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papers from the latest issue:
Towards robust biosensors based on pulsed streaming potentials in microfluidic channels: Online correction and output signal selection
21 August 2012,
09:23:57
Publication year:
2012
Source:Sensors and Actuators B: Chemical
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 865μS cm-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
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 865μS cm-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.
Fiber-optic biosensor based on lossy mode resonances
21 August 2012,
09:23:57
Publication year:
2012
Source:Sensors and Actuators B: Chemical
A.B. Socorro, J.M. Corres, I. Del Villar, F.J. Arregui, I.R. Matías
In this work, a novel fiber-optic immunoglobulin G biosensor based on lossy mode resonances is proposed. This physical phenomenon is obtained by depositing a PAH/PSS layer-by-layer thin-film on a cladding removed optical fiber. A reflective configuration is used to track the generation and response of the electromagnetic resonance in the different phases of the process. According to the results, wavelength displacements of 10nm are visualized when detecting immunoglobulins with a response time of 12minutes for a 50μg/ml concentration.
Source:Sensors and Actuators B: Chemical
A.B. Socorro, J.M. Corres, I. Del Villar, F.J. Arregui, I.R. Matías
In this work, a novel fiber-optic immunoglobulin G biosensor based on lossy mode resonances is proposed. This physical phenomenon is obtained by depositing a PAH/PSS layer-by-layer thin-film on a cladding removed optical fiber. A reflective configuration is used to track the generation and response of the electromagnetic resonance in the different phases of the process. According to the results, wavelength displacements of 10nm are visualized when detecting immunoglobulins with a response time of 12minutes for a 50μg/ml concentration.
Multi-functionalized Biosensor at WO3-TiO2 Modified Electrode for Photoelectrocatalysis of Norepinephrine and Riboflavin
21 August 2012,
09:23:57
Publication year:
2012
Source:Sensors and Actuators B: Chemical
Ying Li, Pei-Chi Hsu, Shen-Ming Chen
The titanium dioxide (TiO2), mixed different ratio tungsten oxide (WO3) hybrid film WO3-TiO2 was prepare on indium tin oxide (ITO) electrode. TiO2: WO3 =9: 3 (v/v) group current value was 5.44mA under irradiation conditions. This group showed highest photocatalytic activity than others, we selected to optimization us in follow-up experiment. In this paper, the electrochemical oxidation and reduction of norepinephrine (NEP) and riboflavin (Vitamin B2) as multi-functionalized biosensor. The TiO2 exhibited a promising enhanced photoelectrocatalytic activity towards analytes. Surface morphology of the modified electrode using atomic force microscopy (AFM), which revealed that WO3 and TiO2 were coated on ITO. The presence of TiO2 enhances the loaded and stability. Electrochemical impedance spectroscopy (EIS) applied diffusion coefficient values and some information about the kinetics of electron transfer during the redox reactions. Cyclic voltammograms (CVs) and Differential pulse voltammetry (DPVs) were used for the determination of analytes. DPVs not only increased the electrocatalytic current linear concentration range, also lowered the overpotential to oxidation or reduction the interferences in the measurements. We simulated more complex system if both norepinephrine and riboflavin are present simultaneously. It also exhibited oxidation and reduction peaks for norepinephrine injection and B complex tablet's real samples determination in pH 7.0 at WO3-TiO2 modified electrode.
Source:Sensors and Actuators B: Chemical
Ying Li, Pei-Chi Hsu, Shen-Ming Chen
The titanium dioxide (TiO2), mixed different ratio tungsten oxide (WO3) hybrid film WO3-TiO2 was prepare on indium tin oxide (ITO) electrode. TiO2: WO3 =9: 3 (v/v) group current value was 5.44mA under irradiation conditions. This group showed highest photocatalytic activity than others, we selected to optimization us in follow-up experiment. In this paper, the electrochemical oxidation and reduction of norepinephrine (NEP) and riboflavin (Vitamin B2) as multi-functionalized biosensor. The TiO2 exhibited a promising enhanced photoelectrocatalytic activity towards analytes. Surface morphology of the modified electrode using atomic force microscopy (AFM), which revealed that WO3 and TiO2 were coated on ITO. The presence of TiO2 enhances the loaded and stability. Electrochemical impedance spectroscopy (EIS) applied diffusion coefficient values and some information about the kinetics of electron transfer during the redox reactions. Cyclic voltammograms (CVs) and Differential pulse voltammetry (DPVs) were used for the determination of analytes. DPVs not only increased the electrocatalytic current linear concentration range, also lowered the overpotential to oxidation or reduction the interferences in the measurements. We simulated more complex system if both norepinephrine and riboflavin are present simultaneously. It also exhibited oxidation and reduction peaks for norepinephrine injection and B complex tablet's real samples determination in pH 7.0 at WO3-TiO2 modified electrode.
