The Research at Oak Ridge National Laboratory's Spallation Neutron Source and Center for Nanophase Materials Sciences was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy. The author, Zhe Zhang, gratefully acknowledges the financial support from J&#252;lich Center for Neutron Science, Research center J&#252;lich.

Note: This protocol requires special care in the handling of nanomaterials. As-purchased single-walled carbon nanotubes (SWNTs) exist in the form of fine powder and thus, they should be considered as nano-hazardous materials before dispersing them in aqueous solutions. Please use appropriate safety equipment described in the material safety data sheets (MSDS).
1. Preparation of Poloxamer 407/SWNT Aqueous Suspensions
Note: Proceed with all the sample preparation procedures at a lower temperature than the critical micellization temperature (CMT) of the block copolymers used. The poloxamer 407/SWNT samples were prepared at 20 &#176;C, below the CMT of poloxamer 407 (30 &#176;C).21
<ol>
	<li>Preparation of Poloxamer 407 aqueous solutions (0.25% w/w)
	<ol>
		<li>Completely dissolve 0.175 g of poloxamer 407 powder in 70 g D2O. 
		Note: D2O is used for SANS measurements. 70 g D2O is approximately 63.2 ml at room temperature. For other purposes, H2O is recommended for use.</li>
	</ol>
	</li>
	<li>Preparation of crude Poloxamer 407/SWNT suspensions
	<ol>
		<li>Add 0.01 g SWNT powder to two 50 ml conical centrifuge tubes (tube 1 and tube 2) separately.</li>
		<li>Add 31.6 ml of the poloxamer 407 solution (1.1.1), into the tube 1 and 31.6 ml of the remaining solution into the tube 2.</li>
		<li>Mix the suspensions in the tube 1 and 2 by vortex-mixing for 5-10 min.</li>
		<li>Place the tube 1 in a water bath. Fix the tube position securely. (Figure 1) Dip the tube until the air-suspension interface reaches the surface of water in the bath.</li>
		<li>Dip the tip of an ultrasonicator into the suspension of the tube 1. Increase the sonication power gradually from 0% at least until the SWNTs deposited at the bottom of the tube start shattering and spreading due to the ultrasound propagated from the ultrasonicator tip. Treat the suspension with ultrasound for 60 min at 20 &#176;C, while keeping the suspension temperature below 25 &#176;C. 
		Note: Do not put the tip end deeper than 1 cm into the suspension. Keep the suspension temperature below 25 &#176;C, either by controlling the temperature of the water reservoir or by refilling the bath appropriately.</li>
		<li>Repeat steps 1.2.4 and 1.2.5 for the tube 2.</li>
	</ol>
	</li>
	<li>Preparation of Poloxamer 407/SWNT suspensions in the absence and presence of 5-Methylsalicylic acid
	<ol>
		<li>Centrifuge the crude suspensions in tubes 1 and 2 at 9,800 &#215; g for 2 hr at 20 &#176;C.</li>
		<li>Move 15 ml of the supernatants from each tube to a new tube, separately.</li>
		<li>Dissolve 0.015 g of 5-methylsalicylic acid (5MS) into the supernatant taken from tube 2, and label this mixture as Sample #2. Label the other supernatant from the tube 1 as Sample #1.</li>
	</ol>
	</li>
</ol>
2. Extended Q-range Small-angle Neutron Scattering (EQ-SANS) Measurements
Note: To work at the beamlines of Spallation Neutron Source (SNS), an accepted beamtime proposal is required. Radiological safety training and other instrument specific training are also required in advance. Access and training details are provided by the SNS User Office and can be found at neutrons.ornl.gov.
<ol>
	<li>Sample loading
	<ol>
		<li>Load 0.3 ml of Sample #1 of into an amorphous quartz banjo cell and Sample #2 into another banjo cell (Figure 2A-i). Put lids on the two cells and seal them by wrapping tape securely around the lids.</li>
		<li>Place one of the sealed cells between spacers (Figure 2A-ii) for an aluminum cell holder (Figure 2A-iii), and assemble the aluminum banjo cell holder (Figure 2B). Assemble the other cell with a different set of banjo cell holder in the same manner.</li>
		<li>Load the assembled cells into different sample positions of the EQ-SANS sample paddle (Figure 3A). Make the list of the sample positions of the paddle.</li>
	</ol>
	</li>
	<li>Measurements
	<ol>
		<li>Set the configurations for the SANS measurements in a script with the help of an instrument scientist, referring to the given example script. 
		Note: An example of the script used during the actual SANS measurements is provided in the supplementary material with brief comment. This example is specifically designed for SANS measurements of two samples (sample #1 and #2) using a wavelength band of 9.1 &#197; &#60; &#955; &#60; 13.2 &#197; at the fixed 1.3 m sample-to-detector distance with a 10 mm sample aperture and a 30 mm beam stop. The example script can be used without any modification for the sample #1 and #2.
