Synthesis of a Lignin/Zinc Oxide Hybrid Nanoparticles System and Its Application by Nano-Priming in Maize

Abstract

Nanotechnologies are attracting attention in various scientific fields for their technological and application potential, including their use as bio-activators and nanocarriers in agriculture. This work aimed to synthesize a hybrid material (ZnO@LNP) consisting of lignin nanoparticles containing zinc oxide (4 wt %). The synthesized ZnO hybrid material showed catalytic effect toward thermal degradation, as evidenced by the TGA investigation, while both spectroscopic and contact angle measurements confirmed a modification of surface hydrophilicity for the lignin nanoparticles due to the presence of hydrophobic zinc oxide. In addition, the antioxidant activity of the ZnO@LNP and the zinc release of this material were evaluated. At the application level, this study proposes for the first time the use of such a hybrid system to prime maize seeds by exploiting the release characteristics of this material. Concerning the dosage applied, ZnO@LNP promoted inductive effects on the early stages of seed development and plant growth and biomass development of young seedlings. In particular, the ZnO@LNP stimulated, in the primed seeds, a higher content of chlorophyll, carotenoids, anthocyanins, total phenols, and a better antioxidant activity, as supported by the lower levels of lipid peroxidation found when compared to the control samples.

Keywords: antioxidant activity; hybrid materials; lignin nanoparticles; nanotechnology; plant growth; seed-priming; zinc oxide.

Figure 1

TG/DTG curves of LNP and ZnO@LNP in air (a), FTIR spectra of LNP, ZnO, and ZnO@LNP (b), water contact angle images for LNP and ZnO@LNP (c,d).

Figure 2

FESEM (a) and TEM (b) images of LNP, ZnO, and ZnO@LNP (the inset images show the color change due to the formation of lignin-derived ZnO), UV spectra (c) and RSA results for LNP and ZnO@LNP.

Figure 3

SEM image of the area analyzed by EDX (a), elemental mapping of Zn (b), EDX spectrum (c), and XRD (d) of ZnO@LNP.

Figure 4

In vitro release profile of Zn⁺² by ZnO@LNP.

Figure 5

Effect of the treatments with ZnO@LNP on the shoot and root length and fresh weight compared to the untreated controls (T1, T2, T3, T4, and T5 refer to the ZnO@LNP concentration used for seed nano-priming). Letters in the figure, if different, indicate statistically significant differences for p < 0.05 between treatments.