This work was generously supported by Brown University and the Advanced Energy Consortium. We gratefully thank Dr. Qingbo Zhang for his established synthetic method of iron oxide MFCs.

1. Synthesis of MFCs with control over MFCs&#39; overall diameter and ferrite composition
<ol>
	<li>Wash and thoroughly dry all glassware to be used in the synthesis. The amount of water in the synthesis impacts the dimensions of the MFCs, so it is crucial to ensure the glassware has no residual water in it16,26.
	<ol>
		<li>To wash the glassware, rinse with water and detergent and scrub with a flask brush to remove debris. Thoroughly rinse to remove all detergent and finish with a rinse of deionized water.</li>
		<li>To dry the glassware, shake water droplets off the surface of the glassware and place into an oven at 60&#176;C until completely dry.</li>
		<li>Rinse the polyphenylene-lined (PPL) reactors with 37% hydrochloric acid to remove any debris from previous use. To do this, place the reactors and their caps in a large beaker and fill with hydrochloric acid until the reactors are completely submerged. Let this sit for 30 min before pouring out the hydrochloric acid. Continuously rinse the beaker containing the reactors with water for 1-2 min, and then place the reactors in the oven to dry.</li>
	</ol>
	</li>
	<li>Use an automatic pipette to transfer 20 mL of ethylene glycol into a 50 mL beaker with a magnetic stir bar.</li>
	<li>Weigh out the required amount of iron(III) chloride (FeCl3&#183;6H2O, solid) to achieve a final concentration of 1.3 mM and add it to the beaker. Put the beaker on a stir plate and turn it on at 480 rpm to begin continuous stirring of the beaker. 
	NOTE: As this is a hydrate, it must be measured and added quickly to avoid unwanted absorption of water from the ambient air.</li>
	<li>Weigh 250 mg of polyacrylic acid (PAA, Mw ~6,000, powder) and add it to the beaker. After the addition of PAA, the solution becomes opaque and slightly lighter in color.</li>
	<li>Weigh 1.2 g of urea (CO(NH2)2, powder) and add it to the beaker.</li>
	<li>Using a pipette, add 0.7 mM manganese(II) chloride (MnCl2&#183;6H2O aq, 3.5 M, 0.2 mL) to the beaker.</li>
	<li>Finally, using a pipette add the required amount (0.5 mL) of ultra-pure water to the beaker.</li>
	<li>Let the solution stir for 30 min and notice the color change. It will present as a translucent, dark orange color.</li>
	<li>Transfer the reaction mixture into the polyphenylene lined (PPL) reactor. Note that after the solution has stirred some solids may have accumulated on the sides of the beaker.
	<ol>
		<li>Use a magnet (cubic permanent rare earth magnet, 40 x 40 x 20 mm, hereafter referred to as a &#34;magnet&#34; for all separation and magnetic collection procedures) to drag the stir bar around the walls of the beaker to ensure any solids that have accumulated on the sides are dispersed into the reaction solution.</li>
		<li>Once the solution is mixed and ready, transfer it into the 50 mL PPL lined reactor.</li>
		<li>Use a clamp and lever to seal the reactor in the stainless-steel autoclave as tightly as possible. Clamp the reactor vessel to a stable surface, and using a rod inserted into the cap as a lever, push the reactor to seal. Note that the sealed reactor should not be able to be opened by hand. This is crucial as the high-pressure environment of the oven requires a tight seal on the reactor.</li>
	</ol>
	</li>
	<li>Place the reactor into an oven for 20 h at 215 &#176;C.</li>
	<li>After the hydrothermal reaction is done, remove the reactor from the oven and allow it to cool down to room temperature. The pressure of the oven will enable the reactor to be opened by hand. Note that at this point, the reactor will contain the MFC product dispersed in ethylene glycol with other impurities, such as unreacted polymer, and will be an opaque black solution. The product will be isolated in the following steps.</li>
</ol>
2. Magnetic separation and purification of MFCs
<ol>
	<li>Place 200 mg of steel wool into a glass vial. Fill the glass vial halfway with the reaction mixture from the reactor. Fill the rest of the vial with acetone and shake well. Note that the steel wool increases the magnetic field strength in the vial and will help magnetic separation of the nanoclusters from the solution.</li>
