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Exploring the Relationship between Intermolecular Interactions and Solid-state Photophysical Properties of Organic Co-crystals
摘要： Five new binary co-crystals have been prepared through molecular self-assembly of π-electron-rich molecules like Phenanthrene (PHEN), Benzo[c]cinnoline (BCC) and Phenazine (PHNZ) in the presence of π-electron-deficient molecules like Tetrafluoro-1,4-benzoquinone (TFQ), Tetrachloro-1,4-benzoquinone (TCQ) and 1,2,4,5-Tetracyanobenzene (TCNB), taken in an equimolar ratio. Crystal structure analysis revealed that in three binary co-crystals the constituent molecules were alternately sandwiched in a cofacial arrangement through π···π interactions, while in the remaining two binary co-crystals the constituent molecules were aligned in a unique edge-to-face manner through lp···π interactions. Co-crystals with π-stacking arrangement were fluorescent, whereas almost complete quenching of luminescence was observed in those having edge-to-face alignment of molecules. The photophysical observations of these co-crystals have been demonstrated via energetic quantification of intermolecular interaction topology, which provides a molecular level understanding of factors controlling their solid-state absorption and luminescence behavior.
关键词： Magnetic,Organic Co-crystals,Plasmonics,Solid-state Photophysical Properties,Intermolecular Interactions,Optical,Hybrid Materials
更新于2025-09-23 15:19:57
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Shaping pulses of radiation detectors into a true Gaussian form
摘要： A digital shaper for conversion of detector pulses with a short leading edge and a long exponential tail into a true Gaussian form is proposed and analysed in this paper. The width of Gaussian pulses can be several times smaller than the rise time of the input pulses, i.e. considerably shorter than the undistorted output pulses provided by standard shapers. The algorithm of the true Gaussian shaper is presented in the paper. The output pulses and noises of the true Gaussian shapers are compared with those of standard shapers for different widths of shaped pulses. The analyses has shown that the true Gaussian shaping can be advantageous for detection of strongly overlapped pulses which appear at high particle fluxes in the detector input.
关键词： Digital signal processing (DSP),Electronic detector readout concepts (solid-state),Solid state detectors,Nuclear instruments and methods for hot plasma diagnostics
更新于2025-09-19 17:15:36
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Mechanochromism induced through the interplay between excimer reaction and excited state intramolecular proton transfer
摘要： Excited-state intramolecular proton transfer (ESIPT) and excimer formation are unimolecular and bimolecular reactions, respectively. The coupling between these two reactions has been rarely observed. Here we show the interplay between ESIPT and excimer formation in CF3-HTTH (2,2′-(thiazolo[5,4-d]thiazole-2,5-diyl)bis(4-(trifluoromethyl)phenol) solid crystal, resulting in the extensively broad multiple emissions spanning from 420 to 750 nm. Comprehensive structural, time-resolved spectroscopic, and two-photon microscopic studies of CF3-HTTH in crystal lattice unveil the pre-equilibrium ESIPT between the normal (N*) and tautomer (T*) form, for which the slow population decay and well-ordered lattice packing facilitate excimeric (E*) formation, rendering N* (460 nm), T* (520 nm) and E* (600 nm) triple emissions. In contrast, the lower degree of packing on the solid surface prohibits excimer formation, showing only the ESIPT process. The correlation between luminescence properties and packing structure sheds light on the corresponding mechanochromic effect based on molecular solid architecture and provide new insight into the aggregation-induced properties.
