Tuning Molecular Solar Thermal properties by modification of a promising norbornadiene photoswitch

摘要： Carefully targeted modifications to the norbornadiene-quadricyclane couple should give molecules with great potential for solar energy storage. Here we report the synthesis of derivatives of a well-studied compound, 2-cyano-3-anisyl norbornadiene (NBD5). The conjugation was extended by conversion of the nitrile into acrylonitrile and acrylate derivatives over two steps. Despite red-shifting the absorbance properties, the metastable quadricyclanes exhibited extremely short lifetimes. Meanwhile, treatment of NBD5 with acetyl halides in the presence of aluminum trihalides led to the formation of 7-acetyl norbornenes through a Meerwein-Wagner rearrangement. Subsequent transformations made it possible to synthesise norbornadienes with varying degrees of steric bulk at the 7-position of the molecular scaffold. It was found that the bulkier this group was, the more stable the quadricyclane form. This reaction sequence allows for the synthesis of norbornadiene derivatives which are more suited to molecular solar thermal applications in domestic heating despite providing a slightly lower energy density.

Femtosecond Optical Annealing Induced Polymer Melting and Formation of Solid Droplets

摘要： Interaction between femtosecond laser pulses with polymeric thin films induced transient optical annealing of the polymer molecules. Melting of the polymer films took place during the transient annealing process, so that a solid-liquid-solid phase transition process was observed. Ultrafast cooling of the melting polymer produced solidified droplets. Microscopic and spectroscopic characterization revealed that the polymer molecules were rearranged with preferable H-aggregation to reach the lowest formation energy during the melting process. Intermolecular coupling was enhanced due to the modified molecular arrangement. This observation of melting of polymeric semiconductors due to the interaction with femtosecond light pulses is potentially important for better understanding laser-matter interactions and for exploring organic optoelectronic devices through special material processing.

Electronic properties of graphene with point defects

摘要： This article attempts a point-by-point review of the electron spectrum of graphene containing defects (adsorbed atoms, substitutional atoms, vacancies) that can be adequately described within the Lifshitz model. In this regard, the known Hamiltonian for this model is calculated for the case of two-dimensional relativistic electrons, and the criteria for occurrence of an impurity resonance near a Dirac point are given. The theory of concentration band structure transformation of graphene is presented, from which it follows that a transport gap is opened upon reaching a strictly defined value of impurity concentration in the neighborhood of the energy of impurity resonance. At the same time, the question of the possibility (or impossibility) of localization in such a {spatially disordered system} of Dirac quasiparticles is analyzed. Based on this, it is possible to provide an explanation and present a description of a phenomenon recently observed in {impure graphene}, the metal-dielectric transition that appears as a direct consequence of the decrease of the Fermi energy of the system in the region of a transport gap. The concept of local spectrum rearrangement of graphene, which also occurs during the process of increased concentration of defects in it, is introduced and substantiated. Physical reasons are formulated, by which the position of the minimum of the low-temperature conductivity of graphene as a function of the Fermi energy of electrons corresponds to the impurity resonance energy rather than to the Dirac point, as has been validated in a number of theoretical and test studies. Here, it appears that the minimum value is not a universal magnitude, but depends on the concentration of defects. Analytical examination of impurity effects is accompanied by numerical modeling of the system under study, as a result of which complete correspondence has been established between these two approaches. In particular, the overall picture of spectrum rearrangement, localization of electron states, and also the effects having local nature are confirmed.

Atomic Scale Imaging of Reversible Ring Cyclization in Graphene Nanoconstrictions

摘要： We present an atomic level study of reversible cyclization processes in suspended nanoconstricted regions of graphene that form linear carbon chains (LCCs). Before the nanoconstricted region reaches a single linear carbon chain (SLCC), we observe that a double linear carbon chain (DLCC) structure often reverts back to a ribbon of sp2 hybridized oligoacene rings, in a process akin to the Bergman rearrangement. When the length of the DLCC system only consists of ～5 atoms in each LCC, full recyclization occurs for all atoms present, but for longer DLCCs we find that only single sections of the chain are modified in their bonding hybridization and no full ring closure occurs along the entire DLCCs. This process is observed in real time using aberration-corrected transmission electron microscopy and simulated using density functional theory and tight binding molecular dynamics calculations. These results show that DLCCs are highly sensitive to the adsorption of local gas molecules or surface diffusion impurities and undergo structural modifications.

[IEEE 2019 28th Wireless and Optical Communications Conference (WOCC) - Beijing, China (2019.5.9-2019.5.10)] 2019 28th Wireless and Optical Communications Conference (WOCC) - Crosstalk Prediction of Cables Based on Cosserat Elastic Rod Theory

摘要： A rhodium(III)-catalyzed domino annulation of simple olefins with diazo oxindoles to give spirooxindole pyrrolone products is described. This reaction can be formally viewed as the result of an anomalous tandem C(cid:2)H activation, carbene insertion, Lossen rearrangement, and a nucleophilic addition process. The potential utility of this reaction was further demonstrated by the late-stage diversification of drug molecules.

