Smart nanocomposites of chitosan/alginate nanoparticles loaded with copper oxide as alternative nanofertilizers

In order to best nutrient use efficiency, as required by the increasing food demand for the future global population, in this work an innovative hybrid nanocomposite was designed as an alternative nanoscale fertilizer. An environmentally friendly chemical preparation based on polyelectrolyte complexation was used. A chitosan and sodium alginate complex was selected as a biodegradable shell to release the nanoscale nutrient, CuO nanoparticles. By optimizing the synthesis conditions, i.e. pH and polymer/cross-linker ratio, good stability and accurate size control of the resulting nanocomposites were achieved. The morphology features were evaluated using scanning and transmission electron microscopy, and chemical characterization was performed using X-ray diffraction, thermogravimetric analysis, Fourier-transform infrared spectroscopy, dynamic light scattering and inductively coupled plasma optical emission spectrometry. All the collected data confirmed spontaneous polymeric aggregation in nanostructures of sperical shape, having a mean diameter of about 300 nm, as well as CuO encapsulation inside the polymeric coating. Moreover, the role of the biopolymer shell in the significant slowing of copper release from the hybrid nanocomposite was reported. Finally, the nanocomposite efficacy in seeding and germination was evaluated on Fortunella margarita Swingle seeds. The tests demonstrated the benefits in the seedling growth together with a synergic effect in developing both the epigean and hypogean parts. The obtained results indicated that the proposed hybrid nanocomposite could be a potential alternative to realize a smart delivery nanofertilizer using an eco-sustainable method. A chitosan and sodium alginate complex acts as a biodegradable shell to release nanoscaled nutrients, CuO nanoparticles, as an alternative smart delivery nanofertilizer.