Amperometric pyruvate sensor based on a pyruvate dehydrogenase-immobilized carbon paste electrode containing vitamin K3 as a mediator

Energy Technology Data Exchange (ETDEWEB)

Miki, K. [Nara National College of Technology, Nara (Japan); Kinoshita, H. [Kawassui Women`s College, Nagasaki (Japan); Yamamoto, Y. [Kyoto Municipal Junior College of Nursing, Kyoto (Japan); Taniguchi, N. [Kyoto Research Center for Hygiene, Kyoto (Japan); Ikeda, T. [Kyoto University, Kyoto (Japan). Faculty of Agriculture

1995-12-05

Pyruvate dehydrogenase (PDH) was immobilized on the surface of a carbon paste electrode containing vitamin K3 (2-Methyl-1,4-naphthoquinone, VK), and the electrode surface was covered with a dialysis membrane. The enzyme electrode produced an anodic current starting from -0.2 V to reach a limiting current at +0.1 V vs. Ag/AgCl due to the enzyme-catalyzed oxidation of pyruvate in a phosphate buffer solution of pH 7.0. The current response to pyruvate depended on the amounts of both the immobilized-PDH and VK mixed in the carbon paste electrode at low amount of the enzyme and VK, and became independent at above 0.15 mg PDH and 0.65% (w/w) VK. The electrode with 0.15mg PDH and 0.65% (w/w) VK could be used as a pyruvate sensor to measure in the range of 2 ,{mu}M to 3mM. The response time was about 60 sec, and the current was independent of pH in the range of 5.7 - 7.2. The presence of L-ascorbic acid didn`t interfere with this measurement. Phosphate ion could also be determined with this electrode in a citrate buffer solution. 14 refs., 6 figs., 1 tab.

Fabrication of flexible and disposable carbon paste-based electrodes and their electrochemical sensing

Science.gov (United States)

Aryasomayajula, Lavanya; Varadan, Vijay K.

2008-03-01

The paper describes a disposable electrochemical biosensor for glucose monitoring. The sensor is based on carbon paste immobilized with glucose oxidase and upon screen printed electrodes. The sensor has been tested effectively for the blood glucose levels corresponding to normal (70 to 99 mg/dL or 3.9 to5.5 mmol/L), pre-diabetic (100 to 125 mg/dL or 5.6 to 6.9 mmol/L) and diabetic (>126 mg/dL or 7.0 mmol/L). The calibration curve and the sensitivity of the sensor were measured.

Metallophthalocyanine based carbon paste electrodes for the determination of 2’,3’-Dideoxyinosine

CSIR Research Space (South Africa)

Ozoemena, KI

2009-07-01

Full Text Available Novel electrochemical sensors based on carbon paste impregnated with metallopthalocyanine (MPc, M¼Co, Fe) complexes, have been constructed for the assay of anti-HIV drug 2’,3’-dideoxyinosine (didanosine, DDI). Both modified electrodes showed...

Paper-based potentiometric pH sensor using carbon electrode drawn by pencil

Science.gov (United States)

Kawahara, Ryotaro; Sahatiya, Parikshit; Badhulika, Sushmee; Uno, Shigeyasu

2018-04-01

A flexible and disposable paper-based pH sensor fabricated with a pencil-drawn working electrode and a Ag/AgCl paste reference electrode is demonstrated for the first time to show pH response by the potentiometric principle. The sensor substrate is made of chromatography paper with a wax-printed hydrophobic area, and various types of carbon pencils are tested as working electrodes. The pH sensitivities of the electrodes drawn by carbon pencils with different hardnesses range from 16.5 to 26.9 mV/pH. The proposed sensor is expected to be more robust against shape change in electrodes on a flexible substrate than other types of chemiresistive/amperometric pH sensors.

A novel electrochemical sensor based on magneto Au nanoparticles/carbon paste electrode for voltammetric determination of acetaminophen in real samples

Energy Technology Data Exchange (ETDEWEB)

Haghshenas, Esmaeel; Madrakian, Tayyebeh, E-mail: madrakian@basu.ac.ir; Afkhami, Abbas

2015-12-01

An electrochemical magneto Au nanoparticles/carbon paste electrodes (MAuNP/CPE) which is used for the determination of acetaminophen (AC) in real samples was developed. Initially, Au nanoparticles were immobilized at the surface of Fe{sub 3}O{sub 4} (AuNPs@Fe{sub 3}O{sub 4}), which was used as a sorbent for capturing AC molecules. After adding AuNPs@Fe{sub 3}O{sub 4} to the AC solution and stirring for 20 min, the AuNPs@Fe{sub 3}O{sub 4} was gathered on the magneto electrode based on its magnetic field. The AC molecules which became adsorbed at AuNPs@Fe{sub 3}O{sub 4} were analyzed by differential pulse voltammetry (DPV). For characterization and investigation of the performance of AuNPs@Fe{sub 3}O{sub 4} and MAuNPs/CPE, various methods, including scanning electron microscopy, X-ray diffraction, UV–Vis spectroscopy, electrochemical impedance spectroscopy, cyclic voltammetry and DPV were used. Under the optimized conditions, the anodic peak current was linear to the concentration of AC in the range of 0.1 to 70.0 μmol L{sup −1} with the detection limit of 4.5 × 10{sup −2} μmol L{sup −1}. This method was also successfully used to detect the concentration of AC in pharmaceutical formulations and human serum samples. In addition, the proposed magneto sensor exhibited good reproducibility, long-term stability and fast current response. - Highlights: • Magneto Au nanoparticle/carbon paste electrode was fabricated. • Au nanoparticles were immobilized at the surface of Fe{sub 3}O{sub 4} (AuNPs@Fe{sub 3}O{sub 4}). • It is the first time AuNPs@Fe{sub 3}O{sub 4} and magneto electrode are used for the determination of AC. • The proposed sensor showed a wide linear range, low detection limit, and high sensitivity. • This sensor is also used for the determination of AC in real samples.

Electrochemical study of oxidation process of promethazine using sensor based on carbon nanotubes paste containing immobilized DNA on inorganic matrix

Directory of Open Access Journals (Sweden)

João Paulo Marco

2014-10-01

Full Text Available In the present work the voltammetric behavior and the oxidation process of promethazine (PHZ in electrochemical sensor based on carbon nanotubes paste containing DNA immobilized on the inorganic matrix prepared by sol-gel process (SiO2/Al2O3/Nb2O5. The method of Laviron verified that the system is irreversible and high speed of electron transfer between the electrode and DNA. The study of the oxidation of PHZ and influence of pH showed slope of 0.054 V / pH (near the nernstian system: 0.0592 V / pH suggesting that it involves the transfer of two protons and two electrons.

Carbon nanostructure-based field-effect transistors for label-free chemical/biological sensors.

Science.gov (United States)

Hu, PingAn; Zhang, Jia; Li, Le; Wang, Zhenlong; O'Neill, William; Estrela, Pedro

2010-01-01

Over the past decade, electrical detection of chemical and biological species using novel nanostructure-based devices has attracted significant attention for chemical, genomics, biomedical diagnostics, and drug discovery applications. The use of nanostructured devices in chemical/biological sensors in place of conventional sensing technologies has advantages of high sensitivity, low decreased energy consumption and potentially highly miniaturized integration. Owing to their particular structure, excellent electrical properties and high chemical stability, carbon nanotube and graphene based electrical devices have been widely developed for high performance label-free chemical/biological sensors. Here, we review the latest developments of carbon nanostructure-based transistor sensors in ultrasensitive detection of chemical/biological entities, such as poisonous gases, nucleic acids, proteins and cells.

Carbon paste electrode with covalently immobilized thionine for electrochemical sensing of hydrogen peroxide

Science.gov (United States)

Thenmozhi, K.; Sriman Narayanan, S.

2017-11-01

A water-soluble redox mediator, thionin was covalently immobilized to the functionalized graphite powder and a carbon paste electrode was fabricated from this modified graphite powder. The immobilization procedure proved to be effective in anchoring the thionin mediator in the graphite electrode setup without any leakage problem during the electrochemical studies. The covalent immobilization of the thionin mediator was studied with FT-IR and the electrochemical response of the thionin carbon paste electrode was optimized on varying the supporting electrolyte, pH and scan rate. The modified electrode exhibited well-defined electrocatalytic activity towards the reduction of H2O2 at a lower potential of -0.266 V with good sensitivity. The developed amperometric sensor was efficient towards H2O2 in the linear range from 2.46 × 10-5 M to 4.76 × 10-3 M, with a detection limit of 1.47 × 10-5 M respectively. Important advantages of this sensor are its excellent electrochemical performance, simple fabrication, easy renewability, reproducible analytical results, acceptable accuracy and good operational and long-term stability.

Preparation and application of a carbon paste electrode modified with multi-walled carbon nanotubes and boron-embedded molecularly imprinted composite membranes.

Science.gov (United States)

Wang, Hongjuan; Qian, Duo; Xiao, Xilin; Deng, Chunyan; Liao, Lifu; Deng, Jian; Lin, Ying-Wu

2018-06-01

An innovative electrochemical sensor was fabricated for the sensitive and selective determination of tinidazole (TNZ), based on a carbon paste electrode (CPE) modified with multi-walled carbon nanotubes (MWCNTs) and boron-embedded molecularly imprinted composite membranes (B-MICMs). Density functional theory (DFT) calculations were carried out to investigate the utility of template-monomer interactions to screen appropriate monomers for the rational design of B-MICMs. The distinct synergic effect of MWCNTs and B-MICMs was evidenced by the positive shift of the reduction peak potential of TNZ at B-MICMs/MWCNTs modified CPE (B-MICMs/MWCNTs/CPE) by about 200 mV, and the 12-fold amplification of the peak current, compared with a bare carbon paste electrode (CPE). Moreover, the coordinate interactions between trisubstituted boron atoms embedded in B-MICMs matrix and nitrogen atoms of TNZ endow the sensor with advanced affinity and specific directionality. Thereafter, a highly sensitive electrochemical analytical method for TNZ was established by different pulse voltammetry (DPV) at B-MICMs/MWCNTs/CPE with a lower detection limit (1.25 × 10 -12  mol L -1 ) (S/N = 3). The practical application of the sensor was demonstrated by determining TNZ in pharmaceutical and biological samples with good precision (RSD 1.36% to 3.85%) and acceptable recoveries (82.40%-104.0%). Copyright © 2018 Elsevier B.V. All rights reserved.

Electrochemical determination of bisphenol A at ordered mesoporous carbon modified nano-carbon ionic liquid paste electrode.

Science.gov (United States)

Li, Yonghong; Zhai, Xiurong; Liu, Xinsheng; Wang, Ling; Liu, Herong; Wang, Haibo

2016-02-01

A simple bisphenol A (BPA) sensor was successfully fabricated based on ordered mesoporous carbon CMK-3 modified nano-carbon ionic liquid paste electrode (CMK-3/nano-CILPE). The nanostructure of CMK-3 and the surface morphologies of modified electrodes were characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Electrochemical properties of the fabricated electrodes were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The fabricated sensor displayed excellent electroactivity towards bisphenol A using linear sweep voltammetry (LSV). Experimental conditions influencing the analytical performance of the modified electrode were optimized. Under optimal conditions, the oxidation peak current was proportional to BPA concentration in the range from 0.2 μM to 150 μM with a detection limit of 0.05 μM (S/N=3). This method was successfully used for determination of BPA leached from drinking bottle and plastic bag with good recoveries. Copyright © 2015 Elsevier B.V. All rights reserved.

Voltammetric sensor for tartrazine determination in soft drinks using poly (p-aminobenzenesulfonic acid/zinc oxide nanoparticles in carbon paste electrode

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Ghasem Karim-Nezhad

2017-04-01

Full Text Available Zinc oxide nanoparticles (ZnO NPs and p-aminobenzenesulfonic acid (p-ABSA were used to fabricate a modified electrode, as a highly sensitive and selective voltammetric sensor, for the determination of tartrazine. A fast and easy method for the fabrication of poly p-ABSA (Pp-ABSA/ZnO NPs-carbon paste electrode (Pp-ABSA/ZnO NPs-CPE by cyclic voltammetry was used. By combining the benefits of Pp-ABSA, ZnO NPs, and CPE, the resulted modified electrode exhibited outstanding electrocatalytic activity in terms of tartrazine oxidation by giving much higher peak currents than those obtained for the unmodified CPE and also other constructed electrodes. The effects of various experimental parameters on the voltammetric response of tartrazine were investigated. At the optimum conditions, the sensor has a linear response in the concentration range of 0349–5.44 μM, a good detection sensitivity (2.2034 μA/μM, and a detection limit of 80 nM of tartrazine. The proposed electrode was used for the determination of tartrazine in soft drinks with satisfactory results.

Gold-copper bimetallic nanoparticles supported on nano P zeolite modified carbon paste electrode as an efficient electrocatalyst and sensitive sensor for determination of hydrazine.

Science.gov (United States)

Amiripour, Fatemeh; Azizi, Seyed Naser; Ghasemi, Shahram

2018-06-01

In this report, a facile, efficient and low cost electrochemical sensor based on bimetallic Au-Cu nanoparticles supported on P nanozeolite modified carbon paste electrode (Au-Cu/NPZ/CPE) was constructed and its efficiency for determination of hydrazine in trace level was studied. For this purpose, agro waste material, stem sweep ash (SSA) was employed as the starting material (silica source) for the synthesis of nano P zeolite (NPZ). After characterization of the synthesized NPZ by analytical instruments (scanning electronic microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy), construction of Au-Cu/NPZ/CPE was performed by three steps procedure involving preparation of nano P zeolite modified carbon paste electrode (NPZ/CPE), introducing Cu +2 ions into nano zeolite structure by ion exchange and electrochemical reduction of Cu +2 ions upon applying constant potential. This procedure is followed by partial replacement of Cu by Au due to galvanic replacement reaction (GRR). The electrochemical properties of hydrazine at the surface of Au-Cu/NPZ/CPE was evaluated using cyclic voltammetry (CV), amperometry, and chronoamperometry methods in 0.1 M phosphate buffer solution (PBS). It was found that the prepared sensor has higher electrocatalytic activity at a relatively lower potential compared to other modified electrodes including Au/NPZ/CPE, Cu/NPZ/CPE, Au-Cu/CPE and etc. Moreover, the proposed electrochemical sensor presented the favorable analytical properties for determination of hydrazine such as low detection limit (0.04 µM), rapid response time (3 s), wide linear range (0.01-150 mM), and high sensitivity (99.53 µA mM -1 ) that are related to the synergic effect of bimetallic of Au-Cu, porous structure and enough surface area of NPZ. In addition, capability of Au-Cu/NPZ/CPE sensor was successfully tested in real samples with good accuracy and precision. Copyright �

Amperometric L-cysteine sensor based on a carbon paste electrode modified with Y_2O_3 nanoparticles supported on nitrogen-doped reduced graphene oxide

International Nuclear Information System (INIS)

Yang, Suling; Li, Gang; Wang, Yuanyuan; Wang, Guifang; Qu, Lingbo

2016-01-01

We describe an electrochemical sensor for L-cysteine that is based on the use of Y_2O_3 nanoparticles (Y_2O_3-NPs) supported on nitrogen-doped reduced graphene oxide (N-rGO). The material was characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and electrochemical methods. Deposited on a carbon paste electrode, the material displays a strongly oxidation peak for L-cysteine at pH 7.0 (compared to an unmodified electrode). The current, measured at a potential 0.7 V (vs. Ag/AgCl), increases linearly in the 1.3 to 720 μM L-cysteine concentration range, and the detection limit is 0.8 μM. The sensor was successfully applied to the determination L-cysteine in spiked syrup. (author)

Electrochemical Investigation of Catechol at Poly(niacinamide Modified Carbon Paste Electrode: A Voltammetric Study

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A. B. Teradale

2016-01-01

Full Text Available A polymeric thin film modified electrode, that is, poly(niacinamide modified carbon paste electrode (MCPE, was developed for the electrochemical determination of catechol (CC by using cyclic voltammetric technique. Compared to bare carbon paste electrode (BCPE, the poly(niacinamide MCPE shows good electrocatalytic activity towards the oxidation of catechol in phosphate buffer solution (PBS of physiological pH 7.4. All experimental parameters were optimized. Poly(niacinamide modified carbon paste electrode gave a linear response between concentration of CC and its anodic peak current in the range within 20.6–229.0 μM. The limit of detection (3S/M and limit of quantification (10S/M were 1.497 μM and 4.99 μM, respectively. From the study of scan rate variation, the electrode process was found to be adsorption-controlled. The involvement of protons and electrons in the oxidation of CC was found to be equal. The probable electropolymerisation mechanism of niacinamide was proposed. Finally, this method can be used in development of a sensor for sensitive determination of CC.

Determination of ascorbic acid in pharmaceutical preparation and fruit juice using modified carbon paste electrode

Directory of Open Access Journals (Sweden)

Simona Žabčíková

2016-06-01

Full Text Available Acrobic acid is key substance in the human metabolism and the rapid and accurate determination in food is of a great interest. Ascorbic acid is an electroactive compound, however poorly responded on the bare carbon paste electrodes. In this paper, brilliant cresyl blue and multi-walled carbon nanotubes were used for the modification of carbon paste electrode. Brilliant cresyl blue acts as a mediator improving the transition of electrons, whereas multiwalled carbon nanotubes increased the surface of the electrode. Both brilliant cresyl blue and multiwalled carbon nanotubes were added directly to the composite material. The electrochemical behavior of modified electode was determined in electrolyte at various pH, and the effect of the scan rate was also performed. It was shown that the electrochemical process on the surface of the modified carbon paste electrode was diffusion-controlled. The resulted modified carbon paste electrode showed a good electrocatalytic activity towards the oxidation of ascorbic acid at a reduced overpotential of +100 mV descreasing the risk of interferences. A linear response of the ascorbic acid oxidation current measured by the amperometry in the range of 0.1 - 350 µmol.L-1 was obtained applying the sensor for the standard solution. The limit of detection and limit of quantification was found to be 0.05 and 0.15 µmol.L-1, respectively. The novel method was applied for the determination of ascorbic acid in pharmaceutical vitamin preparation and fruit juice, and the results were in good agreement with the standard HPLC method. The presented modification of carbon paste electrode is suitable for the fast, sensitive and very accurate determination of ascorbic acid in fruit juices and pharmaceutical preparation.

Pristine carbon nanotubes based resistive temperature sensor

International Nuclear Information System (INIS)

Alam, Md Bayazeed; Saini, Sudhir Kumar; Sharma, Daya Shankar; Agarwal, Pankaj B.

2016-01-01

A good sensor must be highly sensitive, faster in response, of low cost cum easily producible, and highly reliable. Incorporation of nano-dimensional particles/ wires makes conventional sensors more effective in terms of fulfilling the above requirements. For example, Carbon Nanotubes (CNTs) are promising sensing element because of its large aspect ratio, unique electronic and thermal properties. In addition to their use for widely reported chemical sensing, it has also been explored for temperature sensing. This paper presents the fabrication of CNTs based temperature sensor, prepared on silicon substrate using low cost spray coating method, which is reliable and reproducible method to prepare uniform CNTs thin films on any substrate. Besides this, simple and inexpensive method of preparation of dispersion of single walled CNTs (SWNTs) in 1,2 dichlorobenzene by using probe type ultrasonicator for debundling the CNTs for improving sensor response were used. The electrical contacts over the dispersed SWNTs were taken using silver paste electrodes. Fabricated sensors clearly show immediate change in resistance as a response to change in temperature of SWNTs. The measured sensitivity (change in resistance with temperature) of the sensor was found ∼ 0.29%/°C in the 25°C to 60°C temperature range.

Pristine carbon nanotubes based resistive temperature sensor

Energy Technology Data Exchange (ETDEWEB)

Alam, Md Bayazeed, E-mail: bayazeed786@gmail.com [CSIR-Central Electronics Engineering Research Institute (CEERI, Pilani, India) (India); Jamia Millia Islamia (New Delhi, India) (India); Saini, Sudhir Kumar, E-mail: sudhirsaini1310@gmail.com [CSIR-Central Electronics Engineering Research Institute (CEERI, Pilani, India) (India); Sharma, Daya Shankar, E-mail: dssharmanit15@gmail.com [CSIR-Central Electronics Engineering Research Institute (CEERI, Pilani, India) (India); Maulana Azad National Institute of Technology (MANIT, Bhopal, India) (India); Agarwal, Pankaj B., E-mail: agarwalbpankj@gmail.com [CSIR-Central Electronics Engineering Research Institute (CEERI, Pilani, India) (India); Academy for Scientific and Innovative Research (AcSIR, Delhi, India) (India)

2016-04-13

A good sensor must be highly sensitive, faster in response, of low cost cum easily producible, and highly reliable. Incorporation of nano-dimensional particles/ wires makes conventional sensors more effective in terms of fulfilling the above requirements. For example, Carbon Nanotubes (CNTs) are promising sensing element because of its large aspect ratio, unique electronic and thermal properties. In addition to their use for widely reported chemical sensing, it has also been explored for temperature sensing. This paper presents the fabrication of CNTs based temperature sensor, prepared on silicon substrate using low cost spray coating method, which is reliable and reproducible method to prepare uniform CNTs thin films on any substrate. Besides this, simple and inexpensive method of preparation of dispersion of single walled CNTs (SWNTs) in 1,2 dichlorobenzene by using probe type ultrasonicator for debundling the CNTs for improving sensor response were used. The electrical contacts over the dispersed SWNTs were taken using silver paste electrodes. Fabricated sensors clearly show immediate change in resistance as a response to change in temperature of SWNTs. The measured sensitivity (change in resistance with temperature) of the sensor was found ∼ 0.29%/°C in the 25°C to 60°C temperature range.

Highly sensitive and selective determination of methylergometrine maleate using carbon nanofibers/silver nanoparticles composite modified carbon paste electrode.

Science.gov (United States)

Kalambate, Pramod K; Rawool, Chaitali R; Karna, Shashi P; Srivastava, Ashwini K

2016-12-01

A highly sensitive and selective voltammetric method for determination of Methylergometrine maleate (MM) in pharmaceutical formulations, urine and blood serum samples has been developed based on enhanced electrochemical response of MM at carbon nanofibers and silver nanoparticles modified carbon paste electrode (CNF-AgNP-CPE). The electrode material was characterized by various techniques viz., X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy. The electrocatalytic response of MM at CNF-AgNP-CPE was studied by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). Under optimized conditions, the proposed sensor exhibits excellent electrochemical response towards MM. The DPV study shows greatly enhanced electrochemical signal for MM at CNF-AgNP-CPE lending high sensitivity to the proposed sensor for MM detection. The peak (Ip) current for MM is found to be rectilinear in the range 4.0×10(-8)-2.0×10(-5)M with a detection limit of 7.1×10(-9)M using DPV. The feasibility of the proposed sensor in analytical applications was investigated by conducting experiments on commercial pharmaceutical formulations, human urine and blood serum samples, which yielded satisfactory recoveries of MM. The proposed electrochemical sensor offers high sensitivity, selectivity, reproducibility and practical utility. We recommend it as an authentic and productive electrochemical sensor for successful determination of MM. Copyright © 2016. Published by Elsevier B.V.

A simple and efficient electrochemical sensor for folic acid determination in human blood plasma based on gold nanoparticles–modified carbon paste electrode

International Nuclear Information System (INIS)

Arvand, Majid; Dehsaraei, Mohammad

2013-01-01

Folic acid (FA) is a water soluble vitamin that exists in many natural species. The lack of FA causes some deficiencies in human body, so finding a simple and sensitive method for determining the FA is important. A new chemically modified electrode was fabricated for determination of FA in human blood plasma using gold nanoparticles (AuNPs) and carbon paste electrode (CPE). Gold nanoparticles–modified carbon paste electrode (AuNPs/CPE) was characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The experimental parameters such as pH, scan rate (ν) and amount of modifier were studied by cyclic voltammetry and the optimized values were chosen. The electrochemical parameters such as diffusion coefficient of FA (D FA ), electrode surface area (A) and electron transfer coefficient (α) were calculated. Square wave voltammetry as an accurate technique was used for quantitative calculations. A good linear relation was observed between anodic peak current (i pa ) and FA concentration (C FA ) in the range of 6 × 10 −8 to 8 × 10 −5 mol L −1 , and the detection limit (LOD) achieved 2.7 × 10 −8 mol L −1 , that is comparable with recently studies. This paper demonstrated a novel, simple, selective and rapid sensor for determining the FA in the biological samples. - Highlights: • We examine a AuNPs/CPE for direct electrooxidation behavior and determination of FA. • Characterization of the electrode showed an obvious increase in surface area and porosity after modification. • The modified electrode showed good ability to distinguish the electrochemical response of FA. • The results were attributed to the specific characteristics of AuNPs present in the AuNPs/CPE. • This paper demonstrated a simple and rapid sensor for determination of FA in plasma

Electrochemical behavior of an anticancer drug 5-fluorouracil at methylene blue modified carbon paste electrode

International Nuclear Information System (INIS)

Bukkitgar, Shikandar D.; Shetti, Nagaraj P.

2016-01-01

A novel sensor for the determination of 5-fluorouracil was constructed by electrochemical deposition of methylene blue on surface of carbon paste electrode. The electrode surface morphology was studied using Atomic force microscopy and XRD. The electrochemical activity of modified electrode was characterized using cyclic voltammetry and differential pulse method. The developed sensor shows impressive enlargement in sensitivity of 5-fluorouracil determination. The peak currents obtained from differential pulse voltammetry was linear with concentration of 5-fluorouracil in the range 4 × 10 −5 –1 × 10 −7 M and detection limit and quantification limit were calculated to be 2.04 nM and 6.18 nM respectively. Further, the sensor was successfully applied in pharmaceutical and biological fluid sample analysis. - Highlights: • Electrochemical oxidation of 5-fluorouracil has been investigated for first time at methylene blue modified carbon paste electrode • The electrode process was irreversible and diffusion controlled • Probable electrochemical mechanism was proposed which involved two proton and two electron transfer reaction • The LOD and LOQ values were calculated to be 2.04 nM and 6.18 nM, respectively, with good selectivity and sensitivity. • Proposed method was applied to 5-Fluorouracil determination in pharmaceutical and spiked human urine samples

Voltammetric sensor for tartrazine determination in soft drinks using poly (p-aminobenzenesulfonic acid)/zinc oxide nanoparticles in carbon paste electrode.

Science.gov (United States)

Karim-Nezhad, Ghasem; Khorablou, Zeynab; Zamani, Maryam; Seyed Dorraji, Parisa; Alamgholiloo, Mahdieh

2017-04-01

Zinc oxide nanoparticles (ZnO NPs) and p-aminobenzenesulfonic acid (p-ABSA) were used to fabricate a modified electrode, as a highly sensitive and selective voltammetric sensor, for the determination of tartrazine. A fast and easy method for the fabrication of poly p-ABSA (Pp-ABSA)/ZnO NPs-carbon paste electrode (Pp-ABSA/ZnO NPs-CPE) by cyclic voltammetry was used. By combining the benefits of Pp-ABSA, ZnO NPs, and CPE, the resulted modified electrode exhibited outstanding electrocatalytic activity in terms of tartrazine oxidation by giving much higher peak currents than those obtained for the unmodified CPE and also other constructed electrodes. The effects of various experimental parameters on the voltammetric response of tartrazine were investigated. At the optimum conditions, the sensor has a linear response in the concentration range of 0349-5.44 μM, a good detection sensitivity (2.2034 μA/μM), and a detection limit of 80 nM of tartrazine. The proposed electrode was used for the determination of tartrazine in soft drinks with satisfactory results. Copyright © 2016. Published by Elsevier B.V.

CMOS Integrated Carbon Nanotube Sensor

International Nuclear Information System (INIS)

Perez, M. S.; Lerner, B.; Boselli, A.; Lamagna, A.; Obregon, P. D. Pareja; Julian, P. M.; Mandolesi, P. S.; Buffa, F. A.

2009-01-01

Recently carbon nanotubes (CNTs) have been gaining their importance as sensors for gases, temperature and chemicals. Advances in fabrication processes simplify the formation of CNT sensor on silicon substrate. We have integrated single wall carbon nanotubes (SWCNTs) with complementary metal oxide semiconductor process (CMOS) to produce a chip sensor system. The sensor prototype was designed and fabricated using a 0.30 um CMOS process. The main advantage is that the device has a voltage amplifier so the electrical measure can be taken and amplified inside the sensor. When the conductance of the SWCNTs varies in response to media changes, this is observed as a variation in the output tension accordingly.

Carbon paste electrode in a solid-contact minicavity

International Nuclear Information System (INIS)

Ferreira, Antonio Ap. Pupim; Ribeiro, Sidney Jose Lima; Fugivara, Cecilio Sadao; Caiut, Jose Mauricio Almeida; Sargentelli, Vagner; Benedetti, Assis Vicente

2011-01-01

This work describes the preparation of carbon paste electrode (EPC) in a solid-contact minicavity and its evaluation when containing carbon paste without and with SiO 2 (Eu 3+ 2%) and SiO 2 (Eu 3+ 2%)-lysine sub-micrometrics particles. For this study cyclic voltammetry and electrochemical impedance measurements were performed at pH 7.4 in 0.1 mol L -1 PBS containing Fe(CN) 6 -3 / -4 redox species. The impedance results were interpreted based on a charge-transfer reaction involving Fe(CN) 6 -3 / -4 species and/or oxygen at higher frequencies and, diffusion of the electroactive species and carbon paste characteristics at lower frequencies. EPC-minicavity is suitable for electroanalysis using modified carbon paste. (author)

Carbon nanotube-based ethanol sensors

International Nuclear Information System (INIS)

Brahim, Sean; Colbern, Steve; Gump, Robert; Moser, Alex; Grigorian, Leonid

2009-01-01

Sensors containing metal-carbon nanotube (CNT) hybrid materials as the active sensing layer were demonstrated for ethanol vapor detection at room temperature. The metal-CNT hybrid materials were synthesized by infiltrating single wall carbon nanotubes (SWNTs) with the transition metals Ti, Mn, Fe, Co, Ni, Pd or Pt. Each sensor was prepared by drop-casting dilute dispersions of a metal-CNT hybrid onto quartz substrate electrodes and the impedimetric responses to varying ethanol concentration were recorded. Upon exposure to ethanol vapor, the ac impedance (Z') of the sensors was found to decrease to different extents. The sensor containing pristine CNT material was virtually non-responsive at low ethanol concentrations (<50 ppm). In contrast, all metal-CNT hybrid sensors showed extremely high sensitivity to trace ethanol levels with 100-fold or more gains in sensitivity relative to the starting SWNT sensor. All hybrid sensors, with the exception of Ni filled CNT, exhibited significantly larger sensor responses to ethanol vapor up to 250 ppm compared to the starting SWNT sensor.

New pastes with high gauge factor for piezoresistive pressure sensors

International Nuclear Information System (INIS)

Szczepanski, Z.; Kalenik, J.; Gonciara, P.; Jakubowska, M.

1999-01-01

The thick film resistors with gauge factor exhibit high reversible changes of resistance under the influence of external load. The piezoresistivity of thick film resistors is utilized in piezoresistive pressure sensors as well as sensors, those allow force detection. The results of studies concerning piezoresistivity in thick film resistors made of pastes elaborated by the authors are presented in this paper. The GF measurement method has been designed and several resistive pastes were tested. The values of gauge factor for these resistive compositions have been evaluated and piezoresistive properties were compared with ESL resistive composition designed for sensor application. (author)

Development of a novel MWCNTs-triazene-modified carbon paste electrode for potentiometric assessment of Hg(II) in the aquatic environments.

Science.gov (United States)

Mashhadizadeh, Mohammad Hossein; Ramezani, Soleyman; Rofouei, Mohammad Kazem

2015-02-01

In this approach, a new chemically modified carbon paste electrode was assembled for potentiometric assay of mercury(II) ion in the aqueous environments. Hereby, MWCNTs were used in the carbon paste composition to meliorate the electrical conductivity and sensitivity of the carbon paste owing to its exceptional physicochemical characteristics. Likewise, participation of the BEPT as a super-selective ionophore in the carbon paste composition boosted significantly the selectivity of the modified electrode towards Hg(II) ions over a wide concentration range of 4.0 × 10(-9)-2.2 × 10(-3) mol L(-1) with a lower detection limit of 3.1 × 10(-9) mol L(-1). Besides, Nernstian slope of the proposed sensor was 28.9(± 0.4)mV/decade over a pH range of 3.0-5.2 with potentiometric short response time of 10s. In the interim, by storing in the dark and cool dry place during non-usage period, the electrode can be used for at least 30 days without any momentous divergence of the potentiometric response. Eventually, to judge about its practical efficiency, the arranged sensor was utilized successfully as an indicator electrode for potentiometric titration of mercury(II) with standard solution of EDTA. As well, the quantitative analysis of mercury(II) ions in some aqueous samples with sensible accuracy and precision was satisfactorily performed. Copyright © 2014 Elsevier B.V. All rights reserved.

A Review: Carbon Nanotube-Based Piezoresistive Strain Sensors

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Waris Obitayo

2012-01-01

Full Text Available The use of carbon nanotubes for piezoresistive strain sensors has acquired significant attention due to its unique electromechanical properties. In this comprehensive review paper, we discussed some important aspects of carbon nanotubes for strain sensing at both the nanoscale and macroscale. Carbon nanotubes undergo changes in their band structures when subjected to mechanical deformations. This phenomenon makes them applicable for strain sensing applications. This paper signifies the type of carbon nanotubes best suitable for piezoresistive strain sensors. The electrical resistivities of carbon nanotube thin film increase linearly with strain, making it an ideal material for a piezoresistive strain sensor. Carbon nanotube composite films, which are usually fabricated by mixing small amounts of single-walled or multiwalled carbon nanotubes with selected polymers, have shown promising characteristics of piezoresistive strain sensors. Studies also show that carbon nanotubes display a stable and predictable voltage response as a function of temperature.

Carbon nanotube temperature and pressure sensors

Energy Technology Data Exchange (ETDEWEB)

Ivanov, Ilia N.; Geohegan, David B.

2017-09-12

The present invention, in one embodiment, provides a method of measuring pressure or temperature using a sensor including a sensor element composed of a plurality of carbon nanotubes. In one example, the resistance of the plurality of carbon nanotubes is measured in response to the application of temperature or pressure. The changes in resistance are then recorded and correlated to temperature or pressure. In one embodiment, the present invention provides for independent measurement of pressure or temperature using the sensors disclosed herein.

Carbon nanotube temperature and pressure sensors

Science.gov (United States)

Ivanov, Ilia N; Geohegan, David Bruce

2013-10-29

The present invention, in one embodiment, provides a method of measuring pressure or temperature using a sensor including a sensor element composed of a plurality of carbon nanotubes. In one example, the resistance of the plurality of carbon nanotubes is measured in response to the application of temperature or pressure. The changes in resistance are then recorded and correlated to temperature or pressure. In one embodiment, the present invention provides for independent measurement of pressure or temperature using the sensors disclosed herein.

Electrochemical Sensor for Determination of Ascorbic Acid Using a 2-Chlorobenzoyl Ferrocene/Carbon Nanotube Paste Electrode

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Sayed Zia Mohammadi

2016-12-01

Full Text Available A chemically modified carbon paste electrode with 2-chlorobenzoyl ferrocene (2CBF and carbon nanotube (2CBFCNPE was employed to study the electrocatalytic oxidation of ascorbic acid in aqueous solution using cyclic voltammetry, square wave voltammetry and chronoamperometry. The diffusion coefficient (D = 1.42 × 10-6 cm2 s-1, and the kinetic parameter such as the catalytic rate constant (k = 3.7 × 10 3 M-1 s-1 of ascorbic acid oxidation at the surface of 2CBFCNPE were determined using electrochemical approaches. It has been found that under an optimum condition (pH 4.0, the oxidation of ascorbic acid at the surface of such an electrode occurs at a potential about 85 mV less positive than that of an unmodified carbon paste electrode. Applying square wave voltammetry, in phosphate buffer solution (PBS of pH 4.0, the oxidation current increases linearly with two concentration intervals of ascorbic acid, one is 1.0 × 10-7-2.5 × 10-6 M and the other is 2.5 × 10-6-7.0 × 10-5 M. Detection limit (3δ was obtained 64.0 nM. This method was also examined for determination of ascorbic acid in some real samples.

Early Age Carbonation Heat and Products of Tricalcium Silicate Paste Subject to Carbon Dioxide Curing

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Zhen Li

2018-05-01

Full Text Available This paper presents a study on the carbonation reaction heat and products of tricalcium silicate (C3S paste exposed to carbon dioxide (CO2 for rapid curing. Reaction heat was measured using a retrofitted micro-calorimeter. The highest heat flow of a C3S paste subject to carbonation curing was 200 times higher than that by hydration, and the cumulative heat released by carbonation was three times higher. The compressive strength of a C3S paste carbonated for 2 h and 24 h was 27.5 MPa and 62.9 MPa, respectively. The 24-h carbonation strength had exceeded the hydration strength at 28 days. The CO2 uptake of a C3S paste carbonated for 2 h and 24 h was 17% and 26%, respectively. The X-ray diffraction (XRD, transmission electron microscope coupled with energy dispersive spectrometer (TEM-EDS, and 29Si magic angle spinning–nuclear magnetic resonance (29Si MAS-NMR results showed that the products of a carbonated C3S paste were amorphous silica (SiO2 and calcite crystal. There was no trace of calcium silicate hydrate (C–S–H or other polymorphs of calcium carbonate (CaCO3 detected.

Voltammetric determination of carbidopa and folic acid using a modified carbon nanotubes paste electrode

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Keshtkar Nasrin

2015-01-01

Full Text Available A novel electrochemical sensor for the selective and sensitive detection of carbidopa in presence of large excess of folic acid at physiological pH was developed by the bulk modification of carbon paste electrode (CPE with carbon nanotubes (CNTs and vinylferrocene. Large peak separation, good sensitivity and stability allow this modified electrode to analyze carbidopa individually and simultaneously along with folic acid. Applying square wave voltammetry (SWV, a linear dynamic range of 1.0×10-6- 7.0×10-4 M with detection limit of 2.0×10-7 M was obtained for carbidopa. Finally, the proposed method was applied to the determination of carbidopa and folic acid in urine sample.

Carbon paste electrode incorporating multi-walled carbon nanotube ...

Indian Academy of Sciences (India)

The preparation and electrochemical performance of the carbon nanotube paste electrode modified with ferrocene (FCMCNPE) was investigated for electrocatalytic behaviour toward oxidation of -acetyl--cysteine (NAC) in the presence of tryptophan (Trp) using cyclic voltammetry (CV) and differential pulse voltammetry ...

Electrochemical detection of carbidopa using a ferrocene-modified carbon nanotube paste electrode

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FATEMEH KARIMI

2009-12-01

Full Text Available A chemically modified carbon paste electrode (MCPE containing ferrocene (FC and carbon nanotubes (CNT was constructed. The electrochemical behavior and stability of the MCPE were investigated by cyclic voltammetry. The electrocatalytic activity of the MCPE was investigated and it showed good characteristics for the oxidation of carbidopa (CD in phosphate buffer solution (PBS. A linear concentration range of 5 to 600 μM CD, with a detection limit of 3.6±0.17 μM CD, was obtained. The diffusion coefficient of CD and the transfer coefficient ( were also determined. The MCPE showed good reproducibility, remarkable long-term stability and especially good surface renewability by simple mechanical polishing. The results showed that this electrode could be used as an electrochemical sensor for the determination of CD in real samples, such as urine samples.

MWCNT-ruthenium oxide composite paste electrode as non-enzymatic glucose sensor.

Science.gov (United States)

Tehrani, Ramin M A; Ab Ghani, Sulaiman

2012-01-01

A non-enzymatic glucose sensor of multi-walled carbon nanotube-ruthenium oxide/composite paste electrode (MWCNT-RuO(2)/CPE) was developed. The electrode was characterized by using XRD, SEM, TEM and EIS. Meanwhile, cyclic voltammetry and amperometry were used to check on the performances of the MWCNT-RuO(2)/CPE towards glucose. The proposed electrode has displayed a synergistic effect of RuO(2) and MWCNT on the electrocatalytic oxidation of glucose in 3M NaOH. This was possible via the formation of transitions of two redox pairs, viz. Ru(VI)/Ru(IV) and Ru(VII)/Ru(VI). A linear range of 0.5-50mM glucose and a limit of detection of 33 μM glucose (S/N=3) were observed. There was no significant interference observable from the traditional interferences, viz. ascorbic acid and uric acid. Indeed, results so obtained have indicated that the developed MWCNT-RuO(2)/CPE would pave the way for a better future to glucose sensor development as its fabrication was without the use of any enzyme. Copyright © 2012 Elsevier B.V. All rights reserved.

Developing an electrochemical sensor based on a carbon paste electrode modified with nano-composite of reduced graphene oxide and CuFe2O4 nanoparticles for determination of hydrogen peroxide.

Science.gov (United States)

Benvidi, Ali; Nafar, Mohammad Taghi; Jahanbani, Shahriar; Tezerjani, Marzieh Dehghan; Rezaeinasab, Masoud; Dalirnasab, Sudabeh

2017-06-01

In this paper, a highly sensitive voltammetric sensor based on a carbon paste electrode with CuFe 2 O 4 nanoparticle (RGO/CuFe 2 O 4 /CPE) was designed for determination of hydrogen peroxide (H 2 O 2 ). The electrocatalytic reduction of H 2 O 2 was examined using various techniques such as cyclic voltammetry (CV), chronoamperometry, amperometry and differential pulse voltammetry (DPV). CuFe 2 O 4 nanoparticles were synthesized by co-precipitation method and characterized with scanning electron microscopy (SEM), Transmission electron microscopy (TEM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) techniques. Then, a high conductive platform based on a carbon paste electrode modified with RGO and CuFe 2 O 4 nanoparticles was prepared as a suitable platform for determination of hydrogen peroxide. Under the optimum conditions (pH5), the modified electrode indicated a fast amperometric response of determination of hydrogen peroxide. Also, the peak current of differential pulse voltammetry (DPV) of hydrogen peroxide is increased linearly with its concentration in the ranges of 2 to 10μM and 10 to 1000μM. The obtained detection limit for hydrogen peroxide was evaluated to be 0.064μM by DPV. The designed sensor was successfully applied for the assay of hydrogen peroxide in biological and pharmaceutical samples such as milk, green tea, and hair dye cream and mouthwash solution. Copyright © 2017. Published by Elsevier B.V.

Simultaneous determination of hydroquinone and catechol at gold nanoparticles mesoporous silica modified carbon paste electrode

Energy Technology Data Exchange (ETDEWEB)

Tashkhourian, J., E-mail: tashkhourian@susc.ac.ir [Department of Chemistry, College of Sciences, Shiraz University, Shiraz 71456 (Iran, Islamic Republic of); Daneshi, M.; Nami-Ana, F. [Department of Chemistry, College of Sciences, Shiraz University, Shiraz 71456 (Iran, Islamic Republic of); Behbahani, M.; Bagheri, A. [Department of Chemistry, Shahid Beheshti University, G.C., Evin, Tehran (Iran, Islamic Republic of)

2016-11-15

Highlights: • An electrochemical sensor based on gold nanoparticles mesoporous silica modified carbon paste electrode was developed. • The electrode provides an accessible surface for simultaneous determination of hydroquinone and catechol. • Hydroquinone and catechol are highly toxic to both environment and human even at very low concentrations. - Abstract: A new electrochemical sensor based on gold nanoparticles mesoporous silica modified carbon paste electrode (AuNPs-MPS) was developed for simultaneous determination of hydroquinone and catechol. Morphology and structure of the AuNPs-MPS were characterized by transmission electron microscopy, X-ray diffraction and Fourier transform infrared spectroscopy. The electrochemical behavior of hydroquinone and catechol were investigated using square wave voltammetry and the results indicate that the electrochemical responses are improved significantly at the modified electrode. The observed oxidative peaks separation of about 120 mV made possible the simultaneous determination of hydroquinone and catechol in their binary-mixture. Under the optimized condition, a linear dynamic range of 10.0 μM–1.0 mM range for hydroquinone with the detection limit of 1.2 μM and from 30.0 μM–1.0 mM for catechol with the detection limit of 1.1 μM were obtained. The applicability of the method was demonstrated by the recovery studies of hydroquinone and catechol in spiked tap water samples.

An ultrasensitive and selective electrochemical sensor for determination of estrone 3-sulfate sodium salt based on molecularly imprinted polymer modified carbon paste electrode.

Science.gov (United States)

Song, Han; Wang, Yuli; Zhang, Lu; Tian, Liping; Luo, Jun; Zhao, Na; Han, Yajie; Zhao, Feilang; Ying, Xue; Li, Yingchun

2017-11-01

A highly sensitive and selective electrochemical sensor based on carbon paste electrode (CPE) modified with molecularly imprinted polymers (MIPs) has been developed for the determination of estrone 3-sulfate sodium salt (ESS). MIPs were prepared in polar medium via bulk polymerization and characterized by scanning electron microscopy and infrared spectroscopy. Cyclic voltammetry was performed to the study preparation process and binding behavior of the MIP-modified CPE (MIP/CPE) toward ESS. The conditions for preparing MIPs and MIP/CPE as well as ESS detection were optimized. Under the optimal experimental conditions, the detection linear range for ESS is 4 × 10 -12 to 6 × 10 -9  M with a limit of detection of 1.18 × 10 -12  M (S/N = 3). In addition, the sensor exhibits high binding affinity toward ESS over its structural analogues with excellent repeatability and stability. The fabricated MIP/CPE was then successfully employed to detect ESS in pregnant mare urine (PMU) without any pretreatment, and the average recoveries were from 99.6 to 104.9% with relative standard deviation less than 3.0%. High-performance liquid chromatography was adopted as a reference to validate the established approach in detecting ESS and their results showed good agreement. The as-prepared sensor has high potential to be a decent tool for on-site determination of ESS in PMU in a fast and convenient manner. Graphical Abstract ᅟ.

Electrochemical characterisation of novel screen-printed carbon paste electrodes for voltammetric measurements

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Sýs Milan

2017-01-01

Full Text Available This work is focused on the homemade screen-printed carbon paste electrode containing basically graphite powder (or glassy carbon powder, poly(vinylbchloride (PVC and paraffin oil. It compares the electrochemical properties of conventional carbon-based electrodes and prepared screen-printed carbon paste electrodes towards [Fe(CN6]3-/[Fe(CN6]4- and quinone/hydroquinone redox couples. Significant attention is paid to the development of the corresponding carbon inks, printing and the surface characterisation of the resulting electrodes by the scanning electron microscopy. An optimization consisted of the selection of the organic solvent, the optimal content of the used polymer with the chosen paste binder, appropriate isolation of electric contact, etc. Very similar properties of the prepared screen-printed electrodes, containing only corresponding carbon powder and 3 % PVC, with their conventional carbon paste electrode and glassy carbon-based electrodes, were observed during their characterisation. Screen-printed electrodes, with the pasting liquid usually provided satisfactory analytical data. Moreover, they can be used in the flow injection analysis and could undoubtedly replace the carbon paste grooved electrodes. It can be assumed that certain progress in the development of electrode materials was achieved by this research.

A Community Network of 100 Black Carbon Sensors

Science.gov (United States)

Preble, C.; Kirchstetter, T.; Caubel, J.; Cados, T.; Keeling, C.; Chang, S.

2017-12-01

We developed a low-cost black carbon sensor, field tested its performance, and then built and deployed a network of 100 sensors in West Oakland, California. We operated the network for 100 days beginning mid-May 2017 to measure spatially resolved black carbon concentrations throughout the community. West Oakland is a San Francisco Bay Area mixed residential and industrial community that is adjacent to regional port and rail yard facilities and surrounded by major freeways. As such, the community is affected by diesel particulate matter emissions from heavy-duty diesel trucks, locomotives, and ships associated with freight movement. In partnership with Environmental Defense Fund, the Bay Area Air Quality Management District, and the West Oakland Environmental Indicators Project, we deployed the black carbon monitoring network outside of residences and business, along truck routes and arterial streets, and at upwind locations. The sensor employs the filter-based light transmission method to measure black carbon and has good precision and correspondence with current commercial black carbon instruments. Throughout the 100-day period, each of the 100 sensors transmitted data via a cellular network. A MySQL database was built to receive and manage the data in real-time. The database included diagnostic features to monitor each sensor's operational status and facilitate the maintenance of the network. Spatial and temporal patterns in black carbon concentrations will be presented, including patterns around industrial facilities, freeways, and truck routes, as well as the relationship between neighborhood concentrations and the BAAQMD's monitoring site. Lessons learned during this first of its kind black carbon monitoring network will also be shared.

Carbon nanotube—cuprous oxide composite based pressure sensors

International Nuclear Information System (INIS)

Karimov, Kh. S.; Chani, Muhammad Tariq Saeed; Khalid, Fazal Ahmad; Khan, Adam; Khan, Rahim

2012-01-01

In this paper, we present the design, the fabrication, and the experimental results of carbon nanotube (CNT) and Cu 2 O composite based pressure sensors. The pressed tablets of the CNT—Cu 2 O composite are fabricated at a pressure of 353 MPa. The diameters of the multiwalled nanotubes (MWNTs) are between 10 nm and 30 nm. The sizes of the Cu 2 O micro particles are in the range of 3–4 μm. The average diameter and the average thickness of the pressed tablets are 10 mm and 4.0 mm, respectively. In order to make low resistance electric contacts, the two sides of the pressed tablet are covered by silver pastes. The direct current resistance of the pressure sensor decreases by 3.3 times as the pressure increases up to 37 kN/m 2 . The simulation result of the resistance—pressure relationship is in good agreement with the experimental result within a variation of ±2%. (condensed matter: structural, mechanical, and thermal properties)

Sensing nitric oxide with a carbon nanofiber paste electrode modified with a CTAB and nafion composite

International Nuclear Information System (INIS)

Zheng, Dongyun; Liu, Xiaojun; Zhu, Shanying; Cao, Huimin; Chen, Yaguang; Hu, Shengshui

2015-01-01

We describe an electrochemical sensor for nitric oxide that was obtained by modifying the surface of a nanofiber carbon paste microelectrode with a film composed of hexadecyl trimethylammonium bromide and nafion. The modified microelectrode displays excellent catalytic activity in the electrochemical oxidation of nitric oxide. The mechanism was studied by scanning electron microscopy and cyclic voltammetry. Under optimal conditions, the oxidation peak current at a working voltage of 0.75 V (vs. SCE) is related to the concentration of nitric oxide in the 2 nM to 0.2 mM range, and the detection limit is as low as 2 nM (at an S/N ratio of 3). The sensor was successfully applied to the determination of nitric oxide released from mouse hepatocytes. (author)

Polyaniline/MWCNTs/starch modified carbon paste electrode for non-enzymatic detection of cholesterol: application to real sample (cow milk).

Science.gov (United States)

Gautam, Vineeta; Singh, Karan P; Yadav, Vijay L

2018-03-01

Nanocomposite materials are potentially revolutionizing many technologies, including sensors. In this paper, we described the application of "PANI/MWCNTs/Starch" modified carbon paste electrode (PCS-CPE) as a simple and highly sensitive cholesterol sensor. This novel nano-composite material has integrated nano-morphology, where polyaniline could interact effectively with the additives; pi-pi stacking "MWCNTs," and covalently bonded with starch. Specific binding sites (sugar chains), better electro-catalytic properties and fast electron transfer facilitated the oxidation of cholesterol. Fourier transform infrared spectra confirmed the interaction of cholesterol with the composite material. The sensing response of PCS was measured by cyclic voltammetry and chronoamperometry (0.1 M PBS-5 used as supporting electrolyte). As the amount of cholesterol increased in the test solution, cyclic voltammograms showed a rise of peak current (cathodic and anodic). Under the normal experimental conditions, the developed sensor exhibited wide linear dynamic range (0.032 to 5 mM) (upper limit is due to lack of solubility of cholesterol), high sensitivity (800 μAmM -1  cm -2 ), low detection limit (0.01 mM) and shorter response time (within 4-6 s). Analytical specificity, selectivity, and sensitivity during cholesterol estimation were compared with the response of some other analytes (ascorbic acid, glucose, l-dopa, urea and lactic acid). This novel sensor was successfully applied to estimate cholesterol in cow milk (used as a model real sample). The sensing platform is highly sensitive and shows a linear response towards cholesterol without using any additional redox mediator or enzyme, thus this material is extremely promising for the realization of a low-cost integrated cholesterol sensor device. Graphical abstract Cyclic voltammetric response of cholesterol of composite modified carbon paste capillary electrode.

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

Carbon nanotube based pressure sensor for flexible electronics

International Nuclear Information System (INIS)

So, Hye-Mi; Sim, Jin Woo; Kwon, Jinhyeong; Yun, Jongju; Baik, Seunghyun; Chang, Won Seok

2013-01-01

Highlights: • The electromechanical change of vertically aligned carbon nanotubes. • Fabrication of CNT field-effect transistor on flexible substrate. • CNT based FET integrated active pressure sensor. • The integrated device yields an increase in the source-drain current under pressure. - Abstract: A pressure sensor was developed based on an arrangement of vertically aligned carbon nanotubes (VACNTs) supported by a polydimethylsiloxane (PDMS) matrix. The VACNTs embedded in the PDMS matrix were structurally flexible and provided repeated sensing operation due to the high elasticities of both the polymer and the carbon nanotubes (CNTs). The conductance increased in the presence of a loading pressure, which compressed the material and induced contact between neighboring CNTs, thereby producing a dense current path and better CNT/metal contacts. To achieve flexible functional electronics, VACNTs based pressure sensor was integrated with field-effect transistor, which is fabricated using sprayed semiconducting carbon nanotubes on plastic substrate

Carbon nanotube based pressure sensor for flexible electronics

Energy Technology Data Exchange (ETDEWEB)

So, Hye-Mi [Department of Nano Mechanics, Nanomechanical Systems Research Division, Korea Institute of Machinery and Materials, Daejeon 305-343 (Korea, Republic of); Sim, Jin Woo [Advanced Nano Technology Ltd., Seoul 132-710 (Korea, Republic of); Kwon, Jinhyeong [Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, Daejeon 305-701 (Korea, Republic of); Yun, Jongju; Baik, Seunghyun [SKKU Advanced Institute of Nanotechnology (SAINT), Department of Energy Science and School of Mechanical Engineering, Sungkyunkwan University, Suwon, Gyeonggi-do 440-746 (Korea, Republic of); Chang, Won Seok, E-mail: paul@kimm.re.kr [Department of Nano Mechanics, Nanomechanical Systems Research Division, Korea Institute of Machinery and Materials, Daejeon 305-343 (Korea, Republic of)

2013-12-15

Highlights: • The electromechanical change of vertically aligned carbon nanotubes. • Fabrication of CNT field-effect transistor on flexible substrate. • CNT based FET integrated active pressure sensor. • The integrated device yields an increase in the source-drain current under pressure. - Abstract: A pressure sensor was developed based on an arrangement of vertically aligned carbon nanotubes (VACNTs) supported by a polydimethylsiloxane (PDMS) matrix. The VACNTs embedded in the PDMS matrix were structurally flexible and provided repeated sensing operation due to the high elasticities of both the polymer and the carbon nanotubes (CNTs). The conductance increased in the presence of a loading pressure, which compressed the material and induced contact between neighboring CNTs, thereby producing a dense current path and better CNT/metal contacts. To achieve flexible functional electronics, VACNTs based pressure sensor was integrated with field-effect transistor, which is fabricated using sprayed semiconducting carbon nanotubes on plastic substrate.

Application of carbon nanotubes flexible strain sensor in smart textiles

Directory of Open Access Journals (Sweden)

Qiong CHENG

2017-10-01

Full Text Available Smart textiles have not only the necessary functions of daily wear, but also the intelligence. The focus of the current textile materials research is the selection of flexible material. For flexible materials, carbon material is one of the ideal materials for preparing flexible strain gauges. The application of flexible strain sensor prepared by carbon nanotubes as a flexible material in smart textiles is the research content. The research status of carbon nanotubes flexible strain sensor is introduced from the aspects of the structure, properties and application. The characteristics and functions of flexible strain gages prepared with carbon nanotube fibers and carbon nanotube films as flexible materials are discussed in terms of selection, preparation method, performance test and application. At the same time, the advantages and disadvantages of the flexible strain sensor of carbon nanotubes are reviewed from the aspects of preparation difficulty, production cost and practical application effect. High sensitivity with high strain will be a key research direction for carbon nanotube flexible strain sensors.

Carbonation of calcium aluminate cement pastes

Directory of Open Access Journals (Sweden)

Fernández-Carrasco, L.

2001-12-01

Full Text Available This work discusses the results from accelerated tests intended to investigate the ways the different curing methods affect the carbonation of calcium aluminate cements pastes (CAC. The research was focused on the mineralogical composition of hydrated and carbonated samples. The compressive strengths and the porosity of the samples have been determined. Results point out that vaterite and aragonite are formed as a result of carbonation of both cubic and hexagonal calcium aluminate hydrates. The polymorph of calcium carbonate formed does not depend on the curing process. Carbonation rates is higher in hexagonal than in cubic hydrates. Results obtained through this study evidence that, as a consequence of the carbonation process of CAC pastes, in test conditions, an increase of the mechanical strengths occurs.

En el presente trabajo se discuten los resultados obtenidos en los ensayos acelerados llevados a cabo para investigar los efectos de diferentes métodos de curado sobre la carbonatacion de pastas del cemento de aluminato de calcio (CAC. Se estudió la composición mineralógica de las muestras hidratadas y carbonatadas. Además, se determinaron las resistencias mecánicas a compresión y la porosidad de las probetas. Los resultados indican que la vaterita y el aragonito son las polimorfías del CaCO₃ que se forman al carbonatar los aluminatos cálcicos hidratos, tanto los de naturaleza hexagonal como cúbica. El polimorfo del carbonato cálcico formado no depende del proceso de curado. La velocidad de carbonatación de los hidratos hexagonales es mayor que la de los cúbicos. Los resultados obtenidos en el presente trabajo han evidenciado que como consecuencia del proceso de carbonatación sobre pastas de CAC, en las condiciones realizadas, se produce un incremento en las resistencias mecánicas.

