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Real-time process monitoring is still relatively scarce but is fundamental to provide in-situ information about different chemical and electrochemical processes. Particularly, electrochemical filtration has received growing attention in recent years due to the wide range of applications in which it can be successfully employed. Electrochemical removal is considered as an attractive methodology for the treatment of wastewater due to its efficiency in the removal of a huge number of contaminants. In this work, the development of a new device based on the use of UV–vis bare optical fibers in long optical pathway configuration allows us to monitor continuously the electrochemical degradation process during the filtration of different compounds. Spectroelectrochemistry additionally supplies quantitative information allowing us to calculate the efficiency of the electrochemical filtration process. The material selected to fabricate the electrochemical filter was single-walled carbon nanotubes that display not only high physical and chemical stability, but also high electrical conductivity. Therefore, the combination of electrochemical degradation methods, free-standing single-walled carbon nanotube filters and operando spectroelectrochemical techniques makes this outstanding device very interesting in the study of different molecules. As proof of concept, three different systems have been studied to validate the cell and demonstrate the good performance of the spectroelectrochemical device: o -tolidine (reference system), indigo carmine (organic dye), and 4-nitrophenol (hazardous pollutant). [ABSTRACT FROM AUTHOR]

Novel double-doped polymer optical fibers have been fabricated by a bulk polymerization and fiber drawing process for fluorescent fiber solar concentration applications. Poly(methyl methacrylate) has been used as host material and a combination of organic dyes (Perylene/Lumogen Orange/Coumarin 1/Coumarin 6)) and metalorganic materials (Eu(TTFA) 3 Phen) have been employed as dopants. A concise polymer analysis has been carried out, and the obtained fibers have been characterized under standard AM 1.5 G solar simulator excitation. The output power generated at one of the end surfaces of each of the fibers have been measured for 6 cm illuminated fiber length, obtaining a concentrated intensity of 0.31 mW/mm 2 and a fiber conversion efficiency of 0.41% in the best case. Besides, the performance of the fabricated fibers under different weather scenarios have been studied, showing good response at all the simulated day-conditions. Active fiber lengths of more than 6 m have been successfully tested, obtaining output intensities of 1.3 mW/mm 2 . Good performance under constant excitation has also been reported during photostability experiments. The results obtained may have a strong impact in the field of luminescent solar concentrators as they offer a promising cost-effective route to green energy production. [ABSTRACT FROM AUTHOR]

Optical signal amplification in the waveguiding structure of optical fibers can be used for optical telecommunication systems and new light sources constructions. Organic dyes doped materials are interesting for new applications in polymeric optical fibers technology due to their benefits (efficient fluorescence, high absorption cross section, and easy processing). This article presents a numerical simulation of gain in poly(methyl methacrylate) optical fiber doped by Oxazine 170 Perchlorate. The calculated gain characteristic for the used dye molar concentration (0.2·10-6–1.4·10-6) and pump power (1–10 kW) is presented. The fabricated fluorescent polymeric optical fiber is also shown. The presented analysis can be used for optical amplifier construction based on dye-doped polymeric optical fiber (POF). [ABSTRACT FROM AUTHOR]

A stress sensor based on a dye-doped polymeric optical fiber is able to detect stress by simple comparison of two luminescence peaks from a pair of energy transfer organic dyes. Coumarin 540A (donor) and Rhodamine 6G (acceptor) were doped in the core and cladding of the fiber, respectively. For various laser wavelengths, the change in the near-field pattern and visible emission spectrum upon variation in the fiber bending diameter was evaluated. From a comparison with a lownumerical-aperture fiber, it is shown that the sensitivity of the sensor is controllable by optimization of the waveguide parameters. [ABSTRACT FROM AUTHOR]

The present work describes the fabrication and characterization of an optical fiber pH sensor using a sol--gel technique. The sensing head configuration is incorporated using a short section of no-core fiber, coated with tetraethyl orthosilicate and spliced at the end of a single mode fiber with a bulge. Different types of indicators (bromophenol blue, cresol red, and chlorophenol red) were used to achieve a wide pH range from 2 to 13. High sensitivities of the fabricated device were found to be 1.02 and -0.93 nm/pH for acidic and alkaline solutions, respectively. From the characterization results, it was noted that there is an impact of ionic strength and an effect of the temperature of liquid on the response characteristic, which is an advantage of the existing device over the other pH sensors. The fabricated sensor exhibited good reflection spectrum, indicating a blueshift in resonance wavelength for alkaline solutions and a redshift for acidic solutions. [ABSTRACT FROM AUTHOR]

The article presents fabrication and spectroscopic characterization of 7-(Diethylamino)coumarin doped polymeric fibre. The poly(methyl methacrylate) (PMMA) was chosen as it assures direct doping possibility and excellent optical properties in fluorescence spectrum of used dye. The fabricated polymer exhibits an intense luminescence (at dye concentration 1.2 × 10 mol/l) in the range 505-537 nm (exc. 405 nm). Moreover, he coumarin doped PMMA fibre 600/1200 µm (doped core/cladding) fibre was fabricated and characterized. Presented fluorescence spectrum modification possibility can be used for new optical fibre construction optimization. [ABSTRACT FROM AUTHOR]

