ortho‐Methyl effects are exploited to tune steric hindrance between side‐chain N,N′‐diaryls and polycyclic dihydrodibenzoa,cphenazine, and in turn control the conformations of ...N,N′‐diphenyl‐dihydrodibenzoa,cphenazine (DPAC) and its ortho‐methyl derivatives Mx‐My (x=0, 1 or 2, y=1 or 2, x and y correlate with the number of methyl groups in the ortho‐positiond of N,N′‐diphenyl). The magnitude of steric hindrance increases as x and y increase, and the V‐shaped dihydrodibenzoa,cphenazine skeleton is gradually tuned from a bent (DPAC) to planar (M2‐M2) structure in the ground state. As a result, the relaxation of the excited‐state structure of DPAC and its numerous analogues could be mimicked by model structures Mx‐My, demonstrating for the first time the the conformation change from bent‐to‐planar and hence a large range of energy‐gap tuning of polycyclic conjugated structures controlled by the steric hindrance.
Six (D)PAC: ortho‐Methyl effects are exploited to tune the steric hindrance between side‐chain N,N′‐diaryls and polycyclic dihydrodibenzoa,cphenazine, and in turn control the conformation and color of N,N′‐diphenyl‐dihydrodibenzoa,cphenazine (DPAC) and its ortho‐methyl derivatives. The results show that simple insertion of a small methyl group overcomes the energy barrier to planarization in the ground state.
Quasi‐2D Ruddlesden–Popper halide perovskites with a large exciton binding energy, self‐assembled quantum wells, and high quantum yield draw attention for optoelectronic device applications. Thin ...films of these quasi‐2D perovskites consist of a mixture of domains having different dimensionality, allowing energy funneling from lower‐dimensional nanosheets (high‐bandgap domains) to 3D nanocrystals (low‐bandgap domains). High‐quality quasi‐2D perovskite (PEA)2(FA)3Pb4Br13 films are fabricated by solution engineering. Grazing‐incidence wide‐angle X‐ray scattering measurements are conducted to study the crystal orientation, and transient absorption spectroscopy measurements are conducted to study the charge‐carrier dynamics. These data show that highly oriented 2D crystal films have a faster energy transfer from the high‐bandgap domains to the low‐bandgap domains (<0.5 ps) compared to the randomly oriented films. High‐performance light‐emitting diodes can be realized with these highly oriented 2D films. Finally, amplified spontaneous emission with a low threshold 4.16 µJ cm−2 is achieved and distributed feedback lasers are also demonstrated. These results show that it is important to control the morphology of the quasi‐2D films to achieve efficient energy transfer, which is a critical requirement for light‐emitting devices.
Quasi‐2D Ruddlesden–Popper halide perovskite thin films with preferential crystal orientation are achieved via solvent engineering. Such highly oriented quasi‐2D films are shown to be suitable for high‐efficiency light‐emitting diodes and low‐threshold amplified spontaneous emission due to the efficient energy transfer from the high‐bandgap domains to low‐bandgap domains. A green‐emission distributed feedback laser is demonstrated.
By using the thiazolo5,4-dthiazole (TzTz) moiety as the core of a proton acceptor, compounds 2,2′-(thiazolo5,4-dthiazole-2,5-diyl)bis(4-tert-butylphenol) ( t -HTTH) and ...4-tert-butyl-2-(5-(5-tert-butyl-2-methoxyphenyl)thiazolo5,4-dthiazol-2-yl)phenol ( t -MTTH) have been strategically designed and synthesized. Upon photoexcitation, both t -HTTH and t -MTTH undergo a reversible type excited-state intramolecular proton transfer (ESIPT), the underlying mechanism of which has been verified by femtosecond early relaxation dynamics in various solvents. The pre-equilibrium in the excited state leads to both normal (∼440 nm) and proton-transfer tautomer (∼560 nm) emissions, for which the intensity ratio is dependent on both the molecular structure and the polarity of surrounding media. As a result, the emission can be widely tuned from blue to yellow via white-light luminescence. On the basis of t -MTTH, a white organic light emitting diode (WOLED) was successfully fabricated, which achieved external quantum efficiency (ηext) of 1.70% with Commission Internationale de L’Eclairage coordinates of (0.29, 0.33). More importantly, the electroluminescent spectra show superior color stability that is independent of luminance. The result demonstrates for the first time a credible WOLED based on a unimolecular ESIPT reaction, which may have far-reaching implications for practical application.
