Optical detection of toluene in water by using IGI fibers (original) (raw)
Related papers
Optical detection of toluene in water using an IGI optical fiber with a short sensing region
Sensors and Actuators B: Chemical, 2002
Optical detection of toluene in aqueous solutions by means of a sensor employing a 4 cm-long sensing region produced by dip-coating a thin dimethylpolysiloxane layer on the core of a fiber with an inverted parabolic-index profile was investigated. The toluene in solutions was detected through changes of the output signal from the fiber at a wavelength of 850 nm caused by induced changes of the refractive index of the fiber cladding. In experiments, two types of exposures were used-a static exposure, in which the fiber, which was initially in air, was for some time exposed to a solution in rest; and a dynamic exposure, in which the fiber which was initially in flowing water, was for some time exposed to a flowing solution. In 5-min static exposures and 2.5-3-min dynamic exposures detection limits in the low mg/l range were obtained. A possibility of improving the sensitivity by reducing the rate of sampling of the photodetected signal was shown. Effects associated with the observed cross-sensitivity of the fiber to water and an effect of a change of the solution temperature on the output signal were also examined. #
Detection of toluene dissolved in water by using PCS fibers excited by an inclined collimated beam
Sensors and Actuators B: Chemical, 2003
This paper reports results on the sensitivity of straight polymer-clad silica (PCS) detection fibers with short sensing parts coated with polysiloxane polymers to toluene dissolved in water. The detection was based on refractive index changes of the polymers induced by the penetration of toluene into them. These changes were detected by measuring changes of the output power from the detection fibers excited by an inclined collimated beam at 630 nm.
Sensors and Actuators B: Chemical, 2003
This paper deals with the effect of hydrodynamic conditions on the detection of toluene dissolved in water by means of fibers with a truncated parabolic inverted-graded index (IGI) profile. The detection is based on refractive-index changes of a detection layer of polydimethylsiloxane (PDMS) applied on the fiber which are induced by penetration of toluene into the layer. The dependence of the response of the sensing fiber placed in a flow cell on the flow velocity of the detected aqueous solution of toluene has been investigated. The sensing fiber was successively exposed to flows of distilled water and aqueous solutions of toluene. The fiber responses were measured for three chosen concentrations of the toluene solutions and for five flow velocities of the solutions. From these results the dependence of the relative decrease of the output signal on the flow velocity was determined. It has been found that the magnitude of output signal changes is approximately proportional to the solution concentration and the rate of the signal changes in the tested concentration range depends approximately linearly on the solution flow velocity. #
Detection of toluene by using specially coated PCS fibers excited by an inclined collimated beam
Materials Science and Engineering: C, 2002
This paper deals with the detection of toluene dissolved in water by means of straight polymer-clad silica (PCS) detection fibers with short detection regions. The approach is based on the detection of refractive index changes of the polymer cladding induced by toluene. The fibers were excited by an inclined collimated light beam with the aim of finding an alternative to the coiled axially excited fibers which would achieve similar detection sensitivity. Two types of siloxane polymers, thermally curable one with the refractive index of 1.407, and UV curable polymer with the refractive index of 1.423 were used for the modification of fiber properties in the detection area. The polymers were applied as thin layers (5 -20 Am) on the silica core of the sensing fibers. Angular distributions and time -responses of the output optical power to changes of toluene concentration in solutions were measured. Sensitivity curves were drawn on the basis of these results. The best value of the detection sensitivity of about 0.006 dB/(mg/l) was achieved with the UV curable siloxane. This value corresponds to the detection limit of toluene in water of about 15 mg/l. Sensing fibers with beveled input ends were prepared. They exhibited the same sensitivity as fibers with the end perpendicular to the fiber axis when they were excited by the uninclined beam. D
Long period grating based toluene sensor for use with water contamination
Sensors and Actuators B: Chemical, 2014
A demonstration of the use of a calix[4]resorcinarene coated optical fibre long period grating sensor for the detection of toluene in water is presented. Monitoring water quality both for domestic use and around industrial sites is critical to the preservation of clean water provision. Here we show that, by using a fibre optic based sensor system, water quality monitoring can be carried out without the requirement for water sampling or pre-concentration. The results presented demonstrate that this proof-of-concept sensor is capable of sensing ∼100 ppm concentrations of toluene with semi-selectivity and low (<10 ppm) variation.
