Preparation And Study On The SERS Optic Fiber Sensor

Raman spectroscopy is an important analytical tool. It can offerhigh information content for establishing molecular identity and structuralcharacteristics. However, as Raman scattering involves low cross-sections,the signals are generally too weak to be used for sensitive probes.Surface-enhanced Raman scattering (SERS) enhances the sensitivity ofRaman dramatically, monolayer film or even sub-monolayer film adsorbedon a metal surface is possible to be investigated by Raman method.Additionally, the selectivity of Raman is very high and Raman is suitablefor studying aqueous systems; therefore, SERS is extensively employed inmany fields such as in chemistry, biology, medicine, pharmacology andenvironmental science and etc.The combination of the optic fiber and the technology of the SERSspectroscopy is one of the important brances of SERS spectroscopy. SERSoptic fiber sensor has many advantages. For example, giving moreinformation on the molecular structure, providing remote sensing to theharmful environment, in situ monitoring the reaction process for the kineticmechanism, also in situ monitoring some danger process. It can be used asthe complemental sensor to other sensors at the same time. Developingstable, reproducibly prepared, easy to make, and convenient to store and usesubstrates that provide a significant enhancement factor are highly desirablefor analytical applications of SERS optic fiber sensor in routine, on-lineanalyses. Therefore, the methods of preparing SERS substrates have longbeen a matter of great concerns and have an important role in thedevelopment of SERS optic fiber sensor. Our study is outlined as follows:1. The effect of fiber character on design and detection of SERS fibersensorIn this article, through summarizing the contribution of other scholars,the SERS optic fiber sensor with flat tip is designed. We investigated thenumerical aperture of objective lens and optical fiber, and detected theraman signal of CH3OH with different objective lens. The results ofexperiments concluded that the 10* objetive len is better for sensordetection. We detected the raman signal of CH3OH with different diameterof optic fiber too. The diameter of optic fiber is smaller, the raman signal ofCH3OH is stronger. It indicated that the optic fiber with small diameter issuitable for SERS fiber sensor.2. The preparation of the SERS optic fiber by vaccum deposited Agisland film and self-assembly Ag colloid filmThe fiber tips were modified by vaccum deposited Ag island film andself-assembly Ag colloid film. In accord with the previous reports, thebest suitable thickness of Ag island film for SERS is 20 nm, In experiments,BVPP is selected for studying. The response time propertie of sensor arediscussed.The method through Ag colloid is easier and simplier than that of Agisland film. The assembly of silver colloid particles onto the fiber tip byN-metal bond formed a homogeneous and stable film. Self-assembled Agcolloid film had both the optical properties of colloidal particles and theconvenience of the solid substrate after absorbed onto the fiber tip. Itpreserved the aggregation at some degree while avoiding being subject toaggregating to deposit and the unstable property at the same time. It bothshowed the fine enhance ability and uses the character of the fiber.3. Laser-Induced Growth and Deposition of Ag Nanoparticle Film onFiber Tip for SERS Optical Fiber SensorLaser-induced deposition and growth of silver nanoparticles fromsilver ionic solution on an optical fiber tip are described. Comparing withother techniques, there are several advantages for this method. Firstly,laser as a powerful non-contacted tool can rapidly and efficiently inducethin metal film deposition. It is very facile to deposit Ag nanoparticles on afiber tip in a few minutes without any pretreatment such as coating t...