Name: functionalization and dispersion of carbon nanomaterials using an environmentally friendly ultrasonicated ozonolysis process
Uploaded: 2017-05-30T12:30:00
Description: Watch this Scientific Journal Video about Functionalization and Dispersion of Carbon Nanomaterials Using an Environmentally Friendly Ultrasonicated Ozonolysis Process at JoVE.com

The non-salary component of the work was funded by the Commonwealth of Australia. The author from the University of Delaware gratefully acknowledges the support of the US National Science Foundation (Grant #1254540, Dr. Mary Toney, Program Director). The authors thank Mr. Mark Fitzgerald for his assistance with the electrophoretic deposition measurements.

1. Functionalization of CNTs and GNPs by Ultrasonic Ozonolysis
<ol>
	<li>Weigh the nanomaterials in a glove box inside a HEPA filter-equipped fume cupboard. Weigh the desired quantity of nanomaterials into a beaker. Transfer to a bottle and add ultrapure water to make a concentration of 1 g/L.</li>
	<li>Seal the bottle with a lid. Ultrasonicate in a standard ultrasonic bath (see Materials List; frequency: ~43 &#177;2 kHz; power: 60 W) to disperse the CNTs or GNPs. 
	NOTE: CAUTION. See the Work Health and Safety No...

<ol>
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When working with nanoparticles of high hardness, such as CNTs, the potential erosion effect on containers and tubing should not be overlooked. Step 1.14 in the protocol was inserted after the tubing became worn at a bend due to CNTs impinging on the tube side wall, causing a system leak.
Also, note that the CNTs are in suspension, not solution, and that they must be stirred before each use if a homogeneous suspension is desired. For example, this would be necessary to maintain the desired con...

The use of carbon nanomaterials to modify polymeric and composite systems has seen intensive research interest over the past 20 years. Recent reviews on both the use of carbon nanotubes1 (CNTs) and graphene nanoplatelets2 (GNPs) provide an indication of the breadth of research. The high specific stiffness and strength of CNTs and GNPs, as well as their high intrinsic electrical conductivity, make the materials ideally suited for incorporation into polymeric systems to enhance both the mechanical and electrical performance of the nanocomposite materials. CNTs and GNPs have also been used for the development of hierarchical composite structures by using the carbon nanomaterials to modify both fiber interfacial adhesion and matrix stiffness3,4.
The homogeneous dispersion of carbon nanomaterials into polymeric systems often requires processing steps, which chemically alter the nanomaterials to improve the chemical compatibility with the polymer matrix, remove impurities, and reduce or remove agglomerates from the as-received materials. A variety of methods to chemically modify carbon nanomaterials are available and may include wet chemical oxidation using strong acids5,6, modification with surfactants7, electrochemical intercalation and exfoliation8, or dry chemical processing using plasma-based processes9.
The use of strong acids in the oxidation step of CNTs introduces oxygen functional groups and removes impurities. However, it has the disadvantage of significantly reducing the CNT length, introducing damage to the CNT outer walls and using dangerous chemicals, which need to be isolated from the treated material for further processing10. The use of surfactants combined with ultrasonication offers a less aggressive method to prepare stable dispersions, but the surfactant is often difficult to remove from the treated material and may not be compatible with the polymer being used to prepare the nanocomposite materials1,11. The strength of the chemical interaction between the surfactant molecule and CNT or GNP may also be insufficient for mechanical applications. Dry plasma treatment processes conducted under atmospheric conditions may be suitable for functionalizing arrays of CNTs, present on fiber or planar surfaces, used to prepare hierarchical composites9. However, the atmospheric plasma is more difficult to apply to dry powders and does not address the problems with agglomerates present in as-manufactured raw carbon nanomaterials.
In the present work, we introduce a detailed description of the ultrasonicated-ozonolysis (USO) method that we have previously applied to carbon nanomaterials12,13,14. The USO process is used to prepare stable, aqueous dispersions that are suitable for electrophoretically depositing (EPD) both CNTs and GNPs onto carbon and glass fibers. Examples of EPD using USO-functionalized CNTs to deposit thin, uniform films onto stainless steel and carbon fabric substrates will be provided. Methods and typical results used to chemically characterize the functionalized CNTs and GNPs will also be provided, using both X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. A brief discussion of the characterization results in comparison with other functionalization techniques will be provided.
Work Health and Safety Notice
The effects of exposure to nanoparticles such as CNTs, on human health are not well understood. It is recommended that special measures be taken to minimize exposure to and avoid environmental contamination with CNT powders. Suggested hazard isolation measures include working within a HEPA filter-equipped fume cupboard and/or glove box. Occupational hygiene measures include wearing protective clothing and two layers of gloves and performing regular cleaning of surfaces using damp paper towels or a vacuum cleaner with a HEPA filter to remove stray CNT powders. Contaminated articles should be bagged for hazardous waste disposal.
Exposure to ozone can irritate the eyes, lungs, and respiratory system, and at higher concentrations may cause lung damage. It is recommended that measures be taken to minimize personal and environmental exposure to generated ozone gas. Isolation measures include working within a fume cupboard. As the return air stream will contain unused ozone, it should be passed through an ozone destruct unit before being releasing into the atmosphere. Dispersions that have had ozone bubbled through them will contain some dissolved ozone. After ozonolysis operations, allow the dispersions to sit for 1 h before undertaking further processing so that the ozone can undergo natural decomposition.

