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Interaction of nitrogen dioxide with sulfonamide-substituted phthalocyanines: Towards NO2 gas sensor
07 June 2012,
10:40:35
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 169
Sergii Pochekailov, Juraj Nožár, Stanislav Nešpůrek, Jan Rakušan, Marie Karásková
Much of life requires fast, cheap and reliable gas sensors. As nitrogen dioxide is a toxic and environmentally polluting gas, produced by humans in excess, to be able to monitor and detect it is necessary. One of the way to manufacture cheap and reliable gas sensors sensitive to nitrogen dioxide is to use soluble organic materials as the sensing media. In this paper, we study the properties of soluble sulfonamide-substituted zinc and metal-free phthalocyanines. The sensing capabilities of these materials are discussed in detail. We have found that Zn sulfonamide-substituted phthalocyanine (Pc) forms a charge transfer complex with nitrogen dioxide, which results in a change of absorption spectrum and an increase of electrical conductivity as much as two orders of magnitude. On the other hand, metal-free Pc does not form the complex and its interaction with nitrogen dioxide is based on weak Van-der-Waals forces. The absorption spectrum does not change and the electrical conductivity slightly decreases during nitrogen dioxide exposure. We have also found that these materials, unlike literature reported derivatives, are reversibly sensitive to nitrogen dioxide at room temperature. This opens a great potential for the fabrication of cheap and reliable gas sensors.
Source:Sensors and Actuators B: Chemical, Volume 169
Sergii Pochekailov, Juraj Nožár, Stanislav Nešpůrek, Jan Rakušan, Marie Karásková
Much of life requires fast, cheap and reliable gas sensors. As nitrogen dioxide is a toxic and environmentally polluting gas, produced by humans in excess, to be able to monitor and detect it is necessary. One of the way to manufacture cheap and reliable gas sensors sensitive to nitrogen dioxide is to use soluble organic materials as the sensing media. In this paper, we study the properties of soluble sulfonamide-substituted zinc and metal-free phthalocyanines. The sensing capabilities of these materials are discussed in detail. We have found that Zn sulfonamide-substituted phthalocyanine (Pc) forms a charge transfer complex with nitrogen dioxide, which results in a change of absorption spectrum and an increase of electrical conductivity as much as two orders of magnitude. On the other hand, metal-free Pc does not form the complex and its interaction with nitrogen dioxide is based on weak Van-der-Waals forces. The absorption spectrum does not change and the electrical conductivity slightly decreases during nitrogen dioxide exposure. We have also found that these materials, unlike literature reported derivatives, are reversibly sensitive to nitrogen dioxide at room temperature. This opens a great potential for the fabrication of cheap and reliable gas sensors.
Development of a SnO2/CuO-coated surface acoustic wave-based H2S sensor with switch-like response and recovery
07 June 2012,
10:40:35
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 169
Xiudong Wang, Wen Wang, Honglang Li, Chen Fu, Yabing Ke, Shitang He
A new surface acoustic wave (SAW) sensor with switch-like response and recovery was developed for H2S gas sensing, in which, as a sensitive interface material toward H2S, a SnO2/CuO composite film was deposited onto a 147MHz SAW delay line on 36° YXLiTaO3 substrate by the RF magnetron sputtering technique, and annealed at 450°C for 2.5h in the dry air. The adsorption of H2S by the sensitive coating modulates the phase velocity of the acoustic wave due to the mass loading and acoustoelectric effect, thus, the target specific H2S gas can be evaluated by recording the frequency shift of the SAW device. The temperature effect on sensor response characteristics was investigated in temperature range of 70–205°C, and the optimal working temperature of 160°C was extracted experimentally, at which, fast response time (55s) and recovery time (45s), and larger frequency response of 230kHz were observed from the fabricated SAW sensor toward H2S with concentration of 20ppm. Moreover, high sensitivity of 16.9kHzppm−1, excellent selectivity, and superior repeatability were observed.
Source:Sensors and Actuators B: Chemical, Volume 169
Xiudong Wang, Wen Wang, Honglang Li, Chen Fu, Yabing Ke, Shitang He
A new surface acoustic wave (SAW) sensor with switch-like response and recovery was developed for H2S gas sensing, in which, as a sensitive interface material toward H2S, a SnO2/CuO composite film was deposited onto a 147MHz SAW delay line on 36° YXLiTaO3 substrate by the RF magnetron sputtering technique, and annealed at 450°C for 2.5h in the dry air. The adsorption of H2S by the sensitive coating modulates the phase velocity of the acoustic wave due to the mass loading and acoustoelectric effect, thus, the target specific H2S gas can be evaluated by recording the frequency shift of the SAW device. The temperature effect on sensor response characteristics was investigated in temperature range of 70–205°C, and the optimal working temperature of 160°C was extracted experimentally, at which, fast response time (55s) and recovery time (45s), and larger frequency response of 230kHz were observed from the fabricated SAW sensor toward H2S with concentration of 20ppm. Moreover, high sensitivity of 16.9kHzppm−1, excellent selectivity, and superior repeatability were observed.
