[Ba4(S2)][ZnGa4S10]: Design of an Unprecedented Infrared Nonlinear Salt-Inclusion Chalcogenide with Disulfide-Bonds

Salt-inclusion chalcogenides (SICs) have been receiving widespread attention due to their large second harmonic generation (SHG) responses and wide bandgaps, however most of them suffer from small birefringence limiting their technical application. Herein, by introducing the p-conjugated (S-2)(2-) units in the ionic guest of salt-inclusion structure, the first disulfide-bond-containing SIC, [Ba-4(S-2)][ZnGa4S10] has been synthesized. It exhibits the widest bandgap up to 3.39 eV among polychalcogenides and strong SHG response as large as that of AgGaS2 (AGS). Importantly, its birefringence reaches a max value of 0.053@1064 nm among AGS-like SICs, indicating it is a promising IR nonlinear optical (NLO) material. Theoretical calculations reveal that the p-conjugated (S-2)(2-) units and covalent Ga-S layers favor the enhanced birefringence and large SHG response. This work provides not only a new type of SIC for the first time, but also new lights on the design of IR NLO materials.

Automated summary

In this study, the first disulfide-bond-containing salt-inclusion chalcogenide was successfully synthesized, demonstrating the potential application of this material as an infrared nonlinear optical material with the widest bandgap and strong second harmonic generation response. Theoretical calculations revealed that the introduction of the p-conjugated (S-2)(2-) units and covalent Ga-S layers contributed to enhanced birefringence and large SHG response.