Actualizing full singlet exciton yield via a reverse intersystem crossing from the high‐lying triplet state to singlet state, namely, “hot exciton” mechanism, holds great potential for ...high‐performance fluorescent organic light‐emitting diodes (OLEDs). However, incorporating comprehensive insights into the mechanism and effective molecular design strategies still remains challenging. Herein, three blue emitters (CNNPI, 2TriPE‐CNNPI, and 2CzPh‐CNNPI) with a distinct local excited (LE) state and charge‐transfer (CT) state distributions in excited states are designed and synthesized. They show prominent hybridized local and charge‐transfer (HLCT) states and aggregation‐induced emission enhancement properties. The “hot exciton” mechanism based on these emitters reveals that a balanced LE/CT distribution can simultaneously boost photoluminescence efficiency and exciton utilization. In particular, a nearly 100% exciton utilization is achieved in the electroluminescence (EL) process of 2CzPh‐CNNPI. Moreover, employing 2CzPh‐CNNPI as the emitter, emissive dopant, and sensitizing host, respectively, the EL performances of the corresponding nondoped pure‐blue, doped deep‐blue, and HLCT‐sensitized fluorescent OLEDs are among the most efficient OLEDs with a “hot exciton” mechanism to date. These results could shed light on the design principles for “hot exciton” materials and inspire the development of next‐generation high‐performance OLEDs.
Full exciton utilization is achieved in the electroluminescence process of 2CzPh‐CNNPI, owing to the balanced distribution of locally excited and charge‐transfer states. Further, this molecule is the first “hot exciton” material that can be employed as the emitter, emissive dopant, and sensitizing host, respectively, and simultaneously achieve high performance in the corresponding blue and host‐sensitized fluorescent organic light‐emitting diodes.
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Bioconversion of natural microorganisms generally results in a mixture of various compounds. Downstream processing (DSP) which only targets a single product often lacks economic competitiveness due ...to incomplete use of raw material and high cost of waste treatment for by‐products. Here, we show with the efficient microbial conversion of crude glycerol by an artificially evolved strain and how a catalytic conversion strategy can improve the total products yield and process economy of the DSP. Specifically, Clostridium pasteurianum was first adapted to increased concentration of crude glycerol in a novel automatic laboratory evolution system. At m3 scale bioreactor the strain achieved a simultaneous production of 1,3‐propanediol (PDO), acetic and butyric acids at 81.21, 18.72, and 11.09 g/L within only 19 h, respectively, representing the most efficient fermentation of crude glycerol to targeted products. A heterogeneous catalytic step was developed and integrated into the DSP process to obtain high‐value methyl esters from acetic and butyric acids at high yields. The coproduction of the esters also greatly simplified the recovery of PDO. For example, a cosmetic grade PDO (96% PDO) was easily obtained by a simple single‐stage distillation process (with an overall yield more than 77%). This integrated approach provides an industrially attractive route for the simultaneous production of three appealing products from the crude glycerol fermentation broth, which greatly improve the process economy and ecology.
The crude glycerol tolerance and 1,3‐propanediol production of Clostridium pasteurianum were significantly enhanced by subjecting the strain to a novel automatic adaptive laboratory evolution system. A heterogeneous catalytic step was developed and integrated into the downstream process for coproducing high‐value ester of acetic and butyric acids with 1,3‐propanediol. This integrated approach provides an industrially attractive route for simultaneous production of three appealing products from crude glycerol, which greatly improves the process economy and ecology.
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Scanning tunneling microscope (STM) has presented a revolutionary methodology to nanoscience and nanotechnology. It enables imaging of the topography of surfaces, mapping the distribution of ...electronic density of states, and manipulating individual atoms and molecules, all at atomic resolutions. In particular, atom manipulation capability has evolved from fabricating individual nanostructures toward the scalable production of the atomic‐sized devices bottom‐up. The combination of precision synthesis and in situ characterization has enabled direct visualization of many quantum phenomena and fast proof‐of‐principle testing of quantum device functions with immediate feedback to guide improved synthesis. Several representative examples are reviewed to demonstrate the recent development of atomic‐scale manipulation, focusing on progress that addresses quantum properties by design in several technologically relevant materials systems. Integration of several atomically precisely controlled probes in a multiprobe STM system vastly extends the capability of in situ characterization to a new dimension where the charge and spin transport behaviors can be examined from mesoscopic to atomic length scale. The automation of atomic‐scale manipulation and the integration with well‐established lithographic processes further push this bottom‐up approach to a new level that combines reproducible fabrication, extraordinary programmability, and the ability to produce large‐scale arrays of quantum structures.
