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Excited state intramolecular single proton transfer mechanism of pigment yellow 101 in solid state: Experiment and DFT calculation
摘要： To investigate fluorescence mechanism of Pigment Yellow 101 (P. Y. 101) in solid state, three aromatic aldehyde azines (1-3) including P. Y. 101 have been synthesized and compared with each other. Results indicated that P. Y. 101 prepared by solvothermal method is actually the mixture of two polymorphs, whose molecular packing mode can be transformed into each other by recrystallizing or external stimuli such as pressure and grinding. The ESIPT properties of 1-3 were investigated by DFT/TD-DFT calculations and time-correlated single photon counting (TCSPC) technique. Both experimental and theoretical results revealed that the dual fluorescence properties of P. Y. 101 in solid state are ascribed to the excited-state intramolecular single proton transfer fluorescence emissions of two structurally different polymorphs rather than the results of the sequential or concerted excited-state intramolecular double proton transfers, which provide a potential valuable tool for developing multistimuli-responsive luminescent materials.
关键词： Aromatic aldehyde azines,DFT calculation,P. Y. 101,Excited-state intramolecular proton transfer,Polymorphs
更新于2025-11-19 16:56:35
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van der Waals Epitaxy of High-Mobility Polymorphic Structure of Mo <sub/>6</sub> Te <sub/>6</sub> Nanoplates/MoTe <sub/>2</sub> Atomic Layers with Low Schottky Barrier Height
摘要： High contact resistance between two-dimensional (2D) transition metal dichalcogenides (TMDs) and metal electrodes is a practical barrier for applications of 2D TMDs to conventional devices. A promising solution to this is polymorphic integration of 1T′-phase semi-metallic and 2H-phase semiconducting TMD crystals, which can lower the Schottky barrier of the TMDs. Here, we demonstrate the van der Waals epitaxy of density-controlled single isolated 1T′-Mo6Te6 nanoplates on 2H-MoTe2 atomic layers by using metal-organic chemical vapor deposition. Importantly, in situ grown 1T′-Mo6Te6 nanoplates significantly reduce the contact resistance of the 2H-MoTe2 atomic layers, providing a record high mobility of 1,139 cm2/Vs for Pd/1T′-Mo6Te6/2H-MoTe2 back-gated field-effect transistors (FETs), along with a low Schottky barrier height (q?b) of 8.7 meV. These results lead to the possibility of ameliorating the high contact resistance faced by other TMDs, and furthermore, offer polymorphic structures for realizing higher mobility TMD devices.
关键词： 1T′-2H polymorphs,MOCVD,transition metal dichalcogenides,Mo6Te6,MoTe2
更新于2025-09-23 15:22:29
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Portable and benchtop Raman spectrometers coupled to cluster analysis to identify quinine sulfate polymorphs in solid dosage forms and antimalarial drug quantification in solution by AuNPs-SERS with MCR-ALS
摘要： This paper proposes for the first time: (a) a qualitative analytical method based on portable and benchtop backscattering Raman spectrometers coupled to hierarchical cluster analysis (HCA) and multivariate curve resolution – alternating least-squares (MCR-ALS) to identify two polymorphs of antimalarial quinine sulfate in commercial pharmaceutical tablets in their intact forms and (b) a quantitative analytical method based on gold nanoparticles (AuNPs) as active substrates for surface-enhanced Raman scattering (SERS) in combination with MCR-ALS to quantify quinine sulfate in commercial pharmaceutical tablets in solution. The pure concentration and spectral profiles recovered by MCR-ALS proved that both formulation present different polymorphs. These results also were confirmed by two clusters observed in HCA model, according to their similarities within and among the samples that provided useful information about homogeneity of different pharmaceutical manufacturing processes. AuNPs-SERS coupled to MCR-ALS was able to quantify quinine sulfate in the calibration range from 150.00 to 200.00 ng mL-1 even with strong overlapping spectral profile of background SERS signal, proving that is a powerful ultrahigh sensitivity analytical method. This reduced linearity was validated through a large calibration range from 25.00 to 175.00 μg mL-1 used in a reference analytical method based on high performance liquid chromatography with diode array detector (HPLC-DAD) coupled to MCR-ALS for analytical validation purposes even in the presence of coeluted compound. The analytical methods herein developed are fast, because second-order chromatographic data and first-order SERS spectroscopic data where obtained in less than 6 and 2 min, respectively. Concentrations of quinine sulfate were estimated with a low root mean square error of prediction (RMSEP) values and a low relative error of prediction (REP%) in the range 1.8-6.1%.
