Name: hydroquinone based synthesis of gold nanorods
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Description: Watch this Scientific Journal Video about Hydroquinone Based Synthesis of Gold Nanorods at JoVE.com

Funding for this research was provided by the Italian Ministry of Health under the frame of EuroNanoMed II (European Innovative Research &amp; Technological Development Projects in Nanomedicine, project title: ''InNaSERSS'').

1. Synthesis of Gold Nanorods
Note: Use highly purified water throughout.
<ol>
	<li>Preparation of the gold seeds
	<ol>
		<li>Dissolve 364.4 mg of hexadecyltrimethylammonium bromide (CTAB) in 5 ml water, under ultrasonication at 40 &#176;C until the solution becomes clear. Let the CTAB solution cool down to room temperature.</li>
		<li>Separately, prepare 5 ml of tetrachloroauric acid (HAuCl4) in water (0.5 mM).</li>
		<li>Add the HAuCl4 solution to the CTAB solution under ...

<ol>
	<li>Zhou, W., Gao, X., Liu, D., Chen, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gold+Nanoparticles+for+In+Vitro+Diagnostics.">Gold Nanoparticles for In Vitro Diagnostics.</a> Chem Rev. 115 (19), 10575-10636 (2015).</li><li>Bao, C., 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=Gold+nanoprisms+as+optoacoustic+signal+nanoamplifiers+for+in+vivo+bioimaging+of+gastrointestinal+cancers.">Gold nanoprisms as optoacoustic signal nanoamplifiers for in vivo bioimaging of gastrointestinal cancers.</a> Small. 9 (1), 68-74 (2013).</li><li>Han, G., Ghosh, P., Rotello, V. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Functionalized+gold+nanoparticles+for+drug+delivery.">Functionalized gold nanoparticles for drug delivery.</a> Nanomedicine. 2 (1), 113-123 (2007).</li><li>Choi, W. I., 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=Tumor+regression+in+vivo+by+photothermal+therapy+based+on+gold-nanorod-loaded,+functional+nanocarriers.">Tumor regression in vivo by photothermal therapy based on gold-nanorod-loaded, functional nanocarriers.</a> ACS Nano. 5 (3), 1995-2003 (2011).</li><li>Langille, M. R., Personick, M. L., Zhang, J., Mirkin, C. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Defining+Rules+for+the+Shape+Evolution+of+Gold+Nanoparticles+.">Defining Rules for the Shape Evolution of Gold Nanoparticles .</a> J. Am. Chem. Soc. 134 (35), 14542-14554 (2012).</li><li>Lohse, S. E., Murphy, C. 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+Quest+for+Shape+Control:+A+History+of+Gold+Nanorod+Synthesis.">The Quest for Shape Control: A History of Gold Nanorod Synthesis.</a> Chem. Mater. 25 (8), 1250-1261 (2013).</li><li>Weissleder, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+clearer+vision+for+in+vivo+imaging.">A clearer vision for in vivo imaging.</a> Nat. Biotech. 19 (4), 316-317 (2001).</li><li>Sau, T. K., Murphy, C. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Seeded+High+Yield+Synthesis+of+Short+Au+Nanorods+in+Aqueous+Solution.">Seeded High Yield Synthesis of Short Au Nanorods in Aqueous Solution.</a> Langmuir. 20 (15), 6414-6420 (2004).</li><li>Ratto, F., Matteini, P., Rossi, F., Pini, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Size+and+shape+control+in+the+overgrowth+of+gold+nanorods.">Size and shape control in the overgrowth of gold nanorods.</a> J. Nanopart. Res. 12, 2029-2036 (2010).</li><li>Morasso, C., 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=Control+of+size+and+aspect+ratio+in+hydroquinone-based+synthesis+of+gold+nanorods.">Control of size and aspect ratio in hydroquinone-based synthesis of gold nanorods.</a> J. Nanopart. Res. 17, 330-337 (2015).</li><li>Vigderman, L., Zubarev, E. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-yield+synthesis+of+gold+nanorods+with+longitudinal+SPR+peak+greater+than+1200+nm+using+hydroquinone+as+a+reducing+agent.">High-yield synthesis of gold nanorods with longitudinal SPR peak greater than 1200 nm using hydroquinone as a reducing agent.</a> Chem. Mater. 25 (8), 1450-1457 (2013).</li><li>Walsh, M. J., Barrow, S. J., Tong, W., Funston, A. M., Etheridge, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Symmetry+breaking+and+silver+in+gold+nanorod+growth.">Symmetry breaking and silver in gold nanorod growth.</a> ACS Nano. 9 (1), 715-724 (2015).</li></ol>

The protocol presented here applies hydroquinone, an aromatic molecule characterized by a weak reduction potential, to produce gold nanorods. There are two main advantages of the present protocol toward the most commonly employed synthetic route based on the use of ascorbic acid: the first is that hydroquinone is able to almost quantitatively reduce the gold ions allowing the production of higher amount of gold nanorods.11 The latter is given by the fact that it requires a lower amount of CTAB and a subsequent...

