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Optical VOCs detection using poly(3-alkylthiophenes) with different side-chain lengths

GONCALVES, V. C.; BALOGH, Débora Terezia
Fonte: ELSEVIER SCIENCE SA Publicador: ELSEVIER SCIENCE SA
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
47.319707%
The use of conjugated polymers in the gas and volatile organic compounds (VOCs) detections represents an advance in the development of the electronic noses. Polythiophenes show good thermal and environmental stability, are easily synthesized and they have been studied as gas and VOCs sensors using different principles or transduction techniques. Among these techniques, optical sensing has been attracted attention, mainly due to its versatility. However, conjugated polymer-based optical sensors are still less studied. This paper describes the use of two poly(3-alkylthiophenes) for VOCs optical detection. The sensing measurements were carried out using visible spectroscopy. Both polymers showed good sensitivity to the VOCs, showing fast and reversible responses with some hysteresis, and were unable to detect hydroxylated samples. Furthermore, it was demonstrated that the thickness of polymer films influences the intensity of the optical response. Although there is similarity in the superficial composition of the polymers films, demonstrated by their surface energies, they showed significant differences in their optical properties upon exposure to the VOCs. (c) 2009 Elsevier B.V. All rights reserved.; FAPESP; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); CNPq; Ministério da Ciência...

Sistemas de sensores ópticos baseados em fibra óptica de perfil-W dopada com Érbio; Optical sensing systems based on Erbium-doped W-fiber

Mauro Biscaro Elias
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 30/07/2012 PT
Relevância na Pesquisa
57.5331%
Fibras ópticas de casca rebaixada (também conhecidas como fibras ópticas de dupla-casca ou fibras ópticas de perfil-"W") com cortes do modo fundamental proporcionam perdas distribuídas altas em comprimentos de onda longos e perdas baixas em comprimentos de onda curtos. A grandeza da brusca transição entre a perda baixa em comprimentos de onda curtos e a perda alta em comprimentos de onda longos excede 200 dB/km e é extremamente sensível à curvatura aplicada na fibra. O fenômeno é atribuído ao acoplamento modal entre o modo guiado no núcleo e os modos discretos guiados na casca externa. A fibra óptica ativa de casca rebaixada Er: Al/Ge/SiO2 (DC-EDF) pode ser projetada para ter um corte do modo fundamental próximo de 1530 nm o que proporciona supressão distribuída da emissão espontânea amplificada (ASE) na banda-C em proveito da ASE na banda-S. Este fenômeno, associado a um outro, o de perda induzida por curvatura, proporciona um modelo alternativo para obter amplificação óptica na banda-S, exigida para expandir a capacidade de sistemas de multiplexação por divisão de comprimentos de onda (WDM). Um laser à fibra óptica, configurado na forma de anel, de fibra óptica de casca rebaixada dopada com érbio, que pode ser sintonizado através de perdas induzidas por curvatura na fibra óptica...

Optical Sensing Method for Screening Disease in Melon Seeds by Using Optical Coherence Tomography

Lee, Changho; Lee, Seung-Yeol; Kim, Jeong-Yeon; Jung, Hee-Young; Kim, Jeehyun
Fonte: Molecular Diversity Preservation International (MDPI) Publicador: Molecular Diversity Preservation International (MDPI)
Tipo: Artigo de Revista Científica
Publicado em 10/10/2011 EN
Relevância na Pesquisa
47.36533%
We report a noble optical sensing method to diagnose seed abnormalities using optical coherence tomography (OCT). Melon seeds infected with Cucumber green mottle mosaic virus (CGMMV) were scanned by OCT. The cross-sectional sensed area of the abnormal seeds showed an additional subsurface layer under the surface which is not found in normal seeds. The presence of CGMMV in the sample was examined by a blind test (n = 140) and compared by the reverse transcription-polymerase chain reaction. The abnormal layers (n = 40) were quantitatively investigated using A-scan sensing analysis and statistical method. By utilizing 3D OCT image reconstruction, we confirmed the distinctive layers on the whole seeds. These results show that OCT with the proposed data processing method can systemically pick up morphological modification induced by viral infection in seeds, and, furthermore, OCT can play an important role in automatic screening of viral infections in seeds.

