scholarly journals Heat-Up Colloidal Synthesis of Shape-Controlled Cu-Se-S Nanostructures—Role of Precursor and Surfactant Reactivity and Performance in N2 Electroreduction

Nanomaterials ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 3369
Author(s):  
Stefanos Mourdikoudis ◽  
George Antonaropoulos ◽  
Nikolas Antonatos ◽  
Marcos Rosado ◽  
Liudmyla Storozhuk ◽  
...  

Copper selenide-sulfide nanostructures were synthesized using metal-organic chemical routes in the presence of Cu- and Se-precursors as well as S-containing compounds. Our goal was first to examine if the initial Cu/Se 1:1 molar proportion in the starting reagents would always lead to equiatomic composition in the final product, depending on other synthesis parameters which affect the reagents reactivity. Such reaction conditions were the types of precursors, surfactants and other reagents, as well as the synthesis temperature. The use of ‘hot-injection’ processes was avoided, focusing on ‘non-injection’ ones; that is, only heat-up protocols were employed, which have the advantage of simple operation and scalability. All reagents were mixed at room temperature followed by further heating to a selected high temperature. It was found that for samples with particles of bigger size and anisotropic shape the CuSe composition was favored, whereas particles with smaller size and spherical shape possessed a Cu2−xSe phase, especially when no sulfur was present. Apart from elemental Se, Al2Se3 was used as an efficient selenium source for the first time for the acquisition of copper selenide nanostructures. The use of dodecanethiol in the presence of trioctylphosphine and elemental Se promoted the incorporation of sulfur in the materials crystal lattice, leading to Cu-Se-S compositions. A variety of techniques were used to characterize the formed nanomaterials such as XRD, TEM, HRTEM, STEM-EDX, AFM and UV-Vis-NIR. Promising results, especially for thin anisotropic nanoplates for use as electrocatalysts in nitrogen reduction reaction (NRR), were obtained.

2001 ◽  
Vol 703 ◽  
Author(s):  
Ho-Soon Yang ◽  
J.A. Eastman ◽  
L.J. Thompson ◽  
G.-R. Bai

ABSTRACTUnderstanding the role of grain boundaries in controlling heat flow is critical to the success of many envisioned applications of nanocrystalline materials. This study focuses on the effect of grain boundaries on thermal transport behavior in nanocrystalline yttria-stabilized zirconia (YSZ) coatings prepared by metal-organic chemical vapor deposition.


2019 ◽  
Vol 28 (1) ◽  
pp. 74-96
Author(s):  
Baah Aye Kusi ◽  
Abdul Latif Alhassan ◽  
Daniel Ofori-Sasu ◽  
Rockson Sai

Purpose This study aims to examine the hypothesis that the effect of insurer risks on profitability is conditional on regulation, using two main regulatory directives in the Ghanaian insurance market as a case study. Design/methodology/approach This study used the robust ordinary least square and random effect techniques in a panel data of 30 insurers from 2009 to 2015 to test the research hypothesis. Findings The results suggest that regulations on no credit premium and required capital have insignificant effects on profitability of insurers. On the contrary, this study documents evidence that both policies mitigate the effect of underwriting risk on profitability and suggests that regulations significantly mitigate the negative effect of underwriting risk to improve profitability. Practical implications The finding suggests that policymakers and regulators must continue to initiate, design and model regulations such that they help tame risk to improve the performance of insurers in Ghana. Originality/value This study provides first-time evidence on the role of regulations in controlling risks in a developing insurance market.


1985 ◽  
Vol 7 ◽  
pp. 130 ◽  
Author(s):  
P.I. Joe ◽  
R.S. Schemenauer ◽  
J.W. Strapp ◽  
P. Daum

Techniques have been developed for the airborne bulk sampling of cloud and precipitation, including snow, for later chemical analysis. The techniques include the use of cyclones, meshes, riming rods, scoops and slotted collectors. The role of sampling location on the aircraft, flying attitude, collection efficiency, and sampling procedures for clean samples and mixed clouds with respect to the design and performance of the collectors will be discussed. The polyethylene meshes, with thread diameters of 545 and 345 microns, and the riming rods, with diameter of 1.0 cm, collect supercooled droplets with different efficiencies and can be used to examine the dependence of chemistry on the droplet size. Airborne snow samples were collected for the first time, with the cyclone being the most effective collector.


RSC Advances ◽  
2015 ◽  
Vol 5 (63) ◽  
pp. 51201-51207 ◽  
Author(s):  
Lin Shang ◽  
Taiping Lu ◽  
Guangmei Zhai ◽  
Zhigang Jia ◽  
Hua Zhang ◽  
...  