Facile synthesis and enhanced H2S sensing performances of Fe-doped α-MoO3 micro-structures
07 June 2012,
10:40:35
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 169
Qiu-Yun Ouyang, Li Li, Qing-Shan Wang, Yue Zhang, Tie-Shi Wang, Fan-Na Meng, Yu-Jin Chen, Peng Gao
Fe-doped α-MoO3 micro-structures were fabricated by a hydrothermal method, in which the Fe doping amount was easily adjusted to be 0.3, 0.6, 0.7 and 0.9wt.% by only increasing the reaction time. X-ray diffraction and the energy dispersive spectroscopy analyses as well as the difference in the color between the doped and undoped samples provided the evidences for the Fe doping. It was also found that an appropriate Fe doping amount was beneficial to the improvement of H2S sensing performances. The enhanced gas sensing properties of the Fe-doped α-MoO3 sensors were attributed to the small size effect, catalytic effect of Fe dopants, surface reaction dynamics, and the increase in the resistance of the doped samples.
Source:Sensors and Actuators B: Chemical, Volume 169
Qiu-Yun Ouyang, Li Li, Qing-Shan Wang, Yue Zhang, Tie-Shi Wang, Fan-Na Meng, Yu-Jin Chen, Peng Gao
Fe-doped α-MoO3 micro-structures were fabricated by a hydrothermal method, in which the Fe doping amount was easily adjusted to be 0.3, 0.6, 0.7 and 0.9wt.% by only increasing the reaction time. X-ray diffraction and the energy dispersive spectroscopy analyses as well as the difference in the color between the doped and undoped samples provided the evidences for the Fe doping. It was also found that an appropriate Fe doping amount was beneficial to the improvement of H2S sensing performances. The enhanced gas sensing properties of the Fe-doped α-MoO3 sensors were attributed to the small size effect, catalytic effect of Fe dopants, surface reaction dynamics, and the increase in the resistance of the doped samples.
A planar split-ring resonator-based microwave biosensor for label-free detection of biomolecules
07 June 2012,
10:40:35
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 169
Hee-Jo Lee, Jung-Hyun Lee, Hui-Sung Moon, Ik-Soon Jang, Jong-Soon Choi, Jong-Gwan Yook, Hyo-Il Jung
In this study, a planar split-ring resonator (SRR)-based RF biosensor was developed for label-free detection of biomolecules such as the prostate cancer marker, prostate specific antigen (PSA), and cortisol stress hormone. The biosensor has a resonance-assisted transducer and is excited by a time-varying magnetic field component of a local high-impedance microstrip line. The resulting device exhibits an intrinsic S 21 resonance with a quality-factor (or Q-factor) of 50. For the biomolecular interaction, anti-PSA and anti-cortisol were immobilized on the gold surface of the resonator by a protein-G mediated bioconjugation process and corresponding frequency shifts of Δ f 1 p = 30 ± 2 MHz (for anti-PSA) and Δ f 1 c = 20 ± 3 MHz (for anti-cortisol) were observed. The additional frequency shift of each PSA and cortisol antigen with a 100pg/ml concentration was about 5±1.5MHz and 3±1MHz, respectively. From the experimental results, we confirmed that our device is very effective RF biosensor with a limit of detection (LOD) of 100pg/ml and has sufficiently feasibility as a label-free biosensing scheme.
Source:Sensors and Actuators B: Chemical, Volume 169
Hee-Jo Lee, Jung-Hyun Lee, Hui-Sung Moon, Ik-Soon Jang, Jong-Soon Choi, Jong-Gwan Yook, Hyo-Il Jung
In this study, a planar split-ring resonator (SRR)-based RF biosensor was developed for label-free detection of biomolecules such as the prostate cancer marker, prostate specific antigen (PSA), and cortisol stress hormone. The biosensor has a resonance-assisted transducer and is excited by a time-varying magnetic field component of a local high-impedance microstrip line. The resulting device exhibits an intrinsic S 21 resonance with a quality-factor (or Q-factor) of 50. For the biomolecular interaction, anti-PSA and anti-cortisol were immobilized on the gold surface of the resonator by a protein-G mediated bioconjugation process and corresponding frequency shifts of Δ f 1 p = 30 ± 2 MHz (for anti-PSA) and Δ f 1 c = 20 ± 3 MHz (for anti-cortisol) were observed. The additional frequency shift of each PSA and cortisol antigen with a 100pg/ml concentration was about 5±1.5MHz and 3±1MHz, respectively. From the experimental results, we confirmed that our device is very effective RF biosensor with a limit of detection (LOD) of 100pg/ml and has sufficiently feasibility as a label-free biosensing scheme.
