Recent development in nanoscience and nanotechnology has contributed to the wide applications of metal and metal oxides nanoparticles in several field of sciences, research institutes and industries. Among all metal oxides, copper oxide nanoparticles (CuONPs) has gained more attention due to its distinctive properties and applications. The high cost of reagents, equipment and environmental hazards associated with the physical and chemical methods of synthesizing CuONPs has been a major setback. In order to puffer solution to the aforementioned challenges by reducing environmental pollution and production of cheaper nanoparticles with good properties and efficiency, this review focus on collection of comprehensive information from recent developments in the synthesis, characterization and applications from previous scientific findings on biological method of synthesizing CuONPs due to the acclaimed advantages of been cheap, environmentally friendly, convenient and possibility of been scale up in into large scale production reported by numerous researchers. Our finding also support the synthesis of CuONPs from plant sources due to relative abundance of plants for the production of reducing and stabilizing agents required for CuONPs synthesis, potential efficiency of plant biomolecules in enhancing the toxicity effect of CuONPs against microbes, prevention of environmental pollution due of nontoxic chemicals and degradation effectiveness of CuONPs synthesized from plant sources. Furthermore, this study provide useful information on the rapid synthesis of CuONPs with desired properties from plant extracts.

The need to divulge the rapid synthesis, non-hazardous, cost effectiveness and eco-friendly methods for the synthesis of nanoparticles utilizing plants is of great importance. This is as a result of high toxicity associated with the chemical method of synthesizing nanoparticles. The aim of this study was to investigate the potency of the synthesized gold nanoparticle against selected human pathogens. Gold nanoparticles were synthesized by reacting 1 mM gold chloride solution with leaf extract of Annona muricata. The synthesized gold nanoparticles were characterized with UV–visible spectrophotometer, transmission electron microscope (TEM) and Fourier transformed infrared spectroscopy (FTIR). The antibacterial and antifungal activities of the synthesized gold nanoparticles were also investigated. The morphology, size, and structural properties of synthesized gold nanoparticles were determined with TEM analysis which showed spherical mono-dispersed structure with an average particle size of 25.5 nm. FTIR analysis reveal band at 3271.14, 2111.91 and 1637.82 cm⁻¹ corresponding to –N–H, –C=C, and –C–N functional groups that are responsible for the capping and stabilization of synthesized gold nanoparticles. The effectiveness of the gold nanoparticle against the test pathogens increases as the concentration of gold nanoparticle increases. The percentage of zones of inhibition of synthesized gold nanoparticle against test fungi and bacteria ranges from 30 to 66% and 40 to 54%, respectively. The potency of the synthesized gold nanoparticle against the selected fungi and bacteria increases with increase in concentration of gold nanoparticle. Therefore, the antibacterial and antifungal investigation revealed that the synthesized gold nanoparticles exhibited good antimicrobial activity.

Developments in nanotechnology and natural product research toward the search for novel antibacterial agents have drawn the interest of many scientists to the synthesis of silver nanoparticles (AgNPs) from natural product (especially plants) due to its numerous benefits over other methods of synthesis such as been easy, economical, convenient, and environmental friendly. Aside from the aforementioned advantages, the synthesis of AgNPs from medicinal plant has been reported as the best approach of synthesizing AgNPs with great biological activities due to the numerous biomolecules found in plants. Recently, the number of researches toward the improvement of the yield, morphological properties, analytical techniques, and the development of optimal conditions and exact mechanism for synthesizing AgNPs from plants have been increasing tremendously. In this review, we present a comprehensive report on the recent development in the synthesis, optimization conditions, mechanism, and characterization techniques of AgNPs synthesized from plant extracts. Furthermore, a thorough discussion on the recent advances in the application of AgNPs synthesized from plant as therapeutic agent against bacterial infections was made.