	<li>Place the vial on a magnet for magnetic collection to occur. The result will be a translucent solution with precipitate at the bottom.
	<ol>
		<li>Pour off the supernatant solution while the MFCs are magnetically trapped by the steel wool by holding the magnet to the bottom of the vial while pouring. Ethylene glycol will be mostly removed in this step.</li>
		<li>Start washing with the low ratio of acetone to water and increase the ratio in subsequent washes until pure. Do this 3-4 times.</li>
	</ol>
	</li>
	<li>Remove the vial from the magnet and fill it with water. Shake well to dissolve the MFCs. Now the product will be fully dispersed in water.</li>
	<li>Repeat the previous two steps several times until the aqueous solution of the MFCs produces no bubbles when shaken. The result will be a dark, opaque ferrofluid that will respond strongly to magnets. 
	NOTE: In a typical synthesis with 20 mL of ethylene glycol, approximately 80 mg of MFC product will be obtained.</li>
</ol>
3. Surface functionalization of MFCs toward ultra-high colloidal stability
NOTE: The synthesis of nitro-dopamine and Poly(AA-co-AMPS-co-PEG) can be found in our previous work16. The copolymer is made through free radical polymerization. Add 0.20 g of 2,2&#8242;-Azobis(2-methylpropionitrile) (AIBN), 0.25 g of acrylic acid (AA), 0.75 g of 2-Acrylamido-2-methylpropane sulfonic acid (AMPS), and 1.00 g of Poly(ethylene glycol) methyl ether acrylate (PEG) in 10 mL of N,N-Dimethylformamide (DMF). Heat the mixture in a 70 &#176;C water bath for 1 h and transfer it to a dialysis bag (Cellulose Membrane, 3 kDa) in water. The weight ratio of AA, AMPS, and PEG is 1:3:4. Polymerization for these monomers has a 100% conversion rate as confirmed by freeze drying and weighing.
<ol>
	<li>Combine 10 mL of purified nanoparticles (around 100 mg) in a 20 mL vial with 10 mL of saturated N-[2-(3,4-dihydroxyphenyl)ethyl]nitramide (nitro-dopamine) solution (~1 mg/mL). Wait for 5 min.</li>
	<li>Wash the nitro-dopamine coated MFCs using magnetic separation. Pour out the pale-yellow supernatant. Add water and shake vigorously. Then, pour out water using the magnet to retain the product. Repeat this washing several times leaving the dark brown collection in the vial. 
	NOTE: Prepare a aqueous solution with a concentration of 20 mg/mL, a buffer solution with a concentration of 100 mg/mL, and a poly(AA-co-AMPS-co-PEG) polymer solution with a concentration of 20 mg/mL.</li>
	<li>Mix 1 mL of EDC solution, 1 mL of MES buffer, and 3 mL of the polymer solution. Lightly stir by swirling the mixture, and let it sit for approximately 5 min. It should be a clear and colorless solution when fully combined.</li>
	<li>Add this mixture to the MFC collection and place the vial in an ice bath. Lower the probe sonicator into the solution, and then turn it on (250 watts of power at 20 kHz).
	<ol>
		<li>After a 5 min sonication treatment, add roughly 5 mL of ultra-pure water to the vial while the sonicator is still running. Continue monitoring the vessel to ensure that no product spills. Maintain the ice in the ice-water mixture as some of the initial ice will melt due to the intensity and heat of the sonication.</li>
		<li>Allow the mixture to sonicate for an additional 25 min, for a total of 30 min.</li>
	</ol>
	</li>
	<li>Place the vial on top of a magnet to separate the MFCs and pour out the supernatant solution.</li>
	<li>Wash the modified MFCs with deionized water several times.</li>
	<li>Fill the vial containing the MFCs with ultra-pure water. Pipette this fluid into a vacuum filtration system with a 0.1 &#181;m polyethersulfone membrane filter to remove any irreversibly aggregated MFCs. Make sure to flush the walls of the funnel to minimize any loss of product.</li>
	<li>Vacuum filter the solution. Repeat this process 2-3 times. The result will be a purified aqueous solution of monodispersed MFCs. 
	NOTE: Roughly 10% of the product will be irreversibly aggregated and this material will remain on the filter and should be discarded.</li>
</ol>

