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 vigorous magnetic stirring, maintaining the temperature constant at 27 &#176;C.</li>
		<li>Prepare 600 &#181;l of sodium borohydride (NaBH4) solution in water (10 mM) at 4 &#176;C. Add this solution to the mixture under vigorous stirring. Check if the solution&#39;s color immediately changes from yellow to brownish.</li>
		<li>Stir the suspension for 20 min before use. Store the seeds suspension for no longer than 24 hr at room temperature.</li>
		<li>Check the dimensions of the seeds using an UV-Vis spectrophotometer. Ensure that the seeds are small enough (about 2 nm) to be used in the preparation of gold nanorods by UV-visible spectroscopy. 
		Note: Spectrum must be similar to what is reported in Figure 1. Larger seeds identified by the presence of a plasmonic peak around 505-520 nm must not be used because they are likely to produce spherical nanoparticles.</li>
	</ol>
	</li>
	<li>Preparation of the &#34;growth solution&#34; of gold nanorods.
	<ol>
		<li>Dissolve 182.2 mg CTAB together with 22 mg hydroquinone in 5 ml water at 40 &#176;C using ultrasonication. Cool down the solution to 27 &#176;C.</li>
		<li>Prepare 200 &#181;l of 4 mM silver nitrate (AgNO3) solution.</li>
		<li>Separately, prepare 5 ml of 1 mM solution of tetrachloroauric acid (HAuCl4).</li>
		<li>First add the silver nitrate solution prepared in step 1.2.2. Then, add the HAuCl4 solution prepared in step 1.2.3 to the solution of CTAB and hydroquinone prepared in step 1.2.1 under magnetic stirring.</li>
		<li>Immediately after, add under magnetic stirring 12 &#181;l of the seeds suspension previously prepared according to the protocol reported at step 1.1 and let the reaction start. Check if the suspension changes color in about 30 min.</li>
		<li>Control the formation of the nanorods by checking the UV-visible spectrum of the suspension, as described in section 4, every 5 min. Proceed until the spectrum is stable. To allow the complete formation of the nanorods, leave the suspension under stirring for further 30 min (Figure 2).</li>
		<li>Divide the suspension in tubes (1 ml of suspension for each tube) and centrifuge at 10,000 x g for 10 min. Gold nanorods form a dark precipitate at the bottom of the tube.</li>
		<li>Resuspend the precipitate of each tube in 1 ml of water. Mix together the content of the tubes and store the suspension of gold nanorods at room temperature.</li>
		<li>Characterize the obtained nanorods by UV-visible spectroscopy and transmission electron microscopy as described in section 4 (Figure 3).</li>
	</ol>
	</li>
</ol>
2. Tuning the Aspect Ratio of Nanorods by Varying the Concentration of Ag+ Ions
<ol>
	<li>Prepare a silver nitrate solution with a concentration of 4 mM, dissolving 3.4 mg AgNO3 in 5 ml of water.</li>
	<li>Prepare in three different vials the solution with CTAB and hydroquinone as described in section 1.2.1 and add respectively 100 &#181;l, 150 &#181;l or 200 &#181;l of silver nitrate solution.</li>
	<li>Add the HAuCl4 solution prepared according to step 1.2.3 and proceed with the preparation of gold nanorods as described from point 1.2.5.</li>
	<li>Characterize the obtained nanorods by UV-visible spectroscopy and transmission electron microscopy. Vials with lower amounts of Ag+ will result in shorter nanorods (aspect ratio of 2 and 2.2 respectively) (Figure 4).</li>
</ol>
3. Tuning the Aspect Ratio of Nanorods by Varying the Concentration of CTAB
<ol>
	<li>Prepare different batches of gold nanorods with different concentrations of CTAB in the &#34;growth solution&#34;. Use concentrations from 10 mM to 100 mM to produce gold nanorods having different size and aspect ratio. The concentrations of CTAB used in each experiment are summarized in Table 1 with the corresponding amount of milligrams used. Dissolve the different amounts of CTAB always with 22 mg of hydroquinone in 5 ml of water.</li>
	<li>Add 200 &#181;l of silver nitrate solution (prepared according to step 1.2.2) and 5 ml of HAuCl4 solution (prepared according how described in step 1.2.3) in each vial under magnetic stirring.</li>
	<li>Add 12 &#181;l of seeds suspension and observe the change in color of the final mixture.</li>
	<li>Stop the stirring when the suspension&#39;s color and the UV-visible spectrum are stabilized; the reaction time depends on the CTAB concentration in the growth solution.</li>
	<li>Centrifuge at 10,000 x g for 10 min and resuspend in water.</li>
	<li>Characterize the obtained nanorods by UV-visible spectroscopy and transmission electron microscopy. A lower concentration of CTAB will result in shorter nanorods while a higher concentration will give longer but larger nanorods. On contrary the aspect ratio of the nanorods will be higher in the range around 40-50 mM and will decrease both at lower and higher concentrations (Figure 5 and Figure 6).</li>
</ol>
4. Characterization of Gold Nanorods
<ol>
	<li>UV-visible Spectroscopy
	<ol>
		<li>Dilute 100 &#181;l of nanorods solution with 400 &#181;l of water in a plastic micro-cuvette and acquire the UV-visible absorption spectrum (wavelength range between 400 and 840 nm) according to manufacturer&#39;s protocol.</li>
		<li>Collect UV-visible spectra (wavelength range between 400 and 840 nm) of the growth solution every 5 min in order to study the kinetics of the reaction.</li>
	</ol>
	</li>
	<li>Transmission Electron Microscopy (TEM)
	<ol>
		<li>Collect TEM images of each sample of nanorods, for the measurement of the size and of the aspect ratio of the obtained nanorods. Prepare the samples by placing a drop of suspension (4 &#181;l) onto an ultra-thin Formvar-coated 200-mesh copper grids and leave to dry in air at 4 &#176;C. Analyze the sample at TEM using an accelerating voltage of 200 kV according to manufacturer&#39;s protocol.</li>
	</ol>
	</li>
</ol>

