Research And Design Of Optical Gas Sensors Based On Metal Nanoarray Structure

The excitation conditions and characteristics of local surface plasmon resonance(LSPR)are affected by the morphology,size and surrounding dielectric constant of micro-nano structure.Most of these micro-nano structures are periodic and are widely used in the field of sensors.When the frequency of incident photon matches the vibration frequency of conduction electron of precious metal nanoparticles,metal nanoparticles will have a strong local effect on photon energy and form a strong absorption peak on the spectrum.Therefore,this periodic micro-nano structure can be used for refractive index sensing and perfect absorber,etc.At the same time,based on the local characteristics of electric field,it can effectively enhance the detection ability of trace gases or molecules.In this thesis,three different gas sensors based on micro-nano periodic structure are designed by simultaneous LSPR effect and gas sensitive film,which provides ideas for high sensitivity multi-channel gas measurement.The main research contents of this paper are as follows:(1)In this paper,the research progress and application status of local surface plasmon resonance in sensing field are reviewed,and the existing problems and shortcomings of current gas sensors are described.By combining LSPR with gas sensitive film,some problems can be solved and the sensing characteristics can be improved.(2)A LSPR methane sensor based on hexagonal periodic gold nanoarray is designed.Firstly,the effects of structure parameters on the extinction spectrum and the sensitivity of refractive index(RI)were analyzed,and the optimal parameters were obtained.Then,the structure of the sensor is improved by introducing a small size gold ring,and the refractive index sensitivity reaches 550.08 nm/RIU,which is 17.4% higher than the original.Finally,the gold ring is coated with a gas-sensitive material whose refractive index varies linearly with the concentration of methane,so as to determine the concentration of methane.The sensitivity of methane is 1.02 nm /%.The method is also suitable for quantitative analysis of concentration and qualitative analysis of gas composition.(3)A gas-mixture sensor based on LSPR behavior in metal-dielectric-metal(MDM)periodic array is designed.Firstly,the comparisons of gas sensing performance between metal-dielectric(MD)and MDM structure are discussed for single-gas and gas-mixture separately.Next,the influence of MDM structural parameters on the extinction spectrum and gas sensitivity are analyzed to obtain optimal parameters.Finally,by replacing the dielectric with suitable gas-sensitive films,the gas mixture of methane and hydrogen can be accurately measured without interfering with each other.The methane and hydrogen sensitivities can reach to-3.435 nm /% and-0.72 nm /%,respectively.The results also verify the feasibility of multi-channel gas detection and provide an effective method for gas component analysis(4)A high sensitivity gas sensor based on slotted MDM structure is designed.Firstly,the structural parameters of slotted MDM were optimized to obtain the optimal parameters.Next,the effect of slotted symmetry on extinction spectrum is analyzed.Finally,the gas sensitive film was coated at the slit to construct a new MDM structure in the X direction,and the sensitivity was effectively improved by optimizing the parameters.The sensitivity of methane and hydrogen is-4.516nm/% and-1.051 nm/%,respectively.The relation between the polarization Angle of incident light and the extinction spectrum is established,which provides the feasibility for the detection of the polarization Angle.