Molecular wires are covalently bonded to gold electrodes--to form metal-molecule-metal junctions--by functionalizing each end with a -SH group. The conductance of a wide variety of molecular junctions is studied theoretically by using first-principles density functional theory (DFT) combined with the nonequilibrium Green's function (NEGF) formalism. Based on the chain-length-dependent conductance of the series of molecular wires, the attenuation factor beta is obtained and compared with the experimental data. The beta value is quantitatively correlated to the molecular HOMO-LUMO gap. Coupling between the metallic electrode and the molecular bridge plays an important role in electron transport. A contact resistance of 6.0+/-2.0 Kohms is obtained by extrapolating the molecular-bridge length to zero. This value is of the same magnitude as the quantum resistance.

Lead halide perovskite (LHP) semiconductors with the general chemical formula ABX3 are now being widely investigated for a variety of applications including but not limited to high-efficiency photovoltaics (PVs) and light-emitting diodes (LEDs).

In this work, Mn 2+ has been efficiently and homogeneously doped into two-dimensional (2D) distorted single-layered EA 2 PbBr 4 (EA: ethylammonium) via a reprecipitation method. Both the doped and undoped 2D layered lead halide perovskites (LHPs) were characterized using a combination of X-ray, electron microscopy, and spectroscopy techniques. The Mn 2+ -doped EA 2 PbBr 4 (EA 2 PbBr 4 :Mn 2+ ) shows a 78% photoluminescence (PL) quantum yield (QY) with complete quenching of self-trapped exciton emission because of efficient exciton trapping by defects created by dopants and small activation energy (∼9.8 meV) between the defect states and Mn 2+ d states. Compared to the long lifetime (∼1.5 ms) of Mn 2+ emission in CsPbCl 3 , the lifetime in 2D EA 2 PbBr 4 is found to be ∼0.75 ms, resulting from the heavy atom effect. Additionally, the PL QY of Mn 2+ emission can be further increased by codoping Zn 2+ or Cd 2+ , which is attributed to a high density of trap states created by codoping, facilitating exciton to Mn 2+ energy transfer. These results reveal the key role of trap states in the energy transfer of Mn 2+ -doped 2D LHPs.

Highly efficient lead halide perovskites with tunable emission performance have become new candidate materials for light‐emitting devices and displays; however, the toxicity of lead and instability of halide perovskites greatly limits their application. Herein, rapid and large‐scale synthesis of highly emissive organic–inorganic manganese halide perovskites, (C5H6N)2MnBr4 and C5H6NMnCl3, are presented by a one‐pot solution‐based method, of which (C5H6N)2MnBr4 displays a high absolute photoluminescence quantum yield (95%) in the solid‐state. The developed (C5H6N)2MnBr4 perovskite noticeably exhibits high stability. Therefore both as‐synthesized green and red emissive manganese‐based phosphors with superior optical properties are used to fabricate blue light pumped white light‐emitting diodes (WLEDs), displaying excellent quality white light with a high color rendering index value of 91 and a correlated color temperature of 5331 K. This study not only presents the robust large‐scale production synthetic approach for organic–inorganic manganese halide perovskites, but also facilitates the development of high‐performance phosphors for future lighting and display technologies.

The present investigation reports the electrochemical measurements of azurin (Az) adsorbed on a series of alkanethiol self-assembled monolayers (SAMs) under the influence of urea molecules. Theoretical fitting with the Marcus model obtains the electron-transfer rate constant, k et , and the reorganization energy, λ. When the underlying SAM is longer than 10 methylene units, k et shows an obvious chain-length dependence from which an electron-tunneling coefficient, β, of 1.09 per methylene is deduced. Combined with cyclic voltammetric results, variations of both k et and λ imply that urea impact does not penetrate into the ion core part of Az but instead influences the network of molecular hydrogen bonds. The mechanism of urea impact is further discussed by means of the pH dependence of the equilibrium potential.

Photocatalysis as a desirable technology shows great potential in environmental remediation and renewable energy generation, but the recombination of photogenerated carriers is a key limiting factor for efficiency in artificial photosynthesis. Internal electric field (IEF, also known as built‐in electric field) engineering acts an emerging and clearly viable route to increase photocatalytic efficiency by facilitating charge separation and transfer. This review summarizes the basic principles of IEF including the source, the strategies for the enhancement and the measurement of IEF. Highlight is the recent progress in steering photogenerated charge separation of photocatalysts by IEF engineering and related mechanisms. Finally, the challenges in IEF engineering and exciting opportunities to further enhancing charge separation and photocatalytic performance are discussed.Abstractimage

Highly efficient hydrogen evolution reactions carried out via photocatalysis using solar light remain a formidable challenge. Herein, perylenetetracarboxylic acid nanosheets with a monolayer thickness of ~1.5 nm were synthesized and shown to be active hydrogen evolution photocatalysts with production rates of 118.9 mmol g−1 h−1. The carboxyl groups increased the intensity of the internal electric fields of perylenetetracarboxylic acid from the perylene center to the carboxyl border by 10.3 times to promote charge-carrier separation. The photogenerated electrons and holes migrated to the edge and plane, respectively, to weaken charge-carrier recombination. Moreover, the perylenetetracarboxylic acid reduction potential increases from −0.47 V to −1.13 V due to the decreased molecular conjugation and enhances the reduction ability. In addition, the carboxyl groups created hydrophilic sites. This work provides a strategy to engineer the molecular structures of future efficient photocatalysts.

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