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Two Novel Heteropolyniobates Using TeO <sub/>3</sub><sup>2–</sup> as Template and Linker
摘要： By adopting di?erent crystal growth methods, two novel organic?inorganic hybrids, [{Cu(phen)}6(H2O)(Te5Nb15.5Cu0.5O57)]3.5? and its dimer, have been successfully synthesized. These are fabricated by simple compound reactions and directed by the tellurite anions, which act as heteroanion templates and linkers, as well as a pendant ligand. The compounds were characterized by IR spectra, UV/vis, thermogravimetric analysis, and single crystal X-ray di?raction. Furthermore, the solution behavior was also investigated.
关键词： organic?inorganic hybrids,polyoxoniobate clusters,crystal growth methods,tellurite anions,heteropolyniobates
更新于2025-09-23 15:19:57
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Tuning photoionization mechanisms of molecular hybrid materials for EUV lithography applications
摘要： The investigation of the photoionization processes of a series of titanium oxo clusters evidenced that doping their organic shell with extended aromatic structures decreases their ionization energy and stabilises the resulting radical cations. Such tunability of their photochemistry arising from ligand exchange gives these hybrid compounds great potential as EUV photoresists.
关键词： photoionization,titanium oxo clusters,EUV lithography,ligand exchange,photoresists
更新于2025-09-23 15:19:57
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A thirty-fold photoluminescence enhancement induced by secondary ligands in monolayer protected silver clusters
摘要： In this paper, we demonstrate that systematic replacement of the secondary ligand PPh3 leads to an enhancement in the near-infrared (NIR) photoluminescence (PL) of [Ag29(BDT)12(PPh3)4]3?. While the replacement of PPh3 with other monophosphines enhances luminescence slightly, the replacement with diphosphines of increasing chain length leads to a drastic PL enhancement, as high as 30 times compared to the parent cluster, [Ag29(BDT)12(PPh3)4]3?. Computational modeling suggests that the emission is a ligand to metal charge transfer (LMCT) which is affected by the nature of the secondary ligand. Control experiments with systematic replacement of the secondary ligand confirm its influence on the emission. The excited state dynamics shows this emission to be phosphorescent in nature which arises from the triplet excited state. This enhanced luminescence has been used to develop a prototypical O2 sensor. Moreover, a similar enhancement was also found for [Ag51(BDT)19(PPh3)3]3?. The work presents an easy approach to the PL enhancement of Ag clusters for various applications.
关键词： photoluminescence enhancement,phosphorescence,secondary ligands,silver clusters,O2 sensor
更新于2025-09-19 17:15:36
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OmegaWINGS: OmegaCAM-VST observations of WINGS galaxy clusters
摘要： Context. Wide-field observations targeting galaxy clusters at low redshift are complementary to field surveys and provide the local benchmark for detailed studies of the most massive haloes in the local Universe. The Wide-field Nearby Galaxy-cluster Survey (WINGS) is a wide-field multi-wavelength survey of X-ray selected clusters at z = 0.04–0.07. The original 34' × 34' WINGS field of view has now been extended to cover a 1 deg2 field with both photometry and spectroscopy. Aims. We present the Johnson B- and V-band OmegaCAM at the VST observations of 46 WINGS clusters together with the data reduction, data quality, and Sextractor photometric catalogues. Methods. The data reduction was carried out with a modified version of the ESO-MVM (also known as ALAMBIC) reduction package, adding a cross-talk correction, the gain harmonisation, and a control procedure for problematic CCDs. The stray-light component was corrected for by employing our own observations of populated stellar fields. Results. With a median seeing of 1'' in both bands, our 25-min exposures in each band typically reach the 50% completeness level at V = 23.1 mag. The quality of the astrometric and photometric accuracy has been verified by comparison with the 2MASS and SDSS astrometry, and SDSS and previous WINGS imaging. Star-to-galaxy separation and sky-subtraction procedure were tested comparing them with previous WINGS data. Conclusions. The Sextractor photometric catalogues are publicly available at the CDS and will be included in the next release of the WINGS database on the Virtual Observatory together with the OmegaCAM reduced images. These data form the basis for a large ongoing spectroscopic campaign with AAOmega at the AAT and are being employed for a variety of studies.
