**3. Synthesis of Nanodiamonds**

Nanodiamonds can be synthesized using different techniques and also artificial synthesis also available nowadays. Diamonds are allotropes of carbon. Diamonds are natural and found in the Earth's mantle having high temperature and pressure. Once a diamond phase is formed, there is a chance to move to graphitic phase. In order to prevent this phase, it has to undergo a high energy barrier phase transition that will overcome the change of sp2 to sp3 which makes diamond in a metastable phase. Several techniques for the synthesis of Nanodiamonds are depicting here. The most common methods are CVD, detonation technique, laser ablation and HPHT methods (**Figure 2**).