Multiwall carbon nanotubes chemically modified carbon paste electrodes for determination of gentamicin sulfate in pharmaceutical preparations and biological fluids

Energy Technology Data Exchange (ETDEWEB)

Khalil, M.M., E-mail: magdy_mmagdy@yahoo.com; Abed El-aziz, G.M., E-mail: Gamal_abedelaziz@yahoo.com

2016-02-01

This article focused on the construction and characteristics of novel and sensitive gentamicin carbon paste electrodes which are based on the incorporation of multiwall carbon nanotubes (MWCNTs) which improve the characteristics of the electrodes. The electrodes were constructed based on gentamicin-phosphotungstate (GNS-PTA) called CPE{sub 1}, gentamicin-phosphomolybdate (GNS-PMA) called CPE{sub 2}, GNS-PTA + MWMCNTs called MWCPE{sub 1}, and GNS-PMA + MWMCNTs called MWCPE{sub 2}. The constructed electrodes, at optimum paste composition, exhibited good Nernstian response for determination of gentamicin sulfate (GNS) over a linear concentration range from 2.5 × 10{sup −6} to 1 × 10{sup −2}, 3.0 × 10{sup −6} to 1 × 10{sup −2}, 4.9 × 10{sup −7} to 1 × 10{sup −2} and 5.0 × 10{sup −7} to 1 × 10{sup −2} mol L{sup −1}, with lower detection limit 1 × 10{sup −6}, 1 × 10{sup −6}, 1.9 × 10{sup −7} and 2.2 × 10{sup −7} mol L{sup −1}, and with slope values of 29.0 ± 0.4, 29.2 ± 0.7, 31.2 ± 0.5 and 31.0 ± 0.6 mV/decade for CPE{sub 1}, CPE{sub 2}, MWCPE{sub 1} and MWCPE{sub 2}, respectively. The response of electrodes is not affected by pH in the range 3–8 for CPE{sub 1} and CPE{sub 2} and in the range 2.5–8.5 for MWCPE{sub 1} and MWCPE{sub 2}. The results showed fast dynamic response time (about 8–5 s) and long lifetime (more than 2 months) for all electrodes. The sensors showed high selectivity for gentamicin sulfate (GNS) with respect to a large number of interfering species. The constructed electrodes were successfully applied for determination of GNS in pure form, its pharmaceutical preparations and biological fluids using standard addition and potentiometric titration methods with high accuracy and precision. - Graphical abstract: The incorporation of MWCNTs in paste composition improves the characteristics of the MWCPE electrodes which show better responses in terms of sensitivity, Nernstian slope, linear range, faster

Strain measurement in concrete using embedded carbon roving-based sensors

International Nuclear Information System (INIS)

Quadflieg, Till; Gries, Thomas; Stolyarov, Oleg

2016-01-01

This paper presents the results of the application of carbon rovings as strain sensors for measuring the strain in concrete. In this work, three types of electrically conductive carbon roving with different characteristics were used. The possibility of using carbon rovings as a strain sensor is demonstrated via measurements in tensile and four point bending tests. The experimental setups and methods for measuring the electrical resistance of carbon roving in the roving and concrete are described. The results of the characterization of the electrical behavior as a function of strain of carbon rovings and concrete are presented and discussed. The obtained results indicate that the strain range of carbon rovings optimally corresponds to the strain range of concrete. This characteristic behavior makes the carbon rovings well suited for the use as strain sensors. A good correlation has been found between the electrical resistance-strain curve of the carbon roving and the measurements in the concrete.

Manganese dioxide-modified carbon paste electrode for voltammetric determination of riboflavin

International Nuclear Information System (INIS)

Mehmeti, Eda; Kalcher, Kur; Stanković, Dalibor M.; Chaiyo, Sudkate; Švorc, Ľubomir

2016-01-01

A carbon paste electrode bulk was modified with MnO 2 and investigated for use as an electrochemical sensor for riboflavin (vitamin B 2 ) using differential pulse voltammetry (DPV). Riboflavin displays a well expressed oxidation peak at −0.15 V (versus Ag/AgCl) in solutions with a pH value of 2. Effects of pH value, pulse amplitude and pulse time were optimized by employing DPV. The signals obtained are linearly related to the concentrations of riboflavin in the range from 0.02 to 9 μM. Other features include a 15 nM detection limit, and good reproducibility (±3 %) and repeatability (±2 %). Interferences by common compounds were tested, and the method was successfully applied to the determination of riboflavin in pharmaceutical formulations where is gave recoveries in the range from 95 to 97 %. (author)

Recent trends in carbon nanomaterial-based electrochemical sensors for biomolecules: A review

International Nuclear Information System (INIS)

Yang, Cheng; Denno, Madelaine E.; Pyakurel, Poojan; Venton, B. Jill

2015-01-01

Carbon nanomaterials are advantageous for electrochemical sensors because they increase the electroactive surface area, enhance electron transfer, and promote adsorption of molecules. Carbon nanotubes (CNTs) have been incorporated into electrochemical sensors for biomolecules and strategies have included the traditional dip coating and drop casting methods, direct growth of CNTs on electrodes and the use of CNT fibers and yarns made exclusively of CNTs. Recent research has also focused on utilizing many new types of carbon nanomaterials beyond CNTs. Forms of graphene are now increasingly popular for sensors including reduced graphene oxide, carbon nanohorns, graphene nanofoams, graphene nanorods, and graphene nanoflowers. In this review, we compare different carbon nanomaterial strategies for creating electrochemical sensors for biomolecules. Analytes covered include neurotransmitters and neurochemicals, such as dopamine, ascorbic acid, and serotonin; hydrogen peroxide; proteins, such as biomarkers; and DNA. The review also addresses enzyme-based electrodes that are used to detect non-electroactive species such as glucose, alcohols, and proteins. Finally, we analyze some of the future directions for the field, pointing out gaps in fundamental understanding of electron transfer to carbon nanomaterials and the need for more practical implementation of sensors. - Highlights: • We review the types of carbon nanomaterials used in electrochemical sensors. • Different materials and sensor designs are compared for classes of biomolecules. • Future challenges of better sensor design and implementation are assessed

Recent trends in carbon nanomaterial-based electrochemical sensors for biomolecules: A review

Energy Technology Data Exchange (ETDEWEB)

Yang, Cheng; Denno, Madelaine E.; Pyakurel, Poojan; Venton, B. Jill, E-mail: jventon@virginia.edu

2015-08-05

Carbon nanomaterials are advantageous for electrochemical sensors because they increase the electroactive surface area, enhance electron transfer, and promote adsorption of molecules. Carbon nanotubes (CNTs) have been incorporated into electrochemical sensors for biomolecules and strategies have included the traditional dip coating and drop casting methods, direct growth of CNTs on electrodes and the use of CNT fibers and yarns made exclusively of CNTs. Recent research has also focused on utilizing many new types of carbon nanomaterials beyond CNTs. Forms of graphene are now increasingly popular for sensors including reduced graphene oxide, carbon nanohorns, graphene nanofoams, graphene nanorods, and graphene nanoflowers. In this review, we compare different carbon nanomaterial strategies for creating electrochemical sensors for biomolecules. Analytes covered include neurotransmitters and neurochemicals, such as dopamine, ascorbic acid, and serotonin; hydrogen peroxide; proteins, such as biomarkers; and DNA. The review also addresses enzyme-based electrodes that are used to detect non-electroactive species such as glucose, alcohols, and proteins. Finally, we analyze some of the future directions for the field, pointing out gaps in fundamental understanding of electron transfer to carbon nanomaterials and the need for more practical implementation of sensors. - Highlights: • We review the types of carbon nanomaterials used in electrochemical sensors. • Different materials and sensor designs are compared for classes of biomolecules. • Future challenges of better sensor design and implementation are assessed.

Role of heat on the development of electrochemical sensors on bare and modified Co3O4/CuO composite nanopowder carbon paste electrodes.

Science.gov (United States)

Kumar, Mohan; Kumara Swamy, B E

2016-01-01

The Co3O4/CuO composite nanopowder (NP) was synthesized by a mechanochemical method and characterized by using powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). The synthesized Co3O4/CuO NP was used as a modified carbon paste electrode (MCPE) and further the bare carbon paste and Co3O4/CuO NP modified carbon paste was heated at different temperatures (100, 150, 200 and 250 °C) for 10 min. The Co3O4/CuO NP MCPE was used to study the consequences of scan rate and dopamine concentration. Furthermore the preheated modified electrodes were used to study the electrochemical response to dopamine (DA), ascorbic acid (AA) and uric acid (UA). Copyright © 2015 Elsevier B.V. All rights reserved.

Carbon Nanotube Composite SHM Sensor using Additive Manufacturing

Data.gov (United States)

National Aeronautics and Space Administration — We propose to develop a piezoelectric sensors made of carbon nanotube and lead zirconium titanate (PZT) nanopower dispersed in a polymer matrix. These sensors will...

Facile preparation of poly(methylene blue) modified carbon paste electrode for the detection and quantification of catechin

Energy Technology Data Exchange (ETDEWEB)

Manasa, G [Electrochemistry Research Group, Department of Chemistry, St. Joseph' s College, Lalbagh Road, Bangalore, 560027, Karnataka (India); Mascarenhas, Ronald J, E-mail: ronaldmasc2311@yahoo.co.in [Electrochemistry Research Group, Department of Chemistry, St. Joseph' s College, Lalbagh Road, Bangalore, 560027, Karnataka (India); Satpati, Ashis K [Analytical Chemistry Division, Bhabha Atomic Research Centre, Anushakthi Nagar, Trombay, Mumbai 400094, Maharashtra (India); D' Souza, Ozma J [Electrochemistry Research Group, Department of Chemistry, St. Joseph' s College, Lalbagh Road, Bangalore, 560027, Karnataka (India); Dhason, A [Soft Condensed Matter, Raman Research Institute, Sadashivnagar, Bangalore 560080, Karnataka (India)

2017-04-01

Free radicals are formed as byproducts of metabolism, and are highly unstable due to the presence of unpaired electrons. They readily react with other important cellular components such as DNA causing them damage. Antioxidants such as (+)-catechin (CAT), neutralize free radicals in the blood stream. Hence there is a need for detection and quantification of catechin concentration in various food sources and beverages. Electro-oxidative properties of catechin were investigated using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). A carbon paste working electrode modified by electropolymerizing methylene blue (MB) was fabricated. Field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) techniques were used to study the surface morphology of the electrode. Quasi-reversible electron transfer reaction occurred at + 0.260 V through a diffusion controlled process. In comparison to the bare carbon paste electrode (CPE), there was a significant 5.3 times increment in anodic current sensitivity at the modified electrode at physiological pH. Our findings indicate that for the electro-oxidation of CAT, CPE is a better base material for electropolymerization of MB compared to glassy carbon electrode (GCE). Nyquist plot followed the theoretical shape, indicating low interfacial charge transfer resistance of 0.095 kΩ at the modified electrode. Calibration plots obtained by DPV were linear in two ranges of 1.0 × 10{sup −3} to 1.0 × 10{sup −6} and 1.0 × 10{sup −7} to 0.1 × 10{sup −8} M. The limit of detection (LOD) and limit of quantification (LOQ) was 4.9 nM and 14 nM respectively. Application of the developed electrode was demonstrated by detecting catechin in green tea and spiked fruit juice with satisfactory recoveries. The sensor was stable, sensitive, selective and reproducible. - Highlights: • Remarkable electrocatalytic oxidation of Catechin at poly(methylene blue) modified CPE • Complete elimination of signal

Influence of temperature and humidity on carbon based printed flexible sensors

KAUST Repository

Nag, Anindya

2018-03-02

This paper presents the response of two different types of novel printed sensors towards the change in temperature and humidity. The electrodes of all the sensors were based on carbon materials. Followed by the design and fabrication of the sensors, the responses of the sensors were analyzed for different temperature and humidity conditions in an incubator. These results provide a podium to enhance the alternation of the fabrication procedure of carbon-based printed sensors.

Influence of temperature and humidity on carbon based printed flexible sensors

KAUST Repository

Nag, Anindya; Mukhopadhyay, Subhas; Kosel, Jü rgen

2018-01-01

This paper presents the response of two different types of novel printed sensors towards the change in temperature and humidity. The electrodes of all the sensors were based on carbon materials. Followed by the design and fabrication of the sensors, the responses of the sensors were analyzed for different temperature and humidity conditions in an incubator. These results provide a podium to enhance the alternation of the fabrication procedure of carbon-based printed sensors.

A carbon nanotube-based pressure sensor

International Nuclear Information System (INIS)

Karimov, Kh S; Saleem, M; Khan, Adam; Qasuria, T A; Mateen, A; Karieva, Z M

2011-01-01

In this study, a carbon nanotube (CNT)-based Al/CNT/Al pressure sensor was designed, fabricated and investigated. The sensor was fabricated by depositing CNTs on an adhesive elastic polymer tape and placing this in an elastic casing. The diameter of multiwalled nanotubes varied between 10 and 30 nm. The nominal thickness of the CNT layers in the sensors was in the range ∼300-430 μm. The inter-electrode distance (length) and the width of the surface-type sensors were in the ranges 4-6 and 3-4 mm, respectively. The dc resistance of the sensors decreased 3-4 times as the pressure was increased up to 17 kN m -2 . The resistance-pressure relationships were simulated.

Damage identification in cement paste amended with carbon nanotubes

Science.gov (United States)

Soltangharaei, Vafa; Anay, Rafal; Assi, Lateef; Ziehl, Paul; Matta, Fabio

2018-04-01

Cement-based composites have been used as reliable materials in building and civil engineering infrastructure for many decades. Although there are several advantages, some drawbacks such as premature cracking may be problematic for sensitive applications such as those found in nuclear power plants or associated waste storage facilities. In this study, acoustic emission monitoring was employed to detect stress waves associated with damage progression during uniaxial compressive loading. Acoustic emission data resulting from loading of plain cement paste prisms and cement paste prisms amended with carbon nanotubes are compared. Unsupervised pattern recognition is employed to categorize the data. Results indicate that increased acoustic emission activity was recorded for the plain cement paste prisms when compared to prisms amended with carbon nanotubes.

1-ethanone modified carbon paste electrode

African Journals Online (AJOL)

a

7.00) in cyclic voltammetry, the oxidation of L-cysteic acid at the surface of 4FEPEMCPE is occurred at a potential about 220 mV less positive than that an unmodified carbon paste electrode. The kinetic parameters such as electron transfer coefficient, α, and catalytic reaction rate constant, K/ h, were also determined using.

An all-solid-state screen-printed carbon paste reference electrode based on poly(3,4-ethylenedioxythiophene) as solid contact transducer

International Nuclear Information System (INIS)

Xu, Hui; Pan, Yiwen; Chen, Ying; Ye, Ying; Wang, You; Li, Guang

2012-01-01

The paper presents the design of an all-solid-state portable reference electrode based on a screen-printed carbon paste electrode suitable for rapid human serum testing. The electrode was covered by electropolymerized poly(3,4-ethylenedioxythiophene) (PEDOT) doped with poly(styrenesulfonate) (PSS) as an internal solid contact layer and polyvinyl chloride (PVC) membrane containing lipophilic anion and cation additives. The electrochemical properties of PEDOT(PSS) and PEDOT(PSS)/PVC film on a carbon paste electrode were studied by electrochemical impedance spectroscopy and cyclic voltammetry methods. The reference electrode exhibited good potential stability (for H + , Na + , K + , Ca 2+ , Cl − and CO 2− 3 /HCO − 3 ), good reproducibility and long-term stability. The structure is applied as reference electrodes in human serum pH analysis with pH ion selective planar electrodes, forming a serum pH sensor. The response time of such a pH sensor was 15 s and the sensitivity was −52.2 ± 1.0 mV per decade. Other properties, such as repeatability, reproducibility and stability, were also evaluated. Clinical trials were carried out and compared with the results obtained from the routine hospital electrolyte analyzer, which demonstrated that their analytical performance was closely matched. (paper)

Evaluation of a carbon paste electrode modified with Strontium substituted bismuth and titanium oxide nanoparticles in the toxic metal chromium (VI determination potentiometric method

Directory of Open Access Journals (Sweden)

Atefeh Badri

2016-09-01

Full Text Available Strontium substituted bismuth and titanium oxide nanoparticles with aurivillius morphology synthesized by chemical co-precipitation method and were characterized using XRD. The nanopartcles were used in the composition of the carbon paste to improve conductivity and transduction of chemical signal to electrical signal. A procedure for the determination of chromium is described based on pre-concentration of the dichromate anion at a carbon paste electrode modified. A novel potentiometric Cr6+carbon paste electrode incorporating Strontium substituted bismuth and titanium oxide nanoparticles (SSBTO. Ina acetate buffer solution of pH 5, the sensor displays a rapid and linear response for Cr6+ over the concentration range 1.0×10-5 to 1.0×10-1mol L-1 M with an anionic slope of 54.8± 0.2 mV decade ’ and a detection limit of the order of0.002 /µg ml ‘. The sensor is used for determination of Cr6+ by direct monitoring of Cr6+.The average recoveries of Cr6+at concentration levels of 0.5~40 pg/ml ’is 98.3. The electrode has a short response time (<6s and can be used for at least twenty days without any considerable divergence in potentials and the working pH range was 4.5-6.5. The proposed electrode was successfully used as an indicator for potentiometric determination of Cr6+in water sample.

Simulation and fabrication of carbon nanotubes field emission pressure sensors

International Nuclear Information System (INIS)

Qian Kaiyou; Chen Ting; Yan Bingyong; Lin Yangkui; Xu Dong; Sun Zhuo; Cai Bingchu

2006-01-01

A novel field emission pressure sensor has been achieved utilizing carbon nanotubes (CNTs) as the electron source. The sensor consists of the anode sensing film fabricated by wet etching process and multi-wall carbon nanotubes (MWNTs) cathode in the micro-vacuum chamber. MWNTs on the silicon substrate were grown by thermal CVD. The prototype pressure sensor has a measured sensitivity of about 0.17-0.77 nA/Pa (101-550 KPa). The work shows the potential use of CNTs-based field-emitter in microsensors, such as accelerometers and tactile sensors

"Cut-and-Paste" Manufacture of Multiparametric Epidermal Sensor Systems.

Science.gov (United States)

Yang, Shixuan; Chen, Ying-Chen; Nicolini, Luke; Pasupathy, Praveenkumar; Sacks, Jacob; Su, Becky; Yang, Russell; Sanchez, Daniel; Chang, Yao-Feng; Wang, Pulin; Schnyer, David; Neikirk, Dean; Lu, Nanshu

2015-11-04

Multifunctional epidermal sensor systems (ESS) are manufactured with a highly cost and time effective, benchtop, and large-area "cut-and-paste" method. The ESS made out of thin and stretchable metal and conductive polymer ribbons can be noninvasively laminated onto the skin surface to sense electrophysiological signals, skin temperature, skin hydration, and respiratory rate. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Construction of a carbon ionic liquid paste electrode based on multi-walled carbon nanotubes-synthesized Schiff base composite for trace electrochemical detection of cadmium

International Nuclear Information System (INIS)

Afkhami, Abbas; Khoshsafar, Hosein; Bagheri, Hasan; Madrakian, Tayyebeh

2014-01-01

A simple, highly sensitive and selective carbon nanocomposite electrode has been developed for the electrochemical trace determination of cadmium. This sensor was designed by incorporation of multi-walled carbon nanotubes (MWCNTs) and a new synthesized Schiff base into the carbon paste ionic liquid electrode (CPE IL ) which provides remarkably improved sensitivity and selectivity for the electrochemical stripping assay of Cd(II). The detection limit of the method was found to be 0.08 μg L −1 (S/N = 3) that is lower than the maximum contaminant level of Cd(II) allowed by the Environmental Protection Agency (EPA) in standard drinking waters. The proposed electrode exhibits good applicability for monitoring Cd(II) in various real samples. - Highlights: • A new nanocomposite was prepared and applied to the modification of CPE. • The prepared nanocomposite was characterized by scanning electron microscopy. • The electrode was used to the rapid and selective determination of Cd(II)

Experimental and Numerical Investigations on the Mechanical Characteristics of Carbon Fiber Sensors

Directory of Open Access Journals (Sweden)

Salem Bashmal

2017-09-01

Full Text Available Carbon fiber-based materials possess excellent mechanical properties and show linear piezoresistive behavior, which make them good candidate materials for strain measurements. They have the potential to be used as sensors for various applications such as damage detection, stress analysis and monitoring of manufacturing processes and quality. In this paper, carbon fiber sensors are prepared to perform reliable strain measurements. Both experimental and computational studies were carried out on commercially available carbon fibers in order to understand the response of the carbon fiber sensors due to changes in the axial strain. Effects of parameters such as diameter, length, and epoxy-hardener ratio are discussed. The developed numerical model was calibrated using laboratory-based experimental data. The results of the current study show that sensors with shorter lengths have relatively better sensitivity. This is due to the fact short fibers have low initial resistance, which will increase the change of resistance over initial resistance. Carbon fibers with low number of filaments exhibit linear behavior while nonlinear behavior due to transverse resistance is significant in fibers with large number of filaments. This study will allow researchers to predict the behavior of the carbon fiber sensor in real life and it will serve as a basis for designing carbon fiber sensors to be used in different applications.

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.

Facile stripping voltammetric determination of haloperidol using a high performance magnetite/carbon nanotube paste electrode in pharmaceutical and biological samples

International Nuclear Information System (INIS)

Bagheri, Hasan; Afkhami, Abbas; Panahi, Yunes; Khoshsafar, Hosein; Shirzadmehr, Ali

2014-01-01

Multi-walled carbon nanotubes decorated with Fe 3 O 4 nanoparticles were prepared to construct a novel sensor for the determination of haloperidol (Hp) by voltammetric methods. The morphology and properties of electrode surface were characterized by scanning electron microscopy (SEM) and electrochemical impedance spectroscopy. This modified sensor was used as a selective electrochemical sensor for the determination of trace amounts of Hp. The peak currents of differential pulse and square wave voltammograms of Hp increased linearly with its concentration in the ranges of 1.2 × 10 −3 –0.52 and 6.5 × 10 −4 –0.52 μmol L −1 , respectively. The detection limits for Hp were 7.02 × 10 −4 and 1.33 × 10 −4 μmol L −1 for differential pulse and square wave voltammetric methods, respectively. The results show that the combination of multi-walled carbon nanotubes and Fe 3 O 4 nanoparticles causes a dramatic enhancement in the sensitivity of Hp quantification. This sensor was successfully applied to determine Hp in pharmaceutical samples and biological fluids. The fabricated electrode showed excellent reproducibility, repeatability and stability. - Highlights: • A sensitive paste using Fe 3 O 4 /multi-walled carbon nanotubes was fabricated. • Haloperidol determination is based on its adsorption on the surface of Fe 3 O 4 /MWCNTs. • Different electrochemical methods and impedance spectroscopy were used for this study. • Haloperidol was determined in pharmaceutical and biological samples. • In comparison to other conventional methods, this method is simple, rapid, selective and cost-effective

Using a cut-paste method to prepare a carbon nanotube fur electrode

International Nuclear Information System (INIS)

Zhang, H; Cao, G P; Yang, Y S

2007-01-01

We describe and realize an aligned carbon nanotube array based 'carbon nanotube fur (CNTF)' electrode. We removed an 800 μm long aligned carbon nanotube array from the silica substrate, and then pasted the array on a nickel foam current collector to obtain a CNTF electrode. CNTF's characteristics and electrochemical properties were studied systemically in this paper. The cut-paste method is simple, and does not damage the microstructure of the aligned carbon nanotube array. The CNTF electrode obtained a specific capacitance of 14.1 F g -1 and excellent rate capability

Voltammetric Determination of Homocysteine Using Multiwall Carbon Nanotube Paste Electrode in the Presence of Chlorpromazine as a Mediator

Directory of Open Access Journals (Sweden)

Fathali Gholami-Orimi

2012-01-01

Full Text Available We propose chlorpromazine (CHP as a new mediator for the rapid, sensitive, and highly selective voltammetric determination of homocysteine (Hcy using multiwall carbon nanotube paste electrode (MWCNTPE. The experimental results showed that the carbon nanotube paste electrode has a highly electrocatalytic activity for the oxidation of Hcy in the presence of CHP as a mediator. Cyclic voltammetry, double potential step chronoamperometry, and square wave voltammetry (SWV are used to investigate the suitability of CHP at the surface of MWCNTPE as a mediator for the electrocatalytic oxidation of Hcy in aqueous solutions. The kinetic parameters of the system, including electron transfer coefficient, and catalytic rate constant were also determined using the electrochemical approaches. In addition, SWV was used for quantitative analysis. SWV showed wide linear dynamic range (0.1–210.0 μM Hcy with a detection limit of 0.08 μM Hcy. Finally, this method was also examined as a selective, simple, and precise electrochemical sensor for the determination of Hcy in real samples.

Fabrication and Characterization of a Pressure Sensor using a Pitch-based Carbon Fiber

International Nuclear Information System (INIS)

Park, Chang Sin; Kang, Bo Seon; Lee, Dong Weon

2007-01-01

This paper reports fabrication and characterization of a pressure sensor using a pitch-based carbon fiber. Pitch-based carbon fibers have been shown to exhibit the piezoresistive effect, in which the electric resistance of the carbon fiber changes under mechanical deformation. The main structure of pressure sensors was built by performing backside etching on a SOI wafer and creating a suspended square membrane on the front side. An AC electric field which causes dielectrophoresis was used for the alignment and deposition of a carbon fiber across the microscale gap between two electrodes on the membrane. The fabricated pressure sensors were tested by applying static pressure to the membrane and measuring the resistance change of the carbon fiber. The resistance change of carbon fibers clearly shows linear response to the applied pressure and the calculated sensitivities of pressure sensors are 0.25∼0.35 and 61.8 Ω/kΩ·bar for thicker and thinner membrane, respectively. All these observations demonstrated the possibilities of carbon fiber-based pressure sensors

Recent trends in carbon nanomaterial-based electrochemical sensors for biomolecules: A review

Science.gov (United States)

Yang, Cheng; Denno, Madelaine E.; Pyakurel, Poojan; Venton, B. Jill

2015-01-01

Carbon nanomaterials are advantageous for electrochemical sensors because they increase the electroactive surface area, enhance electron transfer, and promote adsorption of molecules. Carbon nanotubes (CNTs) have been incorporated into electrochemical sensors for biomolecules and strategies have included the traditional dip coating and drop casting methods, direct growth of CNTs on electrodes and the use of CNT fibers and yarns made exclusively of CNTs. Recent research has also focused on utilizing many new types of carbon nanomaterials beyond CNTs. Forms of graphene are now increasingly popular for sensors including reduced graphene oxide, carbon nanohorns, graphene nanofoams, graphene nanorods, and graphene nanoflowers. In this review, we compare different carbon nanomaterial strategies for creating electrochemical sensors for biomolecules. Analytes covered include neurotransmitters and neurochemicals, such as dopamine, ascorbic acid, and serotonin; hydrogen peroxide; proteins, such as biomarkers; and DNA. The review also addresses enzyme-based electrodes that are used to detect non-electroactive species such as glucose, alcohols, and proteins. Finally, we analyze some of the future directions for the field, pointing out gaps in fundamental understanding of electron transfer to carbon nanomaterials and the need for more practical implementation of sensors. PMID:26320782

Development of an enzymatic sensor for carbon monoxide

International Nuclear Information System (INIS)

Hurtado, Clara; Gomez, Diana; Larmat, Fernando; Torres, Walter; Cuervo, Raul; Bravo, Enrique; Benitez, Neyla

2003-01-01

The detection and the pursuit of gases that contribute in the increase of the atmospheric contamination are a necessity, for what the electrochemical sensors have potential industrial applications for the control of the quality of the air. The development of amperometric sensor based on enzymes offers advantages, since the use of the biological component provides him high selectivity due to the great specificity of the substrate of the enzyme. The monoxide of carbon (CO) it is a polluting, poisonous gas, taken place during the incomplete combustion of organic materials (natural gas, petroleum, gasoline, coal and vegetable material). The determination of monoxide of carbon (CO) it can be reached by electrochemical mediums using the methylene blue like the electronic mediator for the enzyme monoxide of carbon oxidase (COx)

Effects of Temperature on Polymer/Carbon Chemical Sensors

Science.gov (United States)

Manfireda, Allison; Lara, Liana; Homer, Margie; Yen, Shiao-Pin; Kisor, Adam; Ryan, Margaret; Zhou, Hanying; Shevade, Abhijit; James, Lim; Manatt, Kenneth

2009-01-01

Experiments were conducted on the effects of temperature, polymer molecular weight, and carbon loading on the electrical resistances of polymer/carbon-black composite films. The experiment were performed in a continuing effort to develop such films as part of the JPL Electronic Nose (ENose), that would be used to detect, identify, and quantify parts-per-million (ppm) concentration levels of airborne chemicals in the space shuttle/space station environments. The polymers used in this study were three formulations of poly(ethylene oxide) [PEO] that had molecular weights of 20 kilodaltons, 600 kilodaltons, and 1 megadalton, respectively. The results of one set of experiments showed a correlation between the polymer molecular weight and the percolation threshold. In a second set of experiments, differences among the temperature dependences of resistance were observed for different carbon loadings; these differences could be explained by a change in the conduction mechanism. In a third set of experiments, the responses of six different polymer/carbon composite sensors to three analytes (water vapor, methanol, methane) were measured as a function of temperature (28 to 36 C). For a given concentration of each analyte, the response of each sensor decreased with increasing temperature, in a manner different from those of the other sensors.

Bio-Inspired Carbon Monoxide Sensors with Voltage-Activated Sensitivity

KAUST Repository

Savagatrup, Suchol

2017-09-27

Carbon monoxide (CO) outcompetes oxygen when binding to the iron center of hemeproteins, leading to a reduction in blood oxygen level and acute poisoning. Harvesting the strong specific interaction between CO and the iron porphyrin provides a highly selective and customizable sensor. We report the development of chemiresistive sensors with voltage-activated sensitivity for the detection of CO comprising iron porphyrin and functionalized single-walled carbon nanotubes (F-SWCNTs). Modulation of the gate voltage offers a predicted extra dimension for sensing. Specifically, the sensors show a significant increase in sensitivity toward CO when negative gate voltage is applied. The dosimetric sensors are selective to ppm levels of CO and functional in air. UV/Vis spectroscopy, differential pulse voltammetry, and density functional theory reveal that the in situ reduction of FeIII to FeII enhances the interaction between the F-SWCNTs and CO. Our results illustrate a new mode of sensors wherein redox active recognition units are voltage-activated to give enhanced and highly specific responses.

Humidity Sensor Based on Multi-Walled Carbon Nanotube Thin Films

International Nuclear Information System (INIS)

Cao, C.L.; Hu, C.G.; Fang, L.; Wang, S.X.; Cao, C.L.; Tian, Y.S.; Pan, C.Y.

2009-01-01

The properties of the humidity sensors made of chemically treated and untreated multi-walled carbon nano tube (MWCNT) thin films are investigated systematically. It shows that both the chemically treated and untreated MWCNT thin films demonstrate humidity sensitive properties, but the former have stronger sensitivity than the latter. In the range of 11%-98% relative humidity (RH), the resistances of the chemically treated and untreated MWCNT humidity sensors increase 120% and 28%, respectively. Moreover, the treated humidity sensors showed higher sensitivity and better stability. In addition, the response and recover properties, and stabilization of the humidity sensors are measured, and the humidity sensitive mechanisms of the sensors are analyzed. The humidity sensitivity of carbon nano tube thin films indicates it promise as a kind of humidity sensitive material

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

Facile stripping voltammetric determination of haloperidol using a high performance magnetite/carbon nanotube paste electrode in pharmaceutical and biological samples

Energy Technology Data Exchange (ETDEWEB)

Bagheri, Hasan, E-mail: h.bagheri@srbiau.ac.ir [Chemical Injuries Research Center, Baqiyatallah University of Medical Sciences, Tehran (Iran, Islamic Republic of); Afkhami, Abbas [Faculty of Chemistry, Bu-Ali Sina University, Hamedan (Iran, Islamic Republic of); Panahi, Yunes [Chemical Injuries Research Center, Baqiyatallah University of Medical Sciences, Tehran (Iran, Islamic Republic of); Khoshsafar, Hosein; Shirzadmehr, Ali [Faculty of Chemistry, Bu-Ali Sina University, Hamedan (Iran, Islamic Republic of)

2014-04-01

Multi-walled carbon nanotubes decorated with Fe{sub 3}O{sub 4} nanoparticles were prepared to construct a novel sensor for the determination of haloperidol (Hp) by voltammetric methods. The morphology and properties of electrode surface were characterized by scanning electron microscopy (SEM) and electrochemical impedance spectroscopy. This modified sensor was used as a selective electrochemical sensor for the determination of trace amounts of Hp. The peak currents of differential pulse and square wave voltammograms of Hp increased linearly with its concentration in the ranges of 1.2 × 10{sup −3}–0.52 and 6.5 × 10{sup −4}–0.52 μmol L{sup −1}, respectively. The detection limits for Hp were 7.02 × 10{sup −4} and 1.33 × 10{sup −4} μmol L{sup −1} for differential pulse and square wave voltammetric methods, respectively. The results show that the combination of multi-walled carbon nanotubes and Fe{sub 3}O{sub 4} nanoparticles causes a dramatic enhancement in the sensitivity of Hp quantification. This sensor was successfully applied to determine Hp in pharmaceutical samples and biological fluids. The fabricated electrode showed excellent reproducibility, repeatability and stability. - Highlights: • A sensitive paste using Fe{sub 3}O{sub 4}/multi-walled carbon nanotubes was fabricated. • Haloperidol determination is based on its adsorption on the surface of Fe{sub 3}O{sub 4}/MWCNTs. • Different electrochemical methods and impedance spectroscopy were used for this study. • Haloperidol was determined in pharmaceutical and biological samples. • In comparison to other conventional methods, this method is simple, rapid, selective and cost-effective.

Extraordinarily Stretchable All-Carbon Collaborative Nanoarchitectures for Epidermal Sensors

KAUST Repository

Cai, Yichen

2017-06-16

Multifunctional microelectronic components featuring large stretchability, high sensitivity, high signal-to-noise ratio (SNR), and broad sensing range have attracted a huge surge of interest with the fast developing epidermal electronic systems. Here, the epidermal sensors based on all-carbon collaborative percolation network are demonstrated, which consist 3D graphene foam and carbon nanotubes (CNTs) obtained by two-step chemical vapor deposition processes. The nanoscaled CNT networks largely enhance the stretchability and SNR of the 3D microarchitectural graphene foams, endowing the strain sensor with a gauge factor as high as 35, a wide reliable sensing range up to 85%, and excellent cyclic stability (>5000 cycles). The flexible and reversible strain sensor can be easily mounted on human skin as a wearable electronic device for real-time and high accuracy detecting of electrophysiological stimuli and even for acoustic vibration recognition. The rationally designed all-carbon nanoarchitectures are scalable, low cost, and promising in practical applications requiring extraordinary stretchability and ultrahigh SNRs.

Extraordinarily Stretchable All-Carbon Collaborative Nanoarchitectures for Epidermal Sensors

KAUST Repository

Cai, Yichen; Shen, Jie; Dai, Ziyang; Zang, Xiaoxian; Dong, Qiuchun; Guan, Guofeng; Li, Lain-Jong; Huang, Wei; Dong, Xiaochen

2017-01-01

Multifunctional microelectronic components featuring large stretchability, high sensitivity, high signal-to-noise ratio (SNR), and broad sensing range have attracted a huge surge of interest with the fast developing epidermal electronic systems. Here, the epidermal sensors based on all-carbon collaborative percolation network are demonstrated, which consist 3D graphene foam and carbon nanotubes (CNTs) obtained by two-step chemical vapor deposition processes. The nanoscaled CNT networks largely enhance the stretchability and SNR of the 3D microarchitectural graphene foams, endowing the strain sensor with a gauge factor as high as 35, a wide reliable sensing range up to 85%, and excellent cyclic stability (>5000 cycles). The flexible and reversible strain sensor can be easily mounted on human skin as a wearable electronic device for real-time and high accuracy detecting of electrophysiological stimuli and even for acoustic vibration recognition. The rationally designed all-carbon nanoarchitectures are scalable, low cost, and promising in practical applications requiring extraordinary stretchability and ultrahigh SNRs.

Carbon nanomaterial based electrochemical sensors for biogenic amines

International Nuclear Information System (INIS)

Yang, Xiao; He, Xiulan; Li, Fangping; Fei, Junjie; Feng, Bo; Ding, Yonglan

2013-01-01

This review describes recent advances in the use of carbon nanomaterials for electroanalytical detection of biogenic amines (BAs). It starts with a short introduction into carbon nanomaterials such as carbon nanotubes, graphene, nanodiamonds, carbon nanofibers, fullerenes, and their composites. Next, electrochemical sensing schemes are discussed for various BAs including dopamine, serotonin, epinephrine, norepinephrine, tyramine, histamine and putrescine. Examples are then given for methods for simultaneous detection of various BAs. Finally, we discuss the current and future challenges of carbon nanomaterial-based electrochemical sensors for BAs. The review contains 175 references. (author)

Single Walled Carbon Nanotube Based Air Pocket Encapsulated Ultraviolet Sensor.

Science.gov (United States)

Kim, Sun Jin; Han, Jin-Woo; Kim, Beomseok; Meyyappan, M

2017-11-22

Carbon nanotube (CNT) is a promising candidate as a sensor material for the sensitive detection of gases/vapors, biomarkers, and even some radiation, as all these external variables affect the resistance and other properties of nanotubes, which forms the basis for sensing. Ultraviolet (UV) radiation does not impact the nanotube properties given the substantial mismatch of bandgaps and therefore, CNTs have never been considered for UV sensing, unlike the popular ZnO and other oxide nanwires. It is well-known that UV assists the adsorption/desorption characteristics of oxygen on carbon nanotubes, which changes the nanotube resistance. Here, we demonstrate a novel sensor structure encapsulated with an air pocket, where the confined air is responsible for the UV sensing mechanism and assures sensor stability and repeatability over time. In addition to the protection from any contamination, the air pocket encapsulated sensor offers negligible baseline drift and fast recovery compared to previously reported sensors. The air pocket isolated from the outside environment can act as a stationary oxygen reservoir, resulting in consistent sensor characteristics. Furthermore, this sensor can be used even in liquid environments.

Carbon Nanofiber Cement Sensors to Detect Strain and Damage of Concrete Specimens Under Compression.

Science.gov (United States)

Galao, Oscar; Baeza, F Javier; Zornoza, Emilio; Garcés, Pedro

2017-11-24

Cement composites with nano-additions have been vastly studied for their functional applications, such as strain and damage sensing. The capacity of a carbon nanofiber (CNF) cement paste has already been tested. However, this study is focused on the use of CNF cement composites as sensors in regular concrete samples. Different measuring techniques and humidity conditions of CNF samples were tested to optimize the strain and damage sensing of this material. In the strain sensing tests (for compressive stresses up to 10 MPa), the response depends on the maximum stress applied. The material was more sensitive at higher loads. Furthermore, the actual load time history did not influence the electrical response, and similar curves were obtained for different test configurations. On the other hand, damage sensing tests proved the capability of CNF cement composites to measure the strain level of concrete samples, even for loads close to the material's strength. Some problems were detected in the strain transmission between sensor and concrete specimens, which will require specific calibration of each sensor one attached to the structure.

Ultrasensitive, Stretchable Strain Sensors Based on Fragmented Carbon Nanotube Papers

KAUST Repository

Zhou, Jian; Yu, Hu; Xu, Xuezhu; Han, Fei; Lubineau, Gilles

2017-01-01

The development of strain sensors featuring both ultra high sensitivity and high stretchability is still a challenge. We demonstrate that strain sensors based on fragmented single-walled carbon nanotube (SWCNT) paper embedded in poly

Mercapto-ordered carbohydrate-derived porous carbon electrode as a novel electrochemical sensor for simple and sensitive ultra-trace detection of omeprazole in biological samples

Energy Technology Data Exchange (ETDEWEB)

Kalate Bojdi, Majid [Department of Chemistry, Faculty of Science, Shahid Beheshti University, Tehran 1983963113 (Iran, Islamic Republic of); Faculty of Chemistry, Kharazmi (Tarbiat Moallem) University, Tehran (Iran, Islamic Republic of); Behbahani, Mohammad [Department of Chemistry, Faculty of Science, Shahid Beheshti University, Tehran 1983963113 (Iran, Islamic Republic of); Mashhadizadeh, Mohammad Hosein [Faculty of Chemistry, Kharazmi (Tarbiat Moallem) University, Tehran (Iran, Islamic Republic of); Bagheri, Akbar [Department of Chemistry, Faculty of Science, Shahid Beheshti University, Tehran 1983963113 (Iran, Islamic Republic of); Hosseiny Davarani, Saied Saeed, E-mail: ss-hosseiny@sbu.ac.ir [Department of Chemistry, Faculty of Science, Shahid Beheshti University, Tehran 1983963113 (Iran, Islamic Republic of); Farahani, Ali [Department of Chemistry, Faculty of Science, Shahid Beheshti University, Tehran 1983963113 (Iran, Islamic Republic of)

2015-03-01

We are introducing mercapto-mesoporous carbon modified carbon paste electrode (mercapto-MP-C-CPE) as a new sensor for trace determination of omeprazole (OM) in biological samples. The synthesized modifier was characterized by thermogravimetry analysis (TGA), differential thermal analysis (DTA), transmission electron microscopy (TEM), Fourier transform infrared spectrometry (FT-IR), X-ray diffraction (XRD), elemental analysis (CHN) and N{sub 2} adsorption surface area measurement (BET). The electrochemical response characteristic of the modified-CPE toward OM was investigated by cyclic and differential pulse voltammetry (CV and DPV). The proposed sensor displayed a good electrooxidation response to the OM, its linear range is 0.25 nM to 25 μM with a detection limit of 0.04 nM under the optimized conditions. The prepared modified electrode shows several advantages such as high sensitivity, long-time stability, wide linear range, ease of preparation and regeneration of the electrode surface by simple polishing and excellent reproducibility. - Highlights: • A modified nanoporous carbon as a novel sensor • High stability and good repeatability and reproducibility by the prepared sensor • Trace determination of omeprazole • Biological and pharmaceutical samples.

Mercapto-ordered carbohydrate-derived porous carbon electrode as a novel electrochemical sensor for simple and sensitive ultra-trace detection of omeprazole in biological samples

International Nuclear Information System (INIS)

Kalate Bojdi, Majid; Behbahani, Mohammad; Mashhadizadeh, Mohammad Hosein; Bagheri, Akbar; Hosseiny Davarani, Saied Saeed; Farahani, Ali

2015-01-01

We are introducing mercapto-mesoporous carbon modified carbon paste electrode (mercapto-MP-C-CPE) as a new sensor for trace determination of omeprazole (OM) in biological samples. The synthesized modifier was characterized by thermogravimetry analysis (TGA), differential thermal analysis (DTA), transmission electron microscopy (TEM), Fourier transform infrared spectrometry (FT-IR), X-ray diffraction (XRD), elemental analysis (CHN) and N 2 adsorption surface area measurement (BET). The electrochemical response characteristic of the modified-CPE toward OM was investigated by cyclic and differential pulse voltammetry (CV and DPV). The proposed sensor displayed a good electrooxidation response to the OM, its linear range is 0.25 nM to 25 μM with a detection limit of 0.04 nM under the optimized conditions. The prepared modified electrode shows several advantages such as high sensitivity, long-time stability, wide linear range, ease of preparation and regeneration of the electrode surface by simple polishing and excellent reproducibility. - Highlights: • A modified nanoporous carbon as a novel sensor • High stability and good repeatability and reproducibility by the prepared sensor • Trace determination of omeprazole • Biological and pharmaceutical samples

Construction of a sensitive and selective sensor for morphine using chitosan coated Fe3O4 magnetic nanoparticle as a modifier

International Nuclear Information System (INIS)

Dehdashtian, Sara; Gholivand, Mohammad Bagher; Shamsipur, Mojtaba; Kariminia, Samira

2016-01-01

A simple and sensitive sensor based on carbon paste electrode (CPE) modified by chitosan-coated magnetic nanoparticle (CMNP) was developed for the electrochemical determination of morphine (MO). The proposed sensor was characterized with scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). The electrooxidation of MO was studied on modified carbon paste electrode using cyclic voltammetry, chronoamperometry and differential pulse voltammetry as diagnostic techniques. The oxidation peak potential of morphine on the CMNP/CPE appeared at 380 mV which was accompanied with smaller overpotential and increase in oxidation peak current compared to that obtained on the bare carbon paste electrode (CPE). Under optimum conditions the sensor provides two linear DPV responses in the range of 10–2000 nM and 2–720 μM for MO with a detection limit of 3 nM. The proposed sensor was successfully applied for monitoring of MO in serum and urine samples and satisfactory results were obtained. - Highlights: • A sensitive and selective voltammetric sensor for MO by using a carbon paste electrode modified with CMNP was introduced. • CMNP as a new modifier facilitates the charge transfer of MO oxidation process. • The proposed sensor was used successfully for MO determination in biological fluids such as serum and urine samples. • This sensor is fabricated easily and has good stability and high sensitivity.

Nanomolar simultaneous determination of tryptophan and melatonin by a new ionic liquid carbon paste electrode modified with SnO{sub 2}-Co{sub 3}O{sub 4}@rGO nanocomposite

Energy Technology Data Exchange (ETDEWEB)

Zeinali, Homa [Department of Chemistry, Payame Noor University, Qazvin (Iran, Islamic Republic of); Bagheri, Hasan, E-mail: h.bagheri82@gmail.com [Chemical Injuries Research Center, Baqiyatallah University of Medical Sciences, Tehran (Iran, Islamic Republic of); Monsef-Khoshhesab, Zahra [Department of Chemistry, Payame Noor University, Qazvin (Iran, Islamic Republic of); Khoshsafar, Hosein [Department of Internal Medicine, Zabol University of Medical Sciences, Zabol (Iran, Islamic Republic of); Hajian, Ali [Laboratory for Sensors, Department of Microsystems Engineering (IMTEK), University of Freiburg, Georges Köhler Allee 103, 79110 Freiburg (Germany)

2017-02-01

This work describes the development of a new sensor for simultaneous determination of tryptophan and melatonin. The proposed sensor was an ionic liquid carbon paste electrode modified with reduced graphene oxides decorated with SnO{sub 2}-Co{sub 3}O{sub 4} nanoparticles. The voltammetric oxidation of the analytes by the proposed sensor confirmed that the electrooxidation process undergoes a two-electron/one-proton reaction for melatonin and a two-electron/two-proton reaction for tryptophan in diffusion-controlled processes. Moreover, based on the excellent electrochemical properties of the modified electrode, a sensitive voltammetric method was used for individual and simultaneous determination of melatonin and tryptophan in the aqueous solutions. Under the optimized experimental conditions, a linear response obtained in the range of 0.02 to 6.00 μmol L{sup −1} with detection limits of 4.1 and 3.2 nmol L{sup −1} for melatonin and tryptophan, respectively. The prepared sensor possessed accurate and rapid response toward melatonin and tryptophan with a good sensitivity, selectivity, stability, and repeatability. Finally, the applicability of the proposed sensor was verified by evaluation of melatonin and tryptophan in various real samples including human serum and tablet samples. - Highlights: • Ionic liquid-SnO{sub 2}-Co{sub 3}O{sub 4}@rGO nanocomposite as electrode material • This modifier can promote the electrochemical properties of carbon paste electrode. • Determination of tryptophan and melatonin was investigated.

Cement Pastes and Mortars Containing Nitrogen-Doped and Oxygen-Functionalized Multiwalled Carbon Nanotubes

Directory of Open Access Journals (Sweden)

Mauricio Martínez-Alanis

2016-01-01

Full Text Available Cement pastes and mortars based on ordinary Portland cement containing nitrogen-doped multiwalled carbon nanotubes (MWCNT-Nx or oxygen-functionalized multiwalled carbon nanotubes (MWCNT-Ox are investigated. To incorporate MWCNTs into the cementitious matrix, the as-produced carpets are dispersed over periods of 1 and 2 hours in distilled water at pH levels of 1 and 7. The cement pastes are prepared by adding 0.1 wt% of MWCNTs to cement powder, followed by characterization with SEM and X-ray diffraction (XRD at an early age (first hours of hydration. The mortars are mechanically characterized during the hydration process for a period of 28 days. SEM characterization of cement pastes revealed that the carbon nanotubes are well incorporated in the cementitious matrix, with the hydrated cement grains interconnected by long carbon nanotubes. XRD characterizations demonstrated that, during the hydration of cement pastes, different peaks emerged that were associated with ettringite, hydrated calcium silicate, and calcium hydroxide, among other structures. Results of the compressive strength measurements for mortars simultaneously mixed with MWCNT-Nx and MWCNT-Ox reached an increment of approximately 30% in compressive strength. In addition, density functional theory calculations were performed in nitrogen-doped and oxygen-functionalized carbon nanotubes interacting with a cement grain.

Flexible carbon nanotube nanocomposite sensor for multiple physiological parameter monitoring

KAUST Repository

Nag, Anindya; Mukhopadhyay, Subhas Chandra; Kosel, Jü rgen

2016-01-01

The paper presents the design, development, and fabrication of a flexible and wearable sensor based on carbon nanotube nanocomposite for monitoring specific physiological parameters. Polydimethylsiloxane (PDMS) was used as the substrate with a thin layer of a nanocomposite comprising functionalized multi-walled carbon nanotubes (MWCNTs) and PDMS as electrodes. The sensor patch functionalized on strain-sensitive capacitive sensing from interdigitated electrodes which were patterned with a laser on the nanocomposite layer. The thickness of the electrode layer was optimized regarding strain and conductivity. The sensor patch was connected to a monitoring device from one end and attached to the body on the other for examining purposes. Experimental results show the capability of the sensor patch used to detect respiration and limb movements. This work is a stepping stone of the sensing system to be developed for multiple physiological parameters.

Flexible carbon nanotube nanocomposite sensor for multiple physiological parameter monitoring

KAUST Repository

Nag, Anindya

2016-10-16

The paper presents the design, development, and fabrication of a flexible and wearable sensor based on carbon nanotube nanocomposite for monitoring specific physiological parameters. Polydimethylsiloxane (PDMS) was used as the substrate with a thin layer of a nanocomposite comprising functionalized multi-walled carbon nanotubes (MWCNTs) and PDMS as electrodes. The sensor patch functionalized on strain-sensitive capacitive sensing from interdigitated electrodes which were patterned with a laser on the nanocomposite layer. The thickness of the electrode layer was optimized regarding strain and conductivity. The sensor patch was connected to a monitoring device from one end and attached to the body on the other for examining purposes. Experimental results show the capability of the sensor patch used to detect respiration and limb movements. This work is a stepping stone of the sensing system to be developed for multiple physiological parameters.

Electrochemical Sensors Based on Carbon Nanotubes

Directory of Open Access Journals (Sweden)

Md. Aminur Rahman

2009-03-01

Full Text Available This review focuses on recent contributions in the development of the electrochemical sensors based on carbon nanotubes (CNTs. CNTs have unique mechanical and electronic properties, combined with chemical stability, and behave electrically as a metal or semiconductor, depending on their structure. For sensing applications, CNTs have many advantages such as small size with larger surface area, excellent electron transfer promoting ability when used as electrodes modifier in electrochemical reactions, and easy protein immobilization with retention of its activity for potential biosensors. CNTs play an important role in the performance of electrochemical biosensors, immunosensors, and DNA biosensors. Various methods have been developed for the design of sensors using CNTs in recent years. Herein we summarize the applications of CNTs in the construction of electrochemical sensors and biosensors along with other nanomaterials and conducting polymers.

Construction of a sensitive and selective sensor for morphine using chitosan coated Fe{sub 3}O{sub 4} magnetic nanoparticle as a modifier

Energy Technology Data Exchange (ETDEWEB)

Dehdashtian, Sara [Department of Chemistry, Behbahan Khatam Al-Anbia University of Technology, Behbahan (Iran, Islamic Republic of); Gholivand, Mohammad Bagher, E-mail: mbgholivand@yahoo.com [Department of Analytical Chemistry, Faculty of Chemistry, Razi University, Kermanshah (Iran, Islamic Republic of); Shamsipur, Mojtaba; Kariminia, Samira [Department of Analytical Chemistry, Faculty of Chemistry, Razi University, Kermanshah (Iran, Islamic Republic of)

2016-01-01

A simple and sensitive sensor based on carbon paste electrode (CPE) modified by chitosan-coated magnetic nanoparticle (CMNP) was developed for the electrochemical determination of morphine (MO). The proposed sensor was characterized with scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). The electrooxidation of MO was studied on modified carbon paste electrode using cyclic voltammetry, chronoamperometry and differential pulse voltammetry as diagnostic techniques. The oxidation peak potential of morphine on the CMNP/CPE appeared at 380 mV which was accompanied with smaller overpotential and increase in oxidation peak current compared to that obtained on the bare carbon paste electrode (CPE). Under optimum conditions the sensor provides two linear DPV responses in the range of 10–2000 nM and 2–720 μM for MO with a detection limit of 3 nM. The proposed sensor was successfully applied for monitoring of MO in serum and urine samples and satisfactory results were obtained. - Highlights: • A sensitive and selective voltammetric sensor for MO by using a carbon paste electrode modified with CMNP was introduced. • CMNP as a new modifier facilitates the charge transfer of MO oxidation process. • The proposed sensor was used successfully for MO determination in biological fluids such as serum and urine samples. • This sensor is fabricated easily and has good stability and high sensitivity.

Carbon Nanotube-Based Chemical Sensors.

Science.gov (United States)

Meyyappan, M

2016-04-27

The need to sense gases and vapors arises in numerous scenarios in industrial, environmental, security and medical applications. Traditionally, this activity has utilized bulky instruments to obtain both qualitative and quantitative information on the constituents of the gas mixture. It is ideal to use sensors for this purpose since they are smaller in size and less expensive; however, their performance in the field must match that of established analytical instruments in order to gain acceptance. In this regard, nanomaterials as sensing media offer advantages in sensitivity, preparation of chip-based sensors and construction of electronic nose for selective detection of analytes of interest. This article provides a review of the use of carbon nanotubes in gas and vapor sensing. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Novel gas sensors based on carbon nanotube networks

International Nuclear Information System (INIS)

Sayago, I; Aleixandre, M; Horrillo, M C; Fernandez, M J; Gutierrez, J; Terrado, E; Lafuente, E; Maser, W K; Benito, A M; Martinez, M T; Munoz, E; Urriolabeitia, E P; Navarro, R

2008-01-01

Novel resistive gas sensors based on single-walled carbon nanotube (SWNT) networks as the active sensing element nave been investigated for gas detection. SWNTs networks were fabricated by airbrushing on alumina substrates. As-produced- and Pd-decorated SWNT materials were used as sensitive layers for the detection of NO 2 and H 2 , respectively. The studied sensors provided good response to NO 2 and H 2 as well as excellent selectivities to interfering gases.

Miniaturized remission sensor for carbon dioxide detection

International Nuclear Information System (INIS)

Martan, T; Will, M

2010-01-01

Recently, optical sensors for detection of carbon dioxide (CO 2 ) have been explored for variety of applications in chemistry, industry, and medicine. This paper deals with the development of a planar optical remission sensor employing a dye immobilized in a polymer layer designed for gaseous CO 2 detection. The principle of CO 2 detection was based on colour changes of Tetraethylammonium Cresol red immobilized in a special composed polymer layer that was irradiated by LED diodes. Absorption properties of the dye were changed due to its chemical reaction with CO 2 and corresponding colour changes were detected by PIN diodes. These changes were analyzed by using a PC-controlled board connected by USB. The sensitivity, response time, and the detection limit of the remission sensor were characterized.

Fabrication of gallium hexacyanoferrate modified carbon ionic liquid paste electrode for sensitive determination of hydrogen peroxide and glucose

International Nuclear Information System (INIS)

Haghighi, Behzad; Khosravi, Mehdi; Barati, Ali

2014-01-01

Gallium hexacyanoferrate (GaHCFe) and graphite powder were homogeneously dispersed into n-dodecylpyridinium hexafluorophosphate and paraffin to fabricate GaHCFe modified carbon ionic liquid paste electrode (CILPE). Mixture experimental design was employed to optimize the fabrication of GaHCFe modified CILPE (GaHCFe-CILPE). A pair of well-defined redox peaks due to the redox reaction of GaHCFe through one-electron process was observed for the fabricated electrode. The fabricated GaHCFe-CILPE exhibited good electrocatalytic activity towards reduction and oxidation of H 2 O 2 . The observed sensitivities for the electrocatalytic oxidation and reduction of H 2 O 2 at the operating potentials of + 0.8 and − 0.2 V were about 13.8 and 18.3 mA M −1 , respectively. The detection limit (S/N = 3) for H 2 O 2 was about 1 μM. Additionally, glucose oxidase (GOx) was immobilized on GaHCFe-CILPE using two methodology, entrapment into Nafion matrix and cross-linking with glutaraldehyde and bovine serum albumin, in order to fabricate glucose biosensor. Linear dynamic rage, sensitivity and detection limit for glucose obtained by the biosensor fabricated using cross-linking methodology were 0.1–6 mM, 0.87 mA M −1 and 30 μM, respectively and better than those obtained (0.2–6 mM, 0.12 mA M −1 and 50 μM) for the biosensor fabricated using entrapment methodology. - Highlights: • Gallium hexacyanoferrate modified carbon ionic liquid paste electrode was fabricated. • Mixture experimental design was used to optimize electrode fabrication. • Response trace plot was used to show the effect of electrode materials on response. • The sensor exhibited electrocatalytic activity towards H 2 O 2 reduction and oxidation. • Glucose biosensor was fabricated by immobilization of glucose oxidase on sensor

Vibration monitoring of carbon fiber composites by multiple fiber optic sensors

Science.gov (United States)

Olivero, Massimo; Perrone, Guido; Vallan, Alberto; Chen, Wei; Tosi, Daniele

2014-05-01

This work presents the comparison between the fiber Bragg grating technology and a vibration-measurement technique based on the detection of polarization rotation (polarimetric sensor) in a standard optical fiber, applied to the dynamic structural monitoring of carbon reinforced composites for the automotive industry. A carbon reinforced composite test plate in a 4-layer configuration was equipped with fiber Bragg gratings and polarimetric fiber sensors, then it was mechanically stressed by static and dynamic loads while monitoring the sensors response. The fiber Bragg grating setup exhibited 1.15+/-0.0016 pm/kg static load response and reproduced dynamic excitation with 0.1% frequency uncertainty, while the polarimetric sensing system exhibited a sensitivity of 1.74+/-0.001 mV/kg and reproduced the dynamic excitation with 0.5% frequency uncertainty. It is shown that the polarimetric sensor technology represents a cheap yet efficient alternative to the fiber Bragg grating sensors in the case of vibration-monitoring of small structures at high frequency.

ZnO-carbon nanofibers for stable, high response, and selective H2S sensors.

Science.gov (United States)

Zhang, Jitao; Zhu, Zijian; Chen, Changmiao; Chen, Zhi; Cai, Mengqiu; Qu, Baihua; Wang, Taihong; Zhang, Ming

2018-07-06

Hydrogen sulfide (H 2 S), as a typical atmospheric pollutant, is neurotoxic and flammable even at a very low concentration. In this study, we design stable H 2 S sensors based on ZnO-carbon nanofibers. Nanofibers with 30.34 wt% carbon are prepared by a facial electrospinning route followed by an annealing treatment. The resulting H 2 S sensors show excellent selectivity and response compared to the pure ZnO nanofiber H 2 S sensors, particularly the response in the range of 102-50 ppm of H 2 S. Besides, they exhibited a nearly constant response of approximately 40-20 ppm of H 2 S over 60 days. The superior performance of these H 2 S sensors can be attributed to the protection of carbon, which ensures the high stability of ZnO, and oxygen vacancies that improve the response and selectivity of H 2 S. The good performance of ZnO-carbon H 2 S sensors suggests that composites with oxygen vacancies prepared by a facial electrospinning route may provide a new research strategy in the field of gas sensors, photocatalysts, and semiconductor devices.

Multiwall carbon nanotubes chemically modified carbon paste electrodes for determination of gentamicin sulfate in pharmaceutical preparations and biological fluids.

Science.gov (United States)

Khalil, M M; Abed El-Aziz, G M

2016-02-01

This article focused on the construction and characteristics of novel and sensitive gentamicin carbon paste electrodes which are based on the incorporation of multiwall carbon nanotubes (MWCNTs) which improve the characteristics of the electrodes. The electrodes were constructed based on gentamicin-phosphotungstate (GNS-PTA) called CPE1, gentamicin-phosphomolybdate (GNS-PMA) called CPE2, GNS-PTA+ MWMCNTs called MWCPE1, and GNS-PMA+ MWMCNTs called MWCPE2. The constructed electrodes, at optimum paste composition, exhibited good Nernstian response for determination of gentamicin sulfate (GNS) over a linear concentration range from 2.5×10(-6) to 1×10(-2), 3.0×10(-6) to 1×10(-2), 4.9×10(-7) to 1×10(-2) and 5.0×10(-7) to 1×10(-2)molL(-1), with lower detection limit 1×10(-6), 1×10(-6), 1.9×10(-7) and 2.2×10(-7)molL(-1), and with slope values of 29.0±0.4, 29.2±0.7, 31.2±0.5 and 31.0±0.6mV/decade for CPE1, CPE2, MWCPE1 and MWCPE2, respectively. The response of electrodes is not affected by pH in the range 3-8 for CPE1 and CPE2 and in the range 2.5-8.5 for MWCPE1 and MWCPE2. The results showed fast dynamic response time (about 8-5s) and long lifetime (more than 2months) for all electrodes. The sensors showed high selectivity for gentamicin sulfate (GNS) with respect to a large number of interfering species. The constructed electrodes were successfully applied for determination of GNS in pure form, its pharmaceutical preparations and biological fluids using standard addition and potentiometric titration methods with high accuracy and precision. Published by Elsevier B.V.