We propose a new concept exploiting thermally activated delayed fluorescence (TADF) molecules as photosensitizers, storage units and signal transducers to harness solar thermal energy. Molecular ...composites based on the TADF core phenoxazine-triphenyltriazine (PXZ-TRZ) anchored with norbornadiene (NBD) were synthesized, yielding compounds PZDN and PZTN with two and four NBD units, respectively. Upon visible-light excitation, energy transfer to the triplet state of NBD occurred, followed by NBD → quadricyclane (QC) conversion, which can be monitored by changes in steady-state or time-resolved spectra. The small S
-T
energy gap was found to be advantageous in optimizing the solar excitation wavelength. Upon tuning the molecule's triplet state energy lower than that of NBD (61 kcal/mol), as achieved by another composite PZQN, the efficiency of the NBD → QC conversion decreased drastically. Upon catalysis, the reverse QC → NBD reaction occurred at room temperature, converting the stored chemical energy back to heat with excellent reversibility.
Light‐emitting diodes (LEDs) with directional and polarized light emission have many photonic applications, and beam shaping of these devices is fundamentally challenging because they are Lambertian ...light sources. In this work, using organic and perovskite LEDs (PeLEDs) for demonstrations, by selectively diffracting the transverse electric (TE) waveguide mode while suppressing other optical modes in a nanostructured LED, the authors first demonstrate highly directional light emission from a full‐area organic LED with a small divergence angle less than 3° and a TE to transverse magnetic (TM) polarization extinction ratio of 13. The highly selective diffraction of only the TE waveguide mode is possible due to the planarization of the device stack by thermal evaporation and solution processing. Using this strategy, directional and polarized emission from a perovskite LED having a current efficiency 2.6 times compared to the reference planar device is further demonstrated. This large enhancement in efficiency in the PeLED is attributed to a larger contribution from the TE waveguide mode resulting from the high refractive index in perovskite materials.
Highly directional and polarized light emission is demonstrated in thin‐film light‐emitting diodes (LEDs) by suppressing the background emission and extracting only the transverse electric (TE) waveguide mode. It is found that the TE waveguide mode increases with the refractive index of the emitting layer and a 2.6 times higher current efficiency is achieved in a perovskite LED.
To increase the accuracy of microbiome data analysis, solving the technical limitations of the existing sequencing machines is required. Quality trimming is suggested to reduce the effect of the ...progressive decrease in sequencing quality with the increased length of the sequenced library. In this study, we examined the effect of the trimming thresholds (0-20 for QIIME1 and 0-30 for QIIME2) on the number of reads that remained after the quality control and chimera removal (the good reads). We also examined the distance of the analysis results to the gold standard using simulated samples.
Quality trimming increased the number of good reads and abundance measurement accuracy in Illumina paired-end reads of the V3-V4 hypervariable region.
Our results suggest that the pre-analysis trimming step should be included before the application of QIIME1 or QIIME2.
