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Sample records for highly sensitive colorimetric

  1. Highly Sensitive Colorimetric Detection of Ochratoxin A by a Label-Free Aptamer and Gold Nanoparticles

    PubMed Central

    Luan, Yunxia; Chen, Jiayi; Li, Cheng; Xie, Gang; Fu, Hailong; Ma, Zhihong; Lu, Anxiang

    2015-01-01

    A label-free aptamer-based assay for the highly sensitive and specific detection of Ochratoxin A (OTA) was developed using a cationic polymer and gold nanoparticles (AuNPs). The OTA aptamer was used as a recognition element for the colorimetric detection of OTA based on the aggregation of AuNPs by the cationic polymer. By spectroscopic quantitative analysis, the colorimetric assay could detect OTA down to 0.009 ng/mL with high selectivity in the presence of other interfering toxins. This study offers a new alternative in visual detection methods that is rapid and sensitive for OTA detection. PMID:26690477

  2. Highly Sensitive Colorimetric Detection of Ochratoxin A by a Label-Free Aptamer and Gold Nanoparticles.

    PubMed

    Luan, Yunxia; Chen, Jiayi; Li, Cheng; Xie, Gang; Fu, Hailong; Ma, Zhihong; Lu, Anxiang

    2015-12-10

    A label-free aptamer-based assay for the highly sensitive and specific detection of Ochratoxin A (OTA) was developed using a cationic polymer and gold nanoparticles (AuNPs). The OTA aptamer was used as a recognition element for the colorimetric detection of OTA based on the aggregation of AuNPs by the cationic polymer. By spectroscopic quantitative analysis, the colorimetric assay could detect OTA down to 0.009 ng/mL with high selectivity in the presence of other interfering toxins. This study offers a new alternative in visual detection methods that is rapid and sensitive for OTA detection.

  3. Highly sensitive and specific colorimetric detection of cancer cells via dual-aptamer target binding strategy.

    PubMed

    Wang, Kun; Fan, Daoqing; Liu, Yaqing; Wang, Erkang

    2015-11-15

    Simple, rapid, sensitive and specific detection of cancer cells is of great importance for early and accurate cancer diagnostics and therapy. By coupling nanotechnology and dual-aptamer target binding strategies, we developed a colorimetric assay for visually detecting cancer cells with high sensitivity and specificity. The nanotechnology including high catalytic activity of PtAuNP and magnetic separation & concentration plays a vital role on the signal amplification and improvement of detection sensitivity. The color change caused by small amount of target cancer cells (10 cells/mL) can be clearly distinguished by naked eyes. The dual-aptamer target binding strategy guarantees the detection specificity that large amount of non-cancer cells and different cancer cells (10(4) cells/mL) cannot cause obvious color change. A detection limit as low as 10 cells/mL with detection linear range from 10 to 10(5) cells/mL was reached according to the experimental detections in phosphate buffer solution as well as serum sample. The developed enzyme-free and cost effective colorimetric assay is simple and no need of instrument while still provides excellent sensitivity, specificity and repeatability, having potential application on point-of-care cancer diagnosis.

  4. Highly sensitive colorimetric detection of lead using maleic acid functionalized gold nanoparticles.

    PubMed

    Ratnarathorn, Nalin; Chailapakul, Orawon; Dungchai, Wijitar

    2015-01-01

    Highly sensitive colorimetric detection for Pb(2+) has been developed using maleic acid (MA) functionalized GNP. The -COOH on MA was used to modify GNP surface whereas the other -COOH functional group have strong affinity to coordination behavior of Pb(2+) allowing the selective formation more than other ions. MA-GNPs solution changed from red to blue color after the addition of Pb(2+) due to nanoparticle aggregation. The different optical absorption and discriminate of particle size between the MA-GNPs solution with and without Pb(2+) were characterized by UV-visible spectroscopy and transmission electron microscopy (TEM), respectively. The color intensity as a function of Pb(2+) concentration gave a linear response in the range of 0.0-10.0 µg L(-1) (R(2)=0.990). The detection limit was found at 0.5 µg L(-1) by naked eye and can be completed the analysis within 15 min. The MA-GNPs aggregated with Pb(2+) showed high selectivity when was compared to other metal ions (As(3+), Ca(2+), Cd(2+), Co(2+), Cu(2+), Fe(3+), Hg(2+), Mg(2+), Mn(2+), Ni(2+), Pb(2+) and Zn(2+)) and anions (Cl(-), NO3(-) and SO4(2-)). Our proposed method was also applied for the determination of Pb(2+) in real drinking water samples from 5 sources. The result of real water samples were not statistically significant different from the standard methods at the 95% confidence level (pair t-test method). Moreover, we evaluated our proposed method for the determination of trace Pb(2+) concentration in real breast milk samples. The recoveries were acceptable and ranged from 101 to 104% for spiked Pb(2+) in real breast milk samples. Thus, MA-GNP colorimetric sensing provides a simple, rapid, sensitive, easy-to-use, inexpensive and low detection limit for the monitoring of Pb(2+).

  5. Label-Free Isothermal Amplification Assay for Specific and Highly Sensitive Colorimetric miRNA Detection

    PubMed Central

    2016-01-01

    We describe a new method for the detection of miRNA in biological samples. This technology is based on the isothermal nicking enzyme amplification reaction and subsequent hybridization of the amplification product with gold nanoparticles and magnetic microparticles (barcode system) to achieve naked-eye colorimetric detection. This platform was used to detect a specific miRNA (miRNA-10b) associated with breast cancer, and attomolar sensitivity was demonstrated. The assay was validated in cell culture lysates from breast cancer cells and in serum from a mouse model of breast cancer. PMID:27713932

  6. A simple highly sensitive and selective aptamer-based colorimetric sensor for environmental toxins microcystin-LR in water samples.

    PubMed

    Li, Xiuyan; Cheng, Ruojie; Shi, Huijie; Tang, Bo; Xiao, Hanshuang; Zhao, Guohua

    2016-03-05

    A simple and highly sensitive aptamer-based colorimetric sensor was developed for selective detection of Microcystin-LR (MC-LR). The aptamer (ABA) was employed as recognition element which could bind MC-LR with high-affinity, while gold nanoparticles (AuNPs) worked as sensing materials whose plasma resonance absorption peaks red shifted upon binding of the targets at a high concentration of sodium chloride. With the addition of MC-LR, the random coil aptamer adsorbed on Au NPs altered into regulated structure to form MC-LR-aptamer complexes and broke away from the surface of Au NPs, leading to the aggregation of AuNPs, and the color converted from red to blue due to the interparticle plasmon coupling. Results showed that our aptamer-based colorimetric sensor exhibited rapid and sensitive detection performance for MC-LR with linear range from 0.5 nM to 7.5 μM and the detection limit reached 0.37 nM. Meanwhile, the pollutants usually coexisting with MC-LR in pollutant water samples had not demonstrated disturbance for detecting of MC-LR. The mechanism was also proposed suggesting that high affinity interaction between aptamer and MC-LR significantly enhanced the sensitivity and selectivity for MC-LR detection. Besides, the established method was utilized in analyzing real water samples and splendid sensitivity and selectivity were obtained as well.

  7. Highly sensitive colorimetric sensor for Hg(2+) detection based on cationic polymer/DNA interaction.

    PubMed

    Zhu, Yingyue; Cai, Yilin; Zhu, Yibo; Zheng, Lixue; Ding, Jianying; Quan, Ying; Wang, Limei; Qi, Bin

    2015-07-15

    The detection of ultralow concentrations of mercury is a currently significant challenge. Here, a novel strategy is proposed: the colorimetric detection of Hg(2+) based on the aggregation of gold nanoparticles (AuNPs) driven by a cationic polymer. In this three-component system, DNA combines electrostatically with phthalic diglycol diacrylate (PDDA) in a solution of AuNPs. In the presence of Hg(2+), thymine (T)-Hg(2+)-T induced hairpin turns are formed in the DNA strands, which then do not interact with PDDA, enabling the freed PDDA to subsequently facilitate aggregation of the AuNPs. Thus, according to the change in color from wine-red to blue-purple upon AuNPs aggregation, a colorimetric sensor is established to detect Hg(2+). Under optimal conditions, the color change is clearly seen with the naked eye. A linear range of 0.25-500nM was obtained by absorption spectroscopy with a detection limit of approximately 0.15nM. Additionally, the proposed method shows high selectivity toward Hg(2+) in the presence of other heavy metal ions. Real sample analysis was evaluated with the use of lake water and the results suggest good potential for practical application.

  8. A colorimetric method for highly sensitive and accurate detection of iodide by finding the critical color in a color change process using silver triangular nanoplates.

    PubMed

    Yang, Xiu-Hua; Ling, Jian; Peng, Jun; Cao, Qiu-E; Ding, Zhong-Tao; Bian, Long-Chun

    2013-10-10

    In this contribution, we demonstrated a novel colorimetric method for highly sensitive and accurate detection of iodide using citrate-stabilized silver triangular nanoplates (silver TNPs). Very lower concentration of iodide can induce an appreciable color change of silver TNPs solution from blue to yellow by fusing of silver TNPs to nanoparticles, as confirmed by UV-vis absorption spectroscopy and transmission electron microscopy (TEM). The principle of this colorimetric assay is not an ordinary colorimetry, but a new colorimetric strategy by finding the critical color in a color change process. With this strategy, 0.1 μM of iodide can be recognized within 30 min by naked-eyes observation, and lower concentration of iodide down to 8.8 nM can be detected using a spectrophotometer. Furthermore, this high sensitive colorimetric assay has good accuracy, stability and reproducibility comparing with other ordinary colorimetry. We believe this new colorimetric method will open up a fresh insight of simple, rapid and reliable detection of iodide and can find its future application in the biochemical analysis or clinical diagnosis.

  9. Highly Sensitive and Fast Response Colorimetric Humidity Sensors Based on Graphene Oxides Film.

    PubMed

    Chi, Hong; Liu, Yan Jun; Wang, FuKe; He, Chaobin

    2015-09-16

    Uniform graphene oxide (GO) film for optical humidity sensing was fabricated by dip-coating technique. The resulting GO thin film shows linear optical shifts in the visible range with increase of humidity in the whole relative humidity range (from dry state to 98%). Moreover, GO films exhibit ultrafast sensing to moisture within 250 ms because of the unique atomic thinness and superpermeability of GO sheets. The humidity sensing mechanism was investigated using XRD and computer simulation. The ultrasensitive humidity colorimetric properties of GOs film may enable many potential applications such as disposable humidity sensors for packaging, health, and environmental monitoring.

  10. Highly sensitive and selective colorimetric detection of cartap residue in agricultural products.

    PubMed

    Liu, Wei; Zhang, Daohong; Tang, Yafan; Wang, Yashan; Yan, Fei; Li, Zhonghong; Wang, Jianlong; Zhou, H Susan

    2012-11-15

    The residue of pesticide has posed a serious threat to human health. Fast, broad-spectrum detection methods are necessary for on-site screening of various types of pesticides. With citrate-coated Au nanoparticles (Au NPs) as colorimetric probes, a visual and spectrophotometric method for rapid assay of cartap, which is one of the most important pesticides in agriculture, is reported for the first time. Based on the color change of Au colloid solution from wine-red to blue resulting from the aggregation of Au NPs, cartap could be detected in the concentration range of 0.05-0.6 mg/kg with a low detection limit of 0.04 mg/kg, which is much lower than the strictest cartap safety requirement of 0.1 mg/kg. Due to the limited research on the rapid detection of cartap based on Au NPs, the performance of the present method was evaluated through aggregation kinetics, interference influence, and sample pretreatment. To further demonstrate the selectivity and applicability of the method, cartap detection is realized in cabbage and tea with excellent analyte concentration recovery. These results demonstrate that the present method provides an easy and effective way to analyze pesticide residue in common products, which is of benefit for the rapid risk evaluation and on-site screening of pesticide residue.

  11. High-sensitive and high-efficient biochemical analysis method using a bionic electronic eye in combination with a smartphone-based colorimetric reader system.

    PubMed

    Kaiqi Su; Quchao Zou; Ning Hu; Ping Wang

    2015-01-01

    Bionic electronic eye (Bionic e-Eye), a developed smartphone-based colorimetric reader system, consists of smartphone or pad (iPhone 4s or iPad 3) as detection instrument and portable accessory as illumination provider, integrating with a wide-angle lens, a piece of lowest-power electro luminescent and a custom-made dark hood. A 96-well microtiter plate (MTP) was positioned on the electro luminescent and Bionic e-Eye captures the detection images by the back camera of smartphone. Being similar to human visual system, the hue, saturation and value (HSV, also called hex cone model) color model was employed in image processing algorithm of Bionic e-Eye. Optimized system dimension was determined by the system steadiness experiment of different photograph distances. Moreover, the commercially available BCA protein assay and CCK8 cell number assay were carried out to evaluate this Bionic e-Eye. Analytical performance of Bionic e-Eye had the better precision, higher sensitivity than microtiter plate reader (MTPR) and previous smartphone-based colorimetric reader for both two assays. Also, Bionic e-Eye using optical image detection had simultaneous and synchronous working mode, while MPTR using machine moving detection had asynchronous working mode in high throughput detection. Therefore, Bionic e-Eye will be an ideal point-of-care (POC) colorimetric detection device in the field of clinical application, industrial quality control, environment monitoring, and food assessment.

  12. G-quadruplex DNAzymes-induced highly selective and sensitive colorimetric sensing of free heme in rat brain.

    PubMed

    Li, Ruimin; Jiang, Qin; Cheng, Hanjun; Zhang, Guoqiang; Zhen, Mingming; Chen, Daiqin; Ge, Jiechao; Mao, Lanqun; Wang, Chunru; Shu, Chunying

    2014-04-21

    Direct selective determination of free heme in the cerebral system is of great significance due to the crucial roles of free heme in physiological and pathological processes. In this work, a G-quadruplex DNAzymes-induced highly sensitive and selective colorimetric sensing of free heme in rat brain is established. Initially, the conformation of an 18-base G-rich DNA sequence, PS2.M (5'-GTGGGTAGGGCGGGTTGG-3'), in the presence of K(+), changes from a random coil to a "parallel" G-quadruplex structure, which can bind free heme in the cerebral system with high affinity through π-π stacking. The resulted heme/G-quadruplex complex exhibits high peroxidase-like activity, which can be used to catalyze the oxidation of colorless ABTS(2-) to green ABTS˙(-) by H2O2. The concentration of heme can be evaluated by the naked eye and determined by UV-vis spectroscopy. The signal output showed a linear relationship for heme within the concentration range from 1 to 120 nM with a detection limit of 0.637 nM. The assay demonstrated here was highly selective and free from the interference of physiologically important species such as dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC), ascorbate acid (AA), cysteine, uric acid (UA), glucose and lactate in the cerebral system. The basal dialysate level of free heme in the microdialysate from the striatum of adult male Sprague-Dawley rats was determined to be 32.8 ± 19.5 nM (n = 3). The analytic protocol possesses many advantages, including theoretical simplicity, low-cost technical and instrumental demands, and responsible detection of heme in rat brain microdialysate.

  13. Visual and highly sensitive detection of cancer cells by a colorimetric aptasensor based on cell-triggered cyclic enzymatic signal amplification.

    PubMed

    Zhang, Xianxia; Xiao, Kunyi; Cheng, Liwei; Chen, Hui; Liu, Baohong; Zhang, Song; Kong, Jilie

    2014-06-03

    Rapid and efficient detection of cancer cells at their earliest stages is one of the central challenges in cancer diagnostics. We developed a simple, cost-effective, and highly sensitive colorimetric method for visually detecting rare cancer cells based on cell-triggered cyclic enzymatic signal amplification (CTCESA). In the absence of target cells, hairpin aptamer probes (HAPs) and linker DNAs stably coexist in solution, and the linker DNA assembles DNA-AuNPs, producing a purple solution. In the presence of target cells, the specific binding of HAPs to the target cells triggers a conformational switch that results in linker DNA hybridization and cleavage by nicking endonuclease-strand scission cycles. Consequently, the cleaved fragments of linker DNA can no longer assemble into DNA-AuNPs, resulting in a red color. UV-vis spectrometry and photograph analyses demonstrated that this CTCESA-based method exhibited selective and sensitive colorimetric responses to the presence of target CCRF-CEM cells, which could be detected by the naked eye. The linear response for CCRF-CEM cells in a concentration range from 10(2) to 10(4) cells was obtained with a detection limit of 40 cells, which is approximately 20 times lower than the detection limit of normal AuNP-based methods without amplification. Given the high specificity and sensitivity of CTCESA, this colorimetric method provides a sensitive, label-free, and cost-effective approach for early cancer diagnosis and point-to-care applications.

  14. Luminol functionalized gold nanoparticles as colorimetric and chemiluminescent probes for visual, label free, highly sensitive and selective detection of minocycline

    NASA Astrophysics Data System (ADS)

    He, Yi; Peng, Rufang

    2014-11-01

    In this work, luminol functionalized gold nanoparticles (LuAuNPs) were used as colorimetric and chemiluminescent probes for visual, label free, sensitive and selective detection of minocycline (MC). The LuAuNPs were prepared by simple one-pot reduction of HAuCl4 with luminol, which exhibited a good chemiluminescence (CL) activity owing to the presence of luminol molecules on their surface and surface plasmon resonance absorption. In the absence of MC, the color of LuAuNPs was wine red and their size was relatively small (˜25 nm), which could react with silver nitrate, producing a strong CL emission. Upon the addition of MC at acidic buffer solutions, the electrostatic interaction between positively charged MC and negatively charged LuAuNPs caused the aggregation of LuAuNPs, generating a purple or blue color. Simultaneously, the aggregated LuAuNPs did not effectively react with silver nitrate, producing a weak CL emission. The signal change was linearly dependent on the logarithm of MC concentration in the range from 30 ng to 1.0 μg for colorimetric detection and from 10 ng to 1.0 μg for CL detection. With colorimetry, a detection limit of 22 ng was achieved, while the detection limit for CL detection modality was 9.7 ng.

  15. Luminol functionalized gold nanoparticles as colorimetric and chemiluminescent probes for visual, label free, highly sensitive and selective detection of minocycline.

    PubMed

    He, Yi; Peng, Rufang

    2014-11-14

    In this work, luminol functionalized gold nanoparticles (LuAuNPs) were used as colorimetric and chemiluminescent probes for visual, label free, sensitive and selective detection of minocycline (MC). The LuAuNPs were prepared by simple one-pot reduction of HAuCl₄ with luminol, which exhibited a good chemiluminescence (CL) activity owing to the presence of luminol molecules on their surface and surface plasmon resonance absorption. In the absence of MC, the color of LuAuNPs was wine red and their size was relatively small (∼25 nm), which could react with silver nitrate, producing a strong CL emission. Upon the addition of MC at acidic buffer solutions, the electrostatic interaction between positively charged MC and negatively charged LuAuNPs caused the aggregation of LuAuNPs, generating a purple or blue color. Simultaneously, the aggregated LuAuNPs did not effectively react with silver nitrate, producing a weak CL emission. The signal change was linearly dependent on the logarithm of MC concentration in the range from 30 ng to 1.0 μg for colorimetric detection and from 10 ng to 1.0 μg for CL detection. With colorimetry, a detection limit of 22 ng was achieved, while the detection limit for CL detection modality was 9.7 ng.

  16. Highly sensitive colorimetric detection of glucose in a serum based on DNA-embeded Au@Ag core-shell nanoparticles

    NASA Astrophysics Data System (ADS)

    Kang, Fei; Hou, Xiangshu; Xu, Kun

    2015-10-01

    Glucose is a key energy substance in diverse biology and closely related to the life activities of the organism. To develop a simple and sensitive method for glucose detection is extremely urgent but still remains a key challenge. Herein, we report a colorimetric glucose sensor in a homogeneous system based on DNA-embedded core-shell Au@Ag nanoparticles. In this assay, a glucose substrate was first catalytically oxidized by glucose oxidase to produce H2O2 which would further oxidize and gradually etch the outer silver shell of Au@Ag nanoparticles. Afterwards, the solution color changed from yellow to red and the surface plasmon resonance (SPR) band of Au@Ag nanoparticles declined and red-shifted from 430 to 516 nm. Compared with previous silver-based glucose colorimetric detection strategies, the distinctive SPR band change is superior to the color variation, which is critical to the high sensitivity of this assay. Benefiting from the outstanding optical property, robust stability and well-dispersion of the core-shell Au@AgNPs hybrid, this colorimetric assay obtained a detection limit of glucose as low as 10 nM, which is at least a 10-fold improvement over other AgNPs-based procedures. Moreover, this optical biosensor was successfully employed to the determination of glucose in fetal bovine serum.

  17. MicroRNA-triggered, cascaded and catalytic self-assembly of functional ``DNAzyme ferris wheel'' nanostructures for highly sensitive colorimetric detection of cancer cells

    NASA Astrophysics Data System (ADS)

    Zhou, Wenjiao; Liang, Wenbin; Li, Xin; Chai, Yaqin; Yuan, Ruo; Xiang, Yun

    2015-05-01

    The construction of DNA nanostructures with various sizes and shapes has significantly advanced during the past three decades, yet the application of these DNA nanostructures for solving real problems is still in the early stage. On the basis of microRNA-triggered, catalytic self-assembly formation of the functional ``DNAzyme ferris wheel'' nanostructures, we show here a new signal amplification platform for highly sensitive, label-free and non-enzyme colorimetric detection of a small number of human prostate cancer cells. The microRNA (miR-141), which is catalytically recycled and reused, triggers isothermal self-assembly of a pre-designed, G-quadruplex sequence containing hairpin DNAs into ``DNAzyme ferris wheel''-like nanostructures (in association with hemin) with horseradish peroxidase mimicking activity. These DNAzyme nanostructures catalyze an intensified color transition of the probe solution for highly sensitive detection of miR-141 down to 0.5 pM with the naked eye, and the monitoring of as low as 283 human prostate cancer cells can also, theoretically, be achieved in a colorimetric approach. The work demonstrated here thus offers new opportunities for the construction of functional DNA nanostructures and for the application of these DNA nanostructures as an effective signal amplification means in the sensitive detection of nucleic acid biomarkers.

  18. Colorimetric and Phosphorimetric Dual-Signaling Strategy Mediated by Inner Filter Effect for Highly Sensitive Assay of Organophosphorus Pesticides.

    PubMed

    Zhang, Rong; Li, Na; Sun, Junyong; Gao, Feng

    2015-10-14

    We describe here a colorimetric and phosphorimetric dual-signaling strategy for sensitive assay of organophosphorus pesticides (OPPs). The principle for assay depends on the phenomenon that the phosphorescence of Mn-ZnS quantum dots (QDs) can be dramatically quenched by Au nanoparticles (AuNPs) through the inner filter effect (IFE) and the activity of acetylcholinesterase (AChE), an enzyme that catalytically hydrolyzes acetylthiocholine to thiocholine that can be inhibited by OPPs. By virtue of the variations of absorbance and phosphorescence of the analytical system, a dual-readout assay for OPPs has been proposed. The limits of detection for different OPPs including paraoxon, parathion, omethoate, and dimethyl dichlorovinyl phosphate (DDVP) are found to be 0.29, 0.59, 0.67, and 0.44 ng/L, respectively. The proposed assay was allowed to detect pesticides in real spiked samples and authentic contaminated apples with satisfactory results, suggesting its potential applications to detect pesticides in complicated samples.

  19. High sensitivity, loop-mediated isothermal amplification combined with colorimetric gold-nanoparticle probes for visual detection of high risk human papillomavirus genotypes 16 and 18.

    PubMed

    Kumvongpin, Ratchanida; Jearanaikool, Patcharee; Wilailuckana, Chotechana; Sae-Ung, Nattaya; Prasongdee, Prinya; Daduang, Sakda; Wongsena, Metee; Boonsiri, Patcharee; Kiatpathomchai, Wansika; Swangvaree, Sukumarn Sanersak; Sandee, Alisa; Daduang, Jureerut

    2016-08-01

    High-risk human papillomavirus (HR-HPV) causes cervical cancer. HPV16 and HPV18 are the most prevalent strains of the virus reported in women worldwide. Loop-mediated isothermal amplification (LAMP) is an alternative method for DNA detection under isothermal conditions. However, it results in a turbid amplified product which is not easily detected by the naked eye. This study aimed to develop an improved technique by using gold nanoparticles (AuNPs) attached to a single-stranded DNA probe for the detection of HPV16 and HPV18. Detection of the LAMP product by AuNP color change was compared with detection by visual turbidity. The optimal conditions for this new LAMP-AuNP assay were an incubation time of 20min and a temperature of 65°C. After LAMP amplification was complete, its products were hybridized with the AuNP probe for 5min and then detected by the addition of magnesium salt. The color changed from red to blue as a result of aggregation of the AuNP probe under high ionic strength conditions produced by the addition of the salt. The sensitivity of the LAMP-AuNP assay was greater than the LAMP turbidity assay by up to 10-fold for both HPV genotypes. The LAMP-AuNP assay showed higher sensitivity and ease of visualization than did the LAMP turbidity for the detection of HPV16 and HPV18. Additionally, AuNP-HPV16 and AuNP-HPV18 probes were stable for over 1year. The combination of LAMP and the AuNP-probe colorimetric assay offers a simple, rapid and highly sensitive alternative diagnostic tool for the detection of HPV16 and HPV18 in district hospitals or field studies.

  20. Sensitiveness of the colorimetric estimation of titanium

    USGS Publications Warehouse

    Wells, R.C.

    1911-01-01

    The accuracy of the colorimetric estimation of titanium is practically constant over concentrations ranging from the strongest down to those containing about 1.5 mg. TiO2 in 100 cc. The change in concentration required to produce a perceptible difference in intensity between two solutions, at favorable concentrations, was found to be about 6.5 per cent, which does not differ much from the results of others with chromium and copper solutions. With suitable precautions, such as comparing by substitution and taking the mean of several settings or of the two perceptibly different extremes, the accuracy of the colorimetric comparisons appears to be about 2 per cent.

  1. Highly selective and sensitive paper-based colorimetric sensor using thiosulfate catalytic etching of silver nanoplates for trace determination of copper ions.

    PubMed

    Chaiyo, Sudkate; Siangproh, Weena; Apilux, Amara; Chailapakul, Orawon

    2015-03-25

    A novel, highly selective and sensitive paper-based colorimetric sensor for trace determination of copper (Cu(2+)) ions was developed. The measurement is based on the catalytic etching of silver nanoplates (AgNPls) by thiosulfate (S2O3(2-)). Upon the addition of Cu(2+) to the ammonium buffer at pH 11, the absorption peak intensity of AuNPls/S2O3(2-) at 522 nm decreased and the pinkish violet AuNPls became clear in color as visible to the naked eye. This assay provides highly sensitive and selective detection of Cu(2+) over other metal ions (K(+), Cr(3+), Cd(2+), Zn(2+), As(3+), Mn(2+), Co(2+), Pb(2+), Al(3+), Ni(2+), Fe(3+), Mg(2+), Hg(2+) and Bi(3+)). A paper-based colorimetric sensor was then developed for the simple and rapid determination of Cu(2+) using the catalytic etching of AgNPls. Under optimized conditions, the modified AgNPls coated at the test zone of the devices immediately changes in color in the presence of Cu(2+). The limit of detection (LOD) was found to be 1.0 ng mL(-1) by visual detection. For semi-quantitative measurement with image processing, the method detected Cu(2+) in the range of 0.5-200 ng mL(-1)(R(2)=0.9974) with an LOD of 0.3 ng mL(-1). The proposed method was successfully applied to detect Cu(2+) in the wide range of real samples including water, food, and blood. The results were in good agreement according to a paired t-test with results from inductively coupled plasma-optical emission spectrometry (ICP-OES).

  2. Highly-sensitive colorimetric detection of H2O2 based on the Pt@Te nanorods

    NASA Astrophysics Data System (ADS)

    Wan, Li-Juan; Huang, Xing-Jiu; Liu, Jin-Huai; Zhang, Zhong-Xiang; Hou, Shi-Li; Liu, Wei-Jing

    2015-05-01

    Te nanorods (NRs) were prepared from TeO2 in the presence of hydrazine hydrate without using any surfactants under ambient conditions. Te NRs were then used as sacrificial templates to prepare Pt@Te NRs by spontaneous redox galvanic replacement between Te and Pt ions. The as-synthesized Pt@Te NRs exhibit a strong catalytic activity for the colorimetric detection of H2O2 using 2, 2‧-azino-bis (3-ethylbenzo-thiazoline-6-sulfonic acid) diammonium salt (ABTS) as an indicator.

  3. Hydrophilic-Hydrophobic Patterned Molecularly Imprinted Photonic Crystal Sensors for High-Sensitive Colorimetric Detection of Tetracycline.

    PubMed

    Hou, Jue; Zhang, Huacheng; Yang, Qiang; Li, Mingzhu; Jiang, Lei; Song, Yanlin

    2015-06-01

    A hydrophilic-hydrophobic patterned molecularly imprinted (MIP) photonic crystal (PC) sensor is fabricated for highly sensitive tetracycline detection. The relationship between the tetracycline concentration, its corresponding color of the sensor, and the diameter of MIP-PC dot is found using a fan-shaped color card. This work provides a new strategy to design the sensors with tunable detection ranges for practical applications.

  4. Highly sensitive colorimetric and fluorescent sensor for cyanazine based on the inner filter effect of gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Dong, Liang; Hou, Changjun; Yang, Mei; Fa, Huanbao; Wu, Huixiang; Shen, Caihong; Huo, Danqun

    2016-06-01

    Cyanazine residue poses a great threat to human health and its derivatives would remain in soils, natural waters, and other environmental domains for a long time. Herein, a simple, rapid, and ultra-sensitive analytical method for the determination of cyanazine (CZ) based on inner filter effect (IFE) of Au nanoparticles (AuNPs) on the fluorescence of CdTe quantum dots (QDs) is first described in this study. With the presence of citrate-stabilized AuNPs, the fluorescence of GSH-capped CdTe QDs was remarkably quenched by AuNPs via IFE. The fluorescence of the AuNP-CdTe QD system was recovered upon addition of CZ. CZ can adsorb on to the surface of AuNPs due to its cyano group that has good affinity with gold, which could induce the aggregation of AuNPs accompanying color change from red to blue. Thus, the IFE of AuNPs on CdTe QDs was weakened, and the fluorescence intensity of CdTe QDs was recovered accordingly. A good linear correlation for detection of CZ was exhibited from 0.05 to 9 μM, and the detection limit reached 0.1568 μM, which was much lower than the safety limit required by the USA, the UK, and China. In order to probe into the selectivity of AuNPs towards CZ over other pesticides, various frequently used pesticides were mixed with AuNPs. AuNP composite solution shows good selectivity towards CZ among other pesticides. This method was successfully carried out for the assessment of CZ in real samples with satisfactory results, which revealed many advantages such as high sensitivity, low cost, and non-time-consuming compared with traditional methods.

  5. A significant enhancement of color transition from an on-off type achromatic colorimetric nanosensor for highly sensitive multi-analyte detection with the naked eye.

    PubMed

    Heo, Jun Hyuk; Yi, Gyu Sung; Lee, Byoung Sang; Cho, Hui Hun; Lee, Jin Woong; Lee, Jung Heon

    2016-11-03

    Here, we report the development of an achromatic nanoparticle-based colorimetric sensor (achromatic nanosensor) with an on-off type color change that significantly enhances the color transition and increases the sensitivity of the sensor for naked-eye inspection. The achromatic nanosensor was prepared via a modified CMYK (CRYK) subtractive color model by combining DNA-functionalized gold nanoparticles (AuNPs-DNA), silver nanoparticles (AgNPs-DNA), and gold nanorods (AuNRs-DNA). The initially black-colored achromatic nanosensor not only allowed multiplexed detection by generating target-specific diverse color changes, but also improved the recognition of color changes by the naked eye. Thus, this on-off type color change enabled analysis near the limit of detection (LOD) with the naked eye. In addition, we developed a new image processing method adapted for this achromatic sensor. By quantifying the saturation value of the color images of the achromatic sensor, we could significantly amplify the color signal of the samples, which is difficult to achieve with general colorimetric sensors. The practical application of this achromatic nanosensor for biomarker detection was demonstrated with thrombin and platelet-derived growth factor (PDGF) in human blood plasma. These results provide a new sensing platform that is applicable to most NP-based colorimetric sensing systems for a wide range of applications, including biomolecular diagnosis, chemical pollutant sensing, environmental monitoring, etc.

  6. Polymeric assemblies for sensitive colorimetric assays

    DOEpatents

    Charych, Deborah

    2000-01-01

    The presently claimed invention relates to polymeric assemblies which visibly change color in the presence of analyte. In particular, the presently claimed invention relates to liposomes comprising a plurality of lipid monomers, which comprises a polymerizable group, a hydrophilic head group and a hydrophobic tail group, and one or more ligands. Overall carbon chain length, and polymerizable group positioning on the monomer influence color change sensitivity to analyte concentrations.

  7. Efficient ensemble system based on the copper binding motif for highly sensitive and selective detection of cyanide ions in 100% aqueous solutions by fluorescent and colorimetric changes.

    PubMed

    Jung, Kwan Ho; Lee, Keun-Hyeung

    2015-09-15

    A peptide-based ensemble for the detection of cyanide ions in 100% aqueous solutions was designed on the basis of the copper binding motif. 7-Nitro-2,1,3-benzoxadiazole-labeled tripeptide (NBD-SSH, NBD-SerSerHis) formed the ensemble with Cu(2+), leading to a change in the color of the solution from yellow to orange and a complete decrease of fluorescence emission. The ensemble (NBD-SSH-Cu(2+)) sensitively and selectively detected a low concentration of cyanide ions in 100% aqueous solutions by a colorimetric change as well as a fluorescent change. The addition of cyanide ions instantly removed Cu(2+) from the ensemble (NBD-SSH-Cu(2+)) in 100% aqueous solutions, resulting in a color change of the solution from orange to yellow and a "turn-on" fluorescent response. The detection limits for cyanide ions were lower than the maximum allowable level of cyanide ions in drinking water set by the World Health Organization. The peptide-based ensemble system is expected to be a potential and practical way for the detection of submicromolar concentrations of cyanide ions in 100% aqueous solutions.

  8. Colorimetric Strategy for Highly Sensitive and Selective Simultaneous Detection of Histidine and Cysteine Based on G-Quadruplex-Cu(II) Metalloenzyme.

    PubMed

    Wu, Changtong; Fan, Daoqing; Zhou, Chunyang; Liu, Yaqing; Wang, Erkang

    2016-03-01

    In this present work, we proposed a colorimetric strategy for simultaneous detection of histidine and cysteine based on G-quadruplex-Cu(II) metalloenzyme for the first time. Because of the adding of histidine or cysteine, the formation of G-quadruplex-Cu(II) metalloenzyme will be disturbed, thus the catalytic activity to TMB-H2O2 reaction is inversely proportional to the concentration of histidine or cysteine. With this strategy, the limit of detection in experimental measurement for histidine and cysteine is 10 nM and 5 nM, respectively, which are both lower than previous colorimetric arrays. With the help of NEM, cysteine is alkylated and the reaction between Cu(2+) is inhibited, so the selectivity can also be guaranteed. The cost is quite low since the developed array is label free and enzyme free by using low-cost DNA and Cu(2+). More importantly, the colorimetric detection operation is very simple without any further modification process.

  9. Improving sensitivity of gold nanoparticle based fluorescence quenching and colorimetric aptasensor by using water resuspended gold nanoparticle.

    PubMed

    Liu, Jinchuan; Guan, Zheng; Lv, Zhenzhen; Jiang, Xiaoling; Yang, Shuming; Chen, Ailiang

    2014-02-15

    Gold nanoparticles (AuNPs) based fluorescence quenching or colorimetric aptasensor have been developed for many analytes recently largely because of the ease of detection, high sensitivity, and potential for high-throughput analysis. However, the effects of remnant non-AuNPs components in the colloid gold solution on these assays performance remain unclear. For the first time, we demonstrated that the remnant sodium citrate and the reaction products of three acids play counteractive roles in AuNPs based fluorescence quenching and colorimetric aptasensor in three ways in this study. First, the remnant sodium citrate in the colloid gold solution could increase the fluorescence intensity of FAM labeled on the aptamer that reduce the efficiency of AuNPs fluorescent quenching. Second, the reaction products of citric acid, HCl and ketoglutaric acid reduce the fluorescence recovery by quenching the fluorescence of FAM labeled on the aptamer dissociated from the surface of AuNPs upon addition of target. Lastly, the reaction products of three acids reduce the pH value of the colloid gold solution that reduce the sensitivity of AuNPs based colorimetric aptasensor by increasing the adsorption of aptamer to surface of AuNPs. With sulfadimethoxine and thrombin as model analytes, we found that water resuspended AuNPs can significantly increase the sensitivity by more than 10-fold for AuNPs based fluorescence quenching aptasensor. In the AuNPs based colorimetric aptasensor for sulfadimethoxine using the water resuspended AuNPs, the sensitivity also was increased by 10-fold compared with that of original AuNPs. The findings in this study provide theoretical guidance for further improving AuNPs based fluorescent quenching and colorimetric aptasensor by adjusting the composition of AuNPs solution.

  10. Copper chromogenic reaction based colorimetric immunoassay for rapid and sensitive detection of a tumor biomarker.

    PubMed

    Li, Bo; Lai, Guosong; Zhang, Haili; Hu, Shengli; Yu, Aimin

    2017-04-22

    A new colorimetric immunoassay method was developed for the rapid and sensitive detection of a tumor biomarker of carcinoembryonic antigen (CEA) by combination of a magnetic bead (MB)-based sandwich immunoassay and a copper chromogenic reaction. The magnetic immunoassay platform was constructed through the covalent immobilization of the capture antibody on the surface of carboxylated magnetic beads. After immuno-recognition of CEA, signal antibody-functionalized copper oxide nanoparticle (CuO NP) probes were applied for sandwich immunoreaction to form an immunocomplex. The CuO NP labels quantitatively captured onto the immunocomplex were then dissolved in acid solution to release high-content copper ions. Based on the coordination of these ions with the newly synthesized chromogenic agent of 1,2-diphenyl-2-(2-(pyridin-2-yl)hydrazono)ethanone, a red complex was produced for the colorimetric signal readout, resulting in the successful construction of a sensitive immunoassay method for CEA detection. Under the optimum conditions, this method showed a wide linear range over three orders of magnitude and a low detection limit of 26 pg/mL. Besides, this method showed excellent performance with low cost, rapid and convenient operation as well as satisfactory reproducibility, stability and accuracy, thus providing great potentials for practical applications.

  11. Sensitive and selective colorimetric assay of alkaline phosphatase activity with Cu(II)-phenanthroline complex.

    PubMed

    Hu, Qiong; He, Minhui; Mei, Yaqi; Feng, Wenjie; Jing, Su; Kong, Jinming; Zhang, Xueji

    2017-01-15

    Alkaline phosphatase (ALP) plays a vital role in dephosphorylation- and phosphorylation-related cellular regulation and signaling processes. Accordingly, the development of efficient methods for ALP activity assay is of significant importance in clinical diagnosis. In this work, a simple and practical method is reported for the first time for the sensitive and selective colorimetric assay of ALP activity by exploiting a water-soluble Cu(II)-phenanthroline complex as the probe, on the basis of the distinctive metal-to-ligand charge-transfer (MLCT) properties. This method is simply built on a two-step chromogenic reaction: the enzymatic hydrolysis of the substrate ascorbic acid 2-phosphate to ascorbic acid (AA), followed by the reduction of the colorimetric probe Cu(BPDS)2(2-) (BPDS=bathophenanthroline disulfonate) by AA to its cuprous form. The latter process triggers a turn-on spectral absorption at 424nm and a striking color change of the solution from colorless to blackish-green. Needless of complicated protocols and instrumentation, this method allows a sensitive readout of ALP activity within a wide linear range of 0-200mUmL(-)(1), with a detection limit down to 1.25mUmL(-1). Results also reveal that it is highly selective and holds great potential in ALP inhibitor efficiency evaluation. In addition, quantitative analysis of ALP activity in spiked serum samples has been realized successfully in the linear range of 0-200mUmL(-1), with a detection limit of 1.75mUmL(-1). Advantages of simplicity, wide linear range, high sensitivity and selectivity, low cost, and little background interference render this method great potential in practical applications.

  12. Eco-friendly plasmonic sensors: using the photothermal effect to prepare metal nanoparticle-containing test papers for highly sensitive colorimetric detection.

    PubMed

    Tseng, Shao-Chin; Yu, Chen-Chieh; Wan, Dehui; Chen, Hsuen-Li; Wang, Lon Alex; Wu, Ming-Chung; Su, Wei-Fang; Han, Hsieh-Cheng; Chen, Li-Chyong

    2012-06-05

    Convenient, rapid, and accurate detection of chemical and biomolecules would be a great benefit to medical, pharmaceutical, and environmental sciences. Many chemical and biosensors based on metal nanoparticles (NPs) have been developed. However, as a result of the inconvenience and complexity of most of the current preparation techniques, surface plasmon-based test papers are not as common as, for example, litmus paper, which finds daily use. In this paper, we propose a convenient and practical technique, based on the photothermal effect, to fabricate the plasmonic test paper. This technique is superior to other reported methods for its rapid fabrication time (a few seconds), large-area throughput, selectivity in the positioning of the NPs, and the capability of preparing NP arrays in high density on various paper substrates. In addition to their low cost, portability, flexibility, and biodegradability, plasmonic test paper can be burned after detecting contagious biomolecules, making them safe and eco-friendly.

  13. Doped colorimetric assay liposomes

    DOEpatents

    Charych, Deborah; Stevens, Raymond C.

    2001-01-01

    The present invention provides compositions comprising colorimetric assay liposomes. The present invention also provides methods for producing colorimetric liposomes and calorimetric liposome assay systems. In preferred embodiments, these calorimetric liposome systems provide high levels of sensitivity through the use of dopant molecules. As these dopants allow the controlled destabilization of the liposome structure, upon exposure of the doped liposomes to analyte(s) of interest, the indicator color change is facilitated and more easily recognized.

  14. Highly Uniform Gold Nanobipyramids for Ultrasensitive Colorimetric Detection of Influenza Virus.

    PubMed

    Xu, Shaohua; Ouyang, Wenjun; Xie, Peisi; Lin, Yi; Qiu, Bin; Lin, Zhenyu; Chen, Guonan; Guo, Longhua

    2017-02-07

    Gold nanoparticles (AuNPs) have been frequently utilized for the construction of diverse colorimetric biosensors. Normally, AuNPs with sharp edges could have better sensitivity. However, the poor monodipersity of AuNPs with sharp edges seriously confines their utility for colorimetric biosensing. Herein, we demonstrate the utility of highly uniform gold nanobipyramids (Au NBPs) for ultrasensitive colorimetric detection of H5N1 virus. The proposed method is based on the fact that alkaline phosphatase (ALP) could catalyze the decomposition of 4-aminophenyl phosphate (4-APP) to generate 4-aminophenol (4-AP), which would then reduce silver nitrate to metal silver and then deposited on Au NBPs. The metal silver shell coated on the Au NBPs changed the refractive index of gold and thus resulted in a blue shift of longitudinal localized surface plasmon resonance (LSPR) and accompanied a vivid color change. This method exhibited a higher sensitivity than that of other Au NPs such as gold nanorods due to the high-index-faceted on the tips of the Au NBPs. This method was used to detect the activity of ALP. It exhibited a linear range of 0.1-5 mU/mL with a limit of detection (LOD) of 0.086 mU/mL. Finally, the proposed method was used in immunoassay to detect H5N1 virus. The results showed that the corresponding linear range for the detection of H5N1 virus antigen was 0.001-2.5 ng/mL, and the LOD was determined to be 1 pg/mL, which is more sensitive than those in most of the colorimetric biosensors reported previously.

  15. High-resolution colorimetric imaging of paintings

    NASA Astrophysics Data System (ADS)

    Martinez, Kirk; Cupitt, John; Saunders, David R.

    1993-05-01

    With the aim of providing a digital electronic replacement for conventional photography of paintings, a scanner has been constructed based on a 3000 X 2300 pel resolution camera which is moved precisely over a 1 meter square area. Successive patches are assembled to form a mosaic which covers the whole area at c. 20 pels/mm resolution, which is sufficient to resolve the surface textures, particularly craquelure. To provide high color accuracy, a set of seven broad-band interference filters are used to cover the visible spectrum. A calibration procedure based upon a least-mean-squares fit to the color of patches from a Macbeth Colorchecker chart yields an average color accuracy of better than 3 units in the CMC uniform color space. This work was mainly carried out as part of the VASARI project funded by the European Commission's ESPRIT program, involving companies and galleries from around Europe. The system is being used to record images for conservation research, for archival purposes and to assist in computer-aided learning in the field of art history. The paper will describe the overall system design, including the selection of the various hardware components and the design of controlling software. The theoretical basis for the color calibration methodology is described as well as the software for its practical implementation. The mosaic assembly procedure and some of the associated image processing routines developed are described. Preliminary results from the research will be presented.

  16. Folic acid functionalized silver nanoparticles with sensitivity and selectivity colorimetric and fluorescent detection for Hg2+ and efficient catalysis

    NASA Astrophysics Data System (ADS)

    Su, Dongyue; Yang, Xin; Xia, Qingdong; Zhang, Qi; Chai, Fang; Wang, Chungang; Qu, Fengyu

    2014-09-01

    In this research, folic acid functionalized silver nanoparticles (FA-AgNPs) were selected as a colorimetric and a ‘turn on’ fluorescent sensor for detecting Hg2+. After being added into Hg2+, AgNPs can emit stable fluorescence at 440 nm when the excitation wavelength is selected at 275 nm. The absorbance and fluorescence of the FA-AgNPs could reflect the concentration of the Hg2+ ions. Thus, we developed a simple, sensitive analytical method to detect Hg2+ based on the colorimetric and fluorescence enhancement of FA-AgNPs. The sensor exhibits two linear response ranges between absorbance and fluorescence intensity with Hg2+ concentration, respectively. Meanwhile, a detection limit of 1 nM is estimated based on the linear relationship between responses with a concentration of Hg2+. The high specificity of Hg2+ with FA-AgNPs interactions provided the excellent selectivity towards detecting Hg2+ over other metal ions (Pb2+, Mg2+, Zn2+, Ni2+, Cu2+, Co2+, Ca2+, Mn2+, Fe2+, Cd2+, Ba2+, Cr6+ and Cr3+). This will provide a simple, effective and multifunctional colorimetric and fluorescent sensor for on-site and real-time Hg2+ ion detection. The proposed method can be applied to the analysis of trace Hg2+ in lake water. Additionally, the FA-AgNPs can be used as efficient catalyst for the reduction of 4-nitrophenol and potassium hexacyanoferrate (III).

  17. [Comparative research into sensitivity and specificity of immune-enzyme analysis with chemiluminescence and colorimetric detection for detecting antigens and antibodies to avian influenza viruses and newcastle disease].

    PubMed

    Vitkova, O N; Kapustina, T P; Mikhailova, V V; Safonov, G A; Vlasova, N N; Belousova, R V

    2015-01-01

    The goal of this work was to demonstrate the results of the development of the enzyme-linked immunosorbent tests with chemiluminescence detection and colorimetric detection of specific viral antigens and antibodies for identifying the avian influenza and the Newcastle disease viruses: high sensitivity and specificity of the immuno- chemiluminescence assay, which are 10-50 times higher than those of the ELISA colorimetric method. The high effectiveness of the results and the automation of the process of laboratory testing (using a luminometer) allow these methods to be recommended for including in primary screening tests for these infectious diseases.

  18. A fast, sensitive and easy colorimetric assay for chitinase and cellulase activity detection

    PubMed Central

    2014-01-01

    Background Most of the current colorimetric methods for detection of chitinase or cellulase activities on the insoluble natural polymers chitin and cellulose depend on a chemical redox reaction. The reaction involves the reducing ends of the hydrolytic products. The Schales’ procedure and the 3,5-dinitrosalicylic acid (DNS) method are two examples that are commonly used. However, these methods lack sensitivity and present practical difficulties of usage in high-throughput screening assays as they require boiling or heating steps for color development. Results We report a novel method for colorimetric detection of chitinase and cellulase activity. The assay is based on the use of two oxidases: wild-type chito-oligosaccharide oxidase, ChitO, and a mutant thereof, ChitO-Q268R. ChitO was used for chitinase, while ChitO-Q268R was used for cellulase activity detection. These oxidases release hydrogen peroxide upon the oxidation of chitinase- or cellulase-produced hydrolytic products. The hydrogen peroxide produced can be monitored using a second enzyme, horseradish peroxidase (HRP), and a chromogenic peroxidase substrate. The developed ChitO-based assay can detect chitinase activity as low as 10 μU within 15 minutes of assay time. Similarly, cellulase activity can be detected in the range of 6 to 375 mU. A linear response was observed when applying the ChitO-based assay for detecting individual chito-oligosaccharides and cello-oligosaccharides. The detection limits for these compounds ranged from 5 to 25 μM. In contrast to the other commonly used methods, the Schales’ procedure and the DNS method, no boiling or heating is needed in the ChitO-based assays. The method was also evaluated for detecting hydrolytic activity on biomass-derived substrates, that is, wheat straw as a source of cellulose and shrimp shells as a source of chitin. Conclusion The ChitO-based assay has clear advantages for the detection of chitinase and cellulase activity over the conventional

  19. Colorimetric and luminescent bifunctional iridium(III) complexes for the sensitive recognition of cyanide ions

    NASA Astrophysics Data System (ADS)

    Chen, Xiudan; Wang, Huili; Li, Jing; Hu, Wenqin; Li, Mei-Jin

    2017-02-01

    Two new cyclometalated iridium(III) complexes [(ppy)2Irppz]Cl (1) and [(ppy)2Irbppz]Cl (2) (where ppy = 2-phenylpyridine, ppz = 4,7-phenanthrolino-5,6:5,6-pyrazine, bppz = 2.3-di-2-pyridylpyrazine), were designed and synthesized. The structure of [(ppy)2Irppz]Cl was determined by single crystal X-ray diffraction. Their photophysical properties were also studied. This kind of complexes could coordinate with Cu2 +, the photoluminescence (PL) of the complex was quenched, and the color changed from orange-red to green. The forming M-Cu (M: complexes 1 and 2) ensemble could be further utilized as a colorimetric and emission "turn-on" bifunctional detection for CN-, especially for complex 1-Cu2 + showed a high sensitivity toward CN- with a limit of diction is 97 nM. Importantly, this kind of iridium(III) complexes shows a unique recognition of cyanide ions over other anions which makes it an eligible sensing probe for cyanide ions.

  20. Colorimetric qualification of shear sensitive liquid crystal coatings

    NASA Technical Reports Server (NTRS)

    Muratore, Joseph J., Jr.

    1993-01-01

    The work that has been done to date on the Shear Sensitive Liquid Crystal Project demonstrated that cholesteric liquid crystal coatings respond to both the direction and magnitude of a shearing force. The response of the coating is to selectively scatter incident white light into a spectrum of colors. Discernible color changes at a fixed angle of observation and illumination are the result of an applied shear stress. The intention was to be able to convert these observable color patterns from a flow visualization technique into a quantitative tool. One of the earlier intentions was to be able to use liquid crystals in dynamic flow fields. This was assumed possible because liquid crystals had made it possible to visualize transients in surface shear forces. Although the transients were visualized by color changes to an order one micro second, the time response of a coating to align to a shearing force is dependent on the magnitude of the change between its initial and final states. Unfortunately, the response is not instantaneous. It is for this reason any future attempt at quantifying the magnitude and directions of a shearing force are limited to surface shear stress vector fields in three dimensional steady state flows. This limitation does not significantly detract from the utility of liquid crystal coatings. The measurement of skin friction in the study of transition on wings, prediction of drag forces, performance assessment, and the investigation of boundary layer behavior is of great importance in aerodynamics. There exist numerous examples of techniques for the measurement of surface shear stress. Most techniques require arduous calibrations and necessitate extensive preparation of the receiving surfaces. However, the main draw back of instruments such as Preston tubes, hot films, buried wire gages, and floating element balances is that they only provide a point measurement. The advantages of capturing global shear data would be appreciable when compared

  1. Colorimetric qualification of shear sensitive liquid crystal coatings

    NASA Astrophysics Data System (ADS)

    Muratore, Joseph J., Jr.

    1993-08-01

    The work that has been done to date on the Shear Sensitive Liquid Crystal Project demonstrated that cholesteric liquid crystal coatings respond to both the direction and magnitude of a shearing force. The response of the coating is to selectively scatter incident white light into a spectrum of colors. Discernible color changes at a fixed angle of observation and illumination are the result of an applied shear stress. The intention was to be able to convert these observable color patterns from a flow visualization technique into a quantitative tool. One of the earlier intentions was to be able to use liquid crystals in dynamic flow fields. This was assumed possible because liquid crystals had made it possible to visualize transients in surface shear forces. Although the transients were visualized by color changes to an order one micro second, the time response of a coating to align to a shearing force is dependent on the magnitude of the change between its initial and final states. Unfortunately, the response is not instantaneous. It is for this reason any future attempt at quantifying the magnitude and directions of a shearing force are limited to surface shear stress vector fields in three dimensional steady state flows. This limitation does not significantly detract from the utility of liquid crystal coatings. The measurement of skin friction in the study of transition on wings, prediction of drag forces, performance assessment, and the investigation of boundary layer behavior is of great importance in aerodynamics. There exist numerous examples of techniques for the measurement of surface shear stress. Most techniques require arduous calibrations and necessitate extensive preparation of the receiving surfaces. However, the main draw back of instruments such as Preston tubes, hot films, buried wire gages, and floating element balances is that they only provide a point measurement. The advantages of capturing global shear data would be appreciable when compared

  2. Multifunctional Janus hematite-silica nanoparticles: mimicking peroxidase-like activity and sensitive colorimetric detection of glucose.

    PubMed

    Lu, Chang; Liu, Xiangjiang; Li, Yunfeng; Yu, Fang; Tang, Longhua; Hu, Yanjie; Ying, Yibin

    2015-07-22

    The design and engineering of multifunctional nanostructures with multiple components and synergistic properties are in urgent demand for variety of acceptable biosensing platforms, enabling users to fulfill multiple tasks in a single nanosystem. Herein, we report using an asymmetric hematite-silica hybrid of Janus γ-Fe2O3/SiO2 nanoparticles (JFSNs) as a multifunctional biosensing platform for sensitive colorimetric detection of H2O2 and glucose. It was demonstrated that JFSNs exhibit an intrinsic peroxidase-like catalytic activity. Compared with natural enzyme, JFSNs nanoenzymes could be used over a wider range of pH and temperatures and were more stable over time. Importantly, besides its excellent catalytic activity, the asymmetric properties of the Janus nanoparticle enable it to form the multiple functional utilities for various biosensing applications, including the ease of surface modification without deactivation of catalytic activity and recoverable use by magnetic separation. Thus, we utilized JFSNs with glucose oxidase (GOx) immobilization for glucose-sensitive colorimetric detection, which exhibited both catalytic activity of glucose oxidase and peroxidase with high selectivity and acceptable reproducibility. By combining these two analysis systems into Janus particles, an all-in-one and reusable sensor for blood glucose was formed and has the capability for determination of glucose in complex samples such as serum. These results suggest that such Janus nanosystems have the potential to construct robust nanoarchitecture with multiple functionalities for various biosensing applications.

  3. Nanoparticle-nanocup hybrid array structure with a tunable sensitivity for colorimetric biosensing

    NASA Astrophysics Data System (ADS)

    Seo, Sujin; Liu, Gang L.

    2016-03-01

    Colorimetric detection is cost-effective and user-friendly when used for sensing target analytes without a need of bulky and expensive equipment. The extraordinary transmission phenomena through plasmonic periodic nanocup arrays achieve colorimetric sensing by detecting color changes of transmitted light associated with the refractive index variation. The application of the nanocup arrays, however, is relatively restricted due to a limited sensitivity for monolayered target analyte detections on the surface. In order to improve the sensitivity bounded by the underlying nanostructures, hybrid nanoparticle (NP) - nanocup array substrates are developed for enhancing the sensitivity to the refractive index change. The three dimensionally assembled Au NPs in circle along the sidewall of each nanocup increases the density of hot spots by the heterogeneous plasmonic coupling between the NP and the edge of the nanocup; thus a small refractive index change at the hot spot becomes easily detected than bare nanocup arrays. In addition to the bulk refractive index sensing, an ultrasensitive spectroscopic detection of the antigen-antibody binding is achieved by this three-dimensional self-assembly of Au NPs on the Au nanocup arrays.

  4. Prussian blue nanoparticles as peroxidase mimetics for sensitive colorimetric detection of hydrogen peroxide and glucose.

    PubMed

    Zhang, Weimin; Ma, Diao; Du, Jianxiu

    2014-03-01

    Prussian blue nanoparticles (PB NPs) exhibits an intrinsic peroxidase-like catalytic activity towards the hydrogen peroxide (H2O2)-mediated oxidation of classical peroxidase substrate 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt to produce a colored product. The catalysis follows Michaelis-Menen kinetics and shows strong affinity for H2O2. Using PB NPs as a peroxidase mimetics, a colorimetric method was developed for the detection of 0.05-50.0 μM H2O2, with a detection limit of 0.031 μM. When the catalytic reaction of PB NPs was coupled with the reaction of glucose oxidation catalyzed by glucose oxidase, a sensitive and selective colorimetric method for the detection of glucose was realized. The limit of detection for glucose was determined to be as low as 0.03 μM and the linear range was from 0.1 μM to 50.0 μM. The method was successfully applied to the determination of glucose in human serum. Compared with other nanomaterials-based peroxidase mimetics, PB NPs provides 10-100 times higher sensitivity toward the detection of H2O2 and glucose. The detection platform developed showed great potential applications in varieties of physiological importance substances when merged with appropriate H2O2-producing oxidases.

  5. Sensitive colorimetric assays for α-glucosidase activity and inhibitor screening based on unmodified gold nanoparticles.

    PubMed

    Chen, Hongxia; Zhang, Jiangjiang; Wu, Heng; Koh, Kwangnak; Yin, Yongmei

    2015-05-22

    A colorimetric sensor has been developed in this work to sensitively detect α-glucosidase activity and screen α-glucosidase inhibitors (AGIs) utilizing unmodified gold nanoparticles (AuNPs). The sensing strategy is based on triple-catalytic reaction triggered by α-glucosidase. In the presence of α-glucosidase, aggregation of AuNPs is prohibited due to the oxidation of cysteine to cystine in the system. However, with addition of AGIs, cysteine induced aggregation of AuNPs occurs. Thus, a new method for α-glucosidase activity detection and AGIs screening is developed by measuring the UV-vis absorption or visually distinguishing. A well linear relation is presented in a range of 0.0025-0.05 U mL(-1). The detection limit is found to be 0.001 U mL(-1) for α-glucosidase assay, which is one order of magnitude lower than other reports. The IC50 values of four kinds of inhibitors observed with this method are in accordance with other reports. The using of unmodified AuNPs in this work avoids the complicated and time-consuming modification procedure. This simple and efficient colorimetric method can also be extended to other enzymes assays.

  6. A Sensitive Microplate Assay for Lipase Activity Measurement Using Olive Oil Emulsion Substrate: Modification of the Copper Soap Colorimetric Method.

    PubMed

    Mustafa, Ahmad; Karmali, Amin; Abdelmoez, Wael

    2016-01-01

    The present work involves a sensitive high-throughput microtiter plate based colorimetric assay for estimating lipase activity using cupric acetate pyridine reagent (CAPR). In the first approach, three factors two levels factorial design methodology was used to evaluate the interactive effect of different parameters on the sensitivity of the assay method. The optimization study revealed that the optimum CAPR concentration was 7.5% w/v, the optimum solvent was heptane and the optimum CAPR pH was 6. In the second approach, the optimized colorimetric microplate assay was used to measure lipase activity based on enzymatic hydrolysis of olive oil emulsion substrate at 37°C and 150 rpm. The emulsion substrates were formulated by using olive oil, triton X-100 (10% v/v in pH 8) and sodium phosphate buffer of pH 8 in ratio of 1:1:1 in the case of Candida sp. lipase. While in the case of immobilized lipozyme RMIM, The emulsion substrates were formulated by using olive oil, triton X-100 (1% v/v in pH 8) and sodium phosphate buffer of pH 8 in ratio of 2:1:1. Absorbance was measured at 655 nm. The stability of this assay (in terms of colored heptane phase absorbance readings) retained more than 92.5% after 24 h at 4°C compared to the absorbance readings measured at zero time. In comparison with other lipase assay methods, beside the developed sensitivity, the reproducibility and the lower limit of detection (LOD) of the proposed method, it permits analyzing of 96 samples at one time in a 96-well microplate. Furthermore, it consumes small quantities of chemicals and unit operations.

  7. Nanomolar colorimetric quantitative detection of Fe3 + and PPi with high selectivity

    NASA Astrophysics Data System (ADS)

    Li, Zhanxian; Li, Haixia; Shi, Caixia; Yu, Mingming; Wei, Liuhe; Ni, Zhonghai

    2016-04-01

    A novel rhodamine and 8-hydroxyquinoline-based derivative was synthesized, which is shown to act as a colorimetric chemosensor for Fe3 + in aqueous solution with high selectivity over various environmentally and biologically relevant metal ions and anions with a distinct color change from colorless to pink in very fast response time (< 1 min). Fe3 + can be detected quantitatively in the concentration range from 6.7 to 16 μM and the detection limit (LOD) on UV-vis response of the sensor can be as low as 15 nM. The 'in situ' prepared Fe3 + complex (1 ṡ Fe) showed high selectivity toward PPi against many common anions, and sensitivity (the LOD can be as low as 71 nM). In addition, both the chemosensor and the 'in situ' prepared Fe3 + complex are reusable for the detection of Fe3 + and PPi respectively.

  8. Simple and Sensitive Colorimetric Assay for Pb2+ Based on Glutathione Protected Ag Nanoparticles by Salt Amplification.

    PubMed

    Chen, Zhang; Li, Huidong; Chu, Lin; Liu, Chenbin; Luo, Shenglian

    2015-02-01

    A simple and sensitive colorimetric assay for Pb2+ detection has been reported using glutathione protected silver nanoparticles (AgNPs) by salt amplification. The naked AgNPs aggregate under the influence of salt. Glutathione (GSH) can bind to AgNPs via Ag-S bond, helping AgNPs to against salt-induced aggregation. However, GSH binding to AgNPs can be compromised by the interaction between Pb2+ and GSH. As a result, Pb2+-mediated aggregation of AgNPs under the influence of salt is reflected by the UV-Visible spectrum, and the qualitative and quantitative detection for Pb2+ is accomplished, with the detection range 0.5-4 µM and a detection limit of 0.5 µM. At the same time, Pb2+ in real water sample is detected. Furthermore, the high selectivity and low cost of the assay means it is promising for enviromental applications.

  9. Target recycling amplification for label-free and sensitive colorimetric detection of adenosine triphosphate based on un-modified aptamers and DNAzymes.

    PubMed

    Gong, Xue; Li, Jinfu; Zhou, Wenjiao; Xiang, Yun; Yuan, Ruo; Chai, Yaqin

    2014-05-30

    Based on target recycling amplification, the development of a new label-free, simple and sensitive colorimetric detection method for ATP by using un-modified aptamers and DNAzymes is described. The association of the model target molecules (ATP) with the corresponding aptamers of the dsDNA probes leads to the release of the G-quadruplex sequences. The ATP-bound aptamers can be further degraded by Exonuclease III to release ATP, which can again bind the aptamers of the dsDNA probes to initiate the target recycling amplification process. Due to this target recycling amplification, the amount of the released G-quadruplex sequences is significantly enhanced. Subsequently, these G-quadruplex sequences bind hemin to form numerous peroxidase mimicking DNAzymes, which cause substantially intensified color change of the probe solution for highly sensitive colorimetric detection of ATP down to the sub-nanomolar (0.33nM) level. Our method is highly selective toward ATP against other control molecules and can be performed in one single homogeneous solution, which makes our sensing approach hold great potential for sensitive colorimetric detection of other small molecules and proteins.

  10. Morphometric and colorimetric analyses of human tumor cell line growth and drug sensitivity in soft agar culture.

    PubMed

    Alley, M C; Pacula-Cox, C M; Hursey, M L; Rubinstein, L R; Boyd, M R

    1991-02-15

    Previous studies have demonstrated the suitability of image analysis of tetrazolium-stained colonies to assess growth and drug sensitivity of human tumor cells cultivated in soft agar culture. In the present study, the potential utility of colorimetric analysis to expedite experimental drug evaluations using human tumor cell lines was investigated. The same culture dishes were assessed by image analysis and by formazan colorimetry for purposes of comparing multiple methods of measuring growth as well as growth inhibition. Replicate cultures treated with 2-(p-iodonitrophenyl)-3-p-nitrophenyl-5-phenyltetrazolium chloride or 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide exhibited nearly identical colony count and volume indices as well as excellent correlation in colorimetric end points. Colony-forming unit volume analysis versus colorimetric assessment of the same cultures following dimethyl sulfoxide extraction of protamine sulfate-rinsed, dried soft agar cultures exhibited excellent linear correlation for both growth (Pearson r ranging from 0.95 to 1.00) and drug sensitivity (Pearson r ranging from 0.90 to 0.99, and Spearman r ranging from 0.82 to 0.97) and similar drug sensitivity profiles. Results of the current investigation indicate that end points of soft agar culture remain stable for a period of at least 2 weeks following assay termination. In addition, a colorimetric detection range of 1.3-2.2 log units permits determinations of survival levels ranging from 100 to 5% of respective control levels. Colorimetric analysis is anticipated to expedite soft agar colony formation assay evaluations (a) by reducing the need to use the more rigorous and time-consuming image analysis procedures to measure activity in preliminary drug sensitivity assays and (b) by permitting the determination of effective concentration ranges of new experimental agents for subsequent, more detailed investigations.

  11. Simple and Sensitive Paper-Based Device Coupling Electrochemical Sample Pretreatment and Colorimetric Detection.

    PubMed

    Silva, Thalita G; de Araujo, William R; Muñoz, Rodrigo A A; Richter, Eduardo M; Santana, Mário H P; Coltro, Wendell K T; Paixão, Thiago R L C

    2016-05-17

    We report the development of a simple, portable, low-cost, high-throughput visual colorimetric paper-based analytical device for the detection of procaine in seized cocaine samples. The interference of most common cutting agents found in cocaine samples was verified, and a novel electrochemical approach was used for sample pretreatment in order to increase the selectivity. Under the optimized experimental conditions, a linear analytical curve was obtained for procaine concentrations ranging from 5 to 60 μmol L(-1), with a detection limit of 0.9 μmol L(-1). The accuracy of the proposed method was evaluated using seized cocaine samples and an addition and recovery protocol.

  12. Single-layer MnO2 nanosheets for sensitive and selective detection of glutathione by a colorimetric method

    NASA Astrophysics Data System (ADS)

    Di, Weihua; Zhang, Xiang; Qin, Weiping

    2017-04-01

    The rapid, sensitive and selective detection of glutathione (GSH) is of great importance in the biological systems. In this work, a template-free and one-step method was used to synthesize the single-layer MnO2 nanosheets via a redox reaction. The resulting product was characterized by XRD, TEM, FTIR, XPS and UV-vis absorption. The addition of GSH results in the change of solution color depth owing to the occurrence of a redox reaction between MnO2 and GSH, enabling colorimetric detection of GSH. At a pH of 3.6, the proposed sensor gives a linear calibration over a GSH concentration range of 10-100 μM, with a rapid response of less than 2 min and a low detection limit of 0.5 μM. The relative standard deviation for seven repeated determinations of GSH is lower than 5.6%. Furthermore, the chemical response of the synthesized MnO2 nanosheets toward GSH is selective. Owing to the advantages with good water solubility, rapid response, high sensitivity, good biocompatibility and operation simplicity, this two-dimensional MnO2-based sensing material might be potential for detecting GSH in biological applications.

  13. A highly selective colorimetric and fluorescent turn-on chemosensor for Al3 + based on naphthalimide derivative

    NASA Astrophysics Data System (ADS)

    Kang, Lei; Xing, Zhi-Yong; Ma, Xiao-Yuan; Liu, Ya-Tong; Zhang, Yu

    2016-10-01

    A new chemosensor L based on the naphthalimide moiety was synthesized and characterized. L exhibited the high selectivity and sensitivity for Al3 + in CH3OH, along with colorimetric and fluorometric dual-signaling responses based on the joint contribution of the ICT and CHEF processes. A 1:1 stoichiometry for the L-Al3 + complex was formed with an association constant of 7.6 × 104 M- 1, and the limit of detection for Al3 + was determined as 6.9 μM. In addition, L was successfully applied to the determination of Al3 + in real water samples.

  14. Rapid and sensitive detection of cholera toxin using gold nanoparticle-based simple colorimetric and dynamic light scattering assay.

    PubMed

    Khan, Sadia Afrin; DeGrasse, Jeffrey A; Yakes, Betsy Jean; Croley, Timothy R

    2015-09-10

    Herein, a rapid and simple gold nanoparticle based colorimetric and dynamic light scattering (DLS) assay for the sensitive detection of cholera toxin has been developed. The developed assay is based on the distance dependent properties of gold nanoparticles which cause aggregation of antibody-conjugated gold nanoparticles in the presence of cholera toxin resulting discernible color change. This aggregation induced color change caused a red shift in the plasmon band of nanoparticles which was measured by UV-Vis spectroscopy. In addition, we employed DLS assay to monitor the extent of aggregation in the presence of different concentration of cholera toxin. Our assay can visually detect as low as 10 nM of cholera toxin which is lower than the previously reported colorimetric methods. The reported assay is very fast and showed an excellent specificity against other diarrhetic toxins. Moreover, we have demonstrated the feasibility of our method for cholera toxin detection in local lake water.

  15. A sensitive and selective colorimetric method for detection of copper ions based on anti-aggregation of unmodified gold nanoparticles.

    PubMed

    Hormozi-Nezhad, M Reza; Abbasi-Moayed, Samira

    2014-11-01

    A highly sensitive and selective colorimetric method for detection of copper ions, based on anti-aggregation of D-penicillamine (D-PC) induced aggregated gold nanoparticles (AuNPs) was developed. Copper ions can hinder the aggregation of AuNPs induced by D-PC, through formation of mixed-valence complex with D-PC that is a selective copper chelator. In the presence of a fixed amount of D-PC, the aggregation of AuNPs decreases with increasing concentrations of Cu(2+) along with a color change from blue to red in AuNPs solution and an increase in the absorption ratio (A520/A650). Under the optimum experimental conditions (pH 7, [AuNPs] =3.0 nmol L(-1) and [NaCl]=25 mmol L(-1)), a linear calibration curve for Cu(2+) was obtained within the range of 0.05-1.85 µmol L(-1) with a limit of detection (3Sb) of 30 nmol L(-1). Excellent selectivity toward Cu(2+) was observed among various metal ions due to a specific complex formation between Cu(2+) and D-PC. The proposed method has been successfully applied for the detection of Cu(2+) in various real samples.

  16. A high-throughput colorimetric assay to measure the activity of glutamate decarboxylase.

    PubMed

    Yu, Kai; Hu, Sheng; Huang, Jun; Mei, Le-He

    2011-08-10

    A pH-sensitive colorimetric assay has been established to quantitatively measure glutamate decarboxylase (GAD) activity in bacterial cell extracts using a microplate format. GAD catalyzes the irreversible α-decarboxylation of L-glutamate to γ-aminobutyrate. The assay is based on the color change of bromocresol green due to an increase in pH as protons are consumed during the enzyme-catalyzed reaction. Bromocresol green was chosen as the indicator because it has a similar pK(a) to the acetate buffer used. The corresponding absorbance change at 620 nm was recorded with a microplate reader as the reaction proceeded. A difference in the enzyme preparation pH and optimal pH for GAD activity of 2.5 did not prevent this method from successfully allowing the determination of reaction kinetic parameters and the detection of improvements in enzymatic activity with a low coefficient of variance. Our assay is simple, rapid, requires minimal sample concentration and can be carried out in robotic high-throughput devices used as standard in directed evolution experiments. In addition, it is also applicable to other reactions that involve a change in pH.

  17. Urchin-like (gold core)@(platinum shell) nanohybrids: A highly efficient peroxidase-mimetic system for in situ amplified colorimetric immunoassay.

    PubMed

    Gao, Zhuangqiang; Xu, Mingdi; Lu, Minghua; Chen, Guonan; Tang, Dianping

    2015-08-15

    The development of signal-amplified colorimetric immunoassay relies on the design of highly efficient signal-transduction tags. One promising route is to exploit a novel enzyme mimetic system as the signal label. Herein, we report that urchin-like (gold core)@(platinum shell) nanohybrids (Au@PtNHs) can be utilized as a highly efficient peroxidase mimetic system for in situ amplified colorimetric immunoassay of prostate-specific antigen (PSA, one kind of tumor marker). Initially, urchin-like Au@PtNHs were discovered to outperform horseradish peroxidase (HRP) by a vast margin in terms of the turnover number toward hydrogen peroxide (H2O2)-3,3',5,5'-tetramethylbenzidine (TMB) system and the stability against high temperatures and HRP inhibitors. Based on this discovery, the assay was simply carried out on a capture antibody-immobilized microplate by using the Au@PtNH-labeled detection antibody as a signal-transduction tag with a sandwich-type assay mode. The colorimetric signal stemmed from the labeled Au@PtNHs toward catalytic oxidation of TMB-H2O2 system. Experimental results indicated that the Au@PtNH-based colorimetric immunoassay could display a good colorimetric response toward PSA in the dynamic working range of 5-500 pg mL(-1) with a low detection limit of 2.9 pg mL(-1). Meanwhile, the developed immunoassay exhibited good precision and reproducibility, high specificity and acceptable accuracy for the detection of clinical serum samples. These results open up a new horizon for the development of highly sensitive, highly stable and inexpensive non-enzyme immunoassay platforms as an alternative to conventional enzyme-based immunoassay platforms.

