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Rational design of high efficiency green to deep red/near-infrared emitting materials based on isomeric donor–acceptor chromophores
摘要： A family of compounds TPA-BT-Q, TPA-pyT-N-naph, TPA-N-pyT-naph, and DPA-py-N-BT-naph with the isomeric donor-acceptor conjugation framework were designed and synthesized, and their structure-property relationships, theoretical calculations, and photophysical and electrochemical characteristics were investigated. These isomeric chromophores showed significantly different photophysical properties. Emission wavelengths spanning from green to near-infrared region were observed in different solvents with high photoluminescence quantum yield, exceeding 90% in low polarity solvents and 44–88% in blend films. Organic light-emitting devices displayed strong electroluminescence with emission peaks at 592, 660, 630, and 580 nm; maximum current efficiencies of 7.92, 2.93, 3.56, and 15.37 cd/A; maximum power efficiencies of 4.21, 1.56, 1.81, and 8.24 lm/W; and maximum external quantum efficiencies of 3.15%, 2.75%, 2.66%, and 5.33% for TPA-BT-Q, TPA-pyT-N-naph, TPA-N-pyT-naph, and DPA-py-N-BT-naph doped OLEDs, respectively.
关键词： Donor-Accepter,Near-Infrared,Isomers,Photophysics,Electroluminescence
更新于2025-09-19 17:15:36
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Crosswise Phthalocyanines with Collinear Functionalization: New Paradigmatic Derivatives for Efficient Singlet Oxygen Photosensitization
摘要： We describe here the preparation of a number of trans-ABAB Zn(II) phthalocyanines (ZnPcs) 1a-g, which combine several interesting features. First, these compounds present high solubility and hindered aggregation, due to the functionalization of two facing isoindole constituents (B) of the ZnPc with bis(trifluoromethylphenyl) units. Second, the other two isoindoles (A) hold extra-annulated phthalimide units containing different substituents in the nitrogen positions, this feature resulting in a collinear arrangement of a variety of functional groups. Some of these collinearly functionalized ZnPcs are interesting building blocks for constructing either homo- or heteroarrays containing ZnPc units. On the other hand, the amphiphilic nature of some members of the series renders them interesting candidates for photosensitization of singlet oxygen. Photophysical studies on ZnPc 1c, selected as model compound of the series, have proven these molecules efficient singlet oxygen photosensitizers in both polar and apolar media, with 1O2 quantum yields (ΦΔ) as high as 0.74.
关键词： photophysics,phthalocyanine,fluorescence,collinear functionalization,singlet oxygen
更新于2025-09-19 17:15:36
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On the photo-activation of the S <sub/>0</sub> ?→?S <sub/>1</sub> transition in polyenes
摘要： The evidence provided in this work allows us to conclude that the electronic transition S0 → S1 either for the diphenylhexatriene molecule or for the diphenyloctatetraene molecule is dipole allowed and induced by one‐photon absorption. Consequently, the model to explain the photophysics of these polyenes does not need the existence of an underlying 21Ag excited electronic state, to the converse of what Hudson and Kohler proposed, that the transition S0 → S1 must be induced by two‐photon absorption.
关键词： two‐photon absorption,excitation spectra,photophysics of polyenes
更新于2025-09-19 17:15:36
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Intrinsic photophysics of nitrophenolate ions studied by cryogenic ion spectroscopy
摘要： The intrinsic photophysics of nitrophenolate isomers (meta, para, and ortho) was studied at low temperature using photodissociation mass spectrometry in a cryogenic ion trap instrument. Each isomer has distinct photophysics that affects the excited state lifetimes, as observed experimentally in their spectroscopic linewidths. Visible-light-induced excitation of m-nitrophenolate gives rise to well-resolved vibronic features in the spectrum of the S1 state. The para and ortho isomers have broad spectra – even at cryogenic temperatures – due to their shorter excited state lifetimes and spectral congestion. We present computational evidence for mixing of the first and second excited states of o-nitrophenolate, leading to significant additional broadening in the experimental spectrum.