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	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Ultrasonic bath</td>
			<td style="width:87px;">Soniclean</td>
			<td style="width:119px;">80TD</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Ultrasonic horn</td>
			<td style="width:87px;">Misonix</td>
			<td style="width:119px;">S-4000-010 with CL5 converter</td>
			<td>Daintree Scientific</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Flocell stainless steel water jacketed</td>
			<td style="width:87px;">Misonix</td>
			<td style="width:119px;">800BWJ</td>
			<td>Daintree Scientific</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Peristaltic pump</td>
			<td style="width:87px;">Masterflex easy-load</td>
			<td style="width:119px;">7518-00</td>
			<td></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">Controller for peristaltic pump</td>
			<td style="width:87px;">Masterflex modular controller</td>
			<td style="width:119px;">7553-78</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Ozone generator</td>
			<td style="width:87px;">Ozone Solutions</td>
			<td style="width:119px;">TG-20</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Ozone destruct unit</td>
			<td style="width:87px;">Ozone Solutions</td>
			<td style="width:119px;">ODS-1</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Recirculating liquid cooler</td>
			<td style="width:87px;">Thermoline</td>
			<td style="width:119px;">TRC2-571-T</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Multi-mode power supply unit</td>
			<td style="width:87px;">TTi&#160;</td>
			<td style="width:119px;">EX752M</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">High resolution computing multimeter</td>
			<td style="width:87px;">TTi&#160;</td>
			<td style="width:119px;">1906</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">X-ray photoelectron spectroscopy</td>
			<td style="width:87px;">Kratos Analytical</td>
			<td style="width:119px;">Axis Nova</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">XPS analysis software</td>
			<td style="width:87px;">Casa Software</td>
			<td style="width:119px;">Casa XPS</td>
			<td>www.casaxps.com</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Kratos elemental library for use with Casa XPS</td>
			<td style="width:87px;">Casa Software</td>
			<td style="width:119px;">Download Kratos Related Files</td>
			<td>http://www.casaxps.com/kratos/</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Raman dispersive confocal microscope</td>
			<td style="width:87px;">Thermo</td>
			<td style="width:119px;">DXR</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Field emission scanning electron microscope</td>
			<td style="width:87px;">Leo</td>
			<td style="width:119px;">1530 VP</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Sputter coater with iridium target</td>
			<td style="width:87px;">Cressington</td>
			<td style="width:119px;">208 HR</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Thickness measurement unit</td>
			<td style="width:87px;">Cressington</td>
			<td style="width:119px;">mtm 20</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Magnetic stirrer</td>
			<td style="width:87px;">Stuart</td>
			<td style="width:119px;">CD162</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Analytical balance</td>
			<td style="width:87px;">Kern</td>
			<td style="width:119px;">ALS 220-4N</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Analytical balance</td>
			<td style="width:87px;">Mettler Toledo</td>
			<td style="width:119px;">NewClassic MF MS 2045</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Laboratory balance</td>
			<td style="width:87px;">Shimadzu</td>
			<td style="width:119px;">ELB 3000</td>
			<td></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">Electrodes from 316 stainless steel sheet</td>
			<td style="width:87px;">RS Components</td>
			<td style="width:119px;">559-199</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Sanding sheets, P1000 grade</td>
			<td style="width:87px;">Norton</td>
			<td style="width:119px;">No-Fil A275</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Multi-walled carbon nanotubes</td>
			<td style="width:87px;">Hanwha</td>
			<td style="width:119px;">CM-95</td>
			<td>http://hcc.hanwha.co.kr/eng/business/bus_table/nano_02.jsp</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Graphene nanoplatelets</td>
			<td style="width:87px;">XG Sciences</td>
			<td style="width:119px;">XGNP Grade C</td>
			<td>http://xgsciences.com/products/graphene-nanoplatelets/grade-c/</td>
		</tr>
	</tbody>
</table>

