The aim in the characterization of the supported metal catalysts was to perform a particle analysis of the charge states closely related to the catalytic activity.
Japanese scientists have now calculated the additional cost or loss of a single platinum nanoparticle with a diameter of nearly one hundredth that of a normal virus.
carried Kyushu University and Hitachi, Ltd., the research team achieved this extreme computational feat through hardware and software upgrades that increase the sensitivity of a technology called electronic holography tenfold.
Electron holography uses the wave properties of electrons to examine electric and magnetic fields, in contrast to transmission electron microscopy, which uses an electron beam to analyze materials up to atomic level.
When an electron interacts with a field, its waveform undergoes a phase shift which can be seen by comparing it to the reference wave of the unaltered electron.
In this new study, the scientists focused their microscope on single platinum nanoparticles on a titanium oxide surface. On average, platinum nanoparticles are only 10 nanometers in diameter, so small that it takes about 100,000 to stretch to a millimeter.
Ryotaro Aso, assistant professor at Kyushu University College of Engineering and first author of the research paper in the journal Science, said: While each particle contains several tens of thousands of atoms platinumThe addition or removal of one or two negatively charged electrons causes a significant change in the behavior of the material as a catalyst. “
By measuring the field around platinum nanoparticles, which varies according to the imbalance of positive and negative charges in the particles, in an airless environment, researchers can determine how many additional or missing electrons make up the field.
As mentioned, Among the millions of positive charges proton And the negatively charged electrons balance each other in the nanoparticles, we were able to find out if the number of protons and electrons differs only by one. “
“Although the field was too faint to be observed with conventional techniques, the researchers increased sensitivity using a 1.2 megavolt 3D atomic resolution microscope developed and operated by Hitachi to reduce mechanical and electrical noise and by processing data to separate them from the noise. further, and ultimately used the results to confirm their findings.
The signal processing method, pioneered by Yoshihiro Midoh of Osaka University, co-author of the study, uses the so-called hidden Markov wavelet model (WHMM) to reduce noise without removing very weak signals.
The scientists were able to determine the state of charge of each nanoparticle and relate the difference in the number of electrons, which ranged from one to six, to changes in the crystalline structure of the nanoparticles.
Yasukazu Murakami, professor of Kyushu University School of Engineering and supervisor tim Kyushu Yu, He saidAnd “By combining advances in microscopy devices and signal processing, we can study the phenomenon on an ever-smaller scale.”
“In this first demonstration, we measured the charge on a single nanoparticle in vacuum. In the future, we hope to overcome the challenges that prevent us from performing the same measurements in the presence of gas to obtain information in environments closer to real applications.”
Journal reference:
- Ryotoaro Aso et al. Direct determination of the charge states in single platinum nanoparticles on titanium oxide. Science. DOI: 10.1126 / Saints. abq5868
