Various types of metal oxide nanocomposites are being explored by researchers across the globe for their biological and catalytical applications. Usually, ZnO is used as a precursor and mixed with different types of plant extracts to prepare bio-composite nanoparticles using the precipitation method. Other techniques, such as the sol-gel method, microwave assisted extraction, or vacuum assembly have been reported to enhance yield and reduce the time required to prepare these bio-nanocomposites. The metal oxides have been reported as having catalytic, adsorbent, and luminescent properties as well as acting as biologically active compounds. Their combination with other materials has been explored to enhance catalytic, adsorptive, and biological properties as well as suppressing any toxic effects.

A number of issues face researchers in this field, such as finding compatible materials and their specific ratios to achieve the desired properties and to correctly impart these properties to the nanoparticles. For this purpose, different polymers have been investigated in combination with metal oxides to enhance their catalytic and adsorptive properties. For example, different types of plant extract-based metal oxide composites have been reported to have enhanced cytotoxic capabilities, enabling their use in drug delivery systems and other biological applications. The use of green methodologies to ensure proper characterization and high yield in a cost-effective manner is currently the subject of much research.

The aim of this Special Issue is to gather new research regarding the synthesis of metal oxide-based biomaterials, specifically nanoparticles, using plant extracts, agro-waste, metal oxides, or polymers from native sources, as well as their physio-chemical characterization and studies on their catalytical, biological, or electrochemical applications. We welcome both original research and review articles.

Potential topics include but are not limited to the following:

• Synthesis of novel metal oxide nano-biomaterials by different means, including the sol-gel method or microwave aided assembly
• Synthetic polymer-based metal oxide composites
• Metal oxide composites with different plant wastes in order to recycle agro-waste properly
• On-desk characterization using various physical, chemical, and spectroscopic methods
• Use of biomaterials for detoxification of dyes and other toxic substances from wastewater
• Electrochemical applications of metal oxide composites as super magnetic materials, high temperature conductors, insulators, or catalysts