The adsorption and photocatalytic degradation of Ethyl methylphosphonate (EMPA) on powdery TiO2 film has experimentally investigated using attenuated total reflection-infrared Fourier transform spectroscopy (ATR-FTIR) in ambient condition. Characteristic IR frequency as P-O-C vibration mode as EtO was observed by EMPA adsorbed at the surface of TiO2. By TiO2 photocatalysis, the adsorbed EMPA was decomposed to methyl phosphonic acid and phosphoric acid. The increment of IR intensity of which is assigned to Ti–O-P-O-Ti of EMPA was accompanied with increasing the IR peak intensity assigned to MPA. About that, we suggest that the appearance of the Ti–O-P-O-Ti of EMPA by the TiO2 photocatalysis is regarded as acceleration of the hydrolysis of EMPA by the surface OH groups of TiO2. The plausible adsorption structure and the photocatalytic reaction mechanism of EMPA at the surface of TiO2 photocatalyst were elucidated.
ABSTRACTWe present a new fabrication approach to achieve a high birefringence film by means of photopolymerization based on an alkylthio-containing rod-like liquid crystalline molecule exhibiting large temperature dependence of birefringence. We designed a new reactive mesogen having alkylthio linkages (BPM–S). It was found that BPM–S had a larger increment of birefringence with decreasing temperature, relative to commercially available alkoxy analog LC242. This result could be thought to be due to enhanced intermolecular attractive interaction for an alkylthio mesogen implied by the proximity of laterally neighboring molecules and cybotactic nematic tendency based on wide-angle X-ray measurement. The uniaxially-aligned photo-polymerized film for BPM–S showed higher birefringence than that for LC 242. 相似文献
A concise approach to the algal metabolite 1 is described, which also determines the previously unknown stereostructure of this natural product. Compound 1 is distinguished by a rare brominated 4‐pyrone nucleus linked as a ketene–acetal to a polyunsaturated macrocyclic scaffold comprising an extra homoallylic bromide entity. The synthesis of 1 is based on the elaboration and selective functionalization of the linear precursor 23 endowed with no less than six different sites of unsaturation including the highly enolized oxo‐alkanoate function. Key to success was the formation of the 2‐alkoxy‐4‐pyrone ring by a novel gold‐catalyzed transformation which engages only the acetylenic β‐ketoester substructure of 23 but leaves all other π‐bonds untouched. The synthesis was completed by a ring‐closing alkyne metathesis to forge the signature cycloalkyne motif of 1 followed by selective bromination of the ketene–acetal site in the resulting product 27 without touching the skipped diene–yne substructure resident within the macrocyclic tether. 相似文献
We investigate the degradation path of MAPbI3 (MA=methylammonium) films over flat TiO2 substrates at room temperature by means of X‐ray diffraction, spectroscopic ellipsometry, X‐ray photoelectron spectroscopy, and high‐resolution transmission electron microscopy. The degradation dynamics is found to be similar in air and under vacuum conditions, which leads to the conclusion that the occurrence of intrinsic thermodynamic mechanisms is not necessarily linked to humidity. The process has an early stage, which drives the starting tetragonal lattice in the direction of a cubic atomic arrangement. This early stage is followed by a phase change towards PbI2. We describe how this degradation product is structurally coupled with the original MAPbI3 lattice through the orientation of its constituent PbI6 octahedra. Our results suggest a slight octahedral rearrangement after volatilization of HI+CH3NH2 or MAI, with a relatively low energy cost. Our experiments also clarify why reducing the interfaces and internal defects in the perovskite lattice enhances the stability of the material. 相似文献
The optimization of a porous structure to ensure good separation performances is always a significant issue in high‐performance liquid chromatography column design. Recently we reported the homogeneous embedment of Ag nanoparticles in periodic mesoporous silica monolith and the application of such Ag nanoparticles embedded silica monolith for the high‐performance liquid chromatography separation of polyaromatic hydrocarbons. However, the separation performance remains to be improved and the retention mechanism as compared with the Ag ion high‐performance liquid chromatography technique still needs to be clarified. In this research, Ag nanoparticles were introduced into a macro/mesoporous silica monolith with optimized pore parameters for high‐performance liquid chromatography separations. Baseline separation of benzene, naphthalene, anthracene, and pyrene was achieved with the theoretical plate number for analyte naphthalene as 36 000 m?1. Its separation function was further extended to cis/trans isomers of aromatic compounds where cis/trans stilbenes were chosen as a benchmark. Good separation of cis/trans‐stilbene with separation factor as 7 and theoretical plate number as 76 000 m?1 for cis‐stilbene was obtained. The trans isomer, however, is retained more strongly, which contradicts the long‐ established retention rule of Ag ion chromatography. Such behavior of Ag nanoparticles embedded in a silica column can be attributed to the differences in the molecular geometric configuration of cis/trans stilbenes. 相似文献
Fluorinated tolanes, produced by introducing fluorine atoms into one of the aromatic rings of tolane, emitted almost no fluorescence in a solution state, but the fluorescence intensity increased dramatically in the crystalline state because of intermolecular H⋅⋅⋅F hydrogen bonds. The photoluminescent (PL) colors depend on the molecular orbitals, dipole moments, and molecular aggregated structures can be varied by controlling terminal substituents along the major molecular axis. The introduction of a long alkoxy or semifluoroalkoxy unit as a flexible chain into the terminal positions along the major molecular axis induced the formation of a liquid-crystalline (LC) phase; fluorinated tolanes act both as luminophores and as mesogens, leading to the molecular design of new photoluminescent LC molecules (PLLCs). The results also indicated that a fluorinated tolane dimer, which consists of two fluorinated tolanes linked by a flexible alkylene spacer, also becomes a novel PLLC. 相似文献