Name: effect of microwave synthesis conditions on the structure of nickel hydroxide nanosheets
Uploaded: 2023-08-18T14:20:00.000+00:00
Duration: 7 min 57 s
Description: Watch this Scientific Journal Video about A Rapid, Microwave-Assisted Hydrothermal Synthesis Of Nickel Hydroxide Nanosheets at JoVE.com

S.W.K. and C.P.R. gratefully acknowledge support from the Office of Naval Research Navy Undersea Research Program (Grant No. N00014-21-1-2072). S.W.K. acknowledges support from the Naval Research Enterprise Internship Program. C.P.R and C.M. acknowledge support from the National Science Foundation Partnerships for Research and Education in Materials (PREM) Center for Intelligent Materials Assembly, Award No. 2122041, for analysis of the reaction conditions.

NOTE: The schematic overview of the microwave synthesis process is presented in Figure 1.
1. Microwave synthesis of &#945;-Ni(OH)2 nanosheets
<ol>
	<li>Preparation of precursor solution
	<ol>
		<li>Prepare the precursor solution by mixing 15 mL of ultrapure water (&#8805;18 M&#937;-cm) and 105 mL of ethylene glycol. Add 5.0 g of Ni(NO3)2&#160;&#183; 6&#160;H2O and 4.1 g of urea to the solution and cover.</li>
		<li>Place the precursor solution in an ice and water-filled bath sonicator (40 kHz frequency) and sonicate at full power (no pulse) for 30 min.</li>
	</ol>
	</li>
	<li>Microwave reaction of the precursor solution
	<ol>
		<li>Transfer 20 mL of the precursor solution into a microwave-reaction vial with a polytetrafluoroethylene (PTFE) stir bar and seal the reaction vessel with a locking lid with a PTFE liner.</li>
		<li>Program the microwave reactor to heat to the reaction temperature using the setting as fast as possible (to 120 or 180 &#176;C) and hold at that temperature for 13-30 min. 
		NOTE: Heating as fast as possible is a microwave setting that applies maximum microwave power until the desired temperature is achieved; apply variable power thereafter to maintain the reaction temperature.</li>
		<li>After the reaction is complete, vent the reaction chamber with compressed air until the solution temperature reaches 55 &#176;C. Each stage of the reaction (heating, holding, and cooling) is performed under magnetic stirring at 600 rpm.</li>
	</ol>
	</li>
	<li>Centrifugation and washing the microwave-reaction precipitate.
	<ol>
		<li>Transfer the post-reaction solution to 50 mL centrifuge tubes. Centrifuge the post-reaction solution at 6,000 rpm/6,198 rcf for 4 min at room temperature&#160;and then decant the supernatant.</li>
		<li>Add 25 mL of ultrapure water to resuspend the nanosheets. Centrifuge using the same conditions and then decant the supernatant.</li>
		<li>Repeat the washing, centrifuging, and decanting steps a total of five times using water, and then three times using ethanol. 
		&#8203;NOTE: Isopropyl alcohol can also be used in place of ethanol.</li>
	</ol>
	</li>
	<li>Measuring the pH before and after the microwave reaction
	<ol>
		<li>Measure the pH of the precursor solution before starting the microwave reaction and measure the pH of the supernatant immediately after the first centrifugation.</li>
	</ol>
	</li>
	<li>Drying the sample
	<ol>
		<li>Cover the centrifuge tubes with a tissue or paper towel to act as a porous cover to reduce potential contamination and dry them in a sample oven at 70 &#176;C for 21 h under ambient atmosphere. 
		&#8203;NOTE: The drying time and conditions can influence the relative intensities and 2&#952;&#176; values of (XRD) peaks, as described in the Representative Results.</li>
	</ol>
	</li>
</ol>
2. Material characterization and analysis
<ol>
	<li>Characterizing the morphology and composition using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS)
	<ol>
		<li>Prepare the samples for SEM and EDS analysis by suspending a small amount of Ni(OH)2 powder in 1 mL of ethanol using a water bath sonicator.</li>
		<li>Drop cast the Ni(OH)2/ethanol mixture on an SEM stub and evaporate the ethanol by placing the SEM stub in a sample oven at 70 &#176;C.</li>