Real-time Recognition of Mycobacterium tuberculosis and Lipoarabinomannan using the Quartz Crystal Microbalance
21 August 2012,
09:23:57
Publication year:
2012
Source:Sensors and Actuators B: Chemical
Leslie A. Hiatt, David E. Cliffel
A quartz crystal microbalance (QCM) immunosensor has been successfully employed to screen for both whole Mycobacteria tuberculosis (Mtb) bacilli and a Mtb surface antigen, lipoarabinomannan (LAM). One of the most abundant components of the Mtb cell surface, LAM, may be detected without the presence of the entire bacterium. Using available antibodies with proven utility in enzyme-linked immunoassays (ELISAs), a sensor was designed to measure Mtb bacilli and LAM. Equilibrium association constants (K a ) were determined for the interaction of Mtb with immobilized α-LAM and anti-H37Rv antibodies, where avidity was seen to strengthen this interaction and provide for greater binding than might have otherwise been achieved. The binding of LAM to immobilized α-LAM had a high associate rate constant (k a ) allowing for rapid detection. Evaluating these binding constants helped the compare the sensitivity of these immunosensors to conventional ELISAs. The use of these assays with the better antibodies may allow for immunosensor use in determining LAM as a point-of-care (POC) diagnostic for Mtb.
Source:Sensors and Actuators B: Chemical
Leslie A. Hiatt, David E. Cliffel
A quartz crystal microbalance (QCM) immunosensor has been successfully employed to screen for both whole Mycobacteria tuberculosis (Mtb) bacilli and a Mtb surface antigen, lipoarabinomannan (LAM). One of the most abundant components of the Mtb cell surface, LAM, may be detected without the presence of the entire bacterium. Using available antibodies with proven utility in enzyme-linked immunoassays (ELISAs), a sensor was designed to measure Mtb bacilli and LAM. Equilibrium association constants (K a ) were determined for the interaction of Mtb with immobilized α-LAM and anti-H37Rv antibodies, where avidity was seen to strengthen this interaction and provide for greater binding than might have otherwise been achieved. The binding of LAM to immobilized α-LAM had a high associate rate constant (k a ) allowing for rapid detection. Evaluating these binding constants helped the compare the sensitivity of these immunosensors to conventional ELISAs. The use of these assays with the better antibodies may allow for immunosensor use in determining LAM as a point-of-care (POC) diagnostic for Mtb.
Optochemical ammonia gas sensing properties of meso-substituted porphyrin derivatives immobilized Nafion film on glass slide
21 August 2012,
09:23:57
Publication year:
2012
Source:Sensors and Actuators B: Chemical
Palanisamy Muthukumar, S. Abraham John
We have synthesized free base porphyrin derivatives with different substituents at meso position meso-tetrakis(4-nitrophenyl)porphyrin, meso-tetrakis(4-pyridyl)porphyrin, 5,15-bis(ferrocenyl)-10,20-bis(4-nitrophenyl)porphyrin and 5,15-bis(4-nitrophenyl)-10,20-bis(3,5-dimethoxy-phenyl)porphyrin) and incorporated them into Nafion (Nf) film coated on glass slide to examine the ammonia gas sensing properties by optochemical method. The Soret band of the porphyrin derivatives was red shifted when they incorporated into Nf film in contrast to dichloromethane. The cause for the red shift was due to the protonation of free base porphyrin by the sulfonic acid groups of the Nf film coated on glass slide. When the porphyrins incorporated Nf film was exposed to ammonia gas, the Soret band was blue shifted. Among the different substituted porphyrin derivatives, Nf-meso-tetrakis(4-nitrophenyl)porphyrin (MTNP) was more sensitive towards ammonia gas. When Nf-MTNP film was exposed to ammonia gas, the Soret band was shifted from 447nm to 424nm. The concentration of ammonia gas was monitored from the absorbance changes at 424nm. The detection limit of the Nf-MTNP sensing element towards ammonia gas was found to be 0.025ppm.
