Just Published: Sensors & Actuators A: Physical

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:

Sensors & Actuators A: Physical
http://rss.sciencedirect.com/publication/science/5282

Selected papers from the latest issue:

Photofield effect and photoresponse properties of the transparent oxide-based BaInZnO thin-film transistors

31 January 2013, 09:35:13

15 April 2013
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 193

The photoresponse properties of the BaInZnO (BIZO) thin film transistors were investigated by the output and transfer characteristics. The drain current of the BIZO (10% Ba) and BIZO (20% Ba) transistors in turn-on and turn-off states is significantly increased with light illumination. The photoresponse values of the BIZO (10% Ba) and BIZO (20% Ba) transistors in turn-off and turn-on states were found to be 4.56 and 6.27, respectively, while the photoresponse values of the BIZO (10% Ba) and BIZO (20% Ba) transistors in turn-off and turn-on states were found to be 6.14 and 11.714, respectively. The photoresponse values of the transistors in turn-off state are lower than that of turn-on state. This indicates that the dominant photocurrent mechanism of the BIZO transistors is based on photovoltaic effects. The photoresponse properties of the BIZO transistors were improved with the increasing doping ratio of Ba. The obtained results indicate that BIZO transistors could be used as a photosensor for optoelectronic applications.

Fabrication and characterization of a double-heater based MEMS thermal flow sensor

31 January 2013, 09:35:13

15 April 2013
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 193

This paper presents a micro flow sensor based on two heaters acting also as temperature sensors. The two heating/sensing elements of the sensor are arranged in the diagonal arms of the Wheatstone bridge and suspended in an airflow channel by solid beams. The length of the heater and the distance between the heaters were optimized by numerical modeling. The solid beams were fabricated by a heavily doped p-type silicon layer and a silicon nitride layer, which was immune to airflow disturbances and thermal noises. The experimental results indicated that the micro flow sensor with a high sensitivity of 0.30mV/(ml/min) exhibited an excellent linear response within the range of 0.5–6sccm. This micro sensor demonstrated great potentials in biological applications, micro gas chromatography systems, medical instrumentation and process control.

Highlights

► The device with two heaters working as temperature sensing elements is proposed for the first time. ► The fabrication process of the MEMS based gas flow sensor with optimum heater length and the heaters distance was presented. ► The micro gas flow sensor was applied to flow rate measurement with characterization results described and discussed.

Piezoelectric properties of PVDF/MWCNT nanofiber using near-field electrospinning

31 January 2013, 09:35:13

15 April 2013
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 193

This study reports the use of near-field electrospinning to fabricate polyvinylidene fluoride (PVDF) piezoelectric nanofibers mixed with multiwalled-carbon nanotubes (MWCNT). This study also investigates the mechanical strength and piezoelectric characteristics of a single PVDF/MWCNT nanofiber. The morphology and polarization intensity of piezoelectric fiber can be controlled by adjusting the traveling velocity of the X–Y stage, the DC voltage, and the gap between the needle and collection plate. The optimal parameters of the PVDF solution, such as the PVDF powder weight percentage and MWCNT content, were also determined. X-ray diffraction (XRD) analysis shows a high diffraction peak at 2θ =20.8° in the piezoelectric crystal β-phase structure. ANSYS finite element analysis (FEA) software with coupled field analysis was used to realize piezoelectric actuation behavior of the PVDF fibers. A nano-indentation test (NanoIndenter XP System, MTS co.) was used to investigate Young's modulus of the PVDF fiber. Finally, the fixed–fixed beam structures of PVDF composite fibers were tested using a DC voltage supply. Comparing the polarized fiber with non-polarized fibers, the measurement of the center displacements as a function of electric field was conducted and characterized.

Comparative displacement study of bilayer actuators comprising of conducting polymers, fabricated from polypyrrole, poly(3,4-ethylenedioxythiophene) or poly(3,4-propylenedioxythiophene)

31 January 2013, 09:35:13

15 April 2013
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 193

The stress gradient generated due to electrochemical oxidation/reduction of a conducting polymer in a bilayer actuator causes a bending movement. Here we report a comparative study of the displacement of bilayer actuators prepared using different conducting polymers. The effects of conducting polymers obtained from electrochemical or chemical synthesis route: different polymers (polypyrrole (PPy), poly(3,4-ethylenedioxythiophene) PEDOT and poly(3,3-dihexyl-3-4-dihydro-2H-thieno[3,4b][1,4]-dioxepine [PProDOT(Hx)2]); and different electrolytes (0.1M lithium trifluromethanesulfonate/propylenecarbonate (LiTFSI/PC) and 1-ethyl-3-methyl imidazolium trifluromethanesulfonate (EMITFSI)) on the displacement amplitude and displacement patterns of these actuators were investigated and compared. The results indicate that the bilayer actuator consisting of an electrochemically synthesized conducting polymer exhibits far greater displacements compared to chemically synthesized polymers at the same stimulating voltage. Similarly, amongst the three conducting polymers considered, the PPY actuator showed greater displacement followed by PProDOT and PEDOT. Furthermore, the use of different electrolyte solution during polymerization as well as during actuation was found to affect not only displacement distance but also its pattern.

NiTi/Pb(Zr0.52Ti0.48)O3 thin film heterostructures for vibration damping in MEMS

31 January 2013, 09:35:13

15 April 2013
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 193

We report on the damping properties of NiTi/Pb(Zr0.52Ti0.48)O3 (PZT) heterostructures using nanoindentation technique. Creep and impact tests were performed to obtain hardness (H), elastic modulus (E r ), damping factor (tan δ) and figure of merit (FOM. A hold time of 30s during creep test shows significant improvement in damping factor for NiTi/PZT (0.046) and CrTiN/NiTi/PZT (0.050). Impact test demonstrates highest damping capacity with lowest coefficient of restitution (0.30) in CrTiN/NiTi/PZT. Higher hardness (19.8GPa) and excellent figure of merit (0.751) in CrTiN/NiTi/PZT makes them very attractive damping material for microelectromechanical systems (MEMS).

Development of a multilayer microfluidic device integrated with a PDMS-cellulose composite film for sample pre-treatment and immunoassay

31 January 2013, 09:35:13

15 April 2013
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 193

This work presents an integrated multilayer microfluidic device enabling raw sample pre-treatment and immunoassay based detection where a polydimethylsiloxane (PDMS)-cellulose composite film was used to isolate plasma from raw samples based on the cross-flow principle. The PDMS-cellulose composite film was prepared by the dip-coating method and its morphologies were studied by the SEM technology and the bonding strength was quantified by atmospheric pressure experiments. The integrated microfluidic device was used to detect human immunoglobulin (IgG) in rat whole blood samples, with a quantified detection range of 0.5–5μg/mL and a correlation coefficient of 0.978. A raw urine sample was also tested by the integrated microfluidic device, producing a detection range of 0.6–25μg/mL with a correlation coefficient of 0.969 for human IgG. This integrated microfluidic device may function as a platform technology, enabling on-site detection of raw clinical samples.

