Name: photochemical oxidative growth of iridium oxide nanoparticles on cdse@cds nanorods
Uploaded: 2016-02-11T15:00:00
Description: Watch this Scientific Journal Video about Photochemical Oxidative Growth of Iridium Oxide Nanoparticles on CdSe@CdS Nanorods at JoVE.com

This research was supported by the I-CORE Program of the Planning and Budgeting Committee and The Israel Science Foundation (Grant No. 152/11). We thank the Schulich Faculty of Chemistry and the Technion - Israel Institute of Technology for the renovated laboratory and startup package. We also thank the Royal Society of Chemistry for permission in adapting materials from http://dx.doi.org/10.1039/C4TA06164K for use in this manuscript. Dr. Kalisman thanks the Schulich postdoctoral fellowship for their support. We thank Dr. Yaron Kauffmann for his assistance with HR-TEM and HAADF as well as Dr. Kamira Weinfeld for her assistance with XPS characterization.

1. Synthesis of Quantum Dots21
<ol>
	<li>Preparation of TOP:Se Precursor
	<ol>
		<li>Combine 58 mg of Se powder with 0.360 g of Tri-n-octylphosphine (TOP) in a vial with a septum.</li>
		<li>Sonicate the TOP:Se mixture until it is clear with no solids.</li>
	</ol>
	</li>
	<li>Synthesis of CdSe
	<ol>
		<li>Combine 3.0 g trioctylphosphine oxide (TOPO), 280 mg n-octadecylphosphonic acid (ODPA), and 60 mg CdO with a 3 mm x 8 mm cylindrical stir bar in a 25 ml 3-neck round bottom flask equipped with a thermocoupl...