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The authors have nothing to disclose.

This work demonstrates a modified polyol synthesis of manganese ferrite nanocrystals clustered together into uniform nanoscale aggregates29. In this synthesis, iron(III) chloride and manganese(II) chloride undergo a forced hydrolysis reaction and reduction, forming molecular MnxFe3-xO4. These ferrite molecules form primary nanocrystals under the high temperature and high pressure in the reactors, ultimately assembling into spherical aggregates termed her...

The inclusion of manganese as a dopant in an iron oxide lattice can, under the appropriate conditions, increase the material&#39;s magnetization at high applied fields as compared to pure iron oxides. As a result, manganese ferrite (MnxFe3-xO4) nanoparticles are highly desirable magnetic nanomaterials due to their high saturation magnetization, strong response to external fields, and low cytotoxicity1,2,3,4,5. Both single domain nanocrystals as well as clusters of these nanocrystals, termed multidomain particles, have been investigated in diverse biomedical applications, including drug delivery, magnetic hyperthermia for cancer treatment, and magnetic resonance imaging (MRI)6,7,8. For example, the Hyeon group in 2017 used single domain manganese ferrite nanoparticles as a Fenton catalyst to induce cancer hypoxia and exploited the material&#39;s T2contrast for MRI tracking9. It is surprising in light of these and other positive studies of ferrite materials that there are few in vivo demonstrations as compared to pure iron oxide (Fe3O4) nanomaterials, and no reported applications in humans9,10.
One immense challenge faced in translating the features of ferrite nanomaterials into the clinic is the generation of uniform, non-aggregating, nanoscale clusters11,12,13,14. While conventional synthetic approaches to monodomain nanocrystals are well developed, multidomain clusters of the type of interest in this work are not easily produced in a uniform and controlled fashion15,16. Additionally, ferrite composition is usually non-stoichiometric and not simply related to the starting concentration of the precursors and this can further obscure systematic structure-function characterization of these materials9,12,13,17. Here, we address these issues by demonstrating a synthetic approach that yields independent control over both the cluster dimension and composition of manganese ferrite nanomaterials.
This work also provides a means to overcome the poor colloidal stability of ferrite nanomaterials18,19,20. Magnetic nanoparticles are generally prone to aggregation due to strong particle-particle attraction; ferrites suffer more from this problem as their larger net magnetization amplifies particle aggregation. In relevant biological media, these materials yield large enough aggregates that the materials rapidly collect, thereby limiting their routes of exposure to animals or people20,21,22. Hilt et al. found another consequence of particle-particle aggregation in their study of magnetothermal heating and dye degradation23. At slightly higher particle concentrations, or increased time of exposure to the field, the effectiveness of the materials was reduced as materials aggregated over time and the active particle surface areas decreased. These and other applications would benefit from cluster surfaces designed to provide steric barriers that precluded particle-particle interactions24,25.
Here we report a synthetic approach to synthesize manganese ferrite clusters (MFCs) with controllable dimensions and composition. These multidomain particles consist of an assembly of primary manganese ferrite nanocrystals that are hard aggregated; the close association of the primary nanocrystals enhances their magnetic properties and provides for an overall cluster size, 50-300 nm, well matched to the optimum dimensions for a nanomedicine. By changing the amount of water and manganese chloride precursor, we can independently control the overall diameter and composition. The method utilizes simple and efficient one-pot hydrothermal reactions that allow for frequent experimentation and material optimization. These MFCs can be easily purified into a concentrated product solution, which is further modified by sulfonated polymers that impart colloidal stability. Their tunability, uniformity, and solution phase stability are all features of great value in applications of nanomaterials in biomedical and environmental engineering.

