We acknowledge financial support by the Zernike Institute for Advanced Materials, University of Groningen.

1. Preparation and Characterization of PS-b-P4VP(PDP) Complexes with Double Gyroid Morphology
<ol>
	<li>Weigh out polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) and pentadecylphenol (PDP, Mr = 304.51 g/mol). In order to obtain the gyroid morphology, carefully select the amount of PDP should be (the weight fraction of P4VP(PDP) block (fP4VP(PDP))should be ca. 0.6 according to the phase diagram of linear AB diblock copolymers). Usually, 0.15-0.2 g of a PS-b-P4VP leads to PS-b-P4VP(PDP) films 50-100 &#956;m thick (given that the diameter of a Petri dish used in the step 1.3 is 5-6 cm). Calculate the amount of PDP according to the following equations: 
	<img alt="Equation 1" src="/files/ftp_upload/50673/50673eq1.jpg" /> 
	<img alt="Equation 2" src="/files/ftp_upload/50673/50673eq2.jpg" /> 
	<img alt="Equation 3" src="/files/ftp_upload/50673/50673eq3.jpg" /> 
	<img alt="Equation 4" src="/files/ftp_upload/50673/50673eq4.jpg" /></li>
	<li>Dissolve PS-b-P4VP and PDP in chloroform and stir it for a couple of hours at room temperature. Maintain the concentration of polymer below 2 wt% to ensure the homogeneous complex formation.</li>
	<li>Pour the solution into a glass Petri dish.</li>
	<li>Place the dish into a saturated chloroform atmosphere.</li>
	<li>After about one week, take out the Petri dish. A film of the supramolecular complex is formed.</li>
	<li>Dry the film in vacuum at 30 &#176;C overnight.</li>
	<li>Place the film in a specially designed container, remove the air from the container and then fill it with nitrogen. Anneal the film for 4 days in the oven at 120 &#176;C under N2 atmosphere with 1 bar overpressure.</li>
	<li>Cut the small piece of the film, embed in epoxy and cure it overnight at 40 &#176;C.</li>
	<li>Microtome the sample to a thickness of about 80 nm using a diamond knife at room temperature. The microtomed section will float on water. Pick them up and place on Cu grids.</li>
	<li>Put the grids containing the microtomed sections into a jar with iodine. After 45 min samples are stained and ready for transmission electron microscopy.</li>
	<li>Insert the Cu grids with stained sections in the transmission electron microscope operating at an accelerating voltage of 120 kV and image the sample.</li>
	<li>Insert the piece of the film (obtained after step 1.7) into the sample holder for small angle X-ray scattering and fix it with a Kapton tape. Place the prepared sample holder into the machine for SAXS. Open the X-ray shutter and acquire the 2D scattering pattern. Integrate the obtained 2D pattern and analyze the position of the peaks in 1D pattern.</li>
</ol>
2. Generation and Characterization of the Porous Structure
<ol>
	<li>Put the piece of the film (obtained after step 1.7) in ethanol and keep it for three days.</li>
	<li>Dry the sample.</li>
	<li>Prepare the samples for 1H NMR measurements. Dissolve PDP powder, PS-b-P4VP powder, supramolecular complex PS-b-P4VP(PDP) (after step 1.7), and porous film (after step 2.2) in CDCl3. Record 1H NMR spectra at room temperature.</li>
