We report a cationic porphyrin 5,10,15,20‐tetrakis‐(4‐N‐methylpyridyl)‐porphyrin (TMPyP) that can respond to specific bacteria, followed by adaptable photodynamic/photothermal therapy processes. ...TMPyP could be reduced to phlorin by facultative anaerobes with a strong reducing ability such as E. coli and S. typhimurium in hypoxic environments, possessing strong NIR absorption and remarkable photothermal conversion capacity, thus demonstrating excellent antimicrobial activity (>99 %) by photothermal therapy. While in an aerobic environment with aerobic bacteria, TMPyP functioned as a typical photosensitizer that killed bacteria effectively (>99.9 %) by photodynamic therapy. By forming a host–guest complex with cucurbit7uril, the biocompatibility of TMPyP significantly improved. This kind of bacteria‐responsive porphyrin shows specificity and adaptivity in antimicrobial treatment and holds potential in non‐invasive treatments of bacterial infections.
A cationic porphyrin that can respond to specific bacteria followed by adaptable photodynamic/photothermal therapy is reported. It can be reduced to phlorin by reductive facultative anaerobes in hypoxic environments, possessing NIR photothermal conversion ability and demonstrating excellent antimicrobial activity by photothermal therapy. With aerobic bacteria, it functions as an efficient antibacterial photosensitizer by photodynamic therapy.
Concerning that the residues of photosensitizers (PS) may cause serious side effects under light, it is of great significant to timely switch‐off PS after photodynamic therapy (PDT). Herein, we ...proposed a supramolecular strategy to regulate the activity of PS, fabricating a supramolecular PS with improved reactive oxygen species (ROS) generation efficiency and accelerated self‐degradation ability. During PDT treatment, the supramolecular PS exhibited good therapeutic efficiency as well as reduced dark toxicity. Moreover, the supramolecular PS could be degraded by ROS generated by itself and lose its PDT activities once PDT treatment finished. In this way, the side effects of PDT can be reduced without sacrificing the therapeutic efficiency. This work provides a novel strategy for smarter PDT beacon to further improve the safety of PDT treatment.
A supramolecular photosensitizer with improved ROS generation efficiency and accelerated self‐degradation ability was reported. Apart from the excellent photodynamic therapeutic efficiency and good biocompatibility, the supramolecular photosensitizer could be photodegraded and lose its PDT activity once PDT treatment finished. Therefore, the side effects of PDT can be reduced without sacrificing the therapeutic efficiency.
We use global three-dimensional radiation magnetohydrodynamical simulations to study accretion disks onto a black hole with accretion rates varying from to . We initialize the disks with a weakly ...magnetized torus centered at either 50 or 80 gravitational radii, leading to self-consistent turbulence generated by the magnetorotational instability (MRI). The inner regions of all disks have radiation pressure ∼104-106 times the gas pressure. Nonaxisymmetric density waves that steepen into spiral shocks form as gas flows toward the black hole. Maxwell stress from MRI turbulence can be larger than the Reynolds stress only when the net vertical magnetic flux is sufficiently large. Outflows are formed with a speed of ∼0.1-0.4c. When the accretion rate is smaller than , outflows are launched from ∼10 gravitational radii, and the radiative efficiency is ∼5%-7%. For an accretion rate reaching , most of the funnel region near the rotation axis becomes optically thick, and the outflow is launched from beyond 50 gravitational radii. The radiative efficiency is reduced to 1%. We always find that the kinetic energy luminosity associated with the outflow is at most ∼15%-30% of the radiative luminosity. The mass flux in the outflow is ∼15%-50% of the net mass accretion rates. We discuss the implications of our simulation results on the observational properties of these disks.