关键词： galaxies: fundamental parameters,galaxies: clusters: general,galaxies: photometry,methods: observational,catalogs
更新于2025-09-19 17:15:36
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Symmetry and Topology Code of Cluster Crystal Structure Self-Assembly for Metal Oxides: Cs11O3-mP56, Rb(Cs11O3)-oP30, Cs(Cs11O3)-oP60, Rb3(Rb4)(Cs11O3)-oP84, (Cs4)(Cs6)(Cs11O3)-hP24, Rb9O2-mP22, (Rb3)(Rb9O2)-hP28, and (Rb2O)3(Rb13)-cF176
摘要： Geometric and topologic analysis was carried out for metal oxides Cs11O3-mP56, Rb(Cs11O3)-oP30, Cs(Cs11O3)-oP60, Rb3(Rb4)(Cs11O3)-oP84, (Cs4)(Cs6)(Cs11O3)-hP24, Rb9O2-mP22, (Rb3)(Rb9O2)-hP28, and (Rb2O)3(Rb13)-cF176, which are formed from oxygen-containing metal melts. Special algorithms of partitioning structural graphs into cluster structures (the TOPOS program package) were used to identify the precursor clusters of crystal structures. The precursor clusters participating in crystal structure self-assembly were identified to be three-octahedral Cs11O3, two-octahedral Rb9O2, octahedral Cs6, tetrahedral Cs4 and Rb4, and icosahedral Rb13. The symmetry and topology code of crystal structure self-assembly from precursor clusters was reconstituted as: primary chain → microlayer → microframework. The Cs11O3 and Rb9O2 crystal structures were found to be self-assembled from three-octahedral clusters Cs11O3 and two-octahedral clusters Rb9O2, respectively. The Rb(Cs11O3) and Cs(Cs11O3) framework structures are assembled from clusters Cs11O3 and accommodate Rb and Cs atoms in their voids. The Rb3(Rb4)(Cs11O3) framework structure is assembled from clusters Cs11O3 and Rb4 and accommodates Rb atoms in its voids. The (Cs6)(Cs4)(Cs11O3) framework structure is self-assembled from clusters Cs11O3, Cs6, and Cs4. The Rb3(Rb9O2)-hP28 framework structure is assembled from clusters Rb9O2 and atoms Rb; the (Rb2O)3(Rb13) framework structure is assembled from icosahedra Rb13 and clusters Rb2O.
关键词： octahedral,and icosahedral precursor clusters,crystal structure self-assembly,and Rb metal oxides,Cs,tetrahedral,Rb-,Cs-
更新于2025-09-19 17:15:36
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On a New Method to Estimate the Distance, Reddening, and Metallicity of RR Lyrae Stars Using Optical/Near-infrared ( <i>B, V, I, J, H, K</i> ) Mean Magnitudes: <i>ω</i> Centauri as a First Test Case
摘要： We developed a new approach to provide accurate estimates of the metal content, reddening, and true distance modulus of RR Lyrae stars (RRLs). The method is based on homogeneous optical (BVI) and near-infrared (JHK) mean magnitudes and on predicted period–luminosity–metallicity relations (IJHK) and absolute mean magnitude–metallicity relations (BV). We obtained solutions for three different RRL samples in ω Cen: first overtone (RRc, 90), fundamental (RRab, 80), and global (RRc+RRab) in which the period of first overtones were fundamentalized. The metallicity distribution shows a well defined peak at [Fe/H]～?1.98 and a standard deviation of σ = 0.54 dex. The spread is, as expected, metal-poor ([Fe/H] ≤ ?2.3) objects. The current metallicity distribution is ～0.3 dex more metal-poor than similar estimates for RRLs available in the literature. The difference vanishes if the true distance modulus we estimated is offset by ?0.06/?0.07 mag in true distance modulus. We also found a cluster true distance modulus of μ = 13.720 ± 0.002 ± 0.030 mag, where the former error is the error on the mean and the latter is the standard deviation. Moreover, we found a cluster reddening of E(B ? V) = 0.132 ± 0.002 ± 0.028 mag and spatial variations of the order of a few arcmin across the body of the cluster. Both the true distance modulus and the reddening are slightly larger than similar estimates available in the literature, but the difference is within 1σ. The metallicity dependence of distance diagnostics agrees with theory and observations, but firm constraints require accurate and homogeneous spectroscopic measurements.
