Synthesis Of Composite Magnetic Nanomaterials And Their Application In SERS Detection Research

Escherichia coli is one of the main pathogenic microorganisms that cause foodborne illness,and only low infectious doses are required to cause severe diarrhea and gastrointestinal illness.Pseudomonas aeruginosa,the leading cause of healthcare-associated infections,has evolved multiple mechanisms to resist the action of antibiotics,making infectious diseases increasingly difficult to treat.These bacteria are highly pathogenic and spread widely through environmental media(such as water,air,soil,etc.),posing a serious threat to public health,so we need rapid,economical,and convenient detection methods to identify their potential risks.Surface-enhanced Raman scattering(SERS)spectroscopic detection is an important analytical technique for biosensing and trace detection.Due to its high sensitivity and molecular"fingerprinting"capability,it is widely used in different fields,such as environmental/food/industrial monitoring,clinical Diagnostics,DNA and bacterial testing,etc.The traditional Raman spectroscopy detection signal is weak,and the metal can generate more hot spots under the Raman excitation spot,thereby increasing the Raman signal and obtaining surface-enhanced Raman scattering spectroscopy.Therefore,the key to the application of SERS detection lies in the preparation of high-performance SERS substrates.Superparamagnetic nanoparticles can capture and concentrate targets with the help of an external magnetic field,with high efficiency,low sample loss,simple operation,and avoidance of sample aggregation.Gold-coated magnetic nanoparticles with good magnetic responsiveness,enhanced stability,and biofunctionalization expand the application of magnetic nanocomposites for trapping target bacteria and SERS detection.In this thesis,a gold-coated composite magnetic nanosystem was constructed as a substrate for SERS detection.TEM,laser particle size analyzer,ultraviolet spectrophotometer,vibrating sample magnetometer and other instruments were used to characterize the composite materials of intermediate products and final products in the synthesis process.Superparamagnetic composite nanoparticles with good properties and fast magnetic response.In this thesis,a composite magnetic nanosystem with a magnetic core-gold shell structure was constructed as a substrate for SERS detection.Use TEM,laser particle size analyzer,UV spectrophotometer,vibrating sample magnetometer and other instruments to characterize the intermediate and final products in the synthesis process.After continuous optimization of the synthesis scheme,uniform morphology and particle size,good dispersion and fast magnetic response are obtained.of superparamagnetic composite nanoparticles.After that,two fluorescent dyes,PATP and R6G,were used as reporter molecules to evaluate the SERS detection performance of the composite magnetic nanoparticles,and two opportunistic pathogenic bacteria,Escherichia coli and Pseudomonas aeruginosa,were used as targets to explore the materials for SERS detection.The ability of bacteria to apply.When PATP and R6G were used as reporter molecules,their SERS detection concentrations were significantly reduced to 10^-8 M and 10^-9 M,respectively,under the action of the materials.In its practical application for SERS detection of bacteria,the composite magnetic nanomaterials significantly improved the Raman detection signals of Escherichia coli and Pseudomonas aeruginosa.Using three cell,human hepatoma cells(HepG2),human kidney cells(HEK293)and gastric mucosal cells(GES)as mammalian cell models,the biosafety of the materials was evaluated and the risk of environmental exposure was explored.The survival rate test of the cells after exposure for 24 and 48 hours showed that the toxicity of the material to human kidney cells is very small.The kidney is one of the organs most likely to accumulate toxic substances in the human body.The toxic effects on the human body within the concentration range are small,in other words,the environmental exposure risk of the material is small.Under the action of an external magnetic field,the prepared composite magnetic nanoparticles can concentrate the target detection substance,reduce the sample loss,the operation is simple and fast,and at the same time,a strong Raman signal can be generated under the Raman excitation condition,thereby improving the SERS detection performance.For more efficient and accurate detection.