Enhanced Photovoltage Response of Hematite-X-Ferrite Interfaces (X = Cr, Mn, Co, or Ni)

High-fluorescent p-X-ferrites (XFe(2)O(4); XFO; X = Fe, Cr, Mn, Co, or Ni) embedded in n-hematite (Fe(2)O(3)) surfaces were successfully fabricated via a facile bio-approach using Shewanella oneidensis MR-1. The results revealed that the X ions with high/low work functions modify the unpaired spin Fe(2+)–O(2−) orbitals in the XFe(2)O(4) lattices to become localized paired spin orbitals at the bottom of conduction band, separating the photovoltage response signals (73.36~455.16/−72.63~−32.43 meV). These (Fe(2)O(3))–O–O–(XFe(2)O(4)) interfacial coupling behaviors at two fluorescence emission peaks (785/795 nm) are explained via calculating electron-hole effective masses (Fe(2)O(3)–FeFe(2)O(4) 17.23 × 10(−31) kg; Fe(2)O(3)–CoFe(2)O(4) 3.93 × 10(−31) kg; Fe(2)O(3)–NiFe(2)O(4) 11.59 × 10(−31) kg; Fe(2)O(3)–CrFe(2)O(4) −4.2 × 10(−31) kg; Fe(2)O(3)–MnFe(2)O(4) −11.73 × 10(−31) kg). Such a system could open up a new idea in the design of photovoltage response biosensors.