New Method of Fluorination Using Potassium Fluoride in Ionic Liquid: Significantly Enhanced Reactivity of Fluoride and Improved Selectivity

We have found the new nucleophilic fluorination reaction of some halo- and mesylalkanes to the corresponding fluoroalkanes with KF in the presence of [bmim][BF4] under various reaction conditions. 2-(3-Methanesulfonyloxypropoxy)naphthalene (1) was used as a model compound to optimize this fluorination reaction. Whereas the fluorination of the mesylate 1 with KF in an organic solvent such as CH3CN at 100 °C occurred hardly even after 24 h, the same reaction in ionic liquids, [bmim][BF4], as a reaction solvent was completed within 1.5 h, affording the wanted product 2-(3-fluoropropoxy)naphthalene 2a (85%) together with the alkene byproduct 2c (10%). Very interestingly, however, the addition of water (5 equiv) completely eliminated the formation of the undesired alkene 2c and thus gave higher yield of 2a (92%, entry 2). The use of acetonitrile as a cosolvent did not affect the reactivity of the fluorination. The presence of a proper amount of cosolvent was rather desirable (94% yield of 2a). We performed fluorination reactions with other ionic liquids ([bmim][PF6], [bmim][SbF6], [bmim][OTf], and [bmim][N(Tf)2], and two other cosolvents, to find the optimal ionic liquid and cosolvent. Nine different compounds were examined, including the 10 g-synthesis of 2-(fluoromethyl)naphthalene in 93% of isolated yield

New Method of Fluorination Using Potassium Fluoride in Ionic Liquid: Significantly Enhanced Reactivity of Fluoride and Improved Selectivity

We have found the new nucleophilic fluorination reaction of some halo- and mesylalkanes to the corresponding fluoroalkanes with KF in the presence of [bmim][BF4] under various reaction conditions. 2-(3-Methanesulfonyloxypropoxy)naphthalene (1) was used as a model compound to optimize this fluorination reaction. Whereas the fluorination of the mesylate 1 with KF in an organic solvent such as CH3CN at 100 °C occurred hardly even after 24 h, the same reaction in ionic liquids, [bmim][BF4], as a reaction solvent was completed within 1.5 h, affording the wanted product 2-(3-fluoropropoxy)naphthalene 2a (85%) together with the alkene byproduct 2c (10%). Very interestingly, however, the addition of water (5 equiv) completely eliminated the formation of the undesired alkene 2c and thus gave higher yield of 2a (92%, entry 2). The use of acetonitrile as a cosolvent did not affect the reactivity of the fluorination. The presence of a proper amount of cosolvent was rather desirable (94% yield of 2a). We performed fluorination reactions with other ionic liquids ([bmim][PF6], [bmim][SbF6], [bmim][OTf], and [bmim][N(Tf)2], and two other cosolvents, to find the optimal ionic liquid and cosolvent. Nine different compounds were examined, including the 10 g-synthesis of 2-(fluoromethyl)naphthalene in 93% of isolated yield

Application of Ionic Liquid Halide Nucleophilicity for the Cleavage of Ethers: A Green Protocol for the Regeneration of Phenols from Ethers

We have used the high nucleophilicity of bromide ion in the form of the ionic liquid, 1-n-butyl-3-methylimidazolium bromide ([bmim][Br]), for the nucleophilic displacement of an alkyl group to regenerate a phenol from the corresponding aryl alkyl ether. Using 2-methoxynaphthalene (1) as a model compound, we found that the combination of ionic liquid [bmim][Br] and p-toluenesulfonic acid with warming effected demethylation in 14 h, affording the desired product 2-naphthol (2) in good yield (97%). Various other protic acids (MsOH, hydrochloric acid (35%), dilute sulfuric acid (50%)) could be used as a proton source in this demethylation reaction. Under the same conditions, cleavage of alkyl alkyl ether 2-(3-methoxypropyl)naphthalene yielded mixture of corresponding 2-(3-bromopropyl)naphthalene and 2-(3-hydroxypropyl)naphthalene. Dealkylation of various aryl alkyl ethers could also be achieved using significantly reduced (i.e., stoichiometric) amounts of concentrated hydrobromic acid (47%) in the ionic liquid. Both procedures afforded the desired products in moderate to good yield; however, cleavage of aryl alkyl cyclic ether, 2,3-dihydrobenzofuran, resulted in low yield of the desired product o-2-bromoethylphenol. The convenience of this method for ether cleavage and its effectiveness using only a moderate excess of hydrobromic acid make it attractive as a green chemical method