<table><tbody><tr><td>0.1 Micron Vaccum Filtration Filter</td><td>Thermo Fisher Scientific</td><td>NC9902431</td><td>for filtration of aggregated clusters after synthesis and surface coating to achieve a uniform solution</td></tr><tr><td>2-Acrylamido-2-methylpropane sulfonic acid (AMPS, 99%)</td><td>Sigma-Aldrich</td><td>282731-250G</td><td>reagent used in copolymer to surface coat nanoclusters and functionalize them for biological media</td></tr><tr><td>2,2&amp;prime;-Azobis(2-methylpropionitrile) (AIBN)</td><td>Sigma-Aldrich</td><td>441090-100G</td><td>reagent used in copolymer making as the free ridical generator</td></tr><tr><td>4-Morpholineethanesulfonic acid, 2-(N-Morpholino)ethanesulfonic acid (MES)</td><td>Sigma-Aldrich</td><td>M3671-250G</td><td>acidic buffer used to stabilize nanocluster surface coating process</td></tr><tr><td>Acrylic acid</td><td>Sigma-Aldrich</td><td>147230-100G</td><td>reagent used in copolymer to surface coat nanoclusters and functionalize them for biological media; anhydrous, contains 200 ppm MEHQ as inhibitor, 99%</td></tr><tr><td>Analytical Balance</td><td>Avantor</td><td>VWR-205AC</td><td>used to weigh out solid chemical reagents for use in synthesis and dilution</td></tr><tr><td>Digital Sonifier and Probe</td><td>Branson</td><td>B450</td><td>used to sonicate nanocluster solution during surface coating to break up aggregates</td></tr><tr><td>Dopamine hydrochloride</td><td>Sigma-Aldrich</td><td>H8502-25G</td><td>used in surface coating for ligand exchange reaction</td></tr><tr><td>Ethylene glycol (anhydrous, 99.8%)</td><td>Sigma-Aldrich</td><td>324558-2L</td><td>reagent used as solvent in hydrothermal synthesis of nanoclusters</td></tr><tr><td>Glass Vials (20mL)</td><td>Premium Vials</td><td>B1015</td><td>container for nanocluster solution during washing and surface coating as well as polymer solutions</td></tr><tr><td>Graduated Beaker (100mL)</td><td>Corning</td><td>1000-100</td><td>container for mixing of solid and liquid reagents during hydrothermal synthesis (to be transferred into autoclave reactor before oven)</td></tr><tr><td>Handheld Magnet</td><td>MSC Industrial Supply, Inc.</td><td>92673904</td><td>1/2&quot; Long x 1/2&quot; Wide x 1/8&quot; High, 5 Poles, Rectangular Neodymium Magnet low strength magnet used to precipitate nanoclusters from solution (field strength is increased with steel wool when needed)</td></tr><tr><td>Hydrochloric acid (ACS grade, 37%)</td><td>Fisher Scientific</td><td>7647-01-0</td><td>for removing leftover nanocluster debris and cleaning autoclave reactors for next use</td></tr><tr><td>Hydrothermal Autoclave Reactor</td><td>Toption</td><td>TOPT-HP500</td><td>container for finished reagent mixture to withstand high temperature and pressure created by the oven in hydrothermal synthesis</td></tr><tr><td>Iron(III) Chloride Hexahydrate (FeCl3&amp;middot;6H2O, ACS reagent, 97%)</td><td>ACS</td><td>236489-500G</td><td>reagent used in synthesis of nanoclusters as source of iron (III) that becomes iron (II) in finished nanocluster product (keep dry and weigh out quickly to avoid water contamination)</td></tr><tr><td>Labware Washer Brushes</td><td>Fisher Scientific</td><td>13-641-708</td><td>used to wash and clean glassware before synthesis</td></tr><tr><td>Magnetic Stir Plate</td><td>Thermo Fisher Scientific</td><td>50093538</td><td>for mixing of solid and liquid reagents during hydrothermal synthesis</td></tr><tr><td>Manganese chloride tetrahydrate (MnCl2&amp;middot;4H2O, 99.0%, crystals, ACS)</td><td>Sigma-Aldrich</td><td>1375127-2G</td><td>reagent used in synthesis of nanoclusters as source of manganese</td></tr><tr><td>Micropipette (100-1000&amp;mu;L)</td><td>Thermo Fisher Scientific</td><td>FF-1000</td><td>for transferring liquid reagents such as water and manganese chloride</td></tr><tr><td>N-(3-Dimethylaminopropyl)-N&amp;prime;-ethylcarbodiimide hydrochloride (EDC)</td><td>Sigma-Aldrich</td><td>25952-53-8</td><td>used in surface coating to assist in ligand exchange of copolymer (keep bulk chemical in freezer and diluted solution in refrigerator)</td></tr><tr><td>N,N-Dimethylformamide (DMF)</td><td>Sigma-Aldrich</td><td>227056-2L</td><td>reagent used in copolymer making as the solvent</td></tr><tr><td>Polyacrylic acid sodium salt (PAA, Mw~6,000)</td><td>PolyScience Inc.</td><td>06567-250</td><td>reagent used in hydrothermal synthesis to initially coat the nanoclusters (eventually replaced in surface coating step)</td></tr><tr><td>Poly(ethylene glycol) methyl ether acrylate</td><td>Sigma-Aldrich</td><td>454990-250ML</td><td>reagent used in copolymer to surface coat nanoclusters and functionalize them for biological media; average Mn 480, contains 100 ppm BHT as inhibitor, 100 ppm MEHQ as inhibitor</td></tr><tr><td>Reagents Acetone, 4L, ACS Reagent</td><td>Cole-Parmer</td><td>UX-78920-66</td><td>used as solvent to precipitate nanoclusters during washing</td></tr><tr><td>Single Channel Pipette, Adjustable 1-10 mL</td><td>Eppendorf</td><td>3123000080</td><td>for transferring ethylene glycol and other liquids</td></tr><tr><td>Steel Wool</td><td>Lowe&#039;s</td><td>788470</td><td>used to increase the magnetic field strength in the vial to aid in precipitation of nanoclusters for washing and surface coating</td></tr><tr><td>Stirring Bar</td><td>Thomas Scientific</td><td>8608S92</td><td>for mixing of solid and liquid reagents during hydrothermal synthesis</td></tr><tr><td>Table Clamp</td><td>Grainger</td><td>29YW53</td><td>for tight sealing of autoclave reactor to withstand high pressure of oven during hyrothermal synthesis</td></tr><tr><td>Urea (ACS reagent, 99.0%)</td><td>Sigma-Aldrich</td><td>U5128-500G</td><td>reagent used in hydrothermal synthesis to create a basic solution</td></tr><tr><td>Vaccum Filtration Bottle Tops</td><td>Thermo Fisher Scientific</td><td>596-3320</td><td>for filtration of aggregated clusters after synthesis and surface coating to achieve a uniform solution</td></tr><tr><td>Vacuum Controller V-850</td><td>Buchi</td><td>BU-V850</td><td>for filtration of aggregated clusters after synthesis and surface coating to achieve a uniform solution</td></tr><tr><td>Vacuum Oven</td><td>Fisher Scientific</td><td>13-262-51</td><td>used to create high temperature and pressure needed for nanocluster formation in hydrothermal synthesis</td></tr></tbody></table>