<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 authors have nothing to disclose.

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 ...

hydroquinone-based-synthesis-of-gold-nanorods

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13.6K Views.  Fondazione Don Carlo Gnocchi ONLUS (Don Carlo Gnocchi Foundation). 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.

Video: Hydroquinone Based Synthesis of Gold Nanorods

Template Directed Synthesis of Plasmonic Gold Nanotubes with Tunable IR Absorbance

A nearly parallel array of pores can be produced by anodizing aluminum foils in acidic environments1, 2. Applications of anodic aluminum oxide (AAO) membranes have been under development since the 1990's and have become a common method to template the synthesis of high aspect ratio nanostructures, mostly by electrochemical growth or pore-wetting. Recently, these membranes have become commercially available in a wide range of pore sizes and densities, leading to an extensive library of functional nanostructures being synthesized from AAO membranes. These include composite nanorods, nanowires and nanotubes made of metals, inorganic materials or polymers 3-10. Nanoporous membranes have been used to synthesize nanoparticle and nanotube arrays that perform well as refractive index sensors, plasmonic biosensors, or surface enhanced Raman spectroscopy (SERS) substrates 11-16, as well as a wide range of other fields such as photo-thermal heating 17, permselective transport 18, 19, catalysis 20, microfluidics 21, and electrochemical sensing 22, 23. Here, we report a novel procedure to prepare gold nanotubes in AAO membranes. Hollow nanostructures have potential application in plasmonic and SERS sensing, and we anticipate these gold nanotubes will allow for high sensitivity and strong plasmon signals, arising from decreased material dampening 15.

Solution-suspendable gold nanotubes with controlled dimensions can be synthesized by electrochemical deposition in porous anodic aluminum oxide (AAO) membranes using a hydrophobic polymer core. Gold nanotubes and nanotube arrays hold promise for applications in plasmonic biosensing, surface-enhanced Raman spectroscopy, photo-thermal heating, ionic and molecular transport, microfluidics, catalysis and electrochemical sensing.

