Fast cholesterol detection using flow injection microfluidic device with functionalized carbon nanotubes based electrochemical sensor.

Science.gov (United States)

Wisitsoraat, A; Sritongkham, P; Karuwan, C; Phokharatkul, D; Maturos, T; Tuantranont, A

2010-12-15

This work reports a new cholesterol detection scheme using functionalized carbon nanotube (CNT) electrode in a polydimethylsiloxane/glass based flow injection microfluidic chip. CNTs working, silver reference and platinum counter electrode layers were fabricated on the chip by sputtering and low temperature chemical vapor deposition methods. Cholesterol oxidase prepared in polyvinyl alcohol solution was immobilized on CNTs by in-channel flow technique. Cholesterol analysis based on flow injection chronoamperometric measurement was performed in 150-μm-wide and 150-μm-deep microchannels. Fast and sensitive real-time detection was achieved with high throughput of more than 60 samples per hour and small sample volume of 15 μl. The cholesterol sensor had a linear detection range between 50 and 400 mg/dl. In addition, low cross-sensitivities toward glucose, ascorbic acid, acetaminophen and uric acid were confirmed. The proposed system is promising for clinical diagnostics of cholesterol with high speed real-time detection capability, very low sample consumption, high sensitivity, low interference and good stability. Copyright © 2010 Elsevier B.V. All rights reserved.

Amperometric glucose biosensor based on glucose oxidase dispersed in multiwalled carbon nanotubes/graphene oxide hybrid biocomposite

International Nuclear Information System (INIS)

Palanisamy, Selvakumar; Cheemalapati, Srikanth; Chen, Shen-Ming

2014-01-01

An amperometric glucose biosensor based on enhanced and fast direct electron transfer (DET) of glucose oxidase (GOx) at enzyme dispersed multiwalled carbon nanotubes/graphene oxide (MWCNT/GO) hybrid biocomposite was developed. The fabricated hybrid biocomposite was characterized by transmission electron microscopy (TEM), Raman and infrared spectroscopy (IR). The TEM image of hybrid biocomposite reveals that a thin layer of GOx was covered on the surface of MWCNT/GO hybrid composite. IR results validate that the hybrid biocomposite was formed through the electrostatic interactions between GOx and MWCNT/GO hybrid composite. Further, MWCNT/GO hybrid composite has also been characterized by TEM and UV–visible spectroscopy. A pair of well-defined redox peak was observed for GOx immobilized at the hybrid biocomposite electrode than that immobilized at the MWCNT modified electrode. The electron transfer rate constant (K s ) of GOx at the hybrid biocomposite was calculated to be 11.22 s −1 . The higher K s value revealed that fast DET of GOx occurred at the electrode surface. Moreover, fabricated biosensor showed a good sensitivity towards glucose oxidation over a linear range 0.05–23.2 mM. The limit of detection (LOD) was estimated to be 28 μM. The good features of the proposed biosensor could be used for the accurate detection of glucose in the biological samples. - Highlights: • An amperometric glucose biosensor has been developed at MWCNT/GO hybrid biocomposite. • Enhanced and fast direct electron transfer kinetics of glucose oxidase has been achieved at hybrid biocomposite. • Hybrid biocomposite has been characterized by TEM, IR and Raman spectroscopy. • Highly sensitive and selective for glucose determination

Amperometric glucose biosensor based on glucose oxidase dispersed in multiwalled carbon nanotubes/graphene oxide hybrid biocomposite

Energy Technology Data Exchange (ETDEWEB)

Palanisamy, Selvakumar; Cheemalapati, Srikanth; Chen, Shen-Ming, E-mail: smchen78@ms15.hinet.net

2014-01-01

An amperometric glucose biosensor based on enhanced and fast direct electron transfer (DET) of glucose oxidase (GOx) at enzyme dispersed multiwalled carbon nanotubes/graphene oxide (MWCNT/GO) hybrid biocomposite was developed. The fabricated hybrid biocomposite was characterized by transmission electron microscopy (TEM), Raman and infrared spectroscopy (IR). The TEM image of hybrid biocomposite reveals that a thin layer of GOx was covered on the surface of MWCNT/GO hybrid composite. IR results validate that the hybrid biocomposite was formed through the electrostatic interactions between GOx and MWCNT/GO hybrid composite. Further, MWCNT/GO hybrid composite has also been characterized by TEM and UV–visible spectroscopy. A pair of well-defined redox peak was observed for GOx immobilized at the hybrid biocomposite electrode than that immobilized at the MWCNT modified electrode. The electron transfer rate constant (K{sub s}) of GOx at the hybrid biocomposite was calculated to be 11.22 s{sup −1}. The higher K{sub s} value revealed that fast DET of GOx occurred at the electrode surface. Moreover, fabricated biosensor showed a good sensitivity towards glucose oxidation over a linear range 0.05–23.2 mM. The limit of detection (LOD) was estimated to be 28 μM. The good features of the proposed biosensor could be used for the accurate detection of glucose in the biological samples. - Highlights: • An amperometric glucose biosensor has been developed at MWCNT/GO hybrid biocomposite. • Enhanced and fast direct electron transfer kinetics of glucose oxidase has been achieved at hybrid biocomposite. • Hybrid biocomposite has been characterized by TEM, IR and Raman spectroscopy. • Highly sensitive and selective for glucose determination.

Enhancement of the water flow velocity through carbon nanotubes resulting from the radius dependence of the friction due to electron excitations

Science.gov (United States)

Sokoloff, J. B.

2018-03-01

Secchi et al. [Nature (London) 537, 210 (2016), 10.1038/nature19315] observed a large enhancement of the permeability and slip length in carbon nanotubes when the tube radius is of the order of 15 nm, but not in boron nitride nanotubes. It will be pointed out that none of the parameters that appear in the usual molecular dynamics treatments of water flow in carbon nanotubes have a length scale comparable to 15 nm, which could account for the observed flow velocity enhancement. It will be demonstrated here, however, that if the friction force between the water and the tube walls in carbon nanotubes is dominated by friction due to electron excitations in the tube walls, the enhanced flow can be accounted for by a reduction in the contribution to the friction due to electron excitations in the wall, resulting from the dependence of the electron energy band gap on the tube radius.

Electrochemical evaluation of the a carbon-paste electrode modified with spinel manganese(IV) oxide under flow conditions for amperometric determination of lithium

International Nuclear Information System (INIS)

Raymundo-Pereira, Paulo A.; Martin, Cibely S.; Bergamini, Marcio F.; Bocchi, Nerilso; Teixeira, Marcos F.S.

2011-01-01

The participation of cations in redox reactions of manganese oxides provides an opportunity for development of chemical sensors for non-electroactive ions. This paper describes the amperometric determination of lithium ions using carbon-paste electrode modified with spinel manganese(IV) oxide under flow conditions. Systematic investigations were made to optimize the experimental parameters for lithium sensor by flow injection analysis. The detection was based on the measurement of anodic current generated by oxidation of Mn(III) to Mn(IV) at the surface of the electrode and consequently the lithium ions extraction into the spinel structure. An operating potential of 0.50 V (vs. Ag/AgCl/3 KCl mol/L) was exploited for amperometric monitoring. The amperometric signal was linearly dependent on the lithium ions concentration over the range 4.0 x 10 -5 to 1.0 x 10 -3 mol L -1 . The equilibrium constant of insertion/extraction of the lithium ion in the spinel structure, apparent Gibbs energy of insertion, and surface coverage of the electrode with manganese oxide, were calculated by peak charge (Q) in different concentration under flow conditions. Considering selectivity, the peak charge of the sensor was found to be linearly dependent on the ionic radius of the alkaline and earth-alkaline cations.

Determination of Patulin Using Amperometric Tyrosinase Biosensors Based on Electrodes Modified with Carbon Nanotubes and Gold Nanoparticles

Directory of Open Access Journals (Sweden)

R.M. Varlamova

2016-06-01

Full Text Available New amperometric biosensors based on platinum screen printed electrodes modified with multi-walled carbon nanotubes, gold nanoparticles, and immobilized enzyme – tyrosinase have been developed for determination of patulin in the concentrations of 1·10–6 – 8·10–12 mol/L with an error of no more than 0.063. The best conditions for obtaining gold nanoparticles have been chosen. The conditions for immobilization of multi-walled carbon nanotubes and gold nanoparticles on the surface of the planar electrode have been revealed. The conditions for functioning of the proposed biosensors have been identified. The results have been used to control the content of patulin in food products within and lower than the maximum allowable levels.

Flow-injection amperometric determination of glucose using a biosensor based on immobilization of glucose oxidase onto Au seeds decorated on core Fe₃O₄ nanoparticles.

Science.gov (United States)

Samphao, Anchalee; Butmee, Preeyanut; Jitcharoen, Juthamas; Švorc, Ľubomír; Raber, Georg; Kalcher, Kurt

2015-09-01

An amperometric biosensor based on chemisorption of glucose oxidase (GOx) on Au seeds decorated on magnetic core Fe3O4 nanoparticles (Fe3O4@Au) and their immobilization on screen-printed carbon electrode bulk-modified with manganese oxide (SPCE{MnO2}) was designed for the determination of glucose. The Fe3O4@Au/GOx modified SPCE{MnO2} was used in a flow-injection analysis (FIA) arrangement. The experimental conditions were investigated in amperometric mode with the following optimized parameters: flow rate 1.7 mL min(-1), applied potential +0.38 V, phosphate buffer solution (PBS; 0.1 mol L(-1), pH 7.0) as carrier and 3.89 unit mm(-2) enzyme glucose oxidase loading on the active surface of the SPCE. The designed biosensor in FIA arrangement yielded a linear dynamic range for glucose from 0.2 to 9.0 mmol L(-1) with a sensitivity of 2.52 µA mM(-1) cm(-2), a detection limit of 0.1 mmol L(-1) and a quantification limit of 0.3 mmol L(-1). Moreover, a good repeatability of 2.8% (number of measurements n=10) and a sufficient reproducibility of 4.0% (number of sensors n=3) were achieved. It was found that the studied system Fe3O4@Au facilitated not only a simpler enzyme immobilization but also provided wider linear range. The practical application of the proposed biosensor for FIA quantification of glucose was tested in glucose sirup samples, honeys and energy drinks with the results in good accordance with those obtained by an optical glucose meter and with the contents declared by the producers. Copyright © 2015. Published by Elsevier B.V.

On phonons and water flow enhancement in carbon nanotubes

DEFF Research Database (Denmark)

Cruz-Chu, Eduardo R.; Papadopoulou, Ermioni; Walther, Jens Honore

2017-01-01

The intriguing physics of water transport through carbon nanotubes (CNTs) has motivated numerous studies, reporting flow rates higher than those estimated by continuum models1. The quantification of water transport in CNTs remains unresolved, however, with flow rates reported by different...

Amperometric bienzyme glucose biosensor based on carbon nanotube modified electrode with electropolymerized poly(toluidine blue O) film

International Nuclear Information System (INIS)

Wang Wenju; Wang Fang; Yao Yanli; Hu Shengshui; Shiu, Kwok-Keung

2010-01-01

The amperometric bienzyme glucose biosensor utilizing horseradish peroxidase (HRP) and glucose oxidase (GOx) immobilized in poly(toluidine blue O) (PTBO) film was constructed on multi-walled carbon nanotube (MWNT) modified glassy carbon electrode. The HRP layer could be used to analyze hydrogen peroxide with toluidine blue O (TBO) mediators, while the bienzyme system (HRP + GOx) could be utilized for glucose determination. Glucose underwent biocatalytic oxidation by GOx in the presence of oxygen to yield H 2 O 2 which was further reduced by HRP at the MWNT-modified electrode with TBO mediators. In the absence of oxygen, glucose oxidation proceeded with electron transfer between GOx and the electrode mediated by TBO moieties without H 2 O 2 production. The bienzyme electrode offered high sensitivity for amperometric determination of glucose at low potential, displaying Michaelis-Menten kinetics. The bienzyme glucose biosensor displayed linear response from 0.1 to 1.2 mM with a sensitivity of 113 mA M -1 cm -2 at an applied potential of -0.10 V in air-saturated electrolytes.

Amperometric Acetylcholinesterase Biosensor Based on Multilayer Multiwall Carbon Nanotubes-chitosan Composite

Directory of Open Access Journals (Sweden)

Xia SUN

2011-11-01

Full Text Available A simple method for immobilization of acetylcholinesterase (AChE onto the glassy carbon electrode (GCE modified with five layers of multiwall carbon nanotubes (MWNTs-chitosan (CHIT composite was proposed, and thus a fast, sensitive and stable amperometric sensor for quantitative determination of pesticides was developed. Five layers of MWNTs-CHIT promoted electron transfer reactions at a lower potential and catalyzed the electro-oxidation of thiocholine, thus, it improved the detection sensitivity of biosensor. Based on the inhibition of pesticides to the enzymatic activity of AChE, using carbofuran as a model compound, under optimal conditions, the inhibition of carbofuran was proportional to its concentration in two ranges, from 5×10-4 to 7.5 μg/mL and 7.5 to 20 μg/mL with a detection limit of 1×10-4 μg/mL. The constructed biosensor showed prominent characteristics and performances such as good precision, acceptable stability, fast response and low detection limit, which provided a new promising tool for pesticide analysis.

Amperometric nitrate biosensor based on Carbon nanotube/Polypyrrole/Nitrate reductase biofilm electrode

Energy Technology Data Exchange (ETDEWEB)

Can, Faruk; Korkut Ozoner, Seyda; Ergenekon, Pinar; Erhan, Elif, E-mail: e.erhan@gyte.edu.tr

2012-01-01

This study describes the construction and characterization of an amperometric nitrate biosensor based on the Polypyrrole (PPy)/Carbon nanotubes (CNTs) film. Nitrate reductase (NR) was both entrapped into the growing PPy film and chemically immobilized via the carboxyl groups of CNTs to the CNT/PPy film electrode. The optimum amperometric response for nitrate was obtained in 0.1 M phosphate buffer solution (PBS), pH 7.5 including 0.1 M lithium chloride and 7 mM potassium ferricyanide with an applied potential of 0.13 V (vs. Ag/AgCl, 3 M NaCl). Sensitivity was found to be 300 nA/mM in a linear range of 0.44-1.45 mM with a regression coefficient of 0.97. The biosensor response showed a higher linear range in comparison to standard nitrate analysis methods which were tested in this study and NADH based nitrate biosensors. A minimum detectable concentration of 0.17 mM (S/N = 3) with a relative standard deviation (RSD) of 5.4% (n = 7) was obtained for the biosensor. Phenol and glucose inhibit the electrochemical reaction strictly at a concentration of 1 {mu}g/L and 20 mg/L, respectively. The biosensor response retained 70% of its initial response over 10 day usage period when used everyday. - Highlights: Black-Right-Pointing-Pointer K{sub 3}Fe(CN){sub 6} has been used for the first time as mediator for nitrate reductase. Black-Right-Pointing-Pointer Better performance was obtained in comparison to other nitrate biosensor studies operated with various mediators. Black-Right-Pointing-Pointer Analytical parameters were better than standard nitrate analysis methods.

Amperometric nitrate biosensor based on Carbon nanotube/Polypyrrole/Nitrate reductase biofilm electrode

International Nuclear Information System (INIS)

Can, Faruk; Korkut Ozoner, Seyda; Ergenekon, Pinar; Erhan, Elif

2012-01-01

This study describes the construction and characterization of an amperometric nitrate biosensor based on the Polypyrrole (PPy)/Carbon nanotubes (CNTs) film. Nitrate reductase (NR) was both entrapped into the growing PPy film and chemically immobilized via the carboxyl groups of CNTs to the CNT/PPy film electrode. The optimum amperometric response for nitrate was obtained in 0.1 M phosphate buffer solution (PBS), pH 7.5 including 0.1 M lithium chloride and 7 mM potassium ferricyanide with an applied potential of 0.13 V (vs. Ag/AgCl, 3 M NaCl). Sensitivity was found to be 300 nA/mM in a linear range of 0.44–1.45 mM with a regression coefficient of 0.97. The biosensor response showed a higher linear range in comparison to standard nitrate analysis methods which were tested in this study and NADH based nitrate biosensors. A minimum detectable concentration of 0.17 mM (S/N = 3) with a relative standard deviation (RSD) of 5.4% (n = 7) was obtained for the biosensor. Phenol and glucose inhibit the electrochemical reaction strictly at a concentration of 1 μg/L and 20 mg/L, respectively. The biosensor response retained 70% of its initial response over 10 day usage period when used everyday. - Highlights: ► K 3 Fe(CN) 6 has been used for the first time as mediator for nitrate reductase. ► Better performance was obtained in comparison to other nitrate biosensor studies operated with various mediators. ► Analytical parameters were better than standard nitrate analysis methods.

Carbon film resistor electrode for amperometric determination of acetaminophen in pharmaceutical formulations.

Science.gov (United States)

Felix, Fabiana S; Brett, Christopher M A; Angnes, Lúcio

2007-04-11

Flow injection analysis (FIA) with amperometric detection was employed for acetaminophen quantification in pharmaceutical formulations using a carbon film resistor electrode. This sensor exhibited sharp and reproducible current peaks for acetaminophen without chemical modification of its surface. A wide linear working range (8.0x10(-7) to 5.0x10(-4) mol L(-1)) in phosphate buffer solution as well as high sensitivity (0.143 A mol(-1) L cm(-2)) and low submicromolar detection limit (1.36x10(-7) mol L(-1)) were achieved. The repeatability (R.S.D. for 10 successive injections of 5.0x10(-6) and 5.0x10(-5) mol L(-1) acetaminophen solutions) was 3.1 and 1.3%, respectively, without any memory effect between injections. The new procedure was applied to the analyses of commercial pharmaceutical products and the results were in good agreement with those obtained utilizing a spectrophotometric method. Consequently, this amperometric method has been shown to be very suitable for quality control analyses and other applications with similar requirements.

Amperometric sensor for ascorbic acid based on a glassy carbon electrode modified with gold-silver bimetallic nanotubes in a chitosan matrix

International Nuclear Information System (INIS)

Yang, Penghao; Gao, Xia; Wang, Lisha; Wu, Qi; Chen, Zhichun; Lin, Xianfu

2014-01-01

We report on an amperometric sensor for ascorbic acid (AA) that is based on highly dense gold-silver nanotubes in a chitosan film on a glassy carbon electrode. The nanotubes were synthesized by a poly(vinyl pyrrolidone)-mediated polyol method employing a replacement reaction with silver nanowires as templates, and were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction. Under the optimal conditions, the sensor exhibits good electrocatalytic activity towards the oxidation of AA, and this enables the determination of AA in the 5 μM to 2 mM concentration range, with a detection limit at 2 μM (at an S/N of 3). The response time is 2 s. The sensor displays good reproducibility, selectivity, sensitivity, and long-term stability. (author)

Amperometric biosensor based on carbon nanotubes coated with polyaniline/dendrimer-encapsulated Pt nanoparticles for glucose detection

International Nuclear Information System (INIS)

Xu Lihuan; Zhu Yihua; Yang Xiaoling; Li Chunzhong

2009-01-01

A novel amperometric glucose biosensor based on the nanocomposites of multi-wall carbon nanotubes (CNT) coated with polyaniline (PANI) and dendrimer-encapsulated Pt nanoparticles (Pt-DENs) is prepared. CNT coated with protonated PANI is in situ synthesized and Pt-DENs is absorbed on PANI/CNT composite surface by self-assembly method. Then Glucose oxidase (GOx) is crosslink-immobilizated onto Pt-DENs/PANI/CNT composite film. The results show that the fabricated GOx/Pt-DENs/PANI/CNT electrode exhibits excellent response performance to glucose, such as low detection limit (0.5 μM), wide linear range (1 μM-12 mM), short response time (about 5 s), high sensitivity (42.0 μA mM -1 cm -2 ) and stability (83% remains after 3 weeks).

Flow-Regulated Growth of Titanium Dioxide (TiO2 ) Nanotubes in Microfluidics.

Science.gov (United States)

Fan, Rong; Chen, Xinye; Wang, Zihao; Custer, David; Wan, Jiandi

2017-08-01

Electrochemical anodization of titanium (Ti) in a static, bulk condition is used widely to fabricate self-organized TiO 2 nanotube arrays. Such bulk approaches, however, require extended anodization times to obtain long TiO 2 nanotubes and produce only vertically aligned nanotubes. To date, it remains challenging to develop effective strategies to grow long TiO 2 nanotubes in a short period of time, and to control the nanotube orientation. Here, it is shown that the anodic growth of TiO 2 nanotubes is significantly enhanced (≈16-20 times faster) under flow conditions in microfluidics. Flow not only controls the diameter, length, and crystal orientations of TiO 2 nanotubes, but also regulates the spatial distribution of nanotubes inside microfluidic devices. Strikingly, when a Ti thin film is deposited on silicon substrates and anodized in microfluidics, both vertically and horizontally aligned (relative to the bottom substrate) TiO 2 nanotubes can be produced. The results demonstrate previously unidentified roles of flow in the regulation of growth of TiO 2 nanotubes, and provide powerful approaches to effectively grow long, oriented TiO 2 nanotubes, and construct hierarchical TiO 2 nanotube arrays on silicon-based materials. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A flow-through amperometric sensor based on dialysis tubing and free enzyme reactors

NARCIS (Netherlands)

Bohm, S.; Pijanowska, D.G.; Pijanowska, D.; Olthuis, Wouter; Bergveld, Piet

2001-01-01

A generic flow-through amperometric microenzyme sensor is described, which is based on semi-permeable dialysis tubing carrying the sample to be analyzed. This tubing (300 μm OD) is led through a small cavity, containing the working and reference electrode. By filling this cavity with a few μl of an

Construction of a new functional platform by grafting poly(4-vinylpyridine) in multi-walled carbon nanotubes for complexing copper ions aiming the amperometric detection of L-cysteine

International Nuclear Information System (INIS)

Carvalho Castro e Silva, Cecília de; Breitkreitz, Márcia Cristina; Santhiago, Murilo; Crispilho Corrêa, Cátia; Tatsuo Kubota, Lauro

2012-01-01

Highlights: ► Construction of new nanostructured platform based on MWCNTs–PVP to complex copper(II) ions. ► Development of an amperometric sensor for highly selective determination of Cys in food supplement samples. ► Combination of nanocomposite and the copper(II) ions causes a dramatic enhancement in the sensitivity of Cys quantification at low overpotential. - Abstract: This work describes the preparation of an amperometric sensor for electrocatalytical detection of L-cysteine (Cys). The developed sensor is based on a functional platform to complex copper ions on multi-walled carbon nanotubes (MWCNTs) modified with poly-4-vinylpyridine (PVP) through an in situ polymerization. The obtained values for the kinetic constants of heterogeneous electron transfer rate (k s ) and for chemical reaction (k obs ) between Cu 2+ and cysteine were 5.78 s −1 and 6.96 L mol −1 s −1 , respectively. The analytical curve showed a linear response range for detecting L-cysteine in concentrations from 5 to 60 μmol L −1 . The detection and quantification limits obtained were 1.50 and 5.00 μmol L −1 , respectively with a response time of 0.10 s at an applied potential of 150 mV vs SCE.

Enhancement of C/C-LAS joint using aligned carbon nanotubes prepared by injection chemical vapor deposition

Energy Technology Data Exchange (ETDEWEB)

Zhao, Feng-Ling; Fu, Qian-Gang, E-mail: fuqiangang@nwpu.edu.cn; Feng, Lei; Shen, Qing-Liang

2016-01-05

Carbon nanotubes (CNTs) enhanced carbon/carbon-lithium aluminum silicate (C/C-LAS) joint was prepared by a three-step technique of pack cementation, injection chemical vapor deposition (ICVD) and hot-pressing. A layer of aligned CNTs was grown on the surface of SiC coated C/C composites by ICVD method, and the joint was obtained by hot-pressing with magnesium aluminum silicate (MAS) as the interlayer. SEM observation reveals that the introduced CNTs result in the formation of a dense and crack-free CNT/MAS nanocomposite interface between SiC and MAS. Compared with the joints without CNTs, the average shear strength of the joints reinforced by CNTs was improved by 48% accompanied by an obvious change in failure mode from brittle fracture without CNTs to plastic fracture with CNTs. The pulling-out and bridging of CNTs on the fracture surfaces had a positive effect on the strength enhancement of the C/C-LAS joint.

Label-Free Electrical Detection Using Carbon Nanotube-Based Biosensors

Directory of Open Access Journals (Sweden)

Kenzo Maehashi

2009-07-01

Full Text Available Label-free detections of biomolecules have attracted great attention in a lot of life science fields such as genomics, clinical diagnosis and practical pharmacy. In this article, we reviewed amperometric and potentiometric biosensors based on carbon nanotubes (CNTs. In amperometric detections, CNT-modified electrodes were used as working electrodes to significantly enhance electroactive surface area. In contrast, the potentiometric biosensors were based on aptamer-modified CNT field-effect transistors (CNTFETs. Since aptamers are artificial oligonucleotides and thus are smaller than the Debye length, proteins can be detected with high sensitivity. In this review, we discussed on the technology, characteristics and developments for commercialization in label-free CNT-based biosensors.

Amperometric glucose biosensor based on glucose oxidase dispersed in multiwalled carbon nanotubes/graphene oxide hybrid biocomposite.

Science.gov (United States)

Palanisamy, Selvakumar; Cheemalapati, Srikanth; Chen, Shen-Ming

2014-01-01

An amperometric glucose biosensor based on enhanced and fast direct electron transfer (DET) of glucose oxidase (GOx) at enzyme dispersed multiwalled carbon nanotubes/graphene oxide (MWCNT/GO) hybrid biocomposite was developed. The fabricated hybrid biocomposite was characterized by transmission electron microscopy (TEM), Raman and infrared spectroscopy (IR). The TEM image of hybrid biocomposite reveals that a thin layer of GOx was covered on the surface of MWCNT/GO hybrid composite. IR results validate that the hybrid biocomposite was formed through the electrostatic interactions between GOx and MWCNT/GO hybrid composite. Further, MWCNT/GO hybrid composite has also been characterized by TEM and UV-visible spectroscopy. A pair of well-defined redox peak was observed for GOx immobilized at the hybrid biocomposite electrode than that immobilized at the MWCNT modified electrode. The electron transfer rate constant (Ks) of GOx at the hybrid biocomposite was calculated to be 11.22s(-1). The higher Ks value revealed that fast DET of GOx occurred at the electrode surface. Moreover, fabricated biosensor showed a good sensitivity towards glucose oxidation over a linear range 0.05-23.2mM. The limit of detection (LOD) was estimated to be 28μM. The good features of the proposed biosensor could be used for the accurate detection of glucose in the biological samples. © 2013.

Glucose oxidase-modified carbon-felt-reactor coupled with peroxidase-modified carbon-felt-detector for amperometric flow determination of glucose

International Nuclear Information System (INIS)

Wang Yue; Hasebe, Yasushi

2012-01-01

Glucose oxidase (GOx) and horseradish peroxidase (HRP) were covalently immobilized on a porous carbon-felt (CF) by using cyanuric chloride (CC) as a linking reagent. The resulting GOx-modified-CF (GOx-ccCF) was used as column-type enzyme reactor and placed on upstream of the HRP-ccCF-based H 2 O 2 flow-detector to fabricate amperometric flow-biosensor for glucose. Sensor setting conditions and the operational conditions were optimized, and the analytical performance characteristics of the resulting flow-biosensor were evaluated. The chemical modification of the GOx via CC was found to be effective to obtain larger catalytic activity as compared with the physical adsorption. Under the optimized conditions (i.e., volume ratio of the GOx-ccCF-reactor to the HRP-ccCF-detector is 1.0; applied potential is − 0.12 V vs. Ag/AgCl; carrier pH is 6.5; and carrier flow rate is 4.3 ml/min), highly selective and quite reproducible peak current responses toward glucose were obtained: the RSD for 30 consecutive injections of 3 mM glucose was 1.04%, and no serious interferences were observed for fructose, ethanol, uric acid, urea and tartaric acid for the amperometric measurements of glucose. The magnitude of the cathodic peak currents for glucose was linear up to 5 mM (sensitivity, 6.38 ± 0.32 μA/μM) with the limit detection of 9.4 μM (S/N = 3, noise level, 20 nA). The present GOx-ccCF-reactor and HRP-ccCF-detector-coupled flow-glucose biosensor was utilized for the determination of glucose in beverages and liquors, and the analytical results by the sensor were in fairly good agreement with those by the conventional spectrophotometry. - Highlights: ► Glucose oxidase (GOx) and peroxidase (HRP) were modified on carbon-felt. ► GOx-CF reactor and HRP-CF detector-coupled flow glucose biosensor was developed. ► This flow biosensor enabled the determination of glucose in beverages and liquors.

Glucose oxidase-modified carbon-felt-reactor coupled with peroxidase-modified carbon-felt-detector for amperometric flow determination of glucose

Energy Technology Data Exchange (ETDEWEB)

Wang Yue [School of Chemical Engineering, University of Science and Technology LiaoNing, 185 Qianshan Middle Road, High-tech Zone, Anshan, LiaoNing, 114501 (China); Hasebe, Yasushi, E-mail: hasebe@sit.ac.jp [Department of Life Science and Green Chemistry, Faculty of Engineering, Saitama Institute of Technology, 1690, Fusaiji, Fukaya, Saitama 369-0293 (Japan)

2012-04-01

Glucose oxidase (GOx) and horseradish peroxidase (HRP) were covalently immobilized on a porous carbon-felt (CF) by using cyanuric chloride (CC) as a linking reagent. The resulting GOx-modified-CF (GOx-ccCF) was used as column-type enzyme reactor and placed on upstream of the HRP-ccCF-based H{sub 2}O{sub 2} flow-detector to fabricate amperometric flow-biosensor for glucose. Sensor setting conditions and the operational conditions were optimized, and the analytical performance characteristics of the resulting flow-biosensor were evaluated. The chemical modification of the GOx via CC was found to be effective to obtain larger catalytic activity as compared with the physical adsorption. Under the optimized conditions (i.e., volume ratio of the GOx-ccCF-reactor to the HRP-ccCF-detector is 1.0; applied potential is - 0.12 V vs. Ag/AgCl; carrier pH is 6.5; and carrier flow rate is 4.3 ml/min), highly selective and quite reproducible peak current responses toward glucose were obtained: the RSD for 30 consecutive injections of 3 mM glucose was 1.04%, and no serious interferences were observed for fructose, ethanol, uric acid, urea and tartaric acid for the amperometric measurements of glucose. The magnitude of the cathodic peak currents for glucose was linear up to 5 mM (sensitivity, 6.38 {+-} 0.32 {mu}A/{mu}M) with the limit detection of 9.4 {mu}M (S/N = 3, noise level, 20 nA). The present GOx-ccCF-reactor and HRP-ccCF-detector-coupled flow-glucose biosensor was utilized for the determination of glucose in beverages and liquors, and the analytical results by the sensor were in fairly good agreement with those by the conventional spectrophotometry. - Highlights: Black-Right-Pointing-Pointer Glucose oxidase (GOx) and peroxidase (HRP) were modified on carbon-felt. Black-Right-Pointing-Pointer GOx-CF reactor and HRP-CF detector-coupled flow glucose biosensor was developed. Black-Right-Pointing-Pointer This flow biosensor enabled the determination of glucose in beverages and

A flow-type amperometric sensor in immunoenzyme analysis

Energy Technology Data Exchange (ETDEWEB)

Ivnitskii, D.M.; Aronbaev, D.M.; Kashkin, A.P.; Meringova, L.F.; Yulaev, M.F.

1986-06-01

A portable flow-type amperometric sensor has been made for the immunoenzyme determination of L-asparaginase. The authors show it is possible to determine peroxidase (the marker enzyme) by this method over the concentration range 1.10/sup -11/-4.10/sup -10/ M. The limit of detection for L-asparaginase is 1.8.10/sup -10/ M, which corresponds to clinically significant enzyme concentrations. Various modifications of immunoenzyme analysis (IEA) are used in clinical and research laboratories, and have contributed to diagnosis as regards antigens and serum antibodies. The sensor used here uses the electrical reduction of the molecular ion at the surface of thr measurement electrode. The electrochemical reaction is preceded by a competing antigen-antibody reaction and by the peroxidase oxidation of the iodide in the depressions.

Direct electrodeposition of highly ordered gold nanotube arrays for use in non-enzymatic amperometric sensing of glucose

International Nuclear Information System (INIS)

Tian, Taolei; Dong, Junping; Xu, Jiaqiang

2016-01-01

The authors describe vertically aligned gold nanotube arrays (Au-NTAs) and gold nanowire arrays (Au-NWAs) that were directly grown in alumina oxide templates by galvanostatic deposition. The morphology of the gold arrays can be controlled by adjusting the pH value of the plating bath. Scanning electron microscopy shows the nanoarrays to be highly ordered (with an average length of around 2 μm), and the opening width of the gold nanotube arrays to be uniform (with diameters of around 50 nm). The electrocatalytic activities of the Au-NTAs and Au-NWAs deposited on a glassy carbon electrode toward glucose oxidation were compared by cyclic voltammetry and amperometry at pH 7.2. The Au-NTAs yield higher amperometric currents. The respective glucose sensor, when operated at a working potential of 0.25 V (vs. SCE), exhibits a linear range that extends from 5 μM to 16.4 mM concentrations of glucose, a sensitivity of 44.2 μA mM"−"1 cm"−"2, and a detection limit of 2.1 μM (at an S/N ratio of 3). The excellent sensing performance is attributed to the large surface area and the fast electron transfer rate for the one-dimensional gold nanoarrays (author)

Quantum dots as chemiluminescence enhancers tested by sequential injection technique: Comparison of flow and flow-batch conditions

Energy Technology Data Exchange (ETDEWEB)

Sklenářová, Hana, E-mail: sklenarova@faf.cuni.cz [Charles University in Prague, Faculty of Pharmacy in Hradec Králové, Department of Analytical Chemistry, Hradec Králové (Czech Republic); Voráčová, Ivona [Institute of Analytical Chemistry of the CAS, v. v. i., Brno (Czech Republic); Chocholouš, Petr; Polášek, Miroslav [Charles University in Prague, Faculty of Pharmacy in Hradec Králové, Department of Analytical Chemistry, Hradec Králové (Czech Republic)

2017-04-15

The effect of 0.01–100 µmol L{sup −1} Quantum Dots (QDs) with different emission wavelengths (520–640 nm) and different surface modifications (mercaptopropionic, mercaptoundecanoic, thioglycolic acids and mercaptoethylamine) on permanganate-induced and luminol–hydrogen peroxide chemiluminescence (CL) was studied in detail by a sequential injection technique using a spiral detection flow cell and a flow-batch detection cell operated in flow and stop-flow modes. In permanganate CL system no significant enhancement of the CL signal was observed while for the luminol–hydrogen peroxide CL substantial increase (>100% and >90% with the spiral detection cell in flow and stop-flow modes, respectively) was attained for CdTe QDs. Enhancement exceeding 120% was observed for QDs with emissions at 520, 575 and 603 nm (sizes of 2.8 nm, 3.3 nm and 3.6 nm) using the flow-batch detection cell in the stop-flow mode. Pronounced effect was noted for surface modifications while mercaptoethylamine was the most efficient in CL enhancement compared to mercaptopropionic acid the most commonly applied coating. Significant difference between results obtained in flow and flow-batch conditions based on the entire kinetics of the extremely fast CL reaction was discussed. The increase of the CL signal was always accompanied by reduced lifetime of the CL emission thus application of QDs in flow techniques should be always coupled with the study of the CL lifetime.

Analysis of polyphenols in white wine by CZE with amperometric detection using carbon nanotube-modified electrodes.

Science.gov (United States)

Moreno, Mónica; Arribas, Alberto Sánchez; Bermejo, Esperanza; Zapardiel, Antonio; Chicharro, Manuel

2011-04-01

A method for the simultaneous detection of five polyphenols (caffeic, chlorogenic, ferulic and gallic acids and (+)-catechin) by CZE with electrochemical detection was developed. Separation of these polyphenols was performed in a 100 mM borate buffer (pH 9.2) within 15 min. Under optimized separation conditions, the performance of glassy carbon (GC) electrodes modified with multiwalled carbon nanotube layer obtained from different dispersions was examined. GC electrode modified with a dispersion of multi-walled carbon nanotubes (CNT) in polyethylenimine has proven to be the most suitable CNT-based electrode for its application as amperometric detector for the CZE separation of the studied compounds. The excellent electrochemical properties of this electrode allowed the detection of the selected polyphenols at +200 mV and improved the efficiency and the resolution of their CZE separation. Limits of detection below 3.1 μM were obtained with linear ranges covering the 10⁻⁵ to 10⁻⁴  M range. The proposed method has been successfully applied for the detection (ferulic, caffeic and gallic acids and (+)-catechin) and the quantification (gallic acid and (+)-catechin) of polyphenols in two different white wines without any preconcentration step. A remarkable signal stability was observed on the electrode performance despite the presence of potential fouling substances in wine. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Direct injection in organic SU8 nanowires and nanotubes for waveguiding properties investigation

Science.gov (United States)

Bigeon, J.; Huby, N.; Duvail, Jean-Luc; Bêche, Bruno

2014-05-01

We report photonic concepts related to injection and sub-wavelength propagation in nanofibers (nanowires and nanotubes). These nanostructures are fabricated by the wetting template method leading to aspect ratio of over 250. At first, injection into nanowires and nanotubes of SU8, a photoresist used for integrated photonics, was successfully achieved by using polymer microlensed fibers with sub-micronic radius of curvature. Theoret- ical simulation by finite domain time-dependent (FDTD) method was used to determine the sub-wavelength propagation for nanowires and nanotubes and corroborate this coupling phenomena. The original confinement of energy density into SU8 nanotubes is highlighted. Finally, characterisation of propagation losses is reported by using a cut-back method transposed to such nanotubes and determined to range between 1 and 2 dB/mm. Both injection and cut-back method developed here are compatible with any sub-micronic structures. This work on SU8 nanofibers suggests broader perspectives for future nanophotonics.

An Amperometric Immunosensor Based on Multi-Walled Carbon Nanotubes-Thionine-Chitosan Nanocomposite Film for Chlorpyrifos Detection

Science.gov (United States)

Sun, Xia; Cao, Yaoyao; Gong, Zhili; Wang, Xiangyou; Zhang, Yan; Gao, Jinmei

2012-01-01

In this work, a novel amperometric immunosensor based on multi-walled carbon nanotubes-thionine-chitosan (MWCNTs-THI-CHIT) nanocomposite film as electrode modified material was developed for the detection of chlorpyrifos residues. The nanocomposite film was dropped onto a glassy carbon electrode (GCE), and then the anti-chlorpyrifos monoclonal antibody was covalently immobilized onto the surface of MWCNTs-THI-CHIT/GCE using the crosslinking agent glutaraldehyde (GA). The modification procedure was characterized by using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Under the optimized conditions, a linear relationship between the relative change in peak current of different pulse voltammetry (DPV) and the logarithm of chlorpyrifos solution concentration was obtained in the range from 0.1 to 1.0 × 105 ng/mL with a detection limit of 0.046 ng/mL. The proposed chlorpyrifos immunosensor exhibited high reproducibility, stability, and good selectivity and regeneration, making it a potential alternative tool for ultrasensitive detection of chlorpyrifos residues in vegetables and fruits. PMID:23443396

Layer-by-Layer Self-Assembling Gold Nanorods and Glucose Oxidase onto Carbon Nanotubes Functionalized Sol-Gel Matrix for an Amperometric Glucose Biosensor

Directory of Open Access Journals (Sweden)

Baoyan Wu

2015-09-01

Full Text Available A novel amperometric glucose biosensor was fabricated by layer-by-layer self-assembly of gold nanorods (AuNRs and glucose oxidase (GOD onto single-walled carbon nanotubes (SWCNTs-functionalized three-dimensional sol-gel matrix. A thiolated aqueous silica sol containing SWCNTs was first assembled on the surface of a cleaned Au electrode, and then the alternate self-assembly of AuNRs and GOD were repeated to assemble multilayer films of AuNRs-GOD onto SWCNTs-functionalized silica gel for optimizing the biosensor. Among the resulting glucose biosensors, the four layers of AuNRs-GOD-modified electrode showed the best performance. The sol-SWCNTs-(AuNRs- GOD4/Au biosensor exhibited a good linear range of 0.01–8 mM glucose, high sensitivity of 1.08 μA/mM, and fast amperometric response within 4 s. The good performance of the proposed glucose biosensor could be mainly attributed to the advantages of the three-dimensional sol-gel matrix and stereo self-assembly films, and the natural features of one-dimensional nanostructure SWCNTs and AuNRs. This study may provide a new facile way to fabricate the enzyme-based biosensor with high performance.

Layer-by-Layer Self-Assembling Gold Nanorods and Glucose Oxidase onto Carbon Nanotubes Functionalized Sol-Gel Matrix for an Amperometric Glucose Biosensor.

Science.gov (United States)

Wu, Baoyan; Hou, Shihua; Miao, Zhiying; Zhang, Cong; Ji, Yanhong

2015-09-18

A novel amperometric glucose biosensor was fabricated by layer-by-layer self-assembly of gold nanorods (AuNRs) and glucose oxidase (GOD) onto single-walled carbon nanotubes (SWCNTs)-functionalized three-dimensional sol-gel matrix. A thiolated aqueous silica sol containing SWCNTs was first assembled on the surface of a cleaned Au electrode, and then the alternate self-assembly of AuNRs and GOD were repeated to assemble multilayer films of AuNRs-GOD onto SWCNTs-functionalized silica gel for optimizing the biosensor. Among the resulting glucose biosensors, the four layers of AuNRs-GOD-modified electrode showed the best performance. The sol-SWCNTs-(AuNRs- GOD)₄/Au biosensor exhibited a good linear range of 0.01-8 mM glucose, high sensitivity of 1.08 μA/mM, and fast amperometric response within 4 s. The good performance of the proposed glucose biosensor could be mainly attributed to the advantages of the three-dimensional sol-gel matrix and stereo self-assembly films, and the natural features of one-dimensional nanostructure SWCNTs and AuNRs. This study may provide a new facile way to fabricate the enzyme-based biosensor with high performance.

Enhancement of melting heat transfer of ice slurries by an injection flow in a rectangular cross sectional horizontal duct

International Nuclear Information System (INIS)

Fujii, Kota; Yamada, Masahiko

2013-01-01

Ice slurries are now commonly used as cold thermal storage materials, and have the potential to be applied to other engineering fields such as quenching metals to control properties, emergency cooling systems, and preservation of food and biomaterials at low temperatures. Although ice slurries have been widely utilized because of their high thermal storage densities, previous studies have revealed that the latent heat of ice particles is not completely released on melting because of insufficient contact between the ice particles and a heated surface. In this study, an injection flow that was bifurcated from the main flow of an ice slurry was employed to promote melting heat transfer of ice particles on a horizontal heated surface. The effects of injection angle and injection flow rate on local heat transfer coefficients and heat transfer coefficient ratios were determined experimentally. The results show that from two to three times higher heat transfer coefficients can be obtained by using large injection flow rates and injection angles. However, low injection angles improved the utilization rate of the latent heat of ice near the injection point by approximately a factor of two compared to that without injection. -- Highlights: • Melting of ice slurries were enhanced by the injection under constant total flow rate. • Contribution of ice particles and their latent heat to heat transfer was investigated. • Effect of velocity ratio of injection to that of main flow was examined. • Effect of the angle of injection flow to the main flow was also examined. • Appropriate conditions for the use of latent heat of ice and heat transfer did not coincide

Carbon nanotubes significance in Darcy-Forchheimer flow

Science.gov (United States)

Hayat, Tasawar; Rafique, Kiran; Muhammad, Taseer; Alsaedi, Ahmed; Ayub, Muhammad

2018-03-01

The present article examines Darcy-Forchheimer flow of water-based carbon nanotubes. Flow is induced due to a curved stretchable surface. Heat transfer mechanism is analyzed in presence of convective heating process. Xue model of nanofluid is employed to study the characteristics of both single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs). Results for both single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) are achieved and compared. Appropriate transformations correspond to strong nonlinear ordinary differential system. Optimal homotopy analysis method (OHAM) is used for the solution development of the resulting system. The contributions of different sundry variables on the velocity and temperature are studied. Further the skin friction coefficient and local Nusselt number are analyzed graphically for both SWCNTs and MWCNTs cases.

Injection and waveguiding properties in SU8 nanotubes for sub-wavelength regime propagation and nanophotonics integration

Science.gov (United States)

Bigeon, John; Huby, Nolwenn; Duvail, Jean-Luc; Bêche, Bruno

2014-04-01

We report photonic concepts related to injection and sub-wavelength propagation in nanotubes, an unusual but promising geometry for highly integrated photonic devices. Theoretical simulation by the finite domain time-dependent (FDTD) method was first used to determine the features of the direct light injection and sub-wavelength propagation regime within nanotubes. Then, the injection into nanotubes of SU8, a photoresist used for integrated photonics, was successfully achieved by using polymer microlensed fibers with a sub-micronic radius of curvature, as theoretically expected from FDTD simulations. The propagation losses in a single SU8 nanotube were determined by using a comprehensive set-up and a protocol for optical characterization. The attenuation coefficient has been evaluated at 1.25 dB mm-1 by a cut-back method transposed to such nanostructures. The mechanisms responsible for losses in nanotubes were identified with FDTD theoretical support. Both injection and cut-back methods developed here are compatible with any sub-micronic structures. This work on SU8 nanotubes suggests broader perspectives for future nanophotonics.

Amperometric Determination of Sulfite by Gas Diffusion- Sequential Injection with Boron-Doped Diamond Electrode

Directory of Open Access Journals (Sweden)

Orawon Chailapakul

2008-03-01

Full Text Available A gas diffusion sequential injection system with amperometric detection using aboron-doped diamond electrode was developed for the determination of sulfite. A gasdiffusion unit (GDU was used to prevent interference from sample matrices for theelectrochemical measurement. The sample was mixed with an acid solution to generategaseous sulfur dioxide prior to its passage through the donor channel of the GDU. Thesulfur dioxide diffused through the PTFE hydrophobic membrane into a carrier solution of 0.1 M phosphate buffer (pH 8/0.1% sodium dodecyl sulfate in the acceptor channel of theGDU and turned to sulfite. Then the sulfite was carried to the electrochemical flow cell anddetected directly by amperometry using the boron-doped diamond electrode at 0.95 V(versus Ag/AgCl. Sodium dodecyl sulfate was added to the carrier solution to preventelectrode fouling. This method was applicable in the concentration range of 0.2-20 mgSO32−/L and a detection limit (S/N = 3 of 0.05 mg SO32−/L was achieved. This method wassuccessfully applied to the determination of sulfite in wines and the analytical resultsagreed well with those obtained by iodimetric titration. The relative standard deviations forthe analysis of sulfite in wines were in the range of 1.0-4.1 %. The sampling frequency was65 h−1.

Mediatorless amperometric bienzyme glucose biosensor based on horseradish peroxidase and glucose oxidase cross-linked to multiwall carbon nanotubes

International Nuclear Information System (INIS)

Xu, Shuxia; Zhou, Shiyi; Zhang, Xinfeng; Qi, Honglan; Zhang, Chengxiao

2014-01-01

We report on a bienzyme-channeling sensor for sensing glucose without the aid of mediator. It was fabricated by cross-linking horseradish peroxidase (HRP) and glucose oxidase (GOx) on a glassy carbon electrode modified with multiwalled carbon nanotubes (MWNTs). The bienzyme was cross-linked with the MWNTs by glutaraldehyde and bovine serum albumin. The MWNTs were employed to accelerate the electron transfer between immobilized HRP and electrode. Glucose was sensed by amperometric reduction of enzymatically generated H 2 O 2 at an applied voltage of −50 mV (vs. Ag/AgCl). Factors influencing the preparation and performance of the bienzyme electrode were investigated in detail. The biosensor exhibited a fast and linear response to glucose in the concentration range from 0.4 to 15 mM, with a detection limit of 0.4 mM. The sensor exhibited good selectivity and durability, with a long-term relative standard deviation of <5 %. Analysis of glucose-spiked human serum samples yielded recoveries between 96 and 101 %. (author)

How fast does water flow in carbon nanotubes?

DEFF Research Database (Denmark)

Kannam, Sridhar; Todd, Billy; Hansen, Jesper Schmidt

2013-01-01

The purpose of this paper is threefold. First, we review the existing literature on flow rates of water in carbon nanotubes. Data for the slip length which characterizes the flow rate are scattered over 5 orders of magnitude for nanotubes of diameter 0.81–10 nm. Second, we precisely compute...... the slip length using equilibrium molecular dynamics (EMD) simulations, from which the interfacial friction between water and carbon nanotubes can be found, and also via external field driven non-equilibrium molecular dynamics simulations (NEMD). We discuss some of the issues in simulation studies which...... and reliably extrapolate the results for the slip length to values of the field corresponding to experimentally accessible pressure gradients. Finally, we comment on several issues concerning water flow rates in carbon nanotubes which may lead to some future research directions in this area....

Three-dimensional Nitrogen-Doped Reduced Graphene Oxide/Carbon Nanotube Composite Catalysts for Vanadium Flow Batteries

Energy Technology Data Exchange (ETDEWEB)

Fu, Shaofang [School of Mechanical and Materials Engineering, Washington State University, WA, 99164 USA.; Zhu, Chengzhou [School of Mechanical and Materials Engineering, Washington State University, WA, 99164 USA.; Song, Junhua [School of Mechanical and Materials Engineering, Washington State University, WA, 99164 USA.; Engelhard, Mark H. [Environmental Molecular Science Laboratory, Pacific Northwest National Laboratory, Richland, WA 99354 USA.; Du, Dan [School of Mechanical and Materials Engineering, Washington State University, WA, 99164 USA.; Lin, Yuehe [School of Mechanical and Materials Engineering, Washington State University, WA, 99164 USA.; Environmental Molecular Science Laboratory, Pacific Northwest National Laboratory, Richland, WA 99354 USA.

2017-02-22

The development of vanadium redox flow battery is limited by the sluggish kinetics of the reaction, especially the cathodic VO2+/VO2+ redox couples. Therefore, it is vital to develop new electrocatalyst with enhanced activity to improve the battery performance. Herein, we first synthesized the hydrogel precursor by a facile hydrothermal method. After the following carbonization, nitrogen-doped reduced graphene oxide/carbon nanotube composite was obtained. By virtue of the large surface area and good conductivey, which are ensured by the unique hybrid structure, as well as the proper nitrogen doping, the as-prepared composite presents enhanced catalytic performance toward the VO2+/VO2+ redox reaction. We also demonstrated the composite with carbon nanotube loading of 2 mg/mL exhibits the highest activity and remarkable stability in aqueous solution due to the strong synergy between reduced graphene oxide and carbon nanotubes, indicating that this composite might show promising applications in vanadium redox flow battery.

Growth of highly oriented carbon nanotubes by plasma-enhanced hot filament chemical vapor deposition

Energy Technology Data Exchange (ETDEWEB)

Huang, Z.P.; Xu, J.W.; Ren, Z.F.; Wang, J.H. [Materials Synthesis Laboratory, Departments of Physics and Chemistry, and Center for Advanced Photonic and Electronic Materials (CAPEM), State University of New York at Buffalo, Buffalo, New York 14260 (United States); Siegal, M.P.; Provencio, P.N. [Sandia National Laboratories, Albuquerque, New Mexico 87185-1421 (United States)

1998-12-01

Highly oriented, multiwalled carbon nanotubes were grown on polished polycrystalline and single crystal nickel substrates by plasma enhanced hot filament chemical vapor deposition at temperatures below 666 {degree}C. The carbon nanotubes range from 10 to 500 nm in diameter and 0.1 to 50 {mu}m in length depending on growth conditions. Acetylene is used as the carbon source for the growth of the carbon nanotubes and ammonia is used for dilution gas and catalysis. The plasma intensity, acetylene to ammonia gas ratio, and their flow rates, etc. affect the diameters and uniformity of the carbon nanotubes. {copyright} {ital 1998 American Institute of Physics.}

Amperometric nitrite sensor based on a glassy carbon electrode modified with multi-walled carbon nanotubes and poly(toluidine blue)

International Nuclear Information System (INIS)

Dai, Juan; Deng, Fei; He, Shuang; Deng, Dongli; Yuan, Yali; Zhang, Jinzhong

2016-01-01

An amperometric nitrite sensor modified with multi-walled carbon nanotubes (MWCNTs) and poly(toluidine blue) (PTB) on glassy carbon electrode was constructed. The surface morphology of the composite- modified electrode was characterized by scanning electron microscopy, and the electrochemical response behavior and electrocatalytic oxidation mechanism of nitrite were investigated by cyclic voltammetry. The high surface-to-volume ratio of MWCNTs and PTB brings the electrochemical sensing unit and nitrite in full contact. This renders the electrochemical response extremely sensitive to nitrite. Under the optimal measurement conditions and a working voltage of 0.73 V (vs. SCE), a linear relationship is obtained between the oxidation peak current and nitrite concentration in the range of 39 nM–1.1 mM, and the limit of detection is lowered to 19 nM (at an S/N ratio of 3). The sensor was successfully applied to the determination of nitrite in greenhouse soils. (author)

Molecular dynamics study of Ar flow and He flow inside carbon nanotube junction as a molecular nozzle and diffuser

Directory of Open Access Journals (Sweden)

Itsuo Hanasaki, Akihiro Nakatani and Hiroshi Kitagawa

2004-01-01

Full Text Available A carbon nanotube junction consists of two connected nanotubes with different diameters. It has been extensively investigated as a molecular electronic device since carbon nanotubes can be metallic and semiconductive, depending on their structure. However, a carbon nanotube junction can also be viewed as a nanoscale nozzle andv diffuser. Here, we focus on the nanotube junction from the perspective of an intersection between machine, material and device. We have conducted a molecular dynamics simulation of the molecular flow inside a modeled (12,12–(8,8 nanotube junction. A strong gravitational field and a periodic boundary condition are applied in the flow direction. We investigated dense-Ar flows and dense-He flows while controlling the temperature of the nanotube junction. The results show that Ar atoms tend to be near to the wall and the density of the Ar is higher in the wide (12,12 nanotube than in the narrow (8,8 nanotube, while it is lower in the wide tube when no flow occurs. The streaming velocities of both the Ar and the He are higher in the narrow nanotube than in the wide nanotube, but the velocity of the Ar is higher than the velocity of the He and the temperature of the flowing Ar is higher than the temperature of the He when the same magnitude of gravitational field is applied.

Computational modelling of the flow of viscous fluids in carbon nanotubes

Energy Technology Data Exchange (ETDEWEB)

Khosravian, N [Computational Physical Sciences Research Laboratory, Department of Nano-Science, Institute for Research in Fundamental Sciences (IPM), PO Box 19395-5531, Tehran (Iran, Islamic Republic of); Rafii-Tabar, H [Computational Physical Sciences Research Laboratory, Department of Nano-Science, Institute for Research in Fundamental Sciences (IPM), PO Box 19395-5531, Tehran (Iran, Islamic Republic of)

2007-11-21

Carbon nanotubes will have extensive application in all areas of nano-technology, and in particular in the field of nano-fluidics, wherein they can be used for molecular separation, nano-scale filtering and as nano-pipes for conveying fluids. In the field of nano-medicine, nanotubes can be functionalized with various types of receptors to act as bio-sensors for the detection and elimination of cancer cells, or be used as bypasses and even neural connections. Modelling fluid flow inside nanotubes is a very challenging problem, since there is a complex interplay between the motion of the fluid and the stability of the walls. A critical issue in the design of nano-fluidic devices is the induced vibration of the walls, due to the fluid flow, which can promote structural instability. It has been established that the resonant frequencies depend on the flow velocity. We have studied, for the first time, the flow of viscous fluids through multi-walled carbon nanotubes, using the Euler-Bernoulli classical beam theory to model the nanotube as a continuum structure. Our aim has been to compute the effect of the fluid flow on the structural stability of the nanotubes, without having to consider the details of the fluid-walls interaction. The variations of the resonant frequencies with the flow velocity are obtained for both unembedded nanotubes, and when they are embedded in an elastic medium. It is found that a nanotube conveying a viscous fluid is more stable against vibration-induced buckling than a nanotube conveying a non-viscous fluid, and that the aspect ratio plays the same role in both cases.

Computational modelling of the flow of viscous fluids in carbon nanotubes

International Nuclear Information System (INIS)

Khosravian, N; Rafii-Tabar, H

2007-01-01

Carbon nanotubes will have extensive application in all areas of nano-technology, and in particular in the field of nano-fluidics, wherein they can be used for molecular separation, nano-scale filtering and as nano-pipes for conveying fluids. In the field of nano-medicine, nanotubes can be functionalized with various types of receptors to act as bio-sensors for the detection and elimination of cancer cells, or be used as bypasses and even neural connections. Modelling fluid flow inside nanotubes is a very challenging problem, since there is a complex interplay between the motion of the fluid and the stability of the walls. A critical issue in the design of nano-fluidic devices is the induced vibration of the walls, due to the fluid flow, which can promote structural instability. It has been established that the resonant frequencies depend on the flow velocity. We have studied, for the first time, the flow of viscous fluids through multi-walled carbon nanotubes, using the Euler-Bernoulli classical beam theory to model the nanotube as a continuum structure. Our aim has been to compute the effect of the fluid flow on the structural stability of the nanotubes, without having to consider the details of the fluid-walls interaction. The variations of the resonant frequencies with the flow velocity are obtained for both unembedded nanotubes, and when they are embedded in an elastic medium. It is found that a nanotube conveying a viscous fluid is more stable against vibration-induced buckling than a nanotube conveying a non-viscous fluid, and that the aspect ratio plays the same role in both cases

Flow-driven voltage generation in carbon nanotubes

Indian Academy of Sciences (India)

The flow of various liquids and gases over single-walled carbon nanotube bundles induces an electrical signal (voltage/current) in the sample along the direction of the flow. The electrical response generated by the flow of liquids is found to be logarithmic in the flow speed over a wide range. In contrast, voltage generated ...

Enhanced electrochemical activity using vertically aligned carbon nanotube electrodes grown on carbon fiber

Directory of Open Access Journals (Sweden)

Evandro Augusto de Morais

2011-09-01

Full Text Available Vertically aligned carbon nanotubes were successfully grown on flexible carbon fibers by plasma enhanced chemical vapor deposition. The diameter of the CNT is controllable by adjusting the thickness of the catalyst Ni layer deposited on the fiber. Vertically aligned nanotubes were grown in a Plasma Enhanced Chemical Deposition system (PECVD at a temperature of 630 ºC, d.c. bias of -600 V and 160 and 68 sccm flow of ammonia and acetylene, respectively. Using cyclic voltammetry measurements, an increase of the surface area of our electrodes, up to 50 times higher, was observed in our samples with CNT. The combination of VACNTs with flexible carbon fibers can have a significant impact on applications ranging from sensors to electrodes for fuel cells.

A glassy carbon electrode modified with a polyaniline doped with silicotungstic acid and carbon nanotubes for the sensitive amperometric determination of ascorbic acid

International Nuclear Information System (INIS)

Zhang, X.; Lai, G.; Zhang, H.; Yu, A.

2013-01-01

We report on an electrochemical sensor for the sensitive amperometric determination of ascorbic acid (AA). Aniline containing suspended silicotungstic acid and carbon nanotubes was electropolymerized on the surface of a glassy carbon electrode in a single step which provides a simple and controllable method and greatly improves the electrocatalytic oxidation of AA. The effects of scan rate, solution pH and working potential were studied. A linear relationship exists between the current measured and the concentration of AA in the range from 1 μM to 10 μM and 0.01 mM to 9 mM, with a limit of detection as low as 0.51 μM (S/N = 3). The sensor is selective, stable and satisfyingly reliable in real sample experiments. In our eyes, it has a large potential for practical applications. (author)

An amperometric hydrogen peroxide biosensor based on Co3O4 nanoparticles and multiwalled carbon nanotube modified glassy carbon electrode

International Nuclear Information System (INIS)

Kaçar, Ceren; Dalkiran, Berna; Erden, Pınar Esra; Kiliç, Esma

2014-01-01

Highlights: • Hydrogen peroxide biosensor was constructed by combining the advantageous properties of MWCNTs and Co 3 O 4 . • Incorporating Co 3 O 4 nanoparticles into MWCNTs/gelatin film increased the electron transfer. • Co 3 O 4 /MWCNTs/gelatin/HRP/Nafion/GCE showed strong anti-interference ability. • Hydrogen peroxide was successfully determined in disinfector with an average recovery of 100.78 ± 0.89. - Abstract: In this work a new type of hydrogen peroxide biosensor was fabricated based on the immobilization of horseradish peroxidase (HRP) by cross-linking on a glassy carbon electrode (GCE) modified with Co 3 O 4 nanoparticles, multiwall carbon nanotubes (MWCNTs) and gelatin. The introduction of MWCNTs and Co 3 O 4 nanoparticles not only enhanced the surface area of the modified electrode for enzyme immobilization but also facilitated the electron transfer rate, resulting in a high sensitivity of the biosensor. The fabrication process of the sensing surface was characterized by scanning electron microscopy (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Amperometric detection of hydrogen peroxide was investigated by holding the modified electrode at −0.30 V (vs. Ag/AgCl). The biosensor showed optimum response within 5 s at pH 7.0. The optimized biosensor showed linear response range of 7.4 × 10 −7 –1.9 × 10 −5 M with a detection limit of 7.4 × 10 −7 . The applicability of the purposed biosensor was tested by detecting hydrogen peroxide in disinfector samples. The average recovery was calculated as 100.78 ± 0.89

Enhanced mechanical properties of single walled carbon nanotube-borosilicate glass composite due to cushioning effect and localized plastic flow

Directory of Open Access Journals (Sweden)

Sujan Ghosh

2011-12-01

Full Text Available A borosilicate glass composite has been fabricated incorporating Single Wall Carbon Nanotubes (SWCNT in the glass matrix by melt-quench technique. Hardness and the fracture toughness of the composite, were found to increase moderately with respect to the base glass. Interestingly one can observe accumulation of SWCNT bundles around the crack zone though no such accumulation was observed in the crack free indentation zone. The enhanced hardness of the composite was discussed by correlating the cushioning as well as toughening behavior of the agglomerated SWCNT bundles. On the other hand enhanced plastic flow was proposed to be the prime reason for the accumulation of SWCNT bundles around the crack, which increases the toughness of the composite by reducing the crack length. Moreover to ascertain the enhanced plasticity of the composite than that of the glass we calculated the recovery resistance of glass and the composite where recovery resistance of composite was found to be higher than that of the glass.

Layer-by-layer assemblies of chitosan/multi-wall carbon nanotubes and glucose oxidase for amperometric glucose biosensor applications

International Nuclear Information System (INIS)

Wu Baoyan; Hou Shihua; Yu Min; Qin Xia; Li, Sha; Chen Qiang

2009-01-01

A novel amperometric glucose biosensor based on multilayer films containing chitosan, multi-wall carbon nanotubes (MWCNTs) and glucose oxidase (GOD) was developed. MWCNTs were solubilized in chitosan (Chit-MWCNTs) used to interact with GOD. Poly (allylamine) (PAA) and polyvinylsulfuric acid potassium salt (PVS) were alternately deposited on the cleaned Pt electrode surface ((PVS/PAA) 3 /Pt). The (PVS/PAA) 3 /Pt electrode was alternately immersed in Chit-MWCNTs and GOD to assemble different layers of multilayer films. PBS washing was applied at the end of each assembly deposition for dissociating the weak adsorption. Micrographs of MWCNTs were obtained by scanning electron microscope, and properties of the resulting biosensors were measured by electrochemical measurements. Among the resulting biosensors, the biosensor based on eight layers of multilayer films was best. The resulting biosensor was able to efficiently monitor glucose, with the response time within 8 s, a detection limit of 21 μM estimated at a signal-to-noise ratio of 3, a linear range of 1-10 mM, the sensitivity of 0.45 μA/mM, and well stability. The study can provide a feasible simple approach on developing a new immobilization matrix for biosensors and surface functionalization

Fabrication of an Amperometric Flow-Injection Microfluidic Biosensor Based on Laccase for In Situ Determination of Phenolic Compounds

Directory of Open Access Journals (Sweden)

Juan C. Gonzalez-Rivera

2015-01-01

Full Text Available We aim to develop an in situ microfluidic biosensor based on laccase from Trametes pubescens with flow-injection and amperometry as the transducer method. The enzyme was directly immobilized by potential step chronoamperometry, and the immobilization was studied using cyclic voltammetry and electrochemical impedance spectroscopy. The electrode response by amperometry was probed using ABTS and syringaldazine. A shift of interfacial electron transfer resistance and the electron transfer rate constant from 18.1 kΩ to 3.9 MΩ and 4.6 × 10−2 cm s−1 to 2.1 × 10−4 cm s−1, respectively, evidenced that laccase was immobilized on the electrode by the proposed method. We established the optimum operating conditions of temperature (55°C, pH (4.5, injection flow rate (200 µL min−1, and applied potential (0.4 V. Finally, the microfluidic biosensor showed better lower limit of detection (0.149 µM and sensitivity (0.2341 nA µM−1 for ABTS than previous laccase-based biosensors and the in situ operation capacity.

