Browsing by Author "Lee, Seung-Woo"
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Item Open Access Ammonia sensing using lossy mode resonances in a tapered optical fibre coated with porphyrin-incorporated titanium dioxide(Society of Photo-optical Instrumentation Engineers (SPIE), 2016-05-30) Tiwari, Divya; Mullaney, Kevin; Korposh, Sergiy; James, Stephen W.; Lee, Seung-Woo; Tatam, Ralph P.The development of an ammonia sensor, formed by the deposition of a functionalised titanium dioxide film onto a tapered optical fibre is presented. The titanium dioxide coating allows the coupling of light from the fundamental core mode to a lossy mode supported by the coating, thus creating lossy mode resonance (LMR) in the transmission spectrum. The porphyrin compound that was used to functionalise the coating was removed from the titanium dioxide coating upon exposure to ammonia, causing a change in the refractive index of the coating and a concomitant shift in the central wavelength of the lossy mode resonance. Concentrations of ammonia as small as 1ppm was detected with a response time of less than 1min. © (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.Item Open Access An ammonia sensor based on Lossy Mode Resonances on a tapered optical fibre coated with porphyrin-incorporated titanium dioxide(Elsevier, 2017-04) Tiwari, Divya; Mullaney, Kevin; Korposh, Sergiy; James, Stephen W.; Lee, Seung-Woo; Tatam, Ralph P.The development of a highly sensitive ammonia sensor is described. The sensor is formed by deposition of a nanoscale coating of titanium dioxide, containing a porphyrin as a functional material, onto a tapered optical fibre. The titanium dioxide coating allows coupling of light from the fundamental core mode to a lossy mode supported by the coating, thus creating a Lossy Mode Resonance (LMR) in the transmission spectrum. A change in the refractive index of the coating caused by the interaction of the porphyrin with ammonia causes a change in the centre wavelength of the LMR, allowing concentrations of ammonia in water as low as 0.1 ppm to be detected, with a response time of less than 30 s.Item Open Access Detection of volatile organic compounds (VOCs) using an optical fibre long period grating with a calixarene anchored mesoporous thin film(SPIE, 2013-05-06) Korposh, Sergiy; Davis, Frank; James, Stephen W.; Wang, T.; Lee, Seung-Woo; Higson, Seamus P. J.; Tatam, Ralph P.A long period grating (LPG) modified with a mesoporous film infused with a functional compound, calix[4]arene, was employed for the detection of volatile organic compounds (VOCs). The mesoporous film consisted of an inorganic part, of SiO2 nanoparticles (NPs) along with an organic moiety of poly(allylamine hydrochloride) polycation PAH, which was finally infused with functional compound, p-sulphanatocalix[4]arene (CA[4]). The LPG sensor was designed to operate at the phase matching turning point to provide the highest sensitivity. The sensing mechanism is based on the measurement of the refractive index (RI) change induced by the complexion of the VOCs with calix[4]arene (CA). The LPG modified with 5 cycles of (SiO2 NPs/PAH)5PAA responded to exposure to chloroform and benzene vapours. The sensitivity to humidity as an interfering parameter was also investigated.Item Open Access Fiber optic long period grating sensors with a nanoassembled mesoporous film of SiO2 nanoparticles(Optical Society of America (OSA), 2010-06-07T00:00:00Z) Korposh, Sergiy; James, Stephen W.; Lee, Seung-Woo; Topliss, Stephen M.; Cheung, Sammy C.; Batty, William J.; Tatam, Ralph P.A novel approach to chemical application of long period grating (LPG) optical fibers was demonstrated, which were modified with a film nanoassembled by the alternate deposition of SiO2 nanoparticles (SiO2 NPs) and poly(diallyldimethyl ammonium chloride) (PDDA). Nanopores of the sensor film could be used for sensitive adsorption of chemical species in water, which induced the changes in the refractive index (RI) of the light propagating in the cladding mode of the optical fiber, with a concomitant effect on the transmission spectrum in the LPG region. The prepared fiber sensor was highly sensitive to the change in the RI of the surrounding medium and the response time was very fast within 10 s. In addition, chemical infusion into the film was tested using a porphyrin compound, tetrakis-(4-sulfophenyl)porphine (TSPP), which could be saturated within a few min. The lowest detectable concentration of the TSPP analyte was 10 mu M. The TSPP infusion led to the development of well-pronounced