Surface Modified

Quantum dots show unique properties arising from the high polarizability of electron energy levels, discretization of energy levels, concentration of oscillator strength for particular transitions, etc. The size-induced effects are often complex with the surface effects which are predominant in these systems having a large surface area to volume ratio. It is therefore necessary to separate out the effects of surfaces from the size induced physical phenomena.

Recently, quantum dots have found applications in composites, solar cells and fluorescent biological labels which use both the small particle size and tunable energy levels. Recent advances in chemistry have resulted in the preparation of monolayer-protected, high-quality, monodispersed, crystalline quantum dots as small as 2nm in diameter, which can be conveniently treated and processed as a typical chemical reagent.

Recently“nano-hetrostructures”such as  core/shell colloidal NCs have drawn significant attention because of its interesting optical properties. Overcoming the quantum dots by a higher bandgap semiconductor materialresult in an enhancement in localization of the charge carriers along with the passivation of surface. As a result, both the electron and the hole are mostly confined in the core region, their photoluminescence quantum yield (PL QY), Stability and Optical Amplification gets improve compared to the bare core NCs.

ZnSequantum dots (QDs) are potential candidates for their industrial application in blue light emitting diodes, as they are free from toxic elements and bio-Compatiable.ZnSe/Zns quantum dots can be synthesizedfrom toxic and non-toxiczinc precursors. When the surface of ZnSe is passivated by Zns, ZnSe@Zns core shell quantum dots  is formed and the quantum yield and PL efficiencyis greatly improved compared with that for the bare Zns.

Due to particular electronic properties, and optical properties, such as a particle-size dependent wavelength of fluoroscence-an effect of Znse/Zns quantum dots are used in fabricating optical probes for biomedical and medical imaging.