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papers from the latest issue:
The dual role of Parylene C in chemical sensing: Acting as an encapsulant and as a sensing membrane for pH monitoring applications
10 July 2013,
09:11:32
Publication date: September
2013
Source:Sensors and Actuators B: Chemical, Volume 186
Author(s): Tatiana Trantidou , David J. Payne , Vasileios Tsiligkiridis , Yu-Chun Chang , Christofer Toumazou , Themistoklis Prodromakis
In this work, we demonstrate a new property of Parylene C emphasizing on its application in pH sensing technologies. For many decades the material has been extensively used as a biocompatible inert encapsulant of implantable micro-devices. Toward a new understanding of the material's potential, we explore the transformation of Parylene C from a passive encapsulation membrane into an active H+ sensing membrane using discrete MOSFETs to evaluate its chemical sensing performance. We employ oxygen plasma treatment to functionalize Parylene's H+ sensing capacity and enhance the chemical sensitivity, drift rates, and reliability of the sensing devices. Moreover, we demonstrate a versatile technique that enables the deployment of the material both as an encapsulant and as a sensing membrane in a single platform, in order to benefit from distinguishable and consistent sensitivities, and low leakage currents during pH measurements. Our investigation reveals that the selective modification of Parylene's surface chemistry yields reliable pH sensing devices, ensuring the best combination of sensitivity (16.3mV/pH) and leakage currents (6–10nA) over a reasonably wide pH range (4–10), while drift rates remain in low levels (2.5–20mV/h). We believe that this study opens up new application horizons for Parylene, which is a new promising material in the emerging field of flexible electronics able to deliver low film thicknesses and high biocompatibility, while facilitating the application of mechanical stimulus.
Source:Sensors and Actuators B: Chemical, Volume 186
Author(s): Tatiana Trantidou , David J. Payne , Vasileios Tsiligkiridis , Yu-Chun Chang , Christofer Toumazou , Themistoklis Prodromakis
In this work, we demonstrate a new property of Parylene C emphasizing on its application in pH sensing technologies. For many decades the material has been extensively used as a biocompatible inert encapsulant of implantable micro-devices. Toward a new understanding of the material's potential, we explore the transformation of Parylene C from a passive encapsulation membrane into an active H+ sensing membrane using discrete MOSFETs to evaluate its chemical sensing performance. We employ oxygen plasma treatment to functionalize Parylene's H+ sensing capacity and enhance the chemical sensitivity, drift rates, and reliability of the sensing devices. Moreover, we demonstrate a versatile technique that enables the deployment of the material both as an encapsulant and as a sensing membrane in a single platform, in order to benefit from distinguishable and consistent sensitivities, and low leakage currents during pH measurements. Our investigation reveals that the selective modification of Parylene's surface chemistry yields reliable pH sensing devices, ensuring the best combination of sensitivity (16.3mV/pH) and leakage currents (6–10nA) over a reasonably wide pH range (4–10), while drift rates remain in low levels (2.5–20mV/h). We believe that this study opens up new application horizons for Parylene, which is a new promising material in the emerging field of flexible electronics able to deliver low film thicknesses and high biocompatibility, while facilitating the application of mechanical stimulus.
Positioning of cells flowing in a fluidic channel by negative dielectrophoresis
10 July 2013,
09:11:32
Publication date: September
2013
Source:Sensors and Actuators B: Chemical, Volume 186
Author(s): Tomoyuki Yasukawa , Junko Yamada , Hitoshi Shiku , Fumio Mizutani , Tomokazu Matsue
Control of the flow position of cells in a microchannel is useful for developing cell separation systems. We demonstrated that cells with different sizes were transported through different gaps by a repulsive force generated by negative dielectrophoresis (n-DEP). A device was fabricated by sandwiching a polyester film with a fluidic channel between upper and lower substrates with design same as that of navigator and separator electrodes which were used to concentrate the flowing cells in the center of the channel and to guide them to gaps of different sizes, respectively. The performance of the system was assessed using a human acute monocytic leukemia cell line (THP-1) and red blood cells (RBCs) from preserved equine blood as model cells. The cells flowed along the edges of navigator electrodes to concentrate in the center of the channel because of a strong repulsive force between the upper and lower substrates induced by the application of an AC electric field. THP-1 and RBCs passed through gaps of different sizes in a separator consisting of a microelectrode array. Passage efficiencies for THP-1 and RBCs through the desired gaps were found to be 88% and 44%, respectively. The results indicate the possibility of the continuous separation of cells with different sizes in the fluidic device based on n-DEP.