<ol>
	<li>Maeda, 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=Photocatalyst+releasing+hydrogen+from+water.">Photocatalyst releasing hydrogen from water.</a> Nature. 440 (7082), 295-295 (2006).</li><li>Jacobson, M. Z., Colella, W. G., Golden, D. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cleaning+the+Air+and+Improving+Health+with+Hydrogen+Fuel-Cell+Vehicles.">Cleaning the Air and Improving Health with Hydrogen Fuel-Cell Vehicles.</a> Science. 308 (5730), 1901-1905 (2005).</li><li>Hoffmann, M. R., Martin, S. T., Choi, W., Bahnemann, D. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Environmental+Applications+of+Semiconductor+Photocatalysis.">Environmental Applications of Semiconductor Photocatalysis.</a> Chem. Rev. 95 (1), 69-96 (1995).</li><li>Dukovic, G., Merkle, M. G., Nelson, J. H., Hughes, S. M., 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=Photodeposition+of+Pt+on+Colloidal+CdS+and+CdSe/CdS+Semiconductor+Nanostructures.">Photodeposition of Pt on Colloidal CdS and CdSe/CdS Semiconductor Nanostructures.</a> Adv. Mater. 20 (22), 4306-4311 (2008).</li><li>Menagen, G., Macdonald, J. E., Shemesh, Y., Popov, I., Banin, U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Au+Growth+on+Semiconductor+Nanorods:+Photoinduced+versus+Thermal+Growth+Mechanisms.">Au Growth on Semiconductor Nanorods: Photoinduced versus Thermal Growth Mechanisms.</a> J. Am. Chem. Soc. 131 (47), 17406-17411 (2009).</li><li>Alemseghed, M. G., Ruberu, T. P. A., Vela, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Controlled+Fabrication+of+Colloidal+Semiconductor-Metal+Hybrid+Heterostructures:+Site+Selective+Metal+Photo+Deposition.">Controlled Fabrication of Colloidal Semiconductor-Metal Hybrid Heterostructures: Site Selective Metal Photo Deposition.</a> Chem. Mater. 23 (15), 3571-3579 (2011).</li><li>Frame, F. 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=Photocatalytic+Water+Oxidation+with+Nonsensitized+IrO2+Nanocrystals+under+Visible+and+UV+Light.">Photocatalytic Water Oxidation with Nonsensitized IrO2 Nanocrystals under Visible and UV Light.</a> J. Am. Chem. Soc. 133 (19), 7264-7267 (2011).</li><li>Iwase, A., Kato, H., Kudo, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Novel+Photodeposition+Method+in+the+Presence+of+Nitrate+Ions+for+Loading+of+an+Iridium+Oxide+Cocatalyst+for+Water+Splitting.">A Novel Photodeposition Method in the Presence of Nitrate Ions for Loading of an Iridium Oxide Cocatalyst for Water Splitting.</a> Chemistry Letters. 34 (7), 946-947 (2005).</li><li>Kalisman, P., Kauffmann, Y., Amirav, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Photochemical+oxidation+on+nanorod+photocatalysts.">Photochemical oxidation on nanorod photocatalysts.</a> J. Mater. Chem. 3 (7), 3261-3265 (2015).</li><li>Ryu, W. 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=Crystalline+IrO2-decorated+TiO2+nanofiber+scaffolds+for+robust+and+sustainable+solar+water+oxidation.">Crystalline IrO2-decorated TiO2 nanofiber scaffolds for robust and sustainable solar water oxidation.</a> J. Mater. Chem. A. 2 (16), 5610-5615 (2014).</li><li>Nakagawa, T., Bjorge, N. S., Murray, R. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrogenerated+IrOx+Nanoparticles+as+Dissolved+Redox+Catalysts+for+Water+Oxidation.">Electrogenerated IrOx Nanoparticles as Dissolved Redox Catalysts for Water Oxidation.</a> J. Am. Chem. Soc. 131 (43), 15578-15579 (2009).</li><li>Talapin, D. V., 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=Seeded+Growth+of+Highly+Luminescent+CdSe/CdS+Nanoheterostructures+with+Rod+and+Tetrapod+Morphologies.">Seeded Growth of Highly Luminescent CdSe/CdS Nanoheterostructures with Rod and Tetrapod Morphologies.</a> Nano Lett. 7 (10), 2951-2959 (2007).</li><li>Carbone, L., 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+and+Micrometer-Scale+Assembly+of+Colloidal+CdSe/CdS+Nanorods+Prepared+by+a+Seeded+Growth+Approach.">Synthesis and Micrometer-Scale Assembly of Colloidal CdSe/CdS Nanorods Prepared by a Seeded Growth Approach.</a> Nano Lett. 7 (10), 2942-2950 (2007).</li><li>Amirav, L., 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=Photocatalytic+Hydrogen+Production+with+Tunable+Nanorod+Heterostructures.">Photocatalytic Hydrogen Production with Tunable Nanorod Heterostructures.</a> J. Phys. Chem. Lett. 1 (7), 1051-1054 (2010).</li><li>Nakibli, Y., Kalisman, P., Amirav, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Less+Is+More:+The+Case+of+Metal+Cocatalysts.">Less Is More: The Case of Metal Cocatalysts.</a> J. Phys. Chem. Lett. 6, 2265-2268 (2015).</li><li>Lupo, M. G., 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=Ultrafast+Electron-Hole+Dynamics+in+Core/Shell+CdSe/CdS+Dot/Rod+Nanocrystals.">Ultrafast Electron-Hole Dynamics in Core/Shell CdSe/CdS Dot/Rod Nanocrystals.</a> Nano Lett. 8 (12), 4582-4587 (2008).</li><li>Raino, G., 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=Probing+the+Wave+Function+Delocalization+in+CdSe/CdS+Dot-in-Rod+Nanocrystals+by+Time-+and+Temperature-Resolved+Spectroscopy.">Probing the Wave Function Delocalization in CdSe/CdS Dot-in-Rod Nanocrystals by Time- and Temperature-Resolved Spectroscopy.</a> ACS Nano. 5 (5), 4031-4036 (2011).</li><li>Talapin, D. V., Lee, J. S., Kovalenko, M. V., Shevchenko, E. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Prospects+of+Colloidal+Nanocrystals+for+Electronic+and+Optoelectronic+Applications.">Prospects of Colloidal Nanocrystals for Electronic and Optoelectronic Applications.</a> Chem. Rev. 110 (1), 389-458 (2010).</li><li>Kraus, R. M., 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=Room-Temperature+Exciton+Storage+in+Elongated+Semiconductor+Nanocrystals.">Room-Temperature Exciton Storage in Elongated Semiconductor Nanocrystals.</a> Phys. Rev. Lett. 98 (1), 017401 (2007).</li><li>She, C., Demorti&#232;re, A., Shevchenko, E. V., Pelton, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Using+Shape+to+Control+Photoluminescence+from+CdSe/CdS+Core/Shell+Nanorods.">Using Shape to Control Photoluminescence from CdSe/CdS Core/Shell Nanorods.</a> J. Phys. Chem. Lett. 2 (12), 1469-1475 (2011).</li><li>Manthiram, K., Beberwyck, B. J., Talapin, D. V., 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=Seeded+Synthesis+of+CdSe/CdS+Rod+and+Tetrapod+Nanocrystals.">Seeded Synthesis of CdSe/CdS Rod and Tetrapod Nanocrystals.</a> J. Vis. Exp. (82), (2013).</li><li>Yu, W. W., Qu, L., Guo, W., Peng, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Experimental+Determination+of+the+Extinction+Coefficient+of+CdTe,+CdSe,+and+CdS+Nanocrystals.">Experimental Determination of the Extinction Coefficient of CdTe, CdSe, and CdS Nanocrystals.</a> Chem. Mater. 15 (14), 2854-2860 (2003).</li><li>Miao, M. S., Seshadri, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rh2O3+versus+IrO2:+relativistic+effects+and+the+stability+of+Ir4.">Rh2O3 versus IrO2: relativistic effects and the stability of Ir4.</a> J. Phys. Condens. Matter. 24 (21), 215503 (2012).</li><li>Amirav, L., 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=Luminescence+Studies+of+Individual+Quantum+Dot+Photocatalysts.">Luminescence Studies of Individual Quantum Dot Photocatalysts.</a> J. Am. Chem. Soc. 135 (35), 13049-13053 (2013).</li><li>Vaneski, A., Schneider, J., Susha, A. S., Rogach, A. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Aqueous+synthesis+of+CdS+and+CdSe/CdS+tetrapods+for+photocatalytic+hydrogen+generation.">Aqueous synthesis of CdS and CdSe/CdS tetrapods for photocatalytic hydrogen generation.</a> APL Materials. 2 (1), 012104 (2014).</li></ol>

