This work was supported by an NSF CAREER Award No. 0954345.

1. CVD Synthesis of Nitrogen-doped Carbon Nanotube Cups (NCNCs)
NCNCs were synthesized employing chemical vapor deposition (CVD) technique on quartz substrate using liquid precursors (Figure 1A).
<ol>
	<li>Place a 3 ft long quartz tube (2.5 cm i.d.) in a Lindberg/Blue tube furnace as the reaction chamber. Place a quartz plate (1" &times; 12") inside the tube as the substrate for product collection. Seal the quartz tube using homemade stainless steel caps with built-in gas and liquid injection connections/tubes.</li>
	<li>Make a solution of liquid precursor containing 0.75 wt% ferrocene, 10 wt% acetonitrile and 89.25 wt% xylenes. Before the growth, draw about 5 ml of liquid precursor into a gas tight syringe connected to the inlet to the quartz tube. Place the syringe on a syringe pump.</li>
	<li>Assemble the CVD system. Connect all gas inlet and outlet. Flow Ar (845 sccm) to purge the CVD system and check leakage using Snoop liquid leak detector. After purging for 20 min, turn on H2. Set the flow rate of H2 to 37.5 sccm and Ar to 127 sccm. Turn on the furnace. Set the temperature of the furnace to 800 &deg;C and wait till it is stable at 800 &deg;C.</li>
	<li>Use the syringe pump to inject the liquid precursor into the quartz tube. Set the injection rate at 9 ml/hr for 6 min to fill the dead volume of the injector tube. Then turn down the injection rate to 1 ml/hr for the growth of NCNCs. After 90 min of growth, turn off the syringe pump and H2 gas flow, and shut down the furnace. Keep Ar flowing to maintain an inert atmosphere until the furnace was cooled down to RT.</li>
	<li>Disconnect all gas inlets and outlets, and the injection system. Disassemble the CVD system and take the quartz plate out. Use a one-sided razor blade to peel off the NCNCs film from the quartz plate. Disperse the collected product in ethanol. Respiratory protection is needed to prevent inhaling possible carbon materials if the work is conducted outside of fume hood.</li>
</ol>
2. Oxidation of As-synthesized NCNCs by a Mixture of Acids
<ol>
	<li>Transfer about 10 mg of as-synthesized NCNCs to a 200 ml round-bottom flask. Add 7.5 ml of concentrated HNO3 to the flask. Briefly sonicate the mixture in water bath for better dispersion. Then add 22.5 ml of concentrated H2SO4 slowly. (CAUTION: the strong acid mixture is highly corrosive; carefully handle these acids with safety protection.) Sonicate the reaction mixture in water bath at RT for 4 hr.</li>
	<li>Dilute the reaction mixture with 100 ml of water while cooling down in ice bath. Filter the mixture through a polytetrafluoroethylene(PTFE) membrane with pore size of 220 nm using a water aspirator.</li>
