Name: synthesis of ligand-free cds nanoparticles within a sulfur copolymer matrix
Uploaded: 2016-05-01T15:00:00
Description: Watch this Scientific Journal Video about Synthesis of Ligand-free CdS Nanoparticles within a Sulfur Copolymer Matrix at JoVE.com

The authors would like to acknowledge the State of Washington for supporting this research through the University of Washington Clean Energy Institute Exploratory Fellowship Program, and National Science Foundation (NSF) Sustainable Energy Pathway (SEP) Award CHE-1230615.

Caution: Cadmium precursors are highly toxic and must be handled with great care. Wear proper protective equipment, use appropriate engineering controls and consult relevant materials safety data sheets (MSDS). In addition, the formation of nanoparticles may present additional hazards. The reactions described herein are conducted with a standard vacuum gas manifold, in order to conduct the experiments within an inert atmosphere. All chemicals were purchased commercially and used as received. This protocol is based upon a previously developed...

<ol>
	<li>Rosen, E. L., Buonsanti, R., Llordes, A., Sawvel, A. M., Milliron, D. J., Helms, B. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Exceptionally+Mild+Reactive+Stripping+of+Native+Ligands+from+Nanocrystal+Surfaces+by+Using+Meerwein's+Salt.">Exceptionally Mild Reactive Stripping of Native Ligands from Nanocrystal Surfaces by Using Meerwein's Salt.</a> Angew. Chemie Int. Ed. 51 (3), 684-689 (2012).</li><li>Anderson, N. C., Hendricks, M. P., Choi, J. J., Owen, J. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ligand+exchange+and+the+stoichiometry+of+metal+chalcogenide+nanocrystals:+spectroscopic+observation+of+facile+metal-carboxylate+displacement+and+binding.">Ligand exchange and the stoichiometry of metal chalcogenide nanocrystals: spectroscopic observation of facile metal-carboxylate displacement and binding.</a> J. Am. Chem. Soc. 135 (49), 18536-18548 (2013).</li><li>Owen, J. S., Park, J., Trudeau, P. E., Alivisatos, A. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reaction+chemistry+and+ligand+exchange+at+cadmium-selenide+nanocrystal+surfaces.">Reaction chemistry and ligand exchange at cadmium-selenide nanocrystal surfaces.</a> J. Am. Chem. Soc. 130 (37), 12279-12281 (2008).</li><li>Lokteva, I., Radychev, N., Witt, F., Borchert, H., Parisi, J., Kolny-Olesiak, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Surface+Treatment+of+CdSe+Nanoparticles+for+Application+in+Hybrid+Solar+Cells:+The+Effect+of+Multiple+Ligand+Exchange+with+Pyridine.">Surface Treatment of CdSe Nanoparticles for Application in Hybrid Solar Cells: The Effect of Multiple Ligand Exchange with Pyridine.</a> J. Phys. Chem. C. 114 (29), 12784-12791 (2010).</li><li>Martin, T. R., Mazzio, K. A., Hillhouse, H. W., Luscombe, C. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sulfur+copolymer+for+the+direct+synthesis+of+ligand-free+CdS+nanoparticles.">Sulfur copolymer for the direct synthesis of ligand-free CdS nanoparticles.</a> Chem. Commun. 51 (56), 11244-11247 (2015).</li><li>Chung, W. J., 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+use+of+elemental+sulfur+as+an+alternative+feedstock+for+polymeric+materials.">The use of elemental sulfur as an alternative feedstock for polymeric materials.</a> Nat. Chem. 5 (6), 518-524 (2013).</li><li>Nag, A., Kovalenko, M. V., Lee, J. -. S., Liu, W., Spokoyny, B., Talapin, D. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Metal-free+Inorganic+Ligands+for+Colloidal+Nanocrystals+S2-,+HS-,+Se2-,+HSe-,+Te2-,+HTe-,+TeS32-,+OH-,+and+NH2-+as+Surface.">Metal-free Inorganic Ligands for Colloidal Nanocrystals S2-, HS-, Se2-, HSe-, Te2-, HTe-, TeS32-, OH-, and NH2- as Surface.</a> J. Am. Chem. Soc. 133 (27), 10612-10620 (2011).</li><li>Dong, A., 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=A+generalized+ligand-exchange+strategy+enabling+sequential+surface+functionalization+of+colloidal+nanocrystals.">A generalized ligand-exchange strategy enabling sequential surface functionalization of colloidal nanocrystals.</a> J. Am. Chem. Soc. 133 (4), 998-1006 (2011).</li><li>Cossairt, B. M., Juhas, P., Billinge, S., Owen, J. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tuning+the+Surface+Structure+and+Optical+Properties+of+CdSe+Clusters+Using+Coordination+Chemistry.">Tuning the Surface Structure and Optical Properties of CdSe Clusters Using Coordination Chemistry.</a> J. Phys. Chem. Lett. 2 (4), 3075-3080 (2011).</li><li>Lee, E., Park, S. J., Cho, J. W., Gwak, J., Oh, M. -. K., Min, B. