Long range surface plasmon resonance (LRSPR) based highly sensitive refractive index sensor using Kretschmann prism coupling arrangement

NASA Astrophysics Data System (ADS)

Paliwal, Ayushi; Sharma, Anjali; Tomar, Monika; Gupta, Vinay

2016-04-01

Long range surface plasmon resonance (LRSPR) when exploited for sensing purpose exhibit less losses in comparison to the sensors based on conventional SPR technique leading to the development of highly sensitive refractive index sensor. In order to excite long range surface plasmon (LRSP) mode, a high refractive index prism is used as coupler and a thin metal layer is sandwiched between a dielectric having similar refractive index with that of another semi-infinite dielectric. LRSP mode has been excited in symmetric configuration where metal (Au) layer is sandwiched between the two similar refractive index dielectrics (LiF thin film and a fixed concentration of sugar solution) for realization of a refractive index sensor. When the concentration of sugar solution is slightly increased from 30% to 40%, the LRSPR angle increases from 64.6° to 67.9° and the sensor is found to be highly sensitive with sensitivity of 0.0911 °/(mg/dl).

Fabrication of an SPR Sensor Surface with Antifouling Properties for Highly Sensitive Detection of 2,4,6-Trinitrotoluene Using Surface-Initiated Atom Transfer Polymerization

PubMed Central

Yatabe, Rui; Onodera, Takeshi; Toko, Kiyoshi

2013-01-01

In this study, we modified a surface plasmon resonance immunosensor chip with a polymer using surface-initiated atom transfer polymerization (SI-ATRP) for the highly sensitive detection of 2,4,6-trinitrotoluene (TNT). To immobilize a TNT analogue on the polymer, mono-2-(methacryloyloxy)ethylsuccinate (MES), which has a carboxyl group, was used in this study. However, the anti-TNT antibody may adsorb non-specifically on the polymer surface by an electrostatic interaction because MES is negatively charged. Therefore, a mixed monomer with MES and diethylaminoethylmethacrylate (DEAEM), which has a tertiary amino group and is positively charged, was prepared to obtain electroneutrality for suppressing the nonspecific adsorption. The detection of TNT was performed by inhibition assay using the polymer surface. To ensure high sensitivity to TNT, the affinity between the surface and the antibody was optimized by controlling the density of the initiator for ATRP by mixing two types of self-assembled monolayer reagents. As a result, a limit of detection of 5.7 pg/mL (ppt) for TNT was achieved using the optimized surface. PMID:23877126

Perovskite nanoparticle-sensitized Ga 2O 3 nanorod arrays for CO detection at high temperature

DOE PAGES

Lin, Hui -Jan; Baltrus, John P.; Gao, Haiyong; ...

2016-04-04

Here, noble metal nanoparticles are extensively used for sensitizing metal oxide chemical sensors through the catalytic spillover mechanism. However, due to earth-scarcity and high cost of noble metals, finding replacements presents a great economic benefit. Besides, high temperature and harsh environment sensor applications demand material stability under conditions approaching thermal and chemical stability limits of noble metals. In this study, we employed thermally stable perovskite-type La 0.8Sr 0.2FeO 3 (LSFO) nanoparticle surface decoration on Ga 2O 3 nanorod array gas sensors and discovered an order of magnitude enhanced sensitivity to carbon monoxide at 500 °C. The LSFO nanoparticle catalysts wasmore » of comparable performance to that achieved by Pt nanoparticles, with a much lower weight loading than Pt. Detailed electron microscopy and X-ray photoelectron spectroscopy studies suggested the LSFO nanoparticle sensitization effect is attributed to a spillover-like effect associated with the gas-LSFO-Ga 2O 3 triple-interfaces that spread the negatively charged surface oxygen ions from LSFO nanoparticles surfaces over to β-Ga 2O 3 nanorod surfaces with faster surface CO oxidation reactions.« less

Perovskite Nanoparticle-Sensitized Ga2O3 Nanorod Arrays for CO Detection at High Temperature.

PubMed

Lin, Hui-Jan; Baltrus, John P; Gao, Haiyong; Ding, Yong; Nam, Chang-Yong; Ohodnicki, Paul; Gao, Pu-Xian

2016-04-13

Noble metal nanoparticles are extensively used for sensitizing metal oxide chemical sensors through the catalytic spillover mechanism. However, due to earth-scarcity and high cost of noble metals, finding replacements presents a great economic benefit. Besides, high temperature and harsh environment sensor applications demand material stability under conditions approaching thermal and chemical stability limits of noble metals. In this study, we employed thermally stable perovskite-type La(0.8)Sr(0.2)FeO3 (LSFO) nanoparticle surface decoration on Ga2O3 nanorod array gas sensors and discovered an order of magnitude enhanced sensitivity to carbon monoxide at 500 °C. The LSFO nanoparticle catalysts was of comparable performance to that achieved by Pt nanoparticles, with a much lower weight loading than Pt. Detailed electron microscopy and X-ray photoelectron spectroscopy studies suggested the LSFO nanoparticle sensitization effect is attributed to a spillover-like effect associated with the gas-LSFO-Ga2O3 triple-interfaces that spread the negatively charged surface oxygen ions from LSFO nanoparticles surfaces over to β-Ga2O3 nanorod surfaces with faster surface CO oxidation reactions.

Space-Based Diagnosis of Surface Ozone Sensitivity to Anthropogenic Emissions

NASA Technical Reports Server (NTRS)

Martin, Randall V.; Fiore, Arlene M.; VanDonkelaar, Aaron

2004-01-01

We present a novel capability in satellite remote sensing with implications for air pollution control strategy. We show that the ratio of formaldehyde columns to tropospheric nitrogen dioxide columns is an indicator of the relative sensitivity of surface ozone to emissions of nitrogen oxides (NO(x) = NO + NO2) and volatile organic compounds (VOCs). The diagnosis from these space-based observations is highly consistent with current understanding of surface ozone chemistry based on in situ observations. The satellite-derived ratios indicate that surface ozone is more sensitive to emissions of NO(x) than of VOCs throughout most continental regions of the Northern Hemisphere during summer. Exceptions include Los Angeles and industrial areas of Germany. A seasonal transition occurs in the fall when surface ozone becomes less sensitive to NOx and more sensitive to VOCs.

Highly charged ion based time of flight emission microscope

DOEpatents

Barnes, Alan V.; Schenkel, Thomas; Hamza, Alex V.; Schneider, Dieter H.; Doyle, Barney

2001-01-01

A highly charged ion based time-of-flight emission microscope has been designed, which improves the surface sensitivity of static SIMS measurements because of the higher ionization probability of highly charged ions. Slow, highly charged ions are produced in an electron beam ion trap and are directed to the sample surface. The sputtered secondary ions and electrons pass through a specially designed objective lens to a microchannel plate detector. This new instrument permits high surface sensitivity (10.sup.10 atoms/cm.sup.2), high spatial resolution (100 nm), and chemical structural information due to the high molecular ion yields. The high secondary ion yield permits coincidence counting, which can be used to enhance determination of chemical and topological structure and to correlate specific molecular species.

Plasmonic hydrogen sensor based on integrated microring resonator

NASA Astrophysics Data System (ADS)

Yi, Ya Sha; Wu, Da Chuan

2017-12-01

We have proposed and demonstrated numerically an ultrasmall and highly sensitive plasmonic hydrogen sensor based on an integrated microring resonator, with a footprint size as small as 4×4 μm2. With a palladium (Pd) or platinum (Pt) hydrogen-sensitive layer coated on the inner surface of the microring resonator and the excitation of surface plasmon modes at the interface from the microring resonator waveguide, the device is highly sensitive to low hydrogen concentration variation, and the sensitivity is at least one order of magnitude larger than that of the optical fiber-based hydrogen sensor. We have also investigated the tradeoff between the portion coverage of the Pd/Pt layer and the sensitivity, as well as the width of the hydrogen-sensitive layer. This ultrasmall plasmonic hydrogen sensor holds promise for the realization of a highly compact sensor with integration capability for applications in hydrogen fuel economy.

A new attraction-disseverance model for explaining landsliding in clay-rich tephras

NASA Astrophysics Data System (ADS)

Kluger, M. O.; Moon, V.; Kreiter, S.; Lowe, D.; Churchman, J.; Hepp, D. A.; Seibel, D.; Jorat, E.; Mörz, T.

2016-12-01

Altered tephras are highly susceptible to landsliding and account for fatalities and property damage every year. The clay mineral halloysite is often associated with landslide-prone layers within weathered tephra successions, especially in deposits with high sensitivity, which describes the post-failure strength loss. However, the precise role of halloysite on the development of sensitivity and thus sudden and unpredictable landsliding is unknown. Here we show that an abundance of halloysite, dominated by a distinctive ovate mushroom-cap-shaped (MCS) spherical morphology, governs the development of sensitivity, and hence proneness to landsliding, in weathered rhyolitic tephras in eastern North Island, New Zealand. We found that a highly sensitive layer, which was involved in a retrogressive landslide, has an extraordinarily high content of aggregated MCS spheres with imperfectly-closed exterior surfaces, i.e., the MCS spheres have substantial openings on one side. We suggest that short-range electrostatic and van der Waals' interactions enabled the MCS spheres to form interconnected aggregates by attraction between numerous paired silanol and aluminol layers with a weakly positive, or neutral, charge exposed in the openings and the negatively-charged convex silanol faces on the curved exterior surfaces of the spheres. However, if these weak attractions are overcome during slope failure, the prevailing repulsion between two exterior surfaces result in a low remolded shear strength, i.e., a high sensitivity, and thus a high propensity for flow-like landsliding. Our results indicate that this novel electrostatic attraction-disseverance model explains the high sensitivity and therefore contributes to a general understanding of the mechanisms of landsliding in sensitive altered tephras rich in spherical halloysite.

High-sensitivity four-layer polymer fiber-optic evanescent wave sensor.

PubMed

Xin, Xin; Zhong, Nianbing; Liao, Qiang; Cen, Yanyan; Wu, Ruohua; Wang, Zhengkun

2017-05-15

We present a novel four-layer structure consisting of bottom, second, third, and surface layers in the sensing region, for a D-shaped step-index fiber-optic evanescent wave (FOEW) sensor. To reduce the background noise, the surface of the longitudinal section in the D-shaped region is coated with a light-absorbing film. We check the morphologies of the second and surface layers, examine the refractive indices (RIs) of the third and surface layers, and analyze the composition of the surface layer. We also investigate the effects of the thicknesses and RIs of the third and surface layers and the LA film on the light transmission and sensitivity of the FOEW sensors. The results highlight the very good sensitivity of the proposed FOEW sensor with a four-layer structure, which reached -0.077 (μg/l) -1 in the detection of the target antibody; the sensitivity of the novel FOEW sensor was 7.60 and 1.52 times better than that of a conventional sensor with a core-cladding structure and an FOEW sensor with a three-layer structure doped with GeO 2 . The applications of this high-sensitivity FOEW sensor can be extended to biodefense, disease diagnosis, and biomedical and biochemical analysis. Copyright © 2017 Elsevier B.V. All rights reserved.

Electrophoretic deposition of graphene oxide on magnetic ribbon: Toward high sensitive and selectable magnetoimpedance response

NASA Astrophysics Data System (ADS)

Jamilpanah, L.; Azadian, S.; Shoa e Gharehbagh, J.; Haghniaz Jahromi, S.; Sheykhifard, Z.; Hosseinizadeh, S.; Erfanifam, S.; Hajiali, M. R.; Tehranchi, M. M.; Mohseni, S. M.

2018-07-01

Graphene oxide (GO) layers have shown to be fascinating elements for application in high performance sensors. They can be applied in multi-disciplinary designs based on surface selective sensing mechanisms. One immediate application of such surface sensitive elements is implementing of GO layer in magnetoimpedance (MI) sensors to improve their multi-functionality. In this paper, deposition of GO on the surface of Co-based amorphous ribbons (Co68.15Fe4.35Si12.5B15) is performed using electrophoretic deposition (EPD) method to evaluate the MI response. MI ratio increased from 271% (bare ribbon) up to 281% and 301% EPD GO deposited within 4 and 8 min, respectively. Similar experiment for the ribbon drop coated with GO was carried out while no enhancement in MI response was seen. Vertical growth of GO on the surface of the ribbon in EPD and drop coated layers observed by topographical measurements. We explained the difference between the MI responses based on layers verticality and surface coverage. UV-Visible absorption and Raman spectroscopy were used to study the nature of GO. Gaining a high surface area of GO along with their biocompatible and anticorrosive properties atop the MI sensors can open pathways towards increasing applications of surface selective and high sensitive MI sensors.

Ultrafast and nonlinear surface-enhanced Raman spectroscopy.

PubMed

Gruenke, Natalie L; Cardinal, M Fernanda; McAnally, Michael O; Frontiera, Renee R; Schatz, George C; Van Duyne, Richard P

2016-04-21

Ultrafast surface-enhanced Raman spectroscopy (SERS) has the potential to study molecular dynamics near plasmonic surfaces to better understand plasmon-mediated chemical reactions such as plasmonically-enhanced photocatalytic or photovoltaic processes. This review discusses the combination of ultrafast Raman spectroscopic techniques with plasmonic substrates for high temporal resolution, high sensitivity, and high spatial resolution vibrational spectroscopy. First, we introduce background information relevant to ultrafast SERS: the mechanisms of surface enhancement in Raman scattering, the characterization of plasmonic materials with ultrafast techniques, and early complementary techniques to study molecule-plasmon interactions. We then discuss recent advances in surface-enhanced Raman spectroscopies with ultrafast pulses with a focus on the study of molecule-plasmon coupling and molecular dynamics with high sensitivity. We also highlight the challenges faced by this field by the potential damage caused by concentrated, highly energetic pulsed fields in plasmonic hotspots, and finally the potential for future ultrafast SERS studies.

A nano-patterned self assembled monolayer (SAM) rutile titania cancer chip for rapid, low cost, highly sensitive, direct cancer analysis in MALDI-MS.

PubMed

Manikandan, M; Gopal, Judy; Hasan, Nazim; Wu, Hui-Fen

2014-12-01

We developed a cancer chip by nano-patterning a highly sensitive SAM titanium surface capable of capturing and sensing concentrations as low as 10 cancer cells/mL from the environment by Matrix Assisted Laser Desorption and Ionization Time of Flight Mass Spectrometry (MALDI-TOF MS). The current approach evades any form of pretreatment and sample preparation processes; it is time saving and does not require the (expensive) conventional MALDI target plate. The home made aluminium (Al) target holder cost, on which we loaded the cancer chips for MALDI-TOF MS analysis, is about 60 USD. While the conventional stainless steel MALDI target plate is more than 700 USD. The SAM surface was an effective platform leading to on-chip direct MALDI-MS detection of cancer cells. We compared the functionality of this chip with the unmodified titanium surfaces and thermally oxidized (TO) titanium surfaces. The lowest detectable concentration of the TO chip was 10(3) cells/mL, while the lowest detectable concentration of the control or unmodified titanium chips was 10(6) cells/mL. Compared to the control surface, the SAM cancer chip showed 100,000 times of enhanced sensitivity and compared with the TO chip, 1000 times of increased sensitivity. The high sensitivity of the SAM surfaces is attributed to the presence of the rutile SAM, surface roughness and surface wettability as confirmed by AFM, XRD, contact angle microscope and FE-SEM. This study opens a new avenue for the potent application of the SAM cancer chip for direct cancer diagnosis by MALDI-TOF MS in the near future. Copyright © 2014. Published by Elsevier B.V.

Gene expression analysis using a highly sensitive DNA microarray for colorectal cancer screening.

PubMed

Koga, Yoshikatsu; Yamazaki, Nobuyoshi; Takizawa, Satoko; Kawauchi, Junpei; Nomura, Osamu; Yamamoto, Seiichiro; Saito, Norio; Kakugawa, Yasuo; Otake, Yosuke; Matsumoto, Minori; Matsumura, Yasuhiro

2014-01-01

Half of all patients with small, right-sided, non-metastatic colorectal cancer (CRC) have negative results for the fecal occult blood test (FOBT). In the present study, the usefulness of CRC screening with a highly sensitive DNA microarray was evaluated in comparison with that by FOBT using fecal samples. A total of 53 patients with CRC and 61 healthy controls were divided into "training" and "validation sets". For the gene profiling, total RNA extracted from 0.5 g of feces was hybridized to a highly sensitive DNA chip. The expressions of 43 genes were significantly higher in the patients with CRC than in healthy controls (p<0.05). In the training set, the sensitivity and specificity of the DNA chip assay using six genes were 85.4% and 85.2%, respectively. On the other hand, in the validation set, the sensitivity and specificity of the DNA chip assay were 85.2% and 85.7%, respectively. The sensitivities of the DNA chip assay were higher than those of FOBT in cases of the small, right-sided, early-CRC, tumor invading up to the muscularis propria (i.e. surface tumor) subgroups. In particular, the sensitivities of the DNA chip assay in the surface tumor and early-CRC subgroups were significantly higher than those of FOBT (p=0.023 and 0.019, respectively.). Gene profiling assay using a highly sensitive DNA chip was more effective than FOBT at detecting patients with small, right-sided, surface tumor, and early-stage CRC.

Sensitive Detection of Biomolecules by Surface Enhanced Raman Scattering using Plant Leaves as Natural Substrates

NASA Astrophysics Data System (ADS)

Sharma, Vipul; Krishnan, Venkata

2017-03-01

Detection of biomolecules is highly important for biomedical and other biological applications. Although several methods exist for the detection of biomolecules, surface enhanced Raman scattering (SERS) has a unique role in greatly enhancing the sensitivity. In this work, we have demonstrated the use of natural plant leaves as facile, low cost and eco-friendly SERS substrates for the sensitive detection of biomolecules. Specifically, we have investigated the influence of surface topography of five different plant leaf based substrates, deposited with Au, on the SERS performance by using L-cysteine as a model biomolecule. In addition, we have also compared the effect of sputter deposition of Au thin film with dropcast deposition of Au nanoparticles on the leaf substrates. Our results indicate that L-cysteine could be detected with high sensitivity using these plant leaf based substrates and the leaf possessing hierarchical micro/nanostructures on its surface shows higher SERS enhancement compared to a leaf having a nearplanar surface. Furthermore, leaves with drop-casted Au nanoparticle clusters performed better than the leaves sputter deposited with a thin Au film.

Enhanced electrochemical nanoring electrode for analysis of cytosol in single cells.

PubMed

Zhuang, Lihong; Zuo, Huanzhen; Wu, Zengqiang; Wang, Yu; Fang, Danjun; Jiang, Dechen

2014-12-02

A microelectrode array has been applied for single cell analysis with relatively high throughput; however, the cells were typically cultured on the microelectrodes under cell-size microwell traps leading to the difficulty in the functionalization of an electrode surface for higher detection sensitivity. Here, nanoring electrodes embedded under the microwell traps were fabricated to achieve the isolation of the electrode surface and the cell support, and thus, the electrode surface can be modified to obtain enhanced electrochemical sensitivity for single cell analysis. Moreover, the nanometer-sized electrode permitted a faster diffusion of analyte to the surface for additional improvement in the sensitivity, which was evidenced by the electrochemical characterization and the simulation. To demonstrate the concept of the functionalized nanoring electrode for single cell analysis, the electrode surface was deposited with prussian blue to detect intracellular hydrogen peroxide at a single cell. Hundreds of picoamperes were observed on our functionalized nanoring electrode exhibiting the enhanced electrochemical sensitivity. The success in the achievement of a functionalized nanoring electrode will benefit the development of high throughput single cell electrochemical analysis.

Joint inversion of high-frequency surface waves with fundamental and higher modes

USGS Publications Warehouse

Luo, Y.; Xia, J.; Liu, J.; Liu, Q.; Xu, S.

2007-01-01

Joint inversion of multimode surface waves for estimating the shear (S)-wave velocity has received much attention in recent years. In this paper, we first analyze sensitivity of phase velocities of multimodes of surface waves for a six-layer earth model, and then we invert surface-wave dispersion curves of the theoretical model and a real-world example. Sensitivity analysis shows that fundamental mode data are more sensitive to the S-wave velocities of shallow layers and are concentrated on a very narrow frequency band, while higher mode data are more sensitive to the parameters of relatively deeper layers and are distributed over a wider frequency band. These properties provide a foundation of using a multimode joint inversion to define S-wave velocities. Inversion results of both synthetic data and a real-world example demonstrate that joint inversion with the damped least-square method and the singular-value decomposition technique to invert high-frequency surface waves with fundamental and higher mode data simultaneously can effectively reduce the ambiguity and improve the accuracy of S-wave velocities. ?? 2007.

Transparent, Flexible, Conformal Capacitive Pressure Sensors with Nanoparticles.

PubMed

Kim, Hyeohn; Kim, Gwangmook; Kim, Taehoon; Lee, Sangwoo; Kang, Donyoung; Hwang, Min-Soo; Chae, Youngcheol; Kang, Shinill; Lee, Hyungsuk; Park, Hong-Gyu; Shim, Wooyoung

2018-02-01

The fundamental challenge in designing transparent pressure sensors is the ideal combination of high optical transparency and high pressure sensitivity. Satisfying these competing demands is commonly achieved by a compromise between the transparency and usage of a patterned dielectric surface, which increases pressure sensitivity, but decreases transparency. Herein, a design strategy for fabricating high-transparency and high-sensitivity capacitive pressure sensors is proposed, which relies on the multiple states of nanoparticle dispersity resulting in enhanced surface roughness and light transmittance. We utilize two nanoparticle dispersion states on a surface: (i) homogeneous dispersion, where each nanoparticle (≈500 nm) with a size comparable to the visible light wavelength has low light scattering; and (ii) heterogeneous dispersion, where aggregated nanoparticles form a micrometer-sized feature, increasing pressure sensitivity. This approach is experimentally verified using a nanoparticle-dispersed polymer composite, which has high pressure sensitivity (1.0 kPa -1 ), and demonstrates excellent transparency (>95%). We demonstrate that the integration of nanoparticle-dispersed capacitor elements into an array readily yields a real-time pressure monitoring application and a fully functional touch device capable of acting as a pressure sensor-based input device, thereby opening up new avenues to establish processing techniques that are effective on the nanoscale yet applicable to macroscopic processing. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A cell-surface-anchored ratiometric i-motif sensor for extracellular pH detection.

PubMed

Ying, Le; Xie, Nuli; Yang, Yanjing; Yang, Xiaohai; Zhou, Qifeng; Yin, Bincheng; Huang, Jin; Wang, Kemin

2016-06-14

A FRET-based sensor is anchored on the cell surface through streptavidin-biotin interactions. Due to the excellent properties of the pH-sensitive i-motif structure, the sensor can detect extracellular pH with high sensitivity and excellent reversibility.

Sensitivity of high-frequency Rayleigh-wave data revisited

USGS Publications Warehouse

Xia, J.; Miller, R.D.; Ivanov, J.

2007-01-01

Rayleigh-wave phase velocity of a layered earth model is a function of frequency and four groups of earth properties: P-wave velocity, S-wave velocity (Vs), density, and thickness of layers. Analysis of the Jacobian matrix (or the difference method) provides a measure of dispersion curve sensitivity to earth properties. Vs is the dominant influence for the fundamental mode (Xia et al., 1999) and higher modes (Xia et al., 2003) of dispersion curves in a high frequency range (>2 Hz) followed by layer thickness. These characteristics are the foundation of determining S-wave velocities by inversion of Rayleigh-wave data. More applications of surface-wave techniques show an anomalous velocity layer such as a high-velocity layer (HVL) or a low-velocity layer (LVL) commonly exists in near-surface materials. Spatial location (depth) of an anomalous layer is usually the most important information that surface-wave techniques are asked to provide. Understanding and correctly defining the sensitivity of high-frequency Rayleigh-wave data due to depth of an anomalous velocity layer are crucial in applying surface-wave techniques to obtain a Vs profile and/or determine the depth of an anomalous layer. Because depth is not a direct earth property of a layered model, changes in depth will result in changes in other properties. Modeling results show that sensitivity at a given depth calculated by the difference method is dependent on the Vs difference (contrast) between an anomalous layer and surrounding layers. The larger the contrast is, the higher the sensitivity due to depth of the layer. Therefore, the Vs contrast is a dominant contributor to sensitivity of Rayleigh-wave data due to depth of an anomalous layer. Modeling results also suggest that the most sensitive depth for an HVL is at about the middle of the depth to the half-space, but for an LVL it is near the ground surface. ?? 2007 Society of Exploration Geophysicists.

Quantitative Comparison of Protein Adsorption and Conformational Changes on Dielectric-Coated Nanoplasmonic Sensing Arrays.

PubMed

Ferhan, Abdul Rahim; Jackman, Joshua A; Sut, Tun Naw; Cho, Nam-Joon

2018-04-22

Nanoplasmonic sensors are a popular, surface-sensitive measurement tool to investigate biomacromolecular interactions at solid-liquid interfaces, opening the door to a wide range of applications. In addition to high surface sensitivity, nanoplasmonic sensors have versatile surface chemistry options as plasmonic metal nanoparticles can be coated with thin dielectric layers. Within this scope, nanoplasmonic sensors have demonstrated promise for tracking protein adsorption and substrate-induced conformational changes on oxide film-coated arrays, although existing studies have been limited to single substrates. Herein, we investigated human serum albumin (HSA) adsorption onto silica- and titania-coated arrays of plasmonic gold nanodisks by localized surface plasmon resonance (LSPR) measurements and established an analytical framework to compare responses across multiple substrates with different sensitivities. While similar responses were recorded on the two substrates for HSA adsorption under physiologically-relevant ionic strength conditions, distinct substrate-specific behavior was observed at lower ionic strength conditions. With decreasing ionic strength, larger measurement responses occurred for HSA adsorption onto silica surfaces, whereas HSA adsorption onto titania surfaces occurred independently of ionic strength condition. Complementary quartz crystal microbalance-dissipation (QCM-D) measurements were also performed, and the trend in adsorption behavior was similar. Of note, the magnitudes of the ionic strength-dependent LSPR and QCM-D measurement responses varied, and are discussed with respect to the measurement principle and surface sensitivity of each technique. Taken together, our findings demonstrate how the high surface sensitivity of nanoplasmonic sensors can be applied to quantitatively characterize protein adsorption across multiple surfaces, and outline broadly-applicable measurement strategies for biointerfacial science applications.

Aptamer-functionalized nano-biosensors.

PubMed

Chiu, Tai-Chia; Huang, Chih-Ching

2009-01-01

Nanomaterials have become one of the most interesting sensing materials because of their unique size- and shape-dependent optical properties, high surface energy and surface-to-volume ratio, and tunable surface properties. Aptamers are oligonucleotides that can bind their target ligands with high affinity. The use of nanomaterials that are bioconjugated with aptamers for selective and sensitive detection of analytes such as small molecules, metal ions, proteins, and cells has been demonstrated. This review focuses on recent progress in the development of biosensors by integrating functional aptamers with different types of nanomaterials, including quantum dots, magnetic nanoparticles (NPs), metallic NPs, and carbon nanotubes. Colorimetry, fluorescence, electrochemistry, surface plasmon resonance, surface-enhanced Raman scattering, and magnetic resonance imaging are common detection modes for a broad range of analytes with high sensitivity and selectivity when using aptamer bioconjugated nanomaterials (Apt-NMs). We highlight the important roles that the size and concentration of nanomaterials, the secondary structure and density of aptamers, and the multivalent interactions play in determining the specificity and sensitivity of the nanosensors towards analytes. Advantages and disadvantages of the Apt-NMs for bioapplications are focused.

Demonstration of sub-femtomole sensitivity for small molecules with microsphere ring resonator sensors

NASA Astrophysics Data System (ADS)

White, Ian M.; Oveys, Hesam; Fan, Xudong

2006-02-01

Optical microsphere resonators can function as highly sensitive bio/chemical sensors due to the large Q-factor, which leads to high light-matter interaction. The whispering gallery modes (WGM) arise at the surface of the microsphere, creating a highly enhanced optical field that interacts with matter on or near the microsphere surface. As a result, the spectral position of the WGM is extremely sensitive to refractive index changes near the surface, such as when bio/chemical molecules bind to the sphere. We show the potential feasibility of a microsphere ring resonator as a sensor for small molecules by demonstrating detection of sub-femtomole changes in SiO II molecules at the surface of the microsphere. In this experiment, the silica molecules act as an excellent model for small molecule analytes because of their 60 Dalton molecular weight, and because we know nearly the exact quantity of molecules at the surface, which enables a sensitivity characterization. We measure the spectral shifts in the WGMs when low concentrations of hydrofluoric acid (HF) are added to a solution that is being probed by the microsphere. As the HF molecules break apart the SiO II molecules at the sphere surface, the WGMs shift due to the sub-nano-scale decrease in the size of the microsphere. These calculations show that the sensitivity of this microsphere resonator is on the order of 500 attomoles. Our results will lead to the utilization of optical microspheres for detection of trace quantities of small molecules for such applications as drug discovery, environmental monitoring, and enzyme detection using peptide cleavage.

Temperature sensitive surfaces and methods of making same

DOEpatents

Liang, Liang [Richland, WA; Rieke, Peter C [Pasco, WA; Alford, Kentin L [Pasco, WA

2002-09-10

Poly-n-isopropylacrylamide surface coatings demonstrate the useful property of being able to switch charateristics depending upon temperature. More specifically, these coatings switch from being hydrophilic at low temperature to hydrophobic at high temperature. Research has been conducted for many years to better characterize and control the properties of temperature sensitive coatings. The present invention provides novel temperature sensitive coatings on articles and novel methods of making temperature sensitive coatings that are disposed on the surfaces of various articles. These novel coatings contain the reaction products of n-isopropylacrylamide and are characterized by their properties such as advancing contact angles. Numerous other characteristics such as coating thickness, surface roughness, and hydrophilic-to-hydrophobic transition temperatures are also described. The present invention includes articles having temperature-sensitve coatings with improved properties as well as improved methods for forming temperature sensitive coatings.

Self-Assembled ZnO Nanosheet-Based Spherical Structure as Photoanode in Dye-Sensitized Solar Cells

NASA Astrophysics Data System (ADS)

Ameri, Mohsen; Raoufi, Meysam; Zamani-Meymian, M.-R.; Samavat, Feridoun; Fathollahi, M.-R.; Mohajerani, Ezeddin

2018-03-01

High surface area and enhanced light scattering of ZnO nanosheet aggregates have made them a promising active layer candidate material for fabrication of nanostructure dye-sensitized solar cells. Here, we propose a facile preparation method of such ZnO nanosheet structures, and in order to verify their applicability as photoanode material for dye-sensitized solar cells, we employ morphological, optical, structural and electrical measurements. The results reveal the high surface area available for dye molecules for enhancing adsorption, high light scattering and competitive power conversion efficiencies compared to the works in literature. Finally, the device is optimized with respect to the photoanode thickness. The favorable features shown here can extend the application of the structure to other types of sensitization-based perovskite and quantum dot solar cells.

Dispersion and shape engineered plasmonic nanosensors

NASA Astrophysics Data System (ADS)

Jeong, Hyeon-Ho; Mark, Andrew G.; Alarcón-Correa, Mariana; Kim, Insook; Oswald, Peter; Lee, Tung-Chun; Fischer, Peer

2016-04-01

Biosensors based on the localized surface plasmon resonance (LSPR) of individual metallic nanoparticles promise to deliver modular, low-cost sensing with high-detection thresholds. However, they continue to suffer from relatively low sensitivity and figures of merit (FOMs). Herein we introduce the idea of sensitivity enhancement of LSPR sensors through engineering of the material dispersion function. Employing dispersion and shape engineering of chiral nanoparticles leads to remarkable refractive index sensitivities (1,091 nm RIU-1 at λ=921 nm) and FOMs (>2,800 RIU-1). A key feature is that the polarization-dependent extinction of the nanoparticles is now characterized by rich spectral features, including bipolar peaks and nulls, suitable for tracking refractive index changes. This sensing modality offers strong optical contrast even in the presence of highly absorbing media, an important consideration for use in complex biological media with limited transmission. The technique is sensitive to surface-specific binding events which we demonstrate through biotin-avidin surface coupling.

Vibration-immune high-sensitivity profilometer built with the technique of composite interferometry.

PubMed

Lin, Yu-Kai; Chang, Chun-Wei; Hou, Max T; Hsu, I-Jen

2016-03-10

A prototype of a profilometer was built with the technique of composite interferometry for measurement of the distribution of both the amplitude and phase information of the surface of a material simultaneously. The composite interferometer was composed of a Michelson interferometer for measuring the surface profile of the sample and a Mach-Zehnder interferometer for measuring the phase deviation caused by the scanning component and environmental perturbations. A high-sensitivity surface profile can be obtained by use of the phase compensation mechanism through subtraction of the phases of the interferograms detected in the two interferometers. With the new design and improvement of robustness of the optical system, the measurement speed and accuracy were significantly improved. Furthermore, an additional optical delay component results in a higher sensitivity of the interference signal. This prototype of vibration-immune profilometer was examined to have a displacement sensitivity of 0.64 nm.

High-sensitivity ESCA instrument

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davies, R.D.; Herglotz, H.K.; Lee, J.D.

1973-01-01

A new electron spectroscopy for chemical analysis (ESCA) instrument has been developed to provide high sensitivity and efficient operation for laboratory analysis of composition and chemical bonding in very thin surface layers of solid samples. High sensitivity is achieved by means of the high-intensity, efficient x-ray source described by Davies and Herglotz at the 1968 Denver X-Ray Conference, in combination with the new electron energy analyzer described by Lee at the 1972 Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy. A sample chamber designed to provide for rapid introduction and replacement of samples has adequate facilities for various sample treatmentsmore » and conditiouing followed immediately by ESCA analysis of the sample. Examples of application are presented, demonstrating the sensitivity and resolution achievable with this instrument. Its usefulness in trace surface analysis is shown and some chemical shifts'' measured by the instrument are compared with those obtained by x-ray spectroscopy. (auth)« less

Optical pumping and xenon NMR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Raftery, M.D.

1991-11-01

Nuclear Magnetic Resonance (NMR) spectroscopy of xenon has become an important tool for investigating a wide variety of materials, especially those with high surface area. The sensitivity of its chemical shift to environment, and its chemical inertness and adsorption properties make xenon a particularly useful NMR probe. This work discusses the application of optical pumping to enhance the sensitivity of xenon NMR experiments, thereby allowing them to be used in the study of systems with lower surface area. A novel method of optically-pumping [sup 129]Xe in low magnetic field below an NMR spectrometer and subsequent transfer of the gas tomore » high magnetic field is described. NMR studies of the highly polarized gas adsorbed onto powdered samples with low to moderate surface areas are now possible. For instance, NMR studies of optically-pumped xenon adsorbed onto polyacrylic acid show that xenon has a large interaction with the surface. By modeling the low temperature data in terms of a sticking probability and the gas phase xenon-xenon interaction, the diffusion coefficient for xenon at the surface of the polymer is determined. The sensitivity enhancement afforded by optical pumping also allows the NMR observation of xenon thin films frozen onto the inner surfaces of different sample cells. The geometry of the thin films results in interesting line shapes that are due to the bulk magnetic susceptibility of xenon. Experiments are also described that combine optical pumping with optical detection for high sensitivity in low magnetic field to observe the quadrupoler evolution of 131 Xe spins at the surface of the pumping cells. In cells with macroscopic asymmetry, a residual quadrupolar interaction causes a splitting in the [sup 131]Xe NMR frequencies in bare Pyrex glass cells and cells with added hydrogen.« less

[Diagnostic advantages of the test system "DS-EIA-HBsAg-0.01" for detection of HBV surface antigen].

PubMed

Egorova, N I; Pyrenkova, I Iu; Igolkina, S N; Sharipova, I N; Puzyrev, V F; Obriadina, A P; Burkov, A N; Kornienko, N V; Fields, H A; Korovkin, A S; Shalunova, N V; Bektemirov, T A; Kuznetsov, K V; Koshcheeva, N A; Ulanova, T I

2009-01-01

The new highly sensitive test system "DS-EIA-HBsAg-0.01" (Priority Certificate No. 2006129019 of August 10, 2006) in detecting hepatitis B surface antigen (HBsAg) was assessed. The sensitivity of the test was estimated using the federal standards sample HBsAg 42-28-311-06, panels' samples Boston Biomedica Inc. (West Bridgewater, Mass, USA) and ZeptoMetrix Corp. (Buffalo, NY, USA). The findings have indicated that "DS-EIA-HBsAg-0.01" is equally effective in detecting different subtypes of HBsAg during a seroconversion period earlier than alternative assays. Along with its high analytical and diagnostic sensitivity, the system shows a high diagnostic specificity.

Horizontal film balance having wide range and high sensitivity

DOEpatents

Abraham, B.M.; Miyano, K.; Ketterson, J.B.

1981-03-05

A thin-film, horizontal balance instrument is provided for measuring surface tension (surface energy) of thin films suspended on a liquid substrate. The balance includes a support bearing and an optical feedback arrangement for wide-range, high sensitivity measurements. The force on the instrument is balanced by an electromagnet, the current through the magnet providing a measure of the force applied to the instrument. A novel float construction is also disclosed.

Horizontal film balance having wide range and high sensitivity

DOEpatents

Abraham, B.M.; Miyano, K.; Ketterson, J.B.

1983-11-08

A thin-film, horizontal balance instrument is provided for measuring surface tension (surface energy) of thin films suspended on a liquid substrate. The balance includes a support bearing and an optical feedback arrangement for wide-range, high sensitivity measurements. The force on the instrument is balanced by an electromagnet, the current through the magnet providing a measure of the force applied to the instrument. A novel float construction is also disclosed. 5 figs.

Horizontal film balance having wide range and high sensitivity

DOEpatents

Abraham, Bernard M.; Miyano, Kenjiro; Ketterson, John B.

1983-01-01

A thin-film, horizontal balance instrument is provided for measuring surface tension (surface energy) of thin films suspended on a liquid substrate. The balance includes a support bearing and an optical feedback arrangement for wide-range, high sensitivity measurements. The force on the instrument is balanced by an electromagnet, the current through the magnet providing a measure of the force applied to the instrument. A novel float construction is also disclosed.

Higher sensitivity secondary ion mass spectrometry of biological molecules for high resolution, chemically specific imaging.

PubMed

McDonnell, Liam A; Heeren, Ron M A; de Lange, Robert P J; Fletcher, Ian W

2006-09-01

To expand the role of high spatial resolution secondary ion mass spectrometry (SIMS) in biological studies, numerous developments have been reported in recent years for enhancing the molecular ion yield of high mass molecules. These include both surface modification, including matrix-enhanced SIMS and metal-assisted SIMS, and polyatomic primary ions. Using rat brain tissue sections and a bismuth primary ion gun able to produce atomic and polyatomic primary ions, we report here how the sensitivity enhancements provided by these developments are additive. Combined surface modification and polyatomic primary ions provided approximately 15.8 times more signal than using atomic primary ions on the raw sample, whereas surface modification and polyatomic primary ions yield approximately 3.8 and approximately 8.4 times more signal. This higher sensitivity is used to generate chemically specific images of higher mass biomolecules using a single molecular ion peak.

Pleistocene tropical Pacific temperature sensitivity to radiative greenhouse gas forcing

NASA Astrophysics Data System (ADS)

Dyck, K. A.; Ravelo, A. C.

2011-12-01

How high will Earth's global average surface temperature ultimately rise as greenhouse gas concentrations increase in the future? One way to tackle this question is to compare contemporaneous temperature and greenhouse gas concentration data from paleoclimate records, while considering that other radiative forcing mechanisms (e.g. changes in the amount and distribution of incoming solar radiation associated with changes in the Earth's orbital configuration) also contribute to surface temperature change. Since the sensitivity of surface temperature varies with location and latitude, here we choose a central location representative of the west Pacific warm pool, far from upwelling regions or surface temperature gradients in order to minimize climate feedbacks associated with high-latitude regions or oceanic dynamics. The 'steady-state' or long-term temperature change associated with greenhouse gas radiative forcing is often labeled as equilibrium (or 'Earth system') climate sensitivity to the doubling of atmospheric greenhouse gas concentration. Climate models suggest that Earth system sensitivity does not change dramatically over times when CO2 was lower or higher than the modern atmospheric value. Thus, in our investigation of the changes in tropical SST, from the glacial to interglacial states when greenhouse gas forcing nearly doubled, we use Late Pleistocene paleoclimate records to constrain earth system sensitivity for the tropics. Here we use Mg/Ca-paleothermometry using the foraminifera G. ruber from ODP Site 871 from the past 500 kyr in the western Pacific warm pool to estimate tropical Pacific equilibrium climate sensitivity to a doubling of greenhouse gas concentrations to be ~4°C. This tropical SST sensitivity to greenhouse gas forcing is ~1-2°C higher than that predicted by climate models of past glacial periods or future warming for the tropical Pacific. Equatorial Pacific SST sensitivity may be higher than predicted by models for a number of reasons. First, models may not be adequately representing long-term deep ocean feedbacks. Second, models may incorrectly parameterize tropical cloud (or other short-term) feedback processes. Lastly, either paleo-temperature or radiative forcing may have been incorrectly estimated (e.g. through calibration of paleoclimate evidence for temperature change). Since theory suggests that surface temperature in the high latitudes is more sensitive to radiative forcing changes than surface temperature in the tropics, the results of this study also imply that globally averaged Earth system sensitivity to greenhouse gas concentrations may be higher than most climate models predict.

Switchable polarization-sensitive surface plasmon resonance of highly stable gold nanorods liquid crystals composites

NASA Astrophysics Data System (ADS)

Liu, Qingkun; Qian, Jun; Cai, Fuhong; Smalyukh, Ivan I.; He, Sailing

2011-12-01

In this work, we demonstrate the bulk self-alignment of gold nanorods (GNRs) dispersed in lyotropic nematic liquid crystals (LCs) with high optical absorption coefficient at the surface plasmon resonant wavelength. The polymer-coated GNRs which show spontaneous long-range orientational ordering along the director of LC host exhibit long-term stability as well as high concentration. External magnetic field and shearing allow for alignment and realignment of the orientation of gold nanorods by changing the director of the liquid crystal matrix. This results in a switchable polarization-sensitive surface plasmon resonance exhibiting stark differences from that of the same nanorods in isotropic fluids. The devise-scale bulk nanoparticle alignment may enable optical metamaterial mass production and control of surface plasmon resonance of nanoparticles.

Construction of titanium dioxide nanorod/graphite microfiber hybrid electrodes for a high performance electrochemical glucose biosensor

NASA Astrophysics Data System (ADS)

Zhang, Jian; Yu, Xin; Guo, Weibo; Qiu, Jichuan; Mou, Xiaoning; Li, Aixue; Liu, Hong

2016-04-01

The demand for a highly sensitive and selective glucose biosensor which can be used for implantable or on-time monitoring is constantly increasing. In this work, TiO2 nanorods were synthesized in situ on the surface of graphite microfibers to yield TiO2 nanorod/graphite microfiber hybrid electrodes. The TiO2 nanorods not only retain the high activity of the immobilized glucose molecule, but also promote the direct electron transfer process on the electrode surface. As a working electrode in an electrochemical glucose biosensor in a flowing system, the microfiber hybrid electrodes exhibit high sensitivity, selectivity and stability. Due to its simplicity, low cost, high stability, and unique morphology, the TiO2 nanorod/graphite microfiber hybrid electrode is expected to be an excellent candidate for an implantable biosensor or for in situ flow monitoring.The demand for a highly sensitive and selective glucose biosensor which can be used for implantable or on-time monitoring is constantly increasing. In this work, TiO2 nanorods were synthesized in situ on the surface of graphite microfibers to yield TiO2 nanorod/graphite microfiber hybrid electrodes. The TiO2 nanorods not only retain the high activity of the immobilized glucose molecule, but also promote the direct electron transfer process on the electrode surface. As a working electrode in an electrochemical glucose biosensor in a flowing system, the microfiber hybrid electrodes exhibit high sensitivity, selectivity and stability. Due to its simplicity, low cost, high stability, and unique morphology, the TiO2 nanorod/graphite microfiber hybrid electrode is expected to be an excellent candidate for an implantable biosensor or for in situ flow monitoring. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr01360k

Electrical potential-assisted DNA hybridization. How to mitigate electrostatics for surface DNA hybridization.

PubMed

Tymoczko, Jakub; Schuhmann, Wolfgang; Gebala, Magdalena

2014-12-24

Surface-confined DNA hybridization reactions are sensitive to the number and identity of DNA capture probes and experimental conditions such as the nature and the ionic strength of the electrolyte solution. When the surface probe density is high or the concentration of bulk ions is much lower than the concentration of ions within the DNA layer, hybridization is significantly slowed down or does not proceed at all. However, high-density DNA monolayers are attractive for designing high-sensitivity DNA sensors. Thus, circumventing sluggish DNA hybridization on such interfaces allows a high surface concentration of target DNA and improved signal/noise ratio. We present potential-assisted hybridization as a strategy in which an external voltage is applied to the ssDNA-modified interface during the hybridization process. Results show that a significant enhancement of hybridization can be achieved using this approach.

Molecular Machine Powered Surface Programmatic Chain Reaction for Highly Sensitive Electrochemical Detection of Protein.

PubMed

Zhu, Jing; Gan, Haiying; Wu, Jie; Ju, Huangxian

2018-04-17

A bipedal molecular machine powered surface programmatic chain reaction was designed for electrochemical signal amplification and highly sensitive electrochemical detection of protein. The bipedal molecular machine was built through aptamer-target specific recognition for the binding of one target protein with two DNA probes, which hybridized with surface-tethered hairpin DNA 1 (H1) via proximity effect to expose the prelocked toehold domain of H1 for the hybridization of ferrocene-labeled hairpin DNA 2 (H2-Fc). The toehold-mediated strand displacement reaction brought the electrochemical signal molecule Fc close to the electrode and meanwhile released the bipedal molecular machine to traverse the sensing surface by the surface programmatic chain reaction. Eventually, a large number of duplex structures of H1-H2 with ferrocene groups facing to the electrode were formed on the sensor surface to generate an amplified electrochemical signal. Using thrombin as a model target, this method showed a linear detection range from 2 pM to 20 nM with a detection limit of 0.76 pM. The proposed detection strategy was enzyme-free and allowed highly sensitive and selective detection of a variety of protein targets by using corresponding DNA-based affinity probes, showing potential application in bioanalysis.

Periodic silver nanocluster arrays over large-area silica nanosphere template as highly sensitive SERS substrate

NASA Astrophysics Data System (ADS)

Hou, Xu; Wang, Qi; Mao, Guoming; Liu, Hao; Yu, Rongdi; Ren, Xiaomin

2018-04-01

Periodic Ag nanocluster arrays for surface enhanced Raman spectroscopy (SERS) were fabricated through magnetron sputtering Ag over a large-area monolayer template which is based on silica (SiO2) nanospheres. High-density nanogaps between the adjacent Ag nanoclusters acted as "hot-spots", making a dominant contribution to the high-performance SERS detection. Moreover, the nanospheres and Ag nanoclusters effectively increased the surface roughness and also enlarged the surface area of as-obtained SERS substrate, which resulted in a further enhancement in Raman signals. As-prepared SERS substrates showed very high sensitivity with the enhancement factor (EF) value of 4.1 × 1012 for Rhodamine 6G (R6G), allowing the corresponding detection limit as low as 10-16 M. Additionally, SERS signal of melamine was still strong even though its concentration was lowered to 10-7 M. Our results show that preparing highly sensitive SERS substrate with periodic Ag nanoclusters over SiO2 nanosphere template is a convenient and promising pathway for chemical and biologic sensing.

uleSIMS characterization of silver reference surfaces

NASA Astrophysics Data System (ADS)

Palitsin, V. V.; Dowsett, M. G.; Mata, B. Guzmán de la; Oloff, I. W.; Gibbons, R.

2006-07-01

Ultra low energy SIMS (uleSIMS) is a high sensitivity analytical technique that is normally used for ultra shallow profiling at a depth resolution of up to1 nm. This work describes the use of uleSIMS as both a spectroscopic and depth-profiling tool for the characterization of the early stages of corrosion formed on reference surfaces of silver. These samples are being developed to help with the characterization of tarnished surfaces in a cultural heritage context, and uleSIMS enables the tarnishing to be studied from its very earliest stages due to its high sensitivity (ppm-ppb) and surface specificity. We show that, uleSIMS can be used effectively to study the surface chemistry and aid the development of reference surfaces themselves. In particular, handling contaminants, surface dust, and residues from polishing are relatively easy to identify allowing them to be separated from the parts of the mass spectrum specific to the early stages of corrosion.

Porous silicon ring resonator for compact, high sensitivity biosensing applications

DOE PAGES

Rodriguez, Gilberto A.; Hu, Shuren; Weiss, Sharon M.

2015-01-01

A ring resonator is patterned on a porous silicon slab waveguide to produce a compact, high quality factor biosensor with a large internal surface area available for enhanced recognition of biological and chemical molecules. The porous nature of the ring resonator allows molecules to directly interact with the guided mode. Quality factors near 10,000 were measured for porous silicon ring resonators with a radius of 25 μm. A bulk detection sensitivity of 380 nm/RIU was measured upon exposure to salt water solutions. Specific detection of nucleic acid molecules was demonstrated with a surface detection sensitivity of 4 pm/nM.

Solution Process Synthesis of High Aspect Ratio ZnO Nanorods on Electrode Surface for Sensitive Electrochemical Detection of Uric Acid

NASA Astrophysics Data System (ADS)

Ahmad, Rafiq; Tripathy, Nirmalya; Ahn, Min-Sang; Hahn, Yoon-Bong

2017-04-01

This study demonstrates a highly stable, selective and sensitive uric acid (UA) biosensor based on high aspect ratio zinc oxide nanorods (ZNRs) vertical grown on electrode surface via a simple one-step low temperature solution route. Uricase enzyme was immobilized on the ZNRs followed by Nafion covering to fabricate UA sensing electrodes (Nafion/Uricase-ZNRs/Ag). The fabricated electrodes showed enhanced performance with attractive analytical response, such as a high sensitivity of 239.67 μA cm-2 mM-1 in wide-linear range (0.01-4.56 mM), rapid response time (~3 s), low detection limit (5 nM), and low value of apparent Michaelis-Menten constant (Kmapp, 0.025 mM). In addition, selectivity, reproducibility and long-term storage stability of biosensor was also demonstrated. These results can be attributed to the high aspect ratio of vertically grown ZNRs which provides high surface area leading to enhanced enzyme immobilization, high electrocatalytic activity, and direct electron transfer during electrochemical detection of UA. We expect that this biosensor platform will be advantageous to fabricate ultrasensitive, robust, low-cost sensing device for numerous analyte detection.

A pM leveled photoelectrochemical sensor for microcystin-LR based on surface molecularly imprinted TiO2@CNTs nanostructure.

PubMed

Liu, Meichuan; Ding, Xue; Yang, Qiwei; Wang, Yu; Zhao, Guohua; Yang, Nianjun

2017-06-05

A simple and highly sensitive photoelectrochemical (PEC) sensor towards Microcystin-LR (MC-LR), a kind of typical cyanobacterial toxin in water samples, was developed on a surface molecular imprinted TiO 2 coated multiwalled carbon nanotubes (MI-TiO 2 @CNTs) hybrid nanostructure. It was synthesized using a feasible two-step sol-gel method combining with in situ surface molecular imprinting technique (MIT). With a controllable core-shell tube casing structure, the resultant MI-TiO 2 @CNTs are enhanced greatly in visible-light driven response capacity. In comparison with the traditional TiO 2 (P25) and non-imprinted (NI-)TiO 2 @CNTs, the MI-TiO 2 @CNTs based PEC sensor showed a much higher photoelectric oxidation capacity towards MC-LR. Using this sensor, the determination of MC-LR was doable in a wide linear range from 1.0pM to 3.0nM with a high photocurrent response sensitivity. An outstanding selectivity towards MC-LR was further achieved with this sensor, proven by simultaneously monitoring 100-fold potential co-existing interferences. The superiority of the obtained MC-LR sensor in sensitivity and selectivity is mainly attributed to the high specific surface area and excellent photoelectric activity of TiO 2 @CNTs heterojunction structure, as well as the abundant active recognition sites on its functionalized molecular imprinting surface. A promising PEC analysis platform with high sensitivity and selectivity for MC-LR has thus been provided. Copyright © 2017 Elsevier B.V. All rights reserved.

Role of the Soil Thermal Inertia in the short term variability of the surface temperature and consequences for the soil-moisture temperature feedback

NASA Astrophysics Data System (ADS)

Cheruy, Frederique; Dufresne, Jean-Louis; Ait Mesbah, Sonia; Grandpeix, Jean-Yves; Wang, Fuxing

2017-04-01

A simple model based on the surface energy budget at equilibrium is developed to compute the sensitivity of the climatological mean daily temperature and diurnal amplitude to the soil thermal inertia. It gives a conceptual framework to quantity the role of the atmospheric and land surface processes in the surface temperature variability and relies on the diurnal amplitude of the net surface radiation, the sensitivity of the turbulent fluxes to the surface temperature and the thermal inertia. The performances of the model are first evaluated with 3D numerical simulations performed with the atmospheric (LMDZ) and land surface (ORCHIDEE) modules of the Institut Pierre Simon Laplace (IPSL) climate model. A nudging approach is adopted, it prevents from using time-consuming long-term simulations required to account for the natural variability of the climate and allow to draw conclusion based on short-term (several years) simulations. In the moist regions the diurnal amplitude and the mean surface temperature are controlled by the latent heat flux. In the dry areas, the relevant role of the stability of the boundary layer and of the soil thermal inertia is demonstrated. In these regions, the sensitivity of the surface temperature to the thermal inertia is high, due to the high contribution of the thermal flux to the energy budget. At high latitudes, when the sensitivity of turbulent fluxes is dominated by the day-time sensitivity of the sensible heat flux to the surface temperature and when this later is comparable to the thermal inertia term of the sensitivity equation, the surface temperature is also partially controlled by the thermal inertia which can rely on the snow properties; In the regions where the latent heat flux exhibits a high day-to-day variability, such as transition regions, the thermal inertia has also significant impact on the surface temperature variability . In these not too wet (energy limited) and not too dry (moisture-limited) soil moisture (SM) ''hot spots'', it is generally admitted that the variability of the surface temperature is explained by the soil moisture trough its control on the evaporation. This work suggests that the impact of the soil moisture on the temperature through its impact on the thermal inertia can be as important as its direct impact on the evaporation. Contrarily to the evaporation related soil-moisture temperature negative feedback, the thermal inertia soil-moisture related feedback newly identified by this work is a positive feedback which limits the cooling when the soil moisture increases. These results suggest that uncertainties in the representation of the soil and snow thermal properties can be responsible of significant biases in numerical simulations and emphasize the need to carefully document and evaluate these quantities in the Land Surface Modules implemented in the climate models.

Dual signal amplification of surface plasmon resonance imaging for sensitive immunoassay of tumor marker.

PubMed

Hu, Weihua; Chen, Hongming; Shi, Zhuanzhuan; Yu, Ling

2014-05-15

Surface plasmon resonance imaging (SPRi) is an intriguing technique for immunoassay with the inherent advantages of being high throughput, real time, and label free, but its sensitivity needs essential improvement for practical applications. Here, we report a dual signal amplification strategy using functional gold nanoparticles (AuNPs) followed by on-chip atom transfer radical polymerization (ATRP) for sensitive SPRi immunoassay of tumor biomarker in human serum. The AuNPs are grafted with an initiator of ATRP as well as a recognition antibody, where the antibody directs the specific binding of functional AuNPs onto the SPRi sensing surface to form immunocomplexes for first signal amplification and the initiator allows for on-chip ATRP of 2-hydroxyethyl methacrylate (HEMA) from the AuNPs to further enhance the SPRi signal. High sensitivity and broad dynamic range are achieved with this dual signal amplification strategy for detection of a model tumor marker, α-fetoprotein (AFP), in 10% human serum. Copyright © 2014 Elsevier Inc. All rights reserved.

Easy-to-Fabricate and High-Sensitivity LSPR Type Specific Protein Detection Sensor Using AAO Nano-Pore Size Control

PubMed Central

Kim, Sae-Wan; Lee, Jae-Sung; Lee, Sang-Won; Kang, Byoung-Ho; Kwon, Jin-Beom; Kim, Ok-Sik; Kim, Ju-Seong; Kim, Eung-Soo; Kwon, Dae-Hyuk; Kang, Shin-Won

2017-01-01

In this study, we developed a pore size/pore area-controlled optical biosensor-based anodic aluminum oxide (AAO) nanostructure. As the pore size of AAO increases, the unit cell of AAO increases, which also increases the non-pore area to which the antibody binds. The increase in the number of antibodies immobilized on the surface of the AAO enables effective detection of trace amounts of antigen, because increased antigen-antibody bonding results in a larger surface refractive index change. High sensitivity was thus achieved through amplification of the interference wave of two vertically-incident reflected waves through the localized surface plasmon resonance phenomenon. The sensitivity of the fabricated sensor was evaluated by measuring the change in wavelength with the change in the refractive index of the device surface, and sensitivity was increased with increasing pore-size and non-pore area. The sensitivity of the fabricated sensor was improved and up to 11.8 ag/mL serum amyloid A1 antigen was detected. In addition, the selectivity of the fabricated sensor was confirmed through a reaction with a heterogeneous substance, C-reactive protein antigen. By using hard anodization during fabrication of the AAO, the fabrication time of the device was reduced and the AAO chip was fabricated quickly and easily. PMID:28406469

U-bent plastic optical fiber based plasmonic biosensor for nucleic acid detection

NASA Astrophysics Data System (ADS)

Gowri, A.; Sai, V. V. R.

2017-05-01

This study presents the development of low cost, rapid and highly sensitive plasmonic sandwich DNA biosensor using U-bent plastic optical fiber (POF) probes with high evanescent wave absorbance sensitivity and gold nanoparticles (AuNP) as labels. Plastic optical fiber (PMMA core and fluorinated polymer as cladding) offer ease in machinability and handling due to which optimum U-bent geometry (with fiber and bend diameter of 0.5 and 1.5 mm respectively) for high sensitivity could be achieved. A sensitive fiber optic DNA biosensor is realized by (i) modifying the PMMA surface using ethylenediamine (EDA) in order to maximize the immobilization of capture oligonucleotides (ONs) and (ii) conjugating probe ONs to AuNP labels of optimum size ( 35 nm) with high extinction coefficient and optimal ON surface density. The sandwich hybridization assay on U-bent POF probes results in increase in optical absorbance through the probe with increase in target ON concentration due to the presence of increased number of AuNPs. The absorbance of light passing through the U-bent probe due to the presence of AuNP labels on its surface as result of sandwich DNA hybridization is measured using a halogen lamp and a fiber optic spectrometer. A picomolar limit of detection of target ON (0.2 pM or 1 pg/ml or 5 attomol in 25 μL) is achieved with this biosensing scheme, indicating its potential for the development of a highly sensitive DNA biosensor.

Temperature dependence of low-energy positron-induced Auger-electron emission: Evidence for high surface sensitivity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mayer, R.; Schwab, A.; Weiss, A.

1990-08-01

We report the experimental observation of the temperature dependence of the intensity of low-energy positron-annihilation-induced Auger-electron emission spectroscopy (PAES) from Cu(100). These studies show that the mechanism for stimulating Auger electrons is found to compete with positronium (Ps) emission from a surface. The positrons that induce Auger-electron emission therefore originate from the same surface state from which Ps is thermally desorbed. Hence, PAES should have higher surface sensitivity ({approximately}1 A) relative to conventional methods for generating Auger-electron emission from surfaces ({approximately}5--10 A).

Momentum density and Fermi surface of Nd2-xCexCuO4-δ

NASA Astrophysics Data System (ADS)

Shukla, A.; Barbiellini, B.; Hoffmann, L.; Manuel, A. A.; Sadowski, W.; Walker, E.; Peter, M.

1996-02-01

High-temperature positron two-dimensional angular correlation of annihilation radiation (2D-ACAR) measurements have recently been succesfully applied to map parts of the Fermi surface of YBa2Cu3O7-δ. Using the same principle, we have been able to observe with a bulk sensitive method, the Fermi surface of Nd2-xCexCuO4-δ. Although positron trapping by defects and correlation effects are strong, positron 2D-ACAR measurements provide a signal from the Fermi surface which agrees with band-structure calculations, confirming earlier surface sensitive photoemission experiments.

A high-sensitivity fiber-optic evanescent wave sensor with a three-layer structure composed of Canada balsam doped with GeO2.

PubMed

Zhong, Nianbing; Zhao, Mingfu; Zhong, Lianchao; Liao, Qiang; Zhu, Xun; Luo, Binbin; Li, Yishan

2016-11-15

In this paper, we present a high-sensitivity polymer fiber-optic evanescent wave (FOEW) sensor with a three-layer structure that includes bottom, inter-, and surface layers in the sensing region. The bottom layer and inter-layer are POFs composed of standard cladding and the core of the plastic optical fiber, and the surface layer is made of dilute Canada balsam in xylene doped with GeO2. We examine the morphology of the doped GeO2, the refractive index and composition of the surface layer and the surface luminous properties of the sensing region. We investigate the effects of the content and morphology of the GeO2 particles on the sensitivity of the FOEW sensors by using glucose solutions. In addition, we examine the response of sensors incubated with staphylococcal protein A plus mouse IgG isotype to goat anti-mouse IgG solutions. Results indicate very good sensitivity of the three-layer FOEW sensor, which showed a 3.91-fold improvement in the detection of the target antibody relative to a conventional sensor with a core-cladding structure, and the novel sensor showed a lower limit of detection of 0.2ng/l and a response time around 320s. The application of this high-sensitivity FOEW sensor can be extended to biodefense, disease diagnosis, biomedical and biochemical analysis. Copyright © 2016 Elsevier B.V. All rights reserved.

Heterodyne lock-in thermography of early demineralized in dental tissues

NASA Astrophysics Data System (ADS)

Wang, Fei; Liu, Jun-yan; Mohummad, Oliullah; Wang, Xiao-chun; Wang, Yang

2017-12-01

Heterodyne lock-in thermography (HeLIT) is a highly sensitive method to detect early demineralized in dental tissues, which is based on nonlinear photothermal phenomena of dental tissues. In this paper, the nonlinear photothermal phenomena of dental tissues was introduced, and then the system of HeLIT was developed. The relationship between laser modulated parameters (modulated frequency and laser intensity) and heterodyne lock-in thermal wave signal was investigated. The comparison between HeLIT and homodyne lock-in thermography (HoLIT) for detecting the different types of dental caries (smooth surface caries, proximal surface caries and occlusal surface caries) were carried out. Experimental results illustrate that the HeLIT has the merits of high sensitivity and high specificity in detecting different types of early caries.

A New Kind of Laser Microphone Using High Sensitivity Pulsed Laser Vibrometer

NASA Technical Reports Server (NTRS)

Wang, Chen-Chia; Trivedi, Sudhir; Jin, Feng; Swaminathan, V.; Prasad, Narasimha S.

2008-01-01

We demonstrate experimentally a new kind of laser microphone using a highly sensitive pulsed laser vibrometer. By using the photo-electromotive-force (photo-EMF) sensors, we present data indicating the real-time detection of surface displacements as small as 4 pm.

Optical pumping and xenon NMR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Raftery, M. Daniel

1991-11-01

Nuclear Magnetic Resonance (NMR) spectroscopy of xenon has become an important tool for investigating a wide variety of materials, especially those with high surface area. The sensitivity of its chemical shift to environment, and its chemical inertness and adsorption properties make xenon a particularly useful NMR probe. This work discusses the application of optical pumping to enhance the sensitivity of xenon NMR experiments, thereby allowing them to be used in the study of systems with lower surface area. A novel method of optically-pumping 129Xe in low magnetic field below an NMR spectrometer and subsequent transfer of the gas to highmore » magnetic field is described. NMR studies of the highly polarized gas adsorbed onto powdered samples with low to moderate surface areas are now possible. For instance, NMR studies of optically-pumped xenon adsorbed onto polyacrylic acid show that xenon has a large interaction with the surface. By modeling the low temperature data in terms of a sticking probability and the gas phase xenon-xenon interaction, the diffusion coefficient for xenon at the surface of the polymer is determined. The sensitivity enhancement afforded by optical pumping also allows the NMR observation of xenon thin films frozen onto the inner surfaces of different sample cells. The geometry of the thin films results in interesting line shapes that are due to the bulk magnetic susceptibility of xenon. Experiments are also described that combine optical pumping with optical detection for high sensitivity in low magnetic field to observe the quadrupoler evolution of 131 Xe spins at the surface of the pumping cells. In cells with macroscopic asymmetry, a residual quadrupolar interaction causes a splitting in the 131Xe NMR frequencies in bare Pyrex glass cells and cells with added hydrogen.« less

Studies of metal ion binding by apo-metallothioneins attached onto preformed self-assembled monolayers using a highly sensitive surface plasmon resonance spectrometer

PubMed Central

Zhang, Yintang; Xu, Maotian; Wang, Yanju; Toledo, Freddy; Zhou, Feimeng

2007-01-01

The use of a flow-injection surface plasmon resonance (FI-SPR) spectrometer equipped with a bicell detector or a position-sensitive device for determining coordination of heavy metal ions (Cd2+ and Hg2+) by surface-confined apo-metallothionein (apo-MT) molecules is described. To facilitate the formation of a compact MT adsorbate layer with a uniform surface orientation, MT molecules were attached onto a preformed alkanethiol self-assembled monolayer. The method resorts to the generation of apo-MT at the surface by treating the MT-covered sensor chip with glycine–HCl and the measurement of the apo-MT conformation changes upon metal ion incorporation. Domain-specific metal ion binding processes by the apo-MT molecules were observed. Competitive replacement of one metal ion by another can be monitored in real time by FI-SPR. The tandem use of an immobilization scheme for forming a sub-monolayer of MT molecules at the sensor surface and the highly sensitive FI-SPR instrument affords a low concentration detection level. The detection level for Cd2+ (0.1 μM or 15 ppb) compares favorably with similar studies and the methodology complements to other well-established sensitive analytical techniques. The extent of metal incorporation by apo-MT molecules was also determined. PMID:18493298

Nanophotonics of biomaterials and inorganic nanostructures

NASA Astrophysics Data System (ADS)

Petrik, P.; Agocs, E.; Kalas, B.; Fodor, B.; Lohner, T.; Nador, J.; Saftics, A.; Kurunczi, S.; Novotny, T.; Perez-Feró, E.; Nagy, R.; Hamori, A.; Horvath, R.; Hózer, Z.; Fried, M.

2017-01-01

Optical methods have been used for the sensitive characterization of surfaces and thin films for more than a century. The first ellipsometric measurement was conducted on metal surfaces by Paul Drude in 1889. The word ‘ellipsometer’ was first used by Rothen in a study of antigen-antibody interactions on polished metal surfaces in 1945. The ‘bible’ of ellipsometry has been published in the second half of the ‘70s. The publications in the topic of ellipsometry started to increase rapidly by the end of the ‘80s, together with concepts like surface plasmon resonance, later new topics like photonic crystals emerged. These techniques find applications in many fields, including sensorics or photovoltaics. In optical sensorics, the highest sensitivities were achieved by waveguide interferometry and plasmon resonance configurations. The instrumentation of ellipsometry is also being developed intensively towards higher sensitivity and performance by combinations with plasmonics, scatterometry, imaging or waveguide methods, utilizing the high sensitivity, high speed, non-destructive nature and mapping capabilities. Not only the instrumentation but also the methods of evaluation show a significant development, which leads to the characterization of structures with increasing complexity, including photonic, porous or metal surfaces. This article discusses a selection of interesting applications of photonics in the Centre for Energy Research of the Hungarian Academy of Sciences.

A Novel SPM Probe with MOS Transistor and Nano Tip for Surface Electric Properties

NASA Astrophysics Data System (ADS)

Lee, Sang H.; Lim, Geunbae; Moon, Wonkyu

2007-03-01

In this paper, the novel SPM (Scanning Probe Microscope) probe with the planar MOS (Metal-Oxide-Semiconductor) transistor and the FIB (Focused Ion Beam) nano tip is fabricated for the surface electric properties. Since the MOS transistor has high working frequency, the device can overcome the speed limitation of EFM (Electrostatic Force Microscope) system. The sensitivity is also high, and no bulky device such as lock-in-amplifier is required. Moreover, the nano tip with nanometer scale tip radius is fabricated with FIB system, and the resolution can be improved. Therefore, the probe can rapidly detect small localized electric properties with high sensitivity and high resolution. The MOS transistor is fabricated with the common semiconductor process, and the nano tip is grown by the FIB system. The planar structure of the MOS transistor makes the fabrication process easier, which is the advantage on the commercial production. Various electric signals are applied using the function generator, and the measured data represent the well-established electric properties of the device. It shows the promising aspect of the local surface electric property detection with high sensitivity and high resolution.

Development of high-sensitive, reproducible colloidal surface-enhanced Raman spectroscopy active substrate using silver nanocubes for potential biosensing applications

NASA Astrophysics Data System (ADS)

Hasna, Kudilatt; Lakshmi, Kiran; Ezhuthachan Jayaraj, Madambi Kunjukuttan; Kumar, Kumaran Rajeev; Matham, Murukeshan Vadakke

2016-04-01

Surface-enhanced Raman spectroscopy (SERS) has emerged as one of the thrust research areas that could find potential applications in bio and chemical sensing. We developed colloidal SERS active substrate with excellent sensitivity and high reproducibility using silver nanocube (AgNC) synthesized via the solvothermal method. Finite-difference time-domain simulation was carried out in detail to visualize dipole generation in the nanocube during localized surface plasmon resonance and to locate the respective hot spots in AgNC responsible for the huge Raman enhancement. The prediction is verified by the SERS analysis of the synthesized nanocubes using Rhodamine 6G molecule. An excellent sensitivity with a detection limit of 10-17 M and a very high enhancement factor of 1.2×108 confirms the "hot spots" in the nanocube. SERS activity is also carried out for crystal violet and for food adulterant Sudan I molecule. Finally, label-free DNA detection is performed to demonstrate the versatility of SERS as a potential biosensor.

Automated assessment of the remineralization of artificial enamel lesions with polarization-sensitive optical coherence tomography

PubMed Central

Lee, Robert C.; Kang, Hobin; Darling, Cynthia L.; Fried, Daniel

2014-01-01

Accurate measurement of the highly mineralized transparent surface layer that forms on caries lesions is important for diagnosis of the lesion activity because chemical intervention can slow or reverse the caries process via remineralization. Previous in-vitro and in-vivo studies have demonstrated that polarization-sensitive optical coherence tomography (PS-OCT) can nondestructively image the subsurface lesion structure and the highly mineralized transparent surface zone of caries lesions. The purpose of this study was to develop an approach to automatically process 3-dimensional PS-OCT images and to accurately assess the remineralization process in simulated enamel lesions. Artificial enamel lesions were prepared on twenty bovine enamel blocks using two models to produce varying degree of demineralization and remineralization. The thickness of the transparent surface layer and the integrated reflectivity of the subsurface lesion were measured using PS-OCT. The automated transparent surface layer detection algorithm was able to successfully detect the transparent surface layers with high sensitivity ( = 0.92) and high specificity ( = 0.97). The estimated thickness of the transparent surface layer showed a strong correlation with polarized light microscopy (PLM) measurements of all regions (R2 = 0.90). The integrated reflectivity, ΔR, and the integrated mineral loss, ΔZ, showed a moderate correlation (R2 = 0.32). This study demonstrates that PS-OCT can automatically measure the changes in artificial enamel lesion structure and severity upon exposure to remineralization solutions. PMID:25401009

Label-free peptide aptamer based impedimetric biosensor for highly sensitive detection of TNT with a ternary assembly layer.

PubMed

Li, Yanyan; Zhao, Manru; Wang, Haiyan

2017-11-01

We report a label-free peptide aptamer based biosensor for highly sensitive detection of TNT which was designed with a ternary assembly layer consisting of anti-TNT peptide aptamer (peptamer), dithiothreitol (DTT), and 6-mercaptohexanol (MCH), forming Au/peptamer-DTT/MCH. A linear relationship between the change in electron transfer resistance and the logarithm of the TNT concentration from 0.44 to 18.92 pM, with a detection limit of 0.15 pM, was obtained. In comparison, the detection limit of the aptasensor with a common binary assembly layer (Au/peptamer/MCH) was 0.15 nM. The remarkable improvement in the detection limit could be ascribed to the crucial role of the ternary assembly layer, providing an OH-richer hydrophilic environment and a highly compact surface layer with minimal surface defects, reducing the non-covalent binding (physisorption) of the peptamer and non-specific adsorption of TNT onto the electrode surface, leading to high sensitivity, and which can serve as a general sensing platform for the fabrication of other biosensors.

Highly sensitive hydrogen detection of catalyst-free ZnO nanorod networks suspended by lithography-assisted growth.

PubMed

Huh, Junghwan; Park, Jonghyurk; Kim, Gyu Tae; Park, Jeong Young

2011-02-25

We have successfully demonstrated a ZnO nanorod-based 3D nanostructure to show a high sensitivity and very fast response/recovery to hydrogen gas. ZnO nanorods have been synthesized selectively over the pre-defined area at relatively low temperature using a simple self-catalytic solution process assisted by a lithographic method. The conductance of the ZnO nanorod device varies significantly as the concentration of the hydrogen is changed without any additive metal catalyst, revealing a high sensitivity to hydrogen gas. Its superior performance can be explained by the porous structure of its three-dimensional network and the enhanced surface reaction of the hydrogen molecules with the oxygen defects resulting from a high surface-to-volume ratio. It was found that the change of conductance follows a power law depending on the hydrogen concentration. A Langmuir isotherm following an ideal power law and a cross-over behavior of the activation energy with respect to hydrogen concentration were observed. This is a very novel and intriguing phenomenon on nanostructured materials, which suggests competitive surface reactions in ZnO nanorod gas sensors.

Hybridization chain reaction amplification for highly sensitive fluorescence detection of DNA with dextran coated microarrays.