stable aqueous suspensions of manganese ferrite clusters with tunable nanoscale dimension and composition

Manganese ferrite clusters (MFCs) are spherical assemblies of tens to hundreds of primary nanocrystals whose magnetic properties are valuable in diverse applications. Here we describe how to form these materials in a hydrothermal process that permits the independent control of product cluster size (from 30 to 120 nm) and manganese content of the resulting material. Parameters such as the total amount of water added to the alcoholic reaction media and the ratio of manganese to iron precursor are important factors in achieving multiple types of MFC nanoscale products. A fast purification method uses magnetic separation to recover the materials making production of grams of magnetic nanomaterials quite efficient. We overcome the challenge of magnetic nanomaterial aggregation by applying highly charged sulfonate polymers to the surface of these nanomaterials yielding colloidally stable MFCs that remain non-aggregating even in highly saline environments. These non-aggregating, uniform, and tunable materials are excellent prospective materials for biomedical and environmental applications.

After hydrothermal treatment, the reaction mixture turns into a viscous black dispersion as can be seen in Figure 1. What results after purification is a highly concentrated MFC solution that behaves like a ferrofluid. The fluid in the vial responds within seconds when placed near a handheld magnet (&#60;0.5 T), forming a macroscopic black mass that can be moved around as the magnet is placed at different locations.
This synthesis yields products whose dimension a...

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Stable Aqueous Suspensions of Manganese Ferrite Clusters with Tunable Nanoscale Dimension and Composition

We report a one-pot hydrothermal synthesis of manganese ferrite clusters (MFCs) that offers independent control over material dimension and composition. Magnetic separation allows rapid purification while surface functionalization using sulfonated polymers ensures the materials are non-aggregating in biologically relevant medium. The resulting products are well positioned for biomedical applications.

Manganese ferrite clusters (MFCs) are spherical assemblies of tens to hundreds of primary nanocrystals whose magnetic properties are valuable in diverse ...

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Research

JoVE Journal

Chemistry

4.2K Views.  Brown University. In deze video presenteren we de synthese van super paramagnetische mangaan ferriet nanoclusters. We rapporteren een eenpotige hydrothermale synthese van mangaan ferrietclusters of MFC's die onafhankelijke controle biedt over zowel primaire nanokristal- als clusterdimensie, evenals de verhouding tussen ijzer en mangaan. Magnetische scheiding maakt een snelle monsterzuivering mogelijk, terwijl servicefunctionalisatie met behulp van een gesulfoneerd polymeer ervoor zorgt dat de materialen niet-a...

Video: Stable Aqueous Suspensions of Manganese Ferrite Clusters with Tunable Nanoscale Dimension and Composition

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

Dispersion of Nanomaterials in Aqueous Media: Towards Protocol Optimization

The sonication process is commonly used for de-agglomerating and dispersing nanomaterials in aqueous based media, necessary to improve homogeneity and stability of the suspension. In this study, a systematic step-wise approach is carried out to identify optimal sonication conditions in order to achieve a stable dispersion. This approach has been adopted and shown to be suitable for several nanomaterials (cerium oxide, zinc oxide, and carbon nanotubes) dispersed in deionized (DI) water. However, with any change in either the nanomaterial type or dispersing medium, there needs to be optimization of the basic protocol by adjusting various factors such as sonication time, power, and sonicator type as well as temperature rise during the process. The approach records the dispersion process in detail. This is necessary to identify the time points as well as other above-mentioned conditions during the sonication process in which there may be undesirable changes, such as damage to the particle surface thus affecting surface properties. Our goal is to offer a harmonized approach that can control the quality of the final, produced dispersion. Such a guideline is instrumental in ensuring dispersion quality repeatability in the nanoscience community, particularly in the field of nanotoxicology.

