| With the advance of science and technology and social and economic development,environmental pollution problems such as atmospheric,marine,and urban environmental pollution have emerged to different degrees worldwide.Atmospheric environmental pollution mainly refers to the many particulate matters in the air and the toxic and harmful gases that directly affect the environment and human health,such as nitrogen oxides(NO,NO2),sulfur dioxide,particle pollutants and so on,these pollutants mainly enter the human body through the respiratory tract.These toxic and harmful pollutants go through the respiratory tract of the human body,it will not be decomposed by the liver,but directly attached to the blood and transported to the whole body,bringing great harm to human health.Therefore,there is an urgent need to develop more advanced gas sensor devices to break through the problems of high power consumption,high detection limit,poor selectivity,and extended response/recovery time of existing commercial gas sensing devices.So the selection of a suitable class of sensitive materials is essential to enhance the performance of gas sensors.Researchers have found that metal sulfide-based sensors have become a hot research topic in recent years due to their low energy consumption,large specific surface area,adjustable number of layers,and abundant edge active sites.However,the current single-component metal sulfide sensors still have three problems waiting for breakthroughs:easy material agglomeration,poor selectivity,and extended response recovery time.In view of the above problems,this paper carried out the regulation strategy of p-n heterostructure construction based on Mo S2 sensitive materials.Mo S2 as the active component of composite materials(representative of typical metal sulfide materials),that is,in p-type Mo S2 material,one-dimensional or two-dimensional n-type semiconductor material is introduced as the redox site for absorbing nitrogen dioxide gas molecules,while the introduction of p-n heterostructure can effectively achieve the regulation of heterogeneous interface charge.The synergistic action of the two can realize the highly sensitive selective recognition of redox processes in NO2 gas at room temperature.In this paper,two different Mo S2 heterogeneous nanocomposites are constructed,which are Zn O@Mo S2 and Ti3C2Tx@Ti O2@Mo S2heterointerface composites.The structure and properties of the composite NO2 gas sensing performance is further studied to realize the improvement of the heterogeneous structure of nano-composite NO2 gas sensing mechanism at room temperature.Two parts of this paper are introduced:(1)One-dimensional(1D)Zn O nanorods supported two-dimensional Mo S2structure for NO2 gas detection at room temperature.First,a simple hydrothermal method is employed,by controlling the key experimental factors such as hydrothermal temperature,hydrothermal time,and heat treatment environment,the growth mechanism of ZIF-8 polyhedron converted to nanorod-like Zn O is systematically analyzed:with the increase in temperature,The linked ZIF-8 polyhedra oxidized to form irregular Zn O structures and gradually grew along the[0001]crystal plane during the growth process.Finally,rod-like Zn O structures were obtained at 150.The experimental results found that Zn O@Mo S2 exhibits good gas sensitivity to NO2 at room temperature due to its large specific surface area and strong interaction between Mo S2 and Zn O heterogeneous interface:It exhibits the most significant gas-sensing response to 50 ppm NO2(the gas-sensing response value is 35),and the response/recovery time is speedy(1.5/30.9 s),low detection limit(10 ppb),and has good selectivity and stability to NO2.(2)Two-dimensional(2D)Ti3C2Tx MXene sheet partial oxidation(Ti3C2Tx@Ti O2)supported vertical structure Mo S2 for room temperature NO2 gas detection.In order to further improve the sensing performance of the gas sensor at room temperature,a 2D Ti3C2Tx MXene sheet with large specific surface area was selected to form Ti3C2Tx@Ti O2@Mo S2heterostructure nanocomposites accompanied by dispersed vertically Mo S2(5-7 layers).The morphology,surface properties and structural composition of Ti3C2Tx@Ti O2@Mo S2 heterostructure nanocomposites were further studied by a large number of characterization techniques.The response of the sensor to50 ppm NO2 at room temperature is 55.16,and the detection limit for NO2 is 23 ppb.Compared with the Zn O@Mo S2 composite sensor prepared in the first part of the work,the sensitivity is greatly improved.This may be due to the introduction of defects in Mo S2,the fabrication of more active sites,and the high-density accumulation of electrons at the double heterogeneous interface.Compared with the Mo S2 structure-based gas sensors that have been reported in the literature so far,Zn O@Mo S2,Ti3C2Tx@Ti O2@Mo S2heterostructured composites all have significant advantages for sensing NO2 gas at room temperature. |
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