Comparison of hydrophobicity and durability of functionalized aluminium oxide nanoparticle coatings with magnetite nanoparticles - links between morphology and wettability

HypothesisThe wetting characteristics of coatings created using functionalised nanoparticles and adhesive resins, depends strongly on the particle distribution within the surface layers. Although it has been shown that commercially available adhesives improve the durability of hydrophobic nanoparticle coatings, the wettability of these surfaces is governed by the agglomeration behaviour of the particles within the adhesive. As a consequence of this, coatings where the particles are highly agglomerated within the adhesive show lower hydrophobicity.ExperimentsThe morphology and chemical composition of coatings formed from carboxylate functionalised Al2O3 and magnetite (Fe3O4) nanoparticles and epoxy resin on plastic was studied using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Water contact angle (WCA) measurements were used to investigate how the coatings’ morphological characteristics and loading of the particles within the surface layers influenced their wettability. Infrared (IR) spectroscopy and thermogravimetric analysis (TGA) were used to study carboxylate adsorption onto the magnetite nanoparticles.FindingsCombining the Al2O3 nanoparticles with epoxy resin was observed to create highly hydrophobic coatings that displayed water contact angles (WCAs) between 145-150°. These coatings displayed good durability when sonicated in isopropanol and wiped with tissue. By comparison, coatings formed from the magnetite nanoparticles were substantially less hydrophobic and displayed WCAs between 75-125° when combined with epoxy resin. SEM revealed that the magnetite nanoparticles in the coatings were present as large agglomerates. By comparison, coatings formed from the Al2O3 nanoparticles showed a more homogenous particle distribution. Furthermore, XPS showed that the resin engulfed the magnetite nanoparticles to a far greater extent. The difference in wetting behaviour of these coatings is largely attributed to their different morphologies, since the particles are similar sizes and TGA shows that the particles possess similar carboxylate grafting densities. The uneven distribution of nanoparticles in the magnetite/ epoxy resin coating is due to the particles’ magnetic properties, which drive nanoparticle agglomeration as the coatings solidify. This work demonstrates that it is important to consider inter-particle interactions when fabricating low wettability composite coatings

Perivascular fibroblast activation states in human skin diseases

The perivascular adventitia (PA) senses and responds to injuries in blood vessels and the tissues they feed. Cells in the PA form the outermost vascular layer, joining the circulatory system to other organs. Housing hematopoietic, mesenchymal and neuronal cells allows flexible adventitial responses to diverse perturbations. However, the PA response can also be pathogenic. Thickening of the adventitia may drive ischemia and hypertension. It can also be a niche for local lymphocyte priming in diseases such as idiopathic pulmonary arterial hypertension. Despite their importance, PA contributions to skin diseases were understudied. The hypothesis that contrasting two cutaneous diseases, scleroderma and discoid lupus erythematosus (DLE), would illuminate discrete PA alterations was explored. Vascular changes are prominent, but distinct, in both diseases. Studying perivascular adventitial changes in these diseases may yield insights into both dermal and vascular pathologies. PA fibroblasts in healthy human skin were phenotypically distinct from the surrounding dermal fibroblasts. In both scleroderma and DLE, PA fibroblasts expanded and expressed surface markers not observed in healthy skin including vascular cell adhesion molecule 1 (VCAM1), podoplanin (PDPN) and the p75 low affinity nerve growth factor receptor (NGFR). Elaborated networks of PA fibroblasts in DLE expressed VCAM1 and enmeshed dense, T cell-rich infiltrates. Transcriptional analyses indicated positive correlations between VCAM1, T cell chemoattractants and interleukin (IL)-15, which promotes their survival. Activated PA fibroblasts in DLE likely create a supportive niche for T cells infiltrating the skin. In contrast, enlarged PA fibroblast networks in scleroderma expressed NGFR in the absence of leukocyte infiltrates. This PA fibroblast phenotype was shared among reparative and pathologic scarring, and four dermal tumors. NGFR is a mesenchymal stem cell (MSC) marker, and expanded NGFR+ mesenchymal cells were immediately adjacent to cluster of differentiation (CD)34+ and CD73+ PA MSC. Expression of NGFR by PA fibroblasts is likely associated with reparative responses. Different stimuli induced VCAM1 and NGFR on cultured human dermal fibroblasts, supporting these as discrete activation states. In conclusion, these studies demonstrated the responsive and plastic nature of human dermal PA mesenchymal cells, and pointed to connections with vascular alterations in skin diseases

Size and morphology dependent surface wetting based on hydrocarbon functionalized nanoparticles

HypothesisThe wetting properties of films created using metal oxide nanoparticles can be controlled through roughness and chemical functionality; however, other variations such as the size and shape of the particles play an important role in improved understanding of the wetting behaviour of these materials.ExperimentsInfrared (IR) spectroscopy and thermogravimetric analysis (TGA) were used to study the chemisorption and grafting density of a carboxylic acid onto the surface of nanoparticles. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to investigate the morphology and roughness of the nanoparticle films. To investigate the wettability and surface energy of the films, static and dynamic contact angle (CA) measurements were used.FindingsSmaller, spherical nanoparticles (<50 nm) were observed to create films that displayed greater surface roughness and showed superhydrophobic properties. By comparison, larger, 135 nm spherical nanoparticles showed reduced surface roughness and displayed water contact angles (WCAs) <150°. Since these particles showed similar carboxylate grafting densities, this suggests that there is a particle size limit above which it is not possible to deposit superhydrophobic films. This study also shows that topographical effects brought about by film roughness can be overcome through increasing the carboxylate grafting density on the surface of the nanoparticles. It was observed that films created using mix shape <50 nm nanoparticles with relatively low surface roughness displayed superhydrophobic WCAs and low hysteresis. These particles also possessed a substantially larger carboxylate grafting density, indicating that the extent of functionalization also has a large bearing on the wettability of the films. Herein, we show that particle size, morphology, and reactivity all play important roles in determining the wettability of nanoparticle films