PubMed

Chao, Jie; Li, Zhenhua; Li, Jing; Peng, Hongzhen; Su, Shao; Li, Qian; Zhu, Changfeng; Zuo, Xiaolei; Song, Shiping; Wang, Lianhui; Wang, Lihua

2016-07-15

Microarrays of biomolecules hold great promise in the fields of genomics, proteomics, and clinical assays on account of their remarkably parallel and high-throughput assay capability. However, the fluorescence detection used in most conventional DNA microarrays is still limited by sensitivity. In this study, we have demonstrated a novel universal and highly sensitive platform for fluorescent detection of sequence specific DNA at the femtomolar level by combining dextran-coated microarrays with hybridization chain reaction (HCR) signal amplification. Three-dimensional dextran matrix was covalently coated on glass surface as the scaffold to immobilize DNA recognition probes to increase the surface binding capacity and accessibility. DNA nanowire tentacles were formed on the matrix surface for efficient signal amplification by capturing multiple fluorescent molecules in a highly ordered way. By quantifying microscopic fluorescent signals, the synergetic effects of dextran and HCR greatly improved sensitivity of DNA microarrays, with a detection limit of 10fM (1×10(5) molecules). This detection assay could recognize one-base mismatch with fluorescence signals dropped down to ~20%. This cost-effective microarray platform also worked well with samples in serum and thus shows great potential for clinical diagnosis. Copyright © 2016 Elsevier B.V. All rights reserved.

Rapid, sensitive and direct analysis of exopolysaccharides from biofilm on aluminum surfaces exposed to sea water using MALDI-TOF MS.

PubMed

Hasan, Nazim; Gopal, Judy; Wu, Hui-Fen

2011-11-01

Biofilm studies have extensive significance since their results can provide insights into the behavior of bacteria on material surfaces when exposed to natural water. This is the first attempt of using matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS) for detecting the polysaccharides formed in a complex biofilm consisting of a mixed consortium of marine microbes. MALDI-MS has been applied to directly analyze exopolysaccharides (EPS) in the biofilm formed on aluminum surfaces exposed to seawater. The optimal conditions for MALDI-MS applied to EPS analysis of biofilm have been described. In addition, microbiologically influenced corrosion of aluminum exposed to sea water by a marine fungus was also observed and the fungus identity established using MALDI-MS analysis of EPS. Rapid, sensitive and direct MALDI-MS analysis on biofilm would dramatically speed up and provide new insights into biofilm studies due to its excellent advantages such as simplicity, high sensitivity, high selectivity and high speed. This study introduces a novel, fast, sensitive and selective platform for biofilm study from natural water without the need of tedious culturing steps or complicated sample pretreatment procedures. Copyright © 2011 John Wiley & Sons, Ltd.

High Sensitivity and High Detection Specificity of Gold-Nanoparticle-Grafted Nanostructured Silicon Mass Spectrometry for Glucose Analysis.

PubMed

Tsao, Chia-Wen; Yang, Zhi-Jie

2015-10-14

Desorption/ionization on silicon (DIOS) is a high-performance matrix-free mass spectrometry (MS) analysis method that involves using silicon nanostructures as a matrix for MS desorption/ionization. In this study, gold nanoparticles grafted onto a nanostructured silicon (AuNPs-nSi) surface were demonstrated as a DIOS-MS analysis approach with high sensitivity and high detection specificity for glucose detection. A glucose sample deposited on the AuNPs-nSi surface was directly catalyzed to negatively charged gluconic acid molecules on a single AuNPs-nSi chip for MS analysis. The AuNPs-nSi surface was fabricated using two electroless deposition steps and one electroless etching step. The effects of the electroless fabrication parameters on the glucose detection efficiency were evaluated. Practical application of AuNPs-nSi MS glucose analysis in urine samples was also demonstrated in this study.

Bloch surface wave structures for high sensitivity detection and compact waveguiding

NASA Astrophysics Data System (ADS)

Khan, Muhammad Umar; Corbett, Brian

2016-01-01

Resonant propagating waves created on the surface of a dielectric multilayer stack, called Bloch surface waves (BSW), can be designed for high sensitivity monitoring of the adjacent refractive index as an alternative platform to the metal-based surface plasmon resonance (SPR) sensing. The resonant wavelength and polarization can be designed by engineering of the dielectric layers unlike the fixed resonance of SPR, while the wide bandwidth low loss of dielectrics permits sharper resonances, longer propagation lengths and thus their use in waveguiding devices. The transparency of the dielectrics allows the excitation and monitoring of surface-bound fluorescent molecules. We review the recent developments in this technology. We show the advantages that can be obtained by using high index contrast layered structures. Operating at 1550 nm wavelengths will allow the BSW sensors to be implemented in the silicon photonics platform where active waveguiding can be used in the realization of compact planar integrated circuits for multi-parameter sensing.

Highly sensitive surface enhanced Raman scattering substrates based on Ag decorated Si nanocone arrays and their application in trace dimethyl phthalate detection

NASA Astrophysics Data System (ADS)

Zuo, Zewen; Zhu, Kai; Ning, Lixin; Cui, Guanglei; Qu, Jun; Cheng, Ying; Wang, Junzhuan; Shi, Yi; Xu, Dongsheng; Xin, Yu

2015-01-01

Wafer-scale three-dimensional (3D) surface enhancement Raman scattering (SERS) substrates were prepared using the plasma etching and ion sputtering methods that are completely compatible with well-established silicon device technologies. The substrates are highly sensitive with excellent uniformity and reproducibility, exhibiting an enhancement factor up to 1012 with a very low relative standard deviation (RSD) around 5%. These are attributed mainly to the uniform-distributed, multiple-type high-density hot spots originating from the structural characteristics of Ag nanoparticles (NPs) decorated Si nanocone (NC) arrays. We demonstrate that the trace dimethyl phthalate (DMP) at a concentration of 10-7 M can be well detected using this SERS substrate, showing that the AgNPs-decorated SiNC arrays can serve as efficient SERS substrates for phthalate acid esters (PAEs) detection with high sensitivity.

Sugar nanowires based on cyclodextrin on quartz crystal microbalance for gas sensing with ultra-high sensitivity

NASA Astrophysics Data System (ADS)

Asano, Atsushi; Maeyoshi, Yuta; Watanabe, Shogo; Saeki, Akinori; Sugimoto, Masaki; Yoshikawa, Masahito; Nanto, Hidehito; Tsukuda, Satoshi; Tanaka, Shun-Ichiro; Seki, Shu

2013-03-01

Cyclodextrins (CDs), hosting selectively a wide range of guest molecules in their hydrophobic cavity, were directly fabricated into 1-dimensional nanostructures with extremely wide surface area by single particle nanofabrication technique in the present paper. The copolymers of acrylamide and mono(6-allyl)-β-CD were synthesized, and the crosslinking reaction of the polymer alloys with poly(4-bromostyrene) (PBrS) in SPNT gave nanowires on the quarts substrate with high number density of 5×109 cm-2. Quartz crystal microbalance (QCM) measurement suggested 320 fold high sensitivity for formic acid vapor adsorption in the nanowire fabricated surfaces compared with that in the thin solid film of PBrS, due to the incorporation of CD units and extremely wide surface area of the nanowires.

High-contrast grating resonators for label-free detection of disease biomarkers

PubMed Central

Sun, Tianbo; Kan, Shu; Marriott, Gerard; Chang-Hasnain, Connie

2016-01-01

A label-free optical biosensor is described that employs a silicon-based high-contrast grating (HCG) resonator with a spectral linewidth of ~500 pm that is sensitive to ligand-induced changes in surface properties. The device is used to generate thermodynamic and kinetic data on surface-attached antibodies with their respective antigens. The device can detect serum cardiac troponin I, a biomarker of cardiac disease to 100 pg/ml within 4 mins, which is faster, and as sensitive as current enzyme-linked immuno-assays for cTnI. PMID:27265624

High-contrast grating resonators for label-free detection of disease biomarkers

NASA Astrophysics Data System (ADS)

Sun, Tianbo; Kan, Shu; Marriott, Gerard; Chang-Hasnain, Connie

2016-06-01

A label-free optical biosensor is described that employs a silicon-based high-contrast grating (HCG) resonator with a spectral linewidth of ~500 pm that is sensitive to ligand-induced changes in surface properties. The device is used to generate thermodynamic and kinetic data on surface-attached antibodies with their respective antigens. The device can detect serum cardiac troponin I, a biomarker of cardiac disease to 100 pg/ml within 4 mins, which is faster, and as sensitive as current enzyme-linked immuno-assays for cTnI.

Stable Fe nanomagnets encapsulated inside vertically-aligned carbon nanotubes.

PubMed

Bondino, Federica; Magnano, Elena; Ciancio, Regina; Castellarin Cudia, Carla; Barla, Alessandro; Carlino, Elvio; Yakhou-Harris, Flora; Rupesinghe, Nalin; Cepek, Cinzia

2017-12-06

Well-defined sized (5-10 nm) metallic iron nanoparticles (NPs) with body-centered cubic structure encapsulated inside the tip of millimeter-long vertically aligned carbon nanotubes (VACNTs) of uniform length have been investigated with high-resolution transmission electron microscopy and soft X-ray spectroscopy techniques. Surface-sensitive and chemically-selective measurements have been used to evaluate the magnetic properties of the encapsulated NPs. The encapsulated Fe NPs display magnetic remanence up to room temperature, low coercivity, high chemical stability and no significant anisotropy. Our surface-sensitive measurements combined with the specific morphology of the studied VACNTs allow us to pinpoint the contribution of the surface oxidized or hydroxidized iron catalysts present at the VACNT-substrate interface.

Design and Analysis of a Micromechanical Three-Component Force Sensor for Characterizing and Quantifying Surface Roughness

NASA Astrophysics Data System (ADS)

Liang, Q.; Wu, W.; Zhang, D.; Wei, B.; Sun, W.; Wang, Y.; Ge, Y.

2015-10-01

Roughness, which can represent the trade-off between manufacturing cost and performance of mechanical components, is a critical predictor of cracks, corrosion and fatigue damage. In order to measure polished or super-finished surfaces, a novel touch probe based on three-component force sensor for characterizing and quantifying surface roughness is proposed by using silicon micromachining technology. The sensor design is based on a cross-beam structure, which ensures that the system possesses high sensitivity and low coupling. The results show that the proposed sensor possesses high sensitivity, low coupling error, and temperature compensation function. The proposed system can be used to investigate micromechanical structures with nanometer accuracy.

Surface determination through atomically resolved secondary-electron imaging

PubMed Central

Ciston, J.; Brown, H. G.; D'Alfonso, A. J.; Koirala, P.; Ophus, C.; Lin, Y.; Suzuki, Y.; Inada, H.; Zhu, Y.; Allen, L. J.; Marks, L. D.

2015-01-01

Unique determination of the atomic structure of technologically relevant surfaces is often limited by both a need for homogeneous crystals and ambiguity of registration between the surface and bulk. Atomically resolved secondary-electron imaging is extremely sensitive to this registration and is compatible with faceted nanomaterials, but has not been previously utilized for surface structure determination. Here we report a detailed experimental atomic-resolution secondary-electron microscopy analysis of the c(6 × 2) reconstruction on strontium titanate (001) coupled with careful simulation of secondary-electron images, density functional theory calculations and surface monolayer-sensitive aberration-corrected plan-view high-resolution transmission electron microscopy. Our work reveals several unexpected findings, including an amended registry of the surface on the bulk and strontium atoms with unusual seven-fold coordination within a typically high surface coverage of square pyramidal TiO5 units. Dielectric screening is found to play a critical role in attenuating secondary-electron generation processes from valence orbitals. PMID:26082275

Surface determination through atomically resolved secondary-electron imaging

DOE PAGES

Ciston, J.; Brown, H. G.; D’Alfonso, A. J.; ...

2015-06-17

We report that unique determination of the atomic structure of technologically relevant surfaces is often limited by both a need for homogeneous crystals and ambiguity of registration between the surface and bulk. Atomically resolved secondary-electron imaging is extremely sensitive to this registration and is compatible with faceted nanomaterials, but has not been previously utilized for surface structure determination. Here we show a detailed experimental atomic-resolution secondary-electron microscopy analysis of the c(6 x 2) reconstruction on strontium titanate (001) coupled with careful simulation of secondary-electron images, density functional theory calculations and surface monolayer-sensitive aberration-corrected plan-view high-resolution transmission electron microscopy. Our workmore » reveals several unexpected findings, including an amended registry of the surface on the bulk and strontium atoms with unusual seven-fold coordination within a typically high surface coverage of square pyramidal TiO 5 units. Lastly, dielectric screening is found to play a critical role in attenuating secondary-electron generation processes from valence orbitals.« less

Development of high sensitivity and high speed large size blank inspection system LBIS

NASA Astrophysics Data System (ADS)

Ohara, Shinobu; Yoshida, Akinori; Hirai, Mitsuo; Kato, Takenori; Moriizumi, Koichi; Kusunose, Haruhiko

2017-07-01

The production of high-resolution flat panel displays (FPDs) for mobile phones today requires the use of high-quality large-size photomasks (LSPMs). Organic light emitting diode (OLED) displays use several transistors on each pixel for precise current control and, as such, the mask patterns for OLED displays are denser and finer than the patterns for the previous generation displays throughout the entire mask surface. It is therefore strongly demanded that mask patterns be produced with high fidelity and free of defect. To enable the production of a high quality LSPM in a short lead time, the manufacturers need a high-sensitivity high-speed mask blank inspection system that meets the requirement of advanced LSPMs. Lasertec has developed a large-size blank inspection system called LBIS, which achieves high sensitivity based on a laser-scattering technique. LBIS employs a high power laser as its inspection light source. LBIS's delivery optics, including a scanner and F-Theta scan lens, focus the light from the source linearly on the surface of the blank. Its specially-designed optics collect the light scattered by particles and defects generated during the manufacturing process, such as scratches, on the surface and guide it to photo multiplier tubes (PMTs) with high efficiency. Multiple PMTs are used on LBIS for the stable detection of scattered light, which may be distributed at various angles due to irregular shapes of defects. LBIS captures 0.3mμ PSL at a detection rate of over 99.5% with uniform sensitivity. Its inspection time is 20 minutes for a G8 blank and 35 minutes for G10. The differential interference contrast (DIC) microscope on the inspection head of LBIS captures high-contrast review images after inspection. The images are classified automatically.

Au/NiFe/M(Au, MoS2, graphene) trilayer magnetoplasmonics DNA-hybridized sensors with high record of sensitivity

NASA Astrophysics Data System (ADS)

Faridi, Ehsan; Moradi, Maryam; Ansari, Narges; Ghasemi, Amir Hossein Baradaran; Afshar, Amir; Mohseni, Seyed Majid

2017-12-01

The demonstration of biosensors based on the surface plasmon effect holds promise for future high-sensitive electrodeless biodetection. The combination of magnetic effects with surface plasmon waves brings additional freedom to improve sensitivity and signal selectivity. Stacking biosensors with two-dimensional (2-D) materials, e.g., graphene (Gr) and MoS2, can influence plasmon waves and facilitate surface physiochemical properties as additional versatility aspects. We demonstrate magnetoplasmonic biosensors through the detuning of surface plasmon oscillation modes affected by magnetic effect via the presence of the NiFe (Py) layer and different light absorbers of Gr, MoS2, and Au ultrathin layers in three stacks of Au/Py/M(MoS2, Gr, Au) trilayers. We found minimum reflection, resonance angle shift, and transverse magneto-optical Kerr effect (TMOKE) responses of all sensors in the presence of the ss-DNA monolayer. Very few changes of ˜5×10-7 in the ss-DNA's refractive index result in valuable TMOKE response. We found that the presence of three-layer Gr and two-layer MoS2 on top of the Au/Py bilayer can dramatically increase the sensitivity by nine and four times, respectively, than the conventional Au/Co/Au trilayer. Our results show the highest reported DNA sensitivity based on the coupling of light with 2-D materials in magnetoplasmonic devices.

Distributed modeling of ablation (1996–2011) and climate sensitivity on the glaciers of Taylor Valley, Antarctica

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hoffman, Matthew J.; Fountain, Andrew G.; Liston, Glen E.

Here, the McMurdo Dry Valleys of Antarctica host the coldest and driest ecosystem on Earth, which is acutely sensitive to the availability of water coming from glacial runoff. We modeled the spatial variability in ablation and assessed climate sensitivity of the glacier ablation zones using 16 years of meteorological and surface mass-balance observations collected in Taylor Valley. Sublimation was the primary form of mass loss over much of the ablation zones, except for near the termini where melt, primarily below the surface, dominated. Microclimates in ~10 m scale topographic basins generated melt rates up to ten times higher than overmore » smooth glacier surfaces. In contrast, the vertical terminal cliffs on the glaciers can have higher or lower melt rates than the horizontal surfaces due to differences in incoming solar radiation. The model systematically underpredicted ablation for the final 5 years studied, possibly due to an increase of windblown sediment. Surface mass-balance sensitivity to temperature was ~–0.02 m w.e. K –1, which is among the smallest magnitudes observed globally. We also identified a high sensitivity to ice albedo, with a decrease of 0.02 having similar effects as a 1 K increase in temperature, and a complex sensitivity to wind speed.« less

Distributed modeling of ablation (1996–2011) and climate sensitivity on the glaciers of Taylor Valley, Antarctica

DOE PAGES

Hoffman, Matthew J.; Fountain, Andrew G.; Liston, Glen E.

2016-02-24

Here, the McMurdo Dry Valleys of Antarctica host the coldest and driest ecosystem on Earth, which is acutely sensitive to the availability of water coming from glacial runoff. We modeled the spatial variability in ablation and assessed climate sensitivity of the glacier ablation zones using 16 years of meteorological and surface mass-balance observations collected in Taylor Valley. Sublimation was the primary form of mass loss over much of the ablation zones, except for near the termini where melt, primarily below the surface, dominated. Microclimates in ~10 m scale topographic basins generated melt rates up to ten times higher than overmore » smooth glacier surfaces. In contrast, the vertical terminal cliffs on the glaciers can have higher or lower melt rates than the horizontal surfaces due to differences in incoming solar radiation. The model systematically underpredicted ablation for the final 5 years studied, possibly due to an increase of windblown sediment. Surface mass-balance sensitivity to temperature was ~–0.02 m w.e. K –1, which is among the smallest magnitudes observed globally. We also identified a high sensitivity to ice albedo, with a decrease of 0.02 having similar effects as a 1 K increase in temperature, and a complex sensitivity to wind speed.« less

Addressing Curse of Dimensionality in Sensitivity Analysis: How Can We Handle High-Dimensional Problems?

NASA Astrophysics Data System (ADS)

Safaei, S.; Haghnegahdar, A.; Razavi, S.

2016-12-01

Complex environmental models are now the primary tool to inform decision makers for the current or future management of environmental resources under the climate and environmental changes. These complex models often contain a large number of parameters that need to be determined by a computationally intensive calibration procedure. Sensitivity analysis (SA) is a very useful tool that not only allows for understanding the model behavior, but also helps in reducing the number of calibration parameters by identifying unimportant ones. The issue is that most global sensitivity techniques are highly computationally demanding themselves for generating robust and stable sensitivity metrics over the entire model response surface. Recently, a novel global sensitivity analysis method, Variogram Analysis of Response Surfaces (VARS), is introduced that can efficiently provide a comprehensive assessment of global sensitivity using the Variogram concept. In this work, we aim to evaluate the effectiveness of this highly efficient GSA method in saving computational burden, when applied to systems with extra-large number of input factors ( 100). We use a test function and a hydrological modelling case study to demonstrate the capability of VARS method in reducing problem dimensionality by identifying important vs unimportant input factors.

Rapid and sensitive detection of malachite green in aquaculture water by electrochemical preconcentration and surface-enhanced Raman scattering.

PubMed

Xu, Kai-Xuan; Guo, Mei-Hong; Huang, Yu-Ping; Li, Xiao-Dong; Sun, Jian-Jun

2018-04-01

A highly sensitive and rapid method of in-situ surface-enhanced Raman spectroscopy (SERS) combining with electrochemical preconcentration (EP) in detecting malachite green (MG) in aquaculture water was established. Ag nanoparticles (AgNPs) were synthesized and spread onto the surface of gold electrodes after centrifuging to produce SERS-active substrates. After optimizing the pH values, preconcentration potentials and times, in-situ EP-SERS detection was carried out. A sensitive and rapid analysis of the low-concentration MG was accomplished within 200s and the limit of detection was 2.4 × 10 -16 M. Copyright © 2017 Elsevier B.V. All rights reserved.

High S/N Ratio Slotted Step Piezoresistive Microcantilever Designs for Biosensors

PubMed Central

Ansari, Mohd Zahid; Cho, Chongdu

2013-01-01

This study proposes new microcantilever designs in slotted step configuration to improve the S/N ratio of surface stress-based sensors used in physical, chemical, biochemical and biosensor applications. The cantilevers are made of silicon dioxide with a u-shaped silicon piezoresistor in p-doped. The cantilever step length and piezoresistor length is varied along with the operating voltage to characterise the surface stress sensitivity and thermal drifting sensitivity of the cantilevers when used as immunosensor. The numerical analysis is performed using ANSYS Multiphysics. Results show the surface stress sensitivity and the S/N ratio of the slotted step cantilevers is improved by more than 32% and 22%, respectively, over its monolithic counterparts. PMID:23535637

High S/N ratio slotted step piezoresistive microcantilever designs for biosensors.

PubMed

Ansari, Mohd Zahid; Cho, Chongdu

2013-03-26

This study proposes new microcantilever designs in slotted step configuration to improve the S/N ratio of surface stress-based sensors used in physical, chemical, biochemical and biosensor applications. The cantilevers are made of silicon dioxide with a u-shaped silicon piezoresistor in p-doped. The cantilever step length and piezoresistor length is varied along with the operating voltage to characterise the surface stress sensitivity and thermal drifting sensitivity of the cantilevers when used as immunosensor. The numerical analysis is performed using ANSYS Multiphysics. Results show the surface stress sensitivity and the S/N ratio of the slotted step cantilevers is improved by more than 32% and 22%, respectively, over its monolithic counterparts.

Evanescent field Sensors Based on Tantalum Pentoxide Waveguides – A Review

PubMed Central

Schmitt, Katrin; Oehse, Kerstin; Sulz, Gerd; Hoffmann, Christian

2008-01-01

Evanescent field sensors based on waveguide surfaces play an important role where high sensitivity is required. Particularly tantalum pentoxide (Ta2O5) is a suitable material for thin-film waveguides due to its high refractive index and low attenuation. Many label-free biosensor systems such as grating couplers and interferometric sensors as well as fluorescence-based systems benefit from this waveguide material leading to extremely high sensitivity. Some biosensor systems based on Ta2O5 waveguides already took the step into commercialization. This report reviews the various detection systems in terms of limit of detection, the applications, and the suitable surface chemistry. PMID:27879731

An approach to the diagnosis of metabolic syndrome by the multi-electrode impedance method

NASA Astrophysics Data System (ADS)

Furuya, N.; Sakamoto, K.; Kanai, H.

2010-04-01

It is well known that metabolic syndrome can induce myocardial infarction and cerebral infarction. So, it is very important to measure the visceral fat volume. In the electric impedance method, information in the vicinity of the electrodes is strongly reflected. Therefore, we propose a new multi-electrode arrangement method based on the impedance sensitivity theorem to measure the visceral fat volume. This electrode arrangement is designed to enable high impedance sensitivity in the visceral and subcutaneous fat regions. Currents are simultaneously applied to several current electrodes on the body surface, and one voltage electrode pair is arranged on the body surface near the organ of interest to obtain the visceral fat information and another voltage electrode pair is arranged on the body surface near the current electrodes to obtain the subcutaneous fat information. A simulation study indicates that by weighting the impedance sensitivity distribution, as in our method, a high-sensitivity region in the visceral and the subcutaneous fat regions can be formed. In addition, it was confirmed that the visceral fat volume can be estimated by the measured impedance data.

Near field detector for integrated surface plasmon resonance biosensor applications.

PubMed

Bora, Mihail; Celebi, Kemal; Zuniga, Jorge; Watson, Colin; Milaninia, Kaveh M; Baldo, Marc A

2009-01-05

Integrated surface plasmon resonance biosensors promise to enable compact and portable biosensing at high sensitivities. To replace the far field detector traditionally used to detect surface plasmons we integrate a near field detector below a functionalized gold film. The evanescent field of a surface plasmon at the aqueous-gold interface is converted into photocurrent by a thin film organic heterojunction diode. We demonstrate that use of the near field detector is equivalent to the traditional far field measurement of reflectivity. The sensor is stable and reversible in an aqueous environment for periods of 6 hrs. For specific binding of neutravidin, the detection limit is 4 microg/cm(2). The sensitivity can be improved by reducing surface roughness of the gold layers and optimization of the device design. From simulations, we predict a maximum sensitivity that is two times lower than a comparable conventional SPR biosensor.

Highly Sensitive and Selective Ethanol Sensor Fabricated with In-Doped 3DOM ZnO.

PubMed

Wang, Zhihua; Tian, Ziwei; Han, Dongmei; Gu, Fubo

2016-03-02

ZnO is an important n-type semiconductor sensing material. Currently, much attention has been attracted to finding an effective method to prepare ZnO nanomaterials with high sensing sensitivity and excellent selectivity. A three-dimensionally ordered macroporous (3DOM) ZnO nanostructure with a large surface area is beneficial to gas and electron transfer, which can enhance the gas sensitivity of ZnO. Indium (In) doping is an effective way to improve the sensing properties of ZnO. In this paper, In-doped 3DOM ZnO with enhanced sensitivity and selectivity has been synthesized by using a colloidal crystal templating method. The 3DOM ZnO with 5 at. % of In-doping exhibits the highest sensitivity (∼88) to 100 ppm ethanol at 250 °C, which is approximately 3 times higher than that of pure 3DOM ZnO. The huge improvement to the sensitivity to ethanol was attributed to the increase in the surface area and the electron carrier concentration. The doping by In introduces more electrons into the matrix, which is helpful for increasing the amount of adsorbed oxygen, leading to high sensitivity. The In-doped 3DOM ZnO is a promising material for a new type of ethanol sensor.

Design and numerical analysis of highly sensitive Au-MoS2-graphene based hybrid surface plasmon resonance biosensor

NASA Astrophysics Data System (ADS)

Rahman, M. Saifur; Anower, Md. Shamim; Hasan, Md. Rabiul; Hossain, Md. Biplob; Haque, Md. Ismail

2017-08-01

We demonstrate a highly sensitive Au-MoS2-Graphene based hybrid surface plasmon resonance (SPR) biosensor for the detection of DNA hybridization. The performance parameters of the proposed sensor are investigated in terms of sensitivity, detection accuracy and quality factor at operating wavelength of 633 nm. We observed in the numerical study that sensitivity can be greatly increased by adding MoS2 layer in the middle of a Graphene-on-Au layer. It is shown that by using single layer of MoS2 in between gold and graphene layer, the proposed biosensor exhibits simultaneously high sensitivity of 87.8 deg/RIU, high detection accuracy of 1.28 and quality factor of 17.56 with gold layer thickness of 50 nm. This increased performance is due to the absorption ability and optical characteristics of graphene biomolecules and high fluorescence quenching ability of MoS2. On the basis of changing in SPR angle and minimum reflectance, the proposed sensor can sense nucleotides bonding happened between double-stranded DNA (dsDNA) helix structures. Therefore, this sensor can successfully detect the hybridization of target DNAs to the probe DNAs pre-immobilized on the Au-MoS2-Graphene hybrid with capability of distinguishing single-base mismatch.

Experimental and ecosystem model approach to assessing the sensitivity of High arctic deep permafrost to changes in surface temperature and precipitation

NASA Astrophysics Data System (ADS)

Rasmussen, L. H.; Zhang, W.; Elberling, B.; Cable, S.

2016-12-01

Permafrost affected areas in Greenland are expected to experience large temperature increases within the 21st century. Most previous studies on permafrost consider near-surface soil, where changes will happen first. However, how sensitive the deep permafrost temperature is to near-surface conditions through changes in soil thermal properties, snow depth and soil moisture, is not known. In this study, we measured the sensitivity of thermal conductivity (TC) to gravimetric water content (GWC) in frozen and thawed deep permafrost sediments from deltaic, alluvial and fluvial depositional environments in the Zackenberg valley, NE Greenland. We also calibrated a coupled heat and water transfer model, the "CoupModel", for the two closely situated deltaic sites, one with average snow depth and the other with topographic snow accumulation. With the calibrated model, we simulated deep permafrost thermal dynamics in four scenarios with changes in surface forcing: a. 3 °C warming and 20 % increase in precipitation; b. 3 °C warming and 100 % increase in precipitation; c. 6 °C warming and 20 % increase in precipitation; d. 6 °C warming and 100 % increase in precipitation.Our results indicated that frozen sediments had higher TC than thawed sediments. All sediments showed a positive linear relation between TC and soil moisture when frozen, and a logarithmic one when thawed. Fluvial sediments had high sensitivity, but never reached above 12 % GWC, indicating a field effect of water retention capacity. Alluvial sediments were less sensitive to soil moisture than deltaic and fluvial sediments, indicating the importance of unfrozen water in frozen sediment. The deltaic site with snow accumulation had 1 °C higher annual mean ground temperature than the average snow site. The soil temperature at the depth of 18 m increased with 1.5 °C and 3.5 °C in the scenarios with 3 °C and 6 °C warming, respectively. Precipitation had no significant additional effect to warming. We conclude that below-ground sediment properties affect the sensitivity of TC to GWC, that surface temperature changes can significantly affect the deep permafrost within a short period, and that differences in snow depth affect surface temperatures. Geology, pedology and precipitation should thus be considered if estimating future High arctic deep permafrost sensitivity.

Air-borne and tissue-borne sensitivities of bioacoustic sensors used on the skin surface.

PubMed

Zañartu, Matías; Ho, Julio C; Kraman, Steve S; Pasterkamp, Hans; Huber, Jessica E; Wodicka, George R

2009-02-01

Measurements of body sounds on the skin surface have been widely used in the medical field and continue to be a topic of current research, ranging from the diagnosis of respiratory and cardiovascular diseases to the monitoring of voice dosimetry. These measurements are typically made using light-weight accelerometers and/or air-coupled microphones attached to the skin. Although normally neglected, air-borne sounds generated by the subject or other sources of background noise can easily corrupt such recordings, which is particularly critical in the recording of voiced sounds on the skin surface. In this study, the sensitivity of commonly used bioacoustic sensors to air-borne sounds was evaluated and compared with their sensitivity to tissue-borne body sounds. To delineate the sensitivity to each pathway, the sensors were first tested in vitro and then on human subjects. The results indicated that, in general, the air-borne sensitivity is sufficiently high to significantly corrupt body sound signals. In addition, the air-borne and tissue-borne sensitivities can be used to discriminate between these components. Although the study is focused on the evaluation of voiced sounds on the skin surface, an extension of the proposed methods to other bioacoustic applications is discussed.

Highly sensitive solids mass spectrometer uses inert-gas ion source

NASA Technical Reports Server (NTRS)

1966-01-01

Mass spectrometer provides a recorded analysis of solid material surfaces and bulk. A beam of high-energy inert-gas ions bombards the surface atoms of a sample and converts a percentage into an ionized vapor. The mass spectrum analyzer separates the vapor ionic constituents by mass-to-charge ratio.

Analysis of hepatitis B surface antigen (HBsAg) using high-sensitivity HBsAg assays in hepatitis B virus carriers in whom HBsAg seroclearance was confirmed by conventional assays.

PubMed

Ozeki, Itaru; Nakajima, Tomoaki; Suii, Hirokazu; Tatsumi, Ryoji; Yamaguchi, Masakatsu; Kimura, Mutsuumi; Arakawa, Tomohiro; Kuwata, Yasuaki; Ohmura, Takumi; Hige, Shuhei; Karino, Yoshiyasu; Toyota, Joji

2018-02-01

We investigated the utility of high-sensitivity hepatitis B surface antigen (HBsAg) assays compared with conventional HBsAg assays. Using serum samples from 114 hepatitis B virus (HBV) carriers in whom HBsAg seroclearance was confirmed by conventional HBsAg assays (cut-off value, 0.05 IU/mL), the amount of HBsAg was re-examined by high-sensitivity HBsAg assays (cut-off value, 0.005 IU/mL). Cases negative for HBsAg in both assays were defined as consistent cases, and cases positive for HBsAg in the high-sensitivity HBsAg assay only were defined as discrepant cases. There were 55 (48.2%) discrepant cases, and the range of HBsAg titers determined by high-sensitivity HBsAg assays was 0.005-0.056 IU/mL. Multivariate analysis showed that the presence of nucleos(t)ide analog therapy, liver cirrhosis, and negative anti-HBs contributed to the discrepancies between the two assays. Cumulative anti-HBs positivity rates among discrepant cases were 12.7%, 17.2%, 38.8%, and 43.9% at baseline, 1 year, 3 years, and 5 years, respectively, whereas the corresponding rates among consistent cases were 50.8%, 56.0%, 61.7%, and 68.0%, respectively. Hepatitis B virus DNA negativity rates were 56.4% and 81.4% at baseline, 51.3% and 83.3% at 1 year, and 36.8% and 95.7% at 3 years, among discrepant and consistent cases, respectively. Hepatitis B surface antigen reversion was observed only in discrepant cases. Re-examination by high-sensitivity HBsAg assays revealed that HBsAg was positive in approximately 50% of cases. Cumulative anti-HBs seroconversion rates and HBV-DNA seroclearance rates were lower in these cases, suggesting a population at risk for HBsAg reversion. © 2017 The Japan Society of Hepatology.

Sensitivity of Rayleigh wave ellipticity and implications for surface wave inversion

NASA Astrophysics Data System (ADS)

Cercato, Michele

2018-04-01

The use of Rayleigh wave ellipticity has gained increasing popularity in recent years for investigating earth structures, especially for near-surface soil characterization. In spite of its widespread application, the sensitivity of the ellipticity function to the soil structure has been rarely explored in a comprehensive and systematic manner. To this end, a new analytical method is presented for computing the sensitivity of Rayleigh wave ellipticity with respect to the structural parameters of a layered elastic half-space. This method takes advantage of the minor decomposition of the surface wave eigenproblem and is numerically stable at high frequency. This numerical procedure allowed to retrieve the sensitivity for typical near surface and crustal geological scenarios, pointing out the key parameters for ellipticity interpretation under different circumstances. On this basis, a thorough analysis is performed to assess how ellipticity data can efficiently complement surface wave dispersion information in a joint inversion algorithm. The results of synthetic and real-world examples are illustrated to analyse quantitatively the diagnostic potential of the ellipticity data with respect to the soil structure, focusing on the possible sources of misinterpretation in data inversion.

Surface shear inviscidity of soluble surfactants

PubMed Central

Zell, Zachary A.; Nowbahar, Arash; Mansard, Vincent; Leal, L. Gary; Deshmukh, Suraj S.; Mecca, Jodi M.; Tucker, Christopher J.; Squires, Todd M.

2014-01-01

Foam and emulsion stability has long been believed to correlate with the surface shear viscosity of the surfactant used to stabilize them. Many subtleties arise in interpreting surface shear viscosity measurements, however, and correlations do not necessarily indicate causation. Using a sensitive technique designed to excite purely surface shear deformations, we make the most sensitive and precise measurements to date of the surface shear viscosity of a variety of soluble surfactants, focusing on SDS in particular. Our measurements reveal the surface shear viscosity of SDS to be below the sensitivity limit of our technique, giving an upper bound of order 0.01 μN·s/m. This conflicts directly with almost all previous studies, which reported values up to 103–104 times higher. Multiple control and complementary measurements confirm this result, including direct visualization of monolayer deformation, for SDS and a wide variety of soluble polymeric, ionic, and nonionic surfactants of high- and low-foaming character. No soluble, small-molecule surfactant was found to have a measurable surface shear viscosity, which seriously undermines most support for any correlation between foam stability and surface shear rheology of soluble surfactants. PMID:24563383

Conditions of excitation and sensitivity of diffractively-coupled surface lattice resonances over plasmonic nanoparticle arrays in ATR geometry

NASA Astrophysics Data System (ADS)

Danilov, Artem; Tselikov, Gleb; Wu, Fan; Kravets, Vasyl G.; Ozerov, Igor; Bedu, Frederic; Grigorenko, Alexander N.; Kabashin, Andrei V.

2018-02-01

We investigate conditions of excitation and properties of Plasmonic Surface Lattice Resonances (PSLR) over glass substrate-supported Au nanoparticle dimers ( 100-200 nm) arranged in a periodic metamaterial lattice, in Attenuated Total Reflection (ATR) optical excitation geometry, and assess their sensitivities to variations of refractive index (RI) of the adjacent sample dielectric medium. We show that spectral sensitivity of PSLR to RI variations is determined by the lattice periodicity ( 320 nm per RIU change in our case), while ultranarrow resonance lineshapes (down to a few nm full-widthat-half-maximum) provide very high figure-of-merit values evidencing the possibility of ultrasensitive biosensing measurements. Combining advantages of nanoscale architectures, including a strong concentration of electric field, the possibility of manipulation at the nanoscale etc, and high phase and spectral sensitivities, PSLRs promise a drastic advancement of current state-of-the-art plasmonic biosensing technology.

Laser ablation surface-enhanced Raman microspectroscopy.

PubMed

Londero, Pablo S; Lombardi, John R; Leona, Marco

2013-06-04

Improved identification of trace organic compounds in complex matrixes is critical for a variety of fields such as material science, heritage science, and forensics. Surface-enhanced Raman scattering (SERS) is a vibrational spectroscopy technique that can attain single-molecule sensitivity and has been shown to complement mass spectrometry, but lacks widespread application without a robust method that utilizes the effect. We demonstrate a new, highly sensitive, and widely applicable approach to SERS analysis based on laser ablation in the presence of a tailored plasmonic substrate. We analyze several challenging compounds, including non-water-soluble pigments and dyed leather from an ancient Egyptian chariot, achieving sensitivity as high as 120 amol for a 1:1 signal-to-noise ratio and 5 μm spatial resolution. This represents orders of magnitude improvement in spatial resolution and sensitivity compared to those of other SERS approaches intended for widespread application, greatly increasing the applicability of SERS.

Tamm-plasmon and surface-plasmon hybrid-mode based refractometry in photonic bandgap structures.

PubMed

Das, Ritwick; Srivastava, Triranjita; Jha, Rajan

2014-02-15

The transverse magnetic (TM) polarized hybrid modes formed as a consequence of coupling between Tamm plasmon polariton (TM-TPP) mode and surface plasmon polariton (SPP) mode exhibit interesting dispersive features for realizing a highly sensitive and accurate surface plasmon resonance (SPR) sensor. We found that the TM-TPP modes, formed at the interface of distributed Bragg reflector and metal, are strongly dispersive as compared to SPP modes at optical frequencies. This causes an appreciably narrow interaction bandwidth between TM-TPP and SPP modes, which leads to highly accurate sensing. In addition, appropriate tailoring of dispersion characteristics of TM-TPP as well as SPP modes could ensure high sensitivity of a novel SPR platform. By suitably designing the Au/TiO₂/SiO₂-based geometry, we propose a TM-TPP/SPP hybrid-mode sensor and achieve a sensitivity ≥900  nm/RIU with high detection accuracy (≥30  μm⁻¹) for analyte refractive indices varying between 1.330 and 1.345 in 600-700 nm wavelength range. The possibility to achieve desired dispersive behavior in any spectral band makes the sensing configuration an extremely attractive candidate to design sensors depending on the availability of optical sources.

Simultaneous immobilization of glucose oxidase on the surface and cavity of hollow gold nanospheres as labels for highly sensitive electrochemical immunoassay of tumor marker.

PubMed

Song, Zhongju; Yuan, Ruo; Chai, Yaqin; Jiang, Wen; Su, Huilan; Che, Xin; Ran, Xiaoqi

2011-01-15

A novel tracer, glucose oxidase (GOD)-functionalized hollow gold nanospheres encapsulating glucose oxidase (Au(shell)@GOD), was designed to label the ferrocenemonocarboxylic-grafted secondary antibodies (Fc@Ab(2)) for highly sensitive detection of tumor marker using carboxyl group functionalized multiwall carbon nanotubes as platform. Initially, Au(shell)@GOD was synthesized specially by reverse micelle approach, and then the labeling of antibody and the preparation of GOD-functionalized Au(shell)@GOD were performed by one-pot assembly of Fc@Ab(2) and GOD on the surface of Au(shell)@GOD. The ferrocene used to label antibodies acted as a mediator of electron transfer between GOD and electrode surface. The high-content glucose oxidase in the tracer (on the surface and in the cavity) could significantly amplify the amperometric signal for sandwich-type immunoassay. Using carcinoembryonic antigen (CEA) as model analyte, the designed tracer showed linear range from 0.02 to 5.0 ng mL(-1) with the detection limit down to 6.7 pg mL(-1). The assay results of serum samples with the proposed method were in an acceptable agreement with the reference values. The new protocol showed acceptable stability and reproducibility, high sensitivity, and good precision, which could provide a promising potential for clinical screening and diagnosis of tumor disease. Copyright © 2010 Elsevier B.V. All rights reserved.

Quality and sensitivity of high-resolution numerical simulation of urban heat islands

NASA Astrophysics Data System (ADS)

Li, Dan; Bou-Zeid, Elie

2014-05-01

High-resolution numerical simulations of the urban heat island (UHI) effect with the widely-used Weather Research and Forecasting (WRF) model are assessed. Both the sensitivity of the results to the simulation setup, and the quality of the simulated fields as representations of the real world, are investigated. Results indicate that the WRF-simulated surface temperatures are more sensitive to the planetary boundary layer (PBL) scheme choice during nighttime, and more sensitive to the surface thermal roughness length parameterization during daytime. The urban surface temperatures simulated by WRF are also highly sensitive to the urban canopy model (UCM) used. The implementation in this study of an improved UCM (the Princeton UCM or PUCM) that allows the simulation of heterogeneous urban facets and of key hydrological processes, together with the so-called CZ09 parameterization for the thermal roughness length, significantly reduce the bias (<1.5 °C) in the surface temperature fields as compared to satellite observations during daytime. The boundary layer potential temperature profiles are captured by WRF reasonable well at both urban and rural sites; the biases in these profiles relative to aircraft-mounted senor measurements are on the order of 1.5 °C. Changing UCMs and PBL schemes does not alter the performance of WRF in reproducing bulk boundary layer temperature profiles significantly. The results illustrate the wide range of urban environmental conditions that various configurations of WRF can produce, and the significant biases that should be assessed before inferences are made based on WRF outputs. The optimal set-up of WRF-PUCM developed in this paper also paves the way for a confident exploration of the city-scale impacts of UHI mitigation strategies in the companion paper (Li et al 2014).

MOSFET detectors in quality assurance of tomotherapy treatments.

PubMed

Cherpak, Amanda; Studinski, Ryan C N; Cygler, Joanna E

2008-02-01

The purpose of this work was to characterize metal oxide semiconductor field-effect transistors (MOSFETs) in a 6 MV conventional linac and investigate their use for quality assurance of radiotherapy treatments with a tomotherapy Hi-Art unit. High sensitivity and standard sensitivity MOSFETs were first calibrated and then tested for reproducibility, field size dependence, and accuracy of measuring surface dose in a 6 MV beam as well as in a tomotherapy Hi-Art unit. In vivo measurements were performed on both a RANDO phantom and several head and neck cancer patients treated with tomotherapy and compared to TLD measurements and treatment plan doses to evaluate the performance of MOSFETs in a high gradient radiation field. The average calibration factor found was 0.345+/-2.5%cGy/mV for the high sensitivity MOSFETs tested and 0.901+/-2.4%cGy/mV for the standard sensitivity MOSFETs. MOSFET measured surface doses had an average agreement with ion chamber measurements of 1.55% for the high sensitivity MOSFET and 5.23% for the standard sensitivity MOSFET when averaged over all trials and field sizes tested. No significant dependence on field size was found for the standard sensitivity MOSFETs, however a maximum difference of 5.34% was found for the high sensitivity MOSFET calibration factors in the field sizes tested. Measurements made with MOSFETS on head and neck patients treated on a tomotherapy Hi-Art unit had an average agreement of (3.26+/-0.03)% with TLD measurements, however the average of the absolute difference between the MOSFET measurements and the treatment plan skin doses was (12.2+/-7.5)%. The MOSFET measured patient skin doses also had good reproducibility, with inter-fraction deviations ranging from 1.4% to 6.6%. Similar results were found from trials using a RANDO phantom. The MOSFETs performed well when used in the tomotherapy Hi-Art unit and did not increase the overall treatment set-up time when used for patient measurements. It was found that MOSFETs are suitable detectors for surface dose measurements in both conventional beam and tomotherapy treatments and they can provide valuable skin dose information in areas where the treatment planning system may not be accurate.

Hollow fiber surface plasmon resonance sensor for the detection of liquid with high refractive index.

PubMed

Liu, Bing-Hong; Jiang, Yong-Xiang; Zhu, Xiao-Song; Tang, Xiao-Li; Shi, Yi-Wei

2013-12-30

A new kind of surface plasmon resonance (SPR) sensor based on silver-coated hollow fiber (HF) structure for the detection of liquids with high refractive index (RI) is presented. Liquid sensed medium with high RI is filled in the hollow core of the HF and its RI can be detected by measuring the transmission spectra of the HF SPR sensor. The designed sensors with different silver thicknesses are fabricated and the transmission spectra for filled liquids with different RI are measured to investigate the performances of the sensors. Theoretical analysis is also carried out to evaluate the performance. The simulation results agree well with the experimental results. Factors that might affect sensitivity and detection accuracy of the sensor are discussed. The highest sensitivity achieved is 6,607 nm/RIU, which is comparable to the sensitivities of the other reported fiber SPR sensors.

ZnO nanorod arrays and direct wire bonding on GaN surfaces for rapid fabrication of antireflective, high-temperature ultraviolet sensors

NASA Astrophysics Data System (ADS)

So, Hongyun; Senesky, Debbie G.

2016-11-01

Rapid, cost-effective, and simple fabrication/packaging of microscale gallium nitride (GaN) ultraviolet (UV) sensors are demonstrated using zinc oxide nanorod arrays (ZnO NRAs) as an antireflective layer and direct bonding of aluminum wires to the GaN surface. The presence of the ZnO NRAs on the GaN surface significantly reduced the reflectance to less than 1% in the UV and 4% in the visible light region. As a result, the devices fabricated with ZnO NRAs and mechanically stable aluminum bonding wires (pull strength of 3-5 gf) showed higher sensitivity (136.3% at room temperature and 148.2% increase at 250 °C) when compared with devices with bare (uncoated) GaN surfaces. In addition, the devices demonstrated reliable operation at high temperatures up to 300 °C, supporting the feasibility of simple and cost-effective UV sensors operating with higher sensitivity in high-temperature conditions, such as in combustion, downhole, and space exploration applications.

In situ dynamic tracking of heterogeneous nanocatalytic processes by shell-isolated nanoparticle-enhanced Raman spectroscopy

PubMed Central

Zhang, Hua; Wang, Chen; Sun, Han-Lei; Fu, Gang; Chen, Shu; Zhang, Yue-Jiao; Chen, Bing-Hui; Anema, Jason R.; Yang, Zhi-Lin; Li, Jian-Feng; Tian, Zhong-Qun

2017-01-01

Surface molecular information acquired in situ from a catalytic process can greatly promote the rational design of highly efficient catalysts by revealing structure-activity relationships and reaction mechanisms. Raman spectroscopy can provide this rich structural information, but normal Raman is not sensitive enough to detect trace active species adsorbed on the surface of catalysts. Here we develop a general method for in situ monitoring of heterogeneous catalytic processes through shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) satellite nanocomposites (Au-core silica-shell nanocatalyst-satellite structures), which are stable and have extremely high surface Raman sensitivity. By combining operando SHINERS with density functional theory calculations, we identify the working mechanisms for CO oxidation over PtFe and Pd nanocatalysts, which are typical low- and high-temperature catalysts, respectively. Active species, such as surface oxides, superoxide/peroxide species and Pd–C/Pt–C bonds are directly observed during the reactions. We demonstrate that in situ SHINERS can provide a deep understanding of the fundamental concepts of catalysis. PMID:28537269

Surface plasmon resonance spectroscopy sensor and methods for using same

DOEpatents

Anderson, Brian Benjamin; Nave, Stanley Eugene

2002-01-01

A surface plasmon resonance ("SPR") probe with a detachable sensor head and system and methods for using the same in various applications is described. The SPR probe couples fiber optic cables directly to an SPR substrate that has a generally planar input surface and a generally curved reflecting surface, such as a substrate formed as a hemisphere. Forming the SPR probe in this manner allows the probe to be miniaturized and operate without the need for high precision, expensive and bulky collimating or focusing optics. Additionally, the curved reflecting surface of the substrate can be coated with one or multiple patches of sensing medium to allow the probe to detect for multiple analytes of interest or to provide multiple readings for comparison and higher precision. Specific applications for the probe are disclosed, including extremely high sensitive relative humidity and dewpoint detection for, e.g., moisture-sensitive environment such as volatile chemical reactions. The SPR probe disclosed operates with a large dynamic range and provides extremely high quality spectra despite being robust enough for field deployment and readily manufacturable.

Capturing the sensitivity of land-use regression models to short-term mobile monitoring campaigns using air pollution micro-sensors.

PubMed

Minet, L; Gehr, R; Hatzopoulou, M

2017-11-01

The development of reliable measures of exposure to traffic-related air pollution is crucial for the evaluation of the health effects of transportation. Land-use regression (LUR) techniques have been widely used for the development of exposure surfaces, however these surfaces are often highly sensitive to the data collected. With the rise of inexpensive air pollution sensors paired with GPS devices, we witness the emergence of mobile data collection protocols. For the same urban area, can we achieve a 'universal' model irrespective of the number of locations and sampling visits? Can we trade the temporal representation of fixed-point sampling for a larger spatial extent afforded by mobile monitoring? This study highlights the challenges of short-term mobile sampling campaigns in terms of the resulting exposure surfaces. A mobile monitoring campaign was conducted in 2015 in Montreal; nitrogen dioxide (NO 2 ) levels at 1395 road segments were measured under repeated visits. We developed LUR models based on sub-segments, categorized in terms of the number of visits per road segment. We observe that LUR models were highly sensitive to the number of road segments and to the number of visits per road segment. The associated exposure surfaces were also highly dissimilar. Copyright © 2017 Elsevier Ltd. All rights reserved.

2D layered insulator hexagonal boron nitride enabled surface passivation in dye sensitized solar cells.

PubMed

Shanmugam, Mariyappan; Jacobs-Gedrim, Robin; Durcan, Chris; Yu, Bin

2013-11-21

A two-dimensional layered insulator, hexagonal boron nitride (h-BN), is demonstrated as a new class of surface passivation materials in dye-sensitized solar cells (DSSCs) to reduce interfacial carrier recombination. We observe ~57% enhancement in the photo-conversion efficiency of the DSSC utilizing h-BN coated semiconductor TiO2 as compared with the device without surface passivation. The h-BN coated TiO2 is characterized by Raman spectroscopy to confirm the presence of highly crystalline, mixed monolayer/few-layer h-BN nanoflakes on the surface of TiO2. The passivation helps to minimize electron-hole recombination at the TiO2/dye/electrolyte interfaces. The DSSC with h-BN passivation exhibits significantly lower dark saturation current in the low forward bias region and higher saturation in the high forward bias region, respectively, suggesting that the interface quality is largely improved without impeding carrier transport at the material interface. The experimental results reveal that the emerging 2D layered insulator could be used for effective surface passivation in solar cell applications attributed to desirable material features such as high crystallinity and self-terminated/dangling-bond-free atomic planes as compared with high-k thin-film dielectrics.

Au/NiFe/M(Au, MoS2, graphene) trilayer magnetoplasmonics DNA-hybridized sensors with high record of sensitivity.

PubMed

Faridi, Ehsan; Moradi, Maryam; Ansari, Narges; Baradaran Ghasemi, Amir Hossein; Afshar, Amir; Mohseni Armaki, Seyed Majid

2017-12-01

The demonstration of biosensors based on the surface plasmon effect holds promise for future high-sensitive electrodeless biodetection. The combination of magnetic effects with surface plasmon waves brings additional freedom to improve sensitivity and signal selectivity. Stacking biosensors with two-dimensional (2-D) materials, e.g., graphene (Gr) and MoS2, can influence plasmon waves and facilitate surface physiochemical properties as additional versatility aspects. We demonstrate magnetoplasmonic biosensors through the detuning of surface plasmon oscillation modes affected by magnetic effect via the presence of the NiFe (Py) layer and different light absorbers of Gr, MoS2, and Au ultrathin layers in three stacks of Au/Py/M(MoS2, Gr, Au) trilayers. We found minimum reflection, resonance angle shift, and transverse magneto-optical Kerr effect (TMOKE) responses of all sensors in the presence of the ss-DNA monolayer. Very few changes of ∼5×10-7 in the ss-DNA's refractive index result in valuable TMOKE response. We found that the presence of three-layer Gr and two-layer MoS2 on top of the Au/Py bilayer can dramatically increase the sensitivity by nine and four times, respectively, than the conventional Au/Co/Au trilayer. Our results show the highest reported DNA sensitivity based on the coupling of light with 2-D materials in magnetoplasmonic devices. (2017) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE).

Covalent immobilisation of antibodies in Teflon-FEP microfluidic devices for the sensitive quantification of clinically relevant protein biomarkers.

PubMed

Pivetal, Jeremy; Pereira, Filipa M; Barbosa, Ana I; Castanheira, Ana P; Reis, Nuno M; Edwards, Alexander D

2017-03-13

This study reports for the first time the sensitive colorimetric and fluorescence detection of clinically relevant protein biomarkers by sandwich immunoassays using the covalent immobilisation of antibodies onto the fluoropolymer surface inside Teflon®-FEP microfluidic devices. Teflon®-FEP has outstanding optical transparency ideal for high-sensitivity colorimetric and fluorescence bioassays, however this thermoplastic is regarded as chemically inert and very hydrophobic. Covalent immobilisation can offer benefits over passive adsorption to plastic surfaces by allowing better control over antibody density, orientation and analyte binding capacity, and so we tested a range of different and novel covalent immobilisation strategies. We first functionalised the inner surface of a 10-bore, 200 μm internal diameter FEP microcapillary film with high-molecular weight polyvinyl alcohol (PVOH) without changing the outstanding optical transparency of the device delivered by the matched refractive index of FEP and water. Glutaraldehyde immobilisation was compared with the use of photoactivated linkers and NHS-ester crosslinkers for covalently immobilising capture antibodies onto PVOH. Three clinically relevant sandwich ELISAs were tested against the cytokine IL-1β, the myocardial infarct marker cardiac troponin I (cTnI), and the chronic heart failure marker brain natriuretic peptide (BNP). Overall, glutaraldehyde immobilisation was effective for BNP assays, but yielded unacceptable background for IL-1β and cTnI assays caused by direct binding of the biotinylated detection antibody to the modified PVOH surface. We found NHS-ester groups reacted with APTES-treated PVOH coated fluoropolymers. This facilitated a novel method for capture antibody immobilisation onto fluoropolymer devices using a bifunctional NHS-maleimide crosslinker. The density of covalently immobilised capture antibodies achieved using PVOH/APTES/NHS/maleimide approached levels seen with passive adsorption, and sensitive and quantitative assay performance was achieved using this method. Overall, the PVOH coating provided an excellent surface for controlled covalent antibody immobilisation onto Teflon®-FEP for performing high-sensitivity immunoassays.

Highly sensitive graphene biosensor by monomolecular self-assembly of receptors on graphene surface

NASA Astrophysics Data System (ADS)

Kim, Ji Eun; No, Young Hyun; Kim, Joo Nam; Shin, Yong Seon; Kang, Won Tae; Kim, Young Rae; Kim, Kun Nyun; Kim, Yong Ho; Yu, Woo Jong

2017-05-01

Graphene has attracted a great deal of interest for applications in bio-sensing devices because of its ultra-thin structure, which enables strong electrostatic coupling with target molecules, and its excellent electrical mobility promising for ultra-fast sensing speeds. However, thickly stacked receptors on the graphene's surface interrupts electrostatic coupling between graphene and charged biomolecules, which can reduce the sensitivity of graphene biosensors. Here, we report a highly sensitive graphene biosensor by the monomolecular self-assembly of designed peptide protein receptors. The graphene channel was non-covalently functionalized using peptide protein receptors via the π-π interaction along the graphene's Bravais lattice, allowing ultra-thin monomolecular self-assembly through the graphene lattice. In thickness dependent characterization, a graphene sensor with a monomolecular receptor (thickness less than 3 nm) showed five times higher sensitivity and three times higher voltage shifts than graphene sensors with thick receptor stacks (thicknesses greater than 20 nm), which is attributed to excellent gate coupling between graphene and streptavidin via an ultrathin receptor insulator. In addition to having a fast-inherent response time (less than 0.6 s) based on fast binding speed between biotin and streptavidin, our graphene biosensor is a promising platform for highly sensitive real-time monitoring of biomolecules with high spatiotemporal resolution.

Palladium Gate All Around - Hetero Dielectric -Tunnel FET based highly sensitive Hydrogen Gas Sensor

NASA Astrophysics Data System (ADS)

Madan, Jaya; Chaujar, Rishu

2016-12-01

The paper presents a novel highly sensitive Hetero-Dielectric-Gate All Around Tunneling FET (HD-GAA-TFET) based Hydrogen Gas Sensor, incorporating the advantages of band to band tunneling (BTBT) mechanism. Here, the Palladium supported silicon dioxide is used as a sensing media and sensing relies on the interaction of hydrogen with Palladium-SiO2-Si. The high surface to volume ratio in the case of cylindrical GAA structure enhances the fortuities for surface reactions between H2 gas and Pd, and thus improves the sensitivity and stability of the sensor. Behaviour of the sensor in presence of hydrogen and at elevated temperatures is discussed. The conduction path of the sensor which is dependent on sensors radius has also been varied for the optimized sensitivity and static performance analysis of the sensor where the proposed design exhibits a superior performance in terms of threshold voltage, subthreshold swing, and band to band tunneling rate. Stability of the sensor with respect to temperature affectability has also been studied, and it is found that the device is reasonably stable and highly sensitive over the bearable temperature range. The successful utilization of HD-GAA-TFET in gas sensors may open a new door for the development of novel nanostructure gas sensing devices.

Epidermis Microstructure Inspired Graphene Pressure Sensor with Random Distributed Spinosum for High Sensitivity and Large Linearity.

PubMed

Pang, Yu; Zhang, Kunning; Yang, Zhen; Jiang, Song; Ju, Zhenyi; Li, Yuxing; Wang, Xuefeng; Wang, Danyang; Jian, Muqiang; Zhang, Yingying; Liang, Renrong; Tian, He; Yang, Yi; Ren, Tian-Ling

2018-03-27

Recently, wearable pressure sensors have attracted tremendous attention because of their potential applications in monitoring physiological signals for human healthcare. Sensitivity and linearity are the two most essential parameters for pressure sensors. Although various designed micro/nanostructure morphologies have been introduced, the trade-off between sensitivity and linearity has not been well balanced. Human skin, which contains force receptors in a reticular layer, has a high sensitivity even for large external stimuli. Herein, inspired by the skin epidermis with high-performance force sensing, we have proposed a special surface morphology with spinosum microstructure of random distribution via the combination of an abrasive paper template and reduced graphene oxide. The sensitivity of the graphene pressure sensor with random distribution spinosum (RDS) microstructure is as high as 25.1 kPa -1 in a wide linearity range of 0-2.6 kPa. Our pressure sensor exhibits superior comprehensive properties compared with previous surface-modified pressure sensors. According to simulation and mechanism analyses, the spinosum microstructure and random distribution contribute to the high sensitivity and large linearity range, respectively. In addition, the pressure sensor shows promising potential in detecting human physiological signals, such as heartbeat, respiration, phonation, and human motions of a pushup, arm bending, and walking. The wearable pressure sensor array was further used to detect gait states of supination, neutral, and pronation. The RDS microstructure provides an alternative strategy to improve the performance of pressure sensors and extend their potential applications in monitoring human activities.

High sensitive detection of copper II ions using D-penicillamine-coated gold nanorods based on localized surface plasmon resonance

NASA Astrophysics Data System (ADS)

Hong, Yoochan; Jo, Seongjae; Park, Joohyung; Park, Jinsung; Yang, Jaemoon

2018-05-01

In this paper, we describe the development of a nanoplasmonic biosensor based on the localized surface plasmon resonance (LSPR) effect that enables a sensitive and selective recognition of copper II ions. First, we fabricated the nanoplasmonics as LSPR substrates using gold nanorods (GNR) and the nano-adsorption method. The LSPR sensitivity of the nanoplasmonics was evaluated using various solvents with different refractive indexes. Subsequently, D-penicillamine (DPA)—a chelating agent of copper II ions—was conjugated to the surface of the GNR. The limit of detection (LOD) for the DPA-conjugated nanoplasmonics was 100 pM. Furthermore, selectivity tests were conducted using various divalent cations, and sensitivity tests were conducted on the nanoplasmonics under blood-like environments. Finally, the developed nanoplasmonic biosensor based on GNR shows great potential for the effective recognition of copper II ions, even in human blood conditions.

High sensitive detection of copper II ions using D-penicillamine-coated gold nanorods based on localized surface plasmon resonance.

PubMed

Hong, Yoochan; Jo, Seongjae; Park, Joohyung; Park, Jinsung; Yang, Jaemoon

2018-05-25

In this paper, we describe the development of a nanoplasmonic biosensor based on the localized surface plasmon resonance (LSPR) effect that enables a sensitive and selective recognition of copper II ions. First, we fabricated the nanoplasmonics as LSPR substrates using gold nanorods (GNR) and the nano-adsorption method. The LSPR sensitivity of the nanoplasmonics was evaluated using various solvents with different refractive indexes. Subsequently, D-penicillamine (DPA)-a chelating agent of copper II ions-was conjugated to the surface of the GNR. The limit of detection (LOD) for the DPA-conjugated nanoplasmonics was 100 pM. Furthermore, selectivity tests were conducted using various divalent cations, and sensitivity tests were conducted on the nanoplasmonics under blood-like environments. Finally, the developed nanoplasmonic biosensor based on GNR shows great potential for the effective recognition of copper II ions, even in human blood conditions.

The Sensitivity of U.S. Surface Ozone Formation to NOx, and VOCs as Viewed from Space

NASA Technical Reports Server (NTRS)

Duncan, Bryan N.; Yoshida, Yasuko; Sillman, Sanford; Retscher, Christian; Pickering, Kenneth E.; Martin, Randall V.; Celarier, Edward A.

2009-01-01

We investigated variations in the sensitivity of surface ozone formation in summer to precursor species concentrations of volatile organic compounds (VOCs) and nitrogen oxides (NO(x)) as inferred from the ratio of tropospheric columns of formaldehyde and nitrogen dioxide from the Aura Ozone Monitoring Instrument (OMI). The data indicate that ozone formation became: 1. more sensitive to NO(x) over most of the U.S, from 2005 to 2007 because of substantial decreases in NO(x) emissions primarily from stationary sources, and 2. more sensitive to NO(x) with increasing temperature, in part because emissions of highly reactive, biogenic isoprene increase with temperature, thus increasing the total VOC reactivity. Based on our interpretation of the data, current strategies implemented to reduce unhealthy levels of surface ozone should focus more on reducing NO(x) emissions, except in some downtown areas which have historically benefited from reductions in VOC emissions.

Comparison of the Sensitivity of Surface Downward Longwave Radiation to Changes in Water Vapor at Two High Elevation Sites

NASA Technical Reports Server (NTRS)

Chen, Yonghua; Naud, Catherine M.; Rangwala, Imtiaz; Landry, Christopher C.; Miller, James R.

2014-01-01

Among the potential reasons for enhanced warming rates in many high elevation regions is the nonlinear relationship between surface downward longwave radiation (DLR) and specific humidity (q). In this study we use ground-based observations at two neighboring high elevation sites in Southwestern Colorado that have different local topography and are 1.3 kilometers apart horizontally and 348 meters vertically. We examine the spatial consistency of the sensitivities (partial derivatives) of DLR with respect to changes in q, and the sensitivities are obtained from the Jacobian matrix of a neural network analysis. Although the relationship between DLR and q is the same at both sites, the sensitivities are higher when q is smaller, which occurs more frequently at the higher elevation site. There is a distinct hourly distribution in the sensitivities at both sites especially for high sensitivity cases, although the range is greater at the lower elevation site. The hourly distribution of the sensitivities relates to that of q. Under clear skies during daytime, q is similar between the two sites, however under cloudy skies or at night, it is not. This means that the DLR-q sensitivities are similar at the two sites during daytime but not at night, and care must be exercised when using data from one site to infer the impact of water vapor feedbacks at another site, particularly at night. Our analysis suggests that care should be exercised when using the lapse rate adjustment to infill high frequency data in a complex topographical region, particularly when one of the stations is subject to cold air pooling as found here.

Quasi physisorptive two dimensional tungsten oxide nanosheets with extraordinary sensitivity and selectivity to NO2.

PubMed

Khan, Hareem; Zavabeti, Ali; Wang, Yichao; Harrison, Christopher J; Carey, Benjamin J; Mohiuddin, Md; Chrimes, Adam F; De Castro, Isabela Alves; Zhang, Bao Yue; Sabri, Ylias M; Bhargava, Suresh K; Ou, Jian Zhen; Daeneke, Torben; Russo, Salvy P; Li, Yongxiang; Kalantar-Zadeh, Kourosh

2017-12-14

Attributing to their distinct thickness and surface dependent physicochemical properties, two dimensional (2D) nanostructures have become an area of increasing interest for interfacial interactions. Effectively, properties such as high surface-to-volume ratio, modulated surface activities and increased control of oxygen vacancies make these types of materials particularly suitable for gas-sensing applications. This work reports a facile wet-chemical synthesis of 2D tungsten oxide nanosheets by sonication of tungsten particles in an acidic environment and thermal annealing thereafter. The resultant product of large nanosheets with intrinsic substoichiometric properties is shown to be highly sensitive and selective to nitrogen dioxide (NO 2 ) gas, which is a major pollutant. The strong synergy between polar NO 2 molecules and tungsten oxide surface and also abundance of active surface sites on the nanosheets for molecule interactions contribute to the exceptionally sensitive and selective response. An extraordinary response factor of ∼30 is demonstrated to ultralow 40 parts per billion (ppb) NO 2 at a relatively low operating temperature of 150 °C, within the physisorption temperature band for tungsten oxide. Selectivity to NO 2 is demonstrated and the theory behind it is discussed. The structural, morphological and compositional characteristics of the synthesised and annealed materials are extensively characterised and electronic band structures are proposed. The demonstrated 2D tungsten oxide based sensing device holds the greatest promise for producing future commercial low-cost, sensitive and selective NO 2 gas sensors.

Testing of stack-unit/aquifer sensitivity analysis using contaminant plume distribution in the subsurface of Savannah River Site, South Carolina, USA

USGS Publications Warehouse

Rine, J.M.; Shafer, J.M.; Covington, E.; Berg, R.C.

2006-01-01

Published information on the correlation and field-testing of the technique of stack-unit/aquifer sensitivity mapping with documented subsurface contaminant plumes is rare. The inherent characteristic of stack-unit mapping, which makes it a superior technique to other analyses that amalgamate data, is the ability to deconstruct the sensitivity analysis on a unit-by-unit basis. An aquifer sensitivity map, delineating the relative sensitivity of the Crouch Branch aquifer of the Administrative/Manufacturing Area (A/M) at the Savannah River Site (SRS) in South Carolina, USA, incorporates six hydrostratigraphic units, surface soil units, and relevant hydrologic data. When this sensitivity map is compared with the distribution of the contaminant tetrachloroethylene (PCE), PCE is present within the Crouch Branch aquifer within an area classified as highly sensitive, even though the PCE was primarily released on the ground surface within areas classified with low aquifer sensitivity. This phenomenon is explained through analysis of the aquifer sensitivity map, the groundwater potentiometric surface maps, and the plume distributions within the area on a unit-by- unit basis. The results of this correlation show how the paths of the PCE plume are influenced by both the geology and the groundwater flow. ?? Springer-Verlag 2006.

Field-effect sensors - from pH sensing to biosensing: sensitivity enhancement using streptavidin-biotin as a model system.

PubMed

Lowe, Benjamin M; Sun, Kai; Zeimpekis, Ioannis; Skylaris, Chris-Kriton; Green, Nicolas G

2017-11-06

Field-Effect Transistor sensors (FET-sensors) have been receiving increasing attention for biomolecular sensing over the last two decades due to their potential for ultra-high sensitivity sensing, label-free operation, cost reduction and miniaturisation. Whilst the commercial application of FET-sensors in pH sensing has been realised, their commercial application in biomolecular sensing (termed BioFETs) is hindered by poor understanding of how to optimise device design for highly reproducible operation and high sensitivity. In part, these problems stem from the highly interdisciplinary nature of the problems encountered in this field, in which knowledge of biomolecular-binding kinetics, surface chemistry, electrical double layer physics and electrical engineering is required. In this work, a quantitative analysis and critical review has been performed comparing literature FET-sensor data for pH-sensing with data for sensing of biomolecular streptavidin binding to surface-bound biotin systems. The aim is to provide the first systematic, quantitative comparison of BioFET results for a single biomolecular analyte, specifically streptavidin, which is the most commonly used model protein in biosensing experiments, and often used as an initial proof-of-concept for new biosensor designs. This novel quantitative and comparative analysis of the surface potential behaviour of a range of devices demonstrated a strong contrast between the trends observed in pH-sensing and those in biomolecule-sensing. Potential explanations are discussed in detail and surface-chemistry optimisation is shown to be a vital component in sensitivity-enhancement. Factors which can influence the response, yet which have not always been fully appreciated, are explored and practical suggestions are provided on how to improve experimental design.

H3PO4 treated surface modified CuS counter electrodes with high electrocatalytic activity for enhancing photovoltaic performance of quantum dot-sensitized solar cells

NASA Astrophysics Data System (ADS)

Panthakkal Abdul Muthalif, Mohammed; Sunesh, Chozhidakath Damodharan; Choe, Youngson

2018-05-01

Herein we report a simple synthetic strategy to prepare highly efficient and surface modified CuS counter electrodes (CEs) for quantum dot-sensitized solar cells (QDSSCs) in the presence of phosphoric acid (H3PO4) using the chemical bath deposition method. This is the first report of successful treatment of H3PO4 on the surface of CuS CEs for designing a high-performance QDSSCs with improved photovoltaic properties. After optimization, the 4 ml H3PO4 treated CuS CE-based QDSSC exhibits excellent photovoltaic performance with a conversion efficiency (η) of 4.20% (Voc = 0.592 V, Jsc = 13.35 mA cm-2, FF = 0.532) under one full-sun illumination (100 mW cm-2, AM 1.5 G).

Surface-enhanced raman spectroscopy substrate for arsenic sensing in groundwater

DOEpatents

Yang, Peidong; Mulvihill, Martin; Tao, Andrea R.; Sinsermsuksakul, Prasert; Arnold, John

2015-06-16

A surface-enhanced Raman spectroscopy (SERS) substrate formed from a plurality of monolayers of polyhedral silver nanocrystals, wherein at least one of the monolayers has polyvinypyrrolidone (PVP) on its surface, and thereby configured for sensing arsenic is described. Highly active SERS substrates are formed by assembling high density monolayers of differently shaped silver nanocrystals onto a solid support. SERS detection is performed directly on this substrate by placing a droplet of the analyte solution onto the nanocrystal monolayer. Adsorbed polymer, polyvinypyrrolidone (PVP), on the surface of the nanoparticles facilitates the binding of both arsenate and arsenite near the silver surface, allowing for highly accurate and sensitive detection capabilities.

A climatology of visible surface reflectance spectra

NASA Astrophysics Data System (ADS)

Zoogman, Peter; Liu, Xiong; Chance, Kelly; Sun, Qingsong; Schaaf, Crystal; Mahr, Tobias; Wagner, Thomas

2016-09-01

We present a high spectral resolution climatology of visible surface reflectance as a function of wavelength for use in satellite measurements of ozone and other atmospheric species. The Tropospheric Emissions: Monitoring of Pollution (TEMPO) instrument is planned to measure backscattered solar radiation in the 290-740 nm range, including the ultraviolet and visible Chappuis ozone bands. Observation in the weak Chappuis band takes advantage of the relative transparency of the atmosphere in the visible to achieve sensitivity to near-surface ozone. However, due to the weakness of the ozone absorption features this measurement is more sensitive to errors in visible surface reflectance, which is highly variable. We utilize reflectance measurements of individual plant, man-made, and other surface types to calculate the primary modes of variability of visible surface reflectance at a high spectral resolution, comparable to that of TEMPO (0.6 nm). Using the Moderate-resolution Imaging Spectroradiometer (MODIS) Bidirection Reflectance Distribution Function (BRDF)/albedo product and our derived primary modes we construct a high spatial resolution climatology of wavelength-dependent surface reflectance over all viewing scenes and geometries. The Global Ozone Monitoring Experiment-2 (GOME-2) Lambertian Equivalent Reflectance (LER) product provides complementary information over water and snow scenes. Preliminary results using this approach in multispectral ultraviolet+visible ozone retrievals from the GOME-2 instrument show significant improvement to the fitting residuals over vegetated scenes.

Ultrasensitive Biosensors Using Enhanced Fano Resonances in Capped Gold Nanoslit Arrays

PubMed Central

Lee, Kuang-Li; Huang, Jhih-Bin; Chang, Jhih-Wei; Wu, Shu-Han; Wei, Pei-Kuen

2015-01-01

Nanostructure-based sensors are capable of sensitive and label-free detection for biomedical applications. However, plasmonic sensors capable of highly sensitive detection with high-throughput and low-cost fabrication techniques are desirable. We show that capped gold nanoslit arrays made by thermal-embossing nanoimprint method on a polymer film can produce extremely sharp asymmetric resonances for a transverse magnetic-polarized wave. An ultrasmall linewidth is formed due to the enhanced Fano coupling between the cavity resonance mode in nanoslits and surface plasmon resonance mode on periodic metallic surface. With an optimal slit length and width, the full width at half-maximum bandwidth of the Fano mode is only 3.68 nm. The wavelength sensitivity is 926 nm/RIU for 60-nm-width and 1,000-nm-period nanoslits. The figure of merit is up to 252. The obtained value is higher than the theoretically estimated upper limits of the prism-coupling SPR sensors and the previously reported record high figure-of-merit in array sensors. In addition, the structure has an ultrahigh intensity sensitivity up to 48,117%/RIU. PMID:25708955

Demonstration of near infrared gas sensing using gold nanodisks on functionalized silicon.

