2011
Authors
Queiros, RB; Silva, SO; Noronha, JP; Frazao, O; Jorge, P; Aguilar, G; Marques, PVS; Sales, MGF;
Publication
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
Authors
Jorge, PAS; Maule, C; Soppera, O; Marques, PVS;
Publication
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.
2011
Authors
Silva, JS; Castro, CC; Vicente, AA; Tafulo, P; Jorge, PAS; Martins, RC;
Publication
INTERNATIONAL CONFERENCE ON APPLICATIONS OF OPTICS AND PHOTONICS
Abstract
Saccharomyces cerevisiae morphology is known to be dependent on the cell physiological state and environmental conditions. On their environment, wild yeasts tend to form complex colonies architectures, such as stress response and pseudohyphal filaments morphologies, far away from the ones found inside bioreactors, where the regular cell cycle is observed under controlled conditions (e.g. budding and flocculating colonies). In this work we explore the feasibility of using micro-fiber optics spectroscopy to classify Saccharomyces cerevisiae S288C colony structures in YPD media, under different growth conditions, such as: i) no alcohol; ii) 1 % (v/v) Ethanol; iii) 1 % (v/v) 1-butanol; iv) 1 % (v/v) Isopropanol; v) 1 % (v/v) Tert-Amyl alcohol (2 Methyl-2-butanol); vi) 0,2 % (v/v) 2-Furadehyde; vii) 5 % (w/v) 5 (Hydroxymethyl)-furfural; and viii) 1 % (w/v) (-)-Adenosine3', 5'cyclic monophosphate. The microscopy system includes a hyperspectral camera apparatus and a micro fiber (sustained by micro manipulator) optics system for spectroscopy. Results show that micro fiber optics system spectroscopy has the potential for yeasts metabolic state identification once the spectral signatures of colonies differs from each others. This technique associated with other physico-chemical information can benefit the creation of an information system capable of providing extremely detailed information about yeast metabolic state that will aid both scientists and engineers to study and develop new biotechnological products.
2011
Authors
Tillak, JB; Bernacka Wojcik, I; Barata, D; Jorge, PAS; Aguas, H; Oliva, AG;
Publication
INTERNATIONAL CONFERENCE ON APPLICATIONS OF OPTICS AND PHOTONICS
Abstract
This paper evaluates various strategies proposed for single cell refractometry and spectroscopy using fiber optic sensors and microfluidic chips. Details concerning design, fabrication and characterization of the chips will be addressed. Preliminary results obtained with alternative on-chip configurations using combination of fiber Bragg gratings with mirrored single mode and multimode fibers will be presented indicating the possibility of performing simultaneous assessment of cellular refractive index and absorption properties.
2011
Authors
Zibaii, MI; Jorge, PAS; Frazao, O; Latifi, H;
Publication
INTERNATIONAL CONFERENCE ON APPLICATIONS OF OPTICS AND PHOTONICS
Abstract
A single-mode non-adiabatic tapered optical fiber (NATOF) sensor was inserted into a Sagnac loop interferometer allowing tuning its sensitivity to refractive index (RI) by use of polarization control. By adjusting any polarization controllers inserted in the Sagnac loop interferometer, various cladding modes are selectively excited in each arm of the interferometric taper resulting into different phase changes for the clockwise and counterclockwise beams. By this method, sensitivity of the sensor for RI in the range from 1.3380 to 1.3510 was tuned between 876.24 RIU/nm to 1233.07 RIU/nm.
2011
Authors
Goncalves, LC; Gonzalez Aguilar, G; Baptista, JM; Jorge, PAS;
Publication
21ST INTERNATIONAL CONFERENCE ON OPTICAL FIBER SENSORS
Abstract
This work describes the implementation of an optical fiber interferometric system for differential thermal analysis. The system is based on a white light Mach-Zehnder configuration, with serrodyne phase modulation, to interrogate two identical fiber Bragg gratings (FBG) in a differential scheme. Operation and signal processing with low cost digital instrumentation developed in Labview environment enabled FBG temperature measurement with a +/- 0.012 degrees C resolution nearly matching the performance of standard hardware. Preliminary results were obtained, where mixed samples of acetone and methanol could be successfully identified, indicating the suitability of the system for high accuracy differential thermal analysis using low cost instrumentation.
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