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:
Biosilica-based immobilization strategy for label-free OWLS sensors
02 January 2013,
09:12:39
February 2013
Publication year: 2013
Source:Sensors and Actuators B: Chemical, Volume 177
In the last years, a new group of enzymes, so-called silicateins, have been identified and characterized, which form the axial filaments of the spicules of the siliceous sponges, consisting of amorphous silica. Silicateins are able to catalyze the polycondensation and deposition of silica at mild conditions (low temperature and physiological pH). By means of these enzymes it is possible for the first time to produce silica nanostructures biocatalytically, which opens new ways for construction of biosensors. The cDNAs encoding the responsible enzymes have been isolated and the proteins can be produced in a recombinant way. Here we demonstrate the silicatein-mediated biosilica formation on the surface of SiO2 sensors in model measurements using Optical Waveguide Lightmode Spectroscopy (OWLS) for real-time evaluation. The efficiency of the enzyme reaction on the surface of the SiO2 chips was studied and the parameters of this process were optimized. Silicatein can be expressed in Escherichia coli and the resulting recombinant protein is able to catalyze the formation of silica shell around the bacterial cells. The described immobilization strategy provides a novel technology for the development of microbial biosensors.
Publication year: 2013
Source:Sensors and Actuators B: Chemical, Volume 177
In the last years, a new group of enzymes, so-called silicateins, have been identified and characterized, which form the axial filaments of the spicules of the siliceous sponges, consisting of amorphous silica. Silicateins are able to catalyze the polycondensation and deposition of silica at mild conditions (low temperature and physiological pH). By means of these enzymes it is possible for the first time to produce silica nanostructures biocatalytically, which opens new ways for construction of biosensors. The cDNAs encoding the responsible enzymes have been isolated and the proteins can be produced in a recombinant way. Here we demonstrate the silicatein-mediated biosilica formation on the surface of SiO2 sensors in model measurements using Optical Waveguide Lightmode Spectroscopy (OWLS) for real-time evaluation. The efficiency of the enzyme reaction on the surface of the SiO2 chips was studied and the parameters of this process were optimized. Silicatein can be expressed in Escherichia coli and the resulting recombinant protein is able to catalyze the formation of silica shell around the bacterial cells. The described immobilization strategy provides a novel technology for the development of microbial biosensors.
Effect of 130MeV Au ion irradiation on CO2 gas sensing properties of In2Te3 thin films
02 January 2013,
09:12:39
February 2013
Publication year: 2013
Source:Sensors and Actuators B: Chemical, Volume 177
CO and CO2 are harmful pollutants. The main objective of monitoring CO and CO2 is to prevent intoxication. Though these pollutants were monitored by metal oxide gas sensors, it operated at high temperature. Selectivity of metal oxides over a wide range of gas is limited. Additional contribution of sensor heaters and its associated electronics may induce poor stability of a sensor. In addition to that room temperature gas sensor is always essential to monitor the CO2 pollutant. In the present work, we have prepared In2Te3 thin films from In/Te bilayer by SHI (Au 130MeV) irradiation. Structural, surface morphology, elemental composition and gas sensing behavior of the as grown and irradiated samples were analyzed by XRD, SEM, RBS and I–V analysis. The observed results were discussed in connection with the SHI induced modification at the interface. As fluence increases, the crystallanity also found to increase. In addition to that dewetting structure is observed at higher fluence. The films prepared by SHI route shows better gas sensing behavior of In2Te3 thin film than from conventional method of synthesis.
Publication year: 2013
Source:Sensors and Actuators B: Chemical, Volume 177
CO and CO2 are harmful pollutants. The main objective of monitoring CO and CO2 is to prevent intoxication. Though these pollutants were monitored by metal oxide gas sensors, it operated at high temperature. Selectivity of metal oxides over a wide range of gas is limited. Additional contribution of sensor heaters and its associated electronics may induce poor stability of a sensor. In addition to that room temperature gas sensor is always essential to monitor the CO2 pollutant. In the present work, we have prepared In2Te3 thin films from In/Te bilayer by SHI (Au 130MeV) irradiation. Structural, surface morphology, elemental composition and gas sensing behavior of the as grown and irradiated samples were analyzed by XRD, SEM, RBS and I–V analysis. The observed results were discussed in connection with the SHI induced modification at the interface. As fluence increases, the crystallanity also found to increase. In addition to that dewetting structure is observed at higher fluence. The films prepared by SHI route shows better gas sensing behavior of In2Te3 thin film than from conventional method of synthesis.
