A new issue of this journal has just
been published. To see abstracts of the papers it contains (with links through
to the full papers) click here:
Selected
papers from the latest issue:
Facile synthesis of nanospindle-like Cu2O/straight multi-walled carbon nanotube hybrid nanostructures and their application in enzyme-free glucose sensing
30 May 2012,
09:19:19
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 168
Xuemei Zhou, Huagui Nie, Zhen Yao, Youqing Dong, Zhi Yang, Shaoming Huang
A type of nanospindle-like Cu2O/straight multi-walled carbon nanotubes (SMWNTs) nanohybrids modified electrode for sensitive enzyme-free glucose detection has been fabricated, where the morphology of the nanohybrids were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray powder diffraction (XRD). The electrochemical characteristics of this electrode material were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The as-prepared nanospindle-like Cu2O/SMWNTs nanohybrids exhibit much higher electrocatalytic activity on the oxidation of glucose than the SMWNTs or Cu2O alone as the electrode modifying material, which attributes to high catalytic active sites provided by the nanospindle-like Cu2O and high electron transfer rate provided by an efficient electrical network formed by Cu2O and SMWNTs. The proposed sensors exhibit linear behavior in the concentration range from 500nM to 2.5mM for glucose with a high sensitivity of 2143μAmM−1 cm−2 and a limit of detection of 200nM (3σ). More importantly, the nanohybrids modified electrode also show good stability, reproducibility and high resistance against poisoning by chloride ion and the commonly interfering species such as ascorbic acid, dopamine, uric acid and acetamidophenol. These good analytical performances make the nanospindle-like Cu2O/SMWNTs nanohybrids promising for the future development of enzyme-free glucose sensors.
Source:Sensors and Actuators B: Chemical, Volume 168
Xuemei Zhou, Huagui Nie, Zhen Yao, Youqing Dong, Zhi Yang, Shaoming Huang
A type of nanospindle-like Cu2O/straight multi-walled carbon nanotubes (SMWNTs) nanohybrids modified electrode for sensitive enzyme-free glucose detection has been fabricated, where the morphology of the nanohybrids were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray powder diffraction (XRD). The electrochemical characteristics of this electrode material were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The as-prepared nanospindle-like Cu2O/SMWNTs nanohybrids exhibit much higher electrocatalytic activity on the oxidation of glucose than the SMWNTs or Cu2O alone as the electrode modifying material, which attributes to high catalytic active sites provided by the nanospindle-like Cu2O and high electron transfer rate provided by an efficient electrical network formed by Cu2O and SMWNTs. The proposed sensors exhibit linear behavior in the concentration range from 500nM to 2.5mM for glucose with a high sensitivity of 2143μAmM−1 cm−2 and a limit of detection of 200nM (3σ). More importantly, the nanohybrids modified electrode also show good stability, reproducibility and high resistance against poisoning by chloride ion and the commonly interfering species such as ascorbic acid, dopamine, uric acid and acetamidophenol. These good analytical performances make the nanospindle-like Cu2O/SMWNTs nanohybrids promising for the future development of enzyme-free glucose sensors.
Room temperature CO sensing of selectively grown networked ZnO nanowires by Pd nanodot functionalization
30 May 2012,
09:19:19
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 168
Sun-Woo Choi, Sang Sub Kim
Room temperature sub-ppm CO sensing was realized in selectively grown networked ZnO nanowires by functionalizing their surfaces with Pd nanodots. In particular, the γ-ray radiolysis was applied to the Pd nanodot functionalization. The CO sensing characteristics of the Pd-functionalized ZnO nanowires were compared with those of bare ZnO nanowires. The Pd functionalization sharply improved the resistance responses at CO concentrations in the range of 100ppb–2ppm. At room temperature, the Pd-functionalized ZnO nanowire sensors exhibited a response of 1.02 at as low as 100ppb CO. The improvement of sensing capability by the Pd nanodot functionalization seems to be associated with the combined effect of electronic and chemical sensitizations due to the Pd nanoparticles.
Source:Sensors and Actuators B: Chemical, Volume 168
Sun-Woo Choi, Sang Sub Kim
Room temperature sub-ppm CO sensing was realized in selectively grown networked ZnO nanowires by functionalizing their surfaces with Pd nanodots. In particular, the γ-ray radiolysis was applied to the Pd nanodot functionalization. The CO sensing characteristics of the Pd-functionalized ZnO nanowires were compared with those of bare ZnO nanowires. The Pd functionalization sharply improved the resistance responses at CO concentrations in the range of 100ppb–2ppm. At room temperature, the Pd-functionalized ZnO nanowire sensors exhibited a response of 1.02 at as low as 100ppb CO. The improvement of sensing capability by the Pd nanodot functionalization seems to be associated with the combined effect of electronic and chemical sensitizations due to the Pd nanoparticles.
