In this paper

a new idea was presented for narrowing the size distribution of CdS nanoparticles by utilizing Cd(OH)

2

selective coated and photocorrosion.At first

CdS nanoparticles were synthesized by wet chemical method.Sodium Hexametaphosphate(HMP)was used as stabilizing agent.Then

a layer of Cd(OH)

2

was deposited on the surface of CdS nanoparticles.According to the theory of curve interface growth kinetics

Cd(OH)

2

prior to grow on the surface of the bigger diameter CdS nanoparticles.So

controlling the amount of OH

-

and Cd

2+

the bigger CdS nanoparticles can be selective coated by a layer of Cd(OH)

2

.At last

the whole colloid was irradiated by sunlight.CdS nanoparticles can be decomposed under irradiating of sunlight on the condition of oxygen.But Cd(OH)

2

which deposited on the surface of CdS nanoparticles

can prevent the CdS contacting with the oxygen in the water.So

after several days

those uncoated smaller CdS nanoparticles were photocorroded.Only those coated bigger CdS nanoparticles were still in the colloid.Then

the narrowed size distribution of CdS nanoparticles was gained.This idea was confirmed by the study of PL spectrum of CdS nanopaticles.After selective coated by Cd(OH)

2

the CdS nanoparticles' PL spectrum appears two peaks.The peak of high energy comes from the emission of bandedge of coated bigger CdS nanoparticles.The peak of low energy comes from the emission of surface state of uncoated smaller nanoparticles.During the irradiating by sunlight

the peak of the emission of surface state is disappearing gradully.But the peak of the emission of bandedge is still existent.