		<ol>
			<li>To cover a q-range of 0.01 - 0.4 &#197;-1, select a wavelength band of 9.1 &#197; &#60; &#955; &#60; 13.2 &#197; and a sample-to-detector distance of 1.3 m by inputting 1300 into detector position and 9 into wavelength as shown in the example script.</li>
			<li>To use a 10 mm sample aperture and a 30 mm beam stop, set x-y positions of the beam stops and apertures in the script.</li>
			<li>Set the sample positions and the corresponding names for both transmission and sample scattering measurements.</li>
			<li>Save the script in the folder corresponding to the beam time.</li>
		</ol>
		</li>
		<li>Execute the script to perform measurements by clicking on &#39;Run Script&#39; on the right side of the PyDAS control window (Figure 3B) and loading the saved script.</li>
		<li>Inform the instrument team of the completion of measurements after the experiment is finished.</li>
	</ol>
	</li>
</ol>
3. SANS Data Reduction and Analysis
<ol>
	<li>SANS Data reduction process
	<ol>
		<li>For the reduction of the measured data, use MantidPlot23-24 software provided at analysis.sns.gov, with the help of the instrument team. 
		Note: Detailed instructions to run MantidPlot software can be found at analysis.sns.gov webpage.</li>
		<li>Within MantidPlot, open the EQSANS reduction interface from the interfaces menu. (interface&#62;SANS&#62;ORNL SANS). Input all necessary information for the data reduction process. 
		Note: Most of important information in the data reduction process is provided by the instrument team. For information, relevant screenshots are also provided in the supplementary materials.</li>
		<li>Input all necessary information in the &#39;Reduction Options&#39; tab.
		<ol>
			<li>Input the absolute scale factor from the standard sample measurement. Obtain the absolute intensity from the measurement of a well characterized standard sample whose scattering intensity is known (I(0)=450 cm-1) and fit with a Debye-Buche scattering model.</li>
			<li>Input the dark current file name, which is provided by the instrument team.</li>
			<li>Check options for the &#39;solid angle correction&#39;, &#39;Q resolution&#39;, &#39;use configuration file&#39;, &#39;Correct TOF&#39;, and &#39;user mask from configuration file as applicable&#39;.</li>
			<li>Set sample aperture diameter to 10 mm. Set number of Q bins to 200 with a linear Q binning scheme. Input the mask file name, which is also provided by the instrument team.</li>
		</ol>
		</li>
		<li>Input all necessary information to complete the &#39;Detector&#39; tab.
		<ol>
			<li>Check &#39;Use beam finder&#39; (with fit direct beam option) and &#39;perform sensitivity correction&#39;. Find a beam center &#39;data file&#39; using the run number of the empty beam measurement.</li>
			<li>Input the sensitivity data file name, which is provided by the instrument scientist. Set the allowed sensitivity range to 0.5 and 2.5 for the min and max, respectively. Check &#39;Use sample beam center&#39;.</li>
		</ol>
		</li>
		<li>Input all necessary information for the &#39;Data&#39; tab.
		<ol>
			<li>Enter sample scattering run number at &#39;Scattering data file&#39;. Specify the sample thickness in cm. Select &#39;Calculate transmission&#39;.</li>
			<li>Enter the sample transmission run number at &#39;Sample direct beam data file&#39;. Enter empty beam run number at &#39;Empty direct beam data file&#39;.</li>
			<li>Check &#39;Background data file&#39; and enter background scattering run number. Select &#39;Calculate transmission&#39;. Enter background transmission run number at &#39;Sample direct beam data file&#39;. 
			Note: In this case, the empty banjo cell scattering data file is the background scattering.</li>
			<li>Enter empty beam run number at &#39;Empty direct beam data file&#39;. Typically, this number is same as the empty beam run number (3.1.5.2).</li>
		</ol>
		</li>
		<li>Click on &#39;Reduce&#39; to execute the data reduction. 
		Note: The output is written in the designated folder as #####_Iq.txt where ##### is the run number of the sample scattering file. ASCII format is used for the data files.</li>
	</ol>
	</li>
	<li>Model fitting analysis 
	Note: SasView is a small-angle scattering analysis software package, which was originally developed as part of the NSF DANSE project, and is currently managed by an international collaboration of facilities (http://www.sasview.org/). The software package can be downloaded at http://sourceforge.net/projects/sasview/files/.
	<ol>
		<li>Run SasView, and load a data file by clicking on &#39;Load Data&#39; from the &#39;Data Explorer&#39; window.</li>
		<li>Click on &#39;Send To&#39; with the &#39;Fitting&#39; option, and check the data plot on the popup window.</li>