Here, we present a step-wise protocol for the dispersion of nanomaterials in aqueous media with real-time characterization to identify the optimal sonication conditions, intensity, and duration for improved stability and uniformity of nanoparticle dispersions without impacting the sample integrity.

The sonication process is commonly used for de-agglomerating and dispersing nanomaterials in aqueous based media, necessary to improve homogeneity and ...

Environment

An Available Technique for Preparation of New Cast MnCuNiFeZnAl Alloy with Superior Damping Capacity and High Service Temperature

Manganese (Mn)-copper (Cu)-based alloys have been found to have&#160;damping capacity and can be used to reduce harmful vibrations and noise effectively. M2052 (Mn-20Cu-5Ni-2Fe, at%) is an important branch of Mn-Cu-based alloys, which possesses both excellent damping capacity and processability. In recent decades, lots of studies have been carried out on the performance optimization of M2052, improving the damping capacity, mechanical properties, corrosion resistance, and service temperature, etc. The major methods of performance optimization are alloying, heat treatment, pretreatment, and different ways of molding etc., among which alloying, as well as adopting a reasonable heat treatment, is the simplest and most effective method to obtain perfect and comprehensive performance. To obtain the M2052 alloy with excellent performance for casting molding, we propose to add Zn and Al to the MnCuNiFe alloy matrix and use a variety of heat treatment methods for a comparison in the microstructure, damping capacity, and service temperature. Thus, a new type of cast-aged Mn-22.68Cu-1.89Ni-1.99Fe-1.70Zn-6.16Al (at.%) alloy with&#160;superior damping capacity and high service temperature is obtained by an optimized heat treatment method. Compared with the forging technique, cast molding is simpler and more efficient, and the damping capacity of this as-cast alloy is excellent. Therefore, there is a suitable reason to think that it is a good choice for engineering applications.

Here we present a protocol to obtain a novel Mn-Cu-based alloy with excellent comprehensive performances by a high-quality smelting technology and reasonable heat treatment methods.

Manganese (Mn)-copper (Cu)-based alloys have been found to have&#160;damping capacity and can be used to reduce harmful vibrations and noise effectively. ...

Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses

We demonstrate the use of two nuclear-based analytical methods that can follow the modifications of microstructural arrangement of iron-based metallic glasses (MGs). Despite their amorphous nature, the identification of hyperfine interactions unveils faint structural modifications. For this purpose, we have employed two techniques that utilize nuclear resonance among nuclear levels of a stable 57Fe isotope, namely M&#246;ssbauer spectrometry and nuclear forward scattering (NFS) of synchrotron radiation. The effects of heat treatment upon (Fe2.85Co1)77Mo8Cu1B14 MG are discussed using the results of ex situ and in situ experiments, respectively. As both methods are sensitive to hyperfine interactions, information on structural arrangement as well as on magnetic microstructure is readily available. M&#246;ssbauer spectrometry performed ex situ describes how the structural arrangement and magnetic microstructure appears at room temperature after the annealing under certain conditions (temperature, time), and thus this technique inspects steady states. On the other hand, NFS data are recorded in situ during dynamically changing temperature and NFS examines transient states. The use of both techniques provides complementary information. In general, they can be applied to any suitable system in which it is important to know its steady state but also transient states.

Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses

Here, we present a protocol to describe ex situ and in situ investigations of structural transformations in metallic glasses. We employed nuclear-based analytical methods which inspect hyperfine interactions. We demonstrate the applicability of M&#246;ssbauer spectrometry and nuclear forward scattering of synchrotron radiation during temperature-driven experiments.

We demonstrate the use of two nuclear-based analytical methods that can follow the modifications of microstructural arrangement of iron-based metallic ...

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.

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. ...

Generation of Scalable, Metallic High-Aspect Ratio Nanocomposites in a Biological Liquid Medium

The goal of this protocol is to describe the synthesis of two novel biocomposites with high-aspect ratio structures. The biocomposites consist of copper and cystine, with either copper nanoparticles (CNPs) or copper sulfate contributing the metallic component. Synthesis is carried out in liquid under biological conditions (37 &#176;C) and the self-assembled composites form after 24 hr. Once formed, these composites are highly stable in both liquid media and in a dried form. The composites scale from the nano- to micro- range in length, and from a few microns to 25 nm in diameter. Field emission scanning electron microscopy with energy dispersive X-ray spectroscopy (EDX) demonstrated that sulfur was present in the NP-derived linear structures, while it was absent from the starting CNP material, thus confirming cystine as the source of sulfur in the final nanocomposites. During synthesis of these linear nano- and micro-composites, a diverse range of lengths of structures is formed in the synthesis vessel. Sonication of the liquid mixture after synthesis was demonstrated to assist in controlling average size of the structures by diminishing the average length with increased time of sonication. Since the formed structures are highly stable, do not agglomerate, and are formed in liquid phase, centrifugation may also be used to assist in concentrating and segregating formed composites.

