The Experts below are selected from a list of 180 Experts worldwide ranked by ideXlab platform
Yi Ding - One of the best experts on this subject based on the ideXlab platform.
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molecularly imprinted polymer decorated nanoporous Gold for highly selective and sensitive electrochemical sensors
Scientific Reports, 2015Co-Authors: Yingchun Li, Hui Tang, Dongsheng Zhao, Yi DingAbstract:Electrochemical nanosensors based on nanoporous Gold Leaf (NPGL) and molecularly imprinted polymer (MIP) are developed for pharmaceutical analysis by using metronidazole (MNZ) as a model analyte. NPGL, serving as the loading platform for MIP immobilization, possesses large accessible surface area with superb electric conductivity, while electrochemically synthesized MIP thin layer affords selectivity for specific recognition of MNZ molecules. For MNZ determination, the hybrid electrode shows two dynamic linear range of 5 × 10−11 to 1 × 10−9 mol L−1 and 1 × 10−9 to 1.4 × 10−6 mol L−1 with a remarkably low detection limit of 1.8 × 10−11 mol L−1 (S/N = 3). In addition, the sensor exhibits high binding affinity and selectivity towards MNZ with excellent reproducibility and stability. Finally, the reliability of MIP-NPGL for MNZ detection is proved in real fish tissue samples, demonstrating the potential for the proposed electrochemical sensors in monitoring drug and biological samples.
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nanoporous Gold Leaf for amperometric determination of nitrite
Electroanalysis, 2011Co-Authors: Liqin Wang, Zhaona Liu, Yi DingAbstract:Ultra-thin free-standing nanoporous Gold Leaf made by dealloying exhibits excellent electrocatalytic activities toward nitrite oxidation. The electrochemical responses of nitrite ions on this novel nano-electrode is found not dependent on pH over a wide range from 4.5 to 8.0, which is markedly different from that of Gold oxidation, a process known to be highly pH-sensitive. Amperometric study shows a linear relationship for nitrite determination in a concentration range from 1 µM to 1 mM. This nanostructured Gold electrode displays good stability, repeatability and selectivity which suggests its potential for the development of new electrochemical sensors.
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electrochemiluminescence of cdte quantum dots as labels at nanoporous Gold Leaf electrodes for ultrasensitive dna analysis
Talanta, 2010Co-Authors: Rongyue Wang, Yi Ding, Xiaoli Zhang, Wenrui JinAbstract:Abstract A new electrochemiluminescence (ECL) DNA assay is developed using quantum dots (QDs) as DNA labels. When nanoporous Gold Leaf (NPGL) electrodes are used, sensitivity of the ECL assay is remarkably increased due to ultra-thin nanopores. In this assay, target DNA (t-DNA) is hybridized with capture DNA (c-DNA) bound on the NPGL electrode, which is fabricated by conjugating amino-modified c-DNA to thioglycolic acid (TGA) modified at the activated NPGL electrode. Following that, amino-modified probe DNA is hybridized with the t-DNA, yielding sandwich hybrids on the NPGL electrode. Then, mercaptopropionic acid-capped CdTe QDs are labeled to the amino group end of the sandwich hybrids. Finally, in the presence of S 2 O 8 2− as coreactant, ECL emission of the QD-labeled DNA hybrids on the NPGL electrode is measured by scanning the potential from 0 to −2 V to record the curve of ECL intensity versus potential. The maximum ECL intensity ( I m,ECL ) on the curve is proportional to t-DNA concentration with a linear range of 5 × 10 −15 to 1 × 10 −11 mol/L. The ECL DNA assay can be used to determine DNA corresponding to mRNA in cell extracts in this study.
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platinum decorated nanoporous Gold Leaf for methanol electrooxidation
Chemistry of Materials, 2007Co-Authors: Rongyue Wang, Pengpeng Liu, Yi DingAbstract:Pt-decorated nanoporous Gold (Pt-NPG) Leaf was prepared by depositing an atomically thin layer of Pt over NPG substrate where Pt overlayers grow epitaxially on NPG surfaces. Their catalytic properties toward methanol and CO electrooxidation were studied, and they show structure-sensitive activities and a greatly enhanced antipoisoning effect.
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metallic mesoporous nanocomposites for electrocatalysis
Journal of the American Chemical Society, 2004Co-Authors: Yi Ding, Mingwei Chen, Jonah ErlebacherAbstract:We describe the fabrication, characterization, and applications of ultrathin, free-standing mesoporous metal membranes uniformly decorated with catalytically active nanoparticles. Platinum-plated nanoporous Gold Leaf (Pt-NPG) made by confining a plating reaction to occur within the pores of dealloyed silver/Gold Leaf is 100 nm thick and contains an extremely high, uniform dispersion of 3 nm diameter catalytic particles. This nanostructured composite holds promise as a prototypical member of a new class of fuel cell electrodes, showing good electrocatalytic performance at low platinum loading (less than 0.05 mg cm-2), while also maintaining long-term stability against coarsening and aggregation of catalytic nanoparticles.
