Name: manganese oxide nanoparticle synthesis by thermal decomposition of manganese(ii) acetylacetonate
Uploaded: 2020-06-18T15:00:00.000+00:00
Duration: 9 min 2 s
Description: Watch this Scientific Journal Video about Manganese Oxide Nanoparticle Synthesis by Thermal Decomposition of ManganeseII Acetylacetonate at JoVE.com

This work was supported by WVU Chemical and Biomedical Engineering Department startup funds (M.F.B.). The authors would like to thank Dr. Marcela Redigolo for guidance on grid preparation and image capture of nanoparticles with TEM, Dr. Qiang Wang for support on evaluating XRD and FTIR spectra, Dr. John Zondlo and Hunter Snoderly for programming and integrating the temperature controller into the nanoparticle synthesis protocol, James Hall for his assistance in assembly of the nanoparticle synthesis setup, Alexander Pueschel and Jenna Vito for aiding in quantification of MnO nanoparticle diameters from TEM images, and the WVU Shared Research Facility for use of the TEM, XRD, and FTIR.

The authors have nothing to disclose.

The protocol herein describes a facile, one-pot synthesis of MnO nanoparticles using Mn(II) ACAC, DE, and OA. Mn(II) ACAC is utilized as the starting material to provide a source of Mn2+ for MnO nanoparticle formation. The starting material can be easily substituted to enable production of other metal oxide nanoparticles. For example, when iron(III) ACAC is applied, Fe3O4 nanoparticles can be generated using the same nanoparticle synthesis equipment and protocol described63. DE serves as an ideal organic solvent for thermal decomposition reactions, as it has a high boiling point of 295-298 &#176;C. OA is a commonly used inexpensive stabilizer/mild reducing agent, which aids in capping and coordinating metal oxide nanoparticle nucleation and growth61,63. Similar to DE, OA has a high boiling point of 350 &#176;C to withstand the high temperatures of thermal decomposition. The following two observations can be used as evidence of successful generation of MnO nanoparticles during synthesis: 1) the appearance of a green hue to the reaction mixture during thermal decomposition at 280 &#176;C and 2) the formation of a dark brown large pellet on the bottom of the centrifuge tubes following centrifugation in hexane and ethanol. Resulting nanoparticles should be further characterized by TEM, XRD and FTIR to evaluate size/morphology, bulk composition and surface composition, respectively.
During nanoparticle synthesis, several variables must be noted and controlled to ensure production of uniform nanoparticles with the MnO crystalline phase. First, the ratio of all starting materials should remain the same, as we have shown that decreasing ratios of OA to DE decrease nanoparticle size (Figure 4). Second, the reaction should be vigorously stirred to enable adequate dispersion of nucleating nanoparticles, uniform heating, and reduction of size variation. Third, as temperature plays a large role in controlling metal oxide nanoparticle size47,48,50 and phase composition47,48,50, it is critical to properly immerse the temperature probe tip into the reaction mixture while not contacting the glass of the round bottom flask that will read an inaccurate temperature. Fourth, the flow of nitrogen should be high enough to purge all air from the reaction to encourage formation of the MnO crystalline phase over Mn3O4. As shown in Figure 6A, low nitrogen flow will result in nanoparticles with a mixed MnO/Mn3O4 composition. Correct filling of the mineral oil bubblers with increasing amounts of silicone oil from the left bubbler (1 inch of oil) to the middle bubbler (1.5 inches of oil) to the right bubbler (2 inches of oil) will set the resistance for nitrogen flow to be lowest through the reaction (#4 in Figure 1). The bubbling rate of the middle mineral oil bubbler (by #7,8 in Figure 1) can be used to measure the rate of nitrogen flowing through the reaction. Finally, a stabilizer such as OA must be added to the reaction mixture to coordinate nanoparticle nucleation and growth. As shown in Figure 6B, DE without OA created a small amount of product, mostly of a Mn3O4 (67%) composition. This product was also observed to have an irregular shape with aggregated nanoparticles by TEM, which did not occur when OA was present in the reaction (Figure 6F).
Several variables of the thermal decomposition reaction can be modified to optimize nanoparticle size, morphology, and composition including the type of inert gas47,48,50, peak reaction temperature44,47,48,49, total reaction time44,45,46, and types/ratios of initial chemical compounds utilized in the reaction20,45,47,48,50. Salazar-Alvarez et al.50 and Seo et al.48 have shown that argon flow during thermal decomposition of Mn(II)&#160;forms Mn3O4 at lower peak reaction temperatures ranging from 150 &#176;C to 200 &#176;C. When using nitrogen or air, Nolis et al.47 achieved similar results for Mn(III)&#160;ACAC decomposition where Mn3O4 nanoparticles were produced at lower temperatures (150&#160;oC or 200&#160;oC) and MnO nanoparticles were generated only at higher temperatures (250 &#176;C and 300 &#176;C)47. Higher peak reaction temperatures and longer times held at the peak reaction temperature, also known as the aging time, have also been associated with an increase in nanoparticle size44,45,46,47,48,49. Furthermore, the heating rate of the reaction can impact nanoparticle size. Schladt et al.44 found that increasing the heating rate from 1.5 &#176;C/min up to 90&#160;oC/min dropped nanoparticle size from 18.9 nm to 6.5 nm, respectively. Finally, different chemicals can be added as reducing agents and stabilizers in manganese thermal decomposition reactions; however, OA20,47,48,50 and oleic acid20,45 are most commonly used. The ratio of OA to oleic acid has been proven to affect the chemistry and shape of synthesized MnO nanoparticles. According to Zhang et al.20, OA only resulted in the formation of Mn3O4 nanoparticles, a combination of OA and oleic acid led to a mixture of Mn3O4 and MnO nanoparticles, and oleic acid only produced MnO nanoparticles. Interestingly, experience shows that MnO nanoparticles can be fabricated with OA only, and that oleic acid is not necessary to promote formation of the MnO crystalline phase. Furthermore, the use of OA by itself fabricated spherical nanoparticles, while oleic acid alone generated star shaped nanoparticles20,64. Clearly, there is much flexibility in altering synthesis parameters to impact resulting physical and chemical properties of MnO nanoparticles.
