Tracking a solvation process step by step

December 21, 2017

Chemists of Ruhr-Universität Bochum tracked with unprecedented spatial resolution how individual water molecules attach to an organic molecule. They used low-temperature scanning tunneling microscopy to visualize the processes at a scale smaller than one nanometre. This allowed them to investigate the phenomena of hydrophilicity and hydrophobicity at the molecular level, i.e. why certain parts of organic molecules attract or repel water.

"The results are an important step on the path to understanding solvation processes, that is, how substances dissolve in water", explains Karsten Lucht of the Bochum Chair of Physical Chemistry I. He reports the results with the team led by Prof Dr Karina Morgenstern and colleagues from the Chair of Organic Chemistry II in the journal "Angewandte Chemie". The scientists cooperate in the excellence cluster Ruhr Explores Solvation, or Resolv for short.

The aim of the cluster is to understand how solvents affect the reactions in solution and the use of solvents to control reactions.

Tracking water accumulation step by step

As an organic molecule, the researchers used an azo dye that consists of two carbon rings with attached functional groups that are polar, i.e. slightly positively or negatively charged. They deposited the molecules on a gold single crystal and cooled the system to six Kelvin. Then they added individual water molecules step by step and observed where these attached to the dye.

The first water molecules preferred to attach themselves to the polar functional groups. When the researchers increased the amount of water, the newly added molecules attached themselves to the water molecules that were already bonded. "Our experiments show that hydrophilicity and hydrophobicity can be traced back to molecular level", says Karina Morgenstern. The water molecules avoided non-polar areas of the molecule, polar areas were preferred.

Three complementary procedures

The processes that were observed here with scanning tunneling microscopy are usually investigated spectroscopically or with molecular dynamic simulations. However, the first method does not provide spatial information, and the latter is based on assumptions due to the size of the system. "Every method has its value", explains Karsten Lucht. "The three approaches complement each other."

Ruhr-University Bochum

Related Water Molecules Articles from Brightsurf:

Transport of water to mars' upper atmosphere dominates planet's water loss to space
Instead of its scarce atmospheric water being confined in Mars' lower atmosphere, a new study finds evidence that water on Mars is directly transported to the upper atmosphere, where it is converted to atomic hydrogen that escapes to space.

Water striders learn from experience how to jump up safely from water surface
Water striders jump upwards from the water surface without breaking it.

Chemistry's Feng Lin Lab is splitting water molecules for a renewable energy future
Feng Lin, an assistant professor of chemistry in the Virginia Tech College of Science, is focusing on energy storage and conversion research.

How a crystalline sponge sheds water molecules
How does water leave a sponge? In a new study, scientists answer this question in detail for a porous, crystalline material made from metal and organic building blocks -- specifically, cobalt(II) sulfate heptahydrate, 5-aminoisophthalic acid and 4,4'-bipyridine.

Water molecules are gold for nanocatalysis
Nanocatalysts made of gold nanoparticles dispersed on metal oxides are very promising for the industrial, selective oxidation of compounds, including alcohols, into valuable chemicals.

Liquid water is more than just H2O molecules
Skoltech scientists in collaboration with researchers from the University of Stuttgart showed that the concentration of short-lived ions (H3O+ and OH-) in pure liquid water is much higher than that assumed to evaluate the pH, hence significantly changing our understanding of the dynamical structure of water.

'Pregnancy test for water' delivers fast, easy results on water quality
A new platform technology can assess water safety and quality with just a single drop and a few minutes.

Water molecules dance in three
An international team of scientists has been able to shed new light on the properties of water at the molecular level.

Unique structural fluctuations at ice surface promote autoionization of water molecules
Hydrated protons at the surface of water ice are of fundamental importance in a variety of physicochemical phenomena on earth and in the universe.

Researchers create new tools to monitor water quality, measure water insecurity
A wife-husband team will present both high-tech and low-tech solutions for improving water security at this year's American Association for the Advancement of Science (AAAS) annual meeting in Seattle on Sunday, Feb.

Read More: Water Molecules News and Water Molecules Current Events 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