Source:Sensors and Actuators B: Chemical, Volume 186
Author(s): Tomoyuki Yasukawa , Junko Yamada , Hitoshi Shiku , Fumio Mizutani , Tomokazu Matsue
Control of the flow position of cells in a microchannel is useful for developing cell separation systems. We demonstrated that cells with different sizes were transported through different gaps by a repulsive force generated by negative dielectrophoresis (n-DEP). A device was fabricated by sandwiching a polyester film with a fluidic channel between upper and lower substrates with design same as that of navigator and separator electrodes which were used to concentrate the flowing cells in the center of the channel and to guide them to gaps of different sizes, respectively. The performance of the system was assessed using a human acute monocytic leukemia cell line (THP-1) and red blood cells (RBCs) from preserved equine blood as model cells. The cells flowed along the edges of navigator electrodes to concentrate in the center of the channel because of a strong repulsive force between the upper and lower substrates induced by the application of an AC electric field. THP-1 and RBCs passed through gaps of different sizes in a separator consisting of a microelectrode array. Passage efficiencies for THP-1 and RBCs through the desired gaps were found to be 88% and 44%, respectively. The results indicate the possibility of the continuous separation of cells with different sizes in the fluidic device based on n-DEP.
Construction of a chitosan/polyaniline/graphene oxide nanoparticles/polypyrrole/Au electrode for amperometric determination of urinary/plasma oxalate
10 July 2013,
09:11:32
Publication date: September
2013
Source:Sensors and Actuators B: Chemical, Volume 186
Author(s): Rooma Devi , Shabnam Relhan , C.S. Pundir
Graphene oxide nanoparticles (G@NP) were synthesized from graphite powder of lead pencil and characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). A mixture of G@NPs and polypyrrole (PPy) was electropolymerized onto gold (Au) electrode followed by electrodeposition of a mixture of polyaniline (PANI) and chitosan (CHIT) onto G@NPs/PPy/Au to construct CHIT/PANI/G@NPs/PPy/Au electrode. An oxalate oxidase (OXO) purified from strawberry fruits was immobilized on to this modified Au electrode through chitosan. The enzyme electrode (OXO/CHIT/PANI/G@NPs/PPy/Au electrode) was characterized by cyclic voltammetry (CV), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectrophotometry and electrochemical impedance spectroscopy (EIS) at different stages of its construction. The OXO/G@NPs/PPy/PANI/CHIT/Au electrode as working electrode, Ag/AgCl as reference electrode and Pt wire as auxillary electrode were connected through a potentiostat to fabricate an amperometric oxalate biosensor. The biosensor exhibited optimum response within 3s at pH 5.5, 35°C with a linearity, between 1 and 400μM for oxalic acid and a detection limit of 1μM. Apparent Michaelis–Menten constant (K m) for oxalate was 12.5μM while I max was 0.008mA. The optimized biosensor measured oxalate level in urine and plasma collected from apparently healthy persons and urinary stone formers.