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nearly+carbon-free+printable+CIGS+thin+films+for+solar+cell+applications.">Nearly carbon-free printable CIGS thin films for solar cell applications.</a> Sol. Energy Mater. Sol. Cells. 95 (10), 2928-2932 (2011).</li><li>Bucherl, C. N., Oleson, K. R., Hillhouse, H. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thin+film+solar+cells+from+sintered+nanocrystals.">Thin film solar cells from sintered nanocrystals.</a> Curr. Opin. Chem. Eng. 2 (2), 168-177 (2013).</li><li>Cai, Y., 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=Nanoparticle-induced+grain+growth+of+carbon-free+solution-processed+CuIn(S,Se)2+solar+cell+with+6%+efficiency.">Nanoparticle-induced grain growth of carbon-free solution-processed CuIn(S,Se)2 solar cell with 6% efficiency.</a> ACS Appl. Mater. Inter. 5 (5), 1533-1537 (2013).</li><li>Zhou, H., 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=CZTS+nanocrystals:+a+promising+approach+for+next+generation+thin+film+photovoltaics.">CZTS nanocrystals: a promising approach for next generation thin film photovoltaics.</a> Energy Environ. Sci. 6 (10), 2822-2838 (2013).</li><li>Polizzotti, A., Repins, I. L., Noufi, R., Wei, S. -. H., Mitzi, D. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+state+and+future+prospects+of+kesterite+photovoltaics.">The state and future prospects of kesterite photovoltaics.</a> Energy Environ. Sci. 6 (11), 3171-3182 (2013).</li><li>Suehiro, 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=Solution-Processed+Cu2ZnSnS4+Nanocrystal+Solar+Cells:+Efficient+Stripping+of+Surface+Insulating+Layers+using+Alkylating+Agents.">Solution-Processed Cu2ZnSnS4 Nanocrystal Solar Cells: Efficient Stripping of Surface Insulating Layers using Alkylating Agents.</a> J. Phys. Chem. C. 118 (2), 804-810 (2013).</li><li>Graeser, B. K., 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=Synthesis+of+(CuInS2)0.5(ZnS)0.5+Alloy+Nanocrystals+and+Their+Use+for+the+Fabrication+of+Solar+Cells+via+Selenization.">Synthesis of (CuInS2)0.5(ZnS)0.5 Alloy Nanocrystals and Their Use for the Fabrication of Solar Cells via Selenization.</a> Chem. Mater. 26 (14), 4060-4063 (2014).</li><li>Yin, Y., Alivisatos, A. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Colloidal+nanocrystal+synthesis+and+the+organic-inorganic+interface.">Colloidal nanocrystal synthesis and the organic-inorganic interface.</a> Nature. 437 (7059), 664-670 (2005).</li><li>Alivisatos, A. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Semiconductor+Clusters,+Nanocrystals,+and+Quantum+Dots.">Semiconductor Clusters, Nanocrystals, and Quantum Dots.</a> Science. 271 (5251), 933-937 (1996).</li><li>Alivisatos, A. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Perspectives+on+the+Physical+Chemistry+of+Semiconductor+Nanocrystals.">Perspectives on the Physical Chemistry of Semiconductor Nanocrystals.</a> J. Phys. Chem. 100 (95), 13226-13239 (1996).</li><li>Xiao, Q., Xiao, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Surface-defect-states+photoluminescence+in+CdS+nanocrystals+prepared+by+one-step+aqueous+synthesis+method.">Surface-defect-states photoluminescence in CdS nanocrystals prepared by one-step aqueous synthesis method.</a> Appl. Surf. Sci. 255 (16), 7111-7114 (2009).</li><li>Zhang, J. Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Interfacial+Charge+Carrier+Dynamics+of+Colloidal+Semiconductor+Nanoparticles.">Interfacial Charge Carrier Dynamics of Colloidal Semiconductor Nanoparticles.</a> J. Phys. Chem. B. 104 (31), 7239-7253 (2000).</li><li>Joswig, J. -. O., Springborg, M., Seifert, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Structural+and+Electronic+Properties+of+Cadmium+Sulfide+Clusters.">Structural and Electronic Properties of Cadmium Sulfide Clusters.</a> J. Phys. Chem. B. 104 (12), 2617-2622 (2000).</li><li>Unni, C., Philip, D., Gopchandran, K. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Studies+on+optical+absorption+and+photoluminescence+of+thioglycerol-stabilized+CdS+quantum+dots.">Studies on optical absorption and photoluminescence of thioglycerol-stabilized CdS quantum dots.</a> Spectrochim. Acta. A. Mol. Biomol. Spectrosc. 71 (4), 1402-1407 (2008).</li></ol>

We have developed a method to synthesize CdS nanoparticles within a sulfur copolymer matrix. This sulfur copolymer is composed of elemental sulfur and methylstyrene.5 An important feature of this method is that the copolymer can be used as both a high-temperature solvent and a sulfur source that reacts with a cadmium precursor to produce CdS nanoparticles in solution.5 The critical step in the procedure is the synthesis of the sulfur copolymer with a suitable ratio of methylstyrene and sulfur. The u...

