The Experts below are selected from a list of 26559 Experts worldwide ranked by ideXlab platform
Jay W Grate - One of the best experts on this subject based on the ideXlab platform.
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single walled carbon nanotube paper as a sorbent for organic vapor preconcentration
2006Co-Authors: Feng Zheng, David L Baldwin, Leonard S Fifield, Norman C Anheier, Christopher L Aardahl, Jay W GrateAbstract:Single-walled carbon nanotubes were examined as an adsorptive material for a thermally desorbed preconcentrator for organic Vapors. The nanotubes were processed into a paper form and packed into a metal tube for flow-through sampling. Adsorbed Vapors were released by a temperature-programmed desorption method and detected downstream with a flexural plate wave vapor sensor. The tested Vapors, methyl ethyl ketone, toluene, and dimethyl methylphosphonate, were released from the packed column at different temperatures. The Vapors were retained more strongly than previously observed for the widely used Tenax porous polymer, indicating a significant affinity of the single walled nanotubes for organic Vapors.
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method for unknown vapor characterization and classification using a multivariate sorption detector initial derivation and modeling based on polymer coated acoustic wave sensor arrays and linear solvation energy relationships
1999Co-Authors: Jay W Grate, Barry M Wise, Michael H. AbrahamAbstract:A novel method for the characterization and classification of unknown Vapors based on the response on an array of polymer-coated acoustic wave vapor sensors is presented. Unlike existing classification algorithms, the method does not require that the system be trained on all samples to be identified. Instead, the solvation parameters of the unknown vapor are estimated given the sensor responses and the linear solvation energy relationship coefficients of the sorbent polymer coatings. The Vapors can then be identified from a database of candidate vapor parameters. The method is implemented in a way that is analogous to multivariate calibration with classical least squares, where the individual vapor parameters are treated as pure compounds. It is not necessary to know the vapor concentration of the vapor to perform the classification. In principle, it is possible to estimate the concentration of an unknown vapor for which the system has not been trained or calibrated. It is also possible to implement the m...
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smart sensor system for trace organophosphorus and organosulfur vapor detection employing a temperature controlled array of surface acoustic wave sensors automated sample preconcentration and pattern recognition
1993Co-Authors: Jay W Grate, S L Rosepehrsson, M Klusty, David L Venezky, H WohltjenAbstract:A smart sensor system For the detection of toxic organophosphorus and toxic organosulfur Vapors at trace concentrations has been designed, fabricated, and tested against a wide variety of vapor challenges. The key features of the system are an array of four surface acoustic wave (SAW) vapor sensors, temperature control of the vapor sensors, the use of pattern recognition to analyze the sensor data, and an automated sampling system including thermally desorbed preconcentrator tubes (PCTs). All the electronics necessary to control and operate the various subsystems and to collect and process the data are included in the system
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a smart sensor system for trace organic vapor detection using a temperature controlled array of surface acoustic wave vapor sensors automated preconcentrator tubes and pattern recognition
1993Co-Authors: Jay W Grate, S L Rosepehrsson, M Klusty, H WohltjenAbstract:A smart sensor system for the detection, of toxic organophosphorus and toxic organosulfur Vapors at trace concentrations has been designed, fabricated, and tested against a wide variety of vapor challenges. The key features of the system are: An array of four surface acoustic wave (SAW) vapor sensors, temperature control of the vapor sensors, the use of pattern recognition to analyze the sensor data, and an automated sampling system including thermally-desorbed preconcentrator tubes (PCTs).
Lei Jiang - One of the best experts on this subject based on the ideXlab platform.
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aggregation induced emission molecule microwire based specific organic vapor detector through structural modification
2021Co-Authors: Xiangyu Jiang, Dong Wang, Ce Shi, Jinhui Pang, Xiqi Zhang, Lei JiangAbstract:An optical organic vapor sensor array based on colorimetric or fluorescence changes quantified by spectroscopy provides an efficient method for realizing rapid identification and detection of organic vapor, but improving the sensitivity of the optical organic vapor sensor is challenging. Here, AIE/polymer (AIE, ggregation-induced emission) composites into microwires arrays are fabricated as organic vapor sensors with specific recognition and high sensitivity for different Vapors using the capillary-bridge-mediated assembly method. Such organic vapor sensor successfully detects organic vapor relying on a swelling-induced fluorescence change of the AIE/polymer composites, combating the unique property of AIE molecules and vapor absorption-induced polymer swelling. A series of AIE/polymer composites into microwires arrays with four different groups on the AIE molecule and four different side chains on the polymer is fabricated to detect four different organic Vapors. The mechanism for improved sensitivity of the AIE/polymer composites microwires arrays sensors is the same because of the similar polarity between the group of AIE molecules and the vapor molecules. Molecular design of the side chains of the polymer and the groups of AIE molecules based on the polarity of the targeted vapor molecule can enhance the sensitivity of the sensors to the subparts per million level.
