Ferroelectric nanowires have attracted great attention due to their excellent physical properties. We report the domain structure, ferroelectric, piezoelectric, and conductive properties of bismuth ferrite (BFO, short for BiFeO₃) nanowires characterized by scanning probe microscopy (SPM). The X-ray diffraction (XRD) pattern presents single phase BFO without other obvious impurities. The piezoresponse force microscopy (PFM) results indicate that the nanowires possess a multidomain configuration, and the maximum piezoelectric coefficient (d₃₃) of single BFO nanowire is 22.21 pm/V. Poling experiments and local switching spectroscopy piezoresponse force microscopy (SS-PFM) demonstrate that there is sufficient polarization switching behavior and obvious piezoelectric properties in BFO nanowires. The conducting atomic force microscopy (C-AFM) results show that the current is just hundreds of pA at 8 V. These lay the foundation for the application of BFO nanowires in nanodevices.

Suppressing charge recombination and improving carrier transport are key challenges for the enhancement of photocatalytic activity of heterostructured photocatalysts. Here, we report a ferroelectric polarization-enhanced photocatalysis on the basis of BaTiO₃-TiO₂ core-shell heterostructures synthesized via a hydrothermal process. With an optimal weight ratio of BaTiO₃ to TiO₂, the heterostructures exhibited the maximum photocatalytic performance of 1.8 times higher than pure TiO₂ nanoparticles_. The enhanced photocatalytic activity is attributed to the promotion of charge separation and transport based on the internal electric field originating from the spontaneous polarization of ferroelectric BaTiO_3. High stability of polarization-enhanced photocatalysis is also confirmed from the BaTiO₃-TiO₂ core-shell heterostructures. This study provides evidence that ferroelectric polarization holds great promise for improving the performance of heterostructured photocatalysts.

Ferroelectric functionalized dye-sensitized solar cells were fabricated by using a positively-poled LiNbO₃ substrate coated with ITO (ITO-LiNbO₃) as a collector electrode and demonstrated enhanced power conversion efficiency. Surface potential properties of TiO₂ nanoparticle film coated on the ITO-LiNbO₃ (TiO₂/ITO-LiNbO₃) examined by Kelvin probe force microscopy (KPFM) confirmed that a large electric field (a few 10 V/µm) generated from LiNbO₃ can penetrate through the ITO layer and is applied to TiO₂ film. This polarization-induced electric field leads to an increased photocurrent density by attracting and promoting electrons to direct transport through the mesoporous TiO₂ network toward the collector electrode and a decreased charge recombination by facilitating electrons to pass through fewer boundaries of nanoparticles, resulting in high power conversion efficiency. The power conversion efficiency was enhanced by more than 40% in comparison with that without polarization-induced electric field. Incorporating functional ferroelectrics into photovoltaic cells would be a good strategy in improving photovoltaic performance and is applicable to other types of photovoltaic devices, such as perovskite solar cells.

Assemble metal nanoparticles into various ordered structures with scale up to centimeter area is required to meet diverse needs of lab-on-a-chips and analytic components. Here, we present the uniform and high-yield fabrication of centimeter-scale gold nanoparticles (AuNPs) array for SERS substrates. Ferroelectric-assisted assembly of AuNPs line array is successfully fabricated by using a periodically poled LiNbO₃ (PPLN) single crystal as a template. SNOM-Raman shows that the uniform assembly of AuNPs exhibits a high density of “hot spots” arising from strong electromagnetic (EM) field coupling induced by adjacent AuNPs. Quantitative analysis based on SERS detection describes an excellent reproducibility with an intensity variation less than 7% at 1649 cm⁻¹ of Rhodamine 6G. SERS spectra combined with 3D-FDTD modelling indicate that the EM enhancement occurs at all three excitation wavelength of 515, 561 and 633 nm and the 561-nm-laser displays the strongest Raman enhancement with an enhancement factor in an order of 10⁹. The corresponding experimental and theoretical results present a new strategy to fabricate large-area, highly reproducible and sensitive SERS substrates for practical applications.