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1.
Platinum (II) Porphyrin-Containing Thermoresponsive Poly(N-isopropylacrylamide) Copolymer as Fluorescence Dual Oxygen and Temperature Sensor 总被引:1,自引:0,他引:1
A random copolymer, poly(NIPAAm-co-PtPorphyrin), consisting of N-isopropylacrylamide (NIPAAm) and platinum (II) porphyrin units, behaves as an optical dual sensor for oxygen and temperature. The dual sensor is designed by incorporating an oxygen-sensitive platinum (II) porphyrin (M1) into a temperature-sensitive polymer (PNIPAAm). The polymer exhibited low critical solution temperature (LCST) property at 31.5 °C. This LCST affected the polymer's aggregation status, which in turn affected the nanostructures, fluorescence intensities, and responses to dissolved oxygen. This enables the polymer to functionalize as a dual temperature and dissolved oxygen sensor. Oxygen response of the platinum (II) porphyrin probes in the polymer followed a two-site Stern-Volmer model, indicating the nonuniform distribution of the probes. The copolymer was used to preliminarily monitor the oxygen consumption of Escherichia coli (E. coli) bacteria. The results indicate a potential application of the polymer in biological fields. 相似文献
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用射频磁控溅射方法制备了纯氧化锌(ZnO)薄膜和掺Ag、掺Pt与掺Pd的ZnO三种气敏光学薄膜。测量了这些薄膜在NOx气体中的透射光谱,然后由透射光谱获得了灵敏度的变化规律,并用吸附平衡关系式解释了气敏光透射特性,最终优化得到一种对NOx气体灵敏度高的掺Ag氧化锌薄膜。 相似文献
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An optical biosensor for parallel multi-sample determination of biochemical oxygen demand (BOD) in wastewater samples has been developed. The biosensor monitors the dissolved oxygen (DO) concentration in water through an oxygen sensing film immobilized on the bottom of glass sample vials. The oxygen sensing film contains the tris(4,7-diphenyl-1,10-phenanthroline) ruthenium(II) dye (Ru(dpp)) the luminescence intensity of which varies with oxygen concentration. A computer-controlled moving optrode head with four blue light emitting diodes (LEDs) was scanned sequentially under each sample vial. The luminescence signal was collected by an optical cable and transmitted to a photomultiplier tube (PMT) and processed by a microcomputer. The microbial samples (activated sludge and Bacillus subtilis were immobilized in a sol–gel composite material of silica and poly(vinyl alcohol)-grafted-poly(vinylpyridine) on the oxygen sensing film. The performance of the microbial film as a function of cell loading, thickness, temperature and pH and in the presence of heavy metals as well as its stability and service life have been investigated. The BOD value was determined from the rate of oxygen consumption by the microorganisms in the first 20 min. The BOD values obtained from this biosensor correlates well with the results of the conventional 5-day BOD test. 相似文献
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薄膜型TiO_2氧传感器响应时间的测试与研究 总被引:2,自引:1,他引:1
讨论了氧分压测试的原理、方法,利用计算机实现了数据采集自动化.用Sol-gel方法制备出了薄膜型TiO2氧传感器,并对传感器的响应时间进行了测试与分析,发现温度和催化剂对其响应时间有很大的影响. 相似文献
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An optical fiber-based evanescent gaseous ammonia sensor is designed and developed. The sensing dye, bromocresol purple (BCP), is immobilized in the substitutional cladding using sol–gel process. The sensing properties of the optical fiber sensor to gaseous ammonia at room temperature are presented. This newly developed ammonia sensor exhibits good reversibility and repeatability. The effect of different carrier gases, argon, nitrogen, and air on sensing properties of the ammonia sensor is investigated. The sensor with air as carrier gas has the best response time and sensitivity. In order to improve the response time of the optical fiber evanescent ammonia sensor, an elevated ambient temperature is applied and thoroughly investigated. A fast response time of 10 s was obtained at 55.5 °C with the carrier gas of air or argon. These experimental results have demonstrated that a fast response optical fiber evanescent gaseous ammonia sensor can be constructed by applying slightly elevated ambient temperature. 相似文献
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The purpose of this work is double, to analyze the influence of (i) the addition of different catalysts and (ii) the implementation of different procedures to introduce them in the titanium dioxide (TiO2) thin films, in order to improve the film sensitivity for detecting oxygen. For reaching these objectives, TiO2 thin films were deposited on alumina substrates by the ultrasonic spray pyrolysis (USP) technique employing titanium(IV) oxide acetylacetonate (TiO(acac)2) as a titanium precursor, and pure methanol as a solvent. Iridium, nickel, and rhodium were the three catalysts used, which were incorporated by impregnation and USP onto the TiO2 thin films surface. The electrical characterization, consisting in surface resistance measurements of the films, in a mixture of oxygen and zero-grade air, was performed using interdigitated gold electrodes contacted on the alumina substrates. From these, the film response or resistance change of the TiO2 films was estimated. Single TiO2 thin films measured at 400 °C displayed a response of the order of 0.02 and 0.18 to oxygen of 1000 and 10,000 ppm, respectively, whereas TiO2 thin films using impregnated rhodium proved to have the highest response to O2, with a value in the order of 2.5 to a concentration of 1000 ppm of O2 diluted in zero-grade air at an optimal operating temperature of 250 °C. 相似文献