A nearly parallel array of pores can be produced by anodizing aluminum foils in acidic environments1, 2. Applications of anodic aluminum oxide (AAO) ...

Synthesis and Catalytic Performance of Gold Intercalated in the Walls of Mesoporous Silica

As a promising catalytically active nano reactor, gold nanoparticles intercalated in mesoporous silica (GMS) were successfully synthesized and properties of the materials were investigated. We used a one pot sol-gel approach to intercalate gold nano particles in the walls of mesoporous silica. To start with the synthesis, P123 was used as template to form micelles. Then TESPTS was used as a surface modification agent to intercalate gold nano particles. Following this process, TEOS was added in as a silica source which underwent a polymerization process in acid environment. After hydrothermal processing and calcination, the final product was acquired. Several techniques were utilized to characterize the porosity, morphology and structure of the gold intercalated mesoporous silica. The results showed a stable structure of mesoporous silica after gold intercalation. Through the oxidation of benzyl alcohol as a benchmark reaction, the GMS materials showed high selectivity and recyclability.

Here, we present a protocol with a sol-gel process to synthesize gold intercalated in the walls of mesoporous materials (GMS), which is confirmed to possess a mesoporous matrix with gold intercalated in the walls imparting great stability and recyclability.

As a promising catalytically active nano reactor, gold nanoparticles intercalated in mesoporous silica (GMS) were successfully synthesized and properties ...

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 ...

Synthesis and Evaluation of a Ruthenium-based Mitochondrial Calcium Uptake Inhibitor

We detail the synthesis and purification of a mitochondrial calcium uptake inhibitor, [(OH2)(NH3)4Ru(&#181;-O)Ru(NH3)4(OH2)]5+. The optimized synthesis of this compound commences from [Ru(NH3)5Cl]Cl2 in 1 M NH4OH in a closed container, yielding a green solution. Purification is accomplished with cation-exchange chromatography. This compound is characterized and verified to be pure by UV-vis and IR spectroscopy. The mitochondrial calcium uptake inhibitory properties are assessed in permeabilized HeLa cells by fluorescence spectroscopy.

A protocol for the synthesis, purification, and characterization of a ruthenium-based inhibitor of mitochondrial calcium uptake is presented. A procedure to evaluate its efficacy in permeabilized mammalian cells is demonstrated.

We detail the synthesis and purification of a mitochondrial calcium uptake inhibitor, [(OH2)(NH3)4Ru(&#181;-O)Ru(NH3)4(OH2)]5+. The optimized synthesis of ...

Rapid Nanoprobe Signal Enhancement by In Situ Gold Nanoparticle Synthesis

The use of nanoprobes such as gold, silver, silica or iron-oxide nanoparticles as detection reagents in bioanalytical assays can enable high sensitivity and convenient colorimetric readout. However, high densities of nanoparticles are typically needed for detection. The available synthesis-based enhancement protocols are either limited to gold and silver nanoparticles or rely on precise enzymatic control and optimization. Here, we present a protocol to enhance the colorimetric readout of gold, silver, silica, and iron oxide nanoprobes. It was observed that the colorimetric signal can be improved by up to a 10000-fold factor. The basis for such signal enhancement strategies is the chemical reduction of Au3+ to Au0. There are several chemical reactions that enable the reduction of Au3+ to Au0. In the protocol, Good&#39;s buffers and H2O2 are used and it is possible to favor the deposition of Au0 onto the surface of existing nanoprobes, in detriment of the formation of new gold nanoparticles. The protocol consists of the incubation of the microarray with a solution consisting of chloroauric acid and H2O2 in 2-(N-morpholino)ethanesulfonic acid pH 6 buffer following the nanoprobe-based detection assay. The enhancement solution can be applied to paper and glass-based sensors. Moreover, it can be used in commercially available immunoassays as demonstrated by the application of the method to a commercial allergen microarray. The signal development requires less than 5 min of incubation with the enhancement solution and the readout can be assessed by naked eye or low-end image acquisition devices such as a table-top scanner or a digital camera.

