This work was partly supported by Nippon Sheet Glass Foundation for Materials Science and Engineering and JSPS KAKENHI (Grant-in-Aid for Challenging Exploratory Research, #50362281).

Caution: Always use caution when working with chemicals and solutions. Follow the appropriate safety practices and wear gloves, glasses, and a lab coat at all times. Be aware that nanomaterials may have additional hazards as compared to their bulk counterpart.
1. Preparation of Regents
<ol>
	<li>Prepare the methyl viologen aqueous solution by dissolving 0.0012 g of 1,1&#39;-dimethyl-4,4&#39;-bipyridinium dichloride (methyl viologen; MV2+) in 20 ml of water to give 0.2 mM MV2+.</li>
	<li>Prepare the gold(III) chloride aqueous solution by dissolving 0.1050 g of gold(III) tetrachloride trihydrate (HAuCl4&#8226; 3H2O) in 10 ml of water to give 25 mM HAuCl4.</li>
	<li>Prepare the sodium borohydride aqueous solution by dissolving 0.03844 g of sodium tetrahydroborate (NaBH4) in 10 ml of water to give 100 mM NaBH4.</li>
	<li>Prepare the 2-ammoniumethanethiol aqueous solution by dissolving 0.2985 g of 2-ammoniumethanethiol chloride salt (2-AET+) in 25 ml of water to give 100 mM 2-AET+.</li>
</ol>
2. Synthesis of TNS Colloidal Suspensions
NOTE: Titania nanosheets (TNS; Ti0.91O2) were prepared according to the well-established procedure reported previously22,23,30.
<ol>
	<li>Prepare the starting material of layered cesium titanate Cs0.7Ti1.825O4 by calcining a stoichiometric mixture of Cs2CO3 (0.4040 g) and TiO2 (ST-01; 0.5000 g) at 800 &#176;C for 20 hr22. Repeat this twice.</li>
	<li>Prepare the protonated layered titanate (H0.7Ti1.825O4&#183;H2O) by repeatedly treating 0.8142 g of cesium titanate with an HCl (100 mM, 81.42 ml) aqueous solution by using a shaker (300 Hz) for 12 hr.</li>
	<li>Prepare the exfoliated layered titanate (TNS) colloidal suspensions by stirring the protonated titanate powder (0.0998 g) vigorously (500 rpm) with 25 ml of a 17 mM tetrabutylammonium hydroxide (TBA+ OH&#8722;) aqueous solution for about 2 weeks at ambient temperature under dark conditions. The resulting opalescent suspension contains exfoliated titania nanosheets (TNS; 1.4 g/L, pH = 11~12).</li>
</ol>
3. Synthesis of TNS Films21
<ol>
	<li>Preparation of TNS cast films (c-TNS)
	<ol>
		<li>Pre-clean glass substrates (~20 x 20 mm2) through ultrasonic treatments using an ultrasonic cleaner (27 kHz) in 1 M aqueous sodium hydroxide (NaOH) for 30 min.</li>
		<li>Rinse the substrates with 5-10 mL of ultrapure water (&#60;0.056 &#181;S cm-1).</li>
		<li>Dip a glass substrate in a 0.1 M aqueous hydrochloric acid (HCl) for 3 min and rinse with 5-10 ml of ultrapure water.</li>
		<li>Clean the substrates through ultrasonic treatments (27 kHz) in pure water for 1 hr, and then rinse with pure water. Dry with a hairdryer for 2-3 min (until dry).</li>
		<li>Cast the colloidal suspension of TNS on the glass substrate in 300 &#181;l aliquots.</li>
		<li>Dry at 60 &#176;C for 2 hr using a dry oven to give the c-TNS film.</li>
	</ol>
	</li>
	<li>Preparation of Sintered TNS Film (s-TNS)
	<ol>