Effect of composition on sensing properties of SnO2+In2O3 mixed nanostructured films
07 June 2012,
10:40:35
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 169
L.I. Trakhtenberg, G.N. Gerasimov, V.F. Gromov, T.V. Belysheva, O.J. Ilegbusi
The conductometric response of SnO2 +In2O3 nanocomposite films to hydrogen and carbon monoxide in air are investigated experimentally for varying oxide compositions. The fundamental mechanism of sensory phenomena in such nanocomposite films is also discussed. The experimental results indicate that the response (θ com) of the sensor is determined by the current flow path in the film. For composites with In2O3 composition (X In) less than 20wt.%, current flows through the SnO2 crystals. Due to electron transfer from the In2O3 inclusions to the SnO2 matrix, an increase in X In up to 20wt.% leads to a significant increase in the conductivity of the composite sensor and θ com for both CO and H2. A further increase in X In results in percolation transition for In2O3 nanocrystals, which form conducting clusters (threads) of In2O3, with electrical conductivity that is much higher than that of SnO2. The transition from conduction through the SnO2 crystals to conduction through the In2O3 crystals in the composite films occurs at X In in the range about 20–50wt.%. For X In ≥50wt.%, θ com is entirely determined by the sensory properties of the In2O3 conducting clusters, and electron transfer from In2O3 clusters to SnO2 results in a decrease of θ com.
Source:Sensors and Actuators B: Chemical, Volume 169
L.I. Trakhtenberg, G.N. Gerasimov, V.F. Gromov, T.V. Belysheva, O.J. Ilegbusi
The conductometric response of SnO2 +In2O3 nanocomposite films to hydrogen and carbon monoxide in air are investigated experimentally for varying oxide compositions. The fundamental mechanism of sensory phenomena in such nanocomposite films is also discussed. The experimental results indicate that the response (θ com) of the sensor is determined by the current flow path in the film. For composites with In2O3 composition (X In) less than 20wt.%, current flows through the SnO2 crystals. Due to electron transfer from the In2O3 inclusions to the SnO2 matrix, an increase in X In up to 20wt.% leads to a significant increase in the conductivity of the composite sensor and θ com for both CO and H2. A further increase in X In results in percolation transition for In2O3 nanocrystals, which form conducting clusters (threads) of In2O3, with electrical conductivity that is much higher than that of SnO2. The transition from conduction through the SnO2 crystals to conduction through the In2O3 crystals in the composite films occurs at X In in the range about 20–50wt.%. For X In ≥50wt.%, θ com is entirely determined by the sensory properties of the In2O3 conducting clusters, and electron transfer from In2O3 clusters to SnO2 results in a decrease of θ com.
Room-temperature highly sensitive nitrogen dioxide sensor using zinc complex film
07 June 2012,
10:40:35
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 169
Tiexiang Fu
In this paper, a systematic study of the NO2 gas sensing properties of the sensors based on a [Zn3(bipyO2)4Cl4]Cl2 (bipyO2: 2,2′-bipyridine-N,N′-dioxide) complex film is presented for the first time. The sensors gave a good response to NO2 at room temperature. The response attained more than 1670 at high concentrations and a 15V operating voltage. The responses to other test gases were poor. The influences of the operating voltage and the working temperature on the responses to NO2 gas were also studied. The optimum operating voltage of the sensor was 15V. The sensor showed satisfactory reproducibility and stability in air. The gas-sensing mechanism of the sensor was discussed.
Source:Sensors and Actuators B: Chemical, Volume 169
Tiexiang Fu
In this paper, a systematic study of the NO2 gas sensing properties of the sensors based on a [Zn3(bipyO2)4Cl4]Cl2 (bipyO2: 2,2′-bipyridine-N,N′-dioxide) complex film is presented for the first time. The sensors gave a good response to NO2 at room temperature. The response attained more than 1670 at high concentrations and a 15V operating voltage. The responses to other test gases were poor. The influences of the operating voltage and the working temperature on the responses to NO2 gas were also studied. The optimum operating voltage of the sensor was 15V. The sensor showed satisfactory reproducibility and stability in air. The gas-sensing mechanism of the sensor was discussed.