A colorimetric and fluorometric dual-modal chemosensor for cyanide in water
30 May 2012,
09:19:19
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 168
Jiang-Fei Xu, Hong-Hai Chen, Yu-Zhe Chen, Zhong-Jin Li, Li-Zhu Wu, Chen-Ho Tung, Qing-Zheng Yang
We have developed a new class of benzothiazolium hemicyanine Cu(II) complex based colorimetric and fluorometric dual-modal chemosensor for the toxic cyanide anion in 100% water solution. This dual-modal response was achieved by the removal of Cu(II) ions from sensor complex in the presence of cyanide to recover the internal charge transfer (ICT) character of the hemicyanine dye. The novel sensor shows good sensitivity with μM-level detection limit, and displays high selectivity to cyanide in the presence of other common interference anions.
Source:Sensors and Actuators B: Chemical, Volume 168
Jiang-Fei Xu, Hong-Hai Chen, Yu-Zhe Chen, Zhong-Jin Li, Li-Zhu Wu, Chen-Ho Tung, Qing-Zheng Yang
We have developed a new class of benzothiazolium hemicyanine Cu(II) complex based colorimetric and fluorometric dual-modal chemosensor for the toxic cyanide anion in 100% water solution. This dual-modal response was achieved by the removal of Cu(II) ions from sensor complex in the presence of cyanide to recover the internal charge transfer (ICT) character of the hemicyanine dye. The novel sensor shows good sensitivity with μM-level detection limit, and displays high selectivity to cyanide in the presence of other common interference anions.
Dually tunable inverse opal hydrogel colorimetric sensor with fast and reversible color changes
30 May 2012,
09:19:19
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 168
Jinsub Shin, Sung Gu Han, Wonmok Lee
Through opal-templated photopolymerization of copolymeric hydrogel consisting of 2-hydroxyethyl methacrylate, N-isopropylacrylamide, acrylic acid, and N,N′-methylenebis(acrylamide), a dually tunable inverse opal sensor by temperature and pH has been successfully synthesized. Temperature drop or pH increase induced hydrogel swelling and subsequent color changes of the sensor respectively due to lower critical solution temperature behavior of N-isopropylacrylamide and the altered Donnan potential by acrylic acid units. The color change driven by hydrogel swelling could be quantitatively measured by reflectance spectra. Increased content of N-isopropylacrylamide in the hydrogel resulted in a larger volume change under the same T-drop experiment. On the contrary, higher crosslinker content led to a less swollen hydrogel. From the kinetic investigations, response time for temperature change was measured to be much faster than that for pH variation (0.5s vs. 28s). An exceptionally rapid temperature response could be explained by fast water influx to the thin layers at the top of inverse opal hydrogel after an instantaneous temperature change. A cyclic pH/temperature changes (pH jump–temperature-drop–pH drop–temperature-jump) on a dually tunable sensor showed a perfect restoration of diffraction wavelength as well as the rapid response times for all stimuli. This work facilitates the fabrication of a variety of multi-responsive inverse opal sensors exhibiting rapid response kinetics by simply copolymerizing the individual sensing monomers using the optimized photo-polymerization and the colloidal templating route.
Source:Sensors and Actuators B: Chemical, Volume 168
Jinsub Shin, Sung Gu Han, Wonmok Lee
Through opal-templated photopolymerization of copolymeric hydrogel consisting of 2-hydroxyethyl methacrylate, N-isopropylacrylamide, acrylic acid, and N,N′-methylenebis(acrylamide), a dually tunable inverse opal sensor by temperature and pH has been successfully synthesized. Temperature drop or pH increase induced hydrogel swelling and subsequent color changes of the sensor respectively due to lower critical solution temperature behavior of N-isopropylacrylamide and the altered Donnan potential by acrylic acid units. The color change driven by hydrogel swelling could be quantitatively measured by reflectance spectra. Increased content of N-isopropylacrylamide in the hydrogel resulted in a larger volume change under the same T-drop experiment. On the contrary, higher crosslinker content led to a less swollen hydrogel. From the kinetic investigations, response time for temperature change was measured to be much faster than that for pH variation (0.5s vs. 28s). An exceptionally rapid temperature response could be explained by fast water influx to the thin layers at the top of inverse opal hydrogel after an instantaneous temperature change. A cyclic pH/temperature changes (pH jump–temperature-drop–pH drop–temperature-jump) on a dually tunable sensor showed a perfect restoration of diffraction wavelength as well as the rapid response times for all stimuli. This work facilitates the fabrication of a variety of multi-responsive inverse opal sensors exhibiting rapid response kinetics by simply copolymerizing the individual sensing monomers using the optimized photo-polymerization and the colloidal templating route.