Source:Sensors and Actuators B: Chemical
Palanisamy Muthukumar, S. Abraham John
We have synthesized free base porphyrin derivatives with different substituents at meso position meso-tetrakis(4-nitrophenyl)porphyrin, meso-tetrakis(4-pyridyl)porphyrin, 5,15-bis(ferrocenyl)-10,20-bis(4-nitrophenyl)porphyrin and 5,15-bis(4-nitrophenyl)-10,20-bis(3,5-dimethoxy-phenyl)porphyrin) and incorporated them into Nafion (Nf) film coated on glass slide to examine the ammonia gas sensing properties by optochemical method. The Soret band of the porphyrin derivatives was red shifted when they incorporated into Nf film in contrast to dichloromethane. The cause for the red shift was due to the protonation of free base porphyrin by the sulfonic acid groups of the Nf film coated on glass slide. When the porphyrins incorporated Nf film was exposed to ammonia gas, the Soret band was blue shifted. Among the different substituted porphyrin derivatives, Nf-meso-tetrakis(4-nitrophenyl)porphyrin (MTNP) was more sensitive towards ammonia gas. When Nf-MTNP film was exposed to ammonia gas, the Soret band was shifted from 447nm to 424nm. The concentration of ammonia gas was monitored from the absorbance changes at 424nm. The detection limit of the Nf-MTNP sensing element towards ammonia gas was found to be 0.025ppm.
An electronic nose on flexible substrates integrated into a smart textile
21 August 2012,
09:23:57
Publication year:
2012
Source:Sensors and Actuators B: Chemical
T. Kinkeldei, C. Zysset, N. Münzenrieder, G. Tröster
Fabrication costs of gas sensors are decreasing due to the use of low cost flexible polymer substrates and solution based fabrication processes. This development creates new application possibilities for gas sensors and allows the installation into objects of our daily life, such as textiles. Challenges with the integration of electronic components on flexible substrates arise mainly due to strain introduced by bending the substrate. This plays an important role especially during weaving as strong mechanical forces bend flexible electronic devices to radii below 1 mm. To demonstrate that it is feasible to integrate low cost gas sensors into a textile while preserving the functionality, we developed an electronic nose system for textile integration. The electronic nose consists of four carbon black/polymer gas sensors fabricated on a flexible polymer substrate. After fabrication the substrate was cut into yarn like strips and integrated into a textile to create a smart textile with gas sensing functionalities. We used this smart textile to detect different solvent vapors and classified them accordingly. It was possible to detect single solvents such as acetone until a minimal concentration of 50 ppm. The influence of bending on sensors was studied, signal changes introduced by bending could be separated from changes due to solvent exposure. Bending of single strips to a radius below 1 mm did not alter the sensor functionality. The presented work shows the feasibility of the process in combination with textile integration.
Source:Sensors and Actuators B: Chemical
T. Kinkeldei, C. Zysset, N. Münzenrieder, G. Tröster
Fabrication costs of gas sensors are decreasing due to the use of low cost flexible polymer substrates and solution based fabrication processes. This development creates new application possibilities for gas sensors and allows the installation into objects of our daily life, such as textiles. Challenges with the integration of electronic components on flexible substrates arise mainly due to strain introduced by bending the substrate. This plays an important role especially during weaving as strong mechanical forces bend flexible electronic devices to radii below 1 mm. To demonstrate that it is feasible to integrate low cost gas sensors into a textile while preserving the functionality, we developed an electronic nose system for textile integration. The electronic nose consists of four carbon black/polymer gas sensors fabricated on a flexible polymer substrate. After fabrication the substrate was cut into yarn like strips and integrated into a textile to create a smart textile with gas sensing functionalities. We used this smart textile to detect different solvent vapors and classified them accordingly. It was possible to detect single solvents such as acetone until a minimal concentration of 50 ppm. The influence of bending on sensors was studied, signal changes introduced by bending could be separated from changes due to solvent exposure. Bending of single strips to a radius below 1 mm did not alter the sensor functionality. The presented work shows the feasibility of the process in combination with textile integration.