Effect of the surface organization with carbon nanotubes on the electrochemical detection of bisphenol A
02 January 2013,
09:12:39
February 2013
Publication year: 2013
Source:Sensors and Actuators B: Chemical, Volume 177
This communication reports a comparison study between sensors based on vertically aligned and dispersed single-walled carbon nanotubes on the electrochemical determination of an endocrine disruptor. The vertical alignment of carbon nanotubes enabled an electrocatalytic effect and enhanced the sensitivity of bisphenol A oxidation compared with an electrode modified with dispersed carbon nanotubes. The vertically aligned surface had a remarkable influence on the limit-of-detection obtained for bisphenol A.
Publication year: 2013
Source:Sensors and Actuators B: Chemical, Volume 177
This communication reports a comparison study between sensors based on vertically aligned and dispersed single-walled carbon nanotubes on the electrochemical determination of an endocrine disruptor. The vertical alignment of carbon nanotubes enabled an electrocatalytic effect and enhanced the sensitivity of bisphenol A oxidation compared with an electrode modified with dispersed carbon nanotubes. The vertically aligned surface had a remarkable influence on the limit-of-detection obtained for bisphenol A.
Nanostructured ceria thin film for ethanol and trimethylamine sensing
02 January 2013,
09:12:39
February 2013
Publication year: 2013
Source:Sensors and Actuators B: Chemical, Volume 177
Nanostructured cerium dioxide (CeO2) thin films were deposited on glass substrates at an optimized substrate temperature of 503K, using spray pyrolysis technique under optimized deposition conditions. An aqueous solution of 0.05M concentration of Ce(NO3)3·6H2O was used as precursor. The X-ray diffraction (XRD) pattern confirmed the polycrystalline nature of the film with fluorite type face-centered cubic structure. The scanning electron micrographs (SEM) of the annealed films were observed and it was found to be uniform and free from macroscopic defects. An optical energy band gap of 3.63eV for direct transition was calculated from UV–vis absorbance spectra. Further, the vapour sensing property of annealed CeO2 samples were studied by chemiresistive method for two different volatile organic compounds (VOCs) namely ethanol and trimethylamine at various operating temperatures. Results indicated that the CeO2 thin films changed from n- to p-type character in the presence of ethanol at 323K till to the maximum temperature studied (400K) and showed the higher response at 373K. Conversely, in trimethylamine, the films maintained their n-type character showing appreciable response in the temperature range studied (300–373K). Therefore, the influence of operating temperature on the selectivity of the CeO2 thin film samples can be effectively used for an efficient food quality assessment.
Publication year: 2013
Source:Sensors and Actuators B: Chemical, Volume 177
Nanostructured cerium dioxide (CeO2) thin films were deposited on glass substrates at an optimized substrate temperature of 503K, using spray pyrolysis technique under optimized deposition conditions. An aqueous solution of 0.05M concentration of Ce(NO3)3·6H2O was used as precursor. The X-ray diffraction (XRD) pattern confirmed the polycrystalline nature of the film with fluorite type face-centered cubic structure. The scanning electron micrographs (SEM) of the annealed films were observed and it was found to be uniform and free from macroscopic defects. An optical energy band gap of 3.63eV for direct transition was calculated from UV–vis absorbance spectra. Further, the vapour sensing property of annealed CeO2 samples were studied by chemiresistive method for two different volatile organic compounds (VOCs) namely ethanol and trimethylamine at various operating temperatures. Results indicated that the CeO2 thin films changed from n- to p-type character in the presence of ethanol at 323K till to the maximum temperature studied (400K) and showed the higher response at 373K. Conversely, in trimethylamine, the films maintained their n-type character showing appreciable response in the temperature range studied (300–373K). Therefore, the influence of operating temperature on the selectivity of the CeO2 thin film samples can be effectively used for an efficient food quality assessment.