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提出了一种环保、高效、低成本的传感器制作方法.应用等离子体射流喷枪沉积ZnO半导体材料,其中等离子体射流喷枪的气源为N2,电源采用输出频率为20 kHz的高频高压电源.使用Zn(NO3)2的水溶液作为前驱物,经过雾化装置形成气溶胶,气溶胶在等离子体的氛围中成功在衬底上沉积出一层ZnO半导体材料,通过XRD、SEM、UV-Vis等对其进行表征分析.并对基于该方法制备的ZnO湿度传感器性能进行表征.ZnO沉积时间为5 min时的灵敏度最高,低湿和高湿下分别为0.435 pF/% RH和19.634 pF/% RH,同时该样品的迟滞、响应时间与恢复时间亦是最优. 相似文献
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SnO2超微粒子薄膜的气敏特性研究 总被引:4,自引:0,他引:4
作者用自行设计的直流气体放电活化反应蒸发装置制备出平均粒径约为40nm的SnO_2超微粒子薄膜.研究了不同氧分压下所得SnO_2超微粒膜的形貌、结构和组成等特性,以及不同样品对各种易燃气体的气敏特性,得出了灵敏度随氧分压及灵敏度随工作温度的变化曲线. 相似文献
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Qing-Yuan TangAuthor VitaeY.C. ChanAuthor Vitae Kaili ZhangAuthor Vitae 《Sensors and actuators. B, Chemical》2011,152(1):99-106
In this study, the fast response resistive humidity sensing properties of polyimide/multiwall carbon nanotube (PI/MWNT) composite films were demonstrated. A composite film with a loading of 3 wt% MWNTs possesses a very linear response nature, a linearity correlation (R2) of 0.99157 and a sensitivity of 0.00146/%RH. The response time was less than 5 s and the resistance changed synchronously with different humidities. The recoverable and repeatable resistive responses affirmed the high efficiency of this film for fast humidity detection. A negative temperature effect was found and proper temperature compensation should be considered in the future applications. Moreover, the humidity sensing properties were presented as a bulk effect owing to water penetration. The stability of the films was proven, which further confirmed that the films could be used as reliable sensor materials. The surfaces of the films were found as an organized structure with nano-size dimples, which is helpful for absorption of water molecules. The proposed sensing mechanisms are related with tunnel effects, doping of MWNTs by water and a barrier effect between MWNTs. 相似文献
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Thanh Thuy TrinhAuthor Vitae Ngoc Han TuAuthor VitaeHuy Hoang LeAuthor Vitae Kyung Yul RyuKhac Binh LeAuthor Vitae Krishnakumar PillaiJunsin YiAuthor Vitae 《Sensors and actuators. B, Chemical》2011,152(1):73-81
ZnO and Sn doped ZnO (ZnO:Sn) thin films at various doping concentrations from 1 to 10 at.% were prepared by the sol-gel method for an ethanol sensing application. The Sn doping significantly influenced the film growth, grain size and response of the films. The XRD patterns showed that the hexagonal wurtzite structure of the ZnO film was retained even after the Sn doping. The crystallite grain sizes of the ZnO:Sn thin films at 0, 2 and 4 at.% were estimated by using the typical Scherrer's equation. The crystalline quality of the films at 6, 8 and 10 at.% of Sn was degenerated. Typical FESEM images demonstrated the different morphologies for the ZnO:Sn thin films at various Sn concentrations; many pores of various dimensions were observed depending on the doping level. A TEM analysis of the ZnO:Sn thin films at 0, 2 and 4 at.% was performed to verify the grain size. The optimum Sn doping level of ZnO:Sn thin film for ethanol sensing was estimated to be 4 at.%. The 4 at.% sample obtained the highest response to ethanol vapor in the 10-400 ppm level range at a low operating temperature of 250 °C. The sensing mechanism was explained by a variation in the sensitivity model from a neck-grain-boundary controlled sensitivity to a neck-controlled sensitivity. Our work demonstrates the ability to reduce the working temperature as well as to increase the response of ZnO thin film based gas sensors to detect ethanol, which would be of great merit for commercialized applications. 相似文献