Optimization of spectrophone performance for quartz-enhanced photoacoustic spectroscopy
21 August 2012,
09:23:57
Publication year:
2012
Source:Sensors and Actuators B: Chemical
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 quatz 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
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 quatz 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.
Direct comparison of the performance of Bloch surface wave and surface plasmon polariton sensors
21 August 2012,
09:23:57
Publication year:
2012
Source:Sensors and Actuators B: Chemical
Alberto Sinibaldi, Norbert Danz, Emiliano Descrovi, Peter Munzert, Ulrike Schulz, Frank Sonntag, Lorenzo Dominici, Francesco Michelotti
We report on the direct experimental comparison of the sensitivity and figure of merit of biosensors based either on surface plasmon polaritons on metal layers or on Bloch surface waves on one dimensional photonic crystals. The comparison was carried out by making use of a commercial surface plasmon resonance platform that was slightly adapted for these experiments. Although the experimental conditions are not optimized for Bloch surface waves, our experiments demonstrate that both types of biosensors show a similar figure of merit for biochips deposited on low cost molded plastic substrates. For glass substrates with better optical quality, the increased homogeneity of the photonic crystals results in the Bloch surface wave sensors outperforming the surface plasmon polariton sensors by a factor 1.7 in terms of figure of merit. Considerations on the illumination bandwidth indicate options to further increase such a factor.
Source:Sensors and Actuators B: Chemical
Alberto Sinibaldi, Norbert Danz, Emiliano Descrovi, Peter Munzert, Ulrike Schulz, Frank Sonntag, Lorenzo Dominici, Francesco Michelotti
We report on the direct experimental comparison of the sensitivity and figure of merit of biosensors based either on surface plasmon polaritons on metal layers or on Bloch surface waves on one dimensional photonic crystals. The comparison was carried out by making use of a commercial surface plasmon resonance platform that was slightly adapted for these experiments. Although the experimental conditions are not optimized for Bloch surface waves, our experiments demonstrate that both types of biosensors show a similar figure of merit for biochips deposited on low cost molded plastic substrates. For glass substrates with better optical quality, the increased homogeneity of the photonic crystals results in the Bloch surface wave sensors outperforming the surface plasmon polariton sensors by a factor 1.7 in terms of figure of merit. Considerations on the illumination bandwidth indicate options to further increase such a factor.
Improved H2-sensing performance of nanocluster-based highly porous tungsten oxide films operating at moderate temperature
21 August 2012,
09:23:57
Publication year:
2012
Source:Sensors and Actuators B: Chemical
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 Tsen 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 Tsen 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
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 Tsen 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 Tsen 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.
Accuracy and resolution limits in quartz and silicon substrates with microelectrodes for electrochemical biosensors
21 August 2012,
09:23:57
Publication year:
2012
Source:Sensors and Actuators B: Chemical
M. Carminati, M. Vergani, G. Ferrari, L. Caranzi, M. Caironi, M. Sampietro
Arrays of microelectrodes for electrochemical biosensing are commonly fabricated on standard silicon wafers. This choice positively profits from the optimized microelectronic technology, offering micrometric spatial resolution and the possibility to integrate electronic processing capabilities directly on the sensing chips. This paper analyzes the drawbacks on the accuracy and resolution in impedance detection arising when using such highly conductive substrates. To this aim, a direct experimental comparison is reported for identical 10μm disk electrodes fabricated on quartz (i.e. insulating) and on the silicon dioxide grown on a silicon wafer. The paper shows how the high conductivity of the substrate in contact with the solution promotes additional stray capacitances (in our experiment 280 times larger than the expected interfacial capacitance) that i) heavily modify the measured impedance spectrum, thus affecting the biosensor accuracy, and ii) increase the total current noise of the detector, thus affecting the resolution in the biosensor readout. Although the spectral distortion can be minimized through proper grounding of the substrate, the presence of the stray capacitance still degrades the resolution. We also show that even in the case of a microfluidic encapsulation system coupled to the chip, stray couplings through the substrate still affect the detection. However, as silicon appears irreplaceable for smart analytical micro-systems, the paper discusses the key aspects for an optimal design of the chips in terms of metal trace area, pad size, thickness of the insulating layers and bulk resistivity.