		<li>To achieve thermal fixation of the TNS components on the glass substrate (s-TNS film), sinter the obtained c-TNS film in air at 500 &#176;C for 3 hr (heating from 25 to 500 &#176;C at a rate of 6.8 &#176;C/min) using the oven.</li>
		<li>Repeat the sintering process twice.</li>
	</ol>
	</li>
	<li>Preparation of Films
	<ol>
		<li>When the s-TNS films are immersed in solution, position the deposited s-TNS film so that it faces the top for all experimental procedures.</li>
		<li>Carry out all experiments under dark conditions by covering the setup with aluminum foil to avoid the photoreaction of TNS.</li>
	</ol>
	</li>
	<li>Preparation of Methyl Viologen (MV2+) Intercalated TNS Films (TNS/MV2+)
	<ol>
		<li>Immerse an s-TNS film in an aqueous solution of MV2+ dichloride salt (0.2 mM, 3 ml) in a Petri dish for 7 h at room temperature (RT) under dark conditions.</li>
		<li>Rinse the obtained samples with ultrapure water (5-10 ml) and dry in air at 60 &#176;C using an oven in the dark for ~1 hr.</li>
	</ol>
	</li>
	<li>Preparation of Au(III) Intercalated TNS Films (TNS/Au(III))
	<ol>
		<li>Immerse a TNS/MV2+ film in an aqueous solution of HAuCl4 (25 mM, 3 ml) in a Petri dish for 3 hr at RT under dark conditions.</li>
		<li>Rinse the obtained samples with ultrapure water (5-10 ml) and dry in air at 60 &#176;C using an oven in the dark for ~1 hr.</li>
	</ol>
	</li>
	<li>Synthesis of AuNP within the Interlayer Space of TNS Films (TNS/AuNP)
	<ol>
		<li>Immerse a TNS/Au(III) film in an aqueous solution of NaBH4 (0.1 M, 5 ml) in a Petri dish for 0.5 hr at RT under dark conditions.</li>
		<li>Dry the obtained films in air at 60 &#176;C using an oven in the dark for ~1 hr.</li>
	</ol>
	</li>
	<li>Preparation of 2-AET+ Intercalated TNS Films (TNS/2-AET+)
	<ol>
		<li>Immerse an s-TNS film in an aqueous solution of 2-AET+ Cl&#8722; (0.1 M, 3 ml) in a Petri dish for 24 hr at RT.</li>
		<li>Rinse obtained films with ultrapure water (5-10 ml) and dry in air at 60 &#176;C using an oven in the dark for ~1 hr.</li>
	</ol>
	</li>
	<li>Au(III) and 2-AET+ Co-Intercalated TNS Films (TNS/2-AET+/Au(III)).
	<ol>
		<li>Immerse a TNS/2-AET+ film in an aqueous solution of HAuCl4 (25 mM, 3 ml) for 3 h at RT.</li>
		<li>Rinse the obtained films with ultrapure water (5-10 ml) and dry in air at 60 &#176;C using an oven in the dark for ~1 hr.</li>
	</ol>
	</li>
	<li>Synthesis of AuNP within the Interlayer Space of TNS/2-AET+ Films (TNS/2-AET+/AuNP).
	<ol>
		<li>Immerse a TNS/2-AET+/Au(III) film in an aqueous solution of NaBH4 (0.1 M, 5 ml) in a Petri dish for 0.5 hr at RT under dark conditions.</li>
		<li>Rinse the obtained films with ultrapure water (5-10 ml) and dry in air at 60 &#176;C using oven in the dark for ~1 hr.</li>
	</ol>
	</li>
	<li>Characterizations
	<ol>
		<li>Carry out X-ray diffraction (XRD) analyses21 using a desktop X-ray diffractometer with monochromatized Cu-K&#945; radiation (&#955; = 0.15405 nm), operated at 30 kV and 15 mA.</li>
		<li>Take energy dispersive X-ray spectrometry (EDS) spectra21.</li>
		<li>Employ a multichannel photodetector or steady-state ultraviolet-visible (UV-Vis) absorption spectrophotometer to record UV-Vis absorption spectra for the prepared samples using transmittance mode21.</li>
	</ol>
	</li>
</ol>

We have nothing to disclose.

