Harnessing Intramolecular Chalcogen-Chalcogen Bonding in Merocyanines for Utilization in High-Efficiency Photon-to-Current Conversion Optoelectronics.

A novel series of donor (D)-π-acceptor (A) merocyanine molecules harnessed with intramolecular chalcogen bonding (ChaB) is designed, synthesized, and characterized. ChaB comprises periodic chalcogen atoms, S, Se, and Te, and a neighboring oxygen atom of a carbonyl moiety. Compared to the D-π-A merocyanine dye with nontraditional intramolecular hydrogen bonding, the novel molecules with an intramolecular ChaB exhibit remarkably smaller absorption spectral widths and higher absorption coefficients attributed to their cyanine-like characteristics approaching the resonance parameter (c2) ∼0.5; furthermore, they exhibit better thermal stabilities and electrical charge-carrier transport properties in films. These novel D-π-A merocyanines harnessed with intramolecular ChaB networks are successfully utilized in high-performance color-selective organic photon-to-current conversion optoelectronic devices with excellent thermal stabilities. This study reports that the unique intramolecular ChaB plays an essential role in locking the molecular conformation of merocyanine molecules and enhancing the optical, thermal, and optoelectronic properties of high-performance and high-efficiency organic photon-to-current conversion devices.

Facile and versatile ligand analysis method of colloidal quantum dot.

Colloidal quantum-dots (QDs) are highly attractive materials for various optoelectronic applications owing to their easy maneuverability, high functionality, wide applicability, and low cost of mass-production. QDs usually consist of two components: the inorganic nano-crystalline particle and organic ligands that passivate the surface of the inorganic particle. The organic component is also critical for tuning electronic properties of QDs as well as solubilizing QDs in various solvents. However, despite extensive effort to understand the chemistry of ligands, it has been challenging to develop an efficient and reliable method for identifying and quantifying ligands on the QD surface. Herein, we developed a novel method of analyzing ligands in a mild yet accurate fashion. We found that oxidizing agents, as a heterogeneous catalyst in a different phase from QDs, can efficiently disrupt the interaction between the inorganic particle and organic ligands, and the subsequent simple phase fractionation step can isolate the ligand-containing phase from the oxidizer-containing phase and the insoluble precipitates. Our novel analysis procedure ensures to minimize the exposure of ligand molecules to oxidizing agents as well as to prepare homogeneous samples that can be readily analyzed by diverse analytical techniques, such as nuclear magnetic resonance spectroscopy and gas-chromatography mass-spectrometry.

Green-light-selective organic photodiodes for full-color imaging.

In this work, organic photodiodes (OPDs) based on two newly synthesized p-type dipolar small molecules are reported for application to green-light-selective OPDs. In order to reduce the blue-color absorption induced by the use of C60 as the n-type material in a bulk heterojunction (BHJ), the electron donor:electron acceptor composition ratio is tuned in the BHJ. With this light manipulation approach, the blue-wavelength external quantum efficiency (EQE) is minimized to 18% after reducing the C60 concentration in the center part of the BHJ. The two p-type molecules get a cyanine-like character with intense and sharp absorption in the green color by adjusting the strength of their donating and accepting parts and by choosing a selenophene unit as a π-linker. When combined to C60, the green-wavelength EQE reaches 70% in a complete device composed of two transparent electrodes. Finally, the optical simulation shows the good color-balance performance of hybrid full-color image sensor without an additional filter by using the developed green OPD as the top-layer in stacked device architecture.

A safe and sustainable bacterial cellulose nanofiber separator for lithium rechargeable batteries.

Bacterial cellulose nanofiber (BCNF) with high thermal stability produced by an ecofriendly process has emerged as a promising solution to realize safe and sustainable materials in the large-scale battery. However, an understanding of the actual thermal behavior of the BCNF in the full-cell battery has been lacking, and the yield is still limited for commercialization. Here, we report the entire process of BCNF production and battery manufacture. We systematically constructed a strain with the highest yield (31.5%) by increasing metabolic flux and improved safety by introducing a Lewis base to overcome thermochemical degradation in the battery. This report will open ways of exploiting the BCNF as a "single-layer" separator, a good alternative to the existing chemical-derived one, and thus can greatly contribute to solving the environmental and safety issues.

Mg-Ion Inversion in MgO@MgO-Al2 O3 Oxides: The Origin of Basic Sites.

Although MgO-Al2 O3 is well known as having a spinel structure, the inversion of which occurs by exchange of the trivalent (Al3+ ) and divalent (Mg2+ ) cations, little analytical study of the degree of inversion has been carried out. This study concerns a simple methodology to identify the inversion by solid-state NMR spectroscopy, whereby its correlation with the CO2 capture capacity of MgO-rich MgO@MgO-Al2 O3 spinel structures is verified. Through 27 Al and 25 Mg NMR spectroscopy, temperature-programmed CO2 desorption, and thermogravimetric analysis, higher inversion is found to occur at low Mg/Al ratios and the inversion is found to decrease as the Mg/Al ratio increases. Moreover, the degree of inversion correlates with CO2 sorption, which is associated with the medium-strength basic sites induced by formation of the unsaturated O2- species. These results will open new pathways to exploit defects in complex oxides beyond spinels and their derivatives for desired applications. This demonstration of MgO-Al2 O3 for CO2 sorption can contribute to the design of future CO2 sorbents.

Predictive Guide for Collective CO2 Adsorption Properties of Mg-Al Mixed Oxides.

Although solid adsorption processes offer attractive benefits, such as reduced energy demands and penalties compared with liquid absorption processes, there are still pressing needs for solid adsorbents with high adsorption capacities, thermal efficiencies, and energy-intensive regeneration in gas-treatment processes. The CO2 adsorption capacities of layered double oxides (LDOs), which are attractive solid adsorbents, have an asymmetric volcano-type correlation with their relative crystallinities. Furthermore, new collective adsorption properties (adsorption capacity, adsorptive energy and charge-transfer amount based on the adsorbent weight) are proposed based on density functional theory (DFT) calculations and measured surface areas. The correlation of these collective properties with their crystallinities is in good agreement with the experimentally measured CO2 adsorptive capacity trend, providing a predictive guide for the development of solid adsorbents for gas-adsorption processes.

Macrocycles within Macrocycles: Cyclen, Cyclam, and Their Transition Metal Complexes Encapsulated in Cucurbit[8]uril.

Reminiscent of Russian Matrioshka dolls, tetraazamacrocycles (1,4,7,10-tetraazacyclododecane (cyclen) and 1 , 4 , 8 , 11 - tetraazacyclotetradecane (cyclam)) and their transition metal complexes are encapsulated in the cavity of cucurbit[8]uril (CB[8]). The X-ray crystal structure of the [Cu(cyclen)] in CB[8] complex (see picture; copper: green, oxygen: red, nitrogen: blue, carbon: gray) reveals a five-coordinate CuII center in a square-pyramidal environment with a water molecule bound to the axial position.