Photovoltage response of (XZn)Fe2O4-BiFeO3 (XÂ =Â Mg, Mn or Ni) interfaces for highly selective Cr3+, Cd2+, Co2+ and Pb2+ ions detection

High-photostability fluorescent (XZn)Fe2O4 (X = Mg, Mn or Ni) embedded in BiFeO3 spinel-perovskite nanocomposites were successfully fabricated via a novel bio-induced phase transfer method using shewanella oneidensis MR-1. These nanocomposites have the near-infrared fluorescence response (XZn or Fe)-O-O-(Bi) interfaces (785/832 nm), and the (XZn)Fe2O4/BiFeO3 lattices with high/low potentials (572.15-808.77 meV/206.43-548.1 meV). Our results suggest that heavy metal ion (Cr3+, Cd2+, Co2+ and Pb2+) d↓ orbitals hybridize with the paired-spin X-Zn-Fe d↓-d↓-d↑↓ orbitals to decrease the average polarization angles (−29.78 to 44.71°), qualitatively enhancing the photovoltage response selective potentials (39.57-487.84 meV). The fluorescent kinetic analysis shows that both first-order and second-order equilibrium adsorption isotherms are in line and meet the Langmuir and Freundlich modes. Highly selective fluorescence detection of Co2+, Cr3+ and Cd2+ can be achieved using Fe3O4-BiFeO3 (Langmuir mode), (MgZn)Fe2O4-BiFeO3 and (MnZn)Fe2O4-BiFeO3 (Freundlich mode), respectively. Where the corresponding max adsorption capacities (qmax) are 1.5-1.94, 35.65 and 43.7 multiple, respectively, being more competitive than that of other heavy metal ions. The present bio-synthesized method might be relevant for high-photostability fluorescent spinel-perovskite nanocomposites, for design of heavy metal ion sensors.