The distribution dependent stochastic differential equations (DDSDEs) describe stochastic systems whose evolution is determined by both the microcosmic site and the macrocosmic distribution of the ...particle. The density function associated with a DDSDE solves a nonlinear PDE. Due to the distribution dependence, some standard techniques developed for SDEs do not apply. By iterating in distributions, a strong solution is constructed using SDEs with control. By proving the uniqueness, the distribution of solutions is identified with a nonlinear semigroup Pt∗ on the space of probability measures. The exponential contraction as well as Harnack inequalities and applications are investigated for the nonlinear semigroup Pt∗ using coupling by change of measures. The main results are illustrated by homogeneous Landau equations.
Conspectus In recent decades, research on lignin depolymerization and its downstream product transformation has drawn an enormous amount of attention from academia to industry worldwide, aiming at ...harvesting aromatic compounds from this abundant and renewable biomass resource. Although the lignin conversion can be traced back to the 1930s and various noncatalytic and catalytic methods have been explored to depolymerize lignin via direct lignin conversion research or lignin models conversion studies, the complexity of the lignin structure, various linkages, the high stability of lignin bonds, and the diverse fragments condensation process make lignin depolymerization to monomers a highly challenging task. For the potential practical utilization of lignin, compared with lignin conversion to liquid fuel with extra H2 consumption, maintaining the aromatic structure and preparing high-value aromatic chemicals from renewable lignin is more profitable. Therefore, lignin depolymerization to easy-to-handle aromatic monomers with acceptable conversion and selectivity is of great importance. In this article, we present our recent studies on lignin’s catalytic conversion to aromatic chemicals. First, we introduce our research on protolignin depolymerization via a fragmentation–hydrogenolysis process in alcohol solvents. Then, focusing on the catalytic cleavage of lignin C–C and C–O bonds, we shed light on a recapitulative adjacent functional group modification (AFGM) strategy for the conversion of lignin models. AFGM strategy begins with the adjacent functional group modification of the target C–C or C–O bond to directly decrease the bond dissociation enthalpy (BDE) of targeted bonds or generate new substrate sites to introduce the cleavage reagent for further conversion. Subsequently, on the basis of these two concepts from AFGM, we summarize our strategies on lignin depolymerization, which highlight the effects of lignin structure, catalyst character, and reaction conditions on the efficiency of strategies. In short, the key point for lignin depolymerization to aromatics is promoting the lignin conversion and restraining the condensation. Compared with the complex research on direct lignin conversion, this bottom-up research approach, beginning with lignin model research, can make the conversion mechanism study clear and provide potential methods for the protolignin/technical lignin conversion. In addition, one of our perspectives for lignin utilization is that the products from lignin conversion can be used as monomers for artificial polymerization, such as the simple phenol (PhOH) and other potential acid compounds, or that lignin derivative molecules can be used to synthesize high-value synthetic building blocks.
The use of a chiral, emitting skeleton for axially chiral enantiomers showing activity in thermally activated delayed fluorescence (TADF) with circularly polarized electroluminescence (CPEL) is ...proposed. A pair of chiral stable enantiomers, (−)‐(S)‐Cz‐Ax‐CN and (+)‐(R)‐Cz‐Ax‐CN, was designed and synthesized. The enantiomers, both exhibiting intramolecular π‐conjugated charge transfer (CT) and spatial CT, show TADF activities with a small singlet–triplet energy difference (ΔEST) of 0.029 eV and mirror‐image circularly polarized luminescence (CPL) activities with large glum values. Notably, CP‐OLEDs based on the enantiomers feature blue electroluminescence centered at 468 nm with external quantum efficiencies (EQEs) of 12.5 and 12.7 %, and also show intense CPEL with gEL values of −1.2×10−2 and +1.4×10−2, respectively. These are the first CP‐OLEDs based on TADF‐active enantiomers with efficient blue CPEL.
Let's twist again: Axially chiral molecules with thermally activated delayed fluorescence and circularly polarized electroluminescence (CPEL) are presented. CP‐OLEDs based on these molecules display high efficiencies and blue CPEL with large gEL values.
How do you like your eggs? Amphiphilic carbon dots (CDs) with intense blue fluorescence have been produced from chicken eggs by treatment with plasma. They are used as effective “fluorescent carbon ...inks” for multicolor luminescent inkjet and silk‐screen printing (see image).