  18. Enhancement of Enzymatic Colorimetric Response by Silver Island Films on High Throughput Screening Microplates

    PubMed Central

    Abel, Biebele; Clement, Travis C.; Aslan, Kadir

    2014-01-01

    In this study, we report the use of an enzyme-based hybrid platform, which is comprised of silver island films, enzymes (HRP and AP) and high-throughput screening (HTS) microplates, to enhance the colorimetric response of enzymatic reactions. The hybrid platform was designed in a two-step process: (i) deposition of SIFs onto HTS microplates with low, medium, and high loading (refers to the extent of the surface plasmon resonance peak of SIFs at 460 nm) using Tollen’s reaction scheme; and (ii) attachment of b-BSA or BEA as linkers for the immobilization of enzymes. The presence of SIFs within the wells of the HTS microplates was confirmed using an optical spectrophotometer and real-color photography. Control experiments, where SIFs were omitted from the surfaces were carried out to confirm the effect of SIFs on the enzymatic colorimetric response. Significant colorimetric signal enhancement was observed for HRP or AP on SIFs (high loading) deposited HTS microplates using b-BSA (up to ~ 3-fold for AP and ~6-fold HRP) or BEA (up to ~ 7-fold for both HRP and AP), as compared to our control samples. The observed increase in colorimetric response can be attributed to the nature of BEA, which exposes surface-bound enzymes to the substrate present in bulk more efficiently than b-BSA. This study proves that SIFs can serve as a valuable tool to improve the signal output of existing bioassays carried out in HTS microplates, which can be applicable to the field biosensors and plasmonics. PMID:24950456

  19. A new highly selective, ratiometric and colorimetric fluorescence sensor for Cu(2+) with a remarkable red shift in absorption and emission spectra based on internal charge transfer.

    PubMed

    Goswami, Shyamaprosad; Sen, Debabrata; Das, Nirmal Kumar

    2010-02-19

    A new 1,8-diaminonaphthalene based ratiometric and highly selective colorimetric "off-on" type of fluorescent probe, receptor 2 has been designed and synthesized that senses only Cu(2+) among the other heavy and transition metal ions examined on the basis of internal charge transfer (ICT). The visual sensitivity of the receptor 2 is remarkable, showing dual color changes from colorless (receptor) to purple followed by blue and a large red shift in emission upon Cu(2+) complexation.

  20. Sensitive and specific colorimetric DNA detection by invasive reaction coupled with nicking endonuclease-assisted nanoparticles amplification.

    PubMed

    Zou, Bingjie; Cao, Xiaomei; Wu, Haiping; Song, Qinxin; Wang, Jianping; Kajiyama, Tomoharu; Kambara, Hideki; Zhou, Guohua

    2015-04-15

    Colorimetric DNA detection is preferable to methods in clinical molecular diagnostics, because no expensive equipment is required. Although many gold nanoparticle-based colorimetric DNA detection strategies have been developed to analyze DNA sequences of interest, few of them can detect somatic mutations due to their insufficient specificity. In this study, we proposed a colorimetric DNA detection method by coupling invasive reaction with nicking endonuclease-assisted nanoparticles amplification (IR-NEANA). A target DNA firstly produces many flaps by invasive reaction. Then the flaps are converted to targets of nicking reaction-assisted nanoparticles amplification by ligation reaction to produce the color change of AuNPs, which can be observed by naked eyes. The detection limit of IR-NEANA was determined as 1pM. Most importantly, the specificity of the method is high enough to pick up as low as 1% mutant from a large amount of wild-type DNA backgrounds. The EGFR gene mutated at c.2573 T>G in 9 tissue samples from non-small cell lung cancer patients were successfully detected by using IR-NEANA, suggesting that our proposed method can be used to detect somatic mutations in biological samples.

  1. Highly selective colorimetric bacteria sensing based on protein-capped nanoparticles.

    PubMed

    Qiu, Suyan; Lin, Zhenyu; Zhou, Yaomin; Wang, Donggen; Yuan, Lijuan; Wei, Yihua; Dai, Tingcan; Luo, Linguang; Chen, Guonan

    2015-02-21

    A rapid and cost-effective colorimetric sensor has been developed for the detection of bacteria (Bacillus subtilis was selected as an example). The sensor was designed to rely on lysozyme-capped AuNPs with the advantages of effective amplification and high specificity. In the sensing system, lysozyme was able to bind strongly to Bacillus subtilis, which effectively induced a color change of the solution from light purple to purplish red. The lowest concentration of Bacillus subtilis detectable by the naked eye was 4.5 × 10(3) colony-forming units (CFU) mL(-1). Similar results were discernable from UV-Vis absorption measurements. A good specificity was observed through a statistical analysis method using the SPSS software (version 17.0). This simple colorimetric sensor may therefore be a rapid and specific method for a bacterial detection assay in complex samples.

  2. The Rapid and Sensitive Quantitative Determination of Galactose by Combined Enzymatic and Colorimetric Method: Application in Neonatal Screening.

    PubMed

    Kianmehr, Anvarsadat; Mahrooz, Abdolkarim; Ansari, Javad; Oladnabi, Morteza; Shahbazmohammadi, Hamid

    2016-05-01

    The quantitative measurement of galactose in blood is essential for the early diagnosis, treatment, and dietary monitoring of galactosemia patients. In this communication, we aimed to develop a rapid, sensitive, and cost-effective combined method for galactose determination in dry blood spots. This procedure was based on the combination of enzymatic reactions of galactose dehydrogenase (GalDH), dihydrolipoyl dehydrogenase (DLD), and alkaline phosphates with a colorimetric system. The incubation time and the concentration of enzymes used in new method were also optimized. The analytical performance was studied by the precision, recovery, linearity, and sensitivity parameters. Statistical analysis was applied to method comparison experiment. The regression equation and correlation coefficient (R (2)) were Y = 0.0085x + 0.032 and R (2) = 0.998, respectively. This assay exhibited a recovery in the range of 91.7-114.3 % and had the limit detection of 0.5 mg/dl for galactose. The between-run coefficient of variation (CV) was between 2.6 and 11.1 %. The within-run CV was between 4.9 and 9.2 %. Our results indicated that the new and reference methods were in agreement because no significant biases exist between them. Briefly, a quick and reliable combined enzymatic and colorimetric assay was presented for application in newborn mass screening and monitoring of galactosemia patients.

  3. A novel sensitive colorimetric sensor for Cu(2+) based on in situ formation of fluorescent quantum dots with photocatalytic activity.

    PubMed

    Tang, Shurong; Wang, Meili; Li, Zhijun; Tong, Ping; Chen, Qiang; Li, Guangwen; Chen, Jinghua; Zhang, Lan

    2017-03-15

    This work demonstrates the use of quantum dots (QDs) with photocatalytic activity as a sensitive, inexpensive and rapid colorimetric platform for Cu(2+) sensing. Based on the simple thiol compound mediated QDs growing method, CdS QDs can be quickly formed in situ, which possess excellent photocatalytic ability for the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) to produce a colored product under light irradiation. Cu(2+) can catalyze the oxidation of sulfhydryl groups in glutathione (GSH) which act as a stabilizer for CdS QDs. In the presence of Cu(2+), GSH is oxidized and loss the stabilization ability for the growth of CdS QDs, thus resulting in the decrease of the absorbance. Under optimum conditions, as low as 5.3nM Cu(2+) can be detected. This sensing system is simple, reliable and holds great potential to provide a new general platform for ultrasensitive monitoring of a variety of analytes.

  4. A High Affinity Red Fluorescence and Colorimetric Probe for Amyloid β Aggregates

    NASA Astrophysics Data System (ADS)

    Rajasekhar, K.; Narayanaswamy, Nagarjun; Murugan, N. Arul; Kuang, Guanglin; Ågren, Hans; Govindaraju, T.

    2016-04-01

    A major challenge in the Alzheimer’s disease (AD) is its timely diagnosis. Amyloid β (Aβ) aggregates have been proposed as the most viable biomarker for the diagnosis of AD. Here, we demonstrate hemicyanine-based benzothiazole-coumarin (TC) as a potential probe for the detection of highly toxic Aβ42 aggregates through switch-on, enhanced (~30 fold) red fluorescence (Emax = 654 nm) and characteristic colorimetric (light red to purple) optical outputs. Interestingly, TC exhibits selectivity towards Aβ42 fibrils compared to other abnormal protein aggregates. TC probe show nanomolar binding affinity (Ka = 1.72 × 107 M‑1) towards Aβ42 aggregates and also displace ThT bound to Aβ42 fibrils due to its high binding affinity. The Aβ42 fibril-specific red-shift in the absorption spectra of TC responsible for the observed colorimetric optical output has been attributed to micro-environment change around the probe from hydrophilic-like to hydrophobic-like nature. The binding site, binding energy and changes in optical properties observed for TC upon interaction with Aβ42 fibrils have been further validated by molecular docking and time dependent density functional theory studies.

  5. A sensitive gold nanoparticle-based colorimetric aptasensor for Staphylococcus aureus.

    PubMed

    Yuan, Jinglei; Wu, Shijia; Duan, Nuo; Ma, Xiaoyuan; Xia, Yu; Chen, Jie; Ding, Zhansheng; Wang, Zhouping

    2014-09-01

    In this study, a gold nanoparticle-based colorimetric aptasensor for Staphylococcus aureus (S. aureus) using tyramine signal amplification (TSA) technology has been developed. First, the biotinylated aptamer specific for S. aureus was immobilized on the surface of the wells of the microtiter plate via biotin-avidin binding. Then, the target bacteria (S. aureus), biotinylated-aptamer-streptavidin-HRP conjugates, biotinylated tyramine, hydrogen peroxide and avidin-catalase were successively introduced into the wells of the microtiter plate. After that, the existing catalase consumed the hydrogen peroxide. Finally, the freshly prepared gold (III) chloride trihydrate was added, the color of the reaction production would be changed and the absorbance at 550 nm could be measured with a plate reader. Under optimized conditions, there was a linear relationship between the absorbance at 550 nm and the concentration of S. aureus over the range from 10 to 10(6) cfu mL(-1) (with an R² of 0.9947). The limit of the developed method was determined to be 9 cfu mL(-1).

  6. Influence of polymer composition on the sensitivity towards nitrite and nitric oxide of colorimetric disposable test strips.

    PubMed

    Fabregat, Víctor; Burguete, M Isabel; Galindo, Francisco; Luis, Santiago V

    2016-11-21

    The influence of polymer composition on the sensitivity towards nitrite (NO2(-)) and nitric oxide (NO) of a series of 19 polymeric hydrogel films has been studied. The polymers, based on the hydrophilic monomer 2-hydroxyethylmethacrylate (HEMA), are able to encapsulate the colorimetric indicator 1,2-diaminoanthraquinone (DAQ) and to respond to NO2(-) and NO by visual changes. In the case of nitrite, the calculated limits of detection (LOD) for two of the polymeric sensors (10 μM) are very close to the sensitivity estimated for free DAQ in solution (LOD 5 μM), but with the advantage of a solid supported sensor with the format of a disposable test-strip made with affordable starting chemicals. The results are interpreted taking into account the nature and proportions of monomers and cross-linkers used for the synthesis of polymers. Key factors for obtaining sensitive materials are the hydrophilic character of the film along with the utilization of low levels of cross-linker and the use of an acidic monomer, like acrylic acid, as a building block.

  7. A colorimetric bioassay for high-throughput and cost-effectively assessing anti-foot-and-mouth disease virus activity.

    PubMed

    Ramanathan, Palaniappan; Zhu, James J; Bishop, Elizabeth A; Puckette, Michael C; Hartwig, Ethan; Grubman, Marvin J; Rodriguez, Luis L

    2015-03-15

    Foot-and-mouth disease virus (FMDV) is one of the most contagious animal viruses. This virus is very sensitive to inhibition by type I interferons. Currently, a bioassay based on plaque reduction is used to measure anti-FMDV activity of porcine IFNs. The plaque reduction assay is tedious and difficult to utilize for high-throughput analysis. Using available FMDV susceptible bovine and porcine cells, we developed and tested a colorimetric assay based on cytopathic effect reduction for its ability to quantify FMDV-specific antiviral activity of bovine and porcine type I interferons. Our results show that this new method has significant advantages over other assays in terms of labor intensity, cost, high-throughput capability and/or anti-FMDV specific activity because of simpler procedures and direct measurement of antiviral activity. Several assay conditions were tested to optimize the procedures. The test results show that the assay can be standardized with fixed conditions and a standard or a reference for measuring antiviral activity as units. This is an excellent assay in terms of sensitivity and accuracy based on a statistical evaluation. The results obtained with this assay were highly correlated with a conventional virus titration method.

  8. Synthetic multivalent DNAzymes for enhanced hydrogen peroxide catalysis and sensitive colorimetric glucose detection.

    PubMed

    Yang, Deng-Kai; Kuo, Chia-Jung; Chen, Lin-Chi

    2015-01-26

    A peroxidase-mimic DNAzyme is a G-quadruplex (G4) DNA-hemin complex, in which the G4-DNA resembles an apoenzyme, and hemin is the cofactor for hydrogen peroxide (H2O2) catalysis. Twenty-one-mer CatG4 is a well-proven G4-DNA as well as a hemin-binding aptamer for constituting a DNAzyme. This work studied if a multivalent DNAzyme with accelerated catalysis could be constructed using a multimeric CatG4 with hemin. We compared CatG4 monomer, dimer, trimer, and tetramer, which were prepared by custom oligo synthesis, for G4 structure formation. According to circular dichroism (CD) analysis, we found that a CatG4 multimer exhibited more active G4 conformation than the sum effect of equal-number CatG4 monomers. However, the DNAzyme kinetics was not improved monotonically along with the subunit number of a multimeric CatG4. It was the trivalent DNAzyme, trimeric CatG4:hemin, resulting in the rapidest H2O2 catalysis instead of a tetravalent one. We discovered that the trivalent DNAzyme's highest catalytic rate was correlated to its most stable hemin-binding G4 structure, evidenced by CD melting temperature analysis. Finally, a trivalent DNAzyme-based colorimetric glucose assay with a detection limit as low as 10 μM was demonstrated, and this assay did not need adenosine 5'-tri-phosphate disodium salt hydrate (ATP) as a DNAzyme boosting agent.

  9. Green synthesis of silver nanoparticle for the selective and sensitive colorimetric detection of mercury (II) ion.

    PubMed

    Kumar, Vijay; Singh, Devendra K; Mohan, Sweta; Bano, Daraksha; Gundampati, Ravi Kumar; Hasan, Syed Hadi

    2017-03-01

    An ecofriendly and zero cost approach has been developed for the photoinduced synthesis of more stable AgNPs using an aqueous extract of Murraya koenigii (AEM) as a reducing and stabilizing agent. The exposed reaction mixture of AEM and AgNO3 to sunlight turned dark brown which primarily confirmed the biosynthesis of AgNPs. The biosynthesis was monitored by UV-vis spectroscopy which exhibited a sharp SPR band at 430nm after 30min of sunlight exposure. The optimum conditions for biosynthesis of AgNPs were 30min of sunlight exposure, 2.0% (v/v) of AEM inoculuam dose and 4.0mM AgNO3 concentration. TEM analysis confirmed the presence of spherical AgNPs with average size 8.6nm. The crystalline nature of the AgNPs was confirmed by XRD analysis where the Bragg's diffraction pattern at (111), (200), (220) and (311) corresponded to face centered cubic crystal lattice of metallic silver. The surface texture was analyzed by AFM analysis where the average roughness of the synthesized AgNPs was found 1.8nm. FTIR analysis was recorded between 4000 and 400cm(-1) which confirmed the involvement of various functional groups in the synthesis of AgNPs. On the basis of the linear relationship between SPR band intensity and different concentration of Hg(2+), the synthesized AgNPs can be used for colorimetric detection of Hg(2+) with a linear range from 50nm to 500μM. Based on experimental findings, an oxidation-reduction mechanism between AgNPs and Hg(2+) was also proposed.

  10. Selective and sensitive detection of free bilirubin in blood serum using human serum albumin stabilized gold nanoclusters as fluorometric and colorimetric probe.

    PubMed

    Santhosh, Mallesh; Chinnadayyala, Somasekhar R; Kakoti, Ankana; Goswami, Pranab

    2014-09-15

    We report here a fluorescence quenching based non-enzymatic method for sensitive and reliable detection of free bilirubin in blood serum samples using human serum albumin (HSA) stabilized gold nanoclusters (HSA-AuNCs) as fluorescent probe. The fluorescence of the nanoclusters was strongly quenched by bilirubin in a concentration dependent manner by virtue of the inherent specific interaction between bilirubin and HSA. A strong binding constant of 0.55×10(6) L mole(-1) between the HSA-AuNC and bilirubin was discerned. The nano clusters each with size ~1.0 nm (in diameter) and a core of Au18 were homogeneously distributed in HSA molecules as revealed from the respective high resolution transmission electron microscopic and mass spectroscopic studies. The fluorescence quenching phenomena which obeyed a simple static quenching mechanism, was utilized for interference free detection of bilirubin with minimum detection limit (DL) of 248±12 nM (S/N=3). The fluorescence response of HSA-AuNCs against bilirubin was practically unaltered over a wide pH (6-9) and temperature (25-50 °C) range. Additionally, peroxidase-like catalytic activity of these nanoclusters was exploited for colorimetric detection of bilirubin in serum sample with a DL of 200±19 nM by following the decrease in absorbance (at λ440 nm) of the reaction and its rate constant (Kp) of 2.57±0.63 mL μg(-1) min(-1). Both these fluorometric and colorimetric methods have been successfully used for detection of free bilirubin in blood serum samples.

  11. Paper-Based Colorimetric Sensor System for High-Throughput Screening of C-H Borylation.

    PubMed

    Kim, Han-Sung; Eom, Min Sik; Han, Min Su; Lee, Sunwoo

    2017-03-22

    A paper-based colorimetric sensor system (PBCSS) was developed to detect the amount of bis(pinacolato)diboron (B2Pin2) and applied as a high-throughput screening protocol in Ir-catalyzed C-H borylation. First, 96 ligands were screened for the borylation of benzene, and then 12 of them were selected and tested for five substrates. These reaction mixtures were spotted in the PBCSS, showing a blue-violet color. The value of the gray scale of each reaction was obtained from these colored spots and converted to the extent of conversion of B2Pin2. The extents of conversion of B2Pin2 obtained from the PBCSS showed good correlation with those obtained from gas chromatography analysis. In addition, the modified conversion using blank data showed good correlation with the yield of products.

  12. Enzyme-free and label-free ultra-sensitive colorimetric detection of Pb(2+) using molecular beacon and DNAzyme based amplification strategy.

    PubMed

    Yun, Wen; Cai, Dingzhou; Jiang, JiaoLai; Zhao, Pengxiang; Huang, Yu; Sang, Ge

    2016-06-15

    An enzyme-free and label-free colorimetric Pb(2+) sensor based on DNAzyme and molecular beacon (MB) has been developed and demonstrated by recycle using enzyme strand for signal amplification. The substrate strand DNA (S-DNA) of DNAzyme could be converted into MB structure with base pairs of stem part at the both ends. The MB could hybridize with enzyme strand DNA (E-DNA) to form DNAzyme, and be activated and cleaved in the presence of Pb(2+). The cleaved MB is much less stable, releasing from the DNAzyme as two product pieces. The product pieces of MB are flexible and could bind to unmodified AuNPs to effectively stabilize them against salt-induced aggregation. Then, the E-DNA is liberated to catalyze the next reaction and amplify the response signal. By taking advantage of repeated using of E-DNA, our proposed method exhibited high sensitive for Pb(2+) detection in a linear range from 0.05 to 5 nM with detection limit of 20 pM by UV-vis spectrometer. Moreover, this method was also used for determination of Pb(2+) in river water samples with satisfying results. Importantly, this strategy could reach high sensitivity without any modification and complex enzymatic or hairpins based amplification procedures.

  13. Label-free and pH-sensitive colorimetric materials for the sensing of urea

    NASA Astrophysics Data System (ADS)

    Li, Lu; Long, Yue; Gao, Jin-Ming; Song, Kai; Yang, Guoqiang

    2016-02-01

    This communication demonstrates a facile method for naked-eye detection of urea based on the structure color change of pH-sensitive photonic crystals. The insertion of urease provides excellent selectivity over other molecules. The detection of urea in different concentration ranges could be realized by changing the molar ratio between the functional monomer and cross-linker.This communication demonstrates a facile method for naked-eye detection of urea based on the structure color change of pH-sensitive photonic crystals. The insertion of urease provides excellent selectivity over other molecules. The detection of urea in different concentration ranges could be realized by changing the molar ratio between the functional monomer and cross-linker. Electronic supplementary information (ESI) available: Materials and chemicals, characterization, experimental details, and SEM images. See DOI: 10.1039/c5nr07690k

  14. Development of sensitive colorimetric capture elisas for Clostridium botulinum neurotoxin serotypes A and B.

    PubMed

    Szílagyi, M; Rivera, V R; Neal, D; Merrill, G A; Poli, M A

    2000-03-01

    Sensitive and specific enzyme-linked immunosorbent assays were developed to detect Clostridium botulinum neurotoxin serotypes A (BoNT A) and B (BoNT B) in assay buffer and human serum. The assay is based upon affinity-purified horse polyclonal antibodies directed against the approximately 50 kDa C-fragments of each toxin. Standard curves were linear over the range of 0.1-10 ng mL. Detection was possible at 0.2 ng mL (20 pg/well) and accurate quantitation at 0.5 ng/mL (50 pg well) in assay buffer and 10% human serum. Variations between triplicates was typically 5-10%. Less than 1% cross reactivity occurred between other serotypes when each assay was performed against serotypes A, B and E. When tested against toxins complexed to their associated nontoxic proteins, interference was absent (BoNT B) or < 25% (BoNT A). These assays demonstrate sensitivity close to that of the mouse bioassay without the use of animals and in a much simpler format than other reported assays of similar sensitivity.

  15. Highly selective and quantitative colorimetric detection of mercury(II) ions by carrageenan-functionalized Ag/AgCl nanoparticles.

    PubMed

    Narayanan, Kannan Badri; Han, Sung Soo

    2017-03-15

    The natural algal polysaccharide carrageenan was used for the greener synthesis of silver/silver chloride nanoparticles (Carr-Ag/AgCl NPs) without any toxic chemicals. We report the robust, highly selective, and sensitive colorimetric sensing of Hg(2+) ions using Carr-Ag/AgCl NPs without any further surface modification. The dark-brown color of a solution of Carr-Ag/AgCl NPs turned to white in a concentration-dependent manner with the addition of Hg(2+) ions, confirming the interaction of Carr-Ag/AgCl NPs with Hg(2+) ions. The plot of the extinction ratio of absorbance at 350nm to 450nm (A350/A450) for Carr-Ag/AgCl NPs against the concentration of [Hg(2+)] ions was linear, and the calibration curve was A350/A450=1.05254+0.00318×CHg with a lower detection limit of 1μM. This portable and cost-effective method for mercury(II) ion sensing is widely applicable in on-field qualitative and quantitative measurements of [Hg(2+)] ions in environmental or biological samples.

  16. Gold nanoprobe functionalized with specific fusion protein selection from phage display and its application in rapid, selective and sensitive colorimetric biosensing of Staphylococcus aureus.

    PubMed

    Liu, Pei; Han, Lei; Wang, Fei; Petrenko, Valery A; Liu, Aihua

    2016-08-15

    Staphylococcus aureus (S. aureus) is one of the most ubiquitous pathogens in public healthcare worldwide. It holds great insterest in establishing robust analytical method for S. aureus. Herein, we report a S. aureus-specific recognition element, isolated from phage monoclone GQTTLTTS, which was selected from f8/8 landscape phage library against S. aureus in a high-throughput way. By functionalizing cysteamine (CS)-stabilized gold nanoparticles (CS-AuNPs) with S. aureus-specific pVIII fusion protein (fusion-pVIII), a bifunctional nanoprobe (CS-AuNPs@fusion-pVIII) for S. aureus was developed. In this strategy, the CS-AuNPs@fusion-pVIII could be induced to aggregate quickly in the presence of target S. aureus, resulting in a rapid colorimetric response of gold nanoparticles. More importantly, the as-designed probe exhibited excellent selectivity over other bacteria. Thus, the CS-AuNPs@fusion-pVIII could be used as the indicator of target S. aureus. This assay can detect as low as 19CFUmL(-1)S. aureus within 30min. Further, this approach can be applicable to detect S. aureus in real water samples. Due to its sensitivity, specificity and rapidness, this proposed method is promising for on-site testing of S. aureus without using any costly instruments.

  17. A sensitive colorimetric method for the micro determination of iodine in marine water.

    PubMed

    Agrawal, O; Sunita, G; Gupta, V K

    1999-07-12

    More than 70% of the earth surface is covered by water bodies. Marine pollution is associated with the discharge of oils, petroleum products, sewage agricultural wastes, pesticides, heavy metals, waste substances and dumping of radioactive waters in sea. This in turn results in hazards to human health, hindrance to aquatic organisms and impairment of quality for use of sea water. Sea water is reported to contain iodine but the concentration varies according to the location and depth. Here a simple and sensitive method is described for the determination of iodine using leucocrystal violet as a reagent in different samples of sea water. The method is based on the oxidation of iodine to iodate with bromine water and the liberation of free iodine from the iodate by addition of potassium iodide in acedic medium. This iodine selectively oxidises leucocrystal violet to form the crystal violet dye. Beer's law is obeyed over the concentration range of 0.04-0.36 ppm of iodine at lambda(max) 592 nm. The dye was further extracted in chloroform. The extracting system obeys Beer's law in the range of 0.008-0.08 ppm at lambda(max) 588 nm.

  18. Colorimetric Detection of Some Highly Hydrophobic Flavonoids Using Polydiacetylene Liposomes Containing Pentacosa-10,12-diynoyl Succinoglycan Monomers

    PubMed Central

    Yun, Deokgyu; Jeong, Daham; Cho, Eunae; Jung, Seunho

    2015-01-01

    Flavonoids are a group of plant secondary metabolites including polyphenolic molecules, and they are well known for antioxidant, anti-allergic, anti-inflammatory and anti-viral propertied. In general, flavonoids are detected with various non-colorimetric detection methods such as column liquid chromatography, thin-layer chromatography, and electrochemical analysis. For the first time, we developed a straightforward colorimetric detection system allowing recognition of some highly hydrophobic flavonoids such as alpha-naphthoflavone and beta-naphthoflavone, visually using 10,12-pentacosadiynoic acid (PCDA) derivatized with succinoglycan monomers isolated from Sinorhizobium meliloti. Besides changes in visible spectrum, we also demonstrate fluorescence changes using our detection system in the presence of those flavonoids. The succinoglycan monomers attached to PCDA molecules may function as an unstructured molecular capturer for some highly hydrophobic flavonoids by hydrophobic interactions, and transmit their molecular interactions as a color change throughout the PCDA liposome. PMID:26600071

  19. High-Sensitivity Spectrophotometry.

    ERIC Educational Resources Information Center

    Harris, T. D.

    1982-01-01

    Selected high-sensitivity spectrophotometric methods are examined, and comparisons are made of their relative strengths and weaknesses and the circumstances for which each can best be applied. Methods include long path cells, noise reduction, laser intracavity absorption, thermocouple calorimetry, photoacoustic methods, and thermo-optical methods.…

  20. Efficient reaction based colorimetric probe for sensitive detection, quantification, and on-site analysis of nitrite ions in natural water resources.

    PubMed

    Adarsh, Nagappanpillai; Shanmugasundaram, Madhesh; Ramaiah, Danaboyina

    2013-11-05

    We have developed a novel aza-BODIPY probe for the sensitive colorimetric detection of the nitrite ions in the aqueous medium by a simple and direct method. This probe selectively recognizes the nitrite ions through a distinct visual color change from bright blue to intense green with a sensitivity of 20 ppb. Uniquely, this probe can be coated on a glass surface to fabricate a simple solid-state dipstick device that can be used for the visual detection of the nitrite ions in the presence of other competing anions in distilled as well as natural water resources like a sea, lake, and river. Furthermore, this probe can be used for the sensitive detection of the nitrate ions when coupled to a reduction step. Our results demonstrate that this probe not only can be used for the on-site analysis and quantification but also can replace the conventional spot test carried out for the nitrite ions in the laboratory practical experiments.

  1. Surface plasmon resonance based selective and sensitive colorimetric determination of azithromycin using unmodified silver nanoparticles in pharmaceuticals and human plasma

    NASA Astrophysics Data System (ADS)

    Chavada, Vijay D.; Bhatt, Nejal M.; Sanyal, Mallika; Shrivastav, Pranav S.

    2017-01-01

    In this article we report a novel method for colorimetric sensing and selective determination of a non-chromophoric drug-azithromycin, which lacks native absorbance in the UV-Visible region using unmodified silver nanoparticles (AgNPs). The citrate-capped AgNps dispersed in water afforded a bright yellow colour owing to the electrostatic repulsion between the particles due to the presence of negatively charged surface and showed surface plasmon resonance (SPR) band at 394 nm. Addition of positively charged azithromycin at a concentration as low as 0.2 μM induced rapid aggregation of AgNPs by neutralizing the negative charge on the particle surface. This phenomenon resulted in the colour change from bright yellow to purple which could be easily observed by the naked eye. This provided a simple platform for rapid determination of azithromycin based on colorimetric measurements. The factors affecting the colorimetric response like pH, volume of AgNPs suspension and incubation time were suitably optimized. The validated method was found to work efficiently in the established concentration range of 0.2-100.0 μM using two different calibration models. The selectivity of the method was also evaluated by analysis of nanoparticles-aggregation response upon addition of several anions, cations and some commonly prescribed antibiotics. The method was successfully applied for the analysis of azithromycin in pharmaceuticals and spiked human plasma samples with good accuracy and precision. The simplicity, efficiency and cost-effectiveness of the method hold tremendous potential for the analysis of such non-chromophoric pharmaceuticals.

  2. A sensitive aptasensor for colorimetric detection of adenosine triphosphate based on the protective effect of ATP-aptamer complexes on unmodified gold nanoparticles.

    PubMed

    Huo, Yuan; Qi, Liang; Lv, Xiao-Jun; Lai, Ting; Zhang, Jing; Zhang, Zhi-Qi

    2016-04-15

    Adenosine triphosphate (ATP) is the most direct source of energy in organisms. This study is the first to demonstrate that ATP-aptamer complexes provide greater protection for unmodified gold nanoparticles (AuNPs) against salt-induced aggregation than either aptamer or ATP alone. This protective effect was confirmed using transmission electron microscopy, dynamic light scattering, Zeta potential measurement, and fluorescence polarization techniques. Utilizing controlled particle aggregation/dispersion as a gauge, a sensitive and selective aptasensor for colorimetric detection of ATP was developed using ATP-binding aptamers as the identification element and unmodified AuNPs as the probe. This aptasensor exhibited a good linear relationship between the absorbance and the logarithm concentration of ATP within a 50-1000 nM range. ATP analogs such as guanosine triphosphate, uridine triphosphate and cytidine triphosphate resulted in little or no interference in the determination of ATP.

  3. A Biocompatible Colorimetric Triphenylamine- Dicyanovinyl Conjugated Fluorescent Probe for Selective and Sensitive Detection of Cyanide Ion in Aqueous Media and Living Cells

    PubMed Central

    Zheng, Zi-Hua; Li, Zhi-Ke; Song, Lin-Jiang; Wang, Qi-Wei; Huang, Qing-Fei; Yang, Li

    2017-01-01

    A colorimetric and turn-on fluorescent probe 1 bearing triphenylamine-thiophene and dicyanovinyl groups has been synthesized and used to detect cyanide anion via a nucleophilic addition reaction. Probe 1 exhibited prominent selectivity and sensitivity towards CN− in aqueous media, even in the presence of other anions such as S2−, HS−, SO32−, S2O32−, S2O82−, I−, Br−, Cl−, F−, NO2−, N3−, SO42−, SCN−, HCO3−, CO32− and AcO−. Moreover, a low detection limit (LOD, 51 nM) was observed. In addition, good cell membrane permeability and low cytotoxicity to HeLa cells were also observed, suggesting its promising potential in bio-imaging. PMID:28218723

  4. High-resolution colorimetric assay for rapid visual readout of phosphatase activity based on gold/silver core/shell nanorod.

    PubMed

    Gao, Zhuangqiang; Deng, Kaichao; Wang, Xu-Dong; Miró, Manuel; Tang, Dianping

    2014-10-22

    Nanostructure-based visual assay has been developed for determination of enzymatic activity, but most involve in poor visible color resolution and are not suitable for routine utilization. Herein, we designed a high-resolution colorimetric protocol based on gold/silver core/shell nanorod for visual readout of alkaline phosphatase (ALP) activity by using bare-eyes. The method relied on enzymatic reaction-assisted silver deposition on gold nanorod to generate significant color change, which was strongly dependent on ALP activity. Upon target ALP introduction into the substrate, the ascorbic acid 2-phosphate was hydrolyzed to form ascorbic acid, and then, the generated ascorbic acid reduced silver ion to metal silver and coated on the gold nanorod, thereby resulting in the blue shift of longitudinal localized surface plasmon resonance peak of gold nanorod accompanying a perceptible color change from red to orange to yellow to green to cyan to blue and to violet. Under optimal conditions, the designed method exhibited the wide linear range 5-100 mU mL(-1) ALP with a detection limit of 3.3 mU mL(-1). Moreover, it could be used for the semiquantitative detection of ALP from 20 to 500 mU mL(-1) by using the bare-eyes. The coefficients of variation for intra- and interassay were below 3.5% and 6.2%, respectively. Finally, this method was validated for the analysis of real-life serum samples, giving results matched well with those from the 4-nitrophenyl phosphate disodium salt hexahydrate (pNPP)-based standard method. In addition, the system could even be utilized in the enzyme-linked immunosorbent assay (ELISA) to detect IgG at picomol concentration. With the merits of simplification, low cost, user-friendliness, and sensitive readout, the gold nanorod-based colorimetric assay has the potential to be utilized by the public and opens a new horizon for bioassays.

  5. Phenylboronic acid functionalized gold nanoparticles for highly sensitive detection of Staphylococcus aureus

    NASA Astrophysics Data System (ADS)

    Wang, Jine; Gao, Jingqing; Liu, Dianjun; Han, Dongxue; Wang, Zhenxin

    2012-01-01

    Herein, we report a phenylboronic acid functionalized gold nanoparticle (GNP)-based colorimetric assay for rapid detection of Staphylococcus aureus (S. aureus) with high sensitivity. In this approach, GNPs can bind to S. aureus by the reaction of phenylboronic acid with the cis-diol configuration in glycans on the bacterial surface, providing a colorimetric readout of the binding event. Using this strategy, we have been able to quantify S. aureus at a concentration of 50 cells per mL (three times the standard deviation divided by the slope of the working curve) in aqueous solution.Herein, we report a phenylboronic acid functionalized gold nanoparticle (GNP)-based colorimetric assay for rapid detection of Staphylococcus aureus (S. aureus) with high sensitivity. In this approach, GNPs can bind to S. aureus by the reaction of phenylboronic acid with the cis-diol configuration in glycans on the bacterial surface, providing a colorimetric readout of the binding event. Using this strategy, we have been able to quantify S. aureus at a concentration of 50 cells per mL (three times the standard deviation divided by the slope of the working curve) in aqueous solution. Electronic supplementary information (ESI) available: Details of experimental method and additional figures are available. See DOI: 10.1039/c2nr11657j

  6. Development of simple and sensitive hydrogel based colorimetric sensor array for the real-time quantification of gaseous ammonia.

    PubMed

    Krishnan, Sanduru Thamarai; Son, Kuk Hui; Kim, Namhyoung; Viswanath, Buddolla; Kim, Sanghyo; An, Jeong Ho

    2017-03-01

    A real-time colorimetric sensor array (CSA) offers the advantages of diversity and accuracy for the quantification of multiple analytes; however, traditional sensors require a complex fabrication process. Therefore, to take full advantage of this sensing platform, we have developed a simple CSA system composed of a polymer, a reducing agent, and different pH indicators. Distinctive color response patterns were classified by extracting the hidden information, (i.e., red, green, and blue (RGB) values) from the indicators. This triple-channel sensing platform is further applied for statistical analysis, to quantify different concentrations of ammonia and other analytes. The sensor array showed a limit of detection of 0.3ppm, which is well below the diagnostic criteria for ammonia concentration in the breath of healthy individuals and of patients with end-stage renal disease. As this sensor would be able to quantify gaseous ammonia in the breath, it is relevant to the point-of-care diagnosis of patients with renal diseases.

  7. Simple colorimetric methods for determination of sub-milligram amounts of ultra-high molecular weight polyethylene wear particles.

    PubMed

    Vesely, F; Zolotarevova, E; Spundova, M; Kaftan, F; Slouf, M; Entlicher, G

    2012-05-01

    New colorimetric methods are described for determination of sub-milligram amounts of ultra-high molecular weight polyethylene (UHMWPE) wear particles. These methods are based on the irreversible binding of the fluorescein-conjugated bovine serum albumin or the hydrophobic dye Oil Red O to wear particles. UHMWPE particles bind both substances from their solutions and thus decrease the absorbance of these solutions. The decrease is linearly dependent on the amount of added wear particles in the sub-milligram range suitable for practical use. The newly developed method offers improved accuracy and precision compared to Fourier transformed infrared spectroscopy (Slouf M, et al. Quantification of UHMWPE wear in periprosthetic tissues of hip arthoplasty: description of a new method based on IR and comparison with radiographic appearance. Wear 2008;265:674-684.).

  8. Glutathione Modified Gold Nanoparticles for Sensitive Colorimetric Detection of Pb(2+) Ions in Rainwater Polluted by Leaking Perovskite Solar Cells.

    PubMed

    Yu, Yaming; Hong, Ying; Gao, Peng; Nazeeruddin, Mohammad Khaja

    2016-12-20

    In the past few years, the advent of lead halide perovskite solar cells (PSCs) has revolutionized the prospects of the third- generation photovoltaics and the reported power conversion efficiency (PCE) has been updated to 22%. Nevertheless, two main challenges, including the poisonous content of Pb and the vexing instability toward water, still lie between the lab-based PSCs technology and large scale commercialization. With this background, we first evaluated Pb(2+) concentration from the rainwater samples polluted by three types of markets promising PSCs with inductively coupled plasma mass spectrometry measurements (ICP-MS) as a case study. The influence of possible conditions (pH value and exposure time) on the contents of Pb(2+) from the three PSCs was systematically compared and discussed. Furthermore, an optimized glutathione functionalized gold nanoparticles (GSH-AuNPs) colorimetric sensing assay was used to determine Pb(2+) leaking from PSCs for the first time. The Pb(2+)-induced aggregation of sensing assay could be monitored via both naked eye and UV-vis spectroscopy with a detection limit of 15 and 13 nM, which are all lower than the maximum level in drinking water permitted by WHO. The quantitative detection results were compared and in good agreement with that of ICP-MS. The results indicate that the content of Pb(2+) from three PSCs are in the same order of magnitude under various conditions. By the use of the prepared GSH-AuNPs self-assembled sensing assay, the fast and on-site detection of Pb(2+) from PSCs can be realized.

  9. Highly Lewis Acidic Arylboronate Esters Capable of Colorimetric Turn-On Response.

    PubMed

    Oehlke, Alexander; Auer, Alexander A; Schreiter, Katja; Friebe, Nadine; Spange, Stefan

    2015-12-01

    A series of boronate-π-acceptor compounds containing different types of π bridges (1,4-phenylen or thien-2,5-diyl or furan-2,5-diyl) that link the switchable boronate ester group with the efficient TCF acceptor group (TCF=2-dicyanomethylen-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran) has been synthesized. A TCF chromophore of this type undergoes transition to a donor-π-acceptor compound upon coordination of Lewis bases at the Lewis acidic boron center, which is accompanied by an enhanced intramolecular charge-transfer interaction. The Lewis acid character has been investigated by spectroscopic measurements (UV/Vis, NMR spectroscopies) as well as DFT and ab initio-based calculations. It is shown that the TCF acceptor group and thiophene or furan π-bridges directly bound to the boron atom cooperatively increase the Lewis acidity. UV/Vis titration experiments confirm fluoride binding constants in the range of up to 10(8)  M(-1) in CH2 Cl2 . In addition to the strong boron fluoride binding motif, Lewis interactions also occur with weaker Lewis bases, such as pyridine or aliphatic alcohols. The unique combination of chromophoric and Lewis acidic properties is responsible for the intense colorimetric turn-on response detectable after complex formation.

  10. A colorimetric method for lysyl oxidase activity in copper deficient rats fed a high fructose diet

    SciTech Connect

    Werman, M.J.; Bhathena, S.J. )

    1991-03-11

    Lysyl oxidase is involved in initiating cross link formation in collagen and elastin. The activity of lysyl oxidase is traditionally assessed by the tritium released assay. The authors describe a simplified and modified method for measuring lysyl oxidase activity in rats, based on measuring ammonia release according to the Bertholet colorimetric reaction. Lysyl oxidase activity was measured in copper deficient rats using this method. Sixteen weanling Sprague Dawley male rats were fed for four weeks either copper adequate or copper deficient diets containing 62% fructose. Copper deficiency was confirmed by significant low copper levels in heart, brain, liver and skin, and by nondetectable levels of ceruloplasmin. Lysyl oxidase activity was significantly lower in heart and skin of rats fed a copper deficient diet compared to those fed a copper adequate diet. No significant difference in activity was observed in brain tissue. A correlation was not observed between decreased tissue copper levels and decreased lysyl oxidase activity. Thus, the determination of ammonia liberated during lysyl oxidase activity may serve as an effective tool in assessing lysyl oxidase activity.

  11. Development of a high-throughput colorimetric Zika virus infection assay.

    PubMed

    Müller, Janis A; Harms, Mirja; Schubert, Axel; Mayer, Benjamin; Jansen, Stephanie; Herbeuval, Jean-Philippe; Michel, Detlef; Mertens, Thomas; Vapalahti, Olli; Schmidt-Chanasit, Jonas; Münch, Jan

    2017-04-01

    Zika virus (ZIKV) is an emerging pathogen that causes congenital infections which may result in birth defects, such as microcephaly. Currently, no approved treatment or vaccination is available. ZIKV can be readily detected in cell culture where virally infected cells are normally stained by specific antibodies. As ZIKV regularly causes a cytopathic effect, we were wondering whether this viral property can be used to quantitatively determine viral infectivity. We here describe the use of an 3-[4,5-dimethyl-2-thiazolyl]-2,5-diphenyl-2H-tetrazolium bromide-(MTT)-based cell viability assay that allows to determine ZIKV-induced cell death. We show that this colorimetric assay quantifies ZIKV infection over a broad range of viral dilutions in both monkey and human cells. It allows to determine inhibitory activities of antivirals that block ZIKV or to define the neutralizing antibody titers of ZIKV antisera. This MTT-based ZIKV detection assay can be evaluated by naked eye or computational tools, has a broad linear range, does not require large equipment or costly reagents, and thus represents a promising alternative to antibody-based assays, in particular in resource-poor settings. We propose to use this simple, fast, and cheap method for quantification of ZIKV neutralizing antibodies and testing of antiviral compounds.

  12. Sensitive and selective colorimetric detection of glutathione in human plasma with 2,2‧-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) and Ag+ ion

    NASA Astrophysics Data System (ADS)

    Li, Yinhuan; Liu, Xiaoying; Zhang, Ruyi

    2017-02-01

    Glutathione is of vital importance to human beings through involving in many cellular functions. Simple and sensitive methods capable of detecting glutathione in biological samples are significant to diagnosis and prevention of disease. Here a simple, label-free, and sensitive colorimetric method was developed for the determination of glutathione. It was observed that Ag+ ion could directly oxidize 2,2‧-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), a commonly used peroxidase substrate, to produce a green solution, which possessed a maximum absorbance at 420 nm. The presence of glutathione hindered the oxidation process and decreased the absorbance at 420 nm owing to its ability to bind with Ag+ ion. The procedure allowed the measurement of 0.1-4.0 μM glutathione with a detection limit of 59 nM. The relative standard deviation was 1.8% in eleven replicated measurements of 1.0 μM glutathione solution. The method was applied to the determination of glutathione in human plasma with satisfactory results.

  13. High selectivity of colorimetric detection of p-nitrophenol based on Ag nanoclusters

    NASA Astrophysics Data System (ADS)

    Qu, Fei; Chen, Ping; Zhu, Shuyun; You, Jinmao

    2017-01-01

    Ag nanoclusters (Ag NCs) templated by hyperbranched polyethyleneimine (PEI) with different terminal groups and molecular weights had been developed as a special optical sensor for detecting p-nitrophenol (p-NP). When adding p-NP into Ag NCs, an obvious color change from pale yellow to deep yellow could be observed by naked eyes, accompanying with an apparent red-shift of absorption peak, and the reason was attributed to the formation of oxygen anion of p-NP based on the transfer of H+ from p-NP to amine groups of PEI. The molecular weights of template would greatly affect the sensitivity of p-NP. Ag NCs capped by PEI terminated ethylenediamine (EDA) possessed better sensitivity than other Ag NCs, showing good linear range from 5 to 140 μM with the limit of detection as low as 1.28 μM. Most importantly, this present system displayed high selectivity toward p-NP even in the presence of other nitrophenols and nitrotoluenes. This reliable method had been successfully applied for the detection of p-NP in real water and soil samples.

  14. High selectivity of colorimetric detection of p-nitrophenol based on Ag nanoclusters.

    PubMed

    Qu, Fei; Chen, Ping; Zhu, Shuyun; You, Jinmao

    2017-01-15

    Ag nanoclusters (Ag NCs) templated by hyperbranched polyethyleneimine (PEI) with different terminal groups and molecular weights had been developed as a special optical sensor for detecting p-nitrophenol (p-NP). When adding p-NP into Ag NCs, an obvious color change from pale yellow to deep yellow could be observed by naked eyes, accompanying with an apparent red-shift of absorption peak, and the reason was attributed to the formation of oxygen anion of p-NP based on the transfer of H(+) from p-NP to amine groups of PEI. The molecular weights of template would greatly affect the sensitivity of p-NP. Ag NCs capped by PEI terminated ethylenediamine (EDA) possessed better sensitivity than other Ag NCs, showing good linear range from 5 to 140μM with the limit of detection as low as 1.28μM. Most importantly, this present system displayed high selectivity toward p-NP even in the presence of other nitrophenols and nitrotoluenes. This reliable method had been successfully applied for the detection of p-NP in real water and soil samples.

  15. Enhancing sensitivity and selectivity in a label-free colorimetric sensor for detection of iron(II) ions with luminescent molybdenum disulfide nanosheet-based peroxidase mimetics.

    PubMed

    Wang, Yong; Hu, Jie; Zhuang, Qianfen; Ni, Yongnian

    2016-06-15

    In the present study, we demonstrated that the luminescent molybdenum disulfide (MoS2) nanosheets, which were prepared hydrothermally by using sodium molybdate and thiourea as precursors, possessed peroxidase-like activity, and could catalyze the oxidation of peroxidase substrate o-phenylenediamine (OPD) in the presence of hydrogen peroxide (H2O2) to produce a yellow color reaction. Further addition of Fe(2+) into the nanosheets led to peroxidase mimetics with greatly enhanced catalytic activity. The observation was exploited to develop a label-free colorimetric nanozyme sensor for detection of Fe(2+). The fabricated MoS2/OPD/H2O2 sensor showed a wide linear range of 0.01-0.8 µM with a detection limit of 7 nM. Moreover, it was found that the MoS2/OPD/H2O2 sensor displayed enhanced sensitivity and selectivity toward Fe(2+) compared with the OPD/H2O2 sensor, suggesting that the MoS2 nanosheets could improve the performance of the Fe(2+) sensor. An advanced chemometrics algorithm, multivariate curve resolution by alternating least squares (MCR-ALS), was further applied to interpret the origin of enhancing sensitivity and selectivity in the Fe(2+) sensor with the MoS2 nanosheets. The time-dependent UV-vis spectral data of the studied systems were collected, and submitted to the MCR-ALS. The results showed that the increased sensitivity and selectivity of the MoS2/OPD/H2O2 sensor for Fe(2+) detection likely arose from its large reaction rate constant. Finally, the proposed MoS2/OPD/H2O2 sensor was successfully applied for detection of Fe(2+) in water samples.

  16. Highly sensitive plasmonic silver nanorods.

    PubMed

    Jakab, Arpad; Rosman, Christina; Khalavka, Yuriy; Becker, Jan; Trügler, Andreas; Hohenester, Ulrich; Sönnichsen, Carsten

    2011-09-27

    We compare the single-particle plasmonic sensitivity of silver and gold nanorods with similar resonance wavelengths by monitoring the plasmon resonance shift upon changing the environment from water to 12.5% sucrose solution. We find that silver nanoparticles have 1.2 to 2 times higher sensitivity than gold, in good agreement with simulations based on the boundary-elements-method (BEM). To exclude the effect of particle volume on sensitivity, we test gold rods with increasing particle width at a given resonance wavelength. Using the Drude-model of optical properties of metals together with the quasi-static approximation (QSA) for localized surface plasmons, we show that the dominant contribution to higher sensitivity of silver is the lower background polarizability of the d-band electrons and provide a simple formula for the sensitivity. We improve the reversibility of the silver nanorod sensors upon repeated cycles of environmental changes by blocking the high energy parts of the illumination light.

  17. Amido-Schiff base derivatives as colorimetric fluoride sensor: Effect of nitro substitution on the sensitivity and color change.

    PubMed

    Ghosh, Soumen; Alam, Md Akhtarul; Ganguly, Aniruddha; Guchhait, Nikhil

    2015-01-01

    A series of Schiff bases synthesized by the condensation of benzohydrazide and -NO2 substituted benzaldehyde have been used as selective fluoride ion sensor. Test paper coated with these synthetic Schiff bases (test kits) can detect fluoride ion selectively with a drastic color change and detection can be achieved by just using the naked-eye without the help of any optical instrument. Interestingly, the position of -NO2 group in the amido Schiff bases has an effect on the sensitivity as well as on the change of color of species.

  18. High-Sensitivity Microwave Optics.

    ERIC Educational Resources Information Center

    Nunn, W. M., Jr.

    1981-01-01

    Describes a 3.33-cm wavelength (9 GHz) microwave system that achieves a high overall signal sensitivity and a well-collimated beam with moderate-size equipment. The system has been used to develop microwave versions of the Michelson interferometer, Bragg reflector, Brewster's law and total internal reflection, and Young's interference experiment.…

  19. A high-throughput, precipitating colorimetric sandwich ELISA microarray for shiga toxins

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Shiga toxins 1 and 2 (Stx1 and Stx2) from Shiga toxin-producing E. coli (STEC) bacteria were simultaneously detected with a newly developed, high-throughput antibody microarray platform. The proteinaceous toxins were immobilized and sandwiched between biorecognition elements (monoclonal antibodies)...

  20. A simple colorimetric chemosensor bearing a carboxylic acid group with high selectivity for CN-

    NASA Astrophysics Data System (ADS)

    Park, Gyeong Jin; Choi, Ye Won; Lee, Dongkuk; Kim, Cheal

    2014-11-01

    A new simple ‘naked eye' chemosensor 1 (sodium (E)-2-((2-(3-hydroxy-2-naphthoyl)hydrazono)methyl)benzoate) has been synthesized for detection of CN- in a mixture of DMF/H2O (9:1). The sensor 1 comprises of a naphthoic hydrazide as efficient hydrogen bonding donor group and a benzoic acid as the moiety with the water solubility. The receptor 1 showed high selectivity toward cyanide ions in a 1:1 stoichiometric manner, which induces a fast color change from colorless to yellow for CN- over other anions. Therefore, receptor 1 could be useful for cyanide detection in aqueous environment, displaying a high distinguishable selectivity from hydrogen bonded anions and being clearly visible to the naked eye.

  1. 4-(8-Quinolyl)amino-7-nitro-2,1,3-benzoxadiazole as a new selective and sensitive fluorescent and colorimetric pH probe with dual-responsive ranges in aqueous solutions

    NASA Astrophysics Data System (ADS)

    Li, Xutian; Zhang, Min; Liang, Haipeng; Huang, Zhaowei; Tang, Jiang; Chen, Zhi; Yang, Liting; Ma, Li-Jun; Wang, Yuhai; Xu, Baiping

    2016-01-01

    Fluorescent and colorimetric pH probe possess many advantages including rapid response time, nondestructive testing, and excellent pH sensitivity. However, they usually cannot be utilized simultaneously in both acidic and basic pH ranges. In this study, a new selective and sensitive fluorescent and colorimetric pH probe, 4-(8- quinolyl)amino-7-nitro-2,1,3-benzoxadiazole (1), was designated and synthesized. The optical probe exhibited dual-responsive pH ranges to both acidic and basic aqueous solutions. When the solution pH was gradually increased from 8.5 to 13.3, the absorption spectra of 1 showed an obvious hyperchromicity, accompanied with a red shift of the absorption band at 340 nm, a blue shift of the absorption band at 482 nm, and a distinct color change from orange to violet pink to yellow. Within the pH range from 2.2 to 0.2, the fluorescent spectra of 1 showed a "turn-on" response signal to solution pH. In order to understand the response mechanism of the probe to solution pH, the probe molecule was split into two parts, 8-aminoquinoline (2) and 4-amino-7- nitro-benzofurazan (3). UV-vis absorption and fluorescent experiments of 2 and 3 indicated that both are sensitive optical pH probes. Furthermore, the NMR experiment of 1 was explored in basic and acidic conditions. The results indicated that the colorimetric responses of 1 to pH under basic condition should be attributed to the deprotonation of the imino group on the quinolyl ring, and the fluorescent recognition of 1 to pH under acidic condition was probably due to the protonation of the nitrogen atoms from the benzofurazan and quinolyl rings.

  2. Colorimetric protein assay techniques.

    PubMed

    Sapan, C V; Lundblad, R L; Price, N C

    1999-04-01

    There has been an increase in the number of colorimetric assay techniques for the determination of protein concentration over the past 20 years. This has resulted in a perceived increase in sensitivity and accuracy with the advent of new techniques. The present review considers these advances with emphasis on the potential use of such technologies in the assay of biopharmaceuticals. The techniques reviewed include Coomassie Blue G-250 dye binding (the Bradford assay), the Lowry assay, the bicinchoninic acid assay and the biuret assay. It is shown that each assay has advantages and disadvantages relative to sensitivity, ease of performance, acceptance in the literature, accuracy and reproducibility/coefficient of variation/laboratory-to-laboratory variation. A comparison of the use of several assays with the same sample population is presented. It is suggested that the most critical issue in the use of a chromogenic protein assay for the characterization of a biopharmaceutical is the selection of a standard for the calibration of the assay; it is crucial that the standard be representative of the sample. If it is not possible to match the standard with the sample from the perspective of protein composition, then it is preferable to use an assay that is not sensitive to the composition of the protein such as a micro-Kjeldahl technique, quantitative amino acid analysis or the biuret assay. In a complex mixture it might be inappropriate to focus on a general method of protein determination and much more informative to use specific methods relating to the protein(s) of particular interest, using either specific assays or antibody-based methods. The key point is that whatever method is adopted as the 'gold standard' for a given protein, this method needs to be used routinely for calibration.

  3. Pt74Ag26 nanoparticle-decorated ultrathin MoS2 nanosheets as novel peroxidase mimics for highly selective colorimetric detection of H2O2 and glucose

    NASA Astrophysics Data System (ADS)

    Cai, Shuangfei; Han, Qiusen; Qi, Cui; Lian, Zheng; Jia, Xinghang; Yang, Rong; Wang, Chen

    2016-02-01

    To extend the functionalities of two-dimensional graphene-like layered compounds as versatile materials, the modification of transition metal dichalcogenide nanosheets such as MoS2 with metal nanoparticles is of great and widespread interest. However, few studies are available on the preparation of bimetallic nanoparticles supported on MoS2. Herein, a facile and efficient method to synthesize MoS2-PtAg nanohybrids by decorating ultrathin MoS2 nanosheets with octahedral Pt74Ag26 alloy nanoparticles has been reported. The as-prepared MoS2-Pt74Ag26 nanohybrids were investigated as novel peroxidase mimics to catalyze the oxidation of classical peroxidase substrate 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H2O2, producing a blue colored reaction and exhibiting typical Michaelis-Menten kinetics. MoS2-Pt74Ag26 has a higher affinity for H2O2 than horseradish peroxidase (HRP) and a higher vmax value with TMB as the substrate than MoS2. The improved catalytic activity of hybrids for colorimetric reactions could be attributed to the synergistic effects of octahedral Pt74Ag26 nanoparticles and ultrathin MoS2 nanosheets as supports. Meanwhile, the generation of active oxygen species (&z.rad;OH) by H2O2 decomposition with MoS2-Pt74Ag26 was responsible for the oxidation of TMB. On the basis of these findings, a colorimetric method based on MoS2-Pt74Ag26 nanohybrids that is highly sensitive and selective was developed for glucose detection. Lower values of the limit of detection (LOD) were obtained, which is more sensitive than MoS2 nanosheets.To extend the functionalities of two-dimensional graphene-like layered compounds as versatile materials, the modification of transition metal dichalcogenide nanosheets such as MoS2 with metal nanoparticles is of great and widespread interest. However, few studies are available on the preparation of bimetallic nanoparticles supported on MoS2. Herein, a facile and efficient method to synthesize MoS2-PtAg nanohybrids by decorating

  4. The Relationship Between the Color Characteristics of the RGB Colorimetric System and the Physicochemical Properties of Petroleums and high Boiling Hydrocarbon Distillates

    NASA Astrophysics Data System (ADS)

    Dolomatov, M. Yu.; Yarmuhametova, G. U.

    2016-09-01

    An interrelation was established between physicochemical properties of oils and high boiling hydrocarbon distillates and their solutions' color characteristics defi ned in the RGB colorimetric system using a standard radiation source CIE D65. It was shown that by using color characteristics of solutions of the specifi ed objects, it was possible to determine their relative density, molecular mass, activation energy of viscous fl ow, and the coking value. Research results were confi rmed by statistical data processing using the methods of multivariate regression and correlation analysis.

  5. A Colorimetric Bioassay for Perchlorate

    NASA Astrophysics Data System (ADS)

    Heinnickel, M. L.; Smith, S.; Coates, J. D.

    2007-12-01

    Recognition of perchlorate (ClO4-) as a widespread contaminant across the United States and its potential adverse affects towards human health has motivated the EPA to place ClO4- on its contaminant candidate list for drinking water supplies. While a federal MCL has not yet been set, a recommended public health goal of 1 ppb (μg.L-1) was established by the US EPA in 2002. To date, methods of detection require use of sensitive ion chromatographic equipment that are expensive, time consuming, and require highly trained personnel for use. Our studies are focused on the development of a highly sensitive, simple, and robust colorimetric bioassay based on the primary enzyme involved in microbial ClO4- reduction, the perchlorate reductase (Pcr). A previously published assay used reduced methyl viologen (MV, the dye is reduced with sodium hydrosulfite) as an electron donor to demonstrate Pcr activity. The assay directly correlates the amount of MV oxidized with the amount of ClO4- reduced by assuming a transfer of four electrons. To test this assumption, we compared actual concentrations of MV oxidized to ClO4- reduced in this assay. ClO4- concentrations were determined using a Dionex ICS-500 ion chromatography system, while MV concentrations were determined using a standard curve generated at 578 nm. Comparisons between the two revealed that twelve molecules of MV were oxidized for each molecule of ClO4- reduced. The oxidation of these additional eight MV molecules is explained by the interaction of the dye with chlorite (the product of the Pcr reaction) and other contaminants that could be present in the enzyme prep. This unsettling result indicated this assay would be problematic for the detection of ClO4- in soil, which has many chemicals that could react with MV. To improve upon this assay, we have tried to reduce ClO4- using less reactive dyes and reductants. The reductants ascorbic acid, NADH, and dithiothreitol drive Pcr catalyzed ClO4- reduction, however, they

  6. Content determination of the flavonoids in the different parts and different species of Abelmoschus esculentus L. by reversed phase-high performance liquid chromatograph and colorimetric method

    PubMed Central

    Lin, Yin; Lu, Min-feng; Liao, Hai-bing; Li, Yu-xian; Han, Wei; Yuan, Ke

    2014-01-01

    Background: This research will establish the ultraviolet colorimetric method to determine the total flavonoid content in different species and different parts of Abelmoschus esculentus L. Materials and Methods: We establish the reversed-phase high-performance liquid chromatograph (RP-HPLC) method to determine the content of the three flavonoid glycosides in different species and different parts of the A. esculentus. Adopt the NaNO2-Al (NO3)3-NaOH colorimetric method to determine the total flavonoid content; at the same time, adopt the RP-HPLC method to determine the contents of the three flavonoid glycosides. Using the methods of ultraviolet colorimetry and RP-HPLC, we determined and analyzed the total flavonoid content and the content of the three flavonoid glycosides in different species and different parts of A. esculentus. Results: There are great distribution differences of the total flavonoids and the three flavonoid glycosides in different species and parts of A. esculentus. Among them, the content of the effective constituents in the flower is relatively high, next is in the fruit. In the different species of A. esculentus, the content of the flavonoids of finger relatively high. The HPLC method established in this research is simple and convenient and its results are accurate and reliable. In addition, it has a very good repeatability. Conclusion: The results provided the reference data for the medicinal use of A. esculentus and it can be used in quality analyzing of its effective constituents. PMID:25210315

  7. Functional surface modification of natural cellulose substances for colorimetric detection and adsorption of Hg2+ in aqueous media.

    PubMed

    Zhang, Xuehai; Huang, Jianguo

    2010-09-07

    Immobilization of ruthenium dye or mercaptosilane monolayer onto metal oxide ultrathin film pre-coated cellulose nanofibres of natural cellulose substances yielded colorimetric sensing materials with high sensitivity and selectivity as well as good reversibility, and trapping materials with high efficiency for detection and adsorption of Hg(2+) ions in aqueous media.

  8. High throughput, colorimetric screening of microbial ester biosynthesis reveals high ethyl acetate production from Kluyveromyces marxianus on C5, C6, and C12 carbon sources.

    PubMed

    Löbs, Ann-Kathrin; Lin, Jyun-Liang; Cook, Megan; Wheeldon, Ian

    2016-10-01

    Advances in genome and metabolic pathway engineering have enabled large combinatorial libraries of mutant microbial hosts for chemical biosynthesis. Despite these advances, strain development is often limited by the lack of high throughput functional assays for effective library screening. Recent synthetic biology efforts have engineered microbes that synthesize acetyl and acyl esters and many yeasts naturally produce esters to significant titers. Short and medium chain volatile esters have value as fragrance and flavor compounds, while long chain acyl esters are potential replacements for diesel fuel. Here, we developed a biotechnology method for the rapid screening of microbial ester biosynthesis. Using a colorimetric reaction scheme, esters extracted from fermentation broth were quantitatively converted to a ferric hydroxamate complex with strong absorbance at 520 nm. The assay was validated for ethyl acetate, ethyl butyrate, isoamyl acetate, ethyl hexanoate, and ethyl octanoate, and achieved a z-factor of 0.77. Screening of ethyl acetate production from a combinatorial library of four Kluyveromyces marxianus strains on seven carbon sources revealed ethyl acetate biosynthesis from C5, C6, and C12 sugars. This newly adapted method rapidly identified novel properties of K. marxianus metabolism and promises to advance high throughput microbial strain engineering for ester biosynthesis.

  9. Simple Colorimetric Determination of the Manganese Content in Photosynthetic Membranes

    SciTech Connect

    Semin, B. K.; Seibert, M.

    2009-01-01

    The functional Mn content of intact photosystem II membrane fragments was measured as 4.06 {+-} 0.13 Mn/reaction center when determined using a simple, sensitive colorimetric assay that will also work with thylakoids and core complexes. This procedure requires minimal sample material, does not need expensive assay equipment, requires four simple steps, and only takes 20-30 min to perform. These include (a) removal of the adventitious Mn ions by CaCl{sub 2} treatment of the membranes, (b) extraction of the Mn from the O{sub 2}-evolving complex with hydrochloric acid, (c) purification of the extract by centrifugation followed by filtration of the supernatant through an Acrodisc syringe filter (0.2 {micro}m nylon membrane), and (d) colorimetric determination of Mn in the extract using the reaction of the chromogenic agent, 3,3',5,5'-tetramethylbenzidine, with previously oxidized Mn(II) cations carried out at high pH. The colorimetric assay itself has been used previously by Serrat (Mikrochim Acta 129:77-80, 1998) for assaying Mn concentrations in sea water and drinking water.

  10. A Colorimetric Sensor for the Highly Selective Detection of Sulfide and 1,4-Dithiothreitol Based on the In Situ Formation of Silver Nanoparticles Using Dopamine

    PubMed Central

    Zhao, Lingzhi; Zhao, Liu; Miao, Yanqing; Liu, Chunye; Zhang, Chenxiao

    2017-01-01

    Hydrogen sulfide (H2S) has attracted attention in biochemical research because it plays an important role in biosystems and has emerged as the third endogenous gaseous signaling compound along with nitric oxide (NO) and carbon monoxide (CO). Since H2S is a kind of gaseous molecule, conventional approaches for H2S detection are mostly based on the detection of sulfide (S2−) for indirectly reflecting H2S levels. Hence, there is a need for an accurate and reliable assay capable of determining sulfide in physiological systems. We report here a colorimetric, economic, and green method for sulfide anion detection using in situ formation of silver nanoparticles (AgNPs) using dopamine as a reducing and protecting agent. The changes in the AgNPs absorption response depend linearly on the concentration of Na2S in the range from 2 to 15 μM, with a detection limit of 0.03 μM. Meanwhile, the morphological changes in AgNPs in the presence of S2− and thiol compounds were characterized by transmission electron microscopy (TEM). The as-synthetized AgNPs demonstrate high selectivity, free from interference, especially by other thiol compounds such as cysteine and glutathione. Furthermore, the colorimetric sensor developed was applied to the analysis of sulfide in fetal bovine serum and spiked serum samples with good recovery. PMID:28335506

  11. High-sensitivity magnetic profiling

    SciTech Connect

    Unterberger, R.R.

    1983-05-01

    A high sensitivity rubidium 87 magnetometer, designed and built by the author, is used at sea to make magnetic profiles over subsurface structures of interest. The Texas AandM University Research Vessel GYRE was used to launch, tow and recover a nonmagnetic fiberglass skiff that carried the magnetometer. To avoid magnetic field disturbances of the GYRE, the skiff with the magnetometer was towed 600 ft behind the ship. Loran C, and sometimes SATNAV, position data were used to determine the ship location. Two recording depth finders using 3.5 kHz and 12 kHz respectively were used to profile the bottom. Time marks were plotted on the magnetic and sonar data in accordance with WWV time signals received on 10 MHz. (15 MHz and 5 MHz were also available if there happened to be poor radio transmission at 10 MHz). Magnetic data were recorded in digital form on a strip chart recorder, using the last two digits of the six digit resonance frequency of the Rb 87 atoms.

  12. Colorimetric chemosensor for multi-signaling detection of metal ions using pyrrole based Schiff bases.

    PubMed

    Udhayakumari, Duraisamy; Velmathi, Sivan

    2014-03-25

    Pyrrole based Schiff bases act as a highly sensitive probe for metal ions in aqueous medium. Both receptors R1 and R2 are sensitive towards Fe(3+), Cu(2+), Hg(2+) and Cr(3+) among the other metal ions. The sensing ability of the receptors are investigated via colorimetric, optical and emission spectroscopic studies. The binding stoichiometries of R1 and R2 with metal ions have been determined as 2:1 by using Job's plot. The colorimetric receptors exhibited high sensitivity with a low detection limit of μM levels. In the presence of metal ions both receptors shows fluorescence quenching. This might be due to the photo induced electron transfer mechanism. The quenching constant was further determined using Stern-Volmer plot.

  13. High sensitivity RNA pseudoknot prediction.

    PubMed

    Huang, Xiaolu; Ali, Hesham

    2007-01-01

    Most ab initio pseudoknot predicting methods provide very few folding scenarios for a given RNA sequence and have low sensitivities. RNA researchers, in many cases, would rather sacrifice the specificity for a much higher sensitivity for pseudoknot detection. In this study, we introduce the Pseudoknot Local Motif Model and Dynamic Partner Sequence Stacking (PLMM_DPSS) algorithm which predicts all PLM model pseudoknots within an RNA sequence in a neighboring-region-interference-free fashion. The PLM model is derived from the existing Pseudobase entries. The innovative DPSS approach calculates the optimally lowest stacking energy between two partner sequences. Combined with the Mfold, PLMM_DPSS can also be used in predicting complicated pseudoknots. The test results of PLMM_DPSS, PKNOTS, iterated loop matching, pknotsRG and HotKnots with Pseudobase sequences have shown that PLMM_DPSS is the most sensitive among the five methods. PLMM_DPSS also provides manageable pseudoknot folding scenarios for further structure determination.

  14. High-performance and high-sensitivity applications of graphene transistors with self-assembled monolayers.

    PubMed

    Yeh, Chao-Hui; Kumar, Vinod; Moyano, David Ricardo; Wen, Shao-Hsuan; Parashar, Vyom; Hsiao, She-Hsin; Srivastava, Anchal; Saxena, Preeti S; Huang, Kun-Ping; Chang, Chien-Chung; Chiu, Po-Wen

    2016-03-15

    Charge impurities and polar molecules on the surface of dielectric substrates has long been a critical obstacle to using graphene for its niche applications that involve graphene's high mobility and high sensitivity nature. Self-assembled monolayers (SAMs) have been found to effectively reduce the impact of long-range scatterings induced by the external charges. Yet, demonstrations of scalable device applications using the SAMs technique remains missing due to the difficulties in the device fabrication arising from the strong surface tension of the modified dielectric environment. Here, we use patterned SAM arrays to build graphene electronic devices with transport channels confined on the modified areas. For high-mobility applications, both rigid and flexible radio-frequency graphene field-effect transistors (G-FETs) were demonstrated, with extrinsic cutoff frequency and maximum oscillation frequency enhanced by a factor of ~2 on SiO2/Si substrates. For high sensitivity applications, G-FETs were functionalized by monoclonal antibodies specific to cancer biomarker chondroitin sulfate proteoglycan 4, enabling its detection at a concentration of 0.01 fM, five orders of magnitude lower than that detectable by a conventional colorimetric assay. These devices can be very useful in the early diagnosis and monitoring of a malignant disease.

  15. A highly selective colorimetric and "turn-on" fluorimetric chemosensor for detecting CN- based on unsymmetrical azine derivatives in aqueous media

    NASA Astrophysics Data System (ADS)

    Sun, You; Hu, Jing-Han; Qi, Jing; Li, Jian-Bin

    2016-10-01

    A novel highly selective chemosensor S1 for cyanide based on unsymmetrical azine derivative was successfully designed and synthesized, which showed both colorimetric and fluorescence turn-on responses for cyanide ions in aqueous. This structurally simple chemosensor could detect CN- anion over other anions in aqueous solution DMSO/H2O (v/v = 3:2) undergo deprotonation reaction. Results showed that the chemosensor S1 exhibited 50 fold enhancement in fluorescence at 530 nm and showed an obvious change in color from colorless to yellow that could be detected by naked eye under the UV-lamp after the addition of CN- in aqueous solution. Moreover, the detection limit on fluorescence response of the sensor to CN- is down to 6.17 × 10- 8 M by titration method. Test strips based on S1 were obtain, which could be used as a convenient and efficient CN- test kit to detect CN- in aqueous solution.

  16. A novel reaction-based colorimetric and ratiometric fluorescent sensor for cyanide anion with a large emission shift and high selectivity.

    PubMed

    Wang, Shaodan; Fei, Xiaoliang; Guo, Jing; Yang, Qingbiao; Li, Yaoxian; Song, Yan

    2016-01-01

    A hybrid carbazole-hemicyanine dye (Cac) has been developed as a novel colorimetric and ratiometric fluorescent sensor for cyanide detection. Upon treatment with cyanide, Cac displayed a remarkable fluorescence ratiometric response, with the emission wavelength displaying a very large emission shift (214 nm). The detection of cyanide was performed via the nucleophilic addition of cyanide anion to the indolium group of the sensor, which resulted in the blocking of the intramolecular charge transfer (ICT) process in the sensor, inducing a ratiometric fluorescence change and simultaneously an obvious color change. Furthermore, competitive anions did not showed any significant changes both in color and emission intensity ratio (I381/I595), indicating the high selectivity of the sensor to CN(-).

  17. High sensitivity radon emanation measurements.

    PubMed

    Zuzel, G; Simgen, H

    2009-05-01

    The presented radon detection technique employs miniaturized ultra-low background proportional counters. (222)Rn samples are purified, mixed with a counting gas and filled into a counter using a special glass vacuum line. The absolute sensitivity of the system is estimated to be 40 microBq (20 (222)Rn atoms). For emanation investigations two metal sealed stainless steel vessels and several glass vials are available. Taking into account their blank contributions, measurements at a minimum detectable activity of about 100 microBq can be performed.

  18. 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.

  19. Br-PADAP embedded in cellulose acetate electrospun nanofibers: Colorimetric sensor strips for visual uranyl recognition.

    PubMed

    Hu, Lin; Yan, Xue-Wu; Li, Qi; Zhang, Xue-Ji; Shan, Dan

    2017-05-05

    In this work, a new visual colorimetric strip based on cellulose acetate nanofiber mats modified by 2-(5-Bromo-2-pyridylazo)-5-(diethylamino) phenol was successfully prepared via electrospinning technology. The prepared colorimetric strip showed high sensitivity towards UO2(2+) with the yellow-to-purple color change signal. Upon the optimal conditions of solution pH at 6.0 and response time for 80min, the detection limit for UO2(2+) can reach 50 ppb. Moreover, the strip also exhibited excellent anti-interference ability in the presence of other metal ions. In order to achieve the quantitative detection for UO2(2+), a color-differentiation map was established, which was prepared from converted H values. Finally, the strip was also used to detect UO2(2+) in the seawater and showed high sensitivity.

