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papers from the latest issue:
Fabrication of X-ray compatible microfluidic platforms for protein crystallization
01 October 2012,
08:23:58
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 174
Sudipto Guha, Sarah L. Perry, Ashtamurthy S. Pawate, Paul J.A. Kenis
This paper reports a method for fabricating multilayer microfluidic protein crystallization platforms using different materials to achieve X-ray transparency and compatibility with crystallization reagents. To validate this approach, three soluble proteins, lysozyme, thaumatin, and ribonuclease A were crystallized on-chip, followed by on-chip diffraction data collection. We also report a chip with an array of wells for screening different conditions that consume a minimal amount of protein solution as compared to traditional screening methods. A large number of high quality isomorphous protein crystals can be grown in the wells, after which slices of X-ray data can be collected from many crystals still residing within the wells. Complete protein structures can be obtained by merging these slices of data followed by further processing with crystallography software. This approach of using an X-ray transparent chip for screening, crystal growth, and X-ray data collection enables room temperature data collection from many crystals mounted in parallel, which thus eliminates crystal handling and minimizes radiation damage to the crystals.
Source:Sensors and Actuators B: Chemical, Volume 174
Sudipto Guha, Sarah L. Perry, Ashtamurthy S. Pawate, Paul J.A. Kenis
This paper reports a method for fabricating multilayer microfluidic protein crystallization platforms using different materials to achieve X-ray transparency and compatibility with crystallization reagents. To validate this approach, three soluble proteins, lysozyme, thaumatin, and ribonuclease A were crystallized on-chip, followed by on-chip diffraction data collection. We also report a chip with an array of wells for screening different conditions that consume a minimal amount of protein solution as compared to traditional screening methods. A large number of high quality isomorphous protein crystals can be grown in the wells, after which slices of X-ray data can be collected from many crystals still residing within the wells. Complete protein structures can be obtained by merging these slices of data followed by further processing with crystallography software. This approach of using an X-ray transparent chip for screening, crystal growth, and X-ray data collection enables room temperature data collection from many crystals mounted in parallel, which thus eliminates crystal handling and minimizes radiation damage to the crystals.
Use of digital reflection devices for measurement using hue-based optical sensors
01 October 2012,
08:23:58
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 174
M.M. Erenas, K. Cantrell, J. Ballesta-Claver, I. de Orbe-Payá, L.F. Capitán-Vallvey
In this paper the hue, or H component of the HSV (hue, saturation, value) color space, is used as analytical parameter for bitonal optical sensors. This parameter is characterized by its robustness to variations in the imaging device, illuminant, and sensor membrane. It has a higher precision than either traditional optical parameters, such as absorbance or transflectance, or other color parameters such as RGB coordinates. Here the hue is calculated from digital images obtained in reflection mode (digital camera) rather than images in transmission mode (digital scanner) as demonstrated in previous work. The stability of the H parameter, makes it possible to greatly simplify the procedure used for the optical sensors as well as to use ubiquitous digital cameras to acquire the image.
Source:Sensors and Actuators B: Chemical, Volume 174
M.M. Erenas, K. Cantrell, J. Ballesta-Claver, I. de Orbe-Payá, L.F. Capitán-Vallvey
In this paper the hue, or H component of the HSV (hue, saturation, value) color space, is used as analytical parameter for bitonal optical sensors. This parameter is characterized by its robustness to variations in the imaging device, illuminant, and sensor membrane. It has a higher precision than either traditional optical parameters, such as absorbance or transflectance, or other color parameters such as RGB coordinates. Here the hue is calculated from digital images obtained in reflection mode (digital camera) rather than images in transmission mode (digital scanner) as demonstrated in previous work. The stability of the H parameter, makes it possible to greatly simplify the procedure used for the optical sensors as well as to use ubiquitous digital cameras to acquire the image.