Bromocresol Green/Mesoporous Silica Adsorbent for Ammonia Gas Sensing via an Optical Sensing Instrument

Chang, Yu-Chang; Bai, Hsunling; Li, Shou-Nan; Kuo, Chun-Nan
Fonte: Molecular Diversity Preservation International (MDPI) Publicador: Molecular Diversity Preservation International (MDPI)
Tipo: Artigo de Revista Científica
Publicado em 06/04/2011 EN
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47.38927%
A meso-structured Al-MCM-41 material was impregnated with bromocresol green (BG) dye and then incorporated into a UV-Vis DRA spectroscopic instrument for the online detection of ammonia gas. The absorption response of the Al-MCM-41/BG ammonia sensing material was very sensitive at the optical absorption wavelength of 630 nm. A high linear correlation was achieved for ppmv and sub-ppmv levels of ammonia gas. The response time for the quantitative detection of ammonia gas concentrations ranging from 0.25 to 2.0 ppmv was only a few minutes. The lower detection limit achieved was 0.185 ppmv. The color change process was fully reversible during tens of cycling tests. These features together make this mesoporous Al-MCM-41 material very promising for optical sensing applications.

Continuous sensing of tumor-targeted molecular probes with a vertical cavity surface emitting laser-based biosensor

Parashurama, Natesh; O’Sullivan, Thomas D.; De La Zerda, Adam; El Kalassi, Pascale; Cho, Seongjae; Liu, Hongguang; Teed, Robert; Levy, Hart; Rosenberg, Jarrett; Cheng, Zhen; Levi, Ofer; Harris, James S.; Gambhir, Sanjiv S.
Fonte: Society of Photo-Optical Instrumentation Engineers Publicador: Society of Photo-Optical Instrumentation Engineers
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
57.45702%
Molecular optical imaging is a widespread technique for interrogating molecular events in living subjects. However, current approaches preclude long-term, continuous measurements in awake, mobile subjects, a strategy crucial in several medical conditions. Consequently, we designed a novel, lightweight miniature biosensor for in vivo continuous optical sensing. The biosensor contains an enclosed vertical-cavity surface-emitting semiconductor laser and an adjacent pair of near-infrared optically filtered detectors. We employed two sensors (dual sensing) to simultaneously interrogate normal and diseased tumor sites. Having established the sensors are precise with phantom and in vivo studies, we performed dual, continuous sensing in tumor (human glioblastoma cells) bearing mice using the targeted molecular probe cRGD-Cy5.5, which targets αVβ3 cell surface integrins in both tumor neovasculature and tumor. The sensors capture the dynamic time-activity curve of the targeted molecular probe. The average tumor to background ratio after signal calibration for cRGD-Cy5.5 injection is approximately 2.43±0.95 at 1 h and 3.64±1.38 at 2 h (N=5 mice), consistent with data obtained with a cooled charge coupled device camera. We conclude that our novel...

Compressive sensing with dispersion compensation on non-linear wavenumber sampled spectral domain optical coherence tomography

Xu, Daguang; Huang, Yong; Kang, Jin U.
Fonte: Optical Society of America Publicador: Optical Society of America
Tipo: Artigo de Revista Científica
Publicado em 02/08/2013 EN
Relevância na Pesquisa
47.465347%
We propose a novel compressive sensing (CS) method on spectral domain optical coherence tomography (SDOCT). By replacing the widely used uniform discrete Fourier transform (UDFT) matrix with a new sensing matrix which is a modification of the non-uniform discrete Fourier transform (NUDFT) matrix, it is shown that undersampled non-linear wavenumber spectral data can be used directly in the CS reconstruction. Thus k-space grid filling and k-linear mask calibration which were proposed to obtain linear wavenumber sampling from the non-linear wavenumber interferometric spectra in previous studies of CS in SDOCT (CS-SDOCT) are no longer needed. The NUDFT matrix is modified to promote the sparsity of reconstructed A-scans by making them symmetric while preserving the value of the desired half. In addition, we show that dispersion compensation can be implemented by multiplying the frequency-dependent correcting phase directly to the real spectra, eliminating the need for constructing complex component of the real spectra. This enables the incorporation of dispersion compensation into the CS reconstruction by adding the correcting term to the modified NUDFT matrix. With this new sensing matrix, A-scan with dispersion compensation can be reconstructed from undersampled non-linear wavenumber spectral data by CS reconstruction. Experimental results show that proposed method can achieve high quality imaging with dispersion compensation.

