彩色碳纳米管薄膜的样品，如在制造反应器中产生的。图片：阿尔托大学。
单壁碳纳米管或一个原子厚度的石墨烯层卷成不同的尺寸和形状，已经在电子和新的触摸屏设备中找到了许多用途。本质上，碳纳米管通常是黑色或深灰色。
在他们发表在美国化学学会期刊（JACS）上的新研究中，阿尔托大学的研究人员提出了一种控制碳纳米管薄膜制造的方法，以便它们显示出各种不同的颜色 - 例如绿色，棕色或银灰色。
研究人员认为，这是次通过直接合成生产有色碳纳米管。使用他们的发明，在制造过程中直接引起颜色，而不是在成品合成管上采用一系列净化技术。
通过直接合成，可以生产大量清洁的样品材料，同时避免在净化过程中损坏产品 - 这使其成为具吸引力的应用方法。
“从理论上讲，这些彩色薄膜可以用来制作具有多种不同颜色的触摸屏，或者太阳能电池可以显示出全新的光学特性，”阿尔托大学教授Esko Kauppinen说。
让碳结构显示颜色本身就是一项壮举。实现着色所需的基础技术也意味着对纳米管结构的结构的精细控制。Kauppinen和他的团队独特的方法，使用金属和碳的气溶胶，使他们可以直接从制造过程中仔细操纵和控制纳米管结构。
“在某种程度上，生长碳纳米管就像植树一样：我们需要种子，饲料和太阳热。对我们来说，铁的气溶胶纳米粒子可以作为催化剂或种子，一氧化碳作为碳的来源，所以饲料和“反应堆在850摄氏度以上的温度下发热，”阿尔托大学资深科学家华江博士说。
Kauppinen教授的团队在他们的单一生产方法中使用这些资源的历史悠久。为了增加他们的曲目，他们近尝试在制造过程中施用小剂量的二氧化碳。
“二氧化碳是一种可用于调节各种颜色碳纳米管生长的移植材料，”江解释说。
利用先进的电子衍射技术，研究人员能够找到其薄膜的精确原子尺度结构。他们发现它们具有非常窄的手性分布，这意味着管壁的蜂窝晶格的取向在整个样品中几乎是均匀的。手性或多或少地决定了碳纳米管可具有的电特性以及它们的颜色。
在阿尔托大学开发的方法承诺以高产率制造碳纳米管薄膜的简单且高度可扩展的方法。
“通常你必须在批量生产或对碳纳米管结构有良好控制之间做出选择。凭借我们的突破，我们可以做到这两点，”该集团博士后研究员张强博士表示。
后续工作已在进行中。
“我们希望了解二氧化碳添加如何调整纳米管结构并产生颜色的科学。我们的目标是实现对生长过程的完全控制，以便单壁碳纳米管可用作构建块的基础。下一代纳米电子器件，“Kauppinen教授说。
原文如下：
原文如下：
Researchers present a technique to produce large quantities of pristine single-walled carbon nanotubes in selec shades of the rainbow. The secret is a fine-tuned fabrication process—and a small dose of CO2.
Samples of the colourful carbon nanotube thin films, as produced in the fabrication reactor. Image: Aalto University.
Samples of the colourful carbon nanotube thin films, as produced in the fabrication reactor. Image: Aalto University.
Single-walled carbon nanotubes, or sheets of one atom-thick layers of graphene rolled up into different sizes and shapes, have found many uses in electronics and new touch screen devices. By nature, carbon nanotubes are typically black or a dark grey.
In their new study published in the Journal of the American Chemical Society (JACS), Aalto University researchers present a way to control the fabrication of carbon nanotube thin films so that they display a variety of different colours—for instance, green, brown, or a silvery grey.
The researchers believe this is the first time that coloured carbon nanotubes have been produced by direct synthesis. Using their invention, the colour is induced straight away in the fabrication process, not by employing a range of purifying techniques on finished, synthesized tubes.
With direct synthesis, large quantities of clean sample materials can be produced while also avoiding damage to the product in the purifying process—which makes it the most attractive approach for applications.
"In theory, these coloured thin films could be used to make touch screens with many different colours, or solar cells that display completely new types of optical properties," says Esko Kauppinen, Professor at Aalto University.
To get carbon structures to display colours is a feat in itself. The underlying techniques needed to enable the colouration also imply finely detailed control of the structure of the nanotube structures. Kauppinen and his team’s unique method, which uses aerosols of metal and carbon, allows them to carefully manipulate and control the nanotube structure directly from the fabrication process.
"Growing carbon nanotubes is, in a way, like planting trees: we need seeds, feeds, and solar heat. For us, aerosol nanoparticles of iron work as a catalyst or seed, carbon monoxide as the source for carbon, so feed, and a reactor gives heat at a temperature more than 850 degrees Celsius," says Dr. Hua Jiang, Senior Scientist at Aalto University.
Professor Esko Kauppinen with the fabrication reactor.
Professor Kauppinen’s group has a long history of using these very resources in their singular production method. To add to their repertoire, they have recently experimented with administering small doses of carbon dioxide into the fabrication process.
"Carbon dioxide acts as a kind of graft material that we can use to tune the growth of carbon nanotubes of various colors," explains Jiang.
With an advanced electron diffraction technique, the researchers were able to find out the precise atomic scale structure of their thin films. They found that they have very narrow chirality distributions, meaning that the orientation of the honeycomb-lattice of the tubes’ walls is almost uniform throughout the sample. The chirality more or less dictates the electrical properties carbon nanotubes can have, as well as their colour.
The method developed at Aalto University promises a simple and highly scalable way to fabricate carbon nanotube thin films in high yields.
"Usually you have to choose between mass production or having good control over the structure of carbon nanotubes. With our breakthrough, we can do both," trusts Dr. Qiang Zhang, a postdoctoral researcher in the group.
Follow-up work is already underway.
"We want to understand the science of how the addition of carbon dioxide tunes the structure of the nanotubes and creates colours. Our aim is to achieve full control of the growing process so that single-walled carbon nanotubes could be used as building blocks for the next generation of nanoelectronics devices," says professor Kauppinen.