Sensitive electro-optic sensor using KTa1−xNbxO3 crystal

31 January 2013, 09:35:13

1 April 2013
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 192

KTa1−x Nb x O3 (KTN) is well-known as a crystal having very large EO coefficients. High-quality KTN crystal growth technology has been recently developed, and several applications of KTN are being investigated. We tried to use KTN to make an electric field sensor and, studied its electro-optic properties for this purpose. The modulation depth of the sensor was about 20 times deeper than that of the ZnTe sensor used in our previous system in the frequency range from DC to 1.5MHz.

Low power UV photodetection characteristics of cross-linked ZnO nanorods/nanotetrapods grown on silicon chip

31 January 2013, 09:35:13

1 April 2013
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 192

High-quality cross-linked ZnO nanorods/nanotetrapods have been successfully synthesized via thermal evaporation of Zn metal grains on Si (100) substrates. The growth mechanism for the formation of such cross-linked ZnO nanorods is discussed. The morphological, structural and optical properties of the nanorods have been investigated using scanning electron microscopy, X-ray diffraction, Raman spectroscopy and photoluminescence techniques. Cross-linked ZnO nanorods-based metal-semiconductor-metal UV detectors (Ag-ZnONRs-Ag MSM PD) were fabricated. The device showed a sensitivity of 595. The responsivity (R) of the device is 0.63AW⁻¹, which is 10 times higher than that reported for ZnO-based PDs. Under low power illumination (365nm, 1.5mW/cm²), the device showed a relatively fast response and baseline recovery for UV detection. The prototype device shows a simple method for cross-linked nanorods synthesis and demonstrates the possibility of constructing nanoscale photodetectors for nano-optics applications.

Fully differential current-mode MEMS dual-axis optical inclination sensor

31 January 2013, 09:35:13

1 April 2013
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 192

We demonstrate a tilt sensor fabricated in the MultiMEMS SensoNor process. The system uses an array of four photodiodes to determine the position of a bubble fluid pendulum and the tilt angle with respect to gravity. The entire sensing structure was manufactured in the commercial MultiMEMS process so it can be easily reproduced in large quantities. The device was tested across a range of inclinations to verify performance in sensing two axis tilt. Results for tilt measurements from −45° to +45° show correlation to expected values with an R ² value of 0.99595. The resolution of the device is 0.5° at zero degrees of inclination. The outputs of the sensor are mapped to a fit equation to allow calculation of inclination angle. The small size, simple structure, and minimal power consumption make it well-suited for a number of research and industrial applications.

Highlights

► Design and testing of a MEMS inclination sensor. ► A fluid pendulum affects light transmission to photodiodes. ► Small size, robust operation, and straightforward post-processing. ► Four quadrant design leads to differential measurement and translinear readout. ► Commercial process and minimal post-processing allow for high volume production scaling.

Current sensor based on inline microfiber Mach–Zehnder interferometer

31 January 2013, 09:35:13

1 April 2013
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 192

A compact inline microfiber Mach–Zehnder interferometer (MMZI) is proposed for current sensor application. The MMZI is fabricated using flame-brushing technique where both transition parts of a microfiber are tapered to reduce the waist diameter and form an interference region. The fabricated MMZI shows a good interference fringes with a high extinction ratio of 15dB. The fringe spacing can be tuned from 3.95nm to 3.36nm as the length of the interference region is varied from 4.5mm to 6mm. The shift in the interference fringes is observed to be linearly proportional to the square of the amount of the flowing current and the slope efficiency of the sensor is obtained at 140.26pm/A² with a correlation coefficient of 0.99. Since the refractive index of the fiber core has a different temperature coefficient than that of air, the interferometer can be used as a current sensor by placing the current carrying wire in contact with the waist region of the second part of the tapered fiber.

Ion beam sputtered Ge–Si–O amorphous thin films for microbolometer infrared detectors and their application in earth sensors

31 January 2013, 09:35:13

1 April 2013
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 192

Ge–Si–O thin films are prepared by ion beam sputtering technique with argon (Ar) alone and argon and oxygen as sputtering species, using sputtering targets of different compositions of Ge and SiO2. The deposited thin films are amorphous in nature and have chemical compositions close to that of the target. The study of electrical properties has shown that the activation energy and hence the thermistor constant (β) and electrical resistivity (ρ) are sensitive to oxygen flow rate, and they are the least for thin films prepared with Ar alone as the sputtering species. Different thermal isolation structures (TIS), consisting of silicon nitride (Si3N4) membrane of different thicknesses, Ge–Si–O thin film and, chromium coating on the rear side of the membrane, are prepared by bulk micro-machining technique, whose thermal conductance (G th) properties are evaluated from the experimentally determined current–voltage (I–V) characteristics. G th shows non-linear dependence with respect to raise in temperature of thin film thermistor due to Joule heating. The infrared micro-bolometer detectors, fabricated using one of the TIS structures have shown responsivity (ℜ) close to 115V/W at a bias voltage of 1.5V and chopping frequency of 10Hz, thermal time constant (τ) of 2.5ms and noise voltage of 255nV/Hz^1/2 against the corresponding thermal properties of G th and thermal capacitance C th equal to 9.0×10⁻⁵ W/K and 1.95×10⁻⁷ J/K respectively. The detectors are found to have uniform spectral response in the infrared region from 2 to 20μm, and NEDT in the range from 108 to 574mK when used with an F/1 optical system. The detector, in an infrared earth sensor system, is tested before an extended black body which simulates the earth disc in the laboratory and the results are discussed.

Design and characterization of a novel, robust, tri-axial force sensor

31 January 2013, 09:35:13

1 April 2013
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 192

A novel, robust, tri-axial force sensor has been developed that can be integrated into biomedical and robotic devices thanks to its size and accuracy. It features a titanium alloy body, the components of the force are separated by four basic strain sensing elements. The sensor was modeled by finite element method and the results were validated by experimental data. The sensor's diameter is 2.6mm, its height is 2mm. Proper signal conditioning tools were realized in software and hardware to achieve a sensitivity of 29.63mV/N and minimum detectable force of 4.87mN. The sensing element's structure fits electrical discharge machining technologies. The sensor was calibrated with a Nano 17 force sensor and we found that its performance is comparable to the commercial device.