		<li>In the &#39;Fit Panel&#39;, select &#34;Shapes&#34; under the model category, and choose &#34;CoreShellCylinderModel&#34; from the model drop box.</li>
		<li>Adjust the parameter values, so the model curve is as close to the data curve as possible. 
		Note: Use the SLD (scattering length density) calculator from the Tool menu to calculate scattering length densities.</li>
		<li>Select &#34;Use dQ data&#34; and &#34;Use dI Data&#34; in the Fitting panel. Adjust Q range of the data for fitting. Click on &#39;Fit&#39; to execute data fitting.</li>
	</ol>
	</li>
</ol>
4. Real-space Observation Using Atomic Force Microscopy (AFM)
<ol>
	<li>Sample preparation on Si-wafers using spin coating
	<ol>
		<li>For AFM measurements, take 0.1 ml sample solution from the Sample #1 (1.3.3), and mix it with 1.9 ml de-ionized water.</li>
		<li>Place a clean Si-wafer (12 mm &#215; 12 mm) on a spin coater. Fix the wafer position using a vacuum chuck.</li>
		<li>Set the rotation speed and the running time at 1,500 revolutions per minute (rpm) and 60 sec, respectively. Wet the exposed surface of the wafer with the diluted sample. Start spin coating.</li>
		<li>Turn off the vacuum pump, and remove the coated wafer from the spin coater.</li>
	</ol>
	</li>
	<li>AFM measurements
	<ol>
		<li>Attach the spin-coated wafer (4.1.4) on an iron disk using a double-sided adhesive carbon tape.</li>
		<li>Bring the specimen disk (4.2.1) closer to the edge of the exposed area of the scanner first, and slide the disk toward the center until the bottom surface of the disk completely covers the top of the scanner. 
		Note: Avoid sudden contact because a magnet on the top of the scanner strongly attracts the iron disk. Gently make a contact between two edges of the disk and the scanner.</li>
		<li>Mount the scanning probe microscope (SPM) head on the scanner, and plug in the cable. 
		Note: Extreme care has to be paid while moving the SPM head or docking (removing) it to (from) the scanner. When the head is detached from the scanner stage, keep the bottom surface of the head facing upwards all the time.</li>
		<li>Run the instrument-supplied control software, and select the tapping mode in the &#39;System Configuration&#39; window.</li>
		<li>Place the cantilever tip at the center of the monitor window by adjusting the coarse and fine knobs of the optical microscope and by moving the x- and y- optical stages.</li>
		<li>Align the laser by adjusting the laser alignment knobs on the SPM head. Locate the red laser dot to the cantilever roughly, and move the dot to the middle of the cantilever tip by tracing the dot shown in the monitor. 
		Note: When the laser is properly aligned, the pink reflection spot appears on the laser alignment window.</li>
		<li>Align the detector by locating the pink reflection image at the center of the laser alignment window. Adjusting the photodetector knobs on the SPM head until the quadrant photodiode (QPD) signal sum is greater than 2 V at least (2.1 - 2.4 V).</li>
		<li>Tune the cantilever using AutoTune in the Cantilever Tuning window. Run AutoTune in a frequency range of 0 - 1,000 kHz.</li>
		<li>Bring the wafer surface into focus of the microscope by adjusting the focus knobs.</li>
		<li>Drive the cantilever tip slowly toward the wafer surface using the up and down arrows in the &#39;Motor Stage&#39; window. Stop the movement before the tip touches the sample surface. 
		Note: As the tip approaches the wafer, the blurred black image of the tip appears in the monitor and the image becomes clear when the tip and the wafer surface make contact. Never let the tip physically touch the specimen. It damages both sample and instrument. Stop the tip when the dark blurred image is shown.</li>
		<li>Click on the engage button on the toolbar.</li>
		<li>Select a scan size (5-10 &#181;m), a sampling number (512-1,024), and a scan rate (0.5-0.6 Hz) in the popup window, in order to acquire a large-scale image first.</li>
		<li>Start scanning. Gradually adjust P (proportional gain), I (integral gain), and D (vertical deflection) values if the contrast between the particles and the substrate background is too low to clearly recognize particle shapes and boundaries from the scanned image. 
		Note: When a new PID value set is entered, the scanning process will be automatically restarted.</li>
		<li>If there is any region of interest in the large-scale image, re-run the scan with a proper set of scan size, x-offset, y-offset, and sample number.</li>
		<li>Disengage the probe after measurement. 
		Note: Raise the probe head to prevent any damage on the cantilever tip and the sample. Remove the probe head first, and then, detach the specimen disk.</li>
	</ol>
	</li>
</ol>