PubMed

Rodríguez-Cantó, P J; Martínez-Marco, M; Rodríguez-Fortuño, F J; Tomás-Navarro, B; Ortuño, R; Peransí-Llopis, S; Martínez, A

2011-04-11

In this work, we demonstrate experimentally the use of an array of gold nanodisks on functionalized silicon for chemosensing purposes. The metallic nanostructures are designed to display a very strong plasmonic resonance in the infrared regime, which results in highly sensitive sensing. Unlike usual experiments which are based on the functionalization of the metal surface, we functionalized here the silicon substrate. This silicon surface was modified chemically by buildup of an organosilane self-assembled monolayer (SAM) containing isocyanate as functional group. These groups allow for an easy surface regeneration by simple heating, thanks to the thermally reversible interaction isocyanate-analyte, which allows the cyclic use of the sensor. The technique showed a high sensitivity to surface binding events in gas and allowed the surface regeneration by heating of the sensor at 150 °C. A relative wavelength shift ∆λ(max)λ(0)=0.027 was obtained when the saturation level was reached. © 2011 Optical Society of America

Design of surface modifications for nanoscale sensor applications.

PubMed

Reimhult, Erik; Höök, Fredrik

2015-01-14

Nanoscale biosensors provide the possibility to miniaturize optic, acoustic and electric sensors to the dimensions of biomolecules. This enables approaching single-molecule detection and new sensing modalities that probe molecular conformation. Nanoscale sensors are predominantly surface-based and label-free to exploit inherent advantages of physical phenomena allowing high sensitivity without distortive labeling. There are three main criteria to be optimized in the design of surface-based and label-free biosensors: (i) the biomolecules of interest must bind with high affinity and selectively to the sensitive area; (ii) the biomolecules must be efficiently transported from the bulk solution to the sensor; and (iii) the transducer concept must be sufficiently sensitive to detect low coverage of captured biomolecules within reasonable time scales. The majority of literature on nanoscale biosensors deals with the third criterion while implicitly assuming that solutions developed for macroscale biosensors to the first two, equally important, criteria are applicable also to nanoscale sensors. We focus on providing an introduction to and perspectives on the advanced concepts for surface functionalization of biosensors with nanosized sensor elements that have been developed over the past decades (criterion (iii)). We review in detail how patterning of molecular films designed to control interactions of biomolecules with nanoscale biosensor surfaces creates new possibilities as well as new challenges.

Design of Surface Modifications for Nanoscale Sensor Applications

PubMed Central

Reimhult, Erik; Höök, Fredrik

2015-01-01

Nanoscale biosensors provide the possibility to miniaturize optic, acoustic and electric sensors to the dimensions of biomolecules. This enables approaching single-molecule detection and new sensing modalities that probe molecular conformation. Nanoscale sensors are predominantly surface-based and label-free to exploit inherent advantages of physical phenomena allowing high sensitivity without distortive labeling. There are three main criteria to be optimized in the design of surface-based and label-free biosensors: (i) the biomolecules of interest must bind with high affinity and selectively to the sensitive area; (ii) the biomolecules must be efficiently transported from the bulk solution to the sensor; and (iii) the transducer concept must be sufficiently sensitive to detect low coverage of captured biomolecules within reasonable time scales. The majority of literature on nanoscale biosensors deals with the third criterion while implicitly assuming that solutions developed for macroscale biosensors to the first two, equally important, criteria are applicable also to nanoscale sensors. We focus on providing an introduction to and perspectives on the advanced concepts for surface functionalization of biosensors with nanosized sensor elements that have been developed over the past decades (criterion (iii)). We review in detail how patterning of molecular films designed to control interactions of biomolecules with nanoscale biosensor surfaces creates new possibilities as well as new challenges. PMID:25594599

Fast, high sensitivity dewpoint hygrometer

NASA Technical Reports Server (NTRS)

Hoenk, Michael E. (Inventor)

1998-01-01

A dewpoint/frostpoint hygrometer that uses a surface moisture-sensitive sensor as part of an RF oscillator circuit with feedback control of the sensor temperature to maintain equilibrium at the sensor surface between ambient water vapor and condensed water/ice. The invention is preferably implemented using a surface acoustic wave (SAW) device in an RF oscillator circuit configured to generate a condensation-dependent output signal, a temperature sensor to measure the temperature of the SAW device and to distinguish between condensation-dependent and temperature-dependent signals, a temperature regulating device to control the temperature of the SAW device, and a feedback control system configured to keep the condensation-dependent signal nearly constant over time in the presence of time-varying humidity, corrected for temperature. The effect of this response is to heat or cool the surface moisture-sensitive device, which shifts the equilibrium with respect to evaporation and condensation at the surface of the device. The equilibrium temperature under feedback control is a measure of dewpoint or frostpoint.

Highly sensitive protein detection by biospecific AFM-based fishing with pulsed electrical stimulation.

PubMed

Pleshakova, Tatyana O; Malsagova, Kristina A; Kaysheva, Anna L; Kopylov, Arthur T; Tatur, Vadim Yu; Ziborov, Vadim S; Kanashenko, Sergey L; Galiullin, Rafael A; Ivanov, Yuri D

2017-08-01

We report here the highly sensitive detection of protein in solution at concentrations from 10 -15 to 10 -18 m using the combination of atomic force microscopy (AFM) and mass spectrometry. Biospecific detection of biotinylated bovine serum albumin was carried out by fishing out the protein onto the surface of AFM chips with immobilized avidin, which determined the specificity of the analysis. Electrical stimulation was applied to enhance the fishing efficiency. A high sensitivity of detection was achieved by application of nanosecond electric pulses to highly oriented pyrolytic graphite placed under the AFM chip. A peristaltic pump-based flow system, which is widely used in routine bioanalytical assays, was employed throughout the analysis. These results hold promise for the development of highly sensitive protein detection methods using nanosensor devices.

Impact of high resolution land surface initialization in Indian summer monsoon simulation using a regional climate model

NASA Astrophysics Data System (ADS)

Unnikrishnan, C. K.; Rajeevan, M.; Rao, S. Vijaya Bhaskara

2016-06-01

The direct impact of high resolution land surface initialization on the forecast bias in a regional climate model in recent years over Indian summer monsoon region is investigated. Two sets of regional climate model simulations are performed, one with a coarse resolution land surface initial conditions and second one used a high resolution land surface data for initial condition. The results show that all monsoon years respond differently to the high resolution land surface initialization. The drought monsoon year 2009 and extended break periods were more sensitive to the high resolution land surface initialization. These results suggest that the drought monsoon year predictions can be improved with high resolution land surface initialization. Result also shows that there are differences in the response to the land surface initialization within the monsoon season. Case studies of heat wave and a monsoon depression simulation show that, the model biases were also improved with high resolution land surface initialization. These results show the need for a better land surface initialization strategy in high resolution regional models for monsoon forecasting.

Optical transfer function in corneal topography for clinical contrast sensitivity analysis

NASA Astrophysics Data System (ADS)

Bende, Thomas; Jean, Benedikt J.; Oltrup, Theo

2000-06-01

Customized ablation aiming to optimize visual acuity in refractive surgery requires objective data on corneal surface, like the contrast sensitivity. Fast ray tracing, using the high resolution 3-D elevation data in conjunction with Snell's law describe the diffraction of the incident rays and the resulting image on a 'virtual retina.' A retroprojection leads to a 'surface quality map.' For objective contrast sensitivity measurement a sinus (or cos) wave of different frequencies is used for a calculated projection in analogy to the clinical contrast sensitivity charts. The projection on the individual cornea surface is analyzed for the Modular Transfer Function (MTF) and the Phase Shift Function (PSF) as a function of frequencies. PSF, not yet clinically used, is a parameter to determine even minimal corneal tilt. The resulting corneal aberration map (CAM) as described here and applied to a 4.5 D PRK (OZD equals 6.5 mm) reveals that the area of minimal aberration measures only 4.2 mm. The CAM can likewise be used to describe the 'quality' of a laser system's ablation pattern based upon the area of minimal optical aberrations. The CAM only describes surface aberration with high resolution, an advantage over wave front sensing which measures all accumulated optical aberrations including the changing ones of the lens during accommodation and the transient ones due to lens aging and early cataract formation.

Quantum-Dot-Based Electrochemical Immunoassay for High-Throughput Screening of the Prostate-Specific Antigen

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Jun; Liu, Guodong; Wu, Hong

2008-01-01

In this paper, we demonstrate an electrochemical high-throughput sensing platform for simple, sensitive detection of PSA based on QD labels. This sensing platform uses a microplate for immunoreactions and disposable screen-printed electrodes (SPE) for electrochemical stripping analysis of metal ions released from QD labels. With the 96-well microplate, capturing antibodies are conveniently immobilized to the well surface, and the process of immunoreaction is easily controlled. The formed sandwich complexes on the well surface are also easily isolated from reaction solutions. In particular, a microplate-based electrochemical assay can make it feasible to conduct a parallel analysis of several samples or multiplemore » protein markers. This assay offers a number of advantages including (1) simplicity, cost-effectiveness, (2) high sensitivity, (3) capability to sense multiple samples or targets in parallel, and (4) a potentially portable device with an SPE array implanted in the microplate. This PSA assay is sensitive because it uses two amplification processes: (1) QDs as a label for enhancing electrical signal since secondary antibodies are linked to QDs that contain a large number of metal atoms and (2) there is inherent signal amplification for electrochemical stripping analysis—preconcentration of metal ion onto the electrode surface for amplifying electrical signals. Therefore, the high sensitivity of this method, stemming from dual signal amplification via QD labels and pre-concentration, allows low concentration levels to be detected while using small sample volumes. Thus, this QD-based electrochemical detection approach offers a simple, rapid, cost-effective, and high throughput assay of PSA.« less

Sensitivity Analysis of the Land Surface Model NOAH-MP for Different Model Fluxes

NASA Astrophysics Data System (ADS)

Mai, Juliane; Thober, Stephan; Samaniego, Luis; Branch, Oliver; Wulfmeyer, Volker; Clark, Martyn; Attinger, Sabine; Kumar, Rohini; Cuntz, Matthias

2015-04-01

Land Surface Models (LSMs) use a plenitude of process descriptions to represent the carbon, energy and water cycles. They are highly complex and computationally expensive. Practitioners, however, are often only interested in specific outputs of the model such as latent heat or surface runoff. In model applications like parameter estimation, the most important parameters are then chosen by experience or expert knowledge. Hydrologists interested in surface runoff therefore chose mostly soil parameters while biogeochemists interested in carbon fluxes focus on vegetation parameters. However, this might lead to the omission of parameters that are important, for example, through strong interactions with the parameters chosen. It also happens during model development that some process descriptions contain fixed values, which are supposedly unimportant parameters. However, these hidden parameters remain normally undetected although they might be highly relevant during model calibration. Sensitivity analyses are used to identify informative model parameters for a specific model output. Standard methods for sensitivity analysis such as Sobol indexes require large amounts of model evaluations, specifically in case of many model parameters. We hence propose to first use a recently developed inexpensive sequential screening method based on Elementary Effects that has proven to identify the relevant informative parameters. This reduces the number parameters and therefore model evaluations for subsequent analyses such as sensitivity analysis or model calibration. In this study, we quantify parametric sensitivities of the land surface model NOAH-MP that is a state-of-the-art LSM and used at regional scale as the land surface scheme of the atmospheric Weather Research and Forecasting Model (WRF). NOAH-MP contains multiple process parameterizations yielding a considerable amount of parameters (˜ 100). Sensitivities for the three model outputs (a) surface runoff, (b) soil drainage and (c) latent heat are calculated on twelve Model Parameter Estimation Experiment (MOPEX) catchments ranging in size from 1020 to 4421 km2. This allows investigation of parametric sensitivities for distinct hydro-climatic characteristics, emphasizing different land-surface processes. The sequential screening identifies the most informative parameters of NOAH-MP for different model output variables. The number of parameters is reduced substantially for all of the three model outputs to approximately 25. The subsequent Sobol method quantifies the sensitivities of these informative parameters. The study demonstrates the existence of sensitive, important parameters in almost all parts of the model irrespective of the considered output. Soil parameters, e.g., are informative for all three output variables whereas plant parameters are not only informative for latent heat but also for soil drainage because soil drainage is strongly coupled to transpiration through the soil water balance. These results contrast to the choice of only soil parameters in hydrological studies and only plant parameters in biogeochemical ones. The sequential screening identified several important hidden parameters that carry large sensitivities and have hence to be included during model calibration.

Portable SERS sensor for malachite green and other small dye molecules

NASA Astrophysics Data System (ADS)

Qiu, Suyan; Zhao, Fusheng; Li, Jingting; Shih, Wei-Chuan

2017-02-01

Sensitive detection of specific chemicals on site can be extremely powerful in many fields. Owing to its molecular fingerprinting capability, surface-enhanced Raman scattering has been one of the technological contenders. In this paper, we describe the novel use of DNA topological nanostructure on nanoporous gold nanoparticle (NPG-NP) array chip for chemical sensing. NPG-NP features large surface area and high-density plasmonic field enhancement known as "hotspots". Hence, NPG-NP array chip has found many applications in nanoplasmonic sensor development. This technique can provide novel label-free molecular sensing capability and enables high sensitivity and specificity detection using a portable Raman spectrometer.

Highly sensitive electrochemical detection of cocaine on graphene/AuNP modified electrode via catalytic redox-recycling amplification.

PubMed

Jiang, Bingying; Wang, Min; Chen, Ying; Xie, Jiaqing; Xiang, Yun

2012-02-15

We demonstrated a new strategy for highly sensitive electrochemical detection of cocaine by using two engineered aptamers in connection to redox-recycling signal amplification. The graphene/AuNP nanocomposites were electrochemically deposited on a screen printed carbon electrode to enhance the electron transfers. The cocaine primary binding aptamers were self-assembled on the electrode surface through sulfur-Au interactions. The presence of the target cocaine and the biotin-modified secondary binding aptamers leads to the formation of sandwich complexes on the electrode surface. The streptavidin-conjugated alkaline phosphatases (ALPs) were used as labels to generate quantitative signals. The addition of the ALP substrate and the co-reactant NADH results in the formation of a redox cycle between the enzymatic product and the electrochemically oxidized species and the signal is thus significantly amplified. Because of the effective modification of the sensing surface and signal amplification, low nanomolar (1 nM) detection limit for cocaine is achieved. The proposed aptamer-based sandwich sensing approach for amplified detection of cocaine thus opens new opportunities for highly sensitive determination of other small molecules. Copyright © 2011 Elsevier B.V. All rights reserved.

Optimizing the loss of one-dimensional photonic crystal towards high-sensitivity Bloch-surface-wave sensors under intensity interrogation scheme

NASA Astrophysics Data System (ADS)

Kong, Weijing; Wan, Yuhang; Du, Kun; Zhao, Wenhui; Wang, Shuang; Zheng, Zheng

2016-11-01

The reflected intensity change of the Bloch-surface-wave (BSW) resonance influenced by the loss of a truncated onedimensional photonic crystal structure is numerically analyzed and studied in order to enhance the sensitivity of the Bloch-surface-wave-based sensors. The finite truncated one-dimensional photonic crystal structure is designed to be able to excite BSW mode for water (n=1.33) as the external medium and for p-polarized plane wave incident light. The intensity interrogation scheme which can be operated on a typical Kretschmann prism-coupling configuration by measuring the reflected intensity change of the resonance dip is investigated to optimize the sensitivity. A figure of merit (FOM) is introduced to measure the performance of the one-dimensional photonic crystal multilayer structure under the scheme. The detection sensitivities are calculated under different device parameters with a refractive index change corresponding to different solutions of glycerol in de-ionized (DI)-water. The results show that the intensity sensitivity curve varies similarly with the FOM curve and the sensitivity of the Bloch-surface-wave sensor is greatly affected by the device loss, where an optimized loss value can be got. For the low-loss BSW devices, the intensity interrogation sensing sensitivity may drop sharply from the optimal value. On the other hand, the performance of the detection scheme is less affected by the higher device loss. This observation is in accordance with BSW experimental sensing demonstrations as well. The results obtained could be useful for improving the performance of the Bloch-surface-wave sensors for the investigated sensing scheme.

Real-Time, Single-Step Bioassay Using Nanoplasmonic Resonator With Ultra-High Sensitivity

NASA Technical Reports Server (NTRS)

Zhang, Xiang (Inventor); Chen, Fanqing Frank (Inventor); Su, Kai-Hang (Inventor); Wei, Qi-Huo (Inventor); Ellman, Jonathan A. (Inventor); Sun, Cheng (Inventor)

2014-01-01

A nanoplasmonic resonator (NPR) comprising a metallic nanodisk with alternating shielding layer(s), having a tagged biomolecule conjugated or tethered to the surface of the nanoplasmonic resonator for highly sensitive measurement of enzymatic activity. NPRs enhance Raman signals in a highly reproducible manner, enabling fast detection of protease and enzyme activity, such as Prostate Specific Antigen (paPSA), in real-time, at picomolar sensitivity levels. Experiments on extracellular fluid (ECF) from paPSA-positive cells demonstrate specific detection in a complex bio-fluid background in real-time single-step detection in very small sample volumes.

Real-time, single-step bioassay using nanoplasmonic resonator with ultra-high sensitivity

DOEpatents

Zhang, Xiang; Ellman, Jonathan A; Chen, Fanqing Frank; Su, Kai-Hang; Wei, Qi-Huo; Sun, Cheng

2014-04-01

A nanoplasmonic resonator (NPR) comprising a metallic nanodisk with alternating shielding layer(s), having a tagged biomolecule conjugated or tethered to the surface of the nanoplasmonic resonator for highly sensitive measurement of enzymatic activity. NPRs enhance Raman signals in a highly reproducible manner, enabling fast detection of protease and enzyme activity, such as Prostate Specific Antigen (paPSA), in real-time, at picomolar sensitivity levels. Experiments on extracellular fluid (ECF) from paPSA-positive cells demonstrate specific detection in a complex bio-fluid background in real-time single-step detection in very small sample volumes.

Self-assembled two-dimensional gold nanoparticle film for sensitive nontargeted analysis of food additives with surface-enhanced Raman spectroscopy.

PubMed

Wu, Yiping; Yu, Wenfang; Yang, Benhong; Li, Pan

2018-05-15

The use of different food additives and their active metabolites has been found to cause serious problems to human health. Thus, considering the potential effects on human health, developing a sensitive and credible analytical method for different foods is important. Herein, the application of solvent-driven self-assembled Au nanoparticles (Au NPs) for the rapid and sensitive detection of food additives in different commercial products is reported. The assembled substrates are highly sensitive and exhibit excellent uniformity and reproducibility because of uniformly distributed and high-density hot spots. The sensitive analyses of ciprofloxacin (CF), diethylhexyl phthalate (DEHP), tartrazine and azodicarbonamide at the 0.1 ppm level using this surface-enhanced Raman spectroscopy (SERS) substrate are given, and the results show that Au NP arrays can serve as efficient SERS substrates for the detection of food additives. More importantly, SERS spectra of several commercial liquors and sweet drinks are obtained to evaluate the addition of illegal additives. This SERS active platform can be used as an effective strategy in the detection of prohibited additives in food.

Surface-enhanced Raman scattering (SERS) detection of multiple viral antigens using magnetic capture of SERS-active nanoparticles

USDA-ARS?s Scientific Manuscript database

A highly sensitive immunoassay based on surface-enhanced Raman scattering (SERS) spectroscopy has been developed for multiplex detection of surface envelope and capsid antigens of the viral zoonotic pathogens West Nile virus (WNV) and Rift Valley fever virus (RVFV). Detection was mediated by antibo...

Electrochemically enhanced antibody immobilization on polydopamine thin film for sensitive surface plasmon resonance immunoassay.

PubMed

Chen, Daqun; Mei, Yihong; Hu, Weihua; Li, Chang Ming

2018-05-15

For sensitive immunoassay, it is essentially important to immobilize antibody on a surface with high density and full retention of their recognition activity. Bio-inspired polydopamine (PDA) thin film has been widely utilized as a reactive coating to immobilize antibody on various surfaces. We herein report that the antibody immobilization capacity of PDA thin film is electrochemically enhanced by applying an oxidative potential to convert the surface catechol group to reactive quinone group. Quantitative surface plasmon resonance (SPR) investigation unveils that upon proper electrochemical oxidization, the antibody loading capacity of PDA film is significantly improved (up to 27%) and is very close to the theoretically maximal capacity of a planar surface if concentrated antibody solution is used. Using prostate-specific antigen (PSA) as a model target, it is further demonstrated that the SPR immunoassay sensitivity is greatly enhanced due to the improved antibody immobilization. This work offers an efficient strategy to enhance the reactivity of PDA film towards nucleophiles, and may also facilitate its immunoassay application among others. Copyright © 2018 Elsevier B.V. All rights reserved.

System performance testing of the DVA1 radio telescope

NASA Astrophysics Data System (ADS)

Knee, Lewis B. G.; Baker, Lynn A.; Gray, Andrew D.; Hovey, Gary J.; Kesteven, Michael J.; Lacy, Gordon; Robishaw, Timothy

2016-07-01

DVA1 (Dish Verification Antenna 1) is a highly innovative rim-supported single-piece composite-material dish radio telescope developed at the National Research Council Canada (NRC). It has a feed-high offset Gregorian optical design with a primary effective diameter of 15 m. DVA1 has been undergoing mechanical and astronomical system tests since 2014. Astronomical measurements were made in L band using a prototype front end developed for MeerKAT by EMSS Antennas (South Africa), including aperture efficiency, beam profiles, sensitivity, and tipping curves. The clean shaped optics, careful attention to feed design, and high sensitivity of the L band receiver (Trx 6 K) yield a system with high aperture efficiency ( 0.8), excellent sensitivity ( 9 m2/K), and low spillover ( 4 K). Observations of 21 cm atomic hydrogen lines towards standard sources demonstrate the low stray radiation pickup of the antenna. Ku band holography has measured the effective surface accuracy and stability of the dual-reflector antenna. The effective RMS of 0.85 mm implies a Ruze efficiency of 0.88 at 10 GHz and 0.60 at 20 GHz. The surface is stable ( 10% variation in surface RMS) over the limited range of environmental conditions tested. Testing continues for characterization of pointing, low frequency performance (< 1 GHz), and polarimetric performance. NRC is developing a successor antenna, DVA3, which will have a more accurate surface and be usable at frequencies at least up to Q band (30 - 50 GHz).

Hydroxy-Al and cell-surface negativity are responsible for the enhanced sensitivity of Rhodotorula taiwanensis to aluminum by increased medium pH.

PubMed

Zhao, Xue Qiang; Bao, Xue Min; Wang, Chao; Xiao, Zuo Yi; Hu, Zhen Min; Zheng, Chun Li; Shen, Ren Fang

2017-10-01

Aluminum (Al) is ubiquitous and toxic to microbes. High Al 3+ concentration and low pH are two key factors responsible for Al toxicity, but our present results contradict this idea. Here, an Al-tolerant yeast strain Rhodotorula taiwanensis RS1 was incubated in glucose media containing Al with a continuous pH gradient from pH 3.1-4.2. The cells became more sensitive to Al and accumulated more Al when pH increased. Calculations using an electrostatic model Speciation Gouy Chapman Stern indicated that, the increased Al sensitivity of cells was associated with AlOH 2+ and Al(OH) 2 + rather than Al 3+ . The alcian blue (a positively charged dye) adsorption and zeta potential determination of cell surface indicated that, higher pH than 3.1 increased the negative charge and Al adsorption at the cell surface. Taken together, the enhanced sensitivity of R. taiwanensis RS1 to Al from pH 3.1-4.2 was associated with increased hydroxy-Al and cell-surface negativity.

Graphene-bimetal plasmonic platform for ultra-sensitive biosensing

NASA Astrophysics Data System (ADS)

Tong, Jinguang; Jiang, Li; Chen, Huifang; Wang, Yiqin; Yong, Ken-Tye; Forsberg, Erik; He, Sailing

2018-03-01

A graphene-bimetal plasmonic platform for surface plasmon resonance biosensing with ultra-high sensitivity was proposed and optimized. In this hybrid configuration, graphene nanosheets was employed to effectively absorb the excitation light and serve as biomolecular recognition elements for increased adsorption of analytes. Coating of an additional Au film prevents oxidation of the Ag substrate during manufacturing process and enhances the sensitivity at the same time. Thus, a bimetal Au-Ag substrate enables improved sensing performance and promotes stability of this plasmonic sensor. In this work we optimized the number of graphene layers as well as the thickness of the Au film and the Ag substrate based on the phase-interrogation sensitivity. We found an optimized configuration consisting of 6 layers of graphene coated on a bimetal surface consisting of a 5 nm Au film and a 30 nm Ag film. The calculation results showed the configuration could achieve a phase sensitivity as high as 1 . 71 × 106 deg/RIU, which was more than 2 orders of magnitude higher than that of bimetal structure and graphene-silver structure. Due to this enhanced sensing performance, the graphene-bimetal plasmonic platform proposed in this paper is potential for ultra-sensitive plasmonic sensing.

Visuomotor sensitivity to visual information about surface orientation.

PubMed

Knill, David C; Kersten, Daniel

2004-03-01

We measured human visuomotor sensitivity to visual information about three-dimensional surface orientation by analyzing movements made to place an object on a slanted surface. We applied linear discriminant analysis to the kinematics of subjects' movements to surfaces with differing slants (angle away form the fronto-parallel) to derive visuomotor d's for discriminating surfaces differing in slant by 5 degrees. Subjects' visuomotor sensitivity to information about surface orientation was very high, with discrimination "thresholds" ranging from 2 to 3 degrees. In a first experiment, we found that subjects performed only slightly better using binocular cues alone than monocular texture cues and that they showed only weak evidence for combining the cues when both were available, suggesting that monocular cues can be just as effective in guiding motor behavior in depth as binocular cues. In a second experiment, we measured subjects' perceptual discrimination and visuomotor thresholds in equivalent stimulus conditions to decompose visuomotor sensitivity into perceptual and motor components. Subjects' visuomotor thresholds were found to be slightly greater than their perceptual thresholds for a range of memory delays, from 1 to 3 s. The data were consistent with a model in which perceptual noise increases with increasing delay between stimulus presentation and movement initiation, but motor noise remains constant. This result suggests that visuomotor and perceptual systems rely on the same visual estimates of surface slant for memory delays ranging from 1 to 3 s.

Sensitivity of Fermi level position at Ga-polar, N-polar, and nonpolar m-plane GaN surfaces to vacuum and air ambient

NASA Astrophysics Data System (ADS)

Janicki, Łukasz; Ramírez-López, Manolo; Misiewicz, Jan; Cywiński, Grzegorz; Boćkowski, Michał; Muzioł, Grzegorz; Chèze, Caroline; Sawicka, Marta; Skierbiszewski, Czesław; Kudrawiec, Robert

2016-05-01

Ga-polar, N-polar, and nonpolar m-plane GaN UN+ structures have been examined in air and vacuum ambient by contactless electroreflectance (CER). This technique is very sensitive to the surface electric field that varies with the Fermi level position at the surface. For UN+ GaN structures [i.e., GaN (undoped)/GaN (n-type)/substrate], a homogeneous built-in electric field is expected in the undoped GaN layer that is manifested by Franz-Keldysh oscillation (FKO) in CER spectra. A clear change in FKO has been observed in CER spectra for N-polar and nonpolar m-plane structures when changing from air to vacuum ambient. This means that those surfaces are very sensitive to ambient atmosphere. In contrast to that, only a small change in FKO can be seen in the Ga-polar structure. This clearly shows that the ambient sensitivity of the Fermi level position at the GaN surface varies with the crystallographic orientation and is very high for N-polar and nonpolar m-plane surfaces. This feature of the N-polar and nonpolar m-plane surfaces can be very important for GaN-based devices grown on these crystallographic orientations and can be utilized in some of the devices, e.g., sensors.

Immune biosensors based on the SPR and TIRE: efficiency of their application for bacteria determination

NASA Astrophysics Data System (ADS)

Starodub, N. F.; Ogorodniichuk, J.; Lebedeva, T.; Shpylovyy, P.

2013-11-01

In this work we have designed high-specific biosensors for Salmonella typhimurium detection based on the surface plasmon resonance (SPR) and total internal reflection ellipsometry (TIRE). It has been demonstrated high selectivity and sensitivity of analysis. As a registering part for our experiments the Spreeta (USA) and "Plasmonotest" (Ukraine) with flowing cell have been applied among of SPR device. Previous researches confirmed an efficiency of SPR biosensors using for detecting of specific antigen-antibody interactions therefore this type of reactions with some previous preparations of surface binding layer was used as reactive part. It has been defined that in case with Spreeta sensitivity was on the level 103 - 107 cells/ml. Another biosensor based on the SPR has shown the sensitivity within 101 - 106 cells/ml. Maximal sensitivity was on the level of several cells in 10 ml (up to the fact that less than 5 cells) which has been obtained using the biosensor based on TIRE.

Highly improved ethanol gas-sensing performance of mesoporous nickel oxides nanowires with the stannum donor doping.

PubMed

Wei, Junqi; Li, Xiaoqing; Han, Yanbing; Xu, Jingcai; Jin, Hongxiao; Jin, Dingfeng; Peng, Xiaoling; Hong, Bo; Li, Jing; Yang, Yanting; Ge, Hongliang; Wang, Xinqing

2018-06-15

Mesoporous nickel oxides (NiO) and stannum(Sn)-doped NiO nanowires (NWs) were synthesized by using SBA-15 templates with the nanocasting method. X-ray diffraction, transmission electron microscope, energy dispersive spectrometry, nitrogen adsorption/desorption isotherm and UV-vis spectrum were used to characterize the phase structure, components and microstructure of the as-prepared samples. The gas-sensing analysis indicated that the Sn-doping could greatly improve the ethanol sensitivity for mesoporous NiO NWs. With the increasing Sn content, the ethanol sensitivity increased from 2.16 for NiO NWs up to the maximum of 15.60 for Ni 0.962 Sn 0.038 O 1.038 , and then decreased to 12.24 for Ni 0.946 Sn 0.054 O 1.054 to 100 ppm ethanol gas at 340 °C. The high surface area from the Sn-doping improved the adsorption of oxygen on the surface of NiO NWs, resulting in the smaller surface resistance in air. Furthermore, owing to the recombination of the holes in hole-accumulation lay with the electrons from the donor impurity level and the increasing the body defects for Sn-doping, the total resistance in ethanol gas enhanced greatly. It was concluded that the sensitivity of Sn-doped NiO NWs based sensor could be greatly improved by the higher surface area and high-valence donor substitution from Sn-doping.

Atomic layer deposition in nanostructured photovoltaics: tuning optical, electronic and surface properties

NASA Astrophysics Data System (ADS)

Palmstrom, Axel F.; Santra, Pralay K.; Bent, Stacey F.

2015-07-01

Nanostructured materials offer key advantages for third-generation photovoltaics, such as the ability to achieve high optical absorption together with enhanced charge carrier collection using low cost components. However, the extensive interfacial areas in nanostructured photovoltaic devices can cause high recombination rates and a high density of surface electronic states. In this feature article, we provide a brief review of some nanostructured photovoltaic technologies including dye-sensitized, quantum dot sensitized and colloidal quantum dot solar cells. We then introduce the technique of atomic layer deposition (ALD), which is a vapor phase deposition method using a sequence of self-limiting surface reaction steps to grow thin, uniform and conformal films. We discuss how ALD has established itself as a promising tool for addressing different aspects of nanostructured photovoltaics. Examples include the use of ALD to synthesize absorber materials for both quantum dot and plasmonic solar cells, to grow barrier layers for dye and quantum dot sensitized solar cells, and to infiltrate coatings into colloidal quantum dot solar cell to improve charge carrier mobilities as well as stability. We also provide an example of monolayer surface modification in which adsorbed ligand molecules on quantum dots are used to tune the band structure of colloidal quantum dot solar cells for improved charge collection. Finally, we comment on the present challenges and future outlook of the use of ALD for nanostructured photovoltaics.

Highly improved ethanol gas-sensing performance of mesoporous nickel oxides nanowires with the stannum donor doping

NASA Astrophysics Data System (ADS)

Wei, Junqi; Li, Xiaoqing; Han, Yanbing; Xu, Jingcai; Jin, Hongxiao; Jin, Dingfeng; Peng, Xiaoling; Hong, Bo; Li, Jing; Yang, Yanting; Ge, Hongliang; Wang, Xinqing

2018-06-01

Mesoporous nickel oxides (NiO) and stannum(Sn)-doped NiO nanowires (NWs) were synthesized by using SBA-15 templates with the nanocasting method. X-ray diffraction, transmission electron microscope, energy dispersive spectrometry, nitrogen adsorption/desorption isotherm and UV–vis spectrum were used to characterize the phase structure, components and microstructure of the as-prepared samples. The gas-sensing analysis indicated that the Sn-doping could greatly improve the ethanol sensitivity for mesoporous NiO NWs. With the increasing Sn content, the ethanol sensitivity increased from 2.16 for NiO NWs up to the maximum of 15.60 for Ni0.962Sn0.038O1.038, and then decreased to 12.24 for Ni0.946Sn0.054O1.054 to 100 ppm ethanol gas at 340 °C. The high surface area from the Sn-doping improved the adsorption of oxygen on the surface of NiO NWs, resulting in the smaller surface resistance in air. Furthermore, owing to the recombination of the holes in hole-accumulation lay with the electrons from the donor impurity level and the increasing the body defects for Sn-doping, the total resistance in ethanol gas enhanced greatly. It was concluded that the sensitivity of Sn-doped NiO NWs based sensor could be greatly improved by the higher surface area and high-valence donor substitution from Sn-doping.

Transient partial permeabilization with saponin enables cellular barcoding prior to surface marker staining1

PubMed Central

Behbehani, Gregory K.; Thom, Colin; Zunder, Eli R.; Finck, Rachel; Gaudilliere, Brice; Fragiadakis, Gabriela K.; Fantl, Wendy J.; Nolan, Garry P.

2015-01-01

Fluorescent cellular barcoding and mass-tag cellular barcoding are cytometric methods that enable high sample throughput, minimize inter-sample variation, and reduce reagent consumption. Previously employed barcoding protocols require that barcoding be performed after surface marker staining, complicating combining the technique with measurement of alcohol-sensitive surface epitopes. This report describes a method of barcoding fixed cells after a transient partial permeabilization with 0.02% saponin that results in efficient and consistent barcode staining with fluorescent or mass-tagged reagents while preserving surface marker staining. This approach simplifies barcoding protocols and allows direct comparison of surface marker staining of multiple samples without concern for variations in the antibody cocktail volume, antigen-antibody ratio, or machine sensitivity. Using this protocol, cellular barcoding can be used to reliably detect subtle differences in surface marker expression. PMID:25274027

Proximity charge sensing for semiconductor detectors

DOEpatents

Luke, Paul N; Tindall, Craig S; Amman, Mark

2013-10-08

A non-contact charge sensor includes a semiconductor detector having a first surface and an opposing second surface. The detector includes a high resistivity electrode layer on the first surface and a low resistivity electrode on the high resistivity electrode layer. A portion of the low resistivity first surface electrode is deleted to expose the high resistivity electrode layer in a portion of the area. A low resistivity electrode layer is disposed on the second surface of the semiconductor detector. A voltage applied between the first surface low resistivity electrode and the second surface low resistivity electrode causes a free charge to drift toward the first or second surface according to a polarity of the free charge and the voltage. A charge sensitive preamplifier coupled to a non-contact electrode disposed at a distance from the exposed high resistivity electrode layer outputs a signal in response to movement of free charge within the detector.

Factors dominating 3-dimensional ozone distribution during high tropospheric ozone period.

PubMed

Chen, Xiaoyang; Liu, Yiming; Lai, Anqi; Han, Shuangshuang; Fan, Qi; Wang, Xuemei; Ling, Zhenhao; Huang, Fuxiang; Fan, Shaojia

2018-01-01

Data from an in situ monitoring network and five ozone sondes are analysed during August of 2012, and a high tropospheric ozone episode is observed around the 8th of AUG. The Community Multi-scale Air Quality (CMAQ) model and its process analysis tool were used to study factors and mechanisms for high ozone mixing ratio at different levels of ozone vertical profiles. A sensitive scenario without chemical initial and boundary conditions (ICBCs) from MOZART4-GEOS5 was applied to study the impact of stratosphere-troposphere exchange (STE) on vertical ozone. The simulation results indicated that the first high ozone peak near the tropopause was dominated by STE. Results from process analysis showed that: in the urban area, the second peak at approximately 2 km above ground height was mainly caused by local photochemical production. The third peak (near surface) was mainly caused by the upwind transportation from the suburban/rural areas; in the suburban/rural areas, local photochemical production of ozone dominated the high ozone mixing ratio from the surface to approximately 3 km height. Furthermore, the capability of indicators to distinguish O 3 -precursor sensitivity along the vertical O 3 profiles was investigated. Two sensitive scenarios, which had cut 30% anthropogenic NO X or VOC emissions, showed that O 3 -precursor indicators, specifically the ratios of O 3 /NOy, H 2 O 2 /HNO 3 or H 2 O 2 /NO Z , could partly distinguish the O 3 -precursor sensitivity between VOCs-sensitive and NOx-sensitive along the vertical profiles. In urban area, the O 3 -precursor relationship transferred from VOCs-sensitive within the boundary layer to NOx-sensitive at approximately 1-3 km above ground height, further confirming the dominant roles of transportation and photochemical production in high O 3 peaks at the near-ground layer and 2 km above ground height, respectively. Copyright © 2017 Elsevier Ltd. All rights reserved.

Measurement of surface shear stress vector beneath high-speed jet flow using liquid crystal coating

NASA Astrophysics Data System (ADS)

Wang, Cheng-Peng; Zhao, Ji-Song; Jiao, Yun; Cheng, Ke-Ming

2018-05-01

The shear-sensitive liquid crystal coating (SSLCC) technique is investigated in the high-speed jet flow of a micro-wind-tunnel. An approach to measure surface shear stress vector distribution using the SSLCC technique is established, where six synchronous cameras are used to record the coating color at different circumferential view angles. Spatial wall shear stress vector distributions on the test surface are obtained at different velocities. The results are encouraging and demonstrate the great potential of the SSLCC technique in high-speed wind-tunnel measurement.

Photonic Crystal Enhanced Fluorescence for Early Breast Cancer Biomarker Detection

PubMed Central

Cunningham, Brian T.; Zangar, Richard C.

2013-01-01

Photonic crystal surfaces offer a compelling platform for improving the sensitivity of surface-based fluorescent assays used in disease diagnostics. Through the complementary processes of photonic crystal enhanced excitation and enhanced extraction, a periodic dielectric-based nanostructured surface can simultaneously increase the electric field intensity experienced by surface-bound fluorophores and increase the collection efficiency of emitted fluorescent photons. Through the ability to inexpensively fabricate photonic crystal surfaces over substantial surface areas, they are amenable to single-use applications in biological sensing, such as disease biomarker detection in serum. In this review, we will describe the motivation for implementing high-sensitivity, multiplexed biomarker detection in the context of breast cancer diagnosis. We will summarize recent efforts to improve the detection limits of such assays though the use of photonic crystal surfaces. Reduction of detection limits is driven by low autofluorescent substrates for photonic crystal fabrication, and detection instruments that take advantage of their unique features. PMID:22736539

Highly sensitive surface-enhanced Raman scattering substrate made from superaligned carbon nanotubes.

PubMed

Sun, Yinghui; Liu, Kai; Miao, Jiao; Wang, Zheyao; Tian, Baozhong; Zhang, Lina; Li, Qunqing; Fan, Shoushan; Jiang, Kaili

2010-05-12

Surface-enhanced Raman scattering (SERS) has attracted wide attention because it can enhance normally weak Raman signal by several orders of magnitude and facilitate the sensitive detection of molecules. Conventional SERS substrates are constructed by placing metal nanoparticles on a planar surface. Here we show that, if the planar surface was substituted by a unique nanoporous surface, the enhancement effect can be dramatically improved. The nanoporous surface can be easily fabricated in batches and at low costs by cross stacking superaligned carbon nanotube films. The as-prepared transparent and freestanding SERS substrate is capable of detecting ambient trinitrotoluene vapor, showing much higher Raman enhancement than ordinary planar substrates because of the extremely large surface area and the unique zero-dimensional at one-dimensional nanostructure. These results not only provide a new approach to ultrasensitive SERS substrates, but also are helpful for improving the fundamental understanding of SERS phenomena.

Wireless ultrasound-powered biotelemetry for implants.

PubMed

Towe, Bruce C; Larson, Patrick J; Gulick, Daniel W

2009-01-01

A miniature piezoelectric receiver coupled to a diode is evaluated as a simple device for wireless transmission of bioelectric events to the body surface. The device converts the energy of a surface-applied ultrasound beam to a high frequency carrier current in solution. Bioelectrical currents near the implant modulate the carrier amplitude, and this signal is remotely detected and demodulated to recover the biopotential waveform. This technique achieves millivolt sensitivity in saline tank tests, and further attention to system design is expected to improve sensitivity.

Methods for growth of relatively large step-free SiC crystal surfaces

NASA Technical Reports Server (NTRS)

Neudeck, Philip G. (Inventor); Powell, J. Anthony (Inventor)

2002-01-01

A method for growing arrays of large-area device-size films of step-free (i.e., atomically flat) SiC surfaces for semiconductor electronic device applications is disclosed. This method utilizes a lateral growth process that better overcomes the effect of extended defects in the seed crystal substrate that limited the obtainable step-free area achievable by prior art processes. The step-free SiC surface is particularly suited for the heteroepitaxial growth of 3C (cubic) SiC, AlN, and GaN films used for the fabrication of both surface-sensitive devices (i.e., surface channel field effect transistors such as HEMT's and MOSFET's) as well as high-electric field devices (pn diodes and other solid-state power switching devices) that are sensitive to extended crystal defects.

Theoretical study of surface plasmon resonance sensors based on 2D bimetallic alloy grating

NASA Astrophysics Data System (ADS)

Dhibi, Abdelhak; Khemiri, Mehdi; Oumezzine, Mohamed

2016-11-01

A surface plasmon resonance (SPR) sensor based on 2D alloy grating with a high performance is proposed. The grating consists of homogeneous alloys of formula MxAg1-x, where M is gold, copper, platinum and palladium. Compared to the SPR sensors based a pure metal, the sensor based on angular interrogation with silver exhibits a sharper (i.e. larger depth-to-width ratio) reflectivity dip, which provides a big detection accuracy, whereas the sensor based on gold exhibits the broadest dips and the highest sensitivity. The detection accuracy of SPR sensor based a metal alloy is enhanced by the increase of silver composition. In addition, the composition of silver which is around 0.8 improves the sensitivity and the quality of SPR sensor of pure metal. Numerical simulations based on rigorous coupled wave analysis (RCWA) show that the sensor based on a metal alloy not only has a high sensitivity and a high detection accuracy, but also exhibits a good linearity and a good quality.

Reasonable Temperature Schedules for Cold or Hot Charging of Continuously Cast Steel Slabs

NASA Astrophysics Data System (ADS)

Li, Yang; Chen, Xin; Liu, Ke; Wang, Jing; Wen, Jin; Zhang, Jiaquan

2013-12-01

Some continuously cast steel slabs are sensitive to transverse fracture problems during transportation or handling away from their storage state, while some steel slabs are sensitive to surface transverse cracks during the following rolling process in a certain hot charging temperature range. It is revealed that the investigated steel slabs with high fracture tendency under room cooling condition always contain pearlite transformation delayed elements, which lead to the internal brittle bainitic structure formation, while some microalloyed steels exhibit high surface crack susceptibility to hot charging temperatures due to carbonitride precipitation. According to the calculated internal cooling rates and CCT diagrams, the slabs with high fracture tendency during cold charging should be slowly cooled after cutting to length from hot strand or charged to the reheating furnace directly above their bainite formation temperatures. Based on a thermodynamic calculation for carbonitride precipitation in austenite, the sensitive hot charging temperature range of related steels was revealed for the determination of reasonable temperature schedules.

Sensitive Adsorptive Voltammetric Method for Determination of Bisphenol A by Gold Nanoparticle/Polyvinylpyrrolidone-Modified Pencil Graphite Electrode

PubMed Central

Yaman, Yesim Tugce; Abaci, Serdar

2016-01-01

A novel electrochemical sensor gold nanoparticle (AuNP)/polyvinylpyrrolidone (PVP) modified pencil graphite electrode (PGE) was developed for the ultrasensitive determination of Bisphenol A (BPA). The gold nanoparticles were electrodeposited by constant potential electrolysis and PVP was attached by passive adsorption onto the electrode surface. The electrode surfaces were characterized by electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). The parameters that affected the experimental conditions were researched and optimized. The AuNP/PVP/PGE sensor provided high sensitivity and selectivity for BPA recognition by using square wave adsorptive stripping voltammetry (SWAdSV). Under optimized conditions, the detection limit was found to be 1.0 nM. This new sensor system offered the advantages of simple fabrication which aided the expeditious replication, low cost, fast response, high sensitivity and low background current for BPA. This new sensor system was successfully tested for the detection of the amount of BPA in bottled drinking water with high reliability. PMID:27231912

Interactions Between Mineral Surfaces, Substrates, Enzymes, and Microbes Result in Hysteretic Temperature Sensitivities and Microbial Carbon Use Efficiencies and Weaker Predicted Carbon-Climate Feedbacks

NASA Astrophysics Data System (ADS)

Riley, W. J.; Tang, J.

2014-12-01

We hypothesize that the large observed variability in decomposition temperature sensitivity and carbon use efficiency arises from interactions between temperature, microbial biogeochemistry, and mineral surface sorptive reactions. To test this hypothesis, we developed a numerical model that integrates the Dynamic Energy Budget concept for microbial physiology, microbial trait-based community structure and competition, process-specific thermodynamically ­­based temperature sensitivity, a non-linear mineral sorption isotherm, and enzyme dynamics. We show, because mineral surfaces interact with substrates, enzymes, and microbes, both temperature sensitivity and microbial carbon use efficiency are hysteretic and highly variable. Further, by mimicking the traditional approach to interpreting soil incubation observations, we demonstrate that the conventional labile and recalcitrant substrate characterization for temperature sensitivity is flawed. In a 4 K temperature perturbation experiment, our fully dynamic model predicted more variable but weaker carbon-climate feedbacks than did the static temperature sensitivity and carbon use efficiency model when forced with yearly, daily, and hourly variable temperatures. These results imply that current earth system models likely over-estimate the response of soil carbon stocks to global warming.

Detection of heavy metal ions in contaminated water by surface plasmon resonance based optical fibre sensor using conducting polymer and chitosan.

PubMed

Verma, Roli; Gupta, Banshi D

2015-01-01

Optical fibre surface plasmon resonance (SPR) based sensor for the detection of heavy metal ions in the drinking water is designed. Silver (Ag) metal and indium tin oxide (ITO) are used for the fabrication of the SPR probe which is further modified with the coating of pyrrole and chitosan composite. The sensor works on the wavelength interrogation technique and is capable of detecting trace amounts of Cd(2+), Pb(2+), and Hg(2+) heavy metal ions in contaminated water. Four types of sensing probes are fabricated and characterised for heavy metal ions out of these pyrrole/chitosan/ITO/Ag coated probe is found to be highly sensitive among all other probes. Further, the cadmium ions bind strongly to the sensing surface than other ions and due to this the sensor is highly sensitive for Cd(2+) ions. The sensor's performance is best for the low concentrations of heavy metal ions and its sensitivity decreases with the increasing concentration of heavy metal ions. Copyright © 2014 Elsevier Ltd. All rights reserved.

Surface electronic structure of SmB6(111)

NASA Astrophysics Data System (ADS)

Ohtsubo, Yoshiyuki; Hagiwara, Kenta; Wang, Chengwei; Yukawa, Ryu; Horiba, Koji; Kumigashira, Hiroshi; Hirano, Wataru; Iga, Fumitoshi; Kimura, Shin-ichi

2018-05-01

Samarium hexaboride (SmB6) is the most extensively studied candidate of topological Kondo insulators. To clarify the topological origin of metallic surface states observed on the SmB6(001) surfaces, we studied the surface electronic structure of SmB6 on the other surface orientation, SmB6(111). Although the SmB6(111) surface cannot be obtained by cleaving, we successfully obtained the well-defined clean surface by high-temperature annealing of the mechanically polished single crystal of SmB6(111) in an ultra-high vacuum. The valence band spectra obtained by photoelectron spectroscopy with the bulk and surface-sensitive incident photon energies imply that the surface is covered with B6 cluster without Sm atoms.

Surface Desorption Dielectric-Barrier Discharge Ionization Mass Spectrometry.

PubMed

Zhang, Hong; Jiang, Jie; Li, Na; Li, Ming; Wang, Yingying; He, Jing; You, Hong

2017-07-18

A variant of dielectric-barrier discharge named surface desorption dielectric-barrier discharge ionization (SDDBDI) mass spectrometry was developed for high-efficiency ion transmission and high spatial resolution imaging. In SDDBDI, a tungsten nanotip and the inlet of the mass spectrometer are used as electrodes, and a piece of coverslip is used as a sample plate as well as an insulating dielectric barrier, which simplifies the configuration of instrument and thus the operation. Different from volume dielectric-barrier discharge (VDBD), the microdischarges are generated on the surface at SDDBDI, and therefore the plasma density is extremely high. Analyte ions are guided directly into the MS inlet without any deflection. This configuration significantly improves the ion transmission efficiency and thus the sensitivity. The dependence of sensitivity and spatial resolution of the SDDBDI on the operation parameters were systematically investigated. The application of SDDBDI was successfully demonstrated by analysis of multiple species including amino acids, pharmaceuticals, putative cancer biomarkers, and mixtures of both fatty acids and hormones. Limits of detection (S/N = 3) were determined to be 0.84 and 0.18 pmol, respectively, for the analysis of l-alanine and metronidazole. A spatial resolution of 22 μm was obtained for the analysis of an imprinted cyclophosphamide pattern, and imaging of a "T" character was successfully demonstrated under ambient conditions. These results indicate that SDDBDI has high-efficiency ion transmission, high sensitivity, and high spatial resolution, which render it a potential tool for mass spectrometry imaging.

Investigation of a Photoelectrochemical Passivated ZnO-Based Glucose Biosensor

PubMed Central

Lee, Ching-Ting; Chiu, Ying-Shuo; Ho, Shu-Ching; Lee, Yao-Jung

2011-01-01

A vapor cooling condensation system was used to deposit high quality intrinsic ZnO thin films and intrinsic ZnO nanorods as the sensing membrane of extended-gate field-effect-transistor (EGFET) glucose biosensors. The sensing sensitivity of the resulting glucose biosensors operated in the linear range was 13.4 μA mM−1 cm−2. To improve the sensing sensitivity of the ZnO-based glucose biosensors, the photoelectrochemical method was utilized to passivate the sidewall surfaces of the ZnO nanorods. The sensing sensitivity of the ZnO-based glucose biosensors with passivated ZnO nanorods was significantly improved to 20.33 μA mM−1 cm−2 under the same measurement conditions. The experimental results verified that the sensing sensitivity improvement was the result of the mitigation of the Fermi level pinning effect caused by the dangling bonds and the surface states induced on the sidewall surface of the ZnO nanorods. PMID:22163867

Performance analysis of higher mode spoof surface plasmon polariton for terahertz sensing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yao, Haizi; Tu, Wanli; Zhong, Shuncong, E-mail: zhongshuncong@hotmail.com

2015-04-07

We investigated the spoof surface plasmon polaritons (SSPPs) on 1D grooved metal surface for terahertz sensing of refractive index of the filling analyte through a prism-coupling attenuated total reflection setup. From the dispersion relation analysis and the finite element method-based simulation, we revealed that the dispersion curve of SSPP got suppressed as the filling refractive index increased, which cause the coupling resonance frequency redshifting in the reflection spectrum. The simulated results for testing various refractive indexes demonstrated that the incident angle of terahertz radiation has a great effect on the performance of sensing. Smaller incident angle will result in amore » higher sensitive sensing with a narrower detection range. In the meanwhile, the higher order mode SSPP-based sensing has a higher sensitivity with a narrower detection range. The maximum sensitivity is 2.57 THz/RIU for the second-order mode sensing at 45° internal incident angle. The proposed SSPP-based method has great potential for high sensitive terahertz sensing.« less

Instrumentation in molecular imaging.

PubMed

Wells, R Glenn

2016-12-01

In vivo molecular imaging is a challenging task and no single type of imaging system provides an ideal solution. Nuclear medicine techniques like SPECT and PET provide excellent sensitivity but have poor spatial resolution. Optical imaging has excellent sensitivity and spatial resolution, but light photons interact strongly with tissues and so only small animals and targets near the surface can be accurately visualized. CT and MRI have exquisite spatial resolution, but greatly reduced sensitivity. To overcome the limitations of individual modalities, molecular imaging systems often combine individual cameras together, for example, merging nuclear medicine cameras with CT or MRI to allow the visualization of molecular processes with both high sensitivity and high spatial resolution.

Analysis of dispersion and attenuation of surface waves in poroelastic media in the exploration-seismic frequency band

USGS Publications Warehouse

Zhang, Y.; Xu, Y.; Xia, J.

2011-01-01

We analyse dispersion and attenuation of surface waves at free surfaces of possible vacuum/poroelastic media: permeable-'open pore', impermeable-'closed pore' and partially permeable boundaries, which have not been previously reported in detail by researchers, under different surface-permeable, viscous-damping, elastic and fluid-flowing conditions. Our discussion is focused on their characteristics in the exploration-seismic frequency band (a few through 200 Hz) for near-surface applications. We find two surface-wave modes exist, R1 waves for all conditions, and R2 waves for closed-pore and partially permeable conditions. For R1 waves, velocities disperse most under partially permeable conditions and least under the open-pore condition. High-coupling damping coefficients move the main dispersion frequency range to high frequencies. There is an f1 frequency dependence as a constant-Q model for attenuation at high frequencies. R1 waves for the open pore are most sensitive to elastic modulus variation, but least sensitive to tortuosities variation. R1 waves for partially permeable surface radiate as non-physical waves (Im(k) < 0) at low frequencies. For R2 waves, velocities are slightly lower than the bulk slow P2 waves. At low frequencies, both velocity and attenuation are diffusive of f1/2 frequency dependence, as P2 waves. It is found that for partially permeable surfaces, the attenuation displays -f1 frequency dependence as frequency increasing. High surface permeability, low-coupling damping coefficients, low Poisson's ratios, and low tortuosities increase the slope of the -f1 dependence. When the attenuation coefficients reach 0, R2 waves for partially permeable surface begin to radiate as non-physical waves. ?? 2011 The Authors Geophysical Journal International ?? 2011 RAS.

A Sensitivity Enhanced MWCNT/PDMS Tactile Sensor Using Micropillars and Low Energy Ar⁺ Ion Beam Treatment.

PubMed

Azkar Ul Hasan, Syed; Jung, Youngdo; Kim, Seonggi; Jung, Cho-Long; Oh, Sunjong; Kim, Junhee; Lim, Hyuneui

2016-01-12

High sensitive flexible and wearable devices which can detect delicate touches have attracted considerable attentions from researchers for various promising applications. This research was aimed at enhancing the sensitivity of a MWCNT/PDMS piezoresistive tactile sensor through modification of its surface texture in the form of micropillars on MWCNT/PDMS film and subsequent low energy Ar⁺ ion beam treatment of the micropillars. The introduction of straight micropillars on the MWCNT/PDMS surface increased the sensitivity under gentle touch. Low energy ion beam treatment was performed to induce a stiff layer on the exposed surface of the micropillar structured MWCNT/PDMS film. The low energy ion bombardment stabilized the electrical properties of the MWCNT/PDMS surface and tuned the curvature of micropillars according to the treatment conditions. The straight micropillars which were treated by Ar⁺ ion with an incident angle of 0° demonstrated the enhanced sensitivity under normal pressure and the curved micropillars which were treated with Ar⁺ ion with an incident angle of 60° differentiated the direction of an applied shear pressure. The ion beam treatment on micropillar structured MWCNT/PDMS tactile sensors can thus be applied to reliable sensing under gentle touch with directional discrimination.

High sensitivity, high surface area Enzyme-linked Immunosorbent Assay (ELISA).

PubMed

Singh, Harpal; Morita, Takahiro; Suzuki, Yuma; Shimojima, Masayuki; Le Van, An; Sugamata, Masami; Yang, Ming

2015-01-01

Enzyme-linked immunosorbent assays (ELISA) are considered the gold standard in the demonstration of various immunological reactions with an application in the detection of infectious diseases such as during outbreaks or in patient care. This study aimed to produce an ELISA-based diagnostic with an increased sensitivity of detection compared to the standard 96-well method in the immunologic diagnosis of infectious diseases. A '3DStack' was developed using readily available, low cost fabrication technologies namely nanoimprinting and press stamping with an increased surface area of 4 to 6 times more compared to 96-well plates. This was achieved by stacking multiple nanoimprinted polymer sheets. The flow of analytes between the sheets was enhanced by rotating the 3DStack and confirmed by Finite-Element (FE) simulation. An Immunoglobulin G (IgG) ELISA for the detection of antibodies in human serum raised against Rubella virus was performed for validation. An improved sensitivity of up to 1.9 folds higher was observed using the 3DStack compared to the standard method. The increased surface area of the 3DStack developed using nanoimprinting and press stamping technologies, and the flow pattern between sheets generated by rotating the 3DStack were potential contributors to a more sensitive ELISA-based diagnostic device.

The global distribution of Martian permafrost

NASA Technical Reports Server (NTRS)

Paige, David A.

1991-01-01

Accurately determining the present global distribution of Martian ground ice will be an important step towards understanding the evolution of the Martian surface and atmosphere, and could greatly facilitate human and robotic exploration of the planet. The quantitative Mars permafrost studies demonstrated the potential importance of a number of factors determining the past and present distribution of subsurface ice on Mars, but have not considered the issue of regional variability. To consider the distribution of Mars permafrost in greater detail a new thermal model was developed that can calculate Martian surface and subsurface temperatures as a function of time-of-day and season. The results indicate that the distribution of Martian permafrost is highly sensitive to the bulk thermal properties of the overlying soil. Viking IRTM observations of diurnal surface temperature variations show that the bulk thermal properties of midlatitude surface materials exhibit a high degree of regional inhomogeneity. In general, the results show that the global distribution of permafrost is at least as sensitive to the thermal properties of the overlying surface material as it is to variations in surface isolation due to large scale variations in Mars' orbital and axial elements. In particular, they imply that subsurface ice may exist just a few centimeters below the surface in regions of low thermal inertia and high albedo, which are widespread at latitudes ranging from the equator to +60 degrees latitude.

Phase-Sensitive Surface Plasmon Resonance Sensors: Recent Progress and Future Prospects

PubMed Central

Deng, Shijie; Wang, Peng; Yu, Xinglong

2017-01-01

Surface plasmon resonance (SPR) is an optical sensing technique that is capable of performing real-time, label-free and high-sensitivity monitoring of molecular interactions. SPR biosensors can be divided according to their operating principles into angle-, wavelength-, intensity- and phase-interrogated devices. With their complex optical configurations, phase-interrogated SPR sensors generally provide higher sensitivity and throughput, and have thus recently emerged as prominent biosensing devices. To date, several methods have been developed for SPR phase interrogation, including heterodyne detection, polarimetry, shear interferometry, spatial phase modulation interferometry and temporal phase modulation interferometry. This paper summarizes the fundamentals of phase-sensitive SPR sensing, reviews the available methods for phase interrogation of these sensors, and discusses the future prospects for and trends in the development of this technology. PMID:29206182

Co-deposition of carbon dots and reduced graphene oxide nanosheets on carbon-fiber microelectrode surface for selective detection of dopamine

NASA Astrophysics Data System (ADS)

Fang, Jian; Xie, Zhigang; Wallace, Gordon; Wang, Xungai

2017-08-01

In this work, carbon dots (CD) decorated graphene oxide (GO) nanosheets were electrochemically reduced and deposited onto carbon fiber (CF) to fabricate microelectrodes for highly sensitive and selective dopamine (DA) detection, in the presence of ascorbic acid (AA) and uric acid (UA). The results have shown that surface modification considerably increases the electrocatalytic activity of the carbon fiber microelectrode. Due to possible aggregation of the rGO sheets during deposition, modifying the microelectrode surface with rGO sheets alone cannot achieve the selectivity required for simultaneous detection of DA, AA and UA. Through attaching CD onto GO sheets, the rGO + CD/CF microelectrode performance was significantly improved. The existence of CD on GO sheets can effectively avoid inter-layer stacking of the rGO sheets and provide increased surface area for neurotransmitter-electrode interaction enhancement. The CD can also increase the charge storage capacity of GO sheets. This is the first report on applying both CD and rGO for surface modification of carbon fiber microelectrode. The rGO + CD/CF microelectrode has achieved a linear DA detection concentration range of 0.1-100 μM, with a detection limit of 0.02 μM. The sensitivity of the microelectrode towards DA was as high as 6.5 nA/μM, which is significantly higher than previously reported carbon fiber microelectrodes. The highly sensitive all-carbon based microelectrodes should find use in a number of biomedical applications, such as neurotransmitter detection, neural signal recording and cell physiology studies.

Cu-modified carbon spheres/reduced graphene oxide as a high sensitivity of gas sensor for NO2 detection at room temperature

NASA Astrophysics Data System (ADS)

Su, Zhibin; Tan, Li; Yang, Ruiqiang; Zhang, Yu; Tao, Jin; Zhang, Nan; Wen, Fusheng

2018-03-01

Nitrogen dioxide (NO2) as one of the most serious air pollution is harmful to people's health, therefore high-performance gas sensors is critically needed. Here, Cu-modified carbon spheres/reduced graphene oxide (Cu@CS/RGO) composite have been prepared as NO2 gas sensor material. Carbon sphere in the interlayer of RGO can increase the specific surface area of RGO. Copper nanoparticles decorated on the surface of CS can effectively enhance the adsorption activity of RGO as supplier of free electrons. The experimental results showed that its particular structure improved the gas sensitivity of RGO at different NO2 concentrations at room temperature.

Bio-sensing applications of cerium oxide nanoparticles: Advantages and disadvantages.

PubMed

Charbgoo, Fahimeh; Ramezani, Mohammad; Darroudi, Majid

2017-10-15

Cerium oxide nanoparticles (CNPs) contain several properties such as catalytic activity, fluorescent quencher and electrochemical, high surface area, and oxygen transfer ability, which have attracted considerable attention in developing high-sensitive biosensors. CNPs can be used as a whole sensor or a part of recognition or transducer element. However, reports have shown that applying these nanoparticles in sensor design could remarkably enhance detection sensitivity. CNP's outstanding properties in biosensors which go from high catalytic activity and surface area to oxygen transfer and fluorescent quenching capabilities are also highlighted. Herein, we discuss the advantages and disadvantages of CNPs-based biosensors that function through various detection modes including colorimetric, electrochemistry, and chemoluminescent regarding the detection of small organic chemicals, metal ions and biomarkers. Copyright © 2017 Elsevier B.V. All rights reserved.

Highly sensitive nano-porous lattice biosensor based on localized surface plasmon resonance and interference.

PubMed

Yeom, Se-Hyuk; Kim, Ok-Geun; Kang, Byoung-Ho; Kim, Kyu-Jin; Yuan, Heng; Kwon, Dae-Hyuk; Kim, Hak-Rin; Kang, Shin-Won

2011-11-07

We propose a design for a highly sensitive biosensor based on nanostructured anodized aluminum oxide (AAO) substrates. A gold-deposited AAO substrate exhibits both optical interference and localized surface plasmon resonance (LSPR). In our sensor, application of these disparate optical properties overcomes problems of limited sensitivity, selectivity, and dynamic range seen in similar biosensors. We fabricated uniform periodic nanopore lattice AAO templates by two-step anodizing and assessed their suitability for application in biosensors by characterizing the change in optical response on addition of biomolecules to the AAO template. To determine the suitability of such structures for biosensing applications, we immobilized a layer of C-reactive protein (CRP) antibody on a gold coating atop an AAO template. We then applied a CRP antigen (Ag) atop the immobilized antibody (Ab) layer. The shift in reflectance is interpreted as being caused by the change in refractive index with membrane thickness. Our results confirm that our proposed AAO-based biosensor is highly selective toward detection of CRP antigen, and can measure a change in CRP antigen concentration of 1 fg/ml. This method can provide a simple, fast, and sensitive analysis for protein detection in real-time.

Chemically attached gold nanoparticle-carbon nanotube hybrids for highly sensitive SERS substrate

NASA Astrophysics Data System (ADS)

Beqa, Lule; Singh, Anant Kumar; Fan, Zheng; Senapati, Dulal; Ray, Paresh Chandra

2011-08-01

Surface-enhanced Raman spectroscopy (SERS) has been shown as one of the most powerful analytical tool with high sensitivity. In this manuscript, we report the chemical design of SERS substrate, based on gold nanoparticles of different shapes-decorated with carbon nanotube with an enhancement factor of 7.5 × 1010. Shape dependent result shows that popcorn shape gold nanoparticle decorated SWCNT is the best choice for SERS substrate due to the existence of 'lightning rod effect' through several sharp edges or corners. Our results provide a good approach to develop highly sensitive SERS substrates and can help to improve the fundamental understanding of SERS phenomena.

Wavelength-multiplexing surface plasmon holographic microscopy.

PubMed

Zhang, Jiwei; Dai, Siqing; Zhong, Jinzhan; Xi, Teli; Ma, Chaojie; Li, Ying; Di, Jianglei; Zhao, Jianlin

2018-05-14

Surface plasmon holographic microscopy (SPHM), which combines surface plasmon microscopy with digital holographic microscopy, can be applied for amplitude- and phase-contrast surface plasmon resonance (SPR) imaging. In this paper, we propose an improved SPHM with the wavelength multiplexing technique based on two laser sources and a common-path hologram recording configuration. Through recording and reconstructing the SPR images at two wavelengths simultaneously employing the improved SPHM, tiny variation of dielectric refractive index in near field is quantitatively monitored with an extended measurement range while maintaining the high sensitivity. Moreover, imaging onion tissues is performed to demonstrate that the detection sensitivities of two wavelengths can compensate for each other in SPR imaging. The proposed wavelength-multiplexing SPHM presents simple structure, high temporal stability and inherent capability of phase curvature compensation, as well as shows great potentials for further applications in monitoring diverse dynamic processes related with refractive index variations and imaging biological tissues with low-contrast refractive index distributions in the near field.

ER-mitochondria contacts control surface glycan expression and sensitivity to killer lymphocytes in glioma stem-like cells.

PubMed

Bassoy, Esen Yonca; Kasahara, Atsuko; Chiusolo, Valentina; Jacquemin, Guillaume; Boydell, Emma; Zamorano, Sebastian; Riccadonna, Cristina; Pellegatta, Serena; Hulo, Nicolas; Dutoit, Valérie; Derouazi, Madiha; Dietrich, Pierre Yves; Walker, Paul R; Martinvalet, Denis

2017-06-01

Glioblastoma is a highly heterogeneous aggressive primary brain tumor, with the glioma stem-like cells (GSC) being more sensitive to cytotoxic lymphocyte-mediated killing than glioma differentiated cells (GDC). However, the mechanism behind this higher sensitivity is unclear. Here, we found that the mitochondrial morphology of GSCs modulates the ER-mitochondria contacts that regulate the surface expression of sialylated glycans and their recognition by cytotoxic T lymphocytes and natural killer cells. GSCs displayed diminished ER-mitochondria contacts compared to GDCs. Forced ER-mitochondria contacts in GSCs increased their cell surface expression of sialylated glycans and reduced their susceptibility to cytotoxic lymphocytes. Therefore, mitochondrial morphology and dynamism dictate the ER-mitochondria contacts in order to regulate the surface expression of certain glycans and thus play a role in GSC recognition and elimination by immune effector cells. Targeting the mitochondrial morphology, dynamism, and contacts with the ER could be an innovative strategy to deplete the cancer stem cell compartment to successfully treat glioblastoma. © 2017 The Authors.

Round-patterned ZnO nanostructure coated with siloxane-based polymer for nerve agent detection

NASA Astrophysics Data System (ADS)

Choi, Hyun Ji; Lee, Ji Won; Jeong, Dong-Cheol; Ha, Seonggyun; Song, Changsik; Boo, Jin-Hyo

2018-01-01

The alignment of zinc oxide (ZnO) nanostructures is expected to improve device sensitivities due to large surface areas which can be utilized to capture significant quantities of gas particles. In this study, we investigated patterned ZnO nanorods modified with polystyrene monolayers synthesized directly onto a quartz crystal microbalance (QCM) cell to increase the coating surface area of the sensing material. Also, we designed and synthesized a siloxane-based polymer (S1 polymer) as a sensing material. The patterned ZnO nanorods coated with S1 polymers were fabricated and used for the detection of dimethyl methylphosphonate (DMMP). The resonance frequency of QCM was shifted due to the adsorption and desorption of a compound at the surface of the modified electrodes. We have synthesized an S1 polymer that exhibited high sensitivity to DMMP. The patterned ZnO nanorods coated with the polymer also exhibited improved sensitivity due to an enhanced surface area capable of adsorbing more DMMP vapor.

Resonant characteristics and sensitivity dependency on the contact surface in QCM-micropillar-based system of coupled resonator sensors

NASA Astrophysics Data System (ADS)

Kashan, M. A. M.; Kalavally, V.; Lee, H. W.; Ramakrishnan, N.

2016-05-01

We report the characteristics and sensitivity dependence over the contact surface in coupled resonating sensors (CRSs) made of high aspect ratio resonant micropillars attached to a quartz crystal microbalance (QCM). Through experiments and simulation, we observed that when the pillars of resonant heights were placed in maximum displacement regions the resonance frequency of the QCM increased following the coupled resonance characteristics, as the pillar offered elastic loading to the QCM surface. However, the same pillars when placed in relatively lower displacement regions, in spite of their resonant dimension, offered inertial loading and resulted in a decrease in QCM resonance frequency, as the displacement amplitude was insufficient to couple the vibrations from the QCM to the pillars. Accordingly, we discovered that the coupled resonance characteristics not only depend on the resonant structure dimensions but also on the contact regions in the acoustic device. Further analysis revealed that acoustic pressure at the contact surface also influences the resonance frequency characteristics and sensitivity of the CRS. To demonstrate the significance of the present finding for sensing applications, humidity sensing is considered as the example measurand. When a sensing medium made of resonant SU-8 pillars was placed in a maximum displacement region on a QCM surface, the sensitivity increased by 14 times in comparison to a resonant sensing medium placed in a lower displacement region of a QCM surface.

A novel optical-fiber based surface plasmon resonance sensing architecture and its application to gastric cancer diagnostics

NASA Astrophysics Data System (ADS)

Francois, Alexandre; Boehm, Jonathan; Penno, Megan; Hoffmann, Peter; Monro, Tanya M.

2011-05-01

The management of threats such as pandemics and explosives, and of health and the environment requires the rapid deployment of highly sensitive detection tools. Sensors based on Surface Plasmon Resonance (SPR) allow rapid, labelfree, highly sensitive detection, and indeed this phenomenon underpins the only label-free optical biosensing technology that is available commercially. In these sensors, the existence of surface plasmons is inferred indirectly from absorption features that correspond to the coupling of light to the surface plasmon. Although SPR is not intrinsically a radiative process, under certain conditions the surface plasmon can itself couple to the local photon states, and emit light. Here we show for the first time that by collecting and characterising this re-emitted light, it is possible to realise new SPR sensing architectures that are more compact, versatile and robust than existing approaches. It is applicable to a range of SPR geometries, including optical fibres. As an example, this approach has been used to demonstrate the detection of a protein identified as a being a biomarker for cancer.

Boronic Acid Functionalized Au Nanoparticles for Selective MicroRNA Signal Amplification in Fiber-Optic Surface Plasmon Resonance Sensing System.

PubMed

Qian, Siyu; Lin, Ming; Ji, Wei; Yuan, Huizhen; Zhang, Yang; Jing, Zhenguo; Zhao, Jianzhang; Masson, Jean-François; Peng, Wei

2018-05-25

MicroRNA (miRNA) regulates gene expression and plays a fundamental role in multiple biological processes. However, if both single-stranded RNA and DNA can bind with capture DNA on the sensing surface, selectively amplifying the complementary RNA signal is still challenging for researchers. Fiber-optic surface plasmon resonance (SPR) sensors are small, accurate, and convenient tools for monitoring biological interaction. In this paper, we present a high sensitivity microRNA detection technique using phenylboronic acid functionalized Au nanoparticles (PBA-AuNPs) in fiber-optic SPR sensing systems. Due to the inherent difficulty directly detecting the hybridized RNA on the sensing surface, the PBA-AuNPs were used to selectively amplify the signal of target miRNA. The result shows that the method has high selectivity and sensitivity for miRNA, with a detection limit at 2.7 × 10 -13 M (0.27 pM). This PBA-AuNPs amplification strategy is universally applicable for RNA detection with various sensing technologies, such as surface-enhanced Raman spectroscopy and electrochemistry, among others.

Integrated amplifying nanowire FET for surface and bulk sensing

NASA Astrophysics Data System (ADS)

Chui, Chi On; Shin, Kyeong-Sik

2011-10-01

For over one decade, numerous research have been performed on field-effect transistor (FET) sensors with a quasi-onedimensional (1D) nanostructure channel demonstrating highly sensitive surface and bulk sensing. The high surface and bulk sensing sensitivity respectively arises from the inherently large surface area-to-volume ratio and tiny channel volume. The generic nanowire FET sensors, however, have limitations such as impractically low output current levels especially near the limit of detection (LOD) that would require downstream remote amplification with an appreciable amount of added noise. We have recently proposed and experimentally demonstrated an innovative amplifying nanowire FET sensor structure that seamlessly integrates therein a sensing nanowire and a nanowire FET amplifier. This novel sensor structure embraces the same geometrical advantage in quasi-1D nanostructure yet it offers unprecedented closeproximity signal amplification with the lowest possible added noise. In this paper, we review the device operating principle and amplification mechanism. We also present the prototype fabrication procedures, and surface and bulk sensing experimental results showing significantly enhanced output current level difference as predicted.