David Ganz - One of the best experts on this subject based on the ideXlab platform.
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does substrate colour affect the visual appearance of gilded medieval sculptures part ii sem edx observations on Gold Leaf samples taken from medieval wooden sculptures
Heritage Science, 2020Co-Authors: M Dobeli, Tiziana Lombardo, Katharina Schmidtott, Benjamin Watts, F Nolting, David GanzAbstract:In the previous paper (Part I), the colorimetry and interferometric microscopy measurements on modern Gold Leaf models have revealed that the visual appearance of a gilded surface, both burnished and unburnished, depends strongly on the substrate type, surface roughness and texture, but not on the colour of the substrate. In this second part, we investigate the materials compositions and technical specifications of medieval Gold Leaf through combining literature sources and materials analysis such as scanning electron microscopy coupled with energy dispersive X-ray analysis (SEM–EDX) on samples taken from gilded wooden sculptures. Our study shows that the late medieval Gold Leaf has a high purity of about 23.7 carat and has an average thickness of 160 nm (with a peak value of 138 nm), purer and thicker than the modern Gold leaves studies in Part I. Supportive Rutherford backscattering spectrometry (RBS) measurements on gilded models confirms the accuracy and reliability of the SEM–EDX observations on the medieval Gold Leaf samples. We additionally present observations of a rarely recorded special variant of medieval Gold Leaf—“fine reinforced Gold Leaf”. Combined with the findings from Part I, we conclude that light penetrating the medieval Gold Leaf and reflected from the gilding substrate could not be a significant, or even perceptible contribution to the visual appearance of the gilding. We argue that the misconception surrounding the correlation between the substrate colour and the gilded surface appearance can be attributed to the historical development of gilding and polychromy technologies.
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does substrate colour affect the visual appearance of gilded medieval sculptures part i colorimetry and interferometric microscopy of gilded models
Heritage Science, 2020Co-Authors: Meret Hauldenschild, Tiziana Lombardo, Katharina Schmidtott, Benjamin Watts, F Nolting, Benedikt Rosner, David GanzAbstract:In the history of medieval gilding, a common view has been circulated for centuries that the substrate colour can influence the visual appearance of a gilded surface. In order to fully understand the correlation between the gilding substrate and the colour appearance of the Gold Leaf laid above, in this paper (Part I) analytical techniques such as colorimetry and interferometric microscopy are implemented on models made from modern Gold leaves. This study demonstrates that the substrate colour is not perceptible for Gold Leaf of at least 100 nm thickness, however the surface burnishing can greatly alter the visual appearance of a Gold surface, and the quality of the burnishing is dependent on the substrate materials. Additionally, surface roughness and texture of the substrate can play supplementary roles, which can be visually observed through digital microscopy and quantified through interferometric microscopy. The findings in this paper will form the basis for the study of Gold Leaf samples taken from medieval European gilded sculptures in Part II.
J M Sampaio - One of the best experts on this subject based on the ideXlab platform.
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determination of Gold Leaf thickness using x ray fluorescence spectrometry accuracy comparison using analytical methodology and monte carlo simulations
Applied Radiation and Isotopes, 2019Co-Authors: Sofia Pessanha, M L Carvalho, I Queralt, J M SampaioAbstract:Abstract In this work, we compared the accuracy of Gold leaves thickness determination using X-ray Fluorescence (XRF) setups for different X-ray excitation sources. The sources used consisted on: a) direct Bremsstrahlung from an Amptek Mini-X X-ray tube with Rh target, b) partially monochromatized radiation of the same X-ray tube using combination of Al and Ag filters and, c) monochromatic radiation using secondary target, in a portable setup with triaxial geometry. The performance of the used setups was compared using model samples made with Gold foil standard reference materials of known thicknesses (1, 2 and 2.5 μm). Thickness determination was based on the selective attenuation that the different energies of a given element of an under-layer undergo in the gilded layer. Ideally, as it can be expected from physics fundamentals, monochromatic radiation is needed for improved accuracy. However, considering the difficulties in using monochromatic radiation in portable instrumentation applicable in Cultural Heritage studies, filtered radiation can also be used for reliable results. Moreover, Monte Carlo simulations of the portable setup with conventional planar geometry were performed for comparison and for future application in more complex samples.
