By Josh Perry, Editor
Researchers from Finland and China have demonstrated that extremely high-resolutions images of the surface of silver nanoparticles, including the individual parts of molecules, can be viewed using scanning tunneling microscopy (STM), according to a report from the Academy of Finland.
Researchers demonstrated high-res images of the molecular surfaces of nanoparticles. (Academy of Finland)
This study of surface structure at atomic resolution will enable scientists to better understand the chemical properties of the nanoparticles, the molecular interactions on the surface, and how the particles function in different environments.
Using a previously characterized silver nanoparticle that has 374 silver atoms surrounded by a series of 113 tert-butyl-benzene thiol (TBBT) molecules (each with a set of three carbon groups on its end), the researchers took images that showed “clear sequential modulations” in the tunneling current.
Based on density functional theory, the article explained, researchers showed that each carbon group provided a current maximum in the STM and the observed distance between maxima confirmed the sub-molecular level measurement.
“The simulations also predicted that accurate STM measurement can no longer be successful at room temperature, as the thermal movement of the molecules is so high that the current maxima of individual carbon groups blend into the background,” the article continued.
The research team also “simulated an STM image of the silver particle from 1,665 different orientations and developed a pattern recognition algorithm to determine which simulated images best matched the experimental data.”
The research was recently published in Nature Communications. The abstract read:
“High-resolution real-space imaging of nanoparticle surfaces is desirable for better understanding of surface composition and morphology, molecular interactions at the surface, and nanoparticle chemical functionality in its environment. However, achieving molecular or sub-molecular resolution has proven to be very challenging, due to highly curved nanoparticle surfaces and often insufficient knowledge of the monolayer composition.
“Here, we demonstrate sub-molecular resolution in scanning tunneling microscopy imaging of thiol monolayer of a 5 nm nanoparticle Ag374protected by tert-butyl benzene thiol. The experimental data is confirmed by comparisons through a pattern recognition algorithm to simulated topography images from density functional theory using the known total structure of the Ag374 nanocluster.
“Our work demonstrates a working methodology for investigations of structure and composition of organic monolayers on curved nanoparticle surfaces, which helps designing functionalities for nanoparticle-based applications.”