This manuscript provides a detailed protocol for the in situ synthesis of gold nanoparticles (AuNPs) within the interlayer space of TNS films. This is the first report of the in situ synthesis of AuNPs within the interlayer space of TNS. Moreover, we found that the 2-AET+ works as an effective protective reagent for AuNPs within the interlayer of TNS. These methods hybridized AuNPs and TNS transparent films. TNS films with good optical transparency21 were synthesized through sintering processes (s-TNS films), as presented in the protocol section. The sintering processes are required repeatedly for the complete removal of organic impurities. When the organic impurities remain, the films turn dark gray. Here, the sintering processes were repeated twice as a typical run; however, further repetitions are permissible.
We successfully synthesized AuNP-containing layered TNS films using two intermediate films (i.e., TNS/MV2+ and TNS/2-AET+ films). The two intermediate films were soaked in an aqueous HAuCl4 solution, and considerable amounts of gold species (the occupied space of one Au atom was 1.47-1.61 nm2) were accommodated within the interlayer spaces of the TNS films. This suggests that the MV2+ and 2-AET+ molecules act as effective expanders of the TNS layers (Figures 1B and 2A and Table 1). However, detailed adsorption mechanisms of gold species into the interlayer of TNS are still unclear.
The obtained Au(III)-containing films were soaked in an aqueous NaBH4 solution, and the color of the films immediately changed from clear to purple (Figures 4 and 6), suggesting the formation of AuNPs within the TNS interlayer. Moreover, the AuNP-containing TNS films maintain good optical transparency (see Figure 8A as a typical example) and cohesion against the glass substrate, even when soaked in aqueous MV2+, 2-AET+, and NaBH4 solutions. These methods can apply to other metal ions, such as copper and silver21.
When the TNS/MV2+ film was used as the intermediate, the color of the AuNPs changed within 30 min (Figure 6), suggesting the aggregation of AuNPs within the interlayer space of the TNS. However, the aggregation and color change of the AuNPs were effectively suppressed using the TNS/2-AET+ film as the intermediate (Figure 8). This suggests that 2-AET+ molecules work as effective protective reagents for AuNPs within TNS interlayers, similar to the AuNPs in solution.
The synthesized TNS/2-AET+/AuNPs were stable against oxygen and the characteristic extinction band at 590 nm was maintained beyond 4 months. Such properties and stabilities of AuNPs within TNS interlayers are expected to demonstrate applicability in catalysis, photocatalysis, and the development of cost-effective plasmonic devices.

Various noble metal nanoparticles (MNPs) exhibit characteristic colors or tones due to their localized surface plasmon resonance (LSPR) properties; thus, MNPs can be used in various optical and/or photochemical applications1-4. Recently, combinations of metal oxide semiconductor (MOS) photocatalysts, such as titanium oxide (TiO2) and MNPs, have been thoroughly investigated as new types of photocatalysts5-14. However, in many cases, very small amounts of MNPs exist on the MOS surface, because most MOS particles have relatively low surface areas. On the other hand, layered metal oxide semiconductors (LMOSs) exhibit photocatalytic properties and have a large surface area, typically several hundred square meters per unit g of an LMOS15-17. In addition, various LMOSs have intercalation properties (i.e., various chemical species can be accommodated within their expandable and large interlayer spaces)15-20. Thus, with a combination of MNPs and LMOSs, it is expected that relatively large amounts of MNPs are hybridized with the semiconductor photocatalysts.
We have reported the first in situ synthesis of copper nanoparticles (CuNPs)21 within the interlayer space of LMOS (titania nanosheet; TNS16-30) transparent films through very simple steps. However, the details of the synthetic procedures and the characterization of the other noble MNPs and TNS hybrids have not yet been reported. Moreover, the CuNPs within the TNS layers were easily oxidized and decolorized under ambient conditions21. As such, we focused on gold nanoparticles (AuNPs), because AuNPs are widely used for various optical, photochemical, and catalytic applications, and it is expected that they will be relatively stable against oxidation3-5,7,8,10-14,28,31,32. Here, we report the synthesis of AuNPs within the interlayer space of TNS and show that 2-ammoniumethanethiol (2-AET+; Figure 1 inset) works effectively as a protective reagent for AuNPs within the interlayer of TNS.

