Preparation Of Ag₂W₂O₇@Au Nanobelt And Its Surface Enhanced Raman Scattering And Gas Sensitivity Research

Due to their special structure and properties,one-dimensional nanomaterials are widely used in various fields,such as Surface Enhanced Raman Scattering（SERS）,nanosensor,catalysis,electronics and optoelectronic devices,and solar cells.Surface-enhanced Raman spectroscopy has extremely high sensitivity in some precious metal systems,and the enhancement factor of certain nanomaterials can reach more than ten orders of magnitude,which has reached the level of single molecule detection.The strength of the SERS signal is not only related to the properties of the metal material,but also related to the structure,morphology,and grain spacing of the material.In recent years,people have been committed to other ways to improve the SERS performance of semiconductors and their composite Raman substrates,especially focusing on the semiconductor material and metal composite material.Composite metal particles with semiconductor materials can make the charge transfer between the two,metal particles themselves also can produce electromagnetic fields,and between metal and semiconductor materials can produce coupling electric field.Therefore,the composite materials of semiconductor materials and precious metals can also greatly enhance the SERS performance,even comparable to the fluorescence spectroscopy technology.One-dimensional nanomaterials are also important materials for making semiconductor gas sensor,which can be used to detect different toxic gases.The nanoribbons with high specific surface area and special structure can effectively improve the contact between the material surface and gas molecules,and then enhance the response of the gas sensor.It is reported that modification of noble metal particles on the surface of semiconductor material can enhance the response of gas sensor to a large extent.Based on the above reasons,the experiment in this paper mainly focuses on the research of Ag₂W₂O₇@Au composite material for SERS performance and gas-sensitive performance.The pure Ag₂W₂O₇ nanoribbons were prepared by hydrothermal method,and the Ag₂W₂O₇@Au composite material was further obtained by ion beam sputtering.Characterized by scanning electron microscopy（SEM）,transmission electron microscope（TEM）,uv-vis absorption spectroscopy（UV-vis）,etc.After the analysis,it is found that Au nanoparticles can not only provide a higher specific surface area for the pure Ag₂W₂O₇ nanobelt,but also generate more"hot spots"on the surface of the nanobelt.The combination with the Ag₂W₂O₇ nanobelt can also expand the light absorption range.It can effectively improve the adhesion of detection molecules on the surface of the nanobelt.After understanding the above information,the next step is to analyze the applications of Ag₂W₂O₇ and Ag₂W₂O₇@Au nanobelts as substrates and devices in SERS and gas sensors,respectively.Two kinds of materials were prepared into SERS substrate,and carcinogens methylene blue（MB）,rhodamine B（Rh B）,acridine orange（AO）,Sudan III,rhodamine 6G（R6G）and malachite green（MG）were used as probe molecules to study the performance of the substrate.Found Ag₂W₂O₇@Au composite basement can detect lower concentrations of probe molecules,of which the lowest detection limit of methylene blue,reached 8.281×10^-11 mol/L,and enhancement factor is the highest,reached 1.08×10⁶,then found Ag₂W₂O₇@Au composite Raman basal selectivity of methylene blue.The characteristic peaks of methylene blue on the substrate were 1625,1398 and 1300 cm^-1,and the RSDs were 13.29%,13.09%and 14.45%,and all less than 15%,indicating that Ag₂W₂O₇@Au composite material was an ideal material.In order to expand the application of Ag₂W₂O₇@Au composite materials.The study has been shown that the gold particle-modified Ag₂W₂O₇ nanoribbons have gas sensitivity responses of 76.8,27.06,16.52 and 13.78 to the four gases of acetone,ethanol,formaldehyde,and ammonia at a concentration of 100 ppm at the optimal working temperature（250℃）.They are 76.8,27.06,16.52,and 13.78,respectively.It was found that the response to acetone was the highest,and the detection limit for acetone is calculated to be 22.707 ppb.The detection limit and response of the Ag₂W₂O₇ sensor to 100 ppm acetone are 61.09 ppb and 19.87,respectively.The comparison shows that the response of the Ag₂W₂O₇@Au composite sensor is 3.86times that of the pure Ag₂W₂O₇ nanobelt device.It can be seen that the modification of Ag₂W₂O₇ nanoribbons by gold particles can greatly improve the gas-sensitive response of acetone with good repeatability.