Here we present a protocol to synthesize novel, high-aspect ratio biocomposites under biological conditions and in liquid media. The biocomposites scale from nanometers to micrometers in diameter and length, respectively. Copper nanoparticles (CNPs) and copper sulfate combined with cystine are the key components for the synthesis.

The goal of this protocol is to describe the synthesis of two novel biocomposites with high-aspect ratio structures. The biocomposites consist of copper ...

Bioengineering

Optimizing Magnetic Force Microscopy Resolution and Sensitivity to Visualize Nanoscale Magnetic Domains

Magnetic force microscopy (MFM) enables mapping local magnetic fields across a sample surface with nanoscale resolution. To perform MFM, an atomic force microscopy (AFM) probe whose tip has been magnetized vertically (i.e., perpendicular to the probe cantilever) is oscillated at a fixed height above the sample surface. The resultant shifts in the oscillation phase or frequency, which are proportional to the magnitude and sign of the vertical magnetic force gradient at each pixel location, are then tracked and mapped. Although the spatial resolution and sensitivity of the technique increases with decreasing lift height above the surface, this seemingly straightforward path to improved MFM images is complicated by considerations such as minimizing topographical artifacts due to shorter range van der Waals forces, increasing the oscillation amplitude to further improve sensitivity, and the presence of surface contaminants (in particular water due to humidity under ambient conditions). In addition, due to the orientation of the probe's magnetic dipole moment, MFM is intrinsically more sensitive to samples with an out-of-plane magnetization vector. Here, high-resolution topographical and magnetic phase images of single and bicomponent nanomagnet artificial spin-ice (ASI) arrays obtained in an inert (argon) atmosphere glovebox with &lt;0.1 ppm O2 and H2O are reported. Optimization of lift height and drive amplitude for high resolution and sensitivity while simultaneously avoiding the introduction of topographical artifacts is discussed, and detection of the stray magnetic fields emanating from either end of the nanoscale bar magnets (~250 nm long and &lt;100 nm wide) aligned in the plane of the ASI sample surface is shown. Likewise, using the example of a Ni-Mn-Ga magnetic shape memory alloy (MSMA), MFM is demonstrated in an inert atmosphere with magnetic phase sensitivity capable of resolving a series of adjacent magnetic domains each ~200 nm wide.

Magnetic force microscopy (MFM) employs a vertically magnetized atomic force microscopy probe to measure sample topography and local magnetic field strength with nanoscale resolution. Optimizing MFM spatial resolution and sensitivity requires balancing decreasing lift height against increasing drive (oscillation) amplitude, and benefits from operating in an inert atmosphere glovebox.

Magnetic force microscopy (MFM) enables mapping local magnetic fields across a sample surface with nanoscale resolution. To perform MFM, an atomic force ...

Using Magnetometry to Monitor Cellular Incorporation and Subsequent Biodegradation of Chemically Synthetized Iron Oxide Nanoparticles

Magnetic nanoparticles, made of iron oxide, present a peculiar interest for a wide range of biomedical applications for which they are often internalized in cells and then left within. One challenge is to assess their fate in the intracellular environment with reliable and precise methodologies. Herein, we introduce the use of the vibrating sample magnetometer (VSM) to precisely quantify the integrity of magnetic nanoparticles within cells by measuring their magnetic moment. Stem cells are first labeled with two types of magnetic nanoparticles; the nanoparticles have the same core produced via a fast and efficient microwave-based nonaqueous sol gel synthesis and differ in their coating: the commonly used citric acid molecule is compared to polyacrylic acid. The formation of 3D cell-spheroids is then achieved via centrifugation and the magnetic moment of these spheroids is measured at different times with the VSM. The obtained moment is a direct fingerprint of the nanoparticles&#8217; integrity, with decreasing values indicative of a nanoparticle degradation. For both nanoparticles, the magnetic moment decreases over culture time revealing their biodegradation. A protective effect of the polyacrylic acid coating is also shown, when compared to citric acid.

Iron oxide nanoparticles are synthesized via a nonaqueous sol gel procedure and coated with anionic short molecules or polymer. The use of magnetometry for monitoring the incorporation and biotransformations of magnetic nanoparticles inside human stem cells is demonstrated using a vibrating sample magnetometer (VSM).