<table><tbody><tr><td>Methyl viologen dichloride</td><td>Aldrich Chemical&amp;nbsp; Co., Inc.</td><td>1910-42-5</td><td></td></tr><tr><td>Tetrabutylammonium hydroxide</td><td>TCI</td><td>T1685</td><td></td></tr><tr><td>cesium carbonate</td><td>Kanto Chemical Co., Inc.</td><td>07184-33</td><td></td></tr><tr><td>anatase titanium dixoide</td><td>Ishihara Sangyo Ltd.</td><td>ST-01</td><td></td></tr><tr><td>hydrochloric acid</td><td>Junsei Chemical Co., Ltd.</td><td>20010-0350</td><td></td></tr><tr><td>sodium hydroxide</td><td>Junsei Chemical Co., Ltd.</td><td>195-13775</td><td></td></tr><tr><td>Tetrachloroauric(III) acid trihydrate</td><td>Kanto Chemical Co., Inc.</td><td>17044-60</td><td></td></tr><tr><td>sodium tetrahydroborate</td><td>Junsei Chemical Co., Ltd.</td><td>39245-1210</td><td></td></tr><tr><td>2-ammoniumethanethiol hydrochloride</td><td>TCI</td><td>A0296</td><td></td></tr><tr><td>Ultrapure water (0.056 &amp;micro;S/cm)</td><td></td><td></td><td>Milli-Q water purification system (Direct-Q&lt;sup&gt;&amp;reg;&lt;/sup&gt; 3UV, Millipore)</td></tr><tr><td>Microscope slide (Thickness: 1.0&amp;#8211;1.2 mm)</td><td>Matsunami glass Co., Ltd.</td><td></td><td></td></tr></tbody></table>

in situ synthesis of gold nanoparticles without aggregation in the interlayer space of layered titanate transparent films

Combinations of metal oxide semiconductors and gold nanoparticles (AuNPs) have been investigated as new types of materials. The in situ synthesis of AuNPs within the interlayer space of semiconducting layered titania nanosheet (TNS) films was investigated here. Two types of intermediate films (i.e., TNS films containing methyl viologen (TNS/MV2+) and 2-ammoniumethanethiol (TNS/2-AET+)) were prepared. The two intermediate films were soaked in an aqueous tetrachloroauric(III) acid (HAuCl4) solution, whereby considerable amounts of Au(III) species were accommodated within the interlayer spaces of the TNS films. The two types of obtained films were then soaked in an aqueous sodium tetrahydroborate (NaBH4) solution, whereupon the color of the films immediately changed from colorless to purple, suggesting the formation of AuNPs within the TNS interlayer. When only TNS/MV2+ was used as the intermediate film, the color of the film gradually changed from metallic purple to dusty purple within 30 min, suggesting that aggregation of AuNPs had occurred. In contrast, this color change was suppressed by using the TNS/2-AET+ intermediate film, and the AuNPs were stabilized for over 4 months, as evidenced by the characteristic extinction (absorption and scattering) band from the AuNPs.

Watch this Scientific Journal Video about In Situ Synthesis of Gold Nanoparticles without Aggregation in the Interlayer Space of Layered Titanate Transparent Films at JoVE.com

In Situ Synthesis of Gold Nanoparticles without Aggregation in the Interlayer Space of Layered Titanate Transparent Films

Here, we present a protocol for the in situ synthesis of gold nanoparticles (AuNPs) within the interlayer space of layered titanate films without the aggregation of AuNPs. No spectral change was observed even after 4 months. The synthesized material has expected applications in catalysis, photo-catalysis, and the development of cost-effective plasmonic devices.

