In-Situ Surface Photo-Absorption Study of Movpe Surface

1994 ◽  
Vol 340 ◽  
Author(s):  
Naoki Kobayashi
Keyword(s):  
Dielectric Response ◽  
Surface Structures ◽  
Absorption Study ◽  
Dynamic Changes ◽  
Dynamic Surface ◽  
Time Resolved ◽  
Organic Vapor ◽  
Metal Organic ◽  
Surface Decomposition

ABSTRACTIn-situ surface photo-absorption (SPA) method was applied to study the dynamic surface processes and the static surface structures during metal-organic vapor phase epitaxy (MOVPE). Observed spectra in near-ultaviolet and visible regions consist of an anisotropic dielectric response due to surface dimer-bonds as well as an isotropic response probably due to surface back-bonds. Time-resolved spectra showing dynamic changes of surface can be measured by the use of optical multichannel analyzer. The rate of surface decomposition of source molecule was measured as the change of reflectivity at a fixed wavelength. The decomposition of source molecule was characterized quantitatively, and various effects on the decomposition were studied. The style of decomposition and the activation energy depended on the substituent of source molecule and the rate of decomposition was affected by the surface potential and the strain.

AlN/GaN heterostructures grown by metal organic vapor phase epitaxy with in situ Si3N4 passivation

2011 ◽  
Vol 315 (1) ◽  
pp. 204-207 ◽  
Author(s):  
Kai Cheng ◽  
S. Degroote ◽  
M. Leys ◽  
F. Medjdoub ◽  
J. Derluyn ◽  
...  
Keyword(s):  
Vapor Phase ◽  
Vapor Phase Epitaxy ◽  
Organic Vapor ◽  
Metal Organic

scholarly journals Elucidating the Drug Release from Metal-Organic Framework Nanocomposites via in Situ Synchrotron Microspectroscopy and Theoretical Modelling

2019 ◽  
Author(s):  
Barbara Souza ◽  
Lorenzo Dona ◽  
Kirill Titov ◽  
Paolo Bruzzese ◽  
Zhixin Zeng ◽  
...  
Keyword(s):  
Drug Delivery ◽  
Drug Release ◽  
Density Functional ◽  
Metal Organic Framework ◽  
Density Functional Theory Calculations ◽  
Theoretical Modelling ◽  
Time Resolved ◽  
Drug Molecules ◽  
Metal Organic

Nanocomposites comprising metal-organic frameworks (MOFs) embedded in a polymeric matrix are promising carriers for drug delivery applications. While understanding the chemical and physical transformations of MOFs during the release of confined drug molecules is challenging, this is central to devising better ways for controlled release of therapeutic agents. Herein we demonstrate the efficacy of synchrotron microspectroscopy to track the in situ release of 5-fluorouracil (5-FU) anticancer drug molecules from a drug@MOF/polymer composite (5-FU@HKUST-1/polyurethane). Using experimental time-resolved infrared spectra jointly with newly developed density functional theory calculations, we reveal the detailed dynamics of vibrational motions underpinning the dissociation of 5-FU bound to the framework of HKUST-1 upon water exposure. We discover that HKUST-1 creates hydrophilic channels within the hydrophobic polyurethane matrix hence helping to tune drug release rate. The synergy between a hydrophilic MOF with a hydrophobic polymer can be harnessed to engineer a tunable nanocomposite that alleviates the unwanted burst effect commonly encountered in drug delivery.<br>

scholarly journals Elucidating the Structural Evolution of a Highy Porous Responsive Metal-Organic Framework (DUT-49(M)) upon Guests Desorption by Time-Resolved In-Situ Powder X-Ray Diffraction

2020 ◽  
Author(s):  
Bikash Garai ◽  
Volodymyr Bon ◽  
Francesco Walenszus ◽  
Azat Khadiev ◽  
Dmitri Novikov ◽  
...  
Keyword(s):  
Adsorption Isotherms ◽  
Metal Organic Framework ◽  
Structural Evolution ◽  
Structural Transformations ◽  
X Ray Diffraction ◽  
Time Resolved ◽  
X Ray ◽  
Metal Organic ◽  
Subcritical Fluid

Variation in the metal centres of M-M paddle-wheel SBU results in the formation of isostructural DUT-49(M) frameworks. However, the porosity of the framework was found to be different for each of the structures. While a high and moderate porosity was obtained for DUT-49(Cu) and DUT-49(Ni), respectively, other members of the series [DUT-49(M); M= Mn, Fe, Co, Zn, Cd] show very low porosity and shapes of the adsorption isotherms which is not expected for op phases of these MOFs. Investigation on those MOFs revealed that those frameworks undergo structural collapse during the solvent removal at the activation step. Thus, herein, we aimed to study the detailed structural transformations that are possibly occurring during the removal of the subcritical fluid from the framework.

scholarly journals Elucidating the Drug Release from Metal-Organic Framework Nanocomposites via in Situ Synchrotron Microspectroscopy and Theoretical Modelling

