scholarly journals Diffusion dynamics controlled colloidal synthesis of highly monodisperse InAs nanocrystals

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Taewan Kim ◽  
Seongmin Park ◽  
Sohee Jeong
Keyword(s):  
Molecular Diffusion ◽  
Continuous Process ◽  
Precursor Solution ◽  
Particle Growth ◽  
Injection Rate ◽  
Colloidal Synthesis ◽  
Synthetic Process ◽  
Nanocrystal Growth ◽  
Diffusion Dynamics ◽  
Continuous Injection

AbstractHighly monodisperse colloidal InAs quantum dots (QDs) with superior optoelectronic properties are promising candidates for various applications, including infrared photodetectors and photovoltaics. Recently, a synthetic process involving continuous injection has been introduced to synthesize uniformly sized InAs QDs. Still, synthetic efforts to increase the particle size of over 5 nm often suffer from growth suppression. Secondary nucleation or interparticle ripening during the growth accompanies the inhomogeneity in size as well. In this study, we propose a growth model for the continuous synthetic processing of colloidal InAs QDs based on molecular diffusion. The experimentally validated model demonstrates how precursor solution injection reduces monomer flux, limiting particle growth during synthesis. As predicted by our model, we control the diffusion dynamics by tuning reaction volume, precursor concentration, and injection rate of precursor. Through diffusion-dynamics-control in the continuous process, we synthesize the InAs QDs with a size over 9.0-nm (1Smax of 1600 nm) with a narrow size distribution (12.2%). Diffusion-dynamics-controlled synthesis presented in this study effectively manages the monomer flux and thus overcome monomer-reactivity-originating size limit of nanocrystal growth in solution.

scholarly journals Advanced processing and analysis of conventional confocal microscopy generated scanning FCS data

2017 ◽  
Author(s):  
Dominic Waithe ◽  
Falk Schneider ◽  
Jakub Chojnacki ◽  
Mathias Clausen ◽  
Dilip Shrestha ◽  
...  
Keyword(s):  
Confocal Microscopy ◽  
Spatial Heterogeneity ◽  
Fluorescence Correlation Spectroscopy ◽  
Large Scale ◽  
Molecular Diffusion ◽  
Correlation Spectroscopy ◽  
The Other ◽  
Statistical Accuracy ◽  
Fluorescence Correlation ◽  
Diffusion Dynamics

AbstractScanning Fluorescence Correlation Spectroscopy (scanning FCS) is a variant of conventional point FCS that allows molecular diffusion at multiple locations to be measured simultaneously. It enables disclosure of potential spatial heterogeneity in molecular diffusion dynamics and also the acquisition of a large amount of FCS data at the same time, providing large statistical accuracy. Here, we optimize the processing and analysis of these large-scale acquired sets of FCS data. On one hand we present FoCuS-scan, scanning FCS software that provides an end-to-end solution for processing and analysing scanning data acquired on commercial turnkey confocal systems. On the other hand, we provide a thorough characterisation of large-scale scanning FCS data over its intended time-scales and applications and propose a unique solution for the bias and variance observed when studying slowly diffusing species. Our manuscript enables researchers to straightforwardly utilise scanning FCS as a powerful technique for measuring diffusion across a broad range of physiologically relevant length scales without specialised hardware or expensive software.

Simulation of the Scattering of Continuously Injected Pickup Ions outside the Heliopause

2021 ◽  
Vol 922 (2) ◽  
pp. 271
Author(s):  
Ding Sheng ◽  
Kaijun Liu ◽  
V. Florinski ◽  
J. D. Perez
Keyword(s):  
Magnetic Field ◽  
Pitch Angle ◽  
Injection Rate ◽  
Angle Distribution ◽  
Pickup Ions ◽  
Isotropic Distribution ◽  
Angle Scattering ◽  
Background Magnetic Field ◽  
First Time ◽  
Continuous Injection

Abstract Hybrid simulations in 2D space and 3D velocity dimensions with continuous injection of pickup ions (PUIs) provide insight into the plasma processes that are responsible for the pitch angle scattering of PUIs outside the heliopause. The present investigation includes for the first time continuous injection of PUIs and shows how the scattering depends on the energy of the PUIs and the strength of the background magnetic field as well as the dependence on the injection rate of the time for the isotropization of the pitch angle distribution. The results demonstrate that, with the gradual injection of PUIs of a narrow ring velocity distribution perpendicular to the background magnetic field, oblique mirror mode waves develop first, followed by the growth of quasiparallel propagating ion cyclotron waves. Subsequently, the PUIs are scattered by the excited waves and gradually approach an isotropic distribution. A time for isotropization is defined to be the time at which T ∣∣/T ⊥, i.e., the ratio of the parallel to perpendicular PUI thermal energy changes from ≈0 to ≈0.15. By varying the PUI injection rate, estimates of the time for the PUI distribution to be isotropized are presented. The isotropization time obtained is shorter, ≈ months, than the time, ≈ years, required by the conventional secondary ENA mechanism to explain the IBEX ENA ribbon.

