室温における炭素ナノシートの作製
Summary
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.
Abstract
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.
Introduction
二次元のカーボンナノ構造体が原因で報告された優れた熱、電気だけでなく、機械的特性1-5に大きな注目を集めています。これらの材料は、ポリマー複合6、エネルギー貯蔵装置7と、分子エレクトロニクス8-10の分野における技術的進歩を促進することが期待されます。近年の集中的な研究努力にもかかわらず、しかし、明確に定義されたカーボンナノ材料のより多くの量へのアクセスはまだ技術的応用11,12での大規模な実装を妨げている、制限されています。
カーボンナノ材料は、トップダウンまたはボトムアップのいずれかの方法でアクセスできます。このような表面14-16上に剥離技術13または高エネルギープロセスのような典型的なアプローチは、構造的な完全かつ非常に良好な性能の高い材料を得るために可能性を提供します。目のただし、単離及び精製電子製品が困難なままであり、定義されたナノ構造材料の大規模生産が困難である12。一方、ボトムアップアプローチは、分子前駆体の使用に依存していること、その定義された構造に構成し、カーボンナノ構造体17-23が得られる後続の炭化を用いることができます。この場合、前駆体自体は、より複雑であり、それらの製造は、多くの場合、複数の合成工程を必要とします。これらのアプローチは、得られる材料の化学的および物理的特性を高度に制御提供することがありますし、合わせた材料への直接アクセスを提供することができます。しかし、カーボンナノ材料への前駆体の変換は、典型的には、埋め込 まれた化学官能24-27の損失につながる、800℃以上の温度で行われます。
上記の制限は、そのcaの反応性の高いoligoynesを採用することにより、当社グループで対処されましたnは室温28,29でカーボンナノ材料に変換すること。具体的には、親水性の頭部基とhexayneセグメントを含む両親媒性物質は、臭素化およびパラジウム媒介根岸クロスカップリング反応30,31のシーケンスを介してアクセス可能です。標的構造へのこれらの前駆体分子の変換は、紫外光照射により室温以下に起こります。 oligoyne両親媒性物質の高い反応性は、そのような可能な空気 – 水界面または流体 – 流体界面、のような柔らかいテンプレートを利用します。以前の研究では、我々が正常にhexayne配糖体の両親媒性物質28の溶液から小胞を用意しました。これらの小胞の架橋サンプルのUV照射により温和な条件下で達成されました。さらに、我々は最近、メチルカルボキシレート頭部基とラングミュアトラフ内の空気 – 水界面における疎水性のアルキル尾を持つhexaynesから自己組織化単分子膜を作成しました。密にパックエド分子前駆体は、その後、直接的にUV照射により、室温で自立カーボンナノシートに変換しました。関連するアプローチで定義された分子前駆体は、最近、空気-水界面32-38において二次元拡張ナノシートの製造のために使用されてきました。
この作業の目的は、hexayne両親媒性物質からの炭素ナノシートの調製を可能全体の合成および製造工程の簡潔な、実用的な概要を提供することです。焦点は、実験的なアプローチと取質問にあります。
Protocol
Representative Results
Discussion
所望hexayne両親媒性物質（3）は、直接的に順次臭素52,53及びトリチルエステル（2）（ 図1a）29の最終的な脱保護反応が続くアルキンセグメントのPd触媒伸長30,31、によって調製されます。成功した合成は、13 C NMRスペクトル（ 図1b）と同様にUV-Vis吸収スペクトル（ 図1c）31,54によって確認されます。これは、より高い…
Declarações
The authors have nothing to disclose.
Acknowledgements
Funding from the European Research Council (ERC Grant 239831) and a Humboldt Fellowship (BS) is gratefully acknowledged.
Materials
| Methyllithium lithium bromide complex (2.2M solution in diethylether) | Acros | 18129-1000 | air-sensitive, flammable |
| Zinc chloride (0.7M solution in THF) | Acros | 38945-1000 | air-sensitive, flammable |
| 1,1'-Bis(diphenylphosphino)ferrocene] dichloropalladium(II), DCM adduct |
Boron Molecular | BM187 | |
| N-Bromosuccinimide | Acros | 10745 | light-sensitive |
| Silver fluoride | Fluorochem | 002862-10g | light-sensitive |
| n-Butyllithium (2.5M solution in hexanes) | Acros | 21335-1000 | air-sensitive, flammable |
| Sodium methanolate | Acros | 17312-0050 | |
| Tetrahydrofuran (unstabilized, for HPLC) | Fisher Chemicals | T/0706/PB17 | This solvent was dried as well as degassed using a solvent purification system (Innovative Technology, Inc, Amesbury, MA, USA) |
| Toluene (for HPLC) | Fisher Chemicals | T/2306/17 | This solvent was dried as well as degassed using a solvent purification system (Innovative Technology, Inc, Amesbury, MA, USA) |
| Acetonitrile (for HPLC) | Fisher Chemicals | A/0627/17 | This solvent was dried as well as degassed using a solvent purification system (Innovative Technology, Inc, Amesbury, MA, USA) |
| Dichloromethane (Extra Dry over Molecular Sieve) | Acros | 34846-0010 | |
| Chloroforme (p.a.) | VWR International | 1.02445.1000 | |
| Pentane | Reactolab | 99050 | Purchased as reagent grade and distilled once prior to use |
| Heptane | Reactolab | 99733 | Purchased as reagent grade and distilled once prior to use |
| Dichloromethane | Reactolab | 99375 | Purchased as reagent grade and distilled once prior to use |
| Diethylether | Reactolab | 99362 | Purchased as reagent grade and distilled once prior to use |
| Geduran silica gel (Si 60, 40-60µm) | Merck | 1115671000 | |
| Langmuir trough | R&K, Potsdam | ||
| Thermostat | E1 Medingen | ||
| Hamilton syringe | Model 1810 RN SYR | ||
| Vertex 70 FT-IR spectrometer | Bruker | ||
| External air/water reflection unit (XA-511) | Bruker | ||
| UV lamp (250 W, Ga-doped metal halide bulb) | UV-Light Technology | ||
| Brewster angle microscope (BAM1+) | NFT Göttingen | ||
| Sapphire substrates | Stecher Ceramics | ||
| Quantifoil holey carbon TEM grids | Electron Microscopy Sciences | ||
| Nuclear magnetic resonance spectrometer (Bruker Avance III 400) | Bruker | ||
| JASCO V-670 UV/Vis spectrometer | JASCO | ||
| Scanning Electron Microscope (Zeiss Merlin FE-SEM) | Zeiss |
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