For deeper understanding of the coupling of electronic processes with conformational motions, we exploit a tailored strategy to harness the excited-state planarization of N,N′-disubstituted ...dihydrodibenzoa,cphenazines by halting the structural evolution via a macrocyclization process. In this new approach, 9,14-diphenyl-9,14-dihydrodibenzoa,cphenazine (DPAC) is used as a prototype, in which the para sites of 9,14-diphenyl are systematically enclosed by a dialkoxybenzene-alkyl-ester or -ether linkage with different chain lengths, imposing various degrees of constraint to impede the structural deformation. Accordingly, a series of DPAC-n (n = 1–8) derivatives were synthesized, in which n correlates with the alkyl length, such that the strength of the spatial constraint decreases as n increases. The structures of DPAC-1, DPAC-3, DPAC-4, and DPAC-8 were identified by the X-ray crystal analysis. As a result, despite nearly identical absorption spectra (onset ∼400 nm) for DPAC-1–8, drastic chain-length dependent emission is observed, spanning from blue (n = 1, 2, ∼400 nm) and blue-green (n = 3–5, 500–550 nm) to green-orange (n = 6) and red (n = 7, 8, ∼610 nm) in various regular solvents. Comprehensive spectroscopic and dynamic studies, together with a computational approach, rationalized the associated excited-state structure responding to emission origin. Severing the linkage for DPAC-5 via lipase treatment releases the structural freedom and hence results in drastic changes of emission from blue-green (490 nm) to red (625 nm), showing the brightening prospect of these chemically locked DPAC-n in both fundamental studies and applications.
Phenothiazine derivatives based on the 10‐phenyl‐10H‐phenothiazine (NAS) chromophore, namely 7‐phenyl‐7H‐benzocphenothiazine (NAS‐1) and 12‐phenyl‐12H‐benzoaphenothiazine (NAS‐2), were designed and ...synthesized. NAS‐1 and NAS‐2 are constitutional isomers with different steric strains imposed on the phenothiazine core moiety. In solution, the more‐strained NAS‐2 possesses a bent structure and undergoes photoinduced structural planarization (PISP). In the crystal, despite the absence of PISP, bent NAS‐2 exhibits prominent excimer emission as well as emission mechanochromism, which is not observed in the planar‐like NAS and NAS‐1. This unconventional observation results from the bent core structure facilitating π–π stacking of the peripheral naphthalene moieties. Two‐photon‐coupled depth‐dependent emission shows spectral differences between the surface and kernel of the NAS‐2 crystal, and is believed to be a general phenomenon, at least in part, for materials exhibiting emission mechanochromism.
In ′plane′ view: Phenothiazine derivatives were designed and synthesized. In solution, the more‐strained structure (see image) possesses a bent structure and undergoes photoinduced structural planarization (PISP). In the crystal, despite the absence of PISP, it exhibits prominent excimer emission as well as emission mechanochromism.
Abstract
The gut microbiome is an important determinant in various diseases. Here we perform a cross-sectional study of Japanese adults and identify the
Blautia
genus, especially
B. wexlerae
, as a ...commensal bacterium that is inversely correlated with obesity and type 2 diabetes mellitus. Oral administration of
B. wexlerae
to mice induce metabolic changes and anti-inflammatory effects that decrease both high-fat diet–induced obesity and diabetes. The beneficial effects of
B. wexlerae
are correlated with unique amino-acid metabolism to produce S-adenosylmethionine, acetylcholine, and
l
-ornithine and carbohydrate metabolism resulting in the accumulation of amylopectin and production of succinate, lactate, and acetate, with simultaneous modification of the gut bacterial composition. These findings reveal unique regulatory pathways of host and microbial metabolism that may provide novel strategies in preventive and therapeutic approaches for metabolic disorders.
Extrachromosomal telomere repeat (ECTR) DNA is unique to cancer cells that maintain telomeres through the alternative lengthening of telomeres (ALT) pathway, but the role of ECTRs in ALT development ...remains elusive. We found that induction of ECTRs in normal human fibroblasts activated the cGAS-STING-TBK1-IRF3 signaling axis to trigger IFNβ production and a type I interferon response, resulting in cell-proliferation defects. In contrast, ALT cancer cells are commonly defective in sensing cytosolic DNA. We found that STING expression was inhibited in ALT cancer cell lines and transformed ALT cells. Notably, the ALT suppressors histone H3.3 and the ATRX-Daxx histone chaperone complex were also required to activate the DNA-sensing pathway. Collectively, our data suggest that the loss of the cGAS-STING pathway may be required to evade ECTR-induced anti-proliferation effects and permit ALT development, and this requirement may be exploited for treatments specific to cancers utilizing the ALT pathway.
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