Electrochemical detection of hydroquinone with a gold nanoparticle and graphene modified carbon ionic liquid electrode
30 May 2012,
09:19:19
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 168
Song Hu, Yuhua Wang, Xiuzheng Wang, Li Xu, Jun Xiang, Wei Sun
An ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF4) modified carbon paste electrode was fabricated and used as the substrate electrode. Then a gold nanoparticle and graphene (GR) composite film was co-electrodeposited on the carbon ionic liquid electrode (CILE) surface by immersing CILE in the graphite oxide and tetrachloroauric acid dispersion solution with cyclic voltammetric reduction. The fabricated Au–GR/CILE exhibited good electrochemical performances with higher conductivity and lower electron transfer resistance. Electrochemical behaviors of hydroquinone (HQ) were further investigated on the modified electrode by cyclic voltammetry and differential pulse voltammetry. A pair of well-defined redox peaks appeared with the peak-to-peak separation (ΔE p) as 0.077V in 0.1mol/L pH 2.5 PBS, indicating a fast quasi-reversible electron transfer process. The result could be attributed to the presence of high conductive Au–GR nanocomposites on the electrode surface. The electrochemical parameters of HQ on the Au–GR/CILE were calculated and the experimental conditions were optimized. Under the optimal conditions, the linear relationship between the oxidation peak current of HQ and its concentration can be obtained in the range from 0.06μmol/L to 800.0μmol/L with the detection limit as 0.018μmol/L (3σ). The coexisting catechol exhibited no interference and Au–GR/CILE was applied to the detection of HQ in synthetic wastewater samples with satisfactory results.
Source:Sensors and Actuators B: Chemical, Volume 168
Song Hu, Yuhua Wang, Xiuzheng Wang, Li Xu, Jun Xiang, Wei Sun
An ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF4) modified carbon paste electrode was fabricated and used as the substrate electrode. Then a gold nanoparticle and graphene (GR) composite film was co-electrodeposited on the carbon ionic liquid electrode (CILE) surface by immersing CILE in the graphite oxide and tetrachloroauric acid dispersion solution with cyclic voltammetric reduction. The fabricated Au–GR/CILE exhibited good electrochemical performances with higher conductivity and lower electron transfer resistance. Electrochemical behaviors of hydroquinone (HQ) were further investigated on the modified electrode by cyclic voltammetry and differential pulse voltammetry. A pair of well-defined redox peaks appeared with the peak-to-peak separation (ΔE p) as 0.077V in 0.1mol/L pH 2.5 PBS, indicating a fast quasi-reversible electron transfer process. The result could be attributed to the presence of high conductive Au–GR nanocomposites on the electrode surface. The electrochemical parameters of HQ on the Au–GR/CILE were calculated and the experimental conditions were optimized. Under the optimal conditions, the linear relationship between the oxidation peak current of HQ and its concentration can be obtained in the range from 0.06μmol/L to 800.0μmol/L with the detection limit as 0.018μmol/L (3σ). The coexisting catechol exhibited no interference and Au–GR/CILE was applied to the detection of HQ in synthetic wastewater samples with satisfactory results.
Multi-wall carbon nanotube gas sensors modified with amino-group to detect low concentration of formaldehyde
30 May 2012,
09:19:19
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 168
Haifen Xie, Changhao Sheng, Xin Chen, Xingyan Wang, Zhi Li, Jia Zhou
Gas sensors with multi-wall carbon nanotubes (MWCNTs) modified with amino-groups on interdigitated electrodes (IDE) were fabricated to detect low concentration of formaldehyde at room temperature. Effects of content of amino groups on sensing responses against various interfering circumstances and low concentration of formaldehyde were investigated. The sensor behaved high relative resistance changes to formaldehyde and lower response to interfering gases such as acetone, carbon dioxide, ammonia, toluene and ethanol. When the concentration of formaldehyde was 20ppb, the relative resistance changes of the sensor modified with 18.19% amino-group reached 1.73%. The sensor displayed high chemical selectivity, fast response and good reproducibility to low concentration of formaldehyde, which was attributed to the properties of MWNTs and the interaction between the surface of MWCNTs and amino-group.