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The authors have nothing to disclose.

SANS and AFM measurements showed that SWNTs have been successfully de-bundled and individually dispersed in aqueous solution using a poloxamer 407 triblock copolymer. In this sample preparation method, ultra-sonication and centrifugation processes are the critical steps determining the characteristics of the final suspension. The strong interaction between the SWNTs, which forces uncoated SWNTs to bundle together in solution, must be overcome to stabilize the individual SWNTs with block copolymers. Providing a sufficient...

Carbon nanotubes (CNTs) are hollow cylindrical nanoparticles formed by rolling a micrometer-scale graphite sheet into a nanotube. Because of their extraordinary mechanical, thermal, and electrical properties, CNTs have been extensively investigated as a novel candidate for functional nanoparticles in therapeutic and bio-sensing applications as well as nano-fillers in self-assembled nanocomposite materials.1-3 However, their poor solubility and strong preference toward making bundles in commonly used organic and aqueous solvents hinder easy and environmentally-friendly processing as well as advances in biological applications. Therefore, a variety of functionalization methods, such as ultra-sonication, chemical surface modification, and non-covalent functionalization by using surfactants and block copolymers,4-9 have been developed to modify the CNT surfaces and improve their dispersibility in a wide range of solvents. Non-covalent functionalization methods based on physical surface treatments, in particular, are considered to be a promising and robust strategy, because any surface-modification induced suppression in intrinsic CNT properties can be minimized.10 To date, there have been numerous efforts to improve the dispersion efficiency of non-covalent functionalization methods by employing various types of dispersive agents including basic surfactants (e.g., SDS, CTAB, NaDDBS),7,11 amphiphilic block copolymers,8 bio-materials (e.g., DNA),12,13 and synthetic functional polymers (e.g., conjugated polymer, aromatic polymer).14,15
PEO-PPO-PEO polymers, a kind of triblock copolymer consisting of two hydrophilic poly(ethylene oxide) (PEO) chains at both ends covalently bound to one hydrophobic poly(propylene oxide) (PPO) chain at the center, can extend the potential application of non-covalently functionalized CNTs in aqueous solution. These polymers provide the interface, which is friendly not only to the CNT surfaces but also to aqueous media and other polymer matrices and exhibits tremendous biocompatibility due to the minimal toxicity of the PEO chains. This facilitates easier processing in a wide range of dispersing environments as well as the utilization of polymer-coated CNTs in biomedical applications.12,16-17 Moreover, the rich thermodynamic phase behavior of these polymers based on their sensitive responses to external stimuli enables the fabrication of the smart block copolymer-CNT hybrid nanostructures in which intra- and inter-particle structures can be reversibly and precisely controlled.18-21 Here, we present a protocol for the fabrication of CNT-based hybrid nanoparticles with a tunable encapsulation layer of PEO105-PPO70-PEO105 (poloxamer 407). The resulting structure is characterized by small-angle neutron scattering (SANS). This work is expected to introduce the concept of smart functional building blocks and help non-specialists easily prepare block copolymer-functionalized CNT suspensions and use SANS for the detailed characterization at Oak Ridge National Laboratory.

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			<td height="42" style="height:42px;width:216px;">HiPco Single-walled carbon nanotubes</td>
			<td style="width:71px;">Unidym</td>
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			<td height="21" style="height:21px;width:216px;">Pluronic F127</td>
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			<td>9003-11-6</td>
			<td>Mw = 12.6 kg/mol</td>
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			<td height="42" style="height:42px;width:216px;">5-methylsalicylic acid</td>
			<td style="width:71px;">TCI America</td>
			<td>C0410</td>
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			<td height="42" style="height:42px;width:216px;">Ultrasonic processor</td>
			<td style="width:71px;">Cole-Parmer</td>
			<td>ML-04714-52</td>
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			<td height="42" style="height:42px;width:216px;">Sorvall 6 plus centrifuge</td>
			<td style="width:71px;">Thermo Scientific</td>
			<td align="right" style="width:119px;">46910</td>
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			<td height="21" style="height:21px;width:216px;">Innova AFM&#160;</td>
			<td style="width:71px;">Bruker</td>
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			<td height="89" style="height:89px;width:216px;">Si-wafer</td>
			<td style="width:71px;">Silicon Quest International</td>
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			<td style="width:228px;">150 mm in diameter&#160; ; N type &#60;1-1-1&#62; cut ; 1-10 Ohm/cm ; Single-side polyshed (675 +- 25 um) ; Diced (12 mm x 12 mm)</td>
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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.

Poloxamer 407-coated SWNT nanorod suspensions were fabricated using the sample preparation procedure (Figure 4), which can be divided into two important processes; the physical adsorption process of poloxamer 407 on SWNT surfaces using ultra-sonication, and the fractionation process of individually-stabilized SWNTs from bundled aggregates using centrifugation.
The SANS scattering intensities were obtained for th...