	<li>Analyze PS-b-P4VP powder, supramolecular complex PS-b-P4VP(PDP) (after step 1.7), and porous film (after step 2.2) by differential scanning calorimetry. Use a modulated mode with a heating/cooling rate of 1 &#176;C/min, an oscillation amplitude of 0.5 &#176;C, and an oscillation period of 60 sec. Equilibrate the samples at -30 &#176;C, heat to 180 &#176;C, cool to -30 &#176;C, and then heat again to 180 &#176;C. Use the data from the second heating cycle for the analysis.</li>
	<li>Outgas the porous sample (after step 2.2) for 8 hr at room temperature and for 18 hr at 70 &#176;C and perform nitrogen adsorption measurements at 77 K.</li>
	<li>Use the appropriate software (for example, WinADP) and models to analyze the obtained isotherms.</li>
	<li>Dry the porous sample (after step 2.2) at 50 &#176;C for 8 hr and degas it at room temperature and pressure of 0.5 Pa for 2 hr.</li>
	<li>Perform mercury porosimetry.</li>
</ol>
3. Inserting Nickel in the Polymer Template
<ol>
	<li>Weigh out tin chloride (SnCl2, Mr = 189.60 g/mol) and prepare an aqueous solution (0.1 M SnCl2 / 0.1 M HCl; 1.896 g SnCl2, 0.8 ml HCl, and 100 ml H2O). Put the solution on a shaker overnight to ensure the complete dissolution of SnCl2.</li>
	<li>Weigh out palladium chloride (PdCl2, Mr = 177.33 g/mol) and prepare an aqueous solution (0.0014 M PdCl2 / 0.25 M HCl; 0.025 g PdCl2, 2 ml HCl and 100 ml H2O).</li>
	<li>Prepare part 1 of the nickel plating bath: weigh out 6.78 g nickel sulfate hexahydrate (NiSO4&#8226;6H2O, Mr = 262.85 g/mol) and 2 g sodium citrate (Na3C6H5O7, Mr = 258.06 g/mol) and dissolve them in 80 ml of water. Add 828 &#956;l 85% lactic acid (C3H6O3, Mr = 90.08 g/mol).</li>
	<li>Prepare part 2 of the nickel plating bath: weight out 0.2 g borane dimethylamine complex ((CH3)2NHBH3, Mr = 58.92 g/mol) and dissolve it in 20 ml of water. Borane dimethylamine complex should be handled in a well-ventilated fume hood.</li>
	<li>Immerse the porous film (after step 2.2) in the aqueous solution of tin chloride (step 3.1) for 1 hr.</li>
	<li>Rinse the film thoroughly with deionized water.</li>
	<li>Immerse the film in the aqueous solution of palladium chloride (step&#160;3.2) for 1 hr.</li>
	<li>Rinse the film thoroughly with deionized water.</li>
	<li>Mix part 1 (3.3) and part 2 (3.4) of the nickel plating bath. Adjust the pH to 7.0 using ammonium hydroxide.</li>
	<li>Immerse the film in the nickel plating bath for 1 hr.</li>
	<li>Rinse the film thoroughly with deionized water.</li>
	<li>Dry the sample.</li>
	<li>Prepare the plated sample for electron microscopy as described in steps 1.8-1.9.</li>
	<li>Image the sample as described in step&#160;1.11.</li>
	<li>Insert Cu grids containing the sections of the plated sample in the high-resolution transmission electron microscope. Acquire high-resolution TEM micrographs. Observe the sample under the microscope and choose the area for elemental analysis by EDX (Energy Dispersive Analysis of X-Rays). Perform the EDX analysis of the chosen area and analyze the obtained pattern.</li>
</ol>
4. Exposure of the Inverse Gyroid Nickel Foam
<ol>
	<li>Put the nickel-plated film (after step 3.12) in an oven at 350 &#176;C and keep it from 1 hr up to 4 days.</li>
	<li>Attach the sample to the sample holder using a silver paste.</li>
	<li>Insert the sample into the scanning electron microscope. Acquire several images of the sample.</li>
	<li>Insert the sample into the scanning electron microscope. Observe the sample under the microscope and choose the area for elemental analysis by EDX. Perform the EDX analysis of the chosen area and analyze the obtained pattern.</li>
</ol>

