Novel hybrid optical sensor materials for in-breath O(2) analysis

This study focuses on the optimisation and characterisation of novel, ORganically MOdified SILicate (ORMOSIL)-based, hybrid sensor films for use in the detection of O(2) on a breath-by-breath basis in human health monitoring applications. The sensing principle is based on the luminescence quenching of the O(2)-sensitive ruthenium complex [Ru(ii)-tris(4,7-diphenyl-1,10-phenanthroline)], which has been entrapped in a porous sol-gel film. The detection method employed is that of phase fluorometry using blue LED excitation and photodiode detection. Candidate sensor films include those based on the organosilicon precursors, methyltriethoxysilane, ethyltriethoxysilane, n-propyltriethoxysilane and phenyltriethoxysilane. While it has been established previously by the authors that these films exhibit a stable, highly sensitive response to O(2), this study focuses on selecting the material most suited for use in a breath monitor, based on the sensitivity, response time and humidity sensitivity of these films. Key parameters to be optimised include the O(2) sensitivity of the film and the film polarity, i.e. the degree of hydrophobicity. These parameters are directly linked to the precursors used. In this study a n-propyltriethoxysilane-derived O(2) sensor platform was selected as the optimum material for in-breath O(2) analysis due to its short response time, negligible humidity interference and suitable O(2) sensitivity in the relevant range in addition to its compatibility with a single-point calibration strategy.     

基于钌配合物荧光猝灭原理的新型氟化有机改性溶胶-凝胶氧传感膜的研究

选用3,3,3-三氟丙基三甲氧基硅烷为前驱体,制备氧光化学传感膜材料.利用4,7-二苯基-1,10-邻菲咯啉钌(Ⅱ)([Ru(dpp)3(ClO4)2])为氧荧光猝灭指示剂,通过优化制备条件获得对氧浓度变化具有敏感响应的传感膜.研究结果表明:所制备的氧传感膜对水体中的溶解氧的线性响应范围为0.5～16.0 mg/L,最...     

光学氧传感器的研制

本文根据氧分子能有效地猝灭金属有机络合物的荧光的原理，研制了一种氧传感器。     

Optical Sol-Gel-Based Dissolved Oxygen Sensor: Progress Towards a Commercial Instrument

A dissolved oxygen sensor based on fluorescence quenching of the oxygen-sensitive ruthenium complex, [Ru(II)-tris(4,7-diphenyl-1,10-phenanthroline]2+, which has been immobilized in a porous silica sol-gel-derived film, is reported. Ormosil sensing films were fabricated using modified silica precursors such as methyltriethoxysilane (MTEOS) and ethyltriethoxysilane (ETEOS) and were dip-coated onto planar glass substrates. Tailoring of the films for dissolved oxygen (DO) sensing is described whereby sensor response is optimized by maximizing film hydrophobicity by the use of the modified precursors. Sensor performance parameters such as limit of detection and sensor resolution are reported. Issues such as dye leaching and photobleaching are discussed. Progress towards a commercial instrument is reported.     

Fiber-optic fluorescence sensor for dissolved oxygen detection based on fluorinated xerogel immobilized with ruthenium (II) complex

A fiber-optic sensor based on fluorescence quenching was designed for dissolved oxygen (DO) detection. The fluorinated xerogel-based sensing film of the present sensor was prepared from 3, 3, 3-trifluoropropyltrimethoxysilane (TFP–TriMOS). Oxygen-sensitive fluorophores of tris (2, 2′- bipyridine) ruthenium (II) (Ru(bpy)₃²⁺) were immobilized in the sensing film and the emission fluorescence was quenched by dissolved oxygen. In the sensor fabrication, a two-fiber probe was employed to obtain the best fluorescence collection efficiency and the sensing film was attached to the probe end. Scanning electron microscope (SEM), UV–Vis absorption spectroscopy (UV–Vis) and fourier transform infrared spectroscopy (FTIR) measurements have been used to characterize the sensing film. The sensor sensitivity is quantified by I _deoxy/I _oxy, where I _deoxy and I _oxy represented the detected fluorescence intensities in fully deoxygenated and fully oxygenated environments, respectively. Compared with tetramethoxysilane (TMOS) and methyltriethoxysilane (MTMS)-derived sensing films, TFP–TriMOS-based sensor exhibited excellent performances in dissolved oxygen detection with short response time of 4 s, low limit of detection (LOD) of 0.04 ppm (R.S.D. = 2.5%), linear Stern–Volmer calibration plot from 0 to 40 ppm and long-term stability during the past 10 months. The reasons for the preferable performances of TFP–TriMOS-based sensing film were discussed.     