Higher lung accumulation of intravenously injected organic nanotubes

Directory of Open Access Journals (Sweden)

Maitani Y

2013-01-01

Full Text Available Yoshie Maitani,1 Yuri Nakamura,1 Masao Kon,1 Emi Sanada,1 Kae Sumiyoshi,1 Natsuki Fujine,1 Masumi Asakawa,2 Masaki Kogiso,2 Toshimi Shimizu21Institute of Medicinal Chemistry, Hoshi University, Tokyo, Japan; 2Nanotube Research Center (NTRC, National Institute of Advanced Industrial Science and Technology (AIST, Tsukuba, JapanAbstract: The size and shape of intravenously injected particles can affect their biodistribution and is of importance for the development of particulated drug carrier systems. In this study, organic nanotubes (ONTs with a carboxyl group at the surface, a length of approximately 2 µm and outer diameter of 70–90 nm, were injected intravenously into tumor-bearing mice. To use ONTs as drug carriers, the biodistribution in selected organs of ONTs postinjection was examined using irinotecan, as an entrapped water-soluble marker inside ONTs, and gadolinium-chelated ONT, as an ONT marker, and compared with that of a 3 µm fluorescently labeled spherical microparticle which was similar size to the length of ONTs. It was found that for irinotecan, its active metabolite and gadolinium-chelated ONTs were highly accumulated in the lung, but to a lower level in the liver and spleen. On the other hand, microparticles deposited less in the lung and more highly in the liver. Moreover, histologic examination showed ONTs distributed more in lung tissues in part, whereas microparticles were present in blood vessels postinjection. These preliminary results support the notion of using negatively charged ONTs as intravascular carriers to maximize accumulation in the lung whilst reducing sequestration by the liver and spleen. This finding suggested that ONTs are potential carriers for lung-targeting drug delivery.Keywords: organic nanotube, lung, biodistribution, microparticle, particle shape

Reverse capillary flow of condensed water through aligned multiwalled carbon nanotubes

International Nuclear Information System (INIS)

Yun, Jongju; Jeon, Wonjae; Alam Khan, Fakhre; Lee, Jinkee; Baik, Seunghyun

2015-01-01

Molecular transport through nanopores has recently received considerable attention as a result of advances in nanofabrication and nanomaterial synthesis technologies. Surprisingly, water transport investigations through carbon nanochannels resulted in two contradicting observations: extremely fast transport or rejection of water molecules. In this paper, we elucidate the mechanism of impeded water vapor transport through the interstitial space of aligned multiwalled carbon nanotubes (aligned-MWCNTs)—capillary condensation, agglomeration, reverse capillary flow, and removal by superhydrophobicity at the tip of the nanotubes. The origin of separation comes from the water’s phase change from gas to liquid, followed by reverse capillary flow. First, the saturation water vapor pressure is decreased in a confined space, which is favorable for the phase change of incoming water vapor into liquid drops. Once continuous water meniscus is formed between the nanotubes by the adsoprtion and agglomeration of water molecules, a high reverse Laplace pressure is induced in the mushroom-shaped liquid meniscus at the entry region of the aligned-MWCNTs. The reverse Laplace pressure can be significantly enhanced by decreasing the pore size. Finally, the droplets pushed backward by the reverse Laplace pressure can be removed by superhydrophobicity at the tip of the aligned-MWCNTs. The analytical analysis was also supported by experiments carried out using 4 mm-long aligned-MWCNTs with different intertube distances. The water rejection rate and the separation factor increased as the intertube distance decreased, resulting in 90% and 10, respectively, at an intertube distance of 4 nm. This mechanism and nanotube membrane may be useful for energy-efficient water vapor separation and dehumidification. (paper)

Enzyme-less and low-potential sensing of glucose using a glassy carbon electrode modified with palladium nanoparticles deposited on graphene-wrapped carbon nanotubes

International Nuclear Information System (INIS)

Nayak, Pranati; Nair, Santhosh P.; Ramaprabhu, Sundara

2016-01-01

The article describes an amperometric sensor for enzyme-less detection of glucose based on homogeneously anchored Pd nanoparticles (Pd-NPs) on graphene - wrapped carbon nanotubes (Pd-GWCNTs) as sensing matrix. The unique features of GWCNTs (such as the highly protruded outer graphene layer and an inner tubular morphology) result in enhanced electrochemical performance compared to the use of conventional multi walled carbon nanotubes (MWCNTs). Glucose electro-oxidation occurs at a rather low working potential (+50 mV vs Ag/AgCl), and glucose can be continuously sensed in 0.1 M NaOH solution in concentrations of up to 19.5 mM. The sensor possesses good reproducibility, a fast response time, stable amperometric response and a lower detection limit. Due to its low working potential, it is not interfered by dopamine, uric acid, ascorbic acid, sucrose, fructose and lactose. We presume that these beneficial properties are a result of the synergetic advantages of using catalytic Pd NPs and graphene wrapped CNTs, both of which facilitate low-potential electrooxidation of glucose. (author)

Covalent Coupling of Organophosphorus Hydrolase Loaded Quantum Dots to Carbon Nanotube/Au Nanocomposite for Enhanced Detection of Methyl Parathion

Energy Technology Data Exchange (ETDEWEB)

Du, Dan; Chen, Wenjuan; Zhang, Weiying; Liu, Deli; Li, Haibing; Lin, Yuehe

2010-02-15

An amperometric biosensor for highly selective and sensitive determination of methyl parathion (MP) was developed based on dual signal amplification: (1) a large amount of introduced enzyme on the electrode surface and (2) synergistic effects of nanoparticles towards enzymatic catalysis. The fabrication process includes (1) electrochemical deposition of gold nanoparticles by a multi-potential step technique at multiwalled carbon nanotube (MWCNT) film pre-cast on a glassy carbon electrode and (2) immobilization of methyl parathion degrading enzyme (MPDE) onto a modified electrode through CdTe quantum dots (CdTe QDs) covalent attachment. The introduced MWCNT and gold nanoparticles significantly increased the surface area and exhibited synergistic effects towards enzymatic catalysis. CdTe QDs are further used as carriers to load a large amount of enzyme. As a result of these two important enhancement factors, the proposed biosensor exhibited extremely sensitive, perfectly selective, and rapid response to methyl parathion in the absence of a mediator.

Immobilization of malate dehydrogenase on carbon nanotubes for development of malate biosensor.

Science.gov (United States)

Ruhal, A; Rana, J S; Kumar, S; Kumar, A

2012-12-22

An amperometric malic acid biosensor was developed by immobilizing malate dehydrogenase on multi-walled carbon nanotubes (MWCNT) coated on screen printed carbon electrode. The screen printed carbon electrode is made up of three electrodes viz., carbon as working, platinum as counter and silver as reference electrode. Detection of L-malic acid concentration provides important information about the ripening and shelf life of the fruits. The NADP specific malate dehydrogenase was immobilized on carboxylated multiwalled carbon nanotubes using cross linker EDC [1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide] on screen printed carbon electrode. An amperometric current was measured by differential pulse voltammetry (DPV) which increases with increasing concentrations of malic acid at fixed concentration of NADP. Enzyme electrode was characterized by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. The detection limit of malic acid by the sensor was 60 - 120 μM and sensitivity of the sensor was 60 μM with a response time of 60s. The usual detection methods of malic acid are nonspecific, time consuming and less sensitive. However, an amperometric malic acid nanosensor is quick, specific and more sensitive for detection of malic acid in test samples.

Flow induced vibration and stability analysis of multi wall carbon nanotubes

Energy Technology Data Exchange (ETDEWEB)

Yun, Kyung Jae [Agency for Defense Development, Daejeon (Korea, Republic of); Choi, Jong Woon [Korean Intellectual Property Office, Daejeon (Korea, Republic of); Kim, Sung Kyun [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Song, Oh Seop [Chungnam National Univ., Daejeon (Korea, Republic of)

2012-12-15

The free vibration and flow induced flutter instability of cantilever multi wall carbon nanotubes conveying fluid are investigated and the nanotubes are modeled as thin-walled beams. The non-classical effects of the transverse shear, rotary inertia, warping inhibition, and van der Waals forces between two walls are incorporated into the structural model. The governing equations and associated boundary conditions are derived using Hamilton's principle. A numerical analysis is carried out by using the extended Galerkin method, which enables us to obtain more accurate solutions compared to the conventional Galerkin method. Cantilevered carbon nanotubes are damped with decaying amplitude for a flow velocity below a certain critical value. However, beyond this critical flow velocity, flutter instability may occur. The variations in the critical flow velocity with respect to both the radius ratio and length of the carbon nanotubes are investigated and pertinent conclusions are outlined. The differences in the vibration and instability characteristics between the Timoshenko beam theory and Euler beam theory are revealed. A comparative analysis of the natural frequencies and flutter characteristics of MWCNTs and SWCNTs is also performed.

Determination of carbohydrates using pulsed amperometric detection combined with anion exchange separations

Energy Technology Data Exchange (ETDEWEB)

Edwards, W.T.; Pohl, C.A.; Rubin, R.

1987-06-01

Carbohydrates, including the monosaccharides commonly found in wood and wood pulp hydrolyzates, are separated by anion exchange chromatography using hydroxide and acetate eluants and are determined using pulsed amperometric detection. The detection method is based on oxidizing the sugars in a flow-through electrochemical cell equipped with a gold working electrode. A repeating cycle of three potentials is used: the first to oxidize the carbohydrates and measure the current generated, and two subsequent pulses to clean the electrode surface of oxidation products. The method is fast, sensitive, and requires no pre-column derivatization. It is applied to a sample of hydrolyzed wood pulp, which can be analyzed after minimal sample preparation. Detection limits are of the order of 1 mg/kg for monosaccharides in a 50 micro L injection. (Refs. 8).

Subcutaneous injection of water-soluble multi-walled carbon nanotubes in tumor-bearing mice boosts the host immune activity

International Nuclear Information System (INIS)

Meng Jie; Yang Man; Jia Fumin; Kong Hua; Zhang Weiqi; Xu Haiyan; Wang Chaoying; Xie Sishen; Xing Jianmin

2010-01-01

The immunological responses induced by oxidized water-soluble multi-walled carbon nanotubes on a hepatocarcinoma tumor-bearing mice model via a local administration of subcutaneous injection were investigated. Experimental results show that the subcutaneously injected carbon nanotubes induced significant activation of the complement system, promoted inflammatory cytokines' production and stimulated macrophages' phagocytosis and activation. All of these responses increased the general activity of the host immune system and inhibited the progression of tumor growth.

Subcutaneous injection of water-soluble multi-walled carbon nanotubes in tumor-bearing mice boosts the host immune activity

Science.gov (United States)

Meng, Jie; Yang, Man; Jia, Fumin; Kong, Hua; Zhang, Weiqi; Wang, Chaoying; Xing, Jianmin; Xie, Sishen; Xu, Haiyan

2010-04-01

The immunological responses induced by oxidized water-soluble multi-walled carbon nanotubes on a hepatocarcinoma tumor-bearing mice model via a local administration of subcutaneous injection were investigated. Experimental results show that the subcutaneously injected carbon nanotubes induced significant activation of the complement system, promoted inflammatory cytokines' production and stimulated macrophages' phagocytosis and activation. All of these responses increased the general activity of the host immune system and inhibited the progression of tumor growth.

Subcutaneous injection of water-soluble multi-walled carbon nanotubes in tumor-bearing mice boosts the host immune activity

Energy Technology Data Exchange (ETDEWEB)

Jie, Meng; Man, Yang; Fumin, Jia; Hua, Kong; Weiqi, Zhang; Haiyan, Xu [Department of Biomedical Engineering, Institute of Basic Medical Sciences and School of Basic Medicine, Chinese Academy of Medical Sciences and Peking Union Medical College, 5 Dong Dan San Tiao, Beijing 100005 (China); Chaoying, Wang; Sishen, Xie [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, 8 Nan San Jie, Zhongguancun, Beijing100080 (China); Xing Jianmin, E-mail: xuhy@pumc.edu.cn [Centre for Evidence-Based Chinese Medicine, Beijing University of Chinese Medicine, 11 Bei San Huan Dong Lu, Beijing 100029 (China)

2010-04-09

The immunological responses induced by oxidized water-soluble multi-walled carbon nanotubes on a hepatocarcinoma tumor-bearing mice model via a local administration of subcutaneous injection were investigated. Experimental results show that the subcutaneously injected carbon nanotubes induced significant activation of the complement system, promoted inflammatory cytokines' production and stimulated macrophages' phagocytosis and activation. All of these responses increased the general activity of the host immune system and inhibited the progression of tumor growth.

Flow Injection and Atomic Absorption Spectrometry (FI-AAS) -

DEFF Research Database (Denmark)

Hansen, Elo Harald

1996-01-01

One of the advantages of the flow injection (FI) concept is that it is compatible with virtually all detection techniques. Being a versatile vehicle for enhancing the performance of the individual detection devices, the most spectacular results have possibly been obtained in conjunction with atomic...... the point of sample injection/introduction to the point of detection. Hence, in FI-fAAS this feature allows not only to obtain improved repeatability but also improved accuracy, and because the wash to sample ratio is high it permits the handling of samples with elevated salt contents - which...

Direct current injection and thermocapillary flow for purification of aligned arrays of single-walled carbon nanotubes

Energy Technology Data Exchange (ETDEWEB)

Xie, Xu; Islam, Ahmad E.; Seabron, Eric; Dunham, Simon N.; Du, Frank; Lin, Jonathan; Wilson, William L.; Rogers, John A., E-mail: jrogers@illinois.edu [Department of Materials Science and Engineering, Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States); Wahab, Muhammad A.; Alam, Muhammad A. [School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907 (United States); Li, Yuhang [Institute of Solid Mechanics, Beihang University, Beijing 100191 (China); Tomic, Bojan [Department of Electrical Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States); Huang, Jiyuan [Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States); Burns, Branden [Department of Physics, Purdue University, West Lafayette, Indiana 47907 (United States); Song, Jizhou [Department of Engineering Mechanics and Soft Matter Research Center, Zhejiang University, Hangzhou 310027 (China); Huang, Yonggang [Department of Civil and Environmental Engineering, Department of Mechanical Engineering, Center for Engineering and Health, and Skin Disease Research Center, Northwestern University, Evanston, Illinois 60208 (United States)

2015-04-07

Aligned arrays of semiconducting single-walled carbon nanotubes (s-SWNTs) represent ideal configurations for use of this class of material in high performance electronics. Development of means for removing the metallic SWNTs (m-SWNTs) in as-grown arrays represents an essential challenge. Here, we introduce a simple scheme that achieves this type of purification using direct, selective current injection through interdigitated electrodes into the m-SWNTs, to allow their complete removal using processes of thermocapillarity and dry etching. Experiments and numerical simulations establish the fundamental aspects that lead to selectivity in this process, thereby setting design rules for optimization. Single-step purification of arrays that include thousands of SWNTs demonstrates the effectiveness and simplicity of the procedures. The result is a practical route to large-area aligned arrays of purely s-SWNTs with low-cost experimental setups.

Direct current injection and thermocapillary flow for purification of aligned arrays of single-walled carbon nanotubes

International Nuclear Information System (INIS)

Xie, Xu; Islam, Ahmad E.; Seabron, Eric; Dunham, Simon N.; Du, Frank; Lin, Jonathan; Wilson, William L.; Rogers, John A.; Wahab, Muhammad A.; Alam, Muhammad A.; Li, Yuhang; Tomic, Bojan; Huang, Jiyuan; Burns, Branden; Song, Jizhou; Huang, Yonggang

2015-01-01

Aligned arrays of semiconducting single-walled carbon nanotubes (s-SWNTs) represent ideal configurations for use of this class of material in high performance electronics. Development of means for removing the metallic SWNTs (m-SWNTs) in as-grown arrays represents an essential challenge. Here, we introduce a simple scheme that achieves this type of purification using direct, selective current injection through interdigitated electrodes into the m-SWNTs, to allow their complete removal using processes of thermocapillarity and dry etching. Experiments and numerical simulations establish the fundamental aspects that lead to selectivity in this process, thereby setting design rules for optimization. Single-step purification of arrays that include thousands of SWNTs demonstrates the effectiveness and simplicity of the procedures. The result is a practical route to large-area aligned arrays of purely s-SWNTs with low-cost experimental setups

Comparison between a Direct-Flow SPR Immunosensor for Ampicillin and a Competitive Conventional Amperometric Device: Analytical Features and Possible Applications to Real Samples

Science.gov (United States)

Tomassetti, Mauro; Merola, Giovanni; Martini, Elisabetta; Campanella, Luigi; Sanzò, Gabriella; Favero, Gabriele; Mazzei, Franco

2017-01-01

In this research, we developed a direct-flow surface plasmon resonance (SPR) immunosensor for ampicillin to perform direct, simple, and fast measurements of this important antibiotic. In order to better evaluate the performance, it was compared with a conventional amperometric immunosensor, working with a competitive format with the aim of finding out experimental real advantages and disadvantages of two respective methods. Results showed that certain analytical features of the new SPR immunodevice, such as the lower limit of detection (LOD) value and the width of the linear range, are poorer than those of a conventional amperometric immunosensor, which adversely affects the application to samples such as natural waters. On the other hand, the SPR immunosensor was more selective to ampicillin, and measurements were more easily and quickly attained compared to those performed with the conventional competitive immunosensor. PMID:28394296

Flow injection analysis of sulphide based on its photoelectrocatalytic oxidation at poly-methylene blue modified glassy carbon electrode

International Nuclear Information System (INIS)

Dilgin, Yusuf; Canarslan, Seda; Ayyildiz, Onder; Ertek, Bensu; Nişli, Gürel

2012-01-01

A new approach for photoelectrocatalytic determination of sulphide in a flow injection analysis (FIA) system was studied using a poly-methylene blue modified glassy carbon electrode (poly-MB/GCE). Results from electrochemical measurements have revealed that poly-MB/GCE is capable of signalling electrocatalytic and photoelectrocatalytic activity towards sulphide oxidation. When the surface of poly-MB/GCE was irradiated with a light source (250 W Halogen lamp), the electrocatalytic current increased substantially. A homemade flow electrochemical cell with a suitable transparent window for the irradiation of the electrode surface was used to perform the photoelectrocatalytic determination of sulphide in FIA system. The currents obtained from the photoamperometric measurements in the FIA system at optimum conditions (carrier solution: pH 9.0 Britton Robinson buffer solution containing 0.1 M KCl; flow rate: 1.3 mL min −1 ; transmission tubing length: 10 cm; injection volume: 100 μL; and constant applied potential: +150 mV vs. Ag/AgCl/KCl sat ) were linearly correlated with the sulphide concentration. The calibration curves were obtained for sulphide concentrations in a range of 0.5–500 μM. The detection limits were found to be 0.27 and 0.15 μM for amperometric and photoamperometric methods, respectively. The proposed method was successfully applied to different wastewaters such as municipal sewage or tannery wastewater. Finally, results from the sulphide measurements by poly-MB/GCE were in good agreement with those attained using spectrophotometric method.

Amperometric sensing of anti-HIV drug zidovudine on Ag nanofilm-multiwalled carbon nanotubes modified glassy carbon electrode

Energy Technology Data Exchange (ETDEWEB)

Rafati, Amir Abbas, E-mail: aa_rafati@basu.ac.ir; Afraz, Ahmadreza

2014-06-01

The zidovudine (ZDV) is the first drug approved for the treatment of HIV virus infection. The detection and determination of this drug are very importance in human serum because of its undesirable effects. A new ZDV sensor was fabricated on the basis of nanocomposite of silver nanofilm (Ag-NF) and multiwalled carbon nanotubes (MWCNTs) immobilized on glassy carbon electrode (GCE). The modified electrodes were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), cyclic voltammetry (CV), and linear sweep voltammetry (LSV) techniques. Results showed that the electrodeposited silver has a nanofilm structure and further electrochemical studies showed that the prepared nanocomposite has high electrocatalytic activity and is appropriate for using in sensors. The amperometric technique under optimal conditions is used for the determination of ZDV ranging from 0.1 to 400 ppm (0.37 μM–1.5 mM) with a low detection limit of 0.04 ppm (0.15 μM) (S/N = 3) and good sensitivity. The prepared sensor possessed accurate and rapid response to ZDV and shows an average recovery of 98.6% in real samples. - Highlights: • New anti-HIV drug sensor was fabricated on the basis of nanomaterials composite. • The GCE modified by prepared hydrophilic MWCNT silver nanoparticles. • Silver nanofilm electrodeposited on MWCNT/GCE and characterized by SEM, EDX, CV and LSV • Response of electrode to ZDV was thoroughly investigated by electrochemical techniques.

Amperometric immunosensor based on multiwalled carbon nanotubes/Prussian blue/nanogold-modified electrode for determination of α-fetoprotein.

Science.gov (United States)

Jiang, Wen; Yuan, Ruo; Chai, Ya-Qin; Yin, Bing

2010-12-01

In this article, a conspicuously simple and highly sensitive amperometric immunosensor based on the sequential electrodeposition of Prussian blue (PB) and gold nanoparticles (GNPs) on multiwalled carbon nanotube (MWCNT)-modified glassy carbon electrode (GCE) surface is proposed for the detection of α-fetoprotein (AFP). By comparison with PB, the MWCNT/PB composite film had been proven to show much better electrochemical stability and a larger response current. The electrodeposited GNP film can be used not only to immobilize biomolecules but also to avoid the leakage of PB and to prevent shedding of MWCNT/PB composite film from the electrode surface. The performance and factors influencing the performance of the immunosensor were investigated. Under optimal experimental conditions, the proposed immunosensor for AFP was observed with an ultralow limit of detection (LOD) equal to 3 pg/ml (at 3δ), and the linear working range spanned the concentrations of AFP from 0.01 to 300 ng/ml. Moreover, the immunosensor, as well as a commercially available kit, was examined for use in the determination of AFP in real human serum specimens. More significant, the assay mentioned here is simpler than the traditional enzyme-linked immunosorbent assay (ELISA), and an excellent correlation of levels of AFP measured was obtained, indicating that the developed immunoassay could be a promising alternative approach for detection of AFP and other tumor markers in the clinical diagnosis. Copyright © 2010 Elsevier Inc. All rights reserved.

Platinum decorated carbon nanotubes for highly sensitive amperometric glucose sensing

International Nuclear Information System (INIS)

Xie Jining; Wang Shouyan; Aryasomayajula, L; Varadan, V K

2007-01-01

Fine platinum nanoparticles (1-5 nm in diameter) were deposited on functionalized multi-walled carbon nanotubes (MWNTs) through a decoration technique. A novel type of enzymatic Pt/MWNTs paste-based mediated glucose sensor was fabricated. Electrochemical measurements revealed a significantly improved sensitivity (around 52.7 μA mM -1 cm -2 ) for glucose sensing without using any picoampere booster or Faraday cage. In addition, the calibration curve exhibited a good linearity in the range of 1-28 mM of glucose concentration. Transmission electron microscopy (TEM) and x-ray photoelectron spectroscopy (XPS) were performed to investigate the nanoscale structure and the chemical bonding information of the Pt/MWNTs paste-based sensing material, respectively. The improved sensitivity of this novel glucose sensor could be ascribed to its higher electroactive surface area, enhanced electron transfer, efficient enzyme immobilization, unique interaction in nanoscale and a synergistic effect on the current signal from possible multi-redox reactions

Wireless Amperometric Neurochemical Monitoring Using an Integrated Telemetry Circuit

Science.gov (United States)

Roham, Masoud; Halpern, Jeffrey M.; Martin, Heidi B.; Chiel, Hillel J.

2015-01-01

An integrated circuit for wireless real-time monitoring of neurochemical activity in the nervous system is described. The chip is capable of conducting high-resolution amperometric measurements in four settings of the input current. The chip architecture includes a first-order ΔΣ modulator (ΔΣM) and a frequency-shift-keyed (FSK) voltage-controlled oscillator (VCO) operating near 433 MHz. It is fabricated using the AMI 0.5 μm double-poly triple-metal n-well CMOS process, and requires only one off-chip component for operation. Measured dc current resolutions of ~250 fA, ~1.5 pA, ~4.5 pA, and ~17 pA were achieved for input currents in the range of ±5, ±37, ±150, and ±600 nA, respectively. The chip has been interfaced with a diamond-coated, quartz-insulated, microneedle, tungsten electrode, and successfully recorded dopamine concentration levels as low as 0.5 μM wirelessly over a transmission distance of ~0.5 m in flow injection analysis experiments. PMID:18990633

Wireless amperometric neurochemical monitoring using an integrated telemetry circuit.

Science.gov (United States)

Roham, Masoud; Halpern, Jeffrey M; Martin, Heidi B; Chiel, Hillel J; Mohseni, Pedram

2008-11-01

An integrated circuit for wireless real-time monitoring of neurochemical activity in the nervous system is described. The chip is capable of conducting high-resolution amperometric measurements in four settings of the input current. The chip architecture includes a first-order Delta Sigma modulator (Delta Sigma M) and a frequency-shift-keyed (FSK) voltage-controlled oscillator (VCO) operating near 433 MHz. It is fabricated using the AMI 0.5 microm double-poly triple-metal n-well CMOS process, and requires only one off-chip component for operation. Measured dc current resolutions of approximately 250 fA, approximately 1.5 pA, approximately 4.5 pA, and approximately 17 pA were achieved for input currents in the range of +/-5, +/-37, +/-150, and +/-600 nA, respectively. The chip has been interfaced with a diamond-coated, quartz-insulated, microneedle, tungsten electrode, and successfully recorded dopamine concentration levels as low as 0.5 microM wirelessly over a transmission distance of approximately 0.5 m in flow injection analysis experiments.

Preparation of carbon nanotubes with different morphology by microwave plasma enhanced chemical vapour deposition

Energy Technology Data Exchange (ETDEWEB)

Duraia, El-Shazly M. [Suez Canal University, Faculty of Science, Physics Department, Ismailia (Egypt); Al-Farabi Kazakh National University, 71 Al-Farabi av., 050038 Almaty (Kazakhstan); Institute of Physics and Technology, Ibragimov Street 11, 050032 Almaty (Kazakhstan); Mansurov, Zulkhair [Al-Farabi Kazakh National University, 71 Al-Farabi av., 050038 Almaty (Kazakhstan); Tokmoldin, S.Zh. [Institute of Physics and Technology, Ibragimov Street 11, 050032 Almaty (Kazakhstan)

2010-04-15

In this work we present a part of our results about the preparation of carbon nanotube with different morphologies by using microwave plasma enhanced chemical vapour deposition MPECVD. Well aligned, curly, carbon nanosheets, coiled carbon sheets and carbon microcoils have been prepared. We have investigated the effect of the different growth condition parameters such as the growth temperature, pressure and the hydrogen to methane flow rate ratio on the morphology of the carbon nanotubes. The results showed that there is a great dependence of the morphology of carbon nanotubes on these parameters. The yield of the carbon microcoils was high when the growth temperature was 700 C. There is a linear relation between the growth rate and the methane to hydrogen ratio. The effect of the gas pressure on the CNTs was also studied. Our samples were investigated by scanning electron microscope and Raman spectroscopy (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Biosensing of glucose in flow injection analysis system based on glucose oxidase-quantum dot modified pencil graphite electrode.

Science.gov (United States)

Sağlam, Özlem; Kızılkaya, Bayram; Uysal, Hüseyin; Dilgin, Yusuf

2016-01-15

A novel amperometric glucose biosensor was proposed in flow injection analysis (FIA) system using glucose oxidase (GOD) and Quantum dot (ZnS-CdS) modified Pencil Graphite Electrode (PGE). After ZnS-CdS film was electrochemically deposited onto PGE surface, GOD was immobilized on the surface of ZnS-CdS/PGE through crosslinking with chitosan (CT). A pair of well-defined reversible redox peak of GOD was observed at GOD/CT/ZnS-CdS/PGE based on enzyme electrode by direct electron transfer between the protein and electrode. Further, obtained GOD/CT/ZnS-CdS/PGE offers a disposable, low cost, selective and sensitive electrochemical biosensing of glucose in FIA system based on the decrease of the electrocatalytic response of the reduced form of GOD to dissolved oxygen. Under optimum conditions (flow rate, 1.3mL min(-1); transmission tubing length, 10cm; injection volume, 100μL; and constant applied potential, -500mV vs. Ag/AgCl), the proposed method displayed a linear response to glucose in the range of 0.01-1.0mM with detection limit of 3.0µM. The results obtained from this study would provide the basis for further development of the biosensing using PGE based FIA systems. Copyright © 2015 Elsevier B.V. All rights reserved.

Determination of scandium in acid mine drainage by ICP-OES with flow injection on-line preconcentration using oxidized multiwalled carbon nanotubes.

Science.gov (United States)

Jerez, Javier; Isaguirre, Andrea C; Bazán, Cristian; Martinez, Luis D; Cerutti, Soledad

2014-06-01

An on-line scandium preconcentration and determination system implemented with inductively coupled plasma optical emission spectrometry associated with flow injection was studied. Trace amounts of scandium were preconcentrated by sorption on a minicolumn packed with oxidized multiwalled carbon nanotubes, at pH 1.5. The retained analyte was removed from the minicolumn with 30% (v/v) nitric acid. A total enrichment factor of 225-fold was obtained within a preconcentration time of 300 s (for a 25 mL sample volume). The overall time required for preconcentration and elution of 25 mL of sample was about 6 min; the throughput was about 10 samples per hour. The value of the detection limit was 4 ng L(-1) and the precision for 10 replicate determinations at 100 ng L(-1) Sc level was 5% relative standard deviation, calculated from the peak heights obtained. The calibration graph using the preconcentration system was linear with a correlation coefficient of 0.9996 at levels near the detection limits up to at least 10 mg L(-1). After optimization, the method was successfully applied to the determination of Sc in an acid drainage from an abandoned mine located in the province of San Luis, Argentina. Copyright © 2014 Elsevier B.V. All rights reserved.

Experimental investigation on natural circulation and air-injection enhanced circulation in a simple loop

International Nuclear Information System (INIS)

Walter Ambrosini; Nicola Forgione; Francesco Oriolo; Filippo Pellacani; Mariano Tarantino; Claudio Struckmann

2005-01-01

Full text of publication follows: Natural circulation represents an interesting phenomenon because of both the complex aspects characterising it and for the widespread application in industry. On the other hand, injection of a gas into a rising branch of a loop represents a means to establish or to enhance a circulation flow, as it occurs in the so-called 'air-lift' loops. Both natural circulation and gas-injection enhanced circulation are presently considered for cooling Accelerator Driven System (ADS) reactors. These are subcritical reactors in which the fission reaction chain is maintained by the injection of neutrons obtained by spallation reactions in a target through a high energy proton beam generated in an external accelerator. The capability of such reactors to be used as incinerators of long lived fission products makes them particularly interesting in the light of the closure of the nuclear fuel cycle. Some of the fluids proposed as coolants for these reactors are liquid metals, with main interest for lead and lead-bismuth eutectic (LBE). Experimental activities are being performed in support to the design of the reactor prototype by different organisations. The university of Pisa, in addition to provide cooperation in these large scale activities performed with LBE has set up a specific experimental program aimed at studying the fundamental mechanisms involved in natural circulation and gas-injection enhanced circulation. The adopted experimental facility consists in a simple loop, having a rectangular lay-out (roughly, 4 m tall and 1 m wide), equipped with a 5 kW, 1 m tall heater, a 2 m long pipe-in-pipe heat exchanger, an air injection device and a separator. The fluid adopted in the tests performed up to now is water, though studies for evaluating the feasibility of the adoption of different fluids have been undertaken. Experimental data reported in previous publications concerning this research were related to a relatively high range of gas-injection

O-(β-hydroxyethylrutosides determination by micellar flow injection (FI-spectrofluorimetry

Directory of Open Access Journals (Sweden)

Cecilia Mariana Peralta

2014-12-01

Full Text Available A simple, eco-friendly, sensitive and economic flow injection spectrofluorimetric method was developed for the determination of O-(β-hydroxyethylrutosides. The procedure was based on the use of an anionic surfactant such as sodium dodecyl sulfate to provide an appreciable O-(β-hydroxyethylrutosides fluorescence enhancement, increasing considerably the sensitivity of detection. All the variables affecting the fluorescence intensity were studied and optimized. The flow rate was 5 mL/min with detection at 450 nm (after excitation at 346 nm. A linear correlation between drug amount and peak area was established for O-(β-hydroxyethylrutosides in the range of 0.01–200 µg/mL with a detection limit of 0.001 µg/mL (s/n=3. Validation processes were performed by recovering studies with satisfactory results. The new methodology can be employed for the routine analysis of O-(β-hydroxyethylrutosides in bulks as well as in commercial formulations. Keywords: O-(β-hydroxyethylrutosides, Micellar enhancement, Flow injection, Spectrofluorimetry, Pharmaceuticals

The effects of non-uniform flow velocity on vibrations of single-walled carbon nanotube conveying fluid

Energy Technology Data Exchange (ETDEWEB)

Sadeghi-Goughari, Moslem [Shahid Bahonar University of Kerman, Kerman (Iran, Islamic Republic of); Hosseini, Mohammad [Sirjan University of Technology, Sirjan (Iran, Islamic Republic of)

2015-02-15

The vibrational behavior of a viscous nanoflow-conveying single-walled carbon nanotube (SWCNT) was investigated. The nonuniformity of the flow velocity distribution caused by the viscosity of fluid and the small-size effects on the flow field was considered. Euler-Bernoulli beam model was used to investigate flow-induced vibration of the nanotube, while the non-uniformity of the flow velocity and the small-size effects of the flow field were formulated through Knudsen number (Kn), as a discriminant parameter. For laminar flow in a circular nanotube, the momentum correction factor was developed as a function of Kn. For Kn = 0 (continuum flow), the momentum correction factor was found to be 1.33, which decreases by the increase in Kn may even reach near 1 for the transition flow regime. We observed that for passage of viscous flow through a nanotube with the non-uniform flow velocity, the critical continuum flow velocity for divergence decreased considerably as opposed to those for the uniform flow velocity, while by increasing Kn, the difference between the uniform and non-uniform flow models may be reduced. In the solution part, the differential transformation method (DTM) was used to solve the governing differential equations of motion.

The effects of non-uniform flow velocity on vibrations of single-walled carbon nanotube conveying fluid

International Nuclear Information System (INIS)

Sadeghi-Goughari, Moslem; Hosseini, Mohammad

2015-01-01

The vibrational behavior of a viscous nanoflow-conveying single-walled carbon nanotube (SWCNT) was investigated. The nonuniformity of the flow velocity distribution caused by the viscosity of fluid and the small-size effects on the flow field was considered. Euler-Bernoulli beam model was used to investigate flow-induced vibration of the nanotube, while the non-uniformity of the flow velocity and the small-size effects of the flow field were formulated through Knudsen number (Kn), as a discriminant parameter. For laminar flow in a circular nanotube, the momentum correction factor was developed as a function of Kn. For Kn = 0 (continuum flow), the momentum correction factor was found to be 1.33, which decreases by the increase in Kn may even reach near 1 for the transition flow regime. We observed that for passage of viscous flow through a nanotube with the non-uniform flow velocity, the critical continuum flow velocity for divergence decreased considerably as opposed to those for the uniform flow velocity, while by increasing Kn, the difference between the uniform and non-uniform flow models may be reduced. In the solution part, the differential transformation method (DTM) was used to solve the governing differential equations of motion.

The impact of interpreted flow regimes during constant head injection tests on the estimated transmissivity from injection tests and difference flow logging

Energy Technology Data Exchange (ETDEWEB)

Hjerne, Calle; Ludvigsson, Jan-Erik; Harrstroem, Johan [Geosigma AB, Uppsala (Sweden)

2013-04-15

A large number of constant head injection tests were carried out in the site investigation at Forsmark using the Pipe String System, PSS3. During the original evaluation of the tests the dominating transient flow regimes during both the injection and recovery period were interpreted together with estimation of hydraulic parameters. The flow regimes represent different flow and boundary conditions during the tests. Different boreholes or borehole intervals may display different distributions of flow regimes. In some boreholes good agreement was obtained between the results of the injection tests and difference flow logging with Posiva flow log (PFL) but in other boreholes significant discrepancies were found. The main objective of this project is to study the correlation between transient flow regimes from the injection tests and other borehole features such as transmissivity, depth, geology, fracturing etc. Another subject studied is whether observed discrepancies between estimated transmissivity from difference flow logging and injection tests can be correlated to interpreted flow regimes. Finally, a detailed comparison between transient and stationary evaluation of transmissivity from the injection tests in relation to estimated transmissivity from PFL tests in corresponding sections is made. Results from previous injection tests in 5 m sections in boreholes KFM04, KFM08A and KFM10A were used. Only injection tests above the (test-specific) measurement limit regarding flow rate are included in the analyses. For all of these tests transient flow regimes were interpreted. In addition, results from difference flow logging in the corresponding 5 m test sections were used. Finally, geological data of fractures together with rock and fracture zone properties have been used in the correlations. Flow regimes interpreted from the injection period of the tests are generally used in the correlations but deviations between the interpreted flow regimes from the injection and

Current injection phase thermography for low-velocity impact damage identification in composite laminates

International Nuclear Information System (INIS)

Grammatikos, S.A.; Kordatos, E.Z.; Matikas, T.E.; David, C.; Paipetis, A.S.

2014-01-01

Highlights: • A novel Current injection phase thermography NDE method has been developed. • Blind impact damage has been successfully detected in composite laminates. • Carbon nanotubes enhance detection by improving of through thickness conductivity. • Detection is feasible with considerably less energy than for IR excited thermography. - Abstract: An innovative non-destructive evaluation (NDE) technique is presented based on current stimulated thermography. Modulated electric current is injected to Carbon Fibre Reinforced Plastics (CFRP) laminates as an external source of thermal excitation. Pulsed Phase Thermography (PPT) is concurrently employed to identify low velocity impact induced (LVI) damage. The efficiency of the proposed method is demonstrated for both plain and with Carbon Nanotubes (CNTs) modified laminates, which are subjected to low-velocity impact damaged composite laminates at different energy levels. The presence of the nano reinforcing phase is important in achieving a uniform current flow along the laminate, as it improves the through thickness conductivity. The acquired thermographs are compared with optical PPT, C-scan images and Computer Tomography (CT) representations. The typical energy input for successful damage identification with current injection is three to four orders of magnitude less compared to the energy required for optical PPT

Computational modelling of a non-viscous fluid flow in a multi-walled carbon nanotube modelled as a Timoshenko beam

International Nuclear Information System (INIS)

Khosravian, N; Rafii-Tabar, H

2008-01-01

In the design of nanotube-based fluidic devices, a critical issue is the effect of the induced vibrations in the nanotube arising from the fluid flow, since these vibrations can promote structural instabilities, such as buckling transitions. It is known that the induced resonant frequencies depend on the fluid flow velocity in a significant manner. We have studied, for the first time, the flow of a non-viscous fluid in stubby multi-walled carbon nanotubes, using the Timoshenko classical beam theory to model the nanotubes as a continuum structure. We have obtained the variations of the resonant frequencies with the fluid flow velocity under several experimentally interesting boundary conditions and aspect ratios of the nanotube. The main finding from our work is that, compared to an Euler-Bernoulli classical beam model of a nanotube, the Timoshenko beam predicts the loss of stability at lower fluid flow velocities

Computational modelling of a non-viscous fluid flow in a multi-walled carbon nanotube modelled as a Timoshenko beam

Energy Technology Data Exchange (ETDEWEB)

Khosravian, N; Rafii-Tabar, H [Computational Physical Sciences Research Laboratory, Department of Nano-Science, Institute for Research in Fundamental Sciences (IPM), PO Box 19395-5531, Tehran (Iran, Islamic Republic of)], E-mail: rafii-tabar@nano.ipm.ac.ir

2008-07-09

In the design of nanotube-based fluidic devices, a critical issue is the effect of the induced vibrations in the nanotube arising from the fluid flow, since these vibrations can promote structural instabilities, such as buckling transitions. It is known that the induced resonant frequencies depend on the fluid flow velocity in a significant manner. We have studied, for the first time, the flow of a non-viscous fluid in stubby multi-walled carbon nanotubes, using the Timoshenko classical beam theory to model the nanotubes as a continuum structure. We have obtained the variations of the resonant frequencies with the fluid flow velocity under several experimentally interesting boundary conditions and aspect ratios of the nanotube. The main finding from our work is that, compared to an Euler-Bernoulli classical beam model of a nanotube, the Timoshenko beam predicts the loss of stability at lower fluid flow velocities.

Experimental study on gas-injection enhanced circulation performed with the CIRCE facility

International Nuclear Information System (INIS)

Benamati, G.; Foletti, C.; Forgione, N.; Oriolo, F.; Scaddozzo, G.; Tarantino, M.

2007-01-01

This paper describes the results of an experimental campaign concerning the possibility of achieving a steady state circulation by gas-injection in a pool containing lead-bismuth eutectic (LBE) as working fluid. The activity was aimed at gaining information about the basic mechanisms of the gas injection enhanced circulation intended as a pumping system for a liquid metal cooled reactor. In particular, the paper is focused on the experimental work performed in the CIRCE large-scale facility, installed at the ENEA Brasimone Centre for studying the fluid-dynamic and operating behaviour of ADS reactor plants cooled by LBE. The gas enhanced circulation tests were carried out for different LBE temperatures (from 200 to 320 deg. C), under isothermal conditions and with a wide range of argon injected flow rates (from 0.5 to 7.0 Nl/s). The gas is injected from the bottom of the riser, by means of an appropriate nozzle, and the liquid metal flow rate is measured by a Venturi-Nozzle flow meter installed in the single phase part of the test section. The obtained results allowed formulating a characteristic curve of the system and evaluating the void fraction distribution along the riser path by means differential pressure measurements, which play an important role to generating the driving force for the circulation

Amperometric sensing of NADH and ethanol using a hybrid film electrode modified with electrochemically fabricated zirconia nanotubes and poly (acid fuchsin)

International Nuclear Information System (INIS)

Liu, X.; Li, B.; Zhan, G.; Liu, C.; Li, C.; Ma, M.

2012-01-01

We report on a glassy carbon electrode (GCE) modified with a film of chitosin containing acid fuchsin (AF) adsorbed onto zirconia nanotubes. The mixture was polymerized by cyclic voltammetric scannings in the potential range from - 0. 8 V to +1. 3 V in buffer solution to produce a hybrid film electrode (nano-ZrO 2 /PAF/GCE). The morphology of the hybrid film electrode surface was characterized by scanning electron microscopy. Its electrochemical properties were studied via electrochemical impedance spectroscopy. The electrochemical response of nicotinamide adenine dinucleotide (NADH) was investigated by differential pulse voltammetry and amperometry. The results indicated that the nano-ZrO 2 /PAF/GCE possesses well synergistic catalytic activity towards NADH. Compared to an unmodified GCE, the oxidation overpotential is negatively shifted by 224 mV, and the oxidation current is significantly increased. Under optimal conditions, the amperometric response is linearly proportional to the concentration of NADH in the 1. 0 - 100. 0 μM concentration range. Ethanol also can be determined by amperometry if alcohol dehydrogenase and NADH are added to the sample. Two linear relationships between current and alcohol concentration were obtained. They cover the range from 0. 03 to 1. 0 mM, and from 1. 0 to 12. 0 mM. (author)

Mixing enhancement strategies and their mechanisms in supersonic flows: A brief review

Science.gov (United States)

Huang, Wei

2018-04-01

Achieving efficient fuel-air mixing is a crucial issue in the design of the scramjet engine due to the compressibility effect on the mixing shear layer growth and the stringent flow residence time limitation induced by the high-speed crossflow, and the potential solution is to enhance mixing between air and fuel by introducing of streamwise vortices in the flow field. In this survey, some mixing enhancement strategies based on the traditional transverse injection technique proposed in recent years, as well as their mixing augmentation mechanisms, were reviewed in detail, namely the pulsed transverse injection scheme, the traditional transverse injection coupled with the vortex generator, and the dual transverse injection system with a front porthole and a rear air porthole arranged in tandem. The streamwise vortices, through the large-scale stirring motion that they introduce, are responsible for the extraction of large amounts of energy from the mean flow that can be converted into turbulence, ultimately leading to increased mixing effectiveness. The streamwise vortices may be obtained by taking advantage of the shear layer between a jet and the cross stream or by employing intrusive physical devices. Finally, a promising mixing enhancement strategy in supersonic flows was proposed, and some remarks were provided.

Water-based squeezing flow in the presence of carbon nanotubes between two parallel disks

Directory of Open Access Journals (Sweden)

Haq Rizwan Ul

2016-01-01

Full Text Available Present study is dedicated to investigate the water functionalized carbon nanotubes squeezing flow between two parallel discs. Moreover, we have considered magnetohydrodynamics effects normal to the disks. In addition we have considered two kind of carbon nanotubes named: single wall carbon nanotubes (SWCNT and multiple wall carbon nanotubes (MWCNT with in the base fluid. Under this squeezing flow mechanism model has been constructed in the form of partial differential equation. Transformed ordinary differential equations are solved numerically with the help of Runge-Kutta-Fehlberg method. Results for velocity and temperature are constructed against all the emerging parameters. Comparison among the SWCNT and MWCNT are drawn for skin friction coefficient and local Nusselt number. Conclusion remarks are drawn under the observation of whole analysis.

Double polymer sheathed carbon nanotube supercapacitors show enhanced cycling stability

Science.gov (United States)

Zhao, Wenqi; Wang, Shanshan; Wang, Chunhui; Wu, Shiting; Xu, Wenjing; Zou, Mingchu; Ouyang, An; Cao, Anyuan; Li, Yibin

2015-12-01

Pseudo-materials are effective in boosting the specific capacitance of supercapacitors, but during service their degradation may also be very strong, causing reduced cycling stability. Here, we show that a carbon nanotube sponge grafted by two conventional pseudo-polymer layers in sequence can serve as a porous supercapacitor electrode with significantly enhanced cycling stability compared with single polymer grafting. Creating conformal polymer coatings on the nanotube surface and the resulting double-sheath configuration are important structural factors leading to the enhanced performance. Combining different polymers as double sheaths as reported here might be a potential route to circumvent the dilemma of pseudo-materials, and to simultaneously improve the capacitance and stability for various energy storage devices.Pseudo-materials are effective in boosting the specific capacitance of supercapacitors, but during service their degradation may also be very strong, causing reduced cycling stability. Here, we show that a carbon nanotube sponge grafted by two conventional pseudo-polymer layers in sequence can serve as a porous supercapacitor electrode with significantly enhanced cycling stability compared with single polymer grafting. Creating conformal polymer coatings on the nanotube surface and the resulting double-sheath configuration are important structural factors leading to the enhanced performance. Combining different polymers as double sheaths as reported here might be a potential route to circumvent the dilemma of pseudo-materials, and to simultaneously improve the capacitance and stability for various energy storage devices. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr05978j

Amperometric detector for gas chromatography based on a silica sol-gel solid electrolyte.

Science.gov (United States)

Steinecker, William H; Miecznikowski, Krzysztof; Kulesza, Pawel J; Sandlin, Zechariah D; Cox, James A

2017-11-01

An electrochemical cell comprising a silica sol-gel solid electrolyte, a working electrode that protrudes into a gas phase, and reference and counter electrodes that contact the solid electrolyte comprises an amperometric detector for gas chromatography. Under potentiostatic conditions, a current related to the concentration of an analyte in the gas phase is produced by its oxidation at the three-phase boundary among the sol-gel, working electrode, and the gas phase. The sol-gel is processed to contain an electrolyte that also serves as a humidistat to maintain a constant water activity even in the presence the gas chromatographic mobile phase. Response was demonstrated toward a diverse set of analytes, namely hydrogen, 1,2-ethandithiol, phenol, p-cresol, and thioanisole. Using flow injection amperometry of hydrogen with He as the carrier gas, 90% of the steady-state current was achieved in < 1s at a flow rate of 20mLmin -1 . A separation of 1,2-ethandithiol, phenol, p-cresol, and thioanisole at a 2.2mLmin -1 flow rate was achieved with respective detection limits (k = 3 criterion) of 4, 1, 3, and 70 ppmv when the working electrode potential was 800mV. Copyright © 2017 Elsevier B.V. All rights reserved.

Intraperitoneal Injection Is Not a Suitable Administration Route for Single-Walled Carbon Nanotubes in Biomedical Applications

OpenAIRE

Liu, Xudong; Guo, Qing; Zhang, Yuchao; Li, Jinquan; Li, Rui; Wu, Yang; Ma, Ping; Yang, Xu

2016-01-01

Given the extensive application of carbon nanotubes (CNTs) in biomedical fields, there is increasing concern regarding unintentional health impacts. Research into safe usage is therefore increasingly necessary. This study investigated the responses of the mouse brain to single-walled CNTs (SWCNTs) delivered via intraperitoneal (IP) injection and compared these results with the previous study where SWCNTs were delivered via intravenous (IV) injection so as to explore which administration route...

Alignment enhanced photoconductivity in single wall carbon nanotube films

International Nuclear Information System (INIS)

Liu Ye; Lu Shaoxin; Panchapakesan, Balaji

2009-01-01

In this paper we report, for the first time, the alignment enhanced photoconductivity of single wall carbon nanotube films upon laser illumination. The photoconductivity exhibited an increase, decrease or even 'negative' values when the laser spot was on different positions between contact electrodes, showing a 'position' dependent photoconductivity of partially aligned films of carbon nanotubes. Photon induced charge carrier generation in single wall carbon nanotubes and subsequent charge separation across the metal-carbon nanotube contacts is believed to cause the photoconductivity changes. A net photovoltage of ∼4 mV and a photocurrent of ∼10 μA were produced under the laser intensity of ∼273 mW with a quantum efficiency of ∼7.8% in vacuum. The photocurrent was observed to be in the direction of nanotube alignment. Finally, there was a strong dependence of the polarization of the incident light on the photocurrent and the orientation of the films influenced the dynamics of the rise and fall of the photocurrent. All of these phenomena clearly have significance in the area of design and fabrication of solar cells, micro-opto-mechanical systems and photodetectors based on carbon nanotubes.

Analytical Parameters of an Amperometric Glucose Biosensor for Fast Analysis in Food Samples.

Science.gov (United States)

Artigues, Margalida; Abellà, Jordi; Colominas, Sergi

2017-11-14

Amperometric biosensors based on the use of glucose oxidase (GOx) are able to combine the robustness of electrochemical techniques with the specificity of biological recognition processes. However, very little information can be found in literature about the fundamental analytical parameters of these sensors. In this work, the analytical behavior of an amperometric biosensor based on the immobilization of GOx using a hydrogel (Chitosan) onto highly ordered titanium dioxide nanotube arrays (TiO₂NTAs) has been evaluated. The GOx-Chitosan/TiO₂NTAs biosensor showed a sensitivity of 5.46 μA·mM -1 with a linear range from 0.3 to 1.5 mM; its fundamental analytical parameters were studied using a commercial soft drink. The obtained results proved sufficient repeatability (RSD = 1.9%), reproducibility (RSD = 2.5%), accuracy (95-105% recovery), and robustness (RSD = 3.3%). Furthermore, no significant interferences from fructose, ascorbic acid and citric acid were obtained. In addition, the storage stability was further examined, after 30 days, the GOx-Chitosan/TiO₂NTAs biosensor retained 85% of its initial current response. Finally, the glucose content of different food samples was measured using the biosensor and compared with the respective HPLC value. In the worst scenario, a deviation smaller than 10% was obtained among the 20 samples evaluated.

A highly sensitive hydrogen peroxide amperometric sensor based on MnO2-modified vertically aligned multiwalled carbon nanotubes.

Science.gov (United States)

Xu, Bin; Ye, Min-Ling; Yu, Yu-Xiang; Zhang, Wei-De

2010-07-26

In this report, a highly sensitive amperometric sensor based on MnO(2)-modified vertically aligned multiwalled carbon nanotubes (MnO(2)/VACNTs) for determination of hydrogen peroxide (H(2)O(2)) was fabricated by electrodeposition. The morphology of the nanocomposite was characterized by scanning electron microscopy, energy-dispersive X-ray spectrometer and X-ray diffraction. Cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy were applied to investigate the electrochemical properties of the MnO(2)/VACNTs nanocomposite electrode. The mechanism for the electrochemical reaction of H(2)O(2) at the MnO(2)/VACNTs nanocomposite electrode was also discussed. In borate buffer (pH 7.8, 0.20 M), the MnO(2)/VACNTs nanocomposite electrode exhibits a linear dependence (R=0.998) on the concentration of H(2)O(2) from 1.2 x 10(-6)M to 1.8 x 10(-3)M, a high sensitivity of 1.08 x 10(6) microA M(-1) cm(-2) and a detection limit of 8.0 x 10(-7) M (signal/noise=3). Meanwhile, the MnO(2)/VACNTs nanocomposite electrode is also highly resistant towards typical inorganic salts and some biomolecules such as acetic acid, citric acid, uric acid and D-(+)-glucose, etc. In addition, the sensor based on the MnO(2)/VACNTs nanocomposite electrode was applied for the determination of trace of H(2)O(2) in milk with high accuracy, demonstrating its potential for practical application. Copyright 2010 Elsevier B.V. All rights reserved.

Surface-enhanced Raman detection of RNA and DNA bases following flow-injection analysis or HPLC separation

Science.gov (United States)

Cotton, Therese M.; Sheng, Rong-Sheng; Ni, Fan

1990-11-01

The goal of this study is to develop Surface-enhanced Raman scattering (SERS) detection methods for flow injection analysis (FIA) and high performance liquid chromatography (HPLC). Nucleic acid bases have been chosen for analysis because of their importance in life processes. The advantages to the use of SERS-based detection include its sensitivity, specificity and versatility. With the development of improved methodology, the detection limits should be comparable to UV spectroscopy. However, the specificity is considerably superior to that obtained with electronic spectroscopy in that the Raman spectrum provides a molecular fingerprint of the individual analytes. Raman spectroscopy is very versatile: aqueous samples, gases and solids can be analyzed with equal facility. The results presented here demonstrate that SERS can be used as a detection method for both FIA and HPLC detection. In the following experiments Ag sols have been used as the active substrate. The effect of various parameters such as temperature, pH, flow rate, and the nature of the interface between the HPLC system and the Raman spectrometer have been examined. One of the most significant findings is that the temperature of the Ag sol/HPLC effluent mixture has a dramatic effect on the SERS intensities. This effect is a result of increased colloid aggregation at higher temperatures. Aggregation is known to produce greater enhancement in SERS and proceeds much more rapidly at elevated temperatures. An increase in the temperature of the Ag sol enables SERS detection under flowing conditions and in real time. This is a substantial improvement over many of the previous attempts to interface SERS detection to FIA or HPLC. In most of the previous studies, it was necessary to stop the flow as the analyte eluted from the chromatogram and measure the SERS spectra under static conditions.

Tuning the carbon nanotube photoluminescence enhancement at addition of cysteine through the change of external conditions

Energy Technology Data Exchange (ETDEWEB)

Kurnosov, N.V.; Karachevtsev, M.V.; Leontiev, V.S.; Karachevtsev, V.A., E-mail: karachevtsev@ilt.kharkov.ua

2017-01-15

The enhancement of the photoluminescence (PL) from the semiconducting single-walled carbon nanotubes suspended with single-stranded DNA (ssDNA) in water observed after amino acids doping is the largest at cysteine addition. The PL intensity increased through the passivation of p-defects on the carbon nanotube sidewall by the cysteine molecules due to thiol group. The effect of several external factors on the cysteine-induced enhancement of PL from carbon nanotubes covered with ssDNA was studied: UV irradiation, tip or bath sonication treatment of the suspension, the ionic strength and pH of aqueous suspension. It turned out that all these factors have an essential influence on the dependence of the PL enhancement on the cysteine concentration through inducing of additional defects on nanotube as well as a change of the nanotube surface coverage with polymer. The obtained experimental results demonstrated that PL from carbon nanotubes can be exploited successfully for the monitoring of cysteine concentration in aqueous solution. - Highlights: • Cysteine doping enhances carbon nanotube emission more than other amino acids do. • SWNT emission dependence on cysteine concentration is tuned by UV irradiation and pH. • Type of sonication treatment influences SWNT PL dependence on cysteine concentration. • Polymer coverage and defectiveness of nanotubes effect on nanotube emission. • Graphic abstract.

Application of Ionic Liquids in Amperometric Gas Sensors.

Science.gov (United States)

Gębicki, Jacek; Kloskowski, Adam; Chrzanowski, Wojciech; Stepnowski, Piotr; Namiesnik, Jacek

2016-01-01

This article presents an analysis of available literature data on metrological parameters of the amperometric gas sensors containing ionic liquids as an electrolyte. Four mechanism types of signal generation in amperometric sensors with ionic liquid are described. Moreover, this article describes the influence of selected physico-chemical properties of the ionic liquids on the metrological parameters of these sensors. Some metrological parameters are also compared for amperometric sensors with GDE and SPE electrodes and with ionic liquids for selected analytes.

An experimental study of the flow characteristics of fluidic device in a passive safety injection tank

International Nuclear Information System (INIS)

Cho, Seok; Song, Chul Hwa; Won, Suon Yeon; Min, Kyong Ho; Chung, Moon Ki

1998-01-01

It is considered to adopt passive safety injection tank (SIT) as a enhanced safety feature in KNGR. Passive SIT employs a vortex chamber as a fluidic device, which control injection flow rate passively by the variation of flow resistance produced by vortex intensity within the vortex chamber. To investigate the flow characteristics of the vortex chamber many tests have been carried out by using small-scale test facility. In this report the effects of geometric parameters of vortex chamber on discharge flow characteristics and the velocity measurement result of flow field, measured by PIV, are presented and discussed. (author). 25 refs., 11 tabs., 31 figs

Carbon nanotube enhanced membrane distillation for online preconcentration of trace pharmaceuticals in polar solvents.

Science.gov (United States)

Gethard, Ken; Mitra, Somenath

2011-06-21

Carbon nanotube enhanced membrane distillation (MD) is presented as a novel, online analytical preconcentration method for removing polar solvents thereby concentrating the analytes, making this technique an alternate to conventional thermal evaporation. In a carbon nanotube immobilized membrane (CNIM), the CNTs serve as sorbent sites and provide additional pathways for enhanced solvent vapor transport, thus enhancing preconcentration. Enrichment using CNIM doubled compared to membranes without CNTs, while the methanol flux and mass transfer coefficients increased by 61% and 519% respectively. The carbon nanotube enhanced MD process showed excellent precision (RSD of 3-5%), linearity, and the detection limits were in the range of 0.001 to 0.009 mg L(-1) by HPLC analysis.

Vertically aligned carbon nanotube probes for monitoring blood cholesterol

Science.gov (United States)

Roy, Somenath; Vedala, Harindra; Choi, Wonbong

2006-02-01

Detection of blood cholesterol is of great clinical significance. The amperometric detection technique was used for the enzymatic assay of total cholesterol. Multiwall carbon nanotubes (MWNTs), vertically aligned on a silicon platform, promote heterogeneous electron transfer between the enzyme and the working electrode. Surface modification of the MWNT with a biocompatible polymer, polyvinyl alcohol (PVA), converted the hydrophobic nanotube surface into a highly hydrophilic one, which facilitates efficient attachment of biomolecules. The fabricated working electrodes showed a linear relationship between cholesterol concentration and the output signal. The efficacy of the multiwall carbon nanotubes in promoting heterogeneous electron transfer was evident by distinct electrochemical peaks and higher signal-to-noise ratio as compared to the Au electrode with identical enzyme immobilization protocol. The selectivity of the cholesterol sensor in the presence of common interferents present in human blood, e.g. uric acid, ascorbic acid and glucose, is also reported.

Amperometric biosensor for the detection of hydrogen peroxide using catalase modified electrodes in polyacrylamide.

Science.gov (United States)

Varma, Shailly; Mattiasson, Bo

2005-09-23

A simple biosensor for the detection of hydrogen peroxide in organic solvents has been developed and coupled to a flow injection analysis (FIA) system. Catalase was entrapped in polyacrylamide gel and placed on the surface of platinum (working electrode) fixed in a Teflon holder with Ag-wire (auxiliary electrode), followed by addition of filter paper soaked in KCl. The entrapped catalase gel was held on the electrode using membranes. The effects of cellulose and polytetrafluroethylene (PTFE) membranes on the electrode response towards hydrogen peroxide have been studied. The modified electrode has been used to study the detection of hydrogen peroxide in solvents like water, dimethyl sulfoxide (DMSO), and 1,4-dioxane using amperometric techniques like cyclic voltammetry (CV) and FIA. The CV of modified catalase electrode showed a broad oxidation peak at -150 mV and a clear reduction peak at -212 mV in the presence of hydrogen peroxide. Comparison of CV with hydrogen peroxide in various solvents has been carried out. The electrode showed an irreversible kinetics with DMSO as the solvent. A flow cell has been designed in order to carry on FIA studies to obtain calibration plots for hydrogen peroxide with the modified electrode. The calibration plots in several solvents such as water, dimethyl sulfoxide, 1,4-dioxane have been obtained. The throughput of the enzyme electrode was 10 injections per hour. Due to the presence of membrane the response time of the electrode is concentration dependent.

Enhancement in ballistic performance of composite hard armor through carbon nanotubes

Directory of Open Access Journals (Sweden)

Jason Gibson

2013-12-01

Full Text Available The use of carbon nanotubes in composite hard armor is discussed in this study. The processing techniques to make various armor composite panels consisting of Kevlar®29 woven fabric in an epoxy matrix and the subsequent V50 test results for both 44 caliber soft-point rounds and 30 caliber FSP (fragment simulated projectile threats are presented. A 6.5% improvement in the V50 test results was found for a combination of 1.65 wt% loading of carbon nanotubes and 1.65 wt% loading of milled fibers. The failure mechanism of carbon nanotubes during the ballistic event is discussed through scanning electron microscope images of the panels after the failure. Raman Spectroscopy was also utilized to evaluate the residual strain in the Kevlar®29 fibers post shoot. The Raman Spectroscopy shows a Raman shift of 25 cm−1 for the Kevlar®29 fiber utilized in the composite panel that had an enhancement in the V50 performance by using milled fiber and multi-walled carbon nanotubes. Evaluating both scenarios where an improvement was made and other panels without any improvement allows for understanding of how loading levels and synergistic effects between carbon nanotubes and milled fibers can further enhance ballistic performance.

Enhancing the electrochemical response of myoglobin with carbon nanotube electrodes.

Science.gov (United States)

Esplandiu, M J; Pacios, M; Cyganek, L; Bartroli, J; del Valle, M

2009-09-02

In this paper, the electrochemical behavior of different myoglobin-modified carbon electrodes is evaluated. In particular, the performance of voltammetric biosensors made of forest-like carbon nanotubes, carbon nanotube composites and graphite composites is compared by monitoring mainly the electrocatalytic reduction of H(2)O(2) by myoglobin and their corresponding electroanalytical characteristics. Graphite composites showed the worst electroanalytical performance, exhibiting a small linear range, a limit of detection (LOD) of 9 x 10(-5) M and low sensitivity. However, it was found that the electrochemical response was enhanced with the use of carbon nanotube-based electrodes with LOD up to 5 x 10(-8) M, higher sensitivities and wider linear range response. On the one hand, in the case of the CNT epoxy composite, the improvement in the response can be mainly attributed to its more porous surface which allows the immobilization of higher amounts of the electroactive protein. On the other hand, in the case of the forest-like CNT electrodes, the enhancement is due to an increase in the electron transfer kinetics. These findings encourage the use of myoglobin-modified carbon nanotube electrodes as potential (bio)sensors of H(2)O(2) or O(2) in biology, microbiology and environmental fields.

Flow Injection and Atomic Absorption Spectrometry - An Effective and Attractive Analytical Chemical Combination

DEFF Research Database (Denmark)

Hansen, Elo Harald; Nielsen, Steffen

1998-01-01

One of the advantages of the flow injection (FI) concept is that it is compatible with virtually all detection techniques. Being a versatile vehicle for enhancing the performance of the individual detection devices, the most spectacular results have possibly been obtained in conjunction with atom...

Cobalt hexacyanoferrate modified multi-walled carbon nanotubes/graphite composite electrode as electrochemical sensor on microfluidic chip

International Nuclear Information System (INIS)

Li Xinchun; Chen Zuanguang; Zhong Yuwen; Yang Fan; Pan Jianbin; Liang Yajing

2012-01-01

Highlights: ► CoHCF nanoparticles modified MWCNTs/graphite electrode use for electrochemistry on electrophoresis microchip for the first time. ► Simultaneous, rapid, and sensitive electrochemical detection of hydrazine and isoniazid in real samples. ► An exemplary work of CME sensor assembly onto microchip for determination of analytes with environmental significance. ► Manifestation of the applicability and flexibility of CME sensor for electroanalysis on microfluidic chip. - Abstract: Nanomaterial-based electrochemical sensor has received significant interest. In this work, cobalt hexacyanoferrate modified multi-walled carbon nanotubes/graphite composite electrode was electrochemically prepared and exploited as an amperometric detector for microchip electrophoresis. The prepared sensor displayed rapid and sensitive response towards hydrazine and isoniazid oxidation, which was attributed to synergetic electrocatalytic effect of cobalt hexacyanoferrate and multi-walled carbon nanotubes. The sensitivity enhancement with nearly two orders of magnitude was gained, compared with the bare carbon paste electrode, with the detection limit of 0.91 μM (S/N = 3) for hydrazine. Acceptable repeatability of the microanalysis system was verified by consecutive eleven injections of hydrazine without chip and electrode treatments, the RSDs for peak current and migration time were 3.4% and 2.1%, respectively. Meanwhile, well-shaped electrophoretic peaks were observed, mainly due to fast electron transfer of electroactive species on the modified electrode. The developed microchip-electrochemistry setup was successfully applied to the determination of hydrazine and isoniazid in river water and pharmaceutical preparation, respectively. Several merits of the novel electrochemical sensor coupled with microfluidic platform, such as comparative stability, easy fabrication and high sensitivity, hold great potential for hydrazine compounds assay in the lab-on-a-chip system.

Improvement in glucose biosensing response of electrochemically grown polypyrrole nanotubes by incorporating crosslinked glucose oxidase.

Science.gov (United States)

Palod, Pragya Agar; Singh, Vipul

2015-10-01

In this paper a novel enzymatic glucose biosensor has been reported in which platinum coated alumina membranes (Anodisc™s) have been employed as templates for the growth of polypyrrole (PPy) nanotube arrays using electrochemical polymerization. The PPy nanotube arrays were grown on Anodisc™s of pore diameter 100 nm using potentiostatic electropolymerization. In order to optimize the polymerization time, immobilization of glucose oxidase (GOx) was first performed using physical adsorption followed by measuring its biosensing response which was examined amperometrically for increasing concentrations of glucose. In order to further improve the sensing performance of the biosensor fabricated for optimum polymerization duration, enzyme immobilization was carried out using cross-linking with glutaraldehyde and bovine serum albumin (BSA). Approximately six fold enhancement in the sensitivity was observed in the fabricated electrodes. The biosensors also showed a wide range of linear operation (0.2-13 mM), limit of detection of 50 μM glucose concentration, excellent selectivity for glucose, notable reliability for real sample detection and substantially improved shelf life. Copyright © 2015 Elsevier B.V. All rights reserved.

Analytical Parameters of an Amperometric Glucose Biosensor for Fast Analysis in Food Samples

Directory of Open Access Journals (Sweden)

Margalida Artigues

2017-11-01

Full Text Available Amperometric biosensors based on the use of glucose oxidase (GOx are able to combine the robustness of electrochemical techniques with the specificity of biological recognition processes. However, very little information can be found in literature about the fundamental analytical parameters of these sensors. In this work, the analytical behavior of an amperometric biosensor based on the immobilization of GOx using a hydrogel (Chitosan onto highly ordered titanium dioxide nanotube arrays (TiO2NTAs has been evaluated. The GOx–Chitosan/TiO2NTAs biosensor showed a sensitivity of 5.46 μA·mM−1 with a linear range from 0.3 to 1.5 mM; its fundamental analytical parameters were studied using a commercial soft drink. The obtained results proved sufficient repeatability (RSD = 1.9%, reproducibility (RSD = 2.5%, accuracy (95–105% recovery, and robustness (RSD = 3.3%. Furthermore, no significant interferences from fructose, ascorbic acid and citric acid were obtained. In addition, the storage stability was further examined, after 30 days, the GOx–Chitosan/TiO2NTAs biosensor retained 85% of its initial current response. Finally, the glucose content of different food samples was measured using the biosensor and compared with the respective HPLC value. In the worst scenario, a deviation smaller than 10% was obtained among the 20 samples evaluated.