Highly sensitive antenna using inkjet overprinting with particle-free conductive inks.

PubMed

Komoda, Natsuki; Nogi, Masaya; Suganuma, Katsuaki; Otsuka, Kanji

2012-11-01

Printed antennas with low signal losses and fast response in high-frequency bands have been required. Here we reported on highly sensitive antennas using additive patterning of particle-free metallo-organic decomposition silver inks. Inkjet overprinting of metallo-organic decomposition inks onto copper foil and silver nanowire line produced antenna with mirror surfaces. As a result, the overprinted antennas decreased their return losses at 0.5-4.0 GHz and increased the speed of data communication in WiFi network.

Ultrasensitive Detection of Single-Walled Carbon Nanotubes Using Surface Plasmon Resonance.

PubMed

Jang, Daeho; Na, Wonhwi; Kang, Minwook; Kim, Namjoon; Shin, Sehyun

2016-01-05

Because single-walled carbon nanotubes (SWNTs) are known to be a potentially dangerous material, inducing cancers and other diseases, any possible leakage of SWNTs through an aquatic medium such as drinking water will result in a major public threat. To solve this problem, for the present study, a highly sensitive, quantitative detection method of SWNTs in an aqueous solution was developed using surface plasmon resonance (SPR) spectroscopy. For a highly sensitive and specific detection, a strong affinity conjugation with biotin-streptavidin was adopted on an SPR sensing mechanism. During the pretreatment process, the SWNT surface was functionalized and hydrophilized using a thymine-chain based biotinylated single-strand DNA linker (B-ssDNA) and bovine serum albumin (BSA). The pretreated SWNTs were captured on a sensing film, the surface of which was immobilized with streptavidin on biotinylated gold film. The captured SWNTs were measured in real-time using SPR spectroscopy. Specific binding with SWNTs was verified through several validation experiments. The present method using an SPR sensor is capable of detecting SWNTs of as low as 100 fg/mL, which is the lowest level reported thus far for carbon-nanotube detection. In addition, the SPR sensor showed a linear characteristic within the range of 100 pg/mL to 200 ng/mL. These findings imply that the present SPR sensing method can detect an extremely low level of SWNTs in an aquatic environment with high sensitivity and high specificity, and thus any potential leakage of SWNTs into an aquatic environment can be precisely monitored within a couple of hours.

Highly sensitive photoelectrochemical biosensor for kinase activity detection and inhibition based on the surface defect recognition and multiple signal amplification of metal-organic frameworks.

PubMed

Wang, Zonghua; Yan, Zhiyong; Wang, Feng; Cai, Jibao; Guo, Lei; Su, Jiakun; Liu, Yang

2017-11-15

A turn-on photoelectrochemical (PEC) biosensor based on the surface defect recognition and multiple signal amplification of metal-organic frameworks (MOFs) was proposed for highly sensitive protein kinase activity analysis and inhibitor evaluation. In this strategy, based on the phosphorylation reaction in the presence of protein kinase A (PKA), the Zr-based metal-organic frameworks (UiO-66) accommodated with [Ru(bpy) 3 ] 2+ photoactive dyes in the pores were linked to the phosphorylated kemptide modified TiO 2 /ITO electrode through the chelation between the Zr 4+ defects on the surface of UiO-66 and the phosphate groups in kemptide. Under visible light irradiation, the excited electrons from [Ru(bpy) 3 ] 2+ adsorbed in the pores of UiO-66 injected into the TiO 2 conduction band to generate photocurrent, which could be utilized for protein kinase activities detection. The large surface area and high porosities of UiO-66 facilitated a large number of [Ru(bpy) 3 ] 2+ that increased the photocurrent significantly, and afforded a highly sensitive PEC analysis of kinase activity. The detection limit of the as-proposed PEC biosensor was 0.0049UmL -1 (S/N!=!3). The biosensor was also applied for quantitative kinase inhibitor evaluation and PKA activities detection in MCF-7 cell lysates. The developed visible-light PEC biosensor provides a simple detection procedure and a cost-effective manner for PKA activity assays, and shows great potential in clinical diagnosis and drug discoveries. Copyright © 2017 Elsevier B.V. All rights reserved.

Quantitative and Sensitive Detection of Chloramphenicol by Surface-Enhanced Raman Scattering

PubMed Central

Ding, Yufeng; Yin, Hongjun; Meng, Qingyun; Zhao, Yongmei; Liu, Luo; Wu, Zhenglong; Xu, Haijun

2017-01-01

We used surface-enhanced Raman scattering (SERS) for the quantitative and sensitive detection of chloramphenicol (CAP). Using 30 nm colloidal Au nanoparticles (NPs), a low detection limit for CAP of 10−8 M was obtained. The characteristic Raman peak of CAP centered at 1344 cm−1 was used for the rapid quantitative detection of CAP in three different types of CAP eye drops, and the accuracy of the measurement result was verified by high-performance liquid chromatography (HPLC). The experimental results reveal that the SERS technique based on colloidal Au NPs is accurate and sensitive, and can be used for the rapid detection of various antibiotics. PMID:29261161

Optical bio-chemical sensors on SNOW ring resonators.

PubMed

Khorasaninejad, Mohammadreza; Clarke, Nigel; Anantram, M P; Saini, Simarjeet Singh

2011-08-29

In this paper, we propose and analyze novel ring resonator based bio-chemical sensors on silicon nanowire optical waveguide (SNOW) and show that the sensitivity of the sensors can be increased by an order of magnitude as compared to silicon-on-insulator based ring resonators while maintaining high index contrast and compact devices. The core of the waveguide is hollow and allows for introduction of biomaterial in the center of the mode, thereby increasing the sensitivity of detection. A sensitivity of 243 nm/refractive index unit (RIU) is achieved for a change in bulk refractive index. For surface attachment, the sensor is able to detect monolayer attachments as small as 1 Å on the surface of the silicon nanowires.

Optical bio-chemical sensors on SNOW ring resonators

NASA Astrophysics Data System (ADS)

Khorasaninejad, Mohammadreza; Clarke, Nigel; Anantram, M. P.; Singh Saini, Simarjeet

2011-08-01

In this paper, we propose and analyze novel ring resonator based bio-chemical sensors on silicon nanowire optical waveguide (SNOW) and show that the sensitivity of the sensors can be increased by an order of magnitude as compared to silicon-on-insulator based ring resonators while maintaining high index contrast and compact devices. The core of the waveguide is hollow and allows for introduction of biomaterial in the center of the mode, thereby increasing the sensitivity of detection. A sensitivity of 243 nm/refractive index unit (RIU) is achieved for a change in bulk refractive index. For surface attachment, the sensor is able to detect monolayer attachments as small as 1 Å on the surface of the silicon nanowires.

QCM operating in threshold mode as a gas sensor.

PubMed

Dultsev, Fedor N; Kolosovsky, Eugeny A

2009-10-20

Application of the threshold mode allowed us to use the quartz resonator (quartz crystal microbalance, QCM) as a highly sensitive gas sensor measuring the forces of the rupture of adsorbed gas components from the resonator surface oscillating with increasing amplitude. This procedure allows one to analyze different gas components using the same surface modification, just varying the rupture threshold by varying the amplitude of shear oscillations. The sensitivity of the threshold measurements is 2 to 3 orders of magnitude higher than for the gravimetric procedure. It is demonstrated that the QCM operating as an active element can be used as a gas sensor. This procedure seems to be promising in investigating the reactivity of the surface or the interactions of gaseous components with the surface containing various functional groups, thus contributing to the surface chemistry.

Pressure-Sensitive Paint Measurements on Surfaces with Non-Uniform Temperature

NASA Technical Reports Server (NTRS)

Bencic, Timothy J.

1999-01-01

Pressure-sensitive paint (PSP) has become a useful tool to augment conventional pressure taps in measuring the surface pressure distribution of aerodynamic components in wind tunnel testing. While the PSP offers the advantage of a non-intrusive global mapping of the surface pressure, one prominent drawback to the accuracy of this technique is the inherent temperature sensitivity of the coating's luminescent intensity. A typical aerodynamic surface PSP test has relied on the coated surface to be both spatially and temporally isothermal, along with conventional instrumentation for an in situ calibration to generate the highest accuracy pressure mappings. In some tests however, spatial and temporal thermal gradients are generated by the nature of the test as in a blowing jet impinging on a surface. In these cases, the temperature variations on the painted surface must be accounted for in order to yield high accuracy and reliable data. A new temperature correction technique was developed at NASA Lewis to collapse a "family" of PSP calibration curves to a single intensity ratio versus pressure curve. This correction allows a streamlined procedure to be followed whether or not temperature information is used in the data reduction of the PSP. This paper explores the use of conventional instrumentation such as thermocouples and pressure taps along with temperature-sensitive paint (TSP) to correct for the thermal gradients that exist in aeropropulsion PSP tests. Temperature corrected PSP measurements for both a supersonic mixer ejector and jet cavity interaction tests are presented.

Highly Sensitive and Automated Surface Enhanced Raman Scattering-based Immunoassay for H5N1 Detection with Digital Microfluidics.

PubMed

Wang, Yang; Ruan, Qingyu; Lei, Zhi-Chao; Lin, Shui-Chao; Zhu, Zhi; Zhou, Leiji; Yang, Chaoyong

2018-04-17

Digital microfluidics (DMF) is a powerful platform for a broad range of applications, especially immunoassays having multiple steps, due to the advantages of low reagent consumption and high automatization. Surface enhanced Raman scattering (SERS) has been proven as an attractive method for highly sensitive and multiplex detection, because of its remarkable signal amplification and excellent spatial resolution. Here we propose a SERS-based immunoassay with DMF for rapid, automated, and sensitive detection of disease biomarkers. SERS tags labeled with Raman reporter 4-mercaptobenzoic acid (4-MBA) were synthesized with a core@shell nanostructure and showed strong signals, good uniformity, and high stability. A sandwich immunoassay was designed, in which magnetic beads coated with antibodies were used as solid support to capture antigens from samples to form a beads-antibody-antigen immunocomplex. By labeling the immunocomplex with a detection antibody-functionalized SERS tag, antigen can be sensitively detected through the strong SERS signal. The automation capability of DMF can greatly simplify the assay procedure while reducing the risk of exposure to hazardous samples. Quantitative detection of avian influenza virus H5N1 in buffer and human serum was implemented to demonstrate the utility of the DMF-SERS method. The DMF-SERS method shows excellent sensitivity (LOD of 74 pg/mL) and selectivity for H5N1 detection with less assay time (<1 h) and lower reagent consumption (∼30 μL) compared to the standard ELISA method. Therefore, this DMF-SERS method holds great potentials for automated and sensitive detection of a variety of infectious diseases.

High-quality fiber fabrication in buffered hydrofluoric acid solution with ultrasonic agitation.

PubMed

Zhong, Nianbing; Liao, Qiang; Zhu, Xun; Wang, Yongzhong; Chen, Rong

2013-03-01

An etching method for preparing high-quality fiber-optic sensors using a buffered etchant with ultrasonic agitation is proposed. The effects of etching conditions on the etch rate and surface morphology of the etched fibers are investigated. The effect of surface roughness is discussed on the fibers' optical properties. Linear etching behavior and a smooth fiber surface can be repeatedly obtained by adjusting the ultrasonic power and etchant pH. The fibers' spectral quality is improved as the ratio of the pit depth to size decreases, and the fibers with smooth surfaces are more sensitive to a bacterial suspension than those with rough surfaces.

Fabrication of highly catalytic silver nanoclusters/graphene oxide nanocomposite as nanotag for sensitive electrochemical immunoassay.

PubMed

Wang, Jiamian; Wang, Xiuyun; Wu, Shuo; Song, Jie; Zhao, Yanqiu; Ge, Yanqiu; Meng, Changgong

2016-02-04

Silver nanoclusters and graphene oxide nanocomposite (AgNCs/GRO) is synthesized and functionalized with detection antibody for highly sensitive electrochemical sensing of carcinoembryonic antigen (CEA), a model tumor marker involved in many cancers. AgNCs with large surface area and abundant amount of low-coordinated sites are synthesized with DNA as template and exhibit high catalytic activity towards the electrochemical reduction of H2O2. GRO is employed to assemble with AgNCs because it has large specific surface area, super electronic conductivity and strong π-π stacking interaction with the hydrophobic bases of DNA, which can further improve the catalytic ability of the AgNCs. Using AgNCs/GRO as signal amplification tag, an enzyme-free electrochemical immunosensing protocol is designed for the highly sensitive detection of CEA on the capture antibody functionalized immunosensing interface. Under optimal conditions, the designed immunosensor exhibits a wide linear range from 0.1 pg mL(-1) to 100 ng mL(-1) and a low limit of detection of 0.037 pg mL(-1). Practical sample analysis reveals the sensor has good accuracy and reproducibility, indicating the great application prospective of the AgNCs/GRO in fabricating highly sensitive immunosensors, which can be extended to the detection of various kinds of low abundance disease related proteins. Copyright © 2015 Elsevier B.V. All rights reserved.

Active sites and states in the heterogeneous catalysis of carbon-hydrogen bonds.

PubMed

Somorjai, Gabor A; Marsh, Anderson L

2005-04-15

C-H bond activation for several alkenes (ethylene, propylene, isobutene, cyclohexene and 1-hexene) and alkanes (methane, ethane, n-hexane, 2-methylpentane and 3-methylpentane) has been studied on the (111) crystal face of platinum as a function of temperature at low (10(-6) Torr) and high (>/=1 Torr) pressures in the absence and presence of hydrogen pressures (>/=10 Torr). Sum frequency generation (SFG) vibrational spectroscopy has been used to characterize the adsorbate structures and high pressure scanning tunnelling microscopy (HP-STM) has been used to monitor their surface mobility under reaction conditions during hydrogenation, dehydrogenation and CO poisoning. C-H bond dissociation occurs at low temperatures, approximately 250 K, for all of these molecules, although only at high pressures for the weakly bound alkanes because of their low desorption temperatures. Bond dissociation is known to be surface structure sensitive and we find that it is also accompanied by the restructuring of the metal surface. The presence of hydrogen slows down dehydrogenation and for some of the molecules it influences the molecular rearrangement, thus altering reaction selectivity. Surface mobility of adsorbates is essential to produce catalytic activity. When surface diffusion is inhibited by CO adsorption, ordered surface structures form and the reaction is poisoned. Ethylene hydrogenation is surface structure insensitive, while cyclohexene hydrogenation and dehydrogenation are structure sensitive. n-Hexane and other C6 alkanes form either upright or flat-lying molecules on the platinum surface which react to produce branched isomers or benzene, respectively.

Wearable Resistive Pressure Sensor Based on Highly Flexible Carbon Composite Conductors with Irregular Surface Morphology.

PubMed

Kim, Kang-Hyun; Hong, Soon Kyu; Jang, Nam-Su; Ha, Sung-Hun; Lee, Hyung Woo; Kim, Jong-Man

2017-05-24

Wearable pressure sensors are crucial building blocks for potential applications in real-time health monitoring, artificial electronic skins, and human-to-machine interfaces. Here we present a highly sensitive, simple-architectured wearable resistive pressure sensor based on highly compliant yet robust carbon composite conductors made of a vertically aligned carbon nanotube (VACNT) forest embedded in a polydimethylsiloxane (PDMS) matrix with irregular surface morphology. A roughened surface of the VACNT/PDMS composite conductor is simply formed using a sandblasted silicon master in a low-cost and potentially scalable manner and plays an important role in improving the sensitivity of resistive pressure sensor. After assembling two of the roughened composite conductors, our sensor shows considerable pressure sensitivity of ∼0.3 kPa -1 up to 0.7 kPa as well as stable steady-state responses under various pressures, a wide detectable range of up to 5 kPa before saturation, a relatively fast response time of ∼162 ms, and good reproducibility over 5000 cycles of pressure loading/unloading. The fabricated pressure sensor can be used to detect a wide range of human motions ranging from subtle blood pulses to dynamic joint movements, and it can also be used to map spatial pressure distribution in a multipixel platform (in a 4 × 4 pixel array).

Impedimetric detection of cocaine by using an aptamer attached to a screen printed electrode modified with a dendrimer/silver nanoparticle nanocomposite.

PubMed

Roushani, Mahmoud; Shahdost-Fard, Faezeh

2018-03-12

The authors describe a highly sensitive method for the aptamer (Apt) based impedimetric determination of cocaine. The surface of a screen-printed electrode (SPE) was modified with a nanocomposite of dendrimer and silver nanoparticles (AgNPs). The cocaine-binding Apt was attached to a dendrimer/AgNP/SPE surface, forming a sensitive layer for the determination of cocaine. The incubation with the analyte resulted in the formation of a cocaine/Apt complex on the electrode surface. As a consequence, folding and conformational change in the aptamer structure was induced, this resulting in a change in the impedimetric signal. The aptaassay exhibits highly efficient sensing characteristics with a good linearity of 1 fmol L -1 to 100 nmol L -1 (with two linear ranges) and a limit of detection (LOD) of 333 amol L -1 . Its excellent specificity and high sensitivity suggest that this kind of aptamer-based assay may be applied to detect other targets in this field. Graphical Abstract Designing of an aptaassay via immobilization of a functionalized aptamer with silver nanoparticle (AgNPs-Apt) on the modified screen-printed electrode (SPE) with dendrimer/silver nanoparticle nanocomposite (Den-AgNPs) for impedimetric detection of cocaine.

Terahertz particle-in-liquid sensing with spoof surface plasmon polariton waveguides

NASA Astrophysics Data System (ADS)

Ma, Zhijie; Hanham, Stephen M.; Arroyo Huidobro, Paloma; Gong, Yandong; Hong, Minghui; Klein, Norbert; Maier, Stefan A.

2017-11-01

We present a highly sensitive microfluidic sensing technique for the terahertz (THz) region of the electromagnetic spectrum based on spoof surface plasmon polaritons (SPPs). By integrating a microfluidic channel in a spoof SPP waveguide, we take advantage of these highly confined electromagnetic modes to create a platform for dielectric sensing of liquids. Our design consists of a domino waveguide, that is, a series of periodically arranged rectangular metal blocks on top of a metal surface that supports the propagation of spoof SPPs. Through numerical simulations, we demonstrate that the transmission of spoof SPPs along the waveguide is extremely sensitive to the refractive index of a liquid flowing through a microfluidic channel crossing the waveguide to give an interaction volume on the nanoliter scale. Furthermore, by taking advantage of the insensitivity of the domino waveguide's fundamental spoof SPP mode to the lateral width of the metal blocks, we design a tapered waveguide able to achieve further confinement of the electromagnetic field. Using this approach, we demonstrate the highly sensitive detection of individual subwavelength micro-particles flowing in the liquid. These results are promising for the creation of spoof SPP based THz lab-on-a-chip microfluidic devices that are suitable for the analysis of biological liquids such as proteins and circulating tumour cells in buffer solution.

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

NASA Astrophysics Data System (ADS)

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.

Rapid Detection of Nivalenol and Deoxynivalenol in Wheat Using Surface Plasmon Resonance Immunoassay

USDA-ARS?s Scientific Manuscript database

Surface plasmon resonance immunoassay using a monoclonal antibody was developed to measure nivalenol (NIV) and deoxynivalenol (DON) contamination in wheat. A DON-immobilized sensor chip having high sensitivity and stability was prepared, and an SPR detection procedure was developed. The competitiv...

Crescent shaped Fabry-Perot fiber cavity for ultra-sensitive strain measurement.

PubMed

Liu, Ye; Wang, D N; Chen, W P

2016-12-02

Optical Fabry-Perot interferometer sensors based on inner air-cavity is featured with compact size, good robustness and high strain sensitivity, especially when an ultra-thin air-cavity is adopted. The typical shape of Fabry-Perot inner air-cavity with reflection mode of operation is elliptic, with minor axis along with and major axis perpendicular to the fiber length. The first reflection surface is diverging whereas the second one is converging. To increase the visibility of the output interference pattern, the length of major axis should be large for a given cavity length. However, the largest value of the major axis is limited by the optical fiber diameter. If the major axis length reaches the fiber diameter, the robustness of the Fabry-Perot cavity device would be decreased. Here we demonstrate an ultra-thin crescent shaped Fabry-Perot cavity for strain sensing with ultra-high sensitivity and low temperature cross-sensitivity. The crescent-shape cavity consists of two converging reflection surfaces, which provide the advantages of enhanced strain sensitivity when compared with elliptic or D-shaped FP cavity. The device is fabricated by fusion splicing an etched multimode fiber with a single mode fiber, and hence is simple in structure and economic in cost.

Crescent shaped Fabry-Perot fiber cavity for ultra-sensitive strain measurement

NASA Astrophysics Data System (ADS)

Liu, Ye; Wang, D. N.; Chen, W. P.

2016-12-01

Optical Fabry-Perot interferometer sensors based on inner air-cavity is featured with compact size, good robustness and high strain sensitivity, especially when an ultra-thin air-cavity is adopted. The typical shape of Fabry-Perot inner air-cavity with reflection mode of operation is elliptic, with minor axis along with and major axis perpendicular to the fiber length. The first reflection surface is diverging whereas the second one is converging. To increase the visibility of the output interference pattern, the length of major axis should be large for a given cavity length. However, the largest value of the major axis is limited by the optical fiber diameter. If the major axis length reaches the fiber diameter, the robustness of the Fabry-Perot cavity device would be decreased. Here we demonstrate an ultra-thin crescent shaped Fabry-Perot cavity for strain sensing with ultra-high sensitivity and low temperature cross-sensitivity. The crescent-shape cavity consists of two converging reflection surfaces, which provide the advantages of enhanced strain sensitivity when compared with elliptic or D-shaped FP cavity. The device is fabricated by fusion splicing an etched multimode fiber with a single mode fiber, and hence is simple in structure and economic in cost.

Effect of film thickness on localized surface plasmon enhanced chemical sensor

NASA Astrophysics Data System (ADS)

Kassu, Aschalew; Farley, Carlton; Sharma, Anup; Kim, Wonkyu; Guo, Junpeng

2014-05-01

A highly-sensitive, reliable, simple and inexpensive chemical detection and identification platform is demonstrated. The sensing technique is based on localized surface plasmon enhanced Raman scattering measurements from gold-coated highly-ordered symmetric nanoporous ceramic membranes fabricated from anodic aluminum oxide. To investigate the effects of the thickness of the sputter-coated gold films on the sensitivity of sensor, and optimize the performance of the substrates, the geometry of the nanopores and the film thicknesses are varied in the range of 30 nm to 120 nm. To characterize the sensing technique and the detection limits, surface enhanced Raman scatterings of low concentrations of a standard chemical adsorbed on the gold coated substrates are collected and analyzed. The morphology of the proposed substrates is characterized by atomic force microscopy and the optical properties including transmittance, reflectance and absorbance of each substrate are also investigated.

Selective electrochemical detection of 2,4,6-trinitrotoluene (TNT) in water based on poly(styrene-co-acrylic acid) PSA/SiO2/Fe3O4/AuNPs/lignin-modified glassy carbon electrode.

PubMed

Mahmoud, Khaled A; Abdel-Wahab, Ahmed; Zourob, Mohammed

2015-01-01

A new versatile electrochemical sensor based on poly(styrene-co-acrylic acid) PSA/SiO2/Fe3O4/AuNPs/lignin (L-MMS) modified glassy carbon electrode (GCE) was developed for the selective detection of trace trinitrotoluene (TNT) from aqueous media with high sensitivity. The fabricated magnetic microspheres were characterized by transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). L-MMS films were cast on the GCE surface to fabricate the TNT sensing electrode. The limit of detection (LOD) of TNT determined by the amperometric i-t curve reached 35 pM. The lignin film and well packed Fe3O4/AuNPs facilitated the pre-concentration of trace TNT on the electrode surface resulting in a fast amperometric response of 3 seconds near the detection limit. The high sensitivity and excellent catalytic activity of the modified electrode could be attributed to the lignin layer and highly packed Fe3O4/AuNPs on the electrode surface. The total recovery of TNT from tapwater and seawater matrices was 98% and 96%, respectively. The electrode film was highly stable after five repeated adsorption/desorption cycles. The new electrochemical sensing scheme provides a highly selective, sensitive and versatile assay for the in-situ detection of TNT in complex water media.

Terbium(III) Modified Fluorescent Carbon Dots for Highly Selective and Sensitive Ratiometry of Stringent.

PubMed

Chen, Bin Bin; Liu, Meng Li; Zhan, Lei; Li, Chun Mei; Huang, Cheng Zhi

2018-03-20

Highly selective and sensitive detection of guanosine 3'-diphosphate-5'-diphosphate (ppGpp), namely, the stringent in plants or microorganisms responding to strict or extreme environmental conditions such as stress and starvation, which plays an important role in gene expression, rRNA and antibiotics production, regulations of virulence of bacteria, and growth of plants, faces a great challenge owing to its extreme similarity to normal nucleotides. By modifying the surface groups of a facile two-step hydrothermal route prepared carbon dots (CDs) with terbium ions (Tb 3+ ) in this contribution, a novel fluorescent probe with excellent properties such as highly physical and chemical stability, narrow emission and excitation wavelength-independent emission was prepared. The Tb 3+ ions on the surface of CDs cannot only preserve the intrinsic fluorescence (FL) of CDs but also keep its own coordination capacity with rare earth complex, and thus the clamp structure (four phosphate groups) of ppGpp can specific binding with Tb 3+ ions on the surface of CDs to produce antenna effect. Therefore, a highly selective and sensitive fluorescent ratiometry of ppGpp was developed by terbium-modified carbon dots (CDs-Tb) with the limit of detection as low as 50 nM based on the synergistic effect of antenna effect of Tb 3+ ions and specific recognition capacity of CDs. The applicability of this assay was demonstrated by CDs-Tb-based paper sensor for high distinguishing ppGpp from other nucleotides with similar structure.

Thermo-optical characterization of fluorescent rhodamine B based temperature-sensitive nanosensors using a CMOS MEMS micro-hotplate☆

PubMed Central

Chauhan, Veeren M.; Hopper, Richard H.; Ali, Syed Z.; King, Emma M.; Udrea, Florin; Oxley, Chris H.; Aylott, Jonathan W.

2014-01-01

A custom designed microelectromechanical systems (MEMS) micro-hotplate, capable of operating at high temperatures (up to 700 °C), was used to thermo-optically characterize fluorescent temperature-sensitive nanosensors. The nanosensors, 550 nm in diameter, are composed of temperature-sensitive rhodamine B (RhB) fluorophore which was conjugated to an inert silica sol–gel matrix. Temperature-sensitive nanosensors were dispersed and dried across the surface of the MEMS micro-hotplate, which was mounted in the slide holder of a fluorescence confocal microscope. Through electrical control of the MEMS micro-hotplate, temperature induced changes in fluorescence intensity of the nanosensors was measured over a wide temperature range. The fluorescence response of all nanosensors dispersed across the surface of the MEMS device was found to decrease in an exponential manner by 94%, when the temperature was increased from 25 °C to 145 °C. The fluorescence response of all dispersed nanosensors across the whole surface of the MEMS device and individual nanosensors, using line profile analysis, were not statistically different (p < 0.05). The MEMS device used for this study could prove to be a reliable, low cost, low power and high temperature micro-hotplate for the thermo-optical characterisation of sub-micron sized particles. The temperature-sensitive nanosensors could find potential application in the measurement of temperature in biological and micro-electrical systems. PMID:25844025

A microwave resonator for limiting depth sensitivity for electron paramagnetic resonance spectroscopy of surfaces.

PubMed

Sidabras, Jason W; Varanasi, Shiv K; Mett, Richard R; Swarts, Steven G; Swartz, Harold M; Hyde, James S

2014-10-01

A microwave Surface Resonator Array (SRA) structure is described for use in Electron Paramagnetic Resonance (EPR) spectroscopy. The SRA has a series of anti-parallel transmission line modes that provides a region of sensitivity equal to the cross-sectional area times its depth sensitivity, which is approximately half the distance between the transmission line centers. It is shown that the quarter-wave twin-lead transmission line can be a useful element for design of microwave resonators at frequencies as high as 10 GHz. The SRA geometry is presented as a novel resonator for use in surface spectroscopy where the region of interest is either surrounded by lossy material, or the spectroscopist wishes to minimize signal from surrounding materials. One such application is in vivo spectroscopy of human finger-nails at X-band (9.5 GHz) to measure ionizing radiation dosages. In order to reduce losses associated with tissues beneath the nail that yield no EPR signal, the SRA structure is designed to limit depth sensitivity to the thickness of the fingernail. Another application, due to the resonator geometry and limited depth penetration, is surface spectroscopy in coating or material science. To test this application, a spectrum of 1.44 μM of Mg(2+) doped polystyrene 1.1 mm thick on an aluminum surface is obtained. Modeling, design, and simulations were performed using Wolfram Mathematica (Champaign, IL; v. 9.0) and Ansys High Frequency Structure Simulator (HFSS; Canonsburg, PA; v. 15.0). A micro-strip coupling circuit is designed to suppress unwanted modes and provide a balanced impedance transformation to a 50 Ω coaxial input. Agreement between simulated and experimental results is shown.

A microwave resonator for limiting depth sensitivity for electron paramagnetic resonance spectroscopy of surfaces

PubMed Central

Sidabras, Jason W.; Varanasi, Shiv K.; Mett, Richard R.; Swarts, Steven G.; Swartz, Harold M.; Hyde, James S.

2014-01-01

A microwave Surface Resonator Array (SRA) structure is described for use in Electron Paramagnetic Resonance (EPR) spectroscopy. The SRA has a series of anti-parallel transmission line modes that provides a region of sensitivity equal to the cross-sectional area times its depth sensitivity, which is approximately half the distance between the transmission line centers. It is shown that the quarter-wave twin-lead transmission line can be a useful element for design of microwave resonators at frequencies as high as 10 GHz. The SRA geometry is presented as a novel resonator for use in surface spectroscopy where the region of interest is either surrounded by lossy material, or the spectroscopist wishes to minimize signal from surrounding materials. One such application is in vivo spectroscopy of human finger-nails at X-band (9.5 GHz) to measure ionizing radiation dosages. In order to reduce losses associated with tissues beneath the nail that yield no EPR signal, the SRA structure is designed to limit depth sensitivity to the thickness of the fingernail. Another application, due to the resonator geometry and limited depth penetration, is surface spectroscopy in coating or material science. To test this application, a spectrum of 1.44 μM of Mg2+ doped polystyrene 1.1 mm thick on an aluminum surface is obtained. Modeling, design, and simulations were performed using Wolfram Mathematica (Champaign, IL; v. 9.0) and Ansys High Frequency Structure Simulator (HFSS; Canonsburg, PA; v. 15.0). A micro-strip coupling circuit is designed to suppress unwanted modes and provide a balanced impedance transformation to a 50 Ω coaxial input. Agreement between simulated and experimental results is shown. PMID:25362434

Sensitivity Analysis of the Agricultural Policy/Environmental eXtender (APEX) for Phosphorus Loads in Tile-Drained Landscapes.

PubMed

Ford, W; King, K; Williams, M; Williams, J; Fausey, N

2015-07-01

Numerical modeling is an economical and feasible approach for quantifying the effects of best management practices on dissolved reactive phosphorus (DRP) loadings from agricultural fields. However, tools that simulate both surface and subsurface DRP pathways are limited and have not been robustly evaluated in tile-drained landscapes. The objectives of this study were to test the ability of the Agricultural Policy/Environmental eXtender (APEX), a widely used field-scale model, to simulate surface and tile P loadings over management, hydrologic, biologic, tile, and soil gradients and to better understand the behavior of P delivery at the edge-of-field in tile-drained midwestern landscapes. To do this, a global, variance-based sensitivity analysis was performed, and model outputs were compared with measured P loads obtained from 14 surface and subsurface edge-of-field sites across central and northwestern Ohio. Results of the sensitivity analysis showed that response variables for DRP were highly sensitive to coupled interactions between presumed important parameters, suggesting nonlinearity of DRP delivery at the edge-of-field. Comparison of model results to edge-of-field data showcased the ability of APEX to simulate surface and subsurface runoff and the associated DRP loading at monthly to annual timescales; however, some high DRP concentrations and fluxes were not reflected in the model, suggesting the presence of preferential flow. Results from this study provide new insights into baseline tile DRP loadings that exceed thresholds for algal proliferation. Further, negative feedbacks between surface and subsurface DRP delivery suggest caution is needed when implementing DRP-based best management practices designed for a specific flow pathway. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

A microwave resonator for limiting depth sensitivity for electron paramagnetic resonance spectroscopy of surfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sidabras, Jason W.; Varanasi, Shiv K.; Hyde, James S.

2014-10-15

A microwave Surface Resonator Array (SRA) structure is described for use in Electron Paramagnetic Resonance (EPR) spectroscopy. The SRA has a series of anti-parallel transmission line modes that provides a region of sensitivity equal to the cross-sectional area times its depth sensitivity, which is approximately half the distance between the transmission line centers. It is shown that the quarter-wave twin-lead transmission line can be a useful element for design of microwave resonators at frequencies as high as 10 GHz. The SRA geometry is presented as a novel resonator for use in surface spectroscopy where the region of interest is eithermore » surrounded by lossy material, or the spectroscopist wishes to minimize signal from surrounding materials. One such application is in vivo spectroscopy of human finger-nails at X-band (9.5 GHz) to measure ionizing radiation dosages. In order to reduce losses associated with tissues beneath the nail that yield no EPR signal, the SRA structure is designed to limit depth sensitivity to the thickness of the fingernail. Another application, due to the resonator geometry and limited depth penetration, is surface spectroscopy in coating or material science. To test this application, a spectrum of 1.44 μM of Mg{sup 2+} doped polystyrene 1.1 mm thick on an aluminum surface is obtained. Modeling, design, and simulations were performed using Wolfram Mathematica (Champaign, IL; v. 9.0) and Ansys High Frequency Structure Simulator (HFSS; Canonsburg, PA; v. 15.0). A micro-strip coupling circuit is designed to suppress unwanted modes and provide a balanced impedance transformation to a 50 Ω coaxial input. Agreement between simulated and experimental results is shown.« less

Composite material including nanocrystals and methods of making

DOEpatents

Bawendi, Moungi G.; Sundar, Vikram C.

2010-04-06

Temperature-sensing compositions can include an inorganic material, such as a semiconductor nanocrystal. The nanocrystal can be a dependable and accurate indicator of temperature. The intensity of emission of the nanocrystal varies with temperature and can be highly sensitive to surface temperature. The nanocrystals can be processed with a binder to form a matrix, which can be varied by altering the chemical nature of the surface of the nanocrystal. A nanocrystal with a compatibilizing outer layer can be incorporated into a coating formulation and retain its temperature sensitive emissive properties.

Engineered porous silicon counter electrodes for high efficiency dye-sensitized solar cells.

PubMed

Erwin, William R; Oakes, Landon; Chatterjee, Shahana; Zarick, Holly F; Pint, Cary L; Bardhan, Rizia

2014-06-25

In this work, we demonstrate for the first time, the use of porous silicon (P-Si) as counter electrodes in dye-sensitized solar cells (DSSCs) with efficiencies (5.38%) comparable to that achieved with platinum counter electrodes (5.80%). To activate the P-Si for triiodide reduction, few layer carbon passivation is utilized to enable electrochemical stability of the silicon surface. Our results suggest porous silicon as a promising sustainable and manufacturable alternative to rare metals for electrochemical solar cells, following appropriate surface modification.

Composite material including nanocrystals and methods of making

DOEpatents

Bawendi, Moungi G [Boston, MA; Sundar, Vikram C [New York, NY

2008-02-05

Temperature-sensing compositions can include an inorganic material, such as a semiconductor nanocrystal. The nanocrystal can be a dependable and accurate indicator of temperature. The intensity of emission of the nanocrystal varies with temperature and can be highly sensitive to surface temperature. The nanocrystals can be processed with a binder to form a matrix, which can be varied by altering the chemical nature of the surface of the nanocrystal. A nanocrystal with a compatibilizing outer layer can be incorporated into a coating formulation and retain its temperature sensitive emissive properties

Direct patterning of gold nanoparticles using flexographic printing for biosensing applications

NASA Astrophysics Data System (ADS)

Benson, Jamie; Fung, Chung Man; Lloyd, Jonathan Stephen; Deganello, Davide; Smith, Nathan Andrew; Teng, Kar Seng

2015-03-01

In this paper, we have presented the use of flexographic printing techniques in the selective patterning of gold nanoparticles (AuNPs) onto a substrate. Highly uniform coverage of AuNPs was selectively patterned on the substrate surface, which was subsequently used in the development of a glucose sensor. These AuNPs provide a biocompatible site for the attachment of enzymes and offer high sensitivity in the detection of glucose due to their large surface to volume ratio. The average size of the printed AuNPs is less than 60 nm. Glucose sensing tests were performed using printed carbon-AuNP electrodes functionalized with glucose oxidase (GOx). The results showed a high sensitivity of 5.52 μA mM-1 cm-2 with a detection limit of 26 μM. We have demonstrated the fabrication of AuNP-based biosensors using flexographic printing, which is ideal for low-cost, high-volume production of the devices.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Biassoni, M.; Brofferio, C.; Bucci, C.

Due to their excellent energy resolution values and the vast choice of possible materials, bolometric detectors are currently widely used in the physics of rare events. A limiting aspect for bolometers rises from their inability to discriminate among radiation types or surface from bulk events. It has been demonstrated that the main limitation to sensitivity for purely bolometric detectors is represented by surface alpha contaminations, causing a continuous background that cannot be discriminated. A new scintillation based technique for the rejection of surface alpha background in non- scintillating bolometric experiments is proposed in this work. The idea is to combinemore » a scintillating and a high sensitivity photon detector with a non- scintillating absorber. Finally, we present results showing the possibility to reject events due to alpha decay at or nearby the surface of the crystal.« less

Influence of Lake Stratification Onset on Summer Surface Water Temperature

NASA Astrophysics Data System (ADS)

Woolway, R. I.; Merchant, C. J.

2016-12-01

Summer lake surface water temperatures (LSSWT) are sensitive to climatic warming and have previously been shown to increase at a faster rate than surface air temperatures in some lakes, as a response to thermal stratification occurring earlier in spring. We explore this relationship using a combination of in situ, satellite derived, and simulated temperatures from 144 lakes. Our results demonstrate that LSSWTs of high-latitude and large deep lakes are particularly sensitive to changes in stratification onset and can be expected to display an amplified response to climatic changes in summer air temperature. Climatic modification of LSSWT has numerous consequences for water quality and lake ecosystems, so quantifying this amplified response is important.

Image processing for grazing incidence fast atom diffraction

NASA Astrophysics Data System (ADS)

Debiossac, Maxime; Roncin, Philippe

2016-09-01

Grazing incidence fast atom diffraction (GIFAD, or FAD) has developed as a surface sensitive technique. Compared with thermal energies helium diffraction (TEAS or HAS), GIFAD is less sensitive to thermal decoherence but also more demanding in terms of surface coherence, the mean distance between defects. Such high quality surfaces can be obtained from freshly cleaved crystals or in a molecular beam epitaxy (MBE) chamber where a GIFAD setup has been installed allowing in situ operation. Based on recent publications by Atkinson et al. (2014) and Debiossac et al. (2014), the paper describes in detail the basic steps needed to measure the relative intensities of the diffraction spots. Care is taken to outline the underlying physical assumptions.

Microfluidic Surface Plasmon Resonance Sensors: From Principles to Point-of-Care Applications

PubMed Central

Wang, Da-Shin; Fan, Shih-Kang

2016-01-01

Surface plasmon resonance (SPR) is a label-free, highly-sensitive, and real-time sensing technique. Conventional SPR sensors, which involve a planar thin gold film, have been widely exploited in biosensing; various miniaturized formats have been devised for portability purposes. Another type of SPR sensor which utilizes localized SPR (LSPR), is based on metal nanostructures with surface plasmon modes at the structural interface. The resonance condition is sensitive to the refractive index change of the local medium. The principles of these two types of SPR sensors are reviewed and their integration with microfluidic platforms is described. Further applications of microfluidic SPR sensors to point-of-care (POC) diagnostics are discussed. PMID:27472340

Label-Free Biosensing with High Selectivity in Complex Media using Microtoroidal Optical Resonators

NASA Astrophysics Data System (ADS)

Ozgur, Erol; Toren, Pelin; Aktas, Ozan; Huseyinoglu, Ersin; Bayindir, Mehmet

2015-08-01

Although label-free biosensors comprised of optical microcavities inherently possess the capability of resolving molecular interactions at individual level, this extreme sensitivity restricts their convenience for large scale applications by inducing vulnerability towards non-specific interactions that readily occur within complex media. Therefore, the use of optical microresonators for biosensing is mostly limited within strictly defined laboratory conditions, instead of field applications as early detection of cancer markers in blood, or identification of contamination in food. Here, we propose a novel surface modification strategy suitable for but not limited to optical microresonator based biosensors, enabling highly selective biosensing with considerable sensitivity as well. Using a robust, silane-based surface coating which is simultaneously protein resistant and bioconjugable, we demonstrate that it becomes possible to perform biosensing within complex media, without compromising the sensitivity or reliability of the measurement. Functionalized microtoroids are successfully shown to resist nonspecific interactions, while simultaneously being used as sensitive biological sensors. This strategy could pave the way for important applications in terms of extending the use of state-of-the-art biosensors for solving problems similar to the aforementioned.

High throughput secondary electron imaging of organic residues on a graphene surface

NASA Astrophysics Data System (ADS)

Zhou, Yangbo; O'Connell, Robert; Maguire, Pierce; Zhang, Hongzhou

2014-11-01

Surface organic residues inhibit the extraordinary electronic properties of graphene, hindering the development of graphene electronics. However, fundamental understanding of the residue morphology is still absent due to a lack of high-throughput and high-resolution surface characterization methods. Here, we demonstrate that secondary electron (SE) imaging in the scanning electron microscope (SEM) and helium ion microscope (HIM) can provide sub-nanometer information of a graphene surface and reveal the morphology of surface contaminants. Nanoscale polymethyl methacrylate (PMMA) residues are visible in the SE imaging, but their contrast, i.e. the apparent lateral dimension, varies with the imaging conditions. We have demonstrated a quantitative approach to readily obtain the physical size of the surface features regardless of the contrast variation. The fidelity of SE imaging is ultimately determined by the probe size of the primary beam. HIM is thus evaluated to be a superior SE imaging technique in terms of surface sensitivity and image fidelity. A highly efficient method to reveal the residues on a graphene surface has therefore been established.

Dextran hydrogel coated surface plasmon resonance imaging (SPRi) sensor for sensitive and label-free detection of small molecule drugs

NASA Astrophysics Data System (ADS)

Li, Shaopeng; Yang, Mo; Zhou, Wenfei; Johnston, Trevor G.; Wang, Rui; Zhu, Jinsong

2015-11-01

The label-free and sensitive detection of small molecule drugs on SPRi is still a challenging task, mainly due to the limited surface immobilization capacity of the sensor. In this research, a dextran hydrogel-coated gold sensor chip for SPRi was successfully fabricated via photo-cross-linking for enhanced surface immobilization capacity. The density of the dextran hydrogel was optimized for protein immobilization and sensitive small molecule detection. The protein immobilization capacity of the hydrogel was 10 times greater than a bare gold surface, and 20 times greater than an 11-mercaptoundecanoic acid (MUA) surface. Such a drastic improvement in immobilization capacity allowed the SPRi sensor to detect adequate response signals when probing small molecule binding events. The binding signal of 4 nM liquid-phase biotin to streptavidin immobilized on the dextran surface reached 435 RU, while no response was observed on bare gold or MUA surfaces. The dextran hydrogel-coated SPRi sensor was also applied in a kinetic study of the binding between an immunosuppressive drug (FK506) and its target protein (FKBP12) in a high-throughput microarray format. The measured binding affinity was shown to be consistent with reported literature values, and a detection limit of 0.5 nM was achieved.

Development of a HIV-1 Virus Detection System Based on Nanotechnology.

PubMed

Lee, Jin-Ho; Oh, Byung-Keun; Choi, Jeong-Woo

2015-04-27

Development of a sensitive and selective detection system for pathogenic viral agents is essential for medical healthcare from diagnostics to therapeutics. However, conventional detection systems are time consuming, resource-intensive and tedious to perform. Hence, the demand for sensitive and selective detection system for virus are highly increasing. To attain this aim, different aspects and techniques have been applied to develop virus sensor with improved sensitivity and selectivity. Here, among those aspects and techniques, this article reviews HIV virus particle detection systems incorporated with nanotechnology to enhance the sensitivity. This review mainly focused on four different detection system including vertically configured electrical detection based on scanning tunneling microscopy (STM), electrochemical detection based on direct electron transfer in virus, optical detection system based on localized surface plasmon resonance (LSPR) and surface enhanced Raman spectroscopy (SERS) using plasmonic nanoparticle.

Long range surface plasmon resonance with ultra-high penetration depth for self-referenced sensing and ultra-low detection limit using diverging beam approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Isaacs, Sivan, E-mail: sivan.isaacs@gmail.com; Abdulhalim, Ibrahim; NEW CREATE Programme, School of Materials Science and Engineering, 1 CREATE Way, Research Wing, #02-06/08, Singapore 138602

2015-05-11

Using an insulator-metal-insulator structure with dielectric having refractive index (RI) larger than the analyte, long range surface plasmon (SP) resonance exhibiting ultra-high penetration depth is demonstrated for sensing applications of large bioentities at wavelengths in the visible range. Based on the diverging beam approach in Kretschmann-Raether configuration, one of the SP resonances is shown to shift in response to changes in the analyte RI while the other is fixed; thus, it can be used as a built in reference. The combination of the high sensitivity, high penetration depth and self-reference using the diverging beam approach in which a dark linemore » is detected of the high sensitivity, high penetration depth, self-reference, and the diverging beam approach in which a dark line is detected using large number of camera pixels with a smart algorithm for sub-pixel resolution, a sensor with ultra-low detection limit is demonstrated suitable for large bioentities.« less

Highly sensitive hydrogen sensor based on graphite-InP or graphite-GaN Schottky barrier with electrophoretically deposited Pd nanoparticles

PubMed Central

2011-01-01

Depositions on surfaces of semiconductor wafers of InP and GaN were performed from isooctane colloid solutions of palladium (Pd) nanoparticles (NPs) in AOT reverse micelles. Pd NPs in evaporated colloid and in layers deposited electrophoretically were monitored by SEM. Diodes were prepared by making Schottky contacts with colloidal graphite on semiconductor surfaces previously deposited with Pd NPs and ohmic contacts on blank surfaces. Forward and reverse current-voltage characteristics of the diodes showed high rectification ratio and high Schottky barrier heights, giving evidence of very small Fermi level pinning. A large increase of current was observed after exposing diodes to flow of gas blend hydrogen in nitrogen. Current change ratio about 700,000 with 0.1% hydrogen blend was achieved, which is more than two orders-of-magnitude improvement over the best result reported previously. Hydrogen detection limit of the diodes was estimated at 1 ppm H2/N2. The diodes, besides this extremely high sensitivity, have been temporally stable and of inexpensive production. Relatively more expensive GaN diodes have potential for functionality at high temperatures. PMID:21831273

Nonfaradaic nanoporous electrochemistry for conductometry at high electrolyte concentration.

PubMed

Bae, Je Hyun; Kang, Chung Mu; Choi, Hyoungseon; Kim, Beom Jin; Jang, Woohyuk; Lim, Sung Yul; Kim, Hee Chan; Chung, Taek Dong

2015-02-17

Nanoporous electrified surfaces create a unique nonfaradaic electrochemical behavior that is sensitively influenced by pore size, morphology, ionic strength, and electric field modulation. Here, we report the contributions of ion concentration and applied ac frequency to the electrode impedance through an electrical double layer overlap and ion transport along the nanopores. Nanoporous Pt with uniform pore size and geometry (L2-ePt) responded more sensitively to conductivity changes in aqueous solutions than Pt black with poor uniformity despite similar real surface areas and enabled the previously difficult quantitative conductometry measurements at high electrolyte concentrations. The nanopores of L2-ePt were more effective in reducing the electrode impedance and exhibited superior linear responses to not only flat Pt but also Pt black, leading to successful conductometric detection in ion chromatography without ion suppressors and at high ionic strengths.

Improved phase sensitivity in spectral domain phase microscopy using line-field illumination and self phase-referencing

PubMed Central

Yaqoob, Zahid; Choi, Wonshik; Oh, Seungeun; Lue, Niyom; Park, Yongkeun; Fang-Yen, Christopher; Dasari, Ramachandra R.; Badizadegan, Kamran; Feld, Michael S.

2010-01-01

We report a quantitative phase microscope based on spectral domain optical coherence tomography and line-field illumination. The line illumination allows self phase-referencing method to reject common-mode phase noise. The quantitative phase microscope also features a separate reference arm, permitting the use of high numerical aperture (NA > 1) microscope objectives for high resolution phase measurement at multiple points along the line of illumination. We demonstrate that the path-length sensitivity of the instrument can be as good as 41 pm/Hz, which makes it suitable for nanometer scale study of cell motility. We present the detection of natural motions of cell surface and two-dimensional surface profiling of a HeLa cell. PMID:19550464

An optically detectable CO2 sensor utilizing polyethylenimine and starch functionalized InGaN/GaN multiple quantum wells

NASA Astrophysics Data System (ADS)

Chen, Y. C.; Shih, H. Y.; Chen, J. Y.; Tan, W. J.; Chen, Y. F.

2013-07-01

An optically detectable gas sensor based on the high surface sensitivity of functionalized polyethylenimine/starch In0.15Ga0.85N/GaN strained semiconductor multiple quantum wells (MQWs) has been developed. Due to the excellent piezoelectricity of the MQWs, the change of surface charges caused by chemical interaction can introduce a strain and induce an internal field. In turn, it tilts the energy levels of the MQWs and modifies the optical properties. Through the measurement of the changes in photoluminescence as well as Raman scattering spectra under different concentrations of carbon dioxide gas, we demonstrate the feasibility and high sensitivity of the sensors derived from our methodology.

Highly charged ion secondary ion mass spectroscopy

DOEpatents

Hamza, Alex V.; Schenkel, Thomas; Barnes, Alan V.; Schneider, Dieter H.

2001-01-01

A secondary ion mass spectrometer using slow, highly charged ions produced in an electron beam ion trap permits ultra-sensitive surface analysis and high spatial resolution simultaneously. The spectrometer comprises an ion source producing a primary ion beam of highly charged ions that are directed at a target surface, a mass analyzer, and a microchannel plate detector of secondary ions that are sputtered from the target surface after interaction with the primary beam. The unusually high secondary ion yield permits the use of coincidence counting, in which the secondary ion stops are detected in coincidence with a particular secondary ion. The association of specific molecular species can be correlated. The unique multiple secondary nature of the highly charged ion interaction enables this new analytical technique.

Using Satellites to Investigate the Sensitivity of Longwave Downward Radiation to Water Vapor at High Elevations

NASA Technical Reports Server (NTRS)

Naud, Catherine M.; Miller, James R.; Landry, Chris

2012-01-01

Many studies suggest that high-elevation regions may be among the most sensitive to future climate change. However, in situ observations in these often remote locations are too sparse to determine the feedbacks responsible for enhanced warming rates. One of these feedbacks is associated with the sensitivity of longwave downward radiation (LDR) to changes in water vapor, with the sensitivity being particularly large in many high-elevation regions where the average water vapor is often low. We show that satellite retrievals from the Moderate Resolution Imaging Spectroradiometer (MODIS) and Clouds and the Earth's Radiant Energy System (CERES) can be used to expand the current ground-based observational database and that the monthly averaged clear-sky satellite estimates of humidity and LDR are in good agreement with the well-instrumented Center for Snow and Avalanche Studies ground-based site in the southwestern Colorado Rocky Mountains. The relationship between MODIS-retrieved precipitable water vapor and surface specific humidity across the contiguous United States was found to be similar to that previously found for the Alps. More important, we show that satellites capture the nonlinear relationship between LDR and water vapor and confirm that LDR is especially sensitive to changes in water vapor at high elevations in several midlatitude mountain ranges. Because the global population depends on adequate fresh water, much of which has its source in high mountains, it is critically important to understand how climate will change there. We demonstrate that satellites can be used to investigate these feedbacks in high-elevation regions where the coverage of surface-based observations is insufficient to do so.

Biomimetic self-templating optical structures fabricated by genetically engineered M13 bacteriophage.

PubMed

Kim, Won-Geun; Song, Hyerin; Kim, Chuntae; Moon, Jong-Sik; Kim, Kyujung; Lee, Seung-Wuk; Oh, Jin-Woo

2016-11-15

Here, we describe a highly sensitive and selective surface plasmon resonance sensor system by utilizing self-assembly of genetically engineered M13 bacteriophage. About 2700 copies of genetically expressed peptide copies give superior selectivity and sensitivity to M13 phage-based SPR sensor. Furthermore, the sensitivity of the M13 phage-based SPR sensor was enhanced due to the aligning of receptor matrix in specific direction. Incorporation of specific binding peptide (His Pro Gln: HPQ) gives M13 bacteriophage high selectivity for the streptavidin. Our M13 phage-based SPR sensor takes advantage of simplicity of self-assembly compared with relatively complex photolithography techniques or chemical conjugations. Additionally, designed structure which is composed of functionalized M13 bacteriophage can simultaneously improve the sensitivity and selectivity of SPR sensor evidently. By taking advantages of the genetic engineering and self-assembly, we propose the simple method for fabricating novel M13 phage-based SPR sensor system which has a high sensitivity and high selectivity. Copyright © 2016 Elsevier B.V. All rights reserved.

A high-resolution model of the planetary boundary layer - Sensitivity tests and comparisons with SESAME-79 data

NASA Technical Reports Server (NTRS)

Zhang, D.; Anthes, R. A.

1982-01-01

A one-dimensional, planetary boundary layer (PBL) model is presented and verified using April 10, 1979 SESAME data. The model contains two modules to account for two different regimes of turbulent mixing. Separate parameterizations are made for stable and unstable conditions, with a predictive slab model for surface temperature. Atmospheric variables in the surface layer are calculated with a prognostic model, with moisture included in the coupled surface/PBL modeling. Sensitivity tests are performed for factors such as moisture availability, albedo, surface roughness, and thermal capacity, and a 24 hr simulation is summarized for day and night conditions. The comparison with the SESAME data comprises three hour intervals, using a time-dependent geostrophic wind. Close correlations were found with daytime conditions, but not in nighttime thermal structure, while the turbulence was faithfully predicted. Both geostrophic flow and surface characteristics were shown to have significant effects on the model predictions

Alpha-fetoprotein detection by using a localized surface plasmon coupled fluorescence fiber-optic biosensor

NASA Astrophysics Data System (ADS)

Chang, Ying-Feng; Chen, Ran-Chou; Li, Ying-Chang; Yu, Chih-Jen; Hsieh, Bao-Yu; Chou, Chien

2007-11-01

Alpha-fetoprotein (AFP) detection by using a localized surface plasmon coupled fluorescence (LSPCF) fiber-optic biosensor is setup and experimentally demonstrated. It is based on gold nanoparticle (GNP) and coupled with localized surface plasmon wave on the surface of GNP. In this experiment, the fluorophores are labeled on anti-AFP which are bound to protein A conjugated GNP. Thus, LSPCF is excited with high efficiency in the near field of localized surface plasmon wave. Therefore, not only the sensitivity of LSPCF biosensor is enhanced but also the specific selectivity of AFP is improved. Experimentally, the ability of real time measurement in the range of AFP concentration from 0.1ng/ml to 100ng/ml was detected. To compare with conventional methods such as enzyme-linked immunosorbent assay (ELISA) or radioimmunoassay (RIA), the LSPCF fiber-optic biosensor performs higher or comparable detection sensitivity, respectively.

Rejection of Alpha Surface Background in Non-scintillating Bolometric Detectors: The ABSuRD Project

DOE PAGES

Biassoni, M.; Brofferio, C.; Bucci, C.; ...

2016-01-14

Due to their excellent energy resolution values and the vast choice of possible materials, bolometric detectors are currently widely used in the physics of rare events. A limiting aspect for bolometers rises from their inability to discriminate among radiation types or surface from bulk events. It has been demonstrated that the main limitation to sensitivity for purely bolometric detectors is represented by surface alpha contaminations, causing a continuous background that cannot be discriminated. A new scintillation based technique for the rejection of surface alpha background in non- scintillating bolometric experiments is proposed in this work. The idea is to combinemore » a scintillating and a high sensitivity photon detector with a non- scintillating absorber. Finally, we present results showing the possibility to reject events due to alpha decay at or nearby the surface of the crystal.« less

Supersonic molecular beam-hyperthermal surface ionisation coupled with time-of-flight mass spectrometry applied to trace level detection of polynuclear aromatic hydrocarbons in drinking water for reduced sample preparation and analysis time.

PubMed

Davis, S C; Makarov, A A; Hughes, J D

1999-01-01

Analysis of sub-ppb levels of polynuclear aromatic hydrocarbons (PAHs) in drinking water by high performance liquid chromatography (HPLC) fluorescence detection typically requires large water samples and lengthy extraction procedures. The detection itself, although selective, does not give compound identity confirmation. Benchtop gas chromatography/mass spectrometry (GC/MS) systems operating in the more sensitive selected ion monitoring (SIM) acquisition mode discard spectral information and, when operating in scanning mode, are less sensitive and scan too slowly. The selectivity of hyperthermal surface ionisation (HSI), the high column flow rate capacity of the supersonic molecular beam (SMB) GC/MS interface, and the high acquisition rate of time-of-flight (TOF) mass analysis, are combined here to facilitate a rapid, specific and sensitive technique for the analysis of trace levels of PAHs in water. This work reports the advantages gained by using the GC/HSI-TOF system over the HPLC fluorescence method, and discusses in some detail the nature of the instrumentation used.

Pressure-sensitive paint measurements on a supersonic high-sweep oblique wing model. [conducted in the NASA Ames 9- by 7-ft Supersonic Wind Tunnel

NASA Technical Reports Server (NTRS)

McLachlan, B. G.; Bell, J. H.; Park, H.; Kennelly, R. A.; Schreiner, J. A.; Smith, S. C.; Strong, J. M.; Gallery, J.; Gouterman, M.

1995-01-01

The pressure-sensitive paint method was used in the test of a high-sweep oblique wing model, conducted in the NASA Ames 9- by 7-ft Supersonic Wind Tunnel. Surface pressure data was acquired from both the luminescent paint and conventional pressure taps at Mach numbers between M = 1.6 and 2.0. In addition, schlieren photographs of the outer flow were used to determine the location of shock waves impinging on the model. The results show that the luminescent pressure-sensitive paint can capture both global and fine features of the static surface pressure field. Comparison with conventional pressure tap data shows good agreement between the two techniques, and that the luminescent paint data can be used to make quantitative measurements of the pressure changes over the model surface. The experiment also demonstrates the practical considerations and limitations that arise in the application of this technique under supersonic flow conditions in large-scale facilities, as well as the directions in which future research is necessary in order to make this technique a more practical wind-tunnel testing tool.

Probing Ultrafast Electron Dynamics at Surfaces Using Soft X-Ray Transient Reflectivity Spectroscopy

NASA Astrophysics Data System (ADS)

Baker, L. Robert; Husek, Jakub; Biswas, Somnath; Cirri, Anthony

The ability to probe electron dynamics with surface sensitivity on the ultrafast time scale is critical for understanding processes such as charge separation, injection, and surface trapping that mediate efficiency in catalytic and energy conversion materials. Toward this goal, we have developed a high harmonic generation (HHG) light source for femtosecond soft x-ray reflectivity. Using this light source we investigated the ultrafast carrier dynamics at the surface of single crystalline α-Fe2O3, polycrystalline α-Fe2O3, and the mixed metal oxide, CuFeO2. We have recently demonstrated that CuFeO2 in particular is a selective catalyst for photo-electrochemical CO2 reduction to acetate; however, the role of electronic structure and charge carrier dynamics in mediating catalytic selectivity has not been well understood. Soft x-ray reflectivity measurements probe the M2,3, edges of the 3d transition metals, which provide oxidation and spin state resolution with element specificity. In addition to chemical state specificity, these measurements are also surface sensitive, and by independently simulating the contributions of the real and imaginary components of the complex refractive index, we can differentiate between surface and sub-surface contributions to the excited state spectrum. Accordingly, this work demonstrates the ability to probe ultrafast carrier dynamics in catalytic materials with element and chemical state specificity and with surface sensitivity.

Simulation of a sensor array for multiparameter measurements at the prosthetic limb interface

NASA Astrophysics Data System (ADS)

Rowe, Gabriel I.; Mamishev, Alexander V.

2004-07-01

Sensitive skin is a highly desired device for biomechanical devices, wearable computing, human-computer interfaces, exoskeletons, and, most pertinent to this paper, for lower limb prosthetics. The measurement of shear stress is very important because shear effects are key factors in developing surface abrasions and pressure sores in paraplegics and users of prosthetic/orthotic devices. A single element of a sensitive skin is simulated and characterized in this paper. Conventional tactile sensors are designed for measurement of the normal stress only, which is inadequate for comprehensive assessment of surface contact conditions. The sensitive skin discussed here is a flexible array capable of sensing shear and normal forces, as well as humidity and temperature on each element.

Highly sensitive immunosensing of prostate specific antigen using poly cysteine caped by graphene quantum dots and gold nanoparticle: A novel signal amplification strategy.

PubMed

Malekzad, Hediyeh; Hasanzadeh, Mohammad; Shadjou, Nasrin; Jouyban, Abolghasem

2017-12-01

A mediator-free electrochemical immunosensor for quantitation of prostate specific antigen (PSA) based on dual signal amplification strategy was fabricated. In this work, PSA-antibody (anti-PSA) was immobilized onto a green and biocompatible nanocomposite containing poly l-cysteine (P-Cys) as conductive matrix and graphene quantum dots (GQDs)/gold nanoparticles (GNPs) as dual signal amplification elements. Therefore, a novel multilayer film based on P-Cys, GQDs, and GNPs was exploited to develop a highly sensitive amperometric immunosensor for detection of PSA. Fully electrochemical methodology was used to prepare a new transducer on a gold surface which provided a high surface area to immobilize a high amount of the anti-PSA. Importantly, GNPs prepared by soft template synthesized method lead to compact morphology was achieved. The surface morphology of electrode surface was characterized by high-resolution field emission scanning electron microscope (FE-SEM) and energy dispersive spectroscopy (EDX). Chemical compositions of the gold nanoparticles were analysed by an EDX. The immunosensor was employed for the detection of PSA in physiological pH. Under optimized condition the calibration curve for PSA concentration was linear up to 2-9pgmL -1 with lower limit of quantification of 1.8pgmL -1 . Copyright © 2017 Elsevier B.V. All rights reserved.

Applications of Quantum Cascade Laser Scanners for Remote Detection of Chemical and Biological Threats and Weapons of Mass Destruction

DTIC Science & Technology

2014-07-09

Rivera. Highly Sensitive Filter Paper Substrate for SERS Trace Explosives Detection , International Journal of Spectroscopy, (09 2012): 0. doi: 10.1155...Highly Sensitive Filter Paper Substrate for SERS Field Detection of Trace Threat Chemicals”, PITTCON-2013: Forensic Analysis in the Lab and Crime Scene...the surface. In addition, built-in algorithms were used for nearly real-time sample detection . Trace and bulk concentrations of the other substances

Surface sensitization mechanism on negative electron affinity p-GaN nanowires

NASA Astrophysics Data System (ADS)

Diao, Yu; Liu, Lei; Xia, Sihao; Feng, Shu; Lu, Feifei

2018-03-01

The surface sensitization is the key to prepare negative electron affinity photocathode. The thesis emphasizes on the study of surface sensitization mechanism of p-type doping GaN nanowires utilizing first principles based on density function theory. The adsorption energy, work function, dipole moment, geometry structure, electronic structure and optical properties of Mg-doped GaN nanowires surfaces with various coverages of Cs atoms are investigated. The GaN nanowire with Mg doped in core position is taken as the sensitization base. At the initial stage of sensitization, the best adsorption site for Cs atom on GaN nanowire surface is BN, the bridge site of two adjacent N atoms. Surface sensitization generates a p-type internal surface with an n-type surface state, introducing a band bending region which can help reduce surface barrier and work function. With increasing Cs coverage, work functions decrease monotonously and the "Cs-kill" phenomenon disappears. For Cs coverage of 0.75 ML and 1 ML, the corresponding sensitization systems reach negative electron affinity state. Through surface sensitization, the absorption curves are red shifted and the absorption coefficient is cut down. All theoretical calculations can guide the design of negative electron affinity Mg doped GaN nanowires photocathode.

Silver nanocube aggregation gradient materials in search for total internal reflection with high phase sensitivity

NASA Astrophysics Data System (ADS)

König, Tobias A. F.; Ledin, Petr A.; Russell, Michael; Geldmeier, Jeffrey A.; Mahmoud, Mahmoud. A.; El-Sayed, Mostafa A.; Tsukruk, Vladimir V.

2015-03-01

We fabricated monolayer coatings of a silver nanocube aggregation to create a step-wise optical strip by applying different surface pressures during slow Langmuir-Blodgett deposition. The varying amount of randomly distributed nanocube aggregates with different surface coverages in gradient manner due to changes in surface pressure allows for continuous control of the polarization sensitive absorption of the incoming light over a broad optical spectrum. Optical characterization under total internal reflection conditions combined with electromagnetic simulations reveal that the broadband light absorption depends on the relative orientation of the nanoparticles to the polarization of the incoming light. By using computer simulations, we found that the electric field vector of the s-polarized light interacts with the different types of silver nanocube aggregations to excite different plasmonic resonances. The s-polarization shows dramatic changes of the plasmonic resonances at different angles of incidence (shift of 64 nm per 10° angle of incidence). With a low surface nanocube coverage (from 5% to 20%), we observed a polarization-selective high absorption of 80% (with an average 75%) of the incoming light over a broad optical range in the visible region from 400 nm to 700 nm. This large-area gradient material with location-dependent optical properties can be of particular interest for broadband light absorption, phase-sensitive sensors, and imaging.We fabricated monolayer coatings of a silver nanocube aggregation to create a step-wise optical strip by applying different surface pressures during slow Langmuir-Blodgett deposition. The varying amount of randomly distributed nanocube aggregates with different surface coverages in gradient manner due to changes in surface pressure allows for continuous control of the polarization sensitive absorption of the incoming light over a broad optical spectrum. Optical characterization under total internal reflection conditions combined with electromagnetic simulations reveal that the broadband light absorption depends on the relative orientation of the nanoparticles to the polarization of the incoming light. By using computer simulations, we found that the electric field vector of the s-polarized light interacts with the different types of silver nanocube aggregations to excite different plasmonic resonances. The s-polarization shows dramatic changes of the plasmonic resonances at different angles of incidence (shift of 64 nm per 10° angle of incidence). With a low surface nanocube coverage (from 5% to 20%), we observed a polarization-selective high absorption of 80% (with an average 75%) of the incoming light over a broad optical range in the visible region from 400 nm to 700 nm. This large-area gradient material with location-dependent optical properties can be of particular interest for broadband light absorption, phase-sensitive sensors, and imaging. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr06430e

Advanced technique for ultra-thin residue inspection with sub-10nm thickness using high-energy back-scattered electrons

NASA Astrophysics Data System (ADS)

Han, Jin-Hee

2018-03-01

Recently the aspect ratio of capacitor and via hole of memory semiconductor device has been dramatically increasing in order to store more information in a limited area. A small amount of remained residues after etch process on the bottom of the high aspect ratio structure can make a critical failure in device operation. Back-scattered electrons (BSE) are mainly used for inspecting the defect located at the bottom of the high aspect ratio structure or analyzing the overlay of the multi-layer structure because these electrons have a high linearity with the direction of emission and a high kinetic energy above 50eV. However, there is a limitation on that it cannot detect ultra-thin residue material having a thickness of several nanometers because the surface sensitivity is extremely low. We studied the characteristics of BSE spectra using Monte Carlo simulations for several cases which the high aspect ratio structures have extreme microscopic residues. Based on the assumption that most of the electrons emitted without energy loss are localized on the surface, we selected the detection energy window which has a range of 20eV below the maximum energy of the BSE. This window section is named as the high-energy BSE region. As a result of comparing the detection sensitivity of the conventional and the high-energy BSE detection mode, we found that the detection sensitivity for the residuals which have 2nm thickness is improved by more than 10 times in the high-energy BSE mode. This BSE technology is a new inspection method that can greatly be improved the inspection sensitivity for the ultra-thin residual material presented in the high aspect ratio structure, and its application will be expanded.

Phase sensitive spectral domain interferometry for label free biomolecular interaction analysis and biosensing applications

NASA Astrophysics Data System (ADS)

Chirvi, Sajal

Biomolecular interaction analysis (BIA) plays vital role in wide variety of fields, which include biomedical research, pharmaceutical industry, medical diagnostics, and biotechnology industry. Study and quantification of interactions between natural biomolecules (proteins, enzymes, DNA) and artificially synthesized molecules (drugs) is routinely done using various labeled and label-free BIA techniques. Labeled BIA (Chemiluminescence, Fluorescence, Radioactive) techniques suffer from steric hindrance of labels on interaction site, difficulty of attaching labels to molecules, higher cost and time of assay development. Label free techniques with real time detection capabilities have demonstrated advantages over traditional labeled techniques. The gold standard for label free BIA is surface Plasmon resonance (SPR) that detects and quantifies the changes in refractive index of the ligand-analyte complex molecule with high sensitivity. Although SPR is a highly sensitive BIA technique, it requires custom-made sensor chips and is not well suited for highly multiplexed BIA required in high throughput applications. Moreover implementation of SPR on various biosensing platforms is limited. In this research work spectral domain phase sensitive interferometry (SD-PSI) has been developed for label-free BIA and biosensing applications to address limitations of SPR and other label free techniques. One distinct advantage of SD-PSI compared to other label-free techniques is that it does not require use of custom fabricated biosensor substrates. Laboratory grade, off-the-shelf glass or plastic substrates of suitable thickness with proper surface functionalization are used as biosensor chips. SD-PSI is tested on four separate BIA and biosensing platforms, which include multi-well plate, flow cell, fiber probe with integrated optics and fiber tip biosensor. Sensitivity of 33 ng/ml for anti-IgG is achieved using multi-well platform. Principle of coherence multiplexing for multi-channel label-free biosensing applications is introduced. Simultaneous interrogation of multiple biosensors is achievable with a single spectral domain phase sensitive interferometer by coding the individual sensograms in coherence-multiplexed channels. Experimental results demonstrating multiplexed quantitative biomolecular interaction analysis of antibodies binding to antigen coated functionalized biosensor chip surfaces on different platforms are presented.

On understanding the relationship between structure in the potential surface and observables in classical dynamics: A functional sensitivity analysis approach

NASA Astrophysics Data System (ADS)

Judson, Richard S.; Rabitz, Herschel

1987-04-01

The relationship between structure in the potential surface and classical mechanical observables is examined by means of functional sensitivity analysis. Functional sensitivities provide maps of the potential surface, highlighting those regions that play the greatest role in determining the behavior of observables. A set of differential equations for the sensitivities of the trajectory components are derived. These are then solved using a Green's function method. It is found that the sensitivities become singular at the trajectory turning points with the singularities going as η-3/2, with η being the distance from the nearest turning point. The sensitivities are zero outside of the energetically and dynamically allowed region of phase space. A second set of equations is derived from which the sensitivities of observables can be directly calculated. An adjoint Green's function technique is employed, providing an efficient method for numerically calculating these quantities. Sensitivity maps are presented for a simple collinear atom-diatom inelastic scattering problem and for two Henon-Heiles type Hamiltonians modeling intramolecular processes. It is found that the positions of the trajectory caustics in the bound state problem determine regions of the highest potential surface sensitivities. In the scattering problem (which is impulsive, so that ``sticky'' collisions did not occur), the positions of the turning points of the individual trajectory components determine the regions of high sensitivity. In both cases, these lines of singularities are superimposed on a rich background structure. Most interesting is the appearance of classical interference effects. The interference features in the sensitivity maps occur most noticeably where two or more lines of turning points cross. The important practical motivation for calculating the sensitivities derives from the fact that the potential is a function, implying that any direct attempt to understand how local potential regions affect the behavior of the observables by repeatedly and systematically altering the potential will be prohibitively expensive. The functional sensitivity method enables one to perform this analysis at a fraction of the computational labor required for the direct method.