scholarly journals Fe(III) Precipitation and Copper Loss from Sulphate-Chloride Solutions at 150 °C: A Statistical Approach

Metals ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 669
Author(s):  
Tasawar Javed ◽  
Edouard Asselin
Keyword(s):  
Large Scale ◽  
Particle Growth ◽  
Metal Loss ◽  
Synthetic Process ◽  
Valuable Metal ◽  
Factors Affecting ◽  
Copper Loss ◽  
High Acid ◽  
Sulphate Chloride ◽  
Process Solutions

The purification of hydrometallurgical process solutions by Fe(III) precipitation is a common and large-scale industrial operation. This step is notorious for valuable metal loss occurring with the iron precipitation product, which is usually directed to tailings. In this study, factors affecting Fe(III) precipitation and associated copper loss were studied in synthetic process solutions using statistical methods. The variables studied were: Initial acid concentration, retention time, seed addition, and initial Fe(III), Cu(II), and chloride concentrations. The importance of each variable and its interaction effects were studied against two responses, i.e., percent of Fe(III) precipitated as hematite and percent of Cu lost to solids. The results showed that a combination of high acid and moderate seeding was required to simultaneously achieve high proportions of Fe(III) precipitated as hematite and lower copper loss to the precipitates. High acid concentrations create low supersaturation for Fe(III), which minimizes the consequences of homogeneous nucleation and favors particle growth.

Controlling the size of Pt nanoparticles with a cationic surfactant, CnTABr

CrystEngComm ◽  
2018 ◽  
Vol 20 (14) ◽  
pp. 2010-2015 ◽  
Author(s):  
Jongsu Seo ◽  
Siwon Lee ◽  
Bonjae Koo ◽  
WooChul Jung
Keyword(s):  
Cationic Surfactant ◽  
Pt Nanoparticles ◽  
Particle Growth ◽  
Colloidal Synthesis ◽  
Chemical Affinity ◽  
Organic Complex ◽  
Wide Range ◽  
Chain Lengths

We report how the size of Pt nanoparticles varies by using a wide range of chain lengths and concentrations of CnTABr, a cationic surfactant, in aqueous-based colloidal synthesis and confirm that the chemical affinity between the organic complex formed in the solution and the aggregate of the surfactant is an important factor for Pt particle growth.

Comparison of Pathogens Dispersion in an Aircraft Cabin Using Gas Injection Source Versus a Coughing Manikin

2020 ◽  
Author(s):  
Seif Mahmoud ◽  
James S. Bennett ◽  
Mohammad H. Hosni ◽  
Byron Jones
Keyword(s):  
Gas Injection ◽  
Longitudinal Direction ◽  
Injection Rate ◽  
Sampling Location ◽  
Tracer Gas ◽  
Low Velocity ◽  
Co2 Gas ◽  
Gas Concentration ◽  
Continuous Injection ◽  
Injection Location

Abstract The dispersion characteristics of airborne pathogens were investigated in a Boeing 767 mockup cabin containing 11 rows with 7 seats per row, using two tracer gas source methods: continuous injection at low velocity and a coughing manikin. Both the injection source and the coughing manikin were located on the same seat in the sixth row. The injection source utilized CO2 gas at an injection rate of 5.0 liters per minute mixed with helium at a rate of 3.07 liters per minute to neutralize buoyancy. The manikin coughed approximately once every 75 seconds, with a volume of 4.2 liters of CO2 per cough. To ensure sufficient data were collected at each sampling location, each coughing manikin test was run for 6 coughs and each injection source test for 30 minutes of continuous injection. In both test methods, the tracer gas concentration was measured using CO2 gas analyzers at seated passenger breathing height of 1.2 m and radially up to 3.35 m away from the gas injection location, representing approximately four rows of a standard B767 aircraft. The collected data obtained from each tracer method was then normalized to provide a suitable comparison basis that is independent of tracer gas introduction flowrate. The results showed that both tracer source methods gave similar dispersion trends in diagonal and lateral directions away from the injection location. However, the tracer gas concentration was higher along the longitudinal direction in the coughing manikin tests due to the cough momentum. The results of this work will help researchers analyze different experimental and numerical approaches used to determine contaminant dispersion in various environments and will provide a better understanding of the associated transport phenomena.