The recent developments in atomic‐scale manipulation with scanning tunneling microscopy (STM) are reviewed. In particular, the review focuses on the progress that addresses quantum properties by design through the precise control of atomic structures in several technologically relevant materials systems. In situ characterization with single‐ and multiprobe STM is discussed, which is utilized for thorough determination of electronic structures.
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Searching for low‐cost, high‐efficiency, bifunctional, non‐noble‐metal electrocatalysts for overall water splitting is crucial to renewable energy conversion. Herein, a series of ...component‐controllable CC/CNTs@CoSxSe2(1−x) (CC: carbon cloth, CNT: carbon nanotube) with excellent bifunctional properties in the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) were obtained by chemical vapor deposition. In this strategy, the Zif‐67 precursor served as a structural inducer, which was directly grown on CC and pyrolyzed with the assistance of melamine to form multi‐walled CNT‐encapsulated CoSxSe2(1−x) hierarchical nanostructures. Subsequently, the electrocatalytic properties of the as‐prepared materials were optimized by adjusting the S/Se molar ratio. Of note is that the lattice distortion caused by the different radii of Se and S generated a polarized electric field for easy adsorption of the intermediate products. The CoOOH generated in situ on the surface of CoSxSe2(1−x), as well as n‐ and p‐type domains in carbon, synergistically resulted in abundant active sites to boost the electrocatalytic activity. CC/CNTs@CoS0.74Se0.52 exhibited overpotentials for the HER and OER of 225 and 285 mV, respectively and attained a current density of 10 mA cm−2 in alkaline solution. The as‐prepared electrocatalysts could act as both cathode and anode in a water electrolyzer showing a cell voltage of 1.74 V and delivering 10 mA cm−2, comparable to those of noble‐metal‐based water electrolyzers.
Two in one: Carbon nanotubes (CNTs)@CoSxSe2(1−x) hierarchical nanostructures are directly grown on carbon cloth by chemical vapor deposition. The resulting bifunctional electrocatalysts with controllable composition, highly exposed active sites, and outstanding durability show activity in both the hydrogen and oxygen evolution reactions, and they can act as both anode and cathode in a water electrolyzer.
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•A martingale model for capturing the evolution of forecasting uncertainty of wind energy.•Stochastic programming models for determining operation strategies of hydro-wind hybrid ...system.•Tradeoff effects and influencing mechanism between hydropower and wind energy identified.•Case study that optimizes the integrated operation policies of hydro-wind hybrid system.
Integrated operation of hydropower and wind power, which exploites the former’s regulation flexibility to complement the uncertainty of the latter, enhances the utilization efficiency of wind power at the expense of deteriorating long-term hydropower energy production. This study identified the tradeoff effects of hydro–wind integrated operation by establishing a framework of coupling models. A martingale model that captures the evolution of forecasting uncertainty was used to generate synthetic scenarios of uncertain load demand. A stochastic programming model for integrated operation was established by tracking the influence of wind power uncertainty. A deterministic simulation model for independent operation was developed to derive independent operation strategies. By comparing the differences in operation strategies systematically, we analyzed the optimization and influencing mechanisms through groups of numerical experiments. A hypothetical case study based on the operation of the electrical system of the Three Gorges Dam project in China during the drawdown season revealed the following. (1) The positive effect of reducing wind energy shortfall and curtailment is determined by the ability of regulated hydropower to track the uncertainty of wind power output. (2) The negative effect primarily reduces the end storage and the stored energy of hydropower, thereby increasing the risk of future water/energy shortages and reducing reliability. (3) The positive effect on wind power presents a varied regime, whereas the negative effect on hydropower increases (decreases) with uncertainty level and inflow level (as the initial reservoir storage increases). The proposed methodology provides new insights into quantifying the effects of hybrid hydro–wind operation to inform decision-making.
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Bias‐stress stability is essential to the practical applications of organic field‐effect transistors (OFETs), yet it remains a challenge issue in conventional planar OFETs. Here, the feasibility of ...achieving high bias‐stress stability in vertical structured OFETs (VOFETs) in combination with doping techniques is demonstrated. VOFETs with silver nanowires as source electrodes are fabricated and the device performance is optimized by understanding the influence of device parameters on performance. Then, the bias‐stress stability of the optimized PDVT‐10 VOFETs is investigated and found to be superior to the corresponding planar OFETs, which is attributed to reduced trapping effects of gate dielectrics in the VOFETs. Moreover, the bias‐stress stability can be further improved by doping PDVT‐10 to passivate bulk traps. Consequently, the characteristic time of doped PDVT‐10 VOFETs extracted from stretched exponential equation is found to be over four times larger than that of the planar PDVT‐10 OFETs under the same bias‐stress conditions. These results present the promising applications of VOFETs as well as an effective strategy to achieve highly bias‐stress stable OFETs.
