Eucalyptus extracts-mediated synthesis of metallic and metal oxide nanoparticles: current status and perspectives

In recent decades, nanotechnology has received great attention due to its broad fields of application. The conventional processes applied to the synthesis processes of nanomaterials can be classified in chemical and physical methods. These technologies involve several environmental and cost problems. In order to avoid the problems caused by conventional methods, the use of biological systems such as bacteria, fungi, yeasts, and algae in the synthesis of nanomaterials has recently received extensive attention. To the same purpose, the routes of synthesis of metallic and metal oxides nanoparticles using plant extracts show promising perspectives. The methods involving plant extracts, unlike other biological methods, stand out for their ease and low implementation costs. In addition, the use of plant extracts avoids the risks associated with the use of highly toxic compounds, which are harmful to human health and the environment. This review summarizes the relevance of using plant extracts in the synthesis of metal and metal oxides nanoparticles compared to other synthesis methods and emphasizes the use of extracts of different species of Eucalyptus. The main topics covered by this review include (i) the effect of the synthesis parameters on the features of the nanomaterials; (ii) the effect of the composition of the extracts on the synthesis; (iii) the main mechanisms proposed to explain the formation of the nanoparticles; and (iv) future challenges related to the green synthesis of nanoparticles.