Although proven useful for synthesis, conventional aliphatic ligands present a number of challenges for the implementation of nanoparticles in photonic and electrochemical devices. Aliphatic ligands are highly insulating, hydrophobic, and constitute a significant barrier to electrochemical surface reactions.1 Accordingly, several studies have developed ligand exchange and ligand stripping protocols that replace these aliphatic ligands with functional moieties or that strip away the ligands to reveal a bare nanoparticle surface.1-3 These reactions, however, pose several intrinsic problems. They significantly add to the complexity of the synthetic process, do not always go to completion, and can deteriorate the surface of the nanoparticles, which can in turn impose significant problems during device fabrication when using these techniques.4
We have developed a sulfur copolymer that can be used as both a high temperature solvent and sulfur source during the synthesis of CdS nanoparticles.5 This copolymer is based on a network copolymer developed by Chung et al. that uses elemental sulfur and 1,3-diisopropenylbenzene (DIB).6 In our case, a methylstyrene monomer is implemented instead of DIB. The methylstyrene monomer limits cross-linking reactions, which would otherwise produce a high molecular weight network copolymer.5,6 The presence of only one vinylic functional group on the methylstyrene monomer promotes the formation of oligomeric radicals once heated, which allows the sulfur copolymer to operate as a liquid solvent and sulfur source in parallel during the nanoparticle synthesis.5 Specifically, the sulfur polymer is produced by heating elemental sulfur to 150 &#176;C, which causes the S8 rings to transition into a linearly structured liquid sulfur diradical form. Next, methylstyrene is injected into the liquid sulfur in a 1:50 molar ratio of methylstyrene molecules to sulfur atoms.5 The methylstyrene double bond reacts with the sulfur chains to produce the copolymer, as presented in Figure 1.5 The sulfur copolymer is then cooled and the cadmium precursor is added. This mixture is then reheated to 200 &#176;C, during which, the sulfur copolymer melts and the nanoparticle nucleation and growth processes are initiated within the solution.5 A 20:1 molar ratio of sulfur to cadmium precursor is used, so that only some of the sulfur is consumed during the reaction.5 This copolymer stabilizes the nanoparticles by suspending them within a solid polymer matrix once the reaction has been terminated.5 The copolymer can be removed after the synthesis, resulting in the production of CdS nanoparticles that do not have organic coordinating ligands, as depicted in Figure 2.5
The synthetic method presented in this work is relatively simple in comparison with other methods presented in the literature.1-3,7 It is applicable for a diverse range of applications where traditional ligated nanoparticles have proven problematic or undesirable. This technique can open doors to higher throughput testing, where one batch of nanoparticles can be used to examine a complete spectrum of subsequent functionalizations without the need for complex and time consuming ligand stripping or exchange procedures.2,4,8,9 These unligated nanoparticles also offer opportunities to reduce the number of carbon defects commonly observed in printed nanoparticle devices, by eliminating the carbon source.10-16 This detailed protocol is intended to help others implement this new method and to help spur its active use in a variety of fields that will find it of particular significance.