Despite the detailed protocol, instances may arise that require troubleshooting. The following paragraph details some common issues and solutions. During the reaction, if the temperature seems to stabilize around 100 &#176;C, some water may have leaked into the heating mantle. Visibly inspect the surrounding area for water leakage from the condenser. Do not directly touch the mantle or round bottom flask without heat resistant gloves, as they will be very hot. If water is observed, immediately turn off the temperature controller, unplug the heating mantle, and let it dry overnight. To prevent future leakages, use an interlocked worm gear hose clamp to secure the water tubing to the condenser. In the case that the desired product is MnO, but only Mn3O4 is produced, it is important to check the nitrogen flow during the reaction. The middle bubbler should have a constant stream of bubbles (see the video for correct bubbling rate), while the right bubbler should only have one or two bubbles forming in it. Incorrect nitrogen flow can occur if the differential silicone oil levels in each mineral oil bubbler are not maintained. Check the oil levels before every experiment and fill up the bubblers according to step 1.5 if needed. During nanoparticle collection, the protocol specifies to pour out the supernatant without disturbing the nanoparticle pellet. The best way to discard the supernatant is to pour it out with one fast continuous motion rather than a slow one. However, if the pellet gets easily detached from the centrifuge tube, the use of a transfer pipette is recommended to remove the supernatant. During nanoparticle collection and TEM grid preparation, bath sonication is a key step. If the nanoparticles are not resuspending correctly, move the tube around the water bath sonicator until an area is located where the sonication can be felt by the hand holding the tube. The nanoparticle pellet can also be visibly seen disintegrating under strong bath sonication if the tube is in the correct spot. After nanoparticle resuspension, it is important that the TEM grid is suspended in the air with reverse tweezers rather than placed onto a wipe or directly onto an absorbent bench surface. The wipe or absorbent bench surface will wick the nanoparticle suspension off of the TEM grid before drying, resulting in insufficient nanoparticle deposition on the grid for imaging.
Although the thermal decomposition reaction is fairly simple and straightforward to follow to synthesize MnO nanoparticles, there are some limitations associated with the method. While it is possible to control the physical and chemical properties of nanoparticles to some extent, some variables such as temperature and aging time impact both nanoparticle size and phase composition simultaneously. Therefore, it is difficult to always have precise independent control of nanoparticle properties using this method. In addition, scaling up of the nanoparticle synthesis by tripling or quadrupling the amounts of starting materials can cause the reaction to become unstable and violent. Larger batch size is also associated with a decreased yield. Furthermore, despite storage of MnO nanoparticles inside capped scintillation vials wrapped in paraffin plastic film, we have seen oxidation of the nanoparticle surface to Mn3O4 as evaluated by X-ray photoelectron spectroscopy. Finally, the MnO nanoparticles generated by this technique will be hydrophobic and capped with OA (Figure 7). Further surface modification to transition nanoparticles to a hydrophilic state will need to be applied to enable nanoparticle suspension in aqueous media. Several methods have been established to promote the dispersion of nanoparticles in biological solutions including nanoparticle encapsulation inside of polymers14, coating of the nanoparticle surface with lipids52, or ligand exchange to substitute the OA on the nanoparticle surface with hydrophilic ligands such as poly(acrylic acid)20. To achieve encapsulation of MnO nanoparticles within poly(lactic-co-glycolic acid) (PLGA) polymer, follow McCall and Sirianni&#8217;s detailed JoVE protocol65; MnO nanoparticles can be added directly to the PLGA polymer solution as described for hydrophobic drugs in step 8 of the Nanoparticle Preparation section. MnO nanocrystal distribution inside of PLGA nanoparticles can be assessed using TEM and loading of Mn inside the PLGA polymer can be determined by thermogravimetric analysis as shown in Bennewitz et al.14.
Although MnO nanoparticles can be utilized for a wide variety of applications due to their magnetic, electronic and catalytic properties, we are interested in applying MnO nanoparticles as switchable, T1 MRI contrast agents. Previously, our group and others have shown that intact MnO nanoparticles have negligible T1 MRI contrast (MRI signal is &#8220;OFF&#8221;) at physiological pH 7.4 mimicking the blood14,15,16,17,18,19. However, MnO dissolves to create substantial Mn2+ ions at low pH 5 mimicking cellular endosomes; released Mn2+ will coordinate with surrounding water molecules to turn &#8220;ON&#8221; MRI signal at low pH14,15,16,17,18,19. MnO nanoparticles can be localized to different cells of interest, such as cancer cells, through addition of targeting peptides or antibodies to the nanoparticle surface51,66. Here, we describe the synthesis of MnO nanoparticles with an average diameter ranging from 18.6 nm to 38.8 nm. Control of nanoparticle size can be useful for improving MRI contrast agent effectiveness. Specifically, it is anticipated that larger nanoparticles will have more surface area for attachment of targeting ligands to enhance nanoparticle accumulation at the site of interest such as tumors. However, overall nanoparticle size with added surface groups should be limited to 50-100 nm to maximize tumor accumulation67,68. Smaller nanoparticles, on the other hand, have a higher surface area-to-volume ratio to facilitate faster release of Mn2+ under acidic environments and should allow for enhanced nanoparticle packing volumes inside of polymeric delivery systems. Synthesis of MnO over Mn3O4 should also improve MRI contrast, as MnO has been shown to dissolve faster than Mn3O4 in concentrated acidic solutions to generate more Mn2+ ions69. In summary, we have described a thermal decomposition protocol for fabrication of MnO nanoparticles that is relatively straightforward and customizable to allow for optimizing nanoparticle design for future use in applications such as smart MRI contrast agents, biosensors, catalysts, batteries and water purification.