  20. Cryogenic High-Sensitivity Magnetometer

    NASA Technical Reports Server (NTRS)

    Day, Peter; Chui, Talso; Goodstein, David

    2005-01-01

    A proposed magnetometer for use in a cryogenic environment would be sensitive enough to measure a magnetic-flux density as small as a picogauss (10(exp -16) Tesla). In contrast, a typical conventional flux-gate magnetometer cannot measure a magnetic-flux density smaller that about 1 microgauss (10(exp -10) Tesla). One version of this device, for operation near the low end of the cryogenic temperature range, would include a piece of a paramagnetic material on a platform, the temperature of which would be controlled with a periodic variation. The variation in temperature would be measured by use of a conventional germanium resistance thermometer. A superconducting coil would be wound around the paramagnetic material and coupled to a superconducting quantum interference device (SQUID) magnetometer.

  1. A gold nanoparticles-based colorimetric test to detect single nucleotide polymorphisms for improvement of personalized therapy of psoriasis

    NASA Astrophysics Data System (ADS)

    Marsella, Alessandra; Valentini, Paola; Tarantino, Paolo; Congedo, Maurizio; Pompa, Pier Paolo

    2016-04-01

    We report a simple, rapid and low-cost test, based on gold nanoparticles, for the naked-eye colorimetric detection of a signature of single nucleotide polymorphisms (SNPs) relevant for the personalized medicine of psoriasis patients. We validated the colorimetric assay on real-world DNA samples from a cohort of 30 psoriasis patients and we compared the results, in double-blind, with those obtained with two state-of-the-art instrumental techniques, namely reverse dot blotting and direct sequencing, finding 100% agreement. We demonstrated high accuracy, sensitivity and specificity of the colorimetric test that can be easily adapted for the genotypization of different SNPs, important for the pharmacogenomics of various diseases, and in other fields, such as food traceability and population structure analysis.

  2. Nano-textured high sensitivity ion sensitive field effect transistors

    SciTech Connect

    Hajmirzaheydarali, M.; Sadeghipari, M.; Akbari, M.; Shahsafi, A.; Mohajerzadeh, S.

    2016-02-07

    Nano-textured gate engineered ion sensitive field effect transistors (ISFETs), suitable for high sensitivity pH sensors, have been realized. Utilizing a mask-less deep reactive ion etching results in ultra-fine poly-Si features on the gate of ISFET devices where spacing of the order of 10 nm and less is achieved. Incorporation of these nano-sized features on the gate is responsible for high sensitivities up to 400 mV/pH in contrast to conventional planar structures. The fabrication process for this transistor is inexpensive, and it is fully compatible with standard complementary metal oxide semiconductor fabrication procedure. A theoretical modeling has also been presented to predict the extension of the diffuse layer into the electrolyte solution for highly featured structures and to correlate this extension with the high sensitivity of the device. The observed ultra-fine features by means of scanning electron microscopy and transmission electron microscopy tools corroborate the theoretical prediction.

  3. Improving colorimetric assays through protein enzyme-assisted gold nanoparticle amplification.

    PubMed

    Xie, Xiaoji; Xu, Wei; Liu, Xiaogang

    2012-09-18

    The discovery of the DNA-mediated assembly of gold nanoparticles was a great moment in the history of science; this understanding and chemical control enabled the rational design of functional nanomaterials as novel probes in biodetection. In contrast with conventional probes such as organic dyes, gold nanoparticles exhibit high photostability and unique size-dependent optical properties. Because of their high extinction coefficients and strong distance dependent optical properties, these nanoparticles have emerged over the past decade as a promising platform for rapid, highly sensitive colorimetric assays that allow for the visual detection of low concentrations of metal ions, small molecules, and biomacromolecules. These discoveries have deepened our knowledge of biological phenomena and facilitated the development of many new diagnostic and therapeutic tools. Despite these many advances and continued research efforts, current nanoparticle-based colorimetric detection systems still suffer from several drawbacks, such as limited sensitivity and selectivity. This Account describes the recent development of colorimetric assays based on protein enzyme-assisted gold nanoparticle amplification. The benefits of such detection systems include significantly improved detection sensitivity and selectivity. First, we discuss the general design of enzyme-modified nanoparticle systems in colorimetric assays. We show that a quantitative understanding of the unique properties of different enzymes is paramount for effective biological assays. We then examine the assays for nucleic acid detection based on different types of enzymes, including endonucleases, ligases, and polymerases. For each of these assays, we identify the underlying principles that contribute to the enhanced detection capability of nanoparticle systems and illustrate them with selected examples. Furthermore, we demonstrate that the combination of gold nanoparticles and specific enzymes can probe enzyme dynamics

  4. A colorimetric assay for cytokinin oxidase.

    PubMed

    Libreros-Minotta, C A; Tipton, P A

    1995-11-01

    A simple and rapid colorimetric assay for cytokinin oxidase is described. The assay is based on the formation of a Schiff base between the enzymatic reaction product 3-methyl-2-butenal and p-aminophenol. The assay is effective in the submicromolar concentration range and can be used in crude plant extracts as well as in more highly purified preparations.

  5. Colorimetric sensing of malathion using palladium-gold bimetallic nanozyme.

    PubMed

    Singh, Shefali; Tripathi, Pranav; Kumar, Nitin; Nara, Seema

    2017-06-15

    In this work, a simple, sensitive and selective label free colorimetric assay using palladium-gold nanorod as nanozyme is reported for malathion detection. Study investigates the peroxidase potential of the nanozyme on colorimetric substrates and explores the effect of selected organophosphates on their enzyme mimetic activity. Palladium-gold nanozyme shows excellent peroxidase mimetic activity with O-phenylenediamine in the presence of hydrogen peroxide. Its Kinetic parameters Km and kcat are better than horseradish peroxidase which makes it a superior enzyme. Nanozyme is stable over a broad temperature range (4-70°C) and shows high peroxidase activity from 2 to 6pH. The peroxidase activity of nanozyme is selectively quenched with increasing concentration of malathion and is the principle of developed assay. Assay has a lowest detection limit of 60ng/ml and shows no cross-reaction with other analogous organophosphates or metal salts. Validation on tap water samples spiked with different concentrations of malathion shows good recovery in the range of 80-106%. Assay also displays good intra and inter-assay precision which lie in the range of 2.7-6.1% and 3.2-5.9% respectively. This study demonstrated the catalytic potential of palladium-gold nanorods, which can be employed as nanozyme for developing highly sensitive detection methods.

  6. A colorimetric sensor for determination of cysteine by carboxymethyl cellulose-functionalized gold nanoparticles.

    PubMed

    Wei, Xiaoyi; Qi, Li; Tan, Junjun; Liu, Ruigang; Wang, Fuyi

    2010-06-25

    A simple and sensitive colorimetric method for cysteine detection was established based on the carboxymethyl cellulose-functionalized gold nanoparticles (CMC-AuNPs). The nanoparticles were directly synthesized with sodium carboxymethyl cellulose by a simple approach, which would protect particles against salt-induced aggregation. Then the CMC-AuNPs solution exhibited a high colorimetric selectivity to cysteine. The assay results indicated that the introduction of cysteine could induce the aggregation of the colloidal solutions at the presence of sodium chloride, displaying changes in color and in UV-vis absorption spectra. Thus an exceptionally simple, rapid method for detecting cysteine was obtained at the linear range of 10.0-100.0 microM with the relative coefficient of 0.997. The proposed method possessed the advantages of simplicity and sensitivity, and was applied to real urine sample detection. The results were satisfying and the proposed method was especially appropriate for detection of cysteine in biological samples.

  7. Monolayer g-C3N4 Fluorescent Sensor for Sensitive and Selective Colorimetric Detection of Silver ion from Aqueous Samples.

    PubMed

    Cao, Yujuan; Wu, Wei; Wang, Song; Peng, Hong; Hu, Xiaogang; Yu, Ying

    2016-03-01

    Rapid and sensitive detection of heavy-metal ions in natural water environments worldwide is urgently needed because of their severe threats to human health. In the present work, monolayer graphite-like flake C3N4 (g-C3N4) materials were applied as a new fluorescent sensor for the detection of trace silver ion in aqueous solution. The thickness of synthesized g-C3N4 was 0.45 nm and obtained by exfoliating twice with ultrasonic. With the presence of ethylene diamine tetraacetic acid as a screening agent, the highly sensitive sensor reached a low detection limit of 52.3 nmol/L for silver (I) ion and there was no disturbance when silver (I) ion coexisted with other metal ions in water samples. Under the optimal conditions, the monolayer g-C3N4 was successfully used to detect trace silver (I) ion in different environmental water and drinking water samples.

  8. A colorimetric sensor array for detection of triacetone triperoxide vapor.

    PubMed

    Lin, Hengwei; Suslick, Kenneth S

    2010-11-10

    Triacetone triperoxide (TATP), one of the most dangerous primary explosives, has emerged as an explosive of choice for terrorists in recent years. Owing to the lack of UV absorbance, fluorescence, or facile ionization, TATP is extremely difficult to detect directly. Techniques that are able to detect generally require expensive instrumentation, need extensive sample preparation, or cannot detect TATP in the gas phase. Here we report a simple and highly sensitive colorimetric sensor for the detection of TATP vapor with semiquantitative analysis from 50 ppb to 10 ppm. By using a solid acid catalyst to pretreat a gas stream, we have discovered that a colorimetric sensor array of redox sensitive dyes can detect even very low levels of TATP vapor from its acid decomposition products (e.g., H(2)O(2)) with limits of detection (LOD) below 2 ppb (i.e., <0.02% of its saturation vapor pressure). Common potential interferences (e.g., humidity, personal hygiene products, perfume, laundry supplies, volatile organic compounds, etc.) do not generate an array response, and the array can also differentiate TATP from other chemical oxidants (e.g., hydrogen peroxide, bleach, tert-butylhydroperoxide, peracetic acid).

  9. In Situ Glutamine Synthetase Activity in a Marine Unicellular Alga (Development of a Sensitive Colorimetric Assay and the Effects of Nitrogen Status on Enzyme Activity).

    PubMed Central

    Rees, TAV.; Larson, T. R.; Heldens, JWG.; Huning, FGJ.

    1995-01-01

    A malachite green colorimetric assay for glutamine synthetase is described. Glutamine synthetase activity was determined in situ in the marine diatom Phaeodactylum tricornutum Bohlin using cells permeabilized by freeze/thawing. Higher activities were obtained with cells permeabilized in N-2-hydroxyethylpiperazine-N[prime]-2-ethanesulfonic acid compared with N-tris(hydroxymethyl)methyl-3-aminopropanesulfonic acid, tris(hydroxymethyl)aminomethane, or imidazole, and the optimum pH was 7.9. Activities were higher in cells permeabilized in the presence of reductant, particularly dithiothreitol. Glutamine synthetase activities were markedly decreased in the presence of methionine sulfoximine. In the presence of saturating concentrations of glutamate and ATP, the apparent Km for ammonia was 320 [mu]M, but this value decreased to 110 [mu]M with subsaturating concentrations of glutamate and ATP. The apparent Km values for glutamate and ATP, in the presence of saturating concentrations of ammonia, were 9.7 and 2.9 mM, respectively. Ammonia-grown cells had lower glutamine synthetase activities than did nitrate-grown cells. During nitrogen starvation of both ammonia- and nitrate-grown cells, glutamine synthetase activities increased rapidly during the first 8 h, reaching maximum values after 24 to 48 h. Moreover, the time course for the increases in glutamine synthetase activities and rate of methylamine uptake following the transfer of nitrate-grown cells to nitrogen-deficient medium were very similar. In nitrate-grown cells and cells deprived of combined nitrogen, glutamine synthetase activities and maximum rates of ammonia uptake gave comparable values when measured at the same temperature (20[deg]C). PMID:12228676

  10. A novel colorimetric method for field arsenic speciation analysis.

    PubMed

    Hu, Shan; Lu, Jinsuo; Jing, Chuanyong

    2012-01-01

    Accurate on-site determination of arsenic (As) concentration as well as its speciation presents a great environmental challenge especially to developing countries. To meet the need of routine field monitoring, we developed a rapid colorimetric method with a wide dynamic detection range and high precision. The novel application of KMnO4 and CH4N2S as effective As(III) oxidant and As(V) reductant, respectively, in the formation of molybdenum blue complexes enabled the differentiation of As(III) and As(V). The detection limit of the method was 8 microg/L with a linear range (R2 = 0.998) of four orders of magnitude in total As concentrations. The As speciation in groundwater samples determined with the colorimetric method in the field were consistent with the results using the high performance liquid chromatography atomic fluorescence spectrometry, as evidenced by a linear correlation in paired analysis with a slope of 0.9990-0.9997 (p < 0.0001, n = 28). The recovery of 96%-116% for total As, 85%-122% for As(III), and 88%-127% for As(V) were achieved for groundwater samples with a total As concentration range 100-800 microg/L. The colorimetric result showed that 3.61 g/L As(III) existed as the only As species in a real industrial wastewater, which was in good agreement with the HPLC-AFS result of 3.56 g/L As(III). No interference with the color development was observed in the presence of sulfate, phosphate, silicate, humic acid, and heavy metals from complex water matrix. This accurate, sensitive, and easy-to-use method is especially suitable for field As determination.

  11. Passive Leak Detection Using Commercial Hydrogen Colorimetric Indicator

    SciTech Connect

    Hartmann, Kevin; Buttner, William; Burgess, Robert; Rivkin, Carl

    2016-09-01

    Element One, Inc. (www.elem.com), a small business with in Boulder, CO, has been developing hydrogen detection technology based upon a highly selective colorimetric indicator. In its native state, the indicator pigment is a pale gray color, but becomes black upon exposure to hydrogen. The colorimetric change can be readily observed by the naked eye without the need for supplemental electronics or other hardware. Recently, the colorimetric indicator was integrated into a pliable, self-adhesive tape that can readily wrap around pneumatic fittings to serve as a hydrogen leak detector. A prototype version of the Element One indicator tape was tested within an NREL hydrogen system and successfully identified the unexpected presence of a small leak; a summary document for this case study is presented in Appendix 1. The tape was subsequently configured into 10-foot rolls as a product prototype that has just recently been commercialized and marketed under the tradename DetecTape(R). Figure 1 shows the commercial version of DetecTape along with an indicator sample in its native state and one that had been exposed to hydrogen. DetecTape is a self-adhesive silicone-based tape impregnated with a proprietary hydrogen-sensitive indicator based on transition metal oxides. A length of the tape can be cut from the roll and stretched by a factor of two or three times around a fitting. Due to the self-adhesive property of the tape, this provides a tight seal around the fitting. The seal is not hermetic, and is not intended to prevent the release of a leaking gas. However, a portion of the hydrogen leaking from a wrapped fitting will pass through the tape and react with the active indicator impregnated within the tape, thereby inducing blackening.

  12. Colorimetry and SERS dual-mode detection of telomerase activity: combining rapid screening with high sensitivity

    NASA Astrophysics Data System (ADS)

    Zong, Shenfei; Wang, Zhuyuan; Chen, Hui; Hu, Guohua; Liu, Min; Chen, Peng; Cui, Yiping

    2014-01-01

    As an important biomarker and therapeutic target, telomerase has attracted considerable attention concerning its detection and monitoring. Here, we present a colorimetry and surface enhanced Raman scattering (SERS) dual-mode telomerase activity detection method, which has several distinctive advantages. First, colorimetric functionality allows rapid preliminary discrimination of telomerase activity by the naked eye. Second, the employment of SERS technique results in greatly improved detection sensitivity. Third, the combination of colorimetry and SERS into one detection system can ensure highly efficacious and sensitive screening of numerous samples. Besides, the avoidance of polymerase chain reaction (PCR) procedures further guarantees fine reliability and simplicity. Generally, the presented method is realized by an ``elongate and capture'' procedure. To be specific, gold nanoparticles modified with Raman molecules and telomeric repeat complementary oligonucleotide are employed as the colorimetric-SERS bifunctional reporting nanotag, while magnetic nanoparticles functionalized with telomerase substrate oligonucleotide are used as the capturing substrate. Telomerase can synthesize and elongate telomeric repeats onto the capturing substrate. The elongated telomeric repeats subsequently facilitate capturing of the reporting nanotag via hybridization between telomeric repeat and its complementary strand. The captured nanotags can cause a significant difference in the color and SERS intensity of the magnetically separated sediments. Thus both the color and SERS can be used as indicators of the telomerase activity. With fast screening ability and outstanding sensitivity, we anticipate that this method would greatly promote practical application of telomerase-based early-stage cancer diagnosis.As an important biomarker and therapeutic target, telomerase has attracted considerable attention concerning its detection and monitoring. Here, we present a colorimetry and

  13. A readily available colorimetric and near-infrared fluorescent turn-on probe for rapid and selective detection of cysteine in living cells.

    PubMed

    Xue, Shuanghong; Ding, Shuangshuang; Zhai, Qisong; Zhang, Haiyan; Feng, Guoqiang

    2015-06-15

    A readily available naphthofluorescein-based near-infrared (NIR) fluorescent probe was reported for rapid, colorimetric and NIR fluorescent turn-on detection of cysteine (Cys) with high selectivity and sensitivity over various analytes including the similar structured homocysteine (Hcy) and glutathione (GSH). This probe was successfully applied to bioimage intracellular Cys in living cells with low cytotoxicity.

  14. Colorimetric Sensor Array for White Wine Tasting.

    PubMed

    Chung, Soo; Park, Tu San; Park, Soo Hyun; Kim, Joon Yong; Park, Seongmin; Son, Daesik; Bae, Young Min; Cho, Seong In

    2015-07-24

    A colorimetric sensor array was developed to characterize and quantify the taste of white wines. A charge-coupled device (CCD) camera captured images of the sensor array from 23 different white wine samples, and the change in the R, G, B color components from the control were analyzed by principal component analysis. Additionally, high performance liquid chromatography (HPLC) was used to analyze the chemical components of each wine sample responsible for its taste. A two-dimensional score plot was created with 23 data points. It revealed clusters created from the same type of grape, and trends of sweetness, sourness, and astringency were mapped. An artificial neural network model was developed to predict the degree of sweetness, sourness, and astringency of the white wines. The coefficients of determination (R2) for the HPLC results and the sweetness, sourness, and astringency were 0.96, 0.95, and 0.83, respectively. This research could provide a simple and low-cost but sensitive taste prediction system, and, by helping consumer selection, will be able to have a positive effect on the wine industry.

  15. High sensitivity knitted fabric strain sensors

    NASA Astrophysics Data System (ADS)

    Xie, Juan; Long, Hairu; Miao, Menghe

    2016-10-01

    Wearable sensors are increasingly used in smart garments for detecting and transferring vital signals and body posture, movement and respiration. Existing fabric strain sensors made from metallized yarns have low sensitivity, poor comfort and low durability to washing. Here we report a knitted fabric strain sensor made from a cotton/stainless steel (SS) fibre blended yarn which shows much higher sensitivity than sensors knitted from metallized yarns. The fabric feels softer than pure cotton textiles owing to the ultrafine stainless steel fibres and does not lose its electrical property after washing. The reason for the high sensitivity of the cotton/SS knitted fabric sensor was explored by comparing its sensing mechanism with the knitted fabric sensor made from metallized yarns. The results show that the cotton/SS yarn-to-yarn contact resistance is highly sensitive to strain applied to hooked yarn loops.

  16. High Sensitivity deflection detection of nanowires

    SciTech Connect

    Sanii, Babak; Ashby, Paul

    2009-10-28

    A critical limitation of nanoelectromechanical systems (NEMS) is the lack of a high-sensitivity position detection mechanism. We introduce a noninterferometric optical approach to determine the position of nanowires with a high sensitivity and bandwidth. Its physical origins and limitations are determined by Mie scattering analysis. This enables a dramatic miniaturization of detectable cantilevers, with attendant reductions to the fundamental minimum force noise in highly damping environments. We measure the force noise of an 81{+-}9??nm radius Ag{sub 2}Ga nanowire cantilever in water at 6{+-}3??fN/{radical}Hz.

  17. A colorimetric bioassay for high-througput and cost-effectively assessing anti-foot-and-mouth disease virus activity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Foot-and-Mouth Disease virus (FMDV) is one of the most contagious animal viruses and has a devastating effect on livestock industries if an outbreaks occurs, especially in FMD-free countries. The virus is very sensitive to inhibition by type I interferons. Currently, a reported assay to measure FM...

  18. Colorimetric sensor array for determination and identification of toxic industrial chemicals.

    PubMed

    Feng, Liang; Musto, Christopher J; Kemling, Jonathan W; Lim, Sung H; Zhong, Wenxuan; Suslick, Kenneth S

    2010-11-15

    A low-cost yet highly sensitive colorimetric sensor array for the detection and identification of toxic industrial chemicals (TICs) has been developed. The sensor consists of a disposable array of cross-responsive nanoporous pigments whose colors are changed by diverse chemical interactions with analytes. Clear differentiation among 20 different TICs has been easily achieved at both their IDLH (immediately dangerous to life or health) concentration within 2 min of exposure and PEL (permissible exposure limit) concentration within 5 min of exposure with no errors or misclassifications. Detection limits are generally well below the PEL (in most cases below 5% of PEL) and are typically in the low ppb range. The colorimetric sensor array is not responsive to changes in humidity or temperature over a substantial range. The printed arrays show excellent batch to batch reproducibility and long shelf life (greater than 3 months).

  19. Functionalized magnetic microparticle-based colorimetric platform for influenza A virus detection

    NASA Astrophysics Data System (ADS)

    Chen, Chaohui; Zou, Zhong; Chen, Lu; Ji, Xinghu; He, Zhike

    2016-10-01

    A colorimetric platform for influenza A virus detection was developed by using the high efficiency of enzymatic catalysis and the reduction of gold ions with hydrogen peroxide. Aptamer-functionalized magnetic microparticles were synthesized to capture the influenza A virus. This was followed by the binding of ConA-GOx-AuNPs to the H3N2 virus through the ConA-glycan interaction. The sandwich complex was subsequently dispersed in glucose solution to trigger an enzymatic reaction to produce hydrogen peroxide, which controlled the growth of gold nanoparticles and produced colored solutions. The determination of H3N2 concentration was realized by comparing the two differently colored gold nanoparticles. This method could detect the target virus as low as 11.16 μg ml-1. Furthermore, it opens new opportunities for sensitive and colorimetric detection of viruses and proteins.

  20. An organic indicator functionalized graphene oxide nanocomposite-based colorimetric assay for the detection of sarcosine

    NASA Astrophysics Data System (ADS)

    Xue, Zhonghua; Yin, Bo; Wang, Hui; Li, Mengqian; Rao, Honghong; Liu, Xiuhui; Zhou, Xinbin; Lu, Xiaoquan

    2016-03-01

    Rapid detection of sarcosine is a key requirement for both diagnosis and treatment of disease. We report here a simple yet sensitive colorimetric nanocomposite platform for rapid detection of sarcosine in alkaline media. The approach exploited the benefits of a rapid color-producing reaction between an organic indicator, 1,2-naphthoquinone-4-sulphonic acid sodium salt (NQS), and the analyte of sarcosine species as well as the good catalytic ability of graphene oxide (GO) to the formation of highly colored products due to its good water dispersibility, extremely large surface area and facile surface modification. As a result, a NQS functionalized GO nanocomposite through π-π stacking has been demonstrated to be useful as a highly efficient catalyst system for the selective and sensitive colorimetric determination of sarcosine by providing a nanocomposite-amplified colorimetric response. Meanwhile, the strategy offered excellent selectivity toward sarcosine species against other amino acids as well as a satisfying detection limit of 0.73 μM. More importantly, by using an electrochemical method, a credible sensing mechanism of GO nanocomposite-based colorimetric platform for a special analyte determination can be easily verified and elucidated, which also provides an attractive alternative to conventional characterization strategies.Rapid detection of sarcosine is a key requirement for both diagnosis and treatment of disease. We report here a simple yet sensitive colorimetric nanocomposite platform for rapid detection of sarcosine in alkaline media. The approach exploited the benefits of a rapid color-producing reaction between an organic indicator, 1,2-naphthoquinone-4-sulphonic acid sodium salt (NQS), and the analyte of sarcosine species as well as the good catalytic ability of graphene oxide (GO) to the formation of highly colored products due to its good water dispersibility, extremely large surface area and facile surface modification. As a result, a NQS

  1. High sensitivity optically pumped quantum magnetometer.

    PubMed

    Tiporlini, Valentina; Alameh, Kamal

    2013-01-01

    Quantum magnetometers based on optical pumping can achieve sensitivity as high as what SQUID-based devices can attain. In this paper, we discuss the principle of operation and the optimal design of an optically pumped quantum magnetometer. The ultimate intrinsic sensitivity is calculated showing that optimal performance of the magnetometer is attained with an optical pump power of 20 μW and an operation temperature of 48°C. Results show that the ultimate intrinsic sensitivity of the quantum magnetometer that can be achieved is 327 fT/Hz(½) over a bandwidth of 26 Hz and that this sensitivity drops to 130 pT/Hz(½) in the presence of environmental noise. The quantum magnetometer is shown to be capable of detecting a sinusoidal magnetic field of amplitude as low as 15 pT oscillating at 25 Hz.

  2. Electrostatic sensitivity of secondary high explosives

    SciTech Connect

    Campos, C.A.

    1980-06-01

    An Electrostatic Sensitivity Test System designed at Pantex was used to evaluate the secondary high explosives PETN, HMX, RDX, HNS I, HNS II and TATB. The purpose of this study was to establish test conditions for a standard electrostatic sensitivity test and measure baseline data of a few secondary explosives. Although secondary explosives are often considered quite insensitive to an electrostatic discharge, PETN, HMX, and RDX were initiated. Several external elements to the high explosive were found to have an influence on sensitivity. Initiation appeared to be dependent on the nature of the discharge current curve. Those elements recognized as having a significant effect on the results were held constant in this study. These included: distance between discharge plates; sample moisture content; material density; and system resistance, capacitance and inductance. However, no attempt was made in this study to determine the extent to which the high explosive response to electrostatic discharge is affected by these factors since such correlation is not necessary to determine relative sensitivities.

  3. High efficiency porphyrin sensitized mesoscopic solar cells

    NASA Astrophysics Data System (ADS)

    Giordano, Fabrizio; Yi, Chenyi; Teuscher, Joël.; Zakeeruddin, Shaik M.; Grätzel, Michael

    2014-10-01

    Dye-Sensitized Solar Cells (DSSC) represents a reliable technology, ready for the market and able to compete with silicon solar cells for specific fields of application. Porphyrin dyes allow reaching high power conversion efficiency in conjunction with cobalt redox electrolytes due to larger open circuit potentials. The bigger size of the cobalt complexes compared to standard iodide/triiodide redox couple hampers its percolation through the meso-porous TiO2 network, thus impairing the regeneration process. In case of porphyrin dyes mass transport problems in the electrolyte need to be carefully handled, due to the large size of the sensitizing molecule and the bulky cobalt complexes. Herein we report the study of structural variations on porphyrin sensitizers and their influence on the DSSC performance with cobalt based redox electrolyte.

  4. High blood pressure and visual sensitivity

    NASA Astrophysics Data System (ADS)

    Eisner, Alvin; Samples, John R.

    2003-09-01

    The study had two main purposes: (1) to determine whether the foveal visual sensitivities of people treated for high blood pressure (vascular hypertension) differ from the sensitivities of people who have not been diagnosed with high blood pressure and (2) to understand how visual adaptation is related to standard measures of systemic cardiovascular function. Two groups of middle-aged subjects-hypertensive and normotensive-were examined with a series of test/background stimulus combinations. All subjects met rigorous inclusion criteria for excellent ocular health. Although the visual sensitivities of the two subject groups overlapped extensively, the age-related rate of sensitivity loss was, for some measures, greater for the hypertensive subjects, possibly because of adaptation differences between the two groups. Overall, the degree of steady-state sensitivity loss resulting from an increase of background illuminance (for 580-nm backgrounds) was slightly less for the hypertensive subjects. Among normotensive subjects, the ability of a bright (3.8-log-td), long-wavelength (640-nm) adapting background to selectively suppress the flicker response of long-wavelength-sensitive (LWS) cones was related inversely to the ratio of mean arterial blood pressure to heart rate. The degree of selective suppression was also related to heart rate alone, and there was evidence that short-term changes of cardiovascular response were important. The results suggest that (1) vascular hypertension, or possibly its treatment, subtly affects visual function even in the absence of eye disease and (2) changes in blood flow affect retinal light-adaptation processes involved in the selective suppression of the flicker response from LWS cones caused by bright, long-wavelength backgrounds.

  5. A concise colorimetric and fluorimetric probe for sarin related threats designed via the "covalent-assembly" approach.

    PubMed

    Lei, Zuhai; Yang, Youjun

    2014-05-07

    A turn-on signal from zero background allows sensitive detection of a weak signal and is highly desired. The "covalent-assembly" probe design principle is powerful in this regard. Herein, we report an embodiment of this principle (NA570) for detection of Sarin related threats, based on a phenylogous Vilsmeier-Haack reaction. NA570 bears a concise molecular construct, exhibits a colorimetric and a fluorimetric signal, and has potential for real applications.

  6. A Wash-Free Homogeneous Colorimetric Immunoassay Method

    PubMed Central

    Liu, Huiqiao; Rong, Pengfei; Jia, Hongwei; Yang, Jie; Dong, Bo; Dong, Qiong; Yang, Cejun; Hu, Pengzhi; Wang, Wei; Liu, Haitao; Liu, Dingbin

    2016-01-01

    Rapid and convenient biosensing platforms could be beneficial to timely diagnosis and treatment of diseases in virtually any care settings. Sandwich immunoassays, the most commonly used methods for protein detection, often rely on expensive tags such as enzyme and tedious wash and incubation procedures operated by skilled labor. In this report, we revolutionized traditional sandwich immunoassays by providing a wash-free homogeneous colorimetric immunoassay method without requirement of any separation steps. The proposed strategy was realized by controlling the growth of gold nanoparticles (AuNPs) to mediate the interparticle spacing in the protein-AuNP oligomers. We have demonstrated the successful in vitro detection of cancer biomarker in serum samples from patients with high clinical sensitivity and specificity. PMID:26722373

  7. Self-assembly of graphene oxide with a silyl-appended spiropyran dye for rapid and sensitive colorimetric detection of fluoride ions.

    PubMed

    Li, Yinhui; Duan, Yu; Zheng, Jing; Li, Jishan; Zhao, Wenjie; Yang, Sheng; Yang, Ronghua

    2013-12-03

    Fluoride ion (F(-)), the smallest anion, exhibits considerable significance in a wide range of environmental and biochemical processes. To address the two fundamental and unsolved issues of current F(-) sensors based on the specific chemical reaction (i.e., the long response time and low sensitivity) and as a part of our ongoing interest in the spiropyran sensor design, we reported here a new F(-) sensing approach that, via assembly of a F(-)-specific silyl-appended spiropyran dye with graphene oxide (GO), allows rapid and sensitive detection of F(-) in aqueous solution. 6-(tert-Butyldimethylsilyloxy)-1',3',3'-trimethylspiro [chromene- 2,2'-indoline] (SPS), a spiropyran-based silylated dye with a unique reaction activity for F(-), was designed and synthesized. The nucleophilic substitution reaction between SPS and F(-) triggers cleavage of the Si-O bond to promote the closed spiropyran to convert to its opened merocyanine form, leading to the color changing from colorless to orange-yellow with good selectivity over other anions. With the aid of GO, the response time of SPS for F(-) was shortened from 180 to 30 min, and the detection limit was lowered more than 1 order of magnitude compared to the free SPS. Furthermore, due to the protective effect of nanomaterials, the SPS/GO nanocomposite can function in a complex biological environment. The SPS/GO nanocomposite was characterized by XPS and AFM, etc., and the mechanism for sensing F(-) was studied by (1)H NMR and ESI-MS. Finally, this SPS/GO nanocomposite was successfully applied to monitoring F(-) in the serum.

  8. Developments of highly sensitive DNA sensors

    NASA Astrophysics Data System (ADS)

    Ogata, Naoya

    2011-09-01

    The large enhancements of optical properties of the dye-intercalated DNA lead us to apply the dye-intercalated DNA as various sensors with a high sensitivity to detect environmentally toxic gases such as dioxine, NOx or carbon monoxide. This paper retorts on DNA sensors for the further applications of DNA as materials. Also, bio-medical applications of DNA sensors such as a glucose sensor are reported.

  9. [Clinical interpretation of high sensitivity troponin T].

    PubMed

    Alquézar Arbé, Aitor; Santaló Bel, Miguel; Sionis, Alessandro

    2015-09-21

    Determination of cardiac troponin (cTn) is necessary for the diagnosis of acute myocardial infarction without ST segment elevation. However Tnc can be released in other clinical situations. The development of high-sensitive cTn T assays (hs-cTnT) improves the management of patients with suspected acute coronary syndrome. Here, we provide an overview of the diverse causes of hs-cTnT elevation and recommend strategies for the clinical interpretation of the test result.

  10. Low Cost, Low Power, High Sensitivity Magnetometer

    DTIC Science & Technology

    2008-12-01

    Guedes , A.; et al., 2008: Hybrid - LOW COST, LOW POWER, HIGH SENSITIVITY MAGNETOMETER A.S. Edelstein*, James E. Burnette, Greg A. Fischer, M.G...Edelstein, 2004; Burnette, 2008), we suggested a method for mitigating the problem of 1/f noise. We and others ( Guedes , 2008) have been utilizing...6. Guedes , A.; et al., 2008: Hybrid - 3magnetoresistive/microelectromechanical devices for static field modulation and sensor 1/f noise

  11. High sensitivity neutron detector for Z

    SciTech Connect

    Ruggles, L.E.; Porter, J.L. Jr.; Simpson, W.W.; Vargas, M.F.; Zagar, D.M.; Hartke, R.; Buersgens, F.; Symes, D.R.; Ditmire, T.

    2004-10-01

    We have developed, calibrated, and tested a high sensitivity neutron detector that can be operated in the harsh x-ray bremsstrahlung environment that exists in experiments conducted on the 20 MA Z z-pinch facility located at Sandia National Laboratories in Albuquerque, New Mexico. The detector uses a scintillator coupled to a microchannel-plate photomultiplier tube detector and extensive x-ray shielding.

  12. 4-Aminothiophenol functionalized gold nanoparticle-based colorimetric sensor for the determination of nitramine energetic materials.

    PubMed

    Üzer, Ayşem; Can, Ziya; Akın, Ilknur; Erçağ, Erol; Apak, Reşat

    2014-01-07

    The heterocyclic nitramine compounds, hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), are two most important military-purpose high explosives. Differentiation of RDX and HMX with colorimetric methods of determination has not yet been made because of their similar chemical structures. In this study, a sensitive colorimetric method for the determination of RDX and HMX was proposed on the basis of differential kinetics in the hydrolysis of the two compounds (yielding nitrite as a product) followed by their colorimetric determination using 4-aminothiophenol (4-ATP) modified gold nanoparticles (AuNPs) and naphthylethylene diamine (NED) as coupling agent for azo-dye formation, abbreviated as "4-ATP-AuNP+NED" colorimetric method. After alkaline hydrolysis in a 1 M Na2CO3 + 0.04 M NaOH mixture solution at room temperature, only RDX (but not HMX) was hydrolyzed to give a sufficient colorimetric response in neutralized solution, the molar absorptivity (ε) at 565 nm and the limit of detection (LOD) for RDX being (17.6 ± 1.3) × 10(3) L mol(-1) cm(-1) and 0.55 μg mL(-1), respectively. On the other hand, hot water bath (at 60 °C) hydrolysis enabled both nitramines, RDX and HMX, to give substantial colorimetric responses; i.e., ε and LOD for RDX were (32.8 ± 0.5) × 10(3) L mol(-1)cm(-1) and 0.20 μg mL(-1) and for HMX were (37.1 ± 2.8) × 10(3) L mol(-1)cm(-1) and 0.24 μg mL(-1), respectively. Unlike other AuNP-based nitrite sensors in the literature showing absorbance quenching within a relatively narrow concentration range, the developed sensor operated with an absorbance increase over a wide range of nitrite. Synthetic mixtures of (RDX + HMX) gave additive responses, and the proposed method was statistically validated against HPLC using nitramine mixtures.

  13. Novel salicylic acid-oriented thiourea-type receptors as colorimetric chemosensor: Synthesis, characterizations and selective naked-eye recognition properties

    NASA Astrophysics Data System (ADS)

    Li, Shaowei; Cao, Xiufang; Chen, Changshui; Ke, Shaoyong

    2012-10-01

    Based on the salicylic acid backbone, three highly sensitive and selective colorimetric chemosensors with an acylthiourea binding unit have been designed, synthesized and characterized. These chemosensors have been utilized for selective recognition of fluoride anions in dry DMSO solution by typical spectroscopic titration techniques. Furthermore, the obtained chemosensors AR1-3 have shown naked-eye sensitivity for detection of biologically important fluoride ion over other anions in solution.

  14. Highly sensitive beam steering with plasmonic antenna.

    PubMed

    Rui, Guanghao; Zhan, Qiwen

    2014-08-05

    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.

  15. Nanocellulose-based biosensors: design, preparation, and activity of peptide-linked cotton cellulose nanocrystals having fluorimetric and colorimetric elastase detection sensitivity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Nanocrystalline cellulose is an amphiphilic, high surface area material that can be easily functionalized and is biocom-patible and eco-friendly. It has been used singularly and in combination with other nanomaterials to optimize biosensor design. The attachment of peptides and proteins to nanocryst...

  16. Chitosan-capped silver nanoparticles as a highly selective colorimetric probe for visual detection of aromatic ortho-trihydroxy phenols.

    PubMed

    Chen, Zhaohui; Zhang, Xiaodan; Cao, Haiyan; Huang, Yuming

    2013-04-21

    We reported a new application of silver nanoparticles (NPs) for the visual sensing of aromatic polyphenols, such as gallic acid, pyrogallol and tannic acid, which is based on the intensified plasmon absorbance signals and visual changes from yellow to orange due to hydrogen-bonding recognition and subsequent catalytic oxidation of the target phenols by chitosan-capped Ag NPs (Ch-Ag NPs). The Ch-Ag NPs are generated by the well-known reaction of AgNO3 with NaBH4 and stabilized with chitosan which is a polysaccharide biopolymer with excellent dispersive properties and stability in aqueous media. After optimizing some experimental conditions, a very simple and facile sensing system has been developed for the detection of gallic acid, pyrogallol and tannic acid in water samples. The proposed system promises high selectivity toward gallic acid, pyrogallol and tannic acid, and other phenolic compounds including p-aminobenzoic acid, pentachlorophenol, 2,4,6-trinitrophenol, 2,4-dinitrophenol, p-nitrophenol, 1-naphthol, β-naphthol, p-aminophenol, catechol, hydroquinone, m-dihydroxybenzene, phloroglucin and phenol could not induce a color change even at 0.1 mM. The outstanding selectivity property of the proposed method for gallic acid, pyrogallol and tannic acid resulted from the Ch-Ag NPs-mediated reduction of Ag(+) by the target phenols. Also, a wide linear response range was obtained for the three targets. The linear response ranges for gallic acid, pyrogallol, and tannic acid were from 1 × 10(-5) to 1 × 10(-3) M, 1 × 10(-5) to 1 × 10(-2) M and 1 × 10(-6) to 1 × 10(-4) M with a respective detection limit (DL) of 1 × 10(-5), 1 × 10(-5), and 1 × 10(-6) M. The proposed method was successfully applied to detect target phenols in environmental water samples. Furthermore, because the color change from yellow to orange is observable by the naked eye, it is easy to realize visual detection of the target phenols without any instrumentation or complicated design. The

  17. Method for colorimetric detection of double-stranded nucleic acid using leuco triphenylmethane dyes.

    PubMed

    Miyamoto, Shigehiko; Sano, Sotaro; Takahashi, Koji; Jikihara, Takaaki

    2015-03-15

    Because loop-mediated isothermal amplification (LAMP) can amplify substantial amounts of DNA under isothermal conditions, its applications for simple genetic testing have attracted considerable attention. A positive LAMP reaction is indicated by the turbidity caused by by-products or by the color change after adding a metallochromic indicator to the reaction solution, but these methods have certain limitations. Leuco crystal violet (LCV), a colorless dye obtained after sodium sulfite treatment of crystal violet (CV), was used as a new colorimetric method for detecting LAMP. LCV is reconverted into CV through contact with double-stranded DNA (dsDNA). Therefore, the positive reaction of LAMP is indicated by color change from colorless to violet. The assay is sensitive enough to detect LAMP products, with a detection limit of 7.1 ng/μl for dsDNA. It is also highly selective to dsDNA, and interference with single-stranded DNA and deoxynucleotide triphosphates (dNTPs) is not observed. LCV facilitates direct colorimetric detection of the main product rather than a by-product of the LAMP reaction; therefore, this method can be used under various reaction conditions such as those with added pyrophosphatase in solution. This colorimetric LAMP detection method using LCV is useful for point-of-care genetic testing given its simplicity.

  18. Cooled membrane for high sensitivity gas sampling.

    PubMed

    Jiang, Ruifen; Pawliszyn, Janusz

    2014-04-18

    A novel sample preparation method that combines the advantages of high surface area geometry and cold surface effect was proposed to achieve high sensitivity gas sampling. To accomplish this goal, a device that enables the membrane to be cooled down was developed for sampling, and a gas chromatograph-mass spectrometer was used for separation and quantification analysis. Method development included investigation of the effect of membrane temperature, membrane size, gas flow rate and humidity. Results showed that high sensitivity for equilibrium sampling, such as limonene sampling in the current study could be achieved by either cooling down the membrane and/or using a large volume extraction phase. On the other hand, for pre-equilibrium extraction, in which the extracted amount was mainly determined by membrane surface area and diffusion coefficient, high sensitivity could be obtained by using thinner membranes with a larger surface and/or a higher sampling flow rate. In addition, humidity showed no significant influence on extraction efficiency, due to the absorption property of the liquid extraction phase. Next, the limit of detection (LOD) was found, and the reproducibility of the developed cooled membrane gas sampling method was evaluated. Results showed that LODs with a membrane diameter of 19mm at room temperature sampling were 9.2ng/L, 0.12ng/L, 0.10ng/L for limonene, cinnamaldehyde and 2-pentadecanone, respectively. Intra- and inter-membrane sampling reproducibility revealed RSD% lower than 8% and 13%, respectively. Results uniformly demonstrated that the proposed cooled membrane device could serve as an alternative powerful tool for future gas sampling.

  19. Highly sensitive terahertz sensor for glucose detection

    NASA Astrophysics Data System (ADS)

    Kim, Hyo-Suk; Lee, Dong-Kyu; Lee, Seok; Chung, Youngchul; Seo, Minah

    2015-07-01

    In this report, we present a new type of non-contact detection method for glucose molecule using nano antenna array based bio sensing chip that operates at terahertz frequency range (0.5 - 2.5 THz). Localized and hugely enhanced transmitted terahertz field by nano antenna array in the sensing chip induced enhancement of absorption coefficient of glucose molecule that enables us to detect even very small volume of molecules. Nano antenna based terahertz sensing chip can be expected to offer accurate identification of glucose level as a non-invasive and painless sensing tool with high sensitivity.

  20. Discovering the enzyme mimetic activity of metal-organic framework (MOF) for label-free and colorimetric sensing of biomolecules.

    PubMed

    Wang, Ying; Zhu, Yingjing; Binyam, Atsebeha; Liu, Misha; Wu, Yinan; Li, Fengting

    2016-12-15

    A label-free sensing strategy based on the enzyme-mimicking activity of MOF was demonstrated for colorimetric detection of biomolecules. Firstly obvious blue color was observed due to the high efficiency of peroxidase-like catalytic activity of Fe-MIL-88A (an ion-based MOF material) toward 3,3',5,5'-tetramethylbenzidine (TMB). Then in the presence of target biomolecule and corresponding aptamer, the mimetic activity of Fe-MIL-88A can be strongly inhibited and used directly to realize the colorimetric detection. On the basis of the interesting findings, we designed a straightforward, label-free and sensitive colorimetric method for biomolecule detection by using the enzyme mimetic property of MOF coupling with molecular recognition element. Compared with the existed publications, our work breaks the routine way by setting up an inorganic-organic MOF-aptamer hybrid platform for colorimetric determination of biomolecules, expanding the targets scope from H2O2 or glucose to biomolecules. As a proof of concept, thrombin and thrombin aptamer was used as a model analyte. The limit of detection of 10nM can be achieved with naked eyes and ultrahigh selectivity of thrombin toward numerous interfering substances with 10-fold concentration was demonstrated significantly. Of note, the method was further applied for the detection of thrombin in human serum samples, showing the results in agreement with those values obtained in an immobilization buffer by the colorimetric method. This inorganic-organic MOF-aptamer sensing strategy may in principle be universally applicable for the detection of a range of environmental or biomedical molecules of interests.

  1. High-sensitivity 25-micron microbolometer FPAs

    NASA Astrophysics Data System (ADS)

    Murphy, Daniel F.; Ray, Michael; Wyles, Richard; Asbrock, James F.; Lum, Nancy A.; Wyles, Jessica; Hewitt, C.; Kennedy, Adam; Van Lue, David; Anderson, John S.; Bradley, Daryl; Chin, Richard; Kostrzewa, Thomas

    2002-08-01

    Raytheon Infrared Operations (RIO) has achieved a significant technical breakthrough in uncooled FPAs by reducing the pixel size by a factor of two while maintaining state-of-the-art sensitivity. Raytheon has produced the first high-quality 320x240 microbolometer FPAs with 25 micrometers pitch pixels. The 320 x240 FPAs have a sensitivity that is comparable to microbolometer FPAs with 50 micrometers pixels. The average NETD value for these FPAs is about 35 mK with an f/1 aperture and operating at 30 Hz frame rates. Good pixel operability and excellent image quality have been demonstrated. Pixel operability is greater than 99% on some FPAs, and uncorrected responsivity nonuniformity is less than 4% (sigma/mean). The microbolometer detectors also have a relatively fast thermal time constant of approximately 10 msec. This state-of-the-art performance has been achieved as a result of an advanced micromachining fabrication process. The process allows maximization of both the thermal isolation and the optical fill-factor. The reduction in pixel size offers several potential benefits for IR systems. For a given system resolution (IFOV) requirement, the 25 micrometers pixels allow a factor of two reduction in both the focal length and aperture size of the sensor optics. The pixel size reduction facilitates a significant FPA cost reduction since the number of die printed on a wafer can be increased. The pixel size reduction has enabled the development of a large-format 640x480 FPA array. Raytheon has produced arrays with very good sensitivity, operability, and excellent image quality. These FPAs are applicable to wide-field-of-view, long range surveillance and targeting missions. Raytheon is also developing a high performance 160x128 FPA that is designed for applications where miniaturization and temperature invariance are required as well as low cost and low power.

  2. Photodetector having high speed and sensitivity

    DOEpatents

    Morse, Jeffrey D.; Mariella, Jr., Raymond P.

    1991-01-01

    The present invention provides a photodetector having an advantageous combination of sensitivity and speed; it has a high sensitivity while retaining high speed. In a preferred embodiment, visible light is detected, but in some embodiments, x-rays can be detected, and in other embodiments infrared can be detected. The present invention comprises a photodetector having an active layer, and a recombination layer. The active layer has a surface exposed to light to be detected, and comprises a semiconductor, having a bandgap graded so that carriers formed due to interaction of the active layer with the incident radiation tend to be swept away from the exposed surface. The graded semiconductor material in the active layer preferably comprises Al.sub.1-x Ga.sub.x As. An additional sub-layer of graded In.sub.1-y Ga.sub.y As may be included between the Al.sub.1-x Ga.sub.x As layer and the recombination layer. The recombination layer comprises a semiconductor material having a short recombination time such as a defective GaAs layer grown in a low temperature process. The recombination layer is positioned adjacent to the active layer so that carriers from the active layer tend to be swept into the recombination layer. In an embodiment, the photodetector may comprise one or more additional layers stacked below the active and recombination layers. These additional layers may include another active layer and another recombination layer to absorb radiation not absorbed while passing through the first layers. A photodetector having a stacked configuration may have enhanced sensitivity and responsiveness at selected wavelengths such as infrared.

  3. High sensitivity troponin and valvular heart disease.

    PubMed

    McCarthy, Cian P; Donnellan, Eoin; Phelan, Dermot; Griffin, Brian P; Sarano, Maurice Enriquez-; McEvoy, John W

    2017-01-16

    Blood-based biomarkers have been extensively studied in a range of cardiovascular diseases and have established utility in routine clinical care, most notably in the diagnosis of acute coronary syndrome (e.g., troponin) and the management of heart failure (e.g., brain-natriuretic peptide). The role of biomarkers is less well established in the management of valvular heart disease (VHD), in which the optimal timing of surgical intervention is often challenging. One promising biomarker that has been the subject of a number of recent VHD research studies is high sensitivity troponin (hs-cTn). Novel high-sensitivity assays can detect subclinical myocardial damage in asymptomatic individuals. Thus, hs-cTn may have utility in the assessment of asymptomatic patients with severe VHD who do not have a clear traditional indication for surgical intervention. In this state-of-the-art review, we examine the current evidence for hs-cTn as a potential biomarker in the most commonly encountered VHD conditions, aortic stenosis and mitral regurgitation. This review provides a synopsis of early evidence indicating that hs-cTn has promise as a biomarker in VHD. However, the impact of its measurement on clinical practice and VHD outcomes needs to be further assessed in prospective studies before routine clinical use becomes a reality.

  4. High-sensitivity detection of TNT.

    PubMed

    Pushkarsky, Michael B; Dunayevskiy, Ilya G; Prasanna, Manu; Tsekoun, Alexei G; Go, Rowel; Patel, C Kumar N

    2006-12-26

    We report high-sensitivity detection of 2,4,6-trinitrotoluene (TNT) by using laser photoacoustic spectroscopy where the laser radiation is obtained from a continuous-wave room temperature high-power quantum cascade laser in an external grating cavity geometry. The external grating cavity quantum cascade laser is continuously tunable over approximately 400 nm around 7.3 microm and produces a maximum continuous-wave power of approximately 200 mW. The IR spectroscopic signature of TNT is sufficiently different from that of nitroglycerine so that unambiguous detection of TNT without false positives from traces of nitroglycerine is possible. We also report the results of spectroscopy of acetylene in the 7.3-microm region to demonstrate continuous tunability of the IR source.

  5. Colorimetric detection for paper-based biosensing applications

    NASA Astrophysics Data System (ADS)

    Brink, C.; Joubert, T.-H.

    2016-02-01

    Research on affordable point-of-care health diagnostics is rapidly advancing1. Colorimetric biosensor applications are typically qualitative, but recently the focus has been shifted to quantitative measurements2,3. Although numerous qualitative point-of-care (POC) health diagnostic devices are available, the challenge exists of developing a quantitative colorimetric array reader system that complies with the ASSURED (Affordable, Sensitive, Specific, User-friendly, Rapid and Robust, Equipment-free, Deliverable to end-users) principles of the World Health Organization4. This paper presents a battery powered 8-bit tonal resolution colorimetric sensor circuit for paper microfluidic assays using low cost photo-detection circuitry and a low-power LED light source. A colorimetric 3×3-pixel array reader was developed for rural environments where resources and personnel are limited. The device sports an ultralow-power E-ink paper display. The colorimetric device includes integrated GPS functionality and EEPROM memory to log measurements with geo-tags for possible analysis of regional trends. The device competes with colour intensity measurement techniques using smartphone cameras, but proves to be a cheaper solution, compensating for the typical performance variations between cameras of different brands of smartphones. Inexpensive methods for quantifying bacterial assays have been shown using desktop scanners, which are not portable, and cameras, which suffer severely from changes in ambient light in different environments. Promising colorimetric detection results have been demonstrated using devices such as video cameras5, digital colour analysers6, flatbed scanners7 or custom portable readers8. The major drawback of most of these methods is the need for specialized instrumentation and for image analysis on a computer.

  6. Fe3O4 magnetic nanoparticle peroxidase mimetic-based colorimetric assay for the rapid detection of organophosphorus pesticide and nerve agent.

    PubMed

    Liang, Minmin; Fan, Kelong; Pan, Yong; Jiang, Hui; Wang, Fei; Yang, Dongling; Lu, Di; Feng, Jing; Zhao, Jianjun; Yang, Liu; Yan, Xiyun

    2013-01-02

    Rapid and sensitive detection methods are in urgent demand for the screening of extensively used organophosphorus pesticides and highly toxic nerve agents for their neurotoxicity. In this study, we developed a novel Fe(3)O(4) magnetic nanoparticle (MNP) peroxidase mimetic-based colorimetric method for the rapid detection of organophosphorus pesticides and nerve agents. The detection assay is composed of MNPs, acetylcholinesterase (AChE), and choline oxidase (CHO). The enzymes AChE and CHO catalyze the formation of H(2)O(2) in the presence of acetylcholine, which then activates MNPs to catalyze the oxidation of colorimetric substrates to produce a color reaction. After incubation with the organophosphorus neurotoxins, the enzymatic activity of AChE was inhibited and produced less H(2)O(2), resulting in a decreased catalytic oxidation of colorimetric substrates over MNP peroxidase mimetics, accompanied by a drop in color intensity. Three organophosphorus compounds were tested on the assay: acephate and methyl-paraoxon as representative organophosphorus pesticides and the nerve agent Sarin. The novel assay displayed substantial color change after incubation in organophosphorus neurotoxins in a concentration-dependent manner. As low as 1 nM Sarin, 10 nM methyl-paraoxon, and 5 μM acephate are easily detected by the novel assay. In conclusion, by employing the peroxidase-mimicking activity of MNPs, the developed colorimetric assay has the potential of becoming a screening tool for the rapid and sensitive assessment of the neurotoxicity of an overwhelming number of organophosphate compounds.

  7. Highly Sensitive Electro-Optic Modulators

    SciTech Connect

    DeVore, Peter S

    2015-10-26

    There are very important diagnostic and communication applications that receive faint electrical signals to be transmitted over long distances for capture. Optical links reduce bandwidth and distance restrictions of metal transmission lines; however, such signals are only weakly imprinted onto the optical carrier, resulting in low fidelity transmission. Increasing signal fidelity often necessitates insertion of radio-frequency (RF) amplifiers before the electro-optic modulator, but (especially at high frequencies) RF amplification results in large irreversible distortions. We have investigated the feasibility of a Sensitive and Linear Modulation by Optical Nonlinearity (SALMON) modulator to supersede RF-amplified modulators. SALMON uses cross-phase modulation, a manifestation of the Kerr effect, to enhance the modulation depth of an RF-modulated optical wave. This ultrafast process has the potential to result in less irreversible distortions as compared to a RF-amplified modulator due to the broadband nature of the Kerr effect. Here, we prove that a SALMON modulator is a feasible alternative to an RFamplified modulator, by demonstrating a sensitivity enhancement factor greater than 20 and significantly reduced distortion.

  8. High speed curved position sensitive detector

    DOEpatents

    Hendricks, Robert W.; Wilson, Jack W.

    1989-01-01

    A high speed curved position sensitive porportional counter detector for use in x-ray diffraction, the detection of 5-20 keV photons and the like. The detector employs a planar anode assembly of a plurality of parallel metallic wires. This anode assembly is supported between two cathode planes, with at least one of these cathode planes having a serpentine resistive path in the form of a meander having legs generally perpendicular to the anode wires. This meander is produced by special microelectronic fabrication techniques whereby the meander "wire" fans outwardly at the cathode ends to produce the curved aspect of the detector, and the legs of the meander are small in cross-section and very closely spaced whereby a spatial resolution of about 50 .mu.m can be achieved. All of the other performance characteristics are about as good or better than conventional position sensitive proportional counter type detectors. Count rates of up to 40,000 counts per second with 0.5 .mu.s shaping time constants are achieved.

  9. Smartphone spectrometer for colorimetric biosensing.

    PubMed

    Wang, Yi; Liu, Xiaohu; Chen, Peng; Tran, Nhung Thi; Zhang, Jinling; Chia, Wei Sheng; Boujday, Souhir; Liedberg, Bo

    2016-05-23

    We report on a smartphone spectrometer for colorimetric biosensing applications. The spectrometer relies on a sample cell with an integrated grating substrate, and the smartphone's built-in light-emitting diode flash and camera. The feasibility of the smartphone spectrometer is demonstrated for detection of glucose and human cardiac troponin I, the latter in conjunction with peptide-functionalized gold nanoparticles.

  10. High-sensitivity fiber optic acoustic sensors

    NASA Astrophysics Data System (ADS)

    Lu, Ping; Liu, Deming; Liao, Hao

    2016-11-01

    Due to the overwhelming advantages compared with traditional electronicsensors, fiber-optic acoustic sensors have arisen enormous interest in multiple disciplines. In this paper we present the recent research achievements of our group on fiber-optic acoustic sensors. The main point of our research is high sensitivity interferometric acoustic sensors, including Michelson, Sagnac, and Fabry-Pérot interferometers. In addition, some advanced technologies have been proposed for acoustic or acoustic pressure sensing such as single-mode/multimode fiber coupler, dual FBGs and multi-longitudinal mode fiber laser based acoustic sensors. Moreover, our attention we have also been paid on signal demodulation schemes. The intensity-based quadrature point (Q-point) demodulation, two-wavelength quadrature demodulation and symmetric 3×3 coupler methodare discussed and compared in this paper.

  11. Determination of phosphate using a highly sensitive paired emitter-detector diode photometric flow detector.

    PubMed

    O'Toole, Martina; Lau, King Tong; Shepherd, Roderick; Slater, Conor; Diamond, Dermot

    2007-08-06

    The use of a novel inexpensive photometric device, a paired emitter-detector diode (PEDD) has been applied to the colorimetric determination of phosphate using the malachite green spectrophotometric method. The novel miniaturized flow detector applied within this manifold is a highly sensitive, low cost, miniaturized light emitting diode (LED) based detector. The optical flow cell was constructed from two LEDs, whereby one is the light source and the second is the light detector, with the LED light source forward biased and the LED detector reversed biased. The photocurrent generated by the LED light source discharges the junction capacitance of the detector diode from 5 V (logic 1) to 1.7 V (logic 0) and the time taken for this process to occur is measured using a simple timer circuit. The malachite green (MG) method employed for phosphate determination is based on the formation of a green molybdophosphoric acid complex, the intensity of which is directly related to phosphate concentration. Optimum analytical parameters such as reaction kinetics, reagent to sample concentration ratio and emitter wavelength intensity were investigated for the spectrophotometric method. Linear calibration plots that obeyed the Beer-Lambert law were obtained for phosphate in the range of 0.02-2 microM. The dynamic range, sensitivity and limits of detection are reported.

  12. Highly sensitive silicon microreactor for catalyst testing

    SciTech Connect

    Henriksen, Toke R.; Hansen, Ole; Olsen, Jakob L.; Vesborg, Peter; Chorkendorff, Ib

    2009-12-15

    A novel microfabricated chemical reactor for highly sensitive measurements of catalytic activity and surface kinetics is presented. The reactor is fabricated in a silicon chip and is intended for gas-phase reactions at pressures ranging from 0.1 to 5.0 bar. A high sensitivity is obtained by directing the entire gas flow through the catalyst bed to a mass spectrometer, thus ensuring that nearly all reaction products are present in the analyzed gas flow. Although the device can be employed for testing a wide range of catalysts, the primary aim of the design is to allow characterization of model catalysts which can only be obtained in small quantities. Such measurements are of significant fundamental interest but are challenging because of the low surface areas involved. The relationship between the reaction zone gas flow and the pressure in the reaction zone is investigated experimentally. A corresponding theoretical model is presented, and the gas flow through an on-chip flow-limiting capillary is predicted to be in the intermediate regime. The experimental data for the gas flow are found to be in good agreement with the theoretical model. At typical experimental conditions, the total gas flow through the reaction zone is around 3x10{sup 14} molecules s{sup -1}, corresponding to a gas residence time in the reaction zone of about 11 s. To demonstrate the operation of the microreactor, CO oxidation on low-area platinum thin film circles is employed as a test reaction. Using temperature ramping, it is found that platinum catalysts with areas as small as 15 {mu}m{sup 2} are conveniently characterized with the device.

  13. Highly sensitive silicon microreactor for catalyst testing

    NASA Astrophysics Data System (ADS)

    Henriksen, Toke R.; Olsen, Jakob L.; Vesborg, Peter; Chorkendorff, Ib; Hansen, Ole

    2009-12-01

    A novel microfabricated chemical reactor for highly sensitive measurements of catalytic activity and surface kinetics is presented. The reactor is fabricated in a silicon chip and is intended for gas-phase reactions at pressures ranging from 0.1 to 5.0 bar. A high sensitivity is obtained by directing the entire gas flow through the catalyst bed to a mass spectrometer, thus ensuring that nearly all reaction products are present in the analyzed gas flow. Although the device can be employed for testing a wide range of catalysts, the primary aim of the design is to allow characterization of model catalysts which can only be obtained in small quantities. Such measurements are of significant fundamental interest but are challenging because of the low surface areas involved. The relationship between the reaction zone gas flow and the pressure in the reaction zone is investigated experimentally. A corresponding theoretical model is presented, and the gas flow through an on-chip flow-limiting capillary is predicted to be in the intermediate regime. The experimental data for the gas flow are found to be in good agreement with the theoretical model. At typical experimental conditions, the total gas flow through the reaction zone is around 3×1014 molecules s-1, corresponding to a gas residence time in the reaction zone of about 11 s. To demonstrate the operation of the microreactor, CO oxidation on low-area platinum thin film circles is employed as a test reaction. Using temperature ramping, it is found that platinum catalysts with areas as small as 15 μm2 are conveniently characterized with the device.

  14. Face Transplantation in a Highly Sensitized Recipient.

    PubMed

    Chandraker, Anil; Arscott, Ramon; Murphy, George; Lian, Christine; Bueno, Ericka; Marty, Francisco; Rennke, Helmut; Milford, Edgar; Tullius, Stefan; Pomahac, Bodhan

    2016-05-01

    Face transplantation was performed in a highly sensitized recipient with positive preoperative crossmatch and subsequent antibody-mediated rejection. The recipient was a 45-year-old female with extensive conventional reconstructions after chemical burns over the majority of the body. Residual quality of life and facial functions were poor. Levels of circulating anti-human leukocyte antigen (HLA) antibodies were high, and panel reactive antibody score was 98%. A potential donor was identified; however, with positive T and B cell flow crossmatches. The transplant team proceeded with face transplantation from this donor, under tailored immune suppression and with available salvage options. The operation was successful. Plasmapheresis and induction immune suppression (i.e., thymoglobulin followed by mycophenolate mofetil, tacrolimus, and steroids) were provided. Five days later, there was significant facial swelling, rising anti-HLA antibody titers, and unprecedented evidence of C4d deposits on skin. High doses of steroids and thymoglobulin were provided; however, rejection increased such that by day 19 it was diagnosed grade III in the BANFF scale. After stopping thymoglobulin because of serum sickness, combination therapy of plasmapheresis, eculizumab, bortezomib, and alemtuzumab was provided. HLA antibody levels decreased while swelling and redness improved. At 3 months, there were no longer signs of rejection on biopsy.

  15. A novel colorimetric assay for rapid detection of cysteine and Hg²⁺ based on gold clusters.

    PubMed

    Wang, Yi-Wei; Tang, Shurong; Yang, Huang-Hao; Song, Hongbo

    2016-01-01

    Inhibition and recovery of the catalytic activity of bovine serum albumin-capped gold nanoclusters (BSA-AuNCs) is observed for the first time by introduction of cysteine and Hg(2+). The prepared BSA-AuNCs possess highly intrinsic peroxidase-like activity. It can catalyze the oxidation of 3, 3, 5, 5-tetramethylbenzidine by H2O2 to produce a blue colored product. Based on this phenomenon, a new colorimetric assay for rapid, selective and sensitive detection of cysteine and Hg(2+) in aqueous solution has been demonstrated. The interaction process between target molecule and BSA-AuNCs is very fast, so that the whole test can be completed within ten minutes. Moreover, the fabricated colorimetric sensor is simple and cost-effective, without the need of nucleic acid based recognition element and complicated washing, separation and labeling process, thus holds great promise for routine analysis of cysteine and Hg(2+) in real samples.

  16. Preparation of Co3O4/crumpled graphene microsphere as peroxidase mimetic for colorimetric assay of ascorbic acid.

    PubMed

    Fan, Sisi; Zhao, Minggang; Ding, Longjiang; Li, Hui; Chen, Shougang

    2017-03-15

    The well-dispersed Co3O4 nanoparticles-decorated crumpled graphene microsphere (CGM) was successfully prepared by aerosol-assisted frying self-assembly and annealing process. It is found that the obtained Co3O4/CGM nanohybrid possessed enhanced intrinsic peroxidase-like activity and could catalytically oxidize 3,3',5,5'-tetramethylbenzidine by H2O2 to produce a typical blue product. But the presence of ascorbic acid could induce the reduction of oxTMB to TMB, resulting in a significant blue color fading. Therefore, a simple, sensitive and selective colorimetric method to detect ascorbic acid was established with a good linear relationship (30-140μM) and a low detection limit of 0.19μM. Meanwhile, the selectivity, stability and repeatability were acceptable. It is also a facile route to fabricate nanoparticles/CGM as high-performance enzyme mimetic for colorimetric biosensing.

  17. Transportable high sensitivity small sample radiometric calorimeter

    SciTech Connect

    Wetzel, J.R.; Biddle, R.S.; Cordova, B.S.; Sampson, T.E.; Dye, H.R.; McDow, J.G.

    1998-12-31

    A new small-sample, high-sensitivity transportable radiometric calorimeter, which can be operated in different modes, contains an electrical calibration method, and can be used to develop secondary standards, will be described in this presentation. The data taken from preliminary tests will be presented to indicate the precision and accuracy of the instrument. The calorimeter and temperature-controlled bath, at present, require only a 30-in. by 20-in. tabletop area. The calorimeter is operated from a laptop computer system using unique measurement module capable of monitoring all necessary calorimeter signals. The calorimeter can be operated in the normal calorimeter equilibration mode, as a comparison instrument, using twin chambers and an external electrical calibration method. The sample chamber is 0.75 in (1.9 cm) in diameter by 2.5 in. (6.35 cm) long. This size will accommodate most {sup 238}Pu heat standards manufactured in the past. The power range runs from 0.001 W to <20 W. The high end is only limited by sample size.

  18. A quick colorimetric method for total lipid quantification in microalgae.

    PubMed

    Byreddy, Avinesh R; Gupta, Adarsha; Barrow, Colin J; Puri, Munish

    2016-06-01

    Discovering microalgae with high lipid productivity are among the key milestones for achieving sustainable biodiesel production. Current methods of lipid quantification are time intensive and costly. A rapid colorimetric method based on sulfo-phospho-vanillin (SPV) reaction was developed for the quantification of microbial lipids to facilitate screening for lipid producing microalgae. This method was successfully tested on marine thraustochytrid strains and vegetable oils. The colorimetric method results correlated well with gravimetric method estimates. The new method was less time consuming than gravimetric analysis and is quantitative for lipid determination, even in the presence of carbohydrates, proteins and glycerol.

  19. A Highly Sensitive Fluorescent Sensor for Palladium and Direct Imaging of Its Ecotoxicity in Living Model Organisms.

    PubMed

    Liu, Fei; Du, Juan; Xu, Meiying; Sun, Guoping

    2016-01-01

    Rhodamine is an ideal platform for fluorescence probes owing to its spiro-lactam framework and excellent photochemical properties. Herein, a novel rhodamine-based palladium fluorescent chemosensor, Rd-Eb, showing a fast response time (3 min), high sensitivity for palladium species over other ions, and a low detection limit (1.91×10(-7)  m), was synthesized. It can act as an obvious colorimetric as well as a fluorescent "off/on" sensor for Pd(2+) . In addition, it is also an excellent sensor for in vivo imaging of Pd(2+) in zebra fish and Daphnia magna, illuminating the impact of palladium on organisms at different growth stages with respect to biological toxicology.

  20. Demonstration of high sensitivity laser ranging system

    NASA Technical Reports Server (NTRS)

    Millar, Pamela S.; Christian, Kent D.; Field, Christopher T.

    1994-01-01

    We report on a high sensitivity semiconductor laser ranging system developed for the Gravity and Magnetic Earth Surveyor (GAMES) for measuring variations in the planet's gravity field. The GAMES laser ranging instrument (LRI) consists of a pair of co-orbiting satellites, one which contains the laser transmitter and receiver and one with a passive retro-reflector mounted in an drag-stabilized housing. The LRI will range up to 200 km in space to the retro-reflector satellite. As the spacecraft pair pass over the spatial variations in the gravity field, they experience along-track accelerations which change their relative velocity. These time displaced velocity changes are sensed by the LRI with a resolution of 20-50 microns/sec. In addition, the pair may at any given time be drifting together or apart at a rate of up to 1 m/sec, introducing a Doppler shift into the ranging signals. An AlGaAs laser transmitter intensity modulated at 2 GHz and 10 MHz is used as fine and medium ranging channels. Range is measured by comparing phase difference between the transmit and received signals at each frequency. A separate laser modulated with a digital code, not reported in this paper, will be used for coarse ranging to unambiguously determine the distance up to 200 km.

  1. Highly sensitive direct conversion ultrasound interferometer

    NASA Astrophysics Data System (ADS)

    Svitelskiy, Oleksiy; Grossmann, John; Suslov, Alexey

    2015-03-01

    Being invented more than fifty years ago, the ultrasonic pulse-echo technique has proven itself as a valuable and indispensable non-destructive tool to explore elastic properties of materials in engineering and scientific tasks. We propose a new design for the instrument based on mass-produced integral microchips. In our design the radiofrequency echo-pulse signal is processed by AD8302 RF gain and phase detector (www.analog.com).Its phase output is linearly proportional to the phase difference between the exciting and response signals. The gain output is proportional to the log of the ratio of amplitudes of the received to the exciting signals. To exclude the non-linear fragments and to enable exploring large phase changes, we employ parallel connection of two detectors, fed by in-phase and quadrature signals respectively. The instrument allowed us exploring phase transitions with precision of ΔV / V ~10-7 (V is the ultrasound speed). The high sensitivity of the logarithmic amplifiers embedded into AD8302 requires good grounding and screening of the receiving circuitry.

  2. Highly selective colorimetric detection and estimation of Hg2+ at nano-molar concentration by silver nanoparticles in the presence of glutathione.

    PubMed

    Alam, Ayesha; Ravindran, Aswathy; Chandran, Preethy; Sudheer Khan, S

    2015-02-25

    The present study investigated the colorimetric detection of mercury (Hg(2+)) ions by using silver nanoparticles (Ag NPs) in the presence of glutathione. The nanoparticles used in the study were synthesized biologically by using Polyalthia longifolia leaf extract. The synthesized nanoparticles were characterized by UV-visible spectrophotometer, transmission electron microscope, X-ray diffraction, particle size analyzer and zeta sizer. The particles were spherical in shape and it possesses the effective diameter of 5 nm. The zeta potential of the particles was determined to be -28.6 mV. Ag NPs-glutathione conjugates were able to detect Hg(2+) in nanomolar level. Ag NPs-glutathione conjugates upon interaction with Hg(2+) changes from yellowish brown to pale yellow and finally colorless. The study may be applied for the qualitative and quantitative estimation of mercury at very low concentration.

  3. Colorimetric characterization of LED luminaires

    NASA Astrophysics Data System (ADS)

    Costa, C. L. M.; Vieira, R. R.; Pereira, R. C.; Silva, P. V. M.; Oliveira, I. A. A.; Sardinha, A. S.; Viana, D. D.; Barbosa, A. H.; Souza, L. P.; Alvarenga, A. D.

    2015-01-01

    The Optical Metrology Division of Inmetro - National Institute of Metrology, Quality and Technology has recently started the colorimetric characterization of lamps by implementing Correlated Color Temperature (CCT) and Color Rendering Index (CRI) measurements of incandescent lamps, followed by the CFL, and LED lamps and luminaires. Here we present the results for the verification of the color characterization of samples of SSL luminaires for public as well as indoor illumination that are sold in Brazil.

  4. A selective colorimetric Hg2+ probe featuring a styryl dithiaazacrown containing platinum (II) terpyridine complex through modulation of the relative strength of ICT and MLCT transitions.

    PubMed

    Chung, Sung-Kuang; Tseng, Yong-Ren; Chen, Chan-Yu; Sun, Shih-Sheng

    2011-04-04

    A series of platinum(II) terpyridine complexes featuring an aminostilbene donor-acceptor framework was synthesized. The complex with a dithiaazacrown moiety exhibits a highly sensitive and selective colorimetric response to a Hg(2+) cation through modulation of the relative strength of ICT and MLCT transitions. The results from (1)H NMR titration suggest the existence of a weak Pt(II)···Hg(II) metallophilic interaction at low Hg(2+) concentration.

  5. A ferrofluid-based homogeneous assay for highly sensitive and selective detection of single-nucleotide polymorphisms.

    PubMed

    Shen, Wei; Lim, Cai Le; Gao, Zhiqiang

    2013-09-21

    A simple and low-cost colorimetric assay utilizing ferrofluidic nanoparticulate probes (FNPs) and a ligase for single-nucleotide polymorphism genotyping is described. Excellent sensitivity and selectivity were accomplished through the engagement of the FNPs and a ligase chain reaction.

  6. Colorimetric recognition and sensing of nitrite with unmodified gold nanoparticles based on a specific diazo reaction with phenylenediamine.

    PubMed

    Zhang, Jia; Yang, Cheng; Wang, Xiaolei; Yang, Xiurong

    2012-07-21

    A colorimetric sensor for nitrite ion with high selectivity and sensitivity by unmodified citrate-capped gold nanoparticles (Au NPs) is presented. Recognition of nitrite is developed on the basis of a highly specific diazo reaction between nitrite and phenylenediamine (PDA). PDA caused the Au NPs to aggregate owing to the strong covalent NH-Au bond, with a clear color change of solution from red to blue being visualized. In the presence of phosphoric acid and nitrite, the amines of PDA would readily be converted to diazo bonds, and a red solution was observed after the subsequent addition of Au suspension due to the much less strength of electrostatic interaction between the positive diazo groups and the negative citrate-capped Au NPs. With this colorimetric "light-up" method, <1 ppm of nitrite can be easily detected within 5 min at room temperature without instrumentation. Since the diazo reaction and the colorimetric response are separate, this approach features the use of pristine Au NPs in an assay where acidic environment is a necessity, making it a more convenient and cost-effective method for the sensing of nitrite when compared with those utilizing chemically modified Au NPs.

