Graphene-Molecule Hybrid Structures | Science & Technology | Chemical & Engineering News


Graphene-Molecule Hybrid Structures | Science & Technology | Chemical & Engineering News

viaGraphene-Molecule Hybrid Structures | Science & Technology | Chemical & Engineering News.

„Garbage and other low-value materials make excellent starting materials for high-quality graphene, according to a study by Rice University chemists in ACS Nano (DOI: 10.1021/nn202625c). The report describes a straightforward procedure to convert inexpensive sources of carbon—even  “negative value” materials such as dog feces—to ultrathin films of pure carbon.

Graphene’s large collection of outstanding mechanical, electronic, thermal, and other properties have prompted many scientists  to search for ways to prepare large sheets of this often one-atom-thin form of carbon. Several chemical vapor deposition methods do that job well, but they generally require expensive substrates on which to grow graphene and/or reagents such as methane, acetylene, and organic solids that must be purified before use.

The Rice team, led by James M. Tour, has shown that there’s no need to use costly purified starting materials to grow graphene.  The team, which also includes Gedeng Ruan, Zhengzong Sun, and Zhiwei Peng, prepared graphene from feces, grass, a cockroach leg, bulk polystyrene, chocolate, and Girl Scout cookies.

In all cases, the group placed a solid sample on copper foil in a quartz boat and briefly heated the material to 1,050 °C under a low-pressure hydrogen-argon flow. The team reports that residues containing several elements remained on the sample                           side of the foil after heat treatment. On the back side, however, they found pristine and nearly defect-free graphene, as  judged from analyses based on Raman, UV-visible, and X-ray photoelectron spectroscopies and microscopy analysis.

“These results show convincingly that large-scale high-quality graphene can be grown from impure carbon sources with low or  negative values,” says Changgan Zeng of the University of Science & Technology of China, Hefei. “This is quite amazing, since  we usually assume that high-quality graphene requires pure carbon sources,” Zeng says. He adds that “the idea is brilliant,”  but the mechanism by which graphene forms on the back of the foil is still unknown. “

This might be a further step to improve semiconducturs. Solid matarial out of thermic and enzymatic processes shoud be further investigated.

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Über hinterauer

Pensionated Radiologist, interested in Green Chemistry, Technology, Environment and Share | var addthis_config = {"data_track_clickback":true}; nce.
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5 Antworten zu Graphene-Molecule Hybrid Structures | Science & Technology | Chemical & Engineering News

  1. hinterauer schreibt:

    This is very imortant for the future developement of photovoltaics and computers. Especially for downsizing.

  2. hinterauer schreibt:

    Of equql value is: „white gaphene“ because:
    „Interfaces play a key role in low dimensional materials like graphene or its boron nitrogen analog, white graphene. The edge energy of hexagonal boron nitride (h-BN) has not been determined as its lower symmetry makes it difficult to separate the opposite B-rich and N-rich zigzag sides. We report unambiguous energy values for arbitrary edges of BN, including the dependence on the elemental chemical potentials of B and N species. A useful manifestation of the additional Gibbs degree of freedom in the binary system, this dependence offers a way to control the morphology of pure BN or its carbon inclusions and to engineer their electronic and magnetic properties.“ acs.

    Keywords: Boron-nitride; graphene; edges; interfaces; bandgap; magnetism

  3. hinterauer schreibt:

    How could Graphene be modified?

    Modifying Graphene Via A Classic Route

    ACS Meeting News: Textbook reaction offers customized, covalent functionalization of carbon material’s properties

    Mitch Jacoby

    View Enlarged ImageAdapted from Angew. Chem. Intl. Ed.
    CLASSICALLY TAILORED Classic organic transformations can impart diverse functionality to graphene.

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    Topics Covered

    graphene, functionalized graphene, Claisen rearrangement

    Latest News
    
    August 31, 2011

    » ACS Meetings News

    Modifying Graphene Via A Classic Route

    ACS Meeting News: Textbook reaction offers customized, covalent functionalization of carbon material’s properties.

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    Cheap, Simple Test Spots Protein-Protein Interactions

    Biological Assay: Using graphene oxide, a new method could help researchers find peptide-based drugs.

    Intoxicating Chemistry

    ACS Meeting News: In spirited research, chemists use brand-name liquors as solvents for organic syntheses.