Metal oxide nanoparticles possess magnetic, electric, and catalytic properties, which have been applied in bioimaging1,2,3, sensor technologies4,5, catalysis6,7,8, energy storage9, and water purification10. Within the biomedical field, iron oxide nanoparticles and manganese oxide (MnO) nanoparticles have proven utility as contrast agents in magnetic resonance imaging (MRI)1,2. Iron oxide nanoparticles produce robust negative contrast on T2* MRI and are powerful enough to visualize single labeled cells in vivo11,12,13; however, the negative MRI signal cannot be modulated and remains &#8220;ON&#8221; throughout the duration of typical experiments. Due to endogenous iron present in the liver, bone marrow, blood and spleen, the negative contrast generated from iron oxide nanoparticles may be difficult to interpret. MnO nanoparticles, on the other hand, are responsive to a drop in pH. MRI signal for MnO nanoparticles can transition from &#8220;OFF&#8221; to &#8220;ON&#8221; once the nanoparticles are internalized inside the low pH endosomes and lysosomes of the target cell such as a cancer cell14,15,16,17,18,19. The positive contrast on T1 MRI produced from the dissolution of MnO to Mn2+ at low pH is unmistakable and can improve cancer detection specificity by only lighting up at the target site within a malignant tumor. Control over nanoparticle size, morphology and composition is crucial to achieve maximum MRI signal from MnO nanoparticles. Herein, we describe how to synthesize and characterize MnO nanoparticles using the thermal decomposition method and note different strategies for fine-tuning nanoparticle properties by altering variables in the synthesis process. This protocol can be easily modified to produce other magnetic nanoparticles such as iron oxide nanoparticles.
MnO nanoparticles have been produced by a variety of techniques including thermal decomposition20,21,22,23,24,25, hydro/solvothermal26,27,28,29, exfoliation30,31,32,33,34, permanganates reduction35,36,37,38, and adsorption-oxidation39,40,41,42. Thermal decomposition is the most commonly used technique which involves dissolving manganese precursors, organic solvents, and stabilizing agents at high temperatures (180 &#8211; 360 &#176;C) under the presence of an inert gaseous atmosphere to form MnO nanoparticles43. Out of all of these techniques, thermal decomposition is the superior method to generate a variety of MnO nanocrystals of pure phase (MnO, Mn3O4 and Mn2O3) with a narrow size distribution. Its versatility is highlighted through the ability to tightly control nanoparticle size, morphology and composition by altering reaction time44,45,46, temperature44,47,48,49, types/ratios of reactants20,45,47,48,50 and inert gas47,48,50 used. The main limitations of this method are the requirement for high temperatures, the oxygen-free atmosphere, and the hydrophobic coating of the synthesized nanoparticles, which requires further modification with polymers, lipids or other ligands to increase solubility for biological applications14,51,52,53.
Besides thermal decomposition, the hydro/solvothermal method is the only other technique that can produce a variety of MnO phases including MnO, Mn3O4, and MnO2; all other strategies only form MnO2 products. During hydro/solvothermal synthesis, precursors such as Mn(II) stearate54,55 and Mn(II) acetate27 are heated to between 120-200 &#176;C over several hours to achieve nanoparticles with a narrow size distribution; however, specialized reaction vessels are required and reactions are performed at high pressures. In contrast, the exfoliation strategy involves treatment of a layered or bulk material to promote dissociation into 2D single layers. Its main advantage is in producing MnO2 nanosheets, but the synthesis process is long requiring several days and the resulting size of the sheets is difficult to control. Alternatively, permanganates such as KMnO4 can react with reducing agents such as oleic acid56,57, graphene oxide58 or poly(allylamine hydrochloride)59 to create MnO2 nanoparticles. Use of KMnO4 facilitates nanoparticle formation at room temperature over a few minutes to hours within aqueous conditions43. Unfortunately, the rapid synthesis and nanoparticle growth makes it challenging to finely control resulting nanoparticle size. MnO2 nanoparticles can also be synthesized using adsorption-oxidation whereby Mn2+ ions are adsorbed and oxidized to MnO2 by oxygen under basic conditions. This method will produce small MnO2 nanoparticles with a narrow size distribution at room temperature over several hours in aqueous media; however the requirement for adsorption of Mn2+ ions and alkali conditions limits its widespread application43.
Of the MnO nanoparticle synthesis methods discussed, thermal decomposition is the most versatile to generate different monodisperse pure phase nanocrystals with control over nanoparticle size, shape and composition without requiring specialized synthesis vessels. In this manuscript, we describe how to synthesize MnO nanoparticles by thermal decomposition at 280 &#176;C using manganese(II) acetylacetonate (Mn(II) ACAC) as the source of Mn2+ ions, oleylamine (OA) as the reducing agent and stabilizer, and dibenzyl ether (DE) as the solvent under a nitrogen atmosphere. The glassware and tubing setup for nanoparticle synthesis is explained in detail. One advantage of the technique is the inclusion of a temperature controller, thermocouple probe, and heating mantle to enable precise control over the heating rate, peak temperature, and reaction times at each temperature to fine-tune nanoparticle size and composition. Herein, we show how nanoparticle size can also be manipulated by changing the ratio of OA to DE. Additionally, we demonstrate how to prepare nanoparticle samples and measure nanoparticle size, bulk composition and surface composition using transmission electron microscopy (TEM), x-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR), respectively. Further guidance is included on how to analyze the collected images and spectra from each instrument. To generate uniformly shaped MnO nanoparticles, a stabilizer and adequate nitrogen flow must be present; XRD and TEM results are shown for undesired products formed in the absence of OA and under low nitrogen flow. In the Discussion section, we highlight crucial steps in the protocol, metrics to determine successful nanoparticle synthesis, further variation of the decomposition protocol to modify nanoparticle properties (size, morphology and composition), troubleshooting and limitations of the method, and applications of MnO nanoparticles as contrast agents for biomedical imaging.