The synthesis of CdSe seeds and CdSe@CdS seeded rods has been well studied21,24,25. Slight modifications to the amounts, temperatures, and times for steps of the synthesis of these substrate particles can be used to tune their length, diameter, and/or morphology. The synthetic protocol described herein yields highly photoluminescent seeded-rods of uniform dimensions.
The ligand exchange procedure allows for the use of seeded rods in polar environments, in this case water. At the fin...

Photocatalysis presents an attractive and promising solution for renewable energy generation and other environmental applications such as water treatment and air purification1-3. Overall water splitting, driven by solar energy, could be a source of clean and renewable hydrogen fuel; however, despite decades of research, systems that are sufficiently stable and efficient for practical use have not yet been realized.
Both photodeposition and semiconductor-mediated photocatalysis rely on the same mechanism of separating photo-generated electron-hole pairs and driving them to the surface where they can initiate redox reactions. The similarities between these two processes make photodeposition an attractive synthetic tool for the field of photocatalysis4-6. This method is expected to take photocatalyst production to new and unexplored frontiers. It might potentially offer pristine control over the spatial arrangement of the different components in a heterostructures, and advance the ability to construct sophisticated nanoparticle systems. Ultimately the method will bring us one step closer to realizing an efficient photocatalyst for direct solar-to-fuel energy conversion.
We investigated the growth of IrO2 as a co-catalyst, as it is known to be an efficient catalyst for water oxidation7-11. A tunable structure of quantum dot (CdSe) embedded in a rod (cadmium sulfide)12,13 was used as our photocatalyst substrate14,15. It is currently undetermined whether the oxidative pathway occurs via a mediated pathway, or by a direct hole attack. Here, our knowledge and control over the photogenerated holes in the semiconductor heterostructure can be harnessed for a mechanistic study of oxidation reactions. This is made possible by the substrate architecture, which facilitates localization of confined holes16,17 and formation of a distinct oxidation reaction site on the rod. The use of nanoscale materials with localized charge carrier can be exploited for mechanistic studies of redox reactions by simple examination of the products. In this way photodeposition can be used as a unique probe of both reduction and oxidation reaction pathways. This is one example of the new and exciting possibilities afforded by the combination of photodeposition and cutting edge colloidal synthesis18-20.
The quest to develop an efficient photocatalyst for water splitting and renewable energy conversion has become an important thrust within the materials community. This has spurred worldwide interest in CdS, which is known to be highly active for hydrogen production, though it is hampered by photochemical instability. Our work here treats the Achilles heel of the material. IrO2 decorated CdSe@CdS rods demonstrate remarkable photochemical stability under prolonged illumination in pure water.