Structurally integrated organic light emitting device-based sensors for gas phase and dissolved oxygen

A compact photoluminescence (PL)-based O2 sensor utilizing an organic light emitting device (OLED) as the light source is described. The sensor device is structurally integrated. That is, the sensing element and the light source, both typically thin films that are fabricated on separate glass substrates, are attached back-to-back. The sensing elements are based on the oxygen-sensitive dyes Pt- or Pd-octaethylporphyrin (PtOEP or PdOEP, respectively), which are embedded in a polystyrene (PS) matrix, or dissolved in solution. Their performance is compared to that of a sensing element based on tris(4,7-diphenyl-l,10-phenanthroline) Ru II (Ru(dpp)) embedded in a sol-gel film. A green OLED light source, based on tris(8-hydroxy quinoline Al (Alq3), was used to excite the porphyrin dyes; a blue OLED, based on 4,4'-bis(2,2'-diphenylviny1)-1,1'-biphenyl, was used to excite the Ru(dpp)-based sensing element. The O2 level was monitored in the gas phase and in water, ethanol, and toluene solutions by measuring changes in the PL lifetime tau of the O2-sensitive dyes. The sensor performance was evaluated in terms of the detection sensitivity, dynamic range, gas flow rate, and temperature effect, including the temperature dependence of tau in pure Ar and O2 atmospheres. The dependence of the sensitivity on the preparation procedure of the sensing film and on the PS and dye concentrations in the sensing element, whether a solid matrix or solution, were also evaluated. Typical values of the detection sensitivity in the gas phase, S(g) identical with tau(0% O2)/tau(100% O2), at 23 degrees C, were approximately 35 to approximately 50 for the [Alq3 OLED[/[PtOEP dye] pair; S(g) exceeded 200 for the Alq3/PdOEP sensor. For dissolved oxygen (DO) in water and ethanol, S(DO) (defined as the ratio of tau in de-oxygenated and oxygen-saturated solutions) was approximately 9.5 and approximately 11, respectively, using the PtOEP-based film sensor. The oxygen level in toluene was measured with PtOEP dissolved directly in the solution. That sensor exhibited a high sensitivity, but a limited dynamic range. Effects of aggregation of dye molecules, sensing film porosity, and the use of the OLED-based sensor arrays for O2 and multianalyte detection are also discussed.     

Optimization of Ormosil Films for Optical Sensor Applications

Recent work has indicated that Ormosil films, fabricated from organically modified precursors, produce better sensor performance for some specific applications, compared to films fabricated from conventional sol-gel precursors such as TEOS or TMOS. This paper aims to compare film properties and sensor behavior for films fabricated from tetraethoxysilane (TEOS) and tetramethoxysilane (TMOS) silica precursors and both methyltrimethoxysilane (MTMS) and methyltriethoxysilane (MTES) organically modified precursors. Microstructural differences, for example, porosity changes due to the different precursor backbone structures, are interrogated by monitoring oxygen gas and aqueous-phase sensor response. Oxygen sensing using these films is enabled by incorporating in the films an oxygen-sensitive ruthenium dye whose fluorescence is quenched in the presence of oxygen. Film properties such as thickness, thickness stabilization time, as well as sensor response, are discussed in terms of relative hydrolysis and condensation behavior for the different precursors. Film hydrophobicity, an issue which has been identified as being of crucial importance for optimum dissolved oxygen sensor response, is discussed and contact angle measurements are used to investigate the degree of hydrophobicity for different film types. The main motivation for this work is film optimization for optical gas-phase and dissolved oxygen sensors.     

Optical sensor for sulfur dioxide based on fluorescence quenching

A series of potential indicator dyes is evaluated for use in the development of optical sensors for measuring sulfur dioxide in gaseous samples. Rhodamine B isothiocyanate is selected on the basis of relative sensitivity to dynamic quenching by sulfur dioxide and oxygen. A solid-state fluorometer is described for monitoring the sulfur dioxide induced fluorescence quenching of sensing membranes composed of silicone and rhodamine B isothiocyanate. A modulated blue LED is coupled with the lock-in detection of a photodiode detector to provide high signal-to-noise ratios. The limit of detection is 0.114+/-0.009% for sulfur dioxide in a carrier stream of nitrogen gas. Selectivity measurements indicate no interference from several common gases (HCl, NH(3), NO, and CO(2)). Oxygen alters the sensor response when comparing signals for sulfur dioxide in 0, 20 and 100% oxygen environments.     

