Tag Archives: Esko Kauppinen

Colo(u)ring your carbon nanotubes

Finnish research is highlighted in an August 28, 2018 news item on phys.org,

A method developed at Aalto University, Finland, can produce large quantities of pristine single-walled carbon nanotubes in select shades of the rainbow. The secret is a fine-tuned fabrication process—and a small dose of carbon dioxide. The films could find applications in touch screen technologies or as coating agents for new types of solar cells.

An August 28, 2018 Aalto University press release (also on EurekAlert), which originated the news item, provides more detail,

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 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.

Here’s a link to and a citation for the paper,

Direct Synthesis of Colorful Single-Walled Carbon Nanotube Thin Films by Yongping Liao, Hua Jiang, Nan Wei, Patrik Laiho, Qiang Zhang, Sabbir A. Khan, and Esko I. Kauppinen. J. Am. Chem. Soc., 2018, 140 (31), pp 9797–9800 DOI: 10.1021/jacs.8b05151 Publication Date (Web): July 26, 2018

Copyright © 2018 American Chemical Society

This paper appears to be open access.

For the curious, here’s a peek at the coloured carbon nanotube films,

 

Caption: Samples of the colorful carbon nanotube thin films, as produced in the fabrication reactor. Credit: Authors / Aalto University

Electrochemical measurements of biomolecules

This work comes from Finland and features some new nano shapes. From a Nov. 10, 2016 news item on phys.org,

Tomi Laurila’s research topic has many quirky names.

“Nanodiamond, nanohorn, nano-onion…,” lists off the Aalto University Professor, recounting the many nano-shapes of carbon. Laurila is using these shapes to build new materials: tiny sensors, only a few hundred nanometres across, that can achieve great things due to their special characteristics.

For one, the sensors can be used to enhance the treatment of neurological conditions. That is why Laurila, University of Helsinki Professor Tomi Taira and experts from HUS (the Hospital District of Helsinki and Uusimaa) are looking for ways to use the sensors for taking electrochemical measurements of biomolecules. Biomolecules are e.g. neurotransmitters such as glutamate, dopamine and opioids, which are used by nerve cells to communicate with each other.

A Nov. 10, 2016 Aalto University press release, which originated the news item, expands on the theme,

Most of the drugs meant for treating neurological diseases change the communication between nerve cells that is based on neurotransmitters. If we had real time and individual information on the operation of the neurotransmitter system, it would make it much easier to for example plan precise treatments’, explains Taira.

Due to their small size, carbon sensors can be taken directly next to a nerve cell, where the sensors will report what kind of neurotransmitter the cell is emitting and what kind of reaction it is inducing in other cells.

‘In practice, we are measuring the electrons that are moving in oxidation and reduction reactions’, Laurila explains the operating principle of the sensors.

‘The advantage of the sensors developed by Tomi and the others is their speed and small size. The probes used in current measurement methods can be compared to logs on a cellular scale – it’s impossible to use them and get an idea of the brain’s dynamic’, summarizes Taira.

Feedback system and memory traces

For the sensors, the journey from in vitro tests conducted in glass dishes and test tubes to in vivo tests and clinical use is long. However, the researchers are highly motivated.

‘About 165 million people are suffering from various neurological diseases in Europe alone. And because they are so expensive to treat, neurological diseases make up as much as 80 per cent of health care costs’, tells Taira.

Tomi Laurila believes that carbon sensors will have applications in fields such as optogenetics. Optogenetics is a recently developed method where a light-sensitive molecule is brought into a nerve cell so that the cell’s electric operation can then be turned on or off by stimulating it with light. A few years ago, a group of scientists proved in the scientific journal Nature that they had managed to use optogenetics to activate a memory trace that had been created previously due to learning. Using the same technique, researchers were able to demonstrate that with a certain type of Alzheimer’s, the problem is not that there are no memory traces being created, but that the brain cannot read the traces.

‘So the traces exist, and they can be activated by boosting them with light stimuli’, explains Taira but stresses that a clinical application is not yet a reality. However, clinical applications for other conditions may be closer by. One example is Parkinson’s disease. In Parkinson’s disease, the amount of dopamine starts to decrease in the cells of a particular brain section, which causes the typical symptoms such as tremors, rigidity and slowness of movement. With the sensors, the level of dopamine could be monitored in real time.

