Activity

the signature enaminone system being assembled through a rhodium-catalyzed Pauson-Khand reaction. Sequential, site-selective redox manipulations were developed to arrive at strepatzone A and additional members of the natural product family. Finally, I discuss our work to prepare analogs of complex polyether ionophores featuring functionalized tetronic acids as cation-binding groups. find more A method for the construction of a suitably protected chloromethylidene-modified tetronate is presented which enabled its installation in the full structure through a C-acylation reaction. This work exemplifies how components of abundant polyether ionophores can be recycled and used to access new structures which may possess enhanced biological activities.Tailored optimization of perovskite solar cells (PSCs) is a persistent objective to achieve the ultimate commercialization purpose, in which the electron/hole transport layer with thickness on the nanometer scale is generally required to maximize the charge collection and minimize the series resistance. Therefore, precise control on the fabrication technology of the charge transport layer is important. Herein, one-dimensional (1D) rutile TiO2 nanorod arrays with a thickness of 1.8 μm have been fabricated and employed as a potential electron extraction layer for high-efficiency all-inorganic CsPbBr3 PSCs for the first time. Arising from the sufficient carrier mobility, excellent conductivity, and superior charge extraction ability by means of regulating the donor concentration with nitrogen atoms, a champion efficiency of 8.50% has been achieved with excellent long-term stability after 50 days storage in air conditions, which is comparable to that of the 200 nm-thick TiO2 layer tailored device. The primary results demonstrate that the TiO2 layer with micrometer scale thickness is also feasible to effectively collect the photogenerated carriers and realize considerable solar-to-electric conversion ability, providing multifarious technologies to fabricate the electron extraction layer.Chiral amplification in liquid crystals (LCs) is a well-known strategy. However, current knowledge about the underlying mechanism was still lacking; in particular, how it was realized at the nano scale still remained to be revealed. Here, we provide systematical exploration of chiral amplification of chiral aggregation induced emission (AIE) molecules in LCs from direct visualization of their co-assemblies at the nano scale to theoretical calculation of the molecular packing modes on a single molecular level. Using AFM imaging,we directly visualized the co-assembly formed by chiral AIE molecules/LCs at the nano scale the chiral AIE molecules self-assembled into helical fibers to serve as the helical template for LCs to bind, while the LCs helically bound to the helical fibers to form the co-assembly, giving the morphology of pearled necklaces or thick rods. Theoretical calculation suggested that chiral AIE molecules were packed into left-handed helical fibers with a large volume of empty space between neighboring molecules, which provided the binding cites for LCs. Structural analysis showed that the π-π stacking between aromatic groups from LCs and TPE groups and the σ-π hyperconjugation between LC aromatic groups and cholesterol aliphatic groups play an important role in stabilizing the binding of LCs in the confined space on the surface of the helical assemblies.ConspectusSemiconductor nanocrystals (NCs) fluoresce with a color that strongly depends on their size and shape. Thus, to obtain homogeneous optical properties, researchers have strived to synthesize particles that are uniform. However, because NCs typically grow through continuous, incremental addition of material, slight differences in the growth process between individual crystallites yield statistical distributions in size and shape, leading to inhomogeneities in their optical characteristics. Much work has focused on improving synthetic protocols to control these distributions and enhance performance. Interestingly, during these efforts, several syntheses were discovered that exhibit a different type of growth process. The NCs jump from one discrete size to the next. Through purification methods, one of these sizes can then be isolated, providing a different approach to uniform NCs. Unfortunately, the fundamental mechanism behind such discrete growth and how it differs from the conventional continuous prowth. By understanding the underlying process, we believe that it can be exploited more broadly, potentially moving us toward more uniform nanomaterials.Lithium transition-metal oxides (LiMn2O4 and LiMO2 where M = Ni, Mn, Co, etc.) are widely applied as cathode materials in lithium-ion batteries due to their considerable capacity and energy density. However, multiple processes occurring at the cathode/electrolyte interface lead to overall performance degradation. One key failure mechanism is the dissolution of transition metals from the cathode. This work presents results combining scanning electrochemical microscopy with inductively coupled plasma (ICP) and electron paramagnetic resonance (EPR) spectroscopies to examine cathode degradation products. Our effort employs a LiMn2O4 (LMO) thin film as a model cathode to monitor the Mn dissolution process without the potential complications of conductive additive and polymer binders. We characterize the electrochemical behavior of LMO degradation products in various electrolytes, paired with ICP and EPR, to better understand the properties of Mn complexes formed following metal dissolution. We find that the identity of the lithium salt anions in our electrolyte systems [ClO4-, PF6-, and (CF3SO2)2N-] appears to affect the Mn dissolution process significantly as well as the electrochemical behavior of the generated Mn complexes. This implies that the mechanism for Mn dissolution is at least partially dependent on the lithium salt anion.Topological quad-domain textures with interesting cross-shaped buffer domains (walls) have been recently observed in BiFeO3 (BFO) nanoislands, indicating a new platform for exploring topological defects and multilevel memories. Such domain textures have nevertheless only been limited in BFO nanoislands grown on LaAlO3 substrates with a large lattice mismatch of ∼-4.4%. Here, we report that such exotic domain textures could also form in BFO nanoislands directly grown on a conductive substrate with a much smaller lattice mismatch and the local transport characteristics of the BFO nanoislands are distinct from the previously reported ones. The angle-resolved piezoresponse force images verify that the domain textures consist of center-divergent quad-domains with upward polarizations and cross-shaped buffer domains with downward polarizations. Interestingly, textures with multiple crosses are also observed in nanoislands of larger sizes, besides the previously reported ones with a single cross. The nanoislands exhibit strong diodelike rectifying characteristics and the quad-domains show a higher average conductance than the cross-shaped buffer domains, indicating that there is a certain correlation between the local conductance of the nanoislands and the domain textures.