Source:Sensors and Actuators B: Chemical, Volume 168
Haifen Xie, Changhao Sheng, Xin Chen, Xingyan Wang, Zhi Li, Jia Zhou
Gas sensors with multi-wall carbon nanotubes (MWCNTs) modified with amino-groups on interdigitated electrodes (IDE) were fabricated to detect low concentration of formaldehyde at room temperature. Effects of content of amino groups on sensing responses against various interfering circumstances and low concentration of formaldehyde were investigated. The sensor behaved high relative resistance changes to formaldehyde and lower response to interfering gases such as acetone, carbon dioxide, ammonia, toluene and ethanol. When the concentration of formaldehyde was 20ppb, the relative resistance changes of the sensor modified with 18.19% amino-group reached 1.73%. The sensor displayed high chemical selectivity, fast response and good reproducibility to low concentration of formaldehyde, which was attributed to the properties of MWNTs and the interaction between the surface of MWCNTs and amino-group.
Enhanced acetone sensing performance of Au nanoparticles functionalized flower-like ZnO
30 May 2012,
09:19:19
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 168
Xin-jun Wang, Wei Wang, Yan-Li Liu
ZnO flowers functionalized by Au nanoparticles (NPs) with various Au contents have been developed. The gas sensing properties of the sensors fabricated from these materials were examined and compared at varied working temperatures. Improved sensor response, selectivity and short response and recovery times to acetone vapor were achieved by suitably modulating the weight percent of Au NPs. Experimentally, the formation of Au/ZnO hybrids and surface coarsening of ZnO flowers were found to lead to apparent further enhancement of the sensor performance.
Source:Sensors and Actuators B: Chemical, Volume 168
Xin-jun Wang, Wei Wang, Yan-Li Liu
ZnO flowers functionalized by Au nanoparticles (NPs) with various Au contents have been developed. The gas sensing properties of the sensors fabricated from these materials were examined and compared at varied working temperatures. Improved sensor response, selectivity and short response and recovery times to acetone vapor were achieved by suitably modulating the weight percent of Au NPs. Experimentally, the formation of Au/ZnO hybrids and surface coarsening of ZnO flowers were found to lead to apparent further enhancement of the sensor performance.
Highly sensitive phenolic biosensor based on magnetic polydopamine-laccase-Fe3O4 bionanocomposite
30 May 2012,
09:19:19
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 168
Yunyong Li, Cong Qin, Chao Chen, Yingchun Fu, Ming Ma, Qingji Xie
New polydopamine (PDA)-laccase (Lac)-Fe3O4 magnetic polymeric bionanocomposites (MPBNCs) were prepared through one-pot Lac-catalyzed oxidation of dopamine in an aqueous suspension containing Lac, magnetic Fe3O4 nanoparticles and dopamine. A PDA-Lac-Fe3O4/Au electrode was prepared by facile and efficient magnetic separation/immobilization of the MPBNCs on a magnetic Au electrode for biosensing of hydroquinone (HQ), giving a sensitivity of 374μAmmol−1 Lcm−2, a limit of detection of 30nmolL−1, as well as good selectivity and stability. The biosensing electrode was also used for HQ analysis in real sample matrices with satisfactory results.
Source:Sensors and Actuators B: Chemical, Volume 168
Yunyong Li, Cong Qin, Chao Chen, Yingchun Fu, Ming Ma, Qingji Xie
New polydopamine (PDA)-laccase (Lac)-Fe3O4 magnetic polymeric bionanocomposites (MPBNCs) were prepared through one-pot Lac-catalyzed oxidation of dopamine in an aqueous suspension containing Lac, magnetic Fe3O4 nanoparticles and dopamine. A PDA-Lac-Fe3O4/Au electrode was prepared by facile and efficient magnetic separation/immobilization of the MPBNCs on a magnetic Au electrode for biosensing of hydroquinone (HQ), giving a sensitivity of 374μAmmol−1 Lcm−2, a limit of detection of 30nmolL−1, as well as good selectivity and stability. The biosensing electrode was also used for HQ analysis in real sample matrices with satisfactory results.