Synthesis and characterization of carbon nanofilms for chemical sensing

NASA Astrophysics Data System (ADS)

Kumar, Vivek

Carbon nanofilms obtained by high temperature graphitization of diamond surface in inert atmospheres or vacuum are modified by treatment in plasma of different precursor gases. At temperatures above 1000 °C, a stable conductive film of thickness between 10 - 100 nm and specific resistivity 10-3-10-4 Ωm, depending upon the heating conditions and the growth atmosphere, is formed on diamond surface. A gray, thin film of high surface resistivity is obtained in high vacuum, while at low vacuum (below 10-4 mbar), a thick black film of low surface resistivity forms. It is observed that the exposure to plasma reduces the surface conductance of carbon nanofilms as result of a partial removal of carbon and the plasma-stimulated amorphization. The rate of the reduction of conductance and hence the etching ability of plasma depends on the type of precursor gas. Hydrogen reveals the strongest etching ability, followed by oxygen and argon, whereas SF6 is ineffective. The carbon nanofilms show significant sensitivity of their electrical conductance to temperature and exposure to the vapors of common organic compounds. The oxygen plasma treated films exhibit selective response to acetone and water vapors. The fast response and recovery of the conductance are the features of the carbon nanofilms. The plasma-treated carbon nanofilm on graphitized diamond surface is discussed as a promising sensing material for development of all-carbon chemical sensors, which may be suitable for biological and medical applications. An alternative approach of fabrication of temperature and chemical sensitive carbon nanofilms on insulating substrates is proposed. The films are obtained by direct deposition of sputtered carbon on highly polished quartz substrates followed by subsequent annealing at temperatures above 400 °C. It is observed that the as-deposited films are essentially amorphous, while the heating induces irreversible structural ordering and gradual conversion of amorphous carbon in disordered graphite. This evolution is confirmed by Raman spectroscopy and electrical measurements. The carbon nanofilms grown on diamond and deposited on quartz both show similar exponential dependence of their conductance on temperature, which is essentially different from the usual behavior of the thermally activated conduction and the conduction due to variable range hopping of charge carriers. The observed exponential dependence of conductance is explained by a model based on the thermally vibrating energy barriers. The as-grown nanofilms on diamond surface show a negative response (decrease in conductance) to the vapors of acetone, toluene and hexane, and a positive response (increase in conductance) to the water vapor. Sensitivity (relative change in conductance) to toluene is greater than to water, acetone, and hexane, in that order. Plasma exposure alters the sensitivity to positive for all the organic vapors. Overall, an increase in sensitivity is observed with the plasma exposure time. For acetone and water, an increased exponential dependence on vapor concentration is also observed. The exposure to oxygen plasma renders the carbon films on diamond selectively sensitive to acetone and water vapors. The hydrogen plasma exposure makes the films selectively sensitive to toluene vapor. It is found that the carbon nanofilms on quartz have p-type conductivity, as indicated by the opposite response to NO2 and NH3 analytes. NO2, a known electron acceptor, increases the conductance. NH3, a known electron donor, decreases the conductance. The phenomenological description of the chemical sensitivity of the carbon nanofilms σ = β/τ is proposed as a function of two main parameters: the time constant τ and the maximum relative change in conductance β. τ and β are described as the parameters related to the surface and bulk material properties of the films, respectively.

Conformal and highly luminescent monolayers of Alq3 prepared by gas-phase molecular layer deposition.

PubMed

Räupke, André; Albrecht, Fabian; Maibach, Julia; Behrendt, Andreas; Polywka, Andreas; Heiderhoff, Ralf; Helzel, Jonatan; Rabe, Torsten; Johannes, Hans-Hermann; Kowalsky, Wolfgang; Mankel, Eric; Mayer, Thomas; Görrn, Patrick; Riedl, Thomas

2014-01-22

The gas-phase molecular layer deposition (MLD) of conformal and highly luminescent monolayers of tris(8-hydroxyquinolinato)aluminum (Alq3) is reported. The controlled formation of Alq3 monolayers is achieved for the first time by functionalization of the substrate with amino groups, which serve as initial docking sites for trimethyl aluminum (TMA) molecules binding datively to the amine. Thereby, upon exposure to 8-hydroxyquinoline (8-HQ), the self-limiting formation of highly luminescent Alq3 monolayers is afforded. The growth process and monolayer formation were studied and verified by in situ quartz crystal monitoring, optical emission and absorption spectroscopy, and X-ray photoelectron spectroscopy. The nature of the MLD process provides an avenue to coat arbitrarily shaped 3D surfaces and porous structures with high surface areas, as demonstrated in this work for silica aerogels. The concept presented here paves the way to highly sensitive luminescent sensors and dye-sensitized metal oxides for future applications (e.g., in photocatalysis and solar cells).

Numerical investigation of narrowband infrared absorber and sensor based on dielectric-metal metasurface.

PubMed

Lu, Xiaoyuan; Zhang, Tongyi; Wan, Rengang; Xu, Yongtao; Zhao, Changhong; Guo, Sheng

2018-04-16

Metasurfaces are investigated intensively for biophotonics applications due to their resonant wavelength flexibly tuned in the near infrared region specially matching biological tissues. Here, we present numerically a metasurface structure combining dielectric resonance with surface plasmon mode of a metal plane, which is a perfect absorber with a narrow linewidth 10 nm wide and quality factor 120 in the near infrared regime. As a sensor, its bulk sensitivity and bulk figure of merit reach respectively 840 nm/RIU and 84/RIU, while its surface sensitivity and surface figure of merit are respectively 1 and 0.1/nm. For different types of adsorbate layers with the same thickness of 8 nm, its surface sensitivity and figure of merit are respectively 32.3 and 3.2/RIU. The enhanced electric field is concentrated on top of dielectric patch ends and in the patch ends simultaneously. Results show that the presented structure has high surface (and bulk) sensing capability in sensing applications due to its narrow linewidth and deep modulation depth. This could pave a new route toward dielectric-metal metasurface in biosensing applications, such as early disease detections and designs of neural stem cell sensing platforms.

Sensitivity of the Antarctic surface mass balance to oceanic perturbations

NASA Astrophysics Data System (ADS)

Kittel, C.; Amory, C.; Agosta, C.; Fettweis, X.

2017-12-01

Regional climate models (RCMs) are suitable numerical tools to study the surface mass balance (SMB) of the wide polar ice sheets due to their high spatial resolution and polar-adapted physics. Nonetheless, RCMs are driven at their boundaries and over the ocean by reanalysis or global climate model (GCM) products and are thus influenced by potential biases in these large-scale fields. These biases can be significant for both the atmosphere and the sea surface conditions (i.e. sea ice concentration and sea surface temperature). With the RCM MAR, a set of sensitivity experiments has been realized to assess the direct response of the SMB of the Antarctic ice sheet to oceanic perturbations. MAR is forced by ERA-Interim and anomalies based on mean GCM biases are introduced in sea surface conditions. Results show significant increases (decreases) of liquid and solid precipitation due to biases related to warm (cold) oceans. As precipitation is mainly caused by low-pressure systems that intrude into the continent and do not penetrate far inland, coastal areas are more sensitive than inland regions. Furthermore, warm ocean representative biases lead to anomalies as large as anomalies simulated by other RCMs or GCMs for the end of the 21st century.

Detection of surface impurity phases in high T.sub.C superconductors using thermally stimulated luminescence

DOEpatents

Cooke, D. Wayne; Jahan, Muhammad S.

1989-01-01

Detection of surface impurity phases in high-temperature superconducting materials. Thermally stimulated luminescence has been found to occur in insulating impurity phases which commonly exist in high-temperature superconducting materials. The present invention is sensitive to impurity phases occurring at a level of less than 1% with a probe depth of about 1 .mu.m which is the region of interest for many superconductivity applications. Spectroscopic and spatial resolution of the emitted light from a sample permits identification and location of the impurity species. Absence of luminescence, and thus of insulating phases, can be correlated with low values of rf surface resistance.

CYTOSOL

EPA Pesticide Factsheets

Technical product bulletin: this surface washing agent for oil spill cleanups extracts and recovers weathered petroleum by flotation, remaining residual hydrocarbons are biodegraded. Suitable for sensitive/ high impact sites including fisheries, rip rap.

Fabrication of a self-assembled and flexible SERS nanosensor for explosive detection at parts-per-quadrillion levels from fingerprints.

PubMed

Liyanage, Thakshila; Rael, Ashur; Shaffer, Sidney; Zaidi, Shozaf; Goodpaster, John V; Sardar, Rajesh

2018-04-30

Apart from high sensitivity and selectivity of surface-enhanced Raman scattering (SERS)-based trace explosive detection, efficient sampling of explosive residue from real world surfaces is very important for homeland security applications. Herein, we demonstrate an entirely new SERS nanosensor fabrication approach. The SERS nanosensor was prepared by self-assembling chemically synthesized gold triangular nanoprisms (Au TNPs), which we show display strong electromagnetic field enhancements at the sharp tips and edges, onto a pressure-sensitive flexible adhesive film. Our SERS nanosensor provides excellent SERS activity (enhancement factor = ∼6.0 × 106) and limit of detection (as low as 56 parts-per-quadrillions) with high selectivity by chemometric analyses among three commonly military high explosives (TNT, RDX, and PETN). Furthermore, the SERS nanosensors present excellent reproducibility (<4.0% relative standard deviation at 1.0 μM concentration) and unprecedentedly high stability with a "shelf life" of at least 5 months. Finally, TNT and PETN were analyzed and quantified by transferring solid explosive residues from fingerprints left on solid surfaces to the SERS nanosensor. Taken together, the demonstrated sensitivity, selectivity, and reliability of the measurements as well as with the excellent shelf life of our SERS nanosensors obviate the need for complicated sample processing steps required for other analytical techniques, and thus these nanosensors have tremendous potential not only in the field of measurement science but also for homeland security applications to combat acts of terror and military threats.

Hollow glass microsphere-structured Fabry-Perot interferometric sensor for highly sensitive temperature measurement

NASA Astrophysics Data System (ADS)

Cheng, Junna; Zhou, Ciming; Fan, Dian; Ou, Yiwen

2017-04-01

We propose and demonstrate a miniature Fabry-Perot (F-P) interferometric sensor based on a hollow glass microsphere (HGM) for highly sensitive temperature measurement. The sensor head is fabricated by sticking a HGM on the end face of a single-mode fiber, and it consists of a short air F-P cavity between the front and the rear surfaces of the HGM. A sensor with 135.7280-μm cavity length was tested for temperature measurement from -5 °C to 50 °C. The obtained sensitivity reached up to 24.5 pm/°C and the variation rate of the HGM- F-P's cavity length was2.1 nm/°C. The advantages of compact size, easy fabrication and low cost make the sensor suitable for highly sensitive temperature sensing.

Atomic-resolution transmission electron microscopy of electron beam–sensitive crystalline materials

NASA Astrophysics Data System (ADS)

Zhang, Daliang; Zhu, Yihan; Liu, Lingmei; Ying, Xiangrong; Hsiung, Chia-En; Sougrat, Rachid; Li, Kun; Han, Yu

2018-02-01

High-resolution imaging of electron beam–sensitive materials is one of the most difficult applications of transmission electron microscopy (TEM). The challenges are manifold, including the acquisition of images with extremely low beam doses, the time-constrained search for crystal zone axes, the precise image alignment, and the accurate determination of the defocus value. We develop a suite of methods to fulfill these requirements and acquire atomic-resolution TEM images of several metal organic frameworks that are generally recognized as highly sensitive to electron beams. The high image resolution allows us to identify individual metal atomic columns, various types of surface termination, and benzene rings in the organic linkers. We also apply our methods to other electron beam–sensitive materials, including the organic-inorganic hybrid perovskite CH3NH3PbBr3.

High intensity interval training is associated with greater impact on physical fitness, insulin sensitivity and muscle mitochondrial content in males with overweight/obesity, as opposed to continuous endurance training: a randomized controlled trial.

PubMed

De Strijcker, Dorien; Lapauw, Bruno; Ouwens, D Margriet; Van de Velde, Dominique; Hansen, Dominique; Petrovic, Mirko; Cuvelier, Claude; Tonoli, Cajsa; Calders, Patrick

2018-06-01

To evaluate the effect of high intensity training (HIT) on physical fitness, basal respiratory exchange ratio (bRER), insulin sensitivity and muscle histology in overweight/obese men compared to continuous aerobic training (CAT). 16 male participants with overweight/obesity (age: 42-57 years, body mass index: 28-36 kg/m2) were randomized to HIT (n=8) or CAT (n=8) for 10 weeks, twice a week. HIT was composed of 10 minutes high intensity, 10 minutes continuous aerobic, 10 minutes high intensity exercises. CAT was composed of three times 10 minutes continuous exercising. Changes in anthropometry, physical and metabolic fitness were evaluated. Muscle histology (mitochondria and lipid content) was evaluated by transmission electron microscopy (TEM). HIT showed a significant increase for peak VO2 (P=0.01), for insulin sensitivity (AUC glucose (P<0,001), AUC insulin (P<0,001), OGTT composite score (P=0.007)) and a significant decrease of bRER (P<0.001) compared to CAT. Muscle mitochondrial content was significantly increased after HIT at the subsarcolemmal (P=0.004 number and P=0.001 surface) as well as the intermyofibrillar site (P<0.001 number and P=0.001 surface). High intensity training elicits stronger beneficial effects on physical fitness, basal RER, insulin sensitivity, and muscle mitochondrial content, as compared to continuous aerobic training.

Photonic Crystal Fiber-Based Surface Plasmon Resonance Sensor with Selective Analyte Channels and Graphene-Silver Deposited Core

PubMed Central

Rifat, Ahmmed A.; Mahdiraji, G. Amouzad; Chow, Desmond M.; Shee, Yu Gang; Ahmed, Rajib; Adikan, Faisal Rafiq Mahamd

2015-01-01

We propose a surface plasmon resonance (SPR) sensor based on photonic crystal fiber (PCF) with selectively filled analyte channels. Silver is used as the plasmonic material to accurately detect the analytes and is coated with a thin graphene layer to prevent oxidation. The liquid-filled cores are placed near to the metallic channel for easy excitation of free electrons to produce surface plasmon waves (SPWs). Surface plasmons along the metal surface are excited with a leaky Gaussian-like core guided mode. Numerical investigations of the fiber’s properties and sensing performance are performed using the finite element method (FEM). The proposed sensor shows maximum amplitude sensitivity of 418 Refractive Index Units (RIU−1) with resolution as high as 2.4 × 10−5 RIU. Using the wavelength interrogation method, a maximum refractive index (RI) sensitivity of 3000 nm/RIU in the sensing range of 1.46–1.49 is achieved. The proposed sensor is suitable for detecting various high RI chemicals, biochemical and organic chemical analytes. Additionally, the effects of fiber structural parameters on the properties of plasmonic excitation are investigated and optimized for sensing performance as well as reducing the sensor’s footprint. PMID:25996510

Sensitivity of Offshore Surface Fluxes and Sea Breezes to the Spatial Distribution of Sea-Surface Temperature

NASA Astrophysics Data System (ADS)

Lombardo, Kelly; Sinsky, Eric; Edson, James; Whitney, Michael M.; Jia, Yan

2018-03-01

A series of numerical sensitivity experiments is performed to quantify the impact of sea-surface temperature (SST) distribution on offshore surface fluxes and simulated sea-breeze dynamics. The SST simulations of two mid-latitude sea-breeze events over coastal New England are performed using a spatially-uniform SST, as well as spatially-varying SST datasets of 32- and 1-km horizontal resolutions. Offshore surface heat and buoyancy fluxes vary in response to the SST distribution. Local sea-breeze circulations are relatively insensitive, with minimal differences in vertical structure and propagation speed among the experiments. The largest thermal perturbations are confined to the lowest 10% of the sea-breeze column due to the relatively high stability of the mid-Atlantic marine atmospheric boundary layer (ABL) suppressing vertical mixing, resulting in the depth of the marine layer remaining unchanged. Minimal impacts on the column-averaged virtual potential temperature and sea-breeze depth translates to small changes in sea-breeze propagation speed. This indicates that the use of datasets with a fine-scale SST may not produce more accurate sea-breeze simulations in highly stable marine ABL regimes, though may prove more beneficial in less stable sub-tropical environments.

New reagent for extraction photomeric determination of anionic surface-active substances

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chernova, R.K.; Yastrebova, N.I.; Pankratov, A.N.

1995-02-01

The new reagent 2,6-diphenyl-4-(4-dimethylamino)styrylpyryl chloride is suggested for extraction photometric determination of anionic surface-active substances (SAS). This reagent possesses high sensitivity and selectivity, and can be used for the determination of both individual SAS of any kind and the total amount of anionic SAS. The reagent was used in analysis of highly mineralized statal waters and for the determination of sulfated products in polyoxyethylated alkylphenols.

Parent and conjugated estrogens and progestagens in surface water of the Santa Ana River: Determination, occurrence, and risk assessment

USDA-ARS?s Scientific Manuscript database

This study presents a sensitive analytical method using high performance liquid chromatography tandem mass spectrometry for the simultaneous monitoring of five estrogen conjugates, six estrogens and two progestagens in surface water of the Santa Ana River. Samples at ten representative sites along t...

Aerodynamic shape optimization of a HSCT type configuration with improved surface definition

NASA Technical Reports Server (NTRS)

Thomas, Almuttil M.; Tiwari, Surendra N.

1994-01-01

Two distinct parametrization procedures of generating free-form surfaces to represent aerospace vehicles are presented. The first procedure is the representation using spline functions such as nonuniform rational b-splines (NURBS) and the second is a novel (geometrical) parametrization using solutions to a suitably chosen partial differential equation. The main idea is to develop a surface which is more versatile and can be used in an optimization process. Unstructured volume grid is generated by an advancing front algorithm and solutions obtained using an Euler solver. Grid sensitivity with respect to surface design parameters and aerodynamic sensitivity coefficients based on potential flow is obtained using an automatic differentiator precompiler software tool. Aerodynamic shape optimization of a complete aircraft with twenty four design variables is performed. High speed civil transport aircraft (HSCT) configurations are targeted to demonstrate the process.

An approach to measure parameter sensitivity in watershed ...

EPA Pesticide Factsheets

Hydrologic responses vary spatially and temporally according to watershed characteristics. In this study, the hydrologic models that we developed earlier for the Little Miami River (LMR) and Las Vegas Wash (LVW) watersheds were used for detail sensitivity analyses. To compare the relative sensitivities of the hydrologic parameters of these two models, we used Normalized Root Mean Square Error (NRMSE). By combining the NRMSE index with the flow duration curve analysis, we derived an approach to measure parameter sensitivities under different flow regimes. Results show that the parameters related to groundwater are highly sensitive in the LMR watershed, whereas the LVW watershed is primarily sensitive to near surface and impervious parameters. The high and medium flows are more impacted by most of the parameters. Low flow regime was highly sensitive to groundwater related parameters. Moreover, our approach is found to be useful in facilitating model development and calibration. This journal article describes hydrological modeling of climate change and land use changes on stream hydrology, and elucidates the importance of hydrological model construction in generating valid modeling results.

Photonic crystal fiber-based plasmonic biosensor with external sensing approach

NASA Astrophysics Data System (ADS)

Rifat, Ahmmed A.; Hasan, Md. Rabiul; Ahmed, Rajib; Butt, Haider

2018-01-01

We propose a simple photonic crystal fiber (PCF) biosensor based on the surface plasmon resonance effect. The sensing properties are characterized using the finite element method. Chemically stable gold material is deposited on the outer surface of the PCF to realize the practical sensing approach. The performance of the modeled biosensor is investigated in terms of wavelength sensitivity, amplitude sensitivity, sensor resolution, and linearity of the resonant wavelength with the variation of structural parameters. In the sensing range of 1.33 to 1.37, maximum sensitivities of 4000 nm/RIU and 478 are achieved with the high sensor resolutions of 2.5×10-5 and 2.1×10-5 RIU using wavelength and amplitude interrogation methods, respectively. The designed biosensor will reduce fabrication complexity due to its simple and realistic hexagonal lattice structure. It is anticipated that the proposed biosensor may find possible applications for unknown biological and biochemical analyte detections with a high degree of accuracy.

CMOS image sensor for detection of interferon gamma protein interaction as a point-of-care approach.

PubMed

Marimuthu, Mohana; Kandasamy, Karthikeyan; Ahn, Chang Geun; Sung, Gun Yong; Kim, Min-Gon; Kim, Sanghyo

2011-09-01

Complementary metal oxide semiconductor (CMOS)-based image sensors have received increased attention owing to the possibility of incorporating them into portable diagnostic devices. The present research examined the efficiency and sensitivity of a CMOS image sensor for the detection of antigen-antibody interactions involving interferon gamma protein without the aid of expensive instruments. The highest detection sensitivity of about 1 fg/ml primary antibody was achieved simply by a transmission mechanism. When photons are prevented from hitting the sensor surface, a reduction in digital output occurs in which the number of photons hitting the sensor surface is approximately proportional to the digital number. Nanoscale variation in substrate thickness after protein binding can be detected with high sensitivity by the CMOS image sensor. Therefore, this technique can be easily applied to smartphones or any clinical diagnostic devices for the detection of several biological entities, with high impact on the development of point-of-care applications.

Portable evanescent wave fiber biosensor for highly sensitive detection of Shigella

NASA Astrophysics Data System (ADS)

Xiao, Rui; Rong, Zhen; Long, Feng; Liu, Qiqi

2014-11-01

A portable evanescent wave fiber biosensor was developed to achieve the rapid and highly sensitive detection of Shigella. In this study, a DNA probe was covalently immobilized onto fiber-optic biosensors that can hybridize with a fluorescently labeled complementary DNA. The sensitivity of detection for synthesized oligonucleotides can reach 10-10 M. The surface of the sensor can be regenerated with 0.5% sodium dodecyl sulfate solution (pH 1.9) for over 30 times without significant deterioration of performance. The total analysis time for a single sample, including the time for measurement and surface regeneration, was less than 6 min. We employed real-time polymerase chain reaction (PCR) and compared the results of both methods to investigate the actual Shigella DNA detection capability of the fiber-optic biosensor. The fiber-optic biosensor could detect as low as 102 colony-forming unit/mL Shigella. This finding was comparable with that by real-time PCR, which suggests that this method is a potential alternative to existing detection methods.

Rapid, Sensitive Detection of Botulinum Toxin on a Flexible Microfluidics Platform

DOE Office of Scientific and Technical Information (OSTI.GOV)

Warner, Marvin G.; Dockendorff, Brian P.; Feldhaus, Michael J.

2004-10-30

In this paper we will describe how high affinity reagents and a sensor configuration enabling rapid mass transport can be combined for rapid, sensitive biodetection. The system that we have developed includes a renewable surface immunoassay, which involves on-column detection of a fluorescently labeled secondary antibody in a sandwich immunoassay. Yeast display and directed molecular evolution were used to create high affinity antibodies to the botulinum toxin heavy chain receptor binding domain, AR1 and 3D12. A rotating rod renewable surface microcolumn was used to form a microliter-sized column containing beads functionalized with the capture antibody (AR1). The column was perfusedmore » with sample, wash solutions, and a fluorescently labeled secondary antibody (3D12) while the on-column fluorescence was monitored. Detection was accomplished in less than 5 minutes, with a total processing time of about 10 minutes. On-column detection of botulinum toxin was more sensitive and much faster than flow cytometry analysis on microbeads using the same reagents.« less

Fast and sensitive trace analysis of malachite green using a surface-enhanced Raman microfluidic sensor.

PubMed

Lee, Sangyeop; Choi, Junghyun; Chen, Lingxin; Park, Byungchoon; Kyong, Jin Burm; Seong, Gi Hun; Choo, Jaebum; Lee, Yeonjung; Shin, Kyung-Hoon; Lee, Eun Kyu; Joo, Sang-Woo; Lee, Kyeong-Hee

2007-05-08

A rapid and highly sensitive trace analysis technique for determining malachite green (MG) in a polydimethylsiloxane (PDMS) microfluidic sensor was investigated using surface-enhanced Raman spectroscopy (SERS). A zigzag-shaped PDMS microfluidic channel was fabricated for efficient mixing between MG analytes and aggregated silver colloids. Under the optimal condition of flow velocity, MG molecules were effectively adsorbed onto silver nanoparticles while flowing along the upper and lower zigzag-shaped PDMS channel. A quantitative analysis of MG was performed based on the measured peak height at 1615 cm(-1) in its SERS spectrum. The limit of detection, using the SERS microfluidic sensor, was found to be below the 1-2 ppb level and this low detection limit is comparable to the result of the LC-Mass detection method. In the present study, we introduce a new conceptual detection technology, using a SERS microfluidic sensor, for the highly sensitive trace analysis of MG in water.

Recent advances in surface plasmon resonance imaging: detection speed, sensitivity, and portability

NASA Astrophysics Data System (ADS)

Zeng, Youjun; Hu, Rui; Wang, Lei; Gu, Dayong; He, Jianan; Wu, Shu-Yuen; Ho, Ho-Pui; Li, Xuejin; Qu, Junle; Gao, Bruce Zhi; Shao, Yonghong

2017-06-01

Surface plasmon resonance (SPR) biosensor is a powerful tool for studying the kinetics of biomolecular interactions because they offer unique real-time and label-free measurement capabilities with high detection sensitivity. In the past two decades, SPR technology has been successfully commercialized and its performance has continuously been improved with lots of engineering efforts. In this review, we describe the recent advances in SPR technologies. The developments of SPR technologies focusing on detection speed, sensitivity, and portability are discussed in details. The incorporation of imaging techniques into SPR sensing is emphasized. In addition, our SPR imaging biosensors based on the scanning of wavelength by a solid-state tunable wavelength filter are highlighted. Finally, significant advances of the vast developments in nanotechnology-associated SPR sensing for sensitivity enhancements are also reviewed. It is hoped that this review will provide some insights for researchers who are interested in SPR sensing, and help them develop SPR sensors with better sensitivity and higher throughput.

Potential of groundwater contamination by polybrominated diphenyl ethers (PBDEs) in a sensitive bedrock aquifer (Canada)

NASA Astrophysics Data System (ADS)

Levison, Jana; Novakowski, Kent; Reiner, Eric J.; Kolic, Terry

2012-03-01

It is necessary to understand the presence, movement, and persistence of contaminants in aquifers to develop adequate groundwater protection plans. Fractured bedrock aquifers with thin overburden cover are very sensitive to contamination, and little is known about transport processes from the ground surface to depth in this setting. This study was undertaken to investigate the potential of groundwater contamination by polybrominated diphenyl ethers (PBDEs), which are flame retardants, in a natural fractured bedrock aquifer in Canada proven to be sensitive to contamination. PBDEs, which had not been previously measured in groundwater in detail, were detected in the study aquifer at concentrations greater than those observed in surface-water bodies. Potential sources include manure, septic tanks, and the atmosphere. From this scoping study, it is evident that additional surveys of PBDE concentrations in groundwater are warranted, especially in settings with high potential source concentrations coupled with sensitive aquifers.

High-surface-area architectures for improved charge transfer kinetics at the dark electrode in dye-sensitized solar cells.

PubMed

Hoffeditz, William L; Katz, Michael J; Deria, Pravas; Martinson, Alex B F; Pellin, Michael J; Farha, Omar K; Hupp, Joseph T

2014-06-11

Dye-sensitized solar cell (DSC) redox shuttles other than triiodide/iodide have exhibited significantly higher charge transfer resistances at the dark electrode. This often results in poor fill factor, a severe detriment to device performance. Rather than moving to dark electrodes of untested materials that may have higher catalytic activity for specific shuttles, the surface area of platinum dark electrodes could be increased, improving the catalytic activity by simply presenting more catalyst to the shuttle solution. A new copper-based redox shuttle that experiences extremely high charge-transfer resistance at conventional Pt dark electrodes yields cells having fill-factors of less than 0.3. By replacing the standard Pt dark electrode with an inverse opal Pt electrode fabricated via atomic layer deposition, the dark electrode surface area is boosted by ca. 50-fold. The resulting increase in interfacial electron transfer rate (decrease in charge-transfer resistance) nearly doubles the fill factor and therefore the overall energy conversion efficiency, illustrating the utility of this high-area electrode for DSCs.

A Localized Surface Plasmon Resonance Sensor Using Double-Metal-Complex Nanostructures and a Review of Recent Approaches

PubMed Central

Ahn, Heesang; Song, Hyerin; Kim, Kyujung

2017-01-01

From active developments and applications of various devices to acquire outside and inside information and to operate based on feedback from that information, the sensor market is growing rapidly. In accordance to this trend, the surface plasmon resonance (SPR) sensor, an optical sensor, has been actively developed for high-sensitivity real-time detection. In this study, the fundamentals of SPR sensors and recent approaches for enhancing sensing performance are reported. In the section on the fundamentals of SPR sensors, a brief description of surface plasmon phenomena, SPR, SPR-based sensing applications, and several configuration types of SPR sensors are introduced. In addition, advanced nanotechnology- and nanofabrication-based techniques for improving the sensing performance of SPR sensors are proposed: (1) localized SPR (LSPR) using nanostructures or nanoparticles; (2) long-range SPR (LRSPR); and (3) double-metal-layer SPR sensors for additional performance improvements. Consequently, a high-sensitivity, high-biocompatibility SPR sensor method is suggested. Moreover, we briefly describe issues (miniaturization and communication technology integration) for future SPR sensors. PMID:29301238

Surface-Enhanced Raman Spectroscopy for Staphylococcus aureus DNA Detection by Using Surface-Enhanced Raman Scattering Tag on Au Film Over Nanosphere Substrate.

PubMed

Chen, Jian; Wang, Jun-Feng; Wu, Xue-Zhong; Rong, Zhen; Dong, Pei-Tao; Xiao, Rui

2018-06-01

We developed a high-performance surface-enhanced Raman scattering (SERS) sensing platform that can be used for specific and sensitive DNA detection. The SERS platform combines the advantages of Au film over nanosphere (AuFON) substrate and Ag@PATP@SiO2 SERS tag. SERS tag-on-AuFON is a sensing system that operates by the self-assembly of SERS tag onto an AuFON substrate in the presence of target DNAs. The SERS signals can be dramatically enhanced by the formation of "hot spots" in the interstices between the assembled nanostructures, as confirmed by finite-difference time-domain (FDTD) simulation. As a new sensing platform, SERS tag-on-AuFON was utilized to detect Staphylococcus aureus (S. aureus) DNA with a limit of detection at 1 nM. A linear relationship was also observed between the SERS intensity at Raman peak 1439 cm-1 and the logarithm of target DNA concentrations ranging from 1 μM to 1 nM. Besides, the sensing platform showed good homogeneity, with a relative standard deviation of about 1%. The sensitive SERS platform created in this study is a promising tool for detecting trace biochemical molecules because of its relatively simple and effective fabrication procedure, high sensitivity, and high reproducibility of the SERS effect.

An InN/InGaN Quantum Dot Electrochemical Biosensor for Clinical Diagnosis

PubMed Central

Alvi, Naveed ul Hassan; Gómez, Victor J.; Rodriguez, Paul E.D. Soto; Kumar, Praveen; Zaman, Saima; Willander, Magnus; Nötzel, Richard

2013-01-01

Low-dimensional InN/InGaN quantum dots (QDs) are demonstrated for realizing highly sensitive and efficient potentiometric biosensors owing to their unique electronic properties. The InN QDs are biochemically functionalized. The fabricated biosensor exhibits high sensitivity of 97 mV/decade with fast output response within two seconds for the detection of cholesterol in the logarithmic concentration range of 1 × 10−6 M to 1 × 10−3 M. The selectivity and reusability of the biosensor are excellent and it shows negligible response to common interferents such as uric acid and ascorbic acid. We also compare the biosensing properties of the InN QDs with those of an InN thin film having the same surface properties, i.e., high density of surface donor states, but different morphology and electronic properties. The sensitivity of the InN QDs-based biosensor is twice that of the InN thin film-based biosensor, the EMF is three times larger, and the response time is five times shorter. A bare InGaN layer does not produce a stable response. Hence, the superior biosensing properties of the InN QDs are governed by their unique surface properties together with the zero-dimensional electronic properties. Altogether, the InN QDs-based biosensor reveals great potential for clinical diagnosis applications. PMID:24132228

Schottky-contact plasmonic dipole rectenna concept for biosensing.

PubMed

Alavirad, Mohammad; Mousavi, Saba Siadat; Roy, Langis; Berini, Pierre

2013-02-25

Nanoantennas are key optical components for several applications including photodetection and biosensing. Here we present an array of metal nano-dipoles supporting surface plasmon polaritons (SPPs) integrated into a silicon-based Schottky-contact photodetector. Incident photons coupled to the array excite SPPs on the Au nanowires of the antennas which decay by creating "hot" carriers in the metal. The hot carriers may then be injected over the potential barrier at the Au-Si interface resulting in a photocurrent. High responsivities of 100 mA/W and practical minimum detectable powers of -12 dBm should be achievable in the infra-red (1310 nm). The device was then investigated for use as a biosensor by computing its bulk and surface sensitivities. Sensitivities of ∼ 250 nm/RIU (bulk) and ∼ 8 nm/nm (surface) in water are predicted. We identify the mode propagating and resonating along the nanowires of the antennas, we apply a transmission line model to describe the performance of the antennas, and we extract two useful formulas to predict their bulk and surface sensitivities. We prove that the sensitivities of dipoles are much greater than those of similar monopoles and we show that this difference comes from the gap in dipole antennas where electric fields are strongly enhanced.

Preparation of surface enhanced Raman substrate and its characterization

NASA Astrophysics Data System (ADS)

Liu, Y.; Wang, J. Y.; Wang, J. Q.

2017-10-01

Surface enhanced Raman spectroscopy (SERS) is a fast, convenient and highly sensitive detection technique, and preparing the good effect and repeatable substrate is the key to realize the trace amount and quantitative detection in the field of food safety detection. In this paper, a surface enhanced Raman substrate based on submicrometer silver particles structure was prepared by chemical deposition method, and characterized its structure and optical properties.

NOAA AVHRR Land Surface Albedo Algorithm Development

NASA Technical Reports Server (NTRS)

Toll, D. L.; Shirey, D.; Kimes, D. S.

1997-01-01

The primary objective of this research is to develop a surface albedo model for the National Oceanic and Atmospheric Administration (NOAA) Advanced Very High Resolution Radiometer (AVHRR). The primary test site is the Konza prairie, Kansas (U.S.A.), used by the International Satellite Land Surface Climatology Project (ISLSCP) in the First ISLSCP Field Experiment (FIFE). In this research, high spectral resolution field spectrometer data was analyzed to simulate AVHRR wavebands and to derive surface albedos. Development of a surface albedo algorithm was completed by analysing a combination of satellite, field spectrometer, and ancillary data. Estimated albedos from the field spectrometer data were compared to reference albedos derived using pyranometer data. Variations from surface anisotropy of reflected solar radiation were found to be the most significant albedo-related error. Additional error or sensitivity came from estimation of a shortwave mid-IR reflectance (1.3-4.0 micro-m) using the AVHRR red and near-IR bands. Errors caused by the use of AVHRR spectral reflectance to estimate both a total visible (0.4-0.7 micro-m) and near-IR (0.7-1.3 micro-m) reflectance were small. The solar spectral integration, using the derived ultraviolet, visible, near-IR and SW mid-IR reflectivities, was not sensitive to many clear-sky changes in atmospheric properties and illumination conditions.

Dye-sensitized solar cell employing zinc oxide aggregates grown in the presence of lithium

DOEpatents

Zhang, Qifeng; Cao, Guozhong

2013-10-15

Provided are a novel ZnO dye-sensitized solar cell and method of fabricating the same. In one embodiment, deliberately added lithium ions are used to mediate the growth of ZnO aggregates. The use of lithium provides ZnO aggregates that have advantageous microstructure, morphology, crystallinity, and operational characteristics. Employing lithium during aggregate synthesis results in a polydisperse collection of ZnO aggregates favorable for porosity and light scattering. The resulting nanocrystallites forming the aggregates have improved crystallinity and more favorable facets for dye molecule absorption. The lithium synthesis improves the surface stability of ZnO in acidic dyes. The procedures developed and disclosed herein also help ensure the formation of an aggregate film that has a high homogeneity of thickness, a high packing density, a high specific surface area, and good electrical contact between the film and the fluorine-doped tin oxide electrode and among the aggregate particles.

Capillary-valve-based fabrication of ion-selective membrane junction for electrokinetic sample preconcentration in PDMS chip.

PubMed

Liu, Vincent; Song, Yong-Ak; Han, Jongyoon

2010-06-07

In this paper, we report a novel method for fabricating ion-selective membranes in poly(dimethylsiloxane) (PDMS)/glass-based microfluidic preconcentrators. Based on the concept of capillary valves, this fabrication method involves filling a lithographically patterned junction between two microchannels with an ion-selective material such as Nafion resin; subsequent curing results in a high aspect-ratio membrane for use in electrokinetic sample preconcentration. To demonstrate the concentration performance of this high-aspect-ratio, ion-selective membrane, we integrated the preconcentrator with a surface-based immunoassay for R-Phycoerythrin (RPE). Using a 1x PBS buffer system, the preconcentrator-enhanced immunoassay showed an approximately 100x improvement in sensitivity within 30 min. This is the first time that an electrokinetic microfluidic preconcentrator based on ion concentration polarization (ICP) has been used in high ionic strength buffer solutions to enhance the sensitivity of a surface-based immunoassay.

Development of a highly enantioselective capacitive immunosensor for the detection of alpha-amino acids.

PubMed

Zhang, Song; Ding, Jingjing; Liu, Ying; Kong, Jilie; Hofstetter, Oliver

2006-11-01

This work describes a highly enantioselective and sensitive immunosensor for the detection of chiral amino acids based on capacitive measurement. The sensor was prepared by first binding mercaptoacetic acid to the surface of a gold electrode, followed by modification with tyramine utilizing carbodiimide activation. The hapten 4-amino-D-phenylalanine was then covalently immobilized onto the electrode by diazotization. Stereoselective binding of an anti-D-amino acid antibody to the hapten-modified sensor surface resulted in capacitance changes that were detected with high sensitivity by a potentiostatic step method. Using capacitance measurement, detection limits of 5 pg of antibody/mL were attained. The exquisite stereoselectivity of the antibody was also utilized in a competitive setup to quantitatively determine the concentration of the analyte d-phenylalanine in nonracemic samples containing both enantiomers of this amino acid. Trace impurities of d-phenylalanine as low as 0.001% could be detected.

Surface charge mapping with a nanopipette.

PubMed

McKelvey, Kim; Kinnear, Sophie L; Perry, David; Momotenko, Dmitry; Unwin, Patrick R

2014-10-01

Nanopipettes are emerging as simple but powerful tools for probing chemistry at the nanoscale. In this contribution the use of nanopipettes for simultaneous surface charge mapping and topographical imaging is demonstrated, using a scanning ion conductance microscopy (SICM) format. When a nanopipette is positioned close to a surface in electrolyte solution, the direct ion current (DC), driven by an applied bias between a quasi-reference counter electrode (QRCE) in the nanopipette and a second QRCE in the bulk solution, is sensitive to surface charge. The charge sensitivity arises because the diffuse double layers at the nanopipette and the surface interact, creating a perm-selective region which becomes increasingly significant at low ionic strengths (10 mM 1:1 aqueous electrolyte herein). This leads to a polarity-dependent ion current and surface-induced rectification as the bias is varied. Using distance-modulated SICM, which induces an alternating ion current component (AC) by periodically modulating the distance between the nanopipette and the surface, the effect of surface charge on the DC and AC is explored and rationalized. The impact of surface charge on the AC phase (with respect to the driving sinusoidal signal) is highlighted in particular; this quantity shows a shift that is highly sensitive to interfacial charge and provides the basis for visualizing charge simultaneously with topography. The studies herein highlight the use of nanopipettes for functional imaging with applications from cell biology to materials characterization where understanding surface charge is of key importance. They also provide a framework for the design of SICM experiments, which may be convoluted by topographical and surface charge effects, especially for small nanopipettes.

Modelling high Arctic deep permafrost temperature sensitivity in Northeast Greenland based on experimental and field observations

NASA Astrophysics Data System (ADS)

Rasmussen, Laura Helene; Zhang, Wenxin; Hollesen, Jørgen; Cable, Stefanie; Hvidtfeldt Christiansen, Hanne; Jansson, Per-Erik; Elberling, Bo

2017-04-01

Permafrost affected areas in Greenland are expected to experience a marked temperature increase within decades. Most studies have considered near-surface permafrost sensitivity, whereas permafrost temperatures below the depths of zero annual amplitude is less studied despite being closely related to changes in near-surface conditions, such as changes in active layer thermal properties, soil moisture and snow depth. In this study, we measured the sensitivity of thermal conductivity (TC) to gravimetric water content (GWC) in frozen and thawed permafrost sediments from fine-sandy and gravelly deltaic and fine-sandy alluvial deposits in the Zackenberg valley, NE Greenland. We further calibrated a coupled heat and water transfer model, the "CoupModel", for one central delta sediment site with average snow depth and further forced it with meteorology from a nearby delta sediment site with a topographic snow accumulation. With the calibrated model, we simulated deep permafrost thermal dynamics in four 20-year scenarios with changes in surface temperature and active layer (AL) soil moisture: a) 3 °C warming and AL water table at 0.5 m depth; b) 3 °C warming and AL water table at 0.1 m depth; c) 6 °C warming and AL water table at 0.5 m depth and d) 6 °C warming and AL water table at 0.1 m depth. Our results indicate that frozen sediments have higher TC than thawed sediments. All sediments show a positive linear relation between TC and soil moisture when frozen, and a logarithmic one when thawed. Gravelly delta sediments were highly sensitive, but never reached above 12 % GWC, indicating a field effect of water retention capacity. Alluvial sediments are less sensitive to soil moisture than deltaic (fine and coarse) sediments, indicating the importance of unfrozen water in frozen sediment. The deltaic site with snow accumulation had 1 °C higher mean annual ground temperature than the average snow depth site. Permafrost temperature at the depth of 18 m increased with 1.5 °C and 3.5 °C in the scenarios with 3 °C and 6 °C warming, respectively. Increasing the soil moisture had no important additional effect to warming, although an increase in thermal offset was indicated. We conclude that below-ground sediment properties affect the sensitivity of TC to GWC, that surface temperature changes can influence the deep permafrost within a short time scale, and that differences in snow depth affect surface temperatures. Sediment type and the type of precipitation should thus be considered when estimating future High Arctic deep permafrost sensitivity.

Acceleration sensitivity of micromachined pressure sensors

NASA Astrophysics Data System (ADS)

August, Richard; Maudie, Theresa; Miller, Todd F.; Thompson, Erik

1999-08-01

Pressure sensors serve a variety of automotive applications, some which may experience high levels of acceleration such as tire pressure monitoring. To design pressure sensors for high acceleration environments it is important to understand their sensitivity to acceleration especially if thick encapsulation layers are used to isolate the device from the hostile environment in which they reside. This paper describes a modeling approach to determine their sensitivity to acceleration that is very general and is applicable to different device designs and configurations. It also describes the results of device testing of a capacitive surface micromachined pressure sensor at constant acceleration levels from 500 to 2000 g's.

Sensitivities of ionic explosives

NASA Astrophysics Data System (ADS)

Politzer, Peter; Lane, Pat; Murray, Jane S.

2017-03-01

We have investigated the relevance for ionic explosive sensitivity of three factors that have been demonstrated to be related to the sensitivities of molecular explosives. These are (1) the maximum available heat of detonation, (2) the amount of free space per molecule (or per formula unit) in the crystal lattice and (3) specific features of the electrostatic potential on the molecular or ionic surface. We find that for ionic explosives, just as for molecular ones, there is an overall tendency for impact sensitivity to increase as the maximum detonation heat release is greater. This means that the usual emphasis upon designing explosives with large heats of detonation needs to be tempered somewhat. We also show that a moderate detonation heat release does not preclude a high level of detonation performance for ionic explosives, as was already demonstrated for molecular ones. Relating the free space per formula unit to sensitivity may require a modified procedure for ionic explosives; this will continue to be investigated. Finally, an encouraging start has been made in linking impact sensitivities to the electrostatic potentials on ionic surfaces, although limited so far to ammonium salts.

Cutaway of SEIS (Artist's Concept)

NASA Image and Video Library

2018-04-09

This artist's rendering shows a cutaway of the Seismic Experiment for Interior Structure instrument, or SEIS, which will fly as part of NASA's Mars InSight lander. SEIS is a highly sensitive seismometer that will be used to detect marsquakes from the Red Planet's surface for the first time. There are two layers in this cutaway. The outer layer is the Wind and Thermal Shield -- a covering that protects the seismometer from the Martian environment. The wind on Mars, as well as extreme temperature changes, could affect the highly sensitive instrument. The inside layer is SEIS itself, a brass-colored dome that houses the instrument's three pendulums. These insides are inside a titanium vacuum chamber to further isolate them from temperature changes on the Martian surface. https://photojournal.jpl.nasa.gov/catalog/PIA22320

Novel fabrication of flexible graphene-based chemical sensors with heaters using soft lithographic patterning method.

PubMed

Jung, Min Wook; Myung, Sung; Song, Wooseok; Kang, Min-A; Kim, Sung Ho; Yang, Cheol-Soo; Lee, Sun Sook; Lim, Jongsun; Park, Chong-Yun; Lee, Jeong-O; An, Ki-Seok

2014-08-27

We have fabricated graphene-based chemical sensors with flexible heaters for the highly sensitive detection of specific gases. We believe that increasing the temperature of the graphene surface significantly enhanced the electrical signal change of the graphene-based channel, and reduced the recovery time needed to obtain a normal state of equilibrium. In addition, a simple and efficient soft lithographic patterning process was developed via surface energy modification for advanced, graphene-based flexible devices, such as gas sensors. As a proof of concept, we demonstrated the high sensitivity of NO2 gas sensors based on graphene nanosheets. These devices were fabricated using a simple soft-lithographic patterning method, where flexible graphene heaters adjacent to the channel of sensing graphene were utilized to control graphene temperature.

Advanced Control Surface Seal Development for Future Space Vehicles

NASA Technical Reports Server (NTRS)

DeMange, Jeffrey J.; Dunlap, Patrick H., Jr.; Steinetz, Bruce M.

2004-01-01

High temperature control surface seals have been identified as a critical technology in the development of future space vehicles. These seals must withstand temperatures of up to 2600 F and protect underlying temperature-sensitive structures (such as actuators and sealing capability by remaining resilient during flight conditions. The current baseline seal, used on the Shuttle orbiters and the X-38 vehicle, consists of a Nextel 312 sheath, an internal Inconel X-750 knitted spring tube, and hand-stuffed Saffil batting. Unfortunately at high temperatures (> 1500 F), the seal resiliency significantly degrades due to yielding and creep of the spring tube element. The permanent set in the seals can result in flow passing over the seals and subsequent damage to temperature sensitive components downstream of the seals. Another shortcoming of the baseline seal is that instances have been reported on Shuttle flights where some of the hand-stuffed Saffil batting insulation has been extracted, thus potentially compromising the seal. In vehicles where the thermal protection systems are delicate (such as with Shuttle tiles), the control surface seals must also limit the amount of force applied to the opposing surfaces. Additionally, in many applications the seals are subjected to scrubbing as control surfaces are actuated. The seals must be able to withstand any damage resulting from this high temperature scrubbing and retain their heat/flow blocking abilities.

Computational simulation of biomolecules transport with multi-physics near microchannel surface for development of biomolecules-detection devices.

PubMed

Suzuki, Yuma; Shimizu, Tetsuhide; Yang, Ming

2017-01-01

The quantitative evaluation of the biomolecules transport with multi-physics in nano/micro scale is demanded in order to optimize the design of microfluidics device for the biomolecules detection with high detection sensitivity and rapid diagnosis. This paper aimed to investigate the effectivity of the computational simulation using the numerical model of the biomolecules transport with multi-physics near a microchannel surface on the development of biomolecules-detection devices. The biomolecules transport with fluid drag force, electric double layer (EDL) force, and van der Waals force was modeled by Newtonian Equation of motion. The model validity was verified in the influence of ion strength and flow velocity on biomolecules distribution near the surface compared with experimental results of previous studies. The influence of acting forces on its distribution near the surface was investigated by the simulation. The trend of its distribution to ion strength and flow velocity was agreement with the experimental result by the combination of all acting forces. Furthermore, EDL force dominantly influenced its distribution near its surface compared with fluid drag force except for the case of high velocity and low ion strength. The knowledges from the simulation might be useful for the design of biomolecules-detection devices and the simulation can be expected to be applied on its development as the design tool for high detection sensitivity and rapid diagnosis in the future.

Enhanced H2 sensitivity at room temperature of ZnO nanowires functionalized by Pd nanoparticles

NASA Astrophysics Data System (ADS)

Ren, Shoutian; Fan, Guanghua; Qu, Shiliang; Wang, Qiang

2011-10-01

For sensitive detection of H2, ZnO nanowires networks decorated with photo-decomposed Pd nanoparticles were fabricated between femtosecond laser-writing interdigitated electrodes by chemical vapor deposition method. When H2 concentration is increased from 20 to 4000 ppm at room temperature, sensitivity of the sample is increased from 3.7% to 1017.9%. The high sensitivity can be explained by considering the reaction between the adsorbed O2- and the disassociated H atoms facilitated by Pd nanoparticles. This mechanism is further supported by the H2 response results under UV light illumination, which can reduce the amount of O2- on the ZnO surface, leading to depressed sensitivity. The sensor also shows high selectivity, long-term stability, and ultra-low power consumption of nanowatt level, due to the novel fabrication process.

Short non-coding RNAs as bacteria species identifiers detected by surface plasmon resonance enhanced common path interferometry

NASA Astrophysics Data System (ADS)

Greef, Charles; Petropavlovskikh, Viatcheslav; Nilsen, Oyvind; Khattatov, Boris; Plam, Mikhail; Gardner, Patrick; Hall, John

2008-04-01

Small non-coding RNA sequences have recently been discovered as unique identifiers of certain bacterial species, raising the possibility that they can be used as highly specific Biowarfare Agent detection markers in automated field deployable integrated detection systems. Because they are present in high abundance they could allow genomic based bacterial species identification without the need for pre-assay amplification. Further, a direct detection method would obviate the need for chemical labeling, enabling a rapid, efficient, high sensitivity mechanism for bacterial detection. Surface Plasmon Resonance enhanced Common Path Interferometry (SPR-CPI) is a potentially market disruptive, high sensitivity dual technology that allows real-time direct multiplex measurement of biomolecule interactions, including small molecules, nucleic acids, proteins, and microbes. SPR-CPI measures differences in phase shift of reflected S and P polarized light under Total Internal Reflection (TIR) conditions at a surface, caused by changes in refractive index induced by biomolecular interactions within the evanescent field at the TIR interface. The measurement is performed on a microarray of discrete 2-dimensional areas functionalized with biomolecule capture reagents, allowing simultaneous measurement of up to 100 separate analytes. The optical beam encompasses the entire microarray, allowing a solid state detector system with no scanning requirement. Output consists of simultaneous voltage measurements proportional to the phase differences resulting from the refractive index changes from each microarray feature, and is automatically processed and displayed graphically or delivered to a decision making algorithm, enabling a fully automatic detection system capable of rapid detection and quantification of small nucleic acids at extremely sensitive levels. Proof-of-concept experiments on model systems and cell culture samples have demonstrated utility of the system, and efforts are in progress for full development and deployment of the device. The technology has broad applicability as a universal detection platform for BWA detection, medical diagnostics, and drug discovery research, and represents a new class of instrumentation as a rapid, high sensitivity, label-free methodology.

Compensation of relector antenna surface distortion using an array feed

NASA Technical Reports Server (NTRS)

Cherrette, A. R.; Acosta, R. J.; Lam, P. T.; Lee, S. W.

1988-01-01

The dimensional stability of the surface of a large reflector antenna is important when high gain or low sidelobe performance is desired. If the surface is distorted due to thermal or structural reasons, antenna performance can be improved through the use of an array feed. The design of the array feed and its relation to the surface distortion are examined. The sensitivity of antenna performance to changing surface parameters for fixed feed array geometries is also studied. This allows determination of the limits of usefulness for feed array compensation.

Surface plasmon optical sensor with enhanced sensitivity using top ZnO thin film

NASA Astrophysics Data System (ADS)

Bao, Ming; Li, Ge; Jiang, Dongmei; Cheng, Wenjuan; Ma, Xueming

2012-05-01

Surface plasmon resonance (SPR) is one of the most sensitive label-free detection methods and has been used in a wide range of chemical and biochemical sensing. Upon using a 200 nm top layer of dielectric film with a high value of the real part ɛ' of the dielectric function, on top of an SPR sensor in the Kretschmann configuration, the sensitivity is improved. The refractive index effect of dielectric film on sensitivity is usually ignored. Dielectric films with different refractive indices were prepared by radio frequency magnetron (RF) sputtering and measured with spectroscopic ellipsometry (SE). The imaginary part ɛ'' of the top nanolayer permittivity needs to be small enough in order to reduce the losses and get sharper dips. The stability of the sensor is also improved because the nanolayer is protecting the Ag film from interacting with the environment. The response curves of the Ag/ZnO chips were obtained by using SPR sensor. Theoretical analysis of the sensitivity of the SPR sensors with different ZnO film refractive indices is presented and studied. Both experimental and simulation results show that the Ag/ZnO films exhibit an enhanced SPR over the pure Ag film with a narrower full width at half maximum (FWHM). It shows that the top ZnO layer is effective in enhancing the surface plasmon resonance and thus its sensitivity.

Experimental investigation of edge hardening and edge cracking sensitivity of burr-free parts

NASA Astrophysics Data System (ADS)

Senn, Sergei; Liewald, Mathias

2018-05-01

This experimental study is focused on characterisation of edge hardening of sheet metal and remaining formability of differently prepared cutted edges. Edge cracking sensitivity of counter cutted, shear cutted, recutted and water-jet cutted components are compared and evaluated. Subsequently, edge hardening and hole expansion ratio were correlated for material HC420 LA with sheet thickness of t = 2 mm. As other studies show, the cutting edge surface quality influences the hole expansion ratio: a high clear cut surface increases formability of cutting edges, whereas micro cracks and rough surfaces result into a large fracture surface, which impact remaining formability noticeably. Thus, cutting edges with lower edge hardening behaviour in conjunction with a higher clear cut surface exhibit higher hole expansion ratios. Counter cutting and the recutting do show a similar effect on edge hardening. Using the hole expansion test, it was possible to prove that counter cutted components show a significantly lower edge cracking sensitivity in comparison to conventionally shear cutted components. The hole expansion ratio of counter cutted specimens looks balanced and is comparable to the hole expansion ratio measured from specimens with recutted or water jet cutted edges. The significant difference of the investigated cutting processes is characterized by size of clear cutting area. This area of recutted edges emerges larger than the area of counter cutted specimens, which evidently leads to an increased hole expansion ratio of recutted specimens compared to conventionally shear cutted ones. However, it is important to note that the hole expansion ratio of counter cutted and recutted specimens appear fairly balanced, but counter cutted samples indeed can be produced burr-free. Using counter cutting technology, it is possible to produce burr free surfaces with high edge formability.

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

PubMed

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

2015-02-18

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

Development of chitosan-coated gold nanoflowers as SERS-active probes

NASA Astrophysics Data System (ADS)

Xu, Dan; Gu, Jiangjiang; Wang, Weina; Yu, Xuehai; Xi, Kai; Jia, Xudong

2010-09-01

Surface-enhanced Raman scattering (SERS) has been intensely researched for many years as a potential technique for highly sensitive detection. This work, through the reduction of HAuCl4 with pyrrole in aqueous solutions, investigated a facile one-pot synthesis of flower-like Au nanoparticles with rough surfaces. The formation process of the Au nanoflowers (AuNFs) was carefully studied, and a spontaneous assembly mechanism was proposed based on the time-course experimental results. The key synthesis strategy was to use pyrrole as a weak particle stabilizing and reducing agent to confine crystal growth in the limited ligand protection region. The nanometer-scale surface roughness of AuNFs provided several hot spots on a single particle, which significantly increased SERS enhancement. Good biocompatible stable Raman-active probes were synthesized by coating AuNFs with chitosan. The conservation of the SERS effects in living cells suggested that the chitosan-capped AuNFs could be suitable for highly sensitive detection and have potential for targeting of tumors in vivo.

Maintenance of contamination sensitive surfaces on board long-term space vehicles

NASA Technical Reports Server (NTRS)

Phillips, A.; Maag, C.

1984-01-01

In the current age, highly sensitive instruments are being flown on spacecraft, and questions of contamination have become important. The present investigation is concerned with the available approaches which can provide long-term protection for contamination sensitive surfaces. Aspects and sources of spacecraft contamination are examined, taking into account materials outgassing, particulates, propulsion system interaction, overboard venting, man-made and cosmic debris, and atomic oxygen/ambient atmosphere interaction. Suitable protection approaches provided by current technology are discussed, giving attention to aperture covers, a possibility for a retractable cover design, gaseous purges, options for prolonging the lifetime of the thermal control system, and plume shields. Some new possibilities considered are related to an early warning system for excessive amounts of contamination, a molecular/wake shield, and the use of atomic oxygen.

P-polarized reflectance spectroscopy: A high sensitive real-time monitoring technique to study surface kinetics under steady state epitaxial deposition conditions

NASA Technical Reports Server (NTRS)

Dietz, Nikolaus; Bachmann, Klaus J.

1995-01-01

This paper describes the results of real-time optical monitoring of epitaxial growth processes by p-polarized reflectance spectroscopy (PRS) using a single wavelength application under pulsed chemical beam epitaxy (PCBE) condition. The high surface sensitivity of PRS allows the monitoring of submonolayer precursors coverage on the surface as shown for GaP homoepitaxy and GaP on Si heteroepitaxy as examples. In the case of heteroepitaxy, the growth rate and optical properties are revealed by PRS using interference oscillations as they occur during growth. Super-imposed on these interference oscillations, the PRS signal exhibits a fine structure caused by the periodic alteration of the surface chemistry by the pulsed supply of chemical precursors. This fine structure is modeled under conditions where the surface chemistry cycles between phosphorus supersaturated and phosphorus depleted surfaces. The mathematical model describes the fine structure using a surface layer that increases during the tertiarybutyl phosphine (TBP) supply and decreases during and after the triethylgallium (TEG) pulse, which increases the growing GaP film thickness. The imaginary part of the dielectric function of the surface layer is revealed from the turning points in the fine structure, where the optical response to the first precursor pulse in the cycle sequence changes sign. The amplitude of the fine structure is determined by the surface layer thickness and the complex dielectric functions for the surface layer with the underlying bulk film. Surface kinetic data can be obtained by analyzing the rise and decay transients of the fine structure.

Dust Dynamics Near Planetary Surfaces

NASA Astrophysics Data System (ADS)

Colwell, Joshua; Hughes, Anna; Grund, Chris

Observations of a lunar "horizon glow" by several Surveyor spacecraft in the 1960s opened the study of the dynamics of charged dust particles near planetary surfaces. The surfaces of the Moon and other airless planetary bodies in the solar system (asteroids, and other moons) are directly exposed to the solar wind and ionizing solar ultraviolet radiation, resulting in a time-dependent electric surface potential. Because these same objects are also exposed to bombardment by micrometeoroids, the surfaces are usually characterized by a power-law size distribution of dust that extends to sub-micron-sized particles. Individual particles can acquire a charge different from their surroundings leading to electrostatic levitation. Once levitated, particles may simply return to the surface on nearly ballistic trajectories, escape entirely from the moon or asteroid if the initial velocity is large, or in some cases be stably levitated for extended periods of time. All three outcomes have observable consequences. Furthermore, the behavior of charged dust near the surface has practical implications for planned future manned and unmanned activities on the lunar surface. Charged dust particles also act as sensitive probes of the near-surface plasma environment. Recent numerical modeling of dust levitation and transport show that charged micron-sized dust is likely to accumulate in topographic lows such as craters, providing a mechanism for the creation of dust "ponds" observed on the asteroid 433 Eros. Such deposition can occur when particles are supported by the photoelectron sheath above the dayside and drift over shadowed regions of craters where the surface potential is much smaller. Earlier studies of the lunar horizon glow are consistent with those particles being on simple ballistic trajectories following electrostatic launching from the surface. Smaller particles may be accelerated from the lunar surface to high altitudes consistent with observations of high altitude streams observed by Apollo astronauts and potentially also by the Clementine spacecraft. In addition to the Surveyor images of lunar horizon glow and the high altitude streamer measurements, the Apollo 17 Lunar Ejecta and Meteorite surface package detected signals consistent with the impact of relatively slow-moving dust particles that may have been charged dust electrostatically levitated from the surface. There is renewed interest in this near-surface dust environment with plans to return robotic landers and astronauts to the lunar surface. No Apollo-era instruments were specifically designed to detect or measure dust levitated off the lunar surface. One new experiment under study is the Autonomous Lunar Dust Observer (ALDO). ALDO is a high-sensitivity scanning lidar (laser radar) that autonomously maps and records its 3-D dust environment. Flexibility of programmable scan pattern enables ALDO to characterize the dust context in and around experiment sites. Repeated shallow angle scans in a vertical plane enable high vertical resolution studies of dust levitation near the ground. Single elevation angle sector or full azimuth scans enable large-area statistical surveys of the frequency and size of ejecta plumes from micrometeoroid impacts, and vertical or fixed-angle stares enable very high sensitivity dust profiles to extended ranges. It is estimated that backscatter from dust concentrations as low as 1/cm3 can be measured. The concept is equally applicable to surface and atmospheric studies of other airless bodies.

Initial Steps Toward Next-Generation, Waveform-Based, Three-Dimensional Models and Metrics to Improve Nuclear Explosion Monitoring in the Middle East

DTIC Science & Technology

2008-09-30

propagation effects by splitting apart the longer period surface waves from the shorter period, depth-sensitive Pnl waves. Problematic, or high-error... Pnl waves. Problematic, or high-error, stations and paths were further analyzed to identify systematic errors with unknown sensor responses and...frequency Pnl components and slower, longer period surface waves. All cut windows are fit simultaneously, allowing equal weighting of phases that may be

Flexible Ag-C60 nano-biosensors based on surface plasmon coupled emission for clinical and forensic applications.

PubMed

Mulpur, Pradyumna; Yadavilli, Sairam; Mulpur, Praharsha; Kondiparthi, Neeharika; Sengupta, Bishwambhar; Rao, Apparao M; Podila, Ramakrishna; Kamisetti, Venkataramaniah

2015-10-14

The relatively low sensitivity of fluorescence detection schemes, which are mainly limited by the isotropic nature of fluorophore emission, can be overcome by utilizing surface plasmon coupled emission (SPCE). In this study, we demonstrate directional emission from fluorophores on flexible Ag-C60 SPCE sensor platforms for point-of-care sensing, in healthcare and forensic sensing scenarios, with at least 10 times higher sensitivity than traditional fluorescence sensing schemes. Adopting the highly sensitive Ag-C60 SPCE platform based on glass and novel low-cost flexible substrates, we report the unambiguous detection of acid-fast Mycobacterium tuberculosis (Mtb) bacteria at densities as low as 20 Mtb mm(-2); from non-acid-fast bacteria (e.g., E. coli and S. aureus), and the specific on-site detection of acid-fast sperm cells in human semen samples. In combination with the directional emission and high-sensitivity of SPCE platforms, we also demonstrate the utility of smartphones that can replace expensive and cumbersome detectors to enable rapid hand-held detection of analytes in resource-limited settings; a much needed critical advance to biosensors, for developing countries.

Sensitive X-ray detectors made of methylammonium lead tribromide perovskite single crystals

NASA Astrophysics Data System (ADS)

Wei, Haotong; Fang, Yanjun; Mulligan, Padhraic; Chuirazzi, William; Fang, Hong-Hua; Wang, Congcong; Ecker, Benjamin R.; Gao, Yongli; Loi, Maria Antonietta; Cao, Lei; Huang, Jinsong

2016-05-01

The large mobilities and carrier lifetimes of hybrid perovskite single crystals and the high atomic numbers of Pb, I and Br make them ideal for X-ray and gamma-ray detection. Here, we report a sensitive X-ray detector made of methylammonium lead bromide perovskite single crystals. A record-high mobility-lifetime product of 1.2 × 10-2 cm2 V-1 and an extremely small surface charge recombination velocity of 64 cm s-1 are realized by reducing the bulk defects and passivating surface traps. Single-crystal devices with a thickness of 2-3 mm show 16.4% detection efficiency at near zero bias under irradiation with continuum X-ray energy up to 50 keV. The lowest detectable X-ray dose rate is 0.5 μGyair s-1 with a sensitivity of 80 μC Gy-1air cm-2, which is four times higher than the sensitivity achieved with α-Se X-ray detectors. This allows the radiation dose applied to a human body to be reduced for many medical and security check applications.

Mechanism and Characteristics of Humidity Sensing with Polyvinyl Alcohol-Coated Fiber Surface Plasmon Resonance Sensor.

PubMed

Shao, Yu; Wang, Ying; Cao, Shaoqing; Huang, Yijian; Zhang, Longfei; Zhang, Feng; Liao, Changrui; Wang, Yiping

2018-06-25

A surface plasmon resonance (SPR) sensor based on a side-polished single mode fiber coated with polyvinyl alcohol (PVA) is demonstrated for relative humidity (RH) sensing. The SPR sensor exhibits a resonant dip in the transmission spectrum in ambient air after PVA film coating, and the resonant wavelength shifts to longer wavelengths as the thickness of the PVA film increases. When RH changes, the resonant dip of the sensor with different film-thicknesses exhibits interesting characteristics for optical spectrum evolution. For sensors with initial wavelengths between 550 nm and 750 nm, the resonant dip shifts to longer wavelengths with increasing RH. The averaged sensitivity increases firstly and then drops, and shows a maximal sensitivity of 1.01 nm/RH%. Once the initial wavelength of the SPR sensor exceeds 850 nm, an inflection point of the resonant wavelength shift can be observed with RH increasing, and the resonant dip shifts to shorter wavelengths for RH values exceeding this point, and sensitivity as high as −4.97 nm/RH% can be obtained in the experiment. The sensor is expected to have potential applications in highly sensitive and cost effective humidity sensing.

Determination of Cancer Cell-Based pH-Sensitive Fluorescent Carbon Nanoparticles of Cross-Linked Polydopamine by Fluorescence Sensing of Alkaline Phosphatase Activity on Coated Surfaces and Aqueous Solution.

PubMed

Kang, Eun Bi; Choi, Cheong A; Mazrad, Zihnil Adha Islamy; Kim, Sung Han; In, Insik; Park, Sung Young

2017-12-19

The tumor-specific sensitive fluorescence sensing of cellular alkaline phosphatase (ALP) activity on the basis of host-guest specific and pH sensitivity was conducted on coated surfaces and aqueous states. Cross-linked fluorescent nanoparticles (C-FNP) consisting of β-cyclodextrin (β-CD)/boronic acid (BA) and fluorescent hyaluronic acid [FNP(HA)] were conjugated to fluorescent polydopamine [FNP(pDA)]. To determine the quenching effect of this system, hydrolysis of 4-nitrophenyl phosphate (NPP) to 4-nitrophenol (NP) was performed in the cavity of β-CD in the presence of ALP activated photoinduced electron transfer (PET) between NP and C-FNP. At an ALP level of 30-1000 U/L, NP caused off-emission of C-FNP because of their specific host-guest recognition. Fluorescence can be recovered under pH shock due to cleavage of the diol bond between β-CD and BA, resulting in release of NP from the fluorescent system. Sensitivity of the assays was assessed by confocal imaging not only in aqueous states, but also for the first time on coated surfaces in MDAMB-231 and MDCK cells. This novel system demonstrated high sensitivity to ALP through generation of good electron donor/acceptor pair during the PET process. Therefore, this fluorescence sensor system can be used to enhance ALP monitoring and cancer diagnosis on both coated surfaces and in aqueous states in clinical settings.

Accurate identification of motor unit discharge patterns from high-density surface EMG and validation with a novel signal-based performance metric

NASA Astrophysics Data System (ADS)

Holobar, A.; Minetto, M. A.; Farina, D.

2014-02-01

Objective. A signal-based metric for assessment of accuracy of motor unit (MU) identification from high-density surface electromyograms (EMG) is introduced. This metric, so-called pulse-to-noise-ratio (PNR), is computationally efficient, does not require any additional experimental costs and can be applied to every MU that is identified by the previously developed convolution kernel compensation technique. Approach. The analytical derivation of the newly introduced metric is provided, along with its extensive experimental validation on both synthetic and experimental surface EMG signals with signal-to-noise ratios ranging from 0 to 20 dB and muscle contraction forces from 5% to 70% of the maximum voluntary contraction. Main results. In all the experimental and simulated signals, the newly introduced metric correlated significantly with both sensitivity and false alarm rate in identification of MU discharges. Practically all the MUs with PNR > 30 dB exhibited sensitivity >90% and false alarm rates <2%. Therefore, a threshold of 30 dB in PNR can be used as a simple method for selecting only reliably decomposed units. Significance. The newly introduced metric is considered a robust and reliable indicator of accuracy of MU identification. The study also shows that high-density surface EMG can be reliably decomposed at contraction forces as high as 70% of the maximum.

Adsorption Site of Gas Molecules on Defective Armchair Graphene Nanoribbon Formed Through Ion Bombardment

NASA Astrophysics Data System (ADS)

Auzar, Zuriana; Johari, Zaharah; Sakina, S. H.; Alias, N. Ezaila

2018-02-01

High sensitivity and selectivity is desired in sensing devices. The aim of this study is to investigate the use of the ion bombardment process in creating a defect on graphene nanoribbons (GNR), which significantly affects sensing properties, in particular adsorption energy, charge transfer and sensitivity. A process has been developed to form the defect on the GNR surface using molecular dynamic (MD) with a reactive force field with nitrogen ion. The sensing properties were calculated using the extended Huckel theory when oxygen (O2) and ammonia (NH3) molecules are exposed to different areas on the defective site. Through simulation, it was found that the ion bombardment process formed various types of defects on the GNR surface. Most notably, molecules adsorbed on the ripple area considerably improve the sensitivity by more than 50%. This indicates that the defect on the armchair graphene nanoribbon (AGNR) surface can be a method to enhance graphene-based sensing performance.

Surface plasmon resonance near-infrared spectroscopy.

PubMed

Ikehata, Akifumi; Itoh, Tamitake; Ozaki, Yukihiro

2004-11-01

Near-infrared (NIR) spectroscopy is ill-suited to microanalysis because of its low absorptivity. We have developed a highly sensitive detection method for NIR spectroscopy based on absorption-sensitive surface plasmon resonance (SPR). The newly named SPR-NIR spectroscopy, which may open the way for NIR spectroscopy in microanalysis and surface science, is realized by an attachment of the Kretschmann configuration equipped with a mechanism for fine angular adjustment of incident light. The angular sweep of incident light enables us to make a tuning of a SPR peak for an absorption band of sample medium. From the dependences of wavelength, incident angle, and thickness of a gold film on the intensity of the SPR peak, it has been found that the absorbance can be enhanced by approximately 100 times compared with the absorbance obtained without the gold film under optimum conditions. This article reports the details of the experimental setup and the characteristics of absorption-sensitive SPR in the NIR region, together with some experimental results obtained by using it.

Surface plasmon-enhanced fluorescence on Au nanohole array for prostate-specific antigen detection

PubMed Central

Zhang, Qingwen; Wu, Lin; Wong, Ten It; Zhang, Jinling; Liu, Xiaohu; Zhou, Xiaodong; Bai, Ping; Liedberg, Bo; Wang, Yi

2017-01-01

Localized surface plasmon (LSP) has been widely applied for the enhancement of fluorescence emission for biosensing owing to its potential for strong field enhancement. However, due to its small penetration depth, LSP offers limited fluorescence enhancement over a whole sensor chip and, therefore, insufficient sensitivity for the detection of biomolecules, especially large molecules. We demonstrate the simultaneous excitation of LSP and propagating surface plasmon (PSP) on an Au nanohole array under Kretschmann configuration for the detection of prostate-specific antigen with a sandwich immunoassay. The proposed method combines the advantages of high field enhancement by LSP and large surface area probed by PSP field. The simulated results indicated that a maximum enhancement of electric field intensity up to 1,600 times can be achieved under the simultaneous excitation of LSP and PSP modes. The sandwich assay of PSA carried out on gold nanohole array substrate showed a limit of detection of 140 fM supporting coexcitation of LSP and PSP modes. The limit of detection was approximately sevenfold lower than that when only LSP was resonantly excited on the same substrate. The results of this study demonstrate high fluorescence enhancement through the coexcitation of LSP and PSP modes and pave a way for its implementation as a highly sensitive bioassay. PMID:28392689

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yoo, Yong Kyoung; Center for Biomicrosystems, Korea Institute of Science and Technology, Seoul 136-791; Lee, Sang-Myung

Combining a highly sensitive sensor platform with highly selective recognition elements is essential for micro/nanotechnology-based electronic nose applications. Particularly, the regeneration sensor surface and its conditions are key issues for practical e-nose applications. We propose a highly sensitive piezoelectric-driven microcantilever array chip with highly selective peptide receptors. By utilizing the peptide receptor, which was discovered by a phase display screening process, we immobilized a dinitrotoluene (DNT) specific peptide as well as a DNT nonspecific peptide on the surface of the cantilever array. The delivery of DNT gas via pressure-driven flow led to a greater instant response of ∼30 Hz, compared tomore » diffusion only (∼15 Hz for 15 h). Using a simple pressure-driven air flow of ∼50 sccm, we confirmed that a ratio of ∼70% of the specific-bounded sites from DNT gas molecules could be regenerated, showing re-usability of the peptide receptor in on-site monitoring for electronic nose applications.« less

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

PubMed

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

2007-05-01

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.

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

NASA Astrophysics Data System (ADS)

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

2007-05-01

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.

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

PubMed Central

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

Sensitivity of land surface modeling to parameters: An uncertainty quantification method applied to the Community Land Model

NASA Astrophysics Data System (ADS)

Ricciuto, D. M.; Mei, R.; Mao, J.; Hoffman, F. M.; Kumar, J.

2015-12-01

Uncertainties in land parameters could have important impacts on simulated water and energy fluxes and land surface states, which will consequently affect atmospheric and biogeochemical processes. Therefore, quantification of such parameter uncertainties using a land surface model is the first step towards better understanding of predictive uncertainty in Earth system models. In this study, we applied a random-sampling, high-dimensional model representation (RS-HDMR) method to analyze the sensitivity of simulated photosynthesis, surface energy fluxes and surface hydrological components to selected land parameters in version 4.5 of the Community Land Model (CLM4.5). Because of the large computational expense of conducting ensembles of global gridded model simulations, we used the results of a previous cluster analysis to select one thousand representative land grid cells for simulation. Plant functional type (PFT)-specific uniform prior ranges for land parameters were determined using expert opinion and literature survey, and samples were generated with a quasi-Monte Carlo approach-Sobol sequence. Preliminary analysis of 1024 simulations suggested that four PFT-dependent parameters (including slope of the conductance-photosynthesis relationship, specific leaf area at canopy top, leaf C:N ratio and fraction of leaf N in RuBisco) are the dominant sensitive parameters for photosynthesis, surface energy and water fluxes across most PFTs, but with varying importance rankings. On the other hand, for surface ans sub-surface runoff, PFT-independent parameters, such as the depth-dependent decay factors for runoff, play more important roles than the previous four PFT-dependent parameters. Further analysis by conditioning the results on different seasons and years are being conducted to provide guidance on how climate variability and change might affect such sensitivity. This is the first step toward coupled simulations including biogeochemical processes, atmospheric processes or both to determine the full range of sensitivity of Earth system modeling to land-surface parameters. This can facilitate sampling strategies in measurement campaigns targeted at reduction of climate modeling uncertainties and can also provide guidance on land parameter calibration for simulation optimization.

