The stabilization of black-phase formamidinium lead iodide (α-FAPbI3) perovskite under various environmental conditions is considered necessary for solar cells. However, challenges remain regarding the temperature sensitivity of α-FAPbI3 and the requirements for strict humidity control in its processing. Here we report the synthesis of stable α-FAPbI3, regardless of humidity and temperature, based on a vertically aligned lead iodide thin film grown from an ionic liquid, methylamine formate. The vertically grown structure has numerous nanometer-scale ion channels that facilitate the permeation of formamidinium iodide into the lead iodide thin films for fast and robust transformation to α-FAPbI3. A solar cell with a power-conversion efficiency of 24.1% was achieved. The unencapsulated cells retain 80 and 90% of their initial efficiencies for 500 hours at 85°C and continuous light stress, respectively.

An efficient electron transport layer (ETL) plays a key role in promoting carrier separation and electron extraction in planar perovskite solar cells (PSCs). An effective composite ETL is fabricated using carboxylic‐acid‐ and hydroxyl‐rich red‐carbon quantum dots (RCQs) to dope low‐temperature solution‐processed SnO2, which dramatically increases its electron mobility by ≈20 times from 9.32 × 10−4 to 1.73 × 10−2 cm2 V−1 s−1. The mobility achieved is one of the highest reported electron mobilities for modified SnO2. Fabricated planar PSCs based on this novel SnO2 ETL demonstrate an outstanding improvement in efficiency from 19.15% for PSCs without RCQs up to 22.77% and have enhanced long‐term stability against humidity, preserving over 95% of the initial efficiency after 1000 h under 40–60% humidity at 25 °C. These significant achievements are solely attributed to the excellent electron mobility of the novel ETL, which is also proven to help the passivation of traps/defects at the ETL/perovskite interface and to promote the formation of highly crystallized perovskite, with an enhanced phase purity and uniformity over a large area. These results demonstrate that inexpensive RCQs are simple but excellent additives for producing efficient ETLs in stable high‐performance PSCs as well as other perovskite‐based optoelectronics.

A new fluorescent polyimide covalent organic framework (PI-COF) has been successfully synthesized through solvothermal route using tetra(4-aminophenyl) porphyrin and perylenetracarboxylic dianhydride, which possesses porous crystalline and excellent thermal stability (>500 °C). Furthermore, few-layered PI covalent organic nanosheets (PI-CONs) can be easily obtained from the fluorescent PI-COF through a facile liquid phase exfoliation approach, which were confirmed by atomic force microscopy and transmission electron microscopy analysis. It is interesting that the fluorescent intensity of PI-CONs is obviously enhanced relative to that of PI-COF. The PI-CONs have been successfully utilized as an efficient fluorescent probe for the highly sensitive and selective detection of 2,4,6-trinitrophenol (TNP). The mechanism might be attributed to the combination of electron transfer and inner filter effect based on DFT calculations and spectral overlap data. The system exhibits a good linear response toward TNP over the range from 0.5 to 10 μM with a detection limit of 0.25 μM.

The coordination assembly of 1,3,5-trispyridylbenzene with Cu on a Au(111) surface has been investigated by scanning tunneling microscopy under ultrahigh vacuum conditions. An open two-dimensional (2D) metal-organic network of honeycomb structure is formed as the 2D network covers partial surface. Upon the 2D network coverage of the entire surface, further increment of molecular density on the surface results in a multistep nonreversible structural transformation in the self-assembly. The new phases consist of metal-organic networks of pentagonal, rhombic, zigzag, and eventually triangular structures. In addition to the structural change, the coordination configuration also undergoes a change from the two-fold Cu-pyridyl binding in the honeycomb, pentagonal, rhombic and zigzag structures to the three-fold Cu-pyridyl coordination in the triangular structure. As the increment of molecular packing density on the surface builds up intrinsic in-plane compression pressure in the 2D space, the transformation of the structure, as well as the coordination binding mode, is attributed to the in-plane compression pressure. The quantitative structural analysis of the various phases upon molecular density increment allows us to construct a phase diagram of network structures as a function of the in-plane compression.