<table><tbody><tr><td>&lt;strong&gt;Chemicals and Gases&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Benzyl ether (DE)</td><td>Acros Organics</td><td>AC14840-0010</td><td>Concentration: 99%, 1 L</td></tr><tr><td>Drierite</td><td>W. A. Hammond Drierite Co. LTD</td><td>23001</td><td>Drierite 8 mesh, 1 lb</td></tr><tr><td>Ethanol</td><td>Decon Laboratories&amp;nbsp;</td><td>2701</td><td>200 proof, 4 x 3.7 L</td></tr><tr><td>Hexane</td><td>Macron Fine Chemicals</td><td>5189-08</td><td>Concentration:&amp;nbsp; &amp;ge;98.5%, 4 L</td></tr><tr><td>Hydrochloric acid</td><td>VWR</td><td>BDH3030-2.5LPC</td><td>Concentration: 36.5 - 38.0 % ACS, 2.5 L</td></tr><tr><td>Manganese (II) acetyl acetonate (Mn(II)ACAC)</td><td>Sigma Aldrich</td><td>245763-100G</td><td>100 g</td></tr><tr><td>Nitrogen gas tank</td><td>Airgas</td><td>NI R300</td><td>Research 5.7 grade nitrogen, size 300 cylinder</td></tr><tr><td>Nitrogen regulator</td><td>Airgas</td><td>Y11244D580-AG</td><td>Single stage brass 0-100 psi analytical cylinder regulator CGA-580 with needle outlet</td></tr><tr><td>Oleylamine (OA)</td><td>Sigma Aldrich</td><td>O7805-500G</td><td>Concentration: 70%, technical grade, 500 g</td></tr><tr><td>Silicone oil</td><td>Beantown Chemical</td><td>221590-100G</td><td>100 g</td></tr><tr><td>&lt;strong&gt;Equipment&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Centrifuge</td><td>Beckman-Coulter</td><td>Avanti J-E</td><td>JA-20 fixed-angle aluminum rotor, 8 x 50 mL, 48,400 x g</td></tr><tr><td>Hemisphere mantle</td><td>Ace Glass Inc.</td><td>12035-17</td><td>115 V, 270 W, 500 mL, temperature up to 450 &lt;sup&gt;&amp;deg;&lt;/sup&gt;C</td></tr><tr><td>Hot plate stirrer</td><td>VWR</td><td>97042-642</td><td>120 V, 1000 W, 8.3 A, ceramic top</td></tr><tr><td>Temperature controller</td><td>Yokogawa Electric Corporation</td><td>UP351</td><td></td></tr><tr><td>Temperature probe</td><td>Omega</td><td>KMQXL-040G-12</td><td>Immersion probe, temperature up to 1335 &amp;deg;C</td></tr><tr><td>Vacuum oven</td><td>Fisher Scientific</td><td>282A</td><td>120 V, 1800 W, temperature up to 280 &lt;sup&gt;&amp;deg;&lt;/sup&gt;C</td></tr><tr><td>Vortex mixer</td><td>Fisher Scientific</td><td>02-215-365</td><td>120 V, 50/60 Hz, 150 W</td></tr><tr><td>Water bath sonicator</td><td>Fisher Scientific</td><td>FS30H</td><td>Ultrasonic power 130 W, 3.7 L tank</td></tr><tr><td>&lt;strong&gt;Tools and Materials&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Dumont tweezer</td><td>Electron Microscopy Sciences</td><td>72703D</td><td>Style 5/45, Dumoxel, 109 mm, for picking up TEM grids</td></tr><tr><td>Dumont reverse tweezer</td><td>Ted Pella</td><td>5748</td><td>Style N2a, 118 mm, NM-SS, self-closing, holding TEM grids in place for sample preparation</td></tr><tr><td>Mortar and pestle</td><td>Amazon</td><td>BS0007</td><td>BIPEE agate mortar and pestle, 70 X 60 X 15 mm labware</td></tr><tr><td>Nalgene&amp;trade; Oak Ridge tubes</td><td>ThermoFisher Scientific</td><td>3139-0050</td><td>Polypropylene copolymer, 50,000 x g, 50 mL, pack of 10</td></tr><tr><td>Scintillation vials</td><td>Fisher Scientific</td><td>03-337-4</td><td>20 mL vials with white caps, case of 500</td></tr><tr><td>TEM grids</td><td>Ted Pella</td><td>01813-F</td><td>Carbon Type-B, 300 mesh, copper, pack of 50</td></tr><tr><td>&lt;strong&gt;Glassware Setup&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>4-neck round bottom flask</td><td>Chemglass Life Sciences</td><td>CG-1534-01</td><td>24/40 joint, 500 mL, #7 chem thread for thermometers</td></tr><tr><td>6-port vacuum manifold</td><td>Chemglass Life Sciences</td><td>CG-4430-02</td><td>480 nm, 6 ports, 4 mm PTFE stopcocks</td></tr><tr><td>Adapter</td><td>Chemglass Life Sciences</td><td>CG-1014-01</td><td>24/40 inner joint, 90&lt;sup&gt;&amp;deg;&lt;/sup&gt;</td></tr><tr><td>Condenser</td><td>Chemglass Life Sciences</td><td>CG-1216-03</td><td>24/40 joint, 365 mm, 250 mm jacket length</td></tr><tr><td>Drierite 26800 drying column</td><td>Cole-Parmer&amp;nbsp;</td><td>EW-07193-00</td><td>200 L/hr, 90 psi</td></tr><tr><td>Funnel</td><td>Chemglass Life Sciences</td><td>CG-1720-L-02</td><td>24/40 joint, 100 powder funnel, 195 mm OAL</td></tr><tr><td>Interlocked worm gear hose clamp</td><td>Grainger</td><td>16P292</td><td>1/2&quot; wide stainless steel clamp, 3/8&quot; to 7/8&quot; diameter, to secure condenser tubing, 10 pack&amp;nbsp;</td></tr><tr><td>Keck clips</td><td>Kemtech America Inc</td><td>CS002440</td><td>24/40 joint</td></tr><tr><td>Metal claw clamp</td><td>Fisher Scientific</td><td>05-769-7Q</td><td>22cm, three-prong extension clamps</td></tr><tr><td>Metal claw clamp holder</td><td>Fisher Scientific</td><td>05-754Q</td><td>Clamp regular holder</td></tr><tr><td>Mineral oil bubbler</td><td>Kemtech America Inc</td><td>B257040</td><td>185 mm</td></tr><tr><td>Rotovap trap</td><td>Chemglass Life Sciences</td><td>CG-1319-02</td><td>24/40 joints, 100 mL, self washing rotary evaporator</td></tr><tr><td>Rubber stopper</td><td>Chemglass Life Sciences</td><td>CG-3022-98</td><td>24/40 joints, red rubber</td></tr><tr><td>Tubing for air/water&amp;nbsp;</td><td>McMaster-Carr</td><td>6516T21</td><td>Clear Tygon PVC for air/water, B-44-3, 1/4&quot; ID, 1/16&quot; wall, 25 ft</td></tr><tr><td>Tubing for air/water&amp;nbsp;</td><td>McMaster-Carr</td><td>6516T26</td><td>Clear Tygon PVC for air/water, B-44-3, 3/8&quot; ID, 1/16&quot; wall, 25 ft</td></tr><tr><td>Tubing for chemicals</td><td>McMaster-Carr</td><td>5155T34</td><td>Clear Tygon PVC for chemicals, E-3603, 3/8&quot; ID, 1/16&quot; wall, 50 ft</td></tr><tr><td>&lt;strong&gt;Analysis Programs&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>XRD analysis program</td><td>Malvern Panalytical</td><td>N/A</td><td>X&#039;Pert HighScore Plus</td></tr><tr><td>FTIR analysis program</td><td>Varian, Inc.</td><td>N/A</td><td>Varian Resolutions Pro</td></tr></tbody></table>

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.