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The authors declare no competing financial interests.

Supramolecular complexes are successfully applied as precursors for well-ordered metal nanofoams. In this method, the crucial step is to acquire the appropriate template, i.e.&#160;a template with gyroid morphology. In the phase diagram of block copolymers the gyroid region is very small and it is rather difficult to target. This means that if conventional block copolymers are used as starting materials, the quite elaborate synthesis has to be repeated until the desired composition, that gives rise to the gyroid...

There are several techniques available for the preparation of metal nanofoams: dealloying1-3, sol-gel approaches4,5, nanosmelting6,7, and combustion synthesis8. In the dealloying process, the starting material is usually a binary alloy, for example, an alloy of silver and gold. The less noble metal, silver in this case, can be removed either chemically or electrochemically resulting in a disordered porous gold foam with nanosized ligaments. In combustion synthesis, metal is mixed with an energetic precursor that releases energy during its decomposition and drives the formation of metal nanofoam8. Studies on the mechanical behavior of metal foams indicate that in disordered architectures stresses cannot be transmitted effectively from the ligament nanoscale to the overall macroscale9-11.&#160;Thus well-ordered metal nanofoams are expected to have superior mechanical properties in comparison to the disordered ones.
The idea represented here is to employ block copolymers that self-assemble into ordered nanostructures as precursors to metal nanofoams. Depending on the composition of a block copolymer, the total number of monomer units and the extent of repulsion between the chemically connected blocks, various morphologies appear such as: spherical, cylindrical, lamellar, double gyroid, hexagonally perforated lamellar, and others12-14. Furthermore, polymer blocks can be degraded selectively leading to nanoporous materials15. The most common methods include: ozonolysis16-18, UV irradiation19, reactive ion etching20-22, and dissolution23-26. The generated porous structures can be backfilled with various inorganic materials. Metal oxides (e.g.&#160;SiO2, TiO2) are usually introduced via sol-gel method into the template&#39;s channels27-29. Electrochemical and electroless plating are commonly used to deposit metal into or onto templates30-33. Finally, the remaining polymer can be removed from the polymer/inorganic nanohybrid via pyrolysis2, dissolution34,35, UV degradation28,29, etc.
In our approach, we start from a supramolecular complex of polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) diblock copolymer and amphiphilic pentadecylphenol (PDP) molecules. This complex is a result of the hydrogen bonding between PDP and pyridine rings (Figure 1a). The composition of the starting block copolymer and the amount of added PDP are chosen in such a way that the obtained system self-assembles in the bicontinuous double gyroid morphology with a PS network and a P4VP(PDP) matrix (Figure 1b). PDP molecules become selectively dissolved in ethanol and P4VP chains collapse onto the PS network (Figure 1c). Subsequently, using electroless plating method, nickel is deposited into the pores of the template (Figure 1d). After the removal of the remaining polymer via pyrolysis, a well-ordered gyroid nickel nanofoam is obtained (Figure 1e).

<table border="1">
 <tbody>
 <tr>
 <td>REAGENTS:</td>
 <td></td>
 <td></td>
 <td></td>
 </tr>
 <tr>
 <td>PS-b-P4VP, CAS: 26222-40-2</td>
 <td>Polymer Source Inc.</td>
 <td>P9009-S4VP 
 P136-S4VP 
 P5462-S4VP 
 P3912-S4VP</td>
 <td>additional information are provided in a separate table</td>
 </tr>
 <tr>
 <td>PDP</td>
 <td>Aldrich</td>
 <td>P4402-100G-A</td>
 <td>recrystallized twice from petroleum ether</td>
 </tr>
 <tr>
 <td>SnCl2</td>
 <td>Acros Organics</td>
 <td>196981000</td>
 <td></td>
 </tr>
 <tr>
 <td>PdCl2</td>
 <td>Aldrich</td>
 <td>76050</td>
 <td></td>
 </tr>
 <tr>
 <td>NiSO4 x H2O</td>
 <td>Sigma-Aldrich</td>
 <td>227676</td>
 <td></td>
 </tr>
 <tr>
 <td>lactic acid</td>
 <td>Aldrich</td>
 <td>W261106</td>
 <td></td>
 </tr>
 <tr>
 <td>citric acid trisodium salt</td>
 <td>Sigma-Aldrich</td>
 <td>C3674</td>
 <td></td>
 </tr>
 <tr>
 <td>borane dimethyl amine complex</td>
 <td>Aldrich</td>
 <td>180238</td>
 <td></td>
 </tr>
 <tr>
 <td>PS-b-P4VP catalogue number</td>
 <td>Mn (PS), g/mol</td>
 <td>Mn(P4VP), g/mol</td>
 <td>PDI</td>
 </tr>
 <tr>
 <td>P9009-S4VP</td>
 <td>24000</td>
 <td>9500</td>
 <td>1.1</td>
 </tr>
 <tr>
 <td>P136-S4VP</td>
 <td>31900</td>
 <td>13200</td>
 <td>1.08</td>
 </tr>
 <tr>
 <td>P5462-S4VP</td>
 <td>37500</td>
 <td>16000</td>
 <td>1.3</td>
 </tr>
 <tr>
 <td>P3912-S4VP</td>
 <td>41500</td>
 <td>17500</td>
 <td>1.07</td>
 </tr>
 </tbody>
</table>

