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A fluorescent colorimetric pH sensor and the influences of matrices on sensing performances
06 August 2013,
10:08:24
Publication date: November
2013
Source:Sensors and Actuators B: Chemical, Volume 188
Author(s): Yanqing Tian , Emily Fuller , Summer Klug , Fred Lee , Fengyu Su , Liqiang Zhang , Shih-hui Chao , Deirdre R. Meldrum
A fluorescent colorimetric pH sensor was developed by a polymerization of a monomeric fluorescein based green emitter (SM1) with a monomeric 2-dicyanomethylene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran derived red emitter (SM2) in poly(2-hydroxyethyl methacrylate)-co-polyacrylamide (PHEMA-co-PAM) matrices. Polymerized SM1 (PSM1) in the polymer matrices showed bright emissions at basic conditions and weak emissions at acidic conditions. Polymerized SM2 (PSM2) in the polymer matrices exhibited a vastly different response when compared to PSM1. The emissions of PSM2 are stronger under acidic conditions than those under basic conditions. When SM1 and SM2 were polymerized in the same polymer matrix, a dual emission sensor acting as a ratiometric pH sensor (PSM1,2) was successfully developed. Because the PSM1 and PSM2 exhibited different pH responses and separated emission windows, the changes in the emission colors were clearly observed in their dual color sensor of PSM1,2, which changed emission colors dramatically from green at pH 7 to red at pH 4, which was detected visually and/or by using a color camera under an excitation of 488nm. In addition to the development of the dual color ratiometric pH sensor, we also studied the effects of different matrix compositions, crosslinkers, and charges on the reporting capabilities of the sensors (sensitivity and pK a).
Source:Sensors and Actuators B: Chemical, Volume 188
Author(s): Yanqing Tian , Emily Fuller , Summer Klug , Fred Lee , Fengyu Su , Liqiang Zhang , Shih-hui Chao , Deirdre R. Meldrum
A fluorescent colorimetric pH sensor was developed by a polymerization of a monomeric fluorescein based green emitter (SM1) with a monomeric 2-dicyanomethylene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran derived red emitter (SM2) in poly(2-hydroxyethyl methacrylate)-co-polyacrylamide (PHEMA-co-PAM) matrices. Polymerized SM1 (PSM1) in the polymer matrices showed bright emissions at basic conditions and weak emissions at acidic conditions. Polymerized SM2 (PSM2) in the polymer matrices exhibited a vastly different response when compared to PSM1. The emissions of PSM2 are stronger under acidic conditions than those under basic conditions. When SM1 and SM2 were polymerized in the same polymer matrix, a dual emission sensor acting as a ratiometric pH sensor (PSM1,2) was successfully developed. Because the PSM1 and PSM2 exhibited different pH responses and separated emission windows, the changes in the emission colors were clearly observed in their dual color sensor of PSM1,2, which changed emission colors dramatically from green at pH 7 to red at pH 4, which was detected visually and/or by using a color camera under an excitation of 488nm. In addition to the development of the dual color ratiometric pH sensor, we also studied the effects of different matrix compositions, crosslinkers, and charges on the reporting capabilities of the sensors (sensitivity and pK a).
AC electro-osmotic micromixer using a face-to-face, asymmetric pair of planar electrodes
06 August 2013,
10:08:24
Publication date: November
2013
Source:Sensors and Actuators B: Chemical, Volume 188
Author(s): Jhih-Lin Chen , Wei-Hung Shih , Wen-Hsin Hsieh
This paper is the first to report the mixing performance of an AC electro-osmotic (AC-EO) micromixer based on the two sets of vortices generated by a face-to-face, asymmetric pair of planar electrodes. The larger top electrode of the asymmetric electrode pair was rectangular (30×60mm2) and the much smaller bottom electrode was also rectangular (500×700μm2) and featured two protrusions. Due to the highly three-dimensional flow pattern generated by the unique shape of the face-to-face electrode pair, the mixing enhancement factor (mixing time by diffusion/mixing time by the micromixer) exhibited by the reported micromixer ranged from 290 to 360 and the mixing performance values were uniform across the entire height of the fluid cavity. The usefulness of the mixer in hybridizing single-stranded deoxyribonucleic acids and mixing Escherichia coli with RNA stains was also demonstrated experimentally. A numerical investigation was conducted to study the three-dimensional AC-EO flow patterns induced by the face-to-face, asymmetric electrode pair. This analysis made it possible to identify a detailed flow pattern and the formation mechanism of the vortices. The confluence of inward AC-EO flows from the edges of the bottom-electrode protrusion locally induced a large inward-pumping force and was responsible for the formation of the four vortices at the four corners of the bottom electrode. The numerical and experimental results of this research provide information that will be useful in future applications and research in the area of microfluidic manipulation.