Development of carbon paste electrodes modified by molecularly imprinted polymer as potentiometry sensor of uric acid

Science.gov (United States)

Khasanah, Miratul; Darmokoesoemo, Handoko; Widayanti, Nesti; Kadmi, Yassine; Elmsellem, Hicham; Kusuma, Heri Septya

The development of carbon paste electrodes modified by molecularly imprinted polymer (MIP) for the potentiometric analysis of uric acid was carried out in this study. The aim of the study was to determine the optimum composition of the electrode constituent material, the optimum pH of the uric acid solution, and the performance of the electrode, which was measured by its response time, measurement range, Nernst factor, detection limits, selectivity coefficient, precision, accuracy, and life time. MIP was made from methyl methacrylate as the monomer, ethylene glycol dimethacrylate as the cross-linker, and uric acid as the template. Electrodes that give optimum performance were produced from carbon, MIP, and paraffin with a ratio of 40:25:35 (% w/w). The obtained results show that the measurement of uric acid solution gives optimum results at pH 5, Nernst factor of 30.19 mV/decade, and a measurement range of 10-6-10-3 M. The minimum detection limit of this method was 3.03.10-6 M, and the precision and accuracy toward uric acid with concentration of 10-6-10-3 M ranged between 1.36-2.03% and 63.9-166%. The selectivity coefficient value was less than 1, which indicated that the electrode was selective against uric acid and not interfered with by urea. This electrode has a response time of less than 2 min; its life time is 8 weeks with 104 usage times.

Cyclic Voltammetric Investigation of Dopamine at Poly-(Gabapentin Modified Carbon Paste Electrode

Directory of Open Access Journals (Sweden)

M. T. Shreenivas

2011-01-01

Full Text Available The poly (gabapentin film was prepared on the surface of carbon paste electrode by electrochemical method using cyclic voltammetric technique. The poly (gabapentin film-modified carbon paste electrode was calibrated with standard potassium ferrocyanide solution in 1 M KCl as a supporting electrolyte. The prepared poly (gabapentin film-coated electrode exhibits excellent electrocatalytic activity towards the detection of dopamine at physiological pH. The scan rate effect was found to be diffusion-controlled electrode process. The concentration effect of dopamine was studied, and the redox peak potentials of dopamine were dependant on pH.

A Review of Carbon Nanotubes-Based Gas Sensors

Directory of Open Access Journals (Sweden)

Yun Wang

2009-01-01

Full Text Available Gas sensors have attracted intensive research interest due to the demand of sensitive, fast response, and stable sensors for industry, environmental monitoring, biomedicine, and so forth. The development of nanotechnology has created huge potential to build highly sensitive, low cost, portable sensors with low power consumption. The extremely high surface-to-volume ratio and hollow structure of nanomaterials is ideal for the adsorption of gas molecules. Particularly, the advent of carbon nanotubes (CNTs has fuelled the inventions of gas sensors that exploit CNTs' unique geometry, morphology, and material properties. Upon exposure to certain gases, the changes in CNTs' properties can be detected by various methods. Therefore, CNTs-based gas sensors and their mechanisms have been widely studied recently. In this paper, a broad but yet in-depth survey of current CNTs-based gas sensing technology is presented. Both experimental works and theoretical simulations are reviewed. The design, fabrication, and the sensing mechanisms of the CNTs-based gas sensors are discussed. The challenges and perspectives of the research are also addressed in this review.

Carbon nanotubes paste sensor modified with bismuth film for determination of metallic ions in ethanol fuel

Directory of Open Access Journals (Sweden)

Felipe Augusto Gorla

2015-05-01

Full Text Available In the present study an anodic stripping voltammetric method using a bismuth film modified carbon nanotubes paste electrode for simultaneous determination of metals Zn2+, Cd2+and Pb2+in ethanol fuel is described. The metallic ions were preconcentrated on the bismuth film in the time and deposition potential of 500 s and -1.2 V and the stripping step was carried out by square wave voltammetry (frequency of 15 Hz, pulse amplitude of 25 mV and potential step of 5 mV. Acetate buffer at 0.1 mol L-1concentration and pH 4.5 was used as support electrolyte. The method showed linearity including the analytical blank up to 48.39 ?g L-1 for the metals and the obtained limits of detection were 3.36, 0.32 and 0.47 ?g L-1for Zn2+, Cd2+and Pb2+, respectively. The proposed method was applied in ethanol fuel samples.

Simple electrochemical sensor for caffeine based on carbon and Nafion-modified carbon electrodes.

Science.gov (United States)

Torres, A Carolina; Barsan, Madalina M; Brett, Christopher M A

2014-04-15

A simple, economic, highly sensitive and highly selective method for the detection of caffeine has been developed at bare and Nafion-modified glassy carbon electrodes (GCE). The electrochemical behaviour of caffeine was examined in electrolyte solutions of phosphate buffer saline, sodium perchlorate, and in choline chloride plus oxalic acid, using analytical determinations by fixed potential amperometry, phosphate buffer saline being the best. Modifications of the GCE surface with poly(3,4-ethylenedioxythiophene) (PEDOT), Nafion, and multi-walled carbon nanotubes were tested in order to evaluate possible sensor performance enhancements, Nafion giving the most satisfactory results. The effect of interfering compounds usually found in samples containing caffeine was examined at GCE without and with Nafion coating, to exclude interferences, and the sensors were successfully applied to determine the caffeine content in commercial beverages and drugs. Copyright © 2013 Elsevier Ltd. All rights reserved.

Comparative study on the behavior of carbon resistance temperature sensors at low temperatures

International Nuclear Information System (INIS)

Balteanu, Ovidiu; Cristescu, Ioana; Retevoi, Carmen

2000-01-01

The paper presents the behavior of four carbon resistance sensors, which do not have a calibration curve in comparison with two calibrated sensors. To study this behavior, all these sensors were introduced into a column cooled by a hydrogen cryogenerator of Phillips type. For high accuracy measurements, a PC with a data acquisition board incorporated achieved the data processing. The experiment consists of three cooling-heating cycles that allow studying the time stability of the sensor characteristics. The experimental data were used to draw the R = f(T) and error curves for a single cooling-heating cycle. In addition, we found the polynomial regression for the sensors that do not have a calibration curve. In conclusion it results that the carbon resistance sensors have a higher accuracy at low temperature and time stability is very good. (authors)

Application of graphene oxide/lanthanum-modified carbon paste electrode for the selective determination of dopamine

Energy Technology Data Exchange (ETDEWEB)

Ye, Fengying; Feng, Chenqi; Fu, Ning; Wu, Huihui; Jiang, Jibo, E-mail: jibojiang0506@163.com; Han, Sheng, E-mail: hansheng654321@sina.com

2015-12-01

Highlights: • The effective surface area of the modified CPE has been expanded after self-assembly. • The GO–La composite exhibited excellent electrocatalytic activity toward DA. • The GO–La/CPE presented high selectivity, sensitivity, excellent stability and repeatability. - Abstract: A home-made carbon paste electrode (CPE) was reformed by graphene oxide (GO)/lanthanum (La) complexes, and a modified electrode, called GO–La/CPE, was fabricated for the selective determination of dopamine (DA) by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Several factors affecting the electrocatalytic performance of the modified sensor were investigated. Owning to the combination of GO and La ions, the GO–La/CPE sensor exhibited large surface area, well selectivity, good repeatability and stability in the oxidation reaction of DA. At optimal conditions, the response of the GO–La/CPE electrode for determining DA was linear in the region of 0.01–0.1 μM and 0.1–400.0 μM. The limit of detection was down to 0.32 nM (S/N = 3). In addition, this modified electrode was successfully applied to the detection of DA in real urine and serum samples by using standard adding method, showing its promising application in the electroanalysis of real samples.

Immobilization of Glucose Oxidase on Modified-Carbon-Paste-Electrodes for Microfuel Cell

Directory of Open Access Journals (Sweden)

Laksmi Ambarsari

2016-03-01

Full Text Available Glucose oxidase (GOx is being developed for many applications such as an implantable fuel cell, due to its attractive property of operating under physiological conditions. This study reports the functional immobilization of glucose oxidase onto polyaniline-nanofiber-modified-carbon-paste-electrodes (GOx/MCPE as bioanodes in fuel cell applications. In particular, GOx is immobilized onto the electrode surface via a linker molecule (glutaraldehyde. Polyaniline, synthesized by the interfacial polymerization method, produces a morphological form of nanofibers (100-120 nm which have good conductivity. The performance of the polyaniline-modified-carbon-paste-electrode (MCPE was better than the carbon- paste-electrode (CPE alone. The optimal pH and temperature of the GOx/MCPE were 4.5 (in 100 mM acetate buffer and 65 °C, respectively. The GOx/MCPE exhibit high catalytic performances (activation energy 16.4 kJ mol-1, have a high affinity for glucose (Km value 37.79 µM and can have a maximum current (Imax of 3.95 mA. The sensitivity of the bioelectrode also was high at 57.79 mA mM-1 cm-2.

Focused Ion Beam Nanopatterning for Carbon Nanotube Ropes Based Sensor

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Vera LA FERRARA

2007-11-01

Full Text Available Focused Ion Beam (FIB technology has been used to realize electrode patterns for contacting Single Walled Carbon Nanotubes (SWCNTs ropes for chemical gas sensor applications. Two types of transducers, based on a single rope and on bundles, have been realized starting from silicon/Si3N4 substrate. Electrical behaviour, at room temperature, in toxic gas environments, has been investigated and compared to evaluate contribution of a single rope based sensor respect to bundles one. For all the devices, upon exposure to NO2 and NH3, the conductance has been found to increase or decrease respectively. Conductance signal is stronger for sensor based on bundles, but it also evident that response time in NO2 is faster for device based on a single rope. FIB technology offers, then, the possibility to contact easily a single sensitive nanowire, as carbon nanotube rope.

Non-enzymatic sensing of uric acid using a carbon nanotube ionic-liquid paste electrode modified with poly(β-cyclodextrin)

International Nuclear Information System (INIS)

Li, Yonghong; Ji, Xiaoling; Wang, Ling; Qiu, Hongyan; Zhai, Xiurong; Wang, Haibo; Liu, Xinsheng; Guo, Le; Liu, Xiaoying

2015-01-01

We describe a nonenzymatic electrochemical sensor for uric acid. It is based on a carbon nanotube ionic-liquid paste electrode modified with poly(β-cyclodextrin) that was prepared in-situ by electropolymerization. The functionalized multi-walled carbon nanotubes and the surface morphology of the modified electrodes were characterized by transmission electronic microscopy and scanning electron microscopy. The electrochemical response of uric acid was studied by cyclic voltammetry and linear sweep voltammetry. The effects of scan rate, pH value, electropolymerization cycles and accumulation time were also studied. Under optimized experimental conditions and at a working voltage of 500 mV vs. Ag/AgCl (3 M KCl), response to uric acid is linear in the 0.6 to 400 μΜ and in the 0.4 to 1 mΜ concentration ranges, and the detection limit is 0.3 μΜ (at an S/N of 3). The electrode was successfully applied to the detection of uric acid in (spiked) human urine samples. (author)

Carbon nanotubes: Sensor properties. A review

Directory of Open Access Journals (Sweden)

Irina V. Zaporotskova

2016-12-01

Full Text Available Recent publications dealing with dealing with the fabrication of gas and electrochemical biosensors based on carbon nanotubes have been reviewed. Experimental and theoretical data on the working principles of nanotubes have been presented. The main regularities of the structure, energy parameters and sensor properties of modified semiconducting systems on the basis of cabon nanotubes have been studied by analyzing the mechanisms of nanotubule interaction with functional groups (including carboxyl and amino groups, metallic nanoparticles and polymers leading to the formation of chemically active sensors. The possibility of using boundary modified nanotubes for the identification of metals has been discussed. Simulation results have been reported for the interaction of nanotubes boundary modified by –СООН and –NH2 groups with atoms and ions of potassium, sodium and lithium. The simulation has been carried out using the molecular cluster model and the MNDO and DFT calculation methods. Sensors fabricated using this technology will find wide application for the detection of metallic atoms and their ions included in salts and alkali.

Molecular imprinted polymer functionalized carbon nanotube sensors for detection of saccharides

Science.gov (United States)

Badhulika, Sushmee; Mulchandani, Ashok

2015-08-01

In this work, we report the synthesis and fabrication of an enzyme-free sugar sensor based on molecularly imprinted polymer (MIP) on the surface of single walled carbon nanotubes (SWNTs). Electropolymerization of 3-aminophenylboronic acid (3-APBA) in the presence of 10 M d-fructose and fluoride at neutral pH conditions resulted in the formation of a self-doped, molecularly imprinted conducting polymer (MICP) via the formation of a stable anionic boronic ester complex between poly(aniline boronic acid) and d-fructose. Template removal generated binding sites on the polymer matrix that were complementary to d-fructose both in structure, i.e., shape, size, and positioning of functional groups, thus enabling sensing of d-fructose with enhanced affinity and specificity over non-MIP based sensors. Using carbon nanotubes along with MICPs helped to develop an efficient electrochemical sensor by enhancing analyte recognition and signal generation. These sensors could be regenerated and used multiple times unlike conventional affinity based biosensors which suffer from physical and chemical stability.

Designing multifunctional chemical sensors using Ni and Cu doped carbon nanotubes

DEFF Research Database (Denmark)

Mowbray, Duncan; García Lastra, Juan Maria; Thygesen, Kristian Sommer

2010-01-01

We demonstrate a “bottom up” approach to the computational design of a multifunctional chemical sensor. General techniques are employed for describing the adsorption coverage and resistance properties of the sensor based on density functional theory and non-equilibrium Green's function...... methodologies, respectively. Specifically, we show how Ni and Cu doped metallic (6,6) single-walled carbon nanotubes may work as effective multifunctional sensors for both CO and NH3....

Electrochemical Performance of a Carbon Nanotube/La-Doped TiO2 Nanocomposite and its Use for Preparation of an Electrochemical Nicotinic Acid Sensor

Directory of Open Access Journals (Sweden)

Hanxing Liu

2008-11-01

Full Text Available A carbon nanotube/La-doped TiO2 (La-TiO2 nanocomposite (CLTN was prepared by a procedure similar to a complex/adsorption process. Scanning electron microscopy (SEM images show that the La-TiO2 distributes on the carbon nanotube walls. The CLTN was mixed with paraffin to form a CLTN paste for the CLTN paste electrode (CLTNPE. The electrochemical characteristics of CLTNPE were compared with that of conventional carbon electrodes such as the carbon paste electrode (CPE and glass carbon electrode (GC. The CLTNPE exhibits electrochemical activity and was used to investigate the electrochemistry of nicotinic acid (NA. The modified electrode has a strong electrocatalytic effect on the redox of NA. The cyclic voltammetry (CV redox potential of NA at the CLTNPE is 320 mV. The oxidation process of NA on the CLTNPE is pH dependent. A sensitive chronoamperometric response for NA was obtained covering a linear range from 1.0×10-6 mol·L-1 to 1.2×10-4 mol·L-1, with a detection limit of 2.7×10-7 mol·L-1. The NA sensor displays a remarkable sensitivity and stability. The mean recovery of NA in the human urine is 101.8%, with a mean variation coefficient (RSD of 2.6%.

A thermal comparator sensor for measuring autogenous deformation in hardening Portland cement paste

DEFF Research Database (Denmark)

Østergaard, Thomas; Jensen, Ole Mejlhede

2003-01-01

This paper describes a simple and accurate experimental device specially developed to measure autogenous deformation in hardening cement-based materials. The measuring system consists of a so-called thermal comparator sensor and a modular thermostatically controlled system. The operating principle...... of the thermal comparator is based on thermal expansion of aluminium. A particular characteristic of the measuring system is the fixation of the thermal comparator sensor to the deforming specimen. The modular system ensures effective thermostatic control of the hydrating cement paste samples. The technique...... allows continuous measurement with high accuracy of the linear deformation as well as determination of the activation energy of autogenous deformation....

Mechanism of 3,4-dihydroxybenzaldehyde electropolymerization at carbon paste electrodes : catalytic detection of NADH

Directory of Open Access Journals (Sweden)

Delbem Maria Flávia

2002-01-01

Full Text Available Cyclic voltammetry was used to study 3,4-dihydroxybenzaldehyde (3,4-DHB electropolymerization processes on carbon paste electrodes. The characteristics of the electropolymerized films were highly dependent on pH, anodic switching potential, scan rate, 3,4-DHB concentrations and number of cycles. Film stability was determined in citrate/phosphate buffer solutions at the same pH used during the electropolymerization process. The best conditions to prepare carbon paste modified electrodes were pH 7.8; 0.0 <= Eapl <= 0.25 V; 10 mV s-1; 0.25 mmol L-1 3,4-DHB and 10 scans. These carbon paste modified electrodes were used for NADH catalytic detection at 0.23 V in the range 0.015 <= [NADH] <= 0.21 mmol L-1. Experimental data were used to propose a mechanism for the 3,4--DHB electropolymerization processes, which involves initial phenoxyl radical formation.

Potentiometric Determination of Ketotifen Fumarate in Pharmaceutical Preparations and Urine Using Carbon Paste and PVC Membrane Selective Electrodes

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Eman Y. Z. Frag

2011-01-01

Full Text Available This study compares between unmodified carbon paste (CPE; the paste has no ion pair and polyvinyl chloride (PVC membrane selective electrodes that were used in potentiometric determination of ketotifen fumarate (KTF, where sodium tetraphenylborate (NaTPB was used as titrant. The performance characteristics of these sensors were evaluated according to IUPAC recommendations which reveal a fast, stable, and linear response for KTF over the concentration range of 10−7 to 10−2 mol L−1. The electrodes show Nernstian slope value of 52.51±0.20 and 51.51±0.25 mV decade−1 for CPE and PVC membrane electrodes at 30∘C, respectively. The potential is nearly stable over the pH range 3.0–6.0 and 2.0–7.0 for CPE and PVC membrane electrodes, respectively. Selectivity coefficient values towards different inorganic cations, sugars, and amino acids reflect high selectivity of the prepared electrodes. The electrodes responses at different temperatures were also studied, and long operational lifetime of 12 and 5 weeks for CPE and PVC membrane electrodes, respectively, were found. These are used for determination of ketotifen fumarate using potentiometric titration, calibration, and standard addition methods in pure samples, its pharmaceutical preparations (Zaditen tablets, and biological fluid (urine. The direct potentiometric determination of KTF using the proposed sensors gave recoveries % of 98.97±0.53 and 98.62±0.74 with RSD 1.42 and 0.63% for CPE and PVC membrane selective electrodes, respectively. Validation of the method shows suitability of the proposed sensors for use in quality control assessment of KTF. The obtained results were in a good agreement with those obtained using the reported spectrophotometric method.

Potentiometric determination of ketotifen fumarate in pharmaceutical preparations and urine using carbon paste and PVC membrane selective electrodes.

Science.gov (United States)

Frag, Eman Y Z; Mohamed, Gehad G; Khalil, Mohamed M; Hwehy, Mohammad M A

2011-01-01

This study compares between unmodified carbon paste (CPE; the paste has no ion pair) and polyvinyl chloride (PVC) membrane selective electrodes that were used in potentiometric determination of ketotifen fumarate (KTF), where sodium tetraphenylborate (NaTPB) was used as titrant. The performance characteristics of these sensors were evaluated according to IUPAC recommendations which reveal a fast, stable, and linear response for KTF over the concentration range of 10(-7) to 10(-2) mol L(-1). The electrodes show Nernstian slope value of 52.51 ± 0.20 and 51.51 ± 0.25 mV decade(-1) for CPE and PVC membrane electrodes at 30°C, respectively. The potential is nearly stable over the pH range 3.0-6.0 and 2.0-7.0 for CPE and PVC membrane electrodes, respectively. Selectivity coefficient values towards different inorganic cations, sugars, and amino acids reflect high selectivity of the prepared electrodes. The electrodes responses at different temperatures were also studied, and long operational lifetime of 12 and 5 weeks for CPE and PVC membrane electrodes, respectively, were found. These are used for determination of ketotifen fumarate using potentiometric titration, calibration, and standard addition methods in pure samples, its pharmaceutical preparations (Zaditen tablets), and biological fluid (urine). The direct potentiometric determination of KTF using the proposed sensors gave recoveries % of 98.97 ± 0.53 and 98.62 ± 0.74 with RSD 1.42 and 0.63% for CPE and PVC membrane selective electrodes, respectively. Validation of the method shows suitability of the proposed sensors for use in quality control assessment of KTF. The obtained results were in a good agreement with those obtained using the reported spectrophotometric method.

Soft Pneumatic Bending Actuator with Integrated Carbon Nanotube Displacement Sensor

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Tim Giffney

2016-02-01

Full Text Available The excellent compliance and large range of motion of soft actuators controlled by fluid pressure has lead to strong interest in applying devices of this type for biomimetic and human-robot interaction applications. However, in contrast to soft actuators fabricated from stretchable silicone materials, conventional technologies for position sensing are typically rigid or bulky and are not ideal for integration into soft robotic devices. Therefore, in order to facilitate the use of soft pneumatic actuators in applications where position sensing or closed loop control is required, a soft pneumatic bending actuator with an integrated carbon nanotube position sensor has been developed. The integrated carbon nanotube position sensor presented in this work is flexible and well suited to measuring the large displacements frequently encountered in soft robotics. The sensor is produced by a simple soft lithography process during the fabrication of the soft pneumatic actuator, with a greater than 30% resistance change between the relaxed state and the maximum displacement position. It is anticipated that integrated resistive position sensors using a similar design will be useful in a wide range of soft robotic systems.

Multiwalled carbon nanotubes sensor for organic liquid detection at room temperature

Science.gov (United States)

Chaudhary, Deepti; Khare, Neeraj; Vankar, V. D.

2016-04-01

We have explored the possibility of using multiwalled carbon nanotubes (MWCNTs) as room temperature chemical sensor for the detection of organic liquids such as ethanol, propanol, methanol and toluene. MWCNTs were synthesized by thermal chemical vapor deposition (TCVD) technique. The interdigitated electrodes were fabricated by conventional photolithography technique. The sensor was fabricated by drop depositing MWCNT suspension onto the interdigitated electrodes. The sensing properties of MWCNTs sensor was studied for organic liquids detection. The resistance of sensor was found to increase upon exposure to these liquids. Sensor shows good reversibility and fast response at room temperature. Charge transfer between the organic liquid and sensing element is the dominant sensing mechanism.

Carbon Nanotube Based Chemical Sensors for Space and Terrestrial Applications

Science.gov (United States)

Li, Jing; Lu, Yijiang

2009-01-01

A nanosensor technology has been developed using nanostructures, such as single walled carbon nanotubes (SWNTs), on a pair of interdigitated electrodes (IDE) processed with a silicon-based microfabrication and micromachining technique. The IDE fingers were fabricated using photolithography and thin film metallization techniques. Both in-situ growth of nanostructure materials and casting of the nanostructure dispersions were used to make chemical sensing devices. These sensors have been exposed to nitrogen dioxide, acetone, benzene, nitrotoluene, chlorine, and ammonia in the concentration range of ppm to ppb at room temperature. The electronic molecular sensing of carbon nanotubes in our sensor platform can be understood by intra- and inter-tube electron modulation in terms of charge transfer mechanisms. As a result of the charge transfer, the conductance of p-type or hole-richer SWNTs in air will change. Due to the large surface area, low surface energy barrier and high thermal and mechanical stability, nanostructured chemical sensors potentially can offer higher sensitivity, lower power consumption and better robustness than the state-of-the-art systems, which make them more attractive for defense and space applications. Combined with MEMS technology, light weight and compact size sensors can be made in wafer scale with low cost. Additionally, a wireless capability of such a sensor chip can be used for networked mobile and fixed-site detection and warning systems for military bases, facilities and battlefield areas.

Comparative investigation on electrochemical behavior of hydroquinone at carbon ionic liquid electrode, ionic liquid modified carbon paste electrode and carbon paste electrode

International Nuclear Information System (INIS)

Zhang, Ya; Zheng, Jian Bin

2007-01-01

Ionic liquid, 1-heptyl-3-methylimidazolium hexafluorophosphate (HMIMPF 6 ), has been used to fabricate two new electrodes, carbon ionic liquid electrode (CILE) and ionic liquid modified carbon paste electrode (IL/CPE), using graphite powder mixed with HMIMPF 6 or the mixture of HMIMPF 6 /paraffin liquid as the binder, respectively. The electrochemical behaviors of hydroquinone at the CILE, the IL/CPE and the CPE were investigated in phosphate buffer solution. At all these electrodes, hydroquinone showed a pair of redox peaks. The order of the current response and the standard rate constant of hydroquinone at these electrodes were as follows: CILE > IL/CPE > CPE, while the peak-to-peak potential separation was in an opposite sequence: CILE < IL/CPE < CPE. The results show the superiority of CILE to IL/CPE and CPE, and IL/CPE to CPE in terms of promoting electron transfer, improving reversibility and enhancing sensitivity. The CILE was chosen as working electrode to determine hydroquinone by differential pulse voltammetry, which can be used for sensitive, simple and rapid determination of hydroquinone in medicated skin cosmetic cream

Long-Term, Autonomous Measurement of Atmospheric Carbon Dioxide Using an Ormosil Nanocomposite-Based Optical Sensor

Energy Technology Data Exchange (ETDEWEB)

Kisholoy Goswami

2005-10-11

The goal of this project is to construct a prototype carbon dioxide sensor that can be commercialized to offer a low-cost, autonomous instrument for long-term, unattended measurements. Currently, a cost-effective CO2 sensor system is not available that can perform cross-platform measurements (ground-based or airborne platforms such as balloon and unmanned aerial vehicle (UAV)) for understanding the carbon sequestration phenomenon. The CO2 sensor would support the research objectives of DOE-sponsored programs such as AmeriFlux and the North American Carbon Program (NACP). Global energy consumption is projected to rise 60% over the next 20 years and use of oil is projected to increase by approximately 40%. The combustion of coal, oil, and natural gas has increased carbon emissions globally from 1.6 billion tons in 1950 to 6.3 billion tons in 2000. This figure is expected to reach 10 billon tons by 2020. It is important to understand the fate of this excess CO2 in the global carbon cycle. The overall goal of the project is to develop an accurate and reliable optical sensor for monitoring carbon dioxide autonomously at least for one year at a point remote from the actual CO2 release site. In Phase I of this project, InnoSense LLC (ISL) demonstrated the feasibility of an ormosil-monolith based Autonomous Sensor for Atmospheric CO2 (ASAC) device. All of the Phase I objectives were successfully met.

Carbon paste electrode in a solid-contact minicavity; Eletrodo de pasta de carbono em minicavidade de contato solido

Energy Technology Data Exchange (ETDEWEB)

Ferreira, Antonio Ap. Pupim; Ribeiro, Sidney Jose Lima; Fugivara, Cecilio Sadao; Caiut, Jose Mauricio Almeida; Sargentelli, Vagner; Benedetti, Assis Vicente [UNESP - Universidade Estadual Paulista, Instituto de Quimica, Araraquara SP (Brazil)

2011-07-01

This work describes the preparation of carbon paste electrode (EPC) in a solid-contact minicavity and its evaluation when containing carbon paste without and with SiO{sub 2}(Eu{sup 3+} 2%) and SiO{sub 2}(Eu{sup 3+} 2%)-lysine sub-micrometrics particles. For this study cyclic voltammetry and electrochemical impedance measurements were performed at pH 7.4 in 0.1 mol L{sup -1} PBS containing Fe(CN){sub 6}{sup -3}/{sup -4} redox species. The impedance results were interpreted based on a charge-transfer reaction involving Fe(CN){sub 6}{sup -3}/{sup -4} species and/or oxygen at higher frequencies and, diffusion of the electroactive species and carbon paste characteristics at lower frequencies. EPC-minicavity is suitable for electroanalysis using modified carbon paste. (author)

Precision remote sensor for oxygen and carbon dioxide, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — Mesa Photonics proposes development of a passive optical sensor for simultaneous high-precision measurement of oxygen and carbon dioxide profiles within the full...

Fabrication of gallium hexacyanoferrate modified carbon ionic liquid paste electrode for sensitive determination of hydrogen peroxide and glucose

Energy Technology Data Exchange (ETDEWEB)

Haghighi, Behzad, E-mail: haghighi@iasbs.ac.ir; Khosravi, Mehdi; Barati, Ali

2014-07-01

Gallium hexacyanoferrate (GaHCFe) and graphite powder were homogeneously dispersed into n-dodecylpyridinium hexafluorophosphate and paraffin to fabricate GaHCFe modified carbon ionic liquid paste electrode (CILPE). Mixture experimental design was employed to optimize the fabrication of GaHCFe modified CILPE (GaHCFe-CILPE). A pair of well-defined redox peaks due to the redox reaction of GaHCFe through one-electron process was observed for the fabricated electrode. The fabricated GaHCFe-CILPE exhibited good electrocatalytic activity towards reduction and oxidation of H{sub 2}O{sub 2}. The observed sensitivities for the electrocatalytic oxidation and reduction of H{sub 2}O{sub 2} at the operating potentials of + 0.8 and − 0.2 V were about 13.8 and 18.3 mA M{sup −1}, respectively. The detection limit (S/N = 3) for H{sub 2}O{sub 2} was about 1 μM. Additionally, glucose oxidase (GOx) was immobilized on GaHCFe-CILPE using two methodology, entrapment into Nafion matrix and cross-linking with glutaraldehyde and bovine serum albumin, in order to fabricate glucose biosensor. Linear dynamic rage, sensitivity and detection limit for glucose obtained by the biosensor fabricated using cross-linking methodology were 0.1–6 mM, 0.87 mA M{sup −1} and 30 μM, respectively and better than those obtained (0.2–6 mM, 0.12 mA M{sup −1} and 50 μM) for the biosensor fabricated using entrapment methodology. - Highlights: • Gallium hexacyanoferrate modified carbon ionic liquid paste electrode was fabricated. • Mixture experimental design was used to optimize electrode fabrication. • Response trace plot was used to show the effect of electrode materials on response. • The sensor exhibited electrocatalytic activity towards H{sub 2}O{sub 2} reduction and oxidation. • Glucose biosensor was fabricated by immobilization of glucose oxidase on sensor.

Mechano-Physical Properties and Microstructure of Carbon Nanotube Reinforced Cement Paste after Thermal Load.

Science.gov (United States)

Szeląg, Maciej

2017-09-11

The article presents the results obtained in the course of a study on the use of carbon nanotubes (CNTs) for the modification of a cement matrix. Carbon nanotubes were introduced into a cement paste in the form of an aqueous dispersion in the presence of a surfactant (SDS-sodium dodecyl sulfate), which was sonicated. The selected physical and mechanical parameters were examined, and the correlations between these parameters were determined. An analysis of the local microstructure of the modified cement pastes has been carried out using scanning electron microscope (SEM) and X-ray microanalysis (EDS). In addition, the effect of carbon nanotubes on the change in characteristics of the cementitious material exposed to the sudden, short-term thermal load, was determined. The obtained material was characterized by a much lower density than a traditional cement matrix because the phenomenon of foaming occurred. The material was also characterized by reduced durability, higher shrinkage, and higher resistance to the effect of elevated temperature. Further research on the carbon nanotube reinforced cement paste, with SDS, may contribute to the development of a modified cement binder for the production of a lightweight or an aerated concrete.

Mechano-Physical Properties and Microstructure of Carbon Nanotube Reinforced Cement Paste after Thermal Load

Science.gov (United States)

2017-01-01

The article presents the results obtained in the course of a study on the use of carbon nanotubes (CNTs) for the modification of a cement matrix. Carbon nanotubes were introduced into a cement paste in the form of an aqueous dispersion in the presence of a surfactant (SDS—sodium dodecyl sulfate), which was sonicated. The selected physical and mechanical parameters were examined, and the correlations between these parameters were determined. An analysis of the local microstructure of the modified cement pastes has been carried out using scanning electron microscope (SEM) and X-ray microanalysis (EDS). In addition, the effect of carbon nanotubes on the change in characteristics of the cementitious material exposed to the sudden, short-term thermal load, was determined. The obtained material was characterized by a much lower density than a traditional cement matrix because the phenomenon of foaming occurred. The material was also characterized by reduced durability, higher shrinkage, and higher resistance to the effect of elevated temperature. Further research on the carbon nanotube reinforced cement paste, with SDS, may contribute to the development of a modified cement binder for the production of a lightweight or an aerated concrete. PMID:28891976

Polymer-carbon black composite sensors in an electronic nose for air-quality monitoring

Science.gov (United States)

Ryan, M. A.; Shevade, A. V.; Zhou, H.; Homer, M. L.

2004-01-01

An electronic nose that uses an array of 32 polymer-carbon black composite sensors has been developed, trained, and tested. By selecting a variety of chemical functionalities in the polymers used to make sensors, it is possible to construct an array capable of identifying and quantifying a broad range of target compounds, such as alcohols and aromatics, and distinguishing isomers and enantiomers (mirror-image isomers). A model of the interaction between target molecules and the polymer-carbon black composite sensors is under development to aid in selecting the array members and to enable identification of compounds with responses not stored in the analysis library.

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.

Hydrogen peroxide sensor based on modified vitreous carbon with multiwall carbon nanotubes and composites of Pt nanoparticles-dopamine

Energy Technology Data Exchange (ETDEWEB)

Guzman, C.; Orozco, G. [Electrochemistry Department, Centro de Investigacion y Desarrollo Tecnologico en Electroquimica S.C., P.O. Box 064, C.P. 76700, Pedro Escobedo, Queretaro (Mexico); Verde, Y. [Instituto Tecnologico de Cancun, Av. Kabah Km. 3, C.P. 77500, Cancun, Quintana Roo (Mexico); Jimenez, S. [Unidad Queretaro Centro de Investigacion y de Estudios Avanzados del I.P.N., Juriquilla, Santiago de Queretaro (Mexico); Godinez, Luis A. [Electrochemistry Department, Centro de Investigacion y Desarrollo Tecnologico en Electroquimica S.C., P.O. Box 064, C.P. 76700, Pedro Escobedo, Queretaro (Mexico); Juaristi, E. [Chemistry Department, Centro de Investigacion y de Estudios Avanzados del I.P.N., P.O. Box 14-740, C.P. 07360 Mexico, D.F. (Mexico); Bustos, E. [Electrochemistry Department, Centro de Investigacion y Desarrollo Tecnologico en Electroquimica S.C., P.O. Box 064, C.P. 76700, Pedro Escobedo, Queretaro (Mexico); Chemistry Department, Centro de Investigacion y de Estudios Avanzados del I.P.N., P.O. Box 14-740, C.P. 07360 Mexico, D.F. (Mexico)], E-mail: ebustos@cideteq.mx

2009-02-15

Sensors using nanostructured materials have been under development in the last decade due to their selectivity for the detection and quantification of different compounds. The physical and chemical characteristics of carbon nanotubes provide significant advantages when used as electrodes for electronic devices, fuel cells and electrochemical sensors. This paper presents preliminary results on the modification of vitreous carbon electrodes with Multiwall Carbon Nanotubes (MWCNTs) and composites of Pt nanoparticles-dopamine (DA) as electro-catalytic materials for the hydrogen peroxide (H{sub 2}O{sub 2}) reaction. Chemical pre-treatment and consequent functionalization of MWCNTs with carboxylic groups was necessary to increase the distribution of the composites. In addition, the presence of DA was important to protect the active sites and eliminate the pasivation of the surface after the electro-oxidation of H{sub 2}O{sub 2} takes place. The proposed H{sub 2}O{sub 2} sensor exhibited a linear response in the 0-5 mM range, with detection and quantification limits of 0.3441 mM and 1.1472 mM, respectively.

Hydrogen peroxide sensor based on modified vitreous carbon with multiwall carbon nanotubes and composites of Pt nanoparticles-dopamine

International Nuclear Information System (INIS)

Guzman, C.; Orozco, G.; Verde, Y.; Jimenez, S.; Godinez, Luis A.; Juaristi, E.; Bustos, E.

2009-01-01

Sensors using nanostructured materials have been under development in the last decade due to their selectivity for the detection and quantification of different compounds. The physical and chemical characteristics of carbon nanotubes provide significant advantages when used as electrodes for electronic devices, fuel cells and electrochemical sensors. This paper presents preliminary results on the modification of vitreous carbon electrodes with Multiwall Carbon Nanotubes (MWCNTs) and composites of Pt nanoparticles-dopamine (DA) as electro-catalytic materials for the hydrogen peroxide (H 2 O 2 ) reaction. Chemical pre-treatment and consequent functionalization of MWCNTs with carboxylic groups was necessary to increase the distribution of the composites. In addition, the presence of DA was important to protect the active sites and eliminate the pasivation of the surface after the electro-oxidation of H 2 O 2 takes place. The proposed H 2 O 2 sensor exhibited a linear response in the 0-5 mM range, with detection and quantification limits of 0.3441 mM and 1.1472 mM, respectively

Coaxial Thermoplastic Elastomer-Wrapped Carbon Nanotube Fibers for Deformable and Wearable Strain Sensors

KAUST Repository

Zhou, Jian; Xu, Xuezhu; Xin, Yangyang; Lubineau, Gilles

2018-01-01

performances in these design requirements. Here, achieving highly stretchable and sensitive strain sensors by using a coaxial structure, prepared via coaxial wet spinning of thermoplastic elastomer-wrapped carbon nanotube fibers, is proposed. The sensors attain

Embedding of MEMS pressure and temperature sensors in carbon fiber composites: a manufacturing approach

Science.gov (United States)

Javidinejad, Amir; Joshi, Shiv P.

2000-06-01

In this paper embedding of surface mount pressure and temperature sensors in the Carbon fiber composites are described. A commercially available surface mount pressure and temperature sensor are used for embedding in a composite lay- up of IM6/HST-7, IM6/3501 and AS4/E7T1-2 prepregs. The fabrication techniques developed here are the focus of this paper and provide for a successful embedding procedure of pressure sensors in fibrous composites. The techniques for positioning and insulating, the sensor and the lead wires, from the conductive carbon prepregs are described and illustrated. Procedural techniques are developed and discussed for isolating the sensor's flow-opening, from the exposure to the prepreg epoxy flow and exposure to the fibrous particles, during the autoclave curing of the composite laminate. The effects of the autoclave cycle (if any) on the operation of the embedded pressure sensor are discussed.

Thermal Spray Applications in Electronics and Sensors: Past, Present, and Future

Science.gov (United States)

Sampath, Sanjay

2010-09-01

Thermal spray has enjoyed unprecedented growth and has emerged as an innovative and multifaceted deposition technology. Thermal spray coatings are crucial to the enhanced utilization of various engineering systems. Industries, in recognition of thermal spray's versatility and economics, have introduced it into manufacturing environments. The majority of modern thermal spray applications are "passive" protective coatings, and they rarely perform an electronic function. The ability to consolidate dissimilar material multilayers without substrate thermal loading has long been considered a virtue for thick-film electronics. However, the complexity of understanding/controlling materials functions especially those resulting from rapid solidification and layered assemblage has stymied expansion into electronics. That situation is changing: enhancements in process/material science are allowing reconsideration for novel electronic/sensor devices. This review critically examines past efforts in terms of materials functionality from a device perspective, along with ongoing/future concepts addressing the aforementioned deficiencies. The analysis points to intriguing future possibilities for thermal spray technology in the world of thick-film sensors.

Highly sensitive strain sensors based on fragmentized carbon nanotube/polydimethylsiloxane composites.

Science.gov (United States)

Gao, Yang; Fang, Xiaoliang; Tan, Jianping; Lu, Ting; Pan, Likun; Xuan, Fuzhen

2018-06-08

Wearable strain sensors based on nanomaterial/elastomer composites have potential applications in flexible electronic skin, human motion detection, human-machine interfaces, etc. In this research, a type of high performance strain sensors has been developed using fragmentized carbon nanotube/polydimethylsiloxane (CNT/PDMS) composites. The CNT/PDMS composites were ground into fragments, and a liquid-induced densification method was used to fabricate the strain sensors. The strain sensors showed high sensitivity with gauge factors (GFs) larger than 200 and a broad strain detection range up to 80%, much higher than those strain sensors based on unfragmentized CNT/PDMS composites (GF sensors is ascribed to the sliding of individual fragmentized-CNT/PDMS-composite particles during mechanical deformation, which causes significant resistance change in the strain sensors. The strain sensors can differentiate mechanical stimuli and monitor various human body motions, such as bending of the fingers, human breathing, and blood pulsing.

Highly sensitive strain sensors based on fragmentized carbon nanotube/polydimethylsiloxane composites

Science.gov (United States)

Gao, Yang; Fang, Xiaoliang; Tan, Jianping; Lu, Ting; Pan, Likun; Xuan, Fuzhen

2018-06-01

Wearable strain sensors based on nanomaterial/elastomer composites have potential applications in flexible electronic skin, human motion detection, human–machine interfaces, etc. In this research, a type of high performance strain sensors has been developed using fragmentized carbon nanotube/polydimethylsiloxane (CNT/PDMS) composites. The CNT/PDMS composites were ground into fragments, and a liquid-induced densification method was used to fabricate the strain sensors. The strain sensors showed high sensitivity with gauge factors (GFs) larger than 200 and a broad strain detection range up to 80%, much higher than those strain sensors based on unfragmentized CNT/PDMS composites (GF composite particles during mechanical deformation, which causes significant resistance change in the strain sensors. The strain sensors can differentiate mechanical stimuli and monitor various human body motions, such as bending of the fingers, human breathing, and blood pulsing.

An Overview of Pesticide Monitoring at Environmental Samples Using Carbon Nanotubes-Based Electrochemical Sensors

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Ademar Wong

2017-03-01

Full Text Available Carbon nanotubes have received enormous attention in the development of electrochemical sensors by promoting electron transfer reactions, decreasing the work overpotential within great surface areas. The growing concerns about environmental health emphasized the necessity of continuous monitoring of pollutants. Pesticides have been successfully used to control agricultural and public health pests; however, intense use can cause a number of damages for biodiversity and human health. In this sense, carbon nanotubes-based electrochemical sensors have been proposed for pesticide monitoring combining different electrode modification strategies and electroanalytical techniques. In this paper, we provide a review of the recent advances in the use of carbon nanotubes for the construction of electrochemical sensors dedicated to the environmental monitoring of pesticides. Future directions, perspectives, and challenges are also commented.

A computational analysis of the carbon-nanotube-based resonant-circuit sensors

International Nuclear Information System (INIS)

Grujicic, M.; Cao, G.; Roy, W.N.

2004-01-01

Available values for the molecular polarizability and the dipole moment and the computed adsorption energies to single walled carbon nanotubes (SWCNTs) for a couple of polar (NH 3 and CO) and several non-polar (He, Ar, N 2 and O 2 ) gases are used to help establish a correlation between the adsorbed gas-induced changes in the dielectric constant of the SWCNTs (the sensing material) and the resulting reduction in the resonant frequency of the resonant circuit-based chemical gas sensors. It is found that simple weighting methods which neglect the effect of changes in the electronic structure of the carbon nanotubes during adsorption are generally incapable of predicting correctly the changes in the effective dielectric constant of the carbon nanotubes. Conversely, the use of adsorption-induced changes in the band gap of the carbon nanotubes and a relationship between the band gap and the dielectric constant is found to be a promising approach for assessing the adsorption-induced changes in the effective dielectric constant of the carbon nanotubes and for establishment of their effect on the resonant frequency of resonator-based chemical gas sensors

A Miniaturized Carbon Dioxide Gas Sensor Based on Sensing of pH-Sensitive Hydrogel Swelling with a Pressure Sensor

NARCIS (Netherlands)

Herber, S.; Bomer, Johan G.; Olthuis, Wouter; Bergveld, Piet; van den Berg, Albert

2005-01-01

A measurement concept has been realized for the detection of carbon dioxide, where the CO2 induced pressure generation by an enclosed pH-sensitive hydrogel is measured with a micro pressure sensor. The application of the sensor is the quantification of the partial pressure of CO2 (Pco2) in the

Carbon Nanomaterials Based Electrochemical Sensors/Biosensors for the Sensitive Detection of Pharmaceutical and Biological Compounds

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Bal-Ram Adhikari

2015-09-01

Full Text Available Electrochemical sensors and biosensors have attracted considerable attention for the sensitive detection of a variety of biological and pharmaceutical compounds. Since the discovery of carbon-based nanomaterials, including carbon nanotubes, C60 and graphene, they have garnered tremendous interest for their potential in the design of high-performance electrochemical sensor platforms due to their exceptional thermal, mechanical, electronic, and catalytic properties. Carbon nanomaterial-based electrochemical sensors have been employed for the detection of various analytes with rapid electron transfer kinetics. This feature article focuses on the recent design and use of carbon nanomaterials, primarily single-walled carbon nanotubes (SWCNTs, reduced graphene oxide (rGO, SWCNTs-rGO, Au nanoparticle-rGO nanocomposites, and buckypaper as sensing materials for the electrochemical detection of some representative biological and pharmaceutical compounds such as methylglyoxal, acetaminophen, valacyclovir, β-nicotinamide adenine dinucleotide hydrate (NADH, and glucose. Furthermore, the electrochemical performance of SWCNTs, rGO, and SWCNT-rGO for the detection of acetaminophen and valacyclovir was comparatively studied, revealing that SWCNT-rGO nanocomposites possess excellent electrocatalytic activity in comparison to individual SWCNT and rGO platforms. The sensitive, reliable and rapid analysis of critical disease biomarkers and globally emerging pharmaceutical compounds at carbon nanomaterials based electrochemical sensor platforms may enable an extensive range of applications in preemptive medical diagnostics.

Mercapto-ordered carbohydrate-derived porous carbon electrode as a novel electrochemical sensor for simple and sensitive ultra-trace detection of omeprazole in biological samples.

Science.gov (United States)

Kalate Bojdi, Majid; Behbahani, Mohammad; Mashhadizadeh, Mohammad Hosein; Bagheri, Akbar; Hosseiny Davarani, Saied Saeed; Farahani, Ali

2015-03-01

We are introducing mercapto-mesoporous carbon modified carbon paste electrode (mercapto-MP-C-CPE) as a new sensor for trace determination of omeprazole (OM) in biological samples. The synthesized modifier was characterized by thermogravimetry analysis (TGA), differential thermal analysis (DTA), transmission electron microscopy (TEM), Fourier transform infrared spectrometry (FT-IR), X-ray diffraction (XRD), elemental analysis (CHN) and N2 adsorption surface area measurement (BET). The electrochemical response characteristic of the modified-CPE toward OM was investigated by cyclic and differential pulse voltammetry (CV and DPV). The proposed sensor displayed a good electrooxidation response to the OM, its linear range is 0.25nM to 25μM with a detection limit of 0.04nM under the optimized conditions. The prepared modified electrode shows several advantages such as high sensitivity, long-time stability, wide linear range, ease of preparation and regeneration of the electrode surface by simple polishing and excellent reproducibility. Copyright © 2014 Elsevier B.V. All rights reserved.

Performance of a carbon monoxide sensor based on zirconia-doped ceria

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Noriya Izu

2016-06-01

Full Text Available Resistive-type carbon monoxide sensors were fabricated using zirconia-doped ceria, and their sensing properties were evaluated and compared with equivalent devices based on non-doped ceria. The response of both sensor types was found to increase with decreasing temperature, while the response at 450 °C of a sensor fired at 950 °C was greater than that of a sensor fired at 1100 °C. When fired at 950 °C, however, the response at 450 °C of a sensor created using zirconia-doped ceria was slightly less than that of a sensor constructed from non-doped ceria. Multivariate analysis confirmed that the response of both sensor types is proportional to the resistance raised to the power of about 0.5, and inversely proportional to the particle size raised to a power of about 0.8. The sensor response time can be considered almost the same regardless of whether zirconia doping is used or not.

Fabrication of flex sensors through direct ink write technique and its electrical characterization

Science.gov (United States)

Abas, Muhammad; Rahman, Khalid

2016-11-01

The present work is intended to fabricate low-cost flex sensor from conductive carbon paste using direct ink write (DIW) technique. DIW method is one of the additive manufacturing processes, which is capable to deposit a variety of material on a variety of substrates by a different mechanism to feature resolution at a microns level. It is widely used in the electronic industry for fabrication of PCBS and electrodes for different electronic devices. The DIW system in present study extrudes material stored in the syringe barrel through nozzle using compressed air. This mechanism will assist in creating patterns on a variety of substrates. Pneumatic controller is employed to control deposition of material, while computer-controlled X-Y stage is employed to control pattern generation. For effective and control patterning, printing parameters were optimized using Taguchi design optimization technique. The conductive carbon paste is used as ink for pattern generation on flexible PET substrate. Samples of flex sensor having different dimensions are prepared through DIW. The fabricated sensors were used as flexion sensor, and its electrical characteristic was evaluated. The obtained sensors are stable and reliable in performance.

Comparative VOCs sensing performance for conducting polymer and porphyrin functionalized carbon nanotubes based sensors

Science.gov (United States)

Datta, Kunal; Rushi, Arti; Ghosh, Prasanta; Shirsat, Mahendra

2018-05-01

We report sensors for detection of ethyl alcohol, a prominent volatile organic compound (VOC). Single walled carbon nanotubes were selected as main sensing backbone. As efficiency of sensor is dependent upon the choice of sensing materials, the performances of conducting polymer and porphyrin based sensors were compared. Chemiresistive sensing modality was adopted to observe the performance of sensors. It has been found that porphyrin based sensor shows higher affinity towards ethyl alcohol.

Highly Stretchable Potentiometric pH Sensor Fabricated via Laser Carbonization and Machining of Carbon-Polyaniline Composite.

Science.gov (United States)

Rahimi, Rahim; Ochoa, Manuel; Tamayol, Ali; Khalili, Shahla; Khademhosseini, Ali; Ziaie, Babak

2017-03-15

The development of stretchable sensors has recently attracted considerable attention. These sensors have been used in wearable and robotics applications, such as personalized health-monitoring, motion detection, and human-machine interfaces. Herein, we report on a highly stretchable electrochemical pH sensor for wearable point-of-care applications that consists of a pH-sensitive working electrode and a liquid-junction-free reference electrode, in which the stretchable conductive interconnections are fabricated by laser carbonizing and micromachining of a polyimide sheet bonded to an Ecoflex substrate. This method produces highly porous carbonized 2D serpentine traces that are subsequently permeated with polyaniline (PANI) as the conductive filler, binding material, and pH-sensitive membrane. The experimental and simulation results demonstrate that the stretchable serpentine PANI/C-PI interconnections with an optimal trace width of 0.3 mm can withstand elongations of up to 135% and are robust to more than 12 000 stretch-and-release cycles at 20% strain without noticeable change in the resistance. The pH sensor displays a linear sensitivity of -53 mV/pH (r 2 = 0.976) with stable performance in the physiological range of pH 4-10. The sensor shows excellent stability to applied longitudinal and transverse strains up to 100% in different pH buffer solutions with a minimal deviation of less than ±4 mV. The material biocompatibility is confirmed with NIH 3T3 fibroblast cells via PrestoBlue assays.

Automatic Carbon Dioxide-Methane Gas Sensor Based on the Solubility of Gases in Water

Directory of Open Access Journals (Sweden)

Raúl O. Cadena-Pereda

2012-08-01

Full Text Available Biogas methane content is a relevant variable in anaerobic digestion processing where knowledge of process kinetics or an early indicator of digester failure is needed. The contribution of this work is the development of a novel, simple and low cost automatic carbon dioxide-methane gas sensor based on the solubility of gases in water as the precursor of a sensor for biogas quality monitoring. The device described in this work was used for determining the composition of binary mixtures, such as carbon dioxide-methane, in the range of 0–100%. The design and implementation of a digital signal processor and control system into a low-cost Field Programmable Gate Array (FPGA platform has permitted the successful application of data acquisition, data distribution and digital data processing, making the construction of a standalone carbon dioxide-methane gas sensor possible.

Automatic carbon dioxide-methane gas sensor based on the solubility of gases in water.

Science.gov (United States)

Cadena-Pereda, Raúl O; Rivera-Muñoz, Eric M; Herrera-Ruiz, Gilberto; Gomez-Melendez, Domingo J; Anaya-Rivera, Ely K

2012-01-01

Biogas methane content is a relevant variable in anaerobic digestion processing where knowledge of process kinetics or an early indicator of digester failure is needed. The contribution of this work is the development of a novel, simple and low cost automatic carbon dioxide-methane gas sensor based on the solubility of gases in water as the precursor of a sensor for biogas quality monitoring. The device described in this work was used for determining the composition of binary mixtures, such as carbon dioxide-methane, in the range of 0-100%. The design and implementation of a digital signal processor and control system into a low-cost Field Programmable Gate Array (FPGA) platform has permitted the successful application of data acquisition, data distribution and digital data processing, making the construction of a standalone carbon dioxide-methane gas sensor possible.

Carbon materials-functionalized tin dioxide nanoparticles toward robust, high-performance nitrogen dioxide gas sensor.

Science.gov (United States)

Zhang, Rui; Liu, Xiupeng; Zhou, Tingting; Wang, Lili; Zhang, Tong

2018-08-15

Carbon (C) materials, which process excellent electrical conductivity and high carrier mobility, are promising sensing materials as active units for gas sensors. However, structural agglomeration caused by chemical processes results in a small resistance change and low sensing response. To address the above issues, structure-derived carbon-coated tin dioxide (SnO 2 ) nanoparticles having distinct core-shell morphology with a 3D net-like structure and highly uniform size are prepared by careful synthesis and fine structural design. The optimum carbon-coated SnO 2 nanoparticles (SnO 2 /C)-based gas sensor exhibits a low working temperature, excellent selectivity and fast response-recovery properties. In addition, the SnO 2 /C-based gas sensor can maintain a sensitivity to nitrogen dioxide (NO 2 ) of 3 after being cycled 4 times at 140 °C for, suggesting its good long-term stability. The structural integrity, good synergistic properties, and high gas-sensing performance of SnO 2 /C render it a promising sensing material for advanced gas sensors. Copyright © 2018 Elsevier Inc. All rights reserved.

Ultrasensitive, Stretchable Strain Sensors Based on Fragmented Carbon Nanotube Papers

KAUST Repository

Zhou, Jian

2017-01-17

The development of strain sensors featuring both ultra high sensitivity and high stretchability is still a challenge. We demonstrate that strain sensors based on fragmented single-walled carbon nanotube (SWCNT) paper embedded in poly(dimethylsiloxane) (PDMS) can sustain their sensitivity even at very high strain levels (with a gauge factor of over 10(7) at 50% strain). This record sensitivity is ascribed to the low initial electrical resistance (5-28 Omega) of the SWCNT paper and the wide change in resistance (up to 10(6) Omega) governed by the percolated network of SWCNT in the cracked region. The sensor response remains nearly unchanged after 10 000 strain cycles at 20% proving the robustness of this technology. This fragmentation based sensing system brings opportunities to engineer highly sensitive stretchable sensors.

A Novel of Multi-wall Carbon Nanotubes/Chitosan Electrochemical Sensor for Determination of Cupric ion

Science.gov (United States)

Tan, Funeng; Li, Lei

2018-03-01

A multi-wall carbon nanotubes/Chitosan electrochemical sensor had been fabricated by dropping CHS/MWNT solution directly onto the GC surface. The sensor was charactered by cyclic voltammetry and AC impedance with K3Fe(CN)6 as a electrochemical probe; Cyclic voltammograms(CV) and electrochemical impedance spectroscopy(EIS) indicated that the active area and electrochemical behavior of the sensor increased and improved significantly after the electrode was modified by carbon nanotubes dispersed by the chitosan. The sensor showed good electrocatalytic activity of K3Fe(CN)6. Also, from the cyclic voltammograms, we can see the process was diffusion controlled on the bare electrode and kinetics and diffusion controlled on the modified electrode. Finally Cu2+ responsed sensitively at the sensor which supplied a new method for the detection of Cu2+.

Durable superhydrophobic carbon soot coatings for sensor applications

Science.gov (United States)

Esmeryan, K. D.; Radeva, E. I.; Avramov, I. D.

2016-01-01

A novel approach for the fabrication of durable superhydrophobic (SH) carbon soot coatings used in quartz crystal microbalance (QCM) based gas or liquid sensors is reported. The method uses modification of the carbon soot through polymerization of hexamethyldisiloxane (HMDSO) by means of glow discharge RF plasma. The surface characterization shows a fractal-like network of carbon nanoparticles with diameter of ~50 nm. These particles form islands and cavities in the nanometer range, between which the plasma polymerized hexamethyldisiloxane (PPHMDSO) embeds and binds to the carbon chains and QCM surface. Such modified surface structure retains the hydrophobic nature of the soot and enhances its robustness upon water droplet interactions. Moreover, it significantly reduces the insertion loss and dynamic resistance of the QCM compared to the commonly used carbon soot/epoxy resin approach. Furthermore, the PPHMDSO/carbon soot coating demonstrates durability and no aging after more than 40 probing cycles in water based liquid environments. In addition, the surface layer keeps its superhydrophobicity even upon thermal annealing up to 540 °C. These experiments reveal an opportunity for the development of soot based SH QCMs with improved electrical characteristics, as required for high-resolution gas or liquid measurements.

Cobalt Oxide Nanosheet and CNT Micro Carbon Monoxide Sensor Integrated with Readout Circuit on Chip

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Ching-Liang Dai

2010-03-01

Full Text Available The study presents a micro carbon monoxide (CO sensor integrated with a readout circuit-on-a-chip manufactured by the commercial 0.35 μm complementary metal oxide semiconductor (CMOS process and a post-process. The sensing film of the sensor is a composite cobalt oxide nanosheet and carbon nanotube (CoOOH/CNT film that is prepared by a precipitation-oxidation method. The structure of the CO sensor is composed of a polysilicon resistor and a sensing film. The sensor, which is of a resistive type, changes its resistance when the sensing film adsorbs or desorbs CO gas. The readout circuit is used to convert the sensor resistance into the voltage output. The post-processing of the sensor includes etching the sacrificial layers and coating the sensing film. The advantages of the sensor include room temperature operation, short response/recovery times and easy post-processing. Experimental results show that the sensitivity of the CO sensor is about 0.19 mV/ppm, and the response and recovery times are 23 s and 34 s for 200 ppm CO, respectively.

Carbon Nanotube-Based Ion Selective Sensors for Wearable Applications.

