Synthesis of Single-Crystalline Niobate Nanorods via Ion-Exchange Based on Molten-Salt Reaction

NaNbO3 Nanorods: Photopiezocatalysts for Elevated Bacterial Disinfection and Wastewater Treatment

In the present work, ferroelectric sodium niobate (NaNbO₃) nanorods are formulated to attain photopiezocatalysis for water pollutant degradation and bacterial disinfection. NaNbO₃ nanorods, integrating the advantages of photocatalysis (generation of free charge carriers) and piezocatalysis (separation of these charge carriers), possess synergistic effects, which results in a higher catalytic activity than photocatalysis and piezocatalysis alone. Active species that are involved in the catalytic process are found to be ^•O₂ ^- < OH^• < h⁺, indicating the significance of piezocatalysis and photocatalysis. The degradation efficiency of sodium niobate (NaNbO₃) nanorods for Rhodamine B in the presence of both sunlight and ultrasonic vibration is 98.9% within 60 min (k = 7.6 × 10^-2 min^-1). The piezo potential generated by NaNbO₃ nanorods was reported to be 16 V. The antibacterial activity of the produced sample was found to be effective against Escherichia coli. With inhibitory zones of 23 mm, sodium niobate has a greater antibacterial activity.

Molten salt assisted assembly growth of atomically thin boron carbon nitride nanosheets for photocatalytic H2 evolution

Atomically thin boron carbon nitride nanosheets (BCNNS) with high quality and large lateral size are synthesized via a novel molten salt assisted assembly growth strategy. The BCNNS show enhanced photocatalytic H₂ evolution activity in visible light.

Epitaxial growth and cationic exchange properties of layered KNb3O8 thin films

The KNb₃O₈ potassium triniobate phase is a layered compound that shows excellent photocatalytic activity, intercalation properties and electrochemical performances. K–Sn exchange of KNb₃O₈ films leads to decrease the optical gap towards visible range.

Ferroelectric KNbO3 nanofibers: synthesis, characterization and their application as a humidity nanosensor

By virtue of its non-toxicity, high T c, and non-linear optical and ferroelectric properties, one-dimensional (1D) potassium niobate (KNbO3) may enable the development of numerous nanoscale devices. Despite the progress in 1D perovskite materials, preparing high aspect ratio KNbO3 nanostructures is still a concern. This report presents the successful synthesis of ultra-long KNbO3 nanofibers using a simple sol-gel assisted far-field electrospinning process. At optimized conditions, centimeters long, orthorhombic KNbO3 nanofibers with an average diameter of 100 nm have been obtained. The nanofibers are composed of uniform grains densely stacked along the direction of the nanofiber axis. Due to large surface-volume ratio, a high sensitive humidity nanosensor based on KNbO3 nanofibers displaying a logarithmic-linear dependence behavior of the conductance with the relative humidity (RH) was demonstrated. The conductance increases dramatically from 10(-10) ℧ to 10(-6) ℧ while RH varies from 15% to 95% at room temperature. In addition, the nanosensor exhibits excellent sensing performance, including ultrafast response (≤2 s) and recovery times (≤10 s), good linearity and reproducibility. Furthermore, the change in ferroelectric coercivity with respect to the RH and its effect in the sensing behavior were unveiled. This work could enable broad applications in the fields of environmental sensing and nano-electrical-mechanical systems.

One-Dimensional Ferroelectric Nanostructures: Synthesis, Properties, and Applications

One-dimensional (1D) ferroelectric nanostructures, such as nanowires, nanorods, nanotubes, nanobelts, and nanofibers, have been studied with increasing intensity in recent years. Because of their excellent ferroelectric, ferroelastic, pyroelectric, piezoelectric, inverse piezoelectric, ferroelectric-photovoltaic (FE-PV), and other unique physical properties, 1D ferroelectric nanostructures have been widely used in energy-harvesting devices, nonvolatile random access memory applications, nanoelectromechanical systems, advanced sensors, FE-PV devices, and photocatalysis mechanisms. This review summarizes the current state of 1D ferroelectric nanostructures and provides an overview of the synthesis methods, properties, and practical applications of 1D nanostructures. Finally, the prospects for future investigations are outlined.

A pseudo-tetragonal tungsten bronze superstructure: a combined solution of the crystal structure of K6.4(Nb,Ta)36.3O94 with advanced transmission electron microscopy and neutron diffraction

K_6.4Nb_28.2Ta_8.1O₉₄ has the same framework as literature's K₂Nb₈O₂₁ but a different distribution of cations over different channels.

