Name: advanced compositional analysis of nanoparticle-polymer composites using direct fluorescence imaging
Uploaded: 2016-07-19T14:00:00
Description: Watch this Scientific Journal Video about Advanced Compositional Analysis of Nanoparticle-polymer Composites Using Direct Fluorescence Imaging at JoVE.com

C.R.C. would like to acknowledge the Ramsay Memorial Trust for funding.

1. Preparation of CdSe/ZnS Core/Shell Quantum Dots
<ol>
	<li>Preparation of the trioctylphosphine (TOP)-Se solution
	<ol>
		<li>Prepare a 0.5 M solution of selenium in TOP by mixing the appropriate amount of Se into TOP in a Schlenk flask under nitrogen or in a glovebox (8 ml required per reaction, typically 0.4 g dissolved in 10 ml of TOP).</li>
		<li>Stir the mixture to dissolve the Se for 1 hr, resulting in a grey solution of the TOP-Se complex.</li>
		<li>Ensure the solution is then freeze-pump-tha...

<ol>
	<li>Pumera, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Graphene-based+nanomaterials+and+their+electrochemistry.">Graphene-based nanomaterials and their electrochemistry.</a> Chem. Soc. Rev. 39 (11), 4146-4157 (2010).</li><li>Zhang, Q., Uchaker, E., Candelaria, S. L., Cao, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nanomaterials+for+energy+conversion+and+storage.">Nanomaterials for energy conversion and storage.</a> Chem. Soc. 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Cluster Sci. 21 (3), 427-438 (2010).</li><li>Perni, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+antimicrobial+properties+of+light-activated+polymers+containing+methylene+blue+and+gold+nanoparticles.">The antimicrobial properties of light-activated polymers containing methylene blue and gold nanoparticles.</a> Biomater. 30 (1), 89-93 (2009).</li><li>Noimark, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dual-Mechanism+Antimicrobial+Polymer-ZnO+Nanoparticle+and+Crystal+Violet-Encapsulated+Silicone.">Dual-Mechanism Antimicrobial Polymer-ZnO Nanoparticle and Crystal Violet-Encapsulated Silicone.</a> Adv. Func. Mater. 25 (9), 1367-1373 (2015).</li><li>Gingery, D., B&#252;hlmann, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Formation+of+gold+nanoparticles+on+multiwalled+carbon+nanotubes+by+thermal+evaporation.">Formation of gold nanoparticles on multiwalled carbon nanotubes by thermal evaporation.</a> Carbon. 46 (14), 1966-1972 (2008).</li><li>Abdelmoti, L. G., Zamborini, F. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Potential-Controlled+Electrochemical+Seed-Mediated+Growth+of+Gold+Nanorods+Directly+on+Electrode+Surfaces.">Potential-Controlled Electrochemical Seed-Mediated Growth of Gold Nanorods Directly on Electrode Surfaces.</a> Langmuir. 26 (16), 13511-13521 (2010).</li><li>Crick, C. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Advanced+analysis+of+nanoparticle+composites+-+a+means+toward+increasing+the+efficiency+of+functional+materials.">Advanced analysis of nanoparticle composites - a means toward increasing the efficiency of functional materials.</a> RSC Adv. 5 (66), 53789-53795 (2015).</li><li>Solvas, X. C., Turek, V., Prodromakis, T., Edel, J. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microfluidic+evaporator+for+on-chip+sample+concentration.">Microfluidic evaporator for on-chip sample concentration.</a> Lab Chip. 12 (20), 4049-4054 (2012).</li><li>Solvas, X. 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Cross-sectional fluorescence imaging allows for direct visualization of nanoparticles during swell encapsulation. The kinetics of encapsulation has been shown, with the drive toward a high nanoparticle surface concentration demonstrated. The extent of nanoparticle incorporation is shown to vary with swell encapsulation time (described in section 2.3), with the total amount of incorporated nanoparticles increasing as this time is extended, with the particle concentration localized at the surface if the polymer samples are...