Science.gov (United States)

Roy, Soumyendu; David-Pur, Moshe; Hanein, Yael

2017-10-11

Wearable electronics offer new opportunities in a wide range of applications, especially sweat analysis using skin sensors. A fundamental challenge in these applications is the formation of sensitive and stable electrodes. In this article we report the development of a wearable sensor based on carbon nanotube (CNT) electrode arrays for sweat sensing. Solid-state ion selective electrodes (ISEs), sensitive to Na + ions, were prepared by drop coating plasticized poly(vinyl chloride) (PVC) doped with ionophore and ion exchanger on CNT electrodes. The ion selective membrane (ISM) filled the intertubular spaces of the highly porous CNT film and formed an attachment that was stronger than that achieved with flat Au, Pt, or carbon electrodes. Concentration of the ISM solution used influenced the attachment to the CNT film, the ISM surface morphology, and the overall performance of the sensor. Sensitivity of 56 ± 3 mV/decade to Na + ions was achieved. Optimized solid-state reference electrodes (REs), suitable for wearable applications, were prepared by coating CNT electrodes with colloidal dispersion of Ag/AgCl, agarose hydrogel with 0.5 M NaCl, and a passivation layer of PVC doped with NaCl. The CNT-based REs had low sensitivity (-1.7 ± 1.2 mV/decade) toward the NaCl solution and high repeatability and were superior to bare Ag/AgCl, metals, carbon, and CNT films, reported previously as REs. CNT-based ISEs were calibrated against CNT-based REs, and the short-term stability of the system was tested. We demonstrate that CNT-based devices implemented on a flexible support are a very attractive platform for future wearable technology devices.

Gold nanoparticle/multi-walled carbon nanotube modified glassy carbon electrode as a sensitive voltammetric sensor for the determination of diclofenac sodium

International Nuclear Information System (INIS)

Afkhami, Abbas; Bahiraei, Atousa; Madrakian, Tayyebeh

2016-01-01

A simple and highly sensitive sensor for the determination of diclofenac sodium based on gold nanoparticle/multi-walled carbon nanotube modified glassy carbon electrode is reported. Scanning electron microscopy along with energy dispersive X-ray spectroscopy, electrochemical impedance spectroscopy, cyclic voltammetry and square wave voltammetry was used to characterize the nanostructure and performance of the sensor and the results were compared with those obtained at the multi-walled carbon nanotube modified glassy carbon electrode and bare glassy carbon electrode. Under the optimized experimental conditions diclofenac sodium gave linear response over the range of 0.03–200 μmol L −1 . The lower detection limits were found to be 0.02 μmol L −1 . The effect of common interferences on the current response of DS was investigated. The practical application of the modified electrode was demonstrated by measuring the concentration of diclofenac sodium in urine and pharmaceutical samples. This revealed that the gold nanoparticle/multiwalled carbon nanotube modified glassy carbon electrode shows excellent analytical performance for the determination of diclofenac sodium in terms of a very low detection limit, high sensitivity, very good accuracy, repeatability and reproducibility. - Highlights: • GCE was modified with multiwalled carbon nanotube and gold nanoparticles. • AuNP/MWCNT/GCE was used for the determination of diclofenac sodium. • Modified electrode was characterized by SEM, EDS and EIS. • The proposed method showed excellent analytical figures of merit. • This sensor was used for the determination of diclofenac sodium in real samples.

Gold nanoparticle/multi-walled carbon nanotube modified glassy carbon electrode as a sensitive voltammetric sensor for the determination of diclofenac sodium

Energy Technology Data Exchange (ETDEWEB)

Afkhami, Abbas, E-mail: afkhami@basu.ac.ir; Bahiraei, Atousa; Madrakian, Tayyebeh

2016-02-01

A simple and highly sensitive sensor for the determination of diclofenac sodium based on gold nanoparticle/multi-walled carbon nanotube modified glassy carbon electrode is reported. Scanning electron microscopy along with energy dispersive X-ray spectroscopy, electrochemical impedance spectroscopy, cyclic voltammetry and square wave voltammetry was used to characterize the nanostructure and performance of the sensor and the results were compared with those obtained at the multi-walled carbon nanotube modified glassy carbon electrode and bare glassy carbon electrode. Under the optimized experimental conditions diclofenac sodium gave linear response over the range of 0.03–200 μmol L{sup −1}. The lower detection limits were found to be 0.02 μmol L{sup −1}. The effect of common interferences on the current response of DS was investigated. The practical application of the modified electrode was demonstrated by measuring the concentration of diclofenac sodium in urine and pharmaceutical samples. This revealed that the gold nanoparticle/multiwalled carbon nanotube modified glassy carbon electrode shows excellent analytical performance for the determination of diclofenac sodium in terms of a very low detection limit, high sensitivity, very good accuracy, repeatability and reproducibility. - Highlights: • GCE was modified with multiwalled carbon nanotube and gold nanoparticles. • AuNP/MWCNT/GCE was used for the determination of diclofenac sodium. • Modified electrode was characterized by SEM, EDS and EIS. • The proposed method showed excellent analytical figures of merit. • This sensor was used for the determination of diclofenac sodium in real samples.

Flexible and Transparent Strain Sensors with Embedded Multiwalled Carbon Nanotubes Meshes.

Science.gov (United States)

Nie, Bangbang; Li, Xiangming; Shao, Jinyou; Li, Xin; Tian, Hongmiao; Wang, Duorui; Zhang, Qiang; Lu, Bingheng

2017-11-22

Strain sensors combining high sensitivity with good transparency and flexibility would be of great usefulness in smart wearable/flexible electronics. However, the fabrication of such strain sensors is still challenging. In this study, new strain sensors with embedded multiwalled carbon nanotubes (MWCNTs) meshes in polydimethylsiloxane (PDMS) films were designed and tested. The strain sensors showed elevated optical transparency of up to 87% and high sensitivity with a gauge factor of 1140 at a small strain of 8.75%. The gauge factors of the sensors were also found relatively stable since they did not obviously change after 2000 stretching/releasing cycles. The sensors were tested to detect motion in the human body, such as wrist bending, eye blinking, mouth phonation, and pulse, and the results were shown to be satisfactory. Furthermore, the fabrication of the strain sensor consisting of mechanically blading MWCNTs aqueous dispersions into microtrenches of prestructured PDMS films was straightforward, was low cost, and resulted in high yield. All these features testify to the great potential of these sensors in future real applications.

Carbonation-Induced Mineralogical Changes in Coal Mining Waste Blended Cement Pastes and Their Influence on Mechanical and Microporosity Properties

Directory of Open Access Journals (Sweden)

Moisés Frías

2018-04-01

Full Text Available The worldwide pursuit of new eco-efficient pozzolans is ongoing. Kaolinite-based waste is an eco-friendly source of recycled metakaolinite, a highly pozzolanic product. In this study, a blended cement paste containing 20% activated coal waste (ACW was exposed to a 100% CO2 atmosphere at 65% RH for 7 days. The variations in its phase composition and strength were studied and compared to an OPC control. Both pastes were cured for 28 days prior to the carbonation test. Reaction kinetics were assessed using XRD, SEM/EDX, TG/DTG, FT-IR, Micro-Raman spectroscopy, pore solution pH and the cumulative carbonated fraction. The blended cement carbonated 68% faster than the control. While portlandite carbonation was the main reaction in both cements, decalcification was also observed (more intensely in the 20% ACW paste in other hydraulic calcium phases (C-S-H gel, monocarboaluminate (C4AcH12, ettringite and tetracalcium aluminate (C4AH13. The end product of this reaction was calcium carbonate, mainly in the form of calcite, although traces of aragonite and amorphous carbonate were also detected. Compressive strength values rose with accelerated carbonation time and pore size reduction in both cement pastes.

Potentiometric sensors using cotton yarns, carbon nanotubes and polymeric membranes.

Science.gov (United States)

Guinovart, Tomàs; Parrilla, Marc; Crespo, Gastón A; Rius, F Xavier; Andrade, Francisco J

2013-09-21

A simple and generalized approach to build electrochemical sensors for wearable devices is presented. Commercial cotton yarns are first turned into electrical conductors through a simple dyeing process using a carbon nanotube ink. These conductive yarns are then partially coated with a suitable polymeric membrane to build ion-selective electrodes. Potentiometric measurements using these yarn-potentiometric sensors are demonstrated. Examples of yarns that can sense pH, K(+) and NH4(+) are presented. In all cases, these sensing yarns show limits of detection and linear ranges that are similar to those obtained with lab-made solid-state ion-selective electrodes. Through the immobilization of these sensors in a band-aid, it is shown that this approach could be easily implemented in a wearable device. Factors affecting the performance of the sensors and future potential applications are discussed.

Electrochemical oxidation of ascorbic acid mediated by carbon nano tubes/ Li+/ carbon paste modified solid electrode

International Nuclear Information System (INIS)

Goh, J.K.; Tan, W.T.

2008-01-01

Multi-walled carbon nano tube (MWCNT) was used to modify BPPG electrode because of its unique structure and extraordinary properties. MWCNT modified electrode exhibited obvious enhancing and electro catalyzing effects to the oxidation of ascorbic acid using cyclic voltammetry technique. MWCNT was bonded on BPPG electrode surface using carbon paste with ratio of 30 % (w/ W) carbon paste (binder): 70 % (w/ w) MWCNT. This method of modification has lowered the capacitance background current and enabled lower detection limit of ascorbic acid concentration. The electrical conductivity property of MWCNT modified electrode was further improved with the intercalation with lithium ion and resulted in current enhancement of 2 times on the oxidation current of ascorbic acid. Parameters of pH and temperature showed significant relation to the sensitivity of MWCNT modified electrode. Under the optimized parameters, the calibration curve constructed was linear up from 50 μM to 5 mM with sensitivity of 34.5 mA M -1 . The practical application of MWCNT modified electrode was demonstrated with Vitamin C pill and orange juice. Good reproducibility and recovery of ascorbic acid concentration showed the feasibility of MWCNT modified electrode to be used in the detection of ascorbic acid in aqueous solution. This also proposed MWCNT modified BPPG electrode possessed advantages such as low detection limit, high stability, low cost and simplicity in fabrication. (author)

Nanotechnology: A Tool for Improved Performance on Electrochemical Screen-Printed (BioSensors

Directory of Open Access Journals (Sweden)

Elena Jubete

2009-01-01

Full Text Available Screen-printing technology is a low-cost process, widely used in electronics production, especially in the fabrication of disposable electrodes for (biosensor applications. The pastes used for deposition of the successive layers are based on a polymeric binder with metallic dispersions or graphite, and can also contain functional materials such as cofactors, stabilizers and mediators. More recently metal nanoparticles, nanowires and carbon nanotubes have also been included either in these pastes or as a later stage on the working electrode. This review will summarize the use of nanomaterials to improve the electrochemical sensing capability of screen-printed sensors. It will cover mainly disposable sensors and biosensors for biomedical interest and toxicity monitoring, compiling recent examples where several types of metallic and carbon-based nanostructures are responsible for enhancing the performance of these devices.

Methanol oxidation at carbon paste electrodes modified with (Pt–Ru)/carbon aerogels nanocomposites

Energy Technology Data Exchange (ETDEWEB)

Fort, Carmen I., E-mail: iladiu@chem.ubbcluj.ro [Laboratory of Electrochemical Research and Nonconventional Materials, Babes-Bolyai University, Arany Janos 11, RO-400028, Cluj-Napoca (Romania); Cotet, Liviu C. [Laboratory of Electrochemical Research and Nonconventional Materials, Babes-Bolyai University, Arany Janos 11, RO-400028, Cluj-Napoca (Romania); Vasiliu, Florin [The National Institute of Materials Physics, Atomistilor str. 105 bis, PO Box MG. 7, Magurele, RO 077125, Bucharest (Romania); Marginean, Petre [National Institute for Research and Development of Isotopic and Molecular Technologies, RO 400293, Cluj-Napoca (Romania); Danciu, Virginia; Popescu, Ionel C. [Laboratory of Electrochemical Research and Nonconventional Materials, Babes-Bolyai University, Arany Janos 11, RO-400028, Cluj-Napoca (Romania)

2016-04-01

Mesoporous carbon aerogels (CAs) impregnated with (Pt–Ru) nanoparticles were prepared, incorporated into carbon paste electrodes (CPEs) and investigated as electrocatalysts for CH{sub 3}OH electro-oxidation. The sol–gel method, followed by supercritical drying with liquid CO{sub 2} and thermal pyrolysis in an inert atmosphere, was used to obtain high mesoporous CAs. (Pt–Ru)/CAs nanocomposites with various (Pt–Ru) loading were prepared by using Ru(AcAc){sub 3} and H{sub 2}PtCl{sub 6} as metal precursors and the impregnation method. The morpho-structural peculiarities of the so prepared (Pt–Ru)/CAs electrocatalysts were examined by using elemental analysis, N{sub 2} adsorption-desorption isotherms, transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), energy dispersive X-ray (EDX) and selected area electron diffraction (SAED). Cyclic voltammetry measurements, carried out at (Pt–Ru)/CA-CPEs incorporating nanocomposites with various Pt–Ru loading and different specific surface areas, showed that CA with the highest specific surface area (843 m{sup 2}/g) and impregnated with 6% (w/w) (Pt–Ru) nanoparticles exhibit the best CH{sub 3}OH electro-oxidation efficiency. The Michaelis–Menten formalism was used to describe the dependence of the oxidation peak current on the CH{sub 3}OH concentration, allowing the estimation of the modified electrodes sensitivities. Thus, for (Pt–Ru, 10%)/CA{sub 535}-CPE was observed the highest sensitivity (12.5 ± 0.8 mA/M) and, at the same time, the highest maximum current density ever reported (153.1 mA/cm{sup 2} for 2 M CH{sub 3}OH and an applied potential of 600 mV vs. SHE). - Highlights: • (Pt–Ru) nanoparticles were deposited on high mesoporous carbon aerogels (CAs). • (Pt–Ru)/CAs were characterized by TEM, EDX, SAED and N{sub 2} adsorption-desorption. • Carbon paste electrodes modified with (Pt–Ru)/CA were used for CH{sub 3}OH oxidation. • (Pt–Ru, 10

Ionic Liquid-Based Optical and Electrochemical Carbon Dioxide Sensors

Science.gov (United States)

Behera, Kamalakanta; Pandey, Shubha; Kadyan, Anu; Pandey, Siddharth

2015-01-01

Due to their unusual physicochemical properties (e.g., high thermal stability, low volatility, high intrinsic conductivity, wide electrochemical windows and good solvating ability), ionic liquids have shown immense application potential in many research areas. Applications of ionic liquid in developing various sensors, especially for the sensing of biomolecules, such as nucleic acids, proteins and enzymes, gas sensing and sensing of various important ions, among other chemosensing platforms, are currently being explored by researchers worldwide. The use of ionic liquids for the detection of carbon dioxide (CO2) gas is currently a major topic of research due to the associated importance of this gas with daily human life. This review focuses on the application of ionic liquids in optical and electrochemical CO2 sensors. The design, mechanism, sensitivity and detection limit of each type of sensor are highlighted in this review. PMID:26690155

Ionic Liquid-Based Optical and Electrochemical Carbon Dioxide Sensors.

Science.gov (United States)

Behera, Kamalakanta; Pandey, Shubha; Kadyan, Anu; Pandey, Siddharth

2015-12-04

Due to their unusual physicochemical properties (e.g., high thermal stability, low volatility, high intrinsic conductivity, wide electrochemical windows and good solvating ability), ionic liquids have shown immense application potential in many research areas. Applications of ionic liquid in developing various sensors, especially for the sensing of biomolecules, such as nucleic acids, proteins and enzymes, gas sensing and sensing of various important ions, among other chemosensing platforms, are currently being explored by researchers worldwide. The use of ionic liquids for the detection of carbon dioxide (CO₂) gas is currently a major topic of research due to the associated importance of this gas with daily human life. This review focuses on the application of ionic liquids in optical and electrochemical CO₂ sensors. The design, mechanism, sensitivity and detection limit of each type of sensor are highlighted in this review.

Ionic Liquid-Based Optical and Electrochemical Carbon Dioxide Sensors

Directory of Open Access Journals (Sweden)

Kamalakanta Behera

2015-12-01

Full Text Available Due to their unusual physicochemical properties (e.g., high thermal stability, low volatility, high intrinsic conductivity, wide electrochemical windows and good solvating ability, ionic liquids have shown immense application potential in many research areas. Applications of ionic liquid in developing various sensors, especially for the sensing of biomolecules, such as nucleic acids, proteins and enzymes, gas sensing and sensing of various important ions, among other chemosensing platforms, are currently being explored by researchers worldwide. The use of ionic liquids for the detection of carbon dioxide (CO2 gas is currently a major topic of research due to the associated importance of this gas with daily human life. This review focuses on the application of ionic liquids in optical and electrochemical CO2 sensors. The design, mechanism, sensitivity and detection limit of each type of sensor are highlighted in this review.

Trace detection of hydrogen peroxide vapor using a carbon-nanotube-based chemical sensor.

Science.gov (United States)

Lu, Yijiang; Meyyappan, M; Li, Jing

2011-06-20

The sensitive detection of hydrogen peroxide in the vapor phase is achieved using a nanochemical sensor consisting of single-walled carbon nanotubes as the sensing material. The interdigitated electrode-based sensor is constructed using a simple and standard microfabrication approach. The test results indicate a sensing capability of 25 ppm and response and recovery times in seconds. The sensor array consisting of 32 sensor elements with variations in sensing materials is capable of discriminating hydrogen peroxide from water and methanol. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A Ni-Doped Carbon Nanotube Sensor for Detecting Oil-Dissolved Gases in Transformers.

Science.gov (United States)

Lu, Jia; Zhang, Xiaoxing; Wu, Xiaoqing; Dai, Ziqiang; Zhang, Jinbin

2015-06-09

C2H2, C2H4, and C2H6 are important oil-dissolved gases in power transformers. Detection of the composition and content of oil-dissolved gases in transformers is very significant in the diagnosis and assessment of the state of transformer operations. The commonly used oil-gas analysis methods have many disadvantages, so this paper proposes a Ni-doped carbon nanotube (Ni-CNT) gas sensor to effectively detect oil-dissolved gases in a transformer. The gas-sensing properties of the sensor to C2H2, C2H4, and C2H6 were studied using the test device. Based on the density functional theory (DFT) the adsorption behaviors of the three gases on intrinsic carbon nanotubes (CNTs) and Ni-CNTs were calculated. The adsorption energy, charge transfer, and molecular frontier orbital of the adsorption system were also analyzed. Results showed that the sensitivity of the CNT sensor to the three kinds of gases was in the following order: C2H2 > C2H4 > C2H6. Moreover, the doped Ni improved the sensor response, and the sensor response and gas concentration have a good linear relationship.

Highly sensitive glucose sensor based on monodisperse palladium nickel/activated carbon nanocomposites.

Science.gov (United States)

Koskun, Yağmur; Şavk, Aysun; Şen, Betül; Şen, Fatih

2018-06-20

Glucose enzyme biosensors have been used for a variety of applications such as medical diagnosis, bioprocess engineering, beverage industry and environmental scanning etc. and there is still a growing interest in glucose sensors. For this purpose, addressed herein, as a novel glucose sensor, highly sensitive activated carbon (AC) decorated monodisperse nickel and palladium alloy nanocomposites modified glassy carbon electrode (Ni-Pd@AC/GCE NCs) have been synthesized by in-situ reduction technique. Raman Spectroscopy (RS), X-ray Photoelectron Spectroscopy (XPS), X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), cyclic voltammetry (CV) and chronoamperometry (CA) were used for the characterization of the prepared non-enzymatic glucose sensor. The characteristic sensor properties of the Ni-Pd@AC/GCE electrode were compared with Ni-Pd NCs/GCE, Ni@AC/GCE and Pd@AC/GCE and the results demonstrate that the AC is very effective in the enhancement of the electrocatalytic properties of sensor. In addition, the Ni-Pd@AC/GCE nanocomposites showed a very low detection limit of 0.014 μM, a wide linear range of 0.01 mM-1 mM and a very high sensitivity of 90 mA mM -1  cm -2 . Furthermore, the recommended sensor offer the various advantageous such as facile preparation, fast response time, high selectivity and sensitivity. Lastly, monodisperse Ni-Pd@AC/GCE was utilized to detect glucose in real sample species. Copyright © 2018 Elsevier B.V. All rights reserved.

Development and characterization of a voltammetric carbon-fiber microelectrode pH sensor.

Science.gov (United States)

Makos, Monique A; Omiatek, Donna M; Ewing, Andrew G; Heien, Michael L

2010-06-15

This work describes the development and characterization of a modified carbon-fiber microelectrode sensor capable of measuring real-time physiological pH changes in biological microenvironments. The reagentless sensor was fabricated under ambient conditions from voltammetric reduction of the diazonium salt Fast Blue RR onto a carbon-fiber surface in aprotic media. Fast-scan cyclic voltammetry was used to probe redox activity of the p-quinone moiety of the surface-bound molecule as a function of pH. In vitro calibration of the sensor in solutions ranging from pH 6.5 to 8.0 resulted in a pH-dependent anodic peak potential response. Flow-injection analysis was used to characterize the modified microelectrode, revealing sensitivity to acidic and basic changes discernible to 0.005 pH units. Furthermore, the modified electrode was used to measure dynamic in vivo pH changes evoked during neurotransmitter release in the central nervous system of the microanalytical model organism Drosophila melanogaster.

Enhanced host–guest electrochemical recognition of herbicide MCPA using a b-cyclodextrin carbon nanotube sensor

OpenAIRE

Rahemi, V.; Vandamme, J.J.; Garrido, J.M.P.J.; Borges, F.; Brett, C.M.A.; Garrido, E.M.P.J.

2012-01-01

An electrochemical sensor for the determination of the chlorophenoxy herbicide MCPA has been developed, based on a combination of multi-walled carbon nanotubes with incorporated b-cyclodextrin and a polyaniline film modified glassy carbon electrode. The proposed molecular host–guest recogni-tion based sensor has a high electrochemical sensitivity for the determination of MCPA. The electrochemical behaviour of MCPA at the chemically modified electrode was investigated in detail by cyclic volta...

Comparative study of different alcohol sensors based on Screen-Printed Carbon Electrodes.

Science.gov (United States)

Costa Rama, Estefanía; Biscay, Julien; González García, María Begoña; Julio Reviejo, A; Pingarrón Carrazón, José Manuel; Costa García, Agustín

2012-05-30

Different very simple single-use alcohol enzyme sensors were developed using alcohol oxidase (AOX) from three different yeast, Hansenula sp., Pichia pastoris and Candida boidinii, and employing three different commercial mediator-based Screen-Printed Carbon Electrodes as transducers. The mediators tested, Prussian Blue, Ferrocyanide and Co-phthalocyanine were included into the ink of the working electrode. The procedure to obtain these sensors consists of the immobilization of the enzyme on the electrode surface by adsorption. For the immobilization, an AOX solution is deposited on the working electrode and left until dried (1h) at room temperature. The best results were obtained with the biosensor using Screen-Printed Co-phthalocyanine/Carbon Electrode and AOX from Hansenula sp. The reduced cobalt-phthalocyanine form is amperometrically detected at +0.4V (vs. Ag pseudo reference electrode). This sensor shows good sensitivity (1211 nA mM(-1)), high precision (2.1% RSD value for the slope value of the calibration plot) and wide linear response (0.05-1.00 mM) for ethanol determination. The sensor provides also accurate results for ethanol quantification in alcoholic drinks. Copyright © 2012 Elsevier B.V. All rights reserved.

Low-cost photonic sensors for carbon dioxide exchange rate measurement

Science.gov (United States)

Bieda, Marcin S.; Sobotka, Piotr; Lesiak, Piotr; Woliński, Tomasz R.

2017-10-01

Carbon dioxide (CO2) measurement has an important role in atmosphere monitoring. Usually, two types of measurements are carried out. The first one is based on gas concentration measurement while the second involves gas exchange rate measurement between earth surface and atmosphere [1]. There are several methods which allow gas concentration measurement. However, most of them require expensive instrumentation or large devices (i.e. gas chambers). In order to precisely measure either CO2 concentration or CO2 exchange rate, preferably a sensors network should be used. These sensors must have small dimensions, low power consumption, and they should be cost-effective. Therefore, this creates a great demand for a robust low-power and low-cost CO2 sensor [2,3]. As a solution, we propose a photonic sensor that can measure CO2 concentration and also can be used to measure gas exchange by using the Eddy covariance method [1].

Carbon nanotubes based methanol sensor for fuel cells application.

Science.gov (United States)

Kim, D W; Lee, J S; Lee, G S; Overzet, L; Kozlov, M; Aliev, A E; Park, Y W; Yang, D J

2006-11-01

An electrochemical sensor is built using vertically grown multi-walled carbon nanotubes (MWNTs) micro-array to detect methanol concentration in water. This study is done for the potential use of the array as methanol sensor for portable units of direct methanol fuel cells (DMFCs). Platinum (Pt) nanoparticles electro-deposited CNTs (Pt/CNTs) electrode shows high sensitivity in the measurement of methanol concentration in water with cyclic voltammetry (CV) measurement at room temperature. Further investigation has also been undertaken to measure the concentration by changing the amount of the mixture of methanol and formic acid in water. We compared the performance of our micro array sensor built with Pt/CNTs electrodes versus that of Pt wire electrode using CV measurement. We found that our Pt/CNTs array sensor shows high sensitivity and detects methanol concentrations in the range of 0.04 M to 0.10 M. In addition, we found that co-use of formic acid as electrolyte enables us to measure up to 1.0 M methanol concentration.

Alcohol detection using carbon nanotubes acoustic and optical sensors

Science.gov (United States)

Penza, M.; Cassano, G.; Aversa, P.; Antolini, F.; Cusano, A.; Cutolo, A.; Giordano, M.; Nicolais, L.

2004-09-01

We demonstrate the integration of single-walled carbon nanotubes (SWCNTs) onto quartz crystal microbalance (QCM) and standard silica optical fiber (SOF) sensor for alcohol detection at room temperature. Different transducing mechanisms have been used in order to outline the sensing properties of this class of nanomaterials, in particular the attention has been focused on two key parameters in sensing applications: mass and refractive index changes due to gas absorption. Here, Langmuir-Blodgett (LB) films consisting of tangled bundles of SWCNTs without surfactant molecules have been successfully transferred onto QCM and SOF. Mass-sensitive 10MHz QCM SWCNTs sensor exhibited a resonant frequency decreasing upon tested alcohols exposure; also the normalized optoelectronic signal (λ=1310nm) of the refractive index-sensitive SOF SWCNTs sensor was found to decrease upon alcohols ambient. Highly sensitive, repeatable and reversible responses of the QCM and SOF SWCNTs sensors indicate that the detection, at room temperature, in a wide mmHg vapor pressures range of alcohols and potentially other volatile organic compounds is feasible.

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.

Gold nanoparticle/multi-walled carbon nanotube modified glassy carbon electrode as a sensitive voltammetric sensor for the determination of diclofenac sodium.

Science.gov (United States)

Afkhami, Abbas; Bahiraei, Atousa; Madrakian, Tayyebeh

2016-02-01

A simple and highly sensitive sensor for the determination of diclofenac sodium based on gold nanoparticle/multi-walled carbon nanotube modified glassy carbon electrode is reported. Scanning electron microscopy along with energy dispersive X-ray spectroscopy, electrochemical impedance spectroscopy, cyclic voltammetry and square wave voltammetry was used to characterize the nanostructure and performance of the sensor and the results were compared with those obtained at the multi-walled carbon nanotube modified glassy carbon electrode and bare glassy carbon electrode. Under the optimized experimental conditions diclofenac sodium gave linear response over the range of 0.03-200μmolL(-1). The lower detection limits were found to be 0.02μmolL(-1). The effect of common interferences on the current response of DS was investigated. The practical application of the modified electrode was demonstrated by measuring the concentration of diclofenac sodium in urine and pharmaceutical samples. This revealed that the gold nanoparticle/multiwalled carbon nanotube modified glassy carbon electrode shows excellent analytical performance for the determination of diclofenac sodium in terms of a very low detection limit, high sensitivity, very good accuracy, repeatability and reproducibility. Copyright © 2015 Elsevier B.V. All rights reserved.

Imprinted electrochemical sensor for dopamine recognition and determination based on a carbon nanotube/polypyrrole film

International Nuclear Information System (INIS)

Kan Xianwen; Zhou Hong; Li Chen; Zhu Anhong; Xing Zonglan; Zhao Zhe

2012-01-01

An electrochemical sensor combining a molecular imprinted technique and an electropolymerization method was developed in this work. A molecular imprinted polymer (MIP) film was fabricated by electropolymerizing pyrrole in the presence of dopamine (DA) after electrodepositing carboxyl-functionalized multi-walled carbon nanotubes (MWNTs-COOH) onto a glassy carbon electrode (GCE) surface. Scanning electron microscopy (SEM), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS) were employed to characterize the constructed sensor. The effects of pH, the monomer concentration, the number of cycles for the electropolymerization, and the scan rate for the sensor preparation were optimized. The MIP-based sensor displayed an excellent recognition capacity toward DA compared with other structurally similar molecules. Additionally, the DPV peak current was linear to the DA concentration in the range from 6.25 × 10 −7 to 1 × 10 −4 mol/L, with a detection limit of 6 × 10 −8 mol/L. The prepared sensor also showed stable reproducibility and regeneration capacity.

Potentiometric chemical sensors from lignin-poly(propylene oxide) copolymers doped by carbon nanotubes.

Science.gov (United States)

Rudnitskaya, Alisa; Evtuguin, Dmitry V; Costa, Luis C; Graça, M Pedro F; Fernandes, António J S; Correia, M Rosario P; Gomes, M Teresa S R; Oliveira, J A B P

2013-01-21

Hardwood and softwood lignins obtained from industrial sulphite and kraft and laboratory oxygen-organosolv pulping processes were employed in co-polymerization with tolylene 2,4-diisocyanate terminated poly(propylene glycol). The obtained lignin-based polyurethanes were doped with 0.72 w/w% of multiwall carbon nanotubes (MWCNTs) with the aim of increasing their electrical conductivity to the levels suitable for sensor applications. Effects of the polymer doping with MWCNTs were assessed using electrical impedance (EIS) and UV-Resonance Raman (UV-RR) spectroscopy. Potentiometric sensors were prepared by drop casting of liquid polymer on the surface of carbon glass or platinum electrodes. Lignin-based sensors displayed a very low or no sensitivity to all alkali, alkali-earth and transition metal cations ions except Cr(VI) at pH 2. Response to Cr(VI) values of 39, 50 and 53 mV pX(-1) for the sensors based on kraft, organosolv and lignosulphonate lignins, respectively, were observed. Redox sensitivity values close to the theoretical values of 20 and 21 mV pX(-1) for organosolv and lignosulphonate based sensors respectively were detected in the Cr(III)/Cr(VI) solutions while a very low response was observed in the solutions containing Fe(CN)(6)(3-/4-). Conducting composite lignin-based polyurethanes doped with MWCNTs were suggested as being promising materials for Cr(VI)-sensitive potentiometric sensors.

Nanomolar simultaneous determination of tryptophan and melatonin by a new ionic liquid carbon paste electrode modified with SnO2-Co3O4@rGO nanocomposite.

Science.gov (United States)

Zeinali, Homa; Bagheri, Hasan; Monsef-Khoshhesab, Zahra; Khoshsafar, Hosein; Hajian, Ali

2017-02-01

This work describes the development of a new sensor for simultaneous determination of tryptophan and melatonin. The proposed sensor was an ionic liquid carbon paste electrode modified with reduced graphene oxides decorated with SnO 2 -Co 3 O 4 nanoparticles. The voltammetric oxidation of the analytes by the proposed sensor confirmed that the electrooxidation process undergoes a two-electron/one-proton reaction for melatonin and a two-electron/two-proton reaction for tryptophan in diffusion-controlled processes. Moreover, based on the excellent electrochemical properties of the modified electrode, a sensitive voltammetric method was used for individual and simultaneous determination of melatonin and tryptophan in the aqueous solutions. Under the optimized experimental conditions, a linear response obtained in the range of 0.02 to 6.00μmolL -1 with detection limits of 4.1 and 3.2nmolL -1 for melatonin and tryptophan, respectively. The prepared sensor possessed accurate and rapid response toward melatonin and tryptophan with a good sensitivity, selectivity, stability, and repeatability. Finally, the applicability of the proposed sensor was verified by evaluation of melatonin and tryptophan in various real samples including human serum and tablet samples. Copyright © 2016 Elsevier B.V. All rights reserved.

In situ 3D monitoring of corrosion on carbon steel and ferritic stainless steel embedded in cement paste

International Nuclear Information System (INIS)

Itty, Pierre-Adrien; Serdar, Marijana; Meral, Cagla; Parkinson, Dula; MacDowell, Alastair A.; Bjegović, Dubravka; Monteiro, Paulo J.M.

2014-01-01

Highlights: • The morphology of the corrosion of steel in cement paste was studied in situ. • During galvanostatic corrosion, carbon steel reinforcement corroded homogeneously. • On ferritic stainless steel, deep corrosion pits formed and caused wider cracks. • The measured rate of steel loss correlated well with Faraday’s law of electrolysis. - Abstract: In a X-ray microcomputed tomography study, active corrosion was induced by galvanostatically corroding steel embedded in cement paste. The results give insight into corrosion product build up, crack formation, leaching of products into the cracks and voids, and differences in morphology of corrosion attack in the case of carbon steel or stainless steel reinforcement. Carbon steel was homogeneously etched away with a homogeneous layer of corrosion products forming at the steel/cement paste interface. For ferritic stainless steel, pits were forming, concentrating the corrosion products locally, which led to more extensive damage on the cement paste cover

Carbon-Nanotube-Based Chemical Gas Sensor

Science.gov (United States)

Kaul, Arunpama B.

2010-01-01

Conventional thermal conductivity gauges (e.g. Pirani gauges) lend themselves to applications such as leak detectors, or in gas chromatographs for identifying various gas species. However, these conventional gauges are physically large, operate at high power, and have a slow response time. A single-walled carbon-nanotube (SWNT)-based chemical sensing gauge relies on differences in thermal conductance of the respective gases surrounding the CNT as it is voltage-biased, as a means for chemical identification. Such a sensor provides benefits of significantly reduced size and compactness, fast response time, low-power operation, and inexpensive manufacturing since it can be batch-fabricated using Si integrated-circuit (IC) process technology.

Engineering carbon nanomaterials for future applications: energy and bio-sensor

Science.gov (United States)

Das, Santanu; Lahiri, Indranil; Kang, Chiwon; Choi, Wonbong

2011-06-01

This paper presents our recent results on carbon nanomaterials for applications in energy storage and bio-sensor. More specifically: (i) A novel binder-free carbon nanotubes (CNTs) structure as anode in Li-ion batteries. The interfacecontrolled CNT structure, synthesized through a two-step chemical vapor deposition (CVD) and directly grown on copper current collector, showed very high specific capacity - almost three times as that of graphite, excellent rate capability. (ii) A large scale graphene film was grown on Cu foil by thermal chemical vapor deposition and transferred to various substrates including PET, glass and silicon by using hot press lamination and etching process. The graphene/PET film shows high quality, flexible transparent conductive structure with unique electrical-mechanical properties; ~88.80 % light transmittance and ~ 100 Ω/sq sheet resistance. We demonstrate application of graphene/PET film as flexible and transparent electrode for field emission displays. (iii) Application of individual carbon nanotube as nanoelectrode for high sensitivity electrochemical sensor and device miniaturization. An individual CNT is split into a pair of nanoelectrodes with a gap between them. Single molecular-level detection of DNA hybridization was studied. Hybridization of the probe with its complementary strand results in an appreciable change in the electrical output signal.

A Ni-Doped Carbon Nanotube Sensor for Detecting Oil-Dissolved Gases in Transformers

Directory of Open Access Journals (Sweden)

Jia Lu

2015-06-01

Full Text Available C2H2, C2H4, and C2H6 are important oil-dissolved gases in power transformers. Detection of the composition and content of oil-dissolved gases in transformers is very significant in the diagnosis and assessment of the state of transformer operations. The commonly used oil-gas analysis methods have many disadvantages, so this paper proposes a Ni-doped carbon nanotube (Ni-CNT gas sensor to effectively detect oil-dissolved gases in a transformer. The gas-sensing properties of the sensor to C2H2, C2H4, and C2H6 were studied using the test device. Based on the density functional theory (DFT the adsorption behaviors of the three gases on intrinsic carbon nanotubes (CNTs and Ni-CNTs were calculated. The adsorption energy, charge transfer, and molecular frontier orbital of the adsorption system were also analyzed. Results showed that the sensitivity of the CNT sensor to the three kinds of gases was in the following order: C2H2 > C2H4 > C2H6. Moreover, the doped Ni improved the sensor response, and the sensor response and gas concentration have a good linear relationship.

Thermal Stabilization of Enzymes Immobilized within Carbon Paste Electrodes.

Science.gov (United States)

Wang, J; Liu, J; Cepra, G

1997-08-01

In this note we report on the remarkable thermal stabilization of enzymes immobilized in carbon paste electrodes. Amperometric biosensors are shown for the first time to withstand a prolonged high-temperature (>50 °C) stress. Nearly full activity of glucose oxidase is retained over periods of up to 4 months of thermal stress at 60-80 °C. Dramatic improvements in the thermostability are observed for polyphenol oxidase, lactate oxidase, alcohol oxidase, horseradish peroxidase, and amino acid oxidase. Such resistance to heat-induced denaturation is attributed to the conformational rigidity of these biocatalysts within the highly hydrophobic (mineral oil or silicone grease) pasting liquid. While no chemical stabilizer is needed for attaining such protective action, it appears that low humidity (i.e., low water content) is essential for minimizing the protein mobility. Besides their implications for electrochemical biosensors, such observations should lead to a new generation of thermoresistant enzyme reactors based on nonpolar semisolid supports.

POF based smart sensor for studying the setting dynamics of cement paste

International Nuclear Information System (INIS)

Rajesh, M; Sheeba, M; Nampoori, V P N

2007-01-01

Fiber optic smart sensors are used to monitor the civil structures. One of the important parameters in civil engineering is the setting characteristics of concrete made of cement. The paper discusses how a simple polymer optical fiber can be used to characterise the setting dynamics of various grades of cement. The results explain the comparative performance of polymer fiber over silica fiber. The basic principle underlying the sensor is that as the cement sets, it exerts a stress on the sensing fiber, which is laid within the cement paste. This stress induces strain on the optical fiber, which can be thought of as a series of aperiodic microbends on the surface of the fiber. This in turn changes the characteristics of the light signal transmitted through the fiber and can be viewed as stress induced modulation of light in the fiber. By monitoring the intensity variation of transmitted light signal with time we can determine the cement setting rate. This can be used as an effective tool for quality testing of commercially available cements of different grades

In situ 3D monitoring of corrosion on carbon steel and ferritic stainless steel embedded in cement paste

KAUST Repository

Itty, Pierre-Adrien

2014-06-01

In a X-ray microcomputed tomography study, active corrosion was induced by galvanostatically corroding steel embedded in cement paste. The results give insight into corrosion product build up, crack formation, leaching of products into the cracks and voids, and differences in morphology of corrosion attack in the case of carbon steel or stainless steel reinforcement. Carbon steel was homogeneously etched away with a homogeneous layer of corrosion products forming at the steel/cement paste interface. For ferritic stainless steel, pits were forming, concentrating the corrosion products locally, which led to more extensive damage on the cement paste cover. © 2014 Elsevier Ltd.

In situ 3D monitoring of corrosion on carbon steel and ferritic stainless steel embedded in cement paste

KAUST Repository

Itty, Pierre-Adrien; Serdar, Marijana; Meral, Cagla; Parkinson, Dula; MacDowell, Alastair A.; Bjegović, Dubravka; Monteiro, Paulo J.M.

2014-01-01

In a X-ray microcomputed tomography study, active corrosion was induced by galvanostatically corroding steel embedded in cement paste. The results give insight into corrosion product build up, crack formation, leaching of products into the cracks and voids, and differences in morphology of corrosion attack in the case of carbon steel or stainless steel reinforcement. Carbon steel was homogeneously etched away with a homogeneous layer of corrosion products forming at the steel/cement paste interface. For ferritic stainless steel, pits were forming, concentrating the corrosion products locally, which led to more extensive damage on the cement paste cover. © 2014 Elsevier Ltd.

Dielectrophoresis Aligned Single-Walled Carbon Nanotubes as pH Sensors.

Science.gov (United States)

Li, Pengfei; Martin, Caleb M; Yeung, Kan Kan; Xue, Wei

2011-01-31

Here we report the fabrication and characterization of pH sensors using aligned single-walled carbon nanotubes (SWNTs). The SWNTs are dispersed in deionized (DI) water after chemical functionalization and filtration. They are deposited and organized on silicon substrates with the dielectrophoresis process. Electrodes with "teeth"-like patterns-fabricated with photolithography and wet etching-are used to generate concentrated electric fields and strong dielectrophoretic forces for the SWNTs to deposit and align in desired locations. The device fabrication is inexpensive, solution-based, and conducted at room temperature. The devices are used as pH sensors with the electrodes as the testing pads and the dielectrophoretically captured SWNTs as the sensing elements. When exposed to aqueous solutions with various pH values, the SWNTs change their resistance accordingly. The SWNT-based sensors demonstrate a linear relationship between the sensor resistance and the pH values in the range of 5-9. The characterization of multiple sensors proves that their pH sensitivity is highly repeatable. The real-time data acquisition shows that the sensor response time depends on the pH value, ranging from 2.26 s for the pH-5 solution to 23.82 s for the pH-9 solution. The long-term stability tests illustrate that the sensors can maintain their original sensitivity for a long period of time. The simple fabrication process, high sensitivity, and fast response of the SWNT-based sensors facilitate their applications in a wide range of areas.

Highly sensitive room temperature organic vapor sensor based on polybenzoxazine-derived carbon aerogel thin film composite

International Nuclear Information System (INIS)

Thubsuang, Uthen; Sukanan, Darunee; Sahasithiwat, Somboon; Wongkasemjit, Sujitra; Chaisuwan, Thanyalak

2015-01-01

Graphical abstract: - Highlights: • Activated carbon aerogel with high surface area can be prepared from polybenzoxazine. • Activated carbon aerogel enhances the adsorption capacity of gas sensor. • Organic vapors with very low concentration can be detected by the as-prepared sensor. • The as-prepared sensor shows impressive short exposure and recovery time. • The response to different organic vapors can be tailored by changing polymer matrix. - Abstract: Gas sensing composites were fabricated using polybenzoxazine-based activated carbon aerogel as a conductive filler. The activated carbon aerogel is a nano-porous material, which has high pore volume of 0.57 cm 3 /g and surface area of 917 m 2 /g. The activated carbon aerogel/polybutadiene composite displayed good response of 11.2 and 6.7 to toluene and n-hexane, respectively, compared to those of graphite/polybutadiene composite. The activated carbon aerogel/polybutadiene composite also showed high sensitivity of 3.09 × 10 2 ppm −1 to toluene. However, the sensitivity of activated carbon aerogel/polybutadiene composite drastically decreased to 1.99 ppm −1 and zero when exposed to acetone and water, respectively. Contrarily, when polyvinyl alcohol was used as a matrix, the sensitivity was about 4.19 ppm −1 to water. While the composite was found to be not sensitive to toluene. The activated carbon aerogel/polybutadiene composite also showed good recovery as the electrical resistance came back to the original value within minutes when exposed to nitrogen gas

Electrochemical characterization of screen-printed and conventional carbon paste electrodes

Energy Technology Data Exchange (ETDEWEB)

Fanjul-Bolado, Pablo; Hernandez-Santos, David; Lamas-Ardisana, Pedro Jose [Departamento de Quimica Fisica y Analitica, Universidad de Oviedo, 33006 Oviedo, Asturias (Spain); Martin-Pernia, Alberto [Departamento de Ingenieria Electrica, Electronica de Computadores y Sistemas, Universidad de Oviedo, 33204 Gijon, Asturias (Spain); Costa-Garcia, Agustin [Departamento de Quimica Fisica y Analitica, Universidad de Oviedo, 33006 Oviedo, Asturias (Spain)], E-mail: costa@fq.uniovi.es

2008-04-01

This work compares the electroactivity of a conventional carbon paste electrode and non-pretreated commercially available screen-printed carbon electrodes (from Alderon Biosciences, University of Florence and DropSens) towards some benchmark redox couples like hexaammineruthenium (III), ferricyanide, p-aminophenol and hydroquinone. While cyclic voltammograms of Ru{sup 3+} did not show significative electron transfer reactivity differences between the electrodes tested, the other redox systems exhibited higher reversible behaviours on DropSens electrodes. Scanning electron microscopy and roughness analysis with a profilometer were applied to detect the surface morphology of the working electrodes. The roughness evaluated of the screen-printed carbon working electrodes increased in this order Alderon < University of Florence < DropSens. Finally, the most electrochemically active and rough unpretreated electrode (DropSens commercial screen-printed electrode) was used to study the electrochemical-chemical reaction mechanism of indigo carmine oxidation in 0.1 M sulphuric acid. This study showed that the adsorption of the oxidation product of indigo carmine is stabilized when it is adsorbed on the surface of the electrode.

Electrochemical characterization of screen-printed and conventional carbon paste electrodes

International Nuclear Information System (INIS)

Fanjul-Bolado, Pablo; Hernandez-Santos, David; Lamas-Ardisana, Pedro Jose; Martin-Pernia, Alberto; Costa-Garcia, Agustin

2008-01-01

This work compares the electroactivity of a conventional carbon paste electrode and non-pretreated commercially available screen-printed carbon electrodes (from Alderon Biosciences, University of Florence and DropSens) towards some benchmark redox couples like hexaammineruthenium (III), ferricyanide, p-aminophenol and hydroquinone. While cyclic voltammograms of Ru 3+ did not show significative electron transfer reactivity differences between the electrodes tested, the other redox systems exhibited higher reversible behaviours on DropSens electrodes. Scanning electron microscopy and roughness analysis with a profilometer were applied to detect the surface morphology of the working electrodes. The roughness evaluated of the screen-printed carbon working electrodes increased in this order Alderon < University of Florence < DropSens. Finally, the most electrochemically active and rough unpretreated electrode (DropSens commercial screen-printed electrode) was used to study the electrochemical-chemical reaction mechanism of indigo carmine oxidation in 0.1 M sulphuric acid. This study showed that the adsorption of the oxidation product of indigo carmine is stabilized when it is adsorbed on the surface of the electrode

ONE STEP GREEN SYNTHESIS OF CARBON QUANTUM DOTS AND ITS APPLICATION TOWARDS THE BIOELECTROANALYTICAL AND BIOLABELING STUDIES

International Nuclear Information System (INIS)

Shereema, Rayammarakkar M.; Sankar, Vandana; Raghu, K.G; Rao, Talasila P.; Shankar, S.Sharath

2015-01-01

Highlights: • A green method was adopted for the synthesis of carbon quantum dots. • Being green fluorescent it was used for the cell imaging. • The carbon paste based carbon quantum dot was fabricated. • This quantum dots/carbon paste electrode was found to be capable of detecting dopamine in the nano molar level. • Possible interference from ascorbic acid and uric acid was successfully eliminated by the fabricated electrode. - Abstract: A green luminescent carbon quantum dots were prepared from maltose by Microwave assisted method followed by passivation with NaOH (pH = 7.4). The TEM measurement confirmed the average size of prepared carbon quantum dots to be 2 nm. Surface characterization such as XPS, FTIR and Raman spectroscopy confirm that the functional groups (C=O, C-OH) were attached on the surface of sp 2 hybridized carbon. Electrochemical characterization studies on carbon paste electrode (CPE) revealed that the synthesized carbon quantum dots showed higher electrocatalytic property, conductivity and surface area. Therefore, herein we report the synthesized carbon quantum dots could find its applicability as an electrochemical sensor for the detection of neurotransmitter, dopamine. Cyclic voltammetry and differential pulse voltammetry (DPV) was employed for the detection of DA in presence of common interferences like UA, and AA with carbon quantum dots modified carbon paste electrode. The developed sensor was effectively applied for the real sample analysis with satisfactory results. Moreover, biological studies in He La cell lines proclaimed that the cell viability was unaffected (100% viability) on incubation with the carbon dots. Significant cellular uptake as revealed by fluorescence imaging makes them suitable for cell labeling studies.

Monitoring of Carbon Fiber-Reinforced Old Timber Beams via Strain and Multiresonant Acoustic Emission Sensors

Directory of Open Access Journals (Sweden)

Francisco J. Rescalvo

2018-04-01

Full Text Available This paper proposes the monitoring of old timber beams with natural defects (knots, grain deviations, fissures and wanes, reinforced using carbon composite materials (CFRP. Reinforcement consisted of the combination of a CFRP laminate strip and a carbon fabric discontinuously wrapping the timber element. Monitoring considered the use and comparison of two types of sensors: strain gauges and multi-resonant acoustic emission (AE sensors. Results demonstrate that: (1 the mechanical behavior of the beams can be considerably improved by means of the use of CFRP (160% in bending load capacity and 90% in stiffness; (2 Acoustic emission sensors provide comparable information to strain gauges. This fact points to the great potential of AE techniques for in-service damage assessment in real wood structures.

Monitoring of Carbon Fiber-Reinforced Old Timber Beams via Strain and Multiresonant Acoustic Emission Sensors.

Science.gov (United States)

Rescalvo, Francisco J; Valverde-Palacios, Ignacio; Suarez, Elisabet; Roldán, Andrés; Gallego, Antolino

2018-04-17

This paper proposes the monitoring of old timber beams with natural defects (knots, grain deviations, fissures and wanes), reinforced using carbon composite materials (CFRP). Reinforcement consisted of the combination of a CFRP laminate strip and a carbon fabric discontinuously wrapping the timber element. Monitoring considered the use and comparison of two types of sensors: strain gauges and multi-resonant acoustic emission (AE) sensors. Results demonstrate that: (1) the mechanical behavior of the beams can be considerably improved by means of the use of CFRP (160% in bending load capacity and 90% in stiffness); (2) Acoustic emission sensors provide comparable information to strain gauges. This fact points to the great potential of AE techniques for in-service damage assessment in real wood structures.

Processing and Characterization of a Novel Distributed Strain Sensor Using Carbon Nanotube-Based Nonwoven Composites

Directory of Open Access Journals (Sweden)

Hongbo Dai

2015-07-01

Full Text Available This paper describes the development of an innovative carbon nanotube-based non-woven composite sensor that can be tailored for strain sensing properties and potentially offers a reliable and cost-effective sensing option for structural health monitoring (SHM. This novel strain sensor is fabricated using a readily scalable process of coating Carbon nanotubes (CNT onto a nonwoven carrier fabric to form an electrically-isotropic conductive network. Epoxy is then infused into the CNT-modified fabric to form a free-standing nanocomposite strain sensor. By measuring the changes in the electrical properties of the sensing composite the deformation can be measured in real-time. The sensors are repeatable and linear up to 0.4% strain. Highest elastic strain gage factors of 1.9 and 4.0 have been achieved in the longitudinal and transverse direction, respectively. Although the longitudinal gage factor of the newly formed nanocomposite sensor is close to some metallic foil strain gages, the proposed sensing methodology offers spatial coverage, manufacturing customizability, distributed sensing capability as well as transverse sensitivity.

Piezoresistive Carbon-based Hybrid Sensor for Body-Mounted Biomedical Applications

Science.gov (United States)

Melnykowycz, M.; Tschudin, M.; Clemens, F.

2017-02-01

For body-mounted sensor applications, the evolution of soft condensed matter sensor (SCMS) materials offer conformability andit enables mechanical compliance between the body surface and the sensing mechanism. A piezoresistive hybrid sensor and compliant meta-material sub-structure provided a way to engineer sensor physical designs through modification of the mechanical properties of the compliant design. A piezoresistive fiber sensor was produced by combining a thermoplastic elastomer (TPE) matrix with Carbon Black (CB) particles in 1:1 mass ratio. Feedstock was extruded in monofilament fiber form (diameter of 300 microns), resulting in a highly stretchable sensor (strain sensor range up to 100%) with linear resistance signal response. The soft condensed matter sensor was integrated into a hybrid design including a 3D printed metamaterial structure combined with a soft silicone. An auxetic unit cell was chosen (with negative Poisson’s Ratio) in the design in order to combine with the soft silicon, which exhibits a high Poisson’s Ratio. The hybrid sensor design was subjected to mechanical tensile testing up to 50% strain (with gauge factor calculation for sensor performance), and then utilized for strain-based sensing applications on the body including gesture recognition and vital function monitoring including blood pulse-wave and breath monitoring. A 10 gesture Natural User Interface (NUI) test protocol was utilized to show the effectiveness of a single wrist-mounted sensor to identify discrete gestures including finger and hand motions. These hand motions were chosen specifically for Human Computer Interaction (HCI) applications. The blood pulse-wave signal was monitored with the hand at rest, in a wrist-mounted. In addition different breathing patterns were investigated, including normal breathing and coughing, using a belt and chest-mounted configuration.

Amplified nanostructure electrochemical sensor for simultaneous determination of captopril, acetaminophen, tyrosine and hydrochlorothiazide

Energy Technology Data Exchange (ETDEWEB)

Karimi-Maleh, Hassan, E-mail: h.karimi.maleh@gmail.com [Department of Chemistry, Graduate University of Advanced Technology, Kerman (Iran, Islamic Republic of); Ganjali, Mohammad R.; Norouzi, Parviz; Bananezhad, Asma [Center of Excellence in Electrochemistry, Faculty of Chemistry, University of Tehran, Tehran (Iran, Islamic Republic of)

2017-04-01

A novel nanomaterial-based voltammetric sensor has been developed for use a highly sensitive tool for the simultaneous determination of captopril (CA), acetaminophen (AC), tyrosine (TY) and hydrochlorothiazide (HCTZ). The device is based on the application of NiO/CNTs and (2-(3,4-dihydroxyphenethyl)isoindoline-1,3-dione) (DPID) to modify carbon paste electrodes. The NiO/CNTs nanocomposite was synthesized through a direct chemical precipitation approach and was characterized with X-ray powder diffraction (XRD), and scanning electron microscopy (SEM). The NiO/CNTs/DPID/CPEs were found to facilitate the analysis of CA, AC, TY and HCTZ in the concentration ranges of 0.07–200.0, 0.8–550.0, 5.0–750.0 and 10.0–600.0 μM with the respective detection limits of 9.0 nM, 0.3 μM, 1.0 μM and 5.0 μM. The developed NiO/CNTs/DPID/CPEs were used for the determination of the mentioned analytes in pharmaceutical and biological real samples. - Graphical abstract: In this study a novel sensor based on NiO/CNTs and (2-(3,4-dihydroxyphenethyl)isoindoline-1,3-dione) (DPID) modified carbon paste electrode fabricated for simultaneous determination of captopril, acetaminophen, tyrosine and hydrochlorothiazide for the first time. - Highlights: • Fabrication of NiO/CNTs and new catechol derivative modified carbon paste electrode • Good ability of proposed sensor for biological and pharmaceutical analysis • Simultaneous determination captopril, acetaminophen, tyrosine and hydrochlorothiazide.

Microfabricated photoplastic cantilever with integrated photoplastic/carbon based piezoresistive strain sensor

DEFF Research Database (Denmark)

Gammelgaard, Lauge; Rasmussen, Peter Andreas; Calleja, M.

2006-01-01

We present an SU-8 micrometer sized cantilever strain sensor with an integrated piezoresistor made of a conductive composite of SU-8 polymer and carbon black particles. The composite has been developed using ultrasonic mixing. Cleanroom processing of the polymer composite has been investigated...

IMPROVED SELECTIVE ELECTROCATALYTIC OXIDATION OF PHENOLS BY TYROSINASE-BASED CARBON PASTE ELECTRODE BIOSENSOR

Science.gov (United States)

Tyrosinase-based carbon paste electrodes are evaluated with respect to the viscosity and polarity of the binder liquids. The electrodes constructed using a lower viscosity mineral oil yielded a greater response to phenol and catechol than those using a higher viscosity oil of s...

Deployment of Low-Cost, Carbon Dioxide Sensors throughout the Washington Metropolitan Area - The Capital Climate Initiative

Science.gov (United States)

Caine, Kristen M.; Bailey, D. Michelle; Houston Miller, J.

2016-04-01

According to the IPCC from 1995 to 2005, atmospheric carbon dioxide (CO2) concentrations increased by 19 ppm, the highest average growth rate recorded for any decade since measurements began in the 1950s. Due to its ability to influence global climate change, it is imperative to continually monitor carbon dioxide emission levels, particularly in urban areas where some estimate in excess of 75% of total greenhouse gas emissions occur. Although high-precision sensors are commercially available, these are not cost effective for mapping a large spatial area. A goal of this research is to build out a network of sensors that are accurate and precise enough to provide a valuable data tool for accessing carbon emissions from a large, urban area. This publically available greenhouse gas dataset can be used in numerous environmental assessments and as validation for remote sensing products. It will also be a valuable teaching tool for classes at our university and will promote further engagement of K-12 students and their teachers through education and outreach activities. Each of our sensors (referred to as "PiOxides") utilizes a non-dispersive infrared (NDIR) sensor for the detection of carbon dioxide along with a combination pressure/temperature/humidity sensor. The collection of pressure and temperature increases the accuracy and precision of the CO2 measurement. The sensors communicate using a serial interfaces with a Raspberry Pi microcontroller. Each PiOxide is connected to a website that leverages recent developments in open source GIS tools. In this way, data from individual sensors can be followed individually or aggregated to provide real-time, spatially-resolved data of CO2 trends across a broad area. Our goal for the network is to expand across the entire DC/Maryland/Virginia Region through partnerships with private and public schools. We are also designing GHG Bluetooth beacons that may be accessed by mobile phone users in their vicinity. In two additional

A multi-axis MEMS sensor with integrated carbon nanotube-based piezoresistors for nanonewton level force metrology

International Nuclear Information System (INIS)

Cullinan, Michael A; Panas, Robert M; Culpepper, Martin L

2012-01-01

This paper presents the design and fabrication of a multi-axis microelectromechanical system (MEMS) force sensor with integrated carbon nanotube (CNT)-based piezoresistive sensors. Through the use of proper CNT selection and sensor fabrication techniques, the performance of the CNT-based MEMS force sensor was increased by approximately two orders of magnitude as compared to current CNT-based sensor systems. The range and resolution of the force sensor were determined as 84 μN and 5.6 nN, respectively. The accuracy of the force sensor was measured to be better than 1% over the device’s full range. (paper)

Modelling the inorganic ocean carbon cycle under past and future climate change

International Nuclear Information System (INIS)

Ewan, T.L.

2004-01-01

This study used a coupled ocean-atmosphere-sea ice model with an inorganic carbon component to examine the inorganic ocean carbon cycle with particular reference to how climate feedback influences future uptake. In the last 150 years, the increase in atmosphere carbon dioxide (CO 2 ) concentrations have been higher than any time during the Earth's history. Although the oceans are the largest sink for carbon dioxide, it is not know how the ocean carbon cycle will respond to increasing anthropogenic carbon dioxide concentrations in the future. Climate feedbacks could potentially reduce further uptake of carbon by the ocean. In addition to examining past climate transitions, including both abrupt and glacial-interglacial climate transitions, this study also examined the sensitivity of the inorganic carbon cycle to increased atmospheric carbon dioxide. Atmospheric carbon dioxide levels were also projected under a range of global warming scenarios. Most simulations identified a transient weakening of the North Atlantic and increased sea surface temperatures (SST). These positive feedbacks act on the carbon system to reduce uptake. However, the ocean has the capacity to take up 65 to 75 per cent of the anthropogenic carbon dioxide increases. An analysis of climate feedback on future carbon uptake shows that oceans store 7 per cent more carbon when there are no climate feedbacks acting on the system. Sensitivity experiments using the Gent McWilliams parameterization for mixing associated with mesoscale eddies show a further 6 per cent increase in oceanic uptake. Inclusion of sea ice dynamics resulted in a 2 per cent difference in uptake. This study also examined changes in atmospheric carbon dioxide concentration that occur during abrupt climate change events. Changes in ocean circulation and carbon solubility cause significant increases in atmospheric carbon dioxide concentrations when melt water episodes are simulated in both hemispheres. The response of the carbon

Dielectrophoresis Aligned Single-Walled Carbon Nanotubes as pH Sensors

Directory of Open Access Journals (Sweden)

Wei Xue

2011-01-01

Full Text Available Here we report the fabrication and characterization of pH sensors using aligned single-walled carbon nanotubes (SWNTs. The SWNTs are dispersed in deionized (DI water after chemical functionalization and filtration. They are deposited and organized on silicon substrates with the dielectrophoresis process. Electrodes with “teeth”-like patterns—fabricated with photolithography and wet etching—are used to generate concentrated electric fields and strong dielectrophoretic forces for the SWNTs to deposit and align in desired locations. The device fabrication is inexpensive, solution-based, and conducted at room temperature. The devices are used as pH sensors with the electrodes as the testing pads and the dielectrophoretically captured SWNTs as the sensing elements. When exposed to aqueous solutions with various pH values, the SWNTs change their resistance accordingly. The SWNT-based sensors demonstrate a linear relationship between the sensor resistance and the pH values in the range of 5–9. The characterization of multiple sensors proves that their pH sensitivity is highly repeatable. The real-time data acquisition shows that the sensor response time depends on the pH value, ranging from 2.26 s for the pH-5 solution to 23.82 s for the pH-9 solution. The long-term stability tests illustrate that the sensors can maintain their original sensitivity for a long period of time. The simple fabrication process, high sensitivity, and fast response of the SWNT-based sensors facilitate their applications in a wide range of areas.