Source:Sensors and Actuators B: Chemical
M. Carminati, M. Vergani, G. Ferrari, L. Caranzi, M. Caironi, M. Sampietro
Arrays of microelectrodes for electrochemical biosensing are commonly fabricated on standard silicon wafers. This choice positively profits from the optimized microelectronic technology, offering micrometric spatial resolution and the possibility to integrate electronic processing capabilities directly on the sensing chips. This paper analyzes the drawbacks on the accuracy and resolution in impedance detection arising when using such highly conductive substrates. To this aim, a direct experimental comparison is reported for identical 10μm disk electrodes fabricated on quartz (i.e. insulating) and on the silicon dioxide grown on a silicon wafer. The paper shows how the high conductivity of the substrate in contact with the solution promotes additional stray capacitances (in our experiment 280 times larger than the expected interfacial capacitance) that i) heavily modify the measured impedance spectrum, thus affecting the biosensor accuracy, and ii) increase the total current noise of the detector, thus affecting the resolution in the biosensor readout. Although the spectral distortion can be minimized through proper grounding of the substrate, the presence of the stray capacitance still degrades the resolution. We also show that even in the case of a microfluidic encapsulation system coupled to the chip, stray couplings through the substrate still affect the detection. However, as silicon appears irreplaceable for smart analytical micro-systems, the paper discusses the key aspects for an optimal design of the chips in terms of metal trace area, pad size, thickness of the insulating layers and bulk resistivity.
Greatly-etched fiber Bragg grating hydrogen sensor with Pd/Ni composite film as sensing material
21 August 2012,
09:23:57
Publication year:
2012
Source:Sensors and Actuators B: Chemical
Jixiang Dai, Minghong Yang, Xun Yu, Kun Cao, Junsheng Liao
Pd/Ni composite film was deposited on the side-face of chemically etched fiber Bragg grating as sensing element by magnetron sputtering process. The composition, structure and micro morphology of Pd/Ni composite film were investigated by energy dispersive X-ray analysis (EDAX), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The atomic ratio of Pd:Ni in Pd/Ni composite film is controlled at about 91:9. XRD result proves that the Pd/Ni composite film has good structural stability during hydrogen absorption and desorption process. During the hydrogen response experiment, central wavelength shift of the etched FBG increases linearly with the increase of hydrogen concentration. When the hydrogen concentration is 4% in volume ratio, wavelength shift of the etched FBG is about 60 pm, and the hydrogen sensor is not sensitive to methane. The experimental results show the sensor's hydrogen response is reversible, and the hydrogen sensor may have great potential for hydrogen's distributed measurement.
Source:Sensors and Actuators B: Chemical
Jixiang Dai, Minghong Yang, Xun Yu, Kun Cao, Junsheng Liao
Pd/Ni composite film was deposited on the side-face of chemically etched fiber Bragg grating as sensing element by magnetron sputtering process. The composition, structure and micro morphology of Pd/Ni composite film were investigated by energy dispersive X-ray analysis (EDAX), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The atomic ratio of Pd:Ni in Pd/Ni composite film is controlled at about 91:9. XRD result proves that the Pd/Ni composite film has good structural stability during hydrogen absorption and desorption process. During the hydrogen response experiment, central wavelength shift of the etched FBG increases linearly with the increase of hydrogen concentration. When the hydrogen concentration is 4% in volume ratio, wavelength shift of the etched FBG is about 60 pm, and the hydrogen sensor is not sensitive to methane. The experimental results show the sensor's hydrogen response is reversible, and the hydrogen sensor may have great potential for hydrogen's distributed measurement.