Abstract
Highly efficient recycling of carbon fiber reinforced polymer composites into monomers and fibers is a formidable challenge. Herein, we present a closed‐loop recycling approach for carbon ...fiber reinforced polymer composites using reversible amidation chemistry, which enables the complete recovery of intact carbon fibers and pure monomers. The polymer network, synthesized by amidation between a macromonomer linear polyethyleneimine and a bifunctional maleic anhydride cross‐linker, serves as a matrix for the construction of composites with exceptional mechanical properties, thermal stability and solvent resistance. The matrices can be fully depolymerized under the acidic condition at ambient temperature, allowing the effective separation and recovery of both carbon fibers and the two monomers. The reclaimed carbon fibers retain nearly identical mechanical properties to pristine ones, while pure monomers are recycled with high separation yields (>93 %). They can be reused in for multiple cycles for the manufacture of new composites, whose mechanical properties recover over 95 % of their original properties. This line of research presents a promising approach for the design of high‐performance and sustainable thermoset composites, offering significant environmental and economic benefits.
Organic radicals are important species with single electrons. Because of their open-shell structure, they are widely used in functional materials, such as spin probes, magnetic materials and ...optoelectronic materials. Owing to the high reactivity of single electrons, they often serve as a key intermediate in organic synthesis. Therefore, tuning the stability of radicals is crucial for their functions. Herein, we summarize covalent and non-covalent approaches to tune the stability of organic radicals through steric effects and tuning the delocalization of spin density. Covalent approaches can tune the stability of radicals effectively and non-covalent approaches benefit from dynamicity and reversibility. It is anticipated that the further development of covalent and non-covalent approaches, as well as the interplay between them, may push the fields forward by enriching new radical materials and radical mediated reactions.
Covalent and non-covalent approaches to tune the stability of organic radicals through steric effects and the delocalization of spin density.
ABSTRACT Stream-stream collisions play an important role in the circularization of highly eccentric streams that result from tidal disruption events (TDEs). We perform three-dimensional radiation ...hydrodynamic simulations to show that stream collisions can contribute significant optical and ultraviolet light to the flares produced by TDEs, and can explain the majority of the observed emission. Our simulations focus on the region near the radiation-pressure-dominated shock produced by a collision and track how the kinetic energy of the stream is dissipated by the associated shock. When the mass flow rate of the stream is a significant fraction of the Eddington accretion rate, 2% of the initial kinetic energy is converted to radiation as a result of the collision. In this regime, the collision redistributes the specific kinetic energy into the downstream gas and more than 16% of the mass can become unbound. The fraction of unbound gas decreases rapidly as drops significantly below the Eddington limit, with no unbound gas being produced when drops to 1% of Eddington; we find, however, that the radiative efficiency increases slightly to 8% in these cases of low . The effective radiation temperature and size of the photosphere are determined by the stream velocity and , and we find them to be a few times 104 K and 1014 cm in our calculations, comparable to the values inferred for some TDE candidates. The size of the photosphere is directly proportional to , which can explain its rapidly changing size as seen in TDE candidates such as PS1-10jh.
The development of non‐covalent synthetic strategy to fabricate efficient photocatalysts is of great importance in theranostic and organic materials. Herein, a fluorochrome N,N′‐dimethyl ...2,5‐bis(4‐pyridinium)thiazolo5,4‐dthiazolediiodide (MPT) was transformed into an efficient photocatalyst through supramolecular dimerization in the cavity of cucurbit8uril (CB8). The host‐enhanced charge transfer interaction within the supramolecular dimer 2MPT‐CB8 dramatically promoted intersystem crossing to produce triplet. In addition, the staggered conformation of 2MPT‐CB8 facilitated the energy transfer and electron transfer of the triplet. As a result, 2MPT‐CB8 could serve as a high‐efficiency photocatalyst for the oxidative hydroxylation of arylboronic acids. This supramolecular dimerization strategy enriches the supramolecular engineering of functional π‐systems. It is anticipated that this strategy can be extended to fabricate various π‐systems with tailor‐made functions.
An efficient fluorochrome was transformed into a high‐performance photocatalyst through the facile fabrication of supramolecular dimer. Owing to the host‐enhanced charge transfer interaction, the intersystem crossing was promoted and the followed electron transfer was facilitated. Therefore, the supramolecular dimer exhibited excellent photocatalytic property for the oxidative hydroxylation of arylboronic acids.
