scholarly journals Modeling the Layer-by-Layer Growth of HKUST-1 Metal-Organic Framework Thin Films

Nanomaterials ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1631
Author(s):  
Qiang Zhang ◽  
Yohanes Pramudya ◽  
Wolfgang Wenzel ◽  
Christof Wöll
Keyword(s):  
Thin Films ◽  
Surface Roughness ◽  
Deposition Rate ◽  
Layer Growth ◽  
Coarse Grained ◽  
Structural Defects ◽  
Effect Of Temperature ◽  
Layer By Layer ◽  
Reactant Concentration ◽  
Metal Organic

Metal organic frameworks have emerged as an important new class of materials with many applications, such as sensing, gas separation, drug delivery. In many cases, their performance is limited by structural defects, including vacancies and domain boundaries. In the case of MOF thin films, surface roughness can also have a pronounced influence on MOF-based device properties. Presently, there is little systematic knowledge about optimal growth conditions with regard to optimal morphologies for specific applications. In this work, we simulate the layer-by-layer (LbL) growth of the HKUST-1 MOF as a function of temperature and reactant concentration using a coarse-grained model that permits detailed insights into the growth mechanism. This model helps to understand the morphological features of HKUST-1 grown under different conditions and can be used to predict and optimize the temperature for the purpose of controlling the crystal quality and yield. It was found that reactant concentration affects the mass deposition rate, while its effect on the crystallinity of the generated HKUST-1 film is less pronounced. In addition, the effect of temperature on the surface roughness of the film can be divided into three regimes. Temperatures in the range from 10 to 129 °C allow better control of surface roughness and film thickness, while film growth in the range of 129 to 182 °C is characterized by a lower mass deposition rate per cycle and rougher surfaces. Finally, for T larger than 182 °C, the film grows slower, but in a smooth fashion. Furthermore, the potential effect of temperature on the crystallinity of LbL-grown HKUST-1 was quantified. To obtain high crystallinity, the operating temperature should preferably not exceed 57 °C, with an optimum around 28 °C, which agrees with experimental observations.

Layer-by-Layer Growth Control of Metal–Organic Framework Thin Films Assembled on Polymer Films

2020 ◽  
Vol 12 (45) ◽  
pp. 50784-50792
Author(s):  
Hiroaki Ohara ◽  
Shunsuke Yamamoto ◽  
Daiki Kuzuhara ◽  
Tomoyuki Koganezawa ◽  
Hidetoshi Oikawa ◽  
...  
Keyword(s):  
Thin Films ◽  
Polymer Films ◽  
Metal Organic Framework ◽  
Growth Control ◽  
Layer Growth ◽  
Layer By Layer ◽  
Metal Organic ◽  
Organic Framework

scholarly journals Electrostatic Design of Polar Metal–Organic Framework Thin Films

Nanomaterials ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 2420
Author(s):  
Giulia Nascimbeni ◽  
Christof Wöll ◽  
Egbert Zojer
Keyword(s):  
Thin Films ◽  
Electrostatic Potential ◽  
Energy Gap ◽  
Dipole Moments ◽  
Metal Organic Framework ◽  
Solid Substrate ◽  
Layer Growth ◽  
Layer By Layer ◽  
Metal Organic ◽  
Linker Molecules

In recent years, optical and electronic properties of metal–organic frameworks (MOFs) have increasingly shifted into the focus of interest of the scientific community. Here, we discuss a strategy for conveniently tuning these properties through electrostatic design. More specifically, based on quantum-mechanical simulations, we suggest an approach for creating a gradient of the electrostatic potential within a MOF thin film, exploiting collective electrostatic effects. With a suitable orientation of polar apical linkers, the resulting non-centrosymmetric packing results in an energy staircase of the frontier electronic states reminiscent of the situation in a pin-photodiode. The observed one dimensional gradient of the electrostatic potential causes a closure of the global energy gap and also shifts core-level energies by an amount equaling the size of the original band gap. The realization of such assemblies could be based on so-called pillared layer MOFs fabricated in an oriented fashion on a solid substrate employing layer by layer growth techniques. In this context, the simulations provide guidelines regarding the design of the polar apical linker molecules that would allow the realization of MOF thin films with the (vast majority of the) molecular dipole moments pointing in the same direction.

scholarly journals Comparison of Fabrication Methods of Metal-Organic Framework Optical Thin Films

