Scientists calculate the electric charges in a single catalyzed nanoparticle down to the electron

Scientists calculate the electric charges in a single catalyzed nanoparticle down to the electron

The superior sensitivity and precise measurements of electron holography around platinum nanoparticles such as the one shown here allowed the scientists to calculate the net charge in a single catalyzed nanoparticle with a precision of just one electron for the first time. Credit: Murakami Laboratory, Kyushu University

If you often find yourself separated when counting your socks after washing clothes, you may want to sit down for this.

Scientists in Japan have now counted the number of excess – or missing –shipment down to the precision of only one electron in a single platinum nanoparticle with a diameter of one-tenth the diameter of common viruses.

This new process of carefully studying the differences in net charge on metallic nanoparticles will help further understanding and development of catalysts to break down greenhouse gases and other harmful gases into fuels and benign gases or to efficiently produce the ammonia needed for fertilizers used in agriculture.

Led by Kyushu University and Hitachi Co., Ltd., the research team achieved this feat of extreme counting through hardware and software improvements that increased the sensitivity of a technology called 3D electron imaging by tenfold.

While transmission electron microscope It uses a beam of electrons to monitor materials down to atomic levelAnd the Electron holography It uses the wave-like properties of electrons to explore electric and magnetic fields.

The interaction of the electron with the fields causes a transformation phase in its wavelength which can be determined by comparing it with a reference wave of an unaffected electron.

Scientists calculate the electric charges in a single catalyzed nanoparticle down to the electron

This new study highlights the importance of directly calculating electric charges in a stimulated nanoparticle. For example, in platinum nanoparticles on a titanium oxide surface, visualizing the potential distribution through the noise reduction process developed in electronic holography revealed the negative charge of the nanoparticles with only six additional electrons. This is the first time that the charges for each stimulated nanoparticle have been counted with the precision of a single electronic charge. Credit: Murakami Laboratory, Kyushu University

In the new work, the researchers focused their microscopes on single platinum nanoparticles on a surface of titanium oxide, a mixture of materials already known to act as a catalyst and speed up chemical reactions.

On average, platinum nanoparticles are only 10 nanometers in diameter — so small that it takes about 100,000 to stretch to one millimeter.

“While each particle contains a few tens of thousands of platinum atoms, adding or removing one or two negatively charged electrons leads to significant changes in the behavior of materials as catalysts,” says Ryotaro Aso, assistant professor at Kyushu University College. Engineering and first author on paper in the magazine Sciences Work reporting.

Measurement of the fields around the platinum nanoparticles – which vary depending on the imbalance between cation and Negative fee In a particle – in an airless environment, researchers can determine the number of extra or missing electrons that make up the fields.

“Of the millions of positively charged protons and negatively charged electrons that balance each other out in nanoparticles, we can successfully tell if the number of protons and electrons differs by only one,” Aso explains.

Although the fields are too weak to be observed by previous methods, the researchers improved the sensitivity using a newly developed 1.2 megavolt 3D imaging microscope developed and operated by Hitachi that reduces mechanical and electrical noise and then processes the data to further excite the signal from the noise. .

Scientists calculate the electric charges in a single catalyzed nanoparticle down to the electron

Since 1966, Hitachi has been developing a holographic electron microscope as a tool for direct observation of electric and magnetic fields in very small areas, and in 2014, developed a 1.2 megavolt holographic electron microscope with a grant under the Global Leadership in Research and Development in Science and Technology Program (“First Program”), a national project sponsored by the Japanese Government. Credit: Hitachi Corporation, Ltd.

It was developed by Yoshihiro Midoh of Osaka University, one of the paper’s authors, and Signal processing The technique used the so-called Wavelet Hidden Markov Model (WHMM) to reduce noise without removing the very weak signals of interest.

In addition to determining the charge state of individual nanoparticles, the researchers were able to relate differences in the number of electrons, which ranged from one to six, to differences in the nanoparticles’ crystal structure. Nanoparticles.

While the number of electrons per region was previously reported by measuring the average area of ​​a large number of particles, this is the first time that scientists can measure the difference of a single electron in a single particle.

“By combining advances in microscopy devices and signal processing, we are able to study the phenomenon at increasingly smaller levels,” comments Yasukazu Murakami, a professor at Kyushu University’s School of Engineering and supervisor of the Kyushu Yu team.

“In this first demonstration, we measured the charge on a single nanoparticle in a vacuum. In the future, we hope to overcome challenges that currently prevent us from performing the same measurements in the presence of gas to obtain the information in environments closer to actual applications.”

The optical microscopy strategy allows observers to examine the electrons moving within the gold

more information:
Ryotaro Aso et al, Direct determination of the charge state of a single platinum nanoparticle on titanium oxide, Sciences (2022). DOI: 10.1126 / science.abq5868.

Presented by Kyushu University

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