<table>
	<tbody>
		<tr>
			<td>Sulfur (S8), 99.5%</td>
			<td>Sigma Aldrich</td>
			<td>84683</td>
			<td></td>
		</tr>
		<tr>
			<td>&#945;-methylstyrene, 99%</td>
			<td>Sigma Aldrich</td>
			<td>M80903</td>
			<td></td>
		</tr>
		<tr>
			<td>Cadmium acetylacetonate (Cd(acac)), 99.9%</td>
			<td>Sigma Aldrich</td>
			<td>517585</td>
			<td>Highly Toxic</td>
		</tr>
		<tr>
			<td>Chloroform (CHCl3), 99.5%</td>
			<td>Sigma Aldrich</td>
			<td>C2432</td>
			<td></td>
		</tr>
		<tr>
			<td>Hotplate / magnetic stirrer</td>
			<td>IKA RCT&#160;</td>
			<td>3810001</td>
			<td></td>
		</tr>
		<tr>
			<td>Temperature controller with probe and heating mantle</td>
			<td>Oakton Temp 9000</td>
			<td>WD-89800</td>
			<td></td>
		</tr>
		<tr>
			<td>Centrifuge</td>
			<td>Beckman Coulter Allegra X-22</td>
			<td>392186</td>
			<td></td>
		</tr>
		<tr>
			<td>Centrifuge Tubes</td>
			<td>Thermo Scientific</td>
			<td>3114</td>
			<td>Teflon for resistance to chlorinated solvents</td>
		</tr>
		<tr>
			<td>TEM with attached EDS detector</td>
			<td>FEI Tecnai G2 F-20 with EDAX detector</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>TEM Sample Grid</td>
			<td>Ted Pella</td>
			<td>1824</td>
			<td>Ultrathin carbon film substrate with holey carbon support films on a 400 mesh copper grid</td>
		</tr>
		<tr>
			<td>XRD</td>
			<td>Bruker F-8 Focus Diffractometer</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Molybdenum coated soda lime glass substrates</td>
			<td></td>
			<td></td>
			<td>750 nm thick sputtered molybdenum layer</td>
		</tr>
		<tr>
			<td>Quartz Fluorescence Cuvettes</td>
			<td>Sigma Aldrich</td>
			<td>Z803073</td>
			<td>10 mm by 10 mm, 4 polished sides with screw top</td>
		</tr>
		<tr>
			<td>UV-Vis-NIR</td>
			<td>Perkin Elmer Lambda 1050 Spectrometer</td>
			<td></td>
			<td>With 3D WB Detector Module</td>
		</tr>
		<tr>
			<td>PL</td>
			<td>Horiba FL3-21tau Fluorescence Spectrophotometer</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

synthesis of ligand-free cds nanoparticles within a sulfur copolymer matrix

Aliphatic ligands are typically used during the synthesis of nanoparticles to help mediate their growth in addition to operating as high-temperature solvents. These coordinating ligands help solubilize and stabilize the nanoparticles while in solution, and can influence the resulting size and reactivity of the nanoparticles during their formation. Despite the ubiquity of using ligands during synthesis, the presence of aliphatic ligands on the nanoparticle surface can result in a number of problems during the end use of the nanoparticles, necessitating further ligand stripping or ligand exchange procedures. We have developed a way to synthesize cadmium sulfide (CdS) nanoparticles using a unique sulfur copolymer. This sulfur copolymer is primarily composed of elemental sulfur, which is a cheap and abundant material. The sulfur copolymer has the advantages of operating both as a high temperature solvent and as a sulfur source, which can react with a cadmium precursor during nanoparticle synthesis, resulting in the generation of ligand free CdS. During the reaction, only some of the copolymer is consumed to produce CdS, while the rest remains in the polymeric state, thereby producing a nanocomposite material. Once the reaction is finished, the copolymer stabilizes the nanoparticles within a solid polymeric matrix. The copolymer can then be removed before the nanoparticles are used, which produces nanoparticles that do not have organic coordinating ligands. This nascent synthesis technique presents a method to produce metal-sulfide nanoparticles for a wide variety of applications where the presence of organic ligands is not desired.

The TEM image in Figure 3a shows small CdS nanoparticles (3-4 nm) that have nucleated within the sulfur copolymer before the sulfur copolymer has been completely removed. The image in Figure 3a was acquired by taking an aliquot of the nanoparticle solution immediately after the solution reached 200 &#176;C. Figure 3b shows larger nanoparticles (7-10 nm) that have grown in solution for 30 min before the sulfur copolymer has been completely removed. Figure 3c</stro...

Watch this Scientific Journal Video about Synthesis of Ligand-free CdS Nanoparticles within a Sulfur Copolymer Matrix at JoVE.com

Synthesis of Ligand-free CdS Nanoparticles within a Sulfur Copolymer Matrix

Herein we present a method to synthesize ligand-free cadmium sulfide (CdS) nanoparticles based on a unique sulfur copolymer. The sulfur copolymer operates as a high temperature solvent and a sulfur source during the nanoparticle synthesis and stabilizes the nanoparticles after the reaction.

Aliphatic ligands are typically used during the synthesis of nanoparticles to help mediate their growth in addition to operating as high-temperature ...

