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{Zn <sub/>6</sub> } Cluster Based Metal–Organic Framework with Enhanced Room-Temperature Phosphorescence and Optoelectronic Performances
摘要： Molecule-based solid-state materials with long lifetimes could enable longer migration distances for excitons, which are beneficial for vast applications in optoelectronic field. Herein, we report a hexanuclear zinc cluster based MOF exhibits highly enhanced phosphorescence about 2 orders of magnitude in comparison with the pristine phosphor ligand. The combination of both experimental and computational results suggest that the {Zn6} cluster is very important for adjusting molecular conformations, packing arrangement, and photophysical properties of the organic phosphor ligands within the MOF matrix. Optoelectronic measurements reveal that the MOF-modified electrode is catalytically active to hydrogen evolution under light irradiation in neutral solution. Thus, our study provide an effective way to achieve low-cost metal-based phosphorescence MOF, expanding its further optoelectronic applications.
关键词： optoelectronic performances,metal?organic framework,hexanuclear zinc cluster,room-temperature phosphorescence
更新于2025-11-14 15:23:50
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Cross striation in human permanent and deciduous enamel measured with confocal Raman microscopy
摘要： Dental enamel is the most mineralized tissue in the human body and has a very complex organization. The aim of the present study was to evaluate chemical composition and orientation of crystals in human enamel cross striation using confocal Raman microscope. Slices of teeth were prepared and scanned using a confocal Raman microscope. Cross striation spacing was calculated according to the variation of PO4 3? peak intensity. The measurements showed a characteristic length between two cross striations of 2.70 (SD 0.43) μm for permanent teeth and 1.75 (SD 0.37) for deciduous teeth. Ratios between OH and PO4 3? peaks, for 0 and 90 degrees angulation, are, respectively, 9.18 (SD 0.80) and 44.74 (SD 3.12) for decidual teeth, and 11.72 (SD 1.46) and 22.12 (SD 3.15) for adult teeth. This confirmed that the hydroxyapatite crystal is well oriented along the enamel prism, as reported in the literature, but with a significant increase in deciduous teeth. K‐mean cluster binary images were calculated to compare the ratio of the centroid peaks of the cross striation zone and inter cross striation material. The regions corresponding to inner prism, included cross striations, are more mineralized than the outer part of enamel prism. In the prism, the Pearson correlation test was performed based on the intensity of hydroxyapatite characteristic peaks (ν1 PO4 3?, ν1 CO3 2?, and OH). The variations were well correlated: These results indicated that cross striations corresponded to the variation of hydroxyapatite concentration and not to a variation of crystals orientation.
关键词： Raman microscopy,cross striation,enamel prism,K‐mean cluster analysis,decidual teeth
更新于2025-09-23 15:23:52
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Atomically precise expansion of unsaturated silicon clusters
摘要： Small- to medium-sized clusters occur in various areas of chemistry, e.g. as active species of heterogeneous catalysis or transient intermediates during chemical vapor deposition. The manipulation of stable representatives is mostly limited to the ligand periphery, virtually excluding the systematic variation of the property-determining cluster scaffold. We now report the deliberate expansion of a stable unsaturated silicon cluster from six to seven and finally eight vertices. The consecutive application of lithium/naphthalene as reducing agent and decamethylsilicocene as electrophilic source of silicon results in the expansion of the core by precisely one atom with the potential of infinite repetition.
