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Twenty lake bottom surface layers mud and water samples in the Qilihai Wetland and the Beidagang Reservoir in Tianjin were taken to do diatoms analysis. More than 6000 diatoms were identified and divided into 117 species and 28 genera. Based on the calculation of DAIpo(Diatom Assemblage to organic water pollution), the water pollution level of the Beidagang Reservoir can be divided into: Xenosaprobic, β -oligosaprobic, α -oligosaprobic, β -mesosaprobic, from clear to slightly cloudy water. The water pollution level of Qilihai wetland can be divided into: extremely oligarchy dirt belt, β oligarchy dirt belt, α oligarchy dirt belt, β Medium dirt belt, that is, the water quality is clear to slightly turbid. The water quality of the Beidagang Reservoir is clearer than that of the Qilihai Wetland. The physical and chemical indexes such as EC, pH, TN, TP and CODMn were determined for the water samples, and the correlation between DAIpo and these measured values was analyzed. The results showed that the degree of water pollution detected was consistent with the conclusion obtained by diatom analysis. The results show that the water quality of the Beidagang Reservoir and the Qilihai Wetland was mildly polluted in the spring and summer of 2019, but the eutrophication is more serious.

Tungsten and nitrogen co-doped carbon dots (W, N-CDs) with a high quantum yield of 51.08% were synthesized by a facile hydrothermal process. Doping of tungsten effectively enhanced luminescent properties of the carbon dots, and the quantum yield was increased by 10.3%. The surface composition and morphology of the synthesized W, N-CDs were characterized. W, N-CDs were employed as nanoprobes to develop a sensor for the selective and sensitive determination of Hg2+ and captopril. Under the optimal conditions, the linear response range for Hg2+ and captopril were 0.125 to 9.0 μM and 0.5 to 10 μM with detection limits of 40 nM and 300 nM, respectively. The developed sensor was successfully applied for the determination of Hg2+ in water and captopril in urine with recoveries from 95.50 to 105.50% and 96.33 to 105.13%, which demonstrates suitable accuracy and reliability. The fluorescence mechanisms of W, N-CDs toward Hg2+ and captopril were also evaluated. [ABSTRACT FROM AUTHOR]

Two new Zn2+‐based metal–organic frameworks (MOFs) based on biphenyl‐2,2′,5,5′‐tetracarboxylic acid, i.e. H4(o,m‐bpta), and N‐donor ligands, namely, poly[[(μ4‐biphenyl‐2,2′,5,5′‐tetracarboxylato)bis{[1,3‐phenylenebis(methylene)]bis(1H‐imidazole)}dizinc(II)] dimethylformamide monosolvate dihydrate], {[Zn2(C16H6O8)(C14H14N4)2]·C3H7NO·2H2O}n or {[Zn2(o,m‐bpta)(1,3‐bimb)2]·C3H7NO·2H2O}n (1) {1,3‐bimb = [1,3‐phenylenebis(methylene)]bis(1H‐imidazole)}, and poly[[(μ4‐biphenyl‐2,2′,5,5′‐tetracarboxylato)bis{[1,4‐phenylenebis(methylene)]bis(1H‐imidazole)}dizinc(II)] monohydrate], {[Zn2(C16H6O8)(C14H14N4)2]·H2O}n or {[Zn2(o,m‐bpta)(1,4‐bimb)2]·H2O}n (2) {1,4‐bimb = [1,4‐phenylenebis(methylene)]bis(1H‐imidazole)}, have been synthesized under solvothermal conditions. The complexes were characterized by IR spectroscopy, elemental analysis, single‐crystal X‐ray diffraction and powder X‐ray diffraction analysis. Structurally, the (o,m‐bpta)4− ligands are fully deprotonated and combine with Zn2+ ions in μ4‐coordination modes. Complex 1 is a (3,4)‐connected porous network with honeycomb‐like [Zn2(o,m‐bpta)]n sheets formed by 4‐connected (o,m‐bpta)4− ligands. Complex 2 exhibits a (2,4)‐connected network formed by 4‐connected (o,m‐bpta)4− ligands linking Zn2+ ions in left‐handed helical chains. The cis‐configured 1,3‐bimb and 1,4‐bimb ligands bridge Zn2+ ions to form multi‐membered [Zn2(bimb)2] loops. Optically, the complexes show strong fluorescence and display larger red shifts compared to free H4(o,m‐bpta). Complex 2 shows ferroelectric properties due to crystallizing in the C2v polar point group. [ABSTRACT FROM AUTHOR]

Two new Zn 2+ -based metal-organic frameworks (MOFs) based on biphenyl-2,2',5,5'-tetracarboxylic acid, i.e. H 4 (o,m-bpta), and N-donor ligands, namely, poly[[(μ 4 -biphenyl-2,2',5,5'-tetracarboxylato)bis{[1,3-phenylenebis(methylene)]bis(1H-imidazole)}dizinc(II)] dimethylformamide monosolvate dihydrate], {[Zn 2 (C 16 H 6 O 8 )(C 14 H 14 N 4 ) 2 ]·C 3 H 7 NO·2H 2 O} n or {[Zn 2 (o,m-bpta)(1,3-bimb) 2 ]·C 3 H 7 NO·2H 2 O} n (1) {1,3-bimb = [1,3-phenylenebis(methylene)]bis(1H-imidazole)}, and poly[[(μ 4 -biphenyl-2,2',5,5'-tetracarboxylato)bis{[1,4-phenylenebis(methylene)]bis(1H-imidazole)}dizinc(II)] monohydrate], {[Zn 2 (C 16 H 6 O 8 )(C 14 H 14 N 4 ) 2 ]·H 2 O} n or {[Zn 2 (o,m-bpta)(1,4-bimb) 2 ]·H 2 O} n (2) {1,4-bimb = [1,4-phenylenebis(methylene)]bis(1H-imidazole)}, have been synthesized under solvothermal conditions. The complexes were characterized by IR spectroscopy, elemental analysis, single-crystal X-ray diffraction and powder X-ray diffraction analysis. Structurally, the (o,m-bpta) 4- ligands are fully deprotonated and combine with Zn 2+ ions in μ 4 -coordination modes. Complex 1 is a (3,4)-connected porous network with honeycomb-like [Zn 2 (o,m-bpta)] n sheets formed by 4-connected (o,m-bpta) 4- ligands. Complex 2 exhibits a (2,4)-connected network formed by 4-connected (o,m-bpta) 4- ligands linking Zn 2+ ions in left-handed helical chains. The cis-configured 1,3-bimb and 1,4-bimb ligands bridge Zn 2+ ions to form multi-membered [Zn 2 (bimb) 2 ] loops. Optically, the complexes show strong fluorescence and display larger red shifts compared to free H 4 (o,m-bpta). Complex 2 shows ferroelectric properties due to crystallizing in the C 2v polar point group.