Single axis accelerometer fabricated using printed circuit board techniques and laser ablation

31 January 2013, 09:35:13

1 April 2013
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 192

Low-cost accelerometers could be used in applications where extremely good characteristics are not a requirement. This paper presents an accelerometer fabricated using printed circuit board (PCB) processing techniques, and laser ablation. Laser is used to remove part of the PCB substrate, releasing a mass suspended by copper beams. The structure is easily bonded to another PCB, creating a variable parallel-plate capacitor with a small gap, which capacitance varies with the movement of the mass, caused by external acceleration. The fabricated accelerometer has been compared to a commercial silicon one, showing good agreement in the measurements. The measured sensitivity was 81fF/g.

Non-adiabatic silica microfiber for strain and temperature sensors

31 January 2013, 09:35:13

1 April 2013
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 192

A non-adiabatic silica microfiber is proposed for displacement or strain and high temperature sensing for the first time. The spectral response of the microfiber depends on the difference of the effective refractive indices of the core and the cladding modes, which induces resonant wavelength shift against the strain and temperature. It is observed that the peak wavelength of the transmitted comb spectrum is blue-shifted against displacement at a rate of 4.2pm/μm. The temperature sensitivity of the device was measured to be 12.1pm/°C with an excellent linearity for temperature measurement up to 800°C.

Highlights

► Non-adiabatic silica microfiber for strain and high temperature sensors. ► Strain and temperature variation induces resonant wavelength shift. ► Resonant wavelength is blue-shifted against displacement at a rate of 4.2pm/μm. ► Temperature sensitivity of the device was measured to be 12.1pm/°C.

Nanogaps controlled by liquid nitrogen freezing and the effects on hydrogen gas sensor performance

31 January 2013, 09:35:13

1 April 2013
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 192

A practical strategy for the reduction of nanogap width has been investigated using liquid nitrogen freezing of Pd-sputtered elastomeric substrates. Two types of hydrogen gas sensors, in which no pre-strain and 25% elongation were applied to Pd films on the elastomeric substrates, showed extremely low detection limits of less than 300 and 200ppm, respectively, after liquid nitrogen freezing and recovery to room temperature. For the non-strained sensors, the nanogap width was measured to be about 90nm, whereas it was more reduced to 25nm on the elongated sensors. Both sensors exhibited perfect On–Off switching, fast response, and good reversibility, which are based on the nanogap open–close mechanism upon exposure to hydrogen gas. These results provide a valuable clue for reducing nanogap width, thereby improving the hydrogen-sensing capabilities of nanogap-based On–Off hydrogen sensors.

TNT detection using a voltammetric electronic tongue based on neural networks

31 January 2013, 09:35:13

1 April 2013
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 192

We report here the use of a voltammetric electronic tongue based on simple metallic electrodes for the detection and discrimination of different concentrations of 2,4,6-trinitrotoluene (TNT) in acetonitrile:water 1:1 (v/v) mixtures. The tongue consisted of noble working electrodes made of iridium, rhodium, platinum and gold and non-noble electrodes including silver, copper, cobalt and nickel. Both the self-organizing map (SOM) and multi-layer feed-forward network (MLFN) neural networks were applied to the data obtained from the electronic tongue and TNT solutions. From SOM analysis it was established that a suitable response in terms of a correct classification of the TNT concentration was observed when using only noble metal electrodes and only 5 selected pulses. Similar good classifications were found when using MLFN. Moreover, the algorithm of neural network MLFN was embedded in a microcontroller in order to obtain a smart portable system for discrimination of TNT. In this case an R ² of 0.993 was obtained for predicted vs observed graphs of concentrations of TNT concentrations.

Oxford Instruments’ ‘Nanoscale Plasma Processing’ workshop at MTL, Cambridge, MA, USA was a great success

The first workshop organised by Oxford Instruments Plasma Technology at MIT’s Microsystems Technology Laboratories (MTL), Cambridge, MA in December was attended by a wide audience, and hailed a great success.  It addressed the latest research and technologies in plasma etch and deposition, via technical presentations and discussions focussing on latest innovations, as well as a networking lunch.

Dr. Vicky Diadiuk, Associate Director, Operations, at MTL, commented: ” This was an excellent workshop, and the talks presented a huge amount of very useful information, allowing our students and researchers to learn more about Atomic Layer Deposition and plasma processing from the experts, while also attracting participants from the wider technical community. Many of the attendees have reached out to tell me how much they learnt about the processes discussed. I think this is a really good way for Oxford Instruments to highlight the expertise of its staff.”

“We’ve been hosting these successful seminars worldwide for several years, and were delighted that such recognised speakers as Prof. Erwin Kessels, Technical University Eindhoven and Vince Genova, Cornell University agreed to participate. Their input, together with talks from our own specialists combined to make an informative and interesting day”, said Stuart Mitchell, VP Sales for Oxford Instruments America Inc, “These workshops provide an ideal opportunity for academic and industrial technologists to network and share ideas, and we are delighted to have held this joint workshop with the Microsystems Technology Laboratories.”

Presentations included talks on Atomic Layer Deposition (ALD) process and applications; an overview of plasma etch, PECVD & TEOS processes, as well MEMS & nanoscale applications. These are all key areas of expertise for Oxford Instruments. The company aims to meet its customers’ needs through advanced technology and service, and our global series of Seminars reinforce this.

Just Published: Talanta

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:

Talanta

http://rss.sciencedirect.com/publication/science/5288

Selected papers from the latest issue:

Multi-residue method for the determination of 16 recently used pesticides from various chemical groups in aqueous samples by using DI-SPME coupled with GC–MS

30 January 2013, 00:23:33

30 March 2013
Publication year: 2013
Source:Talanta, Volume 107

A simple and solvent-free multi-residue method has been optimized to determine 16 currently used pesticides from different chemical groups in aqueous samples. The extraction of analytes was carried out with direct immersion solid-phase microextraction (DI-SPME) and for the identification and quantitative determination gas chromatography coupled with mass spectrometry (GC–MS) was applied. Two commonly used adsorbent coatings have been applied and compared: 100μm of polydimethylsiloxane (PDMS) and 85μm of polyacrylate (PA). The method development parameters of DI-SPME, analyte desorption and GC–MS analysis have been outlined along with the final experimental conditions. When the optimum extraction conditions were applied (extraction time 60min, 10% (w/v) NaCl solution, 45°C) the limits of detection (LODs) were in the range of 0.015–0.13μgL⁻¹ and the relative standard deviations (RSDs) were between 1.9 and 9.6%. The developed analytical method was successfully applied to the analysis of natural water samples from the following sources: river, sea, canal and rain.

Highlights

► In this study DI-SPME–GC–MS methodology was developed. ► The 100μm of PDMS and 85μm of PA fibers were applied and compared. ► Sixteen recently used pesticides from various chemical groups were determined. ► Method was validated and applied to the analysis of water samples. ► Methodology is a valuable tool for monitoring selected pesticides in water samples.

