A type of 2

7-carbazole and fluorene based alternating conjugated polymer

poly［(9

9-dioctyl)-2

7-fluorene-co-2

7-N-dodec-carbazole］ (PF27Cz)

was synthesized by Suzuki coupling reaction.With the addition of I- (aqueous NaI)

the fluorescence of PF27Cz (in THF) was sequentially quenched.The apparent color of PF27Cz turned from colorless to light yellow within the titration process.The heavy-atom effect of I- is the possible reason for the alteration of PF27Cz's optical properties.The presence of other common anions did not bring similar influence toward the optical properties of PF27Cz as was done by I-.The detection limit of I- by PF27Cz reaches ca. 9.010-8 mol/L (evaluated by the analysis of the relationship between probe's fluorescence and I- ' s concentration).By taking advantage of the strong association constants and high matching ratio between Hg2+and I-

the fluorescence of PF27Cz-I-assembly restored gradually with the addition of incremental Hg2+

accompanied by the recovery of solution's apparent color (from light yellow to colorless).The detection limit of PF27Cz-I- toward Hg2+ can be evaluated by analyzing the detailed fluorescence alteration within the titration process

to be ca. 1.610-8 mol/L.When the concentration of Hg2+ reached ca. 6.810-5 mol/L

the fluorescence of PF27Cz-I- almost reached the initial value of pristine PF27Cz.Competition experiments about the interference of background metal ions against Hg2+ suggest that the presence of background metal ions just brought slight interference.Results show that PF27Cz can act as a sensitive

high-selective and anti-interfacial turn-on type optical probe for Hg2+.