Source:Sensors and Actuators B: Chemical, Volume 186
Author(s): Rooma Devi , Shabnam Relhan , C.S. Pundir
Graphene oxide nanoparticles (G@NP) were synthesized from graphite powder of lead pencil and characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). A mixture of G@NPs and polypyrrole (PPy) was electropolymerized onto gold (Au) electrode followed by electrodeposition of a mixture of polyaniline (PANI) and chitosan (CHIT) onto G@NPs/PPy/Au to construct CHIT/PANI/G@NPs/PPy/Au electrode. An oxalate oxidase (OXO) purified from strawberry fruits was immobilized on to this modified Au electrode through chitosan. The enzyme electrode (OXO/CHIT/PANI/G@NPs/PPy/Au electrode) was characterized by cyclic voltammetry (CV), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectrophotometry and electrochemical impedance spectroscopy (EIS) at different stages of its construction. The OXO/G@NPs/PPy/PANI/CHIT/Au electrode as working electrode, Ag/AgCl as reference electrode and Pt wire as auxillary electrode were connected through a potentiostat to fabricate an amperometric oxalate biosensor. The biosensor exhibited optimum response within 3s at pH 5.5, 35°C with a linearity, between 1 and 400μM for oxalic acid and a detection limit of 1μM. Apparent Michaelis–Menten constant (K m) for oxalate was 12.5μM while I max was 0.008mA. The optimized biosensor measured oxalate level in urine and plasma collected from apparently healthy persons and urinary stone formers.
A direct gaseous ethanol imaging system for analysis of alcohol metabolism from exhaled breath
10 July 2013,
09:11:32
Publication date: September
2013
Source:Sensors and Actuators B: Chemical, Volume 186
Author(s): Takahiro Arakawa , Xin Wang , Takumi Kajiro , Kumiko Miyajima , Shuhei Takeuchi , Hiroyuki Kudo , Kazuyoshi Yano , Kohji Mitsubayashi
A non-invasive breath gaseous ethanol imaging system with an exhaled breath flow rate control has been developed. The system offers straight-forward, rapid, and painless sampling from patients, and can be applied to diagnose diseases. The system provides an image of ethanol concentration using chemiluminescence (CL) from an enzyme-immobilized support. The system measures ethanol concentrations as intensities of CL by luminol reaction induced by alcohol oxidase and horseradish peroxidase–luminol–hydrogen peroxide system. The spatio-temporal change in CL generates by ethanol in an exhaled breath is detected by an electron multiplier EM-CCD camera and analyzed. An ethanol skin patch test, a simple method of indicating aldehydehydrogenase 2 (ALDH2), is performed on healthy volunteers. Breath samples from volunteers with ALDH2(+) and ALDH2(−) are analyzed. The exhaled breath flow rate control unit can control and optimize the naturally unstable flow rate of human breath without a gas sampling bag. The coefficient of variance in the exhaled breath flow rate is estimated at 2.8% at a flow rate of 200mL/min. Exhaled gaseous ethanol obtained from volunteers is visualized and analyzed over a period of 300min following the oral administration of ethanol at 0.4g/kg body weight. A peak in the exhaled breath ethanol concentration appears at 30min for both ALDH2(+) and ALDH2(−) volunteers, the breath ethanol concentration then gradually decreases over the remainder of the 300min.
Source:Sensors and Actuators B: Chemical, Volume 186
Author(s): Takahiro Arakawa , Xin Wang , Takumi Kajiro , Kumiko Miyajima , Shuhei Takeuchi , Hiroyuki Kudo , Kazuyoshi Yano , Kohji Mitsubayashi
A non-invasive breath gaseous ethanol imaging system with an exhaled breath flow rate control has been developed. The system offers straight-forward, rapid, and painless sampling from patients, and can be applied to diagnose diseases. The system provides an image of ethanol concentration using chemiluminescence (CL) from an enzyme-immobilized support. The system measures ethanol concentrations as intensities of CL by luminol reaction induced by alcohol oxidase and horseradish peroxidase–luminol–hydrogen peroxide system. The spatio-temporal change in CL generates by ethanol in an exhaled breath is detected by an electron multiplier EM-CCD camera and analyzed. An ethanol skin patch test, a simple method of indicating aldehydehydrogenase 2 (ALDH2), is performed on healthy volunteers. Breath samples from volunteers with ALDH2(+) and ALDH2(−) are analyzed. The exhaled breath flow rate control unit can control and optimize the naturally unstable flow rate of human breath without a gas sampling bag. The coefficient of variance in the exhaled breath flow rate is estimated at 2.8% at a flow rate of 200mL/min. Exhaled gaseous ethanol obtained from volunteers is visualized and analyzed over a period of 300min following the oral administration of ethanol at 0.4g/kg body weight. A peak in the exhaled breath ethanol concentration appears at 30min for both ALDH2(+) and ALDH2(−) volunteers, the breath ethanol concentration then gradually decreases over the remainder of the 300min.