	<li>Wash the material on the filter membrane with 200 ml of 0.01 M NaOH solution to remove any acidic residual byproduct.18 Then wash with 200 ml of 0.01 M HCl solution, followed by copious amount of water until a neutral pH of the filtrate was achieved. Disperse the resultant material (oxidized NCNCs) in water (20 ml) by sonication. The resulted suspension can be stored at RT for further experiments.</li>
</ol>
3. Physical Separation of NCNCs by Probe-tip Sonication
<ol>
	<li>Transfer the suspension of oxidized NCNCs in water to a 100 ml plastic cup placed in ice bath. Fill the plastic cup to the 50 ml mark with water. Set the probe-tip sonicator equipped with a 1/4" diameter titanium microtip at 60% maximum magnitude (12 W). Submerge the microtip to the center of the solution and then process for 12 hr with 30 sec on/off interval. Change the ice every 30 min to prevent overheating.</li>
	<li>Stop the sonication. Filter the NCNC suspension through a 220 nm pore-size PTFE filter membrane to remove any large particles. The resultant NCNC samples can be store at RT for further applications.</li>
	<li>(Optional) As a comparison experiment, disperse another sample of as-synthesized NCNCs in DMF and directly sonicate the suspension with probe-tip sonication for 12 hr at the same settings as above.</li>
</ol>
4. Quantitative Analysis of Amine Functional Groups on NCNCs by Kaiser Test
<ol>
	<li>Prepare the reagent A: mix 1 g of phenol and 250 &mu;l of EtOH in 2.5 ml of pyridine, add 50 &mu;l of 0.01 M hydrindantin in H2O to the mixture. Prepare the reagent B: dissolve ninhydrin (50 mg) in 1 ml of EtOH.</li>
	<li>Weighed the NCNCs samples (~0.5 mg) on a microbalance and disperse them in 1 ml of 3:2 EtOH/water in small test tubes. Add 100 &mu;l of Reagent A and 25 &mu;l of Reagent B to the sample suspension. Seal the test tubes with parafilms and heat the mixture at 100 &deg;C oil bath for 10 min. Filter the sample through a syringe filter to remove solid particles and collect the filtrate solution.</li>
	<li>Take the visible spectra on the filtrate for colorimetric analysis with the blank sample made in the same process without adding NCNCs. Record the absorbance of the peak centered at 570 nm and calculate the amine loadings according to the Beer-Lambert law.</li>
</ol>
5. Functionalization of NCNCs with GNPs
<ol>
	<li>Sonicate 4 ml of aqueous suspension containing separated NCNCs (0.01 mg/ml) using a water-bath sonicator for 5 min to achieve a uniform dispersion.</li>
	<li>Add 1 ml of HAuCl4 aqueous solution (1 mg/ml) to the NCNC suspension during sonication. Then add 250 &mu;l of 1 wt% trisodium citrate aqueous solution dropwise. Vigorously stir the reaction mixture was at 70 &deg;C on a hot plate for 2 hr.</li>
	<li>Centrifuge the reaction mixture at 3,400 rpm for 15 min. Collect the NCNCs functionalized with GNPs in the precipitate and wash with water by centrifugation. Disperse the precipitate in water (4 ml).</li>
</ol>