关键词： Solid-state emission,Excimer formation,Excited-state intramolecular proton transfer,Molecular packing,Mechanochromism
更新于2025-09-19 17:15:36
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Atomic-Scale Characterization of Graphene p–n Junctions for Electron-Optical Applications
摘要： Graphene p-n junctions offer a potentially powerful approach towards controlling electron trajectories via collimation and focusing in ballistic solid-state devices. The ability of p-n junctions to control electron trajectories depends crucially on the doping profile and roughness of the junction. Here, we use four-probe scanning tunneling microscopy and spectroscopy (STM/STS) to characterize two state-of-the-art graphene p-n junction geometries at the atomic scale, one with CMOS polySi gates and another with naturally cleaved graphite gates. Using spectroscopic imaging, we characterize the local doping profile across and along the p-n junctions. We find that realistic junctions exhibit non-ideality both in their geometry as well as in the doping profile across the junction. We show that the geometry of the junction can be improved by using the cleaved edge of van der Waals metals such as graphite to define the junction. We quantify the geometric roughness and doping profiles of junctions experimentally and use these parameters in Nonequilibrium Green’s Function based simulations of focusing and collimation in these realistic junctions. We find that for realizing Veselago focusing, it is crucial to minimize lateral interface roughness which only natural graphite gates achieve, and to reduce junction width, in which both devices under investigation underperform. We also find that carrier collimation is currently limited by the non-linearity of the doping profile across the junction. Our work provides benchmarks of the current graphene p-n junction quality and provides guidance for future improvements.
关键词： graphene p-n junctions,collimation,Veselago lensing,scanning tunneling microscopy,solid state electron optics
更新于2025-09-19 17:15:36
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Development of CMOS pixel sensors for the upgrade of the ALICE Inner Tracking System
摘要： The ALICE Collaboration is preparing a major upgrade of the current detector, planned for installation during the second long LHC shutdown in the years 2018-19, in order to enhance its low-momentum vertexing and tracking capability, and exploit the planned increase of the LHC luminosity with Pb beams. One of the cornerstones of the ALICE upgrade strategy is to replace the current Inner Tracking System in its entirety with a new, high resolution, low-material ITS detector. The new ITS will consist of seven concentric layers equipped with Monolithic Active Pixel Sensors (MAPS) implemented using the 0.18 μm CMOS technology of TowerJazz. In this contribution, the main key features of the ITS upgrade will be illustrated with emphasis on the functionality of the pixel chip. The ongoing developments on the readout architectures, which have been implemented in several fabricated prototypes, will be discussed. The operational features of these prototypes as well as the results of the characterisation tests before and after irradiation will also be presented.
关键词： Particle tracking detectors,Particle tracking detectors (Solid-state detectors),Large detector systems for particle and astroparticle physics
更新于2025-09-19 17:15:36
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Mn <sup>4+</sup> -activated BaLaMgSbO <sub/>6</sub> double-perovskite phosphor: a novel high-efficiency far-red-emitting luminescent material for indoor plant growth lighting
摘要： In the present work, novel high-efficiency Mn4+-activated BaLaMgSbO6 (BLMS) far-red-emitting phosphors used for plant growth LEDs were successfully synthesized via a solid-state reaction method. X-ray diffraction (XRD), photoluminescence (PL), temperature-dependent PL, CIE color coordinates, and lifetimes as well as internal quantum efficiency (IQE) were used to characterize the phosphor samples. The excitation spectrum of the as-obtained BLMS:Mn4+ phosphors presented two wide bands covering 250–550 nm and the emission spectrum exhibited a far-red emission band in the range of 650–800 nm peaked at 700 nm. Concentration-dependent PL properties of BLMS:Mn4+ phosphors were studied. The optimal doping concentration of Mn4+ ions was 0.6 mol%, and the concentration quenching mechanism was determined to be the nonradiative energy transfer among the nearest-neighbor Mn4+ activators. Impressively, the BLMS:0.6%Mn4+ sample showed an outstanding IQE of 83%. In addition, the luminescence thermal quenching characteristics were also analyzed. Furthermore, the PL spectrum of BLMS:0.6%Mn4+ sample was compared with the absorption spectrum of phytochrome PFR. Finally, after combining BLMS:0.6%Mn4+ phosphors with a 365 nm near-UV LED chip, a far-red light-emitting diode (LED) device was successfully achieved to demonstrate its possible applications in plant growth LEDs.