Analytical Parameters of an Amperometric Glucose Biosensor for Fast Analysis in Food Samples

Science.gov (United States)

2017-01-01

Amperometric biosensors based on the use of glucose oxidase (GOx) are able to combine the robustness of electrochemical techniques with the specificity of biological recognition processes. However, very little information can be found in literature about the fundamental analytical parameters of these sensors. In this work, the analytical behavior of an amperometric biosensor based on the immobilization of GOx using a hydrogel (Chitosan) onto highly ordered titanium dioxide nanotube arrays (TiO2NTAs) has been evaluated. The GOx–Chitosan/TiO2NTAs biosensor showed a sensitivity of 5.46 μA·mM−1 with a linear range from 0.3 to 1.5 mM; its fundamental analytical parameters were studied using a commercial soft drink. The obtained results proved sufficient repeatability (RSD = 1.9%), reproducibility (RSD = 2.5%), accuracy (95–105% recovery), and robustness (RSD = 3.3%). Furthermore, no significant interferences from fructose, ascorbic acid and citric acid were obtained. In addition, the storage stability was further examined, after 30 days, the GOx–Chitosan/TiO2NTAs biosensor retained 85% of its initial current response. Finally, the glucose content of different food samples was measured using the biosensor and compared with the respective HPLC value. In the worst scenario, a deviation smaller than 10% was obtained among the 20 samples evaluated. PMID:29135931

A volumetric flow sensor for automotive injection systems

International Nuclear Information System (INIS)

Schmid, U; Krötz, G; Schmitt-Landsiedel, D

2008-01-01

For further optimization of the automotive power train of diesel engines, advanced combustion processes require a highly flexible injection system, provided e.g. by the common rail (CR) injection technique. In the past, the feasibility to implement injection nozzle volumetric flow sensors based on the thermo-resistive measurement principle has been demonstrated up to injection pressures of 135 MPa (1350 bar). To evaluate the transient behaviour of the system-integrated flow sensors as well as an injection amount indicator used as a reference method, hydraulic simulations on the system level are performed for a CR injection system. Experimentally determined injection timings were found to be in good agreement with calculated values, especially for the novel sensing element which is directly implemented into the hydraulic system. For the first time pressure oscillations occurring after termination of the injection pulse, predicted theoretically, could be verified directly in the nozzle. In addition, the injected amount of fuel is monitored with the highest resolution ever reported in the literature

A volumetric flow sensor for automotive injection systems

Science.gov (United States)

Schmid, U.; Krötz, G.; Schmitt-Landsiedel, D.

2008-04-01

For further optimization of the automotive power train of diesel engines, advanced combustion processes require a highly flexible injection system, provided e.g. by the common rail (CR) injection technique. In the past, the feasibility to implement injection nozzle volumetric flow sensors based on the thermo-resistive measurement principle has been demonstrated up to injection pressures of 135 MPa (1350 bar). To evaluate the transient behaviour of the system-integrated flow sensors as well as an injection amount indicator used as a reference method, hydraulic simulations on the system level are performed for a CR injection system. Experimentally determined injection timings were found to be in good agreement with calculated values, especially for the novel sensing element which is directly implemented into the hydraulic system. For the first time pressure oscillations occurring after termination of the injection pulse, predicted theoretically, could be verified directly in the nozzle. In addition, the injected amount of fuel is monitored with the highest resolution ever reported in the literature.

Stable and sensitive flow-through monitoring of phenol using a carbon nanotube based screen printed biosensor

Energy Technology Data Exchange (ETDEWEB)

Alarcon, G; Guix, M; Ambrosi, A; Merkoci, A [Nanobioelectronics and Biosensors Group, Catalan Institute of Nanotechnology, Campus UAB, 08193 Bellaterra, Barcelona, Catalonia (Spain); Ramirez Silva, M T [Departamento de Quimica, Universidad Autonoma Metropolitana Iztapalapa, 09340 Mexico Distrito Federal (Mexico); Palomar Pardave, M E, E-mail: arben.merkoci.icn@uab.es [Departamento de Materiales, Universidad Autonoma Metropolitana, Azcapotzalco, 02200 Mexico Distrito Federal (Mexico)

2010-06-18

A stable and sensitive biosensor for phenol detection based on a screen printed electrode modified with tyrosinase, multiwall carbon nanotubes and glutaraldehyde is designed and applied in a flow injection analytical system. The proposed carbon nanotube matrix is easy to prepare and ensures a very good entrapment environment for the enzyme, being simpler and cheaper than other reported strategies. In addition, the proposed matrix allows for a very fast operation of the enzyme, that leads to a response time of 15 s. Several parameters such as the working potential, pH of the measuring solution, biosensor response time, detection limit, linear range of response and sensitivity are studied. The obtained detection limit for phenol was 0.14 x 10{sup -6} M. The biosensor keeps its activity during continuous FIA measurements at room temperature, showing a stable response (RSD 5%) within a two week working period at room temperature. The developed biosensor is being applied for phenol detection in seawater samples and seems to be a promising alternative for automatic control of seawater contamination. The developed detection system can be extended to other enzyme biosensors with interest for several other applications.

Stable and sensitive flow-through monitoring of phenol using a carbon nanotube based screen printed biosensor

International Nuclear Information System (INIS)

Alarcon, G; Guix, M; Ambrosi, A; Merkoci, A; Ramirez Silva, M T; Palomar Pardave, M E

2010-01-01

A stable and sensitive biosensor for phenol detection based on a screen printed electrode modified with tyrosinase, multiwall carbon nanotubes and glutaraldehyde is designed and applied in a flow injection analytical system. The proposed carbon nanotube matrix is easy to prepare and ensures a very good entrapment environment for the enzyme, being simpler and cheaper than other reported strategies. In addition, the proposed matrix allows for a very fast operation of the enzyme, that leads to a response time of 15 s. Several parameters such as the working potential, pH of the measuring solution, biosensor response time, detection limit, linear range of response and sensitivity are studied. The obtained detection limit for phenol was 0.14 x 10 -6 M. The biosensor keeps its activity during continuous FIA measurements at room temperature, showing a stable response (RSD 5%) within a two week working period at room temperature. The developed biosensor is being applied for phenol detection in seawater samples and seems to be a promising alternative for automatic control of seawater contamination. The developed detection system can be extended to other enzyme biosensors with interest for several other applications.

Flow electrochemical biosensors based on enzymatic porous reactor and tubular detector of silver solid amalgam

Energy Technology Data Exchange (ETDEWEB)

Josypčuk, Bohdan, E-mail: josypcuk@jh-inst.cas.cz [J. Heyrovský Institute of Physical Chemistry of AS CR, v.v.i., Department of Biophysical Chemistry, Dolejskova 3, Prague (Czech Republic); Barek, Jiří [Charles University in Prague, Faculty of Science, University Center of Excellence UNCE “Supramolecular Chemistry”, Department of Analytical Chemistry, UNESCO Laboratory of Environmental Electrochemistry, Albertov 6, CZ-128 43 Prague 2 (Czech Republic); Josypčuk, Oksana [J. Heyrovský Institute of Physical Chemistry of AS CR, v.v.i., Department of Biophysical Chemistry, Dolejskova 3, Prague (Czech Republic); Charles University in Prague, Faculty of Science, University Center of Excellence UNCE “Supramolecular Chemistry”, Department of Analytical Chemistry, UNESCO Laboratory of Environmental Electrochemistry, Albertov 6, CZ-128 43 Prague 2 (Czech Republic)

2013-05-17

Graphical abstract: -- Highlights: •Flow amperometric enzymatic biosensor was constructed. •The biosensor is based on a reactor of a novel material – porous silver solid amalgam. •Tubular amalgam detector was used for determination of decrease of O{sub 2} concentration. •Covalent bonds amalgam−thiol−enzyme contributed to the sensor long-term stability. •LOD of glucose was 0.01 mmol L{sup −1} with RSD = 1.3% (n = 11). -- Abstract: A flow amperometric enzymatic biosensor for the determination of glucose was constructed. The biosensor consists of a flow reactor based on porous silver solid amalgam (AgSA) and a flow tubular detector based on compact AgSA. The preparation of the sensor and the determination of glucose occurred in three steps. First, a self-assembled monolayer of 11-mercaptoundecanoic acid (MUA) was formed at the porous surface of the reactor. Second, enzyme glucose oxidase (GOx) was covalently immobilized at MUA-layer using N-ethyl-N′-(3-dimethylaminopropyl) carboimide and N-hydroxysuccinimide chemistry. Finally, a decrease of oxygen concentration (directly proportional to the concentration of glucose) during enzymatic reaction was amperometrically measured on the tubular detector under flow injection conditions. The following parameters of glucose determination were optimized with respect to amperometric response: composition of the mobile phase, its concentration, the potential of detection and the flow rate. The calibration curve of glucose was linear in the concentration range of 0.02–0.80 mmol L{sup −1} with detection limit of 0.01 mmol L{sup −1}. The content of glucose in the sample of honey was determined as 35.5 ± 1.0 mass % (number of the repeated measurements n = 7; standard deviation SD = 1.2%; relative standard deviation RSD = 3.2%) which corresponds well with the declared values. The tested biosensor proved good long-term stability (77% of the current response of glucose was retained after 35 days)

Determination of trace heavy metals in herbs by sequential injection analysis-anodic stripping voltammetry using screen-printed carbon nanotubes electrodes

International Nuclear Information System (INIS)

Injang, Uthaitip; Noyrod, Peeyanun; Siangproh, Weena; Dungchai, Wijitar; Motomizu, Shoji; Chailapakul, Orawon

2010-01-01

A method for the simultaneous determination of Pb(II), Cd(II), and Zn(II) at low μg L -1 concentration levels by sequential injection analysis-anodic stripping voltammetry (SIA-ASV) using screen-printed carbon nanotubes electrodes (SPCNTE) was developed. A bismuth film was prepared by in situ plating of bismuth on the screen-printed carbon nanotubes electrode. Operational parameters such as ratio of carbon nanotubes to carbon ink, bismuth concentration, deposition time and flow rate during preconcentration step were optimized. Under the optimal conditions, the linear ranges were found to be 2-100 μg L -1 for Pb(II) and Cd(II), and 12-100 μg L -1 for Zn(II). The limits of detection (S bl /S = 3) were 0.2 μg L -1 for Pb(II), 0.8 μg L -1 for Cd(II) and 11 μg L -1 for Zn(II). The measurement frequency was found to be 10-15 stripping cycle h -1 . The present method offers high sensitivity and high throughput for on-line monitoring of trace heavy metals. The practical utility of our method was also demonstrated with the determination of Pb(II), Cd(II), and Zn(II) by spiking procedure in herb samples. Our methodology produced results that were correlated with ICP-AES data. Therefore, we propose a method that can be used for the automatic and sensitive evaluation of heavy metals contaminated in herb items.

Enhanced electroluminescence of organic light-emitting diodes by using halloysite nanotubes

Energy Technology Data Exchange (ETDEWEB)

Mondragón, Margarita, E-mail: mmondragon@ipn.mx [Instituto Politécnico Nacional, ESIME Azcapotzalco, Av. de las Granjas 682, 02250 México D.F. (Mexico); Moggio, Ivana; León, Arxel de; Arias, Eduardo [Centro de Investigación en Química Aplicada, CIQA, Blvd. Enrique Reyna 140, 25253 Saltillo, Coahuila (Mexico)

2013-12-15

The effect of halloysite clay nanotubes (HNTs) on the optical and electronic properties of poly(2-methoxy-5-[2′-ethylhexyloxy]-1,4-phenylenevinylene) (MEH-PPV) have been investigated. The UV–vis absorption band of the conjugated polymer remains unchanged upon the incorporation of halloysite nanotubes (HNTs). Photoluminescence (PL) measurements reveal a decreased quantum yield in the MEH-PPV/HNTs nanocomposites, compared with bulk MEH-PPV. Improvement of the electroluminescence of organic light-emitting diodes (OLEDs) was achieved by incorporating high contents of HNTs. The nanotubes act to enhanced polymer aggregates, as revealed by AFM analysis, thus increasing charge transport and therefore electroluminescence but also decreasing PL quantum yield. -- Highlights: • Thin films of nanocomposites of MEH-PPV/HNTs were prepared by spin coating. • Quantum yield in the nanocomposites was decreased compared with bulk MEH-PPV. • Improvement of the EL of OLEDs was achieved by incorporating high contents of HNTs. • The HNTs act to enhanced polymer aggregates, as revealed by AFM.

Enhanced electroluminescence of organic light-emitting diodes by using halloysite nanotubes

International Nuclear Information System (INIS)

Mondragón, Margarita; Moggio, Ivana; León, Arxel de; Arias, Eduardo

2013-01-01

The effect of halloysite clay nanotubes (HNTs) on the optical and electronic properties of poly(2-methoxy-5-[2′-ethylhexyloxy]-1,4-phenylenevinylene) (MEH-PPV) have been investigated. The UV–vis absorption band of the conjugated polymer remains unchanged upon the incorporation of halloysite nanotubes (HNTs). Photoluminescence (PL) measurements reveal a decreased quantum yield in the MEH-PPV/HNTs nanocomposites, compared with bulk MEH-PPV. Improvement of the electroluminescence of organic light-emitting diodes (OLEDs) was achieved by incorporating high contents of HNTs. The nanotubes act to enhanced polymer aggregates, as revealed by AFM analysis, thus increasing charge transport and therefore electroluminescence but also decreasing PL quantum yield. -- Highlights: • Thin films of nanocomposites of MEH-PPV/HNTs were prepared by spin coating. • Quantum yield in the nanocomposites was decreased compared with bulk MEH-PPV. • Improvement of the EL of OLEDs was achieved by incorporating high contents of HNTs. • The HNTs act to enhanced polymer aggregates, as revealed by AFM

Enhanced Photocurrent Efficiency of a Carbon Nanotube Embedded in a Photonic Structure

Energy Technology Data Exchange (ETDEWEB)

Wong, Bryan M. [Sandia National Lab. (SNL-CA), Livermore, CA (United States). Materials Science

2008-08-01

One of the most rapidly-growing areas in nanoscience is the ability to artificially manipulate optical and electrical properties at the nanoscale. In particular, nanomaterials such as single-wall carbon nanotubes offer enhanced methods for converting infrared light to electrical energy due to their unique one-dimensional electronic properties. However, in order for this energy conversion to occur, a realistic nanotube device would require high-intensity light to be confined on a nanometer scale. This arises from the fact that the diameter of a single nanotube is on the order of a nanometer, and infrared light from an external source must be tightly focused on the narrow nanotube for efficient energy conversion. To address this problem, I calculate the theoretical photocurrent of a nanotube p-n junction illuminated by a highly-efficient photonic structure. These results demonstrate the utility of using a photonic structure to couple large-scale infrared sources with carbon nanotubes while still retaining all the unique optoelectronic properties found at the nanoscale.

Melting Heat in Radiative Flow of Carbon Nanotubes with Homogeneous-Heterogeneous Reactions

Science.gov (United States)

Hayat, Tasawar; Muhammad, Khursheed; Muhammad, Taseer; Alsaedi, Ahmed

2018-04-01

The present article provides mathematical modeling for melting heat and thermal radiation in stagnation-point flow of carbon nanotubes towards a nonlinear stretchable surface of variable thickness. The process of homogeneous-heterogeneous reactions is considered. Diffusion coefficients are considered equal for both reactant and autocatalyst. Water and gasoline oil are taken as base fluids. The conversion of partial differential system to ordinary differential system is done by suitable transformations. Optimal homotopy technique is employed for the solutions development of velocity, temperature, concentration, skin friction and local Nusselt number. Graphical results for various values of pertinent parameters are displayed and discussed. Our results indicate that the skin friction coefficient and local Nusselt number are enhanced for larger values of nanoparticles volume fraction.

Flow Injection Analysis in Industrial Biotechnology

DEFF Research Database (Denmark)

Hansen, Elo Harald; Miró, Manuel

2009-01-01

Flow injection analysis (FIA) is an analytical chemical continuous-flow (CF) method which in contrast to traditional CF-procedures does not rely on complete physical mixing (homogenisation) of the sample and the reagent(s) or on attaining chemical equilibria of the chemical reactions involved. Ex...

Amperometric immunosensor for rapid detection of Mycobacterium tuberculosis

International Nuclear Information System (INIS)

Hiraiwa, Morgan; Lee, Hyun-Boo; Inoue, Shinnosuke; Chung, Jae-Hyun; Kim, Jong-Hoon; Becker, Annie L; Weigel, Kris M; Cangelosi, Gerard A; Lee, Kyong-Hoon

2015-01-01

Tuberculosis (TB) has been a major public health problem, which can be better controlled by using accurate and rapid diagnosis in low-resource settings. A simple, portable, and sensitive detection method is required for point-of-care (POC) settings. This paper studies an amperometric biosensor using a microtip immunoassay for a rapid and low-cost detection of Mycobacterium tuberculosis (MTB) in sputum. MTB in sputum is specifically captured on the functionalized microtip surface and detected by electric current. According to the numerical study, the current signal on the microtip surface is linearly changed with increasing immersion depth. Using a reference microtip, the immersion depth is compensated for a sensing microtip. On the microtip surface, target bacteria are concentrated and organized by a coffee-ring effect, which amplifies the electric current. To enhance the signal-to-noise ratio, both the sample processing and rinsing steps are presented with the use of deionized water as a medium for the amperometric measurement. When applied to cultured MTB cells spiked into human sputum, the detection limit was 100 CFU mL −1 , comparable to a more labor-intensive fluorescence detection method reported previously. (paper)

Amperometric immunosensor for rapid detection of Mycobacterium tuberculosis

Science.gov (United States)

Hiraiwa, Morgan; Kim, Jong-Hoon; Lee, Hyun-Boo; Inoue, Shinnosuke; Becker, Annie L.; Weigel, Kris M.; Cangelosi, Gerard A.; Lee, Kyong-Hoon; Chung, Jae-Hyun

2015-05-01

Tuberculosis (TB) has been a major public health problem, which can be better controlled by using accurate and rapid diagnosis in low-resource settings. A simple, portable, and sensitive detection method is required for point-of-care (POC) settings. This paper studies an amperometric biosensor using a microtip immunoassay for a rapid and low-cost detection of Mycobacterium tuberculosis (MTB) in sputum. MTB in sputum is specifically captured on the functionalized microtip surface and detected by electric current. According to the numerical study, the current signal on the microtip surface is linearly changed with increasing immersion depth. Using a reference microtip, the immersion depth is compensated for a sensing microtip. On the microtip surface, target bacteria are concentrated and organized by a coffee-ring effect, which amplifies the electric current. To enhance the signal-to-noise ratio, both the sample processing and rinsing steps are presented with the use of deionized water as a medium for the amperometric measurement. When applied to cultured MTB cells spiked into human sputum, the detection limit was 100 CFU mL-1, comparable to a more labor-intensive fluorescence detection method reported previously.

Flow regime analysis for fluid injection into a confined aquifer: implications for CO2 sequestration

Science.gov (United States)

Guo, B.; Zheng, Z.; Celia, M. A.; Stone, H.

2015-12-01

operations are expected to have low values of Γ. Other subsurface fluid injections can also be analyzed with this regime diagram. One example of water alternating gas enhanced oil recovery (WAG EOR) falls into the flow regime corresponds to the solution (1), and an example of waste disposal falls into the flow regime for solution (3).

Effect of different saline chaser volumes and flow rates on intravascular contrast enhancement in CT using a circulation phantom

International Nuclear Information System (INIS)

Behrendt, Florian F.; Bruners, Philipp; Keil, Sebastian; Plumhans, Cedric; Mahnken, Andreas H.; Das, Marco; Ackermann, Diana; Guenther, Rolf W.; Muehlenbruch, Georg

2010-01-01

Purpose: To evaluate the influence of different saline chaser volumes and different saline chaser flow rates on the intravascular contrast enhancement in MDCT. Materials and methods: In a physiological flow phantom contrast medium (120 ml, 300 mgI/ml, Ultravist 300) was administered at a flow rate of 6 ml/s followed by different saline chaser volumes (0, 30, 60 and 90 ml) at the same injection rate or followed by a 30-ml saline chaser at different injection rates (2, 4, 6 and 8 ml/s). Serial CT-scans at a level covering the pulmonary artery, the ascending and the descending aorta replica were obtained. Time-enhancement curves were computed and both pulmonary and aortic peak enhancement and peak time were determined. Results: Compared to contrast medium injection without a saline chaser the pushing with a saline chaser (30, 60, and 90 ml) resulted in a statistically significant increased pulmonary peak enhancement (all p = 0.008) and prolonged peak time (p = 0.032, p = 0.024 and p = 0.008, respectively). Highest aortic peak enhancement values were detected for a saline chaser volume of 30 ml. A saline chaser flow rate of 8 ml/s resulted in the highest pulmonary peak enhancement values compared to flow rates of 2, 4 and 6 ml/s (all p = 0.008). Aortic peak enhancement showed the highest values for a flow rate of 6 ml/s. Conclusion: A saline chaser volume of 30 ml and an injection rate of 6 ml/s are sufficient to best improve vascular contrast enhancement in the pulmonary artery and the aorta in MDCT.

Sequential injection lab-on-valve: the third generation of flow injection analysis

DEFF Research Database (Denmark)

Wang, Jianhua; Hansen, Elo Harald

2003-01-01

Termed the third generation of flow injection analysis, sequential injection (SI)-lab-on-valve (LOV) has specific advantages and allows novel, unique applications - not least as a versatile front end to a variety of detection techniques. This review presents snd discusses progress to date of the ...

Signal enhancement in amperometric peroxide detection by using graphene materials with low number of defects

International Nuclear Information System (INIS)

Zöpfl, Alexander; Matysik, Frank-Michael; Hirsch, Thomas; Sisakthi, Masoumeh; Eroms, Jonathan; Strunk, Christoph

2016-01-01

Two-dimensional carbon nanomaterials ranging from single-layer graphene to defective structures such as chemically reduced graphene oxide were studied with respect to their use in electrodes and sensors. Their electrochemical properties and utility in terms of fabrication of sensing devices are compared. Specifically, the electrodes have been applied to reductive amperometric determination of hydrogen peroxide. Low-defect graphene (SG) was obtained through mechanical exfoliation of natural graphite, while higher-defect graphenes were produced by chemical vapor deposition (CVDG) and by chemical oxidation of graphite and subsequent reduction (rGO). The carbonaceous materials were mainly characterized by Raman microscopy. They were applied as electrode material and the electrochemical behavior was investigated by chronocoulometry, cyclic voltammetry, electrochemical impedance spectroscopy and amperometry and compared to a carbon disc electrode. It is shown that the quality of the graphene has an enormous impact on the amperometric performance. The use of carbon materials with many defects (like rGO) does not result in a significant improvement in signal compared to a plain carbon disc electrode. The sensitivity is 173 mA · M −1  · cm −2 in case of using CVDG which is about 50 times better than that of a plain carbon disc electrode and about 7 times better than that of rGO. The limit of detection for hydrogen peroxide is 15.1 μM (at a working potential of −0.3 V vs SCE) for CVDG. It is concluded that the application of two-dimensional carbon nanomaterials offers large perspectives in amperometric detection systems due to electrocatalytic effects that result in highly sensitive detection. (author)

Performance experimental investigation of novel multifunctional nanohybrids on enhanced oil recovery

Science.gov (United States)

Gharibshahi, Reza; Jafari, Arezou; Omidkhah, Mohammadreza; Nezhad, Javad Razavi

2018-01-01

The unique characteristics of materials at the nanoscale make them a good candidate to use in the enhanced oil recovery (EOR) processes. Therefore, in this study, the effect of functionalized multi-walled carbon nanotube/silica nanohybrids on the oil recovery factor is investigated experimentally and nanofluids were injected into a glass micromodel for the first time. The nanohybrids synthesized by using sol-gel method. Micromodels as microscale apparatuses considered as 2D porous medium. Because they enable visual observation of phase displacement behavior at the pore scale. Distillated water used as the dispersion medium of nanoparticles for nanofluids preparation. A series of runs designed for flooding operations included water injection, carbon nanotube/water injection and two nanohybrids with different weight of MWCNT to the overall weight of the nanohybrid structure (10% and 70%) into the distilled water. Also, the oil recovery factor was considered as the goal parameter to compare the results. It has been found that functionalized multi-walled carbon nanotube/silica nanohybrids have a great potential in enhanced oil recovery processes. Results showed that addition of nanohybrids into distillate water causes enhancement of sweep efficiency. In other words, the fingering effect decreases and higher surface of porous medium is in contact with the injected fluid. So the higher amount of oil can produce from the porous medium consequently. By injecting nanofluid with 0.1 wt. % of carbon nanotube, the oil recovery factor increases about 11 % in comparison with water injection alone. Also by increasing the weight of MWCNT to the overall weight of the nanohybrid structure from 10% to 70%, the oil recovery factor increases from 35% to 39%.

Direct and mediated electrochemistry of peroxidase and its electrocatalysis on a variety of screen-printed carbon electrodes: amperometric hydrogen peroxide and phenols biosensor.

Science.gov (United States)

Chekin, Fereshteh; Gorton, Lo; Tapsobea, Issa

2015-01-01

This study compares the behaviour of direct and mediated electrochemistry of horseradish peroxidase (HRP) immobilised on screen-printed carbon electrodes (SPCEs), screen-printed carbon electrodes modified with carboxyl-functionalised multi-wall carbon nanotubes (MWCNT-SPCEs) and screen-printed carbon electrodes modified with carboxyl-functionalised single-wall carbon nanotubes (SWCNT-SPCEs). The techniques of cyclic voltammetry and amperometry in the flow mode were used to characterise the properties of the HRP immobilised on screen-printed electrodes. From measurements of the mediated and mediatorless currents of hydrogen peroxide reduction at the HRP-modified electrodes, it was concluded that the fraction of enzyme molecules in direct electron transfer (DET) contact with the electrode varies substantially for the different electrodes. It was observed that the screen-printed carbon electrodes modified with carbon nanotubes (MWCNT-SPCEs and SWCNT-SPCEs) demonstrated a substantially higher percentage (≈100 %) of HRP molecules in DET contact than the screen-printed carbon electrodes (≈60 %). The HRP-modified electrodes were used for determination of hydrogen peroxide in mediatorless mode. The SWCNT-SPCE gave the lowest detection limit (0.40 ± 0.09 μM) followed by MWCNT-SPCE (0.48 ± 0.07 μM) and SPCE (0.98 ± 0.2 μM). These modified electrodes were additionally developed for amperometric determination of phenolic compounds. It was found that the SWCNT-SPCE gave a detection limit for catechol of 110.2 ± 3.6 nM, dopamine of 640.2 ± 9.2 nM, octopamine of 3341 ± 15 nM, pyrogallol of 50.10 ± 2.9 nM and 3,4-dihydroxy-L-phenylalanine of 980.7 ± 8.7 nM using 50 μM H2O2 in the flow carrier.

Amperometric hydrogen peroxide biosensor based on the immobilization of horseradish peroxidase on core-shell organosilica-chitosan nanospheres and multiwall carbon nanotubes composite

International Nuclear Information System (INIS)

Chen Shihong; Yuan Ruo; Chai Yaqin; Yin Bin; Li Wenjun; Min Ligen

2009-01-01

The application of the composites of multiwall carbon nanotubes (MWNTs) and core-shell organosilica-chitosan crosslinked nanospheres as an immobilization matrix for the construction of an amperometric hydrogen peroxide (H 2 O 2 ) biosensor was described. MWNTs and positively charged organosilica-chitosan nanospheres were dispersed in acetic acid solution (0.6 wt%) to achieve organosilica-chitosan/MWNTs composites, which were cast onto a glass carbon electrode (GCE) surface directly. And then, horseradish peroxidase (HRP), as a model enzyme, was immobilized onto it through electrostatic interaction between oppositely charged organosilica-chitosan nanospheres and HRP. The direct electron transfer of HRP was achieved at HRP/organosilica-chitosan/MWNTs/GCE, which exhibited excellent electrocatalytic activity for the reduction of H 2 O 2 . The catalysis currents increased linearly to H 2 O 2 concentration in a wide range of 7.0 x 10 -7 to 2.8 x 10 -3 M, with a sensitivity of 49.8 μA mM -1 cm -2 and with a detection limit of 2.5 x 10 -7 M at 3σ. A Michaelies-Menten constant K M app value was estimated to be 0.32 mM, indicating a high-catalytic activity of HRP. Moreover, the proposed biosensor displayed a rapid response to H 2 O 2 and possessed good stability and reproducibility. When used to detect H 2 O 2 concentration in disinfector samples and sterilized milks, respectively, it showed satisfactory results

Automated injection of slurry samples in flow-injection analysis

NARCIS (Netherlands)

Hulsman, M.H.F.M.; Hulsman, M.; Bos, M.; van der Linden, W.E.

1996-01-01

Two types of injectors are described for introducing solid samples as slurries in flow analysis systems. A time-based and a volume-based injector based on multitube solenoid pinch valves were built, both can be characterized as hydrodynamic injectors. Reproducibility of the injections of dispersed

Cobalt hexacyanoferrate modified multi-walled carbon nanotubes/graphite composite electrode as electrochemical sensor on microfluidic chip

Energy Technology Data Exchange (ETDEWEB)

Li Xinchun [School of Pharmaceutical Sciences, Sun Yat-sen University, 132 Waihuan East Road of Higher Education Mega Centre, Guangzhou 510006 (China); Chen Zuanguang, E-mail: chenzg@mail.sysu.edu.cn [School of Pharmaceutical Sciences, Sun Yat-sen University, 132 Waihuan East Road of Higher Education Mega Centre, Guangzhou 510006 (China); Zhong Yuwen, E-mail: yu0106@163.com [Center for Disease Control and Prevention of Guangdong Province, 176 Xingangxi, Guangzhou 510300 (China); Yang Fan; Pan Jianbin; Liang Yajing [School of Pharmaceutical Sciences, Sun Yat-sen University, 132 Waihuan East Road of Higher Education Mega Centre, Guangzhou 510006 (China)

2012-01-13

Highlights: Black-Right-Pointing-Pointer CoHCF nanoparticles modified MWCNTs/graphite electrode use for electrochemistry on electrophoresis microchip for the first time. Black-Right-Pointing-Pointer Simultaneous, rapid, and sensitive electrochemical detection of hydrazine and isoniazid in real samples. Black-Right-Pointing-Pointer An exemplary work of CME sensor assembly onto microchip for determination of analytes with environmental significance. Black-Right-Pointing-Pointer Manifestation of the applicability and flexibility of CME sensor for electroanalysis on microfluidic chip. - Abstract: Nanomaterial-based electrochemical sensor has received significant interest. In this work, cobalt hexacyanoferrate modified multi-walled carbon nanotubes/graphite composite electrode was electrochemically prepared and exploited as an amperometric detector for microchip electrophoresis. The prepared sensor displayed rapid and sensitive response towards hydrazine and isoniazid oxidation, which was attributed to synergetic electrocatalytic effect of cobalt hexacyanoferrate and multi-walled carbon nanotubes. The sensitivity enhancement with nearly two orders of magnitude was gained, compared with the bare carbon paste electrode, with the detection limit of 0.91 {mu}M (S/N = 3) for hydrazine. Acceptable repeatability of the microanalysis system was verified by consecutive eleven injections of hydrazine without chip and electrode treatments, the RSDs for peak current and migration time were 3.4% and 2.1%, respectively. Meanwhile, well-shaped electrophoretic peaks were observed, mainly due to fast electron transfer of electroactive species on the modified electrode. The developed microchip-electrochemistry setup was successfully applied to the determination of hydrazine and isoniazid in river water and pharmaceutical preparation, respectively. Several merits of the novel electrochemical sensor coupled with microfluidic platform, such as comparative stability, easy fabrication and

Flow injection analysis in inductively coupled plasma spectrometry

International Nuclear Information System (INIS)

Rosias, Maria F.G.G.

1995-10-01

The main features of flow injection analysis (FIA) as contribution to the inductively coupled plasma (Icp) spectrometry are described. A systematic review of researches using the combined FIA-Icp and the benefits of this association are presented. Flow systems were proposed to perform on-line Icp solution management for multielemental determination by atomic emission spectrometry (Icp-AES) or mass spectrometry. The inclusion of on-line ion exchangers in flow systems for matrix separation and/or analyte preconcentration are presented. Together with those applications the new advent of instruments with facilities for multielement detection on flow injection signals are described. (author). 75 refs., 19 figs

Flow improvers for water injection based on surfactants

Energy Technology Data Exchange (ETDEWEB)

Oskarsson, H.; Uneback, I.; Hellsten, M.

2006-03-15

In many cases it is desirable to increase the flow of injection water when an oil well deteriorates. It is very costly in offshore operation to lay down an additional water pipe to the injection site. Flow improvers for the injection water will thus be the most cost-effective way to increase the flow rate. During the last years water-soluble polymers have also been applied for this purpose. These drag-reducing polymers are however only slowly biodegraded which has been an incentive for the development of readily biodegradable surfactants as flow improvers for injection water. A combination of a zwitterionic and an anionic surfactant has been tested in a 5.5 inch, 700 m long flow loop containing sulphate brine with salinity similar to sea water. A drag reduction between 75 and 80% was achieved with 119 ppm in solution of the surfactant blend at an average velocity of 1.9 m/s and between 50 and 55% at 2.9 m/s. The surfactants in this formulation were also found to be readily biodegradable in sea water and low bio accumulating which means they have an improved environmental profile compared to the polymers used today. Due to the self-healing properties of the drag-reducing structures formed by surfactants, these may be added before the pump section - contrary to polymers which are permanently destroyed by high shear forces. (Author)

Enhancing quality of carbon nanotubes through a real-time controlled CVD process with application to next-generation nanosystems

Science.gov (United States)

Laxminarayana, Karthik; Jalili, Nader

2004-07-01

Nanocrystals and nanostructures will be the building blocks for future materials that will exhibit enhanced or entirely new combinations of properties with tremendous opportunity for novel technologies that can have far-reaching impact on our society. It is, however, realized that a major challenge for the near future is the design, synthesis and integration of nanostructures to develop functional nanosystems. In view of this, this exploratory research seeks to facilitate the development of a controlled and deterministic framework for nanomanufacturing of nanotubes as the most suitable choice among nanostructures for a plethora of potential applications in areas such as nanoelectronic devices, biological probes, fuel cell electrodes, supercapacitors and filed emission devices. Specifically, this paper proposes to control and maintain the most common nanotube growth parameters (i.e., reaction temperature and gas flow rate) through both software and hardware modifications. The influence of such growth parameters in a CVD process on some of the most vital and crucial aspects of nanotubes (e.g., length, diameter, yield, growth rate and structure) can be utilized to arrive at some unique and remarkable properties for the nanotubes. The objective here is, therefore, to control the process parameters to pinpoint accuracy, which would enable us to fabricate nanotubes having the desired properties and thereby maximize their ability to function at its fullest potential. To achieve this and in order to provide for experimental validation of the proposed research program, an experimental test-bed using the nanotube processing test chamber and a mechatronics workstation are being constructed.

Plasma Enhanced Chemical Vapour Deposition of Horizontally Aligned Carbon Nanotubes

Directory of Open Access Journals (Sweden)

Matthew T. Cole

2013-05-01

Full Text Available A plasma-enhanced chemical vapour deposition reactor has been developed to synthesis horizontally aligned carbon nanotubes. The width of the aligning sheath was modelled based on a collisionless, quasi-neutral, Child’s law ion sheath where these estimates were empirically validated by direct Langmuir probe measurements, thereby confirming the proposed reactors ability to extend the existing sheath fields by up to 7 mm. A 7 mbar growth atmosphere combined with a 25 W plasma permitted the concurrent growth and alignment of carbon nanotubes with electric fields of the order of 0.04 V μm−1 with linear packing densities of up to ~5 × 104 cm−1. These results open up the potential for multi-directional in situ alignment of carbon nanotubes providing one viable route to the fabrication of many novel optoelectronic devices.

Implantable enzyme amperometric biosensors.

Science.gov (United States)

Kotanen, Christian N; Moussy, Francis Gabriel; Carrara, Sandro; Guiseppi-Elie, Anthony

2012-05-15

The implantable enzyme amperometric biosensor continues as the dominant in vivo format for the detection, monitoring and reporting of biochemical analytes related to a wide range of pathologies. Widely used in animal studies, there is increasing emphasis on their use in diabetes care and management, the management of trauma-associated hemorrhage and in critical care monitoring by intensivists in the ICU. These frontier opportunities demand continuous indwelling performance for up to several years, well in excess of the currently approved seven days. This review outlines the many challenges to successful deployment of chronically implantable amperometric enzyme biosensors and emphasizes the emerging technological approaches in their continued development. The foreign body response plays a prominent role in implantable biotransducer failure. Topics considering the approaches to mitigate the inflammatory response, use of biomimetic chemistries, nanostructured topographies, drug eluting constructs, and tissue-to-device interface modulus matching are reviewed. Similarly, factors that influence biotransducer performance such as enzyme stability, substrate interference, mediator selection and calibration are reviewed. For the biosensor system, the opportunities and challenges of integration, guided by footprint requirements, the limitations of mixed signal electronics, and power requirements, has produced three systems approaches. The potential is great. However, integration along the multiple length scales needed to address fundamental issues and integration across the diverse disciplines needed to achieve success of these highly integrated systems, continues to be a challenge in the development and deployment of implantable amperometric enzyme biosensor systems. Copyright © 2012 Elsevier B.V. All rights reserved.

Enhanced amperometric response of a glucose oxidase and horseradish peroxidase based bienzyme glucose biosensor modified with a film of polymerized toluidine blue containing reduced graphene oxide

International Nuclear Information System (INIS)

Wang, Fang; Gong, Wencheng; Wang, Lili; Chen, Zilin

2015-01-01

Reduced graphene oxide (RGO) was used to construct a bienzyme biosensor containing horseradish peroxidase (HRP) and glucose oxidase (GOx). A poly(toluidine blue) (pTB) film containing RGO acted as both enzyme immobilization matrix and electron transfer mediator. The bienzyme biosensor was characterized by electrochemical techniques and displays a highly sensitive amperometric response to glucose and hydrogen peroxide (H 2 O 2 ) at a potential as low as −0.1 V (vs. SCE). It is shown that use of RGO causes a strong enhancement on the amperometric responses. H 2 O 2 formed by the action of GOx in the presence of oxygen can be further reduced by HRP in the pTB film contacting the RGO modified electrode. In the absence of oxygen, glucose oxidation proceeds by another mechanism in which electron transfer occurs from GOx to the electrode and with pTB acting as the mediator. Amperometric responses to glucose and H2O2 follow Michaelis-Menten kinetics. The experimental conditions were optimized, and under these conditions glucose can be determined in the 80 μM to 3.0 mM range with a detection limit of 50 μM. H 2 O 2 , in turn, can be quantified in up to 30.0 μM concentration with a detection limit of 0.2 μM. The bienzyme biosensor is reproducible, repeatable and stable. Finally, it has been successfully applied to the determination of glucose in plasma samples. (author)

Realistic-contact-induced enhancement of rectifying in carbon-nanotube/graphene-nanoribbon junctions

International Nuclear Information System (INIS)

Zhang, Xiang-Hua; Li, Xiao-Fei; Wang, Ling-Ling; Xu, Liang; Luo, Kai-Wu

2014-01-01

Carbon-nanotube/graphene-nanoribbon junctions were recently fabricated by the controllable etching of single-walled carbon-nanotubes [Wei et al., Nat. Commun. 4, 1374 (2013)] and their electronic transport properties were studied here. First principles results reveal that the transmission function of the junctions show a heavy dependence on the shape of contacts, but rectifying is an inherent property which is insensitive to the details of contacts. Interestingly, the rectifying ratio is largely enhanced in the junction with a realistic contact and the enhancement is insensitive to the details of contact structures. The stability of rectifying suggests a significant feasibility to manufacture realistic all-carbon rectifiers in nanoelectronics

Vertically aligned carbon nanotubes for sensing unidirectional fluid flow

Energy Technology Data Exchange (ETDEWEB)

Kiani, Keivan, E-mail: k_kiani@kntu.ac.ir

2015-05-15

From applied mechanics points of view, potential application of ensembles of single-walled carbon nanotubes (SWCNTs) as fluid flow sensors is aimed to be examined. To this end, useful nonlocal analytical and numerical models are developed. The deflection of the ensemble of SWCNTs at the tip is introduced as a measure of its sensitivity. The influences of the length and radius of the SWCNT, intertube distance, fluid flow velocity, and distance of the ensemble from the leading edge of the rigid base on the deflection field of the ensemble are comprehensively examined. The obtained results display how calibration of an ensemble of SWCNTs can be methodically carried out in accordance with the characteristics of the ensemble and the external fluid flow.

Plasma Enhanced Growth of Carbon Nanotubes For Ultrasensitive Biosensors

Science.gov (United States)

Cassell, Alan M.; Li, J.; Ye, Q.; Koehne, J.; Chen, H.; Meyyappan, M.

2004-01-01

The multitude of considerations facing nanostructure growth and integration lends itself to combinatorial optimization approaches. Rapid optimization becomes even more important with wafer-scale growth and integration processes. Here we discuss methodology for developing plasma enhanced CVD growth techniques for achieving individual, vertically aligned carbon nanostructures that show excellent properties as ultrasensitive electrodes for nucleic acid detection. We utilize high throughput strategies for optimizing the upstream and downstream processing and integration of carbon nanotube electrodes as functional elements in various device types. An overview of ultrasensitive carbon nanotube based sensor arrays for electrochemical biosensing applications and the high throughput methodology utilized to combine novel electrode technology with conventional MEMS processing will be presented.

Proficiency feasibility of multi-walled carbon nanotubes in the presence of polymeric surfactant on enhanced oil recovery

Science.gov (United States)

Nezhad, Javad Razavi; Jafari, Arezou; Abdollahi, Mahdi

2018-01-01

Enhanced heavy oil recovery methods are widely utilized to increase oil recovery. For this purpose, polymer and surfactant flooding have been used extensively. Recently, polymeric surfactant flooding has become an attractive alternative to sole polymer flooding due to their capability of providing an increase in solution viscosity and a decrease in interfacial tension, which are both beneficial for efficiency of the process. Applying nanoparticles as an additive to polymer solutions is a method to improve viscosity and alter rock wettability. Therefore, in this research, multi-walled carbon nanotube (MWCNT) was mixed with a polymeric surfactant of polyacrylamide-graft-lignin copolymer (PAM-g-L) synthesized via radical grafting reaction. Moreover, several solutions with different concentrations of nanoparticles with PAM-g-L were prepared. The solutions were injected into a micromodel to evaluate the PAM-g-L flooding efficiency in presence of the multi-walled carbon nanotubes. The results of micromodel flooding showed that increasing MWCNT concentration results in lower sweep efficiencies; and consequently, oil production will decrease. Therefore, MWCNT along with PAM-g-L has an unacceptable performance in enhanced heavy oil recovery. But data of wettability tests revealed that MWCNT can change the wettability from oil-wet to water-wet. In addition, the combination of the PAM-g-L and MWCNT in a solution will cause more water-wet condition.

Melting heat transfer in stagnation point flow of carbon nanotubes towards variable thickness surface

Directory of Open Access Journals (Sweden)

T. Hayat

2016-01-01

Full Text Available This work concentrates on the mathematical modeling for stagnation point flow of nanofluids over an impermeable stretching sheet with variable thickness. Carbon nanotubes [single-wall carbon nanotubes (SWCNTs and multi-wall carbon nanotubes (MWCNTs] as the nanoparticles are utilized. Water and kerosene oil are taken as the base fluids. Heat transfer through melting effect is discussed. Transformation procedure is adapted to obtain the non-linear ordinary differential equations from the fundamental laws of mass, linear momentum and energy. The optimal values of convergence control parameters and corresponding individual and total residual errors for SWCNTs and MWCNTs are computed by means of homotopy analysis method (HAM based BVPh 2.0. Characteristics of different involved parameters on the velocity, temperature, skin friction coefficient and Nusselt number are discussed. Higher velocity profile is observed for wall thickness parameter in case of water carbon nanotubes when compared with the kerosene oil carbon nanotubes.

MHD flow over a permeable stretching/shrinking sheet of a nanofluid with suction/injection

Directory of Open Access Journals (Sweden)

Sandeep Naramgari

2016-06-01

Full Text Available In this study we analyzed the influence of thermal radiation and chemical reaction on two dimensional steady magnetohydrodynamic flow of a nanofluid past a permeable stretching/shrinking sheet in the presence of suction/injection. We considered nanofluid volume fraction on the boundary is submissive controlled, which makes the present study entirely different from earlier studies and physically more realistic. The equations governing the flow are solved numerically. Effects of non-dimensional governing parameters on velocity, temperature and concentration profiles are discussed and presented through graphs. Also, coefficient of skin friction and local Nusselt number is investigated for stretching/shrinking and suction/injection cases separately and presented through tables. Comparisons with existed results are presented. Present results have an excellent agreement with the existed studies under some special assumptions. Results indicate that the enhancement in Brownian motion and thermophoresis parameters depreciates the nanoparticle concentration and increases the mass transfer rate. Dual solutions exist only for certain range of stretching/shrinking and suction/injection parameters.

Electrical and dielectric properties of foam injection-molded polypropylene/multiwalled carbon nanotube composites

Energy Technology Data Exchange (ETDEWEB)

Ameli, A.; Nofar, M.; Saniei, M.; Hossieny, N.; Park, C. B. [Microcellular Plastics Manufacturing Laboratory, Department of Mechanical and Industrial Engineering, University of Toronto, 5 King’s College Road, Toronto, Ontario, Canada M5S 3G8 (Canada); Pötschke, P. [Leibniz-Institut für Polymerforschung Dresden e.V. (IPF), Hohe Strasse 6, D-01069 Dresden (Germany)

2015-05-22

A combination of high dielectric permittivity (ε′) and low dielectric loss (tan δ) is required for charge storage applications. In percolative systems such as conductive polymer composites, however, obtaining high ε′ and low tan δ is very challenging due to the sharp insulation-conduction transition near the threshold region. Due to the particular arrangement of conductive fillers induced by both foaming and injection molding processes, they may address this issue. Therefore, this work evaluates the application of foam injection molding process in fabricating polymer nanocomposites for energy storage. Polypropylene-multiwalled carbon nanotubes (PP-MWCNT) composites were prepared by melt mixing and foamed in an injection molding process. Electrical conductivity (σ), ε′ and tan δ were then characterized. Also, scanning and transmission electron microscopy (SEM and TEM) was used to investigate the carbon nanotube’s arrangement as well as cellular morphology. The results showed that foam injection-molded composites exhibited highly superior dielectric properties to those of solid counterparts. For instance, foamed samples had ε′=68.3 and tan δ =0.05 (at 1.25 vol.% MWCNT), as opposed to ε′=17.8 and tan δ=0.04 in solid samples (at 2.56 vol.% MWCNT). The results of this work reveal that high performance dielectric nanocomposites can be developed using foam injection molding technologies for charge storage applications.

Contrast-enhanced Harmonic power Doppler ultrasonography: Improved depiction of vascularity and characterization of flow pattern in hepatocellular carcinoma

International Nuclear Information System (INIS)

Baek, Hyung Chul; Yoon, Kwon Ha; Kim, Chang Guhn; Park, Ki Han; Won, Jong Jin

2000-01-01

To evaluate the value of contrast-enhanced harmonic power Doppler ultrasonography (PDUS) in depiction and characterization of tumoral vascularity in hepatocellular carcinoma (HCC). Thirty-three patients with HCC were prospectively evaluated with harmonic PDUS before and after injection of the contrast agent SH U 508A (2.5g, 300 mg/ml ). Unenhanced and serial dynamic scans at 15, 30, 45, 60, 90, 120, 150, 180, 240, 300 seconds after injection of contrast agents were obtained using a tissue harmonic technique with power Doppler imaging. The tumoral vascularity was expressed as percentage of power Doppler area, which was measured quantitatively by a computerized program (Ultrasonic Imaging Tool; Soongsil University, Seoul, Korea). The grade (0, no signal; 1, less than 5%; 2, 5-25%; 3, more than 25%) and flow pattern (intratumoral, detour, basket, and mixed) of tumoral vascularity were analyzed. Peak time of contrast-enhancement was measured on each tumor. After injection of contrast agent, tumoral flow signals increased in all lesions (100%). At unenhanced harmonic PDUS, flow signals were detected in 17 HCCs (52%); 15 tumors (46%) demonstrated grade 1 vascularity; and two (6%), grade 2. At contrast-enhanced harmonic PDUS, all tumors were detected vascularity; five (15%) were grade 1; eight (24%), grade 2; and 20 (61%), grade 3. Flow patterns were demonstated as follows at unenhanced harmonic PDUS; intratumoral pattern in 13 tumors (76%), detour in 2 (12%), and basket in 2 (12%). After injection of contrast agent, intratumoral pattern in 7 tumors (21%), detour 0 (0%), basket in 3 (9%) and mixed in 23 (70%) were demonstrated. Peak time of enhancement after injection of contrast agent was 30- 90 seconds in majority of the patients. Contrast-enhanced harmonic PDUS would be valuable in depiction of vascularity and characterization of flow pattern in HCC.

Contrast-enhanced Harmonic power Doppler ultrasonography: Improved depiction of vascularity and characterization of flow pattern in hepatocellular carcinoma

Energy Technology Data Exchange (ETDEWEB)

Baek, Hyung Chul; Yoon, Kwon Ha; Kim, Chang Guhn; Park, Ki Han; Won, Jong Jin [Wonkwang University School of Medicine, Iksa (Korea, Republic of)

2000-12-15

To evaluate the value of contrast-enhanced harmonic power Doppler ultrasonography (PDUS) in depiction and characterization of tumoral vascularity in hepatocellular carcinoma (HCC). Thirty-three patients with HCC were prospectively evaluated with harmonic PDUS before and after injection of the contrast agent SH U 508A (2.5g, 300 mg/ml ). Unenhanced and serial dynamic scans at 15, 30, 45, 60, 90, 120, 150, 180, 240, 300 seconds after injection of contrast agents were obtained using a tissue harmonic technique with power Doppler imaging. The tumoral vascularity was expressed as percentage of power Doppler area, which was measured quantitatively by a computerized program (Ultrasonic Imaging Tool; Soongsil University, Seoul, Korea). The grade (0, no signal; 1, less than 5%; 2, 5-25%; 3, more than 25%) and flow pattern (intratumoral, detour, basket, and mixed) of tumoral vascularity were analyzed. Peak time of contrast-enhancement was measured on each tumor. After injection of contrast agent, tumoral flow signals increased in all lesions (100%). At unenhanced harmonic PDUS, flow signals were detected in 17 HCCs (52%); 15 tumors (46%) demonstrated grade 1 vascularity; and two (6%), grade 2. At contrast-enhanced harmonic PDUS, all tumors were detected vascularity; five (15%) were grade 1; eight (24%), grade 2; and 20 (61%), grade 3. Flow patterns were demonstated as follows at unenhanced harmonic PDUS; intratumoral pattern in 13 tumors (76%), detour in 2 (12%), and basket in 2 (12%). After injection of contrast agent, intratumoral pattern in 7 tumors (21%), detour 0 (0%), basket in 3 (9%) and mixed in 23 (70%) were demonstrated. Peak time of enhancement after injection of contrast agent was 30- 90 seconds in majority of the patients. Contrast-enhanced harmonic PDUS would be valuable in depiction of vascularity and characterization of flow pattern in HCC.

Computational Design of a Carbon Nanotube Fluorofullerene Biosensor

Directory of Open Access Journals (Sweden)

Shin-Ho Chung

2012-10-01

Full Text Available Carbon nanotubes offer exciting opportunities for devising highly-sensitive detectors of specific molecules in biology and the environment. Detection limits as low as 10−11 M have already been achieved using nanotube-based sensors. We propose the design of a biosensor comprised of functionalized carbon nanotube pores embedded in a silicon-nitride or other membrane, fluorofullerene-Fragment antigen-binding (Fab fragment conjugates, and polymer beads with complementary Fab fragments. We show by using molecular and stochastic dynamics that conduction through the (9, 9 exohydrogenated carbon nanotubes is 20 times larger than through the Ion Channel Switch ICSTM biosensor, and fluorofullerenes block the nanotube entrance with a dissociation constant as low as 37 pM. Under normal operating conditions and in the absence of analyte, fluorofullerenes block the nanotube pores and the polymer beads float around in the reservoir. When analyte is injected into the reservoir the Fab fragments attached to the fluorofullerene and polymer bead crosslink to the analyte. The drag of the much larger polymer bead then acts to pull the fluorofullerene from the nanotube entrance, thereby allowing the flow of monovalent cations across the membrane. Assuming a tight seal is formed between the two reservoirs, such a biosensor would be able to detect one channel opening and thus one molecule of analyte making it a highly sensitive detection design.

Nitrogen-Doped Carbon Nanotube/Graphite Felts as Advanced Electrode Materials for Vanadium Redox Flow Batteries.

Science.gov (United States)

Wang, Shuangyin; Zhao, Xinsheng; Cochell, Thomas; Manthiram, Arumugam

2012-08-16

Nitrogen-doped carbon nanotubes have been grown, for the first time, on graphite felt (N-CNT/GF) by a chemical vapor deposition approach and examined as an advanced electrode for vanadium redox flow batteries (VRFBs). The unique porous structure and nitrogen doping of N-CNT/GF with increased surface area enhances the battery performance significantly. The enriched porous structure of N-CNTs on graphite felt could potentially facilitate the diffusion of electrolyte, while the N-doping could significantly contribute to the enhanced electrode performance. Specifically, the N-doping (i) modifies the electronic properties of CNT and thereby alters the chemisorption characteristics of the vanadium ions, (ii) generates defect sites that are electrochemically more active, (iii) increases the oxygen species on CNT surface, which is a key factor influencing the VRFB performance, and (iv) makes the N-CNT electrochemically more accessible than the CNT.

Effect of tube depth on the photovoltaic performance of CdS quantum dots sensitized ZnO nanotubes solar cells

International Nuclear Information System (INIS)

Yang, Lili; Zhang, Zhiqiang; Yang, Jinghai; Yan, Yongsheng; Sun, Yunfei; Cao, Jian; Gao, Ming

2012-01-01

Highlights: ► ZnO nanotubes as photoanode can enhance the energy conversion efficiency. ► ZnO nanotubes with larger surface area can load more CdS QDs to absorb more light. ► ZnO nanotubes can provide two transfer channels for photo-injected carrier. - Abstract: High-density and vertically-aligned ZnO nanotubes (ZNTs) with different depth and ZnO nanorods (ZNRs) were used as photoelectrodes to assemble the CdS quantum dots sensitized solar cells (QDSSCs). In comparison with the CdS sensitized ZNRs solar cell, up to 170% enhancement in energy conversion efficiency was achieved for the CdS sensitized ZNTs under the white light illumination intensity of 100 mW/cm 2 . The investigation about the effects of tube depth on the photovoltaic performance of ZNTs/CdS electrodes revealed that at least two factors induce the enhancement of their conversion efficiency. One is that the higher surface-volume ratio of ZNTs can effectively increase the loading amount of CdS QDs, which can effectively absorb the light. The other is that the outer and inner wall of ZNTs can provide two transfer channels for photo-injected carriers, which can improve the efficiency of current collection.

Fabrication and flow characterization of vertically aligned carbon-nanotube/polymer membranes

Science.gov (United States)

Castellano, Richard; Meshot, Eric; Fornasiero, Francesco; Shan, Jerry

2017-11-01

Membranes with well-controlled nanopores are of interest for applications as diverse as chemical separations, water purification, and ``green'' power generation. In particular, membranes incorporating carbon nanotubes (CNTs) as through-pores have been shown to pass fluids at rates orders-of-magnitude faster than predicted by continuum theory. However, cost-effective and scalable solutions for fabricating such membranes are still an area of research. We describe a solution-based fabrication technique for creating polymer composite membranes from bulk nanotubes using electric-field alignment and electrophoretic concentration. We then focus on flow characterization of membranes with single-wall nanotube (SWNT) pores. We demonstrate membrane quality by size-exclusion testing and showing that the flowrate of different gasses scales as the square root of molecular weight. The gas flowrates and moisture-vapor-transmission rates are compared with theoretical predictions and with composite membranes -fabricated from CVD-grown SWNT arrays. Funded by DTRA Grant BA12PHM123.

Real-Time Amperometric Recording of Extracellular H2O2 in the Brain of Immunocompromised Mice: An In Vitro, Ex Vivo and In Vivo Characterisation Study

Science.gov (United States)

Reid, Caroline H.; Finnerty, Niall J.

2017-01-01

We detail an extensive characterisation study on a previously described dual amperometric H2O2 biosensor consisting of H2O2 detection (blank) and degradation (catalase) electrodes. In vitro investigations demonstrated excellent H2O2 sensitivity and selectivity against the interferent, ascorbic acid. Ex vivo studies were performed to mimic physiological conditions prior to in vivo deployment. Exposure to brain tissue homogenate identified reliable sensitivity and selectivity recordings up to seven days for both blank and catalase electrodes. Furthermore, there was no compromise in pre- and post-implanted catalase electrode sensitivity in ex vivo mouse brain. In vivo investigations performed in anaesthetised mice confirmed the ability of the H2O2 biosensor to detect increases in amperometric current following locally perfused/infused H2O2 and antioxidant inhibitors mercaptosuccinic acid and sodium azide. Subsequent recordings in freely moving mice identified negligible effects of control saline and sodium ascorbate interference injections on amperometric H2O2 current. Furthermore, the stability of the amperometric current was confirmed over a five-day period and analysis of 24-h signal recordings identified the absence of diurnal variations in amperometric current. Collectively, these findings confirm the biosensor current responds in vivo to increasing exogenous and endogenous H2O2 and tentatively supports measurement of H2O2 dynamics in freely moving NOD SCID mice. PMID:28698470

Amperometric screen-printed algal biosensor with flow injection analysis system for detection of environmental toxic compounds

Energy Technology Data Exchange (ETDEWEB)

Shitanda, Isao [Department of Pure and Applied Chemistry, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510 (Japan)], E-mail: shitanda@rs.noda.tus.ac.jp; Takamatsu, Satoshi; Watanabe, Kunihiro; Itagaki, Masayuki [Department of Pure and Applied Chemistry, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510 (Japan)

2009-08-30

A screen-printed algal biosensor was fabricated for evaluation of toxicity of chemicals. An algal ink was prepared by mixing unicellular microalga Chlorella vulgaris cells, carbon nanotubes and sodium alginate solution. The algal ink was immobilized directly on a screen-printed carbon electrode surface using screen-printing technique. Photosynthetically generated oxygen of the immobilized algae was monitored amperometically. Responses of the algal biosensor to four toxic compounds, 6-chloro-N-ethyl-N-isopropyl-1,3,5-triazine-2,4-diamine (atrazine) and 3-(3,4-dichlorophenyl)-1,1-diethylurea (DCMU) were evaluated as inhibition ratios of the reduction current. The concentrations that gave 50% inhibition of the oxygen reduction current (IC{sup '}{sub 50}) for atrazine and DCMU were 12 and 1 {mu}mol dm{sup -3}, respectively. In comparison with the conventional algal biosensors, in which the algal cells were entrapped in an alginate gel and immobilized on the surface of a transparent indium tin oxide electrode, the present sensor is much smaller and less expensive, with the shorter assay time.

Amperometric screen-printed algal biosensor with flow injection analysis system for detection of environmental toxic compounds

International Nuclear Information System (INIS)

Shitanda, Isao; Takamatsu, Satoshi; Watanabe, Kunihiro; Itagaki, Masayuki

2009-01-01

A screen-printed algal biosensor was fabricated for evaluation of toxicity of chemicals. An algal ink was prepared by mixing unicellular microalga Chlorella vulgaris cells, carbon nanotubes and sodium alginate solution. The algal ink was immobilized directly on a screen-printed carbon electrode surface using screen-printing technique. Photosynthetically generated oxygen of the immobilized algae was monitored amperometically. Responses of the algal biosensor to four toxic compounds, 6-chloro-N-ethyl-N-isopropyl-1,3,5-triazine-2,4-diamine (atrazine) and 3-(3,4-dichlorophenyl)-1,1-diethylurea (DCMU) were evaluated as inhibition ratios of the reduction current. The concentrations that gave 50% inhibition of the oxygen reduction current (IC ' 50 ) for atrazine and DCMU were 12 and 1 μmol dm -3 , respectively. In comparison with the conventional algal biosensors, in which the algal cells were entrapped in an alginate gel and immobilized on the surface of a transparent indium tin oxide electrode, the present sensor is much smaller and less expensive, with the shorter assay time.

Non-enzymatic amperometric sensor for hydrogen peroxide based on a biocomposite made from chitosan, hemoglobin, and silver nanoparticles

International Nuclear Information System (INIS)

Tian, L.; Feng, Y.; Qi, Y.; Wang, B.; Chen, Y.; Fu, X.

2012-01-01

We report on a novel non-enzymatic sensor for hydrogen peroxide (HP) that is based on a biocomposite made up from chitosan (CS), hemoglobin (Hb), and silver nanoparticles (AgNPs). The AgNPs were prepared in the presence of CS and glucose in an ultrasonic bath, and CS is found to act as a stabilizing agent. They were then combined with Hb and CS to construct a carbon paste biosensor. The resulting electrode gave a well-defined redox couple for Hb, with a formal potential of about -0.17 V (vs. SCE) at pH 6. 86 and exhibited a remarkable electrocatalytic activity for the reduction of HP. The sensor was used to detect HP by flow injection analysis, and a linear response is obtained in the 0. 08 to 250 μM concentration range. The detection limit is 0.05 μM (at S/N = 3). These characteristics, along with its long-term stability make the sensor highly promising for the amperometric determination of HP. (author)

Intraperitoneal Injection Is Not a Suitable Administration Route for Single-Walled Carbon Nanotubes in Biomedical Applications.

Science.gov (United States)

Liu, Xudong; Guo, Qing; Zhang, Yuchao; Li, Jinquan; Li, Rui; Wu, Yang; Ma, Ping; Yang, Xu

2016-01-01

Given the extensive application of carbon nanotubes (CNTs) in biomedical fields, there is increasing concern regarding unintentional health impacts. Research into safe usage is therefore increasingly necessary. This study investigated the responses of the mouse brain to single-walled CNTs (SWCNTs) delivered via intraperitoneal (IP) injection and compared these results with the previous study where SWCNTs were delivered via intravenous (IV) injection so as to explore which administration route is potentially better for SWCNTs application. This study suggests SWCNTs delivered via IP injection can have negative effects on the mouse brain through oxidative stress and inflammation at high concentration exposure, but these responses were not consistent and showed no dose-dependent effect. In a previous study, the results showed that IV-delivered SWCNTs induced a more consistent and dose-dependent effect. The comparison of the 2 studies suggested that using SWCNTs at a safe dosage delivered via IV injection may be a better administration route for SWCNTs in biomedical applications.

Towards the conception of an amperometric sensor of L-tyrosine based on Hemin/PAMAM/MWCNT modified glassy carbon electrode

International Nuclear Information System (INIS)

Ma Qiang; Ai Shiyun; Yin Huanshun; Chen Quanpeng; Tang Tiantian

2010-01-01

A novel amperometric sensor was fabricated based on the immobilization of hemin onto the poly (amidoamine)/multi-walled carbon nanotube (PAMAM/MWCNT) nanocomposite film modified glassy carbon electrode (GCE). Electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and ultraviolet visible (UV-vis) adsorption spectroscopy were used to investigate the possible state and electrochemical activity of the immobilized hemin. In the Hemin/PAMAM/MWCNT nanocomposite film, MWCNT layer possessed excellent inherent conductivity to enhance the electron transfer rate, while the layer of PAMAM greatly enlarged the surface average concentration of hemin (Γ) on the modified electrode. Therefore, the nanocomposite film showed enhanced electrocatalytical activity towards the oxidation of L-tyrosine. The kinetic parameters of the modified electrode were investigated. In pH 7.0 phosphate buffer solution (PBS), the sensor exhibits a wide linear range from 0.1 μM to 28.8 μM L-tyrosine with a detection limit of 0.01 μM and a high sensitivity of 0.31 μA μM -1 cm -2 . In addition, the response time of the L-tyrosine sensor is less than 5 s. The excellent performance of the sensor is largely attributed to the electro-generated high reactive oxoiron (IV) porphyrin (O = Fe IV -P) which effectively catalyzed the oxidation of L-tyrosine. A mechanism was herein proposed for the catalytic oxidation of L-tyrosine by oxoiron (IV) porphyrin complexes.

Enhanced Photocatalytic Activity of La3+-Doped TiO2 Nanotubes with Full Wave-Band Absorption

Science.gov (United States)

Xia, Minghao; Huang, Lingling; Zhang, Yubo; Wang, Yongqian

2018-06-01

TiO2 nanotubes doped with La3+ were synthesized by anodic oxidation method and the photocatalytic activity was detected by photodegrading methylene blue. As-prepared samples improved the absorption of both ultraviolet light and visible light and have a great enhancement on the photocatalytic activity while contrasting with the pristine TiO2 nanotubes. A tentative mechanism for the enhancement of photocatalytic activity with full wave-band absorption is proposed.

Dramatic property enhancement in polyetherimide using low-cost commercially functionalized multi-walled carbon nanotubes via a facile solution processing method

International Nuclear Information System (INIS)

Kumar, Sandeep; Li Bin; Caceres, Santiago; Zhong Weihong; Maguire, Russ G

2009-01-01

Polyetherimide (PEI) has excellent mechanical and thermal properties, and exceptional fire resistance. Developing even broader multi-functionality in PEI/carbon nanotube (CNT) composites for industrial applications is an alluring but challenging goal, due to processing difficulties related to the high pressure and temperature needed to achieve effective flow for this polymer, and costly and complex treatments of the CNTs. Here we report the fabrication of PEI nanocomposite films using low-cost commercially functionalized multi-walled carbon nanotubes (MWNTs), and a simple and innovative process, achieving exceptional properties with only 0.5 wt% of MWNTs, including an increase in electrical conductivity of 12 orders of magnitude, accompanied by an unprecedented increase of 86 0 C in thermal decomposition temperature (higher service temperature). Field emission scanning electron microscopy revealed a high degree of uniform dispersion among the MWNTs, superb polymer-MWNT interaction and formation of a spatially homogeneous nanotube network within the matrix. The enhancement in these properties suggests great potential use for this developed processing approach and the resulting nanocomposites for multi-functional coating or interfacing materials in aerospace and electronic industries.

Amorphous and crystalline TiO2 nanotube arrays for enhanced Li-ion intercalation properties.

Science.gov (United States)

Guan, Dongsheng; Cai, Chuan; Wang, Ying

2011-04-01

We have employed a simple process of anodizing Ti foils to prepare TiO2 nanotube arrays which show enhanced electrochemical properties for applications as Li-ion battery electrode materials. The lengths and pore diameters of TiO2 nanotubes can be finely tuned by varying voltage, electrolyte composition, or anodization time. The as-prepared nanotubes are amorphous and can be converted into anatase nanotubes with heat treatment at 480 degrees C. Rutile crystallites emerge in the anatase nanotube when the annealing temperature is increased to 580 degrees C, resulting in TiO2 nanotubes of mixed phases. The morphological features of nanotubes remain unchanged after annealing. Li-ion insertion performance has been studied for amorphous and crystalline TiO2 nanotube arrays. Amorphous nanotubes with a length of 3.0 microm and an outer diameter of 125 nm deliver a capacity of 91.2 microA h cm(-2) at a current density of 400 microA cm(-2), while those with a length of 25 microm and an outer diameter of 158 nm display a capacity of 533 microA h cm-2. When the 3-microm long nanotubes become crystalline, they deliver lower capacities: the anatase nanotubes and nanotubes of mixed phases show capacities of 53.8 microA h cm-2 and 63.1 microA h cm(-2), respectively at the same current density. The amorphous nanotubes show excellent capacity retention ability over 50 cycles. The cycled nanotubes show little change in morphology compared to the nanotubes before electrochemical cycling. All the TiO2 nanotubes demonstrate higher capacities than amorphous TiO2 compact layer reported in literature. The amorphous TiO2 nanotubes with a length of 1.9 microm exhibit a capacity five times higher than that of TiO2 compact layer even when the nanotube array is cycled at a current density 80 times higher than that for the compact layer. These results suggest that anodic TiO2 nanotube arrays are promising electrode materials for rechargeable Li-ion batteries.

