Top-Down synthesis |
Mechanical Milling |
|
This approach includes the disintegration of particle aggregates, particle shape, and particle surface. |
[20,21,22,23] |
Chemical Etching |
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Uses a strong acid or a corrosive liquid to cut a metal surface and create a design in the metal. |
[24,25] |
Sputtering |
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There is a particular sputtering technique called magnetron sputtering, which consists of the delivery of a high voltage across a low-pressure gas (normally argon) to create a plasma of high energy composed of electrons and gas ions, which will strike a target containing the desired coating material. |
[26,27] |
Laser Ablation |
|
Is based on the production of micropatterns through the ablation (removal) of fractions of a substrate through the action of a focused pulsed laser beam. |
[20,28] |
Electro Explosion |
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Single-step process in which a delicate wire of a conductive metal is exploded by an electric discharge that is caused by a high-power DC source. This electronic discharge creates a massive temperature that vaporizes the thin wire, turning it into gas atoms, which in their turn are chilled and, finally, the NPs are synthesized. |
[29,30] |
Bottom-up synthesis |
Chemical Deposition |
|
In particular, electrochemical deposition or electrochemical precipitation involves the passage of an electric current between an anode (sacrificial) and a cathode localized in an electrolyte. The anode is oxidized into metal ions and these are then reduced to metal by the cathode with the help of stabilizers. |
[31,32] |
Spinning |
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This method involves the use of a spinning disc reactor. The disc spins at different speeds and the spinning causes the fusion and precipitation of atoms, which are then collected. |
[5,33] |
Sol–Gel |
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A wet-chemical process, with sol being a colloidal solution of solids suspended in a liquid phase that serves as a metal precursor and is then dispersed into the gel, a host liquid leading to the formation of a solid macromolecule submerged in the solvent. After, there is a separate phase where the gel is dried and dehydrated to recover the NPs. |
[20,24,33,34,35] |
Biosynthesis |
|
Metalsynthesis is bio-mediated by microbes or through biosynthesis. Biological synthesis of nanomaterials is the best alternative being cost-effective, environmentally friendly, advantageous and does not comprise any input of toxic chemicals. Between the candidates to biosynthesize M-NPs are bacteria, fungi and yeast; algae; plants, flowers and fruits; and viruses. |
[18,19,23,36,37,38] |