Polyoxometalates/TiO2 Fenton-like photocatalysts with rearranged oxygen vacancies for enhanced synergetic degradation

摘要： Oxygen vacancy modulation has emerged as a prevalent strategy to improve the performance of heterogeneous catalysts. By far, the impact of oxygen vacancy rearrangement on the efficiency of Fenton-like reaction remains largely unknown. In this paper, Fe-containing polyoxometalates were coupled with defect-rearranged TiO2 to construct defective Fenton-like photocatalysts. Experimental characterizations revealed that defect rearrangement facilitated the interfacial transfer of electrons from TiO2 to polyoxometalate molecules. Fenton-like photocatalysts with rearranged defects exhibited 5 and 3.5 times higher activity for the synergetic degradation of toxic dye and 5-Sulfosalicylic acid than pristine TiO2. This enhancement was ascribed to the beneficial role of oxygen vacancy modulation for activating oxygen and H2O2 molecules into ?O2- and ?OH radicals. Our work provides new opportunities for exploring efficient Fenton-like photocatalysts for environmental remediation.

Optically Switchable Helicenes for an Enantiodivergent Steglich Rearrangement

Influence of Iodine Doping on the Structure, Morphology and Physical Properties of Manganese Phthalocyanine Thin Films

摘要： Doping with halide ions is a popular method to alter the properties of metal phthalocyanines (MPcs), particularly magnetic and electrical nature of organic semiconductors for applications in spintronic or electronic devices. Doping can cause a structural rearrangement in MPc packing and the physical properties may be correlated with molecular packing. Films of a planar and magnetic MPc, manganese(II)phthalocyanine (MnPc) is chosen for iodine doping study. The optical, magnetic and the electrical properties of pristine and iodine doped MnPc thin films are investigated and can be directly associated with their molecular structure. 2D grazing incidence Synchrotron X-ray diffraction reveals structural disorder in MnPc films upon iodine infusion induced by the reorientation of ordered, edge-on molecular configuration to tilted and face-on configurations in a random fashion. The film morphology changes accordingly, where in the uniform crystallites reorganize in a disordered manner. The ferromagnetic nature of the pristine film gets weakened due to iodine species and favors antiferromagnetic coupling. The study of electrical properties at room temperature by conducting atomic force microscopy reveals that the conductance is enhanced independently of the film thickness due to disorder induced by iodine inclusion.

A Reconfiguration Method for Extracting Maximum Power from Non-Uniform Aging Solar Panels

摘要： Aging affects different photovoltaic (PV) modules in a PV array in a non-uniform way, thereby leading to non-uniform working conditions of the PV modules and resulting in variations in the power outputs of the PV array. In this paper, an algorithm is developed for optimising the electrical con?guration of a PV array during the non-uniform aging processes amongst the PV modules. A new PV array recon?guration method is proposed to maximize the power generation from non-uniformly aged PV arrays through rearrangements of the positions of the PV modules without having to replace the aged PV modules with new ones, thereby saving on maintenance costs. This recon?guration strategy requires information about the electrical parameters of the PV modules in an array, so as to choose the optimal recon?guration topology. In this algorithm, the PV modules are sorted iteratively in a hierarchy pattern to reduce the effect of mismatch due to the non-uniform aging processes amongst PV modules. Computer simulation and analysis have been carried out to evaluate the effectiveness of the proposed method for different sizes of non-uniform aged PV arrays (4 × 4, 10 × 10, and 100 × 10 arrays) with MATLAB. The results show an improvement in the power generation from a non-uniformly aged PV array and can be applied to any size of PV array.

A spontaneously resolving breast lesion: imaging and cytological findings of nodular fasciitis of the breast with FISH showing USP6 gene rearrangement

摘要： We report a case of nodular fasciitis of the breast in a 48-year-old woman who presented with a tender rapidly growing right breast lump. Ultrasound guided fine needle aspiration (FNA) of the solid mass was performed. Cytology was reported as atypical spindle cell neoplasm and the patient was referred to a breast surgeon at a tertiary institution for a definitive diagnosis and further management. Follow-up ultrasound showed partial regression and MRI, mammogram after 2–3 weeks confirmed spontaneous and total resolution of the lesion. Nodular fasciitis of the breast is rarely diagnosed on cytology alone and a histological diagnosis is usually required for a definitive diagnosis. However, in this case, the lesion spontaneously resolved prior to core biopsy or diagnostic open biopsy. The cytological features in conjunction with immunohistochemistry and the clinical history strongly suggest nodular fasciitis, which is further supported by a USP6 FISH positive result.