Dye-sensitized Bi2MoO6 for highly efficient photocatalytic degradation of levofloxacin under LED light irradiation

Different from traditional dye sensitization by chemisorption in the dark, this work uses electron trapping sites and positively charged rhodamine B dye molecules to achieve electrostatic interaction under irradiation. As the irradiation time increases, the surface oxygen vacancies of Bi2MoO6 as the electron trapping sites gather a large number of electrons forming negative surface, which are tightly bound to the positive rhodamine B dye molecules. In the dye-sensitized Bi2MoO6 system, the electrons located on the oxygen vacancies can reduce the oxidized dyes to ground state. The newly formed ground-state dyes are photoexcited again and inject electrons into the conduction band of the Bi2MoO6 to participate in photodegradation levofloxacin. Then the newly aggregated electrons on the oxygen vacancies repeat the above cycle. The formation of the cyclic path greatly reduces the recombination of electrons and holes in Bi2MoO6, which increases the efficiency of photocatalytic degradation of levofloxacin from ∼43.5% to ∼98.3% under LED irradiation for 2 h. In addition, the photodegradation pathway of levofloxacin is investigated.