Watch this Scientific Journal Video about Functionalization of Single-walled Carbon Nanotubes with Thermo-reversible Block Copolymers and Characterization by Small-angle Neutron Scattering at JoVE.com

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

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 ...

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9.1K Views.  Oak Ridge National Laboratory. A method for the functionalization of carbon nanotubes with structure-tunable polymeric encapsulation layers and structural characterization using small-angle neutron scattering is presented.

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

Template Directed Synthesis of Plasmonic Gold Nanotubes with Tunable IR Absorbance

A nearly parallel array of pores can be produced by anodizing aluminum foils in acidic environments1, 2. Applications of anodic aluminum oxide (AAO) membranes have been under development since the 1990's and have become a common method to template the synthesis of high aspect ratio nanostructures, mostly by electrochemical growth or pore-wetting. Recently, these membranes have become commercially available in a wide range of pore sizes and densities, leading to an extensive library of functional nanostructures being synthesized from AAO membranes. These include composite nanorods, nanowires and nanotubes made of metals, inorganic materials or polymers 3-10. Nanoporous membranes have been used to synthesize nanoparticle and nanotube arrays that perform well as refractive index sensors, plasmonic biosensors, or surface enhanced Raman spectroscopy (SERS) substrates 11-16, as well as a wide range of other fields such as photo-thermal heating 17, permselective transport 18, 19, catalysis 20, microfluidics 21, and electrochemical sensing 22, 23. Here, we report a novel procedure to prepare gold nanotubes in AAO membranes. Hollow nanostructures have potential application in plasmonic and SERS sensing, and we anticipate these gold nanotubes will allow for high sensitivity and strong plasmon signals, arising from decreased material dampening 15.

Solution-suspendable gold nanotubes with controlled dimensions can be synthesized by electrochemical deposition in porous anodic aluminum oxide (AAO) membranes using a hydrophobic polymer core. Gold nanotubes and nanotube arrays hold promise for applications in plasmonic biosensing, surface-enhanced Raman spectroscopy, photo-thermal heating, ionic and molecular transport, microfluidics, catalysis and electrochemical sensing.

A nearly parallel array of pores can be produced by anodizing aluminum foils in acidic environments1, 2. Applications of anodic aluminum oxide (AAO) ...

Transport of Surface-modified Carbon Nanotubes through a Soil Column

Carbon nanotubes (CNTs) are widely manufactured nanoparticles, which are being utilized in a number of consumer products, such as sporting goods, electronics and biomedical applications. Due to their accelerating production and use, CNTs constitute a potential environmental risk if they are released to soil and groundwater systems. It is therefore essential to improve the current understanding of environmental fate and transport of CNTs. The transport and retention of CNTs in both natural and artificial media have been reported in literature, but the findings widely vary and are thus not conclusive. There are a number of physical and chemical parameters responsible for variation in retention and transport. In this study, a complete procedure of selected multiwalled carbon nanotubes (MWCNTs) is presented starting from their surface modification to a complete set of laboratory column experiments at critical physical and chemical scenarios. Results indicate that the stability of the commercially available MWCNTs are critical with their attached surface functional group which can also influence the transport and retention of MWCNT through the surrounding medium.

Surface properties of a nanoparticle are important for their interaction with the surrounding medium. Therefore the surface modification of carbon nanotubes can be critical for their transport and retention through porous media. Here, lab scale column experiments are used to understand the possible transport and retention of these nanoparticles.

Carbon nanotubes (CNTs) are widely manufactured nanoparticles, which are being utilized in a number of consumer products, such as sporting goods, ...

Synthesis, Characterization, and Functionalization of Hybrid Au/CdS and Au/ZnS Core/Shell Nanoparticles

Plasmonic nanoparticles are an attractive material for light harvesting applications due to their easily modified surface, high surface area and large extinction coefficients which can be tuned across the visible spectrum. Research into the plasmonic enhancement of optical transitions has become popular, due to the possibility of altering and in some cases improving photo-absorption or emission properties of nearby chromophores such as molecular dyes or quantum dots. The electric field of the plasmon can couple with the excitation dipole of a chromophore, perturbing the electronic states involved in the transition and leading to increased absorption and emission rates. These enhancements can also be negated at close distances by energy transfer mechanism, making the spatial arrangement of the two species critical. Ultimately, enhancement of light harvesting efficiency in plasmonic solar cells could lead to thinner and, therefore, lower cost devices. The development of hybrid core/shell particles could offer a solution to this issue. The addition of a dielectric spacer between a gold nanoparticles and a chromophore is the proposed method to control the exciton plasmon coupling strength and thereby balance losses with the plasmonic gains. A detailed procedure for the coating of gold nanoparticles with CdS and ZnS semiconductor shells is presented. The nanoparticles show high uniformity with size control in both the core gold particles and shell species allowing for a more accurate investigation into the plasmonic enhancement of external chromophores.

