A site-specific comparative study of Au102 and Au25 nanoclusters using theoretical EXAFS and l-DOS

2015 ◽  
Vol 93 (1) ◽  
pp. 32-36 ◽  
Author(s):  
Stephen L. Christensen ◽  
Peter Cho ◽  
Amares Chatt ◽  
Peng Zhang
Keyword(s):  
Comparative Study ◽  
Photoelectron Spectroscopy ◽  
Local Structure ◽  
Site Effects ◽  
Local Density ◽  
Site Specific ◽  
X Ray ◽  
Significant Difference ◽  
A Site ◽  
Electronic Character

Recent advances in Au–thiolate nanocluster synthesis have allowed the total structural determination of several nanoclusters by X-ray crystallography. The high-precision structural information of these nanoclusters enables atomic site-specific analysis of local structure and electronic character. In this work, a site-specific comparative study of Au102(SR)44 and Au25(SR)18 was conducted to elucidate the size and site effects on the local environment and electronic character of their common surface structural unit, the –SR–Au–SR–Au–SR– “double-staple” motif. Simulation of the pseudo-radial distribution function from extended X-ray absorption fine structure (EXAFS) shows a significant difference in their local environments despite their identical geometric shape. Local density of states (l-DOS) calculations consistently reveal the difference in their electronic characters for gold d-electron density and d-DOS position. These differences are then related to the unique aurophilic interactions and size- or site-dependent electronic character of Au atoms in the double-staple motif. The differing local structure and electronic behaviour of the “double-staple” motif in Au102(SR)44 and Au25(SR)18 highlight the significance of both size and site effects on the surface structure and electronic property of Au–thiolate nanoclusters. The theoretical results may also be useful in the interpretation of future experimental XAFS and X-ray photoelectron spectroscopy (XPS) data of these nanoclusters.

scholarly journals Organosilane-functionalization of nanostructured indium tin oxide films

2016 ◽  
Vol 6 (6) ◽  
pp. 20160056 ◽  
Author(s):  
R. Pruna ◽  
F. Palacio ◽  
M. Martínez ◽  
O. Blázquez ◽  
S. Hernández ◽  
...  
Keyword(s):  
Surface Area ◽  
Indium Tin Oxide ◽  
Photoelectron Spectroscopy ◽  
Electrochemical Impedance ◽  
Annealing Treatment ◽  
Electrochemical Analysis ◽  
Cyclic Voltammograms ◽  
X Ray ◽  
Chip Technology ◽  
Significant Difference

Fabrication and organosilane-functionalization and characterization of nanostructured ITO electrodes are reported. Nanostructured ITO electrodes were obtained by electron beam evaporation, and a subsequent annealing treatment was selectively performed to modify their crystalline state. An increase in geometrical surface area in comparison with thin-film electrodes area was observed by atomic force microscopy, implying higher electroactive surface area for nanostructured ITO electrodes and thus higher detection levels. To investigate the increase in detectability, chemical organosilane-functionalization of nanostructured ITO electrodes was performed. The formation of 3-glycidoxypropyltrimethoxysilane (GOPTS) layers was detected by X-ray photoelectron spectroscopy. As an indirect method to confirm the presence of organosilane molecules on the ITO substrates, cyclic voltammetry and electrochemical impedance spectroscopy (EIS) were also carried out. Cyclic voltammograms of functionalized ITO electrodes presented lower reduction-oxidation peak currents compared with non-functionalized ITO electrodes. These results demonstrate the presence of the epoxysilane coating on the ITO surface. EIS showed that organosilane-functionalized electrodes present higher polarization resistance, acting as an electronic barrier for the electron transfer between the conductive solution and the ITO electrode. The results of these electrochemical measurements, together with the significant difference in the X-ray spectra between bare ITO and organosilane-functionalized ITO substrates, may point to a new exploitable oxide-based nanostructured material for biosensing applications. As a first step towards sensing, rapid functionalization of such substrates and their application to electrochemical analysis is tested in this work. Interestingly, oxide-based materials are highly integrable with the silicon chip technology, which would permit the easy adaptation of such sensors into lab-on-a-chip configurations, providing benefits such as reduced size and weight to facilitate on-chip integration, and leading to low-cost mass production of microanalysis systems.

scholarly journals Comparative Study of ZnO Thin Films Grown on Quartz Glass and Sapphire (001) Substrates by Means of Magnetron Sputtering and High-Temperature Annealing

2019 ◽  
Vol 9 (21) ◽  
pp. 4509
Author(s):  
Weijia Yang ◽  
Fengming Wang ◽  
Zeyi Guan ◽  
Pengyu He ◽  
Zhihao Liu ◽  
...  
Keyword(s):  
Thin Films ◽  
High Temperature ◽  
Magnetron Sputtering ◽  
Comparative Study ◽  
Quartz Glass ◽  
Photoelectron Spectroscopy ◽  
Zno Thin Films ◽  
High Temperature Annealing ◽  
X Ray ◽  
Glass Substrates

