Name: preparation of carbon nanosheets at room temperature
Uploaded: 2016-03-08T13:00:00.000+00:00
Duration: 10 min 44 s
Description: Watch this Scientific Journal Video about Preparation of Carbon Nanosheets at Room Temperature at JoVE.com

Funding from the European Research Council (ERC Grant 239831) and a Humboldt Fellowship (BS) is gratefully acknowledged.

The authors have nothing to disclose.

The desired hexayne amphiphile (3) is straightforwardly prepared by the sequential bromination52,53 and Pd-catalyzed elongation30,31 of the alkyne segment, followed by a final deprotection reaction of the tritylphenyl ester (2) (Figure&#160;1a)29. The successful synthesis is confirmed by the 13C NMR spectrum (Figure&#160;1b) as well as the UV-Vis absorption spectrum (Figure&#160;1c)31,54. This demonstrates the facile...

Two-dimensional carbon nanostructures attract significant attention due to the reported outstanding electrical, thermal, as well as mechanical properties1-5. These materials are expected to further the technical progress in the fields of polymer composites6, energy storage devices7, and molecular electronics8-10. Despite intensive research efforts in recent years, however, access to larger amounts of well-defined carbon nanomaterials is still limited, which impedes their large-scale implementation in technological applications11,12.
Carbon nanomaterials are accessible by either top-down or bottom-up approaches. Typical approaches such as exfoliation techniques13 or high-energy processes on surfaces14-16 offer the possibility to obtain materials with a high degree of structural perfection and very good performance. However, the isolation and purification of the products remains challenging, and the large-scale production of defined nanostructured materials is difficult12. On the other hand, bottom-up approaches can be employed that rely on the use of molecular precursors, their arrangement into defined structures, and a subsequent carbonization that yields the carbon nanostructures17-23. In this case, the precursors themselves are more complex and their preparation often requires multiple synthetic steps. These approaches may offer a high degree of control over the chemical and physical properties of the resulting materials and may furnish a direct access to tailored materials. However, the conversion of the precursors into carbon nanomaterials is typically performed at temperatures above 800 &#176;C, which leads to a loss of the embedded chemical functionalization24-27.
The above mentioned limitations have been addressed in our group by employing highly reactive oligoynes that can be converted into carbon nanomaterials at room temperature28,29. In particular, amphiphiles comprising a hydrophilic head group and a hexayne segment are accessible through a sequence of bromination and palladium-mediated Negishi cross-coupling reactions30,31. The conversion of these precursor molecules into the target structure occurs at or below room temperature upon irradiation with UV light. The high reactivity of the oligoyne amphiphiles makes the use of soft templates, such as the air-water interface or fluid-fluid interfaces, possible. In previous investigations, we successfully prepared vesicles from solutions of hexayne glycoside amphiphiles28. Cross-linking of these vesicles was achieved under mild conditions by UV irradiation of the samples. Moreover, we recently prepared self-assembled monolayers from hexaynes with a methyl carboxylate head group and a hydrophobic alkyl tail at the air-water interface in a Langmuir trough. The densely packed molecular precursors were then straightforwardly converted into self-supporting carbon nanosheets at room temperature by UV irradiation. In related approaches defined molecular precursors have recently been used for the preparation of two-dimensionally extended nanosheets at the air-water interface32-38.
The aim of this work is to give a concise, practical overview of the overall synthesis and fabrication steps that allow for the preparation of carbon nanosheets from hexayne amphiphiles. The focus is on the experimental approach and preparative questions.

