Optical Sensor For Detection Research Articles

Miniaturized remission sensor for carbon dioxide detection

Recently, optical sensors for detection of carbon dioxide (CO2) have been explored for variety of applications in chemistry, industry, and medicine. This paper deals with the development of a planar optical remission sensor employing a dye immobilized in a polymer layer designed for gaseous CO2 detection. The principle of CO2 detection was based on colour changes of Tetraethylammonium Cresol red immobilized in a special composed polymer layer that was irradiated by LED diodes. Absorption properties of the dye were changed due to its chemical reaction with CO2 and corresponding colour changes were detected by PIN diodes. These changes were analyzed by using a PC-controlled board connected by USB. The sensitivity, response time, and the detection limit of the remission sensor were characterized.

A highly selective regenerable optical sensor for detection of mercury(ii) ion in water using organic–inorganic hybrid nanomaterials containing pyrene

A novel fluorescent chemosensing hybrid material (Py-SBA-15) for detecting Hg2+ ions in water was prepared through the functionalization of mesoporous silica (SBA-15) with a modified fluorescent chromophore, 1-(4′-hydroxyphenyl)-4-pyrenyl-2,3-diaza-1,3-butadiene (Py-OH). Py-OH covalently grafted to the coupling agent 3-(triethoxysilyl)propylisocyanate (TESPIC) was used as the precursor for the preparation of mesoporous hybrid material. The XRD data and TEM images of Py-SBA-15 confirm that the hexagonal ordered mesoporous structure is preserved after functionalization. Py-SBA-15 demonstrates a high selectivity for Hg2+ ions in the presence of other metal ions, which results from a dramatic fluorescence enhancement by the addition of Hg2+ ions upon the suspensions of Py-SBA-15. A good linearity (R2 = 0.9989) between the fluorescence intensity of Py-SBA-15 and the concentration of Hg2+ ions is constructed, and a satisfactory detection limit of 1.7 × 10−7 g mL−1 is obtained. More importantly, Py-SBA-15 shows good regenerative ability due to the greatly minimized leaching effect of the sensing molecules by covalent grafting strategy. These results presented in this paper indicate that this hybrid material could be a promising fluorescence chemosensor for detecting Hg2+ ions.

Phthalocyanine films as active layers of optical sensors for pentachlorophenol detection

In this work, thin films of octasubstituted zinc phthalocyanine derivative (ZnPcR 8) with bulky substituents R = –CH 2N(SO 2C 6H 5–CH 3)CH 2(CH 2) 8CH 3 are investigated as active layers of optical sensors for the detection of pentachlorophenol. Using total internal reflection ellipsometry (TIRE) technique response characteristics of ZnPcR 8 films to pentachlorophenol was studied in the concentration range 0.5–50 μg/l. It was demonstrated that the specific binding of pentachlorophenol molecules causes substantial shift of Δ( λ) spectrum. The minimum registered concentration of pentachlorophenol was 0.8 μg/l. The results are supported by performing attenuated total reflection Fourier transform infrared (ATR-FTIR) difference spectroscopy.

Glucose sensors based on a responsive gel incorporated as a Fabry-Perot cavity on a fiber-optic readout platform

An optical sensor for detection of glucose is implemented by incorporating a carbohydrate sensitive hydrogel as a Fabry-Perot cavity at the end of optical fiber for high sensitivity readout of the gel length. The glucose sensing functionality was achieved by incorporating boronic acid moieties into an acrylamide-based hydrogel. The interaction between glucose and boronic acid changes the driving forces for gel swelling thus inducing a glucose sensitive hydrogel swelling. The effects on the carbohydrate swelling response, with respect to sensitivity and selectivity, by incorporation of a cationic monomer, dimethyl-aminopropyl acrylamide, into the boronic acid functionalized responsive gels were determined. The linear gel swelling response in aqueous solutions at aqueous 2.5mM carbohydrates were determined to −1760nm/mM for glucose whereas mannose, sucrose, fructose and galactose displayed a response of about 10% of the glucose response for the hydrogels containing 10mol% dimethylaminopropyl acrylamide. This gel composition with 10mol% dimethylaminopropyl acrylamide is the most promising for detection of glucose at physiological pH and ionic strength. A mechanism where carbohydrate specific stabilisation of the boronic acid group and possible carbohydrate mediated additional crosslinking of the elastically active polymer chains is suggested.