dual resonance bands, indicating a large increase in the optical thickness of the film. The RI of the film was dramatically increased from 1.200 to ca. 1.540.Item Open Access Films based on bacteriorhodopsin in sol-gel matrices(International Society for Optical Engineering; 1999, 2005-09-26T00:00:00Z) Korposh, Serhiy O.; Sichka, M. Y.; Trikur, I. I.; Sharkan, Y. P.; Yang, D. H.; Lee, Seung-Woo; Ramsden, Jeremy J.The bacteriorhodopsin film in gelatin matrixes which are used as sensitive elements of integrated optic and fibre-optic sensors of various vapor and gases components will not be able to carry out the chemical control of aqueous solutions. In the given paper the results of technological development of obtaining the bacteriorhodopsin (bR) films in a sol-gel matrix are represented. The films are obtained in a broad thickness range (from 0.5 to 20 microns) with various bR concentrations and photosensitize additives. The optimal technological conditions of obtaining of uniform films with given optical parameters are defined. The surface morphology and cross section of the obtained films was studied using an AFM and SEM. The films have a reasonable surface roughness (~ 100 nm) and a uniform distribution of the purple membrane fragments in the nanostructured sol-gel glass matrix along the films surface and thickness. The transmission spectrums have the characteristic for bR the absorption band, the value of which depends on bR concentration and technological features of the films deposition. The investigated photosensitive properties of the obtained films and influence on them of chemical components of aqueous solutions, allow recommending the thin bR films in sol-gel matrixes for creation of planar waveguides in the role of components of the chemical sensors of liquid solutions.Item Open Access Identification and quality assessment of beverages using a long period grating fibre-optic sensor modified with a mesoporous thin film(Elsevier, 2014-07-23) Korposh, Sergiy; Selyanchyn, Roman; James, Stephen; Tatam, Ralph; Lee, Seung-WooIn this study, an optical fibre long period grating (LPG) sensor functionalised with a mesoporous thin film was employed for the identification and quality assessment of beverages. The principle of the discrimination of beverages using an LPG sensor is based on the measurement of the change in refractive index of a sensitive film, induced by the binding of the chemical compounds present in the beverage. The sensitive film deposited onto the LPG consisted of poly(allylamine hydrochloride) (PAH) and silica nanospheres (SiO2 NPs) with diameters ranging from 40 nm to 50 nm. PAH imparts selectivity, while the SiO2 NPs endow the film with high porosity and enhanced sensitivity. In this study, five different types of beverages, red and white wines, brandy, nihonshyu (sake, a Japanese rice wine), and shochu (a Japanese distilled beverage), prepared via distillation and fermentation, were used to assess the capability of the sensor to identify the origin of the beverages. In addition, a selection of red wines was used to evaluate the use of the sensor in the assessment of the quality of beverages. The results obtained were benchmarked against those obtained using gas chromatography–mass spectrometry for the determination of volatile compounds contributing to the flavours of a set of red wines. Principal component analysis (PCA) was employed for data analysis. This approach enabled both quality assessment of beverages and identification of the methods and materials used for their preparation.Item Open Access Label-free creatinine optical sensing using molecularly imprinted titanium dioxide-polycarboxylic acid hybrid thin films: a preliminary study for urine sample analysis(MDPI, 2021-07-17) Lee, Seung-Woo; Ahmed, Soad; Wang, Tao; Park, Yeawon; Matsuzaki, Sota; Tatsumi, Shinichi; Matsumoto, Shigekiyo; Korposh, Sergiy; James, SteveCreatinine (CR) is a representative metabolic byproduct of muscles, and its sensitive and selective detection has become critical in the diagnosis of kidney diseases. In this study, poly(acrylic acid) (PAA)-assisted molecularly imprinted (MI) TiO2 nanothin films fabricated via liquid phase deposition (LPD) were employed for CR detection. The molecular recognition properties of the fabricated films were evaluated using fiber optic long period grating (LPG) and quartz crystal microbalance sensors. Imprinting effects were examined compared with nonimprinted (NI) pure TiO2 and PAA-assisted TiO2 films fabricated similarly without a template. In addition, the