关键词： silicon,cluster compounds,main group elements,subvalent compounds,anions
更新于2025-09-23 15:23:52
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On-line measurement of fluorescent aerosols near an industrial zone in the Yangtze River Delta region using a wideband integrated bioaerosol spectrometer
摘要： In this work, we present on-line fluorescent aerosol measurements by the wideband integrated bioaerosol spectrometer (WIBS-4A) near an industrial zone in Nanjing, a megacity in the Yangtze-River-Delta (YRD) region. The fieldwork was conducted from April 1 to May 8, 2014. A TSI. 3321 aerosol-particle-sizer (APS) was simultaneously deployed to measure the total number size distribution of aerosol with diameter from 0.8–20 μm. Both WIBS-4A and APS reported similar number concentration and temporal profiles (R2 = 0.72). However, the daily average number of potential bioaerosols was only 0.5 ± 0.2% of the total particles detected by the WIBS-4A and displayed a completely different diurnal profile from that of APS. In addition, WIBS-4A can only provide integrated fluorescent signals, which strongly limited the potential to specifically identify the bioaerosols. Accordingly, hierarchical-agglomerative-cluster-analysis (HACA) was utilized to identify and speciate the potential bioaerosols from the WIBS-4A dataset. By maximizing the total distances among all potential cluster centers, a 12-cluster solution was accepted as the optimum result. These clusters were further identified according to their fluorescent signatures, size, and morphology, i.e., non-bioaerosols, bacteria, and fungal spores and/or pollen fragments. Bacteria were the dominant bioaerosol species detected in this work. The diurnal profiles of bioaerosols correlated very well with relatively humidity (RH), reaching daily maxima around 3 AM~6 AM, indicating the presence of humidity controlled bioaerosol emission mechanism, i.e., bacteria may flourish under moderate ambient temperature, RH, and the absence of UV radiation. The size- and AF-distributions of bioaerosols indicated that bioaerosols normally varied substantially in size and assumed a rather irregular shape. Although the number concentration of bioaerosols was relatively small, most bioaerosols can efficiently serve as ice nuclei by providing rough and irregular surfaces, verified by the observation results. Therefore, WIBS-4A measurements can still be informative for investigations of bioaerosols in the atmosphere, especially when HACA method was incorporated into the data processing.
关键词： Hierarchical agglomerative cluster analysis,WIBS-4A,Ice nuclei,Cloud condensation nuclei,Primary biological aerosol
更新于2025-09-23 15:23:52
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Automatic mapping of cracking patterns on concrete surfaces with biological stains using hyper-spectral images processing
摘要： Despite all technological advances, mapping cracks on concrete structures mostly remains to be evaluated through sketches based on on-site observation and photographs. Methods based on image processing have been developed with clear advantages. However, most studies rely on perfectly identified areas or on single cracks without any other pathologies, being therefore unsuitable for on-site application. In addition, the accuracy is not usually quantified due to the absence of ground-truth. Thus, methods for automatic mapping of cracking patterns, sufficiently robust to deal with the surrounding pathologies, are of great interest. The Super Cluster-Crack method (SC-Crack method) is herein presented. It was developed for crack detection in concrete surfaces, with biological stains, by processing hyperspectral images. SC-Crack performs k-means clustering, followed by grouping clusters to composing a super cluster that stands for the cracks. The method was calibrated and validated by classifying hyperspectral images of concrete specimens, within bandwidths of 25 nm in a wavelength range between 425 nm and 950 nm. Results are discussed by comparison with the ground-truth image. Finally, the super cluster composition is also validated. The SC-Crack method performs successfully both on clean and on surface with biological stains. In the latter case, hyperspectral images help to avoid mixing biological stains with crack pattern. Concerning the main goal of mapping the cracking pattern, the method performs perfectly on concrete clean surfaces, allowing to detect all the crack branches. In the case of surface with biological stains, the SC-Crack also detects the majority of cracking pattern, except for the thinner branches.
关键词： image processing,concrete surfaces,super cluster,cracking pattern,hyper-spectral image,automatic mapping
更新于2025-09-23 15:23:52
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Atomic Structures and Electronic Properties of Large-Sized GeN Clusters (N?=?45, 50, 55, 60, 65, 70) by First-Principles Global Search
摘要： A two-step unbiased global search was performed to explore the lowest-energy structures of large GeN clusters with N = 45–70 atoms. It has been revealed that the most stable structures for these large-sized Ge clusters are stuffed cages. Based on the lowest-energy structures, the theoretical results for the size-dependent structural transition, binding energy and ionization potential compare well with the available experimental data. Overall speaking, the structural characteristics and electronic properties of GeN clusters in the considered size range gradually approach the bulk limits, but still with certain deviations.
关键词： Global search,Germanium cluster,Structure
更新于2025-09-23 15:23:52
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[IEEE 2018 15th International Conference on Control, Automation, Robotics and Vision (ICARCV) - Singapore, Singapore (2018.11.18-2018.11.21)] 2018 15th International Conference on Control, Automation, Robotics and Vision (ICARCV) - Quadrotors' Low-cost Vision-based Autonomous Landing Architecture on a Moving Platform
摘要： In this paper, a low-cost vision-based autonomous landing architecture for an unmanned aerial vehicle (UAV) on a moving platform is presented. First, a novel landing pad was designed for a monocular camera to robustly detect the pad in both high and low altitudes. In order to solve mirror effect and occasional misidentification, a 3D points cluster algorithm for relative position estimation is presented. Second, the dynamics of the quadrotor is simplified for this landing task and a PD controller is designed based on the estimated relative position. Finally, the low-cost system architecture of the quadrotor and the experiment results are both presented to show the effectiveness of the proposed method.
