| Pseudomonas aeruginosa is a type of pathogenic bacteria found in the environment that causes significant harm to human health and aquaculture,and pyocyanin is also one of the important virulence factors.Traditional microbial detection methods have limitations that prevent them from meeting the requirements of rapid nondestructive testing.Spectrum technology has demonstrated unique advantages and great potential in analysis and detection due to its high efficiency and non-damage characteristics.Surface-enhanced Raman scattering(SERS)technology,for example,can obtain molecular vibration information of substances in order to detect pyocyanin a with high sensitivity;Terahertz(THz)sensing technology can collect the fingerprint spectrum of biological macromolecules,which is expected to achieve the goal of quantitative detection of Pseudomonas aeruginosa.In this thesis,Pseudomonas aeruginosa and pyocyanin were used as detection objects,and the advantages of SERS technology in high sensitivity detection of small molecules and THz technology in realizing detection of large molecules were combined to create a hierarchical metamaterial that can sense SERS and THz simultaneously.The simultaneous and rapid detection of Pseudomonas aeruginosa and pyocyanin was achieved using this metamaterial method.It suggests a possible application of Raman and terahertz spectroscopy in microbial detection.The main research contents and research results of this paper are as follows:(1)A flexible and transparent SERS substrate was created and used to detect chemical molecules quickly.The crystal violet detection sensitivity of a SERS substrate made by self-assembly of nanoparticles is 1 n M.The relative standard deviation of imaging results is only3.1%,and the signal is stable in the temperature range of 0-50℃,and the signal remains stable after being soaked in 5-500 m M sodium chloride solution for a long time(23 h),indicating that SERS substrate has good sensitivity,uniformity,thermal stability,and corrosion resistance.The SERS substrate has good molecular recognition capability and can detect various chemical molecules with high sensitivity.The pyocyanin detection concentration was 100 n M.However,because direct detection of Pseudomonas aeruginosa is difficult,other optical sensing technologies are required to achieve simultaneous detection of Pseudomonas aeruginosa and pyocyanin.(2)Pseudomonas aeruginosa was detected quickly using a flexible and stretchable THz metasurface.Using an asymmetric dual-wire structure as an example,the dynamic tuning mechanism and mechanical properties of the flexible metasurface are investigated,and its dynamic tuning range is 0.520-0.595 THz.Afterward,a flexible metasurface with symmetrical split ring structure is created to extend the dynamic tuning range(0.46-0.80 THz)and demonstrate its universality.Finally,the metasurface of symmetrical split ring structure was used to detect Pseudomonas aeruginosa.The lowest detection concentrations were 10~5CFU/m L.The sensitivity is low.The structure of metamaterials can be improved further.(3)A multi-frequency THz metamaterial method for Pseudomonas aeruginosa detection was established,and the feasibility of hierarchical metamaterial for pyocyanin detection was investigated.The detection effect is best at 1.168 THz,the detection concentration is lowest at9×10~3 CFU/m L.Pseudomonas aeruginosa imaging was accomplished using the resonance peak.The nanoparticle array and the multi-frequency THz metamaterial are combined to form a hierarchical metamaterial that can be used to improve the Raman spectrum.The surface-enhanced Raman spectrum of pyocyanin is obtained using this hierarchical metamaterial,and the lowest detection concentration can reach 50 n M.Conclusion THz metamaterial combined with SERS substrate can detect Pseudomonas aeruginosa and pyocyanin with high sensitivity.(4)For the detection of Pseudomonas aeruginosa and pyocyanin,an optical sensing method based on the synergistic effect of surface-enhanced Raman spectroscopy and terahertz wave was investigated and established.The response laws of a flexible metasurface and a nano-particle array in the Raman spectrum and terahertz wave were compared and analyzed in the experiment.The optical sensing properties of a flexible metasurface and a nano-particle array during stretching are discussed in detail.The quantitative detection of Pseudomonas aeruginosa(the lowest detection concentration is 5×10~3 CFU/m L)and pyocyanin(the lowest detection concentration is 30 n M)was realized using a detection method that combined Raman spectroscopy with terahertz sensing technology.On this basis,an intelligent sensor tag with rapid detection and information transmission functions is created,which can detect Pseudomonas aeruginosa growth and metabolic process.At the same time,due to the penetration of terahertz waves,it can image Pseudomonas aeruginosa in food packaging.In this paper,for the first time,a hierarchical metamaterial that can enhance Raman signal and realize terahertz resonance was prepared,and its potential in the nondestructive detection of Pseudomonas aeruginosa and pyocyanin was demonstrated.The optical sensing properties of a flexible SERS substrate and a terahertz metasurface are investigated in this paper.The photoelectric properties of multi-frequency metamaterials are investigated,as well as their advantages in microbial detection.By combining terahertz metasurface with flexible surface-enhanced Raman scattering substrate,researchers were able to detect micron-scale microorganisms(Pseudomonas aeruginosa)and sub-nano-scale chemical molecules(pyocyanin).This should encourage the advancement of optical sensing technology in the field of microbial nondestructive testing. |
PDF Full Text Request