gyroid nickel nanostructures from diblock copolymer supramolecules

Nanoporous metal foams possess a unique combination of properties - they are catalytically active, thermally and electrically conductive, and furthermore, have high porosity, high surface-to-volume and strength-to-weight ratio. Unfortunately, common approaches for preparation of metallic nanostructures render materials with highly disordered architecture, which might have an adverse effect on their mechanical properties. Block copolymers have the ability to self-assemble into ordered nanostructures and can be applied as templates for the preparation of well-ordered metal nanofoams. Here we describe the application of a block copolymer-based supramolecular complex - polystyrene-block-poly(4-vinylpyridine)(pentadecylphenol) PS-b-P4VP(PDP) - as a precursor for well-ordered nickel nanofoam. The supramolecular complexes exhibit a phase behavior similar to conventional block copolymers and can self-assemble into the bicontinuous gyroid morphology with two PS networks placed in a P4VP(PDP) matrix. PDP can be dissolved in ethanol leading to the formation of a porous structure that can be backfilled with metal. Using electroless plating technique, nickel can be inserted into the template&#39;s channels. Finally, the remaining polymer can be removed via pyrolysis from the polymer/inorganic nanohybrid resulting in nanoporous nickel foam with inverse gyroid morphology.

The morphology of supramolecular complexes PS-b-P4VP(PDP)x is examined by TEM and SAXS. Figures 2a and 2b display typical gyroid patterns of a representative supramolecular complex: the double-wave and the wagon-wheel patterns that are known to represent projections through the (211) and the (111) plane of the gyroid unit cell, respectively. The PS block domains appear bright while the P4VP(PDP)x block domains appear dark due to iodine staining. Figure 2c repres...

Watch this Scientific Journal Video about Gyroid Nickel Nanostructures from Diblock Copolymer Supramolecules at JoVE.com

Gyroid Nickel Nanostructures from Diblock Copolymer Supramolecules

This article describes the preparation of well-ordered nickel nanofoams via electroless metal deposition onto nanoporous templates obtained from self-assembled diblock copolymer based supramolecules.

Nanoporous metal foams possess a unique combination of properties - they are catalytically active, thermally and electrically conductive, and furthermore, ...

gyroid-nickel-nanostructures-from-diblock-copolymer-supramolecules

Research

JoVE Journal

Chemistry

12.4K vues.  University of Groningen.  Cet article décrit la préparation de nanomousses de nickel bien ordonnés par dépôt électrolytique de métal sur des modèles nanoporeux obtenus à partir de la base supramolécules copolymère dibloc auto-assemblée. 

Vidéo: Gyroid Nickel Nanostructures from Diblock Copolymer Supramolecules

Nucleoside Triphosphates - From Synthesis to Biochemical Characterization

The traditional strategy for the introduction of chemical functionalities is the use of solid-phase synthesis by appending suitably modified phosphoramidite precursors to the nascent chain. However, the conditions used during the synthesis and the restriction to rather short sequences hamper the applicability of this methodology. On the other hand, modified nucleoside triphosphates are activated building blocks that have been employed for the mild introduction of numerous functional groups into nucleic acids, a strategy that paves the way for the use of modified nucleic acids in a wide-ranging palette of practical applications such as functional tagging and generation of ribozymes and DNAzymes. One of the major challenges resides in the intricacy of the methodology leading to the isolation and characterization of these nucleoside analogues.
	