Source:Sensors and Actuators B: Chemical, Volume 188
Author(s): Jhih-Lin Chen , Wei-Hung Shih , Wen-Hsin Hsieh
This paper is the first to report the mixing performance of an AC electro-osmotic (AC-EO) micromixer based on the two sets of vortices generated by a face-to-face, asymmetric pair of planar electrodes. The larger top electrode of the asymmetric electrode pair was rectangular (30×60mm2) and the much smaller bottom electrode was also rectangular (500×700μm2) and featured two protrusions. Due to the highly three-dimensional flow pattern generated by the unique shape of the face-to-face electrode pair, the mixing enhancement factor (mixing time by diffusion/mixing time by the micromixer) exhibited by the reported micromixer ranged from 290 to 360 and the mixing performance values were uniform across the entire height of the fluid cavity. The usefulness of the mixer in hybridizing single-stranded deoxyribonucleic acids and mixing Escherichia coli with RNA stains was also demonstrated experimentally. A numerical investigation was conducted to study the three-dimensional AC-EO flow patterns induced by the face-to-face, asymmetric electrode pair. This analysis made it possible to identify a detailed flow pattern and the formation mechanism of the vortices. The confluence of inward AC-EO flows from the edges of the bottom-electrode protrusion locally induced a large inward-pumping force and was responsible for the formation of the four vortices at the four corners of the bottom electrode. The numerical and experimental results of this research provide information that will be useful in future applications and research in the area of microfluidic manipulation.
Modification of a QCN sensor by SiO2 nanoparticles and MIP for telone determination: Improving its selectivity and sensitivity
06 August 2013,
10:08:24
Publication date: November
2013
Source:Sensors and Actuators B: Chemical, Volume 188
Author(s): A. Mirmohseni , M. Rastgouy-Houjaghan
A quartz crystal nanobalance (QCN) sensor was developed for the selective determination of telone in aqueous solutions. Telone imprinted nanocomposite was synthesized using SiO2 nanopowders and acrylic acid. FTIR spectroscopy, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA) were employed to characterize the morphology and microstructure of the SiO2-MIP nanocomposite. The prepared SiO2-MIP nanocomposite particles were coated on quartz crystal electrode to form complementary structures for the template recognition of telone. The SiO2-MIP coated electrode was used to determine telone levels in solution. The developed sensor demonstrated a high selectivity and sensitivity (4.96Hz per mgL−1) for telone. It can also be used for telone determination in the concentration range between 1 to 40mgL−1. Furthermore, a good reproducibility, R.S.D.=1.66% (n =5) was observed. During its photocatalytic degradation by UV/ZnO, telone residue process was measured by the developed sensor and GC to validate the accuracy of the developed sensor in real world situation. According to the results of the t-test, QCN sensor and GC spectroscopy measurement results enjoy good agreement. Therefore, a fabricated sensing system has the potential for real sample application.