关键词： far-red-emitting,solid-state reaction,Mn4+-activated,internal quantum efficiency,plant growth LEDs,phosphor,BaLaMgSbO6
更新于2025-09-19 17:15:36
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Valence and core excitons in solids from velocity-gauge real-time TDDFT with range-separated hybrid functionals: An LCAO approach
摘要： An atomic-orbital basis set framework is presented for carrying out velocity-gauge real-time time-dependent density functional theory (TDDFT) simulations in periodic systems employing range-separated hybrid functionals. Linear optical response obtained from real-time propagation of the time-dependent Kohn-Sham equations including nonlocal exchange is considered in prototypical solid-state materials such as bulk Si, LiF and monolayer hexagonal-BN. Additionally core excitations in monolayer hexagonal-BN at the B and N K-edges are investigated and the role of long-range and short-range nonlocal exchange in capturing valence and core excitonic effects is discussed. Results obtained using this time-domain atomic orbital basis set framework are shown to be consistent with equivalent frequency-domain planewave results in the literature. The developments discussed lead to a time-domain generalized Kohn-Sham TDDFT implementation for the treatment of core and valence electron dynamics and light-matter interaction in periodic solid-state systems.
关键词： Core-level spectroscopy,TDDFT,Solid-state,Real-time,Excitons,Range-separated hybrid
更新于2025-09-19 17:15:36
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Silver-chalcogen frameworks: crystal and electronic structure of [Ag3S](NO3) and a comparison with [Ag4Te](SO4)
摘要： Crystal and electronic structure of silver-containing metal-inorganic frameworks [Ag3S](NO3) and [Ag4Te](SO4) have been examined. For [Ag3S](NO3), the crystal structure has been re-determined from X-ray single crystal diffraction data and refined to R = 2.7% in order to determine the exact position of the nitrate anion. It is shown that the main structural feature of [Ag3S](NO3) and [Ag4Te](SO4) is the framework based on the combination of silver-chalcogen and silver-silver interactions, with guest oxoanions filling the cavities. Effectively, ionic interactions between guest anions and the framework differ significantly from the interactions within frameworks themselves, where the bonding analysis shows the tendency for more covalent bonding and indicates that the bonding patterns are consistent with what is regarded as metallophilic interactions.
关键词： Frameworks compounds,Silver,Solid-state structures,Metallophilic interactions,Electronic structure
更新于2025-09-19 17:15:36
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Effect of yttrium insertion on the structural, optical, vibrational and dielectric properties of 0.3Bi1?yYyFeO3–0.7Ba0.8Sr0.2TiO3 ceramics
摘要： Perovskite ceramics [Ba0.8Sr0.2]1-x[Bi1-yYy]xTi1-xFexO3 with x = 0.3 and 0.05 \ y \ 0.15 are synthesized by solid-state solution in order to study the effect of yttrium insertion on the physical properties of this material. The XRD patterns showed the formation of single tetragonal phase without any impurities. Using UV–Vis spectroscopy, the absorbance and re?ectance are highlighted. In fact, we note a blueshift on wavelength and the energy band gap is increased with a high doping content. Besides, Raman spectra display a drop in mode intensities, which is followed by the rise of yttrium that can lead to a ?uctuation in the atomic structure. Furthermore, the permittivity and loss dielectric are studied by impedance spectroscopy, revealing that both decrease with rising frequency indicating, as a result, a dielectric dispersion. Finally, the study of permittivity dielectric as a function of temperature exhibits the presence of G-type antiferromagnetic transition.
关键词： Structural analysis,Ba0.8Sr0.2TiO3,Dielectric response,Optical properties,Solid-state reaction,BiFeO3,Raman spectra
更新于2025-09-19 17:15:36
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Laser performance of high repetition frequency on a 970 nm LD side-pumped Er:YSGG crystal operated at 2.79 ??m
摘要： We demonstrate laser performance of high repetition frequency on 970 nm laser diodes side-pumped Er:YSGG crystal rod with concave end faces. The laser performance under different repetition rates and pulse widths was studied with an optimal cavity length. The maximum average output power of 11.81 W operated at a repetition frequency of 500 Hz and 2.79 μm was achieved, corresponding to the slope efficiency of 10.49%. In addition, the beam quality factors M2x/M2y of 7.01/7.10 and far-field divergences Θx/Θy of 9.15/9.18 mrad were also obtained under the high repetition frequency of 500 Hz. These results show that the LD side-pumped Er:YSGG laser crystal rod with concave end faces has the potential of being operated under high repetition frequency.
关键词： Er:YSGG,high repetition frequency,Solid-state laser,concave end face
更新于2025-09-19 17:13:59