Chalcogenide refers to compounds formed from chalcogen elements (including S, Se, Te, Po). In general, chalcogenides not only have unique bonding characteristics and special structures, but also have rich and diverse performances in electrical, optical, and magnetic properties. At present, the research on chalcogenides mainly focuses on the synthesis method and structure of single crystals. The methods of synthesizing chalcogenides include high-temperature solid-phase synthesis and solvothermal synthesis.
Due to the advantages of rich variety and excellent physical and chemical properties, chalcogenide compounds have a wide range of applications in biomedicine, optics and environmental protection.
- Biomedicine: Transition metal dichalcogenide have unique structure and physicochemical properties. Compared with graphene, they have direct band gap, easy chemical modification, good dispersion in solution and good biocompatibility. It has good application prospects in the field of biomedicine. First, transition metal dichalcogenide can be used to make biosensors and is mainly used to convert biological response signals into measurable signals. Because of its high sensitivity, high selectivity and low cost, it has been widely used to detect a variety of biological molecules such as nucleic acid molecules, proteins and enzymes. Secondly, transition metal dichalcogenide nanosheets have high absorption in the near infrared region, which can bring strong photoacoustic signals. Therefore, transition metal dichalcogenide nanosheets have been rapidly developed as a new type of contrast agent and play a role in the field of biological imaging. In addition, Transition metal dichalcogenide nanosheets have small size, ultra-high specific surface area, and unique physicochemical properties, so they are very suitable as nano-platforms for drug and gene delivery and multi-modal treatment, which have great advantages for the treatment of tumors.
Figure 1. Label-free electrochemical immunosensor based on gold nanoparticle-thionine-molybdenum disulfide nanocomposite
- Optics: Chalcogenides have diverse crystal structures and richer physical properties. With the advancement of the synthesis technology, new devices with different structures and functions made from various chalcogenides have appeared one after another. Among them, the energy gap of the semiconductor chalcogenide material covers the spectral range from infrared to deep ultraviolet, so it has broad application prospects in optics. For example, in the aspect of energy storage devices, the composite material prepared by using graphene/MoS2 nanosheets as the anode material still has a very high specific capacity and good cycle characteristics under a large current density. For example, the supercapacitor based on MoS2 is also a new direction for energy storage devices. Its huge specific surface area and interlayer space make MoS2 electrode materials have the advantages of fast electron transfer capability and high capacitance. In terms of piezoelectric devices, the single-layer MoS2 transferred to the PET flexible substrate has an obvious piezoelectric effect. The 0.53% deformation can produce 15mV and 20 pA output signals, showing good piezoelectric performance. In addition, transition metal dichalcogenide photodetectors based on piezoelectric effect show good application potential.
Figure 2. Transition metal chalcogenides have three common atomic structures
- Environmental protection: Chalcogenides can be used as ion exchange materials in the ion exchange process, and have the advantages of rapid ion exchange, high selectivity, and large adsorption capacity during the ion exchange process. Compared with other ion exchange materials, chalcogenide ion exchange materials have two characteristics. The first characteristics is that chalcogenide ion exchange materials have a large atomic radius, strong polarizability, and high affinity and selectivity for soft metal ions. The second characteristic is that the chalcogenide ion exchange material has a wider range of bond angles, making its skeleton structure flexible. In the field of environmental protection, chalcogenide ion exchangers can be used not only to remove radioactive elements in aqueous solutions, but also to remove and recover rare earth elements in water environments.
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- Shuaiming Qiu. (2019), "Structural and electronic properties of transition-metal chalcogenides Mo5S4 nanowires." Chinese Physic B 17, 208-213.