**2.1 Structure of the Nanodiamond**

Diamonds are known as the hardest material and transparent electrical insulator. The structure can be studied in detail by separating the complex structure of Nanodiamond into three ways namely core, an intermediate and the surface layer. Nanodiamonds consists of carbon atoms which are sp3 hybridized and all form distinctive large crystals. The core of the Nanodiamonds (size approximately range from 2 to 3 nm) looks similar to the diamond structure (sp3 C-atoms), but the surface be like graphite (sp2 C-atoms) having hanging bonds edges with functional groups. The inner core holds about major percentage of carbon. The middle sheet which is usually examined as nonhomogeneous translational carbon shell (lesser than 1 nm width). The innermost facet of the shell is detached with onion like carbon rings and the coating composed of graphitic monolayer carbon. The most frequent Nanodiamond outer layer models are (1) a layer of sp2 carbon atoms which are amorphous in nature and (2) a sheet which is graphitic sp2 nature in the form of fullerene, known as "Bucky Diamond" (**Figure 1**) [3].

The most distinguishable feature of the Nanodiamond is its core which is distinct from other carbon materials. The high refractive index of the core creates Nanodiamonds useful in polymer coatings and sunscreen as it robust light scattering. Diamonds are non-conducting material with an optical bandgap of 5.5 eV which shows lucidity from ultraviolet to infrared regions. Still their optical properties can be changed by instituting the dopants or imperfections. Chemical elements like (a) boron introduced as dopant will change its lattice thereby boost electrical conductivity applicable in thin film electronics, (b) nitrogen as a dopant increases the vacancy site inside the lattice improve the fluorescence properties and also used in quantum computing, (c) tritium an allotrope of hydrogen introduced in diamond lattice is applicable in biodistribution application and biolabelling [3].

**Figure 1.** *Structure of the nanodiamond.*
