De-agglomeration of nanoparticles in an impactor-assisted fluidized bed

High surface-to-volume ratio and high activity of nanoparticles cause interesting changes in material properties; however, these features often lead to the formation of undesired agglomerates. When agglomerated, nanoparticles lose their outstanding properties; hence, it is essential to break them up prior to use, and prevent the re-agglomeration. There are several techniques to de-agglomerate nanoparticles, such as rapid expansion of supercritical suspensions (1) and low pressure single stage impactors (2). Utilizing fluidized beds, Pfeffer et al. applied a downwardly facing micro-jet in order to enhance the quality of nanoparticle fluidization (3). Bremer et al. (4) patented a method to de-agglomerate catalyst particles by applying a high velocity jet upwardly in the fluidized bed. Further efforts by Yi (5), using a vibrated fluidized bed, focused on particle mass concentration rather than de-agglomeration of nanoparticles. However, all these attempts were not able to result in long-lasting nano scale particle dispersions. The main objective of this project is to break up the large fractal-shaped agglomerates to smaller clusters, preferably to individual nanoparticles, using an impactor-assisted fluidized bed. In our work, a fluidized bed is equipped with a pulsed-jet and an impaction plate. The force required to destroy the agglomerates is controlled by the gas jet velocity in the impaction zone. Calculating the impcation velocity determines the kinetic energy of particles upon impaction and makes it possible to measure the fragmentation degree of nanoparticles. This impactor-assisted bed also includes a surface functionalization post-treatment, based on photo-initiated chemical vapor deposition (6), to ensure particle stability. REFERENCES 1. To, D., R. Dave, X. Yin, and S. Sundaresan, Deagglomeration of nanoparticle aggregates via rapid expansion of supercritical or high-pressure suspensions. AlChE J., 2009. 55(11): p. 2807-2826. 2. Seipenbusch, M., P. Toneva, W. Peukert, and A.P. Weber, Impact Fragmentation of Metal Nanoparticle Agglomerates. Part. Part. Syst. Char., 2007. 24(3): p. 193-200. 3. Pfeffer, R. and J.A.Q.J. Flesch, Fluidized Bed Systems And Methods Including Micro-Jet Flow. 2008, New Jersey Institute Of Technology Evonik Degussa Gmbh. 4. Bremer, N.J., L.R. Trott, and T.R. McDonel, Method for deagglomerating and re-exposing catalyst in a fluid bed reactor. 1992-06-23 The Standard Oil Company. 5. Nurkiewicz, J.Y.T.R., Nanoparticle aerosol generator, USPTO, Editor. 2014, West Virginia University: US. 6. Dorval Dion, C.A., W. Raphael, E. Tong, and J.R. Tavares, Photo-initiated chemical vapor deposition of thin films using syngas for the functionalization of surfaces at room temperature and near-atmospheric pressure. Surf. Coat. Technol., 2014. 244: p. 98-108

VUV Photodeposition of Thiol-Terminated Films: A Wavelength-Dependent Study

Photoinitiated chemical vapor deposition (PICVD) has become attractive for selective and specific surface functionalization, because it relies on a single energy source, the photons, to carry out (photo-) chemistry. In the present wavelength (λ)-dependent study, thiol (SH)-terminated thin film deposits have been prepared from gas mixtures of acetylene (C2H2) and hydrogen sulfide (H2S) via PICVD using four different vacuum-ultraviolet (VUV) sources, namely, KrL (λpeak = 123.6 nm), XeL (λpeak = 147.0 nm), XeE (λpeak = 172.0 nm), and Hg (λ = 184.9 nm) lamps. Different λ influence the deposition kinetics and film composition, reflecting that photolytic reactions are governed by the gases’ absorption coefficients, k(λ). Thiol concentrations, [SH], up to ∼7.7%, were obtained with the XeL source, the highest reported in the literature so far. Furthermore, all films showed islandlike surface morphology, regardless of λ

Sulfur-rich organic films deposited by plasma- and vacuum-ultraviolet (VUV) photo-polymerization

Thiol (SH)-terminated surfaces have been progressively gaining interest over the past years as a consequence of their widespread potential applications. Here, SH-terminated thin films have been prepared by “co-polymerizing” gas mixtures comprising ethylene (C2H4) or butadiene (C4H6) with hydrogen sulfide (H2S). This has been accomplished by either vacuum-ultraviolet (VUV) irradiation of the flowing gas mixtures with near-monochromatic radiation from a Kr lamp, or by low-pressure r.f. plasma-enhanced chemical vapor deposition (PECVD). Varying the gas mixture ratio, R, allows one to control the films’ sulfur content as well as the thiol concentration [[BOND]SH]. The deposits were characterized by X-ray photoelectron spectroscopy (XPS), before and after chemical derivatization with N-ethylmaleimide, and by ATR FTIR. VUV- and plasma-prepared coatings were found to possess very similar structures and characteristics, showing chemically bonded sulfur concentrations, [S], up to 48 at% and [[BOND]SH] up to 3%. All coatings remained essentially unchanged in thickness after immersion in water for 24 h

Growth mechanisms of sulfur-rich plasma polymers: Binary gas mixtures versus single precursor

