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Research describes a versatile pyridinium salt photoelectrocyclization/aziridine ring cleavage sequence methodology for the synthesis of mannostatin analogues, (+)-4-epimannostatin and (+)-mannostatin A regioisomers.

The photochemistry of selected N-silylalkyl-substituted phthalimides and maleimides is examined to analyze the generality and preparative consequences of a solvent effect on excited-state reaction chemoselectivities and quantum efficiencies. This solvent effect is observed in the photochemistry of N-((trimethylsilyl)butyl)phthalimide 10 and in the photochemistry of the N-silylpropyl-maleimide. The results show the generality of the solvent effect and how it can be applied to improve the preparative utility of the photochemistry of N-(silylalkyl)phthalimides and N-(silylalkyl)maleimides.

The C to O silyl migration occurs in the photochemical reactions of N-trimethylsilylmethyl imides which form azomethine ylide and this pathway is essential for cyclic and acyclic, conjugated silylmethyl imides. The photolysis of N-(trimethylsilyl)methyl maleimide generates the tricyclic product. Azomethine ylide intermediates are formed in the reaction of N-trimethylsilylmethyl aroyl imides where the excited state C to O silyl migration occurs.

The hierarchical porous structure has garnered considerable attention as a multiscale engineering strategy to bring unforeseen synergistic effects in a vast variety of functional materials. Here, we demonstrate a "microporous covalent organic framework (COF) net on mesoporous carbon nanotube (CNT) net" hybrid architecture as a new class of molecularly designed, hierarchical porous chemical trap for lithium polysulfides (Li2Sx) in Li-S batteries. As a proof of concept for the hybrid architecture, self-standing COF-net on CNT-net interlayers (called "NN interlayers") are fabricated through CNT-templated in situ COF synthesis and then inserted between sulfur cathodes and separators. Two COFs with different micropore sizes (COF-1 (0.7 nm) and COF-5 (2.7 nm)) are chosen as model systems. The effects of the pore size and (boron-mediated) chemical affinity of microporous COF nets on Li2Sx adsorption phenomena are theoretically investigated through density functional theory calculations. Benefiting from the chemical/structural uniqueness, the NN interlayers effectively capture Li2Sx without impairing their ion/electron conduction. Notably, the COF-1 NN interlayer, driven by the well-designed microporous structure, allows for the selective deposition/dissolution (i.e., facile solid-liquid conversion) of electrically inert Li2S. As a consequence, the COF-1 NN interlayer provides a significant improvement in the electrochemical performance of Li-S cells (capacity retention after 300 cycles (at charge/discharge rate = 2.0 C/2.0 C) = 84% versus 15% for a control cell with no interlayer) that lies far beyond those accessible with conventional Li-S technologies.

Forthcoming flexible/wearable electronic devices with shape diversity and mobile usability garner a great deal of attention as an innovative technology to bring unprecedented changes in our daily lives. From the power source point of view, conventional rechargeable batteries (one representative example is a lithium-ion battery) with fixed shapes and sizes have intrinsic limitations in fulfilling design/performance requirements for the flexible/wearable electronics. Here, as a facile and efficient strategy to address this formidable challenge, we demonstrate a new class of printable solid-state batteries (referred to as "PRISS batteries"). Through simple stencil printing process (followed by ultraviolet (UV) cross-linking), solid-state composite electrolyte (SCE) layer and SCE matrix-embedded electrodes are consecutively printed on arbitrary objects of complex geometries, eventually leading to fully integrated, multilayer-structured PRISS batteries with various form factors far beyond those achievable by conventional battery technologies. Tuning rheological properties of SCE paste and electrode slurry toward thixotropic fluid characteristics, along with well-tailored core elements including UV-cured triacrylate polymer and high boiling point electrolyte, is a key-enabling technology for the realization of PRISS batteries. This process/material uniqueness allows us to remove extra processing steps (related to solvent drying and liquid-electrolyte injection) and also conventional microporous separator membranes, thereupon enabling the seamless integration of shape-conformable PRISS batteries (including letters-shaped ones) into complex-shaped objects. Electrochemical behavior of PRISS batteries is elucidated via an in-depth analysis of cell impedance, which provides a theoretical basis to enable sustainable improvement of cell performance. We envision that PRISS batteries hold great promise as a reliable and scalable platform technology to open a new concept of cell architecture and fabrication route toward flexible power sources with exceptional shape conformability and aesthetic versatility.