  7. Analysis of molluscan sterols: Colorimetric methods.

    PubMed

    Swift, M L

    1984-08-01

    The wide variety of sterols normally found in extracts of bivalve molluscs leads to high variability in analytical data obtained with colorimetric (chole)sterol methods. Total sterol levels in oyster (Crassostrea virginica) extracts were determined using the Liebermann-Burchard reagent, an acid-FeCl3 reagent and a cholesterol oxidase procedure. The data from the latter two agreed to within 5.4% and yielded about 30% higher estimates of sterol content than the Liebermann-Burchard test. Gas-liquid chromatographic data also are compared.Several pure sterols, selected because of their presence in oyster sterol fractions or because of their structural similarities to such sterols, were examined using each of the three procedures. Sterols, differing from cholesterol only with regard to the side chain, reacted 80-102% as well as cholesterol with the acid-FeCl3 reagent and cholesterol oxidase. The Liebermann-Burchard reaction was more specific for cholesterol. The colorimetric cholesterol oxidase method is recommended for the estimation of total molluscan sterol content.

  8. Highly sensitive visual detection of Avian Influenza A (H7N9) virus based on the enzyme-induced metallization.

    PubMed

    Zhang, Huifang; Ma, Xiaoming; Hu, Shuisheng; Lin, Yue; Guo, Longhua; Qiu, Bin; Lin, Zhenyu; Chen, Guonan

    2016-05-15

    Development of convenient but sensitive method for influenza detection is highly important in immediate and effective clinical treatment. In this study, an ultrasensitive colorimetric approach combining the advantages of the convenience of the enzyme-induced metallization and the high specificity of enzyme-linked immunosorbent assay for the detection of influenza virus A (H7N9 as model) has been developed. Two rounds of amplification are utilized to enhance the detection sensitivity. The amplification of enzymatic reaction combines with the specific optical properties of gold nanoparticles causing the enhancing of the optical signal immensely. In addition, the increased surface area and the magnetic enrichment effect also enable the magnetic bead (MB) to catch a large number of alkaline phosphatase (ALP) and detection antibody (Ab2), thus very small amounts of the virus can be easily detected. Compared with conventional method, this approach exhibits outstanding sensitivity for ALP detection, 0.2U/L of ALP can be distinguished with a spectrometer and 2U/L with the naked eye. And as low as 25 pg/mL of H7N9 can be detected by the naked eye. This approach shows an extensive horizon for bioassays and is available in clinical diagnosis with the advances of simplification, effectiveness, low cost and sensitive readout.

  9. Microfluidic immunosensor for rapid and highly-sensitive salivary cortisol quantification.

    PubMed

    Pinto, V; Sousa, P; Catarino, S O; Correia-Neves, M; Minas, G

    2017-04-15

    This paper presents a novel poly(dimethylsiloxane) (PDMS) microfluidic immunosensor that integrates a complementary metal-oxide-semiconductor (CMOS) optical detection system for a rapid and highly-sensitive quantification of salivary cortisol. The simple and non-invasive method of saliva sampling provides an interesting alternative to the blood, allowing a fast sampling at short intervals, relevant for many clinical diagnostic applications. The developed approach is based on the covalent immobilization of a coating antibody (Ab), a polyclonal anti-IgG, onto a treated PDMS surface. The coating Ab binds the capture Ab, an IgG specific for cortisol, allowing its correct orientation. Horseradish peroxidase (HRP)-labelled cortisol is added to compete with the cortisol in the sample, for the capture Ab binding sites. The HRP-labelled cortisol, bonded to the capture Ab, is measured through the HRP enzyme and the tetramethylbenzidine (TMB) substrate reaction. The cortisol quantification is performed by colorimetric detection of HRP-labelled cortisol, through optical absorption at 450nm, using a CMOS silicon photodiode as the photodetector. Under the developed optimized conditions presented here, e.g., microfluidic channels geometry, immobilization method and immunoassay conditions, the immunosensor shows a linear range of detection between 0.01-20ng/mL, a limit of detection (LOD) of 18pg/mL and an analysis time of 35min, featuring a great potential for point-of-care applications requiring continuous monitoring of the salivary cortisol levels during a circadian cycle.

  10. Highly sensitive ratiometric quantification of cyanide in water with gold nanoparticles via Resonance Rayleigh Scattering.

    PubMed

    Hernández, Yulán; Coello, Yves; Fratila, Raluca M; de la Fuente, Jesús M; Lionberger, Troy A

    2017-05-15

    A highly sensitive and selective ratiometric sensor for the quantification of cyanide (CN(-)) in aqueous samples has been developed using spherical gold nanoparticles (AuNPs) stabilized by polysorbate 40 (PS-40). Three different AuNP sizes (14, 40 and 80nm mean diameters) were used to evaluate the response of the sensor using both colorimetric and Resonance Rayleigh Scattering (RRS) detection schemes. The best results were obtained for the sensor using 40nm AuNPs, for which the limits of detection (LODs) were found to be 100nmolL(-1) in a benchtop instrument and 500nmolL(-1) by the naked eye, values well below the maximum acceptable level for drinking water (1.9µmolL(-1)) set by the World Health Organization (WHO). The practical use of the 40nm-AuNPs RRS sensor was demonstrated with the determination of CN(-) in drinking and fresh waters. Finally, the sensor was successfully implemented in a compact portable device consisting of two light-emitting diodes (LEDs) and a miniature spectrometer, turning this sensor into a very potent tool for its application as a quick routine field-deployable analytical method.

  11. A case of high noise sensitivity

    NASA Astrophysics Data System (ADS)

    Murata, M.; Sakamoto, H.

    1995-10-01

    A case of noise sensitivity with a five-year follow-up period is reported. The patient was a 34-year-old single man who was diagnosed as having psychosomatic disorder triggered by two stressful life events in rapid succession with secondary hypersensitivity to noise. Hypersensitivity to light and cold also developed later in the clinical course. The auditory threshold was within the normal range. The discomfort threshold as a measure of the noise sensitivity secondary to mental illness was measured repeatedly using test tone of audiometry. The discomfort threshold varied depending upon his mental status, ranging from 40-50 dB in the comparatively poorer mental state to 70-95 dB in the relatively good mental state. The features of noise sensitivity, including that secondary to mental illness, are discussed.

  12. High sensitivity gas spectroscopy of porous, highly scattering solids.

    PubMed

    Svensson, Tomas; Andersson, Mats; Rippe, Lars; Johansson, Jonas; Folestad, Staffan; Andersson-Engels, Stefan

    2008-01-01

    We present minimalistic and cost-efficient instrumentation employing tunable diode laser gas spectroscopy for the characterization of porous and highly scattering solids. The sensitivity reaches 3 x 10(-6) (absorption fraction), and the improvement with respect to previous work in this field is a factor of 10. We also provide the first characterization of the interference phenomenon encountered in high-resolution spectroscopy of turbid samples. Revealing that severe optical interference originates from the samples, we discuss important implications for system design. In addition, we introduce tracking coils and sample rotation as new and efficient tools for interference suppression. The great value of the approach is illustrated in an application addressing structural properties of pharmaceutical materials.

  13. Capillarity-based preparation system for optical colorimetric sensor arrays

    NASA Astrophysics Data System (ADS)

    Luo, Xiao-gang; Yi, Xin; Bu, Xiang-nan; Hou, Chang-jun; Huo, Dan-qun; Yang, Mei; Fa, Huan-bao; Lei, Jin-can

    2017-03-01

    In recent years, optical colorimetric sensor arrays have demonstrated beneficial features, including rapid response, high selectivity, and high specificity; as a result, it has been extensively applied in food inspection and chemical studies, among other fields. There are instruments in the current market available for the preparation of an optical colorimetric sensor array, but it lacks the corresponding research of the preparation mechanism. Therefore, in connection with the main features of this kind of sensor array such as consistency, based on the preparation method of contact spotting, combined with a capillary fluid model, Washburn equation, Laplace equation, etc., this paper develops a diffusion model of an optical colorimetric sensor array during its preparation and sets up an optical colorimetric sensor array preparation system based on this diffusion model. Finally, this paper compares and evaluates the sensor arrays prepared by the system and prepared manually in three aspects such as the quality of array point, response of array, and response result, and the results show that the performance index of the sensor array prepared by a system under this diffusion model is better than that of the sensor array of manual spotting, which meets the needs of the experiment.

  14. Capillarity-based preparation system for optical colorimetric sensor arrays.

    PubMed

    Luo, Xiao-Gang; Yi, Xin; Bu, Xiang-Nan; Hou, Chang-Jun; Huo, Dan-Qun; Yang, Mei; Fa, Huan-Bao; Lei, Jin-Can

    2017-03-01

    In recent years, optical colorimetric sensor arrays have demonstrated beneficial features, including rapid response, high selectivity, and high specificity; as a result, it has been extensively applied in food inspection and chemical studies, among other fields. There are instruments in the current market available for the preparation of an optical colorimetric sensor array, but it lacks the corresponding research of the preparation mechanism. Therefore, in connection with the main features of this kind of sensor array such as consistency, based on the preparation method of contact spotting, combined with a capillary fluid model, Washburn equation, Laplace equation, etc., this paper develops a diffusion model of an optical colorimetric sensor array during its preparation and sets up an optical colorimetric sensor array preparation system based on this diffusion model. Finally, this paper compares and evaluates the sensor arrays prepared by the system and prepared manually in three aspects such as the quality of array point, response of array, and response result, and the results show that the performance index of the sensor array prepared by a system under this diffusion model is better than that of the sensor array of manual spotting, which meets the needs of the experiment.

  15. Centrifugal loop-mediated isothermal amplification microdevice for rapid, multiplex and colorimetric foodborne pathogen detection.

    PubMed

    Oh, Seung Jun; Park, Byung Hyun; Jung, Jae Hwan; Choi, Goro; Lee, Doh C; Kim, Do Hyun; Seo, Tae Seok

    2016-01-15

    We present a centrifugal microfluidic device which enables multiplex foodborne pathogen identification by loop-mediated isothermal amplification (LAMP) and colorimetric detection using Eriochrome Black T (EBT). Five identical structures were designed in the centrifugal microfluidic system to perform the genetic analysis of 25 pathogen samples in a high-throughput manner. The sequential loading and aliquoting of the LAMP cocktail, the primer mixtures, and the DNA sample solutions were accomplished by the optimized zigzag-shaped microchannels and RPM control. We targeted three kinds of pathogenic bacteria (Escherichia coli O157:H7, Salmonella typhimurium and Vibrio parahaemolyticus) and detected the amplicons of the LAMP reaction by the EBT-mediated colorimetric method. For the limit-of-detection (LOD) test, we carried out the LAMP reaction on a chip with serially diluted DNA templates of E. coli O157:H7, and could observe the color change with 380 copies. The used primer sets in the LAMP reaction were specific only to the genomic DNA of E. coli O157:H7, enabling the on-chip selective, sensitive, and high-throughput pathogen identification with the naked eyes. The entire process was completed in 60min. Since the proposed microsystem does not require any bulky and expensive instrumentation for end-point detection, our microdevice would be adequate for point-of-care (POC) testing with high simplicity and high speed, providing an advanced genetic analysis microsystem for foodborne pathogen detection.

  16. Colorimetric determination of sildenafil citrate (Viagra) through ion-associate complex formation.

    PubMed

    Amin, Alaa S; Moustafa, Moustafa E; El-Dosoky, Reham

    2009-01-01

    A simple, quick, accurate, and sensitive colorimetric method is described for the determination of sildenafil citrate (SLD). The method is based on the reaction of SLD with Congo Red, Sudan II, and Gentian Violet in buffered aqueous solutions at pH 2.5, 6.5, and 11.0, respectively, to give highly colored soluble ion-associate complex species; the colored products are quantitated colorimetrically at 523, 554, and 569 nm, respectively. The various experimental conditions were optimized. The stoichiometric ratio was found to be 1:1 for all ion associates; the calculated logarithmic stability constants were 8.51, 7.79, and 5.58, respectively. Beer's law was obeyed over the concentration range of 0.2-7.0 microg/mL, whereas the Ringbom optimum concentration range was 0.4-6.5 microg/mL. Values for molar absorptivity, Sandell sensitivity, and detection and quantification limits were also calculated. The proposed method was successfully applied to the determination of SLD in Viagra tablets and in serum samples by using the technique of standard additions with mean accuracy values of 100.06 +/- 1.14, 99.87 +/- 0.70, and 99.86 +/- 0.97% for Viagra tablets and 99.88 +/- 0.60, 99.90 +/- 0.90, and 100.24 +/- 0.80% for serum samples, respectively.

  17. Aptamer-based colorimetric biosensing of abrin using catalytic gold nanoparticles.

    PubMed

    Hu, Jingting; Ni, Pengjuan; Dai, Haichao; Sun, Yujing; Wang, Yilin; Jiang, Shu; Li, Zhuang

    2015-05-21

    In this study we propose a simple and sensitive colorimetric aptasensor for the quantitative analysis of abrin by using catalytic AuNPs for the first time. AuNPs possess the peroxidase-like activity that can catalyse 3,3,5,5-tetramethylbenzidine (TMB) in the presence of H2O2, leading to color change of the solution. It is interesting to find that the peroxidase-like activity of AuNPs can be improved by surface activation with a target-specific aptamer. However, with a target molecule, the aptamer is desorbed from the AuNPs surface, resulting in a decrease of the catalytic abilities of AuNPs. The color change of the solution is relevant to the target concentration, and this can be judged by the naked eye and monitored by using a UV-vis spectrometer. The linear range for the current analytical system was from 0.2 nM to 17.5 nM. The corresponding limit of detection (LOD) was 0.05 nM. Some other proteins such as thrombin (Th), glucose oxidase (GOx), and bovine serum albumin (BSA) all had a negligible effect on the determination of abrin. Furthermore, several practical samples spiked with abrin were analyzed using the proposed method with excellent recoveries. This aptamer-based colorimetric biosensor is superior to other conventional methods owing to its simplicity, low cost, and high sensitivity.

  18. Colorimetric enumeration of bacterial contamination in water based on β-galactosidase gold nanoshell activity.

    PubMed

    Tanvir, Fouzia; Yaqub, Atif; Tanvir, Shazia; Anderson, William A

    2017-04-01

    In this study we report a method for the rapid and sensitive estimation of bacterial cell concentration in solution based on a colorimetric enzyme/gold nanoshells conjugate system. The CTAB capped gold nanoshells are electrostatically attracted by both the bacterial surface and the enzyme β-galactosidase. The preferential binding of cationic (CTAB)-functionalized gold nanoshells to the more negative bacterial surfaces leaves active β-galactosidase in solution, providing an enzyme-amplified colorimetric response of the binding event. A progressive increase in the enzyme activity is evidenced by the conversion of the yellow-orange CPRG substrate into the red chromophore chlorophenol red, which can be correlated with increasing bacterial cell numbers. Using this strategy, the quantification of bacteria at concentrations as low as 10 bacteria/mL of solution has been achieved. The present method of bacterial cell load assessment offers a distinct potential advantage over other conventional methods such as plate counting in terms of ease of operation, rapidity, high sensitivity and quantitative detection of bacterial cells.

  19. Magnetic colorimetric immunoassay for human interleukin-6 based on the oxidase activity of ceria spheres.

    PubMed

    Peng, Juan; Guan, Jufang; Yao, Huiqin; Jin, Xiaoyong

    2016-01-01

    A novel magnetic colorimetric immunoassay strategy was designed for sensitive detection of human interleukin-6 (IL-6) using ceria spheres as labels. Ceria spheres showed excellent oxidase activity, which can directly catalyze the oxidation of substrate o-phenylenediamine (OPD) to a stable yellow product, 2,3-diaminophenazine (oxOPD). The absorbance of oxOPD was recorded to reflect the level of IL-6. The relatively mild conditions made the immunoassay strategy more robust, reliable, and easy. A linear relationship between absorbance intensity and the logarithm of IL-6 concentrations was obtained in the range of 0.0001-10 ng mL(-1) with a detection limit of 0.04 pg mL(-1) (S/N = 3). The colorimetric immunoassay exhibited high sensitivity and specificity for the detection of IL-6. This immunoassay has been successfully applied in the detection of IL-6 in serum samples and can be readily extended toward the on-site monitoring of cancer biomarkers in serum samples.

  20. An improved colorimetric method for the determination of proline in the presence of other ninhydrin-positive compounds

    PubMed Central

    Wren, J. J.; Wiggall, P. H.

    1965-01-01

    1. The conditions required for sensitive and specific colorimetric determination of proline with acidified ninhydrin were investigated. 2. A method applicable to protein samples was developed. 3. The only compound found to interfere appreciably was a hydroxyproline. PMID:14342233

  1. A low-cost smartphone-based platform for highly sensitive point-of-care testing with persistent luminescent phosphors.

    PubMed

    Paterson, Andrew S; Raja, Balakrishnan; Mandadi, Vinay; Townsend, Blane; Lee, Miles; Buell, Alex; Vu, Binh; Brgoch, Jakoah; Willson, Richard C

    2017-02-03

    Through their computational power and connectivity, smartphones are poised to rapidly expand telemedicine and transform healthcare by enabling better personal health monitoring and rapid diagnostics. Recently, a variety of platforms have been developed to enable smartphone-based point-of-care testing using imaging-based readout with the smartphone camera as the detector. Fluorescent reporters have been shown to improve the sensitivity of assays over colorimetric labels, but fluorescence readout necessitates incorporating optical hardware into the detection system, adding to the cost and complexity of the device. Here we present a simple, low-cost smartphone-based detection platform for highly sensitive luminescence imaging readout of point-of-care tests run with persistent luminescent phosphors as reporters. The extremely bright and long-lived emission of persistent phosphors allows sensitive analyte detection with a smartphone by a facile time-gated imaging strategy. Phosphors are first briefly excited with the phone's camera flash, followed by switching off the flash, and subsequent imaging of phosphor luminescence with the camera. Using this approach, we demonstrate detection of human chorionic gonadotropin using a lateral flow assay and the smartphone platform with strontium aluminate nanoparticles as reporters, giving a detection limit of ≈45 pg mL(-1) (1.2 pM) in buffer. Time-gated imaging on a smartphone can be readily adapted for sensitive and potentially quantitative testing using other point-of-care formats, and is workable with a variety of persistent luminescent materials.

  2. ``Red-to-blue'' colorimetric detection of cysteine via anti-etching of silver nanoprisms

    NASA Astrophysics Data System (ADS)

    Li, Yonglong; Li, Zihou; Gao, Yuexia; Gong, An; Zhang, Yujie; Hosmane, Narayan S.; Shen, Zheyu; Wu, Aiguo

    2014-08-01

    The reported strategies for cysteine (Cys) colorimetric detection based on noble metal nanomaterials include triggering aggregation, etching or fluorescence quenching of nanomaterials by Cys. In this study, we propose a new strategy for Cys colorimetric detection, i.e. anti-etching of silver nanoprisms (AgNPRs). In the absence of Cys, iodide ions (I-) could etch the corners and edges of AgNPRs and induce the morphology transition from nanoprism to nanodisk, which results in color change of the AgNPR dispersion from blue to red. In its presence, however, Cys can prevent the AgNPRs from I- attack. In that case, the color of the AgNPR dispersion containing I- and Cys remains blue. The mechanism is confirmed by using UV-vis spectra, TEM, DLS, Raman spectra and XPS spectra. According to the sensing effect of the Cys detection system, the concentration of I- incubated with AgNPRs, incubation time of AgNPRs and I-, and pH of AgNPR dispersions are optimized to 5.0 μM, 10 min, and pH 6.2, respectively. Under the optimized conditions, the proposed Cys detection system has excellent selectivity and high sensitivity. The limit of detection (LOD) of our Cys detection system is 25 nM by the naked eye, which is much better than the reported lowest LOD by eye-vision (100 nM), and 10 nM by UV-vis spectroscopy. The results of Cys detection in rabbit urine or plasma samples reinforce that our Cys detection system is applicable for rapid colorimetric detection of Cys in real body fluid samples.The reported strategies for cysteine (Cys) colorimetric detection based on noble metal nanomaterials include triggering aggregation, etching or fluorescence quenching of nanomaterials by Cys. In this study, we propose a new strategy for Cys colorimetric detection, i.e. anti-etching of silver nanoprisms (AgNPRs). In the absence of Cys, iodide ions (I-) could etch the corners and edges of AgNPRs and induce the morphology transition from nanoprism to nanodisk, which results in color change of the

  3. Colorimetric Solid-Phase Extractor

    NASA Technical Reports Server (NTRS)

    2003-01-01

    The heart of a colorimetric solid phase extractor (CSPE) test kit quickly measures the concentration of the biocides silver or iodine in astronauts' drinking water to determine whether concentrations are safe. When 10 milliliters (ml) of water is drawn through the disk, the disk will turn color (yellow in this picture for iodine) indicating the presence of the biocides. The device could someday be used to test water safety at reservoirs and water treatment plants on Earth. (photo credit: Microanalytical Instrumentation Center, Iowa State University).

  4. Simple colorimetric method determines uranium in tissue

    NASA Technical Reports Server (NTRS)

    Doran, D.; Frigerio, N. A.

    1967-01-01

    Simple colorimetric micromethod determines concentrations of uranium in tissue. The method involves dry ashing organic extraction, and colorimetric determination of uranyl ferrocyanide. This uranium determination technique could be used in agricultural research, tracer studies, testing of food products, or medical research.

  5. Colorimetric determination of melamine in milk using unmodified silver nanoparticles.

    PubMed

    Kumar, Naveen; Kumar, Harish; Mann, Bimlesh; Seth, Raman

    2016-03-05

    Melamine is nitrogen rich chemical compound used as an adulterant in dairy products by unscrupulous people to increase the apparent protein content. This incident prompted the researchers to develop simple methods for easy detection of melamine in food samples. In the present paper, we report a simple and sensitive colorimetric method for detection of melamine in milk based on silver nanoparticles. This method relies upon the principle that melamine causes the aggregation of silver nanoparticles, resulting in abrupt color change from yellow to red under optimized conditions. The concentration of melamine in adulterated sample can be quantitated by monitoring the absorption spectra of silver nanoparticles using ultraviolet-visible (UV-Vis) spectrometer. The present colorimetric method which utilizes silver nanoparticles of 35 nm can reliably detect melamine down to a concentration of 0.04 mg l(-1).

  6. Colorimetric determination of melamine in milk using unmodified silver nanoparticles

    NASA Astrophysics Data System (ADS)

    Kumar, Naveen; Kumar, Harish; Mann, Bimlesh; Seth, Raman

    2016-03-01

    Melamine is nitrogen rich chemical compound used as an adulterant in dairy products by unscrupulous people to increase the apparent protein content. This incident prompted the researchers to develop simple methods for easy detection of melamine in food samples. In the present paper, we report a simple and sensitive colorimetric method for detection of melamine in milk based on silver nanoparticles. This method relies upon the principle that melamine causes the aggregation of silver nanoparticles, resulting in abrupt color change from yellow to red under optimized conditions. The concentration of melamine in adulterated sample can be quantitated by monitoring the absorption spectra of silver nanoparticles using ultraviolet-visible (UV-Vis) spectrometer. The present colorimetric method which utilizes silver nanoparticles of 35 nm can reliably detect melamine down to a concentration of 0.04 mg l- 1.

  7. High Sensitivity Optomechanical Reference Accelerometer over 10 kHz

    DTIC Science & Technology

    2014-06-05

    measurements and observations in seismology and gravimetry. 2 High sensitivity optomechanical reference accele Approved for public release; distribution is...and this category of accelerometers, outlining a path for high sensitivity reference acceleration measurements and observations in seismology and...Traditional applications require either high acceleration resolution, such as in gravimetry or seismology well below 100 Hz, or large bandwidths, as for

  8. High sensitivity leak detection method and apparatus

    DOEpatents

    Myneni, G.R.

    1994-09-06

    An improved leak detection method is provided that utilizes the cyclic adsorption and desorption of accumulated helium on a non-porous metallic surface. The method provides reliable leak detection at superfluid helium temperatures. The zero drift that is associated with residual gas analyzers in common leak detectors is virtually eliminated by utilizing a time integration technique. The sensitivity of the apparatus of this disclosure is capable of detecting leaks as small as 1 [times] 10[sup [minus]18] atm cc sec[sup [minus]1]. 2 figs.

  9. High sensitivity leak detection method and apparatus

    DOEpatents

    Myneni, Ganapatic R.

    1994-01-01

    An improved leak detection method is provided that utilizes the cyclic adsorption and desorption of accumulated helium on a non-porous metallic surface. The method provides reliable leak detection at superfluid helium temperatures. The zero drift that is associated with residual gas analyzers in common leak detectors is virtually eliminated by utilizing a time integration technique. The sensitivity of the apparatus of this disclosure is capable of detecting leaks as small as 1.times.10.sup.-18 atm cc sec.sup.-1.

  10. Achieving High Sensitivity in Cavity Optomechanical Magnetometry

    DTIC Science & Technology

    2014-03-08

    Box 12211 Research Triangle Park, NC 27709-2211 Magnetometry, cavity optomechanical sensing, photonic sensing, microfabrication REPORT DOCUMENTATION...of  experimental  set-­‐up.  FPC:   Fiber  polarization  controller.   Fig.  3  Sensitivity  as  a  function  of...function  of  signal  frequency.   Fig.  5  Photograph  of  assembled  CaF   crystal  resonator  sensor.   Fig.  6

  11. A high sensitive phosphor for dosimetric applications

    SciTech Connect

    Kore, Bhushan P. Dhoble, S. J.; Dhoble, N. S.; Lochab, S. P.

    2015-06-24

    In this study a novel TL phosphor CaMg{sub 3}(SO{sub 4}){sub 4}:Dy{sup 3+} was prepared by acid distillation method. The TL response of this phosphor towards γ-rays and carbon ion beam was tested. Good dosimetric glow curve was observed which is stable against both the type of radiations. The CaMg{sub 3}(SO{sub 4}){sub 4}:Dy{sup 3+} phosphor doped with 0.2 mol% of Dy{sup 3+}, irradiated with γ-ray shows nearly equal sensitivity to that of commercially available CaSO{sub 4}:Dy TLD phosphor whereas 3.5 times more sensitivity than CaSO{sub 4}:Dy, when irradiated with carbon ion beam. The change in glow peak intensities and glow peak temperature with variation in irradiation species and energy of ion beam is discussed here. The effect of these on trapping parameters is also illustrated.

  12. Selenocysteine detection and bioimaging in living cells by a colorimetric and near-infrared fluorescent turn-on probe with a large stokes shift.

    PubMed

    Li, Meixing; Feng, Weiyong; Zhai, Qisong; Feng, Guoqiang

    2017-01-15

    Selenocysteine (Sec) has emerged as an important sensing target in recent years. In this paper, a colorimetric and near-infrared fluorescent turn-on probe for Sec was developed. This probe features a remarkable large Stokes shift (146nm) and shows a rapid, highly selective detection process for Sec with obvious colorimetric and near-infrared fluorescent (Em 706nm with Ex 560nm) turn-on responses. In addition, this probe can be used to quantitatively detect Sec with high sensitivity with a detection limit of 62nM over a wide linear range (0.2-80μM). Moreover, it was further demonstrated that this NIR fluorescent probe can be employed to image both exogenous and endogenous Sec in living cells, indicating that this probe has great potential for biological applications.

  13. Accurate colorimetric feedback for RGB LED clusters

    NASA Astrophysics Data System (ADS)

    Man, Kwong; Ashdown, Ian

    2006-08-01

    We present an empirical model of LED emission spectra that is applicable to both InGaN and AlInGaP high-flux LEDs, and which accurately predicts their relative spectral power distributions over a wide range of LED junction temperatures. We further demonstrate with laboratory measurements that changes in LED spectral power distribution with temperature can be accurately predicted with first- or second-order equations. This provides the basis for a real-time colorimetric feedback system for RGB LED clusters that can maintain the chromaticity of white light at constant intensity to within +/-0.003 Δuv over a range of 45 degrees Celsius, and to within 0.01 Δuv when dimmed over an intensity range of 10:1.

  14. Discrimination of Complex Mixtures by a Colorimetric Sensor Array: Coffee Aromas

    PubMed Central

    Suslick, Benjamin A.; Feng, Liang; Suslick, Kenneth S.

    2010-01-01

    The analysis of complex mixtures presents a difficult challenge even for modern analytical techniques, and the ability to discriminate among closely similar such mixtures often remains problematic. Coffee provides a readily available archetype of such highly multicomponent systems. The use of a low-cost, sensitive colorimetric sensor array for the detection and identification of coffee aromas is reported. The color changes of the sensor array were used as a digital representation of the array response and analyzed with standard statistical methods, including principal component analysis (PCA) and hierarchical clustering analysis (HCA). PCA revealed that the sensor array has exceptionally high dimensionality with 18 dimensions required to define 90% of the total variance. In quintuplicate runs of 10 commercial coffees and controls, no confusions or errors in classification by HCA were observed in 55 trials. In addition, the effects of temperature and time in the roasting of green coffee beans were readily observed and distinguishable with a resolution better than 10 °C and 5 min, respectively. Colorimetric sensor arrays demonstrate excellent potential for complex systems analysis in real-world applications and provide a novel method for discrimination among closely similar complex mixtures. PMID:20143838

  15. Water-soluble colorimetric and ratiometric fluorescent probe for selective imaging of palladium species in living cells.

    PubMed

    Liu, Wei; Jiang, Jie; Chen, Chunyang; Tang, Xiaoliang; Shi, Jinmin; Zhang, Peng; Zhang, Kaiming; Li, Zhiqi; Dou, Wei; Yang, Lizi; Liu, Weisheng

    2014-12-01

    A novel water-soluble colorimetric and ratiometric fluorescent probe was synthesized and applied to imaging palladium species under physiological conditions in phosphate buffered saline (PBS) containing less than 1% organic cosolvent without adding any additional reagents. Based on palladium triggered terminal propargyl ethers cleavage reaction, the probe exhibited a high selectivity and sensitivity for palladium species of all the typical oxidation states (0, +2, +4), with a low detection limit (25 nM, 2.7 μg/L) and an obvious color change. Furthermore, the probe was successfully used for ratiometric fluorescence imaging of palladium in living cells.

  16. Highly sensitive magnetite nano clusters for MR cell imaging.

    PubMed

    Li, Mingli; Gu, Hongchen; Zhang, Chunfu

    2012-03-31

    High sensitivity and suitable sizes are essential for magnetic iron oxide contrast agents for cell imaging. In this study, we have fabricated highly MR sensitive magnetite nanoclusters (MNCs) with tunable sizes. These clusters demonstrate high MR sensitivity. Especially, water suspensions of the MNCs with average size of 63 nm have transverse relaxivity as high as 630 s-1mM-1, which is among the most sensitive iron oxide contrast agents ever reported. Importantly, such MNCs have no adverse effects on cells (RAW 264.7). When used for cell imaging, they demonstrate much higher efficiency and sensitivity than those of SHU555A (Resovist), a commercially available contrast agent, both in vitro and in vivo, with detection limits of 3,000 and 10,000 labeled cells, respectively. The studied MNCs are sensitive for cell imaging and promising for MR cell tracking in clinics.

  17. Highly sensitive magnetite nano clusters for MR cell imaging

    PubMed Central

    2012-01-01

    High sensitivity and suitable sizes are essential for magnetic iron oxide contrast agents for cell imaging. In this study, we have fabricated highly MR sensitive magnetite nanoclusters (MNCs) with tunable sizes. These clusters demonstrate high MR sensitivity. Especially, water suspensions of the MNCs with average size of 63 nm have transverse relaxivity as high as 630 s-1mM-1, which is among the most sensitive iron oxide contrast agents ever reported. Importantly, such MNCs have no adverse effects on cells (RAW 264.7). When used for cell imaging, they demonstrate much higher efficiency and sensitivity than those of SHU555A (Resovist), a commercially available contrast agent, both in vitro and in vivo, with detection limits of 3,000 and 10,000 labeled cells, respectively. The studied MNCs are sensitive for cell imaging and promising for MR cell tracking in clinics. PMID:22462693

  18. MATRIX DISCRIMINANT ANALYSIS WITH APPLICATION TO COLORIMETRIC SENSOR ARRAY DATA

    PubMed Central

    Suslick, Kenneth S.

    2014-01-01

    With the rapid development of nano-technology, a “colorimetric sensor array” (CSA) which is referred to as an optical electronic nose has been developed for the identification of toxicants. Unlike traditional sensors which rely on a single chemical interaction, CSA can measure multiple chemical interactions by using chemo-responsive dyes. The color changes of the chemo-responsive dyes are recorded before and after exposure to toxicants and serve as a template for classification. The color changes are digitalized in the form of a matrix with rows representing dye effects and columns representing the spectrum of colors. Thus, matrix-classification methods are highly desirable. In this article, we develop a novel classification method, matrix discriminant analysis (MDA), which is a generalization of linear discriminant analysis (LDA) for the data in matrix form. By incorporating the intrinsic matrix-structure of the data in discriminant analysis, the proposed method can improve CSA’s sensitivity and more importantly, specificity. A penalized MDA method, PMDA, is also introduced to further incorporate sparsity structure in discriminant function. Numerical studies suggest that the proposed MDA and PMDA methods outperform LDA and other competing discriminant methods for matrix predictors. The asymptotic consistency of MDA is also established. R code and data are available online as supplementary material. PMID:26783371

  19. MATRIX DISCRIMINANT ANALYSIS WITH APPLICATION TO COLORIMETRIC SENSOR ARRAY DATA.

    PubMed

    Zhong, Wenxuan; Suslick, Kenneth S

    2015-09-01

    With the rapid development of nano-technology, a "colorimetric sensor array" (CSA) which is referred to as an optical electronic nose has been developed for the identification of toxicants. Unlike traditional sensors which rely on a single chemical interaction, CSA can measure multiple chemical interactions by using chemo-responsive dyes. The color changes of the chemo-responsive dyes are recorded before and after exposure to toxicants and serve as a template for classification. The color changes are digitalized in the form of a matrix with rows representing dye effects and columns representing the spectrum of colors. Thus, matrix-classification methods are highly desirable. In this article, we develop a novel classification method, matrix discriminant analysis (MDA), which is a generalization of linear discriminant analysis (LDA) for the data in matrix form. By incorporating the intrinsic matrix-structure of the data in discriminant analysis, the proposed method can improve CSA's sensitivity and more importantly, specificity. A penalized MDA method, PMDA, is also introduced to further incorporate sparsity structure in discriminant function. Numerical studies suggest that the proposed MDA and PMDA methods outperform LDA and other competing discriminant methods for matrix predictors. The asymptotic consistency of MDA is also established. R code and data are available online as supplementary material.

  20. Linearization strategies for high sensitivity magnetoresistive sensors

    NASA Astrophysics Data System (ADS)

    Silva, Ana V.; Leitao, Diana C.; Valadeiro, João; Amaral, José; Freitas, Paulo P.; Cardoso, Susana

    2015-10-01

    Ultrasensitive magnetic field sensors envisaged for applications on biomedical imaging require the detection of low-intensity and low-frequency signals. Therefore linear magnetic sensors with enhanced sensitivity low noise levels and improved field detection at low operating frequencies are necessary. Suitable devices can be designed using magnetoresistive sensors, with room temperature operation, adjustable detected field range, CMOS compatibility and cost-effective production. The advent of spintronics set the path to the technological revolution boosted by the storage industry, in particular by the development of read heads using magnetoresistive devices. New multilayered structures were engineered to yield devices with linear output. We present a detailed study of the key factors influencing MR sensor performance (materials, geometries and layout strategies) with focus on different linearization strategies available. Furthermore strategies to improve sensor detection levels are also addressed with best reported values of ˜40 pT/√Hz at 30 Hz, representing a step forward the low field detection at room temperature.

  1. Microstructure-Sensitive Modeling of High Cycle Fatigue (Preprint)

    DTIC Science & Technology

    2009-03-01

    SUBJECT TERMS microplasticity , microstructure-sensitive modeling, high cycle fatigue, fatigue variability 16. SECURITY CLASSIFICATION OF: 17...3Air Force Research Laboratory Wright Patterson Air Force Base, Ohio 45433 Keywords: Microplasticity , microstructure-sensitive modeling, high cycle...cyclic microplasticity ) plays a key role in modeling fatigue resistance. Unlike effective properties such as elastic stiffness, fatigue is

  2. A highly sensitive dual-readout assay based on poly(A) and gold nanoparticles for palmatine hydrochloride.

    PubMed

    Tan, Kejun; Li, Jiayu; Li, Huachun; Wang, Yingying; Yuan, Rui

    2014-03-25

    This report presents a highly sensitive, poly(A)-stabilized gold nanoparticle-based assay with dual readouts (resonance light scattering and colorimetric) for detecting palmatine hydrochloride (PaH) in real samples. The detection mechanism is based on the fact that palmatine hydrochloride has strong affinity to poly(A), which can stabilize gold nanoparticles at high ionic strength, and cause the aggregation of poly(A)-stabilized AuNPs, resulting in the enhanced resonance light scattering (RLS). At the same time, the color change of poly(A)-stabilized AuNPs solution is from red to blue via purple. Thus a highly sensitive RLS assay for PaH has been developed with a linear range of 0.023-2.5 μg/mL. The limit of detection (LOD, 3σ) is 2.3 ng/mL. In this work, the reaction mechanism of this system was investigated by scanning electron microscope (SEM), dark-field light scattering images (DLSI), dynamiclight scattering (DLS) and circular dichroism (CD). This proposed method was also applied successfully for the determination of PaH in pharmaceutical preparations and urine samples with RSD⩽4.0%. The results are in good agreement with those from the official method.

  3. Highly linear, sensitive analog-to-digital converter

    NASA Technical Reports Server (NTRS)

    Cox, J.; Finley, W. R.

    1969-01-01

    Analog-to-digital converter converts 10 volt full scale input signal into 13 bit digital output. Advantages include high sensitivity, linearity, low quantitizing error, high resistance to mechanical shock and vibration loads, and temporary data storage capabilities.

  4. A Rapid In Situ Colorimetric Assay for Cobalt Detection by the Naked Eye

    PubMed Central

    Kang, Sung-Min; Jang, Sung-Chan; Kim, Gi Yong; Lee, Chang-Soo; Huh, Yun Suk; Roh, Changhyun

    2016-01-01

    A simple, rapid, and convenient colorimetric chemosensor of a specific target toward the end user is still required for on-site detection and real-time monitoring applications. In this study, we developed a rapid in situ colorimetric assay for cobalt detection using the naked eye. Interestingly, a yellow to light orange visual color transition was observed within 3 s when a Chrysoidine G (CG) chemosensor was exposed to cobalt. Surprisingly, the CG chemosensor had great selectivity toward cobalt without any interference of other metal ions. Under optimized conditions, a lower detection limit of 0.1 ppm via a spectrophotometer and a visual detection limit of 2 ppm with a linear range from 0.4 to 1 ppm (R2 = 0.97) were determined. Moreover, the CG chemosensor is reversible and maintains its functionality after treatment with chelating agents. In conclusion, we show the superior capabilities of the CG chemosensor, which has the potential to provide extremely facile handling, high sensitivity, and a fast response time for applications of on-site detection to real-time cobalt monitoring for the general public. PMID:27144568

  5. Plasmonic Metasurfaces Based on Nanopin-Cavity Resonator for Quantitative Colorimetric Ricin Sensing.

    PubMed

    Fan, Jiao-Rong; Zhu, Jia; Wu, Wen-Gang; Huang, Yun

    2017-01-01

    In view of the toxic potential of a bioweapon threat, rapid visual recognition and sensing of ricin has been of considerable interest while remaining a challenging task up to date. In this study, a gold nanopin-based colorimetric sensor is developed realizing a multicolor variation for ricin qualitative recognition and analysis. It is revealed that such plasmonic metasurfaces based on nanopin-cavity resonator exhibit reflective color appearance, due to the excitation of standing-wave resonances of narrow bandwidth in visible region. This clear color variation is a consequence of the reflective color mixing defined by different resonant wavelengths. In addition, the colored metasurfaces appear sharp color difference in a narrow refractive index range, which makes them especially well-suited for sensing applications. Therefore, this antibody-functionalized nanopin-cavity biosensor features high sensitivity and fast response, allowing for visual quantitative ricin detection within the range of 10-120 ng mL(-1) (0.15 × 10(-9) -1.8 × 10(-9) m), a limit of detection of 10 ng mL(-1) , and the typical measurement time of less than 10 min. The on-chip integration of such nanopin metasurfaces to portable colorimetric microfluidic device may be envisaged for the quantitative studies of a variety of biochemical molecules.

  6. CUPRAC colorimetric and electroanalytical methods determining antioxidant activity based on prevention of oxidative DNA damage.

    PubMed

    Uzunboy, Seda; Çekiç, Sema Demirci; Eksin, Ece; Erdem, Arzum; Apak, Reşat

    2017-02-01

    An unbalanced excess of oxygen/nitrogen species (ROS/RNS) can give oxidative hazard to DNA and other biomacromolecules under oxidative stress conditions. While the 'comet' assay for measuring DNA damage is neither specific nor practical, monitoring oxidative changes on individual DNA bases and other oxidation products needs highly specialized equipment and operators. Thus, we developed a modified CUPRAC (cupric ion reducing antioxidant capacity) colorimetric method to determine the average total damage on DNA produced by Fenton oxidation, taking advantage of the fact that the degradation products of DNA but not the original macromolecule is CUPRAC-responsive. The DNA-protective effects of water-soluble antioxidants were used to devise a novel antioxidant activity assay, considered to be physiologically more realistic than those using artificial probes. Our method, based on the measurement of DNA oxidative products with CUPRAC colorimetry proved to be 2 orders-of-magnitude more sensitive than the widely used TBARS (thiobarbituric acid-reactive substances) colorimetric assay used as reference. Additionally, the DNA damage was electrochemically investigated using pencil graphite electrodes (PGEs) as DNA sensor platform in combination with differential pulse voltammetry (DPV). The interaction of the radical species with DNA in the absence/presence of antioxidants was detected according to the changes in guanine oxidation signal.

  7. A Rapid In Situ Colorimetric Assay for Cobalt Detection by the Naked Eye.

    PubMed

    Kang, Sung-Min; Jang, Sung-Chan; Kim, Gi Yong; Lee, Chang-Soo; Huh, Yun Suk; Roh, Changhyun

    2016-05-02

    A simple, rapid, and convenient colorimetric chemosensor of a specific target toward the end user is still required for on-site detection and real-time monitoring applications. In this study, we developed a rapid in situ colorimetric assay for cobalt detection using the naked eye. Interestingly, a yellow to light orange visual color transition was observed within 3 s when a Chrysoidine G (CG) chemosensor was exposed to cobalt. Surprisingly, the CG chemosensor had great selectivity toward cobalt without any interference of other metal ions. Under optimized conditions, a lower detection limit of 0.1 ppm via a spectrophotometer and a visual detection limit of 2 ppm with a linear range from 0.4 to 1 ppm (R² = 0.97) were determined. Moreover, the CG chemosensor is reversible and maintains its functionality after treatment with chelating agents. In conclusion, we show the superior capabilities of the CG chemosensor, which has the potential to provide extremely facile handling, high sensitivity, and a fast response time for applications of on-site detection to real-time cobalt monitoring for the general public.

  8. Gold nanoparticle aggregation-based colorimetric assay for β-casein detection in bovine milk samples.

    PubMed

    Li, Y S; Zhou, Y; Meng, X Y; Zhang, Y Y; Song, F; Lu, S Y; Ren, H L; Hu, P; Liu, Z S; Zhang, J H

    2014-11-01

    Traditional Kjeldahl method, used for quality evaluation of bovine milk, has intrinsic defects of time-consuming sample preparation and two analyses to determine the difference between non-protein nitrogen content and total protein nitrogen content. Herein, based upon antibody functionalized gold nanoparticles (AuNPs), we described a colorimetric method for β-casein (β-CN) detection in bovine milk samples. The linear dynamic range and the LOD were 0.08-250 μg mL(-1), and 0.03 μg mL(-1) respectively. In addition, the real content of β-CN in bovine milk was measured by using the developed assay. The results are closely correlated with those from Kjeldahl method. The advantages of β-CN triggered AuNP aggregation-based colorimetric assay are simple signal generation, the high sensitivity and specificity as well as no need of complicated sample preparation, which make it for on-site detection of β-CN in bovine milk samples.

  9. Phenazine-based colorimetric and fluorescent sensor for the selective detection of cyanides based on supramolecular self-assembly in aqueous solution

    NASA Astrophysics Data System (ADS)

    Zhang, Hai-Li; Wei, Tai-Bao; Li, Wen-Ting; Qu, Wen-Juan; Leng, Yan-Li; Zhang, Jian-Hui; Lin, Qi; Zhang, You-Ming; Yao, Hong

    2017-03-01

    Taking advantages of both the well-known phenazine structure and the mechanism of the supramolecular self-assembly and deprotonation process, the fluorescent and colorimetric sensor (ZL) was designed and synthesized, behaving as a circulation utilization (above 10 times) receptor for selective detection of cyanide anion (CN-) in aqueous media. Upon the addition of CN-, the sensor displayed obvious color changes from yellow to jacinth by naked eyes and the fluorescence immediately quenched (< 10 s). With respect to other common anions, the sensor possessed high selectivity and sensitivity (0.05 μM) for cyanide anions. In addition, the test strips of ZL were fabricated, which could serve as practical colorimetric and fluorescent sensor for "in-the-field" measurements.

  10. Highly stable water dispersible calix[4]pyrrole octa-hydrazide protected gold nanoparticles as colorimetric and fluorometric chemosensors for selective signaling of Co(II) ions

    NASA Astrophysics Data System (ADS)

    Bhatt, Keyur D.; Vyas, Disha J.; Makwana, Bharat A.; Darjee, Savan M.; Jain, Vinod K.

    2014-03-01

    Water dispersible stable gold nanoparticles (AuNps) have been synthesized by using calix[4]pyrrole octa-hydrazide (CPOH) as a reducing as well as stabilizing agent. CPOH-AuNps have been characterized by surface plasmon resonance, particle size analyzer and transmission electron microscopy. CPOH-AuNps are water dispersible, highly stable for more than 150 days at neutral pH with a size of less than 10 nm and zeta potential of 15 ± 2 MeV. Ion sensing property of CPOH-AuNps has been investigated for various metal ions Pb(II), Cd(II), Mn(II), Fe(III), Ni(II), Zn(II), Hg(II), Co(II) and Cu(II) by colorimetry and spectrofluorimetry. Among all the metal ions investigated, only Co(II) ions gives sharp colour change from ruby red to blue and is easily detectable by naked-eye. CPOH-AuNps being fluorescent in nature also shows great sensitivity and selectivity for Co(II) ions. Co(II) ions can be selectively detected at very low concentration level of 1 nM in a facile way of fluorescence quenching.

  11. 5-Hydroxymethylfurfural modified rhodamine B dual-function derivative: Highly sensitive and selective optical detection of pH and Cu2+

    NASA Astrophysics Data System (ADS)

    Wang, Enze; Zhou, Yanmei; Huang, Qi; Pang, Lanfang; Qiao, Han; Yu, Fang; Gao, Bin; Zhang, Junli; Min, Yinghao; Ma, Tongsen

    2016-01-01

    A dual-function optical chemosensor (RBF) was designed and easily synthesized by condensation reaction of 5-Hydroxymethylfurfural and rhodamine B hydrazide. RBF exhibited highly sensitive, highly selective and quick response to acidic pH. The fluorescence intensity of RBF exhibited a more than 41-fold increase within the pH range from 7.50 to 3.73 with a pKa value of 5.02, which could be successfully applied to monitor intracellular pH in living PC12 cells and HeLa cells. Additionally, the spectroscopy of UV-Vis and EDTA-adding experiments indicated that RBF was a highly selective and reversible colorimetric chemosensor for Cu2+ in Tris-HCl (10 mM, pH = 7.2) aqueous buffer solution as well as other metal ions had no obvious interference. Moreover, RBF has been successfully applied to detect Cu2+ in real water samples.

  12. Colorimetric Detection of Plasmodium vivax in Urine Using MSP10 Oligonucleotides and Gold Nanoparticles

    PubMed Central

    Alnasser, Yossef; Ferradas, Cusi; Clark, Taryn; Calderon, Maritza; Gurbillon, Alejandro; Gamboa, Dionicia; McKakpo, Uri S.; Quakyi, Isabella A.; Bosompem, Kwabena M.; Sullivan, David J.; Vinetz, Joseph M.; Gilman, Robert H.

    2016-01-01

    Plasmodium vivax is the most prevalent cause of human malaria in the world and can lead to severe disease with high potential for relapse. Its genetic and geographic diversities make it challenging to control. P. vivax is understudied and to achieve control of malaria in endemic areas, a rapid, accurate, and simple diagnostic tool is necessary. In this pilot study, we found that a colorimetric system using AuNPs and MSP10 DNA detection in urine can provide fast, easy, and inexpensive identification of P. vivax. The test exhibited promising sensitivity (84%), high specificity (97%), and only mild cross-reactivity with P. falciparum (21%). It is simple to use, with a visible color change that negates the need for a spectrometer, making it suitable for use in austere conditions. Using urine eliminates the need for finger-prick, increasing both the safety profile and patient acceptance of this model. PMID:27706158

  13. A Liquid-Based Colorimetric Assay of Lysine Decarboxylase and Its Application to Enzymatic Assay.

    PubMed

    Kim, Yong Hyun; Sathiyanarayanan, Ganesan; Kim, Hyun Joong; Bhatia, Shashi Kant; Seo, Hyung-Min; Kim, Jung-Ho; Song, Hun-Seok; Kim, Yun-Gon; Park, Kyungmoon; Yang, Yung-Hun

    2015-12-28

    A liquid-based colorimetric assay using a pH indicator was introduced for high-throughput monitoring of lysine decarboxylase activity. The assay is based on the color change of bromocresol purple, measured at 595 nm in liquid reaction mixture, due to an increase of pH by the production of cadaverine. Bromocresol purple was selected as the indicator because it has higher sensitivity than bromothymol blue and pheonol red within a broad range and shows good linearity within the applied pH. We applied this for simple determination of lysine decarboxylase reusability using 96-well plates, and optimization of conditions for enzyme overexpression with different concentrations of IPTG on lysine decarboxylase. This assay is expected to be applied for monitoring and quantifying the liquid-based enzyme reaction in biotransformation of decarboxylase in a high-throughput way.

  14. Accelerated colorimetric immunosensing using surface-modified porous monoliths and gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Chuag, Shao-Hsuan; Chen, Guan-Hua; Chou, Hsin-Hao; Shen, Shu-Wei; Chen, Chien-Fu

    2013-08-01

    A rapid and sensitive immunoassay platform integrating polymerized monoliths and gold nanoparticles (AuNPs) has been developed. The porous monoliths are photopolymerized in situ within a silica capillary and serve as solid support for high-mass transport and high-density capture antibody immobilization to create a shorter diffusion length for antibody-antigen interactions, resulting in a rapid assay and low reagent consumption. AuNPs are modified with detection antibodies and are utilized as signals for colorimetric immunoassays without the need for enzyme, substrate and sophisticated equipment for quantitative measurements. This platform has been verified by performing a human IgG sandwich immunoassay with a detection limit of 0.1 ng ml-1. In addition, a single assay can be completed in 1 h, which is more efficient than traditional immunoassays that require several hours to complete.

  15. Novel pyridyl based azo-derivative for the selective and colorimetric detection of nickel(II)

    NASA Astrophysics Data System (ADS)

    Biswas, Sujan; Acharyya, Samik; Sarkar, Deblina; Gharami, Saswati; Mondal, Tapan Kumar

    2016-04-01

    A highly sensitive and selective pyridyl based colorimetric chemosensor (H2L) for the efficient detection of Ni2 + has been reported. The synthesized chemosensor H2L is highly efficient in detecting Ni2 + even in the presence of other metal ions that commonly co-exist with Ni2 +. H2L also shows distinct color change from green to deep red visible under naked eye due to specific binding with Ni2 +. This color change is due to formation of a new band at 510 nm upon gradual addition of Ni2 +. The association constant has been found to be 1.27 × 105 M- 1 with limit of detection (LOD) of 8.3 × 10- 7 M. Electronic structure of the H2L-Ni2 + complex and sensing mechanism have been interpreted theoretically by DFT and TDDFT calculations.

  16. "Naked-eye" colorimetric and "turn-on" fluorometric chemosensors for reversible Hg2+ detection.

    PubMed

    Wanichacheva, Nantanit; Praikaew, Panida; Suwanich, Thanapat; Sukrat, Kanjarat

    2014-01-24

    Two new Hg(2+)-colorimetric and fluorescent sensors based on 2-[3-(2-aminoethylsulfanyl) propylsulfanyl]ethanamine covalently bound to one and two units of rhodamine-6G moieties, 1 and 2, were synthesised, and their sensing behaviors toward metal ions were investigated by UV/Vis and fluorescence spectroscopy. Upon the addition of Hg(2+), the sensors exhibited highly sensitive "turn-on" fluorescence enhancement as well as a color change from colorless to pink, which was readily noticeable for naked eye detection. Especially, 1 exhibited the reversible behavior and revealed a very high selectivity in the presence of competitive ions, particularly Cu(2+), Ag(+), Pb(2+), Ca(2+), Cd(2+), Co(2+), Fe(2+), Mn(2+), Na(+), Ni(2+), K(+), Ba(2+), Li(+) and Zn(2+), with a low detection limit of 1.7 ppb toward Hg(2+).

  17. Fluorosurfactant-capped gold nanoparticles-based label-free colorimetric assay for Au³⁺ with tunable dynamic range via a redox strategy.

    PubMed

    Yang, Bin; Zhang, Xiao-Bing; Liu, Wei-Na; Hu, Rong; Tan, Weihong; Shen, Guo-Li; Yu, Ru-Qin

    2013-10-15

    Gold nanoparticles-based colorimetric assay possesses several unique advantages, and has been applied for a wide range of targets, varying from nucleic acids to different metal ions. However, due to the lack of proper coordinating ligand, gold nanoparticles-based colorimetric sensing system for Au³⁺ has not been developed so far. It is well-known that Au³⁺ could induce the oxidation transition of thiol compounds to disulfide compounds. In this article, for the first time we converted such thiol masking reaction into colorimetric sensing system for label-free detection of Au³⁺ via a target-controlled aggregation of nanoparticles strategy. In the new proposed sensing system, fluorosurfactant-capped gold nanoparticles were chosen as signal reporter units, while an Au³⁺-triggered oxidation of cysteine (Cys), which inhibited the aggregation of gold nanoparticles, acted as the recognition unit. By varying the amount of Cys, a tunable response range accompanied with different windows of color change could be obtained for Au³⁺, illustrating the universality of the sensing system for Au³⁺ samples with different sensitivity requirements. Under optimized condition, the proposed sensing system exhibits a high sensitivity towards Au³⁺ with a detection limit of 50 nM, which is lower than previously reported spectroscopic methods. It has also been applied for detection of Au³⁺ in practical water samples with satisfactory result.

  18. Multipurpose High Sensitivity Radiation Detector: Terradex

    NASA Astrophysics Data System (ADS)

    Alpat, Behcet; Aisa, Damiano; Bizzarri, Marco; Blasko, Sandor; Esposito, Gennaro; Farnesini, Lucio; Fiori, Emmanuel; Papi, Andrea; Postolache, Vasile; Renzi, Francesca; Ionica, Romeo; Manolescu, Florentina; Ozkorucuklu, Suat; Denizli, Haluk; Tapan, Ilhan; Pilicer, Ercan; Egidi, Felice; Moretti, Cesare; Dicola, Luca

    2007-05-01

    Terradex project aims to realise an accurate and programmable multiparametric tool which will measure relevant physical quantities such as observation time, energy and type of all decay products of three naturally occurring decay chains of uranium and thorium series present in nature as well as the decay products of man-made radioactivity. The measurements described in this work are based on the performance tests of the first version of an instrument that is designed to provide high counting accuracy, by introducing self-triggering, delayed time-coincidence technique, of products of a given decay chain. In order to qualify the technique and to calibrate the Terradex, a 222Rn source is used. The continuous and accurate monitoring of radon concentration in air is realised by observing the alpha and beta particles produced by the decay of 222Rn and its daughters and tag each of them with a precise occurrence time. The validity of delayed coincident technique by using the state of the art electronics with application of novel data sampling and analysis methods are discussed. The flexibility of sampling protocols and the advantages of online calibration capability to achieve the highest level of precision in natural and man-made radiation measurements are also described.

  19. Optimetric system facilitates colorimetric and fluorometric measurements

    NASA Technical Reports Server (NTRS)

    Haley, F. C.

    1968-01-01

    Compact, unitary optimetric systems uses a single device for colorimetric, fluorometric and spectral absorption measurements. The basic element of the unitary systems is a test cell containing filter elements with uniquely fabricated lenses.

  20. Simple Colorimetric Sensor for Trinitrotoluene Testing

    NASA Astrophysics Data System (ADS)

    Samanman, S.; Masoh, N.; Salah, Y.; Srisawat, S.; Wattanayon, R.; Wangsirikul, P.; Phumivanichakit, K.

    2017-02-01

    A simple operating colorimetric sensor for trinitrotoluene (TNT) determination using a commercial scanner as a captured image was designed. The sensor is based on the chemical reaction between TNT and sodium hydroxide reagent to produce the color change within 96 well plates, which observed finally, recorded using a commercial scanner. The intensity of the color change increased with increase in TNT concentration and could easily quantify the concentration of TNT by digital image analysis using the Image J free software. Under optimum conditions, the sensor provided a linear dynamic range between 0.20 and 1.00 mg mL-1(r = 0.9921) with a limit of detection of 0.10± 0.01 mg mL-1. The relative standard deviation for eight experiments for the sensitivity was 3.8%. When applied for the analysis of TNT in two soil extract samples, the concentrations were found to be non-detectable to 0.26±0.04 mg mL-1. The obtained recovery values (93-95%) were acceptable for soil samples tested.

  1. Optical fiber waveguide sensor for the colorimetric detection of ammonia

    NASA Astrophysics Data System (ADS)

    Schmitt, Katrin; Rist, Jonas; Peter, Carolin; Wöllenstein, Jürgen

    2011-06-01

    We present the development and characterization of a fiber-optic colorimetric gas sensor combined with the electronic circuitry for measurement control and RFID communication. The gas sensor detects ammonia using a 300 μm polyolefin fiber coated with a gas-sensitive polymer film. The spectral and time-dependent sensitivity of various polymer films was tested in transmission measurements. Light from a standard LED at λ = 590 nm was coupled into the polyolefin fiber through the front face. A prototype of the gas sensor with the direct coupling method was tested under realistic measurement conditions, i.e. battery-driven and in a completely autonomous mode. The sensor system showed good sensitivity to the ammonia concentrations and response times in the order of minutes. The achievable power consumption was below 100μW.The films contained the pH-sensitive dyes bromocresol purple or bromophenol blue embedded in either ethyl cellulose or polyvinyl butyral, and optionally tributyl phosphate as plasticizer. The bromophenol blue based films showed a strong reaction to ammonia, with saturation concentrations around 1000 ppm and response times of about 15 seconds to 100ppm. The colorimetric reaction was simulated using a simple kinetic model which was in good agreement with the experimental results.

  2. Colorimetric characterization of LCD based on constrained least squares

    NASA Astrophysics Data System (ADS)

    LI, Tong; Xie, Kai; Wang, Qiaojie; Yao, Luyang

    2017-01-01

    In order to improve the accuracy of colorimetric characterization of liquid crystal display, tone matrix model in color management modeling of display characterization is established by using constrained least squares for quadratic polynomial fitting, and find the relationship between the RGB color space to CIEXYZ color space; 51 sets of training samples were collected to solve the parameters, and the accuracy of color space mapping model was verified by 100 groups of random verification samples. The experimental results showed that, with the constrained least square method, the accuracy of color mapping was high, the maximum color difference of this model is 3.8895, the average color difference is 1.6689, which prove that the method has better optimization effect on the colorimetric characterization of liquid crystal display.

  3. Highly sensitive DNA detection using cascade amplification strategy based on hybridization chain reaction and enzyme-induced metallization.

    PubMed

    Yu, Xu; Zhang, Zhi-Ling; Zheng, Si-Yang

    2015-04-15

    A novel highly sensitive colorimetric assay for DNA detection using cascade amplification strategy based on hybridization chain reaction and enzyme-induced metallization was established. The DNA modified superparamagnetic beads were demonstrated to capture and enrich the target DNA in the hybridization buffer or human plasma. The hybridization chain reaction and enzyme-induced silver metallization on the gold nanoparticles were used as cascade signal amplification for the detection of target DNA. The metalization of silver on the gold nanoparticles induced a significant color change from red to yellow until black depending on the concentration of the target DNA, which could be recognized by naked eyes. This method showed a good specificity for the target DNA detection, with the capabilty to discriminate single-base-pair mismatched DNA mutation (single nucleotide polymorphism). Meanwhile, this approach exhibited an excellent anti-interference capability with the convenience of the magentic seperation and washing, which enabled its usage in complex biological systems such as human blood plasma. As an added benefit, the utilization of hybridization chain reaction and enzyme-induced metallization improved detection sensitivity down to 10pM, which is about 100-fold lower than that of traditional unamplified homogeneous assays.

  4. Colorimetric chemosensor of symmetrical benzoylthiourea derivatives as for detection of Cu2+ in aqueous solution

    NASA Astrophysics Data System (ADS)

    Hamedan, N. A.; Hasan, S.; Zaki, H. M.; Alias, N. Z.

    2017-02-01

    A novel receptor, designed with a combination of oxygen (O), nitrogen (N) and sulfur (S) -binding sites for metal ions was synthesized. Ortho (A), meta (B) and para (C) bearing benzoyl thiourea were designed and synthesized with triamine group to apply as colorimetric chemosensors for detection of Cu2+. The structure was confirmed by characterized the compound using Elemental analysis, Fourier Infrared (FTIR) and proton Nuclear Magnetic Resonance (1H NMR) spectroscopy. Functional groups of C=O, N-H, C=N and C=S were found at 1677 cm-1, 3240 cm-1, 1591 cm-1, 1024 cm-1 respectively while 1H NMR shows peaks of alkane (CH2), benzene (Ar-H), CONH, CSNH at 3.68 – 4.14, 7.16 – 7.86, 8.74, and 9.2 respectively. Elemental analysis for A, B and C C20H21N5O2S2Br2 found was compatible with the expected theoretical calculation. For an application, all of these three sensors showed excellent colorimetric specific selectivity and high sensitivity for Cu2+ in acetonitrile/water binary solutions, so only A was selected for further studies towards sensitivity. When Cu2+ was added to the solution of A, a dramatic color change from yellow to green, while other cations Fe2+, Zn2+, Ni2+, Co2+, Cr3+ and Mn2+ did not interfere with the recognition process for Cu2+. The detection limit of the sensor C toward Cu2+ was 1.15 x 10-5 M, which is less sensitive that sensor A and B with a detection limit of 6.2 x 10-6 M and 1.5 x 10-6 M respectively. This indicated that the sensor A and B might be useful as an efficient chemical sensor.

  5. A Colorimetric Interdental Probe as a Standard Method to Evaluate Interdental Efficiency of Interdental Brush

    PubMed Central

    Bourgeois, D.; Carrouel, F.; Llodra, J.C.; Bravo, M.; Viennot, S.

    2015-01-01

    The aim of this study is to evaluate the concordance between the empirical choice of interdental brushes of different diameters compared to the gold standard, the IAP CURAPROX© calibrating colorimetric probe. It is carried out with the aim of facilitating the consensus development of best practices. All the subjects’ interproximal spaces were evaluated using the reference technique (colorimetric probe), then after a time lapse of 1.2 ± 0.2 hours, using the empirical clinical technique (brushes) by the same examiner. Each examiner explored 3 subjects. The order the patients were examined with the colorimetric interdental probe (CIP) was random. 446 sites were selected in the study out of 468 potential sites. The correspondence of scores between interdental bushes vs. colorimetric probe is 43.0% [95%-CI: 38.5-47.6]. In 33.41% of the 446 sites, the brush is inferior to the probe; in 23.54% of cases, the brush is superior to the probe. Among the discrepancies there is thus a tendency for the subjects to use brushes with smaller diameter than that recommended by the colorimetric probe. This review has found very high-quality evidence that colorimetric probes plus interdental brushing is more beneficial than interdental brushing alone for increase the concordance between the empirical choice of interdental brushes of different diameters compared to the gold standard. Uncertainties remain and further research is required to provide detailed data on user satisfaction. PMID:26966470

  6. Novel ultra-high sensitive 'metal resist' for EUV lithography

    NASA Astrophysics Data System (ADS)

    Fujimori, Toru; Tsuchihashi, Toru; Minegishi, Shinya; Kamizono, Takashi; Itani, Toshiro

    2016-03-01

    This study describes the use of a novel ultra-high sensitive `metal resist' for use in extreme ultraviolet (EUV) lithography. Herein, the development of a metal resist has been studied for improving the sensitivity when using metal-containing non-chemically amplified resist materials; such materials are metal-containing organic-inorganic hybrid compounds and are referred to as EUVL Infrastructure Development Center, Inc. (EIDEC) standard metal EUV resist (ESMR). The novel metal resist's ultra-high sensitivity has previously been investigated for use with electron beam (EB) lithography. The first demonstration of ESMR performance was presented in SPIE2015, where it was shown to achieve 17-nm lines with 1.5 mJ/cm2: equivalent in EUV lithography tool. The sensitivity of ESMR using EUV open-flame exposure was also observed to have the same high sensitivity as that when using EB lithography tool. Therefore, ESMR has been confirmed to have the potential of being used as an ultra-high sensitive EUV resist material. The metal-containing organic-inorganic hybrid compounds and the resist formulations were investigated by measuring their sensitivity and line-width roughness (LWR) improvement. Furthermore, new processing conditions, such as new development and rinse procedures, are an extremely effective way of improving lithographic performance. In addition, the optimal dry-etching selective conditions between the metal resist and spin-on carbon (SOC) were obtained. The etched SOC pattern was successfully constructed from a stacked film of metal resist and SOC.

  7. Highly sensitive long-period fiber-grating strain sensor with low temperature sensitivity.

    PubMed

    Wang, Yi-Ping; Xiao, Limin; Wang, D N; Jin, Wei

    2006-12-01

    A long-period fiber-grating sensor with a high strain sensitivity of -7.6 pm/microepsilon and a low temperature sensitivity of 3.91 pm/ degrees C is fabricated by use of focused CO(2) laser beam to carve periodic grooves on a large- mode-area photonic crystal fiber. Such a strain sensor can effectively reduce the cross-sensitivity between strain and temperature, and the temperature-induced strain error obtained is only 0.5 microepsilon/ degrees C without using temperature compensation.

  8. Photoacoustic and Colorimetric Visualization of Latent Fingerprints.

    PubMed

    Song, Kai; Huang, Peng; Yi, Chenglin; Ning, Bo; Hu, Song; Nie, Liming; Chen, Xiaoyuan; Nie, Zhihong

    2015-12-22

    There is a high demand on a simple, rapid, accurate, user-friendly, cost-effective, and nondestructive universal method for latent fingerprint (LFP) detection. Herein, we describe a combination imaging strategy for LFP visualization with high resolution using poly(styrene-alt-maleic anhydride)-b-polystyrene (PSMA-b-PS) functionalized gold nanoparticles (GNPs). This general approach integrates the merits of both colorimetric imaging and photoacoustic imaging. In comparison with the previous methods, our strategy is single-step and does not require the signal amplification by silver staining. The PSMA-b-PS functionalized GNPs have good stability, tunable color, and high affinity for universal secretions (proteins/polypeptides/amino acids), which makes our approach general and flexible for visualizing LFPs on different substrates (presumably with different colors) and from different people. Moreover, the unique optical property of GNPs enables the photoacoustic imaging of GNPs-deposited LFPs with high resolution. This allows observation of level 3 hyperfine features of LFPs such as the pores and ridge contours by photoacoustic imaging. This technique can potentially be used to identify chemicals within LFP residues. We believe that this dual-modality imaging of LFPs will find widespread use in forensic investigations and medical diagnostics.

  9. A strategy to design highly efficient porphyrin sensitizers for dye-sensitized solar cells.

    PubMed

    Chang, Yu-Cheng; Wang, Chin-Li; Pan, Tsung-Yu; Hong, Shang-Hao; Lan, Chi-Ming; Kuo, Hshin-Hui; Lo, Chen-Fu; Hsu, Hung-Yu; Lin, Ching-Yao; Diau, Eric Wei-Guang

    2011-08-21

    We designed highly efficient porphyrin sensitizers with two phenyl groups at meso-positions of the macrocycle bearing two ortho-substituted long alkoxyl chains for dye-sensitized solar cells; the ortho-substituted devices exhibit significantly enhanced photovoltaic performances with the best porphyrin, LD14, showing J(SC) = 19.167 mA cm(-2), V(OC) = 0.736 V, FF = 0.711, and overall power conversion efficiency η = 10.17%.

  10. Label-free colorimetric detection of cancer related gene based on two-step amplification of molecular machine.

    PubMed

    Xu, Huo; Wu, Dong; Li, Chen-Qiao; Lu, Zheng; Liao, Xiao-Yun; Huang, Jie; Wu, Zai-Sheng

    2017-04-15

    Highly sensitive detection of K-ras gene is of great significance in biomedical research and clinical diagnosis. Here, we developed a colorimetric biosensing system for the detection of proto-oncogene K-ras based on enhanced amplification effect of DNA molecular machine, where dual isothermal circular strand-displacement amplification (D-SDA) occurs on two arms in one-to-one correspondence. Specifically, we designed a primer-locked hairpin probe (HP) and a primer-contained linear polymerization template (PPT). In the presence of target gene, HP can hybridize with PPT, forming a DNA molecular machine with dual functional arms (called DFA-machine). Each of the two probes in this machine is able to be extended by polymerase on its counterpart species. Moreover, with the help of nicking endonuclease, the dual isothermal polymerization is converted into dual circular strand-displacement amplification, generating a large amount of anti-hemin aptamer-contained products. After binding to hemins, the aptamer/hemin duplex, horseradish peroxidase (HRP)-mimicking DNAzyme, was formed and catalyzed the oxidation of colorless ABTS by H2O2, producing a visible green color. The proposed colorimetric assay exhibits a wide linear range from 0.01 to 150nM with a low detection limit of 10pM. More interestingly, the mutations existing in target gene are easily observed by the naked eye. It should be noted that this colorimetric system was proved by the analysis of K-ras gene of SW620 cell lines. The simple and powerful DFA-machine is expected to provide promising potential in the sensitive detection of biomarkers for cancer diagnosis, prognosis and therapy.

  11. Sensing behavior and logic operation of a colorimetric fluorescence sensor for Hg2 +/Cu2 + ions

    NASA Astrophysics Data System (ADS)

    He, Tian; Lin, Cuiling; Gu, Zhengye; Xu, Luonan; Yang, Anle; Liu, Yuanyuan; Fang, Huajun; Qiu, Huayu; Zhang, Jing; Yin, Shouchun

    2016-10-01

    A BODIPY-based 1 as a colorimetric fluorescence sensor was synthesized, and its metal sensing property was investigated. 1 displayed high selectivity and sensitivity towards Hg2 + and Cu2 + ions among 15 different metal cations. The addition of Hg2 + and Cu2 + ions into 1 in CH3CN resulted in a significant bathochromic shift of the UV absorption spectra from 533 nm to 560 nm and 593 nm, respectively, changing the corresponding colors from pink to purple and blue. When excited at 530 nm, the fluorescence intensity of 1 was quenched over 75% upon addition of Hg2 + ions, while 1 with Cu2 + ions exhibited significant fluorescence enhancement with a 23 nm red-shift. Based on these results, three logic gates (OR, IMPLICATION, and INHIBIT) were obtained by controlling the chemical inputs.

  12. A colorimetric biosensor for detection of attomolar microRNA with a functional nucleic acid-based amplification machine.

    PubMed

    Li, Dandan; Cheng, Wei; Yan, Yurong; Zhang, Ye; Yin, Yibing; Ju, Huangxian; Ding, Shijia

    2016-01-01

    A functional nucleic acid-based amplification machine was designed for simple and label-free ultrasensitive colorimetric biosensing of microRNA (miRNA). The amplification machine was composed of a complex of trigger template and C-rich DNA modified molecular beacon (MB) and G-rich DNA (GDNA) as the probe, polymerase and nicking enzyme, and a dumbbell-shaped amplification template. The presence of target miRNA triggered MB mediated strand displacement to cyclically release nicking triggers, which led to a toehold initiated rolling circle amplification to produce large amounts of GDNAs. The formed GDNAs could stack with hemin to form G-quadruplex/hemin DNAzyme, a well-known horseradish peroxidase (HRP) mimic, for catalyzing a colorimetric reaction. The modified MB improved the stringent target recognition and reduced background signal. The proposed sensing strategy showed very high sensitivity and selectivity with a wide dynamic range from 10 aM to 1.0 nM, and enabled successful visual analysis of trace amount of miRNA in real sample by the naked eye. This rapid and highly efficient signal amplification strategy provided a simple and sensitive platform for miRNA detection. It would be a versatile and powerful tool for clinical molecular diagnostics.

  13. Highly sensitive wide bandwidth photodetectors using chemical vapor deposited graphene

    NASA Astrophysics Data System (ADS)

    Goo Kang, Chang; Kyung Lee, Sang; Jin Yoo, Tae; Park, Woojin; Jung, Ukjin; Ahn, Jinho; Hun Lee, Byoung

    2014-04-01

    A photodetector generating a nearly constant photocurrent in a very wide spectral range from ultraviolet (UV) to infrared has been demonstrated using chemical vapor deposited (CVD) graphene. Instability due to a photochemical reaction in the UV region has been minimized using an Al2O3 passivation layer, and a responsivity comparable to that of Highly Ordered Pyrolytic Graphite graphene photodetectors of ˜8 mA/W has been achieved at a 0.1 V bias, despite high defect density in the CVD graphene. A highly sensitive multi-band photodetector using graphene has many potential applications including optical interconnects, multi-band imaging sensors, highly sensitive motion detectors, etc.

