Name: synthesis and functionalization of 3d nano-graphene materials: graphene aerogels and graphene macro assemblies
Uploaded: 2015-11-05T14:00:00.000+00:00
Duration: 10 min 23 s
Description: Watch this Scientific Journal Video about Synthesis and Functionalization of 3D Nano-graphene Materials: Graphene Aerogels and Graphene Macro Assemblies at JoVE.com

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. IM release LLNL-JRNL-667016.

1. Resorcinol-formaldehyde (RF) Derived Graphene Aerogels
<ol>
	<li>Na2CO3 catalyzed carbon aerogel (11% solids, cRF)
	<ol>
		<li>In a 40 ml scintillation vial, add deionized water (7.1 ml) to resorcinol (0.625 g, 5.68 mmol) and mix on a vortex for 1 min. Crush large resorcinol pieces to powder using a mortar and pestle prior to water addition. Note that they may not completely dissolve until the next step.</li>
		<li>Add 37% formaldehyde solution (0.900 g, 11.4 mmol) to the resorcinol slurry and vortex for 1 min.</li>
		<li>Add sodium carbonate (0.003 g, 0.028 mmol) to the reaction mixture and vortex for 1 min.</li>
		<li>Transfer the reaction mixture to glass molds that can be sealed air tight (e.g., vial or glass slides that are separated by a silicone gasket) which define the shape of the resulting solid part.</li>
		<li>Place the sealed molds into an 80 &#176;C oven and cure for 72 hr.</li>
		<li>After curing, remove the solid monoliths from the glass mold and wash with water to remove residual unreacted starting materials and catalyst. Typically we perform 3 x 12 hr washes with fresh DI H2O. The material is now ready for drying.</li>
	</ol>
	</li>
	<li>Acetic acid catalyzed carbon aerogel (AARF)17
	<ol>
		<li>In a 40 ml scintillation vial, add deionized water (15 ml) to resorcinol (12.3 g, 0.112 mol) and mix on a vortex for 1 min. Crush large resorcinol pieces to powder using a mortar and pestle prior to water addition. Note that they may not completely dissolve until the next step.</li>
		<li>Add 37% formaldehyde solution (17.9 g, 0.224 mol) to the resorcinol slurry and vortex for 1 min.</li>
		<li>Add glacial acetic acid (0.44 g, 0.007 mol) to the reaction mixture and vortex for 1 min.</li>
		<li>Transfer the reaction mixture to glass molds that can be sealed air tight (e.g., vial or glass slides that are separated by a silicone gasket), which define the shape of the resulting solid part.</li>
		<li>Place the sealed molds into an 80 &#176;C oven and cure for 72 hr.</li>
		<li>After curing, remove the solid monoliths from the glass mold and wash with water to remove residual unreacted starting materials and catalyst. Typically we perform 3 x 12 hr washes with fresh DI H2O. The material is now ready for drying.</li>
	</ol>
	</li>
	<li>Carbon Additives to the RF precursor solution (CNT, GO)
	<ol>
		<li>Carbon nanotube/RF composite11
		<ol>
			<li>Suspend 1 wt% single-walled carbon nano-tubes in deionized water and thoroughly disperse using an ultrasonic bath (sonic power 90 W, frequency 40 kHz).</li>
			<li>Add resorcinol (1.235 g, 11.2 mmol), formaldehyde (1.791 g, 22.1 mmol), and sodium carbonate catalyst (5.95 mg, 0.056 mmol) to 1.5 g of the CNT dispersion.</li>
			<li>Transfer the reaction mixture to glass molds that can be sealed air tight (e.g., vial or glass slides that are separated by a silicone gasket), which define the shape of the resulting solid part.</li>
			<li>Place the sealed molds into an 80 &#176;C oven and cure for 72 hr.</li>
			<li>After curing, remove the solid monoliths from the glass mold and wash with water to remove residual unreacted starting materials and catalyst. Typically perform 3 x 12 hr washes with fresh DI H2O. The material is now ready for drying.&#160;</li>