<ol>
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R., 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=Unusual+inflammatory+and+fibrogenic+pulmonary+responses+to+single-walled+carbon+nanotubes+in+mice.">Unusual inflammatory and fibrogenic pulmonary responses to single-walled carbon nanotubes in mice.</a> American Journal of Physiology - Lung Cellular and Molecular Physiology. 289 (5), L698-L708 (2005).</li><li>Jia, G., Wang, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cytotoxicity+of+carbon+nanomaterials:+Single-wall+nanotube,+multi-wall+nanotube,+and+fullerene.">Cytotoxicity of carbon nanomaterials: Single-wall nanotube, multi-wall nanotube, and fullerene.</a> Environmental Science &amp; Technology. 39 (5), 1378-1383 (2005).</li><li>Carrero-S&#225;nchez, J. C., El&#237;as, A. 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The authors declare no competing financial interests.

The primary goal of our experiments was to effectively produce graphitic nanocups from nitrogen-doped CNTs. However, nitrogen-doping in the CVD synthesis does not guarantee the formation of the stacked cup-shaped structure. Depending on the chemical composition of the precursor and other growth conditions, the morphology of the resulted product may vary a lot.19 The concentration of nitrogen source is the primary factor influencing the structure because the compartmented structure results from the incompatibil...

With their inherent inner cavities and versatile surface chemistry, hollow carbon-based nanomaterials, such as carbon nanotubes (CNTs), are considered to be good nanocarriers in drug delivery applications.1,2 However, the fibril structure of pristine CNTs has rather inaccessible hollow interiors and may cause severe inflammatory response and cytotoxic effects in biological systems.3,4 Nitrogen-doped CNTs, on the other hand, have been found to possess higher biocompatibility than undoped multiwalled carbon nanotubes (MWCNTs)5,6 and may have better drug delivery performance. Doping of nitrogen atoms into the nanotube graphitic lattices results in a compartmented hollow structure resembling stacked cups which can be separated out to obtain individual nitrogen-doped carbon nanotube cups (NCNCs) with typical length under 200 nm.7,8 With their accessible interiors and nitrogen functionalities which allow for further chemical functionalization, these individual graphitic cups are highly advantageous for drug delivery applications.
Among different synthetic methods for nitrogen-doped CNTs including arc-discharge9 and dc magnetron sputtering,10 chemical vapor deposition (CVD) has been the most prevalent method due to several advantages such as higher yield and easier control over nanotube growth conditions. The vapor-liquid-solid (VLS) growth mechanism is commonly employed to understand the CVD growth process of nitrogen-doped CNTs.11 Generally there are two different schemes to use metal catalyst seeds in the growth. In the "fixed-bed" scheme, iron nanoparticles with defined sizes were first synthesized by thermal decomposition of iron pentacarbonyl and then plated on quartz slides by spin coating for subsequent CVD growth.12 In the "floating catalyst" scheme, iron catalyst (typically ferrocene) was mixed and injected with carbon and nitrogen precursors, and the thermal decomposition of ferrocene provided in situ generation of iron catalytic nanoparticles on which the carbon and nitrogen precursors were deposited. While fixed-bed catalyst provides better size control over the resultant NCNCs, the yield of product is typically lower (&lt;1 mg) compared to the floating catalyst scheme (&gt;5 mg) for the same precursor amount and growth time. As the floating catalyst scheme also provides fairly uniform size distribution of NCNCs, it was adopted in this paper for CVD synthesis of NCNCs.
CVD method affords as-synthesized NCNCs which exhibit fibril morphology comprised of many stacked cups. Although there is no chemical bonding between adjacent cups,8 challenges remain in effective isolation of the individual cups because they are firmly inserted into each other's cavities and held by multiple noncovalent interactions and an outer layer of amorphous carbon.8 Attempts to separate the stacked cups include both chemical and physical approaches. While oxidation treatments in a mixture of strong acids is a typical procedure to cut CNTs and introduce oxygen functionalities,13,14 it can also be applied to cut NCNCs into shorter sections. Microwave plasma etching procedures have been also shown to separate the NCNCs.15 Compared to the chemical approaches, physical separation is more straightforward. Our previous study showed that by simply grinding with a mortar and pestle individual NCNCs can be partially isolated from their stacked structure.7 In addition, high-intensity probe-tip sonication, which was reported to effectively cut single-walled carbon nanotubes (SWCNTs),16 was also shown to have a significant effect on separation of NCNCs.8 The probe-tip sonication delivers high-intensity ultrasonic power to the NCNC solution that essentially "shakes" the stacked cups and disrupts the weak interactions that hold the cups together. While other potential separation methods are either inefficient or destructive to the cup structure, probe-tip sonication provides a highly effective, cost-efficient and less-destructive physical separation method to obtain individual graphitic cups.
The as-synthesized fibril NCNCs were first treated in concentrated H2SO4/HNO3 acid mixture prior to their separation with probe-tip sonication. The resultant separated NCNCs were highly hydrophilic and effectively dispersed in water. We have previously identified nitrogen functionalities such as amine groups on NCNCs and utilized their chemical reactivity for NCNCs functionalization.7,8,17 Compared to our previously reported method of corking NCNCs with commercial nanoparticles,8 in this work, gold nanoparticles (GNPs) were effectively anchored to the surface of the cups by citrate reduction from chloroauric acid. Due to the preferential distribution of nitrogen functionalities on the open rims of NCNCs, the GNPs synthesized in situ from the gold precursors tended to have better interaction with the open rims and form GNP "cork stoppers" on the cups. Such synthesis and functionalization methods have resulted in a novel GNP-NCNC hybrid nanomaterial for potential applications as drug delivery carriers.