关键词： Quinine sulfate pharmaceutical tablets,Raman spectrometer,polymorphs,HCA and MCR-ALS,AuNPs-SERS
更新于2025-09-23 15:19:57
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Come to light: detailed analysis of thermally treated Phenyl modified Carbon Nitride Polymorphs for bright phosphors in lighting applications
摘要： Carbon Nitride and its polymorphs have recently gained large interests for their huge properties and applications in different fields, from lighting to photocatalysis. Further, several attempts were recently devoted to tune and control its optical and electrical properties. In this report we analyze phenyl modified Carbon Nitride structures obtained by simple thermal polymerization at different temperatures (250 to 400 °C) of the starting precursor: 2,4-diamino-6-phenyl-1,3,5-triazine. A multi-technique experimental data (XRD patterns, Raman, TGA and DTG, steady- time and time resolved Luminescence, Photoluminescence Excitation spectra, Reflectivity spectra) was applied to analyze the relationship between structural and optical properties and to give more insight on the effect of synthesis procedure on the final polymer. The optical properties evidenced an interesting shift towards the visible region of the absorption spectrum of the phenyl modified g-C3N4 polymer that, associated with the high optical quantum yield (about 60%) and to a broad emission in the green-red spectral region, makes the samples very suitable for lighting applications. Indeed, we report a first prototype of white LED emission by assembly of a commercial blue LED and the Phenyl modified g-C3N4 powders as phosphor, verifying the structural and optical stability over about 10000 working hours.
关键词： Thermal polymerization,Optical properties,Polymorphs,Carbon Nitride,White LED,Lighting applications
更新于2025-09-19 17:13:59
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Orientation‐Controlled 2D Anisotropic and Isotropic Photon Transport in Cocrystal Polymorph Microplates
摘要： Two-dimensional (2D) anisotropic transport of photons/electrons is crucial for constructing ultracompact on-chip circuits. To date, the photons in organic 2D crystals usually exhibit the isotropic propagation, and the anisotropic behaviors have not yet been fully demonstrated. Herein, an orientation-controlled photon-dipole interaction strategy was proposed to rationally realize the anisotropic and isotropic 2D photon transmissions in two self-assembled cocrystal polymorph microplates. The monoclinic microplate adopting a nearly horizontal molecular transition dipole orientation in the 2D plane, exhibits anisotropic photon-dipole interactions and thus distinct re-absorption waveguide losses for different 2D directions. By contrast, the triclinic microplate with a vertical transition dipole orientation, shows the 2D isotropic photon-dipole interactions and thus the same re-absorption losses along different directions. Based on the anisotropic transport mechanism, a directional signal outcoupler (DSO) was further designed for the high-fidelity transmission of the real signals, which would enlighten the development of 2D anisotropic optical devices.
关键词： transition dipole moment,Cocrystal,polymorphs,two-dimensional photonics,anisotropic optical waveguides
更新于2025-09-16 10:30:52
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Orientation-Controlled 2D Anisotropic and Isotropic Photon Transport in Cocrystal Polymorph Microplates
摘要： Two-dimensional (2D) anisotropic transport of photons/electrons is crucial for constructing ultracompact on-chip circuits. To date, the photons in organic 2D crystals usually exhibit the isotropic propagation, and the anisotropic behaviors have not yet been fully demonstrated. Herein, an orientation-controlled photon-dipole interaction strategy was proposed to rationally realize the anisotropic and isotropic 2D photon transmissions in two self-assembled cocrystal polymorph microplates. The monoclinic microplate adopting a nearly horizontal molecular transition dipole orientation in the 2D plane, exhibits anisotropic photon-dipole interactions and thus distinct re-absorption waveguide losses for different 2D directions. By contrast, the triclinic microplate with a vertical transition dipole orientation, shows the 2D isotropic photon-dipole interactions and thus the same re-absorption losses along different directions. Based on the anisotropic transport mechanism, a directional signal outcoupler (DSO) was further designed for the high-fidelity transmission of the real signals, which would enlighten the development of 2D anisotropic optical devices.