Carbon nanotube/polymer composite electrodes for flexible, attachable electrochemical DNA sensors.

Science.gov (United States)

Li, Jianfeng; Lee, Eun-Cheol

2015-09-15

All-solution-processed, easily-made, flexible multi-walled carbon nanotube (MWCNT)/polydimethylsiloxane (PDMS)-based electrodes were fabricated and used for electrochemical DNA sensors. These electrodes could serve as a recognition layer for DNA, without any surface modification, through π-π interactions between the MWCNTs and DNA, greatly simplifying the fabrication process for DNA sensors. The electrodes were directly connected to an electrochemical analyzer in the differential pulse voltammetry (DPV) and cyclic voltammetry (CV) measurements, where methylene blue was used as a redox indicator. Since neither functional groups nor probe DNA were immobilized on the surfaces of the electrodes, the sensor can be easily regenerated by washing these electrodes with water. The limit of detection was found to be 1.3 × 10(2)pM (S/N=3), with good DNA sequence differentiation ability. Fast fabrication of a DNA sensor was also achieved by cutting and attaching the MWCNT-PDMS composite electrodes at an analyte solution-containable region. Our results pave the way for developing user-fabricated easily attached DNA sensors at low costs. Copyright © 2015 Elsevier B.V. All rights reserved.

Tuning Selectivity of Fluorescent Carbon Nanotube-Based Neurotransmitter Sensors.

Science.gov (United States)

Mann, Florian A; Herrmann, Niklas; Meyer, Daniel; Kruss, Sebastian

2017-06-28

Detection of neurotransmitters is an analytical challenge and essential to understand neuronal networks in the brain and associated diseases. However, most methods do not provide sufficient spatial, temporal, or chemical resolution. Near-infrared (NIR) fluorescent single-walled carbon nanotubes (SWCNTs) have been used as building blocks for sensors/probes that detect catecholamine neurotransmitters, including dopamine. This approach provides a high spatial and temporal resolution, but it is not understood if these sensors are able to distinguish dopamine from similar catecholamine neurotransmitters, such as epinephrine or norepinephrine. In this work, the organic phase (DNA sequence) around SWCNTs was varied to create sensors with different selectivity and sensitivity for catecholamine neurotransmitters. Most DNA-functionalized SWCNTs responded to catecholamine neurotransmitters, but both dissociation constants ( K d ) and limits of detection were highly dependent on functionalization (sequence). K d values span a range of 2.3 nM (SWCNT-(GC) 15 + norepinephrine) to 9.4 μM (SWCNT-(AT) 15 + dopamine) and limits of detection are mostly in the single-digit nM regime. Additionally, sensors of different SWCNT chirality show different fluorescence increases. Moreover, certain sensors (e.g., SWCNT-(GT) 10 ) distinguish between different catecholamines, such as dopamine and norepinephrine at low concentrations (50 nM). These results show that SWCNTs functionalized with certain DNA sequences are able to discriminate between catecholamine neurotransmitters or to detect them in the presence of interfering substances of similar structure. Such sensors will be useful to measure and study neurotransmitter signaling in complex biological settings.

Highly sensitive room temperature organic vapor sensor based on polybenzoxazine-derived carbon aerogel thin film composite

Energy Technology Data Exchange (ETDEWEB)

Thubsuang, Uthen [Materials Science and Engineering, School of Engineering and Resources, Walailak University, Nakhon Si Thammarat 80160 (Thailand); Sukanan, Darunee [The Petroleum and Petrochemical College and the Center of Excellence on Petrochemical and Materials Technology, Chulalongkorn University, Bangkok 10330 (Thailand); Sahasithiwat, Somboon [National Metal and Materials Technology Center, Thailand Science Park (TSP), Khlong Luang, Pathum Thani 12120 (Thailand); Wongkasemjit, Sujitra [The Petroleum and Petrochemical College and the Center of Excellence on Petrochemical and Materials Technology, Chulalongkorn University, Bangkok 10330 (Thailand); Chaisuwan, Thanyalak, E-mail: thanyalak.c@chula.ac.th [The Petroleum and Petrochemical College and the Center of Excellence on Petrochemical and Materials Technology, Chulalongkorn University, Bangkok 10330 (Thailand)

2015-10-15

Graphical abstract: - Highlights: • Activated carbon aerogel with high surface area can be prepared from polybenzoxazine. • Activated carbon aerogel enhances the adsorption capacity of gas sensor. • Organic vapors with very low concentration can be detected by the as-prepared sensor. • The as-prepared sensor shows impressive short exposure and recovery time. • The response to different organic vapors can be tailored by changing polymer matrix. - Abstract: Gas sensing composites were fabricated using polybenzoxazine-based activated carbon aerogel as a conductive filler. The activated carbon aerogel is a nano-porous material, which has high pore volume of 0.57 cm{sup 3}/g and surface area of 917 m{sup 2}/g. The activated carbon aerogel/polybutadiene composite displayed good response of 11.2 and 6.7 to toluene and n-hexane, respectively, compared to those of graphite/polybutadiene composite. The activated carbon aerogel/polybutadiene composite also showed high sensitivity of 3.09 × 10{sup 2} ppm{sup −1} to toluene. However, the sensitivity of activated carbon aerogel/polybutadiene composite drastically decreased to 1.99 ppm{sup −1} and zero when exposed to acetone and water, respectively. Contrarily, when polyvinyl alcohol was used as a matrix, the sensitivity was about 4.19 ppm{sup −1} to water. While the composite was found to be not sensitive to toluene. The activated carbon aerogel/polybutadiene composite also showed good recovery as the electrical resistance came back to the original value within minutes when exposed to nitrogen gas.

Simulation of salinity effects on past, present, and future soil organic carbon stocks.

Science.gov (United States)

Setia, Raj; Smith, Pete; Marschner, Petra; Gottschalk, Pia; Baldock, Jeff; Verma, Vipan; Setia, Deepika; Smith, Jo

2012-02-07

Soil organic carbon (SOC) models are used to predict changes in SOC stocks and carbon dioxide (CO(2)) emissions from soils, and have been successfully validated for non-saline soils. However, SOC models have not been developed to simulate SOC turnover in saline soils. Due to the large extent of salt-affected areas in the world, it is important to correctly predict SOC dynamics in salt-affected soils. To close this knowledge gap, we modified the Rothamsted Carbon Model (RothC) to simulate SOC turnover in salt-affected soils, using data from non-salt-affected and salt-affected soils in two agricultural regions in India (120 soils) and in Australia (160 soils). Recently we developed a decomposition rate modifier based on an incubation study of a subset of these soils. In the present study, we introduce a new method to estimate the past losses of SOC due to salinity and show how salinity affects future SOC stocks on a regional scale. Because salinity decreases decomposition rates, simulations using the decomposition rate modifier for salinity suggest an accumulation of SOC. However, if the plant inputs are also adjusted to reflect reduced plant growth under saline conditions, the simulations show a significant loss of soil carbon in the past due to salinization, with a higher average loss of SOC in Australian soils (55 t C ha(-1)) than in Indian soils (31 t C ha(-1)). There was a significant negative correlation (p < 0.05) between SOC loss and osmotic potential. Simulations of future SOC stocks with the decomposition rate modifier and the plant input modifier indicate a greater decrease in SOC in saline than in non-saline soils under future climate. The simulations of past losses of SOC due to salinity were repeated using either measured charcoal-C or the inert organic matter predicted by the Falloon et al. equation to determine how much deviation from the Falloon et al. equation affects the amount of plant inputs generated by the model for the soils used in this study

Sensors based on carbon nanotube field-effect transistors and molecular recognition approaches

OpenAIRE

Cid Salavert, Cristina Carlota

2009-01-01

The general objective of this thesis is to develop chemical sensors whose sensing capacities are based on the principle of molecular recognition and where the transduction is carried out by single-walled carbon nanotubes (SWCNT).The sensing device used is the carbon nanotube field-effect transistor (CNTFET). The new structure of the CNTFET allows nanotubes to be integrated at the surface of the devices, thus exploiting SWCNTs' sensitivity to changes in their environment. The functionalization...

Presence of Fluorescent Carbon Nanoparticles in Baked Lamb: Their Properties and Potential Application for Sensors.

Science.gov (United States)

Wang, Haitao; Xie, Yisha; Liu, Shan; Cong, Shuang; Song, Yukun; Xu, Xianbing; Tan, Mingqian

2017-08-30

The presence of nanoparticles in food has drawn much attention in recent years. Fluorescent carbon nanoparticles are a new class of nanostructures; however, the distribution and physicochemical properties of such nanoparticles in food remain unclear. Herein, the presence of fluorescent carbon nanoparticles in baked lamb was confirmed, and their physicochemical properties were investigated. The fluorescent carbon nanoparticles from baked lamb emit strong blue fluorescence under ultraviolet light with a 10% fluorescent quantum yield. The nanoparticles are roughly spherical in appearance with a diameter of around 2.0 nm. Hydroxyl, amino, and carboxyl groups exist on the surface of nanoparticles. In addition, the nanoparticles could serve as a fluorescence sensor for glucose detection through an oxidation-reduction reaction. This work is the first report on fluorescent carbon nanoparticles present in baked lamb, which provides valuable insight into the physicochemical properties of such nanoparticles and their potential application in sensors.

Effect of carbon microfiber materials on sensitivity of adenosine and hydroxyadenine at carbon microfiber sensors

Directory of Open Access Journals (Sweden)

K.M.M. Abou El-Nour

2015-07-01

Full Text Available The relationship between the sensitivity measurements and microfiber electrodes made from different carbon microfiber materials, such as polyacrylonitrile (PAN T650 and PAN HCB and Pitch P25 was established in this work. The different microfiber electrodes were nanostructured by an electrochemical pretreatment method. Sensitivity of adenosine (ADO and 2,8-dihydroxyadenine (2,8-DHA was measured at different carbon microfiber sensors made from different carbon microfiber materials. Sensitivity of PAN microfiber electrodes for ADO and 2,8-DHA determinations measured at 500 V s−1 vs. SCE is higher than that measured at Pitch P25 microfiber electrodes due to more defects in PAN microfiber electrodes. Adsorption of ADO and 2,8-DHA is greater at PAN HCB electrodes. High conductivity of PAN fibers correlates with sensitivity determinations of the investigated analytes.

Carbon Nanotube/Polymer Nanocomposites Flexible Stress and Strain Sensors

Science.gov (United States)

Kang, Jin Ho; Sauti, Godfrey; Park, Cheol; Scholl, Jonathan A.; Lowther, Sharon E.; Harrison, Joycelyn S.

2008-01-01

Conformable stress and strain sensors are required for monitoring the integrity of airframe structures as well as for sensing the mechanical stimuli in prosthetic arms. For this purpose, we have developed a series of piezoresistive single-wall carbon nanotube (SWCNT)/polymer nanocomposites. The electromechanical coupling of pressure with resistance changes in these nanocomposites is exceptionally greater than that of metallic piezoresistive materials. In fact, the piezoresistive stress coefficient (pi) of a SWCNT/polymer nanocomposite is approximately two orders of magnitude higher than that of a typical metallic piezoresistive. The piezoresistive stress coefficient is a function of the nanotube concentration wherein the maximum value occurs at a concentration just above the percolation threshold concentration (phi approx. 0.05 %). This response appears to originate from a change in intrinsic resistivity under compression/tension. A systematic study of the effect of the modulus of the polymer matrix on piezoresistivity allowed us to make flexible and conformable sensors for biomedical applications. The prototype haptic sensors using these nanocomposites are demonstrated. The piezocapacitive properties of SWCNT/polymer are also characterized by monitoring the capacitance change under pressure.

Commercial Non-Dispersive Infrared Spectroscopy Sensors for Sub-Ambient Carbon Dioxide Detection

Science.gov (United States)

Swickrath, Michael J.; Anderson, Molly S.; McMillin, Summer; Broerman, Craig

2013-01-01

Carbon dioxide produced through respiration can accumulate rapidly within closed spaces. If not managed, a crew's respiratory rate increases, headaches and hyperventilation occur, vision and hearing are affected, and cognitive abilities decrease. Consequently, development continues on a number of CO2 removal technologies for human spacecraft and spacesuits. Terrestrially, technology development requires precise performance characterization to qualify promising air revitalization equipment. On-orbit, instrumentation is required to identify and eliminate unsafe conditions. This necessitates accurate in situ CO2 detection. Recursive compensation algorithms were developed for sub-ambient detection of CO2 with commercial off-the-shelf (COTS) non-dispersive infrared (NDIR) sensors. In addition, the source of the exponential loss in accuracy is developed theoretically. The basis of the loss can be explained through thermal, Doppler, and Lorentz broadening effects that arise as a result of the temperature, pressure, and composition of the gas mixture under analysis. The objective was to develop a mathematical routine to compensate COTS CO2 sensors relying on NDIR over pressures, temperatures, and compositions far from calibration conditions. The routine relies on a power-law relationship for the pressure dependency of the sensors along with an equivalent pressure to account for the composition dependency. A Newton-Raphson iterative technique solves for actual carbon dioxide concentration based on the reported concentration. Moreover, first principles routines were established to predict mixed-gas spectra based on sensor specifications (e.g., optical path length). The first principles model can be used to parametrically optimize sensors or sensor arrays across a wide variety of pressures/temperatures/ compositions. In this work, heuristic scaling arguments were utilized to develop reasonable compensation techniques. Experimental results confirmed this approach and provided

Development of carbon nanotube paste for dye-sensitized solar cells

Science.gov (United States)

Tsuji, Masaya; Sugiyama, Seiichi; Oya, Takahide

2012-09-01

We propose a new type of dye-sensitized solar cell (DSC) using carbon nanotubes (CNTs). Recently, global warming due to CO2 generated from power plants, cars, and so on has received much attention. Therefore, clean power, e.g., solar power, is gaining in importance. In this study, we focused on a DSC that uses CNTs. Generally, sensitized dyes on semiconducting and metallic electrodes are used for constructing DSCs. In contrast, CNTs have many excellent properties. In particular, they have metallic and semiconducting properties that are used for the electrodes of DSCs. Therefore, we applied CNTs for fabricating a new "painting-type" DSC with semiconducting and metallic electrodes. CNTs are dispersed in water with surfactant to prepare CNT-paste for painting. This resulting CNT-paste has the same properties as a normal CNT. A DSC is comprised of two electrodes. One is a semiconducting electrode with a sensitized dye and another is a metallic one, as mentioned above. We fabricated the two electrodes by painting the CNT-paste onto substrates. Thus, this type of DSC can be applied to various objects, for example, the wall and car and housetop. An electrolyte is required and must be put between the electrodes. The method for fabricating a painting type DSC is very simple. First, two versions of the paste are used. One is a semiconducting CNT-paste that adsorbs a dye and the other is a CNT-paste without a dye. Second, we paint each paste onto two substrates. Finally, the two substrates are stacked. We drip about 10μl of an electrolyte onto the stacked substrates and irradiate them with solar light (1300 W/m2). An electromotive force (EMF) is generated by excited electrons from the dye, which are adsorbed on the semiconducting electrode. The maximum EMF reached about 250 mV and the current reached about 10 μA. These results indicate that the proposed painting-type DSC can be used a new type of solar cell.

Permeability characterization of stitched carbon fiber preforms by fiber optic sensors

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V. Antonucci

2011-12-01

Full Text Available The in-plane and through thickness permeability of unidirectional stitched carbon fiber preforms have been determined through vacuum infusion tests. The impregnation of various dry preforms with different stitching characteristics has been monitored by fiber optic sensors that have been stitched together with the dry tow to manufacture the dry preform. The experimental infusion times have been fitted by a numerical procedure based on Finite Element (FE processing simulations. A good agreement between the numerical and experimental infusion times has been found demonstrating the potentiality of the fiber sensor system as suitable tool to evaluate impregnation times and permeability characteristics.

Carbon Paste Electrodes Made from Different Carbonaceous Materials: Application in the Study of Antioxidants

Science.gov (United States)

Apetrei, Constantin; Apetrei, Irina Mirela; De Saja, Jose Antonio; Rodriguez-Mendez, Maria Luz

2011-01-01

This work describes the sensing properties of carbon paste electrodes (CPEs) prepared from three different types of carbonaceous materials: graphite, carbon microspheres and carbon nanotubes. The electrochemical responses towards antioxidants including vanillic acid, catechol, gallic acid, l-ascorbic acid and l-glutathione have been analyzed and compared. It has been demonstrated that the electrodes based on carbon microspheres show the best performances in terms of kinetics and stability, whereas G-CPEs presented the smallest detection limit for all the antioxidants analyzed. An array of electrodes has been constructed using the three types of electrodes. As demonstrated by means of Principal Component Analysis, the system is able to discriminate among antioxidants as a function of their chemical structure and reactivity. PMID:22319354

Wireless Mid-Infrared Spectroscopy Sensor Network for Automatic Carbon Dioxide Fertilization in a Greenhouse Environment

Directory of Open Access Journals (Sweden)

Jianing Wang

2016-11-01

Full Text Available In this paper, a wireless mid-infrared spectroscopy sensor network was designed and implemented for carbon dioxide fertilization in a greenhouse environment. A mid-infrared carbon dioxide (CO2 sensor based on non-dispersive infrared (NDIR with the functionalities of wireless communication and anti-condensation prevention was realized as the sensor node. Smart transmission power regulation was applied in the wireless sensor network, according to the Received Signal Strength Indication (RSSI, to realize high communication stability and low-power consumption deployment. Besides real-time monitoring, this system also provides a CO2 control facility for manual and automatic control through a LabVIEW platform. According to simulations and field tests, the implemented sensor node has a satisfying anti-condensation ability and reliable measurement performance on CO2 concentrations ranging from 30 ppm to 5000 ppm. As an application, based on the Fuzzy proportional, integral, and derivative (PID algorithm realized on a LabVIEW platform, the CO2 concentration was regulated to some desired concentrations, such as 800 ppm and 1200 ppm, in 30 min with a controlled fluctuation of <±35 ppm in an acre of greenhouse.

Impedance study of the ion-to-electron transduction process for carbon cloth as solid-contact material in potentiometric ion sensors

International Nuclear Information System (INIS)

Mattinen, Ulriika; Rabiej, Sylwia; Lewenstam, Andrzej; Bobacka, Johan

2011-01-01

Carbon cloth was studied as solid-contact material in potentiometric ion sensors by using electrochemical impedance spectroscopy and potentiometry. The ion-to-electron transduction process was studied by electrochemical impedance spectroscopy by using a two-electrode symmetrical cell where a liquid electrolyte was sandwiched between two solid electrodes, including bare glassy carbon (GC), GC/carbon cloth and GC/poly(3,4-ethylenedioxythiophene). Impedance data for different electrode/electrolyte combinations were evaluated and compared. Solid-contact K + -selective electrodes were fabricated by coating the carbon cloth with a conventional plasticized PVC-based K + -selective membrane via drop casting. These K + -sensors showed proper analytical performance and acceptable long-term potential stability (potential drift ≈ 1 mV/day). Solid contact reference electrodes were fabricated in an analogous manner by coating the carbon cloth with a plasticized PVC membrane containing a moderately lipophilic salt. The results indicate that carbon cloth can be used as a solid-contact material in potentiometric ion sensors and pseudo-reference electrodes.

Electrochemical, morphological and microstructural characterization of carbon film resistor electrodes for application in electrochemical sensors

International Nuclear Information System (INIS)

Gouveia-Caridade, Carla; Soares, David M.; Liess, Hans-Dieter; Brett, Christopher M.A.

2008-01-01

The electrochemical and microstructural properties of carbon film electrodes made from carbon film electrical resistors of 1.5, 15, 140 Ω and 2.0 kΩ nominal resistance have been investigated before and after electrochemical pre-treatment at +0.9 V vs SCE, in order to assess the potential use of these carbon film electrodes as electrochemical sensors and as substrates for sensors and biosensors. The results obtained are compared with those at electrodes made from previously investigated 2 Ω carbon film resistors. Cyclic voltammetry was performed in acetate buffer and phosphate buffer saline electrolytes and the kinetic parameters of the model redox system Fe(CN) 6 3-/4- obtained. The 1.5 Ω resistor electrodes show the best properties for sensor development with wide potential windows, similar electrochemical behaviour to those of 2 Ω and close-to-reversible kinetic parameters after electrochemical pre-treatment. The 15 and 140 Ω resistor electrodes show wide potential windows although with slower kinetics, whereas the 2.0 kΩ resistor electrodes show poor cyclic voltammetric profiles even after pre-treatment. Electrochemical impedance spectroscopy related these findings to the interfacial properties of the electrodes. Microstructural and morphological studies were carried out using contact mode Atomic Force Microscopy (AFM), Confocal Raman spectroscopy and X-ray diffraction. AFM showed more homogeneity of the films with lower nominal resistances, related to better electrochemical characteristics. X-ray diffraction and Confocal Raman spectroscopy indicate the existence of a graphitic structure in the carbon films

Highly selective and sensitive detection of neurotransmitters using receptor-modified single-walled carbon nanotube sensors

Science.gov (United States)

Kim, Byeongju; Song, Hyun Seok; Jin, Hye Jun; Park, Eun Jin; Lee, Sang Hun; Lee, Byung Yang; Park, Tai Hyun; Hong, Seunghun

2013-07-01

We present receptor-modified carbon nanotube sensors for the highly selective and sensitive detection of acetylcholine (ACh), one kind of neurotransmitter. Here, we successfully expressed the M1 muscarinic acetylcholine receptor (M1 mAChR), a family of G protein-coupled receptors (GPCRs), in E. coli and coated single-walled carbon nanotube (swCNT)-field effect transistors (FETs) with lipid membrane including the receptor, enabling highly selective and sensitive ACh detection. Using this sensor, we could detect ACh at 100 pM concentration. Moreover, we showed that this sensor could selectively detect ACh among other neurotransmitters. This is the first demonstration of the real-time detection of ACh using specific binding between ACh and M1 mAChR, and it may lead to breakthroughs for various applications such as disease diagnosis and drug screening.

Highly selective and sensitive detection of neurotransmitters using receptor-modified single-walled carbon nanotube sensors

International Nuclear Information System (INIS)

Kim, Byeongju; Jin, Hye Jun; Park, Eun Jin; Hong, Seunghun; Song, Hyun Seok; Lee, Sang Hun; Park, Tai Hyun; Lee, Byung Yang

2013-01-01

We present receptor-modified carbon nanotube sensors for the highly selective and sensitive detection of acetylcholine (ACh), one kind of neurotransmitter. Here, we successfully expressed the M1 muscarinic acetylcholine receptor (M1 mAChR), a family of G protein-coupled receptors (GPCRs), in E. coli and coated single-walled carbon nanotube (swCNT)-field effect transistors (FETs) with lipid membrane including the receptor, enabling highly selective and sensitive ACh detection. Using this sensor, we could detect ACh at 100 pM concentration. Moreover, we showed that this sensor could selectively detect ACh among other neurotransmitters. This is the first demonstration of the real-time detection of ACh using specific binding between ACh and M1 mAChR, and it may lead to breakthroughs for various applications such as disease diagnosis and drug screening. (paper)

PVC membrane, coated-wire, and carbon-paste ion-selective electrodes for potentiometric determination of galantamine hydrobromide in physiological fluids.

Science.gov (United States)

Abdel-Haleem, Fatehy M; Saad, Mohamed; Barhoum, Ahmed; Bechelany, Mikhael; Rizk, Mahmoud S

2018-08-01

We report on highly-sensitive ion-selective electrodes (ISEs) for potentiometric determining of galantamine hydrobromide (GB) in physiological fluids. Galantamine hydrobromide (GB) was selected for this study due to its previous medical importance for treating Alzheimer's disease. Three different types of ISEs were investigated: PVC membrane electrode (PVCE), carbon-paste electrode (CPE), and coated-wire electrode (CWE). In the construction of these electrodes, galantaminium-reineckate (GR) ion-pair was used as a sensing species for GB in solutions. The modified carbon-paste electrode (MCPE) was prepared using graphene oxide (MCPE-GO) and sodium tetrakis (trifluoromethyl) phenyl borate (MCPE-STFPB) as ion-exchanger. The potentiometric modified CPEs (MCPE-GO and MCPE-STFPB) show an improved performance in term of Nernstian slope, selectivity, response time, and response stability compared to the unmodified CPE. The prepared electrodes PVCE, CWE, CPE, MCPE-GO and MCPE-STFPB show Nernstian slopes of 59.9, 59.5, 58.1, 58.3 and 57.0 mV/conc. decade, and detection limits of 5.0 × 10 -6 , 6.3 × 10 -6 , 8.0 × 10 -6 , 6.0 × 10 -6 and 8.0 × 10 -6  mol L -1 , respectively. The prepared ISEs also show high selectivity against cations (i.e. Na + , K + , NH 4 + , Ca 2+ , Al 3+ , Fe 3+ ), amino acids (i.e. glycine, L-alanine alanine), and sugars (i.e. fructose, glucose, maltose, lactose). The prepared ISEs are applicable for determining GB in spiked serums, urines, and pharmaceutical preparations, using a standard addition and a direct potentiometric method. The fast response time (<10 s), long lifetime (1-5 weeks), reversibility and stability of the measured signals facilitate the application of these sensors for routine analysis of the real samples. Copyright © 2018 Elsevier B.V. All rights reserved.

Energy utilization and carbon dioxide emission in the fresh, paste, whole-peeled, diced, and juiced tomato production processes

International Nuclear Information System (INIS)

Karakaya, Ahmet; Ozilgen, Mustafa

2011-01-01

Energy utilization and carbon dioxide emission during the production of fresh, peeled, diced, and juiced tomatoes are calculated. The energy utilization for production of raw and packaging materials, transportation, and waste management are also considered. The energy utilization to produce one-ton retail packaged fresh tomatoes is calculated to be 2412.8 MJ, whereas when the tomatoes are converted into paste, the energy utilization increases almost twofold; processing the same amount into the peeled or diced-tomatoes increases the energy utilization seven times. In case of juice production, the increase is five times. The carbon dioxide emission is determined by the source of energy used and is 189.4 kg/t of fresh tomatoes in the case of retail packaging, and did not change considerably when made into paste. The carbon dioxide emission increased twofold with peeled or diced-tomatoes, and increased threefold when juiced. Chemical fertilizers and transportation made the highest contribution to energy utilization and CO 2 emission. The difference in energy utilization is determined mainly by water to dry solids ratio of the food and increases with the water content of the final product. Environmentally conscious consumers may prefer eating fresh tomatoes or alternatively tomato paste, to minimize carbon dioxide emission. -- Highlights: → Energy utilization for producing one-ton retail packaged fresh tomatoes was 2412.8 MJ → Energy utilization was 2 folds with paste, 7 times with peeled or diced-tomatoes, 5 times with juice. → Energy utilization increases with water content of the final product. → Transportation, packaging, evaporation and chemicals are the major energy consumers. → Carbon dioxide emission is determined by the source of energy.

Flexible carbon nanotube sensors for nerve agent simulants

Energy Technology Data Exchange (ETDEWEB)

Cattanach, Kyle; Kulkarni, Rashmi D; Kozlov, Mikhail; Manohar, Sanjeev K [Alan G MacDiarmid Center for Innovation, Department of Chemistry, University of Texas at Dallas, Richardson 75083-0688 (United States)

2006-08-28

Chemiresistor-based vapour sensors made from network films of single-walled carbon nanotube (SWNT) bundles on flexible plastic substrates (polyethylene terephthalate, PET) can be used to detect chemical warfare agent simulants for the nerve agents Sarin (diisopropyl methylphosphonate, DIMP) and Soman (dimethyl methylphosphonate, DMMP). Large, reproducible resistance changes (75-150%), are observed upon exposure to DIMP or DMMP vapours, and concentrations as low as 25 ppm can be detected. Robust sensor response to simulant vapours is observed even in the presence of large equilibrium concentrations of interferent vapours commonly found in battle-space environments, such as hexane, xylene and water (10 000 ppm each), suggesting that both DIMP and DMMP vapours are capable of selectively displacing other vapours from the walls of the SWNTs. Response to these interferent vapours can be effectively filtered out by using a 2 {mu}m thick barrier film of the chemoselective polymer polyisobutylene (PIB) on the SWNT surface. These network films are composed of a 1-2 {mu}m thick non-woven mesh of SWNT bundles (15-30 nm diameter), whose sensor response is qualitatively and quantitatively different from previous studies on individual SWNTs, or a network of individual SWNTs, suggesting that vapour sorption at interbundle sites could be playing an important role. This study also shows that the line patterning method used in device fabrication to obtain any desired pattern of films of SWNTs on flexible substrates can be used to rapidly screen simulants at high concentrations before developing more complicated sensor systems.

Magnetic core–shell Fe{sub 3}O{sub 4}@SiO{sub 2}/MWCNT nanocomposite modified carbon paste electrode for amplified electrochemical sensing of uric acid

Energy Technology Data Exchange (ETDEWEB)

Arvand, Majid, E-mail: arvand@guilan.ac.ir; Hassannezhad, Morassa

2014-03-01

A new type of nanocomposite based on multi-walled carbon nanotubes decorated with magnetic core–shell Fe{sub 3}O{sub 4}@SiO{sub 2} nanoparticles (Fe{sub 3}O{sub 4}@SiO{sub 2}/MWCNTs) was prepared and used to fabricate a modified carbon paste electrode (CPE). The nanocomposite was characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and Fourier transform infrared spectroscopy (FT-IR) techniques. Electrochemical behavior of uric acid (UA) was investigated on Fe{sub 3}O{sub 4}@SiO{sub 2}/MWCNTs-CPE by cyclic voltammetry (CV) and square wave voltammetry (SWV) in phosphate buffer solution (pH 6.0). Under the optimized conditions, the peak currents increased linearly with the concentration of UA in the range from 0.60 to 100.0 μM, with a detection limit of 0.13 μM. The proposed sensor was successfully applied for the determination of UA in biological fluids. - Highlights: • A simple and rapid sensor for determination of UA in human blood serum and urine was prepared. • The Fe{sub 3}O{sub 4}@SiO{sub 2}/MWCNTs-CPE showed an obvious increase in surface area and sensitivity. • The presence of Fe{sub 3}O{sub 4}@SiO{sub 2} nanoparticles showed good ability to distinguish the response of UA.

An Enzymatic Glucose Sensor Composed of Carbon-Coated Nano Tin Sulfide

Directory of Open Access Journals (Sweden)

Ren-Jei Chung

2017-02-01

Full Text Available In this study, a biosensor, based on a glucose oxidase (GOx immobilized, carbon-coated tin sulfide (SnS assembled on a glass carbon electrode (GCE was developed, and its direct electrochemistry was investigated. The carbon coated SnS (C-SnS nanoparticle was prepared through a simple two-step process, using hydrothermal and chemical vapor deposition methods. The large reactive surface area and unique electrical potential of C-SnS could offer a favorable microenvironment for facilitating electron transfer between enzymes and the electrode surface. The structure and sensor ability of the proposed GOx/C-SnS electrode were characterized using scanning electron microscopy (SEM, X-ray diffraction (XRD, Raman spectroscopy, UV–vis spectroscopy, Fourier transform infrared spectroscopy (FTIR, and cyclic voltammetry study (CV.

Multidirectional flexible force sensors based on confined, self-adjusting carbon nanotube arrays

Science.gov (United States)

Lee, J.-I.; Pyo, Soonjae; Kim, Min-Ook; Kim, Jongbaeg

2018-02-01

We demonstrate a highly sensitive force sensor based on self-adjusting carbon nanotube (CNT) arrays. Aligned CNT arrays are directly synthesized on silicon microstructures by a space-confined growth technique which enables a facile self-adjusting contact. To afford flexibility and softness, the patterned microstructures with the integrated CNTs are embedded in polydimethylsiloxane structures. The sensing mechanism is based on variations in the contact resistance between the facing CNT arrays under the applied force. By finite element analysis, proper dimensions and positions for each component are determined. Further, high sensitivities up to 15.05%/mN of the proposed sensors were confirmed experimentally. Multidirectional sensing capability could also be achieved by designing multiple sets of sensing elements in a single sensor. The sensors show long-term operational stability, owing to the unique properties of the constituent CNTs, such as outstanding mechanical durability and elasticity.

Carbon Dioxide Gas Sensors and Method of Manufacturing and Using Same

Science.gov (United States)

Hunter, Gary W. (Inventor); Xu, Jennifer C. (Inventor)

2014-01-01

A gas sensor comprises a substrate layer; a pair of interdigitated metal electrodes, said electrodes include upper surfaces, the electrodes selected from the group consisting of Pt, Pd, Au, Ir, Ag, Ru, Rh, In, Os, and their alloys. A first layer of solid electrolyte staying in between electrode fingers and partially on said upper surfaces of said electrodes, said first layer selected from NASICON, LISICON, KSICON and.beta.''-Alumina. A second layer of metal carbonate(s) as an auxiliary electrolyte engaging said upper surfaces of the electrodes and the first solid electrolyte. The metal carbonates selected from the group consisting of the following ions Na.sup.+, K.sup.+, Li.sup.+, Ag.sup.+, H.sup.+, Pb.sup.2+, Sr.sup.2+, Ba.sup.2+, and any combination thereof. An extra layer of metal oxide selected from the group consisting of SnO.sub.2, In.sub.2O.sub.3, TiO.sub.2, WO.sub.3, ZnO, Fe.sub.2O.sub.3, ITO, CdO, U.sub.3O.sub.8, Ta.sub.2O.sub.5, BaO, MoO.sub.2, MoO.sub.3, V.sub.2O.sub.5, Nb.sub.2O.sub.5, CuO, Cr.sub.2O.sub.3, La.sub.2O.sub.3, RuO.sub.3, RuO.sub.2, ReO.sub.2, ReO.sub.3, Ag.sub.2O, CoO, Cu.sub.2O, SnO, NiO, Pr.sub.2O.sub.3, BaO, PdO.sub.2, HfO.sub.3, HfO.sub.3 or other metal oxide and their mixtures residing above and in engagement with the second electrolyte to improve sensor performance and/or to reduce sensor heating power consumption.

Imprinted sol-gel electrochemical sensor for the determination of benzylpenicillin based on Fe3O4/SiO2 multi-walled carbon nanotubes-chitosans nanocomposite film modified carbon electrode

International Nuclear Information System (INIS)

Hu Yufang; Li Jiaxing; Zhang Zhaohui; Zhang Huabin; Luo Lijuan; Yao Shouzhuo

2011-01-01

Graphical abstract: A novel imprinted sol-gel electrochemical sensor based on Fe 3 O 4 /SiO 2 -MWNTs-CTS nanocomposite film and a thin MIP film has been developed on a carbon electrode. Highlights: → A novel imprinted sol-gel electrochemical sensor based on Fe 3 O 4 /SiO 2 -MWNTs-CTS nanocomposites has been developed. → Fe 3 O 4 /SiO 2 -MWNTs-CTS nanocomposites act as 'electronic wires' to enhance the electron transfer. → The inherent specificity of the MIPs brings about highly selectivity. The imprinted sensor detects benzylpenicillin in real samples successfully. - Abstract: Herein, a novel imprinted sol-gel electrochemical sensor based on multi-walled carbon nanotubes (MWNTs) doped with chitosan film on a carbon electrode has been developed. Prior to doped, the MWNTs have been decorated with Fe 3 O 4 nanoparticles which have been coated uniformly with SiO 2 layer. The characterization of imprinted sensor has been carried out by X-ray diffraction and scanning electron microscopy. The performance of the proposed imprinted sensor has been investigated using cyclic voltammetry and differential pulse voltammetry. The imprinted sensor offers a fast response and sensitive benzylpenicillin quantification. The fabricated benzylpenicillin imprinted sensor exhibits a linear response from 5.0 x 10 -8 to 1.0 x 10 -3 mol L -1 with a detection limit of 1.5 x 10 -9 mol L -1 . For samples analysis, perfect recoveries of the imprinted sensor for benzylpenicillin indicated that the imprinted sensor was able to detect benzylpenicillin in real samples successfully.

All-Solid-State, PVC Membrane, and Carbon Paste Ion-Selective Electrodes for Determination of Donepezil Hydrochloride in Pharmaceutical Formulation.

Science.gov (United States)

Khamees, Nesreen; Mohamed, Tagreed Abdel-Fattah; Derar, Abeer Rashad; Aziz, Azza

2017-09-01

All-solid-state, polyvinyl chloride (PVC) membrane, and carbon paste potentiometric ion-selective electrodes (ISEs) were proposed for the determination of donepezil hydrochloride (DON) in the drug substance and a pharmaceutical formulation. The potentiometric response toward DON was based on the existence of donepezil-tetraphenyl borate (DON-TPB) in a PVC membrane or a carbon paste in the presence of dioctylphthalate. In contrast, the solid-state electrode was prepared by direct incorporation of DON-TPB into a commercial nail varnish without external additives. The electrodes exhibited Nernstian slopes of 55.0, 57.0, and 53.0 mV/decade over the concentration ranges of 1 × 10-5 to 1 × 10-3, 1 × 10-4 to 10-2, and 1 × 10-4 to 5 × 10-3 for the solid-state, PVC membrane, and carbon paste electrodes, respectively. The response of the electrodes is independent of pH in the range of 2-≤8. The electrodes showed good selectivity for DON with respect to a number of inorganic cations and amino acids. The electrodes were used for the determination of DON in pure solution and in pharmaceutical tablets with high accuracy (±2%) and precision (RSD ≤2%). The solid-state electrode is simple, economical, and rapid when compared to the PVC membrane and carbon paste electrodes.

Selectivity of multi-wall carbon nanotube network sensoric units to ethanol vapors achieved by carbon nanotube oxidation

Czech Academy of Sciences Publication Activity Database

Olejník, R.; Slobodian, P.; Říha, Pavel; Sáha, P.

2012-01-01

Roč. 1, č. 1 (2012), s. 101-106 ISSN 1927-0585 Grant - others:UTB Zlín(CZ) IGA/3/FT/11/D; OP VaVpI(XE) CZ.1.05/2.1.00/03.0111 Institutional research plan: CEZ:AV0Z20600510 Keywords : carbon nanotube network * buckypaper * oxidation * sensor * electrical resistance Subject RIV: BK - Fluid Dynamics

Preparation of alanine and tyrosine functionalized graphene oxide nanoflakes and their modified carbon paste electrodes for the determination of dopamine

International Nuclear Information System (INIS)

Kumar, Mohan; Swamy, B.E. Kumara; Asif, M.H. Mohammed; Viswanath, C.C.

2017-01-01

Highlights: • The prepared graphene oxide was functionalized by alanine and tyrosine. • The prepared materials were used for sensor for dopamine. • The functionalized graphene oxide modified carbon paste electrodes shows good sensitivity, stability and repeatability. - Abstract: Herein, established the synthesis of graphene oxide (GO) by Hummers Method with addition of KMnO_4 followed by thermal heating at 80 °C. The obtained GO was further functionalized by alanine and tyrosine. The prepared GO, alanine functionalized GO nanoflakes (AGONF) and tyrosine functionalized GO nanoflakes (TGONF) were characterized by spectroscopic technique using energy-dispersive spectroscopy (EDS), quantitatively by scanning electron microscopy (SEM) and structural studies along with interlayer distance verified through X-ray diffraction technique. Afterwards, the prepared AGONF and TGONF were used as the modifier for the carbon paste electrode (CPE). The electrochemical behavior of the AGONF and TGONF modified carbon paste electrodes (MCPEs) towards dopamine (DA) in phosphate buffer solution (PBS) were examined by cyclic voltammetric (CV) technique and the obtained consequences showed good electrocatalytic activity of MCPEs by increasing the redox peak current with a lower potential difference compared to the bare CPE (BCPE). The AGONF and TGONF MCPEs were further used for the optimization studies. From the pH studies, it was found that the equal number of proton and electron transfer reaction involved in both the modified electrodes. The scan rate studies demonstrate the adsorption controlled electrode process at AGONF MCPE and diffusion controlled at TGONF MCPE. The oxidation peak current increased linearly with two concentration interval of DA at a range of 2–7 μM and 10–30 μM in presence of PBS (pH 7.4) at MCPEs and the limit of detection (LOD) were found to be 0.84 μM and 0.96 μM for first interval DA concentration range (2–7 μM) at AGONF and TGONF MCPE. The

Preparation of alanine and tyrosine functionalized graphene oxide nanoflakes and their modified carbon paste electrodes for the determination of dopamine

Energy Technology Data Exchange (ETDEWEB)

Kumar, Mohan [Department of P.G. Studies and Research in Industrial Chemistry, Kuvempu University, Shankaraghatta, 577 451, Shimoga, Karnataka (India); Swamy, B.E. Kumara, E-mail: kumaraswamy21@yahoo.com [Department of P.G. Studies and Research in Industrial Chemistry, Kuvempu University, Shankaraghatta, 577 451, Shimoga, Karnataka (India); Asif, M.H. Mohammed [Nanoscience and Technology, Kuvempu University, Shankaraghatta, 577451, Shimoga, Karnataka (India); Viswanath, C.C. [Department of P.G. Studies and Research in Industrial Chemistry, Kuvempu University, Shankaraghatta, 577 451, Shimoga, Karnataka (India)

2017-03-31

Highlights: • The prepared graphene oxide was functionalized by alanine and tyrosine. • The prepared materials were used for sensor for dopamine. • The functionalized graphene oxide modified carbon paste electrodes shows good sensitivity, stability and repeatability. - Abstract: Herein, established the synthesis of graphene oxide (GO) by Hummers Method with addition of KMnO{sub 4} followed by thermal heating at 80 °C. The obtained GO was further functionalized by alanine and tyrosine. The prepared GO, alanine functionalized GO nanoflakes (AGONF) and tyrosine functionalized GO nanoflakes (TGONF) were characterized by spectroscopic technique using energy-dispersive spectroscopy (EDS), quantitatively by scanning electron microscopy (SEM) and structural studies along with interlayer distance verified through X-ray diffraction technique. Afterwards, the prepared AGONF and TGONF were used as the modifier for the carbon paste electrode (CPE). The electrochemical behavior of the AGONF and TGONF modified carbon paste electrodes (MCPEs) towards dopamine (DA) in phosphate buffer solution (PBS) were examined by cyclic voltammetric (CV) technique and the obtained consequences showed good electrocatalytic activity of MCPEs by increasing the redox peak current with a lower potential difference compared to the bare CPE (BCPE). The AGONF and TGONF MCPEs were further used for the optimization studies. From the pH studies, it was found that the equal number of proton and electron transfer reaction involved in both the modified electrodes. The scan rate studies demonstrate the adsorption controlled electrode process at AGONF MCPE and diffusion controlled at TGONF MCPE. The oxidation peak current increased linearly with two concentration interval of DA at a range of 2–7 μM and 10–30 μM in presence of PBS (pH 7.4) at MCPEs and the limit of detection (LOD) were found to be 0.84 μM and 0.96 μM for first interval DA concentration range (2–7 μM) at AGONF and TGONF MCPE

Electrochemical sensors for detection of acetylsalicylic acid

OpenAIRE

Šupálková, Veronika; Petřek, Jiří; Havel, Ladislav; Křížková, Soňa; Petrlová, Jitka; Adam, Vojtěch; Potěšil, David; Babula, Petr; Beklová, Miroslava; Horna, Aleš; Kizek, René

2006-01-01

Acetylsalicylic acid ( AcSA), or aspirin, was introduced in the late 1890s and has been used to treat a variety of inflammatory conditions. The aim of this work was to suggest electrochemical sensor for acetylsalicylic detection. Primarily, we utilized square wave voltammetry ( SWV) using both carbon paste electrode ( CPE) and of graphite pencil electrode ( GPE) as working ones to indirect determination of AcSA. The principle of indirect determination of AcSA bases in its hydrolysis on salicy...

Past explosive outbursts of entrapped carbon dioxide in salt mines provide a new perspective on the hazards of carbon dioxide

DEFF Research Database (Denmark)

Hedlund, Frank Huess

2013-01-01

This paper reports on a source of past carbon dioxide accidents which so far has only been sporadically mentioned in the literature. Violent and highly destructive outbursts of hundreds of tons of CO2 occurred regularly, if not routinely, in the now closed salt mines of the former DDR. The Menzen...

Vertically Aligned Carbon Nanofiber based Biosensor Platform for Glucose Sensor

Energy Technology Data Exchange (ETDEWEB)

Al Mamun, Khandaker A.; Tulip, Fahmida S.; MacArthur, Kimberly; McFarlane, Nicole; Islam, Syed K.; Hensley, Dale

2014-03-01

Vertically aligned carbon nanofibers (VACNFs) have recently become an important tool for biosensor design. Carbon nanofibers (CNF) have excellent conductive and structural properties with many irregularities and defect sites in addition to exposed carboxyl groups throughout their surfaces. These properties allow a better immobilization matrix compared to carbon nanotubes and offer better resolution when compared with the FET-based biosensors. VACNFs can be deterministically grown on silicon substrates allowing optimization of the structures for various biosensor applications. Two VACNF electrode architectures have been employed in this study and a comparison of their performances has been made in terms of sensitivity, sensing limitations, dynamic range, and response time. The usage of VACNF platform as a glucose sensor has been verified in this study by selecting an optimum architecture based on the VACNF forest density. Read More: http://www.worldscientific.com/doi/abs/10.1142/S0129156414500062

Carbon Nanotubes and Carbon Nanotube Fiber Sensors: Growth, Processing and Characterization

Science.gov (United States)

Zhao, Haibo

With multiple outstanding properties, such as high Young's modulus, high strength, good thermal conductivity and electrical conductivity, carbon nanotube (CNT) has been considered as a new generation of material that has many potential applications in many fields. One obstacle that stands in the way of applying CNTs in the real world is the limited growth length. Catalyst instability is one of the many factors that cause the stops of CNT growth. In this research, intermetalic Fe-Zr catalyst was used to grow millimeter long CNT arrays. The Fe-Zr particles enabled the growth of 1.7 millimeter long carbon nanotube arrays in 45 minutes. A comparison with pure Fe catalyst indicated that adding Zr to iron can stabilize the Fe catalyst at the CNT growth temperature and moderate its reactivity. In future, when CNTs are largely used in industrial, mass production of CNTs at a low cost is vital for market competition. In many current CNT growth methods, a process of depositing a thin catalyst film on top of Al 2O3 film on a piece of silicon wafer is required. Thus the size of CNT samples is limited by the size of the largest silicon wafer currently available, which is 8 inch in diameter. In this study, FeCl2 powders were used as the catalyst to grow CNT arrays not only on traditional silicon substrates but also on quartz substrates and carbon sheets. This unique method does not require the thin film deposition step, which shortens the time used for each batch of CNT growth. The simplicity of this method allows an easy scale-up for mass production of CNTs with a low cost. In order to improve this method, HCl was used to assist the CNT growth. HCl was added via flowing a small amount of C2H2 thorough a bubbuler where HCl solution was contained. With the assistance of HCl, CNT growth could be extended to 1 hour. 3 mm tall non-spinnable arrays and 2 mm tall spinnable arrays were produced using this method. With the increasing use of composite materials, real time health

100 nm scale low-noise sensors based on aligned carbon nanotube networks: overcoming the fundamental limitation of network-based sensors

Science.gov (United States)

Lee, Minbaek; Lee, Joohyung; Kim, Tae Hyun; Lee, Hyungwoo; Lee, Byung Yang; Park, June; Jhon, Young Min; Seong, Maeng-Je; Hong, Seunghun

2010-02-01

Nanoscale sensors based on single-walled carbon nanotube (SWNT) networks have been considered impractical due to several fundamental limitations such as a poor sensitivity and small signal-to-noise ratio. Herein, we present a strategy to overcome these fundamental problems and build highly-sensitive low-noise nanoscale sensors simply by controlling the structure of the SWNT networks. In this strategy, we prepared nanoscale width channels based on aligned SWNT networks using a directed assembly strategy. Significantly, the aligned network-based sensors with narrower channels exhibited even better signal-to-noise ratio than those with wider channels, which is opposite to conventional random network-based sensors. As a proof of concept, we demonstrated 100 nm scale low-noise sensors to detect mercury ions with the detection limit of ~1 pM, which is superior to any state-of-the-art portable detection system and is below the allowable limit of mercury ions in drinking water set by most government environmental protection agencies. This is the first demonstration of 100 nm scale low-noise sensors based on SWNT networks. Considering the increased interests in high-density sensor arrays for healthcare and environmental protection, our strategy should have a significant impact on various industrial applications.

100 nm scale low-noise sensors based on aligned carbon nanotube networks: overcoming the fundamental limitation of network-based sensors

Energy Technology Data Exchange (ETDEWEB)

Lee, Minbaek; Lee, Joohyung; Kim, Tae Hyun; Lee, Hyungwoo; Lee, Byung Yang; Hong, Seunghun [Department of Physics and Astronomy, Seoul National University, Shilim-Dong, Kwanak-Gu, Seoul 151-742 (Korea, Republic of); Park, June; Seong, Maeng-Je [Department of Physics, Chung-Ang University, Heukseok-Dong, Dongjak-Gu, Seoul 156-756 (Korea, Republic of); Jhon, Young Min, E-mail: mseong@cau.ac.kr, E-mail: shong@phya.snu.ac.kr [Korea Institute of Science and Technology, Hawolgok-Dong, Seongbuk-Gu, Seoul 136-791 (Korea, Republic of)

2010-02-05

Nanoscale sensors based on single-walled carbon nanotube (SWNT) networks have been considered impractical due to several fundamental limitations such as a poor sensitivity and small signal-to-noise ratio. Herein, we present a strategy to overcome these fundamental problems and build highly-sensitive low-noise nanoscale sensors simply by controlling the structure of the SWNT networks. In this strategy, we prepared nanoscale width channels based on aligned SWNT networks using a directed assembly strategy. Significantly, the aligned network-based sensors with narrower channels exhibited even better signal-to-noise ratio than those with wider channels, which is opposite to conventional random network-based sensors. As a proof of concept, we demonstrated 100 nm scale low-noise sensors to detect mercury ions with the detection limit of {approx}1 pM, which is superior to any state-of-the-art portable detection system and is below the allowable limit of mercury ions in drinking water set by most government environmental protection agencies. This is the first demonstration of 100 nm scale low-noise sensors based on SWNT networks. Considering the increased interests in high-density sensor arrays for healthcare and environmental protection, our strategy should have a significant impact on various industrial applications.

100 nm scale low-noise sensors based on aligned carbon nanotube networks: overcoming the fundamental limitation of network-based sensors

International Nuclear Information System (INIS)

Lee, Minbaek; Lee, Joohyung; Kim, Tae Hyun; Lee, Hyungwoo; Lee, Byung Yang; Hong, Seunghun; Park, June; Seong, Maeng-Je; Jhon, Young Min

2010-01-01

Nanoscale sensors based on single-walled carbon nanotube (SWNT) networks have been considered impractical due to several fundamental limitations such as a poor sensitivity and small signal-to-noise ratio. Herein, we present a strategy to overcome these fundamental problems and build highly-sensitive low-noise nanoscale sensors simply by controlling the structure of the SWNT networks. In this strategy, we prepared nanoscale width channels based on aligned SWNT networks using a directed assembly strategy. Significantly, the aligned network-based sensors with narrower channels exhibited even better signal-to-noise ratio than those with wider channels, which is opposite to conventional random network-based sensors. As a proof of concept, we demonstrated 100 nm scale low-noise sensors to detect mercury ions with the detection limit of ∼1 pM, which is superior to any state-of-the-art portable detection system and is below the allowable limit of mercury ions in drinking water set by most government environmental protection agencies. This is the first demonstration of 100 nm scale low-noise sensors based on SWNT networks. Considering the increased interests in high-density sensor arrays for healthcare and environmental protection, our strategy should have a significant impact on various industrial applications.

Low-Power, Chip-Scale, Carbon Dioxide Gas Sensors for Spacesuit Monitoring

Science.gov (United States)

Rani, Asha; Shi, Chen; Thomson, Brian; Debnath, Ratan; Wen, Boamei; Motayed, Abhishek; Chullen, Cinda

2018-01-01

N5 Sensors, Inc. through a Small Business Technology Transfer (STTR) contract award has been developing ultra-small, low-power carbon dioxide (CO2) gas sensors, suited for monitoring CO2 levels inside NASA spacesuits. Due to the unique environmental conditions within the spacesuits, such as high humidity, large temperature swings, and operating pressure swings, measurement of key gases relevant to astronaut's safety and health such as(CO2), is quite challenging. Conventional non-dispersive infrared absorption based CO2 sensors present challenges inside the spacesuits due to size, weight, and power constraints, along with the ability to sense CO2 in a high humidity environment. Unique chip-scale, nanoengineered chemiresistive gas-sensing architecture has been developed for this application, which can be operated in a typical space-suite environmental conditions. Unique design combining the selective adsorption properties of the nanophotocatalytic clusters of metal-oxides and metals, provides selective detection of CO2 in high relative humidity conditions. All electronic design provides a compact and low-power solution, which can be implemented for multipoint detection of CO2 inside the spacesuits. This paper will describe the sensor architecture, development of new photocatalytic material for better sensor response, and advanced structure for better sensitivity and shorter response times.

Optimization of modified carbon paste electrode with multiwalled carbon nanotube/ionic liquid/cauliflower-like gold nanostructures for simultaneous determination of ascorbic acid, dopamine and uric acid

International Nuclear Information System (INIS)

Afraz, Ahmadreza; Rafati, Amir Abbas; Najafi, Mojgan

2014-01-01

We describe the modification of a carbon paste electrode (CPE) with multiwalled carbon nanotubes (MWCNTs) and an ionic liquid (IL). Electrochemical studies by using a D-optimal mixture design in Design-Expert software revealed an optimized composition of 60% graphite, 14.2% paraffin, 10.8% MWCNT and 15% IL. The optimal modified CPE shows good electrochemical properties that are well matched with model prediction parameters. In the next step, the optimized CPE was modified with gold nanostructures by applying a double-pulse electrochemical technique. The resulting electrode was characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, and electrochemical impedance spectroscopy. It gives three sharp and well-separated oxidation peaks for ascorbic acid (AA), dopamine (DA), and uric acid (UA). The sensor enables simultaneous determination of AA, DA and UA with linear responses from 0.3 to 285, 0.08 to 200, and 0.1 to 450 μM, respectively, and with 120, 30 and 30 nM detection limits (at an S/N of 3). The method was successfully applied to the determination of AA, DA, and UA in spiked samples of human serum and urine. - Highlights: • New method for simultaneous determination of AA, DA and UA was developed. • MWCNT/ionic liquid/cauliflower-like Au nanostructure was used for CPE modification. • Optimization of electrode composition was done by Design-Expert software. • The pH effect, peak separation mechanism and real samples was thoroughly studied

Optimization of modified carbon paste electrode with multiwalled carbon nanotube/ionic liquid/cauliflower-like gold nanostructures for simultaneous determination of ascorbic acid, dopamine and uric acid

Energy Technology Data Exchange (ETDEWEB)

Afraz, Ahmadreza [Department of Physical Chemistry, Faculty of Chemistry, Bu-Ali Sina University, P.O. Box 65174, Hamedan (Iran, Islamic Republic of); Rafati, Amir Abbas, E-mail: aa_rafati@basu.ac.ir [Department of Physical Chemistry, Faculty of Chemistry, Bu-Ali Sina University, P.O. Box 65174, Hamedan (Iran, Islamic Republic of); Najafi, Mojgan [Department of Materials Engineering, Hamedan University of Technology (HUT), 65169 Hamedan (Iran, Islamic Republic of)

2014-11-01

We describe the modification of a carbon paste electrode (CPE) with multiwalled carbon nanotubes (MWCNTs) and an ionic liquid (IL). Electrochemical studies by using a D-optimal mixture design in Design-Expert software revealed an optimized composition of 60% graphite, 14.2% paraffin, 10.8% MWCNT and 15% IL. The optimal modified CPE shows good electrochemical properties that are well matched with model prediction parameters. In the next step, the optimized CPE was modified with gold nanostructures by applying a double-pulse electrochemical technique. The resulting electrode was characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, and electrochemical impedance spectroscopy. It gives three sharp and well-separated oxidation peaks for ascorbic acid (AA), dopamine (DA), and uric acid (UA). The sensor enables simultaneous determination of AA, DA and UA with linear responses from 0.3 to 285, 0.08 to 200, and 0.1 to 450 μM, respectively, and with 120, 30 and 30 nM detection limits (at an S/N of 3). The method was successfully applied to the determination of AA, DA, and UA in spiked samples of human serum and urine. - Highlights: • New method for simultaneous determination of AA, DA and UA was developed. • MWCNT/ionic liquid/cauliflower-like Au nanostructure was used for CPE modification. • Optimization of electrode composition was done by Design-Expert software. • The pH effect, peak separation mechanism and real samples was thoroughly studied.

A Wireless and Batteryless Intelligent Carbon Monoxide Sensor.

Science.gov (United States)

Chen, Chen-Chia; Sung, Gang-Neng; Chen, Wen-Ching; Kuo, Chih-Ting; Chue, Jin-Ju; Wu, Chieh-Ming; Huang, Chun-Ming

2016-09-23

Carbon monoxide (CO) poisoning from natural gas water heaters is a common household accident in Taiwan. We propose a wireless and batteryless intelligent CO sensor for improving the safety of operating natural gas water heaters. A micro-hydropower generator supplies power to a CO sensor without battery (COSWOB) (2.5 W at a flow rate of 4.2 L/min), and the power consumption of the COSWOB is only ~13 mW. The COSWOB monitors the CO concentration in ambient conditions around natural gas water heaters and transmits it to an intelligent gateway. When the CO level reaches a dangerous level, the COSWOB alarm sounds loudly. Meanwhile, the intelligent gateway also sends a trigger to activate Wi-Fi alarms and sends notifications to the mobile device through the Internet. Our strategy can warn people indoors and outdoors, thereby reducing CO poisoning accidents. We also believe that our technique not only can be used for home security but also can be used in industrial applications (for example, to monitor leak occurrence in a pipeline).

A Distributed, Open Source based Data Infrastructure for the Megacities Carbon Project

Science.gov (United States)

Verma, R.; Crichton, D. J.; Duren, R. M.; Salameh, P.; Sparks, A.; Sloop, C.