Nanomaterials ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 676 ◽  
Author(s):  
Yan Huang ◽  
Cheng-an Tao ◽  
Rui Chen ◽  
Liping Sheng ◽  
Jianfang Wang
Keyword(s):  
Thin Films ◽  
Self Assembly ◽  
Metal Organic Framework ◽  
Dip Coating ◽  
Layer Growth ◽  
Layer By Layer ◽  
Active Components ◽  
Growth Method ◽  
Metal Organic ◽  
University Of Oslo

Homogeneous metal-organic frameworks (MOFs)-based optical thin films have attracted increasing attention, since they can potentially be used as active components in optical/opt-electrical devices, and how to fabricate MOF thin films with high quality is the premise of practically using them. Herein, five fabrication methods of MOF films are systematically investigated and compared from the aspects of appearance, reflectivity, micro-morphology, surface roughness, and optical properties of the films. The famous robust Zr-based MOF, UiO-66 (UiO = University of Oslo) is chosen as a model, and the five methods are spin-coating, dip-coating, self-assembly, direct growth, and the stepwise layer by layer growth method. This study provides fundamental support for the application of MOFs in the optical field.

Conformal and highly adsorptive metal–organic framework thin films via layer-by-layer growth on ALD-coated fiber mats

2015 ◽  
Vol 3 (4) ◽  
pp. 1458-1464 ◽  
Author(s):  
Junjie Zhao ◽  
Bo Gong ◽  
William T. Nunn ◽  
Paul C. Lemaire ◽  
Eric C. Stevens ◽  
...  
Keyword(s):  
Thin Films ◽  
Adsorption Capacity ◽  
Metal Organic Framework ◽  
Layer Growth ◽  
Layer By Layer ◽  
High Adsorption ◽  
Fiber Mats ◽  
Coated Fiber ◽  
Metal Organic ◽  
High Adsorption Capacity

Fiber@ALD@MOF structures fabricated via ALD and layer-by-layer MOF synthesis show good conformality and high adsorption capacity.

scholarly journals Terahertz Emission Increase in GaAs Films Exhibiting Structural Defects Grown on Si (100) Substrates Using a Two-Layered LTG-GaAs Buffer System

2021 ◽  
Author(s):  
Karl Cedric Gonzales ◽  
Elizabeth Ann Prieto ◽  
Gerald Angelo Catindig ◽  
Alexander De Los Reyes ◽  
Maria Angela Faustino ◽  
...  
Keyword(s):  
Thin Films ◽  
Growth Temperature ◽  
High Energy ◽  
Layer Growth ◽  
Structural Defects ◽  
Buffer System ◽  
Layer By Layer ◽  
Material System ◽  
Reflection And Transmission ◽  
Gaas On Si

Abstract Terahertz (THz) emission increase is observed for GaAs thin films that exhibit structural defects. The GaAs epilayers are grown by molecular beam epitaxy on exactly oriented Si (100) substrates at three different temperatures (Ts = 320ºC, 520ºC and 630ºC). The growth method involves the deposition of two low-temperature-grown (LTG)-GaAs buffers with subsequent in-situ thermal annealing at Ts = 600ºC. Reflection high energy electron diffraction confirms the layer-by-layer growth mode of the GaAs on Si. X-ray diffraction shows the improvement in crystallinity as growth temperature is increased. The THz time-domain spectroscopy is performed in reflection and transmission excitation geometries. At Ts = 320ºC, the low crystallinity of GaAs on Si makes it an inferior THz emitter in reflection geometry, over a GaAs grown at the same temperature on a semi-insulating GaAs substrate. However, in transmission geometry, the GaAs on Si exhibits less absorption losses. At higher Ts, the GaAs on Si thin films emerge as promising THz emitters despite the presence of antiphase boundaries and threading dislocations as identified from scanning electron microscopy and Raman spectroscopy. An intense THz emission in reflection and transmission excitation geometries is observed for the GaAs on Si grown at Ts = 520ºC, suggesting the existence of an optimal growth temperature for GaAs on Si at which the THz emission is most efficient in both excitation geometries. The results are significant in the growth design and fabrication of GaAs on Si material system intended for future THz photoconductive antenna emitter devices.

Direct Layer-by-Layer Growth of Crystalline Ag-TCNQ Thin Films on Functionalized Au Substrate: How Critical Is the pH of Ag(I) Solution?

2020 ◽  
Vol 11 (24) ◽  
pp. 10548-10551
Author(s):  
Aswani Sathish Lathika ◽  
Shammi Rana ◽  
Anupam Prasoon ◽  
Pooja Sindhu ◽  
Debashree Roy ◽  
...  
Keyword(s):  
Thin Films ◽  
Layer Growth ◽  
Layer By Layer
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