<table><tbody><tr><td colspan="4">&lt;strong&gt;Reagents&lt;/strong&gt;</td></tr><tr><td>H&lt;sub&gt;2&lt;/sub&gt;</td><td>Valley National Gases</td><td>Grade 5.0</td><td></td></tr><tr><td>Ar</td><td>Valley National Gases</td><td>Grade 5.0</td><td></td></tr><tr><td>Ferrocene</td><td>Sigma-Aldrich</td><td>F408-500G</td><td></td></tr><tr><td>Xylenes</td><td>Fisher Scientific</td><td>X5-500</td><td></td></tr><tr><td>Acetonitrile</td><td>EMD</td><td>AXO149-6</td><td></td></tr><tr><td>H&lt;sub&gt;2&lt;/sub&gt;SO&lt;sub&gt;4&lt;/sub&gt;</td><td>Fisher Scientific</td><td>A300-500</td><td></td></tr><tr><td>HNO&lt;sub&gt;3&lt;/sub&gt;</td><td>EMD</td><td>NX0409-2</td><td></td></tr><tr><td>DMF</td><td>Fisher Scientific</td><td>D119-500</td><td></td></tr><tr><td>Ethanol</td><td>Decon</td><td>2716</td><td></td></tr><tr><td>Phenol</td><td>Sigma-Aldrich</td><td>P1037-100G</td><td></td></tr><tr><td>Pyridine</td><td>EMD</td><td>PX2020-6</td><td></td></tr><tr><td>Hydridantin</td><td>Sigma-Aldrich</td><td>H2003-10G</td><td></td></tr><tr><td>Ninhydrin </td><td>Alfa Aesar</td><td>43846</td><td></td></tr><tr><td>HAuCl&lt;sub&gt;4&lt;/sub&gt;</td><td>Sigma-Aldrich</td><td>52918-1G</td><td></td></tr><tr><td>Sodium Citrate</td><td>SAFC</td><td>W302600</td><td></td></tr><tr><td colspan="4">&lt;strong&gt;Equipment&lt;/strong&gt;</td></tr><tr><td>CVD Furnace</td><td>Lindberg/Blue</td><td></td><td></td></tr><tr><td>TEM (low-resolution)</td><td>FEI Morgagni</td><td></td><td></td></tr><tr><td>TEM (high-resolution)</td><td>JOEL</td><td>2100F</td><td></td></tr><tr><td>Probe-tip Sonicator</td><td>Qsonica</td><td>XL-2000</td><td></td></tr><tr><td>UV-Vis Spectrometer</td><td>Perkin-Elmer</td><td>Lambda 900</td><td></td></tr><tr><td>Zeta Potential Analyzer</td><td>Brookheaven</td><td>ZetaPlus</td><td></td></tr><tr><td>EDX spectroscopy</td><td>Phillips</td><td>XL30 FEG</td><td></td></tr></tbody></table>

synthesis and functionalization of nitrogen-doped carbon nanotube cups with gold nanoparticles as cork stoppers

Nitrogen-doped carbon nanotubes consist of many cup-shaped graphitic compartments termed as nitrogen-doped carbon nanotube cups (NCNCs). These as-synthesized graphitic nanocups from chemical vapor deposition (CVD) method were stacked in a head-to-tail fashion held only through noncovalent interactions. Individual NCNCs can be isolated out of their stacking structure through a series of chemical and physical separation processes. First, as-synthesized NCNCs were oxidized in a mixture of strong acids to introduce oxygen-containing defects on the graphitic walls. The oxidized NCNCs were then processed using high-intensity probe-tip sonication which effectively separated the stacked NCNCs into individual graphitic nanocups. Owing to their abundant oxygen and nitrogen surface functionalities, the resulted individual NCNCs are highly hydrophilic and can be effectively functionalized with gold nanoparticles (GNPs), which preferentially fit in the opening of the cups as cork stoppers. These graphitic nanocups corked with GNPs may find promising applications as nanoscale containers and drug carriers.

The as-synthesized NCNCs from CVD growth appeared as a carpet of black material on quartz substrate. Thick films of NCNCs weighing about several mg were obtained by peeling with a razor blade (Figure 1B). TEM images show the morphology of as-synthesized NCNCs at different magnifications (Figure 1). At the lower magnification (Figure 1C), the as-synthesized NCNCs all showed a fibril structure with lengths of typically several micrometers and diameters of 20 - 30 nm. Unlik...