2014-12-01

With the goal of assessing the anthropogenic carbon-emission impact of urban centers on local and global climates, the Megacities Carbon Project has been building carbon-monitoring capabilities for the past two years around the Los Angeles metropolitan area. Hundreds of megabytes (MB) of data are generated daily, and distributed among data centers local to the sensor networks involved. We automatically pull this remotely generated data into a centralized data infrastructure local to the Jet Propulsion Laboratory (JPL), seeking to (1) provide collaboration opportunities on the data, and (2) generate refined data products through community-requested centralized data processing pipelines. The goal of this informatics effort is to ensure near real-time access to generated data products across the Los Angeles carbon monitoring sensor network and meet the data analysis needs of carbon researchers through the production of customized products. We discuss the goals of the informatics effort, its uniqueness, and assess its effectiveness in providing an insight into the carbon sphere of Los Angeles.

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)

Electrochemical behaviour of carbon paste electrodes enriched with tin oxide nanoparticles using voltammetry and electrochemical impedance spectroscopy.

Science.gov (United States)

Muti, Mihrican; Erdem, Arzum; Caliskan, Ayfer; Sınag, Ali; Yumak, Tugrul

2011-08-01

The effect of the SnO(2) nanoparticles (SNPs) on the behaviour of voltammetric carbon paste electrodes were studied for possible use of this material in biosensor development. The electrochemical behaviour of SNP modified carbon paste electrodes (CPE) was first investigated by using cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) techniques. The performance of the SNP modified electrodes were compared to those of unmodified ones and the parameters affecting the response of the modified electrode were optimized. The SNP modified electrodes were then tested for the electrochemical sensing of DNA purine base adenine to explore their further development in biosensor applications. Copyright © 2011 Elsevier B.V. All rights reserved.

An electrochemical sensor for rizatriptan benzoate determination using Fe3O4 nanoparticle/multiwall carbon nanotube-modified glassy carbon electrode in real samples.

Science.gov (United States)

Madrakian, Tayyebeh; Maleki, Somayeh; Heidari, Mozhgan; Afkhami, Abbas

2016-06-01

In this paper a sensitive and selective electrochemical sensor for determination of rizatriptan benzoate (RZB) was proposed. A glassy carbon electrode was modified with nanocomposite of multiwalled carbon nanotubes (MWCNTs) and Fe3O4 nanoparticles (Fe3O4/MWCNTs/GCE). The results obtained clearly show that the combination of MWCNTs and Fe3O4 nanoparticles definitely improves the sensitivity of modified electrode to RZB determination. The morphology and electroanalytical performance of the fabricated sensor were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), square wave voltammetry (SWV) and cyclic voltammetry (CV). Also, the effect of experimental and instrumental parameters on the sensor response was evaluated. The square wave voltammetric response of the electrode to RZB was linear in the range 0.5-100.0 μmol L(-1) with a detection limit of 0.09 μmol L(-1) under the optimum conditions. The investigated method showed good stability, reproducibility and repeatability. The proposed sensor was successfully applied for real life samples of blood serum and RZB determination in pharmaceutical. Copyright © 2016 Elsevier B.V. All rights reserved.

An analytical approach to evaluate the performance of graphene and carbon nanotubes for NH3 gas sensor applications

Directory of Open Access Journals (Sweden)

Elnaz Akbari

2014-05-01

Full Text Available Carbon, in its variety of allotropes, especially graphene and carbon nanotubes (CNTs, holds great potential for applications in variety of sensors because of dangling π-bonds that can react with chemical elements. In spite of their excellent features, carbon nanotubes (CNTs and graphene have not been fully exploited in the development of the nanoelectronic industry mainly because of poor understanding of the band structure of these allotropes. A mathematical model is proposed with a clear purpose to acquire an analytical understanding of the field-effect-transistor (FET based gas detection mechanism. The conductance change in the CNT/graphene channel resulting from the chemical reaction between the gas and channel surface molecules is emphasized. NH3 has been used as the prototype gas to be detected by the nanosensor and the corresponding current–voltage (I–V characteristics of the FET-based sensor are studied. A graphene-based gas sensor model is also developed. The results from graphene and CNT models are compared with the experimental data. A satisfactory agreement, within the uncertainties of the experiments, is obtained. Graphene-based gas sensor exhibits higher conductivity compared to that of CNT-based counterpart for similar ambient conditions.

An analytical approach to evaluate the performance of graphene and carbon nanotubes for NH3 gas sensor applications.

Science.gov (United States)

Akbari, Elnaz; Arora, Vijay Kumar; Enzevaee, Aria; Ahmadi, Mohamad T; Saeidmanesh, Mehdi; Khaledian, Mohsen; Karimi, Hediyeh; Yusof, Rubiyah

2014-01-01

Carbon, in its variety of allotropes, especially graphene and carbon nanotubes (CNTs), holds great potential for applications in variety of sensors because of dangling π-bonds that can react with chemical elements. In spite of their excellent features, carbon nanotubes (CNTs) and graphene have not been fully exploited in the development of the nanoelectronic industry mainly because of poor understanding of the band structure of these allotropes. A mathematical model is proposed with a clear purpose to acquire an analytical understanding of the field-effect-transistor (FET) based gas detection mechanism. The conductance change in the CNT/graphene channel resulting from the chemical reaction between the gas and channel surface molecules is emphasized. NH3 has been used as the prototype gas to be detected by the nanosensor and the corresponding current-voltage (I-V) characteristics of the FET-based sensor are studied. A graphene-based gas sensor model is also developed. The results from graphene and CNT models are compared with the experimental data. A satisfactory agreement, within the uncertainties of the experiments, is obtained. Graphene-based gas sensor exhibits higher conductivity compared to that of CNT-based counterpart for similar ambient conditions.

Experimental and numerical studies on the sensitivity of carbon fibre/silicone rubber composite sensors

International Nuclear Information System (INIS)

Yang, Lili; Ge, Yong; Zhu, Qinghua; Zhang, Ce; Wang, Zongpeng; Liu, Penghuan

2012-01-01

Flexible conductive composite sensors are of great importance for applications in structural monitoring due to their low cost, high durability and excellent compatibility. In this work, carbon fibre/silicone rubber composites were prepared and their sensitivity near the percolation threshold was investigated experimentally and theoretically. Results show that carbon fibre/silicone rubber composites have great mechanical and sensitivity even under high strain conditions. Two models based on the tunnelling effect and general effective medium theory were found to understand the sensitivity of composites with lower and higher fractions of carbon fibre. Moreover, the reversibility of the sensing performance is improved with the increase of carbon fibre addition. (paper)

Fully integrated carbon nanotube composite thin film strain sensors on flexible substrates for structural health monitoring

Science.gov (United States)

Burton, A. R.; Lynch, J. P.; Kurata, M.; Law, K. H.

2017-09-01

Multifunctional thin film materials have opened many opportunities for novel sensing strategies for structural health monitoring. While past work has established methods of optimizing multifunctional materials to exhibit sensing properties, comparatively less work has focused on their integration into fully functional sensing systems capable of being deployed in the field. This study focuses on the advancement of a scalable fabrication process for the integration of multifunctional thin films into a fully integrated sensing system. This is achieved through the development of an optimized fabrication process that can create a broad range of sensing systems using multifunctional materials. A layer-by-layer deposited multifunctional composite consisting of single walled carbon nanotubes (SWNT) in a polyvinyl alcohol and polysodium-4-styrene sulfonate matrix are incorporated with a lithography process to produce a fully integrated sensing system deposited on a flexible substrate. To illustrate the process, a strain sensing platform consisting of a patterned SWNT-composite thin film as a strain-sensitive element within an amplified Wheatstone bridge sensing circuit is presented. Strain sensing is selected because it presents many of the design and processing challenges that are core to patterning multifunctional thin film materials into sensing systems. Strain sensors fabricated on a flexible polyimide substrate are experimentally tested under cyclic loading using standard four-point bending coupons and a partial-scale steel frame assembly under lateral loading. The study reveals the material process is highly repeatable to produce fully integrated strain sensors with linearity and sensitivity exceeding 0.99 and 5 {{V}}/{ε }, respectively. The thin film strain sensors are robust and are capable of high strain measurements beyond 3000 μ {ε }.

TYROSINASE-BASED CARBON PASTE ELECTRODE BIOSENSOR FOR DETECTION OF PHENOLS: BINDER AND PRE-OXIDATION EFFECTS

Science.gov (United States)

Tyrosinase-based carbon paste electrodes are evaluated with respect to the viscosity and polarity of the binder liquids. The electrodes constructed using a lower viscosity mineral oil or paraffin wax oil yielded a greater response to phenol and catechol than those using the hi...

Anodic stripping voltammetric determination of silver ion at a carbon paste electrode modified with carbon nanotubes

International Nuclear Information System (INIS)

Tashkhourian, J.; Javadi, S.; Ana, F.N.

2011-01-01

A carbon paste electrode (CPE) was modified with multi-wall carbon nanotubes and successfully applied to the determination of silver ion by differential pulse anodic stripping voltammetry. Compared to a conventional CPE, a remarkably improved peak current response and sensitivity is observed. The analytical procedure consisted of an open circuit accumulation step for 2 min in -0.4 V, this followed by an anodic potential scan between +0.2 and + 0.6 V to obtain the voltammetric peak. The oxidation peak current is proportional to the concentration of silver ion in the range from 1.0 x 10 -8 to 1.0 x 10 -5 mol L -1 , with a detection limit of 1.8 x 10 -9 mol L -1 after an accumulation time of 120 s. The relative standard deviation for 7 successive determinations of Ag(I) at 0.1 μM concentration is 1.99%. The procedure was validated by determining Ag(I) in natural waters. (author)

Electromagnetic interference shielding with Portland cement paste containing carbon materials and processed fly ash

Directory of Open Access Journals (Sweden)

Zornoza, E.

2010-12-01

Full Text Available The study described in this article explored the effect of adding different types of carbon materials (graphite powder and three types of carbon fibre, fly ash (with 5.6%, 15.9% and 24.3% Fe₂O₃, and a mix of both on electromagnetic interference (EMI shielding in Portland cement pastes. The parameters studied included the type and aspect ratio of the carbonic material, composite material thickness, the frequency of the incident electromagnetic radiation and the percentage of the magnetic fraction in the fly ash. The findings showed that the polyacrylonitrile-based carbon fibres, which had the highest aspect ratio, provided more effective shielding than any of the other carbon materials studied. Shielding was more effective in thicker specimens and at higher radiation frequencies. Raising the magnetic fraction of the fly ash, in turn, also enhanced paste shielding performance. Finally, adding both carbon fibre and fly ash to the paste resulted in the most effective EMI shielding as a result of the synergies generated.

En el presente trabajo se investiga la influencia de la adición de diferentes tipos de materiales carbonosos (polvo de grafito y 3 tipos de fibra de carbono, de una ceniza volante con diferentes contenidos de fase magnética (5,6%, 15,9% y 24,3% de Fe₂O₃ y de una mezcla de ambos, sobre la capacidad de apantallar interferencias electromagnéticas de pastas de cemento Pórtland. Entre los parámetros estudiados se encuentra: el tipo de material carbonoso, la relación de aspecto del material carbonoso, el espesor del material compuesto, la frecuencia de la radiación electromagnética incidente y el porcentaje de fracción magnética en la ceniza volante. Los resultados obtenidos indican que entre los materiales carbonosos estudiados son las fibras de carbono basadas en poliacrilonitrilo con una mayor relación de aspecto las que dan mejores resultados de apantallamiento. Al aumentar

Design and Fabrication of Single-Walled Carbon Nanonet Flexible Strain Sensors

Directory of Open Access Journals (Sweden)

Trung Kien Vu

2012-03-01

Full Text Available This study presents a novel flexible strain sensor for real-time strain sensing. The material for strain sensing is single-walled carbon nanonets, grown using the alcohol catalytic chemical vapor deposition method, that were encapsulated between two layers of Parylene-C, with a polyimide layer as the sensing surface. All of the micro-fabrication was compatible with the standard IC process. Experimental results indicated that the gauge factor of the proposed strain sensor was larger than 4.5, approximately 2.0 times greater than those of commercial gauges. The results also demonstrated that the gauge factor is small when the growth time of SWCNNs is lengthier, and the gauge factor is large when the line width of the serpentine pattern of SWCNNs is small.

Hysteresis Compensation of Piezoresistive Carbon Nanotube/Polydimethylsiloxane Composite-Based Force Sensors

Directory of Open Access Journals (Sweden)

Ji-Sik Kim

2017-01-01

Full Text Available This paper provides a preliminary study on the hysteresis compensation of a piezoresistive silicon-based polymer composite, poly(dimethylsiloxane dispersed with carbon nanotubes (CNTs, to demonstrate its feasibility as a conductive composite (i.e., a force-sensitive resistor for force sensors. In this study, the potential use of the nanotube/polydimethylsiloxane (CNT/PDMS as a force sensor is evaluated for the first time. The experimental results show that the electrical resistance of the CNT/PDMS composite changes in response to sinusoidal loading and static compressive load. The compensated output based on the Duhem hysteresis model shows a linear relationship. This simple hysteresis model can compensate for the nonlinear frequency-dependent hysteresis phenomenon when a dynamic sinusoidal force input is applied.

Voltammetric determination of norepinephrine in the presence of acetaminophen using a novel ionic liquid/multiwall carbon nanotubes paste electrode

International Nuclear Information System (INIS)

Salmanpour, Sadegh; Tavana, Toktam; Pahlavan, Ali; Khalilzadeh, Mohammad A.; Ensafi, Ali A.; Karimi-Maleh, Hassan; Beitollahi, Hadi; Kowsari, Elaheh; Zareyee, Daryoush

2012-01-01

A novel multiwall carbon nanotubes (MWCNTs) modified carbon ionic liquid electrode (CILE) was fabricated and used to investigate the electrochemical behavior of norepinephrine (NP). MWCNTs/CILE was prepared by mixing hydrophilic ionic liquid, 1-methyl-3-butylimidazolium bromide (MBIDZBr), with graphite powder, MWCNTs, and liquid paraffin. The fabricated MWCNTs/CILE showed great electrocatalytic ability to the oxidation of NE. The electron transfer coefficient, diffusion coefficient, and charge transfer resistant (R ct ) of NE at the modified electrode were calculated. Differential pulse voltammetry of NE at the modified electrode exhibited two linear dynamic ranges with slopes of 0.0841 and 0.0231 μA/μM in the concentration ranges of 0.3 to 30.0 μM and 30.0 to 450.0 μM, respectively. The detection limit (3σ) of 0.09 μM NP was achieved. This modified electrode exhibited a good ability for well separated oxidation peaks of NE and acetaminophen (AC) in a buffer solution, pH 7.0. The proposed sensor was successfully applied for the determination of NE in human urine, pharmaceutical, and serum samples. Highlights: ► Electrochemical behavior of norepinephrine study using carbon ionic liquid electrode ► This sensor resolved the overlap response of norepinephrine and acetaminophen. ► This sensor is also used for the determination of above compounds in real samples.

Breakdown voltage reduction by field emission in multi-walled carbon nanotubes based ionization gas sensor

Energy Technology Data Exchange (ETDEWEB)

Saheed, M. Shuaib M.; Muti Mohamed, Norani; Arif Burhanudin, Zainal, E-mail: zainabh@petronas.com.my [Centre of Innovative Nanostructures and Nanodevices, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 31750 Tronoh, Perak (Malaysia)

2014-03-24

Ionization gas sensors using vertically aligned multi-wall carbon nanotubes (MWCNT) are demonstrated. The sharp tips of the nanotubes generate large non-uniform electric fields at relatively low applied voltage. The enhancement of the electric field results in field emission of electrons that dominates the breakdown mechanism in gas sensor with gap spacing below 14 μm. More than 90% reduction in breakdown voltage is observed for sensors with MWCNT and 7 μm gap spacing. Transition of breakdown mechanism, dominated by avalanche electrons to field emission electrons, as decreasing gap spacing is also observed and discussed.

Detection of influenza A virus using carbon nanotubes field effect transistor based DNA sensor

Science.gov (United States)

Tran, Thi Luyen; Nguyen, Thi Thuy; Huyen Tran, Thi Thu; Chu, Van Tuan; Thinh Tran, Quang; Tuan Mai, Anh

2017-09-01

The carbon nanotubes field effect transistor (CNTFET) based DNA sensor was developed, in this paper, for detection of influenza A virus DNA. Number of factors that influence the output signal and analytical results were investigated. The initial probe DNA, decides the available DNA strands on CNTs, was 10 μM. The hybridization time for defined single helix was 120 min. The hybridization temperature was set at 30 °C to get a net change in drain current of the DNA sensor without altering properties of any biological compounds. The response time of the DNA sensor was less than one minute with a high reproducibility. In addition, the DNA sensor has a wide linear detection range from 1 pM to 10 nM, and a very low detection limit of 1 pM. Finally, after 7-month storage in 7.4 pH buffer, the output signal of DNA sensor recovered 97%.

Past and prospective carbon stocks in forests of northern Wisconsin: a report from the Chequamegon-Nicolet National Forest Climate Change Response Framework

Science.gov (United States)

Richard Birdsey; Yude Pan; Maria Janowiak; Susan Stewart; Sarah Hines; Linda Parker; Stith Gower; Jeremy Lichstein; Kevin McCullough; Fangmin Zhang; Jing Chen; David Mladenoff; Craig Wayson; Chris. Swanston

2014-01-01

This report assesses past and prospective carbon stocks for 4.5 million ha of forest land in northern Wisconsin, including a baseline assessment and analysis of the impacts of disturbance and management on carbon stocks. Carbon density (amount of carbon stock per unit area) averages 237 megagrams (Mg) per ha, with the National Forest lands having slightly higher carbon...

Natural Carbonized Sugar as a Low-Temperature Ammonia Sensor Material: Experimental, Theoretical, and Computational Studies.

Science.gov (United States)

Ghule, Balaji G; Shaikh, Shoyebmohamad; Ekar, Satish U; Nakate, Umesh T; Gunturu, Krishna Chaitanya; Shinde, Nanasaheb M; Naushad, Mu; Kim, Kwang Ho; O'Dwyer, Colm; Mane, Rajaram S

2017-12-13

Carbonized sugar (CS) has been synthesized via microwave-assisted carbonization of market-quality tabletop sugar bearing in mind the advantages of this synthesis method, such as being useful, cost-effective, and eco-friendly. The as-prepared CS has been characterized for its morphology, phase purity, type of porosity, pore-size distribution, and so on. The gas-sensing properties of CS for various oxidizing and reducing gases are demonstrated at ambient temperature, where we observe good selectivity toward liquid ammonia among other gases. The highest ammonia response (50%) of a CS-based sensor was noted at 80 °C for 100 ppm concentration. The response and recovery times of the CS sensor are 180 and 216 s, respectively. This unveiling ammonia-sensing study is explored through a plausible theoretical mechanism, which is further well-supported by computational modeling performed using density function theory. The effect of relative humidity on the CS sensor has also been studied at ambient temperature, which demonstrated that the minimum and maximum (20-100%) relative humidity values revealed 16 and 62% response, respectively.

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.

Use of self-sensing piezoresistive Si cantilever sensor for determining carbon nanoparticle mass

Science.gov (United States)

Wasisto, H. S.; Merzsch, S.; Stranz, A.; Waag, A.; Uhde, E.; Kirsch, I.; Salthammer, T.; Peiner, E.

2011-06-01

A silicon cantilever with slender geometry based Micro Electro Mechanical System (MEMS) for nanoparticles mass detection is presented in this work. The cantilever is actuated using a piezoactuator at the bottom end of the cantilever supporting frame. The oscillation of the microcantilever is detected by a self-sensing method utilizing an integrated full Wheatstone bridge as a piezoresistive strain gauge for signal read out. Fabricated piezoresistive cantilevers of 1.5 mm long, 30 μm wide and 25 μm thick have been employed. This self-sensing cantilever is used due to its simplicity, portability, high-sensitivity and low-cost batch microfabrication. In order to investigate air pollution sampling, a nanoparticles collection test of the piezoresistive cantilever sensor is performed in a sealed glass chamber with a stable carbon aerosol inside. The function principle of cantilever sensor is based on detecting the resonance frequency shift that is directly induced by an additional carbon nanoparticles mass deposited on it. The deposition of particles is enhanced by an electrostatic field. The frequency measurement is performed off-line under normal atmospheric conditions, before and after carbon nanoparticles sampling. The calculated equivalent mass-induced resonance frequency shift of the experiment is measured to be 11.78 +/- 0.01 ng and a mass sensitivity of 8.33 Hz/ng is obtained. The proposed sensor exhibits an effective mass of 2.63 μg, a resonance frequency of 43.92 kHz, and a quality factor of 1230.68 +/- 78.67. These results and analysis indicate that the proposed self-sensing piezoresistive silicon cantilever can offer the necessary potential for a mobile nanoparticles monitor.

Structure engineering of hole-conductor free perovskite-based solar cells with low-temperature-processed commercial carbon paste as cathode.

Science.gov (United States)

Zhang, Fuguo; Yang, Xichuan; Wang, Haoxin; Cheng, Ming; Zhao, Jianghua; Sun, Licheng

2014-09-24

Low-temperature-processed (100 °C) carbon paste was developed as counter electrode material in hole-conductor free perovskite/TiO2 heterojunction solar cells to substitute noble metallic materials. Under optimized conditions, an impressive PCE value of 8.31% has been achieved with this carbon counter electrode fabricated by doctor-blading technique. Electrochemical impedance spectroscopy demonstrates good charge transport characteristics of low-temperature-processed carbon counter electrode. Moreover, this carbon counter electrode-based perovskite solar cell exhibits good stability over 800 h.

Processing-structure-property relationships of carbon nanotube and nanoplatelet enabled piezoresistive sensors

Science.gov (United States)

Luo, Sida

Individual carbon nanotubes (CNTs) possess excellent piezoresistive performance, which is manifested by the significant electrical resistance change when subject to mechanical deformation. In comparison to individual CNTs, the CNT thin films, formed by a random assembly of individual tubes or bundles, show much lower piezoresistive sensitivity. Given the progress made to date in developing CNT ensemble based-piezoresistive sensors, the related piezoresistive mechanism(s) are still not well understood. The crucial step to obtain a better understanding of this issue is to study the effects of CNT structure in the dispersion on the piezoresistivity of CNT ensemble based-piezoresistive sensors. To reach this goal, my Ph.D. research first focuses on establishing the processing-structure-property relationship of SWCNT thin film piezoresistive sensors. The key accomplishment contains: 1) developing the combined preparative ultracentrifuge method (PUM) and dynamic light scattering (DLS) method to quantitatively characterized SWCNT particle size in dispersions under various sonication conditions; 2) designing combined ultrasonication and microfluidization processing protocol for high throughput and large-scale production of high quality SWCNT dispersions; 3) fabricating varied SWCNT thin film piezoresistive sensors through spray coating technique and immersion-drying post-treatment; and 4) investigating the effect of microstructures of SWCNTs on piezoresistivity of SWCNT thin film sensors. This experimental methodology for quantitative and systematic investigation of the processing-structure-property relationships provides a means for the performance optimization of CNT ensemble based piezoresistive sensors. As a start to understand the piezoresistive mechanism, the second focus of my Ph.D. research is studying charge transport behaviors in SWCNT thin films. It was found that the temperature-dependent sheet resistance of SWCNT thin films could be explained by a 3D variable

Coaxial Thermoplastic Elastomer-Wrapped Carbon Nanotube Fibers for Deformable and Wearable Strain Sensors

KAUST Repository

Zhou, Jian

2018-01-22

Highly conductive and stretchable fibers are crucial components of wearable electronics systems. Excellent electrical conductivity, stretchability, and wearability are required from such fibers. Existing technologies still display limited performances in these design requirements. Here, achieving highly stretchable and sensitive strain sensors by using a coaxial structure, prepared via coaxial wet spinning of thermoplastic elastomer-wrapped carbon nanotube fibers, is proposed. The sensors attain high sensitivity (with a gauge factor of 425 at 100% strain), high stretchability, and high linearity. They are also reproducible and durable. Their use as safe sensing components on deformable cable, expandable surfaces, and wearable textiles is demonstrated.

Sensitive warfarin sensor based on cobalt oxide nanoparticles electrodeposited at multi-walled carbon nanotubes modified glassy carbon electrode (CoxOyNPs/MWCNTs/GCE)

International Nuclear Information System (INIS)

Gholivand, Mohammad Bagher; Solgi, Mohammad

2017-01-01

In this work, cobalt oxide nanoparticles were electrodeposited on multi-walled carbon nanotubes modified glassy carbon electrode (MWCNTs/GCE) to develop a new sensor for warfarin determination. The modified electrodes were characterized by cyclic voltammetry, scanning electron microscopy (SEM) along with energy dispersive x-ray spectroscopy (EDS), and electrochemical impedance spectroscopy (EIS). The presence of cobalt oxide nanoparticles on the electrode surface enhanced the warfarin accumulation and its result was the improvement in the electrochemical response. The effect of various parameters such as pH, scan rate, accumulation potential, accumulation time and pulse amplitude on the sensor response were investigated. Under optimal conditions, the differential pulse adsorptive anodic stripping voltammetric (DPASV) response of the modified electrode was linear in the ranges of 8 nM to 50 μM and 50 μM to 800 μM with correlation coefficients greater than 0.998. The limit of detection of the proposed method was 3.3 nM. The proposed sensor was applied to determine warfarin in urine and plasma samples.

Electrochemical determination of paraquat in citric fruit based on electrodeposition of silver particles onto carbon paste electrode

OpenAIRE

Abdelfettah Farahi; Mounia Achak; Laila El Gaini; Moulay Abderrahim El Mhammedi; Mina Bakasse

2015-01-01

Carbon paste electrodes (CPEs) modified with silver particles present an interesting tool in the determination of paraquat (PQ) using square wave voltammetry. Metallic silver particle deposits have been obtained via electrochemical deposition in acidic media using cyclic voltammetry. Scanning electron microscopy and X-ray diffraction measurements show that the silver particles are deposited onto carbon surfaces in aggregate form. The response of PQ with modified electrode (Ag-CPE) related to ...

Effect of ordered mesoporous carbon contact layer on the sensing performance of sputtered RuO2 thin film pH sensor.

Science.gov (United States)

Lonsdale, W; Maurya, D K; Wajrak, M; Alameh, K

2017-03-01

The effect of contact layer on the pH sensing performance of a sputtered RuO 2 thin film pH sensor is investigated. The response of pH sensors employing RuO 2 thin film electrodes on screen-printed Pt, carbon and ordered mesoporous carbon (OMC) contact layers are measured over a pH range from 4 to 10. Working electrodes with OMC contact layer are found to have Nernstian pH sensitivity (-58.4mV/pH), low short-term drift rate (5.0mV/h), low hysteresis values (1.13mV) and fast reaction times (30s), after only 1h of conditioning. A pH sensor constructed with OMC carbon contact layer displays improved sensing performance compared to Pt and carbon-based counterparts, making this electrode more attractive for applications requiring highly-accurate pH sensing with reduced conditioning time. Copyright © 2016 Elsevier B.V. All rights reserved.

Modification of glassy carbon electrode with poly(hydroxynaphthol blue)/multi-walled carbon nanotubes composite and construction a new voltammetric sensor for the simultaneous determination of hydroquinone, catechol, and resorcinol

Science.gov (United States)

Daneshinejad, Hassan; Arab Chamjangali, Mansour; Goudarzi, Nasser; Hossain Amin, Amir

2018-03-01

A novel voltammetric sensor is developed based on a poly(hydroxynaphthol blue)/multi-walled carbon nanotubes-modified glassy carbon electrode for the simultaneous determination of the dihydroxybenzene isomers hydroquinone (HQ), catechol (CC), and resorcinol (RS). The preparation and basic electrochemical performance of the sensor are investigated in details. The electrochemical behavior of the dihydroxybenzene isomers at the sensor is studied by the cyclic and differential pulse voltammetric techniques. The results obtained show that this new electrochemical sensor exhibits an excellent electro-catalytic activity towards oxidation of the three isomers. The mechanism of this electro-catalytic activity is discussed. Using the optimum parameters, limit of detection obtained 0.24, 0.24, and 0.26 μmol L-1 for HQ, CC, and RS, respectively. The modified electrode is also successfully applied to the simultaneous determination of dihydroxybenzene in water samples.

Micro-extraction and trace determination of cadmium by square wave voltammetry at the carbon paste electrode impregnated with Ca10(PO4)6(OH)2

International Nuclear Information System (INIS)

El Mhammedi, M.A.; Achak, M.; Najih, R.; Bakasse, M.; Chtaini, A.

2009-01-01

The electrochemical behavior of cadmium ions at hydroxyapatite modified carbon paste electrode (HAP-CPE) is reported. The electrode paste was prepared as a mixture of finely powdered hydroxyapatite (HAP) together with graphite powder. The influence of variables such as the accumulation time, pH solution and apatite loading was tested by square wave voltammetry (SWV). The best results were obtained under the following optimized conditions: 5 min accumulation time, 5 mV pulse amplitude, 1 mV s -1 scan rate in 1.0 mol L -1 HClO 4 . The electrochemical responses obtained by SWV at HAP-CPE were found to be analytically suitable to develop a method for the determination of cadmium at low concentration levels. Under optimized operational conditions, a linear response range from 2 x 10 -8 mol L -1 to 2.5 x 10 -5 mol L -1 was obtained. The detection limit for cadmium determination was 4.0 x 10 -9 mol L -1 . The proposed sensor presented good repeatability, evaluated in terms of relative standard deviation (R.S.D. = 3.8%) for n = 5 and was applied for cadmium determination in water samples. The average recovery for these samples was 104%.

A novel sensor made of Antimony Doped Tin Oxide-silica composite sol on a glassy carbon electrode modified by single-walled carbon nanotubes for detection of norepinephrine.

Science.gov (United States)

Wang, Zhao; Wang, Kai; Zhao, Lu; Chai, Shigan; Zhang, Jinzhi; Zhang, Xiuhua; Zou, Qichao

2017-11-01

In this study, we designed a novel molecularly imprinted polymer (MIP), Antimony Doped Tin Oxide (ATO)-silica composite sol, which was made using a sol-gel method. Then a sensitive and selective imprinted electrochemical sensor was constructed with the ATO-silica composite sol on a glassy carbon electrode modified by single-walled carbon nanotubes (SWNTs). The introduction of SWNTs increased the sensitivity of the MIP sensor. The surface morphology of the MIP and MIP/SWNTs were characterized by scanning electron microscopy (SEM), and the optimal conditions for detection were determined. The oxidative peak current increased linearly with the concentration of norepinephrine in the range of 9.99×10 -8 M to 1.50×10 -5 M, as detected by cyclic voltammetry (CV), the detection limit was 3.33×10 -8 M (S/N=3). In addition, the proposed electrochemical sensors were successfully applied to detect the norepinephrine concentration in human blood serum samples. The recoveries of the sensors varied from 99.67% to 104.17%, indicating that the sensor has potential for the determination of norepinephrine in clinical tests. Moreover, the imprinted electrochemical sensor was used to selectively detect norepinephrine. The analytical application was conducted successfully and yielded accurate and precise results. Copyright © 2017. Published by Elsevier B.V.

A low carbon industrial revolution? Insights and challenges from past technological and economic transformations

International Nuclear Information System (INIS)

Pearson, Peter J.G.; Foxon, Timothy J.

2012-01-01

Recent efforts to promote a transition to a low carbon economy have been influenced by suggestions that a low carbon transition offers challenges and might yield economic benefits comparable to those of the previous industrial revolutions. This paper examines these arguments and the challenges facing a low carbon transition, by drawing on recent thinking on the technological, economic and institutional factors that enabled and sustained the first (British) industrial revolution, and the role of ‘general purpose technologies’ in stimulating and sustaining this and subsequent industrial transformation processes that have contributed to significant macroeconomic gains. These revolutions involved profound, long drawn-out changes in economy, technology and society; and although their energy transitions led to long-run economic benefits, they took many decades to develop. To reap significant long-run economic benefits from a low carbon transition sooner rather than later would require systemic efforts and incentives for low carbon innovation and substitution of high-carbon technologies. We conclude that while achieving a low carbon transition may require societal changes on a scale comparable with those of previous industrial revolutions, this transition does not yet resemble previous industrial revolutions. A successful low carbon transition would, however, amount to a different kind of industrial revolution. - Highlights: ► Investigates lessons for a low carbon transition from past industrial revolutions. ► Explores the implications of ‘general purpose technologies’ and their properties. ► Examines analysis of ‘long waves’ of technological progress and diffusion. ► Draws insights for low carbon transitions and policy.

Robust Chemiresistive Sensor for Continuous Monitoring of Free Chlorine Using Graphene-like Carbon.

Science.gov (United States)

Aryasomayajula, Aditya; Wojnas, Caroline; Divigalpitiya, Ranjith; Selvaganapathy, Ponnambalam Ravi; Kruse, Peter

2018-02-23

Free chlorine is widely used in industry as a bleaching and oxidizing agent. Its concentration is tightly monitored to avoid environmental contamination and deleterious human health effects. Here, we demonstrate a solid state chemiresistive sensor using graphene like carbon (GLC) to detect free chlorine in water. A 15-20 nm thick GLC layer on a PET substrate was modified with a redox-active aniline oligomer (phenyl-capped aniline tetramer, PCAT) to increase sensitivity, improve selectivity, and impart fouling resistance. Both the bare GLC sensor and the PCAT-modified GLC sensor can detect free chlorine continuously and, unlike previous chemiresistive sensors, do not require a reset. The PCAT-modified sensor showed a linear response with a slope of 13.89 (mg/L) -1 to free chlorine concentrations between 0.2 and 0.8 mg/L which is relevant for free chlorine monitoring for drinking water and wastewater applications. The PCAT-modified GLC sensors were found to be selective and showed less than 0.5% change in current in response to species such as nitrates, phosphates and sulfates in water. They also were resistant to fouling from organic material and showed only a 2% loss in signal. Tap water samples from residential area were tested using this sensor which showed good agreement with standard colorimetric measurement methods. The GLC and PCAT-GLC sensors show high sensitivity and excellent selectivity to free chlorine and can be used for continuous automated monitoring of free chlorine.

Electrocatalytic and simultaneous determination of isoproterenol, uric acid and folic acid at molybdenum (VI) complex-carbon nanotube paste electrode

International Nuclear Information System (INIS)

Beitollahi, Hadi; Sheikhshoaie, Iran

2011-01-01

Highlights: → A molybdenum (VI) complex-carbon nanotube paste electrode have been fabricated. → This electrode reduced the oxidation potential of isoproterenol by about 175 mV. → It resolved the voltammetric waves of isoproterenol, uric acid and folic acid. - Abstract: This paper describes the development, electrochemical characterization and utilization of a novel modified molybdenum (VI) complex-carbon nanotube paste electrode for the electrocatalytic determination of isoproterenol (IP). The electrochemical profile of the proposed modified electrode was analyzed by cyclic voltammetry (CV) that showed a shift of the oxidation peak potential of IP at 175 mV to less positive value, compared with an unmodified carbon paste electrode. Differential pulse voltammetry (DPV) in 0.1 M phosphate buffer solution (PBS) at pH 7.0 was performed to determine IP in the range from 0.7 to 600.0 μM, with a detection limit of 35.0 nM. Then the modified electrode was used to determine IP in an excess of uric acid (UA) and folic acid (FA) by DPV. Finally, this method was used for the determination of IP in some real samples.

Exploratory procedures with carbon nanotube-based sensors for propellant degradation determinations

Science.gov (United States)

Ruffin, Paul B.; Edwards, Eugene; Brantley, Christina; McDonald, Brian

2010-04-01

Exploratory research is conducted at the US Army Aviation & Missile Research, Development, and Engineering Center (AMRDEC) in order to perform assessments of the degradation of solid propellant used in rocket motors. Efforts are made to discontinue and/or minimize destructive methods and utilize nondestructive techniques to assure the quality and reliability of the weaponry's propulsion system. Collaborative efforts were successfully made between AMRDEC and NASA-Ames for potential add-on configurations to a previously designed sensor that AMRDEC plan to use for preliminary detection of off-gassing. Evaluations were made in order to use the design as the introductory component for the determination of shelf-life degradation rate of rocket motors. Previous and subsequent sensor designs utilize functionalized single-walled carbon nano-tubes (SWCNTs) as the key sensing element. On-going research is conducted to consider key changes that can be implemented (for the existing sensor design) such that a complete wireless sensor system design can be realized. Results should be a cost-saving and timely approach to enhance the Army's ability to develop methodologies for measuring weaponry off-gassing and simultaneously detecting explosives. Expectations are for the resulting sensors to enhance the warfighters' ability to simultaneously detect a greater variety of analytes. Outlined in this paper are the preliminary results that have been accomplished for this research. The behavior of the SWCNT sensor at storage temperatures is outlined, along with the initial sensor response to propellant related analytes. Preparatory computer-based programming routines and computer controlled instrumentation scenarios have been developed in order to subsequently minimize subjective interpretation of test results and provide a means for obtaining data that is reasonable and repetitively quantitative. Typical laboratory evaluation methods are likewise presented, and program limitations

Nafion® modified-screen printed gold electrodes and their carbon nanostructuration for electrochemical sensors applications.

Science.gov (United States)

García-González, Raquel; Fernández-Abedul, M Teresa; Costa-García, Agustín

2013-03-30

Screen printed electrodes are frequently used in electroanalytical applications because of their properties such as small size, low detection limit, fast response time, high reproducibility and disposable nature. On the other hand, since the discovery of carbon nanotubes there has been enormous interest in exploring and exploiting their properties, especially for their use in chemical (bio)sensors and nanoscale electronic devices. This paper reports the characterization of gold screen printed electrodes, modified with Nafion(®) and nanostructured with carbon nanotubes and carbon nanofibers dispersed on Nafion(®). The dispersing agent and the nanostructure have a marked effect on the analytical signal that, in turn depends on the intrinsic characteristics of the analyte. Several model analytes have been employed in this study. Anionic, cationic and neutral species such as methylene blue, dopamine, iron (III) sulfate, potassium ferrycianide and urea were considered. The importance for the development of nanostructured sensors relies on the fact that depending on these factors the situation may vary from a notorious enhancement of the signal to a blocking or even decrease. Copyright © 2013 Elsevier B.V. All rights reserved.

Chemically modified carbon paste electrode for fast screening of oxalic acid levels in soil solutions

Czech Academy of Sciences Publication Activity Database

Šestáková, Ivana; Jakl, M.; Jaklová Dytrtová, J.

2008-01-01

Roč. 102, - (2008), s. 140-140 E-ISSN 1213-7103. [International Conference on Electroanalysis /12./. 16.06.2008-19.06.2008, Prague] R&D Projects: GA ČR GA521/06/0496 Institutional research plan: CEZ:AV0Z40400503 Keywords : oxalic acid * carbon paste electrodes * soil solutions Subject RIV: CG - Electrochemistry

Description and testing of three moisture sensors for measuring surface wetness on carbonate building stones

Science.gov (United States)

See, R.B.; Reddy, M.M.; Martin, R.G.

1988-01-01

Three moisture sensors were tested as a means for determining the surface wetness on carbonate building stones exposed to conditions that produce deposition of moisture. A relative-humidity probe, a gypsum-coated circuit grid, and a limestone-block resistor were tested as sensors for determining surface wetness. Sensors were tested under laboratory conditions of constant relative humidity and temperature and also under on-site conditions of variable relative humidity and temperature for eight weeks at Newcomb, NY. Laboratory tests indicated that relative humidity alone did not cause sensors to become saturated with water. However, the rates of drying indicated by the sensors after an initial saturation were inversely related to the relative humidity. On-site testing of the relative-humidity probe and the gypsum-coated ciruit grid indicated that they respond to a diurnal wetting and drying cycle; the limestone-block resistor responded only to rainfall.

Vapor Grown Carbon Fiber/Polydicyclopentadiene Composites: Shapeable Pastes to Make Composite Tooling and Plasma Erosion-Resistant Parts

National Research Council Canada - National Science Library

Pittman, Charles

2002-01-01

Vapor grown carbon nanofibers (VGCF) with 60-250nm diameters and 10 to 80 micrometers lengths were blended with the nonpolar organic monomer, dicyclopentadiene, to create liquid dispersions or pastes (based on the wt% fiber used...

Strain gauge sensors comprised of carbon nanotube yarn: parametric numerical analysis of their piezoresistive response

International Nuclear Information System (INIS)

Abot, Jandro L; Kiyono, César Y; Thomas, Gilles P; Silva, Emílio C N

2015-01-01

Carbon nanotube (CNT) yarns are micron-size fibers that contain thousands of intertwined CNTs in their cross sections and exhibit piezoresistance characteristics that can be tapped for sensing purposes. Sensor yarns can be integrated into polymeric and composite materials to measure strain through resistance measurements without adding weight or altering the integrity of the host material. This paper includes the details of novel strain gauge sensor configurations comprised of CNT yarn, the numerical modeling of their piezoresistive response, and the parametric analysis schemes that determines the highest sensor sensitivity to mechanical loading. The effect of several sensor configuration parameters are discussed including the inclination and separation of the CNT yarns within the sensor, the mechanical properties of the CNT yarn, the direction and magnitude of the applied mechanical load, and the dimensions and shape of the sensor. The sensor configurations that yield the highest sensitivity are presented and discussed in terms of the mechanical and electrical properties of the CNT yarn. It is shown that strain gauge sensors consisting of CNT yarn are sensitive enough to measure strain, and could exhibit even higher gauge factors than those of metallic foil strain gauges. (paper)

Carbon Nanotubes-Based Potentiometric Bio-Sensors for Determination of Urea

Directory of Open Access Journals (Sweden)

Ewa Jaworska

2015-07-01

Full Text Available The possibility of using disposable plastic-carbon potentiometric sensors as enzyme biosensors was examined. Urease enzyme was immobilized on poly(vinyl chloride based H+- or NH4+-selective membranes using cellulose acetate. This approach has resulted in a potentiometric response on changing the pH of the solution or NH4+ ion content due to an enzymatic reaction that occurs between urease and urea. Both types of potentiometric biosensors for urea were characterized by good analytical parameters as high sensitivity and fast response time.

Enzymatic and non-enzymatic electrochemical glucose sensor based on carbon nano-onions

Science.gov (United States)

Mohapatra, Jeotikanta; Ananthoju, Balakrishna; Nair, Vishnu; Mitra, Arijit; Bahadur, D.; Medhekar, N. V.; Aslam, M.

2018-06-01

A high sensitive glucose sensing characteristic has been realized in carbon nano-onions (CNOs). The CNOs of mean size 30 nm were synthesized by an energy-efficient, simple and inexpensive combustion technique. These as-synthesized CNOs could be employed as an electrochemical sensor by covalently immobilizing the glucose oxidase enzyme on them via carbodiimide chemistry. The sensitivity achieved by such a sensor is 26.5 μA mM-1 cm-2 with a linear response in the range of 1-10 mM glucose. Further to improve the catalytic activity of the CNOs and also to make them enzyme free, platinum nanoparticles of average size 2.5 nm are decorated on CNOs. This sensor fabricated using Pt-decorated CNOs (Pt@CNOs) nanostructure has shown an enhanced sensitivity of 21.6 μA mM-1 cm-2 with an extended linear response in the range of 2-28 mM glucose. Through these attempts we demonstrate CNOs as a versatile biosensing platform.

Enhanced performance in capacitive force sensors using carbon nanotube/polydimethylsiloxane nanocomposites with high dielectric properties

Science.gov (United States)

Jang, Hyeyoung; Yoon, Hyungsuk; Ko, Youngpyo; Choi, Jaeyoo; Lee, Sang-Soo; Jeon, Insu; Kim, Jong-Ho; Kim, Heesuk

2016-03-01

Force sensors have attracted tremendous attention owing to their applications in various fields such as touch screens, robots, smart scales, and wearable devices. The force sensors reported so far have been mainly focused on high sensitivity based on delicate microstructured materials, resulting in low reproducibility and high fabrication cost that are limitations for wide applications. As an alternative, we demonstrate a novel capacitive-type force sensor with enhanced performance owing to the increased dielectric properties of elastomers and simple sensor structure. We rationally design dielectric elastomers based on alkylamine modified-multi-walled carbon nanotube (MWCNT)/polydimethylsiloxane (PDMS) composites, which have a higher dielectric constant than pure PDMS. The alkylamine-MWCNTs show excellent dispersion in a PDMS matrix, thus leading to enhanced and reliable dielectric properties of the composites. A force sensor array fabricated with alkylamine-MWCNT/PDMS composites presents an enhanced response due to the higher dielectric constant of the composites than that of pure PDMS. This study is the first to report enhanced performance of capacitive force sensors by modulating the dielectric properties of elastomers. We believe that the disclosed strategy to improve the sensor performance by increasing the dielectric properties of elastomers has great potential in the development of capacitive force sensor arrays that respond to various input forces.Force sensors have attracted tremendous attention owing to their applications in various fields such as touch screens, robots, smart scales, and wearable devices. The force sensors reported so far have been mainly focused on high sensitivity based on delicate microstructured materials, resulting in low reproducibility and high fabrication cost that are limitations for wide applications. As an alternative, we demonstrate a novel capacitive-type force sensor with enhanced performance owing to the increased

A built-in sensor with carbon nanotubes coated by Ag clusters for deformation monitoring of glass fibre/epoxy composites

Science.gov (United States)

Slobodian, P.; Riha, P.; Matyas, J.; Olejnik, R.; Lloret Pertegás, S.; Schledjewski, R.; Kovar, M.

2018-03-01

A multiwalled carbon nanotube network embedded in a polyurethane membrane was integrated into a glass fibre reinforced epoxy composite by means of vacuum infusion to become a part of the composite and has been serving for a strain self-sensing functionality. Besides the pristine nanotubes also nanotubes with Ag nanoparticles attached to their surfaces were used to increase strain sensing. Moreover, the design of the carbon nanotube/polyurethane sensor allowed formation of network micro-sized cracks which increased its reversible electrical resistance resulted in an enhancement of strain sensing. The resistance sensitivity, quantified by a gauge factor, increased more than hundredfold in case of a pre-strained sensor with Ag decorated nanotubes in comparison with the sensor with pristine nanotubes.

Manganese oxide nanoflakes/multi-walled carbon nanotubes/chitosan nanocomposite modified glassy carbon electrode as a novel electrochemical sensor for chromium (III) detection

International Nuclear Information System (INIS)

Salimi, Abdollah; Pourbahram, Bahareh; Mansouri-Majd, Samira; Hallaj, Rahman

2015-01-01

Highlights: • CNTs/chitosan/GC electrode used as platform for electrodeposition of MnO x -nanoflakes. • Modified electrode has excellent catalytic activity for oxidation of Cr 3+ at pH 3–7. • Detection limit and sensitivity of sensor for Cr 3+ detection were 0.3 μM and 18.7 nA/μM. • Sensor has good stability and high selectivity in the presence of common interferences. • Sensor applied for the detection of Cr 3+ in real samples with satisfactory results. - Abstract: In this research a nanocomposite containing chitosan (Chit) and maltiwalled carbon nanotubes (MWCNTs) was applied as platform for immobilization of electrodeposited manganese oxide (MnOx) nanostructures. First, glassy carbon (GC) electrode modified with thin film of Chitosan/MWCNTs nanocomposite. Then MnO x nanostructures was electrodeposited onto Chitosan/MWCNTs modified GC electrode using combination of constant potential step (0.6 V) and cyclic voltammetry(0.3–0.6 V) techniques. The XRD patterns and scanning electron microscope images indicated immobilization of uniformly MnOx nanoflakes with high crystallite onto MWCNTs/Chit film. The modified electrode shows a well-defined redox couple for Mn 2+ /MnO 2 system. Charge transfer coefficient (α), electron transfer rate constant (k s ) and surface concentration (Γ) were 0.394, 3.44 s −1 and 3.3 × 10 −11 mol cm −2 , respectively. The modified electrode showed excellent electrocatalytic activity toward oxidation of chromium (III) at natural pH solutions. Cyclic voltammetry and hydrodynamic amperometery were applied as measuring techniques for chromium detection. Detection limit, sensitivity and linear concentration range of the sensor were, 0.3 (μM), 18.7 nAμ M −1 and 3 μM to 200 μM, respectively. Moreover, the sensor retained about 90% of its original response toward Cr(III) after storage three months in ambient condition. Furthermore, the sensor response toward different common interferences was negligible. Finally, the

Thermal interface pastes nanostructured for high performance

Science.gov (United States)

Lin, Chuangang

Thermal interface materials in the form of pastes are needed to improve thermal contacts, such as that between a microprocessor and a heat sink of a computer. High-performance and low-cost thermal pastes have been developed in this dissertation by using polyol esters as the vehicle and various nanoscale solid components. The proportion of a solid component needs to be optimized, as an excessive amount degrades the performance, due to the increase in the bond line thickness. The optimum solid volume fraction tends to be lower when the mating surfaces are smoother, and higher when the thermal conductivity is higher. Both a low bond line thickness and a high thermal conductivity help the performance. When the surfaces are smooth, a low bond line thickness can be even more important than a high thermal conductivity, as shown by the outstanding performance of the nanoclay paste of low thermal conductivity in the smooth case (0.009 mum), with the bond line thickness less than 1 mum, as enabled by low storage modulus G', low loss modulus G" and high tan delta. However, for rough surfaces, the thermal conductivity is important. The rheology affects the bond line thickness, but it does not correlate well with the performance. This study found that the structure of carbon black is an important parameter that governs the effectiveness of a carbon black for use in a thermal paste. By using a carbon black with a lower structure (i.e., a lower DBP value), a thermal paste that is more effective than the previously reported carbon black paste was obtained. Graphite nanoplatelet (GNP) was found to be comparable in effectiveness to carbon black (CB) pastes for rough surfaces, but it is less effective for smooth surfaces. At the same filler volume fraction, GNP gives higher thermal conductivity than carbon black paste. At the same pressure, GNP gives higher bond line thickness than CB (Tokai or Cabot). The effectiveness of GNP is limited, due to the high bond line thickness. A

Microfabricated Chemical Gas Sensors and Sensor Arrays for Aerospace Applications

Science.gov (United States)

Hunter, Gary W.

2005-01-01

Aerospace applications require the development of chemical sensors with capabilities beyond those of commercially available sensors. In particular, factors such as minimal sensor size, weight, and power consumption are particularly important. Development areas which have potential aerospace applications include launch vehicle leak detection, engine health monitoring, and fire detection. Sensor development for these applications is based on progress in three types of technology: 1) Micromachining and microfabrication (Microsystem) technology to fabricate miniaturized sensors; 2) The use of nanocrystalline materials to develop sensors with improved stability combined with higher sensitivity; 3) The development of high temperature semiconductors, especially silicon carbide. This presentation discusses the needs of space applications as well as the point-contact sensor technology and sensor arrays being developed to address these needs. Sensors to measure hydrogen, hydrocarbons, nitrogen oxides (NO,), carbon monoxide, oxygen, and carbon dioxide are being developed as well as arrays for leak, fire, and emissions detection. Demonstrations of the technology will also be discussed. It is concluded that microfabricated sensor technology has significant potential for use in a range of aerospace applications.

Effect of mediator added to modified paste carbon electrodes with immobilized laccase from Aspergillus oryzae

Directory of Open Access Journals (Sweden)

Marcelo Silva Ferreira

2015-05-01

Full Text Available Carbon paste electrodes based on the immobilization of laccase from Aspergillus oryzae were developed and voltammetric measurements were performed to evaluate the amperometric response. The 2,2′-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid diammonium salt  (ABTS functions as substrate and mediator for the laccase enzyme. Electrodes were modified  in two different conditions: without mediator (EPC/laccase and with mediator (EPC/laccase/ABTS. The addition of ABTS as a mediator increased eight-fold the amperometric response. The electrode was sensitive to pH variation with best response at pH 4.0. Studies on different concentrations of laccase and ABTS at different pH rates revealed that the composition 187 U mL-1 in laccase and 200 µL of ABTS obtained the highest amperometric response. The carbon paste electrode modified with ABTS proved to be a good base for the immobilization of the laccase enzyme. Moreover, it is easy to manufacture and inexpensive to produce a modified electrode with potential application in biosensors.

Pore structure and carbonation in blended lime-cement pastes

Directory of Open Access Journals (Sweden)

Álvarez, J. I.

2006-06-01

Full Text Available The present study aims to gain a fuller understandingof the curing process in lime pastes (100, 90, 80, 70,60, 50 and 40% lime blended with cement by analyzingcarbonation in these materials. A hydrated, airslaked lime powder and CEM II A/L 32.5 Portlandcement were used for the blends. These materialswere singled out for research primarily because theymay be used in the restoration of heritage monuments.Variation in weight was used as an indicator for carbonation.A new parameter, A, was found to vary inverselywith the percentage of the cement because of theprevalence of Knudsen diffusion in the paste, in turndue to the characteristics of the pore structure, whichwas studied by mercury intrusion porosimetry (MIP.The hygroscopic study conducted on the different pastesprovided information on water content at a givenhumidity and its location, i.e., adsorbed on the surfaceof the pores or condensed inside them, obstructing thediffusion of CO2. The conclusion drawn from this studyof the curing process was that neither drying nor C3Shydration retarded lime carbonation.En este trabajo se estudia el proceso de carbonatacionen pastas mixtas de cal y cemento (100, 90, 80, 70, 60,50 y 40% de cal con el objeto de obtener un mejorconocimiento del proceso de curado en estos materiales.Para ello se ha empleado una cal aerea hidratada en polvoy un cemento Portland del tipo CEM II A/L 32,5. Enparticular, este estudio investiga estos materiales ya quepueden ser utilizados en la restauracion del PatrimonioCultural. Se ha utilizado la variacion de peso como indicadordel proceso de carbonatacion. Se ha establecidoun nuevo parametro, A, que varia inversamente con elporcentaje de cemento en la pasta, debido al predominiode la difusion de Knudsen como consecuencia de laestructura porosa, que ha sido estudiada por medio deporosimetria de intrusion de mercurio (PIM. El estudiohigroscopico realizado sobre las diversas pastas permiteconocer el contenido en agua a una

Imprinted propyl gallate electrochemical sensor based on graphene/single walled carbon nanotubes/sol-gel film.

Science.gov (United States)

Xu, Guilin; Chi, Yu; Li, Lu; Liu, Shouhua; Kan, Xianwen

2015-06-15

A novel imprinted sol-gel electrochemical sensor for the determination of propyl gallate (PG) was developed based on a composite of graphene and single walled carbon nanotubes (GR-SWCNTs). It was fabricated by stepwise modifying GR-SWCNTs and molecularly imprinted polymers and stored in 0.10 mol L(-1) phosphate buffer solution pH 6.0, which endowed the sensor good sensitivity and selective recognition towards template molecules. The morphology and specific adsorption capacity of the sensor was characterized by scanning electron microscope and electrochemical methods, respectively. Under the optimized conditions, a linear range of the sensor to PG was 8.0 × 10(-8)-2.6 × 10(-3)mo lL(-1) with a limit of detection of 5.0 × 10(-8)mol L(-1) (S/N=3). The sensor exhibited specificity and selectivity towards template molecules as well as excellent reproducibility, regeneration and stability. Furthermore, the sensor could be applied to determine PG in edible oils, instant noodles and cookies with satisfactory results. Copyright © 2015 Elsevier Ltd. All rights reserved.

Proximity gettering technology for advanced CMOS image sensors using carbon cluster ion-implantation technique. A review

Energy Technology Data Exchange (ETDEWEB)

Kurita, Kazunari; Kadono, Takeshi; Okuyama, Ryousuke; Shigemastu, Satoshi; Hirose, Ryo; Onaka-Masada, Ayumi; Koga, Yoshihiro; Okuda, Hidehiko [SUMCO Corporation, Saga (Japan)

2017-07-15

A new technique is described for manufacturing advanced silicon wafers with the highest capability yet reported for gettering transition metallic, oxygen, and hydrogen impurities in CMOS image sensor fabrication processes. Carbon and hydrogen elements are localized in the projection range of the silicon wafer by implantation of ion clusters from a hydrocarbon molecular gas source. Furthermore, these wafers can getter oxygen impurities out-diffused to device active regions from a Czochralski grown silicon wafer substrate to the carbon cluster ion projection range during heat treatment. Therefore, they can reduce the formation of transition metals and oxygen-related defects in the device active regions and improve electrical performance characteristics, such as the dark current, white spot defects, pn-junction leakage current, and image lag characteristics. The new technique enables the formation of high-gettering-capability sinks for transition metals, oxygen, and hydrogen impurities under device active regions of CMOS image sensors. The wafers formed by this technique have the potential to significantly improve electrical devices performance characteristics in advanced CMOS image sensors. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Multi-wall carbon nanotube networks as potential resistive gas sensors for organic vapor detection

Czech Academy of Sciences Publication Activity Database

Slobodian, P.; Říha, Pavel; Lengálová, A.; Svoboda, P.; Sáha, P.

2011-01-01

Roč. 49, č. 7 (2011), s. 2499-2507 ISSN 0008-6223 Institutional research plan: CEZ:AV0Z20600510 Keywords : carbon nanotube network * KMnO 4 oxidation * electrical resistance * organic vapor detection * adsorption /desorption cycles Subject RIV: JB - Sensors, Measurment, Regulation Impact factor: 5.378, year: 2011

Probe Sensor Using Nanostructured Multi-Walled Carbon Nanotube Yarn for Selective and Sensitive Detection of Dopamine

Directory of Open Access Journals (Sweden)

Wed Al-Graiti

2017-04-01

Full Text Available The demands for electrochemical sensor materials with high strength and durability in physiological conditions continue to grow and novel approaches are being enabled by the advent of new electromaterials and novel fabrication technologies. Herein, we demonstrate a probe-style electrochemical sensor using highly flexible and conductive multi-walled carbon nanotubes (MWNT yarns. The MWNT yarn-based sensors can be fabricated onto micro Pt-wire with a controlled diameter varying from 100 to 300 µm, and then further modified with Nafion via a dip-coating approach. The fabricated micro-sized sensors were characterized by electron microscopy, Raman, FTIR, electrical, and electrochemical measurements. For the first time, the MWNT/Nafion yarn-based probe sensors have been assembled and assessed for high-performance dopamine sensing, showing a significant improvement in both sensitivity and selectivity in dopamine detection in presence of ascorbic acid and uric acid. It offers the potential to be further developed as implantable probe sensors.

Surface analysis and electrochemistry of a robust carbon-nanofiber-based electrode platform H_2O_2 sensor

International Nuclear Information System (INIS)

Suazo-Dávila, D.; Rivera-Meléndez, J.; Koehne, J.; Meyyappan, M.; Cabrera, C.R.

2016-01-01

Highlights: • Vertically aligned carbon nanofibers were intercalated with SiO_2 for mechanical strength and isolation of individual electrodes. • Stable and robust electrochemical hydrogen peroxide sensor is stable and robust. • Five consecutive calibration curves were done with different hydrogen peroxide concentrations over a period of 3 days without any deterioration in the electrochemical response. • The sensor was also used for the measurement of hydrogen peroxide as one of the by-products of the reaction of cholesterol oxidase with cholesterol and the sensor response exhibited linear behavior from 50 μM to 1 mM in cholesterol concentration. • In general, the electrochemical sensor is robust, stable, and reproducible, and the detection limit and sensitivity responses were among the best when compared with the literature. - Abstract: A vertically aligned carbon nanofiber-based (VACNF) electrode platform was developed for an enzymeless hydrogen peroxide sensor. Vertical nanofibers have heights on the order of 2–3 μm, and diameters that vary from 50 to 100 nm as seen by atomic force microscopy. The VACNF was grown as individual, vertically, and freestanding structures using plasma-enhanced chemical vapor deposition. The electrochemical sensor, for the hydrogen peroxide measurement in solution, showed stability and reproducibility in five consecutive calibration curves with different hydrogen peroxide concentrations over a period of 3 days. The detection limit was 66 μM. The sensitivity for hydrogen peroxide electrochemical detection was 0.0906 mA cm"−"2 mM"−"1, respectively. The sensor was also used for the measurement of hydrogen peroxide as the by-product of the reaction of cholesterol with cholesterol oxidase as a biosensor application. The sensor exhibits linear behavior in the range of 50 μM–1 mM in cholesterol concentrations. The surface analysis and electrochemistry characterization is presented.