Transparent Flexible Nanoline Field-Effect Transistor Array with High Integration in a Large Area

Transparent flexible transistor array requests large-area fabrication, high integration, high manufacturing throughput, inexpensive process, uniformity in transistor performance, and reproducibility. This study suggests a facile and reliable approach to meet the requirements. We use the Al-coated polymer nanofiber patterns obtained by electrohydrodynamic (EHD) printing as a photomask. We use the lithography and deposition to produce highly aligned nanolines (NLs) of metals, insulators, and semiconductors on large substrates. With these NLs, we demonstrate a highly integrated NL field-effect transistor (NL-FET) array (105/(4 × 4 in2), 254 pixel-per-inch) made of pentacene and indium zinc oxide semiconductor NLs. In addition, we demonstrate a NL complementary inverter (NL-CI) circuit consisting of pentacene and fullerene NLs. The NL-FET array shows high transparency (∼90%), flexibility (stable at 2.5 mm bending radius), uniformity (∼90%), and high performances (mobility = 0.52 cm2/(V s), on–off ratio = 7.0 × 106). The NL-CI circuit also shows high transparency, flexibility, and typical switching characteristic with a gain of 21. The reliable large-scale fabrication of the various NLs proposed in this study is expected to be applied for manufacturing transparent flexible nanoelectronic devices

Precise Tuning of Multiple Perovskite Photoluminescence by Volume-Controlled Printing of Perovskite Precursor Solution on Cellulose Paper

Metal halide perovskite nanocrystals (PeNCs) with a controlled quantum size effect have received intense interest for potential applications in optoelectronics and photonics. Here, we present a simple and innovative strategy to precisely tune the photoluminescence color of PeNCs by simply printing perovskite precursor solutions on cellulose papers. Depending on the volume of the printed precursor solutions, the PeNCs are autonomously grown into three discrete sizes, and their relative size population is controlled; accordingly, not only the number of multiple PL peaks but also their relative intensities can be precisely tuned. This autonomous size control is obtained through the efflorescence, which is advection of salt ions toward the surface of a porous medium during solvent evaporation and also through the confined crystal growth in the hierarchical structure of cellulose fibers. The infiltrated PeNCs are environmentally stable against moisture (for 3 months in air at 70% relative humidity) and strong light exposure by hydrophobic surface treatment. This study also demonstrates invisible encryption and highly secured unclonable anticounterfeiting patterns on deformable cellulose substrates and banknotes

Graphite Fiber Electrode by Continuous Wet-Spinning

In this study, we propose a graphite fiber electrode with electrochemical stability and mechanical flexibility for a possible application as wearable batteries. Graphene oxide (GO)-supported graphite fiber electrodes with a uniform diameter of 50 μm and a length of over 50 m are fabricated by a continuous wet-spinning process. GO, which is a thin sheet with 30–50 μm diameter and exhibits a liquid crystal behavior in its dispersion, can enhance the fiber formability and alignment of the graphite during wet-spinning. Scanning electron microscopy visualizes that the graphite plates with approximately 3 μm diameter are firmly wrapped by the GO sheets. A chemical treatment using hydrazine vapor reduces GO in the fiber, which is confirmed by Raman spectroscopy, X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, and electrical conductivity measurement. As a result, we successfully fabricate the rGO/graphite fiber electrode with graphite content as high as 70%. A fiber cell is assembled using the rGO/graphite fiber electrode and lithium wire counter electrode. The fiber cell shows an initial capacity of 265 mA h g–1 and maintains excellent capacity retention during 100 cycles except for the capacity loss in the initial cycles

