Name: synthesis of cd-free inp/zns quantum dots suitable for biomedical applications
Uploaded: 2016-02-06T14:00:00
Description: Watch this Scientific Journal Video about Synthesis of Cd-free InP/ZnS Quantum Dots Suitable for Biomedical Applications at JoVE.com

The authors gratefully acknowledge the Department of Chemistry and the Graduate College at Missouri State University for their support of this project. We also acknowledge the Electron Microscopy Laboratory at the Frederick National Laboratory for Cancer Research for use of their transmission electron microscope and carbon-coated grids.

1. Synthesis of Indium Phosphide/Zinc Sulfide (InP/ZnS) Quantum Dots
<ol>
	<li>Synthesis of Indium Phosphide (InP) Quantum Dot Cores
	<ol>
		<li>Fit a 100 ml round bottom, 3-neck, flask with a 12-inch condenser. Add 30 ml oleylamine (OLA), 0.398 g indium (III) chloride (InCl3), 0.245 g zinc (II) chloride (ZnCl2) and stir while evacuating at RT using a vacuum for 1 hr. The solution should appear colorless with a white precipitate.</li>
		<li>Using a heating mantle with a thermocoup...

<ol>
	<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=Semicondictor+clusters,+nanocrystals,+and+quantum+dots.">Semicondictor clusters, nanocrystals, and quantum dots.</a> Science. 271 (5251), 933-937 (1996).</li><li>Michalet, X., 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=Quantum+dots+for+live+cells,+in+vivo+imaging,+and+diagnostics.">Quantum dots for live cells, in vivo imaging, and diagnostics.</a> Science. 307 (5709), 538-544 (2005).</li><li>Jaiswal, J. K., Mattoussi, H., Mauro, J. M., Simon, S. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Long-term+multiple+color+imaging+of+live+cells+using+quantum+dot+bioconjugates.">Long-term multiple color imaging of live cells using quantum dot bioconjugates.</a> Nat. Biotechnol. 21 (1), 47-51 (2009).</li><li>Deerinck, T. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+application+of+fluorescent+quantum+dots+to+confocal,+multiphoton,+and+electron+microscopic+imaging.">The application of fluorescent quantum dots to confocal, multiphoton, and electron microscopic imaging.</a> Toxicol. Pathol. 36 (1), 112-116 (2008).</li><li>Smith, A. M., Duan, H., Mohs, A. M., Nie, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bioconjugated+quantum+dots+for+in+vivo+molecular+and+cellular+imaging.">Bioconjugated quantum dots for in vivo molecular and cellular imaging.</a> Adv. Drug Deliv. Rev. 60 (11), 1226-1240 (2008).</li><li>Jamieson, T., 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=Biological+applications+of+quantum+dots.">Biological applications of quantum dots.</a> Biomaterials. 28 (31), 4717-4732 (2007).</li><li>Lidke, D. S., Arndt-Jovin, D. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Imaging+takes+a+quantum+leap.">Imaging takes a quantum leap.</a> Physiology. 19, 322-325 (2004).</li><li>Fichter, K. M., Flajolet, M., Greengard, P., Vu, T. Q. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Kinetics+of+G-protein-couple+receptor+endosomal+trafficking+pathways+revealed+by+single+quantum+dots.">Kinetics of G-protein-couple receptor endosomal trafficking pathways revealed by single quantum dots.</a> Proc. Natl. Acad. Sci. U.S.A. 107 (43), 18658-18663 (2010).</li><li>Smith, A. M., Ruan, G., Rhyner, M. N., Nie, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Engineering+luminescent+quantum+dots+for+in+vitro+molecular+and+cellular+imaging.">Engineering luminescent quantum dots for in vitro molecular and cellular imaging.</a> Ann. Biomed. Eng. 34 (1), 3-14 (2006).</li><li>Derfus, A. M., Chan, W. C. W., Bhatia, S. N. <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+cytotoxicity+of+semiconductor+quantum+dots.">Probing the cytotoxicity of semiconductor quantum dots.</a> Nano Lett. 4 (1), 11-18 (2004).</li><li>Brunetti, 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=InP/ZnS+as+a+safer+alternative+to+CdSe/ZnS+core/shell+quantum+dots:+in+vitro+and+in+vivo+toxicity+assessment.">InP/ZnS as a safer alternative to CdSe/ZnS core/shell quantum dots: in vitro and in vivo toxicity assessment.</a> Nanoscale. 5 (1), 307-317 (2013).</li><li>Song, W., 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=Amine-derived+synthetic+approach+to+color-tunable+InP/ZnS+quantum+dots+with+high+fluorescent+qualities.">Amine-derived synthetic approach to color-tunable InP/ZnS quantum dots with high fluorescent qualities.</a> J. Nanopart. Res. 15 (1750), (1750).