		</ol>
		</li>
		<li>Graphene oxide/RF composite12
		<ol>
			<li>Suspend 1 wt% graphene oxide (GO, 300-800 nm diameter) in deionized water and thoroughly disperse using an ultrasonic bath (sonic power 90 W, frequency 40 kHz).</li>
			<li>Add resorcinol (1.235 g, 11.2 mmol), formaldehyde (1.791 g, 22.1 mmol, 37% solution) and sodium carbonate catalyst (5.95 mg, 0.056 mmol) to 1.5 g of the GO dispersion.</li>
			<li>Transfer the reaction mixture to glass molds that can be sealed air tight (e.g., vial or glass slides that are separated by a silicone gasket) which define the shape of the resulting solid part.</li>
			<li>Place the sealed molds into an 80 &#176;C oven and cure for 72 hr.</li>
			<li>After curing, remove the solid monoliths from the glass mold and wash with water to remove residual unreacted starting materials and catalyst. Typically perform 3 x 12 hr washes with fresh DI H2O. The material is now ready for drying.&#160;</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>Drying
	<ol>
		<li>Supercritical CO2
		<ol>
			<li>Prepare washed samples for drying with supercritical CO2 by exchanging the H2O solvent with acetone. Remove sample from water bath and place into bath containing clean acetone. Replace with fresh acetone two more times at 12 hr intervals.</li>
			<li>Load acetone-exchanged samples into a supercritical drying apparatus, filled with acetone and with circulating coolant at 12-15 &#176;C.</li>
			<li>Seal supercritical dryer and exchange with liquid CO2 until no acetone remains (4-24 hr depending on sample size, density, pore morphology, etc.).</li>
			<li>Shut off CO2 supply and raise temperature of circulating coolant to 55 &#176;C, while maintaining pressure in the supercritical dryer between 1,200-1,600 psi (80-110 bar). Hold at 55 &#176;C for 1 hr.</li>
			<li>Slowly vent CO2 (2-12 hr) while maintaining temperature of circulating coolant at 55 &#176;C. Remove samples.&#160;</li>
		</ol>
		</li>
		<li>Ambient drying (Xerogel)
		<ol>
			<li>Prepare washed samples for drying under ambient conditions by exchanging the H2O solvent with acetone. Remove sample from water bath and place into bath containing clean acetone. Replace with fresh acetone two more times at 12 hr intervals.</li>
			<li>Place acetone-exchanged samples on a clean surface (e.g., Teflon block). To slow the rate of solvent evaporation to prevent cracking and uneven shrinking, cover the sample with an inverted beaker of sufficient volume to provide plenty of headspace.</li>
			<li>Allow solvent to evaporate for (24-72 hr).&#160;</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>Carbonization
	<ol>
		<li>Perform carbonization of the dried foams at 1,050 &#176;C under N2 atmosphere. Ramp from RT at a rate of 5 &#176;C/min, and hold at 1,050 &#176;C for 3 hr. Note that thin samples may need to be placed between two sheets of graphite paper (or other temperature stable, non-reactive material) with weight on top to prevent curling and &#8220;potato chipping.&#8221;</li>
	</ol>
	</li>
	<li>Activation
	<ol>
		<li>Activate an AARF carbon foam part (2 cm &#215; 3 cm &#215; 4 mm, 1.2 g) to generate 3D nanographene (3D-NG) under flowing CO2 (10 sccm) at 950 &#176;C for 5 hr.7</li>
	</ol>
	</li>
</ol>
2. Graphene Oxide Derived Graphene Macro Assemblies
<ol>
	<li>NH4OH catalyzed GO assembly
	<ol>
		<li>In a 40 ml scintillation vial, add deionized water (20 ml) to 400 mg single layer graphene oxide (GO, 300-800 nm diameter). Thoroughly disperse using an ultrasonic bath (sonic power 90 W, frequency 40 kHz) O/N.</li>
		<li>Add concentrated NH4OH solution (0.211 ml per g GO suspension).</li>