Rapid colorimetric detection of sulfide using calix[4]arene modified gold nanoparticles as a probe
30 May 2012,
09:19:19
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 168
Alok Pandya, Kuldeep V. Joshi, Nishith R. Modi, Shobhana K. Menon
An advanced and proficient colorimetric sulfide sensor based on gold nanoparticles (AuNP) modified calix[n]arene assembly has been designed and synthesized by generation of strongly binding dithiocarbamate(DTC). This molecular receptor competently and selectively recognizes sulfide ion via H-bonds. The assembly was characterized by TEM, DLS, UV–vis, FT-IR and 1H NMR spectrometry which demonstrates the higher binding affinity for sulfide via hydrogen bonding. The optimum range for determination of sulfide is from pH 7 to 10. The lower detection limit is found to be 10nM. This method is simple and relatively free from interference of closely associated ions and is successfully applied to the determination of sulfide in real samples of spiked water and leather waste water.
Source:Sensors and Actuators B: Chemical, Volume 168
Alok Pandya, Kuldeep V. Joshi, Nishith R. Modi, Shobhana K. Menon
An advanced and proficient colorimetric sulfide sensor based on gold nanoparticles (AuNP) modified calix[n]arene assembly has been designed and synthesized by generation of strongly binding dithiocarbamate(DTC). This molecular receptor competently and selectively recognizes sulfide ion via H-bonds. The assembly was characterized by TEM, DLS, UV–vis, FT-IR and 1H NMR spectrometry which demonstrates the higher binding affinity for sulfide via hydrogen bonding. The optimum range for determination of sulfide is from pH 7 to 10. The lower detection limit is found to be 10nM. This method is simple and relatively free from interference of closely associated ions and is successfully applied to the determination of sulfide in real samples of spiked water and leather waste water.
Miniaturized F−-selective all-solid-state potentiometric sensors with conductive polymer as an intermediate layer
30 May 2012,
09:19:19
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 168
Alexey Matusevich, Mariusz Pietrzak, Elżbieta Malinowska
In this work, miniaturized F−-selective all-solid-state potentiometric sensors were prepared and characterized. Poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate) (PEDOT:PSS) was used as an intermediate layer between gold internal electrode and polymer membrane of fluoride-selective sensors. The method of PEDOT:PSS deposition was optimized in order to prepare a layer with the best parameters for sensors preparation. Fluoride-selective ionophores working according to different carrier mechanisms (neutral and charged one) and appropriate lipophilic ionic additives were used for membrane preparation. The influence of membrane components on PEDOT:PSS intermediate layer properties has been evaluated. It is shown that the use of PEDOT:PSS deposited between fluoride-selective membrane and sensor internal electrode can enhance charge transfer between them only if membrane is able to provide sufficient cation movement. Working parameters of electrodes with membranes made of polyurethane (PU) and various amounts of plasticizer or non-plasticized PU were compared with electrodes based on conventional poly(vinyl chloride) (PVC) membranes. It was found that non-plasticized PU can successfully replace plasticized PVC in membranes doped with Al-based fluoride-selective ionophores, while for Zr-based ionophore it caused dramatic deterioration of electrodes’ working parameters. Using PU as membrane matrix, the best working parameters were achieved for electrodes based on Al(III)-tetra-tert-butyltetraazaporphine ( log K F − , Y − pot . : Cl− −3.9, Br− −3.8, NO3 − −3.6, SCN− −2.1, ClO4 − −2.5). As a result of studies, miniaturized fluoride-selective all-solid-state potentiometric sensors with response time less than 12s, lifetime more than 3 months and enhanced standard potential (E 0) stability, were prepared.
Source:Sensors and Actuators B: Chemical, Volume 168
Alexey Matusevich, Mariusz Pietrzak, Elżbieta Malinowska
In this work, miniaturized F−-selective all-solid-state potentiometric sensors were prepared and characterized. Poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate) (PEDOT:PSS) was used as an intermediate layer between gold internal electrode and polymer membrane of fluoride-selective sensors. The method of PEDOT:PSS deposition was optimized in order to prepare a layer with the best parameters for sensors preparation. Fluoride-selective ionophores working according to different carrier mechanisms (neutral and charged one) and appropriate lipophilic ionic additives were used for membrane preparation. The influence of membrane components on PEDOT:PSS intermediate layer properties has been evaluated. It is shown that the use of PEDOT:PSS deposited between fluoride-selective membrane and sensor internal electrode can enhance charge transfer between them only if membrane is able to provide sufficient cation movement. Working parameters of electrodes with membranes made of polyurethane (PU) and various amounts of plasticizer or non-plasticized PU were compared with electrodes based on conventional poly(vinyl chloride) (PVC) membranes. It was found that non-plasticized PU can successfully replace plasticized PVC in membranes doped with Al-based fluoride-selective ionophores, while for Zr-based ionophore it caused dramatic deterioration of electrodes’ working parameters. Using PU as membrane matrix, the best working parameters were achieved for electrodes based on Al(III)-tetra-tert-butyltetraazaporphine ( log K F − , Y − pot . : Cl− −3.9, Br− −3.8, NO3 − −3.6, SCN− −2.1, ClO4 − −2.5). As a result of studies, miniaturized fluoride-selective all-solid-state potentiometric sensors with response time less than 12s, lifetime more than 3 months and enhanced standard potential (E 0) stability, were prepared.
