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The potential to improve the efficiency of photovoltaic devices through singlet exciton fission (SF) has raised interest of researchers during the last decade. Organic small molecules of rubrene were fabricated into spherical nanoaggregates (NAs) of diameter ∼250 nm by the re-precipitation method. J-type aggregation inside the NA with pivotal electronic coupling occurs in NAs. Observed strong fluorescence quenching indicates the presence of competing pathways in the NAs: hot and thermally activated SF, triplet–triplet annihilation (TTA), and energy transfer between inhomogeneously broadened NA ensembles. SF which proceeds directly from upper excited electronic states within 340 fs (vs 200 fs in crystals; 30 fs in films) results in a triplet quantum yield of 162%. With an aim to apply rubrene in photovoltaics, a rubrene NA-integrated film was prepared on top of the CH3NH3PbI3 layer. Triplet formation within 25 ps in the NA layer was well-documented. Subsequently, the triplet excitons are accumulated and further upconverted via TTA to populate the conduction band of the perovskite within 39 ps (80%) and ≫10 ns (20%). Our findings are crucial for understanding photophysical mechanisms of rubrene/perovskite interaction after light absorption by rubrene. [ABSTRACT FROM AUTHOR]

Acid‐catalysed Friedländer cyclization of 2‐aminobenzophenones with 1,2‐, 1,3‐, and 1,4‐cyclohexadiones, followed by aromatization, has been used to prepare dibenzophenanthrolines (DBPs) containing 1,10‐, 1,7‐ and 4,7‐phenanthroline units, whose optoelectronic properties have been compared. The LUMO energies for all isomers were similar but the 4,7‐isomers possessed significantly higher HOMOs than the other isomers, resulting in them having smaller HOMO‐LUMO energy gaps. Compared with 1,10‐DBP isomers, the emission of 1,7‐DBPs is strongly quenched due to efficient charge transfer. The 4,7‐DBP isomers show strongly enhanced photoluminescence due to excimer formation but appear to be less photostable due to their higher HOMO levels. Bis(phenylethynyl)‐substituted derivatives demonstrated improved solubility and stronger luminescence properties than their unsubstituted analogues. [ABSTRACT FROM AUTHOR]

New Delhi metallo-β-lactamases (NDMs), including at least 28 variants, are a rapidly emerging family of β-lactamases worldwide, with a variety of infections caused by NDM-positive strains usually associated with very poor prognosis and high mortality. NDMs are the most prevalent carbapenemases in Escherichia coli (E. coli) worldwide, especially in China. The vast majority of bla NDM cases occur on plasmids, which play a vital role in the dissemination of bla NDM. To systematically explore the relationships between plasmids and bla NDM genes in E. coli and obtain an overall picture of the conjugative and mobilizable bla NDM-positive plasmids, we analyzed the variants of bla NDM, replicon types, phylogenetic patterns, conjugative transfer modules, host STs, and geographical distributions of 114 bla NDM-positive plasmids, which were selected from 3786 plasmids from 1346 complete whole genomes of E. coli from the GenBank database. We also established links among the characteristics of bla NDM-positive plasmids in E. coli. Eight variants of bla NDM were found among the 114 bla NDM-positive plasmids, with bla NDM–5 (74 bla NDM–5 genes in 73 plasmids), and bla NDM–1 (31 bla NDM–1 genes in 28 plasmids) being the most dominant. The variant bla NDM–5 was mainly carried by the IncX3 plasmids and IncF plasmids in E. coli , the former were mainly geographically distributed in East Asia (especially in China) and the United States, and the latter were widely distributed worldwide. IncC plasmids were observed to be the predominant carriers of bla NDM–1 genes in E. coli , which were mainly geographically distributed in the United States and China. Other bla NDM–1-carrying plasmids also included IncM2, IncN2, and IncHI1. Moreover, the overall picture of the conjugative and mobilizable bla NDM-positive plasmids in E. coli was described in our study. Our findings enhance our understanding of the genetic diversity and characteristics of bla NDM-positive plasmids in in E. coli. [ABSTRACT FROM AUTHOR]

