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Mechanofluorochromism based on BOPIM complexes: The effect of substituents and regulation of the direction of the emission color changes
摘要： Novel boron 2-(2′-pyridyl)imidazole (BOPIM) complexes T1, T2 and T3 with different substituents (including bromo, tert-butyl and methoxyl) on the benzene ring of BOPIM dyes have been designed and synthesized, and their optical properties in both solution and the solid state were investigated and compared. The three compounds exhibited typical intramolecular charge transfer (ICT) characteristics. Solvent-dependent UV-vis absorption, fluorescence emission spectra and quantum chemical calculation indicated a molecular push-pull electronic structure. Their ICT degrees increased with the sequence of T1 < T2 < T3. The analysis of the X-ray crystal structure revealed the twisted molecular conformation of BOPIM dyes. Furthermore, they showed remarkable reversible mechanofluorochromic (MFC) features under mechanical force. It was found that the MFC activities could be tuned easily by changing the substituents on the BOPIM dyes. T1 exhibited emission color change from bright green to yellowish green with a spectral red-shift of only 22 nm under mechanical stimuli, whereas T2 and T3 gave the large spectral red-shifts of 36 and 30 nm. Electronic and steric effects of the substitutes were proved playing significant roles in regulating the ICT effect and intermolecular interactions. More importantly, the remarkable effect of substituents on the MFC behaviors of BOPIM dyes will provide an effective way to obtain novel high-contrast MFC dyes.
关键词： Mechanofluorochromism,Substituent effect,Intramolecular charge transfer,Solid-state fluorescence,BOPIM complexes
更新于2025-11-14 15:26:12
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Lead Halide Post-Perovskite-Type Chains for High-Efficiency White-Light Emission
摘要： Hybrid metal halides containing perovskite layers have recently shown great potential for applications in solar cells and light-emitting diodes. Such compounds exhibit quantum confinement effects leading to tunable optical and electronic properties. Thus, broadband white-light emission has been observed from diverse metal halides and, owing to high color rendering index, high thermal stability, and low-temperature solution processability, these materials have attracted interest for application in solid-state lighting. However, the reported quantum yields for white photoluminescence (PLQY) remain low (i.e., in the range 0.5–9%) and no approach has shown to successfully increase the intensity of this emission. Here, it is demonstrated that the quantum efficiencies of hybrid metal halides can be greatly enhanced if they contain a polymorph of the [PbX4]2? perovskite-type layers: the [PbX4]2? post-perovskite-type chains showing a PLQY of 45%. Different piperazines lead to a hybrid lead halide with either perovskite layers or post-perovskite chains influencing strongly the presence of self-trapped states for excitons. It is anticipated that this family of hybrid lead halide materials could enhance all the properties requiring the stabilization of trapped excitons.
关键词： trapped excitons,solid-state lighting,post-perovskite,photoluminescence
更新于2025-11-14 15:16:37
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A development of new red phosphor based on europium doped as well as substituted Barium Lanthanum Aluminate (BaLaAlO4: Eu3+)
摘要： New red emitting Eu3+ doped and substituted BaLaAlO4 phosphor powders were synthesized by simple modified solid state reaction method. BaLaAlO4 crystal phase formation studied through powder X-ray diffraction (XRD) analysis. Fourier Transform - Infra Red (FT-IR) analysis was performed to study the formation of the host with respect to temperature increment and metal-oxygen bond vibrations of BaLaAlO4 host lattice. Morphology of the phosphor was appeared as irregular in shapes with agglomeration. Photoluminescence (PL) analysis was performed to study the PL excitation and emission characteristics of the phosphor. It dictates that synthesized phosphors exhibited a strong red emission at 626 nm. Substitution effect of Eu3+ in BaLaAlO4 with various compositions such as Ba(1-x)LaAlO4: Eux3+, BaLa(1-y)AlO4: Euy3+ and BaLaAl(1-z)O4: Euz3+ were studied for PL enhancement. Luminescence decay time of the phosphors was also determined. PL thermal quenching and Commission Internationale de l'Eclairage (CIE) chromaticity analysis were carried out to find thermal stability and colour purity of the phosphor sample respectively. The Judd- Ofelt parameters (Ω2 & Ω4) obtained from the emission spectra of Eu3+ ions in BaLaAlO4 host lattice were evaluated and discussed.