Bulk-type all-solid-state lithium batteries (ASLBs) are considered a promising candidate to outperform the conventional lithium-ion batteries. Unfortunately, the current technology level of ASLBs is in a stage of infancy in terms of cell-based (not electrode-material-based) energy densities and scalable fabrication. Here, we report on the first ever bendable and thin sulfide solid electrolyte films reinforced with a mechanically compliant poly(paraphenylene terephthalamide) nonwoven (NW) scaffold, which enables the fabrication of free-standing and stackable ASLBs with high energy density and high rate capabilities. The ASLB, using a thin (∼70 μm) NW-reinforced SE film, exhibits a 3-fold increase of the cell-energy-density compared to that of a conventional cell without the NW scaffold.

The rapidly approaching smart/wearable energy era necessitates advanced rechargeable power sources with reliable electrochemical properties and versatile form factors. Here, as a unique and promising energy storage system to address this issue, we demonstrate a new class of heterolayered, one-dimensional (1D) nanobuilding block mat (h-nanomat) battery based on unitized separator/electrode assembly (SEA) architecture. The unitized SEAs consist of wood cellulose nanofibril (CNF) separator membranes and metallic current collector-/polymeric binder-free electrodes comprising solely single-walled carbon nanotube (SWNT)-netted electrode active materials (LiFePO4 (cathode) and Li4Ti5O12 (anode) powders are chosen as model systems to explore the proof of concept for h-nanomat batteries). The nanoporous CNF separator plays a critical role in securing the tightly interlocked electrode-separator interface. The SWNTs in the SEAs exhibit multifunctional roles as electron conductive additives, binders, current collectors and also non-Faradaic active materials. This structural/physicochemical uniqueness of the SEAs allows significant improvements in the mass loading of electrode active materials, electron transport pathways, electrolyte accessibility and misalignment-proof of separator/electrode interface. As a result, the h-nanomat batteries, which are easily fabricated by stacking anode SEA and cathode SEA, provide unprecedented advances in the electrochemical performance, shape flexibility and safety tolerance far beyond those achievable with conventional battery technologies. We anticipate that the h-nanomat batteries will open 1D nanobuilding block-driven new architectural design/opportunity for development of next-generation energy storage systems.

Several studies suggested that the cytotoxic effects of quantum dots (QDs) may be mediated by cadmium ions (Cd2+) released from the QDs cores. The objective of this work was to assess the intracellular Cd2+ concentration in human breast cancer MCF-7 cells treated with cadmium telluride (CdTe) and core/shell cadmium selenide/zinc sulfide (CdSe/ZnS) nanoparticles capped with mercaptopropionic acid (MPA), cysteamine (Cys), or N-acetylcysteine (NAC) conjugated to cysteamine. The Cd2+ concentration determined by a Cd2+-specific cellular assay was below the assay detection limit (<5 nM) in cells treated with CdSe/ZnS QDs, while in cells incubated with CdTe QDs, it ranged from approximately 30 to 150 nM, depending on the capping molecule. A cell viability assay revealed that CdSe/ZnS QDs were nontoxic, whereas the CdTe QDs were cytotoxic. However, for the various CdTe QD samples, there was no dose-dependent correlation between cell viability and intracellular [Cd2+], implying that their cytotoxicity cannot be attributed solely to the toxic effect of free Cd2+. Confocal laser scanning microscopy of CdTe QDs-treated cells imaged with organelle-specific dyes revealed significant lysosomal damage attributable to the presence of Cd2+ and of reactive oxygen species (ROS), which can be formed via Cd2+-specific cellular pathways and/or via CdTe-triggered photoxidative processes involving singlet oxygen or electron transfer from excited QDs to oxygen. In summary, CdTe QDs induce cell death via mechanisms involving both Cd2+ and ROS accompanied by lysosomal enlargement and intracellular redistribution.