On-line microwave-based preconcentration device for inductively coupled plasma atomic emission spectrometry: Application to the elemental analysis of spirit samples

30 January 2013, 00:23:33

30 March 2013
Publication year: 2013
Source:Talanta, Volume 107

A microwave-based thermal nebulizer (MWTN) has been employed for the first time as on-line preconcentration device in inductively coupled plasma atomic emission spectrometry (ICP-AES). By the appropriate selection of the experimental conditions, the MWTN could be either operated as a conventional thermal nebulizer or as on-line analyte preconcentration and nebulization device. Thus, when operating at microwave power values above 100W and highly concentrated alcohol solutions, the amount of energy per solvent mass liquid unit (EMR) is high enough to completely evaporate the solvent inside the system and, as a consequence, the analyte is deposited (and then preconcentrated) on the inner walls of the MWTN capillary. When reducing the EMR to the appropriate value (e.g., by reducing the microwave power at a constant sample uptake rate) the retained analyte is swept along by the liquid-gas stream and an analyte-enriched aerosol is generated and next introduced into the plasma cell. Emission signals obtained with the MWTN operating in preconcentration-nebulization mode improved when increasing preconcentration time and sample uptake rate as well as when decreasing the nozzle inner diameter. When running with pure ethanol solution at its optimum experimental conditions, the MWTN in preconcentration-nebulization mode afforded limits of detection up to one order of magnitude lowers than those obtained operating the MWTN exclusively as a nebulizer. To validate the method, the multi-element analysis (i.e. Al, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Na, Pb and Zn) of different commercial spirit samples in ICP-AES has been performed. Analyte recoveries for all the elements studied ranged between 93% and 107% and the dynamic linear range covered up to 4 orders of magnitude (i.e. from 0.1 to 1000μgL⁻¹). In these analysis, both MWTN operating modes afforded similar results. Nevertheless, the preconcentration-nebulization mode permits to determine a higher number of analytes due to its higher detection capabilities.

Highlights

► Microwave-based preconcentration procedure. ► On-line preconcentration and/or nebulization device for ICP-AES. ► Elemental trace and ultra-trace analysis of spirit samples.

Novel application of pyronin Y fluorophore as high sensitive optical sensor of glucose in human serum

30 January 2013, 00:23:33

30 March 2013
Publication year: 2013
Source:Talanta, Volume 107

This paper presents a novel, high sensitive, facile and rapid spectrofluorimetric method for the direct assessment of glucose in human serum samples. The strong fluorescence intensity of pyronin Y (PY) is found to be selectively quenched substantially by adding solutions of glucose. Therefore, a new quantitative method to determine glucose could be developed. The noticeable and specific quenching effect of glucose on PY emission could be attributed to the increase in the nonradiative interactions as a result of a charge-transfer excited state with the location of the positive charge at the xanthenes moiety. Various parameters namely, the best working solvent, the proper pH medium in addition to the concentration of PY fluorophore corresponding to maximum fluorescence intensity were closely investigated. Under optimal conditions, the standard curve was linear in the glucose concentration ranges from 5.0×10⁻⁹ to 1.0×10⁻⁶ molL⁻¹ (r=0.994). The detection limit (S:N=3) (LOD) is 2.9×10⁻⁹ molL⁻¹. Validation of this approach was done by examining glucose concentration in serum samples of twenty patient and ten health donors. Achieved recovery reached 99.63–100.43% and 99.57–100.70%, respectively, in good agreement with those provided from hospital using traditional method. The relative standard deviations (RSD) were estimated between 0.00–0.78% and 0.15–1.91%, respectively.

Highlights

► A novel spectrofluorimetric determination of glucose is established. ► It added a novel function of pyronin Y(PY) as a viable glucose fluorimetric probe. ► The method reveals glucose selective and substantial quenching of PY fluorescence. ► The method is rapid, facile, sensitive, interference free and reproducible.

Development of ultrasensitive direct chemiluminescent enzyme immunoassay for determination of aflatoxin B1 in food products

30 January 2013, 00:23:33

30 March 2013
Publication year: 2013
Source:Talanta, Volume 107

A direct competitive chemiluminescent enzyme-linked immunosorbent assay (CL-ELISA) for determination of aflatoxin B1 (AFB1) was developed. To improve the assay sensitivity, a mixture of 3-(10′-phenothiazinyl)-propane-1-sulfonate and 4-morpholinopyridine previously optimized by a factorial design was used as enhancer of horseradish peroxidase-induced chemiluminescence. Varying the concentrations of the coating anti-AFB1 antibody and conjugate of AFB1 and horseradish peroxidase the conditions of the chemiluminescent assay were optimized. The values of the detection limit value and dynamic working range of CL-ELISA of AFB1 were 0.0015ngmL⁻¹ and 0.003–0.03ngmL⁻¹, respectively. It was shown that a dilution of rice and mung beans extracts in 5 and 10 times, respectively, prevented a matrix effect of the food products in CL-ELISA. The recovery values from the spiked samples of rice and mung beans were in the range of 90–104% and 102–117%, respectively. Studying 8 rice and 8 mung beans samples purchased in commercial stores the developed CL-ELISA allowed to find 3 samples (1 rice and 2 mung beans) containing AFB1, the content of AFB1 in one sample being higher than the maximum acceptable level established in the European Community.

Highlights

► A direct competitive chemiluminescent ELISA for determination of aflatoxin B1 was developed. ► To improve the assay sensitivity a mixture of SPTZ and MORPH was used as chemiluminescence enhancer. ► Values of the LDL and working range of CL-ELISA of AFB1 were 0.0015ngmL⁻¹ and 0.003–0.03ngmL⁻¹. ► The content of AFB1 in commercial samples of rice and mung beans was estimated.

Facile synthesis of titania nanoparticles coated carbon nanotubes for selective enrichment of phosphopeptides for mass spectrometry analysis

30 January 2013, 00:23:33

30 March 2013
Publication year: 2013
Source:Talanta, Volume 107

In this work, titania nanoparticles coated carbon nanotubes (denoted as CNTs/TiO2 composites) were synthesized through a facile but effective solvothermal reaction using titanium isopropoxide as the titania source, isopropyl alcohol as the solvent and as the basic catalyst in the presence of hydrophilic carbon nanotubes. Characterizations using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) indicate that the CNTs/TiO2 composites consist of CNT core and a rough outer layer formed by titania nanoparticles (5–10nm). Measurements using wide angle X-ray diffraction (WAXRD), zeta potential and N2 sorption reveal that the titania shell is formed by anatase titania nanoparticles, and the composites have a high specific surface area of about 104m²/g. By using their high surface area and affinity to phosphopeptides, the CNTs/TiO2 composites were applied to selectively enrich phosphopeptides for mass spectrometry analysis. The high selectivity and capacity of the CNTs/TiO2 composites have been demonstrated by effective enrichment of phosphopeptides from digests of phosphoprotein, protein mixtures of β-casein and bovine serum albumin, human serum and rat brain samples. These results foresee a promising application of the novel CNTs/TiO2 composites in the selective enrichment of phosphopeptides.