Portable reconfigurable instrument for analytical determinations using disposable electrochemiluminescent screen-printed electrodes
07 June 2012,
10:40:35
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 169
M.A. Carvajal, J. Ballesta-Claver, D.P. Morales, A.J. Palma, M.C. Valencia-Mirón, L.F. Capitán-Vallvey
A portable reconfigurable instrument platform for electrochemiluminescence (ECL)-based disposable screen-printed electrodes is described. The reader unit consists of a potentiostat and a photodiode as a light-to-current converter integrated in the same instrument. For powerful and versatile analog conditioning, a very recent electronic solution has been included: a Field Programmable Analog Array (FPAA) capable of reconfiguring filter and gain stages in real time. To check the instrument's performance as a sensor platform, two luminophores (tris(2,2′bipyridyl)ruthenium(II) and luminol) and two representative correactants widely used, triethylamine and cholesterol, were selected. The calibration functions obtained show a linear dependence with dynamic ranges from 0.05 to 10.0mgl−1 for triethylamine, and 2.0·10−5–1.4·10−4 M for cholesterol, with detection limits of 0.2mgl−1 and 1.1·10−5 M, respectively, and a sensor-to-sensor reproducibility (relative standard deviation, RSD) of around 3.2% and 3.3% respectively at the medium-range level. This instrument offers a new advance in the portability of electrochemiluminescent determinations.
Source:Sensors and Actuators B: Chemical, Volume 169
M.A. Carvajal, J. Ballesta-Claver, D.P. Morales, A.J. Palma, M.C. Valencia-Mirón, L.F. Capitán-Vallvey
A portable reconfigurable instrument platform for electrochemiluminescence (ECL)-based disposable screen-printed electrodes is described. The reader unit consists of a potentiostat and a photodiode as a light-to-current converter integrated in the same instrument. For powerful and versatile analog conditioning, a very recent electronic solution has been included: a Field Programmable Analog Array (FPAA) capable of reconfiguring filter and gain stages in real time. To check the instrument's performance as a sensor platform, two luminophores (tris(2,2′bipyridyl)ruthenium(II) and luminol) and two representative correactants widely used, triethylamine and cholesterol, were selected. The calibration functions obtained show a linear dependence with dynamic ranges from 0.05 to 10.0mgl−1 for triethylamine, and 2.0·10−5–1.4·10−4 M for cholesterol, with detection limits of 0.2mgl−1 and 1.1·10−5 M, respectively, and a sensor-to-sensor reproducibility (relative standard deviation, RSD) of around 3.2% and 3.3% respectively at the medium-range level. This instrument offers a new advance in the portability of electrochemiluminescent determinations.
H2S sensing performance of electrospun CuO-loaded SnO2 nanofibers
07 June 2012,
10:40:35
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 169
Sun-Woo Choi, Jin Zhang, Katoch Akash, Sang Sub Kim
We report the synthesis of CuO-loaded SnO2 nanofibers via electrospinning as well as their H2S sensing properties in a comparative manner with unloaded, pure SnO2 nanofibers. Greatly enhanced H2S sensing capability was observed by loading a trace amount of CuO into SnO2 nanofibers. At 10ppm H2S, the CuO-loaded SnO2 nanofibers showed a response of 1.98×104 and response and recovery times of 1 and 10s, respectively. In addition, the CuO-loaded SnO2 nanofibers showed outstanding selectivity to H2S. Along with the unique sensing mechanism based on the creation and disruption of p–n junctions, the high specific surface area provided by the one-dimensional nanofiber shape and the facilitation of p–n junctions due to the presence of nanograins are responsible for the outstanding H2S sensing capability observed in the CuO-loaded SnO2 nanofibers.
Source:Sensors and Actuators B: Chemical, Volume 169
Sun-Woo Choi, Jin Zhang, Katoch Akash, Sang Sub Kim
We report the synthesis of CuO-loaded SnO2 nanofibers via electrospinning as well as their H2S sensing properties in a comparative manner with unloaded, pure SnO2 nanofibers. Greatly enhanced H2S sensing capability was observed by loading a trace amount of CuO into SnO2 nanofibers. At 10ppm H2S, the CuO-loaded SnO2 nanofibers showed a response of 1.98×104 and response and recovery times of 1 and 10s, respectively. In addition, the CuO-loaded SnO2 nanofibers showed outstanding selectivity to H2S. Along with the unique sensing mechanism based on the creation and disruption of p–n junctions, the high specific surface area provided by the one-dimensional nanofiber shape and the facilitation of p–n junctions due to the presence of nanograins are responsible for the outstanding H2S sensing capability observed in the CuO-loaded SnO2 nanofibers.