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	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">Sulfur (S)</td>
			<td style="width:79px;">Sigma</td>
			<td style="width:119px;">84683</td>
			<td style="width:321px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Selenium (Se)</td>
			<td>Sigma</td>
			<td>229865</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Cadmium Oxide (CdO)</td>
			<td>Sigma</td>
			<td>202894</td>
			<td>Highly Toxic</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">n-Octadecylphosphonic acid (ODPA)</td>
			<td>Sigma</td>
			<td>715166</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Propylphosphonic acid (PPA)</td>
			<td>Sigma</td>
			<td>305685</td>
			<td>Highly regulated in some countries and regions</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Butylphosphonic acid (BPA)</td>
			<td>Sigma</td>
			<td>737933</td>
			<td>Alternative to PPA</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Hexylphosphonic acid (HPA)</td>
			<td>Sigma</td>
			<td>750034</td>
			<td>Alternative to PPA</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Trioctylphosphonic oxide (TOPO)</td>
			<td>Sigma</td>
			<td>346187</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Tri-n-octylphosphine, 97% (TOP)</td>
			<td>Sigma</td>
			<td>718165</td>
			<td>Air sensitive</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Spectrochemical Stirbar</td>
			<td>Sigma</td>
			<td><a href="http://www.sigmaaldrich.com/catalog/product/sigma/z363545?lang=en&amp;region=US">Z363545</a></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sodium Hydroxide</td>
			<td>Sigma</td>
			<td>S5881</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Methanol</td>
			<td>Sigma</td>
			<td>322415</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Toluene</td>
			<td>Sigma</td>
			<td>244511</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Hexane</td>
			<td>Sigma</td>
			<td>296090</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Octylamine</td>
			<td>Sigma</td>
			<td>74988</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Nonanoic Acid</td>
			<td>Sigma</td>
			<td>N5502</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Isopropanol</td>
			<td>Sigma</td>
			<td>278475</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Mercaptoundecanoic Acid (MUA)</td>
			<td>Sigma</td>
			<td>674427</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Tetramethylammonium Hydroxide (TMAH)</td>
			<td>Sigma</td>
			<td>T7505</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Apiezon H Grease (high temperature grease)</td>
			<td>Sigma</td>
			<td>Z273562</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sodium Persulfate</td>
			<td>Sigma</td>
			<td>216232</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sodium Nitrate</td>
			<td>Sigma</td>
			<td>229938</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sodium Hexachloroiridate(III) hydrate</td>
			<td>Sigma</td>
			<td>288160</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Mounted 455nm LED</td>
			<td>Thorlabs</td>
			<td>M455L3</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Cuvette Holder</td>
			<td>Thorlabs</td>
			<td>CVH100</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">25mL 3-neck Round Bottom Flask</td>
			<td>Chemglass</td>
			<td>CG-1524-A-02</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Liebig Condensor</td>
			<td>Chemglass</td>
			<td>CG-1218-A-20</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">T-Joint Adapter</td>
			<td>Chemglass</td>
			<td>AF-0509-10</td>
			<td></td>
		</tr>
	</tbody>
</table>

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).

Transmission electron micrographs (TEM) were collected in order to see the distribution of iridium oxide on the seeded rods (Figure 1). TEM samples were prepared by pipetting a drop of dissolved particles onto a TEM grid. X-ray diffraction (XRD, Figure 2) and X-ray photoelectron spectra (XPS, Figure 3) were used to characterize the observed growth as a mix of crystalline IrO2 and Ir2O3. Preparation of XRD ...