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monte carlo simulation of portable x ray fluorescence setup non invasive determination of Gold Leaf thickness in indo portuguese panel paintings
Spectrochimica Acta Part B: Atomic Spectroscopy, 2019Co-Authors: S Pessanha, Marta Manso, M L Carvalho, Vanessa Antunes, J M SampaioAbstract:Abstract In this work, we present the combined use of in situ X ray Fluorescence spectroscopy and Monte Carlo simulation using PENELOPE code for the completely non-invasive determination of Gold Leaf thickness in artworks using lead white as mordant. The methodology used is based on the detection of different characteristic lines of Pb in the X ray fluorescence spectra, attenuated trough the Gold leaves, and determining the thickness of gilding by comparing their attenuation. Firstly, this methodology was calibrated using model samples of simple stratigraphy, namely pure Au Leafs of 1, 2 and 2.5 μm thickness covering a Pb infinitely thick sheet. The modelled X ray setup was then used to study the gilding thickness of three panel paintings belonging to the Museum of Christian Art in Old Goa (India): two paintings, from the 18th century, concerning to the same series but different themes: Our Lady of Sorrows (MoCA1) and Our Lady of Seven Sorrows (MoCA2), and a third painting entitled Monstrance (MoCA3), from the 17th century. These panel paintings were analyzed to understand the differences and similarities between techniques, according to the time/epoch and technique of its manufacture. The obtained values for MoCA2 tend to be slightly lower than for MoCA1, however, the t student test revealed that the differences were not statistically different (p = .37). Regarding the MoCA3 painting, the average thickness was determined to be statistically different (p
Vanessa Antunes - One of the best experts on this subject based on the ideXlab platform.
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monte carlo simulation of portable x ray fluorescence setup non invasive determination of Gold Leaf thickness in indo portuguese panel paintings
Spectrochimica Acta Part B: Atomic Spectroscopy, 2019Co-Authors: S Pessanha, Marta Manso, M L Carvalho, Vanessa Antunes, J M SampaioAbstract:Abstract In this work, we present the combined use of in situ X ray Fluorescence spectroscopy and Monte Carlo simulation using PENELOPE code for the completely non-invasive determination of Gold Leaf thickness in artworks using lead white as mordant. The methodology used is based on the detection of different characteristic lines of Pb in the X ray fluorescence spectra, attenuated trough the Gold leaves, and determining the thickness of gilding by comparing their attenuation. Firstly, this methodology was calibrated using model samples of simple stratigraphy, namely pure Au Leafs of 1, 2 and 2.5 μm thickness covering a Pb infinitely thick sheet. The modelled X ray setup was then used to study the gilding thickness of three panel paintings belonging to the Museum of Christian Art in Old Goa (India): two paintings, from the 18th century, concerning to the same series but different themes: Our Lady of Sorrows (MoCA1) and Our Lady of Seven Sorrows (MoCA2), and a third painting entitled Monstrance (MoCA3), from the 17th century. These panel paintings were analyzed to understand the differences and similarities between techniques, according to the time/epoch and technique of its manufacture. The obtained values for MoCA2 tend to be slightly lower than for MoCA1, however, the t student test revealed that the differences were not statistically different (p = .37). Regarding the MoCA3 painting, the average thickness was determined to be statistically different (p
Xueji Zhang - One of the best experts on this subject based on the ideXlab platform.
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a novel sensitive and selective electrochemical sensor based on molecularly imprinted polymer on a nanoporous Gold Leaf modified electrode for warfarin sodium determination
RSC Advances, 2016Co-Authors: Lu Zhang, Jiang Liu, Shufeng Zhou, Khalid A Alghanim, Shahid Mahboob, Xueji ZhangAbstract:Warfarin sodium (WFS) is a widely used oral anticoagulant drug but has a narrow therapeutic window. Since traditional detection methods applied for therapeutic drug monitoring suffer some shortcomings, including difficulty in obtaining timely reports, high costs and tedious operation, it is necessary to develop a detection system for the rapid monitoring of WFS in biological samples. Here we report a novel electrochemical sensor, which was facilely fabricated by coupling nanoporous Gold Leaf (NPGL) with molecularly imprinted polymer (MIP) to afford ultrasensitive and selective determination of WFS. The morphological characterization via scanning electron microscopy proved the successful modification of the sensor by NPGL followed with MIP layer modification. The influencing parameters including the type of monomer, pH and molar ratio of template to monomer were optimized during electro-polymerization. Using Fe(CN)63−/4− as a probe acting as an electrical indicator, a linear relationship of the current response versus the concentration of WFS was obtained in the range from 1.0 × 10−10 to 8.0 × 10−8 M under the optimal experimental conditions, with a detection limit of 4.1 × 10−11 M (S/N = 3). In addition, the as-prepared sensor exhibited specific detection of WFS over its structural analogues and interferents, and the established electrochemical approach was validated using the standard method – high performance liquid chromatography. Eventually, rapid and accurate determination of WFS in human blood was carried out after easy sample pretreatment.