The application of nanomaterials has long served as an area of increasing interest for novel technologies.1-3 This has included the growing use of nanoparticles in everyday items, including cosmetics, clothes, packaging and electronics.4-6 A major drive toward using nanoparticles in functional materials stems from their higher reactivity relative to the materials, in addition to the ability to tune properties by variation in particle size.7 One further advantage is the capability to easily form composite materials, introducing crucial properties to the host matrix, such as catalytic functionality, material strengthening and tuning of electrical properties.8-12
Nanoparticle-polymer composite materials can be achieved through a range of techniques, the simplest of which is direct integration of the desired nanoparticles during the fabrication of the host matrix.13,14 This results in a homogenous material with an even spacing of nanoparticulate material throughout. However, many applications only require the active material to be present at the external interfaces of the nanocomposites. As a result, direct incorporation does not result in efficient use of sometimes costly nanoparticle material as there is much nanoparticle waste through the bulk of the material.15,16 To achieve direct incorporation, the nanoparticles must also be compatible with host matrix formation. This may be challenging, especially in syntheses that require multifaceted reactions such as in the case of thermosetting polymers that are typically facilitated by metal complex catalysts mechanisms that may be affected by highly active nanoparticles.14
The considerable disadvantages associated with direct nanoparticle incorporation during the polymer synthesis, has led to the development of techniques aimed to limit nanoparticle incorporation to the surface layer.17-21 Swell encapsulation is one of the most successful strategies reported in the literature, to achieve high surface nanoparticle concentrations, with limited wastage in the polymer bulk.17-19 The technique utilizes the solvent driven swelling of polymer matrices, allowing for the incursion of molecular species and nanoparticles. Upon removal of the swelling solvent, the species within the matrix become fixed into place, with the highest concentration of species localized at the surface. To date, most of the reported uses of swell encapsulation are directed toward the fabrication of antimicrobial polymers, where it is key that the active agents are at the material surface. While many of these reports show enhanced antimicrobial activity, the precise surface nanoparticle composition is rarely probed in detail. Crick et al. recently demonstrated a method for the direct visualization of nanoparticle incursion, providing crucial insight into the kinetics and surface nanoparticle concentrations achieved by swell encapsulation.22
This work details the synthesis of cadmium selenide quantum dots (QD), their swell encapsulation into polydimethylsiloxane (PDMS) and the direct visualization of their incorporation using fluorescence imaging. The effect of varying swell encapsulation time and nanoparticle concentration in the swelling solution is explored. The fluorescence visualization technique allows for the direct imaging of nanoparticle incursion into the PDMS and demonstrates that the highest concentration of QDs is at the material surface.

<table border="0" cellpadding="0" cellspacing="0" width="573">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Polydimethylsiloxane sheets</td>
			<td style="width:71px;">NuSil</td>
			<td style="width:119px;">-</td>
			<td style="width:167px;">Medical Grade</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Oleylamine</td>
			<td style="width:71px;">Sigma Aldrich</td>
			<td style="width:119px;">O7805</td>
			<td>Technical Grade</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Trioctylphosphine</td>
			<td style="width:71px;">Sigma Aldrich</td>
			<td style="width:119px;">117854</td>
			<td>Technical Grade</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Trioctylphosphine oxide</td>
			<td style="width:71px;">Sigma Aldrich</td>
			<td style="width:119px;">346187</td>
			<td>Technical Grade</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">1-Octadecene</td>
			<td style="width:71px;">Sigma Aldrich</td>
			<td style="width:119px;">O806</td>
			<td>Technical Grade</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Zinc diethyldithiocarbamate</td>
			<td style="width:71px;">Sigma Aldrich</td>
			<td style="width:119px;">329703</td>
			<td>-</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Oleic acid</td>
			<td style="width:71px;">Sigma Aldrich</td>
			<td style="width:119px;">364525</td>
			<td>Technical Grade</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Triethylamine</td>
			<td style="width:71px;">Sigma Aldrich</td>
			<td style="width:119px;">471283</td>
			<td>-</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Cadmium oxide</td>
			<td style="width:71px;">Alfa Aesar</td>
			<td style="width:119px;">33235</td>
			<td>-</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Hexadecylamine</td>
			<td style="width:71px;">Alfa Aesar</td>
			<td style="width:119px;">B22459</td>
			<td>Technical Grade</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">1-Dodecylphosphonic acid</td>
			<td style="width:71px;">Alfa Aesar</td>
			<td style="width:119px;">H26259</td>
			<td>-</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Selenium powder</td>
			<td style="width:71px;">Acros</td>
			<td style="width:119px;">19807</td>
			<td>-</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Chloroform</td>
			<td style="width:71px;">Sigma Aldrich</td>
			<td style="width:119px;">366919</td>
			<td>-</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">n-Hexane</td>
			<td style="width:71px;">Sigma Aldrich</td>
			<td style="width:119px;">208752</td>
			<td>-</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Microscope slides</td>
			<td style="width:71px;">VWR</td>
			<td style="width:119px;">631-0137</td>
			<td>Thickness No. 1</td>
		</tr>
	</tbody>
</table>

advanced compositional analysis of nanoparticle-polymer composites using direct fluorescence imaging

