Advanced Approaches For Producing Nanocrystalline and Fine-Grained ZrO2-Based Powders (Review) IV. Biological Methods (Green Synthesis)

Biological methods (green synthesis) involving natural sources (bacteria, fungi, algae, plants, etc.) were developed in the 21st century in South and East Asia, South America, and Middle East countries. The mechanism of ZrO₂ nanoparticle formation using microbial systems (bacteria and fungi) includes biosorption and bioreduction. Rounded and rod-shaped primary particles, comprising a mixture of m-ZrO₂ and t-ZrO₂ phases, were synthesized. These powders exhibit effective antimicrobial and antibiofilm activity and are promising for the delivery of pH-sensitive drugs and the development of biosensors. The use of various plant extracts in thermal decomposition, coprecipitation, sol–gel processes, solution combustion, and hydrothermal synthesis was explored. The growth of ZrO₂ nanoparticles during green synthesis proceeds through three stages: activation, growth, and termination. The resulting ZrO₂ powders hold promise for applications in novel antimicrobial agents, anticancer drugs, photocatalysts for wastewater treatment, fillers in polymer nanocomposites, and nanoadditives to enhance the efficiency of diesel engines. Composite powders such as ZrO₂/RGO with improved anticancer properties, ZrO₂/PdO and ZrO₂ : Sm³⁺ (11 mol.%) for photocatalysts, and ZrO₂ : Mg (0.1–5 mol.%) for nanophosphors in display devices were developed. The choice of the synthesis route for the starting powders is based on the intended application of the final material. The synergistic effect of physicochemical and biological approaches in green synthesis expands the potential for microstructural design of functional ZrO₂-based materials for diverse applications.