The role of the nucleation layer thickness on the GaN crystal quality grown by metal organic chemical vapor deposition is explored.


2014 ◽  
Vol 10 ◽  
pp. 259-270 ◽  
Author(s):  
Shinichi Yamabe ◽  
Guixiang Zeng ◽  
Wei Guan ◽  
Shigeyoshi Sakaki

Wolff–Kishner reduction reactions were investigated by DFT calculations for the first time. B3LYP/6-311+G(d,p) SCRF=(PCM, solvent = 1,2-ethanediol) optimizations were carried out. To investigate the role of the base catalyst, the base-free reaction was examined by the use of acetone, hydrazine (H2N–NH2) and (H2O)8. A ready reaction channel of acetone → acetone hydrazine (Me2C=N–NH2) was obtained. The channel involves two likely proton-transfer routes. However, it was found that the base-free reaction was unlikely at the N2 extrusion step from the isopropyl diimine intermediate (Me2C(H)–N=N–H). Two base-catalyzed reactions were investigated by models of the ketone, H2N–NH2 and OH−(H2O)7. Here, ketones are acetone and acetophenone. While routes of the ketone → hydrazone → diimine are similar, those from the diimines are different. From the isopropyl diimine, the N2 extrusion and the C–H bond formation takes place concomitantly. The concomitance leads to the propane product concertedly. From the (1-phenyl)ethyl substituted diimine, a carbanion intermediate is formed. The para carbon of the phenyl ring of the anion is subject to the protonation, which leads to a 3-ethylidene-1,4-cyclohexadiene intermediate. Its [1,5]-hydrogen migration gives the ethylbenzene product. For both ketone substrates, the diimines undergoing E2 reactions were found to be key intermediates.


2006 ◽  
Vol 46 ◽  
pp. 21-26
Author(s):  
Patrick Fiorenza ◽  
Raffaella Lo Nigro ◽  
Vito Raineri ◽  
Salvatore Lombardo ◽  
Roberta G. Toro ◽  
...  

Praseodymium based dielectric thin films have been deposited by Metal-Organic Chemical Vapour Deposition (MOCVD). Special emphasis has been placed upon deposition parameters crucial to obtain Pr2O3 phase and upon interfacial characterization. In addition, dielectric properties have been correlated to structural and compositional characteristics of praseodymium containing films. The breakdown (BD) characteristics of Pr2O3 films have been investigated by an innovative and handling approach based on C-AFM. Moreover, the BD kinetics have been elucidated considering the role of defects in the conduction mechanisms.


2021 ◽  
Author(s):  
Musammat Muthmanna Abdul Kader ◽  
Chil-Hung Cheng

Metal-Organic Frameworks (MOFs) are an emerging group of crystalline microporous materials that exhibit tunability towards various applications in gas storage, catalysts, and others. This project investigated the effects of reaction variables on UiO-66 via solvothermal synthesis. The results via the direct precipitation route at producing UiO-66 suggested that the crystallization rate was rather stagnant during the 30-day synthesis time, rendering the room temperature synthesis infeasible. Subsequently, the project investigated the effects of stirring time of the reactants for the first time in solvothermal synthesis, temperature, reaction time, modulator ratio, and reactant concentrations, on the morphology of UiO-66. Finally, the project studied the effects of adding glycols as co-solvents on UiO-66 crystal morphology. It was observed that only using ethylene glycol as a co-solvent successfully reformed the morphology of UiO-66 crystals from rounded octahedral crystals to anisotropic needle-like fibers. The results also indicated that diethylene glycol significantly improved the crystallinity of UiO-66 than triethylene glycol did.


2021 ◽  
Author(s):  
Jesús Cases ◽  
Mónica Giménez-Marqués

Encapsulation of biomolecules using Metal-Organic Frameworks (MOFs) to form stable biocomposites has been demonstrated a valuable strategy for their preservation and controlled release, which has been however restricted to specific electrostatic surface conditions. We present a general in situ strategy that promotes the spontaneous MOF growth onto a broad variety of proteins, for the first time, regardless of their surface nature. We demonstrate that MOFs based on cations exhibiting considerable inherent acidity such as MIL-100(Fe) enable biomolecule encapsulation, including alkaline proteins previously inaccesible by the welldeveloped in situ encapsulation with azolate-based MOFs. In particular, MIL-100(Fe) scaffold permits effective encapsulation of proteins with very distinct surface nature, retaining their activity and allowing triggered release under biocompatible conditions. This general strategy will enable an ample use of biomolecules in desired biolotechnological applications.


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