2011
Autores
Queiros, RB; Silva, SO; Noronha, JP; Frazao, O; Jorge, P; Aguilar, G; Marques, PVS; Sales, MGF;
Publicação
BIOSENSORS & BIOELECTRONICS
Abstract
Cyanobacteria deteriorate the water quality and are responsible for emerging outbreaks and epidemics causing harmful diseases in Humans and animals because of their toxins. Microcystin-LR (MCT) is one of the most relevant cyanotoxin, being the most widely studied hepatotoxin. For safety purposes, the World Health Organization recommends a maximum value of 1 mu g L(-1) of MCT in drinking water. Therefore, there is a great demand for remote and real-time sensing techniques to detect and quantify MCT. In this work a Fabry-Perot sensing probe based on an optical fibre tip coated with a MCT selective thin film is presented. The membranes were developed by imprinting MCT in a sol-gel matrix that was applied over the tip of the fibre by dip coating. The imprinting effect was obtained by curing the sol-gel membrane, prepared with (3-aminopropyl) trimethoxysilane (APTMS), diphenyl-dimethoxysilane (DPDMS), tetraethoxysilane (TEOS), in the presence of MCT. The imprinting effect was tested by preparing a similar membrane without template. In general, the fibre Fabry-Perot with a Molecular Imprinted Polymer (MIP) sensor showed low thermal effect, thus avoiding the need of temperature control in field applications. It presented a linear response to MCT concentration within 0.3-1.4 mu g L(-1) with a sensitivity of -12.4 +/- 0.7 nm L mu g(-1). The corresponding Non-Imprinted Polymer (NIP) displayed linear behaviour for the same MCT concentration range, but with much less sensitivity, of -5.9 +/- 0.2 nm L mu g(-1). The method shows excellent selectivity for MCT against other species co-existing with the analyte in environmental waters. It was successfully applied to the determination of MCT in contaminated samples. The main advantages of the proposed optical sensor include high sensitivity and specificity, low-cost, robustness, easy preparation and preservation.
2011
Autores
Jorge, PAS; Maule, C; Soppera, O; Marques, PVS;
Publicação
IEEE PHOTONICS TECHNOLOGY LETTERS
Abstract
A technique for the fabrication of luminescence-based fiber-optic optrodes with multiple analyte sensitivity is proposed. Combination of photosensitive polymers doped with different luminescent indicators enabled the production of fiber probes, by self-guiding photo-polymerization, with different geometries and sensing capabilities. Results demonstrating the method flexibility are shown with luminescent probes doped with CdSe/ZnS quantum dots and an organometalic ruthenium complex for simultaneous detection of oxygen and temperature.
2010
Autores
Jorge, PAS; Maule, C; Soppera, O; Marques, PVS;
Publicação
FOURTH EUROPEAN WORKSHOP ON OPTICAL FIBRE SENSORS
Abstract
A technique for the fabrication of luminescence based fiber optic optrodes with multiple analyte sensitivity is proposed. Combination of photosensitive polymers doped with different luminescent indicators was used to produce fiber probes, by self-guiding photopolymerization, having different geometries and sensing capabilities. Results demonstrating the method flexibility are shown with luminescent probes doped with CdSe/ZnS quantum dots and an organometalic ruthenium complex for simultaneous detection of oxygen and temperature.
2009
Autores
Mayeh, M; Viegas, J; Srinivasan, P; Marques, P; Santos, JL; Johnson, EG; Farahi, F;
Publicação
J. Sensors
Abstract
We present optical sensors based on slotted multimode interference waveguides. The sensor can be tuned to highest sensitivity in the refractive index ranges necessary to detect protein-based molecules or other water-soluble chemical or biological materials. The material of choice is low-loss silicon oxynitride (SiON) which is highly stable to the reactivity with biological agents and processing chemicals. Sensors made with this technology are suited to high volume manufacturing. Copyright © 2009 M. Mayeh et al.
2006
Autores
Rego, G; Ivanov, OV; Marques, PVS; Santos, JL;
Publicação
Optics InfoBase Conference Papers
Abstract
By measuring intensity distributions of cladding modes and using an optimization technique we show that the perturbation which forms arc-induced gratings in standard fibers is antisymmetric, while the perturbation in boron-germanium codoped fibers is symmetric. © 2006 Optical Society of America.
2005
Autores
Frazao, O; Melo, M; Romero, R; Marques, PVS; Araujo, FM; Ferreira, LA; Santos, JL;
Publicação
17th International Conference on Optical Fibre Sensors
Abstract
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