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Sample records for nanowire surface-charge sensors

  1. Screening model for nanowire surface-charge sensors in liquid

    DEFF Research Database (Denmark)

    Sørensen, Martin Hedegård; Mortensen, Asger; Brandbyge, Mads

    2007-01-01

    The conductance change of nanowire field-effect transistors is considered a highly sensitive probe for surface charge. However, Debye screening of relevant physiological liquid environments challenge device performance due to competing screening from the ionic liquid and nanowire charge carriers....

  2. Chemical sensors based on surface charge transfer

    Science.gov (United States)

    Mohtasebi, Amirmasoud; Kruse, Peter

    2018-02-01

    The focus of this review is an introduction to chemiresistive chemical sensors. The general concept of chemical sensors is briefly introduced, followed by different architectures of chemiresistive sensors and relevant materials. For several of the most common systems, the fabrication of the active materials used in such sensors and their properties are discussed. Furthermore, the sensing mechanism, advantages, and limitations of each group of chemiresistive sensors are briefly elaborated. Compared to electrochemical sensors, chemiresistive sensors have the key advantage of a simpler geometry, eliminating the need for a reference electrode. The performance of bulk chemiresistors can be improved upon by using freestanding ultra-thin films (nanomaterials) or field effect geometries. Both of those concepts have also been combined in a gateless geometry, where charge transport though a percolation network of nanomaterials is modulated via adsorbate doping.

  3. A variable pressure method for characterizing nanoparticle surface charge using pore sensors.

    Science.gov (United States)

    Vogel, Robert; Anderson, Will; Eldridge, James; Glossop, Ben; Willmott, Geoff

    2012-04-03

    A novel method using resistive pulse sensors for electrokinetic surface charge measurements of nanoparticles is presented. This method involves recording the particle blockade rate while the pressure applied across a pore sensor is varied. This applied pressure acts in a direction which opposes transport due to the combination of electro-osmosis, electrophoresis, and inherent pressure. The blockade rate reaches a minimum when the velocity of nanoparticles in the vicinity of the pore approaches zero, and the forces on typical nanoparticles are in equilibrium. The pressure applied at this minimum rate can be used to calculate the zeta potential of the nanoparticles. The efficacy of this variable pressure method was demonstrated for a range of carboxylated 200 nm polystyrene nanoparticles with different surface charge densities. Results were of the same order as phase analysis light scattering (PALS) measurements. Unlike PALS results, the sequence of increasing zeta potential for different particle types agreed with conductometric titration.

  4. Corrosion detection of nanowires by magnetic sensors

    KAUST Repository

    Kosel, Jürgen

    2017-10-05

    Disclosed are various embodiments related to a corrosion detection device for detecting corrosive environments. A corrosion detection device comprises a magnetic sensor and at least one magnetic nanowire disposed on the magnetic sensor. The magnetic sensor is configured to detect corrosion of the one or more magnetic nanowires based at least in part on a magnetic field of the one or more magnetic nanowires.

  5. Effects of external surface charges on the enhanced piezoelectric potential of ZnO and AlN nanowires and nanotubes

    Directory of Open Access Journals (Sweden)

    Seong Min Kim

    2012-12-01

    Full Text Available We theoretically investigate external surface charge effects on piezoelectric potential of ZnO and AlN nanowires (NWs and nanotubes (NTs under uniform compression. The free carrier depletion caused by negative surface charges via surface functionalization on vertically compressed ZnO and AlN NWs/NTs is simulated using finite element calculation; this indicates the enhancement of piezoelectric potential is due to the free carriers (electrons being fully depleted at the critical surface charge density. Numerical simulations reveal that full coverage of surface charges surrounding the NTs increases the piezoelectric output potential exponentially within a relatively smaller range of charge density compared to the case of NWs for a typical donor concentration (∼1017 cm−3. The model can be used to design functional high-power semiconducting piezoelectric nanogenerators.

  6. Single conducting polymer nanowire based conductometric sensors

    Science.gov (United States)

    Bangar, Mangesh Ashok

    The detection of toxic chemicals, gases or biological agents at very low concentrations with high sensitivity and selectivity has been subject of immense interest. Sensors employing electrical signal readout as transduction mechanism offer easy, label-free detection of target analyte in real-time. Traditional thin film sensors inherently suffered through loss of sensitivity due to current shunting across the charge depleted/added region upon analyte binding to the sensor surface, due to their large cross sectional area. This limitation was overcome by use of nanostructure such as nanowire/tube as transducer where current shunting during sensing was almost eliminated. Due to their benign chemical/electrochemical fabrication route along with excellent electrical properties and biocompatibility, conducting polymers offer cost-effective alternative over other nanostructures. Biggest obstacle in using these nanostructures is lack of easy, scalable and cost-effective way of assembling these nanostructures on prefabricated micropatterns for device fabrication. In this dissertation, three different approaches have been taken to fabricate individual or array of single conducting polymer (and metal) nanowire based devices and using polymer by itself or after functionalization with appropriate recognition molecule they have been applied for gas and biochemical detection. In the first approach electrochemical fabrication of multisegmented nanowires with middle functional Ppy segment along with ferromagnetic nickel (Ni) and end gold segments for better electrical contact was studied. This multi-layered nanowires were used along with ferromagnetic contact electrode for controlled magnetic assembly of nanowires into devices and were used for ammonia gas sensing. The second approach uses conducting polymer, polypyrrole (Ppy) nanowires using simple electrophoretic alignment and maskless electrodeposition to anchor nanowire which were further functionalized with antibodies against

  7. Conductive polymer nanowire gas sensor fabricated by nanoscale soft lithography

    Science.gov (United States)

    Tang, Ning; Jiang, Yang; Qu, Hemi; Duan, Xuexin

    2017-12-01

    Resistive devices composed of one-dimensional nanostructures are promising candidates for the next generation of gas sensors. However, the large-scale fabrication of nanowires is still challenging, which restricts the commercialization of such devices. Here, we report a highly efficient and facile approach to fabricating poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) nanowire chemiresistive gas sensors by nanoscale soft lithography. Well-defined sub-100 nm nanowires are fabricated on silicon substrate, which facilitates device integration. The nanowire chemiresistive gas sensor is demonstrated for NH3 and NO2 detection at room temperature and shows a limit of detection at ppb level, which is compatible with nanoscale PEDOT:PSS gas sensors fabricated with the conventional lithography technique. In comparison with PEDOT:PSS thin-film gas sensors, the nanowire gas sensor exhibits higher sensitivity and a much faster response to gas molecules.

  8. Gas Sensors Based on Semiconducting Nanowire Field-Effect Transistors

    Directory of Open Access Journals (Sweden)

    Ping Feng

    2014-09-01

    Full Text Available One-dimensional semiconductor nanostructures are unique sensing materials for the fabrication of gas sensors. In this article, gas sensors based on semiconducting nanowire field-effect transistors (FETs are comprehensively reviewed. Individual nanowires or nanowire network films are usually used as the active detecting channels. In these sensors, a third electrode, which serves as the gate, is used to tune the carrier concentration of the nanowires to realize better sensing performance, including sensitivity, selectivity and response time, etc. The FET parameters can be modulated by the presence of the target gases and their change relate closely to the type and concentration of the gas molecules. In addition, extra controls such as metal decoration, local heating and light irradiation can be combined with the gate electrode to tune the nanowire channel and realize more effective gas sensing. With the help of micro-fabrication techniques, these sensors can be integrated into smart systems. Finally, some challenges for the future investigation and application of nanowire field-effect gas sensors are discussed.

  9. Graphene/Si-nanowire heterostructure molecular sensors.

    Science.gov (United States)

    Kim, Jungkil; Oh, Si Duk; Kim, Ju Hwan; Shin, Dong Hee; Kim, Sung; Choi, Suk-Ho

    2014-06-20

    Wafer-scale graphene/Si-nanowire (Si-NW) array heterostructures for molecular sensing have been fabricated by vertically contacting single-layer graphene with high-density Si NWs. Graphene is grown in large scale by chemical vapour deposition and Si NWs are vertically aligned by metal-assisted chemical etching of Si wafer. Graphene plays a key role in preventing tips of vertical Si NWs from being bundled, thereby making Si NWs stand on Si wafer separately from each other under graphene, a critical structural feature for the uniform Schottky-type junction between Si NWs and graphene. The molecular sensors respond very sensitively to gas molecules by showing 37 and 1280% resistance changes within 3.5/0.15 and 12/0.15 s response/recovery times under O2 and H2 exposures in air, respectively, highest performances ever reported. These results together with the sensor responses in vacuum are discussed based on the surface-transfer doping mechanism.

  10. Novel fabrication method of conductive polymer nanowires for sensor applications

    DEFF Research Database (Denmark)

    Christiansen, Nikolaj Ormstrup; Andersen, Karsten Brandt; Castillo, Jaime

    2013-01-01

    In this work we demonstrate a new, quiek and low cost fabrication of PEDOT:TsO nanowires using self-assembled peptide nanotubes as a masking material. The peptide nanotubes show a remarkably stability during reactive ion etching and can be dissolved in water afterwards. We have shown that the imp...... that the impedance of the nanowire is changing with backgating the wire, this gives promising possibility for application as a sensor....

  11. Fast humidity sensors based on CeO2 nanowires

    International Nuclear Information System (INIS)

    Fu, X Q; Wang, C; Yu, H C; Wang, Y G; Wang, T H

    2007-01-01

    Fast humidity sensors are reported that are based on CeO 2 nanowires synthesized by a hydrothermal method. Both the response and recovery time are about 3 s, and are independent of the humidity. The sensitivity increases gradually as the humidity increases, and is up to 85 at 97% RH. The resistance decreases exponentially with increasing humidity, implying ion-type conductivity as the humidity sensing mechanism. A model based on the morphology and surface energy of the nanowires is given to explain these results further. Our experimental results indicate a pathway to improving the performance of humidity sensors

  12. Silicon Nanowire Field-effect Chemical Sensor

    NARCIS (Netherlands)

    Chen, S.

    2011-01-01

    This thesis describes the work that has been done on the project “Design and optimization of silicon nanowire for chemical sensing‿, including Si-NW fabrication, electrical/electrochemical modeling, the application as ISFET, and the build-up of Si- NW/LOC system for automatic sample delivery. A

  13. Supersensitive, Fast-Response Nanowire Sensors by Using Schottky Contacts

    KAUST Repository

    Hu, Youfan

    2010-05-31

    A Schottky barrier can be formed at the interface between a metal electrode and a semiconductor. The current passing through the metal-semiconductor contact is mainly controlled by the barrier height and barrier width. In conventional nanodevices, Schottky contacts are usually avoided in order to enhance the contribution made by the nanowires or nanotubes to the detected signal. We present a key idea of using the Schottky contact to achieve supersensitive and fast response nanowire-based nanosensors. We have illustrated this idea on several platforms: UV sensors, biosensors, and gas sensors. The gigantic enhancement in sensitivity of up to 5 orders of magnitude shows that an effective usage of the Schottky contact can be very beneficial to the sensitivity of nanosensors. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Predicting and rationalizing the effect of surface charge distribution and orientation on nano-wire based FET bio-sensors

    DEFF Research Database (Denmark)

    De Vico, L.; Iversen, L.; Sørensen, Martin Hedegård

    2011-01-01

    changes (e.g. a positive signal change due to a net positive protein binding to a p-type conductor) can occur for certain combinations of charge distributions and Debye lengths. The new method is applied to interpret published experimental data on Streptavidin (Ishikawa et al., ACS Nano, 2009, 3, 3969......-3976) and Nucleocapsid protein (Ishikawa et al., ACS Nano, 2009, 3, 1219-1224)....

  15. Silicon Nanowire Field-effect Chemical Sensor

    OpenAIRE

    Chen, S.

    2011-01-01

    This thesis describes the work that has been done on the project “Design and optimization of silicon nanowire for chemical sensing‿, including Si-NW fabrication, electrical/electrochemical modeling, the application as ISFET, and the build-up of Si- NW/LOC system for automatic sample delivery. A novel top-down fabrication technique was presented for single-crystal Si-NW fabrication realized with conventional microfabrication technique. High quality triangular Si-NWs were made with high wafer-s...

  16. Solvothermally synthesized tungsten oxide nanowires/nanorods for NO2 gas sensor applications

    International Nuclear Information System (INIS)

    Qin Yuxiang; Li Xiao; Wang Fei; Hu Ming

    2011-01-01

    Highlights: → Tungsten oxide nanowires and nanorods were solvothermally synthesized by changing reaction solvent. → The sensing characteristics of the tungsten oxide nanowires and nanorods sensors to NO 2 gas were evaluated in detail. → The response time and recovery time for the nanowires or nanorods sensors are much shorter than the oxide nanoparticles or sputtered films. → The nanowires sensor shows a much shorter response time and a relative higher response value to NO 2 gas than the nanorods one. → The NO 2 -sensing mechanism and the possible reason for the better gas sensing properties of the nanowires are analyzed. - Abstract: One-dimensional nanorods or nanowires of W 18 O 49 were synthesized by solvothermal method at 200 deg. C with tungsten hexachloride (WCl 6 ) as precursor and cyclohexanol or 1-propanol as reaction solvent. Their morphology and structure properties were systematically characterized. The NO 2 -sensing properties of the sensors based on nanowires and nanorods were investigated at 100 deg. C up to 250 deg. C over NO 2 concentration ranging from 1 ppm to 20 ppm. The results indicate that both nanowires and nanorods exhibit reversible response to different concentrations of NO 2 , and the highest gas response is achieved at 150 deg. C. In comparison with nanorods, nanowires showed a much quicker response characteristic and a relative higher response value to the same concentration of NO 2 gas due to the smaller diameter and larger specific surface area.

  17. Sensitivity of Pressure Sensors Enhanced by Doping Silver Nanowires

    Directory of Open Access Journals (Sweden)

    Baozhang Li

    2014-06-01

    Full Text Available We have developed a highly sensitive flexible pressure sensor based on a piezopolymer and silver nanowires (AgNWs composite. The composite nanofiber webs are made by electrospinning mixed solutions of poly(inylidene fluoride (PVDF and Ag NWs in a cosolvent mixture of dimethyl formamide and acetone. The diameter of the fibers ranges from 200 nm to 500 nm, as demonstrated by SEM images. FTIR and XRD results reveal that doping Ag NWs into PVDF greatly enhances the content of β phase in PVDF. This β phase increase can be attributed to interactions between the Ag NWs and the PVDF matrix, which forces the polymer chains to be embedded into the β phase crystalline. The sensitivity of the pressure sensors agrees well with the FTIR and XRD characteristics. In our experiments, the measured sensitivity reached up to 30 pC/N for the nanofiber webs containing 1.5 wt% Ag NWs, which is close to that of poly(vinylidene fluoride-trifluoroethylene [P(VDF-TrFE, (77/23]. This study may provide a new method of fabricating high performance flexible sensors at relatively low cost compared with sensors based on [P(VDF-TrFE, (77/23].

  18. Nanowire-nanopore transistor sensor for DNA detection during translocation

    Science.gov (United States)

    Xie, Ping; Xiong, Qihua; Fang, Ying; Qing, Quan; Lieber, Charles

    2011-03-01

    Nanopore sequencing, as a promising low cost, high throughput sequencing technique, has been proposed more than a decade ago. Due to the incompatibility between small ionic current signal and fast translocation speed and the technical difficulties on large scale integration of nanopore for direct ionic current sequencing, alternative methods rely on integrated DNA sensors have been proposed, such as using capacitive coupling or tunnelling current etc. But none of them have been experimentally demonstrated yet. Here we show that for the first time an amplified sensor signal has been experimentally recorded from a nanowire-nanopore field effect transistor sensor during DNA translocation. Independent multi-channel recording was also demonstrated for the first time. Our results suggest that the signal is from highly localized potential change caused by DNA translocation in none-balanced buffer condition. Given this method may produce larger signal for smaller nanopores, we hope our experiment can be a starting point for a new generation of nanopore sequencing devices with larger signal, higher bandwidth and large-scale multiplexing capability and finally realize the ultimate goal of low cost high throughput sequencing.

  19. Solvothermally synthesized tungsten oxide nanowires/nanorods for NO{sub 2} gas sensor applications

    Energy Technology Data Exchange (ETDEWEB)

    Qin Yuxiang, E-mail: qinyuxiang@tju.edu.cn [School of Electronics and Information Engineering, Tianjin University, No. 92, Weijin Road, Nankai District, Tianjin 300072 (China); Li Xiao; Wang Fei; Hu Ming [School of Electronics and Information Engineering, Tianjin University, No. 92, Weijin Road, Nankai District, Tianjin 300072 (China)

    2011-08-18

    Highlights: > Tungsten oxide nanowires and nanorods were solvothermally synthesized by changing reaction solvent. > The sensing characteristics of the tungsten oxide nanowires and nanorods sensors to NO{sub 2} gas were evaluated in detail. > The response time and recovery time for the nanowires or nanorods sensors are much shorter than the oxide nanoparticles or sputtered films. > The nanowires sensor shows a much shorter response time and a relative higher response value to NO{sub 2} gas than the nanorods one. > The NO{sub 2}-sensing mechanism and the possible reason for the better gas sensing properties of the nanowires are analyzed. - Abstract: One-dimensional nanorods or nanowires of W{sub 18}O{sub 49} were synthesized by solvothermal method at 200 deg. C with tungsten hexachloride (WCl{sub 6}) as precursor and cyclohexanol or 1-propanol as reaction solvent. Their morphology and structure properties were systematically characterized. The NO{sub 2}-sensing properties of the sensors based on nanowires and nanorods were investigated at 100 deg. C up to 250 deg. C over NO{sub 2} concentration ranging from 1 ppm to 20 ppm. The results indicate that both nanowires and nanorods exhibit reversible response to different concentrations of NO{sub 2}, and the highest gas response is achieved at 150 deg. C. In comparison with nanorods, nanowires showed a much quicker response characteristic and a relative higher response value to the same concentration of NO{sub 2} gas due to the smaller diameter and larger specific surface area.

  20. Networks of ultrasmall Pd/Cr bilayer nanowires as high performance hydrogen sensors.

    Energy Technology Data Exchange (ETDEWEB)

    Zeng, X.-Q.; Wang, Y.-L.; Deng, H.; Latimer, M. L.; Xiao, Z.-L.; Pearson, J.; Xu, T.; Wang, H.-H.; Welp, U.; Crabtree, G. W.; Kwok, W.-K. (Center for Nanoscale Materials); ( MSD); (Northern Illinois Univ.); (Illinois Math and Science Academy); (Univ. of Illinois at Chicago)

    2011-01-01

    The newly developed hydrogen sensor, based on a network of ultrasmall pure palladium nanowires sputter-deposited on a filtration membrane, takes advantage of single palladium nanowires' characteristics of high speed and sensitivity while eliminating their nanofabrication obstacles. However, this new type of sensor, like the single palladium nanowires, cannot distinguish hydrogen concentrations above 3%, thus limiting the potential applications of the sensor. This study reports hydrogen sensors based on a network of ultrasmall Cr-buffered Pd (Pd/Cr) nanowires on a filtration membrane. These sensors not only are able to outperform their pure Pd counterparts in speed and durability but also allow hydrogen detection at concentrations up to 100%. The new networks consist of a thin layer of palladium deposited on top of a Cr adhesion layer 1-3 nm thick. Although the Cr layer is insensitive to hydrogen, it enables the formation of a network of continuous Pd/Cr nanowires with thicknesses of the Pd layer as thin as 2 nm. The improved performance of the Pd/Cr sensors can be attributed to the increased surface area to volume ratio and to the confinement-induced suppression of the phase transition from Pd/H solid solution ({alpha}-phase) to Pd hydride ({beta}-phase).

  1. Long-Term Stability of Oxide Nanowire Sensors via Heavily Doped Oxide Contact.

    Science.gov (United States)

    Zeng, Hao; Takahashi, Tsunaki; Kanai, Masaki; Zhang, Guozhu; He, Yong; Nagashima, Kazuki; Yanagida, Takeshi

    2017-12-22

    Long-term stability of a chemical sensor is an essential quality for long-term collection of data related to exhaled breath, environmental air, and other sources in the Internet of things (IoT) era. Although an oxide nanowire sensor has shown great potential as a chemical sensor, the long-term stability of sensitivity has not been realized yet due to electrical degradation under harsh sensing conditions. Here, we report a rational concept to accomplish long-term electrical stability of metal oxide nanowire sensors via introduction of a heavily doped metal oxide contact layer. Antimony-doped SnO 2 (ATO) contacts on SnO 2 nanowires show much more stable and lower electrical contact resistance than conventional Ti contacts for high temperature (200 °C) conditions, which are required to operate chemical sensors. The stable and low contact resistance of ATO was confirmed for at least 1960 h under 200 °C in open air. This heavily doped oxide contact enables us to realize the long-term stability of SnO 2 nanowire sensors while maintaining the sensitivity for both NO 2 gas and light (photo) detections. The applicability of our method is confirmed for sensors on a flexible polyethylene naphthalate (PEN) substrate. Since the proposed fundamental concept can be applied to various oxide nanostructures, it will give a foundation for designing long-term stable oxide nanomaterial-based IoT sensors.

  2. Detection of current-driven magnetic domains in [Co/Pd] nanowire by tunneling magnetoresistive sensor

    Science.gov (United States)

    Okuda, Mitsunobu; Miyamoto, Yasuyoshi; Miyashita, Eiichi; Saito, Nobuo; Hayashi, Naoto; Nakagawa, Shigeki

    2015-05-01

    Current-driven magnetic domain walls in magnetic nanowires have attracted a great deal of interest in terms of both physical studies and engineering applications. The anomalous Hall effect measurement is widely used for detecting the magnetization direction of current-driven magnetic domains in a magnetic nanowire. However, the problem with this measurement is that the detection point for current-driven domain wall motion is fixed at only the installed sensing wire across the specimen nanowire. A potential solution is the magnetic domain scope method, whereby the distribution of the magnetic flux leaking from the specimen can be analyzed directly by contact-scanning a tunneling magnetoresistive field sensor on a sample. In this study, we fabricated specimen nanowires consisting of [Co (0.3)/Pd (1.2)]21/Ta(3) films (units in nm) with perpendicular magnetic anisotropy on Si substrates. A tunneling magnetoresistive sensor was placed on the nanowire surface and a predetermined current pulse was applied. Real-time detection of the current-driven magnetic domain motion was successful in that the resistance of the tunneling magnetoresistive sensor was changed with the magnetization direction beneath the sensor. This demonstrates that magnetic domain detection using a tunneling magnetoresistive sensor is effective for the direct analysis of micro magnetic domain motion.

  3. Electrospun ZnO Nanowires as Gas Sensors for Ethanol Detection

    Directory of Open Access Journals (Sweden)

    Huang Po-Jung

    2009-01-01

    Full Text Available Abstract ZnO nanowires were produced using an electrospinning method and used in gas sensors for the detection of ethanol at 220 °C. This electrospinning technique allows the direct placement of ZnO nanowires during their synthesis to bridge the sensor electrodes. An excellent sensitivity of nearly 90% was obtained at a low ethanol concentration of 10 ppm, and the rest obtained at higher ethanol concentrations, up to 600 ppm, all equal to or greater than 90%.

  4. Silicon Nanowire as Virus Sensor in a Total Analysis System

    DEFF Research Database (Denmark)

    Svendsen, Winnie Edith; Jørgensen, Michael; Andresen, Lars

    2011-01-01

    Silicon nanowires are very promising candidates for the sensitive detection of viruses or even early detection of cancer. Due to their small dimensions the attachment of even one particle on their surface leads to detectable changes in their conductivity. In this paper we describe the development...... (fabrication and testing) of a silicon nanowire biosensor equipped with microfludic channels and automatized data aquisition for the detection of antibodies against a small virus (Aleutian Disease Virus) causing plasmacytosis on mink and ferrets....

  5. Mechanical transfer of ZnO nanowires for a flexible and conformal piezotronic strain sensor

    Science.gov (United States)

    Jenkins, Kory; Yang, Rusen

    2017-07-01

    We demonstrate a truly conformal and flexible piezotronic strain sensor using zinc oxide (ZnO) nanowires. Well-aligned, vertical ZnO nanowires are grown by chemical vapor deposition on a silicon wafer with a hydrothermally grown ZnO seed layer. The nanowires are infiltrated with polydimethylsiloxane and mechanically transferred from the silicon substrate. Plasma etching exposes the top surface of the nanowires before deposition of a gold (Au) top electrode. The bottom electrode is formed by silver paint which also adheres the sensor to the measured structure. To demonstrate the sensor’s ability to conform to complex surfaces, a stepped shaft with a shoulder fillet is used. The sensor is attached to the shoulder fillet of the stepped shaft, conforming to both the circumference of the shaft, and the radius of the fillet. A periodic bending displacement is applied to the end of the shaft. The strain induces a piezoelectric potential in the ZnO nanowires which controls the barrier height and conductivity at the gold/ZnO interface, by what is known as the piezotronic effect. The conductivity change is measured for periodically applied strains. The nonlinear current-voltage (I-V) response of the device is due to the Schottky contact between the ZnO nanowires and gold electrode. The geometry of the stepped shaft corresponds to a known stress concentration factor, and the strain experienced by the shaft is estimated with a COMSOL FEA study. The conformal nature of the strain sensor makes it suitable for structural monitoring applications involving complex geometries and stress concentrators.

  6. Complementary surface charge for enhanced capacitive deionization

    NARCIS (Netherlands)

    Gao, X.; Porada, S.; Omosebi, A.; Liu, K.L.; Biesheuvel, P.M.; Landon, J.

    2016-01-01

    Commercially available activated carbon cloth electrodes are treated using nitric acid and ethylenediamine solutions, resulting in chemical surface charge enhanced carbon electrodes for capacitive deionization (CDI) applications. Surface charge enhanced electrodes are then configured in a CDI

  7. Coaxial-structured ZnO/silicon nanowires extended-gate field-effect transistor as pH sensor

    International Nuclear Information System (INIS)

    Li, Hung-Hsien; Yang, Chi-En; Kei, Chi-Chung; Su, Chung-Yi; Dai, Wei-Syuan; Tseng, Jung-Kuei; Yang, Po-Yu; Chou, Jung-Chuan; Cheng, Huang-Chung

    2013-01-01

    An extended-gate field-effect transistor (EGFET) of coaxial-structured ZnO/silicon nanowires as pH sensor was demonstrated in this paper. The oriented 1-μm-long silicon nanowires with the diameter of about 50 nm were vertically synthesized by the electroless metal deposition method at room temperature and were sequentially capped with the ZnO films using atomic layer deposition at 50 °C. The transfer characteristics (I DS –V REF ) of such ZnO/silicon nanowire EGFET sensor exhibited the sensitivity and linearity of 46.25 mV/pH and 0.9902, respectively for the different pH solutions (pH 1–pH 13). In contrast to the ZnO thin-film ones, the ZnO/silicon nanowire EGFET sensor achieved much better sensitivity and superior linearity. It was attributed to a high surface-to-volume ratio of the nanowire structures, reflecting a larger effective sensing area. The output voltage and time characteristics were also measured to indicate good reliability and durability for the ZnO/silicon nanowires sensor. Furthermore, the hysteresis was 9.74 mV after the solution was changed as pH 7 → pH 3 → pH 7 → pH 11 → pH 7. - Highlights: ► Coaxial-structured ZnO/silicon nanowire EGFET was demonstrated as pH sensor. ► EMD and ALD methods were proposed to fabricate ZnO/silicon nanowires. ► ZnO/silicon nanowire EGFET sensor achieved better sensitivity and linearity. ► ZnO/silicon nanowire EGFET sensor had good reliability and durability

  8. Piezoresistive Pressure Sensor Based on Synergistical Innerconnect Polyvinyl Alcohol Nanowires/Wrinkled Graphene Film.

    Science.gov (United States)

    Liu, Weijie; Liu, Nishuang; Yue, Yang; Rao, Jiangyu; Cheng, Feng; Su, Jun; Liu, Zhitian; Gao, Yihua

    2018-03-12

    Piezoresistive sensor is a promising pressure sensor due to its attractive advantages including uncomplicated signal collection, simple manufacture, economical and practical characteristics. Here, a flexible and highly sensitive pressure sensor based on wrinkled graphene film (WGF)/innerconnected polyvinyl alcohol (PVA) nanowires/interdigital electrodes is fabricated. Due to the synergistic effect between WGF and innerconnected PVA nanowires, the as-prepared pressure sensor realizes a high sensitivity of 28.34 kPa -1 . In addition, the device is able to discern lightweight rice about 22.4 mg (≈2.24 Pa) and shows excellent durability and reliability after 6000 repeated loading and unloading cycles. What is more, the device can detect subtle pulse beat and monitor various human movement behaviors in real-time. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Predictive simulations and optimization of nanowire field-effect PSA sensors including screening

    KAUST Repository

    Baumgartner, Stefan

    2013-05-03

    We apply our self-consistent PDE model for the electrical response of field-effect sensors to the 3D simulation of nanowire PSA (prostate-specific antigen) sensors. The charge concentration in the biofunctionalized boundary layer at the semiconductor-electrolyte interface is calculated using the propka algorithm, and the screening of the biomolecules by the free ions in the liquid is modeled by a sensitivity factor. This comprehensive approach yields excellent agreement with experimental current-voltage characteristics without any fitting parameters. Having verified the numerical model in this manner, we study the sensitivity of nanowire PSA sensors by changing device parameters, making it possible to optimize the devices and revealing the attributes of the optimal field-effect sensor. © 2013 IOP Publishing Ltd.

  10. Design of Indium Arsenide nanowire sensors for pH and biological sensing and low temperature transport through p-doped Indium Arsenide nanowires

    DEFF Research Database (Denmark)

    Upadhyay, Shivendra

    remains the primary material of choice. This research is about investigating Indium Arsenide nanowires as alternative platform for sensing charged species - chemical and biological, in solution. Starting with nanowires grown via molecular beam epitaxy in an ultra-high vacuum chamber, we discuss......H sensing, we apply the same to a more complex system - proteins. The sensing protocol involves the functionalization of the sensor surface with a receptor protein followed by the addition of the protein of interest. Sensor response to oppositely charged proteins is used to confirm the sensitivity...... of the sensor to the protein charge....

  11. New Fabrication Methodologies for the Development of Low Power Gas Sensors Based on Semiconducting Nanowires

    OpenAIRE

    Samà Monsonís, Jordi

    2016-01-01

    La tesis titulada New Fabrication Methodologies for the Development of Low Power Gas Sensors Based on Semiconducting Nanowires, se enmarca dentro de los sensores de gas para la monitorización ambiental de la calidad del aire, con el objetivo de detectar la presencia de gases nocivos para la salud humana. El trabajo desarrollado se basa en el uso de sensores de gas resistivos, es decir, que la adsorción de un gas en la superficie del sensor da lugar a un cambio en la conductividad del sens...

  12. Analysis of nanowire transistor based nitrogen dioxide gas sensor – A simulation study

    Directory of Open Access Journals (Sweden)

    Gaurav Saxena

    2015-06-01

    Full Text Available Sensors sensitivity, selectivity and stability has always been a prime design concern for gas sensors designers. Modeling and simulation of gas sensors aids the designers in improving their performance. In this paper, different routes for the modeling and simulation of a semiconducting gas sensor is presented. Subsequently, by employing one of the route, the response of Zinc Oxide nanowire transistor towards nitrogen dioxide ambient is simulated. In addition to the sensing mechanism, simulation study of gas species desorption by applying a recovery voltage is also presented.

  13. Effects of Nanowire Length and Surface Roughness on the Electrochemical Sensor Properties of Nafion-Free, Vertically Aligned Pt Nanowire Array Electrodes

    Directory of Open Access Journals (Sweden)

    Zhiyang Li

    2015-09-01

    Full Text Available In this paper, vertically aligned Pt nanowire arrays (PtNWA with different lengths and surface roughnesses were fabricated and their electrochemical performance toward hydrogen peroxide (H2O2 detection was studied. The nanowire arrays were synthesized by electroplating Pt in nanopores of anodic aluminum oxide (AAO template. Different parameters, such as current density and deposition time, were precisely controlled to synthesize nanowires with different surface roughnesses and various lengths from 3 μm to 12 μm. The PtNWA electrodes showed better performance than the conventional electrodes modified by Pt nanowires randomly dispersed on the electrode surface. The results indicate that both the length and surface roughness can affect the sensing performance of vertically aligned Pt nanowire array electrodes. Generally, longer nanowires with rougher surfaces showed better electrochemical sensing performance. The 12 μm rough surface PtNWA presented the largest sensitivity (654 μA·mM−1·cm−2 among all the nanowires studied, and showed a limit of detection of 2.4 μM. The 12 μm rough surface PtNWA electrode also showed good anti-interference property from chemicals that are typically present in the biological samples such as ascorbic, uric acid, citric acid, and glucose. The sensing performance in real samples (river water was tested and good recovery was observed. These Nafion-free, vertically aligned Pt nanowires with surface roughness control show great promise as versatile electrochemical sensors and biosensors.

  14. Self-assembly of conducting polymer nanowires at air-water interface and its application for gas sensors

    International Nuclear Information System (INIS)

    Xu Jianhua; Jiang Yadong; Yang Yajie; Yu Junsheng

    2009-01-01

    Conducting polymer poly (3, 4-ethylenedioxythiophene) (PEDOT) nanowires were prepared by wetting Al 2 O 3 membrane (AAO) template method, which could be well dispersed in organic solvent with ultrasonic treatment. In order to obtain highly ordered structure of nanowires, the self-assembly film of nanowires at air/water interface was investigated by Langmuir-Blodgett (LB) technique. The results showed that PEDOT nanowire-surfactant complex at air/water interface had well self-assembly capability, and the stable float layer was formed with collapse pressure more than 50 mN/m. This well arranged nanowire film was transferred onto interdigitated electrode successfully as novel gas sensing layer through a vertical dipping method. The as-prepared PEDOT nanowire gas sensor was applied to the precise detection of NH 3 and HCl gas, especially for low gas concentration (lower than 5 ppm), and showed higher gas sensitivity than conventional nanowire gas sensor. The chemical sensors based on ordered PEDOT nanowires presented good reversibility and reproducibility in response. Notably, our work presents an appropriate methodology for fabricating ordered conducting polymer nanomaterial for gas sensor and other applications

  15. Chip-to-chip SnO2 nanowire network sensors for room temperature H2 detection

    Science.gov (United States)

    Köck, A.; Brunet, E.; Mutinati, G. C.; Maier, T.; Steinhauer, S.

    2012-06-01

    The employment of nanowires is a very powerful strategy to improve gas sensor performance. We demonstrate a gas sensor device, which is based on silicon chip-to-chip synthesis of ultralong tin oxide (SnO2) nanowires. The sensor device employs an interconnected SnO2 nanowire network configuration, which exhibits a huge surface-to-volume ratio and provides full access of the target gas to the nanowires. The chip-to-chip SnO2 nanowire device is able to detect a H2 concentration of only 20 ppm in synthetic air with ~ 60% relative humidity at room temperature. At an operating temperature of 300°C a concentration of 50 ppm H2 results in a sensitivity of 5%. At this elevated temperature the sensor shows a linear response in a concentration range between 10 ppm and 100 ppm H2. The SnO2-nanowire fabrication procedure based on spray pyrolysis and subsequent annealing is performed at atmospheric pressure, requires no vacuum and allows upscale of the substrate to a wafer size. 3D-integration with CMOS chips is proposed as viable way for practical realization of smart nanowire based gas sensor devices for the consumer market.

  16. A Ge/Si heterostructure nanowire-based double quantum dot with integrated charge sensor

    DEFF Research Database (Denmark)

    Hu, Yongjie; Churchill, Hugh; Reilly, David

    2007-01-01

    Coupled electron spins in semiconductor double quantum dots hold promise as the basis for solid-state qubits. To date, most experiments have used III-V materials, in which coherence is limited by hyperfine interactions. Ge/Si heterostructure nanowires seem ideally suited to overcome this limitation......: the predominance of spin-zero nuclei suppresses the hyperfine interaction and chemical synthesis creates a clean and defect-free system with highly controllable properties. Here we present a top gate-defined double quantum dot based on Ge/Si heterostructure nanowires with fully tunable coupling between the dots...... and to the leads. We also demonstrate a novel approach to charge sensing in a one-dimensional nanostructure by capacitively coupling the double dot to a single dot on an adjacent nanowire. The double quantum dot and integrated charge sensor serve as an essential building block required to form a solid-state spin...

  17. Heterogeneous metal-oxide nanowire micro-sensor array for gas sensing

    Science.gov (United States)

    DeMeo, Dante; MacNaughton, Sam; Wang, Zhilong; Zhang, Xinjie; Sonkusale, Sameer; Vandervelde, Thomas E.

    2014-04-01

    Vanadium oxide, manganese oxide, tungsten oxide, and nickel oxide nanowires were investigated for their applicability as chemiresistive gas sensors. Nanowires have excellent surface-to-volume ratios which yield higher sensitivities than bulk materials. Sensing elements consisting of these materials were assembled in an array to create an electronic nose platform. Dielectrophoresis was used to position the nanomaterials onto a microfabricated array of electrodes, which was subsequently mounted onto a leadless chip carrier and printed circuit board for rapid testing. Samples were tested in an enclosed chamber with vapors of acetone, isopropanol, methanol, and aqueous ammonia. The change in resistance of each assembly was measured. Responses varied between nanowire compositions, each demonstrating unique and repeatable responses to different gases; this enabled direct detection of the gases from the ensemble response. Sensitivities were calculated based on the fractional resistance change in a saturated environment and ranged from 6 × 10-4 to 2 × 10-5%change ppm-1.

  18. Hybrid Si nanowire/amorphous silicon FETs for large-area image sensor arrays.

    Science.gov (United States)

    Wong, William S; Raychaudhuri, Sourobh; Lujan, René; Sambandan, Sanjiv; Street, Robert A

    2011-06-08

    Silicon nanowire (SiNW) field-effect transistors (FETs) were fabricated from nanowire mats mechanically transferred from a donor growth wafer. Top- and bottom-gate FET structures were fabricated using a doped a-Si:H thin film as the source/drain (s/d) contact. With a graded doping profile for the a-Si:H s/d contacts, the off-current for the hybrid nanowire/thin-film devices was found to decrease by 3 orders of magnitude. Devices with the graded contacts had on/off ratios of ∼10(5), field-effect mobility of ∼50 cm(2)/(V s), and subthreshold swing of 2.5 V/decade. A 2 in. diagonal 160 × 180 pixel image sensor array was fabricated by integrating the SiNW backplane with an a-Si:H p-i-n photodiode.

  19. Highly ordered nanowire arrays on plastic substrates for ultrasensitive flexible chemical sensors

    Science.gov (United States)

    McAlpine, Michael C.; Ahmad, Habib; Wang, Dunwei; Heath, James R.

    2013-01-01

    The development of a robust method for integrating high-performance semiconductors on flexible plastics could enable exciting avenues in fundamental research and novel applications. One area of vital relevance is chemical and biological sensing, which if implemented on biocompatible substrates, could yield breakthroughs in implantable or wearable monitoring systems. Semiconducting nanowires (and nanotubes) are particularly sensitive chemical sensors because of their high surface-to-volume ratios. Here, we present a scalable and parallel process for transferring hundreds of pre-aligned silicon nanowires onto plastic to yield highly ordered films for low-power sensor chips. The nanowires are excellent field-effect transistors, and, as sensors, exhibit parts-per-billion sensitivity to NO2, a hazardous pollutant. We also use SiO2 surface chemistries to construct a ‘nano-electronic nose’ library, which can distinguish acetone and hexane vapours via distributed responses. The excellent sensing performance coupled with bendable plastic could open up opportunities in portable, wearable or even implantable sensors. PMID:17450146

  20. Local sensor based on nanowire field effect transistor from inhomogeneously doped silicon on insulator

    Science.gov (United States)

    Presnov, Denis E.; Bozhev, Ivan V.; Miakonkikh, Andrew V.; Simakin, Sergey G.; Trifonov, Artem S.; Krupenin, Vladimir A.

    2018-02-01

    We present the original method for fabricating a sensitive field/charge sensor based on field effect transistor (FET) with a nanowire channel that uses CMOS-compatible processes only. A FET with a kink-like silicon nanowire channel was fabricated from the inhomogeneously doped silicon on insulator wafer very close (˜100 nm) to the extremely sharp corner of a silicon chip forming local probe. The single e-beam lithographic process with a shadow deposition technique, followed by separate two reactive ion etching processes, was used to define the narrow semiconductor nanowire channel. The sensors charge sensitivity was evaluated to be in the range of 0.1-0.2 e /√{Hz } from the analysis of their transport and noise characteristics. The proposed method provides a good opportunity for the relatively simple manufacture of a local field sensor for measuring the electrical field distribution, potential profiles, and charge dynamics for a wide range of mesoscopic objects. Diagnostic systems and devices based on such sensors can be used in various fields of physics, chemistry, material science, biology, electronics, medicine, etc.

  1. A highly sensitive, label-free gene sensor based on a single conducting polymer nanowire.

    Science.gov (United States)

    Kannan, Bhuvaneswari; Williams, David E; Laslau, Cosmin; Travas-Sejdic, Jadranka

    2012-05-15

    A prerequisite for exploiting sensing devices based on semiconductor nanowires is ultra-sensitive and selective direct electrical detection of biological and chemical species. Here, we constructed a transducer based on copolymer of poly(3,4,-ethylenedioxythiophene) (PEDOT) and carboxylic group functionalised PEDOT single nanowire in between gold electrodes, followed by covalent attachment of amino-modified probe oligonucleotide. The target ODNs specific to Homo sapiens Breast and ovarian cancer cells were detected at femtomolar concentration and incorporation of negative controls (non-complementary ODN) were clearly discriminated by the sensor. The ex situ measurements were performed by using two terminal device setup and the changes in the interface of the nanowire associated with the association or dissociation of ODNs were measured as change in resistance. In addition, in situ measurements were performed by utilizing scanning ion conductance microscopy to measure the change in resistance of probe modified nanowire upon addition of different concentration of target ODNs in presence of relevant buffer. The constructed, nano sensor showed highly sensitive concentration dependent resistance change. Copyright © 2012 Elsevier B.V. All rights reserved.

  2. Wearable, wireless gas sensors using highly stretchable and transparent structures of nanowires and graphene

    Science.gov (United States)

    Park, Jihun; Kim, Joohee; Kim, Kukjoo; Kim, So-Yun; Cheong, Woon Hyung; Park, Kyeongmin; Song, Joo Hyeb; Namgoong, Gyeongho; Kim, Jae Joon; Heo, Jaeyeong; Bien, Franklin; Park, Jang-Ung

    2016-05-01

    Herein, we report the fabrication of a highly stretchable, transparent gas sensor based on silver nanowire-graphene hybrid nanostructures. Due to its superb mechanical and optical characteristics, the fabricated sensor demonstrates outstanding and stable performances even under extreme mechanical deformation (stable until 20% of strain). The integration of a Bluetooth system or an inductive antenna enables the wireless operation of the sensor. In addition, the mechanical robustness of the materials allows the device to be transferred onto various nonplanar substrates, including a watch, a bicycle light, and the leaves of live plants, thereby achieving next-generation sensing electronics for the `Internet of Things' area.Herein, we report the fabrication of a highly stretchable, transparent gas sensor based on silver nanowire-graphene hybrid nanostructures. Due to its superb mechanical and optical characteristics, the fabricated sensor demonstrates outstanding and stable performances even under extreme mechanical deformation (stable until 20% of strain). The integration of a Bluetooth system or an inductive antenna enables the wireless operation of the sensor. In addition, the mechanical robustness of the materials allows the device to be transferred onto various nonplanar substrates, including a watch, a bicycle light, and the leaves of live plants, thereby achieving next-generation sensing electronics for the `Internet of Things' area. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr01468b

  3. Copper Nanowire-Based Aerogel with Tunable Pore Structure and Its Application as Flexible Pressure Sensor.

    Science.gov (United States)

    Xu, Xiaojuan; Wang, Ranran; Nie, Pu; Cheng, Yin; Lu, Xiaoyu; Shi, Liangjing; Sun, Jing

    2017-04-26

    Aerogel is a kind of material with high porosity and low density. However, the research on metal-based aerogel with good conductivity is quite limited, which hinders its usage in electronic devices, such as flexible pressure sensors. In this work, we successfully fabricate copper nanowire (CuNW) based aerogel through a one-pot method, and the dynamics for the assembly of CuNWs into hydrogel is intensively investigated. The "bubble controlled assembly" mechanism is put forward for the first time, according to which tunable pore structures and densities (4.3-7.5 mg cm -3 ) of the nanowire aerogel is achieved. Subsequently, ultralight flexible pressure sensors with tunable sensitivities (0.02 kPa -1 to 0.7 kPa -1 ) are fabricated from the Cu NWs aerogels, and the negative correlation behavior of the sensitivity to the density of the aerogel sensors is disclosed systematically. This work provides a versatile strategy for the fabrication of nanowire-based aerogels, which greatly broadens their application potential.

  4. DETERMINATION OF SURFACE CHARGE DENSITY OF α ...

    African Journals Online (AJOL)

    a

    dissociation of these groups, result into a pH dependent surface charge whose density can be measured by acid-base titration. The surface charge density determined by such method is essentially measured relative to the unknown condition of the oxide/liquid interface prior to reagent addition (i.e. at the point of zero ...

  5. Invisible Surface Charge Pattern on Inorganic Electrets

    DEFF Research Database (Denmark)

    Wang, Fei; Hansen, Ole

    2013-01-01

    We propose an easy method to pattern the surface charge of ${\\rm SiO}_{2}$ electrets without patterning the dielectric layer. By eliminating the use of metal guard electrodes, both the charge efficiency and the surface charge stability in humid environments improve. We apply the concept...

  6. A Ge/Si heterostructure nanowire-based double quantum dot with integrated charge sensor.

    Science.gov (United States)

    Hu, Yongjie; Churchill, Hugh O H; Reilly, David J; Xiang, Jie; Lieber, Charles M; Marcus, Charles M

    2007-10-01

    One proposal for a solid-state-based quantum bit (qubit) is to control coupled electron spins on adjacent semiconductor quantum dots. Most experiments have focused on quantum dots made from III-V semiconductors; however, the coherence of electron spins in these materials is limited by hyperfine interactions with nuclear spins. Ge/Si core/shell nanowires seem ideally suited to overcome this limitation, because the most abundant nuclei in Ge and Si have spin zero and the nanowires can be chemically synthesized defect-free with tunable properties. Here, we present a double quantum dot based on Ge/Si nanowires in which we can completely control the coupling between the dots and to the leads. We also demonstrate that charge on the double dot can be detected by coupling it capacitively to an adjacent nanowire quantum dot. The double quantum dot and integrated charge sensor serve as an essential building block to form a solid-state qubit free of nuclear spin.

  7. Monolithic carbon structures including suspended single nanowires and nanomeshes as a sensor platform.

    Science.gov (United States)

    Lim, Yeongjin; Heo, Jeong-Il; Madou, Marc; Shin, Heungjoo

    2013-11-20

    With the development of nanomaterial-based nanodevices, it became inevitable to develop cost-effective and simple nanofabrication technologies enabling the formation of nanomaterial assembly in a controllable manner. Herein, we present suspended monolithic carbon single nanowires and nanomeshes bridging two bulk carbon posts, fabricated in a designed manner using two successive UV exposure steps and a single pyrolysis step. The pyrolysis step is accompanied with a significant volume reduction, resulting in the shrinkage of micro-sized photoresist structures into nanoscale carbon structures. Even with the significant elongation of the suspended carbon nanowire induced by the volume reduction of the bulk carbon posts, the resultant tensional stress along the nanowire is not significant but grows along the wire thickness; this tensional stress gradient and the bent supports of the bridge-like carbon nanowire enhance structural robustness and alleviate the stiction problem that suspended nanostructures frequently experience. The feasibility of the suspended carbon nanostructures as a sensor platform was demonstrated by testing its electrochemical behavior, conductivity-temperature relationship, and hydrogen gas sensing capability.

  8. UV-Assisted Alcohol Sensors using Gallium Nitride Nanowires Functionalized with Zinc Oxide and Tin Dioxide Nanoparticles

    Science.gov (United States)

    Bajpai, Ritu

    The motivation behind this work has been to address two of the most challenging issues posed to semiconductor gas sensors--- tuning the device selectivity and sensitivity to a wide variety of gases. In a chemiresistor type nanowire sensor, the sensitivity and selectivity depend on the interaction of different chemical analytes with the nanowire surface. Constrained by the surface properties of the nanowire material, most nanowire sensors can detect only specific type of analytes. In order to make a nano-sensor array for a wide range of analytes, there is a need to tune the device sensitivity and selectivity towards different chemicals. Employing the inherent advantages of nanostructure based sensing such as large surface area, miniature size, low power consumption, and nmol/mol (ppb) sensitivity, an attempt has been made to propose a device with tunable selectivity and sensitivity. The idea proposed in this work is to functionalize GaN nanowires which have relatively inactive surface properties (i.e., with no chemiresistive sensitivity to different classes of organic vapors), with analyte dependent active metal oxides. The selectivity of the sensor devices is controlled independent of the surface properties of the nanowire itself. It is the surface properties of the functionalizing metal oxides which determine the selectivity of these sensors. Further facilitated by the proposed fabrication technique, these sensors can be easily tuned to detect different gases. The prototype developed in this work is that of a UV assisted alcohol sensor using GaN nanowires functionalized with ZnO and SnO2 nanoparticles. As opposed to the widely demonstrated metal oxide based sensors assisted by elevated temperature, the operation of photoconductive semiconductor sensor devices such as those fabricated in this work, can also be assisted by UV illumination at room temperature. Temperature assisted sensing requires an integrated on-chip heater, which could impose constraints on the

  9. Wireless Remote Monitoring of Glucose Using a Functionalized ZnO Nanowire Arrays Based Sensor

    Directory of Open Access Journals (Sweden)

    Magnus Willander

    2011-08-01

    Full Text Available This paper presents a prototype wireless remote glucose monitoring system interfaced with a ZnO nanowire arrays-based glucose sensor, glucose oxidase enzyme immobilized onto ZnO nanowires in conjunction with a Nafion® membrane coating, which can be effectively applied for the monitoring of glucose levels in diabetics. Global System for Mobile Communications (GSM services like General Packet Radio Service (GPRS and Short Message Service (SMS have been proven to be logical and cost effective methods for gathering data from remote locations. A communication protocol that facilitates remote data collection using SMS has been utilized for monitoring a patient’s sugar levels. In this study, we demonstrate the remote monitoring of the glucose levels with existing GPRS/GSM network infra-structures using our proposed functionalized ZnO nanowire arrays sensors integrated with standard readily available mobile phones. The data can be used for centralized monitoring and other purposes. Such applications can reduce health care costs and allow caregivers to monitor and support to their patients remotely, especially those located in rural areas.

  10. Self-assembled and highly selective sensors based on air-bridge-structured nanowire junction arrays.

    Science.gov (United States)

    Park, Won Jeong; Choi, Kyung Jin; Kim, Myung Hwa; Koo, Bon Hyeong; Lee, Jong-Lam; Baik, Jeong Min

    2013-08-14

    We describe a strategy for creating an air-bridge-structured nanowire junction array platform that capable of reliably discriminating between three gases (hydrogen, carbon monoxide, and nitrogen dioxide) in air. Alternatively driven dual nanowire species of ZnO and CuO with the average diameter of ∼30 nm on a single substrate are used and decorated with metallic nanoparticles to form two-dimensional microarray, which do not need to consider the post fabrications. Each individual nanowires in the array form n-n, p-p, and p-n junctions at the micro/nanoscale on single substrate and the junctions act as electrical conducting path for carriers. The adsorption of gas molecules to the surface changes the potential barrier height formed at the junctions and the carrier transport inside the straight semiconductors, which provide the ability of a given sensor array to differentiate among the junctions. The sensors were tested for their ability to distinguish three gases (H2, CO, and NO2), which they were able to do unequivocally when the data was classified using linear discriminant analysis.

  11. Cadmium zinc telluride (CZT) nanowire sensors for detection of low energy gamma-ray detection

    Science.gov (United States)

    Gandhi, T.; Raja, K. S.; Misra, M.

    2008-04-01

    Bulk single crystals of CdZnTe compound semiconductor is used for room temperature radiation detection in commercial radiation sensors. A large volume of detector material with low defect density is required for increasing the detection efficiency. Manufacture of such a bulky detector-quality material with low defect density is expensive. In this communication, synthesis of nanowires arrays of CdZnTe that can be used for detecting low energy radiation is reported for the first time. CdZnTe ternary compound semiconductor, referred as CZT, was electrodeposited in the form of nanowires onto a TiO II nanotubular template in non-aqueous electrolytes using a pulse-reverse process at 130 °C. Very high electrical resistivity of the CZT nanowires (in the order of 10 10 Ω-cm) was obtained. Such a high resistivity was attributed to the presence of deep defect states such as cadmium vacancies created by the anodic cycle of the pulse-reverse electrodeposition process. Stacks of series connected CZT nanowire arrays were impressed with different bias potentials. The leakage current was in the order of tens of PicoAmperes. When exposed to a radiation source (Am -241, 60 keV), the current flow in the circuit increased. The preliminary results indicate that the CZT nanowire arrays can be used as radiation detector materials at room temperature with a much low bias potential (0.7 - 2.3 V) as against 300 - 500 V applied to the bulk detector materials.

  12. Optimization of nanowire DNA sensor sensitivity using self-consistent simulation

    KAUST Repository

    Baumgartner, S

    2011-09-26

    In order to facilitate the rational design and the characterization of nanowire field-effect sensors, we have developed a model based on self-consistent charge-transport equations combined with interface conditions for the description of the biofunctionalized surface layer at the semiconductor/electrolyte interface. Crucial processes at the interface, such as the screening of the partial charges of the DNA strands and the influence of the angle of the DNA strands with respect to the nanowire, are computed by a Metropolis Monte Carlo algorithm for charged molecules at interfaces. In order to investigate the sensing mechanism of the device, we have computed the current-voltage characteristics, the electrostatic potential and the concentrations of electrons and holes. Very good agreement with measurements has been found and optimal device parameters have been identified. Our approach provides the capability to study the device sensitivity, which is of fundamental importance for reliable sensing. © IOP Publishing Ltd.

  13. Fabrication of a P3HT-ZnO Nanowires Gas Sensor Detecting Ammonia Gas

    Directory of Open Access Journals (Sweden)

    Chin-Guo Kuo

    2017-12-01

    Full Text Available In this study, an organic-inorganic semiconductor gas sensor was fabricated to detect ammonia gas. An inorganic semiconductor was a zinc oxide (ZnO nanowire array produced by atomic layer deposition (ALD while an organic material was a p-type semiconductor, poly(3-hexylthiophene (P3HT. P3HT was suitable for the gas sensing application due to its high hole mobility, good stability, and good electrical conductivity. In this work, P3HT was coated on the zinc oxide nanowires by the spin coating to form an organic-inorganic heterogeneous interface of the gas sensor for detecting ammonia gas. The thicknesses of the P3HT were around 462 nm, 397 nm, and 277 nm when the speeds of the spin coating were 4000 rpm, 5000 rpm, and 6000 rpm, respectively. The electrical properties and sensing characteristics of the gas sensing device at room temperature were evaluated by Hall effect measurement and the sensitivity of detecting ammonia gas. The results of Hall effect measurement for the P3HT-ZnO nanowires semiconductor with 462 nm P3HT film showed that the carrier concentration and the mobility were 2.7 × 1019 cm−3 and 24.7 cm2∙V−1∙s−1 respectively. The gas sensing device prepared by the P3HT-ZnO nanowires semiconductor had better sensitivity than the device composed of the ZnO film and P3HT film. Additionally, this gas sensing device could reach a maximum sensitivity around 11.58 per ppm.

  14. Fabrication of a P3HT-ZnO Nanowires Gas Sensor Detecting Ammonia Gas.

    Science.gov (United States)

    Kuo, Chin-Guo; Chen, Jung-Hsuan; Chao, Yi-Chieh; Chen, Po-Lin

    2017-12-25

    In this study, an organic-inorganic semiconductor gas sensor was fabricated to detect ammonia gas. An inorganic semiconductor was a zinc oxide (ZnO) nanowire array produced by atomic layer deposition (ALD) while an organic material was a p-type semiconductor, poly(3-hexylthiophene) (P3HT). P3HT was suitable for the gas sensing application due to its high hole mobility, good stability, and good electrical conductivity. In this work, P3HT was coated on the zinc oxide nanowires by the spin coating to form an organic-inorganic heterogeneous interface of the gas sensor for detecting ammonia gas. The thicknesses of the P3HT were around 462 nm, 397 nm, and 277 nm when the speeds of the spin coating were 4000 rpm, 5000 rpm, and 6000 rpm, respectively. The electrical properties and sensing characteristics of the gas sensing device at room temperature were evaluated by Hall effect measurement and the sensitivity of detecting ammonia gas. The results of Hall effect measurement for the P3HT-ZnO nanowires semiconductor with 462 nm P3HT film showed that the carrier concentration and the mobility were 2.7 × 10 19 cm -3 and 24.7 cm²∙V -1 ∙s -1 respectively. The gas sensing device prepared by the P3HT-ZnO nanowires semiconductor had better sensitivity than the device composed of the ZnO film and P3HT film. Additionally, this gas sensing device could reach a maximum sensitivity around 11.58 per ppm.

  15. Surface charge measurement by the Pockels effect

    CERN Document Server

    Sam, Y L

    2001-01-01

    have been observed by applying both impulse and AC voltages to a needle electrode in direct contact with the BSO. AC surface discharge behaviour of polymeric materials bonded to the BSO has also been investigated. The effect of the surrounding environment has been experimentally examined by placing the cell inside a vacuum chamber. Surface charge measurements have been made at various atmospheric pressures. The effect of an electro-negative gas (Sulphur Hexafluoride) on the surface charge distribution has also been investigated. This thesis is concerned with the design and development of a surface charge measurement system using Pockels effect. The measurement of surface charge is important in determining the electrical performance of high voltage insulation materials. The method proposed allows on-line measurement of charge and can generate two-dimensional images that represent the charge behaviour on the surface of the material under test. The measurement system is optical and uses a Pockels crystal as the ...

  16. On-chip growth of semiconductor metal oxide nanowires for gas sensors: A review

    Directory of Open Access Journals (Sweden)

    Chu Manh Hung

    2017-09-01

    Full Text Available Semiconductor metal oxide nanowires (SMO-NWs show great potential for novel gas sensor applications because of their distinct properties, such as a high surface area to volume aspect ratio, high crystallinity and perfect pathway for electron transfer (length of NW. SMO-NW sensors can be configured as resistors or field-effect transistors for gas detection and different configurations, such as a single NW, multiple NWs, and networked NW films, have been established. Surface-functionalizing NWs with catalyst elements and self-heating NWs provide additional advantages for highly selective and low-power consumption gas sensors. However, an appropriate design of SMO-NWs is of practical importance in enhancing the gas-sensing performance of SMO-NW sensors. The on-chip growth of SMO-NWs possesses many advantages which can thus be effectively used for the large-scale fabrication of SMO-NW sensors with improved gas response and stability. This review aims to provide up-to-date information on the on-chip fabrication of SnO2, ZnO, WO3, CuO, and other SMO-NW sensors. It also discusses a variety of promising approaches that help advance the on-chip fabrication of SMO-NW-based gas sensors and other NW-based devices.

  17. Development of a nanowire based titanium needle probe sensor for glucose monitoring

    Science.gov (United States)

    Deshpande, Devesh C.

    glucose monitoring. The working electrode of the sensor comprised of vertically aligned, free standing Au nanowires to utilize the advantages of nanostructures. The sensor was fabricated on biocompatible titanium substrate using Micro/Nano fabrication processes such as Plasma Enhanced Chemical Vapor Deposition (PECVD), Electron Beam Evaporation, Lithography, aligned nanowire growth and wet and plasma etching. Arrays of free-standing nanowires were grown at room temperature and pressure using a novel template based growth process. After fabrication of the sensor, immobilization of an enzyme was carried out on the sensing electrode to ensure selectivity of the sensor to glucose. This was achieved by using self-assembled thiol monolayers and entrapment in a conducting polymer matrix. Glucose oxidase was used for this purpose, which catalyzed the conversion of glucose to gluconic acid, producing hydrogen peroxide in the process. Amperometry was used for glucose detection, in which a constant voltage was applied to the sensor. This potential oxidized the hydrogen peroxide and produced changes in the current which were correlated to the glucose concentration. This dissertation will address the importance of continuous glucose monitoring, current technology and problems faced, the design and fabrication of the sensor and electrochemical sensing to detect glucose levels in solution. Finally, the problems encountered during the process will be discussed and the future work will be detailed.

  18. Transparent and stretchable strain sensors based on metal nanowire microgrids for human motion monitoring.

    Science.gov (United States)

    Cho, Ji Hwan; Ha, Sung-Hun; Kim, Jong-Man

    2018-04-02

    Optical transparency is increasingly considered as one of the most important characteristics required in advanced stretchable strain sensors for application in body-attachable systems. In this paper, we present an entirely solution-processed fabrication route to highly transparent and stretchable resistive strain sensors based on silver nanowire microgrids (AgNW-MGs). The AgNW-MG strain sensors are readily prepared by patterning the AgNWs on a stretchable substrate into a MG geometry via a mesh-template-assisted contact-transfer printing. The MG has a unique architecture comprising the AgNWs and can be stretched to ε = 35%, with high gauge factors of ∼6.9 for ε = 0%-30% and ∼41.1 for ε = 30%-35%. The sensor also shows a high optical transmittance of 77.1% ± 1.5% (at 550 nm) and stably maintains the remarkable optical performance even at high strains. In addition, the sensor responses are found to be highly reversible with negligible hysteresis and are reliable even under repetitive stretching-releasing cycles (1000 cycles at ε = 10%). The practicality of the AgNW-MG strain sensor is confirmed by successfully monitoring a wide range of human motions in real time after firmly laminating the device onto various body parts.

  19. Transparent and stretchable strain sensors based on metal nanowire microgrids for human motion monitoring

    Science.gov (United States)

    Cho, Ji Hwan; Ha, Sung-Hun; Kim, Jong-Man

    2018-04-01

    Optical transparency is increasingly considered as one of the most important characteristics required in advanced stretchable strain sensors for application in body-attachable systems. In this paper, we present an entirely solution-processed fabrication route to highly transparent and stretchable resistive strain sensors based on silver nanowire microgrids (AgNW-MGs). The AgNW-MG strain sensors are readily prepared by patterning the AgNWs on a stretchable substrate into a MG geometry via a mesh-template-assisted contact-transfer printing. The MG has a unique architecture comprising the AgNWs and can be stretched to ɛ = 35%, with high gauge factors of ˜6.9 for ɛ = 0%-30% and ˜41.1 for ɛ = 30%-35%. The sensor also shows a high optical transmittance of 77.1% ± 1.5% (at 550 nm) and stably maintains the remarkable optical performance even at high strains. In addition, the sensor responses are found to be highly reversible with negligible hysteresis and are reliable even under repetitive stretching-releasing cycles (1000 cycles at ɛ = 10%). The practicality of the AgNW-MG strain sensor is confirmed by successfully monitoring a wide range of human motions in real time after firmly laminating the device onto various body parts.

  20. Highly Sensitive Flexible Pressure Sensor Based on Silver Nanowires-Embedded Polydimethylsiloxane Electrode with Microarray Structure.

    Science.gov (United States)

    Shuai, Xingtian; Zhu, Pengli; Zeng, Wenjin; Hu, Yougen; Liang, Xianwen; Zhang, Yu; Sun, Rong; Wong, Ching-Ping

    2017-08-09

    Flexible pressure sensors have attracted increasing research interest because of their potential applications for wearable sensing devices. Herein, a highly sensitive flexible pressure sensor is exhibited based on the elastomeric electrodes and a microarray architecture. Polydimethylsiloxane (PDMS) substrate, coated with silver nanowires (AgNWs), is used as the top electrode, while polyvinylidene fluoride (PVDF) as the dielectric layer. Several transfer processes are applied on seeking facile strategy for the preparation of the bottom electrode via embedding AgNWs into the PDMS film of microarray structure. The flexible pressure sensor integrates the top electrode, dielectric layer, and microarray electrode in a sandwich structure. It is demonstrated that such sensors possess the superiorities of high sensitivity (2.94 kPa -1 ), low detection limit (flexible pressure sensor exhibits good performance even in a noncontact way, such as detecting voice vibrations and air flow. Due to its superior performance, this designed flexible pressure sensor demonstrates promising potential in the application of electronic skins, as well as wearable healthcare monitors.

  1. Development of polypyrrole coated copper nanowires for gas sensor application

    Directory of Open Access Journals (Sweden)

    H. Shokry Hassan

    2015-09-01

    Full Text Available Both polypyrrole (PPy and polypyrrole coated copper thin films were synthesized successfully via two-step methods. PPy nanorods films were first grown chemically, and then PPy thin films were fabricated on glass substrates using dip-coating technique. The resulting films were examined via various characterization methods such as X-ray diffraction (XRD, scanning electron microscopy (SEM, Fourier transform infrared spectroscopy (FT-IR and Thermal Gravimetric Analysis (TGA. Gas sensor devices were fabricated and the gas sensitivity for (PPy coated copper was measured as a function of temperature for both O2 and CO2 gases. The maximum sensitivity for O2 gas was around 160% and the maximum sensitivity for CO2 was 300%.

  2. Fabrication and characterization of metal oxide nanowire sensors.

    Science.gov (United States)

    Shen, Guozhen

    2008-01-01

    Trace detection of chemicals and biological species like industrial gases, proteins, drug molecules, and chemical warfare agents, is an important issue to human health and safety. Central to this issue is the development of high sensitivity, high selectivity, high stability and rapid detection chemical and bio-sensors. With special geometry and chemical and physical properties, one-dimensional (1-D) metal oxide nanostructures have become the promising candidates for chemical and biosensing applications in recent years. Here, we intend to provide an overview on this interesting and important field. In the first part, the patents for rational synthesis of 1-D metal oxide nanostructures on a large scale will be introduced. The patents on chemical and biosensors built on 1-D metal oxide nanostructures are then introduced in the second part. Finally, we provide a review of the recent development of electronic nose systems using 1-D metal oxide nanostructures, which show great potential for the improvement of sensing abilities.

  3. Electrostatic Selectivity of Volatile Organic Compounds Using Electrostatically Formed Nanowire Sensor.

    Science.gov (United States)

    Mahapatra, Niharendu; Ben-Cohen, Avi; Vaknin, Yonathan; Henning, Alex; Hayon, Joseph; Shimanovich, Klimentiy; Greenspan, Hayit; Rosenwaks, Yossi

    2018-03-23

    For the past several decades, there is growing demand for the development of low-power gas sensing technology for the selective detection of volatile organic compounds (VOCs), important for monitoring safety, pollution, and healthcare. Here we report the selective detection of homologous alcohols and different functional groups containing VOCs using the electrostatically formed nanowire (EFN) sensor without any surface modification of the device. Selectivity toward specific VOC is achieved by training machine-learning based classifiers using the calculated changes in the threshold voltage and the drain-source on current, obtained from systematically controlled biasing of the surrounding gates (junction and back gates) of the field-effect transistors (FET). This work paves the way for a Si complementary metal-oxide-semiconductor (CMOS)-based FET device as an electrostatically selective sensor suitable for mass production and low-power sensing technology.

  4. Multiscale modeling of nanowire-based Schottky-barrier field-effect transistors for sensor applications

    International Nuclear Information System (INIS)

    Nozaki, D; Kunstmann, J; Zoergiebel, F; Cuniberti, G; Weber, W M; Mikolajick, T

    2011-01-01

    We present a theoretical framework for the calculation of charge transport through nanowire-based Schottky-barrier field-effect transistors that is conceptually simple but still captures the relevant physical mechanisms of the transport process. Our approach combines two approaches on different length scales: (1) the finite element method is used to model realistic device geometries and to calculate the electrostatic potential across the Schottky barrier by solving the Poisson equation, and (2) the Landauer-Buettiker approach combined with the method of non-equilibrium Green's functions is employed to calculate the charge transport through the device. Our model correctly reproduces typical I-V characteristics of field-effect transistors, and the dependence of the saturated drain current on the gate field and the device geometry are in good agreement with experiments. Our approach is suitable for one-dimensional Schottky-barrier field-effect transistors of arbitrary device geometry and it is intended to be a simulation platform for the development of nanowire-based sensors.