Optical Manipulation and Sensing with Silicon Photonics

Lin, Shiyun
Fonte: Harvard University Publicador: Harvard University
Tipo: Thesis or Dissertation
EN_US
Relevância na Pesquisa
47.775664%
Optical trapping enables the non-contact manipulation of micro and nanoparticles with extremely high precision. Recent research on integrated optical trapping using the evanescent fields of photonic devices has opened up new opportunities for the manipulation of nano- and microparticles in lab-on-a-chip devices. Considerable interest has emerged for the use of optical microcavities as “sensors-on-a-chip”, due to the possibility for the label-free detection of nanoparticles and molecules with high sensitivity. This dissertation focuses on the demonstration of an on-chip optical manipulation system with multiple functionalities, including trapping, buffering, sorting, and sensing. We demonstrate the optically trapping of polystyrene particles with diameters from 110 nm to 5.6 (mu m) using silicon microrings and photonic crystal cavities. By integrating multiple microrings with different resonant wavelengths, we show that tuning the laser wavelength to the resonance wavelengths of different rings enables trapped particles to be transferred back and forth between the rings in a controllable manner. We term this functionality “buffering”. We furthermore demonstrate an integrated microparticle passive sorting system based on the near-field optical forces exerted by a 3-dB optical power splitter that consists of a slot waveguide and a conventional channel waveguide. In related work...

Timing-based dynamic control and optical sensing-based feedback control in DEP microfluidics

Wang, Kai-Liang ; Jones, T. B. (1944 - )
Fonte: University of Rochester Publicador: University of Rochester
Tipo: Tese de Doutorado Formato: Number of Pages:xv, 176 leaves
ENG
Relevância na Pesquisa
57.670566%
Thesis (Ph. D.)--University of Rochester. Materials Science Program, 2008.; Lab-on-a-chip technology is based on the integration of microfluidics for liquid handling with miniaturized analytical devices or diagnostic instruments for the performance of chemical/biomedical protocols. In this dissertation, timing-based dynamic control and optical-sensing based feedback control are developed based on dielectrophoretic (DEP) microfluidics. A dielectric-coated three-electrode device with a T-junction gap is fabricated as a platform for liquid finger actuation and trapping using AC voltage. Upon voltage removal, capillary instability breaks the trapped finger into uniformly spaced droplets following Rayleigh’s theory. Several sets of electrode dimensions, T-junction configurations, and coating materials are tested, and their influences on actuation voltage, finger profile and droplet formation uniformity are examined to optimize actuation reliability. DEP finger actuation is modeled by lumped electromechanics, and a reduced-order hydrodynamic model that incorporates contact line friction. The predicted dynamics is least squares fitted to the experimental data, yielding contact-line-friction coefficients. Based on the prediction, an open-loop scheme using timing control is developed for control of trapped finger length and droplet number. This scheme realizes functional droplet metering; however...