		<li>Collect SEM micrographs and EDS spectra. Collect SEM images using an accelerating voltage of 10 kV and a current of 0.34 nA at magnifications of 6.5 kX, 25 kX, and 100 kX. Collect EDS spectra on selected regions using an accelerating voltage of 10 kV, a current of 1.4 nA, and a magnification of 25 kX.</li>
	</ol>
	</li>
	<li>Analyzing the surface area and porosity using nitrogen physisorption porosimetry
	<ol>
		<li>Prepare the samples for analysis by adding 25 mg of Ni(OH)2 into the sample tube. Perform a pre-analysis degassing and drying procedure under vacuum at 120 &#176;C for 16 h before analysis.</li>
		<li>Transfer the sample tube from the degassing port to the analysis port to collect nitrogen (N2) isotherms.</li>
		<li>Analyze the N2&#160;isotherm data using Brunauer-Emmett-Teller (BET) analysis to determine the specific surface area. Perform the BET analysis according to International Union of Pure and Applied Chemistry (IUPAC) methodologies33. The specific analysis software package used to perform the BET analysis is included in the Table of Materials.</li>
		<li>Analyze the desorption branch of the isotherm using the Barrett-Joyner-Halenda (BJH) method to obtain pore volume, pore diameter, and pore size distribution. Perform the BJH analysis according to IUPAC&#160;methodologies.33 The specific analysis software package used to perform BJH analysis is included in the Table of Materials.</li>
	</ol>
	</li>
	<li>Structural analysis using powder X-ray diffraction (XRD)
	<ol>
		<li>Fill the sample well of a zero-background powder XRD holder with Ni(OH)2, ensuring the powder surface is flat.</li>
		<li>Collect powder X-ray diffractograms using a CuK&#945;&#160;radiation source between 5&#176;-80&#176; 2&#952; using a 0.01-step increment.</li>
		<li>Analyze the d-spacing using Bragg&#39;s law, 
		n&#955; = 2d sin&#952;, 
		where n is an integer,&#160;&#955; is the wavelength of the X-rays, d is the d-spacing, and &#952;&#160;is the angle between the incident rays and the sample.</li>
		<li>Analyze the crystallite domain size, D,&#160;using the Scherrer equation, 
		<img alt="Equation 1" src="/files/ftp_upload/65412/65412eq01.jpg" style="margin: auto;" /> 
		where Ks is the Scherrer constant (a Scherrer constant of 0.92 was used for the analysis), &#955; is the wavelength of the X-rays,&#160;&#946;2&#952; is the integral breadth of the diffraction peak, and&#160;&#952; is the Bragg angle (in radians). For analysis,&#160;&#946;2&#952; was taken as the full width at half maximum (fwhm) and multiplied by a constant of 0.939434.</li>
	</ol>
	</li>
	<li>Characterizing the material using attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR)
	<ol>
		<li>Equip the attenuated total reflectance (ATR) attachment to the Fourier transform infrared (FTIR) spectrometer.</li>
		<li>Press a small amount of Ni(OH)2 powder between two glass slides to create a small pellet.</li>
		<li>Place the Ni(OH)2 pellet on the silicon ATR crystal and obtain an FTIR spectrum between 400 and 4,000 cm-1. Infrared spectra represent the average of 16 individual scans with 4 cm-1 resolution.</li>
	</ol>
	</li>
</ol>

Microwave Synthesis and Characterization of Nickel Hydroxide Nanosheets

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E., Juergens, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Color,+solubility,+and+complex+ion+equilibria+of+nickel+(II)+species+in+aqueous+solution.">Color, solubility, and complex ion equilibria of nickel (II) species in aqueous solution.</a> Journal of Chemical Education. 57 (12), 900-901 (1980).</li></ol>

The authors have no conflicts of interest.

Microwave synthesis provides a route to generate Ni(OH)2 that is significantly faster (13-30 min reaction time) relative to conventional hydrothermal methods (typical reaction times of 4.5 h)38. Using this mildly acidic microwave synthesis route to produce ultrathin &#945;-Ni(OH)2 nanosheets, it is observed that reaction time and temperature influence the reaction pH, yields, morphology, porosity, and structure of the resulting materials. Using an in situ reaction pr...