<table><tbody><tr><td>Methyllithium lithium bromide complex (2.2&amp;nbsp;M solution in diethylether)</td><td>Acros</td><td>18129-1000</td><td>air-sensitive, flammable</td></tr><tr><td>Zinc chloride (0.7&amp;nbsp;M solution in THF)</td><td>Acros</td><td>38945-1000</td><td>air-sensitive, flammable</td></tr><tr><td>1,1&#039;-Bis(diphenylphosphino)ferrocene]&lt;br/&gt; dichloropalladium(II), DCM adduct&amp;nbsp;</td><td>Boron Molecular</td><td>BM187</td><td></td></tr><tr><td>&lt;em&gt;N&lt;/em&gt;-Bromosuccinimide</td><td>Acros</td><td>10745</td><td>light-sensitive</td></tr><tr><td>Silver fluoride</td><td>Fluorochem</td><td>002862-10g</td><td>light-sensitive</td></tr><tr><td>n-Butyllithium (2.5&amp;nbsp;M solution in hexanes)</td><td>Acros</td><td>21335-1000</td><td>air-sensitive, flammable</td></tr><tr><td>Sodium methanolate</td><td>Acros</td><td>17312-0050</td><td></td></tr><tr><td>Tetrahydrofuran (unstabilized, for HPLC)</td><td>Fisher Chemicals</td><td>T/0706/PB17</td><td>This solvent was dried as well as degassed using a solvent purification system (Innovative Technology, Inc, Amesbury, MA, USA)</td></tr><tr><td>Toluene (for HPLC)</td><td>Fisher Chemicals</td><td>T/2306/17</td><td>This solvent was dried as well as degassed using a solvent purification system (Innovative Technology, Inc, Amesbury, MA, USA)</td></tr><tr><td>Acetonitrile (for HPLC)</td><td>Fisher Chemicals</td><td>A/0627/17</td><td>This solvent was dried as well as degassed using a solvent purification system (Innovative Technology, Inc, Amesbury, MA, USA)</td></tr><tr><td>Dichloromethane (Extra Dry over Molecular Sieve)</td><td>Acros</td><td>34846-0010</td><td></td></tr><tr><td>Chloroforme (p.a.)</td><td>VWR International</td><td>1.02445.1000</td><td></td></tr><tr><td>Pentane</td><td>Reactolab</td><td>99050</td><td>Purchased as reagent grade and distilled once prior to use</td></tr><tr><td>Heptane</td><td>Reactolab</td><td>99733</td><td>Purchased as reagent grade and distilled once prior to use</td></tr><tr><td>Dichloromethane</td><td>Reactolab</td><td>99375</td><td>Purchased as reagent grade and distilled once prior to use</td></tr><tr><td>Diethylether</td><td>Reactolab</td><td>99362</td><td>Purchased as reagent grade and distilled once prior to use</td></tr><tr><td>Geduran silica gel (Si 60, 40-60&amp;nbsp;&amp;micro;m)</td><td>Merck</td><td>1115671000</td><td></td></tr><tr><td>Langmuir trough</td><td>R&amp;amp;K, Potsdam</td><td></td><td></td></tr><tr><td>Thermostat&amp;nbsp;</td><td>E1 Medingen</td><td></td><td></td></tr><tr><td>Hamilton syringe&amp;nbsp;</td><td>Model 1810 RN SYR</td><td></td><td></td></tr><tr><td>Vertex 70 FT-IR spectrometer&amp;nbsp;</td><td>Bruker</td><td></td><td></td></tr><tr><td>External air/water reflection unit (XA-511)&amp;nbsp;</td><td>Bruker</td><td></td><td></td></tr><tr><td>UV lamp (250 W, Ga-doped metal halide bulb)</td><td>UV-Light Technology</td><td></td><td></td></tr><tr><td>Brewster angle microscope (BAM1+)&amp;nbsp;</td><td>NFT G&amp;ouml;ttingen</td><td></td><td></td></tr><tr><td>Sapphire substrates</td><td>Stecher Ceramics</td><td></td><td></td></tr><tr><td>Quantifoil holey carbon TEM grids</td><td>Electron Microscopy Sciences</td><td></td><td></td></tr><tr><td>Nuclear magnetic resonance spectrometer (Bruker Avance III 400)</td><td>Bruker</td><td></td><td></td></tr><tr><td>JASCO V-670 UV/Vis spectrometer</td><td>JASCO</td><td></td><td></td></tr><tr><td>Scanning Electron Microscope (Zeiss Merlin FE-SEM)</td><td>Zeiss</td><td></td><td></td></tr></tbody></table>