  5. Improvements in purification of silver nanowires by decantation and fabrication of flexible transparent electrodes. Application to capacitive touch sensors

    International Nuclear Information System (INIS)

    Mayousse, Céline; Celle, Caroline; Moreau, Eléonore; Carella, Alexandre; Simonato, Jean-Pierre; Mainguet, Jean-François

    2013-01-01

    Transparent flexible electrodes made of metallic nanowires, and in particular silver nanowires (AgNWs), appear as an extremely promising alternative to transparent conductive oxides for future optoelectronic devices. Though significant progresses have been made the last few years, there is still some room for improvement regarding the synthesis of high quality silver nanowire solutions and fabrication process of high performance electrodes. We show that the commonly used purification process can be greatly simplified through decantation. Using this process it is possible to fabricate flexible electrodes by spray coating with sheet resistance lower than 25 Ω sq −1 at 90% transparency in the visible spectrum. These electrodes were used to fabricate an operative transparent flexible touch screen. To our knowledge this is the first reported AgNW based touch sensor relying on capacitive technology. (paper)

  6. Self-Passivation by Fluorine Plasma Treatment and Low-Temperature Annealing in SiGe Nanowires for Biochemical Sensors

    Directory of Open Access Journals (Sweden)

    Kow-Ming Chang

    2014-01-01

    Full Text Available Nanowires are widely used as highly sensitive sensors for electrical detection of biological and chemical species. Modifying the band structure of strained-Si metal-oxide-semiconductor field-effect transistors by applying the in-plane tensile strain reportedly improves electron and hole mobility. The oxidation-induced Ge condensation increases the Ge fraction in a SiGe-on-insulator (SGOI and substantially increases hole mobility. However, oxidation increases the number of surface states, resulting in hole mobility degradation. In this work, 3-aminopropyltrimethoxysilane (APTMS was used as a biochemical reagent. The hydroxyl molecule on the oxide surface was replaced by the methoxy groups of the APTMS molecule. We proposed a surface plasma treatment to improve the electrical properties of SiGe nanowires. Fluorine plasma treatment can result in enhanced rates of thermal oxidation and speed up the formation of a self-passivation oxide layer. Like a capping oxide layer, the self-passivation oxide layer reduces the rate of follow-up oxidation. Preoxidation treatment also improved the sensitivity of SiGe nanowires because the Si-F binding was held at a more stable interface state compared to bare nanowire on the SiGe surface. Additionally, the sensitivity can be further improved by either the N2 plasma posttreatment or the low-temperature postannealing due to the suppression of outdiffusion of Ge and F atoms from the SiGe nanowire surface.

  7. Full thermoelectric characterization of InAs nanowires using MEMS heater/sensors.

    Science.gov (United States)

    Karg, S F; Troncale, V; Drechsler, U; Mensch, P; Das Kanungo, P; Schmid, H; Schmidt, V; Gignac, L; Riel, H; Gotsmann, B

    2014-08-01

    Precise measurements of a complete set of thermoelectric parameters on a single indium-arsenide nanowire (NW) have been performed using highly sensitive, micro-fabricated sensing devices based on the heater/sensor principle. The devices were fabricated as micro electro-mechanical systems consisting of silicon nitride membranes structured with resistive gold heaters/sensors. Preparation, operation and characterization of the devices are described in detail. Thermal decoupling of the heater/sensor platforms has been optimized reaching thermal conductances as low as 20 nW K(-1) with a measurements sensitivity below 20 nW K(-1). The InAs NWs were characterized in terms of thermal conductance, four-probe electrical conductance and thermopower (Seebeck coefficient), all measured on a single NW. The temperature dependence of the parameters determining the thermoelectric figure-of-merit of an InAs NW was acquired in the range 200-350 K featuring a minor decrease of the thermal conductivity from 2.7 W (m K)(-1) to 2.3 W (m K)(-1).

  8. Highly selective GaN-nanowire/TiO2-nanocluster hybrid sensors for detection of benzene and related environment pollutants.

    Science.gov (United States)

    Aluri, Geetha S; Motayed, Abhishek; Davydov, Albert V; Oleshko, Vladimir P; Bertness, Kris A; Sanford, Norman A; Rao, Mulpuri V

    2011-07-22

    Nanowire-nanocluster hybrid chemical sensors were realized by functionalizing gallium nitride (GaN) nanowires (NWs) with titanium dioxide (TiO(2)) nanoclusters for selectively sensing benzene and other related aromatic compounds. Hybrid sensor devices were developed by fabricating two-terminal devices using individual GaN NWs followed by the deposition of TiO(2) nanoclusters using RF magnetron sputtering. The sensor fabrication process employed standard microfabrication techniques. X-ray diffraction and high-resolution analytical transmission electron microscopy using energy-dispersive x-ray and electron energy-loss spectroscopies confirmed the presence of the anatase phase in TiO(2) clusters after post-deposition anneal at 700 °C. A change of current was observed for these hybrid sensors when exposed to the vapors of aromatic compounds (benzene, toluene, ethylbenzene, xylene and chlorobenzene mixed with air) under UV excitation, while they had no response to non-aromatic organic compounds such as methanol, ethanol, isopropanol, chloroform, acetone and 1,3-hexadiene. The sensitivity range for the noted aromatic compounds except chlorobenzene were from 1% down to 50 parts per billion (ppb) at room temperature. By combining the enhanced catalytic properties of the TiO(2) nanoclusters with the sensitive transduction capability of the nanowires, an ultra-sensitive and selective chemical sensing architecture is demonstrated. We have proposed a mechanism that could qualitatively explain the observed sensing behavior.

  9. Low-Temperature Rapid Fabrication of ZnO Nanowire UV Sensor Array by Laser-Induced Local Hydrothermal Growth

    Directory of Open Access Journals (Sweden)

    Sukjoon Hong

    2013-01-01

    Full Text Available We demonstrate ZnO nanowire based UV sensor by laser-induced hydrothermal growth of ZnO nanowire. By inducing a localized temperature rise using focused laser, ZnO nanowire array at ~15 μm size consists of individual nanowires with ~8 μm length and 200~400 nm diameter is readily synthesized on gold electrode within 30 min at the desired position. The laser-induced growth process is consecutively applied on two different points to bridge the micron gap between the electrodes. The resultant photoconductive ZnO NW interconnections display 2~3 orders increase in the current upon the UV exposure at a fixed voltage bias. It is also confirmed that the amount of photocurrent can be easily adjusted by changing the number of ZnO NW array junctions. The device exhibits clear response to the repeated UV illumination, suggesting that this process can be usefully applied for the facile fabrication of low-cost UV sensor array.

  10. Design of Highly Selective Gas Sensors via Physicochemical Modification of Oxide Nanowires: Overview

    Directory of Open Access Journals (Sweden)

    Hyung-Sik Woo

    2016-09-01

    Full Text Available Strategies for the enhancement of gas sensing properties, and specifically the improvement of gas selectivity of metal oxide semiconductor nanowire (NW networks grown by chemical vapor deposition and thermal evaporation, are reviewed. Highly crystalline NWs grown by vapor-phase routes have various advantages, and thus have been applied in the field of gas sensors over the years. In particular, n-type NWs such as SnO2, ZnO, and In2O3 are widely studied because of their simple synthetic preparation and high gas response. However, due to their usually high responses to C2H5OH and NO2, the selective detection of other harmful and toxic gases using oxide NWs remains a challenging issue. Various strategies—such as doping/loading of noble metals, decorating/doping of catalytic metal oxides, and the formation of core–shell structures—have been explored to enhance gas selectivity and sensitivity, and are discussed herein. Additional methods such as the transformation of n-type into p-type NWs and the formation of catalyst-doped hierarchical structures by branch growth have also proven to be promising for the enhancement of gas selectivity. Accordingly, the physicochemical modification of oxide NWs via various methods provides new strategies to achieve the selective detection of a specific gas, and after further investigations, this approach could pave a new way in the field of NW-based semiconductor-type gas sensors.

  11. A Transflective Nano-Wire Grid Polarizer Based Fiber-Optic Sensor

    Directory of Open Access Journals (Sweden)

    Yan-Qing Lu

    2011-02-01

    Full Text Available A transflective nano-wire grid polarizer is fabricated on a single mode fiber tip by focused ion beam machining. In contrast to conventional absorptive in-line polarizers, the wire grids reflect TE-mode, while transmitting TM-mode light so that no light power is discarded. A reflection contrast of 13.7 dB and a transmission contrast of 4.9 dB are achieved in the 1,550 nm telecom band using a 200-nm wire grid fiber polarizer. With the help of an optic circulator, the polarization states of both the transmissive and reflective lights in the fiber may be monitored simultaneously. A kind of robust fiber optic sensor is thus proposed that could withstand light power variations. To verify the idea, a fiber pressure sensor with the sensitivity of 0.24 rad/N is demonstrated. The corresponding stress-optic coefficient of the fiber is measured. In addition to pressure sensing, this technology could be applied in detecting any polarization state change induced by magnetic fields, electric currents and so on.

  12. Design of Highly Selective Gas Sensors via Physicochemical Modification of Oxide Nanowires: Overview.

    Science.gov (United States)

    Woo, Hyung-Sik; Na, Chan Woong; Lee, Jong-Heun

    2016-09-20

    Strategies for the enhancement of gas sensing properties, and specifically the improvement of gas selectivity of metal oxide semiconductor nanowire (NW) networks grown by chemical vapor deposition and thermal evaporation, are reviewed. Highly crystalline NWs grown by vapor-phase routes have various advantages, and thus have been applied in the field of gas sensors over the years. In particular, n -type NWs such as SnO₂, ZnO, and In₂O₃ are widely studied because of their simple synthetic preparation and high gas response. However, due to their usually high responses to C₂H₅OH and NO₂, the selective detection of other harmful and toxic gases using oxide NWs remains a challenging issue. Various strategies-such as doping/loading of noble metals, decorating/doping of catalytic metal oxides, and the formation of core-shell structures-have been explored to enhance gas selectivity and sensitivity, and are discussed herein. Additional methods such as the transformation of n -type into p -type NWs and the formation of catalyst-doped hierarchical structures by branch growth have also proven to be promising for the enhancement of gas selectivity. Accordingly, the physicochemical modification of oxide NWs via various methods provides new strategies to achieve the selective detection of a specific gas, and after further investigations, this approach could pave a new way in the field of NW-based semiconductor-type gas sensors.

  13. Nanowire Optoelectronics

    OpenAIRE

    Wang Zhihuan; Nabet Bahram

    2015-01-01

    Semiconductor nanowires have been used in a variety of passive and active optoelectronic devices including waveguides, photodetectors, solar cells, light-emitting diodes (LEDs), lasers, sensors, and optical antennas. We review the optical properties of these nanowires in terms of absorption, guiding, and radiation of light, which may be termed light management. Analysis of the interaction of light with long cylindrical/hexagonal structures with ...

  14. High-Resolution p-Type Metal Oxide Semiconductor Nanowire Array as an Ultrasensitive Sensor for Volatile Organic Compounds.

    Science.gov (United States)

    Cho, Soo-Yeon; Yoo, Hae-Wook; Kim, Ju Ye; Jung, Woo-Bin; Jin, Ming Liang; Kim, Jong-Seon; Jeon, Hwan-Jin; Jung, Hee-Tae

    2016-07-13

    The development of high-performance volatile organic compound (VOC) sensor based on a p-type metal oxide semiconductor (MOS) is one of the important topics in gas sensor research because of its unique sensing characteristics, namely, rapid recovery kinetics, low temperature dependence, high humidity or thermal stability, and high potential for p-n junction applications. Despite intensive efforts made in this area, the applications of such sensors are hindered because of drawbacks related to the low sensitivity and slow response or long recovery time of p-type MOSs. In this study, the VOC sensing performance of a p-type MOS was significantly enhanced by forming a patterned p-type polycrystalline MOS with an ultrathin, high-aspect-ratio (∼25) structure (∼14 nm thickness) composed of ultrasmall grains (∼5 nm size). A high-resolution polycrystalline p-type MOS nanowire array with a grain size of ∼5 nm was fabricated by secondary sputtering via Ar(+) bombardment. Various p-type nanowire arrays of CuO, NiO, and Cr2O3 were easily fabricated by simply changing the sputtering material. The VOC sensor thus fabricated exhibited higher sensitivity (ΔR/Ra = 30 at 1 ppm hexane using NiO channels), as well as faster response or shorter recovery time (∼30 s) than that of previously reported p-type MOS sensors. This result is attributed to the high resolution and small grain size of p-type MOSs, which lead to overlap of fully charged zones; as a result, electrical properties are predominantly determined by surface states. Our new approach may be used as a route for producing high-resolution MOSs with particle sizes of ∼5 nm within a highly ordered, tall nanowire array structure.

  15. A CMOS-Compatible Poly-Si Nanowire Device with Hybrid Sensor/Memory Characteristics for System-on-Chip Applications

    Directory of Open Access Journals (Sweden)

    Chia-Hua Ho

    2012-03-01

    Full Text Available This paper reports a versatile nano-sensor technology using “top-down” poly-silicon nanowire field-effect transistors (FETs in the conventional Complementary Metal-Oxide Semiconductor (CMOS-compatible semiconductor process. The nanowire manufacturing technique reduced nanowire width scaling to 50 nm without use of extra lithography equipment, and exhibited superior device uniformity. These n type polysilicon nanowire FETs have positive pH sensitivity (100 mV/pH and sensitive deoxyribonucleic acid (DNA detection ability (100 pM at normal system operation voltages. Specially designed oxide-nitride-oxide buried oxide nanowire realizes an electrically Vth-adjustable sensor to compensate device variation. These nanowire FETs also enable non-volatile memory application for a large and steady Vth adjustment window (>2 V Programming/Erasing window. The CMOS-compatible manufacturing technique of polysilicon nanowire FETs offers a possible solution for commercial System-on-Chip biosensor application, which enables portable physiology monitoring and in situ recording.

  16. A CMOS-compatible poly-Si nanowire device with hybrid sensor/memory characteristics for System-on-Chip applications.

    Science.gov (United States)

    Chen, Min-Cheng; Chen, Hao-Yu; Lin, Chia-Yi; Chien, Chao-Hsin; Hsieh, Tsung-Fan; Horng, Jim-Tong; Qiu, Jian-Tai; Huang, Chien-Chao; Ho, Chia-Hua; Yang, Fu-Liang

    2012-01-01

    This paper reports a versatile nano-sensor technology using "top-down" poly-silicon nanowire field-effect transistors (FETs) in the conventional Complementary Metal-Oxide Semiconductor (CMOS)-compatible semiconductor process. The nanowire manufacturing technique reduced nanowire width scaling to 50 nm without use of extra lithography equipment, and exhibited superior device uniformity. These n type polysilicon nanowire FETs have positive pH sensitivity (100 mV/pH) and sensitive deoxyribonucleic acid (DNA) detection ability (100 pM) at normal system operation voltages. Specially designed oxide-nitride-oxide buried oxide nanowire realizes an electrically V(th)-adjustable sensor to compensate device variation. These nanowire FETs also enable non-volatile memory application for a large and steady V(th) adjustment window (>2 V Programming/Erasing window). The CMOS-compatible manufacturing technique of polysilicon nanowire FETs offers a possible solution for commercial System-on-Chip biosensor application, which enables portable physiology monitoring and in situ recording.

  17. Highly improved sensibility and selectivity ethanol sensor of mesoporous Fe-doped NiO nanowires

    Science.gov (United States)

    Li, X. Q.; Wei, J. Q.; Xu, J. C.; Jin, H. X.; Jin, D. F.; Peng, X. L.; Hong, B.; Li, J.; Yang, Y. T.; Ge, H. L.; Wang, Xinqing

    2017-12-01

    In this paper, nickel oxides (NiO) and iron (Fe)-doped NiO nanowires (NWs) with the various doping content (from 1 to 9 at%) were synthesized by using SBA-15 templates with the nanocasting method. All samples were synthesized in the same conditions and exhibited the same mesoporous-structures, uniform diameter, and defects. Mesoporous-structures with high surface area created more active sites for the adsorption of oxygen on the surface of all samples, resulting in the smaller surface resistance in air. The impurity energy levels from the donor Fe-doping provided electrons to neutralize the holes of p-type Fe-doped NiO NWs, which greatly enhanced the total resistance. The comparative gas-sensing study between NiO NWs and Fe-doped NiO NWs indicated that the high-valence donor Fe-doping obviously improved the ethanol sensitivity and selectivity for Fe-doped NiO NWs. And Ni0.94Fe0.06O1.03 NWs sensor presented the highest sensitivity of 14.30 toward ethanol gas at 320 °C for the high-valence metal-doping.

  18. Conducting properties of nearly depleted ZnO nanowire UV sensors fabricated by dielectrophoresis

    International Nuclear Information System (INIS)

    García Núñez, C; García Marín, A; Piqueras, J; Pau, J L; Nanterne, P; Kung, P

    2013-01-01

    ZnO nanowires (NWs) with different radii (r NW ) have been aligned between pre-patterned electrodes using dielectrophoresis (DEP) for the fabrication of high gain UV sensors. The DEP conditions (voltage amplitude and frequency) and electrode material, geometry and size were optimized to enhance the efficiency during the DEP process. To understand the alignment mechanism of the ZnO NWs, the dielectrophoretic force (F DEP ) was analyzed as a function of the DEP conditions and NW dimensions. These studies showed that the DEP alignment process tends to trap NWs with a smaller radius. The effects of NW size on device performance were analyzed by means of I–V measurements in darkness and under illumination (200 nm NW decreases due to the reduction of the conduction volume, until saturation is reached for r NW 8 A W −1 (measured at 5 V and λ NW , presenting a clear blue-shift for NWs with a lower radius (r NW 2 reduces the dynamic range of the photoresponse due to a strong increase of the dark current. (paper)

  19. Translating silicon nanowire BioFET sensor-technology to embedded point-of-care medical diagnostics

    DEFF Research Database (Denmark)

    Pfreundt, Andrea; Zulfiqar, Azeem; Patou, François

    2013-01-01

    Silicon nanowire and nanoribbon biosensors have shown great promise in the detection of biomarkers at very low concentrations. Their high sensitivity makes them ideal candidates for use in early-stage medical diagnostics and further disease monitoring where low amounts of biomarkers need to be de......Silicon nanowire and nanoribbon biosensors have shown great promise in the detection of biomarkers at very low concentrations. Their high sensitivity makes them ideal candidates for use in early-stage medical diagnostics and further disease monitoring where low amounts of biomarkers need...... rising fabrication costs. Also the translation of nano-scale sensor technology into daily-use point-of-care devices requires acknowledgement of the end-user requirements, making device portability and human-interfacing a focus point in device development. Sample handling or purification for instance...

  20. Development of GaN-based nanosensors using surface charge lithography

    International Nuclear Information System (INIS)

    Popa, Veaceslav; Braniste, Tudor; Volciuc, Olesea; Pavlidis, Dimitris; Sarua, Andrei; Kuball, Martin; Heard, Peter

    2011-01-01

    Semiconductor nanotechnology is a fast developing branch of modern engineering that offers perspectives for the development of electronic devices with superior parameters. A special and important niche in nanotechnology is allocated to the fabrication of nanosensors which are expected to exhibit higher sensitivity in comparison with classical microelectronic sensors. Various aspects of fabrication of GaN based nanosensors using Surface Charge Lithography are discussed and preliminary tests for gas sensors applications are presented.

  1. Room temperature, ppb-level NO2 gas sensing of multiple-networked ZnSe nanowire sensors under UV illumination

    Directory of Open Access Journals (Sweden)

    Sunghoon Park

    2014-10-01

    Full Text Available Reports of the gas sensing properties of ZnSe are few, presumably because of the decomposition and oxidation of ZnSe at high temperatures. In this study, ZnSe nanowires were synthesized by the thermal evaporation of ZnSe powders and the sensing performance of multiple-networked ZnSe nanowire sensors toward NO2 gas was examined. The results showed that ZnSe might be a promising gas sensor material if it is used at room temperature. The response of the ZnSe nanowires to 50 ppb–5 ppm NO2 at room temperature under dark and UV illumination conditions were 101–102% and 113–234%, respectively. The responses of the ZnSe nanowires to 5 ppm NO2 increased from 102 to 234% with increasing UV illumination intensity from 0 to 1.2 mW/cm2. The response of the ZnSe nanowires was stronger than or comparable to that of typical metal oxide semiconductors reported in the literature, which require higher NO2 concentrations and operate at higher temperatures. The origin of the enhanced response of the ZnSe nanowires towards NO2 under UV illumination is also discussed.

  2. Chitosan-assisted buffer layer incorporated with hydroxypropyl methylcellulose-coated silver nanowires for paper-based sensors

    Science.gov (United States)

    Xu, Duohua; Qiu, Jingshen; Wang, Yucheng; Yan, Jiajun; Liu, Gui-Shi; Yang, Bo-Ru

    2017-06-01

    Fabricating flexible sensors on paper is intriguing. Here, we exploited chitosan as a buffer layer to facilitate the fabrication of silver nanowire (AgNW) networks and flexible devices on commercial paper. We found that the AgNW networks exhibited uniform distribution, smooth surface, and strong adhesion. The enhanced adhesion of AgNWs was attributed to the intermolecular hydrogen bonding between chitosan and hydroxypropyl methylcellulose (HPMC), which can be tailored by tuning the pH of the chitosan aqueous solution. This facile fabrication method utilizing biodegradable polymers and cost-effective AgNW ink holds great promise for portable, wearable, and disposable paper-based electronics.

  3. Facile fabrication of Ag nanowires for capacitive flexible pressure sensors by liquid polyol reduction method

    Science.gov (United States)

    Wei, Xiongbang; Quan, Yong; Zeng, Hongjuan; Huang, Wen; Li, Weizhi; Liao, Jiaxuan; Chen, Zhi

    2018-01-01

    The Ag nanowires (AgNWs) were prepared by improved liquid polyol reduction method, and the AgNWs were successfully applied to the capacitive flexible pressure sensors. Firstly, the one-dimensional radial growth conditions of AgNWs were optimized from four aspects of the molecular weight of the protective agent polyvinyl pyrrolidone (PVP), the molar ratio of AgNO3 and PVP, the anion concentration of the metal salt and the reaction temperature. The effect of polymerization degree of protective agent on one-dimensional radial growth of AgNWs was investigated by using three kinds of protective agents PVP-K-30, PVP-K-60 and PVP-K-90. Three different AgNO3 and PVP molar ratios of 1:1, 1:3 and 1:9 were designed, and the effects of PVP adsorption capacity on one-dimensional radial growth of AgNWs were investigated. Three concentrations of 0 mM NaCl, 16 mM NaCl and 32 mM NaCl were designed to study the effects of anion concentration of the metal salt on the nucleation and etching of silver nanoparticles. The effects of reaction temperature on the growth of AgNWs were studied at three different temperatures of 140 °C, 160 °C and 180 °C, and appropriate temperature design was proposed. In this experiment, the products of AgNWs prepared under various conditions were analyzed by UV–vis Spectrum and SEM, and the experimental conditions were optimized from the synthesis mechanism and reaction conditions.

  4. Evaluation of magnetic flux distribution from magnetic domains in [Co/Pd] nanowires by magnetic domain scope method using contact-scanning of tunneling magnetoresistive sensor

    Energy Technology Data Exchange (ETDEWEB)

    Okuda, Mitsunobu, E-mail: okuda.m-ky@nhk.or.jp; Miyamoto, Yasuyoshi; Miyashita, Eiichi; Hayashi, Naoto [NHK Science and Technology Research Laboratories, 1-10-11 Kinuta Setagaya, Tokyo 157-8510 (Japan)

    2014-05-07

    Current-driven magnetic domain wall motions in magnetic nanowires have attracted great interests for physical studies and engineering applications. The magnetic force microscope (MFM) is widely used for indirect verification of domain locations in nanowires, where relative magnetic force between the local domains and the MFM probe is used for detection. However, there is an occasional problem that the magnetic moments of MFM probe influenced and/or rotated the magnetic states in the low-moment nanowires. To solve this issue, the “magnetic domain scope for wide area with nano-order resolution (nano-MDS)” method has been proposed recently that could detect the magnetic flux distribution from the specimen directly by scanning of tunneling magnetoresistive field sensor. In this study, magnetic domain structure in nanowires was investigated by both MFM and nano-MDS, and the leakage magnetic flux density from the nanowires was measured quantitatively by nano-MDS. Specimen nanowires consisted from [Co (0.3)/Pd (1.2)]{sub 21}/Ru(3) films (units in nm) with perpendicular magnetic anisotropy were fabricated onto Si substrates by dual ion beam sputtering and e-beam lithography. The length and the width of the fabricated nanowires are 20 μm and 150 nm. We have succeeded to obtain not only the remanent domain images with the detection of up and down magnetizations as similar as those by MFM but also magnetic flux density distribution from nanowires directly by nano-MDS. The obtained value of maximum leakage magnetic flux by nano-MDS is in good agreement with that of coercivity by magneto-optical Kerr effect microscopy. By changing the protective diamond-like-carbon film thickness on tunneling magnetoresistive sensor, the three-dimensional spatial distribution of leakage magnetic flux could be evaluated.

  5. A force sensor using nanowire arrays to understand biofilm formation (Conference Presentation)

    Science.gov (United States)

    Sahoo, Prasana K.; Cavalli, Alessandro; Pelegati, Vitor B.; Murillo, Duber M.; Souza, Alessandra A.; Cesar, Carlos L.; Bakkers, Erik P. A. M.; Cotta, Monica A.

    2016-03-01

    Understanding the cellular signaling and function at the nano-bio interface can pave the way towards developing next-generation smart diagnostic tools. From this perspective, limited reports detail so far the cellular and subcellular forces exerted by bacterial cells during the interaction with abiotic materials. Nanowire arrays with high aspect ratio have been used to detect such small forces. In this regard, live force measurements were performed ex-vivo during the interaction of Xylella fastidiosa bacterial cells with InP nanowire arrays. The influence of nanowire array topography and surface chemistry on the response and motion of bacterial cells was studied in detail. The nanowire arrays were also functionalized with different cell adhesive promoters, such as amines and XadA1, an afimbrial protein of X.fastidiosa. By employing the well-defined InP nanowire arrays platform, and single cell confocal imaging system, we were able to trace the bacterial growth pattern, and show that their initial attachment locations are strongly influenced by the surface chemistry and nanoscale surface topography. In addition, we measure the cellular forces down to few nanonewton range using these nanowire arrays. In case of nanowire functionalized with XadA1, the force exerted by vertically and horizontally attached single bacteria on the nanowire is in average 14% and 26% higher than for the pristine array, respectively. These results provide an excellent basis for live-cell force measurements as well as unravel the range of forces involved during the early stages of bacterial adhesion and biofilm formation.

  6. The ethylene glycol template assisted hydrothermal synthesis of Co{sub 3}O{sub 4} nanowires; structural characterization and their application as glucose non-enzymatic sensor

    Energy Technology Data Exchange (ETDEWEB)

    Khun, K., E-mail: kimleang.khun@liu.se [Department of Science and Technology, Linköping University, SE-60174 Norrköping (Sweden); Ibupoto, Z.H. [Dr M.A. Kazi Institute of Chemistry, University of Sindh Jamshoro, Sindh Jamshoro (Pakistan); Liu, X. [Department of Physics, Chemistry and Biology, Linköping University, 58183 Linköping (Sweden); Beni, V. [Biosensors and Biolelectronics Centre, Department of Physics, Chemistry and Biology, Linköping University, 58183 Linköping (Sweden); Willander, M. [Department of Science and Technology, Linköping University, SE-60174 Norrköping (Sweden)

    2015-04-15

    Highlights: • Ethylene glycol assisted Co{sub 3}O{sub 4} nanowires were synthesized by hydrothermal method. • The grown Co{sub 3}O{sub 4} nanowires were used for sensitive non-enzymatic glucose sensor. • The proposed glucose sensor shows a wide linear range with fast response. • The Co{sub 3}O{sub 4} modified electrode is a highly specific enzyme-less glucose sensor. - Abstract: In the work reported herein the ethylene glycol template assisted hydrothermal synthesis, onto Au substrate, of thin and highly dense cobalt oxide (Co{sub 3}O{sub 4}) nanowires and their characterization and their application for non-enzymatic glucose sensing are reported. The structure and composition of Co{sub 3}O{sub 4} nanowires have been fully characterized using scanning electron microscopy, X-ray diffraction, high resolution transmission electron microscopy and X-ray photoelectron spectroscopy. The synthesized Co{sub 3}O{sub 4} nanowires resulted to have high purity and showed diameter of approximately 10 nm. The prepared Co{sub 3}O{sub 4} nanowires coated gold electrodes were applied to the non-enzymatic detection of glucose. The developed sensor showed high sensitivity (4.58 × 10{sup 1} μA mM{sup −1} cm{sup −2}), a wide linear range of concentration (1.00 × 10{sup −4}–1.2 × 10{sup 1} mM) and a detection limit of 2.65 × 10{sup −5} mM. The developed glucose sensor has also shown to be very stable and selective over interferents such as uric acid and ascorbic acid. Furthermore, the proposed fabrication process was shown to be highly reproducible response (over nine electrodes)

  7. M13 Bacteriophage/Silver Nanowire Surface-Enhanced Raman Scattering Sensor for Sensitive and Selective Pesticide Detection.

    Science.gov (United States)

    Koh, Eun Hye; Mun, ChaeWon; Kim, ChunTae; Park, Sung-Gyu; Choi, Eun Jung; Kim, Sun Ho; Dang, Jaejeung; Choo, Jaebum; Oh, Jin-Woo; Kim, Dong-Ho; Jung, Ho Sang

    2018-03-28

    A surface-enhanced Raman scattering (SERS) sensor comprising silver nanowires (AgNWs) and genetically engineered M13 bacteriophages expressing a tryptophan-histidine-tryptophan (WHW) peptide sequence (BPWHW) was fabricated by simple mixing of BPWHW and AgNW solutions, followed by vacuum filtration onto a glass-fiber filter paper (GFFP) membrane. The AgNWs stacked on the GFFP formed a high density of SERS-active hot spots at the points of nanowire intersections, and the surface-coated BPWHW functioned as a bioreceptor for selective pesticide detection. The BPWHW-functionalized AgNW (BPWHW/AgNW) sensor was characterized by scanning electron microscopy, confocal scanning fluorescence microscopy, atomic force microscopy, and Fourier transform infrared spectroscopy. The Raman signal enhancement and the selective pesticide SERS detection properties of the BPWHW/AgNW sensor were investigated in the presence of control substrates such as wild-type M13 bacteriophage-decorated AgNWs (BPWT/AgNW) and undecorated AgNWs (AgNW). The BPWHW/AgNW sensor exhibited a significantly higher capture capability for pesticides, especially paraquat (PQ), than the control SERS substrates, and it also showed a relatively higher selectivity for PQ than for other bipyridylium pesticides such as diquat and difenzoquat. Furthermore, as a field application test, PQ was detected on the surface of PQ-pretreated apple peels, and the results demonstrated the feasibility of using a paper-based SERS substrate for on-site residual pesticide detection. The developed M13 bacteriophage-functionalized AgNW SERS sensor might be applicable for the detection of various pesticides and chemicals through modification of the M13 bacteriophage surface peptide sequence.

  8. Stretchable, Transparent, and Stretch-Unresponsive Capacitive Touch Sensor Array with Selectively Patterned Silver Nanowires/Reduced Graphene Oxide Electrodes.

    Science.gov (United States)

    Choi, Tae Young; Hwang, Byeong-Ung; Kim, Bo-Yeong; Trung, Tran Quang; Nam, Yun Hyoung; Kim, Do-Nyun; Eom, Kilho; Lee, Nae-Eung

    2017-05-31

    Stretchable and transparent touch sensors are essential input devices for future stretchable transparent electronics. Capacitive touch sensors with a simple structure of only two electrodes and one dielectric are an established technology in current rigid electronics. However, the development of stretchable and transparent capacitive touch sensors has been limited due to changes in capacitance resulting from dimensional changes in elastomeric dielectrics and difficulty in obtaining stretchable transparent electrodes that are stable under large strains. Herein, a stretch-unresponsive stretchable and transparent capacitive touch sensor array was demonstrated by employing stretchable and transparent electrodes with a simple selective-patterning process and by carefully selecting dielectric and substrate materials with low strain responsivity. A selective-patterning process was used to embed a stretchable and transparent silver nanowires/reduced graphene oxide (AgNWs/rGO) electrode line into a polyurethane (PU) dielectric layer on a polydimethylsiloxane (PDMS) substrate using oxygen plasma treatment. This method provides the ability to directly fabricate thin film electrode lines on elastomeric substrates and can be used in conventional processes employed in stretchable electronics. We used a dielectric (PU) with a Poisson's ratio smaller than that of the substrate (PDMS), which prevented changes in the capacitance resulting from stretching of the sensor. The stretch-unresponsive touch sensing capability of our transparent and stretchable capacitive touch sensor has great potential in wearable electronics and human-machine interfaces.

  9. Ultra-sensitive and selective detection of mercury ion (Hg2+) using free-standing silicon nanowire sensors

    Science.gov (United States)

    Jin, Yan; Gao, Anran; Jin, Qinghui; Li, Tie; Wang, Yuelin; Zhao, Jianlong

    2018-04-01

    In this paper, ultra-sensitive and highly selective Hg2+ detection in aqueous solutions was studied by free-standing silicon nanowire (SiNW) sensors. The all-around surface of SiNW arrays was functionalized with (3-Mercaptopropyl)trimethoxysilane serving as Hg2+ sensitive layer. Due to effective electrostatic control provided by the free-standing structure, a detection limit as low as 1 ppt was obtained. A linear relationship (R 2 = 0.9838) between log(CHg2+ ) and a device current change from 1 ppt to 5 ppm was observed. Furthermore, the developed SiNW sensor exhibited great selectivity for Hg2+ over other heavy metal ions, including Cd2+. Given the extraordinary ability for real-time Hg2+ detection, the small size and low cost of the SiNW device, it is expected to be a potential candidate in field detection of environmentally toxic mercury.

  10. Silver nanowire/polymer composite soft conductive film fabricated by large-area compatible coating for flexible pressure sensor array

    Science.gov (United States)

    Chen, Sujie; Li, Siying; Peng, Sai; Huang, Yukun; Zhao, Jiaqing; Tang, Wei; Guo, Xiaojun

    2018-01-01

    Soft conductive films composed of a silver nanowire (AgNW) network, a neutral-pH PEDOT:PSS over-coating layer and a polydimethylsiloxane (PDMS) elastomer substrate are fabricated by large area compatible coating processes. The neutral-pH PEDOT:PSS layer is shown to be able to significantly improve the conductivity, stretchability and air stability of the conductive films. The soft conductive films are patterned using a simple maskless patterning approach to fabricate an 8 × 8 flexible pressure sensor array. It is shown that such soft conductive films can help to improve the sensitivity and reduce the signal crosstalk over the pressure sensor array. Project supported by the Science and Technology Commission of Shanghai Municipality (No. 16JC1400603).

  11. Monolithic integration of a silicon nanowire field-effect transistors array on a complementary metal-oxide semiconductor chip for biochemical sensor applications.

    Science.gov (United States)

    Livi, Paolo; Kwiat, Moria; Shadmani, Amir; Pevzner, Alexander; Navarra, Giulio; Rothe, Jörg; Stettler, Alexander; Chen, Yihui; Patolsky, Fernando; Hierlemann, Andreas

    2015-10-06

    We present a monolithic complementary metal-oxide semiconductor (CMOS)-based sensor system comprising an array of silicon nanowire field-effect transistors (FETs) and the signal-conditioning circuitry on the same chip. The silicon nanowires were fabricated by chemical vapor deposition methods and then transferred to the CMOS chip, where Ti/Pd/Ti contacts had been patterned via e-beam lithography. The on-chip circuitry measures the current flowing through each nanowire FET upon applying a constant source-drain voltage. The analog signal is digitized on chip and then transmitted to a receiving unit. The system has been successfully fabricated and tested by acquiring I-V curves of the bare nanowire-based FETs. Furthermore, the sensing capabilities of the complete system have been demonstrated by recording current changes upon nanowire exposure to solutions of different pHs, as well as by detecting different concentrations of Troponin T biomarkers (cTnT) through antibody-functionalized nanowire FETs.

  12. Self-assembled diphenylalanine nanowires for cellular studies and sensor applications

    DEFF Research Database (Denmark)

    Sasso, Luigi; Vedarethinam, Indumathi; Emnéus, Jenny

    2012-01-01

    In this paper we present a series of experiments showing that vertical self-assembled diphenylalanine peptide nanowires (PNWs) are a suitable candidate material for cellular biosensing. We grew HeLa and PC12 cells onto PNW modified gold surfaces and observed no hindrance of cell growth caused by ...

  13. Sensitivity and detection limit analysis of silicon nanowire bio(chemical) sensors

    NARCIS (Netherlands)

    Chen, S.; van den Berg, Albert; Carlen, Edwin

    2015-01-01

    This paper presents an analysis of the sensitivity and detection limit of silicon nanowire biosensors using an analytical model in combination with I-V and current noise measurements. The analysis shows that the limit of detection (LOD) and signal to noise ratio (SNR) can be optimized by determining

  14. Characterization of Bending Magnetostriction in Iron-Gallium Alloys for Nanowire Sensor Applications

    Science.gov (United States)

    2008-01-01

    ferrimagnets and antiferromagnets), which are so named due to iron be- ing the archetype rather than being a necessary element in the composition. In...Varadwaj, Paritosh Mohanty, Sunghun Lee, Younghun Jo, Myung-Hwa Jung , Jinhee Kim, and Bongsoo Kim. Magnetic properties of single-crystalline CoSi nanowires

  15. Improvement of Amperometric Sensor Used for Determination of Nitrate with Polypyrrole Nanowires Modified Electrode

    Directory of Open Access Journals (Sweden)

    Shi-chang Wang

    2005-12-01

    Full Text Available Polypyrrole(PPy nanowire modified electrodes were developed by template-freeelectrochemical method based on graphite electrode. The modified electrode wascharacterized by their amperometric response towards nitrate ions. Before reduction ofnitrate ions, electrochemical solid-phase extraction (EC-SPE of nitrate in/on modifiedelectrodes was conducted. It is found that the unusual nanowired structure of polypyrrolelayer (instead of well known cauliflower structure allows us to increase the effectivesurface area of the electrode and subsequently the sensitivity. And the effects ofelectrochemical preparation parameters of PPy nanowire modified electrodes on theircorresponding characters were evaluated. The experimental results show that theelectrochemical preparation parameters of the modified electrodes such as scan rate,polymerization potential, temperature of polymerization solution and polymerization timehave significantly effects on the morphology of PPy nanowires and subsequently effectivesurface area of the electrode and electroreduction current density of nitrate. Thedetermination sensitivity may be varied according to the modification parameters. Under acertain polymerization conditions, the corresponding sensitivity reaches 336.28 mA/M cm2 and the detection limit is 1.52×10-6 M. The proposed method was successfully applied in thedetection of nitrate in the real samples.

  16. Design of Indium Arsenide nanowire sensors for pH and biological sensing and low temperature transport through p-doped Indium Arsenide nanowires

    DEFF Research Database (Denmark)

    Upadhyay, Shivendra

    remains the primary material of choice. This research is about investigating Indium Arsenide nanowires as alternative platform for sensing charged species - chemical and biological, in solution. Starting with nanowires grown via molecular beam epitaxy in an ultra-high vacuum chamber, we discuss...

  17. A Ge/Si heterostructure nanowire-based double quantum dot with integrated charge sensor

    OpenAIRE

    Hu, Yongjie; Churchill, Hugh; Reilly, David; Xiang, Jie; Lieber, Charles; M. Marcus, Charles

    2007-01-01

    Coupled electron spins in semiconductor double quantum dots hold promise as the basis for solid-state qubits. To date, most experiments have used III-V materials, in which coherence is limited by hyperfine interactions. Ge/Si heterostructure nanowires seem ideally suited to overcome this limitation: the predominance of spin-zero nuclei suppresses the hyperfine interaction and chemical synthesis creates a clean and defect-free system with highly controllable properties. Here we present a top g...

  18. Mapping and Quantifying Surface Charges on Clay Nanoparticles.

    Science.gov (United States)

    Liu, Jun; Gaikwad, Ravi; Hande, Aharnish; Das, Siddhartha; Thundat, Thomas

    2015-09-29

    Understanding the electrical properties of clay nanoparticles is very important since they play a crucial role in every aspect of oil sands processing, from bitumen extraction to sedimentation in mature fine tailings (MFT). Here, we report the direct mapping and quantification of surface charges on clay nanoparticles using Kelvin probe force microscopy (KPFM) and electrostatic force microscopy (EFM). The morphology of clean kaolinite clay nanoparticles shows a layered structure, while the corresponding surface potential map shows a layer-dependent charge distribution. More importantly, a surface charge density of 25 nC/cm(2) was estimated for clean kaolinite layers by using EFM measurements. On the other hand, the EFM measurements show that the clay particles obtained from the tailings demonstrate a reduced surface charge density of 7 nC/cm(2), which may be possibly attributed to the presence of various bituminous compounds residing on the clay surfaces.

  19. A novel nonenzymatic amperometric hydrogen peroxide sensor based on CuO@Cu2O nanowires embedded into poly(vinyl alcohol).

    Science.gov (United States)

    Chirizzi, Daniela; Guascito, Maria Rachele; Filippo, Emanuela; Tepore, Antonio

    2016-01-15

    A new, very simple, rapid and inexpensive nonenzymatic amperometric sensor for hydrogen peroxide (H2O2) detection is proposed. It is based on the immobilization of cupric/cuprous oxide core shell nanowires (CuO@Cu2O-NWs) in a poly(vinyl alcohol) (PVA) matrix directly drop casted on a glassy carbon electrode surface to make a CuO@Cu2O core shell like NWs PVA embedded (CuO@Cu2O-NWs/PVA) sensor. CuO nanowires with mean diameters of 120-170nm and length in the range 2-5μm were grown by a simple catalyst-free thermal oxidation process based on resistive heating of pure copper wires at ambient conditions. The oxidation process of the copper wire surface led to the formation of a three layered structure: a thick Cu2O bottom layer, a CuO thin intermediate layer and CuO nanowires. CuO nanowires were carefully scratched from Cu2O layer with a sharp knife, dispersed into ethanol and sonicated. Then, the NWs were embedded in PVA matrix. The morphological and spectroscopic characterization of synthesized CuO-NWs and CuO@Cu2O-NWs/PVA were performed by transmission electron microscopy (TEM), selected area diffraction pattern (SAD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) analysis. Moreover a complete electrochemical characterization of these new CuO@Cu2O-NWs/PVA modified glassy carbon electrodes was performed by Cyclic Voltammetry (CV) and Cronoamperometry (CA) in phosphate buffer (pH=7; I=0.2) to investigate the sensing properties of this material against H2O2. The electrochemical performances of proposed sensors as high sensitivity, fast response, reproducibility and selectivity make them suitable for the quantitative determination of hydrogen peroxide substrate in batch analysis. Copyright © 2015 Elsevier B.V. All rights reserved.

  20. A universal approach to electrically connecting nanowire arrays using nanoparticles—application to a novel gas sensor architecture

    Science.gov (United States)

    Parthangal, Prahalad M.; Cavicchi, Richard E.; Zachariah, Michael R.

    2006-08-01

    We report on a novel, in situ approach toward connecting and electrically contacting vertically aligned nanowire arrays using conductive nanoparticles. The utility of the approach is demonstrated by development of a gas sensing device employing this nano-architecture. Well-aligned, single-crystalline zinc oxide nanowires were grown through a direct thermal evaporation process at 550 °C on gold catalyst layers. Electrical contact to the top of the nanowire array was established by creating a contiguous nanoparticle film through electrostatic attachment of conductive gold nanoparticles exclusively onto the tips of nanowires. A gas sensing device was constructed using such an arrangement and the nanowire assembly was found to be sensitive to both reducing (methanol) and oxidizing (nitrous oxides) gases. This assembly approach is amenable to any nanowire array for which a top contact electrode is needed.

  1. A universal approach to electrically connecting nanowire arrays using nanoparticles-application to a novel gas sensor architecture

    International Nuclear Information System (INIS)

    Parthangal, Prahalad M; Cavicchi, Richard E; Zachariah, Michael R

    2006-01-01

    We report on a novel, in situ approach toward connecting and electrically contacting vertically aligned nanowire arrays using conductive nanoparticles. The utility of the approach is demonstrated by development of a gas sensing device employing this nano-architecture. Well-aligned, single-crystalline zinc oxide nanowires were grown through a direct thermal evaporation process at 550 deg. C on gold catalyst layers. Electrical contact to the top of the nanowire array was established by creating a contiguous nanoparticle film through electrostatic attachment of conductive gold nanoparticles exclusively onto the tips of nanowires. A gas sensing device was constructed using such an arrangement and the nanowire assembly was found to be sensitive to both reducing (methanol) and oxidizing (nitrous oxides) gases. This assembly approach is amenable to any nanowire array for which a top contact electrode is needed

  2. Design Concepts, Fabrication and Advanced Characterization Methods of Innovative Piezoelectric Sensors Based on ZnO Nanowires

    Directory of Open Access Journals (Sweden)

    Rodolfo Araneo

    2014-12-01

    Full Text Available Micro- and nano-scale materials and systems based on zinc oxide are expected to explode in their applications in the electronics and photonics, including nano-arrays of addressable optoelectronic devices and sensors, due to their outstanding properties, including semiconductivity and the presence of a direct bandgap, piezoelectricity, pyroelectricity and biocompatibility. Most applications are based on the cooperative and average response of a large number of ZnO micro/nanostructures. However, in order to assess the quality of the materials and their performance, it is fundamental to characterize and then accurately model the specific electrical and piezoelectric properties of single ZnO structures. In this paper, we report on focused ion beam machined high aspect ratio nanowires and their mechanical and electrical (by means of conductive atomic force microscopy characterization. Then, we investigate the suitability of new power-law design concepts to accurately model the relevant electrical and mechanical size-effects, whose existence has been emphasized in recent reviews.

  3. Design Concepts, Fabrication and Advanced Characterization Methods of Innovative Piezoelectric Sensors Based on ZnO Nanowires

    Science.gov (United States)

    Araneo, Rodolfo; Rinaldi, Antonio; Notargiacomo, Andrea; Bini, Fabiano; Pea, Marialilia; Celozzi, Salvatore; Marinozzi, Franco; Lovat, Giampiero

    2014-01-01

    Micro- and nano-scale materials and systems based on zinc oxide are expected to explode in their applications in the electronics and photonics, including nano-arrays of addressable optoelectronic devices and sensors, due to their outstanding properties, including semiconductivity and the presence of a direct bandgap, piezoelectricity, pyroelectricity and biocompatibility. Most applications are based on the cooperative and average response of a large number of ZnO micro/nanostructures. However, in order to assess the quality of the materials and their performance, it is fundamental to characterize and then accurately model the specific electrical and piezoelectric properties of single ZnO structures. In this paper, we report on focused ion beam machined high aspect ratio nanowires and their mechanical and electrical (by means of conductive atomic force microscopy) characterization. Then, we investigate the suitability of new power-law design concepts to accurately model the relevant electrical and mechanical size-effects, whose existence has been emphasized in recent reviews. PMID:25494351

  4. Silver Nanowire Embedded Colorless Polyimide Heater for Wearable Chemical Sensors: Improved Reversible Reaction Kinetics of Optically Reduced Graphene Oxide.

    Science.gov (United States)

    Choi, Seon-Jin; Kim, Sang-Joon; Jang, Ji-Soo; Lee, Ji-Hyun; Kim, Il-Doo

    2016-09-14

    Optically reduced graphene oxide (ORGO) sheets are successfully integrated on silver nanowire (Ag NW)-embedded transparent and flexible substrate. As a heating element, Ag NWs are embedded in a colorless polyimide (CPI) film by covering Ag NW networks using polyamic acid and subsequent imidization. Graphene oxide dispersed aqueous solution is drop-coated on the Ag NW-embedded CPI (Ag NW-CPI) film and directly irradiated by intense pulsed light to obtain ORGO sheets. The heat generation property of Ag NW-CPI film is investigated by applying DC voltage, which demonstrates unprecedentedly reliable and stable characteristics even in dynamic bending condition. To demonstrate the potential application in wearable chemical sensors, NO 2 sensing characteristic of ORGO is investigated with respect to the different heating temperature (22.7-71.7 °C) of Ag NW-CPI film. The result reveals that the ORGO sheets exhibit high sensitivity of 2.69% with reversible response/recovery sensing properties and minimal deviation of baseline resistance of around 1% toward NO 2 molecules when the temperature of Ag NW-CPI film is 71.7 °C. This work first demonstrates the improved reversible NO 2 sensing properties of ORGO sheets on flexible and transparent Ag NW-CPI film assisted by Ag NW heating networks. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Chemical Gated Field Effect Transistor by Hybrid Integration of One-Dimensional Silicon Nanowire and Two-Dimensional Tin Oxide Thin Film for Low Power Gas Sensor.

    Science.gov (United States)

    Han, Jin-Woo; Rim, Taiuk; Baek, Chang-Ki; Meyyappan, M

    2015-09-30

    Gas sensors based on metal-oxide-semiconductor transistor with the polysilicon gate replaced by a gas sensitive thin film have been around for over 50 years. These are not suitable for the emerging mobile and wearable sensor platforms due to operating voltages and powers far exceeding the supply capability of batteries. Here we present a novel approach to decouple the chemically sensitive region from the conducting channel for reducing the drive voltage and increasing reliability. This chemically gated field effect transistor uses silicon nanowire for the current conduction channel with a tin oxide film on top of the nanowire serving as the gas sensitive medium. The potential change induced by the molecular adsorption and desorption allows the electrically floating tin oxide film to gate the silicon channel. As the device is designed to be normally off, the power is consumed only during the gas sensing event. This feature is attractive for the battery operated sensor and wearable electronics. In addition, the decoupling of the chemical reaction and the current conduction regions allows the gas sensitive material to be free from electrical stress, thus increasing reliability. The device shows excellent gas sensitivity to the tested analytes relative to conventional metal oxide transistors and resistive sensors.

  6. Semiconductor Nanowires: Epitaxy and Applications

    OpenAIRE

    Mårtensson, Thomas

    2008-01-01

    Semiconductor nanowires are nanoscale objects formed by bottom-up synthesis. In recent years their unique properties have been exploited in fields such as electronics, photonics, sensors and the life sciences. In this work, the epitaxial growth of nanowires and their applications were studied. Heteroepitaxial growth of III-V nanowires on silicon substrates was demonstrated. This may enable direct band gap materials for optoelectronic devices, as well as high-mobility, low-contact resis...

  7. Surface charge algebra in gauge theories and thermodynamic integrability

    International Nuclear Information System (INIS)

    Barnich, Glenn; Compere, Geoffrey

    2008-01-01

    Surface charges and their algebra in interacting Lagrangian gauge field theories are constructed out of the underlying linearized theory using techniques from the variational calculus. In the case of exact solutions and symmetries, the surface charges are interpreted as a Pfaff system. Integrability is governed by Frobenius' theorem and the charges associated with the derived symmetry algebra are shown to vanish. In the asymptotic context, we provide a generalized covariant derivation of the result that the representation of the asymptotic symmetry algebra through charges may be centrally extended. Comparison with Hamiltonian and covariant phase space methods is made. All approaches are shown to agree for exact solutions and symmetries while there are differences in the asymptotic context

  8. Surface Charge and Ion Sorption Properties of Titanium Dioxide

    Science.gov (United States)

    Ridley, M. K.; Machesky, M. L.; Wesolowski, D. J.; Finnegan, M. P.; Palmer, D. A.

    2001-12-01

    The interaction of submicron metal oxide particles with natural aqueous solutions results in the hydroxylation of surface sites, which impart a pH-dependent surface charge. The charged submicron particles influence processes such as nanoparticle assembly and alteration, crystal growth rates and morphologies, colloid flocculation, and contaminant transport. The surface charge and ion sorption properties of metal-oxide particles may be studied by potentiometric titrations, using hydrogen-electrode concentration-cells or traditional glass electrodes and an autotitrator. These techniques have been used to quantify the adsorption of various ions (Na+, Rb+, Ca2+, Sr2+, Cl-) on rutile, at ionic strengths up to 1.0 molality and temperatures to 250° C. The crystalline rutile used in these studies is less than 400 nm in diameter, has a BET surface area of 17 m2/g, and the 110 and 100 faces predominate. The negative surface charge of the rutile was enhanced by increasing temperature, increasing ionic strength, and decreasing the ionic radii of the electrolyte cation. Moreover, the addition of a divalent cation significantly enhances the negative charge of the rutile surface. These data have been rationalized with the MUSIC model of Hiemestra and van Riemsdijk, and a Basic Stern layer description of the electric double layer (EDL). Model fitting of the experimental data provides binding constants for the adsorbed counterions and divalent cations, and capacitance values as well as corresponding electrical potential values of the binding planes. Recently, new studies have been initiated to determine particle size affects on the proton induced surface charge and ion sorption properties of titanium dioxide. In these studies, anatase with a BET surface area of 40 and 100 m2/g (primary particle sizes of 40 and 10 nm, respectively) is being investigated. The complexity of both the experimental and modeling procedures increases with decreasing particle size. For example, the fine

  9. Porous Silicon Nanowires

    Science.gov (United States)

    Qu, Yongquan; Zhou, Hailong; Duan, Xiangfeng

    2011-01-01

    In this minreview, we summarize recent progress in the synthesis, properties and applications of a new type of one-dimensional nanostructures — single crystalline porous silicon nanowires. The growth of porous silicon nanowires starting from both p- and n-type Si wafers with a variety of dopant concentrations can be achieved through either one-step or two-step reactions. The mechanistic studies indicate the dopant concentration of Si wafers, oxidizer concentration, etching time and temperature can affect the morphology of the as-etched silicon nanowires. The porous silicon nanowires are both optically and electronically active and have been explored for potential applications in diverse areas including photocatalysis, lithium ion battery, gas sensor and drug delivery. PMID:21869999

  10. Surface charge compensation for a highly charged ion emission microscope

    International Nuclear Information System (INIS)

    McDonald, J.W.; Hamza, A.V.; Newman, M.W.; Holder, J.P.; Schneider, D.H.G.; Schenkel, T.

    2003-01-01

    A surface charge compensation electron flood gun has been added to the Lawrence Livermore National Laboratory (LLNL) highly charged ion (HCI) emission microscope. HCI surface interaction results in a significant charge residue being left on the surface of insulators and semiconductors. This residual charge causes undesirable aberrations in the microscope images and a reduction of the Time-Of-Flight (TOF) mass resolution when studying the surfaces of insulators and semiconductors. The benefits and problems associated with HCI microscopy and recent results of the electron flood gun enhanced HCI microscope are discussed

  11. Scattered surface charge density: A tool for surface characterization

    KAUST Repository

    Naydenov, Borislav

    2011-11-28

    We demonstrate the use of nonlocal scanning tunneling spectroscopic measurements to characterize the local structure of adspecies in their states where they are significantly less perturbed by the probe, which is accomplished by mapping the amplitude and phase of the scattered surface charge density. As an example, we study single-H-atom adsorption on the n-type Si(100)-(4 × 2) surface, and demonstrate the existence of two different configurations that are distinguishable using the nonlocal approach and successfully corroborated by density functional theory. © 2011 American Physical Society.

  12. 3D electric field calculation with surface charge method

    International Nuclear Information System (INIS)

    Yamada, S.

    1992-01-01

    This paper describes an outline and some examples of three dimensional electric field calculations with a computer code developed at NIRS. In the code, a surface charge method is adopted because of it's simplicity in the mesh establishing procedure. The charge density in a triangular mesh is assumed to distribute with a linear function of the position. The electric field distribution is calculated for a pair of drift tubes with the focusing fingers on the opposing surfaces. The field distribution in an acceleration gap is analyzed with a Fourier-Bessel series expansion method. The calculated results excellently reproduces the measured data with a magnetic model. (author)

  13. Nanowire Optoelectronics

    Directory of Open Access Journals (Sweden)

    Wang Zhihuan

    2015-12-01

    Full Text Available Semiconductor nanowires have been used in a variety of passive and active optoelectronic devices including waveguides, photodetectors, solar cells, light-emitting diodes (LEDs, lasers, sensors, and optical antennas. We review the optical properties of these nanowires in terms of absorption, guiding, and radiation of light, which may be termed light management. Analysis of the interaction of light with long cylindrical/hexagonal structures with subwavelength diameters identifies radial resonant modes, such as Leaky Mode Resonances, or Whispering Gallery modes. The two-dimensional treatment should incorporate axial variations in “volumetric modes,”which have so far been presented in terms of Fabry–Perot (FP, and helical resonance modes. We report on finite-difference timedomain (FDTD simulations with the aim of identifying the dependence of these modes on geometry (length, width, tapering, shape (cylindrical, hexagonal, core–shell versus core-only, and dielectric cores with semiconductor shells. This demonstrates how nanowires (NWs form excellent optical cavities without the need for top and bottommirrors. However, optically equivalent structures such as hexagonal and cylindrical wires can have very different optoelectronic properties meaning that light management alone does not sufficiently describe the observed enhancement in upward (absorption and downward transitions (emission of light inNWs; rather, the electronic transition rates should be considered. We discuss this “rate management” scheme showing its strong dimensional dependence, making a case for photonic integrated circuits (PICs that can take advantage of the confluence of the desirable optical and electronic properties of these nanostructures.

  14. In-situ growth of ZnO nanowire arrays on the sensing electrode via a facile hydrothermal route for high-performance NO2 sensor

    Science.gov (United States)

    Chen, Xiangxiang; Shen, Yanbai; Zhang, Wei; Zhang, Jin; Wei, Dezhou; Lu, Rui; Zhu, Lijia; Li, Hansen; Shen, Yansong

    2018-03-01

    ZnO nanowire (ZNW) arrays were in-situ grown on the sensing electrode via a facile hydrothermal route for NO2 sensing application. ZNW arrays were prepared by a seed layer deposition on the surface of the sensing electrode using a dipping process in a Zn(CH3COO)2·2H2O ethanol solution followed by a seed growth using a hydrothermal route in the Zn(NO3)2·6H2O-HMTA (C6H12N4) system. The microstructural characterizations of the ZNW arrays by means of XRD, FESEM, TEM, FTIR and XPS showed that ZnO nanowires with the diameters of 80-90 nm and the lengths of 0.6-1 μm had a single crystal hexagonal wurtzite structure. Gas sensing properties demonstrated the response of the sensor based on the ZNW arrays was linearly proportional to the NO2 concentration in the range of 1-30 ppm with good reproducibility and selectivity. The maximum sensor response to NO2 was obtained at an operating temperature of 250 °C. The response and recovery times reduced rapidly with increasing the operating temperature. The growth mechanism and sensing mechanism of the ZNW arrays were discussed in accordance with the deposition of the seed layer and the modulation of the depletion layer, respectively.

  15. The protective nature of passivation films on zinc: surface charge

    International Nuclear Information System (INIS)

    Muster, Tim H.; Cole, Ivan S.

    2004-01-01

    The influence of oxide surface charge on the corrosion performance of zinc metals was investigated. Oxidised zinc species (zinc oxide, zinc hydroxychloride, zinc hydroxysulfate and zinc hydroxycarbonate) with chemical compositions similar to those produced on zinc during atmospheric corrosion were formed as particles from aqueous solution, and as passive films deposited onto zinc powder, and rolled zinc, surfaces. Synthesized oxides were characterised by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and electron probe X-ray microanalysis. The zeta potentials of various oxide particles, as determined by microelectrophoresis, are reported as a function of pH. Particulates containing a majority of zinc hydroxycarbonate and zinc hydroxysulfate crystallites were found to possess a negative surface charge below pH 6, whilst zinc oxide-hydroxide and zinc hydroxychloride crystallites possessed isoelectric points (IEP's) higher than pH 8. The ability of chloride species to pass through a bed of 3 μm diameter zinc powder was found to increase for surfaces possessing carboxy and sulfate surface species, suggesting that negatively charged surfaces can aid in the repulsion of chloride ions. Electrochemical analysis of the open-circuit potential as a function of time at a fixed pH of 6.5 showed that the chemical composition of passive films on zinc plates influenced the ability of chloride ions to access anodic sites for periods of approximately 1 h

  16. Surface Charge Transfer Doping of Monolayer Phosphorene via Molecular Adsorption.

    Science.gov (United States)

    He, Yuanyuan; Xia, Feifei; Shao, Zhibin; Zhao, Jianwei; Jie, Jiansheng

    2015-12-03

    Monolayer phosphorene has attracted much attention owing to its extraordinary electronic, optical, and structural properties. Rationally tuning the electrical transport characteristics of monolayer phosphorene is essential to its applications in electronic and optoelectronic devices. Herein, we study the electronic transport behaviors of monolayer phosphorene with surface charge transfer doping of electrophilic molecules, including 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ), NO2, and MoO3, using density functional theory combined with the nonequilibrium Green's function formalism. F4TCNQ shows optimal performance in enhancing the p-type conductance of monolayer phosphorene. Static electronic properties indicate that the enhancement is originated from the charge transfer between adsorbed molecule and phosphorene layer. Dynamic transport behaviors demonstrate that additional channels for hole transport in host monolayer phosphorene were generated upon the adsorption of molecule. Our work unveils the great potential of surface charge transfer doping in tuning the electronic properties of monolayer phosphorene and is of significance to its application in high-performance devices.

  17. Strain-induced electrostatic enhancements of BiFeO3 nanowire loops.

    Science.gov (United States)

    Liu, Jun; Prashanthi, Kovur; Li, Zhi; McGee, Ryan T; Ahadi, Kaveh; Thundat, Thomas

    2016-08-17

    Semiconductor nanowires (NWs), due to their intriguing structural and physical properties, offer tremendous potential for future technological applications. The existence of strain in NWs can greatly affect, for instance, their mechanical, electrical and optical properties. Here, we report an extraordinary electrostatic response of semiconductor BiFeO3 NW loops, based on Kelvin probe force microscopy (KPFM) and electrostatic force microscopy (EFM). A substantial ∼300 mV surface potential difference, accompanied by an ∼29% higher surface charge density, was found on the NW loop. We also found that the electrostatic enhancement is strongly related to the strain present at the curvature of the NW loops. We propose that the electric polarization coupled with mechanical strain (piezoelectric effect) or strain gradient (flexoelectricity) as possible reasons to account for our observation. These findings provide new insights into multiferroic based semiconductor NWs under external stimuli as well as significant inspiration towards strain sensors and electromechanical devices with multifunctional sensing abilities.

  18. Electrokinetics of nanochannels and porous membranes with dynamic surface charges

    DEFF Research Database (Denmark)

    Andersen, Mathias Bækbo

    interesting because it relies on capillary filling, so it avoids the use of external forcing such as electric fields. Basically, during the filling of nanochannels by capillary action, the advancing electrolyte is titrated by deprotonation from the surface. This is observed using the pH-sensitive fluorescent....... Notably, we find that the conductance minimum is mainly caused by hydronium ions, and in our case almost exclusively due to carbonic acid generated from the dissolution of CO2 from the atmosphere. We carry out delicate experiments and measure the conductance of silica nanochannels as a function...... in the literature. Fourth, we use our model to predict a novel phenomenon called currentinduced membrane discharge (CIMD) to explain over-limiting current in ionexchange membranes. The model is based on dynamic surface charges in the membrane in equilibrium with the buffer. However, here we take the next step...

  19. Conducting Polyaniline Nanowire and Its Applications in Chemiresistive Sensing.

    Science.gov (United States)

    Song, Edward; Choi, Jin-Woo

    2013-08-07

    One dimensional polyaniline nanowire is an electrically conducting polymer that can be used as an active layer for sensors whose conductivity change can be used to detect chemical or biological species. In this review, the basic properties of polyaniline nanowires including chemical structures, redox chemistry, and method of synthesis are discussed. A comprehensive literature survey on chemiresistive/conductometric sensors based on polyaniline nanowires is presented and recent developments in polyaniline nanowire-based sensors are summarized. Finally, the current limitations and the future prospect of polyaniline nanowires are discussed.

  20. Stem-loop DNA-assisted silicon nanowires-based biochemical sensors with ultra-high sensitivity, specificity, and multiplexing capability

    Science.gov (United States)

    Xie, Juan; Jiang, Xiangxu; Zhong, Yiling; Lu, Yimei; Wang, Siyi; Wei, Xinpan; Su, Yuanyuan; He, Yao

    2014-07-01

    A class of stem-loop DNA-assisted silicon nanowires (SiNWs)-based fluorescent biosensor is presented in this report. Significantly, the sensor enables rapid and sensitive detection of DNA targets with a concentration as low as 1 pM. Moreover, the large planar surface of SiNWs facilitates simultaneous assembly with different DNA strands, which is favorable for multiplexed DNA detection. On the other hand, the SiNWs-based sensor is highly efficacious for detecting heavy metal ions. Mercury ions (Hg2+) of low concentrations (e.g., 5 pM) are readily identified from its mixture with over 10 kinds of interfering metal ions, even in real water samples. Given that SiNWs can be fabricated in a facile, reproducible and low-cost manner, this kind of SiNWs-based high-performance sensor is expected to be a practical analytical tool for a variety of biological and environment-protection applications.A class of stem-loop DNA-assisted silicon nanowires (SiNWs)-based fluorescent biosensor is presented in this report. Significantly, the sensor enables rapid and sensitive detection of DNA targets with a concentration as low as 1 pM. Moreover, the large planar surface of SiNWs facilitates simultaneous assembly with different DNA strands, which is favorable for multiplexed DNA detection. On the other hand, the SiNWs-based sensor is highly efficacious for detecting heavy metal ions. Mercury ions (Hg2+) of low concentrations (e.g., 5 pM) are readily identified from its mixture with over 10 kinds of interfering metal ions, even in real water samples. Given that SiNWs can be fabricated in a facile, reproducible and low-cost manner, this kind of SiNWs-based high-performance sensor is expected to be a practical analytical tool for a variety of biological and environment-protection applications. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr01097c

  1. Effect of liquid gate bias rising time in pH sensors based on Si nanowire ion sensitive field effect transistors

    Science.gov (United States)

    Jang, Jungkyu; Choi, Sungju; Kim, Jungmok; Park, Tae Jung; Park, Byung-Gook; Kim, Dong Myong; Choi, Sung-Jin; Lee, Seung Min; Kim, Dae Hwan; Mo, Hyun-Sun

    2018-02-01

    In this study, we investigate the effect of rising time (TR) of liquid gate bias (VLG) on transient responses in pH sensors based on Si nanowire ion-sensitive field-effect transistors (ISFETs). As TR becomes shorter and pH values decrease, the ISFET current takes a longer time to saturate to the pH-dependent steady-state value. By correlating VLG with the internal gate-to-source voltage of the ISFET, we found that this effect occurs when the drift/diffusion of mobile ions in analytes in response to VLG is delayed. This gives us useful insight on the design of ISFET-based point-of-care circuits and systems, particularly with respect to determining an appropriate rising time for the liquid gate bias.

  2. Ultrasensitive in situ label-free DNA detection using a GaN nanowire-based extended-gate field-effect-transistor sensor.

    Science.gov (United States)

    Chen, Chin-Pei; Ganguly, Abhijit; Lu, Ching-Ying; Chen, Ting-Yu; Kuo, Chun-Chiang; Chen, Reui-San; Tu, Wen-Hsun; Fischer, Wolfgang B; Chen, Kuei-Hsien; Chen, Li-Chyong

    2011-03-15

    In this study, we have successfully demonstrated that a GaN nanowire (GaNNW) based extended-gate field-effect-transistor (EGFET) biosensor is capable of specific DNA sequence identification under label-free in situ conditions. Our approach shows excellent integration of the wide bandgap semiconducting nature of GaN, surface-sensitivity of the NW-structure, and high transducing performance of the EGFET-design. The simple sensor-architecture, by direct assembly of as-synthesized GaNNWs with a commercial FET device, can achieve an ultrahigh detection limit below attomolar level concentrations: about 3 orders of magnitude higher in resolution than that of other FET-based DNA-sensors. Comparative in situ studies on mismatches ("hotspot" mutations related to human p53 tumor-suppressor gene) and complementary targets reveal excellent selectivity and specificity of the sensor, even in the presence of noncomplementary DNA strands, suggesting the potential pragmatic application in complex clinical samples. In comparison with GaN thin film, NW-based EGFET exhibits excellent performance with about 2 orders higher sensitivity, over a wide detection range, 10(-19)-10(-6) M, reaching about a 6-orders lower detection limit. Investigations illustrate the unique and distinguished feature of nanomaterials. Detailed studies indicate a positive effect of energy band alignment at the biomaterials-semiconductor hybrid interface influencing the effective capacitance and carrier-mobility of the system.

  3. Role of protein surface charge in monellin sweetness.

    Science.gov (United States)

    Xue, Wei-Feng; Szczepankiewicz, Olga; Thulin, Eva; Linse, Sara; Carey, Jannette

    2009-03-01

    A small number of proteins have the unusual property of tasting intensely sweet. Despite many studies aimed at identifying their sweet taste determinants, the molecular basis of protein sweetness is not fully understood. Recent mutational studies of monellin have implicated positively charged residues in sweetness. In the present work, the effect of overall net charge was investigated using the complementary approach of negative charge alterations. Multiple substitutions of Asp/Asn and Glu/Gln residues radically altered the surface charge of single-chain monellin by removing six negative charges or adding four negative charges. Biophysical characterization using circular dichroism, fluorescence, and two-dimensional NMR demonstrates that the native fold of monellin is preserved in the variant proteins under physiological solution conditions although their stability toward chemical denaturation is altered. A human taste test was employed to determine the sweetness detection threshold of the variants. Removal of negative charges preserves monellin sweetness, whereas added negative charge has a large negative impact on sweetness. Meta-analysis of published charge variants of monellin and other sweet proteins reveals a general trend toward increasing sweetness with increasing positive net charge. Structural mapping of monellin variants identifies a hydrophobic surface predicted to face the receptor where introduced positive or negative charge reduces sweetness, and a polar surface where charges modulate long-range electrostatic complementarity.

  4. Influence of surface charge on lysozyme adsorption to ceria nanoparticles

    International Nuclear Information System (INIS)

    Wang Binghui; Wu Peng; Yokel, Robert A.; Grulke, Eric A.

