2D ferroelectrics with robust polar order in the atomic-scale thickness at room temperature are needed to miniaturize ferroelectric devices and tackle challenges imposed by traditional ferroelectrics. These materials usually have polar point group structure regarding as a prerequisite of ferroelectricity. Yet, to introduce polar structure into otherwise nonpolar 2D materials for producing ferroelectricity remains a challenge. Here, by combining first-principles calculations and experimental studies, it is reported that the native Ga vacancy-defects located in the asymmetrical sites in cubic defective semiconductor α‑Ga 2 Se 3 can induce polar structure. Meanwhile, the induced polarization can be switched in a moderate energy barrier. The switched polarization is observed in 2D α‑Ga 2 Se 3 nanoflakes of ≈4 nm with a high switching temperature up to 450 K. Such polarization switching could arise from the displacement of Ga vacancy between neighboring asymmetrical sites by applying an electric field. This work removes the point group limit for ferroelectricity, expanding the range of 2D ferroelectrics into the native defective semiconductors.
Henggang Wang,Shan Sun,Jin Yang,Haoyi Sun,Ke Cheng,Xinxin Wang,Si Li,Hengwei Lin
The efficient treatment of many infectious diseases is hindered by uncontrolled bacterial infections and inflammation induced by reactive oxygen species (ROS). Thus, there is an urgent need for the development of multifunctional therapeutic agents that possessing both antibacterial and antioxidant features. In this study, a novel antibacterial and antioxidant agent, Ga 2 Se 3 nanosheets (NSs), were firstly prepared by the liquid-phase exfoliation method. The Ga 2 Se 3 NSs exhibited broad-spectrum sterilization capabilities, even including multidrug-resistant strains. Noteworthily, Ga 2 Se 3 NSs showed a remarkable 800-fold enhancement in antibacterial efficacy compared to the bulk materials, while also demonstrating low drug resistance compared to the traditional antibiotics. Their superior antibacterial performance is primarily attributed to the disruption of basic bacterial metabolism induced by gallium and selenium components, as well as the dimensional engineering of Ga 2 Se 3 NSs. Cellular studies further confirmed the protective effects of pluronic F127 modified Ga 2 Se 3 NSs against oxidative stress damage, preserving cellular functions through ROS scavenging. This study highlights the superior antibacterial and antioxidant properties of Ga 2 Se 3 NSs, which offers an alternative opportunity for addressing the drug resistance issue in treatment of certain special diseases.
Ling Luo,Linan Wang,Jianbang Chen,Jiazheng Zhou,Zhihua Yang,Shilie Pan,Junjie Li
Large second-harmonic generation (SHG) response and broad band gap are two important and competitive parameters. It is difficult to balance them out in one material. In this work, by coupling alkali earth metal (AEM) octahedra with large highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) gap and nonlinear optical (NLO)-active tetrahedra units, nine noncentrosymmetric (NCS) compounds, belonging to a new quaternary chalcogenide family AIB3IIC3IIIQ8VI with unique windmill-like [Mg3M3IIIQ24] (MIII = Al, Ga; Q = S, Se) units constructed by alternated [MgQ6] octahedra and [MIIIQ4] tetrahedra, are rationally designed and fabricated. The compounds show a stable structural framework but adjustable optical properties. Among them, NaMg3Ga3Se8 shows a large SHG response (∼1 × AgGaS2 (AGS)), wide band gap (in selenide) (2.77 eV), high laser-induced damage threshold (LIDT) (∼2.3 × AGS), and suitable birefringence (0.079@546 nm). It should be a potential candidate for infrared (IR) nonlinear optical (NLO) materials. The results enrich the chemical diversity of chalcogenides and open an avenue for the development of new IR NLO materials through the octahedra and tetrahedra coupled strategy.
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