preparation of carbon nanosheets at room temperature

Amphiphilic molecules equipped with a reactive, carbon-rich "oligoyne" segment consisting of conjugated carbon-carbon triple bonds self-assemble into defined aggregates in aqueous media and at the air-water interface. In the aggregated state, the oligoynes can then be carbonized under mild conditions while preserving the morphology and the embedded chemical functionalization. This novel approach provides direct access to functionalized carbon nanomaterials. In this article, we present a synthetic approach that allows us to prepare hexayne carboxylate amphiphiles as carbon-rich siblings of typical fatty acid esters through a series of repeated bromination and Negishi-type cross-coupling reactions. The obtained compounds are designed to self-assemble into monolayers at the air-water interface, and we show how this can be achieved in a Langmuir trough. Thus, compression of the molecules at the air-water interface triggers the film formation and leads to a densely packed layer of the molecules. The complete carbonization of the films at the air-water interface is then accomplished by cross-linking of the hexayne layer at room temperature, using UV irradiation as a mild external stimulus. The changes in the layer during this process can be monitored with the help of infrared reflection-absorption spectroscopy and Brewster angle microscopy. Moreover, a transfer of the carbonized films onto solid substrates by the Langmuir-Blodgett technique has enabled us to prove that they were carbon nanosheets with lateral dimensions on the order of centimeters.

The 13C nuclear magnetic resonance (NMR) spectrum of the prepared precursor molecule 3 displays the 12&#160;sp-hybridized carbon atoms of the hexayne segment with the corresponding chemical shifts of &#948; = 82-60 ppm (Figure 1b). Moreover, the signals at &#948; = 173 ppm and at &#948; = 52&#160;ppm are assigned to the carbonyl and methyl carbon of the ester, respectively. The signals between &#948; = 33-14 ppm are ascribed to the ali...

Watch this Scientific Journal Video about Preparation of Carbon Nanosheets at Room Temperature at JoVE.com

Preparation of Carbon Nanosheets at Room Temperature

We present the synthesis of an amphiphilic hexayne and its use in the preparation of carbon nanosheets at the air-water interface from a self-assembled monolayer of these reactive, carbon-rich molecular precursors.

Amphiphilic molecules equipped with a reactive, carbon-rich "oligoyne" segment consisting of conjugated carbon-carbon triple bonds self-assemble into ...

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Chemical Bonding: Basic Concepts

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12.0K Views.  Ecole Polytechnique Fédérale de Lausanne (EPFL). We present the synthesis of an amphiphilic hexayne and its use in the preparation of carbon nanosheets at the air-water interface from a self-assembled monolayer of these reactive, carbon-rich molecular precursors.

Video: Preparation of Carbon Nanosheets at Room Temperature

Fabrication, Densification, and Replica Molding of 3D Carbon Nanotube Microstructures

The introduction of new materials and processes to microfabrication has, in large part, enabled many important advances in microsystems, lab-on-a-chip devices, and their applications. In particular, capabilities for cost-effective fabrication of polymer microstructures were transformed by the advent of soft lithography and other micromolding techniques 1, 2, and this led a revolution in applications of microfabrication to biomedical engineering and biology. Nevertheless, it remains challenging to fabricate microstructures with well-defined nanoscale surface textures, and to fabricate arbitrary 3D shapes at the micro-scale. Robustness of master molds and maintenance of shape integrity is especially important to achieve high fidelity replication of complex structures and preserving their nanoscale surface texture. The combination of hierarchical textures, and heterogeneous shapes, is a profound challenge to existing microfabrication methods that largely rely upon top-down etching using fixed mask templates. On the other hand, the bottom-up synthesis of nanostructures such as nanotubes and nanowires can offer new capabilities to microfabrication, in particular by taking advantage of the collective self-organization of nanostructures, and local control of their growth behavior with respect to microfabricated patterns. 
Our goal is to introduce vertically aligned carbon nanotubes (CNTs), which we refer to as CNT "forests", as a new microfabrication material. We present details of a suite of related methods recently developed by our group: fabrication of CNT forest microstructures by thermal CVD from lithographically patterned catalyst thin films; self-directed elastocapillary densification of CNT microstructures; and replica molding of polymer microstructures using CNT composite master molds. In particular, our work shows that self-directed capillary densification ("capillary forming"), which is performed by condensation of a solvent onto the substrate with CNT microstructures, significantly increases the packing density of CNTs. This process enables directed transformation of vertical CNT microstructures into straight, inclined, and twisted shapes, which have robust mechanical properties exceeding those of typical microfabrication polymers. This in turn enables formation of nanocomposite CNT master molds by capillary-driven infiltration of polymers. The replica structures exhibit the anisotropic nanoscale texture of the aligned CNTs, and can have walls with sub-micron thickness and aspect ratios exceeding 50:1. Integration of CNT microstructures in fabrication offers further opportunity to exploit the electrical and thermal properties of CNTs, and diverse capabilities for chemical and biochemical functionalization 3.

