Iron (III) phthalocyanine chloride can be used as a “molecular drone” that lands on a surface, attaches itself to a single atom and thus flies away – leaving a void – researchers from Italy have shown. The result, the team said, could open the door to the rapid manipulation and manufacture of atoms on a relatively large scale.

The ability to manipulate the positions of individual atoms and thus also vacancies has enabled the creation of new types of devices at the atomic level with innumerable possible uses. Proof-of-concept devices manufactured to date include, for example, logic patterns, single-atom information stores, and atomic arrays with potential for use in quantum computers. All of these examples were made by manipulating atoms directly using the tip of a scanning probe microscope (SPM). While this method is groundbreaking, it has certain limitations.

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“The manipulation of atoms through a scanning probe microscope enables absolute spatial control,” explains chemist Massimiliano Cavallini from the Italian National Research Council. “Despite some preliminary parallelization, you can only manipulate atoms one at a time using complex instruments available in a limited number of laboratories.” In addition, most of the atomic-scale devices developed to date have been manufactured in ultra-high vacuum and cryogenic conditions – which means that the patterns generated tend to be unstable under ambient conditions.

Inspired by how some molecules can act similarly to SPM tips – namely, rearranging or replacing atoms with a surface – Cavallini and colleagues turned to ferric phthalocyanine chloride, a compound that uses its metal to form coordination bonds can. ‘Iron (III) has a strong ability to form octahedral complexes. It completes its coordination shell by binding an atom on the surface, in our case iodine, which is a good ligand for iron, ”adds Cavallini. The team used a surface made from iodine (I) modified silver (III). In principle, however, the technology can be used on all non-metallic terminated surfaces, explains Cavallini.

In their demo, the team showed how the reduction in potential in a simple electrochemical cell under ambient conditions led to the “drones” deposited on the surface taking up atoms and leaving vacant spaces behind. In addition, once a vacancy has been formed, a replacement atom can be dropped in its place by underpotential deposition. It might even be possible to customize the drones to add atoms to surfaces without creating a void beforehand, says Cavallini.

Samuel Jarvis, an expert in nanoscale characterization at Lancaster University who was not involved in the study, said the paper shows the beginnings of a viable method of atom manipulation that could be used at great lengths. “This is a great feat, but now the manipulation needs to be controlled to control the pattern being generated, and that’s where SPM still has an advantage,” he explains. “If it’s a molecular drone, the next step is to develop a GoPro so it can see where it’s going.”

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‘There is still a long way to go to control the process, as the paper currently lacks a quantitative description of the spatial distribution of vacancies and in the examples the vacancies are grouped fairly densely – more similar to a good production. well-known ‘etch’, “agrees Sandrine Heutz, a functional molecular materials researcher at the London Center for Nanotechnology and Imperial College London. She adds,” There is an enormous library of phthalocyanine derivatives and growth modes that could be used in the future to translate this discovery into orderly patterns. So there is potential for this to actually work. “

After completing their first study, the researchers have this problem firmly in their crosshairs. ‘At the moment the drone is adjusting its position [from where it was deposited] Cavallini notes that only a few angstroms exploit the interaction between the metal atom of the molecule and an atom on the surface. He adds, however, that “the use of self-assembled monolayers – phthalocyanines tend to form these – will enable the creation of ordered arrays of atomic vacancies with control in the positioning of a few nanometers.”

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