PVP-Assisted Sb-Doped SnO2 Nanofibers Synthesized by Electrospinning Process

2016 ◽  
Vol 675-676 ◽  
pp. 150-153
Author(s):  
Somtop Santibenchakul ◽  
Suwan Chaiyasith ◽  
Wisanu Pecharapa
Keyword(s):  
Crystal Structure ◽  
Tin Oxide ◽  
Doping Concentration ◽  
Precursor Solution ◽  
Injection Rate ◽  
Electrospinning Process ◽  
X Ray Diffraction ◽  
Electrospinning Technique ◽  
X Ray ◽  
Sb Doping

Well-defined Sb-doped tin oxide (ATO) nanofibers were synthesized by electrospinning technique. Polyvinylpyrrolidone (PVP), SnCl4·5H2O and SbCl3 were chosen as suitable precursors for preparing ATO nanofibers. All of precursors were homogeneously dissolved with the mixture solvent of dimethylformamide (DMF) and absolute ethanol. Electrospinning process was carried out at applied voltage of 10 kV and distance between needle tip to aluminium foil collector was fixed at 10 cm. The injection rate of precursor solution was controlled at 0.5 ml/hr. The as-spun nanofibers were calcined at 600°C with heating rate of 5 °C/min in order to remove the PVP template and improve the crystallinity of ATO structure. Effect of Sb doping concentration on their crystal structure was investigated. The morphology and crystal structure of the electrospun fibers were analyzed by scanning electron microscope (SEM) and X-ray diffraction (XRD). In this work, the obtained ATO nanofibers had average range diameter from 150 to 350 nm with rough surface. Sb doping concentration in ATO nanofibers plays a key role on their network morphology. The excellent doping concentration of Sb that offered the continuous fibrous and porous ATO nanofibers was 7%.

scholarly journals Spray-Pyrolysis Preparation of Li4Ti5O12/Si Composites for Lithium-Ion Batteries

2019 ◽  
pp. 69
Author(s):  
A. Terechshenko ◽  
A. Sanbayeva ◽  
M.R. Babaa ◽  
A. Nurpeissova ◽  
Z. Bakenov
Keyword(s):  
Lithium Ion Batteries ◽  
Spray Pyrolysis ◽  
Anode Material ◽  
Spray Pyrolysis Technique ◽  
Continuous Process ◽  
Lithium Ion ◽  
Precursor Solution ◽  
Lithium Nitrate ◽  
Aerosol Formation ◽  
Titanium Tetraisopropoxide

This paper introduces the novel anode material which is Li4Ti5O12/Si prepared by gas-stated method, mainly spray-pyrolysis technique. The literature review performed in this paper revealed two main components which can be potentially mixed into the efficient anode material. Silicon (Si) has the highest possible capacity of 4200 mAh g-1 among all commonly used anodes. Due to its ‘zero-strain’ (<1% volume change) properties and stable cycling, Li4Ti5O12 (LTO) is considered as a promising anode for lithium ion batteries. Combination of these two anode materials is considered as a promising approach to prepare a high performance composite anode. The precursor solution consisted of homogeneous mixture of lithium nitrate and titanium tetraisopropoxide dissolved in deionized water with equimolar concentration of 0.5 M. The aerosol formation was performed at nitrogen environment and the droplets were carried into the quartz tube reactor at the flowrate of 4 L min-1. The rector temperature was held at 800 °C. The spray-pyrolysis synthesis was performed as one-step operation, excluding the need of calcination of as-prepared powders, and continuous process by the mean of peristaltic pump. The as-prepared powders had wide size distribution from nanometers to microns. The materials obtained had well-crystallized structure with insignificant amount of impurities. The powders were analyzed by the following analytical equipment: 1) the presence of Li4Ti5O12 and Si in the obtained composite was confirmed by X-ray diffraction technique (XRD); 2) The structure and morphology of LTO and Si molecules were observed and studied with Scanning Electron Microscopy (SEM).

scholarly journals Group 13 Lewis Acid Catalyzed Synthesis of Cu2O Nanocrystals via Hydroxide Transmetallation

2021 ◽  
Author(s):  
Noah Gibson ◽  
Alexandria R. C. Bredar ◽  
Byron Farnum
Keyword(s):  
Oleyl Alcohol ◽  
Copper Ions ◽  
Colloidal Synthesis ◽  
Esterification Reaction ◽  
Group 13 ◽  
Oleyl Oleate ◽  
Acid Catalyzed ◽  
Uv Visible ◽  
Continuous Injection ◽  
Injection Procedure