Nanoporous silicalite-only cantilevers as micromechanical sensors: Fabrication, resonance response and VOCs sensing performance
30 May 2012,
09:19:19
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 168
I. Pellejero, J. Agustí, M.A. Urbiztondo, J. Sesé, M.P. Pina, J. Santamaría, G. Abadal
Nanoporous microcantilevers entirely constituted by silicalite type zeolite have been fabricated by integrating the seeded growth hydrothermal zeolite synthesis step in a conventional microfabrication scheme using Si technologies. The mechanical properties of the as prepared polycrystalline beams, ranging from 200μm to 2000μm in length and 20 to 120μm in width have been fully characterized. In particular, Young modulus and quality factor of silicalite-only cantilevers before and after detemplation process have been determined by using mechanical resonance excitation and optical read-out. As a “proof of concept”, the nanoporous zeolitic cantilevers have been applied to ethanol detection at ppm level. The sensing performance of the as prepared silicalite-only cantilevers has been compared with the exhibited by conventional cantilevers consisting on microfabricated Si beams coated with individual silicalite crystals.
Source:Sensors and Actuators B: Chemical, Volume 168
I. Pellejero, J. Agustí, M.A. Urbiztondo, J. Sesé, M.P. Pina, J. Santamaría, G. Abadal
Nanoporous microcantilevers entirely constituted by silicalite type zeolite have been fabricated by integrating the seeded growth hydrothermal zeolite synthesis step in a conventional microfabrication scheme using Si technologies. The mechanical properties of the as prepared polycrystalline beams, ranging from 200μm to 2000μm in length and 20 to 120μm in width have been fully characterized. In particular, Young modulus and quality factor of silicalite-only cantilevers before and after detemplation process have been determined by using mechanical resonance excitation and optical read-out. As a “proof of concept”, the nanoporous zeolitic cantilevers have been applied to ethanol detection at ppm level. The sensing performance of the as prepared silicalite-only cantilevers has been compared with the exhibited by conventional cantilevers consisting on microfabricated Si beams coated with individual silicalite crystals.
One-pot hydrothermal synthesis of CuO–ZnO composite hollow spheres for selective H2S detection
30 May 2012,
09:19:19
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 168
Sun-Jung Kim, Chan Woong Na, In-Sung Hwang, Jong-Heun Lee
Pure ZnO and CuO–ZnO composite hollow spheres were prepared by one-pot, glucose-mediated hydrothermal reaction with subsequent heat treatment. The pure ZnO hollow spheres could selectively detect C2H5OH at 475°C. The CuO–ZnO hollow spheres prepared from the solutions with the compositions of [Cu2+]/([Cu2+]+[Zn2+])=0.02 and 0.04 showed high responses to 5ppm H2S (R a /R g =13.3 and 32.4, R a : resistance in air, R g : resistance in gas) with negligible cross responses to 100ppm C2H5OH, C3H8, CO and H2 (R a /R g =1.4–1.8) at 336°C. They also showed selective C2H5OH detection at 475°C. The dual selective detection of H2S and C2H5OH by the composite particles was due to electrochemical interactions with H2S of nano-scale p(CuO)–n(ZnO) junctions within the hollow spheres.
Source:Sensors and Actuators B: Chemical, Volume 168
Sun-Jung Kim, Chan Woong Na, In-Sung Hwang, Jong-Heun Lee
Pure ZnO and CuO–ZnO composite hollow spheres were prepared by one-pot, glucose-mediated hydrothermal reaction with subsequent heat treatment. The pure ZnO hollow spheres could selectively detect C2H5OH at 475°C. The CuO–ZnO hollow spheres prepared from the solutions with the compositions of [Cu2+]/([Cu2+]+[Zn2+])=0.02 and 0.04 showed high responses to 5ppm H2S (R a /R g =13.3 and 32.4, R a : resistance in air, R g : resistance in gas) with negligible cross responses to 100ppm C2H5OH, C3H8, CO and H2 (R a /R g =1.4–1.8) at 336°C. They also showed selective C2H5OH detection at 475°C. The dual selective detection of H2S and C2H5OH by the composite particles was due to electrochemical interactions with H2S of nano-scale p(CuO)–n(ZnO) junctions within the hollow spheres.