The overall goal of this synthesis method is to use a sulfur copolymer to produce cadmium sulfide nanoparticles. This method can provide a route for researchers to develop new nanoparticle surface modification reactions. The main advantage of this technique is that it provides a way to easily synthesize nanoparticles that do not have conventional aliphatic ligands.This synthesis method is potentially useful in a range of fields where conventional nanoparticle ligands can be difficult to remove, exchange or block surface reactions. Demonstrating the procedure will be Trevor Martin, a graduate student from my laboratory. To prepare the molten elemental sulfur, place elemental sulfur in a 15 milliliter three-neck flask with an attached condenser and temperature probe.Perform pump and purge cycles with vacuum and nitrogen several times. Heat under nitrogen to 150 degrees Celsius with stirring. This will cause the sulfur to become a yellow-colored liquid.Once all of the sulfur has dissolved into the liquid, immediately inject alpha-methylstyrene into the solution. Heat the solution to 185 degrees Celsius with stirring at 500 RPM for 10 minutes. As the copolymer forms, the solution will change color from yellow to orange, finally producing a deep-red color.Remove the solution from the heat and cool to room temperature. As it cools, the copolymer will slowly crystallize to form an orange, rubbery solid. At this stage, the copolymer can be stored at room temperature for a subsequent synthesis, or it can be used immediately.Add cadmium acetylacetonate to the three-necked flask from the previous step so that the powder is placed evenly on top of the solid sulfur copolymer. Perform pump and purge cycles on the flask with nitrogen, and vacuum several times. It's important to ensure the cadmium precursor mixes into the liquid sulfur copolymer thoroughly and uniformly as soon as the polymer begins to melt so that the nanoparticle formation can begin homogeneously.Heat the solution to 200 degrees Celsius under nitrogen, with stirring. The sulfur copolymer will melt and mix with the cadmium precursor, allowing the nanoparticle nucleation and growth processes to begin. Allow the nanoparticles to grow for 30 minutes before removing the solution from the heat and cooling to room temperature.Once cooled, remove the solid nanocomposite from the flask, and store at room temperature. To remove the sulfur copolymer, place the 200 milligrams of nanocomposite in a 20 milliliter glass vial, and add 20 milliliters of chloroform. Place the vial in an ultrasonicator and sonicate for one hour to break up the nanocomposite and suspend the nanoparticles within the solution.Following sonication, separate the solution into two 30 milliliter centrifuge tubes, and add another 20 milliliters of chloroform to each. Centrifuge the solution at 8, 736 Gs for 15 minutes. Then, decant the sulfur copolymer from the centrifuge tubes, making sure not to disturb the settled nanonparticles.To isolate the settled nanoparticles, redisperse them by adding chloroform to each centrifuge tube and sonicating for 15 minutes. Repeat the centrifugation and redispersion three more times to ensure that all of the sulfur copolymer has been removed. Once all of the sulfur copolymer is removed, the decanted solution will no longer have an orange color.Collect the final nanoparticles by adding two milliliters of chloroform to each centrifuge tube. Combine the collected nanoparticles in one 20 milliliter glass vial. Place the glass vial under vacuum to remove all of the chloroform and to dry the nanoparticles.At this stage, determine the mass of the resulting nanoparticles. Compare this mass to the starting mass of the precursors to determine the yield of the reaction, using molar ratios of the starting material and product. To characterize the cadmium sulfide nanoparticles by transmission electron microscopy, or TEM, dilute 20 milligrams of the isolated nanoparticles in 20 milliliters of chloroform and ultrasonicate for one hour.Dilute this solution in chloroform and sonicate for 15 minutes. Drop the final solution onto an ultra-thin carbon-film substrate with Holey carbon support films on a 400-mesh copper TEM grid. Place the TEM grid in a glass vial.Hold the vial under vacuum overnight to remove any residual solvent from the sample. Once the drying is completed, acquire TEM images using a 200 kilovolt accelerating voltage, a spot size of three and an attached energy dispersive X-ray spectroscopy, or EDS detector. To characterize the cadmium sulfide nanoparticles by X-ray diffraction, dilute the isolated nanoparticles in chloroform at a concentration of 10 milligrams per milliliter.Then, clean the lipton(mumbles)coated sodalime glass substrates by sonicating in detergent, the ionized water, acetone and isopropyl alcohol for 10 minutes in each solvent. Finally, clean the substrates in an air plasma cleaner for 10 minutes prior to drop casting. Next, drop cast the solution onto the prepared substrates in seven microliter increments.Once the films have dried, acquire X-ray diffraction data. Collect data using 7, 000 data points at a scan rate of one data point per second, with a copper K-alpha X-ray source and an incident wavelength of 1.54059 angstroms. To characterize the cadmium sulfide nanoparticles by solution spectroscopy, disperse the isolated nanoparticles in chloroform at 0.1 milligram per milliliter and sonicate for 30 minutes.Then, place the samples in a sealed quartz cuvette. Prepare two additional samples for analysis by dispersing the nanocomposite as well as the sulfur copolymer in formamide both at one milligram per milliliter. Stir each dispersion at 700 RPM, and heat to 70 degrees Celsius to facilitate suspension of the material.Conduct optical absorbance measurements of all three samples using a spectrometer with a triple detector that extends across the ultraviolet, visible and near-infrared ranges. Finally, conduct photoluminescence measurements of all three samples using a fluorescence spectrophotometer with an excitation wavelength of 330 nanometers. Shown here is a TEM image showing three-to four-nanometer-sized cadmium sulfide nanoparticles forming within the sulfur copolymer at the beginning of the reaction.This TEM image shows aggregated nanoparticles once the copolymer has been removed. The inset shows the stoichiometry of the nanoparticles from EDS spectra. Shown here is the X-ray diffraction pattern for the isolated nanoparticles, which is consistent with the formation of cadmium sulfide.Here, spectroscopy data is shown for the isolated nanoparticles once the sulfur copolymer is removed. Once mastered, this nanoparticle synthesis can be completed in several hours. Don't forget that working with cadmium can be hazardous, and precautions such as wearing proper protective equipment should be taken while performing this procedure.After watching this video, you should have a good understanding of how to synthesize metal sulfide nanoparticles using a sulfur copolymer. We believe that this method will help provide a way to easily tune nanoparticle surface chemistry for a variety of applications.