Cu2+-selective “Off–On” chemsensor based on the rhodamine derivative bearing 8-hydroxyquinoline moiety and its application in live cell imaging
02 January 2013,
09:12:39
February 2013
Publication year: 2013
Source:Sensors and Actuators B: Chemical, Volume 177
A rhodamine-based fluorescence chemsensor bearing the 8-hydroxyquinoline unit is developed as a reversible turn-on chemosensor for Cu2+. It exhibits a highly sensitive fluorescent response toward Cu2+ in aqueous media with an 80-fold fluorescence intensity enhancement under 10equiv. of Cu2+ added. This indicates that the synthesized chemosensor effectively avoided the fluorescence quenching for the paramagnetic nature of Cu2+ via its strong binding capability toward Cu2+. The chemosensor Rh-Q exhibits a dynamic response range for Cu2+ from 2×10−7 to 5×10−5 M, with a detection limit of 0.19μM, and good selectivity for Cu2+ over other heavy and transition metal (HTM) ions in Tris–HCl/EtOH (7:3, v/v, pH 7.4). In addition, the turn-on fluorescent change upon the addition of Cu2+ is also applied in cell imaging.
Publication year: 2013
Source:Sensors and Actuators B: Chemical, Volume 177
A rhodamine-based fluorescence chemsensor bearing the 8-hydroxyquinoline unit is developed as a reversible turn-on chemosensor for Cu2+. It exhibits a highly sensitive fluorescent response toward Cu2+ in aqueous media with an 80-fold fluorescence intensity enhancement under 10equiv. of Cu2+ added. This indicates that the synthesized chemosensor effectively avoided the fluorescence quenching for the paramagnetic nature of Cu2+ via its strong binding capability toward Cu2+. The chemosensor Rh-Q exhibits a dynamic response range for Cu2+ from 2×10−7 to 5×10−5 M, with a detection limit of 0.19μM, and good selectivity for Cu2+ over other heavy and transition metal (HTM) ions in Tris–HCl/EtOH (7:3, v/v, pH 7.4). In addition, the turn-on fluorescent change upon the addition of Cu2+ is also applied in cell imaging.
Graphical abstract
Influence of annealing temperature on the photoelectric gas sensing of Fe-doped ZnO under visible light irradiation
02 January 2013,
09:12:39
February 2013
Publication year: 2013
Source:Sensors and Actuators B: Chemical, Volume 177
Fe-doped ZnO are fabricated by hydrothermal method. The influence of the annealing temperature on structural and photoelectric property was studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV–vis diffuse reflectance spectra (UV–vis DRS). Visible light-illumination room-temperature gas sensing to formaldehyde based on Fe-doped ZnO annealed at different temperatures was subsequently investigated by the surface photocurrent spectra and gas sensor characterization system, respectively. Accompanying with increasing annealing temperature from 400°C to 600°C, the response to formaldehyde was enhanced due to the increase in crystal quality and active sites on the surface of Fe-doped ZnO. However, when the annealing temperature goes over 700°C, the phase of ZnFe2O4 was observed from XRD pattern. The existence of ZnFe2O4 hindered the transfer of photo-generated carriers and decreased the amount of surface active sites. As a result, the photoelectric gas response for formaldehyde was weaken to some extent. Our results demonstrated that annealing temperature is a very important parameter in the determination of the sensitivity of photoelectric gas sensing based on Fe-doped ZnO.
Publication year: 2013
Source:Sensors and Actuators B: Chemical, Volume 177
Fe-doped ZnO are fabricated by hydrothermal method. The influence of the annealing temperature on structural and photoelectric property was studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV–vis diffuse reflectance spectra (UV–vis DRS). Visible light-illumination room-temperature gas sensing to formaldehyde based on Fe-doped ZnO annealed at different temperatures was subsequently investigated by the surface photocurrent spectra and gas sensor characterization system, respectively. Accompanying with increasing annealing temperature from 400°C to 600°C, the response to formaldehyde was enhanced due to the increase in crystal quality and active sites on the surface of Fe-doped ZnO. However, when the annealing temperature goes over 700°C, the phase of ZnFe2O4 was observed from XRD pattern. The existence of ZnFe2O4 hindered the transfer of photo-generated carriers and decreased the amount of surface active sites. As a result, the photoelectric gas response for formaldehyde was weaken to some extent. Our results demonstrated that annealing temperature is a very important parameter in the determination of the sensitivity of photoelectric gas sensing based on Fe-doped ZnO.