Gas Sensors Based on Locally Heated Multiwall Carbon Nanotubes Decorated with Metal Nanoparticles

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R. Savu

2015-01-01

Full Text Available We report the design and fabrication of microreactors and sensors based on metal nanoparticle-decorated carbon nanotubes. Titanium adhesion layers and gold films were sputtered onto Si/SiO2 substrates for obtaining the electrical contacts. The gold layers were electrochemically thickened until 1 μm and the electrodes were patterned using photolithography and wet chemical etching. Before the dielectrophoretic deposition of the nanotubes, a gap 1 μm wide and 5 μm deep was milled in the middle of the metallic line by focused ion beam, allowing the fabrication of sensors based on suspended nanotubes bridging the electrodes. Subsequently, the sputtering technique was used for decorating the nanotubes with metallic nanoparticles. In order to test the as-obtained sensors, microreactors (100 μL volume were machined from a single Kovar piece, being equipped with electrical connections and 1/4′′ Swagelok-compatible gas inlet and outlets for controlling the atmosphere in the testing chamber. The sensors, electrically connected to the contact pins by wire-bonding, were tested in the 10−5 to 10−2 W working power interval using oxygen as target gas. The small chamber volume allowed the measurement of fast characteristic times (response/recovery, with the sensors showing good sensitivity.

3D printing of highly elastic strain sensors using polyurethane/multiwall carbon nanotube composites

Science.gov (United States)

Christ, Josef F.; Hohimer, Cameron J.; Aliheidari, Nahal; Ameli, Amir; Mo, Changki; Pötschke, Petra

2017-04-01

As the desire for wearable electronics increases and the soft robotics industry advances, the need for novel sensing materials has also increased. Recently, there have been many attempts at producing novel materials, which exhibit piezoresistive behavior. However, one of the major shortcomings in strain sensing technologies is in the fabrication of such sensors. While there is significant research and literature covering the various methods for developing piezoresistive materials, fabricating complex sensor platforms is still a manufacturing challenge. Here, we report a facile method to fabricate multidirectional embedded strain sensors using additive manufacturing technology. Pure thermoplastic polyurethane (TPU) and TPU/multiwall carbon nanotubes (MWCNT) nanocomposites were 3D printed in tandem using a low-cost multi-material FDM printer to fabricate uniaxial and biaxial strain sensors with conductive paths embedded within the insulative TPU platform. The sensors were then subjected to a series of cyclic strain loads. The results revealed excellent piezoresistive responses of the sensors with cyclic repeatability in both the axial and transverse directions and in response to strains as high as 50%. Further, while strain-softening did occur in the embedded printed strain sensors, it was predictable and similar to the results found in the literature for bulk polymer nanocomposites. This works demonstrates the possibility of manufacturing embedded and multidirectional flexible strain sensors using an inexpensive and versatile method, with potential applications in soft robotics and flexible electronics and health monitoring.

Laser-engraved carbon nanotube paper for instilling high sensitivity, high stretchability, and high linearity in strain sensors

KAUST Repository

Xin, Yangyang

2017-06-29

There is an increasing demand for strain sensors with high sensitivity and high stretchability for new applications such as robotics or wearable electronics. However, for the available technologies, the sensitivity of the sensors varies widely. These sensors are also highly nonlinear, making reliable measurement challenging. Here we introduce a new family of sensors composed of a laser-engraved carbon nanotube paper embedded in an elastomer. A roll-to-roll pressing of these sensors activates a pre-defined fragmentation process, which results in a well-controlled, fragmented microstructure. Such sensors are reproducible and durable and can attain ultrahigh sensitivity and high stretchability (with a gauge factor of over 4.2 × 10(4) at 150% strain). Moreover, they can attain high linearity from 0% to 15% and from 22% to 150% strain. They are good candidates for stretchable electronic applications that require high sensitivity and linearity at large strains.

A Flexible and Highly Sensitive Piezoresistive Pressure Sensor Based on Micropatterned Films Coated with Carbon Nanotubes

Directory of Open Access Journals (Sweden)

Jia-lin Yao

2016-01-01

Full Text Available Excellent flexibility, high sensitivity, and low consumption are essential characteristics in flexible microtube pressure sensing occasion, for example, implantable medical devices, industrial pipeline, and microfluidic chip. This paper reports a flexible, highly sensitive, and ultrathin piezoresistive pressure sensor for fluid pressure sensing, whose sensing element is micropatterned films with conductive carbon nanotube layer. The flexible pressure sensor, the thickness of which is 40 ± 10 μm, could be economically fabricated by using biocompatible polydimethylsiloxane (PDMS. Experimental results show that the flexible pressure sensor has high sensitivity (0.047 kPa−1 in gas sensing and 5.6 × 10−3 kPa−1 in liquid sensing and low consumption (<180 μW, and the sensor could be used to measure the pressure in curved microtubes.

A tripolar-electrode ionization gas sensor using a carbon nanotube cathode for NO detection

Science.gov (United States)

Song, Hui; Li, Kun; Li, Quanfu

2018-06-01

Nitric oxide accounts for more than 95% of the total NO X emission from power plants, which is a major air pollutant. Therefore, it is imperative to accurately detect NO for environmental protection. A tripolar-electrode ionization sensor with a carbon nanotube (CNT) cathode is proposed for NO detection. The non-self-sustaining discharge state and the tripolar-electrode configuration ensures a long nanotube life, which ensures a good stability and fast response of the sensor. Experimental results demonstrate that the tripolar-electrode ionization sensor with 120 µm separations has an intrinsic monotonously decreasing response to NO and exhibits a fast response time of 7 s and recovery time of 8 s. More consumption of the two metastable states N2(A3  ∑  u +) and N2(aʹ1  ∑  u +) of N2 with the increasing of NO concentration is responsible for this. The tripolar-electrode ionization sensor also shows excellent long-term stability of at least one month due to the long CNT life. In addition, the weak effect of SO2 introduction on NO response indicates a good selectivity of the sensor to NO.

Taste sensor; Mikaku sensor

Energy Technology Data Exchange (ETDEWEB)

Toko, K. [Kyushu University, Fukuoka (Japan)

1998-03-05

This paper introduces a taste sensor having a lipid/polymer membrane to work as a receptor of taste substances. The paper describes the following matters: this sensor uses a hollow polyvinyl chloride rod filled with KCl aqueous solution, and placed with silver and silver chloride wires, whose cross section is affixed with a lipid/polymer membrane as a lipid membrane electrode to identify taste from seven or eight kinds of response patterns of electric potential output from the lipid/polymer membrane; measurements of different substances presenting acidic taste, salty taste, bitter taste, sweet taste and flavor by using this sensor identified clearly each taste (similar response is shown to a similar taste even if the substances are different); different responses are indicated on different brands of beers; from the result of measuring a great variety of mineral waters, a possibility was suggested that this taste sensor could be used for water quality monitoring sensors; and application of this taste sensor may be expected as a maturation control sensor for Japanese sake (wine) and miso (bean paste) manufacturing. 2 figs., 1 tab.

Electrocatalytic behavior of carbon paste electrode modified with metal phthalocyanines nanoparticles toward the hydrogen evolution

International Nuclear Information System (INIS)

Abbaspour, Abdolkarim; Norouz-sarvestani, Fatemeh; Mirahmadi, Ehsan

2012-01-01

Highlights: ► The new construction of a carbon paste electrode impregnated with nanoparticles of Zn and Ni phthalocyanine (nano ZnPc and nano NiPc). ► The decrease overpotential and higher current value obtained in nano ZnPc and nano NiPc compared to bulky ZnPc and bulky NiPc, respectively. ► Types of the catalyst and pH of the solution affect the electro catalytic proton reduction reaction considerably. - Abstract: This paper describes the construction of a carbon paste electrode (CPE) impregnated with nanoparticles of Zn and Ni phthalocyanine (nano ZnPc and nano NiPc). These new electrodes (nano ZnPc-CPE and nano NiPc-CPE) reveal interesting electrocatalytic behavior toward hydrogen evolution reaction (HER). Voltammetric characteristics indicated that the proposed electrodes display better electrocatalytic activity compared to their corresponding bulky modified metal phthalocyanines (MPcs) in minimizing overpotential and increasing the reduction current of HER. Electrocatalytic activities irregularly change with the pH of the solution. However by increasing the pH while nano MPcs are still active, bulky MPcs are almost inactive, and their corresponding ΔE increase by increasing the pH.

Polyaniline–multi-wall-carbon nanotube nanocomposites as a dopamine sensor

Directory of Open Access Journals (Sweden)

REZA EMAMALI SABZI

2010-04-01

Full Text Available A composite of polyaniline with multi-wall-carbon nanotubes (PANi/ /MWCNTs was synthesized by an in situ chemical oxidative polymerization method. The PANi nanoparticles were synthesized chemically using aniline as the monomer and ammonium peroxydisulfate as the oxidant. The nanocomposites were prepared as a carbon paste using functionalized MWCNTs and PANi nanoparticles. The PANi–MWCNTs were characterized physically using scanning electron microscopy (SEM and the electrochemical behavior of the composites in acidic solution (HCl was investigated using cyclic voltammetry. The PANi/MWCNT composite electrode was used for studying dopamine (DA as an electroactive material. The cyclic voltammetric results indicated that multi-wall carbon nanotubes (MWCNTs significantly enhanced the electrocatalytic activity in favor of the oxidation of DA. The kinetics of the catalytic reaction was investigated using the chronoamperometry technique whereby the average va¬lue of the diffusion coefficient (D and the catalytic rate constant (k for DA were determined to be (7.98±0.8×10-7 cm2 s-1 and (8.33±0.072×104 dm3 mol-1 s-1, respectively.

pH-dependence of the optical bio-sensor based on DNA-carbon nanotube

International Nuclear Information System (INIS)

Vu Thuy Huong; Quach Kha Quang; Tran Thanh Thuy; Phan Duc Anh; Ngo Van Thanh; Nguyen Ai Viet

2010-01-01

In 2006, Daniel A. Heller et al. [1] demonstrated that carbon nanotubes (CNNTs) wrapped with DNA can be placed inside living cells and detect trace amounts of harmful contaminants using near infrared light. This discovery could lead to new types of optical sensors and biomarkers at the sub cellular level. The working principle of this optical bio-sensor from DNA and CNNTs can be explained by a simple theoretical model which was introduced in [3]. In this paper, the pH-dependence of DNA and the pH-dependence of solution around CNNTs are shown by using data analysis method. By substituting them into the same model, the pH-dependence of DNA-wrapped CNNTs was elicited in this paper. The range of parameters for workable conditions of this bio-sensor was indicated that the solution should have pH from 6 to 9 and the concentration of ions should be more than a critical value. These results are according to the experimental data and the deduction about pH and salt concentration in solution. They are very useful as using such a new bio-sensor like this in living environment. (author)

Response of a Zn2TiO4 Gas Sensor to Propanol at Room Temperature

Directory of Open Access Journals (Sweden)

Ibrahim Gaidan

2017-08-01

Full Text Available In this study, three different compositions of ZnO and TiO2 powders were cold compressed and then heated at 1250 °C for five hours. The samples were ground to powder form. The powders were mixed with 5 wt % of polyvinyl butyral (PVB as binder and 1.5 wt % carbon black and ethylene-glyco-lmono-butyl-ether as a solvent to form screen-printed pastes. The prepared pastes were screen printed on the top of alumina substrates containing arrays of three copper electrodes. The three fabricated sensors were tested to detect propanol at room temperature at two different concentration ranges. The first concentration range was from 500 to 3000 ppm while the second concentration range was from 2500 to 5000 ppm, with testing taking place in steps of 500 ppm. The response of the sensors was found to increase monotonically in response to the increment in the propanol concentration. The surface morphology and chemical composition of the prepared samples were characterized by Scanning Electron Microscopy (SEM and X-Ray Diffraction (XRD. The sensors displayed good sensitivity to propanol vapors at room temperature. Operation under room-temperature conditions make these sensors novel, as other metal oxide sensors operate only at high temperature.

Carbon paste electrode modified with silver thimerosal for the potentiometric flow injection analysis of silver(I)

Energy Technology Data Exchange (ETDEWEB)

Ibrahim, Hosny [Chemistry Department, Faculty of Science, Cairo University, Cairo (Egypt)]. E-mail: dr_hosny@yahoo.com

2005-07-27

The utility of carbon paste electrode modified with silver ethylmercurythiosalicylate (silver thimerosal) in both static mode and flow injection analysis (FIA) is demonstrated. The electrode was fully characterized in terms of composition, response time, thermal stability, usable pH and ionic strength ranges. It has been shown that diisononyl phthalate (DINP) acts as more suitable solvent mediator for preparation of the electrode, which exhibits linear response range to Ag(I) extending from 5.0 x 10{sup -7} to 1.0 x 10{sup -3} M with detection limit of 2.5 x 10{sup -7} M and Nernstian slope of 59.3 {+-} 1.0 mV/decade. The proposed chemically modified carbon paste electrode shows a very good selectivity for Ag(I) over a wide variety of metal ions and successfully used for the determination of the silver content of silver sulphadiazine (burning cream) and developed radiological films. The electrode was also used as an indicator electrode in the potentiometric titration of thiopental and thimerosal with AgNO{sub 3}.

Increase in observed net carbon dioxide uptake by land and oceans during the past 50 years.

Science.gov (United States)

Ballantyne, A P; Alden, C B; Miller, J B; Tans, P P; White, J W C

2012-08-02

One of the greatest sources of uncertainty for future climate predictions is the response of the global carbon cycle to climate change. Although approximately one-half of total CO(2) emissions is at present taken up by combined land and ocean carbon reservoirs, models predict a decline in future carbon uptake by these reservoirs, resulting in a positive carbon-climate feedback. Several recent studies suggest that rates of carbon uptake by the land and ocean have remained constant or declined in recent decades. Other work, however, has called into question the reported decline. Here we use global-scale atmospheric CO(2) measurements, CO(2) emission inventories and their full range of uncertainties to calculate changes in global CO(2) sources and sinks during the past 50 years. Our mass balance analysis shows that net global carbon uptake has increased significantly by about 0.05 billion tonnes of carbon per year and that global carbon uptake doubled, from 2.4 ± 0.8 to 5.0 ± 0.9 billion tonnes per year, between 1960 and 2010. Therefore, it is very unlikely that both land and ocean carbon sinks have decreased on a global scale. Since 1959, approximately 350 billion tonnes of carbon have been emitted by humans to the atmosphere, of which about 55 per cent has moved into the land and oceans. Thus, identifying the mechanisms and locations responsible for increasing global carbon uptake remains a critical challenge in constraining the modern global carbon budget and predicting future carbon-climate interactions.

Peroxynitrite Sensor Based on a Screen Printed Carbon Electrode Modified with a Poly(2,6-dihydroxynaphthalene Film

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Ioana Silvia Hosu

2016-11-01

Full Text Available For the first time the electropolymerization of 2,6-dihydroxynaphthalene (2,6-DHN on a screen printed carbon electrode (SPCE was investigated and evaluated for peroxynitrite (PON detection. Cyclic voltammetry was used to electrodeposit the poly(2,6-DHN on the carbon electrode surface. The surface morphology and structure of poly(2,6-DHN film were investigated by SEM and FTIR analysis, and the electrochemical features by cyclic voltammetry. The poly(2,6-DHN/SPCE sensor showed excellent electrocatalytic activity for PON oxidation in alkaline solutions at very low potentials (0–100 mV vs. Ag/AgCl pseudoreference. An amperometric FIA (flow injection analysis system based on the developed sensor was optimized for PON measurements and a linear concentration range from 2 to 300 μM PON, with a LOD of 0.2 μM, was achieved. The optimized sensor inserted in the FIA system exhibited good sensitivity (4.12 nA·μM−1, selectivity, stability and intra-/inter-electrode reproducibility for PON determination.

Enhancement of NH3 gas sensitivity at room temperature by carbon nanotube-based sensor coated with Co nanoparticles.

Science.gov (United States)

Nguyen, Lich Quang; Phan, Pho Quoc; Duong, Huyen Ngoc; Nguyen, Chien Duc; Nguyen, Lam Huu

2013-01-30

Multi-walled carbon nanotube (MWCNT) film has been fabricated onto Pt-patterned alumina substrates using the chemical vapor deposition method for NH(3) gas sensing applications. The MWCNT-based sensor is sensitive to NH(3) gas at room temperature. Nanoclusters of Co catalysts have been sputtered on the surface of the MWCNT film to enhance gas sensitivity with respect to unfunctionalized CNT films. The gas sensitivity of Co-functionalized MWCNT-based gas sensors is thus significantly improved. The sensor exhibits good repeatability and high selectivity towards NH(3), compared with alcohol and LPG.

Immobilization of metallothionein to carbon paste electrode surface via anti-MT antibodies and its use for biosensing of silver.

Science.gov (United States)

Trnkova, Libuse; Krizkova, Sona; Adam, Vojtech; Hubalek, Jaromir; Kizek, Rene

2011-01-15

In this paper, heavy metal biosensor based on immobilization of metallothionein (MT) to the surface of carbon paste electrode (CPE) via anti-MT-antibodies is reported. First, the evaluation of MT electroactivity was done. The attention was focused on the capturing of MT to the CPE surface. Antibodies incorporated and mixed into carbon paste were stable; even after two weeks the observed changes in signal height were lower than 5%. Further, the interaction of MT with polyclonal chicken antibodies incorporated in carbon paste electrode was determined by square-wave voltammetry. In the voltammogram, two signals--labelled as cys(MT) and W(a)--were observed. The cys(MT) corresponded to -SH moieties of MT and W(a) corresponded to tryptophan residues of chicken antibodies. Time of interaction (300 s) and MT concentration (125 μg/ml) were optimized to suggest a silver(I) ions biosensor. Biosensor (CPE modified with anti-MT antibody) prepared under the optimized conditions was then used for silver(I) ions detection. The detection limit (3 S/N) for silver(I) ions was estimated as 0.5 nM. The proposed biosensor was tested by detection spiking of silver(I) ions in various water samples (from very pure distilled water to rainwater). Recoveries varied from 74 to 104%. Copyright © 2010 Elsevier B.V. All rights reserved.

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.

Iron filled carbon nanotubes as novel monopole-like sensors for quantitative magnetic force microscopy

Energy Technology Data Exchange (ETDEWEB)

Wolny, F; Muehl, T; Weissker, U; Lipert, K; Schumann, J; Leonhardt, A; Buechner, B, E-mail: f.wolny@ifw-dresden.de, E-mail: t.muehl@ifw-dresden.de [Leibniz Institute for Solid State and Materials Research (IFW) Dresden, Helmholtzstrasse 20, 01069 Dresden (Germany)

2010-10-29

We present a novel ultrahigh stability sensor for quantitative magnetic force microscopy (MFM) based on an iron filled carbon nanotube. In contrast to the complex magnetic structure of conventional MFM probes, this sensor constitutes a nanomagnet with defined properties. The long iron nanowire can be regarded as an extended dipole of which only the monopole close to the sample surface is involved in the imaging process. We demonstrate its potential for high resolution imaging. Moreover, we present an easy routine to determine its monopole moment and prove that this calibration, unlike other approaches, is universally applicable. For the first time this enables straightforward quantitative MFM measurements.

Static and Dynamic Strain Monitoring of Reinforced Concrete Components through Embedded Carbon Nanotube Cement-Based Sensors

Directory of Open Access Journals (Sweden)

Antonella D’Alessandro

2017-01-01

Full Text Available The paper presents a study on the use of cement-based sensors doped with carbon nanotubes as embedded smart sensors for static and dynamic strain monitoring of reinforced concrete (RC elements. Such novel sensors can be used for the monitoring of civil infrastructures. Because they are fabricated from a structural material and are easy to utilize, these sensors can be integrated into structural elements for monitoring of different types of constructions during their service life. Despite the scientific attention that such sensors have received in recent years, further research is needed to understand (i the repeatability and accuracy of sensors’ behavior over a meaningful number of sensors, (ii testing configurations and calibration methods, and (iii the sensors’ ability to provide static and dynamic strain measurements when actually embedded in RC elements. To address these research needs, this paper presents a preliminary characterization of the self-sensing capabilities and the dynamic properties of a meaningful number of cement-based sensors and studies their application as embedded sensors in a full-scale RC beam. Results from electrical and electromechanical tests conducted on small and full-scale specimens using different electrical measurement methods confirm that smart cement-based sensors show promise for both static and vibration-based structural health monitoring applications of concrete elements but that calibration of each sensor seems to be necessary.

Highly sensitive hydrogen peroxide sensor based on a glassy carbon electrode modified with platinum nanoparticles on carbon nanofiber heterostructures

International Nuclear Information System (INIS)

Yang, Yang; Fu, Renzhong; Yuan, Jianjun; Wu, Shiyuan; Zhang, Jialiang; Wang, Haiying

2015-01-01

We are presenting a sensor for hydrogen peroxide (H 2 O 2 ) that is based on the use of a heterostructure composed of Pt nanoparticles (NPs) and carbon nanofibers (CNFs). High-density Pt NPs were homogeneously loaded onto a three-dimensional nanostructured CNF matrix and then deposited in a glassy carbon electrode (GCE). The resulting sensor synergizes the advantages of the conducting CNFs and the nanoparticle catalyst. The porous structure of the CNFs also favor the high-density immobilization of the NPs and the diffusion of water-soluble molecules, and thus assists the rapid catalytic oxidation of H 2 O 2 . If operated at a working voltage of −0.2 V (vs. Ag/AgCl), the modified GCE exhibits a linear response to H 2 O 2 in the 5 μM to 15 mM concentration range (total analytical range: 5 μM to 100 mM), with a detection limit of 1.7 μM (at a signal-to-noise ratio of 3). The modified GCE is not interfered by species such as uric acid and glucose. Its good stability, high selectivity and good reproducibility make this electrode a valuable tool for inexpensive amperometric sensing of H 2 O 2 . (author)

An Easily Fabricated Electrochemical Sensor Based on a Graphene-Modified Glassy Carbon Electrode for Determination of Octopamine and Tyramine

Science.gov (United States)

Zhang, Yang; Zhang, Meiqin; Wei, Qianhui; Gao, Yongjie; Guo, Lijuan; Al-Ghanim, Khalid A.; Mahboob, Shahid; Zhang, Xueji

2016-01-01

A simple electrochemical sensor has been developed for highly sensitive detection of octopamine and tyramine by electrodepositing reduced graphene oxide (ERGO) nanosheets onto the surface of a glassy carbon electrode (GCE). The electrocatalytic oxidation of octopamine and tyramine is individually investigated at the surface of the ERGO modified glassy carbon electrode (ERGO/GCE) by using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Several essential factors including the deposition cycle of reduced graphene oxide nanosheets and the pH of the running buffer were investigated in order to determine the optimum conditions. Furthermore, the sensor was applied to the quantification of octopamine and tyramine by DPV in the concentration ranges from 0.5 to 40 μM and 0.1 to 25 μM, respectively. In addition, the limits of detection of octopamine and tyramine were calculated to be 0.1 μM and 0.03 μM (S/N = 3), respectively. The sensor showed good reproducibility, selectivity and stability. Finally, the sensor successfully detected octopamine and tyramine in commercially available beer with satisfactory recovery ranges which were 98.5%–104.7% and 102.2%–103.1%, respectively. These results indicate the ERGO/GCE based sensor is suitable for the detection of octopamine and tyramine. PMID:27089341

DNA-decorated carbon-nanotube-based chemical sensors on complementary metal oxide semiconductor circuitry

International Nuclear Information System (INIS)

Chen, Chia-Ling; Yang, Chih-Feng; Dokmeci, Mehmet R; Agarwal, Vinay; Sonkusale, Sameer; Kim, Taehoon; Busnaina, Ahmed; Chen, Michelle

2010-01-01

We present integration of single-stranded DNA (ss-DNA)-decorated single-walled carbon nanotubes (SWNTs) onto complementary metal oxide semiconductor (CMOS) circuitry as nanoscale chemical sensors. SWNTs were assembled onto CMOS circuitry via a low voltage dielectrophoretic (DEP) process. Besides, bare SWNTs are reported to be sensitive to various chemicals, and functionalization of SWNTs with biomolecular complexes further enhances the sensing specificity and sensitivity. After decorating ss-DNA on SWNTs, we have found that the sensing response of the gas sensor was enhanced (up to ∼ 300% and ∼ 250% for methanol vapor and isopropanol alcohol vapor, respectively) compared with bare SWNTs. The SWNTs coupled with ss-DNA and their integration on CMOS circuitry demonstrates a step towards realizing ultra-sensitive electronic nose applications.

Past performance and future needs for low carbon climate resilient infrastructure– An investment perspective

International Nuclear Information System (INIS)

Kennedy, Christopher; Corfee-Morlot, Jan

2013-01-01

This article explores the investment implications of moving to low-carbon, climate-resilient infrastructure. It begins with analysis of gross fixed capital formation and decarbonisation trends to examine past performance of OECD countries in reducing GHG emissions from 1997 to 2007. Many OECD countries made progress in decoupling GHG emissions from infrastructure investment in residential buildings, and to a lesser extent from power and industry, but increased efforts are required, especially in the transportation sector. The analysis highlights the need to accelerate the pace and scale of change to reverse GHG emission trends to bring into reach ambitious climate policy goals. It then assesses future global infrastructure needs under low-carbon and business-as-usual (BAU) global warming scenarios, and the incremental costs of going “low-carbon” are estimated to be small relative to the magnitude of the BAU infrastructure investment needs. Global infrastructure needs for 2015–2020, including buildings and transportation vehicles, are approximately 6.7 trillion USD/year under BAU. Incremental costs of low-carbon infrastructure are of the order −70 to +450 billion USD/year. Achieving climate resilient infrastructure may add costs, but there is potentially synergistic overlap with low-carbon attributes. Although estimates are incomplete, the technical and financial inter-dependency between infrastructure systems suggests the potential to generate infrastructure investment to support a “virtuous cycle” of low-carbon growth. - Highlights: • Conceptualisation of interactions between low carbon and climate resilient infrastructure (Fig. 1). • New performance measures of national GHG emissions vs. capital formation (Section 2). • Comparion of global infrastructure costs under low and high carbon scenarios (Table 1). • Understanding of infrastructures that support virtuous cycles of low carbon growth (Fig. 8)

Nanomolecular gas sensor architectures based on functionalized carbon nanotubes for vapor detection

Science.gov (United States)

Hines, Deon; Zhang, Henan; Rümmeli, Mark H.; Adebimpe, David; Akins, Daniel L.

2015-05-01

There is enormous interest in detection of simple & complex odors by mean of electronic instrumentation. Specifically, our work focuses on creating derivatized-nanotube-based "electronic noses" for the detection and identification of gases, and other materials. We have grafted single-walled carbon nanotubes (SWNTs) with an array of electron-donating and electron withdrawing moieties and have characterized some of the physicochemical properties of the modified nanotubes. Gas sensing elements have been fabricated by spin coating the functionalized nanotubes onto interdigitated electrodes (IDE's), creating an array of sensors. Each element in the sensor array can contain a different functionalized matrix. This facilitates the construction of chemical sensor arrays with high selectivity and sensitivity; a methodology that mimics the mammalian olfactory system. Exposure of these coated IDEs to organic vapors and the successful classification of the data obtained under DC monitoring, indicate that the system can function as gas sensors of high repeatability and selectivity for a wide range of common analytes. Since the detection of explosive materials is also of concern in this research, our next phase focuses on explosives such as, TNT, RDX, and Triacetone Triperoxide (TATP). Sensor data from individual detection are assessed on their own individual merits, after which they are amalgamated and reclassified to present each vapor as unique data point on a 2-dimensional map and with minimum loss of information. This approach can assist the nation's need for a technology to defeat IEDs through the use of methods that detect unique chemical signatures associated with explosive molecules and byproducts.

Highly Stable and Flexible Pressure Sensors with Modified Multi-Walled Carbon Nanotube/Polymer Composites for Human Monitoring.

Science.gov (United States)

He, Yin; Ming, Yue; Li, Wei; Li, Yafang; Wu, Maoqi; Song, Jinzhong; Li, Xiaojiu; Liu, Hao

2018-04-26

A facile method for preparing an easy processing, repeatable and flexible pressure sensor was presented via the synthesis of modified multi-walled carbon nanotubes (m-MWNTs) and polyurethane (PU) films. The surface modification of multi-walled carbon nanotubes (MWNTs) simultaneously used a silane coupling agent (KH550) and sodium dodecyl benzene sulfonate (SDBS) to improve the dispersibility and compatibility of the MWNTs in a polymer matrix. The electrical property and piezoresistive behavior of the m-MWNT/PU composites were compared with raw multi-walled carbon nanotube (raw MWNT)/PU composites. Under linear uniaxial pressure, the m-MWNT/PU composite exhibited 4.282%kPa −1 sensitivity within the pressure of 1 kPa. The nonlinear error, hysteresis error and repeatability error of the piezoresistivity of m-MWNT/PU decreased 9%, 16.72% and 54.95% relative to raw MWNT/PU respectively. Therefore, the piezoresistive response of m-MWNT/PU had better stability than that of raw MWNT/PU composites. The m-MWNT/PU sensors could be utilized in wearable devices for body movement detection, monitoring of respiration and pressure detection in garments.

Vibration analysis of carbon nanotubes-based zeptogram masses sensors and taking into account their rotatory inertia

Directory of Open Access Journals (Sweden)

Azrar A.

2018-01-01

Full Text Available In this research work, the transverse vibration behaviour of single-walled carbon nanotubes (SCNT based mass sensors is studied using the Timoshenko beam and nonlocal elasticity theories. The nonlocal constitutive equations are used in the formulations and the CNT with different lengths, attached mass (viruses and bacteria and the general boundary conditions are considered. The dimensionless frequencies and associated modes are obtained for one and two attached masses and different boundary conditions. The effects of transverse shear deformation and rotatory inertia, nonlocal parameter, length of the carbon nanotubes, and attached mass and its location are investigated in detail for each considered problem. The relationship between the frequencies and mode shapes of the sensor and the attached zeptogramme masses are obtained. The sensing devices for biological objects including viruses and bacteria can be elaborated based on the developed sensitivity and frequency shift methodological approach.

Focus on image sensors

NARCIS (Netherlands)

Jos Gunsing; Daniël Telgen; Johan van Althuis; Jaap van de Loosdrecht; Mark Stappers; Peter Klijn

2013-01-01

Robots need sensors to operate properly. Using a single image sensor, various aspects of a robot operating in its environment can be measured or monitored. Over the past few years, image sensors have improved a lot: frame rate and resolution have increased, while prices have fallen. As a result,

Rhodium-Prussian Blue modified carbon paste electrode (Rh-PBMCPE for amperometric detection of hydrogen peroxide

Directory of Open Access Journals (Sweden)

Ivama Viviane Midori

2003-01-01

Full Text Available Prussian Blue was deposited at carbon paste electrode surface from a solution containing 2.0 x 10-3 mol L-1 K3[Fe(CN6], 3.0 x 10-3 mol L-1 FeCl3 and 1.0 x 10-2 mol L-1 HCl using two controlled potentials. To improve the stability of the modified electrode it was 50 times cycled in a solution containing 1.0 x 10-3 mol L-1 RhCl3, 0.50 mol L-1 KCl and 0.010 mol L-1 HCl in the potential range from - 0.40 V to 0.60 V at 60 mV s-1. The Rh - Prussian Blue carbon paste modified electrode (Rh-PBMCPE showed good stability during amperometric catalytic determination of H2O2 at 0.040 V, without ascorbic and uric acids interferences. The current changed linearly with H2O2 concentrations in the range of 5.0 x 10-5 - 8.6 x 10-4 mol L-1. The estimated detection limit was 2.8 x 10-5 mol L-1 with sensibility changing from 1.32 to 0.96 A mol-1 L cm-2 along five days (180 determinations.

Enhancement of NH3 Gas Sensitivity at Room Temperature by Carbon Nanotube-Based Sensor Coated with Co Nanoparticles

Directory of Open Access Journals (Sweden)

Lich Quang Nguyen

2013-01-01

Full Text Available Multi-walled carbon nanotube (MWCNT film has been fabricated onto Pt-patterned alumina substrates using the chemical vapor deposition method for NH3 gas sensing applications. The MWCNT-based sensor is sensitive to NH3 gas at room temperature. Nanoclusters of Co catalysts have been sputtered on the surface of the MWCNT film to enhance gas sensitivity with respect to unfunctionalized CNT films. The gas sensitivity of Co-functionalized MWCNT-based gas sensors is thus significantly improved. The sensor exhibits good repeatability and high selectivity towards NH3, compared with alcohol and LPG.

Development of a 1 x N Fiber Optic Sensor Array for Carbon Sequestration Site Monitoring

Energy Technology Data Exchange (ETDEWEB)

Repasky, Kevin [Montana State Univ., Bozeman, MT (United States)

2014-02-01

A fiber sensor array for sub-surface CO₂ concentrations measurements was developed for monitoring geologic carbon sequestration sites. The fiber sensor array uses a single temperature tunable distributed feedback (DFB) laser operating with a nominal wavelength of 2.004 μm. Light from this DFB laser is direct to one of the 4 probes via an in-line 1 x 4 fiber optic switch. Each of the 4 probes are buried and allow the sub-surface CO₂ to enter the probe through Millipore filters that allow the soil gas to enter the probe but keeps out the soil and water. Light from the DFB laser interacts with the CO₂ before it is directed back through the in-line fiber optic switch. The DFB laser is tuned across two CO₂ absorption features where a transmission measurement is made allowing the CO₂ concentration to be retrieved. The fiber optic switch then directs the light to the next probe where this process is repeated allowing sub-surface CO₂ concentration measurements at each of the probes to be made as a function of time. The fiber sensor array was deployed for fifty-eight days beginning June 19, 2012 at the Zero Emission Research Technology (ZERT) field site where sub-surface CO₂ concentrations were monitored. Background measurements indicate the fiber sensor array can monitor background levels as low as 1,000 parts per million (ppm). A thirty four day sub-surface release of 0.15 tones CO₂/day began on July 10, 2012. The elevated subsurface CO₂ concentration was easily detected by each of the four probes with values ranging to over 60,000 ppm, a factor of greater than 6 higher than background measurements. The fiber sensor array was also deploy at the Big Sky Carbon Sequestration Partnership (BSCSP) site in north-central Montana between July 9th and August 7th, 2013 where background measurements were made in a remote sequestration site with minimal infrastructure. The project

Preparation of polypyrrole/ferrocyanide films modified carbon paste electrode and its application on the electrocatalytic determination of ascorbic acid

Energy Technology Data Exchange (ETDEWEB)

Raoof, Jahan-Bakhsh; Ojani, Reza; Rashid-Nadimi, Sahar

2004-01-15

Functionalized polypyrrole film were prepared by incorporation of (Fe(CN){sub 6}){sup 4-} as doping anion, during the electropolymerization of pyrrole onto a carbon paste electrode (CPE) in aqueous solution by using potentiostatic method. The electrochemical behavior of the (Fe(CN){sub 6}){sup 3-}/(Fe(CN){sub 6}){sup 4-} redox couple in polypyrrole was studied by cyclic voltammetry and double step potential chronoamperometry methods. In this study, an obvious surface redox reaction was observed and dependence of this reaction on the solution pH was illustrated. The electrocatalytic ability of polypyrrole/ferrocyanide films modified carbon paste electrode (Ppy/FCNMCPEs) was demonstrated by oxidation of ascorbic acid. It has been found that under optimum condition (pH 7.00), the oxidation of ascorbic acid at the surface of such electrode occurs at a potential about 540 mV less positive than unmodified carbon paste electrode. The kinetic parameters such as electron transfer coefficient, {alpha} and catalytic reaction rate constant, k{sub h}', were also determined by using various electrochemical approaches. The catalytic oxidation peak current showed a linear dependent on the ascorbic acid concentration and a linear calibration curve was obtained in the range of 4.5x10{sup -4} to 9.62x10{sup -3} M of ascorbic acid with a correlation coefficient of 0.9999. The detection limit (2{sigma}) was determined as 5.82x10{sup -5} M.

In situ corrosion monitoring of PC structures with distributed hybrid carbon fiber reinforced polymer sensors

Science.gov (United States)

Yang, C. Q.; Wu, Z. S.

2007-08-01

Firstly, the fabrication and sensing properties of hybrid carbon fiber reinforced polymer (HCFRP) composite sensors are addressed. In order to provide a distributed sensing manner, the HCFRP sensors were divided into multi-zones with electrodes, and each zone was regarded as a separate sensor. Secondly, their application is studied to monitor the steel corrosion of prestressed concrete (PC) beams. The HCFRP sensors with different gauge lengths were mounted on a PC tendon, steel bar and embedded in tensile and compressive sides of the PC beam. The experiment was carried out under an electric accelerated corrosion and a constant load of about 54 kN. The results reveal that the corrosion of the PC tendon can be monitored through measuring the electrical resistance (ER) change of the HCFRP sensors. For the sensors embedded in tensile side of the PC beam, their ER increases as the corrosion progresses, whereas for the sensors embedded in compressive side, their ER decreases with corrosion time. Moreover, the strains due to the corrosion can be obtained based on the ER change and calibration curves of HCFRP sensors. The strains measured with traditional strain gauges agree with the strains calculated from the ER changes of HCFRP sensors. The electrical behavior of the zones where the corrosion was performed is much different from those of the other zones. In these zones, either there exist jumps in ER, or the ER increases with a much larger rate than those of the other zones. Distributed corrosion monitoring for PC structures is thus demonstrated with the application of HCFRP sensors through a proper installation of multi-electrodes.

Preparation and characterization of green-nano-composite material based on polyaniline, multiwalled carbon nano tubes and carboxymethyl cellulose: For electrochemical sensor applications.

Science.gov (United States)

Gautam, Vineeta; Singh, Karan Pratap; Yadav, Vijay Laxmi

2018-06-01

In this paper, we are presenting the preparation and characterization of "polyaniline/multiwalled carbon nanotubes/carboxymethyl cellulose" based novel composite material. It's morphological, thermal, structural, and electrochemical properties were investigated by using different instrumental techniques. During the in-situ chemical polymerization of aniline in the aqueous suspension of CMC and MWCNTs, the particle size change in two different ways "top to bottom" (low molecular weight oligomers grows in size) and "bottom to top" (long fibers of CMC fragmented in the reaction mixture). The combination of these two processes facilitated the fabrication of an integrated green-nano-composite material. In addition, a little amount of conductive nanofillers (MWCNTs) boosts the electrical and electrocatalytic properties of the material. Electron-rich centers of benzenoid rings exhibited π-π stacking with sp 2 carbon of MWCNTs. CMC dominantly impact on the properties of PANI, negatively charged carboxylate group of CMC ionically bonded with protonated amine/imine. FTIR and Raman analysis confirmed that the material has dominated quinoid units and effective charge transfer. Hydroxyl and carboxyl groups and bonded water molecules of CMC results in a network of hydrogen bonds (which induced directional property). PANI/MWCNTs/CMC have nanobead-like structures (TEM analysis), large surface area, large pore volume, small pore diameter (BET and BJH studies) and good dispersion ability in the aqueous phase. Nanostructures of aligned PANI exhibited excellent electrochemical properties have attracted increasing attention. Modified carbon paste electrode was used for electrocatalytic detection of ascorbic acid (as a model analyte). The sensor exhibited a linear range 0.05 mM-5 mM, sensitivity 100.63 μA mM -1  cm -2 , and limit of detection 0.01 mM. PANI/MWCNTs/CMC is suitable nanocomposite material for apply electroactive/conducting ink and membrane (which could be

Electrochemical sensors and biosensors based on redox polymer/carbon nanotube modified electrodes: a review.

Science.gov (United States)

Barsan, Madalina M; Ghica, M Emilia; Brett, Christopher M A

2015-06-30

The aim of this review is to present the contributions to the development of electrochemical sensors and biosensors based on polyphenazine or polytriphenylmethane redox polymers together with carbon nanotubes (CNT) during recent years. Phenazine polymers have been widely used in analytical applications due to their inherent charge transport properties and electrocatalytic effects. At the same time, since the first report on a CNT-based sensor, their application in the electroanalytical chemistry field has demonstrated that the unique structure and properties of CNT are ideal for the design of electrochemical (bio)sensors. We describe here that the specific combination of phenazine/triphenylmethane polymers with CNT leads to an improved performance of the resulting sensing devices, because of their complementary electrical, electrochemical and mechanical properties, and also due to synergistic effects. The preparation of polymer/CNT modified electrodes will be presented together with their electrochemical and surface characterization, with emphasis on the contribution of each component on the overall properties of the modified electrodes. Their importance in analytical chemistry is demonstrated by the numerous applications based on polymer/CNT-driven electrocatalytic effects, and their analytical performance as (bio) sensors is discussed. Copyright © 2015 Elsevier B.V. All rights reserved.

Copper@carbon coaxial nanowires synthesized by hydrothermal carbonization process from electroplating wastewater and their use as an enzyme-free glucose sensor.

Science.gov (United States)

Zhao, Yuxin; He, Zhaoyang; Yan, Zifeng

2013-01-21

In the pursuit of electrocatalysts with great economic and ecological values for non-enzymatic glucose sensors, one-dimensional copper@carbon (Cu@C) core-shell coaxial nanowires (NWs) have been successfully prepared via a simple continuous flow wet-chemistry approach from electroplating wastewater. The as-obtained products were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, energy dispersive X-ray spectroscopy and Raman spectroscopy. The electrocatalytic activity of the modified electrodes by Cu@C NWs towards glucose oxidation was investigated by cyclic voltammetry and chronoamperometry. It was found that the as-obtained Cu@C NWs showed good electrochemical properties and could be used as an electrochemical sensor for the detection of glucose molecules. Compared to the other electrodes including the bare Nafion/glassy carbon electrode (GCE) and several hot hybrid nanostructures modified GCE, a substantial decrease in the overvoltage of the glucose oxidation was observed at the Cu@C NWs electrodes with oxidation starting at ca. 0.20 V vs. Ag/AgCl (3 M KCl). At an applied potential of 0.65 V, Cu@C NWs electrodes had a high and reproducible sensitivity of 437.8 µA cm(-2) mM(-1) to glucose. Linear responses were obtained with a detection limit of 50 nM. More importantly, the proposed electrode also had good stability, high resistance against poisoning by chloride ion and commonly interfering species. These good analytical performances make Cu@C NWs promising for the future development of enzyme-free glucose sensors.

Self-assembly of nitrogen-doped carbon nanoparticles: a new ratiometric UV-vis optical sensor for the highly sensitive and selective detection of Hg(2+) in aqueous solution.

Science.gov (United States)

Ruan, Yudi; Wu, Lie; Jiang, Xiue

2016-05-23

Water-soluble nitrogen-doped carbon nanoparticles (N-CNPs) prepared by the one-step hydrothermal treatment of uric acid were found to show ratiometric changes in their UV-vis spectra due to Hg(2+)-mediated self-assembly. For the first time, such a property was developed into a UV-vis optical sensor for detecting Hg(2+) in aqueous solutions with high sensitively and selectively (detection limit = 1.4 nM). More importantly, this novel sensor exhibits a higher linear sensitivity over a wider concentration range compared with the fluorescence sensor based on the same N-CNPs. This work opens an exciting new avenue to explore the use of carbon nanoparticles in constructing UV-vis optical sensors for the detection of metal ions and the use of carbon nanoparticles as a new building block to self-assemble into superlattices.

Surface analysis and electrochemistry of a robust carbon-nanofiber-based electrode platform H{sub 2}O{sub 2} sensor

Energy Technology Data Exchange (ETDEWEB)

Suazo-Dávila, D.; Rivera-Meléndez, J. [NASA-MIRO Center for Advanced Nanoscale Materials (CANM), Department of Chemistry, Molecular Sciences Research Center, University of Puerto Rico, Río Piedras Campus, San Juan, PR, 00936 (United States); Koehne, J.; Meyyappan, M. [Center for Nanotechnology, NASA Ames Research Center, Moffett Field, CA 94035 (United States); Cabrera, C.R., E-mail: carlos.cabrera2@upr.edu [NASA-MIRO Center for Advanced Nanoscale Materials (CANM), Department of Chemistry, Molecular Sciences Research Center, University of Puerto Rico, Río Piedras Campus, San Juan, PR, 00936 (United States)

2016-10-30

Highlights: • Vertically aligned carbon nanofibers were intercalated with SiO{sub 2} for mechanical strength and isolation of individual electrodes. • Stable and robust electrochemical hydrogen peroxide sensor is stable and robust. • Five consecutive calibration curves were done with different hydrogen peroxide concentrations over a period of 3 days without any deterioration in the electrochemical response. • The sensor was also used for the measurement of hydrogen peroxide as one of the by-products of the reaction of cholesterol oxidase with cholesterol and the sensor response exhibited linear behavior from 50 μM to 1 mM in cholesterol concentration. • In general, the electrochemical sensor is robust, stable, and reproducible, and the detection limit and sensitivity responses were among the best when compared with the literature. - Abstract: A vertically aligned carbon nanofiber-based (VACNF) electrode platform was developed for an enzymeless hydrogen peroxide sensor. Vertical nanofibers have heights on the order of 2–3 μm, and diameters that vary from 50 to 100 nm as seen by atomic force microscopy. The VACNF was grown as individual, vertically, and freestanding structures using plasma-enhanced chemical vapor deposition. The electrochemical sensor, for the hydrogen peroxide measurement in solution, showed stability and reproducibility in five consecutive calibration curves with different hydrogen peroxide concentrations over a period of 3 days. The detection limit was 66 μM. The sensitivity for hydrogen peroxide electrochemical detection was 0.0906 mA cm{sup −2} mM{sup −1}, respectively. The sensor was also used for the measurement of hydrogen peroxide as the by-product of the reaction of cholesterol with cholesterol oxidase as a biosensor application. The sensor exhibits linear behavior in the range of 50 μM–1 mM in cholesterol concentrations. The surface analysis and electrochemistry characterization is presented.

Non-Enzymatic Glucose Sensor Composed of Carbon-Coated Nano-Zinc Oxide

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Ren-Jei Chung

2017-02-01

Full Text Available Nowadays glucose detection is of great importance in the fields of biological, environmental, and clinical analyzes. In this research, we report a zinc oxide (ZnO nanorod powder surface-coated with carbon material for non-enzymatic glucose sensor applications through a hydrothermal process and chemical vapor deposition method. A series of tests, including crystallinity analysis, microstructure observation, and electrochemical property investigations were carried out. For the cyclic voltammetric (CV glucose detection, the low detection limit of 1 mM with a linear range from 0.1 mM to 10 mM was attained. The sensitivity was 2.97 μA/cm2mM, which is the most optimized ever reported. With such good analytical performance from a simple process, it is believed that the nanocomposites composed of ZnO nanorod powder surface-coated with carbon material are promising for the development of cost-effective non-enzymatic electrochemical glucose biosensors with high sensitivity.

Improved Manufacturing Performance of Screen Printed Carbon Electrodes through Material Formulation.

Science.gov (United States)

Jewell, Eifion; Philip, Bruce; Greenwood, Peter

2016-06-27

Printed carbon graphite materials are the primary common component in the majority of screen printed sensors. Screen printing allows a scalable manufacturing solution, accelerating the means by which novel sensing materials can make the transition from laboratory material to commercial product. A common bottleneck in any thick film printing process is the controlled drying of the carbon paste material. A study has been undertaken which examines the interaction between material solvent, printed film conductivity and process consistency. The study illustrates that it is possible to reduce the solvent boiling point to significantly increase process productivity while maintaining process consistency. The lower boiling point solvent also has a beneficial effect on the conductivity of the film, reducing the sheet resistance. It is proposed that this is a result of greater film stressing increasing charge percolation through greater inter particle contact. Simulations of material performance and drying illustrate that a multi layered printing provides a more time efficient manufacturing method. The findings have implications for the volume manufacturing of the carbon sensor electrodes but also have implications for other applications where conductive carbon is used, such as electrical circuits and photovoltaic devices.

Development of carbon nanotube modified cement paste with microencapsulated phase-change material for structural-functional integrated application.

Science.gov (United States)

Cui, Hongzhi; Yang, Shuqing; Memon, Shazim Ali

2015-04-10

Microencapsulated phase-change materials (MPCM) can be used to develop a structural-functional integrated cement paste having high heat storage efficiency and suitable mechanical strength. However, the incorporation of MPCM has been found to degrade the mechanical properties of cement based composites. Therefore, in this research, the effect of carbon nanotubes (CNTs) on the properties of MPCM cement paste was evaluated. Test results showed that the incorporation of CNTs in MPCM cement paste accelerated the cement hydration reaction. SEM micrograph showed that CNTs were tightly attached to the cement hydration products. At the age of 28 days, the percentage increase in flexural and compressive strength with different dosage of CNTs was found to be up to 41% and 5% respectively. The optimum dosage of CNTs incorporated in MPCM cement paste was found to be 0.5 wt %. From the thermal performance test, it was found that the cement paste panels incorporated with different percentages of MPCM reduced the temperature measured at the center of the room by up to 4.6 °C. Inverse relationship was found between maximum temperature measured at the center of the room and the dosage of MPCM.

Development of Carbon Nanotube Modified Cement Paste with Microencapsulated Phase-Change Material for Structural–Functional Integrated Application

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Hongzhi Cui

2015-04-01

Full Text Available Microencapsulated phase-change materials (MPCM can be used to develop a structural–functional integrated cement paste having high heat storage efficiency and suitable mechanical strength. However, the incorporation of MPCM has been found to degrade the mechanical properties of cement based composites. Therefore, in this research, the effect of carbon nanotubes (CNTs on the properties of MPCM cement paste was evaluated. Test results showed that the incorporation of CNTs in MPCM cement paste accelerated the cement hydration reaction. SEM micrograph showed that CNTs were tightly attached to the cement hydration products. At the age of 28 days, the percentage increase in flexural and compressive strength with different dosage of CNTs was found to be up to 41% and 5% respectively. The optimum dosage of CNTs incorporated in MPCM cement paste was found to be 0.5 wt %. From the thermal performance test, it was found that the cement paste panels incorporated with different percentages of MPCM reduced the temperature measured at the center of the room by up to 4.6 °C. Inverse relationship was found between maximum temperature measured at the center of the room and the dosage of MPCM.

A photovoltaic self-powered gas sensor based on a single-walled carbon nanotube/Si heterojunction.

Science.gov (United States)

Liu, L; Li, G H; Wang, Y; Wang, Y Y; Li, T; Zhang, T; Qin, S J

2017-12-07

We present a novel photovoltaic self-powered gas sensor based on a p-type single-walled carbon nanotube (SWNT) and n-type silicon (n-Si) heterojunction. The energy from visible light suffices to drive the device owing to a built-in electric field (BEF) induced by the differences between the Fermi levels of SWNTs and n-Si.

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

A novel way for detection of antiparkinsonism drug entacapone via electrodeposition of silver nanoparticles/functionalized multi-walled carbon nanotubes as an amperometric sensor

Energy Technology Data Exchange (ETDEWEB)

Baghayeri, Mehdi, E-mail: m.baghayeri@hsu.ac.ir [Department of Chemistry, Faculty of Science, Hakim Sabzevari University, P.O. Box 397, Sabzevar (Iran, Islamic Republic of); Tehrani, Maliheh Barazandeh [Department of Medicinal Chemistry, Faculty of Pharmacy, Pharmaceutical Research Center, Tehran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Amiri, Amirhassan; Maleki, Behrooz; Farhadi, Samaneh [Department of Chemistry, Faculty of Science, Hakim Sabzevari University, P.O. Box 397, Sabzevar (Iran, Islamic Republic of)

2016-09-01

Silver (Ag) nanoparticles were electrochemically deposited on the film of a metformin functionalized multi-walled carbon nanotube modified glassy carbon electrode (Met-MWCNT/GCE), which fabricated an Ag@Met-MWCNT nanocomposite sensor (Ag@Met-MWCNT/GCE) to detect entacapone (ENT). The Ag@Met-MWCNT nanocomposite was characterized by field emission scanning electrochemical microscopy (FESEM), X-ray diffraction (XRD) analysis, FT-IR and electrochemical tests. The modified electrode showed a large electrocatalytic activity for reduction of ENT. This improved activity indicates that Met@MWCNT plays a crucial role in the dispersion and stabilization of Ag nanoparticles on GCE. Under the optimized conditions the linear range for the detection of the ENT was obtained to be 0.05 to 70.0 μM with a low detection limit of 15.3 nM. The proposed sensor can effectively analyse ENT concentration in pharmaceutical formulations and human urine samples, avoiding interference, and is a promising ENT sensor due to good sensitivity, stability and low cost. - Graphical abstract: Schematic graph for fabrication and application of sensor. Display Omitted - Highlights: • Silver nanoparticles were electrochemically deposited on the modified glassy carbon electrode. • The modified electrode showed a large electrocatalytic activity for reduction of entacapone. • The proposed sensor can effectively analyse entacapone concentration in pharmaceutical formulations and human urine samples.

Nitric oxide sensor based on carbon fiber covered with nickel porphyrin layer deposited using optimized electropolymerization procedure

Czech Academy of Sciences Publication Activity Database

Hrbáč, J.; Gregor, Č.; Machová, M.; Králová, Jana; Bystroň, T.; Číž, Milan; Lojek, Antonín

2007-01-01

Roč. 71, č. 1 (2007), s. 46-53 ISSN 1567-5394 Institutional research plan: CEZ:AV0Z50040507; CEZ:AV0Z50040702 Keywords : nitric oxide sensor * electropolymerization * carbon fibre Subject RIV: BO - Biophysics Impact factor: 2.992, year: 2007

Voltammetric determination of ultratrace levels of cerium(III) using a carbon paste electrode modified with nano-sized cerium-imprinted polymer and multiwalled carbon nanotubes

International Nuclear Information System (INIS)

Alizadeh, Taher; Ganjali, Mohammad Reza; Akhoundian, Maede; Norouzi, Parviz

2016-01-01

A carbon paste electrode was modified with a Ce(III)-imprinted polymer (Ce-IP) and used for voltammetric determination of Ce(III) ions in real water samples. Precipitation polymerization was used for synthesis of the nano-sized Ce-IP from vinylpyridine and methacrylic acid (acting as the complexing ligands and functional monomers), divinylbenzene (cross-linker) and AIBN as the radical starter. The Ce-IP was characterized by scanning electron microscopy and zeta potentials. A carbon paste electrode (CPE) was then impregnated with the Ce-IP and used for the extraction and subsequent determination of Ce(III). Oxidative square wave voltammetry showed the electrode to give a significantly better response than an electrode modified with the non-imprinted polymer. The addition of multiwalled carbon nanotubes to the Ce-IP-modified electrode further improves the signal, thereby increasing the sensitivity of the method. The effects of electrode composition, extraction pH value, volume and time were optimized. The electrode, if operated at a voltage of 1.05 V (vs. Ag/AgCl), displays a linear response to Ce(III) in the 1.0 μM to 25 pM concentration range, and the detection limit is 10 pM (at an S/N ratio of 3). The relative standard deviation of 5 separate determinations is 3.1 %. The method was successfully applied to the determination of Ce(III) in the spiked samples of drinking water and sea water. (author)

Development of Microfabricated Chemical Gas Sensors and Sensor Arrays for Aerospace Applications

Science.gov (United States)

Hunter, G. W.; Neudeck, P. G.; Fralick, G.; Thomas, V.; Liu, C. C.; Wu, W. H.; Ward, B.; Makel, D.

2002-01-01

Aerospace applications require the development of chemical sensors with capabilities beyond those of commercially available sensors. In particular, factors such as minimal sensor size, weight, and power consumption are particularly important. Development areas which have potential aerospace applications include launch vehicle leak detection, engine health monitoring, fire detection, and environmental monitoring. Sensor development for these applications is based on progress in three types of technology: 1) Micromachining and microfabrication (Microsystem) technology to fabricate miniaturized sensors. 2) The use of nanocrystalline materials to develop sensors with improved stability combined with higher sensitivity. 3) The development of high temperature semiconductors, especially silicon carbide. However, due to issues of selectivity and cross-sensitivity, individual sensors are limited in the amount of information that they can provide in environments that contain multiple chemical species. Thus, sensor arrays are being developed to address detection needs in such multi-species environments. This paper discusses the needs of space applications as well as the point-contact sensor technology and sensor arrays being developed to address these needs. Sensors to measure hydrogen, hydrocarbons, hydrazine, nitrogen oxides (NO,), carbon monoxide, oxygen, and carbon dioxide are being developed as well as arrays for leak, fire, and emissions detection. Demonstrations of the technology will also be discussed. It is concluded that microfabricated sensor technology has significant potential for use in a range of aerospace applications.

Variability in and agreement between modeled and personal continuously measured black carbon levels using novel smartphone and sensor technologies.

Science.gov (United States)

Nieuwenhuijsen, Mark J; Donaire-Gonzalez, David; Rivas, Ioar; de Castro, Montserrat; Cirach, Marta; Hoek, Gerard; Seto, Edmund; Jerrett, Michael; Sunyer, Jordi

2015-03-03

Novel technologies, such as smartphones and small personal continuous air pollution sensors, can now facilitate better personal estimates of air pollution in relation to location. Such information can provide us with a better understanding about whether and how personal exposures relate to residential air pollution estimates, which are normally used in epidemiological studies. The aims of this study were to examine (1) the variability in personal air pollution levels during the day and (2) the relationship between modeled home and school estimates and continuously measured personal air pollution exposure levels in different microenvironments (e.g., home, school, and commute). We focused on black carbon as an indicator of traffic-related air pollution. We recruited 54 school children (aged 7-11) from 29 different schools around Barcelona as part of the BREATHE study, an epidemiological study of the relation between air pollution and brain development. For 2 typical week days during 2012-2013, the children were given a smartphone with CalFit software to obtain information on their location and physical activity level and a small sensor, the micro-aethalometer model AE51, to measure their black carbon levels simultaneously and continuously. We estimated their home and school exposure to PM2.5 filter absorbance, which is well-correlated with black carbon, using a temporally adjusted PM2.5 absorbance land use regression (LUR) model. We found considerable variation in the black carbon levels during the day, with the highest levels measured during commuting periods (geometric mean = 2.8 μg/m(3)) and the lowest levels at home (geometric mean = 1.3 μg/m(3)). Hourly temporally adjusted LUR model estimates for the home and school showed moderate to good correlation with measured personal black carbon levels at home and school (r = 0.59 and 0.68, respectively) and lower correlation with commuting trips (r = 0.32 and 0.21, respectively). The correlation between modeled home

Use of carbon paste electrodes for the voltammetric detection of silver leached from the oxidative dissolution of silver nanoparticles

Science.gov (United States)

Mullaugh, Katherine M.; Pearce, Olivia M.

2017-04-01

The widespread use of silver nanoparticles (Ag NPs) in consumer goods has raised concerns about the release of silver in environmental waters. Of particular concern is the oxidative dissolution of Ag NPs to release Ag+ ions, which are highly toxic to many aquatic organisms. Here, we have investigated the application of differential pulse stripping voltammetry (DPSV) with carbon paste electrodes (CPEs) in monitoring the oxidation of Ag NPs. Using a commercially available, unmodified carbon paste and 60-s deposition times, a detection limit of 3 nM Ag+ could be achieved. We demonstrate its selectivity for free Ag+ ions over Ag nanoparticles, allowing for analysis of the oxidation of Ag NPs without the need for separation of ions and nanoparticles prior to analysis. We applied this approach to investigate the effect of pH in the oxidative dissolution of Ag NPs, demonstrating the usefulness of CPEs in studies of this type.