Towards robust biosensors based on pulsed streaming potentials in microfluidic channels: Online correction and output signal selection
01 October 2012,
08:23:58
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 174
Jing Wu, Yuan Zhang, Lei Zhao, Lin Zou, Julio C. Alvarez, Qiaosheng Pu
Pulsed streaming potential (SP) measurements in microfluidic format have been explored as a simple and rapid biosensing tool, but large day-to-day variations of the measurements, i.e. relative standard deviation (RSD) greater than 10%, are frequently encountered if the SP values are directly used as the output signal. To improve the long term stability of SP based sensor, a micro conductivity probe and a micro pressure sensor were incorporated into the sensing unit along with the implementation of a reference channel so that corrected SP values were utilized as the response signal. The results showed that day-to-day stability could be significantly improved and RSDs could be reduced from approximately 15% to less than 5% by incorporating a reference channel and using the SP ratio of two channels as the output signal. The variation of SP values caused by conductivity and pressure variation could also be corrected by using a reference channel, RSDs<1% could be achieved with conductivity changing from 186 to 865μScm−1 and pressure increasing from 10 to 70kPa. Utilization of a reference channel is therefore useful for developing a robust label-free biosensing platform based on pulsed SP measurements.
Source:Sensors and Actuators B: Chemical, Volume 174
Jing Wu, Yuan Zhang, Lei Zhao, Lin Zou, Julio C. Alvarez, Qiaosheng Pu
Pulsed streaming potential (SP) measurements in microfluidic format have been explored as a simple and rapid biosensing tool, but large day-to-day variations of the measurements, i.e. relative standard deviation (RSD) greater than 10%, are frequently encountered if the SP values are directly used as the output signal. To improve the long term stability of SP based sensor, a micro conductivity probe and a micro pressure sensor were incorporated into the sensing unit along with the implementation of a reference channel so that corrected SP values were utilized as the response signal. The results showed that day-to-day stability could be significantly improved and RSDs could be reduced from approximately 15% to less than 5% by incorporating a reference channel and using the SP ratio of two channels as the output signal. The variation of SP values caused by conductivity and pressure variation could also be corrected by using a reference channel, RSDs<1% could be achieved with conductivity changing from 186 to 865μScm−1 and pressure increasing from 10 to 70kPa. Utilization of a reference channel is therefore useful for developing a robust label-free biosensing platform based on pulsed SP measurements.
Optimization of spectrophone performance for quartz-enhanced photoacoustic spectroscopy
01 October 2012,
08:23:58
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 174
Yingchun Cao, Wei Jin, Hoi Lut Ho
We numerically investigate the effects of spectrophone parameters, including the operating acoustic frequency, the relative position of the quartz tuning fork and the excitation laser beam, the gap between the resonant tubes and the tuning fork, and the diameter and length of the resonant tubes, on the performance of gas sensors based on quartz-enhanced photoacoustic spectroscopy. A pair of rigid tubes with inner diameter of 0.2mm and length of 5.1mm, placed 0.6mm down from the opening and 20μm away from the edge of the tuning fork, is suggested for optimal performance.
Source:Sensors and Actuators B: Chemical, Volume 174
Yingchun Cao, Wei Jin, Hoi Lut Ho
We numerically investigate the effects of spectrophone parameters, including the operating acoustic frequency, the relative position of the quartz tuning fork and the excitation laser beam, the gap between the resonant tubes and the tuning fork, and the diameter and length of the resonant tubes, on the performance of gas sensors based on quartz-enhanced photoacoustic spectroscopy. A pair of rigid tubes with inner diameter of 0.2mm and length of 5.1mm, placed 0.6mm down from the opening and 20μm away from the edge of the tuning fork, is suggested for optimal performance.
Porous flower-like SnO2 nanostructures as sensitive gas sensors for volatile organic compounds detection
01 October 2012,
08:23:58
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 174
Cuiping Gu, Xiaojuan Xu, Jiarui Huang, Weizhi Wang, Yufeng Sun, Jinhuai Liu
Porous flower-like tin oxide (SnO2) nanostructure is prepared by annealing of the flower-like copper tin sulfur (Cu3SnS4) nanostructures. The morphology and crystal structure of the flower-like SnO2 nanostructures are characterized by field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The as-prepared porous flower-like SnO2 nanostructures exhibit a good response and reversibility to some organic vapors, such as toluene and formaldehyde. The sensing responses to 100ppm of toluene and formaldehyde were 9.7 and 9.5, respectively. Moreover, the sensors exhibit a good response to benzene, methanol, ethanol, and acetone. The relationship between the gas-sensing properties and the microstructure of the as-prepared flower-like SnO2 nanostructures is also investigated.