</li><li>Dabbousi, B. O., 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=(CdSe)ZnS+core-shell+quantum+dots:+Synthesis+and+characterization+of+a+size+series+of+highly+luminescent+nanocrystallites.">(CdSe)ZnS core-shell quantum dots: Synthesis and characterization of a size series of highly luminescent nanocrystallites.</a> J. Phys. Chem. B. 101 (46), 9463-9475 (1997).</li><li>Micic, O. I., Curtis, C. J., Jones, K. M., Sprague, J. R., Nozik, A. J. <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+characterization+of+InP+quantum+dots.">Synthesis and characterization of InP quantum dots.</a> J. Phys. Chem. 98 (19), 4966-4969 (1994).</li><li>Qi, L., Gao, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantum+dot-amphipol+nanocomplex+for+intracellular+delivery+and+realtime+imaging+of+siRNA.">Quantum dot-amphipol nanocomplex for intracellular delivery and realtime imaging of siRNA.</a> ACS Nano. 2 (7), 1403-1410 (2008).</li><li>Xie, R., Zheng, L., 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=Nucleation+kinetics+vs+chemical+kinetics+in+the+initial+formation+of+semiconductor+nanocrystals.">Nucleation kinetics vs chemical kinetics in the initial formation of semiconductor nanocrystals.</a> J. Am. Chem. Soc. 131 (42), 15457-15466 (2009).</li><li>Williams, A. T. R., Winfield, S. A., Miller, J. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Relative+fluorescence+quantum+yields+using+a+computer-controlled+luminescence+spectrometer.">Relative fluorescence quantum yields using a computer-controlled luminescence spectrometer.</a> Analyst. 108, 1067-1071 (1983).</li><li>Schindelin, 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=Fiji:+An+open-source+platform+for+biological-image+analysis.">Fiji: An open-source platform for biological-image analysis.</a> Nat. Methods. 9 (7), 676-682 (2012).</li><li>Schnieder, C. A., Rasband, W. S., Eliceiri, K. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=NIH+image+to+ImageJ:+25+years+of+image+analysis.">NIH image to ImageJ: 25 years of image analysis.</a> Nat. Methods. 9, 671-675 (2012).</li><li>Jin, Y., Kannan, S., Wu, M., Zhao, J. X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Toxicity+of+luminescent+silica+nanoparticles+to+living+cells.">Toxicity of luminescent silica nanoparticles to living cells.</a> Chem. Res. Toxicol. 20 (8), 1126-1133 (2007).</li><li>Corazzari, I., Gilardino, A., Dalmazzo, S., Fubini, B., Lovisolo, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Localization+of+CdSe/ZnS+quantum+dots+in+the+lysosomal+acidic+compartment+of+cultured+neurons+and+its+impact+on+viability:+potential+role+of+ion+release.">Localization of CdSe/ZnS quantum dots in the lysosomal acidic compartment of cultured neurons and its impact on viability: potential role of ion release.</a> Toxicol. In Vitro. 27 (2), 752-759 (2013).</li><li>Pons, T., Uyeda, H. T., Medintz, I., Mattoussi, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hydrodynamic+dimensions,+electrophoretic+mobility,+and+stability+of+hydrophilic+quantum+dots.">Hydrodynamic dimensions, electrophoretic mobility, and stability of hydrophilic quantum dots.</a> J. Phys. Chem. B. 110 (41), 20308-20316 (2006).</li><li>Durisic, N., Wiseman, P., Grutter, P., Heyes, C. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+common+mechanism+underlies+the+dark+fraction+formation+and+fluorescence+blinking+of+quantum+dots.">A common mechanism underlies the dark fraction formation and fluorescence blinking of quantum dots.</a> ACS Nano. 3 (5), 1167-1175 (2009).</li><li>Vermehren-Schmaedick, 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=Heterogeneous+intracellular+trafficking+dynamics+of+brain-derived+neurotropic+factor+complexes+in+the+neuronal+soma+revealed+by+single+quantum+dot+tracking.">Heterogeneous intracellular trafficking dynamics of brain-derived neurotropic factor complexes in the neuronal soma revealed by single quantum dot tracking.</a> PLoS ONE. 9 (4), e95113 (2014).</li></ol>

This protocol details the synthesis of highly fluorescent InP/ZnS QDs that can be used in many biological systems. The QD products synthesized here exhibited a single fluorescence emission peak centered at 600 nm with a FWHM of 73 nm (Figure 1), which is comparable to other previously described syntheses12. Reaction time and reaction temperature are extremely crucial steps due to their profound effect on QD synthesis quality and repeatability. After solubilization in water, the QDs were determ...