Sensitive amperometric immunosensor for α-fetoprotein detection based on multifunctional dumbbell-like Au-Fe3O4 heterostructures
10 July 2013,
09:11:32
Publication date: September
2013
Source:Sensors and Actuators B: Chemical, Volume 186
Author(s): Ganesh K. Parshetti , Fang-hsin Lin , Ruey-an Doong
An ultrasensitive sandwich-type amperometric immunosensor for the detection of cancer biomarker, α-fetoprotein (AFP), was fabricated using Au/chitosan modified glassy carbon electrode (GCE) and antibody-functionalized dumbbell-like Au-Fe3O4 heterostructures as sensing platform and immuno-labels, respectively. The sensing platform was constructed by modifying GCE surface with chitosan and Au nanoparticles (NPs) for effective immobilization of primary antibody (Ab1). To fabricate the labels, nano-Au NPs were first epitaxially growth onto Fe3O4 surface to form the dumbbell-like Au-Fe3O4 followed by conjugation of secondary antibody (Ab2) onto Au surface (Au-Fe3O4-Ab2). Results showed that the GCE modified with chitosan produced high electrochemical response by conjugation of more Au-Ab1 and the dumbbell-like Au-Fe3O4 served as a dual-probe to immobilize Ab2 onto Au as well as to reduce H2O2 by Fe3O4, resulting in enhancement of signal amplification. Under the optimal condition at pH 6.5 and 30°C, the prepared Au-Fe3O4/Ab2/AFP/Ab1/Au/chitosan/GCE immunosensors exhibited a good analytical performance in the presence of 10mM H2O2 with wide dynamic range of 4 orders of magnitude (0.01–40ngmL−1) and low detection limit of 2.3pgmL−1. In addition, the proposed immunoassay also displayed good reproducibility and storage stability. Results obtained in this study clearly demonstrate that the Au-Fe3O4/Ab2/AFP/Ab1/Au/chitosan/GCE immunosensor is a promising biosensing platform for highly sensitive detection of AFP and various tumor makers.
Source:Sensors and Actuators B: Chemical, Volume 186
Author(s): Ganesh K. Parshetti , Fang-hsin Lin , Ruey-an Doong
An ultrasensitive sandwich-type amperometric immunosensor for the detection of cancer biomarker, α-fetoprotein (AFP), was fabricated using Au/chitosan modified glassy carbon electrode (GCE) and antibody-functionalized dumbbell-like Au-Fe3O4 heterostructures as sensing platform and immuno-labels, respectively. The sensing platform was constructed by modifying GCE surface with chitosan and Au nanoparticles (NPs) for effective immobilization of primary antibody (Ab1). To fabricate the labels, nano-Au NPs were first epitaxially growth onto Fe3O4 surface to form the dumbbell-like Au-Fe3O4 followed by conjugation of secondary antibody (Ab2) onto Au surface (Au-Fe3O4-Ab2). Results showed that the GCE modified with chitosan produced high electrochemical response by conjugation of more Au-Ab1 and the dumbbell-like Au-Fe3O4 served as a dual-probe to immobilize Ab2 onto Au as well as to reduce H2O2 by Fe3O4, resulting in enhancement of signal amplification. Under the optimal condition at pH 6.5 and 30°C, the prepared Au-Fe3O4/Ab2/AFP/Ab1/Au/chitosan/GCE immunosensors exhibited a good analytical performance in the presence of 10mM H2O2 with wide dynamic range of 4 orders of magnitude (0.01–40ngmL−1) and low detection limit of 2.3pgmL−1. In addition, the proposed immunoassay also displayed good reproducibility and storage stability. Results obtained in this study clearly demonstrate that the Au-Fe3O4/Ab2/AFP/Ab1/Au/chitosan/GCE immunosensor is a promising biosensing platform for highly sensitive detection of AFP and various tumor makers.