The colloidal synthesis of metal oxide nanocrystals (NCs) in oleyl alcohol requires the metal to catalyze an esterification reaction with oleic acid to produce oleyl oleate ester and M-OH monomers, which then condense to form MxOy solids. Here we show that the synthesis of Cu2O NCs by this method is limited by the catalytic ability of copper to drive esterification and thus produce Cu+ -OH monomers. However, inclusion of 1-15 mol% of a group 13 cation (Al3+, Ga3+ , or In3+) results in increased yields for the consumption of copper ions toward Cu2O formation and exhibits size/morphology control based on the nature of M3+ . Using a continuous-injection procedure where the copper precursor (Cu2+ -oleate) and catalyst (M3+ -oleate) are injected into oleyl alcohol at a controlled rate, we are able to monitor the reactivity of the precursor and M3+ catalyst using UV-visible and FTIR absorbance spectroscopies. These time-dependent measurements clearly show that M3+ catalysts drive esterification to produce M3+ -OH species, which then undergo transmetallation of hydroxide ligands to generate Cu+ -OH monomers required for Cu2O condensation. Ga3+ is found to be the “goldilocks” catalyst, producing NCs with the smallest size and a distinct cubic morphology not observed for any other group 13 metal. This is believed to be due to rapid transmetallation kinetics between Ga3+ -OH and Cu + -oleate. These studies introduce a new mechanism for the synthesis of metal oxides where inherent catalysis by the parent metal (i.e. copper) can be circumvented with the use of a secondary catalyst to generate -OH ligands.

scholarly journals Improvement of Sensing Performance of Impedancemetric C2H2 Sensor Using SmFeO3 Thin-Films Prepared by a Polymer Precursor Method

Sensors ◽  
2019 ◽  
Vol 19 (4) ◽  
pp. 773 ◽  
Author(s):  
Tomohisa Tasaki ◽  
Satoko Takase ◽  
Youichi Shimizu
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Photoelectron Spectroscopy ◽  
Precursor Solution ◽  
Particle Growth ◽  
Polymer Precursor ◽  
X Ray Diffraction ◽  
X Ray ◽  
Sensor Material ◽  
Perovskite Type

A sensitive an impedancemetric acetylene (C2H2) gas sensor device could be fabricated by using perovskite-type SmFeO3 thin-film as a sensor material. The uniform SmFeO3 thin-films were prepared by spin-coating and focusing on the effects of polymer precursor solutions. The prepared precursors and thin-films were characterized by means of thermal analysis,　Fourier-transform infrared spectroscopy, ultraviolet–visible spectroscopy, X-ray diffraction analysis, scanning electron microscopy and X-ray photoelectron spectroscopy . It was found that particle growth and increase in homogeneity of the prepared thin-film could be accelerated by the addition of acetyl acetone (AcAc) as a coordination agent in the polymer precursor solution. Moreover, the highly crystallized thin-film-based sensor showed good response properties and stabilities to a low C2H2 concentration between 0.5 and 2.0 ppm.

Singing Mitigation in an Export Riser via Liquid Injection: A Field Case Study

2014 ◽  
Author(s):  
S. P. C. Belfroid ◽  
H. J. C. Korst ◽  
P. van Beek ◽  
K. Lunde ◽  
I. G. Eidsvik ◽  
...  
Keyword(s):  
Gas Flow ◽  
Field Measurements ◽  
High Amplitude ◽  
Injection Rate ◽  
Norwegian Sea ◽  
Liquid Injection ◽  
Flexible Jumper ◽  
Continuous Injection ◽  
Gas Lift

Flexible Risers are prone to the generation of high amplitude tonal noise, i.e. a so-called singing riser. Recently, severe vibrations and high noise levels were encountered on the turret of an FPSO in the Norwegian Sea, resulting in significantly reduced production. The vibrations could be attributed to pulsations generated either by a flexible jumper (connecting topside to turret), the gas lift riser or the gas export riser. Field measurements showed that the most likely source was the 10 inch gas export riser. Due to the vibrations, a reduced production limit was set. A field measurement campaign was started to inject liquid into the export risers to provisionally increase production, while in the meantime permanent solutions were evaluated and installed. Liquid was injected batch wise and continuously. The main field trial was initiated by a batch of MEG (mono ethylene glycol) (2 times 500 liters) followed by continuous injection of small amounts of MEG. Between settling periods, the gas export rate was increased in steps until vibrations were detected. At detection, the MEG injection rate was increased until vibrations/pulsations disappeared, after which gas export was increased again. This process was repeated to maximum gas flow rate, after which the liquid injection and gas export were similarly stepwise decreased. During this test, the gas export could be increased tenfold with moderate liquid injection rates (up to a maximum of 25 l/hr). Similar tests were done with TEG as injected fluid. However, TEG was far less efficient in suppressing the singing. This is attributed to the higher viscosity of the TEG at the injection temperatures and the method of injection.

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