Ammonia (NH3) is a colorless and toxic gas, which has a pungent odor. which has a pungent odor. This compound has been widely used in agriculture, fertilizer, factories, food processing, power plants, refrigeration systems, medical treatments, and living environments. Inhalation of ammonia may cause various acute respiratory diseases. It is proved that exposure to ammonia above 50 ppm can irritate the eyes, nose, throat and skin, and extended exposure to ammonia above 200 ppm may even cause chemical burns of skin and permanent lung damage. Thus, the development of ammonia sensors is very significant in the applications of environmental monitoring, industrial process control, and food industry and medical diagnostics. The sensing materials of resistant-type ammonia sensors mainly include semiconducting metal oxides, carbon nanomaterials and conducting polymers.

A lot strategies had been applied to improve the enactment of lithium-ion batteries (LIBs) for next-generation electric vehicles (EVs). However, improving the energy density of LIBs is key extend the driving range of current EVs. Graphite has been broadly employed as the industrial standard LIBs anode material. However, graphite suffers from low theoretical capacity. Tungsten disulfide (WS2) is a transmission metal oxide which reveals trigonal prismatic structure and are indirect gap semiconductors in the bulk form with a bandgap of 1∼1.3 eV in the single-layer. This feature is used in a variety of fields, including energy storage, catalysis, solar cell, sensing, and electronic devices.

Air quality monitoring and toxic gas emissions had risen to be a global concern in the past decades. Researchers have been trying various and massive strategies to find an effective gas sensor and its synthesis methods in this field. A practical gas sensor should detect a particular gas among a mixture of gases and continuously monitor an atmosphere. There are many types of gas sensors depend on different classification methods.