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Multifunctional BiFeO3 nanostructure anchored TiO2 nanotubes are fabricated by coupling wet chemical and electrochemical routes. BiFeO3/TiO2 nano-heterostructure exhibits white-light-induced ferroelectricity at room temperature. Studies reveal that the photogenerated electrons trapped at the domain/grain boundaries tune the ferroelectric polarization in BiFeO3 nanostructures. The photon controlled saturation and remnant polarization opens up the possibility to design ferroelectric devices based on BiFeO3. The nano-heterostructure also exhibits substantial photovoltaic effect and rectifying characteristics. Photovoltaic property is found to be correlated with the ferroelectric polarization. Furthermore, the nonvolatile resistive switching in BiFeO3/TiO2 nano-heterostructure has been studied, which demonstrates that the observed resistive switching is most likely caused by the electric-field-induced carrier injection/migration and trapping/detrapping process at the hetero-interfaces. Therefore, BiFeO3/TiO2 nano-heterostructure coupled with logic, photovoltaics and memory characteristics holds promises for long-term technological applications in nanoelectronics devices.

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Noble‐metal nanocatalysts are quite popular, but the use of magnetic catalysts composed of ferrite materials is rare. Here, we have synthesized transition‐metal‐based cube‐shaped nanoparticles of approximately 11 nm in size, the so‐called magnetic nickel ferrite nanocatalyst (NFNC), by a new method and shown its use in the reduction of nitroaromatic compounds. The NFNC was characterized by using XRD, energy‐dispersive X‐ray spectroscopy, TEM, and field‐emission SEM to confirm the structural features and morphology of the particles. The catalytic activity of NFNC was investigated in the reduction of 4‐nitrophenol to 4‐aminophenol by monitoring the reaction by using UV/Vis spectroscopy. The catalytic activity, recyclability and reusability, rate constant of the reaction, and surface area were investigated in detail to understand the catalytic phenomenon. We measured up to 30 cycles of the catalytic reaction using our NFNC, which shows the high stability of the catalyst. BET analysis of the NFNC shows a surface area of 54.60 m2 g−1. Our NFNC has many advantages because it is prepared easily, cost effective, highly stable, and environmentally compatible. The magnetic properties of the NFNC help us to separate the particles easily after its use in the reduction without disturbing the final product.

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We have prepared CoFe2O4 nanoparticles in micellar medium by wet chemical technique and obtained very high coercivity value of 4.4 kOe at room temperature for particle size ∼16 nm. A large coercivity (∼20 kOe) is observed on cooling down to 2.5 K. We annealed the sample at different temperatures to check the role of micelles and particles size in the change in coercivity value. Here we observed micelles as capping agent playing an important role to enhance the coercivity, as after removal of micelles for the same particle size the coercivity drops from 4.4 kOe to small value ∼350 Oe. But the coercivity again increases due to the increase in particle size with increase in annealing temperature from 873 K and above. To obtain structural information and size of particles, we have taken x-ray diffraction spectra from the samples before and after annealing at different temperatures which confirm the spinel phase only.