Topochemical molten salt synthesis for functional perovskite compounds

A topochemical molten salt synthesis (TMSS) method, which is rapid and a modification of the molten salt synthesis method (MSS), to facilitate crystal growth with improved phase-purity and particle homogeneity, is one of the strategic approaches aimed at a controllable morphology synthesis. The TMSS method is an environmentally friendly and mild way to prepare pure and controllable perovskites, which are famous functional materials, used as piezoelectrics, catalysts, ferroelectrics, multiferroics, and negative thermal expansion compounds, at a moderate reaction temperature in a short soaking time. This report reviews various TMSS reactions and their applications in fulfilling the demand for the tunable morphology of perovskite materials, such as one dimensional, two dimensional and three dimensional perovskites in molten salts, which mainly include: piezoelectrics, photocatalysts, negative thermal expansion matters and other functional perovskites. The double and layered perovskites obtained by TMSS methods are also discussed. We believe that a comprehensive understanding of the TMSS method for functional perovskites will definitely promote the development of a clean, efficient and tunable production process for advanced functional materials.

BaTiO3 supercages: unusual oriented nanoparticle aggregation and continuous ordering transition in morphology

Here we report the organic-free mesocrystalline superstructured cages of BaTiO3, i.e., the BaTiO3 supercages, which are synthesized by a one-step templateless and additive-free route using molten hydrated salt as the reaction medium. An unusual three-dimensional oriented aggregation of primary BaTiO3 nanoparticles in the medium of high ionic strength, which normally favors random aggregation, is identified to take place at the early stage of the synthesis. The spherical BaTiO3 aggregates further experience a remarkable continuous ordering transition in morphology, consisting of nanoparticle faceting and nanosheet formation steps. This ordering transition in conjunction with Ostwald ripening-induced solid evacuation leads to the formation of unique supercage structure of BaTiO3. Benefiting from their structure, the BaTiO3 supercages exhibit improved microwave absorption property.

Characterization and humidity properties of MgAl2O4 powders synthesized in a mixed salt composed of KOH and KCl

In this paper, we have tried to prepare MgAl₂O₄ spinel by molten salt synthesis using hydroxide as solvent.

The effects of precursors on the morphology and microstructure of potassium sodium niobate nanorods synthesized by molten salt synthesis

The effects of Nb₂O₅ and K₂Nb₄O₁₁ precursors on the morphology, composition, and piezoelectric properties of potassium sodium niobate (KNN) nanorods were investigated.

Rod-like NaNbO3: mechanisms for stable solvothermal synthesis, temperature-mediated phase transitions and morphological evolution

Solvothermal synthesis is developed for rod-like NaNbO₃, and mechanisms for stable synthesis as well as structural and morphological transitions are proposed.

Synthesis and nonlinear optical properties of single-crystalline KNb3O8 nanowires

Single-crystalline KNb(3)O(8) nanowires with widths of 100-300 nm and lengths up to tens of microns were synthesized by calcining Nb(2)O(5) powders in molten KCl and K(2)SO(4). The phase of the products was determined by means of x-ray diffraction, and the morphology and structure were characterized by using scanning electron microscopy, transmission electron microscopy, high resolution transmission electron microscopy and selected area electron diffraction techniques. The growth direction of the KNb(3)O(8) obtained was determined to be the [001] crystallographic direction. Meanwhile, the polarization response of the second-harmonic generation (SHG) response was investigated. The as-synthesized nanowires clearly exhibited a SHG response, which means that the nanowires were an efficient nanoscale second-harmonic light source. The excellent nonlinear optical property of KNb(3)O(8) shows potential for application in nano-optical devices.

One-dimensional nanostructures of ferroelectric perovskites

Nanorods, nanowires, and nanotubes of ferroelectric perovskites have recently been studied with increasing intensity due to their potential use in non-volatile ferroelectric random access memory, nano-electromechanical systems, energy-harvesting devices, advanced sensors, and in photocatalysis. This Review summarizes the current status of these 1D nanostructures and gives a critical overview of synthesis routes with emphasis on chemical methods. The ferroelectric and piezoelectric properties of the 1D nanostructures are discussed and possible applications are highlighted. Finally, prospects for future research within this field are outlined.

Facile synthesis of magnetic metal (Mn, Fe, Co, and Ni) oxides nanocrystals via a cation-exchange reaction

Magnetic metal (Mn, Fe, Co, and Ni) oxides nanocrystals with small size and uniform size distribution are synthesized via a cation-exchange reaction. Two experimental stages are included in the synthesis of metal oxides nanocrystals. Firstly, Cu(OH)2 decomposes to CuO nanocrystals, induced by free metal cations. Compared to CuO nanocrystals produced without any free metal cation, the free metal cation has an important influence on the shape and size of CuO. Secondly, free metal cations exchange with the Cu2+ cation in the CuO nanocrystals to get Mn3O4, Fe2O3, CoO and NiO nanocrystals by cation-exchange reactions. The magnetic properties of these metal oxides nanocrystals have been investigated, all the nanocrystals are superparamagnetic at room temperature.