Relationship between Band gap and particle size of Cadmium sulfide Quantum Dots

Abstract Nanoparticles at quantum dot level are considered to be larger than individual atoms and molecules but smaller than their bulk solid. In such a condition, they are believed to obey neither absolute quantum chemistry nor laws of classical physics. Therefore they have properties that differ significantly from those expected experimentally. Therefore, there are two major phenomena observed that are responsible for these differences. The first one is the high dispersity of nanocrystalline systems or quantum dots. Its acceptable that as the size of a quantum dot is reduced, the number of dots at the surface of the crystal compared to the number of atoms in the crystal itself, increases and therefore the properties, which are usually determined by the molecular structure of the bulk lattice, now become increasingly dominated by the defect structure of the surface. The main objective of this study was to use synthetic method to prepare certain types of nanoparticles and study the difference in properties between bulk and nanosize semiconducting nanoparticles. Absorbance measurements were collected from the UV-Vis spectrum and used in conjunction with Beer-Lambert’s Law to calculate concentrations of solutions or the absorbance coefficient . Equation required the band gap energy of the nanoparticles were obtained from the UV-Vis results and used to calculate the energy absorbed by a quantum dot.

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