Nanocrystals doped with optically active luminescence centers create new opportunities for luminescent study and application of nanoscale materials.ZnS is the most typical and important crystalline phosphor in both applications and basic science

and doping might change its properties

especially

the transition metallic ions co-activated ZnS nanoparticles form a new class of luminescent materials.The arrested chemical precipitation method is the most popular technique that is used in industrial applications because of its cheap raw materials

easy handing and large-scale production

many doped ZnS nano-particles were prepared by this method.In order to volume-produce homodisperse free-standing

with good surface

and high luminescent doped ZnS nanoparticles

polymer PVP was used as surfactant.Preparation produce was as follows:6.0 g PVP was dissolved in 70~80 mL ultrapure water(

R

≈18 MΩ)

while the solution was stirred

10 mL of 1 mol·L

-1

Zn(CH

3

COO)

2

·2H

2

O

and 1~7 mL of 0.1 mol·L

-1

Mn(CH

3

COO)

2

·4H

2

O

0.1~2 mL of 0.1 mol·L

-1

Pb(CH

3

COO)

2

·3H

2

O were then added.After stirring for 15 min

10 mL of 1 mol·L

-1

Na

2

S·9H

2

O was injected

a suspension occurred immediately.After centrifuging and washing the particles twice with distilled water and once with ethanol.The nano-particles were dried in vacuum.All agents used are analytical pure and without further treatment.Nanocrystalline ZnS:Mn

2+

Pb

2+

have been prepared via the precipitation method at room temperature and under ambient conditions.X-ray diffraction analysis shows that the average crystalline particles size of samples is about 2~4 nm.TEM image shows the nanoparticles are homodisperse.By measurement of the fluorescence spectra

the excitation(λ

exc

≈410 nm) and emission(λ

em

≈510~560 nm) wavelength are both in visible-light range.A novel luminescent property has been observed in the photoluminescence(PL) spectra of the ZnS:Mn

2+

Pb

2+

nanocrystals.These nanocrystals can be doped with Mn

2+

and Pb

2+

during the synthesis without altering the X-ray diffraction pattern

however

the PL intensities of the co-doped samples vary with changing of the impurity mole ratios in the Mn

2+

and Pb

2+

co-doped samples

but the emission wavelength is not changed with the changing of the impurity mole ratios.The PL properties of the co-doped samples are dramatically different from those of Mn

2+

and Pb

2+

single doped ZnS nanorystals

and a probable explanation is presented also.All the results strongly reveal that co-doped ZnS nanocrystals form a new class of luminescent materials.