Spotlights Cite This: J. Phys. Chem. Lett. 2018, 9, 425−425
pubs.acs.org/JPCL
Spotlights: Volume 9, Issue 2
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TUNING ELECTROCHEMILUMINESCENCE IN MULTISTIMULI RESPONSIVE HYDROGEL FILMS Smart materials are not yet ubiquitous, but it’s only a matter of time before our wounds are treated with self-adaptive dressings and our homes alert us to potential health problems based on a quick trip to the restroom. Recently, responsive hydrogels, which undergo conformational modifications upon changes such as pH or temperature, have attracted considerable interest for many applications such as sensing, drug delivery, and tissue engineering. Hydrogels made of cross-linked polymers are particularly attractive because they amplify small changes at the molecular level and translate them into large-volume modifications induced by swelling variations. Moreover, these swelling−deswelling changes can be finely tuned and are reversible. Introducing responsive polymers in electrochemiluminescent (ECL) processes provides the opportunity to manipulate the luminescence not only by the electrode potential but also by an external stimulus. Li et al. (10.1021/ acs.jpclett.7b03119) designed and fabricated new hydrogel materials that incorporate phenylboronic acid as a fructosesensing unit and a redox-active ECL luminophore. They found that the electrochemical response of this multiresponsive material was reversibly modulated by sequential stimuli (fructose and temperature), which control the swelling and the collapse of the films. The ECL signal was remarkably tuned by both stimuli, which operate in opposite directions: Swelling provoked by fructose decreased the ECL intensity, whereas ECL signals were enhanced upon film collapse. The resulting variation of the distance between adjacent ECL luminophores is the main parameter governing the generation of ECL. The ability to modulate the distance and the reactivity in such redox luminescent hydrogels may lead to new multiplexed ECL immunoassays, logic gates in bioelectronic devices, and tunable multicolor ECL systems using stimuli-responsive materials.
NEW INSIGHTS INTO HYDRIDE BONDING, DYNAMICS, AND MIGRATION IN La2LiHO3 OXYHYDRIDE As the field of energy materials has expanded over the past few decades, an array of ions such as O2− and Li+ have proven to be excellent charge carriers in a variety of ionic conductors used in fuel cells and batteries. However, a new exotic class of potential ionic conductors has emerged from the discovery of oxyhydrides, where the anionic sublattice is formally composed of both O2− and H− ions. These developments are exciting, but the goal of better, more viable devices cannot be achieved without an understanding of the structure, bonding, and diffusion mechanism of this new class of materials. Fjellvåg et al. (10.1021/acs.jpclett.7b03098) studied these properties in the hydride anionic conductor La2LiHO3 via the use of a combination of high-resolution inelastic neutron scattering and a set of density functional theory calculations. Using a series of charge density analysis methods, they found that La2LiHO3 has strong anisotropy in its bonding. In particular, they found that the perovskite layer is dominated by ionic bonding, whereas the rock salt layer is characterized by covalent bonding. This covalent character of the bonding in the rock salt layer is seen to hinder hydride migration into and within the rock salt layer, which in other similar structures has been shown to be the favorable anion migration path. As a result, in-plane migration of hydride anions becomes the favorable migration pathway and the dominant anionic transport mechanism with a barrier height of 0.68 eV. The findings lead the authors to propose Ba2MgH2O2 and Sr2MgH2O2 as promising oxyhydride candidates for improved hydride conductivity.
DESIGNING EFFICIENT SOLAR-THERMAL FUELS WITH [n.n](9,10)ANTHRACENE CYCLOPHANES: A THEORETICAL PERSPECTIVE It would be an exaggeration to say that “most” energy storage systems show promise in the quest for carbon-neutral energy options, but “MOST” systems are another story. That is, molecular solar-thermal (MOST) storage devices have emerged as a new approach to storing solar energy. MOST systems exploit the photoisomerization of molecules between a pair of two photoisomers, and they have emerged as a new technology for harvesting solar energy in chemical bonds. An ideal MOST material is an optimal mix of several unique attributes, which means that these materials are extremely limited. Ganguly et al. (10.1021/acs.jpclett.7b03170) studied [n.n](9,10) bis-anthracene cyclophanes and found that they are potential MOST systems, with energy storage and corresponding gravimetric energy storage densities better than previously reported MOST systems. Moreover, the authors expect that these systems have a sufficiently long shelf life for the high-energy photoproduct and can be mildly heated to release the stored solar energy in
Published: January 18, 2018
the form of thermal energy. Their findings show that anthracene-based motifs, which were hitherto ignored as a MOST system, can be efficiently used for solar energy storage.
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© 2018 American Chemical Society
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DOI: 10.1021/acs.jpclett.8b00082 J. Phys. Chem. Lett. 2018, 9, 425−425