The synthesis of uniform gold nanoparticles coated with semiconductor shells of CdS or ZnS is performed. The semiconductor coating is conducted by first depositing a silver sulfide shell and exchanging the silver cations for zinc or cadmium cations.

Plasmonic nanoparticles are an attractive material for light harvesting applications due to their easily modified surface, high surface area and large ...

Facile Preparation of Internally Self-assembled Lipid Particles Stabilized by Carbon Nanotubes

We present a facile method to prepare nanostructured lipid particles stabilized by carbon nanotubes (CNTs). Single-walled (pristine) and multi-walled (functionalized) CNTs are used as stabilizers to produce Pickering type oil-in-water (O/W) emulsions. Lipids namely, Dimodan U and Phytantriol are used as emulsifiers, which in excess water self-assemble into the bicontinuous cubic Pn3m phase. This highly viscous phase is fragmented into smaller particles using a probe ultrasonicator in presence of conventional surfactant stabilizers or CNTs as done here. Initially, the CNTs (powder form) are dispersed in water followed by further ultrasonication with the molten lipid to form the final emulsion. During this process the CNTs get coated with lipid molecules, which in turn are presumed to surround the lipid droplets to form a particulate emulsion that is stable for months. The average size of CNT-stabilized nanostructured lipid particles is in the submicron range, which compares well with the particles stabilized using conventional surfactants. Small angle X-ray scattering data confirms the retention of the original Pn3m cubic phase in the CNT-stabilized lipid dispersions as compared to the pure lipid phase (bulk state). Blue shift and lowering of the intensities in characteristic G and G&#39; bands of CNTs observed in Raman spectroscopy characterize the interaction between CNT surface and lipid molecules. These results suggest that the interactions between the CNTs and lipids are responsible for their mutual stabilization in aqueous solutions. As the concentrations of CNTs employed for stabilization are very low and lipid molecules are able to functionalize the CNTs, the toxicity of CNTs is expected to be insignificant while their biocompatibility is greatly enhanced. Hence the present approach finds a great potential in various biomedical applications, for instance, for developing hybrid nanocarrier systems for the delivery of multiple functional molecules as in combination therapy or polytherapy.

We report on a smart application of carbon nanotubes for kinetic stabilization of lipid particles that contain self-assembled nanostructures in their cores. The preparation of lipid particles requires rather low concentrations of carbon nanotubes permitting their use in biomedical applications such as drug delivery.

We present a facile method to prepare nanostructured lipid particles stabilized by carbon nanotubes (CNTs). Single-walled (pristine) and multi-walled ...

Characterization, Quantification and Compound-specific Isotopic Analysis of Pyrogenic Carbon Using Benzene Polycarboxylic Acids (BPCA)

Fire-derived, pyrogenic carbon (PyC), sometimes called black carbon (BC), is the carbonaceous solid residue of biomass and fossil fuel combustion, such as char and soot. PyC is ubiquitous in the environment due to its long persistence, and its abundance might even increase with the projected increase in global wildfire activity and the continued burning of fossil fuel. PyC is also increasingly produced from the industrial pyrolysis of organic wastes, which yields charred soil amendments (biochar). Moreover, the emergence of nanotechnology may also result in the release of PyC-like compounds to the environment. It is thus a high priority to reliably detect, characterize and quantify these charred materials in order to investigate their environmental properties and to understand their role in the carbon cycle.
Here, we present the benzene polycarboxylic acid (BPCA) method, which allows the simultaneous assessment of PyC&#39;s characteristics, quantity and isotopic composition (13C and 14C) on a molecular level. The method is applicable to a very wide range of environmental sample materials and detects PyC over a broad range of the combustion continuum, i.e., it is sensitive to slightly charred biomass as well as high temperature chars and soot. The BPCA protocol presented here is simple to employ, highly reproducible, as well as easily extendable and modifiable to specific requirements. It thus provides a versatile tool for the investigation of PyC in various disciplines, ranging from archeology and environmental forensics to biochar and carbon cycling research.

Characterization, Quantification and Compound-specific Isotopic Analysis of Pyrogenic Carbon Using Benzene Polycarboxylic Acids BPCA

We present the benzene polycarboxylic acid (BPCA) method for assessing pyrogenic carbon (PyC) in the environment. The compound-specific approach uniquely provides simultaneous information about the characteristics, quantity and isotopic composition (13C and 14C) of PyC.

Fire-derived, pyrogenic carbon (PyC), sometimes called black carbon (BC), is the carbonaceous solid residue of biomass and fossil fuel combustion, such as ...