Quantum dots (QDs) are semiconducting nanocrystals that exhibit fluorescent properties when irradiated with light1. Due to their small size (2-5 nm), which is similar to many larger biomolecules, and ease of biofunctionalization, QDs are an extremely attractive tool for biomedical applications. They have found use in biological labeling, single-molecule live-cell imaging, drug delivery, in vivo imaging, pathogen detection, and cell tracking, among many other uses2-8.
Cd-based QDs have been most commonly used in biomedical applications because of their intense fluorescence and narrow emission peak widths9. However, concerns have been raised due to potential toxicity of Cd2+ ions10 that may be released through degradation of the nanoparticle. Recently, InP-based QDs have been explored as an alternative to Cd-based QDs because they maintain many fluorescence characteristics of Cd-based QDs and may be more biocompatible11. Cd-based QDs have been found to be significantly more toxic than InP-based QDs in in vitro assays at concentrations as low as 10 pM, after only 48 hr11.
The fluorescence emission color of QDs is size-tunable1. That is, as the size of the QD increases, the fluorescence emission is red-shifted. The size and size dispersity of the QD products can be modified by changing the temperature, reaction duration, or precursor concentration conditions during the reaction12. While the emission peak of InP QDs is typically broader and less intense than Cd-based QDs, InP QDs can be made in a large variety of colors designed to avoid spectral overlap, and are sufficiently intense for most biomedical applications12. The synthesis detailed in this protocol yields QDs with a red emission peak centered at 600 nm.
Several steps are taken after synthesis of the QD cores to maintain the optical integrity of the QDs and to make them compatible for biological applications. The surface of the QD core must be protected from oxidation or surface defects that may cause quenching; therefore, a ZnS shell is coated over the core to produce InP/ZnS (core/shell) QDs13. This coating has been shown to protect the photoluminescence of the QD product. The presence of zinc ions during InP QD synthesis has been shown to limit surface defects, as well as decrease size distribution12. Even with the presence of Zn2+ in the reaction medium, synthesis of InZnP are highly unlikely12. After coating, resulting InP/ZnS QDs are coated in hydrophobic ligands such as trioctylphosphine oxide (TOPO) or oleylamine12,14. An amphiphilic polymer can interact with hydrophobic ligands on the QD surface as well as bulk water molecules to impart water solubility15. Amphiphilic polymers with carboxylate chemical groups can be used as &#34;chemical handles&#34; to further functionalize the QDs.
This protocol details the synthesis and functionalization of water-soluble InP/ZnS QDs with very intense fluorescence emission and relatively small size-dispersity. These QDs are potentially less toxic than commonly used CdSe/ZnS QDs. Herein, the synthesis of InP/ZnS QDs provides a practical alternative to Cd-based QDs for biomedical applications.

