Tag Archives: Academy of Finland

Gold atoms: sometimes they’re a metal and sometimes they’re a molecule

Leave a reply

Fascinating work out of Finland shows that a minor change in the number of gold atoms in your gold nanoparticle can mean the difference between a metal and a molecule (coincidentally, this phenomenon is alluded to in my April 14, 2015 post (Nature’s patterns reflected in gold nanoparticles); more about that at the end of this piece. Getting back to Finland and when gold is metal and when it’s a molecule, here’s more from an April 10, 2015 news item on ScienceDaily,

Researchers at the Nanoscience Center at the University of Jyväskylä, Finland, have shown that dramatic changes in the electronic properties of nanometre-sized chunks of gold occur in well-defined size range. Small gold nanoclusters could be used, for instance, in short-term storage of energy or electric charge in the field of molecular electronics. Funded by the Academy of Finland, the researchers have been able to obtain new information which is important, among other things, in developing bioimaging and sensing based on metal-like clusters.

An April 10, 2015 news release (also on EurekAlert) on the Academy of Finland (Suomen Akatemia) website, which originated the news item, describes the work in more detail,

Two recent papers by the researchers at Jyväskylä (1, 2) demonstrate that the electronic properties of two different but still quite similar gold nanoclusters can be drastically different. The clusters were synthesised by chemical methods incorporating a stabilising ligand layer on their surface. The researchers found that the smaller cluster, with up to 102 gold atoms, behaves like a giant molecule while the larger one, with at least 144 gold atoms, already behaves, in principle, like a macroscopic chunk of metal, but in nanosize.

The fundamentally different behaviour of these two differently sized gold nanoclusters was demonstrated by shining a laser light onto solution samples containing the clusters and by monitoring how energy dissipates from the clusters into the surrounding solvent.

“Molecules behave drastically different from metals,” said Professor Mika Pettersson, the principal investigator of the team conducting the experiments. “The additional energy from light, absorbed by the metal-like clusters, transfers to the environment extremely rapidly, in about one hundred billionth of a second, while a molecule-like cluster is excited to a higher energy state and dissipates the energy into the environment with a rate that is at least 100 times slower. This is exactly what we saw: the 102-gold atom cluster is a giant molecule showing even a transient magnetic state while the 144-gold atom cluster is already a metal. We’ve thus managed to bracket an important size region where this fundamentally interesting change in the behaviour takes place.”

“These experimental results go together very well with what our team has seen from computational simulations on these systems,” said Professor Hannu Häkkinen, a co-author of the studies and the scientific director of the nanoscience centre. “My team predicted this kind of behaviour back in 2008-2009 when we saw big differences in the electronic structure of exactly these nanoclusters. It’s wonderful that robust spectroscopic experiments have now proved these phenomena. In fact, the metal-like 144-atom cluster is even more interesting, since we just published a theoretical paper where we saw a big enhancement of the metallic properties of just a few copper atoms mixed with gold.” (3)

Here are links to and citation for the papers,

Ultrafast Electronic Relaxation and Vibrational Cooling Dynamics of Au144(SC2H4Ph)60 Nanocluster Probed by Transient Mid-IR Spectroscopy by Satu Mustalahti, Pasi Myllyperkiö, Tanja Lahtinen, Kirsi Salorinne, Sami Malola, Jaakko Koivisto, Hannu Häkkinen, and Mika Pettersson. J. Phys. Chem. C, 2014, 118 (31), pp 18233–18239 DOI: 10.1021/jp505464z Publication Date (Web): July 3, 2014

Copyright © 2014 American Chemical Society

Copper Induces a Core Plasmon in Intermetallic Au(144,145)–xCux(SR)60 Nanoclusters by Sami Malola, Michael J. Hartmann, and Hannu Häkkinen. J. Phys. Chem. Lett., 2015, 6 (3), pp 515–520 DOI: 10.1021/jz502637b Publication Date (Web): January 22, 2015

Copyright © 2015 American Chemical Society

Molecule-like Photodynamics of Au102(pMBA)44 Nanocluster by Satu Mustalahti, Pasi Myllyperkiö, Sami Malola, Tanja Lahtinen, Kirsi Salorinne, Jaakko Koivisto, Hannu Häkkinen, and Mika Pettersson. ACS Nano, 2015, 9 (3), pp 2328–2335 DOI: 10.1021/nn506711a Publication Date (Web): February 22, 2015

Copyright © 2015 American Chemical Society

These papers are behind paywalls.