    2012-01-01

    Understanding mechanisms for forming protein coronas on nanomaterial surfaces is essential to designing drug delivery systems and designing and interpreting the results of nanomaterial toxicity tests. The study reports the adsorption behavior of a positively charged protein, lysozyme, on cerium dioxide (ceria) nanoparticles with three different surface charges. Adsorption isotherms were modeled with the Toth and Sips equations. Isotherm loading levels were compared to monolayer coverage estimate for ‘side-on’ and ‘end-on’ lysozyme orientations as well as random packing (jamming) and maximum packing limits. Evaluation of adsorption site energy distributions (generated using the model coefficients) suggested that the negatively charged ceria surface had a very broad site energy distribution and that its surface heterogeneity controls the adsorption process. By contrast, the adsorption of lysozyme on the positively charged nanoparticles appears to be influenced by lateral effects from adsorbed protein species. The results illustrate the importance of nanoparticle surface chemistry to protein adsorption. The modeling and site energy distribution evaluations may be useful for interpreting the formation of protein coronas on nanoparticles.

  5. Surface charge modulated aptasensor in a single glass conical nanopore.

    Science.gov (United States)

    Cai, Sheng-Lin; Cao, Shuo-Hui; Zheng, Yu-Bin; Zhao, Shuang; Yang, Jin-Lei; Li, Yao-Qun

    2015-09-15

    In this work, we have proposed a label-free nanopore-based biosensing strategy for protein detection by performing the DNA-protein interaction inside a single glass conical nanopore. A lysozyme binding aptamer (LBA) was used to functionalize the walls of glass nanopore via siloxane chemistry and negatively charged recognition sites were thus generated. The covalent modification procedures and their recognition towards lysozyme of the single conical nanopore were characterized via ionic current passing through the nanopore membrane, which was measured by recording the current-voltage (I-V) curves in 1mM KCl electrolyte at pH=7.4. With the occurring of recognition event, the negatively charged wall was partially neutralized by the positively charged lysozyme molecules, leading to a sensitive change of the surface charge-dependent current-voltage (I-V) characteristics. Our results not only demonstrate excellent selectivity and sensitivity towards the target protein, but also suggest a route to extend this nanopore-based sensing strategy to the biosensing platform designs of a wide range of proteins based on a charge modulation. Copyright © 2015 Elsevier B.V. All rights reserved.

  6. Surface charge effects in protein adsorption on nanodiamonds.

    Science.gov (United States)

    Aramesh, M; Shimoni, O; Ostrikov, K; Prawer, S; Cervenka, J

    2015-03-19

    Understanding the interaction of proteins with charged diamond nanoparticles is of fundamental importance for diverse biomedical applications. Here we present a thorough study of protein binding, adsorption kinetics and structure on strongly positively (hydrogen-terminated) and negatively (oxygen-terminated) charged nanodiamond particles using a quartz crystal microbalance by dissipation and infrared spectroscopy. By using two model proteins (bovine serum albumin and lysozyme) of different properties (charge, molecular weight and rigidity), the main driving mechanism responsible for the protein binding to the charged nanoparticles was identified. Electrostatic interactions were found to dominate the protein adsorption dynamics, attachment and conformation. We developed a simple electrostatic model that can qualitatively explain the observed adsorption behaviour based on charge-induced pH modifications near the charged nanoparticle surfaces. Under neutral conditions, the local pH around the positively and negatively charged nanodiamonds becomes very high (11-12) and low (1-3) respectively, which has a profound impact on the protein charge, hydration and affinity to the nanodiamonds. Small proteins (lysozyme) were found to form multilayers with significant conformational changes to screen the surface charge, while larger proteins (albumin) formed monolayers with minor conformational changes. The findings of this study provide a step forward toward understanding and eventually predicting nanoparticle interactions with biofluids.

  7. nanowires via electrochemical method and its investigations as a ...

    Indian Academy of Sciences (India)

    Administrator

    Abstract. The special behaviour of nanowires with respect to electrical conductivity makes them suitable for sensing application. In this paper, we present a copper–ferrous (CuFe) nanowires based sensor for detection of chemicals. CuFe nanowires were synthesized by template-assisted electrochemical method.

  8. Nanowires: properties, applications and synthesis via porous anodic ...

    Indian Academy of Sciences (India)

    Moreover, periodic arrays of magnetic nanowires hold high potential for recording media application. Nanowires are also potential candidates for sensor and bio-medical applications. In the present article, the physical and chemical properties of nanowires along with their probable applications in different fields have been ...

  9. Surface charge effects in protein adsorption on nanodiamonds

    Science.gov (United States)

    Aramesh, M.; Shimoni, O.; Ostrikov, K.; Prawer, S.; Cervenka, J.

    2015-03-01

    Understanding the interaction of proteins with charged diamond nanoparticles is of fundamental importance for diverse biomedical applications. Here we present a thorough study of protein binding, adsorption kinetics and structure on strongly positively (hydrogen-terminated) and negatively (oxygen-terminated) charged nanodiamond particles using a quartz crystal microbalance by dissipation and infrared spectroscopy. By using two model proteins (bovine serum albumin and lysozyme) of different properties (charge, molecular weight and rigidity), the main driving mechanism responsible for the protein binding to the charged nanoparticles was identified. Electrostatic interactions were found to dominate the protein adsorption dynamics, attachment and conformation. We developed a simple electrostatic model that can qualitatively explain the observed adsorption behaviour based on charge-induced pH modifications near the charged nanoparticle surfaces. Under neutral conditions, the local pH around the positively and negatively charged nanodiamonds becomes very high (11-12) and low (1-3) respectively, which has a profound impact on the protein charge, hydration and affinity to the nanodiamonds. Small proteins (lysozyme) were found to form multilayers with significant conformational changes to screen the surface charge, while larger proteins (albumin) formed monolayers with minor conformational changes. The findings of this study provide a step forward toward understanding and eventually predicting nanoparticle interactions with biofluids.Understanding the interaction of proteins with charged diamond nanoparticles is of fundamental importance for diverse biomedical applications. Here we present a thorough study of protein binding, adsorption kinetics and structure on strongly positively (hydrogen-terminated) and negatively (oxygen-terminated) charged nanodiamond particles using a quartz crystal microbalance by dissipation and infrared spectroscopy. By using two model proteins

  10. Surface charging, discharging and chemical modification at a sliding contact

    International Nuclear Information System (INIS)

    Singh, S. V.; Kusano, Y.; Morgen, P.; Michelsen, P. K.

    2012-01-01

    Electrostatic charging, discharging, and consequent surface modification induced by sliding dissimilar surfaces have been studied. The surface-charge related phenomena were monitored by using a home-built capacitive, non-contact electrical probe, and the surface chemistry was studied by X-ray photoelectron spectroscopy (XPS). The experiments were performed on the disk surface of a ball-on-rotating-disk apparatus; using a glass disk and a Teflon (polytetrafluoroethylene) ball arrangement, and a polyester disks and a diamondlike carbon (DLC) coated steel ball arrangement. The capacitive probe is designed to perform highly resolved measurements, which is sensitive to relative change in charge density on the probed surface. For glass and Teflon arrangement, electrical measurements show that the ball track acquires non-uniform charging. Here not only the increase in charge density, but interestingly, increase in number of highly charged regions on the ball track was resolved. Threefold increase in the number of such highly charged regions per cycle was detected immediately before the gas breakdown-like incidences compared to that of other charge/discharge incidences at a fixed disk rotation speed. We are also able to comment on the behavior and the charge decay time in the ambient air-like condition, once the sliding contact is discontinued. XPS analysis showed a marginal deoxidation effect on the polyester disks due to the charging and discharging of the surfaces. Moreover, these XPS results clearly indicate that the wear and friction (sliding without charging) on the surface can be discarded from inducing such a deoxidation effect.

  11. Specification of the Surface Charging Environment with SHIELDS

    Science.gov (United States)

    Jordanova, V.; Delzanno, G. L.; Henderson, M. G.; Godinez, H. C.; Jeffery, C. A.; Lawrence, E. C.; Meierbachtol, C.; Moulton, J. D.; Vernon, L.; Woodroffe, J. R.; Brito, T.; Toth, G.; Welling, D. T.; Yu, Y.; Albert, J.; Birn, J.; Borovsky, J.; Denton, M.; Horne, R. B.; Lemon, C.; Markidis, S.; Thomsen, M. F.; Young, S. L.

    2016-12-01

    Predicting variations in the near-Earth space environment that can lead to spacecraft damage and failure, i.e. "space weather", remains a big space physics challenge. A recently funded project through the Los Alamos National Laboratory (LANL) Directed Research and Development (LDRD) program aims at developing a new capability to understand, model, and predict Space Hazards Induced near Earth by Large Dynamic Storms, the SHIELDS framework. The project goals are to understand the dynamics of the surface charging environment (SCE), the hot (keV) electrons representing the source and seed populations for the radiation belts, on both macro- and microscale. Important physics questions related to rapid particle injection and acceleration associated with magnetospheric storms and substorms as well as plasma waves are investigated. These challenging problems are addressed using a team of world-class experts in the fields of space science and computational plasma physics, and state-of-the-art models and computational facilities. In addition to physics-based models (like RAM-SCB, BATS-R-US, and iPIC3D), new data assimilation techniques employing data from LANL instruments on the Van Allen Probes and geosynchronous satellites are developed. Simulations with the SHIELDS framework of the near-Earth space environment where operational satellites reside are presented. Further model development and the organization of a "Spacecraft Charging Environment Challenge" by the SHIELDS project at LANL in collaboration with the NSF Geospace Environment Modeling (GEM) Workshop and the multi-agency Community Coordinated Modeling Center (CCMC) to assess the accuracy of SCE predictions are discussed.

  12. A surface diffuse scattering model for the mobility of electrons in surface charge coupled devices

    International Nuclear Information System (INIS)

    Ionescu, M.

    1977-01-01

    An analytical model for the mobility of electrons in surface charge coupled devices is studied on the basis of the results previously obtained, considering a surface diffuse scattering; the importance of the results obtained for a better understanding of the influence of the fringing field in surface charge coupled devices is discussed. (author)

  13. Phosphorus solubility of agricultural soils: a surface charge and phosphorus-31 NMR speciation study

    Science.gov (United States)

    We investigated ten soils from six states in United States to determine the relationship between potentiometric titration derived soil surface charge and Phosphorus-31 (P) nuclear magnetic resonance (NMR) speciation with the concentration of water-extractable P (WEP). The surface charge value at the...

  14. Organic Nanowires

    DEFF Research Database (Denmark)

    Balzer, Frank; Schiek, Manuela; Al-Shamery, Katharina

    Single crystalline nanowires from fluorescing organic molecules like para-phenylenes or thiophenes are supposed to become key elements in future integrated optoelectronic devices [1]. For a sophisticated design of devices based on nanowires the basic principles of the nanowire formation have...... to be well understood [2]. Nanowires from para-phenylenes, from ®-thiophenes, and from phenylene/thiophene co-oligomers, Fig. 1, are investigated exemplarily. Epitaxy and electrostatic interactions determine the microscopic growth mechanism, whereas kinetics ascertains the macroscopic habit. Results from...

  15. Detecting Liquefied Petroleum Gas (LPG) at Room Temperature Using ZnSnO3/ZnO Nanowire Piezo-Nanogenerator as Self-Powered Gas Sensor.

    Science.gov (United States)

    Fu, Yongming; Nie, Yuxin; Zhao, Yayu; Wang, Penglei; Xing, Lili; Zhang, Yan; Xue, Xinyu

    2015-05-20

    High sensitivity, selectivity, and reliability have been achieved from ZnSnO3/ZnO nanowire (NW) piezo-nanogenerator (NG) as self-powered gas sensor (SPGS) for detecting liquefied petroleum gas (LPG) at room temperature (RT). After being exposed to 8000 ppm LPG, the output piezo-voltage of ZnSnO3/ZnO NW SPGS under compressive deformation is 0.089 V, much smaller than that in air ambience (0.533 V). The sensitivity of the SPGS against 8000 ppm LPG is up to 83.23, and the low limit of detection is 600 ppm. The SPGS has lower sensitivity against H2S, H2, ethanol, methanol and saturated water vapor than LPG, indicating good selectivity for detecting LPG. After two months, the decline of the sensing performance is less than 6%. Such piezo-LPG sensing at RT can be ascribed to the new piezo-surface coupling effect of ZnSnO3/ZnO nanocomposites. The practical application of the device driven by human motion has also been simply demonstrated. This work provides a novel approach to fabricate RT-LPG sensors and promotes the development of self-powered sensing system.

  16. Multifunctional Nanowire/film Composites based Bi-modular Sensors for In-situ and Real-time High Temperature Gas Detection

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Pu-Xian; Lei, Yu

    2013-06-01

    This final report to the Department of Energy/National Energy Technology Laboratory for DE-FE0000870 covers the period from 2009 to June, 2013 and summarizes the main research accomplishments, which can be divided in sensing materials innovation, bimodular sensor demonstration, and new understanding and discoveries. As a matter of fact, we have successfully completed all the project tasks in June 1, 2013, and presented the final project review presentation on the 9th of July, 2013. Specifically, the major accomplishments achieved in this project include: 1) Successful development of a new class of high temperature stable gas sensor nanomaterials based on composite nano-array strategy in a 3D or 2D fashion using metal oxides and perovskite nanostructures. 2) Successful demonstration of bimodular nanosensors using 2D nanofibrous film and 3D composite nanowire arrays using electrical resistance mode and electrochemical electromotive force mode. 3) Series of new discoveries and understandings based on the new composite nanostructure platform toward enhancing nanosensor performance in terms of stability, selectivity, sensitivity and mass flux sensing. In this report, we highlight some results toward these accomplishments.

  17. A Novel MOS Nanowire Gas Sensor Device (S3) and GC-MS-Based Approach for the Characterization of Grated Parmigiano Reggiano Cheese

    Science.gov (United States)

    Sberveglieri, Veronica; Bhandari, Manohar Prasad; Núñez Carmona, Estefanía; Betto, Giulia; Sberveglieri, Giorgio

    2016-01-01

    To determine the originality of a typical Italian Parmigiano Reggiano cheese, it is crucial to define and characterize its quality, ripening period, and geographical origin. Different analytical techniques have been applied aimed at studying the organoleptic and characteristic volatile organic compounds (VOCs) profile of this cheese. However, most of the classical methods are time consuming and costly. The aim of this work was to illustrate a new simple, portable, fast, reliable, non-destructive, and economic sensor device S3 based on an array of six metal oxide semiconductor nanowire gas sensors to assess and discriminate the quality ranking of grated Parmigiano Reggiano cheese samples and to identify the VOC biomarkers using a headspace SPME-GC-MS. The device could clearly differentiate cheese samples varying in quality and ripening time when the results were analyzed by multivariate statistical analysis involving principal component analysis (PCA). Similarly, the volatile constituents of Parmigiano Reggiano identified were consistent with the compounds intimated in the literature. The obtained results show the applicability of an S3 device combined with SPME-GC-MS and sensory evaluation for a fast and high-sensitivity analysis of VOCs in Parmigiano Reggiano cheese and for the quality control of this class of cheese. PMID:27999300

  18. Aspirin degradation in surface-charged TEMPO-oxidized mesoporous crystalline nanocellulose.

    Science.gov (United States)

    Carlsson, Daniel O; Hua, Kai; Forsgren, Johan; Mihranyan, Albert

    2014-01-30

    TEMPO-mediated surface oxidation of mesoporous highly crystalline Cladophora cellulose was used to introduce negative surface charges onto cellulose nanofibrils without significantly altering other structural characteristics. This enabled the investigation of the influence of mesoporous nanocellulose surface charges on aspirin chemical stability to be conducted. The negative surface charges (carboxylate content 0.44±0.01 mmol/g) introduced on the mesoporous crystalline nanocellulose significantly accelerated aspirin degradation, compared to the starting material which had significantly less surface charge (0.06±0.01 mmol/g). This effect followed from an increased aspirin amorphisation ability in mesopores of the oxidized nanocellulose. These results highlight the importance of surface charges in formulating nanocellulose for drug delivery. Copyright © 2013 Elsevier B.V. All rights reserved.

  19. Translating silicon nanowire BioFET sensor-technology to embedded point-of-care medical diagnostics

    DEFF Research Database (Denmark)

    Pfreundt, Andrea; Zulfiqar, Azeem; Patou, François

    2013-01-01

    Silicon nanowire and nanoribbon biosensors have shown great promise in the detection of biomarkers at very low concentrations. Their high sensitivity makes them ideal candidates for use in early-stage medical diagnostics and further disease monitoring where low amounts of biomarkers need to be de......Silicon nanowire and nanoribbon biosensors have shown great promise in the detection of biomarkers at very low concentrations. Their high sensitivity makes them ideal candidates for use in early-stage medical diagnostics and further disease monitoring where low amounts of biomarkers need...... to be detected. However, in order to translate this technology from the bench to the bedside, a number of key issues need to be taken into consideration: Integrating nanobiosensors-based technology requires to overcome the difficult tradeoff between imperatives for high device reproducibilty and associated......, which require a specific set of biomakers to be identified and quantified simultaneously, can thus be readily translated onto this platform. After hydrogen termination of the silicon surface an alkyne monolayer is formed based on a hydrosilylation process. Antibodies and other receptor proteins can...

  20. Experimental and Theoretical Investigations of Glass Surface Charging Phenomena

    Science.gov (United States)

    Agnello, Gabriel

    Charging behavior of multi-component display-type (i.e. low alkali) glass surfaces has been studied using a combination of experimental and theoretical methods. Data obtained by way of a Rolling Sphere Test (RST), streaming/zeta potential and surface energy measurements from commercially available display glass surfaces (Corning EAGLE XGRTM and Lotus(TM) XT) suggest that charge accumulation is highly dependent on surface treatment (chemical and/or physical modification) and measurement environment, presumably through reactionary mechanisms at the surface with atmospheric moisture. It has been hypothesized that water dissociation, along with the corresponding hydroxylation of the glass surface, are important processes related to charging in glass-metal contact systems. Classical Molecular Dynamics (MD) simulations, in conjunction with various laboratory based measurements (RST, a newly developed ElectroStatic Gauge (ESG) and Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS)) on simpler Calcium AluminoSilicate (CAS) glass surfaces were used to further explore these phenomena. Analysis of simulated high-silica content (≥50%) (CAS) glass structures suggest that controlled variation of bulk chemistry can directly affect surface defect concentrations, such as non-bridging oxygen (NBO), which can be suitable high-energy sites for hydrolysis-type reactions to occur. Calculated NBO surface concentrations correlate well with charge based measurements on laboratory fabricated CAS surfaces. The data suggest that a directional/polar shift in contact-charge transfer occurs at low silica content (≤50%) where the highest concentrations of NBOs are observed. Surface charging sensitivity with respect to NBO concentration decreases as the relative humidity of the measurement environment increases; which should be expected as the highly reactive sites are progressively covered by liquid water layers. DRIFTS analysis of CAS powders expand on this analysis showing

  1. Conducting Polyaniline Nanowire and Its Applications in Chemiresistive Sensing

    OpenAIRE

    Song, Edward; Choi, Jin-Woo

    2013-01-01

    One dimensional polyaniline nanowire is an electrically conducting polymer that can be used as an active layer for sensors whose conductivity change can be used to detect chemical or biological species. In this review, the basic properties of polyaniline nanowires including chemical structures, redox chemistry, and method of synthesis are discussed. A comprehensive literature survey on chemiresistive/conductometric sensors based on polyaniline nanowires is presented and recent developments in...

  2. Patchy silica-coated silver nanowires as SERS substrates

    Energy Technology Data Exchange (ETDEWEB)

    Hunyadi Murph, Simona E.; Murphy, Catherine J.

    2013-05-08

    We report a class of core-shell nanomaterials that can be used as efficient surface-enhancement Raman scattering (SERS) substrates. The core consists of silver nanowires, prepared through a chemical reduction process, that are used to capture 4- mercaptobenzoic acid (4-MBA), a model analyte. The shell was prepared through a modified Stöber method and consists of patchy or full silica coats. The formation of silica coats was monitored via transmission electron microscopy, UV-visible spectroscopy and phase-analysis light scattering for measuring effective surface charge. Surprisingly, the patchy silica coated silver nanowires are better SERS substrate than silver nanowires; nanomolar concentration of 4-MBA can be detected. In addition, “nano-matryoshka” configurations were used to quantitate/explore the effect of the electromagnetic field at the tips of the nanowire (“hot spots”) in the Raman scattering experiment.

  3. Silicon-on-Insulator Nanowire Based Optical Waveguide Biosensors

    Science.gov (United States)

    Li, Mingyu; Liu, Yong; Chen, Yangqing; He, Jian-Jun

    2016-01-01

    Optical waveguide biosensors based on silicon-on-insulator (SOI) nanowire have been developed for label free molecular detection. This paper reviews our work on the design, fabrication and measurement of SOI nanowire based high-sensitivity biosensors employing Vernier effect. Biosensing experiments using cascaded double-ring sensor and Mach-Zehnder- ring sensor integrated with microfluidic channels are demonstrated

  4. Effect of surface charge on the cellular uptake of fluorescent magnetic nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Kralj, Slavko, E-mail: slavko.kralj@ijs.si [Jozef Stefan Institute, Department for Materials Synthesis (Slovenia); Rojnik, Matija [University of Ljubljana, Faculty of Pharmacy (Slovenia); Romih, Rok [University of Ljubljana, Faculty of Medicine, Institute of Cell Biology (Slovenia); Jagodic, Marko [Institute of Mathematics, Physics and Mechanics (Slovenia); Kos, Janko [University of Ljubljana, Faculty of Pharmacy (Slovenia); Makovec, Darko [Jozef Stefan Institute, Department for Materials Synthesis (Slovenia)

    2012-10-15

    We report on the nanoparticle uptake into MCF10A neoT and PC-3 cells using flow cytometry, confocal microscopy, SQUID magnetometry, and transmission electron microscopy. The aim was to evaluate the influence of the nanoparticles' surface charge on the uptake efficiency. The surface of the superparamagnetic, silica-coated, maghemite nanoparticles was modified using amino functionalization for the positive surface charge (CNPs), and carboxyl functionalization for the negative surface charge (ANPs). The CNPs and ANPs exhibited no significant cytotoxicity in concentrations up to 500 {mu}g/cm{sup 3} in 24 h. The CNPs, bound to a plasma membrane, were intensely phagocytosed, while the ANPs entered cells through fluid-phase endocytosis in a lower internalization degree. The ANPs and CNPs were shown to be co-localized with a specific lysosomal marker, thus confirming their presence in lysosomes. We showed that tailoring the surface charge of the nanoparticles has a great impact on their internalization.

  5. Effect of surface charge on the cellular uptake of fluorescent magnetic nanoparticles

    Science.gov (United States)

    Kralj, Slavko; Rojnik, Matija; Romih, Rok; Jagodič, Marko; Kos, Janko; Makovec, Darko

    2012-10-01

    We report on the nanoparticle uptake into MCF10A neoT and PC-3 cells using flow cytometry, confocal microscopy, SQUID magnetometry, and transmission electron microscopy. The aim was to evaluate the influence of the nanoparticles' surface charge on the uptake efficiency. The surface of the superparamagnetic, silica-coated, maghemite nanoparticles was modified using amino functionalization for the positive surface charge (CNPs), and carboxyl functionalization for the negative surface charge (ANPs). The CNPs and ANPs exhibited no significant cytotoxicity in concentrations up to 500 μg/cm3 in 24 h. The CNPs, bound to a plasma membrane, were intensely phagocytosed, while the ANPs entered cells through fluid-phase endocytosis in a lower internalization degree. The ANPs and CNPs were shown to be co-localized with a specific lysosomal marker, thus confirming their presence in lysosomes. We showed that tailoring the surface charge of the nanoparticles has a great impact on their internalization.

  6. Cytotoxicity of surface-functionalized silicon and germanium nanoparticles: the dominant role of surface charges

    NARCIS (Netherlands)

    Bhattacharjee, S.; Rietjens, I.M.C.M.; Singh, M.P.; Atkins, T.M.; Purkait, T.K.; Xu, Z.; Regli, S.; Shukaliak, A.; Clark, R.J.; Mitchell, B.S.; Alink, G.M.; Marcelis, A.T.M.; Fink, M.J.; Veinot, J.G.C.; Kauzlarich, S.M.; Zuilhof, H.

    2013-01-01

    Although it is frequently hypothesized that surface (like surface charge) and physical characteristics (like particle size) play important roles in cellular interactions of nanoparticles (NPs), a systematic study probing this issue is missing. Hence, a comparative cytotoxicity study, quantifying

  7. Surface charges for gravity and electromagnetism in the first order formalism

    Science.gov (United States)

    Frodden, Ernesto; Hidalgo, Diego

    2018-02-01

    A new derivation of surface charges for 3  +  1 gravity coupled to electromagnetism is obtained. Gravity theory is written in the tetrad-connection variables. The general derivation starts from the Lagrangian, and uses the covariant symplectic formalism in the language of forms. For gauge theories, surface charges disentangle physical from gauge symmetries through the use of Noether identities and the exactness symmetry condition. The surface charges are quasilocal, explicitly coordinate independent, gauge invariant and background independent. For a black hole family solution, the surface charge conservation implies the first law of black hole mechanics. As a check, we show the first law for an electrically charged, rotating black hole with an asymptotically constant curvature (the Kerr–Newman (anti-)de Sitter family). The charges, including the would-be mass term appearing in the first law, are quasilocal. No reference to the asymptotic structure of the spacetime nor the boundary conditions is required and therefore topological terms do not play a rôle. Finally, surface charge formulae for Lovelock gravity coupled to electromagnetism are exhibited, generalizing the one derived in a recent work by Barnich et al Proc. Workshop ‘ About Various Kinds of Interactions’ in honour of Philippe Spindel (4–5 June 2015, Mons, Belgium) C15-06-04 (2016 (arXiv:1611.01777 [gr-qc])). The two different symplectic methods to define surface charges are compared and shown equivalent.

  8. CuO nanowire/microflower/nanowire modified Cu electrode with enhanced electrochemical performance for non-enzymatic glucose sensing.

    Science.gov (United States)

    Li, Changli; Yamahara, Hiroyasu; Lee, Yaerim; Tabata, Hitoshi; Delaunay, Jean-Jacques

    2015-07-31

    CuO nanowire/microflower structure on Cu foil is synthesized by annealing a Cu(OH)2 nanowire/CuO microflower structure at 250 °C in air. The nanowire/microflower structure with its large surface area leads to an efficient catalysis and charge transfer in glucose detection, achieving a high sensitivity of 1943 μA mM(-1) cm(-2), a wide linear range up to 4 mM and a low detection limit of 4 μM for amperometric glucose sensing in alkaline solution. With a second consecutive growth of CuO nanowires on the microflowers, the sensitivity of the obtained CuO nanowire/microflower/nanowire structure further increases to 2424 μA mM(-1) cm(-2), benefiting from an increased number of electrochemically active sites. The enhanced electrocatalytic performance of the CuO nanowire/microflower/nanowire electrode compared to the CuO nanowire/microflower electrode, CuO nanowire electrode and CuxO film electrode provides evidence for the significant role of available surface area for electrocatalysis. The rational combination of CuO nanowire and microflower nanostructures into a nanowire supporting microflower branching nanowires structure makes it a promising composite nanostructure for use in CuO based electrochemical sensors with promising analytical properties.

  9. Study of a QCM Dimethyl Methylphosphonate Sensor Based on a ZnO-Modified Nanowire-Structured Manganese Dioxide Film

    Science.gov (United States)

    Pei, Zhifu; Ma, Xingfa; Ding, Pengfei; Zhang, Wuming; Luo, Zhiyuan; Li, Guang

    2010-01-01

    Sensitive, selective and fast detection of chemical warfare agents is necessary for anti-terrorism purposes. In our search for functional materials sensitive to dimethyl methylphosphonate (DMMP), a simulant of sarin and other toxic organophosphorus compounds, we found that zinc oxide (ZnO) modification potentially enhances the absorption of DMMP on a manganese dioxide (MnO2) surface. The adsorption behavior of DMMP was evaluated through the detection of tiny organophosphonate compounds with quartz crystal microbalance (QCM) sensors coated with ZnO-modified MnO2 nanofibers and pure MnO2 nanofibers. Experimental results indicated that the QCM sensor coated with ZnO-modified nanostructured MnO2 film exhibited much higher sensitivity and better selectivity in comparison with the one coated with pure MnO2 nanofiber film. Therefore, the DMMP sensor developed with this composite nanostructured material should possess excellent selectivity and reasonable sensitivity towards the tiny gaseous DMMP species. PMID:22163653

  10. Nanowire Lasers

    Directory of Open Access Journals (Sweden)

    Couteau C.

    2015-05-01

    Full Text Available We review principles and trends in the use of semiconductor nanowires as gain media for stimulated emission and lasing. Semiconductor nanowires have recently been widely studied for use in integrated optoelectronic devices, such as light-emitting diodes (LEDs, solar cells, and transistors. Intensive research has also been conducted in the use of nanowires for subwavelength laser systems that take advantage of their quasione- dimensional (1D nature, flexibility in material choice and combination, and intrinsic optoelectronic properties. First, we provide an overview on using quasi-1D nanowire systems to realize subwavelength lasers with efficient, directional, and low-threshold emission. We then describe the state of the art for nanowire lasers in terms of materials, geometry, andwavelength tunability.Next,we present the basics of lasing in semiconductor nanowires, define the key parameters for stimulated emission, and introduce the properties of nanowires. We then review advanced nanowire laser designs from the literature. Finally, we present interesting perspectives for low-threshold nanoscale light sources and optical interconnects. We intend to illustrate the potential of nanolasers inmany applications, such as nanophotonic devices that integrate electronics and photonics for next-generation optoelectronic devices. For instance, these building blocks for nanoscale photonics can be used for data storage and biomedical applications when coupled to on-chip characterization tools. These nanoscale monochromatic laser light sources promise breakthroughs in nanophotonics, as they can operate at room temperature, can potentially be electrically driven, and can yield a better understanding of intrinsic nanomaterial properties and surface-state effects in lowdimensional semiconductor systems.

  11. Optical fibre microwire sensors

    OpenAIRE

    Brambilla, G.; Belal, Mohammad; Jung, Y.; Song, Z.; Xu, F.; Newson, T.P.; Richardson, D.J.

    2011-01-01

    This paper reviews sensing applications of optical fibre microwires and nanowires. In addition to the usual benefits of sensors based on optical fibres, these sensors are extremely compact and have fast response speeds. In this review sensors will be grouped in three categories according to their morphology: linear sensors, resonant sensors and tip sensors. While linear and resonant sensors mainly exploit the fraction of power propagating outside the microwire physical boundary, tip sensors t...

  12. Silicon nanowires as field-effect transducers for biosensor development: A review

    Energy Technology Data Exchange (ETDEWEB)

    Noor, M. Omair; Krull, Ulrich J., E-mail: ulrich.krull@utoronto.ca

    2014-05-01

    Highlights: • Nanoscale field-effect transducers interrogate surface charge by conductivity changes. • The nanometer dimensions of SiNWs facilitate sensitive detection of biomolecules. • SiNWs can be fabricated by bottom–up or top–down approaches. • Device parameters and solution-phase conditions strongly influence analytical performance. - Abstract: The unique electronic properties and miniaturized dimensions of silicon nanowires (SiNWs) are attractive for label-free, real-time and sensitive detection of biomolecules. Sensors based on SiNWs operate as field effect transistors (FETs) and can be fabricated either by top–down or bottom–up approaches. Advances in fabrication methods have allowed for the control of physicochemical and electronic properties of SiNWs, providing opportunity for interfacing of SiNW-FET probes with intracellular environments. The Debye screening length is an important consideration that determines the performance and detection limits of SiNW-FET sensors, especially at physiologically relevant conditions of ionic strength (>100 mM). In this review, we discuss the construction and application of SiNW-FET sensors for detection of ions, nucleic acids and protein markers. Advantages and disadvantages of the top–down and bottom–up approaches for synthesis of SiNWs are discussed. An overview of various methods for surface functionalization of SiNWs for immobilization of selective chemistry is provided in the context of impact on the analytical performance of SiNW-FET sensors. In addition to in vitro examples, an overview of the progress of use of SiNW-FET sensors for ex vivo studies is also presented. This review concludes with a discussion of the future prospects of SiNW-FET sensors.

  13. Study of a QCM Dimethyl Methylphosphonate Sensor Based on a ZnO-Modified Nanowire-Structured Manganese Dioxide Film

    Directory of Open Access Journals (Sweden)

    Guang Li

    2010-09-01

    Full Text Available Sensitive, selective and fast detection of chemical warfare agents is necessary for anti-terrorism purposes. In our search for functional materials sensitive to dimethyl methylphosphonate (DMMP, a simulant of sarin and other toxic organophosphorus compounds, we found that zinc oxide (ZnO modification potentially enhances the absorption of DMMP on a manganese dioxide (MnO2 surface. The adsorption behavior of DMMP was evaluated through the detection of tiny organophosphonate compounds with quartz crystal microbalance (QCM sensors coated with ZnO-modified MnO2 nanofibers and pure MnO2 nanofibers. Experimental results indicated that the QCM sensor coated with ZnO-modified nanostructured MnO2 film exhibited much higher sensitivity and better selectivity in comparison with the one coated with pure MnO2 nanofiber film. Therefore, the DMMP sensor developed with this composite nanostructured material should possess excellent selectivity and reasonable sensitivity towards the tiny gaseous DMMP species.

  14. Concentration polarization and desalination in nanochannels: Effect of surface charge dynamics

    Science.gov (United States)

    Andersen, Mathias B.; Bruus, Henrik; Mani, Ali; Bazant, Martin Z.

    2011-11-01

    Mani, Zangle, and Santiago (Langmuir, 25, 3898-3916) have shown that at microchannel-nanochannel junctions the coupled effect of concentration polarization and surface conduction can lead to long range propagation of bulk ion-depletion shocks. Essential for this phenomena is the surface charge which for many materials depends on both the concentration and the pH of the local bulk electrolyte. Standard models predict that the surface charge decreases with decreasing concentration leading to the contradictory expectation that there is little or no surface charge in the depleted region and hence no mechanism to sustain long range propagation of desalination shocks. We show that this simple prediction fails to take into account axial transport terms. As such, we couple a surface charge model with the Poisson-Nernst-Planck equations for electric potential and ionic species combined with the Navier-Stokes and continuity equations for fluid velocity. Motivated by experimental work we consider steady-state solutions at the dead end of a nanochannel against a membrane, a scenario where especially space charge and electroosmotic flow are important. Our results suggest that the surface charge density remains finite and does not vanish, and even grows, as the depletion front propagates through the channel.

  15. Ultra violet sensors based on nanostructured ZnO spheres in network of nanowires: a novel approach

    OpenAIRE

    Hullavarad, SS; Hullavarad, NV; Karulkar, PC; Luykx, A; Valdivia, P

    2007-01-01

    AbstractThe ZnO nanostructures consisting of micro spheres in a network of nano wires were synthesized by direct vapor phase method. X-ray Photoelectron Spectroscopy measurements were carried out to understand the chemical nature of the sample. ZnO nanostructures exhibited band edge luminescence at 383 nm. The nanostructure based ZnO thin films were used to fabricate UV sensors. The photoresponse measurements were carried out and the responsivity was measured to be 50 mA W−1. The rise a...

  16. Ultra violet sensors based on nanostructured ZnO spheres in network of nanowires: a novel approach

    Directory of Open Access Journals (Sweden)

    Luykx A

    2007-01-01

    Full Text Available AbstractThe ZnO nanostructures consisting of micro spheres in a network of nano wires were synthesized by direct vapor phase method. X-ray Photoelectron Spectroscopy measurements were carried out to understand the chemical nature of the sample. ZnO nanostructures exhibited band edge luminescence at 383 nm. The nanostructure based ZnO thin films were used to fabricate UV sensors. The photoresponse measurements were carried out and the responsivity was measured to be 50 mA W−1. The rise and decay time measurements were also measured.

  17. Preparation of electrodeposited cobalt nanowires

    Directory of Open Access Journals (Sweden)

    Valeska da Rocha Caffarena

    2006-06-01

    Full Text Available Nanostructured magnetic materials have great interest because of their applications in high-density magnetic information storage and for magnetic sensors. The electrodeposition of materials into porous alumina arrays is a suitable technique to produce nanomaterials, since highly ordered uniform nanomaterials can be obtained simply and cheaply. In this work, template-assisted Co nanowire arrays were prepared by electrodeposition into nanometer-sized pores of an alumite film using a two-electrode electrochemical cell. The Co nanowires were electrodeposited from a solution of 400 g/L of CoSO4.7H2O and 40 g/L of H3BO3. The morphology of the samples was investigated by means of TEM and AFM. The structural characteristic of the samples was examined using XRD, EDX and FTIR, which confirm the cobalt nanowire formation.

  18. NTERACTION BETWEEN SURFACE CHARGE PHENOMENA AND MULTI-SPECIES DIFFUSION IN CEMENT BASED MATERIALS

    DEFF Research Database (Denmark)

    Johannesson, Björn

    2008-01-01

    Measurements strongly indicate that the ‘inner’ surface of the microscopic structure of cement based materials has a fixed negative charge. This charge contributes to the formation of so-called electrical double layers. In the case of cement based materials the ionic species located in such layers...... are typically potassium -, sodium - and calcium ions. Due to the high specific surface area of hydrated cement, a large amount of ions can be located in theses double layers even if the surface charge is relatively low. The attraction force, caused by the fixed surface charge on ions located close to surfaces...

  19. Laser direct written silicon nanowires for electronic and sensing applications

    Science.gov (United States)

    Nam, Woongsik

    Silicon nanowires are promising building blocks for high-performance electronics and chemical/biological sensing devices due to their ultra-small body and high surface-to-volume ratios. However, the lack of the ability to assemble and position nanowires in a highly controlled manner still remains an obstacle to fully exploiting the substantial potential of nanowires. Here we demonstrate a one-step method to synthesize intrinsic and doped silicon nanowires for device applications. Sub-diffraction limited nanowires as thin as 60 nm are synthesized using laser direct writing in combination with chemical vapor deposition, which has the advantages of in-situ doping, catalyst-free growth, and precise control of position, orientation, and length. The synthesized nanowires have been fabricated into field effect transistors (FETs) and FET sensors. The FET sensors are employed to detect the proton concentration (pH) of an aqueous solution and highly sensitive pH sensing is demonstrated. Both top- and back-gated silicon nanowire FETs are demonstrated and electrically characterized. In addition, modulation-doped nanowires are synthesized by changing dopant gases during the nanowire growth. The axial p-n junction nanowires are electrically characterized to demonstrate the diode behavior and the transition between dopant levels are measured using Kelvin probe force microscopy.

  20. Hydrogen gas sensing with networks of ultra-small palladium nanowires formed on filtration membranes.

    Energy Technology Data Exchange (ETDEWEB)

    Zeng, X. Q.; Latimer, M. L.; Xiao, Z. L.; Panuganti, S.; Welp, U.; Kwok, W. K.; Xu, T. (Materials Science Division); (Northern Illinois Univ.)

    2010-11-29

    Hydrogen sensors based on single Pd nanowires show promising results in speed, sensitivity, and ultralow power consumption. The utilization of single Pd nanowires, however, face challenges in nanofabrication, manipulation, and achieving ultrasmall transverse dimensions. We report on hydrogen sensors that take advantage of single palladium nanowires in high speed and sensitivity and that can be fabricated conveniently. The sensors are based on networks of ultrasmall (<10 nm) palladium nanowires deposited onto commercially available filtration membranes. We investigated the sensitivities and response times of these sensors as a function of the thickness of the nanowires and also compared them with a continuous reference film. The superior performance of the ultrasmall Pd nanowire network based sensors demonstrates the novelty of our fabrication approach, which can be directly applied to palladium alloy and other hydrogen sensing materials.

  1. Theoretical study of the amphoteric oxide nanoparticle surface charge during multi-particle interactions in aqueous solutions

    Science.gov (United States)

    Alfimov, A. V.; Aryslanova, E. M.; Chivilikhin, S. A.

    2015-11-01

    Nanoparticle surface charge plays an important role in many biological applications. In this study, an analytical surface charging model for the amphoteric oxide nanoparticles has been presented. The model accounts for the particle's electric double layer self-action on the charging process and the charge regulation during multi-particle interactions in aqueous solutions. The employment of the model allows to explicitly describe the nanoparticle agglomeration process and the accompanying agglomerate surface charge variation.

  2. Metal-dielectric-CNT nanowires for surface-enhanced Raman spectroscopy

    Science.gov (United States)

    Bond, Tiziana C.; Altun, Ali; Park, Hyung Gyu

    2017-10-03

    A sensor with a substrate includes nanowires extending vertically from the substrate, a hafnia coating on the nanowires that provides hafnia coated nanowires, and a noble metal coating on the hafnia coated nanowires. The top of the hafnia and noble metal coated nanowires bent onto one another to create a canopy forest structure. There are numerous randomly arranged holes that let through scattered light. The many points of contact, hot spots, amplify signals. The methods include the steps of providing a Raman spectroscopy substrate, introducing nano crystals to the Raman spectroscopy substrate, growing a forest of nanowires from the nano crystals on the Raman spectroscopy substrate, coating the nanowires with hafnia providing hafnia coated nanowires, and coating the hafnia coated nanowires with a noble metal or other metal.

  3. Double layer of platinum electrodes: Non-monotonic surface charging phenomena and negative double layer capacitance

    Science.gov (United States)

    Huang, Jun; Zhou, Tao; Zhang, Jianbo; Eikerling, Michael

    2018-01-01

    In this study, a refined double layer model of platinum electrodes accounting for chemisorbed oxygen species, oriented interfacial water molecules, and ion size effects in solution is presented. It results in a non-monotonic surface charging relation and a peculiar capacitance vs. potential curve with a maximum and possibly negative values in the potential regime of oxide-formation.

  4. Surface charge-specific interactions between polymer nanoparticles and ABC transporters in Caco-2 cells

    NARCIS (Netherlands)

    Bhattacharjee, S.; Opstal, van E.J.; Alink, G.M.; Marcelis, A.T.M.; Zuilhof, H.; Rietjens, I.M.C.M.

    2013-01-01

    The surface charge-dependent transport of polymeric nanoparticles (PNPs) across Caco-2 monolayers grown on transwell culture systems as an in vitro model for intestinal transport was tested. The transport of well-characterized, monodisperse, and fluorescent tri-block copolymer nanoparticles

  5. Mapping surface charge density of lipid bilayers by quantitative surface conductivity microscopy

    DEFF Research Database (Denmark)

    Klausen, Lasse Hyldgaard; Fuhs, Thomas; Dong, Mingdong

    2016-01-01

    Local surface charge density of lipid membranes influences membrane-protein interactions leading to distinct functions in all living cells, and it is a vital parameter in understanding membrane-binding mechanisms, liposome design and drug delivery. Despite the significance, no method has so far...

  6. Effect of plasma-induced surface charging on catalytic processes: application to CO2 activation

    Science.gov (United States)

    Bal, Kristof M.; Huygh, Stijn; Bogaerts, Annemie; Neyts, Erik C.

    2018-02-01

    Understanding the nature and effect of the multitude of plasma–surface interactions in plasma catalysis is a crucial requirement for further process development and improvement. A particularly intriguing and rather unique property of a plasma-catalytic setup is the ability of the plasma to modify the electronic structure, and hence chemical properties, of the catalyst through charging, i.e. the absorption of excess electrons. In this work, we develop a quantum chemical model based on density functional theory to study excess negative surface charges in a heterogeneous catalyst exposed to a plasma. This method is specifically applied to investigate plasma-catalytic CO2 activation on supported M/Al2O3 (M = Ti, Ni, Cu) single atom catalysts. We find that (1) the presence of a negative surface charge dramatically improves the reductive power of the catalyst, strongly promoting the splitting of CO2 to CO and oxygen, and (2) the relative activity of the investigated transition metals is also changed upon charging, suggesting that controlled surface charging is a powerful additional parameter to tune catalyst activity and selectivity. These results strongly point to plasma-induced surface charging of the catalyst as an important factor contributing to the plasma-catalyst synergistic effects frequently reported for plasma catalysis.

  7. Characterization of the surface charge distribution on kaolinite particles using high resolution atomic force microscopy

    NARCIS (Netherlands)

    Kumar, Naveen; Zhao, Cunlu; Klaassen, Aram Harold; van den Ende, Henricus T.M.; Mugele, Friedrich Gunther; Sîretanu, Igor

    2016-01-01

    Most solid surfaces, in particular clay minerals and rock surfaces, acquire a surface charge upon exposure to an aqueous environment due to adsorption and/or desorption of ionic species. Macroscopic techniques such as titration and electrokinetic measurements are commonly used to determine the

  8. Negligible water surface charge determined using Kelvin probe and total reflection X-ray fluorescence techniques.

    Science.gov (United States)

    Shapovalov, Vladimir L; Möhwald, Helmuth; Konovalov, Oleg V; Knecht, Volker

    2013-09-07

    The water surface charge has been extensively debated in recent decades. Electrophoretic mobilities of air bubbles in water and disjoining pressures between the surfaces of aqueous films suggest that the surface of water exhibits a significant negative charge. This is commonly attributed to a strong adsorption of hydroxide ions at the interface, though spectroscopic measurements and simulation studies suggest surface depletion of hydroxide ions. Alternatively, the negative surface charge could arise from surface contamination with trace charged surfactants. We have probed the variation in the surface charge of water with pH by measuring surface potentials using the Kelvin probe technique. Independently, the abundance in the interfacial layer of "reporter ions" (Rb(+) and Br(-)), which must be affected by a charged surface, has been monitored using the total reflection X-ray fluorescence (TRXF) technique. Special care was taken to prove the high sensitivity of this technique as well as to avoid surface contaminants. The magnitude of the surface charge was found to be below 1 e per 500 nm(2) (TRXF). No evidence of variations in the surface potential between pH 2-3 and pH 9-12 was detected within the accuracies of the methods (5 mV for Kelvin probe and 2 mV for TRXF). Hence, our findings suggest that the clean water surface exhibits negligible charge in a wide pH range.

  9. Modeling of Lithium Niobate (LiNbO3) and Aluminum Nitride (AlN) Nanowires Using Comsol Multiphysics Software: The Case of Pressure Sensor

    Science.gov (United States)

    Ahmad, A. A.; Alsaad, A.; Al-Bataineh, Q. M.; Al-Naafa, M. A.

    2018-02-01

    In this study, Lithium niobate (LiNbO3) and Aluminum nitride (AlN) nanostructures were designed and investigated using the COMSOL Multiphysics software for pressure sensing applications. The Finite Element Method (FEM) was used for solving the differential equations with various parameters such as size, length, force, etc. The variation of the total maximum displacement as a function of applied force for various NWs lengths and the variation of the voltage as a function of applied force were plotted and discussed. AlN nanowires exhibit a better piezoelectric response than LiNbO3 nanowires do.

  10. The influence of spherical cavity surface charge distribution on the sequence of partial discharge events

    Energy Technology Data Exchange (ETDEWEB)

    Illias, Hazlee A [Department of Electrical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur (Malaysia); Chen, George; Lewin, Paul L, E-mail: h.illias@um.edu.my [Tony Davies High Voltage Laboratory, School of Electronics and Computer Science, University of Southampton, Southampton, SO17 1BJ (United Kingdom)

    2011-06-22

    In this work, a model representing partial discharge (PD) behaviour of a spherical cavity within a homogeneous dielectric material has been developed to study the influence of cavity surface charge distribution on the electric field distribution in both the cavity and the material itself. The charge accumulation on the cavity surface after a PD event and charge movement along the cavity wall under the influence of electric field magnitude and direction has been found to affect the electric field distribution in the whole cavity and in the material. This in turn affects the likelihood of any subsequent PD activity in the cavity and the whole sequence of PD events. The model parameters influencing cavity surface charge distribution can be readily identified; they are the cavity surface conductivity, the inception field and the extinction field. Comparison of measurement and simulation results has been undertaken to validate the model.

  11. A Small Angle Neutron Scattering Study of Cylindrical nanoparticle with Controlled Surface Charge Density

    International Nuclear Information System (INIS)

    Kim, Tae-Hwan; Choi, Sung-Min; Kline, Steven R.

    2007-01-01

    Surfactant molecules in aqueous solution self assemble into various micellar structures such as sphere, rod, vesicle, and lamellar, above critical micelle concentration (CMC). Self-assembled surfactants systems, therefore, have been very popular as templates for preparing various nanostructured materials. Due to their dynamic nature, however, micellar structures are very susceptible to solution conditions such as temperature, concentration, pH and pressure, limiting their applications. In this study, we have developed rigid rod-like nanoparticles with controlled surface charge density by the free radical polymerization of cationic surfactants with polymerizable counterions, cetyltrimethylammonium 4- vinylbenzoate (CTVB), with varying concentration of sodium styrenesulfonate (NaSS). The structure and surface charge density of the nanoparticles were characterized by small angle neutron scattering (SANS) and zeta potential measurements

  12. Electrokinetic effect combined with surface-charge assumption: a possible generation mechanism of coseismic EM signals

    Science.gov (United States)

    Ren, Hengxin; Wen, Jian; Huang, Qinghua; Chen, Xiaofei

    2015-02-01

    According to field observations, electromagnetic (EM) signals accompanying seismic waves can be recorded. The orders of magnitude of observed coseismic electric and magnetic signals associated with earthquakes are usually around 1 to 101 mV km-1 and 10-2 to 1 nT, respectively. In this paper, we carry out numerical simulation of coseismic EM signals associated with seismic waves due to electrokinetic effect and compare with field observations. The seismic source is represented by a finite fault measuring 15 × 9 km2 with a max slip displacement 1.5 m, corresponding to a Mw 5.9 earthquake. While using the EM surface boundary condition of continuous horizontal EM components, the magnetic signals only accompany the late-arriving S waves at receiver near the ground surface. This is obviously different from field observations. Thus, we adopt another EM surface boundary condition which assumes the ground surface carries surface charge. For the used half-space model, a surface-charge density magnitude |Qsc| in excess of 10-4 C m-2 is sufficient to make horizontal magnetic components clearly show up at the whole time duration of seismic waves. When |Qsc| increases, the contribution of surface-charge density to coseismic EM signals becomes more and more dominant comparing with that of the seismically induced streaming-current. We estimate the Qsc expected at the Earth's surface might be a value between -5 × 10-4 and -0.1 C m-2 by the comparison between numerical results and field observations. The vertical magnetic signals only accompany the late-arriving seismic waves, because they are theoretically only induced by SH wave. The field observation results of vertical magnetic signals may be resulted from the scattering effect or the seismic dynamo effect. We conclude that electrokinetic effect combined with surface-charge assumption is one possible generation mechanism of the observed coseismic EM signals.

  13. Mobile colloid generation induced by a cementitious plume: mineral surface-charge controls on mobilization.

    Science.gov (United States)

    Li, Dien; Kaplan, Daniel I; Roberts, Kimberly A; Seaman, John C

    2012-03-06

    Cementitious materials are increasingly used as engineered barriers and waste forms for radiological waste disposal. Yet their potential effect on mobile colloid generation is not well-known, especially as it may influence colloid-facilitated contaminant transport. Whereas previous papers have studied the introduction of cement colloids into sediments, this study examined the influence of cement leachate chemistry on the mobilization of colloids from a subsurface sediment collected from the Savannah River Site, USA. A sharp mobile colloid plume formed with the introduction of a cement leachate simulant. Colloid concentrations decreased to background concentrations even though the aqueous chemical conditions (pH and ionic strength) remained unchanged. Mobile colloids were mainly goethite and to a lesser extent kaolinite. The released colloids had negative surface charges and the mean particle sizes ranged primarily from 200 to 470 nm. Inherent mineralogical electrostatic forces appeared to be the controlling colloid removal mechanism in this system. In the background pH of ~6.0, goethite had a positive surface charge, whereas quartz (the dominant mineral in the immobile sediment) and kaolinite had negative surface charges. Goethite acted as a cementing agent, holding kaolinite and itself onto the quartz surfaces due to the electrostatic attraction. Once the pH of the system was elevated, as in the cementitious high pH plume front, the goethite reversed to a negative charge, along with quartz and kaolinite, then goethite and kaolinite colloids were mobilized and a sharp spike in turbidity was observed. Simulating conditions away from the cementitious source, essentially no colloids were mobilized at 1:1000 dilution of the cement leachate or when the leachate pH was ≤ 8. Extreme alkaline pH environments of cementitious leachate may change mineral surface charges, temporarily promoting the formation of mobile colloids.

  14. Effects of Surface Charges on Dental Implants: Past, Present, and Future

    OpenAIRE

    Cecilia Yan Guo; Jukka Pekka Matinlinna; Alexander Tin Hong Tang

    2012-01-01

    Osseointegration is a major factor influencing the success of dental implantation. To achieve rapid and strong, durable osseointegration, biomaterial researchers have investigated various surface treatment methods for dental subgingival titanium (Ti) implants. This paper focuses on surface-charge modification on the surface of titanium dental implants, which is a relatively new and very promising methodology for improving the implants' osseointegration properties. We give an overview on both ...

  15. One-Step Synthesis of PEGylated Gold Nanoparticles with Tunable Surface Charge

    Directory of Open Access Journals (Sweden)

    Rares Stiufiuc

    2013-01-01

    Full Text Available The present work reports a rapid, simple and efficient one-step synthesis and detailed characterisation of stable aqueous colloids of gold nanoparticles (AuNPs coated with unmodified poly(ethyleneglycol (PEG molecules of different molecular weights and surface charges. By mixing and heating aqueous solutions of PEG with variable molecular chain and gold(III chloride hydrate (HAuCl4 in the presence of NaOH, we have successfully produced uniform colloidal 5 nm PEG coated AuNPs of spherical shape with tunable surface charge and an average diameter of 30 nm within a few minutes. It has been found out that PEGylated AuNPs provide optical enhancement of the characteristic vibrational bands of PEG molecules attached to the gold surface when they are excited with both visible (532 nm and NIR (785 nm laser lines. The surface enhanced Raman scattering (SERS signal does not depend on the length of the PEG molecular chain enveloping the AuNPs, and the stability of the colloid is not affected by the addition of concentrated salt solution (0.1 M NaCl, thus suggesting their potential use for in vitro and in vivo applications. Moreover, by gradually changing the chain length of the biopolymer, we were able to control nanoparticles’ surface charge from −28 to −2 mV, without any modification of the Raman enhancement properties and of the colloidal stability.

  16. Surface charge-specific interactions between polymer nanoparticles and ABC transporters in Caco-2 cells

    Science.gov (United States)

    Bhattacharjee, Sourav; van Opstal, Edward J.; Alink, Gerrit M.; Marcelis, Antonius T. M.; Zuilhof, Han; Rietjens, Ivonne M. C. M.

    2013-06-01

    The surface charge-dependent transport of polymeric nanoparticles (PNPs) across Caco-2 monolayers grown on transwell culture systems as an in vitro model for intestinal transport was tested. The transport of well-characterized, monodisperse, and fluorescent tri-block copolymer nanoparticles (TCNPs/size 45 nm) and polystyrene nanoparticles (PSNPs/size 50 nm), with different surface charges (positive and negative), was quantified. The positive PNPs showed a higher intracellular uptake and flux across the Caco-2 monolayers than the negative PNPs. Multidrug resistance/P-glycoprotein (MDR1/P-gp), a specific ATP-binding cassette (ABC) transporter, was found to play a major role in the cellular efflux of positive PNPs, whereas the multidrug resistance protein 1 took part in the efflux of negative PNPs from Caco-2 cells. The positive PNPs also caused an increased cellular uptake and apical to basolateral transport of the carcinogen PhIP across the Caco-2 monolayer. The flavonoid quercetin, which is known to interact with ABC transporters, promoted the intracellular uptake of different PNPs and interfered with the normal distribution patterns of PNPs in the transwell system. These results indicate that PNPs display surface charge-specific interactions with ABC transporters and can even affect the bioavailability of toxic food-borne compounds (like pro-carcinogens).

  17. Surface charge-specific interactions between polymer nanoparticles and ABC transporters in Caco-2 cells

    Energy Technology Data Exchange (ETDEWEB)

    Bhattacharjee, Sourav, E-mail: sourav.bhattacharjee@wur.nl [Wageningen University, Laboratory of Organic Chemistry (Netherlands); Opstal, Edward J. van; Alink, Gerrit M. [Wageningen University, Division of Toxicology (Netherlands); Marcelis, Antonius T. M.; Zuilhof, Han [Wageningen University, Laboratory of Organic Chemistry (Netherlands); Rietjens, Ivonne M. C. M. [Wageningen University, Division of Toxicology (Netherlands)

    2013-06-15

    The surface charge-dependent transport of polymeric nanoparticles (PNPs) across Caco-2 monolayers grown on transwell culture systems as an in vitro model for intestinal transport was tested. The transport of well-characterized, monodisperse, and fluorescent tri-block copolymer nanoparticles (TCNPs/size {approx}45 nm) and polystyrene nanoparticles (PSNPs/size {approx}50 nm), with different surface charges (positive and negative), was quantified. The positive PNPs showed a higher intracellular uptake and flux across the Caco-2 monolayers than the negative PNPs. Multidrug resistance/P-glycoprotein (MDR1/P-gp), a specific ATP-binding cassette (ABC) transporter, was found to play a major role in the cellular efflux of positive PNPs, whereas the multidrug resistance protein 1 took part in the efflux of negative PNPs from Caco-2 cells. The positive PNPs also caused an increased cellular uptake and apical to basolateral transport of the carcinogen PhIP across the Caco-2 monolayer. The flavonoid quercetin, which is known to interact with ABC transporters, promoted the intracellular uptake of different PNPs and interfered with the normal distribution patterns of PNPs in the transwell system. These results indicate that PNPs display surface charge-specific interactions with ABC transporters and can even affect the bioavailability of toxic food-borne compounds (like pro-carcinogens).

  18. Surface charge-specific interactions between polymer nanoparticles and ABC transporters in Caco-2 cells

    International Nuclear Information System (INIS)

    Bhattacharjee, Sourav; Opstal, Edward J. van; Alink, Gerrit M.; Marcelis, Antonius T. M.; Zuilhof, Han; Rietjens, Ivonne M. C. M.

    2013-01-01

    The surface charge-dependent transport of polymeric nanoparticles (PNPs) across Caco-2 monolayers grown on transwell culture systems as an in vitro model for intestinal transport was tested. The transport of well-characterized, monodisperse, and fluorescent tri-block copolymer nanoparticles (TCNPs/size ∼45 nm) and polystyrene nanoparticles (PSNPs/size ∼50 nm), with different surface charges (positive and negative), was quantified. The positive PNPs showed a higher intracellular uptake and flux across the Caco-2 monolayers than the negative PNPs. Multidrug resistance/P-glycoprotein (MDR1/P-gp), a specific ATP-binding cassette (ABC) transporter, was found to play a major role in the cellular efflux of positive PNPs, whereas the multidrug resistance protein 1 took part in the efflux of negative PNPs from Caco-2 cells. The positive PNPs also caused an increased cellular uptake and apical to basolateral transport of the carcinogen PhIP across the Caco-2 monolayer. The flavonoid quercetin, which is known to interact with ABC transporters, promoted the intracellular uptake of different PNPs and interfered with the normal distribution patterns of PNPs in the transwell system. These results indicate that PNPs display surface charge-specific interactions with ABC transporters and can even affect the bioavailability of toxic food-borne compounds (like pro-carcinogens).

  19. Influence of radioactivity on surface charging and aggregation kinetics of particles in the atmosphere.

    Science.gov (United States)

    Kim, Yong-Ha; Yiacoumi, Sotira; Lee, Ida; McFarlane, Joanna; Tsouris, Costas

    2014-01-01

    Radioactivity can influence surface interactions, but its effects on particle aggregation kinetics have not been included in transport modeling of radioactive particles. In this research, experimental and theoretical studies have been performed to investigate the influence of radioactivity on surface charging and aggregation kinetics of radioactive particles in the atmosphere. Radioactivity-induced charging mechanisms have been investigated at the microscopic level, and heterogeneous surface potential caused by radioactivity is reported. The radioactivity-induced surface charging is highly influenced by several parameters, such as rate and type of radioactive decay. A population balance model, including interparticle forces, has been employed to study the effects of radioactivity on particle aggregation kinetics in air. It has been found that radioactivity can hinder aggregation of particles because of similar surface charging caused by the decay process. Experimental and theoretical studies provide useful insights into the understanding of transport characteristics of radioactive particles emitted from severe nuclear events, such as the recent accident of Fukushima or deliberate explosions of radiological devices.

  20. The interplay between surface charging and microscale roughness during plasma etching of polymeric substrates

    Science.gov (United States)

    Memos, George; Lidorikis, Elefterios; Kokkoris, George

    2018-02-01

    The surface roughness developed during plasma etching of polymeric substrates is critical for a variety of applications related to the wetting behavior and the interaction of surfaces with cells. Toward the understanding and, ultimately, the manipulation of plasma induced surface roughness, the interplay between surface charging and microscale roughness of polymeric substrates is investigated by a modeling framework consisting of a surface charging module, a surface etching model, and a profile evolution module. The evolution of initially rough profiles during plasma etching is calculated by taking into account as well as by neglecting charging. It is revealed, on the one hand, that the surface charging contributes to the suppression of root mean square roughness and, on the other hand, that the decrease of the surface roughness induces a decrease of the charging potential. The effect of charging on roughness is intense when the etching yield depends solely on the ion energy, and it is mitigated when the etching yield additionally depends on the angle of ion incidence. The charging time, i.e., the time required for reaching a steady state charging potential, is found to depend on the thickness of the polymeric substrate, and it is calculated in the order of milliseconds.

  1. Quantifying signal changes in nano-wire based biosensors

    DEFF Research Database (Denmark)

    De Vico, Luca; Sørensen, Martin Hedegård; Iversen, Lars

    2011-01-01

    is a combination of the screening model of surface charge sensors in liquids developed by Brandbyge and co-workers [Sørensen et al., Appl. Phys. Lett., 2007, 91, 102105], with the PROPKA method for predicting the pH-dependent charge of proteins and protein-ligand complexes, developed by Jensen and co-workers [Li...

  2. Group III-nitride nanowire structures for photocatalytic hydrogen evolution under visible light irradiation

    Directory of Open Access Journals (Sweden)

    Faqrul A. Chowdhury

    2015-10-01

    Full Text Available The performance of photochemical water splitting over the emerging nanostructured photocatalysts is often constrained by their surface electronic properties, which can lead to imbalance in redox reactions, reduced efficiency, and poor stability. We have investigated the impact of surface charge properties on the photocatalytic activity of InGaN nanowires. By optimizing the surface charge properties through controlled p-type dopant (Mg incorporation, we have demonstrated an apparent quantum efficiency of ∼17.1% and ∼12.3% for InGaN nanowire arrays under visible light irradiation (400 nm–490 nm in aqueous methanol and in the overall neutral-pH water splitting reaction, respectively.

  3. All Nanowire Integrated Sensor Circuitry

    Science.gov (United States)

    2008-04-01

    Engineering Center: or the U.S. Government." "Approved for public release; distribution unlimited." Problem statement and objective Semiconductor ...a nonlinear behavior. semiconductor NWs. Upon white light illumination (halogen light source. 4.4 mW cm"), a drastic decrease of -lOOx in the device...s? — CUO -Q i/i c il •M c "l_ •£ cu Q. .9P to O O cu c c > o •*-? T3 — u 0) 00 CD E 8 CL) (T3 QJ c .a 00 to °- 03 s

  4. Sensors

    CERN Document Server

    Pigorsch, Enrico

    1997-01-01

    This is the 5th edition of the Metra Martech Directory "EUROPEAN CENTRES OF EXPERTISE - SENSORS." The entries represent a survey of European sensors development. The new edition contains 425 detailed profiles of companies and research institutions in 22 countries. This is reflected in the diversity of sensors development programmes described, from sensors for physical parameters to biosensors and intelligent sensor systems. We do not claim that all European organisations developing sensors are included, but this is a good cross section from an invited list of participants. If you see gaps or omissions, or would like your organisation to be included, please send details. The data base invites the formation of effective joint ventures by identifying and providing access to specific areas in which organisations offer collaboration. This issue is recognised to be of great importance and most entrants include details of collaboration offered and sought. We hope the directory on Sensors will help you to find the ri...

  5. Sensors

    Energy Technology Data Exchange (ETDEWEB)

    Jensen, H. [PBI-Dansensor A/S (Denmark); Toft Soerensen, O. [Risoe National Lab., Materials Research Dept. (Denmark)

    1999-10-01

    A new type of ceramic oxygen sensors based on semiconducting oxides was developed in this project. The advantage of these sensors compared to standard ZrO{sub 2} sensors is that they do not require a reference gas and that they can be produced in small sizes. The sensor design and the techniques developed for production of these sensors are judged suitable by the participating industry for a niche production of a new generation of oxygen sensors. Materials research on new oxygen ion conducting conductors both for applications in oxygen sensors and in fuel was also performed in this project and finally a new process was developed for fabrication of ceramic tubes by dip-coating. (EHS)

  6. Magnetic and superconducting nanowires

    DEFF Research Database (Denmark)

    Piraux, L.; Encinas, A.; Vila, L.

    2005-01-01

    magnetic and superconducting nanowires. Using different approaches entailing measurements on both single wires and arrays, numerous interesting physical properties have been identified in relation to the nanoscopic dimensions of these materials. Finally, various novel applications of the nanowires are also...

  7. Stability of Organic Nanowires

    DEFF Research Database (Denmark)

    Balzer, F.; Schiek, M.; Wallmann, I.

    2011-01-01

    atomic force microscopy (AFM). Aging experiments under ambient conditions already show substantial morphological changes. Nanoscopic organic clusters, which initially coexist with the nanowires, vanish within hours. Thermal annealing of nanowire samples leads to even more pronounced morphology changes...

  8. Corrected Debye-Hückel analysis of surface complexation. II. A theory of surface charging.

    Science.gov (United States)

    Gunnarsson, Magnus; Abbas, Zareen; Ahlberg, Elisabet; Gobom, Sylvia; Nordholm, Sture

    2002-05-01

    A theory of surface charging of colloidal particles suspended in an electrolyte solution is presented. The charging at the particle surface is assumed to originate from the adsorption and desorption of protons and is therefore strongly dependent on the acidity of the solution. The surface binding of protons occurs locally at sites of occupancy zero or one that are described by a binding energy u(0) and a three-dimensional vibration of frequency nu. The diffuse screening of ions at the surface is described by the corrected Debye-Hückel analysis assuming linear response. The model contains a capacitor layer close to the charged surface and the finite size of the electrolyte ions is taken into account. The theory has been applied to titrated surface charge data on goethite (alpha-FeOOH) at NaClO(4) background concentrations ranging from 0.01 to 1.0 M. The protonation mechanism used in the modeling of these data corresponds to the 1-pK approach. A very good description of the experimental data was obtained at the highest ionic strength. Close to the pH(pzc) the theory also gave a good description at lower ionic strengths. However, at low salt concentrations and pH values far away from the pH(pzc) the electrostatic potential outside the capacitor layer becomes so high that nonlinear electrostatic effects become important and the theory therefore underestimates the surface charge. These results were compared with model calculations obtained using existing surface complexation models.

  9. Proton surface charge determination in Spodosol horizons with organically bound aluminum

    Science.gov (United States)

    Skyllberg, Ulf; Borggaard, Ole K.

    1998-05-01

    Net proton surface charge densities were determined in O, E, Bh, and Bs horizons of a sandy till, Spodosol from Denmark, by means of acid-base titration combined with ion adsorption in 0.005 M Ca(NO 3) 2 and independent permanent charge determination. The release of organic anions exceeded the adsorption of NO 3-, resulting in a desorption of anions in all horizons. Data were found to obey the law of balance between surface charges and adsorbed ions only when charges pertaining to Al and organic anions released during the titration experiments were accounted for, in addition to charges pertaining the potential determining ions (PDI) H + and OH - and the index ions Ca 2+ and NO 3-. It was furthermore shown that the point of zero net proton charge (PZNPC) in soils highly depends on the concentration of organically bound Al. Approaches previously used in soils, in which adsorbed Al n+ has been ignored (i.e., considered equivalent to nH + as a PDI), resulted in a PZNPC of 4.1 in the Bs horizon. If instead organically bound Al was accounted for as a counter-ion similar to 3/2Ca 2+, a PZNPC of 2.9 was obtained for the same Bs horizon. Based on PZNPC values estimated by the latter approach, combined with a weak-acid analog, it was shown that organic proton surface charges buffered pH with a similar intensity in the O, E, Bh, and Bs horizons of this study. Because the acidity of Al adsorbed to conjugate bases of soil organic acids is substantially weaker than the acidity of the corresponding protonated form of the organic acids, the point of zero net proton charge (PZNPC) will increase if the concentration of organically adsorbed Al increases at the expense of adsorbed H. This means that PZNPC values determined for soils with unknown concentrations of organically adsorbed Al are highly operational and not very meaningful as references.

  10. Specification of electron radiation environment at GEO and MEO for surface charging estimates

    Science.gov (United States)

    Ganushkina, N.; Dubyagin, S.; Mateo Velez, J. C.; Liemohn, M. W.

