Tomokazu Kiyonaga research paper is titled, “Regioselective chemisorption-induced separate deposition of two types of metal nanoparticles on TiO2”.
A current topic in the field of catalysis is the discovery that gold, dispersed as nanoparticles on metal-oxide supports, such as TiO2, exhibits high thermal and visible photo-catalytic activities, even though it is inactive in the bulk state. It was also observed that recently the separate deposition of Au NPs and other metal NPs on TiO2 was developed. The separate deposition were achieved by the colloid photo-deposition with a hole scavenger (CPH) method using TiO2 photocatalysis, and this was done so as an effective method to enhance the visible photocatalysis of Au nanoparticles. Furthemore, Au and Pd nanoparticles have been separately deposited to develop highly active and selective thermal catalysts based on a hydrogen spillover. Thus, it is becoming clear that the separate deposition of metal nanoparticles is important for the development of new photocatalysts and thermal catalysts.
Tomokazu gained his inspiration that there may be limited to the kinds of support that can be used. Additionally, there were little known about the mechanism of separate deposition in these cases.
The objective of his research was to report a new method, which would involve the chemisorption and the subsequent NaBH4 reduction of Au(III) complex ions on TiO2-Pt (TiO2-Pt: Pt nanoparticles deposited TiO2).
The deposition states of the nanoparticles were observed by transmission electron microscopy (TEM). Au and Pt nanoparticles in Au/TiO2-Pt were recognized by the particle size, and the TEM analysis indicated that 10 nm-Pt nanoparticles and 2.4 nm-Au nanoparticles were individually loaded on the TiO2 surface.
Tomokazu has used X-ray photoelectron spectroscopy (XPS) to provide strong evidence for the separate deposition of Au and Pt nanoparticles. The XPS analysis results were also consistent with the TEM results.
Tomokazu has explained the separate deposition of Au and Pt nanoparticles. The adsorption isotherms of Au (III) complex ions (AuC) in the samples (TiO2, TiO2-Pt and bulk metallic Pt foil) were measured. Since no adsorption was observed on the surface of the bulk metallic Pt foil, Tomokazu found out that the result revealed that AuC was regioselectively chemisorbed on the surface of TiO2. On further analysis, the chemisorption patterns of AuC indicated a mechanism in which Au and Pt nanoparticles were individually deposited on the surface of TiO2.
Furthermore, Tomokazu also observed that the in situ NaBH4 reductions of the regioselectively chemisorbed AuC probably led to the separate deposition of Au and Pt nanoparticles.
Thus, the experimental work by Tomokazu established a new method for the separate deposition of the small Au and Pt nanoparticles on TiO2. Additionally, the mechanism of the separate deposition was clarified. The regioselective chemisorption of Au (III) complex ions, which were present on the surface of TiO2 enabled Au and Pt nanoparticles to be deposited separately.
There are great expectations from this method. It may be useful for specifying the locations at which the small Au nanoparticles and various other metal nanoparticles are deposited.
On the other hand, Tomokazu compared this method with CPH method. It caused the particle size of the deposited colloid Au nanoparticles to increase or decrease in the CPH method. According to Tomokazu, this happened due to the TiO2 photocatalyzed dissolution and redeposition of Au nanoparticles.
Tomokazu also noticed that, in contrast to the CPH method, the new method provided small Au nanoparticles within a narrow size and similar distribution in Au/ TiO2–Pt and Au/TiO2. The fact that the visible photocatalytic activity of Au nanoparticles increases as the size of these nanoparticles decreases has been reported. Therefore, the deposition of small Au NPs with a narrow size distribution would increase the visible photocatalytic activity. Furthermore, the similar distributions of the Au nanoparticles would be helpful to compare the catalytic activities such as those of Au/TiO2-Pt and Au/TiO2.
Additionally, the application of the chemisorption of AuC to SrTiO3, ZnO, In2O3, Al2O3, and so on, has been reported. Therefore, Tomokazu concluded that this new method would be helpful in designing the deposition locations of the small Au nanoparticles and other nanoparticles of various metals such as Pt nanoparticles on various support materials. It was also seen that this attempt might assist in the development of Au catalysts.
Tomokazu has mentioned that the future application of regioselective chemisorption to achieve the separate deposition of metal nanoparticles may aid in the development of new photocatalysts and thermal catalysts.
Tomokazu’s brilliant research has set a precedent in the area of materials science.Many young researchers can take help of this study and make further advances in this subject area. Tomokazu’s research paper shows his deep interest in this field and his relentless effort in arriving at the desired conclusion.
About Tomokazu Kiyonaga:
His research interests include metal-semiconductor coupled photocatalysts, thermal catalysts, inorganic semiconductor quantum dot-sensitized solar cells and porous coordination polymer / metal organic frameworks (PCP/MOFs).
Tomokazu Kiyonaga received his BS (2005), MS (2007) and PhD (2010) inEngineeringfrom Kindai University. He served as a research fellow of the Japan Society for the Promotion of Science (DC2) when he was studying for a PhD (supervisor: Prof. Hiroaki Tada) at Kindai University.
He joined the research group of Prof. Wonyong Choi at Pohang University of Science and Technology (POSTECH) as a postdoctoral fellow in 2010 and subsequently worked as a researcher at Shoei Chemical Inc. from 2011 to 2013. In 2013, he joined the research group of Prof. Susumu Kitagawa at Kyoto University’s Institute for Integrated Cell-Material Sciences (iCeMS) as a research associate. In 2015 he became an assistant professor at the Department of Materials System Engineering at National Institute of Technology, Kurume College.
About Akira Heima:
Akira Heima received his AS (2017) in Engineering from National Institute of Technology, Kurume College. He is currently studying for a BS at National Institute of Technology, Kurume College. His research interests includematerials engineeringand microstructure control.