The fabrication of polymer-nanoparticle composites is extremely important in the development of many functional materials. Identifying the precise composition of these materials is essential, especially in the design of surface catalysts, where the surface concentration of the active component determines the activity of the material. Antimicrobial materials which utilize nanoparticles are a particular focus of this technology. Recently swell encapsulation has emerged as a technique for inserting antimicrobial nanoparticles into a host polymer matrix. Swell encapsulation provides the advantage of localizing the incorporation to the external surfaces of materials, which act as the active sites of these materials. However, quantification of this nanoparticle uptake is challenging. Previous studies explore the link between antimicrobial activity and surface concentration of the active component, but this is not directly visualized. Here we show a reliable method to monitor the incorporation of nanoparticles into a polymer host matrix via swell encapsulation. We show that the surface concentration of CdSe/ZnS nanoparticles can be accurately visualized through cross-sectional fluorescence imaging. Using this method, we can quantify the uptake of nanoparticles via swell encapsulation and measure the surface concentration of encapsulated particles, which is key in optimizing the activity of functional materials.

The quantum dots exhibited red fluorescence, with a lambda max of approximately 600 nm.22,28 The red emission was due to the confinement of the exciton by the quantum rod whose size dimensions are within the strong confinement regime. Li et al. showed that for quantum rods, the emission shifts to lower energy with an increase in either width or length of the rod. They further showed that the emission mainly determined by the lateral confinement, which plays an importan...

Watch this Scientific Journal Video about Advanced Compositional Analysis of Nanoparticle-polymer Composites Using Direct Fluorescence Imaging at JoVE.com

Advanced Compositional Analysis of Nanoparticle-polymer Composites Using Direct Fluorescence Imaging

Here we present a reliable method to monitor the incorporation of nanoparticles into a polymer host matrix via swell encapsulation. We show that the surface concentration of cadmium selenide quantum dots can be accurately visualized through cross-sectional fluorescence imaging.

The fabrication of polymer-nanoparticle composites is extremely important in the development of many functional materials. Identifying the precise ...

The overall goal of this analysis technique is to gain an understanding of nanoparticle incorporation into polymer matrices. The direct imaging of particles allows for an estimation of local concentrations and overall assimilation rates. This method can help answer key questions in materials chemistry, including nanochemistry, concept materials design, and catalysis.The main advantage of this technique is that the incorporation of nanoparticular materials are imaged directly, such that the information gained cannot be achieved by any other straightforward method. Demonstrating the procedure will be Dr.Sacha Noimark, Dr.Joe Bear, and Dr.William Peveler. Post-doc from Professor Parkin's laboratory at UCL.Begin this procedure with preparation of the cadmium selenide cores, as detailed in the text protocol. To a 100 milliliter browned-bottomed flask, add zinc diethyldithiocarbamate, 1-Octadecene, Oleylamine, Trioctylphosphine, and the cores in hexane. Add a stir bar, and exchange the reaction atmosphere to nitrogen.Heat the reaction on a hot plate stirrer at 3.3 degrees Celsius per minute under partial vacuum until 70 degrees Celsius while removing the hexane using the Schlenk line. Switch the atmosphere to nitrogen, and continue heating at this rate to 120 degrees Celsius. Stir at 120 degrees Celsius for two hours.Allow the reaction to cool, and split the mixture between two 15 milliliter centrifuge tubes. Inject chloroform into the sample before pouring the solution into the tubes. Ensure the tubes are topped up to 50 milliliters with ethanol to precipitate the particles and centrifuge at 3600 times g for 10 minutes.Discard the supernatant and redisperse the pellets in a total of 10 milliliters of n-Hexane. Centrifuge the solution once more to remove any insoluble impurities before decanting into a sample tube. Store at four degrees Celsius under a nitrogen atmosphere for up to three months.For the swelling solution preparation, prepare a stock solution of cadmium selenide quantum dots by mixing 36 milliliters of n-Hexane with four milliliters of the synthesized cadmium selenide quantum dot dispersion. Stir the solution magnetically. Set aside two vials, each containing nine milliliters of the stock solution as designated swelling solutions.Use the remainder of the stock solution for the preparation of further swelling solutions of varying quantum dot concentrations. Prepare three swelling solutions of decreasing quantum dot concentration by diluting the stock solution to give a 66%solution, a 50%solution, and a 33%solution, as detailed in the text protocol. Store all of the quantum dot solutions under dark conditions at room temperature.Next, cut out four medical grade silicone squares using a fresh scalpel blade. Immerse a medical grade silicone square in each of the four swelling solutions of varying percent quantum dot concentration:stock solution, 66%50%and 33%After the polymer samples swell at room temperature for 24 hours under dark conditions, remove the swollen polymer samples from the respective swelling solutions. Air dry the samples under dark conditions for 48 hours, during which time the residual solvent evaporates and the polymers shrink back to their initial dimensions.Next, wash the quantum dot incorporated samples thoroughly with deionized water to remove any surface bound materials. Then prepare four more medical grade silicone squares. Immerse them in the stock swelling solution for varying time periods:one hour, three hours, six hours, and 24 hours.After removal from the swelling solution, air dry the swollen polymer samples under dark conditions for 48 hours, such that the sample shrinks back to its previous dimensions. Wash the quantum dot incorporated samples thoroughly with deionized water to remove any surface bound materials or residual solvent. Cut out two swell shrink silicone squares with a fresh scalpel blade.Ensure that this exposes the internal surface of the silicone samples. Place the silicone samples on a microscope slide for imaging. Ensure that the freshly cut side of the polymer makes full contact with the glass slide.Press the silicone portion down lightly to ensure a smooth contact with the microscope slide before completing the lifetime fluorescence measurements, as described in the text protocol. Then place the sample on the stage of the microscope. To complete lifetime fluorescence measurements, directly couple the laser output to an acousto-optic tunable filter system to generate the 488 nanometer laser line.Focus the laser beam using a custom-built laser scanning unit which is reflected by a dichroic mirror into the back aperture of a 10X objective and then onto the sample. Refer to the text protocol for instructions on performing measurements and processing data. Chilled quantum dots are characterized using photoluminescence spectroscopy to measure emission, excitation spectra, and the overall quantum yield.The swell-encapsulated quantum dots are highly photoluminescent, therefore brightness is indicative of successful swell encapsulation. Cross sections of the polymer can be mounted in the fluorescence microscope to measure the degree of swell encapsulation. Once mastered, this technique can be done in around 15 minutes with swell encapsulated samples, if it's performed properly.While attempting the procedure, it is important to remember that the blade used for cutting the polymer samples is uncontaminated and relatively sharp, as inconsistencies at this stage may introduce artifacts in the fluorescence images. Following this procedure, other methods like energy dispersive X-ray spectroscopy in addition to functional testing, can be performed to further gauge encapsulation amount or surface concentration. After its development, this technique paved the way for researchers in the field of material science to explore nanoparticle composite design using a range of host matrices.Don't forget that working with cadmium selenide can be extremely hazardous, and precautions, such as wearing suitable personal protective equipment and working in a fume cupboard, should always be taken while performing this procedure.

