Recent scientific advances on organic-inorganic hybrid perovskites are mainly focused on the improvement of power conversion efficiency. So far, how compression tunes their electronic and structural properties remains less understood. By combining in situ photocurrent, impedance spectroscopy, and X-ray diffraction (XRD) measurements, we have studied the electrical transport and structural properties of compressed CH3NH3PbI3 (MAPbI3) nanorods. The visible light response of MAPbI3 remains robust below 3 GPa while it is suppressed when it becomes amorphous. Pressure-induced electrical transport properties of MAPbI3 including resistance, relaxation frequency, and relative permittivity have been investigated under pressure up to 8.5 GPa by in situ impedance spectroscopy measurements. These results indicate that the discontinuous changes of these physical parameters occur around the structural phase transition pressure. The XRD studies of MAPbI3 under high pressure up to 20.9 GPa show that a phase transformation below 0.7 GPa, could be attributed to the tilting and distortion of PbI6 octahedra. And pressure-induced amorphization is reversible at a low density amorphous state but irreversible at a relatively higher density state. Furthermore, the MAPbI3 nanorods crush into nanopieces around 0.9 GPa which helps us to explain why the mixed phase of tetragonal and orthorhombic was observed at 0.5 GPa. The pressure modulated changes of electrical transport and visible light response properties open up a new approach for exploring CH3NH3PbI3-based photo-electronic applications.

The formic acid catalyzed gas-phase reaction between H(2)O and SO(3) and its reverse reaction are respectively investigated by means of quantum chemical calculations at the CCSD(T)//B3LYP/cc-pv(T+d)z and CCSD(T)//MP2/aug-cc-pv(T+d)z levels of theory. Remarkably, the activation energy relative to the reactants for the reaction of H(2)O with SO(3) is lowered through formic acid catalysis from 15.97 kcal  mol(-1) to -15.12 and -14.83 kcal  mol(-1) for the formed H(2)O⋅⋅⋅SO(3) complex plus HCOOH and the formed H(2)O⋅⋅⋅HCOOH complex plus SO(3), respectively, at the CCSD(T)//MP2/aug-cc-pv(T+d)z level. For the reverse reaction, the energy barrier for decomposition of sulfuric acid is reduced to -3.07 kcal  mol(-1) from 35.82 kcal  mol(-1) with the aid of formic acid. The results show that formic acid plays a strong catalytic role in facilitating the formation and decomposition of sulfuric acid. The rate constant of the SO(3)+H(2)O reaction with formic acid is 10(5) times greater than that of the corresponding reaction with water dimer. The calculated rate constant for the HCOOH+H(2)SO(4) reaction is about 10(-13) cm(3)  molecule(-1)  s(-1) in the temperature range 200-280 K. The results of the present investigation show that formic acid plays a crucial role in the cycle between SO(3) and H(2)SO(4) in atmospheric chemistry.

Herein we report two new TPE‐based 3D MOFs, that is, Sr‐ETTB and Co‐ETTB (TPE=Tetraphenylethylene, H8ETTB=4′,4′′′,4′′′′′,4′′′′′′′‐(ethene‐1,1,2,2‐tetrayl)tetrakis(([1,1′‐biphenyl]‐3,5‐dicarboxylic acid))). Through tailoring outer shell electron configurations of SrII and CoII cations, the fluorescence intensity of the MOFs is tuned from high emission to complete non‐emission. Sr‐ETTB with strong blue fluorescence shows reversible fluorescence variations in response to pressure and temperature, which is directly related to the reversible deformation of the crystal structure. In addition, non‐emissive Co‐ETTB counterpart exhibits a turn‐on fluorescent enhancement under the stimulation of analyte histidine. In the process, TPE‐cored linkers in the MOFs are released through competitive coordination substitution and subsequently reassembled to perform aggregation‐induced luminescence behavior originated from the organic linkers.

Atomically thin, two-dimensional material molybdenum diselenide (MoSe) has been shown to exhibit significant potential for diverse applications. The intrinsic band gap of MoSe allows it to overcome the shortcomings of the zero-band-gap graphene, while its higher electron mobilities when compared to molybdenum disulfide (MoS) make it more appropriate for practical devices in electronics and optoelectronics. However, its controlled growth has been an ongoing challenge for investigations and practical applications of the material. Here, we present an atmospheric pressure chemical vapor deposition (CVD) method to achieve highly crystalline, single- and few-layered MoSe using a SiO/Si substrate. Our findings suggested that careful optimization of the flow rate can result in the controlled growth of large-area MoSe with desired layer numbers due to the adjustment of gaseous MoSe partial pressure and nucleation density. The FETs fabricated on such as-synthesized MoSe displayed different transport behaviors depending on the layer numbers, which can be attributed to the formation of Se vacancies generated during low flow rates. Monolayer MoSe showed n-type characteristics with an I/I ratio of ∼10 and a carrier mobility of ∼19 cm V s, whereas bilayer MoSe showed n-type-dominant ambipolar behavior with an I/I ratio of ∼10 and a higher mobility of ∼65 cm V s for electrons as well as ∼9 cm V s for holes. Our results provide a foundation for property-controlled synthesis of MoSe and offer insight on the potential applications of our synthesized MoSe in electronics and optoelectronics.