Intrinsic Fiber Optic pH Sensor for Measurement of pH Values in the Range of 0.5–6

Nguyen, Thu Hien; Venugopalan, T.; Sun, Tao; Grattan, K. T. V.

doi:10.1109/jsen.2015.2490583

Cited by 49 publications

(24 citation statements)

References 35 publications

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“…Monitoring of the critical meniscus of very low liquid volumes using an optical fiber sensor Leonardo Binetti, Ignacio del Villar, Kasun Dissanayake, Alicja Stankiewicz, Tong Sun, Kenneth T V Grattan, Lourdes S M Alwis A and their small size [11], [12]. This small size feature, taking advantage of the diameter of a standard single mode fiber (SMF) being typically 125 µm, is especially attractive in chemical detection applications where, as will be shown, a much smaller sample volume can be used due to the small size optical fiber.…”

Section: Introductionmentioning

confidence: 99%

Monitoring of the Critical Meniscus of Very Low Liquid Volumes Using an Optical Fiber Sensor

et al. 2020

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A novel sensing system based on single mode optical fiber in reflective configuration has been developed to measure the critical meniscus height (CMH) of low volumes of liquids, which is then used to calculate the contact angle. The sensing system has been designed especially for very low volumes of liquids (e.g. bioliquids) and the work has demonstrated that measurements are possible with a minimum liquid volume of 5 µL. The sensing system is based on monitoring the spectral variation induced by the difference in the refractive index regions surrounding the fiber tip, at the air-liquid or liquid-liquid interfaces. From the experiments performed in water, (by immersing and extracting the fiber sensor in the liquid sample), it can be concluded that the CMH forming on the fiber decreases as the temperature increases. The change of temperature (in this experiment from 22 to 60 ℃) does not influence the CMH of the sample used in the evaluation (P3 mineral oil), giving an indication of its thermal stability. In addition, a fixed fiber was used to measure the variation in the liquid level when another fiber is immersed in the liquid. The error in the liquid level obtained in the work was small, at 0.34 ± 0.04 %. Such a sensor, allowing accurate measurements with very small quantities is especially useful where liquid sample volumes are limited e.g. biologically sourced liquids or specialized, expensive industrial material in the liquid phase.

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Section: Introductionmentioning

confidence: 99%

Monitoring of the Critical Meniscus of Very Low Liquid Volumes Using an Optical Fiber Sensor

et al. 2020

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“…These pH‐sensitive membranes are useful for measuring the pH of strongly acidic solutions such as some media found in the stomach or industrial wastewater. In addition, optode membrane technology can be applied to the fabrication of probes for fiber‐optic pH sensors . In this regard, the development of optode membranes capable of detecting acidic pH values remains as an interesting research field.…”

Section: Methodsmentioning

confidence: 99%

A Fluorescent Optode Membrane Covalently Immobilized with a Donor–Acceptor Conjugated Dye for pH Sensing under Extremely Acidic Conditions