One-pot synthesis of Au-supported ZnO nanoplates with enhanced gas sensor performance
07 June 2012,
10:40:35
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 169
Jun Zhang, Xianghong Liu, Shihua Wu, Bingqiang Cao, Shaohua Zheng
A novel sensor material of Au nanoparticles-functionalized ZnO nanoplates was fabricated via a facile one-pot hydrothermal method. The obtained Au-functionalized ZnO nanoplates were characterized by means of X-ray diffraction (XRD), transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS). Comparative gas sensing studies were carried out on both pristine ZnO and Au/ZnO nanoplates in order to investigate the effect of Au nanoparticles on the sensor performances. Obtained results demonstrated that the Au/ZnO nanoplate sensor exhibited faster response and recovery as well as higher response compared with the pristine ZnO sensor. At 300°C, the response time of Au/ZnO to 5ppm ethanol is 13s, while that of ZnO is up to 135s. The enhanced sensor performances were attributed to the unique chemical properties of Au nanoparticles and the electronic metal–support interaction. A possible sensing mechanism was proposed for the Au/ZnO nanoplates.
Source:Sensors and Actuators B: Chemical, Volume 169
Jun Zhang, Xianghong Liu, Shihua Wu, Bingqiang Cao, Shaohua Zheng
A novel sensor material of Au nanoparticles-functionalized ZnO nanoplates was fabricated via a facile one-pot hydrothermal method. The obtained Au-functionalized ZnO nanoplates were characterized by means of X-ray diffraction (XRD), transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS). Comparative gas sensing studies were carried out on both pristine ZnO and Au/ZnO nanoplates in order to investigate the effect of Au nanoparticles on the sensor performances. Obtained results demonstrated that the Au/ZnO nanoplate sensor exhibited faster response and recovery as well as higher response compared with the pristine ZnO sensor. At 300°C, the response time of Au/ZnO to 5ppm ethanol is 13s, while that of ZnO is up to 135s. The enhanced sensor performances were attributed to the unique chemical properties of Au nanoparticles and the electronic metal–support interaction. A possible sensing mechanism was proposed for the Au/ZnO nanoplates.
CeO2 doped ZnO flower-like nanostructure sensor selective to ethanol in presence of CO and CH4
07 June 2012,
10:40:35
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 169
Naghmeh Faal Hamedani, Ali Reza Mahjoub, Abbas Ali khodadadi, Yadollah Mortazavi
CeO2-doped ZnO nanostructures, with different Ce/Zn ratios, were synthesized via a very fast microwave-assisted method using zinc acetate dihydrate and cerium nitrate as starting materials and water as solvent. The samples were characterized via SEM, EDX, XRD, and BET analyses. Gas sensitivity of the fabricated sensor was studied for selective detection of ethanol in presence of CO and CH4 and effect of CeO2 with different concentrations as a dopant was investigated. 5wt% CeO2 doped sample was shown to improve the sensor response to 500ppm ethanol with high selectivity in presence of CO and CH4. Furthermore presence of ceria reduced the recovery time of the sensor significantly. The CeO2-doped ZnO may be considered a promising sensing material for selective detection of ethanol.
Source:Sensors and Actuators B: Chemical, Volume 169
Naghmeh Faal Hamedani, Ali Reza Mahjoub, Abbas Ali khodadadi, Yadollah Mortazavi
CeO2-doped ZnO nanostructures, with different Ce/Zn ratios, were synthesized via a very fast microwave-assisted method using zinc acetate dihydrate and cerium nitrate as starting materials and water as solvent. The samples were characterized via SEM, EDX, XRD, and BET analyses. Gas sensitivity of the fabricated sensor was studied for selective detection of ethanol in presence of CO and CH4 and effect of CeO2 with different concentrations as a dopant was investigated. 5wt% CeO2 doped sample was shown to improve the sensor response to 500ppm ethanol with high selectivity in presence of CO and CH4. Furthermore presence of ceria reduced the recovery time of the sensor significantly. The CeO2-doped ZnO may be considered a promising sensing material for selective detection of ethanol.