To confirm successful synthesis, MnO nanoparticles should be assayed for size and morphology (TEM), bulk composition (XRD), and surface composition (FTIR). Figure 2 shows representative TEM images of MnO nanoparticles synthesized using decreasing ratios of oleylamine (OA, the stabilizer) to dibenzyl ether (DE, the organic solvent): 60:0, 50:10, 40:20, 30:30, 20:40, 10:50. Ideal TEM images consist of individual nanoparticles (shown as dark rounded octagons in Figure 2), with minimal overlap. It is crucial to achieve adequate separation of nanoparticles for accurate manual sizing of the nanoparticle diameters using the line trace tool in ImageJ.
Figure 3 shows suboptimal TEM sample preparation. If a high concentration of MnO nanoparticles are suspended in ethanol or too many drops of nanoparticle suspension are added to the TEM grid, each image will consist of large agglomerations of nanoparticles (Figure 3A,B). Due to the substantial overlap of nanoparticles, the limits of each nanoparticle diameter cannot be distinguished, which prevents accurate measurement. If a low nanoparticle concentration is prepared in ethanol, nanoparticles could be well separated, but distributed sparsely on the TEM grid (Figure 3C,D). When only one or two nanoparticles appear in each TEM image, more images need to be taken to gain a large enough sample size and the full size distribution may not be precisely captured. The TEM preparation protocol described herein aims to produce TEM images with approximately 10-30 nanoparticles per image (more nanoparticles can be accommodated per image if the diameter is small).
TEM can be used to evaluate changes in nanoparticle size with a variation in synthesis parameters. Figure 4 shows the average diameters of MnO nanoparticles synthesized with decreasing ratios of OA:DE. Diameters for each synthesis condition were quantified from 75 to 90 TEM images, with a total of 900 to 1100 MnO nanoparticles analyzed per condition. To ensure reproducibility, 3 batches of nanoparticles were synthesized for each OA:DE ratio. Overall, a decrease in the ratio of OA:DE yielded smaller MnO nanoparticles with less variation in size; the only exception occurred when OA alone was used during synthesis, which produced similar sized nanoparticles to the 30:30 ratio. Histograms showing the full size distribution of all MnO nanoparticle groups are displayed in Figure S2.
After confirming nanoparticle size and morphology with TEM, the bulk nanoparticle composition can be tested using XRD. Through measuring the angle and intensity of the X-ray beam diffracted by the sample, XRD can be used to determine crystal structure and phase of the nanoparticles. Figure 5A-F shows the raw collected XRD spectra for each synthesized MnO nanoparticle sample with decreasing ratios of OA:DE. The XRD peaks obtained on sample spectra are matched to XRD peaks from known compounds such as MnO and Mn3O4 through the XRD analysis program database. The standard peaks for MnO appear at 35&#176;, 40&#176;, 58&#176;, 70&#176;, 73&#176;, and 87&#176;, which are shown in Figure 5G. When comparing the nanoparticle XRD spectra with known MnO, it is evident that all nanoparticle spectra possess the 5 highest peaks of MnO, indicating successful synthesis of MnO nanoparticles. XRD can also be utilized to estimate nanoparticle size using the Scherrer equation; wider peaks on XRD indicate smaller nanoparticle diameters. For example, Figure 5F with the widest XRD peaks is associated with the smallest nanoparticles as shown by TEM (18.6 &#177; 5.5 nm).
Figure 6 shows XRD spectra of two undesired products in MnO nanoparticle synthesis. To encourage the formation of the MnO phase at high temperatures (280&#160;oC), nitrogen is used during nanoparticle synthesis to purge air out of the system. If inadequate nitrogen flow is applied, a mixed phase composition of Mn3O4 (51%) and MnO (49%) is produced (Figure 6A). Through comparison with the standard peaks of Mn3O4 (Figure 6C) and MnO (Figure 6D), low nitrogen flow produces XRD spectra with the 8 highest peaks for Mn3O4 and the 5 highest peaks for MnO. TEM of nanoparticles synthesized under low nitrogen flow revealed a mixed population of large nanoparticles surrounded by smaller nanoparticles (Figure 6E). Nitrogen flow can be monitored through the nitrogen regulator reading and the rate of bubbling through the mineral oil bubbler. Another critical parameter in MnO nanoparticle synthesis is the inclusion of a stabilizer. In an attempt to produce even smaller MnO nanoparticles than the 10:50 OA:DE ratio, pure DE was used without any OA. A very small amount of an unknown powder was synthesized in the absence of stabilizer. As shown in Figure 6B, the XRD spectra for the 0:60 OA:DE ratio was noisy and contained the 3 highest peaks of Mn3O4. From analysis in the XRD program database, the compound had a chemical composition of 67% Mn3O4 and 33% MnO. As supported by the wide peaks in the XRD spectra, the TEM confirmed that very small nanoparticles were synthesized in the absence of stabilizer (Figure 6F). Nanoparticles also appeared irregularly shaped and agglomerated. Additionally, only a 33% yield was obtained without any stabilizer, meaning that a small amount of product was synthesized. Therefore, high nitrogen flow and inclusion of a stabilizer such as OA or oleic acid is necessary for synthesis of MnO nanoparticles.
To complement bulk nanoparticle composition with XRD, surface composition can be evaluated using FTIR. Figure 7 shows the FTIR spectra of MnO nanoparticles after background correction. All spectra show the symmetric and asymmetric CH2 peaks (2850-2854 and 2918-2926 cm-1, marked by asterisks) associated with oleyl groups60, in addition to the NH2 bending vibration peaks (1593 cm-1 and 3300 cm-1, marked by squares) associated with amine groups61. Since MnO nanoparticles share the same peaks for oleyl groups and amine groups present in the FTIR spectra of OA (Figure S3), it can be concluded that the nanoparticles are coated with a surface layer of OA. Furthermore, all nanoparticle FTIR spectra contain Mn-O and Mn-O-Mn bond vibrations around 600 cm-1 (marked by triangles), which confirm the composition found through XRD62.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/61572/61572fig01.jpg" /> 
Figure 1: Nitrogen and water flow through the MnO nanoparticle synthesis setup. 
Tubing connections are labeled 1-15. Air-free nitrogen enters (1) and exits (2) the drying column and is fed into the inlet of the manifold (3). During the reaction, nitrogen purges air from the system by entering the right stopcock on the manifold (4). Nitrogen flows from the stopcock to the glass elbow adapter (5), rotovap trap, round bottom flask, condenser, glass elbow adapter (6) and through a series of two mineral oil bubblers (7-9). In the manifold, excess nitrogen not flowing through the reaction will leave the system through the left stopcock (10), which is connected to the mineral oil bubbler with the largest amount of silicone oil (11). Stopcock #10 is to always remain open. Water will flow from the faucet (12) through the condenser inlet (13) and outlet (14) and into the fume hood drain (15). The tubing is secured to the condenser with metal clamps. All tubing should be chemical resistant tubing except for the water compatible tubing used for the condenser. The main glassware and equipment are labeled in Figure S1. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/61572/61572fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/61572/61572fig02.jpg" /> 