Source:Sensors and Actuators B: Chemical, Volume 174
Cuiping Gu, Xiaojuan Xu, Jiarui Huang, Weizhi Wang, Yufeng Sun, Jinhuai Liu
Porous flower-like tin oxide (SnO2) nanostructure is prepared by annealing of the flower-like copper tin sulfur (Cu3SnS4) nanostructures. The morphology and crystal structure of the flower-like SnO2 nanostructures are characterized by field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The as-prepared porous flower-like SnO2 nanostructures exhibit a good response and reversibility to some organic vapors, such as toluene and formaldehyde. The sensing responses to 100ppm of toluene and formaldehyde were 9.7 and 9.5, respectively. Moreover, the sensors exhibit a good response to benzene, methanol, ethanol, and acetone. The relationship between the gas-sensing properties and the microstructure of the as-prepared flower-like SnO2 nanostructures is also investigated.
Adsorption-semiconductor hydrogen sensors based on nanosized tin dioxide with cobalt oxide additives
01 October 2012,
08:23:58
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 174
Ludmila P. Oleksenko, Nelly P. Maksymovych, Andrii I. Buvailo, Igor P. Matushko, Norman Dollahon
Co-doped SnO2-based sensor materials with various cobalt contents were synthesized via the ethylene glycol supported sol–gel method. Electrical resistance, sensor response to hydrogen and catalytic activity towards hydrogen oxidation were studied as a function of cobalt doping and were shown to correlate, exhibiting maxima corresponding to the sensor material with 0.2 wt% Co. It was concluded that there are two major reasons leading to the obtained result. First, the formation of active edge sites between promoter particles (cobalt oxide) and tin dioxide surface, with the assumption that such bordering regions are favorable for oxygen chemisorption. Thus, a change in cobalt concentration in sensor materials can cause a change in a chemisorbed oxygen concentration and, hence the correlation between cobalt content and such parameters as electric resistance, sensor response and catalytic activity of corresponding materials. The second reason is the size of the tin dioxide grains. It was found that addition of small amount of cobalt content to the nanosized sensor material led to drastic increase in the resistance of the sensor and hence it's response because of “electronic sensitization” effect.
Source:Sensors and Actuators B: Chemical, Volume 174
Ludmila P. Oleksenko, Nelly P. Maksymovych, Andrii I. Buvailo, Igor P. Matushko, Norman Dollahon
Co-doped SnO2-based sensor materials with various cobalt contents were synthesized via the ethylene glycol supported sol–gel method. Electrical resistance, sensor response to hydrogen and catalytic activity towards hydrogen oxidation were studied as a function of cobalt doping and were shown to correlate, exhibiting maxima corresponding to the sensor material with 0.2 wt% Co. It was concluded that there are two major reasons leading to the obtained result. First, the formation of active edge sites between promoter particles (cobalt oxide) and tin dioxide surface, with the assumption that such bordering regions are favorable for oxygen chemisorption. Thus, a change in cobalt concentration in sensor materials can cause a change in a chemisorbed oxygen concentration and, hence the correlation between cobalt content and such parameters as electric resistance, sensor response and catalytic activity of corresponding materials. The second reason is the size of the tin dioxide grains. It was found that addition of small amount of cobalt content to the nanosized sensor material led to drastic increase in the resistance of the sensor and hence it's response because of “electronic sensitization” effect.