    2017-12-01

    A series of anomalies at GEO have been attributed to electrons of energy below 100 keV, responsible for surface charging. The process at play is charge deposition on covering insulating surfaces and is directly linked to the space environment at a time scale of a few tens of seconds. Even though modern satellites benefited from the analysis of past flight anomalies and losses, it appears that surface charging remains a source of problems. Accurate specification of the space environment at different orbits is of a key importance. We present the operational model for low energy (index. The presented model provides the low energy electron flux at all L-shells and at all satellite orbits, when necessary. IMPTAM is used to simulate the fluxes of low energy electrons inside the Earth's magnetosphere at the time of severe events measured on LANL satellites at GEO. There is no easy way to say what will be the flux of keV electrons at MEO when surface charging events are detected at GEO than to use a model. The maximal electron fluxes obtained at MEO (L = 4.6) within a few tens of minutes hours following the LANL events at GEO have been extracted to feed a database of theoretical/numerical worst-case environments for surface charging at MEO. All IMPTAM results are instantaneous, data have not been average. In order to validate the IMPTAM output at MEO, we conduct the statistical analysis of measured electron fluxes onboard Van Allen Probes (ECT HOPE (20 eV-45 keV) and ECT MagEIS (30 - 300 keV) at distances of 4.6 Re. IMPTAM e- flux at MEO is used as input to SPIS, the Spacecraft Plasma Interaction System Software toolkit for spacecraft-plasma interactions and spacecraft charging modelling (http://dev.spis.org/projects/spine/home/spis). The research leading to these results was funded by the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement No 606716 SPACESTORM and by the European Union's Horizon 2020 research and innovation programme under

  11. Interfacial biocatalysis on charged and immobilized substrates: the roles of enzyme and substrate surface charge.

    Science.gov (United States)

    Feller, Bob E; Kellis, James T; Cascão-Pereira, Luis G; Robertson, Channing R; Frank, Curtis W

    2011-01-04

    An enzyme charge ladder was used to examine the role of electrostatic interactions involved in biocatalysis at the solid-liquid interface. The reactive substrate consisted of an immobilized bovine serum albumin (BSA) multilayer prepared using a layer-by-layer technique. The zeta potential of the BSA substrate and each enzyme variant was measured to determine the absolute charge in solution. Enzyme adsorption and the rate of substrate surface hydrolysis were monitored for the enzyme charge ladder series to provide information regarding the strength of the enzyme-substrate interaction and the rate of interfacial biocatalysis. First, each variant of the charge ladder was examined at pH 8 for various solution ionic strengths. We found that for positively charged variants the adsorption increased with the magnitude of the charge until the surface became saturated. For higher ionic strength solutions, a greater positive enzyme charge was required to induce adsorption. Interestingly, the maximum catalytic rate was not achieved at enzyme saturation but at an invariable intermediate level of adsorption for each ionic strength value. Furthermore, the maximum achievable reaction rate for the charge ladder was larger for higher ionic strength values. We propose that diffusion plays an important role in interfacial biocatalysis, and for strong enzyme-substrate interaction, the rate of diffusion is reduced, leading to a decrease in the overall reaction rate. We investigated the effect of substrate charge by varying the solution pH from 6.1 to 8.7 and by examining multiple ionic strength values for each pH. The same intermediate level of adsorption was found to maximize the overall reaction rate. However, the ionic strength response of the maximum achievable rate was clearly dependent on the pH of the experiment. We propose that this observation is not a direct effect of pH but is caused by the change in substrate surface charge induced by changing the pH. To prove this

  12. Self-Amplified Surface Charging and Partitioning of Ionic Liquids in Nanopores

    Science.gov (United States)

    Neal, Justin N.; Van Aken, K. L.; Gogotsi, Y.; Wesolowski, David J.; Wu, Jianzhong

    2017-09-01

    We study ion partitioning and self-charging of nanoporous electrodes with room-temperature ionic liquids using a classical density-functional theory that accounts for molecular-excluded volume effects and electrostatic correlations. Nanopores of zero electrical potential are predicted to favor adsorption of small ions even without specific surface attraction, and the imbalanced distributions of cations and anions inside the pore induces a net surface charge that promotes further enrichment of small ions. The self-amplified ion partitioning is most significant when the nanopore and the ionic species are of comparable dimension.

  13. Application of »Mass Titration« to Determination of Surface Charge of Metal Oxides

    OpenAIRE

    1998-01-01

    The mass titration method, used for the point of zero charge determination, was extended to the measurement of the surface charge density. The results agree with the common method, which is the acid-base titration of the colloidal suspension. The advantage of mass titration is that one does not need to perform blank titration, instead one simply adds metal oxide powder to the electrolyte aqueous solution of known pH. To cover the pH range above and below the point of zero charge, two experime...

  14. Evaluation of the In Vitro Effect of Gold Nanorod Aspect Ratio, Surface Charge and Chemistry on Cellular Association and Cytotoxicity

    Science.gov (United States)

    2016-03-28

    Nanorods. Analytical Chemistry , 79(2), 572-579. doi: 10.1021/ac061730d 22 LIST OF ACRONYMS ATCC American Type Culture Collection AR Aspect...EVALUATION OF THE IN VITRO EFFECTOF GOLD NANOROD ASPECT RATIO, SURFACE CHARGE AND CHEMISTRY ON CELLULAR ASSOCIATION AND CYTOTOXICITY...July 2012 – Jan 2016 4. TITLE AND SUBTITLE EVALUATION OF THE IN VITRO EFFECT OF GOLD NANOROD ASPECT RATIO, SURFACE CHARGE AND CHEMISTRY ON

  15. Nanotubes and nanowires

    Indian Academy of Sciences (India)

    Unknown

    nanotubes are likely to be useful as nanochips since they exhibit diode properties at the junction. By making use of carbon nanotubes, nanowires of metals, metal oxides and GaN have been obtained. Both the oxide and GaN nanowires are single crystalline. Gold nanowires exhibit plasmon bands varying markedly with.

  16. Super-Joule heating in graphene and silver nanowire network

    International Nuclear Information System (INIS)

    Maize, Kerry; Das, Suprem R.; Sadeque, Sajia; Mohammed, Amr M. S.; Shakouri, Ali; Janes, David B.; Alam, Muhammad A.

    2015-01-01

    Transistors, sensors, and transparent conductors based on randomly assembled nanowire networks rely on multi-component percolation for unique and distinctive applications in flexible electronics, biochemical sensing, and solar cells. While conduction models for 1-D and 1-D/2-D networks have been developed, typically assuming linear electronic transport and self-heating, the model has not been validated by direct high-resolution characterization of coupled electronic pathways and thermal response. In this letter, we show the occurrence of nonlinear “super-Joule” self-heating at the transport bottlenecks in networks of silver nanowires and silver nanowire/single layer graphene hybrid using high resolution thermoreflectance (TR) imaging. TR images at the microscopic self-heating hotspots within nanowire network and nanowire/graphene hybrid network devices with submicron spatial resolution are used to infer electrical current pathways. The results encourage a fundamental reevaluation of transport models for network-based percolating conductors

  17. Boron Nitride Nanoporous Membranes with High Surface Charge by Atomic Layer Deposition.

    Science.gov (United States)

    Weber, Matthieu; Koonkaew, Boonprakrong; Balme, Sebastien; Utke, Ivo; Picaud, Fabien; Iatsunskyi, Igor; Coy, Emerson; Miele, Philippe; Bechelany, Mikhael

    2017-05-17

    In this work, we report the design and the fine-tuning of boron nitride single nanopore and nanoporous membranes by atomic layer deposition (ALD). First, we developed an ALD process based on the use of BBr 3 and NH 3 as precursors in order to synthesize BN thin films. The deposited films were characterized in terms of thickness, composition, and microstructure. Next, we used the newly developed process to grow BN films on anodic aluminum oxide nanoporous templates, demonstrating the conformality benefit of BN prepared by ALD, and its scalability for the manufacturing of membranes. For the first time, the ALD process was then used to tune the diameter of fabricated single transmembrane nanopores by adjusting the BN thickness and to enable studies of the fundamental aspects of ionic transport on a single nanopore. At pH = 7, we estimated a surface charge density of 0.16 C·m -2 without slip and 0.07 C·m -2 considering a reasonable slip length of 3 nm. Molecular dynamics simulations performed with experimental conditions confirmed the conductivities and the sign of surface charges measured. The high ion transport results obtained and the ability to fine-tune nanoporous membranes by such a scalable method pave the way toward applications such as ionic separation, energy harvesting, and ultrafiltration devices.

  18. Method of impressing and reading out a surface charge on a multilayered detector structure

    International Nuclear Information System (INIS)

    Zermeno, A.; Marsh, L.M.; Cowart, R.W.

    1981-01-01

    A latent charge image is recorded on and reproduced from a multilayered detector. Firstly the detector is given a uniform surface charge on its photoconductive layer. This layer is then biased with an electric field of opposite polarity to the surface charge. The detector is then exposed to a modulated radiation flux to cause at least partial discharge of the photoconductive layer. The latent charge image of the modulated radiation flux is thus stored and later read by scanning the surface of the photoconductive layer with a small diameter photon beam to discharge further sequentially the photoconductive layer. The changing electrical potential of this discharge is detected and processed into a video signal by a processor for storage or display. This invention provides a method and apparatus capable of replacing conventional photographic and radiographic films. It also provides an X-ray sensing system which produces radiographic images of a patient using a lower radiation dosage. The output is an analog or digital video signal that may be displayed on a television monitor, recorded on film or directly stored or processed in a computer for image enhancement or pattern recognition. Other aspects are detailed. (U.K.)

  19. Developing an optical chopper-modulated capacitive probe for measuring surface charge.

    Science.gov (United States)

    Ugolini, D; McKinney, R; Harry, G M

    2007-04-01

    Gravitational-wave observatories such as Laser Interferometer Gravitational-Wave Observatory (LIGO) use suspended optics in a Michelson interferometer configuration to measure strains in space between 10 Hz and 3 kHz. One potential noise source in this frequency range is the buildup and motion of surface charge on the optics, which can generate fluctuating electric fields, interfere with position control, and reduce reflectance by attracting dust to the optical surface. We have developed a capacitive probe to measure the magnitude and relaxation time of surface charge deposited on smaller test optics in high vacuum ( approximately 10(-5) Torr). Our device modulates capacitance with a tuning-fork optical chopper between probe and sample, chosen for vacuum compatibility and minimal cost. We have found that the probe has a resolution of (3.5+/-0.5)x10(5) e(-)cm(2) in air, on the order of charging levels that could contribute noise to Advanced LIGO, and sufficient for measuring relaxation times on test optics.

  20. Dependence of Lunar Surface Charging on Solar Wind Plasma Conditions and Solar Irradiation

    Science.gov (United States)

    Stubbs, T. J.; Farrell, W. M.; Halekas, J. S.; Burchill, J. K.; Collier, M. R.; Zimmerman, M. I.; Vondrak, R. R.; Delory, G. T.; Pfaff, R. F.

    2014-01-01

    The surface of the Moon is electrically charged by exposure to solar radiation on its dayside, as well as by the continuous flux of charged particles from the various plasma environments that surround it. An electric potential develops between the lunar surface and ambient plasma, which manifests itself in a near-surface plasma sheath with a scale height of order the Debye length. This study investigates surface charging on the lunar dayside and near-terminator regions in the solar wind, for which the dominant current sources are usually from the pohotoemission of electrons, J(sub p), and the collection of plasma electrons J(sub e) and ions J(sub i). These currents are dependent on the following six parameters: plasma concentration n(sub 0), electron temperature T(sub e), ion temperature T(sub i), bulk flow velocity V, photoemission current at normal incidence J(sub P0), and photo electron temperature T(sub p). Using a numerical model, derived from a set of eleven basic assumptions, the influence of these six parameters on surface charging - characterized by the equilibrium surface potential, Debye length, and surface electric field - is investigated as a function of solar zenith angle. Overall, T(sub e) is the most important parameter, especially near the terminator, while J(sub P0) and T(sub p) dominate over most of the dayside.

  1. Factors influencing the cytotoxicity of zinc oxide nanoparticles: particle size and surface charge

    International Nuclear Information System (INIS)

    Baek, M; Kim, M K; Cho, H J; Lee, J A; Yu, J; Chung, H E; Choi, S J

    2011-01-01

    Zinc oxide (ZnO) nanoparticle is one of the most important materials in diverse applications, since it has UV light absorption, antimicrobial, catalytic, semi-conducting, and magnetic properties. However, there is little information about the toxicological effects of ZnO nanoparticles with respect to physicochemical properties. The aim of this study was, therefore, to evaluate the relationships between cytotoxicity and physicochemical properties of ZnO nanoparticle such as particle size and surface charge in human lung cells. Two different sizes of ZnO nanoparticles (20 and 70 nm) were prepared with positive (+) or negative (-) charge, and then, cytotoxicity of different ZnO nanoparticles was evaluated by measuring cell proliferation in short-term and long-term, membrane integrity, and generation of reactive oxygen species (ROS). The results demonstrated that smaller particles exhibited high cytotoxic effects compared to larger particles in terms of inhibition of cell proliferation, membrane damage, and ROS generation. In addition, positively charged ZnO showed greater ROS production than ZnO with negative charge. These findings suggest that the cytoxicity of ZnO nanoparticles are strongly affected by their particle size and surface charge, highlighting the role of the physicochemical properties of nanoparticles to understand and predict their potential adverse effects on human.

  2. Estimation of Nanodiamond Surface Charge Density from Zeta Potential and Molecular Dynamics Simulations.

    Science.gov (United States)

    Ge, Zhenpeng; Wang, Yi

    2017-04-20

    Molecular dynamics simulations of nanoparticles (NPs) are increasingly used to study their interactions with various biological macromolecules. Such simulations generally require detailed knowledge of the surface composition of the NP under investigation. Even for some well-characterized nanoparticles, however, this knowledge is not always available. An example is nanodiamond, a nanoscale diamond particle with surface dominated by oxygen-containing functional groups. In this work, we explore using the harmonic restraint method developed by Venable et al., to estimate the surface charge density (σ) of nanodiamonds. Based on the Gouy-Chapman theory, we convert the experimentally determined zeta potential of a nanodiamond to an effective charge density (σ eff ), and then use the latter to estimate σ via molecular dynamics simulations. Through scanning a series of nanodiamond models, we show that the above method provides a straightforward protocol to determine the surface charge density of relatively large (> ∼100 nm) NPs. Overall, our results suggest that despite certain limitation, the above protocol can be readily employed to guide the model construction for MD simulations, which is particularly useful when only limited experimental information on the NP surface composition is available to a modeler.

  3. Real-time impedance analysis of silica nanowire toxicity on epithelial breast cancer cells.

    Science.gov (United States)

    Alexander, Frank A; Huey, Eric G; Price, Dorielle T; Bhansali, Shekhar

    2012-12-21

    Silica nanowires have great potential for usage in the development of highly sensitive in vivo biosensors used for biomarker monitoring. However, careful analysis of nanowire toxicity is required prior to placing these sensors within the human body. This paper describes a real-time and quantitative analysis of nanowire cytotoxicity using impedance spectroscopy; improving upon studies that have utilized traditional endpoint assays. Silica nanowires were grown using the vapor liquid solid (VLS) method, mixed with Dulbecco's Modified Eagle Medium (DMEM) and exposed to Hs578T epithelial breast cancer cells at concentrations of 0 μg ml(-1), 1 μg ml(-1), 50 μg ml(-1) and 100 μg ml(-1). Real-time cellular responses to silica nanowires confirm that while not cytotoxic, silica nanowires at high concentrations (≥50 μg ml(-1)) are toxic to cells, and also suggest that cell death is due to mechanical disturbances of high numbers of nanowires.

  4. DNA hybridization on silicon nanowires

    International Nuclear Information System (INIS)

    Singh, Shalini; Zack, Jyoti; Kumar, Dinesh; Srivastava, S.K.; Govind; Saluja, Daman; Khan, M.A.; Singh, P.K.

    2010-01-01

    Nanowire-based detection strategies provide promising new routes to bioanalysis and indeed are attractive to conventional systems because of their small size, high surface-to-volume ratios, electronic, and optical properties. A sequence-specific detection of single-stranded oligonucleotides using silicon nanowires (SiNWs) is demonstrated. The surface of the SiNWs is functionalized with densely packed organic monolayer via hydrosilylation for covalent attachment. Subsequently, deoxyribonucleic acid (DNA) is immobilized to recognize the complementary target DNA. The biomolecular recognition properties of the nanowires are tested via hybridization with γ P 32 tagged complementary and non-complementary DNA oligonucleotides, showing good selectivity and reversibility. No significant non-specific binding to the incorrect sequences is observed. X-ray photoelectron spectroscopy, fluorescence imaging, and nanodrop techniques are used to characterize the modified SiNWs and covalent attachment with DNA. The results show that SiNWs are excellent substrates for the absorption, stabilization and detection of DNA sequences and could be used for DNA microarrays and micro fabricated SiNWs DNA sensors.

  5. In situ biasing and off-axis electron holography of a ZnO nanowire

    Science.gov (United States)

    den Hertog, Martien; Donatini, Fabrice; McLeod, Robert; Monroy, Eva; Sartel, Corinne; Sallet, Vincent; Pernot, Julien

    2018-01-01

    Quantitative characterization of electrically active dopants and surface charges in nano-objects is challenging, since most characterization techniques using electrons [1-3], ions [4] or field ionization effects [5-7] study the chemical presence of dopants, which are not necessarily electrically active. We perform cathodoluminescence and voltage contrast experiments on a contacted and biased ZnO nanowire with a Schottky contact and measure the depletion length as a function of reverse bias. We compare these results with state-of-the-art off-axis electron holography in combination with electrical in situ biasing on the same nanowire. The extension of the depletion length under bias observed in scanning electron microscopy based techniques is unusual as it follows a linear rather than square root dependence, and is therefore difficult to model by bulk equations or finite element simulations. In contrast, the analysis of the axial depletion length observed by holography may be compared with three-dimensional simulations, which allows estimating an n-doping level of 1 × 1018 cm-3 and negative sidewall surface charge of 2.5 × 1012 cm-2 of the nanowire, resulting in a radial surface depletion to a depth of 36 nm. We found excellent agreement between the simulated diameter of the undepleted core and the active thickness observed in the experimental data. By combining TEM holography experiments and finite element simulation of the NW electrostatics, the bulk-like character of the nanowire core is revealed.

  6. Nanodevices based on silicon nanowires.

    Science.gov (United States)

    Wan, Yuting; Sha, Jian; Chen, Bo; Fang, Yanjun; Wang, Zongli; Wang, Yewu

    2009-01-01

    Silicon nanowires (SiNWs) have been demonstrated as one of the promising building blocks for future nanodevices such as field effect transistors, solar cells, sensors and lithium battery; much progress has been made in this field during last decades. In this review paper, the synthesis and physical properties of SiNWs are introduced briefly. Significant advances of SiNWs-related nanodevices reported in recent literature and registered patents are reviewed. The latest development and prospects of SiNWs-related nanodevices are also discussed.

  7. Contact materials for nanowire devices and nanoelectromechanical switches

    KAUST Repository

    Hussain, Muhammad Mustafa

    2011-02-01

    The impact of contact materials on the performance of nanostructured devices is expected to be signifi cant. This is especially true since size scaling can increase the contact resistance and induce many unseen phenomenon and reactions that greatly impact device performance. Nanowire and nanoelectromechanical switches are two emerging nanoelectronic devices. Nanowires provide a unique opportunity to control the property of a material at an ultra-scaled dimension, whereas a nanoelectromechanical switch presents zero power consumption in its off state, as it is physically detached from the sensor anode. In this article, we specifi cally discuss contact material issues related to nanowire devices and nanoelectromechanical switches.

  8. Templated synthesis, characterization, and sensing application of macroscopic platinum nanowire network electrodes

    DEFF Research Database (Denmark)

    Wang, D. H.; Kou, R.; Gil, M. P.

    2005-01-01

    properties of the electrodes, such as electrochemical active area and methanol oxidation, have also been studied. Compared with conventional polycrystalline Pt electrodes, these novel nanowire network electrodes possess high electrochemical active areas and demonstrate higher current densities and a lower...... onset potential for methanol electro-oxidation. Enzymatic Pt nanowire-network-based sensors show higher sensitivity for glucose detection than that using conventional polycrystalline Pt electrode. Such macroscopic nanowire network electrodes provide ideal platforms for sensing and other device...

  9. Biofouling in membrane bioreactors: nexus between polyacrylonitrile surface charge and community composition.

    Science.gov (United States)

    Marbelia, Lisendra; Hernalsteens, Marie-Aline; Ilyas, Shazia; Öztürk, Basak; Szymczyk, Anthony; Springael, Dirk; Vankelecom, Ivo

    2018-02-15

    The influence of membrane surface charge on biofouling community composition during activated sludge filtration in a membrane bioreactor was investigated in this study using polyacrylonitrile-based membranes. Membranes with different surface properties were synthesized by phase inversion followed by a layer-by-layer modification. Various characterization results showed that the membranes differed only in their surface chemical composition and charge, ie two of them were negative, one neutral and one positive. Membrane fouling experiments were performed for 40 days and the biofouling communities were analyzed. PCR-DGGE fingerprinting indicated selective enrichment of bacterial populations from the sludge suspension within the biofilms at any time point. The biofilm community composition seemed to change with time. However, no difference was observed between the biofilm community of differently charged membranes at specific time points. It could be concluded that membrane charges do not play a decisive role in the long-term selection of the key bacterial foulants.

  10. Growth and decay of surface charges in grafts of Teflon in electrets states

    International Nuclear Information System (INIS)

    Spinelli, I.M.M.

    1971-01-01

    The greatest problem founded in a cardiovascular implant is the thrombus formation. Teflon grafts were used in electret state for prothesis in vena cava of dogs. To put these grafts in an electret state a corona discharge in air was used and homocharge was formed predominantly. To measure the formed surface charge the oscillating capacitor technique was used. In the electret state the grafts have showed an initial density of charge of 10- 8 C/cm 2 and the charge decay and time decay of the samples were measured under many conditions. We found two activation energies, E 2 =0.17 e V and E 3 =1.12 e V, due to rapid and slow decay, respectively. The charged grafts were sterilized with ethilene gas oxide and this process apparently did not influence the charges

  11. Dendrimer-induced leukocyte procoagulant activity depends on particle size and surface charge.

    Science.gov (United States)

    Dobrovolskaia, Marina A; Patri, Anil K; Potter, Timothy M; Rodriguez, Jamie C; Hall, Jennifer B; McNeil, Scott E

    2012-02-01

    Thrombogenicity associated with the induction of leukocyte procoagulant activity (PCA) is a common complication in sepsis and cancer. Since nanoparticles are increasingly used for drug delivery, their interaction with coagulation systems is an important part of the safety assessment. The purpose of this study was to investigate the effects of nanoparticle physicochemical properties on leukocyte PCA, and to get insight into the mechanism of PCA induction. A total of 12 formulations of polyamidoamine (PAMAM) dendrimers, varying in size and surface charge, were studied in vitro using recalcification time assay. Irrespective of their size, anionic and neutral dendrimers did not induce leukocyte PCA in vitro. Cationic particles induced PCA in a size- and charge-dependent manner. The mechanism of PCA induction was similar to that of doxorubicin. Cationic dendrimers were also found to exacerbate endotoxin-induced PCA. PAMAM dendrimer-induced leukocyte PCA depends on particle size, charge and density of surface groups.

  12. Influence of nanopore surface charge and magnesium ion on polyadenosine translocation.

    Science.gov (United States)

    Lepoitevin, Mathilde; Coulon, Pierre Eugène; Bechelany, Mikhael; Cambedouzou, Julien; Janot, Jean-Marc; Balme, Sebastien

    2015-04-10

    We investigate the influence of a nanopore surface state and the addition of Mg(2+) on poly-adenosine translocation. To do so, two kinds of nanopores with a low aspect ratio (diameter ∼3-5 nm, length 30 nm) were tailored: the first one with a negative charge surface and the second one uncharged. It was shown that the velocity and the energy barrier strongly depend on the nanopore surface. Typically if the nanopore and polyA exhibit a similar charge, the macromolecule velocity increases and its global energy barrier of entrance in the nanopore decreases, as opposed to the non-charged nanopore. Moreover, the addition of a divalent chelating cation induces an increase of energy barrier of entrance, as expected. However, for a negative nanopore, this effect is counterbalanced by the inversion of the surface charge induced by the adsorption of divalent cations.

  13. Surface charge method for molecular surfaces with curved areal elements I. Spherical triangles

    Science.gov (United States)

    Yu, Yi-Kuo

    2018-03-01

    Parametrizing a curved surface with flat triangles in electrostatics problems creates a diverging electric field. One way to avoid this is to have curved areal elements. However, charge density integration over curved patches appears difficult. This paper, dealing with spherical triangles, is the first in a series aiming to solve this problem. Here, we lay the ground work for employing curved patches for applying the surface charge method to electrostatics. We show analytically how one may control the accuracy by expanding in powers of the the arc length (multiplied by the curvature). To accommodate not extremely small curved areal elements, we have provided enough details to include higher order corrections that are needed for better accuracy when slightly larger surface elements are used.

  14. In situ ZnO nanowire growth to promote the PVDF piezo phase and the ZnO-PVDF hybrid self-rectified nanogenerator as a touch sensor.

    Science.gov (United States)

    Li, Zetang; Zhang, Xu; Li, Guanghe

    2014-03-28

    A PVDF-ZnO nanowires (NWs) hybrid generator (PZHG) was designed. A simple, cost effective method to produce the PVDF β phase by nano force is introduced. With the ZnO NWs growing, the in situ nano extension force promotes the phase change. A theoretical analysis of the ZnO NWs acting as a self-rectifier of the nano generator is established. The ZnO NWs acted as a self-adjustment diode to control the current output of the PZHG by piezo-electric and semi-conductive effects. Based on the self-controllability of the piezoelectric output, three kinds of finger touching are distinguished by the output performances of the PZHG, which is applicable to an LCD touch pad.

  15. Preparation and characterization of electrodeposited cobalt nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Irshad, M. I., E-mail: imrancssp@gmail.com; Mohamed, N. M., E-mail: noranimuti-mohamed@petronas.com.my [Department of Fundamental and Applied Sciences, Universiti Teknologi PETRONAS, 31750 PERAK (Malaysia); Ahmad, F., E-mail: faizahmad@petronas.com.my; Abdullah, M. Z., E-mail: zaki-abdullah@petronas.com.my [Department of Mechanical Engineering, Universiti Teknologi PETRONAS, 31750 PERAK (Malaysia)

    2014-10-24

    Electrochemical deposition technique has been used to deposit cobalt nanowires into the nano sized channels of Anodized Aluminium Oxide (AAO) templates. CoCl{sub 2}Ðœ‡6H2O salt solution was used, which was buffered with H{sub 3}BO{sub 3} and acidified by dilute H{sub 2}SO{sub 4} to increase the plating life and control pH of the solution. Thin film of copper around 150 nm thick on one side of AAO template coated by e-beam evaporation system served as cathode to create electrical contact. FESEM analysis shows that the as-deposited nanowires are highly aligned, parallel to one another and have high aspect ratio with a reasonably high pore-filing factor. The TEM results show that electrodeposited cobalt nanowires are crystalline in nature. The Hysteresis loop shows the magnetization properties for in and out of plane configuration. The in plane saturation magnetization (Ms) is lower than out of plane configuration because of the easy axis of magnetization is perpendicular to nanowire axis. These magnetic nanowires could be utilized for applications such as spintronic devices, high density magnetic storage, and magnetic sensor applications.

  16. Growth Mechanism of Nanowires: Ternary Chalcogenides

    Science.gov (United States)

    Singh, N. B.; Coriell, S. R.; Hopkins, R. H.; Su, Ching Hua; Arnold, B.; Choa, Fow-Sen; Cullum, Brian

    2016-01-01

    In the past two decades there has been a large rise in the investment and expectations for nanotechnology use. Almost every area of research has projected improvements in sensors, or even a promise for the emergence of some novel device technologies. For these applications major focuses of research are in the areas of nanoparticles and graphene. Although there are some near term applications with nanowires in photodetectors and other low light detectors, there are few papers on the growth mechanism and fabrication of nanowire-based devices. Semiconductor nanowires exhibit very favorable and promising optical properties, including high transparency and a several order of magnitude better photocurrent than thin film and bulk materials. We present here an overview of the mechanism of nanowire growth from the melt, and some preliminary results for the thallium arsenic selenide material system. Thallium arsenic selenide (TAS) is a multifunctional material combining excellent acousto-optical, nonlinear and radiation detection properties. We observed that small units of (TAS) nanocubes arrange and rearrange at moderate melt undercooling to form the building block of a nanowire. In some cases very long wires (less than mm) are formed. Since we avoided the catalyst, we observed self-nucleation and uncontrolled growth of wires from different places.

  17. Adsorption of tetracycline on kaolinite with pH-dependent surface charges.

    Science.gov (United States)

    Li, Zhaohui; Schulz, Laura; Ackley, Caren; Fenske, Nancy

    2010-11-01

    Kaolinite is a major type of clay minerals in soils of warm and humid climate. Although it has a much lower cation exchange capacity (CEC) and specific surface area compared to swelling clays, its ubiquitous existence as well as its pH-dependent surface charge makes it an important component to study the interactions between contaminants and soils. Tetracycline (TC) is a group of broad spectrum antibiotics used extensively in human and veterinary medicine. It has a high aqueous solubility and a long environmental half-life. In this study, the interactions between TC and kaolinite in aqueous solution were investigated in batch tests and supplemented by FTIR analyses. The adsorption of TC on kaolinite was mainly on the external surfaces via cation exchange as confirmed by stoichiometric desorption of exchangeable cations and simultaneous adsorption of H(+) rather than due to complexation. Under acidic conditions, a reduction in surface charge, thus the CEC, resulted in more desorption of exchangeable cations compared to TC adsorption. Fitting of the experimental data to the adsorption of different species revealed that TC(+) accounted for 4/5 of the total TC adsorbed with the remaining by zwitterion TC(0), possible via hydrogen bonding. At higher temperature, the pKa2 and pKa3 values seem to shift a pH unit lower. Due to its pH-dependent charge of kaolinite, TC adsorption is more pH dependent. The TC adsorption capacity on kaolinite was much lower compared to that on swelling clays. However, the adsorption rate constant was faster than that on swelling clays owing to surface adsorption instead of intercalation. Despite its low TC adsorption capacity, the ubiquitous existence of kaolinite in soils of warm climate may play a vital role in the fate and transport of TC in these soils. Copyright 2010 Elsevier Inc. All rights reserved.

  18. Characterization of size, surface charge, and agglomeration state of nanoparticle dispersions for toxicological studies

    International Nuclear Information System (INIS)

    Jiang Jingkun; Oberdoerster, Guenter; Biswas, Pratim

    2009-01-01

    Characterizing the state of nanoparticles (such as size, surface charge, and degree of agglomeration) in aqueous suspensions and understanding the parameters that affect this state are imperative for toxicity investigations. In this study, the role of important factors such as solution ionic strength, pH, and particle surface chemistry that control nanoparticle dispersion was examined. The size and zeta potential of four TiO 2 and three quantum dot samples dispersed in different solutions (including one physiological medium) were characterized. For 15 nm TiO 2 dispersions, the increase of ionic strength from 0.001 M to 0.1 M led to a 50-fold increase in the hydrodynamic diameter, and the variation of pH resulted in significant change of particle surface charge and the hydrodynamic size. It was shown that both adsorbing multiply charged ions (e.g., pyrophosphate ions) onto the TiO 2 nanoparticle surface and coating quantum dot nanocrystals with polymers (e.g., polyethylene glycol) suppressed agglomeration and stabilized the dispersions. DLVO theory was used to qualitatively understand nanoparticle dispersion stability. A methodology using different ultrasonication techniques (bath and probe) was developed to distinguish agglomerates from aggregates (strong bonds), and to estimate the extent of particle agglomeration. Probe ultrasonication performed better than bath ultrasonication in dispersing TiO 2 agglomerates when the stabilizing agent sodium pyrophosphate was used. Commercially available Degussa P25 and in-house synthesized TiO 2 nanoparticles were used to demonstrate identification of aggregated and agglomerated samples.

  19. Binding of chloroquine to ionic micelles: Effect of pH and micellar surface charge

    Energy Technology Data Exchange (ETDEWEB)

    Souza Santos, Marcela de, E-mail: marcelafarmausp77@gmail.com [Departamento de Física e Química, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Avenida do Café, s/n, Ribeirão Preto, São Paulo 14040-903 (Brazil); Perpétua Freire de Morais Del Lama, Maria, E-mail: mpemdel@fcfrp.usp.br [Departamento de Física e Química, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Avenida do Café, s/n, Ribeirão Preto, São Paulo 14040-903 (Brazil); Instituto Nacional de Ciência e Tecnologia de Bioanalítica, Departamento de Química Analítica, Universidade Estadual de Campinas, Cidade Universitária Zeferino Vaz, s/n, Campinas, São Paulo 13083-970 (Brazil); Siuiti Ito, Amando, E-mail: amandosi@ffclrp.usp.br [Departamento de Física, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Avenida Bandeirantes, 3900, Ribeirão Preto, São Paulo 14040-901 (Brazil); and others

    2014-03-15

    The pharmacological action of chloroquine relies on its ability to cross biological membranes in order to accumulate inside lysosomes. The present work aimed at understanding the basis for the interaction between different chloroquine species and ionic micelles of opposite charges, the latter used as a simple membrane model. The sensitivity of absorbance and fluorescence of chloroquine to changes in its local environment was used to probe its interaction with cetyltrimethylammonium micelles presenting bromide (CTAB) and sulfate (CTAS) as counterions, in addition to dodecyl sulfate micelles bearing sodium (SDS) and tetramethylammonium (TMADS) counterions. Counterion exchange was shown to have little effect on drug–micelle interaction. Chloroquine first dissociation constant (pKa{sub 1}) shifted to opposite directions when anionic and cationic micelles were compared. Chloroquine binding constants (K{sub b}) revealed that electrostatic forces mediate charged drug–micelle association, whereas hydrophobic interactions allowed neutral chloroquine to associate with anionic and cationic micelles. Fluorescence quenching studies indicated that monoprotonated chloroquine is inserted deeper into the micelle surface of anionic micelles than its neutral form, the latter being less exposed to the aqueous phase when associated with cationic over anionic assemblies. The findings provide further evidence that chloroquine–micelle interaction is driven by a tight interplay between the drug form and the micellar surface charge, which can have a major effect on the drug biological activity. -- Highlights: • Chloroquine (CQ) pKa{sub 1} increased for SDS micelles and decreased for CTAB micelles. • CQ is solubilized to the surface of both CTAB and SDS micelles. • Monoprotonated CQ is buried deeper into SDS micelles than neutral CQ. • Neutral CQ is less exposed to aqueous phase in CTAB over SDS micelles. • Local pH and micellar surface charge mediate interaction of CQ with

  20. Printing nanotube/nanowire for flexible microsystems

    Science.gov (United States)

    Tortorich, Ryan P.; Choi, Jin-Woo

    2014-04-01

    Printing has become an emerging manufacturing technology for mechanics, electronics, and consumer products. Additionally, both nanotubes and nanowires have recently been used as materials for sensors and electrodes due to their unique electrical and mechanical properties. Printed electrodes and conductive traces particularly offer versatility of fabricating low-cost, disposable, and flexible electrical devices and microsystems. While various printing methods such as screen printing have been conventional methods for printing conductive traces and electrodes, inkjet printing has recently attracted great attention due to its unique advantages including no template requirement, rapid printing at low cost, on-demand printing capability, and precise control of the printed material. Computer generated conductive traces or electrode patterns can simply be printed on a thin film substrate with proper conductive ink consisting of nanotubes or nanowires. However, in order to develop nanotube or nanowire ink, there are a few challenges that need to be addressed. The most difficult obstacle to overcome is that of nanotube/nanowire dispersion within a solution. Other challenges include adjusting surface tension and controlling viscosity of the ink as well as treating the surface of the printing substrate. In an attempt to pave the way for nanomaterial inkjet printing, we present a method for preparing carbon nanotube ink as well as its printing technique. A fully printed electrochemical sensor using inkjet-printed carbon nanotube electrodes is also demonstrated as an example of the possibilities for this technology.

  1. Membrane effects of Vitamin E deficiency: bioenergetic and surface-charge-density studies of skeletal muscle and liver mitochondria

    Energy Technology Data Exchange (ETDEWEB)

    Quintanilha, A.T.; Packer, L.; Szyszlo Davies, J.M.; Racanelli, T.L.; Davies, K.J.A.

    1981-12-01

    Vitamin E (dl-..cap alpha..-tocopherol) deficiency in rats increased the sensitivity of liver and muscle mitochondria to damage during incubation at various temperatures, irradiation with visible light, or steady state respiration with substrates. In all cases, vitamin E deficient mitochondria exhibited increased lipid peroxidation, reduced transmembrane potential, decreased respiratory coupling, and lower rates of electron transport, compared to control mitochondria. Muscle mitochondria always showed greater negative inner membrane surface charge density, and were also more sensitive to damage than were liver mitochondria. Vitamin E deficient mitochondria also showed slightly more negative inner membrane surface charge density compared to controls. The relationship between greater negative surface potential and increased sensitivity to damage observed, provides for a new and sensitive method to further probe the role of surface charge in membrane structure and function. Implications of these new findings for the well known human muscle myopathies and those experimentally induced by Vitamin E deficiency in animals, are discussed.

  2. Advances in nanowire bioelectronics

    Science.gov (United States)

    Zhou, Wei; Dai, Xiaochuan; Lieber, Charles M.

    2017-01-01

    Semiconductor nanowires represent powerful building blocks for next generation bioelectronics given their attractive properties, including nanometer-scale footprint comparable to subcellular structures and bio-molecules, configurable in nonstandard device geometries readily interfaced with biological systems, high surface-to-volume ratios, fast signal responses, and minimum consumption of energy. In this review article, we summarize recent progress in the field of nanowire bioelectronics with a focus primarily on silicon nanowire field-effect transistor biosensors. First, the synthesis and assembly of semiconductor nanowires will be described, including the basics of nanowire FETs crucial to their configuration as biosensors. Second, we will introduce and review recent results in nanowire bioelectronics for biomedical applications ranging from label-free sensing of biomolecules, to extracellular and intracellular electrophysiological recording.

  3. From nanodiamond to nanowires.

    Energy Technology Data Exchange (ETDEWEB)

    Barnard, A.; Materials Science Division

    2005-01-01

    Recent advances in the fabrication and characterization of semiconductor and metallic nanowires are proving very successful in meeting the high expectations of nanotechnologists. Although the nanoscience surrounding sp{sup 3} bonded carbon nanotubes has continued to flourish over recent years the successful synthesis of the sp{sup 3} analogue, diamond nanowires, has been limited. This prompts questions as to whether diamond nanowires are fundamentally unstable. By applying knowledge obtained from examining the structural transformations in nanodiamond, a framework for analyzing the structure and stability of diamond nanowires may be established. One possible framework will be discussed here, supported by results of ab initio density functional theory calculations used to study the structural relaxation of nanodiamond and diamond nanowires. The results show that the structural stability and electronic properties of diamond nanowires are dependent on the surface morphology, crystallographic direction of the principal axis, and the degree of surface hydrogenation.

  4. Nanowires and nanobelts, v.2 nanowires and nanobelts of functional materials

    CERN Document Server

    Wang, Zhong Lin

    2010-01-01

    Nanowires, nanobelts, nanoribbons, nanorods ..., are a new class of quasi-one-dimensional materials that have been attracting a great research interest in the last few years. These non-carbon based materials have been demonstrated to exhibit superior electrical, optical, mechanical and thermal properties, and can be used as fundamental building blocks for nano-scale science and technology, ranging from chemical and biological sensors, field effect transistors to logic circuits. Nanocircuits built using semiconductor nanowires demonstrated were declared a ""breakthrough in science"" by Science

  5. MMP-2 detective silicon nanowire biosensor using enzymatic cleavage reaction.

    Science.gov (United States)

    Choi, Jin-Ha; Kim, Han; Kim, Hyun-Soo; Um, Soong Ho; Choi, Jeong-Woo; Oh, Byung-Keun

    2013-04-01

    Matrix metalloproteinases are proteolytic enzymes that play a significant role in tissue remodeling related with various pathological and physiological processes such as tissue repair, angiogenesis, cirrhosis, morphogenesis, arthritis, and metastasis. Especially, MMP-2 has been shown to be related with benign prostatic hyperplasia and prostate cancer. Therefore, there is a need to make sensors with high sensitivity that can measure MMP-2 concentrations precisely. Silicon nanowires have been used in the development of high sensitive chemical sensors and biosensors. The high sensitivity of silicon nanowire based sensor originates in its high surface to volume ratio and ability to field-effect induced local charge transfers. In this study, 100 nm silicon nanowire based field-effect transistors (FET) device was fabricated by electron-beam lithography and MMP-2 was successfully measured by conductance versus time characteristics within 1 pM to 100 nM.

  6. Nanowire field effect transistors principles and applications

    CERN Document Server

    Jeong, Yoon-Ha

    2014-01-01

    Nanowire Field Effect Transistor: Basic Principles and Applications” places an emphasis on the application aspects of nanowire field effect transistors (NWFET). Device physics and electronics are discussed in a compact manner, together with the p-n junction diode and MOSFET, the former as an essential element in NWFET and the latter as a general background of the FET. During this discussion, the photo-diode, solar cell, LED, LD, DRAM, flash EEPROM and sensors are highlighted to pave the way for similar applications of NWFET. Modeling is discussed in close analogy and comparison with MOSFETs. Contributors focus on processing, electrostatic discharge (ESD) and application of NWFET. This includes coverage of solar and memory cells, biological and chemical sensors, displays and atomic scale light emitting diodes. Appropriate for scientists and engineers interested in acquiring a working knowledge of NWFET as well as graduate students specializing in this subject.

  7. Superlattice nanowire pattern transfer (SNAP).

    Science.gov (United States)

    Heath, James R

    2008-12-01

    During the past 15 years or so, nanowires (NWs) have emerged as a new and distinct class of materials. Their novel structural and physical properties separate them from wires that can be prepared using the standard methods for manufacturing electronics. NW-based applications that range from traditional electronic devices (logic and memory) to novel biomolecular and chemical sensors, thermoelectric materials, and optoelectronic devices, all have appeared during the past few years. From a fundamental perspective, NWs provide a route toward the investigation of new physics in confined dimensions. Perhaps the most familiar fabrication method is the vapor-liquid-solid (VLS) growth technique, which produces semiconductor nanowires as bulk materials. However, other fabrication methods exist and have their own advantages. In this Account, I review a particular class of NWs produced by an alternative method called superlattice nanowire pattern transfer (SNAP). The SNAP method is distinct from other nanowire preparation methods in several ways. It can produce large NW arrays from virtually any thin-film material, including metals, insulators, and semiconductors. The dimensions of the NWs can be controlled with near-atomic precision, and NW widths and spacings can be as small as a few nanometers. In addition, SNAP is almost fully compatible with more traditional methods for manufacturing electronics. The motivation behind the development of SNAP was to have a general nanofabrication method for preparing electronics-grade circuitry, but one that would operate at macromolecular dimensions and with access to a broad materials set. Thus, electronics applications, including novel demultiplexing architectures; large-scale, ultrahigh-density memory circuits; and complementary symmetry nanowire logic circuits, have served as drivers for developing various aspects of the SNAP method. Some of that work is reviewed here. As the SNAP method has evolved into a robust nanofabrication

  8. Timoshenko beam model for buckling of piezoelectric nanowires with surface effects

    Science.gov (United States)

    2012-01-01

    This paper investigates the buckling behavior of piezoelectric nanowires under distributed transverse loading, within the framework of the Timoshenko beam theory, and in the presence of surface effects. Analytical relations are given for the critical force of axial buckling of nanowires by accounting for the effects of surface elasticity, residual surface tension, and transverse shear deformation. Through an example, it is shown that the critical electric potential of buckling depends on both the surface stresses and piezoelectricity. This study may be helpful in the characterization of the mechanical properties of nanowires and in the calibration of the nanowire-based force sensors. PMID:22453063

  9. Surface charges and Np(V) sorption on amorphous Al- and Fe- silicates

    International Nuclear Information System (INIS)

    Del Nero, M.; Assada, A.; Barillon, R.; Duplatre, G.; Made, B.

    2005-01-01

    Full text of publication follows: Sorption onto Si-rich alteration layers of crystalline minerals and nuclear glasses, and onto amorphous secondary silicates of rocks and soils, are expected to retard the migration of actinides in the near- and far-field of HLW repositories. We present experimental and modeling studies on the effects of silicate structure and bulk chemistry, and of solution chemistry, on charges and adsorption of neptunyl ions at surfaces of synthetic, amorphous or poorly ordered silica, Al-silicates and Fe-silicates. The Al-silicates display similar pH-dependent surface charges characterized by predominant Si-O - Si sites, and similar surface affinities for neptunyl ions, irrespective to their Si/Al molar ratio (varying from 10 to 4.3). Such experimental features are explained by incorporation of Al atoms in tetrahedral position in the silicate lattice, leading to only trace amounts of high-affinity Al-OH surface groups due to octahedral Al. By contrast, the structure of the Fe-silicates ensures the occurrence of high-affinity Fe-OH surface groups, whose concentration is shown by proton adsorption measurements to increase with decreasing of the silicate Si/Fe molar ratio (from 10 to 2.3). Nevertheless, experimental data of the adsorption of neptunyl and electrolyte ions show unexpectedly weak effect of the Si/Fe ratio, and suggest predominant Si-OH surface groups. A possible explanation is that aqueous silicate anions, released by dissolution, adsorb at OH Fe - surface groups and / or precipitate as silica gel coatings, because experimental solutions were found at near-equilibrium with respect to amorphous silica. Therefore, the environmental sorption of Np(V) onto Si-rich, amorphous or poorly ordered Al-silicates may primarily depend on pH and silicate specific surface areas, given the low overall chemical affinity of such phases for dissolved metals. By contrast, the sorption of Np(V) on natural, amorphous or poorly ordered Fe-silicates may be a

  10. Single cell detection using a magnetic zigzag nanowire biosensor.

    Science.gov (United States)

    Huang, Hao-Ting; Ger, Tzong-Rong; Lin, Ya-Hui; Wei, Zung-Hang

    2013-08-07

    A magnetic zigzag nanowire device was designed for single cell biosensing. Nanowires with widths of 150, 300, 500, and 800 nm were fabricated on silicon trenches by electron beam lithography, electron beam evaporation, and lift-off processes. Magnetoresistance measurements were performed before and after the attachment of a single magnetic cell to the nanowires to characterize the magnetic signal change due to the influence of the magnetic cell. Magnetoresistance responses were measured in different magnetic field directions, and the results showed that this nanowire device can be used for multi-directional detection. It was observed that the highest switching field variation occurred in a 150 nm wide nanowire when the field was perpendicular to the substrate plane. On the other hand, the highest magnetoresistance ratio variation occurred in a 800 nm wide nanowire also when the field was perpendicular to the substrate plane. Besides, the trench-structured substrate proposed in this study can fix the magnetic cell to the sensor in a fluid environment, and the stray field generated by the corners of the magnetic zigzag nanowires has the function of actively attracting the magnetic cells for detection.

  11. Probing the surface charge on the basal planes of Kaolinite particles with high resolution Atomic Force Microscopy

    NARCIS (Netherlands)

    Kumar, Naveen; Andersson, M.P.; van den Ende, Henricus T.M.; Mugele, Friedrich Gunther; Sîretanu, Igor

    2017-01-01

    High-resolution atomic force microscopy is used to map the surface charge on the basal planes of kaolinite nanoparticles in an ambient solution of variable pH and NaCl or CaCl2 concentration. Using DLVO theory with charge regulation, we determine from the measured force–distance curves the surface

  12. The role of surface charge density in cationic liposome-promoted dendritic cell maturation and vaccine-induced immune responses

    Science.gov (United States)

    Ma, Yifan; Zhuang, Yan; Xie, Xiaofang; Wang, Ce; Wang, Fei; Zhou, Dongmei; Zeng, Jianqiang; Cai, Lintao

    2011-05-01

    Cationic liposomes have emerged as a novel adjuvant and antigen delivery system to enhance vaccine efficacy. However, the role of surface charge density in cationic liposome-regulated immune responses has not yet been elucidated. In the present study, we prepared a series of DOTAP/DOPC cationic liposomes with different surface densities by incorporating varying amounts of DOPC (a neutral lipid) into DOTAP (a cationic lipid). The results showed that DOTAP/DOPC cationic liposome-regulated immune responses relied on the surface charge density, and might occur through ROS signaling. The liposomes with a relatively high charge density, such as DOTAP/DOPC 5 : 0 and 4 : 1 liposomes, potently enhanced dendritic cell maturation, ROS generaion, antigen uptake, as well as the production of OVA-specific IgG2a and IFN-γ. In contrast, low-charge liposomes, such as DOTAP/DOPC 1 : 4 liposome, failed to promote immune responses even at high concentrations, confirming that the immunoregulatory effect of cationic liposomes is mostly attributable to their surface charge density. Moreover, the DOTAP/DOPC 1 : 4 liposome suppressed anti-OVA antibody responses in vivo. Overall, maintaining an appropriate surface charge is crucial for optimizing the adjuvant effect of cationic liposomes and enhancing the efficacy of liposome-based vaccines.

  13. Improving energy conversion efficiency for triboelectric nanogenerator with capacitor structure by maximizing surface charge density.

    Science.gov (United States)

    He, Xianming; Guo, Hengyu; Yue, Xule; Gao, Jun; Xi, Yi; Hu, Chenguo

    2015-02-07

    Nanogenerators with capacitor structures based on piezoelectricity, pyroelectricity, triboelectricity and electrostatic induction have been extensively investigated. Although the electron flow on electrodes is well understood, the maximum efficiency-dependent structure design is not clearly known. In this paper, a clear understanding of triboelectric generators with capacitor structures is presented by the investigation of polydimethylsiloxane-based composite film nanogenerators, indicating that the generator, in fact, acts as both an energy storage and output device. Maximum energy storage and output depend on the maximum charge density on the dielectric polymer surface, which is determined by the capacitance of the device. The effective thickness of polydimethylsiloxane can be greatly reduced by mixing a suitable amount of conductive nanoparticles into the polymer, through which the charge density on the polymer surface can be greatly increased. This finding can be applied to all the triboelectric nanogenerators with capacitor structures, and it provides an important guide to the structural design for nanogenerators. It is demonstrated that graphite particles with sizes of 20-40 nm and 3.0% mass mixed into the polydimethylsiloxane can reduce 34.68% of the effective thickness of the dielectric film and increase the surface charges by 111.27% on the dielectric film. The output power density of the triboelectric nanogenerator with the composite polydimethylsiloxane film is 3.7 W m(-2), which is 2.6 times as much as that of the pure polydimethylsiloxane film.

  14. Determination of surface charge density of α-alumina by acid-base titration

    Directory of Open Access Journals (Sweden)

    Justin W. Ntalikwa

    2007-04-01

    Full Text Available The surface charge density (σo of colloidal alpha alumina suspended in various 1:1 electrolytes was measured using acid-base titration. An autotitrator capable of dispensing accurately 25 plus or minus 0.1 μL of titrant was used. The pH and temperature in the titration cell were monitored using single junction electrodes and platinum resistance thermometers, respectively. A constant supply of nitrogen gas in the cell was used to maintain inert conditions. The whole set up was interfaced with a computer for easy data acquisition. It was observed that the material exhibits a point of zero charge (PZC, this occurred at pH of 7.8 plus or minus 0.1, 7.6 plus or minus 0.2, 8.5 plus or minus 0.1, 8.3 plus or minus 0.1 for NaCl, NaNO3, CsCl and CsNO3 systems, respectively. It was also observed that below PZC, σo increases with increase in electrolyte concentration (Co whereas above PZC, σo decreases with increase in Co. It was concluded that σo of this material is a function of pH and Co and that its polarity can be varied through zero by varying these parameters.

  15. Controlling DNA Translocation Speed through Solid-State Nanopores by Surface Charge Modulation

    Science.gov (United States)

    Meller, Amit

    2013-03-01

    The Nanopore method is an emerging technique, which extends gel-electrophoresis to the single-molecule level and allows the analysis of DNAs, RNAs and DNA-protein complexes. The strength of the technique stems from two fundamental facts: First, nanopores due to their nanoscale size can be used to uncoil biopolymers, such as DNA or RNA and slide them in a single file manner that allows scanning their properties. Consequently, the method can be used to probe short as well as extremely long biopolymers, such as genomic DNA with high efficiency. Second, electrostatic focusing of charged biopolymers into the nanopore overcomes thermally driven diffusion, thus facilitating an extremely efficient end-threading (or capture) of DNA. Thus, nanopores can be used to detect minute DNA copy numbers, circumventing costly molecular amplification such as Polymerase Chain Reaction. A critical factor, which determines the ability of nanopore to distinguish fine properties within biopolymers, such as the location of bound small-molecules, proteins, or even the nucleic acid's sequence, is the speed at which molecules are translocated through the pore. When the translocation speed is too high the electrical noise masks the desired signal, thus limiting the utility of the method. Here I will discuss new experimental results showing that modulating the surface charge inside the pore can effectively reduce the translocation speed through solid-state nanopores fabricated in thin silicon nitride membranes. I will present a simple physical model to account for these results.

  16. The role of surface charge in cellular uptake and cytotoxicity of medical nanoparticles

    Directory of Open Access Journals (Sweden)

    Fröhlich E

    2012-11-01

    Full Text Available Eleonore FröhlichCenter for Medical Research, Medical University of Graz, Graz, AustriaAbstract: Many types of nanoparticles (NPs are tested for use in medical products, particularly in imaging and gene and drug delivery. For these applications, cellular uptake is usually a prerequisite and is governed in addition to size by surface characteristics such as hydrophobicity and charge. Although positive charge appears to improve the efficacy of imaging, gene transfer, and drug delivery, a higher cytotoxicity of such constructs has been reported. This review summarizes findings on the role of surface charge on cytotoxicity in general, action on specific cellular targets, modes of toxic action, cellular uptake, and intracellular localization of NPs. Effects of serum and intercell type differences are addressed. Cationic NPs cause more pronounced disruption of plasma-membrane integrity, stronger mitochondrial and lysosomal damage, and a higher number of autophagosomes than anionic NPs. In general, nonphagocytic cells ingest cationic NPs to a higher extent, but charge density and hydrophobicity are equally important; phagocytic cells preferentially take up anionic NPs. Cells do not use different uptake routes for cationic and anionic NPs, but high uptake rates are usually linked to greater biological effects. The different uptake preferences of phagocytic and nonphagocytic cells for cationic and anionic NPs may influence the efficacy and selectivity of NPs for drug delivery and imaging.Keywords: endocytosis, plasma membrane, lysosomes, polystyrene particles, quantum dots, dendrimers

  17. Extracellular Polymeric Substances Govern the Surface Charge of Biogenic Elemental Selenium Nanoparticles

    KAUST Repository

    Jain, Rohan

    2015-02-03

    © 2014 American Chemical Society. The origin of the organic layer covering colloidal biogenic elemental selenium nanoparticles (BioSeNPs) is not known, particularly in the case when they are synthesized by complex microbial communities. This study investigated the presence of extracellular polymeric substances (EPS) on BioSeNPs. The role of EPS in capping the extracellularly available BioSeNPs was also examined. Fourier transform infrared (FT-IR) spectroscopy and colorimetric measurements confirmed the presence of functional groups characteristic of proteins and carbohydrates on the BioSeNPs, suggesting the presence of EPS. Chemical synthesis of elemental selenium nanoparticles in the presence of EPS, extracted from selenite fed anaerobic granular sludge, yielded stable colloidal spherical selenium nanoparticles. Furthermore, extracted EPS, BioSeNPs, and chemically synthesized EPS-capped selenium nanoparticles had similar surface properties, as shown by ζ-potential versus pH profiles and isoelectric point measurements. This study shows that the EPS of anaerobic granular sludge form the organic layer present on the BioSeNPs synthesized by these granules. The EPS also govern the surface charge of these BioSeNPs, thereby contributing to their colloidal properties, hence affecting their fate in the environment and the efficiency of bioremediation technologies.

  18. Toward a Molecular Understanding of Protein Solubility: Increased Negative Surface Charge Correlates with Increased Solubility

    Science.gov (United States)

    Kramer, Ryan M.; Shende, Varad R.; Motl, Nicole; Pace, C. Nick; Scholtz, J. Martin

    2012-01-01

    Protein solubility is a problem for many protein chemists, including structural biologists and developers of protein pharmaceuticals. Knowledge about how intrinsic factors influence solubility is limited due to the difficulty of obtaining quantitative solubility measurements. Solubility measurements in buffer alone are difficult to reproduce, because gels or supersaturated solutions often form, making it impossible to determine solubility values for many proteins. Protein precipitants can be used to obtain comparative solubility measurements and, in some cases, estimations of solubility in buffer alone. Protein precipitants fall into three broad classes: salts, long-chain polymers, and organic solvents. Here, we compare the use of representatives from two classes of precipitants, ammonium sulfate and polyethylene glycol 8000, by measuring the solubility of seven proteins. We find that increased negative surface charge correlates strongly with increased protein solubility and may be due to strong binding of water by the acidic amino acids. We also find that the solubility results obtained for the two different precipitants agree closely with each other, suggesting that the two precipitants probe similar properties that are relevant to solubility in buffer alone. PMID:22768947

  19. Characterizing the surface charge of clay minerals with Atomic Force Microscope (AFM

    Directory of Open Access Journals (Sweden)

    Yuan Guo

    2017-05-01

    Full Text Available The engineering properties of clayey soils, including fluid permeability, erosion resistance and cohesive strength, are quite different from those of non-cohesive soils. This is mainly due to their small platy particle shape and the surrounding diffuse double layer structure. By using the Atomic Force Microscopy (AFM, the surface topography and the interaction force between the silicon dioxide tip and the kaolinite/montmorillonite clay minerals have been measured in the 1.0 mM NaCl solution at neutral pH. From this, the surface potential of the clay minerals is determined by mathematical regression analyses using the DLVO model. The length/thickness ratio of kaolinite and montmorillonite particles measured ranges from 8.0 to 15.0. The surface potential and surface charge density vary with particles. The average surface potential of montmorillonite is −62.8 ± 10.6 mV, and the average surface potential of kaolinite is −40.9 ± 15.5 mV. The measured results help to understand the clay sediment interaction, and will be used to develop interparticle force model to simulate sediment transport during erosion process.

  20. Nanocapsule of cationic liposomes obtained using "in situ" acrylic acid polymerization: stability, surface charge and biocompatibility.

    Science.gov (United States)

    Scarioti, Giovana Danieli; Lubambo, Adriana; Feitosa, Judith P A; Sierakowski, Maria Rita; Bresolin, Tania M B; de Freitas, Rilton Alves

    2011-10-15

    In this work, didecyldimethylammonium bromide (DDAB) and 1,2-dioleoyl-sn-glycero-3-phosphatidylethanolamine (DOPE) (2.5:1) were used to prepare liposomes coated with polyacrylic acid (PAA) using "in situ" polymerization with 2.5, 5 and 25 mM of acrylic acid (AA). The PAA concentrations were chosen to achieve partially to fully covered capsules, and the polymerization reaction was observed with real-time monitoring using dynamic light scattering (NanoDLS). The DDAB:DOPE liposomes showed stability in the tested temperature range (25-70°C), whereas the results confirmed the success of the polymerization according to superficial charge (zeta potential of +66.7±1.2 mV) results and AFM images. For the liposomes that were fully coated with PAA (zeta potential of +0.3±3.9 mV), cytotoxicity was independent of the concentration of albumin. Cationic liposomes and nanocapsules of the stable liposomes coated with PAA were obtained by controlling the surface charge, which was the most important factor related to cytotoxicity. Thus, a potential, safe drug nanocarrier was successfully developed in this work. Copyright © 2011 Elsevier B.V. All rights reserved.

  1. Nanowire Growth for Photovoltaics

    DEFF Research Database (Denmark)

    Holm, Jeppe Vilstrup

    Solar cells commercial success is based on an efficiency/cost calculation. Nanowire solar cells is one of the foremost candidates to implement third generation photo voltaics, which are both very efficient and cheap to produce. This thesis is about our progress towards commercial nanowire solar c...

  2. Nanowire Photovoltaic Devices

    Science.gov (United States)

    Forbes, David

    2015-01-01

    Firefly Technologies, in collaboration with the Rochester Institute of Technology and the University of Wisconsin-Madison, developed synthesis methods for highly strained nanowires. Two synthesis routes resulted in successful nanowire epitaxy: direct nucleation and growth on the substrate and a novel selective-epitaxy route based on nanolithography using diblock copolymers. The indium-arsenide (InAs) nanowires are implemented in situ within the epitaxy environment-a significant innovation relative to conventional semiconductor nanowire generation using ex situ gold nanoparticles. The introduction of these nanoscale features may enable an intermediate band solar cell while simultaneously increasing the effective absorption volume that can otherwise limit short-circuit current generated by thin quantized layers. The use of nanowires for photovoltaics decouples the absorption process from the current extraction process by virtue of the high aspect ratio. While no functional solar cells resulted from this effort, considerable fundamental understanding of the nanowire epitaxy kinetics and nanopatterning process was developed. This approach could, in principle, be an enabling technology for heterointegration of dissimilar materials. The technology also is applicable to virtual substrates. Incorporating nanowires onto a recrystallized germanium/metal foil substrate would potentially solve the problem of grain boundary shunting of generated carriers by restricting the cross-sectional area of the nanowire (tens of nanometers in diameter) to sizes smaller than the recrystallized grains (0.5 to 1 micron(exp 2).

  3. Semiconductor Nanowires: Defects Update

    Science.gov (United States)

    Kavanagh, Karen L.

    2008-05-01

    Structural defects commonly observed in semiconducting nanowires by electron microscopy will be reviewed and their origins discussed. Their effects on electrical and optical properties will be illustrated with examples from GaSb, InAs, and ZnSe nanowires grown by MOCVD and MBE.

  4. Magnetic nanocomposite sensor

    KAUST Repository

    Alfadhel, Ahmed

    2016-05-06

    A magnetic nanocomposite device is described herein for a wide range of sensing applications. The device utilizes the permanent magnetic behavior of the nanowires to allow operation without the application of an additional magnetic field to magnetize the nanowires, which simplifies miniaturization and integration into microsystems. In5 addition, the nanocomposite benefits from the high elasticity and easy patterning of the polymer-based material, leading to a corrosion-resistant, flexible material that can be used to realize extreme sensitivity. In combination with magnetic sensor elements patterned underneath the nanocomposite, the nanocomposite device realizes highly sensitive and power efficient flexible artificial cilia sensors for flow measurement or tactile sensing.

  5. Nanowire Growth for Photovoltaics

    DEFF Research Database (Denmark)

    Holm, Jeppe Vilstrup

    consisting of a single, vertical, gallium arsenide(GaAs) nanowire grown on silicon with a radial p-i-n-junction. The average concentration was ~8, and the peak concentration was ~12. By increasing the number of junctions in solar cells, they can extract more energy per absorbed photon. In ideal multi...... of the nanowires, some of which were removed from their growth substrate and turned into single nanowire solar cells (SNWSC). The best device showed a conversion efficiency of 6.8% under 1.5AMG 1-sun illumination. In order to improve the efficiency a surface passivating shell consisting of highly doped, wide......Solar cells commercial success is based on an efficiency/cost calculation. Nanowire solar cells is one of the foremost candidates to implement third generation photo voltaics, which are both very efficient and cheap to produce. This thesis is about our progress towards commercial nanowire solar...

  6. Probing the Surface Charge on the Basal Planes of Kaolinite Particles with High-Resolution Atomic Force Microscopy

    Science.gov (United States)

    2017-01-01

    High-resolution atomic force microscopy is used to map the surface charge on the basal planes of kaolinite nanoparticles in an ambient solution of variable pH and NaCl or CaCl2 concentration. Using DLVO theory with charge regulation, we determine from the measured force–distance curves the surface charge distribution on both the silica-like and the gibbsite-like basal plane of the kaolinite particles. We observe that both basal planes do carry charge that varies with pH and salt concentration. The silica facet was found to be negatively charged at pH 4 and above, whereas the gibbsite facet is positively charged at pH below 7 and negatively charged at pH above 7. Investigations in CaCl2 at pH 6 show that the surface charge on the gibbsite facet increases for concentration up to 10 mM CaCl2 and starts to decrease upon further increasing the salt concentration to 50 mM. The increase of surface charge at low concentration is explained by Ca2+ ion adsorption, while Cl– adsorption at higher CaCl2 concentrations partially neutralizes the surface charge. Atomic resolution imaging and density functional theory calculations corroborate these observations. They show that hydrated Ca2+ ions can spontaneously adsorb on the gibbsite facet of the kaolinite particle and form ordered surface structures, while at higher concentrations Cl– ions will co-adsorb, thereby changing the observed ordered surface structure. PMID:29140711

  7. Development of gas sensors using ZnO nanostructures

    Indian Academy of Sciences (India)

    Different ZnO nanostructures such as nanowires, nanobelts and tetrapods have been grown and used for preparation of thick film (with random grain boundaries) as well as isolated nanowire/nanobelt gas sensors. Sensitivity of different type of sensors has been studied to H2S and NO gases. The results show that the ...

  8. UV irradiation assisted growth of ZnO nanowires on optical fiber surface

    Energy Technology Data Exchange (ETDEWEB)

    Gong, Bo; Shi, Tielin; Liao, Guanglan; Li, Xiaoping; Huang, Jie; Zhou, Temgyuan; Tang, Zirong, E-mail: zirong@mail.hust.edu.cn

    2017-06-01

    Highlights: • A new fabrication process combined a hydrothermal process with UV irradiation from optical fiber is developed. • The growth of ZnO nanowires is efficient in the utilization of UV light. • A novel hybrid structure which integrates ZnO nanowires on optical fiber surface is synthesized. • The UV assisted growth of ZnO nanowires shows preferred orientation and better quality. • A mechanism of growing ZnO nanowires under UV irradiation is proposed. - Abstract: In this paper, a novel approach was developed for the enhanced growth of ZnO nanowires on optical fiber surface. The method combined a hydrothermal process with the efficient UV irradiation from the fiber core, and the effects of UV irradiation on the growth behavior of ZnO nanowires were investigated. The results show that UV irradiation had great effects on the preferred growth orientation and the quality of the ZnO nanowires. The crystallization velocity along the c-axis would increase rapidly with the increase of the irradiation power, while the growth process in the lateral direction was marginally affected by the irradiation. The structure of ZnO nanowires also shows less oxygen vacancy with UV irradiation of higher power. The developed approach is applicable for the efficient growth of nanowires on the fiber surface, and the ZnO nanowires/optical fiber hybrid structures have great potentials for a wide variety of applications such as optical fiber sensors and probes.

  9. High-sensitivity accelerometer composed of ultra-long vertically aligned barium titanate nanowire arrays.

    Science.gov (United States)

    Koka, Aneesh; Sodano, Henry A

    2013-01-01

    A configuration that shows great promise in sensing applications is vertically aligned piezoelectric nanowire arrays that allow facile interfacing with electrical interconnects. Nano-electromechanical systems developed using piezoelectric nanowires have gained interest primarily for their potential in energy harvesting applications, because they are able to convert several different sources of mechanical energy into useful electrical power. To date, no results have demonstrated the capability to use aligned piezoelectric nanowire arrays as a highly accurate nano-electromechanical system based dynamic sensor with a wide operating bandwidth and unity coherence. Here we report the growth of vertically aligned (~45 μm long) barium titanate nanowire arrays, realized through a two-step hydrothermal synthesis approach, and demonstrate their use as an accurate accelerometer. High sensitivity of up to 50 mV g(-1) is observed from the sensor composed of vertically aligned barium titanate nanowire arrays, thus providing performance comparable to many of the commercial accelerometer systems.

  10. Intrinsic Ge nanowire nonvolatile memory based on a simple core-shell structure

    Science.gov (United States)

    Chen, Wen-Hua; Liu, Chang-Hai; Li, Qin-Liang; Sun, Qi-Jun; Liu, Jie; Gao, Xu; Sun, Xuhui; Wang, Sui-Dong

    2014-02-01

    Intrinsic Ge nanowires (NWs) with a Ge core covered by a thick Ge oxide shell are utilized to achieve nanoscale field-effect transistor nonvolatile memories, which show a large memory window and a high ON/OFF ratio with good retention. The retainable surface charge trapping is considered to be responsible for the memory effect, and the Ge oxide shell plays a key role as the insulating tunneling dielectric which must be thick enough to prevent stored surface charges from leaking out. Annealing the device in air is demonstrated to be a simple and effective way to attain thick Ge oxide on the Ge NW surface, and the Ge-NW-based memory corresponding to thick Ge oxide exhibits a much better retention capability compared with the case of thin Ge oxide.

