If someone wants to use negative molecular ions as single-molecule switching and storage units, an intrinsic problem arises: ions usually deposit with their counterions from solution onto surfaces, forming larger aggregates (quasi small salt crumbs). By mass selection of the anions and soft-landing them in vacuum, these counterions can be excluded and the deposition of single molecular storage units is thereby possible. Initially, the method was not very successful because the switchable anions were simply not stable on surfaces without counterions and decomposed under ambient condition. To counteract this, researchers from the Joint Lab “Molecular Ion Deposition” at IOM used a trick from so-called host-guest chemistry. A circular sugar molecule wraps itself around the negative ion as a "ring" and protects it. Thus, the molecular storage unit remains stable even on surfaces and can be successfully switched through several redox states. This opens up new avenues for the preparation and addressing of memory units with a control of the adsorption properties at the single molecule level.

The results have now been published in the journal ACS Applied Nano Materials (ANM). More information about the article:

Fangshun Yang, Marco Moors, Duc Anh Hoang, Sebastian Schmitz, Markus Rohdenburg, Harald Knorke, Ales Charvat, Xue-Bin Wang, Kirill Yu. Monakhov, and Jonas Warneke
On-Surface Single-Molecule Identification of Mass-Selected Cyclodextrin-Supported Polyoxovanadates for Multistate Resistive-Switching Memory Applications
ACS Appl. Nano Mater. 2022
https://doi.org/10.1021/acsanm.2c03025