Rapid Nanoprobe Signal Enhancement by In Situ Gold Nanoparticle Synthesis

In this work, a protocol for signal enhancement of nanoprobe-based biosensing is presented. The protocol is based on the reduction of chloroauric acid onto the surface of existing nanoprobes that consist of gold, silver, silica or iron-oxide nanoparticles.

The use of nanoprobes such as gold, silver, silica or iron-oxide nanoparticles as detection reagents in bioanalytical assays can enable high sensitivity ...

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 ...

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 ...

Assembly of Gold Nanorods into Chiral Plasmonic Metamolecules Using DNA Origami Templates

The inherent addressability of DNA origami structures makes them ideal templates for the arrangement of metal nanoparticles into complex plasmonic nanostructures. The high spatial precision of a DNA origami-templated assembly allows controlling the coupling between plasmonic resonances of individual particles and enables tailoring optical properties of the constructed nanostructures. Recently, chiral plasmonic systems attracted a lot of attention due to the strong correlation between the spatial configuration of plasmonic assemblies and their optical responses (e.g., circular dichroism [CD]). In this protocol, we describe the whole workflow for the generation of DNA origami-based chiral assemblies of gold nanorods (AuNRs). The protocol includes a detailed description of the design principles and experimental procedures for the fabrication of DNA origami templates, the synthesis of AuNRs, and the assembly of origami-AuNR structures. In addition, the characterization of structures using transmission electron microscopy (TEM) and CD spectroscopy is included. The described protocol is not limited to chiral configurations and can be adapted for the construction of various plasmonic architectures.

We describe the detailed protocol for the DNA origami-based assembly of gold nanorods into chiral plasmonic metamolecules with strong chiroptical responses. The protocol is not limited to chiral configurations and can be easily adapted for the fabrication of various plasmonic architectures.

The inherent addressability of DNA origami structures makes them ideal templates for the arrangement of metal nanoparticles into complex plasmonic ...

Photodeposition of Pd onto Colloidal Au Nanorods by Surface Plasmon Excitation

A protocol is described to photocatalytically guide Pd deposition onto Au nanorods (AuNR) using surface plasmon resonance (SPR). Excited plasmonic hot electrons upon SPR irradiation drive reductive deposition of Pd on colloidal AuNR in the presence of [PdCl4]2-. Plasmon-driven reduction of secondary metals potentiates covalent, sub-wavelength deposition at targeted locations coinciding with electric field &#8220;hot-spots&#8221; of the plasmonic substrate using an external field (e.g., laser). The process described herein details a solution-phase deposition of a catalytically-active noble metal (Pd) from a transition metal halide salt (H2PdCl4) onto aqueously-suspended, anisotropic plasmonic structures (AuNR). The solution-phase process is amenable to making other bimetallic architectures. Transmission UV-vis monitoring of the photochemical reaction, coupled with ex situ XPS and statistical TEM analysis, provide immediate experimental feedback to evaluate properties of the bimetallic structures as they evolve during the photocatalytic reaction. Resonant plasmon irradiation of AuNR in the presence of [PdCl4]2- creates a thin, covalently-bound Pd0 shell without any significant dampening effect on its plasmonic behavior in this representative experiment/batch. Overall, plasmonic photodeposition offers an alternative route for high-volume, economical synthesis of optoelectronic materials with sub-5 nm features (e.g., heterometallic photocatalysts or optoelectronic interconnects).

A protocol for anisotropic photodeposition of Pd onto aqueously-suspended Au nanorods via localized surface plasmon excitation is presented.

A protocol is described to photocatalytically guide Pd deposition onto Au nanorods (AuNR) using surface plasmon resonance (SPR). Excited plasmonic hot ...