Effect of capping agent on the particle size of CdSe nanoparticles.

CdSe nanoparticles were synthesized by green route and chemical route methods. In the green route method the samples were capped by starch and in the chemical route method the samples were capped by mercaptoacetic acid (MAA). The samples were characterized by powder X- ray diffraction (XRD) and transmission electron microscopy (TEM). Both the samples showed zinc blend structure. The optical absorption spectra and Fourier transform infrared (FTIR) spectra were also studied. A blue shift was seen in the absorption spectra as compared with the bulk as well as the sample capped by starch. TEM images showed agglomeration for the starch-capped sample as compared with the MAA-capped sample. The particle size for the sample capped by MAA was found to be less as compared with the starch-capped sample. A blue shift in the photoluminescence (PL) spectra was also recorded for the samples prepared by the chemical route as compared with the sample prepared by the green route as well as the bulk. The PL peak shifted towards the red side and increase in the peak intensity occurred with the change in the excitation wavelength. Change in PL intensity was observed with different pH at 685 nm. Copyright © 2016 John Wiley & Sons, Ltd.