Glucose concentration determination based on silica sol-gel encapsulated glucose oxidase optical biosensor arrays

Optical biosensor arrays for rapidly determining the glucose concentrations in a large number of beverage and blood samples were developed by immobilizing glucose oxidase (GOD) on oxygen sensor layer. Glucose oxidase was first encapsulated in silica based gels through sol-gel approach and then immobilized on 96-well microarrays integrated with oxygen sensing film at the bottom. The oxygen sensing film was made of an organically modified silica film (ORMOSIL) doped with tris(4,7-diphenyl-1,10-phenanthroline) ruthenium dichloride (Ru(dpp)₃Cl₂). The oxidation reaction of glucose by glucose oxidase could be monitored through fluorescence intensity enhancement due to the oxygen consumption in the reaction. The luminescence changing rate evaluated by the dynamic transient method (DTM) was correlated with the glucose concentration with the wide linear range from 0.1 to 5.0 mM (Y = 13.28X − 0.128, R = 0.9968) and low detection limit (0.06 mM). The effects of pH and coexisting ions were systemically studied. The results showed that the optical biosensor arrays worked under a wide range of pH value, and normal interfering species such as Na⁺, K⁺, Cl⁻, PO₄³⁻, and ascorbic acid did not cause apparent interference on the measurement. The activity of glucose oxidase was mostly retained even after 2-month storage, indicating their long-term stability.     

Oxygen-sensing film coated photodetectors for portable instrumentation

A sensor configuration for oxygen determination based on luminescence quenching is presented in which the measured parameter is closely related to the luminescence lifetime. The sensing film is based on the dye platinum octaethylporphyrin complex immobilised in a polystyrene membrane and stabilised with the heterocyclic amine DABCO. In this report, we study the feasibility of using photodiodes as elements to be coated by this oxygen sensing film with the aim of obtaining a sensing device whose small size makes it possible to embed it into a portable measurement system. In addition to the concomitant sensor miniaturisation, several advantages have been demonstrated such as fast response, low energy consumption, the lack of any need for optical filter elements and less tendency to photobleaching than with previous configurations. A complete study of the coated photodetector preparation was carried out in order to optimise the specifications of the portable instrument where the photodetector is included, such as: repeatability, transient response and selectivity. We propose a preparation procedure for coating photodetectors with this film that has demonstrated the capacity to produce repetitive and reliable sensing devices.     

Synthesis, structure and oxygen-sensing properties of iridium(III)-containing coordination polymers with different cations

Four iridium(III)-containing coordination polymers 1-4 using Ir(ppy)(2)(H(2)dcbpy)PF(6) (L-H(2), ppy = 2-phenylpyridine, H(2)dcbpy = 4,4'-dicarboxy-2,2'-bipyridine) as the bridging ligand, [ZnL(2)]·3DMF·5H(2)O (1), [CdL(2)(H(2)O)(2)]·3DMF·6H(2)O (2), [CoL(2)(H(2)O)(2)]·2DMF·8H(2)O (3) and [NiL(2)(H(2)O)(2)]·3DMF·6H(2)O (4), have been synthesized and structurally characterized. The emissions from 1-4 are ascribed to a metal-to-ligand charge transfer transition (MLCT). The absolute emission quantum yields for 1-4 in single crystals were measured in air to be 0.274, 0.193, 0.001 and 0.002, respectively. The noteworthy oxygen-sensing properties of 1-4 as well as L-H(2) in a single crystal were also evaluated. The Stern-Volmer quenching constant, K(SV) values, of 1-4 and L-H(2) can be deduced to be 0.834, 2.820, 1.328, 1.111 and 2.476, respectively. The results show promising K(SV) values (e.g.2) that are competitive or even larger than those of many known Ir-complexes. Moreover, the short response time (e.g. compound 2) and recovery times toward oxygen of 1-4 have been measured in their single crystal forms. The reversibility experiments for 1-4 were carried out for seven repeated cycles. As a result, >75% recovery of intensity for 1 and 2 on each cycle demonstrates a high degree of reproducibility during the sensing process. It should be noted that iridium(III)-containing coordination polymers with high emission intensity and notable oxygen sensing properties are obscure, especially in the single crystal form. This, in combination with its fine reversibility, leads to success in single crystal oxygen recognition based on photoluminescence imaging. The detection limit could be 0.50% for gaseous oxygen. Moreover, the temperature effect of compound 2 in a single crystal upon application as an oxygen sensor was expected.     

