scholarly journals Size-dependent polarizabilities and van der Waals dispersion coefficients of fullerenes from large-scale complex polarization propagator calculations

2021 ◽  
Vol 154 (7) ◽  
pp. 074304
Author(s):  
Manuel Brand ◽  
Karan Ahmadzadeh ◽  
Xin Li ◽  
Zilvinas Rinkevicius ◽  
Wissam A. Saidi ◽  
...  
Keyword(s):  
Large Scale ◽  
Van Der Waals ◽  
Dispersion Coefficients ◽  
Polarization Propagator ◽  
Size Dependent ◽  
Complex Polarization

scholarly journals Establishment and lineage dynamics of the SARS-CoV-2 epidemic in the UK

Science ◽  
2021 ◽  
pp. eabf2946
Author(s):  
Louis du Plessis ◽  
John T. McCrone ◽  
Alexander E. Zarebski ◽  
Verity Hill ◽  
Christopher Ruis ◽  
...  
Keyword(s):  
Large Scale ◽  
Phylogenetic Analyses ◽  
Transmission Dynamics ◽  
Genetic Lineage ◽  
Size Dependent ◽  
Spatio Temporal ◽  
The Uk ◽  
Lineage Structure ◽  
And Control ◽  
Lineage Diversity

The UK’s COVID-19 epidemic during early 2020 was one of world’s largest and unusually well represented by virus genomic sampling. Here we reveal the fine-scale genetic lineage structure of this epidemic through analysis of 50,887 SARS-CoV-2 genomes, including 26,181 from the UK sampled throughout the country’s first wave of infection. Using large-scale phylogenetic analyses, combined with epidemiological and travel data, we quantify the size, spatio-temporal origins and persistence of genetically-distinct UK transmission lineages. Rapid fluctuations in virus importation rates resulted in >1000 lineages; those introduced prior to national lockdown tended to be larger and more dispersed. Lineage importation and regional lineage diversity declined after lockdown, while lineage elimination was size-dependent. We discuss the implications of our genetic perspective on transmission dynamics for COVID-19 epidemiology and control.

scholarly journals Aminophosphine Reduction Mechanisms and the Synthesis of Indium Phosphide Nanomaterials

2021 ◽  
Author(s):  
◽  
Geoffry Laufersky
Keyword(s):  
Indium Phosphide ◽  
Density Functional ◽  
Large Scale ◽  
Visible Spectrum ◽  
Size Dependent ◽  
Reduction Mechanisms ◽  
Highly Sensitive ◽  
Dependent Absorption ◽  
Entire Visible Spectrum ◽  
The Impact

<p>Indium phosphide (InP) nanomaterials are attractive for countless technological applications due to their well-placed band gap energies. The quantum confinement of these semiconductors can give rise to size-dependent absorption and emission features throughout the entire visible spectrum. Therefore, InP materials can be employed as low-toxicity fluorophores that can be implemented in high value avenues such as biological probes, lighting applications, and lasing technologies. However, large scale development of these quantum dots (QDs) has been stymied by the lack of affordable and safe phosphorus precursors. Syntheses have largely been restricted to the use of dangerous chemicals such as tris(trimethylsilyl)phosphine ((TMS)₃P), which is costly and highly sensitive to oxygen and water. Recently, less-hazardous tris(dialkylamino)phosphines have been introduced to produce InP QDs on par with those utilizing (TMS)₃P. However, a poor understanding of the reaction mechanics has resulted in difficulties tuning and optimizing this method.  In this work, density functional theory (DFT) is used to identify the mechanism of this aminophosphine precursor conversion. This understanding is then implemented to design an improved InP QD synthesis, allowing for the production of high-quality materials outside of glovebox conditions. Time is spent understanding the impact of different precursor salts on the reaction mechanisms and discerning their subsequent effects on nanoparticle size and quality. The motivation of this work is to formulate safer and less technical indium phosphide quantum dot syntheses to foster non-specialist and industrial implementation of these materials.</p>

scholarly journals Slight pH Fluctuations in the Gold Nanoparticle Synthesis Process Influence the Performance of the Citrate Reduction Method