3D-CFD Simulation of Confined Cross-Flow Injection Process Using Single Piston Pump

Directory of Open Access Journals (Sweden)

M. Elashmawy

2017-12-01

Full Text Available Injection process into a confined cross flow is quite important for many applications including chemical engineering and water desalination technology. The aim of this study is to investigate the performance of the injection process into a confined cross-flow of a round pipe using a single piston injection pump. A computational fluid dynamics (CFD analysis has been carried out to investigate the effect of the locations of the maximum velocity and minimum pressure on the confined cross-flow process. The jet trajectory is analyzed and related to the injection pump shaft angle of rotation during the injection duty cycle by focusing on the maximum instant injection flow of the piston action. Results indicate a low effect of the jet trajectory within the range related to the injection pump operational conditions. Constant cross-flow was used and injection flow is altered to vary the jet to line flow ratio (QR. The maximum jet trajectory exhibits low penetration inside the cross-flow. The results showed three regions of the flow ratio effect zones with different behaviors. Results also showed that getting closer to the injection port causes a significant decrease on the locations of the maximum velocity and minimum pressure.

Highly enhanced electrochemical activity of Ni foam electrodes decorated with nitrogen-doped carbon nanotubes for non-aqueous redox flow batteries

Science.gov (United States)

Lee, Jungkuk; Park, Min-Sik; Kim, Ki Jae

2017-02-01

Nitrogen-doped carbon nanotubes (NCNTs) are directly grown on the surface of a three-dimensional (3D) Ni foam substrate by floating catalytic chemical vapor deposition (FCCVD). The electrochemical properties of the 3D NCNT-Ni foam are thoroughly examined as a potential electrode for non-aqueous redox flow batteries (RFBs). During synthesis, nitrogen atoms can be successfully doped onto the carbon nanotube (CNT) lattices by forming an abundance of nitrogen-based functional groups. The 3D NCNT-Ni foam electrode exhibits excellent electrochemical activities toward the redox reactions of [Fe (bpy)3]2+/3+ (in anolyte) and [Co(bpy)3]+/2+ (in catholyte), which are mainly attributed to the hierarchical 3D structure of the NCNT-Ni foam electrode and the catalytic effect of nitrogen atoms doped onto the CNTs; this leads to faster mass transfer and charge transfer during operation. As a result, the RFB cell assembled with 3D NCNT-Ni foam electrodes exhibits a high energy efficiency of 80.4% in the first cycle; this performance is maintained up to the 50th cycle without efficiency loss.

Hydrogenated TiO2 nanotube photonic crystals for enhanced photoelectrochemical water splitting.

Science.gov (United States)

Meng, Ming; Zhou, Sihua; Yang, Lun; Gan, Zhixing; Liu, Kuili; Tian, Fengshou; Zhu, Yu; Li, ChunYang; Liu, Weifeng; Yuan, Honglei; Zhang, Yan

2018-04-02

We report the design, fabrication and characterization of novel TiO 2 nanotube photonic crystals with a crystalline core/disordered shell structure as well as substantial oxygen vacancies for photoelectrochemical (PEC) water splitting. The novel TiO 2 nanotube photonic crystals are fabricated by annealing of anodized TiO 2 nanotube photonic crystals in hydrogen atmosphere at various temperatures. The optimized novel TiO 2 nanotube photonic crystals produce a maximal photocurrent density of 2.2 mA cm -2 at 0.22 V versus Ag/AgCl, which is two times higher that of the TiO 2 nanotube photonic crystals annealed in air. Such significant PEC performance improvement can be ascribed to synergistic effects of the disordered surface layer and oxygen vacancies. The reduced band gap owing to the disordered surface layer and localized states induced by oxygen vacancies can enhance the efficient utilization of visible light. In addition, the disordered surface layer and substantial oxygen vacancies can promote the efficiency for separation and transport of the photogenerated carriers. This work may open up new opportunities for the design and construction of the high efficient and low-cost PEC water splitting system.

Dual-phase gas-permeation flow-injection thermometric analysis for the determination of carbon dioxide.

Science.gov (United States)

Liu, S J; Tubino, M

1998-11-01

A flow-injection configuration based on a dual-phase gas-permeation system from a liquid donor to a gas acceptor stream with a thermistor flow-through detector is proposed for the direct analysis of the gas in the acceptor. This system was applied for the determination of carbon dioxide (in the form of carbonate) using the following chemical reaction: CO(2)(g)+2NH(3)(g)+H(2)O(g)=(NH(4))(2)CO(3)(s), with a linear response from 1x10(-3) to 50x10(-3) mol l(-1) of CO(3)(2-). Carbon dioxide was produced in the liquid donor and permeated into the gaseous acceptor stream of air/water vapor. The detection limit is 1x10(-3) mol l(-1) of carbonate, and a sampling frequency of 60 h(-1) is achieved with a relative standard deviation of 4.1% for replicate injections. The dual-phase gas-permeation flow-injection manifold, along with the membrane and phase separations, as well as the chemical reaction, provides enhanced selectivity when compared with the system employing a liquid acceptor stream, as serious interferents in this system, for instance, acetate and formate, among others, do not interfere in the proposed system.

Origin of enhancement in Raman scattering from Ag-dressed carbon-nanotube antennas : experiment and modelling

NARCIS (Netherlands)

Raziman, T.V.; Duenas, J.A.; Milne, W.I.; Martin, O.J.F.; Dawson, P.

2018-01-01

The D- and G-band Raman signals from random arrays of vertically aligned, multi-walled carbon nanotubes are significantly enhanced (up to ∼14×) while the signal from the underlying Si substrate is simultaneously attenuated (up to ∼6×) when the nanotubes are dressed, either capped or coated, with Ag.

The procedure of ethanol determination in wine by enzyme amperometric biosensor

Directory of Open Access Journals (Sweden)

Dzyadevych S. V.

2009-08-01

Full Text Available Aim. Development of the procedure of ethanol determination in wine by an enzyme amperometric biosensor. Methods. The amperometric biosensor method of ethanol analysis has been used in this work. Results. The paper presents comparative analysis of two methods of alcohol oxidase (AO immobilization for development of amperometric biosensor for ethanol determination in wine. The method of AO immobilization in glutaraldehyde vapour was chosen as optimal for this purpose. The selectivity, operational and storage stability, and pH-optimum for operation of the created biosensor were determined. The procedure of ethanol determination in wine by amperometric biosensor on the basis of platinum printed electrode SensLab and AO was optimized. The analysis of ethanol concentration in wine and must samples was carried out using the developed high-stable biosensor. A good correlation between the data obtained by the biosensor and densitometry methods was shown. Conclusion. The proposed method of ethanol analysis could be used in wine production

Mass Transport Through Carbon Nanotube-Polystyrene Bundles

Science.gov (United States)

Lin, Rongzhou; Tran, Tuan

2016-05-01

Carbon nanotubes have been widely used as test channels to study nanofluidic transport, which has been found to have distinctive properties compared to transport of fluids in macroscopic channels. A long-standing challenge in the study of mass transport through carbon nanotubes (CNTs) is the determination of flow enhancement. Various experimental investigations have been conducted to measure the flow rate through CNTs, mainly based on either vertically aligned CNT membranes or individual CNTs. Here, we proposed an alternative approach that can be used to quantify the mass transport through CNTs. This is a simple method relying on the use of carbon nanotube-polystyrene bundles, which are made of CNTs pulled out from a vertically aligned CNT array and glued together by polystyrene. We experimentally showed by using fluorescent tagging that the composite bundles allowed measureable and selective mass transport through CNTs. This type of composite bundle may be useful in various CNT research areas as they are simple to fabricate, less likely to form macroscopic cracks, and offer a high density of CNT pores while maintaining the aligned morphology of CNTs.

Numerical modeling of injection, stress and permeability enhancement during shear stimulation at the Desert Peak Enhanced Geothermal System

Science.gov (United States)

Dempsey, David; Kelkar, Sharad; Davatzes, Nick; Hickman, Stephen H.; Moos, Daniel

2015-01-01

Creation of an Enhanced Geothermal System relies on stimulation of fracture permeability through self-propping shear failure that creates a complex fracture network with high surface area for efficient heat transfer. In 2010, shear stimulation was carried out in well 27-15 at Desert Peak geothermal field, Nevada, by injecting cold water at pressure less than the minimum principal stress. An order-of-magnitude improvement in well injectivity was recorded. Here, we describe a numerical model that accounts for injection-induced stress changes and permeability enhancement during this stimulation. In a two-part study, we use the coupled thermo-hydrological-mechanical simulator FEHM to: (i) construct a wellbore model for non-steady bottom-hole temperature and pressure conditions during the injection, and (ii) apply these pressures and temperatures as a source term in a numerical model of the stimulation. In this model, a Mohr-Coulomb failure criterion and empirical fracture permeability is developed to describe permeability evolution of the fractured rock. The numerical model is calibrated using laboratory measurements of material properties on representative core samples and wellhead records of injection pressure and mass flow during the shear stimulation. The model captures both the absence of stimulation at low wellhead pressure (WHP ≤1.7 and ≤2.4 MPa) as well as the timing and magnitude of injectivity rise at medium WHP (3.1 MPa). Results indicate that thermoelastic effects near the wellbore and the associated non-local stresses further from the well combine to propagate a failure front away from the injection well. Elevated WHP promotes failure, increases the injection rate, and cools the wellbore; however, as the overpressure drops off with distance, thermal and non-local stresses play an ongoing role in promoting shear failure at increasing distance from the well.

Integration of amperometric sensors for microchip capillary electrophoresis application

International Nuclear Information System (INIS)

Dicorato, F; Moore, E; Glennon, J

2011-01-01

Capillary electrophoresis is a technique for the separation and analysis of chemical compounds. Techniques adopted from the microchip technology knowledge have led to recent developments of electrophoresis system with integration on microchip. Microchip Capillary Electrophoresis (μCE) systems offer a series of advantages as easy integration for Lab-on-a-chip applications, high performance, portability, speed, minimal solvent and sample requirements. A new technological challenge aims at the development of an economic modular microchip capillary electrophoresis systems using separable and independent units concerning the sensor. In this project we worked on the development of an interchangeable amperometric sensor in order to provide a solution to such electrode passivation and facilitating the use of tailored sensors for specific analyte detection besides. Fluidic chips have been machined from cyclic olefin polymer pallets (Zeonor) using a micro-injection molding machine.

Integration of amperometric sensors for microchip capillary electrophoresis application

Energy Technology Data Exchange (ETDEWEB)

Dicorato, F; Moore, E [Life Sciences Interface Group, Tyndall National Institute, Lee Maltings, Dyke Parade, Cork (Ireland); Glennon, J, E-mail: eric.moore@tyndall.ie [Chemistry Department, University College Cork, College Road, Cork (Ireland)

2011-08-17

Capillary electrophoresis is a technique for the separation and analysis of chemical compounds. Techniques adopted from the microchip technology knowledge have led to recent developments of electrophoresis system with integration on microchip. Microchip Capillary Electrophoresis ({mu}CE) systems offer a series of advantages as easy integration for Lab-on-a-chip applications, high performance, portability, speed, minimal solvent and sample requirements. A new technological challenge aims at the development of an economic modular microchip capillary electrophoresis systems using separable and independent units concerning the sensor. In this project we worked on the development of an interchangeable amperometric sensor in order to provide a solution to such electrode passivation and facilitating the use of tailored sensors for specific analyte detection besides. Fluidic chips have been machined from cyclic olefin polymer pallets (Zeonor) using a micro-injection molding machine.

Titania nanotubes with adjustable dimensions for drug reservoir sites and enhanced cell adhesion

Energy Technology Data Exchange (ETDEWEB)

Çalışkan, Nazlı; Bayram, Cem; Erdal, Ebru; Karahaliloğlu, Zeynep; Denkbaş, Emir Baki, E-mail: denkbas@hacettepe.edu.tr

2014-02-01

This study aims to generate a bactericidal agent releasing surface via nanotube layer on titanium metal and to investigate how aspect ratio of nanotubes affects drug elution time and cell proliferation. Titania nanotube layers were generated on metal surfaces by anodic oxidation at various voltage and time parameters. Gentamicin loading was carried out via simple pipetting and the samples were tested against S. aureus for the efficacy of the applied modification. Drug releasing time and cell proliferation were also tested in vitro. Titania nanotube layers with varying diameters and lengths were prepared after anodization and anodizing duration was found as the most effective parameter for amount of loaded drug and drug releasing time. Drug elution lasted up to 4 days after anodizing for 80 min of the samples, whereas release completed in 24 h when the samples were anodized for 20 min. All processed samples had bactericidal properties against S. aureus organism except unmodified titanium, which was also subjected to drug incorporation step. The anodization also enhanced water wettability and cell adhesion results. Anodic oxidation is an effective surface modification to enhance tissue–implant interactions and also resultant titania layer can act as a drug reservoir for the release of bactericidal agents. The use of implants as local drug eluting devices is promising but further in vivo testing is required. - Highlights: • Titanium surfaces were anodized and a nanotubular titania layer was obtained. • Drug eluting time was found to be increasing with anodizaton time. • Varying nanotube diameters has no effect in drug elution time but amount of incorporated drug.

Titania nanotubes with adjustable dimensions for drug reservoir sites and enhanced cell adhesion

International Nuclear Information System (INIS)

Çalışkan, Nazlı; Bayram, Cem; Erdal, Ebru; Karahaliloğlu, Zeynep; Denkbaş, Emir Baki

2014-01-01

This study aims to generate a bactericidal agent releasing surface via nanotube layer on titanium metal and to investigate how aspect ratio of nanotubes affects drug elution time and cell proliferation. Titania nanotube layers were generated on metal surfaces by anodic oxidation at various voltage and time parameters. Gentamicin loading was carried out via simple pipetting and the samples were tested against S. aureus for the efficacy of the applied modification. Drug releasing time and cell proliferation were also tested in vitro. Titania nanotube layers with varying diameters and lengths were prepared after anodization and anodizing duration was found as the most effective parameter for amount of loaded drug and drug releasing time. Drug elution lasted up to 4 days after anodizing for 80 min of the samples, whereas release completed in 24 h when the samples were anodized for 20 min. All processed samples had bactericidal properties against S. aureus organism except unmodified titanium, which was also subjected to drug incorporation step. The anodization also enhanced water wettability and cell adhesion results. Anodic oxidation is an effective surface modification to enhance tissue–implant interactions and also resultant titania layer can act as a drug reservoir for the release of bactericidal agents. The use of implants as local drug eluting devices is promising but further in vivo testing is required. - Highlights: • Titanium surfaces were anodized and a nanotubular titania layer was obtained. • Drug eluting time was found to be increasing with anodizaton time. • Varying nanotube diameters has no effect in drug elution time but amount of incorporated drug

Amperometric L-glutamate biosensor based on bacterial cell-surface displayed glutamate dehydrogenase

Energy Technology Data Exchange (ETDEWEB)

Liang, Bo [Laboratory for Biosensing, Key Laboratory of Biofuels, and Shandong Provinicial Key Laboratory of Energy Genetics, Qingdao Institute of Bioenergy & Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao 266101 (China); University of Chinese Academy of Sciences, 19A Yuquan Road, Beijing 100049 (China); Zhang, Shu [Laboratory for Biosensing, Key Laboratory of Biofuels, and Shandong Provinicial Key Laboratory of Energy Genetics, Qingdao Institute of Bioenergy & Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao 266101 (China); Key Laboratory of Marine Chemistry Theory and Technology of Ministry of Education, Ocean University of China, 238 Songling Road, Qingdao 266100 (China); Lang, Qiaolin [Laboratory for Biosensing, Key Laboratory of Biofuels, and Shandong Provinicial Key Laboratory of Energy Genetics, Qingdao Institute of Bioenergy & Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao 266101 (China); Song, Jianxia; Han, Lihui [Key Laboratory of Marine Chemistry Theory and Technology of Ministry of Education, Ocean University of China, 238 Songling Road, Qingdao 266100 (China); Liu, Aihua, E-mail: liuah@qibebt.ac.cn [Laboratory for Biosensing, Key Laboratory of Biofuels, and Shandong Provinicial Key Laboratory of Energy Genetics, Qingdao Institute of Bioenergy & Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao 266101 (China); University of Chinese Academy of Sciences, 19A Yuquan Road, Beijing 100049 (China)

2015-07-16

Highlights: • E. coli surface-dispalyed Gldh exhibiting excellent enzyme activity and stability. • Sensitive amperometric biosensor for glutamate using Gldh-bacteria and MWNTs. • The glutamate biosensor exhibited high specificity and stability. - Abstract: A novel L-glutamate biosensor was fabricated using bacteria surface-displayed glutamate dehydrogenase (Gldh-bacteria). Here the cofactor NADP{sup +}-specific dependent Gldh was expressed on the surface of Escherichia coli using N-terminal region of ice nucleation protein (INP) as the anchoring motif. The cell fractionation assay and SDS-PAGE analysis indicated that the majority of INP-Gldh fusion proteins were located on the surface of cells. The biosensor was fabricated by successively casting polyethyleneimine (PEI)-dispersed multi-walled carbon nanotubes (MWNTs), Gldh-bacteria and Nafion onto the glassy carbon electrode (Nafion/Gldh-bacteria/PEI-MWNTs/GCE). The MWNTs could not only significantly lower the oxidation overpotential towards NAPDH, which was the product of NADP{sup +} involving in the oxidation of glutamate by Gldh, but also enhanced the current response. Under the optimized experimental conditions, the current–time curve of the Nafion/Gldh-bacteria/PEI-MWNTs/GCE was performed at +0.52 V (vs. SCE) by amperometry varying glutamate concentration. The current response was linear with glutamate concentration in two ranges (10 μM–1 mM and 2–10 mM). The low limit of detection was estimated to be 2 μM glutamate (S/N = 3). Moreover, the proposed biosensor is stable, specific, reproducible and simple, which can be applied to real samples detection.

Optimal Synthesis of Horizontally Aligned Single-Walled Carbon Nanotubes and Their Biofunctionalization for Biosensing Applications

Directory of Open Access Journals (Sweden)

Dawoon Jung

2016-01-01

Full Text Available As an influential candidate for highly sensitive biomolecule sensor, which can capture disease related biomolecules, carbon nanotube is useful material due to its unique properties. To adopt as a sensing platform, it is strongly needed to find optimal refined synthetic condition. In order to find the optimal synthetic conditions of horizontally aligned CNT, we performed quantity control of the mixed gases of H2 and CH4 injected. We successfully find that the formation of amorphous-like carbon was critically affected by some gas condition such as the flow rate of injected gases and ratios of gas mixture. Moreover, it should be noted that our horizontally aligned carbon nanotube array platform developed would offer another potential in developing nanoscale light source, where light emission results from electron-hole carrier recombination.

Biofunctionalization of multiwalled carbon nanotubes by electropolymerized poly(pyrrole-concanavalin A) films.

Science.gov (United States)

Papper, Vladislav; Elouarzaki, Kamal; Gorgy, Karine; Sukharaharja, Ayrine; Cosnier, Serge; Marks, Robert S

2014-10-13

The synthesis and electropolymerization of a pyrrolic concanavalin A derivative (pyrrole-Con A) onto a multiwalled carbon nanotube (MWCNT) deposit is reported. Glucose oxidase was then immobilized onto the MWCNT-poly(pyrrole-Con A) coating by affinity carbohydrate interactions with the polymerized Con A protein. The resulting enzyme electrode was applied to the amperometric detection of glucose exhibiting a high sensitivity of 36 mA cm(-2) mol(-1) L and a maximum current density of 350 μA cm(-2) . © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Modeling of Sheath Ion-Molecule Reactions in Plasma Enhanced Chemical Vapor Deposition of Carbon Nanotubes

Science.gov (United States)

Hash, David B.; Govindan, T. R.; Meyyappan, M.

2004-01-01

In many plasma simulations, ion-molecule reactions are modeled using ion energy independent reaction rate coefficients that are taken from low temperature selected-ion flow tube experiments. Only exothermic or nearly thermoneutral reactions are considered. This is appropriate for plasma applications such as high-density plasma sources in which sheaths are collisionless and ion temperatures 111 the bulk p!asma do not deviate significantly from the gas temperature. However, for applications at high pressure and large sheath voltages, this assumption does not hold as the sheaths are collisional and ions gain significant energy in the sheaths from Joule heating. Ion temperatures and thus reaction rates vary significantly across the discharge, and endothermic reactions become important in the sheaths. One such application is plasma enhanced chemical vapor deposition of carbon nanotubes in which dc discharges are struck at pressures between 1-20 Torr with applied voltages in the range of 500-700 V. The present work investigates The importance of the inclusion of ion energy dependent ion-molecule reaction rates and the role of collision induced dissociation in generating radicals from the feedstock used in carbon nanotube growth.

Amperometric Immunosensor for Carbofuran Detection Based on MWCNTs/GS-PEI-Au and AuNPs-Antibody Conjugate

Directory of Open Access Journals (Sweden)

Xiangyou Wang

2013-04-01

Full Text Available In this paper, an amperometric immunosensor for the detection of carbofuran was developed. Firstly, multiwall carbon nanotubes (MWCNTs and graphene sheets-ethyleneimine polymer-Au (GS-PEI-Au nanocomposites were modified onto the surface of a glass carbon electrode (GCE via self-assembly. The nanocomposites can increase the surface area of the GCE to capture a large amount of antibody, as well as produce a synergistic effect in the electrochemical performance. Then the modified electrode was coated with gold nanoparticles-antibody conjugate (AuNPs-Ab and blocked with BSA. The monoclonal antibody against carbofuran was covalently immobilized on the AuNPs with glutathione as a spacer arm. The morphologies of the GS-PEI-Au nanocomposites and the fabrication process of the immunosensor were characterized by X-ray diffraction (XRD, ultraviolet and visible absorption spectroscopy (UV-vis and scanning electron microscopy (SEM, respectively. Under optimal conditions, the immunosensor showed a wide linear range, from 0.5 to 500 ng/mL, with a detection limit of 0.03 ng/mL (S/N = 3. The as-constructed immunosensor exhibited notable performance features such as high specificity, good reproducibility, acceptable stability and regeneration performance. The results are mainly due to the excellent properties of MWCNTs, GS-PEI-Au nanocomposites and the covalent immobilization of Ab with free hapten binding sites for further immunoreaction. It provides a new avenue for amperometric immunosensor fabrication.

PEGylated single-walled carbon nanotubes activate neutrophils to increase production of hypochlorous acid, the oxidant capable of degrading nanotubes

Energy Technology Data Exchange (ETDEWEB)

Vlasova, Irina I., E-mail: irina.vlasova@yahoo.com [Research Institute for Physico-Chemical Medicine, Federal Medico-Biological Agency, Moscow (Russian Federation); Vakhrusheva, Tatyana V. [Research Institute for Physico-Chemical Medicine, Federal Medico-Biological Agency, Moscow (Russian Federation); Sokolov, Alexey V.; Kostevich, Valeria A. [Research Institute for Physico-Chemical Medicine, Federal Medico-Biological Agency, Moscow (Russian Federation); Research Institute for Experimental Medicine, Russian Academy of Medical Science, Saint Petersburg (Russian Federation); Gusev, Alexandr A.; Gusev, Sergey A. [Research Institute for Physico-Chemical Medicine, Federal Medico-Biological Agency, Moscow (Russian Federation); Melnikova, Viktoriya I. [Institute of Developmental Biology, Russian Academy of Science, Moscow (Russian Federation); Lobach, Anatolii S. [Institute of Problems of Chemical Physics, Russian Academy of Science, Chernogolovka (Russian Federation)

2012-10-01

Perspectives for the use of carbon nanotubes in biomedical applications depend largely on their ability to degrade in the body into products that can be easily cleared out. Carboxylated single-walled carbon nanotubes (c-SWCNTs) were shown to be degraded by oxidants generated by peroxidases in the presence of hydrogen peroxide. In the present study we demonstrated that conjugation of poly(ethylene glycol) (PEG) to c-SWCNTs does not interfere with their degradation by peroxidase/H{sub 2}O{sub 2} system or by hypochlorite. Comparison of different heme-containing proteins for their ability to degrade PEG-SWCNTs has led us to conclude that the myeloperoxidase (MPO) product hypochlorous acid (HOCl) is the major oxidant that may be responsible for biodegradation of PEG-SWCNTs in vivo. MPO is secreted mainly by neutrophils upon activation. We hypothesize that SWCNTs may enhance neutrophil activation and therefore stimulate their own biodegradation due to MPO-generated HOCl. PEG-SWCNTs at concentrations similar to those commonly used in in vivo studies were found to activate isolated human neutrophils to produce HOCl. Both PEG-SWCNTs and c-SWCNTs enhanced HOCl generation from isolated neutrophils upon serum-opsonized zymosan stimulation. Both types of nanotubes were also found to activate neutrophils in whole blood samples. Intraperitoneal injection of a low dose of PEG-SWCNTs into mice induced an increase in percentage of circulating neutrophils and activation of neutrophils and macrophages in the peritoneal cavity, suggesting the evolution of an inflammatory response. Activated neutrophils can produce high local concentrations of HOCl, thereby creating the conditions favorable for degradation of the nanotubes. -- Highlights: ► Myeloperoxidase (MPO) product hypochlorous acid is able to degrade CNTs. ► PEGylated SWCNTs stimulate isolated neutrophils to produce hypochlorous acid. ► SWCNTs are capable of activating neutrophils in blood samples. ► Activation of

Titania nanotubes with adjustable dimensions for drug reservoir sites and enhanced cell adhesion.

Science.gov (United States)

Çalışkan, Nazlı; Bayram, Cem; Erdal, Ebru; Karahaliloğlu, Zeynep; Denkbaş, Emir Baki

2014-02-01

This study aims to generate a bactericidal agent releasing surface via nanotube layer on titanium metal and to investigate how aspect ratio of nanotubes affects drug elution time and cell proliferation. Titania nanotube layers were generated on metal surfaces by anodic oxidation at various voltage and time parameters. Gentamicin loading was carried out via simple pipetting and the samples were tested against S. aureus for the efficacy of the applied modification. Drug releasing time and cell proliferation were also tested in vitro. Titania nanotube layers with varying diameters and lengths were prepared after anodization and anodizing duration was found as the most effective parameter for amount of loaded drug and drug releasing time. Drug elution lasted up to 4 days after anodizing for 80 min of the samples, whereas release completed in 24 h when the samples were anodized for 20 min. All processed samples had bactericidal properties against S. aureus organism except unmodified titanium, which was also subjected to drug incorporation step. The anodization also enhanced water wettability and cell adhesion results. Anodic oxidation is an effective surface modification to enhance tissue-implant interactions and also resultant titania layer can act as a drug reservoir for the release of bactericidal agents. The use of implants as local drug eluting devices is promising but further in vivo testing is required. Copyright © 2013 Elsevier B.V. All rights reserved.

An amperometric enzyme electrode and its biofuel cell based on a glucose oxidase-poly(3-anilineboronic acid)-Pd nanoparticles bionanocomposite for glucose biosensing.

Science.gov (United States)

Sun, Lingen; Ma, Yixuan; Zhang, Pei; Chao, Long; Huang, Ting; Xie, Qingji; Chen, Chao; Yao, Shouzhuo

2015-06-01

A new amperometric enzyme electrode and its biofuel cell were fabricated based on a glucose oxidase (GOx)-poly(3-anilineboronic acid) (PABA)-Pd nanoparticles (PdNPs) bionanocomposite for biosensing of glucose. Briefly, Pd was electroplated on a multiwalled carbon nanotubes (MWCNTs)-modified Au electrode, and the GOx-PABA-PdNPs bionanocomposite was prepared on the Pd(plate)/MWCNTs/Au electrode through the chemical oxidation of a GOx-3-anilineboronic acid adduct by Na2PdCl4, followed by electrode-modification with an outer-layer chitosan (CS) film. The thus-prepared CS/GOx-PABA-PdNPs/Pd(plate)/MWCNTs/Au electrode exhibited a linear amperometric response to glucose concentration from 2.0 μM to 4.5 mM with a sensitivity of 160 μA/mM/cm(2), sub-μM detection limit, and excellent operation/storage stability in the first-generation biosensing mode, as well as excellent analytical performance in the second-generation biosensing mode. The good recoveries of glucose obtained from spiked urine samples revealed the application potential of our amperometric enzyme electrode. In addition, a glucose/O2 biofuel cell was constructed using this enzyme electrode as the anode and a Pt/MWCNTs/Au electrode as the cathode, and this biofuel cell as a self-powered biosensing device showed a linear voltage response to glucose concentration from 100 μM to 13.5 mM with a sensitivity of 43.5 mV/mM/cm(2) and excellent operation/storage stability. Copyright © 2015 Elsevier B.V. All rights reserved.

Water transport inside carbon nanotubes mediated by phonon-induced oscillating friction.

Science.gov (United States)

Ma, Ming; Grey, François; Shen, Luming; Urbakh, Michael; Wu, Shuai; Liu, Jefferson Zhe; Liu, Yilun; Zheng, Quanshui

2015-08-01

The emergence of the field of nanofluidics in the last decade has led to the development of important applications including water desalination, ultrafiltration and osmotic energy conversion. Most applications make use of carbon nanotubes, boron nitride nanotubes, graphene and graphene oxide. In particular, understanding water transport in carbon nanotubes is key for designing ultrafiltration devices and energy-efficient water filters. However, although theoretical studies based on molecular dynamics simulations have revealed many mechanistic features of water transport at the molecular level, further advances in this direction are limited by the fact that the lowest flow velocities accessible by simulations are orders of magnitude higher than those measured experimentally. Here, we extend molecular dynamics studies of water transport through carbon nanotubes to flow velocities comparable with experimental ones using massive crowd-sourced computing power. We observe previously undetected oscillations in the friction force between water and carbon nanotubes and show that these oscillations result from the coupling between confined water molecules and the longitudinal phonon modes of the nanotube. This coupling can enhance the diffusion of confined water by more than 300%. Our results may serve as a theoretical framework for the design of new devices for more efficient water filtration and osmotic energy conversion devices.

64-section multidetector CT of the upper abdomen: optimization of a saline chaser injection protocol for improved vascular and parenchymal contrast enhancement

Energy Technology Data Exchange (ETDEWEB)

Marin, Daniele [Duke University Medical Center, Department of Radiology, Durham, NC (United States); University of Rome Sapienza, Department of Radiological Sciences, Rome (Italy); Nelson, Rendon C. [Duke University Medical Center, Department of Radiology, Durham, NC (United States); Guerrisi, Antonino; Passariello, Roberto; Catalano, Carlo [University of Rome Sapienza, Department of Radiological Sciences, Rome (Italy); Barnhart, Huiman [Duke University Medical Center, Department of Biostatistics and Bioinformatics, Durham, NC (United States); Schindera, Sebastian T. [University Hospital of Bern, Institute for Diagnostic, Interventional and Pediatric Radiology, Bern (Switzerland)

2011-09-15

To prospectively investigate the effect of varying the injection flow rates of a saline chaser on vascular and parenchymal contrast enhancement during abdominal MDCT. 100 consecutive patients were randomly assigned to four injection protocols. A fixed dose of contrast medium was administered followed by no saline (Protocol A) or 50 mL of saline at 2, 4, or 8 mL/s (Protocols B, C, and D). Peak, time-to-peak, and duration of 90% peak enhancement were determined for aorta, pancreas, and liver. Aortic peak enhancement was significantly higher for Protocol D (369.5 HU) compared with Protocols A and B (332.9 HU and 326.0 HU, respectively; P < 0.05). Pancreatic peak enhancement was significantly higher for Protocols C and D (110.6 HU and 110.9 HU, respectively) compared to Protocol A (92.5 HU; P < 0.05). Aortic and pancreatic time-to-peak enhancement occurred significantly later for Protocol D compared with Protocol A (42.8 s vs. 36.1 s [P < 0.001] and 49.7 s vs. 45.3 s [P = 0.003]). Injecting a saline chaser at high flow rates yields significantly higher peak aortic and pancreatic enhancement, with a slight longer time-to-peak enhancement. (orig.)

Adaptation of a load-inject valve for a flow injection chemiluminescence system enabling dual-reagent injection enhances understanding of environmental Fenton chemistry

International Nuclear Information System (INIS)

Jones, Matthew R.; Nightingale, Philp D.; Turner, Suzanne M.; Liss, Peter S.

2013-01-01

Graphical abstract: -- Highlights: •Measurement of multiple components of Fenton chemistry; Fe(II) and H 2 O 2 . •Rapid, quasi-simultaneous analysis enables calculation of environmental kinetics. •Low, nano to pico-molar detection limits with dual analyte analysis. •Able to measure complex matrix samples – organically enriched seawater. •Low cost system with appreciable sensitivity compared to single analyte analysis. -- Abstract: Environmental Fenton chemistry has been poorly constrained within the marine environment at a multi-component level. A simple, unique, reconfiguration of a flow-injection analytical system combined with luminol chemiluminescence allows quasi-simultaneously the measurement, using a single load-inject valve and a single photon multiplier tube, of reduced iron, Fe(II), and hydrogen peroxide. The system enables rapid, every 22 s, measurements with good accuracy at environmentally relevant concentrations, less than 5% relative standard deviations on both a 5 nM Fe(II) standard and a 60 nM hydrogen peroxide standard. Limits of detection were as low as 40 pM Fe(II) and 100 pM hydrogen peroxide. The system showed excellent capability by measuring from within an organic rich seawater the photochemically induced production of Fe(II) and hydrogen peroxide and their subsequent cycling and Fenton like interactions

Strong enhancement of straeming current power by application of two phase flow

NARCIS (Netherlands)

Xie, Yanbo; Sherwood, John D.; Shui, Lingling; van den Berg, Albert; Eijkel, Jan C.T.

2011-01-01

We show that the performance of a streaming-potential based microfluidic energy conversion system can be strongly enhanced by the use of two phase flow. Injection of gas bubbles into a liquid-filled channel increases both the maximum output power and the energy conversion efficiency. In single-phase

Enhancing thermal conductivity of fluids with graphite nanoparticles and carbon nanotube

Science.gov (United States)

Zhang, Zhiqiang [Lexington, KY; Lockwood, Frances E [Georgetown, KY

2008-03-25

A fluid media such as oil or water, and a selected effective amount of carbon nanomaterials necessary to enhance the thermal conductivity of the fluid. One of the preferred carbon nanomaterials is a high thermal conductivity graphite, exceeding that of the neat fluid to be dispersed therein in thermal conductivity, and ground, milled, or naturally prepared with mean particle size less than 500 nm, and preferably less than 200 nm, and most preferably less than 100 nm. The graphite is dispersed in the fluid by one or more of various methods, including ultrasonication, milling, and chemical dispersion. Carbon nanotubes with graphitic structure is another preferred source of carbon nanomaterial, although other carbon nanomaterials are acceptable. To confer long term stability, the use of one or more chemical dispersants is preferred. The thermal conductivity enhancement, compared to the fluid without carbon nanomaterial, is proportional to the amount of carbon nanomaterials (carbon nanotubes and/or graphite) added.

Intramuscular Injection of “Site Enhancement Oil”

DEFF Research Database (Denmark)

Petersen, Maria Louise; Colville-Ebeling, Bonnie; Jensen, Thomas Hartvig Lindkær

2015-01-01

The use of intramuscular injection of foreign substances for aesthetic purposes is well known. Complications are usually local to the site of injection but can be potentially lethal. Here, we present a case of "site enhancement oil" use in a 42-year-old man who died from asphyxia due to hanging. ...

Plasma-induced synthesis of Pt nanoparticles supported on TiO2 nanotubes for enhanced methanol electro-oxidation

Science.gov (United States)

Su, Nan; Hu, Xiulan; Zhang, Jianbo; Huang, Huihong; Cheng, Jiexu; Yu, Jinchen; Ge, Chao

2017-03-01

A Pt/C/TiO2 nanotube composite catalyst was successfully prepared for enhanced methanol electro-oxidation. Pt nanoparticles with a particle size of 2 nm were synthesized by plasma sputtering in water, and anatase TiO2 nanotubes with an inner diameter of approximately 100 nm were prepared by a simple two-step anodization method and annealing process. Field-emission scanning electron microscopy images indicated that the different morphologies of TiO2 synthesized on the surface of Ti foils were dependent on the different anodization parameters. The electrochemical performance of Pt/C/TiO2 catalysts for methanol oxidation showed that TiO2 nanotubes were more suitable for use as Pt nanoparticle support materials than irregular TiO2 short nanorods due to their tubular morphology and better electronic conductivity. X-ray photoelectron spectroscopy characterization showed that the binding energies of the Pt 4f of the Pt/C/TiO2 nanotubes exhibited a slightly positive shift caused by the relatively strong interaction between Pt and the TiO2 nanotubes, which could mitigate the poisoning of the Pt catalyst by COads, and further enhance the electrocatalytic performance. Thus, the as-obtained Pt/C/TiO2 nanotubes composites may become a promising catalyst for methanol electro-oxidation.

Degradation-by-design: Surface modification with functional substrates that enhance the enzymatic degradation of carbon nanotubes.

Science.gov (United States)

Sureshbabu, Adukamparai Rajukrishnan; Kurapati, Rajendra; Russier, Julie; Ménard-Moyon, Cécilia; Bartolini, Isacco; Meneghetti, Moreno; Kostarelos, Kostas; Bianco, Alberto

2015-12-01

Biodegradation of carbon-based nanomaterials has been pursued intensively in the last few years, as one of the most crucial issues for the design of safe, clinically relevant conjugates for biomedical applications. In this paper it is demonstrated that specific functional molecules can enhance the catalytic activity of horseradish peroxidase (HRP) and xanthine oxidase (XO) for the degradation of carbon nanotubes. Two different azido coumarins and one cathecol derivative are linked to multi-walled carbon nanotubes (MWCNTs). These molecules are good reducing substrates and strong redox mediators to enhance the catalytic activity of HRP. XO, known to metabolize various molecules mainly in the mammalian liver, including human, was instead used to test the biodegradability of MWCNTs modified with an azido purine. The products of the biodegradation process are characterized by transmission electron microscopy and Raman spectroscopy. The results indicate that coumarin and catechol moieties have enhanced the biodegradation of MWCNTs compared to oxidized nanotubes, likely due to the capacity of these substrates to better interact with and activate HRP. Although azido purine-MWCNTs are degraded less effectively by XO than oxidized nanotubes, the data uncover the importance of XO in the biodegradation of carbon-nanomaterials leading to their better surface engineering for biomedical applications. Copyright © 2015 Elsevier Ltd. All rights reserved.

The behavior after intravenous injection in mice of multiwalled carbon nanotube / Fe3O4 hybrid MRI contrast agents.

Science.gov (United States)

Wu, Huixia; Liu, Gang; Zhuang, Yeming; Wu, Dongmei; Zhang, Haoqiang; Yang, Hong; Hu, He; Yang, Shiping

2011-07-01

Fe(3)O(4) nanoparticles were in situ loaded on the surface of multiwalled carbon nanotubes (MWCNTs) by a solvothermal method using diethylene glycol and diethanolamine as solvents and complexing agents. The as-prepared MWCNT/Fe(3)O(4) hybrids exhibited excellent hydrophilicity, superparamagnetic property at room temperature, and a high T(2) relaxivity of 175.5 mM(-1) s(-1) in aqueous solutions. In vitro experiments revealed that MWCNT/Fe(3)O(4) had an excellent magnetic resonance imaging (MRI) enhancement effect on cancer cells, and importantly, they displayed low cytotoxicity and neglectable hemolytic activity. After intravenous administration, the T(2)-weighted MRI signal in the liver and spleen of mice decreased significantly, suggesting the potential application of the hybrids as MRI contrast agents. The organ biodistribution studies, histological analyses and elimination investigations showed that the hybrids were uptaken by the liver, lung and spleen after intravenous injection, and could be excreted from the liver and kidney. Copyright © 2011 Elsevier Ltd. All rights reserved.

Self-ordering anodized nanotubes: Enhancing the performance by surface plasmon for dye-sensitized solar cell

International Nuclear Information System (INIS)

Agarwala, S.; Ho, G.W.

2012-01-01

In the present work, electrochemical anodization has been used to prepare uniform TiO 2 nanotube array photoelectrode. The average internal diameter, tube length and wall thickness of the optimized morphology is ∼180 nm, 14 μm and 10 nm, respectively. It was found that the tube diameter increases with the anodization voltage. Diffraction data reveals that the nanotubes consist solely of anatase phase. Back illuminated geometry of dye-sensitized solar cell (DSSC), with nanotubes grown at 60 V for 2 h, gave a cell performance of 4.5%. TiO 2 nanotubes are loaded with silver (Ag) nanoparticles synthesized by a hydrothermal route. The Ag particle size is controlled resulting in solar conversion efficiency to increase by 22%. The DSSC based on TiO 2 nanotube with Ag nanoparticles shows power conversion efficiency of 5.5%. Detailed characterization are performed, presented and discussed. - Graphical abstract: Enhanced solar conversion efficiency of dye-sensitized solar cells by decorating TiO 2 nanotube array with Ag nanoparticles. Highlights: ► Uniform array of TiO 2 nanotubes synthesized via electrochemical anodization. ► Back illuminated DSSC gave a cell performance of 4.5%. ► TiO 2 nanotubes are loaded with Ag nanoparticles, which increased the power conversion efficiency to 5.5%.

Numerical simulation of flow characteristics of lean jet to cross-flow in safety injection of reactor cooling system

International Nuclear Information System (INIS)

Wang Haijun; He Huining; Luo Yushan; Wang Weishu

2011-01-01

In the present work, a numerical simulation was performed to study the flow characteristics of lean jet to cross flow in a main tube in the safety injection of reactor cooling system. The influence scope and mixing characteristics of the confined lean jet in cross-flow were studied. It can be concluded that three basic flow regimes are marked, namely the attached lean jet, lift-off lean jet and impinging lean jet. The velocity ratio V R is the key factor in the flow state. The depth and region of jet to main flow are enhanced with the increase of the velocity ratio. The jet flow penetrates through the main flow with the increase of the velocity ratio. At higher velocity ratio, the jet flow strikes the main flow bottom and circumfluence happens in upriver of main flow. The vortex flow characteristics dominate the flow near region of jet to cross-flow and the mixture of jet to cross-flow. At different velocity ratio V R , the vortex grows from the same displacement, but the vortex type and the vortex is different. At higher velocity ratio, the vortex develops fleetly, wears off sharp and dies out sharp. The study is very important to the heat transfer experiments of cross-flow jet and thermal stress analysis in the designs of nuclear engineering. (authors)

Development of flow injection analysis technique for uranium estimation

International Nuclear Information System (INIS)

Paranjape, A.H.; Pandit, S.S.; Shinde, S.S.; Ramanujam, A.; Dhumwad, R.K.

1991-01-01

Flow injection analysis is increasingly used as a process control analytical technique in many industries. It involves injection of the sample at a constant rate into a steady flowing stream of reagent and passing this mixture through a suitable detector. This paper describes the development of such a system for the analysis of uranium (VI) and (IV) and its gross gamma activity. It is amenable for on-line or automated off-line monitoring of uranium and its activity in process streams. The sample injection port is suitable for automated injection of radioactive samples. The performance of the system has been tested for the colorimetric response of U(VI) samples at 410 nm in the range of 35 to 360mg/ml in nitric acid medium using Metrohm 662 Photometer and a recorder as detector assembly. The precision of the method is found to be better than +/- 0.5%. This technique with certain modifications is used for the analysis of U(VI) in the range 0.1-3mg/ailq. by alcoholic thiocynate procedure within +/- 1.5% precision. Similarly the precision for the determination of U(IV) in the range 15-120 mg at 650 nm is found to be better than 5%. With NaI well-type detector in the flow line, the gross gamma counting of the solution under flow is found to be within a precision of +/- 5%. (author). 4 refs., 2 figs., 1 tab

A new amperometric glucose biosensor based on screen printed carbon electrodes with rhenium(IV - oxide as a mediator

Directory of Open Access Journals (Sweden)

ALBANA VESELI

2012-11-01

Full Text Available Rhenium(IV-oxide, ReO2, was used as a mediator for carbon paste (CPE and screen printed carbon (SPCE electrodes for the catalytic amperometric determination of hydro-gen peroxide, whose overpotential for the reduction could be lowered to -0.1 V vs. Ag/AgCl in flow injection analysis (FIA using phosphate buffer (0.1 M, pH=7.5 as a carrier. For hydrogen peroxide a detection limit (3σ of 0.8 mg L-1 could be obtained.ReO2-modified SPCEs were used to design biosensors with a template enzyme, i.e. glucose oxidase, entrapped in a Nafion membrane. The resulting glucose sensor showed a linear dynamic range up to 200 mg L-1 glucose with a detection limit (3σ of 0.6 mg L-1. The repeatability was 2.1 % RSD (n = 5 measurements, the reproducibility 5.4 % (n = 5 sensors. The sensor could be applied for the determination of glucose in blood serum in good agreement with a reference method.

Are Flow Injection-based Approaches Suitable for Automated Handling of Solid Samples?

DEFF Research Database (Denmark)

Miró, Manuel; Hansen, Elo Harald; Cerdà, Victor

Flow-based approaches were originally conceived for liquid-phase analysis, implying that constituents in solid samples generally had to be transferred into the liquid state, via appropriate batch pretreatment procedures, prior to analysis. Yet, in recent years, much effort has been focused...... electrolytic or aqueous leaching, on-line dialysis/microdialysis, in-line filtration, and pervaporation-based procedures have been successfully implemented in continuous flow/flow injection systems. In this communication, the new generation of flow analysis, including sequential injection, multicommutated flow.......g., soils, sediments, sludges), and thus, ascertaining the potential mobility, bioavailability and eventual impact of anthropogenic elements on biota [2]. In this context, the principles of sequential injection-microcolumn extraction (SI-MCE) for dynamic fractionation are explained in detail along...

Amperometric and impedance monitoring systems for biomedical applications

CERN Document Server

Punter-Villagrasa, Jaime; del Campo, Francisco J; Miribel, Pere

2017-01-01

The book presents the conception and realization of a pervasive electronic architecture for electrochemical applications, focusing on electronic instrumentation design and device development, particularly in electrochemical Point-of-Care and Lab-on-a-Chip devices, covering examples based on amperometric (DC) and impedance detection (AC) techniques. The presented electronics combine tailored front-end instrumentation and back-end data post-processing, enabling applications in different areas, and across a variety of techniques, analytes, transducers and environments. It addresses how the electronics are designed and implemented with special interest in the flow process: starting from electronic circuits and electrochemical biosensor design to a final validation and implementation for specific applications. Similarly, other important aspects are discussed throughout the book, such as electrochemical techniques, different analytes, targets, electronics reliability and robustness. The book also describes the use ...

Surface modification of TiO{sub 2} nanotubes with osteogenic growth peptide to enhance osteoblast differentiation

Energy Technology Data Exchange (ETDEWEB)

Lai, Min, E-mail: minlai@jsnu.edu.cn [School of Life Science, Jiangsu Normal University, Xuzhou, Jiangsu 221116 (China); Jin, Ziyang [School of Life Science, Jiangsu Normal University, Xuzhou, Jiangsu 221116 (China); Su, Zhiguo [Department of Pharmacy, The Affiliated hospital of Qingdao University, Qingdao, Shandong 266555 (China)

2017-04-01

To investigate the influence of surface-biofunctionalized substrates on osteoblast behavior, a layer of aligned TiO{sub 2} nanotubes with a diameter of around 70 nm was fabricated on titanium surface by anodization, and then osteogenic growth peptide (OGP) was conjugated onto TiO{sub 2} nanotubes through the intermediate layer of polydopamine. The morphology, composition and wettability of different surfaces were characterized by field-emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and contact angle measurements, respectively. The effects of OGP-modified TiO{sub 2} nanotube substrates on the morphology, proliferation and differentiation of osteoblasts were examined in vitro. Immunofluorescence staining revealed that the OGP-functionalized TiO{sub 2} nanotubes were favorable for cell spreading. However, there was no significant difference in cell proliferation observed among the different groups. Cells grown onto OGP-functionalized TiO{sub 2} nanotubes showed significantly higher (p < 0.05 or p < 0.01) levels of alkaline phosphatase (ALP) and mineralization after 4, 7 and 14 days of culture, respectively. Cells grown on OGP-functionalized TiO{sub 2} nanotubes had significantly higher (p < 0.05 or p < 0.01) expression of osteogenic-related genes including runt related transcription factor 2 (Runx2), ALP, collagen type I (Col I), osteopontin (OPN) and osteocalcin (OC) after 14 days of culture. These data suggest that surface functionalization of TiO{sub 2} nanotubes with OGP was beneficial for cell spreading and differentiation. This study provides a novel platform for the development and fabrication of titanium-based implants that enhance the propensity for osseointegration between the native tissue and implant interface. - Highlights: • The OGP functionalized TiO{sub 2} nanotube substrates were successfully fabricated through a direct and effective method. • The OGP functionalized substrates

Determination of uranium by an amperometric method

International Nuclear Information System (INIS)

John, Mary; Venkataramana, P.; Vaidyanathan, S.; Natarajan, P.R.

1981-01-01

An amperometric method has been standardised for the determination of uranium. Uranium is reduced to its quadrivalent state in concentrated phosphoric acid medium with ferrous iron. The excess iron is destroyed with nitric acid in presence of Mo(VI). The medium is diluted and U(IV) is titrated with standard potassium dichromate to an amperometric end point using a pair of identical plantinum wires as electrodes. The reagent volumes and uranium quantities have been scaled down to 30 ml. and 2-5 mg of uranium in the present work with a view to minimising the problems associated with recovery of plutonium. The results are quantitative with an R.S.D. of 0.2% in the present version of weight based titrations. (author)

Fast batch injection analysis of H{sub 2}O{sub 2} using an array of Pt-modified gold microelectrodes obtained from split electronic chips

Energy Technology Data Exchange (ETDEWEB)

Pacheco, Bruno D.; Valerio, Jaqueline [Centro de Ciencias e Humanidades - Universidade Presbiteriana Mackenzie, Rua da Consolacao, 896, 01302-907 Sao Paulo, SP (Brazil); Angnes, Lucio [Departamento de Quimica Fundamental, Instituto de Quimica da USP, Av. Prof. Lineu Prestes, 748, 05508-000 Cidade Universitaria, Sao Paulo, SP (Brazil); Pedrotti, Jairo J., E-mail: jpedrotti@mackenzie.br [Centro de Ciencias e Humanidades - Universidade Presbiteriana Mackenzie, Rua da Consolacao, 896, 01302-907 Sao Paulo, SP (Brazil)

2011-06-24

Graphical abstract: Highlights: > An array of gold microelectrodes modified with Pt was used for batch injection analysis of H{sub 2}O{sub 2} in rainwater. > The microelectrode array (n = 14) was obtained from electronic chips developed for surface mounted device technology. > The analytical frequency of the method can attain 300 determinations per hour. > The volume-weighted mean concentration of H{sub 2}O{sub 2} in rainwater investigated (n = 25) was 14.2 {mu}mol L{sup -1}. - Abstract: A fast and robust analytical method for amperometric determination of hydrogen peroxide (H{sub 2}O{sub 2}) based on batch injection analysis (BIA) on an array of gold microelectrodes modified with platinum is proposed. The gold microelectrode array (n = 14) was obtained from electronic chips developed for surface mounted device technology (SMD), whose size offers advantages to adapt them in batch cells. The effect of the dispensing rate, volume injected, distance between the platinum microelectrodes and the pipette tip, as well as the volume of solution in the cell on the analytical response were evaluated. The method allows the H{sub 2}O{sub 2} amperometric determination in the concentration range from 0.8 {mu}mol L{sup -1} to 100 {mu}mol L{sup -1}. The analytical frequency can attain 300 determinations per hour and the detection limit was estimated in 0.34 {mu}mol L{sup -1} (3{sigma}). The anodic current peaks obtained after a series of 23 successive injections of 50 {mu}L of 25 {mu}mol L{sup -1} H{sub 2}O{sub 2} showed an RSD < 0.9%. To ensure the good selectivity to detect H{sub 2}O{sub 2}, its determination was performed in a differential mode, with selective destruction of the H{sub 2}O{sub 2} with catalase in 10 mmol L{sup -1} phosphate buffer solution. Practical application of the analytical procedure involved H{sub 2}O{sub 2} determination in rainwater of Sao Paulo City. A comparison of the results obtained by the proposed amperometric method with another one which

Carbon nanotubes integrated in electrically insulated channels for lab-on-a-chip applications

International Nuclear Information System (INIS)

Mogensen, K B; Boggild, P; Kutter, J P; Gangloff, L; Teo, K B K; Milne, W I

2009-01-01

A fabrication process for monolithic integration of vertically aligned carbon nanotubes in electrically insulated microfluidic channels is presented. A 150 nm thick amorphous silicon layer could be used both for anodic bonding of a glass lid to hermetically seal the microfluidic glass channels and for de-charging of the wafer during plasma enhanced chemical vapor deposition of the carbon nanotubes. The possibility of operating the device with electroosmotic flow was shown by performing standard electrophoretic separations of 50 μM fluorescein and 50 μM 5-carboxyfluorescein in a 25 mm long column containing vertical aligned carbon nanotubes. This is the first demonstration of electroosmotic pumping and electrokinetic separations in microfluidic channels with a monolithically integrated carbon nanotube forest.

Carbon nanotubes integrated in electrically insulated channels for lab-on-a-chip applications

DEFF Research Database (Denmark)

Mogensen, Klaus Bo; Gangloff, L.; Bøggild, Peter

2009-01-01

A fabrication process for monolithic integration of vertically aligned carbon nanotubes in electrically insulated microfluidic channels is presented. A 150 nm thick amorphous silicon layer could be used both for anodic bonding of a glass lid to hermetically seal the microfluidic glass channels...... and for de-charging of the wafer during plasma enhanced chemical vapor deposition of the carbon nanotubes. The possibility of operating the device with electroosmotic flow was shown by performing standard electrophoretic separations of 50 mu M fluorescein and 50 mu M 5-carboxyfluorescein in a 25 mm long...... column containing vertical aligned carbon nanotubes. This is the first demonstration of electroosmotic pumping and electrokinetic separations in microfluidic channels with a monolithically integrated carbon nanotube forest....

Retro-review of flow injection analysis

DEFF Research Database (Denmark)

Ruzicka, Jaromir; Hansen, Elo Harald

2008-01-01

It is indeed unusual for authors to review their own monograph – J. Ruzicka, E.H. Hansen, Flow Injection Analysis, 2nd Edition, Wiley, Chichester, West Sussex, UK, 1988. – and even more so if the book was published 20 years ago. Yet such an exercise might yield a perspective on the progress of an...

Amperometric detection of nitrite based on Dawson-type vanodotungstophosphate and carbon nanotubes

International Nuclear Information System (INIS)

Zhang, Di; Ma, Huiyuan; Chen, Yanyan; Pang, Haijun; Yu, Yan

2013-01-01

Graphical abstract: A composite film has been constructed by vanodotungstophosphate α 2 -K 7 P 2 VW 17 O 62 ·18H 2 O (P 2 W 17 V) and carbon nanotubes (CNTs) using the layer-by-layer self-assembly method. The incorporation of CNTs and P 2 W 17 V into the composite film endowed the modified electrode fast electron transfer rate and high electrocatalytic activity of toward nitrite oxidation. This nitrite sensor shows broad linear range, low detection limit, and high sensitivity and stability. Also it did not show any interference with other potential interfering species, and was successfully employed for determination of nitrite in real samples. -- Highlights: •A composite film was constructed by a vanodotungstophosphate and carbon nanotubes. •The composite film showed fast electron transfer rate and high electrocatalytic activity of toward nitrite oxidation. •The proposed sensor can amperometricially detect nitrite with high sensitivity and selectivity. -- Abstract: A nitrite sensor based on Dawson vanodotungstophosphates α 2 -K 7 P 2 VW 17 O 62 ·18H 2 O (P 2 W 17 V) and carbon nanotubes (CNTs) was prepared by electrostatic layer-by-layer self-assembly technique. The sensor {PEI/PSS/[PDDA/P 2 W 17 V-CNTs] n } was characterized by UV–vis spectroscopy, atomic force microscopy (AFM), scanning electron microscopy (SEM) and X-ray photoelectron spectra (XPS). The electron transfer and sensing ability of this sensor were explored using cyclic voltammetry (CV) and electrochemical impedance spectra (EIS) technology. The results show that the incorporation of CNTs and P 2 W 17 V into the composite film endowed the modified electrode with fast transfer rate and high electrocatalytic activity towards oxidation of nitrite. This nitrite sensor with 10 bilayers has a broad linear range of 5 × 10 −8 to 2.13 × 10 −3 M, a low detection limit of 0.0367 μM (S N −1 = 3), a high sensitivity of 0.35 mA mM −1 NO 2 − , an excellent anti-interference property in the

Modified and reverse radiometric flow injection analysis

Energy Technology Data Exchange (ETDEWEB)

Myint, U; Ba, H; Khin, M M; Aung, K; Thida, [Yangon Univ. (Myanmar). Dept. of Chemistry; Toelgyessy, J [Slovak Technical Univ., Bratislava (Slovakia). Dept. of Environmental Science

1994-06-01

Determination of [sup 137]Cs and [sup 60]Co by using modified and reverse radiometric flow injection analysis is described. Two component RFIA was also realized using [sup 60]Co and [sup 137]Cs radionuclides. (author) 2 refs.; 5 figs.

Functionalized Carbon Nanotubes with Gold Nanoparticles to Fabricate a Sensor for Hydrogen Peroxide Determination

Directory of Open Access Journals (Sweden)

Halimeh Rajabzade

2012-01-01

Full Text Available A highly sensitive electrode was prepared based on gold nanoparticles/nanotubes/ionic liquid for measurement of Hydrogen peroxide. Gold nanoparticles of 20–25 nm were synthesized on a nanotube carbon paste electrode by cyclic voltammetry technique while the coverage was controlled by applied potential and time. The gold nanoparticles were modified to form a monolayer on CNT, followed by decoration with ionic liquid for determination of hydrogen peroxide. The experimental conditions, applied potential and pH, for hydrogen peroxide monitoring were optimized, and hydrogen peroxide was determined amperometrically at 0.3 V vs. SCE at pH 7.0. Electrocatalytic effects of gold deposited CNT were observed with respect to unmodified one. The sensitivity obtained was 5 times higher for modified one. The presence of Au particles in the matrix of CNTs provides an environment for the enhanced electrocatalytic activities. The sensor has a high sensitivity, quickly response to H2O2 and good stability. The synergistic influence of MWNT, Au particles and IL contributes to the excellent performance for the sensor. The sensor responds to H2O2 in the linear range from 0.02 µM to 0.3 mM. The detection limit was down to 0.4 µM when the signal to noise ratio is 3.

An improved amperometric L-lactate biosensor based on covalent immobilization of microbial lactate oxidase onto carboxylated multiwalled carbon nanotubes/copper nanoparticles/polyaniline modified pencil graphite electrode.

Science.gov (United States)

Dagar, Kusum; Pundir, C S

2017-01-01

An improved amperometric l-lactate biosensor was constructed based on covalent immobilization of lactate oxidase (LOx) from Pediococcus species onto carboxylated multiwalled carbon nanotubes (cMWCNT)/copper nanoparticles (CuNPs)/polyaniline (PANI) hybrid film electrodeposited on the surface of a pencil graphite electrode (PGE). The enzyme electrode was characterized by cyclic voltammetry (CV), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy and electrochemical impedance spectroscopy (EIS), while CuNPs synthesized by chemical reduction method, were characterized by transmission electron microscopy (TEM), UV spectrascopy and X-ray diffraction (XRD). The biosensor showed maximum response within 5s at pH 8.0 in 0.05M sodium phosphate buffer and 37°C, when operated at 20mVs -1 . The biosensor had a detection limit of 0.25μM with a wide working range between 1μM-2500μM. The biosensor was employed for measurement of l-lactic acid level in plasma of apparently healthy and diseased persons. Analytical recovery of added lactic acid in plasma was 95.5%. Within- and between-batch coefficients of variations were 6.24% and 4.19% respectively. There was a good correlation (R 2 =0.97) between plasma lactate values as measured by standard enzymatic spectrophotometric method and the present biosensor. The working enzyme electrode was used 180 times over a period of 140 days, when stored at 4°C. Copyright © 2016. Published by Elsevier Inc.

Self-ordering anodized nanotubes: Enhancing the performance by surface plasmon for dye-sensitized solar cell

Energy Technology Data Exchange (ETDEWEB)

Agarwala, S., E-mail: agarwala.shweta@gmail.com [Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive, Singapore 117576 (Singapore); Ho, G.W. [Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive, Singapore 117576 (Singapore)

2012-05-15

In the present work, electrochemical anodization has been used to prepare uniform TiO{sub 2} nanotube array photoelectrode. The average internal diameter, tube length and wall thickness of the optimized morphology is {approx}180 nm, 14 {mu}m and 10 nm, respectively. It was found that the tube diameter increases with the anodization voltage. Diffraction data reveals that the nanotubes consist solely of anatase phase. Back illuminated geometry of dye-sensitized solar cell (DSSC), with nanotubes grown at 60 V for 2 h, gave a cell performance of 4.5%. TiO{sub 2} nanotubes are loaded with silver (Ag) nanoparticles synthesized by a hydrothermal route. The Ag particle size is controlled resulting in solar conversion efficiency to increase by 22%. The DSSC based on TiO{sub 2} nanotube with Ag nanoparticles shows power conversion efficiency of 5.5%. Detailed characterization are performed, presented and discussed. - Graphical abstract: Enhanced solar conversion efficiency of dye-sensitized solar cells by decorating TiO{sub 2} nanotube array with Ag nanoparticles. Highlights: Black-Right-Pointing-Pointer Uniform array of TiO{sub 2} nanotubes synthesized via electrochemical anodization. Black-Right-Pointing-Pointer Back illuminated DSSC gave a cell performance of 4.5%. Black-Right-Pointing-Pointer TiO{sub 2} nanotubes are loaded with Ag nanoparticles, which increased the power conversion efficiency to 5.5%.

Methods Reduce Cost, Enhance Quality of Nanotubes

Science.gov (United States)

2009-01-01

For all the challenges posed by the microgravity conditions of space, weight is actually one of the more significant problems NASA faces in the development of the next generation of U.S. space vehicles. For the Agency s Constellation Program, engineers at NASA centers are designing and testing new vessels as safe, practical, and cost-effective means of space travel following the eventual retirement of the space shuttle. Program components like the Orion Crew Exploration Vehicle, intended to carry astronauts to the International Space Station and the Moon, must be designed to specific weight requirements to manage fuel consumption and match launch rocket capabilities; Orion s gross liftoff weight target is about 63,789 pounds. Future space vehicles will require even greater attention to lightweight construction to help conserve fuel for long-range missions to Mars and beyond. In order to reduce spacecraft weight without sacrificing structural integrity, NASA is pursuing the development of materials that promise to revolutionize not only spacecraft construction, but also a host of potential applications on Earth. Single-walled carbon nanotubes are one material of particular interest. These tubular, single-layer carbon molecules - 100,000 of them braided together would be no thicker than a human hair - display a range of remarkable characteristics. Possessing greater tensile strength than steel at a fraction of the weight, the nanotubes are efficient heat conductors with metallic or semiconductor electrical properties depending on their diameter and chirality (the pattern of each nanotube s hexagonal lattice structure). All of these properties make the nanotubes an appealing material for spacecraft construction, with the potential for nanotube composites to reduce spacecraft weight by 50 percent or more. The nanotubes may also feature in a number of other space exploration applications, including life support, energy storage, and sensor technologies. NASA s various

Functional materials based on carbon nanotubes: Carbon nanotube actuators and noncovalent carbon nanotube modification

Science.gov (United States)

Fifield, Leonard S.

Carbon nanotubes have attractive inherent properties that encourage the development of new functional materials and devices based on them. The use of single wall carbon nanotubes as electromechanical actuators takes advantage of the high mechanical strength, surface area and electrical conductivity intrinsic to these molecules. The work presented here investigates the mechanisms that have been discovered for actuation of carbon nanotube paper: electrostatic, quantum chemical charge injection, pneumatic and viscoelastic. A home-built apparatus for the measurement of actuation strain is developed and utilized in the investigation. An optical fiber switch, the first demonstrated macro-scale device based on the actuation of carbon nanotubes, is described and its performance evaluated. Also presented here is a new general process designed to modify the surface of carbon nanotubes in a non-covalent, non-destructive way. This method can be used to impart new functionalities to carbon nanotube samples for a variety of applications including sensing, solar energy conversion and chemical separation. The process described involves the achievement of large degrees of graphitic surface coverage with polycyclic aromatic hydrocarbons through the use of supercritical fluids. These molecules are bifunctional agents that anchor a desired chemical group to the aromatic surface of the carbon nanotubes without adversely disrupting the conjugated backbone that gives rise the attractive electronic and physical properties of the nanotubes. Both the nanotube functionalization work and the actuator work presented here emphasize how an understanding and control of nanoscale structure and phenomena can be of vital importance in achieving desired performance for active materials. Opportunities for new devices with improved function over current state-of-the-art can be envisioned and anticipated based on this understanding and control.

Bioelectrochemistry of heme peptide at seamless three-dimensional carbon nanotubes/graphene hybrid films for highly sensitive electrochemical biosensing.

Science.gov (United States)

Komori, Kikuo; Terse-Thakoor, Trupti; Mulchandani, Ashok

2015-02-18

A seamless three-dimensional hybrid film consisting of carbon nanotubes grown at the graphene surface (CNTs/G) is a promising material for the application to highly sensitive enzyme-based electrochemical biosensors. The CNTs/G film was used as a conductive nanoscaffold for enzymes. The heme peptide (HP) was immobilized on the surface of the CNTs/G film for amperometric sensing of H2O2. Compared with flat graphene electrodes modified with HP, the catalytic current for H2O2 reduction at the HP-modified CNTs/G electrode increased due to the increase in the surface coverage of HP. In addition, microvoids in the CNTs/G film contributed to diffusion of H2O2 to modified HP, resulting in the enhancement of the catalytic cathodic currents. The kinetics of the direct electron transfer from the CNTs/G electrode to compound I and II of modified HP was also analyzed.

Enhanced performance of inverted organic photovoltaic cells using CNTs-TiO(X) nanocomposites as electron injection layer.