	In this video article, we present a detailed protocol for the synthesis of these modified analogues using phosphorous(III)-based reagents. In addition, the procedure for their biochemical characterization is divulged, with a special emphasis on primer extension reactions and TdT tailing polymerization. This detailed protocol will be of use for the crafting of modified dNTPs and their further use in chemical biology.

The protocol described herein aims to explain and abridge the numerous obstacles in the way of the intricate route leading to modified nucleoside triphosphates. Consequently, this protocol facilitates both the synthesis of these activated building-blocks and their availability for practical applications.

The  traditional strategy for the introduction of chemical functionalities is the  use of solid-phase synthesis by appending suitably modified ...

Synthesis of Ligand-free CdS Nanoparticles within a Sulfur Copolymer Matrix

Aliphatic ligands are typically used during the synthesis of nanoparticles to help mediate their growth in addition to operating as high-temperature solvents. These coordinating ligands help solubilize and stabilize the nanoparticles while in solution, and can influence the resulting size and reactivity of the nanoparticles during their formation. Despite the ubiquity of using ligands during synthesis, the presence of aliphatic ligands on the nanoparticle surface can result in a number of problems during the end use of the nanoparticles, necessitating further ligand stripping or ligand exchange procedures. We have developed a way to synthesize cadmium sulfide (CdS) nanoparticles using a unique sulfur copolymer. This sulfur copolymer is primarily composed of elemental sulfur, which is a cheap and abundant material. The sulfur copolymer has the advantages of operating both as a high temperature solvent and as a sulfur source, which can react with a cadmium precursor during nanoparticle synthesis, resulting in the generation of ligand free CdS. During the reaction, only some of the copolymer is consumed to produce CdS, while the rest remains in the polymeric state, thereby producing a nanocomposite material. Once the reaction is finished, the copolymer stabilizes the nanoparticles within a solid polymeric matrix. The copolymer can then be removed before the nanoparticles are used, which produces nanoparticles that do not have organic coordinating ligands. This nascent synthesis technique presents a method to produce metal-sulfide nanoparticles for a wide variety of applications where the presence of organic ligands is not desired.

Herein we present a method to synthesize ligand-free cadmium sulfide (CdS) nanoparticles based on a unique sulfur copolymer. The sulfur copolymer operates as a high temperature solvent and a sulfur source during the nanoparticle synthesis and stabilizes the nanoparticles after the reaction.

Aliphatic ligands are typically used during the synthesis of nanoparticles to help mediate their growth in addition to operating as high-temperature ...

Anionic Polymerization of an Amphiphilic Copolymer for Preparation of Block Copolymer Micelles Stabilized by &#960;-&#960; Stacking Interactions

In this study, an amphiphilic copolymer that includes a core-forming block with phenyl groups was synthesized by living anionic polymerization of phenyl glycidyl ether (PheGE) on methoxy-polyethylene glycol (mPEG-b-PPheGE). Characterization of the copolymer revealed a narrow molecular distribution (PDI &#60; 1.03) and confirmed the degree of polymerization of mPEG122-b-(PheGE)15. The critical micelle concentration of the copolymer was evaluated using an established fluorescence method with the aggregation behavior evaluated by dynamic light scattering and transmission electronic microscopy. The potential of the copolymer for use in drug delivery applications was evaluated in a preliminary manner including in vitro biocompatibility, loading and release of the hydrophobic anti-cancer drug doxorubicin (DOX). A stable micelle formulation of DOX was prepared with drug loading levels up to 14% (wt%), drug loading efficiencies &#62; 60% (w/w) and sustained release of drug over 4 days under physiologically relevant conditions (acidic and neutral pH, presence of albumin). The high drug loading level and sustained release is attributed to stabilizing &#960;-&#960; interactions between DOX and the core-forming block of the micelles.

