Fabrication and Properties of Doped Porous Polysiloxane Sol-Gel Layers on Optical Fibers (original) (raw)
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Sensors and Actuators B: Chemical, 1997
Materials for coating silica optical fibers which are W-curable and consist of a siloxaue chain modified ,with reactive acrylate groups are prepared by the sol-gel method. The value of the refractive index of these organically modified polysiloxanes (ORMOCERs) is controlled by chemical modification of input alkoxysilane precursors in the range 1.48 to 1.56. Several sensing structures based on silica optical fibers coated with the ORMOCERs have been designed and fabricated. Fibers with a core of multicomponent glass, with pure silica core, with pure silica core coated with a thin porous Si-0-Ti sol-gel layer and with a composite optical core have been fabricated and characterized by measuring their attenuation. The sensitivity of the ORMOCER coatings to solvents and to CO2 dissolved in water has been determined in immersion experiments. A new absorption band around 320 nm arising from interaction of the ORMOCERs with SO2 has been observed, which causes the sensitivity of the ORMOCER layer to gaseous SO,.
Pyrene-doped polyorganosiloxane layers over commercial glass fibers
Journal of Fluorescence, 1999
Commercial glass fibers have been subjected to different activation treatments under neutral and acidic conditions to achieve different coating degrees when silanized with y-aminopropyltriethoxisilane (APES). A fluorescent sulfonamide (PSA) was formed between the amine residue and a fluorescent probe, pyrenesulfonyl chloride (PSC). Reflectance UV-Vis spectra of the pyrene-doped fibres show that pyrene is present in the form of preassociated dimers when the coating degree is low. Emission and excitation fluorescence spectra reveal the existence of a charge transfer groundstate complex with exciplex emission at 460-515 nm and absorption red-shifted with respect to the S 0 -> S 1 transition. Lifetime measurements yield three lifetimes, which are assigned to dimer, exciplex, and monomer emission. From the photophysical data it is concluded that the fibers with the highest silane content have an open structure with the highest fraction of isolated fluorescent moieties.
Development Of A Porous Silica Film By Sol-Gel Process
2011
In the present work homogeneous silica film on silicon was fabricated by colloidal silica sol. The silica sol precursor with uniformly granular particle was derived by the alkaline hydrolysis of tetraethoxyorthosilicate (TEOS) in presence of glycerol template. The film was prepared by dip coating process. The templated hetero-structured silica film was annealed at elevated temperatures to generate nano- and meso porosity in the film. The film was subsequently annealed at different temperatures to make it defect free and abrasion resistant. The sol and the film were characterized by the measurement of particle size distribution, scanning electron microscopy, XRD, FTIR spectroscopy, transmission electron microscopy, atomic force microscopy, measurement of the refractive index, thermal conductivity and abrasion resistance. The porosity of the films decreased whereas refractive index and dielectric constant of it `increased with the increase in the annealing temperature. The thermal con...
Sensitive films based on porous sol-gel silica
Optical Fibers and Their Applications 2014, 2014
The paper is devoted to the sensitive films for application in chemical sensors. These films, made of the sol-gel derived porous silica, were fabricated via a sol-gel dip-coating method. We have obtained silica layers of the minimum refractive index of ~ 1.22 and porosity ~47%. These layers were sensitized with a pH indocator -bromocresole purple. The indicator was introduced into porous silica layers by means of impregnation. Methods and results of characterization of porous silica films, before and after sensitization are presented in this paper. It was shown that films are very sensitive toward ammonia.
Optical fibre sensor coated with porous silica layers for gas and chemical vapour detection
Sensors and Actuators B: Chemical, 1997
Fibre optic sensors have been conceived in new technologies for detecting very small amounts of chemical, gaseous and biological species. Recently, new polymer-clad silica (PCS) fibres coated with thin porous silica layers have been developed. These porous layers have been prepared by the sol-gel method using the dip-coating technique. In this work, this new material has been investigated for detecting gases and vapours. By choosing a fixed incident angle, variation of light power transmitted through the fibre is detected as the vapour or gas to be detected is sorbed in the porous silica layer. Good sensitivity and reversibility have been obtained for this system. Moreover, both the response time and the desorption time have been found less than 2 min. Chlorinated hydrocarbons such as trichloroethylene, carbon tetrachloride, chloroform, dichloromethane and alkanes such as propane, butane and hexane can be detected with detection limits of 0.6, 1.5, 1.7, 4, 25, 10 and 5% respectively. © 1997 Elsevier Science S.A. 0925-4005/97/$17.00 © 1997 Elsevier Science S.A. All rights reserved. PII S 0 9 2 5 -4 0 0 5 ( 9 7 ) 0 0 1 7 2 -X A. Abdelghani et al.