		<li>Transfer into glass molds that can be sealed airtight (e.g., vial or glass slides that are separated by a silicone gasket which defines the shape of the resulting solid part).</li>
		<li>Place the sealed molds into an 80 &#176;C oven and cure for 72 hr.</li>
		<li>After curing, remove the solid monoliths from the glass mold and wash with water to remove residual unreacted starting materials and catalyst. Typically perform 3 x 12 hr washes with fresh DI H2O. The material is now ready for drying.&#160;</li>
	</ol>
	</li>
	<li>Drying
	<ol>
		<li>Supercritical CO2
		<ol>
			<li>Prepare washed samples for drying with supercritical CO2 by exchanging the H2O solvent with acetone. Remove sample from water bath and place into bath containing clean acetone. Replace with fresh acetone two more times at 12 hr intervals.</li>
			<li>Load acetone-exchanged samples into a supercritical drying apparatus, filled with acetone and with circulating coolant at 12-15 &#176;C.</li>
			<li>Seal supercritical dryer and exchange with liquid CO2 until no acetone remains (4-24 hr depending on sample size, density, pore morphology, etc.). Complete exchange is indicated by cessation of acetone drips at the exhaust valve of the supercritical dryer.</li>
			<li>Shut off CO2 supply and raise temperature of circulating coolant to 55 &#176;C, while maintaining pressure in the supercritical dryer between 1,200-1,600 psi (80-110 bar). Hold at 55 &#176;C for 1 hr.</li>
			<li>Slowly vent CO2 (2-12 hr) while maintaining temperature of circulating coolant at 55 &#176;C. Remove samples.&#160;</li>
		</ol>
		</li>
		<li>Ambient drying (xerogel) 
		Note that thin samples may need to be placed between two sheets of Teflon (or other non-stick material) with weight on top to prevent curling and &#8220;potato chipping.&#8221;
		<ol>
			<li>Prepare washed samples for drying under ambient conditions by exchanging the H2O solvent with acetone. Remove sample from water bath and place into bath containing clean acetone. Replace with fresh acetone two more times at 12 hr intervals.</li>
			<li>Place acetone-exchanged samples on a clean surface (e.g., Teflon block). To slow the rate of solvent evaporation to prevent cracking and uneven shrinking, cover the sample with an inverted beaker of sufficient volume to provide plenty of headspace.</li>
			<li>Allow solvent to evaporate for (24-72 hr).&#160;</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>Carbonization
	<ol>
		<li>Perform carbonization of the dried foams at 1,050 &#176;C under N2 atmosphere. Ramp from RT at a rate of 5 &#176;C/min, and hold at 1,050 &#176;C for 3 hr. Note that thin samples may need to be placed between two sheets of graphite paper (or other temperature stable, non-reactive material) with weight on top to prevent curling and &#8220;potato chipping.&#8221;</li>
		<li>Thermal anneal for highly crystalline GMA. Perform additional thermal annealing of carbonized foams at temperatures up to 2,500 &#176;C under He atmosphere. Ramp from RT at a rate of 100 &#176;C/min, and hold at elevated temperature for 1 hr.&#160;</li>
	</ol>
	</li>
	<li>Post-carbonization functionalization
	<ol>
		<li>Non-covalent anthraquinone functionalization (AQ-GMA)
		<ol>
			<li>Prepare a 3 mM solution of anthraquinone (AQ) in dry EtOH. Heat in a sealed vial at 75 &#176;C to ensure complete dissolution.</li>
			<li>Add hot AQ solution to GMA sample (~2 ml/mg of sample). Soak in a sealed vial for 2 hr at 75 &#176;C.</li>
			<li>Remove excess AQ solution from vial and allow sample to dry at 75 &#176;C O/N&#160;(vial cap off).&#160;</li>
		</ol>
		</li>
	</ol>
	</li>
</ol>

