| Abstract
| - Reaction of l-cysteine with M(NO3)2·xH2O (M = Cd, Zn) generates M(l-cysteinate), which feature one-dimensional substructures that can be viewed as fragments of bulk structures of CdS (rock salt high pressure phase) and ZnS (würtzite) because of the bridging modes accessible to the sulfur atom of l-cysteine. The MS substructures are arranged in a regular and periodic fashion within the crystal via the carboxylate function of l-cysteine. Considering the structural similarities with bulk materials, the optical properties of M(l-cysteinate) were studied and indicate blue shifts of the band gap of 2.59 eV (M = Cd, compared to CdS rock salt) and 1.37 eV (M = Zn, compared to ZnS würtzite) with respect to the bulk MS structures, due to the low dimensionality of the metal−sulfur arrangement. The chelating nature of the cysteine ligand imposes an unusual mer arrangement of three binding S moieties at Cd with a correspondingly high Cd coordination number in a chalcogenide-based material. Density of states calculations show strong electronic structure similarities with the bulk phases and rationalize the band gap changes.
- Solvothermal reaction of l-cysteine with cadmium nitrate and zinc nitrate generates 3D structures of M(cysteinate), M = Cd, Zn, which display 1D substructures of CdS and ZnS organized in a periodic fashion within the crystal by the organic ligand. These substructures are reminiscent of rock salt CdS and würtzite ZnS and show a significant blue shift of the band gap with respect to the bulk phases, attributed to the decrease in dimensionality and rationalized by density of states calculations.
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