In Situ Synthesis of Gold Nanoparticles without Aggregation in the Interlayer Space of Layered Titanate Transparent Films

Combinations of metal oxide semiconductors and gold nanoparticles (AuNPs) have been investigated as new types of materials. The in situ synthesis of AuNPs ...

in-situ-synthesis-gold-nanoparticles-without-aggregation-interlayer

Nanyang Technological University

Research

JoVE Journal

Engineering

8.0K Views.  Niigata University. Here, we present a protocol for the in situ synthesis of gold nanoparticles (AuNPs) within the interlayer space of layered titanate films without the aggregation of AuNPs. No spectral change was observed even after 4 months. The synthesized material has expected applications in catalysis, photo-catalysis, and the development of cost-effective plasmonic devices.

Video: In Situ Synthesis of Gold Nanoparticles without Aggregation in the Interlayer Space of Layered Titanate Transparent Films

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) ...

Chemistry

A Technique to Functionalize and Self-assemble Macroscopic Nanoparticle-ligand Monolayer Films onto Template-free Substrates

This protocol describes a self-assembly technique to create macroscopic monolayer films composed of ligand-coated nanoparticles1,2. The simple, robust and scalable technique efficiently functionalizes metallic nanoparticles with thiol-ligands in a miscible water/organic solvent mixture allowing for rapid grafting of thiol groups onto the gold nanoparticle surface. The hydrophobic ligands on the nanoparticles then quickly phase separate the nanoparticles from the aqueous based suspension and confine them to the air-fluid interface. This drives the ligand-capped nanoparticles to form monolayer domains at the air-fluid interface.&#160; The use of water-miscible organic solvents is important as it enables the transport of the nanoparticles from the interface onto template-free substrates.&#160; The flow is mediated by a surface tension gradient3,4 and creates macroscopic, high-density, monolayer nanoparticle-ligand films.&#160; This self-assembly technique may be generalized to include the use of particles of different compositions, size, and shape and may lead to an efficient assembly method to produce low-cost, macroscopic, high-density, monolayer nanoparticle films for wide-spread applications.

A simple, robust and scalable technique to functionalize and self-assemble macroscopic nanoparticle-ligand monolayer films onto template-free substrates is described in this protocol.

This protocol describes a self-assembly technique to create macroscopic monolayer films composed of ligand-coated nanoparticles1,2. The simple, robust and ...

Synthesis, Assembly, and Characterization of Monolayer Protected Gold Nanoparticle Films for Protein Monolayer Electrochemistry

Colloidal gold nanoparticles protected with alkanethiolate ligands called monolayer protected gold clusters (MPCs) are synthesized and subsequently incorporated into film assemblies that serve as adsorption platforms for protein monolayer electrochemistry (PME). PME is utilized as the model system for studying electrochemical properties of redox proteins by confining them to an adsorption platform at a modified electrode, which also serves as a redox partner for electron transfer (ET) reactions. Studies have shown that gold nanoparticle film assemblies of this nature provide for a more homogeneous protein adsorption environment and promote ET without distance dependence compared to the more traditional systems modified with alkanethiol self-assembled monolayers (SAM).1-3 In this paper, MPCs functionalized with hexanethiolate ligands are synthesized using a modified Brust reaction4 and characterized with ultraviolet visible (UV-Vis) spectroscopy, transmission electron microscopy (TEM), and proton (1H) nuclear magnetic resonance (NMR). MPC films are assembled on SAM modified gold electrode interfaces by using a "dip cycle" method of alternating MPC layers and dithiol linking molecules. Film growth at gold electrode is tracked electrochemically by measuring changes to the double layer charging current of the system. Analogous films assembled on silane modified glass slides allow for optical monitoring of film growth and cross-sectional TEM analysis provides an estimated film thickness. During film assembly, manipulation of the MPC ligand protection as well as the interparticle linkage mechanism allow for networked films, that are readily adaptable, to interface with redox protein having different adsorption mechanism. For example, Pseudomonas aeruginosa azurin (AZ) can be adsorbed hydrophobically to dithiol-linked films of hexanethiolate MPCs and cytochrome c (cyt c) can be immobilized electrostatically at a carboxylic acid modified MPC interfacial layer. In this report, we focus on the film protocol for the AZ system exclusively. Investigations involving the adsorption of proteins on MPC modified synthetic platforms could further the understanding of interactions between biomolecules and man-made materials, and consequently aid the development of biosensor schemes, ET modeling systems, and synthetic biocompatible materials.5-8