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The authors have nothing to disclose.

It is important to note that the procedures outlined here are only representative. Many adjustments are possible to tune materials for a specific application. For example, varying the starting material concentrations, while keeping resorcinol/formaldehyde (RF) ratio constant, can have an impact on the final material density. Catalyst loading can alter pore morphology, as a higher loading in the RF procedure leads to smaller primary particles and vice-versa. Activation time can play a role as well; at shorter activation t...

Since the isolation of graphene in 2004,1 interest in harnessing its unique properties has led to intense effort directed toward assembling graphene into three-dimensional, monolithic structures that retain the properties of individual graphene sheets.2-5 These efforts have been hampered by the fact that graphene itself is expensive and time consuming to produce and tends to aggregate in solution, which limits the scalability of materials based on graphene building blocks. Additionally, graphene assemblies are typically comprised of physical cross-linking interactions (e.g., van der Walls forces) between the individual graphene sheets, which are much less conductive and mechanically robust than chemical bond cross-links. Lawrence Livermore National Laboratory has been involved in the development of novel porous, low-density carbon materials since the 1980s.6 Several strategies have been identified to fabricate mass-producible graphene-based monolithic bulk materials from both low-cost polymer-derived carbon foams, which are called graphene aerogels (GAs),7 as well as by direct cross-linking of graphene oxide (GO) sheets, which are called graphene macro-assemblies (GMAs).8,9 These ultrahigh surface area bulk materials have high electrical and thermal conductivities, exceptional mechanical strength and elasticity, and tunable pore morphologies. GAs and GMAs have found utility in numerous applications including electrode materials in supercapacitors and rechargeable batteries, advanced catalyst supports, adsorbents, thermal insulation, sensors, and desalinization.10
The synthesis of graphene aerogels begins with sol-gel polymerization of an aqueous solution of resorcinol and formaldehyde to generate highly cross-linked organic gels. These gels are washed with water and acetone, then dried using supercritical CO2 and pyrolyzed in an inert atmosphere to give carbon aerogels with relatively low surface area and pore volume. Carbon aerogels are activated by controlled removal of carbon atoms under mild oxidizing condition (e.g., CO2) to form a cross-linked material composed of both amorphous carbon and graphite nanoplatelets, with higher surface area and open pore morphology.7 A unique advantage of the sol-gel synthesis is that GAs can be fabricated in a variety of forms, including monoliths and thin films, depending on the needs of the application. Carbon nanotubes11 and/or graphene sheets12 can be integrated into GAs by including these additives in the sol-gel precursor solution. This generates composite structures in which the additive becomes a part of the primary carbon network structure. Additionally, the GA framework can be functionalized after carbonization/activation either through modification of the aerogel surface or through the deposition of materials, for example catalyst nanoparticles, onto the framework structure.13
Graphene macro-assemblies (GMAs) are prepared by directly cross-linking suspended graphene oxide (GO) sheets, taking advantage of their inherent chemical functionality.9 GO sheets contain a variety of functional groups, including epoxide and hydroxide moieties, that can serve as chemical cross-linking sites. As in the GA preparation, assembled GMAs are supercritically dried to preserve the porous network, then pyrolized to reduce the chemical cross-links into conductive carbon bridges that provide structural support for the assembly. Due to the covalent carbon bridges between graphene sheets, GMAs have electrical conductivities and mechanical stiffness that are orders of magnitude higher than graphene assemblies formed with physical cross-linking. Additionally, GMAs have surface areas approaching the theoretical value of a single graphene sheet. Post-synthetic thermal treatment at elevated temperatures (&#62;1,050 &#176;C) can significantly improve the crystallinity of GMAs, leading to even higher conductivities and Young&#8217;s moduli as well as better thermal oxidation resistance.14 Post-synthetic chemical treatment of GMAs with redox-active organic molecules such as anthraquinone can enhance charge storage capacity in supercapacitor applications.15
The tunable material properties of GAs and GMAs are, in part, a result of carefully varying synthetic conditions such as reagent and catalyst concentrations, cure time and temperature, drying conditions, and carbonization/activation processes.16 This detailed video protocol aims to resolve ambiguities in the published methods, and to guide researchers attempting to reproduce the materials and conditions.

<table><tbody><tr><td>Single Layer Graphene Oxide</td><td>Cheap Tubes</td><td>n/a</td><td>300-800&amp;#160;nm XY dimensions</td></tr><tr><td>single wall carbon nano tubes (SWCNTs)</td><td>Carbon Solutions</td><td>P2-SWNT</td><td></td></tr><tr><td>resorcinol</td><td>Aldrich</td><td>398047-500G</td><td></td></tr><tr><td>37% formaldehyde solution in water</td><td>Aldrich</td><td>252549</td><td></td></tr><tr><td>acetic acid</td><td>Aldrich</td><td>320099</td><td></td></tr><tr><td>ammonium hydroxide solution 28-30% NH&lt;sub&gt;3&lt;/sub&gt; basis</td><td>Aldrich</td><td>320145</td><td></td></tr><tr><td>sodium carbonate</td><td>Aldrich</td><td>791768</td><td></td></tr><tr><td>anthraquinone</td><td>Aldrich</td><td>a90004</td><td></td></tr><tr><td>Polaron supercritical dryer</td><td>Electron Microscopy Sciences</td><td>EMS 3100</td><td>this is a representative model, any critical point dryer compatible with acetone should work</td></tr></tbody></table>

synthesis and functionalization of 3d nano-graphene materials: graphene aerogels and graphene macro assemblies