  11. The Effect of Superparamagnetic Iron Oxide Nanoparticle Surface Charge on Antigen Cross-Presentation.

    Science.gov (United States)

    Mou, Yongbin; Xing, Yun; Ren, Hongyan; Cui, Zhihua; Zhang, Yu; Yu, Guangjie; Urba, Walter J; Hu, Qingang; Hu, Hongming

    2017-12-01

    Magnetic nanoparticles (NPs) of superparamagnetic iron oxide (SPIO) have been explored for different kinds of applications in biomedicine, mechanics, and information. Here, we explored the synthetic SPIO NPs as an adjuvant on antigen cross-presentation ability by enhancing the intracellular delivery of antigens into antigen presenting cells (APCs). Particles with different chemical modifications and surface charges were used to study the mechanism of action of antigen delivery. Specifically, two types of magnetic NPs, γFe 2 O 3 /APTS (3-aminopropyltrimethoxysilane) NPs and γFe 2 O 3 /DMSA (meso-2, 3-Dimercaptosuccinic acid) NPs, with the same crystal structure, magnetic properties, and size distribution were prepared. Then, the promotion of T-cell activation via dendritic cells (DCs) was compared among different charged antigen coated NPs. Moreover, the activation of the autophagy, cytosolic delivery of the antigens, and antigen degradation mediated by the proteasome and lysosome were measured. Our results indicated that positive charged γFe 2 O 3 /APTS NPs, but not negative charged γFe 2 O 3 /DMSA NPs, enhanced the cross-presentation ability of DCs. Increased cross-presentation ability induced by γFe 2 O 3 /APTS NPs was associated with increased cytosolic antigen delivery. On the contrary, γFe 2 O 3 /DMSA NPs was associated with rapid autophagy. Overall, our results suggest that antigen delivered in cytoplasm induced by positive charged particles is beneficial for antigen cross-presentation and T-cell activation. NPs modified with different chemistries exhibit diverse biological properties and differ greatly in their adjuvant potentials. Thus, it should be carefully considered many different effects of NPs to design effective and safe adjuvants.

  12. Role of plasma membrane surface charges in dictating the feasibility of membrane-nanoparticle interactions

    Science.gov (United States)

    Sinha, Shayandev; Jing, Haoyuan; Sachar, Harnoor Singh; Das, Siddhartha

    2017-12-01

    Receptor-ligand (R-L) binding mediated interactions between the plasma membrane (PM) and a nanoparticle (NP) require the ligand-functionalized NPs to come to a distance of separation (DOS) of at least dRL (length of the R-L complex) from the receptor-bearing membranes. In this letter, we establish that the membrane surface charges and the surrounding ionic environment dictate whether or not the attainment of such a critical DOS is possible. The negatively charged membrane invariably induces a negative electrostatic potential at the NP surface, repelling the NP from the membrane. This is countered by the attractive influences of the thermal fluctuations and van der Waals (vdw) interactions that drive the NP close to the membrane. For a NP approaching the membrane from a distance, the ratio of the repulsive (electrostatic) and attractive (thermal and vdW) effects balances at a critical NP-membrane DOS of dg,c. For a given set of parameters, there can be two possible values of dg,c, namely, dg,c,1 and dg,c,2 with dg,c,1 ≫ dg,c,2. We establish that any R-L mediated NP-membrane interaction is possible only if dRL > dg,c,1. Therefore, our study proposes a design criterion for engineering ligands for a NP that will ensure the appropriate length of the R-L complex in order to ensure the successful membrane-NP interaction in the presence of a given electrostatic environment. Finally, we discuss the manner in which our theory can help designing ligand-grafted NPs for targeted drug delivery, design biomimetics NPs, and also explain various experimental results.

  13. Surface charge-conversion polymeric nanoparticles for photodynamic treatment of urinary tract bacterial infections

    International Nuclear Information System (INIS)

    Liu, Shijie; Shao, Chen; Qiao, Shenglin; Li, Lili; Qi, Guobin; Lin, Yaoxin; Qiao, Zengying; Wang, Hao

    2015-01-01

    Urinary tract infections are typical bacterial infections which result in a number of economic burdens. With increasing antibiotic resistance, it is urgent that new approaches are explored that can eliminate pathogenic bacteria without inducing drug resistance. Antimicrobial photodynamic therapy (PDT) is a new promising tactic. It is a gentle in situ photochemical reaction in which a photosensitizer (PS) generates reactive oxygen species (ROS) under laser irradiation. In this work, we have demonstrated Chlorin e6 (Ce6) encapsulated charge-conversion polymeric nanoparticles (NPs) for efficiently targeting and killing pathogenic bacteria in a weakly acidic urinary tract infection environment. Owing to the surface charge conversion of NPs in an acidic environment, the NPs exhibited enhanced recognition for Gram-positive (ex. S. aureus) and Gram-negative (ex. E. coli) bacteria due to the charge interaction. Also, those NPs showed significant antibacterial efficacy in vitro with low cytotoxicity. The MIC value of NPs to E. coli is 17.91 μg ml −1 , compared with the free Ce6 value of 29.85 μg ml −1 . Finally, a mouse acute cystitis model was used to assess the photodynamic therapy effects in urinary tract infections. A significant decline (P < 0.05) in bacterial cells between NPs and free Ce6 occurred in urine after photodynamic therapy treatment. And the plated counting results revealed a remarkable bacterial cells drop (P < 0.05) in the sacrificed bladder tissue. Above all, this nanotechnology strategy opens a new door for the treatment of urinary tract infections with minimal side effects. (paper)

  14. Cutaneous and mucosal human papillomaviruses differ in net surface charge, potential impact on tropism

    Directory of Open Access Journals (Sweden)

    Wibom Carl

    2008-10-01

    Full Text Available Abstract Papillomaviruses can roughly be divided into two tropism groups, those infecting the skin, including the genus beta PVs, and those infecting the mucosa, predominantly genus alpha PVs. The L1 capsid protein determines the phylogenetic separation between beta types and alpha types and the L1 protein is most probably responsible for the first interaction with the cell surface. Virus entry is a known determinant for tissue tropism and to study if interactions of the viral capsid with the cell surface could affect HPV tropism, the net surface charge of the HPV L1 capsid proteins was analyzed and HPV-16 (alpha and HPV-5 (beta with a mucosal and cutaneous tropism respectively were used to study heparin inhibition of uptake. The negatively charged L1 proteins were all found among HPVs with cutaneous tropism from the beta- and gamma-PV genus, while all alpha HPVs were positively charged at pH 7.4. The linear sequence of the HPV-5 L1 capsid protein had a predicted isoelectric point (pI of 6.59 and a charge of -2.74 at pH 7.4, while HPV-16 had a pI of 7.95 with a charge of +2.98, suggesting no interaction between HPV-5 and the highly negative charged heparin. Furthermore, 3D-modelling indicated that HPV-5 L1 exposed more negatively charged amino acids than HPV-16. Uptake of HPV-5 (beta and HPV-16 (alpha was studied in vitro by using a pseudovirus (PsV assay. Uptake of HPV-5 PsV was not inhibited by heparin in C33A cells and only minor inhibition was detected in HaCaT cells. HPV-16 PsV uptake was significantly more inhibited by heparin in both cells and completely blocked in C33A cells.

  15. The Effect of Superparamagnetic Iron Oxide Nanoparticle Surface Charge on Antigen Cross-Presentation

    Science.gov (United States)

    Mou, Yongbin; Xing, Yun; Ren, Hongyan; Cui, Zhihua; Zhang, Yu; Yu, Guangjie; Urba, Walter J.; Hu, Qingang; Hu, Hongming

    2017-01-01

    Magnetic nanoparticles (NPs) of superparamagnetic iron oxide (SPIO) have been explored for different kinds of applications in biomedicine, mechanics, and information. Here, we explored the synthetic SPIO NPs as an adjuvant on antigen cross-presentation ability by enhancing the intracellular delivery of antigens into antigen presenting cells (APCs). Particles with different chemical modifications and surface charges were used to study the mechanism of action of antigen delivery. Specifically, two types of magnetic NPs, γFe2O3/APTS (3-aminopropyltrimethoxysilane) NPs and γFe2O3/DMSA (meso-2, 3-Dimercaptosuccinic acid) NPs, with the same crystal structure, magnetic properties, and size distribution were prepared. Then, the promotion of T-cell activation via dendritic cells (DCs) was compared among different charged antigen coated NPs. Moreover, the activation of the autophagy, cytosolic delivery of the antigens, and antigen degradation mediated by the proteasome and lysosome were measured. Our results indicated that positive charged γFe2O3/APTS NPs, but not negative charged γFe2O3/DMSA NPs, enhanced the cross-presentation ability of DCs. Increased cross-presentation ability induced by γFe2O3/APTS NPs was associated with increased cytosolic antigen delivery. On the contrary, γFe2O3/DMSA NPs was associated with rapid autophagy. Overall, our results suggest that antigen delivered in cytoplasm induced by positive charged particles is beneficial for antigen cross-presentation and T-cell activation. NPs modified with different chemistries exhibit diverse biological properties and differ greatly in their adjuvant potentials. Thus, it should be carefully considered many different effects of NPs to design effective and safe adjuvants.

  16. Surface charge-conversion polymeric nanoparticles for photodynamic treatment of urinary tract bacterial infections

    Science.gov (United States)

    Liu, Shijie; Qiao, Shenglin; Li, Lili; Qi, Guobin; Lin, Yaoxin; Qiao, Zengying; Wang, Hao; Shao, Chen

    2015-12-01

    Urinary tract infections are typical bacterial infections which result in a number of economic burdens. With increasing antibiotic resistance, it is urgent that new approaches are explored that can eliminate pathogenic bacteria without inducing drug resistance. Antimicrobial photodynamic therapy (PDT) is a new promising tactic. It is a gentle in situ photochemical reaction in which a photosensitizer (PS) generates reactive oxygen species (ROS) under laser irradiation. In this work, we have demonstrated Chlorin e6 (Ce6) encapsulated charge-conversion polymeric nanoparticles (NPs) for efficiently targeting and killing pathogenic bacteria in a weakly acidic urinary tract infection environment. Owing to the surface charge conversion of NPs in an acidic environment, the NPs exhibited enhanced recognition for Gram-positive (ex. S. aureus) and Gram-negative (ex. E. coli) bacteria due to the charge interaction. Also, those NPs showed significant antibacterial efficacy in vitro with low cytotoxicity. The MIC value of NPs to E. coli is 17.91 μg ml-1, compared with the free Ce6 value of 29.85 μg ml-1. Finally, a mouse acute cystitis model was used to assess the photodynamic therapy effects in urinary tract infections. A significant decline (P < 0.05) in bacterial cells between NPs and free Ce6 occurred in urine after photodynamic therapy treatment. And the plated counting results revealed a remarkable bacterial cells drop (P < 0.05) in the sacrificed bladder tissue. Above all, this nanotechnology strategy opens a new door for the treatment of urinary tract infections with minimal side effects.

  17. ZnO nanowires for the modification of evanescence-field sensors and the development of novel solar cells; ZnO-Nanodraehte zur Modifizierung von Evaneszenzfeldsensoren und der Entwicklung neuartiger Solarzellen

    Energy Technology Data Exchange (ETDEWEB)

    Boerner, Susanne

    2008-10-02

    The photoluminescence of single structures and the nanowire ensemble were analyzed and compared. This pursued in dependence on the excitation density and the sample temperature. The excitonic emission contributes essentially to the near-band-edge photoluminescence. The ZnO nanowire ensemble exhibits a laser threshold of 500 kW/cm{sup 2} at room temperature. To the photoluminescence spectra the single exciton processes were assigned. The wave-guiding properties were practically detected by means of optical microscopy and micromanipulation. While the main topic of this thesis lied in the analysis of the optical properties of the ZnO nanowires in the last part the implementation of nanostructures in hybrid solar cells was discussed and first results of the characterization of the material complex of p-conducting polymer (Clevios P) and ZnO nanowires presented.

  18. Silicon nanowire hybrid photovoltaics

    KAUST Repository

    Garnett, Erik C.

    2010-06-01

    Silicon nanowire Schottky junction solar cells have been fabricated using n-type silicon nanowire arrays and a spin-coated conductive polymer (PEDOT). The polymer Schottky junction cells show superior surface passivation and open-circuit voltages compared to standard diffused junction cells with native oxide surfaces. External quantum efficiencies up to 88% were measured for these silicon nanowire/PEDOT solar cells further demonstrating excellent surface passivation. This process avoids high temperature processes which allows for low-cost substrates to be used. © 2010 IEEE.

  19. The impact of membrane surface charges on the ion transport in MoS2 nanopore power generators

    Science.gov (United States)

    Huang, Zhuo; Zhang, Yan; Hayashida, Tomoki; Ji, Ziwei; He, Yuhui; Tsutsui, Makusu; Miao, Xiang Shui; Taniguchi, Masateru

    2017-12-01

    Recent experiments demonstrated giant osmotic effects induced in a single-atomic-layer MoS2 nanopore by imposing a KCl concentration bias, thereby highlighting the prospect of ultrathin nanopores as power generators. In this work, we report on an electrokinetic analysis of the ionic transport in the MoS2 nanopore system. By taking membrane surface chemistry into account, we found profound roles of surface charges in and out of the nanopore on the cross-pore ion transport, which shed light on the intriguing experimental observations of a high pore conductance with a large open-circuit voltage in the MoS2 system. The present work establishes a theoretical model capable of dealing with ultrathin membrane surface charges for evaluating the energy conversion performance of nanopore power generators constructed with two-dimensional materials.

  20. Multispectral absorptance from large-diameter InAsSb nanowire arrays in a single epitaxial growth on silicon

    Science.gov (United States)

    Robson, Mitchell; Azizur-Rahman, Khalifa M.; Parent, Daniel; Wojdylo, Peter; Thompson, David A.; LaPierre, Ray R.

    2017-12-01

    Vertical III-V nanowires are capable of resonant absorption at specific wavelengths by tuning the nanowire diameter, thereby exceeding the absorption of equivalent thin films. These properties may be exploited to fabricate multispectral infrared (IR) photodetectors, directly integrated with Si, without the need for spectral filters or vertical stacking of heterostructures as required in thin film devices. In this study, multiple InAsSb nanowire arrays were grown simultaneously on Si by molecular beam epitaxy with nanowire diameter controlled by the nanowire period (spacing between nanowires). This is the first such study of patterned InAsSb nanowires where control of nanowire diameter and multispectral absorption are demonstrated. The antimony flux was used to control axial and radial growth rates using a selective-area catalyst-free growth method, achieving large diameters, spanning 440–520 nm, which are necessary for optimum IR absorption. Fourier transform IR spectroscopy revealed IR absorptance peaks due to the HE11 resonance of the nanowire arrays in agreement with optical simulations. Due to the dependence of the HE11 resonance absorption on nanowire diameter, multispectral absorption was demonstrated in a single material system and a single epitaxial growth step without the need for bandgap tuning. This work demonstrates the potential of InAsSb nanowires for multispectral photodetectors and sensor arrays in the short-wavelength IR region.

  1. The surface charge of oxides and its role in deposition and transport of radioactivity in water-cooled nuclear reactors

    International Nuclear Information System (INIS)

    Tewari, P.H.; Campbell, A.B.

    1972-01-01

    The role of surface charges in the deposition of suspended oxides on surfaces is discussed. Results of deposition of corrosion-product oxides on surfaces at room temperature and 200 o C are reported. These, together with results of the specific adsorption of Co(II) on negatively charged Fe 3 O 4 suspensions are used to explain the growth of Co-60 radiation fields in water-cooled reactors. (author)

  2. Systematic investigation of the barrier discharge operation in helium, nitrogen, and mixtures: discharge development, formation and decay of surface charges

    Science.gov (United States)

    Tschiersch, R.; Bogaczyk, M.; Wagner, H.-E.

    2014-09-01

    As a logical extension to previous investigations of the barrier discharge (BD) in helium and nitrogen, the present work reports on the operation in any mixtures of both pure gases. Using a well-established plane-parallel discharge cell configuration allows to study the influence of the He/N2 mixing ratio on the formation of different discharge modes. Their characterization was made by measuring the discharge emission development together with the formation and decay of surface charges on a bismuth silicon oxide (Bi12SiO20, BSO) crystal. This was realized by the simultaneous application of the spatio-temporally resolved optical emission spectroscopy, and the electro-optic Pockels effect in combination with a CCD high speed camera. The existence diagram for diffuse and filamentary BDs was determined by varying the amplitude and shape of the applied voltage. Over the entire range of the He/N2 ratio, the diffuse mode can be operated at moderate voltage amplitudes whereas filamentation occurs at significant overvoltage and is favoured by a high voltage slew rate. Irrespective of the discharge mode, the overall charge transfer during a discharge breakdown is found to be in excellent agreement with the amount of accumulated surface charges. An exponential decay of the surface charge deposited on the BSO crystal is induced by LED illumination beyond a typical discharge cycle. During the decay process, a broadening of the radial profiles of positive as well as negative surface charge spots originating from previous microdischarges is observed. The investigations contribute to a better understanding of the charge accumulation at a dielectric.

  3. Effect of inorganic and organic depressants on the cationic flotation and surface charge of rhodonite-rhodochrosite

    OpenAIRE

    Duarte, Renata Santos; Lima, Rosa Malena Fernandes; Leão, Versiane Albis

    2015-01-01

    Abstract Silicates (rhodonite, tephroite, spessartine) and the carbonate (rhodochrosite) of manganese are of economic interest in silicate-carbonated manganese ores. The recovery of both mineral classes by flotation constitutes a challenge; rhodochrosite is a slightly soluble mineral that can release Mn2+ ions in pulp. In this work, the effects of inorganic and organic depressants on the cationic flotation at pH 10 with ether amine acetate and the surface charges of rhodonite and rhodochrosit...

  4. Adsorption of cellular peptides of Microcystis aeruginosa and two herbicides onto activated carbon. Effect of surface charge and interactions

    Czech Academy of Sciences Publication Activity Database

    Hnaťuková, Petra; Kopecká, Ivana; Pivokonský, Martin

    2011-01-01

    Roč. 45, č. 11 (2011), s. 3359-3368 ISSN 0043-1354 R&D Projects: GA AV ČR IAA200600902; GA ČR GPP105/10/P515 Institutional research plan: CEZ:AV0Z20600510 Keywords : cellular organic matter * granular activated carbon * molecular weight distribution * surface charge * cyanobacterial peptides Subject RIV: BK - Fluid Dynamics Impact factor: 4.865, year: 2011

  5. Surface-charge-induced orientation of interfacial water suppresses heterogeneous ice nucleation on α-alumina (0001)

    Science.gov (United States)

    Abdelmonem, Ahmed; Backus, Ellen H. G.; Hoffmann, Nadine; Sánchez, M. Alejandra; Cyran, Jenée D.; Kiselev, Alexei; Bonn, Mischa

    2017-06-01

    Surface charge is one of the surface properties of atmospheric aerosols, which has been linked to heterogeneous ice nucleation and hence cloud formation, microphysics, and optical properties. Despite the importance of surface charge for ice nucleation, many questions remain on the molecular-level mechanisms at work. Here, we combine droplet-freezing assay studies with vibrational sum frequency generation (SFG) spectroscopy to correlate interfacial water structure to surface nucleation strength. We study immersion freezing of aqueous solutions of various pHs on the atmospherically relevant aluminum oxide α-Al2O3 (0001) surface using an isolated droplet on the surface. The high-pH solutions freeze at temperatures higher than that of the low-pH solution, while the neutral pH has the highest freezing temperature. On the molecular level, the SFG spectrum of the interfacial water changes substantially upon freezing. At all pHs, crystallization leads to a reduction of intensity of the 3400 cm-1 water resonance, while the 3200 cm-1 intensity drops for low pH but increases for neutral and high pHs. We find that charge-induced surface templating suppresses nucleation, irrespective of the sign of the surface charge. Heterogeneous nucleation is most efficient for the nominally neutral surface.

  6. Effect of surface charge on the colloidal stability and in vitro uptake of carboxymethyl dextran-coated iron oxide nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Ayala, Vanessa; Herrera, Adriana P.; Latorre-Esteves, Magda; Torres-Lugo, Madeline [University of Puerto Rico, Department of Chemical Engineering (United States); Rinaldi, Carlos, E-mail: carlos.rinaldi@bme.ufl.edu [University of Florida, J. Crayton Pruitt Family Department of Biomedical Engineering (United States)

    2013-08-15

    Nanoparticle physicochemical properties such as surface charge are considered to play an important role in cellular uptake and particle-cell interactions. In order to systematically evaluate the role of surface charge on the uptake of iron oxide nanoparticles, we prepared carboxymethyl-substituted dextrans with different degrees of substitution, ranging from 38 to 5 groups per chain, and reacted them using carbodiimide chemistry with amine-silane-coated iron oxide nanoparticles with narrow size distributions in the range of 33-45 nm. Surface charge of carboxymethyl-substituted dextran-coated nanoparticles ranged from -50 to 5 mV as determined by zeta potential measurements, and was dependent on the number of carboxymethyl groups incorporated in the dextran chains. Nanoparticles were incubated with CaCo-2 human colon cancer cells. Nanoparticle-cell interactions were observed by confocal laser scanning microscopy and uptake was quantified by elemental analysis using inductively coupled plasma mass spectroscopy. Mechanisms of internalization were inferred using pharmacological inhibitors for fluid-phase, clathrin-mediated, and caveola-mediated endocytosis. Results showed increased uptake for nanoparticles with greater negative charge. Internalization patterns suggest that uptake of the most negatively charged particles occurs via non-specific interactions.

  7. The effects of surface-charged submicron polystyrene particles on the structure and performance of PSF forward osmosis membrane

    Science.gov (United States)

    Zuo, Hao-Ran; Fu, Jia-Bei; Cao, Gui-Ping; Hu, Nian; Lu, Hui; Liu, Hui-Qing; Chen, Peng-Peng; Yu, Jie

    2018-04-01

    Monodisperse surface-charged submicron polystyrene particles were designed, synthesized, and blended into polysulfone (PSF) support layer to prepare forward osmosis (FO) membrane with high performance. The membrane incorporated with particles were characterized with respect to morphology, porosity, and internal osmotic pressure (IOP). Results showed that the polymer particles not only increased the hydrophilicity and porosity of support layer, but also generated considerable IOP, which helped markedly decreasing the structure parameter from 1550 to 670 μm. The measured mass transfer parameters further confirmed the beneficial effects of the surface-charged submicron polymer particles on the performance of FO membrane. For instance, the water permeability coefficient (5.37 L m-2 h-1 bar-1) and water flux (49.7 L m-2 h-1) of the FO membrane incorporated with 5 wt% particles were almost twice as much as that of FO membrane without incorporation. This study suggests that monodisperse surface-charged submicron polymer particles are potential modifiers for improving the performance of FO membranes.

  8. Synthesis of copper telluride nanowires using template-based ...

    Indian Academy of Sciences (India)

    using air and chloroform, acetone, ethanol, glycerol, distilled water as liquids having dielectric constants 1, 4·81,. 8·93, 21, 24·55, 42·5 and 80·1, respectively. The results unequivocally prove that copper telluride nanowires can be fabricated as chemical sensors with enhanced sensitivity and reliability. Keywords. CuTe ...

  9. Multi-diameter silicon nanowires: Fabrication, characterization, and modeling

    Science.gov (United States)

    Alagoz, Arif Sinan

    Nanotechnology is a rapidly expanding interdisciplinary field offering novel devices for broad range of applications. Quantum effects and surface to volume ratio of nanostructures are strongly size dependent, and redefine material properties at nanoscale. Silicon is one of the most promising materials for next generation nanostructured transistors, photonics devices, Li-ion batteries, photovoltaic solar cells, and thermoelectric energy generators. Since electrical, optical, and mechanical properties of nanostructures strongly depend on their shape, size, periodicity, and crystal structure; it is crucial to control these parameters in order to optimize device performance for targeted applications. This dissertation is intended to develop a low-cost, low-temperature, high-throughput, and large-area nanowire fabrication method that can produce well-ordered arrays of hierarchical single-crystal silicon nanowires at large scale by using nanosphere lithography and metal-assisted chemical etching. Nanowire morphology was characterized by using scanning electron microscope and optical properties of nanowire arrays were modeled with the help of finite-difference-time domain method. These novel multi-diameter silicon nanowire arrays have the potential applications in many fields including but not limited to next generation nanowire solar cells to field ionization gas sensors.

  10. Biofunctionalized Magnetic Nanowires

    KAUST Repository

    Kosel, Jurgen

    2013-12-19

    Magnetic nanowires can be used as an alternative method overcoming the limitations of current cancer treatments that lack specificity and are highly cytotoxic. Nanowires are developed so that they selectively attach to cancer cells via antibodies, potentially destroying them when a magnetic field induces their vibration. This will transmit a mechanical force to the targeted cells, which is expected to induce apoptosis on the cancer cells.

  11. Multispectral imaging with vertical silicon nanowires.

    Science.gov (United States)

    Park, Hyunsung; Crozier, Kenneth B

    2013-01-01

    Multispectral imaging is a powerful tool that extends the capabilities of the human eye. However, multispectral imaging systems generally are expensive and bulky, and multiple exposures are needed. Here, we report the demonstration of a compact multispectral imaging system that uses vertical silicon nanowires to realize a filter array. Multiple filter functions covering visible to near-infrared (NIR) wavelengths are simultaneously defined in a single lithography step using a single material (silicon). Nanowires are then etched and embedded into polydimethylsiloxane (PDMS), thereby realizing a device with eight filter functions. By attaching it to a monochrome silicon image sensor, we successfully realize an all-silicon multispectral imaging system. We demonstrate visible and NIR imaging. We show that the latter is highly sensitive to vegetation and furthermore enables imaging through objects opaque to the eye.

  12. Scaling Laws for NanoFET Sensors

    OpenAIRE

    Zhou, Fu-Shan; Wei, Qi-Huo

    2007-01-01

    The sensitive conductance change of semiconductor nanowires and carbon nanotubes in response to binding of charged molecules provide a novel sensing modality which is generally denoted as nanoFET sensors. In this paper, we study the scaling laws of nanoplate FET sensors by simplifying nanoplates as random resistor networks with molecular receptors sitting on lattice sites. Nanowire/tube FETs are included as the limiting cases where the device width goes small. Computer simulations show that t...

  13. Microscopic and magnetic properties of template assisted electrodeposited iron nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Irshad, M. I., E-mail: imrancssp@gmail.com; Mohamed, N. M., E-mail: noranimuti-mohamed@petronas.com.my; Yar, A., E-mail: asfandyarhargan@gmail.com [Department of Fundamental & Applied Sciences, Universiti Teknologi PETRONAS, 31750 PERAK (Malaysia); Ahmad, F., E-mail: faizahmad@petronas.com.my; Abdullah, M. Z., E-mail: zaki-abdullah@petronas.com.my [Department of Mechanical Engineering, Universiti Teknologi PETRONAS, 31750 PERAK (Malaysia)

    2015-07-22

    Nanowires of magnetic materials such as Iron, nickel, cobalt, and alloys of them are one of the most widely investigated structures because of their possible applications in high density magnetic recording media, sensor elements, and building blocks in biological transport systems. In this work, Iron nanowires have been prepared by electrodeposition technique using Anodized Aluminium Oxide (AAO) templates. The electrolyte used consisted of FeSO{sub 4.}6H{sub 2}O buffered with H{sub 3}BO{sub 3} and acidized by dilute H{sub 2}SO{sub 4}. FESEM analysis shows that the asdeposited nanowires are parallel to one another and have high aspect ratio with a reasonably high pore-filing factor. To fabricate the working electrode, a thin film of copper (∼ 220 nm thick) was coated on back side of AAO template by e-beam evaporation system to create electrical contact with the external circuit. The TEM results show that electrodeposited nanowires have diameter around 100 nm and are polycrystalline in structure. Magnetic properties show the existence of anisotropy for in and out of plane configuration. These nanowires have potential applications in magnetic data storage, catalysis and magnetic sensor applications.

  14. Conformational response of the phosphatidylcholine headgroup to bilayer surface charge: torsion angle constraints from dipolar and quadrupolar couplings in bicelles.

    Science.gov (United States)

    Semchyschyn, Darlene J; Macdonald, Peter M

    2004-02-01

    The effects of bilayer surface charge on the conformation of the phosphocholine group of phosphatidylcholine were investigated using a torsion angle analysis of quadrupolar and dipolar splittings in, respectively, (2)H and (13)C NMR spectra of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) labelled in the phosphocholine group with either deuterons (POPC-alpha-d(2), POPC-beta-d(2) and POPC-gamma-d(9)) or carbon-13 (POPC-alpha-(13)C and POPC-alphabeta-(13)C(2)) and incorporated into magnetically aligned bicelles containing various amounts of either the cationic amphiphile 1,2-dimyristoyl-3-trimethylammoniumpropane (DMTAP) or the anionic amphiphile 1,2-dimyristoyl-sn-glycero-3-phosphoglycerol (DMPG). Three sets of quadrupolar splittings, one from each of the three deuteron labelling positions, and three sets of dipolar splittings ((13)C(alpha)-(31)P, (13)C(alpha)-(13)C(beta), (13)C(beta)-(14)N), were measured at each surface charge, along with the (31)P residual chemical shift anisotropy. The torsion angle analysis assumed fast anisotropic rotation of POPC about its long molecular axis, thus projecting all NMR interactions onto that director axis of motion. Dipolar, quadrupolar and chemical shift anisotropies were calculated as a function of the phosphocholine internal torsion angles by first transforming into a common reference frame affixed to the phosphocholine group prior to motional averaging about the director axis. A comparison of experiment and calculation provided the two order parameters specifying the director orientation relative to the molecule, plus the torsion angles alpha(3), alpha(4) and alpha(5). Surface charge was found to have little effect on the torsion angle alpha(5) (rotations about C(alpha)-C(beta)), but to have large and inverse effects on torsion angles alpha(3) [rotations about P-O(11)] and alpha(4) [rotations about O(11)-C(alpha)], yielding a net upwards tilt of the P-N vector in the presence of cationic surface charge, and a

  15. Wettability control by DLC coated nanowire topography

    Science.gov (United States)

    Li, Zihui; Meng, Fanhao; Liu, Xuanyong

    2011-04-01

    Here we have developed a convenient method to fabricate wettability controllable surfaces that can be applied to various nanostructured surfaces with complex shapes for different industrial needs. Diamond-like carbon (DLC) films were synthesized on titanium substrate with a nanowire structured surface using plasma immersion ion implantation and deposition (PIII&D). The nanostructure of the DLC films was characterized by field emission scanning electron microscopy and found to grow in a rippling layer-by-layer manner. Raman spectroscopy was used to investigate the different bonding presented in the DLC films. To determine the wettability of the samples, water contact angles were measured and found to vary in the range of 50°-141°. The results indicated that it was critical to construct a proper surface topography for high hydrophobicity, while suitable ID/IG and sp2/sp3 ratios of the DLC films had a minor contribution. Superhydrophobicity could be achieved by further CF4 implantation on suitably structured DLC films and was attributed to the existence of fluorine. In order to maintain the nanostructure during CF4 implantation, it was favorable to pre-deposit an appropriate carbon content on the nanostructure, as a nanostructure with low carbon content would be deformed during CF4 implantation due to local accumulation of surface charge and the following discharge resulting from the low conductivity.

  16. Wettability control by DLC coated nanowire topography.

    Science.gov (United States)

    Li, Zihui; Meng, Fanhao; Liu, Xuanyong

    2011-04-01

    Here we have developed a convenient method to fabricate wettability controllable surfaces that can be applied to various nanostructured surfaces with complex shapes for different industrial needs. Diamond-like carbon (DLC) films were synthesized on titanium substrate with a nanowire structured surface using plasma immersion ion implantation and deposition (PIII&D). The nanostructure of the DLC films was characterized by field emission scanning electron microscopy and found to grow in a rippling layer-by-layer manner. Raman spectroscopy was used to investigate the different bonding presented in the DLC films. To determine the wettability of the samples, water contact angles were measured and found to vary in the range of 50°-141°. The results indicated that it was critical to construct a proper surface topography for high hydrophobicity, while suitable I(D)/I(G) and sp²/sp³ ratios of the DLC films had a minor contribution. Superhydrophobicity could be achieved by further CF₄ implantation on suitably structured DLC films and was attributed to the existence of fluorine. In order to maintain the nanostructure during CF₄ implantation, it was favorable to pre-deposit an appropriate carbon content on the nanostructure, as a nanostructure with low carbon content would be deformed during CF₄ implantation due to local accumulation of surface charge and the following discharge resulting from the low conductivity.

  17. Influence of Surface Charge/Potential of a Gold Electrode on the Adsorptive/Desorptive Behaviour of Fibrinogen

    International Nuclear Information System (INIS)

    Dargahi, Mahdi; Konkov, Evgeny; Omanovic, Sasha

    2015-01-01

    Highlights: • Adsorptive/desorptive behavior of fibrinogen (FG) on an electrochemically-polarized gold substrate is reported. • The adsorption affinity of FG (afFG) is constant on a negatively-charged substrate surface. • The afFG increases linearly with an increase in positive substrate surface charge. • The FG adsorption kinetics is strongly dependant on substrate surface charge. • The adsorbed FG layer can be desorbed by electrochemical evolution of hydrogen and oxygen. - Abstract: The effect of gold substrate surface charge (potential) on adsorptive/desorptive behaviour of fibrinogen (FG) was studied by employing differential capacitance (DC) and polarization modulated infrared reflection absorption spectroscopy (PM-IRRAS), in terms of FG adsorption thermodynamics, kinetics, and desorption kinetics. The gold substrate surface charge was modulated in-situ within the electrochemical double-layer region by means of electrochemical potentiostatic polarization in a FG-containing electrolyte, thus avoiding the interference of other physico-chemical properties of the gold surface on FG’s interfacial behaviour. The FG adsorption equilibrium was modeled using the Langmuir isotherm. Highly negative values of apparent Gibbs free energy of adsorption (ranging from from −52.1 ± 0.4 to −55.8 ± 0.8 kJ mol −1 , depending on the FG adsorption potential) indicated a highly spontaneous and strong adsorption of FG onto the gold surface. The apparent Gibbs free energy of adsorption was found to be independent of surface charge when the surface was negatively charged. However, when the gold surface was positively charged, the apparent Gibbs free energy of adsorption exhibited a pronounced linear relationship with the surface charge, shifting to more negative values with an increase in positive electrode potential. The adsorption kinetics of FG was also found to be dependent on gold surface charge in a similar manner to the apparent Gibbs free energy of adsorption

  18. Microfabricated Formaldehyde Gas Sensors

    Directory of Open Access Journals (Sweden)

    Karen C. Cheung

    2009-11-01

    Full Text Available Formaldehyde is a volatile organic compound that is widely used in textiles, paper, wood composites, and household materials. Formaldehyde will continuously outgas from manufactured wood products such as furniture, with adverse health effects resulting from prolonged low-level exposure. New, microfabricated sensors for formaldehyde have been developed to meet the need for portable, low-power gas detection. This paper reviews recent work including silicon microhotplates for metal oxide-based detection, enzyme-based electrochemical sensors, and nanowire-based sensors. This paper also investigates the promise of polymer-based sensors for low-temperature, low-power operation.

  19. Facile Synthesis of Ultrafine Hematite Nanowire Arrays in Mixed Water-Ethanol-Acetic Acid Solution for Enhanced Charge Transport and Separation.

    Science.gov (United States)

    Wang, Jian; Wang, Menglong; Zhang, Tao; Wang, Zhiqiang; Guo, Penghui; Su, Jinzhan; Guo, Liejin

    2018-04-03

    Nanostructure engineering is of great significance for semiconductor electrode to achieve high photoelectrochemical performance. Herein, we report a novel strategy to fabricate ultrafine hematite (α-Fe 2 O 3 ) nanowire arrays in a mixed water-ethanol-acetic acid (WEA) solvent. To the best of our knowledge, this is the first report on direct growth of ultrafine (∼10 nm) α-Fe 2 O 3 nanowire arrays on fluorine-doped tin oxide substrates through solution-based fabrication process. The effect of WEA ratio on the morphology of nanowires has been systematically studied to understand the formation mechanism. Photoelectrochemical measurements were conducted on both Ti-treated α-Fe 2 O 3 nanowire and nanorod photoelectrodes. It reveals that α-Fe 2 O 3 nanowire electrode has higher photocurrent and charge separation efficiencies than nanorod electrode if the carrier concentration and space-charge carrier width are in the same order of magnitude. Normalized by electrochemically active surface area, the Ti-treated α-Fe 2 O 3 nanowire electrode obtains 6.4 times higher specific photocurrent density than nanorod electrode. This superiority of nanowires arises from the higher bulk and surface charge separation efficiencies, which could be partly attributed to reduced distance that holes must transfer to reach the semiconductor-liquid junction.

  20. Generating electricity from biofluid with a nanowire-based biofuel cell for self-powered nanodevices

    Energy Technology Data Exchange (ETDEWEB)

    Pan, Caofeng; Wu, Hui; Ahmad, Mashkoor; Luo, Zhixiang; Xie, Jianbo; Yan, Xinxu; Wu, Lihua; Zhu, Jing [Beijing National Center for Electron Microscopy, Laboratory of Advanced Materials, State Key Laboratory of New Ceramics and Fine Processing, Department of Material Science and Engineering, Tsinghua University, Beijing 100084 (China); The National Center for Nanoscience and Technology (NCNST) of China, Beijing 100080 (China); Fang, Ying; Li, Qiang [The National Center for Nanoscience and Technology (NCNST) of China, Beijing 100080 (China); Wang, Zhong Lin [School Materials Science and Engineering, Georgia Institute of Technology, Atlanta Georgia 30332-0245 (United States)

    2010-12-14

    We report a nanowire-based biofuel cell based on a single proton conductive polymer nanowire for converting chemical energy from biofluids, such as glucose/blood, into electricity, with glucose oxidase and laccase as catalyst. The glucose is supplied from the biofluid, the nanowire serves as the proton conductor, and the whole cell can be realized at the nano/micrometer scale. The biofuel cell composed of a single nanowire generates an output power as high as 0.5-3 {mu}W, and it has been integrated with a set of nanowire-based sensors for performing self-powered sensing. This study shows the feasibility of building self-powered nanodevices for the biological sciences, environmental monitoring, defense technology, and even personal electronics. (Copyright copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  1. Connecting membrane fluidity and surface charge to pore-forming antimicrobial peptides resistance by an ANN-based predictive model.

    Science.gov (United States)

    Mehla, Jitender; Sood, S K

    2013-05-01

    Efficiency of antibacterial chemotherapy is gradually more challenged by the emergence of pathogenic strains exhibiting high levels of antibiotic resistance. Pore-forming antimicrobial peptides (PF-AMPs) such as alamethicin (Alm) are therefore in the focus of extensive research efforts. In the present study, an artificial neural network (ANN)-based quantitative structure-activity relationship (SAR) modeling of membrane phospholipids vs. PF-AMPs, in context to membrane fluidity and surface charge, was carried out. We observed that the potency of PF-AMPs depends on the fatty acyl chain and polar head group of phospholipids. Alm showed surface interactions with zwitterionic phospholipids however could penetrate deeper inside the hydrophobic core of anionic membranes. Here, the resistance developed in bacterial cells was coupled to membrane fluidity and surface charge, and simultaneously, these principles could be applied for combating resistance against PF-AMPs. The correlation coefficient between observed CR and predicted CR using ANN was found to be 0.757. Thus, ANN could be used as a reliable modeling method for predicting CR, given the structure of the biomimetic membrane in terms of membrane fluidity and surface charge. Fully explored mechanisms of resistance, a forward modeling step in the design cycle of AMPs, can be cross-linked to the inward modeling using ANN to complete the peptide design cycle. The SAR between membrane phospholipids and PF-AMPs could furnish valuable information regarding their design to provide us efficacious peptides against premier pathogens. So far, this is the only report available to predict and quantify interactions of PF-AMPs with membrane phospholipids.

  2. Effect of pullulan nanoparticle surface charges on HSA complexation and drug release behavior of HSA-bound nanoparticles.

    Directory of Open Access Journals (Sweden)

    Xiaojun Tao

    Full Text Available Nanoparticle (NP compositions such as hydrophobicity and surface charge are vital to determine the presence and amount of human serum albumin (HSA binding. The HSA binding influences drug release, biocompatibility, biodistribution, and intercellular trafficking of nanoparticles (NPs. Here, we prepared 2 kinds of nanomaterials to investigate HSA binding and evaluated drug release of HSA-bound NPs. Polysaccharides (pullulan carboxyethylated to provide ionic derivatives were then conjugated to cholesterol groups to obtain cholesterol-modified carboxyethyl pullulan (CHCP. Cholesterol-modified pullulan (CHP conjugate was synthesized with a similar degree of substitution of cholesterol moiety to CHCP. CHCP formed self-aggregated NPs in aqueous solution with a spherical structure and zeta potential of -19.9 ± 0.23 mV, in contrast to -1.21 ± 0.12 mV of CHP NPs. NPs could quench albumin fluorescence intensity with maximum emission intensity gradually decreasing up to a plateau at 9 to 12 h. Binding constants were 1.12 × 10(5 M(-1 and 0.70 × 10(5 M(-1 to CHP and CHCP, respectively, as determined by Stern-Volmer analysis. The complexation between HSA and NPs was a gradual process driven by hydrophobic force and inhibited by NP surface charge and shell-core structure. HSA conformation was altered by NPs with reduction of α-helical content, depending on interaction time and particle surface charges. These NPs could represent a sustained release carrier for mitoxantrone in vitro, and the bound HSA assisted in enhancing sustained drug release.

  3. Selective formation of tungsten nanowires

    Directory of Open Access Journals (Sweden)

    Bien Daniel

    2011-01-01

    Full Text Available Abstract We report on a process for fabricating self-aligned tungsten (W nanowires with polycrystalline silicon core. Tungsten nanowires as thin as 10 nm were formed by utilizing polysilicon sidewall transfer technology followed by selective deposition of tungsten by chemical vapor deposition (CVD using WF6 as the precursor. With selective CVD, the process is self-limiting whereby the tungsten formation is confined to the polysilicon regions; hence, the nanowires are formed without the need for lithography or for additional processing. The fabricated tungsten nanowires were observed to be perfectly aligned, showing 100% selectivity to polysilicon and can be made to be electrically isolated from one another. The electrical conductivity of the nanowires was characterized to determine the effect of its physical dimensions. The conductivity for the tungsten nanowires were found to be 40% higher when compared to doped polysilicon nanowires of similar dimensions.

  4. Hierarchical magnetic assembly of nanowires

    International Nuclear Information System (INIS)

    Hangarter, Carlos M; Rheem, Youngwoo; Yoo, Bongyoung; Yang, Eui-Hyeok; Myung, Nosang V

    2007-01-01

    Magnetic alignment is reported as a facile technique for assembling nanowires into hierarchical structures. Cross junction and T junction nanowire networks are demonstrated using a sequential alignment technique on unpatterned substrates and predefined lithographically patterned ferromagnetic electrodes. The formation of T junctions prevails as nanowires from the first alignment behave as ferromagnetic electrodes under the external magnetic field of the second alignment. The presence of prefabricated ferromagnetic electrodes dominates dipole interactions of localized nanowires for preferential alignment. Application of a magnetic field from a cylindrical coaxial magnet has also been utilized to form radially aligned nanowires. The magnetic field of the coaxial cylindrical magnet produced a dense, concentric nanowire configuration at the centre of the magnetic field as a consequence of the radial field gradient, and sparse nanowire arrangements in the peripheral field, which were utilized as interconnects with a concentric electrode design

  5. Perspectives: Nanofibers and nanowires for disordered photonics

    Directory of Open Access Journals (Sweden)

    Dario Pisignano

    2017-03-01

    Full Text Available As building blocks of microscopically non-homogeneous materials, semiconductor nanowires and polymer nanofibers are emerging component materials for disordered photonics, with unique properties of light emission and scattering. Effects found in assemblies of nanowires and nanofibers include broadband reflection, significant localization of light, strong and collective multiple scattering, enhanced absorption of incident photons, synergistic effects with plasmonic particles, and random lasing. We highlight recent related discoveries, with a focus on material aspects. The control of spatial correlations in complex assemblies during deposition, the coupling of modes with efficient transmission channels provided by nanofiber waveguides, and the embedment of random architectures into individually coded nanowires will allow the potential of these photonic materials to be fully exploited, unconventional physics to be highlighted, and next-generation optical devices to be achieved. The prospects opened by this technology include enhanced random lasing and mode-locking, multi-directionally guided coupling to sensors and receivers, and low-cost encrypting miniatures for encoders and labels.

  6. Electrodeposition of Cobalt Nanowires

    International Nuclear Information System (INIS)

    Ahn, Sungbok; Hong, Kimin

    2013-01-01

    We developed an electroplating process of cobalt nanowires of which line-widths were between 70 and 200 nm. The plating electrolyte was made of CoSO 4 and an organic additive, dimethyldithiocarbamic acid ester sodium salt (DAESA). DAESA in plating electrolytes had an accelerating effect and reduced the surface roughness of plated cobalt thin films. We obtained void-free cobalt nanowires when the plating current density was 6.25 mA/cm 2 and DAESA concentration was 1 mL/L

  7. Optical and morphological properties of graphene sheets decorated with ZnO nanowires via polyol enhancement

    International Nuclear Information System (INIS)

    Sharma, Vinay; Rajaura, Rajveer Singh; Sharma, Preetam K.; Srivastava, Subodh; Vijay, Y. K.; Sharma, S. S.

    2014-01-01

    Graphene-ZnO nanocomposites have proven to be very useful materials for photovoltaic and sensor applications. Here, we report a facile, one-step in situ polymerization method for synthesis of graphene sheets randomly decorated with zinc oxide nanowires using ethylene glycol as solvent. We have used hydrothermal treatment for growth of ZnO nanowires. UV-visible spectra peak shifting around 288nm and 307 nm shows the presence of ZnO on graphene structure. Photoluminiscence spectra (PL) in 400nm-500nm region exhibits the luminescence quenching effect. Scanning electron microscopy (SEM) image confirms the growth of ZnO nanowires on graphene sheets

  8. Low frequency noise sources and mechanisms in semiconductor nanowire transistors

    Science.gov (United States)

    Delker, Collin James

    Semiconductor nanowires are attractive candidates for use in future high-speed electronics, transparent/flexible devices, and chemical sensors. Among other materials, III-V semiconductors have gained considerable interest for their high bulk mobility and low band gap, making them promising for high-speed nanoscale devices. However, nanowire devices also exhibit high levels of low-frequency noise due to their low band gap and high surface-to-volume ratio. The sources and mechanisms of this noise must be understood and controlled in order to realize practical applications of nanowire electronics. This work seeks to understand the underlying noise mechanisms of nanowire transistors in order discover ways to reduce noise levels. It also demonstrates how noise can provide a spectroscopy for analyzing device quality. Most traditional noise studies tend to apply standard MOSFET models to nanowire noise and transport, which lump together all possible independent noise sources in a nanowire, ignoring effects of the contacts or multiple gates, and could lead to misestimation of the noise figures for a device. This work demonstrates how noise in a nanowire transistor can stem from the channel, ungated access regions, metal- semiconductor contacts, and tunnel barriers, all independently adding to the total noise. Each source of noise can contribute and may dominate the overall noise behavior under certain bias regimes and temperatures, as demonstrated in this work through various device structures and measurements. For example, the contacts can influence noise even below the threshold voltage under certain conditions, emphasizing the need for high-quality metal-semiconductor interface technology.

  9. Surface Charge Measurement of SonoVue, Definity and Optison: A Comparison of Laser Doppler Electrophoresis and Micro-Electrophoresis.

    Science.gov (United States)

    Ja'afar, Fairuzeta; Leow, Chee Hau; Garbin, Valeria; Sennoga, Charles A; Tang, Meng-Xing; Seddon, John M

    2015-11-01

    Microbubble (MB) contrast-enhanced ultrasonography is a promising tool for targeted molecular imaging. It is important to determine the MB surface charge accurately as it affects the MB interactions with cell membranes. In this article, we report the surface charge measurement of SonoVue, Definity and Optison. We compare the performance of the widely used laser Doppler electrophoresis with an in-house micro-electrophoresis system. By optically tracking MB electrophoretic velocity in a microchannel, we determined the zeta potentials of MB samples. Using micro-electrophoresis, we obtained zeta potential values for SonoVue, Definity and Optison of -28.3, -4.2 and -9.5 mV, with relative standard deviations of 5%, 48% and 8%, respectively. In comparison, laser Doppler electrophoresis gave -8.7, +0.7 and +15.8 mV with relative standard deviations of 330%, 29,000% and 130%, respectively. We found that the reliability of laser Doppler electrophoresis is compromised by MB buoyancy. Micro-electrophoresis determined zeta potential values with a 10-fold improvement in relative standard deviation. Copyright © 2015 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  10. Influence of carbonate intercalation in the surface-charging behavior of Zn-Cr layered double hydroxides

    Energy Technology Data Exchange (ETDEWEB)

    Rojas, R., E-mail: rrojas@mail.fcq.unc.edu.ar [INFIQC, Departamento de Fisicoquimica, Facultad de Ciencias Quimicas, Universidad Nacional de Cordoba, Ciudad Universitaria, 5000 Cordoba (Argentina); Barriga, C. [Departamento de Quimica Inorganica e Ingenieria Quimica, Edificio Marie Curie, Campus de Rabanales, Universidad de Cordoba, 14071 Cordoba (Spain); De Pauli, C.P. [INFIQC, Departamento de Fisicoquimica, Facultad de Ciencias Quimicas, Universidad Nacional de Cordoba, Ciudad Universitaria, 5000 Cordoba (Argentina); Avena, M.J. [Departamento de Quimica, Universidad Nacional del Sur, Avenida Alem 1253, 8000 Bahia Blanca (Argentina)

    2010-01-15

    The influence of interlayer composition in the surface charge and reactivity of layered double hydroxides (LDHs) has been explored. With this purpose, a chloride-intercalated Zn-Cr-LDH has been synthesized by the constant pH coprecipitation method and afterwards exchanged with carbonate to obtain solids with different Cl{sup -}/CO{sub 3}{sup 2-} ratios. The solids structure has been characterized by elemental chemical analysis, powder X-ray diffraction and infrared spectroscopy, while its surface-charging behavior and reactivity have been studied by acid-base potentiometric titrations and electrophoretic mobility determinations. The chloride-intercalated sample shows an increasing hydroxyl adsorption with increasing pH and decreasing support electrolyte concentration and the particles present positive electrophoretic mobility in the measured pH range. As carbonate content increases in the samples, the total OH{sup -} uptake diminishes and the samples show an isoelectric point at pH around 10. When the gallery is totally occupied by carbonate anions, the OH uptake vs. pH curves registered at different electrolyte concentrations merge at around pH 10. A LDH-water interface model has been used to give an interpretation to the experimental data. The model indicates that as carbonate content increases, the sample behavior becomes similar to that of a metal (hydr)oxide and that surface (bi)carbonate anions undergo acid-base reactions.

  11. Nose to brain delivery in rats: Effect of surface charge of rhodamine B labeled nanocarriers on brain subregion localization.

    Science.gov (United States)

    Bonaccorso, A; Musumeci, T; Serapide, M F; Pellitteri, R; Uchegbu, I F; Puglisi, G

    2017-06-01

    Nose to brain delivery and nanotechnology are the combination of innovative strategies for molecules to reach the brain and to bypass blood brain barriers. In this work we investigated the fate of two rhodamine B labeled polymeric nanoparticles (Z-ave <250nm) of opposite surface charge in different areas of the brain after intranasal administration in rats. A preliminary screening was carried out to select the suitable positive (chitosan/poly-l-lactide-co-glycolide) nanocarrier through photon correlation spectroscopy and turbiscan. Physico-chemical and technological characterizations of poly-l-lactide-co-glycolide (negative) and chitosan/poly-l-lactide-co-glycolide (positive) fluorescent labeled nanoparticles were performed. The animals were allocated to three groups receiving negative and positive polymeric nanoparticles via single intranasal administration or no treatment. The localization of both nanocarriers in different brain areas was detected using fluorescent microscopy. Our data revealed that both nanocarriers reach the brain and are able to persist in the brain up to 48h after intranasal administration. Surface charge influenced the involved pathways in their translocation from the nasal cavity to the central nervous system. The positive charge of nanoparticles slows down brain reaching and the trigeminal pathway is involved, while the olfactory pathway may be responsible for the transport of negatively charged nanoparticles, and systemic pathways are not excluded. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. On the molecular mechanism of surface charge amplification and related phenomena at aqueous polyelectrolyte-graphene interfaces

    Directory of Open Access Journals (Sweden)

    J.M. Simonson

    2011-09-01

    Full Text Available In this communication we illustrate the occurrence of a recently reported new phenomenon of surface-charge amplification, SCA, (originally dubbed overcharging, OC, [Jimenez-Angeles F. and Lozada-Cassou M., J. Phys. Chem. B, 2004, 108, 7286] by means of molecular dynamics simulation of aqueous electrolytes solutions involving multivalent cations in contact with charged graphene walls and the presence of short-chain lithium polystyrene sulfonates where the solvent water is described explicitly with a realistic molecular model. We show that the occurrence of SCA in these systems, in contrast to that observed in primitive models, involves neither contact co-adsorption of the negatively charged macroions nor divalent cations with a large size and charge asymmetry as required in the case of implicit solvents. In fact the SCA phenomenon hinges around the preferential adsorption of water (over the hydrated ions with an average dipolar orientation such that the charges of the water's hydrogen and oxygen sites induce magnification rather than screening of the positive-charged graphene surface, within a limited range of surface-charge density.

  13. Low temperature synthesis of Zn nanowires by physical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Schroeder, Philipp; Kast, Michael; Brueckl, Hubert [Austrian Research Centers GmbH ARC, Nano- Systemtechnologies, Donau-City-Strasse 1, A-1220 Wien (Austria)

    2007-07-01

    We demonstrate catalytic growth of zinc nanowires by physical vapor deposition at modest temperatures of 125-175 C on various substrates. In contrast to conventional approaches using tube furnaces our home-built growth system allows to control the vapor sources and the substrate temperature separately. The silicon substrates were sputter coated with a thin gold layer as metal catalyst. The samples were heated to the growth temperature and subsequently exposed to the zinc vapor at high vacuum conditions. The work pressure was adjusted by the partial pressure of oxygen or argon flow gas. Scanning electron microscopy and atomic force microscopy characterizations revealed that the nanowires exhibit straight, uniform morphology and have diameters in the range of 50-350 nm and lengths up to 70 {mu}m. The Zn nanowires grow independently of the substrates crystal orientation via a catalytic vapor-solid growth mechanism. Since no nanowire formation was observed without gold coating, we expect that the onedimensional growth is initiated by a surface reactive Au seed. ZnO nanowires can be produced in the same preparation chamber by oxidation at 500 C in 1atm (80% Ar, 20% O{sub 2}) for 1 hour. ZnO is highly attractive for sensor applications.

  14. Artificial cilia of magnetically tagged polymer nanowires for biomimetic mechanosensing

    International Nuclear Information System (INIS)

    Schroeder, P; Schotter, J; Shoshi, A; Eggeling, M; Brückl, H; Bethge, O; Hütten, A

    2011-01-01

    Polymeric nanowires of polypyrrole have been implemented as artificial cilia on giant-magneto-resistive multilayer sensors for a biomimetic sensing approach. The arrays were tagged with a magnetic material, the stray field of which changes relative to the underlying sensor as a consequence of mechanical stimuli which are delivered by a piezoactuator. The principle resembles balance sensing in mammals. Measurements of the sensor output voltage suggest a proof of concept at frequencies of around 190 kHz and a tag thickness of ∼300 nm. Characterization was performed by scanning electron microscopy and magnetic force microscopy. Micromagnetic and finite-element simulations were conducted to assess basic sensing aspects.

  15. Development of gas sensors using ZnO nanostructures

    Indian Academy of Sciences (India)

    Administrator

    Different ZnO nanostructures such as nanowires, nanobelts and tetrapods have been grown and used for preparation of thick film (with random ... Gas sensors; nanowires; ZnO; tetrapods; NO; H2S. 1. Introduction. Semiconductor metal-oxide .... at room temperature is shown in figure 3. Here, response is defined by: 100.

  16. Selective Surface Charge Sign Reversal on Metallic Carbon Nanotubes for Facile Ultrahigh Purity Nanotube Sorting.

    Science.gov (United States)

    Wang, Jing; Nguyen, Tuan Dat; Cao, Qing; Wang, Yilei; Tan, Marcus Y C; Chan-Park, Mary B

    2016-03-22

    Semiconducting (semi-) single-walled carbon nanotubes (SWNTs) must be purified of their metallic (met-) counterparts for most applications including nanoelectronics, solar cells, chemical sensors, and artificial skins. Previous bulk sorting techniques are based on subtle contrasts between properties of different nanotube/dispersing agent complexes. We report here a method which directly exploits the nanotube band structure differences. For the heterogeneous redox reaction of SWNTs with oxygen/water couple, the aqueous pH can be tuned so that the redox kinetics is determined by the availability of nanotube electrons only at/near the Fermi level, as predicted quantitatively by the Marcus-Gerischer (MG) theory. Consequently, met-SWNTs oxidize much faster than semi-SWNTs and only met-SWNTs selectively reverse the sign of their measured surface zeta potential from negative to positive at the optimized acidic pH when suspended with nonionic surfactants. By passing the redox-reacted nanotubes through anionic hydrogel beads, we isolate semi-SWNTs to record high electrically verified purity above 99.94% ± 0.04%. This facile charge sign reversal (CSR)-based sorting technique is robust and can sort SWNTs with a broad diameter range.

  17. H2 sensing properties of modified silicon nanowires

    Directory of Open Access Journals (Sweden)

    Latefa Baba Ahmed

    2015-04-01

    Full Text Available It has been found that the silicon nanowires modified with noble metals can be used to fabricate an effective H2 gas sensor in the present study. The preparation and surface modification of silicon nanowires (SiNWs were carried out by chemical methods. The morphology of the silicon nanowires unmodified and modified with nanoparticles of platinum, palladium, silver and gold was investigated using scanning electron microscopy (SEM. The chemical composition of the silicon nanowire layers was studied by secondary ion mass spectroscopy (SIMS and energy dispersive X-ray analysis (EDX. The structures of type metal/SiNWs/p-Si/Al were fabricated. The electrical characterization (I–V was performed in primary vacuum and H2 at different concentrations. It was found that the metal type used to modify the SiNWs strongly influenced the I–V characteristics. The response of these structures toward H2 gas was studied as a function of the metal type. Finally, the sensing characteristics and performance of the sensors were investigated.

  18. Optical transmissivity of metallic nanowires

    Science.gov (United States)

    Nairat, Mazen S.

    2017-08-01

    Optical transmissivity and reflectivity of one dimensional array of metallic nanowires embedded in transparent dielectric is characterized. i employ wave optics simulation to analyze the optical field distribution in both the dielectric and the nanowires. The results indicate that the transmissivity and reflectivity depend on the polarization states of the incident light. The metallic nanowires matrix transmit in-plane polarization but block light out at of-plane polarization.

  19. Simulation of Quantum Phenomena in Nanowire Sensors

    Science.gov (United States)

    2014-12-17

    Advisory Commission of the UNESCO -UNISA Africa Chair in Nanosciences/Nanotechnology, University of South Africa, Pretoria...Italy 2013 Appointed Member of Advisory Commission of the UNESCO -UNISA Africa Chair in Nanosciences/Nanotechnology

  20. Influence of the AC field intensity and frequency on composition and growth mechanism of Au-Pd alloy nanowires.

    Science.gov (United States)

    Zhang, Gaixiu; Yu, Gang; Chang, Fangfang; Tang, Lili; Hu, Bonian

    2013-10-01

    Au-Pd alloy nanowires with controllable morphology and composition are useful sensing materials for chemical and biological sensors. This report describes the preparation of such Au-Pd alloy nanowires from an aqueous solution by alternating current (AC) varied-frequency method, focusing on determining the dependence of the composition and morphology of the alloy nanowires on the electric field intensity and frequency. An electric field varied from 0.1 V x m(-1) to 0.4 x 10(6)V x m(-1) at 300 Hz frequency was used for the nucleation, followed by variation of the frequency between 1 and 20 MHz for the growth of the nanowires. The results showed that the Pd content in the alloy nanowires increased with the field intensity and frequency. The nanowire morphology with a less branching and better alignment was obtained at the increased frequency. XRD results showed that the phase structure of the alloy nanowires was face-centered cubic lattice. The nanowire compositions were shown controllable by changing the AC field intensity, frequency, as well as the metal ion ratio in the solution. The growth of the nanowires was shown to obey the Maxwell-Wanger (M-W) law.

  1. Optical Spectroscopy of Single Nanowires

    OpenAIRE

    Trägårdh, Johanna

    2008-01-01

    This thesis describes optical spectroscopy on III-V semiconductor nanowires. The nanowires were grown by metal-organic vapor phase epitaxy (MOVPE) and chemical beam epitaxy (CBE). Photoluminescence and photocurrent spectroscopy are used as tools to investigate issues such as the size of the band gap, the effects of surface states, and the charge carrier transport in core-shell nanowires. The band gap of InAs1-xPx nanowires with wurtzite crystal structure is measured as a function of ...

  2. Wafer Surface Charge Reversal as a Method of Simplifying Nanosphere Lithography for Reactive Ion Etch Texturing of Solar Cells

    Directory of Open Access Journals (Sweden)

    Daniel Inns

    2007-01-01

    Full Text Available A simplified nanosphere lithography process has been developed which allows fast and low-waste maskings of Si surfaces for subsequent reactive ion etching (RIE texturing. Initially, a positive surface charge is applied to a wafer surface by dipping in a solution of aluminum nitrate. Dipping the positive-coated wafer into a solution of negatively charged silica beads (nanospheres results in the spheres becoming electrostatically attracted to the wafer surface. These nanospheres form an etch mask for RIE. After RIE texturing, the reflection of the surface is reduced as effectively as any other nanosphere lithography method, while this batch process used for masking is much faster, making it more industrially relevant.

  3. Plasma surface treatment to improve surface charge accumulation and dissipation of epoxy resin exposed to DC and nanosecond-pulse voltages

    Science.gov (United States)

    Zhang, Cheng; Lin, Haofan; Zhang, Shuai; Xie, Qin; Ren, Chengyan; Shao, Tao

    2017-10-01

    In this paper, deposition by non-thermal plasma is used as a surface modification technique to change the surface characteristics of epoxy resin exposed to DC and nanosecond-pulse voltages. The corresponding surface characteristics in both cases of DC and nanosecond-pulse voltages before and after the modification are compared and investigated. The measurement of the surface potential provides the surface charge distribution, which is used to show the accumulation and dissipation process of the surface charges. Morphology observations, chemical composition and electrical parameters measurements are used to evaluate the treatment effects. The experimental results show that, before the plasma treatment, the accumulated surface charges in the case of the DC voltage are more than that in the case of the nanosecond-pulse voltage. Moreover, the decay rate of the surface charges for the DC voltage is higher than that for the nanosecond-pulse voltage. However, the decay rate is no more than 41% after 1800 s for both types of voltages. After the plasma treatment, the maximum surface potentials decrease to 57.33% and 32.57% of their values before treatment for the DC and nanosecond-pulse voltages, respectively, indicating a decrease in the accumulated surface charges. The decay rate exceeds 90% for both types of voltages. These changes are mainly attributed to a change in the surface nanostructure, an increase in conductivity, and a decrease in the depth of energy level.

  4. Plasma surface treatment to improve surface charge accumulation and dissipation of epoxy resin exposed to DC and nanosecond-pulse voltages

    International Nuclear Information System (INIS)

    Zhang, Cheng; Lin, Haofan; Zhang, Shuai; Ren, Chengyan; Shao, Tao; Xie, Qin

    2017-01-01

    In this paper, deposition by non-thermal plasma is used as a surface modification technique to change the surface characteristics of epoxy resin exposed to DC and nanosecond-pulse voltages. The corresponding surface characteristics in both cases of DC and nanosecond-pulse voltages before and after the modification are compared and investigated. The measurement of the surface potential provides the surface charge distribution, which is used to show the accumulation and dissipation process of the surface charges. Morphology observations, chemical composition and electrical parameters measurements are used to evaluate the treatment effects. The experimental results show that, before the plasma treatment, the accumulated surface charges in the case of the DC voltage are more than that in the case of the nanosecond-pulse voltage. Moreover, the decay rate of the surface charges for the DC voltage is higher than that for the nanosecond-pulse voltage. However, the decay rate is no more than 41% after 1800 s for both types of voltages. After the plasma treatment, the maximum surface potentials decrease to 57.33% and 32.57% of their values before treatment for the DC and nanosecond-pulse voltages, respectively, indicating a decrease in the accumulated surface charges. The decay rate exceeds 90% for both types of voltages. These changes are mainly attributed to a change in the surface nanostructure, an increase in conductivity, and a decrease in the depth of energy level. (paper)

  5. The Electrostatically Formed Nanowire: A Novel Platform for Gas-Sensing Applications

    Directory of Open Access Journals (Sweden)

    Gil Shalev

    2017-02-01

    Full Text Available The electrostatically formed nanowire (EFN gas sensor is based on a multiple-gate field-effect transistor with a conducting nanowire, which is not defined physically; rather, the nanowire is defined electrostatically post-fabrication, by using appropriate biasing of the different surrounding gates. The EFN is fabricated by using standard silicon processing technologies with relaxed design rules and, thereby, supports the realization of a low-cost and robust gas sensor, suitable for mass production. Although the smallest lithographic definition is higher than half a micrometer, appropriate tuning of the biasing of the gates concludes a conducting channel with a tunable diameter, which can transform the conducting channel into a nanowire with a diameter smaller than 20 nm. The tunable size and shape of the nanowire elicits tunable sensing parameters, such as sensitivity, limit of detection, and dynamic range, such that a single EFN gas sensor can perform with high sensitivity and a broad dynamic range by merely changing the biasing configuration. The current work reviews the design of the EFN gas sensor, its fabrication considerations and process flow, means of electrical characterization, and preliminary sensing performance at room temperature, underlying the unique and advantageous tunable capability of the device.

  6. Synthesis and application of graphene–silver nanowires composite for ammonia gas sensing

    International Nuclear Information System (INIS)

    Tran, Quang Trung; Huynh, Tran My Hoa; Tong, Duc Tai; Tran, Van Tam; Nguyen, Nang Dinh

    2013-01-01

    Graphene, consisting of a single carbon layer in a two-dimensional (2D) lattice, has been a promising material for application to nanoelectrical devices in recent years. In this study we report the development of a useful ammonia (NH 3 ) gas sensor based on graphene–silver nanowires ‘composite’ with planar electrode structure. The basic strategy involves three steps: (i) preparation of graphene oxide (GO) by modified Hummers method; (ii) synthesis of silver nanowires by polyol method; and (iii) preparation of graphene and silver nanowires on two electrodes using spin and spray-coating of precursor solutions, respectively. Exposure of this sensor to NH 3 induces a reversible resistance change at room temperature that is as large as ΔR/R 0 ∼ 28% and this sensitivity is eight times larger than the sensitivity of the ‘intrinsic’ graphene based NH 3 gas sensor (ΔR/R 0 ∼ 3,5%). Their responses and the recovery times go down to ∼200 and ∼60 s, respectively. Because graphene synthesized by chemical methods has many defects and small sheets, it cannot be perfectly used for gas sensor or for nanoelectrical devices. The silver nanowires are applied to play the role of small bridges connecting many graphene islands together to improve electrical properties of graphene/silver nanowires composite and result in higher NH 3 gas sensitivity. (paper)

  7. Calculation of the surface potential and surface charge density by measurement of the three-phase contact angle.

    Science.gov (United States)

    Horiuchi, H; Nikolov, A; Wasan, D T

    2012-11-01

    The silica/silicon wafer is widely used in the semiconductor industry in the manufacture of electronic devices, so it is essential to understand its physical chemistry and determine the surface potential at the silica wafer/water interface. However, it is difficult to measure the surface potential of a silica/silicon wafer directly due to its high electric resistance. In the present study, the three-phase contact angle (TPCA) on silica is measured as a function of the pH. The surface potential and surface charge density at the silica/water surface are calculated by a model based on the Young-Lippmann equation in conjunction with the Gouy-Chapman model for the electric double layer. In measurements of the TPCA on silica, two distinct regions were identified with a boundary at pH 9.5-showing a dominance of the surface ionization of silanol groups below pH 9.5 and a dominance of the dissolution of silica into the aqueous solution above pH 9.5. Since the surface chemistry changes above pH 9.5, the model is applied to solutions below pH 9.5 (ionization dominant) for the calculation of the surface potential and surface charge density at the silica/aqueous interface. In order to evaluate the model, a galvanic mica cell was made of a mica sheet and the surface potential was measured directly at the mica/water interface. The model results are also validated by experimental data from the literature, as well as the results obtained by the potentiometric titration method and the electro-kinetic measurements. Copyright © 2012 Elsevier Inc. All rights reserved.