As for my April 14, 2015 post (Nature’s patterns reflected in gold nanoparticles), researchers at Carnegie Mellon University were researching patterns in different sized gold nanoparticles when this was noted in passing,

… Normally, gold is one of the best conductors of electrical current, but the size of Au133 is so small that the particle hasn’t yet become metallic. …

Electricity without a current

Leave a reply

My imagination fails at the thought of electricity without a current luckily there’s a consortium of scientists at Finland’s Tampere University of  Technology (TUT) who have no trouble with their imaginations, according to the Sept. 12, 2012 news item on Nanowerk (Note: I have removed a link from the following excerpt),

The Academy of Finland has granted €1.6 million to a consortium based at Tampere University of Technology (TUT) under the “Programmable Materials” funding scheme. The project runs from 1 September 2012 to 31 August 2016 and is entitled “Photonically Addressed Zero Current Logic through Nano-Assembly of Functionalised Nanoparticles to Quantum Dot Cellular Automata” ( PhotonicQCA).

The Sept. 12, 2012 news release from TUT which originated the news item explains the ideas and work which support the notion of electricity without current,

The key idea behind the project is the so-called quantum dot cellular automaton (QCA). In QCAs, pieces of semiconductor so small that single electronic charges can be measured and manipulated are arranged into domino like cells. Like dominos, these cells can be arranged so that the position of the charges in one cell affects the position of the charges in the next cell, which allows making logical circuits out of these “quantum dominos”. But, no charge flows from one cell to the next, i.e. no current. This, plus the extremely small size of QCAs, means that they could be used to make electronic circuits at densities and speeds not possible now. However, realisation of the dots and cells and making electrical connections to them has been a huge challenge.

Professors Donald Lupo from Department of Electronics, Mircea Guina and Tapio Niemi from Optoelectronics Research Centre (ORC), and Nikolai Tkachenko and Helge Lemmetyinen from Department of Chemistry and Bioengineering, want to investigate a completely new approach. They want to attach tailor-made molecules, optical nanoantennas, to the quantum dots, which can inject a charge into a dot or enable charge transfer between the dots when light of the right wavelength shines on them. This concept will be combined with the expertise at TUT’s Optoelectronics Research Centre concerning “site-specific epitaxy”, i.e. growing the quantum dots in the right place using nanofabrication techniques, which would enable a solid-state technology platform compatible with standard electronic circuits. If this works, then someday QCAs could be written and read with light.

Project coordinator, Professor Donald Lupo says: “As far as we can tell, no one has ever tried anything like this before. It’s a completely new idea. It was our excellent inter-departmental communication that identified a unique combination of know-how that let us come up with this concept. It’s highly risky because of many technological challenges, but the potential is amazing; being able to get rid of electrical connections and write and read nanoelectronic circuits using only light would be a huge breakthrough”.

Reading the Programmable Materials page on the Academy of Finland website provided some clues for what they hope to achieve with this ‘electricity’ project is all about,

The FinnSight 2015 report published in 2006 underscores the fact that materials research is a cross-disciplinary exercise: new materials are increasingly being developed on a multidisciplinary platform. The report also urges Finnish materials research to step up its efforts to explore the more advanced properties of new materials that are still partly unknown.

Most new materials today are typically static by nature. They are composed of components that have a specific function or quality, but they do not respond to their environment as such. Programmable materials, by contrast, are composed of components that respond in a specific, programmed way to environmental stimuli and signals. Depending on the initial state or code of these components, it is possible to produce various complex, even macroscopic, structures in a controlled way.

Programmable materials represent a new emerging research field in which Finland can play a pioneering role. The programmable properties of different materials are continuing to develop with advances in such fields as nano- and biotechnology, and programmable materials may completely revolutionise applications of functional materials.

…

Materials programming is an emerging, all-new field of research. The aim of this programme is to work with the best international research teams and solidify Finland’s position at the international forefront of research. The strongest countries in this field include the United States, Japan, Russia, India and certain European countries. In addition, China has a strong emerging materials research field.

I threw in that last paragraph because I find their analysis of the international scene quite interesting and notice they list three of the BRICS (Brazil, Russia, India, China, ans South Africa) countries as leaders in this emergent field.

Getting back to this specific ‘electricity’ project, it sounds as if they’re working on an electrical component which could be made to operate when a light is shone on it in a process that reminiscent of photosynthesis (Wikipedia essay on photosynthesis) where a plant converts light into chemical energy.