surface modification of the optical fiber section containing the LPG with a mesoporous base coating of silica nanoparticles, which was conducted before LPD-based TiO2 film deposition, contributed to the improvement of the sensitivity of the MI LPG sensor. The sensitivity and selectivity of LPGs coated with MI films were tested using CR solutions dissolved in different pH waters and artificial urine (near pH 7). The CR binding constants of the MI and NI films, which were calculated from the Benesi–Hildebrand plots of the wavelength shifts of the second LPG band recorded in water at pH 4.6, were estimated to be 67 and 7.8 M−1, respectively, showing an almost ninefold higher sensitivity in the MI film. The mechanism of the interaction between the template and the TiO2 matrix and the film composition was investigated via ultraviolet–visible and attenuated total reflectance Fourier-transform infrared spectroscopy along with X-ray photoelectron spectroscopy analysis. In addition, morphological studies using a scanning electron microscope and atomic force microscope were conducted. The proposed system has the potential for practical use to determine CR levels in urine samples. This LPG-based label-free CR biosensor is innovative and expected to be a new tool to identify complex biomolecules in terms of its easy fabrication and simplicity in methodology.Item Open Access Long Period Grating Based Fibre Optic Chemical Sensors(Springer, 2016-11-03) Korposh, Sergiy; Lee, Seung-Woo; James, Stephen W.The principle of operation of optical fibre long period grating (LPG) sensors is described. In particular, the chapter explores the use of LPGs as a chemical sensing platform, discussing the fabrication of LPGs and the various approaches that have been employed to modify the cladding of the LPG and thus sensitise the LPG. Examples of the practical application of LPG chemical sensors are provided.Item Open Access A long period grating optical fiber sensor with nano-assembled porphyrin layers for detecting ammonia gas(Elsevier, 2016-01-19) Wang, Tao; Yasukochi, Wataru; Korposh, Sergiy; James, Stephen W.; Tatam, Ralph P.; Lee, Seung-WooIn this study, the ability of a long period grating (LPG) optical fiber sensor coated with a multilayer film of poly(diallyldimethyammonium chloride) (PDDA) and tetrakis(4-sulfophenyl)porphine (TSPP) to detect ammonia gas was demonstrated. The nano-assembled thin film was prepared using a layer-by-layer deposition technique. This combination of an LPG and TSPP could allow highly sensitive optical sensors that specifically bind ammonia to be fabricated. An LPG with a period of 100 μm and a PDDA/TSPP coating produced by depositing fifteen layers afforded a limit of detection of 0.67 ppm for ammonia gas. TSPP molecules in the film acted as ammonia receptors because the TSPP morphologically changed from J- or H-aggregates to free base monomers when it was deprotonated by being exposed to ammonia. Interestingly, HCl vapor could be used to increase the relative amount of J-aggregation in the TSPP and to restore the sensor response. The reversibility of the morphological change in the TSPP allowed reversible changes to occur in the properties of the coating, including the refractive index, film thickness and density, and electrostatic interactions; these influenced the transmission spectrum of the LPG.Item Open Access A long period grating-based chemical sensor insensitive to the influence of interfering parameters(Optical Society of America (OSA), 2014-04-07T00:00:00Z) James, Stephen W.; Korposh, Sergiy; Lee, Seung-Woo; Tatam, Ralph P.An optical fibre chemical sensor that is insensitive to interfering parameters including temperature and surrounding refractive index is described. The sensor is based upon a Mach-Zehnder interferometer formed by a pair of identical cascaded long period gratings (LPGs), with the entire device coated with a mesoporous coating of silica nanoparticles. A functional material is infused only into the coating over the section of optical fibre separating the LPGs. The transmission spectrum of the device consists of a channeled spectrum arising from interference of the core and cladding modes within the envelope of the LPG resonance band. Parameters such as temperature, strain and surrounding refractive perturb the entire device, causing the phase of the channeled spectrum and the central wavelength of the envelope shift at the same rate. Exposure of the device to the analyte of interest perturbs only the optical characteristics of the section of fibre into which the functional