Glucose biosensor based on the highly efficient immobilization of glucose oxidase on layer-by-layer films of silsesquioxane polyelectrolyte
10 July 2013,
09:11:32
Publication date: September
2013
Source:Sensors and Actuators B: Chemical, Volume 186
Author(s): Cliciane Guadalupe de Jesus , Dhésmon Lima , Vagner dos Santos , Karen Wohnrath , Christiana Andrade Pessôa
In this paper, LbL films were prepared between 3-n-propylpyridinium silsesquioxane polymer (SiPy+Cl−) and copper (II) tetrasulfophthalocyanine (CuTsPc), denoted as (SiPy+Cl−/CuTsPc) n . The multilayer film modified electrode (SiPy+Cl−/CuTsPc)2 showed excellent electrocatalytic activity for H2O2 reduction with a wide linear range of response, high sensitivity and low detection limit. This film was modified with glucose oxidase (GOx) and a film of Nafion (Nf) which was used to prevent the GOx from leaking off. FTIR, fluorescence spectrometry and CD measurements showed that the GOx enzyme retains its native secondary structure when immobilized on the LbL film. The resulting (SiPy+Cl−/CuTsPc)2(SiPy+Cl−/GOx/Nf) biosensor displayed a current response which varies linearly with the concentration of glucose in the range from 1 to 10mmolL−1 with a detection limit of 0.16mmolL−1, a sensitivity of 1.397×10−7 μA (mmolL−1)−1 and a fast response time. The apparent Michaelis–Menten constant ( k m app ) was 10mmolL−1. In addition, the biosensor also exhibited good reproducibility, excellent stability and long life-time with no decrease in the activity of enzyme over a one week period and remained active in the films for periods longer than three weeks.
Source:Sensors and Actuators B: Chemical, Volume 186
Author(s): Cliciane Guadalupe de Jesus , Dhésmon Lima , Vagner dos Santos , Karen Wohnrath , Christiana Andrade Pessôa
In this paper, LbL films were prepared between 3-n-propylpyridinium silsesquioxane polymer (SiPy+Cl−) and copper (II) tetrasulfophthalocyanine (CuTsPc), denoted as (SiPy+Cl−/CuTsPc) n . The multilayer film modified electrode (SiPy+Cl−/CuTsPc)2 showed excellent electrocatalytic activity for H2O2 reduction with a wide linear range of response, high sensitivity and low detection limit. This film was modified with glucose oxidase (GOx) and a film of Nafion (Nf) which was used to prevent the GOx from leaking off. FTIR, fluorescence spectrometry and CD measurements showed that the GOx enzyme retains its native secondary structure when immobilized on the LbL film. The resulting (SiPy+Cl−/CuTsPc)2(SiPy+Cl−/GOx/Nf) biosensor displayed a current response which varies linearly with the concentration of glucose in the range from 1 to 10mmolL−1 with a detection limit of 0.16mmolL−1, a sensitivity of 1.397×10−7 μA (mmolL−1)−1 and a fast response time. The apparent Michaelis–Menten constant ( k m app ) was 10mmolL−1. In addition, the biosensor also exhibited good reproducibility, excellent stability and long life-time with no decrease in the activity of enzyme over a one week period and remained active in the films for periods longer than three weeks.
Chemical sensing using electrospun polymer/carbon nanotube composite nanofibers with printed-on electrodes
10 July 2013,
09:11:32
Publication date: September
2013
Source:Sensors and Actuators B: Chemical, Volume 186
Author(s): Li Han , Anthony L. Andrady , David S. Ensor
An integrated sensor system was developed using mats formed of electrospun polymer/single-walled carbon nanotube composite nanofibers combined with inter-digitated electrodes directly printed on the surface to detect volatile organic compounds. When the polymer in the fibers swells due to vapor adsorption, the carbon nanotubes separate from each other and increase electrical resistance of the material. The conductivity change of the composite-sensing material was monitored with a multi-meter when exposed to volatile organic compounds. The response to different vapors showed a linear relationship between resistance change and vapor concentration. We obtained both sensitivity and selectivity data on the sensor with several different vapor analytes – methanol is used as an example in this paper.