Intermolecular interactions and spectral and luminescent properties of optical molecular sensors

The effect of intermolecular interactions of different types (universal interactions, H-bonding, electronic donor-acceptor interactions, and interactions with proton transfer) on the absorption and luminescence spectra of organic molecules of different classes, which are or can be used as optical molecular sensors, was considered. The classification of the types of intermolecular interactions and corresponding spectroscopic effects is given, which can be used, particular, in the development of optical sensors for detection of organic molecules in liquid and gaseous media.

An optical sensor for the detection of leaks from subsea pipelines and risers

An optical sensor for the rapid detection of detect leaks of oil, hydraulic fluids or leak detection chemicals from underwater pipelines and risers is reported. The sensor is designed to be deployed on ROVs or AUVs for the rapid survey of underwater pipelines and risers. The system employs ultra-bright LEDs to project a sensing light beam into the water to allow real time detection of ppm concentration plumes of material leaking from pipelines or riser in real time. Typically the system is deployed on an ROV which inspects a pipeline at a height of 2–3m.

Spin-assembled nanofilms for gaseous oxygen sensing

A nanofilm optical sensor for detection and measurement of gaseous oxygen was developed and shown to quantify oxygen concentration over a wide range of conditions. The sensor was fabricated using the spin assembly of an oxygen-sensitive dye entrapped in a dye/polyion interpolyelectrolyte complex. The sensor demonstrated good correlation to the Stern–Volmer relationship, with linear decay in sensitivity of approximately 1.6% per week. The system also demonstrated some level of pressure sensitivity and corresponding variation of the Stern–Volmer constant, facilitating the possible use of the system as a pressure sensor. Oxygen concentration of the sensor was linear over a range of 0–100%, with a resolution of 0.2%. The high sensitivity, inherent linearity and flexibility of this sensor make it suitable for a variety of applications, including biological respiration studies, environmental monitoring, and cell cultures.

Volatile alcoholic compounds fibre optic nanosensor

A fibre optic sensor for detection of some volatile organic compounds (VOCs) is presented. This device is based on a new vapochromic material of formula [Au2Ag2(C6F5)4(C6H5N)2], presented in the form of bright red powders. This material changes its optical properties as colour or refractive index when exposed to some organic vapours, recovering its original state when vapours get disappeared. The sensor head consists of a nanometer-scale Fizeau interferometer doped with the vapochromic material, built onto a cleaved end of a multimode fibre optic pigtail by using the electrostatic self-assembly method (ESA). The fibre optic sensor is used in a reflection scheme, so the other extreme of the optical fibre pigtail is connected to an optical coupler, completing the set-up with an optical source that generates an interrogating signal and an optical detector to register the intensity modulated reflected measure. The response of the sensor has been characterized taking measures of its absorbance spectra and the intensity modulated reflected signal at 850nm for different alcohols. Changes up to 3dB in the reflected optical power were registered.

Novel SnO2 based optical sensor for detection of low ammonia concentrations in water at room temperatures

Novel SnO2 based optical sensor for detection of low ammonia concentrations in water at room temperatures

Fiber Optic Sensors for Detection of Corrosion within Aircraft

The cost of preventing and controlling corrosion in aging aircraft fleets is becoming a significant burden. Early detection of corrosion will reduce the maintenance required to repair the damage, which should result in increased aircraft availability and significant reduction in the cost of ownership. Fluorescent fiber optic sensors that detect aluminum cations from the early stages of the corrosion process are proposed as a means for providing early warning of corrosion in susceptible areas of an aging aircraft. This article will discuss the results for two different carriers of an aluminum-sensing fluorophore and some of the key technical issues that need to be resolved for the development of an effective fiber optic sensing system.

