Search

Temperature-induced sorption in porous materials is a well-known process. What is more challenging is to determine how the rate at which temperature is varied affects these processes. To address this question, we introduce a methodology called ‘‘cyclic thermo-ellipsometry’’ to explore the thermo-kinetics of vapor physisorption in metal–organic framework films. [ABSTRACT FROM AUTHOR]

Varnish layers are optical coatings that act as physico‐chemical barrier between the historical paint layers and the environment. Understanding how varnish materials protect historical paintings over time and in the presence of humidity or organic vapors is of central importance for art preservation. However, probing the behavior of varnish after aging in real conditions remains a challenge. Here the question is addressed by "reshaping" the varnish material from the masterpiece of G. Bellini, the "Transfiguration", into an optical layer; coupling in situ Ultraviolet‐Visible (UV–vis) and Infrared (IR) ellipsometries, the chemical state is correlated, optical properties and swelling of the varnish in presence of water and organic vapors. It shows that the varnish material aged since the 1950s still exhibits effective water repellence. The methodology may be applied to other relevant historical systems beyond paintings and may help in establishing more efficient preservation strategies for historical artworks. [ABSTRACT FROM AUTHOR]

ZnO is an effective photocatalyst applied to the degradation of organic dyes in aqueous media. In this study, the UV-light and sunlight-driven photocatalytic activities of ZnO nanoparticles are evaluated. A handheld Lovibond photometer was purposefully calibrated in order to monitor the dye removal in outdoor conditions. The effect of ZnO defect states, i.e., the presence of zinc and oxygen defects on the photocatalytic activity was probed for two types of dyes: fuchsin and methylene blue. Three morphologies of ZnO nanoparticles were deliberately selected, i.e., spherical, facetted and a mix of spherical and facetted, ascertained via transmission electron microscopy. Aqueous and non-aqueous sol-gel routes were applied to their synthesis in order to tailor their size, morphology and defect states. Raman spectroscopy demonstrated that the spherical nanoparticles contained a high amount of oxygen vacancies and zinc interstitials. Photoluminescence spectroscopy revealed that the facetted nanoparticles harbored zinc vacancies in addition to oxygen vacancies. A mechanism for dye degradation based on the possible surface defects in facetted nanoparticles is proposed in this work. The reusability of these nanoparticles for five cycles of dye degradation was also analyzed. More specifically, facetted ZnO nanoparticles tend to exhibit higher efficiencies and reusability than spherical nanoparticles. [ABSTRACT FROM AUTHOR]

Organic−inorganic hybrid mesostructured silicas are prepared, without stirring (at pH = 0.0) and with stirring (at pH = 0.6) to obtain isolated and gyroidal-like attached silica grains with incorporated triblock P123 poly (ethylene oxide)-poly (propylene oxide)–poly (ethylene oxide) copolymers. Selected hybrids are submitted to various thermal and aging treatments for studying hydrolysis and oxidation of PEO and PPO chains. Two complementary spectroscopic techniques are used: near-infrared (NIR) with measurements performed in diffuse reflectance, as well as 1H and 13C liquid- and solid-state nuclear magnetic resonance (NMR) to study the mobility and stability of PEO and PPO chains. With precipitated fresh hybrids, the ratio of PEO over (PEO + PPO) units is lower (30% ± 5%) than in theory. This ratio also decreases depending on temperature when a hydrothermal treatment is applied. An acidic hydrolysis involving both PEO and PPO chains, with generated fragments eliminated by washing with water and/or synthesis liquor, is then demonstrated. For comparison, another hybrid obtained by spray drying via evaporation-induced self assembly mechanism is also studied. Its NMR signals are much more stable than those of the samples prepared by precipitation. Depending on aging time, thermal history, and materials processing, the textural properties and template decomposition inside mesostructured silica are found significantly different. The influence of the hydrolysis and oxidation of the template onto final materials texture is likely to be as important as the processing conditions. Highlights: Mesostructured "hybrids" containing silica and P123 triblock copolymers obtained by precipitation (in acidic HCl solution) and spray drying are compared. A copolymer acidic hydrolysis is observed for all samples having been heated during synthesis (that is, hydrothermal treatment for synthesis by precipitation, or drying temperature for spray drying experiments). 1,2-ethanediol and peroxide traces associated with the copolymer oxidative decomposition are identified by NMR. The temperature of the heat treatment applied for HT is directly correlated with the remaining EO/(EO + PO) weight %. The NMR study of polymer chains mobility confirms the dehydration and retraction of hydrated PEO chains from silica walls upon temperature increase. We proved for the first time that this effect, now well known for precipitated SBA-15 materials, also occur for spray-dried samples. [ABSTRACT FROM AUTHOR]