material was infused, thus influencing only the phase of the channeled spectrum. Measurement of the phase of the channeled spectrum relative to the central wavelength of the envelope allows the monitoring of the concentration of the analyte with no interference from other parameters.Item Open Access Long-period grating fiber-optic sensors exploiting molecularly imprinted TiO2 nanothin films with photocatalytic self-cleaning ability(Springer, 2020-11-17) Wang, Tao; Korposh, Sergiy; James, Stephen; Lee, Seung-WooHighly sensitive and selective long-period grating (LPG) fiber-optic sensors modified with molecularly imprinted TiO2 nanothin films were fabricated. The films were deposited onto the surface of the optical fiber via liquid-phase deposition (LPD), using tetrakis(N-methylpyridinium-4-yl)porphyrin (TMPyP) as a template. Three LPG resonance bands were monitored during film deposition, which was of duration 4.5 h. Prior to template removal, heat treatment at 60 °C under high-humidity conditions led to an increase in refractive index of the TiO2 film, evidenced by changes in the central wavelengths of the attenuation bands. After template removal using HCl solution (0.01 M), the TMPyP-imprinted film-modified LPG sensor showed higher sensitivity to the template molecule than to structurally related guest molecules. This was measured at the 1st and 2nd resonance bands, with wavelengths ranging from 690 to 738 nm and 815 to 905 nm, respectively. No selective binding of the template was observed with a non-imprinted TiO2 film prepared in the same manner. Furthermore, the heat-treated imprinted films exhibited a substantial enhancement of photocatalytic activity for template irradiation. In particular, the self-cleaning property of the imprinted film-modified LPG sensor under ultraviolet irradiation led to highly efficient and selective binding to the template. The mechanism of the interaction between the template and the TiO2 matrix was investigated by UV–vis and Fourier-transform infrared (FTIR) spectroscopies. Additionally, morphological studies using scanning electron microscopy (SEM) were conducted.Item Open Access Nano-assembled thin film gas sensors. 1. Ammonia detection by a porphyrin-based multilayer film.(Association of Modern Scientific Investigation, 2006-09) Korposh, Serhiy O.; Takahara, Naoki; Ramsden, Jeremy J.; Lee, Seung-Woo; Kunitake, ToyokiA thin film of porphyrin deposited by the layer-by-layer method is employed as the active element for an optical sensor. The usefulness of this film technology and the resulting nanoscale matrix for the detection of volatile organic compounds (VOCs), aromatics and amine-containing substances has been studied. The sensing principle is based on monitoring the optical changes of the Q band at 700 nm, as induced by the analyte in the electrostatic interaction between tetrakis(4-sulfophenyl)porphine (TSPP) and poly(diallyldimethylammonium chloride) (PDDA) layers. Three thin film samples with different thicknesses were prepared to assess the effect of film thickness on the sensitivity. For ammonia, the sensor shows a linear sensitivity in the concentration range 0–100 ppm and the sensor response was within 30 seconds. Sensor response could be regenerated by rinsing in distilled water.Item Open Access Optical gas sensing using gold nanoparticles/polyelectrolyte layer-by-layer films: a case study with poly(acrylic acid) for ammonia detection(Scientific Publishing Division Myu, 2016-03-30) Wang, Tao; Okada, Takuya; Hayashi, Kenshi; James, Stephen W.; Lee, Seung-Woothis study, we demonstrated a new approach for gas sensing using multilayer films selfassembled with cationic gold nanoparticles (AuNPs+) and anionic polyelectrolytes via layerby- layer (LbL) deposition. The surface of AuNPs+ was modified with a cationic disulfide, [–S(CH2)2NHCO(CH2)10(CH3)3N+Br−]2. Two types of LbL film using AuNPs+ were selfassembled with anionic polyelectrolytes, poly(acrylic acid) (PAA), and poly(sodium 4-styrene sulfonate) (PSS) on quartz substrates, and their film growth was confirmed by UV–vis measurements. The 10-cycle AuNPs+/PAA film showed reproducible responses after exposure to ammonia gas (3000 ppm) and HCl treatment (0.1 M), showing absorbance changes of 0.0428 ± 0.0033 at 299 nm and 0.0053 ± 0.0013 at 544 nm for five repeated tests. On the other hand, no significant changes were observed for the 10-cycle AuNPs+/PSS film. Ammonia binding was based on the acid–base interaction between ammonia and the free carboxylic acid groups of PAA. The film's composition and