Conspectus Lanthanide-doped upconversion nanoparticles (UCNPs) are a special class of luminescent nanomaterials that convert multiwavelength near-infrared (NIR) excitation into tunable emissions ...spanning the deep ultraviolet (UV) to NIR regions. In addition to large anti-Stokes shift, UCNPs also feature a sharp emission bandwidth, long excited-state lifetime, as well as high resistance to optical blinking and photobleaching. Therefore, UCNPs have been identified as promising candidates to solve many challenging problems in fields ranging from biological imaging and therapeutics to photovoltaics and photonics. Nevertheless, the progress of utilizing an upconversion process is being hindered by the limited emission intensity, principally due to low oscillator strength in these nanoparticles. UCNPs essentially resemble the optical characteristics of their bulk counterparts, which take advantage of electronic transition within the 4f configuration of the lanthanide dopants to realize photon energy conversions. In general, a high dopant concentration promotes upconversion luminescence by providing a high density of optical centers to collect and to sustain the energy of the excitation light. However, an increase in dopant concentration induces self-quenching processes that offset the emission gain and may eventually result in attenuation of the overall emission intensity. This phenomenon known as concentration quenching represents a major obstacle to constructing bright UCNPs. In recent years, advances in nanoparticle research have led to the emergence of several strategies for mitigating energy loss at elevated dopant concentrations. In consequence, doping high levels of lanthanide ions in UCNPs has become a viable solution to boosting the emission intensity of photon upconversion. On account of extensive energy exchange interaction in heavily doped UCNPs, the spectrum tunability of photon upconversion is also greatly enhanced. These advances have largely expanded the scope of upconversion research. To provide guidelines for enhancing upconversion through heavy doping, we attempt to review recent advances in the understanding and control of concentration quenching in UCNPs. With significant advancements made in the chemical synthesis, we are now able to exquisitely control the doping of lanthanide ions in various nanoparticles of well-defined size, morphology, and core–shell structure. We show that, by confining energy transfer in nanostructured host materials in conjunction with innovative excitation schemes, concentration quenching of upconversion luminescence is largely alleviated. As a result, unusually high dopant concentrations can be used to construct UCNPs displaying high brightness and large anti-Stokes shift. We demonstrate that the development of heavily doped UCNPs enables advanced bioimaging and photonic applications that can hardly be fulfilled by conventional UCNPs comprising low concentrations of lanthanide dopants.
Transition‐metal sulfides are promising electrochemical energy storage materials due to their abundant active sites, large interlayer space, and high theoretical capacities, especially for sodium ...storage. However, the low conductivity and poor cycling stability at high current densities hamper their applications. Herein, a versatile dual‐template method is reported to elaborate ordered mesoporous single‐layered MoS2/carbon composite with high specific area, uniform pore size, and large pore volume. The single‐layered MoS2 is confined in the carbon matrix. The mesopores between the composite nanorods provide fast electrolyte diffusion. The obtained nanocomposite shows a high sodium‐storage capability, excellent rate capacity, and very good cycling performance. A capacity of 310 mAh g−1 can remain at 5.0 A g−1 after 2500 cycles. Furthermore, a sodium‐ion battery (SIB) full cell composed of the MoS2/carbon composite anode and a Na3V2(PO4)3 (NVP) cathode maintains a specific capacity of 330 mAh g−1 at 1.0 A g−1 during 100 cycles. The mechanism is investigated by in situ and ex situ characterizations as well as density functional theory (DFT) calculations.
A mesoporous single‐layered MoS2/carbon composite is successfully synthesized, which displays remarkable electrochemical performance for both sodium‐ion batteries and sodium‐ion full cells. The reaction mechanism is systematically investigated by in situ and ex situ characterizations. This work may be expected to guide the future design protocol for various mesoporous single‐layered transition‐metal sulfide/carbon composite materials.