The electrochemical sensor for methanol detection using silicon epoxy coated platinum nanoparticles
01 October 2012,
08:23:58
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 174
Deog-Su Park, Mi-Sook Won, Rajendra N. Goyal, Yoon-Bo Shim
A platinum (Pt) nanoparticle-based electrochemical sensor has been applied for the detection of methanol in methanol fuel cells. The platinum nanoparticles were electrodeposited on glassy carbon (GC) in HCl containing hydrogen hexachloroplatinate using cyclic voltammetry. The size and distribution of the nanoparticles were found to be dependent on the deposition parameters, such as the concentration of platinum ions, scan rate, and number of cycles. The deposited platinum nanoparticles were spin-coated with silicone epoxy (SE), and scanning electron microscopy (SEM) confirmed the deposition. The concentration of methanol was determined by a double potential step chronoamperometric method using the SE/Pt/GC electrode at the oxidation potential of +0.60V vs. Ag/AgCl electrode. The sensor exhibited a long-term stability for 40h repeat using and has an advantage that adsorption of CO was eliminated by use of SE film. The dynamic range of the analytical method was determined to be from 2.5×10−4 to 10.0M in two slopes with a detection limit of 1.0×10−4 M.
Source:Sensors and Actuators B: Chemical, Volume 174
Deog-Su Park, Mi-Sook Won, Rajendra N. Goyal, Yoon-Bo Shim
A platinum (Pt) nanoparticle-based electrochemical sensor has been applied for the detection of methanol in methanol fuel cells. The platinum nanoparticles were electrodeposited on glassy carbon (GC) in HCl containing hydrogen hexachloroplatinate using cyclic voltammetry. The size and distribution of the nanoparticles were found to be dependent on the deposition parameters, such as the concentration of platinum ions, scan rate, and number of cycles. The deposited platinum nanoparticles were spin-coated with silicone epoxy (SE), and scanning electron microscopy (SEM) confirmed the deposition. The concentration of methanol was determined by a double potential step chronoamperometric method using the SE/Pt/GC electrode at the oxidation potential of +0.60V vs. Ag/AgCl electrode. The sensor exhibited a long-term stability for 40h repeat using and has an advantage that adsorption of CO was eliminated by use of SE film. The dynamic range of the analytical method was determined to be from 2.5×10−4 to 10.0M in two slopes with a detection limit of 1.0×10−4 M.
Ultrasonic synthesis of MoO3 nanorods and their gas sensing properties
01 October 2012,
08:23:58
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 174
Shouli Bai, Song Chen, Liangyuan Chen, Kewei Zhang, Ruixian Luo, Dianqing Li, Chung Chiun Liu
Molybdenum oxide nanorods have been successfully synthesized by a simple probe ultrasonic approach. A possible growth mechanism of the MoO3 nanorods and the influence of ultrasonic times on morphologies have been investigated. The characterization results of field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD) and differential thermal analysis (DTA) demonstrate that the nanorods exhibits hexagonal molybdenum oxide (h-MoO3) and an irreversible phase transition occurs to form orthorhombic α-MoO3 after annealing at 436°C. The gas sensing tests indicate that the MoO3 based sensor has high response to NO2 and the response is not interfered by CO and CH4 at operating temperature of 290°C. The intrinsic sensing performance arises from the non-stoichiometry of MoO3 due to the presence of Mo5+ ions in the lattice of oxide, which has been confirmed by the results of X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR) analysis.
Source:Sensors and Actuators B: Chemical, Volume 174
Shouli Bai, Song Chen, Liangyuan Chen, Kewei Zhang, Ruixian Luo, Dianqing Li, Chung Chiun Liu
Molybdenum oxide nanorods have been successfully synthesized by a simple probe ultrasonic approach. A possible growth mechanism of the MoO3 nanorods and the influence of ultrasonic times on morphologies have been investigated. The characterization results of field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD) and differential thermal analysis (DTA) demonstrate that the nanorods exhibits hexagonal molybdenum oxide (h-MoO3) and an irreversible phase transition occurs to form orthorhombic α-MoO3 after annealing at 436°C. The gas sensing tests indicate that the MoO3 based sensor has high response to NO2 and the response is not interfered by CO and CH4 at operating temperature of 290°C. The intrinsic sensing performance arises from the non-stoichiometry of MoO3 due to the presence of Mo5+ ions in the lattice of oxide, which has been confirmed by the results of X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR) analysis.