morphology were also investigated by Fourier transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM) measurements to clarify the sensing mechanism.Item Open Access Optical Gas Sensor Fabrication Based on Porphyrin-Anchored Electrostatic Self-Assembly onto Tapered Optical Fibers(Taylor & Francis, 2012-07-31T00:00:00Z) Jarzebinska, Renata; Korposh, Sergiy; James, Stephen W.; Batty, William J.; Tatam, Ralph P.; Lee, Seung-WooTapered optical fibers with nano-assembled coatings of thicknesses of order tens of nanometres were used for the detection of ammonia gas. The film coating was composed of alternate layers of tetrakis-(4-sulfophenyl) porphine (TSPP) and poly(allylamine hydrochloride) (PAH), which were deposited using the electrostatic self-assembly process (ESA). Exposure of a PAH/TSPP nano-assembled non-adiabatic tapered optical fiber with a waist diameter of 10µm to ammonia induced significant optical changes in the transmission spectrum of the optical fiber. The fiber optic sensor showed a linear sensitivity to the concentration of ammonia in the range of 10-100ppm, with response and recovery times less than 100 and 240sec, respectively. The 3σ limit of detection (LOD) was estimated to be ca. 2ppm.Item Open Access Porphyrin-nanoassembled fiber-optic gas sensor fabrication: Optimization of parameters for sensitive ammonia gas detection(Elsevier, 2017-11-09) Korposh, Sergiy; Kodaira, Suguru; Selyanchyn, Roman; Ledezma, Francisco H.; James, Stephen W.; Lee, Seung-WooHighly sensitive fiber-optic ammonia gas sensors were fabricated via layer-by-layer deposition of poly(diallyldimethylammonium chloride) (PDDA) and tetrakis(4-sulfophenyl)porphine (TSPP) onto the surface of the core of a hard-clad multimode fiber that was stripped of its polymer cladding. The effects of film thickness, length of sensing area, and depth of evanescent wave penetration were investigated to clearly understand the sensor performance. The sensitivity of the fiber-optic sensor to ammonia was linear in the concentration range of 0.5–50 ppm and the response and recovery times were less than 3 min, with a limit of detection of 0.5 ppm, when a ten-cycle PDDA/TSPP film was assembled on the surface of the core along a 1 cm-long stripped section of the fiber. The sensor’s response towards ammonia was also checked under different relative humidity conditions and a simple statistical data treatment approach, principal component analysis, demonstrated the feasibility of ammonia sensing in environmental relative humidity ranging from dry 7% to highly saturated 80%. Penetration depths of the evanescent wave for the optimal sensor configuration were estimated to be 30 and 33 nm at wavelengths of 420 and 706 nm, which are in a good agreement with the thickness of the 10-cycle deposited film (ca. 30 nm).Item Open Access Refractive index sensitivity of fibre optic long period gratings with SiO2 nanoparticle based mesoporous coatings(2011-12-31T00:00:00Z) Korposh, Sergiy; Lee, Seung-Woo; James, Stephen W.; Tatam, Ralph P.A fibre optic long period grating (LPG) with an nano-assembled mesoporous coating of alternate layers of poly (allylamine hydrochloride) (PAH) and SiO2 nanospheres was used for the development of a fibre-optic refractometer. PAH/ SiO2 films of different thickness have been deposited onto an LPG in order to study the effect of the film thickness on sensor performance. The device showed a sensitivity of 1927 nm/RIU over a RI range of 1.3233-1.4906.Item Open Access Tapered optical fibre sensors: current trends and future perspectives(MDPI, 2019-05-17) Korposh, Sergiy; James, Stephen W.; Lee, Seung-Woo; Tatam, Ralph P.The development of reliable, affordable and efficient sensors is a key step in providing tools for efficient monitoring of critical environmental parameters. This review focuses on the use of tapered optical fibres as an environmental sensing platform. Tapered fibres allow access to the evanescent wave of the propagating mode, which can be exploited to facilitate chemical sensing by spectroscopic evaluation of the medium surrounding the optical fibre, by measurement of the refractive index of the medium, or by coupling to other waveguides formed of chemically sensitive materials. In addition, the reduced diameter of the tapered section of the optical fibre can offer benefits when measuring physical parameters such as strain and temperature. A review of the basic sensing platforms implemented using tapered optical fibres and their application for development of fibre-optic physical, chemical and bio-sensors is presented.