Transparent Flexible Nanoline Field-Effect Transistor Array with High Integration in a Large Area

Transparent flexible transistor array requests large-area fabrication, high integration, high manufacturing throughput, inexpensive process, uniformity in transistor performance, and reproducibility. This study suggests a facile and reliable approach to meet the requirements. We use the Al-coated polymer nanofiber patterns obtained by electrohydrodynamic (EHD) printing as a photomask. We use the lithography and deposition to produce highly aligned nanolines (NLs) of metals, insulators, and semiconductors on large substrates. With these NLs, we demonstrate a highly integrated NL field-effect transistor (NL-FET) array (105/(4 × 4 in2), 254 pixel-per-inch) made of pentacene and indium zinc oxide semiconductor NLs. In addition, we demonstrate a NL complementary inverter (NL-CI) circuit consisting of pentacene and fullerene NLs. The NL-FET array shows high transparency (∼90%), flexibility (stable at 2.5 mm bending radius), uniformity (∼90%), and high performances (mobility = 0.52 cm2/(V s), on–off ratio = 7.0 × 106). The NL-CI circuit also shows high transparency, flexibility, and typical switching characteristic with a gain of 21. The reliable large-scale fabrication of the various NLs proposed in this study is expected to be applied for manufacturing transparent flexible nanoelectronic devices

Preparation of 7-Alkylamino-2-methylquinoline-5,8-diones^†

Several novel 7-alkylamino-2-methylquinoline-5,8-diones (2) were synthesized from 2,5-dimethoxyaniline in five steps via the Skraup reaction followed by demethylations, oxidative bromination, amination, and debromination. We have achieved an unusual hydrobromic acid catalyzed debromination reactions of several 6-bromo-7-alkylamino-2-methylquinoline-5,8-diones, giving 7-alkylamino-2-methylquinoline-5,8-diones in good yields

Preparation of 7-Alkylamino-2-methylquinoline-5,8-diones^†

Several novel 7-alkylamino-2-methylquinoline-5,8-diones (2) were synthesized from 2,5-dimethoxyaniline in five steps via the Skraup reaction followed by demethylations, oxidative bromination, amination, and debromination. We have achieved an unusual hydrobromic acid catalyzed debromination reactions of several 6-bromo-7-alkylamino-2-methylquinoline-5,8-diones, giving 7-alkylamino-2-methylquinoline-5,8-diones in good yields

Realization of High Loading Density Lithium Polymer Batteries by Optimizing Lithium-Ion Transport and Electronic Conductivity

Lithium polymer batteries (LPBs) with a high energy density and safety are being actively studied for their use as an energy storage system. However, bottlenecks to their development include charge-transport resistance and poor interfacial contact. In this paper, we introduce carbon nanofiber (CNF) as a conductive additive and the optimization of porosity in the electrode by calendering to realize a high loading density LPB. A simple dispersion strategy is applied to homogeneously disperse nanofiber additives in the electrode to achieve high electronic conductivity. Calendering with optimized pressing degree was performed on the CNF-based electrode to enhance lithium-ion transport and electron conduction in the LPB. The optimal pressing conditions were confirmed by measuring the electronic conductivity, internal resistance, lithium-ion diffusion coefficient, and charge transport characteristics of the cells. When the electrode was pressed by 35%, optimum electrode wettability by solid polymer electrolyte and contact between particles and current collector were achieved, resulting in the high performance of the LPB. Finally, at the optimized pressing degree, we successfully demonstrate 90% cycle retention during 100 cycles and an improvement of the volumetric energy density by over seven-fold