A BiFeO 3 /TiO 2 p-n heterojunction photocatalyst with ferroelectric synergistic effect under visible-light irradiation was developed through facile hydrolysis and precipitation by forming nanospheres of TiO 2 on BiFeO 3 nanocube to improve the photocatalytic efficiency. Analyses of the microstructure, optical properties , and photoelectrochemical performance indicate the formation of a core–shell heterostructure of BiFeO 3 /TiO 2 with excellent energy band matching. The BiFeO 3 /TiO 2 p-n heterojunction has enlarged specific surface area, higher sensitivity to visible-light, and improved separation and transfer efficiency of photoelectron-hole pairs than single TiO 2 and BiFeO 3 . Moreover, the composite exhibits superior photocatalytic degradation performance for methylene blue (MB) and common antibiotic tetracycline (TC) under UV and visible-light irradiation. The MB degradation rate within 180 min reaches 78.4% and 90.4% under UV and visible-light irradiation, respectively. Furthermore, the enhanced photocatalytic mechanism of BiFeO 3 /TiO 2 is explored by photoluminescence (PL), electrochemical impedance spectroscopy (EIS), transient photocurrent analysis, radical quenching, and band structure characterization.
Herein, a simple and effective visible-light driven photoelectrochemical (PEC) aptasensor was designed using BiFeO 3 @TiO 2 nanocomposites for accurate and rapid detection of microcystin-LR (MC-LR). This composite was obtained by coupling p-type BiFeO 3 nanoparticles with n-type TiO 2 nanosphere to constructed a p-n heterojunction. This p-n heterojunction not only could narrow the band-gap of TiO 2 from 3.14 eV down to 2.14 eV of BiFeO 3 @TiO 2 , resulting in superior utilization of visible light. More importantly, it also could accelerate charge separation/transfer leading to enhanced photoelectrochemical (PEC) performance of BiFeO 3 @TiO 2 . Based on these excellent optoelectronic performances of BiFeO 3 @TiO 2 composite, a PEC aptasensor with “turning on” signal mechanism was constructed by aminated aptamer as a biorecognition probe. The constructed PEC aptasensor performed gratifying analytical property toward MC-LR with a low detection limit of 0.016 pM (S/N = 3) and a wide detection range (5.0 × 10 −5 ∼ 2.5 × 10 2 nM). This PEC aptasensor possessed promising potential application value for its precise selective and ultrasensitive for MC-LR in practical analysis.
Polymer-based dielectric capacitors are well recognized for high energy density and efficiency. However, the energy density is restricted by the deterioration of breakdown strength with excessive addition of inorganic fillers. Herein, an innovative design of the lamellar-structured BiFeO 3 @TiO 2 (BFO@TO) fillers is proposed and a small amount of BFO@TO is added into P(VDF-HFP)/PMMA blended polymer to fabricate BFO@TO-P(VDF-HFP)/PMMA composites, which delivers an outstanding energy density of 19.3 J cm −3 at 549.2 kV mm −1 . The filler possesses a BFO/TO/BFO triple-layered structure. Due to the different Fermi level, electrons are injected from TO into BFO to form electron accumulation layer and construct the heterojunction electric fields between TO and BFO layers. Heterojunction electric fields at two interfaces produced by the triple-layered structure are opposite. The opposite double heterojunction can withstand larger external electric field and improve the breakdown strength. Besides, BFO, as a narrow bandgap semiconductor, is easier for electrons and holes to separate, which further widens the width of the built-in electric field and reduces the dielectric breakdown. Electric field distribution simulations intuitively confirm the enhancement of the breakdown strength. The results provide an effective strategy to address the critical issue of improving the breakdown strength for high energy storage capability.
Inorganic lead-free perovskite Cs 3 B i2 I 9 has attracted extensive attention due to its enhanced stability and environmental friendliness. However, the photon-to-current conversion of Cs 3 B i2 I 9 perovskites is not efficient, partly due to inefficient electron-hole separation. In this manuscript, BiFeO 3 was deposited at the interface of Cs 3 Bi 2 I 9 /TiO 2 as the interface modifier by sol–gel method, and the photocurrent and responsiveness of the Cs 3 B i2 I 9 /BiFeO 3 /TiO 2 were significantly higher than those of the Cs 3 B i2 I 9 /TiO 2 based device. Kelvin probe force microscope, photoelectrochemical impedance spectroscopy and in-situ surface photovoltage spectra demonstrated that a self-polarized electric field of BiFeO 3 contributed to the separation of photogenerated charge carriers at the Cs 3 B i2 I 9 /TiO 2 interface. By analyzing the surface photovoltage phase spectra via a vector model method, complicated surface photovoltage processes were identified, and a detailed relationship between photocurrent generation and transfer characteristic of the photogenerated charge carriers have been discussed.
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