Craftsmen tile walls or floors by hand; but how can you get an ordered monolayer onto a substrate when the “tiles” are microscopically small instead of big and easy to handle? Previously, self-assembly processes have been the method of choice for this scale. Korean researchers have now come to the realization that even such tiny components can be arranged in a “do-it-yourself” method. As they describe in the journal Angewandte Chemie, their manually produced monolayers of microcrystals are qualitatively superior to the self-assembled variety.
How small can components be such that they can still be glued to a surface by hand? And conversely, how big can microscale components be such that they can still be arranged by self-assembly? Which method is best in the size range in which both techniques work? These questions have been investigated by a team led by Kyung Byung Yoon at Sogang University in Seoul. To find answers, they carried out experiments with variously sized zeolite crystals. Zeolites are aluminosilicate minerals with a wide range of applications in many technical fields.
The powdered zeolite was applied by simply rubbing it on with a finger (with and without wearing a latex glove). Alternatively, they were applied in solution, and ultrasound was used to kick-start the self-assembly process. The “glue” between the “mini-tiles” and the substrate was the attraction between oppositely charged groups of atoms, hydrogen bonds, and chemical bonds between reactive groups of atoms.
The experiments demonstrated that self-assembly only works for particles smaller than about 3 µm. Hand-application works for crystals as small as 0.5 µm in diameter. In the overlapping range (0.5 to 3 µm), hand application is preferable to self-assembly for quality: the packing is denser and the microcrystals are oriented more regularly. Whereas self-assembly produces individual crystals grown at a 90° angle onto the monolayer, such “parasites” are simply rubbed off by hand. There are other “handy” advantages of the manual process as well: it is simpler, doesn’t require a solvent or special equipment, runs more smoothly, and allows treatment of larger surfaces.
Author: Kyung Byung Yoon, Sogang University, Seoul (Korea), http://www.sogang.ac.kr/bbs/faculty/2profile.php?para=101191
Title: Manual Assembly of Microcrystal Monolayers on Substrates
Angewandte Chemie International Edition 2007, 46, No. 17, doi: 10.1002/anie.200604367
| Angewandte Chemie
Nanoparticle Exposure Can Awaken Dormant Viruses in the Lungs
16.01.2017 | Helmholtz Zentrum München - Deutsches Forschungszentrum für Gesundheit und Umwelt
Cholera bacteria infect more effectively with a simple twist of shape
13.01.2017 | Princeton University
Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.
While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...
Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales
Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).
Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...
Many pathogens use certain sugar compounds from their host to help conceal themselves against the immune system. Scientists at the University of Bonn have now, in cooperation with researchers at the University of York in the United Kingdom, analyzed the dynamics of a bacterial molecule that is involved in this process. They demonstrate that the protein grabs onto the sugar molecule with a Pac Man-like chewing motion and holds it until it can be used. Their results could help design therapeutics that could make the protein poorer at grabbing and holding and hence compromise the pathogen in the host. The study has now been published in “Biophysical Journal”.
The cells of the mouth, nose and intestinal mucosa produce large quantities of a chemical called sialic acid. Many bacteria possess a special transport system...
10.01.2017 | Event News
09.01.2017 | Event News
05.01.2017 | Event News
17.01.2017 | Earth Sciences
17.01.2017 | Materials Sciences
17.01.2017 | Architecture and Construction