Structural model of the relaxed surface with the positions of three-fold symmetry axes labelled A, B and C. Each surface unit cell contains four six-fold coordinated indium atoms (blue), 12 five-fold coordinated indium atoms (green), 12 three-fold coordinated oxygen atoms (red) and 12 four-fold coordinated oxygen atoms below (shaded red). The four types of three-fold coordinated oxygen atom are labelled α, β, γ and δ
The acidity of single hydroxyl groups on a metal oxide surface has been determined for the first time using non-contact atomic force microscopy (AFM) and a hydroxyl-functionalised tip.
1 With the new setup, researchers in Austria, Germany and the Czech Republic were able to directly assess the proton affinity of individual sites by probing the strength of their hydrogen bonds with the tip. ‘The indium oxide surface we investigated has four different oxygen atoms with different reactivity, which means we can study the proton affinity of four oxygen atoms in one ex
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New Technique Helps Determine the Acidity of Molecules
Written by AZoMApr 29 2021
The chemical behavior of a substance is mainly governed by its degree of acidity or alkalinity. The so-called proton affinity plays a role as a decisive factor and shows how easily an entity emits or attracts a single proton.
Using the modified tip of an atomic force microscope, individual atoms in the surface can be probed. Image Credit: TU Wien.
The measurement of the proton affinity of molecules has been relatively easy than it is for surfaces. This is crucial because atoms on surfaces exhibit extremely different proton affinities, based on where they are located.
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IMAGE: Using the modified tip of an atomic force microscope, individual atoms in the surface can be probed. view more
Credit: TU Wien
The degree of acidity or alkalinity of a substance is crucial for its chemical behavior. The decisive factor is the so-called proton affinity, which indicates how easily an entity accepts or releases a single proton. While it is easy to measure this for molecules, it has not been possible for surfaces. This is important because atoms on surfaces have very different proton affinities, depending on where they sit.
Researchers at TU Wien have now succeeded in making this important physical quantity experimentally accessible for the first time: Using a specially modified atomic force microscope, it is possible to study the proton affinity of individual atoms. This should help to analyze catalysts on an atomic scale. The results have been published in the scientific journal