Single platinum atoms spotted in 2D lattice for first time unlock smarter gas sensors
The research team from the University of Vienna and the Vienna University of Technology (TU Wien), utilized a new method that combines defect engineering in the host material, the controlled placement of platinum atoms, and a cutting-edge, high-contrast electron imaging technique known as ptychography.
Jani Kotakoski, PhD, an expert in the field of physics in nanostructured materials and research group leader, highlighted that the achievement sets the stage for tailoring materials with atomic precision.
Active centers, which are tiny sites on the material's surface where chemical reactions occur or gas molecules can specifically bind, are crucial for enhancing the efficiency, selectivity, and overall performance of materials used in catalysis and gas detection.
These centers are especially effective when made up of single metal atoms like platinum, which they aimed not only to produce, but also to visualize with atomic-level precision.
Known for its highly tunable structure, the host material molybdenum disulfide (MoS₂) is an ultrathin semiconductor. To introduce new active sites, the scientists used helium ion irradiation to deliberately create atomic-scale defects on its surface, such as sulfur vacancies.
These vacancy sites were then selectively filled with individual platinum atoms, allowing the team to engineer the material at the atomic level. This precise atomic substitution, known as doping, enables fine-tuning of the material's properties for specific applications, such as catalysis or gas detection.
However, previous studies had not provided direct evidence of the exact positions of foreign atoms within the atomic lattice, as conventional electron microscopy lacks the contrast needed to clearly distinguish between defect types such as single and double sulfur vacancies.
In a bid to address the challenge, the team has now used a state-of-the-art imaging method known as Single-Sideband Ptychography (SSB), which analyzes electron diffraction patterns to achieve atomic-level resolution.
"With our combination of defect engineering, doping, and ptychography, we were able to visualize even subtle differences in the atomic lattice - and clearly determine whether a platinum atom had been incorporated into a vacancy or merely resting loosely on the surface," David Lamprecht, MSc, a student at the University of Vienna's institute for microelectronics, and lead author of the study, said.
With the help of computer simulations, the scientists were able to precisely identify the different incorporation sites, such as positions originally occupied by sulfur or molybdenum atoms, marking a key advance toward targeted material design.
The team believes that combining targeted atom placement with atomically precise imaging unlocks new possibilities for advanced catalyst design and highly selective gas sensing.
While individual platinum atoms placed at precisely defined sites can serve as highly efficient catalysts, like in eco-friendly hydrogen production, the material can also be tailored to respond selectively to specific gas molecules.
"With this level of control over atom placement, we can develop selectively functionalized sensors - a significant improvement over existing methods," Kotakoski concluded in a press release.
According to the research team, the approach is not limited to platinum and molybdenum disulfide but can also be applied to a wide range of 2D materials and dopant atom combinations.
By gaining more precise control over defect creation and incorporating post-treatment steps, the researchers now hope to further refine the technique. Their final goal is to develop functional materials with customized properties, in which every atom is positioned with absolute precision.
The study has been published in the journal Nano Letters.
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