关键词： BaLaAlO4,Eu3+,Red phosphor,Substitution effect,Solid state reaction
更新于2025-11-14 15:13:28
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Testbeam results of irradiated ams H18 HV-CMOS pixel sensor prototypes
摘要： HV-CMOS pixel sensors are a promising option for the tracker upgrade of the ATLAS experiment at the LHC, as well as for other future tracking applications in which large areas are to be instrumented with radiation-tolerant silicon pixel sensors. We present results of testbeam characterisations of the 4th generation of Capacitively Coupled Pixel Detectors (CCPDv4) produced with the ams H18 HV-CMOS process that have been irradiated with different particles (reactor neutrons and 18 MeV protons) to fluences between 1 × 10^14 and 5 × 10^15 1-MeV- neq/cm^2. The sensors were glued to ATLAS FE-I4 pixel readout chips and measured at the CERN SPS H8 beamline using the FE-I4 beam telescope. Results for all fluences are very encouraging with all hit efficiencies being better than 97% for bias voltages of 85 V. The sample irradiated to a fluence of 1 × 10^15 neq/cm^2 — a relevant value for a large volume of the upgraded tracker — exhibited 99.7% average hit efficiency. The results give strong evidence for the radiation tolerance of HV-CMOS sensors and their suitability as sensors for the experimental HL-LHC upgrades and future large-area silicon-based tracking detectors in high-radiation environments.
关键词： Particle tracking detectors (Solid-state detectors),Solid state detectors,Radiation-hard detectors,Electronic detector readout concepts (solid-state)
更新于2025-09-23 15:23:52
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Excited State Dynamics of [Ru(bpy)3]2+ Thin Films on Sensitized TiO2 and ZrO2
摘要： The excited state dynamics of Tris(2,2'-bipyridine)ruthenium(II) hexafluorophosphate, [Ru(bpy)3(PF6)2], was investigated on the surface of bare and sensitized TiO2 and ZrO2 films. The organic dyes LEG4 and MKA253 were selected as sensitizers. A Stern-Volmer plot of LEG4-sensitized TiO2 substrates with a spin-coated [Ru(bpy)3(PF6)2] layer on top shows considerable quenching of the emission of the latter. Time-resolved emission spectroscopy interestingly reveals the presence of a fast-decay time component (25±5 ns), which is absent when the anatase TiO2 semiconductor is replaced by ZrO2. It should be specified that the positive redox potential of the ruthenium complex prevents electron transfer from the [Ru(bpy)3(PF6)2] ground state into the oxidized sensitizer. Therefore, we speculate that the fast-decaying time component observed may be identified with excited-state electron transfer from [Ru(bpy)3(PF6)2] to the oxidized sensitizer. Solid-state dye sensitized solar cells (ssDSSCs) employing MKA253 and LEG4 dyes, with [Ru(bpy)3(PF6)2] employed as a hole-transporting material (HTM), exhibit 1.2% and 1.1% power conversion efficiency, respectively. This result illustrates the possibility of the hypothesized excited-state electron transfer.
关键词： Photochemistry,Excited-state electron transfer,DSSCs,Ru(bpy)3,Solid state
更新于2025-09-23 15:23:52
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Modification of TiO <sub/>2</sub> (1?1?0)/organic hole transport layer interface energy levels by a dipolar perylene derivative
摘要： Our photoemission study reveals that the work function of TiO2(1 1 0) decreases by up to 1.5 eV upon deposition of 9-(bis-(p-(tert-octyl)phenyl)amino)-perylene-3,4-dicarboxylic anhydride (BOPA-PDCA). This effect is attributed to a chemical reaction of TiO2(1 1 0) and the molecular anhydride group, as well as the molecular dipole. Analysis of the film thickness dependent photoemission and metastable atom electron spectroscopy data reveals that for low coverage the perylene backbone of BOPA-PDCA is almost parallel to the substrate surface and higher coverage leads to an orientational transition to essentially upright standing molecules. Comparing the energy-level alignment between TiO2(1 1 0) and the hole transport materials N,N′-bis(1-naphthyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine (NPB) without and with the BOPA-PDCA interlayer, we find that the perylene derivative has a positive impact on the level alignment for dye-sensitized solar cells with high open-circuit voltages.
关键词： solid state dye-sensitized solar cell,titanium dioxide,energy-level alignment,ultraviolet photoelectron spectroscopy,metastable atom electron spectroscopy,perylene
更新于2025-09-23 15:23:52
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Fabrication of alkali metal sulfate–doped zinc tungstate and their photoluminescence
摘要： The enhancement of photoluminescence of alkali metal sulfate-doped zinc tungstate was investigated. All samples were prepared by solid-state reaction at 800 °C using ZnO, WO3, and alkali metal sulfates as starting powders. The zinc tungstate phase was confirmed from the samples by X-ray diffraction. The emission peak of the samples excited at 275 nm was observed at 465 nm. Rb2SO4 > K2SO4 > Cs2SO4 > undoped > Na2SO4 > Li2SO4 was the order of peak emission intensity of alkali metal sulfate-doped samples. Alkali metals with a large ionic radius (K, Rb, Cs) enhanced the emission of intrinsic luminescence in the blue wavelength region. Moreover, sulfates had the potential to change the luminescence activities of the samples.