Efforts to assemble graphene into three-dimensional monolithic structures have been hampered by the high cost and poor processability of graphene. Additionally, most reported graphene assemblies are held together through physical interactions (e.g., van der Waals forces) rather than chemical bonds, which limit their mechanical strength and conductivity. This video method details recently developed strategies to fabricate mass-producible, graphene-based bulk materials derived from either polymer foams or single layer graphene oxide. These materials consist primarily of individual graphene sheets connected through covalently bound carbon linkers. They maintain the favorable properties of graphene such as high surface area and high electrical and thermal conductivity, combined with tunable pore morphology and exceptional mechanical strength and elasticity. This flexible synthetic method can be extended to the fabrication of polymer/carbon nanotube (CNT) and polymer/graphene oxide (GO) composite materials. Furthermore, additional post-synthetic functionalization with anthraquinone is described, which enables a dramatic increase in charge storage performance in supercapacitor applications.

The evolution of material composition and morphology during fabrication can be tracked in various ways including X-ray diffraction, Raman and NMR spectroscopy, electron microscopy, and porosimetry. For example, in the synthesis, pyrolysis, and CO2 activation of GAs, the conversion was followed by X-ray diffraction (XRD) (Figure 1E). The absence of the stacking-related (002) diffraction peak in the XRD pattern after activation (blue trace) indicates the transition from a structure containing gr...

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Synthesis and Functionalization of 3D Nano-graphene Materials: Graphene Aerogels and Graphene Macro Assemblies

This video method describes the synthesis of high surface area, monolithic 3D graphene-based materials derived from polymer precursors as well as single layer graphene oxide.

Efforts to assemble graphene into three-dimensional monolithic structures have been hampered by the high cost and poor processability of graphene. ...

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Universidad San Sebastian

Research

JoVE Journal

Engineering

14.1K Views.  Lawrence Livermore National Laboratory. This video method describes the synthesis of high surface area, monolithic 3D graphene-based materials derived from polymer precursors as well as single layer graphene oxide.

Video: Synthesis and Functionalization of 3D Nano-graphene Materials: Graphene Aerogels and Graphene Macro Assemblies

Synthesis and Functionalization of Nitrogen-doped Carbon Nanotube Cups with Gold Nanoparticles as Cork Stoppers

Nitrogen-doped carbon nanotubes consist of many cup-shaped graphitic compartments termed as nitrogen-doped carbon nanotube cups (NCNCs). These as-synthesized graphitic nanocups from chemical vapor deposition (CVD) method were stacked in a head-to-tail fashion held only through noncovalent interactions. Individual NCNCs can be isolated out of their stacking structure through a series of chemical and physical separation processes. First, as-synthesized NCNCs were oxidized in a mixture of strong acids to introduce oxygen-containing defects on the graphitic walls. The oxidized NCNCs were then processed using high-intensity probe-tip sonication which effectively separated the stacked NCNCs into individual graphitic nanocups. Owing to their abundant oxygen and nitrogen surface functionalities, the resulted individual NCNCs are highly hydrophilic and can be effectively functionalized with gold nanoparticles (GNPs), which preferentially fit in the opening of the cups as cork stoppers. These graphitic nanocups corked with GNPs may find promising applications as nanoscale containers and drug carriers.

We discussed the synthesis of individual graphitic nanocups using a series of techniques including chemical vapor deposition, acid oxidation and probe-tip sonication. By citrate reduction of HAuCl4, the graphitic nanocups were effectively corked with gold nanoparticles due to the chemically reactive edges of the cups.