  14. Approach to the Highly Sensitized Kidney Transplant Candidate.

    PubMed

    Keith, Douglas S; Vranic, Gayle M

    2016-04-07

    For patients with ESRD, kidney transplant offers significant survival and quality-of-life advantages compared with dialysis. But for patients seeking transplant who are highly sensitized, wait times have traditionally been long and options limited. The approach to the highly sensitized candidate for kidney transplant has changed substantially over time owing to new advances in desensitization, options for paired donor exchange (PDE), and changes to the deceased-donor allocation system. Initial evaluation should focus on determining living-donor availability because a compatible living donor is always the best option. However, for most highly sensitized candidates this scenario is unlikely. For candidates with an incompatible donor, PDE can improve the prospects of finding a compatible living donor but for many highly sensitized patients the probability of finding a match in the relatively small pools of donors in PDE programs is limited. Desensitization of a living donor/recipient pair with low levels of incompatibility is another reasonable approach. But for pairs with high levels of pathologic HLA antibodies, outcomes after desensitization for the patient and allograft are less optimal. Determining the degree of sensitization by calculated panel-reactive antibody (cPRA) is critical in counseling the highly sensitized patient on expected wait times to deceased-donor transplant. For candidates with a high likelihood of finding a compatible deceased donor in a reasonable time frame, waiting for a kidney is a good strategy. For the candidate without a living donor and with a low probability of finding a deceased-donor match, desensitization on the waiting list can be considered. The approach to the highly sensitized kidney transplant candidate must be individualized and requires careful discussion among the transplant center, patient, and referring nephrologist.

  15. Gold nanoparticles based colorimetric nanodiagnostics for cancer and infectious diseases

    NASA Astrophysics Data System (ADS)

    Valentini, Paola; Persano, Stefano; Cecere, Paola; Sabella, Stefania; Pompa, Pier Paolo

    2014-03-01

    Traditional in vitro diagnostics requires specialized laboratories and costly instrumentation, both for the amplification of nucleic acid targets (usually achieved by PCR) and for the assay readout, often based on fluorescence. We are developing hybrid nanomaterials-based sensors for the rapid and low-cost diagnosis of various disease biomarkers, for applications in portable platforms for diagnostics at the point-of-care. To this aim, we exploited the size and distancedependent optical properties of gold nanoparticles (AuNPs) to achieve colorimetric detection. Moreover, in order to avoid the complexity of thermal cycles associated to traditional PCR, the design of our systems includes signal amplification schemes, achieved by the use of enzymes (nucleases, helicase) or DNAzymes. Focused on instrument-free and sensitive detection, we carefully combined the intrinsic sensitivity by multivalency of functionalized AuNPs with isothermal and non-stringent enzyme-aided reaction conditions, controlled AuNPs aggregates, universal reporters and magnetic microparticles, the latter used both as a substrate and as a means for the colorimetric detection. We obtained simple and robust assays for the sensitive (pM range or better) naked-eye detection of cancer or infectious diseases (HPV, HCV) biomarkers, requiring no instrumentation except for a simple heating plate. Finally, we are also developing non-medical applications of these bio-nanosensors, such as in the development of on-field rapid tests for the detection of pollutants and other food and water contaminants.

  16. Colorimetric detection of copper ions in tap water during the synthesis of silver/dopamine nanoparticles.

    PubMed

    Ma, Yu-rong; Niu, Hong-yun; Zhang, Xiao-le; Cai, Ya-qi

    2011-12-21

    A facile, economic and eco-friendly colorimetric sensor for Cu(2+) using dopamine/silver nanoparticles was developed. The sensor shows excellent sensitivity and selectivity toward Cu(2+) in the range of 3.2-512 ppb and can be applied for Cu(2+) detection in tap water.

  17. High sensitivity optical waveguide accelerometer based on Fano resonance.

    PubMed

    Wan, Fenghua; Qian, Guang; Li, Ruozhou; Tang, Jie; Zhang, Tong

    2016-08-20

    An optical waveguide accelerometer based on tunable asymmetrical Fano resonance in a ring-resonator-coupled Mach-Zehnder interferometer (MZI) is proposed and analyzed. A Fano resonance accelerometer has a relatively large workspace of coupling coefficients with high sensitivity, which has potential application in inertial navigation, missile guidance, and attitude control of satellites. Due to the interference between a high-Q resonance pathway and a coherent background pathway, a steep asymmetric line shape is generated, which greatly improves the sensitivity of this accelerometer. The sensitivity of the accelerometer is about 111.75 mW/g. A 393-fold increase in sensitivity is achieved compared with a conventional MZI accelerometer and is approximately equal to the single ring structure.

  18. Colorimetric Biosensor for Detection of Cancer Biomarker by Au Nanoparticle-Decorated Bi2Se3 Nanosheets.

    PubMed

    Xiao, Liangping; Zhu, Aimei; Xu, Qingchi; Chen, Ying; Xu, Jun; Weng, Jian

    2017-03-01

    The colorimetric biosensors have attracted intensive interest; however, their relatively low sensitivity limits their applications in clinic detection. Herein, we develop an effective colorimetric biosensor based on highly catalytic active Au nanoparticle-decorated Bi2Se3 (Au/Bi2Se3) nanosheets. Au/Bi2Se3 nanosheets are facilely synthesized by simply sonicating Au precursor with the as-synthesized Bi2Se3 nanosheets in aqueous solution. Because of the low redox potential and typical topological insulating properties, Bi2Se3 nanosheets is capable of providing and accumulating electrons on its surface. Such unique properties of Bi2Se3 nanosheets contribute to strong synergistic catalytic effects with Au nanoparticles, particularly when Au/Bi2Se3 nanosheets are utilized for catalyzing the reduction of 4-nitrophenol (4-NP) by NaBH4 (K = 386.67 s(-1)g(-1)). The excellent catalytic activity of Au/Bi2Se3 nanosheets can be "switched off" upon treatment of antibody of cancer biomarker such as anticarcinoembryonic antibody (anti-CEA). Addition of the corresponding antigen such as cancer biomarker carcinoembryonic antibody (CEA) can successively help "switch on" the catalytic activity of Au/Bi2Se3 nanosheets, where the resuming degree however depends on the antigen concentration. This cancer biomarker depended catalytic behavior therefore allows Au/Bi2Se3 nanosheets to be employed as a colorimetric sensor for detection of a particular cancer biomarker, for the reduction of 4-nitrophenol (4-NP) by NaBH4 itself involves apparent color change. The sensor shows high sensitivity and selectivity for the cancer biomarker, even for a concentration as low as 160 pg/mL for CEA, which fully satisfies the requirement for real clinical applications. The developed colorimetric sensor shows good generality for detection of different types of cancer biomarkers, such as α-fetoprotein (AFP) and prostate-specific antigen (PSA). Furthermore, real clinic sample analyzing result shows that the

  19. Rapid colorimetric detection of Salmonella typhimuriumusing a selective filtration technique combined with antibody-magnetic nanoparticle nanocomposites.

    PubMed

    Shim, Won-Bo; Song, Jeong-Eon; Mun, Hyoyoung; Chung, Duck-Hwa; Kim, Min-Gon

    2014-01-01

    Detection of pathogenic bacteria that pose a great risk to human health requires a rapid, convenient, reliable, and sensitive detection method. In this study, we developed a selective filtration method using monoclonal antibody (MAb)-magnetic nanoparticle (MNP) nanocomposites for the rapid and sensitive colorimetric detection of Salmonella typhimurium. The method contains two key steps: the immunomagnetic separation of the bacteria using MAb-MNP nanocomposites and the filtration of the nanocomposite-bound bacteria. Color signals from the nanocomposites remaining on the membrane were measured, which reflected the amount of bacteria in test samples. Immunomagnetic capture efficiencies of 8 to 90 % for various concentrations of the pathogen (2 × 10(4)-2 × 10(1) cells) were obtained. After optimization of the method, 2 × 10(1) cells of S. typhimurium in pure culture solution was detectable as well as in artificially inoculated vegetables (100 cells/g). The method was confirmed to be highly specific to S. typhimurium without cross-reaction to other pathogenic bacteria and could be concluded within 45 min, yielding results in a shorter or similar time period as compared with recently reported antibody immobilized on magnetic-particle-based methods. This study also demonstrated direct application of MAb-MNP nanocomposites without a dissociation step of bacteria from magnetic beads in colorimetric assays in practice.

  20. Evaluation of Direct Colorimetric MTT Assay for Rapid Detection of Rifampicin and Isoniazid Resistance in Mycobacterium tuberculosis

    PubMed Central

    Woldemeskel, Dawit; Gessesse, Amare

    2016-01-01

    With the spread of multidrug-resistant tuberculosis (MDR-TB) strains there is an increasing need for new accurate and cost-effective methods for a rapid diagnostic and drug susceptibility testing (DST), particularly in low-income countries where tuberculosis is hyperendemic. A colorimetric assay using 3-(4, 5-dimethylthiazol-2-yl)-2, 5- diphenyltetrazolium bromide (MTT) has been suggested as a promising method for DST, especially to rifampicin. In this study, we standardized and evaluated the MTT assay for a rapid direct detection of rifampicin and isoniazid resistant Mycobacterium tuberculosis strains from sputum specimens using Lowenstein-Jensen (LJ) culture medium as a gold standard. The MTT assay sensitivity, specificity, positive and negative predictive values for rifampicin were 100%, 86%, 100%, 99%, respectively. For isoniazid, the MTT assay had a 100% sensitivity, specificity, positive and negative predictive values. Interestingly, the MTT assay gave interpretable results within two weeks for 94% of the samples compared to 7–14 weeks for LJ media. Overall, an excellent agreement was observed between MTT assay and LJ proportion method (Kappa, 0.91 for rifampicin and 1.00 for isoniazid). In conclusion, the direct colorimetric MTT assay simultaneously detects susceptible and resistant strains of M. tuberculosis within three weeks. It significantly shortens the time required to obtain a DST result and could be a reliable alternative method for rapid detection of drug-resistant TB strains in high-TB-burden resource-limited settings. PMID:28030634

  1. A colorimetric detection of acrylamide in potato chips based on nucleophile-initiated thiol-ene Michael addition.

    PubMed

    Hu, Qinqin; Fu, Yingchun; Xu, Xiahong; Qiao, Zhaohui; Wang, Ronghui; Zhang, Ying; Li, Yanbin

    2016-02-07

    Acrylamide (AA), a neurotoxin and a potential carcinogen, has been found in various thermally processed foods such as potato chips, biscuits, and coffee. Simple, cost-effective, and sensitive methods for the rapid detection of AA are needed to ensure food safety. Herein, a novel colorimetric method was proposed for the visual detection of AA based on a nucleophile-initiated thiol-ene Michael addition reaction. Gold nanoparticles (AuNPs) were aggregated by glutathione (GSH) because of a ligand-replacement, accompanied by a color change from red to purple. In the presence of AA, after the thiol-ene Michael addition reaction between GSH and AA with the catalysis of a nucleophile, the sulfhydryl group of GSH was consumed by AA, which hindered the subsequent ligand-replacement and the aggregation of AuNPs. Therefore, the concentration of AA could be determined by the visible color change caused by dispersion/aggregation of AuNPs. This new method showed high sensitivity with a linear range from 0.1 μmol L(-1) to 80 μmol L(-1) and a detection limit of 28.6 nmol L(-1), and especially revealed better selectivity than the fluorescence sensing method reported previously. Moreover, this new method was used to detect AA in potato chips with a satisfactory result in comparison with the standard methods based on chromatography, which indicated that the colorimetric method can be expanded for the rapid detection of AA in thermally processed foods.

  2. A rhodamine-benzothiazole conjugated sensor for colorimetric, ratiometric and sequential recognition of copper(II) and sulfide in aqueous media.

    PubMed

    Tang, Lijun; Dai, Xin; Wen, Xin; Wu, Di; Zhang, Qiang

    2015-03-15

    A new rhodamine-benzothiazole conjugated colorimetric sensor 1 that exhibits sequential recognition to Cu(2+) and S(2-) in CH3CN/HEPES buffer (v/v=1:1, HEPES 10mM, pH=7.0) solution has been developed. Sensor 1 displays highly selective and sensitive recognition to Cu(2+) with a ratiometric behavior, and the resultant 1-Cu(2+) complex can act as a highly selective S(2-) sensor via Cu(2+) displacement approach. The Cu(2+) and S(2-) recognition processes are rapid and reversible, and the Cu(2+) and S(2-) inputs can result in an INHIBIT logic gate.

  3. A rhodamine-benzothiazole conjugated sensor for colorimetric, ratiometric and sequential recognition of copper(II) and sulfide in aqueous media

    NASA Astrophysics Data System (ADS)

    Tang, Lijun; Dai, Xin; Wen, Xin; Wu, Di; Zhang, Qiang

    2015-03-01

    A new rhodamine-benzothiazole conjugated colorimetric sensor 1 that exhibits sequential recognition to Cu2+ and S2- in CH3CN/HEPES buffer (v/v = 1:1, HEPES 10 mM, pH = 7.0) solution has been developed. Sensor 1 displays highly selective and sensitive recognition to Cu2+ with a ratiometric behavior, and the resultant 1-Cu2+ complex can act as a highly selective S2- sensor via Cu2+ displacement approach. The Cu2+ and S2- recognition processes are rapid and reversible, and the Cu2+ and S2- inputs can result in an INHIBIT logic gate.

  4. Red Emission B, N, S-co-Doped Carbon Dots for Colorimetric and Fluorescent Dual Mode Detection of Fe(3+) Ions in Complex Biological Fluids and Living Cells.

    PubMed

    Liu, Yinghua; Duan, Wenxiu; Song, Wei; Liu, Juanjuan; Ren, Cuiling; Wu, Jiang; Liu, Dan; Chen, Hongli

    2017-04-03

    Colorimetric and fluorescent dual mode detection methods have gained much attention in recent years; however, it is still desirable to develop new colorimetric and fluorescent dual mode nanosensors with more simple preparation procedures, low cost, and excellent biocompatibility. Herein, a colorimetric and fluorescent nanosensor based on B, N, S-co-doped carbon dots (BNS-CDs) was synthesized by one-step hydrothermal treatment of 2,5-diaminobenzenesulfonic acid and 4-aminophenylboronic acid hydrochloride. Using this nanosensor, a highly sensitive assay of Fe(3+) in the range of 0.3-546 μM with a detection limit of 90 nM was provided by quenching the red emission fluorescence. It is more attractive that Fe(3+) can also be visualized by this nanosensor via evident color changes of the solution (from red to blue) under sunlight without the aid of an ultraviolet (UV) lamp. Furthermore, the designed nanosensor can be applied for efficient detection of intracellular Fe(3+) with excellent biocompatibility and cellular imaging capability, and it holds great promise in biomedical applications.

  5. Ultratrace Naked-Eye Colorimetric Detection of Hg(2+) in Wastewater and Serum Utilizing Mercury-Stimulated Peroxidase Mimetic Activity of Reduced Graphene Oxide-PEI-Pd Nanohybrids.

    PubMed

    Zhang, Shouting; Zhang, Dongxu; Zhang, Xuehong; Shang, Denghui; Xue, Zhonghua; Shan, Duoliang; Lu, Xiaoquan

    2017-03-21

    Herein, we developed a general strategy for rapid, highly selective, and ultratrace naked-eye colorimetric detection of Hg(2+) in aqueous solutions. Two dimensional rGO/PEI/Pd nanohybrids, where rGO, PEI, and Pd were referred to as reduced graphene oxide, polyethylenimine, and Pd nanoparticles, respectively, were synthesized and used as mimetic peroxidase for selective and ultrasensitive detection of Hg(2+) in water and human serum samples. In the presence of mercury ions, the peroxidase mimetic activity of rGO/PEI/Pd nanohybrids was found to be stimulated and enhanced significantly, which promoted the effective oxidation and color change of 3,3',5,5'-tetramethylbenzidine (TMB) in solution to dark blue that was detected by the naked-eye and the absorption spectroscopic method. The proposed sensing strategy coupled with spectroscopic detection method showed an ultralow detection limit of 0.39 nM for Hg(2+) in ddH2O and ∼1 nM in wastewater as well as serum samples, respectively. On the basis of the colorimetric assay, a minimum concentration of ∼10 nM for Hg(2+) in wastewater and human serum can be detected with the naked-eye. The naked-eye-based colorimetric assay for sensitive and selective detection of mercury is expected to hold huge potentials in applications such as environmental monitoring, clinical diagnosis, and pharmaceutical analysis.

  6. Visual and colorimetric detection of p-aminophenol in environmental water and human urine samples based on anisotropic growth of Ag nanoshells on Au nanorods.

    PubMed

    Lin, Tianran; Li, Zhihong; Song, Zhiping; Chen, Huan; Guo, Liangqia; Fu, Fengfu; Wu, Zujian

    2016-01-01

    A simple, sensitive, selective and high-resolution colorimetric method has been developed for the detection of p-aminophenol in environmental water and human urine samples. In the presence of p-aminophenol, silver ions are reduced to silver atoms and subsequently Ag nanoshells anisotropically grow on the surface of Au nanorods to generate orange slice-like Au@Ag core-shell nanocrystals, thereby resulting in the blue-shift of longitudinal surface plasmon resonance band of Au nanorods accompanying a sharp-contrast multicolor change. Using Au@Ag core-shell nanocrystals as the transducer, sub-micromolar p-aminophenol can be detected by the colorimetric method and 10 μmol L(-1) p-aminophenol can be visual readout by the naked eyes. Furthermore, a simple, cheap, portable test kit is constructed for the visual assay of urinary p-aminophenol without complicated sample pretreatment and sophisticated instruments. The proposed colorimetric method has the potential for the rapid and on-site analyses of p-aminophenol in environmental water and human urine samples.

  7. Multiplexed Colorimetric Solid-Phase Extraction

    NASA Technical Reports Server (NTRS)

    Gazda, Daniel B.; Fritz, James S.; Porter, Marc D.

    2009-01-01

    Multiplexed colorimetric solid-phase extraction (MC-SPE) is an extension of colorimetric solid-phase extraction (C-SPE) an analytical platform that combines colorimetric reagents, solid phase extraction, and diffuse reflectance spectroscopy to quantify trace analytes in water. In CSPE, analytes are extracted and complexed on the surface of an extraction membrane impregnated with a colorimetric reagent. The analytes are then quantified directly on the membrane surface using a handheld diffuse reflectance spectrophotometer. Importantly, the use of solid-phase extraction membranes as the matrix for impregnation of the colorimetric reagents creates a concentration factor that enables the detection of low concentrations of analytes in small sample volumes. In extending C-SPE to a multiplexed format, a filter holder that incorporates discrete analysis channels and a jig that facilitates the concurrent operation of multiple sample syringes have been designed, enabling the simultaneous determination of multiple analytes. Separate, single analyte membranes, placed in a readout cartridge create unique, analyte-specific addresses at the exit of each channel. Following sample exposure, the diffuse reflectance spectrum of each address is collected serially and the Kubelka-Munk function is used to quantify each water quality parameter via calibration curves. In a demonstration, MC-SPE was used to measure the pH of a sample and quantitate Ag(I) and Ni(II).

  8. White emission magnetic nanoparticles as chemosensors for sensitive colorimetric and ratiometric detection, and degradation of ClO- and SCN- in aqueous solutions based on a logic gate approach

    NASA Astrophysics Data System (ADS)

    Zhi, Lihua; Wang, Zhiyi; Liu, Jian; Liu, Weisheng; Zhang, Haoli; Chen, Fengjuan; Wang, Baodui

    2015-07-01

    Fluorescent chemosensors for detecting single anions have been largely synthesized. However, the simultaneous detection and degradation of multiple anions remain a major challenge. Herein we report the synthesis of a white emission nanoprobe on the basis of a Coumarin-Rhodamine CR1-Eu complex coordinated to dipicolinic acid (dpa)-PEG-Fe3O4 nanoparticles for the selective detection of ClO- and SCN- ions on controlling by a logic gate. The obtained nanoprobe exhibits three individual primary colors (blue, green, and red) as well as white emission at different excitation energies. Interestingly, this nanoprobe shows a marked rose red to violet emission color change in response to ClO-, a reversible violet to rose red emission color change in response to SCN-, and high ClO- and SCN- selectivity and sensitivity with a detection limit of 0.037 and 0.250 nM, respectively. Furthermore, the SCN- and ClO- can degrade simultaneously through the redox reaction between ClO- and SCN-.Fluorescent chemosensors for detecting single anions have been largely synthesized. However, the simultaneous detection and degradation of multiple anions remain a major challenge. Herein we report the synthesis of a white emission nanoprobe on the basis of a Coumarin-Rhodamine CR1-Eu complex coordinated to dipicolinic acid (dpa)-PEG-Fe3O4 nanoparticles for the selective detection of ClO- and SCN- ions on controlling by a logic gate. The obtained nanoprobe exhibits three individual primary colors (blue, green, and red) as well as white emission at different excitation energies. Interestingly, this nanoprobe shows a marked rose red to violet emission color change in response to ClO-, a reversible violet to rose red emission color change in response to SCN-, and high ClO- and SCN- selectivity and sensitivity with a detection limit of 0.037 and 0.250 nM, respectively. Furthermore, the SCN- and ClO- can degrade simultaneously through the redox reaction between ClO- and SCN-. Electronic supplementary

  9. Multiplex paper-based colorimetric DNA sensor using pyrrolidinyl peptide nucleic acid-induced AgNPs aggregation for detecting MERS-CoV, MTB and HPV oligonucleotides.

    PubMed

    Tee-Ngam, Prinjaporn; Siangproh, Weena; Tuantranont, Adisorn; Vilaivan, Tirayut; Chailapakul, Orawon; Henry, Charles S

    2017-04-10

    The development of simple fluorescent and colorimetric assays that enable point-of-care DNA and RNA detection has been a topic of significant research because of the utility of such assays in resource limited settings. The most common motifs utilize hybridization to a complementary detection strand coupled with a sensitive reporter molecule. Here, apaper-based colorimetric assay for DNA detection based on pyrrolidinyl peptide nucleic acid (acpcPNA)-induced nanoparticle aggregationis reported as an alternative to traditional colorimetric approaches. PNA probes are an attractive alternative to DNA and RNA probes because they are chemically and biologically stable, easily synthesized, and hybridize efficiently with the complementary DNA strands. The acpcPNA probe contains a single positive charge from the lysine at C-terminus and causes aggregation of citrate anion-stabilized silver nanoparticles (AgNPs) in the absence of complementary DNA. In the presence of target DNA, formation of the anionic DNA-acpcPNA duplex results in dispersion of the AgNPs as a result of electrostatic repulsion, giving rise to a detectable color change. Factors affecting the sensitivity and selectivity of this assay were investigated, including ionic strength, AgNP concentration, PNA concentration, and DNA strand mismatches. The method was used for screening of synthetic Middle East respiratory syndrome coronavirus (MERS-CoV), mycobacterium tuberculosis (MTB) and human papillomavirus (HPV)DNA based on a colorimetric paper-based analytical device developed using the aforementioned principle. The oligonucleotide targets were detected by measuring the color change of AgNPs, giving detection limits of 1.53 nM (MERS-CoV), 1.27 nM (MTB) and 1.03 nM (HPV).The acpcPNA probe exhibited high selectivity for the complementary oligonucleotides over single-base-mismatch, two-base-mismatch and non-complementary DNA targets. The proposed paper-based colorimetric DNA sensor has potential to be an alternative

  10. High sensitivity cardiac troponin assays in the clinical laboratories.

    PubMed

    Jarolim, Petr

    2015-04-01

    Immunoassays measuring cardiac troponins I or T have become firmly established as critical tools for diagnosing acute myocardial infarction. While most contemporary assays provide adequate diagnostic performance, the increased sensitivity and precision of the new, high sensitivity assays that have already been introduced into clinical practice, provide the potential to further shorten intervals between blood draws or the time needed to detect the first significant troponin elevation. In addition to the relatively modest benefits at the diagnostic end, the high sensitivity assays and the investigational ultrasensitive cardiac troponin assays offer improvements for predicting major adverse cardiovascular events, development of heart failure or transition to end-stage kidney disease. These novel high sensitivity assays can measure troponin concentrations in 50%-100% of healthy individuals and therefore allow for the distribution of troponin values within a healthy cohort to be measured, patient's baseline troponin levels to be monitored, and clinicians to be alerted of deteriorating cardiorenal conditions. We envisage that the high sensitivity assays will become important tools for predicting each patient's risk of future adverse events and for guiding and monitoring corresponding adjustments of preventative therapeutic interventions.

  11. Near-infrared squaraine co-sensitizer for high-efficiency dye-sensitized solar cells.

    PubMed

    Rao, G Hanumantha; Venkateswararao, A; Giribabu, L; Han, Liyuan; Bedja, Idriss; Gupta, Ravindra Kumar; Islam, Ashraful; Singh, Surya Prakash

    2016-06-07

    A combination of squaraine-based dyes (SPSQ1 and SPSQ2) and a ruthenium-based dye (N3) were chosen as co-sensitizers to construct efficient dye-sensitized solar cells. The co-sensitization of squaraine dyes with N3 enhanced their light-harvesting properties as a result of the broad spectral coverage in the region 350-800 nm. The co-sensitized solar cells based on SPSQ2 + N3 showed the highest short circuit current density of 17.10 mA cm(-2), an open circuit voltage of 0.66 V and a fill factor of 0.73, resulting in the highest power conversion efficiency of 8.2%, which is higher than that of the dye-sensitized solar cells based on the individual SPSQ1 and SPSQ2 dyes. The high power conversion efficiency of SPSQ2 + N3 was ascribed to its good light-harvesting properties, which resulted from its broader incident photon current conversion spectrum than that of the individual dyes. The high electron life time and electron recombination, which were the main causes of the higher efficiency of the device, were successfully analysed and correlated using transient absorption spectrometry and intensity-modulated photovoltage spectrometry.

  12. Highly sensitive optical sensor system for blood leakage detection

    NASA Astrophysics Data System (ADS)

    Ueda, Masahiro; Ishikawa, Kazuhiko; Jie, Chen; Sanae, Mizuno; Touma, Yasunori

    A highly sensitive method for the detection of blood leakage has been developed, and a practical sensor system for blood concentration measurement has been constructed. The present method is based on the attenuation of laser light by blood cells. The effects of the fluctuations of the incident laser light power are eliminated by normalizing the attenuated light intensity by the incident light intensity. A part of the incident laser light is reflected by a beam splitter mounted at the entrance of the test cell, of which the power is measured to provide base data for normalization. The optical path is extended to enhance sensitivity by using a pair of side mirrors. This multi-reflection method is very effective to increase sensitivity; the maximum sensitivity obtained for blood concentration is about 4 X 10 -6 by volume, which is significantly higher than that of the conventional sensors.

  13. Colorimetric detection of endogenous hydrogen sulfide production in living cells

    NASA Astrophysics Data System (ADS)

    Ahn, Yong Jin; Lee, Young Ju; Lee, Jaemyeon; Lee, Doyeon; Park, Hun-Kuk; Lee, Gi-Ja

    2017-04-01

    Hydrogen sulfide (H2S) has received great attention as a third gaseous signal transmitter, following nitric oxide and carbon monoxide. In particular, H2S plays an important role in the regulation of cancer cell biology. Therefore, the detection of endogenous H2S concentrations within biological systems can be helpful to understand the role of gasotransmitters in pathophysiology. Although a simple and inexpensive method for the detection of H2S has been developed, its direct and precise measurement in living cells remains a challenge. In this study, we introduced a simple, facile, and inexpensive colorimetric system for selective H2S detection in living cells using a silver-embedded Nafion/polyvinylpyrrolidone (PVP) membrane. This membrane could be easily applied onto a polystyrene microplate cover. First, we optimized the composition of the coating membrane, such as the PVP/Nafion mixing ratio and AgNO3 concentration, as well as the pH of the Na2S (H2S donor) solution and the reaction time. Next, the in vitro performance of a colorimetric detection assay utilizing the silver/Nafion/PVP membrane was evaluated utilizing a known concentration of Na2S standard solution both at room temperature and at 37 °C in a 5% CO2 incubator. As a result, the sensitivity of the colorimetric assay for H2S at 37 °C in the incubator (0.0056 Abs./μM Na2S, R2 = 0.9948) was similar to that at room temperature (0.0055 Abs./μM Na2S, R2 = 0.9967). Moreover, these assays were less sensitive to interference from compounds such as glutathione, L-cysteine (Cys), and dithiothreitol than to the H2S from Na2S. This assay based on the silver/Nafion/PVP membrane also showed excellent reproducibility (2.8% RSD). Finally, we successfully measured the endogenous H2S concentrations in live C6 glioma cells by s-(5‧-adenosyl)-L-methionine stimulation with and without Cys and L-homocysteine, utilizing the silver/Nafion/PVP membrane. In summary, colorimetric assays using silver

  14. Analytical Glycobiology at High Sensitivity: Current Approaches and Directions

    PubMed Central

    Novotny, Milos V.; Alley, William R.; Mann, Benjamin F.

    2013-01-01

    This review summarizes the analytical advances made during the last several years in the structural and quantitative determinations of glycoproteins in complex biological mixtures. The main analytical techniques used in the fields of glycomics and glycoproteomics involve different modes of mass spectrometry and their combinations with capillary separation methods such as microcolumn liquid chromatography and capillary electrophoresis. The needs for high-sensitivity measurements have been emphasized in the oligosaccharide profiling used in the field of biomarker discovery through MALDI mass spectrometry. High-sensitivity profiling of both glycans and glycopeptides from biological fluids and tissue extracts has been aided significantly through lectin preconcentration and the uses of affinity chromatography. PMID:22945852

  15. Scalable photonic crystal chips for high sensitivity protein detection.

    PubMed

    Liang, Feng; Clarke, Nigel; Patel, Parth; Loncar, Marko; Quan, Qimin

    2013-12-30

    Scalable microfabrication technology has enabled semiconductor and microelectronics industries, among other fields. Meanwhile, rapid and sensitive bio-molecule detection is increasingly important for drug discovery and biomedical diagnostics. In this work, we designed and demonstrated that photonic crystal sensor chips have high sensitivity for protein detection and can be mass-produced with scalable deep-UV lithography. We demonstrated label-free detection of carcinoembryonic antigen from pg/mL to μg/mL, with high quality factor photonic crystal nanobeam cavities.

  16. Sensitization trends after renal allograft failure: the role of DQ eplet mismatches in becoming highly sensitized.

    PubMed

    Singh, Pooja; Filippone, Edward J; Colombe, Beth W; Shah, Ashesh P; Zhan, Tingting; Harach, Mary; Gorn, Chad; Frank, Adam M

    2016-01-01

    Sensitization following renal allograft failure (AF) is highly variable. Some patients remain non-sensitized (NS), while others become highly sensitized (HS). We studied 66 NS patients who experienced AF after initial kidney transplantation. Post-failure, two main groups of NS panel reactive antibody (PRA) class I and II <10% and HS patients (PRA class I or II ≥80%) were identified. The impact of acute rejection (AR), immunosuppression withdrawal (ISW) at AF, allograft nephrectomy, graft intolerance syndrome (GIS), and both standard serologic and eplet-based mismatches (MM) in inducing HS status after failure was examined. Late PRA testing post-failure revealed 18 patients remained NS and 34 patients became HS. African American recipients, ISW at AF, DQB1 eplet MM, and presence of GIS were associated with becoming HS. Presence of total zero eplet MM, zero DQA1/B1 eplet MM, continuation of immunosuppression after failure, and a hyporesponsive immune status characterized by recurrent infections were features of NS patients. DQ eplet MM represents a significant risk for becoming HS after AF. Studies comparing ISW vs. continuation in re-transplant candidates with high baseline DQ eplet MM burden should be performed. This may provide insights if sensitization post-AF can be lessened.

  17. Spectrophotometric and colorimetric determination of protein concentration.

    PubMed

    Simonian, Michael H; Smith, John A

    2006-11-01

    This unit describes spectrophotometric and colorimetric methods for measuring the concentration of a sample protein in solution. Absorbance measurement at 280 nm is used to calculate protein concentration by comparison with a standard curve or published absorptivity values for that protein. An alternate protocol uses absorbance at 205 nm to calculate the protein concentration. Both methods can be used to quantitate total protein in crude lysates and purified or partially purified protein. Use of a spectrofluorometer or a filter fluorometer to measure the intrinsic fluorescence emission of a sample solution is also described. The measurement is compared with the emissions from standard solutions to determine the concentration of purified protein. The Bradford colorimetric method, based upon binding of the dye Coomassie brilliant blue to an unknown protein, is also presented, as is the Lowry method, which measures colorimetric reaction of tyrosyl residues in an unknown.

  18. Integrating Deoxyribozymes into Colorimetric Sensing Platforms

    PubMed Central

    Chang, Dingran; Zakaria, Sandy; Deng, Mimi; Allen, Nicholas; Tram, Kha; Li, Yingfu

    2016-01-01

    Biosensors are analytical devices that have found a variety of applications in medical diagnostics, food quality control, environmental monitoring and biodefense. In recent years, functional nucleic acids, such as aptamers and nucleic acid enzymes, have shown great potential in biosensor development due to their excellent ability in target recognition and catalysis. Deoxyribozymes (or DNAzymes) are single-stranded DNA molecules with catalytic activity and can be isolated to recognize a wide range of analytes through the process of in vitro selection. By using various signal transduction mechanisms, DNAzymes can be engineered into fluorescent, colorimetric, electrochemical and chemiluminescent biosensors. Among them, colorimetric sensors represent an attractive option as the signal can be easily detected by the naked eye. This reduces reliance on complex and expensive equipment. In this review, we will discuss the recent progress in the development of colorimetric biosensors that make use of DNAzymes and the prospect of employing these sensors in a range of chemical and biological applications. PMID:27918487

  19. High-sensitivity, high-speed continuous imaging system

    DOEpatents

    Watson, Scott A; Bender, III, Howard A

    2014-11-18

    A continuous imaging system for recording low levels of light typically extending over small distances with high-frame rates and with a large number of frames is described. Photodiode pixels disposed in an array having a chosen geometry, each pixel having a dedicated amplifier, analog-to-digital convertor, and memory, provide parallel operation of the system. When combined with a plurality of scintillators responsive to a selected source of radiation, in a scintillator array, the light from each scintillator being directed to a single corresponding photodiode in close proximity or lens-coupled thereto, embodiments of the present imaging system may provide images of x-ray, gamma ray, proton, and neutron sources with high efficiency.

  20. Large pi-aromatic molecules as potential sensitizers for highly efficient dye-sensitized solar cells.

    PubMed

    Imahori, Hiroshi; Umeyama, Tomokazu; Ito, Seigo

    2009-11-17

    Recently, dye-sensitized solar cells have attracted much attention relevant to global environmental issues. Thus far, ruthenium(II) bipyridyl complexes have proven to be the most efficient TiO(2) sensitizers in dye-sensitized solar cells. However, a gradual increment in the highest power conversion efficiency has been recognized in the past decade. More importantly, considering that ruthenium is a rare metal, novel dyes without metal or using inexpensive metal are desirable for highly efficient dye-sensitized solar cells. Large pi-aromatic molecules, such as porphyrins, phthalocyanines, and perylenes, are important classes of potential sensitizers for highly efficient dye-sensitized solar cells, owing to their photostability and high light-harvesting capabilities that can allow applications in thinner, low-cost dye-sensitized solar cells. Porphyrins possess an intense Soret band at 400 nm and moderate Q bands at 600 nm. Nevertheless, the poor light-harvesting properties relative to the ruthenium complexes have limited the cell performance of porphyrin-sensitized TiO(2) cells. Elongation of the pi conjugation and loss of symmetry in porphyrins cause broadening and a red shift of the absorption bands together with an increasing intensity of the Q bands relative to that of the Soret band. On the basis of the strategy, the cell performance of porphyrin-sensitized solar cells has been improved intensively by the enhanced light absorption. Actually, some push-pull-type porphyrins have disclosed a remarkably high power conversion efficiency (6-7%) that was close to that of the ruthenium complexes. Phthalocyanines exhibit strong absorption around 300 and 700 nm and redox features that are similar to porphyrins. Moreover, phthalocyanines are transparent over a large region of the visible spectrum, thereby enabling the possibility of using them as "photovoltaic windows". However, the cell performance was poor, owing to strong aggregation and lack of directionality in the

  1. Target-induced nanocatalyst deactivation facilitated by core@shell nanostructures for signal-amplified headspace-colorimetric assay of dissolved hydrogen sulfide.

    PubMed

    Gao, Zhuangqiang; Tang, Dianyong; Tang, Dianping; Niessner, Reinhard; Knopp, Dietmar

    2015-10-06

    Colorimetric assay platforms for dissolved hydrogen sulfide (H2S) have been developed for more than 100 years, but most still suffer from relatively low sensitivity. One promising route out of this predicament relies on the design of efficient signal amplification methods. Herein, we rationally designed an unprecedented H2S-induced deactivation of (gold core)@(ultrathin platinum shell) nanocatalysts (Au@TPt-NCs) as a highly efficient signal amplification method for ultrasensitive headspace-colorimetric assay of dissolved H2S. Upon target introduction, Au@TPt-NCs were deactivated to different degrees dependent on H2S levels, and the degrees could be indicated by using a Au@TPt-NCs-triggered catalytic system as a signal amplifier, thus paving a way for H2S sensing. The combination of experimental studies and density functional theory (DFT) studies revealed that the Au@TPt-NCs with only 2-monolayer equivalents of Pt (θPt = 2) were superior for H2S-induced nanocatalyst deactivation owing to their enhanced peroxidase-like catalytic activity and deactivation efficiency stemmed from the unique synergistic structural/electronic effects between Au nanocores and ultrathin Pt nanoshells. Importantly, our analytical results showed that the designed method was indeed highly sensitive for sensing H2S with a wide linear range of 10-100 nM, a slope of 0.013 in the regression equation, and a low detection limit of 7.5 nM. Also the selectivity, reproducibility, and precision were excellent. Furthermore, the method was validated for the analysis of H2S-spiked real samples, and the recovery in all cases was 91.6-106.7%. With the merits of high sensitivity and selectivity, simplification, low cost, and visual readout with the naked eye, the colorimetric method has the potential to be utilized as an effective detection kit for point-of-care testing.

  2. Colorimetric detection of mercury ion based on unmodified gold nanoparticles and target-triggered hybridization chain reaction amplification

    NASA Astrophysics Data System (ADS)

    Wang, Qing; Yang, Xiaohan; Yang, Xiaohai; Liu, Pei; Wang, Kemin; Huang, Jin; Liu, Jianbo; Song, Chunxia; Wang, Jingjing

    2015-02-01

    A novel unmodified gold nanoparticles (AuNPs)-based colorimetric strategy for label-free, specific and sensitive mercury ion (Hg2+) detection was demonstrated by using thymine-Hg2+-thymine (T-Hg2+-T) recognition mechanism and hybridization chain reaction (HCR) amplification strategy. In this protocol, a structure-switching probe (H0) was designed to recognize Hg2+ and then propagated a chain reaction of hybridization events between two other hairpin probes (H1 and H2). In the absence of Hg2+, all hairpin probes could stably coexist in solution, the exposed sticky ends of hairpin probes were capable of stabilizing AuNPs. As a result, salt-induced AuNPs aggregation could be effectively prevented. In the presence of Hg2+, thymine bases of H0 could specifically interact with Hg2+ to form stable T-Hg2+-T complex. Consequently, the hairpin structure of H0 probe was changed. As H1/H2 probes were added, the HCR process could be triggered and nicked double-helixes were formed. Since it was difficult for the formed nicked double-helixes to inhibit salt-induced AuNPs aggregation, a red-to-blue color change was observed in the colloid solution as the salt concentration increased. With the elegant amplification effect of HCR, a detection limit of around 30 nM was achieved (S/N = 3), which was about 1-2 orders of magnitudes lower than that of previous unmodified AuNPs-based colorimetric methods. By using the T-Hg2+-T recognition mechanism, high selectivity was also obtained. As an unmodified AuNPs-based colorimetric strategy, the system was simple in design, convenient in operation, and eliminated the requirements of separation processes, chemical modifications, and sophisticated instrumentations.

  3. Fat spectro-colorimetric characteristics of lambs switched from a low to a high dietary carotenoid level for various durations before slaughter.

    PubMed

    de Oliveira, L; Carvalho, P C F; Prache, S

    2012-12-01

    This study investigated the changes in fat reflectance spectrum characteristics and color in lambs switched from a low to a high dietary carotenoid level for various durations before slaughter. Six treatments, feeding a high dietary carotenoid level for 0, 15, 30, 45, 60 or 75 days before slaughter, were compared in individually indoor penned lambs. Each treatment used 10 Romane lambs; feeding management ensured similar growth pattern and carcass weight for all the treatment groups. There was a change in reflectance spectrum characteristics and yellowness of subcutaneous fat as early as 15 days after the switch. Mean concentration of carotenoid pigments and yellowness of subcutaneous fat increased linearly with the duration of the high dietary carotenoid level. In perirenal fat, the change in reflectance spectrum characteristics was observed as early as 15 days after the switch, but the response to the duration of the high dietary carotenoid level was curvilinear.

  4. [Burner head with high sensitivity in atomic absorption spectroscopy].

    PubMed

    Feng, X; Yang, Y

    1998-12-01

    This paper presents a burner head with gas-sample separate entrance and double access, which is used for atomic absorption spectroscopy. According to comparison and detection, the device can improve sensitivity by a factor of 1 to 5. In the meantime it has properties of high stability and resistance to interference.

  5. Microelectromechanical Resonant Accelerometer Designed with a High Sensitivity

    PubMed Central

    Zhang, Jing; Su, Yan; Shi, Qin; Qiu, An-Ping

    2015-01-01

    This paper describes the design and experimental evaluation of a silicon micro-machined resonant accelerometer (SMRA). This type of accelerometer works on the principle that a proof mass under acceleration applies force to two double-ended tuning fork (DETF) resonators, and the frequency output of two DETFs exhibits a differential shift. The dies of an SMRA are fabricated using silicon-on-insulator (SOI) processing and wafer-level vacuum packaging. This research aims to design a high-sensitivity SMRA because a high sensitivity allows for the acceleration signal to be easily demodulated by frequency counting techniques and decreases the noise level. This study applies the energy-consumed concept and the Nelder-Mead algorithm in the SMRA to address the design issues and further increase its sensitivity. Using this novel method, the sensitivity of the SMRA has been increased by 66.1%, which attributes to both the re-designed DETF and the reduced energy loss on the micro-lever. The results of both the closed-form and finite-element analyses are described and are in agreement with one another. A resonant frequency of approximately 22 kHz, a frequency sensitivity of over 250 Hz per g, a one-hour bias stability of 55 μg, a bias repeatability (1σ) of 48 μg and the bias-instability of 4.8 μg have been achieved. PMID:26633425

  6. A novel "off-on" colorimetric and fluorescent rhodamine-based pH chemosensor for extreme acidity

    NASA Astrophysics Data System (ADS)

    Tan, Jia-Lian; Zhang, Mu-Xue; Zhang, Fang; Yang, Ting-Ting; Liu, Yu; Li, Zhu-Bo; Zuo, Hua

    2015-04-01

    A novel "off-on" colorimetric and fluorescent rhodamine analogue was synthesized and characterized, and used to monitor extreme acidity (below pH 3.5) via the photophysical response to pH. The colorless spirocyclic structure at high pH (pH ⩾ 7.0) opened to the colored and highly fluorescent form at very low pH (pH < 3.0). This sensitive pH probe was characterized with short response time, good reversibility and no interaction with interfering metal ions, and the quantitative relationship between the fluorescence intensity and pH value was consistent with the equilibrium equation pH = pKa - log[(Imax - I)/(I - Imin)]. The fluorescent response to strong acidity was further verified by fluorescent imaging of bacteria, Escherichia coli, which contributed to the development of more useful colorimetric and fluorescent sensors based on the rhodamine platform for measuring intracellular pH in extremely acidic conditions.

  7. Ultrasensitive colorimetric detection of circulating tumor DNA using hybridization chain reaction and the pivot of triplex DNA

    NASA Astrophysics Data System (ADS)

    Li, Ruimin; Zou, Li; Luo, Yanwei; Zhang, Manjun; Ling, Liansheng

    2017-03-01

    This work presents an amplified colorimetric biosensor for circulating tumor DNA (ctDNA), which associates the hybridization chain reaction (HCR) amplification with G-Quadruplex DNAzymes activity through triplex DNA formation. In the presence of ctDNA, HCR occurs. The resulting HCR products are specially recognized by one sequence to include one GGG repeat and the other containing three GGG repeats, through the synergetic effect of triplex DNA and asymmetrically split G-Quadruplex forming. Such design takes advantage of the amplification property of HCR and the high peroxidase-like catalytic activity of asymmetrically split G-Quadruplex DNAzymes by means of triplex DNA formation, which produces color signals in the presence of ctDNA. Nevertheless, in the absence of ctDNA, no HCR happens. Thus, no triplex DNA and G-Quadruplex structure is formed, producing a negligible background. The colorimetric sensing platform is successfully applied in complex biological environments such as human blood plasma for ctDNA detection, with a detection limit corresponding to 0.1 pM. This study unambiguously uses triplex DNA forming as the pivot to integrate nucleic acid amplification and DNAzymes for producing a highly sensitive signal with low background.

  8. Ultrasensitive colorimetric detection of circulating tumor DNA using hybridization chain reaction and the pivot of triplex DNA

    PubMed Central

    Li, Ruimin; Zou, Li; Luo, Yanwei; Zhang, Manjun; Ling, Liansheng

    2017-01-01

    This work presents an amplified colorimetric biosensor for circulating tumor DNA (ctDNA), which associates the hybridization chain reaction (HCR) amplification with G-Quadruplex DNAzymes activity through triplex DNA formation. In the presence of ctDNA, HCR occurs. The resulting HCR products are specially recognized by one sequence to include one GGG repeat and the other containing three GGG repeats, through the synergetic effect of triplex DNA and asymmetrically split G-Quadruplex forming. Such design takes advantage of the amplification property of HCR and the high peroxidase-like catalytic activity of asymmetrically split G-Quadruplex DNAzymes by means of triplex DNA formation, which produces color signals in the presence of ctDNA. Nevertheless, in the absence of ctDNA, no HCR happens. Thus, no triplex DNA and G-Quadruplex structure is formed, producing a negligible background. The colorimetric sensing platform is successfully applied in complex biological environments such as human blood plasma for ctDNA detection, with a detection limit corresponding to 0.1 pM. This study unambiguously uses triplex DNA forming as the pivot to integrate nucleic acid amplification and DNAzymes for producing a highly sensitive signal with low background. PMID:28276503

  9. A colorimetric probe based on desensitized ionene-stabilized gold nanoparticles for single-step test for sulfate ions

    NASA Astrophysics Data System (ADS)

    Arkhipova, Viktoriya V.; Apyari, Vladimir V.; Dmitrienko, Stanislava G.

    2015-03-01

    Desensitized ionene-stabilized gold nanoparticles have been prepared and applied as a colorimetric probe for the single-step test for sulfate ions at the relatively high concentration level. The approach is based on aggregation of the nanoparticles leading to the change in absorption spectra and color of the solution. These nanoparticles are characterized by the decreased sensitivity due to both electrostatic and steric stabilization, which allows for simple, and rapid direct single-step determination of sulfate at the relatively high concentration level in real water samples without sample pretreatment or dilution. Influence of different factors (the time of interaction, pH, the concentrations of sulfate ions and the nanoparticles) on the aggregation and analytical performance of the procedure was investigated. The method allows for the determination of sulfate ions in the mass range of 0.2-0.4 mg with RSD of 5% from the sample volume of less than 2 mL. It has a sharp dependence of the colorimetric response on the concentration of sulfate, which makes it prospective for indicating deviations of the sulfate concentration regarding some declared value chosen within the above range. The time of the analysis is 2 min. The method was applied to the analysis of mineral water samples.

  10. Rapid determination of trace copper in animal feed based on micro-plate colorimetric reaction and statistical partitioning correction.

    PubMed

    Niu, Yiming; Wang, Jiayi; Zhang, Chi; Chen, Yiqiang

    2017-04-15

    The objective of this study was to develop a micro-plate based colorimetric assay for rapid and high-throughput detection of copper in animal feed. Copper ion in animal feed was extracted by trichloroacetic acid solution and reduced to cuprous ion by hydroxylamine. The cuprous ion can chelate with 2,2'-bicinchoninic acid to form a Cu-BCA complex which was detected with high sensitivity by micro-plate reader at 354nm. The whole assay procedure can be completed within 20min. To eliminate matrix interference, a statistical partitioning correction approach was proposed, which makes the detection of copper in complex samples possible. The limit of detection was 0.035μg/mL and the detection range was 0.1-10μg/mL of copper in buffer solution. Actual sample analysis indicated that this colorimetric assay produced results consistent with atomic absorption spectrometry analysis. These results demonstrated that the developed assay can be used for rapid determination of copper in animal feed.

  11. Conjugation of selenophene with bipyridine for a high molar extinction coefficient sensitizer in dye-sensitized solar cells.

    PubMed

    Gao, Feifei; Cheng, Yueming; Yu, Qingjiang; Liu, Shi; Shi, Dong; Li, Yunhui; Wang, Peng

    2009-03-16

    A high molar extinction coefficient heteroleptic polypyridyl ruthenium sensitizer, featuring a conjugated electron-rich selenophene unit in its ancillary ligand, has been synthesized and demonstrated as an efficient sensitizer in dye-sensitized solar cells. A nanocrystalline titania film stained with this sensitizer shows improved optical absorptivity, which is highly desirable for dye-sensitized solar cells with a thin photoactive layer. With preliminary testing, this sensitizer has already achieved a high efficiency of 10.6% measured under the air mass 1.5 global conditions.

  12. 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.

  13. Highly sensitive detection using microring resonator and nanopores

    NASA Astrophysics Data System (ADS)

    Bougot-Robin, K.; Hoste, J. W.; Le Thomas, N.; Bienstman, P.; Edel, J. B.

    2016-04-01

    One of the most significant challenges facing physical and biological scientists is the accurate detection and identification of single molecules in free-solution environments. The ability to perform such sensitive and selective measurements opens new avenues for a large number of applications in biological, medical and chemical analysis, where small sample volumes and low analyte concentrations are the norm. Access to information at the single or few molecules scale is rendered possible by a fine combination of recent advances in technologies. We propose a novel detection method that combines highly sensitive label-free resonant sensing obtained with high-Q microcavities and position control in nanoscale pores (nanopores). In addition to be label-free and highly sensitive, our technique is immobilization free and does not rely on surface biochemistry to bind probes on a chip. This is a significant advantage, both in term of biology uncertainties and fewer biological preparation steps. Through combination of high-Q photonic structures with translocation through nanopore at the end of a pipette, or through a solid-state membrane, we believe significant advances can be achieved in the field of biosensing. Silicon microrings are highly advantageous in term of sensitivity, multiplexing, and microfabrication and are chosen for this study. In term of nanopores, we both consider nanopore at the end of a nanopipette, with the pore being approach from the pipette with nanoprecise mechanical control. Alternatively, solid state nanopores can be fabricated through a membrane, supporting the ring. Both configuration are discussed in this paper, in term of implementation and sensitivity.

  14. 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.

  15. A highly sensitive quantification of phytosterols through an inexpensive derivatization.

    PubMed

    Liu, Songbai; Ruan, Huina

    2013-01-01

    A highly sensitive method for quantification of phytosterols based on HPLC has been developed by derivatization with the benzoyl chromophore. Introduction of the chromophore, benzoyl group, to phytosterols via simple and inexpensive derivatization greatly improved the UV response at 254 nm. Quantification of phytosterols was effectively performed by HPLC analysis with methyl benzoate as the internal standard after derivatization. This new method demonstrated outstanding yield of recovery (> 95%) and excellent sensitivity (ng level) and was applicable for sterols from either plant or animal sources. This method is generally useful in phytosterol studies.

  16. Cardiac troponins and high-sensitivity cardiac troponin assays.

    PubMed

    Conrad, Michael J; Jarolim, Petr

    2014-03-01

    Measurement of circulating cardiac troponins I and T has become integral to the diagnosis of myocardial infarction. This article discusses the structure and function of the troponin complex and the release of cardiac troponin molecules from the injured cardiomyocyte into the circulation. An overview of current cardiac troponin assays and their classification according to sensitivity is presented. The diagnostic criteria, role, and usefulness of cardiac troponin for myocardial infarction are discussed. In addition, several examples are given of the usefulness of high-sensitivity cardiac troponin assays for short-term and long-term prediction of adverse events.

  17. NK sensitivity of neuroblastoma cells determined by a highly sensitive coupled luminescent method

    SciTech Connect

    Ogbomo, Henry; Hahn, Anke; Geiler, Janina; Michaelis, Martin; Doerr, Hans Wilhelm; Cinatl, Jindrich . E-mail: Cinatl@em.uni-frankfurt.de

    2006-01-06

    The measurement of natural killer (NK) cells toxicity against tumor or virus-infected cells especially in cases with small blood samples requires highly sensitive methods. Here, a coupled luminescent method (CLM) based on glyceraldehyde-3-phosphate dehydrogenase release from injured target cells was used to evaluate the cytotoxicity of interleukin-2 activated NK cells against neuroblastoma cell lines. In contrast to most other methods, CLM does not require the pretreatment of target cells with labeling substances which could be toxic or radioactive. The effective killing of tumor cells was achieved by low effector/target ratios ranging from 0.5:1 to 4:1. CLM provides highly sensitive, safe, and fast procedure for measurement of NK cell activity with small blood samples such as those obtained from pediatric patients.

  18. Highly selective colorimetric detection and preconcentration of Bi(III) ions by dithizone complexes anchored onto mesoporous TiO2

    NASA Astrophysics Data System (ADS)

    Faisal, Mohd; Ismail, Adel A.; Harraz, Farid A.; Bouzid, Houcine; Al-Sayari, Saleh A.; Al-Hajry, Ali

    2014-02-01

    We successfully developed a single-step detection and removal unit for Bi(III) ions based on dithizone (DZ) anchored on mesoporous TiO2 with rapid colorometric response and high selectivity for the first time. [(DZ)3-Bi] complex is easily separated and collected by mesoporous TiO2 as adsorbent and preconcentrator without any color change of the produced complex onto the surface of mesoporous TiO2 (TiO2-[(DZ)3-Bi]) at different Bi(III) concentrations. This is because highly potent mesoporous TiO2 architecture provides proficient channeling or movement of Bi(III) ions for efficient binding of metal ion, and the simultaneous excellent adsorbing nature of mesoporous TiO2 provides an extra plane for the removal of metal ions.

  19. Ultra Broadband High Sensitivity Electro-optic Field Sensors

    NASA Astrophysics Data System (ADS)

    Wieting, Terence J.; Qadri, Syed B.; Wu, Dong Ho

    2004-03-01

    We have carried out electro-optics experiments for the development of high sensitivity EO field sensors that detect electric fields noninvasively over a very broad frequency range. Presently we have obtained a maximum field sensitivity about 2 mV/m and the sensor has been tested over the frequency range of 0.1 Hz -200 MHz. We have used various EO materials, which include LiNbO_3, (Sr,Ba)Nb_2O_6, and DAST. Currently we are testing the sensors at frequencies of 200 MHz through 50 GHz, and also improving the sensors to achieve the field sensitivity to be better than 2 μ V/m. We found that even a small variation of materials properties greatly alters the sensors characteristics. We will present detailed sensor's characteristics that are obtained with various materials' chemical and physical properties.

  20. Rapid colorimetric sensing of tetracycline antibiotics with in situ growth of gold nanoparticles.

    PubMed

    Shen, Li; Chen, Jing; Li, Na; He, Pingli; Li, Zhen

    2014-08-11

    A colorimetric assay utilizing the formation of gold nanoparticles was developed to detect tetracycline antibiotics in fluidic samples. Tetracycline antibiotics showed the capability of directly reducing aurate salts into atomic gold which form gold nanoparticles spontaneously under proper conditions. The resulted gold nanoparticles showed characteristic plasmon absorbance at 526 nm, which can be visualized by naked eyes or with a spectrophotometer. UV-vis absorbance of the resulted gold nanoparticles is correlated directly with the concentrations of tetracycline antibiotics in the solution, allowing for quantitative colorimetric detection of tetracycline antibiotics. Reaction conditions, such as pH, temperature, reaction time, and ionic strength were optimized. Sensitivity of the colorimetric assay can be enhanced by the addition of gold nanoparticle seeds, a LOD as low as 20 ng mL(-1) can be achieved with the help of seed particles. The colorimetric assay showed minimum interference from ethanol, methanol, urea, glucose, and other antibiotics such as sulfonamides, amino glycosides etc. Validity of the method was also evaluated on urine samples spiked with tetracycline antibiotics. The method provides a broad spectrum detection method for rapid and sensitive detection of reductive substances such as tetracycline antibiotics in liquid and biological samples.

  1. High-sensitivity linear piezoresistive transduction for nanomechanical beam resonators

    NASA Astrophysics Data System (ADS)

    Sansa, Marc; Fernández-Regúlez, Marta; Llobet, Jordi; San Paulo, Álvaro; Pérez-Murano, Francesc

    2014-07-01

    Highly sensitive conversion of motion into readable electrical signals is a crucial and challenging issue for nanomechanical resonators. Efficient transduction is particularly difficult to realize in devices of low dimensionality, such as beam resonators based on carbon nanotubes or silicon nanowires, where mechanical vibrations combine very high frequencies with miniscule amplitudes. Here we describe an enhanced piezoresistive transduction mechanism based on the asymmetry of the beam shape at rest. We show that this mechanism enables highly sensitive linear detection of the vibration of low-resistivity silicon beams without the need of exceptionally large piezoresistive coefficients. The general application of this effect is demonstrated by detecting multiple-order modes of silicon nanowire resonators made by either top-down or bottom-up fabrication methods. These results reveal a promising approach for practical applications of the simplest mechanical resonators, facilitating its manufacturability by very large-scale integration technologies.

  2. A novel high-sensitivity FBG pressure sensor

    NASA Astrophysics Data System (ADS)

    Yao, Zhenhua; Fu, Tao; Leng, Jinsong

    2007-07-01

    A novel pressure sensor based on FBG is designed in this paper. Not only in normal environment, also does it accurately work in water and petrol where other conventional sensors can not work normally. In this paper, the principle of the novel sensor is introduced, and two experiments are further performed: One is keeping the sensor flatly in the gastight silo whose pressure is supplied by an air compressing engine, and the other one is keeping the sensor in liquid. The analysis of the result data demonstrates that the sensor possesses high sensitivity, high linearity, high precision and repeatability. Its experimental linearity and sensitivity approach 0.99858 and 5.35×10 -3MPa -1, respectively. It is also discussed using the sensor to measure the volume in tank.

  3. Design of highly sensitive multichannel bimetallic photonic crystal fiber biosensor

    NASA Astrophysics Data System (ADS)

    Hameed, Mohamed Farhat O.; Alrayk, Yassmin K. A.; Shaalan, Abdelhamid A.; El Deeb, Walid S.; Obayya, Salah S. A.

    2016-10-01

    A design of a highly sensitive multichannel biosensor based on photonic crystal fiber is proposed and analyzed. The suggested design has a silver layer as a plasmonic material coated by a gold layer to protect silver oxidation. The reported sensor is based on detection using the quasi transverse electric (TE) and quasi transverse magnetic (TM) modes, which offers the possibility of multichannel/multianalyte sensing. The numerical results are obtained using a finite element method with perfect matched layer boundary conditions. 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 according to the quasi TM and quasi TE modes of the proposed sensor, respectively. Further, the reported design can be used as a self-calibration biosensor within an unknown analyte refractive index ranging from 1.33 to 1.35 with high linearity and high accuracy. Moreover, the suggested biosensor has advantages in terms of compactness and better integration of microfluidics setup, waveguide, and metallic layers into a single structure.

  4. High-sensitivity microfluidic calorimeters for biological and chemical applications

    PubMed Central

    Lee, Wonhee; Fon, Warren; Axelrod, Blake W.; Roukes, Michael L.

    2009-01-01

    High-sensitivity microfluidic calorimeters raise the prospect of achieving high-throughput biochemical measurements with minimal sample consumption. However, it has been challenging to realize microchip-based calorimeters possessing both high sensitivity and precise sample-manipulation capabilities. Here, we report chip-based microfluidic calorimeters capable of characterizing the heat of reaction of 3.5-nL samples with 4.2-nW resolution. Our approach, based on a combination of hard- and soft-polymer microfluidics, provides both exceptional thermal response and the physical strength necessary to construct high-sensitivity calorimeters that can be scaled to automated, highly multiplexed array architectures. Polydimethylsiloxane microfluidic valves and pumps are interfaced to parylene channels and reaction chambers to automate the injection of analyte at 1 nL and below. We attained excellent thermal resolution via on-chip vacuum encapsulation, which provides unprecedented thermal isolation of the minute microfluidic reaction chambers. We demonstrate performance of these calorimeters by resolving measurements of the heat of reaction of urea hydrolysis and the enthalpy of mixing of water with methanol. The device structure can be adapted easily to enable a wide variety of other standard calorimeter operations; one example, a flow calorimeter, is described. PMID:19706406

  5. Organometallic carboxylate resists for extreme ultraviolet with high sensitivity

    NASA Astrophysics Data System (ADS)

    Passarelli, James; Murphy, Michael; Re, Ryan Del; Sortland, Miriam; Hotalen, Jodi; Dousharm, Levi; Fallica, Roberto; Ekinci, Yasin; Neisser, Mark; Freedman, Daniel A.; Brainard, Robert L.

    2015-10-01

    We have developed organometallic carboxylate compounds [RnM)] capable of acting as negative-tone extreme ultraviolet (EUV) resists. The most sensitive of these resists contain antimony, three R-groups and two carboxylate groups, and carboxylate groups with polymerizable olefins (e.g., acrylate, methacrylate, or styrenecarboxylate). Evidence suggests that high sensitivity is achieved through the polymerization of olefins in the exposed region. We have performed a systematic sensitivity study of the molecules of the type RnM) where we have studied seven R groups, four main group metals (M), and three polymerizable carboxylate groups (O2CR‧). The sensitivity of these resists was evaluated using Emax or dose to maximum resist thickness after exposure and development. We found that the greatest predictor of sensitivity of the RnSb) resists is their level of polymerizable olefins. We mathematically define the polymerizable olefin loading (POL) as the ratio of the number of olefins versus the number of nonhydrogen atoms. Linear and log plots of Emax versus POL for a variety of molecules of the type R3Sb) lend insight into the behavior of these resists.

  6. Nucleic acid-coupled colorimetric analyte detectors

    DOEpatents

    Charych, Deborah H.; Jonas, Ulrich

    2001-01-01

    The present invention relates to methods and compositions for the direct detection of analytes and membrane conformational changes through the detection of color changes in biopolymeric materials. In particular, the present invention provide for the direct colorimetric detection of analytes using nucleic acid ligands at surfaces of polydiacetylene liposomes and related molecular layer systems.

  7. Visualizing Capsaicinoids: Colorimetric Analysis of Chili Peppers

    ERIC Educational Resources Information Center

    Thompson, Robert Q.; Chu, Christopher; Gent, Robin; Gould, Alexandra P.; Rios, Laura; Vertigan, Theresa M.

    2012-01-01

    A colorimetric method for total capsaicinoids in chili pepper ("Capsicum") fruit is described. The placental material of the pepper, containing 90% of the capsaicinoids, was physically separated from the colored materials in the pericarp and extracted twice with methanol, capturing 85% of the remaining capsaicinoids. The extract, evaporated and…

  8. Colorimetric Integrated PCR Protocol for Rapid Detection of Vibrio parahaemolyticus

    PubMed Central

    Cheng, Kewen; Pan, Daodong; Teng, Jun; Yao, Li; Ye, Yingwang; Xue, Feng; Xia, Fan; Chen, Wei

    2016-01-01

    Rapid detection of pathogens is of great significance for food safety and disease diagnosis. A new colorimetric method for rapid and easy detection of Vibrio parahaemolyticus (V. parahaemolyticus or Vp) has been developed in this research. A specific sequence was designed and integrated with the forward primer for molecular detection of Vp. This specific sequence was tested and treated as the horseradish peroxidase (HRP)-mimicking DNAzyme and could be amplified during the polymerase chain reaction (PCR) process. The products of PCR including the sequence of HRP-mimicking DNAzyme could produce the distinguished color in the presence of catalysis substrates. The optical signal of the catalysis reaction, which is in a linear relationship with the initial template of Vp, could be determined with the naked eye or measured with Ultraviolet-visible (UV-vis) for qualitative and quantitative detections, respectively. Based on the optical signal intensity, rapid and easy detection of Vp was successfully achieved with satisfied sensitivity and specificity. Furthermore, the detection of tdh, trh, tlh and toxR virulence genes of two Vp species (Vp 33847 and Vp 17802) were all performed successfully with this developed colorimetric integrated PCR protocol, which demonstrated potential applicability for the rapid detection of other bacteria. PMID:27690041

  9. High-sensitivity three-mode optomechanical transducer

    SciTech Connect

    Zhao, C.; Fang, Q.; Susmithan, S.; Miao, H.; Ju, L.; Fan, Y.; Blair, D.; Hosken, D. J.; Munch, J.; Veitch, P. J.; Slagmolen, B. J. J.

    2011-12-15

    Three-mode optomechanical interactions have been predicted to allow the creation of very high sensitivity transducers in which very strong optical self-cooling and strong optomechanical quantum entanglement are predicted. Strong coupling is achieved by engineering a transducer in which both the pump laser and a single signal sideband frequency are resonantly enhanced. Here we demonstrate that very high sensitivity can be achieved in a very simple system consisting of a Fabry-Perot cavity with CO{sub 2} laser thermal tuning. We demonstrate a displacement sensitivity of {approx}1x10{sup -17} m/{radical}(Hz), which is sufficient to observe a thermally excited acoustic mode in a 5.6 kg sapphire mirror with a signal-to-noise ratio of more than 20 dB. It is shown that a measurement sensitivity of {approx}2x10{sup -20} m/{radical}(Hz) limited by the quantum shot noise is achievable with optimization of the cavity parameters.

  10. Quantum dots as FRET acceptors for highly sensitive multiplexing immunoassays

    NASA Astrophysics Data System (ADS)

    Geissler, Daniel; Hildebrandt, Niko; Charbonnière, Loïc J.; Ziessel, Raymond F.; Löhmannsröben, Hans-Gerd

    2009-02-01

    Homogeneous immunoassays have the benefit that they do not require any time-consuming separation steps. FRET is one of the most sensitive homogeneous methods used for immunoassays. Due to their extremely strong absorption over a broad wavelength range the use of quantum dots as FRET acceptors allows for large Foerster radii, an important advantage for assays in the 5 to 10 nm distance range. Moreover, because of their size-tunable emission, quantum dots of different sizes can be used with a single donor for the detection of different analytes (multiplexing). As the use of organic dyes with short fluorescence decay times as donors is known to be inefficient with quantum dot acceptors, lanthanide complexes with long luminescence decays are very efficient alternatives. In this contribution we present the application of commercially available biocompatible CdSe/ZnS core/shell quantum dots as multiplexing FRET acceptors together with a single terbium complex as donor in a homogeneous immunoassay system. Foerster radii of 10 nm and FRET efficiencies of 75 % are demonstrated. The high sensitivity of the terbium-toquantum dot FRET assay is shown by sub-100-femtomolar detection limits for two different quantum dots (emitting at 605 and 655 nm) within the same biotin-streptavidin assay. Direct comparison to the FRET immunoassay "gold standard" (FRET from Eu-TBP to APC) yields a three orders of magnitude sensitivity improvement, demonstrating the big advantages of quantum dots not only for multiplexing but also for highly sensitive nanoscale analysis.

  11. Highly Selective Colorimetric and Luminescence Response of a Square-Planar Platinum(II) Terpyridyl Complex to Aqueous TcO4-

    SciTech Connect

    Chatterjee, Sayandev; Norton, Amie E.; Edwards, Matthew K.; Peterson, James M.; Taylor, Stephen D.; Bryan, Samuel A.; Andersen, Amity; Govind, Niranjan; Albrecht-Schmitt, Thomas E.; Connick, William; Levitskaia, Tatiana G.

    2015-10-08

    In an effort to address the need for a rapid, selective and economical detection technique for aqueous pertechnetate (TcO4-) anion based on recognition at the molecular level, simple salts of transition metal complexes that undergo a distinct spectroscopic change upon exposure to aqueous anions were explored. The Pt(II) complex [Pt(tpy)Br]SbF6 (tpy=2,2';6',2"-terpyridine) undergoes a dramatic color change and intense luminescence response upon TcO4- uptake due to concomitant enhancement of Pt•••Pt interactions. The spectroscopic response was highly selective and quantitative for aqueous TcO4- among other competing anions. Complimentary Raman spectroscopy and microscopy techniques, structural determination and theoretical methods were employed to achieve molecular-level understanding of the mechanism of the response to aqueous TcO4-.

  12. A Simple Colorimetric Assay for Specific Detection of Glutathione-S Transferase Activity Associated with DDT Resistance in Mosquitoes

    PubMed Central

    Rajatileka, Shavanti; Steven, Andrew; Hemingway, Janet; Ranson, Hilary; Paine, Mark; Vontas, John

    2010-01-01

    Background Insecticide-based methods represent the most effective means of blocking the transmission of vector borne diseases. However, insecticide resistance poses a serious threat and there is a need for tools, such as diagnostic tests for resistance detection, that will improve the sustainability of control interventions. The development of such tools for metabolism-based resistance in mosquito vectors lags behind those for target site resistance mutations. Methodology/Principal Findings We have developed and validated a simple colorimetric assay for the detection of Epsilon class Glutathione transferases (GST)-based DDT resistance in mosquito species, such as Aedes aegypti, the major vector of dengue and yellow fever worldwide. The colorimetric assay is based on the specific alkyl transferase activity of Epsilon GSTs for the haloalkene substrate iodoethane, which produces a dark blue colour highly correlated with AaGSTE2-2-overexpression in individual mosquitoes. The colour can be measured visually and spectrophotometrically. Conclusions/Significance The novel assay is substantially more sensitive compared to the gold standard CDNB assay and allows the discrimination of moderate resistance phenotypes. We anticipate that it will have direct application in routine vector monitoring as a resistance indicator and possibly an important impact on disease vector control. PMID:20824165

  13. Adaptations of the Saker-Solomons test: simple, reliable colorimetric field assays for chloroquine and its metabolites in urine.

    PubMed Central

    Mount, D. L.; Nahlen, B. L.; Patchen, L. C.; Churchill, F. C.

    1989-01-01

    Two field-adapted colorimetric methods for measuring the antimalarial drug chloroquine in urine are described. Both are modifications of the method of Saker and Solomons for screening urine for phencyclidine and other drugs of abuse, using the colour reagent tetrabromophenolphthalein ethyl ester. One method is semiquantitative, detecting the presence of chloroquine (Cq) and its metabolites in urine with a 1 microgram/ml detection limit; it is more sensitive and reliable than the commonly used Dill-Glazko method and is as easy to apply in the field. The second method uses a hand-held, battery-operated filter photometer to quantify Cq and its metabolites with a 2 microgram/ml detection limit and a linear range up to 8 micrograms/ml. The first method was validated in the field using a published quantitative colorimetric method and samples from a malaria study in Nigeria. The second method was validated in the laboratory against high-performance liquid chromatographic results on paired samples from the Nigerian study. Both methods may be used in remote locations where malaria is endemic and no electricity is available. PMID:2766451

  14. Sensitive and high sensitivity next generation cardiac troponin assays: more than just a name.

    PubMed

    Christenson, Robert H; Phillips, Daniel

    2011-04-01

    In the 20 years that cardiac troponin testing has been available in clinical laboratories, the biomarker has revolutionised testing of patients with acute coronary syndromes. Cardiac troponin I and T testing has become the cornerstone for diagnosis of myocardial infarction and is useful for risk assessment and management of suspected acute coronary syndrome patients. As evidence and knowledge have evolved, it has become clear that even small troponin elevations are associated with adverse health outcomes. As a result there have been several generations of troponin assays, all toward tests that reliably detect lower concentrations of this critical analyte. Guidance for cardiac troponin interpretation has been in the form of myocardial infarction redefinition and evidence-based clinical and analytical guidelines. Although terminology naming generations for cardiac troponin assays has been inconsistent, state-of-the-art cardiac troponin assays are generally referred to as 'sensitive' assays and are in general compliance with analytical guidelines. Evidence shows that use of a sensitive troponin assay can result in diagnosis of myocardial infarction earlier. Next generation cardiac troponin I and T assays will likely be termed 'high sensitivity'; these assays should have the ability to measure troponin with a CV of total error of <10% at concentrations significantly lower than the 99 percentile of the normal reference population. As such, these assays should reliably measure troponin in most normal individuals and detect troponin changes (delta values) below the 99 percentile. This property may result in earlier ACS diagnosis and better management. Utilisation of high sensitivity troponin measurements may be useful for applications other than acute coronary syndromes including risk stratifying patients with renal insufficiency, heart failure, cardiac amyloid and screening elderly patients.

  15. Quantum-Dot-Sensitized Solar Cell with Unprecedentedly High Photocurrent

    PubMed Central

    Lee, Jin-Wook; Son, Dae-Yong; Ahn, Tae Kyu; Shin, Hee-Won; Kim, In Young; Hwang, Seong-Ju; Ko, Min Jae; Sul, Soohwan; Han, Hyouksoo; Park, Nam-Gyu

    2013-01-01

    The reported photocurrent density (JSC) of PbS quantum dot (QD)-sensitized solar cell was less than 19 mA/cm2 despite the capability to generate 38 mA/cm2, which results from inefficient electron injection and fast charge recombination. Here, we report on a PbS:Hg QD-sensitized solar cell with an unprecedentedly high JSC of 30 mA/cm2. By Hg2+ doping into PbS, JSC is almost doubled with improved stability. Femtosecond transient study confirms that the improved JSC is due to enhanced electron injection and suppressed charge recombination. EXAFS reveals that Pb-S bond is reinforced and structural disorder is reduced by interstitially incorporated Hg2+, which is responsible for the enhanced electron injection, suppressed recombination and stability. Thanks to the extremely high JSC, power conversion efficiency of 5.6% is demonstrated at one sun illumination. PMID:23308343

  16. Low frequency/high sensitivity triaxial monolithic sensor

    NASA Astrophysics Data System (ADS)

    Acernese, F.; Canonico, R.; De Rosa, R.; Giordano, G.; Romano, R.; Barone, F.