Synthesis and Characterization of Fe-doped Aluminosilicate Nanotubes with Enhanced Electron Conductive Properties

The goal of the protocol is to synthesize Fe-doped aluminosilicate nanotubes of the imogolite type with the formula (OH)3Al2-xFexO3SiOH. Doping with Fe aims at lowering the band gap of imogolite, an insulator with the chemical formula (OH)3Al2O3SiOH, and at modifying its adsorption properties towards azo-dyes, an important class of organic pollutants of both wastewater and groundwater.
Fe-doped nanotubes are obtained in two ways: by direct synthesis, where FeCl3 is added to an aqueous mixture of the Si and Al precursors, and by post-synthesis loading, where preformed nanotubes are put in contact with a FeCl3&#8226;6H2O aqueous solution. In both synthesis methods, isomorphic substitution of Al3+ by Fe3+ occurs, preserving the nanotube structure. Isomorphic substitution is indeed limited to a mass fraction of ~1.0% Fe, since at a higher Fe content (i.e., a mass fraction of 1.4% Fe), Fe2O3 clusters form, especially when the loading procedure is adopted. The physicochemical properties of the materials are studied by means of X-ray powder diffraction (XRD), N2 sorption isotherms at -196 &#176;C, high resolution transmission electron microscopy (HRTEM), diffuse reflectance (DR) UV-Vis spectroscopy, and &#950;-potential measurements. The most relevant result is the possibility to replace Al3+ ions (located on the outer surface of the nanotubes) by post-synthesis loading on preformed imogolite without perturbing the delicate hydrolysis equilibria occurring during nanotube formation. During the loading procedure, an anionic exchange occurs, where Al3+ ions on the outer surface of the nanotubes are replaced by Fe3+ ions. In Fe-doped aluminosilicate nanotubes, isomorphic substitution of Al3+ by Fe3+ is found to affect the band gap of doped imogolite. Nonetheless, Fe3+ sites on the outer surface of nanotubes are able to coordinate organic moieties, like the azo-dye Acid Orange 7, through a ligand-displacement mechanism occurring in an aqueous solution.

Here, we present a protocol to synthesize and characterize Fe-doped aluminosilicate nanotubes. The materials are obtained by either sol-gel synthesis upon addition of FeCl3&#8226;6H2O to the mixture containing the Si and Al precursors or by post-synthesis ionic exchange of preformed aluminosilicate nanotubes.

The goal of the protocol is to synthesize Fe-doped aluminosilicate nanotubes of the imogolite type with the formula (OH)3Al2-xFexO3SiOH. Doping with Fe ...

Monitoring the Effects of Illumination on the Structure of Conjugated Polymer Gels Using Neutron Scattering

We demonstrate a protocol to effectively monitor the gelation process of a high concentration solution of conjugated polymer both in the presence and absence of white light exposure. By instituting a controlled temperature ramp, the gelation of these materials can be precisely monitored as they proceed through this structural evolution, which effectively mirrors the conditions experienced during the solution deposition phase of organic electronic device fabrication. Using small angle neutron scattering (SANS) and ultra-small angle neutron scattering (USANS) along with appropriate fitting protocols we quantify the evolution of select structural parameters throughout this process. Thorough analysis indicates that continued light exposure throughout the gelation process significantly alters the structure of the ultimately formed gel. Specifically, the aggregation process of poly(3-hexylthiophene-2,5-diyl) (P3HT) nano-scale aggregates is negatively affected by the presence of illumination, ultimately resulting in the retardation of growth in conjugated polymer microstructures and the formation of smaller scale macro-aggregate clusters.

A protocol for the analysis of gels formed from the optoelectronic conjugated polymer poly(3-hexylthiophene-2,5-diyl) (P3HT) using small and ultra-small angle neutron scattering in both the presence and absence of illumination is presented.

We demonstrate a protocol to effectively monitor the gelation process of a high concentration solution of conjugated polymer both in the presence and ...

Grafting Multiwalled Carbon Nanotubes with Polystyrene to Enable Self-Assembly and Anisotropic Patchiness

We demonstrate a straightforward protocol to graft pristine multiwalled carbon nanotubes (MWCNTs) with polystyrene (PS) chains at the sidewalls through a free-radical polymerization strategy to enable the modulation of the nanotube surface properties and produce supramolecular self-assembly of the nanostructures. First, a selective hydroxylation of the pristine nanotubes through a biphasic catalytically mediated oxidation reaction creates superficially distributed reactive sites at the sidewalls. The latter reactive sites are subsequently modified with methacrylic moieties using a silylated methacrylic precursor to create polymerizable sites. Those polymerizable groups can address further polymerization of styrene to produce a hybrid nanomaterial containing PS chains grafted to the nanotube sidewalls. The polymer-graft content, amount of silylated methacrylic moieties introduced and hydroxylation modification of the nanotubes are identified and quantified by Thermogravimetric Analysis (TGA). The presence of reactive functional groups hydroxyl and silylated methacrylate are confirmed by Fourier Transform Infrared Spectroscopy (FT-IR). Polystyrene-grafted carbon nanotube solutions in tetrahydrofuran (THF) provide wall-to-wall collinearly self-assembled nanotubes when cast samples are analyzed by transmission electron microscopy (TEM). Those self-assemblies are not obtained when suitable blanks are similarly cast from analogous solutions containing non-grafted counterparts. Therefore, this method enables the modification of the nanotube anisotropic patchiness at the sidewalls which results into spontaneous auto-organization at the nanoscale.