High Sensitivity Gas Detection Using a Macroscopic Three-Dimensional Graphene Foam Network

PubMed Central

Yavari, Fazel; Chen, Zongping; Thomas, Abhay V.; Ren, Wencai; Cheng, Hui-Ming; Koratkar, Nikhil

2011-01-01

Nanostructures are known to be exquisitely sensitive to the chemical environment and offer ultra-high sensitivity for gas-sensing. However, the fabrication and operation of devices that use individual nanostructures for sensing is complex, expensive and suffers from poor reliability due to contamination and large variability from sample-to-sample. By contrast, conventional solid-state and conducting-polymer sensors offer excellent reliability but suffer from reduced sensitivity at room-temperature. Here we report a macro graphene foam-like three-dimensional network which combines the best of both worlds. The walls of the foam are comprised of few-layer graphene sheets resulting in high sensitivity; we demonstrate parts-per-million level detection of NH3 and NO2 in air at room-temperature. Further, the foam is a mechanically robust and flexible macro-scale network that is easy to contact (without Lithography) and can rival the durability and affordability of traditional sensors. Moreover, Joule-heating expels chemisorbed molecules from the foam's surface leading to fully-reversible and low-power operation. PMID:22355681

Elucidation of high sensitivity of δ-HMX: New insight from first principles simulations

NASA Astrophysics Data System (ADS)

Kuklja, Maija M.; Tsyshevsky, Roman V.; Sharia, Onise

2017-01-01

Understanding of a significant difference in sensitivities of β and δ phases of cyclotetramethylene-tetranitramine (HMX) has been long one of the challenges in the field of high energy density materials. Despite many experimental and theoretical efforts to explain the high sensitivity of the δ phase, convincing reasons behind the HMX behavior remained unclear. We established that the presence of a polar surface in δ-HMX has fundamental implications for stability and overall chemical behavior of the material. A comparative quantum-chemical analysis of decomposition mechanisms in polar δ-HMX and nonpolar β-HMX discovered a considerable difference in dominating dissociation reactions, activation barriers, and reaction rates. The polarization-induced charge transfer offered a logical explanation for different sensitivity of β-HMX and δ-HMX polymorphs to detonation initiation. Our conclusions also removed long-standing contradictions and explained a large range of experimental data on thermal decomposition of HMX.

Stress Related Surface Tension Effects in Hard Elastic Polymers.

DTIC Science & Technology

1982-08-19

tension 4, and viscosity and the ,_;.rain imposed csn the materials. Results indicate that these microfi-r! Slated polymers contain a substantia- surface...modulus, 2) large recoverability (up to 98%), 3) ’energetic’ elasticity, and 4) high porosity. This field was thoroughly reviewed by Cannon, McKenna, and...influenced ’N load bearing microfibrils, open to the environment. The stress sensitivity of hard elastic polymers to changes in environmental surface

Physical and Chemical Behaviors of HCl on Ice Surface: Insights from an XPS and NEXAFS Study

NASA Astrophysics Data System (ADS)

Kong, X.; Waldner, A.; Orlando, F.; Birrer, M.; Artiglia, L.; Ammann, M.; Bartels-Rausch, T.

2016-12-01

Ice and snow play active roles for the water cycle, the energy budget of the Earth, and environmental chemistry in the atmosphere and cryosphere. Trace gases can be taken up by ice, and physical and chemical fates of the impurities could modify surface properties significantly and consequently influence atmospheric chemistry and the climate system. However, the understanding of chemical behaviour of impurities on ice surface are very poor, which is largely limited by the difficulties to apply high sensitivity experimental approaches to ambient air conditions, e.g. studies of volatile surfaces, because of the strict requirements of vacuum experimental conditions. In this study, we employed synchrotron-based X-ray photoelectron spectroscopy (XPS) and partial electron yield Near Edge X-ray Absorption Fine Structure (NEXAFS) in a state-of-the-art near-ambient pressure photoelectron (NAPP) spectroscopy end station. The NAPP enables to utilize the surface sensitive experimental methods, XPS and NEXAFS, on volatile surfaces, i.e. ice at temperatures approaching 0°C. XPS and NEXAFS together provide unique information of hydrogen bonding network, dopants surface concentration, dopant depth profile, and acidic dissociation on the surfaces1. Taking the advantages of the highly sensitive techniques, the adsorption, dissociation and depth profile of Hydrogen Chloride (HCl) on ice were studied. In brief, two states of Chloride on ice surface are identified from the adsorbed HCl, and they are featured with different depth profiles along the ice layers. Combining our results and previously reported constants from literatures (e.g. HCl diffusion coefficients in ice)2, a layered kinetic model has been constructed to fit the depth profiles of two states of Chloride. On the other side, pure ice and doped ice are compared for their surface structure change caused by temperature and the presence of HCl, which shows how the strong acid affect the ice surface in turn. 1. Orlando, F., et al., Top Catal 2016, 59, 591-604. 2. Huthwelker, T.; Malmstrom, M. E.; Helleis, F.; Moortgat, G. K.; Peter, T., J Phys Chem A 2004, 108, 6302-6318.

Raman and photothermal spectroscopies for explosive detection

NASA Astrophysics Data System (ADS)

Finot, Eric; Brulé, Thibault; Rai, Padmnabh; Griffart, Aurélien; Bouhélier, Alexandre; Thundat, Thomas

2013-06-01

Detection of explosive residues using portable devices for locating landmine and terrorist weapons must sat- isfy the application criteria of high reproducibility, specificity, sensitivity and fast response time. Vibrational spectroscopies such as Raman and infrared spectroscopies have demonstrated their potential to distinguish the members of the chemical family of more than 30 explosive materials. The characteristic chemical fingerprints in the spectra of these explosives stem from the unique bond structure of each compound. However, these spectroscopies, developed in the early sixties, suffer from a poor sensitivity. On the contrary, MEMS-based chemical sensors have shown to have very high sensitivity lowering the detection limit down to less than 1 picogram, (namely 10 part per trillion) using sensor platforms based on microcantilevers, plasmonics, or surface acoustic waves. The minimum amount of molecules that can be detected depends actually on the transducer size. The selectivity in MEMS sensors is usually realized using chemical modification of the active surface. However, the lack of sufficiently selective receptors that can be immobilized on MEMS sensors remains one of the most critical issues. Microcantilever based sensors offer an excellent opportunity to combine both the infrared photothermal spectroscopy in their static mode and the unique mass sensitivity in their dynamic mode. Optical sensors based on localized plasmon resonance can also take up the challenge of addressing the selectivity by monitoring the Surface Enhanced Raman spectrum down to few molecules. The operating conditions of these promising localized spectroscopies will be discussed in terms of reliability, compactness, data analysis and potential for mass deployment.

Stress ratio effects in fatigue of lost foam cast aluminum alloy 356

NASA Astrophysics Data System (ADS)

Palmer, David E.

Lost foam casting is a highly versatile metalcasting process that offers significant benefits in terms of design flexibility, energy consumption, and environmental impact. In the present work, the fatigue behavior of lost foam cast aluminum alloy 356, in conditions T6 and T7, was investigated, under both zero and non-zero mean stress conditions, with either as-cast or machined surface finish. Scanning electron microscopy was used to identify and measure the defect from which fatigue fracture initiated. Based on the results, the applicability of nine different fatigue mean stress equations was compared. The widely-used Goodman equation was found to be highly non-conservative, while the Stulen, Topper-Sandor, and Walker equations performed reasonably well. Each of these three equations includes a material-dependent term for stress ratio sensitivity. The stress ratio sensitivity was found to be affected by heat treatment, with the T6 condition having greater sensitivity than the T7 condition. The surface condition (as-cast vs. machined) did not significantly affect the stress ratio sensitivity. The fatigue life of as-cast specimens was found to be approximately 60--70% lower than that of machined specimens at the same equivalent stress. This reduction could not be attributed to pore size alone, and is suspected to be due to the greater concentration of pyrolysis products at the as-cast surface. Directions for future work, including improved testing methods and some possible methods of improving the properties of lost foam castings, are discussed.

Highly sensitive quartz crystal microbalance based biosensor using Au dendrite structure

NASA Astrophysics Data System (ADS)

Asai, Naoto; Terasawa, Hideaki; Shimizu, Tomohiro; Shingubara, Shoso; Ito, Takeshi

2018-02-01

A Au dendrite structure was obtained by only electroplating under a suitable potential. A blanch like nanostructure was formed along the crystal orientation. In this study, we attempted to fabricate a Au dendrite structure on the electrode of a quartz crystal by electroplating to increase the specific surface area. We estimated the effective surface area by cyclic voltammetry (CV) and monitored the frequency shift induced by antigen-antibody interaction by the quartz crystal microbalance (QCM) method. The dendrite structure with the largest surface area was formed under -0.95 V for 5 min. In the measurement of the antigen-antibody interaction, the frequency shifts of 40, 80, and 110 Hz were obtained with the dendrite structured QCM chips formed at the above potential for 1, 1.5, and 2.0 min, respectively. The sensitivity was improved compared with that QCM chip having a flat surface electrode.

Development of a highly sensitive bioluminescent enzyme immunoassay for hepatitis B virus surface antigen capable of detecting divergent mutants.

PubMed

Minekawa, Takayuki; Takehara, Shizuka; Takahashi, Masaharu; Okamoto, Hiroaki

2013-08-01

Hepatitis B virus (HBV) infections are sometimes overlooked when using commercial kits to measure hepatitis B virus surface antigen (HBsAg) due to their low sensitivities and reactivities to mutant strains of various genotypes. We developed an ultrasensitive bioluminescent enzyme immunoassay (BLEIA) for HBsAg using firefly luciferase, which is adaptable to a variety of HBsAg mutants, by combining four monoclonal antibodies with a polyclonal antibody against HBsAg. The measurement of seroconversion panels showed trace amounts of HBsAg during the early infection phase by the BLEIA because of its high sensitivity of 5 mIU/ml. The BLEIA detected HBsAg as early as did PCR in five of seven series and from 2.1 to 9.4 days earlier than commercial immunoassay methods. During the late infection phase, the BLEIA successfully detected HBsAg even 40 days after the disappearance of HBV DNA and the emergence of antibodies against HBsAg. The HBsAg BLEIA successfully detected all 13 recombinant HBsAg and 45 types of HBsAg mutants with various mutations within amino acids 90 to 164 in the S gene product. Some specimens had higher values determined by the BLEIA than those by a commercial chemiluminescent immunoassay; this suggests that such discrepancies were caused by the dissociation of preS1/preS2 peptides from the particle surface. With its highly sensitive detection of low-titer HBsAg, including various mutants, the HBsAg BLEIA is considered to be useful for the early diagnosis and prevention of HBV infection because of the shorter window of infection prior to detection, which facilitates early prediction of recurrence in HBV-infected individuals.

Graphene-based textured surface by pulsed laser deposition as a robust platform for surface enhanced Raman scattering applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tite, T.; Donnet, C.; Loir, A.-S.

We have developed a surface enhanced Raman scattering (SERS)-active substrate based on gold nanoparticles-decorated few-layer (fl) graphene grown by pulsed laser deposition. Diamond-Like Carbon film has been converted to fl-graphene after thermal annealing at low temperature. The formation of fl-graphene was confirmed by Raman spectroscopy, and surface morphology was highlighted by scanning electron microscopy. We found that textured fl-graphene film with nanoscale roughness was highly beneficial for SERS detection. Rhodamine 6G and p-aminothiophenol proposed as test molecules were detected with high sensitivity. The detection at low concentration of deltamethrin, an active molecule of a commercial pesticide was further demonstrated.

Measurement-based climatology of aerosol direct radiative effect, its sensitivities, and uncertainties from a background southeast US site

NASA Astrophysics Data System (ADS)

Sherman, James P.; McComiskey, Allison

2018-03-01

Aerosol optical properties measured at Appalachian State University's co-located NASA AERONET and NOAA ESRL aerosol network monitoring sites over a nearly four-year period (June 2012-Feb 2016) are used, along with satellite-based surface reflectance measurements, to study the seasonal variability of diurnally averaged clear sky aerosol direct radiative effect (DRE) and radiative efficiency (RE) at the top-of-atmosphere (TOA) and at the surface. Aerosol chemistry and loading at the Appalachian State site are likely representative of the background southeast US (SE US), home to high summertime aerosol loading and one of only a few regions not to have warmed during the 20th century. This study is the first multi-year ground truth DRE study in the SE US, using aerosol network data products that are often used to validate satellite-based aerosol retrievals. The study is also the first in the SE US to quantify DRE uncertainties and sensitivities to aerosol optical properties and surface reflectance, including their seasonal dependence.Median DRE for the study period is -2.9 W m-2 at the TOA and -6.1 W m-2 at the surface. Monthly median and monthly mean DRE at the TOA (surface) are -1 to -2 W m-2 (-2 to -3 W m-2) during winter months and -5 to -6 W m-2 (-10 W m-2) during summer months. The DRE cycles follow the annual cycle of aerosol optical depth (AOD), which is 9 to 10 times larger in summer than in winter. Aerosol RE is anti-correlated with DRE, with winter values 1.5 to 2 times more negative than summer values. Due to the large seasonal dependence of aerosol DRE and RE, we quantify the sensitivity of DRE to aerosol optical properties and surface reflectance, using a calendar day representative of each season (21 December for winter; 21 March for spring, 21 June for summer, and 21 September for fall). We use these sensitivities along with measurement uncertainties of aerosol optical properties and surface reflectance to calculate DRE uncertainties. We also estimate uncertainty in calculated diurnally-averaged DRE due to diurnal aerosol variability. Aerosol DRE at both the TOA and surface is most sensitive to changes in AOD, followed by single-scattering albedo (ω0). One exception is under the high summertime aerosol loading conditions (AOD ≥ 0.15 at 550 nm), when sensitivity of TOA DRE to ω0 is comparable to that of AOD. Aerosol DRE is less sensitive to changes in scattering asymmetry parameter (g) and surface reflectance (R). While DRE sensitivity to AOD varies by only ˜ 25 to 30 % with season, DRE sensitivity to ω0, g, and R largely follow the annual AOD cycle at APP, varying by factors of 8 to 15 with season. Since the measurement uncertainties of AOD, ω0, g, and R are comparable at Appalachian State, their relative contributions to DRE uncertainty are largely influenced by their (seasonally dependent) DRE sensitivity values, which suggests that the seasonal dependence of DRE uncertainty must be accounted for. Clear sky aerosol DRE uncertainty at the TOA (surface) due to measurement uncertainties ranges from 0.45 (0.75 W m-2) for December to 1.1 (1.6 W m-2) for June. Expressed as a fraction of DRE computed using monthly median aerosol optical properties and surface reflectance, the DRE uncertainties at TOA (surface) are 20 to 24 % (15 to 22 %) for March, June, and September and 49 (50 %) for DEC. The relatively low DRE uncertainties are largely due to the low uncertainty in AOD measured by AERONET. Use of satellite-based AOD measurements by MODIS in the DRE calculations increases DRE uncertainties by a factor of 2 to 5 and DRE uncertainties are dominated by AOD uncertainty for all seasons. Diurnal variability in AOD (and to a lesser extent g) contributes to uncertainties in DRE calculated using daily-averaged aerosol optical properties that are slightly larger (by ˜ 20 to 30 %) than DRE uncertainties due to measurement uncertainties during summer and fall, with comparable uncertainties during winter and spring.

Grapefruit photonic crystal fiber long period gratings sensor for DNT sensing application

NASA Astrophysics Data System (ADS)

Tao, Chuanyi; Li, Jingke; Zhu, Tenglong

2016-10-01

The detection of explosives and their residues is of great importance in public health, antiterrorism and homeland security applications. The vapor pressures of most explosive compounds are extremely low and attenuation of the available vapor is often great due to diffusion in the environment, making direct vapor detection difficult. In reality bomb dogs are still the most efficient way to quickly detect explosives on the spot. Many formulations of TNT-based explosives contain DNT residues. The use of long period gratings (LPGs) formed in grapefruit photonic crystal fiber (PCF) with thin-film overlay coated on the inner surface of air holes for gas sensing is demonstrated. A gas analyteinduced index variation of the thin-film immobilized on the inner surface of the holey region of the fiber can be observed by a shift of the resonance wavelength. We demonstrate a 2,4-dinitrotoluene (DNT) sensor using grapefruit PCF-LPGs. Coating with gas-sensitive thin-film on the inner surface of the air holes of the grapefruit PCF-LPG could provide a promising platform for rapid highly sensitive gas sensing. A rapid and highly sensitive detection of DNT has been demonstrated using the grapefruit PCF-LPG sensor to show the feasibility of the proposed approach.

Ultrahigh-sensitive sensing platform based on p-type dumbbell-like Co3O4 network

NASA Astrophysics Data System (ADS)

Zhou, Tingting; Zhang, Tong; Zhang, Rui; Lou, Zheng; Deng, Jianan; Wang, Lili

2017-12-01

Development of high performance room temperature sensors remains a grand challenge for high demand of practical application. Metal oxide semiconductors (MOSs) have many advantages over others due to their easy functionalization, high surface area, and low cost. However, they typically need a high work temperature during sensing process. Here, p-type sensing layer is reported, consisting of pore-rich dumbbell-like Co3O4 particles (DP-Co3O4) with intrinsic high catalytic activity. The gas sensor (GS) based DP-Co3O4 catalyst exhibits ultrahigh NH3 sensing activity along with excellent stability over other structure based NH3 GSs in room temperature work environment. In addition, the unique structure of DP-Co3O4 with pore-rich and high catalytic activity endows fast gas diffusion rate and high sensitivity at room temperature. Taken together, the findings in this work highlight the merit of integrating highly active materials in p-type materials, offering a framework to develop high-sensitivity room temperature sensing platforms.

AlN grown on Si(1 1 1) by ammonia-molecular beam epitaxy in the 900-1200 °C temperature range

NASA Astrophysics Data System (ADS)

Tamariz, Sebastian; Martin, Denis; Grandjean, Nicolas

2017-10-01

We present a comprehensive study of AlN growth on Si(1 1 1) substrate by gas source molecular beam epitaxy with ammonia as nitrogen precursor in the high temperature range. We first demonstrate that the observation of the silicon 7 × 7 surface reconstruction by reflection high energy electron diffraction can be misleading as this technique is not sensitive to low density surface defects like SiC crystallites. A careful in situ cleaning procedure with annealing cycles at 1100 °C allows getting rid of any surface defects, as shown by atomic force microscopy imaging. Then, we explore the effect of the growth temperature on the surface morphology and structural properties of 100 nm thick AlN epilayers. At 1200 °C, the growth proceeds with the step flow mode regime, which induces spiral-growth around screw-type dislocations and therefore surface roughening. On the other hand, a smooth surface morphology can be achieved by setting the temperature at 1100 °C, which corresponds to the growth mode transition from two-dimensional nucleation to step flow. A further decrease of the growth temperature to 900 °C leads to surface defects ascribed to polarity inversion domains. Similar defects are observed for growths performed at 1100 °C when the NH3 flow is reduced below 100 sccm. This points out the sensitivity of AlN to the surface stoichiometry.

Flexible Carbon Nanotube Films for High Performance Strain Sensors

PubMed Central

Kanoun, Olfa; Müller, Christian; Benchirouf, Abderahmane; Sanli, Abdulkadir; Dinh, Trong Nghia; Al-Hamry, Ammar; Bu, Lei; Gerlach, Carina; Bouhamed, Ayda

2014-01-01

Compared with traditional conductive fillers, carbon nanotubes (CNTs) have unique advantages, i.e., excellent mechanical properties, high electrical conductivity and thermal stability. Nanocomposites as piezoresistive films provide an interesting approach for the realization of large area strain sensors with high sensitivity and low manufacturing costs. A polymer-based nanocomposite with carbon nanomaterials as conductive filler can be deposited on a flexible substrate of choice and this leads to mechanically flexible layers. Such sensors allow the strain measurement for both integral measurement on a certain surface and local measurement at a certain position depending on the sensor geometry. Strain sensors based on carbon nanostructures can overcome several limitations of conventional strain sensors, e.g., sensitivity, adjustable measurement range and integral measurement on big surfaces. The novel technology allows realizing strain sensors which can be easily integrated even as buried layers in material systems. In this review paper, we discuss the dependence of strain sensitivity on different experimental parameters such as composition of the carbon nanomaterial/polymer layer, type of polymer, fabrication process and processing parameters. The insights about the relationship between film parameters and electromechanical properties can be used to improve the design and fabrication of CNT strain sensors. PMID:24915183

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

PubMed

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

2013-01-30

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

Signal Attenuation Curve for Different Surface Detector Arrays

NASA Astrophysics Data System (ADS)

Vicha, J.; Travnicek, P.; Nosek, D.; Ebr, J.

2014-06-01

Modern cosmic ray experiments consisting of large array of particle detectors measure the signals of electromagnetic or muon components or their combination. The correction for an amount of atmosphere passed is applied to the surface detector signal before its conversion to the shower energy. Either Monte Carlo based approach assuming certain composition of primaries or indirect estimation using real data and assuming isotropy of arrival directions can be used. Toy surface arrays of different sensitivities to electromagnetic and muon components are assumed in MC simulations to study effects imposed on attenuation curves for varying composition or possible high energy anisotropy. The possible sensitivity of the attenuation curve to the mass composition is also tested for different array types focusing on a future apparatus that can separate muon and electromagnetic component signals.

An Investigation into the Effects of Additives on Crystal Characteristics and Impact Sensitivity of RDX

NASA Astrophysics Data System (ADS)

Wang, Dong-Xu; Chen, Shu-Sen; Li, Yan-Yue; Yang, Jia-Yun; Wei, Tian-Yu; Jin, Shao-Hua

2014-07-01

Additives are one of the most important factors that greatly affect the crystal characteristics of the high energy compound hexahydro-1,3,5-trinitro-1,3,5-s-triazine (RDX, C3H6N6O6) and they have an influence on impact sensitivity. In this article, a growth morphology method was applied to obtain the crystal habit of RDX in a vacuum as well as the morphologically important faces, and molecular dynamics simulations were applied to calculate the interaction energy between these crystal faces and additive molecules for prediction of the additive-effect crystal habits of RDX. On this basis, crystal characteristics including crystal morphology, aspect ratio, and total surface charge were investigated. Then the particle size and surface electrostatic voltage of the samples from recrystallization were analyzed experimentally. The impact sensitivity test indicated that acrylamide, which could enhance the regularity and degree of sphericity of RDX crystals and effectively reduce the surface static electricity of RDX, was successful in reducing the impact sensitivity of RDX as an additive for crystallization. The above experimental results were in good agreement with the conclusions based on the theoretical calculations.

Highly sensitive and simultaneous electrochemical determination of 2-aminophenol and 4-aminophenol based on poly(l-arginine)-β-cyclodextrin/carbon nanotubes@graphene nanoribbons modified electrode.

PubMed

Yi, Yinhui; Zhu, Gangbing; Wu, Xiangyang; Wang, Kun

2016-03-15

Owing to the similar characteristics and physiochemical property of 2-aminophenol (2-AP) and 4-aminophenol (4-AP), the highly sensitive simultaneous electrochemical determination of 2- and 4-AP is a great challenge. In this paper, by electropolymerizing β-cyclodextrin (β-CD) and l-arginine (l-Arg) on the surface of carbon nanotubes@graphene nanoribbons (CNTs@GNRs) core-shell heterostructure, a P-β-CD-l-Arg/CNTs@GNRs nanohybrid modified electrode was prepared successfully, and it could exhibit the synergetic effects of β-CD (high host-guest recognition and enrichment ability), l-Arg (excellent electrocatalytic activity) and CNTs@GNRs (prominent electrochemical properties and large surface area), the P-β-CD-l-Arg/CNTs@GNRs modified electrode was used in the electrochemical determination of 2- and 4-AP, the results demonstrated that the highly sensitive and simultaneous determination of 2- and 4-AP is successfully achieved and the modified electrode has a linear response range of 25.0-1300.0 nM for both 2- and 4-AP, and the detection limits of 2- and 4-AP obtained in this work are 6.2 and 3.5 nM, respectively. Copyright © 2015 Elsevier B.V. All rights reserved.

High sensitive formaldehyde graphene gas sensor modified by atomic layer deposition zinc oxide films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mu, Haichuan; Zhang, Zhiqiang; Wang, Keke

2014-07-21

Zinc oxide (ZnO) thin films with various thicknesses were fabricated by Atomic Layer Deposition on Chemical Vapor Deposition grown graphene films and their response to formaldehyde has been investigated. It was found that 0.5 nm ZnO films modified graphene sensors showed high response to formaldehyde with the resistance change up to 52% at the concentration of 9 parts-per-million (ppm) at room temperature. Meanwhile, the detection limit could reach 180 parts-per-billion (ppb) and fast response of 36 s was also obtained. The high sensitivity could be attributed to the combining effect from the highly reactive, top mounted ZnO thin films, and high conductivemore » graphene base network. The dependence of ZnO films surface morphology and its sensitivity on the ZnO films thickness was also investigated.« less

Lens-free imaging of magnetic particles in DNA assays.

PubMed

Colle, Frederik; Vercruysse, Dries; Peeters, Sara; Liu, Chengxun; Stakenborg, Tim; Lagae, Liesbet; Del-Favero, Jurgen

2013-11-07

We present a novel opto-magnetic system for the fast and sensitive detection of nucleic acids. The system is based on a lens-free imaging approach resulting in a compact and cheap optical readout of surface hybridized DNA fragments. In our system magnetic particles are attracted towards the detection surface thereby completing the labeling step in less than 1 min. An optimized surface functionalization combined with magnetic manipulation was used to remove all nonspecifically bound magnetic particles from the detection surface. A lens-free image of the specifically bound magnetic particles on the detection surface was recorded by a CMOS imager. This recorded interference pattern was reconstructed in software, to represent the particle image at the focal distance, using little computational power. As a result we were able to detect DNA concentrations down to 10 pM with single particle sensitivity. The possibility of integrated sample preparation by manipulation of magnetic particles, combined with the cheap and highly compact lens-free detection makes our system an ideal candidate for point-of-care diagnostic applications.

Surface photovoltage in exciton absorption range in CdS

NASA Technical Reports Server (NTRS)

Morawski, A.; Banisch, R.; Lagowski, J.

1977-01-01

The high resolution, intrinsic spectra of surface photovoltage are reported for semiconducting n-type CdS single crystals. At reduced temperatures (120-160 K) the spectra exhibit three sharp maxima due to A, B and C free exciton transitions. Energy positions of these lines and valence band parameters (spin-orbit and crystal field splittings) estimated from surface photovoltage are in good agreement with values obtained by other methods. The excitonic transitions are very sensitive to surface treatment, i.e. polishing, etching, background illumination and surface doping. The mechanism of direct interaction of free excitons with surface states is proposed to explain exciton lines in surface photovoltage.

A Highly Sensitive Diagnostic System for Detecting Dengue Viruses Using the Interaction between a Sulfated Sugar Chain and a Virion.

PubMed

Saksono, Budi; Dewi, Beti Ernawati; Nainggolan, Leonardo; Suda, Yasuo

2015-01-01

We propose a novel method of detecting trace amounts of dengue virus (DENVs) from serum. Our method is based on the interaction between a sulfated sugar chain and a DENV surface glycoprotein. After capturing DENV with the sulfated sugar chain-immobilized gold nanoparticles (SGNPs), the resulting complex is precipitated and viral RNA content is measured using the reverse-transcription quantitative polymerase chain reaction SYBR Green I (RT-qPCR-Syb) method. Sugar chains that bind to DENVs were identified using the array-type sugar chain immobilized chip (Sugar Chip) and surface plasmon resonance (SPR) imaging. Heparin and low-molecular-weight dextran sulfate were identified as binding partners, and immobilized on gold nanoparticles to prepare 3 types of SGNPs. The capacity of these SGNPs to capture and concentrate trace amounts of DENVs was evaluated in vitro. The SGNP with greatest sensitivity was tested using clinical samples in Indonesia in 2013-2014. As a result, the novel method was able to detect low concentrations of DENVs using only 6 μL of serum, with similar sensitivity to that of a Qiagen RNA extraction kit using 140 μL of serum. In addition, this method allows for multiplex-like identification of serotypes of DENVs. This feature is important for good healthcare management of DENV infection in order to safely diagnose the dangerous, highly contagious disease quickly, with high sensitivity.

Non-Faradaic Electrochemical Detection of Exocytosis from Mast and Chromaffin Cells Using Floating-Gate MOS Transistors.

PubMed

Jayant, Krishna; Singhai, Amit; Cao, Yingqiu; Phelps, Joshua B; Lindau, Manfred; Holowka, David A; Baird, Barbara A; Kan, Edwin C

2015-12-21

We present non-faradaic electrochemical recordings of exocytosis from populations of mast and chromaffin cells using chemoreceptive neuron MOS (CνMOS) transistors. In comparison to previous cell-FET-biosensors, the CνMOS features control (CG), sensing (SG) and floating gates (FG), allows the quiescent point to be independently controlled, is CMOS compatible and physically isolates the transistor channel from the electrolyte for stable long-term recordings. We measured exocytosis from RBL-2H3 mast cells sensitized by IgE (bound to high-affinity surface receptors FcεRI) and stimulated using the antigen DNP-BSA. Quasi-static I-V measurements reflected a slow shift in surface potential () which was dependent on extracellular calcium ([Ca]o) and buffer strength, which suggests sensitivity to protons released during exocytosis. Fluorescent imaging of dextran-labeled vesicle release showed evidence of a similar time course, while un-sensitized cells showed no response to stimulation. Transient recordings revealed fluctuations with a rapid rise and slow decay. Chromaffin cells stimulated with high KCl showed both slow shifts and extracellular action potentials exhibiting biphasic and inverted capacitive waveforms, indicative of varying ion-channel distributions across the cell-transistor junction. Our approach presents a facile method to simultaneously monitor exocytosis and ion channel activity with high temporal sensitivity without the need for redox chemistry.

Non-Faradaic Electrochemical Detection of Exocytosis from Mast and Chromaffin Cells Using Floating-Gate MOS Transistors

PubMed Central

Jayant, Krishna; Singhai, Amit; Cao, Yingqiu; Phelps, Joshua B.; Lindau, Manfred; Holowka, David A.; Baird, Barbara A.; Kan, Edwin C.

2015-01-01

We present non-faradaic electrochemical recordings of exocytosis from populations of mast and chromaffin cells using chemoreceptive neuron MOS (CνMOS) transistors. In comparison to previous cell-FET-biosensors, the CνMOS features control (CG), sensing (SG) and floating gates (FG), allows the quiescent point to be independently controlled, is CMOS compatible and physically isolates the transistor channel from the electrolyte for stable long-term recordings. We measured exocytosis from RBL-2H3 mast cells sensitized by IgE (bound to high-affinity surface receptors FcεRI) and stimulated using the antigen DNP-BSA. Quasi-static I-V measurements reflected a slow shift in surface potential () which was dependent on extracellular calcium ([Ca]o) and buffer strength, which suggests sensitivity to protons released during exocytosis. Fluorescent imaging of dextran-labeled vesicle release showed evidence of a similar time course, while un-sensitized cells showed no response to stimulation. Transient recordings revealed fluctuations with a rapid rise and slow decay. Chromaffin cells stimulated with high KCl showed both slow shifts and extracellular action potentials exhibiting biphasic and inverted capacitive waveforms, indicative of varying ion-channel distributions across the cell-transistor junction. Our approach presents a facile method to simultaneously monitor exocytosis and ion channel activity with high temporal sensitivity without the need for redox chemistry. PMID:26686301

Highly Stretchable and Transparent Thermistor Based on Self-Healing Double Network Hydrogel.

PubMed

Wu, Jin; Han, Songjia; Yang, Tengzhou; Li, Zhong; Wu, Zixuan; Gui, Xuchun; Tao, Kai; Miao, Jianmin; Norford, Leslie K; Liu, Chuan; Huo, Fengwei

2018-06-06

An ultrastretchable thermistor that combines intrinsic stretchability, thermal sensitivity, transparency, and self-healing capability is fabricated. It is found the polyacrylamide/carrageenan double network (DN) hydrogel is highly sensitive to temperature and therefore can be exploited as a novel channel material for a thermistor. This thermistor can be stretched from 0 to 330% strain with the sensitivity as high as 2.6%/°C at extreme 200% strain. Noticeably, the mechanical, electrical, and thermal sensing properties of the DN hydrogel can be self-healed, analogous to the self-healing capability of human skin. The large mechanical deformations, such as flexion and twist with large angles, do not affect the thermal sensitivity. Good flexibility enables the thermistor to be attached on nonplanar curvilinear surfaces for practical temperature detection. Remarkably, the thermal sensitivity can be improved by introducing mechanical strain, making the sensitivity programmable. This thermistor with tunable sensitivity is advantageous over traditional rigid thermistors that lack flexibility in adjusting their sensitivity. In addition to superior sensitivity and stretchability compared with traditional thermistors, this DN hydrogel-based thermistor provides additional advantages of good transparency and self-healing ability, enabling it to be potentially integrated in soft robots to grasp real world information for guiding their actions.

Highly sensitive biochemical sensor utilizing Bragg grating in submicron Si/SiO2 waveguides

NASA Astrophysics Data System (ADS)

Tripathi, Saurabh Mani; Kumar, Arun; Meunier, Jean-Pierre; Marin, Emmanuel

2009-05-01

We present a novel highly sensitive biochemical sensor based on a Bragg grating written in the cladding region of a submicron planar Si/SiO2 waveguide. Owing to the high refractive index contrast at the Si/SiO2 boundary the TM modal power is relatively high in low refractive index sensing region, leading to higher sensitivity in this configuration [1]. Waveguide parameters have been optimized to obtain maximum modal power in the sensing region (PSe) and an optimum core width corresponding to maximum sensitivity is found to exist while operating in TM mode configuration, as has been shown in Fig. 1. It has been found that operating in TM mode configuration at optimum core width the structure exhibits extremely high sensitivity, ~ 5×10-6 RIU - 1.35×10-6 RIU for the ambient refractive indices between 1.33 - 1.63. Such high sensitivities are typically attainable for Surface Plasmon Polariton (SPP) based biosensors and is much higher than any non SPP based sensors. Being free from any metallic layer or bulky prism the structure is easy to realize. Owing to its simple structure and small dimensions the proposed sensor can be integrated with planar lightwave circuits and could be used in handy lab-on-a-chip devices. The device may find application in highly sensitive biological/chemical sensing areas in civil and defense sectors where analyzing the samples at the point of need is required rather than sending it to some centralized laboratory.

Accumulation mechanisms and the weathering of Antarctic equilibrated ordinary chondrites

NASA Astrophysics Data System (ADS)

Benoit, P. H.; Sears, D. W. G.

1999-06-01

Induced thermoluminescence (TL) is used to quantitatively evaluate the degree of weathering of meteorites found in Antarctica. We find a weak correlation between TL sensitivity and descriptions of weathering in hand specimens, the highly weathered meteorites having lower TL sensitivity than unweathered meteorites. Analysis of samples taken throughout large meteorites shows that the heterogeneity in TL sensitivity within meteorite finds is not large relative to the range exhibited by different weathered meteorites. The TL sensitivity values can be restored by minimal acid washing, suggesting the lower TL sensitivities of weathered meteorites reflects thin weathering rims on mineral grains or coating of these grains by iron oxides produced by hydration and oxidation of metal and sulfides. Small meteorites may tend to be more highly weathered than large meteorites at the Allan Hills ice fields. We find that meteorite fragments >150 g may take up to 300,000 years to reach the highest degrees of weathering, while meteorites <150 g require <40,000 years. However, at other fields, local environmental conditions and variability in terrestrial history are more important in determining weathering than size alone. Weathering correlates poorly with surface exposure duration, presumably because weathering occurs primarily during interglacial periods. The Allan Hills locality has served as a fairly stable surface over the last 100,000 years or so and has efficiently preserved both small and large meteorites. Meteorites from Lewis Cliff, however, have experienced extensive weathering, probably because of increased surface melt water from nearby outcrops. Meteorites from the Elephant Moraine locality tend to exhibit only minor degrees of weathering, but small meteorites are less weathered than large meteorites, which we suggest is due to the loss of small meteorites by aeolian transport.

Surface-structure sensitivity of CeO 2 nanocrystals in photocatalysis and enhancing the reactivity with nanogold

DOE PAGES

Lei, Wanying; Zhang, Tingting; Gu, Lin; ...

2015-06-19

Structure–function correlations are a central theme in heterogeneous (photo)catalysis. In this research, using aberration-corrected scanning transmission electron microscopy (STEM), the atomic surface structures of well-defined one-dimensional (1D) CeO 2 nanorods (NRs) and 3D nanocubes (NCs) are directly visualized at subangstrom resolution. CeO 2 NCs predominantly expose the {100} facet, with {110} and {111} as minor cutoff facets at the respective edges and corners. Notably, the outermost surface layer of the {100} facet is nearly O-terminated. Neither surface relaxations nor reconstructions on {100} are observed, indicating unusual polarity compensation, which is primarily mediated by near-surface oxygen vacancies. The surface of CeOmore » 2 NRs is highly stepped, with the enclosed {110} facet exposing Ce cations and O anions on terraces. On the basis of STEM profile-view imaging and electronic structure analysis, the photoreactivity of CeO2 nanocrystals toward aqueous methyl orange degradation under UV is revealed to be surface-structure-sensitive, following the order: {110} >> {100}. The underlying surface-structure sensitivity can be attributed to the variation in low-coordinate surface cerium cations between {110} and {100} facets. To further enhance light absorption, Au nanoparticles (NPs) are deposited on CeO 2 NRs to form Au/CeO 2 plasmonic nanocomposites, which dramatically promotes the photoreactivity that is Au particle size- and excitation light wavelength-dependent. The mechanisms responsible for the enhancement of photocatalytic activity are discussed, highlighting the crucial role of photoexcited charge carrier transfer.« less

Do land surface models need to include differential plant species responses to drought? Examining model predictions across a mesic-xeric gradient in Europe

DOE Office of Scientific and Technical Information (OSTI.GOV)

De Kauwe, M. G.; Zhou, S. -X.; Medlyn, B. E.

Future climate change has the potential to increase drought in many regions of the globe, making it essential that land surface models (LSMs) used in coupled climate models realistically capture the drought responses of vegetation. Recent data syntheses show that drought sensitivity varies considerably among plants from different climate zones, but state-of-the-art LSMs currently assume the same drought sensitivity for all vegetation. We tested whether variable drought sensitivities are needed to explain the observed large-scale patterns of drought impact on the carbon, water and energy fluxes. We implemented data-driven drought sensitivities in the Community Atmosphere Biosphere Land Exchange (CABLE) LSMmore » and evaluated alternative sensitivities across a latitudinal gradient in Europe during the 2003 heatwave. The model predicted an overly abrupt onset of drought unless average soil water potential was calculated with dynamic weighting across soil layers. We found that high drought sensitivity at the most mesic sites, and low drought sensitivity at the most xeric sites, was necessary to accurately model responses during drought. Furthermore, our results indicate that LSMs will over-estimate drought impacts in drier climates unless different sensitivity of vegetation to drought is taken into account.« less

Enhancement in sensitivity of graphene-based zinc oxide assisted bimetallic surface plasmon resonance (SPR) biosensor

NASA Astrophysics Data System (ADS)

Kumar, Rajeev; Kushwaha, Angad S.; Srivastava, Monika; Mishra, H.; Srivastava, S. K.

2018-03-01

In the present communication, a highly sensitive surface plasmon resonance (SPR) biosensor with Kretschmann configuration having alternate layers, prism/zinc oxide/silver/gold/graphene/biomolecules (ss-DNA) is presented. The optimization of the proposed configuration has been accomplished by keeping the constant thickness of zinc oxide (32 nm), silver (32 nm), graphene (0.34 nm) layer and biomolecules (100 nm) for different values of gold layer thickness (1, 3 and 5 nm). The sensitivity of the proposed SPR biosensor has been demonstrated for a number of design parameters such as gold layer thickness, number of graphene layer, refractive index of biomolecules and the thickness of biomolecules layer. SPR biosensor with optimized geometry has greater sensitivity (66 deg/RIU) than the conventional (52 deg/RIU) as well as other graphene-based (53.2 deg/RIU) SPR biosensor. The effect of zinc oxide layer thickness on the sensitivity of SPR biosensor has also been analysed. From the analysis, it is found that the sensitivity increases significantly by increasing the thickness of zinc oxide layer. It means zinc oxide intermediate layer plays an important role to improve the sensitivity of the biosensor. The sensitivity of SPR biosensor also increases by increasing the number of graphene layer (upto nine layer).

Do land surface models need to include differential plant species responses to drought? Examining model predictions across a mesic-xeric gradient in Europe

DOE PAGES

De Kauwe, M. G.; Zhou, S. -X.; Medlyn, B. E.; ...

2015-12-21

Future climate change has the potential to increase drought in many regions of the globe, making it essential that land surface models (LSMs) used in coupled climate models realistically capture the drought responses of vegetation. Recent data syntheses show that drought sensitivity varies considerably among plants from different climate zones, but state-of-the-art LSMs currently assume the same drought sensitivity for all vegetation. We tested whether variable drought sensitivities are needed to explain the observed large-scale patterns of drought impact on the carbon, water and energy fluxes. We implemented data-driven drought sensitivities in the Community Atmosphere Biosphere Land Exchange (CABLE) LSMmore » and evaluated alternative sensitivities across a latitudinal gradient in Europe during the 2003 heatwave. The model predicted an overly abrupt onset of drought unless average soil water potential was calculated with dynamic weighting across soil layers. We found that high drought sensitivity at the most mesic sites, and low drought sensitivity at the most xeric sites, was necessary to accurately model responses during drought. Furthermore, our results indicate that LSMs will over-estimate drought impacts in drier climates unless different sensitivity of vegetation to drought is taken into account.« less

Photoionization of environmentally polluting aromatic chlorides and nitrides on the water surface by laser and synchrotron radiations.

PubMed

Sato, Miki; Maeda, Yuki; Ishioka, Toshio; Harata, Akira

2017-11-20

The detection limits and photoionization thresholds of polycyclic aromatic hydrocarbons and their chlorides and nitrides on the water surface are examined using laser two-photon ionization and single-photon ionization, respectively. The laser two-photon ionization methods are highly surface-selective, with a high sensitivity for aromatic hydrocarbons tending to accumulate on the water surface in the natural environment due to their highly hydrophobic nature. The dependence of the detection limits of target aromatic molecules on their physicochemical properties (photoionization thresholds relating to excess energy, molar absorptivity, and the octanol-water partition coefficient) is discussed. The detection limit clearly depends on the product of the octanol-water partition coefficient and molar absorptivity, and no clear dependence was found on excess energy. The detection limits of laser two-photon ionization for these types of molecules on the water surface are formulated.

Real-Time Label-Free Surface Plasmon Resonance Biosensing with Gold Nanohole Arrays Fabricated by Nanoimprint Lithography

PubMed Central

Martinez-Perdiguero, Josu; Retolaza, Aritz; Otaduy, Deitze; Juarros, Aritz; Merino, Santos

2013-01-01

In this work we present a surface plasmon resonance sensor based on enhanced optical transmission through sub-wavelength nanohole arrays. This technique is extremely sensitive to changes in the refractive index of the surrounding medium which result in a modulation of the transmitted light. The periodic gold nanohole array sensors were fabricated by high-throughput thermal nanoimprint lithography. Square periodic arrays with sub-wavelength hole diameters were obtained and characterized. Using solutions with known refractive index, the array sensitivities were obtained. Finally, protein absorption was monitored in real-time demonstrating the label-free biosensing capabilities of the fabricated devices. PMID:24135989

Significance of dual polarized long wavelength radar for terrain analysis

NASA Technical Reports Server (NTRS)

Macdonald, H. C.; Waite, W. P.

1978-01-01

Long wavelength systems with improved penetration capability have been considered to have the potential for minimizing the vegetation contribution and enhancing the surface return variations. L-band imagery of the Arkansas geologic test site provides confirmatory evidence of this effect. However, the increased wavelength increases the sensitivity to larger scale structure at relatively small incidence angles. The regularity of agricultural and urban scenes provides large components in the low frequency-large scale portion of the roughness spectrum that are highly sensitive to orientation. The addition of a cross polarized channel is shown to enable the interpreter to distinguish vegetation and orientational perturbations in the surface return.

Influence of the carrier-envelope phase of few-cycle pulses on ponderomotive surface-plasmon electron acceleration.

PubMed

Irvine, S E; Dombi, P; Farkas, Gy; Elezzabi, A Y

2006-10-06

Control over basic processes through the electric field of a light wave can lead to new knowledge of fundamental light-matter interaction phenomena. We demonstrate, for the first time, that surface-plasmon (SP) electron acceleration can be coherently controlled through the carrier-envelope phase (CEP) of an excitation optical pulse. Analysis indicates that the physical origin of the CEP sensitivity arises from the electron's ponderomotive interaction with the oscillating electromagnetic field of the SP wave. The ponderomotive electron acceleration mechanism provides sensitive (nJ energies), high-contrast, single-shot CEP measurement capability of few-cycle laser pulses.

High-Sensitive Two-Layer Photoresistors Based on p-Cd x Hg1- x Te with a Converted Near-Surface Layer

NASA Astrophysics Data System (ADS)

Ismailov, N. D.; Talipov, N. Kh.; Voitsekhovskii, A. V.

2018-04-01

The results of an experimental study of photoelectric characteristics of two-layer photoresistors based on p-Cd x Hg1- x Te (x = 0.24-0.28) with a thin near-surface layer of n-type obtained by treatment in atmospheric gas plasma are presented. It is shown that the presence of a potential barrier between the p- and n-regions causes high photosensitivity and speed of operation of such photoresistors at T = 77 K

High-Sensitive Two-Layer Photoresistors Based on p-Cd x Hg1-x Te with a Converted Near-Surface Layer

NASA Astrophysics Data System (ADS)

Ismailov, N. D.; Talipov, N. Kh.; Voitsekhovskii, A. V.

2018-04-01

The results of an experimental study of photoelectric characteristics of two-layer photoresistors based on p-Cd x Hg1-x Te (x = 0.24-0.28) with a thin near-surface layer of n-type obtained by treatment in atmospheric gas plasma are presented. It is shown that the presence of a potential barrier between the p- and n-regions causes high photosensitivity and speed of operation of such photoresistors at T = 77 K

Error sources in the retrieval of aerosol information over bright surfaces from satellite measurements in the oxygen A band

NASA Astrophysics Data System (ADS)

Nanda, Swadhin; de Graaf, Martin; Sneep, Maarten; de Haan, Johan F.; Stammes, Piet; Sanders, Abram F. J.; Tuinder, Olaf; Pepijn Veefkind, J.; Levelt, Pieternel F.

2018-01-01

Retrieving aerosol optical thickness and aerosol layer height over a bright surface from measured top-of-atmosphere reflectance spectrum in the oxygen A band is known to be challenging, often resulting in large errors. In certain atmospheric conditions and viewing geometries, a loss of sensitivity to aerosol optical thickness has been reported in the literature. This loss of sensitivity has been attributed to a phenomenon known as critical surface albedo regime, which is a range of surface albedos for which the top-of-atmosphere reflectance has minimal sensitivity to aerosol optical thickness. This paper extends the concept of critical surface albedo for aerosol layer height retrievals in the oxygen A band, and discusses its implications. The underlying physics are introduced by analysing the top-of-atmosphere reflectance spectrum as a sum of atmospheric path contribution and surface contribution, obtained using a radiative transfer model. Furthermore, error analysis of an aerosol layer height retrieval algorithm is conducted over dark and bright surfaces to show the dependence on surface reflectance. The analysis shows that the derivative with respect to aerosol layer height of the atmospheric path contribution to the top-of-atmosphere reflectance is opposite in sign to that of the surface contribution - an increase in surface brightness results in a decrease in information content. In the case of aerosol optical thickness, these derivatives are anti-correlated, leading to large retrieval errors in high surface albedo regimes. The consequence of this anti-correlation is demonstrated with measured spectra in the oxygen A band from the GOME-2 instrument on board the Metop-A satellite over the 2010 Russian wildfires incident.

Multimodal Nonlinear Optical Imaging for Sensitive Detection of Multiple Pharmaceutical Solid-State Forms and Surface Transformations.

PubMed

Novakovic, Dunja; Saarinen, Jukka; Rojalin, Tatu; Antikainen, Osmo; Fraser-Miller, Sara J; Laaksonen, Timo; Peltonen, Leena; Isomäki, Antti; Strachan, Clare J

2017-11-07

Two nonlinear imaging modalities, coherent anti-Stokes Raman scattering (CARS) and sum-frequency generation (SFG), were successfully combined for sensitive multimodal imaging of multiple solid-state forms and their changes on drug tablet surfaces. Two imaging approaches were used and compared: (i) hyperspectral CARS combined with principal component analysis (PCA) and SFG imaging and (ii) simultaneous narrowband CARS and SFG imaging. Three different solid-state forms of indomethacin-the crystalline gamma and alpha forms, as well as the amorphous form-were clearly distinguished using both approaches. Simultaneous narrowband CARS and SFG imaging was faster, but hyperspectral CARS and SFG imaging has the potential to be applied to a wider variety of more complex samples. These methodologies were further used to follow crystallization of indomethacin on tablet surfaces under two storage conditions: 30 °C/23% RH and 30 °C/75% RH. Imaging with (sub)micron resolution showed that the approach allowed detection of very early stage surface crystallization. The surfaces progressively crystallized to predominantly (but not exclusively) the gamma form at lower humidity and the alpha form at higher humidity. Overall, this study suggests that multimodal nonlinear imaging is a highly sensitive, solid-state (and chemically) specific, rapid, and versatile imaging technique for understanding and hence controlling (surface) solid-state forms and their complex changes in pharmaceuticals.

The Design and Optimization of a Highly Sensitive and Overload-Resistant Piezoresistive Pressure Sensor

PubMed Central

Meng, Xiawei; Zhao, Yulong

2016-01-01

A piezoresistive pressure sensor with a beam-membrane-dual-island structure is developed for micro-pressure monitoring in the field of aviation, which requires great sensitivity and overload resistance capacity. The design, fabrication, and test of the sensor are presented in this paper. By analyzing the stress distribution of sensitive elements using the finite element method, a novel structure incorporating sensitive beams with a traditional bossed diaphragm is built up. The proposed structure proved to be advantageous in terms of high sensitivity and high overload resistance compared with the conventional bossed diaphragm and flat diaphragm structures. Curve fittings of surface stress and deflection based on ANSYS simulation results are performed to establish the sensor equations. Fabricated on an n-type single crystal silicon wafer, the sensor chips are wire-bonded to a printed circuit board (PCB) and packaged for experiments. The static and dynamic characteristics are tested and discussed. Experimental results show that the sensor has a sensitivity as high as 17.339 μV/V/Pa in the range of 500 Pa at room temperature, and a high overload resistance of 200 times overpressure. Due to the excellent performance, the sensor can be applied in measuring micro-pressure lower than 500 Pa. PMID:27005627

Highly labeled methylene blue-ds DNA silica nanoparticles for signal enhancement of immunoassays: application to the sensitive detection of bacteria in human platelet concentrates.

PubMed

Bonnet, Romaric; Farre, Carole; Valera, Lionel; Vossier, Ludivine; Léon, Fanny; Dagland, Typhaine; Pouzet, Agnès; Jaffrézic-Renault, Nicole; Fareh, Jeannette; Fournier-Wirth, Chantal; Chaix, Carole

2018-05-15

A nanoparticle-based electrochemical sandwich immunoassay was developed for bacteria detection in platelet concentrates. For the assay, magnetic beads were functionalized with antibodies to allow the specific capture of bacteria from the complex matrix, and innovative methylene blue-DNA/nanoparticle assemblies provided the electrochemical response for amplified detection. This nanoparticular system was designed as a temperature-sensitive nano-tool for electrochemical detection. First, oligonucleotide-functionalized nanoparticles were obtained by direct synthesis of the DNA strands on the nanoparticle surface using an automated oligonucleotide synthesizer. Densely packed DNA coverage was thus obtained. Then, DNA duplexes were constructed on the NP surface with a complementary strand bearing a 3 methylene blue tag. This strategy ultimately produced highly functionalized nanoparticles with electrochemical markers. These assemblies enabled amplification of the electrochemical signal, resulting in a very good sensitivity. A proof-of-concept was carried out for E. coli detection in human platelet concentrates. Bacterial contamination of this complex biological matrix is the highest residual infectious risk in blood transfusion. The development of a rapid assay that could reach 10-102 CFU mL-1 sensitivity is a great challenge. The nanoparticle-based electrochemical sandwich immunoassay carried out on a boron doped diamond electrode proved to be sensitive for E. coli detection in human platelets. Two antibody pairs were used to develop either a generic assay against certain Gram negative strains or a specific assay for E. coli. The methylene blue-DNA/nanoparticles amplify sensitivity ×1000 compared with the assay run without NPs for electrochemical detection. A limit of detection of 10 CFU mL-1 in a biological matrix was achieved for E. coli using the highly specific antibody pair.

High-precision drop shape analysis on inclining flat surfaces: introduction and comparison of this special method with commercial contact angle analysis.

PubMed

Schmitt, Michael; Heib, Florian

2013-10-07

Drop shape analysis is one of the most important and frequently used methods to characterise surfaces in the scientific and industrial communities. An especially large number of studies, which use contact angle measurements to analyse surfaces, are characterised by incorrect or misdirected conclusions such as the determination of surface energies from poorly performed contact angle determinations. In particular, the characterisation of surfaces, which leads to correlations between the contact angle and other effects, must be critically validated for some publications. A large number of works exist concerning the theoretical and thermodynamic aspects of two- and tri-phase boundaries. The linkage between theory and experiment is generally performed by an axisymmetric drop shape analysis, that is, simulations of the theoretical drop profiles by numerical integration onto a number of points of the drop meniscus (approximately 20). These methods work very well for axisymmetric profiles such as those obtained by pendant drop measurements, but in the case of a sessile drop onto real surfaces, additional unknown and misunderstood effects on the dependence of the surface must be considered. We present a special experimental and practical investigation as another way to transition from experiment to theory. This procedure was developed to be especially sensitive to small variations in the dependence of the dynamic contact angle on the surface; as a result, this procedure will allow the properties of the surface to be monitored with a higher precession and sensitivity. In this context, water drops onto a 111 silicon wafer are dynamically measured by video recording and by inclining the surface, which results in a sequence of non-axisymmetric drops. The drop profiles are analysed by commercial software and by the developed and presented high-precision drop shape analysis. In addition to the enhanced sensitivity for contact angle determination, this analysis technique, in combination with innovative fit algorithms and data presentations, can result in enhanced reproducibility and comparability of the contact angle measurements in terms of the material characterisation in a comprehensible way.

High-precision drop shape analysis on inclining flat surfaces: Introduction and comparison of this special method with commercial contact angle analysis

NASA Astrophysics Data System (ADS)

Schmitt, Michael; Heib, Florian

2013-10-01

Drop shape analysis is one of the most important and frequently used methods to characterise surfaces in the scientific and industrial communities. An especially large number of studies, which use contact angle measurements to analyse surfaces, are characterised by incorrect or misdirected conclusions such as the determination of surface energies from poorly performed contact angle determinations. In particular, the characterisation of surfaces, which leads to correlations between the contact angle and other effects, must be critically validated for some publications. A large number of works exist concerning the theoretical and thermodynamic aspects of two- and tri-phase boundaries. The linkage between theory and experiment is generally performed by an axisymmetric drop shape analysis, that is, simulations of the theoretical drop profiles by numerical integration onto a number of points of the drop meniscus (approximately 20). These methods work very well for axisymmetric profiles such as those obtained by pendant drop measurements, but in the case of a sessile drop onto real surfaces, additional unknown and misunderstood effects on the dependence of the surface must be considered. We present a special experimental and practical investigation as another way to transition from experiment to theory. This procedure was developed to be especially sensitive to small variations in the dependence of the dynamic contact angle on the surface; as a result, this procedure will allow the properties of the surface to be monitored with a higher precession and sensitivity. In this context, water drops onto a 111 silicon wafer are dynamically measured by video recording and by inclining the surface, which results in a sequence of non-axisymmetric drops. The drop profiles are analysed by commercial software and by the developed and presented high-precision drop shape analysis. In addition to the enhanced sensitivity for contact angle determination, this analysis technique, in combination with innovative fit algorithms and data presentations, can result in enhanced reproducibility and comparability of the contact angle measurements in terms of the material characterisation in a comprehensible way.

Surface Chemical Properties of Purified Root Cell Walls from Two Tobacco Genotypes Exhibiting Different Tolerance to Manganese Toxicity 1

PubMed Central

Wang, Jian; Evangelou, Bill P.; Nielsen, Mark T.

1992-01-01

Surface chemical characteristics of root cell walls extracted from two tobacco genotypes exhibiting differential tolerance to Mn toxicity were studied using potentiometric pH titration and Fourier transform infrared spectroscopy. The Mn-sensitive genotype KY 14 showed a stronger interaction of its cell wall surface with metal ions than did the Mn-tolerant genotype Tobacco Introduction (T.I.) 1112. This observation may be attributed to the relatively higher ratio of COO− to COOH in KY 14 cell walls than that found in the cell walls of T.I. 1112 in the pH range of 4 to 10. For both genotypes, the strength of binding between metal ions and cell wall surface was in the order of Cu > Ca > Mn > Mg > Na. However, a slightly higher preference of Ca over Mn was observed with the T.I. 1112 cell wall. This may explain the high accumulation of Mn in the leaves of Mn-tolerant genotype T.I. 1112 rather than the high accumulation of Mn in roots, as occurred in Mn-sensitive KY 14. It is concluded that surface chemical characteristics of cell walls may play an important role in plant metal ion uptake and tolerance. PMID:16652989

Fast subsurface fingerprint imaging with full-field optical coherence tomography system equipped with a silicon camera

NASA Astrophysics Data System (ADS)

Auksorius, Egidijus; Boccara, A. Claude

2017-09-01

Images recorded below the surface of a finger can have more details and be of higher quality than the conventional surface fingerprint images. This is particularly true when the quality of the surface fingerprints is compromised by, for example, moisture or surface damage. However, there is an unmet need for an inexpensive fingerprint sensor that is able to acquire high-quality images deep below the surface in short time. To this end, we report on a cost-effective full-field optical coherent tomography system comprised of a silicon camera and a powerful near-infrared LED light source. The system, for example, is able to record 1.7 cm×1.7 cm en face images in 0.12 s with the spatial sampling rate of 2116 dots per inch and the sensitivity of 93 dB. We show that the system can be used to image internal fingerprints and sweat ducts with good contrast. Finally, to demonstrate its biometric performance, we acquired subsurface fingerprint images from 240 individual fingers and estimated the equal-error-rate to be ˜0.8%. The developed instrument could also be used in other en face deep-tissue imaging applications because of its high sensitivity, such as in vivo skin imaging.

In situ XAS of Pt monolayer model fuel cell catalysts: balance of na-nostructure and bimetallic interactions

NASA Astrophysics Data System (ADS)

Friebel, Daniel; Viswanathan, Venkat; Larsen, Ask; Miller, Daniel J.; Ogasawara, Hirohito; Anniyev, Toyli; O'Grady, Christopher P.; Nørskov, Jens; Nilsson, Anders

2012-02-01

The mechanism of the electrochemical oxygen reduction reaction (ORR) has been well understood based on DFT calculations, but there has been a lack of supporting experimental data, due to the difficulties of probing the electrocatalyst surface in situ. Our new approach using Pt monolayer model catalysts provides true surface sensitivity for - originally bulk sensitive - x-ray absorption spectroscopy (XAS) and, owing to the high resolution of the Bragg analyzer at SSRL beamline 6-2, allows for in situ detection of chemisorbed O and OH, whose stability can be used as a descriptor in predicting the activity of new ORR catalyst materials. Our ability to control the growth mode in the Pt/Rh(111) model system allows us to generate Pt nanostructures with highly different O affinities from identical starting materials.

Flower-like self-assembly of gold nanoparticles for highly sensitive electrochemical detection of chromium(VI)

PubMed Central

Ouyang, Ruizhuo; Bragg, Stefanie A.; Chambers, James Q.; Xue, Zi-Ling

2012-01-01

We report here the fabrication of a flower-like self-assembly of gold nanoparticles (AuNPs) on a glassy carbon electrode (GCE) as a highly sensitive platform for ultratrace Cr(VI) detection. Two AuNPs layers are used in the current approach, in which the first is electroplated on the GCE surface as anchors for binding to an overcoated thiol sol-gel film derived from 3-mercaptopropyltrimethoxysilane (MPTS). The second AuNPs layer is then self-assembled on the surface of the sol-gel film, forming flower-like gold nanoelectrodes enlarging the electrode surface. When functionalized by a thiol pyridinium, the fabricated electrode displays a well-defined peak for selective Cr(VI) reduction with an unusually large, linear concentration range of 10–1,200 ng L−1 and a low detection limit of 2.9 ng L−1. In comparison to previous approaches using MPTS and AuNPs on Au electrodes, the current work expands the use of AuNPs to the GCE. Subsequent functionalization of the secondary AuNPs by a thiol pyridinium and adsorption/preconcentration of Cr(VI) lead to the unusually large detection range and high sensitivity. The stepwise preparation of the electrode has been characterized by electrochemical impedance spectroscopy (EIS), scanning electronic microscopy (SEM), and IR. The newly designed electrode exhibits good stability, and has been successfully employed to measure chromium in a pre-treated blood sample. The method demonstrates acceptable fabrication reproducibility and accuracy. PMID:22444528

Photoluminescence-excitation spectroscopy as a highly sensitive probe for carrier transport processes affected by surface damages in AlxGa1-xN/GaN heterostructures

NASA Astrophysics Data System (ADS)

Takeuchi, Hideo; Yamamoto, Yoshitsugu; Kamo, Yoshitaka; Kunii, Tetsuo; Oku, Tomoki; Shirahama, Takeo; Tanaka, Hiroyasu; Nakayama, Masaaki

2007-08-01

We demonstrate that photoluminescence-excitation (PLE) spectroscopy can probe with high sensitivity the effects of plasma-induced surface damages on photogenerated-carrier-transport processes in AlxGa1-xN/GaN heterostructures, on the basis of systematic optical and structural characterization results for the as-grown reference sample and the plasma-exposed sample. It is found from the structural characterizations with atomic force microscopy that the plasma exposure remarkably modifies the atomic step boundaries and the pits on the AlxGa1-xN surface, which leads to a remarkable difference between the PLE spectra of the bound exciton photoluminescence from the underlying GaN layer in the two samples. The PLE spectrum of the reference sample shows a step rising from the AlxGa1-xN fundamental transition energy toward the high energy side, whereas the rising step disappears in the PLE spectrum of the plasma-exposed sample. In contrast, the reflectance characteristics are the same in the two samples; i.e., the excitonic transition itself is not influenced by the plasma exposure. The present findings indicate that the PLE spectral profile is sensitive to the change in efficiency of the photogenerated carrier injection from the AlxGa1-xN layer to the GaN layer. Thus, it is concluded that the PLE characterization is effective to probe the photogenerated-carrier transport in heterostructures.

Design and performance of a Near Ultra High Vacuum Helium Ion Microscope

NASA Astrophysics Data System (ADS)

Poelsema, Bene; van Gastel, Raoul; Hlawacek, Gregor; Zandvliet, Harold J. W.

2012-02-01

The advent of He Ion Microscopy (HIM) as a new nanoscopic technique to image materials has enabled a new look at materials that is based on the interaction of swift light ions with matter. Initial HIM instruments have demonstrated high-resolution imaging, combined with great surface sensitivity, the ability to neutralize charge very efficiently, and with enhanced materials contrast when ion induced secondary electrons are used for imaging. To achieve ultimate performance, the chamber vacuum of the existing platform may be improved. For instance, carbon deposits due to beam interaction are readily seen due to the surface sensitivity of the technique. At high current densities the sharply focused beam may very efficiently decompose residual hydrocarbons. Not only can this obscure a clear view of the sample, thereby negating the benefits of the small spot size, it also limits the available acquisition time. This has proven extremely useful for nanopatterning for sensors, and other device fabrication applications at the sub-10nm level. However, it is undesirable when the instrument is used for materials characterization. We will discuss the basic considerations that went into the design of a Near-UHV He Ion Microscope [1]. First applications that the instrument was used for will be highlighted and its impact in surface physics and other research areas that require increased imaging sensitivity will be discussed. [4pt] [1] R.van Gastel et al, Microscopy and Microanalysis 17, 928-929 (2011)

Archetypal sandwich-structured CuO for high performance non-enzymatic sensing of glucose.

PubMed

Meher, Sumanta Kumar; Rao, G Ranga

2013-03-07

In the quest to enhance the selectivity and sensitivity of novel structured metal oxides for electrochemical non-enzymatic sensing of glucose, we report here a green synthesis of unique sandwich-structured CuO on a large scale under microwave mediated homogeneous precipitation conditions. The physicochemical studies carried out by XRD and BET methods show that the monoclinic CuO formed via thermal decomposition of Cu(2)(OH)(2)CO(3) possesses monomodal channel-type pores with largely improved surface area (~43 m(2) g(-1)) and pore volume (0.163 cm(3) g(-1)). The fascinating surface morphology and pore structure of CuO is formulated due to homogeneous crystallization and microwave induced self assembly during synthesis. The cyclic voltammetry and chronoamperometry studies show diffusion controlled glucose oxidation at ~0.6 V (vs. Ag/AgCl) with extremely high sensitivity of 5342.8 μA mM(-1) cm(-2) and respective detection limit and response time of ~1 μM and ~0.7 s, under a wide dynamic concentration range of glucose. The chronoamperometry measurements demonstrate that the sensitivity of CuO to glucose is unaffected by the absence of dissolved oxygen and presence of poisoning chloride ions in the reaction medium, which essentially implies high poison resistance activity of the sandwich-structured CuO. The sandwich-structured CuO also shows insignificant interference/significant selectivity to glucose, even in the presence of high concentrations of other sugars as well as reducing species. In addition, the sandwich-structured CuO shows excellent reproducibility (relative standard deviation of ~2.4% over ten identically fabricated electrodes) and outstanding long term stability (only ~1.3% loss in sensitivity over a period of one month) during non-enzymatic electrochemical sensing of glucose. The unique microstructure and suitable channel-type pore architecture provide structural stability and maximum accessible electroactive surface for unimpeded mobility of glucose as well as the product molecules, which result in the excellent sensitivity and selectivity of sandwich-structured CuO for glucose under non-enzymatic milieu.

A total internal reflection-fluorescence correlation spectroscopy setup with pulsed diode laser excitation

NASA Astrophysics Data System (ADS)

Weger, Lukas; Hoffmann-Jacobsen, Kerstin

2017-09-01

Fluorescence correlation spectroscopy (FCS) measures fluctuations in a (sub-)femtoliter volume to analyze the diffusive behavior of fluorescent particles. This highly sensitive method has proven to be useful for the analysis of dynamic biological systems as well as in chemistry, physics, and material sciences. It is routinely performed with commercial fluorescence microscopes, which provide a confined observation volume by the confocal technique. The evanescent wave of total internal reflectance (TIR) is used in home-built systems to permit a surface sensitive FCS analysis. We present a combined confocal and TIR-FCS setup which uses economic low-power pulsed diode lasers for excitation. Excitation and detection are coupled to time-correlated photon counting hardware. This allows simultaneous fluorescence lifetime and FCS measurements in a surface-sensitive mode. Moreover, the setup supports fluorescence lifetime correlation spectroscopy at surfaces. The excitation can be easily switched between TIR and epi-illumination to compare the surface properties with those in liquid bulk. The capabilities of the presented setup are demonstrated by measuring the diffusion coefficients of a free dye molecule, a labeled polyethylene glycol, and a fluorescent nanoparticle in confocal as well as in TIR-FCS.

Surface plasmon resonance biosensors for highly sensitive detection in real samples

NASA Astrophysics Data System (ADS)

Sepúlveda, B.; Carrascosa, L. G.; Regatos, D.; Otte, M. A.; Fariña, D.; Lechuga, L. M.

2009-08-01

In this work we summarize the main results obtained with the portable surface plasmon resonance (SPR) device developed in our group (commercialised by SENSIA, SL, Spain), highlighting its applicability for the real-time detection of extremely low concentrations of toxic pesticides in environmental water samples. In addition, we show applications in clinical diagnosis as, on the one hand, the real-time and label-free detection of DNA hybridization and single point mutations at the gene BRCA-1, related to the predisposition in women to develop an inherited breast cancer and, on the other hand, the analysis of protein biomarkers in biological samples (urine, serum) for early detection of diseases. Despite the large number of applications already proven, the SPR technology has two main drawbacks: (i) not enough sensitivity for some specific applications (where pM-fM or single-molecule detection are needed) (ii) low multiplexing capabilities. In order solve such drawbacks, we work in several alternative configurations as the Magneto-optical Surface Plasmon Resonance sensor (MOSPR) based on a combination of magnetooptical and ferromagnetic materials, to improve the SPR sensitivity, or the Localized Surface Plasmon Resonance (LSPR) based on nanostructures (nanoparticles, nanoholes,...), for higher multiplexing capabilities.

Detection of nerve gases using surface-enhanced Raman scattering substrates with high droplet adhesion

NASA Astrophysics Data System (ADS)

Hakonen, Aron; Rindzevicius, Tomas; Schmidt, Michael Stenbæk; Andersson, Per Ola; Juhlin, Lars; Svedendahl, Mikael; Boisen, Anja; Käll, Mikael

2016-01-01

Threats from chemical warfare agents, commonly known as nerve gases, constitute a serious security issue of increasing global concern because of surging terrorist activity worldwide. However, nerve gases are difficult to detect using current analytical tools and outside dedicated laboratories. Here we demonstrate that surface-enhanced Raman scattering (SERS) can be used for sensitive detection of femtomol quantities of two nerve gases, VX and Tabun, using a handheld Raman device and SERS substrates consisting of flexible gold-covered Si nanopillars. The substrate surface exhibits high droplet adhesion and nanopillar clustering due to elasto-capillary forces, resulting in enrichment of target molecules in plasmonic hot-spots with high Raman enhancement. The results may pave the way for strategic life-saving SERS detection of chemical warfare agents in the field.Threats from chemical warfare agents, commonly known as nerve gases, constitute a serious security issue of increasing global concern because of surging terrorist activity worldwide. However, nerve gases are difficult to detect using current analytical tools and outside dedicated laboratories. Here we demonstrate that surface-enhanced Raman scattering (SERS) can be used for sensitive detection of femtomol quantities of two nerve gases, VX and Tabun, using a handheld Raman device and SERS substrates consisting of flexible gold-covered Si nanopillars. The substrate surface exhibits high droplet adhesion and nanopillar clustering due to elasto-capillary forces, resulting in enrichment of target molecules in plasmonic hot-spots with high Raman enhancement. The results may pave the way for strategic life-saving SERS detection of chemical warfare agents in the field. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr06524k

Micro-array versus nano-array platforms: a comparative study for ODN detection based on SPR enhanced ellipsometry

NASA Astrophysics Data System (ADS)

Celen, Burcu; Demirel, Gökhan; Piskin, Erhan

2011-04-01

The rapid and sensitive detection of DNA has recently attracted worldwide attention for a variety of disease diagnoses and detection of harmful bacteria in food and drink. In this paper, we carried out a comparative study based on surface plasmon resonance enhanced ellipsometry (SPREE) for the detection of oligodeoxynucleotides (ODNs) using micro- and nano-array platforms. The micro-arrayed surfaces were fabricated by a photolithography approach using different types of mask having varying size and shape. Well-ordered arrays of high aspect ratio polymeric nanotubes were also obtained using high molecular weight polystyrene (PS) and anodic aluminum oxide (AAO) membranes having 200 nm pore diameters. The SPREE sensors were then prepared by direct coupling of thiolated probe-ODNs, which contain suitable spacer arms, on gold-coated micro- and nano-arrayed surfaces. We experimentally demonstrated that, for the first time, gold-coated free standing polymeric nano-arrayed platforms can easily be produced and lead to a significant sensor sensitivity gain compared to that of the conventional SPREE surfaces of about four times. We believe that such an enhancement in sensor response could be useful for next generation sensor systems.

Triangular laser-induced submicron textures for functionalising stainless steel surfaces

NASA Astrophysics Data System (ADS)

Romano, Jean-Michel; Garcia-Giron, Antonio; Penchev, Pavel; Dimov, Stefan

2018-05-01

Processing technologies that engineer surfaces with sub-micron topographies are of a growing interest to a range of optical, hydrophobic and microbiological applications. One of the promising technologies for creating such topographies employs ultra-short laser pulses to produce laser-induced periodic surface structures (LIPSS) that often result in non-regular, quasi-periodic nanoripples and nanopillars. In this research near infrared ultra-short pulses of 310 fs with a circular polarisation was used to texture ferritic stainless steel workpieces. A single-step process was designed to generate low spatial frequency LIPSS (LSFL) over relatively large areas. Apart from highly regular and homogeneous parallel lines with approximately 900 nm periodicity, extraordinarily uniform triangular-LSFL in hexagonal arrangements was created. The generation of such LSFL was found to be highly repeatable but very sensitive to the used laser processing settings. Therefore, the sensitivity of triangular-LSFL formation to the used laser processing settings, i.e. pulse to pulse distance, pulse fluence and focal plane offsets, were investigated in regard to the resulting morphologies and functional properties, i.e. structural colors and super-hydrophobicity. Finally, the capability of this technology for producing uniform triangular-shaped LSFL on relatively large surface areas of stainless steel plates was studied.

Automated quantification of surface water inundation in wetlands using optical satellite imagery

USGS Publications Warehouse

DeVries, Ben; Huang, Chengquan; Lang, Megan W.; Jones, John W.; Huang, Wenli; Creed, Irena F.; Carroll, Mark L.

