Divij Sharma


Nanoparticles or nanocrystals are of great scientific interest as they are effectively a bridge between a bulk material and atomic or molecular structures. A bulk material should have a constant physical properties regardless of its size ,but at nanoscale this is often not the case .When the size and dimension or dimensions of a material  are reduced from a large or a macroscopic size to a very small size , the properties remains same at first , then small changes begin to occur.

Thus, nanostructures are the structures whose dimensions are between the molecular range and a microscopic range i.e,  between 0.1 nm to 100 nm .Their classification can be made as Quantum Well, Quantum Wire and Quantum Dot . If one dimension is reduced to a nano-range and the  other  two dimensions remains large , then we obtain a structure called as QUANTUM WELL.

If two dimensions are reduced and one is large we obtain QUANTUM  WIRE ,further reducing all the three dimensions to a nano range ,the structure obtained is of QUANTUM DOT .In other words we can define quantum dots as structures whose size is less than the exciton bohr radius of the semiconducting material . The word quantum is associated with  these three types of nano structures because the changes in properties arise from the quantum mechanical nature of physics in the domain of ultra small, thus  the charged particles in the nanostructures are governed  by the laws of quantum mechanics rather than classical  physics  leading to significant changes in their physical  and electrical properties . These effects are pronounced maximum  in QUANTUM  DOTS structures as the quantum confinement is along all the three spatial dimensions in these structures and because of this reason , they are best suited for nonlinear optical device applications such as  tunable lasers , ultra fast optical switching devices , optical computing , optical waveguides, communication network , infrared detectors    and  many more .




Bandgap, Conduction Band, Energy Level, Valence Band, Exciton, Exciton Bohr Radius, Quantum Confinement

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Prem kishore,A.K., Ghosh and Dileep kumar,2009.Use of lignite flyash in Agriculture.A

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