Watch this Scientific Journal Video about Photochemical Oxidative Growth of Iridium Oxide Nanoparticles on CdSe@CdS Nanorods at JoVE.com

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

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 ...

The overall goal of this procedure is to grow iridium oxide nanocrystals on a semiconductor substrate by photochemical oxidation. Photochemical oxidation as a synthetic tool expands the methods by which chemists can create new hybrid materials. They can photocatalyze production to unexplored frontiers.Our work treats the Achilles heel of cadmium sulfide, which is known to be highly active for hydrogen production, but is hampered by photochemical instability. Photochemical oxidation, when applied on nanoscale materials with localized charge carriers can also be exploited from a kinistic styleze of redox reactions by simple examination of the products. To start, first synthesize cadmium sulfide-cadmium selenide seeded rods, and then suspend them in toluene solution indicated in the text protocol.Transfer about half of the solution to a centrifuge tube, and add up to a one-half volume of methanol to precipitate the rods. Centrifuge the tube at 3, 400 Gs for five minutes, and decant the supernatant. Retain the pellet for later use.Next, add 250 milligrams of mercaptoundecanoic acid and 400 milligrams of tetramethylammonium hydroxide to 10 milliliters of methanol in a centrifuge tube. Vortex until all the solids are dissolved. Add the methanol mixture to the cadmium sulfide-cadmium selenide seeded rod pellet, and shake the tube by hand to fully dissolve it.Allow the solution to sit for at least one hour. After one hour, split the solution into two centrifuge tubes, and add 20 milliliters of toluene to each tube. Centrifuge the tubes at 7, 700 Gs for 15 minutes.Carefully decant the clear supernatant, and invert the centrifuge tubes to dry the samples. Add five milliliters of ultrapure water to the pellets, and then store the rods in foil-wrapped vials. To begin, make solutions of iridium precursor, sodium nitrate, sodium persulfate, and sodium hydroxide as indicated in the text protocol.Add 0.50 milliliters of the nitrate solution to 0.20 milliliters of the iridium precursor in a standard polystyrene cuvette equipped with a spectroscopic stir bar. Next, add 0.30 milliliters of the seeded rods in water, followed by 0.50 milliliters of the persulfate solution, and 0.50 milliliters of the sodium hydroxide solution. Place the cuvette in a holder, and stir the solution.Then illuminate the sample at 450 nanometers and 100 milliwatts for up to four hours. The solution should turn green, and then blue. After the desired incubation time, transfer the solution to a tube, and centrifuge for 10 minutes at 7, 700 Gs.Carefully decant the supernatant and retain the pellet.Disperse by sonicating in polar methanol solvent for further use. The visual appearance of the cadmium sulfide-cadmium selenide rods changes when coated with iridium oxide using irradiation. The uncoated rods begin orange-red in color, which after two hours of illumination turns green, and then blue after four hours of illumination.Transmission electron micrographs were used to analyze the growth of the iridium oxide particles on the cadmium sulfide-cadmium selenide seeded rods over time. Control samples with no iridium oxide have rods of four to five nanometers in diameter. Samples illuminated for 10 minutes to four hours show the progression from small to larger particles with a full coating of iridium oxide.Rods that were illuminated for four hours have a total diameter of nine to ten nanometers, with a two to three nanometer thick outer coating of iridium oxide evident after two hours of illumination. Once mastered, this technique can be done in a few hours if it is properly performed. After watching this video, you should have a good understanding of how to photochemically grow iridium oxide on seeded rods.The methods used in this procedure can be extended towards the photochemical growth of other metal oxides as well. Don't forget that working with cadmium oxide and highly caustic solutions can be extremely hazardous, and precautions such as working in a glove box and wearing protective clothing should always be taken while performing this procedure.

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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 ...