synthesis-ligand-free-cds-nanoparticles-within-sulfur-copolymer

Research

JoVE Journal

Chemistry

Seeded Synthesis of CdSe/CdS Rod and Tetrapod Nanocrystals

We demonstrate a method for the synthesis of multicomponent nanostructures consisting of CdS and CdSe with rod and tetrapod morphologies. A seeded synthesis strategy is used in which spherical seeds of CdSe are prepared first using a hot-injection technique. By controlling the crystal structure of the seed to be either wurtzite or zinc-blende, the subsequent hot-injection growth of CdS off of the seed results in either a rod-shaped or tetrapod-shaped nanocrystal, respectively. The phase and morphology of the synthesized nanocrystals are confirmed using X-ray diffraction and transmission electron microscopy, demonstrating that the nanocrystals are phase-pure and have a consistent morphology. The extinction coefficient and quantum yield of the synthesized nanocrystals are calculated using UV-Vis absorption spectroscopy and photoluminescence spectroscopy. The rods and tetrapods exhibit extinction coefficients and quantum yields that are higher than that of the bare seeds. This synthesis demonstrates the precise arrangement of materials that can be achieved at the nanoscale by using a seeded synthetic approach.

A protocol for the seeded synthesis of rod-shaped and tetrapod-shaped multicomponent nanostructures consisting of CdS and CdSe is presented.

We demonstrate a method for the synthesis of multicomponent nanostructures consisting of CdS and CdSe with rod and tetrapod morphologies. A seeded ...

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 ...

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

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

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

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

Photochemical Oxidative Growth of Iridium Oxide Nanoparticles on CdSe@CdS Nanorods

We demonstrate a procedure for the photochemical oxidative growth of iridium oxide catalysts on the surface of seeded cadmium selenide-cadmium sulfide (CdSe@CdS) nanorod photocatalysts. Seeded rods are grown using a colloidal hot-injection method and then moved to an aqueous medium by ligand exchange. CdSe@CdS nanorods, an iridium precursor and other salts are mixed and illuminated. The deposition process is initiated by absorption of photons by the semiconductor particle, which results with formation of charge carriers that are used to promote redox reactions. To insure photochemical oxidative growth we used an electron scavenger. The photogenerated holes oxidize the iridium precursor, apparently in a mediated oxidative pathway. This results in the growth of high quality crystalline iridium oxide particles, ranging from 0.5 nm to about 3 nm, along the surface of the rod. Iridium oxide grown on CdSe@CdS heterostructures was studied by a variety of characterization methods, in order to evaluate its characteristics and quality. We explored means for control over particle size, crystallinity, deposition location on the CdS rod, and composition. Illumination time and excitation wavelength were found to be key parameters for such control. The influence of different growth conditions and the characterization of these heterostructures are described alongside a detailed description of their synthesis. Of significance is the fact that the addition of iridium oxide afforded the rods astounding photochemical stability under prolonged illumination in pure water (alleviating the requirement for hole scavengers).

A protocol for the photochemical oxidative growth of small crystalline iridium oxide nanoparticles on the surface of CdSe@CdS seeded rod nanoparticles is presented.

We demonstrate a procedure for the photochemical oxidative growth of iridium oxide catalysts on the surface of seeded cadmium selenide-cadmium sulfide ...

Anionic Polymerization of an Amphiphilic Copolymer for Preparation of Block Copolymer Micelles Stabilized by &#960;-&#960; Stacking Interactions

In this study, an amphiphilic copolymer that includes a core-forming block with phenyl groups was synthesized by living anionic polymerization of phenyl glycidyl ether (PheGE) on methoxy-polyethylene glycol (mPEG-b-PPheGE). Characterization of the copolymer revealed a narrow molecular distribution (PDI &#60; 1.03) and confirmed the degree of polymerization of mPEG122-b-(PheGE)15. The critical micelle concentration of the copolymer was evaluated using an established fluorescence method with the aggregation behavior evaluated by dynamic light scattering and transmission electronic microscopy. The potential of the copolymer for use in drug delivery applications was evaluated in a preliminary manner including in vitro biocompatibility, loading and release of the hydrophobic anti-cancer drug doxorubicin (DOX). A stable micelle formulation of DOX was prepared with drug loading levels up to 14% (wt%), drug loading efficiencies &#62; 60% (w/w) and sustained release of drug over 4 days under physiologically relevant conditions (acidic and neutral pH, presence of albumin). The high drug loading level and sustained release is attributed to stabilizing &#960;-&#960; interactions between DOX and the core-forming block of the micelles.