Alkanethiolate stabilized gold colloids known as monolayer protected clusters (MPCs) are synthesized, characterized, and assembled into thin films as an adsorption interface for protein monolayer electrochemistry of simple redox protein like Pseudomonas aeruginosa azurin (AZ) and cytochrome c (cyt c).

Colloidal gold nanoparticles protected with alkanethiolate ligands called monolayer protected gold clusters (MPCs) are synthesized and subsequently ...

Bioengineering

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 ...

Synthesis and Reaction Chemistry of Nanosize Monosodium Titanate

This paper describes the synthesis and peroxide-modification of nanosize monosodium titanate (nMST), along with an ion-exchange reaction to load the material with Au(III) ions. The synthesis method was derived from a sol-gel process used to produce micron-sized monosodium titanate (MST), with several key modifications, including altering reagent concentrations, omitting a particle seed step, and introducing a non-ionic surfactant to facilitate control of particle formation and growth. The resultant nMST material exhibits spherical-shaped particle morphology with a monodisperse distribution of particle diameters in the range from 100 to 150&#160;nm. The nMST material was found to have a Brunauer-Emmett-Teller (BET) surface area of 285 m2g-1, which is more than an order of magnitude higher than the micron-sized MST. The isoelectric point of the nMST measured 3.34 pH units, which is a pH unit lower than that measured for the micron-size MST. The nMST material was found to serve as an effective ion exchanger under weakly acidic conditions for the preparation of an Au(III)-exchange nanotitanate. In addition, the formation of the corresponding peroxotitanate was demonstrated by reaction of the nMST with hydrogen peroxide.

The surfactant mediated sol-gel synthesis of nanosized monosodium titanate is described, along with preparation of the corresponding peroxide modified material. An ion-exchange reaction with Au(III) is also presented.

This paper describes the synthesis and peroxide-modification of nanosize monosodium titanate (nMST), along with an ion-exchange reaction to load the ...

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 ...

Fabrication of Periodic Gold Nanocup Arrays Using Colloidal Lithography

Within recent years, the field of plasmonics has exploded as researchers have demonstrated exciting applications related to chemical and optical sensing in combination with new nanofabrication techniques. A plasmon is a quantum of charge density oscillation that lends nanoscale metals such as gold and silver unique optical properties. In particular, gold and silver nanoparticles exhibit localized surface plasmon resonances-collective charge density oscillations on the surface of the nanoparticle-in the visible spectrum. Here, we focus on the fabrication of periodic arrays of anisotropic plasmonic nanostructures. These half-shell (or nanocup) structures can exhibit additional unique light-bending and polarization-dependent optical properties that simple isotropic nanostructures cannot. Researchers are interested in the fabrication of periodic arrays of nanocups for a wide variety of applications such as low-cost optical devices, surface-enhanced Raman scattering, and tamper indication. We present a scalable technique based on colloidal lithography in which it is possible to easily fabricate large periodic arrays of nanocups using spin-coating and self-assembled commercially available polymeric nanospheres. Electron microscopy and optical spectroscopy from the visible to near-infrared (near-IR) was performed to confirm successful nanocup fabrication. We conclude with a demonstration of the transfer of nanocups to a flexible, conformal adhesive film.