2017-01-01

We present a fully automated and scalable algorithm for quantifying surface water inundation in wetlands. Requiring no external training data, our algorithm estimates sub-pixel water fraction (SWF) over large areas and long time periods using Landsat data. We tested our SWF algorithm over three wetland sites across North America, including the Prairie Pothole Region, the Delmarva Peninsula and the Everglades, representing a gradient of inundation and vegetation conditions. We estimated SWF at 30-m resolution with accuracies ranging from a normalized root-mean-square-error of 0.11 to 0.19 when compared with various high-resolution ground and airborne datasets. SWF estimates were more sensitive to subtle inundated features compared to previously published surface water datasets, accurately depicting water bodies, large heterogeneously inundated surfaces, narrow water courses and canopy-covered water features. Despite this enhanced sensitivity, several sources of errors affected SWF estimates, including emergent or floating vegetation and forest canopies, shadows from topographic features, urban structures and unmasked clouds. The automated algorithm described in this article allows for the production of high temporal resolution wetland inundation data products to support a broad range of applications.

m-Cresol purple functionalized surface enhanced Raman scattering paper chips for highly sensitive detection of pH in the neutral pH range.

PubMed

Zou, Xinxin; Wang, Yunqing; Liu, Wanhui; Chen, Lingxin

2017-06-26

Herein, a pH sensitive paper SERS chip was prepared by selecting m-cresol purple, a molecule with halochromic properties in the neutral pH range as a Raman reporter. The adsorbed m-cresol purple underwent a reversible change in its electronic configuration from a non-resonant species to a resonant species, which resulted in a significant Raman signal intensity variation due to the transformation of the sensing mode from SERS to surface-enhanced resonance Raman scattering (SERRS). The chips have a sensitive pH range of 6.0 to 8.0 and exhibited good performance for the detection of natural water samples with detection precision of approximately 0.03 pH units, suggesting great potential for environmental pH monitoring applications.

Polarization-dependent transverse-stress sensing characters of the gold-coated and liquid crystal filled photonic crystal fiber based on Surface Plasmon Resonance

NASA Astrophysics Data System (ADS)

Liu, Hai; Zhu, Chenghao; Wang, Yan; Tan, Ce; Li, Hongwei

2018-03-01

A transverse-stress sensor with enhanced sensitivity based on nematic liquid crystal (NLC) filled photonic crystal fiber (PCF) is proposed and analyzed by using the finite element method (FEM). The central hole of the PCF is infiltrated with NLC material with an adjustable rotation angle to achieve the polarization-dependent wavelength-selective sensing. And the combined use of side-hole structure and Surface Plasmon Resonance (SPR) technology enhanced the transverse-stress sensitivity enormously. Results reveal that the sensor can achieve a high sensitivity based on the polarization filter characteristic at special wavelengths. Besides that, the temperature and the transverse-stress in either direction can be effectively discriminated through dual-parameter demodulation method by adjusting the rotation angle of the NLC to introduce a new degree of freedom for sensing.

Maskless Lithography Using Surface Plasmon Enhanced Illumination

DTIC Science & Technology

2007-04-30

Dale Larson Figure 1. Nanohole array probes exhibiting extraordinary optical transmission of light with a high degree of collimation. Left: a bull’s...Technol. B 22, 3552-3556 (2004). 2. Stark, P., Halleck, A. E. & Larson, D. N. Short order nanohole arrays in metals for highly sensitive probing of local

Frontolysis by surface heat flux in the Agulhas Return Current region with a focus on mixed layer processes: observation and a high-resolution CGCM

NASA Astrophysics Data System (ADS)

Ohishi, Shun; Tozuka, Tomoki; Komori, Nobumasa

2016-12-01

Detailed mechanisms for frontogenesis/frontolysis of the Agulhas Return Current (ARC) Front, defined as the maximum of the meridional sea surface temperature (SST) gradient at each longitude within the ARC region (40°-50°E, 55°-35°S), are investigated using observational datasets. Due to larger (smaller) latent heat release to the atmosphere on the northern (southern) side of the front, the meridional gradient of surface net heat flux (NHF) is found throughout the year. In austral summer, surface warming is weaker (stronger) on the northern (southern) side, and thus the NHF tends to relax the SST front. The weaker (stronger) surface warming, at the same time, leads to the deeper (shallower) mixed layer on the northern (southern) side. This enhances the frontolysis, because deeper (shallower) mixed layer is less (more) sensitive to surface warming. In austral winter, stronger (weaker) surface cooling on the northern (southern) side contributes to the frontolysis. However, deeper (shallower) mixed layer is induced by stronger (weaker) surface cooling on the northern (southern) side and suppresses the frontolysis, because the deeper (shallower) mixed layer is less (more) sensitive to surface cooling. Therefore, the frontolysis by the NHF becomes stronger (weaker) through the mixed layer processes in austral summer (winter). The cause of the meridional gradient of mixed layer depth is estimated using diagnostic entrainment velocity and the Monin-Obukhov depth. Furthermore, the above mechanisms obtained from the observation are confirmed using outputs from a high-resolution coupled general circulation model. Causes of model biases are also discussed.

Highly sensitive and simple SERS substrate based on photochemically generated carbon nanotubes-gold nanorods hybrids.

PubMed

Caires, A J; Vaz, R P; Fantini, C; Ladeira, L O

2015-10-01

We report a simple and easy formation of hybrids between multi-wall carbon nanotubes and gold nanorods by one-pot in situ photochemical synthesis. Measurements of surface-enhanced Raman scattering (SERS) through the effect "coffee ring" in visible and near infrared (NIR) show high sensitivity with detection of nanomolar concentrations of aromatic dyes. The formation of nanocomposites between carbon nanotubes and gold nanorods without chemical binders simplifies the preparation. Photochemical synthesis is an advance over the techniques previously published. Copyright © 2015 Elsevier Inc. All rights reserved.

Impact of surface coupling grids on tropical cyclone extremes in high-resolution atmospheric simulations

DOE PAGES

Zarzycki, Colin M.; Reed, Kevin A.; Bacmeister, Julio T.; ...

2016-02-25

This article discusses the sensitivity of tropical cyclone climatology to surface coupling strategy in high-resolution configurations of the Community Earth System Model. Using two supported model setups, we demonstrate that the choice of grid on which the lowest model level wind stress and surface fluxes are computed may lead to differences in cyclone strength in multi-decadal climate simulations, particularly for the most intense cyclones. Using a deterministic framework, we show that when these surface quantities are calculated on an ocean grid that is coarser than the atmosphere, the computed frictional stress is misaligned with wind vectors in individual atmospheric gridmore » cells. This reduces the effective surface drag, and results in more intense cyclones when compared to a model configuration where the ocean and atmosphere are of equivalent resolution. Our results demonstrate that the choice of computation grid for atmosphere–ocean interactions is non-negligible when considering climate extremes at high horizontal resolution, especially when model components are on highly disparate grids.« less

A highly sensitive biological detection substrate based on TiO2 nanowires supporting gold nanoparticles

NASA Astrophysics Data System (ADS)

Zeng, Yuan; Tan, Hai-jun; Cheng, Xiu-Lan; Chen, Rui; Wang, Ying

2011-12-01

Surface enhanced Raman scattering (SERS) has attracted widespread concern in the field of bioassay because it can enhance normally weak Raman signal by several orders of magnitude and facilitate the highly sensitive detection of molecules. Conventional SERS substrates are prepared by placing metal nanoparticles on a planar surface. Here we show a unique SERS substrate stacked by disordered TiO2 nanowires (TiO2-NWs) supportig gold nanocrystals. The structure can be easily fabricated by chemical synthesis at low cost. The COMSOL model simulation shows the designed SERS substrate is capable of output high Local Field Enhancement (LFE) in the Near Infrared region (NIR) that is the optimal wavelength in bio-detection because of both the unique coupling enhancement effect amony nearby Au nanocrystals on TiO2-NWs and the Suface Plasmon Resonance (SPR) effect of TiO2 -NWs. The as-prepared transparent and freestanding SERS substrate is capable of detecting extremely low concentration R6G molecular, showing much higher Raman signal because of the extremely large surface area and the uniqueTiO2-NWs self-assemblied by Au nanocrystals. These results provide a new approach to ultrasensitive bioassay device.

Surface Plasmon Resonance-Based Fiber Optic Sensors Utilizing Molecular Imprinting

PubMed Central

Gupta, Banshi D.; Shrivastav, Anand M.; Usha, Sruthi P.

2016-01-01

Molecular imprinting is earning worldwide attention from researchers in the field of sensing and diagnostic applications, due to its properties of inevitable specific affinity for the template molecule. The fabrication of complementary template imprints allows this technique to achieve high selectivity for the analyte to be sensed. Sensors incorporating this technique along with surface plasmon or localized surface plasmon resonance (SPR/LSPR) provide highly sensitive real time detection with quick response times. Unfolding these techniques with optical fiber provide the additional advantages of miniaturized probes with ease of handling, online monitoring and remote sensing. In this review a summary of optical fiber sensors using the combined approaches of molecularly imprinted polymer (MIP) and the SPR/LSPR technique is discussed. An overview of the fundamentals of SPR/LSPR implementation on optical fiber is provided. The review also covers the molecular imprinting technology (MIT) with its elementary study, synthesis procedures and its applications for chemical and biological anlayte detection with different sensing methods. In conclusion, we explore the advantages, challenges and the future perspectives of developing highly sensitive and selective methods for the detection of analytes utilizing MIT with the SPR/LSPR phenomenon on optical fiber platforms. PMID:27589746

Biosensors Fabricated through Electrostatic Assembly of Enzymes/Polyelectrolyte Hybrid Layers on Carbon Nanotubes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Yuehe; Liu, Guodong; Wang, Jun

2006-06-01

Carbon nanotubes (CNTs) have emerged as new class of nanomaterials that is receiving considerable interest because of their unique structure, mechanical, and electronic properties. One promising application of CNTs is to fabricate highly sensitive chemo/biosensors.1-4 For construction of these CNT-based sensors, the CNTs first have to be modified with some molecules specific to the interests. Generally, covalent binding, affinity, and electrostatic interaction have been utilized for the modification of CNTs. Among them, the electrostatic method is attractive due to its simplicity and high efficiency. In present work, we have developed highly sensitively amperometric biosensors for glucose, choline, organophosphate pesticide (OPP)more » and nerve agents (NAs) based on electrostatically assembling enzymes on the surface of CNTs. All these biosensors were fabricated by immobilization of enzymes on the negatively charged CNTs surface through alternately assembling a cationic poly(diallydimethylammonium chloride) (PDDA) layer and an enzyme layer. Using this layer-by-layer (LBL) technique, a bioactive nanocomposite film was fabricated on the electrode surface. Owing to the electrocatalytic effect of CNTs, an amplified electrochemical signal was achieved, which leads to low detections limits for glucose, choline, and OPP and NAs.« less

Interference of conically scattered light in surface plasmon resonance.

PubMed

Webster, Aaron; Vollmer, Frank

2013-02-01

Surface plasmon polaritons on thin metal films are a well studied phenomena when excited using prism coupled geometries such as the Kretschmann attenuated total reflection configuration. Here we describe a novel interference pattern in the conically scattered light emanating from such a configuration when illuminated by a focused beam. We observe conditions indicating only self-interference of scattered surface plasmon polaritions without any contributions from specular reflection. The spatial evolution of this field is described in the context of Fourier optics and has applications in highly sensitive surface plasmon based biosensing.

Surface forces between hydrophilic silica surfaces in a moisture-sensitive oleophilic diacrylate monomer liquid

NASA Astrophysics Data System (ADS)

Ito, Shunya; Kasuya, Motohiro; Kurihara, Kazue; Nakagawa, Masaru

2018-02-01

We measured the surface forces generated between fused silica surfaces in a low-viscosity oleophilic diacrylate monomer for reliably repeated ultraviolet (UV) nanoimprinting, and studied the influence of water in monomer liquids on the forces. Fused silica surfaces, with a static contact angle of 52.6 ± 1.7° for water, owing to the low degree of hydroxylation, hardly showed reproducible surface forces with repeated scan cycles, comprising approach and separation, even in an identical liquid monomer medium with both of low and high water content. The monomer liquid with a high water content of approximately 420 ppm showed a greater tendency to increase the surface forces at longer surface-surface distances compared with the monomer liquid with a low water content of approximately 60 ppm. On the other hand, silica surfaces with a water contact angle of < 5° after exposure to vacuum UV (VUV) light under a reduced air pressure showed reproducible profiles of surfaces forces using the monomer with a low water concentration of approximately 60 ppm for repeated surface forces scan cycles even in separately prepared silica surfaces, whilst they showed less reproducible profiles in the liquids with high water content of 430 ppm. These results suggested that water possibly adsorbed on the hydrophilic and hydrophobic silica surfaces in the monomer liquid of the high water concentration influenced the repeatability of the surface forces profiles.

Graphene-interfaced electrical biosensor for label-free and sensitive detection of foodborne pathogenic E. coli O157:H7.

PubMed

Pandey, Ashish; Gurbuz, Yasar; Ozguz, Volkan; Niazi, Javed H; Qureshi, Anjum

2017-05-15

E. coli O157:H7 is an enterohemorrhagic bacteria responsible for serious foodborne outbreaks that causes diarrhoea, fever and vomiting in humans. Recent foodborne E. coli outbreaks has left a serious concern to public health. Therefore, there is an increasing demand for a simple, rapid and sensitive method for pathogen detection in contaminated foods. In this study, we developed a label-free electrical biosensor interfaced with graphene for sensitive detection of pathogenic bacteria. This biosensor was fabricated by interfacing graphene with interdigitated microelectrodes of capacitors that were biofunctionalized with E. coli O157:H7 specific antibodies for sensitive pathogenic bacteria detection. Here, graphene nanostructures on the sensor surface provided superior chemical properties such as high carrier mobility and biocompatibility with antibodies and bacteria. The sensors transduced the signal based on changes in dielectric properties (capacitance) through (i) polarization of captured cell-surface charges, (ii) cells' internal bioactivity, (iii) cell-wall's electronegativity or dipole moment and their relaxation and (iv) charge carrier mobility of graphene that modulated the electrical properties once the pathogenic E. coli O157:H7 captured on the sensor surface. Sensitive capacitance changes thus observed with graphene based capacitors were specific to E. coli O157:H7 strain with a sensitivity as low as 10-100 cells/ml. The proposed graphene based electrical biosensor provided advantages of speed, sensitivity, specificity and in-situ bacterial detection with no chemical mediators, represents a versatile approach for detection of a wide variety of other pathogens. Copyright © 2016 Elsevier B.V. All rights reserved.

Surface stress sensor based on MEMS Fabry-Perot interferometer with high wavelength selectivity for label-free biosensing

NASA Astrophysics Data System (ADS)

Takahashi, Toshiaki; Hizawa, Takeshi; Misawa, Nobuo; Taki, Miki; Sawada, Kazuaki; Takahashi, Kazuhiro

2018-05-01

We have developed a surface stress sensor based on a microelectromechanical Fabry-Perot interferometer with high wavelength selectivity by using Au half-mirrors, for highly sensitive label-free biosensing. When the target molecule is adsorbed by the antigen-antibody reaction onto a movable membrane with a thin Au film, which acts as an upper mirror of the optical interferometer, the amount of deflection of the movable membrane deflected by the change in surface stress can be detected with high sensitivity. To improve the signal at the small membrane deflection region of this biosensor resulting in detection of low concentration molecules, by integrating 50 nm-thick Au half-mirrors, the wavelength selectivity of the optical interferometer has been successfully improved 6.6 times. Furthermore, the peak shift in the reflection spectrum due to the adsorption of bovine serum albumin (BSA) antigen with a concentration of 10 ng ml-l by the antigen-antibody reaction was spectroscopically measured on the fabricated optical interferometer, and the deflection amount of the movable membrane after 10 min treatment was 2.4 times larger than that of nonspecific adsorption with the avidin molecules. This result indicated that the proposed sensor can be used for selective detection of low-concentration target antigen molecules.

A high sensitivity MEA probe for measuring real time rat brain glucose flux.

PubMed

Wei, Wenjing; Song, Yilin; Shi, Wentao; Lin, Nansen; Jiang, Tingjun; Cai, Xinxia

2014-05-15

The mammalian central nervous system (CNS) relies on a constant supply of external glucose for its undisturbed operation. This article presents an implantable Multi-Electrode Array (MEA) probe for brain glucose measurement. The MEA was implemented on Silicon-On-Insulator (SOI) wafer using Micro-Electro-Mechanical-Systems (MEMS) methods. There were 16 platinum recording sites on the probe and enzyme glucose oxidase (GOx) was immobilized on them. The glucose sensitivity of the MEA probe was as high as 489 µA mM(-1) cm(-2). 1,3-Phenylenediamine (mPD) was electropolymerized onto the Pt recording surfaces to prevent larger molecules such as ascorbic acid (AA), 3,4-dihydroxyphenylacetic acid (DOPAC), serotonin (5-HT), and dopamine (DA) from reaching the recording sites surface. The MEA probe was implanted in the anesthetized rat striatum and responded to glucose levels which were altered by intraperitoneal injection of glucose and insulin. After the in vivo experiment, the MEA probe still kept sensitivity to glucose, these suggested that the MEA probe was reliable for glucose monitoring in brain extracellular fluid (ECF). © 2013 Published by Elsevier B.V.

Nanotechnology: a promising method for oral cancer detection and diagnosis.

PubMed

Chen, Xiao-Jie; Zhang, Xue-Qiong; Liu, Qi; Zhang, Jing; Zhou, Gang

2018-06-11

Oral cancer is a common and aggressive cancer with high morbidity, mortality, and recurrence rate globally. Early detection is of utmost importance for cancer prevention and disease management. Currently, tissue biopsy remains the gold standard for oral cancer diagnosis, but it is invasive, which may cause patient discomfort. The application of traditional noninvasive methods-such as vital staining, exfoliative cytology, and molecular imaging-is limited by insufficient sensitivity and specificity. Thus, there is an urgent need for exploring noninvasive, highly sensitive, and specific diagnostic techniques. Nano detection systems are known as new emerging noninvasive strategies that bring the detection sensitivity of biomarkers to nano-scale. Moreover, compared to current imaging contrast agents, nanoparticles are more biocompatible, easier to synthesize, and able to target specific surface molecules. Nanoparticles generate localized surface plasmon resonances at near-infrared wavelengths, providing higher image contrast and resolution. Therefore, using nano-based techniques can help clinicians to detect and better monitor diseases during different phases of oral malignancy. Here, we review the progress of nanotechnology-based methods in oral cancer detection and diagnosis.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kirtley, John R., E-mail: jkirtley@stanford.edu; Rosenberg, Aaron J.; Palmstrom, Johanna C.

Superconducting QUantum Interference Device (SQUID) microscopy has excellent magnetic field sensitivity, but suffers from modest spatial resolution when compared with other scanning probes. This spatial resolution is determined by both the size of the field sensitive area and the spacing between this area and the sample surface. In this paper we describe scanning SQUID susceptometers that achieve sub-micron spatial resolution while retaining a white noise floor flux sensitivity of ≈2μΦ{sub 0}/Hz{sup 1/2}. This high spatial resolution is accomplished by deep sub-micron feature sizes, well shielded pickup loops fabricated using a planarized process, and a deep etch step that minimizes themore » spacing between the sample surface and the SQUID pickup loop. We describe the design, modeling, fabrication, and testing of these sensors. Although sub-micron spatial resolution has been achieved previously in scanning SQUID sensors, our sensors not only achieve high spatial resolution but also have integrated modulation coils for flux feedback, integrated field coils for susceptibility measurements, and batch processing. They are therefore a generally applicable tool for imaging sample magnetization, currents, and susceptibilities with higher spatial resolution than previous susceptometers.« less

Measurement of tissue-radiation dosage using a thermal steady-state elastic shear wave

NASA Astrophysics Data System (ADS)

Chang, Sheng-Yi; Hsieh, Tung-Sheng; Chen, Wei-Ru; Chen, Jin-Chung; Chou, Chien

2017-08-01

A biodosimeter based on thermal-induced elastic shear wave (TIESW) in silicone acellular porcine dermis (SAPD) at thermal steady state has been proposed and demonstrated. A square slab SAPD treated with ionizing radiation was tested. The SAPD becomes a continuous homogeneous and isotropic viscoelastic medium due to the generation of randomly coiled collagen fibers formed from their bundle-like structure in the dermis. A harmonic TIESW then propagates on the surface of the SAPD as measured by a nanometer-scaled strain-stress response under thermal equilibrium conditions at room temperature. TIESW oscillation frequency was noninvasively measured in real time by monitoring the transverse displacement of the TIESW on the SAPD surface. Because the elastic shear modulus is highly sensitive to absorbed doses of ionizing radiation, this proposed biodosimeter can become a highly sensitive and noninvasive method for quantitatively determining tissue-absorbed dosage in terms of TIESW's oscillation frequency. Detection sensitivity at 1 cGy and dynamic ranges covering 1 to 40 cGy and 80 to 500 cGy were demonstrated.

The detection of formaldehyde using microelectromechanical acoustic resonator with multiwalled carbon nanotubes-polyethyleneimine composite coating

NASA Astrophysics Data System (ADS)

Wang, Jingjing; Zhan, Da; Wang, Ke; Hang, Weiwei

2018-01-01

A micro-scale gas sensor based on mass-sensitive film bulk acoustic resonator is demonstrated for the detection of trace formaldehyde at room temperature. The composites mixed with multiwalled carbon nanotubes and polyethyleneimine (MWNTs-PEI) were coated on the resonator surface as the sensitive layer to specifically absorb formaldehyde molecules using a facile spray process. The influence of spraying processes on the formaldehyde sensing properties were investigated. Different response behaviors were determined by both the chemical absorption between formaldehyde molecules and the amine functional groups on PEI and the increase of absorption surface came from the nanostructure. The combination of high frequency of the film bulk acoustic resonator (~4.3 GHz) and the specific absorbability of MWNTs-PEI composites provided a high sensitivity in the detections of trace formaldehyde. The obtained ultra-low limit of detection was as low as 60 ppb with linear response, quick response/recovery time, good reproducibility and selectivity. The proposed sensor shows potential as a portable and convenient gas-sensing system for monitoring the low-level concentration of indoor air pollution.

Measurement of tissue-radiation dosage using a thermal steady-state elastic shear wave.

PubMed

Chang, Sheng-Yi; Hsieh, Tung-Sheng; Chen, Wei-Ru; Chen, Jin-Chung; Chou, Chien

2017-08-01

A biodosimeter based on thermal-induced elastic shear wave (TIESW) in silicone acellular porcine dermis (SAPD) at thermal steady state has been proposed and demonstrated. A square slab SAPD treated with ionizing radiation was tested. The SAPD becomes a continuous homogeneous and isotropic viscoelastic medium due to the generation of randomly coiled collagen fibers formed from their bundle-like structure in the dermis. A harmonic TIESW then propagates on the surface of the SAPD as measured by a nanometer-scaled strain-stress response under thermal equilibrium conditions at room temperature. TIESW oscillation frequency was noninvasively measured in real time by monitoring the transverse displacement of the TIESW on the SAPD surface. Because the elastic shear modulus is highly sensitive to absorbed doses of ionizing radiation, this proposed biodosimeter can become a highly sensitive and noninvasive method for quantitatively determining tissue-absorbed dosage in terms of TIESW’s oscillation frequency. Detection sensitivity at 1 cGy and dynamic ranges covering 1 to 40 cGy and 80 to 500 cGy were demonstrated.

A Potentiometric Indirect Uric Acid Sensor Based on ZnO Nanoflakes and Immobilized Uricase

PubMed Central

Usman Ali, Syed M.; Ibupoto, Zafar Hussain; Kashif, Muhammad; Hashim, Uda; Willander, Magnus

2012-01-01

In the present work zinc oxide nanoflakes (ZnO-NF) structures with a wall thickness around 50 to 100 nm were synthesized on a gold coated glass substrate using a low temperature hydrothermal method. The enzyme uricase was electrostatically immobilized in conjunction with Nafion membrane on the surface of well oriented ZnO-NFs, resulting in a sensitive, selective, stable and reproducible uric acid sensor. The electrochemical response of the ZnO-NF-based sensor vs. a Ag/AgCl reference electrode was found to be linear over a relatively wide logarithmic concentration range (500 nM to 1.5 mM). In addition, the ZnO-NF structures demonstrate vast surface area that allow high enzyme loading which results provided a higher sensitivity. The proposed ZnO-NF array-based sensor exhibited a high sensitivity of ∼66 mV/ decade in test electrolyte solutions of uric acid, with fast response time. The sensor response was unaffected by normal concentrations of common interferents such as ascorbic acid, glucose, and urea. PMID:22736977

High performance NO2 sensor using MoS2 nanowires network

NASA Astrophysics Data System (ADS)

Kumar, Rahul; Goel, Neeraj; Kumar, Mahesh

2018-01-01

We report on a high-performance NO2 sensor based on a one dimensional MoS2 nanowire (NW) network. The MoS2 NW network was synthesized using chemical transport reaction through controlled turbulent vapor flow. The crystal structure and surface morphology of MoS2 NWs were confirmed by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy. Further, the sensing behavior of the nanowires was investigated at different temperatures for various concentrations of NO2 and the sensor exhibited about 2-fold enhanced sensitivity with a low detection limit of 4.6 ppb for NO2 at 60 °C compared to sensitivity at room temperature. Moreover, it showed a fast response (16 s) with complete recovery (172 s) at 60 °C, while sensitivity of the device was decreased at 120 °C. The efficient sensing with reliable selectivity toward NO2 of the nanowires is attributed to a combination of abundant active edge sites along with a large surface area and tuning of the potential barrier at the intersections of nanowires during adsorption/desorption of gas molecules.

Highly sensitive determination of iron (III) ion based on phenanthroline probe: Surface-enhanced Raman spectroscopy methods

NASA Astrophysics Data System (ADS)

Chen, Lei; Ma, Ning; Park, Yeonju; Jin, Sila; Hwang, Hoon; Jiang, Dayu; Jung, Young Mee

2018-05-01

In this paper, we introduced Raman spectroscopy techniques that were based on the traditional Fe3 + determination method with phenanthroline as a probe. Interestingly, surface-enhanced Raman spectroscopy (SERS)-based approach exhibited excellent sensitivities to phenanthroline. Different detection mechanisms were observed for the RR and SERS techniques, in which the RR intensity increased with increasing Fe3 + concentration due to the observation of the RR effect of the phenanthroline-Fe2 + complex, whereas the SERS intensity increased with decreasing Fe3 + concentration due to the observation of the SERS effect of the uncomplexed phenanthroline. More importantly, the determination sensitivity was substantially improved in the presence of a SERS-active substrate, giving a detection limit as low as 0.001 μg/mL, which is 20 times lower than the limit of the UV-vis and RR methods. Furthermore, the proposed SERS method was free from other ions interference and can be used quality and sensitivity for the determination of the city tap water.

Autonomous Aerobraking: Thermal Analysis and Response Surface Development

NASA Technical Reports Server (NTRS)

Dec, John A.; Thornblom, Mark N.

2011-01-01

A high-fidelity thermal model of the Mars Reconnaissance Orbiter was developed for use in an autonomous aerobraking simulation study. Response surface equations were derived from the high-fidelity thermal model and integrated into the autonomous aerobraking simulation software. The high-fidelity thermal model was developed using the Thermal Desktop software and used in all phases of the analysis. The use of Thermal Desktop exclusively, represented a change from previously developed aerobraking thermal analysis methodologies. Comparisons were made between the Thermal Desktop solutions and those developed for the previous aerobraking thermal analyses performed on the Mars Reconnaissance Orbiter during aerobraking operations. A variable sensitivity screening study was performed to reduce the number of variables carried in the response surface equations. Thermal analysis and response surface equation development were performed for autonomous aerobraking missions at Mars and Venus.

Growth Twinning and Generation of High-Frequency Surface Nanostructures in Ultrafast Laser-Induced Transient Melting and Resolidification.

PubMed

Sedao, Xxx; Shugaev, Maxim V; Wu, Chengping; Douillard, Thierry; Esnouf, Claude; Maurice, Claire; Reynaud, Stéphanie; Pigeon, Florent; Garrelie, Florence; Zhigilei, Leonid V; Colombier, Jean-Philippe

2016-07-26

The structural changes generated in surface regions of single crystal Ni targets by femtosecond laser irradiation are investigated experimentally and computationally for laser fluences that, in the multipulse irradiation regime, produce sub-100 nm high spatial frequency surface structures. Detailed experimental characterization of the irradiated targets combining electron back scattered diffraction analysis with high-resolution transmission electron microscopy reveals the presence of multiple nanoscale twinned domains in the irradiated surface regions of single crystal targets with (111) surface orientation. Atomistic- and continuum-level simulations performed for experimental irradiation conditions reproduce the generation of twinned domains and establish the conditions leading to the formation of growth twin boundaries in the course of the fast transient melting and epitaxial regrowth of the surface regions of the irradiated targets. The observation of growth twins in the irradiated Ni(111) targets provides strong evidence of the role of surface melting and resolidification in the formation of high spatial frequency surface structures. This also suggests that the formation of twinned domains can be used as a sensitive measure of the levels of liquid undercooling achieved in short pulse laser processing of metals.

Detection of compression vessels in trigeminal neuralgia by surface-rendering three-dimensional reconstruction of 1.5- and 3.0-T magnetic resonance imaging.

PubMed

Shimizu, Masahiro; Imai, Hideaki; Kagoshima, Kaiei; Umezawa, Eriko; Shimizu, Tsuneo; Yoshimoto, Yuhei

2013-01-01

Surface-rendered three-dimensional (3D) 1.5-T magnetic resonance (MR) imaging is useful for presurgical simulation of microvascular decompression. This study compared the sensitivity and specificity of 1.5- and 3.0-T surface-rendered 3D MR imaging for preoperative identification of the compression vessels of trigeminal neuralgia. One hundred consecutive patients underwent microvascular decompression for trigeminal neuralgia. Forty and 60 patients were evaluated by 1.5- and 3.0-T MR imaging, respectively. Three-dimensional MR images were constructed on the basis of MR imaging, angiography, and venography data and evaluated to determine the compression vessel before surgery. MR imaging findings were compared with the microsurgical findings to compare the sensitivity and specificity of 1.5- and 3.0-T MR imaging. The agreement between MR imaging and surgical findings depended on the compression vessels. For superior cerebellar artery, 1.5- and 3.0-T MR imaging had 84.4% and 82.7% sensitivity and 100% and 100% specificity, respectively. For anterior inferior cerebellar artery, 1.5- and 3.0-T MR imaging had 33.3% and 50% sensitivity and 92.9% and 95% specificity, respectively. For the petrosal vein, 1.5- and 3.0-T MR imaging had 75% and 64.3% sensitivity and 79.2% and 78.1% specificity, respectively. Complete pain relief was obtained in 36 of 40 and 55 of 60 patients undergoing 1.5- and 3.0-T MR imaging, respectively. The present study showed that both 1.5- and 3.0-T MR imaging provided high sensitivity and specificity for preoperative assessment of the compression vessels of trigeminal neuralgia. Preoperative 3D imaging provided very high quality presurgical simulation, resulting in excellent clinical outcomes. Copyright © 2013 Elsevier Inc. All rights reserved.

SU-F-T-474: Evaluation of Dose Perturbation, Temperature and Sensitivity Variation With Accumulated Dose of MOSFET Detector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ganesan, B; Prakasarao, A; Singaravelu, G

Purpose: The use of mega voltage gamma and x-ray sources with their skin sparring qualities in radiation therapy has been a boon in relieving patient discomfort and allowing high tumor doses to be given with fewer restrictions due to radiation effects in the skin. However, high doses given to deep tumors may require careful consideration of dose distribution in the buildup region in order to avoid irreparable damage to the skin. Methods: To measure the perturbation of MOSFET detector in Co60,6MV and 15MV the detector was placed on the surface of the phantom covered with the brass build up cap.more » To measure the effect of temperature the MOSFET detector was kept on the surface of hot water polythene container and the radiation was delivere. In order to measure the sensitivity variation with accumulated dose Measurements were taken by delivering the dose of 200 cGy to MOSFET until the MOSFET absorbed dose comes to 20,000 cGy Results: the Measurement was performed by positioning the bare MOSFET and MOSFET with brass build up cap on the top surface of the solid water phantom for various field sizes in order to find whether there is any attenuation caused in the dose distribution. The response of MOSFET was monitored for temperature ranging from 42 degree C to 22 degree C. The integrated dose dependence of MOSFET dosimeter sensitivity over different energy is not well characterized. This work investigates the dual-bias MOSFET dosimeter sensitivity response to 6 MV and 15 MV beams. Conclusion: From this study it is observed that unlike diode, bare MOSFET does not perturb the radiation field.. It is observed that the build-up influences the temperature dependency of MOSFET and causes some uncertainty in the readings. In the case of sensitivity variation with accumulated dose MOSFET showed higher sensitivity with dose accumulation for both the energies.« less

MARINE GREEN CLEAN PLUS™

EPA Pesticide Factsheets

Technical product bulletin: this surface washing agent is for oil spill cleanups in fresh or salt water, sand beaches, gravel, cobble, coarse/rocky shores, public beaches, other sensitive or high impact sites. Foaming is best in direct applications.

Evaluation of an affinity-amplified immunoassay of graphene oxide using surface plasmon resonance biosensors

NASA Astrophysics Data System (ADS)

Chiu, Nan-Fu; Huang, Teng-Yi; Kuo, Chun-Chuan

2015-05-01

We describe a fundamental study on the plasmonic properties and advanced biosensing mechanisms of functionalized graphene. We discuss a specific design using modified carboxyl groups, which can modulate surface plasmon (SP) coupling and provide an advantage for their binding to the sensing layer with high-performance affinity in an immunological reaction. The functionalized graphene-based surface plasmon resonance (SPR) biosensors have three advantages: high performance, high sensitivity, and excellent molecular kinetic response. In the future, functionalized graphene sheets will make a unique contribution to photonic and SPR diagnosis devices. We wish to highlight the essential characteristics of functionalized graphene-based SPR biosensors to assist researchers in developing and advancing suitable biosensors for unique applications.

Exploring the Surface Sensitivity of ToF-SIMS by Measuring the Implantation and Sampling Depths of Bin and C60 Ions in Organic Films

PubMed Central

Muramoto, Shin; Brison, Jeremy; Castner, David G.

2011-01-01

The surface sensitivity of Binq+ (n = 1, 3, 5, q = 1, 2) and C60q+ (q = 1, 2) primary ions in static time-of-flight secondary ion mass spectrometry (ToF-SIMS) experiments were investigated for molecular trehalose and polymeric tetraglyme organic films. Parameters related to surface sensitivity (impact crater depth, implantation depth, and molecular escape depths) were measured. Under static ToF-SIMS conditions (primary ion doses of 1 × 1012 ions/cm2), the 25 keV Bi1+ primary ions were the most surface sensitive with a molecular escape depth of 1.8 nm for protein films with tetraglyme overlayers, but they had the deepest implantation depth (~18 and 26 nm in trehalose and tetraglyme films, respectively). The 20 keV C60++ primary ions were the second most surface sensitive with a slightly larger molecular escape depth of 2.3 nm. The most important factor that determined the surface sensitivity of the primary ion was its impact crater depth, or the amount of surface erosion. The most surface sensitive primary ions, Bi1+ and C60++, created impact craters with depths of 0.3 and 1.0 nm, respectively, in tetraglyme films. In contrast, Bi5++ primary ions created impact craters with a depth of 1.8 nm in tetraglyme films and were the least surface sensitive with a molecular escape depth of 4.7 nm. PMID:22084828

A Closer Look at Solar Wind Sputtering of Lunar Surface Materials

NASA Technical Reports Server (NTRS)

Barghouty, A. F.; Adams, J. H., Jr.; Meyer, F.; Mansur, L.; Reinhold, C.

2008-01-01

Solar-wind induced potential sputtering of the lunar surface may be a more efficient erosive mechanism than the "standard" kinetic (or physical) sputtering. This is partly based on new but limited laboratory measurements which show marked enhancements in the sputter yields of slow-moving, highly-charged ions impacting oxides. The enhancements seen in the laboratory can be orders of magnitude for some surfaces and highly charged incident ions, but seem to depend very sensitively on the properties of the impacted surface in addition to the fluence, energy and charge of the impacting ion. For oxides, potential sputtering yields are markedly enhanced and sputtered species, especially hydrogen and light ions, show marked dependence on both charge and dose.

Effect of Surface Coverage of Gold Nanoparticles on the Refractive Index Sensitivity in Fiber-Optic Nanoplasmonic Sensing.

PubMed

Wu, Wei-Te; Chen, Chien-Hsing; Chiang, Chang-Yue; Chau, Lai-Kwan

2018-05-31

A simple theoretical model was developed to analyze the extinction spectrum of gold nanoparticles (AuNPs) on the fiber core and glass surfaces in order to aid the determination of the surface coverage and surface distribution of the AuNPs on the fiber core surface for sensitivity optimization of the fiber optic particle plasmon resonance (FOPPR) sensor. The extinction spectrum of AuNPs comprises of the interband absorption of AuNPs, non-interacting plasmon resonance (PR) band due to isolated AuNPs, and coupled PR band of interacting AuNPs. When the surface coverage is smaller than 12.2%, the plasmon coupling effect can almost be ignored. This method is also applied to understand the refractive index sensitivity of the FOPPR sensor with respect to the non-interacting PR band and the coupled PR band. In terms of wavelength sensitivity at a surface coverage of 18.6%, the refractive index sensitivity of the coupled PR band (205.5 nm/RIU) is greater than that of the non-interacting PR band (349.1 nm/RIU). In terms of extinction sensitivity, refractive index sensitivity of the coupled PR band (-3.86/RIU) is similar to that of the non-interacting PR band (-3.93/RIU). Both maximum wavelength and extinction sensitivities were found at a surface coverage of 15.2%.

Highly Sensitive and Selective Gas Sensor Using Hydrophilic and Hydrophobic Graphenes

PubMed Central

Some, Surajit; Xu, Yang; Kim, Youngmin; Yoon, Yeoheung; Qin, Hongyi; Kulkarni, Atul; Kim, Taesung; Lee, Hyoyoung

2013-01-01

New hydrophilic 2D graphene oxide (GO) nanosheets with various oxygen functional groups were employed to maintain high sensitivity in highly unfavorable environments (extremely high humidity, strong acidic or basic). Novel one-headed polymer optical fiber sensor arrays using hydrophilic GO and hydrophobic reduced graphene oxide (rGO) were carefully designed, leading to the selective sensing of volatile organic gases for the first time. The two physically different surfaces of GO and rGO could provide the sensing ability to distinguish between tetrahydrofuran (THF) and dichloromethane (MC), respectively, which is the most challenging issue in the area of gas sensors. The eco-friendly physical properties of GO allowed for faster sensing and higher sensitivity when compared to previous results for rGO even under extreme environments of over 90% humidity, making it the best choice for an environmentally friendly gas sensor. PMID:23736838

Skin inspired fractal strain sensors using a copper nanowire and graphite microflake hybrid conductive network.

PubMed

Jason, Naveen N; Wang, Stephen J; Bhanushali, Sushrut; Cheng, Wenlong

2016-09-22

This work demonstrates a facile "paint-on" approach to fabricate highly stretchable and highly sensitive strain sensors by combining one-dimensional copper nanowire networks with two-dimensional graphite microflakes. This paint-on approach allows for the fabrication of electronic skin (e-skin) patches which can directly replicate with high fidelity the human skin surface they are on, regardless of the topological complexity. This leads to high accuracy for detecting biometric signals for applications in personalised wearable sensors. The copper nanowires contribute to high stretchability and the graphite flakes offer high sensitivity, and their hybrid coating offers the advantages of both. To understand the topological effects on the sensing performance, we utilized fractal shaped elastomeric substrates and systematically compared their stretchability and sensitivity. We could achieve a high stretchability of up to 600% and a maximum gauge factor of 3000. Our simple yet efficient paint-on approach enabled facile fine-tuning of sensitivity/stretchability simply by adjusting ratios of 1D vs. 2D materials in the hybrid coating, and the topological structural designs. This capability leads to a wide range of biomedical sensors demonstrated here, including pulse sensors, prosthetic hands, and a wireless ankle motion sensor.

Sensitive detection of capsaicinoids using a surface plasmon resonance sensor with anti-homovanillic Acid polyclonal antibodies.

PubMed

Nakamura, Shingo; Yatabe, Rui; Onodera, Takeshi; Toko, Kiyoshi

2013-11-13

Recently, highly functional biosensors have been developed in preparation for possible large-scale terrorist attacks using chemical warfare agents. Practically applicable sensors are required to have various abilities, such as high portability and operability, the capability of performing rapid and continuous measurement, as well as high sensitivity and selectivity. We developed the detection method of capsaicinoids, the main component of some lachrymators, using a surface plasmon resonance (SPR) immunosensor as an on-site detection sensor. Homovanillic acid, which has a vanillyl group similar to capsaicinoids such as capsaicin and dihydrocapsaicin, was bound to Concholepas concholepas hemocyanin (CCH) for use as an immunogen to generate polyclonal antibodies. An indirect competitive assay was carried out to detect capsaicinoids using SPR sensor chips on which different capsaicin analogues were immobilized. For the sensor chip on which 4-hydroxy-3-methoxybenzylamine hydrochloride was immobilized, a detection limit of 150 ppb was achieved. We found that the incubation time was not required and the detection can be completed in five minutes.

X-ray lithography using holographic images

DOEpatents

Howells, M.S.; Jacobsen, C.

1997-03-18

Methods for forming X-ray images having 0.25 {micro}m minimum line widths on X-ray sensitive material are presented. A holographic image of a desired circuit pattern is projected onto a wafer or other image-receiving substrate to allow recording of the desired image in photoresist material. In one embodiment, the method uses on-axis transmission and provides a high flux X-ray source having modest monochromaticity and coherence requirements. A layer of light-sensitive photoresist material on a wafer with a selected surface is provided to receive the image(s). The hologram has variable optical thickness and variable associated optical phase angle and amplitude attenuation for transmission of the X-rays. A second embodiment uses off-axis holography. The wafer receives the holographic image by grazing incidence reflection from a hologram printed on a flat metal or other highly reflecting surface or substrate. In this second embodiment, an X-ray beam with a high degree of monochromaticity and spatial coherence is required. 15 figs.

X-ray lithography using holographic images

DOEpatents

Howells, Malcolm S.; Jacobsen, Chris

1997-01-01

Methods for forming X-ray images having 0.25 .mu.m minimum line widths on X-ray sensitive material are presented. A holgraphic image of a desired circuit pattern is projected onto a wafer or other image-receiving substrate to allow recording of the desired image in photoresist material. In one embodiment, the method uses on-axis transmission and provides a high flux X-ray source having modest monochromaticity and coherence requirements. A layer of light-sensitive photoresist material on a wafer with a selected surface is provided to receive the image(s). The hologram has variable optical thickness and variable associated optical phase angle and amplitude attenuation for transmission of the X-rays. A second embodiment uses off-axis holography. The wafer receives the holographic image by grazing incidence reflection from a hologram printed on a flat metal or other highly reflecting surface or substrate. In this second embodiment, an X-ray beam with a high degree of monochromaticity and spatial coherence is required.

Adhesion and friction of iron and gold in contact with elemental semiconductors

NASA Technical Reports Server (NTRS)

Buckley, D. H.; Brainard, W. A.

1977-01-01

Adhesion and friction experiments were conducted with single crystals of iron and gold in contact with single crystals of germanium and silicon. Surfaces were examined in the sputter cleaned state and in the presence of oxygen and a lubricant. All experiments were conducted at room temperature with loads of 1 to 50 grams, and sliding friction was at a sliding velocity of 0.7 mm/min. Results indicate that the friction nature of metals in contact with semiconductors is sensitive to orientation, that strong adhesion of metals to both germanium and silicon occurs, and that friction is lower with silicon than with germanium for the same orientation. Surface effects are highly sensitive to environment. Silicon, for example, behaves in an entirely brittle manner in the clean state, but in the presence of a lubricant the surface deforms plastically.

Detection of Volatile Organic Compounds by Self-assembled Monolayer Coated Sensor Array with Concentration-independent Fingerprints

PubMed Central

Chang, Ye; Tang, Ning; Qu, Hemi; Liu, Jing; Zhang, Daihua; Zhang, Hao; Pang, Wei; Duan, Xuexin

2016-01-01

In this paper, we have modeled and analyzed affinities and kinetics of volatile organic compounds (VOCs) adsorption (and desorption) on various surface chemical groups using multiple self-assembled monolayers (SAMs) functionalized film bulk acoustic resonator (FBAR) array. The high-frequency and micro-scale resonator provides improved sensitivity in the detections of VOCs at trace levels. With the study of affinities and kinetics, three concentration-independent intrinsic parameters (monolayer adsorption capacity, adsorption energy constant and desorption rate) of gas-surface interactions are obtained to contribute to a multi-parameter fingerprint library of VOC analytes. Effects of functional group’s properties on gas-surface interactions are also discussed. The proposed sensor array with concentration-independent fingerprint library shows potential as a portable electronic nose (e-nose) system for VOCs discrimination and gas-sensitive materials selections. PMID:27045012

Charge management for gravitational-wave observatories using UV LEDs

NASA Astrophysics Data System (ADS)

Pollack, S. E.; Turner, M. D.; Schlamminger, S.; Hagedorn, C. A.; Gundlach, J. H.

2010-01-01

Accumulation of electrical charge on the end mirrors of gravitational-wave observatories can become a source of noise limiting the sensitivity of such detectors through electronic couplings to nearby surfaces. Torsion balances provide an ideal means for testing gravitational-wave technologies due to their high sensitivity to small forces. Our torsion pendulum apparatus consists of a movable plate brought near a plate pendulum suspended from a nonconducting quartz fiber. A UV LED located near the pendulum photoejects electrons from the surface, and a UV LED driven electron gun directs photoelectrons towards the pendulum surface. We have demonstrated both charging and discharging of the pendulum with equivalent charging rates of ˜105e/s, as well as spectral measurements of the pendulum charge resulting in a white noise level equivalent to 3×105e/Hz.

Gravimetric chemical sensors based on silica-based mesoporous organic-inorganic hybrids.

PubMed

Xu, Jiaqiang; Zheng, Qi; Zhu, Yongheng; Lou, Huihui; Xiang, Qun; Cheng, Zhixuan

2014-09-01

Silica-based mesoporous organic-inorganic hybrid material modified quartz crystal microbalance (QCM) sensors have been examined for their ability to achieve highly sensitive and selective detection. Mesoporous silica SBA-15 serves as an inorganic host with large specific surface area, facilitating gas adsorption, and thus leads to highly sensitive response; while the presence of organic functional groups contributes to the greatly improved specific sensing property. In this work, we summarize our efforts in the rational design and synthesis of novel sensing materials for the detection of hazardous substances, including simulant nerve agent, organic vapor, and heavy metal ion, and develop high-performance QCM-based chemical sensors.

Solid surface vs. liquid surface: nanoarchitectonics, molecular machines, and DNA origami.

PubMed

Ariga, Katsuhiko; Mori, Taizo; Nakanishi, Waka; Hill, Jonathan P

2017-09-13

The investigation of molecules and materials at interfaces is critical for the accumulation of new scientific insights and technological advances in the chemical and physical sciences. Immobilization on solid surfaces permits the investigation of different properties of functional molecules or materials with high sensitivity and high spatial resolution. Liquid surfaces also present important media for physicochemical innovation and insight based on their great flexibility and dynamicity, rapid diffusion of molecular components for mixing and rearrangements, as well as drastic spatial variation in the prevailing dielectric environment. Therefore, a comparative discussion of the relative merits of the properties of materials when positioned at solid or liquid surfaces would be informative regarding present-to-future developments of surface-based technologies. In this perspective article, recent research examples of nanoarchitectonics, molecular machines, DNA nanotechnology, and DNA origami are compared with respect to the type of surface used, i.e. solid surfaces vs. liquid surfaces, for future perspectives of interfacial physics and chemistry.

Sensitive and rapid immunoassay for parathyroid hormone using magnetic particle labels and magnetic actuation.

PubMed

Dittmer, W U; de Kievit, P; Prins, M W J; Vissers, J L M; Mersch, M E C; Martens, M F W C

2008-09-30

A rapid method for the sensitive detection of proteins using actuated magnetic particle labels, which are measured with a giant magneto-resistive (GMR) biosensor, is described. The technique involves a 1-step sandwich immunoassay with no fluid replacement steps. The various assay binding reactions as well as the bound/free separation are entirely controlled by magnetic forces induced by electromagnets above and below the sensor chip. During the assay, particles conjugated with tracer antibodies are actuated through the sample for target capture, and rapidly brought to the sensor surface where they bind to immobilized capture antibodies. Weakly or unbound labels are removed with a magnetic force oriented away from the GMR sensor surface. For the measurement of parathyroid hormone (PTH), a detection limit in the 10 pM range is obtained with a total assay time of 15 min when 300 nm particles are used. The same sensitivity can be achieved in 5 min when 500 nm particles are used. If 500 nm particles are employed in a 15-minute assay, then 0.8 pM of PTH is detectable. The low sample volume, high analytical performance and high speed of the test coupled with the compact GMR biosensor make the system especially suitable for sensitive testing outside of laboratory environments.

Laser Ablation Surface-Enhanced Raman Spectroscopy (LA-SERS) for the Characterization of Organic Colorants in Cultural Heritage

NASA Astrophysics Data System (ADS)

Londero, Pablo

The characterization of artistic practice throughout history often requires measurements of material composition with microscopic resolution, either due to the fine detail of the material composition or to the amount of sample available. This problem is exacerbated for the detection of organic colorants, which are often embedded in a complex matrix (e.g. oil, natural fibers) and in low concentration due to their high tinting strength. Surface-Enhanced Raman Spectroscopy (SERS) is increasingly used in detection of organic colorants in cultural heritage due to its high sensitivity and inherent preferential sensitivity to small organic molecules. This talk will discuss recent results from a new SERS measurement technique, in which laser ablation is used as a micro-sampling method onto a SERS-active film to characterize art samples with microscopic precision and sensitivity comparable to many mass spectrometry measurements. Furthermore, the nature of the sampling method provides built-in benefits to other SERS-based techniques, such as more quantitative characterization of mixtures, improved sensitivity to some analytes, and reduced background interference. Examples will be shown for measurements of reference materials and art objects, including a restored 16th-century dish and a Renaissance fresco, The Incredulity of San Thomas, by Luca Signorelli. Supported by the National Science Foundation (NSF-CHE-1402750).

Plasma etched surface scanning inspection recipe creation based on bidirectional reflectance distribution function and polystyrene latex spheres

NASA Astrophysics Data System (ADS)

Saldana, Tiffany; McGarvey, Steve; Ayres, Steve

2014-04-01

The continual increasing demands upon Plasma Etching systems to self-clean and continue Plasma Etching with minimal downtime allows for the examination of SiCN, SiO2 and SiN defectivity based upon Surface Scanning Inspection Systems (SSIS) wafer scan results. Historically all Surface Scanning Inspection System wafer scanning recipes have been based upon Polystyrene Spheres wafer deposition for each film stack and the subsequent creation of light scattering sizing response curves. This paper explores the feasibility of the elimination of Polystyrene Latex Sphere (PSL) and/or process particle deposition on both filmed and bare Silicon wafers prior to Surface Scanning Inspection System recipe creation. The study will explore the theoretical maximal Surface Scanning Inspection System sensitivity based on PSL recipe creation in conjunction with the maximal sensitivity derived from Bidirectional Reflectance Distribution Function (BRDF) maximal sensitivity modeling recipe creation. The surface roughness (Root Mean Square) of plasma etched wafers varies dependent upon the process film stack. Decrease of the root mean square value of the wafer sample surface equates to higher surface scanning inspection system sensitivity. Maximal sensitivity SSIS scan results from bare and filmed wafers inspected with recipes created based upon Polystyrene/Particle Deposition and recipes created based upon BRDF modeling will be overlaid against each other to determine maximal sensitivity and capture rate for each type of recipe that was created with differing recipe creation modes. A statistically valid sample of defects from each Surface Scanning Inspection system recipe creation mode and each bare wafer/filmed substrate will be reviewed post SSIS System processing on a Defect Review Scanning Electron Microscope (DRSEM). Native defects, Polystyrene Latex Spheres will be collected from each statistically valid defect bin category/size. The data collected from the DRSEM will be utilized to determine the maximum sensitivity capture rate for each recipe creation mode. Emphasis will be placed upon the sizing accuracy of PSL versus BRDF modeling results based upon automated DRSEM defect sizing. An examination the scattering response for both Mie and Rayleigh will be explored in relationship to the reported sizing variance of the SSIS to make a determination of the absolute sizing accuracy of the recipes there were generated based upon BRDF modeling. This paper explores both the commercial and technical considerations of the elimination of PSL deposition as a precursor to SSIS recipe creation. Successful integration of BRDF modeling into the technical aspect of SSIS recipe creation process has the potential to dramatically reduce the recipe creation timeline and vetting period. Integration of BRDF modeling has the potential to greatly reduce the overhead operation costs for High Volume Manufacturing sites by eliminating the associated costs of third party PSL deposition.

Laser Scanning System for Pressure and Temperature Paints

NASA Technical Reports Server (NTRS)

Sullivan, John

1997-01-01

Acquiring pressure maps of aerodynamic surfaces is very important for improving and validating the performance of aerospace vehicles. Traditional pressure measurements are taken with pressure taps embedded in the model surface that are connected to transducers. While pressure taps allow highly accurate measurements to be acquired, they do have several drawbacks. Pressure taps do not give good spatial resolution due to the need for individual pressure tubes, compounded by limited space available inside models. Also, building a model proves very costly if taps are needed because of the large amount of labor necessary to drill, connect and test each one. The typical cost to install one tap is about $200. Recently, a new method for measuring pressure on aerodynamic surfaces has been developed utilizing a technology known as pressure sensitive paints (PSP). Using PSP, pressure distributions can be acquired optically with high spatial resolution and simple model preparation. Flow structures can be easily visualized using PSP, but are missed using low spatial resolution arrays of pressure taps. PSP even allows pressure distributions to be found on rotating machinery where previously this has been extremely difficult or even impossible. The goal of this research is to develop a laser scanning system for use with pressure sensitive paints that allows accurate pressure measurements to be obtained on various aerodynamic surfaces ranging from wind tunnel models to high speed jet engine compressor blades.

Mapping Critical Loads of Atmospheric Nitrogen Deposition in the Rocky Mountains, USA

NASA Astrophysics Data System (ADS)

Nanus, L.; Clow, D. W.; Stephens, V. C.; Saros, J. E.

2010-12-01

Atmospheric nitrogen (N) deposition can adversely affect sensitive aquatic ecosystems at high-elevations in the western United States. Critical loads are the amount of deposition of a given pollutant that an ecosystem can receive below which ecological effects are thought not to occur. GIS-based landscape models were used to create maps for high-elevation areas across the Rocky Mountain region showing current atmospheric deposition rates of nitrogen (N), critical loads of N, and exceedances of critical loads of N. Atmospheric N deposition maps for the region were developed at 400 meter resolution using gridded precipitation data and spatially interpolated chemical concentrations in rain and snow. Critical loads maps were developed based on chemical thresholds corresponding to observed ecological effects, and estimated ecosystem sensitivities calculated from basin characteristics. Diatom species assemblages were used as an indicator of ecosystem health to establish critical loads of N. Chemical thresholds (concentrations) were identified for surface waters by using a combination of in-situ growth experiments and observed spatial patterns in surface-water chemistry and diatom species assemblages across an N deposition gradient. Ecosystem sensitivity was estimated using a multiple-linear regression approach in which observed surface water nitrate concentrations at 530 sites were regressed against estimates of inorganic N deposition and basin characteristics (topography, soil type and amount, bedrock geology, vegetation type) to develop predictive models of surface water chemistry. Modeling results indicated that the significant explanatory variables included percent slope, soil permeability, and vegetation type (including barren land, shrub, and grassland) and were used to predict high-elevation surface water nitrate concentrations across the Rocky Mountains. Chemical threshold concentrations were substituted into an inverted form of the model equations and applied to estimate critical loads for each stream reach within a basin, from which critical loads maps were created. Atmospheric N deposition maps were overlaid on the critical loads maps to identify areas in the Rocky Mountain region where critical loads are being exceeded, or where they may do so in the future. This approach may be transferable to other high-elevation areas of the United States and the world.

GPS-derived estimates of surface mass balance and ocean-induced basal melt for Pine Island Glacier ice shelf, Antarctica

NASA Astrophysics Data System (ADS)

Shean, David E.; Christianson, Knut; Larson, Kristine M.; Ligtenberg, Stefan R. M.; Joughin, Ian R.; Smith, Ben E.; Stevens, C. Max; Bushuk, Mitchell; Holland, David M.

2017-11-01

In the last 2 decades, Pine Island Glacier (PIG) experienced marked speedup, thinning, and grounding-line retreat, likely due to marine ice-sheet instability and ice-shelf basal melt. To better understand these processes, we combined 2008-2010 and 2012-2014 GPS records with dynamic firn model output to constrain local surface and basal mass balance for PIG. We used GPS interferometric reflectometry to precisely measure absolute surface elevation (zsurf) and Lagrangian surface elevation change (Dzsurf/ Dt). Observed surface elevation relative to a firn layer tracer for the initial surface (zsurf - zsurf0') is consistent with model estimates of surface mass balance (SMB, primarily snow accumulation). A relatively abrupt ˜ 0.2-0.3 m surface elevation decrease, likely due to surface melt and increased compaction rates, is observed during a period of warm atmospheric temperatures from December 2012 to January 2013. Observed Dzsurf/ Dt trends (-1 to -4 m yr-1) for the PIG shelf sites are all highly linear. Corresponding basal melt rate estimates range from ˜ 10 to 40 m yr-1, in good agreement with those derived from ice-bottom acoustic ranging, phase-sensitive ice-penetrating radar, and high-resolution stereo digital elevation model (DEM) records. The GPS and DEM records document higher melt rates within and near features associated with longitudinal extension (i.e., transverse surface depressions, rifts). Basal melt rates for the 2012-2014 period show limited temporal variability despite large changes in ocean temperature recorded by moorings in Pine Island Bay. Our results demonstrate the value of long-term GPS records for ice-shelf mass balance studies, with implications for the sensitivity of ice-ocean interaction at PIG.

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

PubMed Central

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

2013-01-01

Multi-walled carbon nanotube (MWCNT) film has been fabricated onto Pt-patterned alumina substrates using the chemical vapor deposition method for NH3 gas sensing applications. The MWCNT-based sensor is sensitive to NH3 gas at room temperature. Nanoclusters of Co catalysts have been sputtered on the surface of the MWCNT film to enhance gas sensitivity with respect to unfunctionalized CNT films. The gas sensitivity of Co-functionalized MWCNT-based gas sensors is thus significantly improved. The sensor exhibits good repeatability and high selectivity towards NH3, compared with alcohol and LPG. PMID:23364198

The dynamic deformation of a layered viscoelastic medium under surface excitation

NASA Astrophysics Data System (ADS)

Aglyamov, Salavat R.; Wang, Shang; Karpiouk, Andrei B.; Li, Jiasong; Twa, Michael; Emelianov, Stanislav Y.; Larin, Kirill V.

2015-06-01

In this study the dynamic behavior of a layered viscoelastic medium in response to the harmonic and impulsive acoustic radiation force applied to its surface was investigated both theoretically and experimentally. An analytical solution for a layered viscoelastic compressible medium in frequency and time domains was obtained using the Hankel transform. A special incompressible case was considered to model soft biological tissues. To verify our theoretical model, experiments were performed using tissue-like gel-based phantoms with varying mechanical properties. A 3.5 MHz single-element focused ultrasound transducer was used to apply the radiation force at the surface of the phantoms. A phase-sensitive optical coherence tomography system was used to track the displacements of the phantom surface. Theoretically predicted displacements were compared with experimental measurements. The role of the depth dependence of the elastic properties of a medium in its response to an acoustic pulse at the surface was studied. It was shown that the low-frequency vibrations at the surface are more sensitive to the deep layers than high-frequency ones. Therefore, the proposed model in combination with spectral analysis can be used to evaluate depth-dependent distribution of the mechanical properties based on the measurements of the surface deformation.

Novel Surface-Enhanced Raman Scattering-based Assays for Ultra-sensitive Detection of Human Pluripotent Stem Cells

PubMed Central

Han, Jingjia; Qian, Ximei; Wu, Qingling; Jha, Rajneesh; Duan, Jinshuai; Yang, Zhou; Maher, Kevin O.; Nie, Shuming; Xu, Chunhui

2017-01-01

Human pluripotent stem cells (hPSCs) are a promising cell source for regenerative medicine, but their derivatives need to be rigorously evaluated for residual stem cells to prevent teratoma formation. Here, we report the development of novel surface-enhanced Raman scattering (SERS)-based assays that can detect trace numbers of undifferentiated hPSCs in mixed cell populations in a highly specific, ultra-sensitive, and time-efficient manner. By targeting stem cell surface markers SSEA-5 and TRA-1-60 individually or simultaneously, these SERS assays were able to identify as few as 1 stem cell in 106 cells, a sensitivity (0.0001%) which was ~2,000 to 15,000-fold higher than that of flow cytometry assays. Using the SERS assay, we demonstrate that the aggregation of hPSC-based cardiomyocyte differentiation cultures into 3D spheres significantly reduced SSEA-5+ and TRA-1-60+ cells compared with parallel 2D cultures. Thus, SERS may provide a powerful new technology for quality control of hPSC-derived products for preclinical and clinical applications. PMID:27509304

Combining Whispering-Gallery Mode Optical Biosensors with Microfluidics for Real-Time Detection of Protein Secretion from Living Cells in Complex Media.

PubMed

Chen, Ying-Jen; Schoeler, Ulrike; Huang, Chung-Hsuan Benjamin; Vollmer, Frank

2018-05-01

The noninvasive monitoring of protein secretion of cells responding to drug treatment is an effective and essential tool in latest drug development and for cytotoxicity assays. In this work, a surface functionalization method is demonstrated for specific detection of protein released from cells and a platform that integrates highly sensitive optical devices, called whispering-gallery mode biosensors, with precise microfluidics control to achieve label-free and real-time detection. Cell biomarker release is measured in real time and with nanomolar sensitivity. The surface functionalization method allows for antibodies to be immobilized on the surface for specific detection, while the microfluidics system enables detection in a continuous flow with a negligible compromise between sensitivity and flow control over stabilization and mixing. Cytochrome c detection is used to illustrate the merits of the system. Jurkat cells are treated with the toxin staurosporine to trigger cell apoptosis and cytochrome c released into the cell culture medium is monitored via the newly invented optical microfluidic platform. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A monolayer of hierarchical silver hemi-mesoparticles with tunable surface topographies for highly sensitive surface-enhanced Raman spectroscopy

NASA Astrophysics Data System (ADS)

Zhu, Shuangmei; Fan, Chunzhen; Mao, Yanchao; Wang, Junqiao; He, Jinna; Liang, Erjun; Chao, Mingju

2016-02-01

We proposed a facile green synthesis system to synthesize large-scale Ag hemi-mesoparticles monolayer on Cu foil. Ag hemi-mesoparticles have different surface morphologies on their surfaces, including ridge-like, meatball-like, and fluffy-like shapes. In the reaction, silver nitrate was reduced by copper at room temperature in dimethyl sulfoxide via the galvanic displacement reaction. The different surface morphologies of the Ag hemi-mesoparticles were adjusted by changing the reaction time, and the hemi-mesoparticle surface formed fluffy-spherical nanoprotrusions at longer reaction time. At the same time, we explored the growth mechanism of silver hemi-mesoparticles with different surface morphologies. With 4-mercaptobenzoic acid as Raman probe molecules, the fluffy-like silver hemi-mesoparticles monolayer with the best activity of surface enhanced Raman scattering (SERS), the enhancement factor is up to 7.33 × 107 and the detection limit can reach 10-10M. SERS measurements demonstrate that these Ag hemi-mesoparticles can serve as sensitive SERS substrates. At the same time, using finite element method, the distribution of the localized electromagnetic field near the particle surface was simulated to verify the enhanced mechanism. This study helps us to understand the relationship between morphology Ag hemi-mesoparicles and the properties of SERS.

A monolayer of hierarchical silver hemi-mesoparticles with tunable surface topographies for highly sensitive surface-enhanced Raman spectroscopy.

PubMed

Zhu, Shuangmei; Fan, Chunzhen; Mao, Yanchao; Wang, Junqiao; He, Jinna; Liang, Erjun; Chao, Mingju

2016-02-21

We proposed a facile green synthesis system to synthesize large-scale Ag hemi-mesoparticles monolayer on Cu foil. Ag hemi-mesoparticles have different surface morphologies on their surfaces, including ridge-like, meatball-like, and fluffy-like shapes. In the reaction, silver nitrate was reduced by copper at room temperature in dimethyl sulfoxide via the galvanic displacement reaction. The different surface morphologies of the Ag hemi-mesoparticles were adjusted by changing the reaction time, and the hemi-mesoparticle surface formed fluffy-spherical nanoprotrusions at longer reaction time. At the same time, we explored the growth mechanism of silver hemi-mesoparticles with different surface morphologies. With 4-mercaptobenzoic acid as Raman probe molecules, the fluffy-like silver hemi-mesoparticles monolayer with the best activity of surface enhanced Raman scattering (SERS), the enhancement factor is up to 7.33 × 10(7) and the detection limit can reach 10(-10)M. SERS measurements demonstrate that these Ag hemi-mesoparticles can serve as sensitive SERS substrates. At the same time, using finite element method, the distribution of the localized electromagnetic field near the particle surface was simulated to verify the enhanced mechanism. This study helps us to understand the relationship between morphology Ag hemi-mesoparicles and the properties of SERS.

High sensitivity of Franz-Keldysh oscillations in photoreflectance spectra for probing morphology in Al{x}Ga{1-{x}}N/GaN heterostructures

NASA Astrophysics Data System (ADS)

Takeuchi, H.; Yamamoto, Y.; Kamo, Y.; Kunii, T.; Oku, T.; Wakaiki, S.; Nakayama, M.

2007-02-01

We demonstrate that Franz-Keldysh oscillations (FKOs) observed by photoreflectance (PR) spectroscopy are highly sensitive to the surface morphology of Al{x}Ga{1-x}N layers in Al{x}Ga{1-x}N heterostructures. Three Al{0.2}Ga{0.8}N/GaN heterostructures with different surface-morphology profiles, which are confirmed with atomic force microscopy, have been investigated. The X-ray-diffraction patterns are hardly affected by the Al{0.2}Ga{0.8}N/GaN-layer morphology. In contrast, it is revealed that cracks and pits dominating the morphology remarkably reduce the amplitude of the FKOs from the Al{0.2}Ga{0.8}N/GaN layer, which is attributed to the following two mechanisms related to the cracks and pits. One is lifetime broadening due to carrier scattering, and the other is the suppression of the modulation magnitude for the built-in electric field, which is caused by the trapping and recombination of photogenerated carriers at the surface.

Age estimation using cortical surface pattern combining thickness with curvatures

PubMed Central

Wang, Jieqiong; Li, Wenjing; Miao, Wen; Dai, Dai; Hua, Jing; He, Huiguang

2014-01-01

Brain development and healthy aging have been proved to follow a specific pattern, which, in turn, can be applied to help doctors diagnose mental diseases. In this paper, we design a cortical surface pattern (CSP) combining the cortical thickness with curvatures, which constructs an accurate human age estimation model with relevance vector regression. We test our model with two public databases. One is the IXI database (360 healthy subjects aging from 20 to 82 years old were selected), and the other is the INDI database (303 subjects aging from 7 to 22 years old were selected). The results show that our model can achieve as small as 4.57 years deviation in the IXI database and 1.38 years deviation in the INDI database. Furthermore, we employ this surface pattern to age groups classification, and get a remarkably high accuracy (97.77%) and a significantly high sensitivity/specificity (97.30%/98.10%). These results suggest that our designed CSP combining thickness with curvatures is stable and sensitive to brain development, and it is much more powerful than voxel-based morphometry used in previous methods for age estimation. PMID:24395657

Probing the interaction between nanoparticles and lipid membranes by quartz crystal microbalance with dissipation monitoring

NASA Astrophysics Data System (ADS)

Yousefi, Nariman; Tufenkji, Nathalie

2016-12-01

There is increasing interest in using quartz crystal microbalance with dissipation monitoring (QCM-D) to investigate the interaction of nanoparticles (NPs) with model surfaces. The high sensitivity, ease of use and the ability to monitor interactions in real-time has made it a popular technique for colloid chemists, biologists, bioengineers and biophysicists. QCM-D has been recently used to probe the interaction of NPs with supported lipid bilayers (SLBs) as model cell membranes. The interaction of NPs with SLBs is highly influenced by the quality of the lipid bilayers. Unlike many surface sensitive techniques, using QCM-D, the quality of SLBs can be assessed in real-time, hence QCM-D studies on SLB-NP interactions are less prone to the artefacts arising from bilayers that are not well formed. The ease of use and commercial availability of a wide range of sensor surfaces also have made QCM-D a versatile tool for studying NP interactions with lipid bilayers. In this review, we summarize the state-of-the-art on QCM-D based techniques for probing the interactions of NPs with lipid bilayers.

Performance and Shock Sensitivity Evaluations of Reduced Sensitivity Explosives

NASA Astrophysics Data System (ADS)

Bowden, Patrick; Tappan, Bryce; Schmitt, Matthew; Lichthardt, Joseph; Hill, Larry

2017-06-01

Making high explosives that possess insensitivity on par with TATB-based plastic bonded explosives (PBXs), while outperforming them, has proven to be a difficult challenge. Many molecules that have challenged TATB have fallen short in either small-scale sensitivity (impact, friction), thermal stability, or possessing a shock sensitivity that is either too high or too low. Recently, an alternative approach to single-molecule-based PBXs has been blending and/or co-crystallizing explosive molecules to address shortcomings of individual components. With this approach in mind, formulations have been prepared containing 1,1-diamino-2,2-dinitroethene (DADNE or FOX-7) or 3,3'-diamino-4,4'-azoxyfurazan (DAAF) with 3-nitro-1,2,4-triazole-5-one (NTO). Detailed characterization of these mixtures has been described in a concurrent study. Here we focus on in depth performance metrics such as cylinder wall expansion and CJ pressure (via free surface velocity) and shock sensitivity, by small-scale gap-testing, were investigated as a function of weight percentages of the components. Results will be contrasted with known insensitive high explosives.

Direct Growth of Graphene Films on 3D Grating Structural Quartz Substrates for High-Performance Pressure-Sensitive Sensors.

PubMed

Song, Xuefen; Sun, Tai; Yang, Jun; Yu, Leyong; Wei, Dacheng; Fang, Liang; Lu, Bin; Du, Chunlei; Wei, Dapeng

2016-07-06

Conformal graphene films have directly been synthesized on the surface of grating microstructured quartz substrates by a simple chemical vapor deposition process. The wonderful conformality and relatively high quality of the as-prepared graphene on the three-dimensional substrate have been verified by scanning electron microscopy and Raman spectra. This conformal graphene film possesses excellent electrical and optical properties with a sheet resistance of <2000 Ω·sq(-1) and a transmittance of >80% (at 550 nm), which can be attached with a flat graphene film on a poly(dimethylsiloxane) substrate, and then could work as a pressure-sensitive sensor. This device possesses a high-pressure sensitivity of -6.524 kPa(-1) in a low-pressure range of 0-200 Pa. Meanwhile, this pressure-sensitive sensor exhibits super-reliability (≥5000 cycles) and an ultrafast response time (≤4 ms). Owing to these features, this pressure-sensitive sensor based on 3D conformal graphene is adequately introduced to test wind pressure, expressing higher accuracy and a lower background noise level than a market anemometer.

Novel multichannel surface plasmon resonance photonic crystal fiber biosensor

NASA Astrophysics Data System (ADS)

Hameed, Mohamed Farhat O.; Alrayk, Yassmin K. A.; Shaalan, A. A.; El Deeb, Walid S.; Obayya, S. S. A.

2016-04-01

In this paper, a novel design of highly sensitive biosensor based on photonic crystal fiber is presented and analyzed using full vectorial finite element method. The suggested design depends on using silver layer as a plasmonic active material coated by a gold layer to protect silver oxidation. The reported sensor is based on the detection using the quasi transverse electric (TE) and quasi transverse magnetic (TM) modes which offers the possibility of multi-channel/multi-analyte sensing. The sensor geometrical parameters are optimized to achieve high sensitivity for the two polarized modes. High refractive index sensitivity of about 4750 nm/RIU (refractive index unit) and 4300 nm/RIU with corresponding resolutions of 2.1×10-5 RIU, and 2.33×10-5 RIU can be obtained for the quasi TM and quasi TE modes, respectively.

Cleanroom Contaminant Monitor

NASA Technical Reports Server (NTRS)

1997-01-01

Under a Small Business Innovation Research (SBIR) contract from Kennedy Space Center (KSC), Femtometrics, Inc. developed the Real-Time Non-Volatile Residue (NVR) monitor. Criteria established by KSC called for a technology that could regulate the accumulation of nonvolatile residues in cleanroom environments. The company accommodated the Center's need with an advanced, highly sensitive surface acoustic wave (SAW) microsensor capable of detecting sub-monolayer deposition in cleanrooms where aerospace systems are assembled. Years earlier, Femtometrics responded to and received SBIR contracts from Langley Research Center for highly sensitive aerosol detectors for environmental researchers. Stimulated by the SBIR wins, the company set about to develop the SAW resonator technology. A new type of sensor has evolved from the research, one that has the ability to measure a range of chemical vapors by applying chemical-specific coating on the sensing surface. Commercial applications of the Real-Time NVR include Class 1 cleanrooms at semiconductor and hard-disk manufacturing plants.

High resolution regional climate simulation of the Hawaiian Islands - Validation of the historical run from 2003 to 2012

NASA Astrophysics Data System (ADS)

Xue, L.; Newman, A. J.; Ikeda, K.; Rasmussen, R.; Clark, M. P.; Monaghan, A. J.

