Grzegorz Sudolski

Thymol blue immobilized on tapered fibers as optical transducer for pH sensing

The present work is concerned with the optical characterization of an evanescent wave sensor for pH detection. First, the interaction between the solution containing the acid-base indicator and the fiber core was investigated. Then, the acid-base indicator, thymol blue, was covalently immobilized on the core of a 200/380 micrometers fiber by means of a silylation process of the glass surface. The fiber core surface was modified along a section of 8 mm. A comparison was made using both bare and tapered fibers, with a tapering ratio (fiber diameter/waist diameter) of 2.3. An enhancement in sensitivity of a factor 6 was observed with tapered fibers in the 1/2.5 range, and a sensitivity of 0.05 pH units was attained.

Fiber optic sensor for broad range pH detection

In the paper the hybrid optical fibre pH sensor based on absorption and refraction is presented. As an optical transducer pH-sensitive metyl orange dye was exploited. Additionally, variations of the refractive index of the porous silica film with the pH of solution were also utilized. The film, in which the dye was encapsulated, was prepared by means of the sol-gel method and deposited onto the fibre core. It was found that the sensitivity for acidic (2÷6) and basic (7÷10) ranges were 1,0 dB/pH and 3,5 dB/pH, respectively.

Signal of the evanescent wave sensor as a function of its length and the refractive index of the surrounding medium

The paper describes an evanescent wave sensor model operating far from the modal steady state. Assuming that of the numerical aperture varies exponentially with the fibre length and the light losses are proportional to the local and fibre numerical apertures ratio, the sensor description was evaluated. Experiments, in which the sensor absorbance versus the refractive index of the medium surrounding the fibre core and the fibre sensing section length, were made to confirm the theoretical model of the sensor and good agreement was observed.

The coumarine derivative as UV/VIS transducer in optical fiber UV sensor

In the paper the results of investigation of luminescence properties of the coumarine derivative used as an optical UV/VIS transducer in the optical fiber UV sensor are presented. It was found that this compound probably chemically reacts with the polymer matrix in which was dissolved. The arising compound reveals luminescence properties other than initial coumarin derivative and is highly photostable.

Genetic algorithms for optimization of optical fiber UV sensor

In the paper simple genetic algorithm (SGA) as well as its modifications were applied for optimization of an optical fiber UV sensor construction. Influence of the algorithm parameters i.e. the population size, the probability of crossover and mutation from the point of view of algorithm efficiency is discussed herein.

Optical fiber probe for Cu2+ detection

The probe for the copper ions detection was investigated. As an optical transducer porphyrines were used H4TPPS4 and cationic H2TMePyP. The porphyrines were entrapped in a sol-gel film deposited directly on optical fiber core. The performance of the oprtodes was tested. The influence of the response time on gelation conditions of the sol-gel matrix was also investigated.

Fiber optic pH sensor with sol-gel films

The influence of surface properties of sol-gel derived silica on pH sensing is presented. It is observed that the surface charge of silica, caused by pH change, leads to absorption of cations on the porous silica surface. As a consequence, one can observed an increase of refractinve index of the sol-gel material, hence, its optical properties and light propagation conditions. Since the effect is pH-dependent and its magnitude is so strong, it can even be exploited for pH sensing. Theoretical considerations correlate with results of surface charge and optical properties of a model of pH sensor measurements.

5, 10, 15, 20-tetrads (n-methylpridium-4-v1)-porphtine (H2TmEpYp)-based evanescent wave probe for Cu2+ ions detection

The evanescent wave optical fibre probe for Cu2+ ions detection was elaborated. As an optical transducer a porphrine (H2TMePvP) was used. The detection limit of the probe as evaluated to be 5x10-5 mol/1 (3ppm).