Theoretical study of liquid-immersed exposed-core microstructured optical fibers for sensing

Warren-Smith, S.; Afshar Vahid, S.; Monro, T.
Fonte: Optical Soc Amer Publicador: Optical Soc Amer
Tipo: Artigo de Revista Científica
Publicado em //2008 EN
Relevância na Pesquisa
47.61903%
The absorption and fluorescence sensing properties of liquid-immersed exposed-core microstructured optical fibers are explored for the regime where these structures act as supported nanowires with direct access to the sensing environment. For absorption-based sensing we demonstrate that the amount of power propagating in the sensing region of the exposed-core fiber can compete with that of traditional MOFs. For fluorescence-based sensing, we see that in addition to the enhanced fluorescence capture efficiency already predicted for small-core, high refractive index contrast fibers, an improvement of up to 29% can be gained by using liquid-immersed exposed-core fibers. Additionally, calculation of the losses associated with interfaces between filled and unfilled sections predict significant benefit in using high refractive index substrate glasses for liquid-immersed exposed-core fiber sensing. This work demonstrates that, for fiber dimensions of interest, the exposed-core fiber is an attractive new sensor technology.

A low-volume microstructured optical fiber hydrogen peroxide sensor

Schartner, E.; Murphy, D.; Ebendorff-Heidepriem, H.; Monro, T.
Fonte: SPIE - International Society for Optical Engineering; United States Publicador: SPIE - International Society for Optical Engineering; United States
Tipo: Conference paper
Publicado em //2011 EN
Relevância na Pesquisa
47.465347%
Optical fibers are ideal for environmental sensing applications because of their ability to transmit optical signals to and from the sensing region without the use of free-space optics. Through the use of suspended core MOFs we can exploit the interaction between the evanescent field of the fiber and a target molecule to facilitate detection. The aim of this work is to increase the sensitivity of the system, and to examine the primary factors such as the background glass fluorescence currently restricting the detection limit. This work is focused on biological detection in liquid samples using Quantum dots.; E. P. Schartner, D. F. Murphy, H. Ebendorff-Heidepriem, T. M. Monro

Distributed fluorescence sensing with exposed-core microstructured optical fibres

Warren-Smith, S.; Sinchenko, E.; Stoddart, P.; Davis, C.; Monro, T.
Fonte: Australian Optical Society; CDROM Publicador: Australian Optical Society; CDROM
Tipo: Conference paper
Publicado em //2009 EN
Relevância na Pesquisa
47.554106%
We report on fluorescence-based distributed sensing using exposed-core microstructured optical fibres. The optical fibre consists of a suspended optical micro-wire surrounded by a solid jacket where a portion of the jacket is absent to allow access to the evanescent field from the external environment. We demonstrate time-domain distributed sensing by immersing the fibre in a fluorescent liquid.; Stephen C. Warren-Smith, Elena Sinchenko, Paul R. Stoddart, Claire E. Davis and Tanya M. Monro

Magnetic field interaction with guided light for detection of an active gaseous medium within an optical fiber

Englich, F.; Grabka, M.; Lancaster, D.; Monro, T.
Fonte: Optical Soc Amer Publicador: Optical Soc Amer
Tipo: Artigo de Revista Científica
Publicado em //2013 EN
Relevância na Pesquisa
47.416865%
We report a novel fiber-optic sensing architecture for the detection of paramagnetic gases. By interacting a modulated magnetic field with guided light within a microstructured optical fiber, it is possible to exploit Faraday Rotation Spectroscopy (FRS) within unprecedentedly small sample volumes. This approach, which utilizes magnetic circular birefringence and magnetic circular dichroism effects, is applied to a photonic bandgap fiber to detect molecular oxygen and operates at a wavelength of 762.309 nm. The optical fiber sensor has a 4.2 nL detection volume and 14.8 cm long sensing region. The observed FRS spectra are compared with a theoretical model that provides a first understanding of guided-mode FRS signals. This FRS guided-wave sensor offers the prospect of new compact sensing schemes.; Florian V. Englich, Michal Grabka, David G. Lancaster, and Tanya M. Monro

Nanoporous anodic alumina platforms: engineered surface chemistry and structure for optical sensing applications