<table border="0" cellpadding="0" cellspacing="0" width="725">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:232px;">Oleylamine</td>
			<td style="width:92px;">Acros</td>
			<td style="width:119px;">129540010</td>
			<td style="width:283px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:232px;">Zinc (II) chloride</td>
			<td style="width:92px;">Sigma</td>
			<td style="width:119px;">030-003-00-2</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:232px;">Indium (III) chloride</td>
			<td style="width:92px;">Chem-Impex&#160;</td>
			<td style="width:119px;">24560</td>
			<td></td>
		</tr>
		<tr height="27">
			<td height="27" style="height:27px;width:232px;">Tris(dimethylamino)phosphine</td>
			<td style="width:92px;">Encompass</td>
			<td style="width:119px;">50-901-10500</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:232px;">1-dodecanethiol</td>
			<td style="width:92px;">Acros</td>
			<td style="width:119px;">117625000</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:232px;">Hexanes</td>
			<td style="width:92px;">Fisher Sci</td>
			<td style="width:119px;">H292-4</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:232px;">Acetone</td>
			<td style="width:92px;">TransChemical</td>
			<td style="width:119px;">UN 1090</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:232px;">Zinc Stearate</td>
			<td style="width:92px;">Aldrich Chem</td>
			<td style="width:119px;">307564-1KG</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:232px;">Tetrahydrofuran</td>
			<td style="width:92px;">Acros</td>
			<td style="width:119px;">34845-0010</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:232px;">Molecular Water</td>
			<td style="width:92px;">Fisher Sci</td>
			<td style="width:119px;">BP2470-1</td>
			<td></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:232px;">Poly(maleic anhyrdride-alt-1-tetradecene), 3-(dimethylamino)-1-propylamine derivative</td>
			<td style="width:92px;">Sigma</td>
			<td style="width:119px;">90771-1G</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:232px;">Boric acid</td>
			<td style="width:92px;">Fisher Sci</td>
			<td style="width:119px;">BP168-500</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:232px;">Sodium Tetraborate Decahydrate</td>
			<td style="width:92px;">Fisher Sci</td>
			<td style="width:119px;">BP175-500</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:232px;">Rhodamine B</td>
			<td style="width:92px;">Aldrich Chem</td>
			<td style="width:119px;">R95-3</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:232px;">Nitrogen gas</td>
			<td style="width:92px;">Airgas</td>
			<td style="width:119px;">UN1066</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:232px;">Trypan blue</td>
			<td style="width:92px;">Thermo Sci</td>
			<td style="width:119px;">SV30084.01</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:232px;">3 mL plastic Luer-lock syringe</td>
			<td style="width:92px;">BD</td>
			<td style="width:119px;">309657</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:232px;">Luer-lock Needle</td>
			<td style="width:92px;">Air-Tite</td>
			<td style="width:119px;">8300014471</td>
			<td>4 inch, 22 gauge</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:232px;">50 mL polypropyene centrifuge tube</td>
			<td style="width:92px;">Falcon</td>
			<td style="width:119px;">352098</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:232px;">250 mL centrifuge bottle</td>
			<td style="width:92px;">Thermo Sci</td>
			<td>05-562-23</td>
			<td>Nalgene PPCO</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:232px;">5 mL centrifuge tubes</td>
			<td style="width:92px;">Argos-Tech</td>
			<td style="width:119px;">T2076</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:232px;">1.5 mL microcentrifuge tubes</td>
			<td style="width:92px;">Bio Plas</td>
			<td style="width:119px;">4150</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:232px;">0.1 &#956;m Syringe filter</td>
			<td style="width:92px;">Whatman</td>
			<td style="width:119px;">6786-1301</td>
			<td>Puradisc 13 mm nylon filter</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:232px;">Slide-A-Lyzer MINI Dialysis Unit</td>
			<td style="width:92px;">Thermo Sci</td>
			<td style="width:119px;">69590</td>
			<td>20,000 MWCO</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:232px;">Rotary Evaporator</td>
			<td style="width:92px;">Heidolph</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:232px;">Centrifuge 5072</td>
			<td style="width:92px;">Eppendorf</td>
			<td style="width:119px;"></td>
			<td>Swinging Bucket with 50 mL tube adapters</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:232px;">Lambda 650 UV/VIS Spectrometer</td>
			<td style="width:92px;">Perkin Elmer</td>
			<td style="width:119px;"></td>
			<td style="width:283px;">UV-Vis Spectrophotometer</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:232px;">LS 55 Fluorescence Spectrometer</td>
			<td style="width:92px;">Perkin Elmer</td>
			<td style="width:119px;"></td>
			<td style="width:283px;">Fluorometer</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:232px;">Axio Observer.A1</td>
			<td style="width:92px;">Zeiss</td>
			<td style="width:119px;"></td>
			<td>epifluorescence microscope</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:232px;">AxioCam MRm</td>
			<td style="width:92px;">Zeiss</td>
			<td style="width:119px;"></td>
			<td>CCD Camera</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:232px;">Tecnai TF20 Microscope</td>
			<td style="width:92px;">FEI</td>
			<td style="width:119px;"></td>
			<td>Transmisison Electron Miscroscope</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:232px;">TEM Eagle CCD</td>
			<td style="width:92px;">FEI</td>
			<td style="width:119px;"></td>
			<td>TEM CCD Camera</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:232px;">NanoBrook Omni DLS</td>
			<td style="width:92px;">Brookhaven</td>
			<td style="width:119px;"></td>
			<td style="width:283px;">Dynamic Light Scattering Instrument</td>
		</tr>
	</tbody>
</table>