Source:Sensors and Actuators B: Chemical, Volume 188
Author(s): A. Mirmohseni , M. Rastgouy-Houjaghan
A quartz crystal nanobalance (QCN) sensor was developed for the selective determination of telone in aqueous solutions. Telone imprinted nanocomposite was synthesized using SiO2 nanopowders and acrylic acid. FTIR spectroscopy, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA) were employed to characterize the morphology and microstructure of the SiO2-MIP nanocomposite. The prepared SiO2-MIP nanocomposite particles were coated on quartz crystal electrode to form complementary structures for the template recognition of telone. The SiO2-MIP coated electrode was used to determine telone levels in solution. The developed sensor demonstrated a high selectivity and sensitivity (4.96Hz per mgL−1) for telone. It can also be used for telone determination in the concentration range between 1 to 40mgL−1. Furthermore, a good reproducibility, R.S.D.=1.66% (n =5) was observed. During its photocatalytic degradation by UV/ZnO, telone residue process was measured by the developed sensor and GC to validate the accuracy of the developed sensor in real world situation. According to the results of the t-test, QCN sensor and GC spectroscopy measurement results enjoy good agreement. Therefore, a fabricated sensing system has the potential for real sample application.
Slime mould tactile sensor
06 August 2013,
10:08:24
Publication date: November
2013
Source:Sensors and Actuators B: Chemical, Volume 188
Author(s): Andrew Adamatzky
Slime mould Physarum polycephalum is a single cells visible by unaided eye. The cells shows a wide spectrum of intelligent behaviour. By interpreting the behaviour in terms of computation one can make a slime mould based computing device. The Physarum computers are capable to solve a range of tasks of computational geometry, optimisation and logic. Physarum computers designed so far lack of localised inputs. Commonly used inputs — illumination and chemo-attractants and -repellents — usually act on extended domains of the slime mould's body. Aiming to design massive-parallel tactile inputs for slime mould computers we analyse a temporal dynamic of P. polycephalum's electrical response to tactile stimulation. In experimental laboratory studies we discover how the Physarum responds to application and removal of a local mechanical pressure with electrical potential impulses and changes in its electrical potential oscillation patterns.
Source:Sensors and Actuators B: Chemical, Volume 188
Author(s): Andrew Adamatzky
Slime mould Physarum polycephalum is a single cells visible by unaided eye. The cells shows a wide spectrum of intelligent behaviour. By interpreting the behaviour in terms of computation one can make a slime mould based computing device. The Physarum computers are capable to solve a range of tasks of computational geometry, optimisation and logic. Physarum computers designed so far lack of localised inputs. Commonly used inputs — illumination and chemo-attractants and -repellents — usually act on extended domains of the slime mould's body. Aiming to design massive-parallel tactile inputs for slime mould computers we analyse a temporal dynamic of P. polycephalum's electrical response to tactile stimulation. In experimental laboratory studies we discover how the Physarum responds to application and removal of a local mechanical pressure with electrical potential impulses and changes in its electrical potential oscillation patterns.
Highly sensitive gallia-SnO2 nanocomposite sensors to CO and ethanol in presence of methane
06 August 2013,
10:08:24
Publication date: November
2013
Source:Sensors and Actuators B: Chemical, Volume 188
Author(s): Minoo Bagheri , Abbas Ali Khodadadi , Ali Reza Mahjoub , Yadollah Mortazavi
Responses of gallia-SnO2 nanocomposite sensors, containing 0–50wt% Ga2O3 calcined at 500–850°C, to CO, methane and ethanol are investigated. The gallia-SnO2 samples were prepared via a facile co-precipitation method using stannic chloride and gallium nitrate aqueous solutions without any template and characterized by XRD, EDX, TEM, PL and BET surface area techniques. The samples containing up to 25wt% gallia and calcined at 500°C indicate that only tetragonal rutile structure of SnO2 is formed. The Ga4SnO8 and β-Ga2O3 phases are observed for the samples containing 50wt% Ga2O3 and calcined at 850 and 1050°C, respectively. The average particle sizes of the nanocomposites gradually decrease from 21.6 to 6.7nm, as their gallia contents increase from 0 to 25wt%. The highest responses of 315 and 119 are observed for 300ppm CO and ethanol by the sensors containing 5 and 1wt% Ga2O3, respectively. The sensors containing 25wt% Ga2O3 calcined at 850°C and 50wt% gallia calcined at 500 and 850°C are selective to CO and show negligible responses to ethanol and methane.