Anionic Polymerization of an Amphiphilic Copolymer for Preparation of Block Copolymer Micelles Stabilized by &amp;#960;-&amp;#960; Stacking Interactions

The key steps of living anionic polymerization of phenyl glycidyl ether (PheGE) on methoxy-polyethylene glycol (mPEG-b-PPheGE) are described. The resulting block copolymer micelles (BCMs) were loaded with doxorubicin 14% (wt%) and sustained release of drug over 4 days under physiologically relevant conditions was obtained.

In this study, an amphiphilic copolymer that includes a core-forming block with phenyl groups was synthesized by living anionic polymerization of phenyl ...

Synthesis of a Thiol Building Block for the Crystallization of a Semiconducting Gyroidal Metal-sulfur Framework

We present a method for preparing thioester molecules as the masked form of the thiol linkers and their utilization for accessing a semiconducting and porous metal-dithiolene network in the highly ordered single crystalline state. Unlike the highly reactive free-standing thiols, which tend to decompose and complicate the crystallization of metal-thiolate open frameworks, the thioester reacts in situ to provide the thiol species, serving to mitigate the reaction between the mercaptan units and the metal centers, and to improve crystallization consequently. Specifically, the thioester was synthesized in a one-pot procedure: an aromatic bromide (hexabromotriphenylene) reacted with excess sodium thiomethoxide under vigorous conditions to first form the thioether intermediate product. The thioether was then demethylated by the excess thiomethoxide to provide the thiolate anion that was acylated to form the thioester product. The thioester was conveniently purified by standard column chromatography, and then used directly in the framework synthesis, wherein NaOH and ethylenediamine serve to revert in situ the thioester to the thiol linker for assembling the single-crystalline Pb(II)-dithiolene network. Compared with other methods for thiol synthesis (e.g., by cleaving alkyl thioether using sodium metal and liquid ammonia), the thioester synthesis here uses simple conditions and economical reagents. Moreover, the thioester product is stable and can be conveniently handled and stored. More importantly, in contrast to the generic difficulty in accessing crystalline metal-thiolate open frameworks, we demonstrate that using the thioester for in situ formation of the thiol linker greatly improves the crystallinity of the solid-state product. We intend to encourage broader research efforts on the technologically important metal-sulfur frameworks by disclosing the synthetic protocol for the thioester as well as the crystalline framework solid.

Here, we present a one-pot, transition-metal-free synthesis of thiols and thioesters from aromatic halides and sodium thiomethoxide, followed by the preparation of single crystals of a metal-dithiolene network using thiol species generated in situ from the more stable and tractable thioester.

We present a method for preparing thioester molecules as the masked form of the thiol linkers and their utilization for accessing a semiconducting and ...

Synthesis of Bimetallic Pt/Sn-based Nanoparticles in Ionic Liquids

We demonstrate a method for the synthesis of bimetallic nanoparticles consisting of Pt and Sn. A synthesis strategy is used in which the particular physico-chemical properties of ionic liquids (ILs) are exploited to control both nucleation and growth processes. The nanoparticles form colloidal sols of very high colloidal stability in the IL, which is particularly interesting in view of their use as quasi-homogeneous catalysts. Procedures for both nanoparticle extraction in conventional solvents and for nanoparticle precipitation are presented. The size, structure and composition of the synthesized nanocrystals are confirmed using inductively coupled plasma atomic emission spectroscopy (ICP-AES), X-ray diffraction analysis (XRD) and transmission electron microscopy (TEM) with energy-dispersive X-ray spectroscopy (EDX). By this, we show that the nanocrystals are random-type alloy and of small (2-3 nm) size. The catalytic activity and selectivity in the hydrogenation of &#945;,&#946;-unsaturated aldehydes is tested in a semi-continuous batch-type reactor. In this context, the bimetallic Pt/Sn-based nanoparticles reveal a high selectivity towards the unsaturated alcohol.

A protocol for the synthesis of bimetallic nanoparticles in ionic liquids and the procedure of their catalytic testing in the selective hydrogenation of unsaturated aldehydes are described.

We demonstrate a method for the synthesis of bimetallic nanoparticles consisting of Pt and Sn. A synthesis strategy is used in which the particular ...

