Herein, flexible piezoelectric nanogenerators were fabricated based on polymer composites containing synthesized lead-free piezoceramics Ba 0.85 Ca 0.15 Zr 0.10 Ti 0.90 O 3 (BCZT) and zincdoped BCZT (Zn-BCZT). Polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP)-based composites were prepared through the solution casting method. The morphology and microstructure were investigated using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The distributions of crystallinity and β-phase fractions were also studied. Impedance measurements illustrate the accumulation of space charge in the high-frequency range and the existence of a non-Debye relaxation. The results show that a 10 wt % Zn-BCZT/PVDF-HFP nanogenerator can generate a maximum peak-to-peak output voltage of 3.3 V and a power of 2.13 μW for a load resistance of 1 MΩ under mechanical shaking. This nanogenerator can successfully harvest a good output voltage of up to 8 V under daily life movements such as walking. This study demonstrates the importance of doping zinc within BCZT to boost the piezoelectric performance as it contributes to minimize the crystallite particle size and enhance the crystal β-phase transformation of the polymer matrix. Hence, the 10 wt % Zn-BCZT/PVDF-HFP nanogenerator has great potential for use in wearable technologies. Furthermore, the nanogenerator demonstrates good stability over 1800 cycles of repetitive load and good reliability even after 1 year. These results indicate the robustness of the developed nanogenerator in practical applications.
Laurel (Laurus nobilis L.) is a strict endemic species of natural vegetation of the Mediterranean region, which is known for its medicinal, aromatic, forestry, ornamental and culinary properties. This species produces valuable essential oil (EO). The content of EO and its composition depend on different factors, e.g., genetic, cultural practices and environmental conditions. Among these, salt stress is a major limiting factor, which affects almost all plant functions. Similar to essential oils (EOs), biotic and abiotic stresses may stimulate or inhibit the emission of volatile compounds (VCs) in plant materials, suggesting that these substances can be responsible on stress defense strategies. Therefore, an experiment was conducted to assess the effect of different NaCl concentrations (0, 50, 100 and 150 mM) of the irrigation water on VCs of laurel leaves. Our results showed that salt stress affected the volatile metabolites compounds, mainly the major ones. For instance, 1,8-cineole and linalool were negatively affected by high salinity levels, while the opposite was observed for α-terpenyl acetate and methyl eugenol. The proportion of grouped compounds of laurel VCs also differed among the studied treatments. The relative content of oxygenated monoterpenes and monoterpene hydrocarbons, respectively the first and the second largest groups, decreased with increasing NaCl concentration. Differently, the relative amount of sesquiterpene hydrocarbon group increased, especially at 100 mM NaCl. These findings indicate that the cultivation of laurel in marginal lands, characterized by high salinity or low-quality water, must be carefully evaluated because it significantly varies the quality of its products.
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