Atomically Defined Templates for Epitaxial Growth of Complex Oxide Thin Films

Atomically defined substrate surfaces are prerequisite for the epitaxial growth of complex oxide thin films. In this protocol, two approaches to obtain such surfaces are described. The first approach is the preparation of single terminated perovskite SrTiO3 (001) and DyScO3 (110) substrates. Wet etching was used to selectively remove one of the two possible surface terminations, while an annealing step was used to increase the smoothness of the surface. The resulting single terminated surfaces allow for the heteroepitaxial growth of perovskite oxide thin films with high crystalline quality and well-defined interfaces between substrate and film. In the second approach, seed layers for epitaxial film growth on arbitrary substrates were created by Langmuir-Blodgett (LB) deposition of nanosheets. As model system Ca2Nb3O10- nanosheets were used, prepared by delamination of their layered parent compound HCa2Nb3O10. A key advantage of creating seed layers with nanosheets is that relatively expensive and size-limited single crystalline substrates can be replaced by virtually any substrate material.

Various procedures are outlined to prepare atomically defined templates for epitaxial growth of complex oxide thin films. Chemical treatments of single crystalline SrTiO3 (001) and DyScO3 (110) substrates were performed to obtain atomically smooth, single terminated surfaces. Ca2 Nb3 O10- nanosheets were used to create atomically defined templates on arbitrary substrates.

Atomically defined substrate surfaces are prerequisite for the epitaxial growth of complex oxide thin films. In this protocol, two approaches to obtain ...

Hydroquinone Based Synthesis of Gold Nanorods

Gold nanorods are an important kind of nanoparticles characterized by peculiar plasmonic properties. Despite their widespread use in nanotechnology, the synthetic methods for the preparation of gold nanorods are still not fully optimized. In this paper we describe a new, highly efficient, two-step protocol based on the use of hydroquinone as a mild reducing agent. Our approach allows the preparation of nanorods with a good control of size and aspect ratio (AR) simply by varying the amount of hexadecyl trimethylammonium bromide (CTAB) and silver ions (Ag+) present in the "growth solution". By using this method, it is possible to markedly reduce the amount of CTAB, an expensive and cytotoxic reagent, necessary to obtain the elongated shape. Gold nanorods with an aspect ratio of about 3 can be obtained in the presence of just 50 mM of CTAB (versus 100 mM used in the standard protocol based on the use of ascorbic acid), while shorter gold nanorods are obtained using a concentration as low as 10 mM.

This paper describes a protocol for the synthesis of gold nanorods, based on the use of hydroquinone as reducing agent, plus the different mechanisms for controlling their size and aspect ratio.

Gold nanorods are an important kind of nanoparticles characterized by peculiar plasmonic properties. Despite their widespread use in nanotechnology, the ...

In Situ Detection and Single Cell Quantification of Metal Oxide Nanoparticles Using Nuclear Microprobe Analysis

Micro-analytical techniques based on chemical element imaging enable the localization and quantification of chemical composition at the cellular level. They offer new possibilities for the characterization of living systems and are particularly appropriate for detecting, localizing and quantifying the presence of metal oxide nanoparticles both in biological specimens and the environment. Indeed, these techniques all meet relevant requirements in terms of (i) sensitivity (from 1 up to 10 &#181;g.g-1 of dry mass), (ii) micrometer range spatial resolution, and (iii) multi-element detection. Given these characteristics, microbeam chemical element imaging can powerfully complement routine imaging techniques such as optical and fluorescence microscopy. This protocol describes how to perform a nuclear microprobe analysis on cultured cells (U2OS) exposed to titanium dioxide nanoparticles. Cells must grow on and be exposed directly in a specially designed sample holder used on the optical microscope and in the nuclear microprobe analysis stages. Plunge-freeze cryogenic fixation of the samples preserves both the cellular organization and the chemical element distribution. Simultaneous nuclear microprobe analysis (scanning transmission ion microscopy, Rutherford backscattering spectrometry and particle induced X-ray emission) performed on the sample provides information about the cellular density, the local distribution of the chemical elements, as well as the cellular content of nanoparticles. There is a growing need for such analytical tools within biology, especially in the emerging context of Nanotoxicology and Nanomedicine for which our comprehension of the interactions between nanoparticles and biological samples must be deepened. In particular, as nuclear microprobe analysis does not require nanoparticles to be labelled, nanoparticle abundances are quantifiable down to the individual cell level in a cell population, independently of their surface state.