Kumeria, T.; Santos, A.; Losic, D.
Fonte: MDPI AG Publicador: MDPI AG
Tipo: Artigo de Revista Científica
Publicado em //2014 EN
Relevância na Pesquisa
47.38927%
Electrochemical anodization of pure aluminum enables the growth of highly ordered nanoporous anodic alumina (NAA) structures. This has made NAA one of the most popular nanomaterials with applications including molecular separation, catalysis, photonics, optoelectronics, sensing, drug delivery, and template synthesis. Over the past decades, the ability to engineer the structure and surface chemistry of NAA and its optical properties has led to the establishment of distinctive photonic structures that can be explored for developing low-cost, portable, rapid-response and highly sensitive sensing devices in combination with surface plasmon resonance (SPR) and reflective interference spectroscopy (RIfS) techniques. This review article highlights the recent advances on fabrication, surface modification and structural engineering of NAA and its application and performance as a platform for SPR- and RIfS-based sensing and biosensing devices.; Tushar Kumeria, Abel Santos and Dusan Losic

Optical sensing using microspheres with different size and material

Miri, N.; Mohammadzaheri, M.
Fonte: Institute of Electrical and Electronics Engineers Publicador: Institute of Electrical and Electronics Engineers
Tipo: Artigo de Revista Científica
Publicado em //2014 EN
Relevância na Pesquisa
57.63357%
If light is trapped inside a microsphere and resonance occurs, the resonance modes known as whispering gallery modes could be employed for sensing the environment around the microsphere. The discrepancy of the resonance wavelengths for the microsphere surrounded by different media quantifies the sensing ability of the microsphere. However, the microsphere size and material are crucial factors on determining the minimum detection limit (DL) of the microsphere as a sensor. Therefore, through investigating an appropriate size and material for the microsphere, the sensing performance and efficiency of the microresonator increase. In this paper, through a comprehensive experimental study, different refractometric microspheres are presented and their optical properties are measured and analyzed. The microspheres, five different size polystyrene and one size silica microspheres, are coated with quantum dots (QDs) and the QDs are excited by an Nd:YAG laser. Then, the microspheres sensing ability is quantified when their surrounding environment is modified. According to the presented results, the microspheres’ DL, in direct proportion to the microsphere size, corresponds well to the theory. In addition, comparing the optical properties of the microspheres indicates the optimum size for the polymer microspheres to detect the environment. Furthermore...

Switchable multi-wavelength erbium-doped fiber laser for remote sensing

Pérez Herrera, Rosa Ana; Díaz Lucas, Silvia; Fernández Vallejo, Montserrat; López Amo, Manuel; Quintela Incera, María Ángeles; López Higuera, José Miguel
Fonte: SPIE Society of Photo-Optical Instrumentation Engineers Publicador: SPIE Society of Photo-Optical Instrumentation Engineers
Tipo: info:eu-repo/semantics/conferenceObject; publishedVersion
ENG
Relevância na Pesquisa
47.416865%
In this work, we present and experimentally demonstrate a switchable Erbium-doped fiber laser for remote sensing applications. The laser uses four Fiber Bragg Gratings (FBGs) for wavelength selection and for temperature sensing and a 2x4 optical switch. By adjusting the switch combinations, the laser can be switched among the four different wavelength lasing configurations. Stable one- and two- wavelength oscillations were achieved based on the use of this device. An output power instability analysis with the temperature for two different multi-wavelength configurations, one of them using the 2x4 optical switch and the other using a 1x4 coupler, was performed, for a cavity length of 50 km. A comparison between the performances of these topologies is carried out, and their temperature sensitivity and stabilization time are shown.

Characterization of new thermo-responsive hydrogels for optical sensing applications

Rueda Sánchez, Juan Carlos; Contreras Villalobos, Kevin; Coello Paria, Rafael; Lomer Barboza, Mauro Matías; Komber, Hartmut; Zschoche, Stefan; Voit, Brigitte
Fonte: SPIE Society of Photo-Optical Instrumentation Engineers Publicador: SPIE Society of Photo-Optical Instrumentation Engineers
Tipo: info:eu-repo/semantics/conferenceObject; publishedVersion
ENG
Relevância na Pesquisa
77.50426%
We report the use of new hydrogels based on poly-N-isopropylacrilamide and MeOXA in order to measure temperature using optical transmittance. We have obtained thermo-responsive hydrogels based on the radical copolymerization of N-isopropylacrylamide (NIPAAm) and bis-macromonomers of 2-methyl-2-oxazoline (MeOXA). The hydrogels show conformational transitions at defined temperatures, which are a function of the molar ratio NIPAAm / MeOXA inside of the hydrogel. The temperatures of transition have been determined by means of 1H NMR spectroscopy and by turbidity measurements using an optical setup with optical fibers and a diode laser. We show the first experimental results and we discuss some future applications such as an optical switch or a device for optical sensing.