‘A sort of feedback system could be connected to it, so that it would react by giving an electric or optical stimulus to the cells, which would in turn release more dopamine’, envisions Taira.

‘Another application that would have an immediate clinical use is monitoring unconscious and comatose patients. With these patients, the level of glutamate fluctuates very much, and too much glutamate damages the nerve cell – online monitoring would therefore improve their treatment significantly.

Atom by atom

Manufacturing carbon sensors is definitely not a mass production process; it is slow and meticulous handiwork.

‘At this stage, the sensors are practically being built atom by atom’, summarises Tomi Laurila.

‘Luckily, we have many experts on carbon materials of our own. For example, the nanobuds of Professor Esko Kauppinen and the carbon films of Professor Jari Koskinen help with the manufacturing of the sensors. Carbon-based materials are mainly very compatible with the human body, but there is still little information about them. That’s why a big part of the work is to go through the electrochemical characterisation that has been done on different forms of carbon.’

The sensors are being developed and tested by experts from various fields, such as chemistry, materials science, modelling, medicine and imaging. Twenty or so articles have been published on the basic properties of the materials. Now, the challenge is to build them into geometries that are functional in a physiological environment. And taking measurements is not simple, either.

‘Brain tissue is delicate and doesn’t appreciate having objects being inserted in it. But if this were easy, someone would’ve already done it’, conclude the two.

I wish the researchers good luck.

Europe’s search for raw materials and hopes for nanotechnology-enabled solutions

A Feb. 27, 2015 news item on Nanowerk highlights the concerns over the availability of raw materials and European efforts to address those concerns,

Critical raw materials’ are crucial to many European industries but they are vulnerable to scarcity and supply disruption. As such, it is vital that Europe develops strategies for meeting the demand for raw materials. One such strategy is finding methods or substances that can replace the raw materials that we currently use. With this in mind, four EU projects working on substitution in catalysis, electronics and photonics presented their work at the Third Innovation Network Workshop on substitution of Critical Raw Materials hosted by the CRM_INNONET project in Brussels earlier this month [February 2015].

A Feb. 26, 2015 CORDIS press release, which originated the news item, goes on to describe four European Union projects working on nanotechnology-enabled solutions,

NOVACAM

NOVACAM, a coordinated Japan-EU project, aims to develop catalysts using non-critical elements designed to unlock the potential of biomass into a viable energy and chemical feedstock source.

The project is using a ‘catalyst by design’ approach for the development of next generation catalysts (nanoscale inorganic catalysts), as NOVACAM project coordinator Prof. Emiel Hensen from Eindhoven University of Technology in the Netherlands explained. Launched in September 2013, the project is developing catalysts which incorporate non-critical metals to catalyse the conversion of lignocellulose into industrial chemical feedstocks and bio-fuels. The first part of the project has been to develop the principle chemistry while the second part is to demonstrate proof of process. Prof. Hensen predicts that perhaps only two of three concepts will survive to this phase.

The project has already made significant progress in glucose and ethanol conversion, according to Prof. Hensen, and has produced some important scientific publications. The consortium is working with and industrial advisory board comprising Shell in the EU and Nippon Shokubai in Japan.

FREECATS

The FREECATS project, presented by project coordinator Prof. Magnus Rønning from the Norwegian University of Science and Technology, has been working over the past three years to develop new metal-free catalysts. These would be either in the form of bulk nanomaterials or in hierarchically organised structures – both of which would be capable of replacing traditional noble metal-based catalysts in catalytic transformations of strategic importance.

Prof. Magnus Rønning explained that the application of the new materials could eliminate the need for the use for platinum group metals (PGM) and rare earth metals – in both cases Europe is very reliant on other countries for these materials. Over the course of its research, FREECATS targeted three areas in particular – fuel cells, the production of light olefins and water and wastewater purification.

By working to replace the platinum in fuel cells, the project is supporting the EU’s aim of replacing the internal combustion engine by 2050. However, as Prof. Rønning noted, while platinum has been optimized for use over several decades, the materials FREECATS are using are new and thus come with their new challenges which the project is addressing.

