Preparation Of 3D Flower-Like WSe₂ And Regulation Of Gas-Sensing Properties

With the increasingly severe environmental problems,human survival is also facing unprecedented chalenges,so the detection of harmful gases in the air is particularly important,the current gas sensor still has the problem of low sensitivity,high energy consumption,so the development of high performance,low energy consumption of new gas sensor is the focus of the current research.The transition metal disulfide（TMDs）nanomaterials have the characteristics of large specific surface area,excelent electrical conductivity and small band gap,which make it easy to realize gas sensing.However,a single TMDs material still has some defects,such as low surface sensitivity and poor stability.Three-dimensional flowered tungsten selenide（WSe₂）has been proven to be a relatively stable semiconductor in TMDs with an indirect band gap of about 1.2 e V and excelent electrical conductivity and electron mobility.Therefore,systematic gas-sensitive study on the WSe₂ and its composites is expected to promote the rapid development of a new gas-sensitive sensor with high performance and low energy consumption.This paper focuses on the synthesis and gas-sensitive property of WSe₂ and its composite materials（3D floral Au@WSe₂ and 3D floral Ti O₂@WSe₂）.Composite materials with 3D floral WSe₂ and 3D floral WSe₂ were synthesized by hydrothermal method.WSe₂ was characterized by XRD,XPS,SEM,TEM,EDS and other means,and gas sensitivity was further tested on the 3D floral WSe₂ and the composite material with 3D floral WSe₂ by detecting volatile organic compounds（ethanol,isoamyl alcohol,n-butanol,isopropyl alcohol,isobutanol and n-propyl alcohol）.And its sensitive mechanism is analyzed and discussed.Specific research contents are as follows:（1）Synthesis,characterization and gas sensitive test of WSe₂ nanomaterials with three-dimensional floral shapeWSe₂ with a size of 1 micron was synthesized by hydrothermal method.With a3D flowered WSe₂,the WSe₂ sensor was developed to detect organic volatiles.During the experiment,it was found that the WSe₂ gas sensor has a high response to alcohol,including at 1000 ppm.The response values of WSe₂ on ethanol,isoamyl alcohol,n-butanol,isopropyl alcohol,isobutanol,isobutanol and n-propyl alcohol were 23.2,41.82,7.05,4.43,25.53 and 8.03,respectively.The optimal working temperature is215℃.Subsequently,the response-recovery characteristics of WSe₂ gas sensor on ethanol gas were studied,and the response time was 30.9 s and recovery time was19.97 s.In the repeatability cycle test of ethanol gas,it is found that the gas sensor shows good repeatability.This indicates that WSe₂has a good application prospect in gas-sensitive direction.（2）Synthesis,characterization and gas sensitive test of three-dimensional flower-like Au@WSe₂ compositesGold hypochlorite was reduced by ascorbic acid to produce Au@WSe₂,where Au particles were evenly distributed on the"petals"of WSe₂.Compared with a single three-dimensional flower-like WSe₂ sensor,the response values of Au@WSe₂ gas sensor on ethanol,isoamyl alcohol,n-butanol,isopropyl alcohol,isobutanol,isobutanol,isobutanol and n-propyl alcohol increased to 178.5,75,78,15,56.9 and96.5 at 1000 ppm,respectively.Alcohol,n-butanol and n-propyl alcohol showed particularly significant enhancement effects,with values of 8,11 and 12 times of the response value of 3D floral WSe₂ device,respectively.A three-dimensional flower-like WSe₂ device modified by Au nanoparticles can reduce the optimal working temperature from 215℃to 205℃.The response-recovery characteristics of Au@WSe₂ gas sensor to ethanol gas were studied.The measured response time decreased from 30.9 s to 30.0 s,and the response recovery time decreased from 19.97s to 5.12 s.It can be seen that the gas sensor has a better desorption effect.Among the six different alcohols,the device showed the highest response to isoamyl alcohol（up to 44.5）at low gas concentrations（100 ppm）and the highest response to ethanol（up to 178.5）at high gas concentrations（1000 ppm）.In addition,Au@WSe₂ gas sensor tested 1000 ppm ethanol gas repeatedly over 30 days and found the response to be stable and repeatable.The results show that Au@WSe₂ gas sensor has good responsiveness and selectivity,and is a promising gas detection material.（3）Synthesis,characterization and gas sensitive test of three-dimensional flower-like Ti O₂@WSe₂ compositesTi O₂ quantum dots were prepared with Ti Cl₄ by hydrolyzing salt.Ti O₂ quantum dots were evenly embedded on the"petals"of WSe₂,showing a three-dimensional flower bal.Ti O₂@WSe₂ The gas sensor responds 76.08,54.89,44.41,15.38,38.7 and72.38 to ethanol,isoamyl alcohol,n-butanol,isopropyl alcohol,isobutanol,and n-propyl alcohol at 1000 ppm.For the gas sensor produced by Ti O₂ quantum dots,the response values to ethanol,isoamyl alcohol,n-butanol,isopropyl alcohol,isobutanol,and n-propyl alcohol were 16.7,15.3,16.4,10.61,12.44 and 27.6,respectively.With a single Ti O₂and a single WSe₂ as a reference,The composite Ti O₂@WSe₂ gas sensor has more outstanding performance in response and selectivity.The response time of the combined gas sensor decreases from 30.9 s to 20.47 s,indicating that the desorption effect of Ti O₂@WSe₂ gas sensor is more obvious.And within 30 days,Ti O₂@WSe₂gas sensor respectively for 500 ppm and 1000 ppm of two concentrations of ethanol cycle test,test results show that Ti O₂@WSe₂ gas sensor has good cycle stability.