We demonstrate the fabrication of periodic gold nanocup arrays using colloidal lithographic techniques and discuss the importance of nanoplasmonic films.

Within recent years, the field of plasmonics has exploded as researchers have demonstrated exciting applications related to chemical and optical sensing ...

Large Area Substrate-Based Nanofabrication of Controllable and Customizable Gold Nanoparticles Via Capped Dewetting

Recent scientific advances in the utilization of metallic nanoparticle for enhanced energy conversion efficiency, improved optical device performance, and high-density data storage have demonstrated the potential benefit of their use in industrial applications. These applications require precise control over nanoparticle size, spacing, and sometimes shape. These requirements have resulted in the use of time and cost intensive processing steps to produce nanoparticles, thus making the transition to industrial application unrealistic. This protocol will resolve this issue by providing a scalable and affordable method for the large-area production of nanoparticle films with improved nanoparticle control compared to the current techniques. In this article, the process will be demonstrated with gold, but other metals can also be used.

This protocol details a novel nano-manufacturing technique that can be used to make controllable and customizable nanoparticle films over large areas based on the self-assembly of dewetting of capped metal films.

Recent scientific advances in the utilization of metallic nanoparticle for enhanced energy conversion efficiency, improved optical device performance, and ...

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 ...

Gold Nanoparticle Synthesis

Gold nanoparticles (Au nanoparticles) that are ~12 nm in diameter were synthesized by rapidly injecting a solution of 150 mg (0.15 mmol) of tetrachloroauric acid in 3.0 g (3.7 mmol, 3.6 mL) of oleylamine (technical grade) and 3.0 mL of toluene into a boiling solution of 5.1 g (6.4 mmol, 8.7 mL) of oleylamine in 147 mL of toluene. While boiling and mixing the reaction solution for 2 hours, the color of the reaction mixture changed from clear, to light yellow, to light pink, and then slowly to dark red. The heat was then turned off, and the solution was allowed to gradually cool down to room temperature for 1 hour. The gold nanoparticles were then collected and separated from the solution using a centrifuge and washed three times; by vortexing and dispersing the gold nanoparticles in 10 mL portions of toluene, and then precipitating the gold nanoparticles by adding 40 mL portions of methanol and spinning them in a centrifuge. The solution was then decanted to remove any remaining byproducts and unreacted starting materials. Drying the gold nanoparticles in a vacuum environment produced a solid black pellet; which could be stored for long periods of time (up to one year) for later use, and then redissolved in organic solvents such as toluene.

A protocol for synthesizing ~12 nm diameter gold nanoparticles (Au nanoparticles) in an organic solvent is presented. The gold nanoparticles are capped with oleylamine ligands to prevent agglomeration. The gold nanoparticles are soluble in organic solvents such as toluene.

In Situ Synthesis of Gold Nanoparticles without Aggregation in the Interlayer Space of Layered Titanate Transparent Films

Summary

Explore More Videos

Chapters in this video

Template Directed Synthesis of Plasmonic Gold Nanotubes with Tunable IR Absorbance

A Technique to Functionalize and Self-assemble Macroscopic Nanoparticle-ligand Monolayer Films onto Template-free Substrates

Synthesis, Assembly, and Characterization of Monolayer Protected Gold Nanoparticle Films for Protein Monolayer Electrochemistry

Atomically Defined Templates for Epitaxial Growth of Complex Oxide Thin Films

Synthesis and Reaction Chemistry of Nanosize Monosodium Titanate

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

Fabrication of Periodic Gold Nanocup Arrays Using Colloidal Lithography

Large Area Substrate-Based Nanofabrication of Controllable and Customizable Gold Nanoparticles Via Capped Dewetting

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

Gold Nanoparticle Synthesis