Nitrogen-doped carbon  nanotubes consist of many cup-shaped graphitic compartments termed as  nitrogen-doped carbon nanotube cups (NCNCs).  These ...

A Technique to Functionalize and Self-assemble Macroscopic Nanoparticle-ligand Monolayer Films onto Template-free Substrates

This protocol describes a self-assembly technique to create macroscopic monolayer films composed of ligand-coated nanoparticles1,2. The simple, robust and scalable technique efficiently functionalizes metallic nanoparticles with thiol-ligands in a miscible water/organic solvent mixture allowing for rapid grafting of thiol groups onto the gold nanoparticle surface. The hydrophobic ligands on the nanoparticles then quickly phase separate the nanoparticles from the aqueous based suspension and confine them to the air-fluid interface. This drives the ligand-capped nanoparticles to form monolayer domains at the air-fluid interface.&#160; The use of water-miscible organic solvents is important as it enables the transport of the nanoparticles from the interface onto template-free substrates.&#160; The flow is mediated by a surface tension gradient3,4 and creates macroscopic, high-density, monolayer nanoparticle-ligand films.&#160; This self-assembly technique may be generalized to include the use of particles of different compositions, size, and shape and may lead to an efficient assembly method to produce low-cost, macroscopic, high-density, monolayer nanoparticle films for wide-spread applications.

A simple, robust and scalable technique to functionalize and self-assemble macroscopic nanoparticle-ligand monolayer films onto template-free substrates is described in this protocol.

This protocol describes a self-assembly technique to create macroscopic monolayer films composed of ligand-coated nanoparticles1,2. The simple, robust and ...

Chemistry

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 ...

Visible-light Induced Reduction of Graphene Oxide Using Plasmonic Nanoparticle

Present work demonstrates the simple, chemical free, fast, and energy efficient method to produce reduced graphene oxide (r-GO) solution at RT using visible light irradiation with plasmonic nanoparticles. The plasmonic nanoparticle is used to improve the reduction efficiency of GO. It only takes 30 min&#160;at RT by illuminating the solutions with Xe-lamp, the r-GO solutions can be obtained by completely removing gold nanoparticles through simple centrifugation step. The spherical gold nanoparticles (AuNPs) as compared to the other nanostructures is the most suitable plasmonic nanostructure for r-GO preparation. The reduced graphene oxide prepared using visible light and AuNPs was equally qualitative as chemically reduced graphene oxide, which was supported by various analytical techniques such as UV-Vis spectroscopy, Raman spectroscopy, powder XRD and XPS. The reduced graphene oxide prepared with visible light shows excellent quenching properties over the fluorescent molecules modified on ssDNA and excellent fluorescence recovery for target DNA detection. The r-GO prepared by recycled AuNPs is found to be of same quality with that of chemically reduced r-GO. The use of visible light with plasmonic nanoparticle demonstrates the good alternative method for r-GO synthesis.

A simple protocol for the preparation of reduced graphene oxide using visible light and plasmonic nanoparticle is described.

Present work demonstrates the simple, chemical free, fast, and energy efficient method to produce reduced graphene oxide (r-GO) solution at RT using ...

Functionalization of Single-walled Carbon Nanotubes with Thermo-reversible Block Copolymers and Characterization by Small-angle Neutron Scattering

We demonstrate a protocol for single-walled carbon nanotube functionalization using thermo-sensitive PEO-PPO-PEO triblock copolymers in an aqueous solution. In a carbon nanotube/PEO105-PPO70-PEO105 (poloxamer 407) aqueous solution, the amphiphilic poloxamer 407 adsorbs onto the carbon nanotube surfaces and self-assembles into continuous layers, driven by intermolecular interactions between constituent molecules. The addition of 5-methylsalicylic acid changes the self-assembled structure from spherical-micellar to a cylindrical morphology. The fabricated poloxamer 407/carbon nanotube hybrid particles exhibit thermo-responsive structural features so that the density and thickness of poloxamer 407 layers are also reversibly controllable by varying temperature. The detailed structural properties of the poloxamer 407/carbon nanotube particles in suspension can be characterized by small-angle neutron scattering experiments and model fit analyses. The distinct curve shapes of the scattering intensities depending on temperature control or addition of aromatic additives are well described by a modified core-shell cylinder model consisting of a carbon nanotube core cylinder, a hydrophobic shell, and a hydrated polymer layer. This method can provide a simple but efficient way for the fabrication and in-situ characterization of carbon nanotube-based nano particles with a structure-tunable encapsulation.

