Table 1.

Synthesis of IONPs via (a) precipitation, (b) hydrothermal, (c) microemulsion, and (d) sol–gel methods

Chemical synthesis method	Characteristics of the synthesis	Size distribution	Shape	Ref.
Precipitation	Simple method, fast reaction, high yield Possible risks to the environment and living organisms	Reduced control	Irregular shape	[17, 43, 46, 72, 75]
Hydrothermal	Elevated temperatures in an inert atmosphere High degree of crystallinity Long reaction time	Uncoated nanoparticles; tendency toward agglomeration	Spherical shape	[40, 58, 132]
Microemulsion	Ambient temperatures for the reaction, low yield, highly uniform morphology Large quantity of solvent	Narrow size distribution	Spherical shape	[56, 60]
Sol–gel	Simple method, high yields Fast preparation, formation of safe byproducts	Narrow size distribution	Quasi-spherical shape	[57, 59]