Research On Optofluidic Raman Sensor Based On Microstructured Optical Fiber

The combination of fiber optic technology and Surface-enhanced Raman Scattering（SERS）technology has significantly broadened the application of SERS detection technology.In early applications for optical fibers,the fiber was used only as a light-guiding medium to extend light into a cuvette of SERS solution mixed with the sample solution and to collect Raman signals for transmission;this method demonstrates the flexibility of fiber optic probes by testing samples in vivo and in vitro,but this method limiting its ability to detect very low concentration samples.Subsequently,in the study,deposition of SERS substrate on the fiber tip and placed it in a sample pool for testing was proposed,which solves the detection limit problem but still requires a large amount of sample.To achieve trace detection of samples,hollow photonic crystal fibers with nanoparticles coated inside were introduced to achieve trace detection of samples inside the fiber using capillary effect,however,it was not possible to construct a true microfluidic detection platform by making holes on the surface of the photonic crystal fiber.Therefore,in this paper,we propose a microstructured suspended-core optical fiber with a special structure inside the optical fiber to achieve a real sense of microfluidic,trace,fast,sensitive and efficient Raman on-line detection platform of the detected samples.By improving the SERS substrate,this paper explores the application of this microstructured fiber-based optofluidic Raman sensor in the detection of medical and clinical biological samples.The specific research of this thesis is as follows:1.Silver nanoparticles were combined with microstructured suspended-core optical fiber to construct a microfluidic on-line Raman sensing and detection device.Rhodamine R6G was selected as the fiduciary sample,and the enhancement factor of this optofluidic Raman sensor based on microstructured suspended-core optical fiber reached 1.3?10⁹,which means that this device has the ability of highly sensitive detection.In the detection of the same type of quinolone antibiotics（ciprofloxacin and norfloxacin）widely used in medical medication,it exhibits distinguishable,highly sensitive,fast,and trace online Raman detection.2.To improve the problem of silver nanoparticle agglomeration,a composite SERS substrate based on the combination of silver nanoparticles and graphene oxide was introduced and grown on the core surface inside a microstructured suspended-core optical fiber to obtain a fiber probe device with higher Raman enhancement effect.This microfluidic Raman optical fiber probe device has laid a foundation for the development of biomedical diagnostic detection in the field of biomedical diagnostic detection by trace,efficient and rapid online detection of uraemia toxins（creatinine,urea）that are difficult to detect,the concentration range of urea solution showed a good linear relationship in(10^-2-10^-4 mol/L),and has certain application value in the detection of kidney diseases caused by abnormal urea content.3.To create this optical fiber Raman sensing probe with specific binding capability for specific biological samples in a specific biological environment,the properties of a composite SERS substrate with silver nanoparticles combined with graphene oxide were investigated.In addition,the hydrogen bond between（Poly dimethyl diallyl ammonium chloride,PDDA）（in the composite SERS substrate）and adenine molecules can reach 10^-14 mol/L for adenine aqueous solution.It is worth noting that this integrated composite SERS-based fiber optic probe can successfully capture adenine molecules in the crude DNA purification solution without the interference of other base sequences,and achieve rapid and efficient online detection and analysis.4.The low affinity between glucose molecules and metal particles leads to the low detection capability of the original SERS substrate for glucose.The introduction of 4-mercaptophenylboronic acid in the composite SERS substrate can form ester bonds with glucose molecules,breaking the bottleneck of low affinity between glucose and bare metal particles,the concentration range of aqueous glucose solution showed a good linear relationship in（2-10 mmol/L）.In addition,the trace and efficient Raman detection of glucose was achieved in the（Sprague Dawley,SD）rat cerebrospinal fluid environment.This Raman sensor based on the integrated fiber optic probe in SERS provides a simple and rapid detection method for the diagnosis of brain-related diseases caused by abnormal glucose content in cerebrospinal fluid,and according to the sensor structure,it is expected to realize a detection probe for asana indicators.