In Situ Detection and Single Cell Quantification of Metal Oxide Nanoparticles Using Nuclear Microprobe Analysis

We describe a procedure for the detection of chemical elements present in situ in human cells as well as their in vitro quantification. The method is well-suited to any cell type and is particularly useful for quantitative chemical analyses in single cells following in vitro metal oxide nanoparticles exposure.

Micro-analytical techniques based on chemical element imaging enable the localization and quantification of chemical composition at the cellular level. ...

Ligand-Mediated Nucleation and Growth of Palladium Metal Nanoparticles

The size, size distribution and stability of colloidal nanoparticles are greatly affected by the presence of capping ligands. Despite the key contribution of capping ligands during the synthesis reaction, their role in regulating the nucleation and growth rates of colloidal nanoparticles is not well understood. In this work, we demonstrate a mechanistic investigation of the role of trioctylphosphine (TOP) in Pd nanoparticles in different solvents (toluene and pyridine) using in situ SAXS and ligand-based kinetic modeling. Our results under different synthetic conditions reveal the overlap of nucleation and growth of Pd nanoparticles during the reaction, which contradicts the LaMer-type nucleation and growth model. The model accounts for the kinetics of Pd-TOP binding for both, the precursor and the particle surface, which is essential to capture the size evolution as well as the concentration of particles in situ. In addition, we illustrate the predictive power of our ligand-based model through designing the synthetic conditions to obtain nanoparticles with desired sizes. The proposed methodology can be applied to other synthesis systems and therefore serves as an effective strategy for predictive synthesis of colloidal nanoparticles.

The main goal of this work is to elucidate the role of capping agents in regulating the size of palladium nanoparticles by combining in situ small angle x-ray scattering (SAXS) and ligand-based kinetic modeling.

The size, size distribution and stability of colloidal nanoparticles are greatly affected by the presence of capping ligands. Despite the key contribution ...

Solvothermal Synthesis of MIL-96 and UiO-66-NH2 on Atomic Layer Deposited Metal Oxide Coatings on Fiber Mats

Metal-organic frameworks (MOFs), which contain reactive metal clusters and organic ligands allowing for large porosities and surface areas, have proven effective in gas adsorption, separations, and catalysis. MOFs are most commonly synthesized as bulk powder, requiring additional processes to adhere them to functional devices and fabrics that risk decreasing the powder porosity and adsorption capacity. Here, we demonstrate a method of first coating fabrics with metal oxide films using atomic layer deposition (ALD). This process creates conformal films of controllable thickness on each fiber, while providing a more reactive surface for MOF nucleation. By submerging the ALD coated fabric in solution during solvothermal MOF synthesis, the MOFs create a conformal, well-adhered coating on the fibers, resulting in a MOF-functionalized fabric, without additional adhesion materials that may block MOF pores and functional sites. Here we demonstrate two solvothermal synthesis methods. First, we form a MIL-96(Al) layer on polypropylene fibers using synthetic conditions that convert the metal oxide to MOF. Using initial inorganic films of varying thicknesses, diffusion of the organic linker into the inorganic allows us to control the extent of MOF loading on the fabric. Second, we perform a solvothermal synthesis of UiO-66-NH2 in which the MOF nucleates on the conformal metal oxide coating on polyamide-6 (PA-6) fibers, thereby producing a uniform and conformal thin film of MOF on the fabric. The resulting materials can be directly incorporated into filter devices or protective clothing and eliminate the maladroit qualities of loose powder.

Solvothermal Synthesis of MIL-96 and UiO-66-NH2 on Atomic Layer Deposited Metal Oxide Coatings on Fiber Mats

Metal-organic frameworks are effective in gas storage and heterogeneous catalysis, but typical synthesis methods result in loose powders that are difficult to incorporate into smart materials. We demonstrate a method of first coating fabrics with ALD metal oxides, resulting in conformal films of MOF on the fabrics during solvothermal synthesis.

Metal-organic frameworks (MOFs), which contain reactive metal clusters and organic ligands allowing for large porosities and surface areas, have proven ...