2019 ◽  
Author(s):  
Barbara Souza ◽  
Lorenzo Dona ◽  
Kirill Titov ◽  
Paolo Bruzzese ◽  
Zhixin Zeng ◽  
...  
Keyword(s):  
Drug Delivery ◽  
Drug Release ◽  
Density Functional ◽  
Metal Organic Framework ◽  
Density Functional Theory Calculations ◽  
Theoretical Modelling ◽  
Time Resolved ◽  
Drug Molecules ◽  
Metal Organic

Nanocomposites comprising metal-organic frameworks (MOFs) embedded in a polymeric matrix are promising carriers for drug delivery applications. While understanding the chemical and physical transformations of MOFs during the release of confined drug molecules is challenging, this is central to devising better ways for controlled release of therapeutic agents. Herein we demonstrate the efficacy of synchrotron microspectroscopy to track the in situ release of 5-fluorouracil (5-FU) anticancer drug molecules from a drug@MOF/polymer composite (5-FU@HKUST-1/polyurethane). Using experimental time-resolved infrared spectra jointly with newly developed density functional theory calculations, we reveal the detailed dynamics of vibrational motions underpinning the dissociation of 5-FU bound to the framework of HKUST-1 upon water exposure. We discover that HKUST-1 creates hydrophilic channels within the hydrophobic polyurethane matrix hence helping to tune drug release rate. The synergy between a hydrophilic MOF with a hydrophobic polymer can be harnessed to engineer a tunable nanocomposite that alleviates the unwanted burst effect commonly encountered in drug delivery.<br>

scholarly journals In Situ Time-Resolved Decomposition of β-Hydride Phase in Palladium Nanoparticles Coated with Metal-Organic Framework

Metals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 810
Author(s):  
Mikhail V. Kirichkov ◽  
Aram L. Bugaev ◽  
Alina A. Skorynina ◽  
Vera V. Butova ◽  
Andriy P. Budnyk ◽  
...  
Keyword(s):  
Phase Transition ◽  
Particle Size ◽  
Hydrogen Adsorption ◽  
Metal Organic Framework ◽  
Pd Nanoparticles ◽  
Time Resolved ◽  
Metal Organic ◽  
Hydride Phases ◽  
Organic Framework

The formation of palladium hydrides is a well-known phenomenon, observed for both bulk and nanosized samples. The kinetics of hydrogen adsorption/desorption strongly depends on the particle size and shape, as well as the type of support and/or coating of the particles. In addition, the structural properties of hydride phases and their distribution also depend on the particle size. In this work, we report on the in situ characterization of palladium nanocubes coated with HKUST-1 metal-organic framework (Pd@HKUST-1) during desorption of hydrogen by means of synchrotron-based time-resolved X-ray powder diffraction. A slower hydrogen desorption, compared to smaller sized Pd nanoparticles was observed. Rietveld refinement of the time-resolved data revealed the remarkable stability of the lattice parameters of α- and β-hydride phases of palladium during the α- to β- phase transition, denoting the behavior more similar to the bulk materials than nanoparticles. The stability in the crystal sizes for both α- and β-hydride phases during the phase transition indicates that no sub-domains are formed within a single particle during the phase transition.

In Situ Time-Resolved Dynamic Surface Events on the Pt/C Cathode in a Fuel Cell under Operando Conditions

2007 ◽  
Vol 46 (23) ◽  
pp. 4310-4315 ◽  
Author(s):  
Mizuki Tada ◽  
Shigeaki Murata ◽  
Takahiko Asakoka ◽  
Kazutaka Hiroshima ◽  
Kazu Okumura ◽  
...  
Keyword(s):  
Fuel Cell ◽  
Dynamic Surface ◽  
Time Resolved

Electron Beam Enhanced Precipitation in Highly Carbon Doped GaAs Layers

1996 ◽  
Vol 439 ◽  
Author(s):  
P. Werner ◽  
U. Gösele ◽  
H. Kohda
Keyword(s):  
Point Defects ◽  
Growth Direction ◽  
Precipitation Mechanism ◽  
Native Defects ◽  
Carbon Doped ◽  
Organic Vapor ◽  
Transmission Electron ◽  
Metal Organic ◽  
O 10

AbstractHighly carbon doped GaAs layers grown by metal organic vapor phase epitaxy (MOVPE) Has been investigated by transmission electron microscopy (TEM). Electron irradiation has been applied to generate point defects interacting with native defects, e.g., substitutional carbon. This irradiation induces periodically arranged striations perpendicular to the growth direction, which were observed in situ by TEM. Furthermore, precipitates (Ø= 10–15nm) were formed containing non-crystalline material, which most likely is gallium. To explain these phenomena a precipitation mechanism is proposed. It involvs small fluctuations of the incorporated C as well as the interaction of irradiation induced point defects, mainly As and C interstitials and As vacancies.

scholarly journals In Situ, Time-Resolved, and Mechanistic Studies of Metal–Organic Framework Nucleation and Growth

2018 ◽  
Vol 118 (7) ◽  
pp. 3681-3721 ◽  
Author(s):  
Mary J. Van Vleet ◽  
Tingting Weng ◽  
Xinyi Li ◽  
J.R. Schmidt
Keyword(s):  
Metal Organic Framework ◽  
Nucleation And Growth ◽  
Mechanistic Studies ◽  
Time Resolved ◽  
Metal Organic ◽  
Organic Framework
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