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Proceedings of the 90th JSCM Anniversary Conference
J. Jpn. Soc. Colour Mater., 91〔3〕，89–93（2018）

Anti-Bacterial and Photocatalytic Activities of (Mo0.5, W0.5)O3 with Cu(Mo0.5, W0.5)O4
Prepared by Impregnation Method and Mechanochemical Processing
Mai Mizutani＊, Kayano Sunada＊＊, Toshihiro Isobe＊, Sachiko M atsushita＊ 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-ku, Tokyo 152-8552, Japan＊＊ Antibacterial and Antiviral Research Group, Kanagawa Institute of Industrial Science and Technology,

LiSE4c-1, 3-25-13 Tonomachi, Kawasaki-ku, Kawasaki, Kanagawa 210-0821, Japan†Corresponding Author, E-mail: anakajim@ceram.titech.ac.jp(Received November 13, 2017; Accepted December 14, 2017)
Abstract
A tungsten–molybdenum solid solution oxide ((Mo0.5, W0.5)O3) powder hybridized with Cu(Mo0.5, W0.5)O4 was prepared using impregnation
method and mechanochemical processing. The powder prepared through the impregnation method exhibited antibacterial effects both in
the dark and under visible light. The contribution of MoO3 in the powder surface was inferred for activity in the dark. The phase transition
temperature of (Mo0.5, W0.5)O3 was decreased more than 50°C by planetary ball milling. The powder produced through mechanochemical
processing also exhibited photocatalytic decomposition activity on the gaseous 2-propanol under visible light.
Key-words: Mo, W, Cu, Photocatalyst

bandgap of (Mo, W)O316,17). Very recently, we provided
visible light photocatalytic activity to (Mo, W)O3 powder bymodification of Cu(W1-x, Mox)O4 on the surface18). Detailedanalysis revealed that the Hedvall effect19) at the phasetransition of (Mo, W)O3 from orthorhombic to monoclinic
at 400–450°C during heating hastens Cu(W1-x, Mox) O4
formation, and revealed that the resultant constructionof Z-scheme between (Mo, W)O3 and Cu(W1-x, Mox)O4
provides visible light photocatalytic activity.
Although this material might exhibit antibacterial effects
not only under visible light but also in the dark because ofMoO3 in the surface, this activity has not been examinedto date. Moreover, the controllable surface concentration
ratio between (Mo, W)O3 and Cu(W1-x, Mox)O4 is limitedin the previous process because of impregnation of a
CuCl2 solution and subsequent one-time heat treatment for
the Hedvall effect. It is important to develop a different
processing route to evaluate the potential of this material in awide chemical composition range. Based on this background,
we first examined antibacterial activity both in the dark
and under visible light using the (Mo0.5, W0.5)O3 powder
with Cu(W0.5, Mo0.5)O4 prepared in our previous study.
Secondly, mechanochemical processing20,21) was investigatedto hybridize Cu(Mo0.5, W0.5)O4 with (Mo0.5, W0.5)O3. The
photocatalytic activity of the powders prepared throughthis process was evaluated using decomposition of gaseous
2-propanol (IPA) under visible light22).

1．Introduction
Molybdenum trioxide ( MoO 3) , the most stable oxideof molybdenum, comprises layers of edge-shared MoO6
octahedra in an orthorhombic crystal 1 ) . This material
is commonly applied to catalysts 2-5), photochromic orelectrochromic materials6,7), and anti-bacterial agents8,9).
This oxide forms a solid solution (( Mo, W ) O 3) withWO3. Its crystal structure is the same as that of WO31),
a well-known photocatalyst material10). An earlier study
revealed that the particles of (Mo, W)O3 powder preparedusing hydrothermal processing are smaller than particles
of pure MoO311). Its bandgap is smaller than pure WO3.
These characteristics indicate that (Mo, W)O3 is a candidate
photocatalyst material for use in visible light. However, thereduction power of (Mo, W)O3 is insufficient for its use as
photocatalyst by itself because the conduction band (CB)of WO3 decreases (becomes positive) with dissolution ofMo11,12). Based on the reported value of the CB level of (Mo,W)O3, multi-electron reduction of oxygen is infeasible by
the modification of Cu-clusters onto the powder surface,which is effective for provision of visible light photocatalytic
activity to WO3 by the interface charge transfer13).
By contrast, Cu reacts with WO3 and MoO3 and forms
CuWO 4 and CuMoO 4 at 500–800°C in ambient air
atmosphere14,15). Recent reports have revealed that Cu(W1-x,Mo x) O 4 is an n-type semiconductor with a bandgap of
2.1–2.3 eV. Its valence band (VB) level is located in the－9－© 2018 Journal of the Japan Society of Colour Material