Sensors & Transducers, Vol. 27, Special Issue, May 2014, pp. 244-252 244 S S S e e e n n n s s s o o o r r r s s s & & & T T T r r r a a a n n n s s s d d d u u u c c c e e e r r r s s s © 2014 by IFSA Publishing, S. L. http://www.sensorsportal.com U-Shaped Fiber-Optic Detection Elements for Investigation of Photocatalytic Decomposition of Toluene Dissolved in Water 1 Vlastimil MATĚJEC, 1 Ivo BARTOŇ, 1 Jan MRÁZEK, 1 Ondřej PODRAZKÝ 1 Institute of Photonics and Electronics AS CR, v.v.i., Chaberska 57, 182 51 Prague 8, Czech Republic Tel.: +420 266 773 511, fax: +420 284 688 220 E-mail: matejec@ufe.cz Received: 23 November 2013 /Accepted: 12 January 2014 /Published: 26 May 2014 Abstract: 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. Copyright © 2014 IFSA Publishing, S. L. Keywords: Toluene detection, Photocatalytic decomposition, U-Shaped fiber, Polysiloxane membrane, Inclined collimated beam. 1. Introduction In last fifty years optical fibers have been applied in telecommunications, environmental protection, medicine, industry, etc. They are broadly used in telecommunication lines as transmission medium, light sources, amplifiers, couplers, etc. where they create performance for achieving high transmission speeds and bandwidths [1]. They have been tested for transmitting high powers of lasers for medicine, lighting, and heating [2-4]. Optical fibers have also been employed in different types of optical sensors for point, remote and distributed sensing especially for chemical sensors [5-9]. However, the ability of optical fibers to controllable transmit light to a particular place have been employed at chemical microreactors for photoreactions [10-12]. Such microreactors allow us to realize photoreactions with micromolar amounts of reactants under controlled illumination. For such a purpose capillary or photonic crystal fibers have been employed in which the air holes can be used as microreactors and the fiber core enables us to transmit light to reactants in the hole. Moreover, light absorbed or emitted by reactant molecules can be employed to detect temporal concentration changes in the holes which enable us to study reaction kinetics. Article number P_SI_509