Towards microstructured optical fibre sensors: surface analysis of silanised lead silicate glass

Abstract

Author DepositionAllowed Deposition by the author(s) When the author accepts the exclusive Licence to Publish for a journal article, he/she retains certain rights concerning the deposition of the whole article. He/she may: Deposit the accepted version of the submitted article in their institutional repository(ies).There shall be an embargo of making the above deposited material available to the public of 12 months from the date of acceptance. There shall be a link from this article to the PDF of the final published article on the RSC's website once this final version is available. May 2016Journal Name internal surface of the fibre structure. In characterising the fluoroionophore attachment, we observe that the fluorescence intensity from fluorescence imaging, the atomic nitrogen percentage measured by X-ray photoelectron spectroscopy (XPS), the carbonyl bond component (287.5 eV) in the XPS high resolution carbon spectrum, and Principal Component Analysis (PCA) of the time-of-flight secondary ion mass spectrometry (ToF-SIMS) data can be used to provide relative quantification of the concentration of an 15 attached fluoroionophore. We also show the first use of ToF-SIMS imaging and depth profiling of the Pb content within a glass substrate to provide information on the coverage provided by the coating and the relative thickness of an organic coating. Combined, these techniques provide a comprehensive picture of the coated glass surface that facilitates fibre sensor development.

Novel polymer functionalization method for exposed-core optical fiber

“…Some important factors to consider when choosing a functionalization method are the conditions in which the sensor is to be used (for example polyelectrolytes have been found to wash off in acidic conditions [11]), and any additional optical losses that might occur as a result. Also, achieving uniform covalent binding of the sensor molecules along the constrained surface of MOFs in a consistent manner is challenging using silanes or polyelectrolytes [5,8], since results are highly dependent on experimental conditions (temperature, concentration, solvents, hydration and reaction time) as well as pre-and post-treatment processes [5,[10][11][12]. These factors can diminish sensor performance, reducing the achievable light-matter interactions, which in turn decreases sensitivity.…”

“…For such applications it is necessary to immobilize sensor molecules on the glass surface of the MOF exposed core, which can then be used directly within the medium as a sensor without requiring prior pre-mixing of analyte with sensor molecules. Functionalization methods traditionally used include silanes [7,8] or polyelectrolytes [9,10], which provide a functional group on the surface to which the sensor molecules can be covalently attached. These processes require several steps that typically take many hours to perform, due to the incubation times needed to achieve consistent maximized binding efficiency [8,10].…”

“…Functionalization methods traditionally used include silanes [7,8] or polyelectrolytes [9,10], which provide a functional group on the surface to which the sensor molecules can be covalently attached. These processes require several steps that typically take many hours to perform, due to the incubation times needed to achieve consistent maximized binding efficiency [8,10]. Some important factors to consider when choosing a functionalization method are the conditions in which the sensor is to be used (for example polyelectrolytes have been found to wash off in acidic conditions [11]), and any additional optical losses that might occur as a result.…”

Functionalization of exposed core fibers with multiligand binding molecules for fluorescence based ion sensing

“…In order to couple the SP molecules to the exposed core surface, 3-aminopropyltriethoxysilane (APTES) was used which covalently bonds to hydroxyl groups on the silica core surface to provide free amine groups for covalent bonding with the SP carboxylic acid group. 7 The fiber was prepared for APTES functionalization by flame sealing the holes at each end, then clean and hydroxylate the outer surface by immersion in 70% nitric acid for 16 hrs followed by 2 hrs in 70/30 piranha solution (concentrated sulfuric acid and hydrogen peroxide). After rinsing and drying, the prepared fiber was immersed in 5% APTES-toluene solution for 2 hrs then rinsed with toluene and acetonitrile.…”

“…6 To enable direct sensing measurements it is necessary to immobilize sensor molecules on the glass surface of the MOF exposed core. Some of the functionalization methods typically used to achieve this include silane 7 or polyelectrolyte 8 which provide a functional group on the surface to which the sensor molecules can be covalently attached. Fluoroionophores such as 8-Hydroxyquinoline (8-HQ) react with Al 3+ to form a rigid multiligand complex which is strongly florescent when excited at the correct wavelength.…”