Novel Structured Light-addressable Potentiometric Sensor Array Based on PVC Membrane for Determination of Heavy Metals
21 August 2012,
09:23:57
Publication year:
2012
Source:Sensors and Actuators B: Chemical
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 10−5-10−1 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 investegated.
Source:Sensors and Actuators B: Chemical
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 10−5-10−1 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 investegated.
High-sensitivity detection of acetaldehyde
21 August 2012,
09:23:57
Publication year:
2012
Source:Sensors and Actuators B: Chemical
A. Giberti, M.C. Carotta, B. Fabbri, S. Gherardi, V. Guidi, C. Malagù
A set of sensors based on nanostructured single and mixed metal oxides has been prepared and employed in acetaldehyde detection within 0.1-10ppm, this range being useful for many applications. Electrical characterization has been performed in laboratory at several working temperatures, in order to obtain the optimal operating condition. ZnO working within 450-550°C, was found to best respond to acetaldehyde. The response vs. concentration curves for all the sensors was a power law with an exponent of 0.5, compatible with the oxidation of acetaldehyde catalyzed by the surface. A decay in the sensor response to acetaldehyde due to humidity was observed and discussed.
Source:Sensors and Actuators B: Chemical
A. Giberti, M.C. Carotta, B. Fabbri, S. Gherardi, V. Guidi, C. Malagù
A set of sensors based on nanostructured single and mixed metal oxides has been prepared and employed in acetaldehyde detection within 0.1-10ppm, this range being useful for many applications. Electrical characterization has been performed in laboratory at several working temperatures, in order to obtain the optimal operating condition. ZnO working within 450-550°C, was found to best respond to acetaldehyde. The response vs. concentration curves for all the sensors was a power law with an exponent of 0.5, compatible with the oxidation of acetaldehyde catalyzed by the surface. A decay in the sensor response to acetaldehyde due to humidity was observed and discussed.
Role of the host matrix on the thermal sensitivity of Er3+ luminescence in optical temperature sensors
21 August 2012,
09:23:57
Publication year:
2012
Source:Sensors and Actuators B: Chemical
Sergio F. León-Luis, Ulises R. Rodríguez-Mendoza, Patricia Haro-González, Inocencio R. Martín, Víctor Lavín
The influence of the local matrix environment on Er3+ luminescence properties is a key factor in the development of optical temperature sensors. The high sensitivity of Er3+ luminescence to the local structure, where the optically active ions reside, was analyzed along with the ligands type and bond character within the framework of the Judd-Ofelt theory. This model shows that the best thermalized emissions to use as optical temperature sensors are those in which the high energy emitting level is hypersensitive to the local structure, since the more disordered the local environment of the active ion, the better the ratio of emission intensities and the thermal sensitivity. These conclusions are experimentally supported using the fluorescence intensity ratio technique to analyze the relative variations of the luminescence intensities of the 2H11/2 and the 4S3/2 thermalized levels of the Er3+ ion in the green and the near-infrared spectral ranges from room temperature up to 720K in two different matrices: an oxyfluoride glass and a nanocrystalline fluoride-type glass-ceramic. As expected, the best results were found in visible green emissions in oxyfluoride glass, for which a maximum thermal sensitivity of around 66×10−4 K−1 is obtained at around 570K. This result can be understood as due to the higher radiative probabilities of Er3+ ion transitions in the disordered glass, which has higher values for the Ω2 and Ω4 and lower values of the Ω6 Judd-Ofelt parameters than the nanocrystalline glass-ceramic. The potential application of Er3+ ions as optical temperature sensors in these host matrices is also discussed.