  8. A Nose for Hydrogen Gas: Fast, Sensitive H2Sensors Using Electrodeposited Nanomaterials.

    Science.gov (United States)

    Penner, Reginald M

    2017-08-15

    Hydrogen gas (H 2 ) is odorless and flammable at concentrations above 4% (v/v) in air. Sensors capable of detecting it rapidly at lower concentrations are needed to "sniff" for leaked H 2 wherever it is used. Electrical H 2 sensors are attractive because of their simplicity and low cost: Such sensors consist of a metal (usually palladium, Pd) resistor. Exposure to H 2 causes a resistance increase, as Pd metal is converted into more resistive palladium hydride (PdH x ). Sensors based upon Pd alloy films, developed in the early 1990s, were both too slow and too insensitive to meet the requirements of H 2 safety sensing. In this Account, we describe the development of H 2 sensors that are based upon electrodeposited nanomaterials. This story begins with the rise to prominence of nanowire-based sensors in 2001 and our demonstration that year of the first nanowire-based H 2 sensor. The Pd nanowires used in these experiments were prepared by electrodepositing Pd at linear step-edge defects on a graphite electrode surface. In 2005, lithographically patterned nanowire electrodeposition (LPNE) provided the capability to pattern single Pd nanowires on dielectrics using electrodeposition. LPNE also provided control over the nanowire thickness (±1 nm) and width (±10-15%). Using single Pd nanowires, it was demonstrated in 2010 that smaller nanowires responded more rapidly to H 2 exposure. Heating the nanowire using Joule self-heating (2010) also dramatically accelerated sensor response and recovery, leading to the conclusion that thermally activated H 2 chemisorption and desorption of H 2 were rate-limiting steps in sensor response to and recovery from H 2 exposure. Platinum (Pt) nanowires, studied in 2012, showed an inverted resistance response to H 2 exposure, that is, the resistance of Pt nanowires decreased instead of increased upon H 2 exposure. H 2 dissociatively chemisorbs at a Pt surface to form Pt-H, but in contrast to Pd, it stays on the Pt surface. Pt nanowires

  9. Nanowire Field-Effect Transistors : Sensing Simplicity?

    NARCIS (Netherlands)

    Mescher, M.

    2014-01-01

    Silicon nanowires are structures made from silicon with at least one spatial dimension in the nanometer regime (1-100 nm). From these nanowires, silicon nanowire field-effect transistors can be constructed. Since their introduction in 2001 silicon nanowire field-effect transistors have been studied

  10. Long Silver Nanowires Synthesis by Pulsed Electrodeposition

    Directory of Open Access Journals (Sweden)

    M.R. Batevandi

    2015-09-01

    Full Text Available Silver nanowires were pulse electrodeposited into nanopore anodic alumina oxide templates. The effects of continuous and pulse electrodeposition waveform on the microstructure properties of the nanowire arrays were studied. It is seen that the microstructure of nanowire is depend to pulse condition. The off time duration of pulse waveform enables to control the growth direction of Ag nanowires.

  11. Aging of Organic Nanowires

    DEFF Research Database (Denmark)

    Balzer, Frank; Schiek, Manuela; Osadnik, Andreas

    2012-01-01

    Organic semiconductors formed by epitaxial growth from small molecules such as the para-phenylenes or squaraines promise a vast application potential as the active ingredient in electric and optoelectronic devices. Their self-organization into organic nanowires or "nanofibers" adds a peculiar...... attribute, making them especially interesting for light generation in OLEDs and for light-harvesting devices such as solar cells. Functionalization of the molecules allows the customization of optical and electrical properties. However, aging of the wires might lead to a considerable decrease in device...... performance over time. In this study the morphological stability of organic nanoclusters and nanowires from the methoxy functionalized quaterphenylene, 4,4'''dimethoxy-1,1':4',1''4'',1'''-quaterphenylene (MOP4), is investigated in detail. Aging experiments conducted by atomic force microscopy under ambient...

  12. Silicon nanowire transistors

    CERN Document Server

    Bindal, Ahmet

    2016-01-01

    This book describes the n and p-channel Silicon Nanowire Transistor (SNT) designs with single and dual-work functions, emphasizing low static and dynamic power consumption. The authors describe a process flow for fabrication and generate SPICE models for building various digital and analog circuits. These include an SRAM, a baseband spread spectrum transmitter, a neuron cell and a Field Programmable Gate Array (FPGA) platform in the digital domain, as well as high bandwidth single-stage and operational amplifiers, RF communication circuits in the analog domain, in order to show this technology’s true potential for the next generation VLSI. Describes Silicon Nanowire (SNW) Transistors, as vertically constructed MOS n and p-channel transistors, with low static and dynamic power consumption and small layout footprint; Targets System-on-Chip (SoC) design, supporting very high transistor count (ULSI), minimal power consumption requiring inexpensive substrates for packaging; Enables fabrication of different types...

  13. Fabrication of vertically aligned Pd nanowire array in AAO template by electrodeposition using neutral electrolyte

    Directory of Open Access Journals (Sweden)

    Yüzer Hayrettin

    2010-01-01

    Full Text Available Abstract A vertically aligned Pd nanowire array was successfully fabricated on an Au/Ti substrate using an anodic aluminum oxide (AAO template by a direct voltage electrodeposition method at room temperature using diluted neutral electrolyte. The fabrication of Pd nanowires was controlled by analyzing the current–time transient during electrodeposition using potentiostat. The AAO template and the Pd nanowires were characterized by scanning electron microscopy (SEM, energy-dispersive X-ray (EDX methods and X-Ray diffraction (XRD. It was observed that the Pd nanowire array was standing freely on an Au-coated Ti substrate after removing the AAO template in a relatively large area of about 5 cm2, approximately 50 nm in diameter and 2.5 μm in length with a high aspect ratio. The nucleation rate and the number of atoms in the critical nucleus were determined from the analysis of current transients. Pd nuclei density was calculated as 3.55 × 108 cm−2. Usage of diluted neutral electrolyte enables slower growing of Pd nanowires owing to increase in the electrodeposition potential and thus obtained Pd nanowires have higher crystallinity with lower dislocations. In fact, this high crystallinity of Pd nanowires provides them positive effect for sensor performances especially.

  14. Metal-Catalyst-Free Synthesis and Characterization of Single-Crystalline Silicon Oxynitride Nanowires

    Directory of Open Access Journals (Sweden)

    Shuang Xi

    2012-01-01

    Full Text Available Large quantities of single-crystal silicon oxynitride nanowires with high N concentration have been synthesized directly on silicon substrate at 1200°C without using any metal catalyst. The diameter of these ternary nanowires is ranging from 10 to 180 nm with log-normal distribution, and the length of these nanowires varies from a few hundreds of micrometers to several millimeters. A vapor-solid mechanism was proposed to explain the growth of the nanowires. These nanowires are grown to form a disordered mat with an ultrabright white nonspecular appearance. The mat demonstrates highly diffusive reflectivity with the optical reflectivity of around 80% over the whole visible wavelength, which is comparable to the most brilliant white beetle scales found in nature. The whiteness might be resulted from the strong multiscattering of a large fraction of incident light on the disordered nanowire mat. These ultra-bright white nanowires could form as reflecting surface to meet the stringent requirements of bright-white light-emitting-diode lighting for higher optical efficiency. They can also find applications in diverse fields such as sensors, cosmetics, paints, and tooth whitening.

  15. Influence of surface charge on the in vitro protein adsorption and cell cytotoxicity of paclitaxel loaded poly(ε-caprolactone nanoparticles

    Directory of Open Access Journals (Sweden)

    Sathyamoorthy Nandhakumar

    2017-12-01

    Full Text Available The biokinetic fate of polymeric nanoparticles in the physiological milieu is strongly influenced by its properties such as size, surface charge and surface affinity. The electrostatic properties of the polymeric nanoparticles and, thereby, the reliant properties such as cellular interactions, reactivity and toxicity, can be tailored by modulating the surface charge. Therefore, the present study aimed at studying the influence of surface charge on the physicochemical properties, in vitro protein adsorption and cell cytotoxicity of poly(ε-caprolactone (PCL nanoparticles (NPs. Paclitaxel loaded PCL nanoparticles were obtained by emulsion solvent evaporation extraction technique and differently charged using ionic surfactants. The NPs were characterized for size, zeta potential, morphology, entrapment and release. In vitro protein adsorption and cytotoxicity of NPs with different surface charge was investigated. The prepared NPs were rounded with a smooth surface and had a particle size less than 250 nm with narrow distribution and high entrapment efficiency (>80%. The zeta potential of the particles varied between −22 mV and +16 mV depending on its composition. The in vitro protein adsorption studies revealed that positively charged NPs adsorbed more proteins than other formulations. The cytotoxicity studies on MCF-7 cells exhibited that positively charged NPs engender the highest cell inhibition due to preferential uptake based on electrostatic interactions with cell membranes. The results suggest that surface charge could be undeniably significant in determining the protein adsorption and cellular interactions and must be intently considered during the design of colloidal particles to impart better performance in the physiological system. Keywords: Poly(ε-caprolactone, Nanoparticles, Surface charge, Protein adsorption, Cytotoxicity

  16. Improving Gas Sensing Properties of Tin Oxide Nanowires Palladium-Coated Using a Low Cost Technique

    OpenAIRE

    M. Barzegar; M. B. Rahmani; H. Haratizadeh

    2012-01-01

    Thin films of SnO2 nanowires were successfully prepared by using chemical vapor deposition (CVD) process on quartz substrates. Afterwards, a thin  layer of palladium (Pd) as a catalyst was coated on top of nanowires. For the deposition of Pd, a simple and low cost technique of spray pyrolysis was employed, which caused an intensive enhancement on the sensing response of fabricated sensors. Prepared sensor devices were exposed to liquid petroleum gas (LPG) and vapor of ethanol (C2H5OH)...

  17. Enhanced fabrication process of zinc oxide nanowires for optoelectronics

    Energy Technology Data Exchange (ETDEWEB)

    García Núñez, C., E-mail: carlos.garcia@uam.es [Grupo de Electrónica y Semiconductores, Departamento de Física Aplicada, Universidad Autónoma de Madrid, 28049 Madrid (Spain); Pau, J.L.; Ruíz, E.; García Marín, A.; García, B.J.; Piqueras, J. [Grupo de Electrónica y Semiconductores, Departamento de Física Aplicada, Universidad Autónoma de Madrid, 28049 Madrid (Spain); Shen, G.; Wilbert, D.S.; Kim, S.M.; Kung, P. [Department of Electrical and Computer Engineering, the University of Alabama, Tuscaloosa, AL 35487 (United States)

    2014-03-31

    Zinc oxide (ZnO) nanowires (NWs) based ultraviolet (UV) sensors have been fabricated using different assembly techniques to form functional structures, aiming at the improvement of the performance of NW-based sensors for optoelectronic applications. NWs with diameters and lengths varying between 90–870 nm and 2–20 μm, respectively, were synthesized by controlling the growth conditions in a chemical vapor transport system. Optical properties of NWs were studied by means of transmission spectroscopy. Electrical properties of single ZnO NW-based sensors were analyzed in dark and under UV illumination (at photon wavelength of λ < 370 nm) as a function of the NW diameter. Results of the study indicate that reduction of the NW diameter below 200 nm leads to an improvement of the photocurrent (at λ < 370 nm) up to 10{sup 2} μA and a decrease of the decay time around 150 s. These enhancements may help to improve the performance of ZnO-based optoelectronic devices. - Highlights: • ZnO nanowires (NWs) with diameters 90–870 nm were grown by chemical vapor transport. • ZnO NWs showed strong absorption in the UV range. • Different assembly techniques were tested for preparing ZnO NW-based UV sensors. • Sensor photoresponses were around 10{sup 3} A/W. • Reducing NW diameter below 200 nm improved sensor photosensitivity.

  18. Quantum transport in semiconductor nanowires

    NARCIS (Netherlands)

    Van Dam, J.

    2006-01-01

    This thesis describes a series of experiments aimed at understanding the low-temperature electrical transport properties of semiconductor nanowires. The semiconductor nanowires (1-100 nm in diameter) are grown from nanoscale gold particles via a chemical process called vapor-liquid-solid (VLS)

  19. Expanding the versatility of silicon carbide thin films and nanowires

    Science.gov (United States)

    Luna, Lunet

    Silicon carbide (SiC) based electronics and sensors hold promise for pushing past the limits of current technology to achieve small, durable devices that can function in high-temperature, high-voltage, corrosive, and biological environments. SiC is an ideal material for such conditions due to its high mechanical strength, excellent chemical stability, and its biocompatibility. Consequently, SiC thin films and nanowires have attracted interest in applications such as micro- and nano-electromechanical systems, biological sensors, field emission cathodes, and energy storage devices. However to fully realize SiC in such technologies, the reliability of metal contacts to SiC at high temperatures must be improved and the nanowire growth mechanism must be understood to enable strict control of nanowire crystal structure and orientation. Here, we present a novel metallization scheme, utilizing solid-state graphitization of SiC, to improve the long-term reliability of Pt/Ti contacts to polycrystalline n-type SiC films at high temperature. The metallization scheme includes an alumina protection layer and exhibits low, stable contact resistivity even after long-term (500 hr) testing in air at 450 ºC. We also report the crystal structure and growth mechanism of Ni-assisted silicon carbide nanowires using single-source precursor, methyltrichlorosilane. The effects of growth parameters, such as substrate and temperature, on the structure and morphology of the resulting nanowires will also be presented. Overall, this study provides new insights towards the realization of novel SiC technologies, enabled by advanced electron microscopy techniques located in the user facilities at the Molecular Foundry in Berkeley, California. This work was performed in part at the Molecular Foundry, supported by the Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

  20. Extreme Band Engineering of III-Nitride Nanowire Heterostructures for Electronic and Photonic Application

    Science.gov (United States)

    Sarwar, ATM Golam

    Bottom-up nanowires are attractive for realizing semiconductor devices with extreme heterostructures because strain relaxation through the nanowire sidewalls allows the combination of highly lattice mismatched materials without creating dislocations. The resulting nanowires are used to fabricate light-emitting diodes (LEDs), lasers, solar cells, and sensors. The aim of this work is to investigate extreme heterostructures, which are impossible or very hard to realize in conventional planar films, exploiting the strain accommodation property of nanowires and engineer their band structure for novel electronic and photonic applications. To this end, in this thesis, III-Nitride semiconductor nanowires are investigated. In the first part of this work, a complete growth phase diagram of InN nanowires on silicon using plasma assisted molecular beam epitaxy is developed, and structural and optical characteristics are mapped as a function of growth parameters. Next, a novel up-side down pendeoepitaxial growth of InN forming mushroom-like microstructures is demonstrated and detail structural and optical characterizations are performed. Based on this, a method to grow strain-free large area single crystalline InN or thin film is proposed and the growth of InN on patterned GaN is investigated. The optimized growth conditions developed for InN are further used to grow InGaN nanowires graded over the whole composition range. Numerical energy band simulation is performed to better understand the effect of polarization charge on photo-carrier transport in these extremely graded nanowires. A novel photodetector device with negative differential photocurrent is demonstrated using the graded InGaN nanowires. In the second part of this thesis, polarization-induced nanowire light emitting diodes (PINLEDs) are investigated. The electrical and optical properties of the nanowire heterostructure are engineered and optimized for ultraviolet and deep ultraviolet applications. The electrical

  1. Hybrid Integrated Label-Free Chemical and Biological Sensors

    OpenAIRE

    Mehrabani, Simin; Maker, Ashley J.; Armani, Andrea M.

    2014-01-01

    Label-free sensors based on electrical, mechanical and optical transduction methods have potential applications in numerous areas of society, ranging from healthcare to environmental monitoring. Initial research in the field focused on the development and optimization of various sensor platforms fabricated from a single material system, such as fiber-based optical sensors and silicon nanowire-based electrical sensors. However, more recent research efforts have explored designing sensors fabri...

  2. Copper (II) oxide nanowires for p-type conductometric NH{sub 3} sensing

    Energy Technology Data Exchange (ETDEWEB)

    Shao, F. [Catalonia Institute for Energy Research (IREC), C. Jardins de les Dones de Negre 1, 08930 Sant Adrià del Besòs (Spain); Hernández-Ramírez, F., E-mail: fhernandez@irec.cat [Catalonia Institute for Energy Research (IREC), C. Jardins de les Dones de Negre 1, 08930 Sant Adrià del Besòs (Spain); Department of Electronics, University of Barcelona, C. Marti i Franqués 1, 08028 Barcelona (Spain); Prades, J.D. [Department of Electronics, University of Barcelona, C. Marti i Franqués 1, 08028 Barcelona (Spain); Fàbrega, C.; Andreu, T. [Catalonia Institute for Energy Research (IREC), C. Jardins de les Dones de Negre 1, 08930 Sant Adrià del Besòs (Spain); Morante, J.R. [Catalonia Institute for Energy Research (IREC), C. Jardins de les Dones de Negre 1, 08930 Sant Adrià del Besòs (Spain); Department of Electronics, University of Barcelona, C. Marti i Franqués 1, 08028 Barcelona (Spain)

    2014-08-30

    Highlights: • CuO nanowires were grown by thermal oxidation of Cu foils. • Individual nanowires were contacted by focused ion beam/electron beam deposition of Pt. • Higher responses to NH{sub 3} than SnO{sub 2} nanowire sensors were attained. • Gas response of CuO was found to be fully controlled by the presence of adsorbed oxygen species at its surface. - Abstract: Copper (II) oxide (CuO) is a metal oxide suitable for developing solid state gas sensors. Nevertheless, a detailed insight into the chemical-to-electrical transduction mechanisms between gas molecules and this metal oxide is still limited. Here, individual CuO nanowires were evaluated as ammonia (NH{sub 3}) and hydrogen sulphide (H{sub 2}S) sensors, validating the p-type character of this semiconductor. The working principle behind their performance was qualitatively modeled and it was concluded that adsorbed oxygen at the surface plays a key role necessary to explain the experimental data. Compared to their counterparts of SnO{sub 2} nanowires, an appreciable sensitivity enhancement to NH{sub 3} for concentrations below 100 ppm was demonstrated.

  3. Novel low-temperature growth of SnO2 nanowires and their gas-sensing properties

    International Nuclear Information System (INIS)

    Kumar, R. Rakesh; Parmar, Mitesh; Narasimha Rao, K.; Rajanna, K.; Phani, A.R.

    2013-01-01

    Graphical abstract: -- A simple thermal evaporation method is presented for the growth of crystalline SnO 2 nanowires at a low substrate temperature of 450 °C via an gold-assisted vapor–liquid–solid mechanism. The as-grown nanowires were characterized by scanning electron microscopy, transmission electron microscopy and X-ray diffraction, and were also tested for methanol vapor sensing. Transmission electron microscopy studies revealed the single-crystalline nature of the each nanowire. The fabricated sensor shows good response to methanol vapor at an operating temperature of 450 °C.

  4. Evaluation of surface charge density and surface potential by electrophoretic mobility for solid lipid nanoparticles and human brain-microvascular endothelial cells.

    Science.gov (United States)

    Kuo, Yung-Chih; Chen, I-Chun

    2007-09-27

    Electrophoretic mobility, zeta potential, surface charge density, and surface potential of cacao butter-based solid lipid nanoparticles (SLN) and human brain-microvascular endothelial cells (HBMEC) were analyzed in this study. Electrophoretic mobility and zeta potential were determined experimentally. Surface charge density and surface potential were evaluated theoretically via incorporation of ion condensation theory with the relationship between surface charge density and surface potential. The results revealed that the lower the pH value, the weaker the electrostatic properties of the negatively charged SLN and HBMEC. A higher content of cacao butter or a slower stirring rate yielded a larger SLN and stronger surface electricity. On the contrary, storage led to instability of SLN suspension and weaker electrical behavior because of hydrolysis of ionogenic groups on the particle surfaces. Also, high H+ concentration resulted in excess adsorption of H+ onto HBMEC, rendering charge reversal and cell death. The largest normalized discrepancy between surface potential and zeta potential occurred at pH = 7. For a fixed biocolloidal species, the discrepancy was nearly invariant at high pH value. However, the discrepancy followed the order of electrical intensity for HBMEC system at low pH value because mammalian cells were sensitive to H+. The present study provided a practical method to obtain surface charge properties by capillary electrophoresis.

  5. Impact of Environmental Conditions (pH, Ionic Strength, And Electrolyte Type) On The Surface Charge And Aggregation Of Silver Nanoparticles Suspensions

    Science.gov (United States)

    The impact of capping agents and environmental conditions (pH, ionic strength, and background electrolytes) on surface charge and aggregation potential of silver nanoparticles (AgNPs) suspensions were investigated. Capping agents are chemicals used in the synthesis of nanopartic...

  6. Improving the visible light photoactivity of In2S3-graphene nanocomposite via a simple surface charge modification approach.

    Science.gov (United States)

    Yang, Min-Quan; Weng, Bo; Xu, Yi-Jun

    2013-08-20

    We report an efficient and easily accessible self-assembly route to synthesize In2S3-GR nanocomposites via electrostatic interaction of positively charged In2S3 nanoparticles with negatively charged graphene oxide (GO) followed by a hydrothermal process for reduction of GO to graphene (GR). The as-synthesized In2S3-GR nanocomposites exhibit much higher visible light photocatalytic activity toward selective reduction of nitroaromatic compounds in water than bare In2S3 nanoparticles and In2S3-GR-H that is obtained from the simple "hard" integration of GR nanosheets with solid In2S3 nanoparticles without modification of surface charge. On the basis of the joint characterizations and structure-photoactivity correlation it is disclosed that the enhanced photocatalytic performance of In2S3-GR is mainly ascribed to the more efficient interfacial contact between In2S3 and the GR nanosheets than In2S3-GR-H, which would amplify the use of electron conductivity and mobility of GR to improve the lifetime and transfer of photogenerated charge carriers more efficiently and thus boost the photoactivity more effectively. This work highlights the significant effect of preparation methods on the photoactivity of GR-semiconductor nanocomposites. It is expected that such a simple electrostatic self-assembly strategy could aid to rationally fabricate more efficient GR-semiconductor nanocomposites with improved interfacial contact and photocatalytic performance toward various photocatalytic selective transformations.

  7. Effect of surface charge and agglomerate degree of magnetic iron oxide nanoparticles on KB cellular uptake in vitro.

    Science.gov (United States)

    Ge, Yuqing; Zhang, Yu; Xia, Jingguang; Ma, Ming; He, Shiying; Nie, Fang; Gu, Ning

    2009-10-15

    We synthesized three types of magnetic iron oxide nanoparticles (MNPs), which were meso-2,3-dimercaptosuccinic acid (DMSA) coated MNPs (DMSA@MNPs, 17.3+/-4.8 nm, negative charge), chitosan (CS) coated MNPs (CS@MNPs, 16.5+/-6.1 nm, positive charge) and magnetic nanoparticles agglomerates, formed by electronic aggregation between DMSA@MNPs and CS (CS-DMSA@MNPs, 85.7+/-72.9 nm, positive charge) respectively. The interactions of these MNPs with Oral Squamous Carcinoma Cell KB were investigated. The results showed that cellular uptakes of MNPs were on the dependence of incubation time, nanoparticles concentration and nanoparticles properties such as surface charge, size, etc. The cellular uptake was enhanced with the increase of incubation time and nanoparticles concentration. Although all MNPs could enter to cells, we observed apparent differences in the magnitude of nanoparticles uptaken. The cellular uptake of CS-DMSA@MNPs by KB cells was the highest and that of DMSA@MNPs was the lowest among the three types of MNPs. The same conclusions were drawn via the reduction of water proton relaxation times T(2)(*), resulting from the different iron load of labeled cells using a 1.5T clinical MR imager. The finding of this study will have implications in the chemical design of nanomaterials for biomedical applications.

  8. Lattice dislocation in Si nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Omar, M.S., E-mail: dr_m_s_omar@yahoo.co [Department of Physics, College of Science, University of Salahaddin, Arbil, Iraqi Kurdistan (Iraq); Taha, H.T. [Department of Physics, College of Science, University of Salahaddin, Arbil, Iraqi Kurdistan (Iraq)

    2009-12-15

    Modified formulas were used to calculate lattice thermal expansion, specific heat and Bulk modulus for Si nanowires with diameters of 115, 56, 37 and 22 nm. From these values and Gruneisen parameter taken from reference, mean lattice volumes were found to be as 20.03 A{sup 3} for the bulk and 23.63, 29.91, 34.69 and 40.46 A{sup 3} for Si nanowire diameters mentioned above, respectively. Their mean bonding length was calculated to be as 0.235 nm for the bulk and 0.248, 0.269, 0.282 and 0.297 nm for the nanowires diameter mentioned above, respectively. By dividing the nanowires diameter on the mean bonding length, number of layers per each nanowire size was found to be as 230, 104, 65 and 37 for the diameters mentioned above, respectively. Lattice dislocations in 22 nm diameter wire were found to be from 0.00324 nm for the 1st central lattice to 0.2579 nm for the last surface lattice. Such dislocation was smaller for larger wire diameters. Dislocation concentration found to change in Si nanowires according to the proportionalities of surface thickness to nanowire radius ratios.

  9. Spacecraft Surface Charging Handbook

    Science.gov (United States)

    1992-11-01

    discharges however produce replacement currents that can be global. The local effect of punchthrough is illustrated by a small dipole model for the...St’rap I Farda or TEK7103 Scope Power Dipole -- Line tenna To To PA HP05000 and Spectrum X-Y Analyzer Plotter Figure 61. Test setup for surface...Testing Seminar, Los Angeles, CA, p. 77-82, 19817. Levadou, F., "Proprietes Electriques Des Materiaux." Space Environment: Prevention of Risks Related

  10. Optical Binding of Nanowires

    Czech Academy of Sciences Publication Activity Database

    Simpson, Stephen Hugh; Zemánek, Pavel; Marago, O.M.; Jones, P.H.; Hanna, S.

    2017-01-01

    Roč. 17, č. 6 (2017), s. 3485-3492 ISSN 1530-6984 R&D Projects: GA ČR GB14-36681G Grant - others:AV ČR(CZ) CNR-16-12 Program:Bilaterální spolupráce Institutional support: RVO:68081731 Keywords : optical binding nanowires * Brownian motion * self -organization * non-equilibrium thermodynamics * non-equilibrium steady state * spin-orbit coupling * emergent phenomena Subject RIV: BH - Optics, Masers, Lasers OBOR OECD: Optics (including laser optics and quantum optics) Impact factor: 12.712, year: 2016

  11. Superconductivity in nanowires

    CERN Document Server

    Bezryadin, Alexey

    2012-01-01

    The importance and actuality of nanotechnology is unabated and will be for years to come. A main challenge is to understand the various properties of certain nanostructures, and how to generate structures with specific properties for use in actual applications in Electrical Engineering and Medicine.One of the most important structures are nanowires, in particular superconducting ones. They are highly promising for future electronics, transporting current without resistance and at scales of a few nanometers. To fabricate wires to certain defined standards however, is a major challenge, and so i

  12. Fivefold twinned boron carbide nanowires.

    Science.gov (United States)

    Fu, Xin; Jiang, Jun; Liu, Chao; Yuan, Jun

    2009-09-09

    Chemical composition and crystal structure of fivefold twinned boron carbide nanowires have been determined by electron energy-loss spectroscopy and electron diffraction. The fivefold cyclic twinning relationship is confirmed by systematic axial rotation electron diffraction. Detailed chemical analysis reveals a carbon-rich boron carbide phase. Such boron carbide nanowires are potentially interesting because of their intrinsic hardness and high temperature thermoelectric property. Together with other boron-rich compounds, they may form a set of multiply twinned nanowire systems where the misfit strain could be continuously tuned to influence their mechanical properties.

  13. Interactions between semiconductor nanowires and living cells.

    Science.gov (United States)

    Prinz, Christelle N

    2015-06-17

    Semiconductor nanowires are increasingly used for biological applications and their small dimensions make them a promising tool for sensing and manipulating cells with minimal perturbation. In order to interface cells with nanowires in a controlled fashion, it is essential to understand the interactions between nanowires and living cells. The present paper reviews current progress in the understanding of these interactions, with knowledge gathered from studies where living cells were interfaced with vertical nanowire arrays. The effect of nanowires on cells is reported in terms of viability, cell-nanowire interface morphology, cell behavior, changes in gene expression as well as cellular stress markers. Unexplored issues and unanswered questions are discussed.

  14. Gas nanosensor design packages based on tungsten oxide: mesocages, hollow spheres, and nanowires.

    Science.gov (United States)

    Hoa, Nguyen Duc; El-Safty, Sherif A

    2011-12-02

    Achieving proper designs of nanosensors for highly sensitive and selective detection of toxic environmental gases is one of the crucial issues in the field of gas sensor technology, because such designs can lead to the enhancement of gas sensor performance and expansion of their applications. Different geometrical designs of porous tungsten oxide nanostructures, including the mesocages, hollow spheres and nanowires, are synthesized for toxic gas sensor applications. Nanosensor designs with small crystalline size, large specific surface area, and superior physical characteristics enable the highly sensitive and selective detection of low concentration (ppm levels), highly toxic NO(2) among CO, as well as volatile organic compound gases, such as acetone, benzene, and ethanol. The experimental results showed that the sensor response was not only dependent on the specific surface area, but also on the geometries and crystal size of materials. Among the designed nanosensors, the nanowires showed the highest sensitivity, followed by the mesocages and hollow spheres-despite the fact that mesocages had the largest specific surface area of 80.9 m(2) g( - 1), followed by nanowires (69.4 m(2) g( - 1)), and hollow spheres (6.5 m(2) g( - 1)). The nanowire sensors had a moderate specific surface area (69.4 m(2) g( - 1)) but they exhibited the highest sensitivity because of their small diameter (∼5 nm), which approximates the Debye length of WO(3). This led to the depletion of the entire volume of the nanowires upon exposure to NO(2), resulting in an enormous increase in sensor resistance.

  15. Actuation of polypyrrole nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Alexander S; Peteu, Serban F; Ly, James V; Requicha, Aristides A G; Thompson, Mark E; Zhou Chongwu [Laboratory for Molecular Robotics, University of Southern California, Los Angeles, CA 90089 (United States)], E-mail: requicha@usc.edu

    2008-04-23

    Nanoscale actuators are essential components of the NEMS (nanoelectromechanical systems) and nanorobots of the future, and are expected to become a major area of development within nanotechnology. This paper demonstrates for the first time that individual polypyrrole (PPy) nanowires with diameters under 100 nm exhibit actuation behavior, and therefore can potentially be used for constructing nanoscale actuators. PPy is an electroactive polymer which can change volume on the basis of its oxidation state. PPy-based macroscale and microscale actuators have been demonstrated, but their nanoscale counterparts have not been realized until now. The research reported here answers positively the fundamental question of whether PPy wires still exhibit useful volume changes at the nanoscale. Nanowires with a 50 nm diameter and a length of approximately 6 {mu}m, are fabricated by chemical polymerization using track-etched polycarbonate membranes as templates. Their actuation response as a function of oxidation state is investigated by electrochemical AFM (atomic force microscopy). An estimate of the minimum actuation force is made, based on the displacement of the AFM cantilever.

  16. Electric Conductivity of Phosphorus Nanowires

    International Nuclear Information System (INIS)

    Jing-Xiang, Zhang; Hui, Li; Xue-Qing, Zhang; Kim-Meow, Liew

    2009-01-01

    We present the structures and electrical transport properties of nanowires made from different strands of phosphorus chains encapsulated in carbon nanotubes. Optimized by density function theory, our results indicate that the conductance spectra reveal an oscillation dependence on the size of wires. It can be seen from the density of states and current-voltage curves that the structure of nanowires affects their properties greatly. Among them, the DNA-like double-helical phosphorus nanowire exhibits the distinct characteristic of an approximately linear I – V relationship and has a higher conductance than others. The transport properties of phosphorus nanowires are highly correlated with their microstructures. (condensed matter: structure, mechanical and thermal properties)

  17. Semiconductor nanowires: optics and optoelectronics

    Energy Technology Data Exchange (ETDEWEB)

    Agarwal, R. [University of Pennsylvania, Department of Materials Science and Engineering, Philadelphia, PA (United States); Lieber, C.M. [Harvard University, Department of Chemistry and Chemical Biology, and Division of Engineering Applied Sciences, Cambridge, MA (United States)

    2006-11-15

    Single crystalline semiconductor nanowires are being extensively investigated due to their unique electronic and optical properties and their potential use in novel electronic and photonic devices. The unique properties of nanowires arise owing to their anisotropic geometry, large surface to volume ratio, and carrier and photon confinement in two dimensions (1D system). Currently, tremendous efforts are being devoted to rational synthesis of nanowire structures with control over their composition, structure, dopant concentration, characterization, fundamental properties, and assembly into functional devices. In this article we will review the progress made in the area of nanowire optics and optoelectronic devices, including diodes, lasers, detectors, and waveguides, and will outline the general challenges that must be overcome and some potential solutions in order to continue the exponential progress in this exciting area of research. (orig.)

  18. Metal-organic polyhedra-coated si nanowires for the sensitive detection of trace explosives

    NARCIS (Netherlands)

    Cao, Anping; Zhu, Wei; Shang, Jin; Klootwijk, Johan H.; Sudhölter, Ernst J.R.; Huskens, Jurriaan; de Smet, Louis C.P.M.

    2017-01-01

    Surface-modified silicon nanowire-based field-effect transistors (SiNW-FETs) have proven to be a promising platform for molecular recognition in miniature sensors. In this work, we present a novel nanoFET/device for the sensitive and selective detection of explosives based on affinity layers of

  19. IC Compatible Wafer Level Fabrication of Silicon Nanowire Field Effect Transistors for Biosensing Applications

    NARCIS (Netherlands)

    Moh, T.S.Y.

    2013-01-01

    In biosensing, nano-devices such as Silicon Nanowire Field Effect Transistors (SiNW FETs) are promising components/sensors for ultra-high sensitive detection, especially when samples are low in concentration or a limited volume is available. Current processing of SiNW FETs often relies on expensive

  20. Hierarchical Carbon Fibers with ZnO Nanowires for Volatile Sensing in Composite Curing (Postprint)

    Science.gov (United States)

    2014-07-01

    trapped under the pressure of the autoclave. After pressure is removed, these volatiles can expand and cause internal cracking and delaminations... tooth pick dipping. Each ZnO-nanowire on ITO Glass side sensor assembly was placed on a glass slide sample stage patterned with two voltage

  1. Bacterial resistance control on mineral surfaces of hydroxyapatite and human teeth via surface charge-driven antifouling coatings.

    Science.gov (United States)

    Venault, Antoine; Yang, Hui-Shan; Chiang, Yen-Che; Lee, Bor-Shuinn; Ruaan, Ruoh-Chyu; Chang, Yung

    2014-03-12

    This works reports a set of new functionalized polyethyleneimine (PEI) polymers, including a neutral PEGylated polymer PEI-g-PEGMA, a negatively charged polymer PEI-g-SA, and a zwitterionic polymer PEI-g-SBMA, and their use as antibiofouling coating agent for human teeth protection. Polymers were synthesized by Michael addition, XPS analysis revealed that each polymer could be efficiently coated onto hydroxyapatite, ceramic material used as a model tooth. Polymers carrying a negative net charge were more efficiently adsorbed, because of the establishment of electrostatic interactions with calcium ions. Protein adsorption tests revealed that two factors were important in the reduction of protein adsorption. Both the surface charge and the surface ability to bind and entrap water molecules had to be considered. PEI-g-SBMA, which zeta potential in PBS solution was negative, was efficient to inhibit the adsorption of BSA, a negative protein. On the other hand, it also resisted the adsorption of lysozyme, a positive protein, because zwitterionic molecules can easily entrap water and provide a very hydrophilic environment. Streptococcus mutans attachment tests performed unveiled that all modified polymers were efficient to resist this type of bacteria responsible for dental carries. Best results were also obtained with PEI-g-SBMA coating. This polymer was also shown to efficiently resist the adsorption of positively charged bacteria (Stenotrophomonas maltophilia). Tests performed on real human tooth showed that PEI-g-SBMA could inhibit up to 70% of bacteria adhesion, which constitutes a major result considering that surface of teeth is very rough, therefore physically promoting the attachment of proteins and bacteria.

  2. Multilayer Coating of Tetrandrine-loaded PLGA nanoparticles: Effect of surface charges on cellular uptake rate and drug release profile.

    Science.gov (United States)

    Meng, Rui; Li, Ke; Chen, Zhe; Shi, Chen

    2016-02-01

    The effect of surface charges on the cellular uptake rate and drug release profile of tetrandrine-loaded poly(lactic-co-glycolic acid) (PLGA) nanoparticles (TPNs) was studied. Stabilizer-free nanoprecipitation method was used in this study for the synthesis of TPNs. A typical layer-by-layer approach was applied for multi-coating particles' surface with use of poly(styrene sulfonate) sodium salt (PSS) as anionic layer and poly(allylamine hydrochloride) (PAH) as cationic layer. The modified TPNs were characterized by different physicochemical techniques such as Zeta sizer, scanning electron microscopy and transmission electron microscopy. The drug loading efficiency, release profile and cellular uptake rate were evaluated by high performance liquid chromatography and confocal laser scanning microscopy, respectively. The resultant PSS/PAH/PSS/PAH/TPNs (4 layers) exhibited spherical-shaped morphology with the average size of 160.3±5.165 nm and zeta potential of-57.8 mV. The encapsulation efficiency and drug loading efficiency were 57.88% and 1.73%, respectively. Multi-layer coating of polymeric materials with different charges on particles' surface could dramatically influence the drug release profile of TPNs (4 layers vs. 3 layers). In addition, variable layers of surface coating could also greatly affect the cellular uptake rate of TPNs in A549 cells within 8 h. Overall, by coating particles' surface with those different charged polymers, precise control of drug release as well as cellular uptake rate can be achieved simultaneously. Thus, this approach provides a new strategy for controllable drug delivery.

  3. Niosomal carriers enhance oral bioavailability of carvedilol: effects of bile salt-enriched vesicles and carrier surface charge.

    Science.gov (United States)

    Arzani, Gelareh; Haeri, Azadeh; Daeihamed, Marjan; Bakhtiari-Kaboutaraki, Hamid; Dadashzadeh, Simin

    2015-01-01

    Carvedilol (CRV) is an antihypertensive drug with both alpha and beta receptor blocking activity used to preclude angina and cardiac arrhythmias. To overcome the low, variable oral bioavailability of CRV, niosomal formulations were prepared and characterized: plain niosomes (without bile salts), bile salt-enriched niosomes (bilosomes containing various percentages of sodium cholate or sodium taurocholate), and charged niosomes (negative, containing dicetyl phosphate and positive, containing hexadecyl trimethyl ammonium bromide). All formulations were characterized in terms of encapsulation efficiency, size, zeta potential, release profile, stability, and morphology. Various formulations were administered orally to ten groups of Wistar rats (n=6 per group). The plasma levels of CRV were measured by a validated high-performance liquid chromatography (HPLC) method and pharmacokinetic properties of different formulations were characterized. Contribution of lymphatic transport to the oral bioavailability of niosomes was also investigated using a chylomicron flow-blocking approach. Of the bile salt-enriched vesicles examined, bilosomes containing 20% sodium cholate (F2) and 30% sodium taurocholate (F5) appeared to give the greatest enhancement of intestinal absorption. The relative bioavailability of F2 and F5 formulations to the suspension was estimated to be 1.84 and 1.64, respectively. With regard to charged niosomes, the peak plasma concentrations (Cmax) of CRV for positively (F7) and negatively charged formulations (F10) were approximately 2.3- and 1.7-fold higher than after a suspension. Bioavailability studies also revealed a significant increase in extent of drug absorption from charged vesicles. Tissue histology revealed no signs of inflammation or damage. The study proved that the type and concentration of bile salts as well as carrier surface charge had great influences on oral bioavailability of niosomes. Blocking the lymphatic absorption pathway

  4. Interfacing Inorganic Nanowire Arrays and Living Cells for Cellular Function Analysis.

    Science.gov (United States)

    Kwak, Minsuk; Han, Lin; Chen, Jonathan J; Fan, Rong

    2015-11-11

    Inorganic nanowires are among the most attractive functional materials, which have emerged in the past two decades. They have demonstrated applications in information technology and energy conversion, but their utility in biological or biomedical research remains relatively under-explored. Although nanowire-based sensors have been frequently reported for biomolecular detection, interfacing nanowire arrays and living mammalian cells for the direct analysis of cellular functions is a very recent endeavor. Cell-penetrating nanowires enabled effective delivery of biomolecules, electrical and optical stimulation and recording of intracellular signals over a long period of time. Non-penetrating, high-density nanowire arrays display rich interactions between the nanostructured substrate and the micro/nanoscale features of cell surfaces. Such interactions enable efficient capture of rare cells including circulating tumor cells and trafficking leukocytes from complex biospecimens. It also serves as a platform for probing cell traction force and neuronal guidance. The most recent advances in the field that exploits nanowire arrays (both penetrating and non-penetrating) to perform rapid analysis of cellular functions potentially for disease diagnosis and monitoring are reviewed. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Adjustable optical response of amorphous silicon nanowires integrated with thin films.

    Science.gov (United States)

    Dhindsa, Navneet; Walia, Jaspreet; Pathirane, Minoli; Khodadad, Iman; Wong, William S; Saini, Simarjeet Singh

    2016-04-08

    We experimentally demonstrate a new optical platform by integrating hydrogenated amorphous silicon nanowire arrays with thin films deposited on transparent substrates like glass. A 535 nm thick thin film is anisotropically etched to fabricate vertical nanowire arrays of 100 nm diameter arranged in a square lattice. Adjusting the nanowire length, and consequently the thin film thickness permits the optical properties of this configuration to be tuned for either transmission filter response or enhanced broadband absorption. Vivid structural colors are also achieved in reflection and transmission. The optical properties of the platform are investigated for three different etch depths. Transmission filter response is achieved for a configuration with nanowires on glass without any thin film. Alternatively, integrating thin film with nanowires increases the absorption efficiency by ∼97% compared to the thin film starting layer and by ∼78% over nanowires on glass. The ability to tune the optical response of this material in this fashion makes it a promising platform for high performance photovoltaics, photodetectors and sensors.

  6. Selective Laser Direct Patterning of Silver Nanowire Percolation Network Transparent Conductor for Capacitive Touch Panel.

    Science.gov (United States)

    Hong, Sukjoon; Yeo, Junyeob; Lee, Jinhwan; Lee, Habeom; Lee, Phillip; Lee, Seung S; Ko, Seung Hwan

    2015-03-01

    We introduce a facile method to enhance the functionality of a patterned metallic transparent conductor through selective laser ablation of metal nanowire percolation network. By scanning focused nanosecond pulsed laser on silver nanowire percolation network, silver nanowires are selectively ablated and patterned without using any conventional chemical etching or photolithography steps. Various arbitrary patterns of silver nanowire transparent conductors are readily created on the percolation network by changing various laser parameters such as repetition rate and power. The macroscopic optical and electrical properties of the percolation network transparent conductor can be easily tuned by changing the conductor pattern design via digital selective laser ablation. Further investigation on the silver nanowire based electrode line prepared by the ablation process substantiates that the general relation for a conducting thin film fails at a narrow width, which should be considered for the applications that requires a high resolution patterns. Finally, as a proof of concept, a capacitive touch sensor with diamond patterns has been demonstrated by selective laser ablation of metal nanowire percolation network.

  7. Endotaxial silicide nanowires: A review

    Energy Technology Data Exchange (ETDEWEB)

    Bennett, P.A., E-mail: peter.bennett@asu.edu [Physics Department, Arizona State University, Tempe, AZ 85287 (United States); School of Materials, Arizona State University, Tempe, AZ 85287 (United States); He, Zhian [School of Materials, Arizona State University, Tempe, AZ 85287 (United States); Smith, David J. [Physics Department, Arizona State University, Tempe, AZ 85287 (United States); School of Materials, Arizona State University, Tempe, AZ 85287 (United States); Ross, F.M. [IBM T. J. Watson Research Center, Yorktown Heights NY 10598 (United States)

    2011-10-03

    We review the topic of self-assembled endotaxial silicide nanowires on silicon. Crystallographic orientation, lattice mismatch and average dimensions are discussed for a variety of systems including Ti, Mn, Fe, Co, Ni, Pt and several rare earths on Si(100), Si(111) and Si(110) surfaces. In situ observations of growth dynamics support a constant-shape growth model, in which length, width and thickness all change in proportion as the nanowire grows, with thermally activated, facet-dependent rates.

  8. Silicon nanowires: structure and properties

    International Nuclear Information System (INIS)

    Nezhdanov, A.V.; Mashin, A.I.; Razuvaev, A.G.; Ershov, A.V.; Ignatov, S.K.

    2006-01-01

    An attempt to grow silicon nanowires has been made by electron beam evaporation on highly oriented pyrolytic substrate. Needle-like objects are located along the normal to a substrate (density 2 x 10 11 cm -2 ). For modeling quasi-one-dimensional objects calculations of nuclear structure and energy spectra have been accomplished. A fullerene-like structure Si 24 is proposed as a basic atomic configuration of silicon nanowires [ru

  9. Gas sensing properties of zinc stannate (Zn{sub 2}SnO{sub 4}) nanowires prepared by carbon assisted thermal evaporation process

    Energy Technology Data Exchange (ETDEWEB)

    Tharsika, T., E-mail: tharsika@siswa.um.edu.my [Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur (Malaysia); Haseeb, A.S.M.A., E-mail: haseeb@um.edu.my [Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur (Malaysia); Akbar, S.A., E-mail: akbar.1@osu.edu [Center for Industrial Sensors and Measurements (CISM), Department of Materials Science and Engineering, Ohio State University, 2041 College Road, Columbus, OH 43210 (United States); Sabri, M.F.M., E-mail: faizul@um.edu.my [Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur (Malaysia); Wong, Y.H., E-mail: yhwong@um.edu.my [Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur (Malaysia)

    2015-01-05

    Highlights: • Zn{sub 2}SnO{sub 4} nanowires are grown on Au/alumina substrate by a carbon assisted thermal evaporation process. • Optimum growth conditions for Zn{sub 2}SnO{sub 4} nanowires are determined. • Ethanol gas is selectively sensed with high sensitivity. - Abstract: Zn{sub 2}SnO{sub 4} nanowires are successfully synthesized by a carbon assisted thermal evaporation process with the help of a gold catalyst under ambient pressure. The as-synthesized nanowires are characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM) equipped with an energy dispersive X-ray spectroscopy (EDS). The XRD patterns and elemental mapping via TEM–EDS clearly indicate that the nanowires are Zn{sub 2}SnO{sub 4} with face centered spinel structure. HRTEM image confirms that Zn{sub 2}SnO{sub 4} nanowires are single crystalline with an interplanar spacing of 0.26 nm, which is ascribed to the d-spacing of (3 1 1) planes of Zn{sub 2}SnO{sub 4}. The optimum processing condition and a possible formation mechanism of these Zn{sub 2}SnO{sub 4} nanowires are discussed. Additionally, sensor performance of Zn{sub 2}SnO{sub 4} nanowires based sensor is studied for various test gases such as ethanol, methane and hydrogen. The results reveal that Zn{sub 2}SnO{sub 4} nanowires exhibit excellent sensitivity and selectivity toward ethanol with quick response and recovery times. The response of the Zn{sub 2}SnO{sub 4} nanowires based sensors to 50 ppm ethanol at an optimum operating temperature of 500 °C is about 21.6 with response and recovery times of about 116 s and 182 s, respectively.

  10. Synthesis, microstructure, and physical properties of metallic barcode nanowires

    Science.gov (United States)

    Park, Bum Chul; Kim, Young Keun

    2017-05-01

    With rapid progress in nanotechnology, nanostructured materials have come closer to our life. Single-component nanowires are actively investigated because of their novel properties, attributed to their nanoscale dimensions and adjustable aspect ratio, but their technical limitations cannot be resolved easily. Heterostructured nanomaterials gained attention as alternatives because they can improve the existing single-component structure or add new functions to it. Among them, barcode nanowires (BNWs), comprising at least two different functional segments, can perform multiple functions for use in biomedical sensors, information encoding and security, and catalysts. BNW applications require reliable response to the external field. Hence, researchers have been attempting to improve the reliability of synthesis and regulate the properties precisely. This article highlights the recent progress and prospects for the synthesis, properties, and applications of metallic BNWs with focus on the dependence of the magnetic, optical, and mechanical properties on material, composition, shape, and microstructure.

  11. Magnetic Tactile Sensor for Braille Reading

    KAUST Repository

    Alfadhel, Ahmed

    2016-04-27

    We report a biomimetic magnetic tactile sensor for Braille characters reading. The sensor consists of magnetic nanocomposite artificial cilia implemented on magnetic micro sensors. The nanocomposite is produced from the highly elastic polydimethylsiloxane and iron nanowires that exhibit a permanent magnetic behavior. This design enables remote operation and does not require an additional magnetic field to magnetize the nanowires. The highly elastic nanocomposite is easy to pattern, corrosion resistant and thermally stable. The tactile sensors can detect vertical and shear forces, which allows recognizing small changes in surface texture, as in the case of Braille dots. The 6 dots of a braille cell are read from top to bottom with a tactile sensor array consisting of 4 elements and 1 mm long nanocomposite cilia.

  12. Nanowire-templated microelectrodes for high-sensitivity pH detection

    DEFF Research Database (Denmark)

    Antohe, V.A.; Radu, Adrian; Mátéfi-Tempfli, Mária

    2009-01-01

    A highly sensitive pH capacitive sensor has been designed by confined growth of vertically aligned nanowire arrays on interdigited microelectrodes. The active surface of the device has been functionalized with an electrochemical pH transducer (polyaniline). We easily tune the device features...... by combining lithographic techniques with electrochemical synthesis. The reported electrical LC resonance measurements show considerable sensitivity enhancement compared to conventional capacitive pH sensors realized with microfabricated interdigited electrodes. The sensitivity can be easily improved...

  13. Bare and boron-doped cubic silicon carbide nanowires for electrochemical detection of nitrite sensitively

    OpenAIRE

    Tao Yang; Liqin Zhang; Xinmei Hou; Junhong Chen; Kuo-Chih Chou

    2016-01-01

    Fabrication of eletrochemical sensors based on wide bandgap compound semiconductors has attracted increasing interest in recent years. Here we report for the first time electrochemical nitrite sensors based on cubic silicon carbide (SiC) nanowires (NWs) with smooth surface and boron-doped cubic SiC NWs with fin-like structure. Multiple techniques including scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS...

  14. Structural and tunneling properties of Si nanowires

    KAUST Repository

    Montes Muñoz, Enrique

    2013-12-06

    We investigate the electronic structure and electron transport properties of Si nanowires attached to Au electrodes from first principles using density functional theory and the nonequilibrium Green\\'s function method. We systematically study the dependence of the transport properties on the diameter of the nanowires, on the growth direction, and on the length. At the equilibrium Au-nanowire distance we find strong electronic coupling between the electrodes and nanowires, which results in a low contact resistance. With increasing nanowire length we study the transition from metallic to tunneling conductance for small applied bias. For the tunneling regime we investigate the decay of the conductance with the nanowire length and rationalize the results using the complex band structure of the pristine nanowires. The conductance is found to depend strongly on the growth direction, with nanowires grown along the ⟨110⟩ direction showing the smallest decay with length and the largest conductance and current.

  15. Silver nanowires - unique templates for functional nanostructures

    Science.gov (United States)

    Sun, Yugang

    2010-09-01

    This feature article reviews the synthesis and application of silver nanowires with the focus on a polyol process that is capable of producing high quality silver nanowires with high yield. The as-synthesized silver nanowires can be used as both physical templates for the synthesis of metal/dielectric core/shell nanowires and chemical templates for the synthesis of metal nanotubes as well as semiconductor nanowires. Typical examples including Ag/SiO2 coaxial nanocables, single- and multiple-walled nanotubes made of Au-Ag alloy, AgCl nanowires and AgCl/Au core/shell nanowires are discussed in detail to illustrate the versatility of nanostructures derived from silver nanowire templates. Novel properties associated with these one-dimensional nanostructures are also briefly discussed to shed the light on their potential applications in electronics, photonics, optoelectronics, catalysis, and medicine.

  16. Nonlocal Optical Response of Plasmonic Nanowire Metamaterials

    Science.gov (United States)

    2014-01-01

    can be expressed as the product = ()()(). Making this substitution, the differential equation can then be written as 1 ...nanowire geometry and solution method. 61 52 Transmission and reflection of the nanowire metamaterial are now compared for full- vectorial

  17. Thermal conductivity reduction in silicon fishbone nanowires.

    Science.gov (United States)

    Maire, Jeremie; Anufriev, Roman; Hori, Takuma; Shiomi, Junichiro; Volz, Sebastian; Nomura, Masahiro

    2018-03-13

    Semiconductor nanowires are potential building blocks for future thermoelectrics because of their low thermal conductivity. Recent theoretical works suggest that thermal conductivity of nanowires can be further reduced by additional constrictions, pillars or wings. Here, we experimentally study heat conduction in silicon nanowires with periodic wings, called fishbone nanowires. We find that like in pristine nanowires, the nanowire cross-section controls thermal conductivity of fishbone nanowires. However, the periodic wings further reduce the thermal conductivity. Whereas an increase in the wing width only slightly affects the thermal conductivity, an increase in the wing depth clearly reduces thermal conductivity, and this reduction is stronger in the structures with narrower nanowires. Our experimental data is supported by the Callaway-Holland model, finite element modelling and phonon transport simulations.

  18. Quantitative measurements of C-reactive protein using silicon nanowire arrays

    Directory of Open Access Journals (Sweden)

    Min-Ho Lee

    2008-03-01

    Full Text Available Min-Ho Lee, Kuk-Nyung Lee, Suk-Won Jung, Won-Hyo Kim, Kyu-Sik Shin, Woo-Kyeong SeongKorea Electronics Technology Institute, Gyeonggi, KoreaAbstract: A silicon nanowire-based sensor for biological application showed highly desirable electrical responses to either pH changes or receptor-ligand interactions such as protein disease markers, viruses, and DNA hybridization. Furthermore, because the silicon nanowire can display results in real-time, it may possess superior characteristics for biosensing than those demonstrated in previously studied methods. However, despite its promising potential and advantages, certain process-related limitations of the device, due to its size and material characteristics, need to be addressed. In this article, we suggest possible solutions. We fabricated silicon nanowire using a top-down and low cost micromachining method, and evaluate the sensing of molecules after transfer and surface modifications. Our newly designed method can be used to attach highly ordered nanowires to various substrates, to form a nanowire array device, which needs to follow a series of repetitive steps in conventional fabrication technology based on a vapor-liquid-solid (VLS method. For evaluation, we demonstrated that our newly fabricated silicon nanowire arrays could detect pH changes as well as streptavidin-biotin binding events. As well as the initial proof-of-principle studies, C-reactive protein binding was measured: electrical signals were changed in a linear fashion with the concentration (1 fM to 1 nM in PBS containing 1.37 mM of salts. Finally, to address the effects of Debye length, silicon nanowires coupled with antigen proteins underwent electrical signal changes as the salt concentration changed.Keywords: silicon nanowire array, C-reactive protein, vapor-liquid-solid method

  19. Complex Electric-Field Induced Phenomena in Ferroelectric/Antiferroelectric Nanowires

    Science.gov (United States)

    Herchig, Ryan Christopher

    Perovskite ferroelectrics and antiferroelectrics have attracted a lot of attention owing to their potential for device applications including THz sensors, solid state cooling, ultra high density computer memory, and electromechanical actuators to name a few. The discovery of ferroelectricity at the nanoscale provides not only new and exciting possibilities for device miniaturization, but also a way to study the fundamental physics of nanoscale phenomena in these materials. Ferroelectric nanowires show a rich variety of physical characteristics which are advantageous to the design of nanoscale ferroelectric devices such as exotic dipole patterns, a strong dependence of the polarization and phonon frequencies on the electrical and mechanical boundary conditions, as well as a dependence of the transition temperatures on the diameter of the nanowire. Antiferroelectricity also exists at the nanoscale and, due to the proximity in energy of the ferroelectric and antiferroelectric phases, a phase transition from the ferroelectric to the antiferroelectric phase can be facilitated through the application of the appropriate mechanical and electrical boundary conditions. While much progress has been made over the past several decades to understand the nature of ferroelectricity/antiferroelectricity in nanowires, many questions remain unanswered. In particular, little is known about how the truncated dimensions affect the soft mode frequency dynamics or how various electrical and mechanical boundary conditions might change the nature of the phase transitions in these ferroelectric nanowires. Could nanowires offer a distinct advantage for solid state cooling applications? Few studies have been done to elucidate the fundamental physics of antiferroelectric nanowires. How the polarization in ferroelectric nanowires responds to a THz electric field remains relatively underexplored as well. In this work, the aim is to to develop and use computational tools that allow first

  20. Plasmon-enhanced refractometry using silver nanowire coatings on tilted fibre Bragg gratings.

    Science.gov (United States)

    Bialiayeu, A; Bottomley, A; Prezgot, D; Ianoul, A; Albert, J

    2012-11-09

    A novel technique for increasing the sensitivity of tilted fibre Bragg grating (TFBG) based refractometers is presented. The TFBG sensor was coated with chemically synthesized silver nanowires ~100 nm in diameter and several micrometres in length. A 3.5-fold increase in sensor sensitivity was obtained relative to the uncoated TFBG sensor. This increase is associated with the excitation of surface plasmons by orthogonally polarized fibre cladding modes at wavelengths near 1.5 μm. Refractometric information is extracted from the sensor via the strong polarization dependence of the grating resonances using a Jones matrix analysis of the transmission spectrum of the fibre.

  1. Multifunctional Magnetic Nanowires for Biomagnetic Interfacing Concepts

    Science.gov (United States)

    2006-07-14

    1 Final Performance Report Multifunctional Magnetic Nanowires for Biomagnetic Interfacing Concepts AFOSR Agreement Number F49620-02-1-0307 July 14...AND DATES COVERED Final report covering 06/15/02 –12/15/05 4. TITLE AND SUBTITLE Multifunctional Magnetic Nanowires for Biomagnetic Interfacing...nanowires for biomagnetic applications. These include (i) tuning of magnetic and other physical properties of nanowires, (ii) selective

  2. Semiconducting silicon nanowires for biomedical applications

    CERN Document Server

    Coffer, JL

    2014-01-01

    Biomedical applications have benefited greatly from the increasing interest and research into semiconducting silicon nanowires. Semiconducting Silicon Nanowires for Biomedical Applications reviews the fabrication, properties, and applications of this emerging material. The book begins by reviewing the basics, as well as the growth, characterization, biocompatibility, and surface modification, of semiconducting silicon nanowires. It goes on to focus on silicon nanowires for tissue engineering and delivery applications, including cellular binding and internalization, orthopedic tissue scaffol

  3. Controlling nanowire emission profile using conical taper

    DEFF Research Database (Denmark)

    Gregersen, Niels; Nielsen, Torben Roland; Mørk, Jesper

    2008-01-01

    The influence of a conical taper on nanowire light emission is studied. For nanowires with divergent output beams, the introduction of tapers improves the emission profile and increase the collection efficiency of the detection optics.......The influence of a conical taper on nanowire light emission is studied. For nanowires with divergent output beams, the introduction of tapers improves the emission profile and increase the collection efficiency of the detection optics....

  4. Nanowire resonant tunneling diodes

    Science.gov (United States)

    Björk, M. T.; Ohlsson, B. J.; Thelander, C.; Persson, A. I.; Deppert, K.; Wallenberg, L. R.; Samuelson, L.

    2002-12-01

    Semiconductor heterostructures and their implementation into electronic and photonic devices have had tremendous impact on science and technology. In the development of quantum nanoelectronics, one-dimensional (1D) heterostructure devices are receiving a lot of interest. We report here functional 1D resonant tunneling diodes obtained via bottom-up assembly of designed segments of different semiconductor materials in III/V nanowires. The emitter, collector, and the central quantum dot are made from InAs and the barrier material from InP. Ideal resonant tunneling behavior, with peak-to-valley ratios of up to 50:1 and current densities of 1 nA/μm2 was observed at low temperatures.

  5. Indium Arsenide Nanowires

    DEFF Research Database (Denmark)

    Madsen, Morten Hannibal

    is presented. A series of experiments with formation of a droplet on top of the wires has been carried out and pyramidal shaped structures at the NW top with pure zinc blende crystal structure are observed. A novel in-situ experiment with fabrication of NWs and simultanous characterization using x......This thesis is about growth of Au-assisted and self-assisted InAs nanowires (NWs). The wires are synthesized using a solid source molecular beam epitaxy (MBE) system and characterized with several techniques including scanning electron microscopy (SEM), transmission electron microscopy (TEM) and x......-ray diffraction is performed with a MBE system attached to a synchrotron beam line. The evolution in crystal structure is monitored for different growth conditions and can be correlated to post growth analysis in TEM. This type of studies gives much more detailed information on formation of the crystal structure...

  6. Daylight-driven photocatalytic degradation of ionic dyes with negatively surface-charged In2S3 nanoflowers: dye charge-dependent roles of reactive species

    Science.gov (United States)

    Ge, Suxiang; Cai, Lejuan; Li, Dapeng; Fa, Wenjun; Zhang, Yange; Zheng, Zhi

    2015-12-01

    Even though dye degradation is a successful application of semiconductor photocatalysis, the roles of reactive species in dye degradation have not received adequate attention. In this study, we systematically investigated the degradation of two cationic dyes (rhodamine B and methylene blue) and two anionic dyes (methyl orange and orange G) over negatively surface-charged In2S3 nanoflowers synthesized at 80 °C under indoor daylight lamp irradiation. It is notable to find In2S3 nanoflowers were more stable in anionic dyes degradation compared to that in cationic dyes removal. The active species trapping experiments indicated photogenerated electrons were mainly responsible for cationic dyes degradation, but holes were more important in anionic dyes degradation. A surface-charge-dependent role of reactive species in ionic dye degradation was proposed for revealing such interesting phenomenon. This study would provide a new insight for preparing highly efficient daylight-driven photocatalyst for ionic dyes degradation.

  7. 12-Crown-4-based amphipathic lipid and corresponding metal cation complexes for gene therapy applications: FT-IR characterization and surface charge determination

    Science.gov (United States)

    Bruni, P.; Fino, V.; Pisani, M.; Tosi, G.; Stipa, P.; Ferraris, P.; Francescangeli, O.

    2009-02-01

    The new lipid 1,2- O-dioleyl-3- O-{2-[(12-crown-4)-methoxy]-ethyl}- sn-glycerol, 12C4L, has been synthesized. This molecule can coordinate different cations that should make the corresponding liposome a good candidate as vector of genetic material for possible applications in gene therapy. An important feature of the molecule is the possibility to modulate the net surface charge of their complexes with metal cations, which is important to provide efficient DNA transfections. The molecule and its complexes with some metal cations (Mg 2+, Ca 2+, Mn 2+) have been characterized by FT-IR spectroscopy and band attributions confirmed by Density Functional Theory calculations. The net surface charge has been determined by Z potential determinations.

  8. Nanophotonic Image Sensors

    Science.gov (United States)

    Hu, Xin; Wen, Long; Yu, Yan; Cumming, David R. S.

    2016-01-01

    The increasing miniaturization and resolution of image sensors bring challenges to conventional optical elements such as spectral filters and polarizers, the properties of which are determined mainly by the materials used, including dye polymers. Recent developments in spectral filtering and optical manipulating techniques based on nanophotonics have opened up the possibility of an alternative method to control light spectrally and spatially. By integrating these technologies into image sensors, it will become possible to achieve high compactness, improved process compatibility, robust stability and tunable functionality. In this Review, recent representative achievements on nanophotonic image sensors are presented and analyzed including image sensors with nanophotonic color filters and polarizers, metamaterial‐based THz image sensors, filter‐free nanowire image sensors and nanostructured‐based multispectral image sensors. This novel combination of cutting edge photonics research and well‐developed commercial products may not only lead to an important application of nanophotonics but also offer great potential for next generation image sensors beyond Moore's Law expectations. PMID:27239941

  9. Suppression of surface charge accumulation on Al{sub 2}O{sub 3}-filled epoxy resin insulator under dc voltage by direct fluorination

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Boya; Zhang, Guixin, E-mail: guixin@mail.tsinghua.edu.cn; Li, Chuanyang; He, Jinliang [Department of Electrical Engineering, Tsinghua University, Beijing 100084 (China); Wang, Qiang [Department of Electrical Engineering, Tsinghua University, Beijing 100084 (China); School of Mechatronic Engineering, Beijing Institute of Technology, Beijing 100081 (China); An, Zhenlian [Department of Electrical Engineering, Tongji University, Shanghai 201804 (China)

    2015-12-15

    Surface charge accumulation on insulators under high dc voltage is a major factor that may lead to the reduction of insulation levels in gas insulated devices. In this paper, disc insulators made of Al{sub 2}O{sub 3}-filled epoxy resin were surface fluorinated using a F{sub 2}/N{sub 2} mixture (12.5% F{sub 2}) at 50 °C and 0.1 MPa for different durations of 15 min, 30 min and 60 min. A dc voltage was applied to the insulator for 30 min and the charge density on its surface was measured by an electrostatic probe. The results revealed significant lower surface charge densities on the fluorinated insulators in comparison with the original one. Surface conductivity measurements indicated a higher surface conductivity by over three orders of magnitude after fluorination, which would allow the charges to transfer along the surface and thus may suppress their accumulation. Further, attenuated total reflection infrared analysis and surface morphology observations of the samples revealed that the introduction of fluoride groups altered the surface physicochemical properties. These structure changes, especially the physical defects reduced the depth of charge traps in the surface layer, which was verified by the measurement of energy distributions of the electron and hole traps based on the isothermal current theory. The results in this paper demonstrate that fluorination can be a promising and effective method to suppress surface charge accumulation on epoxy insulators in gas insulated devices.

  10. Combined Effects of Surface Charge and Pore Size on Co-enhanced Permeability and Ion Selectivity through RGO-OCNT Nanofiltration Membranes.

    Science.gov (United States)

    Zhang, Haiguang; Quan, Xie; Chen, Shuo; Fan, Xinfei; Wei, Gaoliang; Yu, Hongtao

    2018-04-04

    Nanofiltration (NF) has received much attention for wastewater treatment and desalination. However, NF membranes generally suffer from the trade-off between permeability and selectivity. In this work, the co-enhancement of permeability and ion selectivity was achieved through tuning the surface charge and pore size of oxidized carbon nanotube (OCNT) intercalated reduced graphene oxide (RGO) membranes. With the increase of OCNT content from 0 to 83%, the surface charge and the pore size are increased. The permeability increased to 10.6 L m-2 h-1 bar-1 and rejection rate reached 78.1% for Na2SO4 filtration at a transmembrane pressure of 2 bar, which were 11.8 and 1.3 times higher than those of pristine RGO membrane. The composite membrane also showed 11.1 times higher permeability (11.1 L m-2 h-1 bar-1) and 2.9 times higher rejection rate (35.3%) for NaCl filtration. The analyses based on Donnan steric pore model suggest that the increased permeability is attributed to the combined effects of enlarged pore size and increased surface charge, while the enhanced ion selectivity is mainly dependent on the electrostatic interaction between the membrane and target ions. This finding provides a new insight for the development of high-performance NF membranes in water treatment and desalination.

  11. Magnetic micropillar sensors for force sensing

    KAUST Repository

    Alfadhel, Ahmed

    2015-04-13

    A force sensor system consisting of bioinspired, magnetic and highly elastic micropillars integrated on a magnetic field sensing element is reported. The micro-pillars are made of a nanocomposite consisting of magnetic nanowires incorporated into polydimethylsiloxane. The permanent magnetic behavior of the nanowires allows remote operation without an additional magnetic field to magnetize the nanowires, which simplifies miniaturization and system integration. We demonstrate the potential of this concept by realizing a tactile sensing element. The developed sensor element operates at power consumption of 75 μW and has a detection range between 0–120 kPa and a resolution of 2.7 kPa, which can easily be tuned in a wide range.

  12. Improving Gas Sensing Properties of Tin Oxide Nanowires Palladium-Coated Using a Low Cost Technique

    Directory of Open Access Journals (Sweden)

    M. Barzegar

    2012-12-01

    Full Text Available Thin films of SnO2 nanowires were successfully prepared by using chemical vapor deposition (CVD process on quartz substrates. Afterwards, a thin  layer of palladium (Pd as a catalyst was coated on top of nanowires. For the deposition of Pd, a simple and low cost technique of spray pyrolysis was employed, which caused an intensive enhancement on the sensing response of fabricated sensors. Prepared sensor devices were exposed to liquid petroleum gas (LPG and vapor of ethanol (C2H5OH. Results indicate that SnO2 nanowires sensors coated with Pd as a catalyst show decreasing in response time (~40s to 1000ppm of LPG at a relatively low operating temperature (200o C. SnO2 /Pd nanowire devices show gas sensing response time and recovery time as short as 50s and 10s respectively with a high sensitivity value of ~120 for C2H5OH, that is remarkable in comparison with other reports.

  13. Mapping the local structure of nanowires

    DEFF Research Database (Denmark)

    Persson, Johan Mikael; Wagner, Jakob Birkedal

    2013-01-01

    The crystallographic and compositional structure of heterostructured semiconductor nanowires has been studied by means of transmission electron microscopy. The native geometry of the studied InP-GaAs nanowires (80-100 nm in diameter) is in general too thick for reliable high-resolution TEM imaging....... Nano Beam Electron Diffraction (NBED) is shown to be a powerful technique to reveal strain near the interface of compositional change in heterostructured semiconductor nanowires. Furthermore, the relative orientation of the nanowires is studied by means of NBED revealing the nanowires to be very...

  14. Micromagnetic simulations of cylindrical magnetic nanowires

    KAUST Repository

    Ivanov, Yurii P.

    2015-05-27

    This chapter reviews micromagnetic simulations of cylindrical magnetic nanowires and their ordered arrays. It starts with a description of the theoretical background of micromagnetism. The chapter discusses main magnetization reversal modes, domain wall types, and state diagrams in cylindrical nanowires of different types and sizes. The results of the hysteresis process in individual nanowires and nanowire arrays also are presented. Modeling results are compared with experimental ones. The chapter also discusses future trends in nanowire applications in relation to simulations, such as current-driven dynamics, spintronics, and spincaloritronics. The main micromagnetic programs are presented and discussed, together with the corresponding links.