Science.gov (United States)

Zhang, Hong; Xu, Meifeng; Cui, Rongli; Guo, Xihong; Yang, Shangyuan; Liao, Liangsheng; Jia, Quanjie; Chen, Yu; Dong, Jinquan; Sun, Baoyun

2013-09-06

In this study, we fabricated inverted organic photovoltaic cells with the structure ITO/carbon nanotubes (CNTs)-TiO(X)/P3HT:PCBM/MoO₃/Al by spin casting CNTs-TiO(X) nanocomposite (CNTs-TiO(X)) as the electron injection layer onto ITO/glass substrates. The power conversion efficiency (PCE) of the 0.1 wt% single-walled nanotubes (SWNTs)-TiO(X) nanocomposite device was almost doubled compared with the TiO(X) device, but with increasing concentration of the incorporated SWNTs in the TiO(X) film, the performance of the devices appeared to decrease rapidly. Devices with multi-walled NTs in the TiO(X) film have a similar trend. This phenomenon mainly depends on the inherent physical and chemical characteristics of CNTs such as their high surface area, their electron-accepting properties and their excellent carrier mobility. However, with increasing concentration of CNTs, CNTs-TiO(X) current leakage pathways emerged and also a recombination of charges at the interfaces. In addition, there was a significant discovery. The incorporated CNTs were highly conducive to enhancing the degree of crystallinity and the ordered arrangement of the P3HT in the active layers, due to the intermolecular π-π stacking interactions between CNTs and P3HT.

Enhanced Injection Molding Simulation of Advanced Injection Molds

Directory of Open Access Journals (Sweden)

Béla Zink

2017-02-01

Full Text Available The most time-consuming phase of the injection molding cycle is cooling. Cooling efficiency can be enhanced with the application of conformal cooling systems or high thermal conductivity copper molds. The conformal cooling channels are placed along the geometry of the injection-molded product, and thus they can extract more heat and heat removal is more uniform than in the case of conventional cooling systems. In the case of copper mold inserts, cooling channels are made by drilling and heat removal is facilitated by the high thermal conductivity coefficient of copper, which is several times that of steel. Designing optimal cooling systems is a complex process; a proper design requires injection molding simulations, but the accuracy of calculations depends on how precise the input parameters and boundary conditions are. In this study, three cooling circuit designs and three mold materials (Ampcoloy 940, 1.2311 (P20 steel, and MS1 steel were used and compared using numerical methods. The effect of different mold designs and materials on cooling efficiency were examined using calculated and measured results. The simulation model was adjusted to the measurement results by considering the joint gap between the mold inserts.

Trends and perspectives of flow injection/sequential injection on-line sample-pretreatment schemes coupled to ETAAS

DEFF Research Database (Denmark)

Wang, Jianhua; Hansen, Elo Harald

2005-01-01

Flow injection (FI) analysis, the first generation of this technique, became in the 1990s supplemented by its second generation, sequential injection (SI), and most recently by the third generation (i.e.,Lab-on-Valve). The dominant role played by FI in automatic, on-line, sample pretreatments in ...

A novel multi-walled carbon nanotube-based antibody conjugate for quantitative and semi-quantitative lateral flow assays.

Science.gov (United States)

Sun, Wenjuan; Hu, Xiaolong; Liu, Jia; Zhang, Yurong; Lu, Jianzhong; Zeng, Libo

2017-10-01

In this study, the multi-walled carbon nanotubes (MWCNTs) were applied in lateral flow strips (LFS) for semi-quantitative and quantitative assays. Firstly, the solubility of MWCNTs was improved using various surfactants to enhance their biocompatibility for practical application. The dispersed MWCNTs were conjugated with the methamphetamine (MET) antibody in a non-covalent manner and then manufactured into the LFS for the quantitative detection of MET. The MWCNTs-based lateral flow assay (MWCNTs-LFA) exhibited an excellent linear relationship between the values of test line and MET when its concentration ranges from 62.5 to 1500 ng/mL. The sensitivity of the LFS was evaluated by conjugating MWCNTs with HCG antibody and the MWCNTs conjugated method is 10 times more sensitive than the one conjugated with classical colloidal gold nanoparticles. Taken together, our data demonstrate that MWCNTs-LFA is a more sensitive and reliable assay for semi-quantitative and quantitative detection which can be used in forensic analysis.

Flow Boiling in a Micro-Channel Coated With Carbon Nanotubes

OpenAIRE

Khanikar, Vikash; Mudawar, Issam; Fisher, Timothy

2009-01-01

This study examines the heat transfer enhancement attributes of carbon nanotubes (CNTs) applied to the bottom wall of a shallow rectangular micro-channel. Using deionized water as working fluid, experiments were performed with both a bare copper bottom wall and a CNT-coated copper wall. Boiling curves were generated for both walls, aided by high-speed video analysis of interfacial features. CNT arrays promoted earlier, abundant and intense bubble nucleation at low mass velocities, consistent ...

Perfluorinated acids as ion-pairing agents in the determination of monoamine transmitters and some prominent metabolites in rat brain by high-performance liquid chromatography with amperometric detection.

Science.gov (United States)

Patthy, M; Gyenge, R

1988-09-30

The behaviour of trifluoroacetate and heptafluorobutyrate as pairing ions for the reversed-phase ion-pair separation of monoamine transmitters and related metabolites was studied. The performance of systems with the perfluorinated acids was compared with that of systems containing sodium octyl sulphonate and was found to be better in terms of peak resolution combined with total analysis time, day-to-day reproducibility and the time required for attaining initial chromatographic equilibrium. Rat brain samples were deproteinized in the acidified mobile phase, injected directly on to a high-performance liquid chromatographic column and quantitated using an amperometric detector. Sample run times were 6-8 min, at a relatively low flow-rate. The detection limits achieved are fairly uncommon with conventional bore columns. The two perfluorinated acids studied differ in the dominant mechanisms of ion-pair formation and show selectivity differences as a result.

Amperometric and coulometric methods of platinum metal determination. (Review)

International Nuclear Information System (INIS)

Ezerskaya, N.A.

1981-01-01

Reviewed are works published in the period from 1957-1979, on amperometric and coulometric (potentiostatistic and amperostatistic variant) determination of platinum metals, Ru in particular. During amperometric titration of Ru the following titrantes are used: hydroquinone, thioxne thiourea, Na 2 S 2 O 3 . It is proposed to titrate Ru in the form of ruthenate-ion with hydrazine sulphate in alkal: medium according to the current of reagent oxidation. During coulometric determination of Ru the electrogenerating titrant TiCl 3 or Ti 2 (SO 4 ) 3 (for initial form of Ru [RuCl 6 ] 2- ) is used [ru

Interaction of molybdenum (6) with potassium benzyldithiocarbaminate during amperometric titration

International Nuclear Information System (INIS)

Galushko, S.V.; Usatenko, Yu.I.

1975-01-01

The paper is an amperometric study of the mechanism of interaction between molybdenum (VI) and potassium benzyl dithiocarbamate [BDTC] which was based on the use of voltamperometry, electron paramagnetic resonance, infrared spectroscopy, potentiometry and elemental analysis. In amperometric titration Mo(VI) with BDTC (pH 4-2) forms a red compound of low solubility. In more acidic media the intensity of coloration is increased and a violet hue develops. On the basis of the data obtained it is concluded that in the amperometric titration of Mo(VI) with potassium BDTC there is first formation of a Mo(VI) compound, which subsequently acquires a red colour as a result of the reduction of Mo(VI) to Mo(V). It was also established that the degree of reduction is small where titration is carried out in the range pH 4.8-0.1. Quantitative determination of Mo is performed most effectively in slightly acidic media. Mo reacts with potassium BDTC in a ratio of 1:2. (E.P.)

Carbon nanotubes and graphene modified screen-printed carbon electrodes as sensitive sensors for the determination of phytochelatins in plants using liquid chromatography with amperometric detection.

Science.gov (United States)

Dago, Àngela; Navarro, Javier; Ariño, Cristina; Díaz-Cruz, José Manuel; Esteban, Miquel

2015-08-28

Nanomaterials are of great interest for the development of electrochemical sensors. Multi-walled carbon nanotubes and graphene were used to modify the working electrode surface of different screen-printed carbon electrodes (SPCE) with the aim of improving the sensitivity of the SPCE and comparing it with the conventional glassy carbon electrode. To assay the usability of these sensors, a HPLC methodology with amperometric detection was developed to analyze several phytochelatins in plants of Hordeum vulgare and Glycine max treated with Hg(II) or Cd(II) giving detection limits in the low μmolL(-1) range. Phytochelatins are low molecular weight peptides with the general structure γ-(Glu-Cys)n-Gly (n=2-5) which are synthesized in plants in the presence of heavy metal ions. These compounds can chelate heavy metal ions by the formation of complexes which, are transported to the vacuoles, where the toxicity is not threatening. For this reason phytochelatins are essential in the detoxification of heavy metal ions in plants. The developed HPLC method uses a mobile phase of 1% of formic acid in water with KNO3 or NaCl (pH=2.00) and 1% of formic acid in acetonitrile. Electrochemical detection at different carbon-based electrodes was used. Among the sensors tested, the conventional glassy carbon electrode offers the best sensitivity although modification improves the sensitivity of the SPCE. Glutathione and several isoforms of phytochelatin two were found in plant extracts of both studied species. Copyright © 2015 Elsevier B.V. All rights reserved.

Preliminary study towards photoactivity enhancement using a biocompatible titanium dioxide/carbon nanotubes composite

International Nuclear Information System (INIS)

Cendrowski, Krzysztof; Jedrzejczak, Malgorzata; Peruzynska, Magdalena; Dybus, Andrzej; Drozdzik, Marek; Mijowska, Ewa

2014-01-01

Graphical abstract: Scheme demonstrating the experimental steps toward the formation of titania/multiwalled carbon nanotubes (TiO 2 -MWCNTs) from multiwalled carbon nanotubes (MWCNT). - Highlights: • Easy and efficient method of impregnation carbon nanotubes with titania. • High photoactivity. • Correlation between the interaction of carbon nanotubes with titania on the photocatalytic properties. • High biocompatibility of the nanotubes. - Abstract: Recent research is focused on the enhancement in photoactivity of titanium dioxide/carbon nanotubes through formation of novel nanocomposites that exhibit a high specific surface area, remarkable electron transfer and biocompatibility. Here, we explore a new synthesis route in the system composed of nanocrystalline titanium dioxide supported on external walls and inner space of multiwalled carbon nanotubes (MWCNT). The advantages of this method are: its simplicity, direct fusion of titanium dioxide particles on the carbon material, and formation of chemical bond Ti–O–C between TiO 2 and MWCNT. Photocatalytic performance of this system has been compared to a commercial catalyst (Degussa P25) in a model reaction of phenol decomposition in/under UV light. The efficiency of the process increased by the factor of 2.5 when the TiO 2 –MWCNT photocatalyst was utilized. Further, the photoactive nanocomposite was analysed towards its biocompatibility in order to establish a safe dose of the catalyst. Its influence on the cells viability was studied on mouse fibroblasts and human liver tissue cells, in the range from 0 to 100 μg/mL. This has revealed that the composite in concentrations up to 25 μg/mL exerted low toxicity, which allowed for finding a compromise between the highest safe dose and acceptable photoactivity of the catalyst

Method for producing carbon nanotubes

Science.gov (United States)

Phillips, Jonathan [Santa Fe, NM; Perry, William L [Jemez Springs, NM; Chen, Chun-Ku [Albuquerque, NM

2006-02-14

Method for producing carbon nanotubes. Carbon nanotubes were prepared using a low power, atmospheric pressure, microwave-generated plasma torch system. After generating carbon monoxide microwave plasma, a flow of carbon monoxide was directed first through a bed of metal particles/glass beads and then along the outer surface of a ceramic tube located in the plasma. As a flow of argon was introduced into the plasma through the ceramic tube, ropes of entangled carbon nanotubes, attached to the surface of the tube, were produced. Of these, longer ropes formed on the surface portion of the tube located in the center of the plasma. Transmission electron micrographs of individual nanotubes revealed that many were single-walled.

Charge Injection and Current Flow in Organic Light Emitting Diodes

Science.gov (United States)

Smith, D. L.; Davids, P. S.; Heller, C. M.; Crone, B. K.; Campbell, I. H.; Barashkov, N. N.; Ferraris, J. P.

1997-03-01

We present a comparison between device model calculations and current-voltage measurements for a series of organic LED structures. The Schottky energy barrier of an injecting contact is systematically varied by changing the metal used to form that contact. The current-voltage characteristics of the structures are described using a device model that considers charge injection, transport and space charge effects in the low mobility organic material. Charge injection into the organic material is controlled by the Schottky energy barrier of the metal/organic contact. For Schottky energy barriers greater than about 0.4 eV injection into the organic material is the principal limitation to current flow. In this regime the net injected charge density is relatively small, the electric field in the structure is nearly uniform, and space charge effects are not important. For smaller energy barriers relatively large charge densities are injected into the organic material and space charge effects become the dominant limit to current flow. The measured current-voltage characteristics are quantitatively described by the device model using Schottky barrier values independently determined by internal photoemission and electroabsorption measurements.

Carbon nanotube composite materials

Science.gov (United States)

O'Bryan, Gregory; Skinner, Jack L; Vance, Andrew; Yang, Elaine Lai; Zifer, Thomas

2015-03-24

A material consisting essentially of a vinyl thermoplastic polymer, un-functionalized carbon nanotubes and hydroxylated carbon nanotubes dissolved in a solvent. Un-functionalized carbon nanotube concentrations up to 30 wt % and hydroxylated carbon nanotube concentrations up to 40 wt % can be used with even small concentrations of each (less than 2 wt %) useful in producing enhanced conductivity properties of formed thin films.

Developing the laminar MHD forced convection flow of water/FMWNT carbon nanotubes in a microchannel imposed the uniform heat flux

Energy Technology Data Exchange (ETDEWEB)

Karimipour, Arash; Taghipour, Abdolmajid [Department of Mechanical Engineering, Najafabad Branch, Islamic Azad University, Najafabad (Iran, Islamic Republic of); Malvandi, Amir, E-mail: amirmalvandi@aut.ac.ir [Department of Mechanical Engineering, Neyshabur Branch, Islamic Azad University, Neyshabur (Iran, Islamic Republic of)

2016-12-01

This paper aims to investigate magnetic field and slip effects on developing laminar forced convection of nanofluids in the microchannels. A novel mixture of water and FMWNT carbon nanotubes is used as the working fluid. To do this, fluid flow and heat transfer through a microchannel is simulated by a computer code in FORTRAN language. The mixture of FMWNT carbon nanotubes suspended in water is considered as the nanofluid. Slip velocity is supposed as the hydrodynamic boundary condition while the microchannel's lower wall is insulated and the top wall is under the effect of a constant heat flux. Moreover, the flow field is subjected to a magnetic field with a constant strength. The results are presented as the velocity, temperature and Nusselt number profiles. It is observed that nanofluid composed of water and carbon nanotubes (FMWNT) can work well to increase the heat transfer rate along the microchannel walls. Furthermore, it is indicated that imposing the magnetic field is very effective at the thermally developing region. In contrast, the magnetic field effect at fully developed region is insignificant, especially at low values of Reynolds number. - Highlights: • Simulation of water/FMWNT carbon nanotubes flow in a microchannel. • The effects of magnetic field strength on nanofluid's slip velocity. • The effects of Ha, Re, ϕ and slip coefficient on averaged Nusselt number. • Magnetic field effect at developing flow region is significant.

Batch-processed carbon nanotube wall as pressure and flow sensor

International Nuclear Information System (INIS)

Choi, Jungwook; Kim, Jongbaeg

2010-01-01

A pressure and flow sensor based on the electrothermal-thermistor effect of a batch-processed carbon nanotube wall (CNT wall) is presented. The negative temperature coefficient of resistance (TCR) of CNTs and the temperature dependent tunneling rate through the CNT/silicon junction enable vacuum pressure and flow velocity sensing because the heat transfer rate between CNTs and the surrounding gas molecules differs depending on pressure and flow rate. The CNT walls are synthesized by thermal chemical vapor deposition (CVD) on an array of microelectrodes fabricated on a silicon-on-insulator (SOI) wafer. The CNTs are self-assembled between the microelectrodes and substrate across the thickness of a buried oxide layer during the synthesis process, and the simple batch fabrication results in high throughput and yield. A wide pressure range, down to 3 x 10 -3 from 10 5 Pa, and a nitrogen flow velocity range between 1 and 52.4 mm s -1 , are sensed. Further experimental characterizations of the bias voltage dependent response of the sensor as a vacuum pressure gauge are presented.

Modelling and Simulation of Structural Deformation of Isothermal Subsurface Flow and Carbon Dioxide Injection

KAUST Repository

El-Amin, Mohamed

2011-05-15

Injection of CO2 in hydrocarbon reservoir has double benefit. On the one hand, it is a profitable method due to issues related to global warming, and on the other hand it is an effective mechanism to enhance hydrocarbon recovery. Such injection associates complex processes involving, e.g., solute transport of dissolved materials, in addition to local changes in density of the phases. Also, increasing carbon dioxide injection may cause a structural deformation of the medium, so it is important to include such effect into the model. The structural deformation modelling in carbon sequestration is important to evaluate the medium stability to avoid CO2 leakage to the atmosphere. On the other hand, geologic formation of the medium is usually heterogeneous and consists of several layers of different permeability. In this work we conduct numerical simulation of two-phase flow in a heterogeneous porous medium domain with dissolved solute transport as well as structural deformation effects. The solute transport of the dissolved component is described by concentration equation. The structural deformation for geomechanics is derived from a general local differential balance equation with neglecting the local mass balance of solid phase and the inertial force term. The flux continuity condition is used at interfaces between different permeability layers of the heterogeneous medium. We analyze the vertical migration of a CO2 plume injected into a 2D layered reservoir. Analysis of distribution of flow field components such as saturation, pressures, velocities, and CO2 concentration are presented.

Plasma-induced synthesis of Pt nanoparticles supported on TiO{sub 2} nanotubes for enhanced methanol electro-oxidation

Energy Technology Data Exchange (ETDEWEB)

Su, Nan [College of Materials Science and Engineering, Nanjing Tech University, Xin-Mo-Fan Road No. 5, 210009, Nanjing, Jiangsu (China); The Synergetic Innovation Center for Advanced Materials, Xin-Mo-Fan Road No. 5, 210009, Nanjing, Jiangsu (China); Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Xin-Mo-Fan Road No. 5, 210009, Nanjing, Jiangsu (China); Hu, Xiulan, E-mail: whoxiulan@163.com [College of Materials Science and Engineering, Nanjing Tech University, Xin-Mo-Fan Road No. 5, 210009, Nanjing, Jiangsu (China); The Synergetic Innovation Center for Advanced Materials, Xin-Mo-Fan Road No. 5, 210009, Nanjing, Jiangsu (China); Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Xin-Mo-Fan Road No. 5, 210009, Nanjing, Jiangsu (China); Zhang, Jianbo; Huang, Huihong; Cheng, Jiexu; Yu, Jinchen; Ge, Chao [College of Materials Science and Engineering, Nanjing Tech University, Xin-Mo-Fan Road No. 5, 210009, Nanjing, Jiangsu (China)

2017-03-31

Highlights: • Pt nanoparticles are synthesized by plasma sputtering in water. • Pt/C/TiO{sub 2} nanotubes shows better mass activity and CO-poisoning tolerance than Pt/C. • TiO{sub 2} nanotubes are more suitable for support materials than TiO{sub 2} small particles. • The metal-support interactions between Pt and TiO{sub 2} nanotubes are detected by XPS. - Abstract: A Pt/C/TiO{sub 2} nanotube composite catalyst was successfully prepared for enhanced methanol electro-oxidation. Pt nanoparticles with a particle size of 2 nm were synthesized by plasma sputtering in water, and anatase TiO{sub 2} nanotubes with an inner diameter of approximately 100 nm were prepared by a simple two-step anodization method and annealing process. Field-emission scanning electron microscopy images indicated that the different morphologies of TiO{sub 2} synthesized on the surface of Ti foils were dependent on the different anodization parameters. The electrochemical performance of Pt/C/TiO{sub 2} catalysts for methanol oxidation showed that TiO{sub 2} nanotubes were more suitable for use as Pt nanoparticle support materials than irregular TiO{sub 2} short nanorods due to their tubular morphology and better electronic conductivity. X-ray photoelectron spectroscopy characterization showed that the binding energies of the Pt 4f of the Pt/C/TiO{sub 2} nanotubes exhibited a slightly positive shift caused by the relatively strong interaction between Pt and the TiO{sub 2} nanotubes, which could mitigate the poisoning of the Pt catalyst by CO{sub ads}, and further enhance the electrocatalytic performance. Thus, the as-obtained Pt/C/TiO{sub 2} nanotubes composites may become a promising catalyst for methanol electro-oxidation.

[Amperometric biosensor for ethanol analysis in wines and grape must during wine fermentation].

Science.gov (United States)

Shkotova, L V; Slast'ia, E A; Zhyliakova, T A; Soldatkin, O P; Schuhmann, W; Dziadevych, S V

2005-01-01

The amperometric biosensor for ethanol determination based on alcohol oxidase immobilised by the method of electrochemical polymerization has been developed. The industrial screen-printed platinum electrodes were used as transducers for creation of amperometric alcohol biosensor. Optimal conditions for electrochemical deposition of an active membrane with alcohol oxidase has been determined. Biosensors are characterised by good reproducibility and operational stability with minimal detection limit of ethanol 8 x 10(-5) M. The good correlation of results for ethanol detection in wine and during wine fermentation by using the developed amperometric biosensor with the data obtained by the standard methods was shown (r = 0.995).

Optimal contant time injection policy for enhanced oil recovery and characterization of optimal viscous profiles

Science.gov (United States)

Daripa, Prabir

2011-11-01

We numerically investigate the optimal viscous profile in constant time injection policy of enhanced oil recovery. In particular, we investigate the effect of a combination of interfacial and layer instabilities in three-layer porous media flow on the overall growth of instabilities and thereby characterize the optimal viscous profile. Results based on monotonic and non-monotonic viscous profiles will be presented. Time permitting. we will also present results on multi-layer porous media flows for Newtonian and non-Newtonian fluids and compare the results. The support of Qatar National Fund under a QNRF Grant is acknowledged.

Facile template-directed synthesis of carbon-coated SnO2 nanotubes with enhanced Li-storage capabilities

International Nuclear Information System (INIS)

Zhu, Xiaoshu; Zhu, Jingyi; Yao, Yinan; Zhou, Yiming; Tang, Yawen; Wu, Ping

2015-01-01

Herein, a novel type of carbon-coated SnO 2 nanotubes has been designed and synthesized through a facile two-step hydrothermal approach by using ZnO nanorods as templates. During the synthetic route, SnO 2 nanocrystals and carbon layer have been uniformly deposited on the rod-like templates in sequence, meanwhile ZnO nanorods could be in situ dissolved owing to the generated alkaline and acidic environments during hydrothermal coating of SnO 2 nanocrystals and hydrothermal carbonization of glucose, respectively. When utilized as an anode material in lithium-ion batteries, the carbon-coated SnO 2 nanotubes manifests markedly enhanced Li-storage capabilities in terms of specific capacity and cycling stability in comparison with bare SnO 2 nanocrystals. - Graphical abstract: Display Omitted - Highlights: • C-coated SnO 2 nanotubes prepared via facile ZnO-nanorod-templated hydrothermal route. • Unique morphological and structural features toward lithium storage. • Enhanced Li-storage performance in terms of specific capacity and cycling stability

Zinc oxide nanotubes decorated with silver nanoparticles as an ultrasensitive substrate for surface-enhanced Raman scattering

International Nuclear Information System (INIS)

Gao, M.; Feng, B.; Sun, Y.; Xing, G.; Li, S.; Yang, J.; Yang, L.; Zhang, Y.; Liu, H.; Fan, H.; Sui, Y.; Zhang, Z.; Liu, S.; Song, H.

2012-01-01

We report on the fabrication of a highly aligned silver-decorated array of zinc oxide nanotubes for use in surface-enhanced Raman spectroscopy (SERS). The ZnO nanotube array was first prepared by chemical etching, and the silver nanoparticles (AgNPs) were then deposited on their surface by magnetron sputtering. Such ZnO/Ag hybrid structures are shown to act as SERS-active substrates with remarkable sensitivity. The enhancement factor can be as high as 10 5 when using 4-mercaptopyridine in solution as a SERS probe. The synergistic combination between SERS 'hot spots' and the formation of an interfacial electric field between the zinc oxide nanotubes and the AgNPs in our opinion contribute to the high sensitivity. The relative standard deviations of signal intensities for the major SERS peaks are <7 %. This demonstrates that the optimized ZnO/Ag hybrid represents an excellent SERS substrate that may be used in trace analysis and ultrasensitive molecular sensing. (author)

The Co-axial Flow of Injectable Solid Hydrogels with Encapsulated Cells

Science.gov (United States)

Stewart, Brandon; Pochan, Darrin; Sathaye, Sameer

2013-03-01

Hydrogels are quickly becoming an important biomaterial that can be used for the safe, localized injection of cancer drugs, the injection of stem cells into areas of interest or other biological applications. Our peptides can be self-assembled in a syringe where they form a gel, sheared by injection and, once in the body, immediately reform a localized pocket of stiff gel. My project has been designed around looking at the possibility of having a co-axial strand, in which one gel can surround another. This co-axial flow can be used to change the physical properties of our gel during injection, such as stiffening our gel using hyaluronic acid or encapsulating cells in the gel and surrounding the gel with growth medium or other biological factors. Rheology on hyaluron stiffened gels and cells encapsulated in gels was performed for comparison to the results from co-axial flow. Confocal microscopy was used to examine the coaxial gels after flow and to determine how the co-axial nature of the gels is affected by the concentration of peptide.

Facile fabrication of organic/inorganic nanotube heterojunction arrays for enhanced photoelectrochemical water splitting

Science.gov (United States)

Chen, Yingzhi; Li, Aoxiang; Yue, Xiaoqi; Wang, Lu-Ning; Huang, Zheng-Hong; Kang, Feiyu; Volinsky, Alex A.

2016-07-01

Organic/inorganic heterojunction photoanodes are appealing for making concurrent use of the highly photoactive organic semiconductors, and the efficient dielectric screening provided by their inorganic counterparts. In the present work, organic/inorganic nanotube heterojunction arrays composed of TiO2 nanotube arrays and a semiconducting N,N-(dicyclohexyl) perylene-3,4,9,10-tetracarboxylic diimide (PDi) layer were fabricated for photoelectrochemical water splitting. In this arrayed architecture, a PDi layer with a tunable thickness was coated on anodic TiO2 nanotube arrays by physical vapor deposition, which is advantageous for the formation of a uniform layer and an adequate interface contact between PDi and TiO2. The obtained PDi/TiO2 junction exhibited broadened visible light absorption, and an effective interface for enhanced photogenerated electron-hole separation, which is supported by the reduced charge transfer resistance and prolonged excitation lifetime via impedance spectroscopy analysis and fluorescence emission decay investigations. Consequently, such a heterojunction photoanode was photoresponsive to a wide visible light region of 400-600 nm, and thus demonstrated a highly enhanced photocurrent density at 1.23 V vs. a reversible hydrogen electrode. Additionally, the durability of such a photoanode can be guaranteed after long-time illumination because of the geometrical restraint imposed by the PDi aggregates. These results pave the way to discover new organic/inorganic assemblies for high-performance photoelectric applications and device integration.Organic/inorganic heterojunction photoanodes are appealing for making concurrent use of the highly photoactive organic semiconductors, and the efficient dielectric screening provided by their inorganic counterparts. In the present work, organic/inorganic nanotube heterojunction arrays composed of TiO2 nanotube arrays and a semiconducting N,N-(dicyclohexyl) perylene-3,4,9,10-tetracarboxylic diimide (PDi

Amperometric Noise at Thin Film Band Electrodes

DEFF Research Database (Denmark)

Larsen, Simon T.; Heien, Michael L.; Taboryski, Rafael

2012-01-01

Background current noise is often a significant limitation when using constant-potential amperometry for biosensor application such as amperometric recordings of transmitter release from single cells through exocytosis. In this paper, we fabricated thin-film electrodes of gold and conductive...

Preliminary study towards photoactivity enhancement using a biocompatible titanium dioxide/carbon nanotubes composite

Energy Technology Data Exchange (ETDEWEB)

Cendrowski, Krzysztof, E-mail: kcendrowski@zut.edu.pl [West Pomeranian University of Technology Szczecin, Centre of Knowledge Based Nanomaterials and Technologies, Institute of Chemical and Environment Engineering, Pulaskiego 10, Szczecin 70-322 (Poland); Jedrzejczak, Malgorzata [West Pomeranian University of Technology Szczecin, Faculty of Biotechnology and Animal Science, Laboratory of Molecular Cytogenetic, Dr Judyma 10, Szczecin 71-460 (Poland); Peruzynska, Magdalena [Department of Experimental and Clinical Pharmacology, Pomeranian Medical University, al. Powstancow Wielkopolskich 72, Szczecin 70-111 (Poland); Dybus, Andrzej [West Pomeranian University of Technology Szczecin, Faculty of Biotechnology and Animal Science, Laboratory of Molecular Cytogenetic, Dr Judyma 10, Szczecin 71-460 (Poland); Drozdzik, Marek [Department of Experimental and Clinical Pharmacology, Pomeranian Medical University, al. Powstancow Wielkopolskich 72, Szczecin 70-111 (Poland); Mijowska, Ewa [West Pomeranian University of Technology Szczecin, Centre of Knowledge Based Nanomaterials and Technologies, Institute of Chemical and Environment Engineering, Pulaskiego 10, Szczecin 70-322 (Poland)

2014-08-25

Graphical abstract: Scheme demonstrating the experimental steps toward the formation of titania/multiwalled carbon nanotubes (TiO{sub 2}-MWCNTs) from multiwalled carbon nanotubes (MWCNT). - Highlights: • Easy and efficient method of impregnation carbon nanotubes with titania. • High photoactivity. • Correlation between the interaction of carbon nanotubes with titania on the photocatalytic properties. • High biocompatibility of the nanotubes. - Abstract: Recent research is focused on the enhancement in photoactivity of titanium dioxide/carbon nanotubes through formation of novel nanocomposites that exhibit a high specific surface area, remarkable electron transfer and biocompatibility. Here, we explore a new synthesis route in the system composed of nanocrystalline titanium dioxide supported on external walls and inner space of multiwalled carbon nanotubes (MWCNT). The advantages of this method are: its simplicity, direct fusion of titanium dioxide particles on the carbon material, and formation of chemical bond Ti–O–C between TiO{sub 2} and MWCNT. Photocatalytic performance of this system has been compared to a commercial catalyst (Degussa P25) in a model reaction of phenol decomposition in/under UV light. The efficiency of the process increased by the factor of 2.5 when the TiO{sub 2}–MWCNT photocatalyst was utilized. Further, the photoactive nanocomposite was analysed towards its biocompatibility in order to establish a safe dose of the catalyst. Its influence on the cells viability was studied on mouse fibroblasts and human liver tissue cells, in the range from 0 to 100 μg/mL. This has revealed that the composite in concentrations up to 25 μg/mL exerted low toxicity, which allowed for finding a compromise between the highest safe dose and acceptable photoactivity of the catalyst.

Scalable fabrication of immunosensors based on carbon nanotube polymer composites

Energy Technology Data Exchange (ETDEWEB)

Mendoza, Ernest; Gonzalez-Guerrero, Ana B [Institut Catala de Nanotecnologia, Campus Universitat Autonoma de Barcelona, 08193 Bellaterra (Spain); Orozco, Jahir; Jimenez-Jorquera, Cecilia; Fernandez-Sanchez, Cesar [Instituto de Microelectronica de Barcelona, CNM-IMB (CSIC), Campus Universitat Autonoma de Barcelona, 08193 Bellaterra (Spain); Calle, Ana; Lechuga, Laura M [Instituto de Microelectronica de Madrid, CNM-IMM (CSIC), Isaac Newton 8, 28760 Tres Cantos, Madrid (Spain)], E-mail: Ernest.Mendoza.icn@uab.es

2008-02-20

In this work we present the fabrication and characterization of immunosensors based on polystyrene (PS)-multiwalled carbon nanotube (MWCNT) composites. The electrochemical properties of the sensors have been investigated and show that the surface area is increased upon addition of the MWCNT-PS layer. Furthermore, a plasma activation process is used to partially remove the PS and expose the MWCNTs. This results in a huge increase in the electrochemical area and opens up the possibility of binding biomolecules to the MWCNT wall. The MWCNTs have been functionalized covalently with a model antibody (rabbit IgG). The biosensors have been tested using amperometric techniques and show detection limits comparable to standard techniques such as ELISA.

Fabrication of doped TiO2 nanotube array films with enhanced photo-catalytic activity

Science.gov (United States)

Peighambardoust, Naeimeh-Sadat; Khameneh-asl, Shahin; Khademi, Adib

2018-01-01

In the present work, we investigate the N and Fe-doped TiO2 nanotube array film prepared by treating TiO2 nanotube array film with ammonia solution and anodizing in Fe(NO3)3 solution respectively. This method avoided the use of hazardous ammonia gas, or laborious ion implantation process. N and Fe-doped TiO2 nanotube arrays (TiO2 NTs) were prepared by electrochemical anodization process in 0.5 wt % HF aqueous solution. The anodization was performed at the conditions of 20 V and 20 min, Followed by a wet immersion in NH3.H2O (1M) for N-doping for 2 hr and annealing post-treatment at 450 °C. The morphology and structure of the nanotube films were characterized by field emission scanning electron microscope (FESEM) and EDX. UV-vis. illumination test were done to observe photo-enhanced catalysis. The effect of different annealing temperature on the structure and photo-absorption property of the TiO2-TNTs was investigated. The results showed that N-TNTs nanotubes exhibited higher photocatalytic activity compared whit the Fe-doped and pure TNTs, because doping N promoted the separation of the photogenerated electrons and holes.

High quantum yield graphene quantum dots decorated TiO_2 nanotubes for enhancing photocatalytic activity

International Nuclear Information System (INIS)

Qu, Ailan; Xie, Haolong; Xu, Xinmei; Zhang, Yangyu; Wen, Shengwu; Cui, Yifan

2016-01-01

Highlights: • High concentration yellow GQDs and TiO_2 nanotubes were achieved by a simple and green method. • High quantum yield GQDs enhanced the photodegradation capacity of TiO_2 nanotube. • The catalytic performance of GQDs/TiO_2 depends on the GQDs loading. • The improved photocatalytic activity of GQDs/TiO_2 was attributed to three aspects. - Abstract: Graphene quantum dots (GQDs) with high quantum yield (about 23.6% at an excitation wavelength of 320 nm) and GQDs/TiO_2 nanotubes (GQDs/TiO_2 NTs) composites were achieved by a simple hydrothermal method at low temperature. Photoluminescence characterization showed that the GQDs exhibited the down-conversion PL features at excitation from 300 to 420 nm and up-conversion photoluminescence in the range of 600–800 nm. The photocatalytic activity of prepared GQDs/TiO_2 NTs composites on the degradation of methyl orange (MO) was significantly enhanced compared with that of pure TiO_2 nanotubes (TiO_2 NTs). For the composites coupling with 1.5%, 2.5% and 3.5% GQDs, the degradation of MO after 20 min irradiation under UV–vis light irradiation (λ = 380–780 nm) were 80.52%, 94.64% and 51.91%, respectively, which are much higher than that of pure TiO_2 NTs (35.41%). It was inferred from the results of characterization that the improved photocatalytic activity of the GQDs/TiO_2 NTs composites was attributed to the synergetic effect of up-conversion properties of the GQDs, enhanced visible light absorption and efficient separation of photogenerated electron-holes of the GQDs/TiO_2 composite.

Long-term Biosensors for Metabolite Monitoring by using Carbon Nanotubes

Directory of Open Access Journals (Sweden)

Cristina BOERO

2011-02-01

Full Text Available The key-point for the development of an amperometric sensor is the immobilization of the enzyme. In the present work we use biosensors based on glucose oxidase (GOD onto electrodes nanostructured with carbon nanotubes (CNT, to be employed in cell culture monitoring. The goal is to determine the best immobilization strategy from the point-of-view of sensor lifetime. We compared three types of immobilization: the spontaneous adsorption of the enzyme on nanotubes, the entrapment in a Nafion matrix (optimizing also the quantity, and the cross-linking with glutaraldehyde. The cross-linking gives the best sensitivity, 17.38 µA mM-1 cm-2, and the lowest detection limit, 25 µM. On the other hand, Nafion matrix allows to extend the linear range up to 7.5 mM. Finally, electrodes are tested over 35 days to analyze the lifetime. GOD cross-linking results to have 100% of retained activity after 35 days, while the adsorption and the entrapment retain only the 20 % of the original response.

Comparison of field-enhanced and pressure-assisted field-enhanced sample injection techniques for the analysis of water-soluble vitamins using CZE.

Science.gov (United States)

Liu, Qingqing; Liu, Yaling; Guan, Yu; Jia, Li

2009-04-01

A new online concentration method, namely pressure-assisted field-enhanced sample injection (PA-FESI), was developed and compared with FESI for the analysis of water-soluble vitamins by CZE with UV detection. In PA-FESI, negative voltage and positive pressure were simultaneously applied to initialize PA-FESI. PA-FESI uses the hydrodynamic flow generated by the positive pressure to counterbalance the reverse EOF in the capillary column during electrokinetic sample injection, which allowed a longer injection time than usual FESI mode without compromising the separation efficiency. Using the PA-FESI method, the LODs of the vitamins were at ng/mL level based on the S/N of 3 and the RSDs of migration time and peak area for each vitamin (1 microg/mL) were less than 5.1%. The developed method was applied to the analysis of water-soluble vitamins in corns.

Efficient silver modification of TiO2 nanotubes with enhanced photocatalytic activity

Science.gov (United States)

Huang, Jing; Ding, Lei; Xi, Yaoning; Shi, Liang; Su, Ge; Gao, Rongjie; Wang, Wei; Dong, Bohua; Cao, Lixin

2018-06-01

In this paper, Ag(CH3NH2)2+, Ag(NH3)2+ and Ag+ with different radii have been used as silver sources to find out the distribution of Ag ions on the H-TNT surface, which is critical to the final performance. The influence of this distribution on visible photocatalytic activity is further studied. The results indicate that, when Ag+ used as silver source with low concentration, these small sized silver ions mainly distribute on interlayer spacing of H-TNT. After heat-treatment and photo-reduction, the generated silver nanoparticles uniformly embed in the anatase TiO2 nanotube walls, and bring large interfacial area between Ag particles and TiO2 nanotubes. The separation effect of photogenerated electron-hole pair in TiO2 is enhanced by Ag particles, and achieves the best at 0.15 g/L, much higher than P25, TiO2/0, Ag-N@TiO2 and Ag-C-N@TiO2. This paper provides new ideas for the modification of TiO2 nanotubes.

Enhancement of adhesion between carbon nanotubes and polymer substrates using microwave irradiation

International Nuclear Information System (INIS)

Shim, Hyung Cheoul; Kwak, Yoon Keun; Han, Chang-Soo; Kim, Soohyun

2009-01-01

This paper reports the enhancement of adhesive strength between single-walled carbon nanotubes (SWNTs) and polymer substrates using microwave irradiation of 0-5 min duration at 2.45 GHz and 800 W. Field emission scanning electron microscopy images, ultraviolet-visible data and four-point probe sheet resistance measurement data indicate that microwave irradiation is effective for enhancement of adhesion between SWNTs and polymer substrates. SWNTs could be locally welded onto a polymer substrate due to their active response to microwave irradiation.

In vivo biodistribution and biological impact of injected carbon nanotubes using magnetic resonance techniques

Directory of Open Access Journals (Sweden)

Achraf Al Faraj

2011-02-01

Full Text Available Achraf Al Faraj1,2, Florence Fauvelle3, Nathalie Luciani4, Ghislaine Lacroix5, Michael Levy4, Yannick Crémillieux1, Emmanuelle Canet-Soulas1Université Lyon1, Créatis-LRMN, Lyon, France; 2King Saud University, College of Applied Medical Sciences, Radiological Sciences Department, Riyadh, Kingdom of Saudi Arabia; 3CRSSA, Biophysique Cellulaire et Moléculaire, Laboratoire de RMN, La Tronche, France; 4Université Paris7-Paris Diderot, Matières et Systèmes Complexes, Paris, France; 5Institut National de l’Environnement et des Risques Industriels, Verneuil-en-Halatte, FranceBackground: Single-walled carbon nanotubes (SWCNT hold promise for applications as contrast agents and target delivery carriers in the field of nanomedicine. When administered in vivo, their biodistribution and pharmacological profile needs to be fully characterized. The tissue distribution of carbon nanotubes and their potential impact on metabolism depend on their shape, coating, and metallic impurities. Because standard radiolabeled or fluorescently-labeled pharmaceuticals are not well suited for long-term in vivo follow-up of carbon nanotubes, alternative methods are required.Methods: In this study, noninvasive in vivo magnetic resonance imaging (MRI investigations combined with high-resolution magic angle spinning (HR-MAS, Raman spectroscopy, iron assays, and histological analysis ex vivo were proposed and applied to assess the biodistribution and biological impact of intravenously injected pristine (raw and purified and functionalized SWCNT in a 2-week longitudinal study. Iron impurities allowed raw detection of SWCNT in vivo by susceptibility-weighted MRI.Results: A transitional accumulation in the spleen and liver was observed by MRI. Raman spectroscopy, iron assays, and histological findings confirmed the MRI readouts. Moreover, no acute toxicological effect on the liver metabolic profile was observed using the HR-MAS technique, as confirmed by quantitative real

Stopped-flow injection spectrophotometric method for determination of chlorate in soil

OpenAIRE

Jaroon Jakmunee

2008-01-01

A stopped-flow injection (FI) spectrophotometric procedure based on iodometric reaction for the determination of chlorate has been developed. Standard/sample was injected into a stream of potassium iodide solution and then merged with a stream of hydrochloric acid solution to produce triiodide. By stopping the flow while the sample zone is being in a mixing coil, a slow reaction of chlorate with iodide in acidic medium was promoted to proceed with minimal dispersion of the triiodide product z...

Steam injection and enhanced bioremediation of heavy fuel oil contamination

International Nuclear Information System (INIS)

Dablow, J.; Hicks, R.; Cacciatore, D.

1995-01-01

Steam injection has been shown to be successful in remediating sites impacted by heavy fuel oils. Field demonstrations at both pilot and full scale have removed No. 2 diesel fuel and Navy Special Fuel Oil (No. 5 fuel oil) from impacted soils. Removal mechanisms include enhanced volatilization of vapor- and adsorbed-phase contaminants and enhanced mobility due to decreased viscosity and associated residual saturation of separate- and adsorbed-phase contaminants. Laboratory studies have shown that indigenous biologic populations are significantly reduced, but are not eliminated by steam injection operations. Populations were readily reestablished by augmentation with nutrients. This suggests that biodegradation enhanced by warm, moist, oxygenated environments can be expected to further reduce concentrations of contaminants following cessation of steam injection operations

Sensitive flow-injection spectrophotometric analysis of bromopride

Science.gov (United States)

Lima, Liliane Spazzapam; Weinert, Patrícia Los; Pezza, Leonardo; Pezza, Helena Redigolo

2014-12-01

A flow injection spectrophotometric procedure employing merging zones is proposed for direct bromopride determination in pharmaceutical formulations and biological fluids. The proposed method is based on the reaction between bromopride and p-dimethylaminocinnamaldehyde (p-DAC) in acid medium, in the presence of sodium dodecyl sulfate (SDS), resulting in formation of a violet product (λmax = 565 nm). Experimental design methodologies were used to optimize the experimental conditions. The Beer-Lambert law was obeyed in a bromopride concentration range of 3.63 × 10-7 to 2.90 × 10-5 mol L-1, with a correlation coefficient (r) of 0.9999. The limits of detection and quantification were 1.07 × 10-7 and 3.57 × 10-7 mol L-1, respectively. The proposed method was successfully applied to the determination of bromopride in pharmaceuticals and human urine, and recoveries of the drug from these media were in the ranges 99.6-101.2% and 98.6-102.1%, respectively. This new flow injection procedure does not require any sample pretreatment steps.

Flow-dependent directional growth of carbon nanotube forests by chemical vapor deposition

International Nuclear Information System (INIS)

Kim, Hyeongkeun; Park, Young Chul; Chun, Kyoung-Yong; Kim, Young-Jin; Choi, Jae-Boong; Kim, Keun Soo; Kang, Junmo; Hong, Byung Hee; Boo, Jin-Hyo

2011-01-01

We demonstrated that the structural formation of vertically aligned carbon nanotube (CNT) forests is primarily affected by the geometry-related gas flow, leading to the change of growth directions during the chemical vapor deposition (CVD) process. By varying the growing time, flow rate, and direction of the carrier gas, the structures and the formation mechanisms of the vertically aligned CNT forests were carefully investigated. The growth directions of CNTs are found to be highly dependent on the nonlinear local gas flows induced by microchannels. The angle of growth significantly changes with increasing gas flows perpendicular to the microchannel, while the parallel gas flow shows almost no effect. A computational fluid dynamics (CFD) model was employed to explain the flow-dependent growth of CNT forests, revealing that the variation of the local pressure induced by microchannels is an important parameter determining the directionality of the CNT growth. We expect that the present method and analyses would provide useful information to control the micro- and macrostructures of vertically aligned CNTs for various structural/electrical applications.

Flow-dependent directional growth of carbon nanotube forests by chemical vapor deposition

Energy Technology Data Exchange (ETDEWEB)

Kim, Hyeongkeun; Park, Young Chul; Chun, Kyoung-Yong; Kim, Young-Jin; Choi, Jae-Boong [School of Mechanical Engineering, Sungkyunkwan University, Suwon, 440-746 (Korea, Republic of); Kim, Keun Soo; Kang, Junmo; Hong, Byung Hee [SKKU Advanced Institute of Nanotechnology (SAINT) and Center for Human Interface Nano Technology (HINT), Sungkyunkwan University, Suwon, 440-746 (Korea, Republic of); Boo, Jin-Hyo, E-mail: byunghee@skku.edu, E-mail: boong33@skku.edu [Department of Chemistry, RIAN and Institute of Basic Science, Sungkyunkwan University, Suwon, 440-746 (Korea, Republic of)

2011-03-04

We demonstrated that the structural formation of vertically aligned carbon nanotube (CNT) forests is primarily affected by the geometry-related gas flow, leading to the change of growth directions during the chemical vapor deposition (CVD) process. By varying the growing time, flow rate, and direction of the carrier gas, the structures and the formation mechanisms of the vertically aligned CNT forests were carefully investigated. The growth directions of CNTs are found to be highly dependent on the nonlinear local gas flows induced by microchannels. The angle of growth significantly changes with increasing gas flows perpendicular to the microchannel, while the parallel gas flow shows almost no effect. A computational fluid dynamics (CFD) model was employed to explain the flow-dependent growth of CNT forests, revealing that the variation of the local pressure induced by microchannels is an important parameter determining the directionality of the CNT growth. We expect that the present method and analyses would provide useful information to control the micro- and macrostructures of vertically aligned CNTs for various structural/electrical applications.

Flow Injection/Sequential Injection Analysis Systems: Potential Use as Tools for Rapid Liver Diseases Biomarker Study

Directory of Open Access Journals (Sweden)

Supaporn Kradtap Hartwell

2012-01-01

Full Text Available Flow injection/sequential injection analysis (FIA/SIA systems are suitable for carrying out automatic wet chemical/biochemical reactions with reduced volume and time consumption. Various parts of the system such as pump, valve, and reactor may be built or adapted from available materials. Therefore the systems can be at lower cost as compared to other instrumentation-based analysis systems. Their applications for determination of biomarkers for liver diseases have been demonstrated in various formats of operation but only a few and limited types of biomarkers have been used as model analytes. This paper summarizes these applications for different types of reactions as a guide for using flow-based systems in more biomarker and/or multibiomarker studies.

Enhancement in photo-electrochemical efficiency by reducing recombination rate in branched TiO2 nanotube array on functionalizing with ZnO micro crystals

Science.gov (United States)

Boda, Muzaffar Ahmad; Ashraf Shah, Mohammad

2018-06-01

In this study, branched TiO2 nanotube array were fabricated through electrochemical anodization process at constant voltage using third generation electrolyte. On account of morphological advantage, these nanotubes shows significant enhancement in photo-electrochemical property than compact or conventional titania nanotube array. However, their photo-electrochemical efficiency intensifies on coating with ZnO micro-crystals. ZnO coated branched TiO2 nanotube array shows a photocurrent density of 27.8 mA cm‑2 which is 1.55 times the photocurrent density (17.2 mA cm‑2) shown by bare branched titania nanotubes. The significant enhancement in photocurrent density shown by the resulting ZnO/TiO2 hybrid structure is attributed to suppression in electron–hole recombination phenomenon by offering smooth pathway to photo generated excitons on account of staggered band edge positions in individual semiconductors.

Investigation of grid-enhanced two-phase convective heat transfer in the dispersed flow film boiling regime

International Nuclear Information System (INIS)

Miller, D.J.; Cheung, F.B.; Bajorek, S.M.

2013-01-01

Highlights: • Experiments were done in the RBHT facility to study the droplet flow in rod bundle. • The presence of a droplet field was found to greatly enhance heat transfer. • A second-stage augmentation was observed downstream of a spacer grid. • This augmentation is due to the breakup of liquid ligaments downstream of the grid. - Abstract: A two-phase dispersed droplet flow investigation of the grid-enhanced heat transfer augmentation has been done using steam cooling with droplet injection experimental data obtained from the Penn State/NRC Rod Bundle Heat Transfer (RBHT) facility. The RBHT facility is a vertical, full length, 7 × 7-rod bundle heat transfer facility having 45 electrically heated fuel rod simulators of 9.5 mm (0.374-in.) diameter on a 12.6 mm (0.496-in.) pitch which simulates a portion of a PWR fuel assembly. The facility operates at low pressure, up to 4 bars (60 psia) and has over 500 channels of instrumentation including heater rod thermocouples, spacer grid thermocouples, closely-spaced differential pressure cells along the test section, several fluid temperature measurements within the rod bundle flow area, inlet and exit flows, absolute pressure, and the bundle power. A series of carefully controlled and well instrumented steam cooling with droplet injection experiments were performed over a range of Reynolds numbers and droplet injection flow rates. The experimental results were analyzed to obtain the axial variation of the local heat transfer coefficients along the rod bundle. At the spacer grid location, the flow was found to be substantially disrupted, with the hydrodynamic and thermal boundary layers undergoing redevelopment. Owing to this flow restructuring, the heat transfer downstream of a grid spacer was found to be augmented above the fully developed flow heat transfer as a result of flow disruption induced by the grid. Furthermore, the presence of a droplet field further enhanced the heat transfer as compared to single

Effects of Injection Timing on Fluid Flow Characteristics of Partially Premixed Combustion Based on High-Speed Particle Image Velocimetry

KAUST Repository

Izadi Najafabadi, Mohammad

2017-03-28

Partially Premixed Combustion (PPC) is a promising combustion concept ,based on judicious tuning of the charge stratification, to meet the increasing demands of emission legislation and to improve fuel efficiency. Longer ignition delays of PPC in comparison with conventional diesel combustion provide better fuel/air mixture which decreases soot and NO emissions. Moreover, a proper injection timing and strategy for PPC can improve the combustion stability as a result of a higher level of fuel stratification in comparison with the Homogeneous Charge Compression Ignition (HCCI) concept. Injection timing is the major parameter with which to affect the level of fuel and combustion stratification and to control the combustion phasing and the heat release behavior. The scope of the present study is to investigate the fluid flow characteristics of PPC at different injection timings. To this end, high-speed Particle Image Velocimetry (PIV) is implemented in a light-duty optical engine to measure fluid flow characteristics, including the flow fields, mean velocity and cycle-resolved turbulence, inside the piston bowl as well as the squish region with a temporal resolution of 1 crank angle degree at 800 rpm. Two injectors, having 5 and 7 holes, were compared to see their effects on fluid flow and heat release behavior for different injection timings. Reactive and non-reactive measurements were performed to distinguish injection-driven and combustion-driven turbulence. Formation of vortices and higher turbulence levels enhance the air/fuel interaction, changing the level of fuel stratification and combustion duration. Results demonstrate clearly how turbulence level correlates with heat release behavior, and provide a quantitative dataset for validation of numerical simulations.

Interaction of Liquid Film Flow of Direct Vessel Injection Under the Cross Directional Gas Flow

Energy Technology Data Exchange (ETDEWEB)

Kim, Han-sol; Lee, Jae-young [Handong Global University, Pohang (Korea, Republic of); Euh, Dong-Jin [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2015-10-15

In order to obtain a proper scaling law of the flow, local information of the flow was investigated experimentally and also numerically. A series of experiments were conducted in the 1/20 modified linear scaled plate type test rig to analyze a liquid film from ECC water injection through the DVI nozzle to the downcomer wall. The present study investigates liquid film flow generated in a downcomer of direct vessel injection (DVI) system which is employed as an emergency core cooling (ECC) system during a loss of coolant accident in the Korea nuclear power plant APR1400. During the late reflooding, complicated multi-phase flow phenomena including the wavy film flow, film breakup, entrainment, liquid film shift due to interfacial drag and gas jet impingement occur. A confocal chromatic sensor was used to measure the local instantaneous liquid film thickness and a hydraulic jump in the film flow and boundaries of the film flow. It was found that CFD analysis results without surface tension model showed some difference with the data in surface tension dominated flow region. For the interaction between a liquid film and gas shear flow, CFD results make a good agreement with the real liquid film dynamics in the case of low film Reynolds number or low Weber number flow. In the 1/20 scaled plate type experiment and simulation, the deformed spreading profile results seem to accord with each other at the relatively low We and Re regime.

Purification of carbon nanotubes via selective heating

Science.gov (United States)

Rogers, John A.; Wilson, William L.; Jin, Sung Hun; Dunham, Simon N.; Xie, Xu; Islam, Ahmad; Du, Frank; Huang, Yonggang; Song, Jizhou

2017-11-21

The present invention provides methods for purifying a layer of carbon nanotubes comprising providing a precursor layer of substantially aligned carbon nanotubes supported by a substrate, wherein the precursor layer comprises a mixture of first carbon nanotubes and second carbon nanotubes; selectively heating the first carbon nanotubes; and separating the first carbon nanotubes from the second carbon nanotubes, thereby generating a purified layer of carbon nanotubes. Devices benefiting from enhanced electrical properties enabled by the purified layer of carbon nanotubes are also described.

Adhered Supported Carbon Nanotubes

International Nuclear Information System (INIS)

Johnson, Dale F.; Craft, Benjamin J.; Jaffe, Stephen M.

2001-01-01

Carbon nanotubes (NTs) in excess of 200 μm long are grown by catalytic pyrolysis of hydrocarbon vapors. The nanotubes grow continuously without the typical extinction due to catalyst encapsulation. A woven metal mesh supports the nanotubes creating a metal supported nanotube (MSNT) structure. The 140 μm wide mesh openings are completely filled by 70 nm diameter multiwalled nanotubes (MWNTs). The MWNTs are straight, uniform and highly crystalline. Their wall thickness is about 10 nm (30 graphite layers). The adherent NTs are not removed from the support in a Scotch tape pull test. A 12.5 cm 2 capacitor made from two MSNT structures immersed in 1 M KCl has a capacitance of 0.35 F and an equivalent series resistance of 0.18 Ω. Water flows through the MSNT at a flow velocity of 1 cm/min with a pressure drop of 15 inches of water. With the support removed, the MWNTs naturally form a carbon nanocomposite (CNC) paper with a specific area of 80 m 2 /gm, a bulk density of 0.21 g/cm 3 , an open pore fraction of 0.81, and a resistivity of 0.16 Ω-cm

Core-shell composite metal catalysts incased into natural ceramic nanotubes

International Nuclear Information System (INIS)

Vinokurov, V; Berberov, A; Afonin, D; Borzaev, H; Ivanov, E; Gushchin, P; Lvov, Y

2014-01-01

The bimetallic halloysite nanotubes were prepared by the injection of halloysite- containing aerosols into the microwave plasma reactor. Nanotubes contain metal nanoparticles formed from the metal salt solution in the lumen of nanotubes and the iron oxide nanoparticles at the outer surface of nanotubes. Such halloysite composites may be sputtered onto the surface of the porous carrier forming the nanostructured catalyst, as was shown by the pure halloysite sputtering onto the model porous ceramic surface

Radiometric flow injection analysis with an ASIA (Ismatec) analyzer

Energy Technology Data Exchange (ETDEWEB)

Myint, U; Win, N; San, K; Han, B; Myoe, K M [Yangon Univ. (Myanmar). Dept. of Chemistry; Toelgyessy, J [Slovak Technical Univ., Bratislava (Slovakia). Dept. of Environmental Science

1994-07-01

Radiometric Flow Injection Analysis of a radioactive ([sup 131]I) sample is described. For analysis an ASIA (Ismatec) analyzer with a NaI(Tl) scintillation detector was used. (author) 5 refs.; 3 figs.

High Current Emission from Patterned Aligned Carbon Nanotubes Fabricated by Plasma-Enhanced Chemical Vapor Deposition

Science.gov (United States)

Cui, Linfan; Chen, Jiangtao; Yang, Bingjun; Jiao, Tifeng

2015-12-01

Vertically, carbon nanotube (CNT) arrays were successfully fabricated on hexagon patterned Si substrates through radio frequency plasma-enhanced chemical vapor deposition using gas mixtures of acetylene (C2H2) and hydrogen (H2) with Fe/Al2O3 catalysts. The CNTs were found to be graphitized with multi-walled structures. Different H2/C2H2 gas flow rate ratio was used to investigate the effect on CNT growth, and the field emission properties were optimized. The CNT emitters exhibited excellent field emission performance (the turn-on and threshold fields were 2.1 and 2.4 V/μm, respectively). The largest emission current could reach 70 mA/cm2. The emission current was stable, and no obvious deterioration was observed during the long-term stability test of 50 h. The results were relevant for practical applications based on CNTs.

Heat transfer enhancement in free convection flow of CNTs Maxwell nanofluids with four different types of molecular liquids.

Science.gov (United States)

Aman, Sidra; Khan, Ilyas; Ismail, Zulkhibri; Salleh, Mohd Zuki; Al-Mdallal, Qasem M

2017-05-26

This article investigates heat transfer enhancement in free convection flow of Maxwell nanofluids with carbon nanotubes (CNTs) over a vertically static plate with constant wall temperature. Two kinds of CNTs i.e. single walls carbon nanotubes (SWCNTs) and multiple walls carbon nanotubes (MWCNTs) are suspended in four different types of base liquids (Kerosene oil, Engine oil, water and ethylene glycol). Kerosene oil-based nanofluids are given a special consideration due to their higher thermal conductivities, unique properties and applications. The problem is modelled in terms of PDE's with initial and boundary conditions. Some relevant non-dimensional variables are inserted in order to transmute the governing problem into dimensionless form. The resulting problem is solved via Laplace transform technique and exact solutions for velocity, shear stress and temperature are acquired. These solutions are significantly controlled by the variations of parameters including the relaxation time, Prandtl number, Grashof number and nanoparticles volume fraction. Velocity and temperature increases with elevation in Grashof number while Shear stress minimizes with increasing Maxwell parameter. A comparison between SWCNTs and MWCNTs in each case is made. Moreover, a graph showing the comparison amongst four different types of nanofluids for both CNTs is also plotted.

Hybrid membrane using polyethersulfone-modification of multiwalled carbon nanotubes with silane agent to enhance high performance oxygen separation

Directory of Open Access Journals (Sweden)

Tutuk Djoko Kusworo

2014-04-01

Full Text Available Mixed matrix membrane comprising carbon nanotubes embedded in polymer matrix have become one of the emerging technologies. This study was investigated in order to study the effect of silane agent modification towards carbon nanotubes (CNT surface at different concentration on oxygen enrichment performances of asymmetric mixed matrix membrane. The modified carbon nanotubes were prepared by treating the carbon nanotubes with chemical modification using Dynasylan Ameo (DA silane agent to allow PES chains to be grafted on carbon nanotubes surface. The results from the FESEM, DSC and FTIR analysis confirmed that chemical modification on carbon nanotubes surface had taken place. Sieve-in-a-cage’ morphology observed shows the poor adhesion between polymer and unmodified CNT. The gas separation performance of the asymmetric flat sheet mixed matrix membranes with modified CNT were relatively higher compared to the unmodified CNT. Hence, coated hollow fiber mixed matrix membrane with chemical modification on CNT surface using (3-aminopropyl-triethoxy methyl silane agent can potentially enhance the gas separation performance of O2 and N2.

Determination of carbohydrates by high performance anion chromatography-pulsed amperometric detection in mushrooms.

Science.gov (United States)

Zhou, Shuai; Tang, Qingjiu; Luo, Xi; Xue, Jun-Jie; Liu, Yanfang; Yang, Yan; Zhang, Jingsong; Feng, Na

2012-01-01

A method of detecting carbohydrates (fucose, trehalose, mannitol, arabitol, mannose, glucose, galactose, fructose, and ribose) by high-performance anion chromatography-pulsed amperometric detection (HAPEC-PAD) was established. The conditions are: CarboPac MA1 column, NaOH as the eluent, temperature 30°C, Au working electrode, Ag/AgCl reference electrode, and flow rate 0.4 mL/min. These nine analytes, which yielded high resolution by this method, could be detected in 40 minutes. Mushrooms were tested and good precision, stability, and reproducibility were achieved. This method is suitable for mushroom samples and could support research and development on sugar and sugar alcohol, which contains special effects.

Cross-flow analysis of injection wells in a multilayered reservoir

Directory of Open Access Journals (Sweden)

Mohammadreza Jalali

2016-09-01

Natural and forced cross-flow is modeled for some injection wells in an oil reservoir located at North Sea. The solution uses a transient implicit finite difference approach for multiple sand layers with different permeabilities separated by impermeable shale layers. Natural and forced cross-flow rates for each reservoir layer during shut-in are calculated and compared with different production logging tool (PLT measurements. It appears that forced cross-flow is usually more prolonged and subject to a higher flow rate when compared with natural cross-flow, and is thus worthy of more detailed analysis.

Multi-walled Carbon Nanotubes/Graphite Nanosheets Modified Glassy Carbon Electrode for the Simultaneous Determination of Acetaminophen and Dopamine.

Science.gov (United States)

Zhang, Susu; He, Ping; Zhang, Guangli; Lei, Wen; He, Huichao

2015-01-01

Graphite nanosheets prepared by thermal expansion and successive sonication were utilized for the construction of a multi-walled carbon nanotubes/graphite nanosheets based amperometric sensing platform to simultaneously determine acetaminophen and dopamine in the presence of ascorbic acid in physiological conditions. The synergistic effect of multi-walled carbon nanotubes and graphite nanosheets catalyzed the electrooxidation of acetaminophen and dopamine, leading to a remarkable potential difference up to 200 mV. The as-prepared modified electrode exhibited linear responses to acetaminophen and dopamine in the concentration ranges of 2.0 × 10(-6) - 2.4 × 10(-4) M (R = 0.999) and 2.0 × 10(-6) - 2.0 × 10(-4) M (R = 0.998), respectively. The detection limits were down to 2.3 × 10(-7) M for acetaminophen and 3.5 × 10(-7) M for dopamine (S/N = 3). Based on the simple preparation and prominent electrochemical properties, the obtained multi-walled carbon nanotubes/graphite nanosheets modified electrode would be a good candidate for the determination of acetaminophen and dopamine without the interference of ascorbic acid.

The effects of arbitrary injection angle and flow conditions on venturi-jet mixer

Directory of Open Access Journals (Sweden)

Sundararaj S.

2012-01-01

Full Text Available This paper describes the effect of jet injection angle, cross flow Reynolds number and velocity ratio on entrainment and mixing of jet with incompressible cross flow in venturi-jet mixer. Five different jet injection angles 45o, 60o, 90o, 125o, 135o are tested to evaluate the entrainment of jet and mixing performances of the mixer. Tracer concentration along the downstream of the jet injection, cross flow velocity, jet velocity and pressure drop across the mixer are determined experimentally to characterize the mixing performance of the mixer. The experiments show that the performance of a venturi-jet-mixer substantially improves at high injection angle and can be augmented still by increasing velocity ratio. The jet deflects much and penetrates less in the cross flow as the cross flow Reynolds number is increased. The effect could contribute substantially to the better mixing index with moderate pressure drop. Normalized jet profile, concentration decay, jet velocity profile are computed from equations of conservation of mass, momentum and concentration written in natural co-ordinate systems. The comparison between the experimental and numerical results confirms the accuracy of the simulations. Correlations for jet trajectory and entrainment ratio of the mixer are obtained by multivariate-linear regression analysis using power law.

Analogs of N-cynnamoylphenylhydroxylamine as reagents for amperometric determination of scandium

International Nuclear Information System (INIS)

Shvedene, N.V.; Gallaj, Z.A.; Sheina, N.M.; Zujkova, N.V.

1978-01-01

To decrease the detection limit of scandium and increase selectivity of amperometric determination, oxidation of 2-furylacryloyl-N-p-chlorophenylhydroxylamine (FACPhHA) and 3-styrylacryloyl-N-phenylhydroxylamine (SAPhHA) on a graphite electrode has been studied by volt-amperometry. The possibility has been established of using the oxidation current of the reagent for plotting the titration curves. The solubility of scandium complexes with FACPhHA and SAPhHA under conditions of titration against the background with pH 6.0 has been determined and equals (2.1+-0.3)x10 -6 and (5.3+-0.3)x10 -7 , respectively. The methods have been developed of amperometric determination of scandium with the use of the considered reagents against backgrounds with pH 5.5-6.5. The use of SAPhHA has decreased the limit of scandium detection down to 0.1 mgk/ml. Besides, the amperometric method makes it possible to titrate in turbid and coloured media what is an advantage of this method. The developed method is used for determination of scandium in scandium silicide

Amperometric micro pH measurements in oxygenated saliva.

Science.gov (United States)

Chaisiwamongkhol, Korbua; Batchelor-McAuley, Christopher; Compton, Richard G

2017-07-24

An amperometric micro pH sensor has been developed based on the chemical oxidation of carbon fibre surfaces (diameter of 9 μm and length of ca. 1 mm) to enhance the population of surface quinone groups for the measurement of salivary pH. The pH analysis utilises the electrochemically reversible two-electron, two-proton behaviour of surface quinone groups on the micro-wire electrodes. A Nernstian response is observed across the pH range 2-8 which is the pH range of many biological fluids. We highlight the measurement of pH in small volumes of biological fluids without the need for oxygen removal and specifically the micro pH electrode is examined by measuring the pH of commercial synthetic saliva and authentic human saliva samples. The results correspond well with those obtained by using commercial glass pH electrodes on large volume samples.

