How exactly can we differentiate between single-atom doping and other types of dopings, as in the terms of definition? XANES can tel you that the atoms are not interacting with each other like they would interact in bulk. But doesn't same happen in the case of simple substitution doping? In that case, atoms are also separated and don't really interact with each other. So what's the difference? Or is it just a fancy name for substitution doping? I am aware of the clusters with single atom in the center. I am not talking about those materials.
These are not two competitive phenomena in materials growth, so a direct comparison is not valid. However, doping is the addition of a small amount of an element or more to a matrix. The doping element can go to the lattice in substitution or otherwise or go to the grain boundary affecting, thus, its properties. In both cases mechanical, optical or electrical properties of the matrix could be strongly influenced.
J. Alami Thank you for the reply. I am just asking what is the difference between both? Can we call a doped catalyst a single atom catalyst? Or does it just depend on whether the doped atoms interact with each other or not, like what is determined by EXAAFS, XANES or NMR? So far, I have seen two strategies to prepare Single Atom Catalysts (SACs); one is by calcination of an organic compound containing the element of interest and the second is capturing single atoms with activated surface. But both of these strategies are also used to prepare doped elements. So what precisely makes a SAC different from a common element-doped catalyst? Just the interaction among atoms? If they gets aggregated, they are not SACs, if they don't, they are. I have seen some researchers stating that the existence of SACs or calling these catalysts SACs is still controversial among material scientists.
Some good reads on SACs for other readers.
1. https://doi.org/10.1016/j.joule.2018.06.019
2. https://doi.org/10.1021/ar300361m