Source:Sensors and Actuators B: Chemical, Volume 188
Author(s): Minoo Bagheri , Abbas Ali Khodadadi , Ali Reza Mahjoub , Yadollah Mortazavi
Responses of gallia-SnO2 nanocomposite sensors, containing 0–50wt% Ga2O3 calcined at 500–850°C, to CO, methane and ethanol are investigated. The gallia-SnO2 samples were prepared via a facile co-precipitation method using stannic chloride and gallium nitrate aqueous solutions without any template and characterized by XRD, EDX, TEM, PL and BET surface area techniques. The samples containing up to 25wt% gallia and calcined at 500°C indicate that only tetragonal rutile structure of SnO2 is formed. The Ga4SnO8 and β-Ga2O3 phases are observed for the samples containing 50wt% Ga2O3 and calcined at 850 and 1050°C, respectively. The average particle sizes of the nanocomposites gradually decrease from 21.6 to 6.7nm, as their gallia contents increase from 0 to 25wt%. The highest responses of 315 and 119 are observed for 300ppm CO and ethanol by the sensors containing 5 and 1wt% Ga2O3, respectively. The sensors containing 25wt% Ga2O3 calcined at 850°C and 50wt% gallia calcined at 500 and 850°C are selective to CO and show negligible responses to ethanol and methane.
A promising gold nanocluster fluorescent sensor for the highly sensitive and selective detection of S2−
06 August 2013,
10:08:24
Publication date: November
2013
Source:Sensors and Actuators B: Chemical, Volume 188
Author(s): Ma-Lin Cui , Jia-Ming Liu , Xin-Xing Wang , Li-Ping Lin , Li Jiao , Zhi-Yong Zheng , Li-Hong Zhang , Shu-Lian Jiang
Bright red-emissive gold nanoclusters (AuNCs) were synthesized by a facile one-pot approach in aqueous solution using bovine serum albumin (BSA) as a protecting agent. A new BSA-AuNC fluorescent sensor for the detection of S2− has been designed based on the sharp fluorescence quenching of BSA-AuNCs, which results from the degradation of its structure due to the formation of Au2S by the reaction between Au and S2−. The proposed highly sensitive (the detection limit [LD] was 0.029μM) and selective sensor was applied to the detection of S2− in the presence of high concentrations of different anions in aqueous solution, and the results were in good agreement with those determined by electrochemical methods. The sensor is shown to be environmentally friendly, simple, responsive and practical. Meanwhile, the morphological changes of BSA-AuNCs and BSA-AuNCs-S2− were characterized by high-resolution transmission electron microscopy (HRTEM). Furthermore, the sensing mechanism for the detection of S2− is discussed.
Source:Sensors and Actuators B: Chemical, Volume 188
Author(s): Ma-Lin Cui , Jia-Ming Liu , Xin-Xing Wang , Li-Ping Lin , Li Jiao , Zhi-Yong Zheng , Li-Hong Zhang , Shu-Lian Jiang
Bright red-emissive gold nanoclusters (AuNCs) were synthesized by a facile one-pot approach in aqueous solution using bovine serum albumin (BSA) as a protecting agent. A new BSA-AuNC fluorescent sensor for the detection of S2− has been designed based on the sharp fluorescence quenching of BSA-AuNCs, which results from the degradation of its structure due to the formation of Au2S by the reaction between Au and S2−. The proposed highly sensitive (the detection limit [LD] was 0.029μM) and selective sensor was applied to the detection of S2− in the presence of high concentrations of different anions in aqueous solution, and the results were in good agreement with those determined by electrochemical methods. The sensor is shown to be environmentally friendly, simple, responsive and practical. Meanwhile, the morphological changes of BSA-AuNCs and BSA-AuNCs-S2− were characterized by high-resolution transmission electron microscopy (HRTEM). Furthermore, the sensing mechanism for the detection of S2− is discussed.