Sol-Gel-derived Film for Oxygen Sensor

Oxygen concentration is an important parameter in environmental, chemical and other fields. Oxygen sensor based on luminescence quenching by oxygen have been developed and wide applied. The oxygen quenching process is described by the Stern-Volmer equation. Ruthenium complex are chosen as fluorescence indicator because they are particularly attractive for oxygen sensing, exhibit high luminescent quantum yield, long excited-state lifetime, large Stokes shift, and strong absorption in the blue-green spectral region^[1]. The sensor involves immobilizing the ruthenium complex within a porous sol-gel-processed film. Sol-gel process has many advantages as a method of immobilization. At ambient temperature, it allows the fabrication of a tough, inert, porous glass material with a high surface area. Sol-gel-derived silica film has a low optical absorption in the visible and UV region of the spectrum and is relatively inexpensive to produce^[2].     

Humidity sensors using in situ synthesized sodium polystyrenesulfonate/ZnO nanocomposites

Thin film humidity sensors have been prepared using in situ synthesized inorganic/organic nanocomposites of sodium polystyrenesulfonate (NaPSS) and ZnO. Its humidity sensing characteristics and the sensing mechanism have been investigated by measuring the complex impedance spectra of the sensor at different humidities. The logarithm of the impedance of sensor based on composite film changes linearly by four-orders of magnitude over almost whole humidity range (11-97% RH). Furthermore, the sensor exhibits a quick response (absorption: 2 s, desorption: 2 s) and small hysteresis (less than 2% RH). The composite film shows better sensing properties than NaPSS film, such as better linearity, quicker response. Explanation to the improvement is attempted by taking into account of the composition and structure of the nanocomposites.     

基于氧荧光猝灭速率法的生化需氧量检测

利用氧荧光猝灭速率的方法,结合自行构建的BOD光纤传感装置进行海水中生化需氧量(BOD)含量检测。考察了四种筛选的海洋耗氧菌种在四甲基硅氧烷(TMOS)、二甲基二甲氧基硅烷(Di Me-DMOS)和聚乙烯醇(PVA)包埋固定情况下,对不同浓度的葡萄糖-谷氨酸(GGA)标准溶液的荧光响应情况。BOD敏感膜的荧光响应在0·2~30mg/L浓度范围内呈良好的线性关系,对2mg/L标准溶液测定的相对标准偏差为2·5%(n=6),响应时间(t95%)为4·0min,BOD敏感膜使用寿命大于12个月。实际海水样品检测表明,利用BOD敏感膜检测得到的结果与国标BOD5方法之间存在较好的一致性。     

Enhanced oxygen sensing properties of Pt(II) complex and dye entrapped core-shell silica nanoparticles embedded in sol-gel matrix

This paper presents a highly sensitive oxygen sensor that comprises an optical fiber coated at one end with platinum(II) meso-tetrakis(pentafluorophenyl)porphyrin (PtTFPP) and PtTFPP entrapped core-shell silica nanoparticles embedded in an n-octyltriethoxysilane (Octyl-triEOS)/tetraethylorthosilane (TEOS) composite xerogel. The sensitivity of the optical oxygen sensor is quantified in terms of the ratio I₀/I₁₀₀, where I₀ and I₁₀₀ represent the detected fluorescence intensities in pure nitrogen and pure oxygen environments, respectively. The experimental results show that the oxygen sensor has a sensitivity (I₀/I₁₀₀) of 166. The response time was 1.3 s when switching from pure nitrogen to pure oxygen, and 18.6 s when switching in the reverse direction. The experimental results show that compared to oxygen sensors based on PtTFPP, PtOEP, or Ru(dpp)₃²⁺ dyes, the proposed optical fiber oxygen sensor has the highest sensitivity. In addition to the increased surface area per unit mass of the sensing surface, the dye entrapped in the core of silica nanoparticles also increases the sensitivity because a substantial number of aerial oxygen molecules penetrate the porous silica shell. The dye entrapped core-shell nanoparticles is more prone to oxygen quenching.     