Figure 2: TEM images of MnO nanoparticles synthesized with decreasing ratios of OA:DE. 
The following ratios were used: (A) 60:0, (B) 50:10, (C) 40:20, (D) 30:30, (E) 20:40, (F) 10:50. MnO nanoparticles appear as separate, rounded octagons with minimal overlap to allow for clear delineation of nanoparticle borders. The reactant ratio was observed to affect overall nanoparticle size, with 50:10 synthesizing the largest nanoparticles and 10:50 producing the smallest nanoparticles. Scale bars are 50 nm. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/61572/61572fig02large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/61572/61572fig03.jpg" /> 
Figure 3: Suboptimal TEM images resulting from incorrect TEM grid preparation. 
(A,B) If the nanoparticle suspension is too concentrated or if excess drops of nanoparticle suspension get loaded onto the TEM grid, nanoparticles will aggregate into large masses with substantial overlap. Individual nanoparticles cannot be observed in most areas of the grid. (C,D) Alternatively, a low nanoparticle concentration could result in TEM grids populated with a scarce amount of nanoparticles. Individual nanoparticles are spread far apart, but require more images to capture the sample&#8217;s population size distribution. Scale bars are 50 nm. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/61572/61572fig03large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/61572/61572fig04.jpg" /> 
Figure 4: Average MnO nanoparticle diameters measured from TEM images. 
In general, a lower amount of stabilizer (OA) with a higher amount of organic solvent (DE) resulted in smaller, more uniform MnO nanoparticles. A total of 900 to 1100 nanoparticle diameters were calculated on TEM images using the line trace tool in ImageJ for each group. Error bars show standard deviation. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/61572/61572fig04large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/61572/61572fig05.jpg" /> 
Figure 5: XRD spectra of MnO nanoparticles synthesized with decreasing ratios of OA:DE. 
The following ratios were used: (A) 60:0, (B) 50:10, (C) 40:20, (D) 30:30, (E) 20:40, (F) 10:50. (G) The standard diffraction peaks for MnO are shown from the XRD analysis program database. All nanoparticles produced exhibit the 5 highest intensity XRD peaks for MnO, indicating successful synthesis of MnO nanoparticles. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/61572/61572fig05large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 6" class="xfigimg" src="/files/ftp_upload/61572/61572fig06.jpg" /> 
Figure 6: XRD spectra and TEM images of undesired nanoparticles. 
XRD spectra are shown for MnO nanoparticle synthesis using (A) low nitrogen flow and (B) a 0:60 ratio of OA:DE (no stabilizer is present). The standard diffraction peaks for (C) Mn3O4 and (D) MnO are displayed from the XRD analysis program database. Through comparison with standard spectra, inadequate nitrogen flow (A) created nanoparticles with a mixture of Mn3O4 (51%) and MnO (49%). In the absence of oleylamine (B), a broader XRD spectrum is obtained, which matches the 3 highest peaks of Mn3O4. Based on the analysis performed by the XRD program database, these synthesized nanoparticles are 67% Mn3O4 and 33% MnO. TEM images of (E) nanoparticles synthesized with low nitrogen flow show large nanoparticles surrounded by smaller ones. TEM images of (F) nanoparticles synthesized with a 0:60 ratio of OA:DE display very small aggregated nanoparticles with irregular shape. Scale bars are 50 nm. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/61572/61572fig06large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 7" class="xfigimg" src="/files/ftp_upload/61572/61572fig07.jpg" /> 
Figure 7: FTIR spectra of MnO nanoparticles synthesized with decreasing ratios of OA:DE. 
The following ratios were used: (A) 60:0, (B) 50:10, (C) 40:20, (D) 30:30, (E) 20:40, (F) 10:50. Asterisks and squares correspond to oleyl groups and amine groups, respectively, while triangles indicate the vibration of Mn-O and Mn-O-Mn bonds. The boxed insets highlight the two distinct peaks of oleyl groups. FTIR spectra indicate that MnO nanoparticles are coated with oleylamine, as confirmed through comparison with the oleylamine only FTIR spectrum in Figure S3. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/61572/61572fig07large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
Figure S1: Major glassware and equipment of the MnO nanoparticle synthesis setup. The manifold is secured to the metal lattice by metal claw clamps and disperses nitrogen into the reaction. Mn(II) ACAC, dibenzyl ether, oleylamine and a stir bar are added to the round bottom flask with four necks. The right neck of the flask is attached to the rotovap trap and an elbow adapter, while the left neck is attached to a condenser and an elbow adapter. The middle neck of the round bottom flask is covered with a rubber stopper. The temperature probe is inserted into the smallest opening of the round bottom flask, and is surrounded by an o-ring and paraffin plastic film to form an air-tight seal. The round bottom flask sits on top of a heating mantle and a stir plate to vigorously stir the reaction while heating. The temperature probe and heating mantle are connected to the temperature controller to provide real-time automated regulation of the temperature profile. The round bottom flask and condenser are secured to the metal lattice with metal claw clamps. There are three mineral oil bubblers, two on the left and one on the right, filled with increasing amounts of silicone oil from the left bubbler to right bubbler in the image. The bubblers are also attached to the metal lattice with claw clamps. Green plastic conical joint clips are attached to secure glassware connections before the reaction begins. The tubing connections are detailed in Figure 1. <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/61572/61572supfig01.jpg" target="_blank">Please click here to download this figure.</a>
Figure S2: Histograms showing distribution of MnO nanoparticle size for decreasing ratios of OA:DE. The following ratios were used: (A) 60:0, (B) 50:10, (C) 40:20, (D) 30:30, (E) 20:40, (F) 10:50. Overall as the ratio approaches 10:50, the nanoparticle size distribution shifts to the left (indicating smaller diameters) and becomes more compact (indicating more uniform nanoparticle size). The average diameter for each distribution is shown in Figure 4. <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/61572/61572supfig02.jpg" target="_blank">Please click here to download this figure.</a>
Figure S3: FTIR spectrum of oleylamine. Asterisks and squares represent the oleyl groups and amine groups of oleylamine, respectively. <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/61572/61572supfig03.jpg" target="_blank">Please click here to download this figure.</a>

