Water-colloid cadmium selenide semiconductor nanocrystals were prepared in aqueous solution by using mercaptoacetic acid as stabilizer.The samples were characterized by X-ray photoelectron spectroscopy(XPS) and transmission electron microscopy(TEM).The results of XPSconfirmed the formation of CdSe nanocrystals

and the images of TEMdemonstrated that the average size of CdSe nanocrystals was less than 10nm and the aggregation occurred among the nanocrystals.The changes of the XRDpatterns

Absorption spectra and emission spectra of the CdSe nanocrystals prepared for different time were investigated.The XRDpatterns showed that the crystal structure became more perfect with the increasing preparation time.It was found that the emission peak changed from 550 nm to 572 nm

but no distinct changes for the shape and full width at the half maximum of the spectra were observed

but the Absorption peak changed from 443 nm to 483 nm.The extent of the peak changes became less and less with the reaction time

which was attributed to the growth of the CdSe nanocrystals with the reaction time at the initial moment and the control of the growth due to the stabilizer mercaptoacetic acid at the ultimate moment.The emission spectra for the different molar ratios of the reactant were also investigated

and the results indicated that the wavelength of the emission peak shifted to the longer wavelength as the molar ratio of Se

2-

/Cd

2+

increased

and it could be interpreted as followings: In the competition between the reaction of Cd

2+

with HSe

-

and RS

-

the reaction between Cd

2+

and HSe

-

occupied the predominance with the increasing of Se amount

which made the size of the nanocrystals increase.All the(results) indicated that the varying of the preparation conditions would influence on the luminescence properties greatly.