Source:Sensors and Actuators B: Chemical
Sergio F. León-Luis, Ulises R. Rodríguez-Mendoza, Patricia Haro-González, Inocencio R. Martín, Víctor Lavín
The influence of the local matrix environment on Er3+ luminescence properties is a key factor in the development of optical temperature sensors. The high sensitivity of Er3+ luminescence to the local structure, where the optically active ions reside, was analyzed along with the ligands type and bond character within the framework of the Judd-Ofelt theory. This model shows that the best thermalized emissions to use as optical temperature sensors are those in which the high energy emitting level is hypersensitive to the local structure, since the more disordered the local environment of the active ion, the better the ratio of emission intensities and the thermal sensitivity. These conclusions are experimentally supported using the fluorescence intensity ratio technique to analyze the relative variations of the luminescence intensities of the 2H11/2 and the 4S3/2 thermalized levels of the Er3+ ion in the green and the near-infrared spectral ranges from room temperature up to 720K in two different matrices: an oxyfluoride glass and a nanocrystalline fluoride-type glass-ceramic. As expected, the best results were found in visible green emissions in oxyfluoride glass, for which a maximum thermal sensitivity of around 66×10−4 K−1 is obtained at around 570K. This result can be understood as due to the higher radiative probabilities of Er3+ ion transitions in the disordered glass, which has higher values for the Ω2 and Ω4 and lower values of the Ω6 Judd-Ofelt parameters than the nanocrystalline glass-ceramic. The potential application of Er3+ ions as optical temperature sensors in these host matrices is also discussed.
The electrochemical sensor for methanol detection using silicon epoxy coated platinum nanoparticles
21 August 2012,
09:23:57
Publication year:
2012
Source:Sensors and Actuators B: Chemical
Deog-Su Park, Mi-Sook Won, Rajendra N. Goyal, Yoon-Bo Shim
A platinum (Pt) nanoparticle-based electrochemical sensor 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 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 versus 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
Deog-Su Park, Mi-Sook Won, Rajendra N. Goyal, Yoon-Bo Shim
A platinum (Pt) nanoparticle-based electrochemical sensor 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 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 versus 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.
Characterization of biodegradable polymers with capacitive field-effect sensors
21 August 2012,
09:23:57
Publication year:
2012
Source:Sensors and Actuators B: Chemical
S. Schusser, A. Poghossian, M. Bäcker, M. Leinhos, P. Wagner, M.J. Schöning
In-vitro studies of the degradation kinetic of biopolymers are essential for the design and optimization of implantable biomedical devices. In the presented work, a field-effect capacitive sensor has been applied for the real-time and in-situ monitoring of degradation processes of biopolymers for the first time. The polymer-covered field-effect sensor is, in principle, capable to detect any changes in bulk, surface and interface properties of the polymer induced by degradation processes. The feasibility of this approach has been experimentally proven by using the commercially available biomedical polymer poly(d,l-lactic acid) (PDLLA) as a model system. PDLLA films of different thicknesses were deposited on the Ta2O5-gate surface of the field-effect structure from a polymer solution by means of spin-coating method. The polymer-modified field-effect sensors have been characterized by means of capacitance-voltage and impedance-spectroscopy method. The degradation of the PDLLA was accelerated by changing the degradation medium from neutral (pH 7.2) to alkaline (pH 9) condition, resulting in drastic changes in the capacitance and impedance spectra of the polymer-modified field-effect sensor.
Source:Sensors and Actuators B: Chemical
S. Schusser, A. Poghossian, M. Bäcker, M. Leinhos, P. Wagner, M.J. Schöning
In-vitro studies of the degradation kinetic of biopolymers are essential for the design and optimization of implantable biomedical devices. In the presented work, a field-effect capacitive sensor has been applied for the real-time and in-situ monitoring of degradation processes of biopolymers for the first time. The polymer-covered field-effect sensor is, in principle, capable to detect any changes in bulk, surface and interface properties of the polymer induced by degradation processes. The feasibility of this approach has been experimentally proven by using the commercially available biomedical polymer poly(d,l-lactic acid) (PDLLA) as a model system. PDLLA films of different thicknesses were deposited on the Ta2O5-gate surface of the field-effect structure from a polymer solution by means of spin-coating method. The polymer-modified field-effect sensors have been characterized by means of capacitance-voltage and impedance-spectroscopy method. The degradation of the PDLLA was accelerated by changing the degradation medium from neutral (pH 7.2) to alkaline (pH 9) condition, resulting in drastic changes in the capacitance and impedance spectra of the polymer-modified field-effect sensor.
Ultrasonic synthesis of MoO3 nanorods and their gas sensing properties
21 August 2012,
09:23:57
Publication year:
2012
Source:Sensors and Actuators B: Chemical
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
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.
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