Highly formaldehyde-sensitive, transition-metal doped ZnO nanorods prepared by plasma-enhanced chemical vapor deposition
07 June 2012,
10:40:35
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 169
Peng Hu, Ning Han, Dangwen Zhang, Johnny C. Ho, Yunfa Chen
One of the challenges in realizing metal oxide semiconductor gas sensors is to enhance the sensitivity of active materials in order to respond to the low concentration of detecting gases effectively and efficiently. In this report, transition metals such as Mn, Ni, Cu, and Co are used as dopants for the synthesis of highly formaldehyde-sensitive ZnO nanorods prepared by plasma enhanced chemical vapor deposition (PECVD) method. All the doped ZnO nanorods show improved formaldehyde-sensitivity as compared to undoped ZnO nanorods, and a gas sensitivity maximum of ∼25/ppm was obtained by using 10mol% CdO activated 1.0mol% Mn doped ZnO nanorods. Moreover, the ZnO nanorods have a higher sensitivity as compared to ZnO nanomaterials prepared by other methods such as precipitation and hydrothermal, which can be attributed to the abundant crystal defects induced by the dopants in a short crystallization process in this PECVD method.
Source:Sensors and Actuators B: Chemical, Volume 169
Peng Hu, Ning Han, Dangwen Zhang, Johnny C. Ho, Yunfa Chen
One of the challenges in realizing metal oxide semiconductor gas sensors is to enhance the sensitivity of active materials in order to respond to the low concentration of detecting gases effectively and efficiently. In this report, transition metals such as Mn, Ni, Cu, and Co are used as dopants for the synthesis of highly formaldehyde-sensitive ZnO nanorods prepared by plasma enhanced chemical vapor deposition (PECVD) method. All the doped ZnO nanorods show improved formaldehyde-sensitivity as compared to undoped ZnO nanorods, and a gas sensitivity maximum of ∼25/ppm was obtained by using 10mol% CdO activated 1.0mol% Mn doped ZnO nanorods. Moreover, the ZnO nanorods have a higher sensitivity as compared to ZnO nanomaterials prepared by other methods such as precipitation and hydrothermal, which can be attributed to the abundant crystal defects induced by the dopants in a short crystallization process in this PECVD method.
Determination of metronidazole in pharmaceutical dosage forms based on reduction at graphene and ionic liquid composite film modified electrode
07 June 2012,
10:40:35
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 169
Jinyun Peng, Chuantao Hou, Xiaoya Hu
An electrochemical method has been successfully demonstrated for sensitive determination of Metronidazole (MTZ) with graphene (Gr)-room temperature ionic liquid (IL) of 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6) composite modified glassy carbon electrode (GCE). The cyclic voltammetric results indicate that Gr-IL/GCE can remarkably enhance electrocatalytic activity towards the reduction of MTZ in neutral solutions. MTZ produce a cathodic peak at about −0.69V at this electrode. The electrochemical parameters of MTZ in the composite film were carefully calculated with the results of the charge transfer coefficient (α) as 0.625 and the number of electron transferred (n) as 4. The electrocatalytic behavior was further exploited as a sensitive detection scheme for the MTZ determination by differential-pulse voltammetry (DPV). Under optimized conditions, the concentration range and detection limit were 1.0×10−7–2.5×10−5 molL−1 and 4.7×10−8 molL−1 (S/N =3), respectively for MTZ. The method was successfully applied assay of the drug in the pharmaceutical dosage forms.
Source:Sensors and Actuators B: Chemical, Volume 169
Jinyun Peng, Chuantao Hou, Xiaoya Hu
An electrochemical method has been successfully demonstrated for sensitive determination of Metronidazole (MTZ) with graphene (Gr)-room temperature ionic liquid (IL) of 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6) composite modified glassy carbon electrode (GCE). The cyclic voltammetric results indicate that Gr-IL/GCE can remarkably enhance electrocatalytic activity towards the reduction of MTZ in neutral solutions. MTZ produce a cathodic peak at about −0.69V at this electrode. The electrochemical parameters of MTZ in the composite film were carefully calculated with the results of the charge transfer coefficient (α) as 0.625 and the number of electron transferred (n) as 4. The electrocatalytic behavior was further exploited as a sensitive detection scheme for the MTZ determination by differential-pulse voltammetry (DPV). Under optimized conditions, the concentration range and detection limit were 1.0×10−7–2.5×10−5 molL−1 and 4.7×10−8 molL−1 (S/N =3), respectively for MTZ. The method was successfully applied assay of the drug in the pharmaceutical dosage forms.