A procedure for the synthesis of polystyrene-grafted multiwalled carbon nanotubes using successive chemical modification steps to selectively introduce the polymer chains to the sidewalls and their self-assembly via anisotropic patchiness is presented.

We demonstrate a straightforward protocol to graft pristine multiwalled carbon nanotubes (MWCNTs) with polystyrene (PS) chains at the sidewalls through a ...

Time-resolved Photophysical Characterization of Triplet-harvesting Organic Compounds at an Oxygen-free Environment Using an iCCD Camera

Here, we present a sensible method of the acquisition and analysis of time-resolved photoluminescence using an ultrafast iCCD camera. This system enables the acquisition of photoluminescence spectra covering the time regime from nanoseconds up to 0.1 s. This enables us to follow the changes in the intensity (decay) and emission of the spectra over time. Using this method, it is possible to study diverse photophysical phenomena, such as the emission of phosphorescence, and the contributions of prompt and delayed fluorescence in molecules showing thermally activated delayed fluorescence (TADF). Remarkably, all spectra and decays are obtained in a single experiment. This can be done for solids (thin film, powder, crystal) and liquid samples, where the only limitations are the spectral sensitivity of the camera and the excitation wavelength (532 nm, 355 nm, 337 nm, and 266 nm). This technique is, thus, very important when investigating the excited state dynamics in organic emitters for their application in organic light-emitting diodes and other areas where triplet harvesting is of paramount importance. Since triplet states are strongly quenched by oxygen, emitters with efficient TADF luminescence, or those showing room temperature phosphorescence (RTP), must be correctly prepared in order to remove any dissolved oxygen from solutions and films. Otherwise, no long-lived emission will be observed. The method of degassing solid samples as presented in this work is basic and simple, but the degassing of liquid samples creates additional difficulties and is particularly interesting. A method of minimizing solvent loss and changing the sample concentration, while still enabling to remove oxygen in a very efficient and a repeatable manner, is presented in this work.

Here, we present a method of the spectroscopic characterization of organic molecules by means of time-resolved photoluminescence spectroscopy on the nanosecond-to-millisecond timescale in oxygen-free conditions. Methods to efficiently remove oxygen from the samples and, thus, limit luminescence quenching are also described.

Here, we present a sensible method of the acquisition and analysis of time-resolved photoluminescence using an ultrafast iCCD camera. This system enables ...

DNA-magnetic Particle Binding Analysis by Dynamic and Electrophoretic Light Scattering

Isolation of DNA using magnetic particles is a field of high importance in biotechnology and molecular biology research. This protocol describes the evaluation of DNA-magnetic particles binding via dynamic light scattering (DLS) and electrophoretic light scattering (ELS). Analysis by DLS provides valuable information on the physicochemical properties of particles including particle size, polydispersity, and zeta potential. The latter describes the surface charge of the particle which plays major role in electrostatic binding of materials such as DNA. Here, a comparative analysis exploits three chemical modifications of nanoparticles and microparticles and their effects on DNA binding and elution. Chemical modifications by branched polyethylenimine, tetraethyl orthosilicate and (3-aminopropyl)triethoxysilane are investigated. Since DNA exhibits a negative charge, it is expected that zeta potential of particle surface will decrease upon binding of DNA. Forming of clusters should also affect particle size. In order to investigate the efficiency of these particles in isolation and elution of DNA, the particles are mixed with DNA in low pH (~6), high ionic strength and dehydration environment. Particles are washed on magnet and then DNA is eluted by Tris-HCl buffer (pH = 8). DNA copy number is estimated using quantitative polymerase chain reaction (PCR). Zeta potential, particle size, polydispersity and quantitative PCR data are evaluated and compared. DLS is an insightful and supporting method of analysis that adds a new perspective to the process of screening of particles for DNA isolation.

This protocol describes the synthesis of magnetic particles and evaluation of their DNA-binding properties via dynamic and electrophoretic light scattering. This method focuses on monitoring changes in particle size, their polydispersity and zeta potential of particle surface which play major role in binding of materials such as DNA.

Isolation of DNA using magnetic particles is a field of high importance in biotechnology and molecular biology research. This protocol describes the ...