresponding metal complex monomers having a 9-fluorenylmethyloxycarbonyl (Fmoc)-protected amino acid moiety and 2) their sequential coupling together with other water-soluble organic building units on the surface-functionalized polymeric resin by following the procedures originally developed for the solid-phase synthesis of polypeptides, with proper modifications. Traces of reactions determined by mass spectrometric analysis at the representative coupling steps in stage 2 confirm the selective construction of a predetermined sequence of metal centers along with the peptide backbone. The WSMOCA cleaved from the resin at the end of stage 2 has a certain level of solubility in aqueous media dependent on the pH value and/or salt content, which is useful for the purification of the compound.

A potential general method for the synthesis of water-soluble multimetallic peptidic arrays containing a predetermined sequence of metal centers is presented.

We demonstrate a method for the synthesis of a water-soluble multimetallic peptidic array containing a predetermined sequence of metal centers such as ...

Synthesizing Sodium Tungstate and Sodium Molybdate Microcapsules via Bacterial Mineral Excretion

We present a method, the bacterial mineral excretion (BME), for synthesizing two kinds of microcapsules, sodium tungstate and sodium molybdate, and the two metal oxides&#39; corresponding nanoparticles&#8212;the former being as small as 22 nm and the latter 15 nm. We fed two strains of bacteria, Shewanella algae and Pandoraea sp., with various concentrations of tungstate or molybdate ions. The concentrations of tungstate and molybdate were adjusted to make microcapsules of different length-to-diameter ratios. We found that the higher the concentration the smaller the nanoparticles were. The nanoparticles came in with three length-to-diameter ratios: 10:1, 3:1 and 1:1, which were achieved by feeding the bacteria respectively with a low concentration, a medium concentration, and a high concentration. The images of the hollow microcapsules were taken via the scanning electron microsphere (SEM). Their crystal structures were verified by X-ray diffraction (XRD)&#8212;the crystal structure of molybdate microcapsules is Na2MoO4 and that of tungstate microcapsules is Na2WO4 with Na2W2O7. These syntheses all were accomplished under a near ambient condition.

This work presents a protocol for manufacture sodium tungstate and sodium molybdate microcapsules via bacteria and their corresponding nanoparticles.

We present a method, the bacterial mineral excretion (BME), for synthesizing two kinds of microcapsules, sodium tungstate and sodium molybdate, and the ...

Solvothermal Synthesis of MIL-96 and UiO-66-NH2 on Atomic Layer Deposited Metal Oxide Coatings on Fiber Mats

Metal-organic frameworks (MOFs), which contain reactive metal clusters and organic ligands allowing for large porosities and surface areas, have proven effective in gas adsorption, separations, and catalysis. MOFs are most commonly synthesized as bulk powder, requiring additional processes to adhere them to functional devices and fabrics that risk decreasing the powder porosity and adsorption capacity. Here, we demonstrate a method of first coating fabrics with metal oxide films using atomic layer deposition (ALD). This process creates conformal films of controllable thickness on each fiber, while providing a more reactive surface for MOF nucleation. By submerging the ALD coated fabric in solution during solvothermal MOF synthesis, the MOFs create a conformal, well-adhered coating on the fibers, resulting in a MOF-functionalized fabric, without additional adhesion materials that may block MOF pores and functional sites. Here we demonstrate two solvothermal synthesis methods. First, we form a MIL-96(Al) layer on polypropylene fibers using synthetic conditions that convert the metal oxide to MOF. Using initial inorganic films of varying thicknesses, diffusion of the organic linker into the inorganic allows us to control the extent of MOF loading on the fabric. Second, we perform a solvothermal synthesis of UiO-66-NH2 in which the MOF nucleates on the conformal metal oxide coating on polyamide-6 (PA-6) fibers, thereby producing a uniform and conformal thin film of MOF on the fabric. The resulting materials can be directly incorporated into filter devices or protective clothing and eliminate the maladroit qualities of loose powder.

Solvothermal Synthesis of MIL-96 and UiO-66-NH2 on Atomic Layer Deposited Metal Oxide Coatings on Fiber Mats

Metal-organic frameworks are effective in gas storage and heterogeneous catalysis, but typical synthesis methods result in loose powders that are difficult to incorporate into smart materials. We demonstrate a method of first coating fabrics with ALD metal oxides, resulting in conformal films of MOF on the fabrics during solvothermal synthesis.

Metal-organic frameworks (MOFs), which contain reactive metal clusters and organic ligands allowing for large porosities and surface areas, have proven ...

