Abstract
We have prepared different sizes of CdSe nanoparticles capped by 3-mercaptopropionic acid (MPA) utilizing different cadmium sources and different molar ratios of the starting precursors. The prepared nanoparticles possess different Se/Cd ratios and different quantity of capping molecules as elucidated by Energy dispersive X-ray spectrums analysis. Infrared analysis manifested that the two-function groups of MPA could coordinate to the surface of the nanoparticles core. Optical analysis revealed that the quantity of capping molecules coordinated to the surface of the nanoparticles have influence upon the absorption and emission spectra. The photoluminescence of the sample with a lot of the capping molecules at the surface of the nanoparticles displayed a band edge emission with narrow full width at half maximum, in addition to a small Stokes shift with coupling constant equal 1.2. Also the thermal analysis revealed that the coordination of capping molecule to the surface of the nanoparticles influence on their thermal degradation. On the other hand, we have tested the up-conversion luminescence for one of the prepared samples. The up-conversion luminescence displayed two emission bands with anti-stokes shifts.