We present methods for fabrication of patterned microstructures of vertically aligned carbon nanotubes (CNTs), and their use as master molds for production of polymer microstructures with organized nanoscale surface texture. The CNT forests are densified by condensation of solvent onto the substrate, which significantly increases their packing density and enables self-directed formation of 3D shapes.

The introduction of new materials and processes to microfabrication has, in large part, enabled many important advances in microsystems, lab-on-a-chip ...

Engineering

Dry Oxidation and Vacuum Annealing Treatments for Tuning the Wetting Properties of Carbon Nanotube Arrays

In this article, we describe a simple method to reversibly tune the wetting properties of vertically aligned carbon nanotube (CNT) arrays. Here, CNT arrays are defined as densely packed multi-walled carbon nanotubes oriented perpendicular to the growth substrate as a result of a growth process by the standard thermal chemical vapor deposition (CVD) technique.1,2 These CNT arrays are then exposed to vacuum annealing treatment to make them more hydrophobic or to dry oxidation treatment to render them more hydrophilic. The hydrophobic CNT arrays can be turned hydrophilic by exposing them to dry oxidation treatment, while the hydrophilic CNT arrays can be turned hydrophobic by exposing them to vacuum annealing treatment. Using a combination of both treatments, CNT arrays can be repeatedly switched between hydrophilic and hydrophobic.2 Therefore, such combination show a very high potential in many industrial and consumer applications, including drug delivery system and high power density supercapacitors.3-5
The key to vary the wettability of CNT arrays is to control the surface concentration of oxygen adsorbates. Basically oxygen adsorbates can be introduced by exposing the CNT arrays to any oxidation treatment. Here we use dry oxidation treatments, such as oxygen plasma and UV/ozone, to functionalize the surface of CNT with oxygenated functional groups. These oxygenated functional groups allow hydrogen bond between the surface of CNT and water molecules to form, rendering the CNT hydrophilic. To turn them hydrophobic, adsorbed oxygen must be removed from the surface of CNT. Here we employ vacuum annealing treatment to induce oxygen desorption process. CNT arrays with extremely low surface concentration of oxygen adsorbates exhibit a superhydrophobic behavior.

This article describes a simple method to fabricate vertically aligned carbon nanotube arrays by CVD and to subsequently tune their wetting properties by exposing them to vacuum annealing or dry oxidation treatment.

In this article, we describe a simple method to reversibly  tune the wetting properties of vertically aligned carbon nanotube (CNT) arrays.  Here, CNT ...

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.

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 ...

Simultaneous Synthesis of Single-walled Carbon Nanotubes and Graphene in a Magnetically-enhanced Arc Plasma

Carbon nanostructures such as single-walled carbon nanotubes (SWCNT) and graphene attract a deluge of interest of scholars nowadays due to their very promising application for molecular sensors, field effect transistor and super thin and flexible electronic devices1-4. Anodic arc discharge supported by the erosion of the anode material is one of the most practical and efficient methods, which can provide specific non-equilibrium processes and a high influx of carbon material to the developing structures at relatively higher temperature, and consequently the as-synthesized products have few structural defects and better crystallinity.
 To further improve the controllability and flexibility of the synthesis of carbon nanostructures in arc discharge, magnetic fields can be applied during the synthesis process according to the strong magnetic responses of arc plasmas. It was demonstrated that the magnetically-enhanced arc discharge can increase the average length of SWCNT 5, narrow the diameter distribution of metallic catalyst particles and carbon nanotubes 6, and change the ratio of metallic and semiconducting carbon nanotubes 7, as well as lead to graphene synthesis 8. 
 Furthermore, it is worthwhile to remark that when we introduce a non-uniform magnetic field with the component normal to the current in arc, the Lorentz force along the J&times;B direction can generate the plasmas jet and make effective delivery of carbon ion particles and heat flux to samples. As a result, large-scale graphene flakes and high-purity single-walled carbon nanotubes were simultaneously generated by such new magnetically-enhanced anodic arc method. Arc imaging, scanning electron microscope (SEM), transmission electron microscope (TEM) and Raman spectroscopy were employed to analyze the characterization of carbon nanostructures. These findings indicate a wide spectrum of opportunities to manipulate with the properties of nanostructures produced in plasmas by means of controlling the arc conditions.