关键词： Solid-state reaction,Alkali metal,Zinc tungstate,Sulfate,Photoluminescence
更新于2025-09-23 15:23:52
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Review on metal sulphide-based Z-scheme photocatalysts
摘要： Semiconductor-based heterojunction photocatalysts have received considerable attention for solar energy conversion and environmental purification due to their spatially separated reduction and oxidation sites, effective separation and transportation of photo-excited charge carriers and strong redox ability. With their wide visible-light responsive range and high photocatalytic activity, metal sulphide is an important material in developing photocatalysts. This review summarizes and highlights recent research progress in sulphide-based direct Z-scheme photocatalysts, followed by analysis on the limitations over all-solid-state Z-scheme photocatalyst. Furthermore, the applications and characterization methods of sulphide-based direct Z-scheme photocatalyst are summarized. Finally, the challenges and perspectives of sulphide-based Z-scheme photocatalyst are discussed.
关键词： CdS,direct Z-scheme,All-solid-state Z-scheme,S-scheme,metal sulphide
更新于2025-09-23 15:23:52
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Tunable photoluminescence properties and energy transfer of Ca5(BO3)3F: Tb3+/Eu3+ phosphors for solid state lighting
摘要： A series of Ca5(BO3)3F: Tb3+/Eu3+ phosphors have been prepared via solid-state reaction. Phase purity and crystal structure of as-prepared samples are confirmed by X-ray diffraction measurements. The emission intensity of Ca5(BO3)3F: Tb3+ with Li+, Na+, K+ as charge compensators are remarkably enhanced, and the sample in presence of Na+ exhibits the strongest emission intensity. The emission spectra and fluorescence decays confirm the presence of efficient energy transfers from Tb3+ to Eu3+ in Ca5(BO3)3F: Tb3+/Eu3+ phosphors. The energy transfer mechanism between Tb3+ and Eu3+ has been proven to be resonant type via the electric dipole-dipole interaction. The thermal quenching temperature T50 obtained from the temperature-dependent emission spectra is 478 K, demonstrating a high thermal stability of the as-obtained Ca5(BO3)3F: Tb3+/Eu3+ phosphors. Moreover, by increasing the molar ratio of Eu3+ to Tb3+, the emission colors of Ca5(BO3)3F: Tb3+/Eu3+ phosphors can be tuned from green to orange, and then to red. These results demonstrate that the as-obtained Ca5(BO3)3F: Tb3+/Eu3+ phosphors may have potential applications in solid-state lighting fields.
关键词： Energy transfer,Ca5(BO3)3F,Phosphors,Tunable luminescence,Solid-state reaction
更新于2025-09-23 15:23:52
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Multi-fluorescent Cationic Carbon Dots for Solid-state Fingerprinting
摘要： Carbon nanomaterials have been widely explored in bioimaging and biosensing, but their application in forensic science and technology is rare. In this report, we show one-pot synthesis of cationic Carbon Dots (cCDs) and their application in fingerprinting analysis. The cCDs show narrow size distribution (<10 nm), decent quantum yield (c.a. 46%), and a band gap of 2.75 eV. The cCDs exhibit cationic charge and show excitation-dependent multi-fluorescence characteristics. The cCDs show no production of reactive oxygen species and thus are safe to use. Interestingly, they also possess bright liquid as well as solid-state fluorescence. We demonstrate that a well-resolved patterned fingerprint can be obtained within a short time (2-3 min) from different physical surfaces and can be studied using a simple cell phone camera enabling accurate visualization up to third-degree detailing of the fingerprint. Owing to multi-fluorescence characteristics of cCDs, a detailed investigation of the fluorescent patterns was carried out by a three-dimensional multiphoton confocal microscopy. In comparison to traditional methods, the cCDs fluorescence-based fingerprinting shows improvements towards rapid image capture and analysis. Thus, the cCDs form a promising material for rapid fingerprint detection in forensic sciences.
关键词： solid-state,confocal imaging,carbon dots,cell phone,fingerprint
更新于2025-09-23 15:23:52