In this work, we reported a comparative study of ZnO thin films grown on quartz glass and sapphire (001) substrates through magnetron sputtering and high-temperature annealing. Firstly, the ZnO thin films were deposited on the quartz glass and sapphire (001) substrates in the same conditions by magnetron sputtering. Afterwards, the sputtered ZnO thin films underwent an annealing process at 600 °C for 1 h in an air atmosphere to improve the quality of the films. X-ray diffraction, scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy (XPS), ultraviolet-visible spectra, photoluminescence spectra, and Raman spectra were used to investigate the structural, morphological, electrical, and optical properties of the both as-received ZnO thin films. The ZnO thin films grown on the quartz glass substrates possess a full width of half maximum value of 0.271° for the (002) plane, a surface root mean square value of 0.50 nm and O vacancies/defects of 4.40% in the total XPS O 1s peak. The comparative investigation reveals that the whole properties of the ZnO thin films grown on the quartz glass substrates are comparable to those grown on the sapphire (001) substrates. Consequently, ZnO thin films with high quality grown on the quartz glass substrates can be achieved by means of magnetron sputtering and high-temperature annealing at 600 °C.

Abstract TP236: Eval to Groin Puncture Times: Efficiencies and Deficiencies of Live Physician vs Telemedicine Triage

Stroke ◽  
2020 ◽  
Vol 51 (Suppl_1) ◽  
Author(s):  
David Rosenbaum-Halevi ◽  
Sujan T Reddy ◽  
Alyssa D Trevino ◽  
Muhammad Bilal Tariq ◽  
Mahan Shahrivari ◽  
...  
Keyword(s):  
Primary Outcome ◽  
Categorical Variables ◽  
Continuous Variables ◽  
Chi Square ◽  
Specific Level ◽  
Site Specific ◽  
Exact Test ◽  
Wilcoxon Rank Sum Test ◽  
Significant Difference ◽  
A Site

Introduction: Telemedicine (TM) is increasingly implemented in community hospitals acute ischemic stroke (AIS). The efficiency of TM to facilitate thrombectomy (IAT) is unknown. We addressed this question by studying our spoke hospitals which are staffed by both in-person (IP) consultation (Day: 8am-5pm) and TM (Night: 5pm-8am) to analyze differences between TM and IP and comparing to our university hub which has IP staffing day and night. Methods: We performed a retrospective analysis from 3/2016 to 3/2019 of all IAT cases directly admitted to 4 IAT capable centers (1 hub + 3 spokes) in our system. Demographic, clinical, and time metrics were analyzed. Primary outcome was door to groin (DTG) time. Continuous variables were analyzed with Wilcoxon rank sum test, and categorical variables with chi-square or Fischer’s exact test. Results: Table 1 summarizes the cohort. Eval to tPA (ETPA) time was faster at spokes vs hub (p < 0.0001), with no significant difference in DTG between spoke and hub (p= 0.444). At spokes, while DTPA times were no different between IP and TM at spokes, IP achieved faster DTG times (p<0.0001) (Fig.1A). DTG was equal during day vs. night at the hub. At the spokes, day (IP) DTG times were faster than night (TM) at some but not all spokes (Fig.1B). TPA administration did not delay DTG at either the hub or the spokes (Fig. 1C). At spokes, TM-TPA cases were associated with faster DTG than TM-noTPA (Fig. 1D). Conclusions: While no difference is noted between TM and IP in rapid TPA treatment, our data show delayed DTG at spokes during the TM day and night service. While DTG in TM was prolonged, differences in spoke metrics imply that availability of staff and resources play a significant role. Further analysis is needed to identify factors that prolong DTG at a site-specific level.

Ferroelectric Bi4Ti3O12Films on Si(100) with An Ultrathin Buffer Layer of Silicon Oxynitride: A Comparative Study Using X-Ray Photoelectron Spectroscopy

2001 ◽  
Vol 40 (Part 1, No. 9B) ◽  
pp. 5564-5568 ◽  
Author(s):  
Eiji Rokuta ◽  
Yasushi Hotta ◽  
Jae-hyoung Choi ◽  
Hitoshi Tabata ◽  
Hikaru Kobayashi ◽  
...  
Keyword(s):  
Comparative Study ◽  
Buffer Layer ◽  
Photoelectron Spectroscopy ◽  
Silicon Oxynitride ◽  
X Ray

CO oxidation activity of Pt, Zn and ZnPt nanocatalysts: a comparative study by in situ near-ambient pressure X-ray photoelectron spectroscopy

Nanoscale ◽  
2018 ◽  
Vol 10 (14) ◽  
pp. 6566-6580 ◽  
Author(s):  
Ahmed Naitabdi ◽  
Anthony Boucly ◽  
François Rochet ◽  
Robert Fagiewicz ◽  
Giorgia Olivieri ◽  
...  
Keyword(s):  
Comparative Study ◽  
Co Oxidation ◽  
Chemical Reactions ◽  
Photoelectron Spectroscopy ◽  
Ambient Pressure ◽  
Oxidation Activity ◽  
X Ray

NAP-XPS allows the monitoring of chemical reactions on nanocatalysts.

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