Question

Identify the synthesis method that has the best chance to yield nanoparticles of a uniform size. For comparison, also identify which method we covered that you believe is the least likely to yield uniformly sized particles. Explain your reasoning for selecting these two.

Answer 1

there are various methods for the synthesis of nanoparticles:- 1) physical method 2) chemical method.

here we will talk only about the physical methods

physical method :- Under the physical methods, there are several types. here we mainly focus on mechanical milling and laser ablation methods.

Mechanical milling is a top-down process. Top- down process means, you are converting the bulk material to nanomaterials. Here, the nanoparticles are formed in a mechanical device, generally referred to as a mill. So here we are going to use the metallic ball which will break the bulk material into nano-sized particles.

the fundamental principle of the size reduction in a mechanical device is the energy imparted to the sample, during the impacts between the milling media. So this model represents the moment of collision. in this the particles are trapped between the two colliding balls.

So the metallic drum is rotating and the metallic balls are falling on the powder, which is going to break the micro sized powder into nano size particles. This is called as the mechanical milling or ball milling. We can also call it like a ball milling, because we are using metallic balls. And this is an electron microscopic picture of the particles. for seeing these nanoparticles, we need an electron microscope. .

laser ablation:- in this we will use the laser light to vaporize material. The generation of nanoparticles is by laser ablating a solid target. We can get the nanoparticles in the gaseous or in the liquid environment. As it depends on the environment, the particles which we get can be in the nano powdered form, or it can be in a colloidal solution form. Laser ablation is one of the easiest and fastest methods.

When we compare with other methods, it does not involve long reaction times or multiple steps. Further, it does not require any toxic chemicals for its synthesis. So it is also called as environment friendly or green method. In this method, the resulting nanoparticles which we are obtaining in the colloidal solutions are ultra pure. These particles do not contain any counter ions or any reaction by products, and so we can use these particles as such for biological applications. And again, we can also add ligands to these particles after the synthesis process or in the suitable solvent itself to coat the surface of the nanoparticles.