Restructuring-induced catalytic activity is an intriguing phenomenon of fundamental importance to rational design of high-performance catalyst materials. We study three copper-complex materials for ...electrocatalytic carbon dioxide reduction. Among them, the copper(II) phthalocyanine exhibits by far the highest activity for yielding methane with a Faradaic efficiency of 66% and a partial current density of 13 mA cm
at the potential of - 1.06 V versus the reversible hydrogen electrode. Utilizing in-situ and operando X-ray absorption spectroscopy, we find that under the working conditions copper(II) phthalocyanine undergoes reversible structural and oxidation state changes to form ~ 2 nm metallic copper clusters, which catalyzes the carbon dioxide-to-methane conversion. Density functional calculations rationalize the restructuring behavior and attribute the reversibility to the strong divalent metal ion-ligand coordination in the copper(II) phthalocyanine molecular structure and the small size of the generated copper clusters under the reaction conditions.
Mobile-edge computing (MEC) and wireless power transfer (WPT) have been recognized as promising techniques in the Internet of Things era to provide massive low-power wireless devices with enhanced ...computation capability and sustainable energy supply. In this paper, we propose a unified MEC-WPT design by considering a wireless powered multiuser MEC system, where a multiantenna access point (AP) (integrated with an MEC server) broadcasts wireless power to charge multiple users and each user node relies on the harvested energy to execute computation tasks. With MEC, these users can execute their respective tasks locally by themselves or offload all or part of them to the AP based on a time-division multiple access protocol. Building on the proposed model, we develop an innovative framework to improve the MEC performance, by jointly optimizing the energy transmit beamforming at the AP, the central processing unit frequencies and the numbers of offloaded bits at the users, as well as the time allocation among users. Under this framework, we address a practical scenario where latency-limited computation is required. In this case, we develop an optimal resource allocation scheme that minimizes the AP's total energy consumption subject to the users' individual computation latency constraints. Leveraging the state-of-the-art optimization techniques, we derive the optimal solution in a semiclosed form. Numerical results demonstrate the merits of the proposed design over alternative benchmark schemes.
Besides genome editing, CRISPR-Cas12a has recently been used for DNA detection applications with attomolar sensitivity but, to our knowledge, it has not been used for the detection of small ...molecules. Bacterial allosteric transcription factors (aTFs) have evolved to sense and respond sensitively to a variety of small molecules to benefit bacterial survival. By combining the single-stranded DNA cleavage ability of CRISPR-Cas12a and the competitive binding activities of aTFs for small molecules and double-stranded DNA, here we develop a simple, supersensitive, fast and high-throughput platform for the detection of small molecules, designated CaT-SMelor (CRISPR-Cas12a- and aTF-mediated small molecule detector). CaT-SMelor is successfully evaluated by detecting nanomolar levels of various small molecules, including uric acid and p-hydroxybenzoic acid among their structurally similar analogues. We also demonstrate that our CaT-SMelor directly measured the uric acid concentration in clinical human blood samples, indicating a great potential of CaT-SMelor in the detection of small molecules.
A couple of fluorescent enantiomers, which are suitable for the emitters of high‐efficiency TADF‐sensitized CP‐OLEDs, have been developed. The enantiomers show configurational stability, high PLQY of ...98 %, large kr of 7.8×107 s−1, and intense CPL activities with |glum| values of about 2.5×10−3. Notably, by using matchable TADF sensitizer, the enantiomers were then exploited as emitter to fabricate CP‐OLEDs. The TADF‐sensitized CP‐OLEDs not only show mirror‐image CPEL activities with gEL values of +1.8×10−3 and −1.4×10−3, but also display fast start‐up featuring with low VT of 3.0 V as well as driving voltage of 4.8 V at 10 000 cd m−2. Meaningfully, the TADF‐sensitized fluorescent devices show high EQEmax of 21.5 % and extremely low efficiency roll‐off, whose EQEs are 21.2 % and 15.3 % at 1000 and 10 000 cd m−2, respectively. The obtained EQEs are comparable to those of CP‐TADF emitters, which provides a promising perspective to break through the EL efficiency limit of CP‐FL emitters.
A couple of fluorescent enantiomers with high PLQY of 98 % and mirror‐imaged CPL activities have been developed to fabricate TADF‐sensitized CP‐OLEDs. The resulting devices not only display intense CPEL with |gEL| of about 1.8×10−3, but also show high EQEmax of 21.5 % with remarkably low efficiency roll‐off, whose EQE is 15.3 % even at 10 000 cd m−2.
PDF