Highlights

► Titania nanoparticles coated carbon nanotubes were synthesized via simple hydroythermal reaction. ► The materials were characterized by SEM, TEM and XRD. ► The materials were successfully applied to selective enrichment of phosphopeptides in real samples.

Evaluation of the uncertainty associated with the off line HPLC–GC(FID) determination of 4-desmethyl sterols in vegetable oils

30 January 2013, 00:23:33

30 March 2013
Publication year: 2013
Source:Talanta, Volume 107

This paper discusses the estimation of the uncertainty of the chromatographic determination of 4-desmethyl sterols in vegetable oils, combining the off line HPLC fractionation of the analytes, from the unsaponifiable fraction of the samples, with their determination as TMS derivatives by GC(FID), using the data obtained from a single internal calibration (one surrogate) at one level and “bottom up” approach. The methodology used, makes possible to identify the main uncertainty contributions, find their origins, and reduce them. The final results show that the main contributions to the relative overall uncertainty are those closely related with the chemical aspects of the method, i.e. those related to derivatization reaction and quantification of the analytes, although others aspects, such as the addition of a mass of surrogate, are not negligible.

Highlights

► Uncertainty of determination of 4-desmethyl sterols in vegetable oils is estimated. ► From Bottom-up strategy Ishikawa diagram for identification of the sources is used. ► The methodology implies HPLC fractionation of sterols-quantification by GC(FID). ► The main source arises from chemical stages as derivatization and quantification.

A flow-batch analyzer using a low cost aquarium pump for classification of citrus juice with respect to brand

30 January 2013, 00:23:33

30 March 2013
Publication year: 2013
Source:Talanta, Volume 107

This paper proposes a novel flow-batch analyzer (FBA), which employs a compact, low-cost aquarium air pump as an alternative to a peristaltic pump. The feasibility of using this simple propulsion device is demonstrated in a case study involving the classification of citrus juice samples with respect to brand. For this purpose, UV–vis spectra and SIMCA (soft independent modelling of class analogies), PLS-DA (Partial Least Squares for Discriminant Analysis) and SPA-LDA (Linear Discriminant Analysis with variables selected by the Successive Projections Algorithm) are employed. Good classification results were obtained, thus indicating that the proposed FBA system is a viable alternative to the use of more costly peristaltic pumps. In addition, the smaller size and weight of the aquarium pump are useful features for the construction of portable FBAs to be deployed in field applications.

Highlights

► Novel flow-batch analyzer using a compact, low-cost aquarium pump instead of a peristaltic pump. ► Classification of citrus juice samples with respect to brand on the basis of UV–vis spectra. ► Multivariate classification employing SIMCA, PLS-DA and SPA-LDA. ► Correct classification of all samples by using the proposed flow-batch analyzer.

Disposable terbium (III) salicylate complex imprinted membrane using solid phase surface fluorescence method for fast separation and detection of salicylic acid in pharmaceuticals and human urine

30 January 2013, 00:23:33

30 March 2013
Publication year: 2013
Source:Talanta, Volume 107

In this work, a simple, low cost, selective and sensitive complex imprinted membrane (CIM) for solid-phase fluorescent detection was developed with terbium (III) salicylate as complex template. Terbium-sensitized luminescence was employed for monitoring salicylic acid (SA) based on the fluorescence enhancement effect of benzoic acid derivatives on lanthanide ion Tb (III). The resulting CIM showed good fluorescent response and high selectivity towards SA with Tb as pivot in protic solvents, while demonstrating better analytical performance than the controlled membranes. The optimized adsorption time was 10min, indicating rapid kinetics of the imprinted membrane. The linear response of CIM to SA was from 0.20 to 10mg/L with limit of detection (LOD) of 0.040mg/L. The prepared CIM was successfully applied to the analysis of salicylic acid in pharmaceuticals and spiked human urine with recoveries of 80.6%–88.1%. The analytical results of the proposed method were in good agreement with those obtained by high performance liquid chromatography (HPLC) method, indicating that the developed membrane has acceptable practicability for fast determination of SA in real samples.

Highlights

► A simple, fast and disposable metal complex imprinted membrane was fabricated. ► The CIM was used for detection of salicylic acid on solid phase surface fluorescence. ► Novel method was suitable for rapid analysis of salicylic acid in real samples.

A sensitive enzymeless sensor for hydrogen peroxide based on the polynucleotide-templated silver nanoclusters/graphene modified electrode

30 January 2013, 00:23:33

30 March 2013
Publication year: 2013
Source:Talanta, Volume 107

A novel, sensitive and enzymeless electrochemical sensor based on polynucleotide-templated silver nanoclusters (DNA-AgNCs)/graphene composite film was developed for the detection of hydrogen peroxide. The graphene modified glassy carbon electrode (GCE) was employed because graphene has several advantages including excellent conductivity, biocompatibility, and large surface area to volume ratio. In addition, it was found that DNA-AgNCs have remarkable electrocatalytic activity toward the reduction of hydrogen peroxide, and can be easily immobilized onto the surface of the graphene/GCE by π–π stacking. The sensor based on the (DNA-AgNCs)/graphene/GCE exhibited a rapid response (ca. 3s), a low detection limit (3μM), a wide linear range from 15μM to 23mM, high selectivity, as well as good repeatability. Moreover, the common interfering species, such as ascorbic acid, uric acid, dopamine, glutathione, and l-cysteine, did not result in any interference. This present work may expand the use of silver nanoclusters in the field of electrochemical sensor.

Highlights

► We fabricated the electrochemical sensor with simplicity and high sensitivity. ► DNA-AgNCs were simply synthesized and assembled onto graphene by π–π stacking. ► DNA-AgNCs possess enhanced electrocatalysis toward the reduction of H2O2. Graphene was electrodeposited onto the glassy carbon electrode. ► Graphene is useful for the immobilization of more DNA-AgNCs onto the electrode.

Determination of cadmium in tobacco by solid surface fluorescence using nylon membranes coated with carbon nanotubes

30 January 2013, 00:23:33

30 March 2013
Publication year: 2013
Source:Talanta, Volume 107

A new methodology based on fluorescent signal enhancement of o-cresolphthalein (o-CPT) for traces of cadmium determination is proposed. The dye was retained on membrane filters in the presence of a micellar surfactant solution of carbon nanotubes (CNTs). All the experimental variables that influence both the preconcentration procedure and the fluorimetric sensitivity were carefully optimized. The calibration graph using zeroth order regression was linear from 6.5ngL⁻¹ to 5.65×10⁵ ngL⁻¹, with a correlation coefficient higher than 0.999. Under optimal conditions, the limits of detection and quantification were of 2ngL⁻¹ and 6.5ngL⁻¹. respectively. The proposed method showed good sensitivity and selectivity, with good tolerance to foreign ions, and it was applied to the determination of trace amounts of cadmium in leachate from cigarettes' tobacco samples with satisfactory results. The trueness of the recommended procedure was assessed through parallel analysis of the samples with electrothermal atomization atomic absorption spectrometry. This methodology represents an innovative and attractive application of membrane filters that enables metal traces determination by solid surface fluorescence.

