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Heavy metal carboxylate or soap formation is a widespread deterioration problem affecting oil paintings and other works of art bearing oil‐based media. Lead soaps are prevalent in traditional oil paintings because lead white was the white pigment most frequently chosen by old masters for the paints and in some cases for the ground preparations, until the development of other white pigments from approximately the middle of the 18th century on, and because of the wide use of lead‐tin yellow. In the latter part of the 19th century, lead white began to be replaced by zinc white. The factors that influence soap formation have been the focus of intense study starting in the late 1990s. Since 2014, nuclear magnetic resonance (NMR) studies have contributed a unique perspective on the issue by providing chemical, structural, and dynamic information about the species involved in the process, as well as the effects of environmental conditions such as relative humidity and temperature on the kinetics of the reaction(s). In this review, we explore recent insights into soap formation gained through solid‐state NMR and single‐sided NMR techniques.
Many fall prevention strategies exist with some degree of effectiveness. Evidence to support 1 unique bundling of strategies is limited. The purpose of this article is to describe a staff-driven quality improvement initiative to develop a video in partnership with patients and families to prevent falls when hospitalized. Since the video's release, the fall rate has decreased by 29.4%.
Increasing demand for effective energy conversion materials
and
devices has renewed interest in semiconductors comprised of earth-abundant
and biocompatible elements. Alkaline-earth sulfides doped with rare
earth ions are versatile optical materials. However, relatively little
is known about controlling the dimensionality, surface chemistry,
and inherent optical properties of the undoped versions of alkaline-earth
mono- and polychalcogenides. We describe the colloidal synthesis of
alkaline-earth chalcogenide nanocrystals through the reaction of metal
carboxylates with carbon disulfide or selenourea. Systematic exploration
of the synthetic phase space allows us to tune particle sizes over
a wide range using a mixture of commercially available carboxylate
precursors. Solid-state NMR spectroscopy confirms the phase purity
of the selenide compositions. Surface characterization reveals that
bridging carboxylates and amines preferentially terminate the surface
of the nanocrystals. While these materials are colloidally stable
in the mother solution, the selenides are susceptible to oxidation
over time, eventually degrading to selenium metal through polyselenide
intermediates. As part of these investigations, we have developed
the colloidal syntheses of barium di- and triselenides, two among
few reported nanocrystalline alkaline-earth polychalcogenides. Electronic
structure calculations reveal that both materials are indirect band
gap semiconductors. The colloidal chemistry presented here may enable
the synthesis of more complex, multinary chalcogenide materials containing
alkaline-earth elements.
The quantitative evaluation of the three-dimensional (3D) morphology of porous composite materials is important for understanding mass transport phenomena, which further impact their functionalities and durability. Reactive porous paint materials are composites in nature and widely used in arts and technological applications. In artistic oil paintings, ambient moisture and water and organic solvents used in conservation treatments are known to trigger multiple physical and chemical degradation processes; however, there is no complete physical model that can quantitatively describe their transport in the paint films. In the present study, model oil paints with lead white (2PbCO3·Pb(OH)2) and zinc white (ZnO) pigments, which are frequently found in artistic oil paintings and are associated with the widespread heavy metal soap deterioration, were studied using synchrotron X-ray nano-tomography and unilateral nuclear magnetic resonance. This study aims to establish a relationship among the paints’ compositions, the 3D morphological properties and degradation. This connection is crucial for establishing reliable models that can predict transport properties of solvents used in conservation treatments and of species involved in deterioration reactions, such as soap formation.
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