    2013-04-01

    This paper describes a new mechanical implementation of a triaxial sensor, configurable as seismometer and/or as accelerometer, consisting of three one-dimensional monolithic FP sensors, suitably geometrically positioned. The triaxial sensor is, therefore, compact, light, scalable, tunable instrument (frequency < 100 mHz with large band (10-7 Hz - 10 Hz), high quality factor (Q < 1500 in air) with good immunity to environmental noises, guaranteed by an integrated laser optical readout. The measured sensitivity curve is in very good agreement with the theoretical ones (10-12m/√Hz) in the band (0.1 ÷ 10Hz). Typical applications are in the field of earthquake engineering, geophysics, civil engineering and in all applications requiring large band-low frequency performances coupled with high sensitivities.

  17. Very low frequency/high sensitivity triaxial monolithic inertial sensor

    NASA Astrophysics Data System (ADS)

    Acernese, F.; De Rosa, R.; Giordano, G.; Romano, R.; Barone, F.

    2014-03-01

    This paper describes a new mechanical implementation of a triaxial sensor, configurable as seismometer and/or as accelerometer, consisting of three one-dimensional monolithic FP sensors, suitably geometrically positioned. The triaxial sensor is, therefore, compact, light, scalable, tunable instrument (frequency < 100mHz), with large band (10-7 Hz - 10Hz), high quality factor (Q > 2500 in air) with good immunity to environmental noises, guaranteed by an integrated laser optical readout. The measured sensitivity curve is in very good agreement with the theoretical ones (10-12m/√Hz) in the band (0.1 ÷ 10Hz). Typical applications are in the field of earthquake engineering, geophysics, civil engineering and in all applications requiring large band-low frequency performances coupled with high sensitivities.

  18. Low frequency/high sensitivity triaxial monolithic inertial sensor

    NASA Astrophysics Data System (ADS)

    Acernese, F.; De Rosa, R.; Giordano, G.; Romano, Rocco; Barone, F.

    2013-10-01

    This paper describes a new mechanical implementation of a triaxial sensor, configurable as seismometer and/or as accelerometer, consisting of three one-dimensional monolithic FP sensors, suitably geometrically positioned. The triaxial sensor is, therefore, compact, light, scalable, tunable instrument (frequency < 100mHz), with large band (10-7 Hz - 10Hz), high quality factor (Q < 2500 in air) with good immunity to environmental noises, guaranteed by an integrated laser optical readout. The measured sensitivity curve is in very good agreement with the theoretical ones (10-12m/pHz) in the band (0.1 ÷ 10Hz). Typical applications are in the field of earthquake engineering, geophysics, civil engineering and in all applications requiring large band-low frequency performances coupled with high sensitivities.

  19. Evaluation of the oxidase like activity of nanoceria and its application in colorimetric assays.

    PubMed

    Hayat, Akhtar; Cunningham, Jessica; Bulbul, Gonca; Andreescu, Silvana

    2015-07-23

    Nanomaterial-based enzyme mimics have attracted considerable interest in chemical analysis as alternative catalysts to natural enzymes. However, the conditions in which such particles can replace biological catalysts and their selectivity and reactivity profiles are not well defined. This work explored the oxidase like properties of nanoceria particles in the development of colorimetric assays for the detection of dopamine and catechol. Selectivity of the system with respect to several phenolic compounds, the effect of interferences and real sample analysis are discussed. The conditions of use such as buffer composition, selectivity, pH, reaction time and particle type are defined. Detection limits of 1.5 and 0.2μM were obtained with nanoceria for dopamine and catechol. The same assay could be used as a general sensing platform for the detection of other phenolics. However, the sensitivity of the method varies significantly with the particle type, buffer composition, pH and with the structure of the phenolic compound. The results demonstrate that nanoceria particles can be used for the development of cost effective and sensitive methods for the detection of these compounds. However, the selection of the particle system and experimental conditions is critical for achieving high sensitivity. Recommendations are provided on the selection of the particle system and reaction conditions to maximize the oxidase like activity of nanoceria.

  20. Structural Glycomic Analyses at High Sensitivity: A Decade of Progress

    PubMed Central

    Alley, William R.; Novotny, Milos V.

    2014-01-01

    The field of glycomics has recently advanced in response to the urgent need for structural characterization and quantification of complex carbohydrates in biologically and medically important applications. The recent success of analytical glycobiology at high sensitivity reflects numerous advances in biomolecular mass spectrometry and its instrumentation, capillary and microchip separation techniques, and microchemical manipulations of carbohydrate reactivity. The multimethodological approach appears to be necessary to gain an in-depth understanding of very complex glycomes in different biological systems. PMID:23560930

  1. 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.

  2. 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.

  3. 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.

  4. Highly Sensitive Flexible Magnetic Sensor Based on Anisotropic Magnetoresistance Effect.

    PubMed

    Wang, Zhiguang; Wang, Xinjun; Li, Menghui; Gao, Yuan; Hu, Zhongqiang; Nan, Tianxiang; Liang, Xianfeng; Chen, Huaihao; Yang, Jia; Cash, Syd; Sun, Nian-Xiang

    2016-11-01

    A highly sensitive flexible magnetic sensor based on the anisotropic magnetoresistance effect is fabricated. A limit of detection of 150 nT is observed and excellent deformation stability is achieved after wrapping of the flexible sensor, with bending radii down to 5 mm. The flexible AMR sensor is used to read a magnetic pattern with a thickness of 10 μm that is formed by ferrite magnetic inks.

  5. Structural Glycomic Analyses at High Sensitivity: A Decade of Progress

    NASA Astrophysics Data System (ADS)

    Alley, William R.; Novotny, Milos V.

    2013-06-01

    The field of glycomics has recently advanced in response to the urgent need for structural characterization and quantification of complex carbohydrates in biologically and medically important applications. The recent success of analytical glycobiology at high sensitivity reflects numerous advances in biomolecular mass spectrometry and its instrumentation, capillary and microchip separation techniques, and microchemical manipulations of carbohydrate reactivity. The multimethodological approach appears to be necessary to gain an in-depth understanding of very complex glycomes in different biological systems.

  6. An early warning system for high climate sensitivity? (Invited)

    NASA Astrophysics Data System (ADS)

    Pierrehumbert, R.

    2010-12-01

    The scientific case for the clear and present danger of global warming has been unassailable at least since the release of the Charney Report more than thirty years ago, if not longer. While prompt action to begin decarbonizing energy systems could still head off much of the potential warming, it is distinctly possible that emissions will continue unabated in the coming decades, leading to a doubling or more of pre-industrial carbon dioxide concentrations. At present, we are in the unenviable position of not even knowing how bad things will get if this scenario comes to pass, because of the uncertainty in climate sensitivity. If climate sensitivity is high, then the consequences will be dire, perhaps even catastrophic. As the world continues to warm in response to continued carbon dioxide emissions, will we at least be able to monitor the climate and provide an early warning that the planet is on a high-sensitivity track, if such turns out to be the case? At what point will we actually know the climate sensitivity? It has long been recognized that the prime contributor to uncertainty in climate sensitivity is uncertainty in cloud feedbacks. Study of paleoclimate and climate of the past century has not been able to resolve which models do cloud feedback most correctly, because of uncertainties in radiative forcing. In this talk, I will discuss monitoring requirements, and analysis techniques, that might have the potential to determine which climate models most faithfully represent climate feedbacks, and thus determine which models provide the best estimate of climate sensitivity. The endeavor is complicated by the distinction between transient climate response and equilibrium climate sensitivity. I will discuss the particular challenges posed by this issue, particularly in light of recent indications that the pattern of ocean heat storage may lead to different cloud feedbacks in the transient warming stage than apply once the system has reached equilibrium. Apart

  7. Pulsed Discharge Helium Ionization Detector for Highly Sensitive Aquametry.

    PubMed

    Mowry, Curtis D; Pimentel, Adam S; Sparks, Elizabeth S; Moorman, Matthew W; Achyuthan, Komandoor E; Manginell, Ronald P

    2016-01-01

    Trace moisture quantitation is crucial in medical, civilian and military applications. Current aquametry technologies are limited by the sample volume, reactivity, or interferences, and/or instrument size, weight, power, cost, and complexity. We report for the first time on the use of a pulsed discharge helium ionization detector (PDHID-D2) (∼196 cm(3)) for the sensitive (limit of detection, 0.047 ng; 26 ppm), linear (r(2) >0.99), and rapid (< 2 min) quantitation of water using a small (0.2 - 5.0 μL) volume of liquid or gas. The relative humidity sensitivity was 0.22% (61.4 ppmv) with a limit of detection of less than 1 ng moisture with gaseous samples. The sensitivity was 10 to 100 to fold superior to competing technologies without the disadvantages inherent to these technologies. The PDHID-D2, due to its small footprint and low power requirement, has good size, weight, and power-portability (SWAPP) factors. The relatively low cost (∼$5000) and commercial availability of the PDHID-D2 makes our technique applicable to highly sensitive aquametry.

  8. “Naked-eye” colorimetric and “turn-on” fluorometric chemosensors for reversible Hg2+ detection

    NASA Astrophysics Data System (ADS)

    Wanichacheva, Nantanit; Praikaew, Panida; Suwanich, Thanapat; Sukrat, Kanjarat

    2014-01-01

    Two new Hg2+-colorimetric and fluorescent sensors based on 2-[3-(2-aminoethylsulfanyl) propylsulfanyl]ethanamine covalently bound to one and two units of rhodamine-6G moieties, 1 and 2, were synthesised, and their sensing behaviors toward metal ions were investigated by UV/Vis and fluorescence spectroscopy. Upon the addition of Hg2+, the sensors exhibited highly sensitive “turn-on” fluorescence enhancement as well as a color change from colorless to pink, which was readily noticeable for naked eye detection. Especially, 1 exhibited the reversible behavior and revealed a very high selectivity in the presence of competitive ions, particularly Cu2+, Ag+, Pb2+, Ca2+, Cd2+, Co2+, Fe2+, Mn2+, Na+, Ni2+, K+, Ba2+, Li+ and Zn2+, with a low detection limit of 1.7 ppb toward Hg2+.

  9. High sensitive volumetric imaging of renal microcirculation in vivo using ultrahigh sensitive optical microangiography

    NASA Astrophysics Data System (ADS)

    Zhi, Zhongwei; Jung, Yeongri; Jia, Yali; An, Lin; Wang, Ruikang K.

    2011-03-01

    We present a non-invasive, label-free imaging technique called Ultrahigh Sensitive Optical Microangiography (UHSOMAG) for high sensitive volumetric imaging of renal microcirculation. The UHS-OMAG imaging system is based on spectral domain optical coherence tomography (SD-OCT), which uses a 47000 A-line scan rate CCD camera to perform an imaging speed of 150 frames per second that takes only ~7 seconds to acquire a 3D image. The technique, capable of measuring slow blood flow down to 4 um/s, is sensitive enough to image capillary networks, such as peritubular capillaries and glomerulus within renal cortex. We show superior performance of UHS-OMAG in providing depthresolved volumetric images of rich renal microcirculation. We monitored the dynamics of renal microvasculature during renal ischemia and reperfusion. Obvious reduction of renal microvascular density due to renal ischemia was visualized and quantitatively analyzed. This technique can be helpful for the assessment of chronic kidney disease (CKD) which relates to abnormal microvasculature.

  10. Novel high sensitivity EUV photoresist for sub-7nm node

    NASA Astrophysics Data System (ADS)

    Nagai, Tomoki; Nakagawa, Hisashi; Naruoka, Takehiko; Tagawa, Seiichi; Oshima, Akihiro; Nagahara, Seiji; Shiraishi, Gosuke; Yoshihara, Kosuke; Terashita, Yuichi; Minekawa, Yukie; Buitrago, Elizabeth; Ekinci, Yasin; Yildirim, Oktay; Meeuwissen, Marieke; Hoefnagels, Rik; Rispens, Gijsbert; Verspaget, Coen; Maas, Raymond

    2016-03-01

    Extreme ultraviolet lithography (EUVL) has been recognized as the most promising candidate for the manufacture of semiconductor devices for the 7 nm node and beyond. A key point in the successful introduction of EUV lithography in high volume manufacture (HVM) is the effective EUV dose utilization while simultaneously realizing ultra-high resolution and low line edge roughness (LER). Here we show EUV resist sensitivity improvement with the use of a photosensitized chemically amplified resist PSCARTM system. The evaluation of this new chemically amplified resist (CAR) as performed using EUV interference lithography (EUV-IL) is described and the fundamentals are discussed.

  11. CIE colorimetric system fails to calculate the chroma of a Nd:YAG crystal under the fluorescent illuminant F7

    NASA Astrophysics Data System (ADS)

    Liu, Yan; Chen, Qinghan; Bu, Xianhui; Feng, Pingyun

    2002-06-01

    The rare earth element neodymium doped yttrium aluminum garnet (Nd:YAG) is a laser crystal widely used for producing laser in the infrared range. Neodymium causes many characteristic absorption peaks in the transmittance spectrum of the Nd:YAG crystal in the visible range. The crystal appears pink under daylight and incandescent light, and colorless under fluorescent light. The colorimetric calculation results of chroma under the CIE standard fluorescent illuminant F7 do not agree with the color appearance under fluorescent light. The calculated chroma values should be near zero to agree with a colorless appearance, but it is actually 11.79 in the CIELAB color space. This failure of the colorimetric calculation is caused by the color matching functions of the CIE colorimetric observers. The color matching functions do not agree with the spectral sensitivity curves of the human eye, especially the x(λ) function does not matches the spectral sensitivity curve of the long wavelength cone photoreceptors.

  12. High-sensitive scanning laser magneto-optical imaging system.

    PubMed

    Murakami, Hironaru; Tonouchi, Masayoshi

    2010-01-01

    A high-sensitive scanning laser magneto-optical (MO) imaging system has been developed. The system is mainly composed of a laser source, galvano meters, and a high-sensitive differential optical-detector. Preliminary evaluation of system performance by using a Faraday indicator with a Faraday rotation coefficient of 3.47 x 10(-5) rad/microm Oe shows a magnetic sensitivity of about 5 microT, without any need for accumulation or averaging processing. Using the developed MO system we have succeeded in the fast and quantitative imaging of a rotationally symmetric magnetic field distribution around an YBa(2)Cu(3)O(7-delta) (YBCO) strip line applied with dc-biased current, and also succeeded in the detection of quantized fine signals corresponding to magnetic flux quantum generation in a superconducting loop of an YBCO Josephson vortex flow transistor. Thus, the developed system enables us not only to do fast imaging and local signal detection but also to directly evaluate both the strength and direction of a magnetic signal.

  13. High-sensitivity strain visualization using electroluminescence technologies

    NASA Astrophysics Data System (ADS)

    Xu, Jian; Jo, Hongki

    2016-04-01

    Visualizing mechanical strain/stress changes is an emerging area in structural health monitoring. Several ways are available for strain change visualization through the color/brightness change of the materials subjected to the mechanical stresses, for example, using mechanoluminescence (ML) materials and mechanoresponsive polymers (MRP). However, these approaches were not effectively applicable for civil engineering system yet, due to insufficient sensitivity to low-level strain of typical civil structures and limitation in measuring both static and dynamic strain. In this study, design and validation for high-sensitivity strain visualization using electroluminescence technologies are presented. A high-sensitivity Wheatstone bridge, of which bridge balance is precisely controllable circuits, is used with a gain-adjustable amplifier. The monochrome electroluminescence (EL) technology is employed to convert both static and dynamic strain change into brightness/color change of the EL materials, through either brightness change mode (BCM) or color alternation mode (CAM). A prototype has been made and calibrated in lab, the linearity between strain and brightness change has been investigated.

  14. Polymer-Particle Pressure-Sensitive Paint with High Photostability

    PubMed Central

    Matsuda, Yu; Uchida, Kenta; Egami, Yasuhiro; Yamaguchi, Hiroki; Niimi, Tomohide

    2016-01-01

    We propose a novel fast-responding and paintable pressure-sensitive paint (PSP) based on polymer particles, i.e. polymer-particle (pp-)PSP. As a fast-responding PSP, polymer-ceramic (PC-)PSP is widely studied. Since PC-PSP generally consists of titanium (IV) oxide (TiO2) particles, a large reduction in the luminescent intensity will occur due to the photocatalytic action of TiO2. We propose the usage of polymer particles instead of TiO2 particles to prevent the reduction in the luminescent intensity. Here, we fabricate pp-PSP based on the polystyrene particle with a diameter of 1 μm, and investigate the pressure- and temperature-sensitives, the response time, and the photostability. The performances of pp-PSP are compared with those of PC-PSP, indicating the high photostability with the other characteristics comparable to PC-PSP. PMID:27092511

  15. Sensitivity to Error Fields in NSTX High Beta Plasmas

    SciTech Connect

    Park, Jong-Kyu; Menard, Jonathan E.; Gerhardt, Stefan P.; Buttery, Richard J.; Sabbagh, Steve A.; Bell, Steve E.; LeBlanc, Benoit P.

    2011-11-07

    It was found that error field threshold decreases for high β in NSTX, although the density correlation in conventional threshold scaling implies the threshold would increase since higher β plasmas in our study have higher plasma density. This greater sensitivity to error field in higher β plasmas is due to error field amplification by plasmas. When the effect of amplification is included with ideal plasma response calculations, the conventional density correlation can be restored and threshold scaling becomes more consistent with low β plasmas. However, it was also found that the threshold can be significantly changed depending on plasma rotation. When plasma rotation was reduced by non-resonant magnetic braking, the further increase of sensitivity to error field was observed.

  16. Incorporating gold nanoclusters and target-directed liposomes as a synergistic amplified colorimetric sensor for HER2-positive breast cancer cell detection

    PubMed Central

    Tao, Yu; Li, Mingqiang; Kim, Bumjun; Auguste, Debra T.

    2017-01-01

    Breast cancer is the second leading cause of cancer-related mortality in women. Successful development of sensitive nanoprobes for breast cancer cell detection is of great importance for breast cancer diagnosis and symptomatic treatment. Herein, inspired by the intrinsic peroxidase property of gold nanoclusters, high loading, and targeting ability of ErbB2/Her2 antibody functionalized liposomes, we report that gold nanoclusters-loaded, target-directed, functionalized liposomes can serve as a robust sensing platform for amplified colorimetric detection of HER2-positive breast cancer cells. This approach allows HER2-positive breast cancer cell identification at high sensitivity with high selectivity. In addition, the colorimetric “readout” offers extra advantages in terms of low-cost, portability, and easy-to-use applications. The practicality of this platform was further proved by successful detection of HER2-positive breast cancer cells in human serum samples and in breast cancer tissue, which indicated our proposed method has potential for application in cancer theranostics. PMID:28382162

  17. A CMOS In-Pixel CTIA High Sensitivity Fluorescence Imager

    PubMed Central

    Murari, Kartikeya; Etienne-Cummings, Ralph; Thakor, Nitish; Cauwenberghs, Gert

    2012-01-01

    Traditionally, charge coupled device (CCD) based image sensors have held sway over the field of biomedical imaging. Complementary metal oxide semiconductor (CMOS) based imagers so far lack sensitivity leading to poor low-light imaging. Certain applications including our work on animal-mountable systems for imaging in awake and unrestrained rodents require the high sensitivity and image quality of CCDs and the low power consumption, flexibility and compactness of CMOS imagers. We present a 132×124 high sensitivity imager array with a 20.1 μm pixel pitch fabricated in a standard 0.5 μ CMOS process. The chip incorporates n-well/p-sub photodiodes, capacitive transimpedance amplifier (CTIA) based in-pixel amplification, pixel scanners and delta differencing circuits. The 5-transistor all-nMOS pixel interfaces with peripheral pMOS transistors for column-parallel CTIA. At 70 fps, the array has a minimum detectable signal of 4 nW/cm2 at a wavelength of 450 nm while consuming 718 μA from a 3.3 V supply. Peak signal to noise ratio (SNR) was 44 dB at an incident intensity of 1 μW/cm2. Implementing 4×4 binning allowed the frame rate to be increased to 675 fps. Alternately, sensitivity could be increased to detect about 0.8 nW/cm2 while maintaining 70 fps. The chip was used to image single cell fluorescence at 28 fps with an average SNR of 32 dB. For comparison, a cooled CCD camera imaged the same cell at 20 fps with an average SNR of 33.2 dB under the same illumination while consuming over a watt. PMID:23136624

  18. Label free colorimetric sensing of thiocyanate based on inducing aggregation of Tween 20-stabilized gold nanoparticles.

    PubMed

    Zhang, Zhiyang; Zhang, Jun; Qu, Chengli; Pan, Dawei; Chen, Zhaopeng; Chen, Lingxin

    2012-06-07

    Based on inducing the aggregation of gold nanoparticles (AuNPs), a simple colorimetric method with high sensitivity and selectivity was developed for the sensing of thiocyanate (SCN(-)) in aqueous solutions. Citrate-capped AuNPs were prepared following a classic method and Tween 20 was subsequently added as a stabilizer. With the addition of SCN(-), citrate ions on AuNPs surfaces were replaced due to the high affinity between SCN(-) and Au. As a result, Tween 20 molecules adsorbed on the AuNPs surfaces were separated and the AuNPs aggregated. The process was accompanied by a visible color change from red to blue within 5 min. The sensing of SCN(-) can therefore be easily achieved by a UV-vis spectrophotometer or even by the naked eye. The potential effects of relevant experimental conditions, including concentration of Tween 20, pH, incubation temperature and time, were evaluated to optimize the method. Under optimized conditions, this method yields excellent sensitivity (LOD = 0.2 μM or 11.6 ppb) and selectivity toward SCN(-). Our attempt may provide a cost-effective, rapid and simple solution to the inspection of SCN(-) ions in saliva and environmental aqueous samples.

  19. A novel colorimetric triple-helix molecular switch aptasensor for ultrasensitive detection of tetracycline.

    PubMed

    Ramezani, Mohammad; Mohammad Danesh, Noor; Lavaee, Parirokh; Abnous, Khalil; Mohammad Taghdisi, Seyed

    2015-08-15

    Detection methods of antibiotic residues in blood serum and animal derived foods are of great interest. In this study a colorimetric aptasensor was designed for sensitive, selective and fast detection of tetracycline based on triple-helix molecular switch (THMS) and gold nanoparticles (AuNPs). As a biosensor, THMS shows distinct advantages including high stability, sensitivity and preserving the selectivity and affinity of the original aptamer. In the absence of tetracycline, THMS is stable, leading to the aggregation of AuNPs by salt and an obvious color change from red to blue. In the presence of tetracycline, aptamer binds to its target, signal transduction probe (STP) leaves the THMS and adsorbs on the surface of AuNPs. So the well-dispersed AuNPs remain stable against salt-induced aggregation with a red color. The presented aptasensor showed high selectivity toward tetracyclines with a limit of detection as low as 266 pM for tetracycline. The designed aptasensor was successfully applied to detect tetracycline in serum and milk.

  20. High Sensitivity MEMS Strain Sensor: Design and Simulation

    PubMed Central

    Mohammed, Ahmed A. S.; Moussa, Walied A.; Lou, Edmond

    2008-01-01

    In this article, we report on the new design of a miniaturized strain microsensor. The proposed sensor utilizes the piezoresistive properties of doped single crystal silicon. Employing the Micro Electro Mechanical Systems (MEMS) technology, high sensor sensitivities and resolutions have been achieved. The current sensor design employs different levels of signal amplifications. These amplifications include geometric, material and electronic levels. The sensor and the electronic circuits can be integrated on a single chip, and packaged as a small functional unit. The sensor converts input strain to resistance change, which can be transformed to bridge imbalance voltage. An analog output that demonstrates high sensitivity (0.03mV/με), high absolute resolution (1με) and low power consumption (100μA) with a maximum range of ±4000με has been reported. These performance characteristics have been achieved with high signal stability over a wide temperature range (±50°C), which introduces the proposed MEMS strain sensor as a strong candidate for wireless strain sensing applications under harsh environmental conditions. Moreover, this sensor has been designed, verified and can be easily modified to measure other values such as force, torque…etc. In this work, the sensor design is achieved using Finite Element Method (FEM) with the application of the piezoresistivity theory. This design process and the microfabrication process flow to prototype the design have been presented. PMID:27879841

  1. A high sensitivity inductive sensor for blade tip clearance measurement

    NASA Astrophysics Data System (ADS)

    Du, Li; Zhu, Xiaoliang; Zhe, Jiang

    2014-06-01

    A multiplexed inductive sensor consisting of multiple mini-sized planar spiral coils for detecting multiple tip clearances of rotor blades is presented. The sensor measures the tip clearances by monitoring the inductance changes of planar spiral coils caused by the passage of the rotor blades. A resonance frequency division multiplexing technique and parallel LC resonance measurement were applied to the multiple sensor coils, making it feasible to measure multiple tip clearances using only one set of measurement electronics with high sensitivity and resolution. The results from tests conducted on a bench-top test rig have demonstrated that the sensor is capable of simultaneously measuring multiple tip clearances from 0 to 5 mm with a 10 μm resolution at a high rotary speed up to 80 000 RPM. With its high resolution, high sensitivity and capability of monitoring a large number of tip clearances simultaneously, this sensor can potentially be used for advanced active tip clearance control in turbine machinery.

  2. Hybrid nanosensor for colorimetric and ultrasensitive detection of nuclease contaminations

    NASA Astrophysics Data System (ADS)

    Cecere, Paola; Valentini, Paola; Pompa, Pier Paolo

    2016-04-01

    Nucleases are ubiquitous enzymes that degrade DNA or RNA, thus they can prejudice the good outcome of molecular biology experiments involving nucleic acids. We propose a colorimetric test for the naked-eye detection of nuclease contaminations. The system uses an hybrid nanosensor, based on gold nanoparticles functionalized with DNA probes. Our assay is rapid, instrument-free, simple and low-cost. Moreover, it reaches sensitivity equal or better than those of commercial kits, and presents a lot of advantageous aspects. Therefore, it is very competitive, with a real market potential. This test will be relevant in routine process monitoring in scientific laboratories, and in quality control in clinical laboratories and industrial processes, allowing the simultaneous detection of nucleases with different substrate specificities and large-scale screening.

  3. [Colorimetric detection of human influenza A H1N1 virus by reverse transcription loop mediated isothermal amplification].

    PubMed

    Nie, Kai; Wang, Da-Yan; Qin, Meng; Gao, Rong-Bao; Wang, Miao; Zou, Shu-Mei; Han, Feng; Zhao, Xiang; Li, Xi-Yan; Shu, Yue-Long; Ma, Xue-Jun

    2010-03-01

    A simple, rapid and sensitive colorimetric Reverse Transcription Loop Mediated Isothermal Amplification (RT-LAMP) method was established to detect human influenza A H1N1 virus. The method employed a set of six specially designed primers that recognized eight distinct sequences of the HA gene for amplification of nucleic acid under isothermal conditions at 65 degrees C for one and half hour. The amplification process of RT-LAMP was monitored by the addition of HNB (Hydroxy naphthol blue) dye prior to amplification. A positive reaction was indicated by a color change from violet to sky blue and confirmed by agarose electrophoresis. The specificity of the RT-LAMP assay was validated by cross-reaction with different swine and human influenza virus including human seasonal influenza A /H1N1 A /H3N2, influenza B and swine A /H1N1. The sensitivity of this assay was evaluated by serial dilutions of RNA molecules from in vitro transcription of human influenza A H1N1 HA gene. The assay was further evaluated with 30 clinical specimens with suspected pandemic influenza A H1N1 virus infection in parallel with RT-PCR detection and 26 clinical specimens with seasonal influenza virus infection. Our results showed that the RT-LAMP was able to achieve a sensitivity of 60 RNA copies with high specificity, and detection rate was comparable to that of the RT-PCR with the clinical samples of pandemic influenza A H1N1 infection. The RT-LAMP reaction with HNB could also be measured at 650nm in a microplate reader for quantitative analysis. Thus, we concluded that this colorimetric RT-LAMP assay had potential for the rapid screening of the human influenza A H1N1 virus infection in National influenza monitoring network laboratories and sentinel hospitals of provincial and municipal region in China.

  4. Molecularly imprinted photonic hydrogels as colorimetric sensors for rapid and label-free detection of vanillin.

    PubMed

    Peng, Hailong; Wang, Shenqi; Zhang, Zhong; Xiong, Hua; Li, Jinhua; Chen, Lingxin; Li, Yanbin

    2012-02-29

    A novel colorimetric sensor for the rapid and label-free detection of vanillin, based on the combination of photonic crystal and molecular imprinting technique, was developed. The sensing platform of molecularly imprinted photonic hydrogel (MIPH) was prepared by a noncovalent and self-assembly approach using vanillin as a template molecule. Morphology characterization by scanning electron microscope (SEM) showed that the MIPH possessed a highly ordered three-dimensional (3D) macroporous structure with nanocavities. The vanillin recognition events of the created nonocavities could be directly transferred into readable optical signals through a change in Bragg diffraction of the ordered macropores array of MIPH. The Bragg diffraction peak shifted from 451 to 486 nm when the concentration of the vanillin was increased from 10⁻¹² to 10⁻³ mol L⁻¹ within 60 s, whereas there were no obvious peak shifts for methyl and ethyl vanillin, indicating that the MIPH had high selectivity and rapid response for vanillin. The adsorption results showed that the hierarchical porous structure and homogeneous layers were formed in the MIPH with higher adsorption capacity. The application of such a label-free sensor with high selectivity, high sensitivity, high stability, and easy operation might offer a potential method for rapid real-time detection of trace vanillin.

  5. Highly stretchable and sensitive unidirectional strain sensor via laser carbonization.

    PubMed

    Rahimi, Rahim; Ochoa, Manuel; Yu, Wuyang; Ziaie, Babak

    2015-03-04

    In this paper, we present a simple and low-cost technique for fabricating highly stretchable (up to 100% strain) and sensitive (gauge factor of up to 20 000) strain sensors. Our technique is based on transfer and embedment of carbonized patterns created through selective laser pyrolization of thermoset polymers, such as polyimide, into elastomeric substrates (e.g., PDMS or Ecoflex). Embedded carbonized materials are composed of partially aligned graphene and carbon nanotube (CNT) particles and show a sharp directional anisotropy, which enables the fabrication of extremely robust, highly stretchable, and unidirectional strain sensors. Raman spectrum of pyrolized carbon regions reveal that under optimal laser settings, one can obtain highly porous carbon nano/microparticles with sheet resistances as low as 60 Ω/□. Using this technique, we fabricate an instrumented latex glove capable of measuring finger motion in real-time.

  6. High-sensitivity molecular organometallic resist for EUV (MORE)

    NASA Astrophysics Data System (ADS)

    Passarelli, James; Murphy, Michael; Del Re, Ryan; Sortland, Miriam; Dousharm, Levi; Vockenhuber, Michaela; Ekinci, Yasin; Neisser, Mark; Freedman, Daniel A.; Brainard, Robert L.

    2015-03-01

    We have developed organometallic carboxylate compounds [RnM(O2CR')2] capable of acting as negativetone EUV resists. Overall, the best and fastest resists contain antimony, are pentavalent and the carboxylate group contains a polymerizable olefin (e.g. acrylate, methacrylate or styrenecarboxylate). Evidence suggests that high sensitivity is achieved through the polymerization of olefins in the exposed region. We have performed a systematic sensitivity study of molecules of the type RnM(O2CR')2 where we have studied seven R groups, four main group metals (M), and three polymerizable carboxylate groups (O2CR'). We found that the greatest predictor of sensitivity of the RnSb(O2CR')2 resists is their level of polymerizable olefins. We mathematically define the polymerizable olefin loading (POL) as the ratio of the number of olefins vs. the number of non-hydrogen atoms. Linear and log plots of Emax vs. POL for a variety of molecules of the type R3Sb(O2CR')2 lend insight into the behaviour of these resists.

  7. Piezoelectric rubber films for highly sensitive impact measurement

    NASA Astrophysics Data System (ADS)

    Wang, Jhih-Jhe; Tsai, Jui-Wei; Su, Yu-Chuan

    2013-07-01

    We have successfully demonstrated the microfabrication of piezoelectric rubber films and their application in impact measurement. To realize the desired piezoelectricity and stretchability, cellular polydimethylsiloxane (PDMS) structures with micrometer-sized voids are internally implanted with bipolar charges, which function as dipoles and respond promptly to electromechanical stimuli. In the prototype demonstration, 300 µm thick cellular PDMS films are fabricated and internally coated with a thin polytetrafluoroethylene (PTFE) layer to secure the implanted charges. Meanwhile, the top and bottom surfaces of the cellular PDMS films are deposited with stretchable gold electrodes. An electric field up to 35 MV m-1 is applied across the gold electrodes to ionize the air in the voids and to implant charges on the inner surfaces. The resulting composite structures behave like rubber (with an elastic modulus of about 300 kPa) and show strong piezoelectricity (with a piezoelectric coefficient d33 higher than 1000 pC N-1). While integrated with a wide bandwidth and large dynamic-range charge amplifier, highly sensitive impact measurement (with a stress sensitivity of about 10 mV Pa-1) is demonstrated. As such, the demonstrated piezoelectric rubber films could potentially serve as a sensitive electromechanical material for low-frequency stimuli, and fulfill the needs of a variety of physiological monitoring and wearable electronics applications.

  8. High sensitivity charge amplifier for ion beam uniformity monitor

    DOEpatents

    Johnson, Gary W.

    2001-01-01

    An ion beam uniformity monitor for very low beam currents using a high-sensitivity charge amplifier with bias compensation. The ion beam monitor is used to assess the uniformity of a raster-scanned ion beam, such as used in an ion implanter, and utilizes four Faraday cups placed in the geometric corners of the target area. Current from each cup is integrated with respect to time, thus measuring accumulated dose, or charge, in Coulombs. By comparing the dose at each corner, a qualitative assessment of ion beam uniformity is made possible. With knowledge of the relative area of the Faraday cups, the ion flux and areal dose can also be obtained.

  9. The Georgia Tech High Sensitivity Microwave Measurement System

    NASA Technical Reports Server (NTRS)

    Deboer, David R.; Steffes, Paul G.

    1996-01-01

    As observations and models of the planets become increasingly more accurate and sophisticated, the need for highly accurate laboratory measurements of the microwave properties of the component gases present in their atmospheres become ever more critical. This paper describes the system that has been developed at Georgia Tech to make these measurements at wavelengths ranging from 13.3 cm to 1.38 cm with a sensitivity of 0.05 dB/km at the longest wavelength and 0.6 db/km at the shortest wavelength.

  10. A high-sensitivity small animal SPECT system

    NASA Astrophysics Data System (ADS)

    Mitchell, Gregory S.; Cherry, Simon R.

    2009-03-01

    Medical imaging using single gamma-ray-emitting radionuclides typically makes use of parallel hole collimators or pinholes in order to achieve good spatial resolution. However, a tradeoff in sensitivity is inherent in the use of a collimator, and modern preclinical single photon emission computed tomography (SPECT) systems detect a very small fraction of emitted gamma rays, often less than 0.1%. A system for small animal SPECT imaging which uses no collimators could potentially achieve very high sensitivity—several tens of percent—with reasonably sized detectors. This would allow two significant improvements in preclinical studies: images could be obtained more rapidly, allowing higher throughput for screening applications, or for dynamic processes to be observed with very good time resolution; and images could be obtained with less radioactive tracer, making possible the in vivo imaging of low-capacity receptor systems, aiding research into new tracer compounds, and reducing the cost and easing the regulatory burden of an experiment. Of course, a system with no collimator will not be able to approach the submillimeter spatial resolutions produced by the most advanced pinhole and collimated systems, but a high-sensitivity system with resolution of order 1 cm could nonetheless find significant and new use in the many molecular imaging applications which do not require good spatial resolution—for example, screening applications for drug development or new imaging agents. Rather than as an alternative to high-resolution SPECT systems, the high-sensitivity system is proposed as a radiotracer alternative to optical imaging for small animals. We have developed a prototype system for mouse imaging applications. The scanner consists of two large, thin, closely spaced scintillation detectors. Simulation studies indicate that a FWHM spatial resolution of 7 mm is possible. In an in vivo mouse imaging study using the 99mTc labeled tracer MAG-3, the sensitivity of the

  11. High-Sensitivity Measurement of Density by Magnetic Levitation.

    PubMed

    Nemiroski, Alex; Kumar, A A; Soh, Siowling; Harburg, Daniel V; Yu, Hai-Dong; Whitesides, George M

    2016-03-01

    This paper presents methods that use Magnetic Levitation (MagLev) to measure very small differences in density of solid diamagnetic objects suspended in a paramagnetic medium. Previous work in this field has shown that, while it is a convenient method, standard MagLev (i.e., where the direction of magnetization and gravitational force are parallel) cannot resolve differences in density <10(-4) g/cm(3) for macroscopic objects (>mm) because (i) objects close in density prevent each other from reaching an equilibrium height due to hard contact and excluded volume, and (ii) using weaker magnets or reducing the magnetic susceptibility of the medium destabilizes the magnetic trap. The present work investigates the use of weak magnetic gradients parallel to the faces of the magnets as a means of increasing the sensitivity of MagLev without destabilization. Configuring the MagLev device in a rotated state (i.e., where the direction of magnetization and gravitational force are perpendicular) relative to the standard configuration enables simple measurements along the axes with the highest sensitivity to changes in density. Manipulating the distance of separation between the magnets or the lengths of the magnets (along the axis of measurement) enables the sensitivity to be tuned. These modifications enable an improvement in the resolution up to 100-fold over the standard configuration, and measurements with resolution down to 10(-6) g/cm(3). Three examples of characterizing the small differences in density among samples of materials having ostensibly indistinguishable densities-Nylon spheres, PMMA spheres, and drug spheres-demonstrate the applicability of rotated Maglev to measuring the density of small (0.1-1 mm) objects with high sensitivity. This capability will be useful in materials science, separations, and quality control of manufactured objects.

  12. High Sensitivity Surface Enhanced Raman Scattering Detection of Tryptophan

    NASA Astrophysics Data System (ADS)

    Kandakkathara, Archana

    Raman spectroscopy has the capability of providing detailed information about molecular structure, but the extremely small cross section of Raman scattering prevents this technique from applications requiring high sensitivity. Surface enhanced Raman scattering (SERS) on the other hand provides strongly increased Raman signal from molecules attached to metallic nanostructures. SERS is thus a promising technique for high sensitivity analytical applications. One particular area of interest is the application of such techniques for the analysis of the composition of biological cells. However, there are issues which have to be addressed in order to make SERS a reliable technique such as the optimization of conditions for any given analyte, understanding the kinetic processes of binding of the target molecules to the nanostructures and understanding the evolution and coagulation of the nanostructures, in the case of colloidal solutions. The latter processes introduce a delay time for the observation of maximum enhancement factors which must be taken into account for any given implementation of SERS. In the present thesis the goal was to develop very sensitive SERS techniques for the measurement of biomolecules of interest for analysis of the contents of cells. The techniques explored could be eventually be applicable to microfluidic systems with the ultimate goal of analyzing the molecular constituents of single cells. SERS study of different amino acids and organic dyes were performed during the course of this thesis. A high sensitivity detection system based on SERS has been developed and spectrum from tryptophan (Trp) amino acid at very low concentration (10-8 M) has been detected. The concentration at which good quality SERS spectra could be detected from Trp is 4 orders of magnitude smaller than that previously reported in literature. It has shown that at such low concentrations the SERS spectra of Trp are qualitatively distinct from the spectra commonly reported in

  13. A simple and novel system for colorimetric detection of cobalt ions.

    PubMed

    Liu, Zhimin; Jia, Xinle; Bian, Pingping; Ma, Zhanfang

    2014-02-07

    A simple and novel method for the colorimetric detection of Co(2+) was developed based on controlling the oxidation level of methylene blue (MB). After a complex was formed between MB, 2-aminothiophenol (ATP) and copper nitrate (MB-ATP-Cu(2+)), the sensing of Co(2+) showed high selectivity. The mechanism of sensing has also been discussed.

  14. A new rhodamine-based colorimetric chemosensor for naked-eye detection of Cu2 + in aqueous solution

    NASA Astrophysics Data System (ADS)

    Hu, Yang; Zhang, Jing; Lv, Yuan-Zheng; Huang, Xiao-Huan; Hu, Sheng-li

    2016-03-01

    A new colorimetric probe 1 based on rhodamine B lactam was developed for naked-eye detection of Cu2 +. The optical feature of 1 for Cu2 + was investigated by UV-vis absorption spectroscopy. Upon the addition of Cu2 +, the 1 displayed a distinct color change from colorless to pink, which can be directly detected by the naked eye. The stoichiometry of 1 to Cu2 + complex was found to be 1:1 and the naked-eye detection limit was determined as low as 2 μM. The results suggest that the probe 1 may provide a convenient method for visual detection of Cu2 + with high sensitivity.

  15. A new rhodamine-based colorimetric chemosensor for naked-eye detection of Cu(2+) in aqueous solution.

    PubMed

    Hu, Yang; Zhang, Jing; Lv, Yuan-Zheng; Huang, Xiao-Huan; Hu, Sheng-li

    2016-03-15

    A new colorimetric probe 1 based on rhodamine B lactam was developed for naked-eye detection of Cu(2+). The optical feature of 1 for Cu(2+) was investigated by UV-vis absorption spectroscopy. Upon the addition of Cu(2+), the 1 displayed a distinct color change from colorless to pink, which can be directly detected by the naked eye. The stoichiometry of 1 to Cu(2+) complex was found to be 1:1 and the naked-eye detection limit was determined as low as 2 μM. The results suggest that the probe 1 may provide a convenient method for visual detection of Cu(2+) with high sensitivity.

  16. ALMA: Millimeter/submillimeter Astronomy at high sensitivity and resolution

    NASA Astrophysics Data System (ADS)

    Wootten, Alwyn; Corder, Stuartt Alan; Iono, Daisuke; Testi, Leonardo

    2015-08-01

    Vigorous and transformative investigation of the millimeter/submillimeter sky at high sensitivity and high resolution has benefitted from the recent completion of the Atacama Large Millimeter/submillimeter Array (ALMA), an effort of 22 countries. ALMA, a versatile interferometric telescope at 5000m elevation in the Atacama Desert of northern Chile, is comprised of sixty-six precision telescopes which may be arrayed over a 16 km extent on the high Chajnantor plain. Owing to its large collecting area of over 6600m^2 and its commodious spectral grasp of 8 GHz of spectrum in dual polarizations within an 84-950 GHz range, ALMA provides astronomers with vastly improved spectroscopic sensitivity. Spatial resolutions of 30 milliarcsec were demonstrated recently, revealing rings within the HL Tau protoplanetary disk, the rotating structure of the asteroid Juno and the molecular structure of the z~3 lensed galaxy SDP.81. The astrometric accuracy even at this early stage of deployment is better than 3 milliarcsec, providing improved ephemerides for the encounter of the New Horizons spacecraft with the Pluto-Charon system. Very long baseline capability is expected to bring microarcsecond imaging to a worldwide array anchored by ALMA with potential for imaging nearby Black Holes on the scales of their Event Horizons.ALMA's huge collecting area has enabled detection of lines of C, N and CO and continuum for characterization of massive complexes near the Era of Recombination. ALMA's sensitivity and resolution have enabledmeasurement of molecular emission through cosmic time from numerous molecules characterizing galactic star-forming regions and tracing their kinematics near active nuclei, starbursts, interacting clouds and quiescent disks. ALMA's sensitivity, resolution and spectral grasp have enabled it to image molecules and dust characterizing circumstellar disks and embedded bodies in protostellar, transition and debris stages of development.ALMA is a partnership of ESO

  17. High-sensitivity 25-μm microbolometer FPAs

    NASA Astrophysics Data System (ADS)

    Murphy, Daniel F.; Ray, Michael; Wyles, Richard; Asbrock, James F.; Lum, Nancy A.; Wyles, Jessica; Hewitt, C.; Kennedy, Adam; Van Lue, David; Anderson, John S.; Bradley, Daryl; Chin, Richard; Kostrzewa, Thomas

    2003-01-01

    Raytheon IR Operations (RIO) has achieved a significant technical breakthrough in uncooled FPAs by reducing the pixel size by a factor of two while maintaining state-of-the-art sensitivity. Raytheon has produced the first high-quality 320×240 microbolometer FPAs wiht 25μm pitch pixels. The 320×240 FPAs have a sensitivity that is comparable to microbolometer FPAs with 50μm pixels. The average NETD value for these FPAs is about 35 mK with an f/1 aperture and oepratin at 30 Hz frame rates. Good pixel operability and excellent image quality have been demonstrated. Pixel operability is greater than 99 percent on some FPAs, and uncorrected responsivity nonconformity is less than 4%. The microbolometer detectors also have a relatively fast thermal time constant of approximately 10 msec. This state-of-the-art performance has been acheived as a result of an advanced micromachining fabrication process. The process allwos maximization of both the thermal isolation and the optical fill-factor. The reduction in pixel size offers several potential benefits for IR systems. For a given system resolution requirement, the 25 μm pixels allow a factor of two reduction in both the focal length and aperture size of the sensor optics. The pixel size reduction facilitates a significant FPA cost reduction since the number of die printed on a wafer can be increased. The pixel size reduction has enabled the development of a large-format 640×480 FPA array. Raytheon has produced arrays with very good sensitivity, operability, and excellent image quality. These FPAs are applicable to wide-field-of-view, long range surveillance and targeting missions. Raytheon is also developing a high performance 160×128 FPA that is designed for applications where miniaturizaitno and temperature invariance are required as well as low cost and low power.

  18. A near infrared colorimetric and fluorometric probe for organophosphorus nerve agent mimics by intramolecular amidation.

    PubMed

    Hu, Xiao-Xiao; Su, Yue-Ting; Ma, Yun-Wei; Zhan, Xin-Qi; Zheng, Hong; Jiang, Yun-Bao

    2015-10-21

    A near infrared probe for sensitive colorimetric and fluorimetric detection of nerve agent mimics, DCP and DCNP, was reported based on the activation of a carboxylic acid group by the mimics to conduct an intramolecular amidation reaction in the heptamethine chromophore, where its absorption or excitation maximum wavelength could be greatly red-shifted by attenuating the electron-donating ability of the amine group in the bridgehead site of heptamethine cyanine.

  19. Direct visualization of lead corona and its nanomolar colorimetric detection using anisotropic gold nanoparticles.

    PubMed

    Dwivedi, Charu; Chaudhary, Abhishek; Gupta, Abhishek; Nandi, Chayan K

    2015-03-11

    The study presents dithiothreitol (DTT) functionalized anisotropic gold nanoparticles (GNP) based colorimetric sensor for detection of toxic lead ions in water. Our results demonstrate the selectivity and sensitivity of the developed sensor over various heavy metal ions with detection limit of ∼9 nM. The mechanism of sensing is explained on the basis of unique corona formation around the DTT functionalized anisotropic GNP.

  20. Coumarin-bearing triarylamine sensitizers with high molar extinction coefficient for dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Zhong, Changjian; Gao, Jianrong; Cui, Yanhong; Li, Ting; Han, Liang

    2015-01-01

    Coumarin unit is introduced into triarylamine and three organic sensitizers are designed and synthesized with triarylamine bearing coumarin moiety as the electron donor, conjugated system containing thiophene unit as the π-bridge, and cyanoacetic acid moiety as the electron acceptor. The light-harvesting capabilities and photovoltaic performance of these dyes are investigated systematically with the comparison of different π-bridges. High molar extinction coefficients are observed in these triarylamine dyes and the photocurrent and photovoltage are increased with the introduction of another thiophene or benzene. Optimal photovoltaic performance (η = 6.24%, Voc = 690 mV, Jsc = 14.33 mA cm-2, and ff = 0.63) is observed in the DSSC based on dye with thiophene-phenyl unit as the π-conjugated bridge under 100 mW cm-2 simulated AM 1.5 G solar irradiation.

  1. Colorimetric and fluorimetric methods for determination of panthenol in cosmetic and pharmaceutical formulation.

    PubMed

    Shehata, Mostafa A M; Tawakkol, Shereen M; Abdel Fattah, Laila E

    2002-02-01

    Two methods are suggested for determination of panthenol. The first is colorimetric method where panthenol is subjected to alkaline hydrolysis; the resulting beta-alanol is allowed to react with vanillin (Duquenois reagent) in presence of McIlvain buffer pH 7.5. The color developed is measured at 406 nm. The linearity range was found to be 50-500 microg/ml while the lower limit of detection was about 10 microg/ml. The second is a sensitive and reliable modified fluorimetric method is also suggested, whereas panthenol, after alkaline hydrolysis is treated with ninhydrin. The fluorescent product was found to have excitation lambda(max) at 385 nm and emission lambda(max) at 465 nm. The method showed high sensitivity with linearity range from 0.01 to 3 microg/ml. The lower limit of detection (LOQ) reached 0.005 microg/ml. Validation of both methods was carried out and the two methods were applied for determination of panthenol in some cosmetic and pharmaceutical formulations.

  2. High-sensitivity acoustic sensors from nanofibre webs

    PubMed Central

    Lang, Chenhong; Fang, Jian; Shao, Hao; Ding, Xin; Lin, Tong

    2016-01-01

    Considerable interest has been devoted to converting mechanical energy into electricity using polymer nanofibres. In particular, piezoelectric nanofibres produced by electrospinning have shown remarkable mechanical energy-to-electricity conversion ability. However, there is little data for the acoustic-to-electric conversion of electrospun nanofibres. Here we show that electrospun piezoelectric nanofibre webs have a strong acoustic-to-electric conversion ability. Using poly(vinylidene fluoride) as a model polymer and a sensor device that transfers sound directly to the nanofibre layer, we show that the sensor devices can detect low-frequency sound with a sensitivity as high as 266 mV Pa−1. They can precisely distinguish sound waves in low to middle frequency region. These features make them especially suitable for noise detection. Our nanofibre device has more than five times higher sensitivity than a commercial piezoelectric poly(vinylidene fluoride) film device. Electrospun piezoelectric nanofibres may be useful for developing high-performance acoustic sensors. PMID:27005010

  3. Highly Sensitive Assay for Measurement of Arenavirus-cell Attachment.

    PubMed

    Klaus, Joseph P; Botten, Jason

    2016-03-02

    Arenaviruses are a family of enveloped RNA viruses that cause severe human disease. The first step in the arenavirus life cycle is attachment of viral particles to host cells. While virus-cell attachment can be measured through the use of virions labeled with biotin, radioactive isotopes, or fluorescent dyes, these approaches typically require high multiplicities of infection (MOI) to enable detection of bound virus. We describe a quantitative (q)RT-PCR-based assay that measures Junin virus strain Candid 1 attachment via quantitation of virion-packaged viral genomic RNA. This assay has several advantages including its extreme sensitivity and ability to measure attachment over a large dynamic range of MOIs without the need to purify or label input virus. Importantly, this approach can be easily tailored for use with other viruses through the use of virus-specific qRT-PCR reagents. Further, this assay can be modified to permit measurement of particle endocytosis and genome uncoating. In conclusion, we describe a simple, yet robust assay for highly sensitive measurement of arenavirus-cell attachment.

  4. High Sensitivity, Low Volume Method to Determine Dissolved Phosphorus

    NASA Astrophysics Data System (ADS)

    Haberer, J. L.; Brandes, J. A.

    2001-12-01

    A high sensitivity, low volume method was developed to determine nanomolar concentrations of soluble reactive phosphorus (SRP) using reverse phase HPLC. The technique in determining SRP involved using methods from Strickland and Parsons, 1972 and Karl and Tien, 1992. Various techniques for improving blanks and sensitivity will be discussed. The method was applied to seawater and freshwater samples taken from the estuarine Nueces Delta system, Texas, two sites in the Gulf of Mexico, and within two upland (2400 m) forest catchments in the Peruvian Andes. One catchment was partially deforested within the last 3 years, while the other has remained untouched. Samples in the Gulf of Mexico were taken at a series of coastal and open water stations at various depths. Samples in each of the two upland forest catchments in Peru were obtained at 33.3 m distance intervals along a 100 m reach. Samples were taken in the Nueces River, Texas upland from a marsh estuary and from high and low regions of the marsh. Comparisons are made between the forest catchment sites in addition to comparisons made in the Nueces marsh estuary/river system. Depth profiles of SRP in the Gulf of Mexico are established. Future studies should be conducted to investigate phosphate in sediment pore waters. This method has many potential applications, is scalable across a wide range of sample volumes, and can be automated.

  5. Highly sensitive reduced graphene oxide microelectrode array sensor.

    PubMed

    Ng, Andrew M H; Kenry; Teck Lim, Chwee; Low, Hong Yee; Loh, Kian Ping

    2015-03-15

    Reduced graphene oxide (rGO) has been fabricated into a microelectrode array (MEA) using a modified nanoimprint lithography (NIL) technique. Through a modified NIL process, the rGO MEA was fabricated by a self-alignment of conducting Indium Tin Oxide (ITO) and rGO layer without etching of the rGO layer. The rGO MEA consists of an array of 10μm circular disks and microelectrode signature has been found at a pitch spacing of 60μm. The rGO MEA shows a sensitivity of 1.91nAμm(-1) to dopamine (DA) without the use of mediators or functionalization of the reduced graphene oxide (rGO) active layer. The performance of rGO MEA remains stable when tested under highly resistive media using a continuous flow set up, as well as when subjecting it to mechanical stress. The successful demonstration of NIL for fabricating rGO microelectrodes on flexible substrate presents a route for the large scale fabrication of highly sensitive, flexible and thin biosensing platform.

  6. High sensitivity micro-elastometry: applications in blood coagulopathy.

    PubMed

    Wu, Gongting; Krebs, Charles R; Lin, Feng-Chang; Wolberg, Alisa S; Oldenburg, Amy L

    2013-10-01

    Highly sensitive methods for the assessment of clot structure can aid in our understanding of coagulation disorders and their risk factors. Rapid and simple clot diagnostic systems are also needed for directing treatment in a broad spectrum of cardiovascular diseases. Here we demonstrate a method for micro-elastometry, named resonant acoustic spectroscopy with optical vibrometry (RASOV), which measures the clot elastic modulus (CEM) from the intrinsic resonant frequency of a clot inside a microwell. We observed a high correlation between the CEM of human blood measured by RASOV and a commercial thromboelastograph (TEG), (R = 0.966). Unlike TEG, RASOV requires only 150 μL of sample and offers improved repeatability. Since CEM is known to primarily depend upon fibrin content and network structure, we investigated the CEM of purified clots formed with varying amounts of fibrinogen and thrombin. We found that RASOV was sensitive to changes of fibrinogen content (0.5-6 mg/mL), as well as to the amount of fibrinogen converted to fibrin during clot formation. We then simulated plasma hypercoagulability via hyperfibrinogenemia by spiking whole blood to 150 and 200% of normal fibrinogen levels, and subsequently found that RASOV could detect hyperfibrinogenemia-induced changes in CEM and distinguish these conditions from normal blood.

  7. High Sensitivity Micro-Elastometry: Applications in Blood Coagulopathy

    PubMed Central

    Wu, Gongting; Krebs, Charles R.; Lin, Feng-Chang; Wolberg, Alisa S.; Oldenburg, Amy L.

    2013-01-01

    Highly sensitive methods for the assessment of clot structure can aid in our understanding of coagulation disorders and their risk factors. Rapid and simple clot diagnostic systems are also needed for directing treatment in a broad spectrum of cardiovascular diseases. Here we demonstrate a method for micro-elastometry, named Resonant Acoustic Spectroscopy with Optical Vibrometry (RASOV), which measures the clot elastic modulus (CEM) from the intrinsic resonant frequency of a clot inside a microwell. We observed a high correlation between the CEM of human blood measured by RASOV and a commercial Thromboelastograph (TEG), (R=0.966). Unlike TEG, RASOV requires only 150 μL of sample and offers improved repeatability. Since CEM is known to primarily depend upon fibrin content and network structure, we investigated the CEM of purified clots formed with varying amounts of fibrinogen and thrombin. We found that RASOV was sensitive to changes of fibrinogen content (0.5–6 mg/mL), as well as to the amount of fibrinogen converted to fibrin during clot formation. We then simulated plasma hypercoagulability via hyperfibrinogenemia by spiking whole blood to 150% and 200% of normal fibrinogen levels, and subsequently found that RASOV could detect hyperfibrinogenemia-induced changes in CEM and distinguish these conditions from normal blood. PMID:23649979

  8. Highly sensitive biosensors based on all-dielectric nanoresonators.

    PubMed

    Bontempi, Nicolò; Chong, Katie E; Orton, Henry W; Staude, Isabelle; Choi, Duk-Yong; Alessandri, Ivano; Kivshar, Yuri S; Neshev, Dragomir N

    2017-04-13

    Biosensing based on nanophotonic structures has shown a great potential for cost-efficient, high-speed and compact personal medical diagnostics. While plasmonic nanosensors offer high sensitivity, their intrinsically restricted resonance quality factors and strong heating due to metal absorption impose severe limitations on real life applications. Here, we demonstrate an all-dielectric sensing platform based on silicon nanodisks with strong optically-induced magnetic resonances, which are able to detect a concentration of streptavidin of as low as 10(-10) M (mol L(-1)) or 5 ng mL(-1), thus pushing the current detection limit by at least two orders of magnitudes. Our study suggests a new direction in biosensing based on bio-compatible, non-toxic, robust and low-loss dielectric nanoresonators with potential applications in medicine, including disease diagnosis and drug detection.

  9. Hydrophilic Packaging of Iron Oxide Nanoclusters for Highly Sensitive Imaging

    PubMed Central

    Smith, Cartney E.; Ernenwein, Dawn; Shkumatov, Artem; Clay, Nicholas; Lee, JuYeon; Melhem, Molly; Misra, Sanjay; Zimmerman, Steven C.; Kong, Hyunjoon

    2015-01-01

    Superparamagnetic iron oxide nanoparticles (SPIONs) are used as imaging probes to provide contrast in magnetic resonance images. Successful use of SPIONs in targeted applications greatly depends on their ability to generate contrast, even at low levels of accumulation, in the tissue of interest. In the present study, we report that SPION nanoclusters packaged to a controlled size by a hyperbranched polyglycerol (HPG) can target tissue defects and have a high relaxivity of 719 mM−1s−1, which was close to their theoretical maximal limit. The resulting nanoclusters were able to identify regions of defective vasculature in an ischemic murine hindlimb using MRI with iron doses that were 5–10 fold lower than those typically used in preclinical studies. Such high relaxivity was attributed to the molecular architecture of HPG, which mimics that of the water retentive polysaccharide, glycogen. The results of this study will be broadly useful in sensitive imaging applications. PMID:26291408

  10. Design of a charge sensitive preamplifier on high resistivity silicon

    SciTech Connect

    Radeka, V.; Rehak, P.; Rescia, S.; Gatti, E.; Longoni, A.; Sampietro, M.; Holl, P.; Strueder, L.; Kemmer, J.

    1987-01-01

    A low noise, fast charge sensitive preamplifier was designed on high resistivity, detector grade silicon. It is built at the surface of a fully depleted region of n-type silicon. This allows the preamplifier to be placed very close to a detector anode. The preamplifier uses the classical input cascode configuration with a capacitor and a high value resistor in the feedback loop. The output stage of the preamplifier can drive a load up to 20pF. The power dissipation of the preamplifier is 13mW. The amplifying elements are ''Single Sided Gate JFETs'' developed especially for this application. Preamplifiers connected to a low capacitance anode of a drift type detector should achieve a rise time of 20ns and have an equivalent noise charge (ENC), after a suitable shaping, of less than 50 electrons. This performance translates to a position resolution better than 3..mu..m for silicon drift detectors. 6 refs., 9 figs.

  11. Sensitivity study of reliable, high-throughput resolution metricsfor photoresists

    SciTech Connect

    Anderson, Christopher N.; Naulleau, Patrick P.

    2007-07-30

    The resolution of chemically amplified resists is becoming an increasing concern, especially for lithography in the extreme ultraviolet (EUV) regime. Large-scale screening and performance-based down-selection is currently underway to identify resist platforms that can support shrinking feature sizes. Resist screening efforts, however, are hampered by the absence of reliable resolution metrics that can objectively quantify resist resolution in a high-throughput fashion. Here we examine two high-throughput metrics for resist resolution determination. After summarizing their details and justifying their utility, we characterize the sensitivity of both metrics to two of the main experimental uncertainties associated with lithographic exposure tools, namely: limited focus control and limited knowledge of optical aberrations. For an implementation at EUV wavelengths, we report aberration and focus limited error bars in extracted resolution of {approx} 1.25 nm RMS for both metrics making them attractive candidates for future screening and down-selection efforts.

  12. Coherent Raman Scattering: Methods Towards Imaging with High Sensitivity

    NASA Astrophysics Data System (ADS)

    Bachler, Brandon Richard

    Coherent Raman spectroscopy is a powerful tool for molecular identification. For imaging applications, Raman spectroscopy techniques have offered a way of achieving endogenous chemical contrast without the need for fluorescent labeling. Increasing the sensitivity of Raman scattering microscopy is vital to performing high speed, chemically selective imaging. This thesis presents three experiments with the ultimate goal of increasing the sensitivity and quantifying limitations of different Raman techniques. The first experiment is a comparison of spontaneous and coherent Raman signal strengths under biological imaging conditions. While it is commonly stated in the literature that coherent Raman techniques provide orders of magnitude higher signal than spontaneous Raman, such a comparison has not been done under the low concentration, low excitation power conditions relevant for biological imaging. We determine a critical power above which coherent Raman methods provide higher signal and below which spontaneous Raman methods provide higher sensitivity. Contrary to what is commonly stated in the literature, spontaneous Raman can provide higher signal levels under common biological imaging conditions. The second experiment is a demonstration of the first multiplexed Raman-induced Kerr effect (BIKES) microscopy setup to date. We compare the signal-to-noise ratios between femtosecond stimulated Raman (FSRS) and RIKES for spectroscopy applications in solution and for microscopy applications with polystyrene beads. We find that for our samples, RIKES consistently provides a higher signal-to-noise ratio than FSRS for both applications. We also use RIKES microscopy to map out the distribution of cytoplasm in onion cells. Finally, a surface-enhanced Raman experiment is performed to observe and compare highly enhanced signals for spontaneous and coherent Raman spectroscopy. We use a commercial SERS substrate and observe significantly enhanced spontaneous Raman signals from

  13. Multisite comparison of high-sensitivity multiplex cytokine assays.

    PubMed

    Breen, Elizabeth Crabb; Reynolds, Sandra M; Cox, Christopher; Jacobson, Lisa P; Magpantay, Larry; Mulder, Candice B; Dibben, Oliver; Margolick, Joseph B; Bream, Jay H; Sambrano, Elise; Martínez-Maza, Otoniel; Sinclair, Elizabeth; Borrow, Persephone; Landay, Alan L; Rinaldo, Charles R; Norris, Philip J

    2011-08-01

    The concentrations of cytokines in human serum and plasma can provide valuable information about in vivo immune status, but low concentrations often require high-sensitivity assays to permit detection. The recent development of multiplex assays, which can measure multiple cytokines in one small sample, holds great promise, especially for studies in which limited volumes of stored serum or plasma are available. Four high-sensitivity cytokine multiplex assays on a Luminex (Bio-Rad, BioSource, Linco) or electrochemiluminescence (Meso Scale Discovery) platform were evaluated for their ability to detect circulating concentrations of 13 cytokines, as well as for laboratory and lot variability. Assays were performed in six different laboratories utilizing archived serum from HIV-uninfected and -infected subjects from the Multicenter AIDS Cohort Study (MACS) and the Women's Interagency HIV Study (WIHS) and commercial plasma samples spanning initial HIV viremia. In a majority of serum samples, interleukin-6 (IL-6), IL-8, IL-10, and tumor necrosis factor alpha were detectable with at least three kits, while IL-1β was clearly detected with only one kit. No single multiplex panel detected all cytokines, and there were highly significant differences (P < 0.001) between laboratories and/or lots with all kits. Nevertheless, the kits generally detected similar patterns of cytokine perturbation during primary HIV viremia. This multisite comparison suggests that current multiplex assays vary in their ability to measure serum and/or plasma concentrations of cytokines and may not be sufficiently reproducible for repeated determinations over a long-term study or in multiple laboratories but may be useful for longitudinal studies in which relative, rather than absolute, changes in cytokines are important.

  14. Highly sensitive flow-injection chemiluminescence determination of pyrogallol compounds

    NASA Astrophysics Data System (ADS)

    Kanwal, Shamsa; Fu, Xiaohong; Su, Xingguang

    2009-12-01

    A highly sensitive flow-injection chemiluminescent method for the direct determination of pyrogallol compounds has been developed. Proposed method is based on the enhanced effect of pyrogallol compounds on the chemiluminescence signals of KMnO 4-H 2O 2 system in slightly alkaline medium. Three important pyrogallol compounds, pyrogallic acid, gallic acid and tannic acid, have been detected by this method, and the possible mechanism of the CL reaction is also discussed. The proposed method is simple, convenient, rapid (60 samples h -1), and sensitive, has a linear range of 8 × 10 -10 mol L -1 to 1 × 10 -5 mol L -1, for pyrogallic acid, with a detection limit of 6 × 10 -11 mol L -1, 4 × 10 -8 mol L -1 to 5 × 10 -3 mol L -1 for gallic acid with a detection limit of 9 × 10 -10 mol L -1, and 8 × 10 -8 mol L -1 to 5 × 10 -2 mol L -1 for tannic acid, with a detection limit of 2 × 10 -9 mol L -1, respectively. The relative standard deviation (RSD, n = 15) was 0.8, 1.1 and 1.3% for 5 × 10 -6 mol L -1 pyrogallic acid, gallic acid and tannic acid, respectively. The proposed method was successfully applied to the determination of pyrogallol compounds in tea and coffee samples.

  15. A highly sensitive fiber Bragg grating diaphragm pressure transducer

    NASA Astrophysics Data System (ADS)

    Allwood, Gary; Wild, Graham; Lubansky, Alex; Hinckley, Steven

    2015-10-01

    In this work, a novel diaphragm based pressure transducer with high sensitivity is described, including the physical design structure, in-depth analysis of optical response to changes in pressure, and a discussion of practical implementation and limitations. A flat circular rubber membrane bonded to a cylinder forms the body of the transducer. A fiber Bragg grating bonded to the center of the diaphragm structure enables the fractional change in pressure to be determined by analyzing the change in Bragg wavelength of the reflected spectra. Extensive evaluation of the physical properties and optical characteristics of the transducer has been performed through experimentation, and modeling using small deformation theory. The results show the transducer has a sensitivity of 0.116 nm/kPa, across a range of 15 kPa. Ultra-low cost interrogation of the optical signal was achieved through the use of an optically mismatched Bragg grating acting as an edge filter to convert the spectral change into an intensity change. A numerical model of the intensity based interrogation was implemented in order to validate the experimental results. Utilizing this interrogation technique and housing both the sensing and reference Bragg gratings within the main body of the transducer means it is effectively temperature insensitive and easily connected to electronic systems.

  16. New application of superconductors: High sensitivity cryogenic light detectors

    NASA Astrophysics Data System (ADS)

    Cardani, L.; Bellini, F.; Casali, N.; Castellano, M. G.; Colantoni, I.; Coppolecchia, A.; Cosmelli, C.; Cruciani, A.; D'Addabbo, A.; Di Domizio, S.; Martinez, M.; Tomei, C.; Vignati, M.

    2017-02-01

    In this paper we describe the current status of the CALDER project, which is developing ultra-sensitive light detectors based on superconductors for cryogenic applications. When we apply an AC current to a superconductor, the Cooper pairs oscillate and acquire kinetic inductance, that can be measured by inserting the superconductor in a LC circuit with high merit factor. Interactions in the superconductor can break the Cooper pairs, causing sizable variations in the kinetic inductance and, thus, in the response of the LC circuit. The continuous monitoring of the amplitude and frequency modulation allows to reconstruct the incident energy with excellent sensitivity. This concept is at the basis of Kinetic Inductance Detectors (KIDs) that are characterized by natural aptitude to multiplexed read-out (several sensors can be tuned to different resonant frequencies and coupled to the same line), resolution of few eV, stable behavior over a wide temperature range, and ease in fabrication. We present the results obtained by the CALDER collaboration with 2×2 cm2 substrates sampled by 1 or 4 Aluminum KIDs. We show that the performances of the first prototypes are already competitive with those of other commonly used light detectors, and we discuss the strategies for a further improvement.

  17. Sensitivity of once-shocked, weathered high explosives

    SciTech Connect

    Williams, K.L.; Harris, B.W.

    1998-07-01

    Effects caused by stimulating once-shocked, weathered high explosives (OSW-HE) are investigated. The sensitivity of OSW-HE to mechanical stimuli was determined using standard industry tests. Some initial results are given. Pieces of OSW-HE were collected from active and inactive firing sites and from an area surrounding a drop tower at Los Alamos where skid and spigot tests were done. Samples evaluated were cast explosives or plastic bonded explosive (PBX) formulations containing cyclotrimethylenetrinitramine (RDX), cyclotetramethylene tetranitramine (HMX), 2,4,6-trinitrotoluene (TNT), mock or inert HE [tris(beta-chloroethyl)phosphate (CEF)], barium nitrate, cyanuric acid, talc, and Kel-F. Once-shocked, weathered LX-10 Livermore explosive [HMX/Viton A, (95/5 wt %)], PBX 9011 [HMX/Estane, (90/10 wt %)], PBX 9404 [HMX/nitrocellulose, tris(beta-chloroethyl) phosphate, (94/3/3 wt %)], Composition B or cyclotol (TNT/RDX explosives), and PBX 9007 (90% RDX, 9.1% styrene, 0.5% dioctyl phthalate, and 0.45 resin) were subjected to the hammer test, the drop-weight impact sensitivity test, differential thermal analysis (DTA), the spark test, the Henkin`s critical temperature test, and the flame test. Samples were subjected to remote, wet cutting and drilling; remote, liquid-nitrogen-cooled grinding and crushing; and scanning electron microscope (SEM) surface analyses for morphological changes.

  18. Luminescent Lanthanide Reporters for High-Sensitivity Novel Bioassays.

    SciTech Connect

    Anstey, Mitchell R.; Fruetel, Julia A.; Foster, Michael E.; Hayden, Carl C.; Buckley, Heather L.; Arnold, John

    2013-09-01

    Biological imaging and assay technologies rely on fluorescent organic dyes as reporters for a number of interesting targets and processes. However, limitations of organic dyes such as small Stokes shifts, spectral overlap of emission signals with native biological fluorescence background, and photobleaching have all inhibited the development of highly sensitive assays. To overcome the limitations of organic dyes for bioassays, we propose to develop lanthanide-based luminescent dyes and demonstrate them for molecular reporting applications. This relatively new family of dyes was selected for their attractive spectral and chemical properties. Luminescence is imparted by the lanthanide atom and allows for relatively simple chemical structures that can be tailored to the application. The photophysical properties offer unique features such as narrow and non-overlapping emission bands, long luminescent lifetimes, and long wavelength emission, which enable significant sensitivity improvements over organic dyes through spectral and temporal gating of the luminescent signal.Growth in this field has been hindered due to the necessary advanced synthetic chemistry techniques and access to experts in biological assay development. Our strategy for the development of a new lanthanide-based fluorescent reporter system is based on chelation of the lanthanide metal center using absorbing chromophores. Our first strategy involves "Click" chemistry to develop 3-fold symmetric chelators and the other involves use of a new class of tetrapyrrole ligands called corroles. This two-pronged approach is geared towards the optimization of chromophores to enhance light output.

  19. High-sensitivity quantitative phase microcopy (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Zhou, Renjie; Kuang, Cuifang; Hosseini, Poorya; Chowdhary, Ravi; Yaqoob, Zahid; So, Peter T. C.

    2016-03-01

    In the past decade, various quantitative phase microscopy (QPM) techniques have emerged, driven by the need to study biological samples non-invasively. However, the fundamental limit for phase noise is scarcely discussed in the literature. In a typically off-axis phase microscope system, the phase noise is limited to a few milliradians using a moderate camera. Common-path QPMs offer much reduced phase noise compared to typical Mach-Zehnder-based systems. However, further scaling down the phase noise becomes difficult. Here we propose a high-sensitivity common-path QPM that promises to reduce the phase noise by a factor of 10 (assuming the mechanical noise is negligible). This is achieved by a specifically designed signal filter, leaving only the subtle phase fluctuations coming from the dynamics sample scattering. By working at photon shot-noise limited detection, we can magnify the subtle phase contrast which is proportional to the camera well depth. We expect this system to have the height sensitivity similar to an atomic force microcopy, while measuring biological structures with a full field of view in a single-shot. We plan to use this system to study cell dynamics, particularly lamellipodial height fluctuations as well as stiffer cell membrane fluctuations.

  20. Biologically green synthesized silver nanoparticles as a facile and rapid label-free colorimetric probe for determination of Cu2 + in water samples

    NASA Astrophysics Data System (ADS)

    Basiri, Sedigheh; Mehdinia, Ali; Jabbari, Ali

    2017-01-01

    A highly sensitive and cost-effective colorimetric sensing platform for the selective trace analysis of Cu2 + ions was developed based on the accelerated etching of Riboflavin stabilized silver nanoparticles (R/AgNPs). The R/AgNPs were prepared from the Cucumis melo juice by a green chemistry approach. The bio-synthesized AgNPs were studied by UV-Vis spectroscopy and showed an intense absorption band at 404 nm that were further confirmed by FTIR and EDS analysis. Simultaneous presence of Cu2 + and thiosulfate decreased the absorption intensity of green synthesized AgNPs which resulted in sensitive and selective determination of Cu2 +. The selectivity of R/AgNPs detection system for Cu2 + was excellent. Furthermore, the method offered a wide linear detection range from 5 nM to 100 nM with a detection limit of 1.12 nM. Surprisingly, it was a quick approach and the decolorization of the R/AgNPs solutions occurred only within 5 min. Our results clearly indicate these R/AgNPs could be used as an efficient probe for the colorimetric sensing of Cu2 + in environmental water samples.