Nickel hydroxide, Ni(OH)2, is used for numerous applications including nickel-zinc and nickel-metal hydride batteries1,2,3,4, fuel cells4, water electrolyzers4,5,6,7,8,9, supercapacitors4, photocatalysts4, anion exchangers10, and many other analytical, electrochemical, and sensor applications4,5. Ni(OH)2 has two predominant crystal structures: &#946;-Ni(OH)2 and &#945;-Ni(OH)211. &#946;-Ni(OH)2 adopts a brucite-type Mg(OH)2 crystal structure, while &#945;-Ni(OH)2 is a turbostratically layered form of &#946;-Ni(OH)2 intercalated with residual anions and water molecules from the chemical synthesis4. Within &#945;-Ni(OH)2, the intercalated molecules are not within fixed crystallographic positions but have a degree of orientational freedom, and also function as an interlayer glue stabilizing the Ni(OH)2 layers4,12. The interlayer anions of &#945;-Ni(OH)2 affect the average Ni oxidation state13 and influence the electrochemical performance of &#945;-Ni(OH)2 (relative to &#946;-Ni(OH)2) toward battery2,13,14,15, capacitor16, and water-electrolysis applications17,18.
Ni(OH)2 can be synthesized by chemical precipitation, electrochemical precipitation, sol-gel synthesis, or hydrothermal/solvothermal synthesis4. Chemical precipitation and hydrothermal synthesis routes are widely utilized in the production of Ni(OH)2, and different synthetic conditions alter the morphology, crystal structure, and electrochemical performance. The chemical precipitation of Ni(OH)2 involves adding a highly basic solution to an aqueous nickel (II) salt solution. The phase and crystallinity of the precipitate are determined by the temperature and&#160;identities&#160;and concentrations of the nickel (II) salt and&#160;basic solution used4.
Hydrothermal synthesis of Ni(OH)2 involves heating an aqueous solution of precursor nickel (II) salt in a pressurized reaction vial, allowing the reaction to proceed at higher temperatures than ordinarily allowed under ambient pressure4. Hydrothermal reaction conditions typically favor &#946;-Ni(OH)2, but &#945;-Ni(OH)2 can be synthesized by (i) using an intercalation agent, (ii) using a non-aqueous solution (solvothermal synthesis), (iii) lowering the reaction temperature, or (iv) including urea in the reaction, resulting in ammonia-intercalated &#945;-Ni(OH)24. The hydrothermal synthesis of Ni(OH)2 from nickel salts occurs via a two-step process that involves a hydrolysis reaction (equation 1) followed by an olation condensation reaction (equation 2).19
[Ni(H2O)N]2+ + hH2O &#8596; [Ni(OH)h(H2O) N-h](2-h)++ hH3O+ (1)
Ni-OH + Ni-OH2 Ni-OH-Ni + H2O (2)
Microwave chemistry has been used for the one-pot synthesis of a wide variety of nanostructured materials and is based on the ability of a specific molecule or material to convert microwave energy into heat20. In conventional hydrothermal reactions, the reaction is initiated by the direct absorption of heat through the reactor. In contrast, within microwave-assisted hydrothermal reactions, the heating mechanisms are dipolar polarization of the solvent oscillating in a microwave field and ionic conduction generating localized molecular friction20. Microwave chemistry can increase the reaction kinetics, selectivity, and yield of chemical reactions20, making it of significant interest for a scalable, industrially viable method to synthesize Ni(OH)2.
For alkaline battery cathodes, the &#945;-Ni(OH)2 phase provides improved electrochemical capacity compared with the &#946;-Ni(OH)2 phase13, and synthetic methods to synthesize &#945;-Ni(OH)2 are of particular interest. &#945;-Ni(OH)2 has been synthesized by a variety of microwave-assisted methods, which include microwave-assisted reflux21,22, microwave-assisted hydrothermal techniques23,24, and microwave-assisted base-catalyzed precipitation25. The inclusion of urea within the reaction solution significantly influences the reaction yield26, mechanism26,27, morphology, and crystal structure27. The microwave-assisted decomposition of urea was determined to be a critical component for obtaining &#945;-Ni(OH)227. Water content in an ethylene glycol-water solution has been shown to impact the morphology of microwave-assisted synthesis of &#945;-Ni(OH)2 nanosheets24. The reaction yield of &#945;-Ni(OH)2, when synthesized by a microwave-assisted hydrothermal route using an aqueous nickel nitrate and urea solution, was found to depend on the solution pH26. A prior study of microwave synthesized &#945;-Ni(OH)2 nanoflowers using a precursor solution of EtOH/H2O, nickel nitrate, and urea found that temperature (in the range of 80-120 &#176;C) was not a critical factor, provided the reaction is conducted above the urea hydrolysis temperature (60 &#176;C)27. A recent paper that studied the microwave synthesis of Ni(OH)2 using a precursor solution of nickel acetate tetrahydrate, urea, and water found that at a temperature of 150 &#176;C, the material contained both &#945;-Ni(OH)2 and &#946;-Ni(OH)2 phases, which indicates that temperature can be a critical parameter in the synthesis of Ni(OH)228.
Microwave-assisted hydrothermal synthesis can be used to produce high-surface area &#945;-Ni(OH)2 and &#945;-Co(OH)2 by using a precursor solution composed of metal nitrates and urea dissolved in an ethylene glycol/H2O solution12,29,30,31. Metal-substituted &#945;-Ni(OH)2 cathode materials for alkaline Ni-Zn batteries were synthesized using a scaled-up synthesis designed for a large-format microwave reactor12. Microwave-synthesized &#945;-Ni(OH)2 was also used as a precursor for obtaining &#946;-Ni(OH)2 nanosheets12, nickel-iridium nanoframes for oxygen evolution reaction (OER) electrocatalysts29, and bifunctional oxygen electrocatalysts for fuel cells and water electrolyzers30. This microwave reaction route has also been modified to synthesize Co(OH)2 as a precursor for cobalt-iridium nanoframes for acidic OER electrocatalysts31 and bifunctional electrocatalysts30. Microwave-assisted synthesis was also used to produce Fe-substituted &#945;-Ni(OH)2 nanosheets, and the Fe substitution ratio alters the structure and magnetization32. However, a step-by-step procedure for microwave synthesis of &#945;-Ni(OH)2 and the evaluation of how varying reaction time and temperature within a water-ethylene glycol solution affects the crystalline structure, surface area, and porosity, and local environment of interlayer anions within the material&#160;has not been previously reported.
This protocol establishes procedures for high-throughput microwave synthesis of &#945;-Ni(OH)2 nanosheets using a rapid and scalable technique. The effect of reaction temperature and time were varied and evaluated using in situ reaction monitoring, scanning electron microscopy, energy dispersive X-ray spectroscopy, nitrogen porosimetry, powder X-ray diffraction (XRD), and Fourier transform infrared spectroscopy to understand the effects of synthetic variables on reaction yield, morphology, crystal structure, pore size, and local coordination environment of &#945;-Ni(OH)2 nanosheets.