Thiol (SH)‐terminated surfaces have gained interest over the past years due to their potential applications, especially in the biomedical field. In this work, SH‐terminated films have been prepared by “co‐polymerizing” gas mixtures of acetylene (C2H2) and hydrogen sulfide (H2S) using low‐pressure r.f. plasma‐enhanced chemical vapor deposition. R.f. power greatly influences the deposition rate, sulfur content, [S], and thiol concentration, [SH], of the films, as confirmed by XPS (both before and after chemical derivatization), FTIR, and mass spectrometry measurements. These data are compared with those obtained in a similar discharge by using a single molecule precursor, propanethiol. Among other differences, it is demonstrated that [SH] is higher when using binary gas mixtures compared to the single molecule precursor

Organic coatings from acetylene at atmospheric pressure: UV light versus plasma

ABSTRACT: A versatile pilot-scale reactor has been designed in such a way that it can be readily converted from a dielectric barrier discharge “PECVD” operating mode into a photoinitiated “PICVD” one; in the latter, low-pressure mercury (Hg) lamps replace the high-voltage glow discharge plasma. Both processes operate at ambient temperature and atmospheric pressure, 100 kPa, using acetylene (C2H2) monomer. In both sets of experiments, it was found that efficient gas-to-solid conversion can occur in the form of a nanoparticulate amorphous hydrocarbon polymer-like material. It was found that in the PICVD case, great care was required to exclude even traces of O2 contamination, because it not only reduced the growth rate of solid, but the latter then became highly oxidized ([O] ~50 at.%) and water-soluble

Nanoporous sponges as carbon-based sorbents for atmospheric water generation

Water scarcity threatens more and more people in the world. Moisture adsorption from the atmosphere represents a promising avenue to provide fresh water. Nanoporous sponges (“NPSs” ), new carbon-based sorbents synthesized from the pyrolysis of resorcinol-formaldehyde resin, can achieve comparable performance to metal organic framework-based systems, but at a significantly lower cost. Oxygen and nitrogen functionalities can be added to the NPS surface, through oxidation and addition of phenanthroline to the initial reagent mixture, respectively. The resulting NPS sorbents have high specific surface areas of 347 to 527 m2·g–1 and an average capillary-condensation-compatible pore size of 1.5 nm. When oxidized, the NPS can capture up to 0.28 g of water per gram of adsorbent at a relative pressure of 0.90 (0.14 g·g–1 at P/Psat = 0.40) and maintain this adsorption capacity over multiple adsorption/desorption cycles. Scaled-up synthesis of the NPS was performed and tested in an experimental water capture setup, showing good agreement between small- and larger-scale adsorption properties. Water adsorption isotherms fitted with the theoretical model proposed by Do and Do demonstrate that hydroxyl functionalities are of key importance to NPS behavior

Surface engineering of wood substrates to impart barrier properties: a photochemical approach

In this study, sugar maple and white pine, two species of wood commonly used in indoor and outdoor applications, were treated by photo-initiated chemical vapor deposition to impart barrier properties. After treatment, wood wettability decreased significantly, as evidenced by water contact angle measurements (from 50° to 113° for sugar maple and 87° to 172° for white pine). Further, beyond being able to repel water, the coating shows the ability to breathe, evidenced by standardized vapor sorption tests. However, accelerated weathering via ASTM G155 testing determined that the treatment could not protect the wood from photo-degradation, or retain its properties post-weathering. This treatment could therefore be best suited for wood pre-treatment in combination with other coatings

Expert range maps of global mammal distributions harmonised to three taxonomic authorities

AimComprehensive, global information on species' occurrences is an essential biodiversity variable and central to a range of applications in ecology, evolution, biogeography and conservation. Expert range maps often represent a species' only available distributional information and play an increasing role in conservation assessments and macroecology. We provide global range maps for the native ranges of all extant mammal species harmonised to the taxonomy of the Mammal Diversity Database (MDD) mobilised from two sources, the Handbook of the Mammals of the World (HMW) and the Illustrated Checklist of the Mammals of the World (CMW).LocationGlobal.TaxonAll extant mammal species.MethodsRange maps were digitally interpreted, georeferenced, error-checked and subsequently taxonomically aligned between the HMW (6253 species), the CMW (6431 species) and the MDD taxonomies (6362 species).ResultsRange maps can be evaluated and visualised in an online map browser at Map of Life (mol.org) and accessed for individual or batch download for non-commercial use.Main conclusionExpert maps of species' global distributions are limited in their spatial detail and temporal specificity, but form a useful basis for broad-scale characterizations and model-based integration with other data. We provide georeferenced range maps for the native ranges of all extant mammal species as shapefiles, with species-level metadata and source information packaged together in geodatabase format. Across the three taxonomic sources our maps entail, there are 1784 taxonomic name differences compared to the maps currently available on the IUCN Red List website. The expert maps provided here are harmonised to the MDD taxonomic authority and linked to a community of online tools that will enable transparent future updates and version control

Evaluating the Effects of SARS-CoV-2 Spike Mutation D614G on Transmissibility and Pathogenicity.

Global dispersal and increasing frequency of the SARS-CoV-2 spike protein variant D614G are suggestive of a selective advantage but may also be due to a random founder effect. We investigate the hypothesis for positive selection of spike D614G in the United Kingdom using more than 25,000 whole genome SARS-CoV-2 sequences. Despite the availability of a large dataset, well represented by both spike 614 variants, not all approaches showed a conclusive signal of positive selection. Population genetic analysis indicates that 614G increases in frequency relative to 614D in a manner consistent with a selective advantage. We do not find any indication that patients infected with the spike 614G variant have higher COVID-19 mortality or clinical severity, but 614G is associated with higher viral load and younger age of patients. Significant differences in growth and size of 614G phylogenetic clusters indicate a need for continued study of this variant