Flavone modified-β-cyclodextrin as a highly selective and efficient fluorescent chemosensor for Cu2+ ions and l-histidine
06 August 2013,
10:08:24
Publication date: November
2013
Source:Sensors and Actuators B: Chemical, Volume 188
Author(s): Ismail Abulkalam Azath , Kasi Pitchumani
7-Aminoflavone modified β-cyclodextrin with a hydrazinecarbothioamide linker is synthesised for the first time and characterised by NMR, ESI-MS and elemental analysis. NOESY as well as emission spectra indicate the inclusion of phenyl ring inside the cyclodextrin cavity. The hydrazinecarbothioamide linker acts as the metal binding unit. This flavone modified CD selectively binds with Cu(II) over other metal ions. Binding with Cu(II) makes the complex non-fluorescent. Addition of histidine, among other amino acids, results in regeneration of the fluorescence enhancement. This is due to the fact that l-histidine displaces Cu2+ from Flav-CD-Cu2+ complex to release the free flavone resulting in regeneration of its fluorescence. This turn-on sensor can be utilised effectively to sense both Cu(II) among various metal ions and l-histidine (as well as histamine) among various amino acids.
Source:Sensors and Actuators B: Chemical, Volume 188
Author(s): Ismail Abulkalam Azath , Kasi Pitchumani
7-Aminoflavone modified β-cyclodextrin with a hydrazinecarbothioamide linker is synthesised for the first time and characterised by NMR, ESI-MS and elemental analysis. NOESY as well as emission spectra indicate the inclusion of phenyl ring inside the cyclodextrin cavity. The hydrazinecarbothioamide linker acts as the metal binding unit. This flavone modified CD selectively binds with Cu(II) over other metal ions. Binding with Cu(II) makes the complex non-fluorescent. Addition of histidine, among other amino acids, results in regeneration of the fluorescence enhancement. This is due to the fact that l-histidine displaces Cu2+ from Flav-CD-Cu2+ complex to release the free flavone resulting in regeneration of its fluorescence. This turn-on sensor can be utilised effectively to sense both Cu(II) among various metal ions and l-histidine (as well as histamine) among various amino acids.
Sensitive and selective determination of uric acid in real samples by modified glassy carbon electrode with holmium fluoride nanoparticles/multi-walled carbon nanotube as a new biosensor
06 August 2013,
10:08:24
Publication date: November
2013
Source:Sensors and Actuators B: Chemical, Volume 188
Author(s): M. Noroozifar , M. Khorasani-Motlagh , F. Zareian Jahromi , S. Rostami
A novel modified glassy carbon electrode with holmium fluoride (HoF3) nanoparticles (HoFNPs)-multiwalled carbon nanotubes (MWCNTs) is fabricated and then successfully used for the sensitive and selective determination of uric acid (UA) in the presence of ascorbic acid (AA) and dopamine (DA). HoFNPs are successfully attached on the multi-walled carbon nanotubes (MWCNTs) via the intermediate of noncovalent hydrophobic interactions of the MWCNTs surface with sodium dodecyl sulfate (SDS). A detailed investigation by transmission electron microscopy (TEM) and electrochemistry is performed in order to elucidate the preparation process and properties of the nanocomposites. TEM image shows that the particle size of HoFNPs is about 56nm. Linear calibration plot is obtained over the range 2.0×10−7–5.0×10 −4 M (0.2–500.0μM) with a detection limit 1.6×10−7 M (0.16μM) for UA. The modified carbon electrode proves to have good sensitivity, stability and performance for determination UA in the presence of AA, DA in human blood serum and urine samples.