Highlights

► New methodology for cadmium traces determination in tobacco samples. ► Carbon nanotube have been used for improve the sensitivity of fluorescent detection. ► It is an important contribution at green chemistry. ► This methodology showing good reproducibility with low operation cost. ► It uses non-polluting solvents preserving the analyte and the environment.

Automated Humidity Control for FlexStream™ Calibration Gas Generator

Kin-Tek has added an Automated Humidity Control option to the FlexStream™ Modular Gas Standards Generating System. Adding humidity allows simulation of real sample streams.

The FlexStream™ System dilutes the emission from permeation or diffusion tubes with an inert gas, typically nitrogen or zero air, to create trace concentration – ppm, ppb and pptr – gas mixtures. An internal microprocessor sets the operating mode and adjusts dilution flow to achieve the required concentrations.

The FlexStream™ HG fits into the system as the end module. A portion of the inert dilution gas is saturated with water and mixed with dry, trace component carrying gas to form the humidified mixture. Humidity is adjusted by varying the ratio of wet to dry gas. Typically, values from 20% RH to about 90% RH can be achieved. 

The system can also be controlled remotely by a PC or process computer using Modbus® connectivity. 

New Supercritical Fluid Extractor for the Processing of Natural Products

Supercritical Fluid Technologies (SFT) is pleased to introduce a new pilot scale supercritical extractor for the processing of natural products. The SFT-NPX-10 is designed to simplify the extraction of a wide variety of natural products, and to facilitate the transition from laboratory scale equipment to production processing systems.

The SFT-NPX-10 is designed to perform supercritical fluid extractions in either single or dual 10 Liter sample vessels with single or dual separators, resulting in maximum efficiency. A Coriolis mass flow meter guarantees precise mass flow measurement. A pneumatic CO2 pump with an integral waterless pre-chiller (patent pending) is used to maximize pumping efficiency. Upgrade to an RIO programmable automation controller for automated regulation for pressure, temperature and process cycles.

Using supercritical CO2 to perform extractions on botanicals, herbs, spices and other natural product materials has significant benefits over the use of traditional liquid solvents. While the supercritical fluid possesses many of the same characteristics of a liquid solvent, it adds the benefits of high diffusivity and pressure tunable solvency power. Additionally, no residual solvents are in either the extract or remaining biomass. There is no need to perform a distillation step since, upon dropping pressure, the CO2 becomes a gas. The extracted material is pure and in its natural state. The CO2 may be safely vented or optionally recycled for even greater efficiency. Since the solvency power of the fluid is pressure dependent, it is possible to “fractionate” to obtain multiple compositions from a single raw material. This makes practical some separations that are difficult or impossible to do with traditional liquid solvent and distillation processing.

Just Published: Journal of Analytical and Applied Pyrolysis

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:

Journal of Analytical and Applied Pyrolysis
http://rss.sciencedirect.com/publication/science/5247

Selected papers from the latest issue:

Hydrotreating of Low Temperature Coal Tar to Produce Clean Liquid Fuels

29 January 2013, 09:48:43

Available online 24 January 2013
Publication year: 2013
Source:Journal of Analytical and Applied Pyrolysis

Clean liquid oil was obtained from low temperature coal tar (LCT) via hydrotreating in trickle-bed reactor (TBR) system filled with commercial catalysts. The effects of hydrogen pressure (10–16MPa), reactor temperature (350–410°C) and liquid hourly space velocity (LHSV) (0.25–1h⁻¹) on hydrotreating performance were investigated while hydrogen to oil volume ratio was maintained constant at 1600 LN/L in all cases. The degree of sulfur removal was greater than nitrogen removal with increasing temperature, pressure and contact time over the commercial catalyst. The TBR system was capable of removing nitrogen and sulfur from 1.14 and 0.34wt % in the feed to 63μg·g⁻¹ and 8μg·g⁻¹, respectively in the products. Gasoline (<180°C) and diesel (180–360°C) fraction were separated from the oil products and analyzed. The gasoline fraction produced from LCT by hydrotreating comply with gasoline specifications for distillation range, sulfur content, induction period and gum presence. But it did not meet the specifications for RON (Research Octane Number) specifications. Diesel fraction produced from LCT meet all quality tests as fuels which could be directly used as motor fuels without upgrading. The results indicated that the raw LCT could be considerably upgraded through catalytic hydrotreating and high-quality fuels were obtained.

Highlights

► Clean liquid oil was obtained from low temperature coal tar (LCT) via hydrotreating in trickle-bed reactor (TBR) system filled with commercial catalysts. ► The TBR system was capable of removing nitrogen and sulfur from 1.14 and 0.34wt % in the feed to 63μg·g⁻¹ and 8μg·g⁻¹, respectively in the products. ► Gasoline (<180°C) and diesel (180–360°C) fraction were separated from the hydrotreating products. Gasoline fraction has an aromatics content that is much less than its straight-run equivalent derived from crude oil, being a good feedstock for catalytic reforming. Diesel fraction meet all quality tests as fuels which could be directly use as motor fuels without upgrading.

Adsorption of p-chlorophenol onto microporous activated carbon from Albizia lebbeck seed pods by one-step microwave assisted activation

29 January 2013, 09:48:43

Available online 24 January 2013
Publication year: 2013
Source:Journal of Analytical and Applied Pyrolysis

Agricultural wastes, Albizia lebbeck seed pods, have been utilized as precursors for production of a microporous activated carbon using one step microwave assisted K2CO3 activation. The sorption performance of prepared carbon for p-chlorophenol (PCPh) was investigated by batch adsorption technique. Effects of radiation time, radiation power, and impregnation ratio on the sorption performance were studied to determine the best preparation conditions. Carbon with 26.2% yield and 247.9mg/g PCPh uptake has been obtained at conditions of 8min radiation time, 540W radiation power and 1.5g/g impregnation ratio. The surface area, micropore volume, and mesopore volume of prepared carbon at best conditions were 1676.6 m²/g, 0.527cm³/g, and 0.181cm³/g, respectively. The best fitting for PCPh equilibrium isotherm data was achieved by the three-parameter Sips isotherm with a maximum adsorption capacity of 300.6mg/g. The experimental kinetic data were well represented by the pseudo-second order model.