Anionic Polymerization of an Amphiphilic Copolymer for Preparation of Block Copolymer Micelles Stabilized by &amp;#960;-&amp;#960; Stacking Interactions

The key steps of living anionic polymerization of phenyl glycidyl ether (PheGE) on methoxy-polyethylene glycol (mPEG-b-PPheGE) are described. The resulting block copolymer micelles (BCMs) were loaded with doxorubicin 14% (wt%) and sustained release of drug over 4 days under physiologically relevant conditions was obtained.

In this study, an amphiphilic copolymer that includes a core-forming block with phenyl groups was synthesized by living anionic polymerization of phenyl ...

Facet-to-facet Linking of Shape-anisotropic Colloidal Cadmium Chalcogenide Nanostructures

Here, we describe a protocol that allows for shape-anisotropic cadmium chalcogenide nanocrystals (NCs), such as nanorods (NRs) and tetrapods (TPs), to be covalently and site-specifically linked via their end facets, resulting in polymer-like linear or branched chains. The linking procedure begins with a cation-exchange process in which the end facets of the cadmium chalcogenide NCs are first converted to silver chalcogenide. This is followed by the selective removal of ligands at their surface. This results in cadmium chalcogenide NCs with highly reactive silver chalcogenide end facets that spontaneously fuse upon contact with each other, thereby establishing an interparticle facet-to-facet attachment. Through the judicious choice of precursor concentrations, an extensive network of linked NCs can be produced. Structural characterization of the linked NCs is carried out via low- and high-resolution transmission electron microscopy (TEM), as well as energy-dispersive X-ray spectroscopy, which confirm the presence of silver chalcogenide domains between chains of cadmium chalcogenide NCs.

A protocol detailing how shape-anisotropic colloidal cadmium chalcogenide nanocrystals can be covalently linked via their end facets is presented here.

Here, we describe a protocol that allows for shape-anisotropic cadmium chalcogenide nanocrystals (NCs), such as nanorods (NRs) and tetrapods (TPs), to be ...

Synthesis of Platinum-nickel Nanowires and Optimization for Oxygen Reduction Performance

Platinum-nickel (Pt-Ni) nanowires were developed as fuel cell electrocatalysts, and were optimized for the performance and durability in the oxygen reduction reaction. Spontaneous galvanic displacement was used to deposit Pt layers onto Ni nanowire substrates. The synthesis approach produced catalysts with high specific activities and high Pt surface areas. Hydrogen annealing improved Pt and Ni mixing and specific activity. Acid leaching was used to preferentially remove Ni near the nanowire surface, and oxygen annealing was used to stabilize near-surface Ni, improving durability and minimizing Ni dissolution. These protocols detail the optimization of each post-synthesis processing step, including hydrogen annealing to 250 &#176;C, exposure to 0.1 M nitric acid, and oxygen annealing to 175 &#176;C. Through these steps, Pt-Ni nanowires produced increased activities more than an order of magnitude than Pt nanoparticles, while offering significant durability improvements. The presented protocols are based on Pt-Ni systems in the development of fuel cell catalysts. These techniques have also been used for a variety of metal combinations, and can be applied to develop catalysts for a number of electrochemical processes.

&#160; The protocol describes the synthesis and electrochemical testing of platinum-nickel nanowires. Nanowires were synthesized by the galvanic displacement of a nickel nanowire template. Post-synthesis processing, including hydrogen annealing, acid leaching, and oxygen annealing were used to optimize nanowire performance and durability in the oxygen reduction reaction.

Platinum-nickel (Pt-Ni) nanowires were developed as fuel cell electrocatalysts, and were optimized for the performance and durability in the oxygen ...

