Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Nanodevice, build thyself

15.01.2016

Researchers in Germany studied how a multitude of electronic interactions govern the encounter between a molecule called porphine and copper and silver surfaces

As we continue to shrink electronic components, top-down manufacturing methods begin to approach a physical limit at the nanoscale. Rather than continue to chip away at this limit, one solution of interest involves using the bottom-up self-assembly of molecular building blocks to build nanoscale devices.


Schematic depiction of different energy terms contributing to the adsorption energy, and charge density difference of 2H-P after adsorption onto Cu(111) at 12.8 Angstrom separation.

Credit: M. Müller/TU Munich

Successful self-assembly is an elaborately choreographed dance, in which the attractive and repulsive forces within molecules, between each molecule and its neighbors, and between molecules and the surface that supports them, have to all be taken into account.

To better understand the self-assembly process, researchers at the Technical University of Munich have characterized the contributions of all interaction components, such as covalent bonding and van der Waals interactions between molecules and between molecules and a surface.

"In an ideal case, the smallest possible device has the size of a single atom or molecule," said Katharina Diller, who worked as a postdoctoral researcher in the group of Karsten Reuter at the Technical University of Munich. Reuter and his colleagues present their work this week in The Journal of Chemical Physics, from AIP Publishing.

One such example is a single-porphyrin switch, which occupies a surface area of only one square nanometer. The porphine molecule, which was the object of this study, is even smaller than this. Porphyrins are a group of ringed chemical compounds which notably include heme - responsible for transporting oxygen and carbon dioxide in the bloodstream - and chlorophyll. In synthetically-derived applications, porphyrins are studied for their potential uses as sensors, light-sensitive dyes in organic solar cells, and molecular magnets.

The researchers from TU Munich assessed the interactions of the porphyrin molecule 2H-porphine by using density functional theory, a quantum mechanical computational modelling method used to describe the electronic properties of molecules and materials. Their simulations were performed at the high-performance supercomputer SuperMUC at Leibniz-Rechenzentrum in Garching.

The metallic substrates the researchers chose for the porphyrin molecules to assemble on, the close packed single crystal surfaces of copper and silver, are widely used as substrates in surface science. This is due to the densely packed nature of the surfaces, which allow the molecules to exhibit a smooth adsorption environment. Additionally, copper and silver each react differently with porhyrins - the molecule adsorbs more strongly on copper, whereas silver does a better job of keeping the electronic structure of the molecule intact - allowing the researchers to monitor a variety of competing effects for future applications.

In their simulation, porphyrin molecules were placed on a copper or silver slab, which was repeated periodically to simulate an extended surface. After finding the optimal geometry in which the molecules would adsorb on the surface, the researchers altered the size of the metal slab to increase or decrease the distance between molecules, thus simulating different molecular coverages. The computational setup gave them a switch to turn the energy contributions of neighboring molecules on and off, in order to observe the interplay of the individual interactions.

Diller and Reuter, along with colleagues Reinhard Maurer and Moritz Müller, who is first author on the paper, found that the weak long-range van der Waals interactions yielded the largest contribution to the molecule-surface interaction, and showed that the often employed methods to quantify the electronic charges in the system have to be used with caution. Surprisingly, while interactions directly between molecules are negligible, the researcher found indications for surface-mediated molecule-molecule interactions at higher molecular coverages.

"The analysis of the electronic structure and the individual interaction components allows us to better understand the self-assembly of porphine adsorbed on copper and silver, and additionally enables predictions for more complex porphyrine analogues," Diller said. "These conclusions, however, come without yet considering the effects of atomic motion at finite temperature, which we did not study in this work."

###

The article, "Interfacial charge rearrangement and intermolecular interactions: Density-functional theory study of free-base porphine adsorbed on Ag(111) and Cu(111)," is authored by Moritz Müller, Katharina Diller, Reinhard J. Maurer, and Karsten Reuter. It will appear in the Journal of Chemical Physics on January 11, 2016 (DOI: 10.1063/1.4938259). After that date, it can be accessed at: http://scitation.aip.org/content/aip/journal/jcp/144/2/10.1063/1.4938259

ABOUT THE JOURNAL

The Journal of Chemical Physics publishes concise and definitive reports of significant research in the methods and applications of chemical physics.

http://jcp.aip.org

Media Contact

Jason Socrates Bardi
jbardi@aip.org
240-535-4954

 @jasonbardi

http://www.aip.org 

Jason Socrates Bardi | EurekAlert!

More articles from Physics and Astronomy:

nachricht UNLV study unlocks clues to how planets form
13.12.2018 | University of Nevada, Las Vegas

nachricht Unprecedented Views of the Birth of Planets
13.12.2018 | Universität Heidelberg

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: An energy-efficient way to stay warm: Sew high-tech heating patches to your clothes

Personal patches could reduce energy waste in buildings, Rutgers-led study says

What if, instead of turning up the thermostat, you could warm up with high-tech, flexible patches sewn into your clothes - while significantly reducing your...

Im Focus: Lethal combination: Drug cocktail turns off the juice to cancer cells

A widely used diabetes medication combined with an antihypertensive drug specifically inhibits tumor growth – this was discovered by researchers from the University of Basel’s Biozentrum two years ago. In a follow-up study, recently published in “Cell Reports”, the scientists report that this drug cocktail induces cancer cell death by switching off their energy supply.

The widely used anti-diabetes drug metformin not only reduces blood sugar but also has an anti-cancer effect. However, the metformin dose commonly used in the...

Im Focus: New Foldable Drone Flies through Narrow Holes in Rescue Missions

A research team from the University of Zurich has developed a new drone that can retract its propeller arms in flight and make itself small to fit through narrow gaps and holes. This is particularly useful when searching for victims of natural disasters.

Inspecting a damaged building after an earthquake or during a fire is exactly the kind of job that human rescuers would like drones to do for them. A flying...

Im Focus: Topological material switched off and on for the first time

Key advance for future topological transistors

Over the last decade, there has been much excitement about the discovery, recognised by the Nobel Prize in Physics only two years ago, that there are two types...

Im Focus: Researchers develop method to transfer entire 2D circuits to any smooth surface

What if a sensor sensing a thing could be part of the thing itself? Rice University engineers believe they have a two-dimensional solution to do just that.

Rice engineers led by materials scientists Pulickel Ajayan and Jun Lou have developed a method to make atom-flat sensors that seamlessly integrate with devices...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

ICTM Conference 2019: Digitization emerges as an engineering trend for turbomachinery construction

12.12.2018 | Event News

New Plastics Economy Investor Forum - Meeting Point for Innovations

10.12.2018 | Event News

EGU 2019 meeting: Media registration now open

06.12.2018 | Event News

 
Latest News

Magic number colloidal clusters

13.12.2018 | Life Sciences

UNLV study unlocks clues to how planets form

13.12.2018 | Physics and Astronomy

Live from the ocean research vessel Atlantis

13.12.2018 | Earth Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>