Preparation And Performance Study Of Sensitive Film In The Optical Fiber Iron Ion Sensor

The optic fiber sensor receives more and more attention because of a series ofunique technology superiority of it, such as small bulk, light weight, anti-EMI, easilymultiplexed, remote sensing etc. It can be used in military, chemical, medicine andother special environment. It can work under the harsh environments of strong EMI,flammable and explosive, such as large machinery, petroleum chemical industry, mineetc. Recent years, the optic fiber sensor has been the focus of research as an idealchemical sensor. The fiber cladding is replaced by self-made sensitive film for thesensing part of this kind of sensor. The film can be made by three usual methods,sol-gel, embedding and Layer by layer self-assembly. Electrostatic layer by layerself-assembly technology was used to form film on the surface of fiber optical. Theself-assembled film, which is sensitivity of iron ion as a result of adding iron ionindicator to the film, is obtained in this text.Electrostatic self-assembly technique has the advantage of simple operation, lowcost, environmental friendly, what is more, many material can be used as raw, thethickness and structure of the film is adjustable, and the film’s strength and density ishigher compared with others. It is wildly used in the fields of catalysis, drug releaseand sensor etc. We make multilayer films with two poly diallyl dimethyl ammoniumchloride(PDDA) and poly (sodium4-styrenesulfonate)(PSS) on the quartz plate ofhydroxylation treatment with negative charge. Then we add iron ions sulfosalicylicacid and disodium1-nitroso-2-naphthol-3,6-disulfonate monohydrate to the films anddo the UV visible absorption test and Atomic force microscopy morphology to thefilms.Through comparing the index of this two methods, we can get the best method ofassembling films, which is more sensitive and regularity to the iron ion, and use it inthe field of the assemble of fiber-sensitive film and the test to know how thefiber-sensitive film response to the iron ion. In this text, we have done a research on PDDA/PSS self-assembly process byUV-VIS Spectrum and Contact angle measurement. By Ultraviolet Spectrophoto-meter, results showed that with the increase of layers of PDDA/PSS film, the UVabsorbance increased with perfect linear relation. The wetting property of PDDA/PSSPEMs by contact angle measurement demonstrated that Polyelectrolyte multilayerscomposed of two distinct zones.Zone is premonitory layer comprised of one or a fewpolyelectrolyte layers close to the substrate. ZoneⅡis the “bulk” film comprised ofregularly altenating deposition of two oppositely charged polyelectrolytes.Secondly, we do iron ion response test of sensitive film to which add two kinds ofindicator prepared in polyelectrolyte PDDAand PSS respectively and do UV visibleabsorption test and Atomic force microscopy morphology to different sensitive filmsobtained by adding different content of indicators. The results shows that：(1) thesensitive film added iron ion indicator can enhanced sensitivity of film on iron ion;(2)the sensitive film assembly with two kinds of indicator both has the response behaviorto iron ion, but compare with the regularity of two kinds of sensitive film′s responsebehavior to the iron ion,the film added the indicator disodium1-nitroso-2-naphthol-3,6-disulfonate monohydrate is more obvious than the film addedthe indicator sulfosalicylic acid, so choose the preparation method of the sensitive flmadded the indicator disodium1-nitroso-2-naphthol-3,6-disulfonate monohydrate usedin the experiment to study the response of optical fiber sensing film subsequent to ironions.Finally, we get the sensitive film using disodium1-nitroso-2-naphthol-3,6-disulfonate monohydrate on the optical fiber. Throughobserving the result of the reaction between the sensitive film and differentconcentration gradient of iron ions, we realize optical power output varies obviously.The sensitivity of the film is good, and it is linear connected with the level of iron ions.So, we obtain the relationship of the wave-parameter of the sensitive film and thelevels of iron ions.