Textural characterization of porous silica films prepared by the sol–gel process
Porous thin silica films were prepared on glass plates using the dip-coating process from colloidal solutions of silicon alkoxide dissolved in ethyl alcohol. The influence of solution parameters such as viscosity, pH, dipping velocity and thermal treatment temperature on the film formation was determined. The films were adherent, transparent and free of cracks. The porosity was estimated by the Lorentz–Lorenz equation using the refractive index measured by UV–vis spectroscopy and compared with values obtained by the nitrogen adsorption method. For a certain thickness and porosity, it was possible to prepare antireflective layers, which were identified by the transmission spectra in the visible region.
Acta Physica Polonica A, 2011
The work presents the optical properties of porous silica thin films prepared by TEOS sol-gel method. The films were deposited onto glass substrate using dip-coating technique. The spectroscopic ellipsometry measurements have been performed to determine the optical constants of the films. This technique also enabled evaluation of the depolarization for the investigated layers. Additionally, the spectrophotometric measurements of transmittance and reflectance by the use of integrating sphere and reflectance probe have been made with the aim of possible application of the films as antireflective coatings.
IOSR Journal of Engineering (IOSRJEN) Sol-Gel for Chemical Fiber Sensor Low Cost a
Sol-gel materials may found plenty of applications, e.g., as carriers for various substances, which can be exploited for sensing purposes or as drug releasing carriers. In this work, the fluorescence properties of two photosensitizers immobilized in silica based sol-gel materials were examined. Sol-gel derived silica possess many promising features, including room-temperature preparation procedure, porosity, chemical and physical stability. The material preparation procedure is described and practical remarks on silica-based sol-gels are included. It is reported that sol-gels with entrapped various molecules may be used in construction of implants and coatings with bioactive properties. It is shown how to exploit the sol-gel production route for construction of sol-gel coated fiber optic applicators for chemical sensor. We used a Sodium silicate(Na 2 O 3 Si) instead of the Trathyl Ortho Silicate (TEOS ) (Si (OC 2 H 5 ) 4 ).We study the optical haracteristics for this sample. The sol gel was tested to detect ammonia gas.
Porous silicon and polymer materials for optical chemical sensors
SPIE Newsroom, 2010
The optical characteristics of porous materials depend on their structural properties (porosity, pore size, and pore distribution). Specifically in materials with air-filled pores, the effective refractive index is a weighted average of the refractive indices of the relevant material and air, which is thus directly related to the material's porosity. Mesoporous materials, such as porous silicon and porous polymers, have therefore been exploited to create photonic devices, from simple interference filters to exotic photonic-bandgap (PBG) structures. 1, 2 In addition, the high internal surface area of porous materials provides an excellent host medium to immobilize analyte-specific recognition elements through sequestration. 3 Interactions of the analyte molecules with the sequestered recognition elements often alter the effective index or other optical properties. These optical variations can be employed as a simple and straightforward transduction approach in optical sensing.
Journal of Sol-Gel Science and Technology, 1994
A simple, low-cost technique for fabricating reagent-mediated fibre-optic chemical sensors (optrodes) is described and the performance of a range of such sensors is reported. The technique is based on coating an unclad portion of an optical fibre with a microporous glass film prepared by the sol-gel process. Although tip-and side-coating are both possible with this technique, the latter, which employs evanescent wave interactions, offers particular advantages in terms of sensor performance, control of sensitivity and quality of coating. The sol-gelderived film is used to provide a robust support matrix in which analyte-sensitive dyes are entrapped and into which smaller analyte molecules may diffuse. The benefits of this sol-gel approach to sensor fabrication are illustrated by results from a range of sensors for pH, ammonia and oxygen based on both evanescent wave absorption and evanescent wave excitation of fluorescence.