Schiff-base as highly sensitive and reversible chemosensors for HCl gas
02 January 2013,
09:12:39
February 2013
Publication year: 2013
Source:Sensors and Actuators B: Chemical, Volume 177
Two optochemical sensors based on Schiff-bases doped polymethyl methacrylate (PMMA) films were obtained. The gas sensing behavior of the sensors were investigated with respect to the detection of HCl gas by absorption and fluorescence spectra at room temperature. The detection method is based on the protonation of Schiff-bases by HCl gas. It was found that two sensors exhibited good response, reversibility and stability to HCl gas. The color changes of sensors upon protonation are obvious, which can be observed with naked-eye. The changes of the spectra are likely due to increase in planarity of the molecular framework, which has been confirmed by quantum chemical calculation.
Publication year: 2013
Source:Sensors and Actuators B: Chemical, Volume 177
Two optochemical sensors based on Schiff-bases doped polymethyl methacrylate (PMMA) films were obtained. The gas sensing behavior of the sensors were investigated with respect to the detection of HCl gas by absorption and fluorescence spectra at room temperature. The detection method is based on the protonation of Schiff-bases by HCl gas. It was found that two sensors exhibited good response, reversibility and stability to HCl gas. The color changes of sensors upon protonation are obvious, which can be observed with naked-eye. The changes of the spectra are likely due to increase in planarity of the molecular framework, which has been confirmed by quantum chemical calculation.
Graphical abstract
High temperature oxygen sensing properties of oxygen deficient RBaCo2O5+δ thick films
02 January 2013,
09:12:39
February 2013
Publication year: 2013
Source:Sensors and Actuators B: Chemical, Volume 177
RBaCo2O5+δ (R=Sm, Eu, Dy, Gd, and Y) thick films were prepared by the solid state reaction followed by the spin-coating method. The oxygen resistivity sensor properties of these films were investigated in switching O2/N2 atmosphere. The results show that the RBaCo2O5+δ films are promising as oxygen resistance sensors at elevated temperature. Especially, DyBaCo2O5+δ film shows a fast response speed, high sensitivity and good repeatability at 600°C. The correlation between the sensor properties of RBaCo2O5+δ thick films and their oxygen intake/release properties is also discussed.
Publication year: 2013
Source:Sensors and Actuators B: Chemical, Volume 177
RBaCo2O5+δ (R=Sm, Eu, Dy, Gd, and Y) thick films were prepared by the solid state reaction followed by the spin-coating method. The oxygen resistivity sensor properties of these films were investigated in switching O2/N2 atmosphere. The results show that the RBaCo2O5+δ films are promising as oxygen resistance sensors at elevated temperature. Especially, DyBaCo2O5+δ film shows a fast response speed, high sensitivity and good repeatability at 600°C. The correlation between the sensor properties of RBaCo2O5+δ thick films and their oxygen intake/release properties is also discussed.
Synthesis of embedded and isolated Mg0.5Zn0.5Fe2O4 nano-tubes and investigation on their anomalous gas sensing characteristics
02 January 2013,
09:12:39
February 2013
Publication year: 2013
Source:Sensors and Actuators B: Chemical, Volume 177
We have investigated the gas sensing characteristics of wet chemical synthesized 1D hollow Mg0.5Zn0.5Fe2O4 tubes embedded into porous alumina template and their isolated counterpart coated on quartz substrate. Both embedded and isolated Mg0.5Zn0.5Fe2O4 nano-tubes show promising response towards H2, CO, and N2O gases. During the measurement of gas sensing characteristics, it is observed that irrespective of the test gas (H2, CO, N2O) type, test gas concentration (10–1660ppm) and operating temperature (250–380°C) the embedded tubes exhibit n-type whereas isolated tubes reveal p-type sensing characteristics. Such inversion of dominant charge carriers (from n to p type) from embedded to isolated Mg0.5Zn0.5Fe2O4 nano-tubes is related with the higher chemi-adsorption of oxygen over isolated tubes than their embedded counterpart (when kept in air prior to the exposure of test gas). The present article thus describes the potential gas sensing application of 1D ferrite sensors and illustrates the possibilities of tailoring the electronic characteristics of ferrites by modifying their surface to volume ratios.
