There are various methods to synthesis nanoparticles. These methods are divided into two main types bottom-up and top-down. The type of nanoparticles, desirable size and properties determine the synthesis method. but generally, Chemical methods like co-precipitation and sol-gel are widely used due to their simplicity and good properties. I think this article could help you.

Article Review on nanomaterials: Synthesis and applications

Hydrothermal synthesis nanoparticles is low cost and easy to do in the laboratory. Please see a review paper published recently.

 Chem. Rev.20171171711125-11238

Publication Date:August 3, 2017

https://doi.org/10.1021/acs.chemrev.6b00417

Hydrothermal carbonization route, as mentioned by in the literature

As many people said hydrothermal method is easy in addition to that you can try co precipitation method which will be quicker than the hydrothermal method.

There are physical and chemical methods. Physical methods include vacuum deposition, mixed plasma method and so on. Chemical methods include gas-phase reaction and liquid-phase reaction.