A novel microscope reveals the miracle of molecular oxygen

Researchers on the University of Regensburg monitor step one within the response of 1 single dye pigment with oxygen at an unprecedented decision.

Why do the colours of a t-shirt fade over time within the sun? Why do you get a sunburn, and why do the leaves of a tree flip brown in autumn? These questions all have one theme in widespread—the interaction between dye pigments and ambient oxygen. Every baby learns about this chemical response in class, which is the oxidation process within the air that we breathe. So what may presumably be left to analysis?

Oxygen is an astonishing molecule in that it’s magnetic. In liquid type, at very low temperatures, it may be picked up by a magnet very similar to iron filings can. This property is said to the electrons within the oxygen. All molecules are made up of atomic nuclei and electrons, which behave like miniscule needles of a compass. Usually, these needles prepare in pairs pointing in reverse instructions in order that their magnetic forces cancel out. In an oxygen molecule consisting of two oxygen atoms, nonetheless, the 2 compass needles level in the identical route, making oxygen magnetic.

Dye molecules, corresponding to these used to paint a t-shirt, will not be magnetic as a result of the compass needles of the electrons level in reverse instructions. When gentle shines on such a molecule, a sure colour of the sunshine can be absorbed, giving the dye its attribute look. In this course of of sunshine absorption, the power of the sunshine is transferred to an electron within the dye molecule, breaking the unique pairing of two electrons and permitting the compass needle of the excited electron to spontaneously change its alignment. When this course of occurs, the electron can now not return to its unique state. The dye molecule turns into magnetic, coming into what’s known as a “triplet state.”

An worldwide analysis workforce directed by Prof. Jascha Repp has now succeeded in revealing how this triplet power is transferred from one single dye molecule to 1 single oxygen molecule. This course of is integral to on a regular basis life, the place many oxidation reactions proceed by way of the excited triplet state. As lengthy because the molecule resides on this state, it retains the power imparted on it by the sunshine, thereby facilitating chemical reactions. Most chemical reactions, corresponding to combustion, require some preliminary power corresponding to a spark to start.

A whole dissipation of the power throughout the dye molecule necessitates one other reversal of the alignment of the digital compass needle, which is a sluggish and inconceivable course of. Alternatively, the sunshine power throughout the dye molecule, which corresponds to a magnetic power, might merely switch to an additional magnetic molecule, corresponding to oxygen—a course of very similar to flipping one bar magnet by rotating one other one close by. This switch of power deexcites the dye molecule, but it surely tends to make the oxygen molecule itself extremely reactive, finally destroying the dye molecule. This impact could be seen in bleached t-shirts or sunburns, the place the dye molecules are the pigments within the pores and skin.

The workforce has succeeded in monitoring this switch of power between the dye and the oxygen molecule instantly in space, with out destroying the dye molecule. To do that, single molecules have been positioned on a floor and cooled to very low temperatures near that of the universe. Using a so-called “atomic force microscope” consisting of a really fantastic needle with only one single atom at its tip, the researchers have been in a position to picture the person atoms of the dye molecule by scanning the tip throughout it. By making use of a sequence {of electrical} pulses to the dye molecule, they might drive it into the magnetic triplet state in a managed style. The power switch from this excited triplet state to oxygen molecules close by was then tracked in time by measuring miniscule modifications within the drive performing on the tip.

This novel strategy, reported in Science, allowed the researchers to probe many alternative geometries of the association of dye molecule and oxygen. In this manner, the interaction between molecular preparations on the atomic degree and the velocity at which such power switch happens could possibly be resolved for the primary time. The scientists now purpose to lastly be capable to formulate an underlying microscopic framework of elementary oxidation reactions. In addition to the inconvenient fading of t-shirts, such an interaction between molecular triplet excitations is of central significance to a spread of technological developments, corresponding to in natural light-emitting diodes (OLEDs) and natural solar cells, in photocatalytic power conversion and photosynthesis, and in photodynamic most cancers remedy.