Preparation Of Flower-Like CuO And Its Surfce-Enhanced Raman And Gas-Sensitive Properties

With the development of society,there are plenty of the pollutants that are produced in industry and life,such as industrial fuels,heavy metals,waste water and waste gas.They are increasing,create serious problems for the ecological environment and human health.The detection and monitoring of these hazards have aroused widespread human concern.CuO is a p-type semiconductor with a band gap of about 1.2 e V.Due to its low cost,high stability,and low harm,it is widely used in SERS and gas sensor research the detection of harmful substances.In this paper,a simple hydrothermal method was used to synthesize CuO-based materials and Ag@CuO.Au@CuO composite materials were prepared by using electron beam evaporation system and in-situ reduction method to modify Ag and Au particles on the CuO surface.Use scanning electron microscope（SEM）,transmission electron microscope（TEM）,selected area electron diffraction（SAED）,X-ray diffraction（XRD）,X-ray energy spectrum analysis（XPS）to characterize and analyze the synthesized materials.Furthermore,SERS and gas-sensitivity detection were carried out respectively.The main conclusions are as follows:（1）CuO flower-like material is composed of sheet-like structure.After being modified by Ag and Au,nano-particles can be embedded on the surface of flower-like CuO petals.XRD and XPS analysis show that the CuO flower-like material has a monoclinic structure composed of Cu and O elements.For Ag@CuO composite material and Au@CuO composite material,they are composed of Cu,O,Ag and Cu,O,and Au respectively.Besides,no other impurities are contained.（2）In the application of surface-enhanced Raman scattering（SERS）,for Ag@CuO flower-like composite substrate,firstly,rhodamine 6G（R6G）was used as a probe molecule to study its surface-enhanced Raman performance.Studies have shown that the lowest detection limit（LOD）can reach 3.58′10^-16 M,and the enhancement factor（EF）is 3.99′10¹⁰,which has excellent SERS characteristics.More importantly,it was used as a SERS substrate to detect cadmium ions,and it was found that its lowest detection limit（LOD）reached 2.6′10^-8M,which is lower than the World Health Organization（WHO）and Environmental Protection Agency（EPA）for drinking water.The maximum allowable concentration of Cd²⁺content.It can be seen that the substrate can be used to monitor the pollution of heavy metal ions Cd²⁺in water and soil,and has important applications in environmental monitoring.（3）The CuO flower-like material and the Au@CuO flower-like composite material are made into devices to detect organic volatile substances ethanol（C₂H₆O）,formaldehyde（HCHO）,methanol（CH₃OH）and isopropanol（C₃H₈O）.The experiment found that the best working temperature of the pure CuO gas sensor is reduced from 240℃to 100℃,and the sensitivity of response to the target gas is greatly improved,especially the enhancement effect on ethanol gas.Strong,the sensitivity is increased by about 7 times.It also has an enhancement effect on formaldehyde,isopropanol and methanol gas,and the sensitivity is increased by about4 times,2 times and 1.5 times respectively.Subsequently,we studied the photosynthetic sensitivity of Au@CuO flower-like composites.Under near-ultraviolet light irradiation,the sensitivity to ethanol gas was found to be R_S=127.7（at a concentration of 500 ppm）,which was twice as high as before light irradiation,and the lowest detection concentration could reach 78 ppb.Ultraviolet light improves the gas sensor’s response to ethanol gas,and has the best photochemical sensitivity to ethanol,and has important applications in photochemical sensitive detection.