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a visual and organic vapor sensitive photonic crystal sensor consisting of polymer infiltrated sio2 inverse opal
2015Co-Authors: Yuqi Zhang, Ben Zhong Tang, Jianhua Qiu, Loujun Gao, Liping Heng, Lei JiangAbstract:A photonic crystal (PC) sensor that can selectively detect organic Vapors through visual color changes has been proposed. The sensor was fabricated by infiltrating a tetraphenylethene polymer (TPEP) into the voids of SiO2 inverse opal photonic crystal. When the sensor was exposed to tetrahydrofuran or acetone vapor, a red shift of the stopband of more than 50 nm could be clearly observed; meanwhile, the film's color changed from violet to cyan. Subsequently, when exposed to air, the stopband underwent a blue shift and the color returned to violet. The reason for the observed change is that a reversible adsorption–desorption process occurs on alternate exposure of the sensor to organic vapor and air, due to the high specific surface area of the inverse opal macroporous structure and the high affinity of TPEP to tetrahydrofuran and acetone. The adsorption of vapor analyte can increase the PC's effective refractive index, which will induce the stopband red shift and the resulting color change according to Bragg's Law. The reversible adsorption–desorption of organic Vapors varied the effective refractive index of the sensor repeatedly, causing the reversible stopband shift and color change, and providing a general method for the design of visual vapor sensors.
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a visual film sensor based on silole infiltrated sio2 inverse opal photonic crystal for detecting organic Vapors
2014Co-Authors: Yuqi Zhang, Ben Zhong Tang, Jianhua Qiu, Loujun Gao, Liping Heng, Miaomiao Gao, Lei JiangAbstract:The reversible color change of the silole-infiltrated SiO2 inverse opal photonic crystal (IOPC) film can be obtained by alternating its exposure to different vapor environments. When the film was put in diethyl ether or petroleum ether vapor, a stopband red shift of more than 100 nm could be clearly observed, while the color changed from green to red. When exposed to air, the stopband underwent a blue shift and the color changed back to green. The result is attributed to the silole molecules, hexaphenylsilole (HPS), which can be transformed reversibly between the crystal and amorphous state when alternately exposed to air and Vapors of diethyl ether/petroleum ether. When crystal HPS changed to amorphous HPS in an atmosphere of organic Vapors, both the specific surface area and refractive index of HPS increased. The higher specific surface area of HPS improved the adsorption behavior of organic Vapors. Both the improved adsorption and higher refractive index of HPS increased the effective refractive index of HPS-infiltrated SiO2 IOPC, which resulted in the red shift of the stopband and the color change, according to the Bragg Law. Based on the reversible aggregation state transfer and the adsorption–desorption of organic Vapors, the effective refractive index of the film varied repeatedly, which caused the reversible stopband shift and color change. The visual detection of organic Vapors can be realized because of the remarkable color change of the IOPC film, which provides a simple route for monitoring volatile organic compounds, and is important for chemical and biological sensors.
Edward T Zellers - One of the best experts on this subject based on the ideXlab platform.
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limits of recognition for simple vapor mixtures determined with a microsensor array
2004Co-Authors: Meng Da Hsieh, Edward T ZellersAbstract:The “limit of recognition” (LOR) has been defined as the minimum concentration at which reliable individual vapor recognition can be achieved with a multisensor array, and methodology for determining the LORs of individual Vapors probabilistically on the basis of sensor array response patterns has been reported. This article explores the problems of defining and evaluating LORs for vapor mixtures in terms of the absolute and relative component vapor concentrations, where the mixture must be discriminated from those component Vapors and from the subset of possible lower-order component mixtures. Monte Carlo simulations and principal components regression analyses of an extant database of calibrated responses to a set of 16 Vapors from an array of 6 diverse polymer-coated surface acoustic wave sensors are used to illustrate the approach and to examine trends in LOR values among the 120 possible binary mixtures and 560 possible ternary mixtures in the data set. At concentrations exceeding the LOD, 89% of the...
