基于金银合金薄膜的波长检测型表面等离子体共振传感器

从实验和理论两方面详细研究了金银合金膜表面等离子体共振(SPR)传感器在可见光波段的敏感特性.实验方面,通过在玻璃基底上溅射50 nm厚的金银合金薄膜制备了一种新型的SPR传感芯片,并且自行搭建了基于Kretschmann结构的波长检测型SPR传感器测试平台.利用不同浓度的氯化钠(NaCl)水溶液和浓度为10μmol·L-1的牛血清蛋白(BSA)水溶液分别作为折射率样品和分子吸附样品,研究了传感器的折射率灵敏度和吸附灵敏度,并与金膜和银膜SPR传感器进行了对比研究.结果表明,对于折射率灵敏度的测试,金银合金膜SPR传感器大幅高于金膜SPR传感器,略低于银膜SPR传感器;而对于吸附敏感的研究,金银合金膜SPR传感器的灵敏度与银膜SPR传感器相近,是金膜SPR传感器的3倍.理论方面,利用菲涅尔公式和等效折射率计算公式仿真计算了这三种薄膜结构的SPR传感器的灵敏度和精确度,结果指出金银合金膜SPR传感器的灵敏度与银膜SPR传感器接近,是常规金膜SPR传感器的2.31倍,而半高峰宽仅为金膜和银膜SPR传感器的1.36倍.在稳定性方面,金银合金膜SPR传感器与金膜SPR传感器均具有良好的化学稳定性,而银膜SPR传感器较易氧化,使用寿命低,不常被采用.综上,金银合金膜在改善传感器灵敏度的同时,不会降低精度,是一种高灵敏、低成本、良好稳定性的SPR传感器敏感材料.     

The first fluorescent sensor for boronic and boric acids with sensitivity at sub-micromolar concentrations--a cautionary tale

The first reported fluorescent sensor for boronic and boric acids is actually not a sensor for boronic and boric acids but rather is a sensor for protons; the system is also not the first fluorescent sensor since Alizarin has been used as a fluorescent sensor for boric acids since 1936.     

基于金银合金薄膜的波长检测型表面等离子体共振传感器

从实验和理论两方面详细研究了金银合金膜表面等离子体共振（SPR）传感器在可见光波段的敏感特性. 实验方面,通过在玻璃基底上溅射50 nm厚的金银合金薄膜制备了一种新型的SPR传感芯片,并且自行搭建了基于Kretschmann 结构的波长检测型SPR传感器测试平台. 利用不同浓度的氯化钠（NaCl）水溶液和浓度为10 μmol·L^-1的牛血清蛋白（BSA）水溶液分别作为折射率样品和分子吸附样品,研究了传感器的折射率灵敏度和吸附灵敏度,并与金膜和银膜SPR传感器进行了对比研究. 结果表明,对于折射率灵敏度的测试,金银合金膜SPR传感器大幅高于金膜SPR传感器,略低于银膜SPR传感器;而对于吸附敏感的研究,金银合金膜SPR传感器的灵敏度与银膜SPR传感器相近,是金膜SPR传感器的3倍. 理论方面,利用菲涅尔公式和等效折射率计算公式仿真计算了这三种薄膜结构的SPR传感器的灵敏度和精确度,结果指出金银合金膜SPR传感器的灵敏度与银膜SPR传感器接近,是常规金膜SPR传感器的2.31倍,而半高峰宽仅为金膜和银膜SPR传感器的1.36 倍. 在稳定性方面,金银合金膜SPR传感器与金膜SPR传感器均具有良好的化学稳定性,而银膜SPR传感器较易氧化,使用寿命低,不常被采用. 综上,金银合金膜在改善传感器灵敏度的同时,不会降低精度,是一种高灵敏、低成本、良好稳定性的SPR传感器敏感材料.     

Flow injection analysis as a diagnostic technique for development and testing of chemical sensors

An immobilized urease sensor is developed for continuous, on-line analysis. The sensor consists of the enzyme urease, cross-linked with bovine serum albumin into a cellulose pad, with an acid-base indicator dye covalently bound to the surface of the cellulose. The sensor is placed within a flow-injection optosensing system to monitor the change in pH, and subjected to a through evaluation, using the flow-injection technique; sensor stability (both dye and enzyme stability), speed of sensor response, sensor sensitivity, sensor-to-sensor reproducibility, response to a typical interferent, and sensor lifetime data are obtained. Sensor poisoning upon exposure to low levels of mercury, and subsequent regeneration of the immobilized enzyme pad, is investigated for use as an on-line mercury sensor. The urea sensor is also evaluated for use as a continuous monitor for urea in kidney dialysate. Enzyme Michaelis-Menten constants are determined for the immobilized urease, under given assay conditions, using a stopped-flow flow-injection technique.     