Anodic arc discharge is one of the most practical and efficient methods to synthesize various carbon nanostructures. To increase the arc controllability and flexibility, a non-uniform magnetic field was introduced to process the one-step synthesis of large-scale graphene flakes and high-purity single-walled carbon nanotubes.

Carbon nanostructures such as single-walled carbon nanotubes (SWCNT) and graphene attract a deluge of interest of scholars nowadays due to their very ...

Bioengineering

Synthesis and Functionalization of 3D Nano-graphene Materials: Graphene Aerogels and Graphene Macro Assemblies

Efforts to assemble graphene into three-dimensional monolithic structures have been hampered by the high cost and poor processability of graphene. Additionally, most reported graphene assemblies are held together through physical interactions (e.g., van der Waals forces) rather than chemical bonds, which limit their mechanical strength and conductivity. This video method details recently developed strategies to fabricate mass-producible, graphene-based bulk materials derived from either polymer foams or single layer graphene oxide. These materials consist primarily of individual graphene sheets connected through covalently bound carbon linkers. They maintain the favorable properties of graphene such as high surface area and high electrical and thermal conductivity, combined with tunable pore morphology and exceptional mechanical strength and elasticity. This flexible synthetic method can be extended to the fabrication of polymer/carbon nanotube (CNT) and polymer/graphene oxide (GO) composite materials. Furthermore, additional post-synthetic functionalization with anthraquinone is described, which enables a dramatic increase in charge storage performance in supercapacitor applications.

This video method describes the synthesis of high surface area, monolithic 3D graphene-based materials derived from polymer precursors as well as single layer graphene oxide.

Efforts to assemble graphene into three-dimensional monolithic structures have been hampered by the high cost and poor processability of graphene. ...

Fabrication of Low Temperature Carbon Nanotube Vertical Interconnects Compatible with Semiconductor Technology

We demonstrate a method for the low temperature growth (350 &#176;C) of vertically-aligned carbon nanotubes (CNT) bundles on electrically conductive thin-films. Due to the low growth temperature, the process allows integration with modern low-&#954; dielectrics and some flexible substrates. The process is compatible with standard semiconductor fabrication, and a method for the fabrication of electrical 4-point probe test structures for vertical interconnect test structures is presented. Using scanning electron microscopy the morphology of the CNT bundles is investigated, which demonstrates vertical alignment of the CNT and can be used to tune the CNT growth time. With Raman spectroscopy the crystallinity of the CNT is investigated. It was found that the CNT have many defects, due to the low growth temperature. The electrical current-voltage measurements of the test vertical interconnects displays a linear response, indicating good ohmic contact was achieved between the CNT bundle and the top and bottom metal electrodes. The obtained resistivities of the CNT bundle are among the average values in the literature, while a record-low CNT growth temperature was used.

A method for the growth of low temperature vertically-aligned carbon nanotubes, and the subsequent fabrication of vertical interconnect electrical test structures using semiconductor fabrication is presented.

We demonstrate a method for the low temperature growth (350 &#176;C) of vertically-aligned carbon nanotubes (CNT) bundles on electrically conductive ...

Preparation of Liquid-exfoliated Transition Metal Dichalcogenide Nanosheets with Controlled Size and Thickness: A State of the Art Protocol

We summarize recent advances in the production of liquid-exfoliated transition metal dichalcogenide (TMD) nanosheets with controlled size and thickness. Layered crystals of molybdenum disulphide (MoS2) and tungsten disulphide (WS2) are exfoliated in aqueous surfactant solution by sonication. This yields highly polydisperse mixtures containing nanosheets with broad size and thickness distributions. However, for most purposes, specific sizes (in terms of both lateral dimension and thickness) are required. For example, large and thin nanosheets are desired for (opto) electronic applications, while laterally small nanosheets are interesting for catalytic applications. Therefore, post-exfoliation size selection is an important step that we address here. We provide a detailed protocol on the efficient size selection in large quantities by liquid cascade centrifugation and the size and thickness quantification by statistical microscopic analysis (atomic force microscopy and transmission electron microscopy). The comparison of MoS2 and WS2 shows that both materials are size-selected in a similar way by the same procedure. Importantly, the dispersions of size-selected nanosheets show systematic changes in their optical extinction spectra with size due to edge and confinement effects. We show how these optical changes are related quantitatively to the nanosheets dimensions and describe how mean nanosheets length and layer number can be extracted reliably from the extinction spectra. The exfoliation and size selection protocol can be applied to a broad range of layered crystals as we have previously demonstrated for graphene, gallium sulphide (GaS) and black phosphorus.