Chemical Precipitation Method for the Synthesis of Nb2O5 Modified Bulk Nickel Catalysts with High Specific Surface Area

We demonstrate a method for the synthesis of NixNb1-xO catalysts with sponge-like and fold-like nanostructures. By varying the Nb:Ni ratio, a series of NixNb1-xO nanoparticles with different atomic compositions (x = 0.03, 0.08, 0.15, and 0.20) have been prepared by chemical precipitation. These NixNb1-xO catalysts are characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy. The study revealed the sponge-like and fold-like appearance of Ni0.97Nb0.03O and Ni0.92Nb0.08O on the NiO surface, and the larger surface area of these NixNb1-xO catalysts, compared with the bulk NiO. Maximum surface area of 173 m2/g can be obtained for Ni0.92Nb0.08O catalysts. In addition, the catalytic hydroconversion of lignin-derived compounds using the synthesized Ni0.92Nb0.08O catalysts have been investigated.

Chemical Precipitation Method for the Synthesis of Nb2O5 Modified Bulk Nickel Catalysts with High Specific Surface Area

A protocol for the synthesis of sponge-like and fold-like Ni1-xNbxO nanoparticles by chemical precipitation is presented.

We demonstrate a method for the synthesis of NixNb1-xO catalysts with sponge-like and fold-like nanostructures. By varying the Nb:Ni ratio, a series of ...

Preparation and Characterization of C60/Graphene Hybrid Nanostructures

Physical thermal deposition in a high vacuum environment is a clean and controllable method for fabricating novel molecular nanostructures on graphene. We present methods for depositing and passively manipulating C60 molecules on rippled graphene that advance the pursuit of realizing applications involving 1D C60/graphene hybrid structures. The techniques applied in this exposition are geared towards high vacuum systems with preparation areas capable of supporting molecular deposition as well as thermal annealing of the samples. We focus on C60 deposition at low pressure using a homemade Knudsen cell connected to a scanning tunneling microscopy (STM) system. The number of molecules deposited is regulated by controlling the temperature of the Knudsen cell and the deposition time. One-dimensional (1D) C60 chain structures with widths of two to three molecules can be prepared via tuning of the experimental conditions. The surface mobility of the C60 molecules increases with annealing temperature allowing them to move within the periodic potential of the rippled graphene. Using this mechanism, it is possible to control the transition of 1D C60 chain structures to a hexagonal close packed quasi-1D stripe structure.

Preparation and Characterization of C60/Graphene Hybrid Nanostructures

Here we present a protocol for the fabrication of C60/graphene hybrid nanostructures by physical thermal evaporation. Particularly, the proper manipulation of deposition and annealing conditions allow the control over the creation of 1D and quasi 1D C60 structures on rippled graphene.

Physical thermal deposition in a high vacuum environment is a clean and controllable method for fabricating novel molecular nanostructures on graphene. We ...

Disentangling High Strength Copolymer Aramid Fibers to Enable the Determination of Their Mechanical Properties

Traditionally, soft body armor has been made from poly(p-phenylene terephthalamide) (PPTA) and ultra-high molecular weight polyethylene. However, to diversify the fiber choices in the United States body armor market, copolymer fibers based on the combination of 5-amino-2-(p-aminophenyl) benzimidazole (PBIA) and the more conventional PPTA were introduced. Little is known regarding the long-term stability of these fibers, but as condensation polymers, they are expected to have potential sensitivity to moisture and humidity. Therefore, characterizing the strength of the materials and understanding their vulnerability to environmental conditions is important for evaluating their use lifetime in safety applications. Ballistic resistance and other critical structural properties of these fibers are predicated on their strength. To accurately determine the strength of the individual fibers, it is necessary to disentangle them from the yarn without introducing any damage. Three aramid-based copolymer fibers were selected for the study. The fibers were washed with acetone followed by methanol to remove an organic coating that held the individual fibers in each yarn bundle together. This coating makes it difficult to separate single fibers from the yarn bundle for mechanical testing without damaging the fibers and affecting their strength. After washing, fourier transform infrared (FTIR) spectroscopy was performed on both washed and unwashed samples and the results were compared. This experiment has shown that there are no significant variations in the spectra of poly(p-phenylene-benzimidazole-terephthalamide-co-p-phenylene terephthalamide) (PBIA-co-PPTA1) and PBIA-co-PPTA3 after washing, and only a small variation in intensity for PBIA. This indicates that the acetone and methanol rinses are not adversely affecting the fibers and causing chemical degradation. Additionally, single fiber tensile testing was performed on the washed fibers to characterize their initial tensile strength and strain to failure, and compare those to other reported values. Iterative procedural development was necessary to find a successful method for performing tensile testing on these fibers.