Carbon nanotubes enhanced the lead toxicity on the freshwater fish

International Nuclear Information System (INIS)

Martinez, D S T; Alves, O L; Barbieri, E

2013-01-01

Carbon nanotubes are promising nanostructures for many applications in materials industry and biotechnology. However, it is mandatory to evaluate their toxicity and environmental implications. We evaluated nitric acid treated multiwalled carbon nanotubes (HNO 3 -MWCNT) toxicity in Nile tilapia (Oreochromis niloticus) and also the lead (Pb) toxicity modulation after the nanotube interaction. Industrial grade multiwalled carbon nanotubes [Ctube 100, CNT Co. Ltd] were treated with 9M HNO 3 for 12h at 150°C to generate oxygenated groups on the nanotube surface, to improve water dispersion and heavy metal interaction. The HNO 3 -treated multiwalled carbon nanotubes were physico-chemically characterized by several techniques [e.g. TEM, FE-SEM, TGA, ζ-potential and Raman spectroscopy]. HNO 3 -MWCNT did not show toxicity on Nile tilapia when the concentration ranged from 0.1 to 3.0 mg/L, and the maximum exposure time was 96h. After 24, 48, 72 and 96h the LC50 values of Pb were 1.65, 1.32, 1.10 and 0.99 mg/L, respectively. To evaluate the Pb-nanotube interaction influence on the ecotoxicity, we submitted the Nile tilapia to different concentrations of Pb mixed with a non-toxic concentration of HNO 3 -MWCNT (1.0 mg/L). After 24, 48, 72, 96 h the LC50 values of Pb plus nanotubes were: 0.32, 0.25, 0.20, 0.18 mg/L, respectively. These values showed a synergistic effect after Pb-nanotube interaction since Pb toxicity increased over five times. X-ray energy dispersive spectroscopy (EDS) was used to confirm lead adsorption on the carbon nanotube oxidized surface. The exposure of Nile tilapia to Pb plus HNO 3 -MWCNT caused both oxygen consumption and ammonium excretion decrease, when compared to the control. Finally, our results show that carbon nanotubes interact with classical pollutants drawing attention to the environmental implications.

Carbon Nanotube Chopped Fiber for Enhanced Properties in Additive Manufacturing

Energy Technology Data Exchange (ETDEWEB)

Menchhofer, Paul A [ORNL; Lindahl, John M [ORNL; JohnsonPhD, DR Joseph E. [Nanocomp Technologies, Inc.

2016-06-06

Nanocomp Technologies, Inc. is working with Oak Ridge National Laboratory to develop carbon nanotube (CNT) composite materials and evaluate their use in additive manufacturing (3D printing). The first phase demonstrated feasibility and improvements for carbon nanotube (CNT)- acrylonitrile butadiene styrene (ABS) composite filaments use in additive manufacturing, with potential future work centering on further improvements. By focusing the initial phase on standard processing methods (developed mainly for the incorporation of carbon fibers in ABS) and characterization techniques, a basis of knowledge for the incorporation of CNTs in ABS was learned. The ability to understand the various processing variables is critical to the successful development of these composites. From the degradation effects on ABS (caused by excessive temperatures), to the length of time the ABS is in the melt state, to the order of addition of constituents, and also to the many possible mixing approaches, a workable flow sequence that addresses each processing step is critical to the final material properties. Although this initial phase could not deal with each of these variables in-depth, a future study is recommended that will build on the lessons learned for this effort.

Sensitive detection of hydroxylamine at a simple baicalin carbon nanotubes modified electrode.

Science.gov (United States)

Zhang, Hongfang; Zheng, Jianbin

2012-05-15

A baicalin multi-wall carbon nanotubes (BaMWCNT) modified glassy carbon electrode (GCE) for the sensitive determination of hydroxylamine was described. The BaMWCNT/GCE with dramatic stability was firstly fabricated with a simple adsorption method. And it showed excellent catalytic activity toward the electrooxidation of hydroxylamine. The amperometric response at the BaMWCNT/GCE modified electrode increased linearly to hydroxylamine concentrations in the range of 0.5 μM to 0.4mM with a detection limit of 0.1 μM. The modified electrode was applied to detection hydroxylamine in the tap water, and the average recovery for the standards added was 96.0%. Copyright © 2012 Elsevier B.V. All rights reserved.

Electrical resistivity and thermal properties of compatibilized multi-walled carbon nanotube/polypropylene composites

Directory of Open Access Journals (Sweden)

A. Szentes

2012-06-01

Full Text Available The electrical resistivity and thermal properties of multi-walled carbon nanotube/polypropylene (MWCNT/PP composites have been investigated in the presence of coupling agents applied for improving the compatibility between the nanotubes and the polymer. A novel olefin-maleic-anhydride copolymer and an olefin-maleic-anhydride copolymer based derivative have been used as compatibilizers to achieve better dispersion of MWCNTs in the polymer matrix. The composites have been produced by extrusion followed by injection moulding. They contained different amounts of MWCNTs (0.5, 2, 3 and 5 wt% and coupling agent to enhance the interactions between the carbon nanotubes and the polymer. The electrical resistivity of the composites has been investigated by impedance spectroscopy, whereas their thermal properties have been determined using a thermal analyzer operating on the basis of the periodic thermal perturbation method. Rheological properties, BET-area and adsorption-desorption isotherms have been determined. Dispersion of MWCNTs in the polymer has been studied by scanning electron microscopy (SEM.

Enhancement of heat transfer for thermal energy storage application using stearic acid nanocomposite with multi-walled carbon nanotubes

International Nuclear Information System (INIS)

Li, TingXian; Lee, Ju-Hyuk; Wang, RuZhu; Kang, Yong Tae

2013-01-01

A latent heat storage nanocomposite made of stearic acid (SA) and multi-walled carbon nanotube (MWCNT) is prepared for thermal energy storage application. The thermal properties of the SA/MWCNT nanocomposite are characterized by SEM (scanning electron microscopy) and DSC (differential scanning calorimeter) analysis techniques, and the effects of different volume fractions of MWCNT on the heat transfer enhancement and thermal performance of stearic acid are investigated during the charging and discharging phases. The SEM analysis shows that the additive of MWCNT is uniformly distributed in the phase change material of stearic acid, and the DSC analysis reveals that the melting point of SA/MWCNT nanocomposite shifts to a lower temperature during the charging phase and the freezing point shifts to a higher temperature during the discharging phase when compared with the pure stearic acid. The experimental results show that the addition of MWCNT can improve the thermal conductivity of stearic acid effectively, but it also weakens the natural convection of stearic acid in liquid state. In comparison with the pure stearic acid, the charging rate can be decreased by about 50% while the discharging rate can be improved by about 91% respectively by using the SA/5.0% MWCNT nanocomposite. It appears that the MWCNT is a promising candidate for enhancing the heat transfer performance of latent heat thermal energy storage system. - Highlights: • A nanocomposite made of stearic acid and multi-walled carbon nanotube is prepared for thermal energy storage application. • Effects of multi-walled carbon nanotube on the thermal performance of the nanocomposite are investigated. • Multi-walled carbon nanotube enhances the thermal conductivity but weakens the natural convection of stearic acid. • Discharging/charging rates of stearic acid are increased/decreased by using multi-walled carbon nanotube

Field-Flow Fractionation of Carbon Nanotubes and Related Materials

Energy Technology Data Exchange (ETDEWEB)

John P. Selegue

2011-11-17

During the grant period, we carried out FFF studies of carbonaceous soot, single-walled and multi-walled carbon nanotubes, carbon nano-onions and polyoxometallates. FFF alone does not provide enough information to fully characterize samples, so our suite of characterization techniques grew to include light scattering (especially Photon Correlation Spectroscopy), scanning and transmission electron microscopy, thermogravimetric analysis and spectroscopic methods. We developed convenient techniques to deposit and examine minute FFF fractions by electron microscopy. In collaboration with Arthur Cammers (University of Kentucky), we used Flow Field-Flow Fractionation (Fl-FFF) to monitor the solution-phase growth of keplerates, a class of polyoxometallate (POM) nanoparticles. We monitored the evolution of Mo-POM nanostructures over the course of weeks by by using flow field-flow fractionation and corroborated the nanoparticle structures by using transmission electron microscopy (TEM). Total molybdenum in the solution and precipitate phases was monitored by using inductively coupled plasma analyses, and total Mo-POM concentration by following the UV-visible spectra of the solution phase. We observe crystallization-driven formation of (Mo132) keplerate and solution phase-driven evolution of structurally related nanoscopic species (3-60 nm). FFF analyses of other classes of materials were less successful. Attempts to analyze platelets of layered materials, including exfoliated graphite (graphene) and TaS2 and MoS2, were disappointing. We were not able to optimize flow conditions for the layered materials. The metal sulfides react with the aqueous carrier liquid and settle out of suspension quickly because of their high density.

High quantum yield graphene quantum dots decorated TiO{sub 2} nanotubes for enhancing photocatalytic activity

Energy Technology Data Exchange (ETDEWEB)

Qu, Ailan, E-mail: qal67@163.com; Xie, Haolong; Xu, Xinmei; Zhang, Yangyu; Wen, Shengwu; Cui, Yifan

2016-07-01

Highlights: • High concentration yellow GQDs and TiO{sub 2} nanotubes were achieved by a simple and green method. • High quantum yield GQDs enhanced the photodegradation capacity of TiO{sub 2} nanotube. • The catalytic performance of GQDs/TiO{sub 2} depends on the GQDs loading. • The improved photocatalytic activity of GQDs/TiO{sub 2} was attributed to three aspects. - Abstract: Graphene quantum dots (GQDs) with high quantum yield (about 23.6% at an excitation wavelength of 320 nm) and GQDs/TiO{sub 2} nanotubes (GQDs/TiO{sub 2} NTs) composites were achieved by a simple hydrothermal method at low temperature. Photoluminescence characterization showed that the GQDs exhibited the down-conversion PL features at excitation from 300 to 420 nm and up-conversion photoluminescence in the range of 600–800 nm. The photocatalytic activity of prepared GQDs/TiO{sub 2} NTs composites on the degradation of methyl orange (MO) was significantly enhanced compared with that of pure TiO{sub 2} nanotubes (TiO{sub 2} NTs). For the composites coupling with 1.5%, 2.5% and 3.5% GQDs, the degradation of MO after 20 min irradiation under UV–vis light irradiation (λ = 380–780 nm) were 80.52%, 94.64% and 51.91%, respectively, which are much higher than that of pure TiO{sub 2} NTs (35.41%). It was inferred from the results of characterization that the improved photocatalytic activity of the GQDs/TiO{sub 2} NTs composites was attributed to the synergetic effect of up-conversion properties of the GQDs, enhanced visible light absorption and efficient separation of photogenerated electron-holes of the GQDs/TiO{sub 2} composite.

Analytical and numerical solution of three-dimensional channel flow in presence of a sinusoidal fluid injection and a chemical reaction

Directory of Open Access Journals (Sweden)

Sahin Ahmed

2015-06-01

Full Text Available Modeling of three-dimensional channel flow in a chemically-reacting fluid between two long vertical parallel flat plates in the presence of a transverse magnetic field is presented. The stationary plate is subjected to a transverse sinusoidal injection velocity distribution while the uniformly moving plate is subjected to a constant suction and slip boundary conditions. Due to this type of injection velocity, the flow becomes three dimensional. Comparisons with previously published work are performed and the results are found to be in excellent agreement. An increase in the permeability/magnetic parameter is found to escalate the velocity near the plate in motion. Growing Reynolds number or magnetic parameter enhances the x-component and reduces the z-component of the skin-friction at the wall at rest. The acquired knowledge in our study can be used by designers to control MHD flow as suitable for certain applications which include laminar magneto-aerodynamics, materials processing and MHD propulsion thermo-fluid dynamics.

Enhancements of thermal conductivities with Cu, CuO, and carbon nanotube nanofluids and application of MWNT/water nanofluid on a water chiller system

Directory of Open Access Journals (Sweden)

Lin Mark

2011-01-01

Full Text Available Abstract In this study, enhancements of thermal conductivities of ethylene glycol, water, and synthetic engine oil in the presence of copper (Cu, copper oxide (CuO, and multi-walled carbon nanotube (MWNT are investigated using both physical mixing method (two-step method and chemical reduction method (one-step method. The chemical reduction method is, however, used only for nanofluid containing Cu nanoparticle in water. The thermal conductivities of the nanofluids are measured by a modified transient hot wire method. Experimental results show that nanofluids with low concentration of Cu, CuO, or carbon nanotube (CNT have considerably higher thermal conductivity than identical base liquids. For CuO-ethylene glycol suspensions at 5 vol.%, MWNT-ethylene glycol at 1 vol.%, MWNT-water at 1.5 vol.%, and MWNT-synthetic engine oil at 2 vol.%, thermal conductivity is enhanced by 22.4, 12.4, 17, and 30%, respectively. For Cu-water at 0.1 vol.%, thermal conductivity is increased by 23.8%. The thermal conductivity improvement for CuO and CNT nanofluids is approximately linear with the volume fraction. On the other hand, a strong dependence of thermal conductivity on the measured time is observed for Cu-water nanofluid. The system performance of a 10-RT water chiller (air conditioner subject to MWNT/water nanofluid is experimentally investigated. The system is tested at the standard water chiller rating condition in the range of the flow rate from 60 to 140 L/min. In spite of the static measurement of thermal conductivity of nanofluid shows only 1.3% increase at room temperature relative to the base fluid at volume fraction of 0.001 (0.1 vol.%, it is observed that a 4.2% increase of cooling capacity and a small decrease of power consumption about 0.8% occur for the nanofluid system at a flow rate of 100 L/min. This result clearly indicates that the enhancement of cooling capacity is not just related to thermal conductivity alone. Dynamic effect, such as

Enhancement of electron field emission of vertically aligned carbon nanotubes by nitrogen plasma treatment

Energy Technology Data Exchange (ETDEWEB)

Wang, B.B. [College of Chemistry and Chemical Engineering, Chongqing University of Technology, 69 Hongguang Rd, Lijiatuo, Banan District, Chongqing 400054 (China); Plasma Nanoscience Centre Australia (PNCA), CSIRO Materials Science and Engineering, P.O. Box 218, Lindfield, NSW 2070 (Australia); Cheng, Q.J. [Plasma Nanoscience Centre Australia (PNCA), CSIRO Materials Science and Engineering, P.O. Box 218, Lindfield, NSW 2070 (Australia); Plasma Nanoscience, School of Physics, University of Sydney, Sydney, NSW 2006 (Australia); Chen, X. [College of Materials Science and Engineering, Chongqing University, Chongqing 400044 (China); Ostrikov, K., E-mail: kostya.ostrikov@csiro.au [Plasma Nanoscience Centre Australia (PNCA), CSIRO Materials Science and Engineering, P.O. Box 218, Lindfield, NSW 2070 (Australia); Plasma Nanoscience, School of Physics, University of Sydney, Sydney, NSW 2006 (Australia)

2011-09-22

Highlights: > A new and custom-designed bias-enhanced hot-filament chemical vapor deposition system is developed to synthesize vertically aligned carbon nanotubes. > The carbon nanotubes are later treated with nitrogen plasmas. > The electron field emission characteristics of the carbon nanotubes are significantly improved after the nitrogen plasma treatment. > A new physical mechanism is proposed to interpret the improvement of the field emission characteristics. - Abstract: The electron field emission (EFE) characteristics from vertically aligned carbon nanotubes (VACNTs) without and with treatment by the nitrogen plasma are investigated. The VACNTs with the plasma treatment showed a significant improvement in the EFE property compared to the untreated VACNTs. The morphological, structural, and compositional properties of the VACNTs are extensively examined by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and energy dispersive X-ray spectroscopy. It is shown that the significant EFE improvement of the VACNTs after the nitrogen plasma treatment is closely related to the variation of the morphological and structural properties of the VACNTs. The high current density (299.6 {mu}A/cm{sup 2}) achieved at a low applied field (3.50 V/{mu}m) suggests that the VACNTs after nitrogen plasma treatment can serve as effective electron field emission sources for numerous applications.

Enhancement of electron field emission of vertically aligned carbon nanotubes by nitrogen plasma treatment

International Nuclear Information System (INIS)

Wang, B.B.; Cheng, Q.J.; Chen, X.; Ostrikov, K.

2011-01-01

Highlights: → A new and custom-designed bias-enhanced hot-filament chemical vapor deposition system is developed to synthesize vertically aligned carbon nanotubes. → The carbon nanotubes are later treated with nitrogen plasmas. → The electron field emission characteristics of the carbon nanotubes are significantly improved after the nitrogen plasma treatment. → A new physical mechanism is proposed to interpret the improvement of the field emission characteristics. - Abstract: The electron field emission (EFE) characteristics from vertically aligned carbon nanotubes (VACNTs) without and with treatment by the nitrogen plasma are investigated. The VACNTs with the plasma treatment showed a significant improvement in the EFE property compared to the untreated VACNTs. The morphological, structural, and compositional properties of the VACNTs are extensively examined by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and energy dispersive X-ray spectroscopy. It is shown that the significant EFE improvement of the VACNTs after the nitrogen plasma treatment is closely related to the variation of the morphological and structural properties of the VACNTs. The high current density (299.6 μA/cm 2 ) achieved at a low applied field (3.50 V/μm) suggests that the VACNTs after nitrogen plasma treatment can serve as effective electron field emission sources for numerous applications.

Determination of Optimal Flow Paths for Safety Injection According to Accident Conditions

Energy Technology Data Exchange (ETDEWEB)

Yoo, Kwae Hwan; Kim, Ju Hyun; Kim, Dong Yeong; Na, Man Gyun [Chosun Univ., Gwangju (Korea, Republic of); Hur, Seop; Kim, Changhwoi [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2014-05-15

In case severe accidents happen, major safety parameters of nuclear reactors are rapidly changed. Therefore, operators are unable to respond appropriately. This situation causes the human error of operators that led to serious accidents at Chernobyl. In this study, we aimed to develop an algorithm that can be used to select the optimal flow path for cold shutdown in serious accidents, and to recover an NPP quickly and efficiently from the severe accidents. In order to select the optimal flow path, we applied a Dijkstra algorithm. The Dijkstra algorithm is used to find the path of minimum total length between two given nodes and needs a weight (or length) matrix. In this study, the weight between nodes was calculated from frictional and minor losses inside pipes. That is, the optimal flow path is found so that the pressure drop between a starting node (water source) and a destination node (position that cooling water is injected) is minimized. In case a severe accident has happened, if we inject cooling water through the optimized flow path, then the nuclear reactor will be safely and effectively returned into the cold shutdown state. In this study, we have analyzed the optimal flow paths for safety injection as a preliminary study for developing an accident recovery system. After analyzing the optimal flow path using the Dijkstra algorithm, and the optimal flow paths were selected by calculating the head loss according to path conditions.

A carbon nanotube screen-printed electrode for label-free detection of the human cardiac troponin T.

Science.gov (United States)

Silva, Bárbara V M; Cavalcanti, Igor T; Silva, Mízia M S; Dutra, Rosa F

2013-12-15

Label-free immunosensor based on amine-functionalized carbon nanotubes screen-printed electrode is described for detection of the cardiac troponin T, an important marker of acute myocardial infarction. The disposable sensor was fabricated by tightly squeezing an adhesive carbon ink containing carbon nanotubes onto a polyethylene terephthalate substrate forming a thin film. The use of carbon nanotubes increased the reproducibility and stability of the sensor, and the amine groups permitted nonrandom immobilization of antibodies against cardiac troponin T. Amperometric responses were obtained by differential pulse voltammetry in presence of a ferrocyanide/ferricyanide redox probe after troponin T incubation. The calibration curve indicated a linear response of troponin T between 0.0025 ng mL(-1) and 0.5 ng mL(-1), with a good correlation coefficient (r=0.995; p<0.0001, n=7). The limit of detection (0.0035 ng mL(-1) cardiac troponin T) was lower than any previously described by immunosensors and was comparable with conventional analytical methods. The high reproducibility and clinical range obtained using this immunosensor support its utility as a potential tool for point-of-care acute myocardial infarction diagnostic testing. © 2013 Elsevier B.V. All rights reserved.

Modeling of time-lapse multi-scale seismic monitoring of CO2 injected into a fault zone to enhance the characterization of permeability in enhanced geothermal systems

Science.gov (United States)

Zhang, R.; Borgia, A.; Daley, T. M.; Oldenburg, C. M.; Jung, Y.; Lee, K. J.; Doughty, C.; Altundas, B.; Chugunov, N.; Ramakrishnan, T. S.

2017-12-01

Subsurface permeable faults and fracture networks play a critical role for enhanced geothermal systems (EGS) by providing conduits for fluid flow. Characterization of the permeable flow paths before and after stimulation is necessary to evaluate and optimize energy extraction. To provide insight into the feasibility of using CO2 as a contrast agent to enhance fault characterization by seismic methods, we model seismic monitoring of supercritical CO2 (scCO2) injected into a fault. During the CO2 injection, the original brine is replaced by scCO2, which leads to variations in geophysical properties of the formation. To explore the technical feasibility of the approach, we present modeling results for different time-lapse seismic methods including surface seismic, vertical seismic profiling (VSP), and a cross-well survey. We simulate the injection and production of CO2 into a normal fault in a system based on the Brady's geothermal field and model pressure and saturation variations in the fault zone using TOUGH2-ECO2N. The simulation results provide changing fluid properties during the injection, such as saturation and salinity changes, which allow us to estimate corresponding changes in seismic properties of the fault and the formation. We model the response of the system to active seismic monitoring in time-lapse mode using an anisotropic finite difference method with modifications for fracture compliance. Results to date show that even narrow fault and fracture zones filled with CO2 can be better detected using the VSP and cross-well survey geometry, while it would be difficult to image the CO2 plume by using surface seismic methods.

Preparation of carbon nanotubes by MPECVD

International Nuclear Information System (INIS)

El-Shazly Duraia, M.A.; Mansorov, Z.A.; Tokmoldin, S.Zh.; Klimenov, V.V.; Nevmerzhitsky, I.S.; Dochshanov, A.M.

2009-01-01

Microwave plasma-enhanced chemical vapor deposition (MPECVD) method has been regarded as one of the most promising candidates for the synthesis of CNTs due to the vertical alignment, the large area growth, the lower growth temperature, uniform heat distribution and the good control of the different growth parameters. In this work we present our results about the preparation of carbon nanotube with different morphologies by using microwave plasma enhanced chemical vapor deposition MPECVD. Well aligned, curly and coiled carbon nanotubes have been prepared. We have investigated the effect of the different growth condition parameters such as type of the catalyst, pressure and the hydrogen to methane flow rate ratio on the morphology of the carbon nanotubes. The results were showed that there is a great dependence of the morphology of carbon nanotubes on these parameters. There is a linear relation between the growth rate and the methane to hydrogen ratio. We found that the growth rate has a great dependence on the amount of methane. For example the growth rate varied from the value 1,34 μm/min when the methane flow rate was 10 sccm to more than 14 μm/min when the methane flow rate was raised to 50 sccm. This growth rate is greater than that reported in the literature. The effect of the gas pressure on the CNTs was also studied. The Raman spectra (excitation wavelength 473 nm) of all samples show D-band peak at around 1300 cm -1 and G-band peak at around 1580 cm -1 , which indicate that our CNTs are multi wall CNTs (MWCNTs). The D-band and the G-band correspond to sp 2 and sp 3 carbon stretching modes relatively, and their intensity ratio is a measure of the amount of disorder in the CNTs. The D-band is known to be attributed to the carbonaceous particles, defects in the curved graphitic sheet and tube ends. It has been suggested that lower I g /I d ratios and narrower first and second order D and G bands are suggestive of well-aligned NNTs. The photoluminescence PL

Carbon Nanotubes and Modern Nanoagriculture

KAUST Repository

Serag, Maged F.

2015-01-27

Since their discovery, carbon nanotubes have been prominent members of the nanomaterial family. Owing to their extraordinary physical, chemical, and mechanical properties, carbon nanotubes have been proven to be a useful tool in the field of plant science. They were frequently perceived to bring about valuable biotechnological and agricultural applications that still remain beyond experimental realization. An increasing number of studies have demonstrated the ability of carbon nanotubes to traverse different plant cell barriers. These studies, also, assessed the toxicity and environmental impacts of these nanomaterials. The knowledge provided by these studies is of practical and fundamental importance for diverse applications including intracellular labeling and imaging, genetic transformation, and for enhancing our knowledge of plant cell biology. Although different types of nanoparticles have been found to activate physiological processes in plants, carbon nanotubes received particular interest. Following addition to germination medium, carbon nanotubes enhanced root growth and elongation of some plants such as onion, cucumber and rye-grass. They, also, modulated the expression of some genes that are essential for cell division and plant development. In addition, multi-walled carbon nanotubes were evidenced to penetrate thick seed coats, stimulate germination, and to enhance growth of young tomato seedlings. Multi-walled carbon nanotubes can penetrate deeply into the root system and further distribute into the leaves and the fruits. In recent studies, carbon nanotubes were reported to be chemically entrapped into the structure of plant tracheary elements. This should activate studies in the fields of plant defense and wood engineering. Although, all of these effects on plant physiology and plant developmental biology have not been fully understood, the valuable findings promises more research activity in the near future toward complete scientific understanding of

Flow rate dependent extra-column variance from injection in capillary liquid chromatography.

Science.gov (United States)

Aggarwal, Pankaj; Liu, Kun; Sharma, Sonika; Lawson, John S; Dennis Tolley, H; Lee, Milton L

2015-02-06

Efficiency and resolution in capillary liquid chromatography (LC) can be significantly affected by extra-column band broadening, especially for isocratic separations. This is particularly a concern in evaluating column bed structure using non-retained test compounds. The band broadening due to an injector supplied with a commercially available capillary LC system was characterized from experimental measurements. The extra-column variance from the injection valve was found to have an extra-column contribution independent of the injection volume, showing an exponential dependence on flow rate. The overall extra-column variance from the injection valve was found to vary from 34 to 23 nL. A new mathematical model was derived that explains this exponential contribution of extra-column variance on chromatographic performance. The chromatographic efficiency was compromised by ∼130% for a non-retained analyte because of injection valve dead volume. The measured chromatographic efficiency was greatly improved when a new nano-flow pumping system with integrated injection valve was used. Copyright © 2014 Elsevier B.V. All rights reserved.

Micro-flow-injection analysis (μFIA) immunoassay of herbicide residue 2,6-dichlorobenzamide

DEFF Research Database (Denmark)

Uthuppu, Basil; Heiskanen, Arto; Kofoed, Dan

2015-01-01

As a part of developing new systems for continuously monitoring the presence of pesticides in groundwater, a microfluidic amperometric immunosensor was developed for detecting the herbicide residue 2,6-dichlorobenzamide (BAM) in water. A competitive immunosorbent assay served as the sensing mecha...

Equilibrium structures and flows of polar and nonpolar liquids in different carbon nanotubes

Science.gov (United States)

Abramyan, Andrey K.; Bessonov, Nick M.; Mirantsev, Leonid V.; Chevrychkina, Anastasiia A.

2018-03-01

Molecular dynamics (MD) simulations of equilibrium structures and flows of polar water and nonpolar methane confined by single-walled carbon nanotubes (SWCNTs) with circular and square cross sections and bounding walls with regular graphene structure and random (amorphous) distribution of carbon atoms have been performed. The results of these simulations show that equilibrium structures of both confined liquids depend strongly on the shape of the cross section of SWCNTs, whereas the structure of their bounding walls has a minor influence on these structures. On contrary, the external pressure driven water and methane flows through above mentioned SWCNTs depend significantly on both the shape of their cross sections and the structure of their bounding walls.

Re-injection feasibility study of fracturing flow-back fluid in shale gas mining

Science.gov (United States)

Kang, Dingyu; Xue, Chen; Chen, Xinjian; Du, Jiajia; Shi, Shengwei; Qu, Chengtun; Yu, Tao

2018-02-01

Fracturing flow-back fluid in shale gas mining is usually treated by re-injecting into formation. After treatment, the fracturing flow-back fluid is injected back into the formation. In order to ensure that it will not cause too much damage to the bottom layer, feasibility evaluations of re-injection of two kinds of fracturing fluid with different salinity were researched. The experimental research of the compatibility of mixed water samples based on the static simulation method was conducted. Through the analysis of ion concentration, the amount of scale buildup and clay swelling rate, the feasibility of re-injection of different fracturing fluid were studied. The result shows that the swelling of the clay expansion rate of treated fracturing fluid is lower than the mixed water of treated fracturing fluid and the distilled water, indicating that in terms of clay expansion rate, the treated fracturing flow-back fluid is better than that of water injection after re-injection. In the compatibility test, the maximum amount of fouling in the Yangzhou oilfield is 12mg/L, and the maximum value of calcium loss rate is 1.47%, indicating that the compatibility is good. For the fracturing fluid with high salinity in the Yanchang oilfield, the maximum amount of scaling is 72mg/L, and the maximum calcium loss rate is 3.50%, indicating that the compatibility is better.

Novel amperometric glucose biosensor based on MXene nanocomposite

KAUST Repository

Rakhi, R. B.

2016-11-10

A biosensor platform based on Au/MXene nanocomposite for sensitive enzymatic glucose detection is reported. The biosensor leverages the unique electrocatalytic properties and synergistic effects between Au nanoparticles and MXene sheets. An amperometric glucose biosensor is fabricated by the immobilization of glucose oxidase (GOx) enzyme on Nafion solubilized Au/ MXene nanocomposite over glassy carbon electrode (GCE). The biomediated Au nanoparticles play a significant role in facilitating the electron exchange between the electroactive center of GOx and the electrode. The GOx/Au/MXene/Nafion/GCE biosensor electrode displayed a linear amperometric response in the glucose concentration range from 0.1 to 18 mM with a relatively high sensitivity of 4.2 μAmM−1 cm−2 and a detection limit of 5.9 μM (S/N = 3). Furthermore, the biosensor exhibited excellent stability, reproducibility and repeatability. Therefore, the Au/MXene nanocomposite reported in this work is a potential candidate as an electrochemical transducer in electrochemical biosensors.

Novel amperometric glucose biosensor based on MXene nanocomposite

KAUST Repository

Baby, Rakhi Raghavan; Nayuk, Pranati; Xia, Chuan; Alshareef, Husam N.

2016-01-01

A biosensor platform based on Au/MXene nanocomposite for sensitive enzymatic glucose detection is reported. The biosensor leverages the unique electrocatalytic properties and synergistic effects between Au nanoparticles and MXene sheets. An amperometric glucose biosensor is fabricated by the immobilization of glucose oxidase (GOx) enzyme on Nafion solubilized Au/ MXene nanocomposite over glassy carbon electrode (GCE). The biomediated Au nanoparticles play a significant role in facilitating the electron exchange between the electroactive center of GOx and the electrode. The GOx/Au/MXene/Nafion/GCE biosensor electrode displayed a linear amperometric response in the glucose concentration range from 0.1 to 18 mM with a relatively high sensitivity of 4.2 μAmM−1 cm−2 and a detection limit of 5.9 μM (S/N = 3). Furthermore, the biosensor exhibited excellent stability, reproducibility and repeatability. Therefore, the Au/MXene nanocomposite reported in this work is a potential candidate as an electrochemical transducer in electrochemical biosensors.

Thick-film textile-based amperometric sensors and biosensors.

Science.gov (United States)

Yang, Yang-Li; Chuang, Min-Chieh; Lou, Shyh-Liang; Wang, Joseph

2010-06-01

The incorporation of amperometric sensors into clothing through direct screen-printing onto the textile substrate is described. Particular attention is given to electrochemical sensors printed directly on the elastic waist of underwear that offers tight direct contact with the skin. The textile-based printed carbon electrodes have a well-defined appearance with relatively smooth conductor edges and no apparent defects or cracks. Convenient voltammetric and chronoamperometric measurements of 0-3 mM ferrocyanide, 0-25 mM hydrogen peroxide, and 0-100 muM NADH have been documented. The favorable electrochemical behavior is maintained under folding or stretching stress, relevant to the deformation of clothing. The electrochemical performance and tolerance to mechanical stress are influenced by the physical characteristics of the textile substrate. The results indicate the potential of textile-based screen-printed amperometric sensors for future healthcare, sport or military applications. Such future applications would benefit from tailoring the ink composition and printing conditions to meet the specific requirements of the textile substrate.

Understanding and controlling the rest potential of carbon nanotube-based supercapacitors for energy density enhancement

Science.gov (United States)

Yoo, Young-Eun; Park, Jinwoo; Kim, Woong

2018-03-01

We present a novel method for enhancing the energy density of an electrical double layer capacitor (EDLC). Surface modification of single-walled carbon nanotube (SWNT) electrodes significantly affects the rest potential (E0) of EDLCs; acid treatment and polyethyleneimine (PEI) coating of SWNTs shift E0 toward more positive and more negative values, respectively. Adjusting E0 towards the center of the electrolyte stability window can increase the cell voltage and hence the energy density. PEI coating on SWNTs increases the cell voltage from 0.8 V to 1.7 V in tetrabutylammonium perchlorate (TBAP)/tetrahydrofuran (THF) electrolyte, and from 2.5 V to 3.1 V in tetraethylammonium tetrafluoroborate (TEABF4)/3-cyanopropionic acid methyl ester (CPAME), respectively. Moreover, PEI-SWNT EDLCs exhibit excellent cycling stability (92% of capacitance retention over 10000 cycles). We attribute the shift in E0 to a change in the Fermi level of SWNTs owing to the surface charge modification. Injection of electrical charge into PEI-SWNTs consistently yielded similar trends and thus validated our hypothesis. Our results may help to push various electrolytes that have been overlooked so far to new frontiers for obtaining high energy-density supercapacitors.

Chemically modified carbon nanotubes as material enhanced laser desorption ionisation (MELDI) material in protein profiling

International Nuclear Information System (INIS)

Najam-ul-Haq, M.; Rainer, M.; Schwarzenauer, T.; Huck, C.W.; Bonn, G.K.

2006-01-01

Biomarkers play a potential role in the early detection and diagnosis of a disease. Our aim is to derivatize carbon nanotubes for exploration of the differences in human body fluids e.g. serum, through matrix assisted laser desorption ionisation/time of flight mass spectrometry (MALDI/TOF-MS) that can be related to disease and subsequently to be employed in the biomarker discovery process. This application we termed as the material enhanced laser desorption ionisation (MELDI). The versatility of this technology is meant to increase the amount of information from biological samples on the protein level, which will have a major impact to serve the cause of diagnostic markers. Serum peptides and proteins are immobilized on derivatized carbon nanotubes, which function as binding material. Protein-loaded suspension is placed on a stainless steel target or buckypaper on aluminum target for direct analysis with MALDI-MS. The elution method to wash the bound proteins from carbon nanotubes was employed to compare with the direct analysis procedure. Elution is carried out by MALDI matrix solution to get them out of the entangled nanotubes, which are difficult to desorb by laser due to the complex nanotube structures. The advantage of these optimized methods compared to the conventional screening methods is the improved sensitivity, selectivity and the short analysis time without prior albumin and immunoglobulin depletion. The comparison of similarly modified diamond and carbon nanotubes exhibit differences in their nature to bind the proteins out of serum due to the differences in their physical characteristics. Infrared (IR) spectroscopy provided hint for the presence of tertiary amine peak at the crucial chemical step of iminodiacetic acid addition to acid chloride functionality on carbon nanotubes. Atomic absorption spectroscopy (AAS) was utilized to quantitatively measure the copper capacity of these derivatized carbon nanotubes which is a direct measure of capacity of

Functionalization of carbon nanotubes/graphene by polyoxometalates and their enhanced photo-electrical catalysis

International Nuclear Information System (INIS)

Zhang Shuang-Shuang; Liu Rong-Ji; Zhang Guang-Jin; Gu Zhan-Jun

2014-01-01

Carbon nanotubes and graphene are carbon-based materials, which possess not only unique structure but also properties such as high surface area, extraordinary mechanical properties, high electronic conductivity, and chemical stability. Thus, they have been regarded as an important material, especially for exploring a variety of complex catalysts. Considerable efforts have been made to functionalize and fabricate carbon-based composites with metal nanoparticles. In this review, we summarize the recent progress of our research on the decoration of carbon nanotubes/graphene with metal nanoparticles by using polyoxometalates as key agents, and their enhanced photo-electrical catalytic activities in various catalytic reactions. The polyoxometalates play a key role in constructing the nanohybrids and contributing to their photo-electrical catalytic properties. (invited review — international conference on nanoscience and technology, china 2013)

Rapid dual-injection single-scan 13N-ammonia PET for quantification of rest and stress myocardial blood flows

International Nuclear Information System (INIS)

Rust, T C; DiBella, E V R; McGann, C J; Christian, P E; Hoffman, J M; Kadrmas, D J

2006-01-01

Quantification of myocardial blood flows at rest and stress using 13 N-ammonia PET is an established method; however, current techniques require a waiting period of about 1 h between scans. The objective of this study was to test a rapid dual-injection single-scan approach, where 13 N-ammonia injections are administered 10 min apart during rest and adenosine stress. Dynamic PET data were acquired in six human subjects using imaging protocols that provided separate single-injection scans as gold standards. Rest and stress data were combined to emulate rapid dual-injection data so that the underlying activity from each injection was known exactly. Regional blood flow estimates were computed from the dual-injection data using two methods: background subtraction and combined modelling. The rapid dual-injection approach provided blood flow estimates very similar to the conventional single-injection standards. Rest blood flow estimates were affected very little by the dual-injection approach, and stress estimates correlated strongly with separate single-injection values (r = 0.998, mean absolute difference = 0.06 ml min -1 g -1 ). An actual rapid dual-injection scan was successfully acquired in one subject and further demonstrates feasibility of the method. This study with a limited dataset demonstrates that blood flow quantification can be obtained in only 20 min by the rapid dual-injection approach with accuracy similar to that of conventional separate rest and stress scans. The rapid dual-injection approach merits further development and additional evaluation for potential clinical use

A lactate electrochemical biosensor with a titanate nanotube as direct electron transfer promoter

International Nuclear Information System (INIS)

Yang Mingli; Wang Jin; Li Huaqing; Wu Nianqiang Nick; Zheng Jianguo

2008-01-01

Hydrogen titanate (H 2 Ti 3 O 7 ) nanotubes (TNTs) have been synthesized by a one-step hydrothermal processing. Lactate oxidase (LOx) enzyme has been immobilized on the three-dimensional porous TNT network to make an electrochemical biosensor for lactate detection. Cyclic voltammetry and amperometry tests reveal that the LOx enzyme, which is supported on TNTs, maintains their substrate-specific catalytic activity. The nanotubes offer the pathway for direct electron transfer between the electrode surface and the active redox centers of LOx, which enables the biosensor to operate at a low working potential and to avoid the influence of the presence of O 2 on the amperometric current response. The biosensor exhibits a sensitivity of 0.24 μA cm -2 mM -1 , a 90% response time of 5 s, and a linear response in the range from 0.5 to 14 mM and the redox center of enzyme obviates the need of redox mediators for electrochemical enzymatic sensors, which is attractive for the development of reagentless biosensors

A lactate electrochemical biosensor with a titanate nanotube as direct electron transfer promoter

Science.gov (United States)

Yang, Mingli; Wang, Jin; Li, Huaqing; Zheng, Jian-Guo; Wu, Nianqiang Nick

2008-02-01

Hydrogen titanate (H2Ti3O7) nanotubes (TNTs) have been synthesized by a one-step hydrothermal processing. Lactate oxidase (LOx) enzyme has been immobilized on the three-dimensional porous TNT network to make an electrochemical biosensor for lactate detection. Cyclic voltammetry and amperometry tests reveal that the LOx enzyme, which is supported on TNTs, maintains their substrate-specific catalytic activity. The nanotubes offer the pathway for direct electron transfer between the electrode surface and the active redox centers of LOx, which enables the biosensor to operate at a low working potential and to avoid the influence of the presence of O2 on the amperometric current response. The biosensor exhibits a sensitivity of 0.24 µA cm-2 mM-1, a 90% response time of 5 s, and a linear response in the range from 0.5 to 14 mM and the redox center of enzyme obviates the need of redox mediators for electrochemical enzymatic sensors, which is attractive for the development of reagentless biosensors.

Electrophoretically deposited multiwalled carbon nanotube based amperometric genosensor for E.coli detection

International Nuclear Information System (INIS)

Bhardwaj, Hema; Solanki, Shipra; Sumana, Gajjala

2016-01-01

This work reports on a sensitive and selective genosensor fabrication method for Escherichia coli ( E.coli) detection. The functionalized multiwalled carbon nanotubes (MWCNT) synthesized via chemical vapour deposition have been deposited electrophoretically onto indium tin oxide coated glass surface and have been utilized as matrices for the covalent immobilization of E.coli specific probe oligonucleotide that was identified from the 16s rRNA coding region of the E.coli genome. This fabricated functionalized MWCNT based platform sought to provide improved fundamental characteristics to electrode interface in terms of electro-active surface area and diffusion coefficient. Electrochemical cyclic voltammetry revealed that this genosensor exhibits a linear response to complementary DNA in the concentration range of 10 -7 to 10 -12 M with a detection limit of 1×10 -12 M. (paper)

Effects of carbon nanotube coating on flow boiling in a micro-channel

OpenAIRE

Khanikar, Vikash; Mudawar, Issam; Fisher, Timothy

2009-01-01

Experiments were performed to assess the heat transfer enhancement benefits of coating the bottom wall of a shallow rectangular micro-channel with carbon nanotubes (CNTs). Using water as working fluid, tests were performed with a bare copper surface and three separate, yet identical CNT-coated surfaces. Each of the CNT-coated surfaces was tested repeatedly at the same mass velocity to explore any time dependence of heat transfer performance parameters, especially critical heat flux (CHIF). Ap...

Barriers to Superfast Water Transport in Carbon Nanotube Membranes

DEFF Research Database (Denmark)

Walther, Jens Honore; Ritos, Konstantinos; Cruz-Chu, Eduardo R.

2013-01-01

Carbon nanotube (CNT) membranes hold the promise of extraordinary fast water transport for applications such as energy efficient filtration and molecular level drug delivery. However, experiments and computations have reported flow rate enhancements over continuum hydrodynamics that contradict each...... over the continuum predictions. These rates are far below those reported experimentally. The results suggest that the reported superfast water transport rates cannot be attributed to interactions of water with pristine CNTs alone....

Free vibration of a single-walled carbon nanotube containing a fluid flow using the Timoshenko beam model

International Nuclear Information System (INIS)

Chang, W.-J.; Lee, H.-L.

2009-01-01

The flexural vibration of the fluid-conveying single-walled carbon nanotube (SWCNT) is derived by the Timoshenko beam model, including rotary inertia and transverse shear deformation. The effects of the flow velocity and the aspect ratio of length to diameter on the vibration frequency and mode shape of the SWCNT are analyzed. Results show that the effects of rotary inertia and transverse shear deformation result in a reduction of the vibration frequencies, especially for higher modes of vibration and short nanotubes. The frequency is also compared with the previous study based on Euler beam model. In addition, if the ratio of length to diameter increased to 60, the influence of the shear deformation and rotary inertia on the mode shape and the resonant frequencies can be neglected. However, the influence is very obvious when the ratio decreased to 20. As the flow velocity of the fluid increases in the vicinity of 2π, the SWCNT reveals the divergence instability. It regains stability when the flow velocity reaches about 9. As the velocity increases further, the SWCNT undergoes a coupled-mode flutter and results in a larger amplitude

Elaboration of new method of enzyme adsorption on silicalite and nano beta zeolite for amperometric biosensor creation

Directory of Open Access Journals (Sweden)

Soldatkin O. O.

2014-07-01

Full Text Available Aim. Optimization of a new method of enzyme immobilization for amperometric biosensor creation. Methods. The amperometric biosensor with glucose oxidase immobilized on zeolites as bioselective elements and platinum disk electrode as transducers of biochemical signal into the electric one was used in the work. Results. The biosensors based on glucose oxidase adsorbed on zeolites were characterized by a higher sensitivity to glucose and a better inter-reproducibility. The best analytical characteristics were obtained for the biosensors based on nano beta zeolite. It has been found that an increase in the amount of zeolite on the surface of amperometric transducer may change such biosensor parameters as sensitivity to the substrate and duration of the analysis. Conclusions. The proposed method of enzyme immobilization by adsorption on zeolites is shown to be quite promising in the development of amperometric biosensors and therefore should be further investigated.

Flow Injection Analysis: A Revolution in Modern Analytical Chemistry

DEFF Research Database (Denmark)

Hansen, Elo Harald

1996-01-01

A review is made of the fundamentals of Flow Injection Analysis (FIA), and the versatility and applicability of this analytical concept is demonstrated by a series of examples, comprizing the use of different types of FIA-manifolds and various detection devices (optical and electrochemical...

Electrochemical formation of InP porous nanostructures and its application to amperometric chemical sensors

International Nuclear Information System (INIS)

Sato, Taketomo; Mizohata, Akinori; Fujino, Toshiyuki; Hashizume, Tamotsu

2008-01-01

In this paper, we report the electrochemical formation of the InP porous nanostructures and their feasibility for the application to the amperometric chemical sensors. Our two step electrochemical process consists of the pore formation on a (001) n-type InP substrate and the subsequent etching of pore walls caused by changing the polarity of the InP electrode in a HCl-based electrolyte. By applying the anodic bias to the InP electrode, the high-density array of uniform nanopores was formed on the surface. Next, the cathodic bias was applied to the porous sample to reduce the wall thickness by cathodic decomposition of InP, where the thickness of InP nanowall decreased uniformly along the entire depth of the porous layer. From the amperometric measurements of the porous electrode, it was found that the electrocatalytic activity was much higher than that of the planar electrode. Furthermore, the current sensitivity for the H 2 O 2 detection was much enhanced after the cathodic decomposition process. The InP porous nanostructure formed by the present process is one of the promising structures for the application to the semiconductor-based bio/chemical sensors. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Abdominal vascular and visceral parenchymal contrast enhancement in MDCT: Effects of injection duration

Energy Technology Data Exchange (ETDEWEB)

Tsuge, Yusuke, E-mail: tsugeu@cup.ocn.ne.jp [Department of Radiology, Kizawa Memorial Hospital, 590 Kobityo Shimokobi, Minokamo City, Gifu 505-8503 (Japan); Kanematsu, Masayuki [Department of Radiology, Gifu University Hospital, Gifu (Japan); Department of Radiology Services, Gifu University Hospital, Gifu (Japan); Goshima, Satoshi; Kondo, Hiroshi [Department of Radiology, Gifu University Hospital, Gifu (Japan); Yokoyama, Ryujiro; Miyoshi, Toshiharu [Department of Radiology Services, Gifu University Hospital, Gifu (Japan); Onozuka, Minoru [Department of Physiology and Neuroscience, Kanagawa Dental College, Yokosuka (Japan); Moriyama, Noriyuki [Research Center for Cancer Prevention and Screening, National Cancer Center Hospital, Tsukiji (Japan); Bae, Kyongtae T. [Radiology and Biomedical Engineering, University of Pittsburgh, Pittsburgh, PA (United States)

2011-11-15

Purpose: To evaluate and compare the effect of short and long injection durations on aortic, pancreatic and hepatic enhancement in abdominal MDCT. Methods and materials: Triphasic contrast-enhanced CT images (16-MDCT, 1.25-mm collimation, 5-mm thickness, 6.1-s acquisition time for each phase) were obtained with 2 mL/kg injection of 300 mgI/mL iodine contrast material in 116 patients. Patients were prospectively randomized into two groups: one receiving contrast medium for 25-s injection duration and the other for 35-s injection duration. In both groups, triphasic scans were initiated 5, 15, and 40 s after the completion of contrast injection for the first, second and third phases, respectively. CT values (HU) in the abdominal aorta, liver, spleen, pancreas, splenic and superior mesenteric arteries, and veins (splenic, superior mesenteric, portal, and hepatic) were measured. Quantitative and qualitative analysis for the degree of contrast enhancement between the two groups in various organs was compared at each scan phase. Results: The aortic and arterial enhancements in the first-phase scan were higher for the 25-s group than those of the 35-s group (P < .001). Hepatic enhancement was higher for the 35-s group in the first (P < .001) and second (P < .01) phases, but no difference in the third-phase. No difference was found between the groups for the pancreatic enhancement at any phases. Qualitative results were in good agreement with quantitative results. Conclusion: Contrast administration with shorter injection duration increased peak aortic and arterial enhancement and contributed to improvement in the quality of CT angiograms, but for the solid abdominal organs 35-s protocol is recommended.

Understanding Fast and Robust Thermo-osmotic Flows through Carbon Nanotube Membranes: Thermodynamics Meets Hydrodynamics.

Science.gov (United States)

Fu, Li; Merabia, Samy; Joly, Laurent

2018-04-19

Following our recent theoretical prediction of the giant thermo-osmotic response of the water-graphene interface, we explore the practical implementation of waste heat harvesting with carbon-based membranes, focusing on model membranes of carbon nanotubes (CNT). To that aim, we combine molecular dynamics simulations and an analytical model considering the details of hydrodynamics in the membrane and at the tube entrances. The analytical model and the simulation results match quantitatively, highlighting the need to take into account both thermodynamics and hydrodynamics to predict thermo-osmotic flows through membranes. We show that, despite viscous entrance effects and a thermal short-circuit mechanism, CNT membranes can generate very fast thermo-osmotic flows, which can overcome the osmotic pressure of seawater. We then show that in small tubes confinement has a complex effect on the flow and can even reverse the flow direction. Beyond CNT membranes, our analytical model can guide the search for other membranes to generate fast and robust thermo-osmotic flows.

Screen-printed sensor for batch and flow injection potentiometric chromium(VI) monitoring

Energy Technology Data Exchange (ETDEWEB)

Sanchez-Moreno, Raul A.; Gismera, M.J.; Sevilla, M.T.; Procopio, Jesus R. [Facultad de Ciencias, Universidad Autonoma de Madrid, Departamento de Quimica Analitica y Analisis Instrumental, Madrid (Spain)

2010-05-15

A disposable screen-printed electrode was designed and evaluated for direct detection of chromium(VI) in batch and flow analysis. The carbon screen-printed electrode was modified with a graphite-epoxy composite. The optimal graphite-epoxy matrix contains 37.5% graphite powder, 12.5% diphenylcarbohydrazide, a selective compound for chromium(VI), and 50% epoxy resin. The principal analytical parameters of the potentiometric response in batch and flow analysis were optimized and calculated. The screen-printed sensor exhibits a response time of 20 {+-} 1 s. In flow analysis, the analytical frequency of sampling is 70 injections per hour using 0.1 M NaNO{sub 3} solution at pH 3 as the carrier, a flow rate of 2.5 mL.min{sup -1}, and an injection sample volume of 0.50 mL. The sensor shows potentiometric responses that are very selective for chromium(VI) ions and optimal detection limits in both static mode (2.1 x 10{sup -7} M) and online analysis (9.4 x 10{sup -7} M). The disposable potentiometric sensor was employed to determine toxicity levels of chromium(VI) in mineral, tap, and river waters by flow-injection potentiometry and batch potentiometry. Chromium(VI) determination was also carried out with successful results in leachates from municipal solid waste landfills. (orig.)

Plasma-induced field emission and plasma expansion of carbon nanotube cathodes

International Nuclear Information System (INIS)

Liao Qingliang; Zhang Yue; Qi Junjie; Huang Yunhua; Xia Liansheng; Gao Zhanjun; Gu Yousong

2007-01-01

High intensity electron emission cathodes based on carbon nanotube films have been successfully fabricated. An investigation of the explosive field emission properties of the carbon nanotube cathode in a double-pulse mode was presented and a high emission current density of 245 A cm -2 was obtained. The formation of the cathode plasma layer was proved and the production process of the electron beams from the cathode was explained. The time and space resolution of the electron beams flow from the cathode was investigated. The plasma expanded at a velocity of ∼8.17 cm μs -1 towards the anode and influenced on the intensity and distribution of electron beams obviously. The formation of cathode plasma had no preferential position and the local enhancement of electron beams was random. This carbon nanotube cathode appears to be suitable for high-power microwave device applications

Fabrication and characterization of composite TiO{sub 2} nanotubes/boron-doped diamond electrodes towards enhanced supercapacitors

Energy Technology Data Exchange (ETDEWEB)

Sobaszek, M. [Department of Metrology and Optoelectronics, Faculty of Electronics, Telecommunications and Informatics, Gdańsk University of Technology, 11/12 G. Narutowicza St., 80-233 Gdańsk (Poland); Siuzdak, K.; Sawczak, M. [Centre for Plasma and Laser Engineering, The Szewalski Institute of Fluid-Flow Machinery, Polish Academy of Sciences, 14 Fiszera St., 80-231 Gdansk (Poland); Ryl, J. [Department of Electrochemistry, Corrosion and Material Engineering, Faculty of Chemistry, Gdańsk University of Technology, 11/12 G. Narutowicza St., 80-233 Gdańsk (Poland); Bogdanowicz, R., E-mail: rbogdan@eti.pg.gda.pl [Department of Metrology and Optoelectronics, Faculty of Electronics, Telecommunications and Informatics, Gdańsk University of Technology, 11/12 G. Narutowicza St., 80-233 Gdańsk (Poland)

2016-02-29

The composite TiO{sub 2} nanotubes/boron-doped diamond electrodes were deposited using Microwave Plasma Enhanced Chemical Vapor Deposition resulting in the improved electrochemical performance. This composite electrode can deliver high specific capacitance of 7.46 mF cm{sup −2} comparing to boron-doped diamond (BDD) deposited onto flat Ti plate (0.11 mF cm{sup −2}).The morphology and composition of composite electrode were characterized by scanning electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) techniques. According to XPS and Raman analyses, the structure of TiO{sub 2} was greatly changed during Chemical Vapor Deposition process: formation of Ti{sup 3+} sites, partial anatase to rutile transformation and titanium carbide phase formation. This effect is attributed to the simultaneous presence of activated hydrogen and carbon in the plasma leading to enhanced dehydration of NTs (nanotubes) followed by carbon bonding. The enhanced capacitive effect of TiO{sub 2} NT/BDD could be recognized as: (1) the unique synergistic morphology of NTs and BDD providing more efficient conducting pathway for the diffusion of ions and (2) partial decomposition of NTs and transformation towards to TiC and Ti{sub 2}O{sub 3} fractions. Finally, highly ordered titania nanotubes produced via simply, quick and controllable method — anodization, could act as promising substrate for conductive BDD layer deposition and further application of such composites for supercapacitor construction. - Highlights: • The TiO{sub 2} nanotube (NT)/diamond electrode delivers capacitance of 7.46 mF cm{sup −2}. • The NTs are not affected by diamond growth process and keep their pristine shape. • The BDD overlayer fully encapsulates TiO{sub 2} NTs exhibiting typical columnar growth. • The activated hydrogen and carbon in the plasma lead to enhanced dehydration of NTs. • The presence of TiC and Ti{sub 2}O{sub 3} fractions introducing additional capacitance.

Liquid sprays and flow studies in the direct-injection diesel engine under motored conditions

Science.gov (United States)

Nguyen, Hung Lee; Carpenter, Mark H.; Ramos, Juan I.; Schock, Harold J.; Stegeman, James D.

1988-01-01

A two dimensional, implicit finite difference method of the control volume variety, a two equation model of turbulence, and a discrete droplet model were used to study the flow field, turbulence levels, fuel penetration, vaporization, and mixing in diesel engine environments. The model was also used to study the effects of engine speed, injection angle, spray cone angle, droplet distribution, and intake swirl angle on the flow field, spray penetration and vaporization, and turbulence in motored two-stroke diesel engines. It is shown that there are optimum conditions for injection, which depend on droplet distribution, swirl, spray cone angle, and injection angle. The optimum conditions result in good spray penetration and vaporization and in good fuel mixing. The calculation presented clearly indicates that internal combustion engine models can be used to assess, at least qualitatively, the effects of injection characteristics and engine operating conditions on the flow field and on the spray penetration and vaporization in diesel engines.

Using in-situ polymerization of conductive polymers to enhance the electrical properties of solution-processed carbon nanotube films and fibers.

Science.gov (United States)

Allen, Ranulfo; Pan, Lijia; Fuller, Gerald G; Bao, Zhenan

2014-07-09

Single-walled carbon nanotubes/polymer composites typically have limited conductivity due to a low concentration of nanotubes and the insulating nature of the polymers used. Here we combined a method to align carbon nanotubes with in-situ polymerization of conductive polymer to form composite films and fibers. Use of the conducting polymer raised the conductivity of the films by 2 orders of magnitude. On the other hand, CNT fiber formation was made possible with in-situ polymerization to provide more mechanical support to the CNTs from the formed conducting polymer. The carbon nanotube/conductive polymer composite films and fibers had conductivities of 3300 and 170 S/cm, respectively. The relatively high conductivities were attributed to the polymerization process, which doped both the SWNTs and the polymer. In-situ polymerization can be a promising solution-processable method to enhance the conductivity of carbon nanotube films and fibers.

Electrospinning direct synthesis of magnetic ZnFe{sub 2}O{sub 4}/ZnO multi-porous nanotubes with enhanced photocatalytic activity

Energy Technology Data Exchange (ETDEWEB)

Wang, Chunlei [College of Chemistry and Environmental Engineering, Wuhan Polytechnic University, Wuhan 430023 (China); Tan, Xing [College of Biology and Pharmaceutical Engineering, Wuhan Polytechnic University, Wuhan 430023 (China); Yan, Juntao, E-mail: yanjuntaonihao@163.com [College of Chemistry and Environmental Engineering, Wuhan Polytechnic University, Wuhan 430023 (China); Chai, Bo [College of Chemistry and Environmental Engineering, Wuhan Polytechnic University, Wuhan 430023 (China); Li, Jianfen, E-mail: lijfen@163.com [College of Chemistry and Environmental Engineering, Wuhan Polytechnic University, Wuhan 430023 (China); Chen, Shizhong [College of Food Science and Engineering, Wuhan Polytechnic University, Wuhan 430023 (China)

2017-02-28

Highlights: • ZnFe2O4/ZnO heterojunctions are firstly fabricated by electrospinning method. • ZnFe{sub 2}O{sub 4}/ZnO heterojunctions possess multi-porous nanotube structure. • ZnFe{sub 2}O{sub 4}/ZnO heterojunctions can significantly enhance photocatalytic activity. - Abstract: Magnetic ZnFe{sub 2}O{sub 4}/ZnO (ZFO/ZnO) multi-porous nanotubes have been first fabricated via a facile electrospinning and subsequent calcination process. A series of ZFO/ZnO photocatalysts with different ZFO molar content and morphologies are also obtained by varying the molar ratio of Zn/Fe metal salt and its dosage. The morphology, composition, crystal structure and specific surface area of achieved photocatalysts are systematically examined. TEM images demonstrate ZFO/ZnO-3 multi-porous nanotubes possess perfect 1D nanotube profile with hierarchical pores. HRTEM images confirm the formation of ZFO/ZnO heterojunctions. DRS spectra show that ZFO/ZnO-3 multi-porous nanotubes exhibit an enhanced absorption both in UV and visible-light region. PL spectra and photocurrent responses of ZFO/ZnO-3 multi-porous nanotube demonstrated that the photogenerated electrons and holes are effectively separated. Above all, ZFO/ZnO-3 multi-porous nanotubes photocatalysts with a larger specific surface area of 57.79 m{sup 2} g{sup −1} exhibit the best photocatalytic efficiency of 99% after 150 min under the solar irradiation for the decolorization of RhB. Moreover, ZFO/ZnO photocatalysts not only possess magnetic separation property, but also keep a relatively high photocatalytic efficiency even after four cycles, which is beneficial for practical application. In addition, both the formation and potential photocatalytic mechanisms of ZFO/ZnO-3 multi-porous nanotubes are proposed in detail.

Quantum decoherence in electronic current flowing through carbon nanotubes induced by thermal atomic vibrations

Science.gov (United States)

Ishizeki, Keisuke; Sasaoka, Kenji; Konabe, Satoru; Souma, Satofumi; Yamamoto, Takahiro

2018-06-01

We theoretically investigate quantum decoherence in electronic currents flowing through metallic carbon nanotubes caused by thermal atomic vibrations using the time-dependent Schrödinger equation for an open system. We reveal that the quantum coherence of conduction electrons decays exponentially with tube length at a fixed temperature, and that the decay rate increases with temperature. We also find that the phase relaxation length due to the thermal atomic vibrations is inversely proportional to temperature.

Comparison between amperometric and true potentiometric end-point detection in the determination of water by the Karl Fischer method.

Science.gov (United States)

Cedergren, A

1974-06-01

A rapid and sensitive method using true potentiometric end-point detection has been developed and compared with the conventional amperometric method for Karl Fischer determination of water. The effect of the sulphur dioxide concentration on the shape of the titration curve is shown. By using kinetic data it was possible to calculate the course of titrations and make comparisons with those found experimentally. The results prove that the main reaction is the slow step, both in the amperometric and the potentiometric method. Results obtained in the standardization of the Karl Fischer reagent showed that the potentiometric method, including titration to a preselected potential, gave a standard deviation of 0.001(1) mg of water per ml, the amperometric method using extrapolation 0.002(4) mg of water per ml and the amperometric titration to a pre-selected diffusion current 0.004(7) mg of water per ml. Theories and results dealing with dilution effects are presented. The time of analysis was 1-1.5 min for the potentiometric and 4-5 min for the amperometric method using extrapolation.

Numerical investigation of the air injection effect on the cavitating flow in Francis hydro turbine

Science.gov (United States)

Chirkov, D. V.; Shcherbakov, P. K.; Cherny, S. G.; Skorospelov, V. A.; Turuk, P. A.

2017-09-01

At full and over load operating points, some Francis turbines experience strong self-excited pressure and power oscillations. These oscillations are occuring due to the hydrodynamic instability of the cavitating fluid flow. In many cases, the amplitude of such pulsations may be reduced substantially during the turbine operation by the air injection/ admission below the runner. Such an effect is investigated numerically in the present work. To this end, the hybrid one-three-dimensional model of the flow of the mixture "liquid-vapor" in the duct of a hydroelectric power station, which was proposed previously by the present authors, is augmented by the second gaseous component — the noncondensable air. The boundary conditions and the numerical method for solving the equations of the model are described. To check the accuracy of computing the interface "liquid-gas", the numerical method was applied at first for solving the dam break problem. The algorithm was then used for modeling the flow in a hydraulic turbine with air injection below the runner. It is shown that with increasing flow rate of the injected air, the amplitude of pressure pulsations decreases. The mechanism of the flow structure alteration in the draft tube cone has been elucidated, which leads to flow stabilization at air injection.

Flow injection kinetic spectrofluorimetric determination of trace amounts of osmium

Science.gov (United States)

Tang, Bo; Zhang, Hui; Wang, Yan

2005-07-01

A flow injection (FI) kinetic spectrofluorimetric method is described for the determination of osmium(IV) and the possible mechanism of catalytic reaction is discussed. The method is based on the fluorescence enhancing reaction of o-vanillin furfuralhydrazone (OVFH) with potassium bromate, which is catalyzed by Os(IV) in water medium at pH 6.10 and 45 °C. OVFH is newly synthesized and its ionization, IR and elemental analysis are established. Under these experimental conditions, the oxidized product of OVFH has excitation and emission maxima at 337 and 490 nm, respectively. The linear range of this method is 0-600 ng ml -1 with the R.S.D. of 1.2%. The detection limit is 1.0 ng ml -1 of Os(IV). A high analysis rate of 24 samples h -1 is obtained by the FI method. The proposed method is applied successfully to determine Os(IV) in synthetic mixture and mineral samples, and the results are well consistent with the standard values.

Enhanced Carbon Nanotube Ultracapacitors, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — The proposed innovation utilizes carbon nanotubes (CNTs) coated with pseudo-capacitive MnO2 material as nano-composite electrode and ionic electrolyte for the...

Retracted-Enhanced X-Ray Absorption Property of Gold-Doped Single Wall Carbon Nanotube

Directory of Open Access Journals (Sweden)

Alimin Alimin

2015-11-01

Full Text Available Enhanced X-ray absorption property of single wall carbon nanotube (SWCNT through gold (Au doping (Au@SWCNT has been studied. Mass attenuation coefficient of SWCNT increased 5.2-fold after Au doping treatment. The use of ethanol in the liquid phase adsorption could produce Au nanoparticles as confirmed by the X-ray Diffraction (XRD patterns. The possibility of gold nanoparticles encapsulated in the internal tube space of SWCNT was observed by transmission electron microscope technique. A significant decrease of nitrogen uptakes and upshifts of Radial Breathing Mode (RBM of Au@SWCNT specimen suggest that the nanoparticles might be encapsulated in the internal tube spaces of the nanotube. In addition, a decrease intensity of XRD pattern of Au@SWCNT at around 2θ ≈ 2.6° supports the suggestion that Au nanoparticles are really encapsulated into SWCNT.

Simultaneous synthesis of single-walled carbon nanotubes and graphene in a magnetically-enhanced arc plasma.

Science.gov (United States)

Li, Jian; Shashurin, Alexey; Kundrapu, Madhusudhan; Keidar, Michael

2012-02-02

Carbon nanostructures such as single-walled carbon nanotubes (SWCNT) and graphene attract a deluge of interest of scholars nowadays due to their very promising application for molecular sensors, field effect transistor and super thin and flexible electronic devices(1-4). Anodic arc discharge supported by the erosion of the anode material is one of the most practical and efficient methods, which can provide specific non-equilibrium processes and a high influx of carbon material to the developing structures at relatively higher temperature, and consequently the as-synthesized products have few structural defects and better crystallinity. To further improve the controllability and flexibility of the synthesis of carbon nanostructures in arc discharge, magnetic fields can be applied during the synthesis process according to the strong magnetic responses of arc plasmas. It was demonstrated that the magnetically-enhanced arc discharge can increase the average length of SWCNT (5), narrow the diameter distribution of metallic catalyst particles and carbon nanotubes (6), and change the ratio of metallic and semiconducting carbon nanotubes (7), as well as lead to graphene synthesis (8). Furthermore, it is worthwhile to remark that when we introduce a non-uniform magnetic field with the component normal to the current in arc, the Lorentz force along the J×B direction can generate the plasmas jet and make effective delivery of carbon ion particles and heat flux to samples. As a result, large-scale graphene flakes and high-purity single-walled carbon nanotubes were simultaneously generated by such new magnetically-enhanced anodic arc method. Arc imaging, scanning electron microscope (SEM), transmission electron microscope (TEM) and Raman spectroscopy were employed to analyze the characterization of carbon nanostructures. These findings indicate a wide spectrum of opportunities to manipulate with the properties of nanostructures produced in plasmas by means of controlling the

Continuous-flow ultrasound assisted oxidative desulfurization (UAOD) process: An efficient diesel treatment by injection of the aqueous phase.