2016-12-01

A high-resolution (a 1.5 km grid spacing domain nested within a 4.5 km grid spacing domain) 10-year regional climate simulation over the entire Hawaiian archipelago is being conducted at the National Center for Atmospheric Research (NCAR) using the Weather Research and Forecasting (WRF) model version 3.7.1. Numerical sensitivity simulations of the Hawaiian Rainband Project (HaRP, a filed experiment from July to August in 1990) showed that the simulated precipitation properties are sensitive to initial and lateral boundary conditions, sea surface temperature (SST), land surface models, vertical resolution and cloud droplet concentration. The validations of model simulated statistics of the trade wind inversion, temperature, wind field, cloud cover, and precipitation over the islands against various observations from soundings, satellites, weather stations and rain gauges during the period from 2003 to 2012 will be presented at the meeting.

Simple and robust resistive dual-axis accelerometer using a liquid metal droplet

NASA Astrophysics Data System (ADS)

Huh, Myoung; Won, Dong-Joon; Kim, Joong Gil; Kim, Joonwon

2017-12-01

This paper presents a novel dual-axis accelerometer that consists of a liquid metal droplet in a cone-shaped channel and an electrode layer with four Nichrome electrodes. The sensor uses the advantages of the liquid metal droplet (i.e., high surface tension, electrical conductivity, high density, and deformability). The cone-shaped channel imposes a restoring force on the liquid metal droplet. We conducted simulation tests to determine the appropriate design specifications of the cone-shaped channel. Surface modifications to the channel enhanced the nonwetting performance of the liquid metal droplet. The performances of the sensor were analyzed by a tilting test. When the acceleration was applied along the axial direction, the device showed 6 kΩ/g of sensitivity and negligible crosstalk between the X- and Y-axes. In a diagonal direction test, the device showed 4 kΩ/g of sensitivity.

Cu2 + modulated nitrogen-doped grapheme quantum dots as a turn-off/on fluorescence sensor for the selective detection of histidine in biological fluid

NASA Astrophysics Data System (ADS)

Wang, Zhiyu; Fan, ZheFeng

2018-01-01

A highly sensitive sensor for detection of histidine (His) based on the nitrogen-doped graphene quantum dots (N-GQDs)-Cu2 + system has been designed. The N-GQDs were synthesized by one-step hydrothermal approach according to previous report. The fluorescence of N-GQDs can be effectively quenched by Cu2 + due to the binding between Cu2 + and functional groups on the surface of N-GQDs. The high affinity of His to Cu2 + enables Cu2 + to be dissociated from the surface of N-GQDs and recovering the fluorescence. The sensor displayed a sensitive response to His in the concentration range of 0-35 μmol L- 1, with a detection limit of 72.2 nmol L- 1. The proposed method is successfully applied to detect His in samples with a recovery range of 96-102%.

Current Progress of Nanomaterials in Molecularly Imprinted Electrochemical Sensing.

PubMed

Zhong, Chunju; Yang, Bin; Jiang, Xinxin; Li, Jianping

2018-01-02

Nanomaterials have received much attention during the past decade because of their excellent optical, electronic, and catalytic properties. Nanomaterials possess high chemical reactivity, also high surface energy. Thus, provide a stable immobilization platform for biomolecules, while preserving their reactivity. Due to the conductive and catalytic properties, nanomaterials can also enhance the sensitivity of molecularly imprinted electrochemical sensors by amplifying the electrode surface, increasing the electron transfer, and catalyzing the electrochemical reactions. Molecularly imprinted polymers that contain specific molecular recognition sites can be designed for a particular target analyte. Incorporating nanomaterials into molecularly imprinted polymers is important because nanomaterials can improve the response signal, increase the sensitivity, and decrease the detection limit of the sensors. This study describes the classification of nanomaterials in molecularly imprinted polymers, their analytical properties, and their applications in the electrochemical sensors. The progress of the research on nanomaterials in molecularly imprinted polymers and the application of nanomaterials in molecularly imprinted polymers is also reviewed.

2D zirconium-based metal-organic framework nanosheets for highly sensitive detection of mucin 1: consistency between electrochemical and surface plasmon resonance methods

NASA Astrophysics Data System (ADS)

He, Linghao; Duan, Fenghe; Song, Yingpan; Guo, Chuanpan; Zhao, Hui; Tian, Jia-Yue; Zhang, Zhihong; Liu, Chun-Sen; Zhang, Xiaojing; Wang, Peiyuan; Du, Miao; Fang, Shao-Ming

2017-06-01

Two-dimensional (2D) zirconium-based metal-organic framework (denoted as 521-MOF) nanosheets with the thickness of 6.0-7.5 nm were prepared with the aid of polyvinyl pyrrolidone (PVP) under the mild conditions and low temperature (50 °C). Since 521-MOF nanosheets displayed good electrochemical activity, high surface area, and strong affinity interaction between the MOF and the oligonucleotides sequences, they can impel the immobilization of large amounts of aptamer strands when applied as a platform of biosensor. As a result, the developed aptasensor exhibited sensitive bio-recognition for the cancer determination marker protein, mucin 1 (MUC1). The combination of electrochemical techniques and surface plasmon resonance spectroscopy (SPR) was performed to probe the kinetic processes of the aptamer immobilization and the MUC1 detection. The consistency between different determination approaches was observed, in which the developed aptasensor based on 521-MOF nanosheets exhibits pretty high sensitivity for detecting MUC1 with a low detect limit of 0.12 and 0.65 pg·ml-1 deduced from electrochemical impedance spectroscopy and SPR, respectively, within the broad concentration range of MUC1 from 0.001 to 0.5 ng·ml-1. Simultaneously, a comparable affinity constant, K a, was derived from EIS and SPR, which also demonstrates that this new biosensing strategy has high selectivity, stability, reproducibility, and good applicability for the MUC1 detection in the human serum. The present finding indicates that the synthesized 521-MOF nanosheets can be employed in the fields of the biosensing or biomedical diagnosis and explored for different kinds of biosensors.

High sensitive and high temporal and spatial resolved image of reactive species in atmospheric pressure surface discharge reactor by laser induced fluorescence

NASA Astrophysics Data System (ADS)

Gao, Liang; Feng, Chun-Lei; Wang, Zhi-Wei; Ding, Hongbin

2017-05-01

The current paucity of spatial and temporal characterization of reactive oxygen and nitrogen species (RONS) concentration has been a major hurdle to the advancement and clinical translation of low temperature atmospheric plasmas. In this study, an advanced laser induced fluorescence (LIF) system has been developed to be an effective antibacterial surface discharge reactor for the diagnosis of RONS, where the highest spatial and temporal resolution of the LIF system has been achieved to ˜100 μm scale and ˜20 ns scale, respectively. Measurements on an oxidative OH radical have been carried out as typical RONS for the benchmark of the whole LIF system, where absolute number density calibration has been performed on the basis of the laser Rayleigh scattering method. Requirements for pixel resolved spatial distribution and outer plasma region detection become challenging tasks due to the low RONS concentration (˜ppb level) and strong interference, especially the discharge induced emission and pulsed laser induced stray light. In order to design the highly sensitive LIF system, a self-developed fluorescence telescope, the optimization of high precision synchronization among a tunable pulsed laser, a surface discharge generator, intensified Charge Coupled Device (iCCD) camera, and an oscilloscope have been performed. Moreover, an image BOXCAR approach has been developed to remarkably improve the sensitivity of the whole LIF system by optimizing spatial and temporal gating functions via both hardware and software, which has been integrated into our automatic control and data acquisition system on the LabVIEW platform. In addition, a reciprocation averaging measurement has been applied to verify the accuracy of the whole LIF detecting system, indicating the relative standard deviation of ˜3%.

Nanorice Particles: Hybrid Plasmonic Nanostructures

NASA Technical Reports Server (NTRS)

Le, Fei (Inventor); Halas, Nancy J. (Inventor); Nordlander, Peter (Inventor); Brandl, Daniel (Inventor); Wang, Hui (Inventor)

2010-01-01

A new hybrid nanoparticle, i.e., a nanorice particle, which combines the intense local fields of nanorods with the highly tunable plasmon resonances of nanoshells, is described herein. This geometry possesses far greater structural tunability than previous nanoparticle geometries, along with much larger local field enhancements and far greater sensitivity as a surface plasmon resonance (SPR) nanosensor than presently known dielectric-conductive material nanostructures. In an embodiment, a nanoparticle comprises a prolate spheroid-shaped core having a first aspect ratio. The nanoparticle also comprises at least one conductive shell surrounding said prolate spheroid-shaped core. The nanoparticle has a surface plasmon resonance sensitivity of at least 600 nm RIU(sup.-1). Methods of making the disclosed nanorice particles are also described herein.

High-sensitivity cooled coil system for nuclear magnetic resonance in kHz range

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Tingting; Zhao, Jing, E-mail: zhaojing-8239@jlu.edu.cn; Peter Grünberg Institute

2014-11-15

In several low-field Nuclear Magnetic Resonance (LF-NMR) and surface nuclear magnetic resonance applications, i.e., in the frequency range of kHz, high sensitivity magnetic field detectors are needed. Usually, low-T{sub c} superconducting quantum interference devices (SQUIDs) with a high field sensitivity of about 1 fT/Hz{sup 1/2} are employed as detectors. Considering the flux trapping and operational difficulties associated with low-T{sub c} SQUIDs, we designed and fabricated liquid-nitrogen-cooled Cu coils for NMR detection in the kHz range. A cooled coil system consisting of a 9-cm diameter Cu coil and a low noise preamplifier was systematically investigated and reached a sensitivity of 2more » fT/Hz{sup 1/2} at 77 K, which is 3 times better compared to the sensitivity at 300 K. A Q-switch circuit as an essential element for damping the ringing effects of the pickup coil was developed to acquire free induction decay signals of a water sample with minimum loss of signal. Our studies demonstrate that cooled Cu coils, if designed properly, can provide a comparable sensitivity to low-T{sub c} SQUIDs.« less

Nanostructured Tungsten Oxide Composite for High-Performance Gas Sensors

PubMed Central

Feng-Chen, Siyuan; Aldalbahi, Ali; Feng, Peter Xianping

2015-01-01

We report the results of composite tungsten oxide nanowires-based gas sensors. The morphologic surface, crystallographic structures, and chemical compositions of the obtained nanowires have been investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman scattering, respectively. The experimental measurements reveal that each wire consists of crystalline nanoparticles with an average diameter of less than 250 nm. By using the synthesized nanowires, highly sensitive prototypic gas sensors have been designed and fabricated. The dependence of the sensitivity of tungsten oxide nanowires to the methane and hydrogen gases as a function of time has been obtained. Various sensing parameters such as sensitivity, response time, stability, and repeatability were investigated in order to reveal the sensing ability. PMID:26512670

Regional Climate Response to Volcanic Radiative Forcing in Middle East and North Africa

NASA Astrophysics Data System (ADS)

Stenchikov, G.; Dogar, M.

2012-04-01

We have tested the regional climate sensitivity in the Middle East and North Africa (MENA) to radiation perturbations caused by the large explosive equatorial volcanic eruptions of the second part of 20th century, El Chichon and Pinatubo occurred, respectively, in 1982 and 1991. The observations and reanalysis data show that the surface volcanic cooling in the MENA region is two-three times larger than the global mean response to volcanic forcing. The Red Sea surface temperature appears to be also very sensitive to the external radiative impact. E.g., the sea surface cooling, associated with the 1991 Pinatubo eruption, caused deep water mixing and coral bleaching for a few years. To better quantify these effects we use the Geophysical Fluid Dynamics Laboratory global High Resolution Atmospheric Model (HIRAM) to conduct simulations of both the El Chichon and Pinatubo impacts with the effectively 25-km grid spacing. We find that the circulation changes associated with the positive phase of the arctic oscillation amplified the winter temperature anomalies in 1982-1984 and 1991-1993. The dynamic response to volcanic cooling also is characterized by the southward shift of the inter-tropical convergence zone in summer and associated impact on the precipitation patterns. Thus, these results suggest that the climate regime in the MENA region is highly sensitive to external forcing. This is important for better understanding of the climate variability and change in this region.

Combined sodium ion sensitivity in agonist binding and internalization of vasopressin V1b receptors.

PubMed

Koshimizu, Taka-Aki; Kashiwazaki, Aki; Taniguchi, Junichi

2016-05-03

Reducing Na(+) in the extracellular environment may lead to two beneficial effects for increasing agonist binding to cell surface G-protein coupled receptors (GPCRs): reduction of Na(+)-mediated binding block and reduce of receptor internalization. However, such combined effects have not been explored. We used Chinese Hamster Ovary cells expressing vasopressin V1b receptors as a model to explore Na(+) sensitivity in agonist binding and receptor internalization. Under basal conditions, a large fraction of V1b receptors is located intracellularly, and a small fraction is in the plasma membrane. Decreases in external Na(+) increased cell surface [(3)H]AVP binding and decreased receptor internalization. Substitution of Na(+) by Cs(+) or NH4(+) inhibited agonist binding. To suppress receptor internalization, the concentration of NaCl, but not of CsCl, had to be less than 50 mM, due to the high sensitivity of the internalization machinery to Na(+) over Cs(+). Iso-osmotic supplementation of glucose or NH4Cl maintained internalization of the V1b receptor, even in a low-NaCl environment. Moreover, iodide ions, which acted as a counter anion, inhibited V1b agonist binding. In summary, we found external ionic conditions that could increase the presence of high-affinity state receptors at the cell surface with minimum internalization during agonist stimulations.

Combined sodium ion sensitivity in agonist binding and internalization of vasopressin V1b receptors

PubMed Central

Koshimizu, Taka-aki; Kashiwazaki, Aki; Taniguchi, Junichi

2016-01-01

Reducing Na+ in the extracellular environment may lead to two beneficial effects for increasing agonist binding to cell surface G-protein coupled receptors (GPCRs): reduction of Na+-mediated binding block and reduce of receptor internalization. However, such combined effects have not been explored. We used Chinese Hamster Ovary cells expressing vasopressin V1b receptors as a model to explore Na+ sensitivity in agonist binding and receptor internalization. Under basal conditions, a large fraction of V1b receptors is located intracellularly, and a small fraction is in the plasma membrane. Decreases in external Na+ increased cell surface [3H]AVP binding and decreased receptor internalization. Substitution of Na+ by Cs+ or NH4+ inhibited agonist binding. To suppress receptor internalization, the concentration of NaCl, but not of CsCl, had to be less than 50 mM, due to the high sensitivity of the internalization machinery to Na+ over Cs+. Iso-osmotic supplementation of glucose or NH4Cl maintained internalization of the V1b receptor, even in a low-NaCl environment. Moreover, iodide ions, which acted as a counter anion, inhibited V1b agonist binding. In summary, we found external ionic conditions that could increase the presence of high-affinity state receptors at the cell surface with minimum internalization during agonist stimulations. PMID:27138239

Sensitive electrochemical immunosensor for α-synuclein based on dual signal amplification using PAMAM dendrimer-encapsulated Au and enhanced gold nanoparticle labels.

PubMed

An, Yarui; Jiang, Xiaoli; Bi, Wenji; Chen, Hua; Jin, Litong; Zhang, Shengping; Wang, Chuangui; Zhang, Wen

2012-02-15

A novel electrochemical immunosensor for sensitive detection of α-synuclein (α-SYN), a very important neuronal protein, has been developed based on dual signal amplification strategy. Herein, G4-polyamidoamine dendrimer-encapsulated Au nanoparticles (PAMAM-Au nanocomposites) were covalently bound on the poly-o-aminobenzoic acid (poly-o-ABA), which was initially electropolymerized on the electrode surface to perform abundant carboxyl groups. The formed immunosensor platform, PAMAM-Au, was proved to provide numerous amino groups to allow highly dense immobilization of antigen, and facilitate the improvement of electrochemical responses as well. Subsequently, the enhanced gold nanoparticle labels ({HRP-Ab(2)-GNPs}) were fabricated by immobilizing horseradish peroxidase-secondary antibody (HRP-Ab(2)) on the surface of gold nanoparticles (GNPs). After an immunoassay process, the {HRP-Ab(2)-GNPs} labels were introduced onto the electrode surface, and produced an electrocatalytic response by reduction of hydrogen peroxide (H(2)O(2)) in the presence of enzymatically oxidized thionine. On the basis of the dual signal amplification of PAMAM-Au and {HRP-Ab(2)-GNPs} labels, the designed immunosensor displayed an excellent analytical performance with high sensitivity and stability. This developed strategy was successfully proved as a simple, cost-effective method, and could be easily extended to other protein analysis schemes. Copyright © 2011 Elsevier B.V. All rights reserved.

Sensitivity of Active and Passive Microwave Observations to Soil Moisture during Growing Corn

NASA Astrophysics Data System (ADS)

Judge, J.; Monsivais-Huertero, A.; Liu, P.; De Roo, R. D.; England, A. W.; Nagarajan, K.

2011-12-01

Soil moisture (SM) in the root zone is a key factor governing water and energy fluxes at the land surface and its accurate knowledge is critical to predictions of weather and near-term climate, nutrient cycles, crop-yield, and ecosystem productivity. Microwave observations, such as those at L-band, are highly sensitive to soil moisture in the upper few centimeters (near-surface). The two satellite-based missions dedicated to soil moisture estimation include, the European Space Agency's Soil Moisture and Ocean Salinity (SMOS) mission and the planned NASA Soil Moisture Active/Passive (SMAP) [4] mission. The SMAP mission will include active and passive sensors at L-band to provide global observations of SM, with a repeat coverage of every 2-3 days. These observations can significantly improve root zone soil moisture estimates through data assimilation into land surface models (LSMs). Both the active (radar) and passive (radiometer) microwave sensors measure radiation quantities that are functions of soil dielectric constant and exhibit similar sensitivities to SM. In addition to the SM sensitivity, radar backscatter is highly sensitive to roughness of soil surface and scattering within the vegetation. These effects may produce a much larger dynamic range in backscatter than that produced due to SM changes alone. In this study, we discuss the field observations of active and passive signatures of growing corn at L-band from several seasons during the tenth Microwave, Water and Energy Balance Experiment (MicroWEX-10) conducted in North Central Florida, and to understand the sensitivity of these signatures to soil moisture under dynamic vegetation conditions. The MicroWEXs are a series of season-long field experiments conducted during the growing seasons of sweet corn, cotton, and energy cane over the past six years (for example, [22]). The corn was planted on July 5 and harvested on September 23, 2011 during MicroWEX-10. The size of the field was 0.04 km2 and the soils at the site were Lakeland fine sand, with 89% sand content by volume. The crop was heavily irrigated via a linear move irrigation system. Every 15-minute ground-based passive and active microwave observations at L-band were conducted at an incidence angle of 40°. In addition, concurrent observations were conducted of soil moisture, temperature, heat flux at various depths in the root zone, along with concurrent micrometeorological conditions. Weekly vegetation sampling included measurements of LAI, green and dry biomass of stems, leaves, and ears, crop height and width, vertical distribution of moisture in the canopy, leaf size and orientation, other phonological observations. Such observations at high temporal density allow detailed sensitivity analyses as the vegetation grows.

Upstream vertical cavity surface-emitting lasers for fault monitoring and localization in WDM passive optical networks

NASA Astrophysics Data System (ADS)

Wong, Elaine; Zhao, Xiaoxue; Chang-Hasnain, Connie J.

2008-04-01

As wavelength division multiplexed passive optical networks (WDM-PONs) are expected to be first deployed to transport high capacity services to business customers, real-time knowledge of fiber/device faults and the location of such faults will be a necessity to guarantee reliability. Nonetheless, the added benefit of implementing fault monitoring capability should only incur minimal cost associated with upgrades to the network. In this work, we propose and experimentally demonstrate a fault monitoring and localization scheme based on a highly-sensitive and potentially low-cost monitor in conjunction with vertical cavity surface-emitting lasers (VCSELs). The VCSELs are used as upstream transmitters in the WDM-PON. The proposed scheme benefits from the high reflectivity of the top distributed Bragg reflector (DBR) mirror of optical injection-locked (OIL) VCSELs to reflect monitoring channels back to the central office for monitoring. Characterization of the fault monitor demonstrates high sensitivity, low bandwidth requirements, and potentially low output power. The added advantage of the proposed fault monitoring scheme incurs only a 0.5 dB penalty on the upstream transmissions on the existing infrastructure.

Highly sensitive beam steering with plasmonic antenna

PubMed Central

Rui, Guanghao; Zhan, Qiwen

2014-01-01

In this work, we design and study a highly sensitive beam steering device that integrates a spiral plasmonic antenna with a subwavelength metallic waveguide. The short effective wavelength of the surface plasmon polaritons (SPPs) mode supported by the metallic waveguide is exploited to dramatically miniaturize the device and improve the sensitivity of the beam steering. Through introducing a tiny displacement of feed point with respect to the geometrical center of the spiral plasmonic antenna, the direction of the radiation can be steered at considerably high angles. Simulation results show that steering angles of 8°, 17° and 34° are obtainable for a displacement of 50 nm, 100 nm and 200 nm, respectively. Benefiting from the reduced device size and the shorter SPP wavelength, the beam steering sensitivity of the beam steering is improved by 10-fold compared with the case reported previously. This miniature plasmonic beam steering device may find many potential applications in quantum optical information processing and integrated photonic circuits. PMID:25091405

Enzyme-functionalized thin-cladding long-period fiber grating in transition mode at dispersion turning point for sugar-level and glucose detection

NASA Astrophysics Data System (ADS)

Badmos, Abdulyezir A.; Sun, Qizhen; Sun, Zhongyuan; Zhang, Junxi; Yan, Zhijun; Lutsyk, Petro; Rozhin, Alex; Zhang, Lin

2017-02-01

Enzyme-functionalized dual-peak long-period fiber grating (LPFG) inscribed in 80-μm-cladding B/Ge codoped single-mode fiber is presented for sugar-level and specific glucose detection. Before enzyme functionalization, the dual-peak LPFG was employed for refractive index sensing and sugar-level detection and high sensitivities of ˜4298.20 nm/RIU and 4.6696 nm/% were obtained, respectively. Glucose detection probe was attained by surface functionalization of the dual-peak LPFG via covalent binding with aminopropyl triethoxysilane used as a binding site. Optical micrographs confirmed the presence of enzyme. The surface-functionalized dual-peak LPFG was tested with D-(+)-glucose solution of different concentrations. While the peak 2 at the longer wavelength was suitable only to measure lower glucose concentration (0.1 to 1.6 mg/ml) recording a high sensitivity of 12.21±0.19 nm/(mg/ml), the peak 1 at the shorter wavelength was able to measure a wider range of glucose concentrations (0.1 to 3.2 mg/ml) exhibiting a maximum resonance wavelength shift of 7.12±0.12 nm/mg/ml. The enzyme-functionalized dual-peak LPFG has the advantage of direct inscription of highly sensitive grating structures in thin-cladding fibre without etching, and most significantly, its sensitivity improvement of approximately one order of magnitude higher than previously reported LPFG and excessively tilted fibre grating (Ex-TFG) for glucose detection.

Secondary ion mass spectrometry: The application in the analysis of atmospheric particulate matter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Di; Hua, Xin; Xiu, Guang-Li

Currently, considerable attention has been paid to atmospheric particulate matter (PM) investigation due to its importance in human health and global climate change. Surface characterization of PM is important since the chemical heterogeneity between the surface and bulk may vary its impact on the environment and human being. Secondary ion mass spectrometry (SIMS) is a surface technique with high surface sensitivity, capable of high spatial chemical imaging and depth profiling. Recent research shows that SIMS holds great potential in analyzing both surface and bulk chemical information of PM. In this review, we presented the working principal of SIMS in PMmore » characterization, summarized recent applications in PM analysis from different sources, discussed its advantages and limitations, and proposed the future development of this technique with a perspective in environmental sciences.« less

Projection-based estimation and nonuniformity correction of sensitivity profiles in phased-array surface coils.

PubMed

Yun, Sungdae; Kyriakos, Walid E; Chung, Jun-Young; Han, Yeji; Yoo, Seung-Schik; Park, Hyunwook

2007-03-01

To develop a novel approach for calculating the accurate sensitivity profiles of phased-array coils, resulting in correction of nonuniform intensity in parallel MRI. The proposed intensity-correction method estimates the accurate sensitivity profile of each channel of the phased-array coil. The sensitivity profile is estimated by fitting a nonlinear curve to every projection view through the imaged object. The nonlinear curve-fitting efficiently obtains the low-frequency sensitivity profile by eliminating the high-frequency image contents. Filtered back-projection (FBP) is then used to compute the estimates of the sensitivity profile of each channel. The method was applied to both phantom and brain images acquired from the phased-array coil. Intensity-corrected images from the proposed method had more uniform intensity than those obtained by the commonly used sum-of-squares (SOS) approach. With the use of the proposed correction method, the intensity variation was reduced to 6.1% from 13.1% of the SOS. When the proposed approach was applied to the computation of the sensitivity maps during sensitivity encoding (SENSE) reconstruction, it outperformed the SOS approach in terms of the reconstructed image uniformity. The proposed method is more effective at correcting the intensity nonuniformity of phased-array surface-coil images than the conventional SOS method. In addition, the method was shown to be resilient to noise and was successfully applied for image reconstruction in parallel imaging.

Ultrasensitive Detection of Low-Abundance Surface-Marker Protein using Isothermal Rolling Circle Amplification in Microfluidic Nano-Liter Platform

PubMed Central

Konry, Tania; Yarmush, Joel M.; Irimia, Daniel

2011-01-01

With advances in immunology and cancer biology, there is an unmet need for increasingly sensitive systems to monitor the expression of specific cell markers for the development of new diagnostic and therapeutic tools. To address this challenge, we have applied a highly sensitive labeling method that translates antigen-antibody recognition processes into DNA detection event that can be greatly amplified via isothermal Rolling Circle Amplification (RCA). By merging the single-molecule detection power of RCA reaction with microfluidic technology we were able to demonstrate that identification of specific protein markers can be achieved on tumor cell surface in miniaturized nano-liter reaction droplets. Furthermore, this combined approach of signal amplification in a microfluidic format could extend the utility of existing methods by reducing sample and reagent consumption and enhancing the sensitivities and specificities for various applications, including early diagnosis of cancer. PMID:21294269

Near-surface compressional and shear wave speeds constrained by body-wave polarization analysis

NASA Astrophysics Data System (ADS)

Park, Sunyoung; Ishii, Miaki

2018-06-01

A new technique to constrain near-surface seismic structure that relates body-wave polarization direction to the wave speed immediately beneath a seismic station is presented. The P-wave polarization direction is only sensitive to shear wave speed but not to compressional wave speed, while the S-wave polarization direction is sensitive to both wave speeds. The technique is applied to data from the High-Sensitivity Seismograph Network in Japan, and the results show that the wave speed estimates obtained from polarization analysis are compatible with those from borehole measurements. The lateral variations in wave speeds correlate with geological and physical features such as topography and volcanoes. The technique requires minimal computation resources, and can be used on any number of three-component teleseismic recordings, opening opportunities for non-invasive and inexpensive study of the shallowest (˜100 m) crustal structures.

Highly sensitive BTX detection using surface functionalized QCM sensor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bozkurt, Asuman Aşıkoğlu; Özdemir, Okan; Altındal, Ahmet, E-mail: altindal@yildiz.edu.tr

2016-03-25

A novel organic compound was designed and successfully synthesized for the fabrication of QCM based sensors to detect the low concentrations of BTX gases in indoor air. The effect of the long-range electron orbital delocalization on the BTX vapour sensing properties of azo-bridged Pcs based chemiresistor-type sensors have also been investigated in this work. The sensing behaviour of the film for the online detection of volatile organic solvent vapors was investigated by utilizing an AT-cut quartz crystal resonator. It was observed that the adsorption of the target molecules on the coating surface cause a reversible negative frequency shift of themore » resonator. Thus, a variety of solvent vapors can be detected by using the phthalocyanine film as sensitive coating, with sensitivity in the ppm range and response times in the order of several seconds depending on the molecular structure of the organic solvent.« less

Highly sensitive BTX detection using surface functionalized QCM sensor

NASA Astrophysics Data System (ADS)

Bozkurt, Asuman Aşıkoǧlu; Özdemir, Okan; Altındal, Ahmet

2016-03-01

A novel organic compound was designed and successfully synthesized for the fabrication of QCM based sensors to detect the low concentrations of BTX gases in indoor air. The effect of the long-range electron orbital delocalization on the BTX vapour sensing properties of azo-bridged Pcs based chemiresistor-type sensors have also been investigated in this work. The sensing behaviour of the film for the online detection of volatile organic solvent vapors was investigated by utilizing an AT-cut quartz crystal resonator. It was observed that the adsorption of the target molecules on the coating surface cause a reversible negative frequency shift of the resonator. Thus, a variety of solvent vapors can be detected by using the phthalocyanine film as sensitive coating, with sensitivity in the ppm range and response times in the order of several seconds depending on the molecular structure of the organic solvent.

Innovative nanostructures for highly sensitive vibrational biosensing (Conference Presentation)

NASA Astrophysics Data System (ADS)

Popp, Juergen; Mayerhöfer, Thomas; Cialla-May, Dana; Weber, Karina; Huebner, Uwe

2016-03-01

Employing vibrational spectroscopy (IR-absorption and Raman spectroscopy) allows for the labelfree detection of molecular specific fingerprints of inorganic, organic and biological substances. The sensitivity of vibrational spectroscopy can be improved by several orders of magnitude via the application of plasmonic active surfaces. Within this contribution we will discuss two such approaches, namely surface enhanced Raman spectroscopy (SERS) as well as surface enhanced IR absorption (SEIRA). It will be shown that SERS using metal colloids as SERS active substrate in combination with a microfluidic lab-on-a-chip (LOC) device enables high throughput and reproducible measurements with highest sensitivity and specificity. The application of such a LOC-SERS approach for therapeutic drug monitoring (e.g. quantitative detection of antibiotics in a urine matrix) will be presented. Furthermore, we will introduce innovative bottom-up strategies to prepare SERS-active nanostructures coated with a lipophilic sensor layer as one-time use SERS substrates for specific food analysis (e.g. quantitative detection of toxic food colorants). The second part of this contribution presents a slit array metamaterial perfect absorber for IR sensing applications consisting of a dielectric layer sandwiched between two metallic layers of which the upper layer is perforated with a periodic array of slits. Light-matter interaction is greatly amplified in the slits, where also the analyte is concentrated, as the surface of the substrate is covered by a thin silica layer. Thus, already small concentrations of analytes down to a monolayer can be detected by refractive index sensing and identified by their spectral fingerprints with a standard mid-infrared lab spectrometer.

Probing Dynamically Tunable Localized Surface Plasmon Resonances of Film-Coupled Nanoparticles by Evanescent Wave Excitation

PubMed Central

Mock, Jack J.; Hill, Ryan T.; Tsai, Yu-Ju; Chilkoti, Ashutosh; Smith, David R.

2012-01-01

The localized surface plasmon resonance (LSPR) spectrum associated with a gold nanoparticle (NP) coupled to a gold film exhibits extreme sensitivity to the nano-gap region where the fields are tightly localized. The LSPR of an ensemble of film-coupled NPs can be observed using an illumination scheme similar to that used to excite the surface plasmon resonance (SPR) of a thin metallic film; however, in the present system, the light is used to probe the highly sensitive distance-dependent LSPR of the gaps between NPs and film rather than the delocalized SPR of the film. We show that the SPR and LSPR spectral contributions can be readily distinguished, and we compare the sensitivities of both modes to displacements in the average gap between a collection of NPs and the gold film. The distance by which the NPs are suspended in solution above the gold film is fixed via a thin molecular spacer layer, and can be further modulated by subjecting the NPs to a quasistatic electric field. The observed LSPR spectral shifts triggered by the applied voltage can be correlated with Angstrom scale displacements of the NPs, suggesting the potential for chip-scale or flow-cell plasmonic nanoruler devices with extreme sensitivity. PMID:22429053

Highly sensitive surface plasmon resonance biosensor for the detection of HIV-related DNA based on dynamic and structural DNA nanodevices.

PubMed

Diao, Wei; Tang, Min; Ding, Shijia; Li, Xinmin; Cheng, Wenbin; Mo, Fei; Yan, Xiaoyu; Ma, Hongmin; Yan, Yurong

2018-02-15

Early detection, diagnosis and treatment of human immune deficiency virus (HIV) infection is the key to reduce acquired immunodeficiency syndrome (AIDS) mortality. In our research, an innovative surface plasmon resonance (SPR) biosensing strategy has been developed for highly sensitive detection of HIV-related DNA based on entropy-driven strand displacement reactions (ESDRs) and double-layer DNA tetrahedrons (DDTs). ESDRs as enzyme-free and label-free signal amplification circuit can be specifically triggered by target DNA, leading to the cyclic utilization of target DNA and the formation of plentiful double-stranded DNA (dsDNA) products. Subsequently, the dsDNA products bind to the immobilized hairpin capture probes and further combine with DDTs nanostructures. Due to the high efficiency of ESDRs and large molecular weight of DDTs, the SPR response signal was enhanced dramatically. The proposed SPR biosensor could detect target DNA sensitively and specifically in a linear range from 1pM to 150nM with a detection limit of 48fM. In addition, the whole detecting process can be accomplished in 60min with high accuracy and duplicability. In particular, the developed SPR biosensor was successfully used to analyze target DNA in complex biological sample, indicating that the developed strategy is promising for rapid and early clinical diagnosis of HIV infection. Copyright © 2017 Elsevier B.V. All rights reserved.

Silver nanoparticles-incorporated Nb2O5 surface passivation layer for efficiency enhancement in dye-sensitized solar cells.

PubMed

Suresh, S; Unni, Gautam E; Satyanarayana, M; Sreekumaran Nair, A; Mahadevan Pillai, V P

2018-08-15

Guiding and capturing photons at the nanoscale by means of metal nanoparticles and interfacial engineering for preventing back-electron transfer are well documented techniques for performance enhancement in excitonic solar cells. Drifting from the conventional route, we propose a simple one-step process to integrate both metal nanoparticles and surface passivation layer in the porous photoanode matrix of a dye-sensitized solar cell. Silver nanoparticles and Nb 2 O 5 surface passivation layer are simultaneously deposited on the surface of a highly porous nanocrystalline TiO 2 photoanode, facilitating an absorption enhancement in the 465 nm and 570 nm wavelength region and a reduction in back-electron transfer in the fabricated dye-sensitized solar cells together. The TiO 2 photoanodes were prepared by spray pyrolysis deposition method from a colloidal solution of TiO 2 nanoparticles. An impressive 43% enhancement in device performance was accomplished in photoanodes having an Ag-incorporated Nb 2 O 5 passivation layer as against a cell without Ag nanoparticles. By introducing this idea, we were able to record two benefits - the metal nanoparticles function as the absorption enhancement agent, and the Nb 2 O 5 layer as surface passivation for TiO 2 nanoparticles and as an energy barrier layer for preventing back-electron transfer - in a single step. Copyright © 2018 Elsevier Inc. All rights reserved.

Molecular interferometric imaging study of molecular interactions

NASA Astrophysics Data System (ADS)

Zhao, Ming; Wang, Xuefeng; Nolte, David

2008-02-01

Molecular Interferometric Imaging (MI2) is a sensitive detection platform for direct optical detection of immobilized biomolecules. It is based on inline common-path interferometry combined with far-field optical imaging. The substrate is a simple thermal oxide on a silicon surface with a thickness at or near the quadrature condition that produces a π/2 phase shift between the normal-incident wave reflected from the top oxide surface and the bottom silicon surface. The presence of immobilized or bound biomolecules on the surface produces a relative phase shift that is converted to a far-field intensity shift and is imaged by a reflective microscope onto a CCD camera. Shearing interferometry is used to remove the spatial 1/f noise from the illumination to achieve shot-noise-limited detection of surface dipole density profiles. The lateral resolution of this technique is diffraction limited at 0.4 micron, and the best longitudinal resolution is 10 picometers. The minimum detectable mass at the metrology limit is 2 attogram, which is 8 antibody molecules of size 150 kDa. The corresponding scaling mass sensitivity is 5 fg/mm compared with 1 pg/mm for typical SPR sensitivity. We have applied MI2 to immunoassay applications, and real-time binding kinetics has been measured for antibody-antigen reactions. The simplicity of the substrate and optical read-out make MI2 a promising analytical assay tool for high-throughput screening and diagnostics.

Acoustic method of investigating the material properties and humidity sensing behavior of polymer coated piezoelectric substrates

NASA Astrophysics Data System (ADS)

Caliendo, Cinzia

2006-09-01

The relative humidity (RH) sensing behavior of a polymeric film was investigated by means of polymer coated surface acoustic wave (SAW) delay lines implemented on single crystal piezoelectric substrates, such as quartz and LiNbO3, and on thin piezoelectric polycrystalline films, such as ZnO and AlN, on Si and GaAs. The same SAW delay line configuration was implemented on each substrate and the obtained devices' operating frequency was in the range of 105-156MHz, depending on the type of the substrate, on its crystallographic orientation, and on the SAW propagation direction. The surface of each SAW device was covered by the same type RH sensitive film of the same thickness and the RH sensitivity of each polymer coated substrate, i.e., the SAW relative phase velocity shift per RH unit changes, was investigated in the 0%—80% RH range. The perturbational approach was used to relate the SAW sensor velocity response to the RH induced changes in the physical parameters of the sensitive polymer film: the incremental change in the mass density and shear modulus of the polymer film per unit RH change were estimated. The shift of the bare SAW delay lines operating frequency induced by the presence of the polymer film, at RH =0% and at T =-10°C, allowed the experimental estimation of the mass sensitivity values of each substrate. These values were in good accordance with those reported in the literature and with those theoretically evaluated by exact numerical calculation. The shift of the bare SAW delay lines propagation loss induced by the polymer coating of the device surface, at RH =0% and at ambient temperature, allowed the experimental estimation of the elastic sensitivity of each substrate. These values were found in good accordance with those available from the literature. The temperature coefficient of delay and the electromechanical coupling coefficient of the bare substrates were also estimated. The membrane sensitivity to ethanol, methanol and isopropylic alcohol was tested by means of a high-frequency (670MHz) high-sensitivity Si /AlN resonator sensor.

Antibody modified gold nano-mushroom arrays for rapid detection of alpha-fetoprotein.

PubMed

Li, Wanbo; Jiang, Xueqin; Xue, Jiancai; Zhou, Zhangkai; Zhou, Jianhua

2015-06-15

Localized surface plasmon resonance (LSPR) combined with immunoassay shows greatly potential in fast detection of tumor markers. In this paper, a highly sensitive LSPR substrate has been fabricated and modified for direct detection of alpha-fetoprotein (AFP). The biosensor was prepared by interference lithography, and modified by covalently immobilizing anti-AFP on the surface of gold nano-mushroom arrays (GNMA). The modification process was investigated by Vis-NIR reflectance spectra and cyclic voltammogram measurements. We revealed the optical properties of the modified GNMA by measuring the Vis-NIR reflectance spectra and simulating its electric intensity field distribution under light illumination. The GNMA substrate was highly sensitive, with a refractive index sensitivity of ~465 nm/RIU. The substrate can be applied to label-free detection of AFP, with the linear range and the limit of detection determined to be 20-200 ng/mL and 24 ng/mL (S/N=3), respectively. We also demonstrated its clinical application by directly detecting AFP in human serum samples. It is expected that our biosensor could be integrated on microfluidic chips for high-throughput detection in portable early diagnosis, post-operative and point-of-care (POC) in clinical applications. Copyright © 2015 Elsevier B.V. All rights reserved.

Impact of nitrogen doping of niobium superconducting cavities on the sensitivity of surface resistance to trapped magnetic flux

NASA Astrophysics Data System (ADS)

Gonnella, Dan; Kaufman, John; Liepe, Matthias

2016-02-01

Future particle accelerators such as the SLAC "Linac Coherent Light Source-II" (LCLS-II) and the proposed Cornell Energy Recovery Linac require hundreds of superconducting radio-frequency (SRF) niobium cavities operating in continuous wave mode. In order to achieve economic feasibility of projects such as these, the cavities must achieve a very high intrinsic quality factor (Q0) to keep cryogenic losses within feasible limits. To reach these high Q0's in the case of LCLS-II, nitrogen-doping of niobium cavities has been selected as the cavity preparation technique. When dealing with Q0's greater than 1 × 1010, the effects of ambient magnetic field on Q0 become significant. Here, we show that the sensitivity to RF losses from trapped magnetic field in a cavity's walls is strongly dependent on the cavity preparation. Specifically, standard electropolished and 120 °C baked cavities show a sensitivity of residual resistance from trapped magnetic flux of ˜0.6 and ˜0.8 nΩ/mG trapped, respectively, while nitrogen-doped cavities show a higher sensitivity of residual resistance from trapped magnetic flux of ˜1 to 5 nΩ/mG trapped. We show that this difference in sensitivities is directly related to the mean free path of the RF surface layer of the niobium: shorter mean free paths lead to less sensitivity of residual resistance to trapped magnetic flux in the dirty limit (ℓ ≪ ξ0), while longer mean free paths lead to lower sensitivity of residual resistance to trapped magnetic flux in the clean limit (ℓ ≫ ξ0). These experimental results are also shown to have good agreement with recent theoretical predictions for pinned vortex lines oscillating in RF fields.

A small-displacement sensor using total internal reflection theory and surface plasmon resonance technology for heterodyne interferometry.

PubMed

Wang, Shinn-Fwu

2009-01-01

A small-displacement sensor based on total-internal reflection theory and surface plasmon resonance technology is proposed for use in heterodyne interferometry. A small displacement can be obtained simply by measuring the variation in phase difference between s- and p-polarization states with the small-displacement sensor. The theoretical displacement resolution of the small-displacement sensor can reach 0.45 nm. The sensor has some additional advantages, e.g., a simple optical setup, high resolution, high sensitivity and rapid measurement. Its feasibility is also demonstrated.

U-Shaped and Surface Functionalized Polymer Optical Fiber Probe for Glucose Detection.

PubMed

Azkune, Mikel; Ruiz-Rubio, Leire; Aldabaldetreku, Gotzon; Arrospide, Eneko; Pérez-Álvarez, Leyre; Bikandi, Iñaki; Zubia, Joseba; Vilas-Vilela, Jose Luis

2017-12-25

In this work we show an optical fiber evanescent wave absorption probe for glucose detection in different physiological media. High selectivity is achieved by functionalizing the surface of an only-core poly(methyl methacrylate) (PMMA) polymer optical fiber with phenilboronic groups, and enhanced sensitivity by using a U-shaped geometry. Employing a supercontinuum light source and a high-resolution spectrometer, absorption measurements are performed in the broadband visible light spectrum. Experimental results suggest the feasibility of such a fiber probe as a low-cost and selective glucose detector.

A New Formulation for Fresh Snow Density over Antarctica for the regional climate model Modèle Atmosphérique Régionale (MAR).

NASA Astrophysics Data System (ADS)

Tedesco, M.; Datta, R.; Fettweis, X.; Agosta, C.

2015-12-01

Surface-layer snow density is important to processes contributing to surface mass balance, but is highly variable over Antarctica due to a wide range of near-surface climate conditions over the continent. Formulations for fresh snow density have typically either used fixed values or been modeled empirically using field data that is limited to specific seasons or regions. There is also currently limited work exploring how the sensitivity to fresh snow density in regional climate models varies with resolution. Here, we present a new formulation compiled from (a) over 1600 distinct density profiles from multiple sources across Antarctica and (b) near-surface variables from the regional climate model Modèle Atmosphérique Régionale (MAR). Observed values represent coastal areas as well as the plateau, in both West and East Antarctica (although East Antarctica is dominant). However, no measurements are included from the Antarctic Peninsula, which is both highly topographically variable and extends to lower latitudes than the remainder of the continent. In order to assess the applicability of this fresh snow density formulation to the Antarctic Peninsula at high resolutions, a version of MAR is run for several years both at low-resolution at the continental scale and at a high resolution for the Antarctic Peninsula alone. This setup is run both with and without the new fresh density formulation to quantify the sensitivity of the energy balance and SMB components to fresh snow density. Outputs are compared with near-surface atmospheric variables available from AWS stations (provided by the University of Wisconsin Madison) as well as net accumulation values from the SAMBA database (provided from the Laboratoire de Glaciologie et Géophysique de l'Environnement).

Using well casing as an electrical source to monitor hydraulic fracture fluid injection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wilt, Michael; Nieuwenhuis, Greg; MacLennan, Kris

2016-03-09

The depth to surface resistivity (DSR) method transmits current from a source located in a cased or openhole well to a distant surface return electrode while electric field measurements are made at the surface over the target of interest. This paper presents both numerical modelling results and measured data from a hydraulic fracturing field test where conductive water was injected into a resistive shale reservoir during a hydraulic fracturing operation. Modelling experiments show that anomalies due to hydraulic fracturing are small but measureable with highly sensitive sensor technology. The field measurements confirm the model results,showing that measured differences in themore » surface fields due to hydraulic fracturing have been detected above the noise floor. Our results show that the DSR method is sensitive to the injection of frac fluids; they are detectable above the noise floor in a commercially active hydraulic fracturing operation, and therefore this method can be used for monitoring fracture fluid movement.« less

Unified Application of Vapor Screen Flow Visualization and Pressure Sensitive Paint Measurement Techniques to Vortex- and Shock Wave-Dominated Flow Fields

NASA Technical Reports Server (NTRS)

Erickson, Gary E.

2010-01-01

Laser vapor screen (LVS) flow visualization and pressure sensitive paint (PSP) techniques were applied in a unified approach to wind tunnel testing of slender wing and missile configurations dominated by vortex flows and shock waves at subsonic, transonic, and supersonic speeds. The off-surface cross-flow patterns using the LVS technique were combined with global PSP surface static pressure mappings to characterize the leading-edge vortices and shock waves that coexist and interact at high angles of attack. The synthesis of LVS and PSP techniques was also effective in identifying the significant effects of passive surface porosity and the presence of vertical tail surfaces on the flow topologies. An overview is given of LVS and PSP applications in selected experiments on small-scale models of generic slender wing and missile configurations in the NASA Langley Research Center (NASA LaRC) Unitary Plan Wind Tunnel (UPWT) and 8-Foot Transonic Pressure Tunnel (8-Foot TPT).

Unified Application Vapor Screen Flow Visualization and Pressure Sensitive Paint Measurement Techniques to Vortex- and Shock Wave-Dominated Flow Fields

NASA Technical Reports Server (NTRS)

Erickson, Gary E.

2008-01-01

Laser vapor screen (LVS) flow visualization and pressure sensitive paint (PSP) techniques were applied in a unified approach to wind tunnel testing of slender wing and missile configurations dominated by vortex flows and shock waves at subsonic, transonic, and supersonic speeds. The off-surface cross-flow patterns using the LVS technique were combined with global PSP surface static pressure mappings to characterize the leading-edge vortices and shock waves that coexist and interact at high angles of attack (alpha). The synthesis of LVS and PSP techniques was also effective in identifying the significant effects of passive surface porosity and the presence of vertical tail surfaces on the flow topologies. An overview is given of LVS and PSP applications in selected experiments on small-scale models of generic slender wing and missile configurations in the NASA Langley Research Center (NASA LaRC) Unitary Plan Wind Tunnel (UPWT) and 8-Foot Transonic Pressure Tunnel (8-Foot TPT).

Detection of glycoprotein using fiber optic surface plasmon resonance sensors with boronic acid

NASA Astrophysics Data System (ADS)

Wang, Fang; Zhang, Yang; Liu, Zigeng; Qian, Siyu; Gu, Yiying; Jing, Zhenguo; Sun, Changsen; Peng, Wei

2017-04-01

In this paper, we present a tilted fiber Bragg gratings (TFBG) based surface Plasmon resonance (SPR) label-free sensors with boronic acid derivative (ABA-PBA) as receptor molecule to detect glycoprotein with high sensitivity and selectivity. Tilted fiber Bragg gratings (TFBG) as a near infrared wavelengths detecting element can be able to excite a number of cladding modes whose properties can be detected accurately by measuring the variation of transmitted spectra. A 10° TFBG coated by 50nm gold film was manufactured to stimulate surface plasmon resonance on the surface of the sensor. The sensor was loaded with boronic acid derivative as the recognition molecule which has been widely used in various areas for the recognition matrix of diol-containing biomolecules. The proposed TFBG-SPR sensors exhibit good selectivity and repeatability with the protein concentration sensitivity up to 2.867dB/ (mg/ml) and the limit of detection was 2*10-5g/ml.

Study of concentration of HPV DNA probe immobilization for cervical cancer detection based IDE biosensor

NASA Astrophysics Data System (ADS)

Roshila, M. L.; Hashim, U.; Azizah, N.

2016-07-01

This paper mainly illustrates regarding the detection process of Human Papillomavirus (HPV) DNA probe. HPV is the most common virus that infected to human by a sexually transmitted virus. The most common high-risk HPV are 16 and 18. Interdigitated electrode (IDE) device used as based of Titanium Dioxide (TiO2) acts as inorganic surface, where by using APTES as a linker between inorganic surface and organic surface. A strategy of rapid and sensitive for the HPV detection was proposed by integrating simple DNA extraction with a gene of DNA. The extraction of the gene of DNA will make an efficiency of the detection process. It will depend on the sequence of the capture probes and the way to support their attached. The fabrication, surface modification, immobilization and hybridization processes are characterized by current voltage (I-V) measurement by using KEITHLEY 6487. This strategy will perform a good sensitivity of HPV detection.

Realisation Of Polarisation Sensitive And Frequency Selective Surfaces On Microwave Reflectors By Laser Evaporation

NASA Astrophysics Data System (ADS)

Halm, R.; Kupper, Th.; Fischer, A.

1987-01-01

Gridded reflectors are used on communication satellites antennas to provide frequency reuse in dual linear polarisation mode of operation. The polarisation sensitive surface consists of metallic strips, forming a grid with width and spacings of the order of 0.1 mm. The use of frequency-selective surface (FSS) subreflectors allows the simultaneous generation of different microwave beams with the same main reflector. Such a reflector will require a structure of conductive arrays of either dipoles, rings, squares or square loops with typical dimensions of the order of 3-6 mm. Optimisation of the electrical design leads to critical dimensioning of these structures. By direct ablation of an aluminium surface coating by means of laser evaporation, high accuracies can be achieved. The major requirements were to minimize thermal damage of the substrate material and to produce dimensionally accurate grids. Experiments were carried out using a pulsed TEA-CO2 laser and a Q-switched Alexandrite laser. Details of the experimental set-up and conditions are described.

Contamination of grazing incidence EUV mirrors - An assessment

NASA Technical Reports Server (NTRS)

Osantowski, John F.; Fleetwood, C. F.

1988-01-01

Contamination assessment for space optical systems requires an understanding of the sensitivity of component performance, e.g. mirror reflectance, to materials deposited on the mirror surface. In a previous study, the sensitivity of typical normal incidence mirror coatings to surface deposits of generic hydrocarbons was reported. Recent activity in the development of grazing incidence telescopes for extreme ultraviolet space astronomy has stimulated the need for a similar assessment in the spectral region extending from approximately 100 A to 1000 A. The model used for analysis treats the contamination layer as a continuous thin film deposited on the mirror surface. The mirror surfaces selected for this study are opaque vacuum deposited gold and the uncoated and polished Zerodur. Scatter caused by film irregularities or particulates are not included in this assessment. Parametric evaluations at 100, 500, and 1000 A determine the sensitivity of mirror reflectance to a range of optical constants selected for the generic contaminants. This sensitivity analysis combined with the limited amount of optical data in the EUV for hydrocarbons, is used to select representative optical constants for the three wavelength regions. Reflectance versus contamination layer thickness curves are then calculated and used to determine critical thickness limits based on allowable reflectance change. Initial observations indicate that thickness limits will be highly dependent on the real part of the complex index of refraction of the contaminant film being less than 1.0. Preliminary laboratory measurements of samples contaminated with some commonly encountered hydrocarbons confirm trends indicated in the analytical studies.

Novel Blue Organic Dye for Dye-Sensitized Solar Cells Achieving High Efficiency in Cobalt-Based Electrolytes and by Co-Sensitization.

PubMed

Hao, Yan; Saygili, Yasemin; Cong, Jiayan; Eriksson, Anna; Yang, Wenxing; Zhang, Jinbao; Polanski, Enrico; Nonomura, Kazuteru; Zakeeruddin, Shaik Mohammed; Grätzel, Michael; Hagfeldt, Anders; Boschloo, Gerrit

2016-12-07

Blue and green dyes as well as NIR-absorbing dyes have attracted great interest because of their excellent ability of absorbing the incident photons in the red and near-infrared range region. A novel blue D-π-A dye (Dyenamo Blue), based on the diketopyrrolopyrrole (DPP)-core, has been designed and synthesized. Assembled with the cobalt bipyridine-based electrolytes, the device with Dyenamo Blue achieved a satisfying efficiency of 7.3% under one sun (AM1.5 G). The co-sensitization strategy was further applied on this blue organic dye together with a red D-π-A dye (D35). The successful co-sensitization outperformed a panchromatic light absorption and improved the photocurrent density; this in addition to the open-circuit potential result in an efficiency of 8.7%. The extended absorption of the sensitization and the slower recombination reaction between the blue dye and TiO 2 surface inhibited by the additional red sensitizer could be the two main reasons for the higher performance. In conclusion, from the results, the highly efficient cobalt-based DSSCs could be achieved with the co-sensitization between red and blue D-π-A organic dyes with a proper design, which showed us the possibility of applying this strategy for future high-performance solar cells.

A three-dimensional microelectrode array composed of vertically aligned ultra-dense carbon nanotube networks

NASA Astrophysics Data System (ADS)

Nick, C.; Yadav, S.; Joshi, R.; Schneider, J. J.; Thielemann, C.

2015-07-01

Electrodes based on carbon nanotubes are a promising approach to manufacture highly sensitive sensors with a low limit of signal detection and a high signal-to-noise ratio. This is achieved by dramatically increasing the electrochemical active surface area without increasing the overall geometrical dimensions. Typically, carbon nanotube electrodes are nearly planar and composed of randomly distributed carbon nanotube networks having a limited surface gain for a specific geometrical surface area. To overcome this limitation, we have introduced vertically aligned carbon nanotube (VACNT) networks as electrodes, which are arranged in a microelectrode pattern of 60 single electrodes. Each microelectrode features a very high aspect ratio of more than 300 and thus a dramatically increased surface area. These microelectrodes composed of VACNT networks display dramatically decreased impedance over the entire frequency range compared to planar microelectrodes caused by the enormous capacity increase. This is experimentally verified by electrochemical impedance spectroscopy and cyclic voltammetry.

Incorporation of beams into bossed diaphragm for a high sensitivity and overload micro pressure sensor

NASA Astrophysics Data System (ADS)

Yu, Zhongliang; Zhao, Yulong; Sun, Lu; Tian, Bian; Jiang, Zhuangde

2013-01-01

The paper presents a piezoresistive absolute micro pressure sensor, which is of great benefits for altitude location. In this investigation, the design, fabrication, and test of the sensor are involved. By analyzing the stress distribution of sensitive elements using finite element method, a novel structure through the introduction of sensitive beams into traditional bossed diaphragm is built up. The proposed configuration presents its advantages in terms of high sensitivity and high overload resistance compared with the conventional bossed diaphragm and flat diaphragm structures. Curve fittings of surface stress and deflection based on ANSYS simulation results are performed to establish the equations about the sensor. Nonlinear optimization by MATLAB is carried out to determine the structure dimensions. The output signals in both static and dynamic environments are evaluated. Silicon bulk micromachining technology is utilized to fabricate the sensor prototype, and the fabrication process is discussed. Experimental results demonstrate the sensor features a high sensitivity of 11.098 μV/V/Pa in the operating range of 500 Pa at room temperature, and a high overload resistance of 200 times overpressure to promise its survival under atmosphere. Due to the excellent performance above, the sensor can be applied in measuring the absolute micro pressure lower than 500 Pa.

Wilms tumor gene product: sensitive and contextually specific marker of serous carcinomas of ovarian surface epithelial origin.

PubMed

Hwang, Harry; Quenneville, Louise; Yaziji, Hadi; Gown, Allen M

2004-06-01

Carcinomas of ovarian surface epithelial origin can arise from, and often present at, extraovarian sites. There are few available markers for the positive identification of carcinomas of ovarian surface epithelial origin, which might aid in distinguishing them from metastatic carcinomas, such as of breast, colon, or lung origin. Recently, the Wilms tumor gene product (WT-1) has been shown to be expressed in ovarian surface and mesothelial epithelium. We tested the hypothesis that WT-1 would be a sensitive and specific marker of ovarian surface epithelium carcinomas. An archived series of 116 ovarian carcinomas (57 serous [43 ovarian, 14 extraovarian], 31 mucinous, 15 clear cell, 13 endometrioid), 118 breast carcinomas, 46 colonic carcinomas, and 45 nonsmall cell lung cancers were selected. A polyclonal antibody to the WT-1 gene product was applied to deparaffinized, formalin-fixed tissue sections after epitope retrieval. Fifty-two of 57 (93%) serous carcinomas of ovarian surface epithelial origin were WT-1-positive, in a nuclear pattern, with virtually all the tumor cell population positive in the majority of cases. None of the mucinous, clear cell, or endometrioid ovarian cancers were positive, and only 8 of 118 breast, 0 of 46 colonic, and 0 of 45 lung nonsmall cell carcinomas were WT-1-positive. These findings demonstrate that WT-1 is a highly sensitive and specific marker of serous carcinomas of ovarian surface epithelial origin (both ovarian and extraovarian). These results also contradict recent reports demonstrating WT-1 expression in both breast and lung carcinomas.

Surface-related phase noise in SAW resonators.

PubMed

Enguang, Dai

2002-05-01

With the advent of nanotechnologies, electronic devices are shrinking in thickness and width to reduce mass and, thereby, increase frequency and spe Lithographic approaches are capable of creating metal connections with thickness and lateral dimensions down to about 20 nm, approaching the molecular scale. As a result, the dimensions of outer particles are comparable with, or even larger than, those of active or passive regions in electronics devices. Therefore, directing our attention toward the effect of surface fluctuations is of practical significance. In fact, electronic device surface-related phenomena have already received more and more attention as device size decreases. In connection with surface phase noise, selection of a suitable device with high surface sensitivity is important. In this paper, high Q-value surface acoustic wave resonators were employed because of their strong sensitivity to surface perturbation. Phase noise in SAW resonators related to surface particle motion has been examined both theoretically and experimentally. This kind of noise has been studied from the point of view of a stochastic process resulting from particle molecular adsorption and desorption. Experimental results suggest that some volatile vapors can change flicker noise 1/f and random walk noise 1/f2. An analysis has been made indicating that these effects are not associated with Q value variation, but are generated by the change in the dynamic rate of adsorption and desorption of surface particles. Research on particle motion above the device substrate might explain the differences observed from the model based only on the substrate itself. Results might lead to a better understanding of the phase noise mechanism in micro-electronic devices and help us to build oscillators with improved performance.

Direct ambient noise tomography for 3-D near surface shear velocity structure: methodology and applications

NASA Astrophysics Data System (ADS)

Yao, H.; Fang, H.; Li, C.; Liu, Y.; Zhang, H.; van der Hilst, R. D.; Huang, Y. C.

2014-12-01

Ambient noise tomography has provided essential constraints on crustal and uppermost mantle shear velocity structure in global seismology. Recent studies demonstrate that high frequency (e.g., ~ 1 Hz) surface waves between receivers at short distances can be successfully retrieved from ambient noise cross-correlation and then be used for imaging near surface or shallow crustal shear velocity structures. This approach provides important information for strong ground motion prediction in seismically active area and overburden structure characterization in oil and gas fields. Here we propose a new tomographic method to invert all surface wave dispersion data for 3-D variations of shear wavespeed without the intermediate step of phase or group velocity maps.The method uses frequency-dependent propagation paths and a wavelet-based sparsity-constrained tomographic inversion. A fast marching method is used to compute, at each period, surface wave traveltimes and ray paths between sources and receivers. This avoids the assumption of great-circle propagation that is used in most surface wave tomographic studies, but which is not appropriate in complex media. The wavelet coefficients of the velocity model are estimated with an iteratively reweighted least squares (IRLS) algorithm, and upon iterations the surface wave ray paths and the data sensitivity matrix are updated from the newly obtained velocity model. We apply this new method to determine the 3-D near surface wavespeed variations in the Taipei basin of Taiwan, Hefei urban area and a shale and gas production field in China using the high-frequency interstation Rayleigh wave dispersion data extracted from ambient noisecross-correlation. The results reveal strong effects of off-great-circle propagation of high-frequency surface waves in these regions with above 30% shear wavespeed variations. The proposed approach is more efficient and robust than the traditional two-step surface wave tomography for imaging complex structures. In the future, approximate 3-D sensitivity kernels for dispersion data will be incorporated to account for finite-frequency effect of surface wave propagation. In addition, our approach provides a consistent framework for joint inversion of surface wave dispersion and body wave traveltime data for 3-D Vp and Vs structures.

Highly Sensitive Detection of Target Biomolecules on Cell Surface Using Gold Nanoparticle Conjugated with Aptamer Probe

NASA Astrophysics Data System (ADS)

Kim, Hyonchol; Terazono, Hideyuki; Hayashi, Masahito; Takei, Hiroyuki; Yasuda, Kenji

2012-06-01

A method of gold nanoparticle (Au NP) labeling with backscattered electron (BE) imaging of field emission scanning electron microscopy (FE-SEM) was applied for specific detection of target biomolecules on a cell surface. A single-stranded DNA aptamer, which specifically binds to the target molecule on a human acute lymphoblastic leukemia cell, was conjugated with a 20 nm Au NP and used as a probe to label its target molecule on the cell. The Au NP probe was incubated with the cell, and the interaction was confirmed using BE imaging of FE-SEM through direct counting of the number of Au NPs attached on the target cell surface. Specific Au NP-aptamer probes were observed on a single cell surface and their spatial distributions including submicron-order localizations were also clearly visualized, whereas the nonspecific aptamer probes were not observed on it. The aptamer probe can be potentially dislodged from the cell surface with treatment of nucleases, indicating that Au NP-conjugated aptamer probes can be used as sensitive and reversible probes to label target biomolecules on cells.

Acoustic sensors as a biophysical tool for probing cell attachment and cell/surface interactions.

PubMed

Saitakis, Michael; Gizeli, Electra

2012-02-01

Acoustic biosensors offer the possibility to analyse cell attachment and spreading. This is due to the offered speed of detection, the real-time non-invasive approach and their high sensitivity not only to mass coupling, but also to viscoelastic changes occurring close to the sensor surface. Quartz crystal microbalance (QCM) and surface acoustic wave (Love-wave) systems have been used to monitor the adhesion of animal cells to various surfaces and record the behaviour of cell layers under various conditions. The sensors detect cells mostly via their sensitivity in viscoelasticity and mechanical properties. Particularly, the QCM sensor detects cytoskeletal rearrangements caused by specific drugs affecting either actin microfilaments or microtubules. The Love-wave sensor directly measures cell/substrate bonds via acoustic damping and provides 2D kinetic and affinity parameters. Other studies have applied the QCM sensor as a diagnostic tool for leukaemia and, potentially, for chemotherapeutic agents. Acoustic sensors have also been used in the evaluation of the cytocompatibility of artificial surfaces and, in general, they have the potential to become powerful tools for even more diverse cellular analysis.

The amphoteric effect on friction between the bovine cartilage/cartilage surfaces under slightly sheared hydration lubrication mode.

PubMed

Pawlak, Zenon; Gadomski, Adam; Sojka, Michal; Urbaniak, Wieslaw; Bełdowski, Piotr

2016-10-01

The amphoteric effect on the friction between the bovine cartilage/cartilage contacts has been found to be highly sensitive to the pH of an aqueous solution. The cartilage surface was characterized using a combination of the pH, wettability, as well as the interfacial energy and friction coefficient testing methods to support lamellar-repulsive mechanism of hydration lubrication. It has been confirmed experimentally that phospholipidic multi-bilayers are essentially described as lamellar frictionless lubricants protecting the surface of the joints against wear. At the hydrophilicity limit, the low friction would then be due to (a) lamellar slippage of bilayers and (b) a short-range (nanometer-scale) repulsion between the interfaces of negatively charged (PO4(-)) cartilage surfaces, and in addition, contribution of the extracellular matrix (ECM) collagen fibers, hyaluronate, proteoglycans aggregates (PGs), glycoprotein termed lubricin and finally, lamellar PLs phases. In this paper we demonstrate experimentally that the pH sensitivity of cartilage to friction provides a novel concept in joint lubrication on charged surfaces. Copyright © 2016 Elsevier B.V. All rights reserved.

Surface scattering plasmon resonance fibre sensors: demonstration of rapid influenza A virus detection

NASA Astrophysics Data System (ADS)

Franςois, A.; Boehm, J.; Oh, S. Y.; Kok, T.; Monro, T. M.

2011-06-01

The management of threats such as pandemics and explosives, and of health and the environment requires the rapid deployment of highly sensitive detection tools. Sensors based on Surface Plasmon Resonance (SPR) allow rapid, labelfree, highly sensitive detection, and indeed this phenomenon underpins the only label-free optical biosensing technology that is available commercially. In these sensors, the existence of surface plasmons is inferred indirectly from absorption features that correspond to the coupling of light to the surface plasmon. Although SPR is not intrinsically a radiative process, under certain conditions the surface plasmon can itself couple to the local photon states, and emit light as first described byKretschmann. Here we show that by collecting and characterising this re-emitted light, it is possible to realise new SPR sensing architectures that are more compact, versatile and robust than existing approaches. This approach addresses existing practical limitations associated with current SPR technologies, including bulk, cost and calibration. It is applicable to a range of SPR geometries, including optical fibres, planar waveguides and prism configurations, and is in principle capable of detecting multiple analytes simultaneously. Moreover, this technique allows to combine SPR sensing and fluorescence sensing into a single platform which has never been demonstrated before and consequently use these two methods for a more reliable diagnostic. As an example, this approach has been used to demonstrate the rapid detection of the seasonal influenza virus.

Fast subsurface fingerprint imaging with full-field optical coherence tomography system equipped with a silicon camera.

PubMed

Auksorius, Egidijus; Boccara, A Claude

2017-09-01

Images recorded below the surface of a finger can have more details and be of higher quality than the conventional surface fingerprint images. This is particularly true when the quality of the surface fingerprints is compromised by, for example, moisture or surface damage. However, there is an unmet need for an inexpensive fingerprint sensor that is able to acquire high-quality images deep below the surface in short time. To this end, we report on a cost-effective full-field optical coherent tomography system comprised of a silicon camera and a powerful near-infrared LED light source. The system, for example, is able to record 1.7  cm×1.7  cmen face images in 0.12 s with the spatial sampling rate of 2116 dots per inch and the sensitivity of 93 dB. We show that the system can be used to image internal fingerprints and sweat ducts with good contrast. Finally, to demonstrate its biometric performance, we acquired subsurface fingerprint images from 240 individual fingers and estimated the equal-error-rate to be ∼0.8%. The developed instrument could also be used in other en face deep-tissue imaging applications because of its high sensitivity, such as in vivo skin imaging. (2017) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE).

Separation of density and viscosity influence on liquid-loaded surface acoustic wave devices

NASA Astrophysics Data System (ADS)

Herrmann, F.; Hahn, D.; Büttgenbach, S.

1999-05-01

Love-mode sensors are reported for separate measurement of liquid density and viscosity. They combine the general merits of Love-mode devices, e.g., ease of sensitivity adjustment and robustness, with a highly effective procedure of separate determination of liquid density and viscosity. A model is proposed to describe the frequency response of the devices to liquid loading. Moreover, design rules are given for further optimization and sensitivity enhancement.

High performance dye-sensitized solar cells using graphene modified fluorine-doped tin oxide glass by Langmuir–Blodgett technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roh, Ki-Min; Jo, Eun-Hee; Chang, Hankwon

Since the introduction of dye-sensitized solar cells (DSSCs) with low fabrication cost and high power conversion efficiency, extensive studies have been carried out to improve the charge transfer rate and performance of DSSCs. In this paper, we present DSSCs that use surface modified fluorine-doped tin oxide (FTO) substrates with reduced graphene oxide (r-GO) sheets prepared using the Langmuir–Blodgett (LB) technique to decrease the charge recombination at the TiO{sub 2}/FTO interface. R-GO sheets were excellently attached on FTO surface without physical deformations such as wrinkles; effects of the surface coverage of r-GO on the DSSC performance were also investigated. By usingmore » graphene modified FTO substrates, the resistance at the interface of TiO{sub 2}/FTO was reduced and the power conversion efficiency was increased to 8.44%. - Graphical abstract: DSSCs with graphene modified FTO glass were fabricated with the Langmuir Blodgett technique. GO sheets were transferred to FTO at various surface pressures in order to change the surface density of graphene and the highest power conversion efficiency of the DSSC was 8.44%. - Highlights: • By LB technique, r-GO sheets were coated on FTO without physical deformation. • DSSCs were fabricated with, r-GO modified FTO substrates. • With surface modification by r-GO, the interface resistance of DSSC decreased. • Maximum PCE of the DSSC was increased up to 8.44%.« less

Dual-sensitivity profilometry with defocused projection of binary fringes.

PubMed

Garnica, G; Padilla, M; Servin, M

2017-10-01

A dual-sensitivity profilometry technique based on defocused projection of binary fringes is presented. Here, two sets of fringe patterns with a sinusoidal profile are produced by applying the same analog low-pass filter (projector defocusing) to binary fringes with a high- and low-frequency spatial carrier. The high-frequency fringes have a binary square-wave profile, while the low-frequency binary fringes are produced with error-diffusion dithering. The binary nature of the binary fringes removes the need for calibration of the projector's nonlinear gamma. Working with high-frequency carrier fringes, we obtain a high-quality wrapped phase. On the other hand, working with low-frequency carrier fringes we found a lower-quality, nonwrapped phase map. The nonwrapped estimation is used as stepping stone for dual-sensitivity temporal phase unwrapping, extending the applicability of the technique to discontinuous (piecewise continuous) surfaces. We are proposing a single defocusing level for faster high- and low-frequency fringe data acquisition. The proposed technique is validated with experimental results.

High-sensitivity silicon nanowire phototransistors

NASA Astrophysics Data System (ADS)

Tan, Siew Li; Zhao, Xingyan; Dan, Yaping

2014-08-01

Silicon nanowires (SiNWs) have emerged as a promising material for high-sensitivity photodetection in the UV, visible and near-infrared spectral ranges. In this work, we demonstrate novel planar SiNW phototransistors on silicon-oninsulator (SOI) substrate using CMOS-compatible processes. The device consists of a bipolar transistor structure with an optically-injected base region. The electronic and optical properties of the SiNW phototransistors are investigated. Preliminary simulation and experimental results show that nanowire geometry, doping densities and surface states have considerable effects on the device performance, and that a device with optimized parameters can potentially outperform conventional Si photodetectors.

The impact of standard and hard-coded parameters on the hydrologic fluxes in the Noah-MP land surface model

NASA Astrophysics Data System (ADS)

Thober, S.; Cuntz, M.; Mai, J.; Samaniego, L. E.; Clark, M. P.; Branch, O.; Wulfmeyer, V.; Attinger, S.

2016-12-01

Land surface models incorporate a large number of processes, described by physical, chemical and empirical equations. The agility of the models to react to different meteorological conditions is artificially constrained by having hard-coded parameters in their equations. Here we searched for hard-coded parameters in the computer code of the land surface model Noah with multiple process options (Noah-MP) to assess the model's agility during parameter estimation. We found 139 hard-coded values in all Noah-MP process options in addition to the 71 standard parameters. We performed a Sobol' global sensitivity analysis to variations of the standard and hard-coded parameters. The sensitivities of the hydrologic output fluxes latent heat and total runoff, their component fluxes, as well as photosynthesis and sensible heat were evaluated at twelve catchments of the Eastern United States with very different hydro-meteorological regimes. Noah-MP's output fluxes are sensitive to two thirds of its standard parameters. The most sensitive parameter is, however, a hard-coded value in the formulation of soil surface resistance for evaporation, which proved to be oversensitive in other land surface models as well. Latent heat and total runoff show very similar sensitivities towards standard and hard-coded parameters. They are sensitive to both soil and plant parameters, which means that model calibrations of hydrologic or land surface models should take both soil and plant parameters into account. Sensible and latent heat exhibit almost the same sensitivities so that calibration or sensitivity analysis can be performed with either of the two. Photosynthesis has almost the same sensitivities as transpiration, which are different from the sensitivities of latent heat. Including photosynthesis and latent heat in model calibration might therefore be beneficial. Surface runoff is sensitive to almost all hard-coded snow parameters. These sensitivities get, however, diminished in total runoff. It is thus recommended to include the most sensitive hard-coded model parameters that were exposed in this study when calibrating Noah-MP.

A perceptual space of local image statistics.

PubMed

Victor, Jonathan D; Thengone, Daniel J; Rizvi, Syed M; Conte, Mary M

2015-12-01

Local image statistics are important for visual analysis of textures, surfaces, and form. There are many kinds of local statistics, including those that capture luminance distributions, spatial contrast, oriented segments, and corners. While sensitivity to each of these kinds of statistics have been well-studied, much less is known about visual processing when multiple kinds of statistics are relevant, in large part because the dimensionality of the problem is high and different kinds of statistics interact. To approach this problem, we focused on binary images on a square lattice - a reduced set of stimuli which nevertheless taps many kinds of local statistics. In this 10-parameter space, we determined psychophysical thresholds to each kind of statistic (16 observers) and all of their pairwise combinations (4 observers). Sensitivities and isodiscrimination contours were consistent across observers. Isodiscrimination contours were elliptical, implying a quadratic interaction rule, which in turn determined ellipsoidal isodiscrimination surfaces in the full 10-dimensional space, and made predictions for sensitivities to complex combinations of statistics. These predictions, including the prediction of a combination of statistics that was metameric to random, were verified experimentally. Finally, check size had only a mild effect on sensitivities over the range from 2.8 to 14min, but sensitivities to second- and higher-order statistics was substantially lower at 1.4min. In sum, local image statistics form a perceptual space that is highly stereotyped across observers, in which different kinds of statistics interact according to simple rules. Copyright © 2015 Elsevier Ltd. All rights reserved.