Factorial Experimental Design for Optimization of Zinc Oxide Nanoparticles Production

Background: Biosynthetic nanomaterials have recently received increasing attention because they are non-toxic, clean, environmentally acceptable, safe, and biocompatible. Objective: In the present study, cell-free culture filtrate of Aspergillus sp. was used for extracellular synthesis of zinc oxide (ZnO) nanoparticles. Method: Plackett-Burman and Taguchi designs were implemented to optimize conditions for maximum ZnO nanoparticle production. In the Plackett-Burman design, 15 factors, representing different carbon and nitrogen sources, were studied. For the Taguchi design, an L-27 (313) standard orthogonal array was constructed to examine nine factors. Results: The maximum yield of ZnO nanoparticles of 21.73 g/L was achieved with 1.0 mM ZnSO4 under optimal conditions of peptone extract (20 g/L), yeast extract (10 g/L), meat extract (10 g/L), K2HPO4 (0.25 g/L), FeSO4⋅7H2O (0.002 g/L), NaCl (2.5 g/L), pH 6, 32°C, and a 200-mL volume. The ZnO nanoparticles’ production was confirmed by the formation of white aggregates. The UV absorption spectrum showed one peak at 376 nm, which also confirmed the formation of nanoparticles. Transmission electron microscopy revealed that the nanoparticles were large rods of 11.6-43.97 nm diameter, and 355.91 nm length. Importantly, the ZnO nanoparticles exhibited broad antimicrobial activity against gram-positive and gram-negative bacteria and a unicellular fungus. Conclusion: The concentrations of ZnSO4 ions, ferrous ions, and peptone and meat extracts, and the interactions between them, were observed to be the main parameters influencing ZnO nanoparticles’ yield.

Finding the Additives Incorporation Moment in Hybrid Natural Pigments Synthesis to Improve Bioresin Properties

Interest in applications of natural dye applications has increased because of their antibacterial properties and the possibility of extracting them from nature and residues. Using nanoclays as hosts to reinforce natural dye properties has been successfully demonstrated. However, no one has attempted to optimize the polymer matrix and hybrid pigment properties at the same time to ensure the best final properties for bio-composite applications. Using a statistical design for experiments, we propose the best combination of modifiers with the best nanoclay as the host of three natural dyes: chlorophyll, β-carotene, and betanine. Using the L9 Taguchi designs, we learned both the influence of the nanoclay structure, and the addition moment of surfactant, mordant salt, and silane modifiers. FTIR, XRD, DTG, integration sphere spectrophotometer, and UV-aging tests were used to characterize the hybrid pigments and epoxy bioresin composites. The degradation temperatures of the three natural dyes rose and the reinforcement of the stability of three natural dyes to UV–Vis radiation exposure was demonstrated, which avoided the migration of these dyes from bioresin to wet ribbing. Optimal results were obtained with hydrotalcite clay (calcined or not) by using surfactant and mordant before the natural dye, and before or after silane.