Watch this Scientific Journal Video about Synthesis and Functionalization of Nitrogen-doped Carbon Nanotube Cups with Gold Nanoparticles as Cork Stoppers at JoVE.com

Synthesis and Functionalization of Nitrogen-doped Carbon Nanotube Cups with Gold Nanoparticles as Cork Stoppers

We discussed the synthesis of individual graphitic nanocups using a series of techniques including chemical vapor deposition, acid oxidation and probe-tip sonication. By citrate reduction of HAuCl4, the graphitic nanocups were effectively corked with gold nanoparticles due to the chemically reactive edges of the cups.

Nitrogen-doped carbon  nanotubes consist of many cup-shaped graphitic compartments termed as  nitrogen-doped carbon nanotube cups (NCNCs).  These ...

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22.8K Views.  University of Pittsburgh. We discussed the synthesis of individual graphitic nanocups using a series of techniques including chemical vapor deposition, acid oxidation and probe-tip sonication. By citrate reduction of HAuCl4, the graphitic nanocups were effectively corked with gold nanoparticles due to the chemically reactive edges of the cups.

Video: Synthesis and Functionalization of Nitrogen-doped Carbon Nanotube Cups with Gold Nanoparticles as Cork Stoppers

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

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 ...

Synthesis, Characterization, and Functionalization of Hybrid Au/CdS and Au/ZnS Core/Shell Nanoparticles

Plasmonic nanoparticles are an attractive material for light harvesting applications due to their easily modified surface, high surface area and large extinction coefficients which can be tuned across the visible spectrum. Research into the plasmonic enhancement of optical transitions has become popular, due to the possibility of altering and in some cases improving photo-absorption or emission properties of nearby chromophores such as molecular dyes or quantum dots. The electric field of the plasmon can couple with the excitation dipole of a chromophore, perturbing the electronic states involved in the transition and leading to increased absorption and emission rates. These enhancements can also be negated at close distances by energy transfer mechanism, making the spatial arrangement of the two species critical. Ultimately, enhancement of light harvesting efficiency in plasmonic solar cells could lead to thinner and, therefore, lower cost devices. The development of hybrid core/shell particles could offer a solution to this issue. The addition of a dielectric spacer between a gold nanoparticles and a chromophore is the proposed method to control the exciton plasmon coupling strength and thereby balance losses with the plasmonic gains. A detailed procedure for the coating of gold nanoparticles with CdS and ZnS semiconductor shells is presented. The nanoparticles show high uniformity with size control in both the core gold particles and shell species allowing for a more accurate investigation into the plasmonic enhancement of external chromophores.

The synthesis of uniform gold nanoparticles coated with semiconductor shells of CdS or ZnS is performed. The semiconductor coating is conducted by first depositing a silver sulfide shell and exchanging the silver cations for zinc or cadmium cations.

Plasmonic nanoparticles are an attractive material for light harvesting applications due to their easily modified surface, high surface area and large ...

Functionalization of Single-walled Carbon Nanotubes with Thermo-reversible Block Copolymers and Characterization by Small-angle Neutron Scattering

We demonstrate a protocol for single-walled carbon nanotube functionalization using thermo-sensitive PEO-PPO-PEO triblock copolymers in an aqueous solution. In a carbon nanotube/PEO105-PPO70-PEO105 (poloxamer 407) aqueous solution, the amphiphilic poloxamer 407 adsorbs onto the carbon nanotube surfaces and self-assembles into continuous layers, driven by intermolecular interactions between constituent molecules. The addition of 5-methylsalicylic acid changes the self-assembled structure from spherical-micellar to a cylindrical morphology. The fabricated poloxamer 407/carbon nanotube hybrid particles exhibit thermo-responsive structural features so that the density and thickness of poloxamer 407 layers are also reversibly controllable by varying temperature. The detailed structural properties of the poloxamer 407/carbon nanotube particles in suspension can be characterized by small-angle neutron scattering experiments and model fit analyses. The distinct curve shapes of the scattering intensities depending on temperature control or addition of aromatic additives are well described by a modified core-shell cylinder model consisting of a carbon nanotube core cylinder, a hydrophobic shell, and a hydrated polymer layer. This method can provide a simple but efficient way for the fabrication and in-situ characterization of carbon nanotube-based nano particles with a structure-tunable encapsulation.