Magnetic nanoparticles, made of iron oxide, present a peculiar interest for a wide range of biomedical applications for which they are often internalized ...

Manganese Oxide Nanoparticle Synthesis by Thermal Decomposition of Manganese(II) Acetylacetonate

For biomedical applications, metal oxide nanoparticles such as iron oxide and manganese oxide (MnO), have been used as biosensors and contrast agents in magnetic resonance imaging (MRI). While iron oxide nanoparticles provide constant negative contrast on MRI over typical experimental timeframes, MnO generates switchable positive contrast on MRI through dissolution of MnO to Mn2+ at low pH within cell endosomes to &#8216;turn ON&#8217; MRI contrast. This protocol describes a one-pot synthesis of MnO nanoparticles formed by thermal decomposition of manganese(II) acetylacetonate in oleylamine and dibenzyl ether. Although running the synthesis of MnO nanoparticles is simple, the initial experimental setup can be difficult to reproduce if detailed instructions are not provided. Thus, the glassware and tubing assembly is first thoroughly described to allow other investigators to easily reproduce the setup. The synthesis method incorporates a temperature controller to achieve automated and precise manipulation of the desired temperature profile, which will impact resulting nanoparticle size and chemistry. The thermal decomposition protocol can be readily adapted to generate other metal oxide nanoparticles (e.g., iron oxide) and to include alternative organic solvents and stabilizers (e.g., oleic acid). In addition, the ratio of organic solvent to stabilizer can be changed to further impact nanoparticle properties, which is shown herein. Synthesized MnO nanoparticles are characterized for morphology, size, bulk composition, and surface composition through transmission electron microscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy, respectively. The MnO nanoparticles synthesized by this method will be hydrophobic and must be further manipulated through ligand exchange, polymeric encapsulation, or lipid capping to incorporate hydrophilic groups for interaction with biological fluids and tissues.

Manganese Oxide Nanoparticle Synthesis by Thermal Decomposition of ManganeseII Acetylacetonate

This protocol details a facile, one-pot synthesis of manganese oxide (MnO) nanoparticles by thermal decomposition of manganese(II) acetylacetonate in the presence of oleylamine and dibenzyl ether. MnO nanoparticles have been utilized in diverse applications including magnetic resonance imaging, biosensing, catalysis, batteries, and waste water treatment.

For biomedical applications, metal oxide nanoparticles such as iron oxide and manganese oxide (MnO), have been used as biosensors and contrast agents in ...

Fabrication of Magnetic Platforms for Micron-Scale Organization of Interconnected Neurons

The ability to direct neurons into organized neural networks has great implications for regenerative medicine, tissue engineering, and bio-interfacing. Many studies have aimed at directing neurons using chemical and topographical cues. However, reports of organizational control on a micron-scale over large areas are scarce. Here, an effective method has been described for placing neurons in preset sites and guiding neuronal outgrowth with micron-scale resolution, using magnetic platforms embedded with micro-patterned, magnetic elements. It has been demonstrated that loading neurons with magnetic nanoparticles (MNPs) converts them into sensitive magnetic units that can be influenced by magnetic gradients. Following this approach, a unique magnetic platform has been fabricated on which PC12 cells, a common neuron-like model, were plated and loaded with superparamagnetic nanoparticles. Thin films of ferromagnetic (FM) multilayers with stable perpendicular magnetization were deposited to provide effective attraction forces toward the magnetic patterns. These MNP-loaded PC12 cells, plated and differentiated atop the magnetic platforms, were preferentially attached to the magnetic patterns, and the neurite outgrowth was well aligned with the pattern shape, forming oriented networks. Quantitative characterization methods of the magnetic properties, cellular MNP uptake, cell viability, and statistical analysis of the results are presented. This approach enables the control of neural network formation and improves neuron-to-electrode interface through the manipulation of magnetic forces, which can be an effective tool for in vitro studies of networks and may offer novel therapeutic biointerfacing directions.

This work presents a bottom-up approach to the engineering of local magnetic forces for control of neuronal organization. Neuron-like cells loaded with magnetic nanoparticles (MNPs) are plated atop and controlled by a micro-patterned platform with perpendicular magnetization. Also described are magnetic characterization, MNP cellular uptake, cell viability, and statistical analysis.

The ability to direct neurons into organized neural networks has great implications for regenerative medicine, tissue engineering, and bio-interfacing. ...

Stable Aqueous Suspensions of Manganese Ferrite Clusters with Tunable Nanoscale Dimension and Composition

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