  1. Importance of nanoparticle size in colorimetric and SERS-based multimodal trace detection of Ni(II) ions with functional gold nanoparticles.

    PubMed

    Krpetić, Zeljka; Guerrini, Luca; Larmour, Iain A; Reglinski, John; Faulds, Karen; Graham, Duncan

    2012-03-12

    Colorimetric detection of analytes using gold nanoparticles along with surface-enhanced Raman spectroscopy (SERS) are areas of intense research activity since they both offer sensing of very low concentrations of target species. Multimodal detection promotes the simultaneous detection of a sample by a combination of different techniques; consequently, surface chemistry design in the development of multimodal nanosensors is important for rapid and sensitive evaluation of the analytes by diverse analytical methods. Herein it is shown that nanoparticle size plays an important role in the design of functional nanoparticles for colorimetric and SERS-based sensing applications, allowing controlled nanoparticle assembly and tunable sensor response. The design and preparation of robust nanoparticle systems and their assembly is reported for trace detection of Ni(II) ions as a model system in an aqueous solution. The combination of covalently attached nitrilotriacetic acid moieties along with the L-carnosine dipeptide on the nanoparticle surface represents a highly sensitive platform for rapid and selective detection of Ni(II) ions. This systematic study demonstrates that significantly lower detection limits can be achieved by finely tuning the assembly of gold nanoparticles of different core sizes. The results clearly demonstrate the feasibility and usefulness of a multimodal approach.

  2. Kinetic method for determination of ascorbic acid on flow injection system by using its catalytic effect on the complexation reaction of an ultra sensitive colorimetric reagent of porphyrin with Cu(II)

    NASA Astrophysics Data System (ADS)

    Liu, Jianhua; Itoh, Jun-Ichi

    2007-06-01

    A kinetic method performed on a flow injection system is described for the determination of ascorbic acid by using its catalytic effect on the complexation reaction of Cu(II) with 5,10,15,20-tetrakis(4- N-trimethyl-aminophenyl)porphyrin. The characteristic spectrum of porphyrin (Soret band), which shows intense absorption around 400 nm ( ɛ > 2.0 × 10 5 cm -1 M -1), was used first time for determining ascorbic acid. By incorporating the complexation reaction into a flow injection system, ascorbic acid could be determined either over a broad dynamic range of 0.1-1000 μg/ml or at a trace level below 5 ng/ml. Good repeatability was also achieved by testing a working standard of 0.1 μg/ml with 10 injections at a throughput of 35 h -1, obtaining a relative standard deviation of 0.11%. Substances like amino acids, vitamins, sugars, organic acids and metal ions, showed no or little interference even present at high concentrations. The method was validated in the determination of ascorbic acid contents of some commercially available soft drinks by comparison with the official 2,6-dichloroindophenol method with reasonable agreement.

  3. Highly sensitive biological sensor based on photonic crystal fiber

    NASA Astrophysics Data System (ADS)

    Azzam, Shaimaa I. H.; Hameed, Mohamed F.; Obayya, S. S. A.

    2014-05-01

    A photonic crystal fiber (PCF) surface plasmon resonance (SPR) based sensor is proposed and analysed. The proposed sensor consists of microuidic slots enclosing a dodecagonal layer of air holes cladding and a central air hole. The sensor can perform analyte detection using both HEx 11 and HEy 11 modes with a relatively high sensitivities up to 4000 nm=RIU and 3000 nm=RIU and resolutions of 2.5×10-5 RIU-1 and 3.33×10-5 RIU-1 with HEx11 and HEy11, respectively, with regards to spectral interrogation which to our knowledge are higher than those reported in the literature. Moreover, the structure of the suggested sensor is simple with no fabrication complexities which makes it easy to fabricate with standard PCF fabrication technologies.

  4. Versatile, high-sensitivity faraday cup array for ion implanters

    DOEpatents

    Musket, Ronald G.; Patterson, Robert G.

    2003-01-01

    An improved Faraday cup array for determining the dose of ions delivered to a substrate during ion implantation and for monitoring the uniformity of the dose delivered to the substrate. The improved Faraday cup array incorporates a variable size ion beam aperture by changing only an insertable plate that defines the aperture without changing the position of the Faraday cups which are positioned for the operation of the largest ion beam aperture. The design enables the dose sensitivity range, typically 10.sup.11 -10.sup.18 ions/cm.sup.2 to be extended to below 10.sup.6 ions/cm.sup.2. The insertable plate/aperture arrangement is structurally simple and enables scaling to aperture areas between <1 cm.sup.2 and >750 cm.sup.2, and enables ultra-high vacuum (UHV) applications by incorporation of UHV-compatible materials.

  5. Radiation noise in a high sensitivity star sensor

    NASA Technical Reports Server (NTRS)

    Parkinson, J. B.; Gordon, E.

    1972-01-01

    An extremely accurate attitude determination was developed for space applications. This system uses a high sensitivity star sensor in which the photomultiplier tube is subject to noise generated by space radiations. The space radiation induced noise arises from trapped electrons, solar protons and other ionizing radiations, as well as from dim star background. The solar activity and hence the electron and proton environments are predicted through the end of the twentieth century. The available data for the response of the phototube to proton, electron, gamma ray, and bremsstrahlung radiations are reviewed and new experimental data is presented. A simulation was developed which represents the characteristics of the effect of radiations on the star sensor, including the non-stationarity of the backgrounds.

  6. Broadband terahertz imaging with highly sensitive silicon CMOS detectors.

    PubMed

    Schuster, Franz; Coquillat, Dominique; Videlier, Hadley; Sakowicz, Maciej; Teppe, Frédéric; Dussopt, Laurent; Giffard, Benoît; Skotnicki, Thomas; Knap, Wojciech

    2011-04-11

    This paper investigates terahertz detectors fabricated in a low-cost 130 nm silicon CMOS technology. We show that the detectors consisting of a nMOS field effect transistor as rectifying element and an integrated bow-tie coupling antenna achieve a record responsivity above 5 kV/W and a noise equivalent power below 10 pW/Hz(0.5) in the important atmospheric window around 300 GHz and at room temperature. We demonstrate furthermore that the same detectors are efficient for imaging in a very wide frequency range from ~0.27 THz up to 1.05 THz. These results pave the way towards high sensitivity focal plane arrays in silicon for terahertz imaging.

  7. Magnetic probe array with high sensitivity for fluctuating field.

    PubMed

    Kanamaru, Yuki; Gota, Hiroshi; Fujimoto, Kayoko; Ikeyama, Taeko; Asai, Tomohiko; Takahashi, Tsutomu; Nogi, Yasuyuki

    2007-03-01

    A magnetic probe array is constructed to measure precisely the spatial structure of a small fluctuating field included in a strong confinement field that varies with time. To exclude the effect of the confinement field, the magnetic probes consisting of figure-eight-wound coils are prepared. The spatial structure of the fluctuating field is obtained from a Fourier analysis of the probe signal. It is found that the probe array is more sensitive to the fluctuating field with a high mode number than that with a low mode number. An experimental demonstration of the present method is attempted using a field-reversed configuration plasma, where the fluctuating field with 0.1% of the confinement field is successfully detected.

  8. Highly sensitive on-site detection of glucose in human urine with naked eye based on enzymatic-like reaction mediated etching of gold nanorods.

    PubMed

    Zhang, Zhiyang; Chen, Zhaopeng; Cheng, Fangbin; Zhang, Yaowen; Chen, Lingxin

    2017-03-15

    Based on enzymatic-like reaction mediated etching of gold nanorods (GNRs), an ultrasensitive visual method was developed for on-site detection of urine glucose. With the catalysis of MoO4(2)(-), GNRs were efficiently etched by H2O2 which was generated by glucose-glucose oxidase enzymatic reaction. The etching of GNRs lead to a blue-shift of logitudinal localized surface plasmon resonance of GNRs, accompanied by an obvious color change from blue to red. The peak-shift and the color change can be used for detection of glucose by the spectrophotometer and the naked eyes. Under optimal condition, an excellent sensitivity toward glucose is obtained with a detection limit of 0.1μM and a visual detection limit of 3μM in buffer solution. Benefiting from the high sensitivity, the successful colorimetric detection of glucose in original urine samples was achieved, which indicates the practical applicability to the on-site determination of urine glucose.

  9. High sensitivity moiré interferometry with compact achromatic interferometry

    NASA Astrophysics Data System (ADS)

    Czarnek, Robert

    Experimental observations and measurements are the sources of information essential for correct development of mathematical models of real structural materials. Moiré interferometry offers high sensitivity in full-field measurements of in-plane displacements on the surface of a specimen. Although it is a powerful method in experimental stress analysis, it has some shortcomings. One is that existing systems require highly coherent light. The only sufficient source of light for this application is a long cavity laser, which is relatively expensive and at best cumbersome. Another shortcoming is that measurements must be performed in a vibration-free environment, such as that found on a holographic table. These requirements limit the use of existing moiré interferometers to a holographic laboratory. In this paper a modified concept of compensation is presented, which permits the use of a chromatic source of light in a compact moiré system. The compensator provides order in the angles of incident light for each separate wavelength, so that the virtual reference grating created by each wavelength in a continuous spectrum is identical in frequency and spatial position. The result is a virtual reference grating that behaves exactly like that created in coherent light. With this development the use of a laser diode, which is a non-coherent light source of tiny dimensions, becomes practical. The special configuration of the optics that create the virtual grating allows its synchronization with the specimen grating and leads to an interferometer design that is relatively insensitive to the vibrations found in a mechanical testing laboratory. Sensitivity to relative motion is analyzed theoretically. This development provides the oppurtunity to apply moiré interferometry to solid mechanics problems that cannot be studied in an optics laboratory. Experimental verification of the optical concepts is provided. A compact moiré interferometer based on the presented idea was

  10. An unusual red-to-brown colorimetric sensing method for ultrasensitive silver(I) ion detection based on a non-aggregation of hyperbranched polyethylenimine derivative stabilized gold nanoparticles.

    PubMed

    Liu, Yi; Liu, Yang; Li, Zhongfa; Liu, Junshen; Xu, Li; Liu, Xunyong

    2015-08-07

    Here we have developed a facile and rapid colorimetric method for the sensitive and selective detection of Ag(+) based on the non-aggregation of gold nanoparticles (Au NPs) capped with hyperbranched polyethylenimine derivatives. In the detection process, an unusual colour change from red to brown was observed due to the formation of Au-Ag core-shell nanoparticles, which was more sensitive than that of the usual colorimetric assays (red to blue) based on the aggregation of Au NPs. After the colour changed, the non-aggregation-based Au-Ag core-shell nanomaterials did not aggregate further and could remain stable for a long time, which was convenient to record, detect and observe. The sensing probe exhibited a drastically long observing time for detecting Ag(+) owing to the stability of the Au-Ag core-shell non-aggregates, high sensitivity with a low detection limit of 8.76 nM by the naked eye and 1.09 nM by using a UV-vis spectrophotometer and a good linear relationship within the range from 1.09 to 109 nM. The colour change of the system is very fast, occurring within 1 to 2 minutes. Moreover, the proposed method also showed a remarkably high selectivity toward Ag(+) and was successfully used in tap water and drinking water samples. Therefore, this unusual colorimetric assay based on the non-aggregation of Au NPs has a great potential as a simple, rapid, sensitive and selective detection method for the detection of Ag(+).

  11. A novel aptasensor for the colorimetric detection of S. typhimurium based on gold nanoparticles.

    PubMed

    Ma, Xiaoyuan; Song, Liangjing; Zhou, Nixin; Xia, Yu; Wang, Zhouping

    2017-03-20

    A simple, fast and convenient colorimetric aptasensor was fabricated for the detection of Salmonella typhimurium (S. typhimurium) which was based on the color change effect of gold nanoparticles (GNPs). S. typhimurium is one of the most common causes of food-associated disease. Aptamers with specific recognition toward S. typhimurium was modified to the surface of prepared GNPs. They play a role for the protection of GNPs from aggregation toward high concentrations of NaCl. With the addition of S. typhimurium, aptamers preferably combined to S. typhimurium and the protection effect was broken. With more S. typhimurium, more aptamers detached from GNPs. In such a situation, the exposed GNPs would aggregated to some extent with the addition of NaCl. The color changed from red, purple to blue which could be characterized by UV-Vis spectrophotometer. The absorbance spectra of GNPs redshifted constantly and the intensity ratio of A700/A521 changed regularly. This could be calculated for the basis of quantitative detection of S. typhimurium from 10(2)cfu/mL to 10(7)cfu/mL. The obtained linear correlation equation was y=0.1946x-0.2800 (R(2)=0.9939) with a detection limit as low as 56cfu/mL. This method is simple and rapid, results in high sensitivity and specificity, and can be used to detect actual samples.

  12. A simple "clickable" biosensor for colorimetric detection of copper(II) ions based on unmodified gold nanoparticles.

    PubMed

    Shen, Qinpeng; Li, Wenhua; Tang, Shiyun; Hu, Yufang; Nie, Zhou; Huang, Yan; Yao, Shouzhuo

    2013-03-15

    A novel colorimetric copper(II) biosensor has been developed based on the high specificity of alkyne-azide click reaction to the catalysis of copper ions and unmodified gold nanoparticles (AuNPs) as the signal reporter. The clickable DNA probe consists of two parts: an azide group-modified double-stranded DNA (dsDNA) hybrid with an elongated tail and a short alkyne-modified single-stranded DNA (ssDNA). Because of low melting temperature of the short ssDNA, these two parts are separated in the absence of Cu(2+). Copper ion-induced azide-alkyne click ligation caused a structural change of probe from the separated form to entire dsDNA form. This structural change of probe can be monitored by the unmodified AuNPs via mediating their aggregation with a red-to-blue colorimetric read-out because of the differential ability of ssDNA and dsDNA to protect AuNPs against salt-induced aggregation. Under the optimum conditions, this biosensor can sensitively and specifically detect Cu(2+) with a low detection limit of 250 nM and a linear range of 0.5-10 μM. The method is simple and economic without dual-labeling DNA and AuNPs modification. It is also highly selective for Cu(2+) in the presence of high concentrations of other environmentally relevant metal ions because of the great specificity of the copper-caused alkyne-azide click reaction, which potentially meets the requirement of the detection in real samples.

  13. High-sensitivity (25-um pitch) microbolometer FPAs

    NASA Astrophysics Data System (ADS)

    Murphy, Daniel F.; Ray, Michael; Wyles, Richard; Asbrock, James F.; Lum, Nancy A.; Kennedy, Adam; Wyles, Jessica; Hewitt, C.; Graham, Glen E.; Horikiri, Tad; Anderson, John S.; Bradley, Daryl; Chin, Richard; Kostrzewa, Thomas

    2001-11-01

    RIO has achieved a significant technical breakthrough in uncooled FPAs by reducing the pixel size by a factor of two while maintaining state-of-the-art sensitivity. Raytheon has produced high-quality 320 by 240 micro bolometer FPAs with 25 micrometers pitch pixels. The 320 by 240 FPAs have a sensitivity that is comparable to micro bolometer FPAs with 50 micrometers pixels. The average NETD value for these FPAs is about 35 mK with an f/1 aperture and operating at 30 Hz frame rates. Good pixel operability and excellent image quality have been demonstrated. Pixel operability is greater than 99 percent on some FPAs, and uncorrected responsivity nonuniformity is less than 4 percent. The micro bolometer detectors also have a relatively fast thermal time constant of approximately 10 msec. This state-of-the-art performance has been achieved as a result of an advanced micromachining fabrication process. The process allows maximization of both the thermal isolation and the optical fill-factor. The reduction in pixel size offers several potential benefits for IR systems. For a given system resolution requirement, the 225 micrometers pixels allow a factor of two reduction in both the focal length and aperture size of the sensor optics. The pixel size reduction facilitates a significant FPA cost reduction since the number of die printed on a wafer can be increased. The pixel size reduction has enabled the development of a large-format 640 by 512 FPA array applicable to wide-field-of-view, long range surveillance and targeting missions, and a 160 by 128 array where applications for miniaturization and temperature invariance are required as well as low cost and low power.

  14. 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.

  15. A new, sensitive, high resolution Raman detector based on ionization

    NASA Astrophysics Data System (ADS)

    Smith, B. W.; Omenetto, N.; Winefordner, J. D.

    1989-01-01

    A novel detection method for weak pulsed or cw Raman fluxes is described. The detector is based upon the production of Raman scatter with a tunable pulsed or cw dye laser, collecting a large fraction of the Raman scatter and transferring it efficiently into an ionization detector containing a metal (M) vapor, such as Li. The resonance ionization detector (RID) is simultaneously illuminated by a second dye laser. When the second laser is tuned to an excited state transition of the metal vapor M and when the first laser is at such a wavelength that the Raman scatter appears at the ground state absorption transition of the metal, then a current will be produced in the RID which is proportional to the Raman scatter intensity. Both the production and collection of this current can be made very efficient (approaching 100%) and should result in improved sensitivity compared to conventional dispersive or FT Raman techniques. The new approach should be much less sensitive to scatter, should have a spectral resolution better than 0.1 cm -1 and should allow Raman scatter measurements to be made at wavenumbers below 100 cm -1 and under certain conditions to 0.01 cm -1. The approach should be especially useful in highly scattering environments like Ag-sols in surface enhanced Raman and should be useful for detection of ultratrace levels of drugs and metabolites in biological fluids. The Raman-RID approach should also be useful for resonance Raman since laser scatter and molecular fluorescence should have minimal effects.

  16. High sensitivity dynamic spectral search for flare star radio

    NASA Technical Reports Server (NTRS)

    Abada-Simon, M.; Lecacheux, A.; Louarn, P.; Dulk, G. A.; Belkora, L.; Bookbinder, J. A.; Rosolen, C.

    1994-01-01

    We observed ten well-known flare stars with the Arcibo radio telescope at 1.4 GHz and 5 GHz, using a special observing technique to discriminate between real flares and radio freqeuncy interference. With a high sensitivity of 5.5 K/Jy at 1.4 GHz when averaged over a 50 MHz band, we are able to recognize flux enhancements as weak as approximately 6 mJy above the sky background variations. In about 85 hours of observation, about a dozen bursts were detected, only from AD Leo. All had flux densities lower than 70 mJy, which probably explains their lack of fine structures (except for the strongest one), such as were reported in the literature for stronger flares. Half of the bursts that we recorded are 100% circularly polarized, and half are not circularly polarized. Our results are a first attempt of reliable statistics on dMe flare rates at 1.4 GHz. The high brightness temperatures we infer for the observed bursts are interpreted in terms of coherent emission processes, either the cyclotron maser instability or plasma radiation. Efficiencies are comparable to those of solar or planetary radio emissions in the case of the cyclotron maser, and higher than the solar efficiency in the case of plasma radiation, with the caveat that there are great uncertainties in the coronal model and the source size.

  17. A batteryless temperature sensor based on high temperature sensitive material

    NASA Astrophysics Data System (ADS)

    Bakkali, Asma; Pelegri-Sebastia, José; Laghmich, Youssef; Lyhyaoui, Abdelouahid

    2016-05-01

    The major challenge in wireless sensor networks is the reduction of energy consumption. Passive wireless sensor network is an attractive solution for measuring physical parameters in harsh environment for large range of applications requiring sensing devices with low cost of fabrication, small size and long term measurement stability. Batteryless temperature sensing techniques are an active research field. The approach developed in our work holds a promising future for temperature sensor applications in order to successfully reduce the energy consumption. The temperature sensor presented in this paper is based on the electromagnetic transduction principle using the integration of the high temperature sensitive material into a passive structure. Variation in temperature makes the dielectric constant of this material changing, and such modification induces variation in the resonant frequencies of high-Q whispering-gallery modes (WGM) in the millimeter-wave frequency range. Following the results achieved, the proposed device shows a linear response to the increasing temperature and these variations can be remotely detected from a radar interrogation. Contribution to the topical issue "Materials for Energy Harvesting, Conversion and Storage (ICOME 2015) - Elected submissions", edited by Jean-Michel Nunzi, Rachid Bennacer and Mohammed El Ganaoui

  18. High olfactory sensitivity for dimethyl sulphide in harbour seals

    PubMed Central

    Kowalewsky, Sylvia; Dambach, Martin; Mauck, Björn; Dehnhardt, Guido

    2005-01-01

    Productive areas are patchily distributed at sea and represent important feeding grounds for many marine organisms. Although pinnipeds are known to travel on direct routes and return regularly to particular feeding sites, the environmental information seals use to perform this navigation is as yet unknown. As atmospheric dimethyl sulphide (DMS) has been demonstrated to be a reliable indicator for profitable foraging areas, we tested seals for their ability to smell DMS at concentrations typical for the marine environment. Using a go/no-go response paradigm we determined the DMS detection threshold in two harbour seals (Phoca vitulina vitulina). DMS stimuli from 8.05×108 to 8 pmol (DMS) m−3(air) were tested against a control stimulus using a custom-made olfactometer. DMS-thresholds determined for both seals (20 and 13 pmol m−3) indicate that seals can detect ambient concentrations associated with high primary productivity, e.g. in the North Atlantic. Thus, seals possess an extraordinarily high olfactory sensitivity for DMS, which could provide a sensory basis for identifying or orienting to profitable foraging grounds. PMID:17148339

  19. Comparing standard Bonner spheres and high-sensitivity Bonner cylinders.

    PubMed

    Lee, Kuo-Wei; Yuan, Ming-Chen; Jiang, Shiang-Huei; Sheu, Rong-Jiun

    2014-10-01

    Standard Bonner spheres and proposed high-sensitivity Bonner cylinders were calibrated in a neutron calibration room, using a (252)Cf source. The Bonner sphere system consists of 11 polyethylene (PE) spheres of various diameters and 4 extended spheres that comprise embedded metal shells. Similar to the design of Bonner spheres, a set of Bonner cylinders was assembled using a large cylindrical (3)He tube as the central probe, which was wrapped using various thicknesses of PE. A layer of lead was employed inside one of the PE cylinders to increase the detection efficiency of high-energy neutrons. The central neutron probe used in the Bonner cylinders exhibited an efficiency of ∼17.9 times higher than that of the Bonner spheres. However, compared with the Bonner spheres, the Bonner cylinders are not fully symmetric in their geometry, exhibiting angular dependence in their responses to incoming neutrons. Using a series of calculations and measurements, this study presents a systematic comparison between Bonner spheres and cylinders in terms of their response functions, detection efficiencies, angular dependences and spectrum unfolding.

  20. Bio-functionalized silver nanoparticles for selective colorimetric sensing of toxic metal ions and antimicrobial studies

    NASA Astrophysics Data System (ADS)

    Vinod Kumar, V.; Anbarasan, S.; Christena, Lawrence Rene; SaiSubramanian, Nagarajan; Philip Anthony, Savarimuthu

    2014-08-01

    Hibiscus Sabdariffa (Gongura) plant extracts (leaves (HL) and stem (HS) were used for the first time in the green synthesis of bio-functionalized silver nanoparticles (AgNPs). The bio-functionality of AgNPs has been successfully utilized for selective colorimetric sensing of potentially health and environmentally hazardous Hg2+, Cd2+ and Pb2+ metal ions at ppm level in aqueous solution. Importantly, clearly distinguishable colour for all three metal ions was observed. The influence of extract preparation condition and pH were also explored on the formation of AgNPs. Both selectivity and sensitivity differed for AgNPs synthesized from different parts of the plant. Direct correlation between the stability of green synthesized AgNPs at different pH and its antibacterial effects has been established. The selective colorimetric sensing of toxic metal ions and antimicrobial effect of green synthesized AgNPs demonstrated the multifunctional applications of green nanotechnology.

  1. Accelerated Sensitivity Analysis in High-Dimensional Stochastic Reaction Networks.

    PubMed

    Arampatzis, Georgios; Katsoulakis, Markos A; Pantazis, Yannis

    2015-01-01

    Existing sensitivity analysis approaches are not able to handle efficiently stochastic reaction networks with a large number of parameters and species, which are typical in the modeling and simulation of complex biochemical phenomena. In this paper, a two-step strategy for parametric sensitivity analysis for such systems is proposed, exploiting advantages and synergies between two recently proposed sensitivity analysis methodologies for stochastic dynamics. The first method performs sensitivity analysis of the stochastic dynamics by means of the Fisher Information Matrix on the underlying distribution of the trajectories; the second method is a reduced-variance, finite-difference, gradient-type sensitivity approach relying on stochastic coupling techniques for variance reduction. Here we demonstrate that these two methods can be combined and deployed together by means of a new sensitivity bound which incorporates the variance of the quantity of interest as well as the Fisher Information Matrix estimated from the first method. The first step of the proposed strategy labels sensitivities using the bound and screens out the insensitive parameters in a controlled manner. In the second step of the proposed strategy, a finite-difference method is applied only for the sensitivity estimation of the (potentially) sensitive parameters that have not been screened out in the first step. Results on an epidermal growth factor network with fifty parameters and on a protein homeostasis with eighty parameters demonstrate that the proposed strategy is able to quickly discover and discard the insensitive parameters and in the remaining potentially sensitive parameters it accurately estimates the sensitivities. The new sensitivity strategy can be several times faster than current state-of-the-art approaches that test all parameters, especially in "sloppy" systems. In particular, the computational acceleration is quantified by the ratio between the total number of parameters over the

  2. A new pyrene-based Schiff-base: A selective colorimetric and fluorescent chemosensor for detection of Cu(II) and Fe(III)

    NASA Astrophysics Data System (ADS)

    Bhorge, Yeshwant Ramchandra; Tsai, Haw-Tyng; Huang, Keh-Feng; Pape, Albert J.; Janaki, Sudhakar Narasimha; Yen, Yao-Pin

    2014-09-01

    A new receptor 1 was prepared, for the detection of Cu2+ and Fe3+ in solutions as a colorimetric and fluorescent sensor, respectively. Receptor 1 shows highly selective and sensitive recognition toward Cu2+ and Fe3+ by naked eye UV-Vis and fluorescent color changes in aqueous solution (DMSO/H2O = 8/2, v/v), respectively. The sensitivity toward Cu2+ or Fe3+ was not interfered with by the presence of other metal ions such as Mg2+, Cd2+, Ag+, Zn2+, Ni2+, Co2+, Mn2+, Cr3+, Ca2+, Na+, Pb2+, K+, Fe2+, Li+ and Hg2+ ions. Receptor 1 can be used for semi-quantitative recognition of Cu2+ ions at ppm level. The fluorescence microscopy experiments showed that the receptor is efficient for detection of Fe3+ in vitro, developing a good image of the biological organelles.

  3. A colorimetric and ratiometric fluorescent probe for the imaging of endogenous hydrogen sulphide in living cells and sulphide determination in mouse hippocampus.

    PubMed

    Zhang, Ling; Li, Sai; Hong, Mei; Xu, Yuqing; Wang, Shuaishuai; Liu, Yi; Qian, Yong; Zhao, Jing

    2014-07-28

    A naphthalimide-azide based colorimetric and ratiometric fluorescent probe, NAP-1, has been developed for the selective and sensitive detection of hydrogen sulphide. Advantages of the probe NAP-1 include a low detection limit (110 nM), good selectivity, high sensitivity and excellent photostability. A linear relationship between the emission intensity ratios and sulphide concentrations was observed in PBS buffer and bovine serum, respectively. Our probe facilitates ratiometric determination and imaging of endogenous H2S in living cells. Furthermore, this probe was successfully applied to the measurement of endogenous sulphide in human plasma and mouse hippocampus. A significant reduction in sulphide levels and CBS mRNA expression was observed in the hippocampus of mouse models of lipopolysaccharide-induced neuroinflammation-related diseases, suggesting that decreased levels of endogenous H2S might be involved in the pathogenesis of neuroinflammation-related neurodegenerative diseases.

  4. Highly sensitive and multiplexed platforms for allergy diagnostics

    NASA Astrophysics Data System (ADS)

    Monroe, Margo R.

    Allergy is a disorder of the immune system caused by an immune response to otherwise harmless environmental allergens. Currently 20% of the US population is allergic and 90% of pediatric patients and 60% of adult patients with asthma have allergies. These percentages have increased by 18.5% in the past decade, with predicted similar trends for the future. Here we design sensitive, multiplexed platforms to detect allergen-specific IgE using the Interferometric Reflectance Imaging Sensor (IRIS) for various clinical settings. A microarray platform for allergy diagnosis allows for testing of specific IgE sensitivity to a multitude of allergens, while requiring only small volumes of patient blood sample. However, conventional fluorescent microarray technology is limited by i) the variation of probe immobilization, which hinders the ability to make quantitative, assertive, and statistically relevant conclusions necessary in immunodiagnostics and ii) the use of fluorophore labels, which is not suitable for some clinical applications due to the tendency of fluorophores to stick to blood particulates and require daily calibration methods. This calibrated fluorescence enhancement (CaFE) method integrates the low magnification modality of IRIS with enhanced fluorescence sensing in order to directly correlate immobilized probe (major allergens) density to allergen-specific IgE in patient serum. However, this platform only operates in processed serum samples, which is not ideal for point of care testing. Thus, a high magnification modality of IRIS was adapted as an alternative allergy diagnostic platform to automatically discriminate and size single nanoparticles bound to specific IgE in unprocessed, characterized human blood and serum samples. These features make IRIS an ideal candidate for clinical and diagnostic applications, such a POC testing. The high magnification (nanoparticle counting) modality in conjunction with low magnification of IRIS in a combined instrument

  5. A colorimetric assay for the determination of polyhexamethylene biguanide in pool and spa water using nickel-nioxime.

    PubMed

    Rowhani, Touraj; Lagalante, Anthony F

    2007-02-15

    A novel nickel-nioxime analytical method to measure polyhexamethylene biguanide (PHMB) in swimming pools and spas was developed. This method utilizes nickel(II) chloride and 1,2-cyclohexanedionedioxime (nioxime) chemistry. In the method, nickel ions bind and neutralize PHMB in the solution. Excess, un-reacted nickel ions react with nioxime and the resulting colored solution is measured at 550nm using a colorimetric assay. Currently, the colorimetric method to measure PHMB uses bromophenol blue (BPB). However, high levels of quaternary ammonium based algaecides and surfactant based products interfere with this colorimetric method. A time-consuming and expensive high-performance liquid chromatographic (HPLC) analysis can be used for samples with high levels of quaternary ammonium based algaecides or surfactants. The proposed nickel-nioxime detection method achieves comparable PHMB results to HPLC in about 5min and is a very economical and simple method to perform.

  6. Sensitive Detection of Plasmodium vivax Using a High-Throughput, Colourimetric Loop Mediated Isothermal Amplification (HtLAMP) Platform: A Potential Novel Tool for Malaria Elimination

    PubMed Central

    Britton, Sumudu; Cheng, Qin; Grigg, Matthew J.; Poole, Catherine B.; Pasay, Cielo; William, Timothy; Fornace, Kimberley; Anstey, Nicholas M.; Sutherland, Colin J.; Drakeley, Chris; McCarthy, James S.

    2016-01-01

    Introduction Plasmodium vivax malaria has a wide geographic distribution and poses challenges to malaria elimination that are likely to be greater than those of P. falciparum. Diagnostic tools for P. vivax infection in non-reference laboratory settings are limited to microscopy and rapid diagnostic tests but these are unreliable at low parasitemia. The development and validation of a high-throughput and sensitive assay for P. vivax is a priority. Methods A high-throughput LAMP assay targeting a P. vivax mitochondrial gene and deploying colorimetric detection in a 96-well plate format was developed and evaluated in the laboratory. Diagnostic accuracy was compared against microscopy, antigen detection tests and PCR and validated in samples from malaria patients and community controls in a district hospital setting in Sabah, Malaysia. Results The high throughput LAMP-P. vivax assay (HtLAMP-Pv) performed with an estimated limit of detection of 1.4 parasites/ μL. Assay primers demonstrated cross-reactivity with P. knowlesi but not with other Plasmodium spp. Field testing of HtLAMP-Pv was conducted using 149 samples from symptomatic malaria patients (64 P. vivax, 17 P. falciparum, 56 P. knowlesi, 7 P. malariae, 1 mixed P. knowlesi/P. vivax, with 4 excluded). When compared against multiplex PCR, HtLAMP-Pv demonstrated a sensitivity for P. vivax of 95% (95% CI 87–99%); 61/64), and specificity of 100% (95% CI 86–100%); 25/25) when P. knowlesi samples were excluded. HtLAMP-Pv testing of 112 samples from asymptomatic community controls, 7 of which had submicroscopic P. vivax infections by PCR, showed a sensitivity of 71% (95% CI 29–96%; 5/7) and specificity of 93% (95% CI87-97%; 98/105). Conclusion This novel HtLAMP-P. vivax assay has the potential to be a useful field applicable molecular diagnostic test for P. vivax infection in elimination settings. PMID:26870958

  7. Polyacrylic acid-coated cerium oxide nanoparticles: An oxidase mimic applied for colorimetric assay to organophosphorus pesticides.

    PubMed

    Zhang, Shi-Xiang; Xue, Shi-Fan; Deng, Jingjing; Zhang, Min; Shi, Guoyue; Zhou, Tianshu

    2016-11-15

    It is important and urgent to develop reliable and highly sensitive methods that can provide on-site and rapid detection of extensively used organophosphorus pesticides (OPs) for their neurotoxicity. In this study, we developed a novel colorimetric assay for the detection of OPs based on polyacrylic acid-coated cerium oxide nanoparticles (PAA-CeO2) as an oxidase mimic and OPs as inhibitors to suppress the activity of acetylcholinesterase (AChE). Firstly, highly dispersed PAA-CeO2 was prepared in aqueous solution, which could catalyze the oxidation of TMB to produce a color reaction from colorless to blue. And the enzyme of AChE was used to catalyze the substrate of acetylthiocholine (ATCh) to produce thiocholine (TCh). As a thiol-containing compound with reducibility, TCh can decrease the oxidation of TMB catalyzed by PAA-CeO2. Upon incubated with OPs, the enzymatic activity of AChE was inhibited to produce less TCh, resulting in more TMB catalytically oxidized by PAA-CeO2 to show an increasing blue color. The two representative OPs, dichlorvos and methyl-paraoxon, were tested using our proposed assay. The novel assay showed notable color change in a concentration-dependent manner, and as low as 8.62 ppb dichlorvos and 26.73 ppb methyl-paraoxon can be readily detected. Therefore, taking advantage of such oxidase-like activity of PAA-CeO2, our proposed colorimetric assay can potentially be a screening tool for the precise and rapid evaluation of the neurotoxicity of a wealth of OPs.

  8. Colorimetric sensor strips for lead (II) assay utilizing nanogold probes immobilized polyamide-6/nitrocellulose nano-fibers/nets.

    PubMed

    Li, Yan; Si, Yang; Wang, Xueqin; Ding, Bin; Sun, Gang; Zheng, Gang; Luo, Wenjing; Yu, Jianyong

    2013-10-15

    A facile, ultrasensitive, reproductive and selective sensor strip utilizing electrospun polyamide-6/nitrocellulose (PA-6/NC) nano-fibers/nets (NFN) membranes assemble bovine serum albumin decorated Au nanoparticles (BAu probe) for naked-eye colorimetric assay of Pb²⁺ has successfully prepared through dual-component alternate distribution multifluidic electrospinning technique. Benefiting from the extremely large specific surface areas and high porosity of NFN membranes, the stability of BAu probe dramatically increased and the strips presented a significant absorbance decreasing band at 546 nm which induce the visual color changes from deep pink to white after incubated in Pb²⁺ liquor with a low detection limit of 0.2 μM without any assistance of equipment. Upon exposure to a series of metal ions, only Pb²⁺ could induce a pink-to-white color change, which clearly exhibited that BAu probe immobilized PA-6/NC membranes could act as highly selective strips to detect Pb²⁺ with little interference from other metal ions. Additionally, the colorimetric responses are represented in visualized quantitative by calculated color difference from L*a*b* coordinates which are presented with lightness and chrome values. Furthermore, the sensitivity of NFN membrane-based strips is much higher than that of film-based ones. The results indicate that this promising cost-effective sensing system could potentially allow for assaying of Pb²⁺ in human urine or blood as preliminary screening of lead poisoning.

  9. Characterization of three high efficiency and blue sensitive silicon photomultipliers

    NASA Astrophysics Data System (ADS)

    Otte, Adam Nepomuk; Garcia, Distefano; Nguyen, Thanh; Purushotham, Dhruv

    2017-02-01

    We report about the optical and electrical characterization of three high efficiency and blue sensitive Silicon photomultipliers from FBK, Hamamatsu, and SensL. Key features of the tested devices when operated at 90% breakdown probability are peak photon detection efficiencies between 40% and 55%, temperature dependencies of gain and PDE that are less than 1%/°C, dark rates of ∼50 kHz/mm2 at room temperature, afterpulsing of about 2%, and direct optical crosstalk between 6% and 20%. The characteristics of all three devices impressively demonstrate how the Silicon-photomultiplier technology has improved over the past ten years. It is further demonstrated how the voltage and temperature characteristics of a number of quantities can be parameterized on the basis of physical models. The models provide a deeper understanding of the device characteristics over a wide bias and temperature range. They also serve as examples how producers could provide the characteristics of their SiPMs to users. A standardized parameterization of SiPMs would enable users to find the optimal SiPM for their application and the operating point of SiPMs without having to perform measurements thus significantly reducing design and development cycles.

  10. Ultra-high sensitivity imaging of cancer using SERRS nanoparticles

    NASA Astrophysics Data System (ADS)

    Kircher, Moritz F.

    2016-05-01

    "Surface-enhanced Raman spectroscopy" (SERS) nanoparticles have gained much attention in recent years for in silico, in vitro and in vivo sensing applications. Our group has developed novel generations of biocompatible "surfaceenhanced resonance Raman spectroscopy" (SERRS) nanoparticles as novel molecular imaging agents. Via rigorous optimization of the different variables contributing to the Raman enhancement, we were able to design SERRS nanoparticles with so far unprecedented sensitivity of detection under in vivo imaging conditions (femto-attomolar range). This has resulted in our ability to visualize, with a single nanoparticle, many different cancer types (after intravenous injection) in mouse models. The cancer types we have tested so far include brain, breast, esophagus, stomach, pancreas, colon, sarcoma, and prostate cancer. All mouse models used are state-of-the-art and closely mimic the tumor biology in their human counterparts. In these animals, we were able to visualize not only the bulk tumors, but importantly also microscopic extensions and locoregional satellite metastases, thus delineating for the first time the true extent of tumor spread. Moreover, the particles enable the detection of premalignant lesions. Given their inert composition they are expected to have a high chance for clinical translation, where we envision them to have an impact in various scenarios ranging from early detection, image-guidance in open or minimally invasive surgical procedures, to noninvasive imaging in conjunction with spatially offset (SESORS) Raman detection devices.

  11. Improvement of sensitivity in high-resolution Rutherford backscattering spectroscopy

    SciTech Connect

    Hashimoto, H.; Nakajima, K.; Suzuki, M.; Kimura, K.; Sasakawa, K.

    2011-06-15

    The sensitivity (limit of detection) of high-resolution Rutherford backscattering spectroscopy (HRBS) is mainly determined by the background noise of the spectrometer. There are two major origins of the background noise in HRBS, one is the stray ions scattered from the inner wall of the vacuum chamber of the spectrometer and the other is the dark noise of the microchannel plate (MCP) detector which is commonly used as a focal plane detector of the spectrometer in HRBS. In order to reject the stray ions, several barriers are installed inside the spectrometer and a thin Mylar foil is mounted in front of the detector. The dark noise of the MCP detector is rejected by the coincidence measurement with the secondary electrons emitted from the Mylar foil upon the ion passage. After these improvements, the background noise is reduced by a factor of 200 at a maximum. The detection limit can be improved down to 10 ppm for As in Si at a measurement time of 1 h under ideal conditions.

  12. High-sensitivity immunoassay using a novel upconverting phosphor reporter

    NASA Astrophysics Data System (ADS)

    Wright, William H.; Mufti, Naheed A.; Tagg, N. Troy; Webb, Robert R.; Schneider, Luke V.

    1997-05-01

    A new class of reporter label, consisting of rare earth elements embedded in a crystalline particle, has been developed for in vitro diagnostic applications. These unique labels upconvert low energy (IR) radiation to high energy light by a multiphoton absorption process and subsequent phosphorescence emission. As a result, upconverting phosphors can be visualized with no biological background or autofluorescence signal. In addition, phosphors have narrow absorption and emission bands, making them ideal for simultaneous multianalyte test. The crystalline nature of the phosphors makes them insensitive to environmental conditions, with essentially infinite shelf life and no photobleaching at the irradiances used for excitation. We have covalently coupled (Y0.86Yb0.08Er0.06)6O2S phosphor labels to antibody probes to create a reporter reagent that can be excited by 980 nm radiation from a diode laser and detected by a modified spectrofluorimeter. Target analyte sensitivities of approximately 10 ng/mL to Staphylococcal enterotoxin B have been demonstrated using a sandwich assay in a magnetic bead or capillary wick formats in a non-optimized assay system. These results are directly applicable to the development of assays that can be performed on microfabricated biochips or in microflow channels.

  13. High Speed Pressure Sensitive Paint for Dynamic Testing

    NASA Astrophysics Data System (ADS)

    Pena, Carolina; Chism, Kyle; Hubner, Paul

    2016-11-01

    Pressure sensitive paint (PSP) allows engineers to obtain accurate, high-spatial-resolution measurements of pressure fields over a structure. The pressure is directly related to the luminescence emitted by the paint due to oxygen quenching. Fast PSP has a higher surface area due to its porosity compared to conventional PSP, which enables faster diffusion and measurements to be acquired three orders of magnitude faster than with conventional PSP. A fast time response is needed when testing vibrating structures due to fluid-structure interaction. The goal of this summer project was to set-up, test and analyze the pressure field of an impinging air jet on a vibrating cantilever beam using Fast PSP. Software routines were developed for the processing of the emission images, videos of a static beam coated with Fast PSP were acquired with the air jet on and off, and the intensities of these two cases were ratioed and calibrated to pressure. Going forward, unsteady pressures on a vibrating beam will be measured and presented. Eventually, the long-term goal is to integrate luminescent pressure and strain measurement techniques, simultaneously using Fast PSP and a luminescent photoelastic coating on vibrating structures. Funding from NSF REU site Grant EEC 1358991 is greatly appreciated.

  14. A highly sensitive and multiplexed method for focused transcript analysis.

    PubMed

    Kataja, Kari; Satokari, Reetta M; Arvas, Mikko; Takkinen, Kristiina; Söderlund, Hans

    2006-10-01

    We describe a novel, multiplexed method for focused transcript analysis of tens to hundreds of genes. In this method TRAC (transcript analysis with aid of affinity capture) mRNA targets, a set of amplifiable detection probes of distinct sizes and biotinylated oligo(dT) capture probe are hybridized in solution. The formed sandwich hybrids are collected on magnetic streptavidin-coated microparticles and washed. The hybridized probes are eluted, optionally amplified by a PCR using a universal primer pair and detected with laser-induced fluorescence and capillary electrophoresis. The probes were designed by using a computer program developed for the purpose. The TRAC method was adapted to 96-well format by utilizing an automated magnetic particle processor. Here we demonstrate a simultaneous analysis of 18 Saccharomyces cerevisiae transcripts from two experimental conditions and show a comparison with a qPCR system. The sensitivity of the method is significantly increased by the PCR amplification of the hybridized and eluted probes. Our data demonstrate a bias-free use of at least 16 cycles of PCR amplification to increase probe signal, allowing transcript analysis from 2.5 ng of the total mRNA sample. The method is fast and simple and avoids cDNA conversion. These qualifications make it a potential, new means for routine analysis and a complementing method for microarrays and high density chips.

  15. Highly sensitive chemiluminescent analysis of residual bovine serum albumin (BSA) based on a pair of specific monoclonal antibodies and peroxyoxalate-glyoxaline-PHPPA dimer chemiluminescent system in vaccines.

    PubMed

    Xue, Pan; Zhang, Kui; Zhang, Zhujun; Li, Yun; Liu, Feng; Sun, Yuanjie; Zhang, Xiaoming; Song, Chaojun; Fu, Aihua; Jin, Boquan; Yang, Kun

    2012-03-01

    Enzyme-linked immunosorbent assay (ELISA), horseradish peroxidase (HRP)-catalyzed fluorescent reaction, and oxalate chemiluminescence analysis have been combined to develop a highly sensitive, simple, and rapid method for analysis of bovine serum albumin (BSA) based on a pair of specific monoclonal antibodies in vaccines. A typical "sandwich type" immunoassay was used. Reaction of 3-(4-hydroxyphenyl propionate) (PHPPA) with hydrogen peroxide-urea, catalyzed by HRP, produced fluorescence of 3-(4-hydroxyphenyl propionate) dimer, which was detected by chemiluminescence analysis with the bis(2,4,6-trichlorophenyl)oxalate (TCPO)-H(2)O(2)-glyoxaline-PHPPA dimer chemiluminescent system. This method exhibited high performance with a linear correlation between response and amount of bovine serum albumin (BSA) in the range 0.1 to 100.0 ng mL(-1) (r = 0.9988), and the detection limit was 0.03 ng mL(-1) (S/N = 3). Intra- and interassay coefficient variations were all lower than 9.0% at three concentrations (1.0, 20.0, and 80.0 ng mL(-1)). The proposed method has been used for successful analysis of the amount of residual BSA in vaccines. The results obtained compared well with those obtained by conventional colorimetric ELISA and luminol chemiluminescent ELISA.

  16. Highly sensitive NIR PtSi/Si-nanostructure detectors

    NASA Astrophysics Data System (ADS)

    Li, Hua-gao; Guo, Pei; Yuan, An-bo; Long, Fei; Li, Rui-zhi; Li, Ping; Li, Yi

    2016-10-01

    We report a high external quantum efficiency (EQE) photodiode detector with PtSi/Si-nanostructures. Black silicon nanostructures were fabricated by metal-assist chemical etching (MCE), a 2 nm Pt layer was subsequently deposited on black silicon surface by DC magnetron sputtering system, and PtSi/Si-nanostructures were formed in vacuum annealing at 450 oC for 5 min. As the PtSi/Si-nanostructures presented a spiky shape, the absorption of incident light was remarkably enhanced for the repeat reflection and absorption. The breakdown voltage, dark current, threshold voltage and responsivity of the device were investigated to evaluate the performance of the PtSi/Si-nanostructures detector. The threshold voltage and dark currents of the PtSi/Si-nanostructure photodiode tends to be slightly higher than those of the standard diodes. The breakdown voltage remarkably was reduced because of existing avalanche breakdown in PtSi/Si-nanostructures. However, the photodiodes had high response at room temperature in near infrared region. At -5 V reverse bias voltage, the responsivity was 0.72 A/W in 1064 nm wavelength, and the EQE was 83.9%. By increasing the reverse bias voltage, the responsivity increased. At -60 V reverse bias voltage, the responsivity was 3.5 A/W, and the EQE was 407.5%, which means the quantum efficiency of PtSi/Si-nanostructure photodiodes was about 10 times higher than that of a standard diode. Future research includes how to apply this technology to enhance the NIR sensitivity of image sensors, such as Charge Coupled Devices (CCD).

  17. Colorimetric Signal Amplification Assay for Mercury Ions Based on the Catalysis of Gold Amalgam.

    PubMed

    Chen, Zhengbo; Zhang, Chenmeng; Gao, Qinggang; Wang, Guo; Tan, Lulu; Liao, Qing

    2015-11-03

    Mercury is a major threat to the environment and to human health. It is highly desirable to develop a user-friendly kit for on-site mercury detection. Such a method must be able to detect mercury below the threshold levels (10 nM) for drinking water defined by the U.S. Environmental Protection Agency. Herein, we for the first time reported catalytically active gold amalgam-based reaction between 4-nitrophenol and NaBH4 with colorimetric sensing function. We take advantage of the correlation between the catalytic properties and the surface area of gold amalgam, which is proportional to the amount of the gold nanoparticle (AuNP)-bound Hg(2+). As the concentration of Hg(2+) increases until the saturation of Hg onto the AuNPs, the catalytic performance of the gold amalgam is much stronger due to the formation of gold amalgam and the increase of the nanoparticle surface area, leading to the decrease of the reduction time of 4-nitrophenol for the color change. This sensing system exhibits excellent selectivity and ultrahigh sensitivity up to the 1.45 nM detection limit. The practical use of this system for Hg(2+) determination in tap water samples is also demonstrated successfully.

  18. A novel colorimetric competitive aptamer assay for lysozyme detection based on superparamagnetic nanobeads.

    PubMed

    Mishra, Rupesh K; Hayat, Akhtar; Mishra, Geetesh K; Catanante, Gaëlle; Sharma, Vinay; Marty, Jean-Louis

    2017-04-01

    Lysozyme (Lys) commonly presents in wines and are known to cause toxicological impact on human health. The need of highly sensitive and reliable detection methods are evident in such matrix. In this work, we developed a competitive aptamer based assay for detection of Lys by employing carboxylated magnetic beads as a support to immobilize the target molecule Lys. The used aptamer sequence was biotinylated which further binds with Streptavidin-Alkaline phosphatase (Stp-ALP) in the micro wells. Colorimetric tests were performed in order to optimize different experimental parameters. The Lys assay showed a good linearity in the range of 5-140nM with a limit of detection (LOD) 10nM. The mid-point value (IC50) 110nM and the analysis time (60min) validated the developed aptasensor as a promising tool for routine use. The assay displayed good recoveries of Lys in the range 99.00-99.27% and was demonstrated for the detection of Lys in wine samples.

  19. Seed-mediated grown silver nanoparticles as a colorimetric sensor for detection of ascorbic acid.

    PubMed

    Rostami, Simindokht; Mehdinia, Ali; Jabbari, Ali

    2017-06-05

    A simple and sensitive approach was demonstrated for detection of ascorbic acid (AA) based on seed-mediated growth of silver nanoparticles (Ag NPs). According to the seeding strategy, silver ions existing in the growth solution were reduced to silver atoms on the surface of silver seeds via redox reaction between silver ions and AA. This process -led to appear an absorption band in near 420nm owing to the localized surface plasmon resonance peak of the generated Ag NPs. This change in absorption spectra of Ag NPs caused a change in color of the mixture from colorless to yellow. It was found that the changes in absorption intensity at 420nm have a good relationship with the concentration of AA. Also, detection of AA was achieved through the established colorimetric sensor in the range of 0.25-25μM with detection limit of 0.054μM. Moreover, the selectivity of the method was evaluated with considering potential interferences. The method showed high selectivity toward AA rather than potential interferences and coexisted molecules with AA. It was successfully applied for detection and determination of AA in pharmaceutical tablets and commercial lemonade.

  20. Ultrasmall Pt Nanoclusters as Robust Peroxidase Mimics for Colorimetric Detection of Glucose in Human Serum.

    PubMed

    Jin, Lihua; Meng, Zheng; Zhang, Yongqing; Cai, Shijie; Zhang, Zaihua; Li, Cong; Shang, Li; Shen, Yehua

    2017-02-28

    In this work, a new type of ultrasmall Pt nanoclusters (Pt NCs) has been prepared via a facile one-pot approach by using yeast extract as the reductant and stabilizer. Besides their excellent water-solubility, these yeast extract-stabilized Pt NCs also possess attractive peroxidase mimics property. They can efficiently catalyze the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) in the coexistence of hydrogen peroxide (H2O2). Catalytic mechanism analysis suggested that the peroxidase mimics activity of these Pt NCs might originate from their characteristic of accelerating electron transfer between TMB and H2O2, and their enzymatic kinetics followed typical Michaelis-Menten theory. Based on these findings, we developed a new highly sensitive colorimetric method for glucose detection, and the limit of detection was calculated as low as 0.28 μM (S/N = 3). Further application of the present system for glucose detection in human serum has been successfully demonstrated, suggesting its promising utilization as robust peroxidase mimics in the clinical diagnosis, pharmaceutical and environmental chemistry fields.

  1. Colorimetric assay for S-adenosylhomocysteine hydrolase activity and inhibition using fluorosurfactant-capped gold nanoparticles.

    PubMed

    Lin, Jia-Hui; Chang, Chung-Wei; Wu, Zong-Han; Tseng, Wei-Lung

    2010-11-01

    This study reports a simple colorimetric method for the sensitive detection of S-adenosylhomocysteine hydrolase (SAHH) activity and inhibition using fluorosurfactant-capped gold nanoparticles (FSN-AuNPs). FSN stabilizes the AuNPs against conditions of high ionic strength, and FSN-AuNPs are merely aggregated in the presence of homocysteine (HCys) and cysteine. Because of this feature, FSN-AuNPs were found to be dispersed in the presence of S-adenosylhomocysteine (SAH) that lacks a free thiol group. After SAHH catalyzed the hydrolysis of SAH, the produced HCys molecules were bound to the surface of AuNPs through the formation of Au-S bonds. As a result, the nanoparticle (NP) aggregation occurred through electrostatic attraction between each HCys-attached AuNP. This approach had a minimum detectable concentration of 100 units/L (~6 nM). Additionally, because adenosine analogs are capable of inhibiting SAHH activity, the addition of adenosine analogs to a solution containing SAH and SAHH resulted in the suppression of hydrolyzed SAH-induced NP aggregation. Adenosine analogs exhibited the following trend in the half-maximal inhibitory concentrations: adenosine > adenosine monophosphate > adenosine diphosphate ~ adenosine triphosphate. We have demonstrated that the combination of SAHH inhibition and FSN-AuNPs can be utilized for the selective detection of adenosine.

  2. Magnetic beads-based DNA hybridization chain reaction amplification and DNAzyme recognition for colorimetric detection of uranyl ion in seafood.

    PubMed

    Zhang, Hongyan; Cheng, Xian; Chen, Lian; Mo, Fan; Xu, LiangJun; Fu, FengFu

    2017-03-01

    A novel colorimetric biosensor, which employs DNAzyme-functionalized magnetic beads (MBs) as recognition probe, enzyme-assisted catalytic oxidation of TMB (3,3',5,5'-tetramethylbenzidine sulfate) as signal and DNA hybridization chain reaction as amplification strategy, has been developed for detecting trace uranyl ion (UO2(2+)) in seafood and aqueous environment with high sensitivity and specificity. We demonstrated that UO2(2+) can specifically cleave DNAzyme immobilized on MBs surface to release a short single-strand DNA (primer), and the released primer trigger DNA hybridization chain reaction to form a long one dimensional DNA concatamer on the MBs surface. The resulting long DNA concatamer could capture a large amount of HRP to generate the one UO2(2+)-to-multiple HRP amplification effect. Upon the addition of TMB-H2O2 solution, the HRP-tagged DNA concatamer-MBs conjugates could catalyze the H2O2-mediated oxidation of TMB, and thus results in a color change from colorless to blue in solution. This provided a sensitive and selective sensing platform for the visual or colorimetric detection of UO2(2+). The proposed biosensor has high sensitivity and strong anti-interference capability, it can be used to detect as low as 2.5 ppb (9.25 nM) of UO2(2+) by naked-eye observation and 0.09 ppb (0.33 nM) of UO2(2+) by UV-visible spectrometry with no interference of other ions and a RSD ≤ 6% (n = 5). With the help of this method, we have successfully determined trace UO2(2+) in fish muscle and river water with a recovery of 93-106%. High sensitivity and specificity, as well operation convenience, low cost and strong resistibility to the matrix, which makes our method a potential approach for the on-site detection of UO2(2+) in seafood and aqueous environment.

  3. High-sensitivity high-throughput chip based biosensor array for multiplexed detection of heavy metals

    NASA Astrophysics Data System (ADS)

    Yan, Hai; Tang, Naimei; Jairo, Grace A.; Chakravarty, Swapnajit; Blake, Diane A.; Chen, Ray T.

    2016-03-01

    Heavy metal ions released into the environment from industrial processes lead to various health hazards. We propose an on-chip label-free detection approach that allows high-sensitivity and high-throughput detection of heavy metals. The sensing device consists of 2-dimensional photonic crystal microcavities that are combined by multimode interferometer to form a sensor array. We experimentally demonstrate the detection of cadmium-chelate conjugate with concentration as low as 5 parts-per-billion (ppb).

  4. Proposed Ultra-High Sensitivity High-Frequency Gravitational Wave Detector

    NASA Astrophysics Data System (ADS)

    Baker, Robert M. L.; Stephenson, Gary V.; Li, Fangyu

    2008-01-01

    The paper discusses the proposed improvement of a High-Frequency Relic Gravitational Wave (HFRGW) detector designed by Li, Baker, Fang, Stephenson and Chen in order to greatly improve its sensitivity. The improved detector is inspired by the Laser Interferometer Gravitational Observatory or LIGO, but is sensitive to the high-frequency end of the gravitational-wave spectrum. As described in prior papers it utilizes the Gertsenshtein effect, which introduces the conversion of gravitational waves to electromagnetic (EM) waves in the presence of a static magnetic field. Such a conversion, if it leads to photons moving in a direction perpendicular to the plane of the EM waves and the magnetic field, will allow for ultra-high sensitivity HFRGW detection. The use of sensitive microwave, single photon detectors such as a circuit QED and/or the Rydberg Atom Cavity Detector, or off-the-shelf detectors, could lead to such detection. When the EM-detection photons are focused at the microwave detectors by fractal-membrane reflectors sensitivity is also improved. Noise sources external to the HFRGW detector will be eliminated by placing a tight mosaic of superconducting tiles (e.g., YBCO) and/or fractal membranes on the interior surface of the detector's cryogenic containment vessel in order to provide a perfect Faraday cage. Internal thermal noise will be eliminated by means of a microwave absorbing (or reflecting) interior enclosure shaped to conform to a high-intensity continuous microwave Gaussian beam (GB), will reduce any background photon flux (BPF) noise radiated normal to the GB's axis. Such BPF will be further attenuated by a series of microwave absorbing baffles forming tunnels to the sensitive microwave detectors on each side of the GB and at right angles to the static magnetic field. A HFGW detector of bandwidth of 1 KHz to 10 KHz or less in the GHz band has been selected. It is concluded that the utilization of the new ultra-high-sensitivity microwave detectors

  5. A high sensitive fiber-optic strain sensor with tunable temperature sensitivity for temperature-compensation measurement

    NASA Astrophysics Data System (ADS)

    Hu, Jie; Huang, Hui; Bai, Min; Zhan, Tingting; Yang, Zhibo; Yu, Yan; Qu, Bo

    2017-02-01

    A high sensitive fiber-optic strain sensor, which consists of a cantilever, a tandem rod and a fiber collimator, was proposed. The tandem rod, which transfer the applied strain to the cantilever, was used for tuning the temperature sensitivity from ‑0.15 to 0.19 dB/°C via changing the length ratio of the rods. Moreover, due to the small beam divergence of the collimator, high strain sensitivity can be realized via incident-angle sensitive detection-mechanism. A strain detection-range of 1.1 × 103 με (with a sensing length of 21.5 mm), a detection limit of 5.7 × 10‑3 με, and a maximum operating frequency of 1.18 KHz were demonstrated. This sensor is promising for compensating the thermal-expansion of various target objects.

  6. High angular sensitivity thin film tin oxide sensor

    NASA Astrophysics Data System (ADS)

    Kaur, Davinder; Madaan, Divya; Sharma, V. K.; Kapoor, A.

    2016-05-01

    We present theoretical anlaysis of a thin film SnO2 (Tin Oxide) sensor for the measurement of variation in the refractive index of the bulk media. It is based on lossy mode resonance between the absorbing thin film lossy modes and the evanescent wave. Also the addition of low index dielectric matching layer between the prism and the lossy waveguiding layer future increase the angular sensitivity and produce an efficient refractive index sensor. The angular interrogation is done and obtained sensitivity is 110 degree/RIU. Theoretical analysis of the proposed sensor based on Fresnel reflection coefficients is presented. This enhanced sensitivity will further improve the monitoring of biomolecular interactions and the higher sensitivity of the proposed configurations makes it to be a much better option to be employed for biosensing applications.

  7. Stochastic sensitivity measure for mistuned high-performance turbines

    NASA Technical Reports Server (NTRS)

    Murthy, Durbha V.; Pierre, Christophe

    1992-01-01

    A stochastic measure of sensitivity is developed in order to predict the effects of small random blade mistuning on the dynamic aeroelastic response of turbomachinery blade assemblies. This sensitivity measure is based solely on the nominal system design (i.e., on tuned system information), which makes it extremely easy and inexpensive to calculate. The measure has the potential to become a valuable design tool that will enable designers to evaluate mistuning effects at a preliminary design stage and thus assess the need for a full mistuned rotor analysis. The predictive capability of the sensitivity measure is illustrated by examining the effects of mistuning on the aeroelastic modes of the first stage of the oxidizer turbopump in the Space Shuttle Main Engine. Results from a full analysis mistuned systems confirm that the simple stochastic sensitivity measure predicts consistently the drastic changes due to misturning and the localization of aeroelastic vibration to a few blades.

  8. Very high polarimetric sensitivity to strain of second order mode of highly birefringent microstructured fibre

    NASA Astrophysics Data System (ADS)

    Nasilowski, Tomasz; Skorupski, Krzysztof; Makara, Mariusz; Statkiewicz-Barabach, Gabriela; Mergo, Pawel; Marc, Pawel; Jaroszewicz, Leszek

    2011-05-01

    Microstructured fibres (MSF) or photonic crystal fibres (PCF) possess a number of unique properties enabling a wide range of novel applications either in the telecommunication or in the sensing domain. In this paper we show that highly birefringent (HB) MSF with a dedicated design that allows inscribing fibre Bragg gratings in the MSF core can serve as pressure or stress transducers with extremely large sensitivity of second order mode, while exhibiting a low sensitivity to temperature drifts. Therefore, Bragg gratings inscribed in such MSF may offer a viable alternative to traditional optical fibre sensors of much lower stress sensitivity that require temperature compensation mechanisms and that are not intrinsically capable of distinguishing stress and temperature.

  9. Design of a High Sensitivity GNSS receiver for Lunar missions

    NASA Astrophysics Data System (ADS)

    Musumeci, Luciano; Dovis, Fabio; Silva, João S.; da Silva, Pedro F.; Lopes, Hugo D.

    2016-06-01

    This paper presents the design of a satellite navigation receiver architecture tailored for future Lunar exploration missions, demonstrating the feasibility of using Global Navigation Satellite Systems signals integrated with an orbital filter to achieve such a scope. It analyzes the performance of a navigation solution based on pseudorange and pseudorange rate measurements, generated through the processing of very weak signals of the Global Positioning System (GPS) L1/L5 and Galileo E1/E5 frequency bands. In critical scenarios (e.g. during manoeuvres) acceleration and attitude measurements from additional sensors complementing the GNSS measurements are integrated with the GNSS measurement to match the positioning requirement. A review of environment characteristics (dynamics, geometry and signal power) for the different phases of a reference Lunar mission is provided, focusing on the stringent requirements of the Descent, Approach and Hazard Detection and Avoidance phase. The design of High Sensitivity acquisition and tracking schemes is supported by an extensive simulation test campaign using a software receiver implementation and navigation results are validated by means of an end-to-end software simulator. Acquisition and tracking of GPS and Galileo signals of the L1/E1 and L5/E5a bands was successfully demonstrated for Carrier-to-Noise density ratios as low as 5-8 dB-Hz. The proposed navigation architecture provides acceptable performances during the considered critical phases, granting position and velocity errors below 61.4 m and 3.2 m/s, respectively, for the 99.7% of the mission time.

  10. High sensitivity imaging Thomson scattering for low temperature plasma

    SciTech Connect

    Meiden, H. J. van der; Al, R. S.; Barth, C. J.; Donne, A. J. H.; Goedheer, W. J.; Groot, B. de; Koppers, W. R.; Pol, M. J. van de; Prins, P. R.; Shumack, A. E.; Smeets, P. H. M.; Vijvers, W. A. J.; Westerhout, J.; Wright, G. M.; Rooij, G. J. van; Engeln, R.; Kleyn, A. W.; Lopes Cardozo, N. J.; Schram, D. C.

    2008-01-15

    A highly sensitive imaging Thomson scattering system was developed for low temperature (0.1-10 eV) plasma applications at the Pilot-PSI linear plasma generator. The essential parts of the diagnostic are a neodymium doped yttrium aluminum garnet laser operating at the second harmonic (532 nm), a laser beam line with a unique stray light suppression system and a detection branch consisting of a Littrow spectrometer equipped with an efficient detector based on a ''Generation III'' image intensifier combined with an intensified charged coupled device camera. The system is capable of measuring electron density and temperature profiles of a plasma column of 30 mm in diameter with a spatial resolution of 0.6 mm and an observational error of 3% in the electron density (n{sub e}) and 6% in the electron temperature (T{sub e}) at n{sub e}=4x10{sup 19} m{sup -3}. This is achievable at an accumulated laser input energy of 11 J (from 30 laser pulses at 10 Hz repetition frequency). The stray light contribution is below 9x10{sup 17} m{sup -3} in electron density equivalents by the application of a unique stray light suppression system. The amount of laser energy that is required for a n{sub e} and T{sub e} measurement is 7x10{sup 20}/n{sub e} J, which means that single shot measurements are possible for n{sub e}>2x10{sup 21} m{sup -3}.

  11. Label-free colorimetric detection of cadmium ions in rice samples using gold nanoparticles.

    PubMed

    Guo, Yongming; Zhang, Yi; Shao, Huawu; Wang, Zhuo; Wang, Xuefei; Jiang, Xingyu

    2014-09-02

    A simple and label-free colorimetric method for cadmium ions (Cd(2+)) detection using unmodified gold nanoparticles (AuNPs) is reported. The unmodified AuNPs easily aggregate in a high concentration of NaCl solution, but the presence of glutathione (GSH) can prevent the salt-induced aggregation of AuNPs. When Cd(2+) is added to the stable mixture of AuNPs, GSH, and NaCl, Cd(2+) can coordinate with 4× GSH as a spherical shaped complex, which decreases the amount of free GSH on the surface of gold nanoparticles to weaken the stability of AuNPs, and AuNPs will easily aggregate in high-salt conditions. On the basis of the mechanism, we design a simple, label-free colorimetric method using AuNPs accompanied by GSH in a high-salt environment to detect Cd(2+) in water and digested rice samples.

  12. Field-deployable colorimetric biosensor system for the rapid detection of pathogenic organisms

    NASA Astrophysics Data System (ADS)

    Duy, Janice

    The rapid identification of pathogenic organisms is necessary for recognizing and managing human and environmental health risks. Numerous detection schemes are available, but most are difficult to employ in non-laboratory settings due to their need for bulky, specialized equipment, multiple reagents, or highly trained personnel. To address this problem, a rapid, field-compatible biosensor system based on the colorimetric detection of nucleic acid hybrids was developed. Peptide nucleic acid (PNA) probes were used to capture ribosomal RNA sequences from environmental samples. Non-target nucleic acids, including single-base mismatches flanked by adenines and uracils, were removed with a micrococcal nuclease digestion step. Matched PNA-RNA hybrids remained intact and were indicated by the cyanine dye DiSC2(5). PNA-containing duplexes function as templates for the aggregation of DiSC2(5), visualized as a change in solution color from blue to purple. This transition can be measured as an increase in the solution absorbance at 540 nm (dye aggregate) at the expense of the dye monomer peak at 650 nm. These concomitant spectral changes were used to calculate a "hybridization signal" using the ratio A aggregate/Amonomer ≈ A540/A650. Testing with pathogenic environmental samples was accomplished using two model organisms: the harmful algal bloom-causing dinoflagellate Alexandrium species, and the potato wart disease-causing fungus Synchytrium endobioticum. In both cases, the colorimetric approach was able to distinguish the targets with sensitivities rivaling those of established techniques, but with the advantages of decreased hands-on time and cost. Assay fieldability was tested with a portable colorimeter designed to quantify the dye-indicated hybridization signal and assembled from commercially available components. Side-by-side testing revealed no difference in the sensing performance of the colorimeter compared to a laboratory spectrophotometer (Pearson's r=0

  13. Multi-enzyme co-embedded organic-inorganic hybrid nanoflowers: synthesis and application as a colorimetric sensor

    NASA Astrophysics Data System (ADS)

    Sun, Jiayu; Ge, Jiechao; Liu, Weimin; Lan, Minhua; Zhang, Hongyan; Wang, Pengfei; Wang, Yanming; Niu, Zhongwei

    2013-12-01

    This study reports a facile method for the synthesis of multi-enzyme co-embedded organic-inorganic hybrid nanoflowers, using glucose oxidase (GOx) and horseradish peroxidase (HRP) as the organic components, and Cu3(PO4)2.3H2O as the inorganic component. The synthesized nanoflowers enable the combination of a two-enzyme cascade reaction in one step, in which the GOx component of the nanoflowers oxidizes glucose to generate H2O2, which then reacts with the adjacent HRP component on the nanoflowers to oxidize the chromogenic substrates, resulting in an apparent color change. Given the close proximity of the two enzyme components in a single nanoflower, this novel sensor greatly reduces the diffusion and decomposition of H2O2, and greatly enhances the sensitivity of glucose detection. Thus, the obtained multi-enzyme co-embedded organic-inorganic hybrid nanoflowers can be unquestionably used as highly sensitive colorimetric sensors for the detection of glucose. Notably, this work presents a very facile route for the synthesis of multi-enzyme co-embedded nanomaterials for the simultaneous catalysis of multi-step cascade enzymatic reactions. Furthermore, it has great potential for application in biotechnology, and biomedical and environmental chemistry.This study reports a facile method for the synthesis of multi-enzyme co-embedded organic-inorganic hybrid nanoflowers, using glucose oxidase (GOx) and horseradish peroxidase (HRP) as the organic components, and Cu3(PO4)2.3H2O as the inorganic component. The synthesized nanoflowers enable the combination of a two-enzyme cascade reaction in one step, in which the GOx component of the nanoflowers oxidizes glucose to generate H2O2, which then reacts with the adjacent HRP component on the nanoflowers to oxidize the chromogenic substrates, resulting in an apparent color change. Given the close proximity of the two enzyme components in a single nanoflower, this novel sensor greatly reduces the diffusion and decomposition of H2O2

  14. Colorimetric cholesterol sensor based on peroxidase like activity of zinc oxide nanoparticles incorporated carbon nanotubes.

    PubMed

    Hayat, Akhtar; Haider, Waqar; Raza, Yousuf; Marty, Jean Louis

    2015-10-01

    A sensitive and selective colorimetric method based on the incorporation of zinc oxide nanoparticles (ZnO NPs) on the surface of carbon nanotubes (CNTs) was shown to posses synergistic peroxidase like activity for the detection of cholesterol. The proposed nanocomposite catalyzed the oxidation of 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid (ABTS) in the presence of hydrogen peroxide (H2O2) to produce a green colored product which can be monitored at 405 nm. H2O2 is the oxidative product of cholesterol in the presence of cholesterol oxidase. Therefore, the oxidation of cholesterol can be quantitatively related to the colorimetric response by combining these two reactions. Under the optimal experimental conditions, the colorimetric response was proportional to the concentration of cholesterol in the range of 0.5-500 nmol/L, with a detection limit of 0.2 nmol/L. The applicability of the proposed assays was demonstrated for the determination of cholesterol in milk powder samples with good recovery results.

  15. Standing-wave resonances in plasmonic nanoumbrella cavities for color generation and colorimetric refractive index sensor

    NASA Astrophysics Data System (ADS)

    Fan, Jiaorong; Li, Zhongyuan; Chen, Zhuojie; Wu, Wengang

    2016-10-01

    We theoretically investigate the hybridization of the elemental surface plasmons in umbrella-shape plasmonic nanostructures and experimentally demonstrate the implementation of plasmonic multicolor metasurfaces as well as their application in colorimetric sensing. The three-dimension metallic umbrella arrays consist of a periodic canopy-capped-nanopillars with metal-coated sidewall and a backplane metal-film to form vertical nanocavity of canopy and film. Plasmonic coupling and energy confinement in nanocavity induce a noticeably resonance narrowing of multispectral reflection. The metasurfaced nanostructures appeared in vibrant and tunable colors with broad gamut derived from color blending mechanism due to multiple, narrow-band resonances. Vivid colors varied from red, yellow, green, blue to violet are easily achieved. It is also shown that such plasmonic metasurfaces can work as the feasible and real-time colorimetric refractive index sensor by measuring the distinct color variation to glucose concentration changes. Our sensor scheme shows its spectral sensitivity in the periodic umbrella array with respect to the refractive index change to be 242.5 nm/RIU with a figure of merit of 7.3. Furthermore, a refractive index resolution of colorimetric sensing up to 0.025 RIU has been accomplished.

  16. [Fe(CN)6]4- decorated mesoporous gelatin thin films for colorimetric detection and as sorbents of heavy metal ions.

    PubMed

    Shi, Li; Huang, Hubiao; Sun, Luwei; Lu, Yanping; Du, Binyang; Mao, Yiyin; Li, Junwei; Ye, Zhizhen; Peng, Xinsheng

    2013-09-28

    [Fe(CN)6](4-) decorated mesoporous gelatin films, acting as colorimetric sensors and sorbents for heavy metal ions, were prepared by incorporating [Fe(CN)6](4-) ions into the mesoporous gelatin films through electrostatic interaction. Gelatin-Prussian blue (PB) and gelatin-PB analogue composite films were successfully synthesized by immersing the [Fe(CN)6](4-) decorated gelatin films into aqueous solutions of metal ions, such as Fe(3+), Cu(2+), Co(2+), Pb(2+) and Cd(2+) (all as nitrates). The in situ formation process of PB or its analogues in the films was investigated using quartz crystal microbalance (QCM) measurements. According to the different colors of the PB nanoparticles and its analogues, the [Fe(CN)6](4-) decorated mesoporous gelatin films demonstrated colorimetric sensor abilities for detecting the corresponding metal ions by the naked eye with sufficient sensitivity at 1 ppm level and a quite short response time of 5 minutes. Moreover, due to the [Fe(CN)6](4-) functionality and other functional groups of gelatin itself, this [Fe(CN)6](4-) decorated mesoporous gelatin film shows a tens times higher adsorption ability for heavy metal ions in water than that of activated carbon. Due to both the efficient detection and high adsorption ability for heavy metal ions, this film has wide potential applications for the detection and purification of heavy metal ions from polluted water.

