The aim of our work is to produce enhanced Eu

3+

luminescence in aqueous solution by using energy transfer between ligands

which are linked together by Y

3+

without other additives and micelle formation. We synthesized two bifunctional complexing agents 2

2'

6

6'-tetracarboxy-4

4'-bipyridine (BDPA) and bis(2

6-dicarboxy-4-pyridyl) sulfide (SDPA). In this polymeric network the enhancement of Eu

3+

luminescence is based on two factors. First

a great excess of energy donors (ligands) relative to energy acceptors (Eu

3+

) was used. Excess of ligands was added to obtain maximum absorption and excess of Y

3+

was added to link the ligands and enhance intersystem crossing to triplet state in these ligands. Secondly

the energy absorbed by ligands coordinated to Y

3+

is transferred toward Eu

3+

via triplet-triplet migration. One Eu

3+

is able to be excited either with the energy absorbed by three ligands coordinated to Y

3+

or by several other ligands coordinated directly. This means that when energy is lost non-radiatively during the energy transfer process from the ligand to the Eu

3+

thus Eu

3+

can still be excited by energy transfer process from other ligands coordinated to Y

3+

. The luminescence intensity of the Eu

3+

was plotted against time after mixing of BDPA

Y

3+

and Eu

3+

. The growth of the luminescence signal was quite rapid at the beginning

but slowed down 3min later. The SDPA system showed the same phenomenon. The ligand concentration

Y

3+

concentration and pH were optimized. In two systems with different ligands the effect of pH was investigated in the range 3～11. The luminescence signal was observed to be highest at pH9. The effects of Y

3+

concentration and BDPA concentration on Eu

3+

luminescence were studied respectively. In the case of BDPA

the luminescence intensity of Eu

3+

was highest when the Y

3+

:BDPA ratio was close to the theoretical value 2:3. When the luminescence intensity of Eu

3+

was plotted against the concentration of Eu

3+

it can be seen that there is a quite good linearity within 1

3+

10

-10

～5

3+

10

-7

mol/L range

which enables to be a method used for determination of trace amounts of Eu

3+

.It can be seen that adding of Y

3+

will increase Eu

3+

luminescence greatly. The enhanced Eu

3+

luminescence is most likely due to the presence of efficient energy migration from the ligands coordinated to Y

3+

to the Eu

3+

. The Eu

3+

(Y

3+

)-BDPA system reached the highest luminescence intensity. It might be the result of several factors. The BDPA has a symmetric

conjugated structure. This structure has the shortest distance between different Y

3+

centers and its triplet energy level is suitable for transferring energy to the resonance level of Eu

3+

. It is totally conjugated and planar

which enables the effective energy transfer between ligands. However

the SDPA does not has a conjugated structure

and this may be responsible for the diminished energy transfer compared with that of the BDPA system. The effect of replacing Y

3+

with other lanthanides such as Gd

3+

La

3+

and Lu

3+

was also studied. The sequence of the enhancement is: Gd

3+

>

Y

3+

>

Lu

3+

>

La

3+

. It is noticed that Tb

3+

also enhances Eu

3+

luminescence in this polymer structure.