关键词： stars: variables: RR Lyrae,stars: horizontal-branch,globular clusters: individual (Centauri),stars: distances
更新于2025-09-19 17:15:36
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Interaction between Bi Dopants and Intrinsic Defects in LiNbO <sub/>3</sub> from Local and Hybrid Density Functional Theory Calculations
摘要： The interactions between Bi dopants including Bi-substituting Li (BiLi) and Bi-substituting Nb (BiNb) and the intrinsic antisite defects (NbLi) and Li vacancies (VLi) in LiNbO3 are investigated using local and hybrid density functional theories. Three charge-compensated defect clusters, BiLi4+ + NbLi4+ + 8VLi-, BiLi4+ + 4VLi-, and BiLi0 + 4VLi- + BiNb4+, are modeled in this work to investigate the effects of the Bi concentration. The most stable cluster configurations, the Bi-doping stability in the clusters, and the electronic state interaction between Bi and intrinsic defects have been studied in detail. It is found that BiLi4+ has a stronger electron-capturing ability than NbLi4+ in Bi-doped congruent LiNbO3. The BiLi-doping-induced local lattice distortion and the electron-trapping behavior remain unchanged with increasing Bi-doping concentration. However, the position of the Bi defect states in the band gap is found to be shifted in congruent LiNbO3. This is mainly attributed to the large lattice relaxation induced by the large number of Li vacancies instead of the ionic level redistribution caused by the direct interaction between Bi and intrinsic defects.
关键词： LiNbO3,Bi dopants,lattice distortion,defect clusters,intrinsic defects,density functional theory,electron trapping
更新于2025-09-19 17:15:36
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Nanoplasma properties in metallic clusters driven by a Gaussian laser beam in the presence of helical magnetic undulator
摘要： The motivation of present paper is the investigation of effective permittivity and absorption cross section of cluster nanoplasmas in the interaction of a Gaussian laser beam with a cluster of metallic nanoparticles, in the presence of a helical magnetic undulator. The static magnetic field of the undulator couples with the field of the laser wave, and forms a nonlinear force in the interaction region. As a result, the nonlinear force varies the plasmonic oscillations of the electron of nanoplasmas that leads to electron density modulation, which modifies absorption cross section and effective permittivity of nanoparticles. Using a perturbative method, we analytically derived the nonlinear dispersion waves and dielectric constant of metallic nanoparticles lattice (gold, silver, and copper) in the presence of a helical magnetic undulator. Numerical results indicate that with increasing the undulator magnetic field strength, absorption cross section of cluster nanoplasmas increases and absorption phenomenon occurs at frequencies close to the effective plasma frequency. Besides, with decreasing distance of nanoparticles in the cluster (and with increasing the nanoparticles radius), absorption cross section increases. We also found that the dielectric constant of the cluster nanoplasma medium increases with enhancing undulator magnetic field strength only near the effective plasmonic frequency. This concept opens a path toward new properties of cluster nanoplasmas as quantum dots, diagnostics, and sensors based on magnetic undulator structures.