Ultrasensitive aptasensor based on graphene-3,4,9,10-perylenetetracarboxylic dianhydride as platform and functionalized hollow PtCo nanochains as enhancers
07 June 2012,
10:40:35
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 169
Kanfu Peng, Hongwen Zhao, Xiongfei Wu, Yali Yuan, Ruo Yuan
A novel electrochemical aptasensor for ultrasensitive detection of thrombin is described that uses the conductive graphene-3,4,9,10-perylenetetracarboxylic dianhydride nanocomposites (GPA) as desirable sensor platform and hollow PtCo nanochains–thionine–Pt–HRP labeled secondary thrombin aptamer (HPtCoNCs–Thi–Pt–HRP–TBA, aptamer II) for signal amplification. With the surface area enhanced by GPA nanocomposites, the amount of immobilized primary thrombin aptamer can be improved. More importantly, the synthesized HPtCoNCs also yielded large surface area, which provide substantial binding sites for thionine–Pt–HRP–TBA. The thionine acts as a mediator of electron transfer between HRP and electrode surface. Enhanced sensitivity was achieved by introducing the multibioconjugates of aptamer II onto the electrode surface through “sandwich” reactions. With amplifying factors mentioned above, a wider linear range from 10−15 to 10−9 M was acquired with an ultralow detection limit of 6.5×10−16 M for thrombin. This amplification strategy showed acceptable stability and reproducibility, high sensitivity, and good precision, which could provide a promising potential for clinical screening and point-of-care diagnostics.
Source:Sensors and Actuators B: Chemical, Volume 169
Kanfu Peng, Hongwen Zhao, Xiongfei Wu, Yali Yuan, Ruo Yuan
A novel electrochemical aptasensor for ultrasensitive detection of thrombin is described that uses the conductive graphene-3,4,9,10-perylenetetracarboxylic dianhydride nanocomposites (GPA) as desirable sensor platform and hollow PtCo nanochains–thionine–Pt–HRP labeled secondary thrombin aptamer (HPtCoNCs–Thi–Pt–HRP–TBA, aptamer II) for signal amplification. With the surface area enhanced by GPA nanocomposites, the amount of immobilized primary thrombin aptamer can be improved. More importantly, the synthesized HPtCoNCs also yielded large surface area, which provide substantial binding sites for thionine–Pt–HRP–TBA. The thionine acts as a mediator of electron transfer between HRP and electrode surface. Enhanced sensitivity was achieved by introducing the multibioconjugates of aptamer II onto the electrode surface through “sandwich” reactions. With amplifying factors mentioned above, a wider linear range from 10−15 to 10−9 M was acquired with an ultralow detection limit of 6.5×10−16 M for thrombin. This amplification strategy showed acceptable stability and reproducibility, high sensitivity, and good precision, which could provide a promising potential for clinical screening and point-of-care diagnostics.
Application of modified multiwall carbon nanotubes paste electrode for simultaneous voltammetric determination of morphine and diclofenac in biological and pharmaceutical samples
07 June 2012,
10:40:35
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 169
Ali Mokhtari, Hassan Karimi-Maleh, Ali A. Ensafi, Hadi Beitollahi
A novel modified carbon paste electrode with vinylferrocene/multiwall carbon nanotubes was fabricated. The electrochemical response of the modified electrode toward morphine was studied by means of cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS). The structural morphology of the modified electrode was characterized by SEM technique. The prepared electrode showed an excellent electrocatalytic activity in the oxidation of morphine, leading to remarkable enhancements in the corresponding peak currents and lowering the peak potential. Using square wave voltammetry (SWV), we could measure morphine and diclofenac in one mixture independently from each other by a potential difference of about 300mV for the first time. Square wave voltammetric peaks current of morphine and diclofenac increased linearly with their concentrations in the ranges of 0.2–250.0μmolL−1, and 5.0–600.0μmolL−1, respectively. The detection limits of 0.09 and 2.0μmolL−1 were achieved for morphine and diclofenac, respectively. The proposed voltammetric sensor was successfully applied to the determination of morphine and diclofenac in real samples.
Source:Sensors and Actuators B: Chemical, Volume 169
Ali Mokhtari, Hassan Karimi-Maleh, Ali A. Ensafi, Hadi Beitollahi
A novel modified carbon paste electrode with vinylferrocene/multiwall carbon nanotubes was fabricated. The electrochemical response of the modified electrode toward morphine was studied by means of cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS). The structural morphology of the modified electrode was characterized by SEM technique. The prepared electrode showed an excellent electrocatalytic activity in the oxidation of morphine, leading to remarkable enhancements in the corresponding peak currents and lowering the peak potential. Using square wave voltammetry (SWV), we could measure morphine and diclofenac in one mixture independently from each other by a potential difference of about 300mV for the first time. Square wave voltammetric peaks current of morphine and diclofenac increased linearly with their concentrations in the ranges of 0.2–250.0μmolL−1, and 5.0–600.0μmolL−1, respectively. The detection limits of 0.09 and 2.0μmolL−1 were achieved for morphine and diclofenac, respectively. The proposed voltammetric sensor was successfully applied to the determination of morphine and diclofenac in real samples.