Novel protein based pressure transducer
30 May 2012,
09:19:19
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 168
Christopher M. Sponheimer, Corinne S. Lengsfeld
The need for intra-organ pressure measurement can only be facilitated by adapting existing pressure sensing technology to the specific tissues under test. The customization of these sensors has only increased cost and the need to explore new technologies has become increasingly more important. For this article, we explore the use of electrochemical pressure sensing to provide a low-cost pressure sensor to fill this need. Here we show that gelatin exhibits a change in impedance when pressurized if bubbles are first electrolyzed in the gel creating an aerogel. Using electrochemical impedance spectroscopy and model fitting, it is shown that this effect occurs at the aerogel/hydrogel interface and the change in impedance is linearly related to the change in applied pressure. Micrographs were taken of the interface during pressurization and image analysis demonstrates that the change in surface area of the interface is also linearly related to the change in applied pressure.
Source:Sensors and Actuators B: Chemical, Volume 168
Christopher M. Sponheimer, Corinne S. Lengsfeld
The need for intra-organ pressure measurement can only be facilitated by adapting existing pressure sensing technology to the specific tissues under test. The customization of these sensors has only increased cost and the need to explore new technologies has become increasingly more important. For this article, we explore the use of electrochemical pressure sensing to provide a low-cost pressure sensor to fill this need. Here we show that gelatin exhibits a change in impedance when pressurized if bubbles are first electrolyzed in the gel creating an aerogel. Using electrochemical impedance spectroscopy and model fitting, it is shown that this effect occurs at the aerogel/hydrogel interface and the change in impedance is linearly related to the change in applied pressure. Micrographs were taken of the interface during pressurization and image analysis demonstrates that the change in surface area of the interface is also linearly related to the change in applied pressure.
Highlights
► Surface area of the sol/gel interface of an aerogel is related to its electrochemical properties. ► Impedance of the sol/gel interface is linearly related to the exposed surface area. ► Open circuit voltage of the sol/gel interface is linearly related to the exposed surface area. ► Change in surface area of sol/gel interface is linearly related to the change in applied pressure. ► A linear relationship between pressure and voltage lends itself well to pressure sensors.Electrochemical study of niclosamide at poly(3,4-ethylenedioxythiophene) modified glassy carbon electrode
30 May 2012,
09:19:19
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 168
Solomon Mehretie, Shimelis Admassie, Merid Tessema, Theodros Solomon
A poly(3,4-ethylenedioxythiophene) (PEDOT) modified glassy carbon electrode was constructed for the determination of niclosamide. Cyclic voltammetry and differential pulse anodic stripping voltammetry were used to study the electrochemical reaction of niclosamide at the modified electrode in pH 7.0 phosphate buffer solution. The PEDOT-modified electrode showed a very good electrochemical behavior with a significant enhancement of the peak current compared to the bare electrode. The pH of the solution, accumulation potential and preconcentration time were optimized and the analytical performance of the modified electrode was investigated. A linear voltammetric response for niclosamide was obtained in the concentration range of 0.075–7.50μM, with a detection limit of 1.09×10−8 M. The method was successfully applied for the determination of niclosamide in pharmaceutical formulation and biological sample.
Source:Sensors and Actuators B: Chemical, Volume 168
Solomon Mehretie, Shimelis Admassie, Merid Tessema, Theodros Solomon
A poly(3,4-ethylenedioxythiophene) (PEDOT) modified glassy carbon electrode was constructed for the determination of niclosamide. Cyclic voltammetry and differential pulse anodic stripping voltammetry were used to study the electrochemical reaction of niclosamide at the modified electrode in pH 7.0 phosphate buffer solution. The PEDOT-modified electrode showed a very good electrochemical behavior with a significant enhancement of the peak current compared to the bare electrode. The pH of the solution, accumulation potential and preconcentration time were optimized and the analytical performance of the modified electrode was investigated. A linear voltammetric response for niclosamide was obtained in the concentration range of 0.075–7.50μM, with a detection limit of 1.09×10−8 M. The method was successfully applied for the determination of niclosamide in pharmaceutical formulation and biological sample.