<table><tbody><tr><td>ATR-FTIR</td><td>Bruker</td><td></td><td>Tensor II FT-IR spectrometer equipped with a Harrick Scientific SplitPea ATR micro-sampling accessory</td></tr><tr><td>Bath sonicator</td><td>Fisher Scientific</td><td>15-337-409</td><td>--</td></tr><tr><td>Ethanol&amp;nbsp;</td><td>VWR analytical</td><td>AC61509-0040</td><td>200 proof</td></tr><tr><td>Ethylene Glycol</td><td>VWR analytical</td><td>BDH1125-4LP</td><td>99% purity</td></tr><tr><td>Falcon Centrifuge tubes</td><td>VWR analytical</td><td>21008-940</td><td>50 mL</td></tr><tr><td>KimWipes</td><td>VWR analytical</td><td>21905-026</td><td>--</td></tr><tr><td>Lab Quest 2</td><td>Vernier&amp;nbsp;</td><td>LABQ2</td><td>--</td></tr><tr><td>Microwave Reactor</td><td>Anton Parr</td><td>165741</td><td>Monowave 450</td></tr><tr><td>Ni(NO&lt;sub&gt;3&lt;/sub&gt;)&lt;sub&gt;2&lt;/sub&gt; &amp;middot; 6 H&lt;sub&gt;2&lt;/sub&gt;O</td><td>Ward&#039;s Science</td><td>470301-856</td><td>Research lab grade</td></tr><tr><td>pH Probe</td><td>Vernier&amp;nbsp;</td><td>PH-BTA</td><td>Calibrated vs standard pH solutions (pH= 4, 7, 11)</td></tr><tr><td>Porosemeter</td><td>Micromeritics&amp;nbsp;</td><td>--</td><td>ASAP 2020. Analysis software: Micromeritics, version 4.03</td></tr><tr><td>Powder x-ray diffactometer</td><td>Bruker</td><td></td><td>AXS Advanced Poweder x-ray diffractometer; d-spacing, and crystallite size analyses were performed using Highscore XRD software, and crystal structures were created using VESTA 3 software.</td></tr><tr><td>Reaction vial</td><td>Anton Parr</td><td>82723</td><td>30 mL G30 wideneck, 20 mL max fill capacity</td></tr><tr><td>Reaction vial locking lid</td><td>Anton Parr</td><td>161724</td><td>G30 Snap Cap</td></tr><tr><td>Reaction vial PTFE septum</td><td>Anton Parr</td><td>161728</td><td>Wideneck</td></tr><tr><td>Scanning electron microscope</td><td>FEI</td><td>--</td><td>Helios Nanolab 400</td></tr><tr><td>Urea</td><td>VWR analytical</td><td>BDH4602-500G</td><td>ACS grade</td></tr></tbody></table>