  17. Novel Ruthenium Sensitizers with a Phenothiazine Conjugated Bipyridyl Ligand for High-Efficiency Dye-Sensitized Solar Cells.

    PubMed

    She, Zhijie; Cheng, Yangyang; Zhang, Luoqiang; Li, Xiaoyu; Wu, Di; Guo, Qiang; Lan, Jingbo; Wang, Ruilin; You, Jingsong

    2015-12-23

    Two efficient ruthenium sensitizers with a phenothiazine-modified bipyridine as an ancillary ligand, coded SCZ-1 and SCZ-2, have been developed as dyes in dye-sensitized solar cells (DSSCs). Both sensitizers exhibit low-energy metal-to-ligand charge transfer (MLCT) bands centered at 539 nm with high molar extinction coefficients of 1.77 × 10(4) M(-1) cm(-1) for SCZ-1 and 1.66 × 10(4) M(-1) cm(-1) for SCZ-2, which are significantly higher than the corresponding value for the reference N719 (1.27 × 10(4) M(-1) cm(-1)), indicating that the light-harvesting capacity of ruthenium sensitizers can be reinforced by introducing phenothiazine moieties into the bipyridine ligand. Under AM 1.5G irradiation (100 mW cm(-2)), SCZ-1 and SCZ-2 sensitized DSSC devices show impressive power conversion efficiencies (PCE) up to 10.4% by using of iodide-based electrolytes, which exceeds that of N719 (9.9%) under the same conditions. Both of the open circuit voltage (VOC) and fill factor (FF) of SCZ-sensitized solar cells approximate to those of N719-sensitized cell. The relatively higher efficiencies of the SCZ-sensitized cells than that of N719-sensitized cell come from their higher short-circuit photocurrent density (JSC), which may be mainly attributed to the high absorption coefficient. The absorption spectrum and device efficiency of SCZ-1 are both quite close to those of SCZ-2, suggesting that the difference in alkyl chains on the N atom of phenothiazine is not a decisive factor in affecting the photovoltaic performance of dyes.

  18. A colorimetric reaction to quantify fluid mixing

    NASA Astrophysics Data System (ADS)

    Oates, Peter M.; Harvey, Charles F.

    2006-11-01

    We found the colorimetric reaction of Tiron (1,2-dihydroxybenzene-3,5-disulfonic acid) and molybdate suitable for optical quantification of chemical reaction during fluid-fluid mixing in laboratory chambers. This reaction consists of two colorless reagents that mix to rapidly form colored, stable, soluble products. These products can be digitally imaged and quantified using light absorbance to study fluid-fluid mixing. Here we provide a model and equilibrium constants for the relevant complexation reactions. We also provide methods for relating light absorbance to product concentrations. Practical implementation issues of this reaction are discussed and an example of imaged absorbances for fluid-fluid mixing in heterogeneous porous media is given.

  19. Colorimetric Method for Beryllium Surface Contamination Detection

    SciTech Connect

    MCWHORTER, CHRISTOPHER

    2004-03-11

    To address the need for real-time accurate total beryllium analyses, Savannah River Technology Center Analytical Development Section personnel evaluated and modified a colorimetric screening method developed at Los Alamos National Lab to measure beryllium on surfaces. This method was based on a color complex formed by beryllium and chromium azurol s . SRTC converted this visual method to a quantitative analysis method using spectrophotometric detection. The addition of a cationic surfactant (hexadecyltrimethylammonium bromide, CTAB) to the Be-CAS system shifted the complex absorbance away from the CAS absorbance and allowed for the detection. Assuming complete dissolution and a 10 mL rinse solution volume to remove the beryllium from the wipe, the detection limit was calculated comfortably below the free release limit. The spectrophotometric method was rugged and simple enough that it could be used as a field method.

  20. Colorimetric calibration of coupled infrared simulation system

    NASA Astrophysics Data System (ADS)

    Zhang, Ying; Fei, Jindong; Gao, Yang; Du, Jian

    2015-10-01

    In order to test 2-color infrared sensors, a coupled infrared simulation system can generate radiometric outputs with wavelengths that range from less than 3 microns to more than 12 microns. There are two channels in the coupled simulation system, optically combined by a diachronic beam combiner. Each channel has an infrared blackbody, a filter, a diaphragm, and diaphragm-motors. The system is projected to the sensor under testing by a collimator. This makes it difficult to calibrate the system with only one-band thermal imager. Errors will be caused in the radiance levels measured by the narrow band thermal imager. This paper describes colorimetric temperature measurement techniques that have been developed to perform radiometric calibrations of these infrared simulation systems above. The calibration system consists of two infrared thermal imagers; one is operated at the wavelength range of MW-IR, and the other at the range of LW-IR.

  1. Chemically-modified cellulose paper as smart sensor device for colorimetric and optical detection of hydrogen sulfate in water.

    PubMed

    Rull-Barrull, Jordi; d'Halluin, Martin; Le Grognec, Erwan; Felpin, François-Xavier

    2016-02-11

    A portable, recyclable and highly selective paper-based sensor device for the colorimetric and optical detection of hydrogen sulfate anions in water was developed. The detection system features a rhodamine-based sensor covalently grafted onto the highly hydrophilic surface of cellulose paper.

  2. Highly sensitive flexible pressure sensors with microstructured rubber dielectric layers

    NASA Astrophysics Data System (ADS)

    Mannsfeld, Stefan C. B.; Tee, Benjamin C.-K.; Stoltenberg, Randall M.; Chen, Christopher V. H.-H.; Barman, Soumendra; Muir, Beinn V. O.; Sokolov, Anatoliy N.; Reese, Colin; Bao, Zhenan

    2010-10-01

    The development of an electronic skin is critical to the realization of artificial intelligence that comes into direct contact with humans, and to biomedical applications such as prosthetic skin. To mimic the tactile sensing properties of natural skin, large arrays of pixel pressure sensors on a flexible and stretchable substrate are required. We demonstrate flexible, capacitive pressure sensors with unprecedented sensitivity and very short response times that can be inexpensively fabricated over large areas by microstructuring of thin films of the biocompatible elastomer polydimethylsiloxane. The pressure sensitivity of the microstructured films far surpassed that exhibited by unstructured elastomeric films of similar thickness, and is tunable by using different microstructures. The microstructured films were integrated into organic field-effect transistors as the dielectric layer, forming a new type of active sensor device with similarly excellent sensitivity and response times.

  3. Development of High Temperature/High Sensitivity Novel Chemical Resistive Sensor

    SciTech Connect

    Chen, Chonglin; Nash, Patrick; Ma, Chunrui; Enriquez, Erik; Wang, Haibing; Xu, Xing; Bao, Shangyong; Collins, Gregory

    2013-08-13

    The research has been focused to design, fabricate, and develop high temperature/high sensitivity novel multifunctional chemical sensors for the selective detection of fossil energy gases used in power and fuel systems. By systematically studying the physical properties of the LnBaCo{sub 2}O{sub 5+d} (LBCO) [Ln=Pr or La] thin-films, a new concept chemical sensor based high temperature chemical resistant change has been developed for the application for the next generation highly efficient and near zero emission power generation technologies. We also discovered that the superfast chemical dynamic behavior and an ultrafast surface exchange kinetics in the highly epitaxial LBCO thin films. Furthermore, our research indicates that hydrogen can superfast diffuse in the ordered oxygen vacancy structures in the highly epitaxial LBCO thin films, which suggest that the LBCO thin film not only can be an excellent candidate for the fabrication of high temperature ultra sensitive chemical sensors and control systems for power and fuel monitoring systems, but also can be an excellent candidate for the low temperature solid oxide fuel cell anode and cathode materials.

  4. Single Cell Proteomics with Ultra-High Sensitivity Mass Spectrometry

    SciTech Connect

    Frank, M

    2005-02-16

    This project was a joint LDRD project between PAT, CMS and NAI with the objective to develop an instrument that analyzes the biochemical composition of single cells in real-time using bioaerosol mass spectrometry (BAMS) combined with advanced laser desorption and ionization techniques. Applications include both biological defense, fundamental cell biology and biomedical research. BAMS analyzes the biochemical composition of single, micrometer-sized particles (such as bacterial cells or spores) that can be directly sampled from air or a suspension. BAMS is based on an earlier development of aerosol time of flight mass spectrometry (ATOFMS) by members of our collaboration [1,2]. Briefly, in ATOFMS and BAMS aerosol particles are sucked directly from the atmosphere into vacuum through a series of small orifices. As the particles approach the ion source region of the mass spectrometer, they cross and scatter light from two CW laser beams separated by a known distance. The timing of the two bursts of scattered light created by each ''tracked'' particle reveals the speed, location and size of the particle. This information then enables the firing of a high-intensity laser such that the resulting laser pulse desorbs and ionizes molecules from the tracked particle just as it reaches the center of the ion source region. The full spectrum of ions is then measured using a time-of-flight mass spectrometer. The ability to rapidly analyze individual particles is clearly applicable to the rapid detection of aerosolized biological warfare agents so long as agent particles can be made to produce mass spectra that are distinct from the spectra of harmless background particles. The pattern of ions formed is determined by the properties of the laser pulse, the particle, and, in aerosol matrix-assisted laser desorption/ionization (MALDI), also the MALDI matrix used. As a result, it is critical that the properties of the laser pulses used for desorption and ionization be carefully chosen

  5. Highly sensitive recognition element based on birefringent porous silicon layers

    NASA Astrophysics Data System (ADS)

    Gross, E.; Kovalev, D.; Künzner, N.; Timoshenko, V. Yu.; Diener, J.; Koch, F.

    2001-10-01

    Anisotropically nanostructured silicon layers exhibit a strong in-plane birefringence. Their optical anisotropy parameters are found to be extremely sensitive to the presence of dielectric substances inside of the pores. Polarization-resolved transmittance measurements provide an extremely sensitive tool to analyze the adsorption of various atoms and molecules in negligible quantities. A variation of the transmitted linearly polarized light intensity up to two orders of magnitude combined with a fast optical response in the range of seconds make these layers a good candidate for sensor applications.

  6. High-sensitivity photoacoustic detection of chemical warfare agents

    NASA Astrophysics Data System (ADS)

    Pushkarsky, Michael B.; Webber, Michael E.; MacDonald, Tyson; Patel, C. Kumar N.

    2004-12-01

    We report sensitive and selective detection of Diisopropyl methylphosphonate (DIMP) - a decomposition product of Sarin and a common surrogate for the nerve gases - in presence of several gases expected to be interferences in an urban setting. By employing photoacosutic spectroscopy with broadly tunable CO2 laser as a radiation source we demonstrate detection sensitivity for DIMP in the presence of these interferences of better than 0.5 ppb in 60 second long measurement time, which satisfies most current homeland and military security requirements and validates the photoacoustic spectroscopy as a powerful technology for nerve gas sensing instrumentation.

  7. High Sensitivity SPECT for Small Animals and Plants

    SciTech Connect

    Mitchell, Gregory S.

    2015-02-28

    Imaging systems using single gamma-ray emitting radioisotopes typically implement collimators in order to form the images. However, a tradeoff in sensitivity is inherent in the use of collimators, and modern preclinical single-photon emission computed tomography (SPECT) systems detect a very small fraction of emitted gamma-rays (<0.3%). We have built a collimator-less system, which can reach sensitivity of 40% for 99mTc imaging, while still producing images of sufficient spatial resolution for certain applications in thin objects such as mice, small plants, and well plates used for in vitro experiments.

  8. A high-sensitivity push-pull magnetometer

    SciTech Connect

    Breschi, E.; Grujić, Z. D.; Knowles, P.; Weis, A.

    2014-01-13

    We describe our approach to atomic magnetometry based on the push-pull optical pumping technique. Cesium vapor is pumped and probed by a resonant laser beam whose circular polarization is modulated synchronously with the spin evolution dynamics induced by a static magnetic field. The magnetometer is operated in a phase-locked loop, and it has an intrinsic sensitivity below 20fT/√(Hz), using a room temperature paraffin-coated cell. We use the magnetometer to monitor magnetic field fluctuations with a sensitivity of 300fT/√(Hz)

  9. Sensitive, high-strain, high-rate bodily motion sensors based on graphene-rubber composites.

    PubMed

    Boland, Conor S; Khan, Umar; Backes, Claudia; O'Neill, Arlene; McCauley, Joe; Duane, Shane; Shanker, Ravi; Liu, Yang; Jurewicz, Izabela; Dalton, Alan B; Coleman, Jonathan N

    2014-09-23

    Monitoring of human bodily motion requires wearable sensors that can detect position, velocity and acceleration. They should be cheap, lightweight, mechanically compliant and display reasonable sensitivity at high strains and strain rates. No reported material has simultaneously demonstrated all the above requirements. Here we describe a simple method to infuse liquid-exfoliated graphene into natural rubber to create conducting composites. These materials are excellent strain sensors displaying 10(4)-fold increases in resistance and working at strains exceeding 800%. The sensitivity is reasonably high, with gauge factors of up to 35 observed. More importantly, these sensors can effectively track dynamic strain, working well at vibration frequencies of at least 160 Hz. At 60 Hz, we could monitor strains of at least 6% at strain rates exceeding 6000%/s. We have used these composites as bodily motion sensors, effectively monitoring joint and muscle motion as well and breathing and pulse.

  10. Colorimetric tests for diagnosis of filarial infection and vector surveillance using non-instrumented nucleic acid loop-mediated isothermal amplification (NINA-LAMP)

    PubMed Central

    Poole, Catherine B.; Li, Zhiru; Alhassan, Andy; Guelig, Dylan; Diesburg, Steven; Tanner, Nathan A.; Zhang, Yinhua; Evans, Thomas C.; LaBarre, Paul; Wanji, Samuel; Burton, Robert A.; Carlow, Clotilde K. S.

    2017-01-01

    Accurate detection of filarial parasites in humans is essential for the implementation and evaluation of mass drug administration programs to control onchocerciasis and lymphatic filariasis. Determining the infection levels in vector populations is also important for assessing transmission, deciding when drug treatments may be terminated and for monitoring recrudescence. Immunological methods to detect infection in humans are available, however, cross-reactivity issues have been reported. Nucleic acid-based molecular assays offer high levels of specificity and sensitivity, and can be used to detect infection in both humans and vectors. In this study we developed loop-mediated isothermal amplification (LAMP) tests to detect three different filarial DNAs in human and insect samples using pH sensitive dyes for enhanced visual detection of amplification. Furthermore, reactions were performed in a portable, non-instrumented nucleic acid amplification (NINA) device that provides a stable heat source for LAMP. The efficacy of several strand displacing DNA polymerases were evaluated in combination with neutral red or phenol red dyes. Colorimetric NINA-LAMP assays targeting Brugia Hha I repeat, Onchocerca volvulus GST1a and Wuchereria bancrofti LDR each exhibit species-specificity and are also highly sensitive, detecting DNA equivalent to 1/10-1/5000th of one microfilaria. Reaction times varied depending on whether a single copy gene (70 minutes, O. volvulus) or repetitive DNA (40 min, B. malayi and W. bancrofti) was employed as a biomarker. The NINA heater can be used to detect multiple infections simultaneously. The accuracy, simplicity and versatility of the technology suggests that colorimetric NINA-LAMP assays are ideally suited for monitoring the success of filariasis control programs. PMID:28199317

  11. High-speed high-sensitivity infrared spectroscopy using mid-infrared swept lasers (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Childs, David T. D.; Groom, Kristian M.; Hogg, Richard A.; Revin, Dmitry G.; Cockburn, John W.; Rehman, Ihtesham U.; Matcher, Stephen J.

    2016-03-01

    Infrared spectroscopy is a highly attractive read-out technology for compositional analysis of biomedical specimens because of its unique combination of high molecular sensitivity without the need for exogenous labels. Traditional techniques such as FTIR and Raman have suffered from comparatively low speed and sensitivity however recent innovations are challenging this situation. Direct mid-IR spectroscopy is being speeded up by innovations such as MEMS-based FTIR instruments with very high mirror speeds and supercontinuum sources producing very high sample irradiation levels. Here we explore another possible method - external cavity quantum cascade lasers (EC-QCL's) with high cavity tuning speeds (mid-IR swept lasers). Swept lasers have been heavily developed in the near-infrared where they are used for non-destructive low-coherence imaging (OCT). We adapt these concepts in two ways. Firstly by combining mid-IR quantum cascade gain chips with external cavity designs adapted from OCT we achieve spectral acquisition rates approaching 1 kHz and demonstrate potential to reach 100 kHz. Secondly we show that mid-IR swept lasers share a fundamental sensitivity advantage with near-IR OCT swept lasers. This makes them potentially able to achieve the same spectral SNR as an FTIR instrument in a time x N shorter (N being the number of spectral points) under otherwise matched conditions. This effect is demonstrated using measurements of a PDMS sample. The combination of potentially very high spectral acquisition rates, fundamental SNR advantage and the use of low-cost detector systems could make mid-IR swept lasers a powerful technology for high-throughput biomedical spectroscopy.

  12. A simple ratiometric and colorimetric chemosensor for the selective detection of fluoride in DMSO buffered solution

    NASA Astrophysics Data System (ADS)

    Niu, Hu; Shu, Qinghai; Jin, Shaohua; Li, Bingjun; Zhu, Jiaping; Li, Lijie; Chen, Shusen

    2016-01-01

    A derivative of squaramide (cyclobuta[b]quinoxaline-1, 2(3H, 8H)-dione) has been synthesized for the ratiometric and colorimetric sensing of F- in aqueous solution in competitive fashion. With F-, probe 1 showed a highly selective naked-eye detectable color change along with a characteristic UV-Vis absorbance over other tested ions, which probably originates from the deprotonation occurred between 1 and F-, as proved by the 1H NMR titration experiments and DFT calculations.

  13. Colorimetric detection of catalytic reactivity of nanoparticles in complex matrices.

    PubMed

    Corredor, Charlie; Borysiak, Mark D; Wolfer, Jay; Westerhoff, Paul; Posner, Jonathan D

    2015-03-17

    There is a need for new methodologies to quickly assess the presence and reactivity of nanoparticles (NPs) in commercial, environmental, and biological samples since current detection techniques require expensive and complex analytical instrumentation. Here, we investigate a simple and portable colorimetric detection assay that assesses the surface reactivity of NPs, which can be used to detect the presence of NPs, in complex matrices (e.g., environmental waters, serum, urine, and in dissolved organic matter) at as low as part per billion (ppb) or ng/mL concentration levels. Surface redox reactivity is a key emerging property related to potential toxicity of NPs with living cells, and is used in our assays as a key surrogate for the presence of NPs and a first tier analytical strategy toward assessing NP exposures. We detect a wide range of metal (e.g., Ag and Au) and oxide (e.g., CeO2, SiO2, VO2) NPs with a diameter range of 5 to 400 nm and multiple capping agents (tannic acid (TA), polyvinylpyrrolidone (PVP), branched polyethylenimine (BPEI), polyethylene glycol (PEG)). This method is sufficiently sensitive (ppb levels) to measure concentrations typically used in toxicological studies, and uses inexpensive, commercially available reagents.

  14. Quercetin as colorimetric reagent for determination of zirconium

    USGS Publications Warehouse

    Grimaldi, F.S.; White, C.E.

    1953-01-01

    Methods described in the literature for the determination of zirconium are generally designed for relatively large amounts of this element. A good procedure using colorimetric reagent for the determination of trace amounts is desirable. Quercetin has been found to yield a sensitive color reaction with zirconium suitable for the determination of from 0.1 to 50?? of zirconium dioxide. The procedure developed involves the separation of zirconium from interfering elements by precipitation with p-dimethylaminoazophenylarsonic acid prior to its estimation with quercetin. The quercetin reaction is carried out in 0.5N hydrochloric acid solution. Under the operating conditions it is indicated that quercetin forms a 2 to 1 complex with zirconium; however, a 2 to 1 and a 1 to 1 complex can coexist under special conditions. Approximate values for the equilibrium constants of the complexes are K1 = 0.33 ?? 10-5 and K2 = 1.3 ?? 10-9. Seven Bureau of Standards samples of glass sands and refractories were analyzed with excellent results. The method described should find considerable application in the analysis of minerals and other materials for macro as well as micro amounts of zirconium.

  15. Nanofiber-net-binary structured membranes for highly sensitive detection of trace HCl gas

    NASA Astrophysics Data System (ADS)

    Wang, Xianfeng; Wang, Jialin; Si, Yang; Ding, Bin; Yu, Jianyong; Sun, Gang; Luo, Wenjing; Zheng, Gang

    2012-11-01

    This work describes the detection of trace hydrogen chloride (HCl) gas through analyses of the resonance frequency signal from quartz crystal microbalance (QCM) sensors coated with polyaniline (PANI) functionalized polyamide 6 (PA 6) (PANI-PA 6) nanofiber-net-binary (NNB) structured membranes. The PA 6 NNB substrate comprising nanofibers and spider-web-like nano-nets fabricated by a versatile electro-spinning/netting (ESN) process offered an ideal interface for the uniform PANI functionalization and enhanced sensing performance. Benefiting from the large specific surface area, high porosity, and strong adhesive force to the QCM electrode of the PANI-PA 6 NNB membranes, the developed HCl-selective sensors exhibited a rapid response, good reproducibility and stability, and low detection limit (7 ppb) at room temperature. Additionally, the PANI-PA 6 NNB sensing membranes presented visible color changes upon cycled exposure to HCl and ammonia, suggesting their potential application in the development of colorimetric sensors. The PANI-PA 6 NNB coated QCM sensors are considered to be a promising candidate for trace HCl gas detection in practical applications.

  16. Improvement in the light sensitivity of the ultrahigh-speed high-sensitivity CCD with a microlens array

    NASA Astrophysics Data System (ADS)

    Hayashida, T.,; Yonai, J.; Kitamura, K.; Arai, T.; Kurita, T.; Tanioka, K.; Maruyama, H.; Etoh, T. Goji; Kitagawa, S.; Hatade, K.; Yamaguchi, T.; Takeuchi, H.; Iida, K.

    2008-02-01

    We are advancing the development of ultrahigh-speed, high-sensitivity CCDs for broadcast use that are capable of capturing smooth slow-motion videos in vivid colors even where lighting is limited, such as at professional baseball games played at night. We have already developed a 300,000 pixel, ultrahigh-speed CCD, and a single CCD color camera that has been used for sports broadcasts and science programs using this CCD. However, there are cases where even higher sensitivity is required, such as when using a telephoto lens during a baseball broadcast or a high-magnification microscope during science programs. This paper provides a summary of our experimental development aimed at further increasing the sensitivity of CCDs using the light-collecting effects of a microlens array.

  17. Highly sensitive detection using Herriott cell for laser absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhao, Chongyi; Song, Guangming; Du, Yang; Zhao, Xiaojun; Wang, Wenju; Zhong, Liujun; Hu, Mai

    2016-11-01

    The tunable diode laser absorption spectroscopy combined with the long absorption path technique is a significant method to detect harmful gas. The long optical path could come true by Herriott cell reducing the size of the spectrometers. A 15 cm long Herriott cell with 28.8 m optical absorption path after 96 times reflection was designed that enhanced detection sensitivity of absorption spectroscopy. According to the theory data of calculation, Herriott cell is analyzed and simulated by softwares Matlab and Lighttools.

  18. Adaptive interferometry for high sensitivity optical fiber sensing

    NASA Astrophysics Data System (ADS)

    Peigné, A.; Bortolozzo, U.; Residori, S.; Molin, S.; Dolfi, D.; Huignard, J.-P.

    2015-09-01

    We report on the use of an adaptive holographic interferometer, based on a liquid crystal light valve, to achieve phase shift measurements in an optical fiber. Owing to the physical mechanisms involved, the interferometer adapts itself to slow phase variations. As a consequence, it is possible to use a multimode fiber for sensing, which improves the sensitivity. Moreover, a distributed architecture relying on phase-OTDR principle is presented and a localization experiment is performed.

  19. The strain-rate sensitivity of high-strength high-toughness steels.

    SciTech Connect

    Dilmore, M.F.; Crenshaw, Thomas B.; Boyce, Brad Lee

    2006-01-01

    The present study examines the strain-rate sensitivity of four high strength, high-toughness alloys at strain rates ranging from 0.0002 s-1 to 200 s-1: Aermet 100, a modified 4340, modified HP9-4-20, and a recently developed Eglin AFB steel alloy, ES-1c. A refined dynamic servohydraulic method was used to perform tensile tests over this entire range. Each of these alloys exhibit only modest strain-rate sensitivity. Specifically, the strain-rate sensitivity exponent m, is found to be in the range of 0.004-0.007 depending on the alloy. This corresponds to a {approx}10% increase in the yield strength over the 7-orders of magnitude change in strain-rate. Interestingly, while three of the alloys showed a concominant {approx}3-10% drop in their ductility with increasing strain-rate, the ES1-c alloy actually exhibited a 25% increase in ductility with increasing strain-rate. Fractography suggests the possibility that at higher strain-rates ES-1c evolves towards a more ductile dimple fracture mode associated with microvoid coalescence.

  20. Re-evaluation of colorimetric Cl- data from natural waters with DOC

    USGS Publications Warehouse

    Norton, S.A.; Handlet, M.J.; Kahl, J.S.; Peters, N.E.

    1996-01-01

    Colorimetric Cl- data from natural solutions that contain dissolved organic carbon (DOC) may be biased high. We evaluated aquatic Cl- concentrations in ecosystem compartments at the Bear Brook Watershed, Maine, and from lakes in Maine, using ion chromatography and colorimetry. DOC imparts a positive interference on colorimetric Cl- results proportional to DOC concentrations at approximately 0.8 ??eq Cl-/L per mg DOC/L. The interference is not a function of Cl- concentration. The resulting bias in concentrations of Cl- may be 50% or more of typical environmental values for Cl- in areas remote from atmospheric deposition of marine aerosols. Such biased data in the literature appear to have led to spurious conclusions about recycling of Cl- by forests, the usefulness of Cl- as a conservative tracer in watershed studies, and calculations of elemental budgets, ion balance, charge density of DOC, and dry deposition factors.

  1. Evaluation of tetrazolium-based semiautomatic colorimetric assay for measurement of human antitumor cytotoxicity

    SciTech Connect

    Heo, D.S.; Park, J.G.; Hata, K.; Day, R.; Herberman, R.B.; Whiteside, T.L. )

    1990-06-15

    A 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT)-based colorimetric assay was developed and compared with 51Cr release from different adherent tumor cell targets (human squamous cell carcinoma lines of the head and neck established in our laboratory, melanoma, and colorectal carcinoma) using 5-7-day human lymphokine-activated killer cells and monocyte-depleted peripheral blood lymphocytes as effectors. With adherent tumor cell targets, MTT colorimetry was more sensitive than the 51Cr release assay in measuring the antitumor activity of effectors: median, 4385 (range, 988-8144) versus median, 1061 (range, 582-7294) lytic units (the number of effector cells required to lyse 20% of 5 x 10(3) targets)/10(7) effectors (P less than 0.01). Background effects (without effector cells) were comparable in 4-h assays (9% versus 10%) between MTT colorimetry and 51Cr release. In 24-h assays, MTT colorimetry showed higher antitumor activity (70-100% versus 40-60% lysis at 1:1 effector:target cell ratio) but lower background effects (6% versus 38%) than 51Cr release assay. Thus, MTT colorimetry was more sensitive, did not use radiolabeled targets, required fewer effector cells, and was easier, less expensive, and better adaptable to serial monitoring of effector cell function in cancer patients. This colorimetric assay is especially well suited to adherent tumor cell targets. The use of adherent tumor cell monolayers, as opposed to trypsinized single cell suspensions, provides an opportunity to measure interactions of effector cells with enzymatically unaltered solid tumor targets. Because of the greater sensitivity of the colorimetric assay, the transformation of MTT data into lytic units, as commonly used for 51Cr release assays, required an adjustment to avoid the extrapolation based on the exponential fit equation.

  2. Optimization of colorimetric DET technique for the in situ, two-dimensional measurement of iron(II) distributions in sediment porewaters.

    PubMed

    Bennett, William W; Teasdale, Peter R; Welsh, David T; Panther, Jared G; Jolley, Dianne F

    2012-01-15

    The recently developed colorimetric diffusive equilibration in thin films (DET) technique for the in situ, high-resolution measurement of iron(II) in marine sediments is optimized to allow measurement of the higher iron concentrations typical of freshwater sediment porewaters. Computer imaging densitometry (CID) is used to analyze the retrieved samplers following exposure to ferrozine, a colorimetric reagent selective for iron(II). The effect of ferrozine concentration, image processing parameters and ionic strength are investigated to improve the applicability of this technique to a wider range of aquatic systems than reported in the first publications of this approach. The technique was optimized to allow detection of up to 2,000 μmol L(-1) iron(II), a four-fold increase on the previous upper detection limit of 500 μ mol L(-1). The CID processing of the scanned color image was also optimized to adjust the sensitivity of the assay as required; by processing the image with different color channel filters, the sensitivity of the assay can be optimized for lower concentrations (up to 100 μmol L(-1)) or higher concentrations (up to 2,000 μmol L(-1)) of iron(II), depending on the specific site characteristics. This process does not require separate sampling probes or even separate scans of the DET gels as the color filter and grayscale conversion is done post-image capture. The optimized technique is very simple to use and provides highly representative, high-resolution (1mm) two-dimensional distributions of iron(II) in sediment porewaters. The detection limit of the optimized technique was 4.1±0.3 μmol L(-1) iron(II) and relative standard deviations were less than 6%.

  3. Genetic influence on brain catecholamines: high brain norepinephrine in salt-sensitive rats

    SciTech Connect

    Iwai, J; Friedman, R; Tassinari, L

    1980-01-01

    Rats genetically sensitive to salt-induced hypertension evinced higher levels of plasma norepinephrine and epinephrine than rats genetically resistant to hypertension. The hypertension-sensitive rats showed higher hypothalamic norepinephrine and lower epinephrine than resistant rats. In response to a high salt diet, brain stem norepinephrine increased in sensitive rats while resistant rats exhibited a decrease on the same diet.

  4. Analysis of Cyberbullying Sensitivity Levels of High School Students and Their Perceived Social Support Levels

    ERIC Educational Resources Information Center

    Akturk, Ahmet Oguz

    2015-01-01

    Purpose: The purpose of this paper is to determine the cyberbullying sensitivity levels of high school students and their perceived social supports levels, and analyze the variables that predict cyberbullying sensitivity. In addition, whether cyberbullying sensitivity levels and social support levels differed according to gender was also…

  5. A resorufin-based colorimetric and fluorescent probe for live-cell monitoring of hydrazine.

    PubMed

    Qian, Yong; Lin, Jie; Han, Lujing; Lin, Lin; Zhu, Hailiang

    2014-08-15

    We report a novel colorimetric and red-emitting fluorescent probe for hydrazine detection based on resorufin platform. This OFF-ON fluorescent probe shows a large (117nm) red-shifted absorption spectrum and the color changes from colorless to red upon addition of hydrazine in the aqueous solution, which can serve as a "naked-eye" probe for hydrazine. Moreover, this probe also shows a significant fluorescence increase (~16 folds) and excellent linear relationship at physiological pH. Utilizing this sensitive and selective probe, we have successfully detected hydrazine in living cells.

  6. A low-power, high-sensitivity micromachined optical magnetometer

    NASA Astrophysics Data System (ADS)

    Mhaskar, R.; Knappe, S.; Kitching, J.

    2012-12-01

    We demonstrate an optical magnetometer based on a microfabricated 87Rb vapor cell in a micromachined silicon sensor head. The alkali atom density in the vapor cell is increased by heating the cell with light brought to the sensor through an optical fiber, and absorbed by colored filters attached to the cell windows. A second fiber-optically coupled beam optically pumps and interrogates the atoms. The magnetometer operates on 140 mW of heating power and achieves a sensitivity below 20 fT/√Hz throughout most of the frequency band from 15 Hz to 100 Hz. Such a sensor can measure magnetic fields from the human heart and brain.

  7. Microwave assisted synthesis of tyrosine protected gold nanoparticles for dual (colorimetric and fluorimetric) detection of spermine and spermidine in biological samples.

    PubMed

    Rawat, Karuna A; Bhamore, Jigna R; Singhal, Rakesh Kumar; Kailasa, Suresh Kumar

    2017-02-15

    In this work, tyrosine-protected gold nanoparticles (Tyr-Au NPs) were fabricated by one-step reduction of Au(3+) ion using Tyr as a reducing and capping agent under microwave irradiation. The Tyr-Au NPs were successfully used as a dual probe for colorimetric and fluorescence turn-on assays of spermine and spermidine in biological samples. Upon addition of spermine and spermidine, the characteristic surface plasmon resonance (SPR) band of Tyr-Au NPs was red-shifted to 596 and 616nm and the emission peak (Tyr) at 410nm was gradually increased with increasing concentration of both analytes, confirming the aggregation of Tyr-Au NPs induced by spermine and spermidine, which results to restore fluorescence of Tyr on the surfaces of Au NPs. In addition, it shows high selectivity for sensitive detection of prostatic cancer biomarkers spermine and spermidine in real clinical applications with reduced sample preparations.

  8. Highly Sensitive Immunochromatographic Identification of Tetracycline Antibiotics in Milk

    PubMed Central

    Taranova, N. A.; Kruhlik, A. S.; Zvereva, E. A.; Shmanai, V. V.; Vashkevich, I. I.; Semyonov, D. A.; Eremin, S. A.; Zherdev, A. V.; Dzantiev, B. B.

    2015-01-01

    A rapid immunochromatographic assay was developed for the control of tetracycline (TC). The assay is based on the competition between immobilized TC-protein conjugate and TC in a tested sample for binding with polyclonal anti-TC antibodies conjugated to colloidal gold during the flow of the sample along a membrane strip with immobilized reactants. Conjugation of colloidal gold and the total immunoglobulin (IgG) fraction of polyclonal antibodies was used to increase the assay sensitivity to ensure low content of specific antibodies in the conjugate. This allowed effective inhibition of free TC and conjugate binding in the strip test zone. Photometric marker registration allows control of the reduction of binding, thereby enhancing detection sensitivity. The proposed assay allows TC to be detected at concentrations up to 20 ng/mL, exceeding the limit of detection of the known analogues, in a wide working range (more than two orders) of 60 pg/mL to 10 ng/mL, ensured through the use of polyclonal antibodies. The assay time is 10 min. The efficiency of the designed assay is shown to identify TC in milk; the degree of recovery of TC ranges from 90 to 112%. The precision of the concentrations measurements was no more than 10%. PMID:26689537

  9. Development of a high sensitive MEMS hydrophone using PVDF

    NASA Astrophysics Data System (ADS)

    Varadan, Vijay K.; Zhu, Bei; K. A, Jose

    2002-05-01

    The design and experimental evaluation of a PVDF-based MEMS hydrophone is presented in this paper. The basic structure of the hydrophone was fabricated on a silicon wafer using standard NMOS process technology. A MOSFET with extended gate electrode was designed as the interface circuit to the sensing material, which is a piezoelectric polymer, polyvinylidene difluoride (PVDF). Acoustic impedance possessed by this piezoelectric material provides a reasonable match to water, which makes it very attractive for underwater applications. The electrical signal generated by the PVDF film was directly coupled to the gate of the MOSFET. To minimize the parasitic capacitance underneath the PVDF film and hence improve the device sensitivity, a thick photoresist was first employed as the dielectric layer under the extended gate electrode. For underwater operation, a waterproof Rho-C rubber encapsulated the hydrophone. A silicon nitride layer passivated the active device, which is a good barrier material to most mobile ions and solvents. The device after passivation also shows a lower noise level. The theoretical model developed to predict the sensitivity of the hydrophone shows a reasonable agreement between the theory and the experiment.

  10. Platinum decorated carbon nanotubes for highly sensitive amperometric glucose sensing

    NASA Astrophysics Data System (ADS)

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

    2007-02-01

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

  11. High-throughput, high-sensitivity analysis of gene expression in Arabidopsis.

    PubMed

    Kris, Richard Martin; Felder, Stephen; Deyholos, Michael; Lambert, Georgina M; Hinton, James; Botros, Ihab; Martel, Ralph; Seligmann, Bruce; Galbraith, David W

    2007-07-01

    High-throughput gene expression analysis of genes expressed during salt stress was performed using a novel multiplexed quantitative nuclease protection assay that involves customized DNA microarrays printed within the individual wells of 96-well plates. The levels of expression of the transcripts from 16 different genes were quantified within crude homogenates prepared from Arabidopsis (Arabidopsis thaliana) plants also grown in a 96-well plate format. Examples are provided of the high degree of reproducibility of quantitative dose-response data and of the sensitivity of detection of changes in gene expression within limiting amounts of tissue. The lack of requirement for RNA purification renders the assay particularly suited for high-throughput gene expression analysis and for the discovery of novel chemical compounds that specifically modulate the expression of endogenous target genes.

  12. Advanced Cd(II) complexes as high efficiency co-sensitizers for enhanced dye-sensitized solar cell performance.

    PubMed

    Gao, Song; Fan, Rui Qing; Wang, Xin Ming; Qiang, Liang Sheng; Wei, Li Guo; Wang, Ping; Yang, Yu Lin; Wang, Yu Lei

    2015-11-07

    This work reports on two new complexes with the general formula [Cd3(IBA)3(Cl)2(HCOO)(H2O)]n (1) and {[Cd1.5(IBA)3(H2O)6]·3.5H2O}n (2), which can be synthesized by the reaction of Cd(II) with rigid linear ligand 4-HIBA containing imidazolyl and carboxylate functional groups [4-HIBA = 4-(1H-imidazol-1-yl)benzoic acid]. Single-crystal X-ray diffraction analyses indicate that complex 1 is a 2D "wave-like" layer structure constructed from trinuclear units and complex 2 is just a mononuclear structure. Surprisingly, both complexes 1 and 2 appear as a 3D supramolecular network via intermolecular hydrogen bonding interactions. What's more, due to their strong UV-visible absorption, 1 and 2 can be employed as co-sensitizers in combination with N719 to enhance dye-sensitized solar cell (DSSC) performance. Both of them could overcome the deficiency of the ruthenium complex N719 absorption in the region of ultraviolet and blue-violet, and the charge collection efficiency is also improved when 1 and 2 are used as co-sensitizers, which are all in favor of enhancing the performance. The DSSC devices using co-sensitizers of 1/N719 and 2/N719 show an overall conversion efficiency of 8.27% and 7.73% with a short circuit current density of 17.48 mA cm(-2) and 17.39 mA cm(-2), and an open circuit voltage of 0.75 V and 0.74 V, respectively. The overall conversion efficiency is 27.23% and 18.92% higher than that of a device solely sensitized by N719 (6.50%). Consequently, the prepared complexes are high efficiency co-sensitizers for enhancing the performance of N719 sensitized solar cells.

  13. High temperature probe sensor with high sensitivity based on Michelson interferometer

    NASA Astrophysics Data System (ADS)

    Zhao, Na; Fu, Haiwei; Shao, Min; Yan, Xu; Li, Huidong; Liu, Qinpeng; Gao, Hong; Liu, Yinggang; Qiao, Xueguang

    2015-05-01

    A novel Michelson interferometer based on a bi-taper is achieved. Such a device is fabricated by splicing a section of thin core fiber (TCF) at one end of single-mode fiber (SMF). Due to the fiber bi-taper at the splicing point of SMF and TCF, the light is coupled into the fiber core and cladding from lead in fiber core. The light will be reflected at the end of the fiber and then will be recoupled back into the lead out fiber core by the fiber bi-taper. While the light returns back to the lead out fiber, the intermodal interference will occur for the optical path difference between core mode and cladding mode. A high temperature sensitivity of 0.140 nm/°C is achieved from 30 to 800 °C, and the linearity is 99.9%. The configuration features the advantages of easy fabrication, a compact size, high sensitivity, wide sensing range and high mechanical strength, making it a good candidate for distant temperature sensing and oil prospecting.

  14. High-sensitivity, high-selectivity detection of chemical warfare agents

    NASA Astrophysics Data System (ADS)

    Pushkarsky, Michael B.; Webber, Michael E.; Macdonald, Tyson; Patel, C. Kumar N.

    2006-01-01

    We report high-sensitivity detection of chemical warfare agents (nerve gases) with very low probability of false positives (PFP). We demonstrate a detection threshold of 1.2ppb (7.7μg/m3 equivalent of Sarin) with a PFP of <1:106 in the presence of many interfering gases present in an urban environment through the detection of diisopropyl methylphosphonate, an accepted relatively harmless surrogate for the nerve agents. For the current measurement time of ˜60s, a PFP of 1:106 corresponds to one false alarm approximately every 23months. The demonstrated performance satisfies most current homeland and military security requirements.

  15. Ultra-high sensitive and high resolution optical coherence tomography using a laser induced electromagnetic dipole

    NASA Astrophysics Data System (ADS)

    Kuroda, Hiroto; Baba, Motoyoshi; Suzuki, Masayuki; Yoneya, Shin

    2013-09-01

    Utilizing an optical coherence tomography measurement, we have developed a technique that actively uses a dielectric response due to an induced dipole moment caused by a mode-locked pulsed laser light source. Irradiated laser light in the material induces a photo-induced electric dipole resulting in a refractive index change for its strong electric field. Using this technique, we obtained a highly sensitive fundus retina tomogram of a human eye in vivo with a resolution of 1.3 μm by single scanning for 20 ms using 8 fs mode-locked pulse laser light with a 350 nm spread spectrum.

  16. Research on test technology of high sensitivity and high frame rate of far ultraviolet spectroscopy

    NASA Astrophysics Data System (ADS)

    Sun, Guang-wei; Sun, Hong-sheng; Wang, Jia-peng; Gao, Shu-min

    2015-10-01

    Importance of ultraviolet calibration is growing fast as ultraviolet payloads are wildly used in national space plan. Calibration device for UV radiation celestial body simulator is established especially for the calibration of instantaneous radiation parameters and high-sensitivity radiation parameters. Parameters such as spectral radiance, spectral irradiance can be calibrated from 200 nm to 400 nm. The uncertainty of spectral radiance is 15% (k=2 and the uncertainty of spectral irradiance is 20% (k=2 .The calibration device is perspective for its application in national defense system.

  17. Multi-enzyme co-embedded organic-inorganic hybrid nanoflowers: synthesis and application as a colorimetric sensor.

    PubMed

    Sun, Jiayu; Ge, Jiechao; Liu, Weimin; Lan, Minhua; Zhang, Hongyan; Wang, Pengfei; Wang, Yanming; Niu, Zhongwei

    2014-01-07

    This study reports a facile method for the synthesis of multi-enzyme co-embedded organic-inorganic hybrid nanoflowers, using glucose oxidase (GOx) and horseradish peroxidase (HRP) as the organic components, and Cu3(PO4)2 · 3H2O as the inorganic component. The synthesized nanoflowers enable the combination of a two-enzyme cascade reaction in one step, in which the GOx component of the nanoflowers oxidizes glucose to generate H2O2, which then reacts with the adjacent HRP component on the nanoflowers to oxidize the chromogenic substrates, resulting in an apparent color change. Given the close proximity of the two enzyme components in a single nanoflower, this novel sensor greatly reduces the diffusion and decomposition of H2O2, and greatly enhances the sensitivity of glucose detection. Thus, the obtained multi-enzyme co-embedded organic-inorganic hybrid nanoflowers can be unquestionably used as highly sensitive colorimetric sensors for the detection of glucose. Notably, this work presents a very facile route for the synthesis of multi-enzyme co-embedded nanomaterials for the simultaneous catalysis of multi-step cascade enzymatic reactions. Furthermore, it has great potential for application in biotechnology, and biomedical and environmental chemistry.

  18. High sensitivity infrared 10.6 micrometer heterodyne receiver development

    NASA Technical Reports Server (NTRS)

    1972-01-01

    The results are presented for a study on the design of an infrared 10.6-micrometer quantum-noise-limited optical receiver subsystem. Performance measurements of the HgCdTe photomixer preamplifier combination were carried out for photomixer temperatures up to 152 K and a photomixer frequency response of up to 420 MHz was obtained. Results of temperature and bias cycling of HgCdTe photomixers are reported. Design considerations for an operational 10.6 micrometer heterodyne receiver are presented. These consist of design data on required laser LO illumination, heat load levels for photomixer cooler, photomixer uniformity and the effects of photomixer impedance match on receiver sensitivity. Analysis and measurements of 10.6 micrometer heterodyne detection in an extrinsic photoconductive (p-type) HgCdTe photomixer are also presented.

  19. Highly sensitive humidity sensing properties of carbon quantum dots films

    SciTech Connect

    Zhang, Xing; Ming, Hai; Liu, Ruihua; Han, Xiao; Kang, Zhenhui; Liu, Yang; Zhang, Yonglai

    2013-02-15

    Graphical abstract: Display Omitted Highlights: ► A humidity sensing device was fabricated based on carbon quantum dots (CQDs) films. ► The conductivity of the CQDs films shows a linear and rapid response to atmosphere humidity. ► The humidity sensing property was due to the hydrogen bonds between the functional groups on CQDs. -- Abstract: We reported the fabrication of a humidity sensing device based on carbon quantum dots (CQDs) film. The conductivity of the CQDs film has a linear and rapid response to relative humidity, providing the opportunity for the fabrication of humidity sensing devices. The mechanism of our humidity sensor was proposed to be the formation of hydrogen bonds between carbon quantum dots and water molecules in the humidity environment, which significantly promote the electrons migration. In a control experiment, this hypothesis was confirmed by comparing the humidity sensitivity of candle soot (i.e. carbon nanoparticles) with and without oxygen containing groups on the surfaces.

  20. Carbon nanotube quantum dots as highly sensitive THz spectrometers

    NASA Astrophysics Data System (ADS)

    Rinzan, Mohamed; Jenkins, Greg; Drew, Dennis; Shafranjuk, Serhii; Barbara, Paola

    2012-02-01

    We show that carbon nanotube quantum dots (CNT-Dots) coupled to antennas are extremely sensitive, broad-band, terahertz quantum detectors. Their response is due to photon-assisted single-electron tunneling (PASET)[1], but cannot be fully understood with orthodox PASET models[2]. We consider intra-dot excitations and non-equilibrium cooling to explain the anomalous response. REFERENCES: [1] Y. Kawano, S. Toyokawa, T. Uchida and K. Ishibashi, THz photon assisted tunneling in carbon-nanotube quantum dots, Journal of Applied Physics 103, 034307 (2008). [2] P. K. Tien and J. P. Gordon, Multiphoton Process Observed in the Interaction of Microwave Fields with the Tunneling between Superconductor Films, Phys. Rev. 129, 647 (1963).

  1. Development of highly sensitive sensor system for methane utilizing cataluminescence.

    PubMed

    Gong, Gu; Zhu, Hua

    2016-02-01

    A gaseous sensor system was developed for the detection of methane based on its cataluminescence emission. Cataluminescence characteristics and optimal conditions were studied in detail under optimized experimental conditions. Results showed that the methane cataluminescence sensor system could cover a linear detection range from 10 to 5800 ppm (R = 0.9963, n = 7) and the detection limit was about 7 ppm (S/N = 3), which was below the standard permitted concentration. Moreover, a linear discriminant analysis method was used to test the recognizable performance of the methane sensor. It was found that methane, ethane, propane and pentane could be distinguished clearly. Its methane sensing properties, including improved sensitivity, selectivity, stability and recognition demonstrated the TiO2/SnO2 materials to be promising candidates for constructing a cataluminescence-based gas sensor that could be used for detecting explosive gas contaminants.

  2. Genome-wide synteny through highly sensitive sequence alignment: Satsuma

    PubMed Central

    Grabherr, Manfred G.; Russell, Pamela; Meyer, Miriah; Mauceli, Evan; Alföldi, Jessica; Di Palma, Federica; Lindblad-Toh, Kerstin

    2010-01-01

    Motivation: Comparative genomics heavily relies on alignments of large and often complex DNA sequences. From an engineering perspective, the problem here is to provide maximum sensitivity (to find all there is to find), specificity (to only find real homology) and speed (to accommodate the billions of base pairs of vertebrate genomes). Results: Satsuma addresses all three issues through novel strategies: (i) cross-correlation, implemented via fast Fourier transform; (ii) a match scoring scheme that eliminates almost all false hits; and (iii) an asynchronous ‘battleship’-like search that allows for aligning two entire fish genomes (470 and 217 Mb) in 120 CPU hours using 15 processors on a single machine. Availability: Satsuma is part of the Spines software package, implemented in C++ on Linux. The latest version of Spines can be freely downloaded under the LGPL license from http://www.broadinstitute.org/science/programs/genome-biology/spines/ Contact: grabherr@broadinstitute.org PMID:20208069

  3. Novel Characteristics of Photodamage to PSII in a High-Light-Sensitive Symbiodinium Phylotype.

    PubMed

    Karim, Widiastuti; Seidi, Azadeh; Hill, Ross; Chow, Wah S; Minagawa, Jun; Hidaka, Michio; Takahashi, Shunichi

    2015-06-01

    Dinoflagellates from the genus Symbiodinium form symbiotic relationships with many marine invertebrates, including reef-building corals. Symbiodinium is genetically diverse, and acquiring suitable Symbiodinium phylotypes is crucial for the host to survive in habitat environments, such as high-light conditions. The sensitivity of Symbiodinium to high light differs among Symbiodinium phylotypes, but the mechanism that controls light sensitivity has not yet been fully resolved. In the present study using high-light-tolerant and -sensitive Symbiodinium phylotypes, we examined what determines sensitivity to high light. In growth experiments under different light intensities, Symbiodinium CS-164 (clade B1) and CCMP2459 (clade B2) were identified as high-light-tolerant and -sensitive phylotypes, respectively. Measurements of the maximum quantum yield of photosystem II (PSII) and the maximum photosynthetic oxygen production rate after high-light exposure demonstrated that CCMP2459 is more sensitive to photoinhibition of PSII than CS-164, and tends to lose maximum photosynthetic activity faster. Measurement of photodamage to PSII under light of different wavelength ranges demonstrated that PSII in both Symbiodinium phylotypes was significantly more sensitive to photodamage under shorter wavelength regions of light spectra (<470 nm). Importantly, PSII in CCMP2459, but not CS-164, was also sensitive to photodamage under the regions of light spectra around 470-550 and 630-710 nm, where photosynthetic antenna proteins of Symbiodinium have light absorption peaks. This finding indicates that the high-light-sensitive CCMP2459 has an extra component of photodamage to PSII, resulting in higher sensitivity to high light. Our results demonstrate that sensitivity of PSII to photodamage differs among Symbiodinium phylotypes and this determines their sensitivity to high light.

  4. Basic design principles of colorimetric vision systems

    NASA Astrophysics Data System (ADS)

    Mumzhiu, Alex M.

    1998-10-01

    Color measurement is an important part of overall production quality control in textile, coating, plastics, food, paper and other industries. The color measurement instruments such as colorimeters and spectrophotometers, used for production quality control have many limitations. In many applications they cannot be used for a variety of reasons and have to be replaced with human operators. Machine vision has great potential for color measurement. The components for color machine vision systems, such as broadcast quality 3-CCD cameras, fast and inexpensive PCI frame grabbers, and sophisticated image processing software packages are available. However the machine vision industry has only started to approach the color domain. The few color machine vision systems on the market, produced by the largest machine vision manufacturers have very limited capabilities. A lack of understanding that a vision based color measurement system could fail if it ignores the basic principles of colorimetry is the main reason for the slow progress of color vision systems. the purpose of this paper is to clarify how color measurement principles have to be applied to vision systems and how the electro-optical design features of colorimeters have to be modified in order to implement them for vision systems. The subject of this presentation far exceeds the limitations of a journal paper so only the most important aspects will be discussed. An overview of the major areas of applications for colorimetric vision system will be discussed. Finally, the reasons why some customers are happy with their vision systems and some are not will be analyzed.

  5. A high sensitive fiber-optic strain sensor with tunable temperature sensitivity for temperature-compensation measurement

    PubMed Central

    Hu, Jie; Huang, Hui; Bai, Min; Zhan, TingTing; Yang, ZhiBo; Yu, Yan; Qu, Bo

    2017-01-01

    A high sensitive fiber-optic strain sensor, which consists of a cantilever, a tandem rod and a fiber collimator, was proposed. The tandem rod, which transfer the applied strain to the cantilever, was used for tuning the temperature sensitivity from −0.15 to 0.19 dB/°C via changing the length ratio of the rods. Moreover, due to the small beam divergence of the collimator, high strain sensitivity can be realized via incident-angle sensitive detection-mechanism. A strain detection-range of 1.1 × 103 με (with a sensing length of 21.5 mm), a detection limit of 5.7 × 10−3 με, and a maximum operating frequency of 1.18 KHz were demonstrated. This sensor is promising for compensating the thermal-expansion of various target objects. PMID:28205595

  6. Vertically stacked plasmonic nanoparticles in a circular arrangement: a key to colorimetric refractive index sensing.

    PubMed

    Seo, Sujin; Gartia, Manas Ranjan; Liu, Gang Logan

    2014-10-21

    True colorimetric sensing produces a linear spectral response of a single peak within the visible light range with various surrounding media refractive indices. We demonstrate how the circular arrangement of hemispheric silver nanoparticles achieves colorimetric properties without modifying the associated full-width-half-maximum values in a broad range of surrounding media refractive indices. We also show that the vertical out-of-plane arrangement of each circular array in nanoholes enhances the signal-to-noise ratio. High electric field confinement at the interface of the nanoparticles and the supporting substrate reveals the effect of the dielectric constant of the substrate and the morphology of the 3D nanoparticle arrays on achieving a single resonance peak in the visible range with a change in the surrounding refractive index. This study opens up the pathway to top-down fabricated nanostructure platform based plasmonic colorimetric sensing with a single resonance peak in the visible range. The studied rich set of tunable geometrical nanostructures enables broadening of the working optical range of the device.

  7. Colorimetric detection of Shewanella oneidensis based on immunomagnetic capture and bacterial intrinsic peroxidase activity

    NASA Astrophysics Data System (ADS)

    Wen, Junlin; Zhou, Shungui; Chen, Junhua

    2014-06-01

    Rapid detection and enumeration of target microorganisms is considered as a powerful tool for monitoring bioremediation process that typically involves cleaning up polluted environments with functional microbes. A novel colorimetric assay is presented based on immunomagnetic capture and bacterial intrinsic peroxidase activity for rapidly detecting Shewanella oneidensis, an important model organism for environmental bioremediation because of its remarkably diverse respiratory abilities. Analyte bacteria captured on the immunomagnetic beads provided a bacterial out-membrane peroxidase-amplified colorimetric readout of the immunorecognition event by oxidizing 3, 3', 5, 5'-tetramethylbenzidine (TMB) in the present of hydrogen peroxide. The high-efficiency of immunomagnetic capture and signal amplification of peroxidase activity offers an excellent detection performance with a wide dynamic range between 5.0 × 103 and 5.0 × 106 CFU/mL toward target cells. Furthermore, this method was demonstrated to be feasible in detecting S. oneidensis cells spiked in environmental samples. The proposed colorimetric assay shows promising environmental applications for rapid detection of target microorganisms.

  8. Variation of phlorotannins among three populations of Fucus vesiculosus as revealed by HPLC and colorimetric quantification.

    PubMed

    Koivikko, R; Eränen, J K; Loponen, J; Jormalainen, V

    2008-01-01

    In ecological studies, phlorotannins have conventionally been quantified as a group with similar functionality. Since this group consists of oligo- and polymers, the quantification of their pooled contents alone may not sufficiently describe the variation of these metabolites. Genetic variation, plastic responses to environment, and the ecological functions of separate phlorotannin oligo- and polymers may differ. Two analyses, i.e., the colorimetric Folin-Ciocalteu assay and a normal-phase high-performance liquid chromatographic (HPLC) method were used to study genetic and environmental variation in phlorotannins of the brown alga Fucus vesiculosus (L.). The colorimetric method provides the total phlorotannin content, the latter a profile of 14 separate traces from the phenolic extract that represent an individual or groups of phlorotannins. We reared the algae that originated from three separate populations in a common garden for 3 months under ambient and enriched-nutrient availability and found that they differed in both their total phlorotannin content and in phlorotannin profiles. Some individual traces of the profiles separated the populations more clearly than the colorimetric assay. Although nutrient enrichment decreased total phlorotannin content, it did not show a significant influence on the phlorotannin profile. This implies that plastic responses of compounds other than phlorotannins may interfere with the determination of total phlorotannins. However, the phlorotannin profile and the total content showed genetic variation among local populations of F. vesiculosus; therefore, phlorotannins may respond to natural selection and evolve both quantitatively and qualitatively.

  9. Illumination and device independence for colorimetric detection of urinary biomarkers with smartphone.

    PubMed

    Karisen, Haakon; Tao Dong

    2016-08-01

    Diaper wearing elderly with functional impairments and/or incontinence is at high risk of contracting urinary tract infections. Nurses struggle with collection of urine samples for analysis. Therefore, a smartphone application is under development as a rapid screening device to work in conjunction with a colorimetric diaper assay that collects and tests urine within a diaper. The focus of this work is to make a practical and useful tool that medical personnel (the user) can use for rapid screening on patients in the field, only with a smartphone and assay available. The main challenge is to achieve illumination and device independency for a wide range of colorimetric biomarkers without using any standardization, such as attachments, special lamps, or boxes. We achieved illumination and device independent semi-quantitative detection by using discriminant analysis and classification of simultaneously photographed colorimetric test results and reference colors to ensure that any variation in image conditions applies approximately equal for reference and test. This requires retraining of classifiers on each analysis, but appears to be the most viable solution to solving the challenges while maintaining the user-friendliness.

  10. Colorimetric detection of melamine based on p-chlorobenzenesulfonic acid-modified AuNPs

    NASA Astrophysics Data System (ADS)

    Li, Jianfang; Huang, Pengcheng; Wu, Fangying

    2016-06-01

    A highly selective and sensitive method is developed for colorimetric detection of melamine using gold nanoparticles (AuNPs) functionalized with p-chlorobenzenesulfonic acid. The addition of melamine induced the aggregation of AuNPs, as evidenced from the morphological characterizations and the color changed from red wine to blue, which could also be monitored by the UV-visible spectrometer and even naked eyes. This process caused a significant increase in the absorbance ratio (A650nm/A520nm) of p-chlorobenzenesulfonic acid-AuNPs. Under optimized conditions, the system exhibited a linear response to melamine in the range of 6.0 × 10-7-1.5 × 10-6 mol L-1 with a correlation coefficient of 0.997, and the limit of detection can even be 2.3 nM, which was much lower than some other methods and the safe limits (20 μM in both the USA and EU, 8.0 μM for infant formula in China, 1.2 μM in the CAC (Codex Alimentarius Commission) review for melamine in liquid infant formula). More importantly, the developed method presented excellent tolerance to coexisting common metal ions such as Ca2+, Zn2+, whose concentration is 1000 times of melamine, so that it had been applied to the analysis of melamine in liquid milk and milk powder with the recovery of 97.0-101 % and 100-103 %, respectively, indicating that the proposed method is quite a highly effective means to determine melamine in milk products.

  11. High fat diet-fed obese rats are highly sensitive to doxorubicin-induced cardiotoxicity

    SciTech Connect

    Mitra, Mayurranjan S.; Donthamsetty, Shashikiran; White, Brent; Mehendale, Harihara M.

    2008-09-15

    Often, chemotherapy by doxorubicin (Adriamycin) is limited due to life threatening cardiotoxicity in patients during and posttherapy. Recently, we have shown that moderate diet restriction remarkably protects against doxorubicin-induced cardiotoxicity. This cardioprotection is accompanied by decreased cardiac oxidative stress and triglycerides and increased cardiac fatty-acid oxidation, ATP synthesis, and upregulated JAK/STAT3 pathway. In the current study, we investigated whether a physiological intervention by feeding 40% high fat diet (HFD), which induces obesity in male Sprague-Dawley rats (250-275 g), sensitizes to doxorubicin-induced cardiotoxicity. A LD{sub 10} dose (8 mg doxorubicin/kg, ip) administered on day 43 of the HFD feeding regimen led to higher cardiotoxicity, cardiac dysfunction, lipid peroxidation, and 80% mortality in the obese (OB) rats in the absence of any significant renal or hepatic toxicity. Doxorubicin toxicokinetics studies revealed no change in accumulation of doxorubicin and doxorubicinol (toxic metabolite) in the normal diet-fed (ND) and OB hearts. Mechanistic studies revealed that OB rats are sensitized due to: (1) higher oxyradical stress leading to upregulation of uncoupling proteins 2 and 3, (2) downregulation of cardiac peroxisome proliferators activated receptor-{alpha}, (3) decreased plasma adiponectin levels, (4) decreased cardiac fatty-acid oxidation (666.9 {+-} 14.0 nmol/min/g heart in ND versus 400.2 {+-} 11.8 nmol/min/g heart in OB), (5) decreased mitochondrial AMP-{alpha}2 protein kinase, and (6) 86% drop in cardiac ATP levels accompanied by decreased ATP/ADP ratio after doxorubicin administration. Decreased cardiac erythropoietin and increased SOCS3 further downregulated the cardioprotective JAK/STAT3 pathway. In conclusion, HFD-induced obese rats are highly sensitized to doxorubicin-induced cardiotoxicity by substantially downregulating cardiac mitochondrial ATP generation, increasing oxidative stress and downregulating

  12. Digitizing Gold Nanoparticle-Based Colorimetric Assay by Imaging and Counting Single Nanoparticles.

    PubMed

    Yuan, Liang; Wang, Xian; Fang, Yimin; Liu, Chenbin; Jiang, Dan; Wo, Xiang; Wang, Wei; Chen, Hong-Yuan

    2016-02-16

    Gold colloid changes its color when the internanoparticle distance changes. On the basis of analyte-induced aggregation or disaggregation behavior of gold nanoparticles (AuNPs), versatile colorimetric assays have been developed for measuring various kinds of analytes including proteins, DNA, small molecules, and ions. Traditional read-out signals, which are usually measured by a spectrometer or naked eyes, are based on the averaged extinction properties of a bulk solution containing billions of nanoparticles. Averaged extinction property of a large amount of nanoparticles diminished the contribution from rare events when the analyte concentration was low, thus resulting in limited detection sensitivity. Instead of measuring the averaged optical property from bulk colloid, in the present work, we proposed a digital counterpart of the colorimetric assay by imaging and counting individual AuNPs. This method quantified the analyte concentration with the number percentage of large-sized AuNPs aggregates, which were digitally counted with surface plasmon resonance microscopy (SPRM), a plasmonic imaging technique recently developed by us and other groups. SPRM was able to identify rare AuNPs aggregates despite their small population and greatly improved the detection sensitivity as demonstrated by two model systems based on analyte-induced aggregation and disaggregation, respectively. Furthermore, besides plasmonic AuNPs, SPRM is also suitable for imaging and counting nonplasmonic nanomaterials such as silica and metal oxide with poor extinction properties. It is thus anticipated that the present digitized assay holds a great potential for expanding the colorimetric assay to broad categories of nonplasmonic nanoparticles.

  13. From CIE 2006 physiological model to improved age-dependent and average colorimetric observers.

    PubMed

    Sarkar, Abhijit; Autrusseau, Florent; Viénot, Françoise; Le Callet, Patrick; Blondé, Laurent

    2011-10-01

    In the context of color perception on modern wide-gamut displays with narrowband spectral primaries, we performed a theoretical analysis on various aspects of physiological observers proposed by CIE TC 1-36 (CIEPO06). We allowed certain physiological factors to vary, which was not considered in the CIEPO06 framework. For example, we analyzed that the long-wave-sensitive (LWS) or medium-wave-sensitive (MWS) peak wavelength shift in the photopigment absorption spectra, a factor not modeled in CIEPO06, contributed more toward observer variability than some of the factors considered in the model. Further, we compared the color-matching functions derived from the CIEPO06 model and the CIE 10° standard colorimetric observer to the average observer data from three distinct subgroups of Stiles-Burch observers, formed on the basis of observer ages (22-23 years, 27-29 years, and 49-50 years). The errors in predicting the x(λ) and y(λ) color-matching functions of the intragroup average observers in the long-wave range and in the medium-wave range, respectively, were generally more in the case of the CIEPO06 model compared to the 10° standard colorimetric observer and manifested in both spectral and chromaticity space. In contrast, the short-wave-sensitive z₁₀(λ) function of the 10° standard colorimetric observer performed poorly compared to the CIEPO06 model for all three subgroups. Finally, a constrained nonlinear optimization on the CIEPO06 model outputs showed that a peak wavelength shift of photopigment density alone could not improve the model prediction errors at higher wavelengths. As an alternative, two optimized weighting functions for each of the LWS and MWS cone photopigment densities led to significant improvement in the prediction of intra-age-group average data for both the 22-23 year and 49-50 year age groups. We hypothesize that the assumption in the CIEPO06 model that the peak optical density of visual pigments does not vary with age is false and is

  14. Highly sensitive glucose biosensor based on Au-Ni coaxial nanorod array having high aspect ratio.

    PubMed

    Hsu, Che-Wei; Wang, Gou-Jen

    2014-06-15

    An effective glucose biosensor requires a sufficient amount of GOx immobilizing on the electrode surface. An electrode of a 3D nanorod array, having a larger surface-to-volume ratio than a 2D nanostructure, can accommodate more GOx molecules to immobilize onto the surface of the nanorods. In this study, a highly sensitive Au-Ni coaxial nanorod array electrode fabricated through the integration of nano electroforming and immersion gold (IG) method for glucose detection was developed. The average diameter of the as-synthesized Ni nanorods and that of the Au-Ni nanorods were estimated to be 150 and 250 nm, respectively; both had a height of 30 μm. The aspect ratio was 120. Compared to that of a flat Au electrode, the effective sensing area was enhanced by 79.8 folds. Actual glucose detections demonstrated that the proposed Au-Ni coaxial nanorod array electrode could operate in a linear range of 27.5 μM-27.5mM with a detection limit of 5.5μM and a very high sensitivity of 769.6 μA mM(-1)cm(-2). Good selectivity of the proposed sensing device was verified by sequential injections of uric acid (UA) and ascorbic acid (AA). Long-term stability was examined through successive detections over a period of 30 days.

  15. High-sensitivity in situ QCLAS-based ammonia concentration sensor for high-temperature applications

    NASA Astrophysics Data System (ADS)

    Peng, W. Y.; Sur, R.; Strand, C. L.; Spearrin, R. M.; Jeffries, J. B.; Hanson, R. K.

    2016-07-01

    A novel quantum cascade laser (QCL) absorption sensor is presented for high-sensitivity in situ measurements of ammonia (hbox {NH}_3) in high-temperature environments, using scanned wavelength modulation spectroscopy (WMS) with first-harmonic-normalized second-harmonic detection (scanned WMS-2 f/1 f) to neutralize the effect of non-absorption losses in the harsh environment. The sensor utilized the sQ(9,9) transition of the fundamental symmetric stretch band of hbox {NH}_3 at 10.39 {\\upmu }hbox {m} and was sinusoidally modulated at 10 kHz and scanned across the peak of the absorption feature at 50 Hz, leading to a detection bandwidth of 100 Hz. A novel technique was used to select an optimal WMS modulation depth parameter that reduced the sensor's sensitivity to spectral interference from hbox {H}_2hbox {O} and hbox {CO}_2 without significantly sacrificing signal-to-noise ratio. The sensor performance was validated by measuring known concentrations of hbox {NH}_3 in a flowing gas cell. The sensor was then demonstrated in a laboratory-scale methane-air burner seeded with hbox {NH}_3, achieving a demonstrated detection limit of 2.8 ± 0.26 ppm hbox {NH}_3 by mole at a path length of 179 cm, equivalence ratio of 0.6, pressure of 1 atm, and temperatures of up to 600 K.

  16. Highly Sensitive and Robust Damage Detection of Periodic Structures with Piezoelectric Networking

    DTIC Science & Technology

    2008-05-01

    REPORT TYPE Final 3. DATES COVERED (From - To) December 15. 2006 to May 3 1. 2008 4. TITLE AND SUBTITLE Highly Sensitive and Robust Damage...localization characteristics of such periodic structures to enhance damage detection sensitivity and robustness through piezoelectric circuitry...ANSI Sid Z39 18 Adobe Professional 7.0 Highly Sensitive and Robust Damage Detection of Periodic Structures with Piezoelectric Networking GRANT

  17. High sensitivity of northeastern broadleaf forest trees to water availability

    NASA Astrophysics Data System (ADS)

    Levesque, M.; Pederson, N.; Andreu-Hayles, L.

    2015-12-01

    Temperate deciduous forests of eastern US provide goods and services to millions of people and play a vital role in the terrestrial carbon and hydrological cycles. However, ongoing climate change and increased in CO2 concentration in the atmosphere (ca) are expected to alter growth and gas exchange of trees, and ultimately forest productivity. Still, the magnitude of these effects is unclear. A better comprehension of the species-specific responses to environmental changes will better inform models and managers on the vulnerability and resiliency of these forests. Tree-ring analysis was combined with δ¹³C and δ18O measurements to investigate growth and physiological responses of red oak (Quercus rubra L.) and tulip poplar (Liriodendron tulipifera L.) in northeastern US to changes in water availability and ca for the period 1950-2014. We found very strong correlations between summer climatic water balance (June-August) and isotopic tree-ring series for δ¹³C (r = -0.65 and -0.73), and δ18O (r = -0.59 and -0.70), for red oak and tulip poplar, respectively. In contrast, tree-ring width was less sensitive to summer water availability (r = 0.33-0.39). Prior to the mid 1980s, low water availability resulted in low stomatal conductance, photosynthesis, and growth. Since that period, pluvial conditions occurring in northeastern US have increased stomatal conductance, carbon uptake, and growth of both species. These findings demonstrate that broadleaf trees in this region could be more sensitive to drought than expected. This appears especially true since much of the calibration period looks wet in a multi-centennial perspective. Further, stronger spatial correlations were found between climate data with tree-ring isotopes than with tree-ring width and the geographical area of the observed δ18O-precipitation response (i.e. the area over which correlations are > 0.5) covers most of the northeastern US. Given the good fit between the isotopic time series and water

  18. Highly sensitive homogenous chemiluminescence immunoassay using gold nanoparticles as label

    NASA Astrophysics Data System (ADS)

    Luo, Jing; Cui, Xiang; Liu, Wei; Li, Baoxin

    2014-10-01

    Homogeneous immunoassay is becoming more and more attractive for modern medical diagnosis because it is superior to heterogeneous immunoassay in sample and reagent consumption, analysis time, portability and disposability. Herein, a universal platform for homogeneous immunoassay, using human immunoglobulin G (IgG) as a model analyte, has been developed. This assay relies upon the catalytic activity of gold nanoparticles (AuNPs) on luminol-AgNO3 chemiluminescence (CL) reaction. The immunoreaction of antigen and antibody can induce the aggregation of antibody-functionalized AuNPs, and after aggregation the catalytic activity of AuNPs on luminol-AgNO3 CL reaction is greatly enhanced. Without any separation steps, a CL signal is generated upon addition of a trigger solution, and the CL intensity is directly correlated to the quantity of IgG. The detection limit of IgG was estimated to be as low as 3 pg/mL, and the sensitivity was better than that of the reported AuNPs-based CL immunoassay for IgG.

  19. Achieving tunable sensitivity in composite high-energy density materials

    NASA Astrophysics Data System (ADS)

    Kuklja, Maija M.; Tsyshevsky, Roman V.; Rashkeev, Sergey

    2017-01-01

    Laser irradiation provides a unique opportunity for selective, predictive, and controlled initiation of energetic materials. We propose a consistent micro-scale mechanism of photoexcitation at the interface, formed by a molecular energetic material and a metal oxide. A specific PETN-MgO model composite is used to illustrate and explain seemingly puzzling experiments on selective laser initiation of energetic materials, which reported that the presence of metal oxide additives triggered the photoinitiation by an unusually low energy. We suggest that PETN photodecomposition is catalyzed by oxygen vacancies (F0 centers) at the MgO surface. The proposed model suggests ways to tune sensitivity of energetic molecular materials to photoinitiation. Our quantum-chemical calculations suggest that the structural point defects (e.g., oxygen vacancies) strongly interact with the molecular material (e.g., adsorbed energetic molecules) by inducing a charge transfer at the interface and hence play an imperative role in governing both energy absorption and energy release in the system. Our approach and conclusions provide a solid basis for novel design of energetic interfaces with desired properties and offers a new perspective in the field of explosive materials and devices.

  20. Silver Nanoclusters with Specific Ion Recognition Modulated by Ligand Passivation toward Fluorimetric and Colorimetric Copper Analysis and Biological Imaging.

    PubMed

    Sun, Zongzhao; Li, Shuying; Jiang, Yao; Qiao, Yuchun; Zhang, Liyan; Xu, Lulu; Liu, Jinghui; Qi, Wei; Wang, Hua

    2016-02-05

    Silver nanoclusters were synthesized and passivated by glutathione (GSH) ligand, with high aqueous stability and powerful red fluorescence and UV-vis yellow colour. Importantly, the specific recognition of the AgNCs was modulated from Hg(2+) ions to Cu(2+) ions upon the GSH passivation, of which the unique GSH-Cu(2+) chelating reaction could conduct the fluorescence quenching of AgNCs. Strong UV-vis absorbance of GSH-passivated AgNCs could also be realized depending on the Cu(2+) levels. Moreover, the Cu(2+)-induced loss of fluorescence and UV-vis absorbance of GSH-passivated AgNCs could be well restored by using stronger Cu(2+) chelating agent. A simultaneous and reversible fluorimetric and colorimetric sensing method was thereby developed for probing Cu(2+) ions in blood with high sensitivity and selectivity. Subsequently, the fluorescence-trackable imaging for live tissues and cells was demonstrated towards the analysis Cu(2+) ions using GSH-passivated AgNCs as the fluorescent probes. This study indicates that the use of functional ligands like GSH could not only modulate the specific ion recognition of AgNCs, but also endow them the high aqueous stability and powerful red fluorescence towards the wide applications for ion sensing and biological imaging in the complicated media like blood.