Coherent states and entropy

Let $H_k$, $k\in {\mathbb{N}}$, be the Hilbert spaces of geometric quantization on a K\"ahler manifold $M$. With two points in $M$ we associate a Bell-type state $b_k \in H_k\otimes H_k$. When $M$ is compact or when $M$ is ${\mathbb{C}}^n$, we provide positive lower bounds for the entanglement entropy of $b_k$ (asymptotic in $k$, as $k\to\infty$).Comment: Proc. Geom. Sci. Inf. Conf. (Saint-Malo, France, 2023), Lecture Notes Comp. Sci., 14071, Springer, 2023, pp. 516-52

Carboxylation and Decarboxylation of Aluminum Oxide Nanoparticles Using Bifunctional Carboxylic Acids and Octylamine

The carboxylation of alumina nanoparticles (NPs), with bifunctional carboxylic acids, provides molecular anchors that are used for building more complexed structures via either physisorption or chemisorption. Colloidal suspensions of the NPs may be prepared by covalently bonding a series of carboxylic acids with secondary functional groups (HO2C-R-X) to the surface of the NPs: lysine (X = NH2), p-hydroxybenzoic acid (X = OH), fumaric acid (X = CO2H), and 4-formylbenzoic acid (X = C(O)H). Subsequent reaction with octylamine at either 25°C or 70°C was investigated. Fourier transform IR-attenuated reflectance spectroscopy (FTIR-ATR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) along with energy dispersive X-ray (EDX) analysis were used to characterize the bifunctionalized monolayers and/or multilayer corona surrounding the alumina NPs and investigate the reaction mechanism of octylamine with the functional groups (X) of the NPs. Except for the fumaric functionalized NPs, addition of octylamine to the functionalized NPs leads to removal of excess carboxylic acid corona from the surface via an amide formation. The extent of the multilayer is dependent on the strength of the acid⋯acid interaction

Controlling the wettability of plastic by thermally embedding coated aluminium oxide nanoparticles into the surface

HypothesisNanoparticle embedding into the surface of plastics provides an effective anchor that improves the durability of coatings formed from functionalized nanoparticles. Coatings formed from thermally embedded particles show superior wear resistance relative to coatings formed from non-embedded particles. As a consequence of this, embedded nanoparticles functionalized with hydrophilic and hydrophobic carboxylates are better suited for controlling the wettability of plastics than when the nanoparticles are deposited onto the plastic under ambient conditions.ExperimentsCarboxylate-functionalized Al2O3 nanoparticles were embedded into ethylene vinyl acetate through spray coating the particles onto the substrate during heating. Sonication was used to remove excess particles that did not become embedded into the material. Coatings formed from the embedded particles were characterized through scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). The wettability of the coatings was characterized using static and dynamic contact angle (CA) measurements to measure the apparent water contact angles, and sliding angle measurements, whilst the durability of the coatings was studied using scratch testing, tape peel tests, and abrasion tests. The build-up of fog on the substrates was also studied through exposing the surfaces to water vapour.FindingsThermal embedding of the particles into the surface of the plastic was observed to occur when the material was heated to temperatures around its melting temperature. AFM and SEM showed that plastic embedded with the nanoparticles possessed a morphology that was substantially rougher than the untreated plastic. CA measurements showed that plastic embedded with hydrophobic isostearate functionalized nanoparticles was highly hydrophobic and displayed a CA of approximately 152°. Dynamic CA measurements and sliding angle measurements revealed that plastic embedded with the isostearate functionalized nanoparticles showed petal-like wetting behavior. Furthermore, it was observed that the CA of the plastic could be varied from highly hydrophobic to highly hydrophilic through embedding varying amounts of isostearate and hydrophilic 2-[2-(2-methoxyethoxy)ethoxy]acetate functionalized Al2O3 nanoparticles into the surface of the material. Scratch testing showed that thermally embedding the nanoparticles into the plastic substantially improved their abrasion resistance, relative to when the nanoparticles are deposited onto the non-heated material. This methodology indicates that embedding nanoparticles into plastics creates durable coatings that can display variable wettability. Consequently, this methodology could be useful in applications where it is desirable to keep plastics dry, such as for food packaging or medical devices

Methodology to Adapt and Update a Life Cycle Cost Calculator for Your Institution: A Step-by-Step Guide

This guide provides a methodology for adapting a life cycle cost (LCC) calculator to your institution. An LCC calculator can be used to examine the present and future costs of any expenditure and can include a proxy carbon price in its analysis. Adapting an existing tool saves time and resources when compared to building from scratch. It also provides the most accurate information by accounting for specifics of context, such as energy costs and the greenhouse gas emission rates of energy sources, which vary by region. This guide outlines a five-step process for adapting an LCC calculator to match your institutional context. Step one is identifying all assumptions and utilities that may be needed to complete a life cycle cost estimate (e.g. electricity, central plant steam). Step two is collecting the data for all identified utility rates and assumptions. Step three is preparing the tool for the data update. Step four is entering institutionally specific variables into the calculator. Step five is updating the tool with the best available data to maintain accurac