关键词： landing pad design,PD controller,quadrotor,moving platform,low-cost,vision-based,3D points cluster algorithm,autonomous landing
更新于2025-09-23 15:23:52
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Optical spectroscopy of the Au4+ cluster: Resolved vibronic structure indicates an unexpected isomer**
摘要： The knowledge of the geometric and electronic structure of gold clusters and nanoparticles is vital for understanding their catalytic and photochemical properties at the molecular level. Herein, we report the vibronic optical photodissociation spectrum of cold and mass-selected Au4+ clusters measured at a resolution high enough to allow for comparison with Franck-Condon simulations of the excited state transitions based on time-dependent density functional theory calculations. The three vibrational frequencies identified for the lowest-lying optically accessible excited state at 2.17 eV stem from the Y-shaped isomer (C2v) and not from the rhombic isomer (D2h) that is considered to be the ground state structure of Au4+. This study demonstrates that an analysis of low-resolution electronic spectra by calculations of vertical transitions alone is not sufficient for a reliable isomer assignment of such metal clusters.
关键词： gold,UV/Vis spectroscopy,structure elucidation,cluster compounds,electronic structure
更新于2025-09-23 15:23:52
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Using first principles calculations to interpret XANES experiments: Extracting the Size-dependence of the (<i>p, T</i>) phase diagram of sub-nanometer Cu clusters in an O<sub>2</sub> environment
摘要： We have used ab initio density functional theory together with ab initio atomistic thermodynamics, and in situ X-ray absorption near edge spectroscopy (XANES) experiments, to study the oxidation of sub-nanometer clusters of CunOx supported on a hydroxylated amorphous alumina substrate in an O2-rich environment. We obtain (p, T) phase diagrams; these differ notably for the nanoclusters compared to the bulk. Both theory and experiment suggest that in the presence of oxygen, the cluster will oxidize from its elemental state to the oxidized state as temperature decreases. We obtain a clear trend for the transition Cun→ CunOn/2: we see that smaller the cluster, greater is the tendency toward oxidation. However, we do not see a monotonic size-dependent trend for the transition CunOn/2→ CunOn. We suggest that theoretically computed Bader charges constitute a simple yet quantitative way to align experimental measures of XANES edges with theoretical calculations, so as to yield oxidation states for nanoclusters. Our results have important implications for the use of small clusters in fields such as nanocatalysis and nanomedicine.
关键词： cluster,DFT,XANES,copper,oxidation
更新于2025-09-23 15:23:52
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Tuning the Spectrum Properties of Fullerene C60: Using a Strong External Electric Field
摘要： The electric ?eld can change the absorption of fullerene C60 to different wavelengths of light by affecting the vibrational modes and electronic transitions. The IR spectrum of fullerene C60 under the strong electric ?eld is studied on B3LYP/6-31G* basis set using density function theory. With the external electric ?eld decreasing, silent modes Hg(1), Ag(1), Gu(2), Hg(5), Ag(2), Hu(7) become active. Meanwhile, UV–Vis spectrum, the excitation energy, excitation wavelength and oscillator strength of ?rst fourteen excited states of fullerene C60 under the ?eld are also studied in B3LYP/6-31G* basis set using time-dependent density functional theory. With the electric ?eld increasing, the absorption peak of fullerene C60 occurs then shifts towards the long-wave region. The excitation energy decrease and the excitation wavelength increase correspondingly, and external electric ?eld makes fullerene C60 absorb energy from 1.01 to 2.31 eV in theory. The energy gap decreases drastically from 2.74 to 1.38 eV, which contributed to tune the energy gap of fullerene C60 by the effect of the electric ?eld in a wide range. It is possible to use electric ?eld to tune fullerene C60 into new energy storage material.
关键词： External electric ?eld,Excited state,Cluster,IR spectrum,Fullerene C60
更新于2025-09-23 15:23:52