Interaction of Evaporated Nickel Nanoparticles with Highly Oriented Pyrolytic Graphite:  Back-bonding to Surface Defects, as Studied by X-ray Photoelectron Spectroscopy

2005 ◽  
Vol 109 (41) ◽  
pp. 19329-19334 ◽  
Author(s):  
D.-Q. Yang ◽  
E. Sacher
Keyword(s):  
Photoelectron Spectroscopy ◽  
Nickel Nanoparticles ◽  
Surface Defects ◽  
Pyrolytic Graphite ◽  
Highly Oriented Pyrolytic Graphite ◽  
X Ray ◽  
Back Bonding

scholarly journals Cryptand-Functionalized Highly Oriented Pyrolytic Graphite Electrodes

2021 ◽  
Vol 13 (8) ◽  
pp. 4158
Author(s):  
Marcos A. Bento ◽  
Sara Realista ◽  
Ana S. Viana ◽  
Ana M. Ferraria ◽  
Paulo N. Martinho
Keyword(s):  
Photoelectron Spectroscopy ◽  
Diazonium Salt ◽  
Pyrolytic Graphite ◽  
Coupling Reaction ◽  
Modified Electrodes ◽  
Current Response ◽  
Highly Oriented Pyrolytic Graphite ◽  
Graphite Electrodes ◽  
Pyrolytic Graphite Electrode ◽  
20 Nm

Reproducible materials that have detection properties towards a certain molecule are very important for applications in the fabrication of devices. Among all the substrates that are used, highly oriented pyrolytic graphite allows to clearly image a monolayer. On the other hand, cryptand molecules are versatile because they can sense certain analytes with high selectivity. The highly oriented pyrolytic graphite electrode was first functionalized with an aryl bearing a bromine or an alkyne group to further attach cryptand molecules to its surface. The functionalization was performed through the electroreduction of aryl diazonium salts. While functionalization with an aryl-bromine produced a 20 nm-thick dendritic layer, functionalization of the surface with an aryl bearing a terminal alkyne produced a 9.7 nm-thick multilayer. However, if the diazonium salt is prepared in situ, a 0.9 nm monolayer with aryl–alkyne groups is formed. The alkyne functionalized electrode reacted with a bromo-cryptand through a Sonogashira C–C coupling reaction yielding electrodes functionalized with cryptands. These were immersed in a solution of a Co(II) salt resulting in Co(II)-cryptate modified electrodes, highlighting the ability of the cryptands’ modified electrode to sense metal ions. The electrode surface was analyzed by X-ray photoelectron spectroscopy after each modification step, which confirmed the successful functionalization of the substrate with both the cryptand and the cryptate. Cyclic voltammetry studies showed stable current response after approximately six cycles. Different reduction processes were detected for both cryptand (−1.40 V vs. SCE) and cryptate (−1.22 V vs. SCE) modified highly oriented pyrolytic graphite.

STM Analysis of a Chiral Helical Onedimensional Nickel(II) Coordination Polymer

2008 ◽  
Vol 63 (12) ◽  
pp. 1443-1446 ◽  
Author(s):  
Mohammad Sahabul Alam ◽  
Andreas Scheurer ◽  
Rolf W. Saalfrank ◽  
Paul Müller
Keyword(s):  
Coordination Polymer ◽  
Single Crystals ◽  
Excellent Agreement ◽  
Pyrolytic Graphite ◽  
Highly Oriented Pyrolytic Graphite ◽  
X Ray ◽  
X Ray Crystallography ◽  
Salen Complexes ◽  
Polymeric Chains ◽  
Dimeric Aggregates

C2-symmetric nickel(II) salen complexes [NiL] 1 were deposited on a highly oriented pyrolytic graphite (HOPG) surface from their acetone solutions. They aggregate easily to single, segregated, homochiral polymeric chains of (M)-1D- 1n [NiL] (2) on the substrate as also found in single crystals. In STM topography, the single helical 1D structures 2 found on the surface were in excellent agreement with the dimension of aligned dimeric aggregates of 1 obtained from X-ray crystallography. Weak intermolecular NiII...OMe coordinations (dMeO−Ni = 0.35 nm) were found to be responsible for the formation of the chiral, helical and 1D assemblies on the substrate.

scholarly journals Improvement of Quantum Dot Light Emitting Device Characteristics by CdSe/ZnS Blended with HMDS (Hexamethyldisilazane)

2020 ◽  
Vol 10 (17) ◽  
pp. 6081
Author(s):  
Junekyun Park ◽  
Eunkyu Shin ◽  
Jongwoo Park ◽  
Yonghan Roh
Keyword(s):  
Quantum Dot ◽  
Photoelectron Spectroscopy ◽  
Surface Defects ◽  
Hole Transport ◽  
Transport Layer ◽  
Electron Transport Layer ◽  
Hole Transport Layer ◽  
Atmospheric Conditions ◽  
Light Emitting ◽  
X Ray

We demonstrated the way to improve the characteristics of quantum dot light emitting diodes (QD-LEDs) by adding a simple step to the conventional fabrication process. For instance, we can effectively deactivate the surface defects of quantum dot (QD) (e.g., CdSe/ZnS core-shell QDs in the current work) with the SiO bonds by simply mixing QDs with hexamethyldisilazane (HMDS) under atmospheric conditions. We observed the substantial improvement of device characteristics such that the current efficiency, the maximum luminance, and the QD lifetime were improved by 1.7–1.8 times, 15–18%, and nine times, respectively, by employing this process. Based on the experimental data (e.g., energy dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS)), we estimated that the growth of the SiOx on the surface of QDs is self-limited: the SiOx are effective to passivate the surface defects of QDs without deteriorating the intrinsic properties including the color-purity of QDs. Second, we proposed that the emission profiling study can lead us to the fundamental understanding of charge flow in each layer of QD-LEDs. Interestingly enough, many problems related to the charge-imbalance phenomenon were simply solved by selecting the combination of thicknesses of the hole transport layer (HTL) and the electron transport layer (ETL).

Double Bragg scattering observed in small-angle X-ray scattering from highly oriented pyrolytic graphite

2016 ◽  
Vol 49 (3) ◽  
pp. 835-844 ◽  
Author(s):  
Yoshinori Ohmasa ◽  
Susumu Shimomura ◽  
Ayano Chiba
Keyword(s):  
Small Angle ◽  
Small Deviation ◽  
Pyrolytic Graphite ◽  
Bragg Scattering ◽  
Highly Oriented Pyrolytic Graphite ◽  
Finite Sample ◽  
X Ray ◽  
Sample Rotation ◽  
X Ray Scattering ◽  
Ray Scattering

In small-angle X-ray scattering from highly oriented pyrolytic graphite, radial streak patterns are observed. The streaks change their direction with sample rotation and appear and disappear in pairs. This streak pattern can be explained by double Bragg scattering. The directions of the streaks calculated as functions of the rotation angle are in good agreement with experiment. In addition, asymmetry in the intensity of the streaks and a small deviation from the radial pattern are observed, and they can be explained by the finite sample-size effect. The necessity of taking double Bragg scattering into account in small-angle X-ray scattering studies of crystalline materials is emphasized.

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