Source:Sensors and Actuators B: Chemical, Volume 186
Author(s): Li Han , Anthony L. Andrady , David S. Ensor
An integrated sensor system was developed using mats formed of electrospun polymer/single-walled carbon nanotube composite nanofibers combined with inter-digitated electrodes directly printed on the surface to detect volatile organic compounds. When the polymer in the fibers swells due to vapor adsorption, the carbon nanotubes separate from each other and increase electrical resistance of the material. The conductivity change of the composite-sensing material was monitored with a multi-meter when exposed to volatile organic compounds. The response to different vapors showed a linear relationship between resistance change and vapor concentration. We obtained both sensitivity and selectivity data on the sensor with several different vapor analytes – methanol is used as an example in this paper.
Two novel fluorescein-based fluorescent probes for hypochlorite and its real applications in tap water and biological imaging
10 July 2013,
09:11:32
Publication date: September
2013
Source:Sensors and Actuators B: Chemical, Volume 186
Author(s): Xilang Jin , Likai Hao , Yanling Hu , Mengyao She , Yanning Shi , Martin Obst , Jianli Li , Zhen Shi
Two novel fluorescein-based OCl− chemosensors were designed, synthesized and characterized. Both fluorescence probes utilize an irreversible OCl−-promoted oxidation reaction to trigger the activation of fluorescence. These probes were shown to be highly selective for OCl−, and showed real time responses as well as a positive linear relationship to OCl− concentrations. The probes were successfully applied for the detection of OCl− in tap water and for fluorescence imaging of OCl− in bacterial Rhodobacter ferrooxidans sp. strain SW2 cell–EPS–mineral aggregates.
Source:Sensors and Actuators B: Chemical, Volume 186
Author(s): Xilang Jin , Likai Hao , Yanling Hu , Mengyao She , Yanning Shi , Martin Obst , Jianli Li , Zhen Shi
Two novel fluorescein-based OCl− chemosensors were designed, synthesized and characterized. Both fluorescence probes utilize an irreversible OCl−-promoted oxidation reaction to trigger the activation of fluorescence. These probes were shown to be highly selective for OCl−, and showed real time responses as well as a positive linear relationship to OCl− concentrations. The probes were successfully applied for the detection of OCl− in tap water and for fluorescence imaging of OCl− in bacterial Rhodobacter ferrooxidans sp. strain SW2 cell–EPS–mineral aggregates.
One-step synthesis and gas sensing characteristics of urchin-like In2O3
10 July 2013,
09:11:32
Publication date: September
2013
Source:Sensors and Actuators B: Chemical, Volume 186
Author(s): Xiumei Xu , Xiaodong Mei , Peilu Zhao , Peng Sun , Yangfeng Sun , Xiaolong Hu , Geyu Lu
In this work, urchin-like In2O3 microspheres were fabricated using a solvothermal method in the presence of SDS (sodium dodecyl sulfonate) and urea. The as-synthesized samples were characterized using X-ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM). The results indicate that the synthesized urchin-like In2O3 microspheres were constructed by nanorods. Moreover, the gas sensing properties of as-prepared products were investigated. It was found that the sensor based on such novel urchin-like In2O3 microspheres exhibited high response and good selectivity to O3.
Source:Sensors and Actuators B: Chemical, Volume 186
Author(s): Xiumei Xu , Xiaodong Mei , Peilu Zhao , Peng Sun , Yangfeng Sun , Xiaolong Hu , Geyu Lu
In this work, urchin-like In2O3 microspheres were fabricated using a solvothermal method in the presence of SDS (sodium dodecyl sulfonate) and urea. The as-synthesized samples were characterized using X-ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM). The results indicate that the synthesized urchin-like In2O3 microspheres were constructed by nanorods. Moreover, the gas sensing properties of as-prepared products were investigated. It was found that the sensor based on such novel urchin-like In2O3 microspheres exhibited high response and good selectivity to O3.