A new evanescent wave ammonia sensor based on polyaniline composite

A single-mode TE(0)-TM(0) optical planar waveguide ammonia sensor based on polyaniline/polymethyl methacrylate (PANI/PMMA) composite is designed and developed. The sensing properties of the photonic sensor to ammonia at room temperature are studied. A significant change is observed in the guided light output power of the sensor after it is exposed to ammonia gas. The metrological parameters (sensitivity, response time and recovery time) of the sensor are strongly influenced by the interaction length (length of sensing region). Compared with the conventional optical ammonia sensor based on absorption spectroscopy, the integrated optical sensor is more sensitive to ammonia.     

A microfabricated amperometric moisture sensor

We describe a microfabricated moisture sensor with interdigitated Au or Pt electrodes on a silicon substrate. The sensor active area is covered with a spin-coated, baked-on layer of Nafion(R) perfluorosulfonate ionomer of submicron thickness. The sensor responds to moisture with a 10-90% rise time of 50-100 ms and a 90-10% fall time of 20-30 ms, faster than any other presently available sensor. The logarithm of the sensor current is related to the cube root of the moisture level at a given temperature. At 23 degrees C, the sensor easily measures relative humidities as low as 10%. The sensor response at a given absolute humidity level decreases exponentially with increasing temperature. The film is stable up to a temperature of 150 degrees C, permitting elevated temperature moisture measurement. Since sorbed water is actively decomposed electrolytically, the sensors exhibit negligible hysteresis. Response reproducibility of an individual sensor is <1%, that between identically made sensors is <5%, suggesting mass production techniques without individual calibration will be acceptable for all but the most demanding situation.     

Coulometric sensors,the application of a sensor-actuator system for long-term stability in chemical sensing

We present a new type of chemical transducer, the coulometric sensor. This sensor is in fact an integrated sensor-actuator system that is able to measure the concentration of acids and bases by means of coulometric titration. An ISFET is used as the sensor to monitor the pH changes induced by the actuator, which is a gold electrode that fits closely around the ISFET's gate area. Coulometry is an absolute method and therefore the output of the new sensor is only determined by its dimensions and is not subject to changes in offset and sensitivity of the indicator electrode. It is thus expected that the operation of the sensor will be stable for a long time, so that only a one-time calibration is needed. As a first example of this new class of chemical transducers, a carbon dioxide sensor is presented. It is shown that the stability is some orders of magnitude better than that for a ‘classical” potentiometric sensor.     

Multiparameter Sensor Chip with Barium Strontium Titanate as Multipurpose Material

It is well known that biochemical and biotechnological processes are strongly dependent and affected by a variety of physico‐chemical parameters such as pH value, temperature, pressure and electrolyte conductivity. Therefore, these quantities have to be monitored or controlled in order to guarantee a stable process operation, optimization and high yield. In this work, a sensor chip for the multiparameter detection of three physico‐chemical parameters such as electrolyte conductivity, pH and temperature is realized using barium strontium titanate (BST) as multipurpose material. The chip integrates a capacitively coupled four‐electrode electrolyte‐conductivity sensor, a capacitive field‐effect pH sensor and a thin‐film Pt‐temperature sensor. Due to the multifunctional properties of BST, it is utilized as final outermost coating layer of the processed sensor chip and serves as passivation and protection layer as well as pH‐sensitive transducer material at the same time. The results of testing of the individual sensors of the developed multiparameter sensor chip are presented. In addition, a quasi‐simultaneous multiparameter characterization of the sensor chip in buffer solutions with different pH value and electrolyte conductivity is performed. To study the sensor behavior and the suitability of BST as multifunctional material under harsh environmental conditions, the sensor chip was exemplarily tested in a biogas digestate.     

A wireless pH sensor using magnetoelasticity for measurement of body fluid acidity.

The determination of body fluid acidity using a wireless magnetoelastic pH-sensitive sensor is described. The sensor was fabricated by casting a layer of pH-sensitive polymer on a magnetoelastic ribbon. In response to an externally applied time-varying magnetic field, the magnetoelastic sensor mechanically vibrates at a characteristic frequency that is inversely dependent upon the mass of the pH polymer film, which varies as the film swells and shrinks in response to pH. As the magnetoelastic sensor is magnetostrictive, the mechanical vibrations of the sensor launch magnetic flux that can be detected remotely using a pickup coil. The sensor can be used for direct measurements of body fluid acidity without a pretreatment of the sample by using a filtration membrane. A reversible and linear response was obtained between pH 5.0 and 8.0 with a measurement resolution of pH 0.1 and a slope of 0.2 kHz pH(-1). Since there are no physical connections between the sensor and the instrument, the sensor can be applied to in vivo and in situ monitoring of the physiological pH and its fluctuations.     

