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Tuning the photophysical properties of carboranyl luminophores by <i>closo</i> - to <i>nido</i> -carborane conversion and application to OFF–ON fluoride sensing
摘要： A family of closo-carborane-appended luminophores (closo-OXD1–2 and closo-DPS1–2) in which 2-R-o-carboranes (R = H, Me) are attached to the diphenyl-1,3,4-oxadiazole (OXD) or diphenyl-sulfone (DPS) acceptor groups were prepared and characterized. Deboronation of the closo-carborane cage produced the corresponding nido-carboranyl luminophores (nido-OXD1–2 and nido-DPS1–2). Whereas the closo-compounds were poorly emissive in THF (ΦPL < 0.01), the nido-luminophores exhibited an intense fluorescence with good quantum yields (ΦPL = 0.1–0.45). Electrochemical studies showed that while the closo-OXD and -DPS compounds displayed only carborane-centred, quasi-reversible reduction, the nido-compounds exhibited the typical features for nido-carborane-centred, irreversible oxidation and acceptor-centred, reversible reduction. Theoretical studies suggested that while the 1ππ* state of closo-compounds is nonemissive due to the contribution of closo-carborane to the LUMO in the S1 excited state, the intramolecular charge transfer (ICT) state from the nido-carborane to acceptor moieties in nido-compounds leads to an efficient fluorescence. Finally, THF solutions of closo-OXD1 and -DPS1 showed strong fluorescence upon the addition of fluoride anions under mild heating, but were intact to other anions, including cyanide, allowing the selective OFF–ON fluorescence sensing of fluoride.
关键词： fluoride sensing,carborane,fluorescence,photophysical properties,luminophores
更新于2025-11-20 15:33:11
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A new multi-analyte fluorogenic sensor for efficient detection of Al <sup>3+</sup> and Zn <sup>2+</sup> ions based on ESIPT and CHEF features
摘要： The fluorogenic chemosensor 3-(((2-hydroxy-4-methylphenyl)imino)methyl)-[1,10-biphenyl]-4-ol (H2L) efficiently detects Zn2+ and Al3+ ions and subsequently fluoride ion in methanol–water (4/1, v/v, pH = 7.2) solution. The probe itself is non-emissive but upon treatment with Al3+ and Zn2+, it exhibits high fluorescence emission at two different wavelengths of 546 nm and 529 nm, respectively. Both excited-state intramolecular proton transfer (ESIPT) and chelation enhanced fluorescence (CHEF) processes play important roles in the enhancement of fluorescence intensity. Chelation of Zn2+ and Al3+ with the probe (H2L) inhibits CQN isomerization and ESIPT which consequently enhances the emission intensity. The emission intensity of H2L–Al3+ is selectively quenched upon titration with F- anions. The structure of the probe is confirmed by the single crystal X-ray diffraction method. The electronic structure and sensing mechanism of the probe (H2L) are supported by density functional theory (DFT) and time-dependent density functional theory (TDDFT).
关键词： Zn2+ detection,fluoride detection,CHEF,fluorogenic sensor,ESIPT,Al3+ detection
更新于2025-11-19 16:46:39
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RbF post deposition treatment for narrow bandgap Cu(In,Ga)Se2 solar cells
摘要： Multi-junction solar cells are known to have a considerably increased efficiency potential over their typical single junction counterparts. In order to produce low cost and lightweight multi-junction devices, the availability of suitable narrow (<1.1 eV) bandgap bottom cells is paramount. A possible absorber for such a bottom cell is the Cu(In,Ga)Se2 (CIGS) compound semiconductor, one of the most efficient thin film materials to date. In this contribution we report on the RbF post deposition treatment of narrow bandgap CIGS absorbers grown with a single bandgap grading approach. We discuss the necessary deposition conditions and the observed improvements on solar cells performance. A certified record efficiency of 18.0 % for an absorber with 1.00 eV optoelectronic bandgap is presented and its suitability for perovskite/CIGS tandem devices is shown.
关键词： Post deposition treatment,Narrow bandgap,Tandem solar cells,Thin film solar cells,photovoltaics,Rubidium fluoride,Copper indium gallium selenide
更新于2025-11-14 17:28:48
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[IEEE 2017 IEEE 44th Photovoltaic Specialists Conference (PVSC) - Washington, DC (2017.6.25-2017.6.30)] 2017 IEEE 44th Photovoltaic Specialist Conference (PVSC) - Interface Effects of Alkali Treatment on Cu-Rich Thin Film Solar Cells
摘要： CuInSe2 absorbers grown under Cu-excess have better current collection compared to those grown as Cu-poor. However, cells based on Cu-excess absorbers show lower efficiency due to a worse absorber-buffer interface where the interface recombination is the dominant recombination path. In this paper, potassium fluoride post-deposition treatment is used to improve this interface, as evidenced by an activation energy of the main recombination path close to the band gap energy. The treatment also succeeded in eliminating the 200-meV step observed in admittance measurements; a main characteristic of Cu-excess CuInSe2 cells.