Science.gov (United States)

Rahimi, Masoud; Shahhosseini, Shahrokh; Movahedirad, Salman

2017-11-01

A new continuous-flow ultrasound assisted oxidative desulfurization (UAOD) process was developed in order to decrease energy and aqueous phase consumption. In this process the aqueous phase is injected below the horn tip leading to enhanced mixing of the phases. Diesel fuel as the oil phase with sulfur content of 1550ppmw and an appropriate mixture of hydrogen peroxide and formic acid as the aqueous phase were used. At the first step, the optimized condition for the sulfur removal has been obtained in the batch mode operation. Hence, the effect of more important oxidation parameters; oxidant-to-sulfur molar ratio, acid-to-sulfur molar ratio and sonication time were investigated. Then the optimized conditions were obtained using Response Surface Methodology (RSM) technique. Afterwards, some experiments corresponding to the best batch condition and also with objective of minimizing the residence time and aqueous phase to fuel volume ratio have been conducted in a newly designed double-compartment reactor with injection of the aqueous phase to evaluate the process in a continuous flow operation. In addition, the effect of nozzle diameter has been examined. Significant improvement on the sulfur removal was observed specially in lower sonication time in the case of dispersion method in comparison with the conventional contact between two phases. Ultimately, the flow pattern induced by ultrasonic device, and also injection of the aqueous phase were analyzed quantitatively and qualitatively by capturing the sequential images. Copyright © 2017 Elsevier B.V. All rights reserved.

Amperometric sensor for carbon dioxide: design, characteristics, and perforance

International Nuclear Information System (INIS)

Evans, J.; Pletcher, D.; Warburton, P.R.G.; Gibbs, T.K.

1989-01-01

A new sensor for atmospheric carbon dioxide is described. It is an amperometric device based on a porous electrode in a three-electrode cell and the electrolyte is a copper diamine complex in aqueous potassium chloride. The platinum cathode, held at constant potential, is used to detect the formation of Cu 2+ following the change in the pH of the solution when the sensor is exposed to an atmosphere containing carbon dioxide. The sensor described is designed to monitor carbon dioxide concentrations in the range 0-5%, although with some modifications, other ranges would be possible. The response to a change in the carbon dioxide content of the atmosphere is rapid (about 10s) while the monitored current is strongly (but nonlinearly) dependent on carbon dioxide concentration. Unlike other amperometric devices for carbon dioxide, there is no interference from oxygen although other acid gases would lead to an interfering response

Enhanced Photocatalytic Properties of Ag-Loaded N-Doped Tio2 Nanotube Arrays

Directory of Open Access Journals (Sweden)

Gao Dawei

2018-03-01

Full Text Available Highly ordered TiO2 nanotube (TiO2 NT arrays were prepared by anodic oxidizing method on the surface of the Ti substrate. Nitrogen-doped TiO2 nanotube (N-TiO2 NT arrays were carried out by ammonia solution immersion, and Ag nanoparticles loaded N-doped TiO2 nanotube (Ag/N-TiO2 NT arrays were obtained by successive ionic layer adsorption and reaction (SILAR technique. The samples were characterized by the X-ray diffraction (XRD, X-ray photoelectron spectroscopy (XPS, field emission scanning electron microscopy (FESEM, high-resolution transmission electron microscopy (HRTEM, photoluminescence (PL emission spectra, ultraviolet–visible (UV–vis diffuse reflectance spectroscopy (DRS. The result indicated that the diameter and wall thickness of the TiO2 NT are 100–120 and 20–30 nm, respectively. Moreover, the morphology and structure of the highly ordered TiO2 NTs were not affected by N-doping. Furthermore, Ag nanoparticles were evenly deposited on the surface of TiO2 NTs in the form of elemental silver. Finally, the photocatalytic activity of Ag/N-TiO2 NTs was evaluated by degradation of methyl orange (MO under visible-light irradiation. The Ag/N-TiO2 NTs exhibited enhanced photocatalytic properties, which could reach 95% after 90-min irradiation.

Effects of the gate dielectric on the subthreshold transport of carbon nanotube network transistors grown by using plasma-enhanced chemical vapor deposition

International Nuclear Information System (INIS)

Jeong, Seung Geun; Park, Wan Jun

2010-01-01

In this study, we investigated the subthreshold slope of random network carbon nanotube transistors with different geometries and passivations. Single-wall carbon nanotubes with lengths of 1-2 m were grown by using plasma-enhanced chemical vapor deposition to form the transistor channels. A critical channel length, where the subthreshold slope was saturated, of 7 μm was obtained. This was due to the percolational behavior of the nanotube random networks. With the dielectric passivation, the subthreshold slope was dramatically reduced from 9 V/decade to 0.9 V/decade by reducing interfacial trap sites, which then reduced the interface capacitance between the nanotube network and the gate dielectric.

Study on effect of mixing mechanism by the transverse gaseous injection flow in scramjet engine with variable parameters

Science.gov (United States)

Yadav, Siddhita; Pandey, K. M.

2018-04-01

In scramjet engine the mixing mechanism of fuel and atmospheric air is very complicated, because the fuel have time in milliseconds for mixing with atmospheric air in combustion chamber having supersonic speed. Mixing efficiency of fuel and atmospheric air depends on mainly these parameters: Aspect ratio of injector, vibration amplitude, shock type, number of injector, jet to transverse flow momentum flux ratio, injector geometry, injection angle, molecular weight, incoming air stream angle, jet to transverse flow pressure ratio, spacing variation, mass flow rate of fuel etc. here is a very brief study of these parameters from previously done research on these parameters for the improvement of mixing efficiency. The mixing process have the significant role for the working of engine, and mixing between the atmospheric air and the jet fuel is significant factor for improving the overall thrust of the engine. The results obtained by study of papers are obtained by the 3D-Reynolds Average-Nervier-Stokes(RANS) equations along with the 2-equation k-ω shear-stress-transport (SST) turbulence model. Engine having multi air jets have 60% more mixing efficiency than single air jet, thus if the jets are increased, the mixing efficiency of engine can also be increased up to 150% by changing jet from 1 to 16. When using delta shape of injector the mixing efficiency is inversely proportional to the pressure ratio. When the fuel is injected inside the combustor from the top and bottom walls of the engine efficiency of mixing in reacting zone is higher than the single wall injection and in comparison to parallel flow, the transverse type flow is better as the atmospheric air jet can penetrate smoothly in the fuel jets and mixes well in less time. Hence this study of parameters and their effects on mixing can enhance the efficiency of mixing in engine.

Numerical Simulation of Polymer Injection in Turbulent Flow Past a Circular Cylinder

KAUST Repository

Richter, David; Shaqfeh, Eric S. G.; Iaccarino, Gianluca

2011-01-01

Using a code developed to compute high Reynolds number viscoelastic flows, polymer injection from the upstream stagnation point of a circular cylinder is modeled at Re = 3900. Polymer stresses are represented using the FENE-P constitutive equations. By increasing polymer injection rates within realistic ranges, significant near wake stabilization is observed. Rather than a turbulent detached shear layer giving way to a chaotic primary vortex (as seen in Newtonian flows at high Re), a much more coherent primary vortex is shed, which possesses an increased core pressure as well as a reduced level of turbulent energy. © 2011 American Society of Mechanical Engineers.

Detailed evaluation of the natural circulation mass flow rate of water propelled by using an air injection

International Nuclear Information System (INIS)

Park, Rae-Joon; Ha, Kwang-Soon; Kim, Jae-Cheol; Hong, Seong-Wan; Kim, Sang-Baik

2008-01-01

One-dimensional (1D) air-water two-phase natural circulation flow in the thermohydraulic evaluation of reactor cooling mechanism by external self-induced flow - one-dimensional' (THERMES-1D) experiment has been verified and evaluated by using the RELAP5/MOD3 computer code. Experimental results on the 1D natural circulation mass flow rate of water propelled by using an air injection have been evaluated in detail. The RELAP5 results have shown that an increase in the air injection rate to 50% of the total heat flux leads to an increase in the water circulation mass flow rate. However, an increase in the air injection rate from 50 to 100% does not affect the water circulation mass flow rate, because of the inlet area condition. As the height increases in the air injection part, the void fraction increases. However, the void fraction in the upper part of the air injector maintains a constant value. An increase in the air injection mass flow rate leads to an increase in the local void fraction, but it has no influence on the local pressure. An increase in the coolant inlet area leads to an increase in the water circulation mass flow rate. However, the water outlet area does not have an influence on the water circulation mass flow rate. As the coolant outlet moves to a lower position, the water circulation mass flow rate decreases. (author)

Portable cholesterol detection with polyaniline-carbon nanotube film based interdigitated electrodes

International Nuclear Information System (INIS)

Nguyen, Le Huy; Nguyen, Ngoc Thinh; Nguyen, Hai Binh; Tran, Dai Lam; Nguyen, Tuan Dung

2012-01-01

Polyaniline-carboxylic multiwalled carbon nanotubes composite film (PANi-MWCNT) has been polymerized on the surface of interdigitated platinum electrode (fabricated by MEMS technology) which was compatibly connected to Autolab interface via universal serial bus (USB). An amperometric biosensor based on covalent immobilization of cholesterol oxidase (ChOx) on PANi–MWCNT film with potassium ferricyanide (FeCN) as the redox mediator was developed. The mediator helps to shuttle the electrons between the immobilized ChOx and the PANi-MWCNT electrode, therefore operating at a low potential of −0.3 V compared to the saturated calomel electrode (SCE). This potential precludes the interfering compounds from oxidization. The bio-electrode exhibits good linearity from 0.02 to 1.2 mM cholesterol concentration with a correlation coefficient of 0.9985

Decompositions of injection patterns for nodal flow allocation in renewable electricity networks

Science.gov (United States)

Schäfer, Mirko; Tranberg, Bo; Hempel, Sabrina; Schramm, Stefan; Greiner, Martin

2017-08-01

The large-scale integration of fluctuating renewable power generation represents a challenge to the technical and economical design of a sustainable future electricity system. In this context, the increasing significance of long-range power transmission calls for innovative methods to understand the emerging complex flow patterns and to integrate price signals about the respective infrastructure needs into the energy market design. We introduce a decomposition method of injection patterns. Contrary to standard flow tracing approaches, it provides nodal allocations of link flows and costs in electricity networks by decomposing the network injection pattern into market-inspired elementary import/export building blocks. We apply the new approach to a simplified data-driven model of a European electricity grid with a high share of renewable wind and solar power generation.

Enhanced performance of starter lighting ignition type lead-acid batteries with carbon nanotubes as an additive to the active mass

Science.gov (United States)

Marom, Rotem; Ziv, Baruch; Banerjee, Anjan; Cahana, Beni; Luski, Shalom; Aurbach, Doron

2015-11-01

Addition of various carbon materials into lead-acid battery electrodes was studied and examined in order to enhance the power density, improve cycle life and stability of both negative and positive electrodes in lead acid batteries. High electrical-conductivity, high-aspect ratio, good mechanical properties and chemical stability of multi-wall carbon nanotubes (MWCNT, unmodified and mofified with carboxylic groups) position them as viable additives to enhance the electrodes' electrical conductivity, to mitigate the well-known sulfation failure mechanism and improve the physical integration of the electrodes. In this study, we investigated the incorporation-effect of carbon nanotubes (CNT) to the positive and the negative active materials in lead-acid battery prototypes in a configuration of flooded cells, as well as gelled cells. The cells were tested at 25% and 30% depth-of-discharge (DOD). The positive effect of the carbon nanotubes (CNT) utilization as additives to both positive and negative electrodes of lead-acid batteries was clearly demonstrated and is explained herein based on microscopic studies.

Modeling and flow analysis of pure nylon polymer for injection molding process

International Nuclear Information System (INIS)

Nuruzzaman, D M; Kusaseh, N; Basri, S; Hamedon, Z; Oumer, A N

2016-01-01

In the production of complex plastic parts, injection molding is one of the most popular industrial processes. This paper addresses the modeling and analysis of the flow process of the nylon (polyamide) polymer for injection molding process. To determine the best molding conditions, a series of simulations are carried out using Autodesk Moldflow Insight software and the processing parameters are adjusted. This mold filling commercial software simulates the cavity filling pattern along with temperature and pressure distributions in the mold cavity. In the modeling, during the plastics flow inside the mold cavity, different flow parameters such as fill time, pressure, temperature, shear rate and warp at different locations in the cavity are analyzed. Overall, this Moldflow is able to perform a relatively sophisticated analysis of the flow process of pure nylon. Thus the prediction of the filling of a mold cavity is very important and it becomes useful before a nylon plastic part to be manufactured. (paper)

Modeling and flow analysis of pure nylon polymer for injection molding process

Science.gov (United States)

Nuruzzaman, D. M.; Kusaseh, N.; Basri, S.; Oumer, A. N.; Hamedon, Z.

2016-02-01

In the production of complex plastic parts, injection molding is one of the most popular industrial processes. This paper addresses the modeling and analysis of the flow process of the nylon (polyamide) polymer for injection molding process. To determine the best molding conditions, a series of simulations are carried out using Autodesk Moldflow Insight software and the processing parameters are adjusted. This mold filling commercial software simulates the cavity filling pattern along with temperature and pressure distributions in the mold cavity. In the modeling, during the plastics flow inside the mold cavity, different flow parameters such as fill time, pressure, temperature, shear rate and warp at different locations in the cavity are analyzed. Overall, this Moldflow is able to perform a relatively sophisticated analysis of the flow process of pure nylon. Thus the prediction of the filling of a mold cavity is very important and it becomes useful before a nylon plastic part to be manufactured.

High Temperature Resin/Carbon Nanotube Composite Fabrication

Science.gov (United States)

Ghose, Sayata; Watson, Kent A.; Sun, Keun J.; Criss, Jim M.; Siochi, Emilie J.; Connell, John W.

2006-01-01

For the purpose of incorporating multifunctionality into advanced composites, blends of phenylethynyl terminated imides-330 (PETI-330) and multi-walled carbon nanotubes (MWCNTs) were prepared, characterized and fabricated into moldings. PETI-330/MWCNT mixtures were prepared at concentrations ranging from 3 to 25 weight percent by dry mixing the components in a ball mill. The resulting powders were characterized for degree of mixing, thermal and rheological properties. Based on the characterization results, PETI-330/MWCNT samples were scaled up to approximately 300 g and used to fabricate moldings by injecting the mixtures at 260-280 deg C into a stainless steel tool followed by curing for 1 h at 371 deg C. The tool was designed to impart a degree of shear during the injection process in an attempt to achieve some alignment of the MWCNTs in the flow direction. Obtained moldings were subsequently characterized for thermal, mechanical, and electrical properties. The degree of dispersion and alignment of MWCNTs were investigated using high-resolution scanning electron microscopy. The preparation and preliminary characterization of PETI-330/MWCNT composites will be discussed.

Water-assisted growth of graphene on carbon nanotubes by the chemical vapor deposition method.

Science.gov (United States)

Feng, Jian-Min; Dai, Ye-Jing

2013-05-21

Combining carbon nanotubes (CNTs) with graphene has been proved to be a feasible method for improving the performance of graphene for some practical applications. This paper reports a water-assisted route to grow graphene on CNTs from ferrocene and thiophene dissolved in ethanol by the chemical vapor deposition method in an argon flow. A double injection technique was used to separately inject ethanol solution and water for the preparation of graphene/CNTs. First, CNTs were prepared from ethanol solution and water. The injection of ethanol solution was suspended and water alone was injected into the reactor to etch the CNTs. Thereafter, ethanol solution was injected along with water, which is the key factor in obtaining graphene/CNTs. Transmission electron microscopy, scanning electron microscopy, X-ray diffraction, and Raman scattering analyses confirmed that the products were the hybrid materials of graphene/CNTs. X-ray photo-electron spectroscopy analysis showed the presence of oxygen rich functional groups on the surface of the graphene/CNTs. Given the activity of the graphene/CNT surface, CdS quantum dots adhered onto it uniformly through simple mechanical mixing.

Flow injection on-line spectrophotometric determination of thorium(IV) after preconcentration on XAD-4 resin impregnated with oxytetracycline

Energy Technology Data Exchange (ETDEWEB)

Shahida, Shabnam; Khan, Muhammad Haleem [Univ. of Azad Jammu and Kashmir, Muzaffarabad (Pakistan). Dept. of Chemistry; Ali, Akbar [Pakistan Institute of Nuclear Science and Technology, Islamabad (Pakistan). Chemistry Div.

2014-02-15

A very sensitive, selective and simple flow injection time-based method was developed for on-line preconcentration and determination of thorium(IV) at micro g L{sup -1} levels in environmental samples. The system operation was based on thorium(IV) ion retention at pH 4.0 in the minicolumn at a flow rate of 15.2 mL min{sup -1}. The trapped complex was then eluted with 3.6 mol L{sup -1} HCl at a flow rate of 4.9 mL min{sup -1}. The amount of thorium(IV) in the eluate was measured spectrophotometrically at 651 nm using arsenazo-III solution (0.05 % in 3.6 mol L{sup -1} HCl stabilized with 1 % triton X-100, 4.9 mL min{sup -1}) as colorimetric reagent. All chemical, and flow injection variables were optimized for the quantitative preconcentration of metal and a study of interference level of various ions was also carried out. The system offered low backpressure and improved sensitivity and selectivity. At a preconcentration time of 60 s and a sample frequency of 40 h{sup -1}, the enhancement factor was 97, the detection limit was 0.25 μg L{sup -1}, and the precision expressed as relative standard deviation was 1.08 % (at 50 μg L{sup -1}), whereas for 300 s of the preconcentration time and a sample frequency of 10 h{sup -1}, the enhancement factor of 357, the detection limit (3s) of 0.069 μg L{sup -1} and the precision of 1.32 % (at 10 μg L{sup -1}) was reported. The accuracy of the developed method was sufficient and evaluated by the analysis of certified reference material IAEA-SL-1 (Lake Sediment) and spiked water samples.

Flow injection on-line spectrophotometric determination of thorium(IV) after preconcentration on XAD-4 resin impregnated with oxytetracycline

International Nuclear Information System (INIS)

Shahida, Shabnam; Khan, Muhammad Haleem; Ali, Akbar

2014-01-01

A very sensitive, selective and simple flow injection time-based method was developed for on-line preconcentration and determination of thorium(IV) at micro g L"-"1 levels in environmental samples. The system operation was based on thorium(IV) ion retention at pH 4.0 in the minicolumn at a flow rate of 15.2 mL min"-"1. The trapped complex was then eluted with 3.6 mol L"-"1 HCl at a flow rate of 4.9 mL min"-"1. The amount of thorium(IV) in the eluate was measured spectrophotometrically at 651 nm using arsenazo-III solution (0.05 % in 3.6 mol L"-"1 HCl stabilized with 1 % triton X-100, 4.9 mL min"-"1) as colorimetric reagent. All chemical, and flow injection variables were optimized for the quantitative preconcentration of metal and a study of interference level of various ions was also carried out. The system offered low backpressure and improved sensitivity and selectivity. At a preconcentration time of 60 s and a sample frequency of 40 h"-"1, the enhancement factor was 97, the detection limit was 0.25 μg L"-"1, and the precision expressed as relative standard deviation was 1.08 % (at 50 μg L"-"1), whereas for 300 s of the preconcentration time and a sample frequency of 10 h"-"1, the enhancement factor of 357, the detection limit (3s) of 0.069 μg L"-"1 and the precision of 1.32 % (at 10 μg L"-"1) was reported. The accuracy of the developed method was sufficient and evaluated by the analysis of certified reference material IAEA-SL-1 (Lake Sediment) and spiked water samples.

Study of process parameters on two phase flow agitated by top blowing lance injection into a bath

Energy Technology Data Exchange (ETDEWEB)

Xia Jiliang; Ahokainen, T.; Holappa, L.

1998-12-31

Numerical investigation has been carried out for two phase flow in a bath agitated by top blowing lance injection. Eulerian two phase flow model is used. Lance immersion depth, injection gas flow rate, nozzle diameter, and bubble size have been systematically changed to examine their influence on the flow characteristics in the bath. It is found that there appear three typical flow patterns: one-vortex, two-vortex, and three-vortex type, with changing the injection gas flow rate or/and the nozzle diameter at moderate lance immersion depth. Predicted velocities are in a good agreement with Iguchi et al.`s experimental data and the main findings are also consistent with the measurements and observations of Chatterjee and Hsiao and Lehner. (orig.) 24 refs. Computational Fluid Dynamics Technology Programme

Functionalized carbon nanotube doping of P3HT:PCBM photovoltaic devices for enhancing short circuit current and efficiency

Directory of Open Access Journals (Sweden)

Rohit Bhatia

2017-03-01

Full Text Available We have successfully functionalized multiwalled carbon nanotubes (MWCNTs using nitrene approach employing the two aryl azides as a precursor for nitrene generation. The dispersion of functionalized MWCNTs has been enhanced in various organic solvents. These functionalized MWCNTs have been successfully doped in various concentrations in the bulk heterojunction (BHJ organic photovoltaic (OPV cells with a poly (3-hexyl thiophene (P3HT and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM photoactive blended layer. The incorporation of MWCNTs with aryl functional groups, in active the layer, results in enhanced performance with respect to a reference cell. The maximum power conversion efficiency of 1.86% is achieved with adduct I while in the case of adduct II it gets double to 2.0% in comparison with a reference cell. This improvement in the device performance is attributed to enhanced exciton dissociation and improved charge transport properties due to the formation of a nanotube percolation network in the photoactive composite layer.

Flow-injection determination of total organic fluorine with off-line defluorination reaction on a solid sorbent bed.

Science.gov (United States)

Musijowski, Jacek; Trojanowicz, Marek; Szostek, Bogdan; da Costa Lima, José Luis Fontes; Lapa, Rui; Yamashita, Hiroki; Takayanagi, Toshio; Motomizu, Shoji

2007-09-26

Considering recent reports on widespread occurrence and concerns about perfluoroalkyl substances (PFAS) in environmental and biological systems, analysis of these compounds have gained much attention in recent years. Majority of analyte-specific methods are based on a LC/MS/MS or a GC/MS detection, however many environmental or biological studies would benefit from a total organic fluorine (TOF) determination. Presented work was aimed at developing a method for TOF determination. TOF is determined as an amount of inorganic fluoride obtained after defluorination reaction conducted off-line using sodium biphenyl reagent directly on the sorbent without elution of retained analytes. Recovered fluoride was analyzed using flow-injection system with either fluorimetric or potentiometric detection. The TOF method was tested using perfluorocarboxylic acids (PFCA), including perfluorooctanoic acid (PFOA), as model compounds. Considering low concentrations of PFAS in natural samples, solid-phase extraction as a preconcentration procedure was evaluated. Several carbon-based sorbents were tested, namely multi-wall carbon nanotubes, carbon nanofibres and activated carbon. Good sorption of all analytes was achieved and defluorination reaction was possible to carry out directly on a sorbent bed. Recoveries obtained for PFCAs, adsorbed on an activated carbon sorbent, and measured as TOF, were 99.5+/-1.7, 110+/-9.4, 95+/-26, 120+/-32, 110+/-12 for C4, C6, C8, C10 and C12-PFCA, respectively. Two flow systems that would enable the defluorination reaction and fluoride determination in a single system were designed and tested.

Non-Darcy flow of water-based carbon nanotubes with nonlinear radiation and heat generation/absorption

Science.gov (United States)

Hayat, T.; Ullah, Siraj; Khan, M. Ijaz; Alsaedi, A.; Zaigham Zia, Q. M.

2018-03-01

Here modeling and computations are presented to introduce the novel concept of Darcy-Forchheimer three-dimensional flow of water-based carbon nanotubes with nonlinear thermal radiation and heat generation/absorption. Bidirectional stretching surface induces the flow. Darcy's law is commonly replace by Forchheimer relation. Xue model is implemented for nonliquid transport mechanism. Nonlinear formulation based upon conservation laws of mass, momentum and energy is first modeled and then solved by optimal homotopy analysis technique. Optimal estimations of auxiliary variables are obtained. Importance of influential variables on the velocity and thermal fields is interpreted graphically. Moreover velocity and temperature gradients are discussed and analyzed. Physical interpretation of influential variables is examined.

Preparation of aligned nanotube membranes for water and gas separation applications

Science.gov (United States)

Lulevich, Valentin; Bakajin, Olgica; Klare, Jennifer E.; Noy, Aleksandr

2016-01-05

Fabrication methods for selective membranes that include aligned nanotubes can advantageously include a mechanical polishing step. The nanotubes have their ends closed off during the step of infiltrating a polymer precursor around the nanotubes. This prevents polymer precursor from flowing into the nanotubes. The polishing step is performed after the polymer matrix is formed, and can open up the ends of the nanotubes.

Transport properties of field effect transistors with randomly networked single walled carbon nanotubes grown by plasma enhanced chemical vapour deposition

International Nuclear Information System (INIS)

Kim, Un Jeong; Park, Wanjun

2009-01-01

The transport properties of randomly networked single walled carbon nanotube (SWNT) transistors with different channel lengths of L c = 2-10 μm were investigated. Randomly networked SWNTs were directly grown for the two different densities of ρ ∼ 25 μm -2 and ρ ∼ 50 μm -2 by water plasma enhanced chemical vapour deposition. The field effect transport is governed mainly by formation of the current paths that is related to the nanotube density. On the other hand, the off-state conductivity deviates from linear dependence for both nanotube density and channel length. The field effect mobility of holes is estimated as 4-13 cm 2 V -1 s -1 for the nanotube transistors based on the simple MOS theory. The mobility is increased for the higher density without meaningful dependence on the channel lengths.

Mathematical modeling of flow-injection techniques and their applications for environmental monitoring

International Nuclear Information System (INIS)

Begum, N.N.; Ahmed, J.

2006-01-01

A classification of the existing mathematical models of flow-injection (FI) manifolds based on the main principles on which they are built, have been proposed. Numerous mathematical models of FI systems employing ideas from different scientific areas (e.g. mathematical statistics, chemical engineering, chromatography) have been developed so far. The models have been compared with respect to their predictive power, the complexity of their mathematical treatment, and the requirements for computation time when applied to single-line, multi-channel and conjugated two-line FI systems. It is concluded that the axially dispersed plug flow model deserves special attention because it offers an acceptable compromise between the conflicting requirements for maximal possible mathematical simplicity and maximal possible precision. Applicability of these existing flow-injection models to single-line, multi-channel and conjugated two-line systems for environmental monitoring have been discussed. (author)

Transverse injection into Mach 2 flow behind a rearward-facing step - A 3-D, compressible flow test case for hypersonic combustor CFD validation

Science.gov (United States)

Mcdaniel, James C.; Fletcher, Douglas G.; Hartfield, Roy J.; Hollo, Steven D.

1991-01-01

A spatially-complete data set of the important primitive flow variables is presented for the complex, nonreacting, 3D unit combustor flow field employing transverse injection into a Mach 2 flow behind a rearward-facing step. A unique wind tunnel facility providing the capability for iodine seeding was built specifically for these measurements. Two optical techniques based on laser-induced-iodine fluorescence were developed and utilized for nonintrusive, in situ flow field measurements. LDA provided both mean and fluctuating velocity component measurements. A thermographic phosphor wall temperature measurement technique was developed and employed. Data from the 2D flow over a rearward-facing step and the complex 3D mixing flow with injection are reported.

Improvement of Power Flow Calculation with Optimization Factor Based on Current Injection Method

Directory of Open Access Journals (Sweden)

Lei Wang

2014-01-01

Full Text Available This paper presents an improvement in power flow calculation based on current injection method by introducing optimization factor. In the method proposed by this paper, the PQ buses are represented by current mismatches while the PV buses are represented by power mismatches. It is different from the representations in conventional current injection power flow equations. By using the combined power and current injection mismatches method, the number of the equations required can be decreased to only one for each PV bus. The optimization factor is used to improve the iteration process and to ensure the effectiveness of the improved method proposed when the system is ill-conditioned. To verify the effectiveness of the method, the IEEE test systems are tested by conventional current injection method and the improved method proposed separately. Then the results are compared. The comparisons show that the optimization factor improves the convergence character effectively, especially that when the system is at high loading level and R/X ratio, the iteration number is one or two times less than the conventional current injection method. When the overloading condition of the system is serious, the iteration number in this paper appears 4 times less than the conventional current injection method.

Electrical Characteristics of Carbon Nanotubes by Plasma and Microwave Surface Treatments

Energy Technology Data Exchange (ETDEWEB)

Cho, Sangjin; Lee, Soonbo; Boo, Jinhyo [Sungkyunkwan Univ., Suwon (Korea, Republic of); Shrestha, Shankar Prasad [Tribhuvan Univ., Kathmandu (Nepal)

2014-03-15

The plasma and microwave surface treatments of carbon nanotubes that loaded on plastic substrates were carried out with expecting a change of carbon nanotube dispersion by increasing treatment time. The microwave treatment process was undergone by commercial microwave oven (800 W). The electrical property was measured by hall measurement and resistance was increased by increasing O{sub 2} flow rate of plasma, suggesting an improvement of carbon nanotube dispersion and a possibility of controlling the resistances of carbon nanotubes by plasma surface treatment. The resistance was increased in both polyethylene terephthalate and polyimide substrates by increasing O{sub 2} flow rate. Resistance changes only slightly with different O{sub 2} flow treatment in measure rho for all polyimide samples. Sheet resistance is lowest in polyimide substrate not due to high carbon nanotube loading but due to tendency to remain in elongated structure. O{sub 2} or N{sub 2} plasma treatments on both polyethylene terephthalate and polyimide substrates lead to increase in sheet resistance.

Electrical Characteristics of Carbon Nanotubes by Plasma and Microwave Surface Treatments

International Nuclear Information System (INIS)

Cho, Sangjin; Lee, Soonbo; Boo, Jinhyo; Shrestha, Shankar Prasad

2014-01-01

The plasma and microwave surface treatments of carbon nanotubes that loaded on plastic substrates were carried out with expecting a change of carbon nanotube dispersion by increasing treatment time. The microwave treatment process was undergone by commercial microwave oven (800 W). The electrical property was measured by hall measurement and resistance was increased by increasing O 2 flow rate of plasma, suggesting an improvement of carbon nanotube dispersion and a possibility of controlling the resistances of carbon nanotubes by plasma surface treatment. The resistance was increased in both polyethylene terephthalate and polyimide substrates by increasing O 2 flow rate. Resistance changes only slightly with different O 2 flow treatment in measure rho for all polyimide samples. Sheet resistance is lowest in polyimide substrate not due to high carbon nanotube loading but due to tendency to remain in elongated structure. O 2 or N 2 plasma treatments on both polyethylene terephthalate and polyimide substrates lead to increase in sheet resistance

Recent Development in Optical Chemical Sensors Coupling with Flow Injection Analysis

Directory of Open Access Journals (Sweden)

Fuensanta Sánchez Rojas

2006-10-01

Full Text Available Optical techniques for chemical analysis are well established and sensors based on thesetechniques are now attracting considerable attention because of their importance in applications suchas environmental monitoring, biomedical sensing, and industrial process control. On the other hand,flow injection analysis (FIA is advisable for the rapid analysis of microliter volume samples and canbe interfaced directly to the chemical process. The FIA has become a widespread automatic analyticalmethod for more reasons; mainly due to the simplicity and low cost of the setups, their versatility, andease of assembling. In this paper, an overview of flow injection determinations by using opticalchemical sensors is provided, and instrumentation, sensor design, and applications are discussed. Thiswork summarizes the most relevant manuscripts from 1980 to date referred to analysis using opticalchemical sensors in FIA.

Coupled Viscous Fluid Flow and Joint Deformation Analysis for Grout Injection in a Rock Joint

Science.gov (United States)

Kim, Hyung-Mok; Lee, Jong-Won; Yazdani, Mahmoud; Tohidi, Elham; Nejati, Hamid Reza; Park, Eui-Seob

2018-02-01

Fluid flow modeling is a major area of interest within the field of rock mechanics. The main objective of this study is to gain insight into the performance of grout injection inside jointed rock masses by numerical modeling of grout flow through a single rock joint. Grout flow has been widely simulated using non-Newtonian Bingham fluid characterized by two main parameters of dynamic viscosity and shear yield strength both of which are time dependent. The increasing value of these properties with injection time will apparently affect the parameters representing the grouting performance including grout penetration length and volumetric injection rate. In addition, through hydromechanical coupling a mutual influence between the injection pressure from the one side and the joint opening/closing behavior and the aperture profile variation on the other side is anticipated. This is capable of producing a considerable impact on grout spread within the rock joints. In this study based on the Bingham fluid model, a series of numerical analysis has been conducted using UDEC to simulate the flow of viscous grout in a single rock joint with smooth parallel surfaces. In these analyses, the time-dependent evolution of the grout fluid properties and the hydromechanical coupling have been considered to investigate their impact on grouting performance. In order to verify the validity of these simulations, the results of analyses including the grout penetration length and the injection flow rate were compared with a well-known analytical solution which is available for the simple case of constant grout properties and non-coupled hydraulic analysis. The comparison demonstrated that the grout penetration length can be overestimated when the time-dependent hardening of grout material is not considered. Moreover, due to the HM coupling, it was shown that the joint opening induced by injection pressure may have a considerable increasing impression on the values of penetration length and

A sensor tip based on carbon nanotube-ink printed electrode for the dengue virus NS1 protein.

Science.gov (United States)

Dias, Ana Carolina M S; Gomes-Filho, Sérgio L R; Silva, Mízia M S; Dutra, Rosa F

2013-06-15

An immunosensor for the non-structural protein 1 (NS1) of the dengue virus based on carbon nanotube-screen printed electrodes (CNT-SPE) was successfully developed. A homogeneous mixture containing carboxylated carbon nanotubes was dispersed in carbon ink to prepare a screen printed working electrode. Anti-NS1 antibodies were covalently linked to CNT-SPE by an ethylenediamine film strategy. Amperometrical responses were generated at -0.5 V vs. Ag/AgCl by hydrogen peroxide reaction with peroxidase (HRP) conjugated to the anti-NS1. An excellent detection limit (in the order of 12 ng mL(-1)) and a sensitivity of 85.59 μA mM(-1)cm(-2) were achieved permitting dengue diagnostic according to the clinical range required. The matrix effect, as well as the performance of the assays, was successfully evaluated using spiked blood serum sample obtaining excellent recovery values in the results. Carbon nanotubes incorporated to the carbon ink improved the reproducibility and sensitivity of the CNT-SPE immunosensor. This point-of-care approach represents a great potential value for use in epidemic situations and can facilitate the early screening of patients in acute phase of dengue virus. Copyright © 2012 Elsevier B.V. All rights reserved.

The efficacy of IntraFlow intraosseous injection as a primary anesthesia technique.

Science.gov (United States)

Remmers, Todd; Glickman, Gerald; Spears, Robert; He, Jianing

2008-03-01

The purpose of this study was to compare the efficacy of intraosseous injection and inferior alveolar (IA) nerve block in anesthetizing mandibular posterior teeth with irreversible pulpitis. Thirty human subjects were randomly assigned to receive either intraosseous injection using the IntraFlow system (Pro-Dex Inc, Santa Ana, CA) or IA block as the primary anesthesia method. Pulpal anesthesia was evaluated via electric pulp testing at 4-minute intervals for 20 minutes. Two consecutive 80/80 readings were considered successful pulpal anesthesia. Anesthesia success or failure was recorded and groups compared. Intraosseous injection provided successful anesthesia in 13 of 15 subjects (87%). The IA block provided successful anesthesia in 9 of 15 subjects (60%). Although this difference was not statistically significant (p = 0.2148), the results of this preliminary study indicate that the IntraFlow system can be used as the primary anesthesia method in teeth with irreversible pulpitis to achieve predictable pulpal anesthesia.

Jet flow analysis of liquid poison injection in a CANDU reactor using source term

International Nuclear Information System (INIS)

Chae, Kyung Myung; Choi, Hang Bok; Rhee, Bo Wook

2001-01-01

For the performance analysis of Canadian deuterium uranium (CANDU) reactor shutdown system number 2 (SDS2), a computational fluid dynamics model of poison jet flow has been developed to estimate the flow field and poison concentration formed inside the CANDU reactor calandria. As the ratio of calandria shell radius over injection nozzle hole diameter is so large (1055), it is impractical to develop a full-size model encompassing the whole calandria shell. In order to reduce the model to a manageable size, a quarter of one-pitch length segment of the shell was modeled using symmetric nature of the jet; and the injected jet was treated as a source term to avoid the modeling difficulty caused by the big difference of the hole sizes. For the analysis of an actual CANDU-6 SDS2 poison injection, the grid structure was determined based on the results of two-dimensional real- and source-jet simulations. The maximum injection velocity of the liquid poison is 27.8 m/s and the mass fraction of the poison is 8000 ppm (mg/kg). The simulation results have shown well-established jet flow field. In general, the jet develops narrowly at first but stretches rapidly. Then, the flow recirculates a little in r-x plane, while it recirculates largely in r-θ plane. As the time goes on, the adjacent jets contact each other and form a wavy front such that the whole jet develops in a plate form. his study has shown that the source term model can be effectively used for the analysis of the poison injection and the simulation result of the CANDU reactor is consistent with the model currently being used for the safety analysis. In the future, it is strongly recommended to analyze the transient (from helium tank to injection nozzle hole) of the poison injection by applying Bernoulli equation with real boundary conditions

Fluoroscopically Guided Extraforaminal Cervical Nerve Root Blocks: Analysis of Epidural Flow of the Injectate with Respect to Needle Tip Position

Science.gov (United States)

Shipley, Kyle; Riew, K. Daniel; Gilula, Louis A.

2013-01-01

Study Design Retrospective evaluation of consecutively performed fluoroscopically guided cervical nerve root blocks. Objective To describe the incidence of injectate central epidural flow with respect to needle tip position during fluoroscopically guided extraforaminal cervical nerve root blocks (ECNRBs). Methods Between February 19, 2003 and June 11, 2003, 132 consecutive fluoroscopically guided ECNRBs performed with contrast media in the final injected material (injectate) were reviewed on 95 patients with average of 1.3 injections per patient. Fluoroscopic spot images documenting the procedure were obtained as part of standard quality assurance. An independent observer not directly involved in the procedures retrospectively reviewed the images, and the data were placed into a database. Image review was performed to determine optimal needle tip positioning for injectate epidural flow. Results Central epidural injectate flow was obtained in only 28.9% of injections with the needle tip lateral to midline of the lateral mass (zone 2). 83.8% of injectate went into epidural space when the needle tip was medial to midline of the lateral mass (zone 3). 100% of injectate flowed epidurally when the needle tip was medial to or at the medial cortex of the lateral mass (zone 4). There was no statistically significant difference with regards to central epidural flow and the needle tip position on lateral view. Conclusion To ensure central epidural flow with ECNRBs one must be prepared to pass the needle tip medial to midplane of the lateral mass or to medial cortex of the lateral mass. Approximately 16% of ECNRBs with needle tip medial to midline of the lateral mass did not flow into epidural space. One cannot claim a nerve block is an epidural block unless epidural flow of injectate is observed. PMID:24494176

Polypyrrole/carbon nanotube nanocomposite enhanced the electrochemical capacitance of flexible graphene film for supercapacitors

Science.gov (United States)

Lu, Xiangjun; Dou, Hui; Yuan, Changzhou; Yang, Sudong; Hao, Liang; Zhang, Fang; Shen, Laifa; Zhang, Luojiang; Zhang, Xiaogang

2012-01-01

The flexible electrodes have important potential applications in energy storage of portable electronic devices for their powerful structural properties. In this work, unique flexible films with polypyrrole/carbon nanotube (PPy/CNT) composite homogeneously distributed between graphene (GN) sheets are successfully prepared by flow-assembly of the mixture dispersion of GN and PPy/CNT. In such layered structure, the coaxial PPy/CNT nanocables can not only enlarge the space between GN sheets but also provide pseudo-capacitance to enhance the total capacitance of electrodes. According to the galvanostatic charge/discharge analysis, the mass and volume specific capacitances of GN-PPy/CNT (52 wt% PPy/CNT) are 211 F g-1 and 122 F cm-3 at a current density of 0.2 A g-1, higher than those of the GN film (73 F g-1 and 79 F cm-3) and PPy/CNT (164 F g-1 and 67 F cm-3). Significantly, the GN-PPy/CNT electrode shows excellent cycling stability (5% capacity loss after 5000 cycles) due to the flexible GN layer and the rigid CNT core synergistical releasing the intrinsic differential strain of PPy chains during long-term charge/discharge cycles.

Development of an automated flow injection analysis system for determination of phosphate in nutrient solutions.

Science.gov (United States)

Karadağ, Sevinç; Görüşük, Emine M; Çetinkaya, Ebru; Deveci, Seda; Dönmez, Koray B; Uncuoğlu, Emre; Doğu, Mustafa

2018-01-25

A fully automated flow injection analysis (FIA) system was developed for determination of phosphate ion in nutrient solutions. This newly developed FIA system is a portable, rapid and sensitive measuring instrument that allows on-line analysis and monitoring of phosphate ion concentration in nutrient solutions. The molybdenum blue method, which is widely used in FIA phosphate analysis, was adapted to the developed FIA system. The method is based on the formation of ammonium Mo(VI) ion by reaction of ammonium molybdate with the phosphate ion present in the medium. The Mo(VI) ion then reacts with ascorbic acid and is reduced to the spectrometrically measurable Mo(V) ion. New software specific for flow analysis was developed in the LabVIEW development environment to control all the components of the FIA system. The important factors affecting the analytical signal were identified as reagent flow rate, injection volume and post-injection flow path length, and they were optimized using Box-Behnken experimental design and response surface methodology. The optimum point for the maximum analytical signal was calculated as 0.50 mL min -1 reagent flow rate, 100 µL sample injection volume and 60 cm post-injection flow path length. The proposed FIA system had a sampling frequency of 100 samples per hour over a linear working range of 3-100 mg L -1 (R 2  = 0.9995). The relative standard deviation (RSD) was 1.09% and the limit of detection (LOD) was 0.34 mg L -1 . Various nutrient solutions from a tomato-growing hydroponic greenhouse were analyzed with the developed FIA system and the results were found to be in good agreement with vanadomolybdate chemical method findings. © 2018 Society of Chemical Industry. © 2018 Society of Chemical Industry.

Structural interpretations of deformation and fracture behavior of polypropylene/multi-walled carbon nanotube composites

International Nuclear Information System (INIS)

Ganss, Martin; Satapathy, Bhabani K.; Thunga, Mahendra; Weidisch, Roland; Poetschke, Petra; Jehnichen, Dieter

2008-01-01

The deformation and crack resistance behavior of polypropylene (PP) multi-walled carbon nanotube (MWNT) composites have been studied and their interrelation to the structural attributes studied by transmission electron microscopy (TEM), atomic force microscopy (AFM), scanning electron microscopy (SEM), wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC) and polarization light microscopy has been discussed. The composites were produced from industrial available MWNT by extrusion melt-mixing and injection-molding. In stress-strain measurements a strong increase in the yield stress and the Young's modulus at low MWNT contents has been observed, which was attributed to an efficient load transfer between the carbon nanotubes and polypropylene matrix through a good polymer-nanotube adhesion as indicated by SEM. The extent of enhancement in mechanical properties above 1.5 wt.% of MWNT decreased due to an apparently increased tendency of clustering of carbon nanotubes. Several theoretical models have been taken into account to explain the mechanical properties and to demonstrate the applicability of such models to the system under investigation. The crack resistance behavior has been studied with the essential work of fracture (EWF) approach based on post-yield fracture mechanics (PYFM) concept. A maximum in the non-essential work of fracture was observed at 0.5 wt.% MWNT demonstrating enhanced toughness compared to pure PP, followed by a sharp decline as the MWNT content was increased to 1.5 wt.% reveals a ductile-to-semi-ductile transition. Studies on the kinetics of crack propagation aspects have revealed a qualitative picture of the nature of such a transition in the fracture modes

Amperometric Carbon Fiber Nitrite Microsensor for In Situ Biofilm Monitoring

Science.gov (United States)

A highly selective needle type solid state amperometric nitrite microsensor based on direct nitrite oxidation on carbon fiber was developed using a simplified fabrication method. The microsensor’s tip diameter was approximately 7 µm, providing a high spatial resolution of at lea...

Facile Synthesis of Ternary Boron Carbonitride Nanotubes

Directory of Open Access Journals (Sweden)

Luo Lijie

2009-01-01

Full Text Available Abstract In this study, a novel and facile approach for the synthesis of ternary boron carbonitride (B–C–N nanotubes was reported. Growth occurred by heating simple starting materials of boron powder, zinc oxide powder, and ethanol absolute at 1150 °C under a mixture gas flow of nitrogen and hydrogen. As substrate, commercial stainless steel foil with a typical thickness of 0.05 mm played an additional role of catalyst during the growth of nanotubes. The nanotubes were characterized by SEM, TEM, EDX, and EELS. The results indicate that the synthesized B–C–N nanotubes exhibit a bamboo-like morphology and B, C, and N elements are homogeneously distributed in the nanotubes. A catalyzed vapor–liquid–solid (VLS mechanism was proposed for the growth of the nanotubes.

An amperometric biosensor based on acetylcholinesterase immobilized onto iron oxide nanoparticles/multi-walled carbon nanotubes modified gold electrode for measurement of organophosphorus insecticides

Energy Technology Data Exchange (ETDEWEB)

Chauhan, Nidhi [Department of Biochemistry, M.D. University, Rohtak 124001, Haryana (India); Pundir, Chandra Shekhar, E-mail: pundircs@rediffmail.com [Department of Biochemistry, M.D. University, Rohtak 124001, Haryana (India)

2011-09-02

Graphical abstract: The stepwise amperometric biosensor fabrication process and immobilized acetylcholinesterase inhibition in pesticide solution. Highlights: {center_dot} Constructed a novel composite material using Fe{sub 3}O{sub 4}NP and c-MWCNT at Au electrode for electrocatalysis. {center_dot} The properties of nanoparticles modified electrodes were studied by SEM, FTIR, CVs and EIS. {center_dot} The biosensor exhibited good sensitivity (0.475 mA {mu}M{sup -1}) {center_dot} The half life of electrode was 2 months. {center_dot} The sensor was suitable for trace detection of OP pesticide residues in milk and water. - Abstract: An acetylcholinesterase (AChE) purified from maize seedlings was immobilized covalently onto iron oxide nanoparticles (Fe{sub 3}O{sub 4}NP) and carboxylated multi walled carbon nanotubes (c-MWCNT) modified Au electrode. An organophosphorus (OP) biosensor was fabricated using this AChE/Fe{sub 3}O{sub 4}/c-MWCNT/Au electrode as a working electrode, Ag/AgCl as standard and Pt wire as an auxiliary electrode connected through a potentiostat. The biosensor was based on inhibition of AChE by OP compounds/insecticides. The properties of nanoparticles modified electrodes were studied by scanning electron microscopy (SEM), Fourier transform infrared (FTIR), cyclic voltammograms (CVs) and electrochemical impedance spectroscopy (EIS). The synergistic action of Fe{sub 3}O{sub 4}NP and c-MWCNT showed excellent electrocatalytic activity at low potential (+0.4 V). The optimum working conditions for the sensor were pH 7.5, 35 deg. C, 600 {mu}M substrate concentration and 10 min for inhibition by pesticide. Under optimum conditions, the inhibition rates of OP pesticides were proportional to their concentrations in the range of 0.1-40 nM, 0.1-50 nM, 1-50 nM and 10-100 nM for malathion, chlorpyrifos, monocrotophos and endosulfan respectively. The detection limits were 0.1 nM for malathion and chlorpyrifos, 1 nM for monocrotophos and 10 nM for endosulfan. The

In situ growth rate measurements during plasma-enhanced chemical vapour deposition of vertically aligned multiwall carbon nanotube films

International Nuclear Information System (INIS)

Joensson, M; Nerushev, O A; Campbell, E E B

2007-01-01

In situ laser reflectivity measurements are used to monitor the growth of multiwalled carbon nanotube (MWCNT) films grown by DC plasma-enhanced chemical vapour deposition (PECVD) from an iron catalyst film deposited on a silicon wafer. In contrast to thermal CVD growth, there is no initial increase in the growth rate; instead, the initial growth rate is high (as much as 10 μm min -1 ) and then drops off rapidly to reach a steady level (2 μm min -1 ) for times beyond 1 min. We show that a limiting factor for growing thick films of multiwalled nanotubes (MWNTs) using PECVD can be the formation of an amorphous carbon layer at the top of the growing nanotubes. In situ reflectivity measurements provide a convenient technique for detecting the onset of the growth of this layer

Effect of mixture ratios and nitrogen carrier gas flow rates on the morphology of carbon nanotube structures grown by CVD

CSIR Research Space (South Africa)

Malgas, GF

2008-02-01

Full Text Available This paper reports on the growth of carbon nanotubes (CNTs) by thermal Chemical Vapour Deposition (CVD) and investigates the effects of nitrogen carrier gas flow rates and mixture ratios on the morphology of CNTs on a silicon substrate by vaporizing...

Flow injection microfluidic device with on-line fluorescent derivatization for the determination of Cr(III) and Cr(VI) in water samples after solid phase extraction

Energy Technology Data Exchange (ETDEWEB)

Peng, Guilong [Key Laboratory of Eco-Environment of Three Gorges Region of Ministry of Education, Chongqing University, Chongqing, 400045 (China); Department of Chemistry, Beijing Key Laboratory of Microanalytical Methods and Instrumentation, Tsinghua University, Beijing, 100084 (China); He, Qiang, E-mail: heqiang0980@163.com [Key Laboratory of Eco-Environment of Three Gorges Region of Ministry of Education, Chongqing University, Chongqing, 400045 (China); Lu, Ying [Department of Mathematics and Physics, Armed Police College, Chengdu, 610213 (China); Huang, Jing [Research Center for Advanced Computation, College of Science, Xihua University, Chengdu, 610039 (China); Lin, Jin-Ming, E-mail: jmlin@mail.tsinghua.edu.cn [Department of Chemistry, Beijing Key Laboratory of Microanalytical Methods and Instrumentation, Tsinghua University, Beijing, 100084 (China)

2017-02-22

In this paper, a rapid and simple method using magnetic multi-walled carbon nanotubes (MWCNTS), as a solid-phase extraction (SPE) sorbent, was successfully developed for extraction and preconcentration trace amounts of Cr(III) in water samples. The synthesized magnetic-MWCNTs nanocomposite was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). A rhodamine derivative (R1) was synthesized and characterized as a highly selective and sensitive fluorescent derivatizing agent for Cr(III). After SPE procedure, Cr(III) analysis was performed by flow injection microfluidic chip with on-line fluorescent derivatization and laser-induced fluorescence (LIF) spectroscopy detection. The parameters, which affected the efficiency of the developed method were investigated and optimized. Under the optimized conditions, the method exhibited a linear dynamic range of 0–10.0 nM, with a detection limit of 0.094 nM and an enrichment factor of 38. Furthermore, real water samples were analyzed and good recoveries were obtained from 91.0 to 101.6%. - Graphical abstract: Flow injection microfluidic device with on-line fluorescent derivatization and detection coupled to LIF. - Highlights: • A highly selective and sensitive derivatizing reagent for Cr(III) was synthesized and characterized. • The magnetic-MWCNTs nanocomposite as a SPE sorbent was successfully synthesized and characterized. • A new portable detection system was developed for microfluidic chip FIA platform.

Contrast-enhanced magnetic resonance angiography: first-pass arterial enhancement as a function of gadolinium-chelate concentration, and the saline chaser volume and injection rate.

Science.gov (United States)

Husarik, Daniela B; Bashir, Mustafa R; Weber, Paul W; Nichols, Eli B; Howle, Laurens E; Merkle, Elmar M; Nelson, Rendon C

2012-02-01

To evaluate the effect of the contrast medium (CM) concentration and the saline chaser volume and injection rate on first-pass aortic enhancement characteristics in contrast-enhanced magnetic resonance angiography using a physiologic flow phantom. Imaging was performed on a 3.0-T magnetic resonance system (MAGNETOM Trio, Siemens Healthcare Solutions, Inc, Erlangen, Germany) using a 2-dimensional fast low angle shot T1-weighted sequence (repetition time, 500 milliseconds; echo time, 1.23 milliseconds; flip angle, 8 degrees; 1 frame/s × 60 seconds). The following CM concentrations injected at 2 mL/s were used with 3 different contrast agents (gadolinium [Gd]-BOPTA, Gd-HP-DO3A, Gd-DTPA): 20 mL of undiluted CM (100%) and 80%, 40%, 20%, 10%, 5%, and 2.5% of the full amount, all diluted in saline to a volume of 20 mL to ensure equal bolus volume. The CM was followed by saline chasers of 20 to 60 mL injected at 2 mL/s and 6 mL/s. Aortic signal intensity (SI) was measured, and normalized SI versus time (SI/Tn) curves were generated. The maximal SI (SI(max)), bolus length, and areas under the SI/Tn curve were calculated. Decreasing the CM concentration from 100% to 40% resulted in a decrease of SI(max) to 86.1% (mean). Further decreasing the CM concentration to 2.5% decreased SI(max) to 5.1% (mean). Altering the saline chaser volume had no significant effect on SI(max). Increasing the saline chaser injection rate had little effect (mean increase, 2.2%) on SI(max) when using ≥40% of CM. There was a larger effect (mean increase, 19.6%) when ≤20% of CM were used. Bolus time length was significantly shorter (P < 0.001), and area under the SI/T(n) curve was significantly smaller (P < 0.01) for the CM protocols followed by a saline chaser injected at 6 mL/s compared with a saline chaser injected at 2 mL/s. With 40% of CM and a fast saline chaser, SImax close to that with undiluted CM can be achieved. An increased saline chaser injection rate has a more pronounced effect on

Amperometric biosensor for total monoamines using a glassy carbon paste electrode modified with human monoamine oxidase B and manganese dioxide particles

International Nuclear Information System (INIS)

Aigner, Maximilian; Telsnig, Dietlind; Teubl, Christian; Ortner, Astrid; Kalcher, Kurt; Macheroux, Peter; Wallner, Silvia; Edmondson, Dale

2015-01-01

We have prepared a biosensor for the determination of the total monoamine content in complex matrices by immobilizing a human monoamine oxidase B (hMAO B) on a glassy carbon paste electrode and adding manganese dioxide microparticles as the mediator. The enzyme hMAO B (expressed in Pichia pastoris and immobilized by using a dialysis membrane) catalyzes the oxidative deamination of monoamines, and this results in the formation of the corresponding aldehyde, ammonia and hydrogen peroxide. The latter was detected at pH 7.5 at a working voltage of 400 mV (vs. Ag/AgCl) by differential pulse voltammetry and amperometrically by applying flow injection analysis. Analytical parameters were established by using phenylethylamine (PEA) as a standard substrate. Peak height and concentration of PEA are linearly related in the 0.5 to 150 μg mL −1 concentration range, and the limits of detection and of quantification are 0.15 and 0.5 μg mL −1 of PEA, respectively. Substrate specificity was investigated with different monoamines including PEA, serotonin, benzylamine, dopamine, tyramine, and norepinephrine. The applicability of the biosensor was successfully tested in a commercial fish sauce that served as a complex matrix. The total monoamine content was calculated as PEA-equivalents. (author)

Enhanced field emission properties of tilted graphene nanoribbons on aggregated TiO{sub 2} nanotube arrays

Energy Technology Data Exchange (ETDEWEB)

Hung, Shang-Chao, E-mail: schung99@gmail.com [Department of Information Technology & Communication, Shih Chien University Kaohsiung Campus, Neimen, Kaohsiung 845, Taiwan (China); Chen, Yu-Jyun [Graduate Institute of Electro-Optical Engineering & Department of Electronic Engineering, National Taiwan University of Science and Technology, Taipei 106, Taiwan (China)

2016-07-15

Highlights: • Graphene nanoribbons (GNBs) slanted on aggregate TiO{sub 2} nanotube (A-TNTs) as field-emitters. • Turn-on electric field and field enhancement factor β are dependent on the substrate morphology. • Various quantities of GNRs are deposited on top of A-TNTs (GNRs/A-TNTs) with different morphologies. • With an increase of GNBs compositions, the specimens' turn-on electric field is reduced to 2.8 V/μm. • The field enhancement factor increased rapidly to about 1964 with the addition of GNRs. - Abstract: Graphene nanoribbons (GNRs) slanted on aggregate TiO{sub 2} nanotube arrays (A-TNTs) with various compositions as field-emitters are reported. The morphology, crystalline structure, and composition of the as-obtained specimens were characterized by field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD) and Raman spectrometry. The dependence of the turn-on electric field and the field enhancement factor β on substrate morphology was studied. An increase of GNRs reduces the specimens’ turn-on electric field to 2.8 V/μm and the field enhancement factor increased rapidly to about 1964 with the addition of GNRs. Results show a strong dependence of the field emission on GNR composition aligned with the gradient on the top of the A-TNT substrate. Enhanced FE properties of the modified TNTs can be mainly attributed to their improved electrical properties and rougher surface morphology.

Nanocomposite fibers and film containing polyolefin and surface-modified carbon nanotubes

Science.gov (United States)

Chu,Benjamin; Hsiao, Benjamin S.

2010-01-26

Methods for modifying carbon nanotubes with organic compounds are disclosed. The modified carbon nanotubes have enhanced compatibility with polyolefins. Nanocomposites of the organo-modified carbon nanotubes and polyolefins can be used to produce both fibers and films having enhanced mechanical and electrical properties, especially the elongation-to-break ratio and the toughness of the fibers and/or films.

Plasma-activated multi-walled carbon nanotube-polystyrene composite substrates for biosensing

International Nuclear Information System (INIS)

Fernandez-Sanchez, Cesar; Orozco, Jahir; Jimenez-Jorquera, Cecilia; Pellicer, Eva; Lechuga, Laura M; Mendoza, Ernest

2009-01-01

Carbon nanotube-polymer composites have shown to be suitable materials for the fabrication of electrochemical transducers. The exposed surface of these materials is commonly passivated by a very thin layer of the polymer component that buries the conductive carbon particles. Working with multi-walled carbon nanotube-polystyrene (MWCNT-PS) composite structures, it was previously described how a simple low power oxygen plasma process produced an effective etching of the composite surface, thereby exposing the conductive surface of CNTs. This work shows how this plasma process not only gave rise to a suitable composite conductive surface for electrochemical sensing but simultaneously exposed and created a high density of oxygen-containing functional groups at both the CNT and the PS components, without affecting the material's mechanical stability. These chemical groups could be effectively modified for the stable immobilization of biological receptors. A detailed chemical characterization of the plasma-activated composite surface was possible using x-ray photoelectron spectroscopy. The material reactivity towards the tethering of a protein was studied and protein-protein interactions were then evaluated on the modified composite transducers by scanning electron microscopy. Finally, an amperometric immunosensor approach for the detection of rabbit Immunoglobulin G target analyte was described and a minimum concentration of 3 ng ml -1 was easily measured.

Plasma-activated multi-walled carbon nanotube-polystyrene composite substrates for biosensing

Energy Technology Data Exchange (ETDEWEB)

Fernandez-Sanchez, Cesar; Orozco, Jahir; Jimenez-Jorquera, Cecilia [Instituto de Microelectronica de Barcelona, IMB-CNM (CSIC), Campus UAB, E-08193 Bellaterra, Barcelona (Spain); Pellicer, Eva; Lechuga, Laura M; Mendoza, Ernest, E-mail: cesar.fernandez@imb-cnm.csic.e [Nanobiosensors and Molecular Nanobiophysics Group, Research Center on Nanoscience and Nanotechnology (CIN2) CSIC-ICN, ETSE, Campus UAB-Edificio Q, E-08193 Bellaterra, Barcelona (Spain)

2009-08-19

Carbon nanotube-polymer composites have shown to be suitable materials for the fabrication of electrochemical transducers. The exposed surface of these materials is commonly passivated by a very thin layer of the polymer component that buries the conductive carbon particles. Working with multi-walled carbon nanotube-polystyrene (MWCNT-PS) composite structures, it was previously described how a simple low power oxygen plasma process produced an effective etching of the composite surface, thereby exposing the conductive surface of CNTs. This work shows how this plasma process not only gave rise to a suitable composite conductive surface for electrochemical sensing but simultaneously exposed and created a high density of oxygen-containing functional groups at both the CNT and the PS components, without affecting the material's mechanical stability. These chemical groups could be effectively modified for the stable immobilization of biological receptors. A detailed chemical characterization of the plasma-activated composite surface was possible using x-ray photoelectron spectroscopy. The material reactivity towards the tethering of a protein was studied and protein-protein interactions were then evaluated on the modified composite transducers by scanning electron microscopy. Finally, an amperometric immunosensor approach for the detection of rabbit Immunoglobulin G target analyte was described and a minimum concentration of 3 ng ml{sup -1} was easily measured.

Enhancement of pool boiling heat transfer coefficients using carbon nanotubes

International Nuclear Information System (INIS)

Park, Ki Jung; Jung, Dong Soo

2007-01-01

In this study, the effect of carbon nanotubes (CNTs) on nucleate boiling heat transfer is investigated. Three refrigerants of R22, R123, R134a, and water were used as working fluids and 1.0 vol.% of CNTs was added to the working fluids to examine the effect of CNTs. Experimental apparatus was composed of a stainless steel vessel and a plain horizontal tube heated by a cartridge heater. All data were obtained at the pool temperature of 7 .deg. C for all refrigerants and 100 .deg. C for water in the heat flux range of 10∼80 kW/m 2 . Test results showed that CNTs increase nucleate boiling heat transfer coefficients for all fluids. Especially, large enhancement was observed at low heat fluxes of less than 30 kW/m 2 . With increasing heat flux, however, the enhancement was suppressed due to vigorous bubble generation. Fouling on the heat transfer surface was not observed during the course of this study. Optimum quantity and type of CNTs and their dispersion should be examined for their commercial application to enhance nucleate boiling heat transfer in many applications

Polyaniline/carbon nanotube/CdS quantum dot composites with enhanced optical and electrical properties

Energy Technology Data Exchange (ETDEWEB)

Goswami, Mrinmoy [Department of Physics, National Institute of Technology, Durgapur, 713209 (India); Ghosh, Ranajit, E-mail: ghosh.ranajit@gmail.com [CSIR-Central Mechanical Engineering Research Institute, Durgapur, 713209 (India); Maruyama, Takahiro [Department of Applied Chemistry, Meijo University, Nagoya, 4688502 (Japan); Meikap, Ajit Kumar [Department of Physics, National Institute of Technology, Durgapur, 713209 (India)

2016-02-28

Graphical abstract: - Highlights: • A new kind of polyaniline/carbon nanotube/CdS quantum dot composites have been synthesized via in-situ polymerization of aniline monomer. • A degree of increase in conductivity. • Size-dependent optical properties of CdS quantum dots have been observed. - Abstract: A new kind of polyaniline/carbon nanotube/CdS quantum dot composites have been developed via in-situ polymerization of aniline monomer in the presence of dispersed CdS quantum dots (size: 2.7–4.8 nm) and multi-walled carbon nanotubes (CNT), which exhibits enhanced optical and electrical properties. The existences of 1st order, 2nd order, and 3rd order longitudinal optical phonon modes, strongly indicate the high quality of synthesized CdS quantum dots. The occurrence of red shift of free exciton energy in photoluminescence is due to size dependent quantum confinement effect of CdS. The conductivity of the composites (for example PANI/CNT/CdS (2 wt.% CdS)) is increased by about 7 of magnitude compared to that of pure PANI indicating a charge transfer between CNT and polymer via CdS quantum dots. This advanced material has a great potential for high-performance of electro-optical applications.

Home-Made Micro Valve for Determining Malachite Green Dye by Flow Injection Analysis

Directory of Open Access Journals (Sweden)

Amal Saadoon Majeed

2017-07-01

Full Text Available The research is included studying and designing micro flow injection system which is characterized with rapidity, simplicity, and low cost for the determination of green malachite dye. The study of flow rate of carrier stream, repeatability, dispersion coefficient, and calibration graph are conducted. It is found that the optimum conditions for the determination of mentioned dye are flow rate 4.200 mL/min, sampling rate 102 sample/h, limit of detection 0.05 ppm, linear range (0.05-18.00 ppm with linearity (R2=0.9700, RSD is 0.355, the repeatability for seven successive injections is studied for the two concentrations 5 ppm and 12 ppm, and the dispersion coefficient values are 1.73 and 1.28 at the two concentrations 2 ppm and 9 ppm respectively.

Synthesis and growth mechanism of Fe-catalyzed carbon nanotubes by plasma-enhanced chemical vapor deposition

International Nuclear Information System (INIS)

Jiang Jun; Feng Tao; Cheng Xinhong; Dai Lijuan; Cao Gongbai; Jiang Bingyao; Wang Xi; Liu Xianghuai; Zou Shichang

2006-01-01

Plasma-enhanced chemical vapor deposition (PECVD) was used to grow Fe-catalyzed carbon nanotubes (CNTs). The nanotubes had a uniform diameter in the range of about 10-20 nm. A base growth mode was responsible for the CNTs growth using a mixture of H 2 (60 sccm) and C 2 H 2 (15 sccm). For a mixture of H 2 (100 sccm) and C 2 H 2 (25 sccm), a complicated growth mechanism took place involving both the base growth and the tip growth. X-ray photoelectron spectroscopy measurements revealed that the grown CNTs contained C-H covalent bonds and Fe-C bonds located at the interface between them and the substrates. The factors determining the growth mechanism of CNTs are discussed and their growth mechanisms with the different gas ratios are suggested

Stopped-flow injection spectrophotometric method for determination of chlorate in soil

Directory of Open Access Journals (Sweden)

Jaroon Jakmunee

2008-06-01

Full Text Available A stopped-flow injection (FI spectrophotometric procedure based on iodometric reaction for the determination of chlorate has been developed. Standard/sample was injected into a stream of potassium iodide solution and then merged with a stream of hydrochloric acid solution to produce triiodide. By stopping the flow while the sample zone is being in a mixing coil, a slow reaction of chlorate with iodide in acidic medium was promoted to proceed with minimal dispersion of the triiodide product zone. When the flow started again, a concentrated product zone was pushed into a flow cell and a signal profile due to light absorption of the product was recorded. Employing a lab-built semi-automatic stopped-FI analyser, the analysis can be performed with higher degree of automation and low chemical consumption. Linear calibration graph in the range of 5-50 mg ClO3- L-1 was obtained, with detection limit of 1.4 mg ClO3- L-1. Relative standard deviation of 2.2% (30 mg ClO3- L-1, n=10 and sample throughput of about 20 h-1 were achieved. The system was applied to soil samples and validated by batch spectrophotometric and standard titrimetric methods.

Novel polypropylene biocomposites reinforced with carbon nanotubes and hydroxyapatite nanorods for bone replacements

Energy Technology Data Exchange (ETDEWEB)

Liao, Cheng Zhu; Li, Kai [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon (Hong Kong); Wong, Hoi Man; Tong, Wing Yin; Yeung, Kelvin Wai Kwok [Department of Orthopedics and Traumatology, The University of Hong Kong (Hong Kong); Tjong, Sie Chin, E-mail: aptjong@cityu.edu.hk [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon (Hong Kong)

2013-04-01

Multi-walled carbon nanotubes (MWNTs) of 0.1 and 0.3 wt.% and hydoxyapatite nanorods (nHAs) of 8–20 wt.% were incorporated into polypropylene (PP) to form biocomposites using melt-compounding and injection molding techniques. The structural, mechanical, thermal and in vitro cell responses of the PP/MWNT–nHA hybrids were investigated. Tensile and impact tests demonstrated that the MWNT additions are beneficial in enhancing the stiffness, tensile strength and impact toughness of the PP/nHA nanocomposites. According to thermal analysis, the nHA and MWNT fillers were found to be very effective to improve dimensional and thermal stability of PP. The results of osteoblast cell cultivation and dimethyl thiazolyl diphenyl tetrazolium (MTT) tests showed that the PP/MWNT–nHA nanocomposites are biocompatible. Such novel PP/MWNT–nHA hybrids are considered to be potential biomaterials for making orthopedic bone implants. - Highlights: ► Multiwalled carbon nanotubes (MWNTs) and hydroxyapatite nanorods (nHA) are used as hybrid fillers to reinforce polypropylene. ► MWNT additions are beneficial in enhancing tensile strength and stiffness of PP/nHA composites. ► Hybridizing MWNT with nHA fillers enhance thermal and dimensional stability of PP significantly. ► Hybridizing MWNT with nHA greatly enhance osteoblast adhesion and proliferation. ► PP/MWNT–nHA composites show attractive applications as load-bearing materials in orthopedics.