Source:Sensors and Actuators B: Chemical, Volume 188
Author(s): M. Noroozifar , M. Khorasani-Motlagh , F. Zareian Jahromi , S. Rostami
A novel modified glassy carbon electrode with holmium fluoride (HoF3) nanoparticles (HoFNPs)-multiwalled carbon nanotubes (MWCNTs) is fabricated and then successfully used for the sensitive and selective determination of uric acid (UA) in the presence of ascorbic acid (AA) and dopamine (DA). HoFNPs are successfully attached on the multi-walled carbon nanotubes (MWCNTs) via the intermediate of noncovalent hydrophobic interactions of the MWCNTs surface with sodium dodecyl sulfate (SDS). A detailed investigation by transmission electron microscopy (TEM) and electrochemistry is performed in order to elucidate the preparation process and properties of the nanocomposites. TEM image shows that the particle size of HoFNPs is about 56nm. Linear calibration plot is obtained over the range 2.0×10−7–5.0×10 −4 M (0.2–500.0μM) with a detection limit 1.6×10−7 M (0.16μM) for UA. The modified carbon electrode proves to have good sensitivity, stability and performance for determination UA in the presence of AA, DA in human blood serum and urine samples.
A simple homemade light emitting diode based photometer for chromium speciation
06 August 2013,
10:08:24
Publication date: November
2013
Source:Sensors and Actuators B: Chemical, Volume 188
Author(s): Mohammad-Hossein Sorouraddin , Masoud Saadati , Hasan Karimi baneshat
A simple spectrophotometric method utilizing a homemade light emitting diode (LED) based photometer is developed for chromium (VI) and total chromium determination in water samples. The photometer is composed of an LED (white color) as light source and a programmable light-to-frequency converter (three arrays of photodiodes each with a red, green or blue filter) as a detector. The chromium speciation is based on the complex formation reaction of Cr(VI) with 1,5-diphenylcarbazide. Considering the maximum absorption wavelength of the complex, the determination was performed using green filter detector. Prior to the total chromium determination, Cr(III) was oxidized to Cr(VI) with Ce(IV). Cr(III) concentration was calculated from the difference between total Cr and Cr(VI) concentrations. Under the optimum conditions, the calibration graph was linear in 10–200μgL−1 chromium concentration range. The relative standard deviation (n =5) and the limit of detection was calculated to be 2.45 and 2.99μgL−1 respectively. The proposed method was successfully applied to chromium speciation in spiked water samples.
Source:Sensors and Actuators B: Chemical, Volume 188
Author(s): Mohammad-Hossein Sorouraddin , Masoud Saadati , Hasan Karimi baneshat
A simple spectrophotometric method utilizing a homemade light emitting diode (LED) based photometer is developed for chromium (VI) and total chromium determination in water samples. The photometer is composed of an LED (white color) as light source and a programmable light-to-frequency converter (three arrays of photodiodes each with a red, green or blue filter) as a detector. The chromium speciation is based on the complex formation reaction of Cr(VI) with 1,5-diphenylcarbazide. Considering the maximum absorption wavelength of the complex, the determination was performed using green filter detector. Prior to the total chromium determination, Cr(III) was oxidized to Cr(VI) with Ce(IV). Cr(III) concentration was calculated from the difference between total Cr and Cr(VI) concentrations. Under the optimum conditions, the calibration graph was linear in 10–200μgL−1 chromium concentration range. The relative standard deviation (n =5) and the limit of detection was calculated to be 2.45 and 2.99μgL−1 respectively. The proposed method was successfully applied to chromium speciation in spiked water samples.
Synthesis of hierarchical SnO2 nanostructures assembled with nanosheets and their improved gas sensing properties
06 August 2013,
10:08:24
Publication date: November
2013
Source:Sensors and Actuators B: Chemical, Volume 188
Author(s): Liwei Wang , Shurong Wang , Yanshuang Wang , Hongxin Zhang , Yanfei Kang , Weiping Huang
Well-defined three-dimensional (3D) hierarchical tin dioxide (SnO2) nanoflowers (NFs) constructed by two-dimensional (2D) nanosheets (NSs) are successfully fabricated by a simple one-pot low-temperature (90°C) hydrothermal strategy. The influence of the experiment parameters on the morphology of the products is investigated in detail. Field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) demonstrate that the size and shape of the 3D hierarchical SnO2 NFs can be tailored by modulating the molar ratio of OH− to Sn2+, reaction time and reaction temperature in the process of hydrothermal synthesis. A possible formation process and growth mechanism for such fabricated 3D hierarchical SnO2 nanostructures has been proposed based on the experimental results. The gas sensing tests of the SnO2 NF sensor for several reducing volatile organic compounds (VOCs) including ethanol, n-butanol, acetone, methanol, chloroform and benzene have been performed at the relatively low operating temperature of 240°C. The excellent gas sensing performances of the unique 3D hierarchical SnO2 NFs at low operating temperature of 240°C indicate their potential application as gas sensors. The unique 3D hierarchical SnO2 NFs with high accessible surface area and commodious inter space can also be expected to use as catalyst, dye-sensitive solar cell and Li ion battery materials.