Chemoselective Preparation of 1-Iodoalkynes, 1,2-Diiodoalkenes, and 1,1,2-Triiodoalkenes Based on the Oxidative Iodination of Terminal Alkynes

We present the chemoselective synthesis of 1-(iodoethynyl)-4-methylbenzene, 1-(1,2-diiodovinyl)-4-methylbenzene, and 1-methyl-4-(1,2,2-triiodovinyl)benzene as representative examples for the practical chemoselective preparation of 1-iodoalkynes, 1,2-diiodoalkenes, and 1,1,2-triiodoalkenes from the chemoselective iodination of terminal alkynes mediated by hypervalent-iodine reagents. The chemoselectivity was confirmed by using p-tolylethyne as a model substrate to screen a variety of iodine sources and/or the hypervalent-iodine reagents. A combination of tetrabutylammonium iodide (TBAI) and (diacetoxyiodo)benzene (PIDA) selectively generates 1-iodoalkynes, while a combination of KI and PIDA generates 1,2-diiodoalkenes. A one-pot synthesis based on both TBAI-PIDA and KI-PIDA yields the corresponding 1,1,2-triiodoalkenes. These protocols were subsequently applied to the synthesis of synthetically important aromatic and aliphatic 1-iodoalkynes, 1,2-diiodoalkenes, and 1,1,2-triiodoalkenes, which were obtained in good yield with excellent chemoselectivity.

Herein, detailed protocols for the oxidative iodination of terminal alkynes using hypervalent-iodine reagents are presented, which chemoselectively afford 1-iodoalkynes, 1,2-diiodoalkenes, and 1,1,2-triiodoalkenes.

We present the chemoselective synthesis of 1-(iodoethynyl)-4-methylbenzene, 1-(1,2-diiodovinyl)-4-methylbenzene, and ...

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. ...

Growth of Gold Dendritic Nanoforests on Titanium Nitride-coated Silicon Substrates

In this study, a high-power impulse magnetron sputtering system is used to coat a flat and firm titanium nitride (TiN) film on silicon (Si) wafers, and a fluoride-assisted galvanic replacement reaction (FAGRR) is employed for the rapid and easy deposition of gold dendritic nanoforests (Au DNFs) on the TiN/Si substrates. Scanning electron microscopy (SEM) images and energy-dispersive X-ray spectroscopy patterns of TiN/Si and Au DNFs/TiN/Si samples validate that the synthesis process is accurately controlled. Under the reaction conditions in this study, the thickness of the Au DNFs increases linearly to 5.10 &#177; 0.20 &#181;m within 15 min of the reaction. Therefore, the employed synthesis procedure is a simple and rapid approach for preparing Au DNFs/TiN/Si composites.

This study presents a feasible procedure for synthesizing gold dendritic nanoforests on titanium nitride/silicon substrates. The thickness of gold dendritic nanoforests increases linearly within 15 min of a synthesis reaction.

In this study, a high-power impulse magnetron sputtering system is used to coat a flat and firm titanium nitride (TiN) film on silicon (Si) wafers, and a ...

Design, Synthesis, and Photochemical Properties of Clickable Caged Compounds

Caged compounds enable the photo-mediated manipulation of the cell physiology with high spatiotemporal resolution. However, the limited structural diversity of currently available caging groups and the difficulties in synthetic modification without sacrificing their photolysis efficiencies are obstacles to expanding the repertoire of caged compounds for live cell applications. As the chemical modification of coumarin-type photo-caging groups is a promising approach for the preparation of caged compounds with diverse physical and chemical properties, we report a method for the synthesis of clickable caged compounds that can be modified easily with various functional units via the copper(I)-catalyzed Huisgen cyclization. The modular platform molecule contains a (6-bromo-7-hydroxycoumarin-4-yl)methyl (Bhc) group as a photo-caging group, which exhibits a high photolysis efficiency compared to those of the conventional 2-nitrobenzyls. General procedures for the preparation of clickable caged compounds containing amines, alcohols, and carboxylates are presented. Additional properties such as the water solubility and cell targeting ability can be readily incorporated into clickable caged compounds. Furthermore, the physical and photochemical properties, including the photolysis quantum yield, were measured and were found to be superior to those of the corresponding Bhc caged compounds. The described protocol could therefore be considered a potential solution for the lack of structural diversity in the available caged compounds.

A protocol for the synthesis and measurement of the photochemical properties of modular caged compounds with clickable moieties is presented.