Sensors and Actuators B: Chemical, 1997
A fiber-optic sensor for the monitoring of organic pollutants in air and water is presented. The UV absorption spectra are used for the measurement of concentration via the evanescent field of silica fibers. Special hydrophobic polymers which are solvents for hydrocarbons are used as cladding materials. The fibers coated with the tested siloxanes and Teflon show different sensitivities and time response behaviour. Further improvement of the sensitivity is reached through coiling of the fiber.
The Open Environmental & Biological Monitoring Journal, 2008
Recent preliminary studies have demonstrated the feasibility of using Single-Walled Carbon Nanotubes (SWCNTs) as sensitive coatings of optical fiber sensors for the detection of chemical traces in water at room temperature. A low-finesse extrinsic Fabry-Perot configuration was adopted as sensing scheme and Langmuir-Blodgett thin SWCNT films have been integrated to form the sensing optical cavity. This contribution reports on the improvement of the performance of such SWCNTs-based chemo-optic transducers based on a proper choice of the number of carbon nanotube monolayers. The results here shown reveal a strong enhancement in term of sensor sensitivity of more than one order of magnitude, combined with a significant reduction of the response times. The achieved sub-ppm resolution, the response rapidity, and the complete and fast recovery of the initial output signal corresponding to the condition of uncontaminated water reveal the potentiality of the improved version of the sensor to be applied for water monitoring applications.
DOAJ (DOAJ: Directory of Open Access Journals), 2014
Several fiber-optic sensing elements consisting of a U-shaped fiber coated by a detection membrane of polydimethylsiloxane have been prepared with arc radii from 0.3 to 2 mm. Angular distributions of the output optical power from the elements have been measured. A high decrease of the transmitted power of paraxial rays has been observed for elements with arc radii below 1 mm. When elements with arc radii above 1 mm were excited by an inclined collimated beam and brought into contact with toluene solutions a maximum sensitivity of 1 dB/mM was determined. Sensing elements have been tested for monitoring the decomposition of toluene dissolved in water by means of photocatalytic TiO 2 nanoparticles applied on silica optical fibers. Differences between concentration data obtained by UV spectrophotometry and those obtained by the element on levels of 10-15% have been observed.
Optochemical fiber sensor for Toluidine Blue detection in high turbidity media
Sensors and Actuators B: Chemical, 2015
We report the analytical performance of an optochemical fiber optic sensor for the detection of dyes in aqueous media with high turbidity. Specifically, the analytical performance of this sensor was evaluated for the quantitative detection of Toluidine Blue (TB) in aqueous solution and also in turbid suspensions of TiO 2 anatase nanoparticles. The detection limit attained was 5 x 10-7 M with a linear sensitivity of 7 × 10 4 M-1 across a linear range from 5 x 10-7 M to 5 x 10-6 M. We used the optochemical sensor for two main purposes: 1) In-situ characterization of the adsorption isotherm of Toluidine Blue on TiO 2 nanoparticles; 2) In-situ characterization of the photodegradation of Toluidine Blue mediated by UV irradiation of TiO 2 nanoparticles. The main aim of this report is to establish the construction and performance of a simple, cheap and small optochemical sensor with clear applications in the field of dye-polluted environmental monitoring.
Fiber-optic detection of chlorine in water
Sensors and Actuators B: Chemical, 2009
Monitoring of the chlorine content represents important issue of the control of water quality. Crucial points of this control are detection of low chlorine concentrations around 1 ppm and reversibility of chemical reactions between strong oxidation agent, chlorine and opto-chemical transducers used for the detection. This paper deals with fiber-optic detection of chlorine in water by using a commercially available absorption transducer o-phenylenediamine (o-PDA) electrochemically immobilized onto fiberoptic substrates coated with Indium-Tin-Oxide (ITO).