Layer-layer assembly for extremely stable glucose sensors

A novel fabrication of an amperometric glucose sensor by layer after layer approach is described. The sensor electrode is fabricated by arranging a layer of Pt black, a layer of glucose oxidase (GOD) and a layer of stabilizer gelatin on a shapable electro-conductive (SEC) film surface. Finally, the dried layered-assembly is cross-linked by exposing to a diluted glutaraldehyde solution. The performance of the developed sensor is evaluated by a FIA system at 37°C and under a continuous polarization at 0.4 V (vs. Ag/AgCl). The sensitivity of the sensor was dependent on the amount of GOD loaded. The highest sensitivity (3.6 μA/mM cm⁻²) of the sensor was obtained at a GOD loading of 160 μg/cm², and the linear dynamic range was extended to 80 mM level when the sensor was covered with a polycarbonate membrane. The sensor shows an extremely stable response for several weeks and a storage stability of over 2 years.     

Optimising of the sensing chamber of an array of a volatile detection system

A fluid dynamic analysis was performed to optimise the positioning of sensor elements in a coated quartz crystal microbalance (QCM) based volatile detection system. The computational fluid dynamic (CFD) code used solves the Navier-Stokes equations statically and dynamically in 2D, discretised by finite elements. In the original sensor chamber, the sensor elements were positioned in a staggered pattern and at 90° to the incoming flow. The numerical analysis shows that, with the exception of the front face of the first sensor, only 45% of the flow passed over the sensors. It is shown that the response of sensor elements is strongly dependent on the sensor position. An optimised sensor chamber design was developed where the sensors are at 0° to the flow direction and a baffle plate diffuses the flow evenly over the sensor elements. The sensors are shown to receive the same flow and respond identically irrespective of position. This revised version was published online in July 2006 with corrections to the Cover Date.     

A High‐Affinity Fluorescent Sensor for Catecholamine: Application to Monitoring Norepinephrine Exocytosis

A fluorescent sensor for catecholamines, NS510, is presented. The sensor is based on a quinolone fluorophore incorporating a boronic acid recognition element that gives it high affinity for catecholamines and a turn‐on response to norepinephrine. The sensor results in punctate staining of norepinephrine‐enriched chromaffin cells visualized using confocal microscopy indicating that it stains the norepinephrine in secretory vesicles. Amperometry in conjunction with total internal reflection fluorescence (TIRF) microscopy demonstrates that the sensor can be used to observe destaining of individual chromaffin granules upon exocytosis. NS510 is the highest affinity fluorescent norepinephrine sensor currently available and can be used for measuring catecholamines in live‐cell assays.     

Improved Nafion-based amperometric sensor for hydrogen in argon

An improved polymer electrolyte membrane fuel cell-based amperometric hydrogen sensor has been developed. The sensor operates at room temperature, and the electrolyte used in the sensor is Nafion which is a proton-conducting solid polymer electrolyte. Platinum black is used as both anode and cathode. The sensor functions as a fuel cell, H₂/Pt//Nafion//Pt/O₂, and a mechanical barrier limits the supply of hydrogen to the sensing side electrode. The limiting current is found to be linearly related to the hydrogen concentration. The sensor can be used to measure hydrogen in argon in parts per million and percentage levels. The basic principle, details of assembly, and response behavior of the sensor are discussed.     

Preparation and spectroscopic properties of multiluminophore luminescent oxygen and temperature sensor films

A new luminescent oxygen and temperature sensor has been developed that utilizes two luminescent dyes, 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin platinum(II) (PtTFPP, the oxygen sensor) and tris(1,10-phenanthroline)ruthenium(II) dichloride (Ruphen, the temperature sensor). The two dyes are dispersed in an oxygen-permeable polymer binder consisting of a copolymer of 4-tert-butylstyrene (tBS) and 2,2,2-trifluoroethyl methacrylate (p-tBS-co-TFEM). To alleviate energy transfer and other quenching interactions between the two luminescent dyes in the p-tBS-co-TFEM binder, the Ruphen temperature sensor is encapsulated in polyacrylonitrile (PAN) polymer nanospheres that are prepared by coprecipitation of PAN and Ruphen from N,N-dimethylformamide solution. The temperature and air-pressure response of the emission from the sensor film is fully characterized by using emission spectroscopy. The emission from the two luminescent dyes is spectrally well-separated. The intensity of the Ruphen emission varies strongly with temperature (approximately 1.4% degrees C(-1)), whereas the intensity of the PtTFPP emission varies with temperature and air pressure. The two-dye luminescent coating is useful as a pressure-sensitive paint (PSP), where the emission from the Ruphen temperature sensor is used to correct for the temperature dependence of the pressure response of the PtTFPP sensor. To demonstrate the PSP application, a coupon coated with the sensor was imaged using a CCD camera, and the CCD images were analyzed by intensity ratio methods. Spectroscopic studies were also carried out on a sensor that contains three dyes in order to demonstrate the feasibility of including an intensity reference dye along with the temperature and pressure dyes into the sensor.     