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    By applying a classic organic chemistry reaction to graphene, researchers at MIT have come up with a customizable route to covalently modify this ultrathin form of carbon. The work may lead to procedures for attaching various functional groups to graphene and hence altering its chemical and physical properties—a prerequisite to broadening the material’s applications.

    The research was led by MIT chemistry professor Timothy M. Swager, who reported on the work on Aug. 29 at a Division of Organic Chemistry symposium at the American Chemical Society national meeting in Denver. The group also published the study in Angewandte Chemie International Edition (DOI: 10.1002/anie.201101371).

    Because of graphene’s outstanding mechanical, electronic, thermal, and other properties, scientists in many countries are working on ways to exploit graphene in microelectronics, energy storage, and other applications. In many cases, the scope or performance of graphene-based applications or simply the ease of handling the material could be improved by chemically modifying it. Yet only a few such modifications have been developed.

    The MIT group has just extended that list by demonstrating that graphene can be functionalized via Claisen rearrangement chemistry. Specifically, the team showed that allylic alcohol groups on the surface of graphite oxide, a common starting material in graphene research, can be directly converted into carbon-bound N,N-dimethylamide groups by reacting graphite oxide with the commercial vinyl transfer agent N,N-dimethylacetamide dimethyl acetal. The results were confirmed by X-ray photoelectron spectroscopy measurements and other types of analyses.

    Then the group showed that additional functionality could be imparted to the graphene derivative by reacting the newly installed amide groups with potassium hydroxide solution. That process converted the amides into surface carboxylate groups, which increased the graphene derivative’s water solubility and its colloidal stability.

    „This method offers a powerful means to covalently attach functional groups to the surface of graphene,“ says University of Texas, Austin, chemistry professor Christopher W. Bielawski. „It is likely to pave the way to new carbon functionalization schemes.“

    Bielawski adds that despite graphene’s extraordinary properties, it remains challenging to manipulate the material. „There is good reason to believe that chemical modification will alleviate these challenges and enhance performance in applications,“ he says.

    Elaborating on that point, Bielawski notes that by modifying graphene with water-solubilizing functional groups, Swager’s team tailored the material’s solubility in aqueous media. „Now we can think about new ways of transferring graphene between various substrates—a basic manipulation that may accelerate development of graphene applications,“ he says.

    Chemical & Engineering NewsISSN 0009-2347 Copyright © 2011 American Chemical Society

  4. hinterauer schreibt:

    A graphene oxide-based assay could provide chemists with an inexpensive means to detect protein-protein interactions (Anal. Chem., DOI: 10.1021/ac200617k).

    To discover peptide-based drug candidates, researchers often monitor how a disease-related protein interacts with libraries of small peptides. The biggest challenge is developing an easily measurable signal for when the proteins bind to peptides, says Chun-Hua Lu of Fuzhou University, in China. Fluorescence resonance energy transfer (FRET) spectroscopy, which monitors the distance between fluorescent molecules attached to the proteins, is commonly used, but to generate a signal, it often requires a protein to change shape upon binding. To study proteins that don’t shape shift, Lu and his colleagues developed a more general approach.

    To the end of a peptide, the researchers attach pyrene and measure its fluorescence with a spectrometer. Then, they mix the tagged peptide with graphene oxide, which pyrene binds to. Graphene oxide, made from the same inexpensive graphite at the core of most pencils, quenches the fluorescent signal from the pyrene-bound peptide when pyrene stacks onto its flat surface. Finally, the researchers add the protein of interest. If it binds to the peptide, the tagged peptide leaves the graphene oxide and the fluorescent signal returns.

    The team tested the assay with a well-studied system: a peptide that is a hallmark of HIV infection along with a human antibody that binds it. They found that as little as 200 pM of the antibody rekindled pyrene’s glow.

    To test their method further, the researchers next applied the antibody in samples of human saliva and serum, which contain molecules that could disrupt the protein-peptide interaction. Even with the additional chemicals present, the assay had detection limits of 2 nM in saliva and 5 nM in a solution made from human serum. These limits match those of existing methods, Lu says.

    To test their method with other protein-peptide pairs, the researchers successfully detected binding between different peptides and a second HIV antibody, as well as with a protein called α-bungarotoxin from snake venom.

    Kevin Plaxco of the University of California, Santa Barbara, is „cautiously optimistic“ about the new assay. Since Lu’s team looked at three different protein-peptide systems, he says the method probably works more broadly, but he thinks more research is needed to prove it.

  5. rudolfhinterauer schreibt:

    silicene and graphene are the future of thin-layer physiks.

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