Nav: Home

Amazingly 'green' synthesis method for high-tech dyes

August 10, 2018

They not only impress due to their radiant and intense colour, they also have an important technological significance: organic dyes are a class of materials with extremely special properties. From flat screens to electronic paper through to chip cards: in future, many technologies are likely to be based on organic molecules like these.

Previously, such materials could only be prepared using complex synthesis methods that are incredibly harmful to the environment. However, researchers at TU Wien have now successfully synthesized several typical representatives of this materials class in an entirely new and different way: toxic solvents have been replaced by plain water. But how is this done? When water is heated to extremely high temperatures, its properties change significantly. Details of the new preparation method recently published in the prestigious scientific journal Angewandte Chemie.

The properties of the water change without the need for additives

"If you were to listen to your initial gut feeling, you would actually suspect that water is the worst solvent imaginable for synthesising and crystallising these molecules," says Miriam Unterlass from the Institute of Materials Chemistry at TU Wien. "The reason for this expectation is that the dyes we produce are extremely water-repellent." If you, for example, drop a small droplet of water on some dry dye powder, the droplet just rolls off. The dye cannot be mixed with water.

But this behaviour only applies to water as we know it from everyday use. However, the researchers at TU Wien used water heated to at least 180°C in special pressure vessels. Under these conditions, pressure rises drastically, so that the majority of water remains liquid despite the elevated temperatures. The chemical and physical properties of water change drastically under these conditions.

Too hot for hydrogen bonding

"The properties of cold, liquid water are strongly influenced by what is known as hydrogen bonding," explains Miriam Unterlass. "These are weak bonds between water molecules that are constantly broken and reformed." On average, each water molecule is linked to three or four other water molecules at any time at room temperature. In a pressure cooker, the number of these hydrogen bonds per molecule decreases.

"This also means that many more ions are present in water at high temperatures than under standard conditions - a certain amount of H2O molecules can become H3O+ or OH-," explains Miriam Unterlass. And this dramatically changes the properties of the water: in a certain sense, it behaves like an acid and a base at the same time - it can act both as an acidic and a basic catalyst and therefore accelerate certain reactions or even enable them in the first place.

Amongst other things, the higher number of ions in the water at elevated temperatures is a key cause for allowing the dissolution of organic substances that are entirely insoluble under normal conditions. Consequently, the dye molecules studied can not only be synthesised in water, but also crystallised: they dissolve at sufficiently high temperatures and then crystallise as they cool down.

"Normally, toxic solvents are needed to prepare or crystallise such dyes. In our case, though, pure water adopts the desired solvent properties - all you need is pressure and heat," says Miriam Unterlass.

Crystals for the electronics of tomorrow

"In a highly crystalline state - i.e. at a high degree of order at the molecular level - the electronic properties of these materials improve. It is therefore particularly important for applications in organic electronics to have a high level of control over the crystallisation process," stresses Unterlass.

For the crystals obtained, however, there are also some quite different potential applications. "They can be used wherever the requirements for dyes are rather demanding", says Unterlass. "One such application would be car paint, or other areas where extreme chemical or thermal conditions prevail, as the materials also become more stable the more crystalline they are."
-end-
Download: https://www.tuwien.ac.at/dle/pr/aktuelles/downloads/2018/high-tech-farbstoffe

Vienna University of Technology

Related Water Molecules Articles:

The inner lives of molecules
Researchers from Canada, the UK and Germany have developed a new experimental technique to take 3-D images of molecules in action.
Jumping water striders know how to avoid breaking of the water surface
When escaping from attacking predators, different water strider species adjust their jump performance to their mass and morphology in order to jump off the water as fast and soon as possible without breaking of the water surface.
For the first time, scientists catch water molecules passing the proton baton
Water conducts electricity, but the process by which this familiar fluid passes along positive charges has puzzled scientists for decades.
Water, water -- the two types of liquid water
There are two types of liquid water, according to research carried out by an international scientific collaboration.
Just add water? New MRI technique shows what drinking water does to your appetite, stomach and brain
Stomach MRI images combined with functional fMRI of the brain activity have provided scientists new insight into how the brain listens to the stomach during eating.
At attention, molecules!
University of Iowa chemists have learned about a molecular assembly that may help create quicker, more responsive touch screens, among other applications.
A single ion impacts a million water molecules
EPFL researchers have found that water molecules are 10,000 times more sensitive to ions than previously thought.
Artificial molecules
A new method allows scientists at ETH Zurich and IBM to fabricate artificial molecules out of different types of microspheres.
UM researchers found shallow-water corals are not related to their deep-water counterparts
A new study led by scientists at the University of Miami Rosenstiel School of Marine and Atmospheric Science found that shallow-reef corals are more closely related to their shallow-water counterparts over a thousand miles away than they are to deep-water corals on the same reef.
Saline water better than soap and water for cleaning wounds, researchers find
Researchers found that very low water pressure was an acceptable, low-cost alternative for washing out open fractures, and that the reoperation rate was higher in the group that used soap.

Related Water Molecules Reading:

Wanda the Water Molecule

WATER: THE MIRACLE MOLECULE (Understanding the Biological Importance of Water)
by Mr Jonathan Clark (Author)

The Hydrogen Bond and the Water Molecule: The Physics and Chemistry of Water, Aqueous and Bio-Media
by Yves Marechal (Author)

Water, Pure and Simple: The Infinite Wisdom of an Extraordinary Molecule
by Dr. Paolo Consigli MD (Author)

The Hidden Secrets of Water: Discovering the Powers of the Magical Molecule of Life
by Dr. Paolo Consigli (Author)

Explaining Biological Molecules: Proteins, Carbohydrates and Water

The Miracle Molecule: Explaining The Biological Importance Of Water

Water: The Forgotten Biological Molecule
by Denis Le Bihan (Editor), Hidenao Fukuyama (Editor)

Quantum Physics of Atoms, Molecules, Solids, Nuclei, and Particles
by Robert Eisberg (Author), Robert Resnick (Author)

Water: The Origin of Life from Water to the Molecules of Life
by BookBaby

Best Science Podcasts 2018

We have hand picked the best science podcasts for 2018. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Hacking The Law
We have a vision of justice as blind, impartial, and fair — but in reality, the law often fails those who need it most. This hour, TED speakers explore radical ways to change the legal system. Guests include lawyer and social justice advocate Robin Steinberg, animal rights lawyer Steven Wise, political activist Brett Hennig, and lawyer and social entrepreneur Vivek Maru.
Now Playing: Science for the People

#495 Earth Science in Space
Some worlds are made of sand. Some are made of water. Some are even made of salt. In science fiction and fantasy, planet can be made of whatever you want. But what does that mean for how the planets themselves work? When in doubt, throw an asteroid at it. This is a live show recorded at the 2018 Dragon Con in Atlanta Georgia. Featuring Travor Valle, Mika McKinnon, David Moscato, Scott Harris, and moderated by our own Bethany Brookshire. Note: The sound isn't as good as we'd hoped but we love the guests and the conversation and we wanted to...