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Low-humidity sensors were made by layer-by-layer (LBL) self-assembly of poly(4-styrenesulfonic acid-co-maleic acid) (PSSMA) or poly(styrenesulfonic acid) sodium salt (PSS) and poly(allylamine hydrochloride) (PAH) into multilayer thin films on a gold electrode of quartz crystal microbalance (QCM). The thin films were characterized by QCM and atomic force microscopy (AFM). The effects of maleic acid (MA) in PSSMA, the number of layers and the ionic strength on the low-humidity sensing properties (sensitivity) were compared with those of PSS. The sensitivity of the PSSMA/PAH multilayer thin film exceeded that of the PSS/PAH multilayer thin film when the multilayered thin films of polyelectrolytes were prepared from solutions without NaCl. The sensitivity of both PSSMA/PAH and PSS/PAH multilayered thin films was increased by increasing the number of layers and by adding salt to the deposition solution. The PSS/PAH multilayered thin film that was prepared from the solutions with NaCl had the highest sensitivity (1.923 −ΔHz/Δppmv at 27.5 ppmv) and a short response time. Spin-coating was also adopted to fabricate PSS-based low-humidity sensors for comparison. 相似文献
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This work describes the fabrication of ZrO2/Au nano-composite films and its application for voltammetric detection of organophosphate pesticides. The nano-composite ZrO2/Au film was prepared through a combination of sol–gel procedure and electroless plating that can be carried out in a general chemistry lab with no need for special facilities and reagents. The sensing performance of the ZrO2/Au nano-composite film electrode toward parathion was studied with square wave voltammetry. The nano-ZrO2 showed a strong affinity toward the phosphate group on parathion molecules, which provides sensitivity and selectivity of the sensing film. A linear relationship was obtained between the peak currents and the concentration of parathion, with a detection limit for standard samples of 3 ng/ml. In addition, interference studies showed that structurally similar compounds without phosphate groups would not interfere with the response toward parathion of the film electrode. 相似文献
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Solvatochromic effects in the UV/VIS spectra of dyes can be applied to the monitoring of solvents in the gaseous phase. Within the class of solvatochromic dyes Reichhardt's betaine reveals an outstanding hypsochromic effect on protic solvents with a band shift of up to 350 nm. For vapor detection, the sensor behavior was optimized according to the linearity of the response signal, the sensitivity and a minimum influence of humidity by hydrophobizing siloxanes as additives. Furthermore, the dyes were immobilized under mild conditions by a sol–gel process which generates a high porosity for easy analyte access. The detection principle could be further extended to aprotic, polar solvents by embedding the dyes in protic matrices that form hydrogen bonds to the betaine oxygen. Then, the analyte disturbs the hydrogen bonds resulting in a bathochromic band shift resembling a back titration. Finally, the betaine phenol blue even allows the detection of halogenated hydrocarbons that lack a pronounced functionality but nonetheless a hyperchromic effect occurs during analyte exposition. Mechanistic aspects of these solvent absorption processes were traced by mass-sensitive measurements. 相似文献
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Thin films of hafnium oxide were deposited by electron beam evaporation. The effects of the film thickness and preparation conditions (films prepared on the heated substrate with or without the presence of oxygen environment during deposition) on the optical and carbon monoxide sensing properties of the films were studied. The films were characterized using X-ray diffraction and X-ray photoelectron spectroscopy and optical spectroscopy techniques. Films deposited on unheated substrates were amorphous, whereas those deposited on heated substrates showed a mixture of amorphous and polycrystalline structure. It was found that the sensitivity of the films to CO increased with the thickness and the porosity (as reflected by the refractive indices) of the films. 相似文献
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《Sensors and actuators. B, Chemical》2002,81(2-3):158-164
Pure polyaniline (PAN) film, polyaniline and acetic acid (AA) mixed film, as well as PAN and polystyrenesulfonic acid (PSSA) composite film with various number of layers were prepared by Langmuir–Blodgett (LB) and self-assembly (SA) techniques. These ultra-thin films were characterized by ultraviolet–visible (UV–VIS) spectroscopy and ellipsometry. It is found that the thickness of PAN-based ultra-thin films increases linearly with the increase of the number of film layers. The gas-sensitivity of these ultra-thin films with various layers to NO2 was studied. It is found that pure polyaniline films prepared by LB technique had good sensitivity to NO2, while SA films exhibited faster recovery property. The response time to NO2 and the relative change of resistance of ultra-thin films increased with the increase of the number of film layers. The response time of three-layer PAN film prepared by LB technique to 20 ppm NO2 was about 10 s, two-layer SA film was about 8 s. The mechanism of sensitivity to NO2 of PAN-based ultra-thin films was also discussed. 相似文献