New distributed optical sensor for detection and localization of liquid hydrocarbons

This paper reports the second part of a work that introduces and describes the testing of a new optical distributed sensor. This new sensor is capable of detecting and locating liquid hydrocarbon leaks on long pipelines. In the first part of this work a number of advantages of this new design were presented. The present part deals specifically with the influence of elastomer preparation on the performance of this sensor, and in a more general way, with the performance of any distributed optical sensor based on optical fiber bending by a swelled elastomer. The results show that the optimal sensor response is obtained when the osmotic pressure developed by the elastomer due to hydrocarbon absorption and the swelling of the elastomer are balanced. Therefore, by modifying the cross-linking density of the elastomer, it is possible to optimize the sensor performance, by finding the condition where the pressure against the fiber is large enough to surpass the resistance of the optical fiber to be bended and, at the same time, the elastomer absorbs enough solvent to bend the fiber at an optimum level.

A luminescence endotoxin biosensor prepared by the sol–gel method

Abstract Silicate thin films with terminal amino groups were prepared via the sol–gel technique and selected biological molecules labeled with luminophores were covalently attached to their surfaces. The obtained thin films with covalently bound Concanavalin-A (Con-A) labeled with fluorescein (FITC) were immersed in a buffer and polarized emission spectra were measured. In the next step, the samples were incubated with a lipopolysaccharide (LPS) isolated from Hafnia alvei PCM 1186 bacterial strain and the emission spectra were collected again. The influence of LPS binding to Con-A on the luminescence depolarization has been proven. The system based on the this effect can be employed as an optical sensor for detection of certain types of bacteria.

RAPTOR: A fluoroimmunoassay-based fiber optic sensor for detection of biological threats

The RAPTOR was developed to meet the need for a small, portable, easily operated biosensor for the detection of biological threats in the field. This device has evolved over a number of years to reach its current level of maturity. This paper describes details of the RAPTOR's design, including the recent upgrades to the fluidics and optics subsystems, as well as design improvements that have increased both system reliability and sensitivity. Working with these system upgrades, we also investigated biochemical methods that further improve assay sensitivity. The use of NeutrAvidin/biotin chemistry to improve immobilization of the capture antibody, coupled with use of the fluorophore Alexa Fluor 647 to label the tracer antibody, has resulted in a two- to four-fold signal enhancement. These gains, in combination with redesigned optics and instrumentation, have resulted in approximately a log-order improvement over earlier systems. These improvements are shown for an assortment of analytes of interest, including Staphylococcal enterotoxin type-B, Francisella tularensis, Bacillus anthracis, and Bacillus globigii spores.

New distributed optical sensor for detection and localization of liquid leaks

This work introduces and describes the tests of a new optical distributed sensor. This new sensor is capable of detecting and locating liquid hydrocarbon leaks on long pipelines. It is an improvement over the current fiber bending distributed sensors that use a polymer cable that interacts with an optical fiber by means of a helicoidal wire. When a liquid or gas compatible with the polymer within this type of sensor comes in contact with it, the liquid is absorbed and causes the swelling of the polymer and the concomitant compression of the optical fiber against the helicoidal wire. This phenomenon bends the fiber and increases the optical attenuation of a signal that travels through the fiber. The signal attenuation permits the detection of a specific liquid presence in the vicinity of the sensor and the reflection of the same signal allows to pinpoint the location of this event. The new sensor introduced in this paper has the following advantages over similar devices: (a) the swelling of the polymer is conducted in a preferential direction permitting to concentrate the osmotic pressure towards the optical fiber, which improves significantly the response speed of the sensor. (b) The fiber is placed within a channel located eccentrically in the polymer cable. Therefore, no additional protection is needed to protect the fiber. Of even greater importance, the signal attenuation caused by stress and deformations due to direct contact of the fiber with the helicoidal wire is avoided. (c) An optimal bending period, that considers the polymer nature, was found and employed. Experimental prototypes of this sensor were fabricated using an optical fiber attached to a polymer cable. The experimental results confirm the benefits of this new design.

Optical sensors for detection of bacteria. 1. General concepts and initial development.

The concept of using immobilized nucleic acid stains as detection chemistry to fabricate optical bacterial sensors is first demonstrated. SYTO 13 (a green fluorescent cell stain) is used as the molecular recognition element and fluorescent reporter in the sensor. The sensor responds to aqueous and aerosolized bacterial samples in 15 and 30 min, respectively. In addition, the sensor can discriminate a change in Pseudomonas aeruginosa (Pa) cell concentration of 1 order of magnitude or less and can detect down to 2.4 x 10(5) cells/mL of Pa cells. The utility of the sensor is demonstrated by monitoring the growth of a Pa cell culture over a period of 50 h.