Highlights

► Microporous carbon was prepared from Albizia lebbek seed pods. ► One-step microwave activation was adopted for preparation. ► High surface area of 1676.6 m²/g was characterized. ► Maximum capacity of 300.6mg/g was reported for p-chlorophenol. ► Sorption mechanisms of p-chlorophenol were illustrated.

Experimental and theoretical studies of pyrolysis of chrysophanol and its derivatives

29 January 2013, 09:48:43

Available online 23 January 2013
Publication year: 2013
Source:Journal of Analytical and Applied Pyrolysis

Rhubarb has been used as a tobacco additive recently. In order to understand the smoke emissions of herbal cigarettes with rhubarb additive, the pyrolysis of major components of rhubarb: chrysophanol and its derivatives (emodin, rhein and aloe-emodin) have been studied by synchrotron VUV photoionization mass spectrometry (SVUV-PIMS) combined with molecular-beam sampling technique. Various pyrolysis products are observed due to the different substituent groups. The main pyrolysis products of chrysophanol come from the CO and H2O elimination reactions. The CO, CO2 and HCOOH elimination reactions are the primary pyrolysis processes for rhein. Besides, elimination of H2 from aloe-emodin and loss of OH radical from both emodin and rhein also occur in the pyrolysis process. Furthermore, theoretical calculations are used to deduce the decomposition pathways and determine the geometries of pyrolysis products. Our work shows that the combination of SVUV-PIMS measurements and theoretical calculations is powerful to study pyrolysis behavior of complex organic compounds.

Highlights

► Pyrolysis behavior of chrysophanol and its derivatives was studied by SVUV-PIMS. ► Tunable SVUV photoionization benefits the measurement of pyrolytic products. ► The initial formation temperatures of all pyrolytic products have been determined. ► Theoretical calculations validated the decomposition pathways of studied compounds. ► SVUV-PIMS combined theoretical calculations perform well in pyrolysis analysis.

Use of thermogravimetry for single characterisation of samples of the composting process from sewage sludge

29 January 2013, 09:48:43

Available online 23 January 2013
Publication year: 2013
Source:Journal of Analytical and Applied Pyrolysis

Pyrolysis and combustion of different samples from a sewage sludge composting tunnel plant were studied by thermogravimetry. Two series of samples were analyzed: initially, 8 samples were taken at 8 different points from different stages of the process; later, 5 samples from different points at the end of the composting tunnel were taken. The experiments were carried out at 10°Cmin⁻¹, in N2 atmosphere and N2:O2 4:1 atmosphere. The results were discussed to analyze the heterogeneity of the samples. In addition, the compositions of the samples taken for the analysis were deduced using the decomposition kinetics as correlation of weight loss vs. time. The fractions considered were sewage sludge, straw and sawdust. The compositions deduced were compared with the toxicity concentration of dioxins, in order to analyze the possible variations of toxicity determined.

Highlights

► TG, DTG and kinetics have been useful for analyzing the uniformity. ► The determination of dioxin concentration in compost samples is not easy. ► There is a great variation of dioxin concentration in similar samples.

Formation of nanoporous carbon materials in conditions of thermocatalytic synthesis

29 January 2013, 09:48:43

Available online 23 January 2013
Publication year: 2013
Source:Journal of Analytical and Applied Pyrolysis

A study of the volatile products formed in the process of thermocatalytic destruction of a hardwood and the carbonizates on its basis in the presence and absence of acidic (H3PO4) and alkaline (NaOH) activators was performed by thermogravimetry/mass spectrometry (TG/MS) method. Ranges of formation temperatures and the amount of water and the main gaseous products were determined. It is shown that, in the case of activation with alkali, the chemical composition and structure of the precursor have a pronounced effect on the process. Nanoporous carbon materials with high indices of the porous structure were obtained.

Highlights

► Volatiles of wood and carbonizates catalytic destruction were tested by TG/MS ► H3PO4 and NaOH were used as activation agents ► Nanoporous activated carbons were synthesized ► Porous structure of activated carbons were tested by N2 sorption.

Thermal kinetic parameters and evolved gas analysis (TG-FTIR-MS) for thiourea-formaldehyde based polymer metal complexes

29 January 2013, 09:48:43

Available online 18 January 2013
Publication year: 2013
Source:Journal of Analytical and Applied Pyrolysis

Two polymer metal complexes with a general formula of TUF-M(II) (M=Co, Cu) were synthesized by the reaction of a thiourea-formaldehyde resin (TUF) and transition metal ions. The thermal degradation of TUF-M(II) was investigated using thermogravimetric analysis (TGA) and differential thermal analysis (DTA) during pyrolysis and combustion. The kinetic parameters for the thermal degradation were evaluated using the Coats–Redfern and Friedman equations. An evolved gas analysis (EAG) during the thermal decomposition of TUF-M(II) was performed for the pyrolysis and combustion up to 800°C using both online coupled TG-FTIR and simultaneous TG-MS. The emissions of CS2, NH3, SO2, COS, HCN, H2NCN and HNCS were identified during the thermal degradation of TUF-M(II). The total mass loss resulting from the pyrolysis of TUF-Cu(II) at 775°C was 73.26%, while 44.02% of the original mass was lost at 225°C - 325°C. The activation energy for the second stage of degradation of the combustion (189.2 KJ mol⁻¹, 184.5 KJ mol⁻¹) was higher than that of the pyrolysis (179.8 KJ mol⁻¹, 175.1 KJ mol⁻¹) at a similar stage for both complexes using the Coats-Redfern method.

Highlights

► The thermal degradation of TUF-M(II) was investigated using TGA and DTA technique. ► The thermal kinetic parameters during pyrolysis and combustion were evaluated using Coats–Redfern and Friedman equation. ► The evolved gas analysis (EAG) during thermal decomposition of polymer metal complexes was determined using TG-FTIR-MS technique.

The GRAUTHERMIC-Tyres process for the recycling of granulated scrap tyres

29 January 2013, 09:48:43

Available online 12 January 2013
Publication year: 2013
Source:Journal of Analytical and Applied Pyrolysis

The influence of thermolysis temperature (range 500–700°C) on the products produced from granulated scrap tyres (GST) (2–6mm Ø) in a semi-batch pilot plant that uses several fixed bed reactors in parallel (GRAUTHERMIC-Tyres^® process) was examined. This pilot unit consisted of six vertical fixed bed reactors in parallel, each with a capacity of 12kg GST. Thermolysis proceeded in a normal air atmosphere. The solid (char), liquid (tyre-derived oil [TDO]) and gaseous products generated at each temperature were characterised. The incondensable gas fraction was used to produce electricity via a gas turbine. The yields of the gas, TDO and char fractions were 15–22wt.%, 34–46wt.% and 39–44wt.% respectively, values that represent major recoveries from the GST feedstock. The TDOs were mainly a mixture of aliphatic and aromatic hydrocarbons and had very high GCVs (41–43MJ/kg), higher than those of conventional liquid fuels. A large increase was seen in the polycyclic aromatic hydrocarbon content above 550°C. The non-condensable gases obtained had a high GCV value (64–83MJ/Nm³), and produced 4.1–6.5kWhelectricity/g of GST in a gas turbine. The chars had a GCV of 27–28MJ/kg, high ash (17–21wt.%) and zinc contents, and an essentially macroporous texture with a low BET surface area (46–78m²/g). The thermolysis of GSTs with co-generation of gases by the GRAUTHERMIC-Tyres^® method would appear to be a viable means of valorising GST.