Novel structured light-addressable potentiometric sensor array based on PVC membrane for determination of heavy metals
01 October 2012,
08:23:58
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 174
D. Ha, N. Hu, C.X. Wu, Dmitry Kirsanov, Andrey Legin, Maria Khaydukova, P. Wang
The paper discussed a novel structured light-addressable potentiometric sensor (LAPS) array based on PVC membrane for determination of heavy metal cations simultaneously. For LAPS array fabrication, part of the silicon substrate which was defined as non-sensitive area was heavily doped with boron and had thick oxide formation. Then PVC (polyvinyl chloride) membrane for respective cations (Pb2+, Cb2+, Zn2+) was prepared uniformly on corresponding sensitive area. Through new structure, the elaborated LAPS array had the advantages of excellent calibration stability (e.g. lower standard deviation from ±3.1mV to ±0.5mV for Pb-LAPS) and reasonable good selectivity. Sensors based on these membranes had showed a Nernstian response of slope (28.7–29.3mV/dec) over the concentration ranges of 10−5 to 10−1 mol/L. At the meantime, the electrochemical behavior in terms of the detection limit, linear response range, response time, long-time stability and effect of silanization had also been investigated.
Source:Sensors and Actuators B: Chemical, Volume 174
D. Ha, N. Hu, C.X. Wu, Dmitry Kirsanov, Andrey Legin, Maria Khaydukova, P. Wang
The paper discussed a novel structured light-addressable potentiometric sensor (LAPS) array based on PVC membrane for determination of heavy metal cations simultaneously. For LAPS array fabrication, part of the silicon substrate which was defined as non-sensitive area was heavily doped with boron and had thick oxide formation. Then PVC (polyvinyl chloride) membrane for respective cations (Pb2+, Cb2+, Zn2+) was prepared uniformly on corresponding sensitive area. Through new structure, the elaborated LAPS array had the advantages of excellent calibration stability (e.g. lower standard deviation from ±3.1mV to ±0.5mV for Pb-LAPS) and reasonable good selectivity. Sensors based on these membranes had showed a Nernstian response of slope (28.7–29.3mV/dec) over the concentration ranges of 10−5 to 10−1 mol/L. At the meantime, the electrochemical behavior in terms of the detection limit, linear response range, response time, long-time stability and effect of silanization had also been investigated.
Improved H2-sensing performance of nanocluster-based highly porous tungsten oxide films operating at moderate temperature
01 October 2012,
08:23:58
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 174
Meng Zhao, Chung Wo Ong
Many nano-metal oxides are claimed to be responsive to H2 at room-temperature, but their response rates may be too low for the signal to reach equilibrium quickly. We investigated the H2-induced resistive response of palladium-coated supersonic cluster beam deposited tungsten oxide (Pd/SCBD WO3) films at temperatures T sen between 20 and 140°C. They are constructed of genuine nano WO3 clusters (3–5nm) loosely packed together, and have a high porosity. Slight increase of T sen from room-temperature greatly speeds up the response rate and gives a strong apparent sensor response. Other advantages include excellent cyclic stability and selectivity against vapors of various organic compounds; negligible influence from moisture and mild ambient pressure dependence.
Source:Sensors and Actuators B: Chemical, Volume 174
Meng Zhao, Chung Wo Ong
Many nano-metal oxides are claimed to be responsive to H2 at room-temperature, but their response rates may be too low for the signal to reach equilibrium quickly. We investigated the H2-induced resistive response of palladium-coated supersonic cluster beam deposited tungsten oxide (Pd/SCBD WO3) films at temperatures T sen between 20 and 140°C. They are constructed of genuine nano WO3 clusters (3–5nm) loosely packed together, and have a high porosity. Slight increase of T sen from room-temperature greatly speeds up the response rate and gives a strong apparent sensor response. Other advantages include excellent cyclic stability and selectivity against vapors of various organic compounds; negligible influence from moisture and mild ambient pressure dependence.
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