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.

Influence of reaction temperature and time on the synthesis of &#945;-Ni(OH)2 
Before the reaction, the precursor solution [Ni(NO3)2 &#183; 6 H2O, urea, ethylene glycol, and water] is a transparent green color with a pH of 4.41 &#177; 0.10 (Figure 2A and Table 1). The temperature of the microwave reaction (either 120 &#176;C or 180 &#176;C) influences the in situ reaction pressure and color of the sol...

Watch this Scientific Journal Video about A Rapid, Microwave-Assisted Hydrothermal Synthesis Of Nickel Hydroxide Nanosheets at JoVE.com

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.

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 ...

effect-microwave-synthesis-conditions-on-structure-nickel-hydroxide

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1.7K Views.  Texas State University. We ontwikkelden een protocol voor snelle microgolf-geassisteerde hydrothermale synthese van nikkelhydroxide nanosheets. Ons werk onderzoekt hoe de temperatuur en tijd van de microgolfreactie de structuur en de productopbrengst beïnvloeden. Het structureren of uitdrukken van het materiaal op nanoschaal heeft een aanzienlijke invloed op de eigenschappen van het materiaal.Wat wij en anderen hebben aangetoond, is dat wanneer we op nanoscopisch niveau werken, de structuur van nikkelhydroxi...

Video: Auteur in de schijnwerpers: een snelle, microgolfondersteunde hydrothermale synthese van nikkelhydroxide nanosheets 

Microwave-assisted Intramolecular Dehydrogenative Diels-Alder Reactions for the Synthesis of Functionalized Naphthalenes/Solvatochromic Dyes

Functionalized naphthalenes have applications in a variety of research fields ranging from the synthesis of natural or biologically active molecules to the preparation of new organic dyes. Although numerous strategies have been reported to access naphthalene scaffolds, many procedures still present limitations in terms of incorporating functionality, which in turn narrows the range of available substrates. The development of versatile methods for direct access to substituted naphthalenes is therefore highly desirable.
The Diels-Alder (DA) cycloaddition reaction is a powerful and attractive method for the formation of saturated and unsaturated ring systems from readily available starting materials. A new microwave-assisted intramolecular dehydrogenative DA reaction of styrenyl derivatives described herein generates a variety of functionalized cyclopenta[b]naphthalenes that could not be prepared using existing synthetic methods. When compared to conventional heating, microwave irradiation accelerates reaction rates, enhances yields, and limits the formation of undesired byproducts.
The utility of this protocol is further demonstrated by the conversion of a DA cycloadduct into a novel solvatochromic fluorescent dye via a Buchwald-Hartwig palladium-catalyzed cross-coupling reaction. Fluorescence spectroscopy, as an informative and sensitive analytical technique, plays a key role in research fields including environmental science, medicine, pharmacology, and cellular biology. Access to a variety of new organic fluorophores provided by the microwave-assisted dehydrogenative DA reaction allows for further advancement in these fields.