A method for the functionalization of carbon nanotubes with structure-tunable polymeric encapsulation layers and structural characterization using small-angle neutron scattering is presented.

We demonstrate a protocol for single-walled carbon nanotube functionalization using thermo-sensitive PEO-PPO-PEO triblock copolymers in an aqueous ...

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 ...

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 ...

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 ...

Microscopic Visualization of Porous Nanographenes Synthesized through a Combination of Solution and On-Surface Chemistry

On-surface synthesis has recently been regarded as a promising approach for the generation of new molecular structures. It has been particularly successful in the synthesis of graphene nanoribbons, nanographenes and intrinsically reactive and instable, yet attractive species. It is based on the combination of solution chemistry aimed at preparation of appropriate molecular precursors for further ultra-high vacuum surface assisted transformations. This approach also owes its success to an incredible development of characterization techniques, such as scanning tunneling/atomic force microscopy and related methods, which allow detailed, local characterization at atomic scale. While the surface-assisted synthesis can provide molecular nanostructures with outstanding precision, down to single atoms, it suffers from basing on metallic surfaces and often limited yield. Therefore, the extension of the approach away from metals and the struggle to increase productivity seem to be significant challenges toward wider applications. Herein, we demonstrate the on-surface synthesis approach for generation of non-planar nanographenes, which are synthesized through a combination of solution chemistry and sequential surface-assisted processes, together with the detailed characterization by scanning probe microscopy methods.

A combination of solution and surface assisted synthesis opens new directions in the atomically precise synthesis of nanostructures. Scanning tunneling microscopy (STM) supplemented by non-contact atomic force microscopy (nc-AFM) enables detailed characterization of newly designed and generated carbon-based nano-objects.

On-surface synthesis has recently been regarded as a promising approach for the generation of new molecular structures. It has been particularly ...

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.

Gold nanoparticles (Au nanoparticles) that are ~12 nm in diameter were synthesized by rapidly injecting a solution of 150 mg (0.15 mmol) of ...

Synthesis of Metal Nanoparticles Supported on Carbon Nanotube with Doped Co and N Atoms and its Catalytic Applications in Hydrogen Production

A method for facile synthesis of nanostructured catalysts supported on carbon nanotubes with atomically dispersed cobalt and nitrogen dopant is presented herein. The novel strategy is based on a facile one-pot pyrolysis treatment of cobalt (II) acetylacetonate and nitrogen-rich organic precursors under Ar atmosphere at 800 &#176;C, resulting in the formation of Co- and N- co-doped carbon nanotube with earthworm-like morphology. The obtained catalyst was found to have a high density of defect sites, as confirmed by Raman spectroscopy. Here, cobalt (II) nanoparticles were stabilized on the atomically dispersed cobalt- and nitrogen-doped carbon nanotubes. The catalyst was confirmed to be effective in the catalytic hydrolysis of ammonia borane, in which the turnover frequency was 5.87 mol H2&#183;molCo-1&#183;min-1, and the specific hydrogen generation rate was determined to be 2447 mL H2&#183;gCo-1&#183;min-1. A synergistic function between the Co nanoparticle and the doped carbon nanotubes was proposed for the first time in the catalytic hydrolysis of ammonia borane reaction under a mild condition. The resulting hydrogen production with its high energy density and minimal refueling time could be suitable for future development as energy sources for mobile and stationary applications such as road trucks and forklifts in transport and logistics.

Here, we present a protocol to synthesize Co nanoparticles supported on carbon nanotubes with Co- and N- dopants for hydrogen productions.

A method for facile synthesis of nanostructured catalysts supported on carbon nanotubes with atomically dispersed cobalt and nitrogen dopant is presented ...