关键词： excited state lifetimes,cryogenic ion spectroscopy,photophysics,spectral broadening,nitrophenolate
更新于2025-09-19 17:15:36
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Remote Modification of Bidentate Phosphane Ligands Controlling the Photonic Properties in Their Complexes: Enhanced Performance of [Cu(RNa??xantphos)(N <sup>^</sup> N)][PF <sub/>6</sub> ] in Lighta??Emitting Electrochemical Cells
摘要： A series of copper(I) complexes of the type [Cu(HN-xantphos)(N^N)][PF6] and [Cu(BnN-xantphos)(N^N)][PF6], in which N^N = bpy, Mebpy, and Me2bpy, HN-xantphos = 4,6-bis(diphenylphosphanyl)-10H-phenoxazine and BnN-xantphos = 10-benzyl-4,6-bis(diphenylphosphanyl)-10H-phenoxazine is described. The single crystal structures of [Cu(HN-xantphos)(Mebpy)][PF6] and [Cu(BnN-xantphos)(Me2bpy)][PF6] confirm the presence of N^N and P^P chelating ligands with the copper(I) atoms in distorted coordination environments. Solution electrochemical and photophysical properties of the BnN-xantphos-containing compounds (for which the highest-occupied molecular orbital is located on the phenoxazine moiety) are reported. The first oxidation of [Cu(BnN-xantphos)(N^N)][PF6] occurs on the BnN-xantphos ligand. Time-dependent density functional theory (TD-DFT) calculations have been used to analyze the solution absorption spectra of the [Cu(BnN-xantphos)(N^N)][PF6] compounds. In the solid-state, the compounds show photoluminescence in the range 518–555 nm for [Cu(HN-xantphos)(N^N)][PF6] and 520–575 nm for [Cu(BnN-xantphos)(N^N)][PF6] with a blue-shift on going from bpy to Mebpy to Me2bpy. [Cu(BnN-xantphos)(Me2bpy)][PF6] exhibits a solid-state photoluminescence quantum yield of 55% with an excited state lifetime of 17.4 μs. Bright light-emitting electrochemical cells are obtained using this complex, and it is shown that the electroluminescence quantum yield can be enhanced by using less conducting hole injection layers.
关键词： DFT calculations,electroluminescence,photophysics,light-emitting electrochemical cells,ionic copper complexes
更新于2025-09-19 17:13:59
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Bis-Cyclometalated Iridium Complexes Containing 4,4a?2-Bis(phosphonomethyl)-2,2a?2-bipyridine Ligands: Photophysics, Electrochemistry, and High-Voltage Dye-Sensitized Solar Cells
摘要： In this report, the synthesis and characterization of two bis-cyclometalated iridium(III) complexes are presented. Single-crystal X-ray diffraction shows [Ir(ppy)2(4,4′-bis(diethylphosphonomethyl)-2,2′-bipyridine)]PF6 adopts a pseudo-octahedral geometry. The complexes have an absorption feature in the near-visible?UV region and emit green light with excited-state lifetimes in hundreds of nanoseconds. The redox properties of these complexes show reversible behavior for both oxidative and reductive events. [Ir(ppy)2(4,4′-bis(phosphonomethyl)-2,2′-bipyridine)]PF6 readily binds to metal oxide supports, like nanostructured SnIV-doped In2O3 and TiO2, while still retaining reversible redox chemistry. When incorporated as the photoanode in dye-sensitized solar cells, the devices exhibit open-circuit voltages of >1 V, which is a testament to their strength of these iridium(III) complexes as photochemical oxidants.
关键词： high-voltage,dye-sensitized solar cells,bis-cyclometalated iridium(III) complexes,electrochemistry,photophysics
更新于2025-09-19 17:13:59
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Neutral Cyclometalated Iridium(III) Complexes Bearing Substituted N-Heterocyclic Carbene (NHC) Ligands for High-Performance Yellow OLED Application
摘要： The synthesis, crystal structure, and photophysics of a series of neutral cyclometalated iridium(III) complexes bearing substituted N-heterocyclic carbene (NHC) ancillary ligands ((C∧N)2Ir(R-NHC), where C∧N and NHC refer to the cyclometalating ligand benzo[h]quinoline and 1-phenylbenzimidazole, respectively) are reported. The NHC ligands were substituted with electron-withdrawing or -donating groups on C4′ of the phenyl ring (R = NO2 (Ir1), CN (Ir2), H (Ir3), OCH3 (Ir4), N(CH3)2 (Ir5)) or C5 of the benzimidazole ring (R = NO2 (Ir6), N(CH3)2 (Ir7)). The configuration of Ir1 was confirmed by a single-crystal X-ray diffraction analysis. The ground- and excited-state properties of Ir1?Ir7 were investigated by both spectroscopic methods and time-dependent density functional theory (TDDFT) calculations. All complexes possessed moderately strong structureless absorption bands at ca. 440 nm that originated from the C∧N ligand based 1π,π*/1CT (charge transfer)/1d,d transitions and very weak spin?forbidden 3MLCT (metal-to-ligand charge transfer)/3LLCT (ligand-to-ligand charge transfer) transitions beyond 500 nm. Electron-withdrawing substituents caused a slight blue shift of the 1π,π*/1CT/1d,d band, while electron-donating substituents induced a red shift of this band in comparison to the unsubstituted complex Ir3. Except for the weakly emissive nitro-substituted complexes Ir1 and Ir6 that had much shorter lifetimes (≤160 ns), the other complexes are highly emissive in organic solutions with microsecond lifetimes at ca. 540?550 nm at room temperature, with the emitting states being predominantly assigned to 3π,π*/3MLCT states. Although the effect of the substituents on the emission energy was insignificant, the effects on the emission quantum yields and lifetimes were drastic. All complexes also exhibited broad triplet excited-state absorption at 460?700 nm with similar spectral features, indicating the similar parentage of the lowest triplet excited states. The highly emissive Ir2 was used as a dopant for organic light-emitting diode (OLED) fabrication. The device displayed a yellow emission with a maximum current efficiency (ηc) of 71.29 cd A?1, a maximum luminance (Lmax) of 32747 cd m?2, and a maximum external quantum efficiency (EQE) of 20.6%. These results suggest the potential of utilizing this type of neutral Ir(III) complex as an efficient yellow phosphorescent emitter.