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dual chemiresistor gc detector employing monolayer protected metal nanocluster interfaces
2002Co-Authors: Qing Yun Cai, Edward T ZellersAbstract:The synthesis and testing of two gold−thiolate monolayer-protected (nano)clusters as interfacial layers on a dual-chemiresistor vapor sensor array are described. Responses (changes in dc resistance) to each of 11 organic solvent Vapors are rapid, reversible, and linear with concentration at low vapor concentrations, becoming sublinear at higher concentrations. Limits of detection (LODs) range from 0.1 to 24 parts per million and vary inversely with solvent vapor pressure. When configured as a GC detector and used to analyze 0.5-L preconcentrated samples of the 11-vapor mixture, the array provides LODs of ≤700 parts per trillion for most Vapors, comparing favorably with those from an integrated array of polymer-coated surface acoustic wave sensors configured and tested similarly. This first report on the use of such an array as a GC detector shows that the combination of response patterns and GC retention times improves capabilities for vapor recognition compared to the sensor array alone or to single-dete...
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vapor recognition with small arrays of polymer coated microsensors a comprehensive analysis
1999Co-Authors: Jeongim Park, William A Groves, Edward T ZellersAbstract:A comprehensive analysis of vapor recognition as a function of the number of sensors in a vapor−sensor array is presented. Responses to 16 organic Vapors collected from six polymer-coated surface acoustic wave (SAW) sensors were used in Monte Carlo simulations coupled with pattern recognition analyses to derive statistical estimates of vapor recognition rates as a function of the number of sensors in the array (≤6), the polymer sensor coatings employed, and the number and concentration of Vapors being analyzed. Results indicate that as few as two sensors can recognize individual Vapors from a set of 16 possibilities with 5 × LOD for the array. At lower concentrations, a minimum of three sensors is required, but arrays of 3−6 sensors provide comparable results. Analyses also revealed that individual-vapor recognition hinges more on the similarity of the vapor response patterns than on the total number of possible Vapors considered. Vap...
Xudong Fan - One of the best experts on this subject based on the ideXlab platform.
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self referenced composite fabry perot cavity vapor sensors
2012Co-Authors: Karthik Reddy, Xudong FanAbstract:We develop a versatile, self-referenced composite Fabry-Perot (FP) sensor and the corresponding detection scheme for rapid and precise measurement of Vapors. The composite FP vapor sensor is formed by etching two juxtaposed micron-deep wells, with a precisely controlled offset in depth, on a silicon wafer. The wells are then coated with a vapor sensitive polymer and the reflected light from each well is detected by a CMOS imager. Due to its self-referenced nature, the composite FP sensor is able to extract the change in thickness and refractive index of the polymer layer upon exposure to analyte Vapors, thus allowing for accurate vapor quantitation regardless of the polymer thickness, refractive index, and light incident angle and wavelength. Theoretical analysis is first performed to elucidate the underlying detection principle, followed by experimental demonstration at two different incident angles showing rapid and consistent measurement of the polymer changes when the polymer is exposed to three different analytes at various concentrations. The vapor detection limit is found to be on the order of a few pico-grams (~100 ppb)
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on chip fabry perot interferometric sensors for micro gas chromatography detection
2011Co-Authors: Karthik Reddy, Yunbo Guo, Jing Liu, Wonsuk Lee, Maung Kyaw Khaing Oo, Xudong FanAbstract:Abstract We fabricated and characterized on-chip Fabry–Perot (FP) vapor sensors for the development of on-column micro-gas chromatography (μGC) detectors. The FP sensors were made by coating a thin layer of polymer on a silicon wafer. The air–polymer and polymer–silicon interfaces form an FP cavity, whose resonance wavelengths change in response to the vapor absorption/desorption, thus allowing for rapid detection and quantification of Vapors. For proof-of-concept, two polymers (PDMS and SU-8) were used independently and placed in an array in a microfluidic channel, and showed different sensitivities for different Vapors. A sub-nano-gram detection limit and sub-second response time were achieved, representing orders of magnitude improvement over those previously reported. This on-chip design will enable the unprecedented integration of optical vapor sensors with μGC systems.
Nathan S. Lewis - One of the best experts on this subject based on the ideXlab platform.
