Colorimetric detection of sulfide based on target-induced shielding against the peroxidase-like activity of gold nanoparticles.

Colorimetric recognition and sensing of sulfide with high sensitivity was proposed based on target-induced shielding against the peroxidase-like activity of bare gold nanoparticles. Significant features of the new assay system are its simplicity and cost-effectiveness. The recognition of sulfide by bare gold nanoparticles can be fulfilled in a few seconds and the assay can be accomplished in about 10 min. Furthermore, the new assay system does not require surface modification of GNPs to obtain the specificity for sulfide, and a salt-induced aggregation step is not needed. The detection limit of this method for sulfide was 80 nM. These features make this sensor a potentially powerful tool for the quantitative determination of sulfide in water samples.

Diaqua-bis(2,2'-biimidazole)zinc(II) 4,4'-di-carboxybiphenyl-3,3'-di-carboxyl-ate.

In the title compound, [Zn(C(6)H(6)N(4))(2)(H(2)O)(2)](C(16)H(8)O(8)), the Zn(II) atom, located on an inversion centre, is coordinated by two aqua and two bidentate biimidizole ligands, resulting in a slightly distorted octa-hedral ZnO(2)N(4) geometry. The four N atoms from the two biimidizole ligands lie in the equatorial plane and the two aqua O atoms lie in the axial sites. The biphenyl-tetra-carboxyl-ate anion also lies on an inversion centre. The Zn(II) complex cation and the anion are held together by N-H⋯O hydrogen bonds, forming a zigzag chain along [21]. The chains are further connected by water mol-ecules via O-H⋯O hydrogen bonds.