Cr2O72− anion fluorescent probe effective detection based on novel highly stable cadmium coordination polymers material

Abstract

Coordination polymers (CPs) have been used in fluorescent probes because of their brilliant fluorescence features and Unique structural. As a result, a few Cd-CPs were applied in detecting metal ions, inorganic anions, and small molecules. In this work, four novel and effective fluorescent probe CPs materials using 4,4-bis-(imidazolyl)-biphenyl (BIB), small moleculeorganic acid ligands (Pimelicacid (H2PCA), Suberic acid (H2SCA), Diglycolic acid (DCA), Iminodiacetic acid (ICA)) and Cd2+ by solvothermal method were designed and prepared, namely [Cd(BIB) (SCA)]n (1), [Cd2(BIB)2(PCA)2]n (2), [Cd(BIB) (ICA) (H2O)]n (3), [Cd(BIB) (DCA) (H2O)]n‧n (H2O) (4), showing excellent fluorescence performance in detecting Cr2O72− in aqueous solution. Analysis of single crystal structure determination results, CP-1 and 2 presents adouble layer 2D structure with different coordination environments for center Cd2+. CP-3 and 4 possess 3D supramolecular structure, and which stability is enhanced by multiple and strong π‧‧‧π stacking interactions. In each of the four probes, the voilet-emission signal is attributed to the charge transfer within the BIB ligand in CPs 1–4, which can selectively detect Cr2O72− anions in the solution with excellent selectivity and sensitivity. The individual high quenching percentage (CP-1:98.86%, CP-2:99.38%, CP-3:99.19%, CP-4: 99.15%), quenching efficiency Ksv (CP-1:1.41 ​× ​105, CP-2:1.31 ​× ​105, CP-3:1.16 ​× ​105, CP-4: 1.11 ​× ​105) and detection limits (CP-1: 1.37 ​× ​10−6, CP-2: 7.33 ​× ​10−7, CP-3: 1.48 ​× ​10−7, CP-4: 3.29 ​× ​10−7) were regarded as the excellent CPs sensors for detecting Cr2O72− anions. The relevant parameters are approximate to the permissible limits allowed by the USEPA. The mechanism for Cr2O72− quenching involves overlap of the excitation or emission bands of CPs 1–4 with absorption bands of recognition anions. As far as we know, this is a good example of using fluorescence properties to detect Cr2O72−. This method possesses potential application for the determination of Cr2O72− in various sewage solutions.