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    1. Mechanism of the blue color and H2O2 oxidizing
  2. During the electrochemical anodizing process of Mo metal rods (Figure 1), water splitting produces OH- on the surface of the anode electrode, which leads to the oxidation of molybdenum and the growth of a thin oxide layer [42].
  3. The presence of weak van der Waals bonds across certain crystallographic orientations of molybdenum oxide lattice is the main reason for its tendency to flake [43,44].
  4. Accordingly, we believe that as soon as an oxide layer is formed, these bonds develop through, causing them to exfoliate before being completely oxidized to 6+ oxidation state.
  5. As a consequence, a colloidal solution consisting of highly defective MoO3-x with LSPR absorption in the NIR region is formed.
  6. The underlying mechanism of the appearing of LSPR band and the blue color in MoO3-x colloids can be understood in terms of releasing these electrons to conduction band due to formation of lattice oxygen vacancy during the anodizing process [45,46].
  7. Therefore, appearing of blue color is due to absorption of red region of the visible light.
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