关键词： Gaussian laser beam,Effective permittivity,Metallic clusters,Nanoplasma,Absorption cross section,Helical magnetic undulator
更新于2025-09-19 17:13:59
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{Nanoa??gold, Iron (III)a??1,3,5a??benzene tricarboxylate Metal Organic Framework (MOF)} nanoa??composite as precursor for Laser Ablation Generation of golda??iron AumFen+/a?? (m = 1a??35, n=1a??5) clusters. Mass spectrometric study
摘要： Gold-iron bimetallic materials have applications in many fields, especially in nanotechnology and biomedicine. The chemistry of iron doped gold clusters is still not fully understood but opens up the possibility of developing new materials, e.g. of gold cages doped with iron atoms. There have been several theoretical studies on these clusters but only a few experimental studies. Laser desorption ionisation (LDI) was used for the generation of Au-Fe bimetallic clusters via laser ablation (337 nm nitrogen laser) of the synthesised nano-composite {nano-gold; Fe(III) 1,3,5-benzene tricarboxylate}, i.e. {AuNPs, Fe-MOF}, while a quadrupole ion trap time of flight mass spectrometer, equipped with a reflectron, was used to acquire mass spectra. A {AuNPs, Fe-MOF} nano-composite was prepared and found suitable for the LDI generation of AumFen clusters. In addition to Aum+/- (m = 1-35) clusters, a series of positively and negatively charged gold-iron AumFen+/- ones were generated. The mass spectra exhibited evidence for the clusters containing up to five iron atoms. In total, 113 binary AumFen+/- clusters (m = 1-35, n =1-5) were identified in the gas phase. A synthesised {AuNPs, Iron (III)-1,3,5-benzene tricarboxylate MOF} nano-composite was found suitable for the generation of many new gold-iron clusters and mass spectrometry was shown to be an efficient technique for the determination of the cluster stoichiometry. A broad series of over 100 bimetallic AumFen clusters, some of them suggested to be gold cages doped with iron atoms (for m = 12 and higher), not only demonstrate a rich and complex chemistry, but also open wide possibilities of biomedical applications.
关键词： nanoparticles,Mass spectrometry,MOF,Gold-iron,Laser desorption ionisation,Clusters,Nano-composite
更新于2025-09-19 17:13:59
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Rationally assembled nonanuclear lanthanide clusters: Dy <sub/>9</sub> displays slow relaxation of magnetization and Tb <sub/>9</sub> serves as luminescent sensor for Fe <sup>3+</sup> , CrO <sub/>4</sub><sup>2?</sup> and Cr <sub/>2</sub> O <sub/>7</sub><sup>2?</sup>
摘要： The utilization of a Schi? base ligand 2-((2-hydroxy-4-methoxy-benzylideneamino)methyl)phenol (H2L) a?orded five nonanuclear lanthanide(III) clusters of formula [Ln9L8(m3-OH)8(m5-O)2(DMF)8][H3O](cid:3)nH2O (Ln = Eu, n = 1 (1[H3O](cid:3)H2O); Ln = Gd, n = 4 (2[H3O](cid:3)4H2O); Ln = Tb, n = 3 (3[H3O](cid:3)3H2O); Ln = Dy, n = 6 (4[H3O](cid:3)6H2O); Ln = Ho, n = 2 (5[H3O](cid:3)2H2O)). Single-crystal X-ray di?raction analysis revealed that all of the complexes were isomorphous and had a diabolo-like topology. The intriguing Ln9 core was constructed by two square pyramidal units that shared a vertex metal centre. Variable-temperature dc magnetic susceptibility studies indicated weak antiferromagnetic interactions for 2[H3O](cid:3)4H2O, 3[H3O](cid:3)3H2O, 4[H3O](cid:3)6H2O and 5[H3O](cid:3)2H2O. The DyIII 9 cluster displayed a slow relaxation of magnetization. Fluorescence measurements revealed an intense green photoluminescence for the TbIII 9 compound. The luminescence tests showed that the TbIII 9 analogue could perform as a highly sensitive, selective and recyclable luminescence sensing material for Fe3+, CrO4 2(cid:2). In this work, the H2L ligand was derived by finely modifying the previously designed compounds (((2-hydroxy-3-methoxybenzyl)imino)- 2(cid:2) and Cr2O7 2(cid:2)? *a and methyl)-6-ethoxyphenol and (((2-hydroxy-3-methoxybenzyl)imino)methyl)-6-methoxyphenol, from which the Ln2 and Ln4 clusters were successfully prepared and reported. Noticeably, the decisive decrease in the steric hindrance of the predesigned ligands resulted in the expansion of the nuclearity. This work demonstrated the synthetic potential for assembling the large clusters by rationally decreasing the steric rsc.li/njc hindrance of the analogous ligands.
关键词： magnetization,Fe3+,CrO4 2(cid:2),luminescent sensor,Cr2O7 2(cid:2),lanthanide clusters
更新于2025-09-16 10:30:52