A method for the functionalization of carbon nanotubes with structure-tunable polymeric encapsulation layers and structural characterization using small-angle neutron scattering is presented.

We demonstrate a protocol for single-walled carbon nanotube functionalization using thermo-sensitive PEO-PPO-PEO triblock copolymers in an aqueous ...

Preparation and Characterization of C60/Graphene Hybrid Nanostructures

Physical thermal deposition in a high vacuum environment is a clean and controllable method for fabricating novel molecular nanostructures on graphene. We present methods for depositing and passively manipulating C60 molecules on rippled graphene that advance the pursuit of realizing applications involving 1D C60/graphene hybrid structures. The techniques applied in this exposition are geared towards high vacuum systems with preparation areas capable of supporting molecular deposition as well as thermal annealing of the samples. We focus on C60 deposition at low pressure using a homemade Knudsen cell connected to a scanning tunneling microscopy (STM) system. The number of molecules deposited is regulated by controlling the temperature of the Knudsen cell and the deposition time. One-dimensional (1D) C60 chain structures with widths of two to three molecules can be prepared via tuning of the experimental conditions. The surface mobility of the C60 molecules increases with annealing temperature allowing them to move within the periodic potential of the rippled graphene. Using this mechanism, it is possible to control the transition of 1D C60 chain structures to a hexagonal close packed quasi-1D stripe structure.

Preparation and Characterization of C60/Graphene Hybrid Nanostructures

Here we present a protocol for the fabrication of C60/graphene hybrid nanostructures by physical thermal evaporation. Particularly, the proper manipulation of deposition and annealing conditions allow the control over the creation of 1D and quasi 1D C60 structures on rippled graphene.

Physical thermal deposition in a high vacuum environment is a clean and controllable method for fabricating novel molecular nanostructures on graphene. We ...

A Rapid Synthesis Method for Au, Pd, and Pt Aerogels Via Direct Solution-Based Reduction

Here, a method to synthesize gold, palladium, and platinum aerogels via a rapid, direct solution-based reduction is presented. The combination of various precursor noble metal ions with reducing agents in a 1:1 (v/v) ratio results in the formation of metal gels within seconds to minutes compared to much longer synthesis times for other techniques such as sol-gel. Conducting the reduction step in a microcentrifuge tube or small volume conical tube facilitates a proposed nucleation, growth, densification, fusion, equilibration model for gel formation, with final gel geometry smaller than the initial reaction volume. This method takes advantage of the vigorous hydrogen gas evolution as a by-product of the reduction step, and as a consequence of reagent concentrations. The solvent accessible specific surface area is determined with both electrochemical impedance spectroscopy and cyclic voltammetry. After rinsing and freeze drying, the resulting aerogel structure is examined with scanning electron microscopy, X-ray diffractometry, and nitrogen gas adsorption. The synthesis method and characterization techniques result in a close correspondence of aerogel ligament sizes. This synthesis method for noble metal aerogels demonstrates that high specific surface area monoliths may be achieved with a rapid and direct reduction approach.

A rapid, direct solution-based reduction synthesis method to obtain Au, Pd, and Pt aerogels is presented.

Here, a method to synthesize gold, palladium, and platinum aerogels via a rapid, direct solution-based reduction is presented. The combination of various ...

Fabrication of Three-Dimensional Graphene-Based Polyhedrons via Origami-Like Self-Folding

The assembly of two-dimensional (2D) graphene into three-dimensional (3D) polyhedral structures while preserving the graphene's excellent inherent properties has been of great interest for the development of novel device applications. Here, fabrication of 3D, microscale, hollow polyhedrons (cubes) consisting of a few layers of 2D graphene or graphene oxide sheets via an origami-like self-folding process is described. This method involves the use of polymer frames and hinges, and aluminum oxide/chromium protection layers that reduce tensile, spatial, and surface tension stresses on the graphene-based membranes when the 2D nets are transformed into 3D cubes. The process offers control of the size and shape of the structures as well as parallel production. In addition, this approach allows the creation of surface modifications by metal patterning on each face of the 3D cubes. Raman spectroscopy studies show the method allows the preservation of the intrinsic properties of the graphene-based membranes, demonstrating the robustness of our method.