Aerosol processing is long known and implemented industrially to obtain various types of divided materials and nanomaterials. The atomisation of a liquid solution or suspension produces a mist of aerosol droplets which can then be transformed via a diversity of processes including spray-drying, spray pyrolysis, flame spray pyrolysis, thermal decomposition, micronisation, gas atomisation, etc. The attractive technical features of these aerosol processes make them highly interesting for the continuous, large scale, and tailored production of heterogeneous catalysts. Indeed, during aerosol processing, each liquid droplet undergoes well-controlled physical and chemical transformations, allowing for example to dry and aggregate pre-existing solid particles or to synthesise new micro- or nanoparticles from mixtures of molecular or colloidal precursors. In the last two decades, more advanced reactive aerosol processes have emerged as innovative means to synthesise tailored-made nanomaterials with tunable surface properties, textures, compositions, etc. In particular, the “aerosol-assisted sol–gel” process (AASG) has demonstrated tremendous potential for the preparation of high-performance heterogeneous catalysts. The method is mainly based on the low-cost, scalable, and environmentally benign sol–gel chemistry process, often coupled with the evaporation-induced self-assembly (EISA) concept. It allows producing micronic or submicronic, inorganic or hybrid organic–inorganic particles bearing tuneable and calibrated porous structures at different scales. In addition, pre-formed nanoparticles can be easily incorporated or formed in a “one-pot” bottom-up approach within the porous inorganic or hybrid spheres produced by such spray drying method. Thus, multifunctional catalysts with tailored catalytic activities can be prepared in a relatively simple way. This account is an overview of aerosol processed heterogeneous catalysts which demonstrated interesting performance in various relevant chemical reactions like isomerisation, hydrogenation, olefin metathesis, pollutant total oxidation, selective oxidation, CO2 methanation, etc. A short survey of patents and industrial applications is also presented. Our objective is to demonstrate the tremendous possibilities offered by the coupling between bottom up synthesis routes and these aerosol processing technologies which will most probably represent a major route of innovation in the mushrooming field of catalyst preparation research. [ABSTRACT FROM AUTHOR]

A straightforward crack-patterning method is reported allowing the direct formation of periodic cracks in metal-organic framework (MOF) nanoparticle films during dip-coating deposition. The crack propagation and periodicity can be easily tailored by controlling the evaporation front and the withdrawal speed. Several MOF-patterned films can be fabricated on large surfaces and on several substrates (flat, curved or flexible) including the inner surface of a tube, not achievable by other lithographic techniques. We demonstrate that the periodic cracked arrays diffract light and, due to the MOF sorption properties, photonic vapor sensors are fabricated. A new concept of 'in-tube', MOF-based diffraction grating sensors is proposed with outstanding sensitivity that can be easily tuned 'on-demand' as function of the desired detection range. [ABSTRACT FROM AUTHOR]

Despite increasing interest in metal–organic frameworks (MOFs) in the biomedical field, developing specific formulations suitable for different administration routes is still a main challenge. Here, we propose a simple, fast and bio-friendly press-molding method for the preparation of cutaneous patches based on composites made from the drug nanocarrier MIL-100(Fe) and biopolymers. The physicochemical properties of the patches (structure, hydration, bioadhesive and swelling properties), as well as their encapsulation and release capabilities (both in ex vitro and ex vivo models), were evaluated using active ingredients such as the challenging cosmetic liporeductor, caffeine, and the model analgesic and anti-inflammatory drug, ibuprofen. In particular, very high caffeine loadings were entrapped within these cutaneous devices with progressive releases under simulated cutaneous physiological conditions as a consequence of the swelling of the hydrophilic patches. Despite the absence of any cutaneous bioadhesive character, these patches provided progressive and suitable permeation of their cosmetic cargo through the skin, interestingly reaching the targeted adipose tissue. This makes these cosmetic-containing composite MOF-based patches promising candidates for new cutaneous devices in cosmetic applications. [ABSTRACT FROM AUTHOR]