Research

JoVE Journal

Engineering

Preparation and Evaluation of Hybrid Composites of Chemical Fuel and Multi-walled Carbon Nanotubes in the Study of Thermopower Waves

When a chemical fuel at a certain position in a hybrid composite of the fuel and a micro/nanostructured material is ignited, chemical combustion occurs ...

Failure Analysis of Batteries Using Synchrotron-based Hard X-ray Microtomography

Imaging morphological changes that occur during the lifetime of rechargeable batteries is necessary to understand how these devices fail. Since the advent ...

Advanced Experimental Methods for Low-temperature Magnetotransport Measurement of Novel Materials

Novel electronic materials are often produced for the first time by synthesis processes that yield bulk crystals (in contrast to single crystal thin film ...

Ultrasonic Welding of Thermoplastic Composite Coupons for Mechanical Characterization of Welded Joints through Single Lap Shear Testing

This paper presents a novel straightforward method for ultrasonic welding of thermoplastic-composite coupons in optimum processing conditions. The ...

Use of a Multi-compartment Dynamic Single Enzyme Phantom for Studies of Hyperpolarized Magnetic Resonance Agents

Imaging of hyperpolarized substrates by magnetic resonance shows great clinical promise for assessment of critical biochemical processes in real time. Due ...

Using Synchrotron Radiation Microtomography to Investigate Multi-scale Three-dimensional Microelectronic Packages

Synchrotron radiation micro-tomography (SR&#181;T) is a non-destructive three-dimensional (3D) imaging technique that offers high flux for fast data ...

Nanostructured Ag-zeolite Composites as Luminescence-based Humidity Sensors

Small silver clusters confined inside zeolite matrices have recently emerged as a novel type of highly luminescent materials. Their emission has high ...

Synchrotron X-ray Microdiffraction and Fluorescence Imaging of Mineral and Rock Samples

In this report, we describe a detailed procedure for acquiring and processing&#160;x-ray microfluorescence (&#956;XRF), and Laue and powder ...

Expression of Cementitious Pore Solution and the Analysis of Its Chemical Composition and Resistivity Using X-ray Fluorescence

The goal of this method is to determine the chemical composition and electrical resistivity of cementitious pore solution expressed from a fresh paste ...

Excitation-Scanning Hyperspectral Imaging Microscopy to Efficiently Discriminate Fluorescence Signals

Several techniques rely on detection of fluorescence signals to identify or study phenomena or to elucidate functions. Separation of these fluorescence ...