Facile preparation of polyaniline/MnO2 nanofibers and its electrochemical application in the simultaneous determination of catechol, hydroquinone, and resorcinol
10 July 2013,
09:11:32
Publication date: September
2013
Source:Sensors and Actuators B: Chemical, Volume 186
Author(s): M.U. Anu Prathap , Biswarup Satpati , Rajendra Srivastava
In this study, polyaniline/MnO2 nanofibers were synthesized by the simple mixing of aqueous dispersed solution of polyaniline (PANI) nanofibers and KMnO4 aqueous solution. Materials were characterized by X-ray diffraction, nitrogen sorption, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, and FT-IR. The electrochemical oxidation of hydroquinone, catechol, and resorcinol was investigated using cyclic and differential pulse voltammetries at PANI/MnO2 modified electrode. PANI/MnO2 exhibited high current sensitivity for these analytes compared to MnO2 and PANI modified electrodes, which is due to the presence of highly dispersed MnO2 in PANI matrix. The performance of this material was demonstrated in the detection of hydroquinone, catechol, and resorcinol in water samples. The reliability and stability of the modified electrode provides a good possibility for applying the technique in routine analysis for a selected class of electroactive organic/bio-molecules.
Source:Sensors and Actuators B: Chemical, Volume 186
Author(s): M.U. Anu Prathap , Biswarup Satpati , Rajendra Srivastava
In this study, polyaniline/MnO2 nanofibers were synthesized by the simple mixing of aqueous dispersed solution of polyaniline (PANI) nanofibers and KMnO4 aqueous solution. Materials were characterized by X-ray diffraction, nitrogen sorption, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, and FT-IR. The electrochemical oxidation of hydroquinone, catechol, and resorcinol was investigated using cyclic and differential pulse voltammetries at PANI/MnO2 modified electrode. PANI/MnO2 exhibited high current sensitivity for these analytes compared to MnO2 and PANI modified electrodes, which is due to the presence of highly dispersed MnO2 in PANI matrix. The performance of this material was demonstrated in the detection of hydroquinone, catechol, and resorcinol in water samples. The reliability and stability of the modified electrode provides a good possibility for applying the technique in routine analysis for a selected class of electroactive organic/bio-molecules.
Graphical abstract
Humidity sensing properties of a single Sb doped SnO2 nanowire field effect transistor
10 July 2013,
09:11:32
Publication date: September
2013
Source:Sensors and Actuators B: Chemical, Volume 186
Author(s): Ming Zhuo , Yuejiao Chen , Jia Sun , Haiming Zhang , Di Guo , Haonan Zhang , Qiuhong Li , Taihong Wang , Qing Wan
This work reports the humidity dependent properties of a single Sb doped SnO2 nanowire field effect transistor (NWFET). The NWFET is fabricated by a lithography method on a highly doped silicon substrate as back gate covered by oxide as gate dielectric. The electric properties of the device under different relative humidities (RHs) at room temperature are investigated. The NWFET exhibits a field effect mobility of 108.7cm2/(Vs), a subthreshold swing of 70mV/decade, and a drain current on/off ratio of 106. The threshold voltage shifts from −11.2V to −14.6V as RH increases from 22% to 40%. The NWFET exhibits sensitive behaviors to the humidity, which is promising for the application in humidity sensors
Source:Sensors and Actuators B: Chemical, Volume 186
Author(s): Ming Zhuo , Yuejiao Chen , Jia Sun , Haiming Zhang , Di Guo , Haonan Zhang , Qiuhong Li , Taihong Wang , Qing Wan
This work reports the humidity dependent properties of a single Sb doped SnO2 nanowire field effect transistor (NWFET). The NWFET is fabricated by a lithography method on a highly doped silicon substrate as back gate covered by oxide as gate dielectric. The electric properties of the device under different relative humidities (RHs) at room temperature are investigated. The NWFET exhibits a field effect mobility of 108.7cm2/(Vs), a subthreshold swing of 70mV/decade, and a drain current on/off ratio of 106. The threshold voltage shifts from −11.2V to −14.6V as RH increases from 22% to 40%. The NWFET exhibits sensitive behaviors to the humidity, which is promising for the application in humidity sensors
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