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Synthesis, Photophysical and Electrochemical Studies on Peripherally Ruthenated Tetraphenylporphyrin
摘要： Ruthenium(II) complexes of 5-(4-hydroxyphenyl)-10,15,20-tris-(4-methylphenyl)porphyrin and 5,10,15,20-tetrakis(4-hydroxyphenyl)-porphyrin have been synthesized in basic medium and spectroscopically characterized. The complexes show broad bands in the visible region due to overlap of porphyrin transitions with the metal-to-ligand charge transfer (MLCT) transitions arising from cis-Ru(bipy)2Cl2. 1H NMR indicates π-electron interactions between the porphyrin ring and bipyridyl rings. The complexes are emissive both at room temperature and at 77 K with two independent emissions at 77 K, one from the excited state of the porphyrin moiety at 650 and 720 nm and the other from the excited state of the ruthenium moiety at 700 nm. No excited state intramolecular energy transfer reactions have been detected. However the quantum yield of the complexes is reduced due to heavy atom effect. Time resolved fluorescence decay analyses show dual life time at 1.5 and 7.7 ns in dichloromethane. The shorter life time is assigned to singlet-excited state of ruthenium and longer life time to porphyrin singlet excited state. Electrochemical analysis of these species in dichloromethane exhibits three anodic peaks at around 0.68, 0.98 and 1.42 V versus SCE, analogous to the Ru3+/2+ couple and two successive one-electron oxidation processes on the porphyrin ring, respectively. On the other hand, cathodic potentials at around -0.8, -1.4 and -1.54 V versus SCE, with first two peaks corresponding to two successive reduction taking place at the porphyrin ring and the third peak corresponding to reduction of bipyridyl unit. All spectroscopic studies reveal perturbation on the electronic levels of both porphyrin ring and ruthenium chromophore.
关键词： Porphyrin,Ruthenated,Life time,Perturbation,Emission,Electrochemistry
更新于2025-09-23 15:22:29
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Fluorene – Triazine Conjugated Porous Organic Polymer Framework for Superamplified Sensing of Nitroaromatic Explosives
摘要： A porous organic polymer with fluorene and triazine units (PTF), was synthesised through a simple cost effective method. The material was well characterised by FT-IR, solid state 13C NMR and X-ray photoelectron spectroscopic studies. Absorption spectrum indicated the electronic coupling between the two units in the polymer backbone. Experiments proved high thermal and chemical stability, and porous nature of the material. Luminescence of PTF was quenched, on the addition of ppb level concentration of nitroaromatic compounds. This was attributed to the photo induced electron transfer from the electron rich polymer backbone to the electron deficient nitro aromatic compounds. The observed superamplification effect in the fluorescence quenching was studied extensively by a series of ground state absorption, steady state and time resolved fluorescence experiments. Finally, the superamplified quenching was successfully assigned to static quenching by quenching sphere of action model. High value of static quenching constant of the order of 3.9 × 103 M-1, for picric acid combined with detection limit as low as 89 ppb envisages PTF as an effective chemosensor for nitroaromatic explosives.
关键词： sphere of action model,porous polymer,fluorescence life-time,Stern-Volmer plot,cyanuric chloride,fluorescence quenching
更新于2025-09-23 15:21:21
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Light scattering effect of polyvinyl-alcohol/titanium dioxide nanofibers in the dye-sensitized solar cell
摘要： In the present work, polyvinyl-alcohol/titanium dioxide (PVA/TiO2) nanofibers are utilized as a light scattering layer (LSL) on top of the TiO2 nanoparticles photoanode. The TiO2 nanoparticles decorated PVA/TiO2 nanofibers display a power conversion efficiency (PCE) of 4.06%, which is 33% higher than tio2 nanoparticles without LSL, demonstrating the incorporation of PVA/TiO2 nanofibers as LSL reduces the radiation loss and increases the excitation of the electron that leads to high PCE. The incorporation of PVA/TiO2 nanofibers as LSL also increases the electron life time and charge collection efficiency in comparison to the TiO2 nanoparticles without LSL.
关键词： power conversion efficiency,dye-sensitized solar cell,PVA/TiO2 nanofibers,light scattering layer,electron life time
更新于2025-09-19 17:13:59
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Carrier lifetime exceeding 81 ns in single crystalline perovskite nanowires enable large on-off ratio photodetectors
摘要： Single crystalline perovskite nanowires are ideal candidates for photodetection and other optoelectronic applications due to their unique advantage of allowing the manipulation of light and carriers in nanoscale via the naturally formed boundaries. Although significant efforts have been made to grow high quality single crystalline perovskite nanowires, their carrier life times are much shorter than their bulk single crystal counterparts. Here, based on the surface initiated solution growth method with fine kinetic control, we fabricate high quality single crystalline MAPbI3 nanowires with the carrier life time as long as 81 ns, which outperforms the performances of all other solution processed single crystalline MAPbI3 nanowires. The as-prepared metal-semiconductor-metal photodetector has an extremely low dark current of 180 fA under 1 V bias, and a current of 340 pA under illumination of 10.2 mW/cm2, corresponding to an on-off current ratio of 1880, which is the largest on-off ratio in photodetectors based on MAPbI3 nanowires without any passivation treatment. Such superior performance is attributed to the long carrier life time of the as-grown MAPbI3 nanowires with reduced grain boundaries. The realized high performance MAPbI3 nanowire photodetector would find potential applications in imaging sensors.
关键词： Nanowire,Perovskite,Single-crystalline,Photodetection,Carrier life time
更新于2025-09-19 17:13:59