Molten-Salt Synthesis of Complex Metal Oxide Nanoparticles

The development of feasible synthesis methods is critical for the successful exploration of novel properties and potential applications of nanomaterials. Here, we introduce the molten-salt synthesis (MSS) method for making metal oxide nanomaterials. Advantages over other methods include its simplicity, greenness, reliability, scalability, and generalizability. Using pyrochlore lanthanum hafnium oxide (La2Hf2O7) as a representative, we describe the MSS protocol for the successful synthesis of complex metal oxide nanoparticles (NPs). Furthermore, this method has the unique ability to produce NPs with different material features by changing various synthesis parameters such as pH, temperature, duration, and post-annealing. By fine-tuning these parameters, we are able to synthesize highly uniform, non-agglomerated, and highly crystalline NPs. As a specific example, we vary the particle size of the La2Hf2O7&#160;NPs by changing the concentration of the ammonium hydroxide solution used in the MSS process, which allows us to further explore the effect of particle size on various properties. It is expected that the MSS method will become a more popular synthesis method for nanomaterials and more widely employed in the nanoscience and nanotechnology community in the upcoming years.

Here, we demonstrate a unique, relatively low-temperature, molten-salt synthesis method for preparing uniform complex metal oxide lanthanum hafnate nanoparticles.

The development of feasible synthesis methods is critical for the successful exploration of novel properties and potential applications of nanomaterials. ...

Synthesis and Characterization of Amphiphilic Gold Nanoparticles

Gold nanoparticles covered with a mixture of 1-octanethiol (OT) and 11-mercapto-1-undecane sulfonic acid (MUS) have been extensively studied because of their interactions with cell membranes, lipid bilayers, and viruses. The hydrophilic ligands make these particles colloidally stable in aqueous solutions and the combination with hydrophobic ligands creates an amphiphilic particle that can be loaded with hydrophobic drugs, fuse with the lipid membranes, and resist nonspecific protein adsorption. Many of these properties depend on nanoparticle size and the composition of the ligand shell. It is, therefore, crucial to have a reproducible synthetic method and reliable characterization techniques that allow the determination of nanoparticle properties and the ligand shell composition. Here, a one-phase chemical reduction, followed by a thorough purification to synthesize these nanoparticles with diameters below 5 nm, is presented. The ratio between the two ligands on the surface of the nanoparticle can be tuned through their stoichiometric ratio used during synthesis. We demonstrate how various routine techniques, such as transmission electron microscopy (TEM), nuclear magnetic resonance (NMR), thermogravimetric analysis (TGA), and ultraviolet-visible (UV-Vis) spectrometry, are combined to comprehensively characterize the physicochemical parameters of the nanoparticles.

Amphiphilic gold nanoparticles can be used in many biological applications. A protocol to synthesize gold nanoparticles coated by a binary mixture of ligands and a detailed characterization of these particles is presented.

Gold nanoparticles covered with a mixture of 1-octanethiol (OT) and 11-mercapto-1-undecane sulfonic acid (MUS) have been extensively studied because of ...

Synthesis of Terpolymers at Mild Temperatures Using Dynamic Sulfur Bonds in Poly(S-Divinylbenzene)

Elemental sulfur (S8) is a byproduct of the petroleum industry with millions of tons produced annually. Such abundant production and limited applications lead to sulfur as a cost-efficient reagent for polymer synthesis. Inverse vulcanization combines elemental sulfur with a variety of monomers to form functional polysulfides without the need for solvents. Short reaction times and straight forward synthetic methods have led to rapid expansion of inverse vulcanization. However, high reaction temperatures (&#62;160 &#176;C) limit the types of monomers that can be used. Here, the dynamic sulfur bonds in poly(S-divinylbenzene) are used to initiate polymerization at much lower temperatures. The S-S bonds in the prepolymer are less stable than S-S bonds in S8, allowing radical formation at 90 &#176;C rather than 159 &#176;C. A variety of allyl and vinyl ethers have been incorporated to form terpolymers. The resulting materials were characterized by 1H NMR, gel permeation chromatography, and differential scanning calorimetry, as well as examining changes in solubility. This method expands on the solvent-free, thiyl radical chemistry utilized by inverse vulcanization to create polysulfides at mild temperatures. This development broadens the range of monomers that can be incorporated thus expanding the accessible material properties and possible applications.

Synthesis of Terpolymers at Mild Temperatures Using Dynamic Sulfur Bonds in PolyS-Divinylbenzene

The goal of this protocol is to initiate polymerization using dynamic sulfur bonds in poly(S-divinylbenzene) at mild temperatures (90 &#176;C) without using solvents. Terpolymers are characterized by GPC, DSC and 1H NMR, and tested for changes in solubility.

Elemental sulfur (S8) is a byproduct of the petroleum industry with millions of tons produced annually. Such abundant production and limited applications ...