Publication year: 2013
Source:Sensors and Actuators B: Chemical, Volume 177
We have investigated the gas sensing characteristics of wet chemical synthesized 1D hollow Mg0.5Zn0.5Fe2O4 tubes embedded into porous alumina template and their isolated counterpart coated on quartz substrate. Both embedded and isolated Mg0.5Zn0.5Fe2O4 nano-tubes show promising response towards H2, CO, and N2O gases. During the measurement of gas sensing characteristics, it is observed that irrespective of the test gas (H2, CO, N2O) type, test gas concentration (10–1660ppm) and operating temperature (250–380°C) the embedded tubes exhibit n-type whereas isolated tubes reveal p-type sensing characteristics. Such inversion of dominant charge carriers (from n to p type) from embedded to isolated Mg0.5Zn0.5Fe2O4 nano-tubes is related with the higher chemi-adsorption of oxygen over isolated tubes than their embedded counterpart (when kept in air prior to the exposure of test gas). The present article thus describes the potential gas sensing application of 1D ferrite sensors and illustrates the possibilities of tailoring the electronic characteristics of ferrites by modifying their surface to volume ratios.
Determination of lactose by a novel third generation biosensor based on a cellobiose dehydrogenase and aryl diazonium modified single wall carbon nanotubes electrode
02 January 2013,
09:12:39
February 2013
Publication year: 2013
Source:Sensors and Actuators B: Chemical, Volume 177
In this paper a new third-generation amperometric biosensor for lactose determination is described. The biosensor is based on the highly efficient direct electron transfer (DET) between cellobiose dehydrogenase (CDH) from Phanerochaete sordida (PsCDH) and single walled carbon nanotubes (SWCNT). The SWNCTs were surface modified with aryl diazonium salts of p-phenylenediamine (NH2-PD) and deposited on top of a glassy carbon (GC) electrode. The PsCDH NH2-PD/SWCNT-GC biosensor showed very efficient DET and exhibited an extraordinary high current density of 500μAcm−2 in a 5mM lactose solution at pH 3.5. The biosensor has a detection limit for lactose of 0.5μM, a large linear range from 1 to 150μM lactose and a high sensitivity (476.8nAμM−1 cm−2). It shows also a fast response time (4s), good reproducibility (RSD=1.75%) and good stability (half-life 12 days). In addition, it is easy, simple to manufacture, and cheap because a low amount of enzyme is required and highly selective, as no significant interference was observed. For these reasons, it can represent a valid alternative to HPLC measurements for lactose determination in milk and dairy products.
Publication year: 2013
Source:Sensors and Actuators B: Chemical, Volume 177
In this paper a new third-generation amperometric biosensor for lactose determination is described. The biosensor is based on the highly efficient direct electron transfer (DET) between cellobiose dehydrogenase (CDH) from Phanerochaete sordida (PsCDH) and single walled carbon nanotubes (SWCNT). The SWNCTs were surface modified with aryl diazonium salts of p-phenylenediamine (NH2-PD) and deposited on top of a glassy carbon (GC) electrode. The PsCDH NH2-PD/SWCNT-GC biosensor showed very efficient DET and exhibited an extraordinary high current density of 500μAcm−2 in a 5mM lactose solution at pH 3.5. The biosensor has a detection limit for lactose of 0.5μM, a large linear range from 1 to 150μM lactose and a high sensitivity (476.8nAμM−1 cm−2). It shows also a fast response time (4s), good reproducibility (RSD=1.75%) and good stability (half-life 12 days). In addition, it is easy, simple to manufacture, and cheap because a low amount of enzyme is required and highly selective, as no significant interference was observed. For these reasons, it can represent a valid alternative to HPLC measurements for lactose determination in milk and dairy products.
No comments:
Post a Comment