关键词： admittance measurements,Cu-excess,interface recombination,potassium fluoride post-deposition treatment,CuInSe2
更新于2025-11-14 17:28:48
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Photoluminescent behaviour of Ce3+ ions in mixed fluoride structures
摘要： Investigations were done to modify the photoluminescence (PL) spectra of a cerium (Ce3+) doped strontium fluoride (SrF2:Ce3+) phosphor for better sensitization for solar cell application. For optimum sensitization it is needed that Ce3+ emission overlaps with Lanthanide (Ln3+) ions’ excitation energy ranges. SrF2:Ce3+ emission, however, does not overlap well with different 4f-4f Ln3+ ions’ excitation ranges. The PL behavior of Ce3+ in Sr1-xMxF2:Ce3+ (where M = Ca, Ba, Mg, La) was therefore investigated. Noticeable changes were observed in the shape of the excitation and emission spectra of Ce3+. The Sr0.49Ba0.50Ce0.01F2 phosphor produced a significant red shift with a broad emission band. The excitation spectrum of this sample was blue shifted if compared to the singly doped sample.
关键词： fluoride structure,XPS,luminescence,Ce3+
更新于2025-11-14 15:28:36
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Study of the Electronic and Electrical Properties of the C60F18 Polar Molecule on Au(111) Surface
摘要： For adequate description of the adsorption and self-assembly of C60F18 polar molecules on the surface Au(111), quantum-chemical studies of the electronic and electrical properties of a single molecule are performed. Using various procedures of density functional theory, the electric dipole moment of the molecule, distributions of the electrostatic potential, electric-field magnitude and electron density are calculated with controlled accuracy for the first time. An improved value of the electric dipole moment of the C60F18 molecule is obtained in a range from 10 to 11 D. The known approximation of a point dipole for electric-field strength is shown to be fulfilled within an accuracy of 30% even at distances twice greater than the size of the molecule. The structural fragments of the calculated lowest unoccupied and highest occupied molecular orbitals are assigned to their images, which were previously obtained using scanning tunneling microscopy and spectroscopy.
关键词： density functional theory,lowest unoccupied and highest occupied molecular orbitals,electric dipole moment,scanning tunneling spectroscopy,fullerene fluoride
更新于2025-09-23 15:23:52
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Optical investigation of radiation-induced color centers in lithium fluoride thin films for low-energy proton-beam detectors
摘要： In the last few years, the peculiar photoluminescence properties of radiation-induced color centers in lithium fluoride (LiF) films have been successfully used for advanced diagnostics of low-energy proton beams produced by the TOP-IMPLART linear accelerator for protontheraphy under development at ENEA C.R. Frascati. The two-dimensional spatial dose map of the transversal section of proton beams was fully reconstructed in a wide interval of doses. In this work the optical emission properties of LiF thin films, grown by thermal evaporation on glass and Si (100) substrates and subsequently irradiated by proton beams of nominal energy 3 MeV at doses higher than 105 Gy, were carefully investigated. Their structural and morphological analyses were performed by X-ray diffraction and atomic force microscopy. A careful comparison of the photoluminescence and photoluminescence-excitation spectra of F2 and F3+ electronic defects was performed. Substrate-enhanced photoluminescence intensity increase up to 100% was observed in colored LiF films grown on Si substrates with respect to glass ones. This behavior can be substantially ascribed to the reflective properties of the Si substrate at the emission wavelengths of F2 and F3+ CCs, although other complex effects due to the polycrystalline nature of the films cannot be excluded.
关键词： Photoluminescence,Lithium fluoride,Radiation detectors,Color centers,Thin films
更新于2025-09-23 15:23:52
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Optical and photoconductive properties of indium sulfide fluoride thin films
摘要： This work reports on transparent semiconducting indium sulfide fluoride (ISF) thin-films exhibiting high sensitivity to ultraviolet radiation. The films were deposited on fused silica and silicon substrates using a radio-frequency plasma-enhanced reactive thermal evaporation system. The deposition was performed evaporating pure indium in SF6 plasma at a substrate temperature of 423 K. Rutherford backscattering measurements were used to determine the chemical composition of the films deposited on silicon substrates. The surface morphology was studied using scanning electron microscopy technique. The film characterization includes electrical, optical, and photoconductivity measurements. The synthesized compound is highly-resistive (~700 MΩ-cm at 300 K) and exhibits an evident semiconducting behavior. The activation energy of 0.88 eV is deduced from the temperature dependence of electrical resistivity. The indirect band energy gap of 2.8 eV is determined from transmittance spectra of the ISF films. The photoconductivity band is centered at 345 nm wavelength. The photoconductivity spectrum also shows the Urbach tail with a characteristic energy of 166 meV. ISF is a promising candidate for a buffer layer in chalcogenide-based solar cells.