With the low-carbon revolution, many firms face the continuous challenge for reducing carbon emissions in their supply chain activities. Built upon the strategic safety stock placement model, in this paper, we model the carbon emissions for each stage of a multi-echelon supply chain as a function of the service time guaranteed by this stage to its immediate downstream stages. We establish that there is a negative correlation between service time and carbon emissions at each stage. Based on this, we develop two models to study the trade-off between service time and carbon emissions for safety stock placement in multi-echelon supply chains by considering carbon cap and carbon tax, respectively. Both of them are solved using iterative piecewise linear approximations. We implement these two models to study how carbon cap, carbon emission cost rate and guaranteed service time affect the optimal safety stock placement using a real chain. [ABSTRACT FROM PUBLISHER]

Although the cobalt complex, [Co(CR)X2]+ (CR = 2,12-dimethyl-3,7,11,17-tetraazabicyclo[11.3.1]heptadeca-1(17),2,11,13,15-pentaene), has been studied as a catalyst for electro- and photochemical H2 generation and CO2 reduction for more than thirty years, only the unfunctionalized one was used as a free catalyst in bulk solutions. Considering that the immobilization of functionalized molecular catalysts (MCs) on the surface of light harvesting materials through a stable covalent linkage was often an effective strategy to boost the activity of semiconductor/MC hybrid photocatalytic systems, we prepared the first anchoring group-functionalized [Co(CR)X2]+ complex (C1, X = Br), which bears a (2′,6′-dicarboxypyridin-4′-yl) group at position 15 of the macrocyclic ligand. The covalent attachment of C1 to the surface of CuInS2/ZnS (CISZ) core–shell quantum dots (QDs) afforded the C1@CISZ hybrid assembly. Comparative studies on the visible-light-induced H2 evolution performances of C1@CISZ and the non-bonded reference system comprising the unfunctionalized [Co(CR)Br2]+ complex (C2) and CISZ QDs (denoted as C2+CISZ) revealed that the photocatalytic activity of C1@CISZ was twice to thrice as high as that of C2+CISZ under the same conditions. Appealingly, the isolated C1@CISZ assembly was more stable than the C2+CISZ system in long-term photolysis. Moreover, photoluminescence (PL) and transient absorption (TA) spectroscopic studies demonstrated that covalent immobilization of C1 on the surface of CISZ QDs accelerated the electron transfer from QDs to the catalyst and meanwhile retarded the charge recombination process on the surface of QDs. The evidently improved charge separation efficiency resulted in the higher activity of the hybrid assembly C1@CISZ than that of C2+CISZ for photocatalytic hydrogen production. [ABSTRACT FROM AUTHOR]

Fundamental photocatalytic limitations of solar CO2 reduction remain due to low efficiency, serious charge recombination, and short lifetime of catalysts. Herein, two‐dimensional graphitic carbon nitride nanosheets with nitrogen vacancies (g‐C3Nx) located at both three‐coordinate N atoms and uncondensed terminal NHx species were prepared by one‐step tartaric acid‐assistant thermal polymerization of dicyandiamide. Transient absorption spectra revealed that the defects in g‐C3N4 act as trapped states of charges to result in prolonged lifetimes of photoexcited charge carriers. Time‐resolved photoluminescence spectroscopy revealed that the faster decay of charges is due to the decreased interlayer stacking distance in g‐C3Nx in favor of hopping transition and mobility of charge carriers to the surface of the material. Owing to the synergic virtues of strong visible‐light absorption, large surface area, and efficient charge separation, the g‐C3Nx nanosheets with negligible loss after 15 h of photocatalysis exhibited a CO evolution rate of 56.9 μmol g−1 h−1 under visible‐light irradiation, which is roughly eight times higher than that of pristine g‐C3N4. This work presents the role of defects in modulating light absorption and charge separation, which opens an avenue to robust solar‐energy conversion performance. Between the sheets: Graphitic carbon nitride (g‐C3N4) nanosheets rich in nitrogen defects were obtained by one‐step tartaric acid‐assisted thermal polymerization of dicyandiamide. The defects in g‐C3N4 act as charge trapped states to prolong the lifetime of charge carriers, and the decreased interlayer distance caused by nitrogen vacancies favors of charge transport and mobility to the surface (see figure). Deficient g‐C3N4 exhibits the enhanced photocatalytic activity in CO2 reduction. [ABSTRACT FROM AUTHOR]