Numerical study of the enhancement of combustion performance in a scramjet combustor due to injection of electric-discharge-activated oxygen molecules

International Nuclear Information System (INIS)

Starik, A M; Bezgin, L V; Kopchenov, V I; Loukhovitski, B I; Sharipov, A S; Titova, N S

2013-01-01

A comprehensive analysis of the efficiency of an approach based on the injection of a thin oxygen stream, subjected to a tailored electric discharge, into a supersonic H 2 –air flow to enhance the combustion performance in the mixing layer and in the scramjet combustor is conducted. It is shown that for such an approach there exist optimal values of reduced electric field E/N and transversal dimension d of the injected oxygen stream, which provide the minimal length of induction zone in the mixing layer. The optimal values of E/N and d depend on air flow parameters and the specific energy put into the oxygen. The injection of a thin oxygen stream (d = 1 mm) subjected to an electric discharge with E/N = 50–100 Td, which produces mostly singlet oxygen O 2 (a  1 Δ g ) and O 2 (b 1 Σ g + ) molecules and atomic oxygen, allows one to arrange stable combustion in a scramjet duct at an extremely low air temperature T air  = 900 K and pressure P air  = 0.3 bar even at a small specific energy put into the oxygen E s  = 0.2 J ncm −3 , and to provide rather high combustion completeness η = 0.73. The advance in the energy released during combustion is much higher (hundred times), in this case, than the energy supplied to the oxygen stream in the electric discharge. This approach also makes it possible to ensure the rather high combustion completeness in the scramjet combustor with reduced length. The main reason for the combustion enhancement of the H 2 –air mixture in the scramjet duct is the intensification of chain-branching reactions due to the injection of a small amount of cold non-equilibrium oxygen plasma comprising highly reactive species, O 2 (a  1 Δ g ) and O 2 (b 1 Σ g + ) molecules and O atoms, into the H 2 –air supersonic flow. (paper)

Continuous-Flow Production of Injectable Liposomes via a Microfluidic Approach

Science.gov (United States)

Zizzari, Alessandra; Bianco, Monica; Perrone, Elisabetta; Amato, Francesco; Maruccio, Giuseppe; Rendina, Filippo; Arima, Valentina

2017-01-01

Injectable liposomes are characterized by a suitable size and unique lipid mixtures, which require time-consuming and nonstraightforward production processes. The complexity of the manufacturing methods may affect liposome solubility, the phase transition temperatures of the membranes, the average particle size, and the associated particle size distribution, with a possible impact on the drug encapsulation and release. By leveraging the precise steady-state control over the mixing of miscible liquids and a highly efficient heat transfer, microfluidic technology has proved to be an effective and direct methodology to produce liposomes. This approach results particularly efficient in reducing the number of the sizing steps, when compared to standard industrial methods. Here, Microfluidic Hydrodynamic Focusing chips were produced and used to form liposomes upon tuning experimental parameters such as lipids concentration and Flow-Rate-Ratios (FRRs). Although modelling evidenced the dependence of the laminar flow on the geometric constraints and the FRR conditions, for the specific formulation investigated in this study, the lipids concentration was identified as the primary factor influencing the size of the liposomes and their polydispersity index. This was attributed to a predominance of the bending elasticity modulus over the vesiculation index in the lipid mixture used. Eventually, liposomes of injectable size were produced using microfluidic one-pot synthesis in continuous flow. PMID:29232873

Evaluation of permselective membranes for optimization of intracerebral amperometric glutamate biosensors

NARCIS (Netherlands)

Wahono, N.; Qin, S.; Oomen, P.; Cremers, T. I. F.; de Vries, M. G.; Westerink, B. H. C.

2012-01-01

Monitoring of extracellular brain glutamate concentrations by intracerebral biosensors is a promising approach to further investigate the role of this important neurotransmitter. However, amperometric biosensors are typically hampered by Faradaic interference caused by the presence of other

An Effective Amperometric Biosensor Based on Gold Nanoelectrode Arrays

Directory of Open Access Journals (Sweden)

Zhu Yingchun

2008-01-01

Full Text Available Abstract A sensitive amperometric biosensor based on gold nanoelectrode array (NEA was investigated. The gold nanoelectrode array was fabricated by template-assisted electrodeposition on general electrodes, which shows an ordered well-defined 3D structure of nanowires. The sensitivity of the gold NEA to hydrogen peroxide is 37 times higher than that of the conventional electrode. The linear range of the platinum NEA toward H2O2is from 1 × 10−6to 1 × 10−2 M, covering four orders of magnitudes with detection limit of 1 × 10−7 M and a single noise ratio (S/N of four. The enzyme electrode exhibits an excellent response performance to glucose with linear range from 1 × 10−5to 1 × 10−2 M and a fast response time within 8 s. The Michaelis–Menten constantkm and the maximum current densityi maxof the enzyme electrode were 4.97 mM and 84.60 μA cm−2, respectively. This special nanoelectrode may find potential application in other biosensors based on amperometric signals.

Carbon nanotube-graphene composite film as transparent conductive electrode for GaN-based light-emitting diodes

KAUST Repository

Kang, Chun Hong

2016-08-23

Transparent conductive electrodes (TCE) made of carbon nanotube (CNT) and graphene composite for GaN-based light emitting diodes (LED) are presented. The TCE with 533-Ω/□ sheet resistance and 88% transmittance were obtained when chemical-vapor-deposition grown graphene was fused across CNT networks. With an additional 2-nm thin NiOx interlayer between the TCE and top p-GaN layer of the LED, the forward voltage was reduced to 5.12 V at 20-mA injection current. Four-fold improvement in terms of light output power was observed. The improvement can be ascribed to the enhanced lateral current spreading across the hybrid CNT-graphene TCE before injection into the p-GaN layer.

Carbon nanotube-graphene composite film as transparent conductive electrode for GaN-based light-emitting diodes

KAUST Repository

Kang, Chun Hong; Shen, Chao; M. Saheed, M. Shuaib; Mohamed, Norani Muti; Ng, Tien Khee; Ooi, Boon S.; Burhanudin, Zainal Arif

2016-01-01

Transparent conductive electrodes (TCE) made of carbon nanotube (CNT) and graphene composite for GaN-based light emitting diodes (LED) are presented. The TCE with 533-Ω/□ sheet resistance and 88% transmittance were obtained when chemical-vapor-deposition grown graphene was fused across CNT networks. With an additional 2-nm thin NiOx interlayer between the TCE and top p-GaN layer of the LED, the forward voltage was reduced to 5.12 V at 20-mA injection current. Four-fold improvement in terms of light output power was observed. The improvement can be ascribed to the enhanced lateral current spreading across the hybrid CNT-graphene TCE before injection into the p-GaN layer.

Polymerization initated at sidewalls of carbon nanotubes

Science.gov (United States)

Tour, James M. (Inventor); Hudson, Jared L. (Inventor); Krishnamoorti, Ramanan (Inventor); Yurekli, Koray (Inventor); Mitchell, Cynthia A. (Inventor)

2011-01-01

The present invention is directed to aryl halide (such as aryl bromide) functionalized carbon nanotubes that can be utilized in anionic polymerization processes to form polymer-carbon nanotube materials with improved dispersion ability in polymer matrices. In this process the aryl halide is reacted with an alkyllithium species or is reacted with a metal to replace the aryl-bromine bond with an aryl-lithium or aryl-metal bond, respectively. It has further been discovered that other functionalized carbon nanotubes, after deprotonation with a deprotonation agent, can similarly be utilized in anionic polymerization processes to form polymer-carbon nanotube materials. Additionally or alternatively, a ring opening polymerization process can be performed. The resultant materials can be used by themselves due to their enhanced strength and reinforcement ability when compared to their unbound polymer analogs. Additionally, these materials can also be blended with pre-formed polymers to establish compatibility and enhanced dispersion of nanotubes in otherwise hard to disperse matrices resulting in significantly improved material properties. The resultant polymer-carbon nanotube materials can also be used in drug delivery processes due to their improved dispersion ability and biodegradability, and can also be used for scaffolding to promote cellular growth of tissue.

A Conductive Porous Structured Chitosan-grafted Polyaniline Cryogel for use as a Sialic Acid Biosensor

International Nuclear Information System (INIS)

Fatoni, Amin; Numnuam, Apon; Kanatharana, Proespichaya; Limbut, Warakorn; Thavarungkul, Panote

2014-01-01

Highlights: • A novel chitosan grafted polyaniline cryogel was used as support for a highly stable and sensitive biosensor. • The use of two enzymes mediated with ferrocene showed a high selectivity for sialic acid. • The biosensor provided a rapid sialic acid detection in blood. - Abstract: A porous conductive supporting material base on chitosan grafted polyaniline (CPANI) cryogel was developed for the fabrication of a sialic acid biosensor. Two enzymes, N-acetylneuraminic acid aldolase (NAL) and pyruvate oxidase (PYO), were employed together with an electrochemical detector. The electron transfer was further enhanced by using multiwalled carbon nanotubes (MWCNTs) and mediated by ferrocene (Fc) entrapped in the cryogel pores wall. A sialic acid derived electroactive product was detected amperometrically in a flow injection system. The fabricated sialic acid biosensor provided excellent analytical performances with a wide linear range of 0.025 to 15.0 mM and a limit of detection of 18 μM. Under the low applied potential of 0.20 V versus a Ag/AgCl, common electroactive interfering compounds such as ascorbic acid, uric acid and pyruvic acid were not detected and they have no effect on the analysis of sialic acid. The fabricated sialic acid biosensor also demonstrated a high stability after up to 100 injections. The reliability of the biosensor to detect sialic acid in blood plasma was in good agreement (P > 0.05) with a standard periodic-resorcinol spectrophotometric method. This easy to prepare conductive and biocompatible porous structure should be a prospective supporting material for biosensor development

Stability Analysis of High-Speed Boundary-Layer Flow with Gas Injection

Science.gov (United States)

2014-06-01

laminar-turbulent transition on slender bodies in a hypersonic flow at small angles of attack is caused by amplification of acoustic waves trapped in...x decreases and slowly approaches the no-blow distribution. These CFD data demonstrate that the injection strongly affects the near-wall flow...conclusion. Figure 10 shows that the spatial growth rates ( )  are maximal for mode 0 corresponding to the Mack second mode – typical for hypersonic

Water-processed carbon nanotube/graphene hybrids with enhanced field emission properties

International Nuclear Information System (INIS)

Song, Meng; Xu, Peng; Wang, Xu; Wu, Huizhen; Wang, Miao; Song, Yenan; Li, Zhenhua; Zhao, Pei; Shang, Xuefu

2015-01-01

Integrating carbon nanotubes (CNTs) and graphene into hybrid structures provides a novel approach to three dimensional (3D) materials with advantageous properties. Here we present a water-processing method to create integrated CNT/graphene hybrids and test their field emission properties. With an optimized mass ratio of CNTs to graphene, the hybrid shows a significantly enhanced field emission performance, such as turn-on electric field of 0.79 V/μm, threshold electric field of 1.05 V/μm, maximum current density of 0.1 mA/cm 2 , and field enhancement factor of ∼1.3 × 10 4 . The optimized mass ratio for field emission emphasizes the importance of both CNTs and graphene in the hybrid. We also hypothesize a possible mechanism for this enhanced field emission performance from the CNT/graphene hybrid. During the solution treatment, graphene oxide behaves as surfactant sheets for CNTs to form a well dispersed solution, which leads to a better organized 3D structure with more conducting channels for electron transport

Water-processed carbon nanotube/graphene hybrids with enhanced field emission properties

Energy Technology Data Exchange (ETDEWEB)

Song, Meng; Xu, Peng; Wang, Xu; Wu, Huizhen; Wang, Miao, E-mail: peizhao@zju.edu.cn, E-mail: miaowang@css.zju.edu.cn [Department of Physics, Zhejiang University, Hangzhou 310027 (China); Song, Yenan; Li, Zhenhua; Zhao, Pei, E-mail: peizhao@zju.edu.cn, E-mail: miaowang@css.zju.edu.cn [Institute of Applied Mechanics, Zhejiang University, Hangzhou 310027 (China); Shang, Xuefu [Department of Physics, Faculty of Science, Jiangsu University, Zhenjiang 212013 (China)

2015-09-15

Integrating carbon nanotubes (CNTs) and graphene into hybrid structures provides a novel approach to three dimensional (3D) materials with advantageous properties. Here we present a water-processing method to create integrated CNT/graphene hybrids and test their field emission properties. With an optimized mass ratio of CNTs to graphene, the hybrid shows a significantly enhanced field emission performance, such as turn-on electric field of 0.79 V/μm, threshold electric field of 1.05 V/μm, maximum current density of 0.1 mA/cm{sup 2}, and field enhancement factor of ∼1.3 × 10{sup 4}. The optimized mass ratio for field emission emphasizes the importance of both CNTs and graphene in the hybrid. We also hypothesize a possible mechanism for this enhanced field emission performance from the CNT/graphene hybrid. During the solution treatment, graphene oxide behaves as surfactant sheets for CNTs to form a well dispersed solution, which leads to a better organized 3D structure with more conducting channels for electron transport.

Theoretical considerations of Flow Injection Analysis in the Absence of Chemical Reactions

DEFF Research Database (Denmark)

Andersen, Jens Enevold Thaulov

2000-01-01

The fundamental mechanism of flow injection analysis (FIA) is assumed to be simple dissusion and the response of the detector is included in a model description that provide information about the shape of the FIA peak in terms of, basically, five parameters. Two of the five parameters are associa...... that any deviation from the features of the present model and the results of a tentative chemical reaction with one of the test compounds, is related to chemical kinetics.......The fundamental mechanism of flow injection analysis (FIA) is assumed to be simple dissusion and the response of the detector is included in a model description that provide information about the shape of the FIA peak in terms of, basically, five parameters. Two of the five parameters...

Silicon nanotube field effect transistor with core-shell gate stacks for enhanced high-performance operation and area scaling benefits

KAUST Repository

Fahad, Hossain M.; Smith, Casey; Rojas, Jhonathan Prieto; Hussain, Muhammad Mustafa

2011-01-01

We introduce the concept of a silicon nanotube field effect transistor whose unique core-shell gate stacks help achieve full volume inversion by giving a surge in minority carrier concentration in the near vicinity of the ultrathin channel and at the same time rapid roll-off at the source and drain junctions constituting velocity saturation-induced higher drive current-enhanced high performance per device with efficient real estate consumption. The core-shell gate stacks also provide superior short channel effects control than classical planar metal oxide semiconductor field effect transistor (MOSFET) and gate-all-around nanowire FET. The proposed device offers the true potential to be an ideal blend for quantum ballistic transport study of device property control by bottom-up approach and high-density integration compatibility using top-down state-of-the-art complementary metal oxide semiconductor flow. © 2011 American Chemical Society.

Silicon nanotube field effect transistor with core-shell gate stacks for enhanced high-performance operation and area scaling benefits

KAUST Repository

Fahad, Hossain M.

2011-10-12

We introduce the concept of a silicon nanotube field effect transistor whose unique core-shell gate stacks help achieve full volume inversion by giving a surge in minority carrier concentration in the near vicinity of the ultrathin channel and at the same time rapid roll-off at the source and drain junctions constituting velocity saturation-induced higher drive current-enhanced high performance per device with efficient real estate consumption. The core-shell gate stacks also provide superior short channel effects control than classical planar metal oxide semiconductor field effect transistor (MOSFET) and gate-all-around nanowire FET. The proposed device offers the true potential to be an ideal blend for quantum ballistic transport study of device property control by bottom-up approach and high-density integration compatibility using top-down state-of-the-art complementary metal oxide semiconductor flow. © 2011 American Chemical Society.

Flutter and divergence instability of supported piezoelectric nanotubes conveying fluid

Science.gov (United States)

Bahaadini, Reza; Hosseini, Mohammad; Jamali, Behnam

2018-01-01

In this paper, divergence and flutter instabilities of supported piezoelectric nanotubes containing flowing fluid are investigated. To take the size effects into account, the nonlocal elasticity theory is implemented in conjunction with the Euler-Bernoulli beam theory incorporating surface stress effects. The Knudsen number is applied to investigate the slip boundary conditions between the flow and wall of nanotube. The nonlocal governing equations of nanotube are obtained using Newtonian method, including the influence of piezoelectric voltage, surface effects, Knudsen number and nonlocal parameter. Applying Galerkin approach to transform resulting equations into a set of eigenvalue equations under the simple-simple (S-S) and clamped-clamped (C-C) boundary conditions. The effects of the piezoelectric voltage, surface effects, Knudsen number, nonlocal parameter and boundary conditions on the divergence and flutter boundaries of nanotubes are discussed. It is observed that the fluid-conveying nanotubes with both ends supported lose their stability by divergence first and then by flutter with increase in fluid velocity. Results indicate the importance of using piezoelectric voltage, nonlocal parameter and Knudsen number in decrease of critical flow velocities of system. Moreover, the surface effects have a significant role on the eigenfrequencies and critical fluid velocity.

Electroluminescence from single-wall carbon nanotube network transistors.

Science.gov (United States)

Adam, E; Aguirre, C M; Marty, L; St-Antoine, B C; Meunier, F; Desjardins, P; Ménard, D; Martel, R

2008-08-01

The electroluminescence (EL) properties from single-wall carbon nanotube network field-effect transistors (NNFETs) and small bundle carbon nanotube field effect transistors (CNFETs) are studied using spectroscopy and imaging in the near-infrared (NIR). At room temperature, NNFETs produce broad (approximately 180 meV) and structured NIR spectra, while they are narrower (approximately 80 meV) for CNFETs. EL emission from NNFETs is located in the vicinity of the minority carrier injecting contact (drain) and the spectrum of the emission is red shifted with respect to the corresponding absorption spectrum. A phenomenological model based on a Fermi-Dirac distribution of carriers in the nanotube network reproduces the spectral features observed. This work supports bipolar (electron-hole) current recombination as the main mechanism of emission and highlights the drastic influence of carrier distribution on the optoelectronic properties of carbon nanotube films.

Carbon nanotubes-assisted polyacrylamide gel electrophoresis for enhanced separation of human serum proteins and application in liverish diagnosis.

Science.gov (United States)

Jiang, Fubin; Wang, Yanan; Hu, Xinfang; Shao, Na; Na, Na; Delanghe, Joris R; Ouyang, Jin

2010-11-01

The application of pore-gradient polyacrylamide gel electrophoresis (PG-PAGE) incorporated with carbon nanotube modified by Triton X-100 and carboxylation so as to improve the separation of human serum proteins is reported. The novel PG-PAGE was made by adding water-soluble single-walled carbon nanotubes (CNTs) when preparing the polyacrylamide gel. Significant improvements in separation of complement C3 protein and haptoglobin (Hp) in human serum were achieved. It was estimated that the interactions between the hydrophilic groups on the proteins and the surface of the CNTs result in different adsorption kinetics of complement C3 and Hp subtype on the nanoparticles incorporated in the gel, thus enhancing the separation of the two proteins in serum. This new CNT matrix-assisted PG-PAGE method for enhanced separation of complement C3 and Hp in human serum was successfully applied to distinguish the samples from liverish patients and healthy people.

Chemical Reaction and Flow Modeling in Fullerene and Nanotube Production

Science.gov (United States)

Scott, Carl D.; Farhat, Samir; Greendyke, Robert B.

2004-01-01

The development of processes to produce fullerenes and carbon nanotubes has largely been empirical. Fullerenes were first discovered in the soot produced by laser ablation of graphite [1]and then in the soot of electric arc evaporated carbon. Techniques and conditions for producing larger and larger quantities of fullerenes depended mainly on trial and error empirical variations of these processes, with attempts to scale them up by using larger electrodes and targets and higher power. Various concepts of how fullerenes and carbon nanotubes were formed were put forth, but very little was done based on chemical kinetics of the reactions. This was mainly due to the complex mixture of species and complex nature of conditions in the reactors. Temperatures in the reactors varied from several thousand degrees Kelvin down to near room temperature. There are hundreds of species possible, ranging from atomic carbon to large clusters of carbonaceous soot, and metallic catalyst atoms to metal clusters, to complexes of metals and carbon. Most of the chemical kinetics of the reactions and the thermodynamic properties of clusters and complexes have only been approximated. In addition, flow conditions in the reactors are transient or unsteady, and three dimensional, with steep spatial gradients of temperature and species concentrations. All these factors make computational simulations of reactors very complex and challenging. This article addresses the development of the chemical reaction involved in fullerene production and extends this to production of carbon nanotubes by the laser ablation/oven process and by the electric arc evaporation process. In addition, the high-pressure carbon monoxide (HiPco) process is discussed. The article is in several parts. The first one addresses the thermochemical aspects of modeling; and considers the development of chemical rate equations, estimates of reaction rates, and thermodynamic properties where they are available. The second part

Power system security enhancement with unified power flow controller under multi-event contingency conditions

Directory of Open Access Journals (Sweden)

S. Ravindra

2017-03-01

Full Text Available Power system security analysis plays key role in enhancing the system security and to avoid the system collapse condition. In this paper, a novel severity function is formulated using transmission line loadings and bus voltage magnitude deviations. The proposed severity function and generation fuel cost objectives are analyzed under transmission line(s and/or generator(s contingency conditions. The system security under contingency conditions is analyzed using optimal power flow problem. An improved teaching learning based optimization (ITLBO algorithm has been presented. To enhance the system security under contingency conditions in the presence of unified power flow controller (UPFC, it is necessary to identify an optimal location to install this device. Voltage source based power injection model of UPFC, incorporation procedure and optimal location identification strategy based on line overload sensitivity indexes are proposed. The entire proposed methodology is tested on standard IEEE-30 bus test system with supporting numerical and graphical results.

Enhanced endothelial cell functions on rosette nanotube-coated titanium vascular stents

Directory of Open Access Journals (Sweden)

Eli Fine

2009-04-01

Full Text Available Eli Fine1, Lijie Zhang1, Hicham Fenniri2, Thomas J Webster1 1Department of Engineering, Brown University, Providence, RI, USA; 2National Institute for Nanotechnology and Department of Chemistry, University of Alberta, Edmonton, AB, CanadaAbstract: One of the main problems with current vascular stents is a lack of endothelial cell interactions, which if sufficient, would create a uniform healthy endothelium masking the underlying foreign metal from inflammatory cell interference. Moreover, if endothelial cells from the arterial wall do not adhere to the stent, the stent can become loose and dislodge. Therefore, the objective of this in vitro study was to design a novel biomimetic nanostructured coating (that does not contain drugs on conventional vascular stent materials (specifically, titanium for improving vascular stent applications. Rosette nanotubes (RNTs are a new class of biomimetic nanotubes that self-assemble from DNA base analogs and have been shown in previous studies to sufficiently coat titanium and enhance osteoblast cell functions. RNTs have many desirable properties for use as vascular stent coatings including spontaneous self-assembly in body fluids, tailorable surface chemistry for specific implant applications, and nanoscale dimensions similar to those of the natural vascular extracellular matrix. Importantly, the results of this study provided the first evidence that RNTs functionalized with lysine (RNT–K, even at low concentrations, significantly increase endothelial cell density over uncoated titanium. Specifically, 0.01 mg/mL RNT–K coated titanium increased endothelial cell density by 37% and 52% compared to uncoated titanium after 4 h and three days, respectively. The excellent cytocompatibility properties of RNTs (as demonstrated here for the first time for endothelial cells suggest the need for the further exploration of these novel nanostructured materials for vascular stent applications.Keywords: stents

Influence of the Particle Length of Carbon Nanotube for Pool Boiling Critical Heat Flux Enhancement of Nanofluids

International Nuclear Information System (INIS)

Park, Sung Seek; Kim, Yong Hwan; Kim, Nam Jin

2013-01-01

The results of this experiment were that the CHF of the two nanofluids increased along with the volumetric fraction until 0.001 vol%, and the two types of nanofluids are the highest CHF at 0.001 vol%. Also, the results show clearly that the rate of CHF increase of the CM-100 MWCNT nanofluid with longer-length nanoparticles is higher than that of the CM-95 MWNCT nanofluid. These results indicate that the length of carbon nanotube influences the pool boiling CHF of carbon nanotube nanofluid and that long-length MWCNT, as above-noted, offers a superior effect in this regard. Boiling heat transfer is used in a variety of industrial processes and applications, such as refrigeration, power generation, heat exchangers, cooling of high-power electronics components and cooling of nuclear reactors. The critical heat flux (CHF) phenomenon is the thermal limit during a boiling heat transfer phase change; at the CHF point the heat transfer is maximised, followed by a drastic degradation after the CHF point. The consequence is a substantial increase in wall temperature which may result in physical failure phenomenon of heat transfer systems. Therefore, the CHF is important being considered in the cooling device design, such as nuclear reactor and nuclear fuels, steam generators, high-density electronic component, etc. And, CHF enhancement is essential for safety of heat transfer system. Recently, CHF reported increased when applied to the nanofluids, with its high (higher-than-base-fluid) thermal characteristic in the nuclear power plant system. Therefore, in this study, carried out the pool boiling CHF experiments by the particle length using carbon nanotube nanofluids, and the results are compared and analyzed for the CHF enhancement. The pool boiling CHF of experiments of carbon nanotube nanofluids carried out by the length of particles and the various concentrations

Transition from annular flow to plug/slug flow in condensation of steam in microchannels

Energy Technology Data Exchange (ETDEWEB)

Quan, Xiaojun; Cheng, Ping; Wu, Huiying [School of Mechanical and Power Engineering, Shanghai Jiaotong University, 800 Dong Chuan Road, Shanghai 200240 (China)

2008-02-15

A visualization study has been conducted to investigate the transition from annular flow to plug/slug flow in the condensation of steam in two different sets of parallel microchannels, having hydraulic diameters of 90 {mu}m and 136 {mu}m, respectively. The steam in the parallel microchannels was cooled on the bottom by forced convection of water and by natural convection of air from the top. It is found that the location, where the transition from annular flow to plug/slug flow takes place, depends on mass flux and cooling rate of steam. The effects of mass flux and cooling rate on the occurrence frequency of the injection flow in a single microchannel, having a hydraulic diameter of 120 {mu}m and 128 {mu}m, respectively, are investigated. It is found that two different shapes of injection flow occur in the smooth annular flow in microchannels: injection flow with unsteady vapor ligament occurring at low mass flux (or high cooling rate) and injection flow with steady vapor ligament occurring at high mass flux (or low cooling rate). It is also found that increase of steam mass flux, decrease of cooling rate, or decrease of the microchannel diameter tends to enhance instability of the condensate film on the wall, resulting in occurrence of the injection flow further toward the outlet with an increase in occurrence frequency. (author)

Gold nanoparticles/water-soluble carbon nanotubes/aromatic diamine polymer composite films for highly sensitive detection of cellobiose dehydrogenase gene

Energy Technology Data Exchange (ETDEWEB)

Zeng Guangming, E-mail: zgming@hnu.cn [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082 (China); Li Zhen, E-mail: happylizhen@yeah.ne [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082 (China); Tang Lin; Wu Mengshi; Lei Xiaoxia; Liu Yuanyuan; Liu Can; Pang Ya; Zhang Yi [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082 (China)

2011-05-01

Highlights: > Gold nanoparticles/multiwalled carbon nanotubes/poly (1,5-naphthalenediamine) modified electrode was fabricated. > The sensor was applied for the detection of cellobiose dehydrogenase genes. > An effective method to distribute MWCNTs and attach to the electrode was proposed. > The composite films greatly improved the sensitivity and enhanced the DNA immobilization. > The DNA biosensor exhibited fairly high sensitivity and quite low detection limit. - Abstract: An electrochemical sensor based on gold nanoparticles (GNPs)/multiwalled carbon nanotubes (MWCNTs)/poly (1,5-naphthalenediamine) films modified glassy carbon electrode (GCE) was fabricated. The effectiveness of the sensor was confirmed by sensitive detection of cellobiose dehydrogenase (CDH) gene which was extracted from Phanerochaete chrysosporium using polymerase chain reaction (PCR). The monomer of 1,5-naphthalenediamine was electropolymerized on the GCE surface with abundant free amino groups which enhanced the stability of MWCNTs modified electrode. Congo red (CR)-functionalized MWCNTs possess excellent conductivity as well as high solubility in water which enabled to form the uniform and stable network nanostructures easily and created a large number of binding sites for electrodeposition of GNPs. The continuous GNPs together with MWCNTs greatly increased the surface area, conductivity and electrocatalytic activity. This electrode structure significantly improved the sensitivity of sensor and enhanced the DNA immobilization and hybridization. The thiol modified capture probes were immobilized onto the composite films-modified GCE by a direct formation of thiol-Au bond and horseradish peroxidase-streptavidin (HRP-SA) conjugates were labeled to the biotinylated detection probes through biotin-streptavidin bond. Scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were used to investigate the film assembly and DNA hybridization processes

Enhancement of ECR performances by means of carbon nano-tubes based electron guns

International Nuclear Information System (INIS)

Odorici, F.; Cuffiani, M.; Malferrari, L.; Rizzoli, R.; Veronese, G.P.; Celona, L.; Gammino, S.; Mascali, D.; Miracoli, R.; Romano, F.P.; Gambino, N.; Castro, G.; Ciavola, G.; Serafino, T.

2012-01-01

The CANTES experiment at INFN-LNS tested the use of carbon nano-tubes (CNTs) to emit electrons by field emission effect, in order to provide additional electrons to the plasma core of an ECR ion source. This technique was used with the Caesar source, demonstrating that the total extracted ion current is increased and that a relevant reduction of the number of 'high energy' electrons (above 100 keV) may be observed. The injection of additional electrons inside the plasma increases the amount of cold and warm electrons, and then the number of ionizing collisions. Details of the construction of CNTs based electron gun and of the improvement of performances of the Caesar ECR ion source will be presented. The paper is followed by the associated poster. (authors)

Modification of glassy carbon electrode with multi-walled carbon nanotubes and iron(III)-porphyrin film: Application to chlorate, bromate and iodate detection

International Nuclear Information System (INIS)

Salimi, Abdollah; MamKhezri, Hussein; Hallaj, Rahman; Zandi, Shiva

2007-01-01

In this study, multi-wall carbon nanotubes (MWCTs) is evaluated as a transducer, stabilizer and immobilization matrix for the construction of amperometric sensor based on iron-porphyrin. 5,10,15,20-Tetraphenyl-21H,23H-porphine iron(III) chloride (Fe(III)P) adsorbed on MWCNTs immobilized on the surface of glassy carbon electrode. Cyclic voltammograms of the Fe(III)P-incorporated-MWCNTs indicate a pair of well-defined and nearly reversible redox couple with surface confined characteristics at wide pH range (2-12). The surface coverage (Γ) and charge transfer rate constant (k s ) of Fe(III)P immobilized on MWCNTs were 7.68 x 10 -9 mol cm -2 and 1.8 s -1 , respectively, indicating high loading ability of MWCNTs for Fe(III)P and great facilitation of the electron transfer between Fe(III)P and carbon nanotubes immobilized on the electrode surface. Modified electrodes exhibit excellent electrocatalytic activity toward reduction of ClO 3 - , IO 3 - and BrO 3 - in acidic solutions. The catalytic rate constants for catalytic reduction of bromate, chlorate and iodate were 6.8 x 10 3 , 7.4 x 10 3 and 4.8 x 10 2 M -1 s -1 , respectively. The hydrodynamic amperometry of rotating-modified electrode at constant potential versus reference electrode was used for detection of bromate, chlorate and iodate. The detection limit, linear calibration range and sensitivity for chlorate, bromate and iodate detections were 0.5 μM, 2 μM to 1 mM, 8.4 nA/μM, 0.6 μM, 2 μM to 0.15 mM, 11 nA/μM, and 2.5 μM, 10 μM to 4 mM and 1.5 nA/μM, respectively. Excellent electrochemical reversibility of the redox couple, good reproducibility, high stability, low detection limit, long life time, fast amperometric response time, wide linear concentration range, technical simplicity and possibility of rapid preparation are great advantages of this sensor. The obtained results show promising practical application of the Fe(III)P-MWCNTs-modified electrode as an amperometric sensor for chlorate, iodate and

Modification of glassy carbon electrode with multi-walled carbon nanotubes and iron(III)-porphyrin film: Application to chlorate, bromate and iodate detection

Energy Technology Data Exchange (ETDEWEB)

Salimi, Abdollah [Department of Chemistry, University of Kurdistan, P.O. Box 416, Sanandaj (Iran, Islamic Republic of); Nanotechnology Research Center of University of Kurdistan, P.O. Box 416, Sanandaj (Iran, Islamic Republic of); E-mail: absalimi@uok.ac.ir; MamKhezri, Hussein [Department of Chemistry, University of Kurdistan, P.O. Box 416, Sanandaj (Iran, Islamic Republic of); Hallaj, Rahman [Department of Chemistry, University of Kurdistan, P.O. Box 416, Sanandaj (Iran, Islamic Republic of); Zandi, Shiva [Laboratory of Biochemistry, Kurdistan Medical University, Sanandaj (Iran, Islamic Republic of)

2007-06-10

In this study, multi-wall carbon nanotubes (MWCTs) is evaluated as a transducer, stabilizer and immobilization matrix for the construction of amperometric sensor based on iron-porphyrin. 5,10,15,20-Tetraphenyl-21H,23H-porphine iron(III) chloride (Fe(III)P) adsorbed on MWCNTs immobilized on the surface of glassy carbon electrode. Cyclic voltammograms of the Fe(III)P-incorporated-MWCNTs indicate a pair of well-defined and nearly reversible redox couple with surface confined characteristics at wide pH range (2-12). The surface coverage ({gamma}) and charge transfer rate constant (k {sub s}) of Fe(III)P immobilized on MWCNTs were 7.68 x 10{sup -9} mol cm{sup -2} and 1.8 s{sup -1}, respectively, indicating high loading ability of MWCNTs for Fe(III)P and great facilitation of the electron transfer between Fe(III)P and carbon nanotubes immobilized on the electrode surface. Modified electrodes exhibit excellent electrocatalytic activity toward reduction of ClO{sub 3} {sup -}, IO{sub 3} {sup -} and BrO{sub 3} {sup -} in acidic solutions. The catalytic rate constants for catalytic reduction of bromate, chlorate and iodate were 6.8 x 10{sup 3}, 7.4 x 10{sup 3} and 4.8 x 10{sup 2} M{sup -1} s{sup -1}, respectively. The hydrodynamic amperometry of rotating-modified electrode at constant potential versus reference electrode was used for detection of bromate, chlorate and iodate. The detection limit, linear calibration range and sensitivity for chlorate, bromate and iodate detections were 0.5 {mu}M, 2 {mu}M to 1 mM, 8.4 nA/{mu}M, 0.6 {mu}M, 2 {mu}M to 0.15 mM, 11 nA/{mu}M, and 2.5 {mu}M, 10 {mu}M to 4 mM and 1.5 nA/{mu}M, respectively. Excellent electrochemical reversibility of the redox couple, good reproducibility, high stability, low detection limit, long life time, fast amperometric response time, wide linear concentration range, technical simplicity and possibility of rapid preparation are great advantages of this sensor. The obtained results show promising practical

Development of a dynamic flow imaging phantom for dynamic contrast-enhanced CT

International Nuclear Information System (INIS)

Driscoll, B.; Keller, H.; Coolens, C.

2011-01-01

Purpose: Dynamic contrast enhanced CT (DCE-CT) studies with modeling of blood flow and tissue perfusion are becoming more prevalent in the clinic, with advances in wide volume CT scanners allowing the imaging of an entire organ with sub-second image frequency and sub-millimeter accuracy. Wide-spread implementation of perfusion DCE-CT, however, is pending fundamental validation of the quantitative parameters that result from dynamic contrast imaging and perfusion modeling. Therefore, the goal of this work was to design and construct a novel dynamic flow imaging phantom capable of producing typical clinical time-attenuation curves (TACs) with the purpose of developing a framework for the quantification and validation of DCE-CT measurements and kinetic modeling under realistic flow conditions. Methods: The phantom is based on a simple two-compartment model and was printed using a 3D printer. Initial analysis of the phantom involved simple flow measurements and progressed to DCE-CT experiments in order to test the phantoms range and reproducibility. The phantom was then utilized to generate realistic input TACs. A phantom prediction model was developed to compute the input and output TACs based on a given set of five experimental (control) parameters: pump flow rate, injection pump flow rate, injection contrast concentration, and both control valve positions. The prediction model is then inversely applied to determine the control parameters necessary to generate a set of desired input and output TACs. A protocol was developed and performed using the phantom to investigate image noise, partial volume effects and CT number accuracy under realistic flow conditionsResults: This phantom and its surrounding flow system are capable of creating a wide range of physiologically relevant TACs, which are reproducible with minimal error between experiments (σ/μ 2 ) for the input function between 0.95 and 0.98, while the maximum enhancement differed by no more than 3.3%. The

Determination of albumin in bronchoalveolar lavage fluid by flow-injection fluorometry using chromazurol S.

Science.gov (United States)

Sato, Takaji; Saito, Yoshihiro; Chikuma, Masahiko; Saito, Yutaka; Nagai, Sonoko

2008-03-01

A highly sensitive flow injection fluorometry for the determination of albumin was developed and applied to the determination of albumin in human bronchoalveolar lavage fluids (BALF). This method is based on binding of chromazurol S (CAS) to albumin. The calibration curve was linear in the range of 5-200 microg/ml of albumin. A highly linear correlation (r=0.986) was observed between the albumin level in BALF samples (n=25) determined by the proposed method and by a conventional fluorometric method using CAS (CAS manual method). The IgG interference was lower in the CAS flow injection method than in the CAS manual method. The albumin level in BALF collected from healthy volunteers (n=10) was 58.5+/-13.1 microg/ml. The albumin levels in BALF samples obtained from patients with sarcoidosis and idiopathic pulmonary fibrosis were increased. This finding shows that the determination of albumin levels in BALF samples is useful for investigating lung diseases and that CAS flow injection method is promising in the determination of trace albumin in BALF samples, because it is sensitive and precise.

Double-walled ZrO{sub 2} nanotube array. Preparation and enhanced photocatalytic activity

Energy Technology Data Exchange (ETDEWEB)

Xue, Chaorui; Hu, Shengliang; Chang, Qing; Wang, Yanzhong [School of Materials Science and Engineering, North University of China, Taiyuan (China); Yang, Jinlong [School of Materials Science and Engineering, North University of China, Taiyuan (China); School of Materials Science and Engineering, Tsinghua University, Beijing (China)

2017-11-15

This work demonstrates the formation of self-ordered double-walled ZrO{sub 2} nanotube array via electrochemical anodization in glycerol-based electrolyte. Compared with its counterpart of single-walled ZrO{sub 2} nanotube array, the tube wall of double-walled ZrO{sub 2} nanotube split into outer and inner layers for the decomposition of glycerol during anodization process. Moreover, the double-walled structure showed its advantage of achieving improved utilization of light and higher specific surface area of nanotube array. Due to the unique double-walled structure, the double-walled ZrO{sub 2} nanotube array exhibited better photocatalytic activity than the single-walled ZrO{sub 2} nanotube array. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Selective Functionalization of Carbon Nanotubes: Part II

Science.gov (United States)

Meyyappan, Meyya; Khare, Bishun

2010-01-01

An alternative method of low-temperature plasma functionalization of carbon nanotubes provides for the simultaneous attachment of molecular groups of multiple (typically two or three) different species or different mixtures of species to carbon nanotubes at different locations within the same apparatus. This method is based on similar principles, and involves the use of mostly the same basic apparatus, as those of the methods described in "Low-Temperature Plasma Functionalization of Carbon Nanotubes" (ARC-14661-1), NASA Tech Briefs, Vol. 28, No. 5 (May 2004), page 45. The figure schematically depicts the basic apparatus used in the aforementioned method, with emphasis on features that distinguish the present alternative method from the other. In this method, one exploits the fact that the composition of the deposition plasma changes as the plasma flows from its source in the precursor chamber toward the nanotubes in the target chamber. As a result, carbon nanotubes mounted in the target chamber at different flow distances (d1, d2, d3 . . .) from the precursor chamber become functionalized with different species or different mixtures of species. In one series of experiments to demonstrate this method, N2 was used as the precursor gas. After the functionalization process, the carbon nanotubes from three different positions in the target chamber were examined by Fourier-transform infrared spectroscopy to identify the molecular groups that had become attached. On carbon nanotubes from d1 = 1 cm, the attached molecular groups were found to be predominantly C-N and C=N. On carbon nanotubes from d2 = 2.5 cm, the attached molecular groups were found to be predominantly C-(NH)2 and/or C=NH2. (The H2 was believed to originate as residual hydrogen present in the nanotubes.) On carbon nanotubes from d3 = 7 cm no functionalization could be detected - perhaps, it was conjectured, because this distance is downstream of the plasma source, all of the free ions and free radicals of

Non-Darcy flow of water-based carbon nanotubes with nonlinear radiation and heat generation/absorption

Directory of Open Access Journals (Sweden)

T. Hayat

2018-03-01

Full Text Available Here modeling and computations are presented to introduce the novel concept of Darcy-Forchheimer three-dimensional flow of water-based carbon nanotubes with nonlinear thermal radiation and heat generation/absorption. Bidirectional stretching surface induces the flow. Darcy’s law is commonly replace by Forchheimer relation. Xue model is implemented for nonliquid transport mechanism. Nonlinear formulation based upon conservation laws of mass, momentum and energy is first modeled and then solved by optimal homotopy analysis technique. Optimal estimations of auxiliary variables are obtained. Importance of influential variables on the velocity and thermal fields is interpreted graphically. Moreover velocity and temperature gradients are discussed and analyzed. Physical interpretation of influential variables is examined. Keywords: Porous medium, Heat generation/absorption, SWCNTs and MWCNTs, Nonlinear radiation

Muscle enhancement using intramuscular injections of oil in bodybuilding

DEFF Research Database (Denmark)

Schäfer, Ch. N.; Hvolris, Jørgen Jesper; Karlsmark, Tonny

2012-01-01

BACKGROUND: Self-administered intramuscular injection of site enhancement oil (SEO) is a cosmetic and performance-enhancing procedure used to reshape muscles in the bodybuilder subculture, but its consequences and complications are only sporadically described. Methods: A systematic search...... in MEDLINE and EMBASE databases during the spring of 2009 and 2010. Internet searches were performed, and bodybuilder pharmacopoeias were consulted to describe SEO use and the clinical complications known. Results: One review and seven case reports were identified. Eight case reports describe oleomas caused...

Enhanced Electro-Static Modulation of Ionic Diffusion through Carbon Nanotube Membranes by Diazonium Grafting Chemistry

Science.gov (United States)

Majumder, Mainak; Keis, Karin; Zhan, Xin; Meadows, Corey; Cole, Jeggan

2013-01-01

A membrane structure consisting of an aligned array of open ended carbon nanotubes (~ 7 nm i.d.) spanning across an inert polymer matrix allows the diffusive transport of aqueous ionic species through CNT cores. The plasma oxidation process that opens CNTs tips inherently introduces carboxylic acid groups at the CNT tips, which allows for a limited amount of chemical functional at the CNT pore entrance. However for numerous applications, it is important to increase the density of carboxylic acid groups at the pore entrance for effective separation processes. Aqueous diazonium based electro-chemistry significantly increases the functional density of carboxylic acid groups. pH dependent dye adsorption-desorption and interfacial capacitance measurements indicate ~ 5–6 times increase in functional density. To further control the spatial location of the functional chemistry, a fast flowing inert liquid column inside the CNT core is found to restrict the diazonium grafting to the CNT tips only. This is confirmed by the increased flux of positively charged Ru(bi-py)3+2 with anionic functionality. The electrostatic enhancement of ion diffusion is readily screened in 0.1(M) electrolyte solution consistent with the membrane pore geometry and increased functional density. PMID:25132719

Non-darcy flow behavior mean high-flux injection wells in porous and fractured formations

Energy Technology Data Exchange (ETDEWEB)

Wu, Yu-Shu

2003-04-25

This paper presents a study of non-Darcy fluid flow through porous and fractured rock, which may occur near wells during high-flux injection of waste fluids into underground formations. Both numerical and analytical models are used in this study. General non-Darcy flow is described using the Forchheimer equation, implemented in a three-dimensional, multiphase flow reservoir simulator. The non-Darcy flow through a fractured reservoir is handled using a general dual continuum approach, covering commonly used conceptual models, such as double porosity, dual permeability, explicit fracture, etc. Under single-phase flow conditions, an approximate analytical solution, as an extension of the Warren-Root solution, is discussed. The objectives of this study are (1) to obtain insights into the effect of non-Darcy flow on transient pressure behavior through porous and fractured reservoirs and (2) to provide type curves for well test analyses of non-Darcy flow wells. The type curves generated include various types of drawdown, injection, and buildup tests with non-Darcy flow occurring in porous and fractured reservoirs. In addition, non-Darcy flow into partially penetrating wells is also considered. The transient-pressure type curves for flow in fractured reservoirs are based on the double-porosity model. Type curves provided in this work for non-Darcy flow in porous and fractured reservoirs will find their applications in well test interpretation using a type-curve matching technique.

Electrodeposition of gold-platinum alloy nanoparticles on carbon nanotubes as electrochemical sensing interface for sensitive detection of tumor marker

Energy Technology Data Exchange (ETDEWEB)

Li Ya [Key Laboratory on Luminescence and Real-Time Analysis, Ministry of Education, College of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715 (China); Yuan Ruo, E-mail: yuanruo@swu.edu.cn [Key Laboratory on Luminescence and Real-Time Analysis, Ministry of Education, College of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715 (China); Chai Yaqin; Song Zhongju [Key Laboratory on Luminescence and Real-Time Analysis, Ministry of Education, College of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715 (China)

2011-07-30

Graphical abstract: Electrodeposition of gold-platinum alloy (Au-PtNPs) on carbon nanotubes as electrochemical sensing interface and HRP as blocking agent for the fabrication of high sensitive immunosensor. Display Omitted Highlights: > In this work, we proposed a novel electrochemical sensing surface. > The sensing surface possessed larger electro-active areas and higher conductivity due to the introduction of MWCNTs. > The signal could be amplified effectively by synergetic catalysis effect of Au-PtNPs and HRP towards the reduction of H{sub 2}O{sub 2}. > Biomolecules could be immobilized on the surface of Au-PtNPs tightly with the bioactivity kept well. > The simple fabrication method provided a new potential for the future development of practical devices for clinical diagnosis application. - Abstract: A novel electrochemical sensing interface, electrodeposition of gold-platinum alloy nanoparticles (Au-PtNPs) on carbon nanotubes, was proposed and used to fabricate a label-free amperometric immunosensor. On the one hand, the multiwalled carbon nanotubes (MWCNTs) could increase active area of the electrode and enhance the electron transfer ability between the electrode and redox probe; on the other hand, the Au-PtNPs not only could be used to assemble biomolecules with bioactivity kept well, but also could further facilitate the shuttle of electrons. In the meanwhile, horseradish peroxidase (HRP) instead of bovine serum albumin (BSA) was employed to block the possible remaining active sites and avoid the nonspecific adsorption. With the synergetic catalysis effect of Au-PtNPs and HRP towards the reduction of hydrogen peroxide (H{sub 2}O{sub 2}), the signal could be amplified and the sensitivity could be enhanced. Using alpha-fetoprotein (AFP) as model analyte, the fabricated immunosensor exhibited two wide linear ranges in the concentration ranges of 0.5-20 ng mL{sup -1} and 20-200 ng mL{sup -1} with a detection limit of 0.17 ng mL{sup -1} at a signal-to-noise of

Polyaniline/carbon nanotube/CdS quantum dot composites with enhanced optical and electrical properties

Science.gov (United States)

Goswami, Mrinmoy; Ghosh, Ranajit; Maruyama, Takahiro; Meikap, Ajit Kumar

2016-02-01

A new kind of polyaniline/carbon nanotube/CdS quantum dot composites have been developed via in-situ polymerization of aniline monomer in the presence of dispersed CdS quantum dots (size: 2.7-4.8 nm) and multi-walled carbon nanotubes (CNT), which exhibits enhanced optical and electrical properties. The existences of 1st order, 2nd order, and 3rd order longitudinal optical phonon modes, strongly indicate the high quality of synthesized CdS quantum dots. The occurrence of red shift of free exciton energy in photoluminescence is due to size dependent quantum confinement effect of CdS. The conductivity of the composites (for example PANI/CNT/CdS (2 wt.% CdS)) is increased by about 7 of magnitude compared to that of pure PANI indicating a charge transfer between CNT and polymer via CdS quantum dots. This advanced material has a great potential for high-performance of electro-optical applications.

Titanate nanotube thin films with enhanced thermal stability and high-transparency prepared from additive-free sols

Energy Technology Data Exchange (ETDEWEB)

Koroesi, Laszlo, E-mail: korosi@enviroinvest.hu [Supramolecular and Nanostructured Materials Research Group of the Hungarian Academy of Sciences, University of Szeged, Aradi vertanuk tere 1, H-6720 Szeged (Hungary); Department of Biotechnology, Nanophage Therapy Center, Enviroinvest Corporation, Kertvaros utca 2, H-7632 Pecs (Hungary); Papp, Szilvia [Supramolecular and Nanostructured Materials Research Group of the Hungarian Academy of Sciences, University of Szeged, Aradi vertanuk tere 1, H-6720 Szeged (Hungary); Department of Biotechnology, Nanophage Therapy Center, Enviroinvest Corporation, Kertvaros utca 2, H-7632 Pecs (Hungary); Hornok, Viktoria [Supramolecular and Nanostructured Materials Research Group of the Hungarian Academy of Sciences, University of Szeged, Aradi vertanuk tere 1, H-6720 Szeged (Hungary); Oszko, Albert [Department of Physical Chemistry and Materials Science, University of Szeged, Aradi vertanuk tere 1, H-6720 Szeged (Hungary); Petrik, Peter; Patko, Daniel; Horvath, Robert [Institute for Technical Physics and Materials Science MFA, Research Center for Natural Sciences, Konkoly-Thege ut 29-33, H-1121 Budapest (Hungary); Dekany, Imre [Supramolecular and Nanostructured Materials Research Group of the Hungarian Academy of Sciences, University of Szeged, Aradi vertanuk tere 1, H-6720 Szeged (Hungary)

2012-08-15

Titanate nanotubes were synthesized from TiO{sub 2} in alkaline medium by a conventional hydrothermal method (150 Degree-Sign C, 4.7 bar). To obtain hydrogen titanates, the as-prepared sodium titanates were treated with either HCl or H{sub 3}PO{sub 4} aqueous solutions. A simple synthesis procedure was devised for stable titanate nanotube sols without using any additives. These highly stable ethanolic sols can readily be used to prepare transparent titanate nanotube thin films of high quality. The resulting samples were studied by X-ray diffraction, N{sub 2}-sorption measurements, Raman spectroscopy, transmission and scanning electron microscopy, X-ray photoelectron spectroscopy and spectroscopic ellipsometry. The comparative results of using two kinds of acids shed light on the superior thermal stability of the H{sub 3}PO{sub 4}-treated titanate nanotubes (P-TNTs). X-ray photoelectron spectroscopy revealed that P-TNTs contains P in the near-surface region and the thermal stability was enhanced even at a low ({approx}0.5 at%) concentration of P. After calcination at 500 Degree-Sign C, the specific surface areas of the HCl- and H{sub 3}PO{sub 4}-treated samples were 153 and 244 m{sup 2} g{sup -1}, respectively. The effects of H{sub 3}PO{sub 4} treatment on the structure, morphology and porosity of titanate nanotubes are discussed. - Graphical Abstract: TEM picture (left) shows P-TNTs with diameters about 5-6 nm. Inset shows a stable titanate nanotube sol illuminated by a 532 nm laser beam. Due to the presence of the nanoparticles the way of the light is visible in the sol. Cross sectional SEM picture (right) as well as ellipsometry revealed the formation of optical quality P-TNT films with thicknesses below 50 nm. Highlights: Black-Right-Pointing-Pointer H{sub 3}PO{sub 4} treatment led to TNTs with high surface area even after calcination at 500 Degree-Sign C. Black-Right-Pointing-Pointer H{sub 3}PO{sub 4}-treated TNTs preserved their nanotube morphology up to 500

Vesicle Motion during Sustained Exocytosis in Chromaffin Cells: Numerical Model Based on Amperometric Measurements.

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Daungruthai Jarukanont

Full Text Available Chromaffin cells release catecholamines by exocytosis, a process that includes vesicle docking, priming and fusion. Although all these steps have been intensively studied, some aspects of their mechanisms, particularly those regarding vesicle transport to the active sites situated at the membrane, are still unclear. In this work, we show that it is possible to extract information on vesicle motion in Chromaffin cells from the combination of Langevin simulations and amperometric measurements. We developed a numerical model based on Langevin simulations of vesicle motion towards the cell membrane and on the statistical analysis of vesicle arrival times. We also performed amperometric experiments in bovine-adrenal Chromaffin cells under Ba2+ stimulation to capture neurotransmitter releases during sustained exocytosis. In the sustained phase, each amperometric peak can be related to a single release from a new vesicle arriving at the active site. The amperometric signal can then be mapped into a spike-series of release events. We normalized the spike-series resulting from the current peaks using a time-rescaling transformation, thus making signals coming from different cells comparable. We discuss why the obtained spike-series may contain information about the motion of all vesicles leading to release of catecholamines. We show that the release statistics in our experiments considerably deviate from Poisson processes. Moreover, the interspike-time probability is reasonably well described by two-parameter gamma distributions. In order to interpret this result we computed the vesicles' arrival statistics from our Langevin simulations. As expected, assuming purely diffusive vesicle motion we obtain Poisson statistics. However, if we assume that all vesicles are guided toward the membrane by an attractive harmonic potential, simulations also lead to gamma distributions of the interspike-time probability, in remarkably good agreement with experiment. We

Vesicle Motion during Sustained Exocytosis in Chromaffin Cells: Numerical Model Based on Amperometric Measurements.

Science.gov (United States)

Jarukanont, Daungruthai; Bonifas Arredondo, Imelda; Femat, Ricardo; Garcia, Martin E

2015-01-01

Chromaffin cells release catecholamines by exocytosis, a process that includes vesicle docking, priming and fusion. Although all these steps have been intensively studied, some aspects of their mechanisms, particularly those regarding vesicle transport to the active sites situated at the membrane, are still unclear. In this work, we show that it is possible to extract information on vesicle motion in Chromaffin cells from the combination of Langevin simulations and amperometric measurements. We developed a numerical model based on Langevin simulations of vesicle motion towards the cell membrane and on the statistical analysis of vesicle arrival times. We also performed amperometric experiments in bovine-adrenal Chromaffin cells under Ba2+ stimulation to capture neurotransmitter releases during sustained exocytosis. In the sustained phase, each amperometric peak can be related to a single release from a new vesicle arriving at the active site. The amperometric signal can then be mapped into a spike-series of release events. We normalized the spike-series resulting from the current peaks using a time-rescaling transformation, thus making signals coming from different cells comparable. We discuss why the obtained spike-series may contain information about the motion of all vesicles leading to release of catecholamines. We show that the release statistics in our experiments considerably deviate from Poisson processes. Moreover, the interspike-time probability is reasonably well described by two-parameter gamma distributions. In order to interpret this result we computed the vesicles' arrival statistics from our Langevin simulations. As expected, assuming purely diffusive vesicle motion we obtain Poisson statistics. However, if we assume that all vesicles are guided toward the membrane by an attractive harmonic potential, simulations also lead to gamma distributions of the interspike-time probability, in remarkably good agreement with experiment. We also show that

Carbon nanotube-based coatings to induce flow enhancement in hydrophilic nanopores

DEFF Research Database (Denmark)

Wagemann, Enrique; Walther, Jens Honore; Zambrano, Harvey

2016-01-01

With the emergence of the field of nanofluidics, the transport of water in hydrophilic nanopores has attracted intensive research due to its many promising applications. Experiments and simulations have found that flow resistance in hydrophilic nanochannels is much higher than those in macrochann......With the emergence of the field of nanofluidics, the transport of water in hydrophilic nanopores has attracted intensive research due to its many promising applications. Experiments and simulations have found that flow resistance in hydrophilic nanochannels is much higher than those...

Enhancement of superconducting critical current by injection of quasiparticles in superconductor semiconductor devices

DEFF Research Database (Denmark)

Kutchinsky, Jonatan; Taboryski, Rafael Jozef; Sørensen, C. B.

2000-01-01

We report new measurements on 3-terminal superconductor semiconductor injection devices, demonstrating enhancement of the supercurrent by injection from a superconducting injector electrode. Two other electrodes were used as detectors. Applying a small voltage to the injector, reduced the maximum...

Continuous-Flow Production of Injectable Liposomes via a Microfluidic Approach

Directory of Open Access Journals (Sweden)

Alessandra Zizzari

2017-12-01

Full Text Available Injectable liposomes are characterized by a suitable size and unique lipid mixtures, which require time-consuming and nonstraightforward production processes. The complexity of the manufacturing methods may affect liposome solubility, the phase transition temperatures of the membranes, the average particle size, and the associated particle size distribution, with a possible impact on the drug encapsulation and release. By leveraging the precise steady-state control over the mixing of miscible liquids and a highly efficient heat transfer, microfluidic technology has proved to be an effective and direct methodology to produce liposomes. This approach results particularly efficient in reducing the number of the sizing steps, when compared to standard industrial methods. Here, Microfluidic Hydrodynamic Focusing chips were produced and used to form liposomes upon tuning experimental parameters such as lipids concentration and Flow-Rate-Ratios (FRRs. Although modelling evidenced the dependence of the laminar flow on the geometric constraints and the FRR conditions, for the specific formulation investigated in this study, the lipids concentration was identified as the primary factor influencing the size of the liposomes and their polydispersity index. This was attributed to a predominance of the bending elasticity modulus over the vesiculation index in the lipid mixture used. Eventually, liposomes of injectable size were produced using microfluidic one-pot synthesis in continuous flow.

Enhanced dispersion of carbon nanotubes in hyperbranched polyurethane and properties of nanocomposites

International Nuclear Information System (INIS)

Rana, Sravendra; Karak, Niranjan; Cho, Jae Whan; Kim, Young Ho

2008-01-01

Hyperbranched polyurethane (HBPU) nanocomposites with multi-walled carbon nanotubes (MWNTs) were prepared by in situ polymerization on the basis of poly(ε-caprolactone)diol as the soft segment, 4,4'-methylene bis(phenylisocyanate) as the hard segment, and castor oil as the multifunctional group for the hyperbranched structure. A dominant improvement in the dispersion of MWNTs in the HBPU matrix was found, and good solubility of HBPU-MWNT nanocomposites in organic solvents was shown. Due to the well-dispersed MWNTs, the nanocomposites resulted in achieving excellent shape memory properties as well as enhanced mechanical properties compared to pure HBPU.

Role of direct covalent bonding in enhanced heat dissipation property of flexible graphene oxide–carbon nanotube hybrid film

International Nuclear Information System (INIS)

Hwang, Yongseon; Kim, Myeongjin; Kim, Jooheon

2013-01-01

The thermal conductivity of graphene oxide/multiwalled carbon nanotube (GO/MWCNT) hybrid films with and without covalent bonding is examined in this study. To fabricate chemically bonded GO/MWCNT hybrid films, chlorinated GO and amino-functionalized MWCNTs are bonded covalently. The mixtures of surface modified GO and MWCNT were filtered and then subjected to hot pressing to fabricate stacked films. Examination of these chemically bonded hybrid films reveal that chlorine-doped GO exhibits enhanced electrical properties because it creates hole charge carriers by attracting the electrons in GO towards chlorine. Enhanced electrical conductivity and low sheet resistance are observed also with increasing MWCNT loadings. On comparing the through-plane thermal properties, the chemically bonded hybrid films were found to exhibit higher thermal conductivity than do the physically bonded hybrid films because of the synergetic interaction of functional groups in GO and MWCNTs in the former films. However, excess addition of MWCNTs to the films leads to an increasing phonon scattering density and a decreased thermal conductivity. - Highlights: • Graphene oxide/carbon nanotube (GO/CNT) films are bonded covalently. • GO/CNT hybrid films are prepared through filtering and hot-pressing method. • Chemically bonded hybrid films exhibit enhanced electrical and thermal properties. • Enhanced thermal conductivity is explained according to increasing CNT contents

Torsional carbon nanotube artificial muscles.

Science.gov (United States)

Foroughi, Javad; Spinks, Geoffrey M; Wallace, Gordon G; Oh, Jiyoung; Kozlov, Mikhail E; Fang, Shaoli; Mirfakhrai, Tissaphern; Madden, John D W; Shin, Min Kyoon; Kim, Seon Jeong; Baughman, Ray H

2011-10-28

Rotary motors of conventional design can be rather complex and are therefore difficult to miniaturize; previous carbon nanotube artificial muscles provide contraction and bending, but not rotation. We show that an electrolyte-filled twist-spun carbon nanotube yarn, much thinner than a human hair, functions as a torsional artificial muscle in a simple three-electrode electrochemical system, providing a reversible 15,000° rotation and 590 revolutions per minute. A hydrostatic actuation mechanism, as seen in muscular hydrostats in nature, explains the simultaneous occurrence of lengthwise contraction and torsional rotation during the yarn volume increase caused by electrochemical double-layer charge injection. The use of a torsional yarn muscle as a mixer for a fluidic chip is demonstrated.

Entropy Generation in a Rotating Couette Flow with Suction/Injection

Directory of Open Access Journals (Sweden)

S. Das

2015-05-01

Full Text Available The present paper is concerned with an analytical study of entropy generation in viscous incompressible Couette flow with suction/injection in a rotating frame of reference. One of the plate is held at rest and the other one moves with an uniform velocity.The flow induced by the moving plate. An exact solution of governing equations has been obtained in closed form. The entropy generation number and the Bejan number are also obtained. The influences of each of the governing parameters on velocity, temperature, entropy generation and Bejan number are discussed with the help of graphs.

Enzymatic amplification of a flow-injected thermometric enzyme-linked immunoassay for human insulin.

Science.gov (United States)

Mecklenburg, M; Lindbladh, C; Li, H; Mosbach, K; Danielsson, B

1993-08-01

A flow-injected thermometric enzyme linked immunoassay for human insulin which employs the lactate dehydrogenase/lactate oxidase (LDH/LOD) substrate recycling system for signal amplification is described. The system is composed of two columns, an immunosorbent column containing immobilized anti-insulin antibodies for sensing and a recycling column containing immobilized LDH/LOD/Catalase for detection. The effect of flow rates, conjugate concentrations, and chromatographic support material upon the sensitivity of the assay are investigated. The assay has a detection limit of 0.025 microgram/ml and a linear range from 0.05 to 2 micrograms/ml. This corresponds to a 10-fold increase in sensitivity over the unamplified system. A recombinant human insulin-proinsulin conjugate was also tested. The results show that enzymatic amplification can be employed to increase the sensitivity and reproducibility of flow injection assay-based biosensors. The implications of these results upon on-line analysis are discussed.

Geckolike high shear strength by carbon nanotube fiber adhesives

Science.gov (United States)

Maeno, Y.; Nakayama, Y.

2009-01-01

Carbon nanotube adhesives can adhere strongly to surfaces as a gecko does. The number of carbon nanotube layers is an important determinant of the contact area for adhesion. Balancing the catalyst ratio and buffer layer used for chemical vapor deposition processing controls the number of carbon nanotube layers and their distribution. The features of carbon nanotubes determine the shear strength of adhesion. Carbon nanotubes with a broad distribution of layers exhibit enhanced shear strength with equivalent adhesive capability to that of a natural Tokay Gecko (Gekko gecko)

Seasonal Variability in Regional Ice Flow Due to Meltwater Injection Into the Shear Margins of Jakobshavn Isbræ

Science.gov (United States)

Cavanagh, J. P.; Lampkin, D. J.; Moon, T.

2017-12-01

The impact of meltwater injection into the shear margins of Jakobshavn Isbræ via drainage from water-filled crevasses on ice flow is examined. We use Landsat-8 Operational Land Imager panchromatic, high-resolution imagery to monitor the spatiotemporal variability of seven water-filled crevasse ponds during the summers of 2013 to 2015. The timing of drainage from water-filled crevasses coincides with an increase of 2 to 20% in measured ice velocity beyond Jakobshavn Isbræ shear margins, which we define as extramarginal ice velocity. Some water-filled crevasse groups demonstrate multiple drainage events within a single melt season. Numerical simulations show that hydrologic shear weakening due to water-filled crevasse drainage can accelerate extramarginal flow by as much as 35% within 10 km of the margins and enhance mass flux through the shear margins by 12%. This work demonstrates a novel mechanism through which surface melt can influence regional ice flow.

Flow injection analysis: Emerging tool for laboratory automation in radiochemistry

International Nuclear Information System (INIS)

Egorov, O.; Ruzicka, J.; Grate, J.W.; Janata, J.

1996-01-01

Automation of routine and serial assays is a common practice of modern analytical laboratory, while it is virtually nonexistent in the field of radiochemistry. Flow injection analysis (FIA) is a general solution handling methodology that has been extensively used for automation of routine assays in many areas of analytical chemistry. Reproducible automated solution handling and on-line separation capabilities are among several distinctive features that make FI a very promising, yet under utilized tool for automation in analytical radiochemistry. The potential of the technique is demonstrated through the development of an automated 90 Sr analyzer and its application in the analysis of tank waste samples from the Hanford site. Sequential injection (SI), the latest generation of FIA, is used to rapidly separate 90 Sr from interfering radionuclides and deliver separated Sr zone to a flow-through liquid scintillation detector. The separation is performed on a mini column containing Sr-specific sorbent extraction material, which selectively retains Sr under acidic conditions. The 90 Sr is eluted with water, mixed with scintillation cocktail, and sent through the flow cell of a flow through counter, where 90 Sr radioactivity is detected as a transient signal. Both peak area and peak height can be used for quantification of sample radioactivity. Alternatively, stopped flow detection can be performed to improve detection precision for low activity samples. The authors current research activities are focused on expansion of radiochemical applications of FIA methodology, with an ultimate goal of creating a set of automated methods that will cover the basic needs of radiochemical analysis at the Hanford site. The results of preliminary experiments indicate that FIA is a highly suitable technique for the automation of chemically more challenging separations, such as separation of actinide elements