关键词： two-dimensional photonics,anisotropic optical waveguides,Cocrystal,polymorphs,transition dipole moment
更新于2025-09-12 10:27:22
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Selective brookite polymorph formation related to the amorphous precursor state in TiO2 thin films
摘要： A wide variety of brookite TiO2 synthesis methods have been published over the past several decades, but few studies discuss the underlying mechanism that stabilizes brookite over its stable counterparts, rutile and anatase. Here, we investigate of the effect of pulsed laser deposition parameters on the as-deposited amorphous precursor titania thin films, which subsequently crystallize into stable and metastable TiO2 polymorphs upon annealing. We find that oxygen pressure in the deposition chamber strongly influences the non-equilibrium state of the amorphous precursor, which ultimately allows for selective polymorph formation. Rutile forms as the dominant phase at low pO2 < 0.1 mTorr, while anatase is favored at high pO2 > 5 mTorr. Brookite forms primarily at intermediate pO2 (0.5–1.0 mTorr). Controlling the amorphous structure (i.e. Ti—O bonding and polyhedral arrangement) of the precursors via oxygen deficiency is therefore likely for the selective formation of crystalline TiO2 polymorphs from sub-stoichiometric amorphous precursors. Directing phase selectivity by manipulating the structure and internal energy of the precursor amorphous state may have tremendous potential for synthesis of metastable crystalline phases that exhibit more desirable properties in comparison to their stable counterparts.
关键词： Amorphous precursors,Selective crystallization,Polymorphs,Oxygen deficiency,Thin films,TiO2
更新于2025-09-10 09:29:36
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Molybdenum Disulfid: Differentiating Polymorphs in Molybdenum Disulfide via Electron Microscopy (Adv. Mater. 47/2018)
摘要： The presence of rich polymorphs and stacking polytypes in molybdenum disulfide (MoS2) endows it with a diverse range of properties. This has stimulated a lot of interest in the unique properties associated with each polymorph. In article number 1802397, Kian Ping Loh and co-workers discuss the use of electron microscopy for identifying the atomic structures of several important polymorphs in MoS2 and establishing the correlation between structure and properties.
关键词： polymorphs,electron microscopy,stacking polytypes,molybdenum disulfide,MoS2
更新于2025-09-09 09:28:46
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Formation and Evolution of Ultrathin Silica Polymorphs on Ru(0001) Studied with Combined in Situ, Real-Time Methods
摘要： Silica mono- and bilayer films on Ru(0001) can be physisorbed or chemisorbed, with ordered or vitreous structures, depending on the particular preparation procedures applied. Using the SMART spectro-microscope at BESSY-II with its capabilities for μ-spectroscopy, μ-diffraction, and LEEM imaging with lateral resolution below 5 nm, in situ and in real time and applied to identical areas, we have investigated the formation of these layers, defined and characterized their properties and their connected morphology, and followed their evolution. Two distinct chemisorbed monolayers and three bilayers (physisorbed crystalline and vitreous, and chemisorbed zigzag phases), and some transitions between them, have been studied. We found that, apart from the deposited silicon amount, the most important parameter for steering the evolution to a particular well-defined layer is the oxygen content at the Ru interface. Nucleation and growth of all layers are homogeneous on the scale of our resolution, leading to rather small domains (20 – 40 nm), mostly of the same phase, separated by defect lines. We discuss these and other basic findings in context and point out open questions. We also offer alternative recipes for the preparation of some phases, to obtain more homogeneous layers on a mesoscopic scale.
关键词： Silica films,SMART spectro-microscope,real-time methods,in situ,LEEM,chemisorbed,physisorbed,polymorphs,Ru(0001),μ-spectroscopy,μ-diffraction
更新于2025-09-04 15:30:14