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Detalhes

Detalhes

  • Nome

    Orlando Frazão
  • Cargo

    Responsável de Área
  • Desde

    01 junho 1999
014
Publicações

2024

Enhanced Sensitivity in Optical Sensors through Self-Image Theory and Graphene Oxide Coating

Autores
Cunha, C; Monteiro, C; Vaz, A; Silva, S; Frazao, O; Novais, S;

Publicação
SENSORS

Abstract
This paper presents an approach to enhancing sensitivity in optical sensors by integrating self-image theory and graphene oxide coating. The sensor is specifically engineered to quantitatively assess glucose concentrations in aqueous solutions that simulate the spectrum of glucose levels typically encountered in human saliva. Prior to sensor fabrication, the theoretical self-image points were rigorously validated using Multiphysics COMSOL 6.0 software. Subsequently, the sensor was fabricated to a length corresponding to the second self-image point (29.12 mm) and coated with an 80 mu m/mL graphene oxide film using the Layer-by-Layer technique. The sensor characterization in refractive index demonstrated a wavelength sensitivity of 200 +/- 6 nm/RIU. Comparative evaluations of uncoated and graphene oxide-coated sensors applied to measure glucose in solutions ranging from 25 to 200 mg/dL showed an eightfold sensitivity improvement with one bilayer of Polyethyleneimine/graphene. The final graphene oxide-based sensor exhibited a sensitivity of 10.403 +/- 0.004 pm/(mg/dL) and demonstrated stability with a low standard deviation of 0.46 pm/min and a maximum theoretical resolution of 1.90 mg/dL.

2023

Measurement of Paracetamol Concentration Using an Erbium-Doped Fiber Ring Cavity

Autores
Soares, L; Perez Herrera, RA; Novais, S; Ferreira, A; Silva, S; Frazao, O;

Publicação
PHOTONICS

Abstract
Process Analytical Technology (PAT) has been increasingly used in the pharmaceutical industry to monitor essential parameters in real-time during pharmaceutical processes. The concentration of Active Pharmaceutical Ingredients (APIs), such as paracetamol, is one of these parameters, and controlling its variations allows for optimization of the production process. In this study, a refractometric sensor, implemented by an interrogation system based on an Erbium-Doped Fiber Ring Cavity (EDFRC), was presented and experimentally demonstrated. The Cavity Ring proposed included a 1 x 3 coupler. One port of the coupler was used to increase the optical power of the system through a Fiber Bragg Grating (FBG), and the other two ports were used as sensing head and reference. The sensor detected variations of paracetamol concentration with a sensitivity of [(-1.00 +/- 0.05) x 10(-3)] nW/(g/kg) and a resolution of 5.53 g/kg. The results demonstrate the potential of this technology as a possible non-invasive PAT tool.

2023

Fiber Loop Mirror Based on Optical Fiber Circulator for Sensing Applications

Autores
Robalinho, P; Soares, B; Lobo, A; Silva, S; Frazao, O;

Publicação
SENSORS

Abstract
In this paper, a different Fiber Loop Mirror (FLM) configuration with two circulators is presented. This configuration is demonstrated and characterized for sensing applications. This new design concept was used for strain and torsion discrimination. For strain measurement, the interference fringe displacement has a sensitivity of (0.576 +/- 0.009) pm.mu epsilon(-1). When the FFT (Fast Fourier Transformer) is calculated and the frequency shift and signal amplitude are monitored, the sensitivities are (-2.1 +/- 0.3) x 10(-4) nm(-1) mu epsilon(-1) and (4.9 +/- 0.3) x 10(-7) mu epsilon(-1), respectively. For the characterization in torsion, an FFT peaks variation of (-2.177 +/- 0.002) x 10(-12) nm(-1)/degrees and an amplitude variation of (1.02 +/- 0.06) x 10(-3)/degrees are achieved. This configuration allows the use of a wide range of fiber lengths and with different refractive indices for controlling the free spectral range (FSR) and achieving refractive index differences, i.e., birefringence, higher than 10(-2), which is essential for the development of high sensitivity physical parameter sensors, such as operating on the Vernier effect. Furthermore, this FLM configuration allows the system to be balanced, which is not possible with traditional FLMs.

2023

Measurement of paracetamol concentration using a fiber laser system

Autores
Soares, L; Perez-Herrera, RA; Novais, S; Ferreira, A; Frazao, O; Silva, S;

Publicação
2023 IEEE 7TH PORTUGUESE MEETING ON BIOENGINEERING, ENBENG

Abstract
A linear fiber laser system for measurements of paracetamol concentration is experimentally demonstrated. The cavity is based on a fiber loop mirror and an FBG centered at 1567.8 nm. The sensing head corresponds to a refractometric sensor, whose which principle of operation is based on Fresnel reflection in the fiber tip (FBG side). The system works at detected variations of paracetamol concentrations with a sensitivity of [(8.74 +/- 0.34) x10(-5)] mu W/(g/kg) and a resolution of 2.77 g/kg. The results prove that the fiber laser system could be an asset for processing industries, specifically for non-invasive and real-time measurements of concentration.

2023

Transmissive glucose concentration plasmonic Au sensor based on unclad optical fiber

Autores
Cunha, C; Assuncao, AS; Monteiro, CS; Leitao, C; Mendes, JP; Silva, S; Frazao, O; Novais, S;

Publicação
2023 IEEE 7TH PORTUGUESE MEETING ON BIOENGINEERING, ENBENG

Abstract
Using surface resonance (SPR) as a sensitivity enhancer, this work describes the development of a transmissive multimode optical fiber sensor with a gold (Au) thin film that measures glucose concentration. The fiber's cladding was initially removed, and an Au layer was then sputtered onto its surface to simultaneously excite SPR and reflect light, making the SPR sensor extremely sensitive to changes in the environment's refractive index. A range of glucose concentrations, from 0.0001 to 0.5000 g/ml, were tested on the sensor. A maximum sensitivity of 161.302 nm/(g/mL) was attained for the lowest glucose concentration, while the highest concentration yielded a sensitivity of 312.000 nm/(g/mL). The proposed sensor's compact size, high sensitivity, good stability and practicality make it a promising candidate for a range of applications, including detecting diabetes.

Teses
supervisionadas

2023

Estudo e desenvolvimento de novas configurações de sensores em fibra ótica para monitorização de cristalizadores na área farmacêutica

Autor
Liliana Patrícia Santos Soares

Instituição
UP-FEUP

2023

High Power Fiber Laser and Atmospheric Propagation

Autor
Paulo Manuel Ribeiro Robalinho

Instituição
UP-FEUP

2023

Large-area optical scattering setup for high-performance optical surfaces

Autor
Beatriz da Fonseca Lopes

Instituição
UP-FCUP

2023

Study and Development of Optical Fibre Sensors for Refractometric Measurements

Autor
Cristina do Carmo Gonçalves da Cunha

Instituição
UP-FCUP

2023

Study and development of optical fiber structures based on graphene

Autor
Catarina da Silva Monteiro

Instituição
UP-FEUP