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Plasmon-induced Circular Dichroism and Asymmetric Hot-electrons Generation Triggered by a Chiral Molecule for Polarization-dependent Chemical Reactions
Renaud Arthur Léon Vallée
Issue:
Volume 7, Issue 4, December 2021
Pages:
59-65
Received:
11 September 2021
Accepted:
5 October 2021
Published:
15 October 2021
Abstract: Performing chiral photodetection, photocatalysis or photochemical reactions at the molecular level has always been a nearly impossible task, due to the very low efficiency of the generated optical circular dichroism signals. On the contrary, chiral colloidal nanocrystals have been shown recently to offer a very large differential response to circularly polarized light. Such a response is able to generate hot-electrons with a very strong asymmetry, thus potentially able to perform the aforementioned tasks. In this paper, an intermediate picture is chosen, for which an achiral small assembly of identical particles triggered by a chiral molecule is able to generate large plasmon-induced circular dichroism (PICD), in turn able to generate the required asymmetry in the generation rates of hot-electrons. By performing Finite Difference Time Domain simulations based on the combination of a classical model of PICD generation and a quantum-based model of hot-electrons generation, the simple design of an achiral gold NPs’ dimer triggered by a chiral molecule located in the center and oriented with its transition electric dipole moment parallel to the dimer axis is shown to be able to generate a strong asymmetry in its HEs’ generation response. The PICDs and related hot-electrons generation rates increase as a function of volume, surface, respectively, of the considered systems, thereby providing a way to trigger chemical reactions.
Abstract: Performing chiral photodetection, photocatalysis or photochemical reactions at the molecular level has always been a nearly impossible task, due to the very low efficiency of the generated optical circular dichroism signals. On the contrary, chiral colloidal nanocrystals have been shown recently to offer a very large differential response to circul...
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Electronegative Promotion in the Synthesis by DC HF CCVD Growth Method of Carbon Nanotubes: A Review
Nyangono Kouma Jean Michel,
Mane Mane Jeannot,
Mengata Mengounou Ghislain,
Moukouri Mikano Jonas,
Asse Jean Bernard
Issue:
Volume 7, Issue 4, December 2021
Pages:
66-81
Received:
29 August 2021
Accepted:
24 September 2021
Published:
10 November 2021
Abstract: From the technological point of view, the synthesis of carbon nanotubes (CNTs) aims at optimizing their field emission properties. Among all the synthesis methods, the CVD method is the most suitable for the growth of carbon nanotubes. In this method, transition metal atoms (Fe, Ni, Co) are used. The carbon nanotubes obtained with these transition metals present some major defects associated with some rather complex purification conditions. Starting from the fact that the electronegative atom (oxygen) participates in the promotion of the adsorption of the alkenes on the dense faces of the transition metals, this leads to think that the deposition of oxygen on transition metal catalyst before the CVD synthesis would weaken the bond between the graphitic surfaces and the transition particles. The interaction of electronegative atoms (oxygen) with transition metal particles prior to the CVD process results in a removal of charge from the metal atoms that results in a change in the d-band surface density, thereby lowering the amount of charge density in the mixed catalyst formed. This charge density could have interacted further with donation, and retro-donation of the alkene and back to the alkyne atoms during and after the CVD process. This oxygen-transition metal interaction is described in the framework of the Dewar-Chatt- Duncanson (DCD) model. It is expected that the carbon nanotubes thus obtained will have minor defects, have a somewhat reduced height, be of better quality compared to those obtained without promotion and allow easier purification conditions, while considering a popcorn model to lift the catalyst particles by thermal stirring. The expected experimental results can be verified using surface analysis techniques such as vibrational spectroscopy through the shifts of the band transitions that occur, photoelectron spectroscopy for resonance line position shifts.
Abstract: From the technological point of view, the synthesis of carbon nanotubes (CNTs) aims at optimizing their field emission properties. Among all the synthesis methods, the CVD method is the most suitable for the growth of carbon nanotubes. In this method, transition metal atoms (Fe, Ni, Co) are used. The carbon nanotubes obtained with these transition ...
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Clay and Magnetic Sand Biomass Based Composite for Methylene Blue Adsorption (Effects of Composition Ratios of Functional Materials and Synthesis Conditions)
Mih Venasius Nsom,
Ekane Peter Etape,
Beckley Victorine Namondo,
Josepha Foba-Tendo,
Lena Yoh Elango Ekaney
Issue:
Volume 7, Issue 4, December 2021
Pages:
82-95
Received:
28 October 2021
Accepted:
17 November 2021
Published:
25 November 2021
Abstract: In recent times, iron oxide based magnetic nanoparticles (mainly magnetite (Fe3O4) or maghemite (γ-Fe2O3)) as well as clay and clay based composites, have become very important in the elimination of persistent organic compounds from waste water systems. This has been carried out by magnetic assisted chemical separation (MACS) process. The feasibility of using two locally sourced materials: magnetic black sand from down beach Limbe and clay from Bamessing Ndop for the removal of methylene blue (MB) dye from aqueous solution have been studied. The effects of contact time, pH, adsorbent dosage, temperature, grinding / length of grinding, composition ratios of the functional materials such as peel, pectin and starch, hydrothermal carbonization and concentration of dye solution were investigated. The test samples have exhibited great potentials for use in waste water purification for the removal of persistent organic compounds such as methylene blue dye. The results revealed that, varying various compositional ratios of the functional materials such as peel, pectin and starch to increase their affinity, selectivity, or degradation capacity towards targeted compounds influenced the activities of the adsorbents. The results also indicated that maximum performance was reached at pH value of 8 for Iron oxide (sand) based adsorbents and 12 for clay based adsorbents. Grinding / increase in grinding time have shown positive effects on the adsorbent properties of the composite from black sand and maximum grinding time varied depending on the compositional ratios of functional materials. Also within a certain threshold, hydrothermal carbonization improved on the adsorbent efficiency of the samples formulated with saccharides. The adsorption kinetic of methylene blue onto the adsorbents could be better fitted by the linear Langmuir isotherm and the pseudo-second-order model was a better model fitting the kinetics of the adsorption in this study.
Abstract: In recent times, iron oxide based magnetic nanoparticles (mainly magnetite (Fe3O4) or maghemite (γ-Fe2O3)) as well as clay and clay based composites, have become very important in the elimination of persistent organic compounds from waste water systems. This has been carried out by magnetic assisted chemical separation (MACS) process. The feasibili...
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