96Original Research Paper

J. Jpn. Soc. Colour Mater., 96〔3〕，96–103（2023）

Processing of Cerium Molybdates by Solid Phase Process and their Antiviral Activity
Shunta Iwakura＊, Takuro Ito＊, Tatsunori Sakai＊, Kayano Sunada＊＊, Yasuhide Mochizuki＊, Toshihiro Isobe＊,
Sachiko M atsushita＊, Takeshi Nagai＊＊, Hitoshi Ishiguro＊＊ and Akira Nakajima＊,†＊ Department of Materials Science and Engineering, School of Materials and Chemical Technology, Tokyo Institute of Technology,

2-12-1 O-okayama, Meguro, Tokyo 152-8550, Japan＊＊ Life Science Technology Project, Kanagawa Institute of Industrial Science and Technology,

LiSE4c-1, 3-25-13 Tonomachi, Kawasaki-ku, Kawasaki, Kanagawa 210-0821, Japan†Corresponding Author, E-mail: nakajima.a.aa@m.titech.ac.jp(Received October 27, 2022; Accepted January 10, 2023 )Abstract
Single-phase powders of γ-Ce 2 Mo 3 O 13 , Ce 8 Mo 12 O 49 , and Ce 2 Mo 4 O 15 were prepared using the solid-phase method. Then, the antiviral
activity of these powders against the non-enveloped virus bacteriophage Qβ and the enveloped virus bacteriophage Φ6 were evaluated.
Moreover, H 2 O 2 assay and catalase inactivation test were performed. Regarding the antiviral activity of the prepared samples, the activity
against bacteriophage Φ6 was higher than the activity against bacteriophage Qβ. The antiviral activity order for bacteriophage Φ6 wascorrelated with the amount of H 2 O 2 generated and the catalase inactivation rate. It depended also on the eluted Ce/Mo ratio. These results
imply that the antiviral activity on bacteriophage Qβ is influenced by neutralization of the negative charge of capsid by rare earth ionsand by adsorption of heteropolyacids to specific sites of the virus. Results suggest that the oxidation reaction of Ce (IV) or of the H 2 O 2 ,and the adsorption of heteropolyacids formed by Ce and molybdate ions affect the antiviral activity against bacteriophage Φ6. Among thecompounds examined this time, γ-Ce 2 Mo 3 O 13 exhibited the highest antiviral activity against bacteriophage Φ6.
Key-words: Mo, Ce, Antiviral, Solid phase, Virus

1．Introduction
The new coronavirus pandemic is continuing worldwide,and seeing the direction of convergence is still difficult.
This viral pandemic has underscored the impossibility ofhalting economic and social activities completely, even underdifficult circumstances. To continue certain economic andsocial activities until vaccines are widely used, technology
and knowledge of “prevention” and “suppression of spread” ofinfection are as important as “development of vaccines andtreatment methods”. In recent years, antiviral materials haveattracted great attention as one technology for that purpose.
Inorganic antibacterial and antiviral materials have ashorter history of development than organic ones, but theyare less temperature-dependent, effective against various
bacteria and viruses, and make it difficult for viruses toacquire resistance. Conventional inorganic antibacterial andantiviral materials include noble-metal-based materials (Ag,Cu, etc. 1-3 )), photocatalysts (TiO 2 , etc. 4,5 )), and others (ZnO,alkaline oxides, etc. 6,7 )). Nevertheless, several difficulties
exist such as cost, deterioration of antibacterial and antiviral
activity over time, coloring, and a limited usage environment.
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© 2023 Journal of the Japan Society of Colour Material－2－We recently prepared La 2 Mo 2 O 9 ( LMO ) using thecomplex polymerization method, which revealed that thisrare earth molybdate complex oxide is an antibacterial
and antiviral material that overcomes these difficulties 8 ).
Furthermore, by substituting La of this material with Ce, theantiviral activity against enveloped viruses was improved 9 ).
Actually, γ-Ce 2 Mo 3 O 13 , which consists only of Ce andMo, exhibited extremely high antiviral activity againstenveloped viruses including the new coronavirus (SARSCoV-2 ) 10 ). From results of these studies conducted to date,
it is considered that the antiviral activity of these materials
originates from ions or polyacid ions eluted in water.
Although oxides of molybdenum exhibit a certain solubility
in water, it is suppressed and the sustained release of ionsbecomes feasible by forming a complex oxide with La orCe 9 ). The antiviral activity of γ-Ce 2 Mo 3 O 13 against SARSCoV- 2 surpassed that of LMO or MoO 3 , indicating theeffectiveness of the combination of Ce and Mo.
Because both Ce and Mo are polyvalent metal elements,cerium molybdate has complex oxides with various element
ratios 11 ). Therefore, unless appropriate conditions are set,a single phase powder cannot be obtained. As describedin an earlier report 10 ), we prepared single-phase powdersof γ-Ce 2 Mo 3 O 13 and Ce 2 Mo 3 O 12 respectively usinghydrothermal method and complex polymerization method.