Microwave-assisted intramolecular dehydrogenative Diels-Alder (DA) reactions provide concise access to functionalized cyclopenta[b]naphthalene building blocks. The utility of this methodology is demonstrated by one-step conversion of the dehydrogenative DA cycloadducts into novel solvatochromic fluorescent dyes via Buchwald-Hartwig palladium-catalyzed cross-coupling reactions.

Functionalized naphthalenes have applications in a variety of research fields ranging from the synthesis of natural or biologically active molecules to ...

Gyroid Nickel Nanostructures from Diblock Copolymer Supramolecules

Nanoporous metal foams possess a unique combination of properties - they are catalytically active, thermally and electrically conductive, and furthermore, have high porosity, high surface-to-volume and strength-to-weight ratio. Unfortunately, common approaches for preparation of metallic nanostructures render materials with highly disordered architecture, which might have an adverse effect on their mechanical properties. Block copolymers have the ability to self-assemble into ordered nanostructures and can be applied as templates for the preparation of well-ordered metal nanofoams. Here we describe the application of a block copolymer-based supramolecular complex - polystyrene-block-poly(4-vinylpyridine)(pentadecylphenol) PS-b-P4VP(PDP) - as a precursor for well-ordered nickel nanofoam. The supramolecular complexes exhibit a phase behavior similar to conventional block copolymers and can self-assemble into the bicontinuous gyroid morphology with two PS networks placed in a P4VP(PDP) matrix. PDP can be dissolved in ethanol leading to the formation of a porous structure that can be backfilled with metal. Using electroless plating technique, nickel can be inserted into the template&#39;s channels. Finally, the remaining polymer can be removed via pyrolysis from the polymer/inorganic nanohybrid resulting in nanoporous nickel foam with inverse gyroid morphology.

This article describes the preparation of well-ordered nickel nanofoams via electroless metal deposition onto nanoporous templates obtained from self-assembled diblock copolymer based supramolecules.

Nanoporous metal foams possess a unique combination of properties - they are catalytically active, thermally and electrically conductive, and furthermore, ...

Particles without a Box: Brush-first Synthesis of Photodegradable PEG Star Polymers under Ambient Conditions

Convenient methods for the rapid, parallel synthesis of diversely functionalized nanoparticles will enable discovery of novel formulations for drug delivery, biological imaging, and supported catalysis. In this report, we demonstrate parallel synthesis of brush-arm star polymer (BASP) nanoparticles by the &#34;brush-first&#34; method. In this method, a norbornene-terminated poly(ethylene glycol) (PEG) macromonomer (PEG-MM) is first polymerized via ring-opening metathesis polymerization (ROMP) to generate a living brush macroinitiator. Aliquots of this initiator stock solution are added to vials that contain varied amounts of a photodegradable bis-norbornene crosslinker. Exposure to crosslinker initiates a series of kinetically-controlled brush+brush and star+star coupling reactions that ultimately yields BASPs with cores comprised of the crosslinker and coronas comprised of PEG. The final BASP size depends on the amount of crosslinker added. We carry out the synthesis of three BASPs on the benchtop with no special precautions to remove air and moisture. The samples are characterized by gel permeation chromatography (GPC); results agreed closely with our previous report that utilized inert (glovebox) conditions. Key practical features, advantages, and potential disadvantages of the brush-first method are discussed.

Poly(ethylene glycol) (PEG) brush-arm star polymers (BASPs) with narrow mass distributions and tunable nanoscopic sizes are synthesized in via ring opening metathesis polymerization (ROMP) of a PEG-norbornene macromonomer followed by transfer of portions of the resulting living brush initiator to vials containing varied amounts of a rigid, photo-cleavable bis-norbornene crosslinker.

