A simple surfactant assisted solution-phase approach is demonstrated here for the preparation of lithium niobate (LiNbO3) nanoparticles with an average size of 30 nm. This solution-phase process results in the formation of crystalline, uniform nanoparticles of LiNbO3 at 220 o C with an optimal reaction time of 36 h. Advantages of this method also include the preparation of crystalline nanoparticles of LiNbO3 without the need for further heat treatment or the use of an inert atmosphere. The growth of these nanoparticles began with a controlled agglomeration of nuclei. The reaction subsequently underwent a process of oriented attachment and Ostwald ripening, which dominated and controlled the further growth of the nanoparticles. These processes produced single-crystalline nanoparticles of LiNbO3. The average dimensions of the nanoparticles were tuned from 30 to 95 nm by increasing the reaction time of the solvothermal process. The LiNbO3 nanoparticles were characterized using transmission electron microscopy (TEM), selected area electron diffraction (SAED), high resolution TEM, X-ray diffraction, and Raman spectroscopy techniques. The nanoparticles were also confirmed to be optically active for second harmonic generation (SHG). These particles could enable further development of SHG based microscopy techniques.

Sub-10 nm single-crystalline LiNbO3, nanocrystals that exhibit a tunable non-linear optical response were prepared by a one-pot solution-phase synthesis.

This paper describes a solution-phase hydrothermal synthesis of crystalline niobium pentoxide (Nb2O5) nanorods. The methods reported herein yield uniform Nb2O5 nanorods with average diameters of 6 nm and lengths of 38 nm, which are directly synthesized from niobic acid by a hydrothermal process. The formation of Nb2O5 nanorods from niobic acid was studied in the presence of surfactants that stabilize the nanostructures. The crystalline Nb2O5 nanorods were relatively uniform in size and shape. The size of the Nb2O5 nanorods could be tuned through the choice of surfactant even in the absence of a worm-like micellar morphology. Amine, amide, ammonium, carboxylate, sulfonate and sulfate containing surfactants were systematically evaluated for their influence on the ability to form uniform Nb2O5 nanorods. The surfactants in this study had hydrophobic tails that were either straight or branched, such as a polymer, and contained either a single or multiple head groups. The nanorods grew by a process of oriented attachment of nanoparticles that was regulated by the surfactants added into the reaction mixture. The results of these studies indicate that this synthetic approach serves as a tunable platform to prepare single crystalline niobium oxide based nanostructures with well-defined morphologies and dimensions. This surfactant assisted formation of crystalline Nb2O5 nanorods could also have important implications in the design of other transition metal oxide based nanomaterials.

Halide perovskite nanocrystals of cesium bismuth iodide (Cs3Bi2I9) were prepared by a facile sonication-assisted method using a green solvent. The photoluminescence properties were tuned by anion exchange with tetraalkylammonium halides.