We investigated the thermodynamic processes of two-dimensional (2D) metallo-supramolecular self-assembly at molecular resolution using scanning tunneling microscopy and variable-temperature low-energy electron diffraction. On a Au(111) substrate, tripyridyl ligands coordinated with Cu in a twofold Cu-pyridyl binding mode or with Fe in a threefold Fe-pyridyl binding mode, forming a 2D open network structure in each case. The network structures exhibited remarkable thermal stability (600 K for the Cu-coordinated network and 680 K for the Fe-coordinated network). The Fe-pyridyl binding was selected thermodynamically as well as kinetically in self-assembly involving both modes. The selectivity can be effectively suppressed in a specifically designed self-assembly route.

Members of the Ras superfamily regulate many cellular processes. They are down-regulated by a GTPase reaction in which GTP is cleaved into GDP and P i by nucleophilic attack of a water molecule. Ras proteins accelerate GTP hydrolysis by a factor of 10 5 compared to GTP in water. GTPase-activating proteins (GAPs) accelerate hydrolysis by another factor of 10 5 compared to Ras alone. Oncogenic mutations in Ras and GAPs slow GTP hydrolysis and are a factor in many cancers. Here, we elucidate in detail how this remarkable catalysis is brought about. We refined the protein-bound GTP structure and protein-induced charge shifts within GTP beyond the current resolution of X-ray structural models by combining quantum mechanics and molecular mechanics simulations with timeresolved Fourier-transform infrared spectroscopy. The simulations were validated by comparing experimental and theoretical IR difference spectra. The reactant structure of GTP is destabilized by Ras via a conformational change from a staggered to an eclipsed position of the nonbridging oxygen atoms of the γ-relative to the β-phosphates and the further rotation of the nonbridging oxygen atoms of α-relative to the β-and γ-phosphates by GAP. Further, the γ-phosphate becomes more positive although two of its oxygen atoms remain negative. This facilitates the nucleophilic attack by the water oxygen at the phosphate and proton transfer to the oxygen. Detailed changes in geometry and charge distribution in the ligand below the resolution of X-ray structure analysis are important for catalysis. Such high resolution appears crucial for the understanding of enzyme catalysis.enzyme catalysis | reaction mechanism | free energy of activation M any cellular processes are regulated by members of the Ras superfamily. They are switched "on" by GDP-to-GTP exchange and "off" by a GTPase reaction. GTP hydrolysis is vitally important for the regulation of several signal-transduction processes in living cells (1, 2). In the case of Ras, external growth signals are transduced to the nucleus. Site-specific oncogenic mutations inhibit the GTPase reaction and the growth signal can no longer be down-regulated. This contributes to uncontrolled cell growth, eventually leading to cancer (3). Common to all members of the Ras superfamily is the catalysis of GTP hydrolysis by the G domain (4). Ras-catalyzed GTP hydrolysis is five orders of magnitude faster than in water (30 min vs. 200 d) (5). However, to control growth signals in the living cell, a further increase of five orders of magnitude in the reaction rate (30 min to 50 ms) is enabled. This is effected by GTPase-activating proteins (GAPs) that interact with Ras (6). The mechanisms of GTP hydrolysis have been extensively investigated both theoretically (7-22) and experimentally by X-ray crystallography (23-27), electron spin resonance (28-30), and FTIR spectroscopy (5,6,(31)(32)(33).Determination of the three-dimensional structures of Ras and GAP by X-ray crystallography represents an important milestone in the understanding of t...

An amphiphilic surfactant, oleamide, was applied to dope the PCBM electron transport layer (ETL) of inverted structure perovskite solar cells (ISPSCs), resulting in a dramatic efficiency enhancement. Under the optimized oleamide doping ratio of 5.0 wt %, the power conversion efficiency of the CH3NH3PbIxCl(3-x) perovskite-based ISPSC device is enhanced from 10.05% to 12.69%, and this is primarily due to the increases of both fill factor and short-circuit current. According to the surface morphology study of the perovskite/PCBM bilayer film, oleamide doping improves the coverage of PCBM ETL onto the perovskite layer, and this is beneficial for the interfacial contact between the perovskite layer and the Ag cathode and consequently the electron transport from perovskite to the Ag cathode. Such an improved electron transport induced by oleamide doping is further evidenced by the impedance spectroscopic study, revealing the prohibited electron-hole recombination at the interface between the perovskite layer and the Ag cathode.

The origins of unique gold-catalyzed C–H functionalization of phenols with diazo compounds were disclosed by combined computational and experimental studies.