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detection of ammonia 2 4 6 trinitrotoluene and common organic Vapors using thin film carbon black metalloporphyrin composite chemiresistors
2013Co-Authors: Edgardo Garciaberrios, Jordan C Theriot, Marc D Woodka, Nathan S. LewisAbstract:Thin-film chemiresistive composites of octaethylporphine-based transition-metal complexes (Ph(M), M = Co, Cu and Zn) and carbon black (CB) have been fabricated and tested as chemical vapor sensors. The sensing performance of such sensor composites was compared to the sensing performance of composites of metallophthalocyanines (Phtc(M)) and CB. The relative differential resistance response of Ph(M)/CB sensor films upon exposure to organic Vapors, such as n-hexane, n-heptane, n-octane, iso-octane, cyclohexane, toluene, ethyl acetate and ethanol, was dependent on the nature of the metal center. An array of chemiresistive Ph(M)/CB vapor sensors therefore provided discrimination between the organic vapor analytes that had different polarities, specifically classifying non-polar Vapors, aprotic polar Vapors and protic polar Vapors. However, discrimination was not observed for analytes that had mutually similar polarities. The Ph(M)/CB sensors showed reversible responses toward ammonia, NH_3(g), at concentrations below the 8 h permissible exposure level (50 ppm). Ph(M)/CB composites exhibited a slightly larger resistance response than Phtc(M)/CB composites, consistent with the Ph(M) species having less π-stacked molecular aggregates, resulting in an increase in the number of adsorption sites relative to the Phtc(M)/CB composites. Resistance responses with a signal-to-noise ratio value of ∼900 were obtained upon exposure to vapor pulses saturated with 2,4,6-trinitrotoluene.
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response versus chain length of alkanethiol capped au nanoparticle chemiresistive chemical vapor sensors
2010Co-Authors: Edgardo Garciaberrios, Marc D Woodka, Ting Gao, Stephen Maldonado, Bruce S Brunschwig, Mark W Ellsworth, Nathan S. LewisAbstract:Au nanoparticles capped with a homologous series of straight chain alkanethiols (containing 4−11 carbons in length) have been investigated as chemiresistive organic vapor sensors. The series of alkanethiols was used to elucidate the mechanisms of vapor detection by such capped nanoparticle chemiresistive films and to highlight the molecular design principles that govern enhanced detection. The thiolated Au nanoparticle chemiresistors demonstrated rapid and reversible responses to a set of test Vapors (n-hexane, n-heptane, n-octane, iso-octane, cyclohexane, toluene, ethyl acetate, methanol, ethanol, isopropanol, and 1-butanol) that possessed a variety of analyte physicochemical properties. The resistance sensitivity to nonpolar and aprotic polar Vapors systematically increased as the chain length of the capping reagent increased. Decreases in the nanoparticle film resistances, which produced negative values of the differential resistance response, were observed upon exposure of the sensor films to alcohol Vapors. The response signals became more negative with higher alcohol vapor concentrations, producing negative values of the sensor sensitivity. Sorption data measured on Au nanoparticle chemiresistor films using a quartz crystal microbalance allowed for the measurement of the partition coefficients of test Vapors in the Au nanoparticle films. This measurement assumed that analyte sorption only occurred at the organic interface and not the surface of the Au core. Such an assumption produced partition coefficient values that were independent of the length of the ligand. Furthermore, the value of the partition coefficient was used to obtain the particle-to-particle interfacial effective dielectric constant of films upon exposure to analyte Vapors. The values of the dielectric constant upon exposure to alcohol Vapors suggested that the observed resistance response changes observed were not significantly influenced by this dielectric change, but rather were primarily influenced by morphological changes and by changes in the interparticle spacing.
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an investigation of the concentration dependence and response to analyte mixtures of carbon black insulating organic polymer composite vapor detectors
2000Co-Authors: Erik J Severin, Brett J Doleman, Nathan S. LewisAbstract:The responses relative to an air background of carbon black/polymer composite vapor detectors have been determined as a function of the concentration of a homologous series of alcohols (n-CnH2n+1OH, 1 ≤ n ≤ 8), a homologous series of alkanes (n-CnH2n+2, 5 ≤ n ≤ 10 and n = 12, 14), and a set of diverse solvent Vapors. In all cases, the steady-state relative differential resistance responses, ΔR/Rb, of the carbon black/polymer composite vapor detectors were well-described by a linear relationship with respect to the analyte partial pressure, at least over the tested concentration range (P/P° = 0.005−0.03, where P° is the vapor pressure of the analyte). When two Vapors in air were simultaneously presented to the detectors, the ΔR/Rb response, relative to an air background, was the sum of the ΔR/Rb values obtained when each analyte was exposed separately to the carbon black/polymer composite detectors under study. Similarly, when an analyte was exposed to the detectors on top of a background level of another ...