synthesis of cd-free inp/zns quantum dots suitable for biomedical applications

Fluorescent nanocrystals, specifically quantum dots, have been a useful tool for many biomedical applications. For successful use in biological systems, quantum dots should be highly fluorescent and small/monodisperse in size. While commonly used cadmium-based quantum dots possess these qualities, they are potentially toxic due to the possible release of Cd2+ ions through nanoparticle degradation. Indium-based quantum dots, specifically InP/ZnS, have recently been explored as a viable alternative to cadmium-based quantum dots due to their relatively similar fluorescence characteristics and size. The synthesis presented here uses standard hot-injection techniques for effective nanoparticle growth; however, nanoparticle properties such as size, emission wavelength, and emission intensity can drastically change due to small changes in the reaction conditions. Therefore, reaction conditions such temperature, reaction duration, and precursor concentration should be maintained precisely to yield reproducible products. Because quantum dots are not inherently soluble in aqueous solutions, they must also undergo surface modification to impart solubility in water. In this protocol, an amphiphilic polymer is used to interact with both hydrophobic ligands on the quantum dot surface and bulk solvent water molecules. Here, a detailed protocol is provided for the synthesis of highly fluorescent InP/ZnS quantum dots that are suitable for use in biomedical applications.

The uncoated InP cores do not demonstrate substantial visible fluorescence by eye. However, InP/ZnS (core/shell) quantum dots appear to fluoresce brightly by eye under UV irradiation. The fluorescence of InP/ZnS QDs was characterized using fluorescence spectroscopy. The fluorescence spectrum of QDs in hexanes (Figure 1) excited at 533 nm demonstrates one major peak centered at 600 nm with a full width at half maximum (FWHM) of 73 nm. While absorbance (0.2) offset in <stro...

Watch this Scientific Journal Video about Synthesis of Cd-free InP/ZnS Quantum Dots Suitable for Biomedical Applications at JoVE.com

Synthesis of Cd-free InP/ZnS Quantum Dots Suitable for Biomedical Applications

In this protocol, the synthesis of Cd-free InP/ZnS quantum dots (QDs) is detailed. InP-based QDs are gaining popularity due to the toxicity of Cd2+ ions that may be released through nanoparticle degradation. After synthesis, QDs are solubilized in water using an amphiphilic polymer for use in biomedical applications.

Fluorescent nanocrystals, specifically quantum dots, have been a useful tool for many biomedical applications. For successful use in biological systems, ...

Research

JoVE Journal

Chemistry

Preparation of Hydrophobic Metal-Organic Frameworks via Plasma Enhanced Chemical Vapor Deposition of Perfluoroalkanes for the Removal of Ammonia

Plasma enhanced chemical vapor deposition (PECVD) of perfluoroalkanes has long been studied for tuning the wetting properties of surfaces. For high ...

Synthesis of Immunotargeted Magneto-plasmonic Nanoclusters

Magnetic and plasmonic properties combined in a single nanoparticle provide a synergy that is advantageous in a number of biomedical applications ...

Synthesis of Indoxyl-glycosides for Detection of Glycosidase Activities

Indoxyl glycosides proved to be valuable and versatile tools for monitoring glycosidase activities. Indoxyls are released by enzymatic hydrolysis and are ...

Synthesis and Characterization of Supramolecular Colloids

Control over colloidal assembly is of utmost importance for the development of functional colloidal materials with tailored structural and mechanical ...

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 ...

Fabrication and Testing of Photonic Thermometers

In recent years, a push for developing novel silicon photonic devices for telecommunications has generated a vast knowledge base that is now being ...

Synthesis of Core-shell Lanthanide-doped Upconversion Nanocrystals for Cellular Applications

Lanthanide-doped upconversion nanocrystals (UCNs) have attracted much attention in recent years based on their promising and controllable optical ...

Probing the Structure and Dynamics of Interfacial Water with Scanning Tunneling Microscopy and Spectroscopy

Water/solid interfaces are ubiquitous and play a key role in many environmental, biophysical, and technological processes. Resolving the internal ...

Synthesis of Substrate-Bound Au Nanowires Via an Active Surface Growth Mechanism

Advancing synthetic capabilities is important for the development of nanoscience and nanotechnology. The synthesis of nanowires has always been a ...

Escherichia coli-Based Cell-Free Protein Synthesis: Protocols for a robust, flexible, and accessible platform technology

Escherichia coli-Based Cell-Free Protein Synthesis: Protocols for a robust, flexible, and accessible platform technology

Over the last 50 years, Cell-Free Protein Synthesis (CFPS) has emerged as a powerful technology to harness the transcriptional and translational capacity ...