Optical sensor for detection of errors in Nd:YAG laser overlap welding of zinc-coated steel

Laser overlap welding of zinc-coated steel is an attractive process for the automotive industry, but specific problems can occur where apparently good welds may be produced but with no join between the two sheets of material. This paper describes a simple and reliable technique for detecting these errors by analysing the light generated by the welding process, using an optical sensor which is non-intrusive to the process.

Development and cellular applications of fiber optic nitric oxide sensors based on a gold-adsorbed fluorophore.

A new design for optochemical sensors has been applied to the development of a nitric oxide selective fiber optic sensor. This sensor is composed of a fluorescein derivative dye attached to colloidal gold. The fluorescein dye rearranges as nitric oxide adsorbs onto the gold, inducing a decrease in the fluorescence intensity of the dye. This mechanism has allowed preparation of fiber optic dye-based nitric oxide sensors, which have been made ratio-metric by addition of reference dye microspheres. Previously developed fast, selective optical sensors for detection of aqueous nitric oxide involved a protein, such as cytochrome c'. The new fluorescein derivative chemical sensors have characteristics similar to those of the protein-based biosensors, including fast response times, excellent selectivity, and complete reversibility. In addition, the chemical sensors have advantages such as greater stability and commercially available components. These sensors were utilized to measure nitric oxide production by BALB/c mouse macrophages.

Investigation of a robust flow-through Cu(I) optical sensor using 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline immobilized into a Nafion film

A robust optical sensor for detection of Cu(I) in water and using fiber optic interrogation is demonstrated. The reagent bathocuproine (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline or BCP) is immobilized into a film of Nafion and the absorbance changes associated with the formation of a Cu(I)–BCP complex are used to detect and quantify Cu(I) in water. The response of the sensor is determined for varying concentrations of Cu(I) in water. Two different measurement techniques are investigated. In the recycled technique the Cu(I)–BCP complex is eluted with 0.1 M nitric acid after each measurement, whereas in the continuous technique the sensor is exposed to consecutively larger concentrations of Cu(I). Detection of ppb levels of Cu(I) is demonstrated and calibration curves for both techniques are constructed.

Evanescent wave fibre optic sensor for detection of L. donovani specific antibodies in sera of kala azar patients

An easy-to-use technique for detection of antibodies specific for the parasite L. donovani in human serum sample has been developed. The method is based on an evanescent wave generated from a tapered configuration of decladded optical fibre and does not require any volumetric measurement. Tapered fibres are immobilized with the purified cell surface protein of L. donovani by covalent bonding. Treated fibres are incubated with the patient serum for 10 min followed by incubation with goat anti human IgG tagged FITC. Fluorescent intensity from the fibre has been shown to be proportional to L. donovani specific antibodies present in the test sera. Direct readings can be obtained after signal enhancement through a photomultiplier tube within 5 min. The system, when tested on 12 positive sera, did not show any false negative result. Also, no false positive result was obtained with serum samples of patients infected with leprosy, tubercolosis, typhoid and malaria, showing the specificity of the sensor and efficacy of the technique.

A Fiber Optic Ultrasonic System to Monitor the Cure of Epoxy

A fiber optic ultrasonic system is described which monitors the cure of an epoxy resin. Ultrasound is generated using a high-power optical fiber to deliver high-energy pulses of light to the prepared surface of an aluminum mold that contains the curing epoxy resin. The generated ultrasound is detected using a local fiber optic ultrasound sensor embedded in the curing epoxy resin. The system was used to measure the ultrasonic signal velocity and ultrasonic attenuation throughout the cure of a neat epoxy resin at room temperature. Similar measurements also were performed using a piezoelectric transducer for ultrasound generation and an embedded fiber optic sensor for detection, which provided verification of the results using the complete fiber optic system. The complete fiber optic system demonstrated adequate sensitivity throughout the entire cure to measure the ultrasonic signal velocity and ultrasonic attenuation.