Highlights

► We performed the thermolysis of granulated scrap tyres in a pilot scale. ► We examine changes in the oils, gases and chars composition about temperature. ► We examine the electricity production in gas turbine.

Characteristics of activated carbon prepared from waste PET by carbon dioxide activation

29 January 2013, 09:48:43

Available online 11 January 2013
Publication year: 2013
Source:Journal of Analytical and Applied Pyrolysis

Poly(ethylene)terephthalate (PET) waste was subjected to carbonization in a nitrogen stream at 1098K. The coke was then activated in a carbon dioxide stream under various conditions: temperatures of 1173, 1198 and 1213K as well as process times of 4, 5, 6 and 8h. The activated carbons were characterized using various methods: the structure from Raman and XRD measurements, the porosity from low temperature nitrogen adsorption, the surface properties from cyclic voltammetry and the hydrogen storage capacity from the low temperature adsorption isotherm of H2. The results demonstrated the importance of the temperature and the duration of the process. Higher temperatures results in the etching of graphitic domains of better crystallinity. A relatively small increase in activation time at the highest temperature used yielded a significant increase in the degree of burn-off and porous structure development. The microporosity of these carbons is similar to that of commercial activated carbons. They also have a similar capacity to adsorb water pollutants (e.g. 4-chlorophenol). The PET carbon sample with maximum burn-off exhibited higher values of the microporous structure parameters and the electric double layer capacity in electrolyte solution than the other three samples. The same sample exhibits a sufficient hydrogen storage capacity, which after optimization of the activation conditions should yield an effective storage material. This confirms the possibility of producing activated carbon from waste PET with satisfactory properties by the simple processes of carbonization and activation. The activated carbons obtained have potential use as water pollutant adsorbents, low-cost materials for hydrogen storage and electrode materials in supercapacitors or fuel cells.

Highlights

► Activated carbon was obtained from waste PET by carbonization and activation. ► Its porous structure can be regulated by the temperature and/or activation time. ► It is a low-cost material for water pollutant adsorption and hydrogen storage. ► Another use is as an electrode material in supercapacitors or fuel cells.

Feasibility of monomer aromatic substances as calibration standards for lignin quantitative analyses in Pyrolysis-GCMS

29 January 2013, 09:48:43

Available online 11 January 2013
Publication year: 2013
Source:Journal of Analytical and Applied Pyrolysis

In this paper, the feasibilities of five different monomer aromatic substances as calibration standards by analytical pyrolysis with gas chromatographic separation and mass selective detection (Py-GC/MS) were applied for the quantification of lignin in paper and pulp. The stabilities of these substances in the pyrolysis process were evaluated and the curves of peak response area to mass also were obtained. The results showed that the substances with exact same substituions on the benzene ring as lignin units had good stablities in the pyrolysis process with good lineabilities of peak response area to the mass curves, which implicated these substances can be applied as calibration standards in the liginin quick quantitative analyse without tedious pretreatments and structure changes.

Highlights

► Good linearlities of selected monommers in GCMS without Pyrolysis ► Better stablities of monomers with same substitutions on the ring as lignin units ► Feasilble and reliable for lignin analyse with greater enthalpy calibration standards.

Thermal degradation and combustion behavior of reconstituted tobacco sheet treated with ammonium polyphosphate

29 January 2013, 09:48:43

Available online 5 January 2013
Publication year: 2013
Source:Journal of Analytical and Applied Pyrolysis

In this paper, the APP-modified reconstituted tobacco sheet (RTS) was prepared by a paper-making process. Thermogravimetric analysis coupled to Fourier transform infrared spectrometer (TG-FTIR) had been used to investigate the influences of APP on the thermal degradation and the formation of evolved volatile products of RTS. TG-FTIR results illustrated that the incorporation of APP into RTS could retard the thermal degradation of the major components of RTS and meanwhile lead to the formation of more thermally stable char. Moreover, the main gases released during the pyrolysis of RTS and APP-modified RTS were H2O, CO2, CO, NH3, carbonyl compounds, alcohols and alkanes. The presence of APP changed the formation of evolved volatile products of RTS obviously. The effects of APP on the combustion behavior of RTS were studied by micro-scale combustion calorimetry (MCC), cone calorimetry (CCO) and infrared thermography (IRT). Results demonstrated that the formation of combustible gases was mainly determined by the thermal decomposition stage occurred in the temperature range of 150–600°C. The incorporation of APP into RTS influenced the release of fuel gases and the char formation in the process of the thermal decomposition of RTS, and eventually retarded the flammability of RTS. In addition, it had been found that the maximum firecone temperature of untreated RTS was higher than that of APP-modified RTS.

Highlights

► The APP-modified reconstituted tobacco sheet (RTS) has been prepared successfully by a paper-making process. ► APP can retard the thermal degradation of the major components of RTS and change the formation of evolved volatile products of RTS obviously. ► APP can influence the release of fuel gases and the char formation in the process of the thermal decomposition of RTS, and thus retard the flammability of RTS.

Properties of spray deposited Cu2ZnSnS4 (CZTS) thin films

29 January 2013, 09:48:43

Available online 5 January 2013
Publication year: 2013
Source:Journal of Analytical and Applied Pyrolysis

A new solar absorber material, Cu2ZnSnS4 (CZTS) in thin film form has been deposited onto glass substrates using spray pyrolysis technique. The thickness dependent (244–754nm) structural, morphological, optical and electrical properties of CZTS films have been studied. The X–ray diffraction studies revealed the formation of polycrystalline CZTS films. The surface morphological studies revealed the formation of smooth, compact and uniform CZTS surface. Absorption coefficient was of the order of 10⁴ cm⁻¹ and depending on film thickness the direct transition was observed with band gap in the range from 1.6 to 1.67eV. The thermoemf measurement revealed that the CZTS films exhibit p–type electrical conductivity.

Highlights

► Detail film formation mechanisms of CZTS thin film. ► Simple and inexpensive method is for the synthesis of CZTS films. ► The Structural, morphological and optical properties. ► In the present manuscript, the work is novel in the context that for the first time, the effect of different film thickness [244-754nm] on physicochemical properties of CZTS thin films.