Watch this Scientific Journal Video about Manganese Oxide Nanoparticle Synthesis by Thermal Decomposition of ManganeseII Acetylacetonate at JoVE.com

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.

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 ...

manganese-oxide-nanoparticle-synthesis-thermal-decomposition

Nanyang Technological University

Research

JoVE Journal

Bioengineering

12.9K Views.  West Virginia University. In vergelijking met andere synthesemethoden genereert thermische afbraak uniforme metaaloxidenanodeeltjes met een strakke controle over de deeltjesgrootte, vorm en chemische samenstelling. Deze techniek is een eenvoudige potsynthese die gebruik maakt van drie reagentia, een metalen precursor, een organisch oplosmiddel en een stabilisator. Het kan verschillende soorten nanodeeltjes produceren, waaronder mangaanoxide en ijzeroxide.Het aantonen van de procedure zal Celia Martinez De La To...

Video: Manganese Oxide Nanoparticle Synthesis by Thermal Decomposition of ManganeseII Acetylacetonate

Preparation of Silica Nanoparticles Through Microwave-assisted Acid-catalysis

Microwave-assisted synthetic techniques were used to quickly and reproducibly produce silica nanoparticle sols using an acid catalyst with nanoparticle diameters ranging from 30-250 nm by varying the reaction conditions. Through the selection of a microwave compatible solvent, silicic acid precursor, catalyst, and microwave irradiation time, these microwave-assisted methods were capable of overcoming the previously reported shortcomings associated with synthesis of silica nanoparticles using microwave reactors. The siloxane precursor was hydrolyzed using the acid catalyst, HCl. Acetone, a low-tan &#948; solvent, mediates the condensation reactions and has minimal interaction with the electromagnetic field. Condensation reactions begin when the silicic acid precursor couples with the microwave radiation, leading to silica nanoparticle sol formation. The silica nanoparticles were characterized by dynamic light scattering data and scanning electron microscopy, which show the materials&#39; morphology and size to be dependent on the reaction conditions. Microwave-assisted reactions produce silica nanoparticles with roughened textured surfaces that are atypical for silica sols produced by St&#246;ber&#39;s methods, which have smooth surfaces.

Silica nanoparticles were prepared using acid-catalysis of a siloxane precursor and microwave-assisted synthetic techniques resulting in the controlled growth of nanomaterials ranging from 30-250 nm in diameter. The growth dynamics can be controlled by varying the initial silicic acid concentration, time of the reaction, and temperature of reaction.

Microwave-assisted synthetic techniques were used to quickly and reproducibly produce silica nanoparticle sols using an acid catalyst with nanoparticle ...

Chemistry

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 ...

Nanothermite with Meringue-like Morphology: From Loose Powder to Ultra-porous Objects

The goal of the protocol described in this article is to prepare aluminothermic compositions (nanothermites) in the form of porous, monolithic objects. Nanothermites are combustible materials made up of inorganic fuel and an oxidizer. In nanothermite foams, aluminum is the fuel and aluminum phosphate and tungsten trioxide are the oxidizing moieties. The highest flame propagation velocities (FPVs) in nanothermites are observed in loose powders and FPVs are strongly decreased by pelletizing nanothermite powders. From a physical standpoint, nanothermite loose powders are metastable systems. Their properties can be altered by unintentional compaction induced by shocks or vibrations or by the segregation of particles over time by settling phenomena, which originates from the density differences of their components. Moving from a powder to an object is the challenge that must be overcome to integrate nanothermites in pyrotechnic systems. Nanothermite objects must have both a high open porosity and good mechanical strength. Nanothermite foams meet both of these criteria, and they are prepared by dispersing a nano-sized aluminothermic mixture (Al/WO3) in orthophosphoric acid. The reaction of aluminum with the acid solution gives the AlPO4 &#34;cement&#34; in which Al and WO3 nanoparticles are embedded. In nanothermite foams, aluminum phosphate plays the dual role of binder and oxidizer. This method can be used with tungsten trioxide, which is not altered by the preparation process. It could probably be extended to some oxides, which are commonly used for the preparation of high performance nanothermites. The WO3-based nanothermite foams described in this article are particularly insensitive to impact and friction, which makes them far safer to handle than loose Al/WO3 powder. The fast combustion of these materials has interesting applications in pyrotechnic igniters. Their use in detonators as primers would require the incorporation of a secondary explosive in their composition.

This manuscript describes the synthesis of combustible aluminophosphate matrices by the reaction of orthophosphoric acid (H3PO4) with aluminum nanopowder. When this reaction is carried out with excess aluminum in the presence of tungsten trioxide nanopowder, it leads to a solid, porous nanothermite foam.

The goal of the protocol described in this article is to prepare aluminothermic compositions (nanothermites) in the form of porous, monolithic objects. ...

Chemical Precipitation Method for the Synthesis of Nb2O5 Modified Bulk Nickel Catalysts with High Specific Surface Area

We demonstrate a method for the synthesis of NixNb1-xO catalysts with sponge-like and fold-like nanostructures. By varying the Nb:Ni ratio, a series of NixNb1-xO nanoparticles with different atomic compositions (x = 0.03, 0.08, 0.15, and 0.20) have been prepared by chemical precipitation. These NixNb1-xO catalysts are characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy. The study revealed the sponge-like and fold-like appearance of Ni0.97Nb0.03O and Ni0.92Nb0.08O on the NiO surface, and the larger surface area of these NixNb1-xO catalysts, compared with the bulk NiO. Maximum surface area of 173 m2/g can be obtained for Ni0.92Nb0.08O catalysts. In addition, the catalytic hydroconversion of lignin-derived compounds using the synthesized Ni0.92Nb0.08O catalysts have been investigated.

Chemical Precipitation Method for the Synthesis of Nb2O5 Modified Bulk Nickel Catalysts with High Specific Surface Area

A protocol for the synthesis of sponge-like and fold-like Ni1-xNbxO nanoparticles by chemical precipitation is presented.