Novel membrane-based sensor for online membrane integrity monitoring

A novel membrane-based sensor device for upstream membrane integrity monitoring has been developed and evaluated in this study. The sensor is based on relative trans-membrane pressures created by two membranes in series inside the sensor device that detects deposition from the sample stream onto the first of the sensor membranes. The sensor pressure signals can distinguish between intact or damaged membranes in the upstream membrane filtration process. Studies were conducted to evaluate both stabilities and sensitivities of the relative trans-membrane pressure monitoring technique. Sensitivity, based on the response times of the membrane sensor for particle detection, was determined for a range of operating conditions, membrane sandwich configurations, and particle concentrations in both simulated membrane failures and for actual pin-hole defects on a submerged MF membrane. The results showed that both sensitivities and stability strongly depended on membrane sandwich configurations (membrane characteristics) in the sensor, and mode of operation (pressurized or vacuum). The membrane sensor detected bentonite particles with a concentration of 0.3 mg/L (turbidity ∼0.3 NTU) in approximately 35 min in the vacuum mode. The sensor is reliable, sensitive and low cost. It has potential applications in decentralized systems or in multichannel monitoring of local conditions in a large plant. Possible applications of the membrane sensor for fouling monitoring are also discussed.     

Submicrometer cavity surface plasmon sensors

A miniaturized spherical surface plasmon sensor for measuring the binding kinetics of unlabeled molecules is introduced. The sensor has a submicrometer footprint with a sensitivity that rivals that of state-of-the-art commercial planar surface plasmon sensors, which makes it valuable for applications requiring integration of detection of molecular species in microfluidic channels. The basic principle of the sensor is exploiting the wavelength shifts of the cavity resonances of a metal-coated submicrometer sphere embedded in an opaque metal film due to molecular adsorption. The sensor has been found to be exquisitely responsive in air to water and ethanol vapor adsorption on the bare gold sensor surface. When immersed in a liquid, the sensor can detect the adsorption of less than one monolayer of dodecanethiol (approximately 1.5 nm) on the gold coating of the sphere.     

Comparison of microbial sensors based on amperometric and potentiometric electrodes

Microbial sensors based on oxygenn and carbon dioxide electrodes coupled with immobilized Saccharomyces are compared for measurements of glucose and other carbohydrates. With the oxygen sensor, the yeast works under aerobic conditions but anaerobically with the carbon dioxide sensor. The two metabolisms of the same strain make little difference to the lifetimes (> 15 days), selectivities and response rates (5–10 min) of the sensors. The effects of pH are very different owing to the pH sensitivity of the carbon dioxide sensor. The viable concentration ranges overlap; the oxygen-based sensor is more useful for low concentrations of glucose (0.01–1 mmol l^?1) while the carbon dioxide-based sensor is better suited for 1–10 mmol l^?1. With the oxygen-based sensor, the response time is governed by the rate of metabolism; with the carbon dioxide-based sensor, the response time of the potentiometric carbon dioxide electrode is the rate determining step.     

Integrated-optic ammonia sensor

Fibre coupled optical sensors for chemical and biologial species are important for process control, environmental control and pollution detection. An integrated optic ammonia sensor is described here; this is based on evanescent field absorption. The sensitive element of this sensor is a strip waveguide, fabricated by field assisted ion exchange, coated with a immobilized indicator dye. The sensor has a short response time and a long lifetime. An experimental arrangement is shown which has been built up for the characterization of different integrated optic sensor elements. Spectral response characteristics, response times and the generation of reference signals are reported in detail. The simple temperature dependence, the humidity independence and the very low cross sensitivity of this ammonia sensor is illustrated.     

A coated piezoelectric crystal sensor for acetic acid vapour determination

A novel sensor for acetic acid vapour determination is proposed. This sensor is based on a piezoelectric crystal covered with a film of diethylenetriamine. For the sensor development a system of our own design-consisting of testing chamber, oscillator circuit and measure instruments-has been employed. The sensor shows its activity to the acetic acid vapours for more than 60 days. The selectivity is adequate although some vapours interfere: hydrochloric acid, formic acid, formaldehyde, tributyl phosphate, chloroform, chlorobenzene, acetone and isobutylmethylketone. The sensor described can be applied to detect acetic acid vapours in the presence of other vapours: acetonitrile, acrolein, benzene, n-hexane, ethanol, propanol, n-butyl acetate, isopropyl ether, isoamyl alcohol, ethyl ether, methylene chloride, carbon tetrachloride and toluene. The major advantages of the proposed sensor over other existing techniques are its simplicity, reduced cost and capacity for use in situ.