Abstract
Harvesting long-lived free triplets in high yields by utilizing organic singlet fission materials can be the cornerstone for increasing photovoltaic efficiencies potentially. However, except ...for polyacenes, which are the most studied systems in the singlet fission field, spin-entangled correlated triplet pairs and free triplets born through singlet fission are relatively poorly characterized. By utilizing transient absorption and photoluminescence spectroscopy in supramolecular aggregate thin films consisting of Hamilton-receptor-substituted diketopyrrolopyrrole derivatives, we show that photoexcitation gives rise to the formation of spin-0 correlated triplet pair
1
(TT) from the lower Frenkel exciton state. The existence of
1
(TT) is proved through faint Herzberg-Teller emission that is enabled by vibronic coupling and correlated with an artifact-free triplet-state photoinduced absorption in the near-infrared. Surprisingly, transient electron paramagnetic resonance reveals that long-lived triplets are produced through classical intersystem crossing instead of
1
(TT) dissociation, with the two pathways in competition. Moreover, comparison of the triplet-formation dynamics in J-like and H-like thin films with the same energetics reveals that spin-orbit coupling mediated intersystem crossing persists in both. However,
1
(TT) only forms in the J-like film, pinpointing the huge impact of intermolecular coupling geometry on singlet fission dynamics.
Molecular triplet excitons produced through singlet fission (SF) usually have shorter triplet lifetimes due to exciton–exciton recombination and relaxation pathways, thereby resulting in complex ...device architectures for SF-boosted solar cells. Using broadband transient absorption spectroscopy, we here show that the photoexcitation of nanostructured lycopene H-aggregates at room temperature produces free triplets with an unprecedented 35-fold enhancement in the lifetime compared to those localized on the monomer backbone. The observed rise of a spectrally blue-shifted correlated T–T pair state in ∼19 ps with distinct vibronic features provides the basis for SF-induced triplet generation.
The self‐assembly of a well‐defined and astutely designed, low‐molecular weight gelator (LMWG) based linker with a suitable metal ion is a promising method for preparing photocatalytically active ...coordination polymer gels. Here, we report the design, synthesis, and gelation behaviour of a tetrapodal LMWG based on a porphyrin core connected to four terpyridine units (TPY‐POR) through amide linkages. The self‐assembly of TPY‐POR LMWG with RuII ions results in a Ru‐TPY‐POR coordination polymer gel (CPG), with a nanoscroll morphology. Ru‐TPY‐POR CPG exhibits efficient CO2 photoreduction to CO (3.5 mmol g−1 h−1) with >99 % selectivity in the presence of triethylamine (TEA) as a sacrificial electron donor. Interestingly, in the presence of 1‐benzyl‐1,4‐dihydronicotinamide (BNAH) with TEA as the sacrificial electron donor, the 8e−/8H+ photoreduction of CO2 to CH4 is realized with >95 % selectivity (6.7 mmol g−1 h−1). In CPG, porphyrin acts as a photosensitizer and covalently attached Ru(TPY)22+ acts as a catalytic center as demonstrated by femtosecond transient absorption (TA) spectroscopy. Further, combining information from the in situ DRIFT spectroscopy and DFT calculation, a possible reaction mechanism for CO2 reduction to CO and CH4 was outlined.
A porphyrin‐based coordination polymer gel (CPG) has been developed for visible/sunlight‐driven CO2 reduction. Notably, the product of CO2 reduction can be modulated by changing the sacrificial electron donor (SED). Ru‐TPY‐POR CPG upon photocatalytic CO2 reduction produces CO (3.5 mmol g−1 h−1 with >99 % selectivity in presence of TEA as SED), whereas in presence of both BNAH and TEA as SED, Ru‐TPY‐POR CPG produces CH4 (6.7 mmol g−1 h−1 with >95 % selectivity).
Erythema nodosum leprosum (ENL) or Type-2 lepra reaction is a manifestation of type-III hypersensitivity response, and usually occurs in certain cases of lepromatous and borderline lepromatous ...leprosy. ENL may present as widespread crops of erythematous, inflamed nodules and papules. Rare variants of ENL mimicking pemphigus or Sweet's syndrome (SS) have been documented. Here, we report an unusual case of persistent ENL in a 52-year-old lady, which we could diagnose with the help of skin biopsy and histopathological examination.
Atypical manifestations of dengue fever (DF) and dengue haemorrhagic fever (DHF) involving different organs are being increasingly recognised, especially in the dengue endemic areas. We report an ...atypical presentation of DF in a 22 year old lady presenting with fever and acute pain in the right hypochondrium, diagnosed to be acute acalculus cholecystitis (AAC).
Spontaneous spinal epidural hematoma Das, Tanima; Kundu, Arup K; Ghosh, Sandip ...
Journal of the Association of Physicians of India
60
Journal Article
There has been a widespread interest in developing self-assembled porphyrin nanostructures to mimic nature’s light-harvesting processes. Herein, porphyrin-based coordination polymer gel (CPG) has ...been developed as a “soft” photocatalyst material for hydrogen (H2) production from water under visible light. The CPG offers a hierarchical nanofibrous network structure obtained through self-assembly of a terpyridine alkyl-amide appended porphyrin (TPY-POR)-based low molecular weight gelator with ruthenium ions (RuII) and produces H2 with a rate of 5.7 mmol g–1 h–1 in the presence of triethylamine (TEA) as a sacrificial electron donor. Further, the Fe2(bdt)(CO)6 (dbt = 1,2-benzenedithiol) cocatalyst, which can mimic the activity of iron hydrogenase, is coassembled in the CPG and shows remarkable improvement in H2 evolution (catalytic activity; rate ∼10.6 mmol g–1 h–1 and turnover number ∼1287). The significant enhancement in catalytic activity was supported by several controlled experiments, including femtosecond transient absorption (TA) spectroscopy and also DFT calculation. The TA study supported the cascade electron transfer process from porphyrin core to Ru(TPY)22+ center, and subsequently, the electron transfers to the cocatalyst Fe2(bdt)(CO)6 for H2 production.
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