Tag: nanostructures

Caught in the frame: the birth of nanostructures

Caught in the frame: the birth of nanostructures

A team led by prof. Magdalena Parlińska-Wojtan from the Institute of Nuclear Physics of the Polish Academy of Sciences conducted advanced research on the process of electrodeposition of metallic nanostructures, using unique microscopic techniques in a liquid environment. International cooperation, including the Silesian University of Technology, the University of Warsaw, the SOLARIS Center, ETH Zurich, and the Fritz Haber Institute in Berlin, resulted in a publication in the prestigious journal Nano Letters.

Modern microscopes and a special electrochemical flow cell allowed scientists from the IFJ PAN to observe the process of creating metal nanoparticles with unprecedented precision. This is a step towards better design of future materials – from fuel cells to advanced sensors. 

Electrodeposition is the process of depositing a metal layer on the surface of an electrode immersed in an electrolyte under the influence of voltage. Although known for a long time, until now it has been difficult to observe its course in detail in real time. Thanks to a special flow cell, in which a microscopic volume is separated by two very thin membranes (and one of them is additionally equipped with electrodes), it became possible to track the formation of a platinum-nickel (PtNi) nanolayer. 

The experiment recorded two mechanisms: direct growth of the PtNi layer on the electrode and the formation of nanoparticles in solution and their deposition on the electrode surface, especially where the electron beam reached. More detailed observations showed that the nanostructures have a spherical shape and a dendritic surface. 
In the next stage of the experiment, carried out in cooperation with the Fritz Haber Institute (Max Planck Gesellschaft), the reaction parameters were modified, which allowed for the recording of nucleation and the growth and dissolution cycles of nanoparticles. Observations showed that the growth rate prevailed over dissolution, thanks to which a durable layer was created. 

Further studies were conducted in the STXM microscope at the SOLARIS center in Krakow. Although the resolution of STXM is lower than TEM, the STXM microscope allows for more precise chemical analysis. It was determined that the PtNi layer consists of metallic platinum and nickel(II) oxide. 

The research opens up new possibilities for controlled synthesis of nanostructures that can be used in energy, electronics and medicine. The recognition of the importance of the work was the inclusion of a graphic from the publication on the cover of the 40th issue of Nano Letters.

Read more on SOLARIS website

Helium droplets for studies of nanostructures

Helium droplets for studies of nanostructures

Using a conical nozzle, an international research team has generated vortex-free droplets of superfluid helium that are larger than any created before. The droplets are big enough to be resolved in X-ray diffraction images, making them ideal for studying the self-assembly of a wide range of nanostructures forming inside a superfluid environment.  

A superfluid, such as very cold liquefied helium, flows without any internal friction. Droplets of superfluid helium therefore provide a perfect environment for researchers to investigate the formation of self-organized nanostructures made from various dopant materials, i.e. atoms and molecules specifically inserted into the droplets. However, the occurrence of vortices inside the droplets can hinder the assembly of such nanostructures, as many dopants are easily attracted to them. Now, a team of scientists led by researchers from TU Berlin has used a special nozzle at the European XFEL’s SQS instrument to create swirl-free helium nanodroplets and explore the size range in which they can be produced.

“Our conical nozzle enabled us to generate vortex-free droplets from the condensation of expanding helium gas that contain up to a thousand times more helium atoms than possible with previous methods,” explains Rico Tanyag, previously at TU Berlin in Germany and now at Aarhus University in Denmark, one of the principal investigators of the experiment. “This large size allows us to image both the droplets and the dopant nanostructures inside them using the ultrashort pulses of X-ray free-electron lasers such as the European XFEL,” adds Daniela Rupp from ETH Zürich in Switzerland, the other main proposer of the study. “Our experiment thus paves the way for exploring in atomic detail how such nanostructures form.”

Using a technique called X-ray coherent diffractive imaging on helium droplets doped with xenon atoms, the scientists found that single compact xenon structures, which are associated with vortex-free formation, prevailed up to a droplet size of a hundred million helium atoms—a thousand times more than previously feasible. Larger droplets, on the other hand, contained xenon filaments, indicating the presence of vortices that disturbed the structure formation. 

Read more on XFEL website

Image: The SQS instrument at European XFEL.

Credit: European XFEL/Axel Heimken