Sensors ◽  
2018 ◽  
Vol 18 (7) ◽  
pp. 2246 ◽  
Author(s):  
Braulio Contreras-Trigo ◽  
Víctor Díaz-García ◽  
Enrique Guzmán-Gutierrez ◽  
Ignacio Sanhueza ◽  
Pablo Coelho ◽  
...  
Keyword(s):  
Large Scale ◽  
Colloidal Suspension ◽  
Nanoparticle Synthesis ◽  
Trisodium Citrate ◽  
Gold Surface ◽  
Point Of View ◽  
Synthesis Process ◽  
Reaction Yield ◽  
Size Dependent ◽  
Gold Nanoparticle Synthesis

Gold nanoparticles (AuNPs) are currently under intense investigation for biomedical and biotechnology applications, thanks to their ease in preparation, stability, biocompatibility, multiple surface functionalities, and size-dependent optical properties. The most commonly used method for AuNP synthesis in aqueous solution is the reduction of tetrachloroauric acid (HAuCl4) with trisodium citrate. We have observed variations in the pH and in the concentration of the gold colloidal suspension synthesized under standard conditions, verifying a reduction in the reaction yield by around 46% from pH 5.3 (2.4 nM) to pH 4.7 (1.29 nM). Citrate-capped AuNPs were characterized by UV-visible spectroscopy, TEM, EDS, and zeta-potential measurements, revealing a linear correlation between pH and the concentration of the generated AuNPs. This result can be attributed to the adverse effect of protons both on citrate oxidation and on citrate adsorption onto the gold surface, which is required to form the stabilization layer. Overall, this study provides insight into the effect of the pH over the synthesis performance of the method, which would be of particular interest from the point of view of large-scale manufacturing processes.

Large-scale synthesis of van der Waals 1-dimensional material Mo6S3I6 by using a MoI2 precursor

2019 ◽  
Vol 803 ◽  
pp. 499-504
Author(s):  
Seungbae Oh ◽  
Sudong Chae ◽  
Kyung Hwan Choi ◽  
Bum Jun Kim ◽  
Sang Hoon Lee ◽  
...  
Keyword(s):  
Large Scale ◽  
Van Der Waals ◽  
Large Scale Synthesis

scholarly journals Self-selective van der Waals heterostructures for large scale memory array

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Linfeng Sun ◽  
Yishu Zhang ◽  
Gyeongtak Han ◽  
Geunwoo Hwang ◽  
Jinbao Jiang ◽  
...  
Keyword(s):  
Large Scale ◽  
Van Der Waals ◽  
Van Der Waals Heterostructures ◽  
Memory Array

scholarly journals Observation of site-controlled localized charged excitons in CrI3/WSe2 heterostructures

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Arunabh Mukherjee ◽  
Kamran Shayan ◽  
Lizhong Li ◽  
Jie Shan ◽  
Kin Fai Mak ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Large Scale ◽  
Information Science ◽  
Van Der Waals ◽  
Spatial Location ◽  
Band Alignment ◽  
Tungsten Diselenide ◽  
Electrostatic Doping ◽  
Localized Excitons ◽  
Quantum Emitters

Abstract Isolated spins are the focus of intense scientific exploration due to their potential role as qubits for quantum information science. Optical access to single spins, demonstrated in III-V semiconducting quantum dots, has fueled research aimed at realizing quantum networks. More recently, quantum emitters in atomically thin materials such as tungsten diselenide have been demonstrated to host optically addressable single spins by means of electrostatic doping the localized excitons. Electrostatic doping is not the only route to charging localized quantum emitters and another path forward is through band structure engineering using van der Waals heterojunctions. Critical to this second approach is to interface tungsten diselenide with other van der Waals materials with relative band-alignments conducive to the phenomenon of charge transfer. In this work we show that the Type-II band-alignment between tungsten diselenide and chromium triiodide can be exploited to excite localized charged excitons in tungsten diselenide. Leveraging spin-dependent charge transfer in the device, we demonstrate spin selectivity in the preparation of the spin-valley state of localized single holes. Combined with the use of strain-inducing nanopillars to coordinate the spatial location of tungsten diselenide quantum emitters, we uncover the possibility of realizing large-scale deterministic arrays of optically addressable spin-valley holes in a solid state platform.

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