  15. Photoelectrochemistry of Semiconductor Nanowire Arrays

    Energy Technology Data Exchange (ETDEWEB)

    Mallouk, Thomas E; Redwing, Joan M

    2009-11-10

    This project supported research on the growth and photoelectrochemical characterization of semiconductor nanowire arrays, and on the development of catalytic materials for visible light water splitting to produce hydrogen and oxygen. Silicon nanowires were grown in the pores of anodic aluminum oxide films by the vapor-liquid-solid technique and were characterized electrochemically. Because adventitious doping from the membrane led to high dark currents, silicon nanowire arrays were then grown on silicon substrates. The dependence of the dark current and photovoltage on preparation techniques, wire diameter, and defect density was studied for both p-silicon and p-indium phosphide nanowire arrays. The open circuit photovoltage of liquid junction cells increased with increasing wire diameter, reaching 350 mV for micron-diameter silicon wires. Liquid junction and radial p-n junction solar cells were fabricated from silicon nano- and microwire arrays and tested. Iridium oxide cluster catalysts stabilized by bidentate malonate and succinate ligands were also made and studied for the water oxidation reaction. Highlights of this project included the first papers on silicon and indium phosphide nanowire solar cells, and a new procedure for making ligand-stabilized water oxidation catalysts that can be covalently linked to molecular photosensitizers or electrode surfaces.

  16. Modular chemiresistive sensor

    Energy Technology Data Exchange (ETDEWEB)

    Alam, Maksudul M.; Sampathkumaran, Uma

    2018-02-20

    The present invention relates to a modular chemiresistive sensor. In particular, a modular chemiresistive sensor for hypergolic fuel and oxidizer leak detection, carbon dioxide monitoring and detection of disease biomarkers. The sensor preferably has two gold or platinum electrodes mounted on a silicon substrate where the electrodes are connected to a power source and are separated by a gap of 0.5 to 4.0 .mu.M. A polymer nanowire or carbon nanotube spans the gap between the electrodes and connects the electrodes electrically. The electrodes are further connected to a circuit board having a processor and data storage, where the processor can measure current and voltage values between the electrodes and compare the current and voltage values with current and voltage values stored in the data storage and assigned to particular concentrations of a pre-determined substance such as those listed above or a variety of other substances.

  17. Electrically Injected UV-Visible Nanowire Lasers

    Energy Technology Data Exchange (ETDEWEB)

    Wang, George T.; Li, Changyi; Li, Qiming; Liu, Sheng; Wright, Jeremy Benjamin; Brener, Igal; Luk, Ting -Shan; Chow, Weng W.; Leung, Benjamin; Figiel, Jeffrey J.; Koleske, Daniel D.; Lu, Tzu-Ming

    2015-09-01

    There is strong interest in minimizing the volume of lasers to enable ultracompact, low-power, coherent light sources. Nanowires represent an ideal candidate for such nanolasers as stand-alone optical cavities and gain media, and optically pumped nanowire lasing has been demonstrated in several semiconductor systems. Electrically injected nanowire lasers are needed to realize actual working devices but have been elusive due to limitations of current methods to address the requirement for nanowire device heterostructures with high material quality, controlled doping and geometry, low optical loss, and efficient carrier injection. In this project we proposed to demonstrate electrically injected single nanowire lasers emitting in the important UV to visible wavelengths. Our approach to simultaneously address these challenges is based on high quality III-nitride nanowire device heterostructures with precisely controlled geometries and strong gain and mode confinement to minimize lasing thresholds, enabled by a unique top-down nanowire fabrication technique.

  18. Methods for synthesizing metal oxide nanowires

    Science.gov (United States)

    Sunkara, Mahendra Kumar; Kumar, Vivekanand; Kim, Jeong H.; Clark, Ezra Lee

    2016-08-09

    A method of synthesizing a metal oxide nanowire includes the steps of: combining an amount of a transition metal or a transition metal oxide with an amount of an alkali metal compound to produce a mixture; activating a plasma discharge reactor to create a plasma discharge; exposing the mixture to the plasma discharge for a first predetermined time period such that transition metal oxide nanowires are formed; contacting the transition metal oxide nanowires with an acid solution such that an alkali metal ion is exchanged for a hydrogen ion on each of the transition metal oxide nanowires; and exposing the transition metal oxide nanowires to the plasma discharge for a second predetermined time period to thermally anneal the transition metal oxide nanowires. Transition metal oxide nanowires produced using the synthesis methods described herein are also provided.

  19. Electronic and mechanical properties of chemically functionalized nanowires

    Science.gov (United States)

    Bidasaria, Sanjay K.

    2009-12-01

    Organic and inorganic nanostructured materials, nano- and mesoscale objects and devices, and their integration into existing microelectronic technologies have been at the center of recent fundamental and applied research in nanotechnology. One of the critical needs is to develop an enhanced predictive capability of structure-property correlations and enable robust high performance systems by design. My thesis work was concerned with the theoretical and experimental studies of electronic and mechanical properties of chemically functionalized nanowires. I will first describe a theoretical approach for investigating structure-property correlations in atomic-sized metallic wires based on the Density Functional Theory (DFT) for structure calculations and the Non-equilibrium Green's Function (NEGF) technique for electronic transport properties simulations. This synergistic approach is shown to yield the atomic structure of the smallest niobium nanowires. Furthermore, the method was applied to simulate electronic properties of chemically functionalized graphene nanoribbons. Further, I will demonstrate an experimental technique for simultaneous measurements of force and conductance in atomic-size objects based on quartz tuning fork piezoelectric sensors. A peculiar scaling effect, relevant for a broad range of test and measurement applications, namely the squeeze film effect, was observed during the development of the sensors. Using theoretical analysis based on finite element simulations of the hydrodynamic behavior of the sensors in a broad range of ambient conditions, I explain the observed phenomenon.

  20. Optical absorption of silicon nanowires

    International Nuclear Information System (INIS)

    Xu, T.; Lambert, Y.; Krzeminski, C.; Grandidier, B.; Stiévenard, D.; Lévêque, G.; Akjouj, A.; Pennec, Y.; Djafari-Rouhani, B.

    2012-01-01

    We report on simulations and measurements of the optical absorption of silicon nanowires (NWs) versus their diameter. We first address the simulation of the optical absorption based on two different theoretical methods: the first one, based on the Green function formalism, is useful to calculate the scattering and absorption properties of a single or a finite set of NWs. The second one, based on the finite difference time domain (FDTD) method, is well-adapted to deal with a periodic set of NWs. In both cases, an increase of the onset energy for the absorption is found with increasing diameter. Such effect is experimentally illustrated, when photoconductivity measurements are performed on single tapered Si nanowires connected between a set of several electrodes. An increase of the nanowire diameter reveals a spectral shift of the photocurrent intensity peak towards lower photon energies that allow to tune the absorption onset from the ultraviolet radiations to the visible light spectrum.

  1. Tunneling magnetoresistance in Si nanowires

    KAUST Repository

    Montes Muñoz, Enrique

    2016-11-09

    We investigate the tunneling magnetoresistance of small diameter semiconducting Si nanowires attached to ferromagnetic Fe electrodes, using first principles density functional theory combined with the non-equilibrium Green\\'s functions method for quantum transport. Silicon nanowires represent an interesting platform for spin devices. They are compatible with mature silicon technology and their intrinsic electronic properties can be controlled by modifying the diameter and length. Here we systematically study the spin transport properties for neutral nanowires and both n and p doping conditions. We find a substantial low bias magnetoresistance for the neutral case, which halves for an applied voltage of about 0.35 V and persists up to 1 V. Doping in general decreases the magnetoresistance, as soon as the conductance is no longer dominated by tunneling.

  2. Electrochemical synthesis of multisegmented nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Kok, Kuan-Ying; Ng, Inn-Khuan; Saidin, Nur Ubaidah [Malaysian Nuclear Agency, Bangi, 43000 Kajang (Malaysia)

    2012-11-27

    Electrochemical deposition has emerged as a promising route for nanostructure fabrication in recent years due to the many inherent advantages it possesses. This study focuses on the synthesis of high-aspect-ratio multisegmented Au/Ni nanowires using template-directed sequential electrochemical deposition techniques. By selectively removing the Ni segments in the nanowires, high-yield of pure gold nanorods of predetermined lengths was obtained. Alternatively, the sacrificial Ni segments in the nanowires can be galvanically displaced with Bi and Te to form barbells structures with Bi{sub x}Te{sub y} nanotubes attached to neighbouring gold segments. Detailed studies on the nanostructures obtained were carried out using various microscopy, diffraction and probebased techniques for structural, morphological and chemical characterizations.

  3. True reference nanosensor realized with silicon nanowires.

    Science.gov (United States)

    Tarasov, A; Wipf, M; Bedner, K; Kurz, J; Fu, W; Guzenko, V A; Knopfmacher, O; Stoop, R L; Calame, M; Schönenberger, C

    2012-06-26

    Conventional gate oxide layers (e.g., SiO(2), Al(2)O(3), or HfO(2)) in silicon field-effect transistors (FETs) provide highly active surfaces, which can be exploited for electronic pH sensing. Recently, great progress has been achieved in pH sensing using compact integrateable nanowire FETs. However, it has turned out to be much harder to realize a true reference electrode, which--while sensing the electrostatic potential--does not respond to the proton concentration. In this work, we demonstrate a highly effective reference sensor, a so-called reference FET, whose proton sensitivity is suppressed by as much as 2 orders of magnitude. To do so, the Al(2)O(3) surface of a nanowire FET was passivated with a self-assembled monolayer of silanes with a long alkyl chain. We have found that a full passivation can be achieved only after an extended period of self-assembling lasting several days at 80 °C. We use this slow process to measure the number of active proton binding sites as a function of time by a quantitative comparison of the measured nonlinear pH-sensitivities to a theoretical model (site-binding model). Furthermore, we have found that a partially passivated surface can sense small changes in the number of active binding sites reaching a detection limit of δN(s) ≈ 170 μm(-2) Hz(-1/2) at 10 Hz and pH 3.

  4. Semiconductor nanowires and templates for electronic applications

    Energy Technology Data Exchange (ETDEWEB)

    Ying, Xiang

    2009-07-15

    This thesis starts by developing a platform for the organized growth of nanowires directly on a planar substrate. For this, a method to fabricate horizontal porous alumina membranes is studied. The second part of the thesis focuses on the study of nanowires. It starts by the understanding of the growth mechanisms of germanium nanowires and follows by the structural and electrical properties at the single nanowire level. Horizontally aligned porous anodic alumina (PAA) was used as a template for the nanowire synthesis. Three PAA arrangements were studied: - high density membranes - micron-sized fingers - multi-contacts Membranes formed by a high density of nanopores were obtained by anodizing aluminum thin films. Metallic and semiconducting nanowires were synthesized into the PAA structures via DC deposition, pulsed electro-depostion and CVD growth. The presence of gold, copper, indium, nickel, tellurium, and silicon nanowires inside PAA templates was verified by SEM and EDX analysis. Further, room-temperature transport measurements showed that the pores are completely filled till the bottom of the pores. In this dissertation, single crystalline and core-shell germanium nanowires are synthesized using indium and bismuth as catalyst in a chemical vapor deposition procedure with germane (GeH{sub 4}) as growth precursor. A systematic growth study has been performed to obtain high aspect-ratio germanium nanowires. The influence of the growth conditions on the final morphology and the crystalline structure has been determined via scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). In the case of indium catalyzed germanium nanowires, two different structures were identified: single crystalline and crystalline core-amorphous shell. The preferential growth axis of both kinds of nanowires is along the [110] direction. The occurrence of the two morphologies was found to only depend on the nanowire dimension. In the case of bismuth

  5. Multi-peak ferromagnetic resonance in Co nanowires array

    Czech Academy of Sciences Publication Activity Database

    Kraus, Luděk; Lynnyková, Anna; Azamat, Dmitry; Drahokoupil, Jan; Kopeček, Jaromír; Rameš, Michal

    2017-01-01

    Roč. 421, Jan (2017), s. 241-249 ISSN 0304-8853 R&D Projects: GA MŠk LO1409; GA MŠk LM2015088; GA ČR GAP102/12/2177 Grant - others:FUNBIO(XE) CZ.2.16/3.1.00/21568 Institutional support: RVO:68378271 Keywords : nanowires * ferromagnetic resonance * dipolar interactions * surface anisotropy * spin waves Subject RIV: JB - Sensors, Measurment, Regulation OBOR OECD: Electrical and electronic engineering Impact factor: 2.630, year: 2016

  6. Copper nanowire coated carbon fibers as efficient substrates for detecting designer drugs using SERS.

    Science.gov (United States)

    Halouzka, Vladimir; Halouzkova, Barbora; Jirovsky, David; Hemzal, Dusan; Ondra, Peter; Siranidi, Eirini; Kontos, Athanassios G; Falaras, Polycarpos; Hrbac, Jan

    2017-04-01

    Miniature Surface Enhanced Raman Scattering (SERS) sensors were fabricated by coating the carbon fiber microelectrodes with copper nanowires. The coating procedure, based on anodizing the copper wire in ultrapure water followed by cathodic deposition of the anode-derived material onto carbon fiber electrodes, provides a "clean" copper nanowire network. The developed miniature (10µm in diameter and 2mm in length) and nanoscopically rough SERS substrates are applicable in drug sensing, as shown by the detection and resolving of a range of seized designer drugs in trace amounts (microliter volumes of 10 -10 -10 -12 M solutions). The copper nanowire modified carbon microfiber substrates could also find further applications in biomedical and environmental sensing. Copyright © 2016 Elsevier B.V. All rights reserved.

  7. Amperometric Morphine Detection Using Pt-Co Alloy Nanowire Array-modified Electrode

    International Nuclear Information System (INIS)

    Tao, Manlan; Xu, Feng; Li, Yueting; Xu, Quanqing; Chang, Yanbing; Yang, Yunhui; Wu, Zaisheng

    2010-01-01

    Pt-Co alloy nanowire array was directly synthesized by electrochemical deposition with polycarbonate template at -1.0V and subsequent chemical etching of the template. The use of Pt-Co alloy nanowire array-modified electrode (Pt- Co NAE) for the determination of morphine (MO) is described. The morphology of the Pt-Co alloy nanowire array has been investigated by scanning electron microscopy (SEM) and energy disperse X-ray spectroscopy (EDS) analysis), respectively. The resulting Pt-Co NAE offered a linear amperometric response for morphine ranging from 2.35 x 10 -5 to 2.39 x 10 -3 M with a detection limit of 7.83 x 10 -6 M at optimum conditions. This sensor displayed high sensitivity and long-term stability

  8. Indium Arsenide Nanowires

    DEFF Research Database (Denmark)

    Madsen, Morten Hannibal

    This thesis is about growth of Au-assisted and self-assisted InAs nanowires (NWs). The wires are synthesized using a solid source molecular beam epitaxy (MBE) system and characterized with several techniques including scanning electron microscopy (SEM), transmission electron microscopy (TEM) and ...... tumor cells (CTCs) have been fabricated. The CTC concentration is extremely low and highly effective devices for capturing the CTCs may improve the treatment of cancer patients....... is presented. A series of experiments with formation of a droplet on top of the wires has been carried out and pyramidal shaped structures at the NW top with pure zinc blende crystal structure are observed. A novel in-situ experiment with fabrication of NWs and simultanous characterization using x...... and its dependence on growth parameters. By fabricating the NWs on silicon-on-insulator substrates we demonstrate electrically addressable NWs that are still standing vertically on the substrate and can potentially be used for intra-cellular recordings. Devices for biological experiments using vertically...

  9. Germanium nanowires grown using different catalyst metals

    Energy Technology Data Exchange (ETDEWEB)

    Gouveia, R.C., E-mail: riama@ifsp.edu.br [Departamento de Física – NanO Lab, Universidade Federal de São Carlos, Rod. Washington Luís, Km 235 – SP 310, São Carlos, CEP 13565-905 (Brazil); Área de Ciências, Instituto Federal de Educação Ciência e Tecnologia de São Paulo, Rua Américo Ambrósio, 269, Jd. Canaã, Sertãozinho, CEP 14169-263 (Brazil); Kamimura, H.; Munhoz, R.; Rodrigues, A.D. [Departamento de Física – NanO Lab, Universidade Federal de São Carlos, Rod. Washington Luís, Km 235 – SP 310, São Carlos, CEP 13565-905 (Brazil); Leite, E.R. [Departamento de Química – LIEC, Universidade Federal de São Carlos, São Carlos, CEP 13565-905 (Brazil); Chiquito, A.J. [Departamento de Física – NanO Lab, Universidade Federal de São Carlos, Rod. Washington Luís, Km 235 – SP 310, São Carlos, CEP 13565-905 (Brazil)

    2016-11-01

    Germanium nanowires have been synthesized by the well known vapor-liquid-solid growth mechanism using gold, silver, cooper, indium and nickel as catalyst metals. The influence of metal seeds on nanowires structural and electronic transport properties was also investigated. Electron microscopy images demonstrated that, despite differences in diameters, all nanowires obtained presented single crystalline structures. X-ray patterns showed that all nanowires were composed by germanium with a small amount of germanium oxide, and the catalyst metal was restricted at the nanowires' tips. Raman spectroscopy evidenced the long range order in the crystalline structure of each sample. Electrical measurements indicated that variable range hopping was the dominant mechanism in carrier transport for all devices, with similar hopping distance, regardless the material used as catalyst. Then, in spite of the differences in synthesis temperatures and nanowires diameters, the catalyst metals have not affected the composition and crystalline quality of the germanium nanowires nor the carrier transport in the germanium nanowire network devices. - Highlights: • Ge nanowires were grown by VLS method using Au, Ag, Cu, In and Ni as catalysts. • All nanowires presented high single crystalline quality and long range order. • Devices showed semiconducting behavior having VRH as dominant transport mechanism. • The metal catalyst did not influence structural properties or the transport mechanism.

  10. High frequency III-V nanowire MOSFETs

    Science.gov (United States)

    Lind, Erik

    2016-09-01

    III-V nanowire transistors are promising candidates for very high frequency electronics applications. The improved electrostatics originating from the gate-all-around geometry allow for more aggressive scaling as compared with planar field-effect transistors, and this can lead to device operation at very high frequencies. The very high mobility possible with In-rich devices can allow very high device performance at low operating voltages. GaN nanowires can take advantage of the large band gap for high voltage operation. In this paper, we review the basic physics and device performance of nanowire field- effect transistors relevant for high frequency performance. First, the geometry of lateral and vertical nanowire field-effect transistors is introduced, with special emphasis on the parasitic capacitances important for nanowire geometries. The basic important high frequency transistor metrics are introduced. Secondly, the scaling properties of gate-all-around nanowire transistors are introduced, based on geometric length scales, demonstrating the scaling possibilities of nanowire transistors. Thirdly, to model nanowire transistor performance, a two-band non-parabolic ballistic transistor model is used to efficiently calculate the current and transconductance as a function of band gap and nanowire size. The intrinsic RF metrics are also estimated. Finally, experimental state-of-the-art nanowire field-effect transistors are reviewed and benchmarked, lateral and vertical transistor geometries are explored, and different fabrication routes are highlighted. Lateral devices have demonstrated operation up to 350 GHz, and vertical devices up to 155 GHz.

  11. Magnetic properties of mosaic nanocomposites composed of nickel and cobalt nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Castillo-Sepúlveda, S.; Corona, R.M. [Departamento de Física, Universidad de Santiago de Chile (USACH), Av. Ecuador 3493, 9170124 Santiago (Chile); Altbir, D. [Departamento de Física, Universidad de Santiago de Chile (USACH), Av. Ecuador 3493, 9170124 Santiago (Chile); Center for the Development of Nanoscience and Nanotechnology (CEDENNA), 9170124 Santiago (Chile); Escrig, J., E-mail: juan.escrig@usach.cl [Departamento de Física, Universidad de Santiago de Chile (USACH), Av. Ecuador 3493, 9170124 Santiago (Chile); Center for the Development of Nanoscience and Nanotechnology (CEDENNA), 9170124 Santiago (Chile)

    2016-10-15

    Mosaic nanocomposites composed of nickel and cobalt nanowires arranged in different configurations were investigated using Monte Carlo simulations and a simple model that considers single-domain structures including length corrections due to the shape anisotropy. Our results showed that for an ordered array both the coercivity and the remanence decrease linearly as a function of the concentration of nickel nanowires. Besides, we obtained that the magnetic properties of an array of a certain hard magnetic material (cobalt) will not change, unless we have more than 50% of nanowires of other soft magnetic material (nickel) in the array. In principle the second material could be other soft magnetic material, but could also be a nonmagnetic material or could even be a situation in which some of the pore arrays were not filled by electrodeposition. Therefore, our results allow us to predict the behavior of magnetic mosaic nanocomposites that are promising candidates for functional electrodes, sensors, and model catalysts. - Highlights: • Mosaic nanocomposites composed of magnetic nanowires were investigated. • Magnetic properties can be adjusted by varying the concentration of nanowires. • Our results allow us to predict the behavior of magnetic mosaic nanocomposites.

  12. CHANGES IN THE ELECTRICAL SURFACE CHARGE AND TRANSPLANTATION PROPERTIES OF TA3 ASCITES TUMOR CELLS DURING SHORT-TERM MAINTENANCE IN AN ISOTONIC SALT SOLUTION

    Energy Technology Data Exchange (ETDEWEB)

    Tenforde, T. S.; Richards, W. R.; Kelly, L. S.

    1980-12-01

    TA3 ascites tumor cells maintained in vitro as a dilute suspension in 0.9% NaCl solution (physiological saline) were found to undergo time-dependent degenerative processes leading to alterations in both membrane characteristics and tumor transplantation properties. A 30% decrease in the negative cellular surface charge density occurred within 2 hr. when TA3 cells were incubated in a 0.9% NaCl solution at 23 °C. A similar reduction in negative surface charge density occurred within 0.5 hr. when the medium was maintained at 37 °C. This time-dependent reduction in surface charge was prevented when cellular metabolism was blocked either by maintaining the medium at 4 °C. or by adding 1 mM cyanide ion to a 23 °C medium. TA3 cells incubated as a dilute suspension in 0.9% NaCl solution at 23 °C also exhibited a large 9 time-dependent reduction in proliferative capacity in isogeneic LAF1/J hosts, as indicated by an increase in the tumor dose for 50% mortality (TD50). Lowering the temperature of the medium to 4 °C was observed to slow the onset of the degenerative processes that lead to a decreased transplantability of TA3 cells. The modification in growth properties of TA3 cells maintained in vitro was found to be attributable in part to an alteration in tumor histocompatibility. This effect was demonstrated by comparing the tumor growth kinetics and TD50 values in normal hosts versus hosts that had been immunosuppressed by whole-body irradiation. Following the in vitro maintenance of TA3 cells, nigrosin dye exclusion tests were performed as a means of assessing cell viability. Evidence obtained in this series of experiments indicated that vital staining is an inadequate criterion for judging either the extent of cell membrane damage or the loss of cellular proliferative capacity.

  13. Electrostatic contribution of surface charge residues to the stability of a thermophilic protein: benchmarking experimental and predicted pKa values.

    Directory of Open Access Journals (Sweden)

    Chi-Ho Chan

    Full Text Available Optimization of the surface charges is a promising strategy for increasing thermostability of proteins. Electrostatic contribution of ionizable groups to the protein stability can be estimated from the differences between the pKa values in the folded and unfolded states of a protein. Using this pKa-shift approach, we experimentally measured the electrostatic contribution of all aspartate and glutamate residues to the stability of a thermophilic ribosomal protein L30e from Thermococcus celer. The pKa values in the unfolded state were found to be similar to model compound pKas. The pKa values in both the folded and unfolded states obtained at 298 and 333 K were similar, suggesting that electrostatic contribution of ionizable groups to the protein stability were insensitive to temperature changes. The experimental pKa values for the L30e protein in the folded state were used as a benchmark to test the robustness of pKa prediction by various computational methods such as H++, MCCE, MEAD, pKD, PropKa, and UHBD. Although the predicted pKa values were affected by crystal contacts that may alter the side-chain conformation of surface charged residues, most computational methods performed well, with correlation coefficients between experimental and calculated pKa values ranging from 0.49 to 0.91 (p<0.01. The changes in protein stability derived from the experimental pKa-shift approach correlate well (r = 0.81 with those obtained from stability measurements of charge-to-alanine substituted variants of the L30e protein. Our results demonstrate that the knowledge of the pKa values in the folded state provides sufficient rationale for the redesign of protein surface charges leading to improved protein stability.

  14. Cleaved-Coupled Nanowire Lasers

    Science.gov (United States)

    2013-01-15

    nanowires with a 40-nm gap show significant modulation of the threshold gain among different lasing modes (Fig. 4, blue dia- monds ). Within the...spectrometer (Princeton Instruments/Acton) equipped with a 1,200-groove/mm grating blazed at 300 nm and a liquid N2-cooled charge-coupled device. The

  15. Photonic nanowires for quantum optics

    DEFF Research Database (Denmark)

    Munsch, M.; Claudon, J.; Bleuse, J.

    Photonic nanowires (PWs) are simple dielectric structures for which a very efficient and broadband spontaneous emission (SE) control has been predicted [1]. Recently, a single photon source featuring a record high efficiency was demonstrated using this geometry [2]. Using time-resolved micro-phot...

  16. Optical properties of semiconducting nanowires

    NARCIS (Netherlands)

    Vugt, L.K. van

    2007-01-01

    Semiconductor nanowires of high purity and crystallinity hold promise as building blocks for opto-electronical devices at the nanoscale.. They are commonly grown via a Vapor-Liquid-Solid (VLS) mechanism in which metal (nano) droplets collect the semiconductor precursors to form a solution which,

  17. Tunneling and Transport in Nanowires

    International Nuclear Information System (INIS)

    Goldman, Allen M.

    2016-01-01

    The goal of this program was to study new physical phenomena that might be relevant to the performance of conductive devices and circuits of the smallest realizable feature sizes possible using physical rather than biological techniques. Although the initial scientific work supported involved the use of scanning tunneling microscopy and spectroscopy to ascertain the statistics of the energy level distribution of randomly sized and randomly shaped quantum dots, or nano-crystals, the main focus was on the investigation of selected properties, including superconductivity, of conducting and superconducting nanowires prepared using electron-beam-lithography. We discovered a magnetic-field-restoration of superconductivity in out-of-equilibrium nanowires driven resistive by current. This phenomenon was explained by the existence of a state in which dissipation coexisted with nonvanishing superconducting order. We also produced ultra-small superconducting loops to study a predicted anomalous fluxoid quantization, but instead, found a magnetic-field-dependent, high-resistance state, rather than superconductivity. Finally, we developed a simple and controllable nanowire in an induced charged layer near the surface of a masked single-crystal insulator, SrTiO 3 . The layer was induced using an electric double layer transistor employing an ionic liquid (IL). The transport properties of the induced nanowire resembled those of collective electronic transport through an array of quantum dots.

  18. Tunneling and Transport in Nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Goldman, Allen M. [Univ. of Minnesota, Minneapolis, MN (United States)

    2016-08-16

    The goal of this program was to study new physical phenomena that might be relevant to the performance of conductive devices and circuits of the smallest realizable feature sizes possible using physical rather than biological techniques. Although the initial scientific work supported involved the use of scanning tunneling microscopy and spectroscopy to ascertain the statistics of the energy level distribution of randomly sized and randomly shaped quantum dots, or nano-crystals, the main focus was on the investigation of selected properties, including superconductivity, of conducting and superconducting nanowires prepared using electron-beam-lithography. We discovered a magnetic-field-restoration of superconductivity in out-of-equilibrium nanowires driven resistive by current. This phenomenon was explained by the existence of a state in which dissipation coexisted with nonvanishing superconducting order. We also produced ultra-small superconducting loops to study a predicted anomalous fluxoid quantization, but instead, found a magnetic-field-dependent, high-resistance state, rather than superconductivity. Finally, we developed a simple and controllable nanowire in an induced charged layer near the surface of a masked single-crystal insulator, SrTiO3. The layer was induced using an electric double layer transistor employing an ionic liquid (IL). The transport properties of the induced nanowire resembled those of collective electronic transport through an array of quantum dots.

  19. Electron Transport in Si Nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Ramayya, E [Arizona State University, Tempe, AZ (United States); Vasileska, D [Arizona State University, Tempe, AZ (United States); Goodnick, S M [Arizona State University, Tempe, AZ (United States); Knezevic, I [University of Wisconsin, Madison, WI (United States)

    2006-05-15

    We investigate electron transport in silicon nanowires taking into account acoustic, non-polar optical phonons and surface/interface roughness scattering. We find that at very high transverse fields the reduced density of final states to which the carriers can scatter into gives rise to a reduced influence of interface-roughness scattering, which is promising result from a fabrication point of view.

  20. Morphology of living cells cultured on nanowire arrays with varying nanowire densities and diameters.

    Science.gov (United States)

    Li, Zhen; Persson, Henrik; Adolfsson, Karl; Oredsson, Stina; Prinz, Christelle N

    2018-04-02

    Vertical nanowire arrays are increasingly investigated for their applications in steering cell behavior. The geometry of the array is an important parameter, which influences the morphology and adhesion of cells. Here, we investigate the effects of array geometry on the morphology of MCF7 cancer cells and MCF10A normal-like epithelial cells. Different gallium phosphide nanowire array-geometries were produced by varying the nanowire density and diameter. Our results show that the cell size is smaller on nanowires compared to flat gallium phosphide. The cell area decreases with increasing the nanowire density on the substrate. We observed an effect of the nanowire diameter on MCF10A cells, with a decreased cell area on 40 nm diameter nanowires, compared to 60 and 80 nm diameter nanowires in high-density arrays. The focal adhesion morphology depends on the extent to which cells are contacting the substrate. For low nanowire densities and diameters, cells are lying on the substrate and we observed large focal adhesions at the cell edges. In contrast, for high nanowire densities and diameters, cells are lying on top of the nanowires and we observed point-like focal adhesions distributed over the whole cell. Our results constitute a step towards the ability to fine-tune cell behavior on nanowire arrays.

  1. Direct observation of shear piezoelectricity in poly-l-lactic acid nanowires

    Directory of Open Access Journals (Sweden)

    Michael Smith

    2017-07-01

    Full Text Available Piezoelectric polymers are capable of interconverting mechanical and electrical energy, and are therefore candidate materials for biomedical applications such as sensors, actuators, and energy harvesters. In particular, nanowires of these materials are attractive as they can be unclamped, flexible and sensitive to small vibrations. Poly-l-lactic acid (PLLA nanowires have been investigated for their use in biological applications, but their piezoelectric properties have never been fully characterised, even though macroscopic films and fibres have been shown to exhibit shear piezoelectricity. This piezoelectric mode is particularly interesting for in vivo applications where shear forces are especially relevant, and is similar to what has been observed in natural materials such as bone and DNA. Here, using piezo-response force microscopy (PFM, we report the first direct observation of shear piezoelectricity in highly crystalline and oriented PLLA nanowires grown by a novel template-wetting method. Our results are validated using finite-element simulations and numerical analysis, which importantly and more generally allow for accurate interpretation of PFM signals in soft nanostructured materials. Our work opens up the possibility for the development of biocompatible and sustainable piezoelectric nanogenerators and sensors based on polymer nanowires.

  2. Direct observation of shear piezoelectricity in poly-l-lactic acid nanowires

    Science.gov (United States)

    Smith, Michael; Calahorra, Yonatan; Jing, Qingshen; Kar-Narayan, Sohini

    2017-07-01

    Piezoelectric polymers are capable of interconverting mechanical and electrical energy, and are therefore candidate materials for biomedical applications such as sensors, actuators, and energy harvesters. In particular, nanowires of these materials are attractive as they can be unclamped, flexible and sensitive to small vibrations. Poly-l-lactic acid (PLLA) nanowires have been investigated for their use in biological applications, but their piezoelectric properties have never been fully characterised, even though macroscopic films and fibres have been shown to exhibit shear piezoelectricity. This piezoelectric mode is particularly interesting for in vivo applications where shear forces are especially relevant, and is similar to what has been observed in natural materials such as bone and DNA. Here, using piezo-response force microscopy (PFM), we report the first direct observation of shear piezoelectricity in highly crystalline and oriented PLLA nanowires grown by a novel template-wetting method. Our results are validated using finite-element simulations and numerical analysis, which importantly and more generally allow for accurate interpretation of PFM signals in soft nanostructured materials. Our work opens up the possibility for the development of biocompatible and sustainable piezoelectric nanogenerators and sensors based on polymer nanowires.

  3. Magnetostatic Interaction in Fe-Co Nanowires

    Directory of Open Access Journals (Sweden)

    Laura Elbaile

    2012-01-01

    Full Text Available Arrays of Fe-Co alloy nanowires with diameter around 35 nm and several micrometers in length have been synthesized by codepositing Fe and Co into porous anodic alumina. The morphology, structure, and magnetic properties of the nanowires (hysteresis loops and remanence curves were characterized by SEM, TEM, X-ray diffraction (XRD, and VSM, respectively. The XRD patterns indicate that the Fe-Co nanowires present a body-centered cubic (bcc structure and a preferred (110 orientation perpendicular to the template surface. From the hysteresis loops obtained with the magnetic field applied in the axis direction of the nanowires, we can observe that the coercive field slightly decreases when the nanowire length increases. This magnetic behaviour is analyzed considering the shape anisotropy and the dipolar interactions among nanowires.

  4. Magnetic crossover effect in Nickel nanowire arrays

    Energy Technology Data Exchange (ETDEWEB)

    Ghaddar, A. [Laboratoire de Magnetisme de Bretagne, CNRS-FRE 3117, C.S. 93837, 29238 Brest, Cedex (France); Gloaguen, F. [Laboratoire de Chimie, Electrochimie Moleculaire et Chimie Analytique, CNRS-UMR 6521, C. S. 93837 Brest Cedex 3 (France); Gieraltowski, J. [Laboratoire de Magnetisme de Bretagne, CNRS-FRE 3117, C.S. 93837, 29238 Brest, Cedex (France); Tannous, C., E-mail: tannous@univ-brest.f [Laboratoire de Magnetisme de Bretagne, CNRS-FRE 3117, C.S. 93837, 29238 Brest, Cedex (France)

    2011-05-01

    A crossover effect in the magnetic reversal mechanism within arrays of Nickel nanowires whose diameter varies from 15 to 100 nm is observed around 50 nm. Hysteresis loops and FMR measurements confirm that nanowire diameter controls effectively the nanowire easy axis as well as the magnetization reversal mechanism. This might be very interesting for spintronic devices based on current-induced domain motion such as non-volatile magnetic memory elements (MRAM) and low Ohmic loss devices.

  5. Effects of Surface Charge and Functional Groups on the Adsorption and Binding Forms of Cu and Cd on Roots of indica and japonica Rice Cultivars

    Directory of Open Access Journals (Sweden)

    Zhao-Dong Liu

    2017-08-01

    Full Text Available This work was designed to understand the mechanisms of adsorption of copper (Cu and cadmium (Cd on roots of indica and japonica varieties of rice. Six varieties each of indica and japonica rice were grown in hydroponics and the chemical properties of the root surface were analyzed, including surface charges and functional groups (-COO- groups as measured by the streaming potential and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR. Binding forms of heavy metals adsorbed on rice roots were identified using sequential extraction methods. In rice roots exposed to Cu and Cd solutions, Cu existed mainly in both exchangeable and complexed forms, whereas Cd existed mainly in the exchangeable form. The amounts of exchangeable Cu and Cd and total adsorbed metal cations on the roots of indica varieties were significantly greater than those on the roots of japonica varieties, and the higher negative charges and the larger number of functional groups on the roots of indica varieties were responsible for their higher adsorption capacity and greater binding strength for Cu and Cd. Surface charge and functional groups on roots play an important role in the adsorption of Cu and Cd on the rice roots.

  6. Enhanced ionized impurity scattering in nanowires

    Science.gov (United States)

    Oh, Jung Hyun; Lee, Seok-Hee; Shin, Mincheol

    2013-06-01

    The electronic resistivity in silicon nanowires is investigated by taking into account scattering as well as the donor deactivation from the dielectric mismatch. The effects of poorly screened dopant atoms from the dielectric mismatch and variable carrier density in nanowires are found to play a crucial role in determining the nanowire resistivity. Using Green's function method within the self-consistent Born approximation, it is shown that donor deactivation and ionized impurity scattering combined with the charged interface traps successfully to explain the increase in the resistivity of Si nanowires while reducing the radius, measured by Björk et al. [Nature Nanotech. 4, 103 (2009)].

  7. Diluted magnetic semiconductor nanowires exhibiting magnetoresistance

    Science.gov (United States)

    Yang, Peidong [El Cerrito, CA; Choi, Heonjin [Seoul, KR; Lee, Sangkwon [Daejeon, KR; He, Rongrui [Albany, CA; Zhang, Yanfeng [El Cerrito, CA; Kuykendal, Tevye [Berkeley, CA; Pauzauskie, Peter [Berkeley, CA

    2011-08-23

    A method for is disclosed for fabricating diluted magnetic semiconductor (DMS) nanowires by providing a catalyst-coated substrate and subjecting at least a portion of the substrate to a semiconductor, and dopant via chloride-based vapor transport to synthesize the nanowires. Using this novel chloride-based chemical vapor transport process, single crystalline diluted magnetic semiconductor nanowires Ga.sub.1-xMn.sub.xN (x=0.07) were synthesized. The nanowires, which have diameters of .about.10 nm to 100 nm and lengths of up to tens of micrometers, show ferromagnetism with Curie temperature above room temperature, and magnetoresistance up to 250 Kelvin.

  8. Composite-Nanoparticles Thermal History Sensors

    Science.gov (United States)

    2014-05-01

    developing composite nanostructure-based (core-shell nanoparticles, heterostructure nanowires , and nano-flakes) temperature history sensors for recording the...shell microspheres …………………………………….. 72 7.2 Ga2O3 nanowires …………………………………………….. 76 7.3 GaN porous microtubes …………………………………….. 79 7.4 Coated CNTs...HRTEM experiments of nanoparticles and holey Al2O3 supporting films for high temperature experiments of nanowires . The sandwiched carbon films or

  9. Single crystalline PtSi nanowires, PtSi/Si/PtSi nanowire heterostructures, and nanodevices.

    Science.gov (United States)

    Lin, Yung-Chen; Lu, Kuo-Chang; Wu, Wen-Wei; Bai, Jingwei; Chen, Lih J; Tu, K N; Huang, Yu

    2008-03-01

    We report the formation of PtSi nanowires, PtSi/Si/PtSi nanowire heterostructures, and nanodevices from such heterostructures. Scanning electron microscopy studies show that silicon nanowires can be converted into PtSi nanowires through controlled reactions between lithographically defined platinum pads and silicon nanowires. High-resolution transmission electron microscopy studies show that PtSi/Si/PtSi heterostructure has an atomically sharp interface with epitaxial relationships of Si[110]//PtSi[010] and Si(111)//PtSi(101). Electrical measurements show that the pure PtSi nanowires have low resistivities approximately 28.6 microOmega.cm and high breakdown current densities>1x10(8) A/cm2. Furthermore, using single crystal PtSi/Si/PtSi nanowire heterostructures with atomically sharp interfaces, we have fabricated high-performance nanoscale field-effect transistors from intrinsic silicon nanowires, in which the source and drain contacts are defined by the metallic PtSi nanowire regions, and the gate length is defined by the Si nanowire region. Electrical measurements show nearly perfect p-channel enhancement mode transistor behavior with a normalized transconductance of 0.3 mS/microm, field-effect hole mobility of 168 cm2/V.s, and on/off ratio>10(7), demonstrating the best performing device from intrinsic silicon nanowires.

  10. Copper (II) oxide nanowires for p-type conductometric NH3 sensing

    Science.gov (United States)

    Shao, F.; Hernández-Ramírez, F.; Prades, J. D.; Fàbrega, C.; Andreu, T.; Morante, J. R.

    2014-08-01

    Copper (II) oxide (CuO) is a metal oxide suitable for developing solid state gas sensors. Nevertheless, a detailed insight into the chemical-to-electrical transduction mechanisms between gas molecules and this metal oxide is still limited. Here, individual CuO nanowires were evaluated as ammonia (NH3) and hydrogen sulphide (H2S) sensors, validating the p-type character of this semiconductor. The working principle behind their performance was qualitatively modeled and it was concluded that adsorbed oxygen at the surface plays a key role necessary to explain the experimental data. Compared to their counterparts of SnO2 nanowires, an appreciable sensitivity enhancement to NH3 for concentrations below 100 ppm was demonstrated.

  11. Current distribution in conducting nanowire networks

    Science.gov (United States)

    Kumar, Ankush; Vidhyadhiraja, N. S.; Kulkarni, Giridhar U.

    2017-07-01

    Conducting nanowire networks find diverse applications in solar cells, touch-screens, transparent heaters, sensors, and various related transparent conducting electrode (TCE) devices. The performances of these devices depend on effective resistance, transmittance, and local current distribution in these networks. Although, there have been rigorous studies addressing resistance and transmittance in TCE, not much attention is paid on studying the distribution of current. Present work addresses this compelling issue of understanding current distribution in TCE networks using analytical as well as Monte-Carlo approaches. We quantified the current carrying backbone region against isolated and dangling regions as a function of wire density (ranging from percolation threshold to many multiples of threshold) and compared the wired connectivity with those obtained from template-based methods. Further, the current distribution in the obtained backbone is studied using Kirchhoff's law, which reveals that a significant fraction of the backbone (which is believed to be an active current component) may not be active for end-to-end current transport due to the formation of intervening circular loops. The study shows that conducting wire based networks possess hot spots (extremely high current carrying regions) which can be potential sources of failure. The fraction of these hot spots is found to decrease with increase in wire density, while they are completely absent in template based networks. Thus, the present work discusses unexplored issues related to current distribution in conducting networks, which are necessary to choose the optimum network for best TCE applications.

  12. In Situ Study of Noncatalytic Metal Oxide Nanowire Growth

    DEFF Research Database (Denmark)

    Rackauskas, Simas; Jiang, Hua; Wagner, Jakob Birkedal

    2014-01-01

    The majority of the nanowire synthesis methods utilize catalyst particles to guide the nanowire geometry. In contrast, catalyst-free methods are attractive for facile fabrication of pure nanowires without the need for catalyst preparation. Nonetheless, how nanowire growth is guided without...

  13. Nanowire NMOS Logic Inverter Characterization.

    Science.gov (United States)

    Hashim, Yasir

    2016-06-01

    This study is the first to demonstrate characteristics optimization of nanowire N-Channel Metal Oxide Semiconductor (NW-MOS) logic inverter. Noise margins and inflection voltage of transfer characteristics are used as limiting factors in this optimization. A computer-based model used to produce static characteristics of NW-NMOS logic inverter. In this research two circuit configuration of NW-NMOS inverter was studied, in first NW-NMOS circuit, the noise margin for (low input-high output) condition was very low. For second NMOS circuit gives excellent noise margins, and results indicate that optimization depends on applied voltage to the inverter. Increasing gate to source voltage with (2/1) nanowires ratio results better noise margins. Increasing of applied DC load transistor voltage tends to increasing in decreasing noise margins; decreasing this voltage will improve noise margins significantly.

  14. Schottky-Gated Probe-Free ZnO Nanowire Biosensor

    KAUST Repository

    Yeh, Ping-Hung

    2009-12-28

    (Figure Presented) A nanowire-based nanosensor for detecting biologically and chemically charged molecules that is probe-free and highly sensitive is demonstrated. The device relies on the nonsymmetrical Schottky contact under reverse bias (see figure) and is much more sensitive than the device based on the symmetric ohmic contact. This approach serves as a guideline for designing more practical chemical and biochemical sensors. © 2009 WILEY-VCH Verlag GmbH & Co. KGaA.

  15. Multisensor system based on bisphthalocyanine nanowires for the detection of antioxidants

    International Nuclear Information System (INIS)

    Gay Martín, Mónica; Saja, José Antonio de; Muñoz, Raquel; Rodríguez-Méndez, María Luz

    2012-01-01

    Highlights: ► Sensors based on LnPc 2 nanowires can be prepared by electrodeposition (EDP). ► An electronic tongue can be constructed by combining EDP sensors with a data treatment system. ► The e-tongue is able to discriminate antioxidants of interest in the food industry. ► The fast preparation and excellent performance of these nanostructured sensors is an advantage. - Abstract: Electrophoretic deposition has been used to prepare thin films based on nanowires of three lanthanoid bisphthalocyaninates (including dysprosium, gadolinium and lutetium). Nanowires of similar structural characteristics have been obtained for the three compounds by tuning the electrophoretic conditions according to the redox properties of each phthalocyanine. The three electrodes have been used to form an array of sensors that has been employed to discriminate phenolic antioxidants of interest in the food industry including caffeic, gallic, vanillic and ferulic acids. The Principal Component Analysis (PCA) and the Partial Least Squares Discriminant Analysis (PLS-DA) of the electrochemical signals has allowed a clear discrimination of the four phenols analyzed according to the number of phenolic groups attached to the structure (monophenol, diphenol or triphenol). The PCA loading plots indicate that the three electrodes bring complementary information facilitating the discrimination of the studied solutions. In addition, good correlations between the intensity of the redox processes observed in the electrodes and the concentration of phenolic compounds have been found with detection limits in the range of 10 −5 –10 −6 mol L −1 and good reproducibility. The fast preparation of these nanowires based films and their excellent performance offer a new sensing platform for the detection of antioxidants in a fast, reliable way.

  16. Angular Magnetoresistance of Nanowires with Alternating Cobalt and Nickel Segments

    KAUST Repository

    Mohammed, Hanan

    2017-06-22

    Magnetization reversal in segmented Co/Ni nanowires with varying number of segments was studied using angular Magnetoresistance (MR) measurements on isolated nanowires. The MR measurements offer an insight into the pinning of domain walls within the nanowires. Angular MR measurements were performed on nanowires with two and multiple segments by varying the angle between the applied magnetic field and nanowire (−90° ≤θ≤90°). The angular MR measurements reveal that at lower values of θ the switching fields are nearly identical for the multisegmented and two-segmented nanowires, whereas at higher values of θ, a decrease in the switching field is observed in the case of two segmented nanowires. The two segmented nanowires generally exhibit a single domain wall pinning event, whereas an increased number of pinning events are characteristic of the multisegmented nanowires at higher values of θ. In-situ magnetic force microscopy substantiates reversal by domain wall nucleation and propagation in multisegmented nanowires.

  17. Pulsed laser deposition of aluminum nitride nanowires

    Science.gov (United States)

    Yunusova, N. R.; Kargin, N. I.; Ryndya, S. M.; Gusev, A. S.; Antonenko, S. V.; Timofeev, A. A.

    2018-01-01

    The possibility of AlN nanowires deposition on single-crystal silicon substrates by pulsed laser deposition in vacuum is shown in this work. Experimental samples were investigated by scanning electron microscopy and infrared Fourier spectroscopy. It is shown that the possible mechanism for the AlN nanowires formation is the "vapor-liquid-crystal" mechanism.

  18. Functionalization of magnetic nanowires by charged biopolymers

    DEFF Research Database (Denmark)

    Magnin, D.; Callegari, V.; Mátéfi-Tempfli, Stefan

    2008-01-01

    We report on a facile method for the preparation of biocompatible and bioactive magnetic nanowires. The method consists of the direct deposition of polysaccharides by layer-by-layer (LbL) assembly onto a brush of metallic nanowires; obtained by electrodeposition of the metal within the nanopores ...

  19. Optical properties of nanowire metamaterials with gain

    DEFF Research Database (Denmark)

    Isidio de Lima, Joaquim Junior; Adam, Jost; Rego, Davi

    2016-01-01

    The transmittance, reflectance and absorption of a nanowire metamaterial with optical gain are numerically simulated and investigated. It is assumed that the metamaterial is represented by aligned silver nanowires embedded into a semiconductor matrix, made of either silicon or gallium phosphide...

  20. Moessbauer study of Fe-Co nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Chen Ziyu [Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou (China)]. E-mail: chenzy@lzu.edu.cn; Zhan Qingfeng; Xue Desheng; Li Fashen [Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou (China); Zhou Xuezhi; Kunkel, Henry; Williams, Gwyn [Department of Physics and Astronomy, the University of Manitoba (Canada)

    2002-01-28

    Arrays of Fe{sub 1-x}Co{sub x} (0.0{<=}x{<=}0.92) nanowires have been prepared by an electrochemical process, co-depositing Fe and Co atoms into the pores of anodic aluminium; their compositions were determined by atomic absorption spectroscopy. Transmission electron microscope results show that the nanowires are regularly spaced and uniform in shape with lengths of about 7.5 {mu}m and diameters of 20 nm. The x-ray diffraction indicates a texture in the deposited nanowires. For the composition below 82 at.% cobalt, the nanowires had a body-centred-cubic structure with a [110] preferred orientation. For the 92 at.% cobalt sample, the alloy exhibited a mixture of bcc and face-centred-cubic structure. The room temperature {sup 57}Fe Moessbauer spectra of the arrays of Fe{sub 1-x}Co{sub x} nanowires have second and fifth absorption lines of the six-line pattern with almost zero intensity, indicating that the internal magnetic field in the nanowires lies along the long axis of the nanowire. The maximum values of the hyperfine field (B{sub hf} 36.6{+-}0.1 T) and isomer shift (IS=0.06{+-}0.01 mm s-1) occur for 44 at.% cobalt. The variations of the isomer shift and the linewidths with composition indicate that the Fe{sub 1-x}Co{sub x} alloy nanowires around the equiatomic composition are in an atomistic disordered state. (author)

  1. High-Performance Single Nanowire Tunnel Diodes

    DEFF Research Database (Denmark)

    Wallentin, Jesper; Persson, Johan Mikael; Wagner, Jakob Birkedal

    2010-01-01

    We demonstrate single nanowire tunnel diodes with room temperature peak current densities of up to 329 A/cm(2). Despite the large surface to volume ratio of the type-II InP-GaAs axial heterostructure nanowires, we measure peak to valley current ratios (PVCR) of up to 8.2 at room temperature and 27...

  2. Growth and structural characterization of III-V semiconductor nanowires

    OpenAIRE

    Rieger, Torsten

    2015-01-01

    In this thesis, the growth and structural properties of III-V semiconductor nanowires and nanowire heterostructures are studied. These nanowires represent structures suitable for both fundamental physics and applications in electronic devices such as (tunnel) field effect transistors. The III-V nanowires are grown with molecular beam epitaxy, high κ dielectric layers are deposited conformally around the nanowires by atomic layer deposition. The morphological and structural characteristics of ...

  3. Superconductive silicon nanowires using gallium beam lithography.

    Energy Technology Data Exchange (ETDEWEB)

    Henry, Michael David; Jarecki, Robert Leo,

    2014-01-01

    This work was an early career LDRD investigating the idea of using a focused ion beam (FIB) to implant Ga into silicon to create embedded nanowires and/or fully suspended nanowires. The embedded Ga nanowires demonstrated electrical resistivity of 5 m-cm, conductivity down to 4 K, and acts as an Ohmic silicon contact. The suspended nanowires achieved dimensions down to 20 nm x 30 nm x 10 m with large sensitivity to pressure. These structures then performed well as Pirani gauges. Sputtered niobium was also developed in this research for use as a superconductive coating on the nanowire. Oxidation characteristics of Nb were detailed and a technique to place the Nb under tensile stress resulted in the Nb resisting bulk atmospheric oxidation for up to years.

  4. Diamond nanowires: fabrication, structure, properties, and applications.

    Science.gov (United States)

    Yu, Yuan; Wu, Liangzhuan; Zhi, Jinfang

    2014-12-22

    C(sp(3) )C-bonded diamond nanowires are wide band gap semiconductors that exhibit a combination of superior properties such as negative electron affinity, chemical inertness, high Young's modulus, the highest hardness, and room-temperature thermal conductivity. The creation of 1D diamond nanowires with their giant surface-to-volume ratio enhancements makes it possible to control and enhance the fundamental properties of diamond. Although theoretical comparisons with carbon nanotubes have shown that diamond nanowires are energetically and mechanically viable structures, reproducibly synthesizing the crystalline diamond nanowires has remained challenging. We present a comprehensive, up-to-date review of diamond nanowires, including a discussion of their synthesis along with their structures, properties, and applications. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Nanowire-decorated microscale metallic electrodes

    DEFF Research Database (Denmark)

    Vlad, A.; Mátéfi-Tempfli, M.; Antohe, V.A.

    2008-01-01

    of lithographically defined metallic microelectrodes. The anodization of the aluminum permits electroplating only on top of the metallic electrodes, leading to the nanowire patterns having the same shape as the underlying metallic tracks. The variation in the fabricated structures between the patterned and non......The fabrication of metallic nanowire patterns within anodic alumina oxide (AAO) membranes on top of continuous conducting substrates are discussed. The fabrication protocol is based on the realization of nanowire patterns using supported nanoporous alumina templates (SNAT) prepared on top......-patterned substrates can be interpreted in terms of different behavior during anodization. The improved quality of fabricated nanowire patterns is clearly demonstrated by the SEM imaging and the uniform growth of nanowires inside the alumina template is observed without any significant height variation....

  6. Nanowires, nanostructures and devices fabricated therefrom

    Science.gov (United States)

    Majumdar, Arun; Shakouri, Ali; Sands, Timothy D.; Yang, Peidong; Mao, Samuel S.; Russo, Richard E.; Feick, Henning; Weber, Eicke R.; Kind, Hannes; Huang, Michael; Yan, Haoquan; Wu, Yiying; Fan, Rong

    2005-04-19

    One-dimensional nanostructures having uniform diameters of less than approximately 200 nm. These inventive nanostructures, which we refer to as "nanowires", include single-crystalline homostructures as well as heterostructures of at least two single-crystalline materials having different chemical compositions. Because single-crystalline materials are used to form the heterostructure, the resultant heterostructure will be single-crystalline as well. The nanowire heterostructures are generally based on a semiconducting wire wherein the doping and composition are controlled in either the longitudinal or radial directions, or in both directions, to yield a wire that comprises different materials. Examples of resulting nanowire heterostructures include a longitudinal heterostructure nanowire (LOHN) and a coaxial heterostructure nanowire (COHN).

  7. Synthesis and properties of antimonide nanowires

    Science.gov (United States)

    Mattias Borg, B.; Wernersson, Lars-Erik

    2013-05-01

    Antimonide semiconductors are suitable for low-power electronics and long-wavelength optoelectronic applications. In recent years research on antimonide nanowires has become a rapidly growing field, and nano-materials have promising applications in fundamental physics research, for tunnel field-effect transistors, and long-wavelength detectors. In this review, we give an overview of the field of antimonide nanowires, beginning with a description of the synthesis of these nano-materials. Here we summarize numerous reports on antimonide nanowire growth, with the aim to give an overall picture of the distinctive properties of antimonide nanowire synthesis. Secondly, we review the data on the physical properties and emerging applications for antimonide nanowires, focusing on applications in electronics and optics.

  8. Multisegment CdTe nanowire homojunction photodiode

    International Nuclear Information System (INIS)

    Matei, Elena; Enculescu, Ionut; Ion, Lucian; Antohe, Stefan; Neumann, Reinhard

    2010-01-01

    Electrochemical deposition in nanoporous ion track membranes is used for the preparation of multisegment CdTe-homojunction diode nanowires. Our study is based on the fact that the deposition overpotential strongly influences the composition of the compound semiconductor nanowires. Therefore, the transport behavior of the nanowire devices can be tailored by appropriately choosing a certain sequence of electrodeposition potentials. The wires were characterized using scanning electron microscopy, energy dispersive x-ray analysis, optical spectroscopy and x-ray diffraction. The current-voltage characteristics measured prove that, by appropriately choosing the voltage pulse pattern, one can fabricate nanowires with ohmic or rectifying behavior. The semiconducting nanowires are sensitive to light, their spectral sensitivity being characteristic of CdTe. The preparation of functional nanostructures in such a simple approach provides, as a major advantage, an increase in the process reproducibility and opens a wide field of potential optoelectronic applications.

  9. The surface charge of liposomal adjuvants is decisive for their interactions with the Calu-3 and A549 airway epithelial cell culture models

    DEFF Research Database (Denmark)

    Ingvarsson, Pall Thor; Rasmussen, Ida Svahn; Viaene, Michelle

    2014-01-01

    One of the main reasons for the unmet medical need for mucosal vaccines is the lack of safe and efficacious mucosal adjuvants. The cationic liposome-based adjuvant system composed of dimethyldioctadecylammonium (DDA) bromide and trehalose 6,6'-dibehenate (TDB) is a versatile adjuvant that has sho...... and viability of the mucus-covered Calu-3 cells. Our in vitro results thus indicate that DDA/TDB liposomes might be efficiently and safely used as an adjuvant system for vaccines targeting the mucus-covered epithelium of the upper respiratory tract and the conducting airways....... potential for mucosal vaccination via the airways. The purpose of this study was to investigate the importance of the liposomal surface charge on the interaction with lung epithelial cells. Thus, the cationic DDA in the liposomes was subjected to a step-wise replacement with the zwitterionic...

  10. Precise Placement of Metallic Nanowires on a Substrate by Localized Electric Fields and Inter-Nanowire Electrostatic Interaction

    Directory of Open Access Journals (Sweden)

    U Hyeok Choi

    2017-10-01

    Full Text Available Placing nanowires at the predetermined locations on a substrate represents one of the significant hurdles to be tackled for realization of heterogeneous nanowire systems. Here, we demonstrate spatially-controlled assembly of a single nanowire at the photolithographically recessed region at the electrode gap with high integration yield (~90%. Two popular routes, such as protruding electrode tips and recessed wells, for spatially-controlled nanowire alignment, are compared to investigate long-range dielectrophoretic nanowire attraction and short-range nanowire-nanowire electrostatic interaction for determining the final alignment of attracted nanowires. Furthermore, the post-assembly process has been developed and tested to make a robust electrical contact to the assembled nanowires, which removes any misaligned ones and connects the nanowires to the underlying electrodes of circuit.

  11. In vitro cytotoxicity of SiO2 or ZnO nanoparticles with different sizes and surface charges on U373MG human glioblastoma cells

    Directory of Open Access Journals (Sweden)

    Kim JE

    2014-12-01

    Full Text Available Jung-Eun Kim,1,* Hyejin Kim,1,* Seong Soo A An,2 Eun Ho Maeng,3 Meyoung-Kon Kim,4 Yoon-Jae Song1 1Department of Life Science, 2Department of Bionano Technology, Gachon University, Seongnam-Si, South Korea; 3Korea Testing and Research Institute, Seoul, South Korea; 4Department of Biochemistry and Molecular Biology, Korea University Medical School and College, Seoul, South Korea *These authors contributed equally to this work Abstract: Silicon dioxide (SiO2 and zinc oxide (ZnO nanoparticles are widely used in various applications, raising issues regarding the possible adverse effects of these metal oxide nanoparticles on human cells. In this study, we determined the cytotoxic effects of differently charged SiO2 and ZnO nanoparticles, with mean sizes of either 100 or 20 nm, on the U373MG human glioblastoma cell line. The overall cytotoxicity of ZnO nanoparticles against U373MG cells was significantly higher than that of SiO2 nanoparticles. Neither the size nor the surface charge of the ZnO nanoparticles affected their cytotoxicity against U373MG cells. The 20 nm SiO2 nanoparticles were more toxic than the 100 nm nanoparticles against U373MG cells, but the surface charge had little or no effect on their cytotoxicity. Both SiO2 and ZnO nanoparticles activated caspase-3 and induced DNA fragmentation in U373MG cells, suggesting the induction of apoptosis. Thus, SiO2 and ZnO nanoparticles appear to exert cytotoxic effects against U373MG cells, possibly via apoptosis. Keyword: apoptosis

  12. Ethylene Gas Sensing Properties of Tin Oxide Nanowires Synthesized via CVD Method

    Science.gov (United States)

    Akhir, Maisara A. M.; Mohamed, Khairudin; Rezan, Sheikh A.; Arafat, M. M.; Haseeb, A. S. M. A.; Uda, M. N. A.; Nuradibah, M. A.

    2018-03-01

    This paper studies ethylene gas sensing performance of tin oxide (SnO2) nanowires (NWs) as sensing material synthesized using chemical vapor deposition (CVD) technique. The effect of NWs diameter on ethylene gas sensing characteristics were investigated. SnO2 NWs with diameter of ∼40 and ∼240 nm were deposited onto the alumina substrate with printed gold electrodes and tested for sensing characteristic toward ethylene gas. From the finding, the smallest diameter of NWs (42 nm) exhibit fast response and recovery time and higher sensitivity compared to largest diameter of NWs (∼240 nm). Both sensor show good reversibility features for ethylene gas sensor.

  13. Vibrational spectra of nanowires measured using laser doppler vibrometry and STM studies of epitaxial graphene : an LDRD fellowship report.

    Energy Technology Data Exchange (ETDEWEB)

    Biedermann, Laura Butler

    2009-09-01

    A few of the many applications for nanowires are high-aspect ratio conductive atomic force microscope (AFM) cantilever tips, force and mass sensors, and high-frequency resonators. Reliable estimates for the elastic modulus of nanowires and the quality factor of their oscillations are of interest to help enable these applications. Furthermore, a real-time, non-destructive technique to measure the vibrational spectra of nanowires will help enable sensor applications based on nanowires and the use of nanowires as AFM cantilevers (rather than as tips for AFM cantilevers). Laser Doppler vibrometry is used to measure the vibration spectra of individual cantilevered nanowires, specifically multiwalled carbon nanotubes (MWNTs) and silver gallium nanoneedles. Since the entire vibration spectrum is measured with high frequency resolution (100 Hz for a 10 MHz frequency scan), the resonant frequencies and quality factors of the nanowires are accurately determined. Using Euler-Bernoulli beam theory, the elastic modulus and spring constant can be calculated from the resonance frequencies of the oscillation spectrum and the dimensions of the nanowires, which are obtained from parallel SEM studies. Because the diameters of the nanowires studied are smaller than the wavelength of the vibrometer's laser, Mie scattering is used to estimate the lower diameter limit for nanowires whose vibration can be measured in this way. The techniques developed in this thesis can be used to measure the vibrational spectra of any suspended nanowire with high frequency resolution Two different nanowires were measured - MWNTs and Ag{sub 2}Ga nanoneedles. Measurements of the thermal vibration spectra of MWNTs under ambient conditions showed that the elastic modulus, E, of plasma-enhanced chemical vapor deposition (PECVD) MWNTs is 37 {+-} 26 GPa, well within the range of E previously reported for CVD-grown MWNTs. Since the Ag{sub 2}Ga nanoneedles have a greater optical scattering efficiency than

  14. Magneto-mechanical modeling study of CO-based amorphous micro- and nanowires for acoustic sensing medical applications

    Energy Technology Data Exchange (ETDEWEB)

    Atitoaie, Alexandru, E-mail: atitoaie@phys-iasi.ro [National Institute of Research and Development for Technical Physics, Iasi (Romania); Department of Physics, “Alexandru Ioan Cuza” University, 700506 Iasi (Romania); Stancu, Alexandru [Department of Physics, “Alexandru Ioan Cuza” University, 700506 Iasi (Romania); Ovari, Tibor-Adrian; Lupu, Nicoleta; Chiriac, Horia [National Institute of Research and Development for Technical Physics, Iasi (Romania)

    2016-04-01

    Magnetic nanowires are potential candidates for substituting, within enhanced cochlear implants, the role played by hair cilia from the inner ear, which are responsible for the transduction of acoustic vibrations into electric signals. The sound waves pressure that is bending the magnetic wires induces stresses that are leading to changes in magnetic properties, such as magnetization and permeability. These changes can be detected by a GMR sensor placed below the nanowire array or, in the case of different designs, by a pick-up coil wrapped around the fixed-end of the wires. For the latter case, we are studying the stress distributions caused by bending deformations using the COMSOL finite element software package. We are also proposing a theoretical method for the evaluation of magnetic permeability variation vs. induced stress dependence. The study is performed on CoFeSiB amorphous micro- and nanowires subjected to mechanical perturbations similar to the ones produced by sound pressure waves.

  15. Broadband High-Performance Infrared Antireflection Nanowires Facilely Grown on Ultrafast Laser Structured Cu Surface.

    Science.gov (United States)

    Fan, Peixun; Bai, Benfeng; Long, Jiangyou; Jiang, Dafa; Jin, Guofan; Zhang, Hongjun; Zhong, Minlin

    2015-09-09

    Infrared antireflection is an essential issue in many fields such as thermal imaging, sensors, thermoelectrics, and stealth. However, a limited antireflection capability, narrow effective band, and complexity as well as high cost in implementation represent the main unconquered problems, especially on metal surfaces. By introducing precursor micro/nano structures via ultrafast laser beforehand, we present a novel approach for facile and uniform growth of high-quality oxide semiconductor nanowires on a Cu surface via thermal oxidation. Through the enhanced optical phonon dissipation of the nanowires, assisted by light trapping in the micro structures, ultralow total reflectance of 0.6% is achieved at the infrared wavelength around 17 μm and keeps steadily below 3% over a broad band of 14-18 μm. The precursor structures and the nanowires can be flexibly tuned by controlling the laser processing procedure to achieve desired antireflection performance. The presented approach possesses the advantages of material simplicity, structure reconfigurability, and cost-effectiveness for mass production. It opens a new path to realize unique functions by integrating semiconductor nanowires onto metal surface structures.

  16. Non-resonant Mie scattering: emergent optical properties of core-shell polymer nanowires.

    Science.gov (United States)

    Khudiyev, Tural; Huseyinoglu, Ersin; Bayindir, Mehmet

    2014-04-09

    We provide the in-depth characterization of light-polymer nanowire interactions in the context of an effective Mie scattering regime associated with low refractive index materials. Properties of this regime sharply contrast with these of resonant Mie scattering, and involve the formation of strictly forward-scattered and coupling-free optical fields in the vicinity of core-shell polymer nanowires. Scattering from these optical fields is shown to be non-resonant in nature and independent from incident polarization. In order to demonstrate the potential utility of this scattering regime in one-dimensional (1D) polymeric nanostructures, we fabricate polycarbonate (PC) - polyvinylidene difluoride (PVDF) core-shell nanowires using a novel iterative thermal drawing process that yields uniform and indefinitely long core-shell nanostructures. These nanowires are successfully engineered for novel nanophotonics applications, including size-dependent structural coloration, efficient light capture on thin-film solar cells, optical nano-sensors with ultrahigh sensitivity and a mask-free photolithography method suitable for the straightforward production of 1D nanopatterns.

  17. Confinement-guided shaping of semiconductor nanowires and nanoribbons: "writing with nanowires".

    Science.gov (United States)

    Pevzner, Alexander; Engel, Yoni; Elnathan, Roey; Tsukernik, Alexander; Barkay, Zahava; Patolsky, Fernando

    2012-01-11

    To fully exploit their full potential, new semiconductor nanowire building blocks with ab initio controlled shapes are desired. However, and despite the great synthetic advances achieved, the ability to control nanowire's geometry has been significantly limited. Here, we demonstrate a simple confinement-guided nanowire growth method that enables to predesign not only the chemical and physical attributes of the synthesized nanowires but also allows a perfect and unlimited control over their geometry. Our method allows the synthesis of semiconductor nanowires in a wide variety of two-dimensional shapes such as any kinked (different turning angles), sinusoidal, linear, and spiral shapes, so that practically any desired geometry can be defined. The shape-controlled nanowires can be grown on almost any substrate such as silicon wafer, quartz and glass slides, and even on plastic substrates (e.g., Kapton HN). © 2011 American Chemical Society

  18. Charged Nanowire-Directed Growth of Amorphous Calcium Carbonate Nanosheets in a Mixed Solvent for Biomimetic Composite Films.

    Science.gov (United States)

    Liu, Yangyi; Liu, Lei; Chen, Si-Ming; Chang, Fu-Jia; Mao, Li-Bo; Gao, Huai-Ling; Ma, Tao; Yu, Shu-Hong

    2018-04-19

    Bio-inspired mineralization is an effective way for fabricating complicated inorganic materials, which inspires us to develop new methods to synthesize materials with fascinating properties. In this article, we report that the charged tellurium nanowires (TeNWs) can be used as bio-macromolecule analogues to direct the formation of amorphous calcium carbonate (ACC) nanosheets (ACCNs) in a mixed solvent. The effects of surface charges and the concentration of the TeNWs on the formation of ACCNs have been investigated. Particularly, the produced ACCNs can be functionalized by Fe3O4 nanoparticles to produce magnetic ACC/Fe3O4 hybrid nanosheets, which can be used to construct ACC/Fe3O4 composite films through a self-evaporation process. Moreover, sodium alginate-ACC nanocomposite films with remarkable toughness and good transmittance can also be fabricated by using such ACCNs as nanoscale building blocks. This mineralization approach in a mixed solvent using charged tellurium nanowires as bio-macromolecule analogues provides a new way for the synthesis of ACCNs, which can be used as nanoscale building blocks for fabrication of biomimetic composite films.

