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Summary
Abstract
Introduction
Protocol
Results
Discussion
Disclosures
Acknowledgements
Materials
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화학

碳纳米片在室温下准备

Published: March 08, 2016
doi:
10.3791/53505
, , , , ,
1Institute of Materials,Ecole Polytechnique Fédérale de Lausanne (EPFL), 2Colloid Chemistry Department,Max Planck Institute of Colloids and Interfaces

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

二维碳纳米结构吸引显著关注，因为报告的优秀电，热和机械性能1-5。这些材料有望进一步在聚合物复合材料6中 ，能量存储装置7，和分子电子8-10的领域的技术进步。尽管近年来深入研究的努力，但是，获得更大量的定义良好的碳纳米的仍然有限，阻碍他们在技术应用11,12大规模实施。

碳纳米材料是由两种自上而下或自下而上的方法进行访问。典型的方法，如剥脱技术，13或表面上的14-16高能过程提供可能获得的材料具有高度的结构完美，非常不错的表现的。然而，隔离和第纯化Ë产品仍然具有挑战性，而大规模生产定义纳米材料是困难的12。另一方面，自下而上途径可以采用依赖于使用分子前体，它们的布置成定义的结构，以及产生的碳纳米结构17-23后续碳化。在这种情况下，前体本身是更复杂的，它们的制备方法常常需要多个合成步骤。这些方法可以提供一个高度上所产生的材料的化学和物理性质的控制，并且可以提供到定制材料直接访问。但是，前体转化成碳纳米材料在温度高于800℃，这导致了嵌入式化学官能24-27的损失典型地进行。

上述限制已经通过采用高活性oligoynes了CA在我们的小组讨论在室温下28,29 N为转化成碳纳米材料。特别是，它包括一个亲水性首基和hexayne段两亲物是通过溴化和钯介导的根岸交叉偶联反应30,31的序列进行访问。这些前体分子进入靶结构的转换发生在等于或低于照射时室温用UV光。所述oligoyne两亲物的高反应性，使得使用软模板，例如空气 – 水界面或流体 – 流体界面，可能的。在以前的调查中，我们成功地制备了囊泡从hexayne苷两亲分子28的解决方案。这些囊泡的交联是由样品的UV照射温和的条件下实现的。此外，我们最近制备的自组装单层从与甲基羧酸头基团和在朗缪尔槽的空气 – 水界面的疏水性烷基尾hexaynes。密集包编分子前体然后直截了当通过UV照射转变成自支撑碳纳米片在室温下。在相关的方法中定义的分子前体，最近被用于在空气-水界面32-38制备二维扩展纳米片。

这个工作的目的是，得到的，其允许从hexayne两亲物的制备碳纳米片的总合成和制造步骤以简洁，实用的概述。焦点是关于实验方法和制备的问题。

Protocol

注意：请确保使用任何化学化合物的前咨询相关材料安全数据表（MSDS）。一些在这些合成中使用的化学品是剧毒和致癌性。相比，他们的大部分对手准备纳米材料可能有额外的危害。当务之急是进行反应（通风柜）和个人防护装备（护目镜，手套，实验室外套，全长裤，封闭趾鞋）时使用所有适当的安全措施。如果没有另外说明以下过程涉及标准Schlenk技术39。 1.前体?…

Representative Results

制备的前体分子的13 C核磁共振（NMR）谱3显示hexayne段与δ= 82-60 ppm的（ 图1b）的相应的化学位移的12 藻 -杂化的碳原子。此外，在δ= 173 ppm或在δ= 52 ppm的所述信号被分别分配到酯的羰基和甲基碳。 δ= 33-14 ppm的之间的信号被归因于十二烷基残基的脂肪族碳。的3对应的紫外/可见吸收光谱示出了hexayne（ 图1c）的?…

Discussion

所需hexayne两亲物（3）直接地通过顺序溴化52,53编写并由tritylphenyl酯（2）（ 图1a）29的最终的脱保护反应Pd催化的炔段的伸长30,31，接着。成功合成由13 C NMR谱（ 图1b），以及紫外吸收光谱（ 图1c）31,54证实。这表明随和的个性由更高的同系物oligoyne可以通过发达的合成方法30,31准备。然而，为了保持oligoyne衍生物?…

Disclosures

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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Tags

Carbon NanosheetsRoom TemperatureWet Chemical PreparationSelf-assemblyAmphiphilic MoleculesCarbonizationUV IrradiationHexayneLangmuir TroughInfrared Reflection Absorption Spectroscopy
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Schrettl, S., Schulte, B., Stefaniu, C., Oliveira, J., Brezesinski, G., Frauenrath, H. Preparation of Carbon Nanosheets at Room Temperature. J. Vis. Exp. (109), e53505, doi:10.3791/53505 (2016).
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