A novel amperometric sensor based on screen-printed electrode modified with multi-walled carbon nanotubes and molecularly imprinted membrane for rapid determination of ractopamine in pig urine
30 May 2012,
09:19:19
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 168
Hongcai Zhang, Guoyan Liu, Chunyan Chai
Screen-printed electrodes were modified with multi-wall carbon nanotubes (MWCNT) and molecularly imprinted membranes (MIM) were directly synthesized on these modified electrodes using the in situ thermal polymerization techniques. The sensing system was easily established by connecting the screen-printed electrode modified with MWCNT-MIM to an electrochemical analyzer through an electrode slot. The signal for the determination of ractopamine was recorded using differential pulse voltammetry (DPV) and the optimization for the experimental conditions was also conducted. The results showed that the response of the sensor to concentration of ractopamine displayed a linear correlation over a range from 20nM to 200nM with a detection limit of 6nM, demonstrating favorable sensitivity and selectivity for the detection of ractopamine. The recoveries reached 87.7–96.9% based on pig urine samples.
Source:Sensors and Actuators B: Chemical, Volume 168
Hongcai Zhang, Guoyan Liu, Chunyan Chai
Screen-printed electrodes were modified with multi-wall carbon nanotubes (MWCNT) and molecularly imprinted membranes (MIM) were directly synthesized on these modified electrodes using the in situ thermal polymerization techniques. The sensing system was easily established by connecting the screen-printed electrode modified with MWCNT-MIM to an electrochemical analyzer through an electrode slot. The signal for the determination of ractopamine was recorded using differential pulse voltammetry (DPV) and the optimization for the experimental conditions was also conducted. The results showed that the response of the sensor to concentration of ractopamine displayed a linear correlation over a range from 20nM to 200nM with a detection limit of 6nM, demonstrating favorable sensitivity and selectivity for the detection of ractopamine. The recoveries reached 87.7–96.9% based on pig urine samples.
Development of a micro-flame ionization detector using a diffusion flame
30 May 2012,
09:19:19
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 168
Jihyung Kim, Byunghoon Bae, James Hammonds, Taekyu Kang, Mark A. Shannon
A micro-flame ionization detector (micro-FID) design is presented that is targeted for use in a portable gas sensor. Our micro-FID is based on a diffusion flame and features a folded flame structure that is more sensitive than a counter-flow flame designs. Unlike conventional FIDs that use a premixed or open diffusion flame, an air–hydrogen diffusion flame is employed and tested in an encapsulated structure of Quartz–Macor–Quartz layers. Diffusion flames are generally known to be more controllable and stable than premixed flames, where the stability of the micro-FID plays an important role for portable gas sensors. Various channel designs for oxidant and fuel flows meeting with different angles at the burner cavity are tested to obtain a stable flame and high output sensitivity over methane test samples. To verify the empirically designed microchannel, we simulate the temperature distribution in the microchannel by using computational fluid dynamics (CFD) software. To gauge the sensitivity of the device, the collected electric charges per mole (C/mol) is calculated and taken as a reference value of ionization efficiency. The result of the folded flame design is 1.959×10−2 C/mol for methane that is about 34 times higher than the result using a counter-flow flame, which is 5.73×10−4 C/mol for methane, while one of the commercial macro FIDs’ is 10−1 C/mol. This result shows that the micro-FID using the folded flame structure has higher ionization efficiency with less leakage of the analytes than of the classical counter-flow flame design.
Source:Sensors and Actuators B: Chemical, Volume 168
Jihyung Kim, Byunghoon Bae, James Hammonds, Taekyu Kang, Mark A. Shannon
A micro-flame ionization detector (micro-FID) design is presented that is targeted for use in a portable gas sensor. Our micro-FID is based on a diffusion flame and features a folded flame structure that is more sensitive than a counter-flow flame designs. Unlike conventional FIDs that use a premixed or open diffusion flame, an air–hydrogen diffusion flame is employed and tested in an encapsulated structure of Quartz–Macor–Quartz layers. Diffusion flames are generally known to be more controllable and stable than premixed flames, where the stability of the micro-FID plays an important role for portable gas sensors. Various channel designs for oxidant and fuel flows meeting with different angles at the burner cavity are tested to obtain a stable flame and high output sensitivity over methane test samples. To verify the empirically designed microchannel, we simulate the temperature distribution in the microchannel by using computational fluid dynamics (CFD) software. To gauge the sensitivity of the device, the collected electric charges per mole (C/mol) is calculated and taken as a reference value of ionization efficiency. The result of the folded flame design is 1.959×10−2 C/mol for methane that is about 34 times higher than the result using a counter-flow flame, which is 5.73×10−4 C/mol for methane, while one of the commercial macro FIDs’ is 10−1 C/mol. This result shows that the micro-FID using the folded flame structure has higher ionization efficiency with less leakage of the analytes than of the classical counter-flow flame design.
No comments:
Post a Comment