In this report, hierarchical ZnO nano- and microstructures were directly grown for the first time on a bacterial cellulose substrate and on two additional different papers by hydrothermal synthesis without any surface modification layer. Compactness and smoothness of the substrates are two important parameters that allow the growth of oriented structures.

Flexible sensors have attracted significant attention due to their currently desirable properties and possibility to be applied to any surface and conditions such as wearable electronic devices. Therefore, we prepared volatile organic compound (VOC) sensors based on WO₃·0.33H₂O nano-needles and their composites with reduced graphene oxide (RGO) on flexible polyethylene terephthalate (PET) substrates. The materials were synthesized via a combination of the ultrasonic spray nozzle (USN) and microwave-assisted hydrothermal (MAH) methods to obtain a single WO₃·0.33H₂O orthorhombic crystalline phase. The VOC sensing properties of the materials deposited on PET electrodes were studied at room temperature (22 °C) and 55% relative humidity. The materials were exposed to acetone, ethanol, isopropanol, acetic acid, and methanol to determine their selectivity. The materials exhibited a good selectivity for isopropanol. The 5%RGO–WO₃·0.33H₂O composite presented a superior isopropanol-sensing performance, with a response of 4.96 to 100 ppm, which was ∼1.6 times higher than that of the pure WO₃·0.33H₂O nano-needles. The materials behaved as p-type semiconductors due to an inversion of the sensitive layer promoted by the adsorption of water molecules on the surface of the material.

The structural and dielectric properties of both pure and ${\mathrm{Nd}}^{3+}$ -doped ${\mathrm{Ba}}_{0.77}{\mathrm{Ca}}_{0.23}{\mathrm{TiO}}_3$ (BCT23) ceramics obtained from solid-state reaction were investigated. The BCT23 ceramics sintered at 1300 °C for 3 h showed a dense microstructure without the presence of secondary phases. The use of ${\mathrm{Nd}}^{3+}$ as a dopant affected the microstructure of these ceramics. Samples prepared with ${\mathrm{Nd}}^{3+}$ exhibit a more homogeneous microstructure without a liquid phase on the grain boundaries. The dielectric constant and Raman scattering measurements indicate that the Curie temperature of the ferroelectric phase transition depends on ${\mathrm{Nd}}^{3+}$ content. It shifts toward lower temperatures with ${\mathrm{Nd}}^{3+}$ addition.