Fabrication of Three-Dimensional Graphene-Based Polyhedrons via Origami-Like Self-Folding

Here, we present a protocol for fabrication of 3D graphene-based polyhedrons via origami-like self-folding.

The assembly of two-dimensional (2D) graphene into three-dimensional (3D) polyhedral structures while preserving the graphene's excellent inherent ...

Synthesis Method for Cellulose Nanofiber Biotemplated Palladium Composite Aerogels

Here, a method to synthesize cellulose nanofiber biotemplated palladium composite aerogels is presented. Noble metal aerogel synthesis methods often result in fragile aerogels with poor shape control. The use of carboxymethylated cellulose nanofibers (CNFs) to form a covalently bonded hydrogel allows for the reduction of metal ions such as palladium on the CNFs with control over both nanostructure and macroscopic aerogel monolith shape after supercritical drying. Crosslinking the carboxymethylated cellulose nanofibers is achieved using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) in the presence of ethylenediamine. The CNF hydrogels maintain their shape throughout synthesis steps including covalent crosslinking, equilibration with precursor ions, metal reduction with high concentration reducing agent, rinsing in water, ethanol solvent exchange, and CO2 supercritical drying. Varying the precursor palladium ion concentration allows for control over the metal content in the final aerogel composite through a direct ion chemical reduction rather than relying on the relatively slow coalescence of pre-formed nanoparticles used in other sol-gel techniques. With diffusion as the basis to introduce and remove chemical species into and out of the hydrogel, this method is suitable for smaller bulk geometries and thin films. Characterization of the cellulose nanofiber-palladium composite aerogels with scanning electron microscopy, X-ray diffractometry, thermal gravimetric analysis, nitrogen gas adsorption, electrochemical impedance spectroscopy, and cyclic voltammetry indicates a high surface area, metallized palladium porous structure.

A synthesis method for cellulose nanofiber biotemplated palladium composite aerogels is presented.The resulting composite aerogel materials offer potential for catalysis, sensing, and hydrogen gas storage applications.

Here, a method to synthesize cellulose nanofiber biotemplated palladium composite aerogels is presented. Noble metal aerogel synthesis methods often ...

Synthesis of Graphene Nanofluids with Controllable Flake Size Distributions

A method for synthesizing graphene nanofluids with controllable flake size distributions is presented. Graphene nanoflakes can be obtained by the exfoliation of graphite in the liquid phase, and the exfoliation time is used to control the lower limits of the graphene nanoflake size distributions. Centrifugation is successfully used to control the upper limits of the nanoparticle size distributions. The objective of this work is to combine exfoliation and centrifugation to control the graphene nanoflake size distributions in the resulting suspensions.

A method for synthesizing graphene nanofluids with controllable flake size distributions is presented.

Synthesis and Functionalization of 3D Nano-graphene Materials: Graphene Aerogels and Graphene Macro Assemblies

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Rozdziały w tym wideo

Synthesis and Functionalization of Nitrogen-doped Carbon Nanotube Cups with Gold Nanoparticles as Cork Stoppers

A Technique to Functionalize and Self-assemble Macroscopic Nanoparticle-ligand Monolayer Films onto Template-free Substrates

Preparation of Carbon Nanosheets at Room Temperature

Visible-light Induced Reduction of Graphene Oxide Using Plasmonic Nanoparticle

Functionalization of Single-walled Carbon Nanotubes with Thermo-reversible Block Copolymers and Characterization by Small-angle Neutron Scattering

Preparation and Characterization of C₆₀/Graphene Hybrid Nanostructures

A Rapid Synthesis Method for Au, Pd, and Pt Aerogels Via Direct Solution-Based Reduction

Fabrication of Three-Dimensional Graphene-Based Polyhedrons via Origami-Like Self-Folding

Synthesis Method for Cellulose Nanofiber Biotemplated Palladium Composite Aerogels

Synthesis of Graphene Nanofluids with Controllable Flake Size Distributions