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Exciton behavior is crucial for improving the optoelectronic property of a light‐emitting conjugated polymer. Herein, the photoexcitation dynamics of exciton migration and energy transfer in a self‐doped β‐conformation film of the polydiarylfluorenes (poly[4‐(octyloxy)‐9,9‐diphenylfluoren‐2,7‐diyl]‐co‐[5‐(octyloxy)‐9,9‐ diphenylfluoren‐2,7‐diyl], PODPF) are demonstrated. Compared to the first generation of the β‐conformation polyfluorene, poly(9,9‐dioctylfluorene) (PFO), energy transfer occurs in PODPF β‐conformation films in a time period of ≈150 ps, much longer than those of the PFO ones (<5 ps), associated with the effective intrachain energy transfer (few hundred picoseconds), rather than interchain Förster energy transfer (a few picoseconds). Similar to PFO, the PODPF β‐conformation also displays well‐resolved vibronic emission peaks at 20 K, attributed to the planar and rigid conformation. Interestingly, a residual 0‐0 band emission of nonplanar conformation chain segments (435 nm, 2.85 eV) at 20 K also further confirms the exciton migration from the amorphous state to the β‐conformation domain in PODPF films. Therefore, the stable dual amplified spontaneous emission (ASE) behavior of the PODPF self‐doped films at 461 nm (2.69 eV) and 483 nm (2.57 eV), originates from the individual amorphous and β‐conformation domains. [ABSTRACT FROM AUTHOR]

Background: It is important that population cohorts at increased risk of hospitalisation and death following a COVID‐19 infection are identified and protected. Objectives: We identified risk factors associated with increased risk of hospitalisation, intensive care unit (ICU) admission and mortality in inner North East London (NEL) during the first UK COVID‐19 wave. Methods: Multivariate logistic regression analysis on linked primary and secondary care data from people aged 16 or older with confirmed COVID‐19 infection between 01/02/2020 and 30/06/2020 determined odds ratios (OR), 95% confidence intervals (CI) and P‐values for the association between demographic, deprivation and clinical factors with COVID‐19 hospitalisation, ICU admission and mortality. Results: Over the study period, 1781 people were diagnosed with COVID‐19, of whom 1195 (67%) were hospitalised, 152 (9%) admitted to ICU and 400 (23%) died. Results confirm previously identified risk factors: being male, or of Black or Asian ethnicity, or aged over 50. Obesity, type 2 diabetes and chronic kidney disease (CKD) increased the risk of hospitalisation. Obesity increased the risk of being admitted to ICU. Underlying CKD, stroke and dementia increased the risk of death. Having learning disabilities was strongly associated with increased risk of death (OR = 4.75, 95% CI = [1.91, 11.84], P =.001). Having three or four co‐morbidities increased the risk of hospitalisation (OR = 2.34, 95% CI = [1.55, 3.54], P <.001; OR = 2.40, 95% CI = [1.55, 3.73], P <.001 respectively) and death (OR = 2.61, 95% CI = [1.59, 4.28], P <.001; OR = 4.07, 95% CI = [2.48, 6.69], P <.001 respectively). Conclusions: We confirm that age, sex, ethnicity, obesity, CKD and diabetes are important determinants of risk of COVID‐19 hospitalisation or death. For the first time, we also identify people with learning disabilities and multi‐morbidity as additional patient cohorts that need to be actively protected during COVID‐19 waves. [ABSTRACT FROM AUTHOR]

The effect of substituting o‐carborane into the most sterically hindered positions of phenanthrene and benzo(k)tetraphene is reported. Synthesised via a Bull–Hutchings–Quayle benzannulation, the crystal structures of these non‐linear acenes exhibited the highest aromatic deformation parameters observed for any reported carborane compound to date, and among the largest carboranyl C−C bond length of all organo‐substituted o‐carboranes. Photoluminescence studies of these compounds demonstrated efficient intramolecular charge‐transfer, leading to aggregation induced emission properties. Additionally, an unusual low‐energy excimer was observed for the phenanthryl compound. These are two new members of the family of carborane‐functionalised non‐linear acenes, notable for their peculiar structures and multi‐luminescent properties. [ABSTRACT FROM AUTHOR]

The role of the carborane isomer is investigated on the structural and photophysical properties of molecules comprising a carborane cluster and a conjugated organic moiety is investigated by synthesizing isomeric o‐, m‐, and p‐carboranyl‐anthracene donor–acceptor dyads. While appending a carborane leads to emission from a low energy intramolecular charge transfer state for the o‐isomer, as well as emission from an excited state localized on the anthracene, this is not the case for the m‐ and p‐carborane derivatives. This difference is attributed to a lower electron affinity for the latter two isomers. However, adding both m‐ and p‐ deforms the aromatic backbone and increases its structural rigidity, reducing non‐radiative decay pathways and hence enhancing photoluminescence quantum efficiency relative to anthracene. [ABSTRACT FROM AUTHOR]

Abstract: The synthesis of a highly twisted chrysene derivative incorporating two electron deficient o‐carboranyl groups is reported. The molecule exhibits a complex, excitation‐dependent photoluminescence, including aggregation‐induced emission (AIE) with good quantum efficiency and an exceptionally long singlet excited state lifetime. Through a combination of detailed optical studies and theoretical calculations, the excited state species are identified, including an unusual excimer induced by the presence of o‐carborane. This is the first time that o‐carborane has been shown to induce excimer formation ab initio, as well as the first observation of excimer emission by a chrysene‐based small molecule in solution. Bis‐o‐carboranyl chrysene is thus an initial member of a new family of o‐carboranyl phenacenes exhibiting a novel architecture for highly‐efficient multi‐luminescent fluorophores. [ABSTRACT FROM AUTHOR]

ABSTRACT Poly(phenylene methylene) (PPM) exhibits pronounced blue fluorescence in solutions as well as in the solid state despite its non-π-conjugated nature. Optical spectroscopy was used to explore the characteristics and the physical origin of its unexpected optical properties, namely absorption in the 350-450 nm and photoluminescence in the 400-600 nm spectral regions. It is shown that PPM possesses two discrete optically active species, and a relatively long photoluminescence lifetime (>8 ns) in the solid-state. Given the evidence reported herein, π-stacking and aggregation/crystallization, as well as the formation of anthracene-related impurities, are excluded as the probable origins of the optical properties. Instead there is sufficient evidence that PPM supports homoconjugation, that is: π-orbital overlap across adjacent repeat units enabled by particular chain conformation(s), which is confirmed by DFT calculations. Furthermore, poly(2-methylphenylene methylene) and poly(2,4,6-trimethylphenylene methylene) - two derivatives of PPM - were synthesized and found to exhibit comparable spectroscopic properties, confirming the generality of the findings reported for PPM. Cyclic voltammetry measurements revealed the HOMO-LUMO gap to be 3.2-3.3 eV for all three polymers. This study illustrates a new approach to the design of light-emitting polymers possessing hitherto unknown optical properties. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 707-720 [ABSTRACT FROM AUTHOR]