  19. Kinetic parameter estimation and fluctuation analysis of CO at SnO2 single nanowires.

    Science.gov (United States)

    Tulzer, Gerhard; Baumgartner, Stefan; Brunet, Elise; Mutinati, Giorgio C; Steinhauer, Stephan; Köck, Anton; Barbano, Paolo E; Heitzinger, Clemens

    2013-08-09

    In this work, we present calculated numerical values for the kinetic parameters governing adsorption/desorption processes of carbon monoxide at tin dioxide single-nanowire gas sensors. The response of such sensors to pulses of 50 ppm carbon monoxide in nitrogen is investigated at different temperatures to extract the desired information. A rate-equation approach is used to model the reaction kinetics, which results in the problem of determining coefficients in a coupled system of nonlinear ordinary differential equations. The numerical values are computed by inverse-modeling techniques and are then used to simulate the sensor response. With our model, the dynamic response of the sensor due to the gas-surface interaction can be studied in order to find the optimal setup for detection, which is an important step towards selectivity of these devices. We additionally investigate the noise in the current through the nanowire and its changes due to the presence of carbon monoxide in the sensor environment. Here, we propose the use of a wavelet transform to decompose the signal and analyze the noise in the experimental data. This method indicates that some fluctuations are specific for the gas species investigated here.

  20. Kinetic parameter estimation and fluctuation analysis of CO at SnO 2 single nanowires

    KAUST Repository

    Tulzer, Gerhard

    2013-07-12

    In this work, we present calculated numerical values for the kinetic parameters governing adsorption/desorption processes of carbon monoxide at tin dioxide single-nanowire gas sensors. The response of such sensors to pulses of 50 ppm carbon monoxide in nitrogen is investigated at different temperatures to extract the desired information. A rate-equation approach is used to model the reaction kinetics, which results in the problem of determining coefficients in a coupled system of nonlinear ordinary differential equations. The numerical values are computed by inverse-modeling techniques and are then used to simulate the sensor response. With our model, the dynamic response of the sensor due to the gas-surface interaction can be studied in order to find the optimal setup for detection, which is an important step towards selectivity of these devices. We additionally investigate the noise in the current through the nanowire and its changes due to the presence of carbon monoxide in the sensor environment. Here, we propose the use of a wavelet transform to decompose the signal and analyze the noise in the experimental data. This method indicates that some fluctuations are specific for the gas species investigated here. © 2013 IOP Publishing Ltd.

  1. Mechanisms involved in the hydrothermal growth of ultra-thin and high aspect ratio ZnO nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Demes, Thomas [Univ. Grenoble Alpes, CNRS, Grenoble-INP, LMGP, F-38000 Grenoble (France); Ternon, Céline, E-mail: celine.ternon@grenoble-inp.fr [Univ. Grenoble Alpes, CNRS, Grenoble-INP, LMGP, F-38000 Grenoble (France); Univ. Grenoble Alpes, CNRS, LTM, F-38000 Grenoble (France); Morisot, Fanny [Univ. Grenoble Alpes, CNRS, Grenoble-INP, LMGP, F-38000 Grenoble (France); Univ. Grenoble Alpes, CNRS, Grenoble-INP" 2, IMEP-LaHC, F-38000 Grenoble (France); Riassetto, David [Univ. Grenoble Alpes, CNRS, Grenoble-INP, LMGP, F-38000 Grenoble (France); Legallais, Maxime [Univ. Grenoble Alpes, CNRS, Grenoble-INP, LMGP, F-38000 Grenoble (France); Univ. Grenoble Alpes, CNRS, Grenoble-INP" 2, IMEP-LaHC, F-38000 Grenoble (France); Roussel, Hervé; Langlet, Michel [Univ. Grenoble Alpes, CNRS, Grenoble-INP, LMGP, F-38000 Grenoble (France)

    2017-07-15

    Highlights: • ZnO nanowires are grown on sol-gel ZnO seed layers by hydrothermal synthesis. • Ultra-thin and high aspect ratio nanowires are obtained without using additives. • Nanowire diameter is 20–25 nm regardless of growth time and seed morphology. • A nanowire growth model is developed on the basis of thermodynamic considerations. • The nanowires are intended for integration into electrically conductive nanonets. - Abstract: Hydrothermal synthesis of ZnO nanowires (NWs) with tailored dimensions, notably high aspect ratios (AR) and small diameters, is a major concern for a wide range of applications and still represents a challenging and recurring issue. In this work, an additive-free and reproducible hydrothermal procedure has been developed to grow ultra-thin and high AR ZnO NWs on sol-gel deposited ZnO seed layers. Controlling the substrate temperature and using a low reagent concentration (1 mM) has been found to be essential for obtaining such NWs. We show that the NW diameter remains constant at about 20–25 nm with growth time contrary to the NW length that can be selectively increased leading to NWs with ARs up to 400. On the basis of investigated experimental conditions along with thermodynamic and kinetic considerations, a ZnO NW growth mechanism has been developed which involves the formation and growth of nuclei followed by NW growth when the nuclei reach a critical size of about 20–25 nm. The low reagent concentration inhibits NW lateral growth leading to ultra-thin and high AR NWs. These NWs have been assembled into electrically conductive ZnO nanowire networks, which opens attractive perspectives toward the development of highly sensitive low-cost gas- or bio-sensors.

  2. Highly integrated synthesis of heterogeneous nanostructures on nanowire heater array.

    Science.gov (United States)

    Jin, Chun Yan; Yun, Jeonghoon; Kim, Jung; Yang, Daejong; Kim, Dong Hwan; Ahn, Jae Hyuk; Lee, Kwang-Cheol; Park, Inkyu

    2014-11-06

    We have proposed a new method for the multiplexed synthesis of heterogeneous nanostructures using a top-down fabricated nanowire heater array. Hydrothermally synthesized nanostructures can be grown only on the heated nanowire through nanoscale temperature control using a Joule heated nanowire. We have demonstrated the selective synthesis of zinc oxide (ZnO) nanowires and copper oxide (CuO) nanostructures, as well as their surface modification with noble metal nanoparticles, using a nanowire heater array. Furthermore, we could fabricate an array of heterogeneous nanostructures via Joule heating of individual nanowire heaters and changing of the precursor solutions in a sequential manner. We have formed a parallel array of palladium (Pd) coated ZnO nanowires and gold (Au) coated ZnO nanowires, as well as a parallel array of ZnO nanowires and CuO nanospikes, in the microscale region by using the developed method.

  3. Molecular modeling in design of polyaniline for polymer-based carbon dioxide sensor

    OpenAIRE

    Chen, X.P.

    2013-01-01

    Conducting polymers are attractive chemical sensing materials due to their outstanding characteristics including low cost, room-temperature operations, easy device fabrication, high sensitivity and short response time. The new nanowires architecture, with high surface-to-volume ratio, makes possible the conducting polymers an ultra fast detection of chemical at low concentrations. Polymer-coated nanowires are thus the potential cost effective solution for the new generation gas sensors. As a ...

  4. Advances in nanowire transistors for biological analysis and cellular investigation.

    Science.gov (United States)

    Li, Bor-Ran; Chen, Chiao-Chen; Kumar, U Rajesh; Chen, Yit-Tsong

    2014-04-07

    Electrical biosensors based on silicon nanowire field-effect transistors (SiNW-FETs) have attracted enormous interest in the biosensing field. SiNW-FETs have proven to be significant and efficient in detecting diverse biomolecular species with the advantages of high probing sensitivity, target selectivity, real-time recording and label-free detection. In recent years, significant advances in biosensors have been achieved, particularly for cellular investigation and biomedical diagnosis. In this critical review, we will report on the latest developments in biosensing with SiNW-FETs and discuss recent advancements in the innovative designs of SiNW-FET devices. This critical review introduces the basic instrumental setup and working principle of SiNW-FETs. Technical approaches that attempted to enhance the detection sensitivity and target selectivity of SiNW-FET sensors are discussed. In terms of applications, we review the recent achievements with SiNW-FET biosensors for the investigations of protein-protein interaction, DNA/RNA/PNA hybridization, virus detection, cellular recording, biological kinetics, and clinical diagnosis. In addition, the novel architecture designs of the SiNW-FET devices are highlighted in studies of live neuron cells, electrophysiological measurements and other signal transduction pathways. Despite these remarkable achievements, certain improvements remain necessary in the device performance and clinical applications of FET-based biosensors; thus, several prospects about the future development of nanowire transistor-based instruments for biosensing employments are discussed at the end of this review.

  5. Large, Tunable Magnetoresistance in Nonmagnetic III-V Nanowires.

    Science.gov (United States)

    Li, Sichao; Luo, Wei; Gu, Jiangjiang; Cheng, Xiang; Ye, Peide D; Wu, Yanqing

    2015-12-09

    Magnetoresistance, the modulation of resistance by magnetic fields, has been adopted and continues to evolve in many device applications including hard-disk, memory, and sensors. Magnetoresistance in nonmagnetic semiconductors has recently raised much attention and shows great potential due to its large magnitude that is comparable or even larger than magnetic materials. However, most of the previous work focus on two terminal devices with large dimensions, typically of micrometer scales, which severely limit their performance potential and more importantly, scalability in commercial applications. Here, we investigate magnetoresistance in the impact ionization region in InGaAs nanowires with 20 nm diameter and 40 nm gate length. The deeply scaled dimensions of these nanowires enable high sensibility with less power consumption. Moreover, in these three terminal devices, the magnitude of magnetoresistance can be tuned by the transverse electric field controlled by gate voltage. Large magnetoresistance between 100% at room temperature and 2000% at 4.3 K can be achieved at 2.5 T. These nanoscale devices with large magnetoresistance offer excellent opportunity for future high-density large-scale magneto-electric devices using top-down fabrication approaches, which are compatible with commercial silicon platform.

  6. TiO2 nanowire-templated hierarchical nanowire network as water-repelling coating

    Science.gov (United States)

    Hang, Tian; Chen, Hui-Jiuan; Xiao, Shuai; Yang, Chengduan; Chen, Meiwan; Tao, Jun; Shieh, Han-ping; Yang, Bo-ru; Liu, Chuan

    2017-01-01

    Extraordinary water-repelling properties of superhydrophobic surfaces make them novel candidates for a great variety of potential applications. A general approach to achieve superhydrophobicity requires low-energy coating on the surface and roughness on nano- and micrometre scale. However, typical construction of superhydrophobic surfaces with micro-nano structure through top-down fabrication is restricted by sophisticated fabrication techniques and limited choices of substrate materials. Micro-nanoscale topographies templated by conventional microparticles through surface coating may produce large variations in roughness and uncontrollable defects, resulting in poorly controlled surface morphology and wettability. In this work, micro-nanoscale hierarchical nanowire network was fabricated to construct self-cleaning coating using one-dimensional TiO2 nanowires as microscale templates. Hierarchical structure with homogeneous morphology was achieved by branching ZnO nanowires on the TiO2 nanowire backbones through hydrothermal reaction. The hierarchical nanowire network displayed homogeneous micro/nano-topography, in contrast to hierarchical structure templated by traditional microparticles. This hierarchical nanowire network film exhibited high repellency to both water and cell culture medium after functionalization with fluorinated organic molecules. The hierarchical structure templated by TiO2 nanowire coating significantly increased the surface superhydrophobicity compared to vertical ZnO nanowires with nanotopography alone. Our results demonstrated a promising strategy of using nanowires as microscale templates for the rational design of hierarchical coatings with desired superhydrophobicity that can also be applied to various substrate materials. PMID:29308265

  7. TiO2 nanowire-templated hierarchical nanowire network as water-repelling coating

    Science.gov (United States)

    Hang, Tian; Chen, Hui-Jiuan; Xiao, Shuai; Yang, Chengduan; Chen, Meiwan; Tao, Jun; Shieh, Han-ping; Yang, Bo-ru; Liu, Chuan; Xie, Xi

    2017-12-01

    Extraordinary water-repelling properties of superhydrophobic surfaces make them novel candidates for a great variety of potential applications. A general approach to achieve superhydrophobicity requires low-energy coating on the surface and roughness on nano- and micrometre scale. However, typical construction of superhydrophobic surfaces with micro-nano structure through top-down fabrication is restricted by sophisticated fabrication techniques and limited choices of substrate materials. Micro-nanoscale topographies templated by conventional microparticles through surface coating may produce large variations in roughness and uncontrollable defects, resulting in poorly controlled surface morphology and wettability. In this work, micro-nanoscale hierarchical nanowire network was fabricated to construct self-cleaning coating using one-dimensional TiO2 nanowires as microscale templates. Hierarchical structure with homogeneous morphology was achieved by branching ZnO nanowires on the TiO2 nanowire backbones through hydrothermal reaction. The hierarchical nanowire network displayed homogeneous micro/nano-topography, in contrast to hierarchical structure templated by traditional microparticles. This hierarchical nanowire network film exhibited high repellency to both water and cell culture medium after functionalization with fluorinated organic molecules. The hierarchical structure templated by TiO2 nanowire coating significantly increased the surface superhydrophobicity compared to vertical ZnO nanowires with nanotopography alone. Our results demonstrated a promising strategy of using nanowires as microscale templates for the rational design of hierarchical coatings with desired superhydrophobicity that can also be applied to various substrate materials.

  8. Optical properties of heavily doped GaAs nanowires and electroluminescent nanowire structures.

    Science.gov (United States)

    Lysov, A; Offer, M; Gutsche, C; Regolin, I; Topaloglu, S; Geller, M; Prost, W; Tegude, F-J

    2011-02-25

    We present GaAs electroluminescent nanowire structures fabricated by metal organic vapor phase epitaxy. Electroluminescent structures were realized in both axial pn-junctions in single GaAs nanowires and free-standing nanowire arrays with a pn-junction formed between nanowires and substrate, respectively. The electroluminescence emission peak from single nanowire pn-junctions at 10 K was registered at an energy of around 1.32 eV and shifted to 1.4 eV with an increasing current. The line is attributed to the recombination in the compensated region present in the nanowire due to the memory effect of the vapor-liquid-solid growth mechanism. Arrayed nanowire electroluminescent structures with a pn-junction formed between nanowires and substrate demonstrated at 5 K a strong electroluminescence peak at 1.488 eV and two shoulder peaks at 1.455 and 1.519 eV. The main emission line was attributed to the recombination in the p-doped GaAs. The other two lines correspond to the tunneling-assisted photon emission and band-edge recombination in the abrupt junction, respectively. Electroluminescence spectra are compared with the micro-photoluminescence spectra taken along the single p-, n- and single nanowire pn-junctions to find the origin of the electroluminescence peaks, the distribution of doping species and the sharpness of the junctions.

  9. Fabrication of nanowires and nanostructures

    DEFF Research Database (Denmark)

    Mátéfi-Tempfli, Stefan; Mátéfi-Tempfli, M.; Piraux, L.

    2009-01-01

    We report on different approaches that we have adopted and developed for the fabrication of nanowires and nanostructures. Methods based on template synthesis and on self organization seem to be the most promising for the fabrication of nanomaterials and nanostructures due to their easiness and low...... cost. The development of a supported nanoporous alumina template and the possibility of using this template to combine electrochemical synthesis with lithographic methods open new ways for the fabrication of complex nanostructures. The numerous advantages of the supported template and its compatibility...

  10. Polyaniline-coated silver nanowires

    Czech Academy of Sciences Publication Activity Database

    Bober, Patrycja; Stejskal, Jaroslav; Trchová, Miroslava; Hromádková, Jiřina; Prokeš, J.

    2010-01-01

    Roč. 70, č. 9 (2010), s. 656-662 ISSN 1381-5148 R&D Projects: GA MŠk LA09028; GA ČR GA202/09/1626; GA ČR GA203/08/0686; GA AV ČR IAA100500902; GA AV ČR IAA400500905; GA AV ČR KAN200520704 Institutional research plan: CEZ:AV0Z40500505 Keywords : conducting polymer * conductivity * nanowire Subject RIV: CD - Macromolecular Chemistry Impact factor: 2.546, year: 2010

  11. Structural and compositional characterization of Bi{sub 1−x}Sb{sub x} nanowire arrays grown by pulsed deposition to improve growth uniformity

    Energy Technology Data Exchange (ETDEWEB)

    Cassinelli, M. [Material Research Department, GSI Helmholtz Centre for Heavy Ion Research GmbH, Plankstr. 1, 64291 Darmstadt (Germany); Technische Universität Darmstadt, Material- und Geowisenschaften, Petersenstrasse 23, 64287 Darmstadt (Germany); Müller, S. [Material Research Department, GSI Helmholtz Centre for Heavy Ion Research GmbH, Plankstr. 1, 64291 Darmstadt (Germany); Aabdin, Z.; Peranio, N.; Eibl, O. [Institute for Applied Physics, Auf der Morgenstelle 10, 72076 Tübingen (Germany); Trautmann, C. [Material Research Department, GSI Helmholtz Centre for Heavy Ion Research GmbH, Plankstr. 1, 64291 Darmstadt (Germany); Technische Universität Darmstadt, Material- und Geowisenschaften, Petersenstrasse 23, 64287 Darmstadt (Germany); Toimil-Molares, M.E. [Material Research Department, GSI Helmholtz Centre for Heavy Ion Research GmbH, Plankstr. 1, 64291 Darmstadt (Germany)

    2015-12-15

    Arrays of Bi{sub 1−x}Sb{sub x} nanowire with various compositions (0 ⩽ x ⩽ 1) are grown in etched ion-track membranes by pulsed electrochemical deposition. Nanowires of diameter from 130 nm down to 18 nm are characterized by means of X-ray diffraction and high-resolution electron microscopy combined with electron diffraction and energy dispersive X-ray analysis. Compared to potentiostatic deposition, the pulsed synthesis method leads to a more uniform growth and higher filling rate of the wires across the entire template. By tuning the deposition parameters, we demonstrate excellent control over the wire composition and crystallographic orientation. The deposition process presented facilitates the development of future nanowire-based thermoelectric sensors, which are expected to exhibit a higher sensitivity and a faster response compared to thin film sensors.

  12. Optical Properties of Rotationally Twinned Nanowire Superlattices

    DEFF Research Database (Denmark)

    Bao, Jiming; Bell, David C.; Capasso, Federico

    2008-01-01

    blende InP nanowires. We have constructed the energy band diagram of the resulting multiquantum well heterostructure and have performed detailed quantum mechanical calculations of the electron and hole wave functions. The excitation power dependent blue-shift of the photoluminescence can be explained...... a heterostructure in a chemically homogeneous nanowire material and alter in a major way its optical properties opens new possibilities for band-structure engineering.......We have developed a technique so that both transmission electron microscopy and microphotoluminescence can be performed on the same semiconductor nanowire over a large range of optical power, thus allowing us to directly correlate structural and optical properties of rotationally twinned zinc...

  13. Antimonide Heterostructure Nanowires - Growth, Physics and Devices

    OpenAIRE

    Borg, Mattias

    2012-01-01

    This thesis investigates the growth and application of antimonide heterostructure nanowires for low-power electronics. In the first part of the thesis, GaSb, InSb and InAsSb nanowire growth is presented, and the distinguishing features of the growth are described. It is found that the presence of Sb results in more than 50 at. % group-III concentration in the Au seed particle on top of the nanowires. It is further concluded that the effective V/III ratio inside the seed particle is reduced co...

  14. Growth of HgTe nanowires

    Science.gov (United States)

    Selvig, E.; Hadzialic, S.; Skauli, T.; Steen, H.; Hansen, V.; Trosdahl-Iversen, L.; van Rheenen, A. D.; Lorentzen, T.; Haakenaasen, R.

    2006-09-01

    HgTe nanowires nucleated by Au particles have been grown on Si and GaAs substrates by molecular beam epitaxy. The wires are polycrystalline. They evolve from crooked to straight during growth and have rounded to rectangular cross-sections. The widths are in the range 20-500 nm, with lengths up to 4 μm. The height of the nanowires is typically less than the width. The nanowires have been characterized by scanning electron microscopy, x-ray photoelectron spectroscopy, transmission electron microscopy and atomic force microscopy. The effects of substrate material, substrate preparation and growth conditions have been investigated.

  15. Rare earth silicide nanowires on silicon surfaces

    International Nuclear Information System (INIS)

    Wanke, Martina

    2008-01-01

    The growth, structure and electronic properties of rare earth silicide nanowires are investigated on planar and vicinal Si(001) und Si(111) surfaces with scanning tunneling microscopy (STM), low energy electron diffraction (LEED) and angle-resolved photoelectron spectroscopy (ARPES). On all surfaces investigated within this work hexagonal disilicides are grown epitaxially with a lattice mismatch of -2.55% up to +0.83% along the hexagonal a-axis. Along the hexagonal c-axis the lattice mismatch is essentially larger with 6.5%. On the Si(001)2 x 1 surface two types of nanowires are grown epitaxially. The socalled broad wires show a one-dimensional metallic valence band structure with states crossing the Fermi level. Along the nanowires two strongly dispersing states at the anti J point and a strongly dispersing state at the anti Γ point can be observed. Along the thin nanowires dispersing states could not be observed. Merely in the direction perpendicular to the wires an intensity variation could be observed, which corresponds to the observed spacial structure of the thin nanowires. The electronic properties of the broad erbium silicide nanowires are very similar to the broad dysprosium silicide nanowires. The electronic properties of the DySi 2 -monolayer and the Dy 3 Si 5 -multilayer on the Si(111) surface are investigated in comparison to the known ErSi 2 /Si(111) and Er 3 Si 5 /Si(111) system. The positions and the energetic locations of the observed band in the surface Brillouin zone will be confirmed for dysprosium. The shape of the electron pockets in the vector k parallel space is elliptical at the anti M points, while the hole pocket at the anti Γ point is showing a hexagonal symmetry. On the Si(557) surface the structural and electronic properties depend strongly on the different preparation conditions likewise, in particular on the rare earth coverage. At submonolayer coverage the thin nanowires grow in wide areas of the sample surface, which are oriented

  16. Boron carbide nanowires with uniform CNx coatings

    Science.gov (United States)

    Zhang, H. Z.; Wang, R. M.; You, L. P.; Yu, J.; Chen, H.; Yu, D. P.; Chen, Y.

    2007-01-01

    Boron carbide nanowires with uniform carbon nitride coating layers were synthesized on a silicon substrate using a simple thermal process. The structure and morphology of the as-synthesized nanowires were characterized using x-ray diffraction, scanning and transmission electron microscopy and electron energy loss spectroscopy. A correlation between the surface smoothness of the nanowire sidewalls and their lateral sizes has been observed and it is a consequence of the anisotropic formation of the coating layers. A growth mechanism is also proposed for these growth phenomena.

  17. Fabrication and properties of silicon carbide nanowires

    Science.gov (United States)

    Shim, Hyun Woo

    2008-12-01

    Silicon carbide (SiC), with excellent electrical, thermal, and mechanical properties, is a promising material candidate for future devices such as high-temperature electronics and super-strong lightweight structures. Combined with superior intrinsic properties, the nanomaterials of SiC show further advantages thanks to nanoscale effects. This thesis reports the growth mechanism, the self-integration, and the friction of SiC nanowires. The study involves nanowires fabrication using thermal evaporation, structure characterization using electron microscopy, friction measurement, and theoretical modeling. The study on nanowire growth mechanism requires understanding of the surfaces and interfaces of nanowire crystal. The catalyzed growth of SiC nanowires involves interfaces between source vapor, catalytic liquid, and nanowire solid. Our experimental observation includes the periodical twinning in a faceted SiC nanowire and three stage structure transitions during the growth. The proposed theoretical model shows that such phenomenon is the result of surface energy minimization process during the catalytic growth. Surface interactions also exist between nanowires, leading to their self-integration. Our parametric growth study reveals novel self-integration of SiC-SiO 2 core-shell nanowires as a result of SiO2 joining. Attraction between nanowires through van der Waals force and enhanced SiO2 diffusion at high temperature transform individual nanowires to the integrated nanojunctions, nanocables, and finally nanowebs. We also show that such joining process becomes effective either during growth or by annealing. The solid friction is a result of the interaction between two solid surfaces, and it depends on the adhesion and the deformation of two contacting solids among other factors. Having strong adhesion as shown from gecko foot-hairs, nanostructured materials should also have strong friction; this study is the first to investigate friction of nanostructures under

  18. Semiconductor Nanowires for Photoelectrochemical Water Splitting

    Science.gov (United States)

    Hwang, Yun Jeong

    Photolysis of water with semiconductor materials has been investigated intensely as a clean and renewable energy resource by storing solar energy in chemical bonds such as hydrogen. One-dimensional (1D) nanostructures such as nanowires can provide several advantages for photoelectrochemical (PEC) water splitting due to their high surface areas and excellent charge transport and collection efficiency. This dissertation discusses various nanowire photoelectrodes for single or dual semiconductor systems, and their linked PEC cells for self-driven water splitting. After an introduction of solar water splitting in the first chapter, the second chapter demonstrates water oxidative activities of hydrothermally grown TiO2 nanowire arrays depending on their length and surface properties. The photocurrents with TiO2 nanowire arrays approach saturation due to their poor charge collection efficiency with longer nanowires despite increased photon absorption efficiency. Epitaxial grains of rutile atomic layer deposition (ALD) shell on TiO2 nanowire increase the photocurrent density by 1.5 times due to improved charge collection efficiency especially in the short wavelength region. Chapter three compares the photocurrent density of the planar Si and Si nanowire arrays coated by anatase ALD TiO 2 thin film as a model system of a dual bandgap system. The electroless etched Si nanowire coated by ALD TiO2 (Si EENW/TiO2) shows 2.5 times higher photocurrent density due to lower reflectance and higher surface area. Also, this chapter illustrates that n-Si/n-TiO2 heterojunction is a promising structure for the photoanode application of a dual semiconductor system, since it can enhance the photocurrent density compared to p-Si/n-TiO 2 junction with the assistance of bend banding at the interface. Chapter four demonstrates the charge separation and transport of photogenerated electrons and holes within a single asymmetric Si/TiO2 nanowire. Kelvin probe force microscopy measurements show

  19. Functionalization and microfluidic integration of silicon nanowire biologically gated field effect transistors

    DEFF Research Database (Denmark)

    Pfreundt, Andrea; Svendsen, Winnie Edith; Dimaki, Maria

    2016-01-01

    This thesis deals with the development of a novel biosensor for the detection of biomolecules based on a silicon nanowire biologically gated field-effect transistor and its integration into a point-of-care device. The sensor and electrical on-chip integration was developed in a different project....... The presented research is based on this sensor structure and investigates its potential as a versatile biomarker detection platform by evaluating different functionalization approaches. The functionalization of the silicon sensor surface with organic molecules was investigated in detail to determine...... the suitability of different methods for the preparation of organic interfaces for protein attachment. Oxide-free silicon surfaces offer unique possibilities to create highly sensitive sensor surfaces for charge detection due to the lack of an insulating oxide layer, but the highly reactive surface presents...

  20. Functionalization and microfluidic integration of silicon nanowire biologically gated field effect transistors

    DEFF Research Database (Denmark)

    Pfreundt, Andrea

    This thesis deals with the development of a novel biosensor for the detection of biomolecules based on a silicon nanowire biologically gated field-effect transistor and its integration into a point-of-care device. The sensor and electrical on-chip integration was developed in a different project....... The presented research is based on this sensor structure and investigates its potential as a versatile biomarker detection platform by evaluating different functionalization approaches. The functionalization of the silicon sensor surface with organic molecules was investigated in detail to determine...... the suitability of different methods for the preparation of organic interfaces for protein attachment. Oxide-free silicon surfaces offer unique possibilities to create highly sensitive sensor surfaces for charge detection due to the lack of an insulating oxide layer, but the highly reactive surface presents...

  1. Room temperature detection of NO2 using InSb nanowire

    Science.gov (United States)

    Paul, Rajat Kanti; Badhulika, Sushmee; Mulchandani, Ashok

    2011-07-01

    Room temperature detection of NO2 down to one part-per-million (ppm) using single crystalline n-type InSb nanowires (NWs) chemiresistive gas sensor is presented. These sensors were synthesized and fabricated by the combination of chemical vapor deposition and dielectrophoresis alignment techniques. The sensor devices showed an increase in resistance upon exposure to successive increments of NO2 concentration up to 10 ppm. The reduction in conductance of n-type InSb NWs when exposed to NO2 is made possible due to the charge transfer from the InSb NW surface to the adsorbed electron acceptor NO2 molecules. The demonstrated results suggest InSb NW as a promising candidate in sensing applications as well as being environmental friendly over existing arsenic and/or phosphorous-based III-V NW sensors.

  2. Size Matters: Problems and Advantages Associated with Highly Miniaturized Sensors

    OpenAIRE

    Dahlin, Andreas B.

    2012-01-01

    There is no doubt that the recent advances in nanotechnology have made it possible to realize a great variety of new sensors with signal transduction mechanisms utilizing physical phenomena at the nanoscale. Some examples are conductivity measurements in nanowires, deflection of cantilevers and spectroscopy of plasmonic nanoparticles. The fact that these techniques are based on the special properties of nanostructural entities provides for extreme sensor miniaturization since a single structu...

  3. Lateral nanowire/nanobelt based nanogenerators, piezotronics and piezo-phototronics

    KAUST Repository

    Wang, Zhong Lin

    2010-11-01

    Relying on the piezopotential created in ZnO under straining, nanogenerators, piezotronics and piezo-phototronics developed based on laterally bonded nanowires on a polymer substrate have been reviewed. The principle of the nanogenerator is a transient flow of electrons in external load as driven by the piezopotential created by dynamic straining. By integrating the contribution made by millions of nanowires, the output voltage has been raised to 1.2 V. Consequently, self-powered nanodevices have been demonstrated. This is an important platform technology for the future sensor network and the internet of things. Alternatively, the piezopotential can act as a gate voltage that can tune/gate the transport process of the charge carriers in the nanowire, which is a gate-electrode free field effect transistor (FET). The device fabricated based on this principle is called the piezotronic device. Piezo-phototronic effect is about the tuning and controlling of electro-optical processes by strain induced piezopotential. The piezotronic, piezophotonic and pieozo-phototronic devices are focused on low frequency applications in areas involving mechanical actions, such as MEMS/NEMS, nanorobotics, sensors, actuators and triggers. © 2010 Elsevier B.V. All rights reserved.

  4. Vertically aligned patterned peptide nanowires for cellulars studies

    DEFF Research Database (Denmark)

    Taskin, Mehmet; Sasso, Luigi; Vedarethinam, Indumathi

    2012-01-01

    , our group has demonstrated that vertically aligned diphenylalanine based peptide nanowires (VAPNW) are an useful tool for cellular studies and sensor applications. To expand this study, we patterned VAPNWs into strips of various widths onto an electrode surface to evaluate these structures’ effects...... on cell growth and adherence using PC12 cells, which are neuronal stem cell models. With this method we are able to obtain important information about the cells’ preference for culture substrate, comparing the adhesion of cells to a forest of VAPNWs with standard protein substrate enhancers...... such as laminine. Combining this work with other approaches like discrete functionalization of VAPNWs will reveal possible future tools for cellular studies and biosensing....

  5. Topological Insulator Nanowires and Nanoribbons

    KAUST Repository

    Kong, Desheng

    2010-01-13

    Recent theoretical calculations and photoemission spectroscopy measurements on the bulk Bi2Se3 material show that it is a three-dimensional topological insulator possessing conductive surface states with nondegenerate spins, attractive for dissipationless electronics and spintronics applications. Nanoscale topological insulator materials have a large surface-to-volume ratio that can manifest the conductive surface states and are promising candidates for devices. Here we report the synthesis and characterization of high quality single crystalline Bi2Se5 nanomaterials with a variety of morphologies. The synthesis of Bi 2Se5 nanowires and nanoribbons employs Au-catalyzed vapor-liquid-solid (VLS) mechanism. Nanowires, which exhibit rough surfaces, are formed by stacking nanoplatelets along the axial direction of the wires. Nanoribbons are grown along [1120] direction with a rectangular cross-section and have diverse morphologies, including quasi-one-dimensional, sheetlike, zigzag and sawtooth shapes. Scanning tunneling microscopy (STM) studies on nanoribbons show atomically smooth surfaces with ∼ 1 nm step edges, indicating single Se-Bi-Se-Bi-Se quintuple layers. STM measurements reveal a honeycomb atomic lattice, suggesting that the STM tip couples not only to the top Se atomic layer, but also to the Bi atomic layer underneath, which opens up the possibility to investigate the contribution of different atomic orbitais to the topological surface states. Transport measurements of a single nanoribbon device (four terminal resistance and Hall resistance) show great promise for nanoribbons as candidates to study topological surface states. © 2010 American Chemical Society.

  6. Nanopatterning of ultrananocrystalline diamond nanowires.

    Science.gov (United States)

    Wang, Xinpeng; Ocola, Leonidas E; Divan, Ralu S; Sumant, Anirudha V

    2012-02-24

    We report the fabrication of horizontally aligned ultrananocrystalline diamond (UNCD) nanowires (NWs) via two different approaches. First, with the top-down approach by using electron beam lithography (EBL) and reactive ion etching (RIE) with a photo resist layer as an etch mask. Using this approach, we demonstrate fabrication of 50 µm long UNCD NWs with widths as narrow as 40 nm. We further present an alternative approach to grow UNCD NWs at pre-defined positions through a selective seeding process. No RIE was needed either to etch the NWs or to remove the mask. In this case, we achieved UNCD NWs with lengths of 50 µm and smallest width of 90 nm respectively. Characterization of these nanowires by using scanning electron microscopy (SEM) and atomic force microscopy (AFM) shows that the UNCD NWs are well defined and fully released, with no indication of residual stress. Characterization using visible and ultraviolet (UV) Raman spectroscopy indicates that in both fabrication approaches, UNCD NWs maintain their intrinsic diamond structure.

  7. Flexible electronics-compatible non-enzymatic glucose sensing via transparent CuO nanowire networks on PET films

    Science.gov (United States)

    Bell, Caroline; Nammari, Abdullah; Uttamchandani, Pranay; Rai, Amit; Shah, Pujan; Moore, Arden L.

    2017-06-01

    Diabetic individuals need simple, accurate, and cost effective means by which to independently assess their glucose levels in a non-invasive way. In this work, a sensor based on randomly oriented CuO nanowire networks supported by a polyethylene terephthalate thin film is evaluated as a flexible, transparent, non-enzymatic glucose sensing system analogous to those envisioned for future wearable diagnostic devices. The amperometric sensing characteristics of this type of device architecture are evaluated both before and after bending, with the system’s glucose response, sensitivity, lower limit of detection, and effect of applied bias being experimentally determined. The obtained data shows that the sensor is capable of measuring changes in glucose levels within a physiologically relevant range (0-12 mM glucose) and at lower limits of detection (0.05 mM glucose at +0.6 V bias) consistent with patient tears and saliva. Unlike existing studies utilizing a conductive backing layer or macroscopic electrode setup, this sensor demonstrates a percolation network-like trend of current versus glucose concentration. In this implementation, controlling the architectural details of the CuO nanowire network could conceivably allow the sensor’s sensitivity and optimal sensing range to be tuned. Overall, this work shows that integrating CuO nanowires into a sensor architecture compatible with transparent, flexible electronics is a promising avenue to realizing next generation wearable non-enzymatic glucose diagnostic devices.

  8. Boron carbide nanowires: Synthesis and characterization

    Science.gov (United States)

    Guan, Zhe

    Bulk boron carbide has been widely used in ballistic armored vest and the property characterization has been heavily focused on mechanical properties. Even though boron carbides have also been projected as a promising class of high temperature thermoelectric materials for energy harvesting, the research has been limited in this field. Since the thermal conductivity of bulk boron carbide is still relatively high, there is a great opportunity to take advantage of the nano effect to further reduce it for better thermoelectric performance. This dissertation work aims to explore whether improved thermoelectric performance can be found in boron carbide nanowires compared with their bulk counterparts. This dissertation work consists of four main parts. (1) Synthesis of boron carbide nanowires. Boron carbide nanowires were synthesized by co-pyrolysis of diborane and methane at low temperatures (with 879 °C as the lowest) in a home-built low pressure chemical vapor deposition (LPCVD) system. The CVD-based method is energy efficient and cost effective. The as-synthesized nanowires were characterized by electron microscopy extensively. The transmission electron microscopy (TEM) results show the nanowires are single crystalline with planar defects. Depending on the geometrical relationship between the preferred growth direction of the nanowire and the orientation of the defects, the as-synthesized nanowires could be further divided into two categories: transverse fault (TF) nanowires grow normal to the defect plane, while axial fault (AF) ones grow within the defect plane. (2) Understanding the growth mechanism of as-synthesized boron carbide nanowires. The growth mechanism can be generally considered as the famous vapor-liquid-solid (VLS) mechanism. TF and AF nanowires were found to be guided by Ni-B catalysts of two phases. A TF nanowire is lead by a hexagonal phase catalyst, which was proved to be in a liquid state during reaction. While an AF nanowires is catalyzed by a

  9. Ballistic transport in gold [110] nanowire

    Science.gov (United States)

    Kurui, Yoshihiko; Oshima, Yoshifumi; Okamoto, Masakuni; Takayanagi, Kunio

    2009-03-01

    Conductance of gold nanowire elongated along the [110] direction (gold [110] nanowire) was measured during many breaking procedures, while simultaneously acquiring transmission electron microscope images. The conductance histogram exhibits a series of peaks whose conductance values increased nearly in steps of the conductance quantum, G0 =2e^2/h. However thick nanowires above 10G0 showed dequantization, where the increment was only 0.9G0. The structure for each peak was determined to be either an atomic sheet or a hexagonal prism. The number of conductance channels calculated for each atomic structure by first principles theory, coincided well with the peak index in the conductance histogram. The present study shows that the [110] nanowire behave as ballistic conductors, and a conductance peak appears whenever a conductance channel is opened.

  10. Nonradiative Step Facets in Semiconductor Nanowires.

    Science.gov (United States)

    Sanchez, Ana M; Zhang, Yunyan; Tait, Edward W; Hine, Nicholas D M; Liu, Huiyun; Beanland, Richard

    2017-04-12

    One of the main advantages of nanowires for functional applications is their high perfection, which results from surface image forces that act on line defects such as dislocations, rendering them unstable and driving them out of the crystal. Here we show that there is a class of step facets that are stable in nanowires, with no long-range strain field or dislocation character. In zinc-blende semiconductors, they take the form of Σ3 (112) facets with heights constrained to be a multiple of three {111} monolayers. Density functional theory calculations show that they act as nonradiative recombination centers and have deleterious effects on nanowire properties. We present experimental observations of these defects on twin boundaries and twins that terminate inside GaAsP nanowires and find that they are indeed always multiples of three monolayers in height. Strategies to use the three-monolayer rule during growth to prevent their formation are discussed.

  11. High-performance single nanowire tunnel diodes.

    Science.gov (United States)

    Wallentin, Jesper; Persson, Johan M; Wagner, Jakob B; Samuelson, Lars; Deppert, Knut; Borgström, Magnus T

    2010-03-10

    We demonstrate single nanowire tunnel diodes with room temperature peak current densities of up to 329 A/cm(2). Despite the large surface to volume ratio of the type-II InP-GaAs axial heterostructure nanowires, we measure peak to valley current ratios (PVCR) of up to 8.2 at room temperature and 27.6 at liquid helium temperature. These sub-100-nm-diameter structures are promising components for solar cells as well as electronic applications.

  12. Transport of ARS-labeled hydroxyapatite nanoparticles in saturated granular media is influenced by surface charge variability even in the presence of humic acid

    Science.gov (United States)

    Wang, Dengjun; Bradford, Scott A.; Harvey, Ronald W.; Hao, Xiuzhen; Zhou, Dongmei

    2012-01-01

    Hydroxyapatite nanoparticle (nHAP) is increasingly being used to remediate soils and water polluted by metals and radionuclides. The transport and retention of Alizarin red S (ARS)-labeled nHAP were investigated in water-saturated granular media. Experiments were carried out over a range of ionic strength (Ic, 0–50 mM NaCl) conditions in the presence of 10 mg L−1 humic acid. The transport of ARS-nHAP was found to decrease with increasing suspension Ic in part, because of enhanced aggregation and chemical heterogeneity. The retention profiles (RPs) of ARS-nHAP exhibited hyperexponential shapes (a decreasing rate of retention with increasing transport distance) for all test conditions, suggesting that some of the attachment was occurring under unfavorable conditions. Surface charge heterogeneities on the collector surfaces and especially within the ARS-nHAP population were contributing causes for the hyperexponential RPs. Consideration of the effect(s) of Ic in the presence of HA is needed to improve the efficacy of nHAP for scavenging metals and actinides in real soils and groundwater environments.

  13. Effects of adhesions of amorphous Fe and Al hydroxides on surface charge and adsorption of K+ and Cd2+ on rice roots.

    Science.gov (United States)

    Liu, Zhao-Dong; Wang, Hai-Cui; Zhou, Qin; Xu, Ren-Kou

    2017-11-01

    Iron (Fe) and aluminum (Al) hydroxides in variable charge soils attached to rice roots may affect surface-charge properties and subsequently the adsorption and uptake of nutrients and toxic metals by the roots. Adhesion of amorphous Fe and Al hydroxides onto rice roots and their effects on zeta potential of roots and adsorption of potassium (K + ) and cadmium (Cd 2+ ) by roots were investigated. Rice roots adsorbed more Al hydroxide than Fe hydroxide because of the greater positive charge on Al hydroxide. Adhesion of Fe and Al hydroxides decreased the negative charge on rice roots, and a greater effect of the Al hydroxide. Consequently, adhesion of Fe and Al hydroxides reduced the K + and Cd 2+ adsorption by rice roots. The results of attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and desorption of K + and Cd 2+ from rice roots indicated that physical masking by Fe and Al hydroxides and diffuse-layer overlapping between the positively-charged hydroxides and negatively-charged roots were responsible for the reduction of negative charge on roots induced by adhesion of the hydroxides. Therefore, the interaction between Fe and Al hydroxides and rice roots reduced negative charge on roots and thus inhibited their adsorption of nutrient and toxic cations. Copyright © 2017 Elsevier Inc. All rights reserved.

  14. Behaviour of total surface charge in SiO2-Si system under short-pulsed ultraviolet irradiation cycles characterised by surface photo voltage technique

    International Nuclear Information System (INIS)

    Kang, Ban-Hong; Lee, Wah-Pheng; Yow, Ho-Kwang; Tou, Teck-Yong

    2009-01-01

    Effects of time-accumulated ultraviolet (UV) irradiation and surface treatment on thermally oxidized p-type silicon wafers were investigated by using the surface photo voltage (SPV) technique via the direct measurement of the total surface charge, Q SC . The rise and fall times of Q sc curves, as a function of accumulated UV irradiation, depended on the thermal oxide thickness. A simple model was proposed to explain the time-varying characteristics of Q sc based on the UV-induced bond breaking of SiOH and SiH, and photoemission of bulk electrons to wafer surface where O 2 - charges were formed. While these mechanisms resulted in charge variations and hence in Q sc , these could be removed by rinsing the silicon wafers in de-ionized water followed by spin-dry or blow-dry by an ionizer fan. Empirical parameters were used in the model simulations and curve-fitting of Q SC . The simulated results suggested that initial changes in the characteristic behaviour of Q sc were mainly due to the net changes in the positive and negative charges, but subsequently were dominated by the accumulation of O 2 - during the UV irradiation.

  15. Design of asymmetric particles containing a charged interior and a neutral surface charge: comparative study on in vivo circulation of polyelectrolyte microgels.

    Science.gov (United States)

    Chen, Kai; Xu, Jing; Luft, J Christopher; Tian, Shaomin; Raval, Jay S; DeSimone, Joseph M

    2014-07-16

    Lowering the modulus of hydrogel particles could enable them to bypass in vivo physical barriers that would otherwise filter particles with similar size but higher modulus. Incorporation of electrolyte moieties into the polymer network of hydrogel particles to increase the swelling ratio is a straightforward and quite efficient way to decrease the modulus. In addition, charged groups in hydrogel particles can also help secure cargoes. However, the distribution of charged groups on the surface of a particle can accelerate the clearance of particles. Herein, we developed a method to synthesize highly swollen microgels of precise size with near-neutral surface charge while retaining interior charged groups. A strategy was employed to enable a particle to be highly cross-linked with very small mesh size, and subsequently PEGylated to quench the exterior amines only without affecting the internal amines. Acidic degradation of the cross-linker allows for swelling of the particles to microgels with a desired size and deformability. The microgels fabricated demonstrated extended circulation in vivo compared to their counterparts with a charged surface, and could potentially be utilized in in vivo applications including as oxygen carriers or nucleic acid scavengers.

  16. Charge reversal and surface charge amplification in asymmetric valence restricted primitive model planar electric double layers in the modified Poisson-Boltzmann theory

    Directory of Open Access Journals (Sweden)

    L.B. Bhuiyan

    2017-12-01

    Full Text Available The modified Poisson-Boltzmann theory of the restricted primitive model double layer is revisited and recast in a fresh, slightly broader perspective. Derivation of relevant equations follow the techniques utilized in the earlier MPB4 and MPB5 formulations and clarifies the relationship between these. The MPB4, MPB5, and a new formulation of the theory are employed in an analysis of the structure and charge reversal phenomenon in asymmetric 2:1/1:2 valence electrolytes. Furthermore, polarization induced surface charge amplification is studied in 3:1/1:3 systems. The results are compared to the corresponding Monte Carlo simulations. The theories are seen to predict the "exact" simulation data to varying degrees of accuracy ranging from qualitative to almost quantitative. The results from a new version of the theory are found to be of comparable accuracy as the MPB5 results in many situations. However, in some cases involving low electrolyte concentrations, theoretical artifacts in the form of un-physical "shoulders" in the singlet ionic distribution functions are observed.

  17. High reproducibility and sensitivity of bifacial copper nanowire array for detection of glucose

    Directory of Open Access Journals (Sweden)

    Hanqing Zhang

    2017-06-01

    Full Text Available The ordered bifacial copper nanowire array (Cu BNWA was synthesized by a template assisted electrochemical deposition method. The morphology and structure of the as-prepared samples were investigated by field emission scanning electron microscope (FESEM and X-ray diffraction (XRD. The results show that the ordered Cu nanowire array with uniform geometrical dimensions covered both side of the Cu substrate. When used as the electrode for glucose detection, the minimum detectable concentration of glucose can be reached as low as 0.2 mM. Impressively, the sample still showed high sensitivity and stability for glucose detection after two months placement in ambient environment. These excellent performances of the Cu BNWA make it a promising non-enzyme glucose detection sensor for various applications.

  18. Growth and characterization of bismuth telluride nanowires

    International Nuclear Information System (INIS)

    Picht, Oliver

    2010-01-01

    Polycrystalline Bi 2 Te 3 nanowires are electrochemically grown in ion track-etched polycarbonate membranes. Potentiostatic growth is demonstrated in templates of various thicknesses ranging from 10 to 100 μm. The smallest observed nanowire diameters are 20 nm in thin membranes and approx. 140-180 nm in thicker membranes. The influence of the various deposition parameters on the nanowire growth rate is presented. Slower growth rates are attained by selective change of deposition potentials and lower temperatures. Nanowires synthesized at slower growth rates have shown to possess a higher degree of crystalline order and smoother surface contours. With respect to structural properties, X-ray diffraction and transmission electron microscopy verified the growth of Bi 2 Te 3 and evidenced the stability of specific properties, e.g. grain size or preferential orientation, with regard to variations in the deposition conditions. The interdependency of the fabrication parameters, i.e. temperature, deposition potential and nanochannel diameters, is demonstrated for wires grown in 30 μm thick membranes. It is visible from diffraction analysis that texture is tunable by the growth conditions but depends also on the size of the nanochannels in the template. Both (015) and (110) reflexes are observed for the nanowire arrays. Energy dispersive X-ray analysis further points out that variation of nanochannel size could lead to a change in elemental composition of the nanowires. (orig.)

  19. Growth and characterization of bismuth telluride nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Picht, Oliver

    2010-05-26

    Polycrystalline Bi{sub 2}Te{sub 3} nanowires are electrochemically grown in ion track-etched polycarbonate membranes. Potentiostatic growth is demonstrated in templates of various thicknesses ranging from 10 to 100 {mu}m. The smallest observed nanowire diameters are 20 nm in thin membranes and approx. 140-180 nm in thicker membranes. The influence of the various deposition parameters on the nanowire growth rate is presented. Slower growth rates are attained by selective change of deposition potentials and lower temperatures. Nanowires synthesized at slower growth rates have shown to possess a higher degree of crystalline order and smoother surface contours. With respect to structural properties, X-ray diffraction and transmission electron microscopy verified the growth of Bi{sub 2}Te{sub 3} and evidenced the stability of specific properties, e.g. grain size or preferential orientation, with regard to variations in the deposition conditions. The interdependency of the fabrication parameters, i.e. temperature, deposition potential and nanochannel diameters, is demonstrated for wires grown in 30 {mu}m thick membranes. It is visible from diffraction analysis that texture is tunable by the growth conditions but depends also on the size of the nanochannels in the template. Both (015) and (110) reflexes are observed for the nanowire arrays. Energy dispersive X-ray analysis further points out that variation of nanochannel size could lead to a change in elemental composition of the nanowires. (orig.)

  20. Hydrogen Generation from Photocatalytic Silver|Zinc Oxide Nanowires: Towards Multifunctional Multisegmented Nanowire Devices

    NARCIS (Netherlands)

    Maijenburg, A.W.; Rodijk, E.J.B.; Maas, M.G.; Enculescu, Monica; Blank, David H.A.; ten Elshof, Johan E.

    2011-01-01

    Photoactive nanowires: A novel photo-electrochemical nanowire diode that catalyzes the conversion of methanol and water to hydrogen under UV light is demonstrated. The wire consists of a metal and a metal oxide segment that are connected via a Schottky barrier. Other functions, such as remote-

  1. Optical haze of randomly arranged silver nanowire transparent conductive films with wide range of nanowire diameters

    Directory of Open Access Journals (Sweden)

    M. Marus

    2018-03-01

    Full Text Available The effect of the diameter of randomly arranged silver nanowires on the optical haze of silver nanowire transparent conductive films was studied. Proposed simulation model behaved similarly with the experimental results, and was used to theoretically study the optical haze of silver nanowires with diameters in the broad range from 30 nm and above. Our results show that a thickening of silver nanowires from 30 to 100 nm results in the increase of the optical haze up to 8 times, while from 100 to 500 nm the optical haze increases only up to 1.38. Moreover, silver nanowires with diameter of 500 nm possess up to 5% lower optical haze and 5% higher transmittance than 100 nm thick silver nanowires for the same 10-100 Ohm/sq sheet resistance range. Further thickening of AgNWs can match the low haze of 30 nm thick AgNWs, but at higher transmittance. The results obtained from this work allow deeper analysis of the silver nanowire transparent conductive films from the perspective of the diameter of nanowires for various optoelectronic devices.

  2. Nanowire assembly, e.g. for optical probes, comprises optically trapping high aspect ratio semiconductor nanowire with infrared single-beam optical trap and attaching nanowire to organic or inorganic structure

    OpenAIRE

    Pauzauskie, P.; Radenovic, A.; Trepagnier, E.; Liphardt, J.; Yang, P.

    2007-01-01

    NOVELTY - A nanowire assembly method comprises optically trapping a semiconductor nanowire with an infrared single-beam optical trap and attaching the nanowire to an organic or inorganic structure by laser fusing. The nanowire is further trapped in a fluid environment. The optical trap has a beam wavelength of 1064 nm. The nanowire has an aspect ratio greater than 100 and a diameter less than 100 (preferably less than 80) nm. The nanowire and the organic or inorganic structure form a heterost...

  3. UV-enhanced room-temperature gas sensing of ZnGa2O4 nanowires functionalized with Au catalyst nanoparticles

    Science.gov (United States)

    Park, Sunghoon; An, Soyeon; Mun, Youngho; Lee, Chongmu

    2014-03-01

    ZnGa2O4 nanowires were synthesized using a thermal evaporation technique. Scanning electron microscopy, transmission electron microscopy, and X-ray diffraction revealed that the nanowires were single crystals 30-200 nm in diameter and ranged up to ˜100 μm in length. The sensing properties of multiple networked ZnGa2O4 nanowire sensors functionalized with Au catalyst nanoparticles with diameters of a few nanometers toward NO2 gas at room temperature under UV irradiation were examined. The sensors showed a remarkably enhanced response and far reduced response and recovery times toward NO2 gas at room temperature under 254 nm-ultraviolet (UV) illumination. The response of ZnGa2O4 nanowires to NO2 gas at room temperature increased from ˜100 to ˜861 % with increasing the UV intensity from 0 to 1.2 mW/cm2. The significant improvement in the response of ZnGa2O4 nanowires to NO2 gas by UV irradiation is attributed to the increased change in resistance due to the increase in the number of electrons participating in the reactions with NO2 molecules by photo-generation of electron-hole pairs.

  4. Resistance Fluctuations in GaAs Nanowire Grids

    Directory of Open Access Journals (Sweden)

    Ivan Marasović

    2014-01-01

    Full Text Available We present a numerical study on resistance fluctuations in a series of nanowire-based grids. Each grid is made of GaAs nanowires arranged in parallel with metallic contacts crossing all nanowires perpendicularly. Electrical properties of GaAs nanowires known from previous experimental research are used as input parameters in the simulation procedure. Due to the nonhomogeneous doping, the resistivity changes along nanowire. Allowing two possible nanowire orientations (“upwards” or “downwards”, the resulting grid is partially disordered in vertical direction which causes resistance fluctuations. The system is modeled using a two-dimensional random resistor network. Transfer-matrix computation algorithm is used to calculate the total network resistance. It is found that probability density function (PDF of resistance fluctuations for a series of nanowire grids changes from Gaussian behavior towards the Bramwell-Holdsworth-Pinton distribution when both nanowire orientations are equally represented in the grid.

  5. Silicon nanowire field-effect transistors for the detection of proteins

    Science.gov (United States)

    Madler, Carsten

    In this dissertation I present results on our efforts to increase the sensitivity and selectivity of silicon nanowire ion-sensitive field-effect transistors for the detection of biomarkers, as well as a novel method for wireless power transfer based on metamaterial rectennas for their potential use as implantable sensors. The sensing scheme is based on changes in the conductance of the semiconducting nanowires upon binding of charged entities to the surface, which induces a field-effect. Monitoring the differential conductance thus provides information of the selective binding of biological molecules of interest to previously covalently linked counterparts on the nanowire surface. In order to improve on the performance of the nanowire sensing, we devised and fabricated a nanowire Wheatstone bridge, which allows canceling out of signal drift due to thermal fluctuations and dynamics of fluid flow. We showed that balancing the bridge significantly improves the signal-to-noise ratio. Further, we demonstrated the sensing of novel melanoma biomarker TROY at clinically relevant concentrations and distinguished it from nonspecific binding by comparing the reaction kinetics. For increased sensitivity, an amplification method was employed using an enzyme which catalyzes a signal-generating reaction by changing the redox potential of a redox pair. In addition, we investigated the electric double layer, which forms around charges in an electrolytic solution. It causes electrostatic screening of the proteins of interest, which puts a fundamental limitation on the biomarker detection in solutions with high salt concentrations, such as blood. We solved the coupled Nernst-Planck and Poisson equations for the electrolyte under influence of an oscillating electric field and discovered oscillations of the counterion concentration at a characteristic frequency. In addition to exploring different methods for improved sensing capabilities, we studied an innovative method to supply power

  6. All oxide ultraviolet photodetectors based on a p-Cu{sub 2}O film/n-ZnO heterostructure nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Ok, Yul Ho; Lee, Ki Ryong; Jung, Byung Oh; Kwon, Yong Hun; Cho, Hyung Koun, E-mail: chohk@skku.edu

    2014-11-03

    All-oxide ultraviolet (UV) photodetectors based on a p-Cu{sub 2}O thin film and n-ZnO nanowires were fabricated on Corning glass substrates. The p-Cu{sub 2}O film was fabricated by a sol–gel method and two-step thermal treatment on the ZnO nanowire arrays grown on ZnO doped with 5 at.% Al bottom electrode/glass for the formation of a p–n diode. The sol–gel coating of a Cu{sub 2}O layer produced the thin p-Cu{sub 2}O film with good uniformity on the ZnO nanowires and polycrystals with the (111) preferred orientation. It resulted in continuous interconnection of the ZnO nanowire arrays despite the solution process. The current–voltage (I–V) characteristics of the fabricated p–n heterostructure showed a typical rectifying behavior with a current rise at about 2 V and an I (illumination)/I (dark) ratio of about 3.89 × 10{sup 2} at − 6 V. The p-Cu{sub 2}O/n-ZnO nanowire-based UV photodetectors show the responsivity of ∼ 50 A/W with a peak position at 360 nm in reverse bias, together with weak photoresponse in the visible region. Consequently, we found that the introduction of the p-type Cu{sub 2}O layer in the ZnO nanowire-based UV photodetectors provided effective all-oxide p–n junctions without degrading UV/visible selectivity. - Highlights: • P-type Cu{sub 2}O films were deposited by a sol–gel method on the ZnO nanowires. • The p-Cu{sub 2}O/n-ZnO nanowire structure was fabricated for ultraviolet sensors. • Cu{sub 2}O films were optimized by spin coating speed and mole concentration. • Continuous Cu{sub 2}O films were produced as a hole injection or transport layer. • Cu{sub 2}O/ZnO nanowire photodetectors showed improved sensing performance.

  7. New Chemically Functionalized Nanomaterials for Electrical Nerve Agents Sensors

    International Nuclear Information System (INIS)

    Simonato, Jean-Pierre; Clavaguera, Simon; Carella, Alexandre; Delalande, Michael; Raoul, Nicolas; Lenfant, Stephane; Vuillaume, Dominique; Dubois, Emmanuel

    2011-01-01

    A chemical receptor specific to traces of organophosphorus nerve agents (OPs) has been synthesized and grafted to carbon nanotubes and silicon nanowires in order to make electrical sensors. Our results show that it is possible to detect efficiently sub-ppm traces of OPs with excellent selectivity notably with the use of silicon nanowires by monitoring the Drain-Source current of the SiNW-FET at an optimum back Gate voltage as a function of time. First developments of a prototype have also been realized.

  8. Si, Ge and SiGe wires for sensor application

    International Nuclear Information System (INIS)

    Druzhinin, A.A.; Khoverko, Yu.M.; Ostrovskii, I.P.; Nichkalo, S.I.; Nikolaeva, A.A.; Konopko, L.A.; Stich, I.

    2011-01-01

    Resistance and magnetoresistance of Si, Ge and Si-Ge micro- and nanowires were studied in temperature range 4,2-300 K at magnetic fields up to 14 T. The wires diameters range from 200 nm to 20 μm. Ga-In gates were created to wires and ohmic I-U characteristics were observed in all temperature range. It was found high elastic strain for Ge nanowires (of about 0,7%) as well as high magnitude of magnetoresistance (of about 250% at 14 T), which was used to design multifunctional sensor of simultaneous measurements of strain and magnetic field intensity. (authors)

  9. Long-range magnetostatic interactions in arrays of nanowires

    CERN Document Server

    Raposo, V; González, J M; Vázquez, M

    2000-01-01

    Experimental measurements and micromagnetic simulations of the hysteresis loops of arrays of cobalt nanowires are compared here. Arrays of cobalt nanowires (200 nm in diameter) were electrodeposited into the pores of alumina membranes (thickness 60 mu m). Their hysteresis loops along the axial direction of nanowires were measured using vibrating sample magnetometry. Micromagnetic simulations were performed considering dipolar interaction between nanowires leading to similar hysteresis loops as those obtained experimentally.

  10. Probing strain in bent semiconductor nanowires with Raman spectroscopy.

    Science.gov (United States)

    Chen, Jianing; Conache, Gabriela; Pistol, Mats-Erik; Gray, Struan M; Borgström, Magnus T; Xu, Hongxing; Xu, H Q; Samuelson, Lars; Håkanson, Ulf

    2010-04-14

    We present a noninvasive optical method to determine the local strain in individual semiconductor nanowires. InP nanowires were intentionally bent with an atomic force microscope and variations in the optical phonon frequency along the wires were mapped using Raman spectroscopy. Sections of the nanowires with a high curvature showed significantly broadened phonon lines. These observations together with deformation potential theory show that compressive and tensile strain inside the nanowires is the physical origin of the observed phonon energy variations.

  11. Understanding InP Nanowire Array Solar Cell Performance by Nanoprobe-Enabled Single Nanowire Measurements.

    Science.gov (United States)

    Otnes, Gaute; Barrigón, Enrique; Sundvall, Christian; Svensson, K Erik; Heurlin, Magnus; Siefer, Gerald; Samuelson, Lars; Åberg, Ingvar; Borgström, Magnus T

    2018-04-27

    III-V solar cells in the nanowire geometry might hold significant synthesis-cost and device-design advantages as compared to thin films and have shown impressive performance improvements in recent years. To continue this development there is a need for characterization techniques giving quick and reliable feedback for growth development. Further, characterization techniques which can improve understanding of the link between nanowire growth conditions, subsequent processing, and solar cell performance are desired. Here, we present the use of a nanoprobe system inside a scanning electron microscope to efficiently contact single nanowires and characterize them in terms of key parameters for solar cell performance. Specifically, we study single as-grown InP nanowires and use electron beam induced current characterization to understand the charge carrier collection properties, and dark current-voltage characteristics to understand the diode recombination characteristics. By correlating the single nanowire measurements to performance of fully processed nanowire array solar cells, we identify how the performance limiting parameters are related to growth and/or processing conditions. We use this understanding to achieve a more than 7-fold improvement in efficiency of our InP nanowire solar cells, grown from a different seed particle pattern than previously reported from our group. The best cell shows a certified efficiency of 15.0%; the highest reported value for a bottom-up synthesized InP nanowire solar cell. We believe the presented approach have significant potential to speed-up the development of nanowire solar cells, as well as other nanowire-based electronic/optoelectronic devices.

  12. Piezo-phototronic sensor

    Science.gov (United States)

    Wang, Zhong L.; Hu, Youfan; Zhang, Yan

    2013-10-15

    A device includes a substrate having a first surface. A piezoelectric nanowire is disposed on the first surface of the substrate. The piezoelectric nanowire has a first end and an opposite second end. The piezoelectric nanowire is subjected to an amount of strain. A first Schottky contact is in electrical communication with the first end of the piezoelectric nanowire. A second Schottky contact is in electrical communication with the second end of the piezoelectric nanowire. A bias voltage source is configured to impart a bias voltage between the first Schottky contact and the second Schottky contact. A mechanism is configured to measure current flowing through the piezoelectric nanowire. The amount of strain is selected so that a predetermined current will flow through the piezoelectric nanowire when light of a selected intensity is applied to a first location on the piezoelectric nanowire.

  13. Facile synthesis of hierarchically mesoporous NiCo2O4 nanowires for sensitive nonenzymatic glucose detection

    Science.gov (United States)

    Qin, Zhenhua; Cheng, Qunpeng; Lu, Yao; Li, Jianfen

    2017-07-01

    Glucose nonenzymatic detection is of significance in the fields of biological, environmental, food monitoring, and clinical analysis. By employing mesoporous NiCo2O4 nanowires as electrochemical sensor, highly sensitive nonenzymatic detection of glucose has been realized. The NiCo2O4 nanowires were synthesized via a facile hydrothermal method and subsequent thermal treatment. Their crystalline structures were analyzed by X-ray diffraction, and morphologies were characterized using scanning electron microscopy and transmission electron microscopy. The porous characteristics and real surface areas of the synthesized NiCo2O4 were studied by Brunauer-Emmett-Teller method. Electro-catalytic oxidation of glucose on the NiCo2O4 electrode was investigated by cyclic voltammetry, linear sweep voltammetry, and amperometry. The nonenzymatic sensor based on NiCo2O4 exhibited superior performance for glucose detection, with a low detection limit and excellent sensitivity.

  14. Controlled growth of single nanowires within a supported alumina template

    DEFF Research Database (Denmark)

    Vlad, A.; Mátéfi-Tempfli, M.; Faniel, S.

    2006-01-01

    A simple technique for fabricating single nanowires with well-defined position is presented. The process implies the use of a silicon nitride mask for selective electrochemical growth of the nanowires in a porous alumina template. We show that this method allows the realization of complex nanowire...

  15. Nanowires: properties, applications and synthesis via porous anodic ...

    Indian Academy of Sciences (India)

    TECS

    Abstract. Quasi one-dimensional nanowires possess unique electrical, electronic, thermoelectrical, optical, magnetic and chemical properties, which are different from that of their parent counterpart. The physical properties of nanowires are influenced by the morphology of the nanowires, diameter dependent band gap,.

  16. Microbial nanowires and methods of making and using

    Energy Technology Data Exchange (ETDEWEB)

    Reguera, Gemma; Cologgi, Dena; Worden, Robert Mark; Castro-Forero, Angelines A.; Steidl, Rebecca

    2017-03-21

    Electrically conductive nanowires, and genetically or chemically modified production and use of such nanowires with altered conductive, adhesive, coupling or other properties are described. The disclosed nanowires are used as device or device components or may be adapted for soluble metal remediation.

  17. Nanowires: properties, applications and synthesis via porous anodic ...

    Indian Academy of Sciences (India)

    Quasi one-dimensional nanowires possess unique electrical, electronic, thermoelectrical, optical, magnetic and chemical properties, which are different from that of their parent counterpart. The physical properties of nanowires are influenced by the morphology of the nanowires, diameter dependent band gap, carrier ...

  18. Failure mechanisms and electromechanical coupling in semiconducting nanowires

    Directory of Open Access Journals (Sweden)

    Peng B.

    2010-06-01

    Full Text Available One dimensional nanostructures, like nanowires and nanotubes, are increasingly being researched for the development of next generation devices like logic gates, transistors, and solar cells. In particular, semiconducting nanowires with a nonsymmetric wurtzitic crystal structure, such as zinc oxide (ZnO and gallium nitride (GaN, have drawn immense research interests due to their electromechanical coupling. The designing of the future nanowire-based devices requires component-level characterization of individual nanowires. In this paper, we present a unique experimental set-up to characterize the mechanical and electromechanical behaviour of individual nanowires. Using this set-up and complementary atomistic simulations, mechanical properties of ZnO nanowires and electromechanical properties of GaN nanowires were investigated. In ZnO nanowires, elastic modulus was found to depend on nanowire diameter decreasing from 190 GPa to 140 GPa as the wire diameter increased from 5 nm to 80 nm. Inconsistent failure mechanisms were observed in ZnO nanowires. Experiments revealed a brittle fracture, whereas simulations using a pairwise potential predicted a phase transformation prior to failure. This inconsistency is addressed in detail from an experimental as well as computational perspective. Lastly, in addition to mechanical properties, preliminary results on the electromechanical properties of gallium nitride nanowires are also reported. Initial investigations reveal that the piezoresistive and piezoelectric behaviour of nanowires is different from bulk gallium nitride.

  19. Topological Insulator Nanowires and Nanoribbons

    Energy Technology Data Exchange (ETDEWEB)

    Kong, D.S.

    2010-06-02

    Recent theoretical calculations and photoemission spectroscopy measurements on the bulk Bi{sub 2}Se{sub 3} material show that it is a three-dimensional topological insulator possessing conductive surface states with nondegenerate spins, attractive for dissipationless electronics and spintronics applications. Nanoscale topological insulator materials have a large surface-to-volume ratio that can manifest the conductive surface states and are promising candidates for devices. Here we report the synthesis and characterization of high quality single crystalline Bi{sub 2}Se{sub 3} nanomaterials with a variety of morphologies. The synthesis of Bi{sub 2}Se{sub 3} nanowires and nanoribbons employs Au-catalyzed vapor-liquid-solid (VLS) mechanism. Nanowires, which exhibit rough surfaces, are formed by stacking nanoplatelets along the axial direction of the wires. Nanoribbons are grown along [11-20] direction with a rectangular crosssection and have diverse morphologies, including quasi-one-dimensional, sheetlike, zigzag and sawtooth shapes. Scanning tunneling microscopy (STM) studies on nanoribbons show atomically smooth surfaces with {approx}1 nm step edges, indicating single Se-Bi-Se-Bi-Se quintuple layers. STM measurements reveal a honeycomb atomic lattice, suggesting that the STM tip couples not only to the top Se atomic layer, but also to the Bi atomic layer underneath, which opens up the possibility to investigate the contribution of different atomic orbitals to the topological surface states. Transport measurements of a single nanoribbon device (four terminal resistance and Hall resistance) show great promise for nanoribbons as candidates to study topological surface states.

  20. All-Electrical Graphene DNA Sensor Array.

    Science.gov (United States)

    Abbott, Jeffrey; Ham, Donhee; Xu, Guangyu

    2017-01-01

    Electrical sensing of biomolecules has been an important pursuit due to the label-free operation and chip-scale construct such sensing modality can enable. In particular, electrical biomolecular sensors based on nanomaterials such as semiconductor nanowires, carbon nanotubes, and graphene have demonstrated high sensitivity, which in the case of nanowires and carbon nanotubes can surpass typical optical detection sensitivity. Among these nanomaterials, graphene is well suited for a practical candidate for implementing a large-scale array of biomolecular sensors, as its two-dimensional morphology is readily compatible with industry standard top-down fabrication techniques. In our recent work published in 2014 Nature Communications, we demonstrated these benefits by creating DNA sensor arrays from chemical vapor deposition (CVD) graphene. The present chapter, which is a review of this recent work, outlines procedures demonstrating the use of individual graphene sites of the array in dual roles--electrophoretic electrodes for site specific probe DNA immobilization and field effect transistor (FET) sensors for detection of target DNA hybridization. The 100 fM detection sensitivity achieved in 7 out of 8 graphene FET sensors in the array combined with the alternative use of the graphene channels as electrophoretic electrodes for probe deposition represent steps toward creating an all-electrical multiplexed DNA array.