Creating switchable plasmons in plastics

December 09, 2019

Researchers in the Organic Photonics and Nano-optics goup at the Laboratory of Organic Electronics have developed optical nanoantennas made from a conducting polymer. The antennas can be switched on and off, and will make possible a completely new type of controllable nano-optical components.

Plasmons arise when light interacts with metallic nanoparticles. The incident light sets off a collective oscillation, a unified forwards and backwards motion, of the electrons in the particles. It is this collective oscillation that is the plasmon. Metallic nanostructures and their ability to shape light on a scale of nanometres are studied by many research groups around the world for use in, for example, biosensors and energy conversion devices, and to reinforce other optical phenomena. Other potential fields of use include miniature medical equipment and windows that control the amount of light and heat admitted to or emitted from a building.

In an article in Nature Nanotechnology, scientists from Linköping University present optical nanoantennas, made from a conducting polymer instead of a traditional metal, such as gold or silver. In this case, they used a variant of PEDOT, which is a widely used polymer in many other areas, including thermoelectrics and bioelectronics.

"We show that light can be converted to plasmons in nanostructures of the organic material", says Magnus Jonsson, leader of the Organic Photonics and Nano-optics group at the Laboratory of Organic Electronics.

It is, however, not electrons that create plasmons in the conducting polymer, but polarons. A polymer consists of a long chain of connected atoms and in the conducting polymer that the researchers have worked with, it is positive charges along the polymer chain that are responsible for the electrical conductivity. Together with associated chain distrorions these positive charges form polarons, which start collective oscillations when light is incident on the nanostructure.

"Our organic antennas can be transparent to visible light while reacting to light at somewhat longer wavelengths, making them interesting for applications such as smart windows", says Magnus Jonsson.

The researchers initially carried out theoretical calculations and used simulations to design experiments, which they were subsequently able to carry out. Shangzhi Chen, doctoral student in the group, has managed to produce billions of tiny nanometre-sized disks of the organic conducting material on a surface. These small disks react to light and act as tiny antennas.

The researchers have shown that both the diameter and the thickness of the disks determine the frequency of light to which they react. It is thus possible to control this wavelength by changing the geometry of the disk. The thicker the disk, the higher the frequency. They are also hoping that they can increase the range of wavelengths to which the nanoantennas react by changing the polymer used.

Another innovation they have explored is the ability to switch the organic nanoantennas on and off, which is difficult with conventional metals. The material manufactured in the laboratory is initially in an oxidised state, and the nanoantennas are switched on.

"We have shown that when we reduce the material by exposing it to a vapour, we can switch off the conduction and in this way also the antennas. If we then reoxidise it using, for example, sulphuric acid, it regains its conductivity and the nanoantennas switch on again. This is a relatively slow process at the moment, but we have taken the first steps and shown that it is possible", says Magnus Jonsson.

"While this is basic research, our results make possible a new type of controllable nano-optical components that we believe can to be used for many applications."
-end-
The study was performed in collaboration between several researchers from the Laboratory of Organic Electronics and the Terahertz Materials Analysis Center at Linköping University. Financial support includes for example funding from the Swedish Research Council and the Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linköping University.

Conductive polymer nanoantennas for dynamic organic plasmonics, Shangzhi Chen, Evan S. H. Kang, Mina S. Chaharsoughi, Vallery Stanishev, Philipp Ku?hne, Hengda Sun, Chuanfei Wang, Mats Fahlman, Simone Fabiano, Vanya Darakchieva and Magnus P. Jonsson, Nature Nanotechnology 2019, doi 10.1038/s41565-019-0583-y https://www.nature.com/articles/s41565-019-0583-y

Footnote:

It is plasmons that create the beautiful glowing colours in the stained-glass windows of medieval churches and mosques. The colours of the glass arise from metal particles embedded in it. But at the time, the craftsmen didn't know that the metals give rise to plasmons. An early example of plasmons is the Lycurgus Cup at British Museum, London.

https://www.sciencedirect.com/topics/engineering/lycurgus-cup

Contact: Magnus Jonsson, magnus.jonsson@liu.se +46 11 363403

Linköping University

Related Science Articles from Brightsurf:

75 science societies urge the education department to base Title IX sexual harassment regulations on evidence and science
The American Educational Research Association (AERA) and the American Association for the Advancement of Science (AAAS) today led 75 scientific societies in submitting comments on the US Department of Education's proposed changes to Title IX regulations.

Science/Science Careers' survey ranks top biotech, biopharma, and pharma employers
The Science and Science Careers' 2018 annual Top Employers Survey polled employees in the biotechnology, biopharmaceutical, pharmaceutical, and related industries to determine the 20 best employers in these industries as well as their driving characteristics.

Science in the palm of your hand: How citizen science transforms passive learners
Citizen science projects can engage even children who previously were not interested in science.

Applied science may yield more translational research publications than basic science
While translational research can happen at any stage of the research process, a recent investigation of behavioral and social science research awards granted by the NIH between 2008 and 2014 revealed that applied science yielded a higher volume of translational research publications than basic science, according to a study published May 9, 2018 in the open-access journal PLOS ONE by Xueying Han from the Science and Technology Policy Institute, USA, and colleagues.

Prominent academics, including Salk's Thomas Albright, call for more science in forensic science
Six scientists who recently served on the National Commission on Forensic Science are calling on the scientific community at large to advocate for increased research and financial support of forensic science as well as the introduction of empirical testing requirements to ensure the validity of outcomes.

World Science Forum 2017 Jordan issues Science for Peace Declaration
On behalf of the coordinating organizations responsible for delivering the World Science Forum Jordan, the concluding Science for Peace Declaration issued at the Dead Sea represents a global call for action to science and society to build a future that promises greater equality, security and opportunity for all, and in which science plays an increasingly prominent role as an enabler of fair and sustainable development.

PETA science group promotes animal-free science at society of toxicology conference
The PETA International Science Consortium Ltd. is presenting two posters on animal-free methods for testing inhalation toxicity at the 56th annual Society of Toxicology (SOT) meeting March 12 to 16, 2017, in Baltimore, Maryland.

Citizen Science in the Digital Age: Rhetoric, Science and Public Engagement
James Wynn's timely investigation highlights scientific studies grounded in publicly gathered data and probes the rhetoric these studies employ.

Science/Science Careers' survey ranks top biotech, pharma, and biopharma employers
The Science and Science Careers' 2016 annual Top Employers Survey polled employees in the biotechnology, biopharmaceutical, pharmaceutical, and related industries to determine the 20 best employers in these industries as well as their driving characteristics.

Three natural science professors win TJ Park Science Fellowship
Professor Jung-Min Kee (Department of Chemistry, UNIST), Professor Kyudong Choi (Department of Mathematical Sciences, UNIST), and Professor Kwanpyo Kim (Department of Physics, UNIST) are the recipients of the Cheong-Am (TJ Park) Science Fellowship of the year 2016.

Read More: Science News and Science Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.