A new sensor based on glassy carbon electrode modified with nanocomposite for simultaneous determination of acetaminophen, ascorbic acid and uric acid

Directory of Open Access Journals (Sweden)

Mohammad Afrasiabi

2016-09-01

Full Text Available A chemically-modified electrode has been constructed based on a single walled carbon nanotube/chitosan/room temperature ionic liquid nanocomposite modified glassy carbon electrode (SWCNTs–CHIT–RTIL/GCE. It was demonstrated that this sensor could be used for simultaneous determination of acetaminophen (ACT, uric acid (URI and ascorbic acid (ASC. The measurements were carried out by application of differential pulse voltammetry (DPV, cyclic voltammetry (CV and chronoamperometry (CA methods. Electrochemical studies suggested that the RTIL and SWCNTs provided a synergistic augmentation that can increase current responses by improvement of electron transfers of these compounds on the electrode surface. The presence of the CHIT in the modified electrode can enhance the repeatability of the sensor by its antifouling effect. The modified electrode showed electrochemical responses with high sensitivity for ACT, URI and ASC determination, which makes it a suitable sensor for simultaneous sub-μmol L−1 detection of ACT, URI and ASC in aqueous solutions. The analytical performance of this sensor has been evaluated for detection of ACT, URI and ASC in human serum and urine with satisfactory results.

LIBS Sensor for Sub-surface CO2 Leak Detection in Carbon Sequestration

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Jinesh JAIN

2017-07-01

Full Text Available Monitoring carbon sequestration poses numerous challenges to the sensor community. For example, the subsurface environment is notoriously harsh, with large potential mechanical, thermal, and chemical stresses, making long-term stability and survival a challenge to any potential in situ monitoring method. Laser induced breakdown spectroscopy (LIBS has been demonstrated as a promising technology for chemical monitoring of harsh environments and hard to reach places. LIBS has a real- time monitoring capability and can be used for the elemental and isotopic analysis of solid, liquid, and gas samples. The flexibility of the probe design and the use of fiber- optics has made LIBS particularly suited for remote measurements. The paper focuses on developing a LIBS instrument for downhole high-pressure, high-temperature brine experiments, where CO2 leakage could result in changes in the trace mineral composition of an aquifer. The progress in fabricating a compact, robust, and simple LIBS sensor for widespread subsurface leak detection is presented.

Carbon-dot-based fluorescent turn-on sensor for selectively detecting sulfide anions in totally aqueous media and imaging inside live cells.

Science.gov (United States)

Hou, Xianfeng; Zeng, Fang; Du, Fangkai; Wu, Shuizhu

2013-08-23

Sulfide anions are generated not only as a byproduct from industrial processes but also in biosystems. Hence, robust fluorescent sensors for detecting sulfide anions which are fast-responding, water soluble and biocompatible are highly desirable. Herein, we report a carbon-dot-based fluorescent sensor, which features excellent water solubility, low cytotoxicity and a short response time. This sensor is based on the ligand/Cu(II) approach so as to achieve fast sensing of sulfide anions. The carbon dot (CD) serves as the fluorophore as well as the anchoring site for the ligands which bind with copper ions. For this CD-based system, as copper ions bind with the ligands which reside on the surface of the CD, the paramagnetic copper ions efficiently quench the fluorescence of the CD, affording the system a turn-off sensor for copper ions. More importantly, the subsequently added sulfide anions can extract Cu(2+) from the system and form very stable CuS with Cu(2+), resulting in fluorescence enhancement and affording the system a turn-on sensor for sulfide anions. This fast-responding and selective sensor can operate in totally aqueous solution or in physiological milieu with a low detection limit of 0.78 μM. It displays good biocompatibility, and excellent cell membrane permeability, and can be used to monitor S(2-) levels in running water and living cells.

Fabrication of Nonenzymatic Glucose Sensors Based on Multiwalled Carbon Nanotubes with Bimetallic Pt-M (M = Ru and Sn Catalysts by Radiolytic Deposition

Directory of Open Access Journals (Sweden)

Sun-Young Kwon

2012-01-01

Full Text Available Nonenzymatic glucose sensors employing multiwalled carbon nanotubes (MWNTs with highly dispersed Pt-M (M = Ru and Sn nanoparticles (Pt-M@PVP-MWNTs were fabricated by radiolytic deposition. The Pt-M nanoparticles on the MWNTs were characterized by transmittance electron microscopy, elemental analysis, and X-ray diffraction. They were found to be well dispersed and to exhibit alloy properties on the MWNT support. Electrochemical testing showed that these nonenzymatic sensors had larger currents (mA than that of a bare glassy carbon (GC electrode and one modified with MWNTs. The sensitivity (A mM−1, linear range (mM, and detection limit (mM (S/N = 3 of the glucose sensor with the Pt-Ru catalyst in NaOH electrolyte were determined as 18.0, 1.0–2.5, 0.7, respectively. The corresponding data of the sensor with Pt-Sn catalyst were 889.0, 1.00–3.00, and 0.3, respectively. In addition, these non-enzymatic sensors can effectively avoid interference arising from the oxidation of the common interfering species ascorbic acid and uric acid in NaOH electrolyte. The experimental results show that such sensors can be applied in the detection of glucose in commercial red wine samples.

Imparting improvements in electrochemical sensors: evaluation of different carbon blacks that give rise to significant improvement in the performance of electroanalytical sensing platforms

International Nuclear Information System (INIS)

Vicentini, Fernando Campanhã; Ravanini, Amanda E.; Figueiredo-Filho, Luiz C.S.; Iniesta, Jesús; Banks, Craig E.; Fatibello-Filho, Orlando

2015-01-01

Three different carbon black materials have been evaluated as a potential modifier, however, only one demonstrated an improvement in the electrochemical properties. The carbon black structures were characterised with SEM, XPS and Raman spectroscopy and found to be very similar to that of amorphous graphitic materials. The modifications utilised were constructed by three different strategies (using ultrapure water, chitosan and dihexadecylphosphate). The fabricated sensors are electrochemically characterised using N,N,N',N'-tetramethyl-para-phenylenediamine and both inner-sphere and outer-sphere redox probes, namely potassium ferrocyanide(II) and hexaammineruthenium(III) chloride, in addition to the biologically relevant and electroactive analytes, dopamine (DA) and acetaminophen (AP). Comparisons are made with an edge-plane pyrolytic graphite and glassy-carbon electrode and the benefits of carbon black implemented as a modifier for sensors within electrochemistry are explored, as well as the characterisation of their electroanalytical performances. We reveal significant improvements in the electrochemical performance (excellent sensitivity, faster heterogeneous electron transfer rate (HET)) over that of a bare glassy-carbon and edge-plane pyrolytic graphite electrode and thus suggest that there are substantial advantages of using carbon black as modifier in the fabrication of electrochemical based sensors. Such work is highly important and informative for those working in the field of electroanalysis where electrochemistry can provide portable, rapid, reliable and accurate sensing protocols (bringing the laboratory into the field), with particular relevance to those searching for new electrode materials

Micro-Raman spectroscopy investigation of the carbonation reaction in a lime paste produced with a traditional technology

Czech Academy of Sciences Publication Activity Database

Ševčík, Radek; Mácová, Petra; Sotiriadis, Konstantinos; Pérez-Estébanez, Marta; Viani, Alberto; Šašek, Petr

2016-01-01

Roč. 47, č. 12 (2016), s. 1452-1457 ISSN 0377-0486 R&D Projects: GA ČR(CZ) GP14-20374P; GA MŠk(CZ) LO1219 Keywords : calcite * carbonation * lime paste * micro-Raman spectroscopy * portlandite Subject RIV: AL - Art, Architecture, Cultural Heritage Impact factor: 2.969, year: 2016 http://onlinelibrary.wiley.com/doi/10.1002/jrs.4929/full

Electrochemically decorated ZnTe nanodots on single-walled carbon nanotubes for room-temperature NO2 sensor application.

Science.gov (United States)

Kim, Donguk; Park, Ki-Moon; Shanmugam, Rajakumar; Yoo, Bongyoung

2014-11-01

A gas sensor with ZnTe nanodot-modified single-walled carbon nanotubes (SWCNTs) is demonstrated for NO2 detection at room temperature. ZnTe nanodots are electrochemically deposited in an aqueous solution containing ZnSO4, TeO2 and citrate. A deposition potential range of ZnTe formation of -0.65 to -0.9 V is determined by cyclic voltammetry, and an intermetallic ZnTe compound is formed at above 50 degrees C bath. SWCNT-based sensors show the highly sensitive response down to 1 ppm NO2 gas at room temperature. In particular, the sensitivity of ZnTe nanodot-modified SWCNTs is increased by 6 times as compared to that of pristine SWCNT sensors. A selectivity test of SWCNT-ZnTe nanodots sensors is carried out with ammonia gas (NH3) and methanol vapor (MeOH), and the result confirms an excellent selectivity to NO2 gas.

A fluorescent sensor for selective detection of cyanide using mesoporous graphitic carbon(IV) nitride.

Science.gov (United States)

Lee, Eun Zoo; Lee, Sun Uk; Heo, Nam-Su; Stucky, Galen D; Jun, Young-Si; Hong, Won Hi

2012-04-25

A turn-on fluorescence sensor, Cu(2+)-c-mpg-C(3)N(4), was developed for detection of CN(-) in aqueous solution by simply mixing cubic mesoporous graphitic carbon nitride (c-mpg-C(3)N(4)) and aqueous solution of Cu(NO(3))(2). The highly sensitive detection of CN(-) with a detection limit of 80 nM is not only possible in aqueous solution but also in human blood serum.

Cu-modified carbon spheres/reduced graphene oxide as a high sensitivity of gas sensor for NO2 detection at room temperature

Science.gov (United States)

Su, Zhibin; Tan, Li; Yang, Ruiqiang; Zhang, Yu; Tao, Jin; Zhang, Nan; Wen, Fusheng

2018-03-01

Nitrogen dioxide (NO2) as one of the most serious air pollution is harmful to people's health, therefore high-performance gas sensors is critically needed. Here, Cu-modified carbon spheres/reduced graphene oxide (Cu@CS/RGO) composite have been prepared as NO2 gas sensor material. Carbon sphere in the interlayer of RGO can increase the specific surface area of RGO. Copper nanoparticles decorated on the surface of CS can effectively enhance the adsorption activity of RGO as supplier of free electrons. The experimental results showed that its particular structure improved the gas sensitivity of RGO at different NO2 concentrations at room temperature.

Comparison of two fabricated aptasensors based on modified carbon paste/oleic acid and magnetic bar carbon paste/Fe3O4@oleic acid nanoparticle electrodes for tetracycline detection.

Science.gov (United States)

Jahanbani, Shahriar; Benvidi, Ali

2016-11-15

In this research, we have improved two aptasensors based on a modified carbon paste electrode (CPE) with oleic acid (OA), and a magnetic bar carbon paste electrode (MBCPE) with Fe3O4 magnetic nanoparticles and oleic acid (OA). After the immobilization process of anti-TET at the electrode surfaces, the aptasensors were named CPE/OA/anti-TET and MBCPE/Fe3O4NPs/OA/anti-TET respectively. In this paper, the detection of tetracycline is compared using CPE/OA/anti-TET and MBCPE/Fe3O4NPs/OA/anti-TET aptasensors. These modified electrodes were characterized by infrared spectroscopy (IR), scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), UV-vis spectroscopy, and voltammetric methods. The linear range and the detection limit for TET with the CPE/OA/anti-TET aptasensor were found to be 1.0×10(-12)-1.0×10(-7)M and 3.0×10(-13)M respectively by EIS method. The linear range and the detection limit for TET with the CPE/OA/anti-TET aptasensor were found to be 1.0×10(-10)-1.0×10(-7)M with a limit of detection of 2.9×10(-11)M using differential pulse voltammetry (DPV) technique. The MBCPE/Fe3O4NPs/OA/anti-TET aptasensor was used for determination of TET, and a liner range of 1.0×10(-14)-1.0×10(-6)M with a detection limit of 3.8×10(-15)M was obtained by EIS method. Also, the linear range and detection limit of 1.0×10(-12)-1.0×10(-6)M and 3.1×10(-13)M respectively, were obtained for MBCPE/Fe3O4NPs/OA/anti-TET aptasensor using DPV. The proposed aptasensors were applied for determination of tetracycline in some real samples such as drug, milk, honey and blood serum samples. Copyright © 2016 Elsevier B.V. All rights reserved.

From carbonization to decarbonization?-Past trends and future scenarios for China's CO2 emissions

International Nuclear Information System (INIS)

Steckel, Jan Christoph; Jakob, Michael; Marschinski, Robert; Luderer, Gunnar

2011-01-01

Along the lines of the Kaya identity, we perform a decomposition analysis of historical and projected emissions data for China. We compare the results with reduction requirements implied by globally cost-effective mitigation scenarios and official Chinese policy targets. For the years 1971-2000 we find that the impact of high economic growth on emissions was partially compensated by a steady fall in energy intensity. However, the end - and even reversal - of this downward trend, along with a rising carbon intensity of energy, resulted in rapid emission growth during 2000-2007. By applying an innovative enhanced Kaya-decomposition method, we also show how the persistent increase in the use of coal has caused carbon intensity to rise throughout the entire time-horizon of the analysis. These insights are then compared to model scenarios for future energy system developments generated by the ReMIND-R model. The analysis reaffirms China's indispensable role in global efforts to implement any of three exemplary stabilization targets (400, 450, or 500 ppm CO 2 -only), and underscore the increasing importance of carbon intensity for the more ambitious targets. Finally, we compare China's official targets for energy intensity and carbon intensity of GDP to projections for global cost-effective stabilization scenarios, finding them to be roughly compatible in the short-to-mid-term. - Highlights: → An extended Kaya-decomposition is applied to historical data and ReMIND-R scenario results for China. → Reversing a historic trend, energy intensity has increased in recent years. → The contribution of coal in increasing carbon intensity and emissions has been constant in the past. → Decarbonization becomes increasingly important with increasingly ambitious climate targets. → Chinese targets for carbon intensity of GDP are in line with a 450 ppm CO 2 -only stabilization scenario.

Electrochemical behavior of labetalol at an ionic liquid modified carbon paste electrode and its electrochemical determination

Directory of Open Access Journals (Sweden)

Zhang Yan-Mei

2013-01-01

Full Text Available Electrochemical behavior of labetalol (LBT at carbon paste electrode (CPE and an ionic liquid1-benzyl-3-methylimidazolehexafluorophosphate([BnMIM]PF6modified carbon paste electrode([BnMIM]PF6/CPEin Britton-Robinson buffer solution (pH 2.0 was investigated by cyclic voltammetry (CV and square wave voltammetric (SWV. The experimental results showed that LBT at both the bare CPE and [BnMIM]PF6/CPEshowed an irreversible oxidation process, but at [BnMIM]PF6/CPE its oxidation peak current increased greatly and the oxidation peak potential shifted negatively. The electrode reaction process is a diffusion-controlled process involving one electron transferring accompanied by a participation of one proton at [BnMIM]PF6/CPE. At the same time, the electrochemical kinetic parameters were determined. Under the optimized electrochemical experimental conditions, the oxidation peak currents were proportional to LBT concentration in the range of 7.0 x 10-6-1.0 x 10-4 mol L-1 with the limit of detection(LOD, S/N=3 of 4.810 x 10-8 mol L-1and the limit of quantification(LOQ, S/N=10 of 1.60 x 10-7 mol L-1, respectively. The proposed method was successfully applied in the determination of LBT content in commercial tablet samples.

Synthesis, Characterization and Utility of Carbon Nanotube Based Hybrid Sensors in Bioanalytical Applications

Science.gov (United States)

Badhulika, Sushmee

The detection of gaseous analytes and biological molecules is of prime importance in the fields of environmental pollution control, food and water - safety and analysis; and medical diagnostics. This necessitates the development of advanced and improved technology that is reliable, inexpensive and suitable for high volume production. The conventional sensors are often thin film based which lack sensitivity due to the phenomena of current shunting across the charge depleted region when an analyte binds with them. One dimensional (1-D) nanostructures provide a better alternative for sensing applications by eliminating the issue of current shunting due to their 1-D geometries and facilitating device miniaturization and low power operations. Carbon nanotubes (CNTs) are 1-D nanostructures that possess small size, high mechanical strength, high electrical and thermal conductivity and high specific area that have resulted in their wide spread applications in sensor technology. To overcome the issue of low sensitivity of pristine CNTs and to widen their scope, hybrid devices have been fabricated that combine the synergistic properties of CNTs along with materials like metals and conducting polymers (CPs). CPs exhibit electronic, magnetic and optical properties of metals and semiconductors while retaining the processing advantages of polymers. Their high chemical sensitivity, room temperature operation and tunable charge transport properties has made them ideal for use as transducing elements in chemical sensors. In this dissertation, various CNT based hybrid devices such as CNT-conducting polymer and graphene-CNT-metal nanoparticles based sensors have been developed and demonstrated towards bioanalytical applications such as detection of volatile organic compounds (VOCs) and saccharides. Electrochemical polymerization enabled the synthesis of CPs and metal nanoparticles in a simple, cost effective and controlled way on the surface of CNT based platforms thus resulting in

The Retentive Strength of Cemented Zirconium Oxide Crowns after Dentin Pretreatment with Desensitizing Paste Containing 8% Arginine and Calcium Carbonate

Science.gov (United States)

Pilo, Raphael; Harel, Noga; Nissan, Joseph; Levartovsky, Shifra

2016-01-01

The effect of dentin pretreatment with Desensitizing Paste containing 8% arginine and calcium carbonate on the retention of zirconium oxide (Y-TZP) crowns was tested. Forty molar teeth were mounted and prepared using a standardized protocol. Y-TZP crowns were produced using computer-aided design and computer-aided manufacturing (CAD-CAM) technology. The 40 prepared teeth were either pretreated with Desensitizing Paste or not pretreated. After two weeks, each group was subdivided into two groups, cemented with either Resin Modified Glass Ionomer Cement (RMGIC) or Self Adhesive Resin Cement (SARC)). Prior to cementation, the surface areas of the prepared teeth were measured. After aging, the cemented crown-tooth assemblies were tested for retentive strength using a universal testing machine. The debonded surfaces of the teeth and crowns were examined microscopically at 10× magnification. Pretreating the dentin surfaces with Desensitizing Paste prior to cementation did not affect the retention of the Y-TZP crowns. The retentive values for RMGIC (3.04 ± 0.77 MPa) were significantly higher than those for SARC (2.28 ± 0.58 MPa). The predominant failure modes for the RMGIC and SARC were adhesive cement-dentin and adhesive cement-crown, respectively. An 8.0% arginine and calcium carbonate in-office desensitizing paste can be safely used to reduce post-cementation sensitivity without reducing the retentive strength of Y-TZP crowns. PMID:27023532

The Retentive Strength of Cemented Zirconium Oxide Crowns after Dentin Pretreatment with Desensitizing Paste Containing 8% Arginine and Calcium Carbonate

Directory of Open Access Journals (Sweden)

Raphael Pilo

2016-03-01

Full Text Available The effect of dentin pretreatment with Desensitizing Paste containing 8% arginine and calcium carbonate on the retention of zirconium oxide (Y-TZP crowns was tested. Forty molar teeth were mounted and prepared using a standardized protocol. Y-TZP crowns were produced using computer-aided design and computer-aided manufacturing (CAD-CAM technology. The 40 prepared teeth were either pretreated with Desensitizing Paste or not pretreated. After two weeks, each group was subdivided into two groups, cemented with either Resin Modified Glass Ionomer Cement (RMGIC or Self Adhesive Resin Cement (SARC. Prior to cementation, the surface areas of the prepared teeth were measured. After aging, the cemented crown-tooth assemblies were tested for retentive strength using a universal testing machine. The debonded surfaces of the teeth and crowns were examined microscopically at 10× magnification. Pretreating the dentin surfaces with Desensitizing Paste prior to cementation did not affect the retention of the Y-TZP crowns. The retentive values for RMGIC (3.04 ± 0.77 MPa were significantly higher than those for SARC (2.28 ± 0.58 MPa. The predominant failure modes for the RMGIC and SARC were adhesive cement-dentin and adhesive cement-crown, respectively. An 8.0% arginine and calcium carbonate in-office desensitizing paste can be safely used to reduce post-cementation sensitivity without reducing the retentive strength of Y-TZP crowns.

Potentiometric stripping analysis of antimony based on carbon paste electrode modified with hexathia crown ether and rice husk

International Nuclear Information System (INIS)

Gadhari, Nayan S.; Sanghavi, Bankim J.; Srivastava, Ashwini K.

2011-01-01

Highlights: → Potentiometric stripping analysis (PSA) employed for the determination of antimony. → Hexathia-18C6 and rice husk modified carbon paste electrode developed for the analysis. → Lowest detection limit obtained for the determination of Sb(III) using PSA. → Analysis of Sb in pharmaceutical formulations, human hair, blood serum, urine and sea water. → Rice husk used as a modifier for the first time in electrochemistry. - Abstract: An electrochemical method based on potentiometric stripping analysis (PSA) employing a hexathia 18C6 (HT18C6) and rice husk (RH) modified carbon paste electrode (HT18C6-RH-CPE) has been proposed for the subnanomolar determination of antimony. The characterization of the electrode surface has been carried out by means of scanning electron microscopy, cyclic voltammetry, electrochemical impedance spectroscopy and chronocoulometry. By employing HT18C6-RH-CPE, a 12-fold enhancement in the PSA signal (dt/dE) was observed as compared to plain carbon paste electrode (PCPE). Under the optimized conditions, dt/dE (s V -1 ) was proportional to the Sb(III) concentration in the range of 1.42 x 10 -8 to 6.89 x 10 -11 M (r = 0.9944) with the detection limit (S/N = 3) of 2.11 x 10 -11 M. The practical analytical utilities of the modified electrode were demonstrated by the determination of antimony in pharmaceutical formulations, human hair, sea water, urine and blood serum samples. The prepared modified electrode showed several advantages, such as simple preparation method, high sensitivity, very low detection limit and excellent reproducibility. Moreover, the results obtained for antimony analysis in commercial and real samples using HT18C6-RH-CPE and those obtained by inductively coupled plasma-atomic emission spectrometry (ICP-AES) are in agreement at the 95% confidence level.

Potentiometric stripping analysis of antimony based on carbon paste electrode modified with hexathia crown ether and rice husk

Energy Technology Data Exchange (ETDEWEB)

Gadhari, Nayan S.; Sanghavi, Bankim J. [Department of Chemistry, University of Mumbai, Vidyanagari, Santacruz (East), Mumbai 400098 (India); Srivastava, Ashwini K., E-mail: aksrivastava@chem.mu.ac.in [Department of Chemistry, University of Mumbai, Vidyanagari, Santacruz (East), Mumbai 400098 (India)

2011-10-03

Highlights: {yields} Potentiometric stripping analysis (PSA) employed for the determination of antimony. {yields} Hexathia-18C6 and rice husk modified carbon paste electrode developed for the analysis. {yields} Lowest detection limit obtained for the determination of Sb(III) using PSA. {yields} Analysis of Sb in pharmaceutical formulations, human hair, blood serum, urine and sea water. {yields} Rice husk used as a modifier for the first time in electrochemistry. - Abstract: An electrochemical method based on potentiometric stripping analysis (PSA) employing a hexathia 18C6 (HT18C6) and rice husk (RH) modified carbon paste electrode (HT18C6-RH-CPE) has been proposed for the subnanomolar determination of antimony. The characterization of the electrode surface has been carried out by means of scanning electron microscopy, cyclic voltammetry, electrochemical impedance spectroscopy and chronocoulometry. By employing HT18C6-RH-CPE, a 12-fold enhancement in the PSA signal (dt/dE) was observed as compared to plain carbon paste electrode (PCPE). Under the optimized conditions, dt/dE (s V{sup -1}) was proportional to the Sb(III) concentration in the range of 1.42 x 10{sup -8} to 6.89 x 10{sup -11} M (r = 0.9944) with the detection limit (S/N = 3) of 2.11 x 10{sup -11} M. The practical analytical utilities of the modified electrode were demonstrated by the determination of antimony in pharmaceutical formulations, human hair, sea water, urine and blood serum samples. The prepared modified electrode showed several advantages, such as simple preparation method, high sensitivity, very low detection limit and excellent reproducibility. Moreover, the results obtained for antimony analysis in commercial and real samples using HT18C6-RH-CPE and those obtained by inductively coupled plasma-atomic emission spectrometry (ICP-AES) are in agreement at the 95% confidence level.

Use of carbon paste electrodes for the voltammetric detection of silver leached from the oxidative dissolution of silver nanoparticles

International Nuclear Information System (INIS)

Mullaugh, Katherine M.; Pearce, Olivia M.

2017-01-01

The widespread use of silver nanoparticles (Ag NPs) in consumer goods has raised concerns about the release of silver in environmental waters. Of particular concern is the oxidative dissolution of Ag NPs to release Ag"+ ions, which are highly toxic to many aquatic organisms. Here, we have investigated the application of differential pulse stripping voltammetry (DPSV) with carbon paste electrodes (CPEs) in monitoring the oxidation of Ag NPs. Using a commercially available, unmodified carbon paste and 60-s deposition times, a detection limit of 3 nM Ag"+ could be achieved. We demonstrate its selectivity for free Ag"+ ions over Ag nanoparticles, allowing for analysis of the oxidation of Ag NPs without the need for separation of ions and nanoparticles prior to analysis. We applied this approach to investigate the effect of pH in the oxidative dissolution of Ag NPs, demonstrating the usefulness of CPEs in studies of this type.

Use of carbon paste electrodes for the voltammetric detection of silver leached from the oxidative dissolution of silver nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Mullaugh, Katherine M., E-mail: mullaughkm@cofc.edu; Pearce, Olivia M. [College of Charleston, Department of Chemistry & Biochemistry (United States)

2017-04-15

The widespread use of silver nanoparticles (Ag NPs) in consumer goods has raised concerns about the release of silver in environmental waters. Of particular concern is the oxidative dissolution of Ag NPs to release Ag{sup +} ions, which are highly toxic to many aquatic organisms. Here, we have investigated the application of differential pulse stripping voltammetry (DPSV) with carbon paste electrodes (CPEs) in monitoring the oxidation of Ag NPs. Using a commercially available, unmodified carbon paste and 60-s deposition times, a detection limit of 3 nM Ag{sup +} could be achieved. We demonstrate its selectivity for free Ag{sup +} ions over Ag nanoparticles, allowing for analysis of the oxidation of Ag NPs without the need for separation of ions and nanoparticles prior to analysis. We applied this approach to investigate the effect of pH in the oxidative dissolution of Ag NPs, demonstrating the usefulness of CPEs in studies of this type.

Preparation of carbon paste electrodes including poly(styrene) attached glycine-Pt(IV) for amperometric detection of glucose.

Science.gov (United States)

Dönmez, Soner; Arslan, Fatma; Sarı, Nurşen; Kurnaz Yetim, Nurdan; Arslan, Halit

2014-04-15

In this study, a novel carbon paste electrode that is sensitive to glucose was prepared using the nanoparticles modified (4-Formyl-3-methoxyphenoxymethyl) with polystyren (FMPS) with L-Glycine-Pt(IV) complexes. Polymeric nanoparticles having Pt(IV) ion were prepared from (4-Formyl-3-methoxyphenoxymethyl) polystyren, glycine and PtCl4 by template method. Glucose oxidase enzyme was immobilized to a modified carbon paste electrode (MCPE) by cross-linking with glutaraldehyde. Determination of glucose was carried out by oxidation of enzymatically produced H2O2 at 0.5 V vs. Ag/AgCl. Effects of pH and temperature were investigated, and optimum parameters were found to be 8.0 and 55°C, respectively. Linear working range of the electrode was 5.0×10(-6)-1.0×10(-3) M, R(2)=0.997. Storage stability and operational stability of the enzyme electrode were also studied. Glucose biosensor gave perfect reproducible results after 10 measurements with 2.3% relative standard deviation. Also, it had good storage stability (gave 53.57% of the initial amperometric response at the end of 33th day). © 2013 Published by Elsevier B.V.

Wearable Wireless Tyrosinase Bandage and Microneedle Sensors: Toward Melanoma Screening.

Science.gov (United States)

Ciui, Bianca; Martin, Aida; Mishra, Rupesh K; Brunetti, Barbara; Nakagawa, Tatsuo; Dawkins, Thomas J; Lyu, Mengjia; Cristea, Cecilia; Sandulescu, Robert; Wang, Joseph

2018-04-01

Wearable bendable bandage-based sensor and a minimally invasive microneedle biosensor are described toward rapid screening of skin melanoma. These wearable electrochemical sensors are capable of detecting the presence of the tyrosinase (TYR) enzyme cancer biomarker in the presence of its catechol substrate, immobilized on the transducer surface. In the presence of the surface TYR biomarker, the immobilized catechol is rapidly converted to benzoquinone that is detected amperometrically, with a current signal proportional to the TYR level. The flexible epidermal bandage sensor relies on printing stress-enduring inks which display good resiliency against mechanical deformations, whereas the hollow microneedle device is filled with catechol-coated carbon paste for assessing tissue TYR levels. The bandage sensor can thus be used directly on the skin whereas microneedle device can reach melanoma tissues under the skin. Both wearable sensors are interfaced to an ultralight flexible electronic board, which transmits data wirelessly to a mobile device. The analytical performance of the resulting bandage and microneedle sensing systems are evaluated using TYR-containing agarose phantom gel and porcine skin. The new integrated conformal portable sensing platforms hold considerable promise for decentralized melanoma screening, and can be extended to the screening of other key biomarkers in skin moles. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Estimation of local concentration from measurements of stochastic adsorption dynamics using carbon nanotube-based sensors

International Nuclear Information System (INIS)

Jang, Hong; Lee, Jay H.; Braatz, Richard D.

2016-01-01

This paper proposes a maximum likelihood estimation (MLE) method for estimating time varying local concentration of the target molecule proximate to the sensor from the time profile of monomolecular adsorption and desorption on the surface of the sensor at nanoscale. Recently, several carbon nanotube sensors have been developed that can selectively detect target molecules at a trace concentration level. These sensors use light intensity changes mediated by adsorption or desorption phenomena on their surfaces. The molecular events occurring at trace concentration levels are inherently stochastic, posing a challenge for optimal estimation. The stochastic behavior is modeled by the chemical master equation (CME), composed of a set of ordinary differential equations describing the time evolution of probabilities for the possible adsorption states. Given the significant stochastic nature of the underlying phenomena, rigorous stochastic estimation based on the CME should lead to an improved accuracy over than deterministic estimation formulated based on the continuum model. Motivated by this expectation, we formulate the MLE based on an analytical solution of the relevant CME, both for the constant and the time-varying local concentrations, with the objective of estimating the analyte concentration field in real time from the adsorption readings of the sensor array. The performances of the MLE and the deterministic least squares are compared using data generated by kinetic Monte Carlo (KMC) simulations of the stochastic process. Some future challenges are described for estimating and controlling the concentration field in a distributed domain using the sensor technology.

Voltammetric sensor for caffeine based on a glassy carbon electrode modified with Nafion and graphene oxide

International Nuclear Information System (INIS)

Zhao, F.; Wang, F.; Zhao, W.; Zhou, J.; Liu, Y.; Zou, L.; Ye, B.

2011-01-01

We report on a voltammetric sensor for caffeine that is based on a glassy carbon electrode modified with Nafion and graphene oxide (GO). It exhibits a good affinity for caffeine (resulting from the presence of Nafion), and excellent electrochemical response (resulting from the pressence of GO) for the oxidation of caffeine. The electrode enables the determination of caffeine in the range from 4.0 x 10 -7 to 8.0 x 10 -5 mol L -1 , with a detection limit of 2.0 x 10 -7 mol L -1 . The sensor displays good stability, reproducibility, and high sensitivity. It was successfully applied to the quantitative determination of caffeine in beverages. (author)

Investigation of the Antioxidant Properties of Metallothionein in Transgenic Tobacco Plants using Voltammetry at a Carbon Paste Electrode

Czech Academy of Sciences Publication Activity Database

Shetivska, V.; Adam, V.; Prášek, J.; Macek, Tomáš; Macková, M.; Havel, L.; Dioplan, V.; Zehnálek, J.; Hubálek, J.; Kižek, R.

2011-01-01

Roč. 6, č. 7 (2011), s. 2869-2883 ISSN 1452-3981 Grant - others:GA ČR(CZ) GA522/07/0692; GA ČR(CZ) GA102/08/1546 Institutional research plan: CEZ:AV0Z40550506 Keywords : square wave voltammetry * carbon paste electrode * DNA * metallothionein Subject RIV: CG - Electrochemistry Impact factor: 3.729, year: 2011

Application of Crunch-Flow Routines to Constrain Present and Past Carbon Fluxes at Gas-Hydrate Bearing Sites

Energy Technology Data Exchange (ETDEWEB)

Torres, Marta [Oregon State Univ., Corvallis, OR (United States). College of Earth, Ocean, and Atmospheric Sciences

2014-01-31

In November 2012, Oregon State University initiated the project entitled: Application of Crunch-Flow routines to constrain present and past carbon fluxes at gas-hydrate bearing sites. Within this project we developed Crunch-Flow based modeling modules that include important biogeochemical processes that need to be considered in gas hydrate environments. Our modules were applied to quantify carbon cycling in present and past systems, using data collected during several DOE-supported drilling expeditions, which include the Cascadia margin in US, Ulleung Basin in South Korea, and several sites drilled offshore India on the Bay of Bengal and Andaman Sea. Specifically, we completed modeling efforts that: 1) Reproduce the compositional and isotopic profiles observed at the eight drilled sites in the Ulleung Basin that constrain and contrast the carbon cycling pathways at chimney (high methane flux) and non-chimney sites (low methane, advective systems); 2) Simulate the Ba record in the sediments to quantify the past dynamics of methane flux in the southern Hydrate Ridge, Cascadia margin; and 3) Provide quantitative estimates of the thickness of individual mass transport deposits (MTDs), time elapsed after the MTD event, rate of sulfate reduction in the MTD, and time required to reach a new steady state at several sites drilled in the Krishna-Godavari (K-G) Basin off India. In addition we developed a hybrid model scheme by coupling a home-made MATLAB code with CrunchFlow to address the methane transport and chloride enrichment at the Ulleung Basins chimney sites, and contributed the modeling component to a study focusing on pore-scale controls on gas hydrate distribution in sediments from the Andaman Sea. These efforts resulted in two manuscripts currently under review, and contributed the modeling component of another pare, also under review. Lessons learned from these efforts are the basis of a mini-workshop to be held at Oregon State University (Feb 2014) to instruct

Flexible Temperature Sensors on Fibers

Directory of Open Access Journals (Sweden)

Marcin Sloma

2010-08-01

Full Text Available The aim of this paper is to present research dedicated to the elaboration of novel, miniaturized flexible temperature sensors for textronic applications. Examined sensors were manufactured on a single yarn, which ensures their high flexibility and good compatibility with textiles. Stable and linear characteristics were obtained by special technological process and applied temperature profiles. As a thermo-sensitive materials the innovative polymer compositions filled with multiwalled carbon nanotubes were used. Elaborated material was adapted to printing and dip-coating techniques to produce NTC composites. Nanotube sensors were free from tensometric effect typical for other carbon-polymer sensor, and demonstrated TCR of 0.13%/K. Obtained temperature sensors, compatible with textile structure, can be applied in rapidly developing smart textiles and be used for health and protections purposes.

Carbon-based layer-by-layer nanostructures: from films to hollow capsules

Science.gov (United States)

Hong, Jinkee; Han, Jung Yeon; Yoon, Hyunsik; Joo, Piljae; Lee, Taemin; Seo, Eunyong; Char, Kookheon; Kim, Byeong-Su

2011-11-01

Over the past years, the layer-by-layer (LbL) assembly has been widely developed as one of the most powerful techniques to prepare multifunctional films with desired functions, structures and morphologies because of its versatility in the process steps in both material and substrate choices. Among various functional nanoscale objects, carbon-based nanomaterials, such as carbon nanotubes and graphene sheets, are promising candidates for emerging science and technology with their unique physical, chemical, and mechanical properties. In particular, carbon-based functional multilayer coatings based on the LbL assembly are currently being actively pursued as conducting electrodes, batteries, solar cells, supercapacitors, fuel cells and sensor applications. In this article, we give an overview on the use of carbon materials in nanostructured films and capsules prepared by the LbL assembly with the aim of unraveling the unique features and their applications of carbon multilayers prepared by the LbL assembly.

An Electrochemical Sensor Based on Novel Ion Imprinted Polymeric Nanoparticles for Selective Detection of Lead Ions

Directory of Open Access Journals (Sweden)

Masoud Ghanei-Motlagh

1999-11-01

Full Text Available In this study, the novel surface ion-imprinted polymer (IIP particles were prepared and applied as a electrode modifier in stripping voltammetric detection of lead(II ion. A carbon paste electrode (CPE modified with IIP nanoparticles and multi-walled carbon nanotubes (MWCNTs was used for accumulation of toxic lead ions. Various factors that govern on electrochemical signals including carbon paste composition, pH of the preconcentration solution, supporting electrolyte, stirring time, reduction potential and time were studied in detail. The best electrochemical response for Pb(II ions was obtained with a paste composition of 7% (w/w of lead IIP, 10% MWCNTs, 53% (w/w of graphite powder and 30% (w/w of paraffin oil using a solution of 0.1 mol L-1 acetat buffer solution (pH=4.5 with a extraction time of 15 min. A sensitive response for Pb(II ions in the concentration range of 3 to 55 µg L-1 was achived. The proposed electrochemical sensor showed low detection limit (0.5 µg L-1, remarkable selectivity and good reproducibility (RSD = 3.1%. Determination of lead(II content in different environmental water samples was also realized adopting graphite furnace atomic absorptions spectrometry (GF-AAS and the obtained results were satisfactory.

Soil-modified carbon paste electrode: a useful tool in environmental assessment of heavy metal ion binding interactions.

Science.gov (United States)

Svegl, I G; Ogorevc, B

2000-08-01

Carbon paste electrodes (CPEs) modified with different soils in their native form were prepared to create a soil-like solid phase suitable for application in studies of heavy metal ion uptake and binding interactions. The preparation of CPEs modified with five different soils was examined and their heavy metal ion uptake behavior investigated using a model Cu(II) aqueous solution. Metal ions were accumulated under open circuit conditions and were determined after a medium exchange using differential pulse anodic stripping voltammetry, applying preelectrolysis at -0.7 V. The soil-modified CPE accumulation behavior, including the linearity of the current response versus Cu(II) concentration, the influence of the pH on the solution, and the uptake kinetics, was thoroughly investigated. The correlation between the soil-modified CPE uptake capability and the standard soil parameters, such as ion exchange capacity, soil pH, organic matter and clay content, were evaluated for all five examined soils. The influence of selected endogenous cations (K(I), Ca(II), Fe(III)) on the transfer of Cu(II) ions from a solution to the simulated soil solid phase was examined and is discussed. Preliminary examinations of the soil-modified CPE uptake behavior with some exogenous heavy metal ions of strong environmental interest (Pb(II), Hg(II), Cd(II) and Ag(I)) are also presented. This work demonstrates some attractive possibilities for the application of a soil-modified CPE in studying soil-heavy metal ion binding interactions, with a further potential use as a new environmental sensor appropriate for fist on-site testing of polluted soils.

Functionalized Multiwalled Carbon Nanotube Electrochemical Sensor for Determination of Anticancer Drug Flutamide

Science.gov (United States)

Farias, Julianna Santos; Zanin, Hudson; Caldas, Adriana Silva; dos Santos, Clenilton Costa; Damos, Flavio Santos; de Cássia Silva Luz, Rita

2017-10-01

An electrochemical sensor based on functionalized multiwalled carbon nanotubes (MWCNTf) has been developed and applied for determination of anticancer drug flutamide in pharmaceutical and artificial urine samples. The electrode was prepared by modifying a glassy carbon electrode with MWCNTf, denoted herein as MWCNTf/GCE. The MWCNTf/GCE electrode exhibited high catalytic activity, high sensitivity, and high stability and was applicable over a wide concentration range for flutamide. The effects of the scan rate, pH, and nature of the electrolyte on the electrochemical behavior of flutamide on the MWCNTf/GCE were investigated. The results showed that this electrode presented the best square-wave voltammetric response to flutamide in Britton-Robinson buffer solution at pH 5.0 at frequency of 50 Hz and amplitude of 0.06 V. The proposed sensor presents a wide linear response range from concentration of 0.1 μmol L-1 up to 1000 μmol L-1 (or 27.6 μg L-1 up to 0.27 g L-1), with limit of detection, limit of quantification, and sensitivity of 0.03 μmol L-1, 0.1 μmol L-1, and 0.30 μA μmol-1 L, respectively. The MWCNTf/GCE electrode was successfully applied for determination of flutamide in pharmaceutical formulations and artificial urine samples, giving results in agreement with those obtained by a comparative method described in literature. A paired Student's t-test revealed no statistical difference between the reference and proposed method at 95% confidence level. The average recovery for fortified samples was 101 ± 1%.

Sensitivity Enhancement of Benzene Sensor Using Ethyl Cellulose-Coated Surface-Functionalized Carbon Nanotubes

Directory of Open Access Journals (Sweden)

Thanattha Chobsilp

2018-01-01

Full Text Available A hybrid sensor based on the integration of functionalized multiwalled carbon nanotubes (MWCNTs with ethyl cellulose (EC was fabricated for sensitivity enhancement of benzene detection. To functionalize the surface of MWCNTs, MWCNTs were treated with hydrochloric acid for 60 min (A60-MWCNTs, while other MWCNTs were treated with oxygen plasma for 30, 60, 90, and 120 min (P30-MWCNTs, P60-MWCNTs, P90-MWCNTs, and P120-MWCNTs, resp.. Pristine MWCNTs, A-MWCNTs, and P-MWCNTs were dispersed in 1,2-dichloroethane, then dropped onto a printed circuit board consisting of Cu/Au electrodes used as the sensor platform. Next, EC was separately spin coated on the pristine MWCNTs, A-MWCNTs, and P-MWCNTs (EC/MWCNTs, EC/A-MWCNTs, and EC/P-MWCNTs, resp.. All sensors responded to benzene vapor at room temperature by increasing their electrical resistance which was sensitive to benzene vapor. The EC/P90-MWCNTs enabled an approximately 11-fold improvement in benzene detection compared to EC/MWCNTs. The sensitivity of all sensors would be attributed to the swelling of EC, resulting in the loosening of the MWCNT network after benzene vapor exposure. The differences of the sensing responses of the EC/MWCNTs, EC/A-MWCNTs, and EC/P-MWCNTs would be ascribed to the differences in crystallinity and functionalization of MWCNT sidewalls, suggesting that acid and oxygen plasma treatments of MWCNTs would be promising techniques for the improvement of benzene detection.

Preparation of calcium phosphate paste

International Nuclear Information System (INIS)

Mohd Reusmaazran Yusof; Norzita Yaacob; Idris Besar; Che Seman Mahmood; Rusnah Mustafa

2010-01-01

Calcium phosphate paste were prepared by mixing between calcium sodium potassium phosphate, Ca 2 NaK (PO 4 ) 2 (CSPP) and monocalcium phosphate monohydrate, Ca(H 2 PO 4 ) 2 .H 2 O (MCPM). CSPP were obtained by reaction between calcium hydrogen phosphate (CaHPO 4 ), potassium carbonate (K 2 CO 3 ) and sodium carbonate (Na 2 CO 3 ) in solid state sintering process followed by quenching in air at 1000 degree Celsius. The paste was aging in simulated body fluid (SBF) for 0.5, 1, 3, 6, 12, 24, 48 hrs, 3, 7 and 14 days. The morphological investigation indicated the formation of apatite crystal were first growth after 24 hours. The obvious growth of apatite crystal was shown at 3 days. The obvious growth of apatite crystal was shown in 7 and 14 days indicated the prediction of paste would have rapid reaction with bone after implantation. (author)

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.

Leak detection of CO2 pipelines with simple atmospheric CO2 sensors for carbon capture and storage

NARCIS (Netherlands)

van Leeuwen, Charlotte; Hensen, Arjan; Meijer, Harro A. J.

2013-01-01

This paper presents a field test performed with five relatively simple CO2 sensors (Vaisala Carbocap GMP343) that were placed for more than one year in a field in Ten Post, Groningen, The Netherlands. Aim was to investigate their potential use in monitoring pipelines transporting CO2 for carbon

Direction sensitive bending sensors based on multi-wall carbon nanotube/epoxy nanocomposites

International Nuclear Information System (INIS)

Wichmann, Malte H G; Buschhorn, Samuel T; Boeger, Lars; Schulte, Karl; Adelung, Rainer

2008-01-01

In the present work, a direction sensitive bending strain sensor consisting of a single block of epoxy/multi-wall carbon nanotube composite was developed. Moreover, the manufacturing could be realized in a straightforward single-step processing route. The directional sensitivity to bending deformations is related to the change in electrical resistance, which becomes positive or negative, depending on the direction of bending deflection. This effect is achieved by generating a gradient in electrical conductivity throughout the material. The resistance versus strain behaviour of these devices is investigated in detail and related to the microstructure of the nanocomposites.

Electrochemical sensor for nitrite using a glassy carbon electrode modified with gold-copper nanochain networks

International Nuclear Information System (INIS)

Huang, Su-Su; Mei, Li-Ping; Zhou, Jia-Ying; Guo, Fei-Ying; Wang, Ai-Jun; Feng, Jiu-Ju; Liu, Li

2016-01-01

Bimetallic gold-copper nanochain networks (AuCu NCNs) were prepared by a single-step wet-chemical approach using metformin as a growth-directing agent. The formation mechanism was investigated in detail, and the AuCu NCNs were characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The nanocrystals were deposited on glassy carbon electrode and this resulted in a highly sensitive sensor for nitrite. Features include a low working potential (best at 0.684 V vs. SCE), fair sensitivity (17.55 μA mM −1 ), a wide linear range (0.01 to 4.0 mM), a low detection limit (0.2 μM, S/N = 3), and superior selectivity as compared to other sensors. (author)

An electrochemical sensor for rizatriptan benzoate determination using Fe{sub 3}O{sub 4} nanoparticle/multiwall carbon nanotube-modified glassy carbon electrode in real samples

Energy Technology Data Exchange (ETDEWEB)

Madrakian, Tayyebeh, E-mail: madrakian@basu.ac.ir; Maleki, Somayeh; Heidari, Mozhgan; Afkhami, Abbas

2016-06-01

In this paper a sensitive and selective electrochemical sensor for determination of rizatriptan benzoate (RZB) was proposed. A glassy carbon electrode was modified with nanocomposite of multiwalled carbon nanotubes (MWCNTs) and Fe{sub 3}O{sub 4} nanoparticles (Fe{sub 3}O{sub 4}/MWCNTs/GCE). The results obtained clearly show that the combination of MWCNTs and Fe{sub 3}O{sub 4} nanoparticles definitely improves the sensitivity of modified electrode to RZB determination. The morphology and electroanalytical performance of the fabricated sensor were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), square wave voltammetry (SWV) and cyclic voltammetry (CV). Also, the effect of experimental and instrumental parameters on the sensor response was evaluated. The square wave voltammetric response of the electrode to RZB was linear in the range 0.5–100.0 μmol L{sup −1} with a detection limit of 0.09 μmol L{sup −1} under the optimum conditions. The investigated method showed good stability, reproducibility and repeatability. The proposed sensor was successfully applied for real life samples of blood serum and RZB determination in pharmaceutical. - Highlights: • Simple and sensitive Fe{sub 3}O{sub 4}/MWCNTs/GCE for rizatriptan benzoate determination • The surface morphology of nanocomposite was characterized by SEM and EDS. • Rizatriptan benzoate was measured at 0.09 μmol L{sup −1} with good sensitivity and selectivity. • The electrode has been successfully applied in serum and pharmaceutical samples. • The nanocomposite had excellent electrocatalytic activity and biocompatibility.

Semantically-Enabled Sensor Plug & Play for the Sensor Web

Science.gov (United States)

Bröring, Arne; Maúe, Patrick; Janowicz, Krzysztof; Nüst, Daniel; Malewski, Christian

2011-01-01

Environmental sensors have continuously improved by becoming smaller, cheaper, and more intelligent over the past years. As consequence of these technological advancements, sensors are increasingly deployed to monitor our environment. The large variety of available sensor types with often incompatible protocols complicates the integration of sensors into observing systems. The standardized Web service interfaces and data encodings defined within OGC’s Sensor Web Enablement (SWE) framework make sensors available over the Web and hide the heterogeneous sensor protocols from applications. So far, the SWE framework does not describe how to integrate sensors on-the-fly with minimal human intervention. The driver software which enables access to sensors has to be implemented and the measured sensor data has to be manually mapped to the SWE models. In this article we introduce a Sensor Plug & Play infrastructure for the Sensor Web by combining (1) semantic matchmaking functionality, (2) a publish/subscribe mechanism underlying the SensorWeb, as well as (3) a model for the declarative description of sensor interfaces which serves as a generic driver mechanism. We implement and evaluate our approach by applying it to an oil spill scenario. The matchmaking is realized using existing ontologies and reasoning engines and provides a strong case for the semantic integration capabilities provided by Semantic Web research. PMID:22164033

Stable isotopes of pedogenic carbonates from the Somma-Vesuvius area, southern Italy, over the past 18 kyr: palaeoclimatic implications

Science.gov (United States)

Zanchetta, G.; di Vito, M.; Fallick, A. E.; Sulpizio, R.

2000-12-01

Stable isotopes were measured in the carbonate and organic matter of palaeosols in the Somma-Vesuvius area, southern Italy in order to test whether they are suitable proxy records for climatic and ecological changes in this area during the past 18000 yr. The ages of the soils span from ca. 18 to ca. 3 kyr BP. Surprisingly, the Last Glacial to Holocene climate transition was not accompanied by significant change in 18O of pedogenic carbonate. This could be explained by changes in evaporation rate and in isotope fractionation between water and precipitated carbonate with temperature, which counterbalanced the expected change in isotope composition of meteoric water. Because of the rise in temperature and humidity and the progressive increase in tree cover during the Holocene, the Holocene soil carbonates closely reflect the isotopic composition of meteoric water. A cooling of about 2°C after the Avellino eruption (3.8 ka) accounts for a sudden decrease of about 1 in 18O of pedogenic carbonate recorded after this eruption. The 13C values of organic matter and pedogenic carbonate covary, indicating an effective isotope equilibrium between the organic matter, as the source of CO2, and the pedogenic carbonate. Carbon isotopes suggest prevailing C3 vegetation and negligible mixing with volcanogenic or atmospheric CO2.

A Spray-On Carbon Nanotube Artificial Neuron Strain Sensor for Composite Structural Health Monitoring

Directory of Open Access Journals (Sweden)

Gyeongrak Choi

2016-07-01

Full Text Available We present a nanocomposite strain sensor (NCSS to develop a novel structural health monitoring (SHM sensor that can be easily installed in a composite structure. An NCSS made of a multi-walled carbon nanotubes (MWCNT/epoxy composite was installed on a target structure with facile processing. We attempted to evaluate the NCSS sensing characteristics and benchmark compared to those of a conventional foil strain gauge. The response of the NCSS was fairly good and the result was nearly identical to the strain gauge. A neuron, which is a biomimetic long continuous NCSS, was also developed, and its vibration response was investigated for structural damage detection of a composite cantilever. The vibration response for damage detection was measured by tracking the first natural frequency, which demonstrated good result that matched the finite element (FE analysis.

A carbon nanotube based resettable sensor for measuring free chlorine in drinking water

International Nuclear Information System (INIS)

Hsu, Leo H. H.; Hoque, Enamul; Kruse, Peter; Ravi Selvaganapathy, P.

2015-01-01

Free chlorine from dissolved chlorine gas is widely used as a disinfectant for drinking water. The residual chlorine concentration has to be continuously monitored and accurately controlled in a certain range around 0.5–2 mg/l to ensure drinking water safety and quality. However, simple, reliable, and reagent free monitoring devices are currently not available. Here, we present a free chlorine sensor that uses oxidation of a phenyl-capped aniline tetramer (PCAT) to dope single wall carbon nanotubes (SWCNTs) and to change their resistance. The oxidation of PCAT by chlorine switches the PCAT-SWCNT system into a low resistance (p-doped) state which can be detected by probing it with a small voltage. The change in resistance is found to be proportional to the log-scale concentration of the free chlorine in the sample. The p-doping of the PCAT-SWCNT film then can be electrochemically reversed by polarizing it cathodically. This sensor not only shows good sensing response in the whole concentration range of free chlorine in drinking water but is also able to be electrochemically reset back many times without the use of any reagents. This simple sensor is ideally suited for measuring free chlorine in drinking water continuously

Highly sensitive simultaneous electrochemical determination of trace amounts of Pb(II) and Cd(II) using a carbon paste electrode modified with multi-walled carbon nanotubes and a newly synthesized Schiff base

International Nuclear Information System (INIS)

Afkhami, Abbas; Ghaedi, Hamed; Madrakian, Tayyebeh; Rezaeivala, Majid

2013-01-01

Highlights: ► A new chemically modified carbon paste electrode was constructed and used. ► A new Schiff base and multi-walled carbon nanotube was used as modifiers. ► The electrochemical properties of the modified electrode were studied. ► The electrode was used to the simultaneous determination of Pb 2+ and Cd 2+ . -- Abstract: A new chemically modified electrode was constructed for rapid, simple, accurate, selective and highly sensitive simultaneous determination of lead and cadmium using square wave anodic stripping voltammetry (SWASV). The electrode was prepared by incorporation of new synthesized Schiff base and multi-walled carbon nanotubes (MWCNT) in carbon paste electrode. The limit of detection was found to be 0.25 ng mL −1 and 0.74 ng mL −1 for Pb 2+ and Cd 2+ , respectively. The stability constants of the complexes of the ligand with several metal cations in ethanol medium were determined. The effects of different cations and anions on the simultaneous determination of metal ions were studied and it was found that the electrode is highly selective. The proposed chemically modified electrode was used for the determination of lead and cadmium in several foodstuffs and water samples

Gas sensors for ammonia detection based on polyaniline-coated multi-wall carbon nanotubes

International Nuclear Information System (INIS)

He Lifang; Jia Yong; Meng Fanli; Li Minqiang; Liu Jinhuai

2009-01-01

Polyaniline-coated multi-wall carbon nanotubes (PANI-coated MWNTs) were prepared by in situ polymerization method. Field emission scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and thermogravimetric analysis were used to characterize the as-prepared PANI-coated MWNTs. Obtained results indicated that PANI was uniformly coated on MWNTs, and the thickness of the coatings can be controlled by changing the weight ratios of aniline monomer and MWNTs in the polymerization process. Sensors were fabricated by spin-coating onto pre-patterned electrodes, and ammonia gas sensing properties of the as-prepared PANI-coated MWNTs were studied. The results showed a good response and reproducibility towards ammonia at room temperature. In addition, PANI-coated MWNTs exhibited a linear response to ammonia in the range of 0.2-15 ppm. The effects of the thickness of PANI coatings on the gas sensing properties were also investigated in detail. The results suggest a potential application of PANI-coated MWNTs in gas sensor for detecting ammonia.

Wearable bio and chemical sensors

OpenAIRE

Coyle, Shirley; Curto, Vincenzo F.; Benito-Lopez, Fernando; Florea, Larisa; Diamond, Dermot

2014-01-01

Chemical and biochemical sensors have experienced tremendous growth in the past decade due to advances in material chemistry combined with the emergence of digital communication technologies and wireless sensor networks (WSNs) [1]. The emergence of wearable chemical and biochemical sensors is a relatively new concept that poses unique challenges to the field of wearable sensing. This is because chemical sensors have a more complex mode of operation, compared to physical transducers, in that t...

Poisson effect enhances compression force sensing with oxidized carbon nanotube network/polyurethane sensor

Czech Academy of Sciences Publication Activity Database

Slobodian, P.; Říha, Pavel; Olejník, R.; Matyáš, J.; Kovář, M.

2018-01-01

Roč. 271 (2018), s. 76-82 ISSN 0924-4247 R&D Projects: GA MŠk ED2.1.00/19.0409 Grant - others:Ministerstvo školství, mládeže a tělovýchovy (MŠMT)(CZ) LO1504; TBU in Zlin(CZ) IGA/CPS/2015/001 Institutional research plan: CEZ:AV0Z20600510 Keywords : compression force sensor * carbon nanotubes * polyurethane * polymer composite * nanocracks Subject RIV: BK - Fluid Dynamics OBOR OECD: Nano-processes (applications on nano-scale) Impact factor: 2.499, year: 2016

High sensitivity of a carbon nanowall-based sensor for detection of organic vapours

Czech Academy of Sciences Publication Activity Database

Slobodian, P.; Cvelbar, U.; Říha, Pavel; Olejník, R.; Matyáš, J.; Filipič, G.; Watanabe, H.; Tajima, S.; Kondo, H.; Sekine, M.; Hori, M.

2015-01-01

Roč. 110, č. 5 (2015), s. 90515-90520 ISSN 2046-2069 Grant - others:Ministerstvo školství, mládeže a tělovýchovy (MŠMT)(CZ) LO1504; Slovenian Research Agency(SI) L2-6769; Slovenian Research Agency(SI) Bi-JAP-2015-2017-3; JSPS Grant-in-Aid for Exploratory Research(JP) 25600123 Institutional research plan: CEZ:AV0Z20600510 Institutional support: RVO:67985874 Keywords : carbon nanowalls * sensing properties * volatile organic vapours Subject RIV: JB - Sensors, Measurment, Regulation Impact factor: 3.289, year: 2015

Incorporating a hybrid urease-carbon nanotubes sensitive nanofilm on capacitive field-effect sensors for urea detection.

Science.gov (United States)

Siqueira, José R; Molinnus, Denise; Beging, Stefan; Schöning, Michael J

2014-06-03

The ideal combination among biomolecules and nanomaterials is the key for reaching biosensing units with high sensitivity. The challenge, however, is to find out a stable and sensitive film architecture that can be incorporated on the sensor's surface. In this paper, we report on the benefits of incorporating a layer-by-layer (LbL) nanofilm of polyamidoamine (PAMAM) dendrimer and carbon nanotubes (CNTs) on capacitive electrolyte-insulator-semiconductor (EIS) field-effect sensors for detecting urea. Three sensor arrangements were studied in order to investigate the adequate film architecture, involving the LbL film with the enzyme urease: (i) urease immobilized directly onto a bare EIS [EIS-urease] sensor; (ii) urease atop the LbL film over the EIS [EIS-(PAMAM/CNT)-urease] sensor; and (iii) urease sandwiched between the LbL film and another CNT layer [EIS-(PAMAM/CNT)-urease-CNT]. The surface morphology of all three urea-based EIS biosensors was investigated by atomic force microscopy (AFM), while the biosensing abilities were studied by means of capacitance-voltage (C/V) and dynamic constant-capacitance (ConCap) measureaments at urea concentrations ranging from 0.1 mM to 100 mM. The EIS-urease and EIS-(PAMAM/CNT)-urease sensors showed similar sensitivity (~18 mV/decade) and a nonregular signal behavior as the urea concentration increased. On the other hand, the EIS-(PAMAM/CNT)-urease-CNT sensor exhibited a superior output signal performance and higher sensitivity of about 33 mV/decade. The presence of the additional CNT layer was decisive to achieve a urea based EIS sensor with enhanced properties. Such sensitive architecture demonstrates that the incorporation of an adequate hybrid enzyme-nanofilm as sensing unit opens new prospects for biosensing applications using the field-effect sensor platform.

Sensitive methanol sensor based on PMMA-G-CNTs nanocomposites deposited onto glassy carbon electrodes.

Science.gov (United States)