functionalization and dispersion of carbon nanomaterials using an environmentally friendly ultrasonicated ozonolysis process

Functionalization of carbon nanomaterials is often a critical step that facilitates their integration into larger material systems and devices. In the as-received form, carbon nanomaterials, such as carbon nanotubes (CNTs) or graphene nanoplatelets (GNPs), may contain large agglomerates. Both agglomerates and impurities will diminish the benefits of the unique electrical and mechanical properties offered when CNTs or GNPs are incorporated into polymers or composite material systems. Whilst a variety of methods exist to functionalize carbon nanomaterials and to create stable dispersions, many the processes use harsh chemicals, organic solvents, or surfactants, which are environmentally unfriendly and may increase the processing burden when isolating the nanomaterials for subsequent use. The current research details the use of an alternative, environmentally friendly technique for functionalizing CNTs and GNPs. It produces stable, aqueous dispersions free of harmful chemicals. Both CNTs and GNPs can be added to water at concentrations up to 5 g/L and can be recirculated through a high-powered ultrasonic cell. The simultaneous injection of ozone into the cell progressively oxidizes the carbon nanomaterials, and the combined ultrasonication breaks down agglomerates and immediately exposes fresh material for functionalization. The prepared dispersions are ideally suited for the deposition of thin films onto solid substrates using electrophoretic deposition (EPD). CNTs and GNPs from the aqueous dispersions can be readily used to coat carbon- and glass-reinforcing fibers using EPD for the preparation of hierarchical composite materials.

Figure 3 shows the XPS wide-scan characterization of CNTs that had undergone USO treatment. CNTs that had not undergone USO show almost no oxygen content. As the USO time increases, the surface oxygen level increases. Figure 4 charts the oxygen-to-carbon ratio increases as a function of USO time. Table 1 shows the deconvoluted carbon species atomic concentrations of GNP treated with USO. The peak fitting used a combination of constrained ...

Watch this Scientific Journal Video about Functionalization and Dispersion of Carbon Nanomaterials Using an Environmentally Friendly Ultrasonicated Ozonolysis Process at JoVE.com

Functionalization and Dispersion of Carbon Nanomaterials Using an Environmentally Friendly Ultrasonicated Ozonolysis Process

Here, a novel method for the functionalization and stable dispersion of carbon nanomaterials in aqueous environments is described. Ozone is injected directly into an aqueous dispersion of carbon nanomaterial that is continuously recirculated through a high-powered ultrasonic cell.

Functionalization of carbon nanomaterials is often a critical step that facilitates their integration into larger material systems and devices. In the ...

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