Barium nitrate ba no3 2

Arrays of BaTiO₃ VANTs were synthesized on anodic aluminium oxide (AAO) templates [18] (link). AAO templates are commercially available filtration membranes (Whatman, Anodisc, diameter 47 mm or 13 mm, thickness 60 µm; pore diameter 200 nm).
Briefly, ammonium hexafluorotitanate ((NH₄)₂TiF₆ 10 mM, Sigma-Aldrich Co) and barium nitrate (Ba(NO₃)₂ 10 mM, Sigma-Aldrich Co) were dissolved in aqueous solution of boric acid (30 mM, Sigma-Aldrich Co) at room temperature. The pH was adjusted to 2.0 by adding 6 M HCl drop wise. The AAO membranes were vertically immersed in the precursor solution and held at 60°C in a bath for 20 h. The membranes were then removed from the solution and rinsed with deionized water for 5 min (2 times) and with phosphate buffered solution (PBS) for 5 min (2 times). As control group, a non nano-structured (NNS) layer of BaTiO₃ was deposited by using as template material a round glass coverslip (diameter 13 mm), processed as described for AAO membranes.
The AAO membrane naked and filled with the BaTiO₃ nanotubes and the glass coverslip coated with BaTiO₃ will be hereafter labelled as AAO, AAO-NT and NNS, respectively.

To synthesize BSTO NPs, barium nitrate (Ba(NO₃)₂, 99.999% trace metals basis, Sigma-Aldrich, USA), strontium nitrate (Sr(NO₃)₂, 99.995% trace metals basis, Sigma-Aldrich, USA), and titanium (IV) butoxide (Ti(OCH₂CH₂CH₂CH₃)₄, reagent grade, 97%, Sigma-Aldrich, USA) were used as the starting materials; n-butanol (99.5%, Duksan, South Korea) and deionized water were used as the solvents; and sodium hydroxide (NaOH, reagent grade, ≥98%, pellets (anhydrous), Sigma-Aldrich, USA) was used as the reactive agent. A modified LSS process with control of the Ba-Sr composition was used (see Supporting Information). The crystalline phase of the BSTO NPs were determined by X-ray diffraction (XRD, Ultima, Rigaku, Japan) analysis using Cu-Kα radiation with a wavelength of 1.5418 Å at 2θ = 20°–80°. A particle size analyzer (PSA, Nanotrac Wave, Microtrac, USA) and a scanning electron microscopy (SEM) apparatus (AIS-2000C, SERON, South Korea) were used to observe the morphology and size distribution of the NPs. Fourier-transform infrared spectroscopy (FT-IR, Perkin Elmer, USA) was employed to confirm the ligands of the BSTO NPs. A current–voltage (C–V) meter (B1500A, Agilent, USA) was used to determine the dielectric properties of the NPs, such as the dielectric constant and loss tangent.