Convenient methods for the rapid, parallel synthesis of diversely functionalized nanoparticles will enable discovery of novel formulations for drug ...

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 ...

A Simple Method for the Size Controlled Synthesis of Stable Oligomeric Clusters of Gold Nanoparticles under Ambient Conditions

Reducing dilute aqueous HAuCl4 with sodium thiocyanate (NaSCN) under alkaline conditions produces 2 to 3 nm diameter nanoparticles. Stable grape-like oligomeric clusters of these yellow nanoparticles of narrow size distribution are synthesized under ambient conditions via two methods. The delay-time method controls the number of subunits in the oligoclusters by varying the time between the addition of HAuCl4 to alkaline solution and the subsequent addition of reducing agent, NaSCN. The yellow oligoclusters produced range in size from ~3 to ~25 nm. This size range can be further extended by an add-on method utilizing hydroxylated gold chloride (Na+[Au(OH4-x)Clx]-) to auto-catalytically increase the number of subunits in the as-synthesized oligocluster nanoparticles, providing a total range of 3 nm to 70 nm. The crude oligocluster preparations display narrow size distributions and do not require further fractionation for most purposes. The oligoclusters formed can be concentrated &#62;300 fold without aggregation and the crude reaction mixtures remain stable for weeks without further processing. Because these oligomeric clusters can be concentrated before derivatization they allow expensive derivatizing agents to be used economically. In addition, we present two models by which predictions of particle size can be made with great accuracy.

We describe a simple method for producing highly stable oligomeric clusters of gold nanoparticles via the reduction of chloroauric acid (HAuCl4) with sodium thiocyanate (NaSCN). The oligoclusters have a narrow size distribution and can be produced with a wide range of sizes and surface coats.

Reducing dilute aqueous HAuCl4 with sodium thiocyanate (NaSCN) under alkaline conditions produces 2 to 3 nm diameter nanoparticles. Stable grape-like ...

Preparation of Carbon Nanosheets at Room Temperature

Amphiphilic molecules equipped with a reactive, carbon-rich "oligoyne" segment consisting of conjugated carbon-carbon triple bonds self-assemble into defined aggregates in aqueous media and at the air-water interface. In the aggregated state, the oligoynes can then be carbonized under mild conditions while preserving the morphology and the embedded chemical functionalization. This novel approach provides direct access to functionalized carbon nanomaterials. In this article, we present a synthetic approach that allows us to prepare hexayne carboxylate amphiphiles as carbon-rich siblings of typical fatty acid esters through a series of repeated bromination and Negishi-type cross-coupling reactions. The obtained compounds are designed to self-assemble into monolayers at the air-water interface, and we show how this can be achieved in a Langmuir trough. Thus, compression of the molecules at the air-water interface triggers the film formation and leads to a densely packed layer of the molecules. The complete carbonization of the films at the air-water interface is then accomplished by cross-linking of the hexayne layer at room temperature, using UV irradiation as a mild external stimulus. The changes in the layer during this process can be monitored with the help of infrared reflection-absorption spectroscopy and Brewster angle microscopy. Moreover, a transfer of the carbonized films onto solid substrates by the Langmuir-Blodgett technique has enabled us to prove that they were carbon nanosheets with lateral dimensions on the order of centimeters.

We present the synthesis of an amphiphilic hexayne and its use in the preparation of carbon nanosheets at the air-water interface from a self-assembled monolayer of these reactive, carbon-rich molecular precursors.

Amphiphilic molecules equipped with a reactive, carbon-rich "oligoyne" segment consisting of conjugated carbon-carbon triple bonds self-assemble into ...

