Nanotunnel Structures within Metal Oxides Induce Active Sites for the Strong Self-Reduction of Mn IV to Mn II .

Zn2 SiO4 , Zn2 GeO4 , and CdAl2 O4 possess high electron density in their six-membered-ring nanotunnels, manganese from MnO2 was successfully doped into them, and green or blue phosphors were produced in air. It is nanotunnel A with high electron density that induces active sites for the reduction of MnIV . MnIV is captured and reduced to MnII on active sites by seizing two electrons from native defect VO × (VO × + Mn4+ → VO ·· + Mn2+ ). CdB4 O7 :0.02Mn2+ was also synthesized from MnO2 or MnCO3 to confirm the role of nanotunnels. Such inorganic crystals with unique nanotunnel structure may bring more amazing performances in the field of materials in the future.