HARFIR

Prof. Atsufumi Hirohata of the University of York in the United Kingdom, project coordinator of HARFIR, described how the project aims to discover an antiferromagnetic alloy that does not contain the rare metal Iridium. Iridium is becoming more and more widely used in numerous spin electronic storage devices, including read heads in hard disk drives. The world supply depends on Platinum ore that comes mainly from South Africa. The situation is much worse than for other rare earth elements as the price has been shooting up over recent years, according to Prof. Hirohata.

The HARFIR team, divided between Europe and Japan, aims to replace Iridium alloys with Heusler alloys. The EU team, led by Prof. Hirohata, has been working on the preparation of polycrystalline and epitaxial thin films of Heusler Alloys, with the material design led by theoretical calculations. The Japanese team, led by Prof. Koki Takanashi at Tohoku University, is meanwhile working on the preparation of epitaxial thin films, measurements of fundamental properties and structural/magnetic characterisation by neutron and synchrotron x-ray beams.

One of the biggest challenges has been that Heusler alloys have a relatively complicated atomic structure. In terms of HARFIR’s work, if any atomic disordering at the edge of nanopillar devices, the magnetic properties that are needed are lost. The team is exploring solutions to this challenge.

IRENA

Prof. of Esko Kauppinen Aalto University in Finland closed off the first session of the morning with his presentation of the IRENA project. Launched in September 2013, the project will run until mid 2017 working towards the aim of developing high performance materials, specifically metallic and semiconducting single-walled carbon nanotube (SWCNT) thin films to completely eliminate the use of the critical metals in electron devices. The ultimate aim is to replace Indium in transparent conducting films, and Indium and Gallium as a semiconductor in thin film field effect transistors (TFTs).

The IRENA team is developing an alternative that is flexible, transparent and stretchable so that it can meet the demands of the electronics of the future – including the possibility to print electronics.

IRENA involves three partners from Europe and three from Japan. The team has expertise in nanotube synthesis, thin film manufacturing and flexible device manufacturing, modelling of nanotube growth and thin film charge transport processes, and the project has benefitted from exchanges of team members between institutions. One of the key achievements so far is that the project has succeeded in using a nanotube thin film for the first time as the both the electrode and hole blocking layer in an organic solar cell.

You’ll note that Japan is a partner in all of these projects. In all probability, these initiatives have something to do with rare earths which are used in much of today’s electronics technology and Japan is sorely lacking in those materials. China, by comparison, has dominated the rare earths export industry and here’s an excerpt from my Nov. 1, 2013 posting where I outline the situation (which I suspect hasn’t changed much since),

As for the short supply mentioned in the first line of the news item, the world’s largest exporter of rare earth elements at 90% of the market, China, recently announced a cap according to a Sept. 6, 2013 article by David Stanway for Reuters. The Chinese government appears to be curtailing exports as part of an ongoing, multi-year strategy. Here’s how Cientifica‘s (an emerging technologies consultancy, etc.) white paper (Simply No Substitute?) about critical materials published in 2012 (?), described the situation,

Despite their name, REE are not that rare in the Earth’s crust. What has happened in the past decade is that REE exports from China undercut prices elsewhere, leading to the closure of mines such as the Mountain Pass REE mine in California. Once China had acquired a dominant market position, prices began to rise. But this situation will likely ease. The US will probably begin REE production from the Mountain Pass mine later in 2012, and mines in other countries are expected to start operation soon as well.

Nevertheless, owing to their broad range of uses REE will continue to exert pressures on their supply – especially for countries without notable REE deposits. This highlights two aspects of importance for strategic materials: actual rarity and strategic supply issues such as these seen for REE. Although strategic and diplomatic supply issues may have easier solutions, their consideration for manufacturing industries will almost be the same – a shortage of crucial supply lines.

Furthermore, as the example of REE shows, the identification of long-term supply problems can often be difficult, and not every government has the same strategic foresight that the Chinese demonstrated. And as new technologies emerge, new elements may see an unexpected, sudden demand in supply. (pp. 16-17)

Meanwhile, in response to China’s decision to cap its 2013 REE exports, the Russian government announced a $1B investment to 2018 in rare earth production,, according to a Sept. 10, 2013 article by Polina Devitt for Reuters.

I’m not sure you’ll be able to access Tim Harper’s white paper as he is now an independent, serial entrepreneur. I most recently mentioned him in relation to his articles (on Azonano) about the nanotechnology scene in a Feb. 12, 2015 posting where you’ll also find contact details for him.