Source:Sensors and Actuators B: Chemical, Volume 188
Author(s): Liwei Wang , Shurong Wang , Yanshuang Wang , Hongxin Zhang , Yanfei Kang , Weiping Huang
Well-defined three-dimensional (3D) hierarchical tin dioxide (SnO2) nanoflowers (NFs) constructed by two-dimensional (2D) nanosheets (NSs) are successfully fabricated by a simple one-pot low-temperature (90°C) hydrothermal strategy. The influence of the experiment parameters on the morphology of the products is investigated in detail. Field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) demonstrate that the size and shape of the 3D hierarchical SnO2 NFs can be tailored by modulating the molar ratio of OH− to Sn2+, reaction time and reaction temperature in the process of hydrothermal synthesis. A possible formation process and growth mechanism for such fabricated 3D hierarchical SnO2 nanostructures has been proposed based on the experimental results. The gas sensing tests of the SnO2 NF sensor for several reducing volatile organic compounds (VOCs) including ethanol, n-butanol, acetone, methanol, chloroform and benzene have been performed at the relatively low operating temperature of 240°C. The excellent gas sensing performances of the unique 3D hierarchical SnO2 NFs at low operating temperature of 240°C indicate their potential application as gas sensors. The unique 3D hierarchical SnO2 NFs with high accessible surface area and commodious inter space can also be expected to use as catalyst, dye-sensitive solar cell and Li ion battery materials.
Direct nitrate sensing in water using an array of copper-microelectrodes from flat flexible cables
06 August 2013,
10:08:24
Publication date: November
2013
Source:Sensors and Actuators B: Chemical, Volume 188
Author(s): Iranaldo S. da Silva , William R. de Araujo , Thiago R.L.C. Paixão , Lúcio Angnes
Nitrate determination plays a very important role in the analysis of environmental samples. In this paper, an activation procedure for nitrate sensing using a modified copper electrode made from flat flexible cables in presence of a low amount of chloride is reported. The proposed method exhibits enhanced electrocatalytic behaviour in the reduction of nitrate compared to a bare copper electrode. The proposed method showed linear response for nitrate in the concentration range 10–1070μmolL−1, with a regression coefficient R 2 =0.999 (n =12) and a limit of detection of 1.8μmolL−1. According to the procedure based on the standard addition technique, the recovery values obtained were 93–103%, showing the accuracy of the proposed method. In addition, the proposed sensor was applied to the determination of nitrate in mineral water samples and the results are in good agreement (for a 95% confidence level according to the Student's t-test) with those obtained using the capillary electrophoresis procedure.
Source:Sensors and Actuators B: Chemical, Volume 188
Author(s): Iranaldo S. da Silva , William R. de Araujo , Thiago R.L.C. Paixão , Lúcio Angnes
Nitrate determination plays a very important role in the analysis of environmental samples. In this paper, an activation procedure for nitrate sensing using a modified copper electrode made from flat flexible cables in presence of a low amount of chloride is reported. The proposed method exhibits enhanced electrocatalytic behaviour in the reduction of nitrate compared to a bare copper electrode. The proposed method showed linear response for nitrate in the concentration range 10–1070μmolL−1, with a regression coefficient R 2 =0.999 (n =12) and a limit of detection of 1.8μmolL−1. According to the procedure based on the standard addition technique, the recovery values obtained were 93–103%, showing the accuracy of the proposed method. In addition, the proposed sensor was applied to the determination of nitrate in mineral water samples and the results are in good agreement (for a 95% confidence level according to the Student's t-test) with those obtained using the capillary electrophoresis procedure.