关键词： Thin-films,Indium sulfide fluoride,Optical properties,Photoconductivity,Photovoltaics,Amorphous semiconductors
更新于2025-09-23 15:23:52
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Hydrophilic Poly(vinylidene Fluoride) Film with Enhanced Inner Channels for Both Water- and Ionic Liquid-Driven Ion-Exchange Polymer Metal Composite Actuators
摘要： This study presents a novel and facile strategy to fabricate a hydrophilic poly(vinylidene fluoride) (PVDF) electrolyte film with enhanced inner channels for a high-performance and cost-effective ion-exchange polymer metal composite (IPMC) actuator. The resultant PVDF composite film is composed of hierarchical micro/nanoscale structures: well-defined polymer grains with a diameter of ～20 μm and much finer particles with a diameter of ～390 nm, producing three-dimensional interconnected, hierarchical inner channels to facilitate ion migration of the electrolyte matrix film has a high porosity of 15.8% and yields a high water uptake of 44.2% and an ionic liquid (IL, [EMIm]·[BF4]) uptake of 38.1% to make both water-driven and IL-driven IPMC actuators because of the introduction of polar polyvinyl pyrrolidone. Compared to the conventional PVDF/IL-based IPMC, both water-driven and IL-driven PVDF-based IPMCs exhibit high ion migration rates, thus effectively improving the actuation frequency and producing remarkably higher levels of actuation force and displacement. Specifically, the force outputs are increased by 13.4 and 3.0 folds, and the displacement outputs are increased by 2.2 and 1.9 folds. Using an identical electrolyte matrix, water-driven IPMC exhibits stronger electromechanical performance, benefiting to make IPMC actuator with high levels of force and power outputs, whereas IL-driven IPMC exhibits a more stable electromechanical performance, benefiting to make long lifetime IPMC actuator in air. Thus, the resultant IPMCs are promising in the design of artificial muscles with tunable electromechanical performance for flexible actuators or displacement/vibration sensors at low cost.
关键词： ionic exchange polymer metal composite (IPMC),ionic liquid (IL),poly(vinylidene fluoride) (PVDF),inner channel,electromechanical response,polyvinyl pyrrolidone (PVP)
更新于2025-09-23 15:23:52
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Comparative study of Sm3+ ions doped phosphate based oxide and oxy-fluoride glasses for solid state lighting applications
摘要： The physical and luminescent properties of Sm3+-doped oxide and oxy-fluoride phosphate glasses were investigated. The glass samples with chemical composition of 69P2O5-10BaO-10ZnO-10Gd2O3-1Sm2O3 and 69P2O5-10BaO-10ZnO-10GdF3-1Sm2O3 were prepared by conventional melt quenching technique. The prepared glass samples were characterized with density, molar volume, refractive index, FTIR, UV-Vis-NIR, photoluminescence, radio luminescence, decay time profile, and CIE diagram. The density and refractive index of the oxide glass have higher values as compared to the oxy-fluoride glass. The FTIR spectra show the reduction of O-H group in oxy-fluoride glass. The characteristic peaks of Sm3+ are observed at 360, 372, 402, 438, 419, 473, 944, 1077, 1227, 1373, 1474, 1529 and1585 nm in UV-VIS-NIR spectra. These peaks are related respectively to the transitions from ground state 6H5/2 to 4D3/2, 6P7/2, 6P3/2, 4I11/2, 6F11/2, 6F9/2, 6F7/2, 6F5/2, 6F3/2, 6H15/2 and 6F1/2 excited states. From photoluminescence and radio-luminescence it is observed that the oxy-fluoride glass samples show better emission intensity than the oxide glass. The Judd-Ofelt theory (J-O theory) was used to find J-O intensity ?λ (λ=2,4 and 6) parameters and radiative properties such as transition probability, stimulated emission cross section and branching ratios for titled glasses. The trend observed in the J-O parameters is ?4 >?2 >?6. The transition probability, emission cross section and branching ratio have the highest values for the 4G5/2→6H7/2 transition. The CIE coordinates of the prepared glass samples are positioned in the orange region and the CCT value is 3776.105 for oxide and oxyfluoride glass. The oxy-fluoride glass has shorter decay time as compared to the oxide glass and it is recorded to be 1.62 and 1.32 ms for oxide and oxy-fluoride respectively. According to the results obtained in this work, it is obvious that these glass samples can be good candidate materials for producing cool orange light.
关键词： Judd-Ofelt theory,Oxy-fluoride glass,Rare earths,Photoluminescence,CIE coordinates
更新于2025-09-23 15:23:52