Lawsone (2-hydroxy-1,4-naphthoquinone) as a sensitive cyanide and acetate sensor
07 June 2012,
10:40:35
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 169
Yousef M. Hijji, Belygona Barare, Yongchao Zhang
Lawsone (2-hydroxy-1,4-naphthoquinone), the essential component of henna, is used as a sensitive colorimetric and electrochemical sensor for anions such as cyanide, acetate, fluoride and dihydrogen phosphate (DHP) in acetonitrile. These anions cause a color change in Lawsone's solution from yellow to orange-red. Other anions, such as chloride, bromide, iodide, perchlorate, do not show a significant change. Cyanide changes the color of Lawsone in water:acetonitrile (95:5) solution significantly while acetate causes a slight color change. On the other hand, hydrogen sulfate anion fades the yellow color of the solution. Job's plots show a 1:1 host:guest complex in acetonitrile for cyanide, acetate and fluorides and 1:2 for DHP. In water/acetonitrile the stoichiometry is 1:1 for host:anion. The binding constants show strong binding with cyanide and acetate in both solvent systems.
Source:Sensors and Actuators B: Chemical, Volume 169
Yousef M. Hijji, Belygona Barare, Yongchao Zhang
Lawsone (2-hydroxy-1,4-naphthoquinone), the essential component of henna, is used as a sensitive colorimetric and electrochemical sensor for anions such as cyanide, acetate, fluoride and dihydrogen phosphate (DHP) in acetonitrile. These anions cause a color change in Lawsone's solution from yellow to orange-red. Other anions, such as chloride, bromide, iodide, perchlorate, do not show a significant change. Cyanide changes the color of Lawsone in water:acetonitrile (95:5) solution significantly while acetate causes a slight color change. On the other hand, hydrogen sulfate anion fades the yellow color of the solution. Job's plots show a 1:1 host:guest complex in acetonitrile for cyanide, acetate and fluorides and 1:2 for DHP. In water/acetonitrile the stoichiometry is 1:1 for host:anion. The binding constants show strong binding with cyanide and acetate in both solvent systems.
Graphical abstract
Preparation of tungsten oxide nanowires and their application to NO2 sensing
07 June 2012,
10:40:35
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 169
Dan Meng, N.M. Shaalan, T. Yamazaki, T. Kikuta
Tungsten oxide nanowires were prepared by a vapor transport method using WO3 powder as a raw material. The crystal structure and morphology of WO3 nanowires were investigated by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The obtained nanowires were hexagonal WO3. The major factors that influenced the morphology were the furnace temperature and the substrate position. The diameter of the nanowires decreased as the distance of the substrate from the raw material increased. Sensors were fabricated by pouring a few drops of nanowire-suspended ethanol onto oxidized Silicon substrates equipped with a pair of interdigitated Pt electrodes. The sensor made of the nanowires as thin as 50nm showed the highest response to NO2 at a low operating temperature of 100°C. The temperature dependence of the response was discussed in relation to the formation of NO2 − and NO3 − ions on the surface of WO3. The response slightly increased with decreasing diameter if the nanowires are regional depleted in NO2, while it largely increased if the nanowires are in volume depletion. A theoretical calculations based on assumptions were proposed in order to clarify the correlation between the nanowire response and their diameter.
Source:Sensors and Actuators B: Chemical, Volume 169
Dan Meng, N.M. Shaalan, T. Yamazaki, T. Kikuta
Tungsten oxide nanowires were prepared by a vapor transport method using WO3 powder as a raw material. The crystal structure and morphology of WO3 nanowires were investigated by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The obtained nanowires were hexagonal WO3. The major factors that influenced the morphology were the furnace temperature and the substrate position. The diameter of the nanowires decreased as the distance of the substrate from the raw material increased. Sensors were fabricated by pouring a few drops of nanowire-suspended ethanol onto oxidized Silicon substrates equipped with a pair of interdigitated Pt electrodes. The sensor made of the nanowires as thin as 50nm showed the highest response to NO2 at a low operating temperature of 100°C. The temperature dependence of the response was discussed in relation to the formation of NO2 − and NO3 − ions on the surface of WO3. The response slightly increased with decreasing diameter if the nanowires are regional depleted in NO2, while it largely increased if the nanowires are in volume depletion. A theoretical calculations based on assumptions were proposed in order to clarify the correlation between the nanowire response and their diameter.
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