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

High-fluorescent p-X-ferrites (XFe2O4; XFO; X = Fe, Cr, Mn, Co, or Ni) embedded in n-hematite (Fe2O3) 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 XFe2O4 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 (Fe2O3)-O-O-(XFe2O4) interfacial coupling behaviors at two fluorescence emission peaks (785/795 nm) are explained via calculating electron-hole effective masses (Fe2O3-FeFe2O4 17.23 × 10(-31) kg; Fe2O3-CoFe2O4 3.93 × 10(-31) kg; Fe2O3-NiFe2O4 11.59 × 10(-31) kg; Fe2O3-CrFe2O4 -4.2 × 10(-31) kg; Fe2O3-MnFe2O4 -11.73 × 10(-31) kg). Such a system could open up a new idea in the design of photovoltage response biosensors.