We study the structure of accretion disks around supermassive black holes in the radial range of -100 gravitational radii, using a three-dimensional radiation magnetohydrodynamic simulation. For ...typical conditions in this region of active galactic nuclei (AGNs), the Rosseland mean opacity is expected to be larger than the electron scattering value. We show that the iron opacity bump causes the disk to be convectively unstable. Turbulence generated by convection puffs up the disk due to additional turbulent pressure support and enhances the local angular momentum transport. This also results in strong fluctuations in surface density and heating of the disk. The opacity drops with increasing temperature and convection is suppressed. The disk cools down and the whole process repeats again. This causes strong oscillations of the disk scale height and luminosity variations by more than a factor of 3-6 over a few years' timescale. Since the iron opacity bump will move to different locations of the disk for black holes with different masses and accretion rates, we suggest that this is a physical mechanism that can explain the variability of AGN with a wide range of amplitudes over a timescale of years to decades.
Cucurbit[n]urils for Supramolecular Catalysis Tang, Bohan; Zhao, Jiantao; Xu, Jiang‐Fei ...
Chemistry : a European journal,
December 1, 2020, Letnik:
26, Številka:
67
Journal Article
Recenzirano
The control over chemical reactivity and selectivity are always pursued. Using non‐covalent interactions to achieve efficient and selective catalysis is an essential goal of supramolecular catalysis. ...Supramolecular catalysis based on cucurbitnurils (CBns) possesses distinct characteristics for the unique structure of CBns. CBns are a family of pumpkin‐shaped host molecules with various molecular sizes, rigid structures, electronegative portals and wealthy host‐guest chemistry. Herein, we summarize the three major mechanisms of CBns based supramolecular catalysis. Owing to the structural properties of CBns, CBns can serve as nanoreactors and steric hindrance to modulate the reactivity of substrates. They can also catalyze the reactions by modulating the reactivity of ionized intermediates. Recent progresses on the CBns based supramolecular catalysis are introduced in this Minireview and the future development in this field is discussed. It is anticipated that this review provides insights into the mechanism of CBns based supramolecular catalysis and may help scientists find new opportunities in this field.
The major mechanisms of CBns based supramolecular catalysis are summarized. CBns can serve as nanoreactors and steric hindrance to modulate the reactivity of substrates. They can also catalyze the reactions by modulating the reactivity of ionized intermediates. Recent progresses on the CBns‐based supramolecular catalysis are also introduced. It is anticipated that this review helps scientists find new opportunities in this field.
Numerical solutions of the cosmic-ray (CR) magnetohydrodynamic equations are dogged by a powerful numerical instability, which arises from the constraint that CRs can only stream down their gradient. ...The standard cure is to regularize by adding artificial diffusion. Besides introducing ad hoc smoothing, this has a significant negative impact on either computational cost or complexity and parallel scalings. We describe a new numerical algorithm for CR transport, with close parallels to two-moment methods for radiative transfer under the reduced speed of light approximation. It stably and robustly handles CR streaming without any artificial diffusion. It allows for both isotropic and field-aligned CR streaming and diffusion, with arbitrary streaming and diffusion coefficients. CR transport is handled explicitly, while source terms are handled implicitly. The overall time step scales linearly with resolution (even when computing CR diffusion) and has a perfect parallel scaling. It is given by the standard Courant condition with respect to a constant maximum velocity over the entire simulation domain. The computational cost is comparable to that of solving the ideal MHD equation. We demonstrate the accuracy and stability of this new scheme with a wide variety of tests, including anisotropic streaming and diffusion tests, CR-modified shocks, CR-driven blast waves, and CR transport in multiphase media. The new algorithm opens doors to much more ambitious and hitherto intractable calculations of CR physics in galaxies and galaxy clusters. It can also be applied to other physical processes with similar mathematical structure, such as saturated, anisotropic heat conduction.
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