Polymer optical fibers (POFs) doped with organic dyes can be used to make efficient lasers and amplifiers due to the high gains achievable in short distances. This paper analyzes the peculiarities of light amplification in POFs through some experimental data and a computational model capable of carrying out both power and spectral analyses. We investigate the emission spectral shifts and widths and on the optimum signal wavelength and pump power as functions of the fiber length, the fiber numerical aperture and the radial distribution of the dopant. Analyses for both step-index and graded-index POFs have been done. [ABSTRACT FROM AUTHOR]

[Display omitted] • SiO 2 , TiO 2 , and SiO 2 -TiO 2 are synthesized and encapsulated by a mixture of four organic dyes by sol-gel method at (60 °C–80 °C). • Crack-free morphology, surface roughness, and thermal stability is attributed to the effect of dyes immobilization on the host matrices. • The sensitivity ∼ 16.34 a.u./pH for d -SNPs, 133.06 a.u./pH for d -TNPs, and 45.14 a.u./pH for d -STNPs matrix is reported. • The fast time response is estimated as 0.35 s, 0.33 s, and 0.31 s in pH 12 for d -SNPs, d -TNPs, and d -STNPs matrices, respectively. Owing to opto-chemical sensing, three matrices i.e., SiO 2 , TiO 2 , and SiO 2 -TiO 2 are synthesized and a mixture of four different organic dyes encapsulated in them through the sol-gel method. Thermally stable, large surface area 434 m2/gm, 197 m2/gm, 332 m2/g, and refractive index 1.49, 1.8, 1.5 at 632 nm are observed for d -SNPs (dyes encapsulated silica nanoparticles), d -TNPs (dyes encapsulated titania nanoparticles), and d -STNPs (dyes encapsulated silica-titania nanoparticles), respectively. When the evanescent field interacts with the fiber optic coating, absorption varied due to pH change and the output intensity is recorded as a sensor response in terms of transmission. The prepared sensors exhibited linear response, non-leachability, and stability towards high pH 12. The fast time response is estimated ∼ 0.35 s, 0.33 s, and 0.31 s in pH 12 for d -SNPs, d -TNPs, and d -STNPs, respectively. Therefore, these prepared optical fiber sensing devices have the potential for practical pH sensing applications. [ABSTRACT FROM AUTHOR]

Abstract: Some pH sensors based on optical fibers use organic dyes which are sensitive to the pH levels. Such dyes are deposited over the fiber and they are supported by a matrix, typically SiO2. In the present work there is introduced the fabrication and characterization of a pH sensor based on a multimodal optical fiber that uses a sensing film deposited by the sol–gel technique (immersion method). The TiO2:dye sensing film was obtained from a precursor solution of titanium tetra-isopropoxide (TTIP) doped with different organic dyes: brilliant green, rhodamine 6G, rhodamine B and coumarin. TiO2 was used since it is more resistant and it has a longer lifetime than SiO2 films. Therefore it can be expected than such time would be longer for this kind of sensors. It was found that each dye is sensitive to different pH ranges so that with the combination of all of them it is possible to cover a dynamic range of pH levels that varies from 2 to 12. Furthermore, there was found that the device sensitivity increases with a decrease of the operation wavelength. [Copyright &y& Elsevier]

In this paper, useful models that enable time-efficient computational analyses of the performance of luminescent solar concentrators (LSCs) are developed and thoroughly described. These LSCs are based on polymer optical fibers codoped with organic dyes and/or europium chelates. The interest in such dopants lies in the availability of new dyes with higher quantum yields and in the photostability and suitable absorption and emission bands of europium chelates. Time-efficiency without compromising accuracy is especially important for the simulation of europium chelates, in which non-radiative energy transfers from the absorbing ligands to the europium ion and vice versa are so fast that the discretization in time, in the absence of some simplifying assumptions, would have to be very fine. Some available experimental results are also included for the sake of comparison. [ABSTRACT FROM AUTHOR]

Abstract: Fiber-coupled organic plastic scintillators enable dose rate monitoring in conjunction with pulsed radiation sources like linear medical accelerators. The accelerator, however, generates a significant amount of stray ionizing radiation. This radiation excites the long optical fiber cable (15–20m), connecting the scintillator with the optical detector circuit, causing parasitic luminescence in the optical fiber. In this paper we propose a method for circumventing this problem. The method is based on the use of an organic scintillator with a long luminescent lifetime (room temperature phosphorescence). The long lifetime of the scintillator signal facilitates a temporal gating of the dose rate signal with respect to the parasitic luminescence from the optical fiber. [Copyright &y& Elsevier]