Study On The Enhancement Mechanism Of Molecular Fingerprint Sensing Based On Nanomaterials

In biochemical detection,label-free optical detection technology has attracted research interests because it enables molecular to be measured without interference from fluorescent or other external markers.Although the surface plasmon resonance biosensor reduced the complexity of the device and can judge the change of refractive index during the process of molecular binding,it lacks the ability to identify the type of molecule from the source.Metasurface refers to a kind of artificial layered material whose thickness is less than the wave length.By reasonably designing the size and material parameters of the device,the vibration band of the molecule under test can be coupled with the electromagnetic component of the incident electromagnetic wave,so as to enhance the interaction between the molecule under test and the incident light,thus achieving the effect of amplifying the absorption pattern of the molecular fingerprint.It has broad application prospects in food safety,environmental monitoring,biomedicine and other fields,but it also has some problems such as high detection cost and limited application scenarios.In view of the problems such as insufficient amplification of fingerprint signal,limited detection range and complex preparation technology in the current field of molecular fingerprint sensing,this thesis studied the mechanism of molecular fingerprint sensing enhancement based on Guided Mode Resonance theory and Fabry-Perot cavity,and revealed the influence of metasurface structure,photoregulatory means and preparation technology on the sensing performance.The excitation conditions of strong coupling between light and matter were obtained for the significant amplification of molecular fingerprint signal,so as to realize the recognition of molecular fingerprint absorption pattern in the broadband range.The results are as follows:1.Based on the theory of Guided Mode Resonance and taking boron carbide（B₄C）,silicon dioxide（Si O₂）and calcium sulfate（Ca SO₄）molecules with specific characteristics of mid-infrared as the research object,an all-dielectric grating metasurface was proposed,which combined with optical polarization,angle multiplexing and other optical control means to enhance the interaction between incident light and the molecules to be measured.In the process of numerical simulation,the reflection coefficient at each incident angle was correlated with the molecular absorption coefficient at the corresponding resonance frequency,and the absorption fingerprint after the metasurface coating of the molecules under test was obtained successfully.In the middle infrared region,the molecular fingerprint signal is greater than 123 times.2.In the terahertz region,an ultrastructural grating based on guided mode resonance theory is proposed,which is composed of polymer polypropylene（PP）substrate and cyclic olefin copolymer（COC）grating arranged periodically.In this work,the enhancement mechanism of terahertz molecular fingerprint recognition is elaborated,and the finite-difference time-domain method is used for numerical simulation.The absorption fingerprints of tyrosine,plastic explosive（C₄）and red lead（Pb₃O₄）molecules are extracted by comparing a series of reflection spectra before and after the analytes are coated with the meta-grating.Finally,the sensing capability is evaluated by calculating the magnification of the molecular fingerprint signal.This work provides a new method for establishing terahertz fingerprint database and realizing rapid screening of molecular detection.3.Based on Fabry-Perot（FP）cavity,a planar film superimposed color radiant cooler is designed and prepared,and the color saturation is adjustable.Color control is carried out by changing the thickness of dielectric layer in Metal-Insulation-Metal（MIM）structure.Outdoor test results show that the MIM color layer structure reverse evaporation on polyethylene terephthalate（PET）radiation layer will make the color radiation refrigeration has a better cooling effect,in direct sunlight can achieve 6.92℃cooling,refrigeration ability is higher than the same color commercial coatings.