We demonstrate a method for the synthesis of NixNb1-xO catalysts with sponge-like and fold-like nanostructures. By varying the Nb:Ni ratio, a series of ...

Preparation of Polyoxometalate-based Photo-responsive Membranes for the Photo-activation of Manganese Oxide Catalysts

This paper presents a method to prepare charge-transfer chromophores using polyoxotungstate (PW12O403-), transition metal ions (Ce3+ or Co2+), and organic polymers, with the aim of photo-activating oxygen-evolving manganese oxide catalysts, which are important components in artificial photosynthesis. The cross-linking technique was applied to obtain a self-standing membrane with a high PW12O403- content. Incorporation and structure retention of PW12O403- within the polymer matrix were confirmed by FT-IR and micro-Raman spectroscopy, and optical characteristics were investigated by UV-Vis spectroscopy, which revealed successful construction of the metal-to-metal charge transfer (MMCT) unit. After deposition of MnOx oxygen evolving catalysts, photocurrent measurements under visible light irradiation verified the sequential charge transfer, Mn &#8594; MMCT unit &#8594; electrode, and&#160;the photocurrent intensity was consistent with the redox potential of the donor metal (Ce or Co). This method provides a new strategy for preparing integrated systems involving catalysts and photon-absorption parts for use with photo-functional materials.

Here, we present a protocol to prepare charge transfer chromophores based on a polyoxometalate/polymer composite membrane.

This paper presents a method to prepare charge-transfer chromophores using polyoxotungstate (PW12O403-), transition metal ions (Ce3+ or Co2+), and organic ...

Microwave-driven Synthesis of Iron Oxide Nanoparticles for Fast Detection of Atherosclerosis

A fast and reproducible microwave-driven protocol has been developed for the synthesis of neridronate-functionalized nanoparticles. Starting from the synthesis of hydrophobic nanoparticles, our method is based on an adaptation from thermal decomposition method to microwave driven synthesis. The new methodology produces a decrease in the reaction times in comparison with traditional procedures. Moreover, the use of the microwave technology increases the reproducibility of the reactions, something important from the point of view of clinical applications. The novelty of this iron oxide nanoparticle is the attachment of Neridronate. The use of this molecule leads a bisphosphonate moiety towards the outside of the nanoparticle that provides Ca2+ binding properties in vitro and selective accumulation in vivo in the atheroma plaque. The protocol allows the synthesis and plaque detection in about 3 hr since the initial synthesis from organic precursors. Their accumulation in the atherosclerotic area in less than 1 hr provides a contrast agent particularly suitable for clinical applications.

Microwave technology enables extremely fast synthesis of iron oxide nanoparticles for atherosclerosis plaque characterization. The use of an aminobisphosphonate in the external side of the nanoparticle provides a fast accumulation in the atherosclerotic area.

A fast and reproducible microwave-driven protocol has been developed for the synthesis of neridronate-functionalized nanoparticles. Starting from the ...

Synthesis of Metal Nanoparticles Supported on Carbon Nanotube with Doped Co and N Atoms and its Catalytic Applications in Hydrogen Production

A method for facile synthesis of nanostructured catalysts supported on carbon nanotubes with atomically dispersed cobalt and nitrogen dopant is presented herein. The novel strategy is based on a facile one-pot pyrolysis treatment of cobalt (II) acetylacetonate and nitrogen-rich organic precursors under Ar atmosphere at 800 &#176;C, resulting in the formation of Co- and N- co-doped carbon nanotube with earthworm-like morphology. The obtained catalyst was found to have a high density of defect sites, as confirmed by Raman spectroscopy. Here, cobalt (II) nanoparticles were stabilized on the atomically dispersed cobalt- and nitrogen-doped carbon nanotubes. The catalyst was confirmed to be effective in the catalytic hydrolysis of ammonia borane, in which the turnover frequency was 5.87 mol H2&#183;molCo-1&#183;min-1, and the specific hydrogen generation rate was determined to be 2447 mL H2&#183;gCo-1&#183;min-1. A synergistic function between the Co nanoparticle and the doped carbon nanotubes was proposed for the first time in the catalytic hydrolysis of ammonia borane reaction under a mild condition. The resulting hydrogen production with its high energy density and minimal refueling time could be suitable for future development as energy sources for mobile and stationary applications such as road trucks and forklifts in transport and logistics.

Here, we present a protocol to synthesize Co nanoparticles supported on carbon nanotubes with Co- and N- dopants for hydrogen productions.

A method for facile synthesis of nanostructured catalysts supported on carbon nanotubes with atomically dispersed cobalt and nitrogen dopant is presented ...

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.

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 ...

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.

There is a significant global demand for improvements in synthesis techniques and their optimal characteristics, especially for industrial-scale ...

Microwave Synthesis and Characterization of Nickel Hydroxide Nanosheets

Effect of Microwave Synthesis Conditions on the Structure of Nickel Hydroxide Nanosheets

A protocol for rapid, microwave-assisted hydrothermal synthesis of nickel hydroxide nanosheets under mildly acidic conditions is presented, and the effect of reaction temperature and time on the material&#39;s structure is examined. All reaction conditions studied result in aggregates of layered &#945;-Ni(OH)2 nanosheets. The reaction temperature and time strongly influence the structure of the material and product yield. Synthesizing &#945;-Ni(OH)2 at higher temperatures increases the reaction yield, lowers the interlayer spacing, increases crystalline domain size, shifts the frequencies of interlayer anion vibrational modes, and lowers the pore diameter. Longer reaction times increase reaction yields and result in similar crystalline domain sizes. Monitoring the reaction pressure in situ shows that higher pressures are obtained at higher reaction temperatures. This microwave-assisted synthesis route provides a rapid, high-throughput, scalable process that can be applied to the synthesis and production of a variety of transition metal hydroxides used for numerous energy storage, catalysis, sensor, and other applications.

Author Spotlight: A Rapid, Microwave-Assisted Hydrothermal Synthesis Of Nickel Hydroxide Nanosheets 

Nickel hydroxide nanosheets are synthesized by a microwave-assisted hydrothermal reaction. This protocol demonstrates that the reaction temperature and time used for microwave synthesis affects the reaction yield, crystal structure, and local coordination environment.

A protocol for rapid, microwave-assisted hydrothermal synthesis of nickel hydroxide nanosheets under mildly acidic conditions is presented, and the effect ...

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

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