Vertical organic field‐effect transistors (VOFETs) are shown to possess superior bias‐stress stability (BSS) than planar OFETs counterparts due to the special operation mechanism of them, and doping organic semiconductor layers in VOFETs to passivate bulk traps can further enhance BSS. The work presents an effective strategy to achieve highly bias‐stress stable OFETs.
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The exploration of biocompatible materials with circularly polarized luminescence (CPL) activity is becoming an attractive topic due to the great potential application in biosensing and bioimaging. ...Here, we describe a strategy to fabricate new CPL-active biomaterials using achiral carbazole-based biscyanine fluorophores coassembled with chiral deoxyribonucleic acid (DNA) molecules. This cyanine molecule has been shown to behave as a DNA detecting probe, featuring strong fluorescent emission induced by restriction of intramolecular rotation (RIR). When the achiral cyanine molecules are bound to the minor groove of DNA via electrostatic attraction in aqueous solution, the chirality of the DNA molecules can be transferred to the confined RIR cyanine dyes, triggering a remarkable circularly polarized luminescent emission. The chirality of the CPL signal can be regulated by the structures of the DNA templates. Stimuli-responsive CPL activates were observed from DNA–cyanine complexes. We further verified this strategy on different DNA-based nanomaterials, including DNA origami nanostructure. Our design presents a new avenue to fabricate compatible CPL materials.
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In the bottom-up synthesis of graphene nanoribbons (GNRs) from self-assembled linear polymer intermediates, surface-assisted cyclodehydrogenations usually take place on catalytic metal surfaces. Here ...we demonstrate the formation of GNRs from quasi-freestanding polymers assisted by hole injections from a scanning tunnelling microscope (STM) tip. While catalytic cyclodehydrogenations typically occur in a domino-like conversion process during the thermal annealing, the hole-injection-assisted reactions happen at selective molecular sites controlled by the STM tip. The charge injections lower the cyclodehydrogenation barrier in the catalyst-free formation of graphitic lattices, and the orbital symmetry conservation rules favour hole rather than electron injections for the GNR formation. The created polymer-GNR intraribbon heterostructures have a type-I energy level alignment and strongly localized interfacial states. This finding points to a new route towards controllable synthesis of freestanding graphitic layers, facilitating the design of on-surface reactions for GNR-based structures.
•A spark-based parallel dynamic programming (SPDP) method is proposed.•A spark-based parallel particle swarm optimization (SPPSO) method is proposed.•Simulation experiments of the two methods are ...performed on the cloud computing.•The parallel performance of SPDP and SPPSO are investigated.•Results verify the performance of DP is better than PSO via parallel cloud computing.
The joint optimal operation of a large-scale reservoir system is a complex optimization problem with high-dimensional, multi-stage, and nonlinear features. As the number of reservoirs and discrete states increase, the runtime of optimal operation model increases exponentially, leading to the phenomenon of “curse of dimensionality”. Traditional multi-core parallel computing can improve the efficiency to a certain extent, but it is difficult to expand and break through the hardware limitation, which is not suitable for the optimization of the large-scale reservoir system and its refined management. Different from the current literature about reservoir operations that focus on the comparisons of dynamic programming (DP) with particle swarm optimization (PSO) algorithm in serial mode, this paper pays emphasis on a comparison study of parallel DP with parallel PSO via cloud computing. This study proposes the spark-based parallel dynamic programming (SPDP) and spark-based parallel particle swarm optimization (SPPSO) methods via cloud computing. Taking the cascade eight-reservoir system in the Yuanshui basin in China as an example, simulation experiments are carried out for the comparison between SPDP and SPPSO in terms of parallel performance, precision, efficiency, and stability. The results are as follows: (1) The parallel performance of SPDP in the cloud environment is better than SPPSO. (2) Under the same runtime, the precision of SPDP is generally higher than that of SPPSO. (3) Setting the same precision, the runtime of SPPSO is on average 255.18% longer than SPDP, and it does not reach the precision of SPDP. (4) SPPSO has a fast convergence speed and the ability to jump out of the local optimal solution, but its precision increases by 0.41%, while the runtime increases by 229.55% with the increase of iterations. DP solves more accurately and efficiently than PSO via parallel cloud computing, which ensures the global search capability of the algorithm. Moreover, cloud computing is flexible, economical, and safe, with high practical value and application prospects.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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