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Application Of Polyelectrolyte Layer-by-layer Self-assembly Multilayers On Fiber-optic Sensors

Posted on:2012-01-16Degree:MasterType:Thesis
Country:ChinaCandidate:M J YinFull Text:PDF
GTID:2178330332983608Subject:Polymer Chemistry and Physics
Abstract/Summary:PDF Full Text Request
Of many nano-fabrication methods, the water-based layer-by-layer (LbL) assembly technique, offers the finest control and tunability of materials properties and architecture at the nanometre scale. Because the materials that can be chosen for LbL process are ranging widely, various functional multilayers could be obtained by the LbL technique. In this study, optical fiber was used as substrate for LbL assembly, preparing various fiber-optic sensors to detect pH, metal ion and relative humidity, respectively.The process of preparing multilayers on quartz slides and AT-cut quartz crystals with gold electrode was followed by UV-vis spectroscopy and quartz crystal microbalance (QCM), respectively. It was shown that multilayers, such as (PDDA/PAA)1.5(PAA/P4VP)10 multilayers, (P4VP·HCl/PSS)10 multilayers and (P4VPHCl/PVS)10 multilayers and so on, display a linear growth with bilayer number, which indicates that the films are uniform. Moreover, the surface morphology of multilayers was characterized by atomic force microscope (AFM) and scanning electronic microscope (SEM). It is found that the surface roughness of multilayers influences the respond time of fiber-optic sensor, that is the larger the surface roughness, the shorter the respond time.(PAH/PAA)25 multilayers were LbL self-assembled onto the surface of thin-core fiber modal interferometer (TCFMI), fabricating a fiber-optic pH sensor. When immersed into different pH solution, the wavelength of TCFMI pH sensor increased firstly with the pH growth, and then it became decrease as pH still growing. Moreover, the sensitivities of the fabricated TCFMI pH sensor were 0.32 nm/pH unit and-0.45 nm/pH unit for acid and alkali solutions, respectively. And respond time of it was 120 s. Then polyelectrolyte complex (PEC) was introduced into LbL multilayers. Due to the large size of PEC nanoparticles, the performance of new TCFMI pH sensor was greatly improved. The sensitivities of it were 0.6nm/pH unit and-0.85 nm/pH unit for acid and alkali solutions, respectively. And respond time of it was only 30 s.(PDDA/PAA)1.5(PAA/P4VP)10 multilayers were LbL self-assembled onto the surface of TCFMI, fabricating a fiber-optic heavy metal ion sensor. The sensor could detect many kinds of heavy metal ion, such as Cu2+, Fe2+ and Zn2+. Its limit of detection (LOD) was 10-8 M and the respond time was 60 s. More importantly, it could be used repeatedly. Another TCFMI metal ion sensor based on (P4VP·HCl/PSS)10 multilayers was fabricated. The sensor showed high selectivity to Hg2+ and it displayed the best performance when the HgCl2 solution was at pH=5. And its LOD was 10-9 M and the respond time was 30 s.(P4VP·HCl/PVS)10 multilayers were self-assembled on the surface of fiber Bragg grating (FBG) by LbL technique to prepare a TCFMI-FBG humidity sensor. The sensor was tested with the relative humidity ranging from 20% to 90% at three different temperatures:20℃,40℃and 60℃. The experiments indicated that it did have temperature compensation effect as a humidity sensor. The sensitivity of it was 0.1nm/1% relative humidity and the respond time was 2s.
Keywords/Search Tags:polyelectrolyte, polyelectrolyte complex, layer-by-layer self-assemble, thin-core fiber modal interferometer, fiber-optic pH sensor, fiber-optic heavy metal ion sensor, fiber-optic Hg2+ sensor, fiber-optic humidity sensor
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