Synthesis of Protein Bioconjugates via Cysteine-maleimide Chemistry

The chemical linking or bioconjugation of proteins to fluorescent dyes, drugs, polymers and other proteins has a broad range of applications, such as the development of antibody drug conjugates (ADCs) and nanomedicine, fluorescent microscopy and systems chemistry. For many of these applications, specificity of the bioconjugation method used is of prime concern. The Michael addition of maleimides with cysteine(s) on the target proteins is highly selective and proceeds rapidly under mild conditions, making it one of the most popular methods for protein bioconjugation.
We demonstrate here the modification of the only surface-accessible cysteine residue on yeast cytochrome c with a ruthenium(II) bisterpyridine maleimide. The protein bioconjugation is verified by gel electrophoresis and purified by aqueous-based fast protein liquid chromatography in 27% yield of isolated protein material. Structural characterization with MALDI-TOF MS and UV-Vis is then used to verify that the bioconjugation is successful. The protocol shown here is easily applicable to other cysteine - maleimide coupling of proteins to other proteins, dyes, drugs or polymers.

Synthesis of Protein Bioconjugates via Cysteine-maleimide Chemistry

This protocol details the important steps required for the bioconjugation of a cysteine containing protein to a maleimide, including reagent purification, reaction conditions, bioconjugate purification and bioconjugate characterization.

The chemical linking or bioconjugation of proteins to fluorescent dyes, drugs, polymers and other proteins has a broad range of applications, such as the ...

Synthesis of Platinum-nickel Nanowires and Optimization for Oxygen Reduction Performance

Platinum-nickel (Pt-Ni) nanowires were developed as fuel cell electrocatalysts, and were optimized for the performance and durability in the oxygen reduction reaction. Spontaneous galvanic displacement was used to deposit Pt layers onto Ni nanowire substrates. The synthesis approach produced catalysts with high specific activities and high Pt surface areas. Hydrogen annealing improved Pt and Ni mixing and specific activity. Acid leaching was used to preferentially remove Ni near the nanowire surface, and oxygen annealing was used to stabilize near-surface Ni, improving durability and minimizing Ni dissolution. These protocols detail the optimization of each post-synthesis processing step, including hydrogen annealing to 250 &#176;C, exposure to 0.1 M nitric acid, and oxygen annealing to 175 &#176;C. Through these steps, Pt-Ni nanowires produced increased activities more than an order of magnitude than Pt nanoparticles, while offering significant durability improvements. The presented protocols are based on Pt-Ni systems in the development of fuel cell catalysts. These techniques have also been used for a variety of metal combinations, and can be applied to develop catalysts for a number of electrochemical processes.

&#160; The protocol describes the synthesis and electrochemical testing of platinum-nickel nanowires. Nanowires were synthesized by the galvanic displacement of a nickel nanowire template. Post-synthesis processing, including hydrogen annealing, acid leaching, and oxygen annealing were used to optimize nanowire performance and durability in the oxygen reduction reaction.

Platinum-nickel (Pt-Ni) nanowires were developed as fuel cell electrocatalysts, and were optimized for the performance and durability in the oxygen ...

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 ...

Tuning the Acidity of Pt/ CNTs Catalysts for Hydrodeoxygenation of Diphenyl Ether

We herein present a method for the synthesis of HNbWO6, HNbMoO6, HTaWO6 solid acid nanosheet modified Pt/CNTs. By varying the weight of various solid acid nanosheets, a series of Pt/xHMNO6/CNTs with different solid acid compositions (x = 5, 20 wt%; M = Nb, Ta; N = Mo, W) have been prepared by carbon nanotube pretreatment, protonic exchange, solid acid exfoliation, aggregation and finally Pt particles impregnation. The Pt/xHMNO6/CNTs are characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and NH3-temperature programmed desorption. The study revealed that HNbWO6 nanosheets were attached on CNTs, with some edges of the nanosheets being bent in shape. The acid strength of the supported Pt catalysts increases in the following order: Pt/CNTs &#60; Pt/5HNbWO6/CNTs &#60; Pt/20HNbMoO6/CNTs &#60; Pt/20HNbWO6/CNTs &#60; Pt/20HTaWO6/CNTs. In addition, the catalytic hydroconversion of lignin-derived model compound: diphenyl ether using the synthesized Pt/20HNbWO6 catalyst has been investigated.

A protocol for the synthesis of HNbWO6, HNbMoO6, HTaWO6 solid acid nanosheet modified Pt/CNTs is presented.

We herein present a method for the synthesis of HNbWO6, HNbMoO6, HTaWO6 solid acid nanosheet modified Pt/CNTs. By varying the weight of various solid acid ...

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

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