A protocol for the liquid exfoliation of layered materials to nanosheets, their size selection and size measurement by microscopic and spectroscopic techniques is presented.

We summarize recent advances in the production of liquid-exfoliated transition metal dichalcogenide (TMD) nanosheets with controlled size and thickness. ...

Grafting Multiwalled Carbon Nanotubes with Polystyrene to Enable Self-Assembly and Anisotropic Patchiness

We demonstrate a straightforward protocol to graft pristine multiwalled carbon nanotubes (MWCNTs) with polystyrene (PS) chains at the sidewalls through a free-radical polymerization strategy to enable the modulation of the nanotube surface properties and produce supramolecular self-assembly of the nanostructures. First, a selective hydroxylation of the pristine nanotubes through a biphasic catalytically mediated oxidation reaction creates superficially distributed reactive sites at the sidewalls. The latter reactive sites are subsequently modified with methacrylic moieties using a silylated methacrylic precursor to create polymerizable sites. Those polymerizable groups can address further polymerization of styrene to produce a hybrid nanomaterial containing PS chains grafted to the nanotube sidewalls. The polymer-graft content, amount of silylated methacrylic moieties introduced and hydroxylation modification of the nanotubes are identified and quantified by Thermogravimetric Analysis (TGA). The presence of reactive functional groups hydroxyl and silylated methacrylate are confirmed by Fourier Transform Infrared Spectroscopy (FT-IR). Polystyrene-grafted carbon nanotube solutions in tetrahydrofuran (THF) provide wall-to-wall collinearly self-assembled nanotubes when cast samples are analyzed by transmission electron microscopy (TEM). Those self-assemblies are not obtained when suitable blanks are similarly cast from analogous solutions containing non-grafted counterparts. Therefore, this method enables the modification of the nanotube anisotropic patchiness at the sidewalls which results into spontaneous auto-organization at the nanoscale.

A procedure for the synthesis of polystyrene-grafted multiwalled carbon nanotubes using successive chemical modification steps to selectively introduce the polymer chains to the sidewalls and their self-assembly via anisotropic patchiness is presented.

We demonstrate a straightforward protocol to graft pristine multiwalled carbon nanotubes (MWCNTs) with polystyrene (PS) chains at the sidewalls through a ...

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 ...

Tuning the Acidity of Pt/ CNTs Catalysts for Hydrodeoxygenation of Diphenyl Ether

We herein present a method for the synthesis of HNbWO6, HNbMoO6, HTaWO6 solid acid nanosheet modified Pt/CNTs. By varying the weight of various solid acid nanosheets, a series of Pt/xHMNO6/CNTs with different solid acid compositions (x = 5, 20 wt%; M = Nb, Ta; N = Mo, W) have been prepared by carbon nanotube pretreatment, protonic exchange, solid acid exfoliation, aggregation and finally Pt particles impregnation. The Pt/xHMNO6/CNTs are characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and NH3-temperature programmed desorption. The study revealed that HNbWO6 nanosheets were attached on CNTs, with some edges of the nanosheets being bent in shape. The acid strength of the supported Pt catalysts increases in the following order: Pt/CNTs &#60; Pt/5HNbWO6/CNTs &#60; Pt/20HNbMoO6/CNTs &#60; Pt/20HNbWO6/CNTs &#60; Pt/20HTaWO6/CNTs. In addition, the catalytic hydroconversion of lignin-derived model compound: diphenyl ether using the synthesized Pt/20HNbWO6 catalyst has been investigated.

A protocol for the synthesis of HNbWO6, HNbMoO6, HTaWO6 solid acid nanosheet modified Pt/CNTs is presented.

We herein present a method for the synthesis of HNbWO6, HNbMoO6, HTaWO6 solid acid nanosheet modified Pt/CNTs. By varying the weight of various solid acid ...