The primary goal of the study is to develop a protocol to prepare consistent specimens for accurate mechanical testing of high strength copolymer aramid fibers, by removing a coating and disentangling the individual fiber strands without introducing significant chemical or physical degradation.

Traditionally, soft body armor has been made from poly(p-phenylene terephthalamide) (PPTA) and ultra-high molecular weight polyethylene. However, to ...

Stable DNA Motifs, 1D and 2D Nanostructures Constructed from Small Circular DNA Molecules

This article presents a detailed protocol for synthesis of small circular DNA molecules, annealing of circular DNA motifs, and construction of 1D and 2D DNA nanostructures. Over decades, the rapid development of DNA nanotechnology is attributed to the use of linear DNAs as the source materials. For example, the DAO (double crossover, antiparallel, odd half-turns) tile is well-known as a building block for construction of 2D DNA lattices; the core structure of DAO is made from two linear single-stranded (ss) oligonucleotides, like two ropes making a right hand granny&#160;knot. Herein, a new type of DNA tiles called cDAO (coupled DAO) are built using a small circular ss-DNA of c64nt or c84nt (circular 64 or 84 nucleotides) as the scaffold strand and several linear ss-DNAs as the staple strands. Perfect 1D and 2D nanostructures are assembled from cDAO tiles: infinite nanowires, nanospirals, nanotubes, nanoribbons; and finite nano-rectangles. Detailed protocols are described: 1) preparation by T4 ligase and purification by denaturing PAGE (polyacrylamide gel electrophoresis) of small circular oligonucleotides, 2) annealing of stable circular tiles, followed by native PAGE analysis, 3) assembling of infinite 1D nanowires, nanorings, nanospirals, infinite 2D lattices of nanotubes and nanoribbons, and finite 2D nano-rectangles, followed by AFM (Atomic Force Microscopy) imaging. The method is simple, robust, and affordable for most labs.

This article presents a detailed protocol for T4 ligation and denaturing PAGE purification of small circular DNA molecules, annealing and native PAGE analysis of circular tiles, assembling and AFM imaging of 1D and 2D DNA nanostructures, as well as agarose gel electrophoresis and centrifugation purification of finite DNA nanostructures.

This article presents a detailed protocol for synthesis of small circular DNA molecules, annealing of circular DNA motifs, and construction of 1D and 2D ...

Gene-therapy Inspired Polycation Coating for Protection of DNA Origami Nanostructures

DNA origami nanostructures hold an immense potential to be used for biological and medical applications. However, low-salt conditions and nucleases in physiological fluids induce denaturation and degradation of self-assembled DNA nanostructures. In non-viral gene delivery, enzymatic degradation of DNA is overcome by the encapsulation of the negatively charged DNA in a cationic shell. Herein, inspired by gene delivery advancements, a simple, one-step and robust methodology is presented for the stabilization of DNA origami nanostructures by coating them with chitosan and linear polyethyleneimine. The polycation coating efficiently protects DNA origami nanostructures in Mg-depleted and nuclease-rich media. This method also preserves the full addressability of enzyme- and aptamer-based functionalization of DNA nanostructures.

Here, a protocol for the protection of DNA origami nanostructures in Mg-depleted and nuclease-rich media using natural cationic polysaccharide chitosan and synthetic linear polyethyleneimine (LPEI) coatings is presented.

DNA origami nanostructures hold an immense potential to be used for biological and medical applications. However, low-salt conditions and nucleases in ...