Synthesis of Bimetallic Pt/Sn-based Nanoparticles in Ionic Liquids

We demonstrate a method for the synthesis of bimetallic nanoparticles consisting of Pt and Sn. A synthesis strategy is used in which the particular physico-chemical properties of ionic liquids (ILs) are exploited to control both nucleation and growth processes. The nanoparticles form colloidal sols of very high colloidal stability in the IL, which is particularly interesting in view of their use as quasi-homogeneous catalysts. Procedures for both nanoparticle extraction in conventional solvents and for nanoparticle precipitation are presented. The size, structure and composition of the synthesized nanocrystals are confirmed using inductively coupled plasma atomic emission spectroscopy (ICP-AES), X-ray diffraction analysis (XRD) and transmission electron microscopy (TEM) with energy-dispersive X-ray spectroscopy (EDX). By this, we show that the nanocrystals are random-type alloy and of small (2-3 nm) size. The catalytic activity and selectivity in the hydrogenation of &#945;,&#946;-unsaturated aldehydes is tested in a semi-continuous batch-type reactor. In this context, the bimetallic Pt/Sn-based nanoparticles reveal a high selectivity towards the unsaturated alcohol.

A protocol for the synthesis of bimetallic nanoparticles in ionic liquids and the procedure of their catalytic testing in the selective hydrogenation of unsaturated aldehydes are described.

We demonstrate a method for the synthesis of bimetallic nanoparticles consisting of Pt and Sn. A synthesis strategy is used in which the particular ...

A Salt-Templated Synthesis Method for Porous Platinum-based Macrobeams and Macrotubes

The synthesis of high surface area porous noble metal nanomaterials generally relies on time consuming coalescence of pre-formed nanoparticles, followed by rinsing and supercritical drying steps, often resulting in mechanically fragile materials. Here, a method to synthesize nanostructured porous platinum-based macrotubes and macrobeams with a square cross section from insoluble salt needle templates is presented. The combination of oppositely charged platinum, palladium, and copper square planar ions results in the rapid formation of insoluble salt needles. Depending on the stoichiometric ratio of metal ions present in the salt-template and the choice of chemical reducing agent, either macrotubes or macrobeams form with a porous nanostructure comprised of either fused nanoparticles or nanofibrils. Elemental composition of the macrotubes and macrobeams, determined with x-ray diffractometry and x-ray photoelectron spectroscopy, is controlled by the stoichiometric ratio of metal ions present in the salt-template. Macrotubes and macrobeams may be pressed into free standing films, and the electrochemically active surface area is determined with electrochemical impedance spectroscopy and cyclic voltammetry. This synthesis method demonstrates a simple, relatively fast approach to achieve high-surface area platinum-based macrotubes and macrobeams with tunable nanostructure and elemental composition that may be pressed into free-standing films with no required binding materials.

A synthesis method to obtain porous platinum-based macrotubes and macrobeams with a square cross section through chemical reduction of insoluble salt-needle templates is presented.

The synthesis of high surface area porous noble metal nanomaterials generally relies on time consuming coalescence of pre-formed nanoparticles, followed ...

Metal Oxide Heterojunction for Photocatalytic Activities

There is a significant global demand for improvements in synthesis techniques and their optimal characteristics, especially for industrial-scale applications. Sol-gel-based solution combustion synthesis (SG-SCS) is a simple method to produce ordered porous materials. In this regard, Pearson&#39;s hard and soft acids and bases theory assists in selecting host-dopant reactivity to form a proper heterojunction.
The formation of a heterojunction also changes the essential properties of the materials, improving photocatalysis via charge transfer or synergistic activities. A calcination temperature of 500 &#176;C is ideal for this process based on the results of the stability assessment via a differential thermogravimetry ratio analysis (DTG).
The nanoscale dimensions of the nanoparticles (NPs) and nanocomposites (NCs) generated were validated using X-ray diffraction and high-resolution transmission electron microscopy (HRTEM). Furthermore, the scanning electron microscopy micrographs and BET analyses confirmed the porosity nature of the materials. HRTEM, X-ray photoelectron spectroscopy, and energy-dispersive X-ray investigations established the materials composition. The study found that NCs degraded the acid orange 8 (AO8) color more efficiently than bare ZnO.

The development of a heterojunction boosts the photocatalytic activities of solution combustion synthesis, which is a time-/energy-efficient process. Advanced analytical characterization techniques were used in this protocol to evaluate the materials&#39; characteristics, and nanocomposites demonstrated improved acid orange-8 dye degradation.

Molten-Salt Synthesis of Complex Metal Oxide Nanoparticles

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