关键词： cyclometalated iridium(III) complexes,phosphorescent emitter,OLED,photophysics,N-heterocyclic carbene (NHC) ligands
更新于2025-09-19 17:13:59
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Electronic State and Photophysics of 2-Ethylhexyl-4-methoxycinnamate as UV-B Sunscreen under Jet-Cooled Condition
摘要： The title compound, 2-ethylhexyl-4-methoxycinnamate (2EH4MC), is known as a typical ingredient of sunscreen cosmetics that effectively converts the absorbed UV-B light to thermal energy. This energy conversion process includes the nonradiative decay (NRD): trans?cis isomerization and finally going back to the original structure with a release of thermal energy. In this study, we performed UV spectroscopy for jet-cooled 2EH4MC to investigate the electronic/geometrical structures as well as the NRD mechanism. Laser-induced-fluorescence (LIF) spectroscopy gave the well-resolved vibronic structure of the S1?S0 transition; UV?UV hole-burning (HB) spectroscopy and density functional theory (DFT) calculations revealed the presence of syn and anti isomers, where the methoxy (?OCH3) groups orient in opposite directions to each other. Picosecond UV?UV pump?probe spectroscopy revealed the NRD process from the excited singlet (S1 (1ππ*)) state occurs at a rate constant of ～1010?1011 s?1, attributed to internal conversion (IC) to the 1nπ* state. Nanosecond UV?deep UV (DUV) pump?probe spectroscopy identified a transient triplet (T1 (3ππ*)) state, whose energy (from S0) and lifetime are 18 400 cm?1 and 20 ns, respectively. These results demonstrate that the photoisomerization of 2EH4MC includes multistep internal conversions and intersystem crossings, described as "S1 (trans, 1ππ*) → 1nπ* → T1 (3ππ*) → S0 (cis)".
关键词： nonradiative decay,photophysics,DFT calculations,trans?cis isomerization,jet-cooled spectroscopy,2-ethylhexyl-4-methoxycinnamate,UV-B sunscreen
更新于2025-09-19 17:13:59
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Co-doping metal oxide nanotubes: superlinear photoresponse and multianalyte sensing
摘要： Metal oxide nanotubes and standalone membranes have been extensively researched for potential applications ranging from electronics, optoelectronics, and photocatalysis, to ?ltration and gas sensing. Although the wide-bandgap of these nanotubes poses challenges for their utilization for photochemical conversion and charge transport, doped metal-oxide nanotubes provide an alternative to lower their bandgap and provide charge carriers for conduction and photochemistry. While many single-dopants have been successfully used, co-dopants can be used to manipulate the electronic density of states, photophysical and photochemical properties to obtain new and unexpected functionalities, sometimes even completely different from the individual dopants. Here the co-doped titanium dioxide (TiO2) nanotube membranes are described where the combined properties of the co-dopants differ from their monodoped counterparts. A detailed mechanistic model is provided to explain the new photophysical and photochemical properties of these co-doped metal oxide membranes, and novel functionalities resulting from such properties like superlinear photoresponse and enhanced gas sensing response. In addition, the potential applications of these functionalities are shown in photodetection and multianalyte sensing as portable devices.
关键词： electronic properties,multianalyte sensors,metal-oxide nanotubes,co-doping,photophysics
更新于2025-09-19 17:13:59
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Synthesis and Characterization of CNT Composites for Lasera??Generated Ultrasonic Waves
摘要： In the last few years, extensive progress in ultrasonic wave generation by using multiwalled carbon nanotubes (MWCNTs) in combination with polydimethylsiloxane (PDMS), functional composites, has been achieved. Due to high optical absorption of MWCNTs as perfect absorbers for laser beams and the high thermal expansion coefficient of PDMS, a compact transducer for ultrasonic wave generation at higher frequency can be realized. This study reports a novel method to synthesize MWCNT–PDMS composites deposited on a glass substrate by spray coating, which is done in a short time of 2 h. The layers (0.9–32.2 μm) show low optical transmission properties of 13.9–0.0% at a wavelength of 1047 nm. Apart from using a 1% Triton-X-100 stock solution and then diluted to a 0.1% relatively nonhazardous solution, no toxic chemicals are used. The Triton-X-100 solution is not hazardous for lab handling and is a commonly used lab detergent for the treatment of biological cells. The achieved sound pressure level is 3.4 MPa with a frequency bandwidth of 9.7 MHz. These results show the potential for a fast and nontoxic production of laser-generated ultrasonic transducers, which can be used well in the field of nondestructive material testing of layered materials or in medicine with an appropriate frequency range.
关键词： laser-generated ultrasonic waves,spray-coating methods,multi-walled CNTs,photophysics,nanocomposites,nanoparticles
更新于2025-09-16 10:30:52