Polarization-based oxygen sensor

A new approach to oxygen sensing based on the luminescence polarization observed from a novel type of sensor is described. The oxygen sensor consists of an oxygen-sensitive silicone film containing tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) chloride [Ru(dpp)3Cl2] and an oxygen-insensitive film of Styryl 7 in poly(vinyl alcohol). Polarizers are used to select orthogonally polarized emission components from Ru(dpp)3Cl2 and Styryl 7. The polarization of the combined emission was found to be highly sensitive to the partial pressure of oxygen. This method of polarization sensing is generic and can be used with any fluorophore which displays an analyte-dependent change in intensity.     

Optimisation of Sol-Gel-Derived Silica Films for Optical Oxygen Sensing

Sol-gel-derived silica films were fabricated by dip-coating onto planar and optical fibre substrates. The films were pre-doped with the oxygen-sensitive ruthenium complex [Ru(II)-tris(4,7-diphenyl-1,10-phenanthroline)], whose fluorescence is quenched in the presence of oxygen. The structure and behaviour of sol-gel films is related to the fabrication parameters. In order to optimise the films for oxygen sensing in gaseous and in aqueous media, the quenching behaviour was monitored as a function of dip-speed and water: precursor ratio. By adjusting the above parameters, film properties can be tailored to optimise oxygen quenching in particular concentration ranges and environments.     

High‐Performance Oxygen Sensors Based on EuIII Complex/Polystyrene Composite Nanofibrous Membranes Prepared by Electrospinning

An optical oxygen sensor based on an Eu^III complex/polystyrene (PS) composite nanofibrous membrane is prepared by electrospinning. The emission intensity of [Eu(TTA)₃(phencarz)] (TTA=2‐thenoyltrifluoroacetonate, phencarz=2‐(N‐ethylcarbazolyl‐4)imidazo[4,5‐f]1,10‐phenanthroline) decreases with increasing oxygen concentration, and thus the [Eu(TTA)₃ (phencarz)]/PS composite nanofibrous membranes can be used as an optical oxygen‐sensing material based on emission quenching caused by oxygen. Elemental analysis, UV/Vis absorption spectra, scanning electron microscopy (SEM), fluorescence microscopy, luminescence‐intensity quenching Stern–Volmer plots, and excited‐state decay analysis are used to characterize the obtained oxygen‐sensing materials. A high sensitivity (I_N2/I_O2) of 3.38 and short response and recovery times (t_↓=5.0, t_↑=8.0 s) are obtained. These results are the best values reported for oxygen sensors based on Eu^III complexes. The high surface area‐to‐volume ratio and porous structure of the electrospun nanofibrous membranes are taken to be responsible for the outstanding performance.     

A novel oxygen and/or carbon dioxide-sensitive optical transducer

A novel oxygen (O(2)) and/or carbon dioxide (CO(2))-sensitive transducer for the measurement of both gaseous O(2) and CO(2) over the concentration ranges of O(2), 0-100% and CO(2), 0-10% has been described employing a solution of 10.6 muM fluorescein (FL) and 190 muM potassium hydroxide in a solvent mixtures of 1:1 (v/v) N,N'-diethylaniline (DEA) and N,N-dimethylformamide. Increasing O(2) concentrations cause the absorbance of the solution at a wavelength of 400 nm to increase owing to a contact charge transfer reaction existing between O(2) and DEA molecules, and increasing CO(2) concentrations produce a non-linear fall in absorbance at 520 nm as the colour of FL changes from its orange dianion form to the colourless neutral, lactonic form. Both processes are independent of each other and reversible. The response to changes in O(2) concentrations is in good agreement with Beer-Lambert's law and the response to changes in CO(2) concentrations in non-linear. A fibre optic sensing system based on this solvent-dye solution has been set up for continuous and reversible determination of both gaseous O(2) and CO(2). Possible applications include environmental and physiological monitoring of O(2) over the ranges of 0-100% and CO(2), 0-10%.     

纳米结构CuO为敏感电极的阻抗谱型NO2传感器

以浸渍技术制备的纳米CuO颗粒作敏感电极,以YSZ作为固体电解质制备了阻抗谱型NO2传感器。采用XRD、SEM对NO2传感器敏感材料的相组成和微观形貌进行了表征,应用电化学工作站测试了传感器的敏感性能。结果表明:浸渍法制得的CuO颗粒均匀分布在电解质的多孔层内,粒径在200 nm左右。在450～550℃,传感器对NO2有良好的敏感性,在0.1 Hz总阻抗|Z|=(Z′2+Z″2)～(1/2)姨与NO2浓度(0～200 mL.m-3)呈良好的线性关系。传感器的固有响应时间为50 s,共存的O2和CO2气体对传感器敏感性能几乎没有影响。