Lim

Kim

2019

Bulletin Korean Chem Soc

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Monitoring pH changes is important for chemical and biological analyses, environmental monitoring, chemical/ bio-process control, and other scientific and industrial applications. Therefore, the development of a robust sensor membrane by immobilizing dyes on a solid support for optical pH sensing is important because such an optode membrane would be reusable, prevent samples from being contaminated by dyes, and allow for analyte monitoring in real time. In particular, membrane-based optical pH sensing technology has many advantages over conventional electrochemical pH detection using glass electrodes, because it does not pose the risk of electric shock or require a reference electrode; exhibits a fast response time; and allows for the measurable pH range to be adjusted by the selection of appropriate dyes. 1,2 Although many pH optode membranes have been developed to date, most respond to neutral pH (5-9) common in biological pH measurements. 3-14 Only a few optode membranes that can operate under acidic conditions below pH 3 have been reported. 15-18 These pH-sensitive membranes are useful for measuring the pH of strongly acidic solutions such as some media found in the stomach or industrial wastewater. In addition, optode membrane technology can be applied to the fabrication of probes for fiber-optic pH sensors. [19][20][21] In this regard, the development of optode membranes capable of detecting acidic pH values remains as an interesting research field.Recently, we reported that a donor-acceptor conjugated dye (SPM; Scheme 1) exhibited an internal charge transfer (ICT) process for pH sensing under acidic conditions. 22 As part of our ongoing program for developing a pH-sensitive fluorescent sensor membrane for acidic conditions, the ICT dye (SPM) was covalently immobilized on a silanized glass support via photo-copolymerization with 2-hydroxyethyl methacrylate (HEMA) in the presence of a cross-linker. This optode membrane was very sensitive in the acidic range below pH 2.0. Herein, we report the preparation of a pH-sensitive fluorescent membrane incorporating SPM, and its pH-sensing properties.As shown in Scheme 1, the acryloyl group-bonded dye 3 was designed for covalent immobilization on a glass support. Compound 2 was synthesized via the base-catalyzed condensation of compound 1 with 4-{(2-hydroxyethyl) (methyl)amino}benzaldehyde and was subsequently treated with an equivalent amount of acryloyl chloride in the presence of triethyl amine to afford dye 3 in good yield.The optode membrane was prepared by immobilizing dye 3 on a silyl-modified glass support via the photoinitiated copolymerization of dye 3 with a mixture of HEMA and triethylene glycol dimethacrylate in the presence of a photoinitiator. The thickness of the prepared membrane was approximately 21 μm ( Figure S1), as determined using scanning electron microscopy. HEMA-based polymer membranes are useful for preparing pH-sensitive membranes used in aqueous solutions because they exhibit hydrophilic properties. 9,10,15,17 The absorption and emission s...

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“…The fabrication of the sensing probe requires a multi-step process which has been previously described 10 . The prepolymerization mixture was prepared by mixing a solution containing coumarin dipicolylamine 1 (1.5 mg, 0.0032 mmol), PRP reference polymer (5 mg) and poly(ethylene glycol) diacrylate (Mn = 575) (30 mg) in N,Ndimethylacetamide (500 µL) with a 40% acrylamide solution in water (500 µL) and a 25 mM phosphate buffer pH 7 solution (500 µL).…”

Section: Experimental 21 Sensor Probe Fabricationmentioning

confidence: 99%

A turn-on fluorescence-based fibre optic sensor for the detection of cadmium

Nguyen

Sun

Grattan

2019

Seventh European Workshop on Optical Fibre Sensors

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A stable, compact and portable optical fibre sensor for the real time detection of cadmium ions in dilute aqueous media has been designed, developed and evaluated. The sensing mechanism was based on fluorescence turn-on of a coumarin (acting as the fluorophore) bearing a dipicolylamine moiety (acting as the metal ion receptor) in the presence of metal ions via photoinduced electron transfer (PET). The fluorophore was covalently immobilized onto the fibre surface by polymerisation and exhibited a significant increase in fluorescence intensity in response to Cd 2+ in the µM concentration range. A referencing scheme allowing for corrections due to fluctuations of the excitation light and transmission properties of the optical fibre or environmental perturbation to the sensor system has been introduced using a highly stable perylene red based material as the internal reference. A high selectivity, excellent photo-stability and reversibility have also been demonstrated, making this type of sensor potentially well suited for in-situ monitoring of the metal in the environment.

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Intrinsic Fiber Optic pH Sensor for Measurement of pH Values in the Range of 0.5–6

Cited by 49 publications

References 35 publications

Monitoring of the Critical Meniscus of Very Low Liquid Volumes Using an Optical Fiber Sensor

Monitoring of the Critical Meniscus of Very Low Liquid Volumes Using an Optical Fiber Sensor

A Fluorescent Optode Membrane Covalently Immobilized with a Donor–Acceptor Conjugated Dye for pH Sensing under Extremely Acidic Conditions

A turn-on fluorescence-based fibre optic sensor for the detection of cadmium

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