Going small for big solutions: Sub-nanoparticle catalysts made from
coinage elements as effective catalysts

Date:
September 15, 2020
Source:
Tokyo Institute of Technology
Summary:
'Sub-nanometer' particles (SNPs) are very popular because of
their diverse applications, but technical difficulties in their
synthesis has hindered research in this field. Scientists used an
'atom-hybridization method' to overcome this barrier they developed
to study the reactivity of alloy SNPs made from three coinage metal
elements. Their findings are an important step in improving the
knowledge about properties of finite elements and help in building
a sustainable society.



FULL STORY ==========================================================================
Due to their small size, nanoparticles find varied applications in fields ranging from medicine to electronics. Their small size allows them a high reactivity and semiconducting property not found in the bulk states. Sub- nanoparticles (SNPs) have an extremely small diameter of around 1 nm,
making them even smaller than nanoparticles. Almost all atoms of SNPs
are available and exposed for reactions, and therefore, SNPs are expected
to have extraordinary functions beyond the properties of nanoparticles, particularly as catalysts for industrial reactions. However, preparation
of SNPs requires fine control of the size and composition of each
particle on a sub-nanometer scale, making the application of conventional production methods near impossible.


==========================================================================
To overcome this, researchers at the Tokyo Institute of Technology led
by Dr.

Takamasa Tsukamoto and Prof. Kimihisa Yamamoto previously developed the
atom hybridization method (AHM) which surpasses the previous trials
of SNP synthesis. Using this technique, it is possible to precisely
control and diversely design the size and composition of the SNPs using a "macromolecular template" called phenylazomethine dendrimer. This improves their catalytic activity than the NP catalysts.

Now, in their latest study published in Angewandte Chemie International Edition, the team has taken their research one step further and has investigated the chemical reactivity of alloy SNPs obtained through
the AHM.

"We created monometallic, bimetallic, and trimetallic SNPs (containing
one, combination of two, and combination of three metals respectively),
all composed of coinage metal elements (copper, silver, and gold),
and tested each to see how good of a catalyst each of them is," reports
Dr Tsukamoto.

Unlike corresponding nanoparticles, the SNPs created were found to
be stable and more effective. Moreover, SNPs showed a high catalytic performance even under the milder conditions, in direct contrast to conventional catalysts.

Monometallic, bimetallic, and trimetallic SNPs demonstrated the formation
of different products, and this hybridization or combination of metals
seemed to show a higher turnover frequency (TOF). The trimetallic
combination "Au4Ag8Cu16" showed the highest TOF because each metal element plays a unique role, and these effects work in concert to contribute to
high reaction activity.

Furthermore, SNP selectively created hydroperoxide, which is a high-energy compound that cannot be normally obtained due to instability. Mild
reactions without high temperature and pressure realized in SNP catalysts resulted in the stable formation of hydroperoxide by suppressing its decomposition.

When asked about the relevance of these findings, Prof Yamamoto states:
"We demonstrate for the first time ever, that olefin hydroperoxygenation
can been catalyzed under extremely mild conditions using metal particles
in the quantum size range. The reactivity was significantly improved in
the alloyed systems especially for the trimetallic combinations, which
has not been studied previously." The team emphasized that because of
the extreme miniaturization of the structures and the hybridization of different elements, the coinage metals acquired a high enough reactivity
to catalyze the oxidation even under the mild condition. These findings
will prove to be a pioneering key in the discovery of innovative sub-nanomaterials from a wide variety of elements and can solve energy
crises and environmental problems in the years to come.


========================================================================== Story Source: Materials provided by Tokyo_Institute_of_Technology. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Kimihisa Yamamoto, Tatsuya Moriai, Takamasa Tsukamoto, Makoto
Tanabe,
Tetsuya Kambe. Selective Hydroperoxygenation of Olefin Realized
by Coinage Multimetallic 1‐nanometer Catalyst. Angewandte
Chemie International Edition, 2020; DOI: 10.1002/anie.202010190 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200915140130.htm

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