Electrochemical immunosensor based on graphene–polyaniline composites and carboxylated graphene oxide for estradiol detection
06 August 2013,
10:08:24
Publication date: November
2013
Source:Sensors and Actuators B: Chemical, Volume 188
Author(s): Jie Li , Su Liu , Jinghua Yu , Wenjing Lian , Min Cui , Wei Xu , Jiadong Huang
A novel estradiol immunosensor based on graphene–polyaniline (GR–PANI) composites and carboxylated graphene oxide (GO) was developed. GR–PANI composites were used to enhance the electroactivity and stability of the electrode. The current response of the immunosensor was remarkably improved due to the synergistic effects of GR and PANI. Horseradish peroxidase–graphene oxide–antibody (HRP–GO–Ab) conjugates which were constructed by using the carboxylated GO as the carrier of the antibody and horseradish peroxidase as the label improved the catalytic activity for hydrogen reduction of the electrode. A competitive immunoassay was facilitated between 17β-estradiol and the HRP–GO–Ab conjugates. Based on this competitive immunoassay, the immunosensor showed a wide linear response to estradiol in the range 0.04–7.00ng/mL and a limit of detection of 0.02ng/mL (S/N=3). The developed immunosensor was successfully applied to the detection of estradiol in real samples.
Source:Sensors and Actuators B: Chemical, Volume 188
Author(s): Jie Li , Su Liu , Jinghua Yu , Wenjing Lian , Min Cui , Wei Xu , Jiadong Huang
A novel estradiol immunosensor based on graphene–polyaniline (GR–PANI) composites and carboxylated graphene oxide (GO) was developed. GR–PANI composites were used to enhance the electroactivity and stability of the electrode. The current response of the immunosensor was remarkably improved due to the synergistic effects of GR and PANI. Horseradish peroxidase–graphene oxide–antibody (HRP–GO–Ab) conjugates which were constructed by using the carboxylated GO as the carrier of the antibody and horseradish peroxidase as the label improved the catalytic activity for hydrogen reduction of the electrode. A competitive immunoassay was facilitated between 17β-estradiol and the HRP–GO–Ab conjugates. Based on this competitive immunoassay, the immunosensor showed a wide linear response to estradiol in the range 0.04–7.00ng/mL and a limit of detection of 0.02ng/mL (S/N=3). The developed immunosensor was successfully applied to the detection of estradiol in real samples.
Simultaneous detection of benzene and toluene using a pulsed ion mobility spectrometer
06 August 2013,
10:08:24
Publication date: November
2013
Source:Sensors and Actuators B: Chemical, Volume 188
Author(s): Stefan Zimmermann , Frank Gunzer
Ion mobility spectrometry (IMS) is a well known method for fast trace gas detection in air. Having simple instrumentation, IMS is especially suited when portability and highest sensitivity are required. However, due to competing chemical ionization processes in the reaction region of IMS, it can be difficult or even impossible to detect small amounts of certain substances in a complex mixture. A prominent example is the detection of low benzene concentrations in the presence of higher toluene concentrations. In this paper we present experimental results of simultaneous toluene and benzene detection by using a pulsed electron source for ionization and demonstrate how this can help to overcome the major issue of atmospheric pressure chemical ionization (APCI).
Source:Sensors and Actuators B: Chemical, Volume 188
Author(s): Stefan Zimmermann , Frank Gunzer
Ion mobility spectrometry (IMS) is a well known method for fast trace gas detection in air. Having simple instrumentation, IMS is especially suited when portability and highest sensitivity are required. However, due to competing chemical ionization processes in the reaction region of IMS, it can be difficult or even impossible to detect small amounts of certain substances in a complex mixture. A prominent example is the detection of low benzene concentrations in the presence of higher toluene concentrations. In this paper we present experimental results of simultaneous toluene and benzene detection by using a pulsed electron source for ionization and demonstrate how this can help to overcome the major issue of atmospheric pressure chemical ionization (APCI).
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