Gold nanoparticles (AuNPs) are one of the most widespread and promising nanostructures to be used in biomedical applications. Their use is essential in many point-of-care in vitro diagnostics products.1 They have been proposed as an effective tool for a number of other different applications: as a contrast agent in imaging studies,2 as a drug delivery system3 and as drugs for light-induced thermotherapy (or photothermal therapy).4 The great potential of AuNPs has driven, in the last twenty years, intense research on the development of new synthesis that is able to increase the control on the size and shape obtained.5 This is because different kinds of AuNPs are in fact more suitable than others for specific applications.
Among the different gold nanostructures, gold nanorods (AuNRs) have emerged as one of the most interesting systems. AuNRs are characterized by two plasmonic peaks associated with the oscillation of electrons along the longitudinal and the transverse axes, respectively.6 It is particularly important that the position of the most intense longitudinal peak can be tuned precisely between 620 and 800 nm, depending on the aspect ratio of the rods. This region matches the biological window,7 where the human tissues almost do not absorb light, allowing the development of a number of in vivo photonic applications involving AuNPs.
Despite a huge interest in this kind of nanostructures, the synthetic protocols for the preparation of AuNRs suffer from several limitations. In most of the cases, nanorods are prepared according to a two-step method developed by Sau and coworkers.8 In their protocol, nanorods are synthesized by reducing gold ions using ascorbic acid in presence of preformed gold seeds, silver ions and a large amount of hexadecyl trimethylammonium bromide (CTAB), a cationic linear surfactant.
The drawback of this protocol is that the reduction yield of gold ions is relatively low (about 20%) 9 and that a high amount of CTAB, an expensive reagent that accounts for more than half of the total cost for the reagents in the synthesis, is needed. The development of a new and more efficient synthetic route is thence considered to be an important need, allowing the spreading of biomedical approaches based on AuNRs.
In the first part of the present paper, we present an optimized protocol for the preparation of AuNR having an aspect ratio of about three. The synthesis is based on the use of hydroquinone as a mild reducing agent and it allows the preparation of AuNR with an almost quantitative reduction of gold ions, making use of a reduced amount of CTAB.10 This protocol for the preparation of the AuNRs is based on a two-step approach where gold seeds are used in a &#34;growth solution&#34;.
In the second part, we show how to finely tune the size and aspect ratio of the obtained AuNR in two ways. The first way, similar to the standard protocol based on ascorbic acid, is to vary the amount of silver ions present in the &#34;growth solution&#34;. The second way is based on the variation of the amount of CTAB that can be reduced down to a concentration of 10 mM (close to the critical micellar concentration reported by the supplier) to obtain well defined short nanorods.

<table border="0" cellpadding="0" cellspacing="0" width="756">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Gold(III) chloride trihydrate</td>
			<td style="width:115px;">Sigma Aldrich</td>
			<td style="width:99px;">520918</td>
			<td style="width:327px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Hydroquinone</td>
			<td>Sigma Aldrich</td>
			<td>H17902</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Silver Nitrate</td>
			<td>Sigma Aldrich</td>
			<td>209139</td>
			<td>toxic</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sodium Borohydride</td>
			<td>Sigma Aldrich</td>
			<td>480886</td>
			<td></td>
		</tr>
		<tr height="148">
			<td height="148" style="height:148px;width:216px;">Hexadecyltrimethylammonium bromide (CTAB)</td>
			<td>Sigma Aldrich</td>
			<td>H5882</td>
			<td style="width:327px;">Acute Tox. (oral). In this study we tested three different batches of CTAB (H5882) from Sigma Aldrich. Two of them were marked as made in China while one as made in India. In our experience only the batches marked as made in China were effective for the preparation of AuNR</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Spectrophotometer</td>
			<td style="width:115px;">Thermo scientific&#160;</td>
			<td style="width:99px;">Nanodrop 2000C</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:216px;">TEM</td>
			<td style="width:115px;">JEOL</td>
			<td>2100</td>
			<td></td>
		</tr>
	</tbody>
</table>

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.

UV visible spectra of the gold seeds can be seen in Figure 1. UV visible spectra acquired at different times after the injection of the gold seeds are presented in Figure 2. UV visible spectra and transmission electron microscopic (TEM) images of the obtained gold nanorods are shown in Figure 3. UV visible spectra and transmission electron microscopic (TEM) images of gold nanorods with different aspect ratio obtained by varying the amount...

Watch this Scientific Journal Video about Hydroquinone Based Synthesis of Gold Nanorods at JoVE.com

Hydroquinone Based Synthesis of Gold Nanorods

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 ...

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