Synthesis of novel PVA–starch formulation-supported Cu–Zn nanoparticle carrying carbon nanofibers as a nanofertilizer: controlled release of micronutrients

Recent applications of nanotechnology in agriculture have successfully demonstrated the utility of nanomaterials as a potential plant-growth regulator. Practical application of nanomaterial-based fertilizers in agricultural lands requires a suitable substrate to effectively disperse the nanomaterials. In this study, a polymeric formulation of PVA–starch was synthesized as a substrate for the slow release of the Cu–Zn micronutrient carrying carbon nanofibers (CNFs). The Cu–Zn/CNFs were in situ dispersed in the PVA–starch blend during a polymerization step. The effectiveness of the prepared nanofertilizer was demonstrated using chickpea as a model plant and different doses, viz. 0.25, 0.50, 1.0, 2.0 and 4.0 g of PBMC per kg of soil (garden) up to 30 days. The dissolution of PBMC increased with increasing amounts of starch in the PBMC matrix, indicating the biodegradability of PVA in the blend. Scanning electron microscopy and elemental analysis confirmed the translocation of the Cu–Zn/CNFs from roots to shoots of the plant. The PBMC(1-1)-grown plants were measured to be the tallest (~ 33 cm), whereas the control plants reached a length of ~ 18 cm only, indicating the effectiveness of the prepared micronutrient in sustaining the plant growth. The superoxide anion radicals and hydrogen peroxide in the control plants were measured to be 207 ± 3.15 and 272 ± 5.74 nmol/g of the plant, whereas PBMC(1-1)-grown plants contained 129 ± 3.25 and 194 ± 6.47 nmol/g of the reactive oxygen species, respectively, indicating that the Zn nanoparticles were effective in scavenging the reactive species. The metal release profiles of PBMC indicated the Cu and Zn concentrations to be 5.3 ± 0.05 and 2.8 ± 0.1 mg/g-CNF, respectively, which were significantly lower from Cu–Zn/CNF, attributed to the slow release of the metals from the prepared polymeric formulation. The proposed integration of the biodegradable polymeric formulation with the micronutrient carrying CNFs opens a new perspective on the application of nanotechnology in agricultural practices.