The application of distributed optical sensing for monitoring support in underground excavations

Forbes, BRADLEY
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN; EN
Relevância na Pesquisa
57.521963%
An observational approach to excavation design and construction is commonly employed in order to assess excavation driven displacements which, in turn, affects the design of support systems used to maintain the stability within underground projects. A correct and accurate evaluation of the support system performance will therefore, be critical to both the safety and economics of the construction process. This necessitates a monitoring program capable of capturing the support system behaviour in order to verify assumptions made at the design stage and as the excavation advances. Conventionally, this has been approached from an external perspective where the behaviour of individual support elements has been inferred from the measurements of the excavation periphery (e.g. geodetic monitoring) and displacements surrounding the support (e.g. multi-point-borehole-extensometers). This is possibly due to the difficulties of operationally instrumenting ground support. However, this has ultimately lead to a gap in knowledge in terms of the distinct performance of each support element in isolation and as part of a multi-component support system. Within this context, a novel distributed optical strain sensing (DOS) technology has been implemented with rock bolt and forepole support elements. Unlike conventional...

Tunable Yagi-Uda-type plasmonic nanoantennas: implications for nanoscale optical sensing

Maksymov, Ivan; Miroshnichenko, Andrey; Kivshar, Yuri
Fonte: SPIE - The International Society for Optical Engineering Publicador: SPIE - The International Society for Optical Engineering
Tipo: Conference paper
Relevância na Pesquisa
57.126724%
We introduce broadband and tunable Yagi-Uda-type plasmonic nanoantennas created by arrays of metal nanorods of varying length, and explore their use for nanoscale optical sensing. We suggest placing active nanoparticles, sensitive to chemical substances a

Chip Scale Integrated Optical Sensing Systems with Digital Microfluidic Systems

Luan, Lin
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Dissertação
Publicado em //2010
Relevância na Pesquisa
57.912886%

Data acquisition and diagnostics for chemical and biological analytes are critical to medicine, security, and the environment. Miniaturized and portable sensing systems are especially important for medical and environmental diagnostics and monitoring applications. Chip scale integrated planar photonic sensing systems that can combine optical, electrical and fluidic functions are especially attractive to address sensing applications, because of their high sensitivity, compactness, high surface specificity after surface customization, and easy patterning for reagents. The purpose of this dissertation research is to make progress toward a chip scale integrated sensing system that realizes a high functionality optical system integration with a digital microfluidics platform for medical diagnostics and environmental monitoring.

This thesis describes the details of the design, fabrication, experimental measurement, and theoretical modeling of chip scale optical sensing systems integrated with electrowetting-on-dielectric digital microfluidic systems. Heterogeneous integration, a technology that integrates multiple optical thin film semiconductor devices onto arbitrary host substrates, has been utilized for this thesis. Three different integrated sensing systems were explored and realized. First...

Ultra-High resolution strain sensing by phase-sensitive interrogation of a passive fiber Bragg resonator

Gray, Malcolm; Chow, Jong; Littler, Ian C M; McClelland, David
Fonte: SPIE - The International Society for Optical Engineering Publicador: SPIE - The International Society for Optical Engineering
Tipo: Conference paper
Relevância na Pesquisa
47.38927%
We demonstrate and compare two similar pico-strain sensing techniques by laser frequency locking to a passive Bragg grating Fabry-Perot resonator. One technique uses auxiliary phase modulation while the other employs current modulation of the diode laser